KR20200079838A - Polarizing plate and liquid crystal display apparatus comprising the same - Google Patents

Abstract

Provided are a polarizing plate and liquid crystal display device including the same, wherein the polarizing plate includes: a polarizing film; and a brightness enhancing film laminated on a light incident surface of the polarizing film, wherein a coating layer having a refractive index of 1.1 or more and 1.4 or less is directly formed on the light emitting surface of the brightness enhancing film. Therefore, the polarizing plate can minimize the loss of brightness and contrast of light.

Description

Polarizing plate and liquid crystal display device including the same {POLARIZING PLATE AND LIQUID CRYSTAL DISPLAY APPARATUS COMPRISING THE SAME}

The present invention relates to a polarizing plate and a liquid crystal display device including the same.

In the liquid crystal display device, a plurality of optical elements such as a light source, a light guide plate, a diffusion film, a condensing film, a polarization reflection luminance enhancement film (hereinafter referred to as "brightness enhancement film"), and a polarizing plate are laminated. In recent years, in accordance with the tendency of light and small size reduction of a liquid crystal display device, a technique of laminating the above-described optical elements and including them in the liquid crystal display device has been developed.

Particularly, by laminating the light source-side polarizing plate and the luminance-enhancing film, it is possible to simultaneously obtain the above-described light-thinning effect and the effect of preventing damage to the luminance-enhancing film. However, when laminating the light source-side polarizing plate and the luminance-enhancing film, there is a problem in that the luminance and contrast ratio fall. In order to improve this, a method of minimizing haze of the brightness enhancing film or increasing the polarization degree of the light source side polarizing plate is considered. However, in this case, the luminance enhancement efficiency of the luminance-enhancing film is lowered, so that a desired effect cannot be obtained, or when the polarization degree of the polarizing plate is increased, the transmittance of the polarizing plate may be lowered, and thus there may be a problem that cannot be used in the liquid crystal display device.

Background art of the present invention is disclosed in Japanese Patent Publication No. 2006-251659.

An object of the present invention is to provide a polarizing plate capable of minimizing loss of brightness and contrast ratio of light emitted from a brightness enhancing film through a polarizing film in a laminate of a polarizing film and a brightness enhancing film.

Another object of the present invention is to provide a polarizing plate excellent in polarization and light transmittance as a laminate of a polarizing film and a brightness enhancing film.

Another object of the present invention is to provide a polarizing plate capable of reducing the overall thickness of a laminate of a polarizing film and a brightness enhancing film and preventing deformation of the brightness enhancing film due to heat and/or moisture.

One aspect of the present invention is a polarizing plate.

1. The polarizing plate is a polarizing film; And a brightness enhancing film laminated on the light incident surface of the polarizing film, and a coating layer having a refractive index of 1.1 or more and 1.4 or less is directly formed on the light emitting surface of the brightness enhancing film.

In 2.1, the coating layer may have a refractive index of 1.2 or more and 1.3 or less.

In 3.1-2, the coating layer may be formed of a composition for a coating layer comprising a carbosilane-siloxane copolymer.

In 4.3, the carbosilane-siloxane copolymer can be represented by the following formula (3):

[Formula 3]

(R ⁴ R ⁵ R ⁶ SiO _1/2 ) _M (R ⁷ R ⁸ SiO _2/2 ) _D (R ⁹ SiO _3/2 ) _T1 (SiO _3/2 -Y-SiO _3/2 ) _T2 (SiO _{4 /2} ) _Q

(In the formula 3,

R ⁴ to R ⁹ are hydrogen, C1 to C30 alkyl group, C2 to C30 alkenyl group, C6 to C30 aryl group, C3 to C30 cycloalkyl group, C1 to C30 alkoxy group, carboxyl group, R(C=O)-, R(C=O)O- (where R is a C1 to C30 alkyl group, C3 to C30 cycloalkyl group, C6 to C30 aryl group), epoxy group-containing monovalent organic group, (meth)acrylic group, (meth)acrylic A C1 to C30 alkyl group substituted with a (meth)acrylic group, a C1 to C30 alkyl group substituted with a (meth)acrylate, or a combination thereof,

Y is a C1 to C30 alkylene group, a C2 to C30 alkenylene group, a C3 to C30 cycloalkylene group, a C6 to C30 arylene group, or a combination thereof,

0≤M≤0.5, 0≤D≤0.5, 0<T1≤0.95, 0<T2≤0.2, 0<Q≤0.9, and M+D+T1+T2+Q=1).

In 5.4, in Chemical Formula 3, M=0, D=0, 0.3≤T1≤0.9, 0.01≤T2≤0.15, and 0.05≤Q≤0.65.

In 6.3, the cured product of the carbosilane-siloxane copolymer may be included in 50% by weight or more and 99% by weight or less in the coating layer.

In 7.3, pores may be formed in the coating layer.

In 8.3, the composition for the coating layer may further include a surfactant for forming pores.

In 9.8, the surfactant for pore formation may include an ammonium salt represented by Formula 4 below:

[Formula 4]

(In the formula 4, R ^a to R ^d are each independently a C1 to C30 alkyl group,

X is a halogen atom).

In 10.1-9, the coating layer may include an adhesive layer having a refractive index of 1.1 or more and 1.4 or less.

In 11.1-10, the brightness enhancing film may include a single layer or a multilayer reflective polarizing film.

In 12.1-11, the brightness enhancement film may have a refractive index of 1.4 or more and 1.8 or less in the uppermost layer.

In 13.1-12, the brightness enhancing film may include a core layer including a plurality of plate-like polymers therein.

In 14.1-13, the polarizing film is a polarizer; A first protective layer formed on one surface of the polarizer; And it may include a second protective layer formed on the other side of the polarizer.

In 15.14, the first protective layer may have a plane direction retardation of 5,000 nm or more at a wavelength of 550 nm, and the second protective layer may have a plane direction retardation (Re) of a wavelength of 550 nm or less of 60 nm or less.

In 16.14, the first protective layer or the second protective layer may be adhered to the coating layer by an adhesive layer having a refractive index of more than 1.4 and 1.6 or less.

