KR20100106121A - Method for preparing polarizer, polarizer and polarizing plate comprising the same - Google Patents

Abstract

PURPOSE: A manufacturing method of a polarizer, a polarizer, and a polarizing plate thereof are provided to have an optical property and a superior polarizing property. CONSTITUTION: A soaking process and a non-soaking process of a polymer film(120) are sequentially executed in a swelling tank(100) by using a guide roll. The rate of the distance between the surface of the swelling solution from the center of the guide roll and the rate of the distance between the guide roll and the guide roll which is arranged in the swelling solution is less than 1.

Description

Method of manufacturing polarizer, polarizer and polarizing plate provided therewith {METHOD FOR PREPARING POLARIZER, POLARIZER AND POLARIZING PLATE COMPRISING THE SAME}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polarizer, in particular a method for producing a wide polarizer with excellent polarization and optical properties, a polarizer and a polarizing plate provided therewith.

In order to provide images with high brightness and excellent color reproducibility to various image display devices such as liquid crystal display (LCD), electroluminescence (EL) display, plasma display (PDP) and field emission display (FED), Constant research has been conducted, and as a result, it has been found that high polarization characteristics and optical characteristics of polarizers are important factors.

Until now, most polarizers swell a polymer film such as a polyvinyl alcohol (PVA) film, dye the swollen polymer film to adsorb a substance such as dichroic iodine or dichroic dye, and then perform a crosslinking reaction. It was prepared by fixing the adsorbed dye and orienting the fixed dye through stretching.

On the other hand, in recent years, liquid crystal display devices have gradually increased in size, and the demand for improved functions and brightness has increased rapidly. Therefore, not only the polarizing plate used for the liquid crystal display device is being enlarged but also the uniformity of the in-plane polarization degree of such a large polarizing plate and the improvement of the optical characteristic are calculated | required.

In order to manufacture a large polarizing plate, it is necessary to uniformly uniaxially stretch a wide polymer film to prepare a polarizer. Such a process is known to have many difficulties in practical application. In particular, in the case of the wide polarizer, the uniformity of the degree of polarization in the plane of the film is lowered and there is a problem that the optical properties are also lowered due to the tendency to deteriorate.

In addition, the production of the wide polarizer should be considered to improve productivity through shortening of the production time. In order to shorten the production time, if the speed of the manufacturing process of the existing polarizer is rapidly controlled, the polarization in the plane of the wide polarizer is uneven. It is easy to occur, and as a result, there is a problem that the production yield is greatly reduced.

In order to solve this problem, Japanese Laid-Open Patent Publication No. 2004-078208 (published on Jan. 2004. 1) arranges at least a first guide roll in a swelling bath, and immerses the polymer film in the swelling solution until the swelling becomes saturated. A manufacturing method of light polarizer which exhibits uniform display characteristics by suppressing the display stain by dichroic substance content by contacting a 1st guide roll is disclosed. However, when such a method is applied to a wide polarizer, there is still a problem that nonuniformity of polarization degree is generated in the plane of the polarizer due to the swelling state of the swelling.

An object of the present invention is to provide a method for producing a polarizer having a uniform polarization degree in the plane of a polarizer, especially a wide polarizer, no foreign matter being adsorbed, exhibiting a large maximum absorption wavelength value, and excellent polarization characteristics and optical characteristics.

In addition, an object of the present invention is to provide an economical method of manufacturing a polarizer that can shorten the manufacturing time to improve productivity, prevent breakage of the polarizer and also increase the yield.

In addition, another object of the present invention is to provide a polarizer manufactured by the above production method.

In addition, another object of the present invention is to provide a polarizing plate and a liquid crystal display device provided with the polarizer.

The present inventors have conducted intensive studies to solve the above problems, when the swelling step in the manufacture of the polarizer, when the polymer film is immersed in the aqueous solution for swelling and then taken out of the aqueous solution alternately, the degree of swelling It can be suppressed that the saturation saturation state by adjusting the, it was confirmed that the problem of breakage of the polarizer due to the conventional swelling saturation state and the problem of nonuniformity of the degree of polarization in the plane can be solved, and based on this, the present invention has been completed.

The present invention provides a method of manufacturing a polarizer comprising a swelling step of alternately performing immersion and non-immersion of the polymer film in the swelling tank using a guide roll.

The present invention also provides a polarizer produced by the above method.

In addition, the present invention provides a polarizing plate in which a protective film is laminated on at least one surface of the polarizer.

In addition, the present invention provides a liquid crystal display device having the polarizing plate on at least one side of the liquid crystal cell.

