WO2015046962A1 - Method for manufacturing nearly-natural black polarizing plate and polarizing plate manufactured thereby - Google Patents

Abstract

The present invention relates to a method for manufacturing a polarizing plate and a polarizing plate manufactured thereby, the method comprising the sequential steps of: preparing a polarizing member comprising a polyvinyl alcohol-based polarizer dyed with iodine and/or a dichroic dye; irradiating, on the polarizing member, a light having a specific wavelength selected from a wavelength range from 200nm to 800nm; and supplying moisture to the polarizing member.

Description

Method for manufacturing polarizing plate close to natural black and polarizing plate manufactured using same

The present invention relates to a method of manufacturing a polarizing plate and a polarizing plate manufactured using the same, and more particularly, a method of manufacturing a polarizing plate that can be used in an image display device such as a liquid crystal display, an organic light emitting display, and a plasma display panel (PDP). And to a polarizing plate produced by the above method.

In general, in the liquid crystal display device, in order to provide a bright and good color reproducibility, it is necessary to arrange the polarizers on both sides of the glass substrate forming the liquid crystal surface panel. The polarizer is generally produced by dyeing a polyvinyl alcohol (PVA) -based film with a dichroic material such as iodine, crosslinking with a crosslinking agent, and oriented by a method such as uniaxial stretching. Since a polarizer is produced by extending | stretching, it is easy to shrink | contract, especially since a polyvinyl alcohol-type film uses a hydrophilic polymer, it is easy to deform | transform under humid heat conditions. In addition, since the mechanical strength of the film itself is weak, a problem that the film is torn may occur. Therefore, a polarizing plate supplementing the strength by adhering a protective film on both sides or one side of the polarizer is used.

On the other hand, the liquid crystal display device has recently been expanded to a wide range of applications from portable terminals to large TVs for home use. As a result, technology development has been conducted to ensure excellent display quality in each liquid crystal display device. Physical properties as important as polarization degree in the display quality of the liquid crystal display device are the color of the polarizer and the polarizing plate.

Conventionally, in order to control the color of the polarizing plate, methods such as adjusting the time for which the polyvinyl alcohol-based film is immersed in the treatment bath, adjusting the temperature and the like have been used.

However, the method of adjusting the time and temperature in the treatment bath as described above has a problem that color adjustment is difficult because the time and temperature conditions in the treatment bath must also be adjusted when the stretching conditions are changed in the stretching step.

Therefore, in the related art, a complementary color process of immersing a PVA-based film drawn in a KI aqueous solution was added when a PVA-based polarizer was prepared. Complementary color process using KI aqueous solution of the polarizer manufacturing process corresponds to a process that can adjust the total light characteristics of the polarizing plate, in particular the color by increasing the absorbance of the short wavelength region corresponding to the reduced 400 to 500nm after the stretching process.

However, in the complementary color process using KI as in the above method, when KI is excessively used to increase the complementary color effect, the amount of KI remaining inside the polarizer manufactured by the above-described manufacturing process increases, so that the nic Increase the occurrence of foreign body defects. In addition, when exposed for a long time under a high temperature condition of 80 ℃ or more, the overall heat resistance such as a decrease in the degree of polarization and color change of the polarizing plate is caused.

As such, the conventional polarizer color control method is difficult to control, and the development of a new method for polarizer color control is required because of the problem that the properties of the manufactured polarizer are also degraded.

In order to solve the above problems of the present invention, it is simpler than the conventional color control method of the polarizing plate, minimizes the occurrence of defects, such as the kunky, glitter and polarizing plate, and excellent heat resistance polarizing plate manufacturing method and the polarizing plate manufactured through Its purpose is to provide.

According to one embodiment of the present invention, the present invention comprises the steps of preparing a polarizing member comprising a polyvinyl alcohol-based polarizer in which at least one of iodine and dichroic dye is dyed; Irradiating the polarizing member with light having a specific wavelength selected from a wavelength range of 200 nm to 800 nm; And it provides a polarizing plate manufacturing method comprising the step of supplying water to the polarizing member sequentially.

At this time, the step of irradiating the light may be performed at an intensity of 0.5 to 550 J / cm ² .

In addition, the step of irradiating the light may use a light emitting diode (LED) or a laser lamp.

At this time, the step of supplying the moisture may be performed by a method of leaving the polarizing member for 10 minutes to 3 hours at 40 ℃ to 70 ℃ and 90% or more relative humidity.

According to another embodiment of the present invention, a ratio of orthogonal absorbance measured at 460 nm to orthogonal absorbance measured at 620 nm, in which at least one of iodine and dichroic dye includes a polyvinyl alcohol-based polarizer, is 1: 0.8 to 1 A polarizing plate of: 1.1 is provided.

At this time, it is preferable that the single color b value of the said polarizing plate is 3.5-4.6, and the orthogonal color b value is -1-0.

After exposing the polarizing plate for 500 hours at a high temperature of 80 ° C. or higher, the polarization degree is preferably 99.9% or more, and the single transmittance is preferably 42% to 45%.

According to another embodiment, the present invention provides a display panel; And the polarizing plate attached to one or both surfaces of the display panel.

