KR20170053037A - Polarizer and method of preparing the same - Google Patents

Abstract

The present invention relates to a polarizer and a manufacturing method thereof, and more particularly to a polarizer, which has excellent optical properties and a low contractile force by having a degree of orientation of 2.5 to 4.0 and a contractile force of 3.5 N or less.

Description

POLARIZER AND METHOD OF PREPARING THE SAME [0002]

The present invention relates to a polarizer and a method of manufacturing the same, and more particularly, to a polarizer having excellent optical characteristics and small shrinkage force, and a method of manufacturing the polarizer.

Polarizing plates used in various image display devices such as a liquid crystal display (LCD), an electroluminescence (EL) display, a plasma display (PDP), a field emission display (FED) and an OLED are generally made of polyvinyl alcohol alcohol, PVA) film comprises a polarizer in which an iodine compound or a dichroic polarizing material is adsorbed and oriented, a polarizer protective film is laminated on one side of the polarizer, a polarizer protective film is provided on the other side of the polarizer, And a release film laminated in this order.

The polarizer constituting the polarizing plate is required to have basically a high transmittance and a high degree of polarization in order to provide an image excellent in color reproducibility by being applied to an image display apparatus. In order to realize this, a polarizer was prepared by modifying the polyvinyl alcohol film itself or using a non-migrating dichroic dye instead of a sublimable iodine polarizing element.

On the other hand, a polarizer usually has a polarizing function by aligning the internal molecular arrangement in a predetermined direction by stretching a polarizer-forming film produced using a polymer. Therefore, the stretching process is an indispensable step in the production of the polarizer.

However, such a stretching process causes a shrinking force to be developed when the polarizer is placed under a predetermined environment in the future, and this shrinking force causes the polarizer to be deformed. Thus, reducing the retractive force is an important consideration in making an improved polarizer.

However, since the degree of orientation increases with higher orientation, the stretching ratio must be increased in order to realize excellent polarization characteristics. On the other hand, implementation of a high degree of orientation and low shrinkage force, And there is no known polarizer that achieves both high degree of orientation and low shrinkage force.

Japanese Laid-Open Patent Application No. 2010-145866 discloses a method of producing a polarizer having a small shrinkage stress, but fails to provide a satisfactory alternative to the above problem.

Japanese Laid-Open Patent Application No. 2010-145866

An object of the present invention is to provide a polarizer having a small retraction force while maintaining a high degree of orientation and a method for producing the same.

1. A polarizer having a degree of orientation of 2.5 to 4.0 and a retractive force of 3.5 N or less.

2. The polarizer according to 1 above, wherein the degree of orientation is 3.0 to 4.0.

3. The polarizer according to item 1 above, wherein the orientation degree is obtained from the following formula:

[Equation 1]

(Wherein, A _MD is a polarized IR MD direction absorbance, A _TD is the polarized IR TD direction absorbance, A _large is the high absorption of the A _MD and A _TD, A _samll low absorbance of A _MD and A _TD being).

4. A polarizer-forming film comprising swelling, dyeing, stretching, crosslinking, complementing and drying steps,

Wherein the crosslinking step includes a first crosslinking step of stretching the polarizer forming film to 2.0 to 3.0 times and a second crosslinking step of stretching the polarizing film for forming a polarizer after the first crosslinking step to 1.0 times or less,

Wherein the film for polarizer formation is stretched at the complementary coloring step at a stretching ratio higher than the second crosslinking step and lower than the first crosslinking step.

5. The method of producing a polarizer according to 4 above, wherein the film for forming a polarizer is stretched by 0.85 to 1.0 times in the second crosslinking step.

6. The method of producing a polarizer according to 4 above, wherein the polarizer-forming film is stretched 1.02 to 1.25 times in the complementary coloring step.

7. A polarizer comprising a polarizer according to any one of claims 1 to 3 and a polarizer protective film bonded to at least one side of the polarizer.

8. An image display device comprising the polarizing plate of 7 above.

The polarizer of the present invention has a degree of orientation and shrinkage in a predetermined range, so that it can exhibit small shrinking force while having excellent optical properties without deteriorating other physical properties.

