KR102530227B1 - Polarizer and production method therefor - Google Patents

Abstract

A polarizer satisfies the following expression.
0.7≤A700/A480≤1.0
A700=-Log ₁₀ {(T _{MD , 700} × T _{TD , 700} )/10000}
A480=-Log ₁₀ {(T _{MD , 480} × T _{TD , 480} )/10000}
T _{MD , 700} and T _{TD , 700} are the transmittance at a wavelength of 700 nm obtained when the polarizer is placed in a state where the absorption axis of the polarizer is orthogonal to and parallel to the linearly polarized light of the measurement light, T _{MD , 480} and T _{TD and 480} are transmittances at a wavelength of 480 nm obtained when the polarizer is disposed in a state in which the absorption axis of the polarizer is orthogonal to and parallel to the linearly polarized light of the measurement light, respectively, and these units are all %.

Description

Polarizer and its manufacturing method {POLARIZER AND PRODUCTION METHOD THEREFOR}

The present invention relates to a polarizer and a manufacturing method thereof.

Polarizers used in various image display devices such as liquid crystal display (LCD), electroluminescence (EL) display, plasma display (PDP), field emission display (FED), and organic light emitting diode (OLED) are generally It includes a polarizer in which an iodine-based compound or a dichroic polarizing material is adsorbed and oriented on a polyvinyl alcohol (PVA)-based film, and a polarizer protective film is laminated on one side of the polarizer, and a polarizer protective film on the other side of the polarizer. , It has a multilayer structure in which an adhesive layer bonded to a liquid crystal cell and a release film are sequentially laminated.

A polarizer constituting a polarizing plate is applied to an image display device and is required to have both high transmittance and polarization degree in order to provide an image with excellent color reproducibility. In addition, as the application of image display devices to each field expands and the trend of large size becomes more pronounced, there are cases in which various image display devices such as liquid crystal displays are used for a long time in a high temperature state, resulting in poor polarization performance and optical performance. Along with the improvement, the demand for improved durability has also increased, and as a result, the conditions for the performance of the polarizer have become very strict. In addition, image display devices having characteristics suitable for various environments and uses are currently required, and optical durability including color change under high temperature and high humidity conditions and high contrast through high orientation and high transmittance are required.

Korean Patent Publication No. 2009-70085 discloses a method for manufacturing a polarizer, but failed to present an alternative to the above problems.

Korean Patent Publication No. 2009-70085

An object of the present invention is to provide a polarizer having improved color durability and excellent polarization degree.

Another object of the present invention is to provide a method for manufacturing a polarizer having improved color durability and excellent polarization degree.

1. A polarizer that satisfies Expression 1 below.

0.7≤A700/A480≤1.0 (1)

In the formula, A700 is defined by the following formula 2,

A700=-Log ₁₀ {(T _{MD , 700} × T _{TD , 700} )/10000} (2)

T _{MD , 700} is the transmittance at a wavelength of 700 nm obtained when the polarizer is arranged in a state in which the absorption axis of the polarizer is orthogonal to the linearly polarized light of the measurement light,

T _{TD , 700} is the transmittance at a wavelength of 700 nm obtained when the polarizer is placed in a state in which the absorption axis of the polarizer is parallel to the linearly polarized light of the measurement light, and these units are all %,

A480 is defined by Equation 3 below,

A480=-Log ₁₀ {(T _{MD , 480} × T _{TD , 480} )/10000} (3)

T _{MD , 480} is the transmittance at a wavelength of 480 nm obtained when the polarizer is placed in a state in which the absorption axis of the polarizer is orthogonal to the linearly polarized light of the measurement light;

T _{TD , 480} is the transmittance at a wavelength of 480 nm obtained when the polarizer is placed in a state where the absorption axis of the polarizer is parallel to the linearly polarized light of the measurement light, and all units are %.

2. The polarizer according to 1 above, wherein the polarizer contains a metal salt.

3. The polarizer according to 2 above, wherein the metal salt is at least one selected from the group consisting of zinc nitrate, copper nitrate, aluminum nitrate, magnesium nitrate, and zinc acetate.

4. The polarizer according to 2 above, wherein the metal salt is included in an amount of 0.05 to 1.5% by weight based on the total weight of the polarizer.

5. A polarizing plate having a protective layer on at least one surface of the polarizer of any one of items 1 to 4 above.

6. The polarizing plate according to 5 above, wherein the protective layer is a protective film or a resin coating layer.

7. An image display device having the polarizing plate of 5 above.

8. Swelling, dyeing, crosslinking, complementary color and stretching the film for forming a polarizer;

In the dyeing step, the distance between crystals in the film for forming a polarizer in the stretching direction is 20 to 40 nm;

The dye solution contains a boric acid compound;

A method for producing a polarizer using a crosslinking solution and a complementary color solution containing a metal salt, respectively, in the crosslinking and complementary color steps.

9. The method of manufacturing a polarizer according to 8 above, wherein the stretching direction is an MD direction.

10. The method of producing a polarizer according to 8 above, wherein the boric acid compound is included in 0.3 to 5% by weight of the total weight of the dyeing solution.

11. The method for producing a polarizer according to 8 above, wherein the cumulative stretch ratio until the end of the dyeing step is 2.0 to 3.0 times.

12. The method of producing a polarizer according to 8 above, wherein the crosslinking solution contains a boric acid compound, and the concentration of the boric acid compound in the dyeing solution in the dyeing step is lower than the concentration of the boric acid compound in the crosslinking solution in the crosslinking step.

13. The method for producing a polarizer according to 8 above, wherein the crosslinking step includes at least first and second crosslinking steps.

14. The method for producing a polarizer according to 8 above, wherein the metal salt is at least one selected from the group consisting of zinc nitrate, copper nitrate, aluminum nitrate, magnesium nitrate and zinc acetate.

15. The method for producing a polarizer according to 8 above, wherein the metal salt is included in 0.5 to 4% by weight based on the total weight of the crosslinking solution.

16. The method of producing a polarizer according to 8 above, wherein the metal salt is included in 0.5 to 4% by weight of the total weight of the complementary color solution.

17. The method of manufacturing a polarizer according to 8 above, wherein the polarizer manufactured by the manufacturing method satisfies Expression 1 below.

0.7≤A700/A480≤1.0 (1)

In the formula, A700 is defined by the following formula 2,

A700=-Log ₁₀ {(T _{MD , 700} × T _{TD , 700} )/10000} (2)

T _{MD , 700} is the transmittance at a wavelength of 700 nm obtained when the polarizer is arranged in a state in which the absorption axis of the polarizer is orthogonal to the linearly polarized light of the measurement light,

T _{TD , 700} is the transmittance at a wavelength of 700 nm obtained when the polarizer is placed in a state in which the absorption axis of the polarizer is parallel to the linearly polarized light of the measurement light, and these units are all %,

A480 is defined by Equation 3 below,

A480=-Log ₁₀ {(T _{MD , 480} × T _{TD , 480} )/10000} (3)

T _{MD , 480} is the transmittance at a wavelength of 480 nm obtained when the polarizer is placed in a state in which the absorption axis of the polarizer is orthogonal to the linearly polarized light of the measurement light;

T _{TD , 480} is the transmittance at a wavelength of 480 nm obtained when the polarizer is placed in a state where the absorption axis of the polarizer is parallel to the linearly polarized light of the measurement light, and all units are %.

The polarizer of the present invention has improved color durability and can minimize color change even when exposed to high temperature conditions for a long time.

Moreover, the polarizer of this invention is excellent in polarization degree.

In addition, the method of the present invention can manufacture a polarizer having improved color durability and excellent polarization degree.

The present invention relates to a polarizer having improved color durability and excellent optical properties and a manufacturing method thereof by satisfying Equation 1.

Hereinafter, the present invention will be described in detail.

<Polarizer>

The PVA (polyvinyl alcohol)-based polarizer includes a PVA-I ₅ complex, and under high temperature and high humidity conditions, the PVA-I ₅ complex area is reduced and the PVA-I ₅ complex becomes unstable, so that the PVA-I ₅ complex is decomposed, The content of the PVA-I ₅ complex in the region absorbing light of 700 nm or more is reduced. Accordingly, the stability of the dichroic material complex may decrease, and the polarizer may be discolored (decreased durability).

