Method for manufacturing polarizers

Abstract

The present invention provides a method for manufacturing polarizers that exhibit excellent heat resistance at high temperatures of 110°C or higher. [Solution] The present invention relates to a method for manufacturing a polarizer, comprising the steps of swelling, dyeing, crosslinking, complementary coloring, washing, and drying a polarizer-forming film, wherein between the washing and drying steps, 0.16 to 0.72 J / cm² per unit area of ​​the polarizer-forming film is applied. 2 The present invention relates to a method for manufacturing a polarizer, which includes an infrared irradiation step in which energy is applied. According to the manufacturing method of the present invention, a highly heat-resistant polarizer can be manufactured at high temperatures of 110°C or higher with minimal hue change before and after heat resistance.

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a polarizer, and more specifically, to a method for manufacturing a polarizer that exhibits excellent heat resistance at high temperatures of 110°C or higher. [Background technology]

[0002] Polarizing plates used in liquid crystal display devices and the like are generally formed by attaching a protective film to one or both sides of a polarizer. The polarizer is manufactured by a process that includes uniaxial stretching of a polyvinyl alcohol-based (PVA) resin film, dyeing the polyvinyl alcohol-based resin film with a dichroic dye and adsorbing the dichroic dye, treating the polyvinyl alcohol-based resin film on which the dichroic dye has been adsorbed with a boric acid aqueous solution to crosslink it, and washing it with water.

[0003] In the aforementioned dyeing process, polarizers using iodine as the dichroic dye are called iodine-based polarizers, and polarizers using dichroic dyes are called dye-based polarizers. Of these, iodine-based polarizers are widely used because they exhibit higher transmittance and higher polarization (higher contrast) compared to dye-based polarizers.

[0004] However, while iodine-based polarizers have superior optical properties compared to dye-based polarizers, they have lower optical durability. For example, if an iodine-based polarizer or a polarizing plate containing such a polarizer is left under dry heat, problems such as decreased transmittance and discoloration can occur.

[0005] In recent years, with the expansion of liquid crystal display applications and advancements in related technologies, interest in automotive displays has been growing. However, polarizing plates used in automotive displays require a higher heat resistance temperature than those used in conventional TVs and mobile devices.

[0006] Korean Published Patent No. 2019-0004228 discloses a method for increasing the heat resistance of a polarizer by irradiating a polyvinyl alcohol-based resin film that has undergone a crosslinking process with electromagnetic waves. However, polarizers manufactured by this method still exhibit significant hue changes before and after heat resistance at temperatures above 110°C, and there has been a need for the development of polarizers with superior high-temperature heat resistance. [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] One objective of the present invention is to provide a method for manufacturing polarizers that exhibit excellent heat resistance at high temperatures of 110°C or higher.

[0008] Another object of the present invention is to provide a polarizer manufactured by the above manufacturing method.

[0009] Another object of the present invention is to provide a polarizing plate in which a protective film is laminated on at least one side of the polarizer. [Means for solving the problem]

[0010] On the other hand, the present invention relates to a method for manufacturing a polarizer, comprising the steps of swelling, dyeing, crosslinking, complementary coloring, washing, and drying a polarizer-forming film, wherein, during the washing and drying steps, 0.16 to 0.72 J / cm² per unit area of ​​the polarizer-forming film is applied. 2 The present invention provides a method for manufacturing a polarizer, which includes an infrared irradiation step in which energy is added.

[0011] In one embodiment of the present invention, the infrared light may have a wavelength of 1 to 5 μm.

[0012] In one embodiment of the present invention, the irradiation time of the infrared light may be 0.1 to 5 minutes.

[0013] In one embodiment of the present invention, the polarizer-forming film may be a polyvinyl alcohol-based film.

[0014] On the other hand, the present invention provides a polarizer manufactured by the manufacturing method.

[0015] On the other hand, the present invention provides a polarizing plate in which a protective film is laminated on at least one side of the polarizer.

