Polarizing plate and optical display apparatus

Abstract

Provided are a polarizing plate and an optical display apparatus comprising same, in which the polarizing plate comprises a polarizer, the polarizer consists of a polyvinyl alcohol-based film containing a dichroic material, and 1.5 to 5.0 wt% of boron, 0.3 to 1.0 wt% of potassium, 0.1 to 1.0 wt% of zinc, and 0.0001 to 0.1 wt% of nitrogen are contained in the polarizer.

Description

Polarizing plates and optical display devices

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

[0002]

[0003] Polarizing plates are commonly used in light-emitting displays or liquid crystal displays. Polarizing plates essentially include a polarizer, which provides polarizing functionality. This polarizing functionality can be implemented using a dichroic material, such as an iodine-based or dichroic dye.

[0004] Polarizing plates must have an appropriate range of color values. This range ensures that polarizing plates can provide excellent image quality without compromising image quality when applied to optical displays. Furthermore, polarizing plates generally require high reliability after prolonged exposure to high temperatures. Specifically, polarizing plates should exhibit minimal color value change after prolonged exposure to high temperatures. Polarizing plates exhibiting high color value change after prolonged exposure to high temperatures can affect the color of the display screen within the optical display, adversely affecting its reliability.

[0005] The background technology of the present invention is disclosed in Korean Patent Publication No. 2020-0115071, etc.

[0006]

[0007] The purpose is to provide a polarizing plate that provides excellent screen quality when applied to an optical display device.

[0008] The purpose is to provide a polarizing plate with excellent reliability at high temperatures, as the amount of change in color value is significantly low after long-term exposure to high temperatures.

[0009]

[0010] According to one embodiment, a polarizing plate is provided.

[0011] 1. A polarizing plate has a polarizer, and the polarizer is composed of a polyvinyl alcohol-based film containing a dichroic material, and the polarizer contains 1.5 to 5.0 wt% of boron, 0.3 to 1.0 wt% of potassium, 0.1 to 1.0 wt% of zinc, and 0.0001 to 0.1 wt% of nitrogen.

[0012] 2.1 The ratio of boron content to nitrogen content in the polarizer may be 2000 or more.

[0013] In 3.1-2, the ratio of nitrogen content to potassium content among the polarizers may be 200 or more.

[0014] In 4.1-3, the ratio of nitrogen content to zinc content among the polarizers may be 300 or more.

[0015] In 5.1-4, the weight ratio of boron to the total of potassium and zinc in the polarizer may be 2 or more.

[0016] In 6.1-5, the total amount of zinc, boron and potassium in the polarizer may be 95 wt% or more of the total amount of metals and metalloids in the polarizer.

[0017] In 7.1-6, the nitrogen may be derived from zinc nitrate.

[0018] In 8.1-7, the polyvinyl alcohol-based film may include a polyvinyl alcohol resin having a polymerization degree of 3000 to 5000, or a derivative resin of the polyvinyl alcohol.

[0019] In 9.1-8, the polyvinyl alcohol-based film may include a polyvinyl alcohol resin having a saponification degree of 98 mol% or more, or a derivative resin of the polyvinyl alcohol.

[0020] In 10.1-9, the polyvinyl alcohol-based film may include a derivative of polyvinyl alcohol having a hydrophilic functional group and a hydrophobic functional group.

[0021] In 11.1-10, a protective layer may be further laminated on at least one side of the polarizer.

[0022] According to another embodiment, an optical display device is provided.

[0023] The optical display device includes the above polarizing plate.

[0024]

[0025] A polarizing plate providing excellent screen quality when applied to an optical display device was provided.

[0026] After long-term exposure to high temperatures, the change in color value was significantly reduced, providing a polarizing plate with excellent reliability at high temperatures.

[0027]

[0028] Figure 1 is a cross-sectional view of a polarizing plate of one embodiment.

[0029] Figure 2 shows the results of the appearance evaluation after leaving Example 1 at 105°C for 48 hours, and Figure 3 shows the results of the appearance evaluation after leaving Example 1 at 105°C for 250 hours.

[0030] Figure 4 shows the results of the appearance evaluation after leaving the product at 105°C for 48 hours in Example 2, and Figure 5 shows the results of the appearance evaluation after leaving the product at 105°C for 250 hours in Example 2.

[0031] Figure 6 shows the results of the appearance evaluation after leaving Comparative Example 1 at 105°C for 48 hours, and Figure 7 shows the results of the appearance evaluation after leaving Comparative Example 1 at 105°C for 250 hours.

[0032] Figure 8 shows the results of the appearance evaluation after leaving Comparative Example 2 at 105°C for 48 hours, and Figure 9 shows the results of the appearance evaluation after leaving Comparative Example 2 at 105°C for 250 hours.

[0033]

[0034] 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.

[0035] 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.

[0036] When describing a numerical range in this specification, “X to Y” means X or more and Y or less (X≤ and ≤Y).

[0037] As used herein, “(meth)acrylic” means acrylic and / or methacrylic.

[0038] In this specification, zinc, potassium, and boron among the polarizers can be measured by the following methods.

[0039] [Method for measuring zinc, potassium, and boron in polarizers]

[0040] Among the polarizers, zinc, potassium, and boron were measured using the ICP-OES (Inductively Coupled Plasma-Optical Emission Spectrometer) measurement method.