According to the present invention, in the swelling step, the degree of swelling of the polymer film is controlled and the swelling saturation state is suppressed so that the dichroic material is uniformly adsorbed and oriented so that the degree of polarization in the plane of the polarizer, especially the width polarizer having a width of 2300 mm or more. The uniformity and orthogonal transmittance can be improved, and foreign matters can be prevented from being adsorbed, thereby making it possible to manufacture polarizers having excellent polarization characteristics and display characteristics without display unevenness. In addition, by improving the adsorption efficiency of a blue dichroic material such as I ₅ ^- to have a high maximum absorption wavelength value of 580nm or more it is possible to manufacture a polarizer excellent in both color and optical properties. In addition, the process time performed in the range of 180 seconds or less, including the immersion time of 5 seconds to 120 seconds, to shorten the manufacturing time of the wide polarizer to improve productivity, and prevent the breakage of the polarizer to increase the yield. It is economical.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polarizer, in particular a method for producing a wide polarizer with excellent polarization and optical properties, a polarizer and a polarizing plate provided therewith.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

The method of manufacturing a polarizer of the present invention is characterized in that it comprises a swelling step of alternately immersing and unimmersing the polymer film in the swelling tank using a guide roll.

The polymer film for producing the polarizer is not particularly limited in kind, for example, PVA film, partially saponified PVA film; Hydrophilic polymer films such as polyethylene terephthalate films, ethylene-vinyl acetate copolymer films, cellulose films, partially gumified films thereof, and polyene alignment films such as dehydrated PVA films and dehydrochlorinated polyvinyl chloride, etc. Can be mentioned. Among these, PVA film is more preferable in that it is excellent in the effect which strengthens the uniformity of polarization degree in surface, and excellent in dyeing affinity with respect to a dichroic substance like iodine as a polarizer.

The method for producing the PVA film is not particularly limited, and examples thereof include a flow cast method, a cool drum cast method, an extrusion method, and the like, which form a film by flow casting a polymer stock solution decomposed into water or an organic solvent. In this case, in order to obtain the polarizer which is excellent in the uniformity of the polarization degree in the surface of a film, it is preferable that the in-plane retardation deviation of a PVA system film is small. Therefore, the retardation deviation in the PVA-based film as the raw material film before processing is preferably 1 to 100 nm, more preferably 10 nm or less, most preferably 5 nm or less when measured at a measurement wavelength of 1000 nm.

The degree of polymerization of the PVA-based film is usually 500 to 10,000, preferably 1000 to 6,000, and more preferably 1,400 to 4,000. In the case of the PVA-based saponification film, the saponification degree is preferably 95.0 mol% or more, more preferably 99.0 mol% or more, and most preferably 99.9 mol% or more from the viewpoint of solubility.

Usually, the method of manufacturing a polarizer includes a swelling step, a dyeing step, a crosslinking step, an stretching step, and a washing and drying step, and are mainly classified according to the stretching method. For example, a dry stretching method for stretching and dyeing a polymer film as a raw material by stretching in a hot roll, a wet stretching method for simultaneously stretching and crosslinking in the state of impregnation with hot water, or a combination of the two stretching methods. Hybrid drawing method is mentioned. Hereinafter, the manufacturing method of the polarizer of the present invention will be described based on the wet stretching method, but is not limited thereto.

The remaining steps except the drying step are performed in a state in which the PVA-based polymer film is immersed in a constant temperature bath filled with at least one solution selected from several types of solutions.

In addition, the order of the swelling step, the dyeing step, the crosslinking step, the stretching step, the washing and drying steps and the number of repetition are not particularly limited, and the steps may be performed simultaneously or sequentially, and some steps may be omitted. It may be. For example, the stretching step may be performed before the dyeing step or after the dyeing step, or may be performed simultaneously with the swelling step or the dyeing step.

Hereinafter, with reference to the accompanying drawings will be described in detail the manufacturing method of the polarizer of the present invention, for example, iodine adsorption-oriented polarizer on a PVA-based film.

The swelling step is immersed in a swelling tank filled with swelling aqueous solution (deionized water) before dyeing the unstretched PVA film to remove impurities such as dust or blocking agent deposited on the surface and swelling the PVA film to draw efficiency It is a step for improving the physical properties of the polarizer by improving and preventing the dyeing non-uniformity.

The swelling step is performed by alternately immersing and not immersing the polymer film in the swelling tank, and such immersion and non-immersion are performed using a plurality of guide rolls alternately arranged inside and outside the surface of the aqueous solution for swelling.

Swelling step according to an embodiment of the present invention is a step in which the immersion and non-impregnation is alternately repeated two times, as shown in Figure 1 is filled with the aqueous solution for swelling 110, inside and outside the water surface of the swelling aqueous solution (110) The first to fourth guide rolls 30 to 33 alternately arranged are performed in the swelling tank 100.

