KR102498953B1 - Method for preparing polarizing plate, polarizing plate prepared from the same and display appartus comprising polarizing plate prepared from the same - Google Patents

Abstract

Forming a polarization depolarization region having a single transmittance of 80% or more by irradiating a femtosecond laser to a polarizer dyed with at least one of iodine and a dichroic dye or a laminate having a protective film formed on at least one surface of the polarizer, wherein the femtosecond A method for manufacturing a polarizing plate in which the laser includes at least two types selected from a wavelength region of 340 nm to 346 nm and a wavelength region of 510 nm to 520 nm, respectively, a polarizing plate manufactured therefrom, and a display device including the polarizing plate manufactured therefrom is provided .

Description

A method for manufacturing a polarizing plate, a polarizing plate manufactured therefrom, and a display device including the polarizing plate manufactured therefrom

The present invention relates to a method for manufacturing a polarizing plate, a polarizing plate manufactured therefrom, and a display device including the polarizing plate manufactured therefrom.

The polarizer functions to polarize and emit light emitted from a liquid crystal panel among optical display devices. The polarizing plate includes a polarizer and a protective film laminated on at least one surface of the polarizer. Recently, optical display devices are generally added with various functions such as a camera and a video call as well as a display function for displaying a screen. Since the polarizing plate does not transmit more than 50% of the amount of light due to its polarization function, when the polarizing plate is used in the camera area as it is, visibility may be deteriorated.

In order to implement this, there is a method of chemically treating a portion of the polarizer or physically punching a hole in the polarizer. However, if the polarizer is physically treated, the entire polarizer may be damaged, and if the polarizer is chemically treated, polarization is depolarized even to an area where depolarization is not required, which may reduce practicality.

Accordingly, recently, a method of forming a polarization depolarization region by irradiating a laser beam on only a partial region of a polarizing plate has been considered. As the laser, a millisecond, nanosecond, picosecond, or femtosecond laser may be used depending on the pulse width. In particular, the femtosecond laser has a smaller pulse width than that of millisecond, nanosecond, and picosecond, and thus can reduce external deformation of the polarizer during laser irradiation. On the other hand, the inventors of the present invention confirmed that even if the polarization depolarization region is formed with a conventional femtosecond laser, when the polarizing plate is left at high temperature and high humidity for a long time, the increased single transmittance and the lowered polarization degree return to the state before laser irradiation. In order to prevent this, a barrier layer and/or a barrier film may be provided, but this is not good in manufacturing processability and economical efficiency. Recently, a polarizing plate in which a protective film is formed on only one side of the polarizer and a barrier layer is added to the other side has been developed, but it is not clear whether or not the aforementioned problem can be solved. Meanwhile, a method of forming a transmission region by irradiating a femtosecond laser in a wavelength region of 500 nm has recently been developed, but the above-described restoration problem cannot be solved.

The background art of the present invention is disclosed in Korean Patent Publication No. 2017-0037854 and the like.

It is an object of the present invention to provide a method for manufacturing a polarizing plate having excellent reliability at high temperature and high humidity, in which a polarization depolarization region exists and the change rate of single transmittance and/or polarization degree in the depolarization region is low even when left at high temperature and high humidity for a long period of time.

Another object of the present invention is to provide a method for manufacturing a polarizing plate, which does not require a separate barrier layer and/or barrier film, is excellent in manufacturing processability and economy, and has a thinning effect.

Another object of the present invention is to provide a method for manufacturing a polarizing plate without cracks and/or external deformation at the interface between the polarization depolarization area and the polarization area.

One aspect of the present invention is a method for manufacturing a polarizing plate.

1. A method for manufacturing a polarizing plate is to form a polarization depolarization region having a single transmittance of 80% or more by irradiating a femtosecond laser to a polarizer dyed with at least one of iodine and dichroic dye or a laminate having a protective film on at least one surface of the polarizer The femtosecond laser includes at least two types each selected from a wavelength range of 340 nm to 346 nm and a wavelength range of 510 nm to 520 nm.

In 1, the femtosecond laser may be selected from wavelengths of 343 nm and 515 nm, respectively.

In 1-2, the femtosecond laser may be irradiated with a pulse width of 100 femtoseconds (fs) to 500 femtoseconds (fs) and a frequency of 100 kHz to 500 kHz.

