Polarizer and optical display including the same

Abstract

A polarizer and an optical display including the polarizer. The polarizer includes: a polarizer; and a protective film formed on at least one surface of the polarizer, wherein the polarizer has a high transmittance region formed at at least a portion of the polarizer, and the high transmittance region has a depolarization index of about 2% or less at a wavelength of about 550 nanometers.

Description

Technical Field

[0001] The present invention relates to a polarizer and an optical display including the polarizer. More specifically, the present invention relates to a polarizer having a high light transmittance region, which enables images captured therethrough to have improved color quality and clarity, and an optical display including the polarizer. Background Art

[0002] The polarizer is used to emit polarized light by polarizing the light emitted from the liquid crystal panel of the optical display. The polarizer includes a polarizer and a protective film laminated on at least one surface of the polarizer. In general, the optical display has various functions such as a camera function and a video call function as well as a display function. Since the polarizer transmits only less than 50% of the incident light due to the polarization function of the polarizer, the polarizer disposed in the camera area may cause visibility to deteriorate. To solve this problem, it is necessary to form a high transmittance area at at least a portion of the polarizer.

[0003] Recently, portable electronic devices including smart phones and smart tablets (smartpads) are equipped with various functions. Specifically, the camera is an important component of the smart phone. In order to add a camera function to the smart phone, a camera component must be present on the front side of the smart phone. With the gradual increase in the screen-to-body ratio, the camera part is placed in the screen area (i.e., in the display area). At present, the image is not displayed on the camera component placed inside the screen area. Therefore, a method is being developed that enables the screen not to be displayed on the light receiving part of the camera when shooting with the camera, and enables the screen to be displayed on the light receiving part at other times. However, in this case, even when the polarizer has a high transmittance area, there are limitations in improving the color quality and clarity of the image shot through the high transmittance area. Summary of the invention

[0004] Technical issues

[0005] An object of the present invention is to provide a polarizer having a high light transmittance region that enables images captured therethrough to have improved color quality and clarity.

[0006] Technical Solution

[0007] One embodiment of the present invention relates to a polarizer.

[0008] Embodiment 1. The polarizer comprises: a polarizer; and a protective film formed on at least one surface of the polarizer, wherein the polarizer has a high transmittance region formed at at least a portion of the polarizer, and the high transmittance region has a depolarization index of about 2% or less at a wavelength of about 550 nanometers.

[0009] Embodiment 2 In embodiment 1, the high light transmittance region may have a light transmittance of about 60% to about 92%.

[0010] Embodiment 3. In embodiments 1 and 2, the high light transmittance region may be placed on a camera disposed in a display region of an optical display.

[0011] Another embodiment of the present invention relates to an optical display including the polarizer according to the present invention.

[0012] Beneficial effects

[0013] The present invention provides a polarizer having a high light transmittance region, which enables images captured therethrough to have improved color quality and clarity. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 is a plan view of a polarizer having a high light transmittance region and a region other than the high light transmittance region formed therein according to an embodiment of the present invention. DETAILED DESCRIPTION

[0015] The embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can thoroughly understand the present invention. It should be understood that the present invention can be implemented in different ways and is not limited to the following embodiments.

[0016] As used herein, the expression “X to Y” to express a specific numerical range means “greater than or equal to X and less than or equal to Y (X≤ and ≤Y)”.

[0017] One embodiment of the present invention relates to a polarizer. The polarizer according to the present invention includes a polarizer and a protective film formed on at least one surface of the polarizer. In one embodiment, the polarizer includes a polarizer and a protective film formed on both surfaces of the polarizer. In another embodiment, the polarizer includes a polarizer and a protective film formed only on one surface of the polarizer.

[0018] The polarizer has a high light transmittance region formed at at least a portion of a plane of the polarizer.

[0019] In one embodiment, the polarizer consists of a high transmittance region and a region other than the high transmittance region (also referred to as a “polarization region”).

[0020] As used herein, the term “high transmittance region” refers to a region formed on one surface of a polarizer and having a transmittance of about 60% or more (e.g., 60% to 92% (e.g., 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, or 92%) in the visible spectrum (e.g., at a wavelength of 380 nm to 780 nm) and A zone having a degree of polarization of about 50% or less than 50% (e.g., 1% to 50% (e.g., 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, or 50%)). When the polarizer is used in an optical display, the high light transmittance region is installed in a region of the optical display where a camera is provided, thereby enabling an image (eg, a picture) to be captured through the high light transmittance region.