[0041] In this specification, the “color value change △E1” of the polarizing plate can be obtained according to the following equation 1:

[0042] [Formula 1]

[0043] △E1 = [(△L) 2 + (△a*) 2 + (△b*) 2 ] 1 / 2

[0044] (In the above equation 1,

[0045] △L is L2- L1

[0046] △a* is (a*)2- (a*)1

[0047] △b* is (b*)2- (b*)1,

[0048] L1 is the L of the initial polarizing plate, L2 is the L of the initial polarizing plate after leaving it at 105℃ for 250 hours,

[0049] (a*)1 is the a* of the initial polarizing plate, (a*)2 is the a* after leaving the initial polarizing plate at 105℃ for 250 hours,

[0050] (b*)1 is the b* of the initial polarizing plate, and (b*)2 is the b* of the initial polarizing plate after leaving it at 105℃ for 250 hours.

[0051] In this specification, the “color value change △E2” of the polarizing plate can be obtained according to Equation 2 below:

[0052] [Formula 2]

[0053] △E2 = [(△L) 2 + (△a*) 2 + (△b*) 2 ] 1 / 2

[0054] (In the above equation 2,

[0055] △L is L2- L1

[0056] △a* is (a*)2- (a*)1

[0057] △b* is (b*)2- (b*)1,

[0058] L1 is the L of the initial polarizing plate, L2 is the L of the initial polarizing plate after leaving it at 105℃ for 48 hours,

[0059] (a*)1 is the a* of the initial polarizing plate, (a*)2 is the a* of the initial polarizing plate after leaving it at 105℃ for 48 hours,

[0060] (b*)1 is the b* of the initial polarizing plate, and (b*)2 is the b* of the initial polarizing plate after leaving it at 105℃ for 48 hours.

[0061] In the above equations 1 and 2, the ‘initial polarizing plate’ refers to the polarizing plate before being left at 105°C for 250 hours and before being left at 105°C for 48 hours.

[0062] The above 'L', 'a*', and 'b*' refer to color values ​​according to the CIE 1976 standard, and can be measured with a colorimeter (e.g., Konica Minolta, CM-3700A), but are not limited thereto.

[0063] In this specification, the “polarization degree (PE)” of the polarizing plate is a value measured at a wavelength of 380 to 780 nm.

[0064] In this specification, the “group transmittance (Ts)” of the polarizing plate may be the average value of the total optical transmittance measured at a wavelength of 380 to 780 nm.

[0065] In this specification, the “orthogonal transmittance (Tc)” of the polarizing plate may be an average value of the orthogonal transmittance measured at a wavelength of 380 to 780 nm.

[0066] According to one embodiment, a polarizing plate is provided that provides excellent screen quality when applied to an optical display device. Specifically, the polarizing plate provides excellent screen quality by having an appropriate range of color values.

[0067] In one specific example, the polarizing plate may have a color value as of -2.0 to 0, for example, -2.0, -1.9, -1.8, -1.7, -1.6, -1.5, -1.4, -1.3, -1.2, -1.1, -1.0, -0.9, -0.8, -0.7, -0.6, -0.5, -0.4, -0.3, -0.2, -0.1, or 0, for example, -1.5 to 0, and a color value bs of 1.0 to 4.0, for example, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1. 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9 or 4.0, for example, 2.0 to 3.0. In the above range, when the polarizing plate is applied to an optical display device, excellent screen quality can be provided.

[0068] According to one embodiment, a polarizing plate having remarkably low color value changes after long-term exposure at high temperatures, thereby exhibiting excellent reliability at high temperatures, is provided. In particular, the polarizing plate comprises a polarizer comprising zinc, boron, and potassium in the content ranges described below, thereby exhibiting remarkably low color value changes after long-term exposure at high temperatures, thereby significantly enhancing reliability at high temperatures.

[0069] According to one embodiment, the polarizing plate has a polarizer, and the polarizer is composed of a polyvinyl alcohol-based film containing a dichroic material, and the polarizer contains 1.5 to 5.0 wt% of boron, 0.3 to 1.0 wt% of potassium, 0.1 to 1.0 wt% of zinc, and 0.0001 to 0.1 wt% of nitrogen.

[0070] The above polarizing plate may have a group transmittance of 40% or more, for example, 40 to 45%. Within the above range, the polarizing plate can provide excellent screen quality when applied to an optical display device.

[0071] The polarizing plate may have an orthogonal transmittance of 0.001% or less, for example, 0.0001, 0.0002, 0.0003, 0.0004, 0.0005, 0.0006, 0.0007, 0.0008, 0.0009, or 0.001%, for example, 0.0001 to 0.001%. In the above range, when the polarizing plate is applied to an optical display device, excellent screen quality can be provided.

[0072] The above polarizer is a linear light absorption polarizer, which can provide a polarization function by transmitting only light in one direction among the incident light and absorbing light in a direction perpendicular to the one direction.

[0073] The above polarizer is a polyvinyl alcohol (PVA) film polarizer. Here, the polyvinyl alcohol film may include at least one of a polyvinyl alcohol resin and a polyvinyl alcohol derivative resin.

[0074] In one specific example, the polyvinyl alcohol derivative may contain a hydrophilic functional group and a hydrophobic functional group. The hydrophobic functional group is present in addition to a hydroxyl group (OH group), which is a hydrophilic functional group present in the polyvinyl alcohol. The hydrophobic functional group may be present in at least one of the main chain and the side chain of the polyvinyl alcohol derivative resin. The "main chain" refers to a portion forming the main skeleton of the polyvinyl alcohol derivative, 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 derivative.