In 1-3, the femtosecond laser irradiated in the wavelength region of 510 nm to 520 nm is irradiated at 0.01 J/(cm ² ㆍ pulse) to 0.20 J/(cm ² ㆍ pulse) for 0.1 second to 1000 seconds, and the wavelength 340 nm The femtosecond laser irradiated in the region of 346 nm to 0.01 J/(cm ² ㆍ pulse) to 0.17 J/(cm ² ㆍ pulse) may be irradiated for 0.1 second to 1000 seconds.

In 1-4, the step of preparing the polarizer may be prepared by dyeing, crosslinking, and stretching the polyvinyl alcohol-based film with at least one of the iodine and dichroic dyes.

In 1-5, the polarizing plate manufactured by the manufacturing method of the polarizing plate may have a rate of change in single transmittance of Equation 1 below of 10% or less.

[Equation 1]

Change rate of single transmittance = │T2 - T1│/T1 x 100

(In Equation 1, T1 is the initial single transmittance of the laser-irradiated region of the polarizer or polarizer (unit: %)

T2 is the single transmittance (unit: %) of the area irradiated with the laser after the polarizer or polarizer is left at 60° C. and 95% relative humidity for 500 hours.

In 1-6, the method of manufacturing the polarizing plate may not include laminating a barrier layer or a barrier film on at least one surface of the polarizer or the laminate.

The polarizing plate of the present invention includes a polarizing plate manufactured by the manufacturing method of the polarizing plate of the present invention.

The polarizer may have a single transmittance change rate of 10% or less of Equation 3 below:

[Equation 3]

Change rate of single transmittance = │T2 - T1│/T1 x 100

(In Equation 3 above, T1 is the first single transmittance of the region where the single transmittance is 80% or more (unit: %)

T2 is the single transmittance (unit: %) of the area where the single transmittance is 80% or more after the polarizer is left at 60° C. and 95% relative humidity for 500 hours.

The display device of the present invention includes a polarizing plate manufactured by the manufacturing method of the polarizing plate of the present invention.

The present invention provides a method for manufacturing a polarizing plate having excellent reliability at high temperature and high humidity, in which a depolarization region exists and the change rate of single transmittance and/or polarization degree in the depolarization region is low even when left at high temperature and high humidity for a long period of time.

The present invention provides a method for manufacturing a polarizing plate that does not require a separate barrier layer and/or barrier film, is excellent in manufacturing processability and economy, and has a thinning effect.

The present invention provides a method for manufacturing a polarizer having no cracks and/or external deformation at the interface between the polarization depolarization area and the polarization area.

The present invention will be described in detail by the accompanying examples so that those skilled in the art can easily practice it. This invention may be embodied in many different forms and is not limited to the embodiments set forth herein.

In this specification, "single transmittance" is a value measured at a wavelength of 400 nm to 800 nm.

In the present specification, when describing a numerical range, "X to Y" means X or more and Y or less (X≤ and ≤Y).

The method for manufacturing a polarizing plate of the present invention includes irradiating a femtosecond laser to a polarizer dyed with at least one of iodine and a dichroic dye or a laminate having a protective film formed on at least one surface of the polarizer, wherein the femtosecond laser has a wavelength At least two types of femtosecond lasers selected from a range of 340 nm to 346 nm and a wavelength range of 510 nm to 520 nm are included. Through this, it is possible to form a transmission region having a single transmittance of 80% or more in a partial region of the polarizer or the laminate. In addition, at least two types of femtosecond lasers each selected from a wavelength range of 340 nm to 346 nm and a wavelength range of 510 nm to 520 nm may increase reliability of the polarizer or polarizer at high temperature and high humidity. Reliability at high temperature and high humidity will be described in more detail below.

Hereinafter, a method of manufacturing a polarizing plate according to an embodiment of the present invention will be described.

A method of manufacturing a polarizing plate includes irradiating a femtosecond laser to a polarizer dyed with at least one of iodine and dichroic dye, wherein the femtosecond laser is at least two selected from a wavelength range of 340 nm to 346 nm and a wavelength range of 510 nm to 520 nm, respectively. species of femtosecond lasers.

