KR101718937B1 - Method of preparing polarizer for led - Google Patents

Abstract

More particularly, the present invention relates to a method for producing a polarizer by swelling, dyeing and crosslinking a polyvinyl alcohol-based film, wherein the iodine content in the dyeing is 1.0 to 3.0 mmol / L It is possible to provide a polarizer having improved light transmittance in a long wavelength region (550 to 780 nm) by using an aqueous solution for dyeing and causing the cumulative stretching ratio during swelling, dyeing and crosslinking to be 5.50 times or less, The present invention relates to a method for manufacturing an LED polarizer capable of improving brightness by being applied to an image display apparatus using a light source having a light emission luminance spectrum.

Description

METHOD OF PREPARING POLARIZER FOR LED [

The present invention relates to a polarizer capable of providing a polarizer having improved light transmittance in a long wavelength region (550 to 780 nm) and capable of improving luminance by applying it to an image display apparatus using a light source having a relative light emission luminance spectrum similar to that of LED And a manufacturing method thereof.

In order to provide an image with excellent color reproducibility in various image display devices such as a liquid crystal display (LCD), an electroluminescence (EL) display, a plasma display (PDP), and a field emission display As a result, it has been found that the optical characteristics of the polarizer are important factors.

Until now, most polarizers have been used for cleaning and swelling polymer films such as polyvinyl alcohol (PVA) films, staining swollen polymer films to adsorb materials such as dichroic iodine or dichroic dyes, To fix the adsorbed dye, and orienting the fixed dye through stretching.

BACKGROUND ART [0002] Recent image display devices are required to have an increased size, various functions, and improved luminance. One such method is the use of an LED light source instead of a CCFL light source.

The general-purpose polarizing plate used in the image display apparatus is designed to be suitable for a CCFL light source, so that when an LED light source having different emission wavelengths is used, the polarizing plate transmittance and the like may be different. Since the transmittance is closely related to the optical properties such as the brightness of the image display apparatus, it is necessary to improve the physical properties of the polarizing plate so as to be suitable for the LED light source.

The present invention provides a method of manufacturing a polarizer capable of improving the light transmittance in a long wavelength region (550 to 780 nm).

The present invention also provides a method of manufacturing a polarizer capable of improving the transmittance of light in a long wavelength region (550 to 780 nm) and improving the luminance of an image display apparatus using a light source having a relatively light emission luminance spectrum similar to that of an LED or the like .

1. A method for producing a polarizer by swelling, dyeing and crosslinking a polyvinyl alcohol film, wherein an aqueous dyeing solution having an iodine content of 1.0 to 3.0 mmol / L at the time of dyeing is used, and the swelling, dyeing and crosslinking Wherein the cumulative stretching ratio is 5.50 times or less.

2. The method for producing a polarizer for LED according to 1 above, wherein the cumulative stretching ratio is 4.50 to 5.50 times.

3. The method for producing a polarizer for LED according to 1 above, wherein the swelling ratio is 1.0 to 1.3 times at swelling, the swelling ratio is 1.4 to 1.7 at dyeing, and the swelling ratio is 2.5 to 2.8 at crosslinking.

4. The method for producing a polarizer for LED according to 1 above, wherein an aqueous crosslinking solution containing 0.5 to 5% by weight of an organic crosslinking agent is used at the time of crosslinking.

5. The method of producing a polarizer for LED according to 4 above, wherein the organic crosslinking agent is at least one selected from the group consisting of polyaldehyde compounds, polyvalent carboxylic acid compounds and derivatives thereof.

6. A polarizing plate for LED comprising a polarizer protective film laminated on at least one surface of a polarizing plate for LED manufactured by the manufacturing method according to any one of 1 to 5 above.

7. The polarizing plate for LED of claim 6, wherein at least one selected from the group consisting of a retardation film, a viewing angle compensation film, and a brightness enhancement film is further laminated on the LED polarizer or the polarizer protective film.