[0075] Polyvinyl alcohol derivatives having hydrophilic and hydrophobic functional groups introduced therein can be prepared by polymerizing one or more vinyl ester monomers such as vinyl acetate, vinyl formate, vinyl propionate, vinyl butyrate, vinyl pivalate, and isopropenyl acetate with 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.

[0076] The above polyvinyl alcohol resin and the polyvinyl alcohol derivative resin may each have a polymerization degree of 3000 to 5000, for example, 3000 to 4000. Within the above range, the polarizer containing the above-described zinc, boron, potassium, and nitrogen may be easily manufactured. Here, the 'polymerization degree' may be an average polymerization degree measured in accordance with the JIS K6726-1994 standard.

[0077] The polarizer may include a cross-linked structure using a boron compound such as boric acid. However, if the boric acid ester is dissociated by hydrolysis or the like, the degree of polymerization of the polyvinyl alcohol resin or polyvinyl alcohol derivative resin does not substantially change. Therefore, the degree of polymerization of the polarizer may be substantially the same as the degree of polymerization of the polyvinyl alcohol resin or polyvinyl alcohol derivative resin.

[0078] The polyvinyl alcohol resin and the polyvinyl alcohol derivative resin may each have a saponification degree of 98 mol% or more, for example, 98 to 100 mol%. Within the above range, polyvinyl alcohol is not eluted during the manufacturing process of the polarizer, there is no deterioration in polarization performance, and the manufacturing of the polarizer containing zinc, boron, potassium, and nitrogen of the above-described polarizer can be facilitated.

[0079] In this specification, the degree of saponification of each polyvinyl alcohol resin and polyvinyl alcohol derivative resin refers to the ratio (mol%) of the number of moles of the vinyl alcohol unit to the total number of moles of the vinyl alcohol unit and the structural unit (typically a vinyl ester unit) that can be converted into a vinyl alcohol unit by saponification of the polyvinyl alcohol resin or polyvinyl alcohol derivative resin.

[0080] The above saponification degree can be measured according to the description of JIS K6726-1994. In addition, the polyvinyl alcohol resin or polyvinyl alcohol derivative resin film, which is the raw film of the polarizer, and the polyvinyl alcohol resin or polyvinyl alcohol derivative resin film in the obtained polarizer may have substantially the same saponification degree.

[0081] The above polyvinyl alcohol-based film may have a thickness of 50 μm or less, for example, 10 μm to 50 μm. Within the above range, the film may not melt or break when stretched.

[0082] The above polyvinyl alcohol-based film may use M4516 (Mitsubishi, Japan) polyvinyl alcohol-based film, but is not limited thereto.

[0083] The polarizer contains a dichroic material. Specifically, the dichroic material can be dyed onto the polarizer. The dichroic material may be an iodine-based material, or may include a dichroic dye such as an azo dye as a non-iodine-based material. Generally, polarizers can be classified into iodine-based polarizers containing iodine-based materials and dye-based polarizers containing dichroic dyes. Although not necessarily, iodine-based polarizers, compared to dye-based polarizers, easily generate I2 substances due to the decomposition of the iodine-based material at high temperatures and / or high temperatures and high humidity, which can cause color changes through improper absorption in the visible light region.

[0084] According to one embodiment, the nitrogen content in the polyvinyl alcohol-based film may be 0 wt%.

[0085] The above polarizer contains nitrogen in an amount of 0.0001 to 0.1 wt%. The nitrogen content in the above polarizer was taken into consideration to significantly reduce the color value change amount, i.e., the above-described △E1, after long-term exposure at high temperatures in a polarizing plate having a polarizer containing boron, potassium, and zinc among the polarizers described below.

[0086] In particular, the nitrogen content of the polarizer was considered to significantly reduce the amount of color value change in both cases where the polarizing plate was left at 105°C for 48 hours and 105°C for 250 hours, when comparing the cases where the polarizing plate was left at 105°C for 48 hours and 105°C for 250 hours. Even if the color value change is low in a polarizing plate left at 105°C for 48 hours, the color value change may be high in a polarizing plate left at 105°C for 250 hours. On the other hand, the polarizing plate according to one embodiment had a significantly low amount of color value change in both cases where it was left at 105°C for 48 hours and 105°C for 250 hours.

[0087] In one specific example, the polarizing plate may have a color value change amount △E1 of the above formula 1 of 7.0 or less, for example, 0 to 7.0, 0.1 to 7.0. In the above range, the reliability of the polarizing plate and the optical display device at high temperatures may be excellent.

[0088] In one specific example, the polarizing plate may have a color value change amount △E2 of the above formula 2 of 5.0 or less, for example, 0 to 5.0, 0.1 to 5.0.

[0089] If the nitrogen content in the polarizer is less than 0.0001 wt%, the effect of reducing the color value change may be insignificant even after the polarizer is left at a high temperature for a long period of time. If the nitrogen content in the polarizer is more than 0.1 wt%, the effect of reducing the color value change may be insignificant even after the polarizer is left at a high temperature for a long period of time, or it may be difficult to control the zinc content in the polarizer, making it difficult to manufacture a polarizer that satisfies the zinc content range in the polarizer of the present invention, or there may be a problem of the appearance and optical properties (e.g., polarization degree and / or light transmittance) of the polarizer deteriorating.

