KR101459119B1 - Polarizing film and liquid crystal display provided with the same - Google Patents

Abstract

The polarizing film of the present invention comprises a polarizer; And a protective film formed on one surface or both surfaces of the polarizer, wherein a coating layer containing particles having a thermal conductivity of 10 to 500 W / m · K is formed on the light incident surface of the polarizing film, The heat generated from the backlight can be diffused to the front of the panel more quickly, thereby reducing the temperature deviation and improving the light leakage.

Description

TECHNICAL FIELD [0001] The present invention relates to a polarizing film and a liquid crystal display device including the polarizing film.

The present invention relates to a polarizing film and a liquid crystal display including the polarizing film. More specifically, the present invention relates to a polarizing film and a liquid crystal display including the polarizing film, which can reduce a temperature deviation by forming a specific coating layer on a polarizing film to spread heat generated from the backlight more quickly on the entire surface of the panel.

BACKGROUND ART [0002] Liquid crystal displays (LCDs) are one of the most widely used flat panel displays. The liquid crystal display device includes a liquid crystal display panel including two display panels on which an electric field generating electrode is formed and a liquid crystal layer interposed therebetween. A voltage is applied to the electric field generating electrode to generate an electric field in the liquid crystal layer, The orientation of the liquid crystal molecules is determined and the polarization of the incident light is controlled to display an image.

The liquid crystal device includes a case and a liquid crystal module built in the case. The liquid crystal module is composed of a liquid crystal panel, a backlight unit (BLU), and a chassis supporting the backlight unit (BLU). A voltage is applied to the liquid crystal panel to control the direction of the liquid crystal to change the light transmittance and display an image. In addition, the liquid crystal panel has a BLU with a light source on its back side. The BLU is composed of a light source, a light guide plate, a reflection plate, a lens sheet, and a diffusion plate. Light sources include cathode fluorescent lamps and LEDs. Liquid crystal display devices are expected to have improved brightness, thinness, cost reduction, and an increase in edge type backlight in which a light source is disposed in an edge.

However, when an edge type BLU is used, a large temperature difference is generated within the panel surface. Thermal stress is generated in the surface of the liquid crystal panel according to the temperature difference, and a phase difference similar to a temperature distribution is generated in the glass surface of the liquid crystal panel. This phase difference causes light leakage in the portion where the alignment angle of the polarizing film in the black display and the deviation between the Slow axis or the Fast axis, which is a phase axis generated in Glass, become significant, and the display uniformity of the liquid crystal panel due to display unevenness is lowered. This temperature deviation causes a phase delay of the display panel, which causes a light leakage phenomenon at the upper and lower ends of the display panel in the TN (Twisted Nematic) mode and at four corners in the VA (Vertical Alignment) mode or IPS (In- .

Korean Patent Laid-Open Publication No. 2008-62108 discloses a method of improving the light leakage by emitting heat generated from the lamp to the outside by forming a protruding pattern on the upper and lower ends of the storage container in contact with the lamp cover.

Further, Japanese Patent Application Laid-Open No. 2002-40241 discloses an optical compensation sheet having a feature that the thermal conductivity of the retardation film is improved and only a single polymer film having a thermal conductivity of 1 W / (mK) or more is included.

Japanese Unexamined Patent Publication (Kokai) No. 2009-92788 discloses a heat insulating means for blocking heat conduction from a back chassis supporting a BLU, a top chassis surrounding a liquid crystal panel, and a backlight light source having a middle chassis disposed therebetween.

Japanese Laid-Open Patent Publication No. 2005-321593 discloses a liquid crystal display device in which a heat insulating sheet is disposed between a liquid crystal cell and a backlight.

However, when the above-mentioned techniques are applied to a liquid crystal display device using an edge type backlight unit, a large temperature deviation occurs in the panel surface as shown in Fig. Particularly, since the corner portion has the highest temperature, the in-plane temperature deviation becomes about 10 degrees or more. Thermal stress is generated in the liquid crystal panel due to the temperature difference, and a phase difference is generated in a shape similar to the temperature distribution in the glass surface. This phase difference causes light leakage in a portion where the orientation angle of the polarizing film in the black display and the slack axis or the fast axis, which is the phase axis generated in the glass, become significant, and the display quality of the liquid crystal panel due to display unevenness is lowered. The phase delay of the display panel affects the polarization of the polarizer. As a result, as shown in FIG. 2, light leakage occurs at the four corner portions in VA mode or IPS mode. In the TN mode, .

It is an object of the present invention to provide a polarizing film capable of reducing the temperature difference within a plane of a display panel which is a fundamental cause of a light spot of a liquid crystal display device by allowing heat generated in a backlight to be quickly transmitted to the entire surface of the panel.