8. Image display device including LED polarizer and LED light source in above 6.

The method of producing a polarizer according to the present invention can improve the transmittance by reducing the content of I < ^5- > contained in the polarizer and blocking light in the long wavelength region (550 to 780 nm).

Also, the method of manufacturing a polarizer according to the present invention can be usefully used for improving the luminance of an image display apparatus using an LED or the like having a relatively low relative-emission luminance in a long wavelength region as a light source.

Also, the polarizer according to the present invention can produce a polarizer in which flexibility is imparted by using an aqueous crosslinking solution containing an organic crosslinking agent to prevent cracking (warp) due to thermal shock.

FIG. 1 shows the transmittance change in the TD spectrum according to the content of iodine in the dyeing solution of the present invention,
2 is a graph showing the change in transmittance in the TD spectrum according to the cumulative stretching ratio of the present invention,
3 is a relative emission luminance spectrum of a white LED (Light Emitting Diode) and a CCFL (Cold Cathode Fluorescent Lamp).

The present invention relates to a method for producing a polarizer by swelling, dyeing and crosslinking a polyvinyl alcohol-based film, wherein an aqueous dyeing solution having an iodine content of 1.0 to 3.0 mmol / L at the time of dyeing is used and the swelling, (550 to 780 nm) can be provided by improving the transmittance of light in the long wavelength region (550 to 780 nm) and by applying the present invention to an image display device using a light source having a relative light emission luminance spectrum similar to LED or the like And a method of manufacturing a polarizer for LED capable of improving brightness.

Hereinafter, the present invention will be described in detail.

The present invention relates to a method for producing a polarizer by swelling, dyeing and crosslinking a polyvinyl alcohol-based film, wherein an aqueous dyeing solution having an iodine content of 1.0 to 3.0 mmol / L at the time of dyeing is used and the swelling, Of 5.50 times or less.

In the present specification, "cumulative stretching ratio" represents the product of the stretching ratio at each step.

The polymer film for producing the polarizer is not particularly limited as long as it is a film which can be dyed with a dichroic substance, for example, iodine, and specifically, a polyvinyl alcohol film, a partially saponified polyvinyl alcohol film; A hydrophilic polymer film such as a polyethylene terephthalate film, an ethylene-vinyl acetate copolymer film, an ethylene-vinyl alcohol copolymer film, a cellulose film, a partially saponified film thereof and the like; Or a dehydrated polyvinyl alcohol film, a dehydrochloric acid-treated polyvinyl alcohol film, and the like. Among them, a polyvinyl alcohol film or an ethylene-vinyl alcohol copolymer film is preferable because it has an excellent effect of enhancing the uniformity of the degree of polarization in the plane, is excellent in dyeing affinity for the dichroic substance and small in the tensile force applied to the same stretching ratio, Vinyl alcohol copolymer film is preferable, and an ethylene-vinyl alcohol copolymer film is more preferable. In particular, in the case of the ethylene-vinyl alcohol copolymer film, the content of vinyl alcohol is preferably 70% by weight or more based on 100% by weight of the copolymer.

The degree of polymerization of the polyvinyl alcohol-based film is usually 500 to 10,000, preferably 1,000 to 6,000, and more preferably 1,400 to 4,000. In the case of the polyvinyl alcohol based 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 in terms of solubility.

The polyvinyl alcohol-based film may have a thickness of 80 탆 or less, and preferably 60 탆 or less.

The production method of the polarizer is mainly classified into a stretching method, for example, a dry stretching method, a wet stretching method, or a hybrid stretching method in which the two kinds of stretching methods are mixed. Hereinafter, a method of producing the polarizer of the present invention will be described with reference to a wet drawing method, but the present invention is not limited thereto.

In addition, the swelling, dyeing, crosslinking and stretching steps, except for the drying step, are carried out in a state in which the polyvinyl alcohol film is immersed in a constant temperature bath filled with at least one solution selected from various kinds of solutions, respectively.

