KR20110097078A - Liquid crystal display device - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly, a polarizer having a water vapor transmission rate at 40 ° C. and 90% RH of 200 g / m 2 · day or less on the viewer side of the polarizer of the upper polarizer and the backlight side of the polarizer of the lower polarizer, respectively. The protective film is provided to suppress the curling and swelling of the polarizer due to moisture in high humidity conditions, and to prevent curling of the polarizing plate, and to improve durability in high temperature and high humidity conditions.

Description

Liquid Crystal Display {LIQUID CRYSTAL DISPLAY DEVICE}

The present invention relates to a liquid crystal display device which can prevent curling of a polarizing plate under high humidity and improve durability at high temperature and high humidity due to the low moisture-permeable polarizer protective film of the polarizing plate positioned at the outermost portion of the liquid crystal display device.

Liquid crystal display devices (LCDs) are used in various applications such as notebooks, mobile phones, liquid crystal TVs, etc., and generally include a liquid crystal cell containing a liquid crystal, a polarizing plate, and an adhesive layer or an adhesive layer for bonding them. do.

In addition, a polarizing plate used in a liquid crystal display device is generally referred to as a polarizer (or 'polarizing film') in which an iodine compound or a dichroic polarizing material is adsorbed on a polyvinyl alcohol (PVA) resin film arranged in a fixed direction. On both sides of the polarizer, a polarizer protective film represented by a triacetyl cellulose (TAC) is laminated through an adhesive, respectively, and one side of the polarizer protective film is bonded to the liquid crystal cell It has a multilayered structure in which the pressure-sensitive adhesive layer is laminated.

Since each constituent film of the polarizing plate is made of a material having a different molecular structure and composition, they have different physical and chemical properties. The polarizer, which is a PVA stretched film, is contracted or expanded in a humid condition, and the constituent films of the polarizing plate are bent, and the protective film and the polarizer are easily separated under high temperature and high humidity, and there is a problem in that bubbles are generated.

In particular, in recent years, the market for slim liquid crystal display devices such as slim large wall-mounted TVs, mobile-type computers, vehicle TVs, displays of vehicle navigation systems, mobile phones, and the like, has been rapidly expanding. Accordingly, in order to thin the entire module of the liquid crystal display device, an ultra thin polarizing plate (UTP), which is thinner and lighter, is required.

As a method for manufacturing an ultra-thin polarizing plate, a method of thinly adjusting the thickness of a polarizer or a polarizer protective film, and a polarizer protective film on one side may be omitted instead of a structure in which protective films are laminated on both sides of the polarizer, and thus, an adhesive layer or a pressure-sensitive adhesive layer. The method of manufacturing a thin polarizing plate by laminating | stacking directly to a polarizer was proposed. However, when using this method, the shrinkage and expansion ratio of the polarizer are further increased, thereby maximizing the problem of curl generation and light leakage. In addition, durability deteriorated much according to environmental conditions.

Korean Laid-Open Patent Publication No. 2007-76318 discloses a polarizing plate arranged in the order of a transparent protective film-water-based adhesive-polarizer-adhesive layer-temporary protective film from the upper side and a liquid crystal display device using the same. This technology manufactures a liquid crystal display device by removing the temporary protective film and then bonding the adhesive layer and the liquid crystal cell. However, since the transparent protective film uses triacetyl cellulose with high moisture permeability, it does not protect the polarizer from moisture, which reduces durability and curls. May occur.

An object of the present invention is to provide a liquid crystal display device that can prevent the curl of the polarizing plate in a humid condition by placing a low-moisture-permeability protective film on the outermost portion of the liquid crystal display device.

Another object of the present invention is to provide a liquid crystal display device capable of improving the durability of the polarizing plate and reducing the thickness of the polarizing plate under high temperature and high humidity conditions using a low moisture permeability protective film.

1. A liquid crystal display device comprising a polarizer protective film having a moisture permeability at 40 ° C. and 90% RH of 200 g / m 2 · day or less on the visual side of the polarizer of the upper polarizer and the backlight side of the polarizer of the lower polarizer, respectively.

2. In the above 1, wherein the pressure-sensitive adhesive layer is formed on at least one other side of the polarizer of the upper polarizing plate and the polarizer of the lower polarizing plate.

3. In the above 2, between the polarizer and the pressure-sensitive adhesive layer of the polarizing plate polyester film, polyolefin film, acetyl cellulose film, polycarbonate film, polyvinyl alcohol film, polyether sulfone film, polyarylate film And a protective film selected from the group consisting of a polyimide film, a polyamideimide film, a polyamide film, and a polyacetate film.