On the other hand, the PVA-based polarizer also includes a PVA-I ₃ complex, and the PVA-I ₃ complex contributes to the expression of the degree of polarization.

Therefore, it is determined that it is necessary to appropriately maintain the contents of the PVA-I ₅ complex and the PVA-I ₃ complex in the polarizer.

However, during manufacture of the polarizer, iodine is added as iodine molecules or iodine salts, and is converted to I ₃ ^- or I ₅ ^- depending on the specific environment or conditions of the chemical bath (dyeing bath, crosslinking bath, and/or complementary coloring bath) to form PVA and Since a complex is formed, it is difficult to directly control the content (concentration) of I ₃ ^- or I ₅ ^- .

Accordingly, the inventors of the present invention found that A700 of the polarizer is related to the PVA-I ₅ complex content and A480 is related to the PVA-I ₃ complex content, and in particular, the ratio of A700 and A480 makes the polarizer have a good degree of polarization. The present invention was devised with attention to being an indicator that can indicate the PVA-I ₅ complex content and the PVA-I ₃ complex content, which prevent discoloration even under high temperature and high humidity conditions while maintaining color change.

The polarizer of the present invention maintains very good polarization degree, optical characteristics and durability by satisfying the following formula 1.

0.7≤A700/A480≤1.0 (1)

In the formula, A700 is defined by the following formula 2,

A700=-Log ₁₀ {(T _{MD , 700} × T _{TD , 700} )/10000} (2)

T _{MD , 700} is the transmittance at a wavelength of 700 nm obtained when the polarizer is arranged in a state in which the absorption axis of the polarizer is orthogonal to the linearly polarized light of the measurement light,

T _{TD , 700} is the transmittance at a wavelength of 700 nm obtained when the polarizer is placed in a state in which the absorption axis of the polarizer is parallel to the linearly polarized light of the measurement light, and these units are all %,

A480 is defined by Equation 3 below,

A480=-Log ₁₀ {(T _{MD , 480} × T _{TD , 480} )/10000} (3)

T _{MD , 480} is the transmittance at a wavelength of 480 nm obtained when the polarizer is placed in a state in which the absorption axis of the polarizer is orthogonal to the linearly polarized light of the measurement light;

T _{TD , 480} is the transmittance at a wavelength of 480 nm obtained when the polarizer is placed in a state where the absorption axis of the polarizer is parallel to the linearly polarized light of the measurement light, and all units are %. That is, T _MD and T _TD are transmittances when linearly polarized light of a specific wavelength is incident on the polarizer in a specific direction, respectively.

If the value of A700/A480 of the polarizer is less than 0.7, the degree of polarization may decrease, and if the value of A700/A480 exceeds 1, the orthogonal color b may approach blue, resulting in a defect. A700/A480 may be greater than or equal to 0.73 or greater than or equal to 0.80. A700/A480 may be less than or equal to 0.95, and may be less than or equal to 0.90.

A polarizer satisfying Equation 1 may be achieved in a variety of ways. For example, the characteristics of the polarizer-forming film, the use of a crosslinking solution or complementary solution containing a metal salt in the manufacture of a polarizer, the concentration of a boric acid compound in a crosslinking solution or a complementary solution, the temperature, the concentration of a boric acid compound in a dyeing solution, or the stretching ratio adjustment It can be achieved through methods such as

Among them, taking the case of using a metal salt as an example, in the case of using a cross-linking solution and a complementary color solution containing a metal salt when manufacturing a polarizer, the metal salt and the PVA-I ₅ complex are chemically bonded to form the PVA-I ₅ complex. By being stabilized, the PVA-I ₅ complex is not decomposed, and the occurrence of red stool can be suppressed.

Any metal salt capable of preventing decomposition of the PVA-I ₅ complex through chemical bonding with the PVA-I ₅ complex may be used without particular limitation. Specific examples include zinc nitrate, copper nitrate, aluminum nitrate, magnesium nitrate, and zinc acetate. Among them, zinc nitrate is preferred in terms of improving durability.

The metal salt may be included in an amount of 0.05 to 1.5% by weight based on the total weight of the polarizer, preferably 0.1 to 1% by weight. Within the above range, the color durability and optical properties of the polarizer may be well maintained.

<Method for manufacturing polarizer>

In addition, the present invention provides a method for manufacturing a polarizer according to the present invention described above.

The method for manufacturing a polarizer according to the present invention includes the steps of swelling, dyeing, crosslinking, complementing, and stretching a film for forming a polarizer, and at the end of the dyeing step, the distance between crystals in the film for forming a polarizer in the stretching direction is 20 to 40 nm , The dye solution contains a boric acid compound, and by using a crosslinking solution and a complementary solution containing a metal salt in the crosslinking and complementary color steps, respectively, it is possible to prepare a polarizer with minimized color change even when exposed to high temperature conditions for a long period of time.

In general, iodine and iodine salt are added to the dyeing solution in the dyeing step of the manufacturing process of the polarizer. At this time, when manufacturing the transmittance to be high, there is a problem that the polarization degree cannot be solved. Boric acid during the manufacturing process of the polarizer When the cross-linking step is performed by including the compound in the cross-linking liquid, the stability of the dichroic material complex is lowered, resulting in a change in color or lower durability of the polarizer.

However, in the manufacturing method of the polarizer of the present invention, at the end of the dyeing step, the distance between crystals in the polarizer-forming film (polymer) in the stretching direction is 20 to 40 nm, and the dye solution contains a boric acid compound, so that boric acid before the crosslinking reaction is performed The retention time of the compound is improved, and the initial polarization degree is improved by increasing the complex formation rate of iodine, which is a dichroic material, in the film for forming a polarizer. When the distance between crystals is out of the above range or the dye solution does not contain a boric acid compound, problems such as discoloration of the polarizer, decrease in durability, and decrease in initial polarization may occur.

In addition, the method for producing a polarizer of the present invention uses a crosslinking solution and a complementary solution containing a metal salt in the crosslinking and complementary steps, respectively, so that the metal salt and the dichroic material complex are chemically bonded to stabilize the dichroic material complex. Since the complex is not decomposed, the occurrence of red stool is suppressed.

Therefore, according to the manufacturing method of the polarizer of the present invention, it is possible to manufacture a polarizer in which color change is minimized even when exposed to high temperature conditions for a long period of time.

Hereinafter, one embodiment of the manufacturing method of the polarizer of the present invention will be described in more detail. Hereinafter, the embodiments of the manufacturing method of the present invention serve to further understand the technical idea of the present invention together with the contents of the above-described invention, so the present invention should not be construed as being limited to the matters described in the following embodiments.

The number of repetitions of each manufacturing step of the polarizer of the present invention, process conditions, etc. are not particularly limited as long as they do not deviate from the object of the present invention, and the stretching step is performed as an independent step, or one or more steps of swelling, dyeing, and crosslinking steps and may be performed simultaneously.

The type of film for forming a polarizer is not particularly limited as long as it is a dichroic material, that is, a film that can be dyed with iodine, and the like. For example, a polyvinyl alcohol film, a partially saponified polyvinyl alcohol film; hydrophilic polymer films such as polyethylene terephthalate films, ethylene-vinyl acetate copolymer films, ethylene-vinyl alcohol copolymer films, cellulose films, and partially saponified films thereof; or a polyene oriented film such as a dehydrated polyvinyl alcohol-based film or a dehydrochloric acid-treated polyvinyl alcohol-based film. Among these, a polyvinyl alcohol-based film is preferable in that it has an excellent effect of reinforcing the uniformity of polarization degree in the plane and an excellent dyeing affinity for iodine.

swelling stage

In the swelling step, the unstretched film for forming a polarizer is immersed in a swelling tank filled with an aqueous solution for swelling before dyeing to remove impurities such as dust and antiblocking agents deposited on the surface of the film for forming a polarizer, and the film for forming a polarizer This is a step for improving the physical properties of the polarizer by swelling to improve the drawing efficiency and suppressing the dyeing non-uniformity.