In one embodiment, the polarizer may include a polarizer made of a polyvinyl alcohol-based resin film. The polyvinyl alcohol-based resin film has high light transmittance for light in the wavelength range of 340 nm to 346 nm and the wavelength range of 510 nm to 520 nm, both before and after dyeing, so that deformation does not occur even when irradiated with the laser in the above two regions. In addition, light in the 340 nm to 346 nm region and the wavelength region of 510 nm to 520 nm may be effectively possible without thermal deformation of the polarizer and/or the polarizing plate even when the light is directly irradiated to the polarizer without a protective film.

In the present invention, a femtosecond laser is irradiated to form a polarization depolarization region having a single transmittance of 80% or more on at least a portion of the polarizer or polarizer. Compared to millisecond, nanosecond, and picosecond lasers, femtosecond lasers can reduce the width of the region where optical characteristics change at the interface between the laser irradiated surface and the non-laser irradiated surface by suppressing thermal deformation during laser irradiation to the polarizer, and bubble generation And / or there is no problem such as generation of bends on the surface of the polarizer, it is possible to provide the effect of improving the appearance.

Light in the wavelength range of 510 nm to 520 nm decomposes iodine and dichroic dyes by transitioning the iodine and dichroic dyes dyed on the polarizer from the ground state to the excited state, thereby eliminating the polarization function in the irradiated area and simultaneously increasing the single transmittance can be increased to 80% or more. When at least two types of femtosecond lasers selected from the wavelength range of 340 nm to 346 nm and the wavelength range of 510 nm to 520 nm are irradiated to the polarizer, the above-described polarization function is eliminated, the single transmittance is increased, and the high-temperature, high-humidity reliability of the polarizer or polarizer is increased. can Here, “high temperature and high humidity reliability” means that the degree of change in single transmittance and/or polarization degree in a light-irradiated region is small when the polarizer or polarizer is left at high temperature and high humidity for a long period of time.

Specifically, the region irradiated with the laser in the polarizer or polarizing plate may have a change rate of single transmittance of 10% or less, for example, 0% to 2% according to Equation 1 below: Even if the polarizing plate is left in the above range at high temperature and high humidity for a long time Since the degree to which the single transmittance of the region irradiated with the laser returns to the state before laser irradiation is low, the polarizer does not need to be frequently replaced when used in a display device. Although not particularly limited, a region having a single transmittance of 80% or more may be a region where a camera module or the like is formed when applied to a display device.

[Equation 1]

Change rate of single transmittance = │T2 - T1│/T1 x 100

(In Equation 1, T1 is the initial single transmittance of the laser-irradiated region of the polarizer or polarizer (unit: %)

T2 is the single transmittance (unit: %) of the area irradiated with the laser after the polarizer or polarizer is left at 60° C. and 95% relative humidity for 500 hours.

Specifically, the area irradiated with the laser in the polarizer or polarizing plate may have a change rate of 10% or less, for example, 0% to 5%, according to Equation 2 below: Since the polarization degree of the irradiated area is low to the state before laser irradiation, it is not necessary to frequently replace the polarizer when used in a display device. A region having a single transmittance of 80% or more may be a region where a camera module or the like is formed when applied to a display device.

[Equation 2]

Change rate of polarization degree = │P2 - P1│/P1 x 100

(In Equation 2, P1 is the initial polarization degree of the laser-irradiated region of the polarizer or polarizer (unit: %)

P2 is the degree of polarization (unit: %) of the area irradiated with the laser after the polarizer or polarizer was left at 60° C. and 95% relative humidity for 500 hours.

As described above, the method for manufacturing a polarizing plate of the present invention irradiates at least two types of femtosecond lasers having different wavelengths selected from a wavelength region of 340 nm to 346 nm and a wavelength region of 510 nm to 520 nm, respectively, to form a depolarization region in a partial region of the polarizer. At the same time, the reliability of the polarizer at high temperature and high humidity is improved.

When irradiating only a femtosecond laser selected from the wavelength range of 340 nm to 346 nm, the iodine PVA Complex I ₅ ^- and I ₃ ^- ions in the long wavelength range of 460 nm to 620 nm cannot be dissociated in a short time to form a polarization depolarization region, but the laser irradiation time is long. may not be economical.