[0016] On the other hand, the present invention provides an in-vehicle display including the polarizing plate.

[0017] On the other hand, the present invention provides a smart window including the polarizing plate.

Effect of the Invention

[0018] According to the manufacturing method of the present invention, even after being left at a high temperature of 110 °C or higher for a long time, there is little change in hue, and a polarizer that can be effectively used for an in-vehicle display or a smart window can be manufactured.

Embodiments for Carrying out the Invention

[0019] Hereinafter, the present invention will be described in more detail.

[0020] One embodiment of the present invention is a method for manufacturing a polarizer including steps of swelling, dyeing, crosslinking, complementary coloring, washing, and drying a film for forming a polarizer, and between the washing step and the drying step, infrared irradiation for applying energy of 0.16 to 0.72 J / cm per unit area of the film for forming a polarizer. 2 The present invention relates to a method for manufacturing a polarizer including an infrared irradiation step.

[0021] In the method for manufacturing a polarizer according to the present invention, by including the infrared irradiation step, the high-temperature heat resistance of the manufactured polarizer can be improved, and in particular, a high heat-resistant polarizer with little change in hue before and after heat resistance at a high temperature of 110 °C or higher can be manufactured.

[0022] The polarizer-forming film is not particularly limited in type as long as it is a film that can be dyed with a dichroic substance, i.e., iodine. Examples include polyvinyl alcohol-based films, partially saponified polyvinyl alcohol-based films; hydrophilic polymer films such as polyethylene terephthalate films, ethylene-vinyl acetate copolymer films, ethylene-vinyl alcohol copolymer films, cellulose films, and partially saponified versions thereof; or polyene-oriented films such as dehydrated polyvinyl alcohol-based films and dehydrochlorinated polyvinyl chloride films. Of these, polyvinyl alcohol-based films are preferred because they not only have an excellent effect in enhancing the uniformity of polarization within the plane, but also have excellent dyeing affinity for iodine.

[0023] Polyvinyl alcohol-based films typically have a degree of polymerization of 500 to 10,000, preferably 1,000 to 6,000, and more preferably 1,400 to 4,000. In the case of saponified polyvinyl alcohol-based films, a degree of saponification of 95.0 mol% or more, more preferably 99.0 mol% or more, and even more preferably 99.9 mol% or more is used, from the perspective of solubility.

[0024] The thickness of the polarizer is not particularly limited, but is, for example, in the range of 5 to 40 μm, preferably in the range of 10 to 30 μm, and more preferably in the range of 15 to 25 μm.

[0025] In a method for manufacturing a polarizer according to one embodiment of the present invention, a polarizer manufactured through a swelling step, a dyeing step, a crosslinking step, and a complementary color step is washed, irradiated with infrared light, and then dried to produce a polarizer.

[0026] The swelling step is a step in which, before dyeing the unstretched polarizer-forming film, it is immersed in a swelling tank filled with a swelling aqueous solution to remove impurities such as dust and blocking inhibitors accumulated on the surface of the polarizer-forming film, thereby swelling the polarizer-forming film to improve stretching efficiency and prevent dyeing non-uniformity, and thus improving the physical properties of the polarizer.

[0027] For the swelling aqueous solution, water (pure water, deionized water) can usually be used alone. Adding a small amount of glycerin or potassium iodide to this solution can improve both the swelling of the polarizer-forming film and its processability. Preferably, the glycerin content is 5% by weight or less and the potassium iodide content is 10% by weight or less per 100% by weight of the swelling aqueous solution.

[0028] The temperature of the swelling bath is preferably 20 to 45°C, and more preferably 25 to 40°C. The duration of the swelling step (immersion time in the swelling bath) is preferably 180 seconds or less, and more preferably 120 seconds or less. When the immersion time is within the above range, it is possible to suppress excessive swelling and saturation, prevent breakage due to softening of the polarizer-forming film, and improve the degree of polarization by ensuring uniform adsorption of iodine during the dyeing stage.

