KR20120015753A

KR20120015753A - Polarizer, polarizing plate, liquid crystal display and method for preparing polarizer

Info

Publication number: KR20120015753A
Application number: KR1020100078152A
Authority: KR
Inventors: 조성우; 최윤석
Original assignee: 동우 화인켐 주식회사
Priority date: 2010-08-13
Filing date: 2010-08-13
Publication date: 2012-02-22

Abstract

PURPOSE: A polarizer and a polarizing plate using the same and a liquid crystal display device including the same are provided to improve durability and reliability. CONSTITUTION: A polarizing plate includes a transparent protective layer which is laminated in one side of a polarizer. A liquid crystal display device includes a liquid crystal panel including a liquid crystal cell and the polarizing plate which is laminated in both sides of the crystal cell. A polyvinyl alcohol film is swelled. The swollen polyvinyl alcohol film swelled is dyed by iodine. The dyed polyvinyl alcohol is cross-linked. Rs/Rc is less than 0.5 to 1.3 in case Rs is swelling draw ratio and Rc is crosslink draw ratio. The concentration of the iodine is 2.0mM-5.0mM.

Description

A polarizer, a polarizer using a polarizer, a liquid crystal display including a polarizer and a manufacturing method of a polarizer {POLARIZER, POLARIZING PLATE, LIQUID CRYSTAL DISPLAY AND METHOD FOR PREPARING POLARIZER}

The present invention relates to a polarizer, a polarizer using a polarizer, a liquid crystal display device including a polarizer and a manufacturing method of the polarizer, and more particularly, a light polarizer, a polarizer having a high durability and a low transmittance and color change at high temperatures The present invention relates to a polarizing plate used, a liquid crystal display including a polarizing plate, and a manufacturing method of a polarizer.

In the liquid crystal display device, it is indispensable to arrange | position a polarizer on both sides of the glass substrate which forms the liquid crystal panel surface from the image formation system surface. The polarizer is generally obtained by dyeing with a dichroic material such as a polyvinyl alcohol (hereinafter referred to as PVA) -based film and iodine, then crosslinking with a crosslinking agent, uniaxially stretching to form a film. . Since the polarizer is produced by stretching, it tends to shrink, and in particular, since the polyvinyl alcohol-based film uses a hydrophilic polymer, it is easy to deform under particularly humid humid conditions. In addition, since the mechanical strength of the film itself is weak, there is a problem that the film is torn. Therefore, the polarizing plate which supplemented the intensity | strength by adhering a protective film to the both sides or one side of a polarizer is used.

Background Art [0002] Recently, the liquid crystal display device has been widely used, and has been widely developed from portable terminals to large TVs for home use. As a result, technology development for ensuring excellent display quality in each liquid crystal display device has been progressed.

When preparing a polarizer, when the PVA-based film is dyed in iodine, iodine is present in the form of I ₃ which is an iodine trivalent ion or I ₅ ⁻ which is an iodine pentaion. Of these, I ₃ ^- If there is an equilibrium reaction overused reactions easily get up, but made much, I ₅ ^- If there unless the PVA film in only, and not least the orientation schedule of the PVA film does not easily made, made Even if only a small amount is made. Therefore, it is very difficult to adjust the dyeing amount of I ₅ ^{− in} the polarizer. In addition, simply changing the residence time makes it difficult to control the amount of dyeing of I ₅ ⁻ .

Controlling the dyeing amount of I ₅ ⁻ is an important problem in terms of improving image display quality. If iodine is intensively adsorbed on the surface layer, sublimation of iodine and structural breakage of I ₅ ⁻ may occur under high temperature. As a result, light in the long wavelength region (700 nm) absorbed by I ₅ ⁻ is leaked out, and the amount of change in transmittance and dichroic boiling in the long wavelength region is increased, resulting in deterioration of the image quality of the liquid crystal display device.

On the contrary, when iodine is concentrated at the center, the overall average transmittance in the entire visible light region is lowered. Therefore, in the process of adjusting the single transmittance, the transmittance of the long wavelength region is increased, so that the structure breakage of I ₅ ^- at high temperatures is particularly sensitive to 700 nm wavelength. Decreases the optical characteristic at, and causes the yellowing as a whole to increase the amount of change of the single-b value, resulting in deterioration of the display quality.

