TW202240211A - Polarizing plate - Google Patents

Abstract

Provided is a polarizing plate that has excellent adhesion to a polarizer, and can prevent fading of color from an edge. The polarizing plate according to the present invention has: a polarizer; and a protective layer on at least one surface of the polarizer. The protective layer is formed of a solidified product of a coating film of an organic solvent solution containing a thermoplastic cycloolefin resin and a boronic acid compound.

Description

polarizer

The invention relates to a polarizing plate.

Polarizers are 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). It is known that the polarizer absorbs moisture in a hot and humid environment, and the iodine complex is destroyed, resulting in the dissolution of iodine, thereby reducing the degree of polarization and increasing the transmittance (fading). Moisture intrudes from the end of the polarizer, so discoloration tends to become noticeable at the end of the polarizer.

In recent years, with the improvement of design, some people have proposed a frameless image display device which is narrower than the frame part. For a frameless image display device, after the human body touches the end of the polarizer, the color of the end of the polarizer may fade due to sweat. Therefore, there is a need for a polarizing plate that can provide an image display device with high designability without causing disadvantages such as fading.

prior art literature patent documents Patent Document 1: Japanese Patent No. 5048120 Patent Document 2: Japanese Patent Laid-Open No. 2013-156391

The problem to be solved by the invention The present invention is made to solve the above-mentioned conventional problems, and its main object is to provide a polarizing plate that can prevent defects such as discoloration from the edge.

(式中，A表示-NH ₂、-NHR及-NRR'，R ¹表示未取代、或是被甲基或乙基取代之芳香族環、脂肪族環、或具有碳數1~10之直鏈或支鏈的烴；A藉由單鍵或羰基來與R ¹鍵結；R及R'如同上述)。 在一實施形態中，上述R ¹為未取代、或是被甲基或乙基取代之芳香族環。 在一實施形態中，上述熱塑性環烯烴系樹脂係具有極性骨架之環烯烴系樹脂。 在一實施形態中，上述保護層之厚度為0.3µm~3µm。 在一實施形態中，上述偏光件之厚度為8µm以下。 MEANS TO SOLVE THE PROBLEM A polarizing plate of the present invention has a polarizer and a protective layer on at least one surface of the polarizer. The protective layer is composed of cured product of coating film in organic solvent solution, and the organic solvent solution includes thermoplastic cycloolefin resin and boric acid compound. In one embodiment, in the organic solvent solution, the content of the boric acid compound is not less than 1 part by weight and not more than 10 parts by weight relative to 100 parts by weight of the thermoplastic cycloolefin-based resin. In one embodiment, the above-mentioned boronic acid compound is a compound having a substituent and a boronic acid group in the molecule, and the substituent is selected from -NH ₂ , -NHR and -NRR' (R and R' represent methyl or At least one of the group consisting of ethyl, R and R′ may be the same or different). In one embodiment, the above-mentioned boric acid compound is a compound represented by the following formula: [Chemical Formula 1]

(In the formula, A represents -NH ₂ , -NHR and -NRR', R ¹ represents an aromatic ring, aliphatic ring, or a straight ring with 1 to 10 carbons that is unsubstituted or substituted by methyl or ethyl chain or branched hydrocarbon; A is bonded to R by ^a single bond or carbonyl; R and R' are as above). In one embodiment, the above-mentioned R ¹ is an aromatic ring that is unsubstituted or substituted by methyl or ethyl. In one embodiment, the thermoplastic cycloolefin-based resin is a cycloolefin-based resin having a polar skeleton. In one embodiment, the protective layer has a thickness of 0.3 µm to 3 µm. In one embodiment, the polarizer has a thickness of 8 µm or less.

Invention effect According to the present invention, it is possible to provide a polarizing plate capable of preventing disadvantages such as discoloration from an edge. The protective layer of the polarizing plate of the present invention can fully adhere to the polarizing element, and can also prevent appearance defects such as embossing and peeling. Therefore, it is not necessary to separately form an adhesive layer, and it can contribute to further thinning. Moreover, even when it is used in a frameless image display device, it can still prevent defects such as fading, and can provide an image display device with higher designability.

form for carrying out the invention Preferred embodiments of the present invention will be described below, but the present invention is not limited to these embodiments.

A. Polarizer The polarizing plate of the present invention has: a polarizer, and a protective layer on at least one side of the polarizer. The protective layer is composed of cured product of coating film in organic solvent solution, and the organic solvent solution includes thermoplastic cycloolefin resin and boric acid compound. The protective layer has excellent adhesion to the polarizer. Therefore, even when the thickness of the polarizer is thin, it is possible to prevent appearance defects such as embossing and peeling of the protective layer from the polarizer. In addition, discoloration from the end of the polarizer can also be prevented. In addition, even when the end portion is in contact with the human body, it is possible to prevent discoloration and other disadvantages.