[0029] The stretching step may be carried out together with the swelling step, and in this case, the stretching ratio is preferably about 1.1 to 3.5 times.

[0030] The swelling step may be omitted, or swelling may be performed simultaneously with the staining step.

[0031] The staining step involves immersing the polarizer-forming film in a staining tank filled with an aqueous staining solution containing iodine, thereby adsorbing iodine onto the polarizer-forming film.

[0032] The aqueous solution for staining may contain water, a water-soluble organic solvent, or a mixture thereof, and iodine.

[0033] The iodine content is preferably 0.4 to 400 mmol / L, more preferably 0.8 to 275 mmol / L, and even more preferably 1 to 200 mmol / L.

[0034] To further improve dyeing efficiency, iodides may be added as solubilizers. Potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and titanium iodide may be used individually or in combination of two or more. Of these, potassium iodide is preferred due to its high solubility in water. The iodide content is preferably 0.01 to 10% by weight, and more preferably 0.1 to 5% by weight, based on 100% by weight of the dyeing aqueous solution.

[0035] The temperature of the staining bath is preferably 5 to 42°C, and more preferably 10 to 35°C. The immersion time of the polarizer-forming film in the staining bath is not particularly limited, but is preferably 1 to 20 minutes, more preferably 2 to 10 minutes.

[0036] The stretching step may be performed together with the dyeing step, in which case the cumulative stretch ratio is preferably 1.1 to 4.0 times. In this specification, "cumulative stretch ratio" refers to the product of the stretch ratios at each step.

[0037] The crosslinking step involves immersing the dyed polarizer-forming film in a crosslinking aqueous solution to fix the adsorbed iodine molecules, so that the dyeability due to physically adsorbed iodine molecules does not decrease due to the external environment. Dichroic dyes do not often leach in humid environments, but iodine molecules often dissolve or sublimate depending on the environment if the crosslinking reaction is unstable, so a sufficient crosslinking reaction is required.

[0038] The crosslinking aqueous solution contains water as a solvent, boron compounds such as boric acid and sodium borate, iodide, and metal nitrates, and may further contain organic solvents that are mutually soluble with water.

[0039] Boron compounds play a role in improving handling by forming short crosslink bonds, thereby imparting rigidity and suppressing wrinkle formation during the process, as well as in forming iodine orientation.

[0040] The content of the boron compound is preferably 1 to 10% by weight, and more preferably 2 to 6% by weight, based on 100% by weight of the crosslinking aqueous solution. If the content is less than 1% by weight, the crosslinking effect of the boron compound is reduced, making it difficult to impart rigidity. If it exceeds 10% by weight, the crosslinking reaction of the inorganic crosslinking agent is excessively activated, making it difficult for the crosslinking reaction of the organic crosslinking agent to proceed effectively.

[0041] Iodide is used to ensure uniformity of polarization within the polarizer surface and to prevent the desorption of dyed iodine. The iodide may be the same as that used in the dyeing stage, and its content may be 0.05 to 15% by weight, preferably 0.5 to 11% by weight, based on 100% by weight of the crosslinking aqueous solution. If the content is less than 0.05% by weight, iodide ions will escape from the film, increasing the transmittance and changing the hue value of the polarizer, requiring an additional step to adjust this. If it exceeds 15% by weight, iodide ions in the aqueous solution will penetrate the film, causing a decrease in transmittance.

[0042] Metallic nitrates are used to improve the heat resistance of polarizers.

[0043] The aforementioned metal nitrate may be a nitrate of a metal selected from the group consisting of Li, Na, K, Rb, Cs, Ag, Mg, Ca, Sr, Ba, Cu, Zn, Fe, Co, Ni, Ru, Rh, Pd, Zr, Pt, Al, Ga, In, Ti, La, Ce, Eu, Gd, Y, Nd, Sm, Pr, Tm, Er, Sn, Zr, V, Cr, Mo, and Mn. From the viewpoint of high-temperature durability, a nitrate of a metal selected from the group consisting of Zn, Cu, Al, Mg, and Zr is preferred, and zinc nitrate is more preferred.