According to the method of manufacturing a polarizing plate of the present invention, by directly irradiating light to a polarizing member including a polyvinyl alcohol-based polarizer in which iodine-based or dichroic dyes are dyed, and then supplying water, the transmittance of the short wavelength region of the polarizing plate is reduced. By lowering it can be produced a polarizing plate having a color close to natural black (natural black).

The polarizing plate manufactured by the manufacturing method can reduce the generation of foreign substances generated when undergoing a separate chemical complementary color process and has excellent heat resistance.

1 is a graph showing absorption spectra of orthogonal absorbances of polarizing plates prepared in Example 1 and Comparative Examples 1 to 3. FIG.

FIG. 2 is a graph showing a change in the orthogonal transmittance of the absorption axis according to the standing time when the polarizing plate prepared by the Preparation Example is irradiated with light of 532 nm wavelength at an intensity of 20 J / cm ² and then left under 90% relative humidity.

Hereinafter, preferred embodiments of the present invention will be described. However, embodiments of the present invention may be modified in various other forms, and the scope of the present invention is not limited to the embodiments described below. In addition, the embodiments of the present invention are provided to more completely explain the present invention to those skilled in the art.

The inventors of the present invention, in order to develop a method for adjusting the color of the polarizing plate irrespective of the complementary color step performed in the stretching step of the polarizer, resulted in iodine and / or dichroic dyes. Preparing a polarizing member including a polyvinyl alcohol polarizer; Irradiating the polarizing member with light having a specific wavelength selected from a wavelength range of 200 nm to 800 nm; And sequentially supplying water to the polarizing member, thereby simplifying, minimizing foreign matter generation, etc. of the Kunic, the polarizing plate, excellent heat resistance, and manufacturing a polarizing plate close to natural black. It was found and completed the present invention.

Method for producing a polarizing plate according to the present invention comprises the steps of preparing a polarizing member comprising a polyvinyl alcohol-based polarizer in which at least one of iodine and dichroic dye is dyed; Irradiating the polarizing member with light having a specific wavelength selected from a wavelength range of 200 nm to 800 nm; And sequentially supplying water to the polarizing member.

In this case, the polarizing member including a polyvinyl alcohol polarizer in which at least one of iodine and dichroic dye is dyed is a polyvinyl alcohol polarizer in which iodine and / or dichroic dye is salted or a protective film on at least one surface of the polarizer. It includes a polarizing plate attached with.

On the other hand, the step of preparing a polarizing member comprising a polyvinyl alcohol-based polarizer in which the iodine and / or dichroic dye is dyed, the dyeing of a polyvinyl alcohol polymer film with iodine and / or dichroic dye It may be carried out through a dyeing step, a crosslinking step of crosslinking the polyvinyl alcohol-based film and a dye, and a stretching step of stretching the polyvinyl alcohol-based film.

First, the dyeing step is for dyeing iodine molecules and / or dye molecules having a dichroic to a polyvinyl alcohol-based film, the iodine molecules and / or dye molecules absorb light that vibrates in the stretching direction of the polarizing plate, vertical The light vibrating in the direction can be passed to obtain polarized light having a specific vibration direction. In this case, generally, dyeing may be performed by impregnating the polyvinyl alcohol-based film in a treatment bath containing a solution containing a dichroic substance such as an iodine solution.

At this time, water is generally used as the solvent used in the solution of the dyeing step, but an appropriate amount of an organic solvent having compatibility with water may be added. On the other hand, iodine and / or dichroic dye may be used in a ratio of 0.06 parts by weight to 0.25 parts by weight with respect to 100 parts by weight of the solvent. This is because, when the iodine and / or dichroic dye is in the above range, the transmittance of the polarizer produced after stretching may satisfy the range of 42.0% to 47.0%.

On the other hand, in the case of using iodine as the dichroic substance, it is preferable to further contain an auxiliary such as iodide in order to improve the dyeing efficiency, the auxiliary agent in a ratio of 0.3 parts by weight to 2.5 parts by weight with respect to 100 parts by weight of the solvent. Can be used. At this time, the reason for adding an auxiliary agent such as iodide is to increase the solubility of iodine in water because the solubility in water is low in the case of iodine. On the other hand, the mixing ratio of the iodine and iodide is preferably about 1: 5 to 1:10.

At this time, specific examples of iodide that may be added in the present invention, potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, titanium iodide or these Mixtures, and the like, but are not limited thereto.

On the other hand, the temperature of the treatment bath may be maintained at about 25 ℃ to 40 ℃, the reason is that the dyeing efficiency may be lower at a lower temperature of less than 25 ℃, iodine and / or dichroic at too high temperature above 40 ℃ This is because a large amount of sublimation of the dye may occur to increase the amount of iodine and / or dichroic dye used. In addition, the time for immersing the polyvinyl alcohol-based film in the treatment bath may be about 30 seconds to 120 seconds, because, when the immersion time is less than 30 seconds, the dyeing may not be uniformly made to the polyvinyl alcohol-based film. If it exceeds 120 seconds, the dyeing is saturated and there is no need for further dipping.