The optical display device of the present invention includes a liquid crystal panel; And a polarizing plate of the present invention formed on the light incident surface of the liquid crystal panel.

The present invention provides a polarizing plate capable of minimizing loss of luminance and contrast ratio of light emitted from a luminance-enhancing film through a polarizing film in a laminate of a polarizing film and a luminance-enhancing film.

The present invention provides a polarizing plate excellent in polarization and light transmittance as a laminate of a polarizing film and a brightness enhancing film.

The present invention provides a polarizing plate capable of reducing the overall thickness of a laminate of a polarizing film and a brightness enhancing film and preventing deformation of the brightness enhancing film due to heat and/or moisture.

1 is a cross-sectional view of a polarizing plate according to an embodiment of the present invention.
2 is a cross-sectional view of a brightness enhancing film according to an embodiment of the present invention.

With reference to the accompanying drawings it will be described in detail so that those skilled in the art to which the present invention pertains can be easily carried out by examples. The present invention can be implemented in many different forms and is not limited to the embodiments described herein. In order to clearly describe the present invention in the drawings, parts irrelevant to the description are omitted, and the same reference numerals are assigned to the same or similar elements throughout the specification. The length and size of each component in the drawings are for describing the present invention, and the present invention is not limited to the length and size of each component described in the drawings.

In this specification, "upper" and "lower" are defined on the basis of drawings, and "upper" can be changed to "lower" and "lower" to "upper" according to a city perspective, and "on" or What is referred to as "on" may include not only directly above, but also through other structures in the middle. On the other hand, what is referred to as “directly on”, “directly above” or “directly forming” or “directly forming” means that there is no intervening structure.

As used herein, "(meth)acrylic" means acrylic and/or methacrylic.

In the present specification, the "plane-direction phase difference (Re)" is represented by Equation A below, and the "thickness phase retardation (Rth)" is represented by Equation B below:

<Equation A>

Re = (nx-ny) x d

<Equation B>

Rth = ((nx + ny)/2-nz) x d

(In the formulas A and B, nx, ny, and nz are refractive indexes in the slow axis direction, the fast axis direction, and the thickness direction of the corresponding protective layer, respectively, at a wavelength of 550 nm, and d is the corresponding protective layer. Is the thickness (unit: nm)).

When describing a numerical range in this specification, "X to Y" means X or more and Y or less (X≤ and ≤Y).

The inventor of the present invention is a light source side polarizing plate of a liquid crystal display device, comprising: a polarizing film; And a brightness enhancing film laminated on the light incident surface of the polarizing film, and a coating layer having a refractive index of 1.1 or more and 1.4 or less is directly formed on the light emitting surface of the brightness enhancing film, thereby significantly reducing the contrast ratio and significantly reducing the luminance loss. While being able to confirm that the light transmittance and the polarization were excellent at the same time, the present invention was completed. The "light source side polarizing plate" means a polarizing plate disposed on the light source side of the liquid crystal panel among the liquid crystal display devices.

In one embodiment, the polarizing plate may have a polarization degree of 98% or more, for example, 99% to 100%. In one embodiment, the polarizing plate may have a light transmittance (for example, light transmittance in a visible light region) of 40% or more, for example, 42% to 45%. In the above range, it can be used as a light source side polarizing plate in a liquid crystal display device.

Hereinafter, a polarizing plate according to an embodiment of the present invention will be described with reference to FIG. 1.

Referring to FIG. 1, the polarizing plate includes a polarizing film 100, a coating layer 200, and a brightness enhancing film 300. As in FIG. 1, the polarizing film 100, the coating layer 200, and the brightness enhancing film 300 are integrally formed to form a laminate. The term “one-piece” means that the polarizing film, the coating layer, and the brightness enhancing film are not separated from each other by physical force. Although not shown in FIG. 1, the polarizing plate may be adhered to the liquid crystal panel by further forming an adhesive layer on the upper surface of the polarizing film 100 (ie, the surface not contacting the coating layer in the polarizing film).

Coating layer

The coating layer 200 is directly formed on the light exit surface of the brightness enhancement film 300. The "directly formed" means that any other adhesive layer, adhesive layer, point adhesive layer, and/or optical film is not interposed between the brightness enhancing film 300 and the coating layer 200 and there is no air. As described below, the coating layer may be formed by directly coating and curing the composition for the coating layer on the light exit surface of the brightness enhancing film.

The coating layer 200 has a refractive index of 1.1 or more and 1.4 or less. In the above range, luminance loss and contrast ratio loss can be minimized by entering the polarizing film without losing light emitted from the luminance enhancement film. Preferably, the coating layer may have a refractive index of 1.15 or more and 1.4 or less, more preferably 1.2 or more and 1.35 or less, and most preferably 1.2 or more and 1.3 or less.

The coating layer 200 may be formed directly on the light exit surface of the brightness enhancement film 300 and have the above-described refractive index range, thereby realizing the effect of the present invention.

In one embodiment, the coating layer may be a primer layer of a brightness enhancing film. The coating layer becomes a primer layer of a brightness enhancing film, thereby increasing the adhesion of the brightness enhancing film to the polarizing film while simultaneously realizing the effect of minimizing the contrast ratio and brightness loss of the present invention as described above. In addition, since the coating layer becomes a primer layer of the luminance-enhancing film, it is possible to prevent deformation of the luminance-enhancing film due to heat and/or moisture compared to when the polarizing film and the luminance-enhancing film are directly attached to the adhesive layer. In particular, when the brightness enhancing film is poorly adhered to the polarizing film, the coating layer can easily integrate the brightness improving film and the polarizing film.

The coating layer may have a thickness of 0.05 μm to 4 μm, preferably 0.5 μm to 2 μm, and 0.6 μm to 2 μm. In the above range, it is easy to obtain the effect of the above-described coating layer and the laminate can be thinned.

The composition for the coating layer includes a carbosilane-siloxane copolymer, an organic polymer, and a surfactant. The composition for the coating layer may further include a solvent. This will be described in detail.

