KR102094761B1 - Liquid Crystal Display Device - Google Patents

Abstract

The present invention relates to a liquid crystal display device, and more specifically, by controlling the amount of warp of the lower polarizing plate compared to the amount of warping of the upper polarizing plate, thereby adjusting the warping balance as a whole, reducing light leakage phenomenon even after the heat resistance test, which is one of the reliability tests of the conventional panel, high quality It relates to a liquid crystal display device that can implement the screen of the.

Description

Liquid crystal display device

The present invention relates to a liquid crystal display device with reduced light leakage.

A liquid crystal display device (LCD) is one of image display devices, and has the advantage of realizing lighter size and lower power consumption than a cathode-ray tube (CRT), which is a typical image display device. .

Unlike the CRT, the liquid crystal display device does not emit light itself, and thus requires a light source in addition to the liquid crystal panel. A fluorescent lamp is mainly used as a light source for such a liquid crystal display device, and an upper polarizing plate and a lower polarizing plate are attached to both sides of the liquid crystal panel of the liquid crystal display. These upper and lower polarizers block or pass light from the lamp.

More specifically, as shown in FIG. 1, the liquid crystal display device 1 includes a light source 11, a reflector 12, a light guide plate 13 and a backlight unit 10 equipped with a diffusion plate 14, A liquid crystal panel 30, an upper polarizing plate 20 and a lower polarizing plate 40 are stacked on the upper and lower portions thereof.

The upper and lower polarizing plates 20 and 40 have a structure in which a pressure-sensitive adhesive layer for bonding with a liquid crystal panel is formed on one surface of a laminate in which a polarizer is positioned between a pair of transparent protective films. At this time, as a polarizer, a polyvinyl alcohol (PVA) film drawn in a certain direction and dyed with a dichroic dye is used.

At this time, the upper polarizing plate 20 includes a PVA film stretched in a short side direction (90 degrees) as a polarizer, and the lower polarizing plate 40 includes a PVA film stretched in a long side direction (0 degrees). However, the stretched PVA film contracts in the direction of stretching and contraction according to a change in temperature or humidity, thereby causing a panel warpage phenomenon in which the liquid crystal panel is also bent.

As a result, the liquid crystal panel 30 is convexly curved in the direction of the backlight unit 10 due to the difference in shrinkage stress of the polarizing plates 20 and 40 attached to both sides of the liquid crystal panel 30, and thereby the direction of the liquid crystal panel 30 Convexly.

The panel warpage occurs more under heat or moist heat conditions, and as a result, light leakage (ie, light leakage), static electricity, and the like occur, and stains occur to cause defects in the liquid crystal panel. In particular, panel warpage occurs more seriously in the lower polarizer.

Accordingly, various methods have been proposed to prevent panel warpage.

As an example, there was a method of limiting the material of the protective film in contact with the polarizer, and in this regard, Korean Patent Publication No. 2004-0016382 attaches a protective film having different absorption expansion coefficients with respect to the absorption axis direction of the polarizer, thereby A method for reducing the occurrence of warpage was proposed.

In addition, a method of controlling the pressure-sensitive adhesive has been proposed. For example, Republic of Korea Patent Publication No. 2006-0020037 discloses a method of preventing warpage to control the difference in thermal expansion coefficient of the adhesive for the first and second polarizing plates of the liquid crystal panel, and No. 2007-0035749 is the upper and lower parts of the liquid crystal panel. A method of differently controlling the adhesive composition of the polarizing plate was proposed, and in 2006-0060264, a method of adjusting the difference in the adhesive force between the upper and lower polarizing plates was suggested according to the bending direction of the polarizing plate.

In addition, the Republic of Korea Patent Publication No. 2011-0037001 mentions that it is possible to improve light leakage on the side by disposing a λ / 4 phase difference plate having a limited refractive index in the thickness direction on the upper and lower polarizing plates.

There has been an effort to improve the light leakage phenomenon through structural changes along with the above-described material changes.

Republic of Korea Patent Publication No. 2012-0132961 proposed to improve the light leakage phenomenon by maintaining the warp balance of the liquid crystal panel by making the lower polarizing plate thicker than the thickness of the upper polarizing plate. It is disclosed that the light leakage phenomenon can be improved by maintaining the warpage balance of the liquid crystal panel by making the thickness thinner than the upper polarizing plate.

However, despite such various efforts, the light leakage phenomenon in the liquid crystal display device has not been solved satisfactorily.

In particular, the light leakage phenomenon is exacerbated by various factors as well as the shrinkage of the polarizer, the panel warpage mentioned in the above patents.

That is, in the case of a multi-layer structure such as a polarizing plate, an adhesive or an adhesive is used for bonding each film. In this case, when the adhesive force between the films is weak, the adhesive force or the adhesive force becomes weak, and peeling between films occurs. Such peeling occurs seriously in the protective film and the adhesive layer, and as a result, the panel not only wheels, but also light leakage occurs.

Accordingly, a method of changing the composition of the pressure-sensitive adhesive or the adhesive has been implemented to increase the adhesion between the films, and in particular, a method using a UV adhesive is generally used. Although the adhesion improvement effect between films could be secured to some extent by the use of the UV adhesive, panel warpage and light leakage still occurred due to peeling in the heat resistance test, which is one of the reliability tests of the polarizing plate, even with this.