In more detail, the PVA film 120 is supplied to the swelling tank 100 using the pinch roll 10 and the guide roll 20 for transport, and the aqueous solution 110 for swelling using the first guide roll 30 is provided. After immersing in the inside), the second guide roll 31 is used to take out the swelling aqueous solution 110 outside and then to be immersed. Then, the second guide roll 31 is immersed in the swelling solution 110 using the third guide roll 32. After the fourth guide roll 33 is removed, it is taken out to the outside of the swelling aqueous solution 110 and transferred to the next step. At this time, the transfer guide roll 20 for supplying the PVA-based film 120 to the swelling tank may be replaced by a heat roll, and to provide a separate drying furnace with the guide roll 20 to swell the PVA-based film 120 It may also be annealed before.

The guide rolls 30 to 33 disposed in the swelling tank 100 may use the same diameter, or may use different ones.

The distance from the center of the first or third guide rolls 30 and 32 to the water surface of the swelling aqueous solution and the center of the first and third guide rolls are represented by H and L, respectively. More specifically, L shows the distance from the center of the first immersion guide roll 30 to the center of the next immersion guide roll 32 after passing through the non-immersion guide roll 31. The first and third guide rolls 30 and 32 disposed in the water surface of the swelling aqueous solution 110 may be disposed anywhere in the water surface, but the height from the bottom of the swelling tank to the water surface is assumed to be 1 from the water surface. It is preferable to be arrange | positioned where the distance to the center of a roll becomes 0.8 or less of the height from the bottom of the said swelling tank to the water surface, More preferably, it is 0.6 or less. In addition, the first and third guide rolls 30 and 32 may be disposed at the same position in the water surface. In this case, the ratio (H / L) of the distance H from the center of the first or third guide rolls 30 and 32 to the water surface of the swelling aqueous solution and the center of the first and third guide rolls L ) Is preferably 1 or less. If the H / L value exceeds 1, the length of the retention field becomes too long, resulting in a decrease in uniform stretching of the film and uniformity of the degree of polarization, and a decrease in productivity as the production speed is slowed. Therefore, the H / L value is preferably 1 or less, and in this range, the degree of polarization is good and the difference is small, and the degree of uniformity of the degree of polarization is also good.

In addition, the second and fourth guide rolls 31 and 33 disposed outside the water surface of the swelling aqueous solution 100 may be disposed anywhere other than the water surface, but the center of the first or third guide rolls 30 and 32 from the water surface. The distance H between the water and the distance between the centers of the second or fourth guide rolls 31 and 33 from the surface (not shown) may be disposed at a ratio of 1: 5 or less. In addition, it is good in terms of economic production that the ratio between the length L between the first and third guide rolls and the length of the PVA-based film introduced in the swelling step, that is, the length of the retention field is 1: 3 or less. They may be located at the same location outside of the water or at different locations.

As shown in FIG. 2, according to another embodiment of the present invention, the first guide roll 30 and the third guide roll 32 may be disposed at different positions in the water surface of the aqueous solution 100 for swelling. In this case, the distance (H) from the water surface of the swelling aqueous solution 100 of the first guide roll 30 and the third guide roll 32 to the water surface of the swelling aqueous solution from the center of the guide roll further disposed below. Calculate the H / L ratio as a reference.

The first to fourth guide rolls 30 to 33 may be replaced with one or more selected from crown rolls, bentrols, expander rolls, pinch rolls, and sparrel rolls.

Deionized water can be used alone as the aqueous solution for swelling, and when a small amount of glycerin and potassium iodide are added thereto, the processability of the PVA film can also be improved. The content of glycerin is 5% by weight or less and the content of potassium iodide is 10% by weight or less with respect to 100% by weight of the aqueous solution for swelling.

It is preferable that the temperature of the swelling aqueous solution of a swelling tank is 20-50 degreeC, More preferably, it is 25-40 degreeC.

In the present invention, the swelling time is based on the passage time from the center of the guide roll (in the case of Figure 1, the feed guide roll 20 for feeding) in the swelling tank to the center of the final guide roll 33, At this time, the immersion time is defined as the time that the film is immersed in the swelling aqueous solution.

The total running time of the swelling step is preferably 180 seconds or less, among which the immersion time is preferably 5 to 120 seconds, and the non-immersion time is adjusted according to the immersion time. When the time of immersion and non-immersion is adjusted to the above range during the total execution time of the swelling step, the swelling can be prevented from becoming saturated due to excessive swelling, preventing breakage due to softening of the PVA-based film, and dichroism in the dyeing step. Adsorption of the substance can be made uniform, thereby improving the degree of polarization.

As shown in Figure 3, according to another embodiment of the present invention, immersion and non-impregnation may be repeated three times.