The polarizer of the present invention can produce the polarizer according to the present invention by stretching the polarizer-forming film at the stretching ratio within a specific range in the crosslinking step and the complementary coloring step. In particular, the method for producing a polarizer of the present invention can control the degree of orientation while having low shrinkage force.

The present invention relates to a polarizer having excellent optical characteristics and small shrinkage force, having a degree of orientation of 2.5 to 4.0 and a shrinkage force of 3.5 N or less, and a method for producing the same.

Hereinafter, the present invention will be described in detail.

As described above, conventionally, it is known that the high degree of orientation of the polarizer and the small retraction force are in a trade-off relationship, and an example of realizing a polarizer having an excellent degree of orientation and a small retraction force is not known.

However, the inventors of the present invention have produced a polarizer satisfying both high degree of orientation and small contracting power through the production of a polarizer capable of controlling the degree of orientation. Further, when the degree of orientation and the retraction force are adjusted to a specific range, a polarizer having a small shrinking force without deterioration of optical characteristics can be obtained.

The polarizer of the present invention may have an orientation degree of 2.5 to 4.0, preferably 3.0 to 4.0. When the degree of orientation is less than 2.5, the degree of polarization is lowered. When the degree of orientation is more than 4.0, the shrinking force is increased and the deflection of the polarizer is increased.

The degree of orientation according to the present invention can be obtained from the difference in absorbance of the polarized IR with respect to the TD and MD directions of the polarizer using FT-IR. A specific relational expression for obtaining a specific orientation degree is shown in Equation 1 below.

[Equation 1]

(Wherein, A _MD is a polarized IR MD direction absorbance, A _TD is the polarized IR TD direction absorbance, A _large is the high absorption of the A _MD and A _TD, A _samll low absorbance of A _MD and A _TD being).

The present invention also provides a method for producing the polarizer described above.

The method for producing a polarizer of the present invention includes swelling, dyeing, stretching, crosslinking, complementary coloring and drying of a film for forming a polarizer, wherein the crosslinking step includes a first crosslinking step of stretching the polarizing film to 2.0 to 3.0 times, And a second crosslinking step of stretching the film for forming a polarizer after the first crosslinking step to 1.0 times or less to alleviate the stress, wherein in the complementary coloring step, a polarizer is formed at a stretching ratio higher than the second crosslinking step and lower than the first crosslinking step The film for use is stretched. By adjusting the degree of orientation and retraction of the polarizer through the above-described control of the stretching ratio of the crosslinking step and the complementary coloring step, a high degree of orientation and a small contracting force can be realized.

The method for producing the polarizer of the present invention will be described in more detail as follows.

The polarizer-forming film for producing a polarizer may be a polymer film used for producing a polarizing plate, and a film that can be dyed by a dichroic substance (for example, iodine) known in the art may be used without any particular limitation, 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-based film, a dehydrochlorinated acid-treated polyvinyl alcohol-based film, or the like can be used. Of these, a polyvinyl alcohol-based film may be preferable in that it has an excellent effect of enhancing the uniformity of the degree of polarization in the plane and is excellent in dye affinity for iodine.

The method for producing a polarizer according to the present invention may include a swelling step, a dyeing step, a crosslinking step, a complementary coloring step, a stretching step, a washing step and a drying step, and may be classified by 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 can be used. Hereinafter, a method of manufacturing a polarizer according to an embodiment of the present invention will be described with reference to a wet drawing method, but the present invention is not limited thereto.

The steps other than the drying step may be performed 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.

<Swelling 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.

As the swelling aqueous solution, a swelling aqueous solution known in the art can be used without any particular limitation, and for example, water (pure water, deionized water) can be used alone, and a small amount of glycerin or potassium iodide is added thereto The processability can be improved with the swelling of the polymer film. The content of glycerin is preferably 5% by weight or less based on 100% by weight of the aqueous swelling solution, and the content of potassium iodide is preferably 10% by weight or less.

The temperature of the swelling bath is not particularly limited, but may be 20 to 45 캜, and may be, for example, 25 to 40 캜.