As the aqueous solution for swelling, usually water (pure water, deionized water) alone may be used, or a small amount of glycerin may be added to improve processability of the polymer film.

When glycerin is included, its content is not particularly limited, and may be, for example, 5% by weight or less of the total weight of the aqueous solution for swelling.

The temperature of the swelling tank is not particularly limited, and may be, for example, 20 to 45°C, preferably 20 to 40°C. When the temperature of the swelling tank is within the above range, the subsequent stretching and dyeing efficiency is excellent, and expansion of the film due to excessive swelling can be prevented.

The duration of the swelling step (immersion time in the swelling tank) is not particularly limited, and may be, for example, 180 seconds or less, preferably 90 seconds or less. When the swelling tank immersion time is within the above range, excessive swelling can be suppressed from becoming saturated, preventing breakage due to softening of the film for forming a polarizer, and adsorption of iodine becomes uniform in the dyeing step to improve polarization. can

The swelling step and the stretching step may be performed together, and in this case, the stretching ratio may be about 1.1 to 3.5 times, preferably 1.5 to 3.0 times. If the stretch ratio is less than 1.1 times, wrinkles may occur, and if it exceeds 3.5 times, initial optical properties may be deteriorated.

In the swelling step, an expander roll, a spiral roll, a crown roll, a cross guider, a band bar, or the like may be installed in the bath and/or at the entrance and exit of the bath.

staining step

The dyeing step is a step of adsorbing iodine to the film for forming a polarizer by immersing the film for forming a polarizer in a dyeing tank filled with a dye containing a dichroic material, for example, iodine.

At the end of the dyeing step of the present invention, the distance between crystals in the film (polymer) for forming a polarizer in the stretching direction is 20 to 40 nm, preferably 20 to 35 nm, more preferably 20 to 32 nm, and the dye solution is boric acid By including the compound, the retention time of the boric acid compound before performing the crosslinking reaction can be improved, thereby increasing the PVA-I ₅ complex and PVA-I ₃ complex formation rate of the film for forming a polarizer. Accordingly, the color durability of the polarizer can be improved and the degree of polarization is improved.

Also, the stretching direction is preferably an MD direction. MD direction is the longitudinal direction (vertical direction) of the film for polarizer formation, and is also the conveyance direction of the film for polarizer formation in the manufacturing method of this invention.

At the end of the dyeing step, the distance between crystals in the film for forming the polarizer in the stretching direction can be achieved by adjusting the type of polarizing protective film or the stretching ratio, and preferably, the cumulative stretching ratio at the end of the dyeing step is 2.0 to 3.0 times. A method of adjusting within the range can be used.

The type of the boric acid compound is not particularly limited, and examples of the boric acid compound include boric acid, sodium borate, potassium borate, and lithium borate. These can be used individually or in mixture of 2 or more types, respectively.

The concentration of the boric acid compound in the dyeing solution is not particularly limited, but may be, for example, 0.3 to 5% by weight, preferably 0.5 to 3% by weight, based on the total weight of the dyeing solution. If the concentration of the boric acid compound in the dyeing solution is less than 0.3% by weight, the effect of increasing the formation of iodine complexes is reduced, and if it exceeds 5% by weight, cutting may occur due to stress increase.

In addition, the boric acid compound in the dye solution may be included to have a lower concentration than the boric acid compound added to the crosslinking solution of the crosslinking step performed thereafter.

The dye solution may further contain water, a water-soluble organic solvent, or a mixed solvent thereof and iodine. The concentration of iodine in the staining solution may be 0.4 to 400 mmol/L, preferably 0.8 to 275 mmol/L, and more preferably 1 to 200 mmol/L.

The dye solution may further contain iodide as a solubilizing agent for the purpose of improving dyeing efficiency.

The type of iodide is not particularly limited, and examples thereof include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and titanium iodide. , potassium iodide is preferred in view of its high solubility in water. These can be used individually or in mixture of 2 or more types.

The content of iodide is not particularly limited, and may be, for example, 0.01 to 10% by weight, preferably 0.1 to 5% by weight, based on the total weight of the dye solution.

The temperature of the dye bath is not particularly limited, and may be, for example, 5 to 42°C, preferably 10 to 35°C.

The time for immersing the film for polarizer formation in the dye bath is not particularly limited, and may be, for example, 1 to 20 minutes, preferably 2 to 10 minutes.

The stretching step may be performed together with the dyeing step, and in this case, the stretching ratio may be 1.01 to 2.0 times, preferably 1.1 to 1.8 times.

In addition, the cumulative stretching ratio of the polarizer until the end of the dyeing step including the swelling and stretching step is preferably 2.0 to 3.0 times. The distance between crystals according to the present invention can be expressed within the above range, and it is possible to solve the problem of appearance defects due to wrinkles of the film or deterioration of initial optical properties.

bridging step

The crosslinking step is a step of fixing the adsorbed iodine molecules by immersing the dyed film for forming a polarizer in a crosslinking solution so that the dyeability by the physically adsorbed iodine molecules is not lowered by the external environment.

Since the crosslinking solution used in the crosslinking step of the present invention contains a metal salt, since the metal salt and the dichroic material complex are chemically bonded, durability can be improved by suppressing the mechanism of changing the color of the polarizer.

When the crosslinking reaction of iodine, which is a dichroic dye, is unstable, iodine molecules may be desorbed due to a moist heat environment, so a sufficient crosslinking reaction is required.

The crosslinking step according to the present invention may be performed in a first crosslinking step and a second crosslinking step, and a metal salt may be included in the crosslinking liquid used in at least one of the crosslinking steps.

The metal salt may be used without particular limitation as described above, but specific examples include zinc nitrate, copper nitrate, aluminum nitrate, magnesium nitrate, zinc acetate, and the like, and zinc nitrate is preferable in terms of durability improvement.

The concentration of the metal salt in the crosslinking solution is not particularly limited, but may be, for example, 0.5 to 4% by weight of the total weight of the crosslinking solution. When the concentration of the metal salt in the cross-linking solution is less than 0.5% by weight, color change, in particular, the effect of suppressing the occurrence of redness does not appear, and when it exceeds 4% by weight, problems such as a decrease in polarization and color defects may occur.

The crosslinking liquid of the present invention may further contain a boric acid compound. By including a boric acid compound, crosslinking efficiency can be improved to suppress wrinkles of the film during the process, and optical properties can be improved by forming orientation of the dichroic material.

The concentration of the boric acid compound in the crosslinking solution is not particularly limited, but may be, for example, 1 to 10% by weight, preferably 2 to 6% by weight, based on the total weight of the crosslinking solution. If the concentration of the boric acid compound in the crosslinking solution is less than 1% by weight, the crosslinking effect may be reduced and the orientation of the film may deteriorate, and if the concentration exceeds 10% by weight, cutting may occur due to excessive crosslinking.

The boric acid compound may be the same as that used in the dyeing step.

The crosslinking solution of the present invention may contain water used as a solvent and an organic solvent mutually soluble with water, and a small amount of iodide is further added to prevent the uniformity of polarization degree in the plane of the polarizer and the desorption of dyed iodine. may include

The iodide may be the same as that used in the dyeing step, and the concentration of the iodide is not particularly limited. For example, it may be 0.05 to 15% by weight, preferably 0.5 to 11% by weight, based on the total weight of the crosslinking solution. It is good to be. When the concentration of iodide in the crosslinking bath satisfies the above range, the iodine ion adsorbed in the dyeing step is prevented from escaping from the film or the iodine ion included in the crosslinking liquid is prevented from penetrating into the film, thereby suppressing a change in transmittance.

The temperature of the crosslinking bath is not particularly limited, but may be, for example, 20 to 70°C, preferably 40 to 60°C.

The time for immersing the film for polarizer formation in the crosslinking tank is not particularly limited, and may be, for example, 1 second to 15 minutes, preferably 5 seconds to 10 minutes.