A coating layer comprising a carbosilane-siloxane copolymer may be formed by applying a composition for a coating layer comprising a carbosilane-siloxane copolymer on a brightness enhancing film and curing the coating layer. In addition, as described below, pores are formed in the coating layer. Therefore, the coating layer can lower the refractive index at a thin thickness and minimize the contrast ratio loss and luminance loss of the present invention.

In one embodiment, the composition for the coating layer may include (a) a carbosilane-siloxane copolymer, (b) an organic polymer having a boiling point at 100°C to 200°C, (c) a surfactant, and (d) a solvent. .

(a) Carbosilane - Siloxane Copolymer

The carbosilane-siloxane copolymer may be prepared by hydrolysis condensation reaction of a silane compound represented by Chemical Formula 1 and a carbosilane compound represented by Chemical Formula 2:

[Formula 1]

(R ¹ ) _n -Si-(OR ² ) _4-n

(In Formula 1,

R ¹ is hydrogen, C1 to C30 alkyl group, C2 to C30 alkenyl group, C6 to C30 aryl group, C3 to C30 cycloalkyl group, C1 to C30 alkoxy group, carboxyl group, R(C=O)-, R(C =O)O- (where R is a C1 to C30 alkyl group, C3 to C30 cycloalkyl group, C6 to C30 aryl group), an epoxy group-containing monovalent organic group, (meth)acrylic group, (meth)acrylate group, A C1 to C30 alkyl group substituted with a (meth)acrylic group, a C1 to C30 alkyl group substituted with a (meth)acrylate group, or a combination thereof,

R ² represents any one of hydrogen, a C1 to C30 alkyl group, a C3 to C30 cycloalkyl group, a C2 to C30 alkenyl group, and a C6 to C30 aryl group,

n represents the integer of 0≤n<4).

[Formula 2]

(In the formula 2,

R ³ represents hydrogen, a C1 to C30 alkyl group, a C3 to C30 cycloalkyl group, a C2 to C30 alkenyl group, or a C6 to C30 aryl group,

Y represents a C1 to C30 alkylene group, a C2 to C30 alkenylene group, a C3 to C30 cycloalkylene group, a C6 to C30 arylene group, or a combination thereof).

In Chemical Formula 1, n may be an integer of 0≤n<3.

The silane compound represented by Formula 1 and the carbosilane-siloxane copolymer prepared from the carbosilane compound represented by Formula 2 may be represented by the following Formula 3:

[Formula 3]

(R ⁴ R ⁵ R ⁶ SiO _1/2 ) _M (R ⁷ R ⁸ SiO _2/2 ) _D (R ⁹ SiO _3/2 ) _T1 (SiO _3/2 -Y-SiO _3/2 ) _T2 (SiO _{4 /2} ) _Q

(In the formula 3,

R ⁴ to R ⁹ are hydrogen, C1 to C30 alkyl group, C2 to C30 alkenyl group, C6 to C30 aryl group, C3 to C30 cycloalkyl group, C1 to C30 alkoxy group, carboxyl group, R(C=O)-, R(C=O)O- (where R is a C1 to C30 alkyl group, C3 to C30 cycloalkyl group, C6 to C30 aryl group), epoxy group-containing monovalent organic group, (meth)acrylic group, (meth)acrylic A C1 to C30 alkyl group substituted with a (meth)acrylic group, a C1 to C30 alkyl group substituted with a (meth)acrylate, or a combination thereof,

Y is a C1 to C30 alkylene group, C2 to C30 alkenylene group, C3 to C30 cycloalkylene group, C6 to C30 arylene group, or a combination thereof,

0≤M≤0.5, 0≤D≤0.5, 0<T1≤0.95, 0<T2≤0.2, 0<Q≤0.9, and M+D+T1+T2+Q=1).

In one embodiment, M=0 in Chemical Formula 3, 0<D≤0.2, 0.1≤T1≤0.95, 0<T2<0.2, 0.05≤Q≤0.9, and D+T1+T2+Q=1.

In another embodiment, M=0 and D=0 of Chemical Formula 3, 0.3≤T1≤0.95, 0<T2<0.2, 0.05≤Q≤0.8, preferably 0.3≤T1≤0.9, 0.01≤T2 ≤0.15, 0.05≤Q≤0.65, and T1+T2+Q=1.

The weight average molecular weight (Mw) in terms of polystyrene of the carbosilane-siloxane copolymer is 5,000 to 5,000,000, for example 10,000 to 5,000,000, for example 100,000 to 5,000,000, for example, 200,000 to 5,000,000, for example 300,000 To 5,000,000, e.g., 400,000 to 5,000,000, e.g., 500,000 to 5,000,000, e.g., 500,000 to 4,500,000, e.g., 500,000 to 3,000,000, e.g., 500,000 to 4,000,000, e.g., 500,000 to 3,500,000 , For example, 500,000 to 3,000,000, but is not limited thereto.

The carbosilane-siloxane copolymer, based on the total weight of the composition for the coating layer, 30% by weight or less, for example, 1% to 25% by weight, for example, 1.5% to 20% by weight, for example For example, 2% to 15% by weight, for example 2.5% to 10% by weight, for example 3% to 10% by weight, for example 3.5% to 10% by weight, for example 4.5% to 10% by weight, for example, 5% to 10% by weight may be included, but is not limited to these ranges.

The cured product of the carbosilane-siloxane copolymer may include 50 wt% or more and 99 wt% or less of the coating layer, preferably 50 wt% to 95 wt%, preferably 50 wt% to 90 wt%. In the above range, an appropriate amount of an organic polymer having a boiling point of 100°C to 200°C, which is described below, may be included, thereby reducing the refractive index.

(b) the boiling point is 100 ℃ to 200 ℃ abandonment Polymer

The composition for the coating layer includes an organic polymer having a boiling point of 100°C to 200°C, together with the carbosilane-siloxane copolymer.