A-1. Overview of Polarizing Plates Fig. 1 is a schematic cross-sectional view of a polarizing plate according to an embodiment of the present invention. The polarizing plate 100 illustrated in the figure includes a polarizer 10 and a protective layer 20 formed on at least one side of the polarizer. The protective layer 20 is composed of a cured coating film of an organic solvent solution, and the organic solvent solution includes a thermoplastic cycloolefin resin and a boric acid compound. The protective layer is composed of a cured film of an organic solvent solution containing thermoplastic cycloolefin resin and boric acid compound, thereby improving the adhesion between the protective layer and the polarizer. Therefore, intrusion of moisture from the end of the polarizer can be prevented, and discoloration from the end can be prevented. Moreover, even if the human body directly touches the end of the polarizer, it can still prevent the polarizer from being discolored by sweat. Moreover, even if the protective layer 20 is formed on only one side of the polarizer 10, it can still prevent the polarizer from fading from the end. Therefore, it also contributes to thinning the polarizing plate 100 . In the example shown in the figure, the protective layer 20 is only formed on one side of the polarizer 10 , but the protective layer 20 may also be formed on both sides of the polarizer 10 . Also, the protective layer 20 may be formed on one surface of the polarizer 10 , and another protective layer may be formed on the other surface of the polarizer 10 . The protection layer 20 represents that the upper system is directly formed on the polarizer 10 (without an adhesive layer or an adhesive layer). By directly forming the protective layer on the polarizer, it can contribute to the thinning of the polarizer. Also, by directly forming the protective layer, the adhesion between the polarizer and the protective layer can be improved.

The polarizing plate 100 may further include any appropriate functional layer other than the protective layer 20 according to the purpose. The functional layer may, for example, be a retardation layer, a light diffusion layer, an antireflection layer, a reflective polarizer, or the like. The functional layer can be laminated on the side of the polarizer 10 or on the side of the protective layer 20 . In addition, multiple functional layers may be included.

B. Polarizer The polarizer represents a resin film containing a dichroic substance. Examples of dichroic substances include iodine and organic dyes. The dichroic substances may be used alone or in combination of two or more. Iodine is preferably included.

In one embodiment, the iodine content of the polarizer 10 is preferably 2% by weight to 25% by weight. In another embodiment of the present invention, the iodine content of the polarizer 10 is preferably 10 wt %-25 wt %, more preferably 15 wt %-25 wt %. The fading of polarizers with high iodine content will become more obvious in hot and humid environments. Therefore, the effect of forming a protective layer that is a cured product of a coating film of an organic solvent solution containing a thermoplastic cycloolefin resin and a boric acid compound can be more exerted. "Iodine content" in this specification means: the total amount of iodine contained in the polarizer (PVA-based resin film). More specifically, iodine exists in polarizers in the form of iodide ions (I ^- ), iodine molecules (I ₂ ), polyiodide ions (I ₃ ^- , I ₅ ^- ), and the iodine content in this specification means Refers to: the amount of iodine in which all of these forms are included. The iodine content can be calculated by, for example, a calibration curve method of X-ray fluorescence analysis. In addition, polyiodide ions exist in the state of forming PVA-iodine complexes in the polarizer. By forming the complexes, absorption dichroism can be exhibited in the wavelength range of visible light. Specifically, the complex of PVA and triiodide ions (PVA·I ₃ ^- ) has an absorption peak near 470nm, while the complex of PVA and pentaiodide ions (PVA·I ₅ ^- ) has an absorption peak near 600nm Absorption peak. As a result, polyiodide ions can absorb light in a wide range of visible light depending on their morphology. On the other hand, iodide ion (I ⁻ ) has an absorption peak around 230 nm, which is substantially independent of the absorption of visible light. Therefore, the polyiodide ions existing in the complex state with PVA are mainly related to the absorption performance of the polarizer.

The thickness of the polarizer is preferably less than 8 µm, preferably more than 0.6 µm and less than 8 µm. In one embodiment, the thickness of the polarizer is preferably 5 μm or less.

The single transmittance of the polarizer is, for example, 30% or more. In addition, the theoretical upper limit of the monomer transmittance is 50%, while the practical upper limit is 46%. In addition, the single transmittance (Ts) is measured with the 2-degree field of view (C light source) of JIS Z8701 and the Y value after the sensitivity correction is performed. For example, a spectrophotometer with an integrating sphere (manufactured by JASCO Co., Ltd., product name : V7100) for determination.

Also, the degree of polarization of the polarizer is, for example, 99.0% or higher, preferably 99.5% or higher, more preferably 99.9% or higher. As mentioned above, the polarizing plate of this invention can prevent discoloration from an edge part. Therefore, even when the polarization degree of the polarizer is high, good polarization degree can still be maintained.

B-1. Manufacturing method of polarizer Polarizers can be manufactured by any suitable method. For example, it can manufacture by subjecting a PVA-type resin film to a swelling process, a dyeing process, a crosslinking process, an extension process, a washing process, and a drying process. In one embodiment, the PVA-based resin film may also be a PVA-based resin layer formed on a substrate. The laminate of the base material and the resin layer can be obtained by, for example, a method of applying a coating liquid containing the above-mentioned PVA-based resin to the base material, or a method of laminating a PVA-based resin film on the base material. Any suitable resin substrate can be used as the substrate, for example, a thermoplastic resin substrate can be used.