On the other hand, as a crosslinking step, a deposition method performed by immersing a polyvinyl alcohol-based film in boric acid aqueous solution or the like is generally used, but may be performed by a coating method or a spraying method for spraying a solution on the film.

At this time, as an example of the crosslinking step, the immersion method, when the iodine and / or dichroic dye is dyed to the polyvinyl alcohol-based film by the dyeing step, using the crosslinking agent to the polyvinyl iodine and / or dichroic dye It is made to adsorb | suck on the polymer matrix of an alcoholic film, and it is performed by immersing a polyvinyl alcohol-type film in the crosslinking bath with the solution containing a crosslinking agent. This is because, if iodine molecules are not properly adsorbed on the polymer matrix, the polarization degree is lowered, and thus the polarizing plate cannot perform its role.

At this time, the solvent used in the solution of the cross-linking bath is generally used water, an appropriate amount of an organic solvent having compatibility with water may be added, the cross-linking agent is 0.5 to 5.0 parts by weight based on 100 parts by weight of the solvent It can be added in negative proportions. In this case, when the crosslinking agent is contained in less than 0.5 parts by weight, the crosslinking in the polyvinyl alcohol-based film is insufficient, the strength of the polyvinyl alcohol-based film in water may fall, if exceeding 5.0 parts by weight, excessive crosslinking is formed It is possible to reduce the stretchability of the polyvinyl alcohol-based film.

Moreover, as a specific example of the said crosslinking agent, boron compounds, such as boric acid and borax, glyoxal, glutaraldehyde, etc. are mentioned, These can be used individually or in combination.

On the other hand, the temperature of the cross-linking bath depends on the amount and the stretching ratio of the cross-linking agent, but is not limited to this, it is generally preferred that the 45 ℃ to 60 ℃. In general, when the amount of the crosslinking agent is increased, the temperature of the crosslinking bath is controlled at high temperature conditions in order to improve the mobility of the polyvinyl alcohol-based film chains. Adjust the temperature. However, in the present invention, since the stretching process is 5 times or more, the temperature of the crosslinking bath must be maintained at 45 ° C. or higher to improve the stretchability of the polyvinyl alcohol-based film.

On the other hand, the time for immersing the polyvinyl alcohol-based film in the crosslinking bath is preferably about 30 seconds to 120 seconds. The reason for this is that when the immersion time is less than 30 seconds, the crosslinking may not be uniformly performed on the polyvinyl alcohol-based film, and when the immersion time is longer than 120 seconds, the crosslinking is saturated and there is no need for further immersion. .

On the other hand, stretching in the stretching step refers to stretching the film uniaxially to orient the polymer of the film in a certain direction. The stretching method can be divided into wet stretching method and dry stretching method, and dry stretching method is again an inter-roll stretching method, a heating roll stretching method, a compression stretching method, a tenter stretching method, or the like. The wet stretching method is classified into a tenter stretching method, an inter-roll stretching method, and the like. In the present invention, the stretching method is not particularly limited, and both the wet stretching method and the dry stretching method can be used, and a combination thereof may be used if necessary.

At this time, in the stretching step, it is preferable to stretch the polyvinyl alcohol-based film at a stretching ratio of 4 to 7 times, preferably at a stretching temperature of 45 ° C to 60 ° C. Because, in order to impart polarization performance to the polyvinyl alcohol-based film, it is necessary to orient the chain of the polyvinyl alcohol-based film, the chain orientation may not sufficiently occur at a draw ratio of less than 4 times, polyvinyl at a draw ratio of more than 7 times This is because the alcohol-based film chain can be cut. In addition, the stretching temperature may vary depending on the content of the crosslinking agent, at a temperature of less than 45 ℃ polyvinyl alcohol-based film chain fluidity may be lowered, the stretching efficiency may be reduced, if the temperature exceeds 60 ℃, polyvinyl alcohol This is because the system film may be softened and the strength may be weakened.

On the other hand, the stretching step may be carried out simultaneously or separately with the dyeing step or crosslinking step. When the stretching step is performed at the same time as the dyeing step, it is preferable that the deposition step is carried out in an iodine solution, and if it is carried out simultaneously with the crosslinking step, it is preferably carried out in an aqueous solution of boric acid.

On the other hand, the polarizing member of the present invention may be a polarizer manufactured by the method described above, or may be a polarizing plate with a protective film on at least one surface of the polarizer. Since the polarizer is very thin, a polarizer is generally formed by attaching a protective film to one or both sides of the polarizer in order to protect the polarizer. A protective film is formed on both sides of the polarizer to protect the polarizer. As referring to the transparent film, acetate-based, polyester-based, polyethersulfone-based, polycarbonate-based, polyamide-based, polyimide-based, and polyolefin-based resin films such as TriAcetyl Cellulose (TAC) may be used. It is not limited to this.

In this case, the protective film may be laminated using an adhesive, but the adhesive may be a polyvinyl alcohol-based water-based adhesive, but is not limited thereto. In addition, the polarizing plate may additionally include a functional film such as a wide viewing angle compensation plate or a brightness enhancing film in order to further improve the function in addition to the protective film.