Republic of Korea Patent Publication No. 2006-0020037 Republic of Korea Patent Publication No. 2007-0035749 Republic of Korea Patent Publication No. 2006-0060264 Republic of Korea Patent Publication No. 2011-0037001 Republic of Korea Patent Publication No. 2012-0132961 Republic of Korea Patent Publication No. 2013-0036904

Accordingly, the present applicant has studied variously to reduce the light leakage phenomenon, and consequently focused on the concept of reducing the peeling between films after the heat resistance test and the concept that the light leakage phenomenon can be sufficiently reduced even after the heat resistance test if the panel bending balance is simultaneously adjusted. In order to increase the adhesion between the films, an easy-to-adhesive layer is introduced into the polarizing plate, but a liquid crystal display device in which the introduction position of the easy-to-adhesive layer is controlled so as to adjust the warp balance of the upper and lower polarizing plates by increasing the amount of warping of the lower polarizing plate. The present invention was completed by manufacturing.

Accordingly, an object of the present invention is to provide a liquid crystal display device having a reduced light leakage phenomenon even after a heat resistance test.

In order to achieve the above object, the present invention is a liquid crystal panel positioned between the upper and lower polarizing tubes sequentially stacked with an outer film, an adhesive, a polarizer, an adhesive, a protective film, and an adhesive layer, and upper and lower polarizing plates through the adhesive layer. It provides a liquid crystal display device having a.

At this time, the upper polarizing plate is characterized in that between the polarizer and the protective film, the lower polarizing plate is disposed between the pressure-sensitive adhesive layer and the protective film.

In addition, the easy-to-adhesive layer comprises at least one binder resin selected from the group consisting of polyester-based resin, polyvinyl alcohol-based resin, polyurethane-based resin, polyimide-based resin, polyamide-based resin, acrylic-based resin and combinations thereof. It is characterized by including.

At this time, the adhesive layer is characterized in that the thickness is 2.0 to 500nm.

In addition, in the liquid crystal display, the outer film includes at least one protective film and an additional functional layer.

In addition, the outer film, the polarizer, and the protective film of the upper and lower polarizing plates are characterized by being bonded with a photo-curable adhesive.

At this time, the photo-curable adhesive is characterized in that it has a thickness of 5㎛ or less.

The present invention can control the amount of warping of the lower polarizing plate compared to the amount of warping of the upper polarizing plate of the liquid crystal display device, thereby controlling the overall warping balance, thereby reducing the light leakage phenomenon even after the heat resistance test, which is one of the reliability tests of the conventional panel, to realize a high-quality screen.

1 is a schematic configuration diagram of a liquid crystal display device.
2 is a perspective view showing a liquid crystal panel and a polarizing plate according to a first embodiment of the present invention.
3 is a view showing a bending state of the liquid crystal panel and the polarizing plates according to the first embodiment of the present invention.
4 is a perspective view showing a liquid crystal panel and a polarizing plate according to a second embodiment of the present invention.
5 is a view showing a bending state of the liquid crystal panel and the polarizing plates according to the second embodiment of the present invention.
6A is a schematic diagram showing a case where the difference in the amount of bending deformation of the upper and lower polarizing plates is large, and (B) is a schematic diagram showing a small case.
7 is a cross-sectional view showing a liquid crystal panel and a polarizing plate according to the present invention.
8 is a view showing an image of the bending state of the polarizing plates of Example 1 and Comparative Examples 1 to 5.
9 is a photograph showing the light leakage phenomenon of the liquid crystal display device of Example 1 and Comparative Examples 1 to 5.

The present invention proposes a liquid crystal display device in which light leakage is reduced in a liquid crystal display device composed of an upper and lower polarizing plate and a liquid crystal panel including an adhesive layer.

In the case of a liquid crystal display device having upper and lower polarizing plates, the amount of warping of the upper polarizing plate in which the stretching direction of the polarizer is located at the longer side is increased than the lower polarizing plate in which the stretching direction of the polarizer is located at the short side. This occurs more severely under heat-resistant reliability conditions. Thus, as a component of the lower polarizing plate, the adhesive layer located between the polarizer and the protective film has a lower adhesive force than the adhesive film, and the adhesive layer is disposed between the adhesive layer and the adhesive force to increase the shrinkage of the polarizer in the heat-resistant state, which greatly affects the amount of warping of the polarizing plate. Eventually, the amount of warping of the lower polarizing plate is increased, thereby balancing the warping of the upper and lower polarizing plates. In addition, the upper polarizing plate arranges an adhesive layer between the polarizer and the protective film, and minimizes the warpage of the polarizing plate by moisture by using a photocurable adhesive rather than a water-based adhesive for the adhesion between the polarizer and the protective film.

Hereinafter, the present invention will be described in more detail with reference to the drawings.

[Example 1]

2 is a perspective view showing a liquid crystal panel and a polarizing plate according to a first embodiment of the present invention, and FIG. 3 is a view showing a bending state of the liquid crystal panel and a polarizing plate according to the first embodiment of the present invention.

Referring to FIG. 2, the liquid crystal display device is usually disposed with the liquid crystal panel 30a as the center, and the upper polarizing plate 20a and the lower polarizing plate 40a.

Specifically, the absorption axis of the upper polarizing plate 20a is 80 to 100 degrees, and the absorption axis of the lower polarizing plate 40a is -10 to 10 degrees, and they are arranged such that the absorption axes of each other form 90 degrees. The absorption axis of the upper polarizing plate 20b in FIG. 2 is 0 degrees, and the absorption axis of the lower polarizing plate 40b is 90 degrees.

Referring to FIG. 3, when the absorption axis of the upper polarizing plate 20a is 0 degrees, and the absorption axis of the lower polarizing plate 40a is 90 degrees, the upper polarizing plate 20a undergoes left and right contraction, resulting in bending in the ∪ type, The lower polarizing plate 20a contracts up and down, and warping of the upper polarizing plate 20a and the lower polarizing plate 40a occurs.