4. In the above 3, wherein the protective film is an optical compensation film liquid crystal display device.

5. The polarizer protective film of any one of the above 1 to 4, wherein the water vapor transmission rate at 40 ° C. and 90% RH is 200 g / m 2 · day or less of cycloolefin polymer (COP), cycloolefin copolymer (COC), polynovo Liquid crystal display device is selected from the group consisting of (PNB), polyethylene terephthalate (PET) and polypropylene (PP).

The liquid crystal display of the present invention can prevent the polarizer from contracting and expanding due to moisture in a humid condition, thereby preventing curling of the polarizer.

The liquid crystal display of the present invention has excellent durability of the polarizing plate even in high temperature and high humidity conditions, so that the liquid crystal display device may be usefully used when transported or used in high temperature and high humidity areas such as the tropics, the sea, and the equator. .

The liquid crystal display of the present invention can be effectively used even when the backlight with a large amount of heat is generated or thinned for better clarity and the backlight distance is reduced.

1 is a vertical sectional view of a conventional liquid crystal display device;
2 is a vertical cross-sectional view of a liquid crystal display according to an embodiment of the present invention;
3 is a vertical cross-sectional view of a liquid crystal display according to another exemplary embodiment of the present invention.

The present invention provides a polarizer protective film having a moisture permeability at 40 ° C. and 90% RH of 200 g / m 2 · day or less on the visible side of the polarizer of the upper polarizing plate and the backlight side of the polarizer of the lower polarizing plate, respectively. The present invention relates to a liquid crystal display device capable of preventing curling of a polarizing plate by suppressing shrinkage and expansion of polarizers, and improving durability at high temperature and high humidity.

Hereinafter, the present invention will be described in more detail.

The liquid crystal display device of the present invention is not particularly limited, and examples thereof include a liquid crystal display device using a TFT (Thin Film Transistor) of an active driving method.

As shown in FIG. 1, a conventional liquid crystal display device is designed such that a triacetyl cellulose-based protective film is provided on only one side of the polarizer and an adhesive layer is provided on the other side. However, since the triacetyl cellulose protective film has a moisture permeability of 500 to 1000 g / ㎡ · day is not excellent in the moisture protection function, the polarizer (polyvinyl alcohol-based) weak to moisture absorbs moisture. Therefore, since the polarizer shrinks and expands due to moisture and changes in size, curling of the polarizing plate itself is severely generated under high humidity and durability is also reduced. In particular, durability fell further in the high temperature and high humidity conditions.

The polarizing plate has hygroscopicity and moisture permeability determined according to a protective film provided at the outermost part, and durability and curling occur according to environmental conditions.

In order to solve this problem, the liquid crystal display of the present invention includes a polarizer protective film having a low moisture permeability on the outermost surface of the upper polarizing plate provided on the upper surface of the liquid crystal cell and the lower polarizing plate provided on the lower surface of the liquid crystal cell. The protective film having a low moisture permeability includes, for example, a protective film having a water vapor transmission rate at 40 ° C. and 90% RH of 200 g / m 2 · day or less, preferably 0.1 to 200 g / m 2 · day, and specific examples include cycloolefin polymer (COP), And a film selected from the group consisting of cycloolefin copolymer (COC), polynorbornene (PNB), polyethylene terephthalate (PET) and polypropylene (PP). If the water vapor transmission rate of the polarizer protective film is more than 200g / ㎡ · day can not protect the polarizer from moisture, durability is lowered and curling may occur.

In addition, an adhesive layer is formed on one or more other surfaces of the polarizer of the upper polarizing plate and the polarizer of the lower polarizing plate to adhere to the liquid crystal cell. Further, when the pressure-sensitive adhesive layer is formed on both the polarizer of the upper polarizing plate and the other side of the polarizer of the lower polarizing plate, a thin film type liquid crystal display device can be made.

Specifically, for example, the structure of the polarizing plate included in the liquid crystal display of the present invention, as shown in FIG. 2, the upper plate polarizing plate is 40 ° C. on the other side of the polarizer having an adhesive layer on one side thereof, for example, on the side of the viewer. And a polarizer protective film having a moisture permeability of 200 g / m 2 · day or less at 90% RH, and a moisture permeability at 40 ° C. and 90% RH on the other side of the polarizer having a pressure-sensitive adhesive layer on the lower polarizing plate, such as a backlight side. A polarizer protective film of less than / m 2 · day is provided.