Therefore, there is a demand for the development of a technology capable of improving the display quality by adjusting the ratio of the dyeing amount of I ₅ ^- deposited on the central portion and the surface layer portion of the polarizer within a specific range.

The present invention is to solve the above-mentioned problems, the object of the present invention is to provide a reliable polarizer, a polarizer using a polarizer, a polarizer, a liquid crystal display device including a polarizer and a polarizer having a low transmittance and color change at a high temperature and excellent durability To provide a method.

Polarizer comprising a polyvinyl alcohol-based film dyed with iodine according to an aspect of the present invention for achieving the above object is the maximum of the Raman spectrum in the range of 160 ± 10cm ^- ¹ of the central portion of the thickness direction of the cross section of the polarizer la, and a value Vc, 160 ± 10cm of the surface layer in the thickness direction of the polarizer of the ^{cross-section} is that when the maximum value of the Raman spectrum in the ^first range Vs, is Vc / Vs 0.9 to 1.0.

According to another aspect of the invention, there is provided a polarizing plate comprising the polarizer and a transparent protective layer laminated on at least one surface of the polarizer.

According to another aspect of the present invention, there is provided a liquid crystal display including a liquid crystal panel including a liquid crystal cell and the polarizing plates stacked on both sides of the liquid crystal cell.

According to another aspect of the invention, the swelling step of swelling the polyvinyl alcohol-based film; A dyeing step of dyeing the swollen polyvinyl alcohol-based film with iodine; And a crosslinking step of crosslinking the dyed polyvinyl alcohol-based film; wherein the swelling draw ratio in the swelling step is Rs, and the crosslinking draw ratio in the crosslinking step is Rc, and Rs / Rc is 0.5 to 1.3 or less. The concentration of iodine is provided in the polarizer manufacturing method is 2.0mM to 5.0mM. Complementary color step after crosslinking step; And a drying step.

The polarizer according to the present invention has a small amount of adsorption of iodine 5 ions (I ₅ ⁻ ) in the central portion and the surface layer along the thickness direction of the polarizer, so that the transmittance and color change at a high temperature are small, so the durability is excellent and reliable polarizer, There is an effect that can produce a polarizing plate and a liquid crystal display device.

Hereinafter, embodiments of the present invention will be described. However, embodiments of the present invention may be modified in various other forms, and the scope of the present invention is not limited to the embodiments described below. Embodiments of the present invention are provided to more fully describe the present invention to those skilled in the art.

The polarizer according to the present invention is prepared by dyeing a polyvinyl alcohol-based film with iodine. Polarizer 160 ± 10cm in the direction of the thickness of the polarizer-sided ^heart-up of the Raman spectrum at ^one range ^- 160 ± 10cm of the thickness direction of the Raman spectrum is a maximum value Vc La, and polarizer in the ^first range of cross-sectional surface layer When the value is referred to as Vs, Vc / Vs is 0.9 to 1.0.

The polarizer is prepared by dyeing and orienting a hydrophilic polymer film with iodine and a dichroic dye, and as the hydrophilic polymer film, a film such as a PVA-based film, a partially gummed PVA-based film, or the like is used.

The polyvinyl alcohol-based film has a polymerization degree of usually 500 to 10,000, preferably 1,000 to 6,000, more preferably 1,400 to 4,000 can be used, in the case of polyvinyl alcohol-based safflower film, saponification degree is solubility aspect Is preferably at least 95.0 mol%, more preferably at least 99.0 mol%, and most preferably at least 99.9 mol% may be used.

The hydrophilic polymer film is not particularly limited as long as it is a film that can be dyed with iodine in addition to the polyvinyl alcohol-based film. For example, hydrophilic polymer films such as polyethylene terephthalate film, ethylene-vinyl acetate copolymer film, ethylene-vinyl alcohol copolymer film, cellulose film, and partially gumified films thereof, and polyvinyl alcohol based on dehydration treatment Films, and polyene oriented films such as dechlorinated polyvinyl chloride and the like can be used.

Although the thickness of the polarizer of this invention is not restrict | limited especially, For example, it is the range of 5-40 micrometers, A preferable thing is the range of 10-30 micrometers, Preferably, it is the range of 15-25 micrometers.