Next, the present invention is characterized in that it comprises the step of irradiating the polarizing member with light of a specific wavelength selected from the wavelength range of 200nm to 800nm.

According to the research of the present inventors, as shown in the present invention, irradiating the polarizing member with light of a specific wavelength selected from the wavelength range may be performed by iodine and / or dichroic dye absorbing light of the wavelength range present in the polarizer. Vibronic excitation is induced. The molecular vibrational motion causes the molecules of iodine and / or dichroic dye to transition from the electronic ground state to the electronic excited state. Thereafter, dissociation of the iodine and / or dichroic dye in the electron excited state breaks the chemical bond, whereby the iodine and / or the dichroic dye having absorption in the wavelength range is short-wavelength region (UV region or It is decomposed into a compound absorbing a short wavelength visible light region), and thus the polarization function is eliminated in the region of 400 nm to 800 nm, which is the visible light region of the polarizing plate, thereby increasing the overall transmittance and making the polarizing plate transparent.

Subsequently, as will be described below, when the water supply step is performed, the polarization function and the color of the polarizing plate are changed by the reaction between the decomposed iodine and / or the dichroic dye. When water is supplied, the permeability is lowered again due to the recombination of the decomposed iodine, and the color is determined according to the concentrations of the iodine compound absorbing the short wavelength region and the iodine compound absorbing the long wavelength region.

On the other hand, during the irradiation, it is possible to use ultraviolet light or visible light having a specific wavelength selected from the wavelength range of 200nm to 800nm, more preferably 400nm to 750nm light can be used. Since the decomposition of chemical bonds occurs due to the strong vibrational movement accompanied by heat after electrons of iodine are transferred to the excited state, light in the wavelength range that can be absorbed by iodine should be irradiated. However, more preferably, decomposition of chemical bonds may occur more easily in the 400 nm to 750 nm region in which iodine absorbs more light (absorption coefficient, wavelength range with a large extinction coefficient).

 In addition, the step of irradiating the light is preferably performed at an intensity of 0.5J / ㎠ to 550J / ㎠, more preferably at an intensity of 0.8J / ㎠ to 50J / ㎠. For example, light may be irradiated at an intensity of 1 J / cm 2 to 20 J / cm 2. The degree of polarization resolution and color of the polarizer can be controlled by the intensity of the irradiation. When the intensity is more than 550 J / ㎠, the polarizing member is twisted by the strong energy, or may adversely affect the orientation of the polyvinyl alcohol-based polymer film, if less than 0.5 J / ㎠, the color of the polarizing plate by the irradiation of light The change of color is insignificant, and color control may be difficult.

On the other hand, the exposure may be irradiated with light to the polarizing member, that is, the polarizer or the polarizing plate by using a masking method, a light emitting diode (LED) or a laser lamp, etc., using a light emitting diode (LED) or a laser lamp More preferred. In the case of the light emitting diode (LED) or the laser lamp, due to the straightness of the light, it can be accurately exposed to the target location (target) accurately, thereby adjusting the color of the polarizing plate appropriately.

When using a light emitting diode (LED) or a laser, it is preferable to adjust the polarization of the light source due to the characteristics of the polarizing plate having an axis for absorbing light and an axis for transmitting light. The polarization direction of the light source should coincide in parallel with the absorption axis direction of the polarizing plate so that more effective increase in transmittance and decrease in polarization degree can be observed and power loss consumed by the light source can be prevented. If the polarization direction of the light source coincides with the direction of the absorption axis of the polarizer, the incident angle of the light source incident on the polarizer is irrelevant. However, when the polarization direction of the light source and the absorption axis direction of the polarizing plate do not coincide, the effect of the polarization cancellation becomes remarkably low. More specifically, the method used in the Examples was irradiated with light of 532nm using a Verdi laser of Coherent, and irradiated to the polarizing plate at a distance of 40cm in front of the focal length using an optical lens. In addition, the polarization of the light source was 100: 1 or more, the laser was used to oscillate vertically predominantly, the absorption axis of the polarizing plate and the polarization of the light source was irradiated within 5 degrees. The polarizing plate caused localized polarization cancellation and transmittance increase of 1 cm in diameter.

Finally, the present invention is characterized in that it comprises the step of supplying moisture to the polarizing member that has undergone the step of irradiating the light.

The step of supplying the moisture is not limited thereto, but the method may be used for 10 minutes to 3 hours at 40 ° C. to 70 ° C. and a relative humidity of 80% or more, and 20 at 60 ° C. and a relative humidity of 90% or more. More preferably left to stand for 1 minute to 1 hour. Moisture supply can be carried out using a thermo-hygrostat that can control temperature and humidity. If the step of supplying the moisture exceeds 70 ℃, may affect the optical properties of the polarizer.

On the other hand, as can be seen in Figure 2, the longer the water supply time, in both the short wavelength region (460nm) and the long wavelength region (620nm), the transmittance of the absorption axis of the polarizing plate is reduced, in particular, it is confirmed that the transmittance rapidly decreases around 20 minutes Can be.