B-1-1.PVA-based resin film Examples of the PVA-based resin forming the PVA-based resin film include polyvinyl alcohol and ethylene-vinyl alcohol copolymer. Polyvinyl alcohol can be obtained by saponifying polyvinyl acetate. Ethylene-vinyl alcohol copolymer can be obtained by saponifying ethylene-vinyl acetate copolymer. The degree of saponification of the PVA-based resin is usually more than 85 mol% and less than 100 mol%, preferably 95.0 mol% to 99.99 mol%, more preferably 99.0 mol% to 99.99 mol%. The degree of saponification can be obtained in accordance with JIS K 6726-1994. By using a PVA-based resin having such a degree of saponification, a polarizer excellent in durability can be obtained.

The average degree of polymerization of the PVA-based resin can be appropriately selected according to the purpose. The average degree of polymerization is usually 1000-10000, preferably 1200-4500, more preferably 1500-4300. In addition, the average degree of polymerization can be obtained in accordance with JIS K 6726-1994.

The thickness of the PVA-based resin film can be set according to the desired thickness of the polarizer. The thickness of the PVA-based resin film is, for example, 0.5 µm to 200 µm. By using the dyeing solution described below, for example, even if the PVA-based resin film is smaller than 10 µm, it can be dyed sufficiently in a short time, and it can be given the characteristics that can fully function as a polarizer.

As described above, the polarizer can be manufactured by, for example, subjecting a PVA-based resin film to a swelling step, a dyeing step, a crosslinking step, an extending step, a washing step, and a drying step. Each step can be performed at any suitable timing. In addition, optional steps other than the dyeing step may be omitted, and multiple steps may be performed at the same time, or each step may be performed multiple times. The following describes each step.

B-1-2. Extension In the stretching process, it means that the upper PVA-based resin film is uniaxially stretched to 3 to 7 times the original length. In one embodiment, the above-mentioned PVA-based resin film is subjected to dry stretching. Dry stretching is preferable because stretching can be performed over a wider temperature range. The temperature during dry stretching is, for example, 50°C-200°C, preferably 80°C-180°C, more preferably 90°C-160°C. The stretching direction may be the long side direction (MD direction) of the film, or may be the width direction (TD direction) of the film. In addition, the extending direction may correspond to the absorption axis direction of the obtained polarizer.

B-1-3. Dyeing The dyeing step is a step of dyeing the PVA-based resin film with a dichroic substance. This is preferably done by allowing it to adsorb a dichroic substance. The adsorption method can be, for example, a method of immersing the PVA-based resin film in a dyeing solution containing a dichroic substance, a method of applying the dyed solution to the PVA-based resin film, and spraying the dyed solution onto the PVA-based resin film. method of resin film, etc. A method of immersing the PVA-based resin film in a dyeing solution is preferable. Because it can adsorb dichroic substances well.

The dichroic substance mentioned above includes iodine and a dichroic dye. Preferably it is iodine. When using iodine as a dichroic substance, an iodine aqueous solution can be suitably used as a dyeing liquid. The iodine content of the iodine aqueous solution is preferably 0.04 to 5.0 parts by weight relative to 100 parts by weight of water. In one embodiment, the iodine content in the iodine aqueous solution is preferably 0.3 parts by weight or more with respect to 100 parts by weight of water. In order to increase the solubility of iodine in water, it is advisable to mix iodide in the iodine aqueous solution. Potassium iodide is preferably used as the iodide. The content of iodide is preferably 0.3 to 15 parts by weight relative to 100 parts by weight of water.

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

The content of iodide contained in the dyeing solution is preferably 1 to 40 parts by weight, more preferably 3 to 30 parts by weight, relative to 100 parts by weight of the solvent. If the content of iodide is in the above range, enough polyiodide ions can be formed in the dyeing solution. Examples of iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, titanium iodide and the like. Potassium iodide is preferred.

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

B-1-4. Swelling The swelling step is usually performed before the dyeing step. In one embodiment, the swelling step can also be performed together with the dyeing step in the same immersion bath. The swelling step can be performed, for example, by immersing the PVA-based resin film in a swelling bath. Any suitable liquid can be used for the swelling bath, for example, distilled water, pure water and the like can be used. The swelling bath may also contain any suitable other components besides water. Examples of other components include solvents such as alcohols, additives such as surfactants, iodides, and the like. As the iodide, those exemplified above can be used. Potassium iodide is preferably used. The temperature of the swelling bath is, for example, 20°C to 45°C. Also, the immersion time is, for example, 10 seconds to 300 seconds.

B-1-5. Crosslinking In the crosslinking step, boron compounds are generally used as crosslinking agents. As boron compound, boric acid, borax etc. are mentioned, for example. Preferably it is boric acid. In the crosslinking step, the boron compound is usually used in the form of an aqueous solution.

When a boric acid aqueous solution is used, the boric acid concentration of the boric acid aqueous solution is, for example, 2% by weight to 15% by weight, preferably 3% by weight to 13% by weight. The boric acid aqueous solution may further contain iodides such as potassium iodide; zinc compounds such as zinc sulfate and zinc chloride.

The crosslinking step can be carried out by any suitable method. For example, a method of immersing a PVA-based resin film in an aqueous solution of a boron-containing compound, a method of applying an aqueous solution of a boron-containing compound to a PVA-based resin film, or spraying an aqueous solution of a boron-containing compound onto a PVA-based resin film Methods. It is preferably immersed in an aqueous solution of boron-containing compounds.