Examples of the organic polymer having a boiling point of 100°C to 200°C include one or more of polyalkylene oxide-based copolymers, polyarylene oxide copolymers, and glycol-based copolymers. Examples of the glycol-based copolymers include polyethylene glycol (poly(ethylene) glycol), polyflopropylene glycol (poly(propylene) glycol), and the like. Examples of the polyalkylene oxide-based or polyarylene oxide-based copolymers include polyethylene oxide, polypropylene oxide, and poly(phenylene) oxide.

The number average molecular weight (Mn) of the organic polymer is 100 to 10,000, for example, 100 to 8,000, for example, 200 to 7,000, for example, 300 to 6,000, for example, 350 to 5,000, for example, 400 to 4,500, for example 450 to 4,000, for example 500 to 4,000, for example 500 to 3,500, for example 600 to 3,000, for example 650 to 3,000, for example 700 to 3,000, for example, 800 to 3,000, for example, 900 to 3,000, for example, 1,000 to 3,000, for example, 1,000 to 2,500, for example, 1,000 to 2,000, and the like. .

When the organic polymer having a boiling point of 100°C to 200°C is included in the composition for a coating layer together with a solvent and the carbosilane-siloxane copolymer, the composition is coated on a brightness enhancing film and then heated to cure the carbosilane-siloxane copolymer When the temperature is increased to 100°C to 200°C, the organic polymer having a boiling point between 100°C and 200°C is evaporated from the composition for forming a coating layer applied on the brightness enhancing film. As the organic polymer evaporates, pores, specifically, nano-pores having a nano-diameter diameter, may be formed in the coating layer coating the composition for forming the coating layer. The coating layer including the carbosilane-siloxane copolymer having such pores may have a lower refractive index than the coating layer prepared from the carbosilane-siloxane copolymer without the organic polymer. Therefore, in forming a coating layer having a low refractive index, including a carbosilane-siloxane copolymer, a coating layer having a lower refractive index can be easily formed by including the organic polymer.

The organic polymer having a boiling point of 100°C to 200°C may be included in an amount of 10 parts by weight to 150 parts by weight, for example, 10 parts by weight to 100 parts by weight based on 100 parts by weight of the carbosilane-siloxane copolymer.

In addition, after the organic polymer is pre-mixed with the surfactant described below, based on the total weight of the composition for the coating layer, the solid content of the organic polymer is 30% by weight or less, for example, 1% by weight to 25% by weight, For example, 1.5% to 20% by weight, for example 2% to 15% by weight, for example 2.5% to 10% by weight, for example 3% to 10% by weight, for example For example, 3.5 wt% to 10 wt%, for example, 4.5 wt% to 10 wt%, for example, 5 wt% to 10 wt% may be included, but is not limited to these ranges.

(c) surfactant for pore formation

The composition for a coating layer according to one embodiment further includes a surfactant structure for forming additional pores.

The surfactant forms additional nanopores while allowing the organic polymer having a boiling point of 100°C to 200°C to be mixed smoothly in a solvent with the carbosilane-siloxane copolymer having inorganic properties and the organic property. Such surfactants have a weight ratio of 1:9 to 9:1 with an organic polymer having a boiling point of 100°C to 200°C, for example, a weight ratio of 2:8 to 8:2, for example, 3:7 to 7: 3, for example, 4:6 to 6:4, for example, after pre-mixing in a weight ratio of 5:5, it may be mixed with the carbosilane-siloxane copolymer.

The surfactant may include an ammonium salt represented by Formula 4 below:

[Formula 4]

In Formula 4, R ^a to R ^d are each independently a C1 to C30 alkyl group,

X may be a halogen atom, for example F, Cl, Br, or I.

In one embodiment, three of R ^a to R ^d in Chemical Formula 4 are all methyl groups, and the other one may be a C10 to C30 alkyl group.

Specific examples of the surfactant represented by Chemical Formula 4 include cetyltrimethylammonium chloride (hexadecyltrimethylammonium chloride, cetyltrimethylammonium chloride), dodecyltrimethylammonium chloride, and the like. Does not work.

(d) solvent

As the solvent for forming the coating layer, any solvent that can be used at a process temperature of 200° C. or higher can be used. For example, the solvent may be an alcohol-type solvent, for example, butanol, isopropanol, and the like, a ketone-type solvent, for example, PMEA, DIBK (diisobutyl ketone), etc., and other known in the art Any solvent that can be used at or above the above process temperature can be used as a mixed solvent.

The solvent may be included in 300 to 2,000 parts by weight based on 100 parts by weight of the carbosilane-siloxane copolymer, and may be appropriately adjusted according to the total solid content.

(e) curing catalyst

The composition for the coating layer may further include a thermosetting curing catalyst for accelerating curing of unreacted silanol groups at the siloxane resin end of the carbosilane-siloxane copolymer, but these catalysts may be used depending on the carbosilane-siloxane resin used. It may not be included. Examples of curable catalysts may include those having an ammonium salt form such as tetrabutylammonium acetate (TBAA).

When using the curing catalyst, the catalyst may include 5 parts by weight or less, for example, 3 parts by weight or less, for example, 1 part by weight or less based on 100 parts by weight of the carbosilane-siloxane copolymer.

(f) Other additives

The composition for the coating layer may further include various additives known in the art. As such an additive, a surfactant for improving coating property and preventing defect generation when coating the composition for a coating layer may further include, for example, a fluorine-based surfactant, but is not limited thereto. These additives are 10 parts by weight or less, for example, 8 parts by weight or less, for example, 5 parts by weight or less, for example, 3 parts by weight or less, for example, 100 parts by weight of the carbosilane-siloxane copolymer , 2 parts by weight or less, for example, 1 part by weight or less.

When the coating layer is a primer layer, the coating layer may be a non-adhesive layer. At this time, the polarizing plate, a polarizing film, an adhesive layer, a coating layer, and a brightness enhancing film may be sequentially stacked. At this time, the coating layer may have a refractive index of 1.1 or more and 1.4 or less, and the adhesive layer may have a refractive index of 1.4 or more and 1.6 or less, preferably 1.4 or more and 1.55 or less.

