KR20210117786A - Method of local decolorization of polarizing plate - Google Patents

Abstract

According to exemplary embodiments of the present invention, provided is a local decolorization method of a polarizing plate, which prepares a polarizing plate including a polarizer dyed with at least one of iodine and a dichroic dye. A high transmittance portion is formed by irradiating a plurality of pulses in a wavelength band including a visible light region to a predetermined region of the polarizing plate with an integrated energy amount of 4 to 70 J/cm 2. It is possible to efficiently decolorize some areas of the polarizing plate without physical or chemical damage.

Description

Method of local decolorization of a polarizing plate

The present invention relates to a method for local decolorization of a polarizing plate. More specifically, it relates to a local decolorization method of a polarizing plate that decolorizes a partial area of a dyed polarizer.

An optical film such as a retardation film, a polarizing film, or a luminance enhancing film may be inserted into an image display device such as a liquid crystal display (LCD) or an organic light emitting diode (OLED) display device. In the case of a smartphone to which the image display device is coupled, it is necessary to remove a part of the optical film or remove optical characteristics in order to implement additional functions such as a camera, a speaker, and a home button, respectively, on the upper and lower parts.

For example, Korean Patent Application Laid-Open No. 10-2016-0130360 discloses a method of locally eliminating the degree of polarization in a polarizing plate. However, local resolution of the degree of polarization requires complex physical and chemical processes, and complete resolution of the degree of polarization is practically difficult.

Therefore, it is proposed to use a physical and chemical method to remove a portion of the optical film to create a hole. However, the chemical hole processing method also requires a separate and complicated chemical process, and thus, is expensive. In the physical hole processing method, a clean processing surface may not be formed depending on the material of the optical film, and cracks may occur around the hole.

Korean Patent Publication No. 10-2016-0130360

One object of the present invention is to provide a method for local decolorization of a polarizing plate having improved efficiency.

1. Preparing a polarizing plate including a polarizer dyed with at least one of iodine and a dichroic dye; and irradiating a pulse in a wavelength band including a visible ray region to a predetermined region of the polarizing plate with an integrated energy amount of 4 to 70 J/cm ² to form a high transmittance portion.

2. The method according to 1 above, wherein the step of forming the high transmittance portion comprises irradiating the pulse through the opening of the mask in which the opening is formed.

3. The method according to 1 above, wherein the forming of the high transmittance portion includes at least partially removing at least one of the iodine and the dichroic dye from a predetermined region of the polarizer.

4. The method according to 1 above, wherein the wavelength range of the pulse is 200 to 1200 nm.

5. The method of 1 above, wherein the cumulative irradiation time of the pulses is less than 1 second, the local decolorization method of the polarizing plate.

6. The method according to the above 5, wherein the pulse is applied 1 to 50 times during the cumulative irradiation time, a method for local decolorization of a polarizing plate.

7. The method of 1 above, wherein the output of the unit pulses of the plurality of pulses in the wavelength band including the visible ray region is 1 to 10 kW/cm ² , the local decolorization method of the polarizing plate.

8. The method of 1 above, wherein the polarizer further comprises a polarizer protective film disposed on at least one surface of the polarizer, and the pulse is applied through the polarizer protective film.

9. The method of 1 above, wherein the high transmittance portion is formed in an area corresponding to at least one of a camera hole, a speaker hole, and a sensor hole of an image display device.

According to exemplary embodiments of the present invention, it is possible to partially decolorize the polarizing plate by irradiating a plurality of pulses in a wavelength band including a visible ray region of a predetermined amount of integrated energy to a predetermined region of the polarizing plate. It is possible to partially bleach the polarizing plate in a simplified process compared to the physical or chemical bleaching process.

In addition, the manufactured polarizing plate can be decolorized at a desired time, and the discoloration position can be easily adjusted. Therefore, since partial discoloration is possible after being applied to the display device, a precise alignment process is not required when laminating it on other members of the display device.

In addition, with the decolorization method of the present invention, it is possible to decolorize only a predetermined area of the polarizer without affecting other components of the polarizing plate. Accordingly, the degree of polarization of the discolored region may be effectively reduced, and optical properties such as single transmittance and transparency may be improved.