The execution time of the swelling step (swelling bath immersion time) can be applied without any particular limitation, for example, 180 seconds or less, preferably 90 seconds or less. When the immersion time is within the above range, excessive swelling and saturation can be suppressed, so that breakage due to softening of the polyvinyl alcohol film can be prevented, the adsorption of iodine can be uniformed in the dyeing step, have.

The stretching step may be carried out together with the swelling step, wherein the stretching ratio may be about 1.1 to 3.5 times, but is not limited, and preferably 1.5 to 3.0 times. If the stretching ratio is less than 1.1 times, wrinkles may occur. If the stretching ratio is more than 3.5 times, initial optical characteristics may become weak.

<Stage of dyeing>

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 aqueous solution for dyeing may be an aqueous solution for dyeing known in the art without any particular limitation, and may contain water, a water-soluble organic solvent or a mixed solvent thereof and iodine. The content of iodine may be in the range of 0.4 to 400 mmol / L in the dyeing aqueous solution, but is not limited thereto, preferably 0.8 to 275 mmol / L, and most preferably 1 to 200 mmol / L.

The dyeing aqueous solution may further contain iodide as a dissolution aid so that the dyeing efficiency can be improved. As the iodide, iodide known in the art can be used without limitation, and examples thereof include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, calcium iodide, iodide Tin, and titanium iodide. Of these, potassium iodide may be preferable in view of high solubility in water. The content of iodide may be 0.01 to 10% by weight, but is not limited to, preferably 0.1 to 5% by weight based on 100% by weight of the dyeing aqueous solution.

In addition, to increase the iodine complex content in the polyvinyl alcohol-based film, boric acid in the dye bath may be added in an amount of 0.3 to 5 wt%, but is not limited thereto. If the dye sets of boric acid than 0.3% by weight PVA-I ₃ ^- complex and PVA-I ₅ ^- and may not be effective to complex content is increased, if the dye sets of boric acid less than 5% by weight can be as high a risk of cutting.

The temperature of the dye bath may be 5 to 42 째 C, but is not limited thereto, preferably 10 to 35 째 C. The immersing time of the polyvinyl alcohol film in the dyeing bath is not particularly limited and may be 1 to 20 minutes, preferably 2 to 10 minutes.

The stretching step may be performed together with the dyeing step according to an embodiment of the present invention. The stretching ratio may be 1.01 to 2.0 times, but not limited thereto, preferably 1.1 to 1.8 times.

The cumulative stretching ratio up to the dyeing step including the swelling and the dyeing step may be 1.2 to 4.0 times. If the cumulative stretching ratio is less than 1.2 times, wrinkles of the film may occur to cause appearance defects. If the cumulative stretching ratio exceeds 4.0 times, the initial optical characteristics may be poor.

<Bridging stage>

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.

Although dichroic dyes are rarely eluted in a humidity environment, iodine molecules are often dissolved or sublimated depending on the environment when the crosslinking reaction is unstable, so that a sufficient crosslinking reaction is required. In addition, in order to improve the optical characteristics by orienting the iodine molecules positioned between the polyvinyl alcohol molecule and the molecule, it can be stretched to the greatest stretch ratio in the crosslinking step.

The method for producing a polarizer of the present invention may be such that a crosslinking step includes a first crosslinking step and a second crosslinking step and at least one of the first and second crosslinking steps may be carried out using an aqueous crosslinking solution containing a boron compound. Whereby the optical characteristics and color durability of the polarizer can be improved.

The crosslinking aqueous solution may be a crosslinked aqueous solution known in the art without any particular limitation. For example, water as a solvent and a boron compound such as boric acid and sodium borate may be contained, and an organic solvent mutually soluble with water and / Iodide may be further included.

The boron compound imparts short crosslinking and rigidity to suppress wrinkling in the process, thereby improving handling properties and forming iodine orientation.

The content of the boron compound may be a content known in the art, for example, 1 to 10% by weight, preferably 2 to 6% by weight based on 100% by weight of the aqueous crosslinking solution. When the content is less than 1% by weight, the crosslinking effect of the boron compound may be decreased and it may be difficult to impart rigidity. When the content is more than 10% by weight, the crosslinking reaction of the inorganic crosslinking agent is excessively activated, .