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

B-1-6. Washing The washing step uses water or the above-mentioned iodide-containing aqueous solution. Typically, this can be performed by immersing a PVA-based resin film in an aqueous solution of potassium iodide. 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-1-7. Drying The drying step can be performed by any suitable method. Examples thereof include natural drying, air drying, reduced-pressure drying, and heat drying, and heat drying can be suitably used. When heat drying is performed, the heating temperature is, for example, 30°C to 100°C. In addition, the drying time is, for example, 10 seconds to 10 minutes.

C. Protective layer The protection layer 20 is formed on at least one side of the polarizer 10 . The protective layer 20 is composed of a cured coating film of an organic solvent solution, and the organic solvent solution includes a thermoplastic cycloolefin resin and a boric acid compound. The protective layer is composed of a cured product of the coating film, whereby a polarizing plate capable of preventing defects such as discoloration from the edge can be provided. In addition, the protective layer 20 is sufficiently adhered to the polarizer 10 , and appearance defects such as embossing and peeling can be prevented. Therefore, it is not necessary to separately form an adhesive layer, and it can contribute to further thinning.

The thickness of the protective layer 20 can be set to any appropriate value according to the thickness of the polarizer and the like. In one embodiment, the thickness of the protective layer is preferably 0.1 µm-8 µm, more preferably 0.2 µm-5 µm, more preferably 0.3 µm-3 µm. The thickness of the protective layer is within the above-mentioned range, thereby contributing to the thinning of the polarizing plate. As described above, the protective layer 20 can properly protect the polarizer 10 even when the thickness is thin, and can prevent discoloration from the end. If the thickness of the protective layer 20 is greater than 8 µm, the adhesion between the polarizer and the protective layer may decrease.

C-1. Thermoplastic cycloolefin resin As the thermoplastic cycloolefin-based resin, any appropriate cycloolefin-based resin, such as a northylene-based resin, can be used. Cycloolefin-based resins may be used alone or in combination of two or more.

The thermoplastic cycloolefin-based resin may have any appropriate polar group. By having a polar group, the adhesion with the polarizer and the compatibility with the boric acid compound can be adjusted. Polar groups include, for example, carboxyl groups, hydroxyl groups, amino groups, ester groups, and the like. The polar group may be only 1 type, and may have 2 or more types.

As the thermoplastic cycloolefin-based resin, a commercially available one can also be used. Commercially available thermoplastic cycloolefin-based resins include the trade name "ARTON" manufactured by JSR Corporation, the trade name "ZEONOR" manufactured by Japan ZEON Corporation, the trade name "APEL" manufactured by Mitsui Chemicals, and the product manufactured by Polyplastics Co., Ltd. Product name "TOPAS" etc.

In one embodiment, the ammonia permeability of the protective layer is preferably 2.5 µg/mL or less, more preferably 2.0 µg/mL or less, more preferably 1.0 µg/mL or less. Discoloration of the end of the polarizer due to sweat is a problem. One of the main causes of decolorization may be ammonia. Since the ammonia permeability of the cycloolefin resin is low, it can further suppress discoloration of the end of the polarizer due to sweat. When the ammonia permeability is in the above range, even if the human body directly touches the edge of the polarizing plate, discoloration from the edge can be prevented in this case. In this specification, the ammonia permeability can be measured by the following method. A sample obtained by coating a coating solution in which a cycloolefin-based resin is dissolved on one side of a triacetyl cellulose (TAC) film to a thickness of 2 µm, and punching the sample into a 10mmφ, and making the TAC film side to be ammonia liquid The face side is clamped with spacers and set on the cover. Add 1mL of 1% ammonia solution into a 20mL SHS vial, and fix it with a cap equipped with a sample. Then, the vial and 20 mL of collected liquid (ultrapure water) were put into a PP container, then capped, and heated in a dryer at 60° C. for 2 hours. Lock the lid tightly after 10 minutes in the dryer. After heating, cool naturally for 30 minutes and measure the collected solution by IC. The analysis apparatus and conditions are as follows. Analyzer IC (cation): manufactured by Thermo Fisher Scientific, brand name: DX-320 Measurement conditions IC (cation) Separation column: Dionex Ion Pac CS16 (5mm×250mm) Protection column: Dionex Ion Pac CG16 (5mm×50mm) Removal system: Dionex CDRS-600 (reuse mode) Detector: Conductivity detector Eluent: methanesulfonic acid aqueous solution Eluent flow rate: 1.0mL/min Sample injection volume: 25µL

In one embodiment, the moisture absorption rate of the protective layer is preferably 2.0% or less, more preferably 1.5% or less, more preferably 1.0% or less. The main reason for the discoloration of the end of the polarizer in a hot and humid environment is the intrusion of water from the polarizer. With the moisture absorption rate of the protective layer within the above range, discoloration from the edge of the polarizing plate can be prevented. In this specification, moisture permeability can be measured by the following method. A sample obtained by applying a coating liquid in which a cycloolefin-based resin is dissolved so that the thickness becomes 10 µm on one side of a polyethylene terephthalate (PET) film, and taking 5 cm ² (1 cm×5 cm) of the sample , cut into about 1cm square. Then, pre-drying was performed under reduced pressure (60° C.), and moisture adsorption and desorption measurement was performed using IGA-sorp under the measurement conditions shown below. Analysis device Moisture adsorption and desorption measurement device: Hiden, trade name IGA-sorp Measurement conditions Measurement mode: Continuous mode Drying step: 90°C (heater heating) for 2 hours Dry weight confirmation: 1 hour at 60°C, 0%RH Hygroscopic step: 12 hours at 60°C, 90%RH

C-2. Boric acid compound As the boric acid compound, any appropriate compound having a boric acid group can be used. The adhesion of the protective layer to the polarizer can be improved by using an organic solvent solution containing thermoplastic cycloolefin resin and boric acid compound. A boric-acid compound may use only 1 type and may use it in combination of 2 or more types.

