KR20210147422A - Retardation film, polarizing plate comprising the same and optical display apparatus comprising the same - Google Patents

Abstract

Provided is a retardation film, a polarizing plate comprising the same, and an optical display device comprising the same, wherein the retardation film includes a substrate layer and a positive C plate retardation layer formed on at least one surface of the substrate layer, wherein the positive C plate retardation layer satisfying formula 1. Therefore, adhesion between the substrate layer and the positive C plate retardation layer is excellent.

Description

Retardation film, polarizing plate including same, and optical display device including same

The present invention relates to a retardation film, a polarizing plate including the same, and an optical display device including the same.

As the recent trend of thinning the polarizing plate continues, attempts to develop a retardation film including a base film and a coating layer by coating a composition for a coating layer on a base film rather than adhering two films by an adhesive layer are continuing. In the retardation film, the retardation is generally expressed by the coating layer rather than the base film. Therefore, increasing the adhesion between the base film and the coating layer is important when considering the use of the retardation film. In order to increase the adhesion, a method of changing one or more materials among the base film and the coating layer may be considered, but there is a limit to improving the adhesion.

Meanwhile, as one of the liquid crystal display devices, there is an IPS (in plane switching) mode liquid crystal display device. An IPS mode liquid crystal display displays an image by driving a nematic liquid crystal that is homogeneously oriented by a transverse electric field in the absence of an electric field. The liquid crystal display in IPS mode has an advantage in that the viewing angle is wider than that of liquid crystal displays in other driving modes.

The liquid crystal display device in the IPS mode has a problem in that the color tone change (also referred to as lateral color shift) of the image depending on the viewing angle of the screen is large. Attempts have been made to overcome the color tone change of an image by using viewing angle compensation and multiple optical compensation films. However, these techniques were not sufficiently effective in improving the color tone change. Recently, as liquid crystal displays become thinner and larger, the color tone of the image becomes more prominent. Accordingly, there is a demand for an IPS mode liquid crystal display device that is thin and effective in a large area.

Background art of the present invention is disclosed in Japanese Patent Application Laid-Open No. 2006-251659 and the like.

It is an object of the present invention to provide a retardation film having excellent adhesion between a substrate layer and a positive C plate retardation layer and excellent warpage improvement effect.

Another object of the present invention is to provide a retardation film excellent in the effect of improving the front contrast ratio, the effect of improving the side color shift, and the effect of improving the sense of black.

Another object of the present invention is to provide a polarizing plate having excellent reliability, low warpage, and excellent front contrast ratio improvement effect, side color shift improvement effect, and black luminance improvement effect.

One aspect of the present invention is a retardation film.

1. The retardation film is a base layer; and a positive C plate retardation layer formed on at least one surface of the base layer, wherein the positive C plate retardation layer satisfies the following Equation 1:

[Equation 1]

0 < A/B ≤ 1950

(In Equation 1 above,

A is the content of the first solvent in the positive C plate retardation layer (unit: mg/kg)

B is the thickness of the positive C plate retardation layer (unit: μm).

In 2.1, A/B in Equation 1 may be 100 to 1800.

In 3.1-2, in Formula 1, A may be 500 mg/kg to 15,000 mg/kg, and B may be 15 μm or less.

In 4.1-3, the base layer may include an optically anisotropic film or an optically isotropic film.

In 5.1-4, the base layer may include a film including a cellulose ester-based resin.

In 6.1-5, the positive C plate retardation layer may contain at least one of a cellulose ester compound, an aromatic compound, or a polymer thereof.

In 7.1-6, the first solvent may include a solvent that dissolves the base layer.

In 8.1-7, the first solvent may include a solvent having a boiling point of 60°C to 200°C.

In 9.8, the first solvent may include one or more of propylene glycol methyl ether, methyl isopropyl ketone, methyl isobutyl ketone, toluene, and xylene.

In 10.1-9, the positive C plate retardation layer may further include a second solvent having a boiling point of 30°C to 150°C.

In 11.10, the second solvent may include at least one of methyl ethyl ketone, methanol, ethyl acetate, dichloromethane, cyclopentanone, tetrahydrofuran, and methyl tertiary butyl ether.

In 12.1-11, the positive C plate retardation layer may satisfy at least one of Equation 2 and Equation 3 below:

[Equation 2]

Re(450)/Re(550) > Re(650)/Re(550)

(In Equation 2, Re (450), Re (550), and Re (650) are as described below)

[Equation 3]

｜Rth(450)｜/｜Rth(550)｜ > ｜Rth(650)｜/｜Rth(550)｜

(In Equation 3, Rth(450), Rth(550), and Rth(650) are as described below).

In 13.1-12, the retardation film may satisfy at least one of Equation 4 and Equation 5 below:

[Equation 4]

Re(450)/Re(550) > Re(650)/Re(550)

(In Equation 4, Re (450), Re (550), and Re (650) are as described below)

[Equation 5]

｜Rth(450)｜/｜Rth(550)｜ > ｜Rth(650)｜/｜Rth(550)｜

(In Equation 5, Rth(450), Rth(550), and Rth(650) are as described below).

In 14.13, Re(450)/Re(550) in Equation 4 may be 0.1 to 10, and Re(650)/Re(550) may be 0.1 to 5.

In 15.13, in Equation 5, |Rth(450)|/|Rth(550)| may be 0.1 to 10, and |Rth(650)|/|Rth(550)| may be 0.1 to 5.

Another aspect of the present invention is a polarizing plate.

16. The polarizing plate contains the retardation film of the present invention.

In 17.16, the polarizing plate may include a polarizer, the retardation film disposed on a lower surface that is a light incident surface of the polarizer, and a protective layer disposed on an upper surface that is a light output surface of the polarizer.