[0021] Herein, the term "polarizing region" refers to a region having a typical polarizing function and having a transmittance of about 45% or less (e.g., about 10% to 45%) and a polarization degree of about 90% or greater (e.g., about 90% to 100%) in the visible spectrum.

[0022] The high transmittance area has a depolarization index of about 2% or less at a wavelength of 550 nanometers. In this article, the term "depolarization index" refers to the degree of reduction in polarization when polarized light passes through an optical system. Within this depolarization index range, images taken by a camera through the high transmittance area can be clean and clear. Specifically, the high transmittance area can have a depolarization index of about 0% to about 2% (for example, 0%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8% or 1.9% or 2.0%). Specifically, for an optical display having a camera disposed in its display area, even when the optical display adopts a method that enables the screen not to be displayed on the light receiving part of the camera when photographing with the camera, and enables the screen to be displayed on the light receiving part at other times, the placement of the high light transmittance area of ​​the polarizer according to the present invention on the camera enables the image photographed with the camera to be clean and clear. Herein, the term "display area" refers to an area of ​​the optical display in which light emitting diodes and the like are disposed to display the screen.

[0023] According to the present invention, in addition to designing a high transmittance area in a polarizer for shooting with a camera as in the related art, the high transmittance area is also designed to have a depolarization index of about 2% or less at a wavelength of about 550 nanometers. The inventors of the present invention have confirmed that images shot through the high transmittance area according to the present invention can have significantly improved color quality and clarity compared to images shot through a high transmittance area having a depolarization index of greater than about 2% at a wavelength of about 550 nanometers.

[0024] In one embodiment, the high transmittance region of the polarizer may be formed on a portion of the entire area of ​​the polarizer, the portion excluding the corners of the polarizer. Figure 1 The polarizer is formed with a high-transmittance region 10 and a region 20 other than the high-transmittance region, wherein the high-transmittance region 10 is surrounded by the region 20 other than the high-transmittance region.

[0025] The polarizer may have a thickness of about 5 micrometers to 50 micrometers, specifically about 5 micrometers to 30 micrometers. Within this range, the polarizer can be used in the polarizer.

[0026] The polarizer of the polarizer is manufactured so that the high transmittance region has a depolarization index of about 2% or less. Next, a method of manufacturing the polarizer will be described.

[0027] The polarizer can be made by dyeing a polyvinyl alcohol film with at least one selected from iodine and a dichroic dye and then stretching it; and applying a pulsed laser beam of about 510 nm to 520 nm to a region of the dyed and stretched polyvinyl alcohol film that will form a high transmittance region.

[0028] First, a dyed and stretched polyvinyl alcohol film is prepared.

[0029] The dyed and stretched polyvinyl alcohol film can be manufactured by dyeing, stretching, cross-linking and color correction processes. In the method for manufacturing a polarizer according to the present invention, the order of performing the dyeing and stretching processes is not particularly restricted. That is, the polyvinyl alcohol film can be stretched after dyeing, can be dyed after stretching, or can be dyed and stretched at the same time.

[0030] The polyvinyl alcohol film may include any typical polyvinyl alcohol film commonly used to make polarizers. Specifically, the polyvinyl alcohol film may be a film formed by polyvinyl alcohol or its derivatives. The polyvinyl alcohol film may have a degree of polymerization of about 1,000 to about 5,000, a degree of saponification of about 80 mol % to 100 mol % and a thickness of about 1 micron to 30 microns, specifically 3 microns to 30 microns. Within these ranges, the polyvinyl alcohol film can be used to make a thin polarizer.

[0031] Before the polyvinyl alcohol film is subjected to dyeing and stretching, the polyvinyl alcohol film may be subjected to washing with water and swelling. Washing the polyvinyl alcohol film with water can remove foreign matter from the surface of the polyvinyl alcohol film. Swelling the polyvinyl alcohol film can facilitate dyeing or stretching of the polyvinyl alcohol film. Here, as is well known to those skilled in the art, swelling of the polyvinyl alcohol film can be carried out by leaving the polyvinyl alcohol film in a swelling bath containing an aqueous solution. The temperature and swelling time of the swelling bath are not particularly limited. The swelling bath may further contain boric acid, an inorganic acid, a surfactant and the like, and the content thereof may be appropriately adjusted.