In addition, as shown in FIG. 3, the upper polarizing plate is a polarizer protective film having a water vapor transmission rate of 200 g / m 2 · day or less on the other side of the polarizer provided with a conventional protective film having an adhesive layer on one side thereof, for example, the side of the viewer. The lower polarizing plate is provided with a polarizer protective film having a water vapor transmission rate of 200 g / m 2 · day or less on the other side of the polarizer, for example, the backlight side, provided with the usual protective film having the pressure-sensitive adhesive layer. In this case, the upper polarizing plate is formed on the side facing the user, and the lower polarizing plate is formed on the backlight, so that the viewer side and the backlight side where the polarizer protective film is positioned mean the outermost angle of the polarizing plate, for example, the outermost angle of the liquid crystal display.

Except for the protective film on the visible side of the polarizer of the upper polarizing plate and the backlight side of the polarizer of the lower polarizing plate, the other polarizer protective film may use a conventional one which does not affect the function of the liquid crystal display, and the range of moisture permeability is particularly It is not limited. For example, in the group consisting of polyester, polyolefin, acetyl cellulose, polycarbonate, polyvinyl alcohol, polyether sulfone, polyarylate, polyimide, polyamideimide, polyamide and polyacetate The film selected, etc. are mentioned, Among these, it is preferable to use the acetate type film which is excellent in the external appearance and planar smoothness of a film, and which can adjust permeability. In addition, a conventional protective film may be subjected to surface treatment in order to increase the adhesive force with the polarizer and the liquid crystal cell.

Polarizers are designed to be equipped with a layer to protect the polarizer from UV light because the directionality of iodine in the polarizer is degraded when exposed to UV light. do. Therefore, the polarizer protective film having the same polarization efficiency as time passes and the moisture permeability at 40 ° C. and 90% RH or less than 200 g / m 2 in order to protect the polarizer from UV light sources such as backlight lamps or sunlight is included with UV absorbers. It is preferable that the composition or the UV absorbing layer is provided on the upper and lower surfaces of the polarizer protective film. In addition, a UV absorber may be added to the adhesive for bonding the polarizer and the polarizer protective film. In particular, if the UV absorbing resistance of the polarizer protective film provided in the outermost of the liquid crystal display device is excellent, the UV absorbing resistance of the conventional protective film present on the opposite side of the polarizer protective film may be small, disposed between the sunlight and the polarizer. It is important to impart UV absorption resistance to the polarizer protective film.

It is preferable that the polarizer protective film whose water vapor transmission rate at 40 degreeC and 90% RH is 200 g / m <2> * days or less is 20-100 micrometers normally.

In addition, the polarizer protective film may be prepared by adding an anti-blocking agent (anti-blocking agent), lubricants, antistatic agents, stabilizers and the like.

The polarizer and the polarizer protective film may be bonded with a common adhesive, and specific examples thereof include organic adhesives, water-based adhesives, ultraviolet curing adhesives, thermosetting adhesives, and the like, and more specifically, polyvinyl alcohol-based and polyurethane-based adhesives. There is this. Among them, an organic adhesive or an aqueous adhesive is preferable in terms of productivity.

In the liquid crystal display of the present invention, an antireflection layer, a low reflection coating layer, a UV absorbing layer, a brightness enhancement layer, an antistatic coating layer, a hard coating layer, and the like may be provided on the upper surface of the polarizer protective film provided on the viewer side of the upper polarizing plate.

The polarizer used in the present invention may be a film in which the stretched polyvinyl alcohol-based film is arranged in a predetermined direction and adsorbed with iodine or dichroic material. Specific examples thereof include boric acid after adsorbing iodine to a polyvinyl alcohol-based film. Polyvinyl alcohol iodine polarizer uniaxially stretched in a bath; Polyvinyl alcohol-dye polarizers uniaxially stretched by diffusing and adsorbing a dichroic dye onto a polyvinyl alcohol-based film; Polyvinyl alcohol-polyvinylene polarizer having a polyvinylene structure by adsorbing and stretching iodine on a polyvinyl alcohol-based film; Polyvinyl alcohol-metal polarizer which adsorb | sucked metals, such as silver, mercury, and iron, to the polyvinyl alcohol-type film; Near-ultraviolet polarizer which treated the polyvinyl alcohol-type film with the boric acid solution containing potassium iodide and sodium thioric acid; Polarizers having dichroic dyes on the surface and / or inside of a polyvinyl alcohol-based film made of modified polyvinyl alcohol containing a cationic group in a molecule, but are not limited thereto, and those known in the art may be used. .