The stretching step may be performed together with the crosslinking step, and in this case, the stretching ratio in the first crosslinking step may be 1.4 to 3.0 times, preferably 1.5 to 2.5 times. Also, the stretching ratio in the second crosslinking step may be 1.01 to 2.0 times, preferably 1.2 to 1.8 times.

The cumulative stretching ratio of the first crosslinking step and the second crosslinking step may be 1.5 to 5.0 times, preferably 1.7 to 4.5 times. When the cumulative stretching ratio is less than 1.5 times, the effect of increasing crosslinking efficiency may be insignificant, and when it exceeds 5.0 times, breakage of the film may occur due to excessive stretching and production efficiency may decrease.

complementary color step

The complementary coloring step is a step of adjusting the color by immersing the film that has undergone the crosslinking step in a complementary solution containing a metal salt, a boric acid compound, and iodide.

The complementary color solution used in the complementary color step of the present invention includes a metal salt, and accordingly, the metal salt and the dichroic material complex are chemically bonded to increase the stability of the dichroic material complex, thereby suppressing the color change of the polarizer and further improving durability. can do.

The metal salt may be the same as that used in the crosslinking step.

The concentration of the metal salt in the complementary solution is not particularly limited, but may be, for example, 0.5 to 4% by weight of the total weight of the complementary solution. If the concentration of the metal salt in the complementary solution is less than 0.5% by weight, color change, in particular, the effect of suppressing the occurrence of redness does not appear, and if it exceeds 4% by weight, polarization degree and color defects may occur.

Moreover, the complementary liquid of this invention may further contain a boric acid compound. The boric acid compound may be the same as that used in the dyeing step.

The concentration of the boric acid compound in the complementary solution is not particularly limited, but may be, for example, 1 to 10% by weight, preferably 2 to 6% by weight, based on the total weight of the complementary solution. If the concentration of the boric acid compound in the complementary solution is less than 1% by weight, the iodine orientation cannot be improved, so the effect of suppressing color change and improving durability may be insignificant, and if it exceeds 10% by weight, tension in the film during stretching due to excessive crosslinking This occurs greatly, making it difficult to stretch and the film may break.

Preferably, the concentration of the boric acid compound in the complementary coloring solution of the present invention is lower than the concentration of the boric acid compound in the crosslinking solution.

The concentration ratio is not particularly limited, and for example, the concentration of the boric acid compound in the crosslinking solution and the concentration of the boric acid compound in the complementary solution may have a ratio of 1:0.4 to 0.8. If the boric acid compound in the complementary solution is included in a small amount and the concentration ratio is less than 1:0.4, the iodine orientation cannot be improved, and the effect of suppressing color change and improving durability may be insignificant. A large tension is generated in the film, which makes stretching difficult and may cause the film to break.

The complementary color solution of the present invention may contain water used as a solvent and an organic solvent mutually soluble with water, and a small amount of iodide is further added to prevent the uniformity of polarization degree in the plane of the polarizer and the desorption of dyed iodine. may include

The iodide may be the same as that used in the dyeing step and the crosslinking step, and the concentration of the iodide is not particularly limited, and may be, for example, 0.05 to 15% by weight of the total weight of the complementary solution, preferably 0.5 to 15% by weight. It is preferable that it is 11% by weight. When the concentration of iodide in the complementary solution satisfies the above range, unadsorbed iodine ions in the dyeing and crosslinking steps can be adsorbed onto the film, and the penetration of iodine ions included in the complementary solution into the film is increased to improve color and Transmittance can be adjusted.

Preferably, the concentration of iodide in the complementary color solution of the present invention is lower than the concentration of iodide in the crosslinking solution.

Iodide in the cross-linking solution serves to prevent iodine ions adsorbed in the dyeing step from escaping from the film. In the case where a large amount of iodide is included in the complementary solution at a level similar to that of the cross-linking solution, or when exposed to high-temperature heat for a long time In this case, the iodine complex may be decomposed and the durability of the polarizer may be deteriorated.

The concentration ratio is not particularly limited, and for example, the concentration of iodide in the crosslinking solution and the concentration of iodide in the complementary solution may have a ratio of 1:0.2 to 0.6. If iodine in the complementary solution is included in a small amount and the concentration ratio is less than 1:0.2, color control cannot be performed, and if it is included in an excessive amount and exceeds 1:0.6, the iodine complex is decomposed when exposed to high temperature heat for a long time, and durability is lowered It can be.

The temperature of the complementary color bath is 20 to 70°C, and the immersion time of the polyvinyl alcohol-based film in the complementary color bath may be 1 second to 15 minutes, preferably 5 seconds to 10 minutes.

By performing stretching of the film for forming a polarizer in the complementary color step, it is possible to improve the stability by increasing the degree of orientation of the dichroic material complex, and accordingly, the polarizer prepared by the method of the present invention minimizes the decomposition of the complex even after exposure to high temperature for a long period of time. It has excellent color durability.

The stretching may be performed at a stretching ratio of 1.01 to 1.1 times. If the stretching ratio is less than 1.01 times, the orientation improvement effect of the dichroic material complex is insignificant, and if it is more than 1.1 times, the film may be broken due to excessive stretching.

stretching step

As described above, the stretching step may be performed together with at least one of a swelling step, a dyeing step, a crosslinking step, and a complementary coloring step, or may be performed in air or an inert gas while transporting the film after the above steps, and filled with a stretching liquid. It may also be performed as an independent stretching step using a separate drawing tank. Alternatively, after stretching the unstretched polyvinyl alcohol-based film in air or an inert gas before the swelling step, swelling, dyeing, crosslinking, complementary coloring, washing with water, and drying the film may be performed.

Stretching may be performed in one step or in two or more steps, but is preferably performed in two or more steps. Stretching may be performed by a method such as providing a difference in circumferential speed of the nip rolls. Similarly to the swelling step, an expander roll, a spiral roll, a crown roll, a cross guider, a band bar, or the like may be installed in the bath and/or at the entrance and exit of the bath.

The total cumulative stretching ratio of the present invention is preferably 4.0 to 7.0 times, and "accumulated stretching ratio" in the present specification means a value multiplied by the stretching ratio of each stage.

flush step

If necessary, the manufacturing method of the polarizer of the present invention may further include a water washing step after the complementary color is completed.

The water washing step is a step of immersing the complementary color-completed film for polarizer formation in a water washing tank filled with a washing solution to remove unnecessary residues attached to the film for polarizer formation in previous steps.

The water washing solution may be water (deionized water), or iodide may be further added thereto. As the iodide, the same as that used in the dyeing step may be used, and among these, sodium iodide or potassium iodide is preferably used. The content of iodide is not particularly limited, and may be, for example, 0.1 to 10 weight, preferably 3 to 8 weight, based on the total weight of the aqueous solution for washing.

The temperature of the water washing bath is not particularly limited, and may be, for example, 10 to 60°C, preferably 15 to 40°C.

The water washing step can be omitted, and may be performed whenever previous steps such as a dyeing step, a crosslinking step, a stretching step, or a complementary coloring step are completed. Moreover, it may be repeated once or more, and the number of repetitions is not particularly limited.

drying step

The drying step is a step of drying the washed film for forming a polarizer and further improving the orientation of iodine molecules dyed with neck-in according to drying to obtain a polarizer having excellent optical properties.

As a drying method, methods such as natural drying, air drying, heat drying, microwave drying, and hot air drying can be used. Recently, microwave treatment that activates and dries only the water in the film is newly used, and hot air treatment and far-infrared rays are commonly used. processing is mainly used.

The temperature at the time of hot air drying is not particularly limited, but it is preferably performed at a relatively low temperature in order to prevent deterioration of the polarizer, for example, it may be 20 to 90 ° C, preferably 20 to 80 ° C, more preferably It is preferable that it is 20-60 degreeC.

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

Thus, the polarizer manufactured by the manufacturing method of the present invention exhibits excellent durability and polarization degree, and satisfies the following formula 1.