[0032] The polyvinyl alcohol film can be dyed by immersing the polyvinyl alcohol film in a dyeing bath containing at least one selected from iodine and dichroic dyes. In the dyeing process, the polyvinyl alcohol film can be immersed in a dyeing solution. Here, the dyeing solution can be an aqueous solution selected from at least one of iodine and dichroic dyes. Specifically, iodine is provided in the form of an iodine-based dye. Here, the iodine-based dye can include at least one selected from potassium iodide, hydrogen iodide, lithium iodide, sodium iodide, zinc iodide, lithium iodide, aluminum iodide, lead iodide and copper iodide. The dyeing solution can be an aqueous solution containing 1% to 5% by weight of at least one selected from iodine and dichroic dyes. In this range, the polarizer can have a degree of polarization within the range specified herein, and can therefore be used in an optical display.

[0033] The temperature of the dye bath may range from about 20° C. to 45° C., and the time period for which the polyvinyl alcohol film is immersed in the dye bath may range from about 10 seconds to 300 seconds. Within these ranges, a polarizer having a high degree of polarization may be obtained.

[0034] The dyed polyvinyl alcohol film is stretched in a stretching bath to have polarized properties due to the orientation of at least one selected from iodine and dichroic dyes. Specifically, the stretching of the dyed polyvinyl alcohol film can be carried out by a dry stretching method or a wet stretching method. The dry stretching method may include inter-roll stretching, compression stretching, heated roll stretching, and the like, and the wet stretching method may include stretching the dyed polyvinyl alcohol film in an aqueous wet stretching bath at 35° C. to 65° C. The wet stretching bath may further contain boric acid to improve the stretching efficiency.

[0035] The polyvinyl alcohol film can be stretched to a predetermined elongation. Specifically, the polyvinyl alcohol film can be stretched to a total elongation of about 5 times to about 7 times, specifically about 5.5 times to about 6.5 times. Within this elongation range, the polyvinyl alcohol film can be free from tearing or wrinkling during stretching, and a polarizer with high polarization and high transmittance can be obtained. Here, the polyvinyl alcohol film can be uniaxially stretched. In addition, the stretching of the polyvinyl alcohol film can be implemented in a single stage. Alternatively, the stretching of the polyvinyl alcohol film can be implemented in multiple stages (e.g., two stages, three stages, and the like), so that a thin polarizer can be obtained without breaking the polyvinyl alcohol film.

[0036] Although the polyvinyl alcohol film is stretched after dyeing in the above embodiment, it should be understood that the present invention is not limited thereto, and dyeing and stretching of the polyvinyl alcohol film may be performed in the same reaction bath.

[0037] The dyed polyvinyl alcohol film may be subjected to crosslinking in a crosslinking bath before or after stretching. Through the crosslinking process, the polyvinyl alcohol film may be more strongly dyed with at least one selected from iodine and a dichroic dye. Here, boric acid may be used as a crosslinking agent. The crosslinking bath may further contain a phosphoric acid compound, potassium iodide, and the like to improve the crosslinking efficiency.

[0038] The dyed and stretched polyvinyl alcohol film can be subjected to color correction in a color-correction bath. In the color correction process, the dyed and stretched polyvinyl alcohol film is immersed in a color correction bath containing a color correction solution containing potassium iodide. In this way, the color value of the polarizer can be reduced, and iodine anions (I 2) can be removed from the polarizer. - ), thereby improving the durability of the polarizer. The temperature of the color correction bath may range from about 20° C. to 45° C., and the time period for which the polyvinyl alcohol film is immersed in the color correction bath may range from about 10 seconds to 300 seconds.

[0039] Then, the pulsed laser beam of about 510 nm to about 520 nm is applied to a portion of the dyed and stretched polyvinyl alcohol film, thereby manufacturing a polarizer partially formed with a high light transmittance region.

