Classifications

• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B5/00—Optical elements other than lenses
  • G02B5/30—Polarising elements
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
  • H05B33/00—Electroluminescent light sources
  • H05B33/02—Details

Definitions

• the present invention relates to a method for manufacturing a polarizer.
• a polarizing plate generally includes a polarizer in which an iodine compound or a dichroic polarizing material is adsorbed and oriented on a polyvinyl alcohol (PVA) film, and a polarizer protective film is laminated on one surface of the polarizer.
• PVA polyvinyl alcohol
• the other surface of the polarizer has a multilayer structure in which a polarizer protective film, an adhesive layer bonded to a liquid crystal cell, and a release film are sequentially laminated.
• a polarizer constituting a polarizing plate is applied to an image display device, and is required to have a high transmittance and polarization degree in order to provide an image excellent in color reproducibility.
• a polarizer is manufactured using a method of modifying the polyvinyl alcohol film itself or using a non-sublimation dichroic dye instead of a sublimable iodine-based polarizing element. Yes.
• high transmittance can be realized by using a thin polyvinyl alcohol film.
• the film is easily cut during the manufacturing process (especially, dyeing or crosslinking step), and polarized light. There was a problem that the optical characteristics such as the degree of remarkably deteriorated.
• Korean Patent No. 10-2009-0070085 discloses a method for manufacturing a polarizer, but it cannot provide an alternative to the above problem.
• the present invention provides a method for producing a polarizer capable of producing a polarizer having excellent optical characteristics, reducing the occurrence of cutting of the polarizer-forming film during the production process, and improving productivity.
• the purpose is to do.
• the dry stretching step is performed at 120 to 140 ° C.
• the stress relaxation step is performed by immersing in a stress relaxation aqueous solution at 20 to 50 ° C.
• the dyeing step is performed by immersing in an aqueous dyeing solution at 5 to 42 ° C.
• the dyeing step is performed for 60 seconds to 200 seconds.
• the crosslinking step is performed by immersing in a crosslinking aqueous solution at 20 to 90 ° C.
• the method for producing a polarizer further comprising a water washing and drying step after the crosslinking step.
• the film is cut during the production process by performing a dry stretching process before entering the wet process and setting the crystallinity of the film within a specific range during the dry process. Excellent productivity.
• the method for producing a polarizer of the present invention can produce a polarizer having excellent optical characteristics.
• the present invention relates to a method for producing a polarizer, and more specifically, during a production process performed in a step of dry stretching, stress relaxation, dyeing and crosslinking of a polarizer forming film, the dry stretching step is performed with a crystallinity of 0. .6 to 0.8 is satisfied, so that even if a thin film is used, the film is not cut in the dyeing or crosslinking step, so that the productivity of the polarizer can be improved and the optical characteristics are excellent.
• the present invention relates to a method capable of manufacturing a polarizer.
• a polarizer is manufactured by appropriately adjusting the material and process conditions of a film for forming a polarizer in order to realize optical characteristics required by an applied display.
• a polarizer having a high transmittance may be required.
• a thin film for forming a polarizer was used. In this case, the film is easily cut during the manufacturing process (especially dyeing or crosslinking step).
• optical characteristics such as the degree of polarization are remarkably deteriorated.
• the present invention performs a dry stretching process before entering the wet process, and manufactures a film having an appropriate crystallinity through the dry stretching step, so that the above-described problem does not occur even if a thin film is used.
• the production method was derived.
• the method for producing a polarizer of the present invention is carried out in steps of dry stretching, stress relaxation, dyeing and crosslinking of a polarizer forming film.
• the manufacturing method of the polarizer by this invention performs the process of dry-stretching the film for polarizer formation, before entering a wet process.
• the film is stretched so that the degree of crystallinity satisfies 0.6 to 0.8, so that the strength of the film is improved, and a wet process (especially described later) even if manufactured into a thin film.
• Dyeing and cross-linking steps can reduce the incidence of film cutting, thereby improving the productivity of the polarizer.