The number of repetitions of immersion and unimmersion in the swelling step may be 10 times or less, and preferably 1 to 5 times controls the saturation state of the swelling and is economical.

As shown in FIG. 4, according to another embodiment of the present invention, the non-impregnation may be performed using two guide rolls by placing additional guide rolls 31 ′ and 33 ′. At this time, the arrangement order of the second guide roll 31 and the additional 2-1 guide roll 31 ′ is not particularly limited, and may be disposed at the same position or at different positions outside the water surface of the swelling aqueous solution 100. have. As such, when the two guide rolls are used in the non-immersion step, the non-immersion time can be effectively extended, so that there is a buffering effect of swelling of the film due to the immersion. It is possible to improve the coloring efficiency of iodine in the next dyeing step.

As described above, in the swelling step in which immersion and non-impregnation are performed alternately, in particular, the immersion effect is provided by cleaning the film during immersion, and during immersion, the PVA system is transferred to air having a lower temperature than the swelling aqueous solution after immersion. The film shrinks instantaneously and at the same time a constant tension is generated in the film, thereby controlling the degree of swelling and speed, thereby adjusting the degree of swelling of the PVA-based film, and suppressing excessive swelling.

Through this, foreign matter adhering on the surface of the PVA-based film is removed, the PVA-based film is appropriately softened and the drawing efficiency is improved to prevent the breakage of the final polarizer and the dichroic material is uniformly adsorbed so that it is in the plane of the polarizer. The uniform polarization degree of can be obtained.

In addition, generally, the polarization performance and the optical performance of the polarizer may be given to the degree of iodine ions and their orientation. In particular, it is known that the polarization performance and the optical performance are affected by the type of iodine ion adsorbed. Iodine ions have been confirmed through various technical documents that two kinds of I ₃ ^- and I ₅ ^- are oriented in PVA film to form complex ions. Absorption wavelengths of these iodine complex ions are known to be in the range of approximately 400-500 nm and 580-700 nm, respectively. The absorption wavelengths are red when I ₃ ⁻ is large and blue when I ₅ ⁻ is large. In order to satisfy the optical performance of the polarizer required in the liquid crystal display, both types of iodine complex ions are required. Among these, it is preferable to adsorb a relatively large amount of blue I ₅ ⁻ . For the application of a swelling phase comprising a magazine dropped below a continuous process, I ₃ ^{- -} immersed under the terms of this invention than I ₅ ^- is much absorption can indicate the maximum absorption wavelength is equal to or greater than 580㎚ optical performance can also be improved Will be.

In addition, according to the swelling step, even in the case of manufacturing a large polarizer, it is possible to manufacture a polarizer having physical properties equal to or higher, even though the process time is shortened, thereby improving productivity, and preventing breakage of the polarizer, thereby improving yield.

The swelling step may be performed together with the stretching step, in which case the draw ratio is preferably 1.1 to 1.5 times.

The stretching step is a step of stretching the unstretched PVA film, and the stretching method is not particularly limited. For example, an interroll stretching method, a heating roll stretching method, a compression stretching method, a tenter stretching method, or the like, which performs stretching based on the difference in circulation speed between the rolls, can be used.

The dyeing step is a step of adsorbing iodine to the PVA-based film by immersing the swollen PVA-based film in a dye bath filled with an aqueous solution for dyeing containing iodine.

The aqueous solution for dyeing may include deionized water or a water-soluble organic solvent and iodine. The content of iodine is preferably 0.010 to 10% by weight, more preferably 0.020 to 7% by weight, most preferably 0.025 to 5% by weight based on 100% by weight of the aqueous solution for dyeing. Iodide may be further included together with iodine to further improve dyeing efficiency. As iodide, potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, titanium iodide, etc. may be used alone or in combination of two or more thereof. Of these, potassium iodide is preferred. The content of iodide is preferably 0.010 to 10% by weight, more preferably 0.10 to 5% by weight relative to 100% by weight of the aqueous solution for dyeing.

The weight ratio of iodine to iodide (potassium iodide) is preferably 1: 5 to 1: 100, more preferably 1: 6 to 1:80, and most preferably 1: 7 to 1:70.

Moreover, it is preferable that the aqueous solution for dyeing further contains a small amount of crosslinking agents. As the crosslinking agent, one or more selected from boron compounds such as boric acid and sodium borate, glyoxal and glutaraldehyde can be used, and preferably, a combination of boric acid and sodium borate is used. When such a component is further included, there is an effect of further strengthening the crosslinking of the iodine molecule. The content of the crosslinking agent is preferably 0.01 to 6% by weight, more preferably 0.10 to 3% by weight based on 100% by weight of the aqueous solution for dyeing.

