Polarizing plate, liquid crystal panel and display device

Abstract

The present disclosure relates to a polarizing plate including: a polarizer, and a first hard coating layer having a thickness of 10 um or less and an anti-reflection film which are positioned so as to face each other around the polarizer, wherein the anti-reflection film includes a light-transmitting substrate and a second hard coating layer, and wherein a ratio (a/b) of a transmittance (a) at a wavelength of 400 nm of the second hard coating layer to the transmittance (b) at a wavelength of 500 nm of the second hard coating layer is 0.95 or less, or 0.85 to 0.95.

Claims

1. A polarizing plate comprising: a polarizer, and a first hard coating layer having a thickness of 10 μm or less and an anti-reflection film, the first hard coating layer and the anti-reflection film being positioned on either side of the polarizer so as to face each other with respect to the polarizer, wherein the first hard coating layer directly contacts the polarizer, wherein the anti-reflection film includes a light-transmitting substrate and a second hard coating layer, wherein the first hard coating layer and the second hard coating layer include a binder resin; and organic fine particles having a particle size of 0.5 μm to 10 μm, and inorganic fine particles having a particle size of 1 nm to 500 nm dispersed in the binder resin, wherein the binder resin contained in the first hard coating layer comprises a photocurable resin, wherein the second hard coating layer has a ratio (a/b) of a transmittance (a) at a wavelength of 400 nm to a transmittance (b) at a wavelength of 500 nm, of 0.95 or less, wherein the transmittance (a) is 85% to 95% at the wavelength of 400 nm, wherein the light-transmitting substrate has a thickness direction retardation (Rth) measured at a wavelength of 400 nm to 800 nm of 3,000 nm or more, wherein the light-transmitting substrate has a moisture permeation amount of 100 g/m.sup.2 or less as measured for 24 hours under the conditions of 40° C. and 100% humidity, and wherein the light-transmitting substrate has a ratio of a heat shrinkage force in a second direction of the light-transmitting substrate to a heat shrinkage force in a first direction of the light-transmitting substrate perpendicular to the second direction in the temperature range of 60° C. to 100° C. of 0.6 to 1.5.

2. The polarizing plate of claim 1, wherein the second hard coating layer further includes an initiator that absorbs at least 95% of light in the wavelength range of 380 nm to 400 nm.

3. The polarizing plate of claim 1, wherein the second hard coating layer has the transmittance (b) of 98% to 100% at a wavelength of 500 nm.

4. The polarizing plate of claim 1, wherein the first direction of the light-transmitting substrate is an MD direction (machine direction) of the light-transmitting substrate, and the second direction of the light-transmitting substrate is a TD direction (transverse direction) of the light-transmitting substrate.

5. The polarizing plate of claim 1, wherein the light-transmitting substrate has a moisture permeation amount of 10 to 100 g/m.sup.2 as measured for 24 hours under the conditions of 40° C. and 100% humidity.

6. The polarizing plate of claim 1, wherein a ratio of the thickness of the first hard coating layer to a thickness of the light-transmitting substrate is 0.02 to 0.25.

7. The polarizing plate of claim 1, wherein the total thickness of the polarizer, the first hard coating layer and the light-transmitting substrate is 200 μm or less.

8. The polarizing plate of claim 1, wherein the second hard coating layer has a thickness of 1 μm to 30 μm.

9. The polarizing plate of claim 1, wherein the anti-reflection film further includes a low refractive index layer formed on one surface of the second hard coating layer opposite to the light transmitting substrate.

10. The polarizing plate of claim 9, wherein the low refractive index layer has a refractive index of 1.20 to 1.60 in the wavelength range of 380 nm to 780 nm.

11. The polarizing plate of claim 1, further comprising an adhesive layer disposed between the polarizer and the light-transmitting substrate and having a thickness of 0.1 μm to 5 μm.