In this step, iodide can be used 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 0.05 to 15% by weight, but is not limited to, preferably 0.5 to 11% by weight based on 100% by weight of the aqueous crosslinking solution . If the content is less than 0.05% by weight, the iodide ion in the film may escape to increase the transmittance, and if it exceeds 15% by weight, the iodide ion in the aqueous solution may penetrate into the film and the transmittance may be decreased.

The temperature of the crosslinking bath according to an embodiment of the present invention may be 20 to 70 캜, but is not limited thereto. The immersing time of the polyvinyl alcohol-based film in the crosslinking bath may be 1 second to 15 minutes, , Preferably 5 seconds to 10 minutes.

The crosslinking step of the present invention comprises a first and a second crosslinking step, and the stretching step is carried out together.

The stretching ratio of the first crosslinking step may be 2.0 to 3.0 times, preferably 2.2 to 2.8 times. The first crosslinking step according to the present invention enhances the mechanical properties of the polarizer by stretching the polarizer-forming film at a high stretching ratio and prevents the polarizer-forming film from being cut in the subsequent second crosslinking step. If the stretching ratio of the first crosslinking step is less than 2.0 times, the desired degree of orientation is not exhibited and the mechanical properties are not secured. If the stretching ratio is more than 3.0 times, the contracting force may increase.

The stretching ratio of the second crosslinking step may be 1.0 or less, preferably 0.85 to 1.0, and more preferably 0.9 to 1.0. The second crosslinking step according to the present invention is a step of relaxing the stress generated in the first crosslinking step and preventing the polarizer forming film from being cut and reducing the shrinking force. If the stretching ratio of the second crosslinking step exceeds 1.0 times, there is a problem that the film may be cut and the shrinkage force is increased.

Also, the cumulative stretching ratio of the first and second crosslinking steps may be 1.5 to 3.0 times, preferably 1.98 to 2.8 times. If the cumulative stretching ratio is less than 1.5 times, the polyvinyl alcohol alignment effect may be insufficient. If the cumulative stretching ratio is more than 3.0 times, the stress due to stretching may increase and the contraction force may increase.

<Complementary phase>

The complementary step is a step of stabilizing the iodine complex by orienting the iodine complex positioned between the molecule and the molecule near the bridge of the boric acid in a polyvinyl alcohol film on which the iodine complex is physically adsorbed. Also, the color of the polyvinyl alcohol-based film on which the iodine complex is not satisfactory in the crosslinking step can be corrected through the complementary coloring step.

The complementary color aqueous solution for the complementary color step may further comprise, for example, water as a solvent and boric acid, and an organic solvent and an iodide mutually soluble together with water.

The boron compound according to an embodiment of the present invention may shorten cross-linking and rigidity to suppress wrinkling in the process, thereby improving handleability and forming iodine orientation.

The content of the boron compound may be 1 to 10% by weight based on 100% by weight of the aqueous solution for complementary color, but is not limited thereto, and preferably 2 to 6% by weight. If the content is less than 1% by weight, the crosslinking effect of the boron compound may be reduced and the polarizer may not be rigid. If the content is more than 10% by weight, the crosslinking reaction of the inorganic crosslinking agent is excessively activated and the crosslinking reaction of the organic crosslinking agent is effectively It can be difficult to proceed.

In this step, iodide can be used 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. The content of iodide may be 0.05 to 15% by weight based on 100% by weight of the aqueous solution for complementary color, but is not limited thereto, preferably 0.5 to 11% Lt; / RTI &gt; If the content is less than 0.05% by weight, the iodide ion in the film may escape to increase the transmittance of the polarizer, and if it exceeds 15% by weight, the iodide ion in the aqueous solution may penetrate into the film and transmittance of the polarizer may decrease.

The temperature of the complementary color bath according to an embodiment of the present invention may be 20 to 70 ° C, and the immersion time of the polyvinyl alcohol film in the sub-color bath may be 1 second to 15 minutes, but is not limited thereto, 5 seconds to 10 minutes.