It is preferable that the temperature of a dye bath is 5-42 degreeC, More preferably, it is 10-35 degreeC. Moreover, the immersion time of a PVA system film in a dyeing tank is not specifically limited, Preferably it is 1 to 20 minutes, More preferably, it is 2 to 10 minutes.

The stretching step may be performed together with the dyeing step, and in this case, the stretching is preferably performed such that the cumulative stretching ratio is 1.1 to 4.0 times.

In addition to the above-described dyeing method, a method of applying or spraying a dye solution containing iodine on the PVA-based film may be used, or iodine may be dyed by mixing with PVA resin before casting the PVA-based film.

The crosslinking step is a step of fixing the adsorbed iodine molecules by immersing the dyed PVA film in an aqueous solution for crosslinking.

The aqueous solution for crosslinking may include at least one crosslinking agent selected from deionized water as a solvent, a boron compound such as boric acid, sodium borate, glyoxal and glutaldehyde. In addition, the organic solvent may be further dissolved together with the deionized water. The content of the crosslinking agent is not particularly limited and is preferably 1 to 10% by weight, more preferably 2 to 6% by weight based on 100% by weight of the aqueous solution for crosslinking.

In addition, the aqueous solution for dyeing may further include a small amount of iodide in order to obtain uniformity of the degree of polarization in the plane of the polarizer. Iodide may be the same as the one used in the dyeing step, the content may be 0.05 to 20% by weight, preferably 0.50 to 13% by weight relative to 100% by weight of the aqueous solution for crosslinking. Most preferably, a combination of boric acid and potassium iodide is used, and in this case, the weight ratio of boric acid and potassium iodide is preferably 1: 0.1 to 1: 5, more preferably 1: 0.5 to 1: 3.5.

The temperature of the crosslinking bath is 20 to 70 ° C., and the immersion time of the PVA film in the crosslinking bath may be 1 second to 15 minutes, preferably 5 seconds to 10 minutes.

The stretching step may be performed together with the crosslinking step.

In addition to the crosslinking method as described above, other methods such as in the dyeing step may be used.

After the crosslinking step, an independent stretching step using a separate drawing tank filled with an aqueous solution for stretching may be performed.

The type of the aqueous solution for stretching is not particularly limited, and may be a solution containing at least one selected from a solvent such as water, ethanol or an organic solvent and a metal salt, iodine, boron, and a zinc compound. In particular, a solution containing 2 to 18% by weight boric acid, 2 to 10% by weight potassium iodide or mixtures thereof is preferred. In addition, when boric acid and potassium iodide are used together, their weight ratio is preferably 1: 0.1 to 1: 4, more preferably 1: 0.5 to 1: 3.

It is preferable that the temperature of a drawing tank is 40-67 degreeC, More preferably, it is 50-62 degreeC.

The stretching method is not particularly limited and, for example, in the case of roll stretching, a stretching method is used based on the difference in circulation speed between rolls.

The stretching direction may be the longitudinal direction (flow direction of the process) or the width direction of the PVA-based film, it is preferably stretched so that the final cumulative stretching ratio is 3.0 to 7.0 times.

The washing step is to remove unnecessary residues such as boric acid deposited on the PVA film in the previous steps by immersing the PVA-based film completed crosslinking and stretching in a cleaning tank filled with an aqueous solution for cleaning.

The aqueous cleaning solution may be deionized water, and an iodine compound may be further added thereto. As the iodide, the same ones as used in the dyeing step can be used, and among them, it is preferable to use sodium iodide or potassium iodide. The content of potassium iodide may be 0.1 to 10% by weight with respect to 100% by weight of the aqueous solution for washing, preferably 3 to 8% by weight.

It is preferable that the temperature of a washing tank is 10-60 degreeC, More preferably, it is 15-40 degreeC.

The washing step may be repeated one or more times, and the number of repetitions is not particularly limited. In addition, the type and content of the component of the aqueous solution for cleaning may be changed according to the number of times repeated.

The washing step may be performed whenever previous steps such as swelling step, dyeing step, crosslinking step or stretching step are completed.

The drying step is a step of obtaining a polarizer in which iodine is adsorbed and oriented by drying the washed PVA film.

As a drying method, a method such as natural drying, air drying, heating drying, etc. may be used, and heat drying is preferably used. For example, it may be heat dried at 20 to 80 ° C. for 1 to 10 minutes. The drying temperature is preferably low in order to prevent deterioration of the polarizer, more preferably 80 ° C. or lower, most preferably 60 ° C. or lower.

In the steps as described above, when the PVA-based film is raised in the air from the reaction tank, in order to prevent the liquid, such as a solution attached to the PVA-based film from falling, conventionally known liquid cutting rolls such as pinch rolls ( A liquid-cutting roll may be used, or excess solution may be removed by a liquid cutting method using an air knife.