Polarizer of the present invention is 160 ± 10cm of the center portion and surface layer portion of the thickness direction of the polarizer of the ^{cross-section} is characterized by the ratio of the maximum value of the Raman spectrum in the ^first range. That is, the Raman spectrum is measured to confirm the ratio of the adsorption amount of iodine pentaion (I ₅ ⁻ ) in the central portion and the surface layer portion along the thickness direction of the polarizer. The maximum value of the Raman spectrum in the range ¹ ^- 160 ± 10cm of the surface layer in the thickness direction of the cross section of the Raman spectrum is a maximum value Vc La, and the polarizer in the range of 160 ± 10cm ^-1 in the thickness direction of the cross-sectional center of the polarizer When it is called Vs, it is preferable that Vc / Vs is 0.9-1.0.

If the Vc / Vs value is less than 0.9, since iodine is concentrated on the surface layer, sublimation of iodine and structural breakage of I ₅ ⁻ may occur at a high temperature. As a result, light in the long wavelength region (700 nm) absorbed by I ₅ ⁻ is leaked, and the amount of change in the transmittance and dichroic ratio of the long wavelength region is increased, resulting in deterioration of the image quality of the liquid crystal display device.

On the contrary, if the Vc / Vs value is larger than 1.0, iodine may be concentrated in the center, and thus the overall average transmittance in the entire visible light region is lowered. The structure breakage of ₅ ⁻ is particularly sensitive to deterioration of optical characteristics at the 700 nm wavelength, and to a large amount of change in the single-b value, resulting in yellowing as a whole, thereby degrading display quality.

Therefore, when Vc / Vs is 0.9 to 1.0, the polarizing plate using the polarizer having such characteristics exhibits excellent heat resistance with little color change under high temperature.

According to another aspect of the present invention, a polarizer including a polarizer according to the present invention and a transparent protective layer laminated on at least one surface of the polarizer is provided. The polarizing plate includes a transparent protective layer on one side or both sides of the polarizer. In general, the transparent protective layer may be a coating layer or a transparent polymer film using a thermosetting or ultraviolet curable resin, and the transparent protective layer may be formed of a material having excellent transparency, mechanical strength, thermal stability, and moisture shielding properties. It is preferable.

For example, as a transparent polymer film, Polyester type films, such as polyethylene terephthalate, polyethylene isophthalate, polyethylene naphthalate, and polybutylene terephthalate; 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; Polycarbonate film; Polyolefin-based films such as polyethylene, polypropylene, cyclo-based or norbornene-structured polyolefin and ethylene propylene copolymer; Vinyl chloride film; Amide films such as nylon and aromatic polyamides; Imide film; Polyether sulfone-based film; Sulfone film; Polyether ether ketone film; Sulfided polyphenylene-based films; Vinyl alcohol film; Vinylidene chloride-based film; Polyoxymethylene film; Epoxy type film etc. are mentioned.

Moreover, as a thermosetting or ultraviolet curable resin, the hardened layer formed from an aryl resin, a urethane resin, an acryl- urethane resin, an epoxy resin, or a silicone resin may be sufficient. Among these, in consideration of polarization characteristics or durability, a cellulose-based film having a surface saponified by alkali or the like is generally widely used.

The transparent protective layer may further or integrally include a layer having a function such as a hard coat, an antireflection layer or an antiglare layer. The hard coat serves to protect the surface of the polarizing plate from external damage, and generally can be installed by coating and curing UV curable resins such as acrylic, epoxy, and silicone resins on the surface of the protective film.

The antireflection layer is implemented for the purpose of antireflection of external light on the surface of the polarizing plate, and is generally made by providing a thin film having a different refractive index on one side of a protective film in a multilayer structure. In addition, the antiglare layer may be carried out to prevent external light from being reflected from the surface of the polarizing plate to hinder the visibility of transmitted light through the polarizing plate, and a method of blending the roughening method by sandblasting or embossing and organic / inorganic particles. It can implement by providing a fine uneven structure to the surface of a protective film using appropriate methods, such as these.

The polarizer and the transparent protective layer are bonded using an adhesive. Examples of the adhesive include water-soluble water such as isocyanate adhesive, polyvinyl alcohol adhesive, melamine based, gelatin adhesive, vinyl polymer adhesive, and water soluble polyester adhesive. Thermosetting and ultraviolet curable adhesives, such as an adhesive agent, a urethane type, an epoxy type, an acryl type, and a silicone type, are mentioned. Generally, the adhesive agent used for a polarizer and a transparent protective film is a polyvinyl alcohol-type adhesive agent, and it is preferable that it contains 0.5 to 10 weight% of solid content. More preferably, it is 1.5 to 5.0 weight%. The thickness of the adhesive layer is not particularly limited, but is generally about 0.1 to 5 mu m.