[0090] In one specific example, the nitrogen content in the polarizer is, for example, 0.0001, 0.0002, 0.0003, 0.0004, 0.0005, 0.0006, 0.0007, 0.0008, 0.0009, 0.001, 0.0011, 0.0012, 0.0013, 0.0014, 0.0015, 0.0016, 0.0017, 0.0018, 0.0019, 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.009, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1%, for example, 0.0005 to 0.01 wt%, 0.0005 to 0.005 wt%, 0.0005 to 0.002 wt%.

[0091] The nitrogen content in the polarizer can be measured by combustion-ion chromatography, a method of combusting the polarizer and then subjecting it to ion chromatography. For a more detailed measurement method, refer to the experimental examples below.

[0092] The nitrogen content of the above polarizer can be achieved by controlling the polymerization degree of the polyvinyl alcohol resin or polyvinyl alcohol derivative resin in the polyvinyl alcohol film during the polarizer manufacturing process and the content of the nitrogen-containing source in the complementary color solution. This will be described in detail in the polarizer manufacturing process below.

[0093] Among the polarizers, boron is contained in an amount of 1.5 to 5.0 wt%. Within this range, the color values ​​a* and b* of the polarizing plate can be easily achieved. In one specific example, the boron in the polarizer may be 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5.0%, for example, 1.5 to 4.0% by weight, 2.0 to 4.0% by weight, or 2.5 to 4.0% by weight.

[0094] The boron content of the above polarizer can be achieved by using a boron-containing source during the manufacture of the polarizer and controlling the amount of the boron-containing source used. This will be described in detail in the polarizer manufacturing process below.

[0095] Potassium in the polarizer is contained in an amount of 0.3 to 1.0 wt%. Within this range, the color values ​​a* and b* of the polarizing plate can be easily achieved. In one specific example, potassium in the polarizer may be, for example, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1.0%, for example, 0.3 to 0.8 wt%, 0.3 to 0.6 wt%, or 0.3 to 0.5 wt%.

[0096] The potassium content of the above polarizer can be achieved by using a potassium-containing source during the manufacture of the polarizer and controlling the amount of the potassium-containing source used. This will be described in detail in the polarizer manufacturing process below.

[0097] The above polarizer contains zinc in an amount of 0.1 to 1.0 wt%. Within this range, the color values ​​a* and b* of the polarizing plate can be easily achieved, and the appearance of the polarizer can be excellent. In one specific example, the amount of zinc in the polarizer can be 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1.0%, for example, 0.1 to 0.8 wt%, 0.3 to 0.8 wt%.

[0098] The zinc content of the above polarizer can be achieved by using a zinc-containing source during the manufacture of the polarizer and controlling the amount of the zinc-containing source used. This will be described in detail in the polarizer manufacturing process below.

[0099] The contents of boron, zinc, and potassium in the polarizer can be measured by ICP-OES (inductively coupled plasma optical emission spectrometry) without burning the polarizer. For a more detailed measurement method, refer to the experimental example below. The ICP-OES is a method for measuring boron, zinc, and potassium themselves or their cations.

[0100] In one specific example, the weight ratio of boron to the sum of potassium and zinc in the polarizer may be 2 or more, for example, 2, 3, 4, 5, 6, 7, 8, 9, 10, for example, 2 to 10, for example, 2 to 8, 2 to 5. In the above range, the present effect may be easily realized.

[0101] In one specific example, the ratio of boron content to nitrogen content in the polarizer may be 2000 or more, for example, 2000, 2500, 3000, 3500, 4000, 4500, 5000, 5500, 6000, for example, 2000 to 6000. In the above range, the present effect may be easily realized.

[0102] In one specific example, the ratio of potassium content to nitrogen content in the polarizer may be 200 or more, for example, 200, 250, 300, 350, 400, 450, 500, 550, 600, 650, 700, 750, 800, for example, 200 to 800. In the above range, the present effect may be easily realized.

[0103] In one specific example, the ratio of the zinc content to the nitrogen content in the polarizer may be 300 or more, for example, 300, 350, 400, 450, 500, 550, 600, 650, 700, 750, 800, for example, 300 to 800. In the above range, the present effect may be easily realized.

[0104] In one specific example, the total amount of zinc, boron, and potassium in the polarizer may be 95 wt% or more, for example, 95 to 100 wt%, of the total amount of metals and metalloids in the polarizer. Within this range, the present invention's effects may be easily realized.

[0105] The polarizer may have a thickness of 30 μm or less, for example, greater than 0 μm and less than 30 μm, for example, from 10 μm to 25 μm. In the above range, it may be used in a polarizing plate.

[0106] Below, the manufacturing method of the polarizer is described in detail.

[0107] A polarizer can be manufactured using a manufacturing method that includes a dyeing process, a stretching process, and a complementary color process. In one specific example, the polarizer can be manufactured in the following order: dyeing, stretching, and complementary color processes. The order of the dyeing and stretching processes may be changed.

[0108] The content of boron, potassium, and zinc in the polarizer may be derived from materials used in the dyeing process, stretching process, or complementary color process during the polarizer manufacturing process. The content of nitrogen in the polarizer may be derived from materials used in the complementary color process during the polarizer manufacturing process.