The final draw ratio of the PVA film produced by such steps is preferably 3.0 to 7.0 times, more preferably 5.5 to 6.2 times. When the draw ratio of the polarizer is less than 3.0 times, it is difficult to obtain a polarizer having high polarization efficiency, and when the draw ratio exceeds 7.0 times, the polarizer is easily broken.

In addition to the above method, any other method including the swelling step of the present invention may produce a PVA-based film in which iodine is adsorbed and oriented. For example, a method of kneading a dichroic material and a resin and then stretching, a method of using a dichroic dye as a guest and a liquid crystal oriented in a single axis as a host (US Patent No. 5,523,863, Japanese Patent Application Publication No. 1991-503321) Or a method using a dichroic solution liquid crystal (US Pat. No. 6,049,428), or the like.

The polarizer of the present invention is characterized in that it is produced by the manufacturing method of the polarizer.

The width of the polarizer is a wide polarizer of 2300 mm or more, preferably 2300 to 4500 mm.

The thickness of the polarizer may be usually 5 to 80 μm, preferably 5 to 40 μm. In the case of the thickness range as described above, mechanical strength and optical properties can be maintained, and thinning can be achieved when applied to an image display device.

It is preferable that the single transmittance of a polarizer is 42.0% or more, More preferably, it is 43.0-45.0%.

It is preferable that the orthogonal transmittance measured at the condition of superimposing two sheets so that the absorption axes of the polarizers cross each other by 90 ° is low, preferably 0.030% or less, more preferably 0.020% or less, most preferably 0.010% It is as follows.

When applied to the actual product, the degree of polarization is preferably 99.990% to 100%, more preferably 99.993 to 100%. In addition, the difference in polarization degree in the plane of the polarizer, that is, the difference in the polarization degree between the central portion and the edge portion of the polarizer is preferably 0.010% or less, and more preferably 0.005% or less in terms of uniformity of polarization degree.

It is preferable that the maximum absorption wavelength of the visible light of a polarizer is 580 nm or more, More preferably, it is 600-700 nm in terms of optical performance.

Polarizing plate of the present invention is characterized in that the protective film is laminated on at least one side of the polarizer.

The structure of the polarizing plate is not particularly limited, and various kinds of optical layers capable of satisfying required optical characteristics may be stacked on the polarizer. For example, a structure in which a polarizer protective film for protecting the polarizer is laminated on at least one surface of the polarizer; A structure in which a surface treatment layer such as a hard coating layer, an antireflection layer, an anti-sticking layer, a diffusion barrier layer, an antiglare layer, or the like is laminated on at least one surface of the polarizer or the polarizer protective film; It may have a structure in which an alignment liquid crystal layer or another functional film is laminated on at least one surface of the polarizer or the polarizer protective film. In addition, a phase difference including a wavelength plate (including a λ plate) such as an optical film, a reflector, a semi-transmissive plate, a 1/2 wave plate, or a quarter wave plate, such as a polarization conversion device used to form various image display devices At least one of the plate, the viewing angle compensation film, and the brightness enhancement film may be laminated with an optical layer. More specifically, a polarizer having a structure in which a polarizer protective film is laminated on one surface of a polarizer, the polarizing plate having a reflector or a semi-transparent polarizer having a reflector or a semi-transparent reflector laminated on the laminated polarizer protective film; An oval or circular polarizing plate in which retardation plates are stacked; A wide viewing angle polarizer on which a viewing angle compensation layer or a viewing angle compensation layer is stacked; Or the polarizing plate in which the brightness improving film was laminated | stacked is preferable.

As a polarizer protective film, a film excellent in transparency, mechanical strength, thermal stability, moisture shielding, and isotropy may be used. Specific examples thereof include polyester such as polyethylene terephthalate, polyethylene isophthalate, polyethylene naphthalate, and polybutylene terephthalate. System film; Cellulose films such as diacetyl cellulose and triacetyl cellulose; Polycarbonate film; Acrylic films such as polymethyl (meth) acrylate and polyethyl (meth) acrylate; Styrene films such as polystyrene and acrylonitrile-styrene copolymers; Polyolefin-based films such as polyethylene, polypropylene, cyclo-based or norbornene-structured polyolefins, ethylene propylene copolymers; Vinyl chloride film; Amide films such as nylon and aromatic polyamides; Imide film; Polyether sulfone-based film; Sulfone film; Polyether ether ketone film; Polyphenylene sulfide films; Vinyl alcohol film; Vinylidene chloride-based film; Polyoxymethylene film; Epoxy type film etc. are mentioned. In addition, the polarizer protective film may be a cured layer formed from a thermosetting or ultraviolet curable resin such as aryl resin, urethane resin, acrylic-urethane resin, epoxy resin, silicone resin and the like. Among these, especially the cellulose type film which has the surface saponified by alkali etc. is preferable in consideration of polarization characteristic or durability.

