Polarizing plate and optical display device

Abstract

Provided are a polarizing plate and an optical display device comprising same, the polarizing plate comprising: a polarizer; and a phase difference layer formed on at least one surface of the polarizer, wherein the polarizer has a thickness of 10 ㎛ or less, and the polarizing plate has a coefficient of thermal expansion (CTE) of 100 ㎛ / (mㆍ℃) or less as measured in the machine direction of the polarizer after thermal shock conditions.

Description

Polarizing plates and optical display devices

[0001] It relates to a polarizing plate and an optical display device including the same.

[0002]

[0003] Organic light-emitting diode displays suffer from reduced visibility and contrast due to reflection of external light. To address this issue, a polarizing plate containing a polarizer and a phase-shift film can be used. A polarizing plate can provide anti-reflection functionality by preventing reflected external light from leaking out. A polarizing plate includes a polarizer and a phase-shift layer.

[0004] Polarizers are typically manufactured by uniaxial stretching in the mechanical direction (MD) at high magnification. Such highly stretched polarizers typically shrink under thermal shock, altering the direction of their optical absorption axes. It may be desirable to provide antireflection even under thermal shock conditions. Furthermore, by implementing antireflection on both the front and side surfaces, it may be desirable to achieve low reflection color dispersion between the front and side surfaces.

[0005] The background technology of the present invention is disclosed in Korean Patent Publication No. 10-2013-0078606, etc.

[0006]

[0007] The purpose is to provide a polarizing plate with excellent reliability due to low reflection color dispersion and low reflectivity even after thermal shock.

[0008]

[0009] According to one embodiment, a polarizing plate has a polarizer and a phase difference layer formed on at least one surface of the polarizer, the polarizer has a thickness of 10 μm or less, and the polarizing plate has a coefficient of thermal expansion (CTE) of 100 μm / (mㆍ℃) or less measured in the machine direction of the polarizer after the following thermal shock conditions:

[0010] [Thermal shock conditions]

[0011] The above polarizing plate sample was heated from 25℃ to 80℃ at a heating rate of 5℃ / min →

[0012] Cooling from 80℃ to -40℃ at a cooling rate of 5℃ / min →

[0013] Temperature increase from -40℃ to 80℃ at a heating rate of 5℃ / min →

[0014] Cooling from 80℃ to -40℃ at a cooling rate of 5℃ / min →

[0015] Temperature increase from -40℃ to 80℃ at a heating rate of 5℃ / min →

[0016] Temperature reduction from 80℃ to -40℃ at a temperature reduction rate of 5℃ / min.

[0017] According to another embodiment, the optical display device includes the polarizing plate.

[0018]

[0019] A polarizing plate with excellent reliability was provided, with low reflection color dispersion and low reflectivity even after thermal shock.

[0020]

[0021] Figure 1 is a cross-sectional view of a polarizing plate of one embodiment.

[0022] Figure 2 shows the TMA measurement results measured under thermal shock conditions for the polarizing plate of Example 1.

[0023] Figure 3 shows the TMA measurement results measured under thermal shock conditions for the polarizing plate of Comparative Example 1.

[0024] Figure 4 shows the results of the reflection color distribution when the polarizing plate of Example 1 is applied.

[0025] In Figure 4, the X-axis represents the reflection color value a* value, the Y-axis represents the reflection color value b* value, ■ represents the color dispersion at an azimuth of 8°, □ represents the azimuth of 30°, ○ represents the azimuth of 45°, and ● represents the color dispersion at an azimuth of 60°.

[0026]

[0027] The present invention is described in detail with reference to the drawings and attached examples so that those skilled in the art can easily practice it. The present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[0028] The terminology used herein is for the purpose of describing exemplary embodiments only and is not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise.

[0029] In this specification, the "thermal expansion coefficient" of the polarizing plate, polarizer, and phase difference layer refers to the linear thermal expansion coefficient obtained through thermomechanical analysis (TMA (thermomechanical analyzer), Q400, TA Instrument) for the measurement target. The thermal expansion coefficient can be measured by the same method both before and after applying thermal shock conditions to the measurement target.

[0030] When the target of the thermal expansion coefficient measurement is a polarizing plate including a polarizer and a phase difference layer formed on at least one surface of the polarizer, a polarizing plate sample of 8 mm x 5 mm (MD (machine direction) of the polarizer x TD (transverse direction) of the polarizer) is prepared, and the thermal expansion coefficient can be obtained after the polarizing plate sample is heated from 25°C to 80°C at a temperature increase rate of 5°C / min under a nitrogen atmosphere with a load of 0.02 N to 0.05 N in the stretching direction of the polarizer (MD of the polarizer).

[0031] As used herein, “thermal shock conditions” are as follows:

[0032] The above polarizing plate sample was heated from 25℃ to 80℃ at a heating rate of 5℃ / min →

[0033] Cooling from 80℃ to -40℃ at a cooling rate of 5℃ / min →

[0034] Temperature increase from -40℃ to 80℃ at a heating rate of 5℃ / min →

[0035] Cooling from 80℃ to -40℃ at a cooling rate of 5℃ / min →

[0036] Temperature increase from -40℃ to 80℃ at a heating rate of 5℃ / min →

[0037] Temperature reduction from 80℃ to -40℃ at a temperature reduction rate of 5℃ / min.