The polarizing plate provided in the present invention can be used as an optical film in which another optical layer is laminated for the purpose of improving the performance of the image display apparatus. Although there is no restriction | limiting in particular about optical layers, Optical layers, such as a phase difference plate (1/2 wave plate and a quarter wave plate), and a viewing angle compensation film, satisfy the optical characteristic calculated | required according to the mode and the kind of liquid crystal display device. One or more optical layers may be stacked to make it possible.

For example, a polarizing plate can be used as an elliptical polarizing plate and circular polarizing plate which laminated | stacked the phase difference plate. These polarizing plates can convert linearly polarized light into elliptical polarization or circularly polarized light, convert elliptical polarization or circularly polarized light into linearly polarized light, or convert the polarization direction of linearly polarized light by the function of a phase difference plate. A quarter wave plate (λ / 4 plate) can be used for converting circularly polarized light into linearly polarized light or for converting linearly polarized light into circularly polarized light. Used to change the polarization direction.

The elliptical polarizing plate can be used to compensate for coloration caused by birefringence of the liquid crystal layer of a super twisted nematic (STN) type liquid crystal display device. For example, the retardation plate can be used to compensate for the coloration due to birefringence, viewing angle, and the like of various wavelength plates and liquid crystal layers. Optical characteristics, such as a phase difference, can be adjusted using the laminated body which has two or more types of phase difference plates which have an appropriate phase difference value according to each objective. As a retardation plate, Birefringent film which extended | stretched the film which consists of polycarbonate resin, norbornin resin, polyvinyl alcohol, polystyrene, polymethylmethacrylate, polypropylene, polyallylate, polyamide, etc .; Alignment films containing liquid crystals such as liquid crystal polymers; The film etc. which support the alignment layer of a liquid crystal substance are mentioned. The retardation plate may be a retardation plate in which two or more kinds of retardation plates are laminated so as to adjust optical characteristics such as retardation.

The viewing angle compensation film is a film that enlarges the viewing angle so that an image can be clearly seen even when viewed in an inclined direction. Like the viewing angle compensation retardation plate, a bidirectional stretched film such as a film having a birefringence characteristic treated by uniaxial stretching or an orthogonal bidirectional stretching and an inclined alignment film may be used. The viewing angle compensation film can be appropriately combined for the purpose of preventing coloration due to a change in display angle based on a phase difference by a liquid crystal cell or the like, and a change in display angle extension having excellent visibility. In addition, in view of achieving a wide viewing angle of excellent visibility, a compensation plate in which an optically anisotropic layer composed of an alignment layer of a liquid crystal polymer, in particular an inclined array layer of a discotic liquid crystal polymer, is supported by a triacetyl cellulose film can be preferably used. .

According to another aspect of the present invention, there is provided a liquid crystal display including a liquid crystal panel including a liquid crystal cell and the polarizing plates stacked on both sides of the liquid crystal cell. The LCD may be manufactured by attaching a polarizing plate to a liquid crystal cell, and may further include a control unit for controlling an image display of the liquid crystal panel, a backlight unit for supplying light to the liquid crystal panel, and the like.

In order to bond the polarizing plate to the liquid crystal cell, pressure sensitive adhesives (Pressure Sensitive-Adhesives) may be applied to one side of the polarizing plate. As a method of application, all generally known methods can be applied. The main polymer used for the pressure-sensitive adhesive is not particularly limited, acrylic polymer; Silicone-based polymers; Polyesters, polyurethanes, polyamides, polyethers; Fluoride and rubber polymers are mainly used. In particular, an adhesive such as an acrylic adhesive is generally used, which is excellent in optical transparency and has moderate cohesiveness and adhesion. In addition, it has low hygroscopicity, remarkable weather resistance and heat resistance in terms of durability. Such characteristics are important for suppressing bubble generation and peeling phenomenon due to moisture absorption.

The thickness of the pressure-sensitive adhesive layer can be appropriately determined according to the purpose of use and rework, and is generally 1 to 500 µm, preferably 5 to 200 µm, and more preferably 10 to 100 µm.