[0044] The aforementioned metal nitrate may be present in an amount of 0.1 to 10% by weight, preferably 0.5 to 7.0% by weight, based on 100% by weight of the crosslinking aqueous solution. If the content is less than 0.1% by weight, the effect of the metal nitrate may be insufficient, and if it exceeds 10% by weight, excessive chemical bonding between the metal salt and polyvinyl alcohol may cause fracture problems and reduce production efficiency.

[0045] The temperature of the crosslinking tank is 20 to 70°C, and the immersion time of the polarizer-forming film in the crosslinking tank may be 1 second to 15 minutes, and preferably 5 seconds to 10 minutes.

[0046] The stretching stage may be carried out together with the crosslinking stage, and in this case, it is preferable that the stretching is performed so that the total cumulative stretching ratio is 3.0 to 8.0 times.

[0047] As described above, the stretching step may be carried out together with the swelling step, the staining step, and the crosslinking step, or it may be carried out as an independent stretching step after the crosslinking step using a separate stretching tank filled with a stretching aqueous solution.

[0048] The complementary color stage is a step in which iodine molecules that were lacking in the cross-linking stage are further fixed.

[0049] The complementary aqueous solution contains a boron compound. By containing the boron compound, the complementary aqueous solution can improve crosslinking efficiency, suppress the occurrence of wrinkles during the process, and improve optical properties by forming iodine orientation.

[0050] The content of the boron compound is 0.5 to 10% by weight, preferably 1 to 5% by weight, based on 100% by weight of the complementary aqueous solution. If the content is less than 0.5% by weight, the degree of polarization may decrease, and if it exceeds 10% by weight, the shrinkage force may increase.

[0051] The boron compound may be the same one used in the crosslinking stage.

[0052] The complementary aqueous solution may contain water used as a solvent and an organic solvent that is mutually soluble with water, and may further contain a small amount of iodide to ensure uniformity of polarization within the polarizer plane and to prevent desorption of the dyed iodine.

[0053] The iodide content may be 1 to 15% by weight, preferably 5 to 11% by weight, based on 100% by weight of the complementary aqueous solution. If the content is less than 1% by weight, the degree of polarization will decrease, and if it exceeds 15% by weight, the heat resistance will decrease, and a reddening phenomenon may occur when exposed to high temperatures for a long time.

[0054] The iodide used may be the same one used in the staining stage.

[0055] The temperature of the complementary color bath is not particularly limited, but may be, for example, 20 to 70°C, and preferably 40 to 60°C.

[0056] The time for immersing the polarizer-forming film in the complementary color bath is not particularly limited and may be, for example, 1 second to 15 minutes, preferably 5 seconds to 10 minutes.

[0057] The stretching step may be performed together with the complementary color step, in which case the stretching ratio of the complementary color step may be 1 to 1.15 times, preferably 1.01 to 1.1 times.

[0058] The cumulative stretch ratio in the complementary color stage may be 1.5 to 7 times, preferably 1.7 to 6 times. If the cumulative stretch ratio is less than 1.5 times, the effect of increasing crosslinking efficiency may be poor, and if it exceeds 7 times, excessive stretching may cause the film to break, reducing production efficiency.

[0059] The washing stage involves immersing the polarizer-forming film, which has undergone crosslinking and stretching, in a washing tank filled with a washing solution to remove any unwanted residues, such as boric acid, that may have adhered to the polarizer-forming film in the previous stage.

[0060] The aqueous solution for rinsing may be water, or it may be water to which iodide has been further added.

[0061] The water temperature of the washing tank is preferably 10 to 60°C, and more preferably 10 to 40°C. The washing stage is usually performed for 1 to 60 seconds, preferably 3 to 30 seconds, and more preferably 5 to 20 seconds.