[Second implementation example]

The same applies when the absorption axes of the upper and lower polarizing plates are different in relation to the bending phenomenon.

4 is a perspective view showing a liquid crystal panel and a polarizing plate according to a second embodiment of the present invention, and FIG. 5 is a view showing a bending state of the liquid crystal panel and a polarizing plate according to the second embodiment of the present invention.

Referring to FIG. 4, in the liquid crystal display device according to the second embodiment, the upper polarizing plate 20b and the lower polarizing plate 40b are disposed with the liquid crystal panel 30b as the center.

Preferably, the absorption axis of the upper polarizing plate 20a is -10 to 10 degrees, the absorption axis of the lower polarizing plate 40a is 80 to 100 degrees, and they are arranged such that the absorption axis forms 90 degrees. The absorption axis of the upper polarizing plate 20b in FIG. 4 is 90 degrees, and the absorption axis of the lower polarizing plate 40b is 0 degrees.

Referring to FIG. 5, the upper polarizing plate 20b is vertically contracted to cause bending in an n type, and the lower polarizing plate 40b is contracted to the left and right, resulting in bending of the upper polarizing plate 20a and the lower polarizing plate 40b. do.

The bendings presented in FIGS. 3 and 5 occur more seriously in the upper polarizing plates 20a and 20b, resulting in light leakage. Accordingly, in the present invention, the bending balance of the upper and lower polarizing plates 20a and 40a is adjusted by matching the bending of the lower polarizing plates 40a and 40b to the degree of bending of the upper polarizing plates 20a and 20b.

6 (A) is a schematic diagram showing a case where the difference in the amount of bending deformation of the upper and lower polarizing plates is large, and (B) is a schematic diagram showing a small case. Referring to FIGS. 6A and 6B, it can be seen that the smaller the difference in the amount of bending deformation of the upper and lower polarizing plates, the smaller the amount of bending of the entire liquid crystal display.

Preferably, in the liquid crystal display device according to the present invention, the amount of deflection of the upper polarizing plate and the lower polarizing plate has an absolute value of 1.0 or less.

Panel warpage is the height of panel warpage with a 3D measuring machine (equipment name: VMR-6555, company name: Nikon) after leaving the glass substrate at 80 ° C for 250 hours and then leaving for 23 hours under conditions of 50% relative humidity. The difference was measured.

The panel warpage is expressed as + warp for the ∪ type and-warpage for the ∩ type, which means that the lower the measured absolute value, the less the panel warpage, and preferably has a value of 0.9 mm or less. Under these conditions, light leakage of the liquid crystal display device does not occur.

The bending control of the upper and lower polarizing plates of the above bar is influenced by the arrangement and material of components constituting each polarizing plate.

The upper and lower polarizing plates according to the present invention have a structure in which an outer film, a polarizer, a protective film and an adhesive layer are sequentially stacked, wherein the outer film, the polarizer and the protective film are bonded with an adhesive layer located between them.

Preferably, in the present invention, it is characterized in that an adhesive easy layer (a primer layer, an anchor layer, or an anchor coating layer) is formed to increase the adhesion of each layer, but the positions of the upper and lower polarizing plates are differently arranged. That is, the upper polarizing plate is disposed between the polarizer and the protective film, and the lower polarizing plate is disposed between the pressure-sensitive adhesive layer and the protective film.

The above configuration will be described in more detail with reference to the drawings.

7 is a cross-sectional view of a liquid crystal display device according to an exemplary embodiment of the present invention.

Referring to FIG. 7, the liquid crystal display device includes a liquid crystal panel 30 and an upper polarizing plate 20 and a lower polarizing plate 40 located at upper and lower portions thereof.

Specifically, the upper polarizing plate 20 is the first outer film 21, the first adhesive layer 22, the first polarizer 23, the second adhesive layer 24, the first adhesive layer 25 from the top , Has a structure laminated in the order of the first protective film 26 and the first adhesive layer 27.

In addition, the lower polarizing plate 40 is the second outer film 41, the third adhesive layer 42, the second polarizer 43, the fourth adhesive layer 44, the second protective film 46, the first from the bottom It has a stacked structure in the order of the two-adhesive layer 45 and the second adhesive layer 47.

At this time, the first adhesive layer 27 and the second adhesive layer 47 are bonded to the liquid crystal panel 30.

In FIG. 7, the first and second adhesive layers 25 and 45 disposed on the upper polarizing plate 20 and the lower polarizing plate 40 are used to increase adhesion between the layers in contact therewith, in particular, the lower polarizing plate 40. The second adhesive layer 45 is disposed between the second adhesive layer 47 and the second protective film 46 to further increase the adhesion between them, thereby controlling the amount of warpage of the lower polarizing plate 40. .

Looking at a preferred experimental example of the present invention, depending on the arrangement of the second adhesive layer 45 of the lower polarizing plate 40, there is a difference in the amount of bending of the lower polarizing plate 40, particularly the second polarizer 43 and the second When the second adhesive layer 45 is positioned between the second adhesive layer 47 and the second protective film 46 than when it is positioned between the protective films 46, the amount of warping of the lower polarizing plate 40 is increased. , It was possible to adjust the warpage balance of the entire polarizing plate.

These results showed similar results in the upper polarizer. The first adhesive layer 25 in the upper polarizing plate 20 of the present invention is located between the first polarizer 23 and the first protective film 25, wherein the first adhesive layer 25 is lower When positioned between the first protective film 26 and the first adhesive layer 27 as in the polarizing plate 40, the amount of bending of the upper polarizing plate 20 becomes larger, and the amount of bending of the lower polarizing plate 40 to compensate for it It is not easy to control.

The components of the liquid crystal display according to the first and second embodiments of the present invention will be described as follows.