The thickness of the polarizer protective film is not particularly limited, and may be usually 500 μm or less, preferably 1 to 300 μm, more preferably 5 to 200 μm.

The liquid crystal display of the present invention is characterized in that the polarizing plate is provided on at least one side of the liquid crystal cell.

In the present invention, since the liquid crystal display device is well known to those skilled in the art of the present invention, a detailed description of each configuration is omitted.

In addition to the liquid crystal display device, the present invention can be applied to various image display devices such as electroluminescent display devices, plasma display devices, and field emission display devices.

Hereinafter, preferred examples are provided to aid the understanding of the present invention, but the following examples are merely for exemplifying the present invention, and it will be apparent to those skilled in the art that various changes and modifications can be made within the scope and spirit of the present invention. It is natural that such variations and modifications fall within the scope of the appended claims.

Example 1

The first to fourth guide rolls 30-33, each filled with 30 deg. C deionized water and having the same diameter, are alternately disposed at the same position inside and outside the water surface of the deionized water, so that The swelling step was performed in the swelling tank 100 whose value was adjusted to 1/2. The transparent unstretched PVA film (VF-PS, manufactured by Kuraresa) having a degree of saponification of 99.9% or more is transferred to the swelling tank 100 using the pinch roll 10 and the transfer guide roll 20, and the first to fourth The PVA film was cross immersed in deionized water for 120 seconds using guide rolls 30-33. At this time, the immersion time was 60 seconds. The swollen PVA film was uniaxially stretched 2.0 times in the lengthwise direction (progression direction) of the PVA film while being dyed by immersion for 3 minutes in an aqueous solution for dyeing at 30 ° C. containing 1.6 mM iodine and 0.7 M potassium iodide. The dyed PVA film was immersed in a 60 ° C aqueous solution for crosslinking containing 5.6M potassium iodide and 6.6M boric acid for 3 minutes to crosslink, and uniaxially stretched 2.5 times in the longitudinal direction (progression direction) of the PVA film. The draw ratio was set to 5.0 times. When crosslinking and stretching were completed, the PVA film was washed with a washing water solution, placed in an oven, and dried at 60 ° C. for 5 minutes to obtain a PVA film having iodine adsorption orientation.

A triacetyl cellulose (TAC) film was laminated on both sides of the prepared polarizer to prepare a polarizing plate.

Example 2

In the same manner as in Example 1, but using the first to third guide rolls arranged so that the value of H / L is 1/3, it was cross-immersed for 120 seconds, but soaking time was 30 seconds.

Example 3

In the same manner as in Example 1, but was cross-immersed for 180 seconds, so that the immersion time was 120 seconds.

Example 4

In the same manner as in Example 1, as shown in Figure 3, the first to sixth guide rolls (30-35) for 180 seconds in the swelling tank alternately disposed at the same position inside and outside the surface of the deionized water, respectively Three cross immersions were allowed, so that the immersion time was 90 seconds.

Example 5

In the same manner as in Example 1, but the cross-immersion for 180 seconds using the first to third guide rolls arranged so that the value of H / L is 2, the immersion time was 60 seconds.

Comparative Example 1

In the same manner as in Example 1, but did not perform the swelling step.

Comparative Example 2

In the same manner as in Example 1, but did not go through the non-immersion was performed for 180 seconds.

Comparative Example 3

The same procedure as in Example 1 was carried out, but the immersion was performed for 60 seconds without passing through the non-immersion.

Test Example

Physical properties of the polarizers prepared in Examples and Comparative Examples were measured by the following methods, and the results are shown in Table 1 below.

(1) polarization degree (%), orthogonal transmittance (%)

The specimen was prepared by cutting the center part of the polarizer and the part 1 cm away from the left and right sides, and after attaching each specimen to the measurement holder, using an ultraviolet visible spectrometer (V-7100, manufactured by JASCO). It was measured by.

(2) polarization degree difference, polarization degree uniformity

The difference between the polarization degree of the center part and the left side or the right side is calculated using the polarization degree value measured in the above (1), and is represented by the larger value among them.

○: polarization difference ≤ 0.005%

△: 0.005% <polarization difference ≤ 0.010%

×: 0.010% <polarization difference (defect)

(3) Whether white spot foreign material exists

When the produced polarizer was reflected on white light, foreign matters that appeared as white spots were visually observed and evaluated.