According to another aspect of the invention, the swelling step of swelling the polyvinyl alcohol-based film; A dyeing step of dyeing the swollen polyvinyl alcohol-based film with iodine; And a crosslinking step of crosslinking the dyed polyvinyl alcohol-based film; wherein the swelling draw ratio in the swelling step is Rs, and the crosslinking draw ratio in the crosslinking step is Rc, and Rs / Rc is 0.5 to 1.3 or less. The concentration of iodine is provided in the polarizer manufacturing method is 2.0mM to 5.0mM.

In the polarizer manufacturing method according to the present invention, a polarizer is manufactured through a swelling step, a dyeing step and a crosslinking step.

The swelling step is a step of immersing the unstretched PVA film in a swelling tank filled with an aqueous solution for swelling before dyeing with iodine. Through this step, impurities such as dust or blocking agents deposited on the surface of the PVA-based film can be cleaned, and the PVA-based film is swollen to improve the stretching efficiency, prevent dye non-uniformity and improve dyeing properties, thereby improving physical properties of the polarizer. Can be improved.

Deionized water may be used alone as the aqueous solution for swelling, and when a small amount of glycerin, potassium iodide or boric acid is added thereto, the processability may be improved along with the swelling of the PVA-based film. The content of glycerin in 100% by weight of the aqueous solution for swelling is preferably 5% by weight or less, and the content of potassium iodide is 10% by weight or less.

It is preferable that the temperature of a swelling tank is 20-45 degreeC, More preferably, it is 25-40 degreeC. The execution time (immersion time) of the swelling step is preferably 180 seconds or less. When the immersion time is within the above range, the swelling can be prevented from becoming saturated due to excessive swelling, preventing breakage due to softening of the PVA-based film, and uniform adsorption of iodine in the dyeing step can improve the degree of polarization.

The stretching step may be performed together with the swelling step, wherein the stretching ratio is preferably 1.7 to 2.4 times.

The dyeing step is performed by immersing a non-plasticized polyvinyl alcohol-based film containing no plasticizer in a dye bath filled with a dyeing solution containing iodine in a dry state without swelling and swelling and adsorbing iodine on the polyvinyl alcohol-based film. can do.

The aqueous solution for dyeing may include deionized water or a water-soluble organic solvent and iodine. The content of iodine is preferably 0.1 to 10.0 mM, more preferably 0.5 to 7.0 mM, most preferably 1.0 to 5.0 mM.

In particular, iodide may be further included as a dissolution aid for further improving the dyeing efficiency in the manufacture of the iodine-based polarizer. As the iodide, at least one of 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. Potassium iodide is most commonly used because of its high solubility in water. The iodide content is preferably 1.0 to 5.0 parts by weight based on 100 parts by weight of the mixed solvent with deionized water or a water-soluble organic solvent.

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, dicarboxylic acid compounds and dialdehyde compounds may be used. Preferably, boric acid and sodium borate may be used in combination. In the case of further comprising a crosslinking agent, 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. The immersion time of the PVA-based film in the dye bath is not particularly limited, and is preferably 1 to 20 minutes, more preferably 2 to 10 minutes.

The stretching step may be performed together with the dyeing step, wherein the cumulative stretching ratio is preferably 1.10 to 1.80 times. More preferably, it is 1.30 times-1.60 times.

The crosslinking step is to fix the adsorbed iodine molecules or dye molecules by immersing a polyvinyl alcohol-based film in which the iodine and the dichroic dye are adsorbed and physically bonded so that dyeability may be degraded by an external environment in an aqueous solution for crosslinking. to be. In the case of dyes, they are not eluted in a moisture resistant environment. In the case of iodine, iodine molecules are dissolved or sublimed depending on the environment. Therefore, the crosslinking treatment between the polyvinyl alcohol molecules by the crosslinking solution is very important in order to adsorb the iodine molecules on the oriented polyvinyl alcohol molecules to exhibit the optical properties stably.

The aqueous solution for crosslinking is a polyhydric carboxylic acid containing two or more carboxyl groups such as deionized water, a boric compound such as boric acid and sodium borate, dicarboxylic acid, and tricarboxylic acid, and derivatives thereof, dialdehyde, and aldehyde groups such as trialdehyde. It may include one or more organic crosslinking agents selected from more than one polyvalent aldehyde and derivatives thereof. 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 7% by weight based on the total content of the aqueous solution for crosslinking (100% by weight).