[0038] The subject of thermal expansion coefficient measurement may be a polarizing plate or a phase difference layer. Even if the subject of measurement is a phase difference layer, the measurement can be performed using substantially the same method as for the polarizing plate.

[0039] In this specification, the “thermal expansion coefficient” of the protective layer can be obtained by preparing a sample of 8 mm x 5 mm (MD (machine direction) x TD (transverse direction)), and heating the sample from 20°C to 100°C under a temperature increasing condition of 5°C / min under a load of 0.02 N to 0.05 N in MD under a nitrogen atmosphere.

[0040] When describing a numerical range in this specification, “X to Y” means X or more and Y or less (X ≤ and ≤ Y).

[0041] As used herein, “(meth)acrylic” means acrylic and / or methacrylic.

[0042] A polarizing plate according to one embodiment can be an anti-reflection polarizing plate for a light-emitting display device. The polarizing plate can provide an anti-reflection effect even after thermal shock conditions, and can provide an anti-reflection effect on both the front and side surfaces, thereby providing low reflection color dispersion.

[0043] A polarizing plate according to one embodiment comprises a polarizer and a phase difference layer formed on at least one surface of the polarizer, wherein the polarizer has a thickness of 10 μm or less, and the polarizing plate has a coefficient of thermal expansion (CTE) measured in the mechanical direction of the polarizer after the following thermal shock conditions of 100 μm / (mㆍ℃) or less.

[0044] The above coefficient of thermal expansion is set to ensure that the polarizing plate provides low reflection color dispersion even after thermal shock conditions.

[0045] The above thermal expansion coefficient is set so that the polarizing plate having the first phase difference layer and the second phase difference layer described below can provide low reflection color dispersion by reducing the angular change between the light absorption axis of the polarizer and the ground axis in the in-plane direction of the phase difference layer even after thermal shock conditions.

[0046] Within the above thermal expansion coefficient range, the polarizing plate can provide low reflection color dispersion even after thermal shock conditions. For example, the polarizing plate can have a thermal expansion coefficient of 10 μm / (mㆍ℃) to 100 μm / (mㆍ℃), 90 μm / (mㆍ℃) to 100 μm / (mㆍ℃), or 95 μm / (mㆍ℃) to 100 μm / (mㆍ℃) after thermal shock conditions.

[0047] To provide the above low reflection color dispersion, the angular variation △θr-p defined by Equation 1 below can be 2.5° or less, for example, 0 to 2.5°:

[0048] [Formula 1]

[0049] △θr-p

[0050] (In the above equation 1, △θr-p is the absolute value of the difference between the angle between the light absorption axis of the polarizer and the slow axis of the phase difference layer before applying a thermal shock to the polarizer, and the angle between the light absorption axis of the polarizer and the slow axis of the phase difference layer after applying a thermal shock to the polarizer).

[0051] In one specific example, the phase difference layer may be a first phase difference layer described below.

[0052] In one specific example, the polarizing plate may have a coefficient of thermal expansion of 20 μm / (mㆍ℃) or less before the thermal shock condition treatment.

[0053] The above thermal expansion coefficient can be implemented by including a polarizer as described below.

[0054] polarizer

[0055] The polarizer has a thickness of 10 μm or less. Within this range, the polarizing plate can provide a thin thickness, enabling the thinning of finished products (e.g., mobile phones), has excellent bending characteristics, making it applicable to foldable devices, and can provide the effect of achieving high reliability by minimizing shrinkage and expansion under reliability conditions. According to one embodiment, the polarizer may preferably have a thickness of more than 0 μm and less than 9 μm, 0.5 μm to 8 μm, and more preferably 0.5 μm to 7 μm.

[0056] The above polarizer comprises a polarizer manufactured using the polyvinyl alcohol-based film and manufacturing process described below. Through this, the polarizing plate can easily secure a thermal expansion coefficient of 100 ㎛ / (mㆍ℃) or less measured after thermal shock conditions.

[0057] A polyvinyl alcohol film contains hydrophilic functional groups and hydrophobic functional groups. The hydrophobic functional group exists in addition to the hydroxyl group (OH group), which is a hydrophilic functional group present in the polyvinyl alcohol film. By manufacturing a polyvinyl alcohol film containing both the hydrophilic functional group and the hydrophobic functional group by the process described below, it is easy for the polarizing plate to reach a thermal expansion coefficient of 100 ㎛ / (mㆍ℃) or less.

[0058] The hydrophobic functional group is present in at least one of the main chain and side chain of the polyvinyl alcohol-based resin constituting the polyvinyl alcohol-based film. The "main chain" refers to a portion forming the main skeleton of the polyvinyl alcohol-based resin, and the "side chain" refers to a skeleton connected to the main chain. Preferably, the hydrophobic functional group may be present in the main chain of the polyvinyl alcohol-based resin.

[0059] Polyvinyl alcohol-based resins having hydrophilic and hydrophobic functional groups introduced therein can be produced by polymerizing one or more vinyl ester monomers such as vinyl acetate, vinyl formate, vinyl propionate, vinyl butyrate, vinyl pivalate, and isopropenyl acetate, and a monomer providing a hydrophobic functional group. Preferably, the vinyl ester monomer may include vinyl acetate. The monomer providing the hydrophobic functional group may include a monomer providing a hydrocarbon repeating unit including ethylene, propylene, or the like.