Another object of the present invention is to provide a polarizing film which is suitable for a liquid crystal display device in which a backlight position is located on the upper and lower sides or an edge type backlight is applied.

Another object of the present invention is to provide a liquid crystal display device capable of improving light leakage by introducing a transparent material having a high thermal conductivity into a polarizing film surface without complicated device design.

The technical objects to be achieved by the present invention are not limited to the above-mentioned technical problems, and other technical subjects which are not mentioned can be understood by those skilled in the art from the following description.

An aspect of the present invention relates to a polarizing film. Wherein the polarizing film comprises a polarizer; And a protective film formed on one surface or both surfaces of the polarizer, characterized in that a coating layer containing particles having a thermal conductivity of 10 to 500 W / m · K is formed.

In an embodiment, the coating layer may be formed between the protective film and the backlight unit.

 Wherein the coating layer has a haze rise of 0.5 or less and a total light transmittance reduction of 0.3 or less.

The coating layer may contain 10 to 40% by weight of particles having a thermal conductivity of 10 to 500 W / m · K in the entire coating layer.

The particles may have an average particle diameter of 0.1 to 500 nm.

The particles may include one or more of a metal, a metal oxide, a metal carbide, a metal boride, or a metal nitride. For example, the particles Ag, Bi, Co, Cr, Cu, Fe, In, Ni, Pb, Sn, ZnO, Al ₂ O _3, Bi ₂ O _3, CeO _2, CuO, CoO, Fe ₂ O ₃ , Mn ₃ O ₄ , Ho ₂ O ₃ , SnO ₂ , Y ₂ O ₃ , BeO, ATO, ITO, LaCrO ₃ , B ₄ C, ZrC, SiC, TaC, TiB ₂ , ZrB ₂ , CrB ₂ , BN, AlN, HfN, TiN, and the like.

In one embodiment, the coating layer may comprise a UV curable resin and particles having a thermal conductivity of 10 to 500 W / mK.

The UV curable resin may be a polyester resin, an acrylic resin, a urethane resin, an amide resin, a silicone resin, an epoxy resin, or the like.

In another embodiment, the coating layer further comprises a UV curable monomer, a UV curable oligomer, a polymerization initiator, a photosensitizer, a plasticizer, a tackifier, a coupling agent, a dispersant, a leveling agent, a polymerization inhibitor, an antioxidant, .

In an embodiment, the polarizing film may have a luminance difference (? L) of less than 0.06 Cd / m2 between an edge portion and a center portion according to the following formula:

? L = [(a + b + d + e) / 4] -c

(Where a, b, d, and e are luminance averages at positions corresponding to 1/16 of the total area from the end portions of the respective sides of the optical member, and c is the average luminance of 1/32 area of the center of the optical member) .

The polarizing film may have an in-plane temperature deviation (maximum in-plane temperature - minimum in-plane temperature) of less than 10 ° C.

Another aspect of the present invention relates to a liquid crystal display device. The liquid crystal display device includes the polarizing film, and the polarizing film is formed between the liquid crystal panel and the backlight.

In an embodiment, the backlight may be an edge-type backlight.

The present invention can rapidly transfer heat generated from the backlight to the entire surface of the panel, thereby reducing the temperature difference between the in-plane display panel, which is a fundamental cause of the light spot of the LCD, It is an object of the present invention to provide a liquid crystal display device capable of improving a light leakage phenomenon by introducing a transparent material having a high thermal conductivity into the surface of a polarizing film without providing a complicated device design and providing a polarizing film suitable for the applied liquid crystal display device.

1 is a photograph showing a temperature variation in a conventional liquid crystal display device using an edge type backlight unit.
2 is a photograph showing light leakage phenomenon in a VA mode or an IPS mode and a TN mode.
3 is a schematic cross-sectional view of a polarizing film according to one embodiment of the present invention.
4 is a schematic cross-sectional view of a liquid crystal display device according to one embodiment of the present invention.

3 is a schematic cross-sectional view of a polarizing film according to one embodiment of the present invention. As shown in the figure, the polarizing film of the present invention is a polarizing film comprising a polarizer 10 and protective films 11A and 11B formed on one or both surfaces of the polarizer, and has a thermal conductivity of 10 to 500 W / mK And a coating layer 12 containing particles is formed.

The polarizing film may be applied to a back polarizing film attached to the rear side of the liquid crystal display panel.