In the organic solvent solution, the content of the boric acid compound is preferably 0.1 to 10 parts by weight, more preferably 0.5 to 10 parts by weight, more preferably 1 part by weight or more and 10 parts by weight relative to 100 parts by weight of the thermoplastic cycloolefin resin. parts by weight or less. When the content of the boric acid compound in the organic solvent solution is within the above range, discoloration from the end of the polarizer can be prevented, and a protective layer excellent in adhesion to the polarizer can also be formed.

In one embodiment, the boronic acid compound preferably has a substituent and a boronic acid group, and the substituent is at least one selected from the group consisting of -NH ₂ , -NHR, and -NRR'. The above-mentioned R and R' represent a methyl group or an ethyl group, and R and R' may be the same or different.

The boric acid compound is preferably a compound having -NH ₂ and/or -NHR, more preferably a compound having -NH ₂ .

(式中，A表示-NH ₂、-NHR或-NRR'，R ¹表示未取代、或是被甲基或乙基取代之芳香族環、脂肪族環、或具有碳數1~10之直鏈或支鏈的烴；A藉由單鍵或羰基來與R ¹鍵結；R及R'如同上述)。 In one embodiment, the boric acid compound is preferably a compound represented by the following formula. [chemical formula 2]

(In the formula, A represents -NH ₂ , -NHR or -NRR', R ¹ represents an aromatic ring, aliphatic ring, or a straight ring with 1 to 10 carbons that is unsubstituted or substituted by methyl or ethyl chain or branched hydrocarbon; A is bonded to R by ^a single bond or carbonyl; R and R' are as above).

The above-mentioned A represents -NH ₂ , -NHR or -NRR´. A is bonded to R1 via ^a single bond or a carbonyl group. R ¹ represents an aromatic ring, an aliphatic ring, or a straight-chain or branched-chain hydrocarbon having 1 to 10 carbons that is unsubstituted or substituted by a methyl or ethyl group. R ¹ is preferably an aromatic ring or an aliphatic ring that is unsubstituted or substituted by methyl or ethyl, more preferably an aromatic ring that is unsubstituted or substituted by methyl or ethyl.

The boric acid compound specifically includes the following compounds. [chemical formula 3]

C-3. Organic solvents Organic solvent Any appropriate organic solvent can be used. As the organic solvent, toluene, cyclopentylmethyl ether, 1,2,4-trichlorobenzene, methylcyclohexane, ethylcyclohexane, limonene, dichloromethane, and the like can be used suitably. These solvents may be used alone or in combination of two or more.

C-4. Additives Additives Any appropriate additives can be used. Examples thereof include surfactants, ultraviolet absorbers, antioxidants, thickeners, and the like. Additives may be used alone or in combination of two or more. These additives may be used in any suitable amount.

C-5. Preparation method of organic solvent solution The above-mentioned organic solvent solution can be prepared by any appropriate method. For example, it can be prepared by mixing a thermoplastic cycloolefin resin, a boric acid compound, and any appropriate additives as needed in any appropriate organic solvent.

C-6. Formation method of protective layer The above protective layer can be formed by any appropriate method. For example, it can be formed by coating an organic solvent solution containing a thermoplastic cycloolefin resin, a boric acid compound, and any appropriate additives, and curing it. In one embodiment, relative to 100 parts by weight of the organic solvent, the concentration of the thermoplastic cycloolefin-based resin in the organic solvent solution is preferably 3 parts by weight to 20 parts by weight. If it is the said resin concentration, the uniform coating film adhered to a polarizer can be formed.

The organic solvent solution can be coated on any suitable substrate, and can also be coated on a polarizer. When the solution is applied to the substrate, the cured product of the coating film formed on the substrate will be transferred to the polarizer. When the solution is applied to the polarizer, the coating film is dried (cured), whereby a protective layer is directly formed on the polarizer. Preferably, the solution is coated on the polarizer, thereby directly forming a protective layer on the polarizer. According to the above structure, the adhesive layer or adhesive layer required for transfer can be omitted, so the polarizing plate can be made thinner. Any appropriate method can be adopted for the coating method of the solution. Specific examples include roll coating, spin coating, wire bar coating, dip coating, die coating, curtain coating, spray coating, and knife coating (cutting wheel coating, etc.).

By drying (curing) the coating film of the solution, a cured product of the coating film, that is, a protective layer can be formed. The drying temperature should be below 100°C, more preferably 50°C~70°C. When the drying temperature is within the above-mentioned range, adverse effects on the polarizer can be prevented. Drying time may vary depending on drying temperature. The drying time may be, for example, 1 minute to 10 minutes.