1 is a schematic perspective view illustrating a method for local decolorization of a polarizing plate according to exemplary embodiments.
2 is a schematic cross-sectional view of a polarizing plate that has been locally bleached according to exemplary embodiments.
3 is a schematic plan view of a polarizing plate that has been locally bleached according to exemplary embodiments.
4 is a schematic plan view of an image display device to which a locally decolorized polarizing plate is applied, according to exemplary embodiments.

Exemplary embodiments of the present invention prepare a polarizing plate including a polarizer dyed with at least one of iodine and a dichroic dye, and integrate a plurality of pulses in a wavelength band including a visible light region in a predetermined region of the polarizing plate. Energy amount 4 to 70J/ Provided is a method for local decolorization of a polarizing plate that forms a high transmittance portion by irradiating with cm ^{2 .} It is possible to efficiently decolorize some areas of the polarizing plate without physical or chemical damage.

Hereinafter, with reference to the drawings, embodiments of the present invention will be described in more detail. However, the following drawings attached to the present specification illustrate preferred embodiments of the present invention, and serve to further understand the technical spirit of the present invention together with the above-described content of the present invention, so the present invention is described in such drawings It should not be construed as being limited only to the matters.

1 is a schematic perspective view illustrating a method for local decolorization of a polarizing plate according to exemplary embodiments.

Referring to FIG. 1 , a polarizing plate 100 may be prepared, and a plurality of pulses in a wavelength band including a visible ray region may be irradiated with a pulse irradiation device 220 to manufacture a locally decolored polarizing plate.

2 is a schematic cross-sectional view of a polarizing plate that has been locally bleached according to exemplary embodiments.

Referring to FIG. 2 , the polarizing plate 100 may include a polarizer 120 and a high transmittance unit 110 . The polarizer 100 may include a polarizer protective film 130 disposed on at least one surface of the polarizer 120 .

The polarizer 120 may include a resin film dyed with at least one of iodine and a dichroic dye.

The resin film may include a polyvinyl alcohol-based resin, an ethylene-vinyl acetate copolymer resin, an ethylene-vinyl alcohol copolymer resin, a cellulose resin, and a film obtained by saponification, dehydration or dehydrochloric acid treatment. Preferably, a polyvinyl alcohol-based resin may be included in order to achieve a high affinity with iodine and a dichroic dye and a uniform degree of polarization.

The polarizer 120 may be manufactured by dyeing the resin film with the iodine or dichroic dye, crosslinking, and stretching in a specific direction.

The iodine or the dichroic dye may be aligned in a specific direction within the resin film. For example, when the dyed resin film is stretched in a predetermined direction, the iodine or the dichroic dye may be aligned in the specific direction.

The thickness of the polarizer 120 may be, for example, 5 to 80 μm, but is not limited thereto.

The polarizer protective film 130 may be disposed on at least one surface of the polarizer 120 . The polarizer protective film 130 may reinforce the polarizing plate 100 with mechanical strength, moisture shielding property, thermal stability, and the like. Although the polarizer protective film 130 is disposed on both surfaces of the polarizer 120 in FIG. 2 , the polarizer protective film 130 on one side may be omitted.

The pulse may be applied to the polarizer 120 through the polarizer protective film 130 .

For example, the polarizer protective film 130 may include a cellulose-based resin such as diacetyl cellulose and triacetyl cellulose, a (meth)acrylic resin, a cycloolefin-based resin, an olefin-based resin such as polypropylene, and a polyethylene terephthalate-based resin. It may include an ester-based resin, a polyamide-based resin, a polyimide-based resin, a polyethersulfone-based resin, a polycarbonate-based resin, an acrylic resin, and copolymers thereof.

The thickness of the polarizer protective film 130 may be, but is not limited to, 1 to 500 μm. Preferably, the thickness of the polarizer protective film 130 may be 1 to 300 μm.

The polarizer 120 and the polarizer protective film 130 may be bonded by an adhesive. In this case, an adhesive layer may be interposed between the polarizer 120 and the polarizer protective film 130 . The pressure-sensitive adhesive may include an acryl-based, silicone-based, styrene-based, polyester-based, rubber-based, urethane-based, and a combination thereof.

The high transmittance part 110 may be formed by irradiating a plurality of pulses (hereinafter, electromagnetic wave pulses) in a wavelength band including a visible light region to a predetermined region of the polarizing plate 100 .