In another embodiment, the coating layer may be an adhesive layer, an adhesive layer, or a point adhesive layer that adheres or adheres the brightness enhancing film and the polarizing film. Hereinafter, an adhesive layer, an adhesive layer, or a point adhesive layer is described as a "point (adhesive) adhesive layer".

Since the point (adhesive) adhesive layer is laminated between the brightness enhancing film and the polarizing film, it is not necessary to use another additional point (adhesive) adhesive layer, so that the polarizing plate can be thinned. The point (adhesive) adhesive layer is not particularly limited as long as it can exhibit an adhesive or adhesive layer while securing the refractive index of 1.1 or more and 1.4 or less. For example, the point (adhesive) adhesive layer may be formed of at least one composition of (meth)acrylic, silicone, urethane, and epoxy. The refractive index may be realized by adjusting the monomer composition, monomer content ratio, etc. of the (meth)acrylic, silicone, urethane, and epoxy adhesive resins included in the composition.

Preferably, the coating layer can be a primer layer.

The coating layer may be a single layer, such as the primer layer and the point (adhesive) layer described above, but may be multi-layered by stacking two or more layers.

In one embodiment, the coating layer may be a laminate composed of two layers of a first coating layer and a second coating layer. Any one of the first coating layer and the second coating layer may be a primer layer, the first coating layer, and the other of the second coating layer may be a point (adhesive) adhesion layer. Each of the first coating layer and the second coating layer may have a refractive index of 1.1 or more and 1.4 or less.

Brightness enhancement film

The brightness enhancing film 300 is formed on the light incident surface of the polarizing film 100. The luminance-enhancing film can emit luminance of light emitted from the light source of the liquid crystal display device with high luminance. The brightness enhancing film can include conventional brightness enhancing films known to those skilled in the art.

The brightness enhancing film 300 may include a reflective polarizing film. Through this, the light emitted from the light source (not shown in FIG. 1) is reflected and polarized to emit light to obtain a luminance enhancement effect.

The brightness enhancement film 300 may be a single-layer structure film or a multi-layer structure film in which a plurality of layers are stacked. The top layer of the brightness enhancing film 300, that is, the layer in contact with the coating layer 200 may have a refractive index of 1.4 or more and 1.8 or less, preferably more than 1.4 and 1.8 or less, more preferably 1.5 or more and 1.7 or less. In the above range, since the refractive index of the layer contacting the coating layer is higher than that of the coating layer, luminance loss and contrast ratio loss can be minimized.

In one embodiment, the brightness enhancing film includes a core layer, and the core layer may include a substrate and a plurality of plate-like polymers inside the substrate. The plate-shaped polymer has a refractive index different in at least one axial direction from the core layer, and the core layer is extended in at least one axial direction. Each of the plate-shaped polymers is formed of a plurality of groups for reflecting a transverse wave of a desired wavelength, and the average optical thickness of the plate-shaped polymers between the groups is different from each other. Through this, the luminance-enhancing film passes through only the polarization (P polarization) perpendicular to the stretching direction among the light incident from the light source and reaches the luminance-enhancing film, and the remaining polarization (S polarization) of the stretching direction is reflected downward, and this process In S, polarization is re-reflected from the bottom, and the re-reflected S-polarized light again passes through the P-polarized light and the S-polarized light is reflected, thereby improving luminance. In the case of the brightness-enhancing film, because the refractive index of the plate-shaped polymer and the refractive index of the matrix are different from each other, the characteristics of the transmitted light generally show scattered characteristics. When the luminance-enhancing film and the polarizing film are laminated in a conventional manner, contrast ratio and luminance loss occur due to scattering characteristics of the luminance-enhancing film. The brightness-enhancing film may be a commercially available product.

Plate-shaped polymers are polyethylene naphthalate, copolyethylene naphthalate, polyethylene terephthalate, polycarbonate, polycarbonate alloy, polystyrene, heat-resistant polystyrene, polymethylmethacrylate, polybutylene terephthalate, polypropylene, polyethylene, acrylonitrile butadiene Styrene, polyurethane, polyimide, polyvinyl chloride, styrene acrylonitrile, vinyl ethylene acetate, polyamide, polyacetal, phenol, epoxy, urea, melanin, unsaturated polyester, silicone, cycloolefin polymer It can contain. Preferably, the plate-shaped polymer may be polyethylene naphthalate or the like.

The base material is polyethylene naphthalate, copolyethylene naphthalate, polyethylene terephthalate, polycarbonate, polycarbonate alloy, polystyrene, heat-resistant polystyrene, polymethyl methacrylate, polybutylene terephthalate, polypropylene, polyethylene, acrylonitrile butadiene styrene , Polyurethane, polyimide, polyvinyl chloride, styrene acrylonitrile, ethylene vinyl acetate, polyamide, polyacetal, phenol, epoxy, urea, melanin, unsaturated polyester, silicone, cycloolefin polymer. can do. Preferably, dimethyl-2,6-naphthalene dicarboxylate, dimethyl terephthalate and ethylene glycol, cyclohexanedimethanol, or the like may be polymerized copolyethylene naphthalate.

Referring to FIG. 2, a luminance enhancing film according to an embodiment of the present invention will be described.

2, the brightness enhancement film includes a core layer 10. In the core layer 10, group A and group B are sequentially formed in the thickness direction of the core layer 10, and group A and group B are integrally formed. Group A includes plate-like polymers 11 and 12, and Group B includes plate-like polymers 13 and 14. The plate-shaped polymers 11 and 12 and the plate-shaped polymers 13 and 14 are respectively impregnated in the substrate (not shown in Fig. 2). The optical thickness between the plate-shaped polymers included in group A and the optical thickness between the plate-shaped polymers 13 and 14 included in group B are different from each other. Through this, it is possible to reflect different wavelength regions of light. FIG. 2 shows a case in which two groups are formed of group A and group B, but the number of groups included in the core layer is not particularly limited as long as a luminance enhancement effect can be obtained.