In the case of supplying the moisture, iodine and / or dichroic dye decomposed into a compound absorbing a short wavelength region due to dissociation in the step of irradiating light has a high mobility of the decomposed molecules by moisture. Is increased. This results in recombination between some molecules due to van der Waals forces between the molecules, resulting in a compound that absorbs the long wavelength region that has been degraded. Specifically, two I reacts first to form I _{2, so} that transmittance decreases first in the short wavelength region (460 nm), followed by recombination of five I to reduce the transmittance in the long wavelength region (620 nm). That is, the color can be adjusted according to the adjustment of the humidification time. As a result, as compared with the initial polarizer, the balance between the long and short wavelength absorbing compounds is achieved, and the absorption of light in the short wavelength is increased to approach the black color as a whole.

More specifically, when the polyvinyl alcohol film subjected to the dyeing process using potassium iodide (KI) is stretched, a polyvinyl alcohol and a iodine complex (PVA-Ix complex) form a linear array. The iodine has a form arranged in atomic chains between the films. At this time, the color of the polarizing plate is different depending on the distribution of iodine dyed in polyvinyl alcohol (PVA). The iodine dyeing a polyvinyl alcohol film, _{^{I 5 -, I 3 -,}} I 2 , and I ^- are present in various forms such as. Each iodine absorbs light in different wavelength bands. The more I ₅ ^- is present, the more blueish it is. The more I ₂ and I ₃ ^- are present, the more reddish or yellowish it is. ) Color.

Mainly, after initial dyeing and stretching, I ₅ ⁻ (620 nm) which mainly absorbs light in the long wavelength region is mainly produced, so that the polarizing plate becomes blue. Therefore, when I ₅ ⁻ is dissociated through light irradiation, I ₅ ⁻ is decomposed into I ₃ ⁻ and 2I. Then, after the step of supplying water, the mobility of 2I decomposed by water increases, and due to the increase in fluidity, unstable 2I is first combined into I ₂ so that the permeability decreases in the short wavelength region (460 nm) first. Then, in combination with I ₃ ⁻ , again producing I ₅ ⁻ , reducing the transmittance of the long wavelength region (620 nm). Therefore, as a result, I ₅ ⁻ decreases and I ₂ increases, so that the polarizer that absorbs light of long wavelength mainly increases the absorption amount of light of short wavelength, and thus has a color close to natural black.

On the other hand, in general, the conventional complementary color step is adjusted to a black color by inducing a positive reaction of the following formula 1 by supplying I ^- to the PVA-Ix complex during or after the stretching process. One way to promote the forward reaction of Equation 1 below is to supply KI to make the forward reaction dominant or to apply heat. However, the forward to the deep sea floor, most of the iodine ion species of formula I ₃ 1 ^-, I _2, I ^-, so as to present, there is, since the polarization characteristic becomes vulnerable color polarizer is very reddening, difficulty in color control.

[Formula 1]

_{^{I 5 - + I - → I}} 2 + I 3 - + I ^-

In particular, in the case of using the chemical complementary color step using KI, which is mainly performed, the residual amount of KI is increased in the manufactured polarizer and the polarizing plate, resulting in an increase in the occurrence of poor slicing, glittering, and polarization of the polarizing plate. In addition, when exposed for a long time under high temperature conditions, it causes a problem that the overall heat resistance, such as a decrease in polarization degree and color change of the polarizing plate is lowered. This is because the residue of KI added in the complementary color step reacts with KI ₅ at high temperature to increase I ₃ ⁻ and I ₂ and decrease the color and optical properties of the polarizing member. On the other hand, in the case of the production method of the present invention, the addition of additional chemicals and the manufacturing step does not increase, there is an advantage that can minimize the foreign matter defects and overcome the problem of lowering the heat resistance.

On the other hand, as can be seen in the graph of Figure 1, before the light irradiation step and the humidification step (Comparative Example 1) the absorption of the short wavelength band is insufficient, but after the process according to the present invention in the short wavelength band 400nm to 550nm wavelength range It can be seen that the absorption is greatly increased, similar to the absorption in the wavelength range of 551nm to 700nm long wavelength band. That is, the polarizing plate, which mainly absorbs light of a long wavelength band and becomes blue, has a color close to natural black after the above process due to the increase in light absorption of the short wavelength band. This can be seen that there is a significant effect compared to the case of the conventional chemical complementary process (Comparative Example 3).

In another aspect of the present invention, a polarizing plate manufactured by the above production method is provided.

Specifically, the polarizing plate according to the present invention comprises a polyvinyl alcohol-based polarizer prepared by the above-described manufacturing method, in which at least one of iodine and dichroic dye is dyed, and measured at 460 nm vs. orthogonal absorbance at 620 nm. It is preferable that the ratio of orthogonal absorbance measured is 1: 0.8-1: 1.1.

As described above, the polarizing plate of the present invention is irradiated with light of a specific wavelength and then supplied with moisture to regenerate iodine and / or dichroic dyes absorbing visible light in long and short wavelength bands, and finally visible. The light of the wavelength range can be absorbed uniformly. However, as can be seen in the graph of FIG. 1, the polarizer having undergone the conventional chemical complementary color process has a low absorption of light in the short wavelength band, and thus the orthogonal absorbance measured at about 460 nm is only about 1.8 and orthogonal absorbance measured at 460 nm. The ratio of orthogonal absorbance measured at 620 nm is about 1: 1.5.