[0062] The aforementioned infrared irradiation step involves irradiating the washed polarizer-forming film with an infrared radiation of 0.16 to 0.72 J / cm² per unit area. 2 This is done by adding energy. The energy added by the infrared irradiation is 0.16 J / cm². 2 If it is less than 0.72 J / cm², the effect of improving high-temperature heat resistance will be poor, and also 0.72 J / cm² 2 If the temperature exceeds a certain level, the polarizer-forming film may break.

[0063] Furthermore, from the standpoint of improving high-temperature heat resistance and preventing film breakage, the wavelength of the infrared radiation may be 1 to 5 μm, and the duration of the infrared irradiation step may be 0.1 to 5 minutes.

[0064] The infrared irradiation step is preferably performed in a water rinsing tank immediately after washing the polarizer-forming film.

[0065] The drying stage involves drying the polarizer-forming film, which has been irradiated with infrared light after washing, to further improve the orientation of the dyed iodine molecules through neck-in during drying, thereby obtaining a polarizer with excellent optical properties.

[0066] Drying methods include natural drying, air drying, heat drying, far-infrared drying, microwave drying, and hot air drying. Recently, microwave drying, which activates and dries only the water in the film, has been newly adopted, although hot air drying is usually the main method used. For example, hot air drying may be performed at 20-90°C for 1-10 minutes. Furthermore, the drying temperature should be lower to prevent deterioration of the polarizer, more preferably 80°C or lower, and even more preferably 70°C or lower.

[0067] One embodiment of the present invention relates to a polarizer manufactured by the above manufacturing method.

[0068] One embodiment of the present invention relates to a polarizing plate in which a protective film is laminated on at least one side of the polarizer.

[0069] The protective film is not particularly limited as long as it is a film that is excellent in terms of transparency, mechanical strength, thermal stability, moisture shielding, isotropy, etc. Specifically, examples include films made of thermoplastic resins such as polyester resins such as polyethylene terephthalate, polyethylene isophthalate, and polybutylene terephthalate; cellulosin resins such as diacetylcellulose and triacetylcellulose; polycarbonate resins; acrylic resins such as polymethyl (meth)acrylate and polyethyl (meth)acrylate; styrene resins such as polystyrene and acrylonitrile-styrene copolymers; polyolefin resins such as polyethylene, polypropylene, polyolefins having a cyclo- or norbornene structure, and ethylene propylene copolymers; vinyl chloride resins; polyamide resins such as nylon and aromatic polyamides; imide resins; polyethersulfone resins; sulfone resins; polyetherketone resins; sulfurized polyphenylene resins; vinyl alcohol resins; vinylidene chloride resins; vinyl butyral resins; arylate resins; polyoxymethylene resins; and epoxy resins. Films made of blends of the above thermoplastic resins may also be used. Furthermore, films made of thermosetting resins such as (meth)acrylic, urethane, epoxy, or silicone, or UV-curable resins may be used. Of these, cellulose-based films or acrylic films having a surface saponified with alkali or the like are particularly preferred when considering polarization properties or durability. The protective film may also incorporate the functions of the optical layer described below.

[0070] In the present invention, the structure of the polarizer is not particularly limited, and various optical layers capable of satisfying the required optical properties may be laminated on the polarizer. For example, it may have a structure in which a protective film to protect the polarizer is laminated on at least one side of the polarizer; a structure in which a surface treatment layer such as a hard coating layer, an anti-reflective layer, an anti-adhesion layer, an anti-diffusion layer, or an anti-glare layer is laminated on at least one side of the polarizer or on the protective film; or a structure in which an aligning liquid crystal layer or another functional film that compensates for the viewing angle is laminated on at least one side of the polarizer or on the protective film. Furthermore, it may have a structure in which one or more of the following are laminated as optical layers: an optical film, a reflector, a semi-transparent plate, a phase difference plate including a wave plate (including a λ plate) such as a half-wave plate or a quarter-wave plate, a viewing angle compensation film, or a brightness enhancement film, such as in a polarization conversion device used to form various image display devices. More specifically, preferred polarizers are those with a structure in which a protective film is laminated on one side of the polarizer, wherein a reflective plate or a semi-transparent reflective plate is laminated on the laminated protective film; elliptical or circular polarizers with a phase difference plate laminated on top; wide-angle polarizers with a field-viewing angle compensation layer or field-viewing angle compensation film laminated on top; or polarizers with a brightness-enhancing film laminated on top.