The high transmittance portion 110 may refer to a specific region of the polarizing plate 100 in which polarization ability is at least partially weakened. In example embodiments, the iodine or the dichroic dye may be at least partially removed (discolored) from a specific region of the polarizer 120 to form the high transmittance portion 110 .

An electromagnetic wave pulse may be irradiated to a region in which the high transmission portion 110 of the polarizing plate 100 is to be formed. The electromagnetic wave pulse may at least partially remove the iodine or the dichroic dye from the polarizer 120 . The high transmittance portion 110 may be formed in the region from which the iodine or the dichroic dye is removed. Accordingly, the polarization degree of the high transmittance portion 110 may be reduced, and the single transmittance and transparency may be increased compared to the portion in which the iodine and the dichroic dye are not removed.

For example, the electromagnetic wave pulse may apply strong energy to the iodine or the dichroic dye momentarily to separate the iodine and the dichroic dye from the resin film. The iodine and the dichroic dye may be evaporated and/or sublimed by the electromagnetic wave pulse to be removed from the polarizer 120 .

The electromagnetic wave pulse may include electromagnetic waves intermittently irradiated with a predetermined period (frequency).

The electromagnetic wave pulse may be irradiated so that the accumulated energy amount is 4 to 70 J/cm ^{2 .} The integrated energy amount may mean a total sum of energy of unit pulses of the electromagnetic wave pulse. When the accumulated energy amount is ^{less than 4J/cm 2} , iodine and the dichroic dye may not be removed. When the amount of integrated energy exceeds 70J/cm ² , physical or chemical damage (denaturation) of the polarizer 100 may occur in addition to partial discoloration of the polarizer 120 . For example, the polarizer protective film 130 may be deformed (shrinked or wrinkled) or denatured. Preferably, the integrated energy amount may be 4 to 30J/cm ² or 5 to 20J/cm ² .

In example embodiments, the wavelength of the electromagnetic wave pulse may be 200 to 1,200 nm. The electromagnetic wave pulse can effectively remove iodine and the dichroic dye, including wavelengths in the visible, near-ultraviolet, and near-infrared regions. When the wavelength is less than 200 nm, other components of the polarizing plate 100 (eg, the polarizer protective film 130 ) may be denatured. If the wavelength exceeds 1,200 nm, it may not be possible to remove iodine and the dichroic dye. Preferably, the wavelength of the electromagnetic wave pulse may be 300 to 800 nm.

In some embodiments, the electromagnetic wave pulse may be irradiated through a UV blocking filter. In this case, electromagnetic waves in the ultraviolet region are filtered to prevent damage to the polarizer protective film 130 .

Degeneration of the polarizer protective film 130 may occur due to overexposure to the electromagnetic wave pulse. For example, excessive heat is generated inside the polarizer protective film 130 that has excessively absorbed the electromagnetic wave pulse, so that the chemical properties (molecular shape, internal bonding structure, etc.) of the polarizer protective film 130 change, or physical Deformation may occur.

In example embodiments, the cumulative irradiation time of the electromagnetic wave pulses may be 1 second or less. The cumulative irradiation time may mean the sum of the time the electromagnetic wave pulses are irradiated. When the cumulative irradiation time exceeds 1 second, the polarizer protective film 130 may be denatured. For example, the color of the portion irradiated with the electromagnetic wave pulse of the polarizer protective film 130 may change. Accordingly, since the high-transmission part 110 has a predetermined color (eg, yellow), the transparency of the high-transmission part 110 may decrease.

In example embodiments, the electromagnetic wave pulse may be applied 1 to 50 times during the cumulative irradiation time. When the number of times is greater than 50, the time during which the unit pulse is continuously irradiated to the polarizer protective film 130 increases, and damage to the polarizer protective film 130 may occur. Preferably, the electromagnetic wave pulse may be applied 1 to 15 times during the cumulative irradiation time.

In some embodiments, the irradiation time of each unit pulse of the electromagnetic wave pulse may be 1 to 10 ms. When the irradiation time is less than 1 ms, iodine and the dichroic dye may not be sufficiently stimulated. When the irradiation time exceeds 10 ms, the polarizing plate may be damaged or denatured by exposure to excessive energy.

In example embodiments, the output of the unit pulses of the electromagnetic wave pulse may be ^{1 to 10 kW/cm 2 .} When the output is ^{less than 1 kW/cm 2} , the unit pulse may not separate iodine and the dichroic dye. When the output is greater ^{than 10kW/cm 2} , the polarizer protective film 130 may be denatured to reduce transparency. Preferably. The output of the unit pulses of the electromagnetic wave pulse may be ^{3 to 8 kW/cm 2 .}

In some embodiments, the electromagnetic wave pulse may be irradiated in the form of a beam.