Although not illustrated in FIG. 2, the core layer may be protected by additionally forming a skin layer protecting the core layer on one or both surfaces of the core layer. In this case, the refractive index of the skin layer may be 1.4 or more and 1.8 or less, preferably 1.5 or more and 1.7 or less. In this range, since the refractive index of the layer contacting the coating layer is higher than that of the coating layer, luminance loss and contrast ratio loss can be minimized.

The skin layer is polyethylene terephthalate, polycarbonate, polycarbonate alloy, polystyrene, heat-resistant polystyrene, polymethyl methacrylate, polybutylene terephthalate, polypropylene, polyethylene, acrylonitrile butadiene styrene, polyurethane, polyimide, poly Vinyl chloride, styrene acrylonitrile, ethylene vinyl acetate, polyamide, polyacetal, phenol, epoxy, urea, melanin, unsaturated polyester, silicone, and cycloolefin polymer. Preferably, the skin layer may be polycarbonate or polycarbonate alloy.

Polarizing film

The polarizing film 100 may transmit light by polarizing light incident from a light source (not shown in FIG. 1) of the optical display device. The polarizing film 100 includes a polarizer.

In one embodiment, the polarizing film can be the polarizer itself. The polarizer may include a polyvinyl alcohol-based polarizer prepared by uniaxially stretching a polyvinyl alcohol-based film or a polyene-based polarizer prepared by dehydrating a polyvinyl alcohol-based film. The polarizer 100 may have a thickness of 5 μm to 60 μm. In the above range, it can be used in an optical display device.

In another embodiment, the polarizing film may include a polarizer and a protective layer formed on the light exit surface of the polarizer. In another embodiment, the polarizing film may include a polarizer and a protective layer formed on the light incident surface of the polarizer. In another embodiment, the polarizing film comprises a polarizer; It may include a protective layer formed on the light exit surface of the polarizer and a protective layer formed on the light incident surface of the polarizer.

The protective layer is formed on one surface or both surfaces of the polarizer to protect the polarizer. The protective layer may have a light transmittance of 90% or more, for example, 90% to 100% in the visible light region. In the above range, light can be transmitted without affecting incident light. The thickness of the protective layer may be 5 μm to 200 μm, specifically, 30 μm to 120 μm. In the above range, it can be used for a polarizing plate.

The protective layer can be a protective film or a protective coating layer.

The protective film may also include a case where a plurality of optically transparent resin films of a single layer or a plurality of resin films of a single layer are laminated. The protective film can be formed by melting and extruding the resin. If necessary, a further stretching process may be added. The resins include cellulose ester-based resins including triacetyl cellulose, cyclic polyolefin-based resins including amorphous cyclic polyolefins, polycarbonate-based resins, polyester-based resins including polyethylene terephthalate, and polyethersulfone-based resins. Polyacrylate-based resins, polyvinyl alcohol-based resins, polyvinyl chloride-based resins, including resins, polysulfone-based resins, polyamide-based resins, polyimide-based resins, acyclic-polyolefin-based resins, polymethylmethacrylate resins, and the like Resin, polyvinylidene chloride-based resin may include one or more. The protective coating layer may be formed of a composition comprising an active energy ray-curable compound and a polymerization initiator. The active energy ray-curable compound may include at least one of a cationic polymerizable curable compound, a radically polymerizable curable compound, a urethane resin, and a silicone resin.

In one embodiment, the protective layer has a range of in-plane retardations (Re). For example, the protective layer may have a plane direction retardation of 5,000 nm or more at a wavelength of 550 nm, specifically 5,000 nm to 15,000 nm, more specifically 6,000 nm to 13,000 nm, and most specifically 8,000 nm to 12,000 nm. In the above range, there may be an effect of improving Mura and minimizing contrast ratio loss.

In another embodiment, the protective layer has a range of in-plane retardations (Re). For example, the protective layer has a plane direction retardation (Re) of 60 nm or less at a wavelength of 550 nm, a thickness direction retardation (Rth) of 150 nm or less, specifically Re of 0 nm to 60 nm, 45 nm to 60 nm, and Rth of 0 nm to 150 nm, 100 nm to 140 nm, more specifically, Re may be 50 nm to 60 nm, and Rth may be 120 nm to 140 nm. In the above range, there may be a phase difference compensation effect according to the viewing angle in the VA mode panel.

In one embodiment, the polarizing film is formed on one side of the polarizer, the first protective layer having a plane direction retardation (Re) of 5,000 nm or more at a wavelength of 550 nm, and a plane direction retardation (Re) of a wavelength of 550 nm formed on the other side of the polarizer ) May include a second protective layer of 60 nm or less. In the above range, the effect of the present invention can be well implemented. Preferably, the polarizing film may include a polarizer, a first protective layer formed on the light incident surface of the polarizer, and a second protective layer formed on the light exit surface of the polarizer.

A surface treatment layer such as a primer layer, a hard coating layer, an anti-fingerprint layer, an anti-reflection layer, an anti-glare layer, a low-reflection layer, or an ultra-low-reflection layer may be further formed on at least one surface (at least one of the upper and lower surfaces) of the protective layer. . The hard coating layer, anti-fingerprint layer, anti-reflection layer, etc. may provide additional functions such as a protective layer or a polarizing plate.

In one embodiment, the polarizing film comprises a polarizer; A first protective layer formed on one surface of the polarizer; And it may include a second protective layer formed on the other side of the polarizer. When the coating layer is a point (adhesive) adhesive layer, the first protective layer or the second protective layer may be directly formed on the coating layer. When the coating layer is a non-adhesive layer, for example, a primer layer, the first protective layer or the second protective layer may be adhered or adhered to the coating layer by a point (adhesive) adhesive layer.

The liquid crystal display device of the present invention may include the polarizing plate of the present invention.