Moreover, the manufacturing method of a polyvinyl alcohol-type polarizer is not specifically limited, For example, the method of adsorbing iodine ion after extending | stretching a polyvinyl alcohol-type film; Dyeing a polyvinyl alcohol-based film with a dichroic dye and then stretching the film; A method of dyeing with a dichroic dye after stretching the polyvinyl alcohol-based film; A method of stretching the dichroic dye after printing the polyvinyl alcohol-based film; And a method of printing a dichroic dye after stretching the polyvinyl alcohol-based film.

In addition, the liquid crystal cell used in the present invention is not particularly limited, and for example, a liquid crystal cell such as an IPS mode, a TN mode, or a VA mode can be used.

In the liquid crystal display of the present invention, a protective film positioned between the upper polarizing plate and the lower polarizing plate and the liquid crystal cell may be an optical compensation film or may further include an optical compensation film.

Hereinafter, the present invention will be described in more detail with reference to Examples. It is obvious that the examples are not intended to limit the scope of the present invention but only to show an example belonging to the present invention. It is natural that modifications and variations of the embodiments fall within the scope of the present invention without departing from the basic technical spirit of the present invention.

[Example]

Example 1

The upper plate polarizing plate was provided with a cycloolefin polymer film (ZEON, ZF14) having a water vapor transmission rate of 6.3 g / m 2 · day at 40 ° C. and 90% RH on one side of the polarizer, and a direct pressure-sensitive adhesive layer on the other side. The lower polarizing plate was provided with a cycloolefin polymer film (ZEON, ZF14) having a water vapor transmission rate of 6.3 g / m 2 · day at 40 ° C. and 90% RH on one side, and a direct pressure-sensitive adhesive layer on the other side. The pressure-sensitive adhesive layer of the upper polarizing plate was bonded to the upper surface of the liquid crystal cell, and the pressure-sensitive adhesive layer of the lower polarizing plate was bonded to the lower surface of the liquid crystal cell to manufacture a thin film type liquid crystal display device.

Example 2

In the same manner as in Example 1, 40 ℃ and 90% in place of the cycloolefin polymer film (ZEON, ZF14) having a moisture permeability of 6.3g / ㎡ · day at 40 ℃ and 90% RH on the upper and lower polarizing plates A thin film type liquid crystal display device was manufactured using a cycloolefin polymer film (OXIS-40, OKURA Co., Ltd.) having a water vapor transmission rate of 74.6 g / m 2 · day.

Comparative Example 1

In the same manner as in Example 1, 40 ℃ and 90% in place of the cycloolefin polymer film (ZEON, ZF14) having a moisture permeability of 6.3g / ㎡ · day at 40 ℃ and 90% RH on the upper and lower polarizing plates A liquid crystal display device was manufactured using a triacetyl cellulose film (FUJI, TD-80UL) having a water vapor transmission rate of 602 g / m 2 · day.

Comparative Example 2

In the same manner as in Example 1, 40 ℃ and 90% in place of the cycloolefin polymer film (ZEON, ZF14) having a moisture permeability of 6.3g / ㎡ · day at 40 ℃ and 90% RH on the upper and lower polarizing plates A liquid crystal display device was manufactured using a triacetyl cellulose film (FUJI, TD-40UL) having a water vapor transmission rate of 1015 g / m 2 · day.

Comparative Example 3

The same method as in Example 1, except that the lower polarizing plate at 40 ℃ and 90% RH moisture permeability at 40 ℃ and 90% RH instead of cycloolefin polymer film (ZEON, ZF14) of 6.3g / ㎡ · day The liquid crystal display device was manufactured using the triacetyl cellulose film (FUJI Co., TD-40UL) whose water vapor transmission rate is 1015g / m <2> * day.

Comparative Example 4

The same method as in Example 1, except that the upper polarizing plate at 40 ℃ and 90% RH moisture permeability at 40 ℃ and 90% RH instead of cycloolefin polymer film (ZEON, ZF14) of 6.3 g / ㎡ · day A cycloolefin polymer film having a moisture permeability of 74.6 g / m 2 · day (OKURA, OXIS-40) was used, and a cycloolefin polymer film having a moisture permeability of 6.3 g / m 2 · day at 40 ° C. and 90% RH in a lower polarizing plate (ZEON A liquid crystal display was manufactured using a triacetyl cellulose film (FUJI, TD-40UL) having a water vapor transmission rate of 1015 g / m 2 · day at 40 ° C. and 90% RH instead of ZF14).