However, in the present invention, the ratio of orthogonal absorbance measured at 460 nm to orthogonal absorbance measured at 620 nm is 1: 0.8 to 1: 1.1, more preferably 1: 0.9 to 1: 1.1. When the orthogonal absorbance measured at the wavelength satisfies the above range, the light absorption of the short wavelength and long wavelength bands of the polarizer becomes similar to have a color close to natural black.

At this time, the orthogonal absorbance is a value obtained by measuring the orthogonal transmittances (Tc) at 460 nm and 620 nm of the polarizing plates, respectively, using an ultraviolet visible spectrophotometer, and obtained by (orthogonal absorbance) =-Log ₁₀ Tc.

On the other hand, the polarizer and the polarizing plate is the same as the above-mentioned content, detailed description thereof will be omitted.

At this time, it is preferable that the single color b value of the said polarizing plate is 3.5-4.6, and it is preferable that orthogonal color b value is -1-0.

The group color used herein refers to a color obtained when natural light is irradiated to one polarizing plate, and the orthogonal color refers to two polarizing plates having different polarizing plates stacked on one polarizing plate so that absorption axes are perpendicular to each other at right angles. The color obtained when irradiated.

In addition, the color a and the color b refers to a value representing the color in the CIE coordinate system, and more specifically, the color a value is a = 500 [(X / Xn) ¹ / ^3- (Y / Yn) ^{1 / 3} ], where + a means red and -a means green. In addition, the color b value is calculated as b = 200 [(Y / Yn) ¹ / ^3- (Z / Zn) ^1/3 ], + b means yellow and -b means blue. (Where Xn, Yn, and Zn correspond to X, Y, and Z of the reference white color)

That is, the group colors a and b values refer to the color a and b values in the CIE coordinate system measured by using a colorimeter with a single polarizer color, and the orthogonal colors a and b values indicate that a pair of polarizers are orthogonal to the absorption axis. Means the color a and b values in the CIE coordinate system measured using a color difference meter when the color is arranged in a state.

Specifically, it is preferable that the group color b value generally satisfies the range of 3.5 to 4.6, and the reason is that when the group color b value is less than 3.5 when the polarizing plates are arranged orthogonally, a bluish color feeling is obtained. If it is greater than 4.6, it may be difficult to implement a natural black color by showing a yellowish color, and may lower the ratio (CR).

More specifically, conventionally, when the conditions of dyeing, crosslinking, and stretching stages are changed, the group color b value of the polarizer is changed, and thus, it is necessary to change other conditions for controlling the group color b value. At this time, as discussed above, it was difficult to control the single color b value of the polarizer in the dyeing, crosslinking and stretching steps. However, the method of manufacturing a polarizing plate of the present invention has the advantage of controlling the single color b value by simply irradiating light and supplying water when the simple color b value is not the desired color range after dyeing, crosslinking and stretching. There is this.

On the other hand, as the orthogonal color b value is closer to 0, a natural black color may be realized, and more preferably, a value of -1 to 0 is more preferable.

The polarization degree (DOP) of the polarizing plate manufactured by the manufacturing method of the present invention may be 99.9% or more, for example, more preferably 99.98% or more. When the degree of polarization is high, it is possible to make a polarizing plate excellent in the CR (Contrast Ratio), when adjusting the color of the polarizer by irradiating ultraviolet rays according to the manufacturing method of the present invention, the advantage of manufacturing a polarizing plate having an excellent polarization degree of 99.98% or more There is this.

Moreover, after performing heat resistance evaluation which exposes the said polarizing plate for 500 hours under 80 degreeC or more high temperature conditions, the polarization degree of a polarizing plate is 99.9% or more, More preferably, it is 99.98% or more. In addition, the single transmittance (Ts) of the polarizing plate is preferably 42% to 45%. This is different from the conventional chemical complementary process, which does not undergo chemical treatment, irradiates light to decompose iodine and / or dichroic dye first, and then recombines by water supply to form a compound that absorbs short and long wavelengths. As a result, the thermal stability is superior to the conventional chemical complementary color process using KI. Complementary color process using KI did not have good thermal stability such as the residual KI decomposes KI ₅ at high temperature and produces KI ₃ and I ₂ to reduce long wavelength absorption and increase short wavelength absorption.

Meanwhile, the degree of polarization is determined by orthogonal transmittance (Tc) obtained after orthogonally crossing each other so that the absorption axes are 90 ° and the parallel transmittance (Tp) obtained when the two polarizing plates are arranged in parallel with the absorption axes. It is defined by Equation 1 below.

[Equation 1]

Polarization degree = [(Tp-Tc) / (Tp + Tc)] ^1/2

On the other hand, the polarizing plate of the present invention as described above is attached to one side or both sides of the display panel can be usefully applied to the image display device. The display panel may be a liquid crystal panel, a plasma panel, and an organic light emitting panel. Accordingly, the image display device may include a liquid crystal display (LCD), a plasma display panel (PDP), and an organic light emitting display device. The display device may be an organic light emitting diode (OLED).