The polarizer 10 can be generally made of stretched polyvinyl alcohol (PVA). For example, a polyvinyl alcohol film is stretched, and after adsorbing iodine or a dichroic dye thereto, . ≪ / RTI >

As the protective films 11A and 11B, triacetyl cellulose (TAC), cellulose acetate propionate and / or WV-TAC (wide view-TAC) may be used.

The coating layer 12 is formed on the light incident surface of the polarizing film and is formed between the surface of the protective film 11B formed near the backlight unit, that is, between the protective film 11B and the backlight unit 13.

The coating layer 12 may be coated with a coating composition using a bar coater or a gravure coating method to form a coating layer. The method of forming the coating is not limited to the above. The coating may be in various forms such as a front coating or a fine mesh shape. It is also possible to change the coating pattern by applying it to various light source lamp shapes and designs.

The coating layer 12 includes particles having a thermal conductivity of 10 to 500 W / mK. Within the above range, the target thermal conductivity of the present invention can be obtained. Preferably 20 to 400 W / m 占 K, more preferably 25 to 300 W / m 占.. Most preferably 25 to 120 W / m · K.

The particles have an average particle diameter of 0.1 to 500 nm. In the above range, the optical properties, thermal conductivity and dispersibility are excellent. Preferably 1 to 200 nm, and more preferably 5 to 100 nm. Most preferably 10 to 70 nm.

When the particles are applied to an optical film, a material exhibiting visible light absorption characteristics in which reflection of light and scattering absorption in the visible light region of the coating film are low and coloring of the transmitted light is not performed can be used. In embodiments, the particles may include one or more of a metal, a metal oxide, a metal carbide, a metal boride, or a metal nitride. For example, the particles Ag, Bi, Co, Cr, Cu, Fe, In, Ni, Pb, Sn, ZnO, Al ₂ O _3, Bi ₂ O _3, CeO _2, CuO, CoO, Fe ₂ O ₃ , Mn ₃ O ₄ , Ho ₂ O ₃ , SnO ₂ , Y ₂ O ₃ , BeO, ATO, ITO, LaCrO ₃ , B ₄ C, ZrC, SiC, TaC, TiB ₂ , ZrB ₂ , CrB ₂ , BN, AlN, HfN, TiN, and the like. These may be used alone or in combination of two or more.

The coating layer 12 may contain 10 to 40% by weight, preferably 15 to 35% by weight, of particles having a thermal conductivity of 10 to 500 W / m · K in the entire coating layer. In this range, there is an advantage that the thermal conductivity is excellent and light leakage improving effect can be obtained and excellent durability is obtained.

In one embodiment, the coating layer 12 may comprise a UV curable resin and particles having a thermal conductivity of 10 to 500 W / mK.

The UV curable resin may be a polyester resin, an acrylic resin, a urethane resin, an amide resin, a silicone resin, an epoxy resin, or the like, but is not limited thereto. These may be used alone or in combination of two or more. It is also possible to use thermosetting resin instead of UV curing resin.

In another embodiment, the coating layer further comprises a UV curable monomer, a UV curable oligomer, a polymerization initiator, a photosensitizer, a plasticizer, a tackifier, a coupling agent, a dispersant, a leveling agent, a polymerization inhibitor, an antioxidant, .

As described above, by forming the coating layer containing particles having a thermal conductivity of 10 to 500 W / m · K on the light incident surface of the polarizing film, the heat generated in the backlight light source lamp is rapidly transferred in the in- The temperature gradient can be relaxed.

It is possible to design a high thermal conductive addition polarizing film corresponding to various panel sizes and backlight light source lamp types by adjusting particle size, particle density and coating thickness of the particles.

The coating layer of the present invention may be 0.1 to 10 mu m, preferably 0.5 to 5 mu m.

 The coating layer has a haze rise of 0.5 or less, preferably 0 to 0.3, and a total light transmittance reduction of 0.3 or less, preferably 0 to 0.2.

It is also preferable that color change, which is one of the indexes of optical characteristics, does not occur. In the specific example, it is preferable that the change amount of the single color a is 0.3 or less and the change amount of the single color b is 0.5 or less.

In embodiments in which the edge portion (edge) and the brightness difference (ΔL) between the center due to the the polarizing film expression 0.06 Cd / m ² or less, preferably from 0.001 to 0.05 Cd / m ^2, more preferably from 0.001 to 0.035 Cd / m < ² >, and most preferably from 0.001 to 0.025 Cd / m < ^{2 &}

? L = [(a + b + d + e) / 4] -c

(Where a, b, d, and e are luminance averages at positions corresponding to 1/16 of the total area from the end portions of the respective sides of the optical member, and c is the average luminance of 1/32 area of the center of the optical member) .