On the other hand, when irradiating only a femtosecond laser selected from the wavelength range of 510 nm to 520 nm, iodine ions I ₃ ^- and I ₂ in the short wavelength range of 250 nm to 450 nm cannot be completely dissociated, and thus the PVA Complex I ₅ ^- and I ₃ ^- are re-formed at high temperature and high humidity. It may be difficult to reach the above-described high-temperature, high-humidity reliability due to a phenomenon in which the transmittance of the polarization depolarization region is lowered. In general, when irradiated with a femtosecond laser to form a transmittance region of 80% or more of single transmittance, the polarizer may drop to less than 80% as the depolarization function is restored when left at high temperature and high humidity for a long period of time. In order to solve this problem, there is a problem in that a barrier layer or barrier film having low water permeability should be additionally laminated on at least one surface of the polarizer, even if the polarizer manufactured by the method for manufacturing a polarizer of the present invention does not include the barrier layer or barrier film. After being left for a long time at high temperature and high humidity, the single transmittance can be maintained at 80% or more. The "barrier layer" and "barrier film" may include conventional types known to those skilled in the art that have low water permeability and can suppress penetration of moisture from the outside.

Specifically, femtosecond lasers with wavelengths of 340 nm, 341 nm, 342 nm, 343 nm, 344 nm, 345 nm, 346 nm, and preferably 343 nm may be selected in the wavelength range of 340 nm to 346 nm. Specifically, femtosecond lasers with wavelengths of 510 nm, 511 nm, 512 nm, 513 nm, 514 nm, 515 nm, 516 nm, 517 nm, 518 nm, 519 nm, 520 nm, and preferably 515 nm may be selected in the wavelength range of 510 nm to 520 nm. Optimally, a femtosecond laser may be irradiated at a wavelength of 343 nm and a wavelength of 515 nm, respectively.

At least two types of femtosecond lasers each selected from a wavelength range of 340 nm to 346 nm and a wavelength range of 510 nm to 520 nm may be irradiated simultaneously or sequentially. Preferably, irradiation of 515 nm and then irradiation of 343 nm can further lower the degree of single transmittance recovery in the polarization depolarization region.

In the present invention, the effect of the present invention can be better implemented by irradiating the femtosecond lasers selected from the wavelengths of the two regions and simultaneously adjusting the intensity of the femtosecond laser irradiated in each region. Specifically, the femtosecond laser irradiated in the wavelength range of 340 nm to 346 nm is 0.01 J/(cm ² ㆍ pulse) to 0.17 J/(cm ² ㆍ pulse), preferably 0.08 J/(cm ² ㆍ pulse) to 0.011 J/ (cm ² · pulse). The femtosecond laser irradiated in the wavelength range of 510 nm to 520 nm is 0.01 J/(cm ² ㆍ pulse) to 0.20 J/(cm ² ㆍ pulse), preferably 0.15 J (cm ² ㆍ pulse) to 0.17 J/ (cm ² ㆍ pulse) can be irradiated. In the above range, I ₂ , I ₃ ^- , I ₅ ^- ions present in short wavelengths (300 to 450 nm) and long wavelengths (450 to 560 nm) are effectively dissociated in a short time, the transmittance is 80% or more, and iodine recombines under high temperature and high humidity. There may be an effect of preventing the permeability decrease phenomenon caused by. The 'J/(cm ² ㆍ pulse)' is defined as a value obtained by dividing the total energy irradiated to the polarizer per pulse by the total area irradiated with the femtosecond laser in the femtosecond laser irradiation wavelength.

The femtosecond laser has a pulse width of 100 femtoseconds (fs) to 500 femtoseconds (fs), preferably 200 femtoseconds (fs) to 400 femtoseconds (fs), and 100 kHz to 500 kHz, preferably 150 kHz to 350 kHz in each of the above wavelength regions. can be investigated at a frequency of Within the above range, it is possible to form a depolarization region having no surface carbonization or laser hatching of the processed surface due to heat and a precision of 50 μm or less, more preferably 10 μm or less at the irradiation interface.

The femtosecond laser may be irradiated for 0.1 second to 1000 seconds, for example, 0.1 second to 100 seconds in each of the above wavelength ranges. Within the above range, it is possible to form a more neutral, colorless, high transmittance portion by increasing the irradiation time or frequency under the irradiation conditions without thermal deformation of the polarizer and the protective film.

The femtosecond laser may be irradiated at 30°C to 120°C, preferably 60°C to 90°C in each of the above wavelength ranges. Within the above range, it is possible to form a more neutral, colorless, high transmittance part by increasing the irradiation time or frequency under the above irradiation conditions without thermal deformation of the polarizer and the protective film.