Polarizer

The first and second polarizers 23 and 43 of the upper and lower polarizing plates 20 and 40 are films comprising a polyvinyl alcohol-based resin in which a dichroic dye is adsorbed and oriented.

Specifically, the polyvinyl alcohol-based resin is a saponified polyvinyl acetate-based resin.

The saponification degree of the polyvinyl alcohol-based resin is 85 mol% or more, preferably 90 mol% or more, and more preferably 99 to 100 mol%. In addition to polyvinyl acetate, which is a homopolymer of vinyl acetate, polyvinyl acetate-based resins include copolymers of vinyl acetate and other monomers copolymerizable therewith. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and unsaturated amines. The degree of polymerization of the polyvinyl alcohol-based resin is usually about 1,000 to 10,000, preferably about 1,500 to 5,000.

These polyvinyl alcohol-based resins may be modified, for example, polyvinyl formal modified with aldehydes, polyvinyl acetal, polyvinyl butyral, and the like can be used. Usually, an unstretched film of a polyvinyl alcohol-based resin having a thickness of 20 to 100 µm, preferably 30 to 80 µm, is used as the disk of the polarizing film.

At this time, the first and second polarizers 23 and 43 are usually a process of uniaxially stretching a polyvinyl alcohol-based resin film, a process of dyeing the stretched film with a dichroic dye to adsorb the dye, and a film of adsorbing the dye. It can be manufactured through a process of treating with a boric acid aqueous solution, and a process of washing with water. In this case, as the dichroic dye, iodine or an organic dye of dichroism may be used.

Protection film

The first and second protective films 26 and 46 of the upper and lower polarizing plates 20 and 40 are films for protecting the polarizers 23 and 43, respectively.

The first and second protective films 26 and 46 are not particularly limited in the present invention, and any of the transparent materials known in the art can be used. Typically, as the first and second protective films 26 and 46, for example, films containing acetyl cellulose-based resins such as triacetyl cellulose or diacetyl cellulose, polyethylene terephthalate, polyethylene naphthalate, and polybutylene And films containing a polyester resin such as terephthalate, films containing a polycarbonate resin, and films containing a cycloolefin resin having a cyclic olefin such as norbornene as a major monomer. As a commercially available thermoplastic cycloolefin resin, for example, Topas sold by Ticona, Germany, Aton sold by JSR Co., Ltd., and Zeono sold by Nihon Zeon Co., Ltd. There are Anazeonex and Apel (all trade names) sold by Mitsui Chemicals. When a film formed from such a cycloolefin-based resin is used as a protective film, a known method such as a solvent casting method or a melt extrusion method is appropriately used for the film formation. Cycloolefin-based resin films formed on the market are also commercially available, for example, Essina or SCA40 sold by Sekisui Chemical Co., Ltd.

The thickness of the first and second protective films 26 and 46 is preferably thin, but if too thin, the strength decreases and workability deteriorates. On the other hand, if the thickness is too thick, transparency decreases or the curing time required after lamination increases. Problems arise. Therefore, a suitable thickness of the protective film is, for example, about 5 to 200 μm, preferably 10 to 150 μm, more preferably 10 to 100 μm.

At this time, in order to improve the adhesion between the first and second protective films 26 and 46, the second and fourth adhesive layers 24 and 44 or the first and second polarizers 23 and 43, the polarizing film And / or surface treatment such as corona treatment, flame treatment, plasma treatment, ultraviolet irradiation, primer coating treatment, and saponification treatment may be performed on the protective film.

In addition, the first and second protective films 26 and 46 have anti-glare treatment, anti-reflection treatment, hard coating treatment, anti-static treatment, retardation treatment, antifouling treatment, surface treatment, respectively, or two or more. It can be carried out in combination. In addition, the protective film and / or the protective film surface protective layer may have an ultraviolet absorber such as a benzophenone-based compound or a benzotriazole-based compound, or a plasticizer such as a phenylphosphate-based compound or a phthalic acid ester compound. At this time, the first and second protective films 26 and 46 may be bonded to one side of the first and second polarizers 23 and 43, or may be bonded to both sides.

In a preferred embodiment of the present invention, a phase difference compensation transparent acrylic resin film was used as a protective film.

Although the acrylic resin is not particularly limited, it is generally a polymer having a methacrylic acid ester as a main monomer, and it is preferably a copolymer in which a small amount of other comonomer components are copolymerized. The methacrylic acid ester which is the main component of the acrylic resin is usually an alkyl methacrylate, and methyl methacrylate is particularly preferably used. Moreover, as a comonomer component, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethyl-hexyl acrylate, etc. are generally used. In addition, an aromatic vinyl compound such as styrene or a vinyl cyan compound such as acrylonitrile may be used as a comonomer component.

Outside film

The first and second outer films 21 and 41 are layers for protecting the polarizer or the polarizing plate, and include at least one protective film, and further include a functional layer.

The functional layer that can be used with the protective film is in the group consisting of an adhesive layer, an adhesive layer, a hard coating layer, an anti-reflection layer, an anti-adhesion layer, a diffusion prevention layer, an anti-glare layer, a phase difference compensation layer, a viewing angle compensation layer, a luminance enhancement layer, and combinations thereof. It may be one or more selected.

Such a functional layer may be used by forming a layer through processing or forming a film. At this time, the method of forming a layer or the production of a film is not limited to the present invention and follows a known method. In the case of a film, a commercially available product may be purchased and used. However, the composition and thickness of each layer is not particularly limited in the present invention, and may be any film having a composition and thickness range commonly used in the art.

In the embodiment of the present invention, an anti-glare treated acrylate film was used.