More specifically, the image display device may be a liquid crystal display device including a liquid crystal panel and polarizing plates provided on both surfaces of the liquid crystal panel, wherein at least one of the polarizing plates may be a polarizing plate according to the present invention. That is, the polarizing plate is a process of supplying water to the polarizing member after irradiating light of a specific wavelength selected from a wavelength range of 200nm to 800nm with a polarizing member including a polyvinyl alcohol-based polarizer dye iodine and / or dichroic dye It is produced through, characterized in that the single color b value has a value of 3.5 to 4.6.

 In this case, the type of liquid crystal panel included in the liquid crystal display device is not particularly limited. For example, a panel of a passive matrix type such as, but not limited to, a twisted nematic (TN) type, a super twisted nematic (STN) type, a ferrolectic (F) type, or a polymer dispersed (PD) type; Active matrix panels such as two-terminal or three-terminal; All known panels, such as an In Plane Switching (IPS) panel and a Vertical Alignment (VA) panel, can be applied. In addition, other configurations constituting the liquid crystal display device, for example, types of upper and lower substrates (eg, color filter substrates or array substrates) are not particularly limited, and configurations known in the art may be employed without limitation. Can be.

Hereinafter, the present invention will be described in more detail with reference to Examples. The following examples are provided to aid the understanding of the present invention and thus do not limit the present invention.

Production Example

After swelling the polyvinyl alcohol-based film (Japan Synthetic Co., Ltd. M3000 grade 30㎛) for 15 seconds in a 25 ° C. pure solution, a dyeing process was performed for 60 seconds in a 0.2 wt% concentration and a 25 ° C. iodine solution. Then, after 30 seconds in a 1 wt% boric acid, 45 ℃ solution, the washing process was carried out a 6-fold stretching process in a solution of boric acid 2.5wt%, 52 ℃. Thereafter, a polarizer having a thickness of 12 μm was prepared by drying in an oven at 60 ° C. for 5 minutes.

The polarizer 40 μm triacetyl cellulose (TAC) film prepared above was placed on both sides of the PVA polarizer and laminated with a laminator through a PVA-based water-soluble adhesive, followed by drying in an oven at 80 ° C. for 5 minutes to form a polarizing plate having a TAC / PVA / TAC structure. Was prepared.

Example 1

After cutting the polarizing plate prepared according to the above preparation to 60mm × 60mm, using a laser (Verdi V2, Coherent) exposed to a 532nm wavelength at 20J / cm ² intensity, at 60 ℃ and 90% relative humidity It was stored in a thermo-hygrostat (TH-I-300, YOKOGAWA Co., Ltd.) for 60 minutes to prepare a polarizing plate subjected to a complementary color process.

Comparative Example 1

With the polarizing plate prepared by the above Preparation Example, a polarizing plate was not subjected to any additional steps.

Comparative Example 2

After cutting the polarizing plate prepared by the above preparation to 60mm × 60mm, a polarizing plate that was subjected to a step of exposing the 532nm wavelength at 20J / cm ² intensity using a laser (Verdi V2, Coherent) was prepared.

Comparative Example 3

After swelling the polyvinyl alcohol-based film (Japan Synthetic Co., Ltd. M3000 grade 30㎛) for 15 seconds in a 25 ° C. pure solution, a dyeing process was performed for 60 seconds in a 0.2 wt% concentration and a 25 ° C. iodine solution. Then, after 30 seconds in a 1 wt% boric acid, 45 ℃ solution, the washing process was carried out a 6-fold stretching process in a solution of boric acid 2.5wt%, 52 ℃. After stretching, a polarizer having a thickness of 12 μm was prepared by performing a complementary color process in a 5 wt% KI solution and drying in an oven at 60 ° C. for 5 minutes.

The polarizer 40 μm triacetyl cellulose (TAC) film prepared above was placed on both sides of the PVA polarizer and laminated with a laminator through a PVA-based water-soluble adhesive, followed by drying in an oven at 80 ° C. for 5 minutes to form a polarizing plate having a TAC / PVA / TAC structure. Was prepared.

Experimental Example 1 Evaluation of Optical Properties

1. Measurement of optical properties

The polarizing plates prepared in Example 1 and Comparative Examples 1 to 3 were cut to a size of 40 mm × 40 mm, and the specimen was fixed to a measurement holder, followed by an ultraviolet visible spectrometer (V-7100, manufactured by JASCO). The initial optical properties, that is, the single transmittance (Ts), the polarization degree, and the color (group a, group b, orthogonal a, orthogonal b) were measured. The single transmittance (Ts) and the single color (a, b) are measured values for one polarizing plate, and the orthogonal color (orthogonal a, orthogonal b) is orthogonal to each other so that the absorption axis of the two polarizing plates is 90 °. After the measurement, it is shown in Table 1.

The polarization degree is defined by the following Equation 1 by the orthogonal transmittance Tc obtained after orthogonal to each other so that the parallel transmittance Tp obtained when the two polarizing plates are arranged in parallel with the absorption axis and the absorption axis becomes 90 °.