The complementary coloring step according to the present invention is performed together with the stretching step, wherein the stretching ratio of the complementary coloring step is higher than that of the second crosslinking step and lower than that of the first crosslinking step. The complementary coloring step according to the present invention realizes a high degree of orientation by stretching the film for forming a polarizer at a relatively high stretching ratio, thereby maintaining a small contracting force while improving optical characteristics.

More specific examples of the stretching ratio of the complementary color step may be 1.01 to 1.25, and preferably 1.05 to 1.20. The effect of the complementary color step described above can be excellently exhibited in the range of the draw ratio. If the stretching ratio is less than 1.01 times, the iodine complex stabilization and the degree of orientation of polyvinyl alcohol may be lowered. If the stretching ratio is more than 1.25 times, excessive stretching may cause breakage of the film and production efficiency may be lowered.

<Stretching step>

In the present invention, the stretching step may be performed simultaneously with the crosslinking step and the complementary coloring step, as described above, or may be performed together with other steps, and may be additionally performed as a separate step.

According to the production method of the present invention, it is preferable that the total cumulative stretching ratio of the polarizer is 5.0 times or more, for example, it may be preferably 5.0 to 7.0 times, and more preferably 5.3 to 6.0 times.

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

<Washing step>

In the method for producing a polarizer of the present invention, if necessary, the crosslinked and stretched polyvinyl alcohol film is immersed in a water bath filled with an aqueous solution for washing to remove unnecessary residues such as boric acid attached to the polyvinyl alcohol film in the previous steps And a water washing step of removing water.

The aqueous solution for washing according to an embodiment of the present invention can be used without any particular limitation, and can be, for example, water, and iodide may be further added thereto, but the present invention is not limited thereto .

The temperature of the water bath according to an embodiment of the present invention may be 10 to 60 캜, but is not limited thereto, and may be preferably 15 to 40 캜.

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

<Drying step>

In the manufacturing method of the present invention, the drying step is a step of drying the washed polyvinyl alcohol-based film, and the orientation of the molecules of the iodine dyed in the neck-in by drying is further improved, .

As the drying method, a drying method known in the art can be used in combination without limitation. For example, natural drying, hot air drying, air drying, heat drying, far infrared ray drying and microwave drying can be used. Microwave drying which activates only water in the film to dry it is newly used, and usually, hot air drying is mainly used.

In the hot-air drying, the temperature is not particularly limited, but it is preferably carried out at a relatively low temperature in order to prevent deterioration of the polarizer. For example, it may be 20 to 90 ° C, preferably 80 ° C or less, Deg.] C or less.

The execution time of the hot air drying is not particularly limited, and may be, for example, 1 to 10 minutes.

The polarizer according to the present invention may be provided as a polarizer by bonding a polarizer protective film to at least one side thereof.

The type of the protective film is not particularly limited as long as it is a film excellent in transparency, mechanical strength, thermal stability, moisture barrier property, isotropy, etc. Specific examples thereof include polyester type such as polyethylene terephthalate, polyethylene isophthalate and polybutylene terephthalate Suzy; Cellulose-based resins such as diacetylcellulose and triacetylcellulose; Polycarbonate resin; Polyacrylic 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, cycloolefins or norbornene structures, polyolefins and ethylene propylene copolymers; 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. Further, the protective film may have the function of the optical layer described below.

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.

The bonding of the polarizer and the polarizer protective film can be carried out using an adhesive composition. The bonding of the polarizing film and the protective film using the adhesive composition can be carried out by an appropriate method. For example, the polarizing film and / or the polarizing film can be bonded by a flexible method, a Meyer bar coating method, a gravure coating method, a die coating method, an immersion coating method, Or a method in which an adhesive composition is applied to the adhesive surface of the protective film and the both are overlapped. The flexible method is a method in which an adhesive composition is applied to a surface of a polarizing film or a protective film, which is a material to be coated, while moving the film in a generally vertical direction, usually in a horizontal direction, or in an inclined direction therebetween.

After applying the adhesive composition, the polarizing film and the protective film are sandwiched by a nip roll.