• the degree of polarization is unlikely to decrease.
• crystallinity means the ratio of the polymer crystalline portion and the amorphous portion of the polymer constituting the film to the crystalline portion of the polarizer-forming film that has undergone the dry stretching process.
• the crystallinity can be measured through a method generally known in the art.
• the film at the end of the dry stretching when the degree of crystallinity of the film at the end of the dry stretching is less than 0.6, the film is easily crystallized at the end of the dry stretching because cutting easily occurs in the dyeing and cross-linking steps described later. If the degree exceeds 0.8, the optical properties, particularly the degree of polarization, may be reduced.
• the crystallinity of the film may be preferably 0.61 to 0.75. In this case, superior optical characteristics can be realized without the above-described problems.
• the crystallinity can be realized by a method known in the art. For example, if the stretch ratio in the MD direction is increased, the crystallinity after stretching tends to increase. Can also be realized by adjusting the temperature of the film, the material of the film for forming a polarizer, the type and content of additives (such as a plasticizer), the moisture content of the film, etc. to an appropriate range, It is not limited to this.
• the film for forming a polarizer according to the present invention can be easily subjected to the above-described dry stretching process of the present invention, and the type thereof is particularly a film that can be dyed with a dichroic material, that is, iodine.
• a dichroic material that is, iodine.
• polyvinyl alcohol film partially saponified polyvinyl alcohol film; polyethylene terephthalate film, ethylene-vinyl acetate copolymer film, ethylene-vinyl alcohol copolymer film, cellulose film, these partially saponified And a hydrophilic polymer film such as a coated film; or a polyene oriented film such as a dehydrated polyvinyl alcohol film and a dehydrochlorinated polyvinyl alcohol film.
• a polyvinyl alcohol film is preferable because it not only has an excellent effect of enhancing the uniformity of the degree of polarization in the plane, but also has an excellent dyeing affinity for iodine.
• the thickness of the polarizer-forming film is not particularly limited, but may be, for example, 10 to 30 ⁇ m. If the above range is satisfied, excellent transmittance can be realized, and the manufacturing process of the present invention can be used. It is suitable because sufficient strength is secured and the film is not cut in the wet process described later.
• the stretch ratio of the film is not particularly limited, but may be about 4 to 5 times, preferably 4.0 to 4.8 times.
• the above range is satisfied, it is suitable for realizing the appropriate crystallinity as described above, and when it exceeds about 5 times, it is difficult to realize the required optical characteristics due to a decrease in the dyeability of iodine in the dyeing process. .
• the performance temperature of the dry stretching step of the present invention is not particularly limited, but may be, for example, 120 to 140 ° C, preferably 125 to 135 ° C. If the above range is satisfied, it is suitable for realizing the above-mentioned appropriate crystallinity, and if it exceeds 140 ° C., the crystallinity becomes excessively high, and the dyeability of iodine decreases in the dyeing process. It is difficult to realize the optical characteristics.
• the execution time of the dry stretching step of the present invention is not particularly limited, but can be appropriately performed within the range reaching the above-described appropriate crystallinity, for example, 1 second to 1 minute, preferably It can be performed for 5 to 30 seconds.
• the method for performing the dry stretching step of the present invention is not particularly limited.
• a method of applying tension to the film and rolling with a pressure roll, a method of applying tension to the film and bringing it into contact with the heating roll, and the inside of the heating oven Or a method of stretching while applying a tensile force while heating the film between rolls installed outside, a method of compressing and stretching by passing between two heating rolls, etc., at this time, the dry stretching step described above
• the performing temperature can be realized by adjusting the temperature of a drawing roll or an oven.
• the polarizer-forming film can be stretched simultaneously by a wet process (stress relaxation, dyeing, crosslinking process, etc.) described later, in addition to the dry stretching step.
• ⁇ Stress relaxation step> The manufacturing process of the polarizer according to the present invention performs a stress relaxation step after dry stretching.