12. A display device comprising the polarizing plate of claim 1.

13. A liquid crystal panel having a polarizing plate on at least one surface of a liquid crystal cell, wherein the polarizing plate comprises: a polarizer, and a first hard coating layer having a thickness of 10 μm or less and an anti-reflection film, the first hard coating layer and the anti-reflection film being positioned on either side of the polarizer so as to face each other with respect to the polarizer, wherein the first hard coating layer directly contacts the polarizer, wherein the anti-reflection film includes a light-transmitting substrate and a second hard coating layer, wherein the first hard coating layer and the second hard coating layer include a binder resin; and organic fine particles having a particle size of 0.5 μm to 10 μm, and inorganic fine particles having a particle size of 1 nm to 500 nm dispersed in the binder resin, wherein the second hard coating layer has a ratio (a/b) of a transmittance (a) at a wavelength of 400 nm of the second hard coating layer to a transmittance (b) at a wavelength of 500 nm of the second hard coating layer is 0.95 or less, wherein the transmittance (a) is 85% to 95% at the wavelength of 400 nm, wherein the light-transmitting substrate has a thickness direction retardation (Rth) measured at a wavelength of 400 nm to 800 nm of 3,000 nm or more, wherein the light-transmitting substrate has a moisture permeation amount of 100 g/m.sup.2 or less as measured for 24 hours under the conditions of 40° C. and 100% humidity, and wherein the light-transmitting substrate has a ratio of a heat shrinkage force in a second direction of the light-transmitting substrate to a heat shrinkage force in a first direction of the light-transmitting substrate perpendicular to the second direction in the temperature range of 60° C. to 100° C. of 0.6 to 1.5.

14. The liquid crystal panel of claim 13, wherein the polarizing plate is formed on both surfaces of the liquid crystal cell such that a MD direction of the polarizer of the polarizing plate formed on one surface of the liquid crystal cell and a MD direction of the polarizer of the polarizing plate formed on the other surface are perpendicular to each other.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows an example of a polarizing plate of an embodiment of the present disclosure.

(2) FIG. 2 shows another example of a polarizing plate of an embodiment of the present disclosure.

(3) FIG. 3 shows an example of a liquid crystal panel of an embodiment of the present disclosure.

(4) FIG. 4 shows another example of a liquid crystal panel of an embodiment of the present disclosure.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(5) Hereinafter, embodiments of the present disclosure are described in further detail with reference to examples. However, these examples are for illustrative purposes only and are not intended to limit the scope of the present disclosure.

PREPARATION EXAMPLE

Preparation Example 1: Preparation of Anti-Reflection Film

(6) (1) Preparation of Coating Liquid for Forming a Hard Coating Layer (Second Hard Coating Layer) of an Anti-Reflection Film

(7) The components shown in Table 1 were mixed to prepare a coating liquid (B1, B2, B3, B4, B5) for forming a hard coating layer of the anti-reflection film.

(8) TABLE-US-00001 TABLE 1 (Unit: g) B1 B2 B3 B4 B5 DPHA 12.5 12.5 12.5 12.5 12.5 UA-306T 12.5 12.5 12.5 12.5 12.5 I184 — — — 0.4 0.2 D1173 — — — 0.4 0.2 IRG 819 0.8 — 0.4 — — IRG 369 — 0.8 0.4 — — 2-BuOH 40 40 40 40 40 MIBK 20 20 20 20 20 PGMEA 10 10 10 10 10 XX-113BQ(2.0 μm 1.555) 1.5 1.5 1.5 1.5 1.5 MA-ST(30% in MeOH) 0.5 0.5 0.5 0.5 0.5

(9) DPHA: dipentaerythritol hexaacrylate

(10) PETA: pentaerythritol triacrylate

(11) UA-306T: urethane acrylate series, reaction product with toluene diisocyanate and pentaerythritol triacrylate (manufactured by Kyoeisha Chemical)

(12) IRG-819: initiator (Irgacure 819, Ciba Specialty Chemicals)

(13) IRG-369: initiator (Irgacure 369, Ciba Specialty Chemicals)

(14) D-1173: initiator (Darocur 1173, Ciba Specialty Chemicals)

(15) 2-BuOH: 2-butylalcohol

(16) MIBK: methyl isobutyl ketone

(17) PGMEA: propylene glycol monomethyl ether acetate

(18) XX-113BQ (2.0 μm, reflective index: 1.515): copolymerized particles of polystyrene and polymethyl methacrylate (manufactured by Sekisui Plastic)

(19) MA-ST (30% in MeOH): Dispersion in which silica nanoparticles with a size of 10˜15 nm are dispersed in methyl alcohol (manufacture by Nissan Chemical)

(20) (2) Preparation of Coating Liquid (C) for Forming Low Reflective Index Layer

(21) 100 g of trimethylolpropane triacrylate (TMPTA), 283 g of hollow silica nanoparticles (diameter range: about 42 nm to 66 nm, JSC Catalyst and Chemicals), 59 g of solid silica nanoparticles (diameter range: about 12 nm to 19 nm), 115 g of a first fluorine-containing compound (X-71-1203M, Shin-Etsu), 15.5 g of a second fluorine-containing compound (RS-537, DIC Corporation) and 10 g of an initiator (Irgacure 127, Ciba) were diluted in a MIBK (methyl isobutyl ketone) solvent so as to have a solid content of 3% by weight, thereby preparing a coating liquid for forming a low reflective index layer.