Adhesive layer

The first to fourth adhesive layers 22, 24, 42, and 44 are the first and second protective films 26, 46 or the outer films 21, 41 and the first and second polarizers 23, 43. Used for bonding.

Materials of the first to fourth adhesive layers 22, 24, 42, and 44 are usually isocyanate adhesives, polyvinyl alcohol adhesives, gelatin adhesives, vinyl polymer latex adhesives, water-soluble polyester adhesives, and hydrophilic groups A water-based adhesive such as an urethane-based adhesive having is used. However, in the case of the water-based adhesive, the moisture in the adhesive directly contacts and affects the polarizer even after drying due to moisture present in the adhesive, which may cause warping of the polarizer.

Accordingly, in the present invention, the first to fourth adhesive layers 22, 24, 42, and 44 use a photocurable adhesive rather than a water-based adhesive.

The photocurable adhesive that can be used is not particularly limited in the present invention, and any photocurable adhesive known in the art can be used. Representatively, adhesive compositions as described in Korean Patent Publication Nos. 2010-0100695, 2010-0014583, and 2011-0112217 No. 2011-0000525 may be used.

In one example, the photocurable adhesive composition constituting the first and second adhesive layers may have (A) 20 to 60% by weight of an epoxy compound having two or more epoxy groups and one or more aromatic rings in the molecule, and (B) an ester skeleton. Di (meth) acrylate of diols having 5 to 10 carbon atoms (except for ether compounds), preferably 5 to 45% by weight, and (C) 0.5 to 10% by weight of a photocationic polymerization initiator.

In the photocurable adhesive, the epoxy compound serving as the component (A) has at least two epoxy groups in the molecule and at least one aromatic ring, and various known curable epoxy compounds can be used.

Examples of the component (A) include bisphenol-type epoxy resins such as diglycidyl ether of bisphenol A, diglycidyl ether of bisphenol F, and diglycidyl ether of brominated bisphenol A; Novolac-type epoxy resins such as phenol novolac-type epoxy resins and cresol novolac-type epoxy resins; Other biphenyl-type epoxy resins, hydroquinone glycidyl ether, resorcin diglycidyl ether, terephthalic acid diglycidyl ester, phthalic acid diglycidyl ester, terminal carboxylic acid polybutadiene and bisphenol A type epoxy resin addition reactants, etc. Can be lifted.

In the photocurable adhesive of the present invention, the di (meth) acrylate serving as the component (B) is (B) a diol having 5 to 10 carbon atoms which may have an ester skeleton (except for ether compounds). Meta) acrylate.

When the number of (meth) acryloyl groups in the molecule is 3 or more as the component (B), adhesion to the polarizer is liable to be poor. In addition, when the number of (meth) acryloyl groups in the molecule is 1, the residual monomer may remain when the amount of ultraviolet irradiation is small, resulting in poor adhesion and durability. Moreover, even if it is a diol which has 5-10 carbon atoms, what is an ether compound becomes that adhesiveness to a polarizer is insufficient.

By using the component (B), it is excellent in adhesiveness and durability even when bonding with a polarizer having a high dryness while lowering the viscosity of the composition.

(B) As specific examples of the di (di) methacrylate of diol having 5 to 10 carbon atoms in the component, neopentyl glycol di (meth) acrylate, 1,6-hexanedioldi (meth) acrylate, 3-methyl -1,5-pentanediol di (meth) acrylate, 2-butyl-2-ethyl-1,3-propanediol di (meth) acrylate and 1,9-nonanediol di (meth) acrylate. You can.

The component (B) may have an ester skeleton, and specific examples thereof include esterification reaction products of neopentyl glycol, hydroxypivalic acid, and (meth) acrylic acid.

The photocurable adhesive of the present invention contains the above-mentioned epoxy compound (A) as a curing component and, if necessary, a later oxetane compound, and since they are all cured by cationic polymerization, a photocationic polymerization initiator is incorporated as the component (C). . This photocationic polymerization initiator generates cationic species or Lewis acids by irradiation with active energy rays such as visible light, ultraviolet light, X-rays, and electron beams, and initiates a polymerization reaction of an epoxy group or an oxetanyl group.

By blending a photocationic polymerization initiator as the component (C), curing at room temperature becomes possible, and the need to take into account the heat resistance of the polarizer or deformation due to expansion or contraction is reduced, and the protective film can be favorably adhered. In addition, since the photocationic polymerization initiator acts catalytically by irradiation of active energy rays, it is excellent in storage stability and workability even when mixed with an epoxy compound (A) and an oxetane compound (B). Examples of the compound that generates cationic species or Lewis acids by irradiation with active energy rays include, for example, aromatic diazonium salts, onium salts such as aromatic iodonium salts and aromatic sulfonium salts, and iron-allene complexes.

The photocurable adhesive may contain an oxetane compound, a photoradical polymerization initiator, and a leveling agent. In addition to these, ion trapping agents, antioxidants, light stabilizers, chain transfer agents, tackifiers, thermoplastic resins, metal oxide fine particles, antifoaming agents, pigments, organic solvents, etc. may be blended as long as the effects of the present invention are not impaired.

The first to fourth adhesive layers 22, 24, 42, and 44 made of such a photocurable adhesive are preferably formed to have a thickness of 5 µm or less in consideration of adhesive performance.

Adhesive layer

The first and second easy-to-adhesive layers 25 and 45 are also referred to as primer layers, anchor layers or anchor coating layers, and are used to improve two types of film adhesion.

It is preferable that the first and second adhesive layers 25 and 45 have excellent transparency, thermal stability, and low birefringence. Typically, one or more binder resins selected from the group consisting of polyester resins, polyvinyl alcohol resins, polyurethane resins, polyimide resins, polyamide resins, acrylic resins, and combinations thereof can be used.