Further, in order to improve the adhesiveness, the surface of the polarizing film and / or the protective film may be appropriately subjected to surface treatment such as plasma treatment, corona treatment, ultraviolet ray irradiation treatment, frame treatment and saponification treatment. As the saponification treatment, a method of immersing in an aqueous solution of an alkali such as sodium hydroxide, potassium hydroxide or the like may be mentioned.

After the polarizing film and the polarizer protective film are laminated, a drying treatment is performed. The drying treatment is carried out, for example, by spraying hot air, but the temperature at that time is suitably selected in the range of 50 to 100 degrees. The drying time is usually 30 to 1,000 seconds.

The polarizing plate according to the present invention can be applied to various image display devices such as an organic light emitting display (OLED), a plasma display, and a field emission display as well as a conventional liquid crystal display.

It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to be illustrative of the invention and are not intended to limit the scope of the claims. It will be apparent to those skilled in the art that such variations and modifications are within the scope of the appended claims.

Example

A transparent unoriented polyvinyl alcohol film (PE60, manufactured by KURARAY Co.) having a degree of saponification of 99.9% or more was immersed in water (deionized water) at 25 DEG C for 1 minute and 20 seconds to swell, followed by 1.25 mM / L of iodine and 1.25% And 0.3% by weight of boric acid was dipped in an aqueous solution for dyeing at 30 DEG C for 2 minutes and 30 seconds. At this time, stretching was performed at a stretching ratio of about 1.7184 times and about 1.5214 times at the swelling and dyeing stages, respectively, and the stretching ratio was increased to 2.614 times to the dyeing bath. Subsequently, the substrate was immersed in an aqueous solution for crosslinking at 56 ° C containing 13.9% by weight of potassium iodide and 3% by weight of boric acid for 26 seconds to effect crosslinking (first crosslinking step) and stretching at a draw ratio of 2.36 times. Thereafter, the substrate was immersed in a crosslinking aqueous solution at 56 ° C containing 13.9% by weight of potassium iodide and 3% by weight of boric acid for 20 seconds and crosslinked (second crosslinking step), and stretched at a stretching ratio of 0.90.

Then, it was stretched by 1.08 times while immersing for 10 seconds in a complementary color aqueous solution at 40 캜 containing 5% by weight of potassium iodide and 2% by weight of boric acid.

At this time, the total cumulative stretching ratio of the swelling, dyeing, crosslinking, and complementary phases was six times. After completion of the crosslinking, the polyvinyl alcohol film was washed with deionized water and then dried in an oven at 80 DEG C for 5 minutes to prepare a polarizer having a transmittance of 42.5%.

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

Example  2 to 16 and Comparative Example  One

A polarizing plate was prepared in the same manner as in Example 1 except that the stretching ratio was adjusted as shown in Table 1 below.

division To dyeing tank
Cumulative stretch ratio 1 set of bridging 2 sets of bridging Bose Hue
Stretching cost all
Cumulative draw ratio Example 1 2.61 2.36 0.90 1.08 5.99 Example 2 2.61 2.50 0.85 1.08 6.00 Example 3 2.61 2.23 0.95 1.08 5.97 Example 4 2.61 2.20 0.97 1.08 6.02 Example 5 2.61 2.23 0.98 1.05 6.00 Example 6 2.61 2.23 0.90 1.15 6.02 Example 7 2.61 2.15 0.90 1.19 6.01 Example 8 2.61 2.00 0.92 1.25 6.00 Example 9 2.25 2.82 0.90 1.05 6.00 Example 10 2.05 3.00 0.85 1.15 6.01 Comparative Example 1 2.61 1.90 1.19 1.02 6.02 Comparative Example 2 2.61 1.90 1.10 1.25 6.82 Comparative Example 3 2.61 2.55 0.95 0.95 6.01 Comparative Example 4 2.05 2.2 1.1 1.21 6.00 Comparative Example 5 2.61 1.90 1.00 1.21 6.00 Comparative Example 6 2.05 3.2 0.80 1.15 6.04

Test Example

The physical properties of the polarizers prepared in the above Examples and Comparative Examples were measured by the following methods, and the results are shown in Table 2 below.