[0060] The polyvinyl alcohol-based film may have a softening point of 66°C to 70°C, for example, 67°C to 69°C. Within this range, the film may be free from melting and breakage during the stretching process, and may have the effect of easily reaching the polarizer of the present invention. The 'softening point' may be measured using a conventional softening point measuring method known to those skilled in the art.

[0061] The polyvinyl alcohol-based film may have a tensile strength of 95 MPa to 105 MPa, preferably 97 MPa to 99 MPa, measured in the machine direction of the film. Within this range, there is no melting or breakage during the stretching process, the polyvinyl alcohol molecular chains are effectively oriented, and the polarization degree can be high, and the polarizer of the present invention can be easily reached. The tensile strength of the polyvinyl alcohol-based film can be measured at 25°C using a Universal Testing Machine (UTM) according to ASTM D882 standards.

[0062] The polyvinyl alcohol film may have a thickness of 50 μm or less, for example, 10 μm to 50 μm. Within this range, the film may not melt or break during stretching.

[0063] Polyvinyl alcohol-based films can use TS-#2000 (Kuraray, Japan) PVA film.

[0064] The polarizer is manufactured by processing the polyvinyl alcohol-based film in the following order: dyeing process, stretching process, and crosslinking process. Through this, the polarizing plate can easily secure a thermal expansion coefficient of 100㎛ / (mㆍ℃) or less measured after thermal shock conditions.

[0065] The dyeing process involves treating a polyvinyl alcohol-based film in a dyeing bath containing a dichroic substance. In the dyeing process, the polyvinyl alcohol-based film is immersed in the dyeing bath containing the dichroic substance. The dyeing bath containing the dichroic substance contains an aqueous solution containing the dichroic substance and boric acid. The dyeing bath contains both the dichroic substance and a boron compound, thereby dyeing the polyvinyl alcohol-based film and allowing the polyvinyl alcohol-based film to be stretched without breaking under the stretching conditions described below.

[0066] The dichroic substance may include at least one of iodine, potassium iodide, hydrogen iodide, lithium iodide, sodium iodide, zinc iodide, lithium iodide, aluminum iodide, lead iodide, and copper iodide. The dichroic substance may be included in the dyeing bath, preferably in the dyeing solution, at 0.5 mol / ml to 10 mol / ml, preferably 0.5 mol / ml to 5 mol / ml. Within the above range, uniform dyeing may be achieved.

[0067] Boron compounds can help prevent melting and fracture of polyvinyl alcohol-based films during stretching. Boron compounds can help prevent melting and fracture of polyvinyl alcohol-based films even when stretched at high temperatures and high stretch ratios during a stretching process performed after a dyeing process.

[0068] The boron compound may include at least one of boric acid and borax. The boron compound may be included in the dyeing bath, preferably in an amount of 0.1 to 5 wt%, and preferably 0.3 to 3 wt%, of the dyeing aqueous solution. Within this range, there may be an effect of achieving high reliability without melting or fracture during the stretching process.

[0069] The temperature of the dyeing solution may preferably be 20°C to 50°C, specifically 25°C to 40°C. The dyeing process may be performed by immersing the polyvinyl alcohol-based film in a dyeing tank for 30 to 120 seconds, specifically 40 to 80 seconds.

[0070] The stretching process includes stretching the dyed polyvinyl alcohol-based film at a stretching ratio of 5.7 times or more, for example, 5.7 to 7 times, at a stretching temperature of 57°C or more, for example, 57°C to 65°C. Conventional polyvinyl alcohol-based films cannot be manufactured as polarizers when stretched at the above-described stretching ratio and stretching temperature due to melting and / or fracture of the polyvinyl alcohol-based film.

[0071] The stretching process is performed by either wet stretching or dry stretching. Preferably, the stretching process includes wet stretching to apply a boron compound in the stretching process. Wet stretching involves uniaxially stretching a polyvinyl alcohol-based film in the mechanical direction in an aqueous solution containing a boron compound.

[0072] The boron compound may include at least one of boric acid and borax, preferably boric acid. The boron compound may be present in an amount of 0.5 to 10 wt% in the stretching bath, preferably in the stretching solution. Within this range, the effect of achieving high reliability without melting or fracture during the stretching process may be achieved. Preferably, the boron compound may be present in an amount of 1 to 5 wt%. Within this range, the effect and the thermal expansion coefficient of the polarizing plate may be easily achieved.

[0073] The crosslinking process is performed to enhance the adsorption of dichroic substances in polyvinyl alcohol-based films that have undergone a stretching process. The crosslinking solution used in the crosslinking process contains a boron compound. The boron compound enhances the adsorption of the aforementioned dichroic substances and can help improve the reliability of the polarizer even when exposed to thermal shock.

[0074] The boron compound may include at least one of boric acid and borax. The boron compound may be included in the crosslinking agent, preferably in an amount of 0.5 to 10 wt%, in the crosslinking aqueous solution. Within this range, the effect of achieving high reliability without melting or fracture during the stretching process may be achieved. Preferably, the boron compound may be included in an amount of 1 to 5 wt%. Within this range, the above effect may be achieved and the thermal expansion coefficient of the polarizing plate may be easily reached.

[0075] The temperature of the crosslinking solution may preferably be 20°C to 50°C, specifically 25°C to 40°C. The crosslinking process may be performed by immersing the polyvinyl alcohol-based film in the crosslinking bath for 30 to 120 seconds, specifically 40 to 80 seconds.