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

The swelling step is carried out by immersing the unstretched polyvinyl alcohol film in a swelling tank filled with a swelling aqueous solution before dyeing to remove impurities such as dust and anti-blocking agent deposited on the surface of the polyvinyl alcohol film, Is a step for improving the physical properties of the polarizer by improving the stretching efficiency and preventing uneven dyeing by swelling the film.

Water (pure water, deionized water) can usually be used as a swelling aqueous solution, and when a small amount of glycerin is added thereto, the swelling of the polymer film and the processability can be improved. The content of glycerin is preferably 5% by weight or less based on 100% by weight of the aqueous swelling solution.

The swelling bath temperature is preferably 20 to 45 캜, more preferably 25 to 40 캜.

The execution time (swelling tank immersion time) of the swelling step is preferably 180 seconds or less, more preferably 120 seconds or less. When the immersion time is within the above range, it is possible to prevent the swelling from becoming excessive and saturation, to prevent breakage due to softening of the polyvinyl alcohol film and to improve the polarization degree by uniformly adsorbing iodine in the dyeing step have.

The stretching step may be performed together with the swelling step, and the stretching ratio is preferably 1.0 to 1.3 times. The present invention provides a polarizer having a uniform thickness by performing stepwise stretching during swelling, dyeing and crosslinking, respectively. The thickness of the polarizer is closely related to the mechanical properties such as optical properties and tensile strength, such as the degree of polarization of the prepared polarizer.

That is, the stepwise stretching is performed in order to maintain the optical properties and the mechanical properties of the polarizer, and the controlled stretching ratio at each step is a controlled range so that the cumulative stretching ratio can be satisfied at 5.5 times or less while simultaneously performing the intended purpose.

The dyeing step is a step of dipping the polyvinyl alcohol-based film in a dyeing bath filled with an aqueous solution for dyeing containing a dichroic substance, for example, iodine to adsorb iodine on the polyvinyl alcohol-based film.

The dyeing aqueous solution may comprise water, a water-soluble organic solvent or a mixed solvent thereof and iodine. The content of iodine is preferably 1.0 to 3.0 mmol / L, more preferably 1.5 to 2.5 mmol / L, based on 100 wt% of the aqueous solution for dyeing. To further improve the dyeing efficiency, iodide may be further included as a dissolution aid. As the iodide, 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 alone or in combination of two or more. Of these, potassium iodide is preferable in view of high solubility in water. The content of iodide is controlled within a range that can maintain the content of iodine according to the present invention.

That is, the sum of the iodine content and the iodine content in the iodide is preferably 1.0 to 3.0 mmol / L based on 100 wt% of the dyeing aqueous solution.

The temperature of the dye bath is preferably 5 to 42 ° C, more preferably 10 to 35 ° C. The immersion time of the polyvinyl alcohol film in the dyeing bath is not particularly limited, and is preferably 1 to 20 minutes, and more preferably 2 to 10 minutes.

The stretching step may be carried out together with the dyeing step, and in this case, the stretching ratio is preferably 1.4 to 1.7 times.

The crosslinking step is a step of immobilizing the adsorbed iodine molecules by immersing the dyed polyvinyl alcohol film in a crosslinking aqueous solution so that the dyeability due to physically adsorbed iodine molecules is not lowered by the external environment. In the case of dichroic dyes, the iodine molecules often dissolve or sublimate depending on the environment in the case of iodine, although they are not often eluted in the humidity environment. Therefore, in order to stably exhibit the optical property by the iodine molecule, the crosslinking reaction is very important.

The aqueous crosslinking solution may contain water as a solvent and a boron compound crosslinking agent such as boric acid, sodium borate and / or organic crosslinking agent, and may further comprise an organic solvent mutually soluble with water.