0.7≤A700/A480≤1.0 (1)

In the formula, A700 is defined by the following formula 2,

A700=-Log ₁₀ {(T _{MD , 700} × T _{TD , 700} )/10000} (2)

T _{MD , 700} is the transmittance at a wavelength of 700 nm obtained when the polarizer is arranged in a state in which the absorption axis of the polarizer is orthogonal to the linearly polarized light of the measurement light,

T _{TD, 700} is the transmittance at a wavelength of 700 nm obtained when the polarizer is placed in a state in which the absorption axis of the polarizer is parallel to the linearly polarized light of the measurement light, and these units are all %,

A480 is defined by Equation 3 below,

A480=-Log ₁₀ {(T _{MD , 480} × T _{TD , 480} )/10000} (3)

T _{MD , 480} is the transmittance at a wavelength of 480 nm obtained when the polarizer is placed in a state in which the absorption axis of the polarizer is orthogonal to the linearly polarized light of the measurement light;

T _{TD , 480} is the transmittance at a wavelength of 480 nm obtained when the polarizer is placed in a state where the absorption axis of the polarizer is parallel to the linearly polarized light of the measurement light, and all units are %.

As described above, if the value of A700/A480 of the polarizer is less than 0.7, the degree of polarization may decrease, and if the value of A700/A480 exceeds 1, the orthogonal color b may approach blue, resulting in a defect. In addition, as described above, the metal salt contained in the crosslinking solution and the complementary solution chemically binds to the PVA-I ₅ complex to prevent decomposition of the PVA-I ₅ complex, thereby satisfying the range of Equation 1 and improving the durability of the polarizer. there is.

<Polarizer>

In addition, the present invention provides a polarizing plate provided with a protective layer on at least one surface of the polarizer manufactured by the above method.

The protective layer provided on at least one surface of the polarizer serves to protect the polarizer, and may be, for example, a protective film in the form of a film or a resin coating layer in the form of a coating layer.

The type of the protective film is not particularly limited as long as it has excellent transparency, mechanical strength, thermal stability, moisture shielding property, isotropic property, etc. Specific examples include polyester resins such as polyethylene terephthalate, polyethylene isophthalate, and polybutylene terephthalate. ; cellulosic resins such as diacetyl cellulose and triacetyl cellulose; polycarbonate-based resin; polyacrylic resins such as polymethyl (meth)acrylate and polyethyl (meth)acrylate; styrenic resins such as polystyrene and acrylonitrile-styrene copolymer; polyolefin-based resins such as polyethylene, polypropylene, polyolefins having a cyclo-based or norbornene structure, and ethylene-propylene copolymers; polyamide-based resins such as nylon and aromatic polyamide; imide-based resins; polyethersulfone-based resins; sulfone-based resins; polyether ketone-based resins; sulfurized polyphenylene-based resins; vinyl alcohol-based resin; vinylidene chloride-based resins; vinyl butyral-based resins; allylate-based resins; polyoxymethylene-based resin; A film made of a thermoplastic resin such as an epoxy resin may be used, and a film made of a blend of the thermoplastic resin may also be used. In addition, a film made of a thermosetting resin such as (meth)acrylic, urethane, epoxy, silicone or ultraviolet curable resin may be used. Among these, a cellulose-based film having a surface saponified by an alkali or the like is preferable considering polarization characteristics or durability. In addition, the protective film may also have the function of the following optical layer.

Further, the resin coating layer may be a layer formed by coating and curing a curable resin composition on at least one surface of the polarizer.

The curable resin composition is preferably an active energy ray curable resin composition, which may also contain an acrylate-based compound and an optical radical initiator.

Acrylate-based compounds are substances that can be polymerized by irradiation with active energy rays (eg, ultraviolet rays, visible light, electron rays, X-rays, etc.), and have one or more (meth)acryloyloxy groups in the molecular structure (meth). It is an acrylic compound.

A (meth)acrylic compound having one or more (meth)acryloyloxy groups in a molecule is a (meth)acrylate monomer having one or more (meth)acryloyloxy groups in a molecule, and two or more (meth)acrylic compounds in a molecule. At least 1 sort(s) of (meth)acryloyloxy group containing compounds, such as a (meth)acrylate oligomer which has a loyloxy group, is mentioned.

In the present specification, the (meth)acryloyloxy group refers to an acryloyloxy group and a methacryloyloxy group, and the (meth)acrylic compound refers to an acrylic acid ester derivative and a methacrylic acid ester derivative, respectively, and the (meth)acrylate monomer is An acrylate monomer and a methacrylate monomer, and (meth)acrylate oligomer refer to an acrylate oligomer or a methacrylate oligomer, respectively.

The (meth)acrylate monomer is a monofunctional (meth)acrylate monomer having one (meth)acryloyloxy group in the molecule, and a bifunctional (meth)acrylate monomer having two (meth)acryloyloxy groups in the molecule. and polyfunctional (meth)acrylate monomers having at least three (meth)acryloyloxy groups in the molecule. These (meth)acrylate monomers can be used singly or in combination of two or more.

More specific examples of the monofunctional (meth)acrylate monomer are tetrahydrofurfuryl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxy Propyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate , 2-ethylhexyl (meth)acrylate, cyclohexyl (meth)acrylate, dicyclopentenyl (meth)acrylate, benzyl (meth)acrylate, isobornyl (meth)acrylate, phenoxyethyl (meth) Acrylates Dicyclopentenyloxyethyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, trimethylolpropane (meth)acrylate, pentaerythritol (meth)acrylate, phenoxypolyethylene glycol (meth)acrylate , 2-(meth)acryloyloxyethyl phthalic acid, 2-(meth)acryloyloxyethylhexahydrophthalic acid, carboxyethyl (meth)acrylate, 2-(meth)acrylic acid as a carboxyl group-containing (meth)acrylate monomer Royloxyethyl succinic acid, N-(meth)acryloyloxy-N',N'-dicarboxy-p-phenylenediamine, 4-(meth)acryloyloxyethyl trimellitic acid, and the like. Further, monofunctional (meth)acrylate monomers include (meth)acryloylamino group-containing monomers such as 4-(meth)acryloylamino-1-carboxymethylpiperidine.

Examples of the bifunctional (meth)acrylate monomer include alkylene glycol di(meth)acrylates, polyoxyalkylene glycol di(meth)acrylates, halogen-substituted alkylene glycol di(meth)acrylates, and aliphatic polyols. of di(meth)acrylates, di(meth)acrylates of hydrogenated dicyclopentadiene or tricyclodecane dialkanol, di(meth)acrylates of dioxane glycol or dioxane dialkanol, bisphenol A or Di(meth)acrylates of alkylene oxide adducts of bisphenol F, epoxy di(meth)acrylates of bisphenol A or bisphenol F, and the like can be used.

More specific examples of the bifunctional (meth)acrylate monomer are ethylene glycol di(meth)acrylate, 1,3-butanediol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-butanediol di(meth)acrylate, Hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, neopentylglycol di(meth)acrylate, trimethylolpropane di(meth)acrylate, pentaerythritol di(meth)acrylate Rate, ditrimethylolpropane di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate Acrylates, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, polytetramethylene glycol di(meth)acrylate, silicone di(meth)acrylate, hydroxy pivalic acid ester neopentyl glycol Di(meth)acrylate, 2,2-bis[4-(meth)acryloyloxyethoxyethoxyphenyl]propane, 2,2-bis[4-(meth)acryloyloxyethoxyethoxycyclo Hexyl] propane, hydrogenated dicyclopentadienyl di(meth)acrylate, tricyclodecane dimethanol di(meth)acrylate, 1,3-dioxane-2,5-diyl di(meth)acrylate (trade name : DIOXAN LIKOR), an acetal compound of hydroxypivalaldehyde and trimethylolpropane (chemical name: 2-(2-hydroxy-1,1-dimethylethyl)-5-ethyl-5-hydroxymethyl-1,3- Di(meth)acrylate of dioxane), di(meth)acrylate of 1,3,5-tris(2-hydroxyethyl) isocyanurate, etc. are mentioned.