• the film for forming a polarizer after dry stretching is immersed in a stress relaxation tank filled with an aqueous solution for stress relaxation before the dyeing process, and impurities such as dust or anti-blocking agent deposited on the film surface.
• This is a step for reducing the stress of the polarizer-forming film, improving the dyeability, preventing uneven dyeing, and improving the physical properties of the polarizer.
• water pure water, deionized water
• glycerin or potassium iodide may be added to improve the processability of the polymer film. Good.
• the content is not particularly limited, and may be, for example, 5% by weight or less and 10% by weight or less, respectively, in the total weight of the aqueous solution for stress relaxation.
• the performance temperature of the stress relaxation step (temperature of the stress relaxation aqueous solution) is not particularly limited, and may be, for example, 20 to 50 ° C., preferably 25 to 40 ° C.
• the temperature of the stress relaxation step is within the above range, the stress relaxation is appropriately performed, and the occurrence of cutting of the film can be significantly reduced.
• the execution time of the stress relaxation step is not particularly limited, and may be, for example, 40 seconds to 180 seconds or less, and preferably 90 seconds or less.
• stress relaxation bath immersion time is not particularly limited, and may be, for example, 40 seconds to 180 seconds or less, and preferably 90 seconds or less.
• the wet stretching step can be performed simultaneously with the stress relaxation step.
• the stretching ratio of the stress relaxation step may be about 0.9 to 1 times, and within the above range, without deterioration of the optical properties. Stress relaxation can be performed within an appropriate range.
• ⁇ Dyeing step> In the method for manufacturing a polarizer according to the present invention, a dyeing step is performed after the stress relaxation step.
• the dyeing step is a step of immersing the polarizer-forming film in a dyeing tank filled with a dichroic substance, for example, an aqueous dye-containing solution, and adsorbing iodine to the polarizer-forming film.
• a dichroic substance for example, an aqueous dye-containing solution, and adsorbing iodine to the polarizer-forming film.
• the aqueous dyeing solution may contain water, a water-soluble organic solvent, or a mixed solvent thereof and iodine.
• the concentration of iodine in the dyeing aqueous solution may be 0.4 to 400 mmol / L, preferably 0.8 to 275 mmol / L, more preferably 1 to 200 mmol / L in the dyeing solution. .
• the aqueous solution for dyeing may further contain iodide as a solubilizing agent for improving the dyeing efficiency.
• the type of iodide is not particularly limited.
• titanium iodide, and potassium iodide is preferred in that it has a high solubility in water. You may use these individually or in mixture of 2 or more types.
• the content of the iodide is not particularly limited, and may be, for example, 0.01 to 10% by weight, preferably 0.1 to 5% by weight, based on the total weight of the aqueous dyeing solution.
• the aqueous dyeing solution may further contain boric acid in order to increase the iodine complex content of the polarizer-forming film.
• the boric acid content is not particularly limited, and may be, for example, 0.3 to 5% by weight in the total weight of the aqueous dyeing solution. If within the ranges described above, PVA-I 3 - complex and PVA-I 5 - preferably for the content of the complex is increased, however, if it exceeds 5 wt%, so that the risk of cutting of the film is increased .
• the performance temperature of the dyeing step (temperature of the dyeing aqueous solution) is not particularly limited, but may be, for example, 5 to 42 ° C, and preferably 10 to 35 ° C.
• temperature of the dyeing step is within the above range, iodine can be effectively adsorbed on the film without cutting the film, thereby realizing excellent optical properties.
• the performance time of the dyeing step is not particularly limited, and may be, for example, 60 to 200 seconds, and preferably 80 to 150 seconds.
• time of the dyeing step is within the above range, iodine can be effectively adsorbed on the film without cutting the film, thereby realizing excellent optical properties.
• the wet stretching step can be performed simultaneously with the dyeing step.
• the stretching ratio of the dyeing step may be about 1 to 1.1 times, and excellent optical performance without cutting the film within the above range.
• the characteristics can be embodied.