In addition, the aqueous solution for crosslinking may further include a small amount of iodide in order to obtain uniformity of the degree of polarization in the polarizer plane. Iodide may be the same as the one used in the dyeing step, the content may be 0.05 to 15% by weight, preferably 0.5 to 11% by weight relative to the total content (100% by weight) of the aqueous solution for crosslinking. Most preferably, boric acid and potassium iodide are used in combination, and 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 ° C., and the immersion time of the polyvinyl alcohol-based film in the crosslinking bath may be 1 second to 15 minutes, and preferably 5 seconds to 10 minutes.

In the method of manufacturing a polarizer according to the present invention, the polarizer is manufactured through a swelling step, a dyeing step, and a crosslinking step, and may further include a complementary color step and a drying step of adjusting the color of the polarizer after the crosslinking step.

Complementary color step is a process for controlling the color by immersing in the aqueous solution mixed with boric acid and potassium iodide to the film which has been dyed and stretched.

The drying step is a step of obtaining an iodine-based polarizer having excellent optical properties by drying the polyvinyl alcohol-based film that has undergone dyeing, crosslinking and extension, and further improving the orientation of iodine molecules adsorbed by the neck-in by drying.

As a drying method, natural drying, air drying, far-infrared drying, microwave drying, heat drying, hot air drying, etc. may be used. Recently, a microwave drying method for activating and evaporating and drying only water in a film is newly introduced. The drying method most commonly used among the above-mentioned drying methods is hot air drying. For example, the polarizer may be hot air dried at 20 to 90 ° 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 less, and most preferably 60 ° C. or less.

Hereinafter, although an Example demonstrates this invention still in detail, this invention is not limited by these examples.

Example 1

As a polymer film for polarizers, a polyvinyl alcohol film having a saponification degree of 99.9% or more and a thickness of 75 microns was swelled for 2 minutes in deionized water (swelling bath) at 30 ° C. for 2 minutes and simultaneously stretched. Iodine (2.5 mM) and potassium iodide were dyed by immersion for 4 minutes while stretching 1.40 times in an aqueous solution for dyeing at 30 ° C. (dyeing tank) mixed at a weight ratio of 1:17. The dyed PVA-based film was immersed for 3 minutes in a crosslinking solution (crosslinking bath) at 55 ° C. mixed at a weight ratio of boric acid and potassium iodide 1: 3 (crosslinked bath) at 2.08 times, and crosslinked. After crosslinking, the polarizer was immersed for 30 seconds without stretching in an aqueous solution for complementary colors (complementary bath) at 40 ° C. mixed with a weight ratio of boric acid and potassium iodide 1: 1, and dried in a drying oven at 60 ° C. for 4 minutes to prepare a polarizer. . At this time, the total cumulative stretching ratio was 6.40 times. A triacetyl cellulose (TAC) film was laminated on both surfaces of the prepared polarizer to prepare a polarizing plate.

[Example 2]

A polarizer was prepared in the same manner as in Example 1 except that the swelling draw ratio was 2.35 and the crosslinking draw ratio was 1.95, and a polarizing plate was manufactured using the same.

Example 3

A polarizer was manufactured in the same manner as in Example 1 except that the swelling draw ratio was 2.05 and the crosslinking draw ratio was 2.23.

Example 4

A polarizer was prepared in the same manner as in Example 1 except that the swelling draw ratio was set to 1.90 and the crosslinking draw ratio was set to 2.41.

Example 5

A polarizer was prepared in the same manner as in Example 1 except that the swelling draw ratio was set to 1.70 and the crosslinking draw ratio was set to 2.69.

[Example 6]

A polarizer was prepared in the same manner as in Example 1 except that the iodine content of the aqueous solution for dyeing was 2.5 mM in the dyeing process, and a polarizing plate was prepared using the same.

Example 7

A polarizer was prepared in the same manner as in Example 1 except that the iodine content of the aqueous solution for dyeing was 4.5 mM in the dyeing process, and a polarizing plate was prepared using the same.

Comparative Example 1

A polarizer was prepared in the same manner as in Example 1 except that the swelling draw ratio was 2.50 and the crosslinking draw ratio was 2.08.

Comparative Example 2

A polarizer was manufactured in the same manner as in Example 1 except that the swelling draw ratio was set to 1.50 and the crosslinking draw ratio was set to 3.05.

Comparative Example 3

A polarizer was prepared in the same manner as in Example 1 except that the swelling draw ratio was set to 1.30 and the crosslinking draw ratio was set to 3.52.