Examples of multifunctional (meth)acrylate monomers include glycerin tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, ditrimethylolpropane tri(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate , Pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate Representative examples include poly(meth)acrylates of trivalent or higher aliphatic polyols such as )acrylates, poly(meth)acrylates of trivalent or higher halogen-substituted polyols, and tri(meth)acrylates of alkylene oxide adducts of glycerin. , tri(meth)acrylate of alkylene oxide adduct of trimethylolpropane, 1,1,1-tris[(meth)acryloyloxyethoxyethoxy]propane, 1,3,5-tris(2-hydroxy) Tri(meth)acrylate of oxyethyl)isocyanurate, silicon hexa(meth)acrylate, etc. are mentioned.

Photoradical initiators are used for curing acrylate-based compounds.

The photoradical initiator that can be used is not particularly limited in the present invention, and any photocuring initiator can be used as long as it can initiate photocuring by irradiation with known active energy rays. At this time, active energy rays include visible light, ultraviolet rays, X-rays, electron rays, and the like.

Examples of photoradical initiators include acetophenone, 3-methylacetophenone, benzyldimethylketal, 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropan-1-one, 2-methyl-1-4 acetophenone-based initiators including -(methylthio)phenyl]-2-morpholinopropan-1-one and 2-hydroxy-2-methyl-1-phenylpropan-1-one; benzophenone-based initiators including benzophenone, 4-chlorobenzophenone, and 4,4'-diaminobenzophenone; benzoin ether-based initiators including benzoin propyl ether and benzoin ethyl ether; Thioxanthone-based initiators including 4-isopropylthioxanthone; Other examples include xanthone, fluorenone, camphaquinone, benzaldehyde, and anthraquinone, but are not limited thereto.

The active energy ray-curable resin composition containing the above-mentioned acrylate compound and photoradical initiator may further contain other compositions.

If necessary, the active energetic curable resin composition of the present invention may further contain an epoxy compound, a cationic polymerization initiator, and an oxetane compound.

Epoxy-based compounds are used to increase the adhesive strength and adhesiveness of the cured film, and preferably, hydrogenated epoxy-based compounds, alicyclic epoxy-based compounds, aliphatic epoxy-based compounds, or mixtures thereof may be used.

The hydrogenated epoxy-based compound means a resin obtained by selectively hydrogenating an aromatic epoxy resin under pressure in the presence of a catalyst. Examples of the aromatic epoxy resin include bisphenol-type epoxy resins such as diglycidyl ether of bisphenol A, diglycidyl ether of bisphenol F, and diglycidyl ether of bisphenol S; novolak-type epoxy resins such as phenol novolac epoxy resins, cresol novolak epoxy resins, and hydroxybenzaldehyde phenol novolak epoxy resins; and polyfunctional epoxy resins such as glycidyl ether of tetrahydroxyphenylmethane, glycidyl ether of tetrahydroxybenzophenone, and epoxidized polyvinylphenol. Although the parent nucleus hydrogenated substance of these aromatic epoxy resins becomes a hydrogenated epoxy resin, it is preferable to use the glycidyl ether of bisphenol A hydrogenated among these.

An alicyclic epoxy-based compound refers to an alicyclic compound containing at least one epoxy group in a molecule. Specific examples of the alicyclic epoxy-based compound include an ester product of 7-oxabicyclo[4.1.0]heptane-3-carboxylic acid and (7-oxabicyclo[4.1.0]hepto-3-yl)methanol, 4 -Methyl-7-oxabicyclo[4.1.0]heptane-3-carboxylic acid with (4-methyl-7-oxabicyclo[4.1.0]hepto-3-yl)methanol esterified, 7-oxa Esterification of bicyclo[4.1.0]heptane-3-carboxylic acid with 1,2-ethanediol, esterification of (7-oxabicyclo[4.1.0]hepto-3-yl)methanol with adipic acid , (4-methyl-7-oxabicyclo[4.1.0]hepto-3-yl)methanol and adipic acid ester, (7-oxabicyclo[4.1.0]hepto-3-yl)methanol and etherified compounds with 1,2-ethanediol; and the like.

The alicyclic epoxy-based compound may be an alicyclic diepoxy carboxylate, and examples of the alicyclic diepoxy carboxylate include 3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexanecarboxylate, 2 -(3,4-epoxycyclohexyl-5,5-spiro-3,4-epoxy)cyclohexane-meta-dioxane, bis(3,4-epoxycyclohexylmethyl) adipate, bis((3,4 -Epoxy-6-methylcyclohexyl)methyl)adipate, 3,4-epoxy-6-methylcyclohexyl-3',4'-epoxy-6'-methylcyclohexanecarboxylate, ε-caprolactone modified 3 ,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexanecarboxylate, trimethylcaprolactone modified 3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexanecarboxylate, β-methyl -δ-valerolactone-modified 3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexanecarboxylate, methylenebis(3,4-epoxycyclohexane), di(3,4-epoxycyclohexane) of ethylene glycol Epoxycyclohexylmethyl) ether, ethylenebis(3,4-epoxycyclohexane carboxylate), dioctyl epoxycyclohexahydrophthalate, di-2-ethylhexyl epoxycyclohexahydrophthalate, and the like.

Examples of the aliphatic epoxy-based compound include polyglycidyl ether of an aliphatic polyhydric alcohol or an alkylene oxide adduct thereof. Specific examples include diglycidyl ether of 1,4-butanediol, diglycidyl ether of 1,6-hexanediol, triglycidyl ether of glycerin, triglycidyl ether of trimethylolpropane, and diglycidyl of polyethylene glycol. obtained by adding one or more alkylene oxides (ethylene oxide, propylene oxide, etc.) to an aliphatic polyhydric alcohol such as diglycidyl ether, diglycidyl ether of propylene glycol, ethylene glycol, propylene glycol, or glycerin. Polyglycidyl ether of polyether polyol etc. are mentioned.

The hydrogenated epoxy-based compound, alicyclic epoxy-based compound, and aliphatic epoxy-based compound may be used alone or in combination of two or more.

A cationic polymerization initiator is used for curing the epoxy compound, and is a compound that generates cations or Lewis acids by irradiation with active energy rays or heating, and initiates a polymerization reaction of the epoxy compound.

The usable cationic polymerization initiator is not particularly limited in the present invention, and examples thereof include, but are not limited to, aromatic diazonium salts, aromatic iodine aluminum salts, onium salts such as aromatic sulfonium salts, and iron-alene complexes.

Examples of the aromatic diazonium salt include benzenediazonium hexafluoro antimonate, benzenediazonium hexafluoro phosphate, benzenediazonium hexafluoro borate and the like.

Examples of aromatic iodine aluminum salts include diphenyliodonium tetrakis(pentafluorophenyl)borate, diphenyliodonium hexafluorophosphate, diphenyliodonium hexafluoroantimonate, di(4-nonylphenyl)iodine nium hexafluoro phosphate and the like are possible.

Examples of aromatic sulfonium salts include triphenylsulfonium hexafluoro phosphate, triphenylsulfonium hexafluoro antimonate, triphenylsulfonium tetrakis (pentafluorophenyl) borate, 4,4'-bis[diphenyl Sulfonio] diphenyl sulfide bishexafluoro phosphate, 4,4'-bis[di(β-hydroxyethoxy)phenylsulfonio]diphenyl sulfide bishexafluoro antimonate, 4,4 '-bis[di(β-hydroxyethoxy)phenylsulfonio]diphenyl sulfide bishexafluorophosphate, 7-[di(p-toluyl)sulfonio]-2-isopropylthioxanthone Hexafluoro antimonate, 7-[di(p-toluyl)sulfonio]-2-isopropylthioxanthone tetrakis(pentafluorophenyl)borate, 4-phenylcarbonyl-4'-diphenyl Sulfonio-diphenyl sulfide hexafluoro phosphate, 4-(p-tert-butylphenylcarbonyl)-4'-diphenylsulfonio-diphenyl sulfide hexafluoro antimonate, 4-(p -tert-butylphenylcarbonyl)-4'-di(p-toluyl)sulfonio-diphenyl sulfide tetrakis(pentafluorophenyl)borate; and the like.