(22) (3) Preparation of Anti-reflection Film Formed on Light-Transmitting Substrate

(23) Each of the prepared coating liquids for forming a hard coating layer (B1, B2, B3, B4, B5) was coated onto the respective polyethylene terephthalate (PET) films shown in Tables 2 and 3 below using a #12 Mayer bar, and then dried at the temperature shown in Tables 2 and 3 below for 2 minutes, and UV-cured to form a hard coating layer (coating thickness of 5 μm). The H bulb was used as a UV lamp and a curing reaction was performed under nitrogen atmosphere. The amount of UV light irradiated upon curing was 100 mJ/cm.sup.2.

(24) At this time, the ratio(a/b) of the transmittance (a) at the wavelength of 400 nm of the second hard coating layer to the transmittance (b) at the wavelength of 500 nm of the second hard coating layer formed on the substrate was obtained by measuring the transmittance of the hard coating film in the range of 780 to 350 nm using a UV spectrophotometer (Solidspec-3700, Shimadzu). The results are shown in Tables 2 and 3 below

(25) The coating liquid (C) for forming the low reflective index layer was coated onto the hard coating film using a #4 Mayer bar so that the thickness was about 110 to 120 nm, and then dried and cured for 1 minute at the temperature shown in Tables 2 and 3 below. During the curing, the dried coating was irradiated with ultraviolet light of 252 mJ/cm.sup.2 under a nitrogen purge.

Preparation Example 2: Preparation of Coating Liquid for Forming First Hard Coating Layer and Preparation of Polarizer with First Hard Coating Layer Having Thickness of 10 um or less Formed Thereon

(26) (1) Preparation of Coating Liquid (A) for Forming First Hard Coating Layer

(27) 28 g of trimethylolpropane triacrylate, 2 g of KBE-403, 0.1 g of initiator KIP-100f, and 0.06 g of leveling agent (Tego wet 270) were uniformly mixed to prepare a hard coating composition.

(28) (2) Preparation of Polarizer with First Hard Coating Layer Formed Thereon

(29) Polyvinyl alcohol polarizer (thickness: 25 um, manufacturer: LG Chem) was bonded onto the light-transmitting substrate of the anti-reflection film prepared in Preparation Example 1 using a UV adhesive, then the coating liquid (A) for forming the hard coating layer was coated onto the opposite side of the light-transmitting substrate to a thickness of 7 um, and the dried coating was irradiated with ultraviolet light of 500 mJ/cm.sup.2 under nitrogen purge to form a first hard coating layer.

EXAMPLES AND COMPARATIVE EXAMPLES

Preparation of Polarizing Plate and Liquid Crystal Panel

(30) (1) Preparation of Polarizing Plate

(31) The anti-reflection film formed on the light-transmitting substrate obtained in Preparation Example 1 and the polarizer were joined using a UV-curable adhesive, and then a first hard coating layer prepared in Preparation Example 2 was formed on the other side of the polarizer to prepare the polarizing plate of each of Examples and Comparative Examples described in Table 2 and Table 3 below. At this time, the polarizing plate was manufactured such that the absorption axis of a polarizer and the TD direction of a light-transmitting substrate were parallel.

(32) 1) Measurement of the Ratio of Heat Shrinkage Force

(33) In this case, the ratio of heat shrinkage force in the MD direction of the polyethylene terephthalate (PET) film used in each of Examples and Comparative Examples: the heat shrinkage force in the TD direction was measured using a DMA instrument (dynamic mechanical analyzer) (TA Instruments).

(34) The temperature was set to increase by 25° C. per minute from 25° C. and then reach 75° C. after 3 minutes, and then the temperature was set to reach 80° C. after 7 minutes. The measurement time was 2 hours. The values of the heat shrinkage force in the MD direction and the heat shrinkage force in the TD direction of the PET film after 2 hours were measured 2 hours after stabilization at 80° C.

(35) The heat shrinkage force in the MD direction and the heat shrinkage force in the TD direction of the PET film were respectively determined by fastening a sample cut into a width of 6 mm and a length of 50 mm to a clamp and then pulling and fixing the sample so as to maintain 0.1% of strain in the 0.01 N preload state, and then measuring the shrinkage force required to maintain 0.1% of strain at a high temperature. The heat shrinkage force in the MD direction and the heat shrinkage force in the TD direction of the PET film were respectively measured and their ratios were determined.