[0040] The pulsed laser beam of about 510 nm to about 520 nm can induce transition of iodine and / or a dichroic dye dyed in a polarizer from a ground state to an excited state, thereby decomposing the iodine and / or the dichroic dye and thus increasing the transmittance of a portion irradiated with the pulsed laser beam.

[0041] Specifically, the pulsed laser beam of about 510 nm to about 520 nm may be a pulsed laser beam having a wavelength 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.

[0042] The pulsed laser beam of about 510 nm to about 520 nm is applied at an energy density of about 0.17 J / cm2 / pulse or less. Within this range, the high transmittance region can have a depolarization index of 2% or less while preventing heat-induced carbonization or laser hatching phenomenon of the treated surface of the polyvinyl alcohol film. Preferably, the pulsed laser beam of about 510 nm to about 520 nm is applied at an energy density of 0.03 J / cm2 / pulse to 0.17 J / cm2 / pulse.

[0043] As used herein, the term "energy density" means the energy per pulse per unit area of ​​a high transmittance region of a polarizer.

[0044] The pulsed laser beam of about 510 nm to about 520 nm may be applied at each of the above wavelengths for about 1 second to 1,000 seconds (e.g., about 1 second to 100 seconds). Within this range, by increasing the beam application time or frequency under the aforementioned conditions, a more neutral and colorless high transmittance region may be formed without thermally deforming the polarizer and the protective film.

[0045] The pulsed laser beam of about 510 nm to about 520 nm may be applied for a scan number of 1 to 20. Within this range, by increasing the beam application time or frequency under the aforementioned conditions, a more neutral and colorless high transmittance region may be formed without thermally deforming the polarizer and the protective film.

[0046] As used herein, the term "scan number" refers to the number of times a pulsed laser beam passes through a particular point for a given mapping level.

[0047] The high light transmittance region can be formed by applying the pulsed laser beam of about 510 nm to about 520 nm to the polarizer. Alternatively, the high light transmittance region can be formed by applying a pulsed laser beam at an energy density within the range specified herein to a laminate composed of a polarizer and a protective film formed on at least one surface of the polarizer.

[0048] The protective film may include any typical protective film commonly used in polarizers. For example, the protective film may include a protective film formed of at least one selected from the following: cellulose resins including triacetyl cellulose and the like; polyester resins including polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, and the like; cyclic polyolefin resins, polycarbonate resins; polyether sulfone resins, polysulfone resins, polyamide resins; polyimide resins; polyolefin resins; polyarylate resins; polyvinyl alcohol resins; polyvinyl chloride resins; and polyvinylidene chloride resins.

[0049] The protective film may have a thickness of about 10 to 100 micrometers, for example, about 10 to 60 micrometers. The lamination of the protective film on the polarizer may be performed through an adhesive by any typical method known in the art.

[0050] Another embodiment of the present invention relates to an optical display.

[0051] The optical display according to the present invention includes the polarizer according to the present invention. Examples of the optical display may include a liquid crystal display, an organic light emitting display, and the like.

[0052] Next, the present invention will be described in more detail with reference to some examples. However, it should be noted that these examples are provided only for illustration and cannot be interpreted as limiting the present invention in any way.

[0053] The details of the components used in the Examples and Comparative Examples are as follows:

[0054] (1) Polarizer: Polyvinyl alcohol film (VF-PE3000, Kuraray Co., Ltd., Japan, thickness: 30 μm)

[0055] (2) Protective film: triacetyl cellulose film (KC4UYW, Konica Minolta Inc., Japan, thickness: 40 μm)

[0056] Example 1

[0057] The polyvinyl alcohol film rinsed with water was subjected to swelling in an aqueous swelling bath at 30°C.

[0058] The polyvinyl alcohol film that had passed through the swelling bath was treated in a dyeing bath containing a 3 wt % potassium iodide aqueous solution at 30° C. for 30 seconds to 200 seconds. The polyvinyl alcohol film that had passed through the dyeing bath was allowed to pass through a wet crosslinking bath containing a 3 wt % boric acid aqueous solution at 30° C. to 60° C. The polyvinyl alcohol film that had passed through the crosslinking bath was stretched to a total elongation of 6 times in a stretching bath containing a 3 wt % boric acid aqueous solution at 50° C. to 60° C., thereby producing a polarizer. Then, a protective film was bonded to both surfaces of the produced polarizer by an adhesive (Z-200, Nippon Gohsei), thereby producing a laminate.