Example Hereinafter, the present invention is described in detail with examples, but the present invention is not limited by these examples.

[Manufacturing example 1] Production of polarizer laminate The base material is an amorphous isophthalic acid-copolymerized polyethylene terephthalate (IPA-copolyester) film (thickness: 100µm) with a water absorption rate of 0.75% and a Tg of 75°C. Apply corona treatment to one side of the substrate, and apply the following aqueous solution on the corona-treated surface at 25°C and dry to form a PVA-based resin layer with a thickness of 13 µm to produce a laminate; the aqueous solution is 9 The ratio of : 1 contains: polyvinyl alcohol (polymerization degree 4200, saponification degree 99.2 mole%), and acetoacetyl modified PVA (polymerization degree 1200, acetoacetyl modification degree 4.6%, saponification degree 99.0 Mole% or more, manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name: GOHSEFIMER Z200). In an oven at 130°C, the obtained laminate was uniaxially stretched at the free end to 2.4 times in the longitudinal direction (longitudinal direction) between rollers with different peripheral speeds (assisted stretching in the air). Next, the laminated body was immersed in an insoluble bath (an aqueous solution of boric acid obtained by mixing 4 parts by weight of boric acid with respect to 100 parts by weight of water) at a liquid temperature of 40° C. for 30 seconds (insoluble treatment). Next, the laminate was immersed in a dyeing solution (an aqueous solution obtained by adding 7.0 parts by weight of potassium iodide and 1.0 parts by weight of solid iodine to 100 parts by weight of water) at 30°C so that the transmittance of the obtained polarizer became 42% or more. , to perform dyeing (dyeing treatment). Then, it was immersed in a cross-linking bath (a boric acid aqueous solution obtained by mixing 3 parts by weight of potassium iodide with respect to 100 parts by weight of water and 5 parts by weight of boric acid with respect to 100 parts by weight of water) at a liquid temperature of 40°C for 35 seconds (cross-linking treatment). ). Then, while the laminate was immersed in a boric acid aqueous solution (boric acid concentration: 4.0% by weight) at a liquid temperature of 70°C, it was uniaxially stretched in the longitudinal direction (longitudinal direction) between rolls with different peripheral speeds so that the total stretching ratio Up to 5.5 times (extended in water). Thereafter, the laminate was immersed in a cleaning bath (an aqueous solution obtained by mixing 4 parts by weight of potassium iodide with respect to 100 parts by weight of water) at a liquid temperature of 20° C. for 3 seconds (washing treatment). Next, it was dried in an oven at 60° C. for 60 seconds to obtain a laminate having a PVA-based resin layer (polarizer) with a thickness of 5 μm. On the surface of the polarizer side of the obtained laminate, the above-mentioned ultraviolet curable adhesive was applied so that the thickness after curing was 1 µm, and a (meth)acrylic resin film A (thickness 40 µm) having a lactone ring structure was applied. The corona-treated surface is attached to the coated surface to harden the ultraviolet curable adhesive. Then, the PET film was peeled off from the laminate to obtain a single-sided protective polarizer laminate (protective layer (40 µm)/adhesive layer (1 µm)/polarizer (5 µm)).

[Manufacturing example 2] Preparation of acrylic adhesive A monomer mixture containing 99 parts by weight of butyl acrylate and 1 part by weight of 4-hydroxybutyl acrylate was fed into a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas introduction tube, and a cooler. With respect to 100 parts by weight of the above-mentioned monomer mixture (solid content), 0.1 part by weight of 2,2´-azobisisobutyronitrile as a polymerization initiator was fed together with ethyl acetate, and nitrogen gas was introduced while slowly stirring. After nitrogen substitution, the liquid temperature in the flask was maintained at about 60°C, and the polymerization reaction was carried out for 7 hours. Then, ethyl acetate was added to the obtained reaction liquid to adjust the solid content concentration to 30%. In the above-mentioned manner, a solution of an acrylic polymer (base polymer) having a weight average molecular weight of 1.4 million was prepared. 0.095 parts by weight of trimethylolpropane diisocyanate stubble (manufactured by Mitsui Chemicals, trade name: TAKENATE D110N) and two 0.3 parts by weight of benzoyl peroxide, 0.2 parts by weight of organosilane (manufactured by Soken Chemical Co., Ltd., trade name: A100) as a silane coupling agent, and 0.2 parts by weight of silane coupling agent containing thiol groups (manufactured by Shin-Etsu Chemical Industry Co., Ltd., trade name : X41-1810) 0.2 weight part, and an antioxidant (BASF company make, brand name: Irganox 1010) 0.3 weight part, and the acrylic adhesive (solution) was prepared.

[Example 1] Production of Polarizing Plate 1 100 parts by weight of thermoplastic cycloolefin-based resin (manufactured by JSR Corporation, trade name: ARTON R5000, polar group: methyl carboxyl group, ammonia permeability: 2.5 µg/mL, water absorption rate: 1.2%) was mixed with 0.1 parts by weight of m-aminophenylboronic acid. Parts by weight were dissolved in 10 parts by weight of an organic solvent (cyclopentyl methyl ether) to obtain an organic solvent solution. The obtained organic solvent solution was coated on the surface of the polarizer of the polarizer laminate using a wire bar to form a coating film. Next, the coating film was heated at 60° C. for 3 minutes to form a protective layer (thickness 1 μm) made of a cured product of the coating film, thereby obtaining a polarizing plate.