[0076] Before the dyeing process, the polyvinyl alcohol-based film may additionally include one or more of a washing process and a swelling process.

[0077] The washing process is to wash the polyvinyl alcohol film with water to remove foreign substances on the polyvinyl alcohol film.

[0078] The swelling process can facilitate the dyeing and stretching of a dichroic material by immersing a polyvinyl alcohol-based film in a swelling bath at a predetermined temperature range. The swelling process may include treating the film in water at a temperature of 15°C to 35°C, preferably 20°C to 30°C, for 30 to 50 seconds.

[0079] After the crosslinking process, the polyvinyl alcohol-based film can be further treated with a complementary color process. The complementary color treatment can improve the durability of the polyvinyl alcohol-based film. The complementary color bath can contain more than 0 wt% and less than 10 wt% of potassium iodide. The complementary color solution can preferably be at a temperature of 20°C to 50°C, specifically 25°C to 40°C. The complementary color treatment can be performed by immersing the polyvinyl alcohol-based film in the complementary color bath for 5 to 50 seconds, specifically 5 to 20 seconds.

[0080] The coefficient of thermal expansion measured after the thermal shock condition of the polarizer may be the same as or different from the coefficient of thermal expansion measured after the thermal shock condition of the polarizing plate.

[0081] In one specific example, the coefficient of thermal expansion measured after the thermal shock condition of the polarizer may be 50% to 250%, preferably 130% to 170%, of the coefficient of thermal expansion measured after the thermal shock condition of the polarizing plate. Within this range, the effects of the present invention can be easily realized, and the protective film and adhesive layer can be easily controlled.

[0082] The boric acid content in the polarizer may be 15 wt% to 30 wt%, preferably 17 wt% to 27 wt%, and more preferably 20 wt% to 24 wt%. Within this range, the thermal expansion coefficient of the present invention can be easily achieved even when the polarizer has a thickness of 10 μm or less. The boric acid content may be determined by controlling the boric acid content used in the stretching process and crosslinking process during the manufacturing process of the polarizer, but is not limited thereto.

[0083] The boric acid content of the above polarizer is not particularly limited, but 1 g of polarizer and 50 g of deionized water were placed in a beaker and heated to completely dissolve the polarizer, and then 10 g of a mannitol solution (mannitol: distilled water = 1:7 weight ratio) was mixed, and the solution was titrated with a 0.1 N NaOH aqueous solution to measure the boric acid content, which was then calculated as a weight ratio relative to the polarizer.

[0084] phase difference layer

[0085] The phase difference layer can provide an anti-reflection effect by circularly polarizing linearly polarized light incident from the outside and passing through a polarizer, and then reflecting the circularly polarized light and circularly polarizing it again.

[0086] The phase difference layer may include a first phase difference layer having a ground axis in the in-plane direction.

[0087] According to one embodiment, the ground axis of the first phase difference layer may be 40° to 50°, preferably 45°, with respect to the light absorption axis (MD of the polarizer). Within this range, it may be easy to provide an anti-reflection effect of the polarizing plate.

[0088] The first phase difference layer may have reverse wavelength dispersion. The reverse wavelength dispersion may facilitate the polarizing plate to provide an anti-reflection effect. Here, the reverse wavelength dispersion is such that when the in-plane phase difference of the first phase difference layer at a wavelength of 450 nm is Re(450), the in-plane phase difference at a wavelength of 550 nm is Re(550), and the in-plane phase difference at a wavelength of 650 nm is Re(650), Re(450) <Re(550)<Re(650)의 관계가 있는 것을 의미한다.

[0089] In one specific example, the first phase difference layer may have Re(450) / Re(550) of less than 1.0, for example, 0.8 or more and less than 1.0, and Re(650) / Re(550) of greater than 1.0, for example, greater than 1.0 and less than 1.2. In the above range, excellent anti-reflection performance can be realized.

[0090] In one specific example, the first phase difference layer may have an in-plane phase difference of 100 to 300 nm, for example, 100 to 200 nm, at a wavelength of 550 nm. In this range, it may be easy to achieve an anti-reflection effect.

[0091] The first phase difference layer may be a liquid crystal layer or a non-liquid crystal layer. Preferably, the first phase difference layer may be a liquid crystal layer. The liquid crystal layer may be manufactured using a common liquid crystal known to those skilled in the art, such as a nematic liquid crystal, a cholesteric liquid crystal, or a discotic liquid crystal. The coefficient of thermal expansion of the polarizing plate after thermal shock can facilitate reducing the dispersion of reflected colors while providing an anti-reflection effect even after thermal shock when the polarizing plate includes a liquid crystal layer as the phase difference layer.

[0092] The first phase difference layer may have a thickness of 1.0 μm to 5.0 μm, for example, 2.0 μm to 3.0 μm.

[0093] The phase difference layer may further include a second phase difference layer having a different in-plane phase difference than the first phase difference layer.

[0094] The second phase difference layer can further enhance the anti-reflection effect of the first phase difference layer.

[0095] In one specific example, the second phase difference layer may be a positive C layer satisfying nz > nx ≒ ny.

[0096] In one specific example, the positive C layer may have a thickness-wise phase difference of -150 nm to 0 nm, specifically -130 nm to -10 nm, and more specifically -110 nm to -20 nm at a wavelength of 550 nm. Within this range, the effects of the present invention may be further improved.