[0059] The laminate was cut into a predetermined size, and then a 515 nm pulsed laser beam was applied to a portion of the laminate under the conditions shown in Table 1, thereby manufacturing a polarizer having a high transmittance region.

[0060] Example 2 to Example 25

[0061] Polarizers having a high transmittance region were produced in the same manner as in Example 1, except that a 515 nm pulsed laser beam was applied under different conditions shown in Tables 1 to 3.

[0062] Comparative Example 1

[0063] A polarizer having a high transmittance region was produced in the same manner as in Example 1, except that a 400 nm to 800 nm pulsed laser beam was applied under the conditions shown in Table 3 instead of a 515 nm pulsed laser beam under the conditions shown in Table 1.

[0064] Comparative Example 2

[0065] A polarizer having a high transmittance region was produced in the same manner as in Example 1, except that a 532 nm pulsed laser beam was applied under the conditions shown in Table 3 instead of a 515 nm pulsed laser beam being applied under the conditions shown in Table 1.

[0066] Comparative Example 3

[0067] A polarizer having a high transmittance region was produced in the same manner as in Example 1, except that a 515 nm pulsed laser beam was applied under the conditions shown in Table 3 instead of applying the 515 nm pulsed laser beam under the conditions shown in Table 1.

[0068] The high light transmittance region of each of the polarizers produced in the examples and comparative examples was evaluated for the following properties:

[0069] (1) Depolarization index (unit: %): The depolarization index of the high transmittance region of each of the polarizers prepared in Examples and Comparative Examples was measured at a wavelength of 550 nm using an AXOSCAN system.

[0070] (2) Transmittance (unit: %): The average transmittance of the high transmittance region of each of the polarizers produced in Examples and Comparative Examples was measured at a wavelength of 380 nm to 780 nm using a spectrophotometer (V730, JASCO Corporation).

[0071] (3) Polarization degree (unit: %): The polarization degree of each of the polarizers prepared in Examples and Comparative Examples in a high transmittance region was measured at a wavelength of 550 nm using a spectrophotometer (V730, JASCO Corporation).

[0072] (4) Image clarity achieved through the high transmittance area (visibility evaluation): Taking age and gender into account, women in their twenties have the best vision. Five women in their twenties who have not used vision correction devices (e.g., glasses) in their daily lives were selected as the test group. When the visual acuity measured by the general vision test method is the same as the visual acuity measured through the high transmittance area of ​​the polarizer, the corresponding polarizer is rated as "Good", and when the visual acuity measured by the general vision test method is different from the visual acuity measured through the high transmittance area of ​​the polarizer, the corresponding polarizer is rated as "Poor".

[0073] Table 1

[0074]

[0075] Table 2

[0076]

[0077] Table 3

[0078]

[0079] As shown in Tables 1 to 3, the polarizer according to the present invention can enable images photographed through the high transmittance area to have improved color quality and clarity.

[0080] In contrast, the polarizers of Comparative Examples 1 to 3, whose high transmittance regions have a depolarization index of less than 2%, exhibit poor properties in terms of color quality and clarity of images captured through the high transmittance regions, compared to the case of the examples.

[0081] It should be understood that various modifications, changes, variations and equivalent embodiments may be made by those skilled in the art without departing from the spirit and scope of the present invention.

Claims

1. A polarizer, comprising: polarizer; as well as a protective film formed on at least one surface of the polarizer, wherein the polarizer has a high light transmittance region formed at at least a portion of the polarizer, wherein the high transmittance region has a depolarization index of 2% or less at a wavelength of 550 nanometers, wherein in the high transmittance region of the polarizer, iodine and / or dichroic dye is decomposed, and The high light transmittance region is formed by applying a 510 nm to 520 nm pulsed laser beam at an energy density of 0.03 J / cm2 / pulse to 0.17 J / cm2 / pulse. 2 . The polarizer according to claim 1 , wherein the high transmittance region has a transmittance of 60% to 92%. 3 . The polarizer according to claim 1 , wherein the high light transmittance area is placed on a camera, and the camera is arranged in a display area of ​​an optical display.

4. An optical display comprising the polarizer according to any one of claims 1 to 3.

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