Comparative Example 5

The same method as in Example 1, except that the upper polarizing plate at 40 ℃ and 90% RH moisture permeability at 40 ℃ and 90% RH instead of cycloolefin polymer film (ZEON, ZF14) of 6.3 g / ㎡ · day A cycloolefin polymer film having a moisture permeability of 74.6 g / m 2 · day (OKURA, OXIS-40) was used, and a cycloolefin polymer film having a moisture permeability of 6.3 g / m 2 · day at 40 ° C. and 90% RH in a lower polarizing plate (ZEON A liquid crystal display device was manufactured using a triacetylcellulose film (FUJI, TD-80UL) having a water vapor transmission rate of 602 g / m 2 · day at 40 ° C. and 90% RH instead of ZF14).

Test Example

One. Measurement of durability

The polarizing plates prepared in Examples and Comparative Examples were cut into 150 mm × 150 mm and then bonded to Corning Eagle XG glass to prepare specimens. The prepared specimens were treated in an autoclave for 5 minutes at 50 ° C. for 20 minutes and then left in 60 ° C. and 90% RH oven for 300 hours. Peeling phenomenon such as lifting and peeling of the specimen left undisturbed, and whether bubbles were generated were visually confirmed and evaluated based on the following criteria.

(Double-circle): No peeling phenomenon and bubble generation (very good)

(Circle): Peeling phenomenon and generation | occurrence | production of a bubble are hardly (good)

△: peeling phenomenon and bubbles are somewhat generated (usually)

×: peeling phenomenon and bubbles are generated (defect)

2. Measurement of curl

The polarizing plates prepared in Examples and Comparative Examples were cut into 150 mm x 150 mm and then left on a horizontal and flat sample bed in a constant temperature and humidity chamber at 25 ° C. and 65% RH for 3 hours. Since the four edges were heard from the sample stage when curling occurred in the film after standing, the lifted height was measured by the scale, and the average value of the four corner values expressed in mm was evaluated by the curl value.

Since the permissible curl of a polarizing plate is 20 mm or less, the case where it is 20 mm or less is OK and the case where it is more than 20 mm was described as NG.

division durability curl Top polarizer Bottom plate polarizer Top polarizer Bottom plate polarizer Example 1 ◎ ◎ OK OK Example 2 ○ ○ OK OK Comparative Example 1 △ △ NG NG Comparative Example 2 × × NG NG Comparative Example 3 ◎ × OK NG Comparative Example 4 △ × OK NG Comparative Example 5 △ △ OK NG

As shown in the above table, the liquid crystal display device of Examples 1 to 2 equipped with a polarizer protective film having a water vapor transmission rate of 200 g / m 2 · day or less in the outermost part of the polarizing plate according to the present invention has high temperature and high humidity conditions compared to Comparative Examples 1 to 5. In the durability of the polarizing plate was improved, it was confirmed that the curl of the polarizing plate is suppressed in the humid conditions.

Claims (5)

A liquid crystal display device comprising a polarizer protective film having a moisture permeability at 40 ° C. and 90% RH of 200 g / m 2 · day or less on the visual side of the polarizer of the upper polarizing plate and the backlight side of the polarizer of the lower polarizing plate, respectively.
The liquid crystal display device according to claim 1, wherein an adhesive layer is formed on at least one other surface of the polarizer of the upper polarizing plate and the polarizer of the lower polarizing plate.
3. The polyester film, the polyolefin film, the acetyl cellulose film, the polycarbonate film, the polyvinyl alcohol film, the polyether sulfone film, the polyarylate film, and the poly A liquid crystal display device provided with a protective film selected from the group consisting of a mid film, a polyamideimide film, a polyamide film, and a polyacetate film.
The liquid crystal display device of claim 3, wherein the protective film is an optical compensation film.
The polarizer protective film according to any one of claims 1 to 4, wherein the polarizer protective film having a water vapor transmission rate at 40 ° C. and 90% RH is 200 g / m 2 · day or less is cycloolefin polymer (COP), cycloolefin copolymer (COC), polynorbornene. (PNB), polyethylene terephthalate (PET) and polypropylene (PP).

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