○: no white spot foreign material (excellent)

×: White spot foreign material exists (bad)

(4) Maximum absorption wavelength (nm)

The absorber in the visible region was measured by using an ultraviolet visible spectrometer (V-7100, manufactured by JASCO). At this time, the wavelength showing the most absorbance is represented by the maximum absorption wavelength.

division Cross immersion

(H / L) Swelling Time /
Immersion time
(second) Polarization degree

(%) Ortho
Transmittance
(%) Polarization degree
Difference
(%) Polarization degree
Judgment White spot
Whether Absorption
wavelength
(Nm) Example 1 2 applications
(1/2) 120 /
60 99.923 0.0287 0.001 ○ ○ 605 Example 2 2 applications
(1/3) 120 /
30 99.964 0.0208 0.002 ○ ○ 615 Example 3 2 applications
(1/2) 180 /
120 99.892 0.0287 0.005 ○ ○ 605 Example 4 3 times
(1/2) 180 /
90 99.907 0.0231 0.003 ○ ○ 610 Example 5 2 times
(2) 180 /
60 99.819 0.0325 0.009 △ ○ 600 Comparative Example 1 Unapplied
(-) - 99.872 0.0451 0.005 ○ × 610 Comparative Example 2 Unapplied
(-) 180 /
180 99.503 0.0924 0.043 × ○ 465 Comparative Example 3 Unapplied
(-) 60 /
60 99.793 0.0516 0.029 × ○ 590

As shown in Table 1, the polarizers of Examples 1 to 5 in which the degree of swelling is controlled and the swelling saturation is suppressed through swelling steps in which immersion and non-immersion are alternately performed according to the present invention do not have foreign substances, and The degree of orthogonal transmittance is excellent and the polarization degree is small so that not only the uniformity of the polarization degree in the surface is improved but also the optical absorption performance is excellent because the maximum absorption wavelength value is higher than 600 nm even though the same immersion time is performed. I could confirm it. In particular, when H / L ratio is 1/2 or 1/3 or less, since in-plane polarization degree is more uniform, it was more preferable. In addition, in the examples, even in the case of shortening the production time compared to Comparative Example 2, it is possible to manufacture a polarizer having better physical properties, thereby improving productivity.

On the other hand, the polarizer of Comparative Example 1, which did not undergo the swelling step, had foreign substances, and the polarizers of Comparative Examples 2 and 3, which were prepared through the normal swelling step without performing immersion, had a large difference in polarization degree. Was not uniform, and the polarizer of Comparative Example 2 had a low maximum absorption wavelength value, which was not good in comparison with the Examples in terms of optical performance.

As described above, the polarizer manufactured according to the manufacturing method of the polarizer of the present invention is a polarizer requiring uniform in-plane uniform polarization characteristics and excellent optical characteristics, especially a large liquid crystal display device, an electroluminescence display device, a plasma display device or an electric field. It can be applied as a wide-angle polarizer for a large polarizing plate applied to an emission display device or the like.

1 is a process diagram of the swelling step in one embodiment of the present invention,

2 is a process chart of the swelling step according to another embodiment of the present invention,

3 and 4 are each a process diagram of the expanded swelling step according to another embodiment of the present invention.

Description of the Related Art [0002]

10, 11: pinch roll 20: guide roll for feed

30-35: Guide rolls 31 ', 33': Additional guide rolls for non-immersion

100: swelling tank 110: aqueous solution for swelling

120: polymer film (PVA-based film)

Claims (11)

A method of manufacturing a polarizer comprising a swelling step of alternately immersing and not immersing a polymer film in a swelling tank using a guide roll. The distance (H) from the center of the guide roll disposed in the water surface of the swelling aqueous solution to the water surface of the swelling aqueous solution and the distance (L) between the guide roll and the center of the guide roll disposed in the swelling aqueous solution. The manufacturing method of the polarizer whose ratio (H / L) is one or less. The method of claim 1, wherein the non-impregnation is performed using two or more guide rolls continuously arranged in addition to the water surface of the swelling aqueous solution.  The method of claim 1, wherein the swelling step is performed in a total of 180 seconds or less, including 5 to 120 seconds of immersion time. The method of manufacturing a polarizer according to claim 1, wherein the number of repetitions of immersion and non-immersion is 5 or less. The manufacturing method of light polarizer of Claim 1 whose width | variety is 2300 mm or more. The polarizer manufactured by the manufacturing method of any one of Claims 1-6. The polarizer according to claim 7, wherein the polarization degree difference is 0.010% or less. The polarizer according to claim 7, wherein the maximum absorption wavelength of visible light is at least 580 nm. A polarizing plate in which a protective film is laminated on at least one side of the polarizer of claim 7. A liquid crystal display device comprising the polarizing plate of claim 10 on at least one side of a liquid crystal cell.

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