In one embodiment, the liquid crystal display includes a liquid crystal panel, a polarizing plate of the present invention (light source side polarizing plate) laminated on a light incident surface of a liquid crystal panel, and a polarizing plate (viewing side polarizing plate) disposed on a light emitting surface of a liquid crystal panel. The polarizing plate disposed on the light exit surface includes a polarizing plate commonly known to those skilled in the art. The liquid crystal display includes a light source on the lower surface of the light source side polarizing plate. The light source may include a light source having a continuous emission spectrum. For example, the light source is a white LED (White LED) light source, a quantum dot (QD) light source, a metal fluoride red phosphor light source, specifically a KSF (K ₂ SiF ₆ :Mn ^{4 +} ) phosphor or a KTF (K ₂ TiF ₆ : Mn ^{4 +} ) phosphor-containing light source and the like. The liquid crystal panel may include conventional liquid crystal panels such as VA mode, IPS mode, and TN mode.

Hereinafter, the configuration and operation of the present invention will be described in more detail through preferred embodiments of the present invention. However, the following examples are intended to help understanding of the present invention, and the scope of the present invention is not limited to the following examples.

Synthesis Example 1

1 kg of a mixed solvent in which water and propylene glycol monoethyl ether acetate (PEGMEA) were mixed in a 1:80 weight ratio was added to a 3-neck flask, and 1 g of a 60% HNO ₃ aqueous solution was added as a catalyst while maintaining at 25°C. Subsequently, a mixture of methyltrimethoxysilane, tetraethylorthosilicate, and bis(trimethoxysilyl)ethane as a monomer was added at a molar ratio of 0.55:0.40:0.05. After all of the solvent, monomer and catalyst were added, the temperature was raised to 60° C., and a condensation polymerization reaction was performed while heating to reflux for 72 hours. When the molecular weight (in terms of polystyrene) of the obtained carbosilane-siloxane copolymer was measured by GPC, the weight average molecular weight was 4,000.

Synthesis Example 2

After adding 570 g of isopropyl alcohol to a 1-liter 4-neck jacketed reactor, methyltrimethoxysilane, tetraethylorthosilicate, and bis(trimethoxysilyl)ethane were maintained at 25°C at a molar ratio of 0.55:0.40:0.05. The mixed mixture was added. Thereafter, 1 g of a Tetramethylammonium hydroxide (TMAH) aqueous solution having a concentration of 20% and 27 g of distilled water were mixed, and then dropped into the jacket reactor with one-drop and stirred. Thereafter, the reactor was heated to 60° C. and the silicone polymer was grown to obtain a carbosilane-siloxane copolymer. When the molecular weight (in terms of polystyrene) of the obtained carbosilane-siloxane copolymer was measured by GPC, the weight average molecular weight was 50,000.

Example One

The polyvinyl alcohol film was uniaxially stretched 3 times at 60°C and adsorbed iodine, and then stretched 2.5 times in a boric acid aqueous solution at 40°C to prepare a polarizer (thickness: 22 µm).

PET film on the light incident surface of the polarizer (Toyobo, thickness: 80 μm, Re: 10,000 nm at a wavelength of 550 nm), COP film on the light exit surface of the polarizer (ZEON, thickness: 80 μm, Re: 52 nm at a wavelength of 550 nm) , Rth: 125nm) were respectively bonded with a polarizing plate adhesive (Z-200, Nippon Goshei) to prepare a polarizing film.

The composition for the coating layer was 13.0% by weight based on the solid content of the carbosilane-siloxane copolymer of Synthesis Example 1, and 5.0% by weight based on the organic polymer solid content obtained by mixing PPO (Mn=2,000, propylene oxide polymer) and cetyltrimethylammonium chloride in a 5:5 weight ratio. , Surfactant (F-552) It was prepared by mixing 0.01% based on solid content, dissolving with diisobutyl ketone for 30 minutes so that the solid content concentration was 15.0% by weight, and then filtering with a 0.1 μm millipore filter.

A coating layer (refractive index: 1.31) is formed by coating and coating the composition for the prepared coating layer (refractive index: 1.31) to a thickness of 1 μm on one surface of a brightness enhancing film (NRP300, Toray Chemical, reflective polarizing film), and preparing the above. An acrylic adhesive (refractive index 1.47) was further coated to a thickness of 20 μm on one side of one coating layer. The acrylic adhesive was prepared by mixing 100 g of an acrylic copolymer adhesive resin (PL-8540, SAIDEN) with 80 g of methyl ethyl ketone as a diluting solvent and stirring at 500 rpm for 30 minutes.

A polarizing plate in which a COP film-a polarizer-a PET film-an adhesive layer-a coating layer-a brightness enhancing film was sequentially stacked was prepared by laminating the brightness improving film having the coating layer and the adhesive layer formed on the PET film side of the prepared polarizing film. .

Example 2

The composition for the coating layer was 3.0 wt% based on the solid content of the carbosilane-siloxane copolymer of Synthesis Example 2, 3.0 wt% based on the organic polymer solid content of PPO (Mn=2,000) and cetyltrimethylammonium chloride in a 5:5 weight ratio, Surfactant (F -552) It was prepared by mixing 0.01% based on solid content, dissolving with diisobutyl ketone for 30 minutes to be 6.0% by weight based on solid content, and filtering with a millipore filter of 0.1 µm.

In Example 1, a polarizing plate was prepared in the same manner, except that the refractive index of the coating layer was changed to 1.22 using the composition for a coating layer prepared above.

Example 3

In Example 2, the same method as in Example 2 was performed without laminating a PET film on one side of the polarizer, thereby producing a polarizing plate in which COP films-polarizers-adhesive layers-coating layers-brightness enhancing films were sequentially stacked.

Comparative example One

In Example 1, except that the thickness of the adhesive layer (refractive index: 1.47) was changed to 15 μm and the coating layer was not formed, the same method as in Example 1 was carried out to perform COP film-polarizer-PET film-adhesive layer-luminance A polarizing plate in which the enhancement films were sequentially stacked was prepared.

Reference example One

A polarizing film in which COP films prepared in the same manner as in Example 1-polarizers-PET films were sequentially stacked was used as a polarizing plate.

The following physical properties were evaluated for the polarizing plates of Examples and Comparative Examples, and the results are shown in Table 1 below.