[0097] In one specific example, the positive C layer may have an in-plane phase difference of 0 nm to 10 nm, specifically 0 nm to 5 nm, at a wavelength of 550 nm. Within this range, the effects of the present invention may be further improved.

[0098] The positive C layer may be a liquid crystal layer or a non-liquid crystal layer. Preferably, the positive C layer may be a liquid crystal layer. The liquid crystal layer may be manufactured using a conventional liquid crystal known to those skilled in the art, such as a nematic liquid crystal, a cholesteric liquid crystal, or a discotic liquid crystal. The coefficient of thermal expansion of the polarizing plate after thermal shock can be easily reduced to provide an antireflection effect and reduce the dispersion of reflected colors even after thermal shock when the polarizing plate includes a laminate of liquid crystal layers as a phase difference layer.

[0099] The positive C layer may have a thickness of 0.1 μm to 5.0 μm, for example, 0.5 μm to 3.5 μm. In the above range, it can be used in a polarizing plate.

[0100] In one specific example, the first phase difference layer and the second phase difference layer may be sequentially laminated from the polarizer. In this case, when the thermal expansion coefficient is satisfied after the above-described thermal shock conditions, the reflection color dispersion may be low.

[0101] The polarizing plate may further include a protective layer described below on one or both sides of the polarizer. The protective layer is different from the phase difference layer.

[0102] protective layer

[0103] A protective layer is laminated on one or both sides of a polarizer to protect the polarizer and increase the mechanical strength of the polarizing plate.

[0104] In one embodiment, the protective layer may comprise an optically transparent protective film.

[0105] In one specific example, when the protective layer laminated on one side of the polarizer is referred to as a first protective layer and the protective layer laminated on the other side of the polarizer is referred to as a second protective layer, the first protective layer and the second protective layer may have the same or different thermal expansion coefficients.

[0106] The first protective layer, the second protective layer, the protective layer, for example, the protective film, may have a thermal expansion coefficient of 30 µm / (mㆍ℃) or more, for example, 30 µm / (mㆍ℃) to 140 µm / (mㆍ℃), 40 µm / (mㆍ℃) to 140 µm / (mㆍ℃), 30 µm / (mㆍ℃) to 100 µm / (mㆍ℃). In the above range, the thermal expansion coefficient of the polarizing plate of the present invention may not be affected or may not increase the thermal expansion coefficient.

[0107] The coefficient of thermal expansion of the above protective layer, for example, the protective film, can be implemented by changing the resin forming the protective film and the melting and extrusion conditions when forming the protective film using the resin.

[0108] In one specific embodiment, the protective film may be formed by melting and extruding an optically transparent resin. If necessary, a stretching process may be added.

[0109] The above resin may include at least one of a cellulose ester resin including triacetyl cellulose (TAC), a cyclic polyolefin resin including amorphous cyclic polyolefin (cyclic olefin polymer, COP), a polycarbonate resin, a polyester resin including polyethylene terephthalate (PET), a polyethersulfone resin, a polysulfone resin, a polyamide resin, a polyimide resin, an acyclic-polyolefin resin, a polyacrylate resin including polymethyl methacrylate resin, a polyvinyl alcohol resin, a polyvinyl chloride resin, and a polyvinylidene chloride resin.

[0110] In one specific example, when the protective layer is a triacetylcellulose film, the coefficient of thermal expansion may be 30 µm / (mㆍ℃) to 100 µm / (mㆍ℃), for example, 45 µm / (mㆍ℃) to 55 µm / (mㆍ℃).

[0111] The thickness of the above protective layer may be 5 µm to 200 µm, specifically, 15 µm to 40 µm. Within the above range, it can be used in a polarizing plate.

[0112] A functional coating layer, such as a hard coating layer, an anti-fingerprint layer, an anti-reflection layer, etc., may be further formed on one or both sides of the above protective layer.

[0113] The phase difference layer and protective layer of the polarizing plate may be bonded by an adhesive layer or a pressure-sensitive adhesive layer, respectively. The adhesive layer may be formed using a conventional adhesive for polarizing plates known to those skilled in the art. For example, the adhesive layer may be formed using a water-based adhesive or a photocurable adhesive.

[0114] The water-based adhesive may include a polyvinyl alcohol-based adhesive resin, a crosslinking agent, etc.

[0115] The photocurable adhesive may include at least one of an epoxy compound and a (meth)acrylic compound, and an initiator. The initiator may include at least one of a photoradical initiator and a photocationic initiator, preferably a mixture of a photoradical initiator and a photocationic initiator. The photocurable adhesive may further include conventional additives such as an antioxidant and a pigment.

[0116] The adhesive layer may be an adhesive layer formed of a pressure-sensitive adhesive (PSA). For example, the adhesive layer may be formed of a composition including a (meth)acrylic resin as the adhesive resin.

[0117] The adhesive layer or adhesive layer may have a thickness of 0.05 μm to 13 μm. It can be used in an optical display device within the above range.

[0118] Fig. 1 is a cross-sectional view of a polarizing plate according to an embodiment. Referring to Fig. 1, the polarizing plate may include a polarizer 100, a protective layer 300 laminated on an upper surface of the polarizer, a first phase difference layer 210, and a second phase difference layer 220 sequentially laminated on a lower surface of the polarizer.