As described above, the region irradiated with the femtosecond laser has a single transmittance of 80% or more, specifically 80% to 100%, and a polarization degree of 40% or less, specifically 0% to 40%, so that when applied to a display device, the camera module It is applied to the formation area to improve camera visibility. An area of the polarizer to which the femtosecond laser is irradiated is a partial area of the polarizer, and may be, for example, greater than 0% and less than 50% of the polarizer, for example, 10% to 50%. A region of the polarizer to which the femtosecond laser is not irradiated may have a single transmittance of 40% or more, for example, 40% to 50%, and a polarization degree of 80% or more, for example, 80% to 100%.

A femtosecond laser is irradiated to a polarizer dyed with at least one of iodine and dichroic dye. A polarizer dyed with at least one of iodine and dichroic dyes can be manufactured by a method described in detail below.

The polarizer may be manufactured by dyeing, stretching, crosslinking, and complementary color processes. In the manufacturing method of the polarizer of the present invention, the order of dyeing and stretching is not limited. That is, the polyvinyl alcohol-based film may be stretched after dyeing, or dyed after stretching, or dyeing and stretching may be performed simultaneously.

As the polyvinyl alcohol-based film, a conventional polyvinyl alcohol-based film used in manufacturing a conventional polarizer may be used. Specifically, a film formed of polyvinyl alcohol or a derivative thereof may be used. The degree of polymerization of polyvinyl alcohol may be 1000 to 5000, the degree of saponification may be 80 mol% to 100 mol%, and the thickness may be 1 μm to 30 μm, specifically 3 μm to 30 μm, in the above range , can be used for manufacturing a thin polarizer.

The polyvinyl alcohol-based film may be subjected to water washing and swelling treatment before being dyed and stretched. By washing the polyvinyl alcohol-based film with water, foreign substances adhering to the surface of the polyvinyl alcohol-based film can be removed. By subjecting the polyvinyl alcohol-based film to swelling, the dyeing or stretching of the polyvinyl alcohol-based film can be improved. As known to those skilled in the art, the swelling treatment may be performed by leaving the polyvinyl alcohol-based film in an aqueous solution in a swelling tank. The temperature of the swelling tank and the swelling treatment time are not particularly limited. The swelling tank may further include boric acid, inorganic acid, surfactant 　, and the like, and their contents may be adjusted.

The polyvinyl alcohol-based film can be dyed by dyeing the polyvinyl alcohol-based film in a dyeing bath containing at least one of iodine and dichroic dye. In the dyeing process, the polyvinyl alcohol-based film is immersed in a dyeing solution, and the dyeing solution may be an aqueous solution containing iodine and a dichroic dye. Specifically, iodine is provided from an iodine-based dye, and the iodine-based dye may include one or more of potassium iodide, hydrogen iodide, lithium iodide, sodium iodide, zinc iodide, lithium iodide, aluminum iodide, lead iodide, and copper iodide. . The dyeing solution may be an aqueous solution containing 1% to 5% by weight of at least one of iodine and dichroic dye. Within this range, it can be used in a display device having a degree of polarization within a predetermined range.

The temperature of the dye bath may be 20° C. to 45° C., and the immersion time of the polyvinyl alcohol-based film in the dye bath may be 10 to 300 seconds. A polarizer having a high degree of polarization may be implemented within the above range.

By stretching the dyed polyvinyl alcohol-based film in a stretching bath, the polyvinyl alcohol-based film is oriented with at least one of iodine and dichroic dye to have polarization. Specifically, both dry stretching and wet stretching methods may be used for stretching. Dry stretching may include interroll stretching, compression stretching, heating roll stretching, and the like, and wet stretching may be performed in a wet stretching bath containing water at 35 to 65°C. The wet stretching bath may increase the stretching effect by further including boric acid.

The polyvinyl alcohol-based film may be stretched at a predetermined stretching ratio, specifically, it may be stretched so that the total stretching ratio is 5 to 7 times, specifically 5.5 to 6.5 times, and the cutting phenomenon of the polyvinyl alcohol-based film stretched within the above range. , wrinkles, etc. can be prevented, and a polarizer with high polarization degree and transmittance can be implemented. Stretching may be uniaxial stretching, and stretching may be performed in one stage, but it may be possible to prevent breakage while manufacturing a thin polarizer by multi-stage stretching such as two-stage or three-stage stretching.