[Comparative Example 4]

A polarizer was manufactured in the same manner as in Example 1 except that the swelling draw ratio was set to 1.10 and the crosslinking draw ratio was set to 4.16.

[Comparative Example 5]

A polarizer was prepared in the same manner as in Example 1 except that the swelling draw ratio was set to 1.00 and the crosslinking draw ratio was set to 4.57, thereby preparing a polarizer.

[Comparative Example 6]

A polarizer was prepared in the same manner as in Example 1 except that the iodine content of the aqueous solution for dyeing was 1.0 mM in the dyeing process, and a polarizing plate was prepared using the same.

Comparative Example 7

A polarizer was manufactured in the same manner as in Example 1 except that the iodine content of the aqueous solution for dyeing was 6.0 mM in the dyeing process, and a polarizing plate was prepared using the same.

[Test Example]

The polarizing plates produced in Examples 1 to 7 and Comparative Examples 1 to 7 were tested as follows.

(1) Optical property evaluation (polarization degree, single transmittance, dichroic ratio)

The polarizer thus prepared was cut to a size of 4 cm × 4 cm, and then measured using an ultraviolet visible light spectrometer (V-7100, manufactured by JASCO). The polarization degree P is defined by Equation 1 below, and the dichroic ratio DR is defined by Equation 2.

[Equation 1]

P = [(T ₁ -T ₂ ) / (T ₁ + T ₂ )] ^1/2

In the formula, T ₁ is a parallel transmittance is obtained when placing the polarizing plate of the pair in a state parallel to the absorption axis, T ₂ is a cross transmissivity is obtained when placing the polarizing plate of the pair to a state of the absorption axis orthogonal.

[Equation 2]

DR = Log ₁₀ {(Ty / 100) (1-Py / 100)} / Log ₁₀ {(Ty / 100) (1 + Py / 100)}

In the formula, Ty is a single transmittance obtained when one sheet of polarizing plate transmits natural light, and Py is a degree of polarization when the pair of polarizing plates is arranged in a state where the absorption axis is orthogonal.

(2) heat resistance evaluation

After cutting the prepared polarizing plate to 4cm × 4cm size, the ultraviolet ray visible spectrometer (V-7100, manufactured by JASCO Co., Ltd.), polarization degree, transmittance (Ty), simplex b, A700 (Equation 3) and 80 ° C After 500hr of measurement, the change amounts ΔDR (700), Δ single group b, ΔTy and ΔA700 were calculated.

&Quot; (3) "

A700 =-Log ₁₀ {(T _MD _{, 700} × T _TD _{, 700} ) / 10000}

In the formula, T _MD _{, 700} is a parallel transmittance at a wavelength of 700 nm obtained when the pair of polarizers are arranged in parallel with the absorption axis, and T _TD _, ₇₀₀ is a pair of polarizers in the state where the absorption axis is orthogonal to each other. It is orthogonal transmittance | permeability in 700 nm wavelength obtained when.

Table 1 below shows the process conditions of Examples 1 to 7 and Comparative Examples 1 to 7 and the results of the Raman spectrum value and durability test of the manufactured polarizing plate.

Process conditions Raman spectrum durability swelling
Elongation ratio
(Rs) dyeing
density
(mM) Bridge
Elongation ratio
(Rc) Rs / Rc Vc / Vs Δ group b ΔTy
(%) ΔDR (700) ΔA700 Example 1 2.20 3.0 2.08 1.06 0.964 1.59 0.34 -4.775 -0.84 Example 2 2.35 3.0 1.95 1.21 0.988 1.35 0.42 -4.131 -0.80 Example 3 2.05 3.0 2.23 0.92 0.961 1.32 0.37 -4.592 -0.81 Example 4 1.90 3.0 2.41 0.79 0.961 1.40 0.40 -4.444 -0.83 Example 5 1.70 3.0 2.69 0.63 0.927 1.27 0.31 -3.907 -0.76 Example 6 2.20 2.5 2.08 1.06 0.950 1.88 0.44 -4.795 -0.93 Example 7 2.20 4.5 2.08 1.06 0.993 1.69 0.48 -4.319 -0.73 Comparative Example 1 2.50 3.0 2.08 1.39 1.105 2.21 0.28 -6.492 -1.10 Comparative Example 2 1.50 3.0 3.05 0.49 0.893 2.36 0.88 -5.154 -1.08 Comparative Example 3 1.30 3.0 3.52 0.37 0.844 2.54 1.10 -6.435 -1.17 Comparative Example 4 1.10 3.0 4.16 0.26 0.829 2.89 1.26 -5.168 -1.25 Comparative Example 5 1.00 3.0 4.57 0.22 0.806 3.14 1.41 -6.703 -1.05 Comparative Example 6 2.20 1.0 2.08 1.06 0.661 3.72 2.59 -10.092 -1.04 Comparative Example 7 2.20 6.0 2.08 1.06 1.030 4.02 0.26 -6.416 -1.85