[0071] Such polarizing plates can be applied not only to conventional liquid crystal displays but also to various image display devices such as electroluminescent displays, plasma displays, and field emission displays. In particular, their excellent high-temperature resistance makes them suitable for use in automotive displays or smart windows.

[0072] The smart window including the polarizing plate according to the present invention has excellent high-temperature heat resistance and can be used in the windshield, rear window, side window and sunroof window of automobiles, or in architectural glass, and can also be used for partitioning interior spaces of vehicles or buildings or for protecting privacy.

[0073] The present invention will now be described in more detail with reference to examples. It should be noted that these examples are merely for illustrative purposes, and the scope of the present invention is not limited to these examples, as will be obvious to those skilled in the art.

[0074] Example 1: Polarizer Manufacturing A transparent, unstretched polyvinyl alcohol film (VF-PS, manufactured by KURARAY) with a saponification degree of 99.9% or higher was immersed in 30°C water (deionized water) for 2 minutes to swell, and then immersed in a 30°C dyeing aqueous solution containing 3.5 mM iodine and 2% by weight of potassium iodide for 4 minutes to stain. During this process, the film was stretched to a ratio of 1.3 times and 1.4 times during the swelling and dyeing stages, respectively. Next, it was crosslinked by immersing it in a 53°C crosslinking aqueous solution containing 10% by weight of potassium iodide, 3.7% by weight of boric acid, and 3% by weight of zinc nitrate for 2 minutes. During this crosslinking stage, the total cumulative stretch ratio was set to 5.8 times. Next, in the complementary color stage, it was immersed for 10 seconds in a 50°C complementary color aqueous solution containing 10% by weight of potassium iodide and 3.7% by weight of boric acid. During this complementary color stage, the total cumulative stretch ratio was set to 6 times. Afterward, immediately after washing with a 10°C aqueous solution for 20 seconds, an infrared lamp was used to apply 2.5 μm wavelength infrared light at a rate of 0.16 J / cm² per unit area. 2 The film was irradiated with this energy for 0.1 minutes. After that, the polyvinyl alcohol film, which had been washed with water and irradiated with infrared light, was dried in a 70°C oven for 4 minutes to produce a polarizer.

[0075] Example 2: Polarizer Manufacturing Infrared radiation at 0.48 J / cm² per unit area 2 The polarizer was manufactured in the same manner as in Example 1, except that it was irradiated with the specified energy.

[0076] Example 3: Polarizer Manufacturing Infrared radiation at 0.72 J / cm² per unit area 2 The polarizer was manufactured in the same manner as in Example 1, except that it was irradiated with the specified energy.

[0077] Comparative Example 1: Polarizer Manufacturing A polarizer was produced in the same manner as in Example 1, except that the washed polyvinyl alcohol film was not irradiated with infrared rays.

[0078] Comparative Example 2: Production of polarizer A polarizer was produced in the same manner as in Example 1, except that infrared rays were irradiated after the complementary color process and before washing.

[0079] Comparative Example 3: Production of polarizer A polarizer was produced in the same manner as in Example 2, except that infrared rays were irradiated after the complementary color process and before washing.