In particular, when the organic crosslinking agent is stretched at a low draw ratio of 5.50 or less, the thickness of the polarizer can be made thin to enable thinning and enlargement of the polarizer, and the residual stress can be controlled to improve the dimensional stability and prevent durability deterioration. Flexibility of the polarizer can be prevented, and the breakage of the polarizer due to thermal shock can be prevented.

As the organic crosslinking agent, a polyaldehyde compound containing two or more aldehyde groups, a polyvalent carboxylic acid compound containing two or more carboxyl groups, and derivatives thereof may be used alone or in combination of two or more. Specifically, examples of polyaldehyde compounds include dialdehyde compounds such as glyoxal, malondialdehyde, succinic aldehyde, glutaraldehyde and adipodialdehyde; Trialdehyde compounds; A semi-aldehyde compound; And derivatives thereof. Examples of the polyvalent carboxyl group compound include oxalic acid, malonic acid, succinic acid and derivatives thereof such as fumaric acid, tartaric acid, malic acid, glutaric acid, adipic acid, pimelic acid, Dicarboxylic acid compound; Tricarboxylic acid compounds such as citric acid; Polyfunctional aromatic carboxylic acid compounds such as terephthalic acid; And derivatives thereof. Of these, dialdehyde compounds, dicarboxylic acid compounds and derivatives thereof are preferable.

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 crosslinking aqueous solution. In particular, the content of the organic crosslinking agent is preferably 0.5 wt% to 5 wt% with respect to 100 wt% of the aqueous crosslinking solution. If the content is less than 0.5% by weight, effects such as thinning of the organic cross-linking agent and improvement in durability are difficult to be exhibited. If it exceeds 5% by weight, cross-linking of boric acid may be impeded and orientation of the adsorbed iodide ion may be deteriorated, have.

The organic crosslinking agent is preferably used together with the boron compound rather than alone, and the weight ratio of the organic crosslinking agent to the boron compound is preferably 1: 1 to 1: 3.

In addition, the aqueous crosslinking solution may further contain a small amount of iodide to prevent the uniformity of the degree of polarization in the plane of polarizers and the desorption of dyed iodine. The iodide may be the same as that used in the dyeing step, and its content may be from 0.05 to 15% by weight, preferably from 0.5 to 11% by weight, based on 100% by weight of the aqueous crosslinking solution. In this case, the weight ratio of boric acid and potassium iodide is preferably 1: 0.1 to 1: 3.5, more preferably 1: 0.5 to 1: 2.5 .

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

The stretching step may be carried out together with the crosslinking step, and in this case, the stretching ratio is preferably 2.5 to 2.8 times.

As described above, the stretching step may be carried out with the swelling step, the dyeing step, the crosslinking step, and may be carried out as an independent stretching step using a separate stretching tank filled with the running aqueous solution after the crosslinking step.

The washing step is a step of immersing the crosslinked and stretched polyvinyl alcohol film in a water bath filled with water for washing to remove unnecessary residues such as boric acid attached to the polyvinyl alcohol film in the previous steps.

The aqueous solution for washing may be water (deionized water), and iodide may be further added thereto.

The temperature of the water bath is preferably 10 to 60 ° C, more preferably 15 to 40 ° C.

The wash step may be omitted and may be performed each time previous steps such as a dyeing step, a crosslinking step, or an elongating step are completed. It may also be repeated one or more times, and the number of repetition is not particularly limited.

The drying step is a step of drying the washed polyvinyl alcohol-based film and further improving the orientation of the iodine molecules dyed by the necking by drying, thereby obtaining a polarizer excellent in optical characteristics.

As the drying method, natural drying, air drying, heating and drying, far infrared ray drying, microwave drying, hot air drying and the like can be used. Recently, microwave drying in which only water in the film is activated and dried is newly used, Drying is mainly used. For example, it may be hot air dried at 20 to 90 DEG 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, and most preferably 60 ° C or lower.