In addition, the first and second adhesive layer (25, 45) is the composition for forming the first and second adhesive layer (25, 45), if necessary, in a range that does not harm the physical properties of the composition, couples Ingredients such as ringing agents, crosslinking agents, plasticizers, heat stabilizers, light stabilizers, lubricants, antioxidants, UV absorbers, flame retardants, colorants, antistatic agents, compatibilizers, thickeners, waxes, organic particulates, inorganic particulates, antifoaming agents, etc. may be further included. .

In one example, the coupling agent is a silane-based coupling agent having a reactive functional group such as an amino group, a vinyl group, an epoxy group, a mercapto group, a chlor group, and a hydrolyzable alkoxysilyl group in the same molecule, and an organic hydrolyzable hydrophilic group containing titanium in the same molecule A titanate-based coupling agent having a functional group, an aluminate-based coupling agent having a hydrolyzable hydrophilic group containing aluminum in the same molecule and an organic functional group, and the like are possible.

In addition, as the crosslinking agent, acrylic crosslinking agent, epoxy crosslinking agent, polyvinyl alcohol crosslinking agent, oxazoline crosslinking agent, organic silane crosslinking agent, blocked isocyanate crosslinking agent, carbodiimide crosslinking agent, organic titanate crosslinking agent, organic zirconate System crosslinking agent and one or more selected from the group consisting of these are possible.

The content of these additives is preferably 10 parts by weight or less, more preferably 5 parts by weight or less, and most preferably 3 parts by weight based on 100 parts by weight of the total solid content in the first and second adhesive layers 25 and 45 Use it as follows.

The formation of the first and second adhesive layers 25 and 45 may be performed, for example, by applying a composition for forming an adhesive layer to each film and drying the composition. At this time, the coating and drying are not particularly limited in the present invention, and follow the technology of the known bar.

The first and second adhesive layers 25 and 45 may have any suitable thickness, and have a thickness of 2.0 to 500 nm, preferably 10 to 200 nm. If the thickness is less than the above range, the adhesion strengthening effect is not sufficient. On the contrary, if the thickness exceeds the above range, the optical properties of the polarizing plate are affected.

Adhesive layer

The first and second adhesive layers 27 and 47 are layers for bonding with the liquid crystal panel 30, such as acrylic, silicone, polyester, polyurethane, polyamide, polyether, fluorine or rubber. It can be formed of a conventional adhesive. The adhesive layer absorbs moisture in consideration of the moldability of the image display device which is excellent in quality and durability, such as peeling phenomenon due to moisture absorption, prevention of bubble generation, warping of the liquid crystal cell due to a difference between thermal expansion coefficients, and prevention of deterioration of optical properties. It is preferable that the rate is low and the heat resistance is excellent. In addition, it is preferable that no high temperature treatment such as curing or drying is required in consideration of optical properties, or that long-term curing or drying is not required. From this viewpoint, an acrylic adhesive is preferably used.

At this time, the first and second adhesive layers 27 and 47 may include known antistatic agents such as alkali metal salts, ionic compounds, conductive polymers, metal oxides, and CNTs, if necessary. Among these, it is more preferable to include an ionic compound. Further, it further includes a copolymer containing a crosslinkable functional group, a crosslinking agent, and a silane coupling agent.

The thickness of the first and second adhesive layers 27 and 47 can be appropriately determined according to the purpose of use and rework, and is generally 1 to 500 μm, preferably 5 to 200 μm, more preferably It is 10 to 100㎛.

Add Possible floor

The structures of the upper and lower polarizing plates 20 and 40 according to the present invention are not particularly limited, and various types of optical layers capable of satisfying required optical properties may be stacked on the polarizer.

For example, a structure in which a polarizer protective film for protecting a polarizer is laminated on at least one surface of the polarizer; A structure in which surface treatment layers such as a hard coating layer, an anti-reflection layer, an anti-sticking layer, an anti-diffusion layer, and an anti-glare layer are laminated on at least one surface of the polarizer or the polarizer protective film; It may have a structure in which an alignment liquid crystal layer or another functional film for compensating the viewing angle is stacked on at least one surface of the polarizer or the polarizer protective film. In addition, a phase difference including a wavelength plate (including a lambda plate) such as an optical film, a reflector, a semi-transmissive plate, a half wave plate, or a quarter wave plate, such as a polarization converter used to form various image display devices It may be a structure in which at least one of a plate, a viewing angle compensation film, and a brightness enhancing film is laminated with an optical layer. More specifically, a polarizing plate having a structure in which a polarizer protective film is laminated on one surface of a polarizer, a reflective polarizing plate or a semi-transmissive polarizing plate in which a reflector or a transflective reflector is laminated on the laminated polarizer protective film; An elliptical or circular polarizing plate in which a phase difference plate is stacked; A wide viewing angle polarizer on which a viewing angle compensation layer or a viewing angle compensation film is stacked; Alternatively, a polarizing plate or the like in which a luminance-enhancing film is laminated is preferable.

The production of the upper and lower polarizing plates having the above-described configuration is not particularly limited in the present invention, and can be easily produced through a known method.

In one example, the polarizer

(S1) preparing a protective film, a polarizer and an outer film on which an adhesive easy layer is formed,

(S2) placing a protective film and an outer film on both sides with a polarizer therebetween,

(S3) step of bonding while applying a photo-curable adhesive to one of these films,

(S4) curing the photocurable adhesive through light irradiation, and

(S5) It is manufactured through the step of bonding the pressure-sensitive adhesive layer to one side of the protective film.