[0119] Below, an optical display device according to an implementation example is described.

[0120] The optical display device may include the polarizer or the polarizing plate. The optical display device may include at least one of a liquid crystal display device and a light-emitting display device. The light-emitting display device may refer to a light-emitting element, including an organic or organic-inorganic light-emitting element, and a device including a light-emitting material such as an LED (light emitting diode), an OLED (organic light emitting diode), a QLED (quantum dot light emitting diode), or a phosphor.

[0121]

[0122] Hereinafter, the structure and operation of the present invention will be described in more detail through preferred embodiments of the present invention. However, these are presented as preferred examples of the present invention and should not be construed as limiting the present invention in any way.

[0123]

[0124] Example 1

[0125] (1) Manufacturing of polarizers

[0126] A polyvinyl alcohol film (TS-#2000, Kuraray, Japan, containing a hydrophobic functional group in the main chain, thickness: 20 μm, softening point: 68 °C, tensile strength (98 MPa at 25 °C) washed with water at 25 °C was subjected to swelling treatment in a swelling tank containing water at 30 °C.

[0127] The film, which passed through the swelling tank, was treated for 65 seconds in a dyeing tank at 30°C containing an aqueous solution containing 1 mol / ml of potassium iodide and 1 wt% of boric acid. The film, which passed through the dyeing tank, was stretched at a stretch ratio of 5.7 times in a wet stretching tank containing an aqueous solution containing 3 wt% of boric acid at 60°C. The film, which passed through the wet stretching tank, was treated for 65 seconds in a crosslinking tank containing an aqueous solution containing 3 wt% of boric acid at 25°C.

[0128] The film passed through the crosslinking bath was treated for 10 seconds in a complementary bath containing a complementary solution, which is a 30°C aqueous solution containing 4.5 wt% potassium iodide. The film passed through the complementary bath was washed and dried to produce a polarizer (thickness: 7 μm, boric acid content: 20 wt%).

[0129]

[0130] (2) Manufacturing of polarizing plates

[0131] A water-based adhesive (containing polyvinyl alcohol-based adhesive resin) was applied to both sides of the polarizer manufactured above, and a triacetyl cellulose (TAC) film (thickness: 25 μm, KonicaTAC, KM, thermal expansion coefficient: 45 μm / (mㆍ℃) to 55 μm / (mㆍ℃)) was laminated to one side of the polarizer, and a triacetyl cellulose (TAC) film (thickness: 20 μm, KonicaTAC, KM, thermal expansion coefficient: 45 μm / (mㆍ℃) to 55 μm / (mㆍ℃)) was laminated to the other side of the polarizer. A polarizing plate was manufactured by laminating a laminate of a first phase difference layer, a liquid crystal layer, and a second phase difference layer, a liquid crystal layer (laminated layer thickness: 2.5 ㎛, first phase difference layer: reverse wavelength dispersion, second phase difference layer: positive C layer) onto the other side of the triacetyl cellulose film using a PSA layer. The structure of the final polarizing plate is TAC - polarizer - TAC - PSA - first phase difference layer - PSA layer - second phase difference layer.

[0132]

[0133] Examples 2 and 3

[0134] A polarizer and a polarizing plate were manufactured in the same manner as in Example 1, except that the contents of each component in the dyeing tank, stretching tank, and crosslinking tank were changed in Example 1, and the stretching temperature and stretching ratio were changed as shown in Table 1 below.

[0135]

[0136] Comparative Example 1

[0137] A polyvinyl alcohol film (PE-#3000, Kuraray, Japan, containing no hydrophobic functional group in the main chain, thickness: 30 μm) washed with water at 25°C was subjected to swelling treatment in a swelling tank containing water at 30°C.

[0138] The film, which passed through the swelling tank, was treated for 65 seconds in a dyeing tank at 30°C containing an aqueous solution containing 1 mol / ml of potassium iodide and 1 wt% of boric acid. The film, which passed through the dyeing tank, was stretched at a stretch ratio of 5.7 times in a wet stretching tank containing an aqueous solution containing 3 wt% of boric acid at 53°C. The film, which passed through the stretching tank, was treated for 65 seconds in a crosslinking tank containing an aqueous solution containing 3 wt% of boric acid at 25°C.

[0139] The film, which had passed through the crosslinking bath, was treated for 10 seconds in a complementary bath containing a complementary solution, which is a 30°C aqueous solution containing 4.5 wt% potassium iodide. The film, which had passed through the complementary bath, was washed and dried to produce a polarizer (thickness: 12 μm).

[0140] A polarizing plate was manufactured using the same method as Example 1 using the manufactured polarizer.

[0141]

[0142] Comparative Example 2

[0143] A polyvinyl alcohol film (TS-#3000, Kuraray, Japan, containing a hydrophobic functional group in the main chain, thickness: 30 ㎛, softening point: 66 ℃, tensile strength (98 MPa at 25 ℃)) was used, and a polarizer having a thickness of 12 ㎛ was manufactured by changing the draw ratio and draw temperature in Example 1. A polarizing plate was manufactured using the manufactured polarizer in the same manner as in Example 1.