Figure 1 shows the change in transmittance in the TD spectrum according to the iodine content in the dyeing solution. As shown in FIG. 1, as the iodine content increases, the transmittance of the long wavelength region decreases. Therefore, when the image display apparatus using an LED or the like having a spectrum having a relatively low relative luminance in the long wavelength region as a light source is used, the overall luminance of the image display apparatus is reduced .

2 is a change in transmittance in the TD spectrum according to the cumulative stretching ratio. At this time, the total amount of iodine is the same. As shown in FIG. 2, it can be seen that the transmittances of the short wavelength region and the long wavelength region are inversely proportional to each other. That is, as the stretching ratio decreases, the transmittance of the short wavelength region decreases and the transmittance of the long wavelength region increases.

3 is a relative emission luminance spectrum of a white LED (Light Emitting Diode) and a CCFL (Cold Cathode Fluorescent Lamp). Relatively white LED has a tendency that the relative luminescence brightness in the long wavelength region is low. The present invention lowers the production of I < ^5- > in the polarizer in order to improve the transmittance of light in the long wavelength region. Iodine in a polarizer is typically co-exist with I and I ^{3- 5-} form, ^double-5- I is known to block the light in the long wavelength region.

The present invention controls the cumulative stretching ratio and the iodine content in the dye solution to a specific range in order to lower the production of I < ⁵ >.

The present invention provides a polarizing plate in which a protective film is laminated on at least one surface of a polarizer produced by the above production method.

The protective film is not particularly limited as long as it is a film excellent in transparency, mechanical strength, thermal stability, moisture barrier property, isotropy, and the like. Specifically, polyester resins such as polyethylene terephthalate, polyethylene isophthalate and polybutylene terephthalate; Cellulose-based resins such as diacetylcellulose and triacetylcellulose; Polycarbonate resin; Acrylic resins such as polymethyl (meth) acrylate and polyethyl (meth) acrylate; Styrene resins such as polystyrene and acrylonitrile-styrene copolymer; Polyolefin resins such as polyethylene, polypropylene, cyclo- or norbornene-structured polyolefins, and ethylene propylene copolymers; Vinyl chloride resin; Polyamide resins such as nylon and aromatic polyamide; Imide resin; Polyether sulfone type resin; Sulfone based resin; Polyether ketone resin: a polyphenylene sulfide resin; Vinyl alcohol-based resin; Vinylidene chloride resins; Vinyl butyral resin; Allylate series resin; Polyoxymethylene type resin; Epoxy resin, and the like, and a film composed of the blend of the thermoplastic resin may also be used. Further, a film made of a thermosetting resin such as (meth) acrylic, urethane, epoxy, or silicone or a film made of an ultraviolet curable resin may be used. Among them, a cellulose-based film having a surface saponified (saponified) by alkali or the like is preferable in consideration of polarization characteristics or durability.

In the present invention, the structure of the polarizing plate is not particularly limited, and various kinds of optical layers capable of satisfying the required optical characteristics may be laminated on the polarizer. For example, a structure in which a protective film for protecting a polarizer is laminated on at least one side of a polarizer; A structure in which a surface treatment layer such as a hard coating layer, an antireflection layer, an anti-adhesion layer, a diffusion prevention layer, and an anti-glare layer is laminated on at least one surface of a polarizer or on a protective film; Or a structure in which an alignment liquid crystal layer or another functional film is laminated on at least one surface of the polarizer or on the protective film to compensate for the viewing angle. Further, it is also possible to use an optical film such as a polarization conversion device used for forming various image display devices, a retardation film including a reflector, a half-transparent plate, a half-wave plate or a quarter- A plate, a viewing angle compensating film, and a luminance improving film may be laminated with an optical layer. More specifically, a polarizing plate having a structure in which a protective film is laminated on one side of a polarizer, includes: a reflective polarizing plate or a transflective polarizing plate in which a reflector or a transflective reflector is laminated on a laminated protective film; An elliptic or circular polarizer in which a retarder is stacked; A wide viewing angle polarizer in which a viewing angle compensation layer or a viewing angle compensation film is laminated; Or a polarizing plate in which a brightness enhancement film is laminated.