[0109] Before the dyeing process, the polyvinyl alcohol-based film may additionally include at least one of a first washing process and a swelling process.

[0110] The first washing process is to wash the polyvinyl alcohol film with water to remove foreign substances on the polyvinyl alcohol film.

[0111] The swelling process can facilitate the dyeing and stretching of a dichroic material by immersing a polyvinyl alcohol-based film in a swelling bath within a predetermined temperature range. The swelling process may include processing at a temperature of 15°C to 35°C, preferably 20°C to 30°C, for 30 to 50 seconds.

[0112] [Dyeing process]

[0113] The dyeing process involves treating a polyvinyl alcohol-based film in a dyeing bath containing a dyeing solution containing a dichroic substance. The dyeing process may involve immersing the polyvinyl alcohol-based film in the dyeing solution containing the dichroic substance.

[0114] The dyeing solution containing the above-mentioned dichroic substance may include an aqueous solution containing the dichroic substance. The above-mentioned dichroic substance is a substance containing iodine, and may include, for example, at least one of iodine (I2), potassium iodide, hydrogen iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, and copper iodide.

[0115] According to one embodiment, iodine is included in a small amount compared to potassium iodide in the dyeing solution, and iodine may be included in an amount of 0.05 to 0.5 wt%, for example, 0.05 to 0.3 wt%, and potassium iodide may be included in an amount of 0.1 to 5 wt%, for example, 0.1 to 1 wt%. In the above range, the production of a polarizer having the above-described content of the polarizer may be facilitated.

[0116] The above-mentioned dichroic material may be included in the dyeing solution at 0.1 to 10 wt%, for example, 0.5 to 5 wt%. Within the above range, uniform dyeing may be achieved.

[0117] The above dyeing solution may further include a boron compound. The boron compound may help prevent melting and fracture of the polyvinyl alcohol-based film during stretching. The boron compound may help prevent melting and fracture of the polyvinyl alcohol-based film even when stretching the polyvinyl alcohol-based film at a high temperature and high stretch ratio in a stretching process performed after the dyeing process.

[0118] The above boron compound may include at least one of boric acid and borax. The boron compound may be included in the dyeing solution at 0.1 to 5 wt%, preferably 0.3 to 3 wt%. Within the above range, there may be an effect of achieving high reliability without melting or fracture during the stretching process.

[0119] 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 the dyeing solution for 100 to 180 seconds, specifically 120 to 150 seconds. Within the above range, the polarizer of one embodiment may be easily manufactured.

[0120] [Cleaning process]

[0121] A polyvinyl alcohol film that has undergone a dyeing process may be additionally subjected to a cleaning process before being subjected to the following stretching process.

[0122] The above cleaning process is to clean a polyvinyl alcohol-based film that has undergone a dyeing process with a cleaning solution.

[0123] The above cleaning solution may contain at least one of the boron compounds, preferably boric acid and borax. The boron compound may be contained in the cleaning solution in an amount of 0.1 to 5 wt%, preferably 0.3 to 3 wt%.

[0124] The temperature of the above cleaning solution may preferably be 20°C to 70°C, specifically 40°C to 60°C. The above cleaning process may be performed by immersing the polyvinyl alcohol-based film in the cleaning solution for 30 to 120 seconds, specifically 40 to 80 seconds.

[0125] [Extension process]

[0126] The stretching process includes stretching the dyed polyvinyl alcohol-based film at a stretching ratio of 5 times or more, for example, 6 to 7 times, at a stretching temperature of 55°C or more, for example, 55°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.

[0127] 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 may include uniaxially stretching a polyvinyl alcohol-based film in the mechanical direction in a stretching solution containing a boron compound.

[0128] The boron compound may include at least one of boric acid and borax, preferably boric acid. The boron compound may be included in the stretching solution, preferably in the stretching aqueous solution, at an amount of 0.5 to 10 wt%, preferably 1 to 5 wt%. Within this range, there may be an effect of achieving high reliability without melting or fracture during the stretching process.

[0129] The above stretching solution may further comprise the above dichroic substance. For example, the above stretching solution may further comprise at least one of potassium iodide, hydrogen iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, and copper iodide, preferably potassium iodide.

[0130] The above-mentioned dichroic material may be included in the stretching solution, preferably in an amount of 0.5 wt% to 10 wt%, preferably 1 wt% to 5 wt%, in the stretching solution. Within the above range, there may be an effect of achieving high reliability without melting or fracture during the stretching process.

[0131] [Second Washing Process]

[0132] A polyvinyl alcohol film that has undergone a stretching process may be additionally subjected to a second washing process before being subjected to the following complementary color process.

[0133] The above second washing process is to wash the polyvinyl alcohol-based film that has undergone the stretching process with a second washing solution.

[0134] The second washing solution may be water.

[0135] The second washing solution may preferably be at a temperature of 10°C to 50°C, specifically 15°C to 25°C. The second washing process may be performed by immersing the polyvinyl alcohol-based film in the second washing solution for 1 second to 20 seconds, specifically 5 seconds to 10 seconds.

[0136] [Complementary color process]

[0137] The complementary color process involves treating the polyvinyl alcohol-based film, which has undergone the stretching process, in a complementary color solution. The complementary color process can enable the production of a polarizer having the nitrogen content described above. Furthermore, the complementary color process can facilitate the adjustment of the color value of the polarizer.