In example embodiments, the electromagnetic wave pulse may be irradiated through the mask 200 .

The mask 200 may include an opening 210 . The opening 210 may be formed at a position corresponding to the region in which the high transmission portion 110 is to be formed. For example, when a plurality of high-transmission portions 110 are formed, the openings 210 may be arranged according to the spacing and positions of the plurality of high-transmission portions 110 . The electromagnetic wave pulse may be irradiated to the polarizing plate 100 through the opening 210 . The electromagnetic wave pulse may be blocked in a region where the opening 210 of the mask 200 is not formed. The mask 200 may be made of a material that absorbs or reflects the electromagnetic wave pulse to block it, but is not limited thereto.

3 is a schematic plan view of a polarizing plate that has been locally bleached according to exemplary embodiments.

Referring to FIG. 3 , the polarizing plate 100 may include a plurality of high transmittance portions 110 . A portion requiring high transmittance of the image display device may be disposed on the bottom surface (opposite side of the viewing side) of the high transmittance unit 110 . The portion requiring the high transmittance may include a camera hole, a sensor hole, and the like.

4 is a schematic plan view of an image display device to which a locally decolorized polarizing plate is applied, according to exemplary embodiments.

Referring to FIG. 4 , the image display device may include a camera hole 300 , a sensor hole 310 , a speaker hole 320 , and a display unit 330 .

The sensor hole 310 may include an iris or face recognition sensor using infrared rays, lasers, or the like. The display unit 330 may also include a camera or a biometric sensor.

For example, when a polarizing plate is disposed on the front (viewing side) of a camera or various sensors, the polarizing plate emits or obtains electromagnetic waves (eg, visible light, near infrared rays and near ultraviolet rays) from the camera or various sensors. ) can be absorbed. In this case, the amount of information (eg, image brightness) of data acquired by the camera or the various sensors may be reduced.

According to exemplary embodiments of the present invention, the polarizing plate 100 including the high-transmission part 110 has the high-transmission part 110 in front of the camera hole 300 , the sensor hole 310 , the speaker hole 320 , and the like. It can be placed to be located in In this case, a high-quality image may be obtained by increasing the dose of electromagnetic waves obtained from the camera and the sensor, and sensing performance may be improved.

According to exemplary embodiments, the single transmittance of the high transmittance unit 110 may be 80% or more. The polarization degree of the high transmittance part 110 may be less than 20%. Accordingly, the high transmittance portion 110 may have excellent transmittance and transparency (colorlessness), and may have a low degree of polarization. In this case, the change in the dose of the electromagnetic wave passing through the high transmission unit 110 may be minimized.

In some embodiments, the color difference between the high transmission portion 110 and the peripheral portion (non-discolored portion) of the high transmission portion 110 may be 90 or more. The color difference may be defined by Equation 1 below in the L*a*b* color space.

[Equation 1]

ΔE ^* _ab = [(ΔL ^* ) ² + (Δa ^* ) ² + (Δb ^* ) ² ] ^1/2

ΔL ^* = L ^* _t - L ^* , Δa ^* = a ^* _t - a ^* , Δb ^* = b ^* _t - b ^* , and L ^* _t , a ^* _t , b ^* _t ^{is L *} a ^* b at the periphery ^{* is an} index, and L ^* , a ^* , b ^* may be an L ^* a ^* b ^* index of the high transmittance part.

In this case, the high transmittance portion 110 may be discolored with sufficient strength to lower the polarization degree and increase the single transmittance.

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

Example 1

A polarizing plate was prepared by forming a triacetyl cellulose (TAC) protective film on both sides of a polyvinyl alcohol (PVA)-based film dyed with iodine.

A mask including an opening was placed on the upper portion of the polarizing plate, and a unit pulse of a wavelength of 200 nm to 1200 nm was irradiated once for 3.5 ms at an intensity of ^{5.5 kW/cm 2 on the mask.} At this time, the amount of accumulated energy applied was 15 J/cm ² .