The polarizing film may have an in-plane temperature deviation (maximum in-plane temperature - minimum in-plane temperature) of less than 10 ° C.

Another aspect of the present invention relates to a liquid crystal display device. In an embodiment, the liquid crystal display device includes the polarizing film, and the polarizing film is formed between the liquid crystal panel and the backlight.

In one embodiment, the liquid crystal display device includes a liquid crystal display panel including a first substrate and a second substrate facing each other, and a liquid crystal layer interposed between the first substrate and the second substrate, And a second polarizer disposed between the liquid crystal display panel and the backlight unit. The backlight unit includes a backlight unit for supplying light to the liquid crystal display panel, a first polarizer disposed on a front side of the liquid crystal display panel, and a second polarizer disposed between the liquid crystal display panel and the backlight unit. In the present invention, a polarizing film having the coating layer of the present invention is applied to the second polarizing plate.

4 is one embodiment of the liquid crystal display of the present invention. As shown in the figure, the liquid crystal panel 8 and the polarizing film 100 are laminated via an adhesive layer 9, and the polarizing film includes a protective film 11A, a polarizer 10, a protective film 11B, And a coating layer 12 are sequentially laminated. The coating layer 12 is formed between the protective film 11B and the backlight unit 13 on the side of the protective film 11B formed near the backlight unit.

The shape of the backlight unit 13 is not particularly limited, but may be suitably applied to an edge type backlight. In one embodiment, the backlight unit 13 may be an Edge type backlight unit having optical members such as a light guide plate, a reflection plate, a lens sheet, and a diffusion plate, and having a light source lamp on the upper and lower sides of the panel.

Hereinafter, the configuration and operation of the present invention will be described in more detail with reference to preferred embodiments of the present invention. It is to be understood, however, that the same is by way of illustration and example only and is not to be construed in a limiting sense.

The contents not described here are sufficiently technically inferior to those skilled in the art, and a description thereof will be omitted.

Example  One

A UV curable resin, tripropylene glycol diacrylate (TPGDA) monomer and 2-hydroxy-2-methyl-1-phenylpropanone as a reaction initiator were mixed with alumina (Al ₂ O ₃ ) particles having a size of 20 nm to prepare a coating composition . The prepared coating composition was applied to a polarizing plate with a bar coater and then UV-irradiated to prepare a sample. The prepared samples were laminated to a VA-mode panel to evaluate light leakage.

Example  2 to 7

The procedure of Example 1 was repeated except that the particle type, size and content were changed as shown in Table 1 below.

Comparative Example   One

The procedure of Example 1 was repeated except that no particles were used.

Comparative Example   2

Except that 800 nm aluminum particles were used instead of 20 nm alumina (Al ₂ O ₃ ) particles.

Property evaluation method:

(1) Light leakage: The luminance of the front panel (VA-mode 20 inch) of the display panel was measured at a height of 1 m by using a ProMetric luminance measuring device (ProMetric 1400; Radiant Imaging) after driving the liquid crystal display device. The degree of light leakage was quantified through the brightness of the lowest luminance center and the luminance difference of the edge where the light leakage appeared. The lower the ΔL value, the better the light leakage.

? L = [(a + b + d + e) / 4] -c

(Where a, b, d, and e are luminance averages at positions corresponding to 1/16 of the total area from the end portions of the respective sides of the optical member, and c is the average luminance of 1/32 area of the center of the optical member) .

0 ≤ ΔL <0.06: No light leakage at observation

0.06 ≤ΔL <0.1: No improvement in light leakage

In addition, the degree of light leakage was observed by observing from the front of a 1 m distance from the display panel in the dark room. A visual assessment was conducted according to the following criteria.

Mood Assessment Criteria

 ◎: No light leakage during observation

 ○: Weak light

 Δ: Reduction of light leakage

X: No light leakage improvement

(2) Rise of haze: Measured by HR-100 (manufactured by Murakami Color Research Laboratory).

(3) Reduction of total light transmittance: Ultraviolet ray was measured with a near-infrared spectrophotometer (V-7000).

(4) Adhesiveness: The crosscut method was used. The 11 lines of 11 lines in height and 11 lines were cut with a cutter at intervals of 1 mm, cellophane tape was stuck thereon, and the cells were rubbed with an eraser. After several minutes, the tape was pulled in a right angle direction to evaluate the peeled number.