(36) PET1: shrinkage force ratio (MD:TD) is about 1

(37) PET2: shrinkage force ratio (MD:TD) is about 2

(38) PET3: shrinkage force ratio (MD:TD) is about 0.5

(39) 2) Measurement of the Ratio of Heat Shrinkage Rate

(40) The ratio of a heat shrinkage rate in the MD direction: a heat shrinkage rate in the TD direction of the polyethylene terephthalate (PET) film used in each of Examples and Comparative Examples was calculated by cutting each PET film into a size of 30 cm*30 cm (width*length), allowing to stand at 80° C. for 30 minutes and then determining the shrinkage rate (modified length/initial length) in each of the MD and TD directions.

(41) PET 1: The ratio of heat shrinkage rate (MD:TD) is about 0.9˜1.1

(42) PET 2: The ratio of heat shrinkage rate (MD:TD) is about 10˜12

(43) PET 3: The ratio of heat shrinkage rate (MD:TD) is about 4.5˜6

(44) (2) Preparation of Sample for Thermal Shock Evaluation

(45) The polarizing plate cut into a square where the length of one side was 10 cm was bonded to one surface of the glass for TV (12 cm wide, 12 cm long, and 0.7 mm thick) to prepare a sample for thermal shock evaluation. At this time, the polarizing plate was cut so that the MD direction of the polarizer was parallel to one side of the square.

EXPERIMENTAL EXAMPLE

Experimental Example 1: Light-Resistant Adhesion Test and Hardness Measurement of Anti-Reflection Film

(46) (1) Light-Resistant Adhesion Test of Anti-Reflection Film

(47) The polarizing plate cut into a square having a length 10 cm of one side was exposed to a UVB (280-360 nm) light resistance exposure apparatus (UV tester, Coretech Korea Co., Ltd.) for 24 hours. The film was arranged so that the coating surface was directed toward a UV light source, and the distance between the UV light source and the coating film was 15 to 30 cm.

(48) After 24 hours, scratches were made so as to form 100 grids within a size of 1 cm*1 cm to 2 cm*2 cm using a cutter knife and attached using a Nichiban Tape, and then a peel test was performed. The peel test was performed twice on the same surface, and the adhesive strength was evaluated from the 5B (no peel) level to 0B (fully peeled) according to the peeled level.

Evaluation Criteria

(49) 5B (not peeled) 4B (1-5 grids containing the peeled portion) 3B (6-15 grids containing the peeled portion) 2B (16-35 grids containing the peeled portion) 1B (36-50 grids containing the peeled portion) 0B (51 or more grids containing the peeled portion)

(50) (2) Hardness Measurement of Anti-reflection Film

(51) The polarizing plate without the adhesive layer or the polarizing plate from which the adhesive layer was removed was cut into a size of 5 cm*5 cm. The film was fixed to a sample table of the pencil hardness tester (Chungbuk Tech) so that it could be measured in the direction perpendicular to the MD direction of the film, then the film was fixed at an angle of 45 degrees, and then the pencil hardness was measured at a speed of 300 mm/min under a load of 500 g.

(52) One measurement length was 45 mm and measurement was performed five times in total. In the state where the press of 5 mm at the initial stage of the measurement, pressing and scratching of the remaining portion were evaluated with the naked eye, and it was determined as OK if there were no scratches four or more times.

Experimental Example 2: Thermal Shock Evaluation

(53) For the prepared polarizing plate and a sample for evaluation to which the polarizing plate was joined, the thermal shock test was conducted under the following conditions and the following three items were measured and confirmed.

(54) Preparation of Samples for Thermal Shock Evaluation

(55) The polarizing plate cut into a square having a length 10 cm of one side was bonded to one surface of a glass for TV (12 cm wide, 12 cm long, and 0.7 mm thick) to prepare a sample for thermal shock evaluation. At this time, the polarizing plate was cut so that the MD direction of a polarizer was parallel to one side of the square.

(56) Measuring Conditions:

(57) The polarizing plate and the sample for thermal shock evaluation were placed upright on a thermal shock chamber. The process in which the temperature was raised from room temperature to 80° C. and left for 30 minutes, after which the temperature was lowered to −30° C. and left for 30 minutes, and then the temperature was controlled to room temperature was defined as 1 cycle, and a total of 100 cycles were repeated.