[Example 2] Production of Polarizing Plate 2 A polarizing plate 2 was obtained in the same manner as in Example 1, except that 0.6 parts by weight of aminophenylboronic acid was used to prepare an organic solvent solution.

[Example 3] Production of Polarizing Plate 3 A polarizing plate 3 was obtained in the same manner as in Example 1, except that 1 part by weight of aminophenylboronic acid was used to prepare an organic solvent solution.

[Example 4] Production of Polarizing Plate 4 A polarizing plate 4 was obtained in the same manner as in Example 1 except that 10 parts by weight of aminophenylboronic acid was used to prepare an organic solvent solution.

[Example 5] Production of Polarizing Plate 5 In addition to using ARTON RH4900 (manufactured by JSR Corporation) (polar group: methyl ester group, ammonia permeability: 2.3µg/mL, water absorption rate: 1.1%) instead of ARTON R5000 (manufactured by JSR Corporation) as a thermoplastic cycloolefin-based resin to prepare an organic Except for the solvent solution, a polarizing plate 5 was obtained in the same manner as in Example 1.

[Example 6] Production of Polarizing Plate 6 A polarizing plate 6 was obtained in the same manner as in Example 5, except that 0.6 parts by weight of aminophenylboronic acid was used to prepare an organic solvent solution.

[Example 7] Production of Polarizing Plate 7 A polarizing plate 7 was obtained in the same manner as in Example 5, except that 1 part by weight of aminophenylboronic acid was used to prepare an organic solvent solution.

[Embodiment 8] Production of Polarizing Plate 8 A polarizing plate 8 was obtained in the same manner as in Example 5, except that 10 parts by weight of aminophenylboronic acid was used to prepare an organic solvent solution.

(Comparative Example 1) Production of Polarizing Plate C1 Polarizing plate C1 was obtained in the same manner as in Example 1 except that m-aminophenylboronic acid was not added.

(Comparative Example 2) Production of Polarizing Plate C2 Polarizing plate C2 was obtained in the same manner as in Example 5 except that m-aminophenylboronic acid was not added.

(Comparative example 3) Production of polarizing plate C3 100 parts by weight of mixed epoxy resin (manufactured by Mitsubishi Chemical Co., trade name: jER (registered trademark) YX6954BH30, weight average molecular weight: 36000, ammonia permeability: 2.9 µg/mL, water absorption rate: 1.7%) and m-aminobenzene 0.45 parts by weight of boronic acid was used to prepare a resin composition for polarizer protection. The obtained resin composition for polarizer protection was coated on the polarizer-side surface of the polarizer laminate to form a protective layer so that the thickness after drying became 0.4 µm, and a polarizer C3 was obtained.

(Comparative Example 4) Production of polarizing plate C4 A polarizing plate C4 was obtained in the same manner as in Example 1 except that no protective layer was formed.

(Comparative Example 5) Production of polarizing plate C5 A cycloolefin-based resin film with a thickness of 13 µm (trade name: ZeonorFilm ZF14, manufactured by ZEON Corporation, Japan) was used as a protective layer, and an acrylic adhesive (composition: hydroxyethylacrylamide (manufactured by KJ Chemicals Corporation) 12.5 parts by weight, LIGHT ACRYLATE 1.9ND-A (manufactured by Kyoeisha Chemical Co., Ltd.) 36 parts by weight, LIGHT ACRYLATE HPP-A (manufactured by Kyoeisha Chemical Co., Ltd.) 12.5 parts by weight, ARONIX M-5700 (manufactured by Toagosei) 221 parts by weight, diethylpropylene Amide (manufactured by KJ Chemicals Corporation) 6 parts by weight, 4-vinylphenylboronic acid (manufactured by Tokyo Chemical Industry Co., Ltd.) 1 part by weight) was obtained in the same manner as in Example 1 except that the protective layer was laminated on the polarizer. Polarizer C5.

[Evaluate] (Manufacture of polarizing plate with adhesive layer) Using a spray coating machine, the acrylic adhesive composition obtained in Production Example 2 was uniformly coated on the surface of the polyethylene terephthalate film (separator) treated with a silicone release agent, Then, it was dried in an air-circulating constant temperature oven at 155° C. for 2 minutes, and an adhesive layer with a thickness of 20 μm was formed on the surface of the separator. Next, this adhesive layer was transferred to the surface side of the polarizer protective layer (cured layer of the coating film) of the polarizing plate obtained in Examples or Comparative Examples to obtain a polarizing plate with an adhesive layer. Regarding Comparative Example 4, a polarizing plate with an adhesive layer was produced by transferring an adhesive layer on the surface of a polarizer. The following evaluation was performed using the obtained polarizing plate with an adhesive layer attached. In addition, until the evaluation, it was preserved in the state which laminated|stacked the separator on the adhesive layer. List the results in Table 1.