Such a polarizing plate is applicable not only to a general liquid crystal display but also to various image display devices such as an electroluminescent display device, a plasma display device, and a field emission display device.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the present invention. Such variations and modifications are intended to be within the scope of the appended claims.

Example 1

A transparent unoriented polyvinyl alcohol film having a degree of saponification of 99.9% or more (VF-PS 70 μm, Kuraray Co.) was immersed in water (deionized water) at 30 ° C. for 2 minutes and swelled. Lt; 0 > C for 4 minutes. At this time, stretching was 1.13 times and 1.67 times in the swelling and dyeing steps, respectively. Subsequently, the substrate was immersed in the first and second aqueous crosslinking solutions of 50 ° C containing 10% by weight of potassium iodide and 3.5% by weight of boric acid for 2 minutes and 1 minute, respectively, for crosslinking. At this time, the first and second crosslinking steps were performed such that the total stretching ratio was 2.70 times, so that the cumulative stretching ratio was 5.09 times. After the crosslinking was completed, the polyvinyl alcohol film was dried in an oven at 70 DEG C for 4 minutes to prepare a polarizer.

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

Example 2

The procedure of Example 1 was repeated, 3% by weight of glutaric acid as an organic crosslinking agent was added to the aqueous crosslinking solution to prepare a polarizing plate.

Example 3

The procedure of Example 1 was repeated except that the stretching step and the dyeing step were not performed but the stretching ratio was increased to 5.09 times in the crosslinking step to prepare a polarizing plate.

Example 4

A polarizing plate was prepared in the same manner as in Example 1 except that the iodine content in the aqueous dyeing solution was 1.5 mmol / L (4-1) and 2.5 mmol / L (4-2).

Example 5

The procedure of Example 1 was repeated except that the stretching ratio was 2.0 times (5-1), 3.0 times (5-2), and 4.0 times (5-3), to prepare a polarizing plate.

Comparative Example 1

A polyvinyl alcohol film having a degree of saponification of 99.9% or more and having a thickness of 75 탆 and containing 12.5% by weight of a glycerin plasticizer was immersed in water (swelling aqueous solution) at 30 캜 for 2 minutes and stretched to 1.36 times while swelling. 3.0 mmol / L of iodine Was immersed in an aqueous solution for dyeing at 30 DEG C for 4 minutes and stretched 1.32 times while being dyed. Subsequently, it was immersed in a crosslinking aqueous solution at 53 DEG C containing 10% by weight of potassium iodide and 3.5% by weight of boric acid for 3 minutes and stretched 3.39 times so as to have a total cumulative stretching ratio of about 6.09 times. After the crosslinking was completed, the polyvinyl alcohol film was dried in an oven at 60 DEG C for 4 minutes to prepare a polarizer.

A triacetyl cellulose (TAC) film was laminated on both sides of the prepared polarizer using a polyvinyl alcohol-based adhesive to prepare a polarizing plate.

Comparative Example 2

A polarizing plate was prepared in the same manner as in Example 1 except that the iodine content in the dyeing aqueous solution was 4.0 mmol / L.

Test Example

The physical properties in the above Examples and Comparative Examples were measured by the following methods, and the results are shown in Table 1 below.

1. Optical characteristics (polarization degree, transmittance)

The prepared polarizer was cut into a size of 4 cm x 4 cm and then measured using an ultraviolet ray spectrophotometer (V-7100, manufactured by JASCO). At this time, the polarization degree is defined by the following equation (1).

(Wherein T ₁ is the parallel transmittance obtained when the pair of polarizers are arranged in parallel with the absorption axis, and T ₂ is the orthogonal transmittance obtained when the pair of polarizers are arranged so that the absorption axes are perpendicular to each other) .