In addition, examples of the iron-alene complex include xylene-cyclopentadienyl iron (II) hexafluoroantimonate, cumene-cyclopentadienyl iron (II) hexafluoro phosphate, xylene-cyclopentadienyl iron (II )-tris(trifluoromethylsulfonyl)methanide and the like.

These cationic polymerization initiators may be used alone or in combination of two or more of the above-mentioned compositions. Among them, especially when an aromatic sulfonium salt is used, curability is excellent and mechanical properties and adhesive strength of the cured film can be further improved.

The cationic polymerization initiator may be directly prepared and used, or a commercially available one may be purchased and used. For example, as commercially available products, Kayarad PCI-220 and Kayarad PCI-620 manufactured by Nihon Kayaku Co., Ltd., UVI-6990 manufactured by Union Carbide Co., Ltd., Adeka Optomer SP-150 and Adeka Optomer SP-170 manufactured by ADEKA Co., Ltd., CI-5102, CIT-1370, CIT-1682, CIP-1866S, CIP-2048S and CIP-2064S manufactured by Nippon Soda Co., Ltd., DPI-101, DPI-102, DPI-103, DPI-105, MPI manufactured by Midori Kagaku Co., Ltd. -103, MPI-105, BBI-101, BBI-102, BBI-103, BBI-105, TPS-101, TPS-102, TPS-103, TPS-105, MDS-103, MDS-105, DTS-102 and DTS-103, Rhodia Japan's PI-2074, and the like.

The content of the cationic polymerization initiator may be limited so as to sufficiently cure the epoxy compound and not to affect physical properties of the coating film. Preferably, it may be used in an amount of 0.01 to 10 parts by weight, more preferably 1 to 6 parts by weight, based on 100 parts by weight of the acrylate-based compound. If the content of the cationic polymerization initiator is less than the above range, curing of the epoxy compound is insufficient, resulting in a decrease in mechanical strength or adhesive strength of the cured film. Since there is a possibility that optical durability performance may decrease due to increased moisture absorption, it may be appropriately adjusted and used within the above range.

The oxetane compound not only facilitates the film manufacturing process by lowering the viscosity of the active energy ray-curable resin composition, but also increases the curing speed, and suppresses yellowing of the finally obtained cured film to improve optical performance.

The oxetane compound is preferably used when an epoxy-based compound is applied to the active energy ray-curable resin composition, and a compound having at least one oxetane ring (four-membered ring ether) in the molecular structure may be used.

The oxetane compound that can be used is not particularly limited in the present invention, and examples thereof include 3-ethyl-3-hydroxymethyloxetane and 1,4-bis[(3-ethyl-3-oxetanyl)methoxymethyl]. Benzene, 3-ethyl-3-(phenoxymethyl)oxetane, di(3-ethyl-3-oxetanyl)methyl]ether, 3-ethyl-3-(2-ethylhexyloxymethyl)oxetane, phenol Novolac oxetane etc. are mentioned.

These oxetane compounds may be directly prepared or commercially available materials may be purchased and used. For example, Alonoxetane OXT-101, Alonoxetane OXT-121, Alonoxetane OXT-211, and Alonoxetane OXT from Toagosei Co., Ltd. -221, allone oxetane OXT-212, etc. are mentioned.

The content of the oxetane compound can be controlled to maximize the effects related to adhesion improvement, viscosity, and optical performance. For example, 10 to 50 parts by weight, preferably 20 to 50 parts by weight, based on 100 parts by weight of the epoxy compound. 40 parts by weight can be used. If the content of the oxetane compound is less than the above range, the viscosity due to the addition of the oxetane compound is lowered or the effect of improving optical performance is not sufficient, and if the content exceeds the above range, a problem in that adhesion to the polarizer is lowered may occur. It is preferable to use it appropriately within the above range.

In addition to the above components, the curable resin composition according to the present invention is an antioxidant, a leveling agent, a surface lubricant, a dye, a pigment, You may further contain various additives, such as an antifoamer, a filler, and a light stabilizer.

A method for preparing the curable resin composition is not particularly limited in the present invention, and may be prepared according to a known method.

The structure of the polarizing plate according to the present invention is not particularly limited, and various optical layers capable of satisfying required optical properties may be laminated on the polarizer or polarizing plate. For example, a structure in which a protective layer for protecting the polarizer is laminated on at least one surface of the polarizer; A structure in which a surface treatment layer such as a hard coating layer, an anti-reflection layer, an anti-sticking layer, an anti-diffusion layer, and an anti-glare layer is laminated on at least one surface of the polarizer or the protective layer; It may have a structure in which an alignment liquid crystal layer for compensating the viewing angle or another functional film is laminated on at least one surface of the polarizer or the protective layer. In addition, optical films such as polarization converters used to form various image display devices, retardation plates including wave plates (including λ plates) such as reflectors, transflective plates, 1/2 wave plates or 1/4 wave plates, A structure in which at least one of the viewing angle compensation film and the luminance improving film is laminated as an optical layer may be used. More specifically, as a polarizing plate having a structure in which a protective layer is laminated on one surface of a polarizer, a reflector or a transflective polarizer in which a reflector or a transflective reflector is laminated on the laminated protective layer; an elliptical or circular polarizing plate on which retardation plates are stacked; a viewing angle compensation layer or a wide viewing angle polarizer on which a viewing angle compensation film is laminated; Alternatively, a polarizing plate having a luminance enhancing film laminated thereon is preferable.

Such a polarizing plate can be applied to various image display devices such as an electroluminescent display device, a plasma display device, and a field emission display device as well as a general liquid crystal display device.

Hereinafter, preferred embodiments are presented to aid understanding of the present invention, but these embodiments are merely illustrative of the present invention, but do not limit the scope of the appended claims, and embodiments within the scope and spirit of the present invention It is obvious to those skilled in the art that various changes and modifications to the are possible, and it is natural that these variations and modifications fall within the scope of the appended claims.

Examples and Comparative Examples

(1) Example 1

A transparent unstretched polyvinyl alcohol (PVA) film (PE60, KURARAY) having a saponification degree of 99.9% or more was immersed in 25°C water (deionized water) for 1 minute and 20 seconds to swell, followed by iodine 1mM/L and potassium iodide 1 It was dyed by immersing for 2 minutes and 30 seconds in an aqueous solution for dyeing at 30 ° C containing 0.3% by weight of boric acid. At this time, the fabric was stretched at a stretch ratio of 1.56 times and 1.64 times in the swelling and dyeing stages, respectively, so that the cumulative draw ratio after passing through the dyeing tank was 2.56 times. Then, 13.9% by weight of potassium iodide, 3% by weight of boric acid, and 0.5% by weight of zinc nitrate of Daejeong Hwa Keumsa were immersed in an aqueous solution for crosslinking at 56 ° C for 26 seconds (first crosslinking step) to crosslink, and at a stretch ratio of 1.7 times. stretched. Thereafter, 13.9% by weight of potassium iodide, 3% by weight of boric acid, and 0.5% by weight of zinc nitrate from Daejeonghwa Keumsa were immersed in an aqueous solution for crosslinking at 56 ° C. for 20 seconds (second crosslinking step) to crosslink, and at the same time, 1.34 times the Stretching was performed at a stretching ratio. Subsequently, it was stretched 1.01 times while immersed for 10 seconds in an aqueous solution for complementary coloring at 40° C. containing 5% by weight of potassium iodide, 2% by weight of boric acid, and 0.5% by weight of zinc nitrate from Daejeong Hwa Keumsa.

At this time, the total cumulative stretching ratio in the MD direction of the swelling, dyeing, crosslinking and complementary coloring steps was set to 6 times. After crosslinking was completed, the polyvinyl alcohol film was dried in an oven at 70° C. for 4 minutes to prepare a polarizer.

A polarizing plate was prepared by laminating a triacetyl cellulose (TAC) film on both sides of the prepared polarizer.

(2) Examples 2 to 8 and Comparative Examples 1 to 3

A polarizing plate in the same manner as in Example 1 except for the composition (type and concentration) of the metal salt of the crosslinking solution or complementary coloring solution shown in Tables 1 and 2 below, temperature, total cumulative stretching ratio, and the content of the metal salt relative to the total weight of the polarizer. was manufactured.

analysis example

The distance between crystals in PVA of the polarizers prepared in Examples and Comparative Examples was measured by the following method.