In the above, the polyvinyl alcohol-based film has been described in the order of stretching after dyeing, but dyeing and stretching may be performed in the same reaction vessel.

Before stretching the dyed polyvinyl alcohol-based film or after dyeing, the stretched polyvinyl alcohol-based film may be crosslinked in a crosslinking bath. Crosslinking is a process of making at least one set of iodine and dichroic dye more strongly dyed on a polyvinyl alcohol-based film, and boric acid may be used as a crosslinking agent. A phosphoric acid compound, potassium iodide, and the like may be further included to increase the crosslinking effect.

The dyed and stretched polyvinyl alcohol-based film may be treated with a complementary color in a complementary color bath. The complementary color treatment is to immerse the dyed and stretched polyvinyl alcohol-based film in a complementary color bath containing a complementary color solution containing potassium iodide. Through this, it is possible to improve durability by lowering the color value of the polarizer and removing iodine anion I ^- in the polarizer. The temperature of the complementary color tone may be 20° C. to 45° C., and the polyvinyl alcohol-based film may have a immersion time of 10 seconds to 300 seconds.

The polarizer manufactured by the method of the present invention may have a thickness of 1 μm to 30 μm, specifically 3 μm to 30 μm. Within this range, it can be used for a polarizing plate.

The manufacturing method of the polarizing plate may further include laminating a protective film on at least one surface of the polarizer. As the protective film, a protective film commonly used as a protective film of a polarizer may be used. For example, the protective film is cellulose-based including triacetyl cellulose, polyester-based including polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, etc., cyclic polyolefin-based, polycarbonate A protective film made of one or more resins selected from the group consisting of polyethersulfone, polysulfone, polyamide, polyimide, polyolefin, polyarylate, polyvinyl alcohol, polyvinyl chloride, and polyvinylidene chloride. can include The protective film may have a thickness of 10 μm to 100 μm, for example, 10 μm to 60 μm. The lamination may be performed with an adhesive, and this is by a conventional method known to those skilled in the art.

Hereinafter, a method for manufacturing a polarizing plate according to another embodiment of the present invention will be described.

A method for manufacturing a polarizing plate includes irradiating a femtosecond laser to a laminate in which a protective film is formed on at least one surface of a polarizer dyed with at least one of iodine and a dichroic dye, wherein the femtosecond laser has a wavelength of 340 nm to 346 nm and a wavelength of It includes at least two types of femtosecond lasers each selected from a range of 510 nm to 520 nm. The manufacturing method of the polarizing plate of the embodiment is substantially the same except that the femtosecond laser is not irradiated to the polarizer but to the laminate of the polarizer and the protective film. The laser is transmitted in the order of the upper protective film and the polarizer of the polarizer, and the lasers with wavelengths of 340 nm to 346 nm and 510 nm to 520 nm have a transmittance of 90% or more in the upper protective film, so that the depolarization region can be properly formed in the polarizer and at the same time Thermal deformation may be prevented from the upper protective film, the polarizer, and the polarizer.

Hereinafter, a polarizing plate according to an embodiment of the present invention will be described.

The polarizing plate according to the present embodiment may be manufactured by the above-described manufacturing method of the polarizing plate of the present invention. In the polarizing plate, at least a portion of a region having a single transmittance of 80% or more is formed by irradiation with a femtosecond laser. The thickness of the polarizing plate may be 30 μm to 200 μm. Within the above range, it can be used for a polarizing plate for a liquid crystal display device. In one embodiment, the polarizer may have a single transmittance change rate of 10% or less, for example, 0% to 2% of Equation 3 below:

[Equation 3]

Change rate of single transmittance = │T2 - T1│/T1 x 100

(In Equation 3 above, T1 is the first single transmittance of the region in which the single transmittance of the polarizer is 80% or more (unit: %)

T2 is the single transmittance (unit: %) of the area where the single transmittance is 80% or more after the polarizer is left at 60° C. and 95% relative humidity for 500 hours.

Hereinafter, a display device according to an embodiment of the present invention will be described.

The display device of the present invention may include the polarizing plate of the present invention or the polarizer of the present invention. The display device may include a liquid crystal display device, an organic light emitting display device, and the like.

Hereinafter, the configuration and operation of the present invention will be described in more detail through preferred embodiments of the present invention. However, this is presented as a preferred example of the present invention and cannot be construed as limiting the present invention by this in any sense.