[0138] The above complementary color process can be performed by placing a polyvinyl alcohol-based film in a complementary color bath containing a complementary color solution and leaving it to stand. The complementary color solution may preferably be at a temperature of 10°C to 50°C, specifically 15°C to 25°C.

[0139] The complementary solution may include a nitrogen-containing source. The nitrogen-containing source may be a nitrogen-containing salt, for example, at least one of zinc nitrate (Zn(NO3)2) and sodium nitrate (NaNO3). The nitrogen-containing source may be included in the complementary solution in an amount of 0.1 to 10 wt%, for example, 0.1 to 5 wt%. Within this range, the nitrogen concentration in the polarizer of the present invention can be easily achieved.

[0140] According to one embodiment, the polarizer can be manufactured by applying the nitrogen-containing source in a complementary process. If the nitrogen-containing source is applied to a process other than a dyeing process, a stretching process, or a complementary process, it may be difficult for boron, zinc, and potassium from the boron source, zinc source, and potassium source to penetrate into the polarizer, and thus it may be difficult to reach a nitrogen concentration in the polarizer.

[0141] The above complementary solution may further include at least one of a boron source, a zinc source, and a potassium source.

[0142] The boron source may include at least one of boric acid and borax, preferably boric acid. The boron compound may be included in the complementary solution in an amount of 0.5 to 10 wt%, preferably 1 to 5 wt%. Within this range, the boron compound can be easily reached by the polarizer of the present invention.

[0143] The zinc source may be one or more of zinc sulfate, zinc chloride, zinc iodide, zinc nitrate, and zinc acetate. Preferably, the zinc is derived from zinc nitrate, thereby facilitating the concentration of nitrogen and zinc in the polarizer by using a single compound.

[0144] The zinc source may be contained in the complementary solution at 0.01 to 5 wt%, for example, 0.02 to 3 wt%. Within this range, the zinc source can be easily reached by the polarizer of the present invention.

[0145] The potassium source may be potassium iodide. The potassium iodide in the complementary solution may be present in an amount of more than 0% by weight and up to 10% by weight, preferably 1% to 5% by weight. Within this range, the polarizer of the present invention can easily reach the solution.

[0146] The polarizing plate may further include one or more protective layers on at least one surface of the polarizer. The protective layers may be a first protective layer or a second protective layer.

[0147] The first protective layer is laminated on the upper surface of the polarizer to protect the polarizer and increase the mechanical strength of the polarizing plate. The first protective layer may include an optically transparent protective film.

[0148] The above protective film can be formed by melting and extruding a composition for a protective film that is optically transparent and includes at least one organic component among resins, oligomers, and monomers. If necessary, a stretching process can be further added. The organic component can include at least one of a cellulose ester type including triacetyl cellulose, a cyclic polyolefin type including an amorphous cyclic polyolefin (cyclic olefin polymer, COP), a polycarbonate type, a polyester type including polyethylene terephthalate (PET), a polyethersulfone type, a polysulfone type, a polyamide type, a polyimide type, an acyclic-polyolefin type, a polyacrylate type including polymethyl methacrylate, a polyvinyl alcohol type, a polyvinyl chloride type, and a polyvinylidene chloride type resin.

[0149] In one embodiment, the first protective layer may be a single-layer or multi-layer film laminate.

[0150] In one specific example, the first protective layer may be formed of a composition comprising more than 95 wt% of the organic component.

[0151] The thickness of the first protective layer may be 5 µm to 200 µm, specifically 10 µm to 100 µm, and more specifically 60 µm to 100 µm. Within the above range, it can be used in a polarizing plate.

[0152] A functional coating layer, such as a hard coating layer, an anti-fingerprint layer, an anti-reflection layer, etc., may be further formed on the upper surface of the first protective layer.

[0153] The second protective layer is laminated on the lower surface of the polarizer to protect the polarizer and increase the mechanical strength of the polarizing plate. The second protective layer may include a film formed of the same or different resin as the first protective layer.

[0154] In one specific example, when the first protective layer is a polyester resin film including polyethylene terephthalate (PET) or the like, the second protective layer may be a cyclic polyolefin resin including an amorphous cyclic polyolefin (COP) or a cellulose ester resin film including triacetylcellulose or the like.

[0155] In another specific example, when the first protective layer is a cellulose ester resin film including triacetylcellulose or the like, the second protective layer may be a cellulose ester resin film including triacetylcellulose or the like.

[0156] The second protective layer may have the same or different thickness as the first protective layer.

[0157] Figure 1 is a cross-sectional view of a polarizing plate according to one embodiment.

[0158] Referring to FIG. 1, the polarizing plate may include a polarizer (10), a first protective layer (20) laminated on one side of the polarizer (10), and a second protective layer (30) laminated on the other side of the polarizer (10).

[0159] Although not shown in Fig. 1, the first protective layer and the second protective layer may be laminated to the polarizer by an adhesive layer.

[0160] The adhesive layer can be formed using a conventional polarizing plate adhesive known to those skilled in the art. For example, the adhesive layer can be formed using a water-based adhesive or a photocurable adhesive.

[0161] The water-based adhesive may include a polyvinyl alcohol-based adhesive resin, a crosslinking agent, etc.

[0162] 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.

[0163] The adhesive layer may have a thickness of 0.05 μm to 10 μm. It can be used in an optical display device within the above range.