In addition, the upper and lower polarizers are manufactured by arranging the adhesive layer formed on the protective film toward the pressure-sensitive adhesive layer.

Hereinafter, each step will be described in more detail.

First, a protective film, a polarizer, and an outer film having an easy-to-adhesive layer are prepared (S1).

The easy-to-adhesive layer is formed to a predetermined thickness on the protective film through a normal coating process.

At this time, the coating is not particularly limited in the present invention, for example, a doctor blade, a wire bar, a die coater, a comma coater, a gravure coater, etc. may be used in various coating methods.

Next, a protective film and an outer film are disposed on both sides with a polarizer interposed therebetween (S2).

Next, while applying a photocurable adhesive to one of these films, they are bonded (S3).

At this time, the application follows the method as mentioned above.

For bonding, a method of uniformly compressing the photocurable adhesive between the polarizer and the protective film by pressing it with a roll or the like can also be used. Here, the material of the roll may be metal or rubber. The rolls disposed on both sides may be of the same material or different materials.

Next, the photocurable adhesive is cured through light irradiation (S4).

Light irradiation is performed through irradiation of active energy rays such as visible light, ultraviolet light, X-rays, and electron beams. In general, ultraviolet light is preferably used because it is easy to handle and has a sufficient curing speed. The light source of the active energy ray is not particularly limited, but has a luminous distribution at a wavelength of 400 nm or less, for example, low pressure mercury lamp, medium pressure mercury lamp, high pressure mercury lamp, ultra high pressure mercury lamp, chemical lamp, black light lamp, microwave excitation mercury lamp, metal halide lamp , LED lamps, etc. can be used.

Other light irradiation time, irradiation intensity, etc. may vary depending on the composition of the photo-curable adhesive used, and may be appropriately selected by those skilled in the art.

Next, through the step of bonding the pressure-sensitive adhesive layer to one surface of the protective film to prepare the upper and lower polarizer (S5).

The upper and lower polarizing plates manufactured through the above steps are prepared by attaching the pressure-sensitive adhesive layers of each polarizing plate to the liquid crystal panel.

It can be seen that the liquid crystal display device according to the present invention has almost no warpage of the panel and also has a good level of light leakage.

At this time, the liquid crystal display device is not particularly limited, for example, reflective, transmissive and transflective liquid crystal display (LCD) and liquid crystal display of various driving methods such as TN, STN, OCB, HAN, VA, IPS A device (LCD) can be preferably used.

In the present invention, since the liquid crystal display device is well known to those skilled in the art of the present invention, detailed description of each component will be omitted.

[Example]

Hereinafter, a preferred embodiment is provided to help the understanding of the present invention, but the following examples are merely illustrative of the present invention, and it is apparent to those skilled in the art that various changes and modifications are possible within the scope and technical scope of the present invention. It is no wonder that such variations and modifications fall within the scope of the appended claims.

Example  1, Comparative Examples 1 to 5

(1) Production of upper and lower polarizer

Although the acrylic resin film of the polarizer film was arrange | positioned, these film surfaces were laminated | stacked through a UV adhesive using a coating apparatus, and were adhered with a rolling roll.

After curing by irradiating ultraviolet rays with an accumulated light amount of 300 mJ / cm 2 (UV-B) in an ultraviolet irradiation device (a lamp uses “Fusion H valve” manufactured by Fusion Corporation) with a belt conveyor attached to the surface of the obtained laminated film. , PSA adhesive sheet was attached to prepare a polarizing plate.

At this time, the upper and lower polarizing plates were performed by changing the directions of the OXIS film, and specific configurations are shown in Table 1 below.

<Used film>

1. PMMA: Acrylic resin film, thickness 60㎛, trade name "Technoloy S001", Sumitomo Chemical Co., Ltd. product. After corona discharge treatment was performed on one surface of this film, it was provided for bonding with a polarizer.

2. AG-PMMA: Anti-glare film on one side of the PMMA film, the thickness is 65㎛, and the anti-glare film is 1%.

3. OXIS: phase difference compensation acrylic protective film with easy-to-adhesive layer, Okura Kogyo, 40㎛ thick

The bonding layer is a urethane-based resin and has a thickness of about 500 nm.

4. Polarizer: Polyurethane alcohol (product name VF-PE6000) from Kurare, Japan

 It is a uniaxially stretched film with a thickness of about 23㎛.

5. Adhesive: As a UV curable adhesive, epoxy resin composition (Adeca [KR series], viscosity: 44 mPa · s, including cationic polymerization initiator)

6. PSA: A pressure sensitive adhesive containing a butylacrylic monomer and an isocyanate crosslinking agent. 20 μm thick.

Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Upper polarizer (layered)

AG-PMMA AG-PMMA AG-PMMA AG-PMMA AG-PMMA AG-PMMA glue glue glue glue glue glue Polarizer Polarizer Polarizer Polarizer Polarizer Polarizer glue glue glue glue Adhesive layer glue OXIS glue OXIS Adhesive layer OXIS OXIS OXIS Adhesive layer OXIS PSA PSA PSA PSA PSA PSA LCD cell LCD cell LCD cell LCD cell LCD cell LCD cell Lower polarizer
(Layer structure) PSA PSA PSA PSA PSA PSA Adhesive layer OXIS OXIS OXIS OXIS OXIS OXIS glue glue Adhesive layer glue Adhesive layer glue Polarizer Polarizer glue Polarizer glue Polarizer Polarizer Polarizer glue glue glue glue glue glue PMMA PMMA PMMA PMMA PMMA PMMA

(2) LCD panel bonding

The upper and the polarizing plates prepared above were mounted on the upper and lower portions of the 5.5 inch panel (0.4T) of LG Display.