• the cumulative stretch ratio in the stress relaxation step and the dyeing step is preferably 0.9 to 1.1 times.
• the cumulative stretch ratio is less than 0.9 times, the film is wrinkled and the appearance is poor. May occur, and if it exceeds 1.1 times, stretching unevenness may occur.
• ⁇ Crosslinking step> In the method for producing a polarizer according to the present invention, a crosslinking step is performed after the dyeing step.
• the dyed film for forming a polarizer is immersed in an aqueous solution for cross-linking so that the dyeability by physically adsorbed iodine molecules does not deteriorate due to the external environment.
• This is a fixing step.
• iodine which is a dichroic dye
• the polarizer-forming film is preferably stretched at a large stretch ratio in the cross-linking step in order to align iodine molecules located between the molecules and improve optical properties.
• the cross-linking step can be performed by the first cross-linking step and the second cross-linking step.
• a cross-linking aqueous solution containing a boron compound may be used, and in this case, depending on the boron compound, It is preferable because the color durability can be improved simultaneously with the improvement of the optical characteristics of the polarizer.
• the aqueous solution for crosslinking may contain water and a boron compound, and may further contain an organic solvent and iodide that can interact with water.
• Boron compounds provide short cross-linking and film rigidity, and suppress wrinkling of the film during the process, thereby improving the handleability and forming the iodine orientation.
• the concentration of the boron compound in the aqueous solution for crosslinking is not particularly limited, and may be, for example, 1 to 10% by weight based on the total weight of the aqueous solution for crosslinking.
• the optical characteristics can be realized. Moreover, when it is less than 1% by weight, the crosslinking effect may be reduced and the rigidity of the film may be lowered. When it exceeds 10% by weight, the film may be cut due to excessive crosslinking.
• the aqueous solution for crosslinking may further contain an iodide in order to prevent uniformity of the degree of polarization in the plane of the polarizer and desorption of dyed iodine.
• the iodide content in the aqueous solution for crosslinking is not particularly limited, but may be, for example, 0.05 to 15% by weight, preferably 0.5 to 11% by weight, based on the total weight of the aqueous solution for crosslinking. Good. When the above range is satisfied, it is possible to prevent the iodine ions adsorbed in the dyeing step from escaping from the film or the iodine ions contained in the cross-linking solution from penetrating into the film, thereby suppressing a change in transmittance. .
• the performance temperature of the crosslinking step (temperature of the aqueous solution for crosslinking) is not particularly limited, but may be, for example, 20 to 90 ° C, preferably 50 to 75 ° C, and the temperature of the crosslinking step is within the above range. In this case, iodine is oriented in an appropriate range without cutting the film, and excellent optical properties can be realized.
• the performance time of the crosslinking step is not particularly limited, and may be, for example, 1 second to 15 minutes, preferably 5 seconds to 10 minutes.
• time of the crosslinking step is within the above range, iodine is oriented in an appropriate range without cutting the film, and excellent optical properties can be realized.
• a wet stretching step can be performed simultaneously with the cross-linking step, in which case the stretch ratio of the cross-linking step may be about 0.99 to 1.65 times, and within the above range without iodine film cutting. Can be oriented in an appropriate range and can realize excellent optical characteristics, thereby improving the productivity of the polarizer.
• the stretch ratio of the first cross-linking step may be about 1.1 to 1.5 times
• the cumulative draw ratio of the first and second crosslinking steps may be about 1.1 to 2.5 times.
• the method for producing a polarizer of the present invention may further include a water washing step after the crosslinking step is completed.
• the water washing step is a step of immersing the film for forming a polarizer, which has been stretched and crosslinked, in a water washing tank filled with an aqueous solution for water washing, and removing unnecessary residues attached to the film for forming a polarizer in the previous step.
• the aqueous solution for washing may be water (deionized water), and iodide may be further added thereto.
• the performance temperature of the washing step (temperature of the washing aqueous solution) is not particularly limited, and may be, for example, 0 to 60 ° C, preferably 5 to 30 ° C.