1. Optical properties (polarization degree)

The prepared polarizer was cut into a size of 4 cm x 4 cm and the transmittance was measured using an ultraviolet-visible light spectrometer (V-7100, manufactured by JASCO). At this time, the polarization degree is defined by the following equation (2).

&Quot; (2) &quot;

Degree of polarization _{(P) = [(T 1} - T 2) / (T 1 + T 2)] 1/2

(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. Orientation

The prepared polarizer was cut into a size of 4 cm x 4 cm and the IR beam was polarized using a polarized ATR apparatus (VeeMAX III, PIKE, incident angle: 45 °), and the polarized IR beam and the MD direction of the polarizer sample were parallel FT-IR is measured (MDTE) (Nicolet Continuum XL, Thermo). The FT-IR is measured (TDTE) parallel to the TD direction of the polarized sample and the polarized IR beam.

When the molecules are arranged, the vibration direction is also arranged in one direction, and the arranged vibration is absorbed when the IR beam is hit. In this principle, the absorbance at 1290 cm ^-1 , which shows the difference in absorbance in the MD and TD directions, was measured.

The measured absorbance was substituted into the above equation (1) to obtain the degree of orientation.

3. Shrinkage

The polarizers prepared in Examples and Comparative Examples were cut into a size of 3.0 cm x 2 mm and then measured for shrinkage force at 80 DEG C for 4 hours with DMA Q800 (Dynamic mechanical analyzer, TA). At this time, the pre-load was used to measure the pre-load to maintain the polarizer before the measurement.

division Polarization degree (%) Orientation Shrinkage (N) Example 1 99.996 3.20 2.90 Example 2 99.993 3.00 2.70 Example 3 99.997 3.34 3.00 Example 4 99.997 3.36 3.05 Example 5 99.996 3.35 3.01 Example 6 99.995 3.29 2.96 Example 7 99.996 3.30 3.20 Example 8 99.997 3.63 3.41 Example 9 99.992 2.85 2.71 Example 10 99.992 2.91 2.80 Comparative Example 1 99.995 3.20 3.91 Comparative Example 2 99.997 3.87 4.82 Comparative Example 3 99.983 2.40 2.57 Comparative Example 4 99.997         4.10 4.2 Comparative Example 5 99.995 3.58 3.89 Comparative Example 6 99.977 2.45 2.7

Referring to Table 2, it can be confirmed that the polarizers of the present invention satisfy both the high degree of orientation and the small retraction, and thus the polarization degree is also excellent.

However, in the comparative examples, it can be seen that when the degree of polarization is high, the shrinking force is high, and when the shrinking force is low, the degree of polarization is low.

Claims (8)

A degree of orientation of 2.5 to 4.0 and a retractive force of 3.5 N or less.
The polarizer according to claim 1, wherein the orientation degree is 3.0 to 4.0.
[2] The polarizer according to claim 1,
[Equation 1]

(Wherein, A _MD is a polarized IR MD direction absorbance, A _TD is the polarized IR TD direction absorbance, A _large is the high absorption of the A _MD and A _TD, A _samll low absorbance of A _MD and A _TD being).
A step of swelling, dyeing, stretching, crosslinking, complementing and drying the film for forming a polarizer,
Wherein the crosslinking step includes a first crosslinking step of stretching the polarizer-forming film to 2.0 to 3.0 times and a second crosslinking step of stretching the polarizer-forming film after the first crosslinking step to 1.0 times or less,
And the film for polarizer formation is stretched at the complementary coloring step at a higher stretching ratio than the second crosslinking step and lower than the first crosslinking step.
5. The method of producing a polarizer according to claim 4, wherein the film for forming a polarizer is stretched by 0.85 to 1.0 times in the second crosslinking step.
5. The method of producing a polarizer according to claim 4, wherein the polarizer-forming film is stretched 1.02 to 1.25 times in the complementary coloring step.
A polarizer comprising a polarizer according to any one of claims 1 to 3 and a polarizer protective film bonded to at least one side of the polarizer.
An image display device comprising the polarizer of claim 7.