Specific specifications of the components used in the following Examples and Comparative Examples are as follows.

(1) Material of polarizer: polyvinyl alcohol film (VF-PE3000, Kuraray Co., Japan, thickness: 30㎛)

(2) Protective film: triacetyl cellulose film (KC4UYW, Konica Co., Japan, thickness 40㎛)

Example 1

The polyvinyl alcohol-based film washed with water was subjected to a swelling treatment in a water swelling tank at 30°C.

The polyvinyl alcohol-based film passing through the swelling tank was treated in a dyeing tank at 30° C. containing an aqueous solution containing 3% by weight of potassium iodide for 30 seconds to 200 seconds. The polyvinyl alcohol-based film that had passed through the dye bath was passed through a wet cross-linking bath containing 3% by weight of boric acid at 30° C. to 60° C. as an aqueous solution. A polarizer was prepared by stretching the polyvinyl alcohol-based film that had passed through the crosslinking bath in an aqueous solution at 50° C. to 60° C. containing 3% by weight of boric acid so that the total stretching ratio was 6 times. A laminate was prepared by adhering a protective film to both sides of the prepared polarizer using an adhesive (Z-200, Nippon Goshei Co.).

The laminate is cut to a predetermined size, and a femtosecond laser having a wavelength of 515 nm is irradiated for 0.5 seconds at an intensity of 0.17 J/(cm ² ㆍ pulse) using a laser on only a portion of the laminate, and a femtosecond laser having a wavelength of 343 nm was irradiated for 0.5 seconds at an intensity of 0.09 J/(cm ² ㆍ pulse) to prepare a polarizing plate having a polarization depolarization region.

Example 2

A polarizing plate was manufactured in the same manner as in Example 1, except that the number of irradiations was changed from 1 to 10 in Example 1.

Comparative Example 1

A polarizing plate was prepared in the same manner as in Example 1 except that the femtosecond laser having a wavelength of 343 nm was irradiated for only 0.5 seconds at an intensity of 0.09 J/(cm ² ㆍ pulse) without irradiating a femtosecond laser having a wavelength of 515 nm in Example 1. manufactured.

Comparative Example 2

A polarizing plate was manufactured in the same manner as in Example 1 except that in Example 1, a femtosecond laser having a wavelength of 515 nm was irradiated for 0.5 seconds at an intensity of 0.17 J/(cm ² ㆍ pulse) without irradiating a femtosecond laser having a wavelength of 343 nm. did

Comparative Example 3

In Example 1, a femtosecond laser having a wavelength of 533 nm was irradiated at an intensity of 0.23 J/(cm ² ㆍ pulse) for 0.5 seconds, and a femtosecond laser having a wavelength of 343 nm was irradiated at an intensity of 0.09 J/(cm ² ㆍ pulse) for 0.5 second. A polarizing plate was prepared in the same manner as in Example 1 except for the above.

Comparative Example 4

In Example 1, a femtosecond laser having a wavelength of 515 nm was irradiated at an intensity of 0.17 J/(cm ² ㆍ pulse) for 0.5 seconds, and a femtosecond laser having a wavelength of 265 nm was irradiated for 0.5 second at an intensity of 0.09 J/(cm ² ㆍ pulse). A polarizing plate was prepared in the same manner as in Example 1 except for the above.

The following physical properties were evaluated for the polarizing plates prepared in Examples and Comparative Examples.

(1) Appearance: Bubbles and surface waviness were evaluated at the interface between the area where the laser was irradiated and the area where the laser was not irradiated. It was evaluated as good when bubbles and surface waviness did not occur, and bad when bubbles and surface waviness occurred. After the polarizing plate was left at 60° C. and 95% relative humidity for 500 hours, the appearance was evaluated after durability evaluation in the same manner.

(2) Initial single transmittance and polarization: Single transmittance and polarization were measured using a JASCO V7100 for a polarizing plate at a wavelength of 400 nm to 800 nm. Single transmittance and polarization were measured in the area where the femtosecond laser was irradiated and the area where the femtosecond laser was not irradiated, respectively.

(3) Single transmittance and polarization degree after high temperature and high humidity: The polarizing plate was left at 60° C. and 95% relative humidity for 500 hours. In the same way as in (2), single transmittance and polarization were measured in the area where the femtosecond laser was irradiated.