(58) (1) Number of Occurrence of Cracks

(59) The cracks occurred between the polarizers of the sample for evaluation and the gaps formed between the polarizing plates were confirmed with the naked eye, and the number of occurrence of cracks with a length of 1 cm was confirmed.

(60) (2) Bubble

(61) The bubbles occurred between the polarizer and the protective film of the evaluation sample and the bubbles occurred between the polarizer and the hard coating layer were confirmed with the naked eye and the number of bubbles having a diameter of 5 mm or more was confirmed.

(62) (3) Peeling

(63) A detachment occurred between the polarizer and the protective film of the sample for thermal shock evaluation, a detachment in four vertices, a detachment between the second hard coating layer and the protective film, and a detachment between the polarizer and the first hard coating layer were confirmed with the naked eye. It was evaluated either as NG if peeling occurred at any one of the locations, or as OK if no peeling occurred.

(64) (4) Vertex Detachment (mm), 10×10/Film

(65) The four vertices of the polarizing plate sample were observed, and the detachment between the coating layer and the polarizer, the peeling between the polarizer and the protective film, and the peeling and bending between the hard coating and the cohesive layer were observed. When the detachment occurred and bending appeared, the bending height from the floor in a state where the sample placed flat on the floor was measured to calculate the average height.

(66) TABLE-US-00002 TABLE 2 Example 1 Example 2 Example 3 Anti-reflection low reflective index Coating liquid Coating liquid Coating liquid film layer (C) (C) (C) Second hard coating layer B1 B2 B3 Thickness of second hard 6.1 μm 4.5 μm 5.7 μm coating layer a/b 0.9 0.9 0.92 Drying temperature of low 40° C. 40° C. 40° C. reflective index layer Drying temperature of 60° C. 60° C. 60° C. anti-glare layer Low moisture permeable PET 1 PET 1 PET 1 substrate Result of light-resistant adhesion test of 5B 5B 5B anti-reflection film Harness measurement of anti-reflection film 3H OK 3H OK 3H OK (polarizing plate) Result of thermal Number of cracks 0 0 0 shock Bubble 0 0 0 evaluation Peeling OK OK OK Vertex detachment (mm), 0 0 0 10 × 10/film *a/b: the ratio(a/b) of the transmittance (a) at a wavelength of 400 nm of the second hard coating layer to the transmittance (b) at the wavelength of 500 nm of the second hard coating layer

(67) TABLE-US-00003 TABLE 3 Comparative Comparative Comparative Example 1 Example 2 Example 3 Anti-reflection low reflective index Coating liquid Coating liquid Coating liquid film layer (C) (C) (C) Second hard coating B4 B5 B5 layer Thickness of second hard 3.8 μm 6.0 μm 4.0 μm coating layer a/b 0.99 0.99 0.99 Drying temperature of low 40° C. 90° C. 90° C. reflective index layer Drying temperature of 60° C. 100° C. 60° C. anti-glare layer Low moisture permeable PET 2 PET 3 PET 3 substrate Result of light-resistant adhesion test of 1B 0B 0B anti-reflection film Harness measurement of anti-reflection film 3H NG 3H OK 3H NG (polarizing plate) Result of thermal Number of cracks 0 1 1 shock Bubble 0 2 1 evaluation Peeling NG NG NG Vertex detachment (mm), 1 4 3 10 × 10/film

(68) As shown in Table 2 and Table 3 above, it was confirmed that the polarizing plates of Examples including a second hard coating layer in which the ratio (a/b) of the transmittance (a) at a wavelength of 400 nm to the transmittance (b) at the wavelength of 500 nm of the second hard coating layer is 0.95 realize excellent effects in the light-resistant adhesion test of the polarizing plate or the hardness test according to the thickness as compared with Comparative Examples.

(69) In addition, it was confirmed that the polarizing plates of Examples not only have a stable internal structure together with high surface hardness, but also have excellent bending balance, prevent the occurrent of cracks and exhibit excellent effects in the light-resistant adhesion test of the polarizing plate or the hardness test according to the thickness as compared with Comparative Examples, and further can prevent a light leakage phenomenon of a liquid crystal display device.

EXPLANATION OF SIGN

(70) 10: light-transmitting substrate 20: polarizer 30: first hard coating layer 40: second hard coating layer 50: adhesive layer 60: cohesive layer 70 liquid crystal cell 100 polarizing plate 200 liquid crystal panel