(1) Distance between decisions in PVA (Long Period)

Pohang Accelerator Laboratory (PAL)'s Synchrotron Beam is used and the distance from the sample to the detector is set to 3.0m at an X-ray wavelength of 1.567 angstroms, and the direction of stretching within the PVA according to the cumulative stretching ratio from the beam path 1mm to the dyeing tank passage The intercrystal distance at was measured based on the peak of the scattering vector q.

At the end of the dyeing step of the polarizers prepared in the above Examples and Comparative Examples, the distance between crystals in the film for forming a polarizer in the stretching direction was 27 nm.

test example

The physical properties of the polarizers prepared in the Examples and Comparative Examples were measured by the following methods, and the results are shown in Tables 3 and 4 below.

1. Optical properties (polarization degree, transmittance, A700, A480)

After cutting the prepared polarizer into a size of 4 cm × 4 cm, the transmittance was measured using a UV-visible ray spectrometer (V-7100, manufactured by JASCO). At this time, the degree of polarization is defined by Equation 4 below. In addition, it should be noted that even a difference of about 0.001 degree of polarization greatly affects the contrast ratio. When the degree of polarization is less than 99.990, the contrast ratio is lowered, making it difficult to realize real black.

^Degree of Polarization (P)=[(T ₁ -T ₂ )/(T ₁ +T ₂ )] ^1/2 ×100 (4)

In the formula, T ₁ is a parallel transmittance obtained when a pair of polarizers are arranged in a state in which absorption axes are parallel, and T ₂ is an orthogonal transmittance obtained when a pair of polarizers are arranged in a state in which absorption axes are orthogonal to each other. In addition, the unit of polarization degree (P) is %.

A700 and A480 are absorbances defined by Equations 2 and 3 above.

When the absorbance values of A700 and A480 are high, it means that the PVA-I ₅ and PVA-I ₃ complex contents are high and the polarization degree is high.

2. Heat resistance evaluation

The spectral transmittance τ (λ) before and after leaving the polarizers prepared in Examples and Comparative Examples at 105 ° C. for 30 minutes was measured with a spectrophotometer (V7100, Nippon Spectroscopy Co., Ltd.) to obtain an orthogonal spectral transmission spectrum from this, Color b and A700 defined by Equation 2 above were obtained.

Orthogonal color b may be defective if it is out of ±0.3 based on -0.4.

After the heat resistance evaluation, the presence or absence of red discoloration of the polarizing plate was confirmed by visual observation.

If A700 is 2.1 or less after heat resistance, red discoloration may be observed when the polarizing plate is observed with the naked eye, which means that the content of the PVA-I ₅ complex in the region absorbing light of 700 nm or more is reduced.

The results are shown in Tables 3 and 4. Referring to these tables, the examples satisfying Equation 1 of the present invention exhibited excellent optical properties, exhibited high absorbance even after the heat resistance test, and did not cause red discoloration. In Table 4, X indicates that red discoloration did not occur, and ○ indicates that red discoloration occurred.

On the other hand, in the case of Comparative Examples 1 to 3, which do not satisfy Equation 1 of the present invention, the optical properties are lowered, and red discoloration occurs by the heat resistance test, or the orthogonal color b value is significantly lowered, confirming that defects have occurred. .

Claims (17)

A polarizer that satisfies Expression 1 below.
0.7≤A700/A480≤1.0 (1)
In the formula, A700 is defined by the following formula 2,
A700=-Log ₁₀ {(T _{MD , 700} × T _{TD , 700} )/10000} (2)
T _{MD , 700} is the transmittance at a wavelength of 700 nm obtained when the polarizer is arranged in a state in which the absorption axis of the polarizer is orthogonal to the linearly polarized light of the measurement light,
T _{TD , 700} is the transmittance at a wavelength of 700 nm obtained when the polarizer is placed in a state in which the absorption axis of the polarizer is parallel to the linearly polarized light of the measurement light, and these units are all %,
A480 is defined by Equation 3 below,
A480=-Log ₁₀ {(T _{MD , 480} × T _{TD , 480} )/10000} (3)
T _{MD , 480} is the transmittance at a wavelength of 480 nm obtained when the polarizer is placed in a state in which the absorption axis of the polarizer is orthogonal to the linearly polarized light of the measurement light;
T _{TD , 480} is the transmittance at a wavelength of 480 nm obtained when the polarizer is placed in a state where the absorption axis of the polarizer is parallel to the linearly polarized light of the measurement light, and all units are %. The method of claim 1,
The polarizer is a polarizer containing a metal salt. The method of claim 2,
The metal salt is at least one polarizer selected from the group consisting of zinc nitrate, copper nitrate, aluminum nitrate, magnesium nitrate and zinc acetate. According to claim 2 or 3,
The metal salt is a polarizer contained in 0.05 to 1.5% by weight relative to the total weight of the polarizer. A polarizing plate comprising the polarizer of claim 1 or 2 and a protective layer provided on at least one surface of the polarizer. The method of claim 5,
The protective layer is a polarizing plate of a protective film or a resin coating layer. An image display device comprising the polarizing plate according to claim 5. Including the steps of swelling, dyeing, crosslinking, complementary and stretching the film for forming a polarizer,
At the end of the dyeing step, the distance between crystals in the film for forming a polarizer in the stretching direction is 20 to 40 nm,
The dye solution contains a boric acid compound,
In the crosslinking and complementary coloring steps, a crosslinking solution and a complementary solution containing a metal salt are used, respectively,
The crosslinking solution contains a boric acid compound, and the concentration of the boric acid compound in the dyeing solution in the dyeing step is lower than the concentration of the boric acid compound in the crosslinking solution in the crosslinking step. The method of claim 8,
The stretching direction is a method for producing a polarizer in the MD direction. According to claim 8 or 9,
The boric acid compound is a method for producing a polarizer included in 0.3 to 5% by weight of the total weight of the dyeing solution. According to claim 8 or 9,
A method for producing a polarizer having a cumulative stretch ratio of 2.0 to 3.0 times until the end of the dyeing step. delete According to claim 8 or 9,
The crosslinking step is a method for producing a polarizer including at least first and second crosslinking steps. According to claim 8 or 9,
The metal salt is at least one selected from the group consisting of zinc nitrate, copper nitrate, aluminum nitrate, magnesium nitrate and zinc acetate, a method for producing a polarizer. According to claim 8 or 9,
The metal salt is a method for producing a polarizer included in 0.5 to 4% by weight of the total weight of the crosslinking solution. According to claim 8 or 9,
The metal salt is a method for producing a polarizer included in 0.5 to 4% by weight of the total weight of the complementary color solution. According to claim 8 or 9,
The polarizer manufactured by the manufacturing method satisfies the following formula 1, a method for manufacturing a polarizer.
0.7≤A700/A480≤1.0 (1)
In the formula, A700 is defined by the following formula 2,
A700=-Log ₁₀ {(T _{MD, 700} × T _{TD, 700} )/10000} (2)
T _{MD, 700} is the transmittance at a wavelength of 700 nm obtained when the polarizer is placed in a state in which the absorption axis of the polarizer is orthogonal to the linearly polarized light of the measurement light,
T _{TD, 700} is the transmittance at a wavelength of 700 nm obtained when the polarizer is placed in a state in which the absorption axis of the polarizer is parallel to the linearly polarized light of the measurement light, and these units are all %,
A480 is defined by Equation 3 below,
A480=-Log ₁₀ {(T _{MD, 480} × T _{TD, 480} )/10000} (3)
T _{MD, 480} is the transmittance at a wavelength of 480 nm obtained when the polarizer is placed in a state in which the absorption axis of the polarizer is orthogonal to the linearly polarized light of the measurement light,
T _{TD, 480} is the transmittance at a wavelength of 480 nm obtained when the polarizer is placed in a state in which the absorption axis of the polarizer is parallel to the linearly polarized light of the measurement light, and these units are all %.