Particle type Particle thermal conductivity
(w / mK) Average particle diameter
(nm) content
(wt%) Rating light Optical characteristic Adhesiveness
(Crosscut) The luminance? L (Cd / m ² ) Moxie Hayes
(Δ%) Transmittance
T single
(Δ%) Example 1 Alumina 20 20 30 0.048 △ <0.3 &Lt; 0.1 100/100 OK Example 2 Alumina 20 40 30 0.032 ○ <0.3 &Lt; 0.1 100/100 OK Example 3 Zinc oxide 25 40 30 0.038 ○ <0.3 &Lt; 0.1 100/100 OK Example 4 Zinc oxide 25 40 15 0.042 ○ <0.2 &Lt; 0.1 100/100 OK Example 5 Boron nitride 40 to 60 45 30 0.029 ◎ <0.3 <0.2 100/100 OK Example 6 nitrification
aluminum 70 ~ 120 40 30 0.024 ◎ <0.3 &Lt; 0.1 100/100 OK Example 7 Cu 398 5 20 0.025 ◎ <0.3 &Lt; 0.1 100/100 OK Comparative Example 1 - - - 0.070 × &Lt; 0.1 &Lt; 0.1 100/100 OK Comparative Example 2 aluminum 237 800 20 0.030 × 45 3 100/100 OK

As shown in Table 1, the light leakage in the light leakage of the liquid crystal display using the edge type backlight was improved in Examples 1 to 7 in which the contrast coating layer was applied.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. It is therefore to be understood that the embodiments described above are in all respects illustrative and not restrictive.

8: liquid crystal panel 9: adhesive layer
10: Polarizers 11A and 11B: Protective film
12: Coating layer 13: Backlight unit

Claims (14)

A polarizer; And a protective film formed on one surface or both surfaces of the polarizer, wherein the polarizing film comprises particles having a thermal conductivity of 10 to 500 W / m · K, a thickness of 0.1 to 10 μm, and an average particle diameter of 0.1 to 45 nm And a coating layer formed on the polarizing film.

The polarizing film according to claim 1, wherein the coating layer contains particles having a thermal conductivity of 40 to 400 W / mK.
The polarizing film according to claim 1, wherein the coating layer is formed between the protective film and the backlight unit.
The polarizing film according to claim 1, wherein the coating layer has a haze rise of 0.5 or less and a total light transmittance reduction of 0.3 or less.
The polarizing film according to claim 1, wherein the coating layer contains 10 to 40% by weight of particles having a thermal conductivity of 10 to 500 W / m · K in the entire coating layer.
The polarizing film according to claim 5, wherein the particles comprise at least one of a metal, a metal oxide, a metal carbide, a metal boride and a metal nitride.
7. The method of claim 6 wherein the particles are Ag, Bi, Co, Cr, Cu, Fe, In, Ni, Pb, Sn, ZnO, Al ₂ O _3, Bi ₂ O _3, CeO _2, CuO, CoO, Fe ₂ O ₃ , Mn ₃ O ₄ , Ho ₂ O ₃ , SnO ₂ , Y ₂ O ₃ , BeO, ATO, ITO, LaCrO ₃ , Wherein the polarizing film comprises at least one selected from the group consisting of B ₄ C, ZrC, SiC, TaC, TiB ₂ , ZrB ₂ , CrB ₂ , BN, AlN, HfN and TiN.
The polarizing film according to claim 1, wherein the coating layer comprises a UV curable resin and particles having a thermal conductivity of 10 to 500 W / mK.
The polarizing film according to claim 8, wherein the UV curable resin comprises at least one member selected from the group consisting of a polyester resin, an acrylic resin, a urethane resin, an amide resin, a silicone resin and an epoxy resin.
The coating layer according to claim 1, wherein the coating layer comprises a UV curable monomer, a UV curable oligomer, a polymerization initiator, a photosensitizer, a plasticizer, a tackifier, a coupling agent, a dispersant, a leveling agent, a polymerization inhibitor, an antioxidant and a stabilizer Wherein the polarizing film further comprises at least one selected from the group consisting of polypropylene and polypropylene.
The polarizing film according to claim 1, wherein the polarizing film has a luminance difference (? L) of less than 0.06 Cd / m ² between an edge portion and a center portion according to the following formula:

? L = [(a + b + d + e) / 4] -c
(Where a, b, d, and e are luminance averages at positions corresponding to 1/16 of the total area from the end portions of the respective sides of the optical member, and c is the average luminance of 1/32 area of the center of the optical member) .
The polarizing film according to claim 1, wherein the polarizing film has an in-plane temperature deviation (maximum in-plane temperature - minimum in-plane temperature) of less than 10 ° C.
A liquid crystal display device comprising the polarizing film of any one of claims 1 to 12, wherein the polarizing film is formed between a liquid crystal panel and a backlight.
14. The liquid crystal display device according to claim 13, wherein the backlight is an edge type backlight.

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