[Equation 1]

Polarization degree = [(Tp-Tc) / (Tp + Tc)] ^1/2

2. Heat resistance evaluation

After exposing the polarizing plates prepared in Examples and Comparative Examples for 500 hours under 80 ° C. conditions, the polarization degree and single transmittance were measured by the method described above, and the results are shown in Table 1.

Table 1 Classification Group color a Color b Ortho color a Ortho color b Initial polarization degree Initial Group Permeability (%) After polarization at high temperature Permeability after leaving at high temperature (%) Example 1 -1.38 3.95 0.40 -0.90 99.98 42.32 99.98 42.50 Comparative Example 1 -0.72 1.61 -0.12 -6.06 99.82 42.39 99.31 44.95 Comparative Example 2 -8.6 18.6 -11.31 24.18 8.43 86.35 8.31 86.36 Comparative Example 3 -1.34 4.76 0.41 -0.13 99.98 42.55 99.30 44.17

As can be seen in Table 1, the polarizing plate of Example 1 has a single color b value and orthogonal color b value is included in the range of 3.5 to 4.6 and -0.1 to 0, respectively, the color is close to natural black, 500 hours Even when it is left at a high temperature for a while, there is almost no change in polarization degree and single transmittance, and the numerical value is also very good and it can be confirmed that the heat resistance is excellent.

Experimental Example 2-Absorption Spectrum Measurement

In Example 1 and Comparative Examples 1 to 3 using the polarizing plate as a light source DH-2000 (Ocean optics, Inc.) and the detector using the USB4000 (Ocean optics, Inc.) to measure the absorption spectrum (Absorption Spectrum) in Figure 1 Indicated.

First, referring to FIG. 1, the polarizing plate manufactured by the manufacturing method of Example 1 of the present invention has a high orthogonal absorbance of a short wavelength region (about 450 nm to 550 nm) as compared to the polarizing plate of Comparative Example 1 that is not subjected to the exposure and moisture supply steps. Is similar to the orthogonal absorbance in the long wavelength region (about 551 nm to 650 nm). This shows that the polarizer of the present invention exhibits a color close to natural black because the orthogonal absorbance of light is similar in the short wavelength and long wavelength regions.

In addition, in the polarizing plate of Comparative Example 3 manufactured through a conventional chemical complementary color process, the absorbance of the short wavelength region (about 450 nm to 550 nm) was slightly increased compared to that of the polarizing plate not subjected to the complementary color process, but the polarizing plate of Example 1 had a short wavelength region. Compared with the maximum absorbance at about 3, it can be seen that in the polarizing plate of Comparative Example 3, the maximum absorbance in the short wavelength region is less than 2.

In addition, in Comparative Example 2 after the exposure step, but not through the water supply step, it can be seen that the absorbance is significantly reduced in the entire visible light region by decomposition of the iodine compound.

Experimental Example 3-Measurement of change with time of supplying moisture

When the 60 mm × 60 mm polarizing plate prepared according to the above production example was irradiated with an intensity of 20 J / cm 2 using a 532 nm laser (Verdi V2, Coherent Co., Ltd.), and then left at 60 ° C. and a relative humidity of 90%, absorption according to the standing time The change in the transmittance of the axis was measured and shown in FIG. 2.

Looking at Figure 2, after the step of irradiating light, when the water supply, it can be confirmed that the water absorption time is rapidly decreased in the absorption axis at each wavelength after 20 minutes.

Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and variations can be made without departing from the technical spirit of the present invention described in the claims. It will be obvious to those who have ordinary knowledge of.

Claims (10)

Preparing a polarizing member including a polyvinyl alcohol polarizer in which at least one of iodine and dichroic dye is dyed; Irradiating the polarizing member with light having a specific wavelength selected from a wavelength range of 200 nm to 800 nm; And Method of manufacturing a polarizing plate comprising sequentially supplying water to the polarizing member. The method of claim 1, Irradiating the light is a polarizing plate manufacturing method performed at an intensity of 0.5 to 550 J / cm ² . The method of claim 1, Irradiating the light is a polarizing plate manufacturing method using a light emitting diode (LED) or a laser lamp. The method of claim 1, The step of supplying water is a polarizing plate manufacturing method performed by a method for leaving the polarizing member for 10 minutes to 3 hours at 40 ℃ to 70 ℃ and relative humidity 90% or more. At least one of iodine and dichroic dye comprises a polyvinyl alcohol polarizer, A polarizing plate having a ratio of orthogonal absorbance measured at 460 nm to orthogonal absorbance measured at 620 nm from 1: 0.8 to 1: 1.1. The method of claim 5, The polarizing plate whose single color b value of the said polarizing plate is 3.5-4.6. The method of claim 5, The polarizing plate whose orthogonal color b value of the said polarizing plate is -1-0. The method of claim 5, A polarizing plate having a polarization degree of 99.9% or more after exposing the polarizing plate for 500 hours at 80 ° C. or higher. The method of claim 5, After exposing the polarizing plate for 500 hours at a high temperature of 80 ° C. or more, the polarizing plate has a single transmittance of 42% to 45%. Display panel; And An image display device attached to one side or both sides of the display panel, comprising a polarizing plate according to claim 5.

Images