[0144]

[0145] Comparative Example 3

[0146] Polyvinyl alcohol film (TS-#3000, Kuraray, Japan, containing a hydrophobic functional group in the main chain, thickness: 30 μm, softening point: 66°C, tensile strength (98 MPa at 25°C)) was used. In order to manufacture a polarizer with a thickness of 10 μm, the stretching ratio in Example 1 was changed to 6.0 times and the stretching temperature was changed to 65°C. However, the polyvinyl alcohol film broke during the stretching process, and a polarizer with a thickness of 10 μm could not be manufactured.

[0147]

[0148] Comparative Example 4

[0149] A polyvinyl alcohol film (TS-#3000, Kuraray, Japan, containing a hydrophobic functional group in the main chain, thickness: 30 μm, softening point: 66°C, tensile strength (98 MPa at 25°C)) was used. In order to manufacture a polarizer with a thickness of 7 μm, the stretching ratio in Example 1 was changed to 7.0 times and the stretching temperature was changed to 65°C. However, the polyvinyl alcohol film broke during the stretching process, and a polarizer with a thickness of 7 μm could not be manufactured.

[0150]

[0151] Comparative Example 5

[0152] A polyvinyl alcohol film (TS-#2000, Kuraray, Japan, containing a hydrophobic functional group in the main chain, thickness: 20 μm, softening point: 68 °C, tensile strength (98 MPa at 25 °C) washed with water at 25 °C was subjected to swelling treatment in a swelling tank with water at 30 °C.

[0153] The film passed through the swelling tank was treated for 65 seconds in a dyeing tank at 30°C containing an aqueous solution containing 1 mol / ml of potassium iodide and 2.5 wt% of boric acid. The film passed through the dyeing tank was stretched at a stretch ratio of 5.7 times in a wet stretching tank containing an aqueous solution at 60°C containing 6 wt% of boric acid. The film passed through the wet stretching tank was treated for 65 seconds in a crosslinking tank containing an aqueous solution at 25°C containing 6 wt% of boric acid.

[0154] The film passed through the crosslinking bath was treated for 10 seconds in a complementary bath containing a complementary solution, which is a 30°C aqueous solution containing 4.5 wt% potassium iodide. The film passed through the complementary bath was washed and dried to manufacture a polarizer (thickness: 7 μm, boric acid content: 35 wt%).

[0155] A polarizing plate was manufactured using the same method as in Example 1.

[0156]

[0157] The properties of the polarizing plates manufactured in the examples and comparative examples were evaluated in Table 1 below, and the results are shown in Table 1 and Figures 2 to 4 below.

[0158] (1) Coefficient of thermal expansion (unit: ㎛ / (mㆍ℃)): The coefficient of thermal expansion was obtained through thermomechanical analysis (TMA). The polarizing plates manufactured in the examples and comparative examples were cut into 8 mm x 5 mm (MD of polarizer x TD of polarizer) to prepare polarizing plate samples, and the following thermal shock conditions were applied. Then, the polarizing plate sample was heated from 25℃ to 80℃ at a temperature increase condition of 5℃ / min under a load of 0.02N to 0.05N in the stretching direction of the polarizer (MD of the polarizer) in a nitrogen atmosphere, and the thermal expansion coefficient measured in the machine direction of the polarizer was obtained.

[0159] [Thermal shock conditions]

[0160] The above polarizing plate sample was heated from 25℃ to 80℃ at a heating rate of 5℃ / min →

[0161] Cooling from 80℃ to -40℃ at a cooling rate of 5℃ / min →

[0162] Temperature increase from -40℃ to 80℃ at a heating rate of 5℃ / min →

[0163] Cooling from 80℃ to -40℃ at a cooling rate of 5℃ / min →

[0164] Temperature increase from -40℃ to 80℃ at a heating rate of 5℃ / min →

[0165] Temperature reduction from 80℃ to -40℃ at a temperature reduction rate of 5℃ / min.

[0166] (2) Change in the angle difference between the light absorption axis of the polarizer and the slow axis of the first phase difference layer before and after thermal shock (△θr-p, unit: °): The angle between the light absorption axis of the polarizer and the slow axis of the first phase difference layer was measured in the polarizing plates of the examples and comparative examples. After applying the thermal shock in (1) to the polarizing plates, the angle between the light absorption axis of the polarizer and the slow axis of the first phase difference layer was measured. The change in angle was calculated from this. The angle between the light absorption axis of the polarizer and the slow axis of the first phase difference layer was measured using AXO Scan.

[0167] (3) Reflectance at the front (unit: %): The thermal shock conditions in (1) were applied to the polarizing plates of the examples and comparative examples. Then, they were attached to the Galaxy S7 panel, and the SCE (specular component excluded) reflectance was measured using DMS803 (Instrument Systems, Germany) equipment.

[0168] (4) Reflection color dispersion: The thermal shock conditions in (1) were applied to the polarizing plates of the examples and comparative examples. Then, the color dispersion according to the azimuth was evaluated by the SCE reflection measurement method according to (3). The color dispersion was measured based on the CIE a*, b* values, and the polarizing plates of the examples and comparative examples were attached to the Galaxy S7 panel and evaluated by the SCE reflection measurement method. From the results obtained, the reflection color shift distance was calculated by azimuth, and a numerical value for evaluating the color dispersion was obtained. The color dispersion represents the difference in the color value at a polar angle of 60° when the azimuth changes from 0° to 180°. A lower numerical value means a lower reflection color dispersion and better screen quality.