Example 2

The polarizing plate was locally decolorized in the same manner as in Example 1, except that a unit pulse of 5 kW/cm ² intensity was irradiated twice for 3.5 ms each, and the accumulated energy amount ^{was adjusted to 26 J/cm 2 .}

Example 3

The polarizing plate was locally decolorized in the same manner as in Example 1, except that a unit pulse of 5 kW/cm ² intensity was irradiated once for 18 ms, and a pulse of an integrated energy amount of 64 J/cm ^{2 was irradiated.}

Example 4

A polarizing plate was prepared by forming a triacetyl cellulose (TAC) protective film on both sides of a polyvinyl alcohol (PVA)-based film dyed with a dichroic dye, and the polarizing plate was locally decolorized in the same manner as in Example 1.

Example 5

A polarizing plate was prepared by forming a triacetyl cellulose (TAC) protective film on both sides of a polyvinyl alcohol (PVA)-based film dyed with iodine and a dichroic dye, and the polarizing plate was locally decolorized in the same manner as in Example 1.

Comparative Example 1

The polarizing plate was locally decolorized in the same manner as in Example 1, except that the accumulated energy obtained by irradiating a unit pulse of 2 kW/cm ^{2 intensity 10 times for 2.5 ms was adjusted to 78 J/cm 2 .}

Comparative Example 2

The polarizing plate was locally decolorized in the same manner as in Example 1, except that a single electromagnetic wave having an energy amount of 3.5 J/cm ^{2 was continuously irradiated through the opening for 1 second.}

Experimental example

The polarization degree, single transmittance, and color difference of the high transmittance part and the non-discolored part of the locally bleached polarizing plate were evaluated, and are shown in Table 1 below.

The single transmittance, the degree of polarization, and the color difference were measured and calculated using an ultraviolet-visible spectrometer (V-7100; JASCO). The color difference was calculated based on ^{the L *} a ^* b ^* index of the non-discolored part.

division Polarization degree group penetration color difference non-pigmented part 99.98% 42.72% 0 Example 1 0.92% 90.09% 90.40 Example 2 2.33% 88.96% 93.07 Example 3 2.75% 85.62% 97.40 Example 4 3.54% 86.44% 90.64 Example 5 2.21% 88.99% 90.50 Comparative Example 1 26.30% 71.13% 77.34 Comparative Example 2 43.15% 62.66% 66.03

Referring to Table 1, it was confirmed that the degree of discoloration of the high transmittance portion of Comparative Examples was low, and thus the degree of polarization increased and the single transmittance decreased compared to the high transmittance portion of Examples. This may be attributed to the denaturation of the polarizer protective film due to excessive exposure to electromagnetic wave pulses.

100: polarizing plate 110: high transmittance part
120: polarizer 130: polarizer protective film
200: mask 210: opening
220: pulse irradiation device 300: camera hall
310: sensor hole 320: speaker hole
330: display unit

Claims (9)

Preparing a polarizing plate including a polarizer dyed with at least one of iodine and a dichroic dye; and
A method for local decolorization of a polarizing plate, comprising: irradiating a pulse in a wavelength band including a visible ray region to a predetermined region of the polarizing plate with an integrated energy amount of 4 to 70 J/cm ^{2 to form a high-transmittance part.}
The method according to claim 1, wherein the forming of the high transmittance portion comprises irradiating the pulse through the opening of a mask in which the opening is formed.
The method according to claim 1, wherein the forming of the high transmittance portion comprises at least partially removing at least one of the iodine and the dichroic dye from a predetermined region of the polarizer.
The method according to claim 1, wherein the wavelength range of the pulse is 200 to 1200 nm, the local decolorization method of the polarizing plate.
The method according to claim 1, wherein the cumulative irradiation time of the pulse is less than 1 second, the local decolorization method of the polarizing plate.
The method of claim 5 , wherein the pulse is applied 1 to 50 times during the cumulative irradiation time.
The method according to claim 1, wherein the output of the unit pulses of the plurality of pulses in the wavelength band including the visible light region is 1 to 10 kW/cm ² , the local decolorization method of the polarizing plate.
The method according to claim 1, wherein the polarizer further comprises a polarizer protective film disposed on at least one surface of the polarizer,
The pulse is applied through the polarizer protective film, the local decolorization method of the polarizing plate.
The method according to claim 1, wherein the high transmittance part is formed in an area corresponding to at least one of a camera hole, a speaker hole, and a sensor hole of an image display device.

Images