2. Tensile Strength (MPa)

The tensile strength of the polyvinyl alcohol film before drying was measured when the film was stretched at the final cumulative stretching ratio in a crosslinking bath using a roll equipped with a road cell. In this case, the risk of breakage is considered to be large when the pressure is 10 MPa or more.

3. TD spectrum

The prepared polarizer was cut into a size of 4 cm x 4 cm and then measured using an ultraviolet ray spectrophotometer (V-7100, manufactured by JASCO). The TD spectrum And the transmittance spectrum when the produced polarizer has the lowest transmittance.

division accumulate
Stretching cost
(ship) iodine
content
(mmol / L) Optical characteristic The tensile strength
(MPa) Polarization degree
(%) Orthogonal
Transmittance
(%) Example 1 5.09 3.0 99.994 0.03 9 Example 2 5.09 3.0 99.994 0.02 6 Example 3 5.09 3.0 99.993 0.03 11 Example 4-1 5.09 1.5 99.994 0.03 9 Example 4-2 5.09 2.5 99.993 0.02 8 Example 5-1 2.0 3.0 99.992 0.03 9 Example 5-2 3.0 3.0 99.994 0.02 9 Example 5-3 4.0 3.0 99.994 0.03 8 Comparative Example 1 6.09 3.0 99.994 0.03 9 Comparative Example 2 5.09 4.0 99.993 0.03 10

The polarizers of Examples 1 to 5, which were prepared by controlling the iodine content in the dyeing aqueous solution according to the present invention and stretching at a low draw ratio of 5.5 or less using a polyvinyl alcohol film according to the present invention, And it was confirmed that it represents strength.

Particularly, in Example 2, the flexibility was increased by the organic cross-linking agent and the tensile strength was lowered. In Example 3, the tensile strength was higher in Example 3 than in Example 1, there was.

FIG. 1 shows that the transmittance in the long wavelength region decreases as the content increases with the change in the content of iodine (1.5, 2.5, 3.0 and 4.0 mmol / L) in the TD spectrum.

2 shows the TD spectrum according to the variation of the cumulative stretching ratios (2.0, 3.0, 4.0, 5.5 and 6.0 times) when the content of iodine contained is the same.

FIG. 2 can relatively confirm that the absorption in a short wavelength region increases as the stretching ratio decreases and the absorption in a relatively long wavelength region decreases.

Claims (8)

A method for producing a polarizer by swelling, dyeing and crosslinking a polyvinyl alcohol-based film,
An aqueous solution for dyeing in which the amount of iodine in the dyeing and the amount of iodine in the iodide calculated on the basis of the sum is 1.0 to 3.0 mmol / L, and the cumulative stretching ratio during swelling, dyeing and crosslinking is 5.50 times or less A method for producing a polarizer.
The method of claim 1, wherein the cumulative stretching ratio is 4.50 to 5.50 times.
The method according to claim 1, wherein the stretching ratio is 1.0 to 1.3 times at the time of swelling, the stretching ratio is 1.4 to 1.7 at the time of dyeing, and the stretching ratio is 2.5 to 2.8 times at the time of crosslinking.
The method for producing a polarizer for LED according to claim 1, wherein an aqueous crosslinking solution containing 0.5 to 5% by weight of an organic crosslinking agent at the time of crosslinking is used.
[5] The method according to claim 4, wherein the organic crosslinking agent is at least one selected from the group consisting of polyvalent aldehyde compounds, polyvalent carboxylic acid compounds, and derivatives thereof.
A polarizing plate for LED comprising a polarizer protective film laminated on at least one surface of an LED polarizer produced by the manufacturing method according to any one of claims 1 to 5.
The polarizing plate for LED according to claim 6, wherein at least one selected from the group consisting of a retardation film, a viewing angle compensation film, and a brightness enhancement film is further laminated on the LED polarizer or the polarizer protective film.
An image display apparatus comprising the polarizing plate for LED and the LED light source according to claim 6.

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