[0080] Comparative Example 4: Production of polarizer A polarizer was produced in the same manner as in Example 1, except that it was irradiated with infrared rays at an energy of 0.04 J / cm per unit area. 2

[0081] Comparative Example 5: Production of polarizer A polarizer was produced in the same manner as in Example 1, except that it was irradiated with infrared rays at an energy of 0.88 J / cm per unit area. 2

[0082] Comparative Example 6: Production of polarizer A polarizer was produced in the same manner as in Example 3, except that the washed and infrared-irradiated polyvinyl alcohol film was not dried separately.

[0083] Experimental Example 1: Measurement of high heat resistance A polarizing plate was produced by laminating a triacetyl cellulose (TAC) film on both sides of the polarizer produced in the above Examples and Comparative Examples. The physical properties of the produced polarizing plate were measured by the following method, and the results are shown in Table 1 below.

[0084] (1) Single body color phase L * 、a * 、b * Measurement After cutting the polarizing plate to a size of 4cm x 4cm, the single hue L1 was determined using an ultraviolet-visible light spectrometer (V-7100, manufactured by JASCO Corporation). * a1 * , b1 * After measuring the values, the polarizing plate whose hue was measured was placed in a 110°C oven for 500 hours and then removed from the oven to obtain the L2 single hue value. * a2 * , b2 * The value was measured.

[0085] (2) Measurement of hue change before and after heat resistance Single-element hue L measured before and after heat resistance * a * , b * The values ​​were substituted into the following mathematical formula 1 to measure the change in hue before and after heat resistance.

number

[0086] [Table 1]

[0087] As shown in Table 1 above, the washing and drying stages involve a flow rate of 0.16 to 0.72 J / cm² per unit area. 2 Polarizing plates manufactured using polarizers from Examples 1-3, which were produced by irradiating them with infrared light to which the energy of the polarizer was added, were confirmed to show little change in hue before and after heating at 110°C.

[0088] In contrast, without irradiating with infrared light, or by irradiating with infrared light before the washing stage, or between the washing and drying stages, 0.16 J / cm² per unit area is used. 2 Polarizing plates manufactured using the polarizers of Comparative Examples 1-4 and 6, which were produced by irradiating them with infrared light with an energy of less than 1, or without a drying step after infrared irradiation, were found to exhibit a large change in hue before and after heat resistance at 110°C. Furthermore, 0.72 J / cm² per unit area was observed during the washing and drying stages. 2The polarizer of Comparative Example 5, which was manufactured by irradiating it with infrared light exceeding a certain energy level, fracture occurred during the manufacturing process, making it impossible to measure the hue change of the polarizer.

[0089] Although specific parts of the present invention have been described in detail above, it is clear to any person with ordinary skill in the art to which the present invention belongs that such specific descriptions are merely preferred examples and do not limit the scope of the present invention. A person with ordinary skill in the art to which the present invention belongs will be able to make various applications and modifications within the scope of the present invention based on the above content.

[0090] Therefore, the substantial scope of the present invention can be defined by the claims and their equivalents.

Claims

1. A method for manufacturing a polarizer, comprising the steps of swelling, dyeing, crosslinking, complementary coloring, washing and drying a polarizer-forming film, During the washing and drying steps, 0.16 to 0.72 J / cm² per unit area of ​​the polarizer-forming film is applied. ２ A method for manufacturing a polarizer, comprising an infrared irradiation step in which energy is applied.

2. The method for manufacturing a polarizer according to claim 1, wherein the infrared radiation has a wavelength of 1 to 5 μm.

3. The method for manufacturing a polarizer according to claim 1, wherein the irradiation time of the infrared light is 0.1 to 5 minutes.

4. The method for producing a polarizer according to claim 1, wherein the polarizer-forming film is a polyvinyl alcohol-based film.

5. A polarizer manufactured by the manufacturing method described in any one of claims 1 to 4.

6. A polarizing plate having a protective film laminated on at least one side of the polarizer according to claim 5.

7. An in-vehicle display comprising the polarizing plate described in claim 6.

8. A smart window comprising the polarizing plate described in claim 6.

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