[0169] Example Comparative Example 123125 PVA Film Type TS-#2000 TS-#2000 TS-#2000 PE-#3000 TS-#3000 TS-#2000 Stretching Temperature 60 57 60 53 60 60 Stretching Ratio 5.7 5.7 5.9 5.7 5.9 5.7 Polarizer Thickness 77.8 712 127 Coefficient of Thermal Expansion 97.3 9 8.5 100.0 13 0.2 10 8.4 12 5.6 △θr-p 0.9 1.2 1.3 3.12 9 3.8 Reflectivity 0.19 0.2 10.18 0.38 0.35 0.46 Reflection Color Dispersion 2.8 3.2 2.6 6.7 6.2 7.1

[0170]

[0171] As shown in Table 1 above, the polarizing plate of the present invention had low △θr-p, reflectance, and reflection color dispersion of Equation 1 even after thermal shock. Therefore, although not shown in Table 1 above, the polarizing plate of the present invention is expected to have excellent reliability in reflectance and reflection color dispersion even after thermal shock conditions. On the other hand, the polarizing plate of the comparative example is expected to have low reliability because the △θr-p, reflectance, and reflection color dispersion of Equation 1 are overall higher than those of the example.

[0172] As shown in Fig. 2, the polarizing plate of Example 1 was confirmed to have a coefficient of thermal expansion (CTE) of 97.3 ㎛ / (mㆍ℃) as a result of thermomechanical analysis under thermal shock conditions (4 repetitions of heating and cooling).

[0173] On the other hand, as shown in Fig. 3, the polarizing plate of Comparative Example 1 can be confirmed to have a coefficient of thermal expansion (CTE) of 130.2 ㎛ / (mㆍ℃) as a result of thermomechanical analysis under thermal shock conditions (4 repetitions of heating and cooling).

[0174] Additionally, as shown in Fig. 4, it can be confirmed that the polarizing plate of the embodiment has remarkably low reflection color dispersion even after thermal shock conditions.

[0175]

[0176] Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications can be made within the scope of the claims, the detailed description of the invention, and the attached drawings, and it is obvious that this also falls within the scope of the present invention.

Claims

1. A polarizing plate having a polarizer and a phase difference layer formed on at least one surface of the polarizer, The above polarizer has a thickness of 10㎛ or less, The polarizing plate has a coefficient of thermal expansion (CTE) of 100㎛ / (mㆍ℃) or less measured in the machine direction of the polarizer after the following thermal shock conditions: [Thermal shock conditions] The above polarizing plate sample was heated from 25℃ to 80℃ at a heating rate of 5℃ / min → Cooling from 80℃ to -40℃ at a cooling rate of 5℃ / min → Temperature increase from -40℃ to 80℃ at a heating rate of 5℃ / min → Cooling from 80℃ to -40℃ at a cooling rate of 5℃ / min → Temperature increase from -40℃ to 80℃ at a heating rate of 5℃ / min → Temperature reduction from 80℃ to -40℃ at a temperature reduction rate of 5℃ / min.

2. A polarizing plate according to claim 1, wherein the polarizer comprises a polyvinyl alcohol-based film, and the polyvinyl alcohol-based film has both a hydrophilic functional group and a hydrophobic functional group.

3. A polarizing plate according to claim 1, wherein the polarizer comprises a polyvinyl alcohol-based film, and the polyvinyl alcohol-based film has a softening point of 66°C to 70°C.

4. A polarizing plate in accordance with claim 1, wherein the thermal expansion coefficient of the polarizer measured under the thermal shock conditions is 50% to 250% of the thermal expansion coefficient of the polarizing plate measured under the thermal shock conditions.

5. A polarizing plate according to claim 1, wherein the polarizer has a boric acid content of 15% to 30% by weight.

6. In the first paragraph, the polarizing plate has a coefficient of thermal expansion of 20㎛ / (mㆍ℃) or less before the thermal shock condition treatment.

7. A polarizing plate according to claim 1, wherein the phase difference layer includes a first phase difference layer and a second phase difference layer sequentially laminated from the polarizer.

8. A polarizing plate in accordance with claim 7, wherein the first phase difference layer and the second phase difference layer are each liquid crystal layers.

9. A polarizing plate in the first paragraph, wherein the ground axis of the first phase difference layer is at an angle of 40° to 50° with respect to the light absorption axis of the polarizer.

10. A polarizing plate according to claim 1, wherein a protective layer is further laminated on one or both sides of the polarizer.

11. In the first paragraph, the polarizing plate further includes a first protective layer laminated on one side of the polarizer and a second protective layer laminated on the other side of the polarizer, and the first protective layer and the second protective layer have the same or different thermal expansion coefficients.

12. A polarizing plate according to claim 11, wherein the first protective layer and the second protective layer each have a thermal expansion coefficient of 30 ㎛ / (mㆍ℃) or more.

13. In the first paragraph, the polarizing plate is a polarizing plate in which the angle change amount △θr-p defined by Equation 1 below is 2.5° or less: [Formula 1] △θr-p (In the above equation 1, △θr-p is the absolute value of the difference between the angle between the light absorption axis of the polarizer and the slow axis of the phase difference layer before applying a thermal shock to the polarizer, and the angle between the light absorption axis of the polarizer and the slow axis of the phase difference layer after applying a thermal shock to the polarizer).

14. An optical display device comprising a polarizing plate according to any one of claims 1 to 13.

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