(1) Relative luminance (unit: %): A liquid crystal display device comprising an edge type LED light source by assembling a module for an LED light source, a light guide plate, and a liquid crystal display device using the polarizing plates of Examples and Comparative Examples (polarizing plates of Examples and Comparative Examples) Samsung TV (55-inch, 16-year manufacturing model name: UN55KS8000F), except that is used as a light source-side polarizing plate was prepared. Using the EZCONTRAST X88RC (EZXL-176R-F422A4, ELDIM Co., Ltd.) for the manufactured liquid crystal display module, white mode and black mode are respectively performed in front of the spherical coordinate system (0°, 0°). The luminance value was measured at. (Luminance values in Examples and Comparative Examples/Luminance values in Reference Example 1) Relative luminance was calculated in the white mode and the black mode, respectively, by x100.

In Reference Example 1, a luminance-enhancing film used in Example 1 was disposed on a lower surface of a polarizing film to prepare a liquid crystal display device.

(2) Contrast ratio (unit: %): The contrast ratio was calculated using the values obtained in (1). (Relative luminance in white mode/relative luminance in black mode) The contrast ratio was calculated by x100.

(3) Polarization degree (unit: %): The polarization degree of the polarizing plates of Examples and Comparative Examples was measured using JASCO (V-7100).

Example Comparative example One 2 3 One Refractive index of coating layer 1.31 1.22 1.22 1.47
(Adhesive layer) Relative luminance @White mode 96 97 98 94 @Black Mode 111 107 104 113 Contrast 86 91 94 83 Polarization degree 99.993 99.994 99.996 99.995

As shown in Table 1, the polarizing plate of the present invention minimizes the luminance loss and contrast ratio loss of light emitted through the polarizing film from the luminance-enhancing film in the laminate of the polarizing film and the luminance-enhancing film, and has excellent polarization. Further, the overall thickness of the laminate of the brightness enhancing film can be reduced.

On the other hand, in Comparative Example 1 outside the refractive index range of the coating layer of the present invention, the contrast ratio was Arthur's, so the contrast ratio was lost.

Simple modifications or changes of the present invention can be easily carried out by those skilled in the art, and all such modifications or changes can be considered to be included in the scope of the present invention.

Claims (17)

Polarizing film; And a brightness enhancing film laminated on the light incident surface of the polarizing film, wherein a coating layer having a refractive index of 1.1 or more and 1.4 or less is directly formed on the light emitting surface of the brightness enhancing film.
The polarizing plate according to claim 1, wherein the coating layer has a refractive index of 1.2 or more and 1.3 or less.
The polarizing plate of claim 1, wherein the coating layer is formed of a composition for a coating layer including a carbosilane-siloxane copolymer.
The polarizing plate according to claim 3, wherein the carbosilane-siloxane copolymer is represented by the following Chemical Formula 3:
[Formula 3]
(R ⁴ R ⁵ R ⁶ SiO _1/2 ) _M (R ⁷ R ⁸ SiO _2/2 ) _D (R ⁹ SiO _3/2 ) _T1 (SiO _3/2 -Y-SiO _3/2 ) _T2 (SiO _{4 /2} ) _Q
(In the formula 3,
R ⁴ to R ⁹ are hydrogen, C1 to C30 alkyl group, C2 to C30 alkenyl group, C6 to C30 aryl group, C3 to C30 cycloalkyl group, C1 to C30 alkoxy group, carboxyl group, R(C=O)-, R(C=O)O- (where R is a C1 to C30 alkyl group, C3 to C30 cycloalkyl group, C6 to C30 aryl group), epoxy group-containing monovalent organic group, (meth)acrylic group, (meth)acrylic A C1 to C30 alkyl group substituted with a (meth)acrylic group, a C1 to C30 alkyl group substituted with a (meth)acrylate, or a combination thereof,
Y is a C1 to C30 alkylene group, a C2 to C30 alkenylene group, a C3 to C30 cycloalkylene group, a C6 to C30 arylene group, or a combination thereof,
0≤M≤0.5, 0≤D≤0.5, 0<T1≤0.95, 0<T2≤0.2, 0<Q≤0.9, and M+D+T1+T2+Q=1).
The polarizing plate according to claim 4, wherein in the formula (3), M=0, D=0, 0.3≤T1≤0.9, 0.01≤T2≤0.15, 0.05≤Q≤0.65.
The polarizing plate of claim 3, wherein the cured product of the carbosilane-siloxane copolymer is contained in an amount of 50% to 99% by weight in the coating layer.
The polarizing plate of claim 3, wherein pores are formed in the coating layer.
The polarizing plate of claim 3, wherein the composition for the coating layer further includes a surfactant for forming pores.
According to claim 8, The surfactant for forming the pores will include an ammonium salt represented by the formula (4), polarizing plate:
[Formula 4]

(In the formula 4, R ^a to R ^d are each independently a C1 to C30 alkyl group,
X is a halogen atom).
The polarizing plate according to claim 1, wherein the coating layer comprises an adhesive layer having a refractive index of 1.1 or more and 1.4 or less.
The polarizing plate of claim 1, wherein the brightness enhancing film comprises a single layer or a multilayer reflective polarizing film.
The polarizing plate according to claim 1, wherein the brightness enhancement film has a refractive index of 1.4 or more and 1.8 or less in the uppermost layer.
The polarizing plate of claim 1, wherein the brightness enhancing film includes a core layer including a plurality of plate-like polymers therein.
The method of claim 1, wherein the polarizing film is a polarizer; A first protective layer formed on one surface of the polarizer; And a second protective layer formed on the other surface of the polarizer.
The polarizing plate according to claim 14, wherein the first protective layer has a plane direction retardation of 5,000 nm or more at a wavelength of 550 nm, and the second protective layer has a plane direction retardation (Re) of a wavelength of 550 nm or less of 60 nm or less.
The polarizing plate according to claim 14, wherein the first protective layer or the second protective layer is adhered to the coating layer by an adhesive layer having a refractive index of more than 1.4 and 1.6 or less.
Liquid crystal panel; And a polarizing plate of any one of claims 1 to 16 formed on a light incident surface of the liquid crystal panel.

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