1. PVA Adhesion Adhesion (100 grid peel test) The polarizing plates obtained in the respective examples and comparative examples were cut into a size of 50 mm×150 mm, and used as evaluation samples. Use the NT cutter and the jig for adhesion test to draw a 10×10 cross-cut cut on the central part of the protective layer side of the evaluation sample. The scarring angle was set at 35°±10°. Next, apply SEKISUI tape (No.252, 24mm wide) so as to cover the entire incision, and use a spatula for crimping to thoroughly rub and crimp the portion where the tape is applied back and forth 10 times. After that, peel off the tape at high speed in a 45° direction by hand. Repeat the sticking and peeling of the tape twice, and check whether there is peeling with the naked eye. After rounding off the number of objects, 40 or less peeled objects were evaluated as good, 41 or more and less than 50 objects were evaluated as acceptable, and 50 or more objects were evaluated as unfavorable.

2. Faded ends Cut the above-mentioned polarizing plate with adhesive layer (protective film/adhesive/polarizer/protective layer/adhesive/separator) into a square of 50mm×50mm. Then, the separator is peeled off and pasted on the non-alkali glass through the adhesive layer. Then, place it for 170 hours under the conditions of temperature 65 degrees and humidity 90%. Thereafter, the four corners of the sample were confirmed with an optical microscope (manufactured by Olympus, product name: MX61L). Measured in the MD direction and the TD direction, respectively, and calculated the average value.

3. Artificial sweat test Cut the above-mentioned polarizing plate with adhesive layer (protective film/adhesive/polarizer/protective layer/adhesive/separator) into a square of 50mm×50mm. Then, the separator is peeled off and pasted on the non-alkali glass through the adhesive layer. Next, transfer the adhesive to the side of the protective film, and then attach it to the alkali-free glass (alkali-free glass/adhesive/protective film/adhesive/polarizer/protective layer/adhesive/alkali-free glass). Wrap the polarizing plate sandwiched by the above-mentioned non-alkali glass with non-woven fabric soaked in 1mL of artificial sweat, put it into a plastic bag and seal it, and then place it at a temperature of 55°C and a humidity of 90% for 48 hours. Thereafter, the four corners of the sample were confirmed with an optical microscope (manufactured by Olympus, product name: MX61L). Measured in the MD direction and TD direction, respectively, and determine the average value. In addition, the artificial sweat system uses the following: after dissolving 2.5g of sodium chloride, 19g of ammonium chloride, 0.63g of urea, 1.88g of lactic acid, and 0.32g of acetic acid in 125g of pure water, add sodium hydroxide, and use a pH meter (pH Meter HORIBA portable pH ORP meter D-72) to adjust the pH to 9.5.

[Table 1]

Regarding the polarizing plates obtained in Examples 1 to 8, they prevented discoloration from the end of the polarizer even when the thickness of the protective layer was thin. In addition, the adhesiveness between the polarizer and the protective layer is also excellent, and both the prevention of discoloration from the edge and the adhesiveness with the polarizer are taken into account.

Industrial availability The resin composition for protecting a polarizer of the present invention can provide a polarizing plate having excellent adhesion to a polarizer and preventing discoloration of the end portion even if it is thin. The polarizing plate of the present invention can be widely used on LCD panels of LCD TVs, LCD monitors, mobile phones, digital cameras, video cameras, handheld game consoles, car navigation, photocopiers, printers, fax machines, clocks, microwave ovens, etc. .

10: Polarizer 20: protective layer 100: polarizer

Fig. 1 is a schematic cross-sectional view of a polarizing plate according to an embodiment of the present invention.

10: Polarizer

20: protective layer

100: polarizer

Claims (8)

A polarizing plate, comprising a polarizer and a protective layer on at least one side of the polarizer; The protective layer is composed of cured product of coating film in organic solvent solution, and the organic solvent solution includes thermoplastic cycloolefin resin and boric acid compound. The polarizing plate according to claim 1, wherein in the organic solvent solution, the content of the boric acid compound is not less than 1 part by weight and not more than 10 parts by weight relative to 100 parts by weight of the thermoplastic cycloolefin resin. The polarizing plate as in claim 1 or 2, wherein the aforementioned boronic acid compound is a compound having a substituent and a boronic acid group in the molecule, and the substituent is selected from the group consisting of -NH ₂ , -NHR and -NRR´(R and R ´ represents a methyl group or an ethyl group, and R and R´ may be the same or different) at least one of the group consisting of. The polarizing plate according to any one of Claims 1 to 3, wherein the aforementioned boric acid compound is a compound represented by the following formula: [Chemical Formula 1]

(In the formula, A represents NH ₂ , -NHR and -NRR´, R ¹ represents an aromatic ring, aliphatic ring, or a straight chain with 1 to 10 carbons that is unsubstituted, or substituted by methyl or ethyl or a branched hydrocarbon; A is bonded to R by ^a single bond or a carbonyl group; R and R' are as described above). The polarizing plate according to claim 4, wherein the aforementioned R ¹ is an aromatic ring that is unsubstituted or substituted by methyl or ethyl. The polarizing plate according to any one of claims 1 to 5, wherein the thermoplastic cycloolefin-based resin is a cycloolefin-based resin having a polar skeleton. The polarizing plate according to any one of claims 1 to 6, wherein the thickness of the protective layer is 0.3 µm to 3 µm. The polarizing plate according to any one of claims 1 to 7, wherein the thickness of the polarizer is 8 μm or less.

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