[0164] According to one embodiment, the optical display device includes the polarizing plate.

[0165] The optical display device may include one or more of a liquid crystal display device and a light-emitting display device.

[0166] A light-emitting display device is a light-emitting element, and may refer to an element including an organic or organic-inorganic light-emitting element and 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. The light-emitting display device may include a light-emitting element and a polarizing plate of the present invention laminated on a light-emitting surface emitted from the light-emitting element.

[0167] A liquid crystal display device includes a backlight unit, a liquid crystal panel, a light source-side polarizing plate arranged between the backlight unit and one side of the liquid crystal panel, and a viewer-side polarizing plate arranged on the other side of the liquid crystal panel, and at least one of the light source-side polarizing plate and the viewer-side polarizing plate may include the polarizing plate of the present invention.

[0168]

[0169] 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.

[0170]

[0171] Example 1

[0172] (1) Manufacturing of polarizers

[0173] A polyvinyl alcohol film (M4516, degree of polymerization: 3200, degree of saponification: 98 mol%, Mitsubishi, Japan, containing a hydrophobic functional group in the main chain, thickness: 45 μm) washed for the first time with water at 25°C was subjected to swelling treatment in a swelling tank with water at 21°C.

[0174] The film that passed through the swelling tank was treated for 150 seconds in a dyeing tank containing a dyeing solution containing 0.1 wt% of iodine (I2) and 0.2 wt% of potassium iodide (KI) at 30°C.

[0175] The film that passed through the above dyeing tank was washed by passing it through a washing tank containing a washing solution containing 3 wt% boric acid at 50°C.

[0176] The film, which had passed through the washing tank, was stretched at a stretching ratio of 6 times along the MD axis of the film in a wet stretching tank containing a 60°C stretching solution containing 2.74 wt% boric acid and 3 wt% potassium iodide.

[0177] The film that passed through the above-mentioned stretching tank was subjected to a second washing treatment by passing it through a second washing tank containing water at 17°C.

[0178] The film that passed through the second washing tank was treated for 10 seconds in a complementary bath containing a complementary solution at 25°C containing 4.5 wt% potassium iodide, 1 wt% boric acid, and 2.0 wt% zinc nitrate.

[0179] The film that passed through the above complementary color filter was washed and dried with hot air to manufacture a polarizer (thickness: 17㎛).

[0180]

[0181] (2) Manufacturing of polarizing plates

[0182] A water-based adhesive (containing polyvinyl alcohol-based adhesive resin) was applied to both sides of the polarizer manufactured above, a triacetyl cellulose film (thickness: 45 μm, DNP) having a hard coating layer formed on the upper surface of the polarizer was laminated, and a triacetyl cellulose (TAC) film (thickness: 20 μm, Konica) was laminated on the lower surface of the polarizer to manufacture a polarizing plate.

[0183]

[0184] Comparative Examples 1 to 3

[0185] A polarizer and a polarizing plate were manufactured in the same manner as in Example 1, except that the concentrations of each component in the dyeing tank, wet stretching tank, and complementary color tank were changed.

[0186]

[0187] The properties of the polarizing plates manufactured in the examples and comparative examples were evaluated in Table 2 below, and the results are shown in Table 2 below and Figures 2 to 9.

[0188]

[0189] (1) Content of zinc, boron, and potassium in polarizers (unit: weight%): Measured using polarizers manufactured in Examples and Comparative Examples according to the ICP-OES measurement method (without combustion process of polarizer) using 5100 series (Agilent). Detailed measurement conditions are as follows.

[0190] 1. Weigh 0.3g of polarizer as a sample into the microwave vessel.

[0191] 2. After adding 5g of nitric acid, close and lock the lid of the microwave vessel.

[0192] 3. Microwave digestion at 200 degrees for 1 hour

[0193] 4. After cooling, transfer the sample and dilute it with dilution solvent (distilled water) to make 75g.

[0194] 5. Analysis using ICP OES

[0195] (2) Nitrogen content in polarizer (unit: weight%): The polarizers manufactured in the examples and comparative examples were combusted using a combustion device (AQF-2100H, Mitsubishi Chemical Corporation) under the conditions below, and then the nitrogen content was measured using ion chromatography (IC-5000S, DIONEX) under the conditions below.

[0196] *Combustion conditions

[0197] Combustion

[0198] - Automatic sampler: 1 ~ 50 mg sampling

[0199] - Furnace: (950 ~ 1050) ℃

[0200] - Absorption Solvent: 900 mg / kg H2O2 solution, 2.2 Ion Chromatography

[0201] - Column: IonPac AS17 (with Guard AG17)

[0202] - Eluent: Contains potassium hydroxide.

[0203] timeconcentration (mM)00711510304031.94032139stop run

[0204] - Eluent Source: EGC KOH Cartridge

[0205] - Flow rate: 0.25 mL / min

[0206] - Injection Volume: 50 uL

[0207] - Detector: Conductivity detector (Range: 50μS Volt: 1V)

[0208] - Automatic sampler: 1 ~ 50 mg sampling

[0209] - Suppressor: ASRS ultra Ⅱ, 2 mm

[0210] - Oven Temperature: 30℃

[0211] *Ion chromatography conditions:

[0212] 1) Clean the sampler of the automatic combustion device through boat prebake.