Experimental example  One

After the heat resistance test of the liquid crystal panel with a polarizing plate prepared in Example 1 and Comparative Examples 1 to 5, the amount of warpage was measured, the light leakage phenomenon was observed, and the results are shown in Table 2 below.

(1) Measurement of panel warpage

Panel deflection (mm) was left for 2 hours under conditions of 23 degrees and 50% relative humidity after leaving the LCD panel at 250 ° C for 250 hours, and then using a 3D measuring device (equipment name: VMR-6555, company name: Nikon). The height difference of the warpage was measured.

In addition, the average bending amount in the Bent 3D-Image together with the FOS Image and the Bent 3D-Image associated with the curvature image for each polarizing plate is shown in FIG. 8.

(2) Light source  observe

After the liquid crystal panel provided with the prepared Examples 1 and Comparative Examples 1 to 5 was placed in an oven at 80 ° C. for 250 hours, and then left at room temperature for 1 hour, mounted on a backlight and photographed to observe whether light leakage occurred. Did. At this time, Fig. 9 shows a photograph showing whether the liquid crystal display of Examples and Comparative Examples leaks.

◎: Light leakage occurs at the edge.

△: Light leakage occurs finely at the edge.

×: No light leakage occurred.

Of the upper polarizer
Average bending amount (mm) Of the lower polarizer
Average bending amount (mm) Of the upper-lower polarizer
Bending amount difference (mm) Light leakage Example 1 1.818 0.954 0.864 × Comparative Example 1 1.564 0.835 0.729 △ Comparative Example 2 1.818 0.835 0.983 ◎ Comparative Example 3 1.564 0.862 0.702 △ Comparative Example 4 1.929 0.835 1.094 ◎ Comparative Example 5 1.818 0.862 0.956 ◎

Referring to Table 2, the light leakage phenomenon did not occur in the panel of Example 1 according to the present invention.

In comparison, in the case of Comparative Example 1 in which the adhesive layer was not used, the difference in warpage amount was 0.729 mm, which was lower than in Example 1, but it can be seen from FIG. 8 that light leakage occurs substantially.

In addition, in Comparative Examples 2 to 4 in which the adhesive layer was used only for the upper or lower polarizing plates, light leakage occurred. Specifically, in Comparative Examples 2 and 4 in which the adhesive layer was used only on the upper polarizing plate, the light leakage phenomenon was serious, and in Comparative Example 3 applied only on the lower polarizing plate, the light leakage phenomenon also occurred.

In addition, in the case of Comparative Example 5 in which the position of the adhesive layer of the lower polarizing plate was different, as compared with Example 1, it can be seen that light leakage occurs as well as the amount of warpage.

From these results, it can be seen that the adhesion layer can control the generation of light leakage depending on the presence of the polarizing plate as well as the existence of the adhesive layer.

1: LCD device 10: backlight unit
11: Light source 12: Reflector
13: light guide plate 14: diffuser plate
20, 20a, 20b: upper polarizing plate 21: first outer film
22: first adhesive layer 23: first polarizer
24: second adhesive layer 25: first adhesive layer
26: first protective film 27: first adhesive layer
41: second outer film 42: third adhesive layer
43: second polarizer 44: fourth adhesive layer
45: second adhesive layer 46: second protective film
47: second adhesive layer

Claims (10)

In the liquid crystal display device having an outer film, an adhesive, a polarizer, an adhesive, a protective film, and an upper and lower polarizing tube sequentially stacked with an adhesive layer, and a liquid crystal panel positioned between the upper and lower polarizing plates through the adhesive layer,
The upper polarizing plate is disposed between the polarizer and the protective film, the lower polarizing plate is disposed an adhesive layer between the pressure-sensitive adhesive layer and the protective film,
In the lower polarizing plate, the polarizer and the protective film are directly laminated through an adhesive,
In the upper polarizing plate, the protective film and the adhesive layer are directly laminated,
A liquid crystal display device characterized in that the outer film, the polarizer and the protective film of the upper and lower polarizing plates are bonded with a photo-curable adhesive. The method according to claim 1, The adhesive layer is one or more selected from the group consisting of polyester-based resin, polyvinyl alcohol-based resin, polyurethane-based resin, polyimide-based resin, polyamide-based resin, acrylic resin and combinations thereof. A liquid crystal display device comprising a binder resin. The method according to claim 1, The adhesive layer is a liquid crystal display device characterized in that the thickness is 2.0 to 500nm. The method according to claim 1, The outer film is a liquid crystal display device, characterized in that it comprises at least one protective film. The method according to claim 4, The outer film is additionally composed of an adhesive layer, an adhesive layer, a hard coating layer, an anti-reflection layer, an anti-adhesion layer, a diffusion preventing layer, an anti-glare layer, a phase difference compensation layer, a viewing angle compensation layer, a brightness enhancement layer, and combinations thereof A liquid crystal display device comprising at least one functional layer selected from the group. delete The liquid crystal display device of claim 1, wherein the photocurable adhesive has a thickness of 5 μm or less. The liquid crystal display device according to claim 1, wherein the polarizer is a dichroic dye or iodine-dyed polyvinyl alcohol-based resin. The method according to claim 1, The absorption side of the upper polarizing plate is 80 to 100 degrees, the absorption axis of the lower polarizing plate is -10 to 10 degrees,
The upper and lower polarizing plates are arranged such that the absorption axes are 90 degrees to each other. The method according to claim 1, The absorption axis of the upper polarizing plate is -10 to 10 degrees, the absorption side of the lower polarizing plate is 80 to 100 degrees,
The upper and lower polarizing plates are arranged such that the absorption axes are 90 degrees to each other.

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