Usually, when determining the durability of a polarizing plate, after 500hr of 80 degreeC, the change rate of a color value (single-b) transmittance, the change rate of a dichroic ratio, the absorbance change rate in 700 nm wavelength, etc. are taken as a reference. The durability can be judged to be good when the rate of change in transmittance is 0.5% or less, the rate of change in dichroic ratio is -5.0 or less, and the amount of change in absorbance at 700 nm wavelength is 1.0 or less.

In Examples 1 to 7, when the swelling / crosslinking ratio ratio is adjusted to 0.5 to 1.3 or less, all of the Raman spectrum ratios (Vc / Vs) have a value of 0.9 to 1.0. It turns out that it is favorable. On the contrary, in Comparative Examples 1 to 7, the values of Raman spectrum ratios (Vc / Vs) are all out of the range of 0.9 to 1.0, and the durability is poor.

In particular, in Comparative Examples 6 to 7, the swelling / crosslinking ratio ratio (Rc / Rs) is in the range of 0.5 to 1.3, but the values of the Raman spectrum ratios (Vc / Vs) are all out of the range of values of 0.9 to 1.0. This is because the dyeing concentrations of Comparative Examples 6 to 7 are too low or too high, such as 1.0 mM and 6.0 mM, so that the dyeability is different. As a result, the values of Raman spectrum ratio (Vc / Vs) are all out of the range of values of 0.9 to 1.0. This is degraded. Therefore, the Raman spectrum ratio (Vc / Vs) is mainly affected by the swelling / crosslinking ratio ratio (Rc / Rs), but it can be seen that control is possible depending on the dye concentration.

When the Raman spectrum ratio (Vc / Vs) is greater than 1, as in Comparative Example 1, the change in transmittance is small, but the change in the dichroic ratio and absorbance in the long wavelength region (700 nm) was found to increase.

Therefore, as in the present invention, it can be seen that Rs / Rc is 0.5 to 1.3 or less, and the concentration of iodine in the dyeing process is excellent in durability of the polarizing plate manufactured by the polarizing plate manufacturing method of 2.0mM to 5.0mM.

The invention is not to be limited by the foregoing embodiments and the accompanying drawings, but should be construed by the appended claims. In addition, it will be apparent to those skilled in the art that various forms of substitution, modification, and alteration are possible within the scope of the present invention without departing from the technical spirit of the present invention.

Claims

In the polarizer comprising a polyvinyl alcohol-based film dyed with iodine,
160 ± 10cm of the cross-sectional thickness of the polarizer direction ^center-of Raman spectrum in the range of 160 ± 10cm ^-1 surface layer part of the La to the maximum value of the Raman spectrum in the ^first range of Vc, and the cross-sectional thickness of the polarizer direction up When the value is Vs, Vc / Vs is 0.9 to 1.0, The polarizer characterized by the above-mentioned.

Polarizer comprising a polarizer according to claim 1 and a transparent protective layer laminated on at least one surface of the polarizer.

A liquid crystal display comprising a liquid crystal panel comprising a liquid crystal cell and a polarizing plate according to claim 2 stacked on both surfaces of the liquid crystal cell.

A swelling step of swelling the polyvinyl alcohol-based film;
A dyeing step of dyeing the swollen polyvinyl alcohol-based film with iodine; And
And a crosslinking step of crosslinking the dyed polyvinyl alcohol-based film.
When the swelling draw ratio in the swelling step is referred to as Rs, and the crosslinking draw ratio in the crosslinking step is referred to as Rc, Rs / Rc is 0.5 to 1.3 or less, and the concentration of iodine is 2.0mM to 5.0mM. Manufacturing method.

The method of claim 4,
A complementary color step after the crosslinking step; And a drying step; polarizer manufacturing method comprising a.