[0213] 2) Weigh a certain amount of sample, transfer it to a sample boat, and then install it on the autosampler.

[0214] 3) After checking the conditions within the automatic combustion device, such as absorption solvent and rinse, analysis is performed.

[0215] (3) Group transmittance (Ts), orthogonal transmittance (Tc), and polarization degree (PE) of polarizing plates (unit: %): The polarizing plates of the examples and comparative examples were cut to MD x TD (4 cm x 4 cm) of the polarizer and attached to a jig with a measurement area opened to prepare specimens. Group transmittance, orthogonal transmittance, and polarization degree of the prepared specimens were measured using V-7100 (Jasco), respectively.

[0216] (4) Color values ​​as and bs of polarizing plates: The polarizing plates of the examples and comparative examples were cut to MD x TD (4 cm x 4 cm) of the polarizer and attached to a jig with a measurement area opened to manufacture a specimen. The color values ​​as and bs of the manufactured specimens were measured using V-7100 (Jasco).

[0217] (5) Color value change of polarizing plate △E1 and △E2: The polarizing plates of the examples and comparative examples were cut to MD x TD (6 cm x 6 cm) of the polarizer, adhered to a glass plate using an acrylic adhesive (SDI), and then the adhesive and glass plate were covered over the polarizing plate to prepare a specimen. The manufactured specimens were left at 105℃ for 48 hours and 250 hours, respectively, and then the color value a* and color value b* were measured using a colorimeter (CM-3700A, Konica Minolta). The color value change △E1 and △E2 were measured using the above equations 1 and 2, respectively.

[0218] Boron Potassium Zinc Nitrogen TsTcPEasbs△E2△E1Example 13.70.460.390.000741.80.000399.999-1.12.64.05.4Example 23.60.450.750.0011441.70.000399.999-1.12.34.36.6Comparative Example 13.8 0.70.42042.00.000799.998-1.12.83.019.6Comparative Example 23.90.630.04042.10.000499.999-1.03.43.978.8Comparative Example 33.50.410.10.1541.80.000599.998-1.12.54.1552.4

[0219]

[0220] As shown in Table 2 above, the polarizing plate of the present invention satisfies the color value range described above before being left at high temperatures. Therefore, it is expected to provide excellent screen quality when applied to an optical display device. In addition, the polarizing plate of the present invention showed a remarkably low change in color value after being left at high temperatures for a long period of time, indicating excellent reliability at high temperatures. In particular, the change in color value was remarkably low both when left at 105°C for 48 hours and 250 hours. This can also be seen in FIGS. 2 to 5. Referring to FIGS. 2 to 5, the color value of the polarizing plate did not change when left at 105°C for 48 hours (FIGS. 2 and 4) or when left at 250 hours (FIGS. 3 and 5).

[0221] On the other hand, the polarizing plate of the comparative example could not obtain all the effects of the polarizing plate of the present invention described above. This can also be seen in FIGS. 6 to 9. Referring to FIGS. 6 to 9, it can be confirmed that the color value of the polarizing plate did not change when left at 105°C for 48 hours (FIGS. 6 and 8), but when left at 105°C for 250 hours (FIGS. 7 and 9), the color value of the polarizing plate changed significantly.

[0222]

[0223] Simple modifications or changes of the present invention can be easily implemented by a person having ordinary skill in the art, and all such modifications or changes can be considered to be included in the scope of the present invention.

Claims

1. Equip yourself with a polarizer, The above polarizer is composed of a polyvinyl alcohol-based film containing a dichroic material, A polarizing plate, wherein the polarizer comprises 1.5 to 5.0 wt% of boron, 0.3 to 1.0 wt% of potassium, 0.1 to 1.0 wt% of zinc, and 0.0001 to 0.1 wt% of nitrogen.

2. A polarizing plate in the first paragraph, wherein the ratio of the boron content to the nitrogen content in the polarizer is 2000 or more.

3. A polarizing plate in the first paragraph, wherein the ratio of the nitrogen content to the potassium content in the polarizer is 200 or more.

4. A polarizing plate in the first paragraph, wherein the ratio of nitrogen content to zinc content among the polarizers is 300 or more.

5. A polarizing plate in the first paragraph, wherein the weight ratio of boron to the total sum of potassium and zinc in the polarizer is 2 or more.

6. A polarizing plate in the first paragraph, wherein the total amount of zinc, boron, and potassium in the polarizer is 95% by weight or more of the total amount of metals and metalloids in the polarizer.

7. A polarizing plate according to claim 1, wherein the nitrogen is derived from zinc nitrate.

8. In the first paragraph, the polyvinyl alcohol-based film is a polarizing plate comprising a polyvinyl alcohol resin having a polymerization degree of 3000 to 5000, or a derivative resin of the polyvinyl alcohol.

9. In the first paragraph, the polyvinyl alcohol-based film is a polarizing plate comprising a polyvinyl alcohol resin having a saponification degree of 98 mol% or more, and a derivative resin of the polyvinyl alcohol.

10. A polarizing plate according to claim 1, wherein the polyvinyl alcohol-based film comprises a derivative of polyvinyl alcohol having a hydrophilic functional group and a hydrophobic functional group.

11. A polarizing plate in accordance with claim 1, wherein a protective layer is further laminated on at least one surface of the polarizer.

12. An optical display device comprising a polarizing plate according to any one of claims 1 to 11.

Images