• the water washing step can be omitted and can be performed each time previous steps such as the stress relaxation step, the dyeing step, and the crosslinking step are completed. Further, it may be repeated one or more times, and the number of repetitions is not particularly limited.
• the drying step is a step of drying the washed polarizer-forming film, further improving the orientation of iodine molecules dyed by neck-in by drying, and obtaining a polarizer having excellent optical characteristics.
• the drying method is not particularly limited, but natural drying, air drying, heat drying, far-infrared drying, microwave drying, hot air drying, etc. can be used. Recently, only water in the film is activated to dry. Microwave processing is newly used, and hot air processing and far infrared processing are mainly used.
• the temperature for performing the hot air drying is not particularly limited, but is preferably performed at a relatively low temperature in order to prevent the deterioration of the polarizer, and may be, for example, 20 to 105 ° C., preferably 100 ° C. or less. It is good.
• the time for performing the hot air drying is not particularly limited, and can be performed, for example, for 1 to 10 minutes.
• all of the remaining steps except the dry stretching step and the drying step among the steps described above may be performed by immersing the polarizer forming film in a thermostatic water bath. Good.
• the polarizer can be used to produce a polarizing plate having a protective film laminated on at least one surface.
• the type of the protective film is not particularly limited as long as it is a film excellent in transparency, mechanical strength, thermal stability, moisture shielding property, isotropy, etc.
• Specific examples include polyethylene terephthalate, polyethylene Polyester resins such as isophthalate and polybutylene terephthalate; Cellulosic resins such as diacetyl cellulose and triacetyl cellulose; Polycarbonate resins; Polyacrylic resins such as polymethyl (meth) acrylate and polyethyl (meth) acrylate; Polystyrene and acrylonitrile Styrene resins such as styrene copolymers; Polyolefin resins such as polyethylene, polypropylene, cyclo- or norbornene-structured polyolefins, ethylene-propylene copolymers; nylons, aromatic polyamides, etc.
• examples include oxymethylene resins; films composed of thermoplastic resins such as epoxy resins, and films composed of blends of the thermoplastic resins can also be used.
• a film made of a thermosetting resin such as (meth) acrylic, urethane, epoxy, or silicon, or an ultraviolet curable resin can be used.
• a cellulose-based film having a surface saponified with alkali or the like is particularly preferable in consideration of polarization characteristics or durability.
• the protective film may have a function of the following optical layer.
• the structure of the polarizing plate is not particularly limited, and various types of optical layers that can satisfy necessary optical characteristics may be laminated on a polarizer.
• a structure in which a protective film for protecting a polarizer is laminated on at least one surface of a polarizer; a hard coating layer, an antireflection layer, an anti-adhesion layer, a diffusion prevention layer, an antiglare layer on at least one surface of the polarizer or on the protective film A structure in which a surface treatment layer such as a layer is laminated; a structure in which an alignment liquid crystal layer for compensating a viewing angle or another functional film is laminated on at least one surface of a polarizer or a protective film Good.
• Wave plates such as optical films such as polarization conversion devices, reflectors, transflective plates, half-wave plates, or quarter-wave plates used to form various image display devices
• Such a polarizing plate is applicable not only to a normal liquid crystal display device but also to various image display devices such as an organic electroluminescence display device (OLED), a plasma display device, and a field emission display device.
• OLED organic electroluminescence display device
• plasma display device a plasma display device
• field emission display device a field emission display device
• Example 1 A transparent unstretched polyvinyl alcohol film (PE30, KURARAY) having a thickness of 30 ⁇ m and a saponification degree of 99.9% or more was stretched four times by a hot roll at 120 ° C. The crystallinity of the film was measured after stretching.
• PE30, KURARAY polyvinyl alcohol film having a thickness of 30 ⁇ m and a saponification degree of 99.9% or more was stretched four times by a hot roll at 120 ° C. The crystallinity of the film was measured after stretching.