Example comparative example One 2 One 2 3 4 Exterior Good Good Good Good error error Single transmittance (%) of the area where the laser is not irradiated 43.2 43.2 43.2 43.2 43.2 43.2 Polarization degree of the area not irradiated with laser (%) 99.996 99.996 99.996 99.996 99.996 99.996 laser irradiated area Single transmittance (%) the first 88.2 89.5 59.4 87.5 73.3 75.1 after high temperature and high humidity 89.3 89.8 45.4 55.4 48.5 52.1 Value in Equation 1 (%) 1.2 0.3 23.5 36.7 33.8 30.6 Polarization degree (%) the first 0.668 0.558 51.586 12.121 29.988 21.125 after high temperature and high humidity 0.636 0.541 91.060 60.154 88.176 84.132 Value in Equation 2 (%) 4.8 3.0 76.5 396 194 298 Appearance after durability Good Good Good Good error error

As shown in Table 1, the manufacturing method of the polarizing plate of the present invention has excellent reliability at high temperature and high humidity in the polarization depolarization area due to low single transmittance change rate and polarization degree change rate in the depolarization area even when left at high temperature and high humidity for a long period of time, and the initial appearance and durability are excellent. After evaluation, the appearance was excellent. On the other hand, when femtosecond irradiation is performed with any one wavelength of 340 nm to 346 nm and 510 nm to 520 nm, or when the femtosecond irradiation is out of the wavelength range of the present invention, all effects of the present invention cannot be obtained.

Simple modifications or changes of the present invention can be easily performed by those skilled in the art, and all such modifications or changes can be considered to be included in the scope of the present invention.

Claims (10)

Forming a polarization depolarization region having a single transmittance of 80% or more by irradiating a femtosecond laser to a polarizer dyed with at least one of iodine and a dichroic dye or a laminate in which a protective film is formed on at least one surface of the polarizer,
Wherein the femtosecond laser includes at least two types each selected from a wavelength range of 340 nm to 346 nm and a wavelength range of 510 nm to 520 nm.
The method of claim 1 , wherein the femtosecond laser is selected from wavelengths of 343 nm and 515 nm, respectively.
The method of claim 1 , wherein the femtosecond laser is irradiated with a pulse width of 100 femtoseconds (fs) to 500 femtoseconds (fs) and a frequency of 100 kHz to 500 kHz.
The method of claim 1, wherein the femtosecond laser irradiated in the wavelength range of 510 nm to 520 nm is irradiated at 0.01 J/(cm ² ㆍ pulse) to 0.20 J/(cm ² ㆍ pulse) for 0.1 second to 1000 seconds, and the wavelength 340 nm The femtosecond laser irradiated in the region of 346 nm to 0.01 J/(cm ² ㆍ pulse) to 0.17 J/(cm ² ㆍ pulse) for 0.1 second to 1000 seconds, a method for manufacturing a polarizing plate.
The method of claim 1, wherein the preparing of the polarizer is prepared by dyeing, crosslinking, and stretching the polyvinyl alcohol-based film with at least one of the iodine and the dichroic dye.
The method of claim 1, wherein the polarizing plate manufactured by the manufacturing method of the polarizing plate has a change rate of single transmittance of 10% or less of Equation 1 below:
[Equation 1]
Change rate of single transmittance = │T2 - T1│/T1 x 100
(In Equation 1, T1 is the first single transmittance of the laser-irradiated region of the polarizer or polarizer (unit: %),
T2 is the single transmittance (unit: %) of the area irradiated with the laser after the polarizer or polarizer is left at 60° C. and 95% relative humidity for 500 hours.
The method of claim 1 , wherein the method of manufacturing the polarizing plate does not include laminating a barrier layer or a barrier film on at least one surface of the polarizer or the laminate.
A polarizing plate manufactured by the method of any one of claims 1 to 7.
The polarizing plate according to claim 8, wherein the polarizing plate has a single transmittance change rate of 10% or less of Equation 3 below:
[Equation 3]
Change rate of single transmittance = │T2 - T1│/T1 x 100
(In Equation 3 above, T1 is the first single transmittance of the region where the single transmittance is 80% or more (unit: %)
T2 is the single transmittance (unit: %) of the area where the single transmittance is 80% or more after the polarizer is left at 60° C. and 95% relative humidity for 500 hours.
A display device comprising the polarizer of claim 8.