• the dry-stretched film was immersed in 25 ° C. water (deionized water) for 1 minute and 20 seconds to relieve the stress, and then iodine 1.25 mM / L, potassium iodide 1.25 wt%, boric acid 0
• the sample was dyed by being immersed in an aqueous solution for dyeing at 30 ° C. containing 3% by weight for 2 minutes.
• the film was stretched at a stretching ratio of 0.92 times and 1.002 times in the stress relaxation and dyeing steps, respectively, so that the cumulative stretching ratio from the stress relaxation tank to the dyeing tank was 0.922.
• the film was stretched at a stretch ratio of 1.3 times while being crosslinked by being immersed in a crosslinking solution at 65 ° C. containing 10% by weight of potassium iodide and 8% by weight of boric acid for 30 seconds (first crosslinking step). After that, the film was stretched at a stretch ratio of 1.03 while being immersed in a crosslinking solution at 65 ° C. containing 10% by weight of potassium iodide and 8% by weight of boric acid for 20 seconds (second crosslinking step). .
• the total cumulative draw ratio of the stress relaxation, dyeing and crosslinking steps was 1.234 times.
• the polyvinyl alcohol film was dried in an oven at 100 ° C. for 1 minute to produce a polarizer.
• the transmittance of the produced polarizer was 43.5%.
• Example 2 to 7 A polarizer was produced in the same manner as in Example 1 except that the dry draw ratio and dry draw temperature described in Table 1 below were adjusted.
• Example 5 A polarizer was produced in the same manner as in Example 1 except that dry stretching was not performed.
• Example 8 A polarizer was produced in the same manner as in Example 1 except that the thickness of the polyvinyl alcohol film was different at 20 ⁇ m.
• Example 9 A polarizer was produced in the same manner as in Example 1 except that the stress was relaxed by immersion in water for 1 minute and 30 seconds.
• Example 10 A polarizer was produced in the same manner as in Example 1 except that the stress was relaxed by immersion in water at 40 ° C.
• Example 11 A polarizer was produced in the same manner as in Example 1 except that the stress was relaxed by immersion in water at 40 ° C. for 1 minute and 30 seconds.
• Comparative Example 6 A polarizer was produced in the same manner as in Comparative Example 1 except that the thickness of the polyvinyl alcohol film was different at 60 ⁇ m.
• the crystallinity is obtained using the following formula.
• (C crystallinity)
• a 1143 , A 1093 and A 2000 are absorbances at wave numbers 1143 , 1093 and 2000 cm ⁇ 1, respectively.
• the manufactured polarizer was cut to a size of 4 cm ⁇ 4 cm, and then the transmittance was measured using an ultraviolet-visible light spectrometer (V-7100, manufactured by JASCO). At this time, the degree of polarization is defined by the following formula (1).
• Polarization degree (P) [(T 1 ⁇ T 2 ) / (T 1 + T 2 )] 1/2 (1)
• T 1 is a parallel transmittance obtained when a pair of polarizers are arranged in a state where the absorption axes are parallel
• T 2 is a case where a pair of polarizers is arranged in a state where the absorption axes are orthogonal to each other. It is the orthogonal transmittance obtained).
• the polarizer produced by the production method according to the present invention showed excellent optical properties and no cutting occurred during the production process.
• Example 8 and Comparative Example 6 were compared, in the case of Example 8, there was no cutting even when a 20 ⁇ m thin film was used, but Comparative Example 8 in which the crystallinity departs from the scope of the present invention. It was confirmed that the film had been cut twice or less in spite of 60 ⁇ m.

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Optics & Photonics (AREA)
• Polarising Elements (AREA)
• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Health & Medical Sciences (AREA)
• Manufacturing & Machinery (AREA)
• Ophthalmology & Optometry (AREA)

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• 2015
  • 2015-07-10 KR KR1020150098157A patent/KR20170006855A/ko unknown
• 2016
  • 2016-07-05 WO PCT/JP2016/069912 patent/WO2017010354A1/ja active Application Filing
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