In 18.17, when an axis having a high refractive index in an in-plane direction of the polarizer is referred to as a reference (0°), an angle formed by an axis having a low refractive index in an in-plane direction of the protective layer may be -5° to +5°.

In 19.17-18, the high refractive index axis is a machine direction (MD) of the polarizer, and the low refractive index axis is a mechanical direction, a transverse direction (TD) or an inclination direction with respect to the width direction of the protective layer. can be

In 20.17-19, the passivation layer may have an in-plane retardation of 5000 nm or more at a wavelength of 550 nm.

In 21.18-20, the base layer and the positive C plate retardation layer may be stacked in this order from the lower surface of the polarizer, or the positive C plate retardation layer and the base layer may be stacked in this order from the lower surface of the polarizer .

Another aspect of the present invention is an optical display device.

The optical display device includes the polarizing plate of the present invention.

The present invention provides a retardation film having excellent adhesion between the substrate layer and the positive C plate retardation layer and excellent warpage improvement effect.

The present invention provides a retardation film excellent in the effect of improving the front contrast ratio, the effect of improving the side color shift, and the effect of improving the sense of blackness.

The present invention provides a polarizing plate having excellent reliability, low warpage, and excellent front contrast ratio improvement effect, side color shift improvement effect, and black luminous effect improvement effect.

1 is a cross-sectional view of a polarizing plate according to an embodiment of the present invention.
FIG. 2 is a conceptual diagram illustrating a relationship between an axis having a high refractive index in an in-plane direction of a polarizer and an axis having a low refractive index in an in-plane direction of a protective layer of the polarizing plate of FIG. 1 .

With reference to the accompanying drawings, the present invention will be described in detail so that those of ordinary skill in the art can easily carry out the present invention. The present invention may be embodied in many different forms and is not limited to the embodiments described herein. In order to clearly explain 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 components throughout the specification. The length and size of each component in the drawings are for explaining 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 based on the drawings, and depending on the perspective of the city, "upper" may be changed to "lower" and "lower" to "upper", and "on" or What is referred to as “on” may include cases where other structures are interposed in the middle as well as immediately above. On the other hand, reference to “directly on”, “directly on” or “directly formed” or “directly formed directly on” means without intervening other structures.

In this specification, "in-plane retardation (Re)," "thickness direction retardation (Rth)," and "degree of biaxiality (NZ)" are expressed by the following formulas A, B, and C:

[Formula A]

Re = (nx - ny) x d

[Formula B]

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

[Formula C]

NZ = (nx - nz)/(nx - ny)

(In the above formulas A, B, and C, nx, ny, and nz are the refractive indices of the optical element in the x-axis direction, the y-axis direction of the optical element, and the thickness direction, respectively, at the measurement wavelength, and d is the thickness of the optical element (unit: nm)). The measurement wavelength may be 450 nm, 550 nm and/or 650 nm.

In the present invention, the x-axis direction is defined as a slow axis direction of the optical element, and the y-axis direction is defined as a fast axis direction of the optical element. The optical element may be a positive C plate retardation layer, a base layer, and/or a protective layer.

As used herein, “(meth)acryl” means acrylic and/or methacrylic.

In the present specification, "front" and "side" are, respectively, based on the horizontal direction, when (θ, φ) by a spherical coordinate system, the front is (0°, 0°), and the left end Let the point be (90°, 0°) and the right end point (90°, 180°), the sides are from (60°, 45°) to (60°, 135°) or (45°, 45°) to (45°, 135°).

In the present specification, "content of the first solvent in the positive C plate retardation layer" may be analyzed by gas chromatography. For detailed analysis methods by gas chromatography, refer to the following experimental examples.

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

The retardation film of the present invention has excellent adhesion between the base layer and the positive C plate retardation layer, and has an excellent effect of lowering warpage when combined with a polarizer. Through this, the retardation film can be applied to a large-area light emitting device panel or a liquid crystal panel.

In addition, the retardation film of the present invention provided the effect of improving the front contrast ratio and the side color shift by making the difference in left and right luminance similar without causing the internal polarization of the positive C plate retardation layer to be resolved. The front contrast ratio is calculated as the ratio of the luminance in the white mode to the luminance in the black mode ((luminance in white mode/(luminance in black mode)). In addition, the retardation film of the present invention is included in the polarizing plate, By implementing true black by lowering light leakage, the effect of improving the black visual perception is increased Thus, in one embodiment, the retardation film of the present invention may be used as a retardation film for IPS mode.

Hereinafter, the retardation film of an embodiment of the present invention will be described.

The retardation film of this embodiment includes a base layer; and a positive C plate retardation layer formed on at least one surface of the base layer, wherein the positive C plate retardation layer satisfies the following Equation 1:

[Equation 1]

0 < A/B ≤ 1950

(In Equation 1 above,

A is the content of the first solvent in the positive C plate retardation layer (unit: mg/kg)

B is the thickness of the positive C plate retardation layer (unit: μm).

In the present invention, a positive C plate retardation layer was introduced among retardation films for use in a polarizing plate for IPS mode. In addition, by satisfying Equation 1, the positive C plate retardation layer has excellent adhesion to the base layer, and the effect of lowering the warpage when combined with the polarizer, the effect of improving the front contrast ratio and the side color shift may be excellent.

Equation 1 is the ratio of the content of the first solvent in the positive C plate retardation layer to the thickness of the positive C plate retardation layer. That is, Equation 1 means the content of the first solvent remaining in the positive C plate retardation layer per unit thickness of the positive C plate retardation layer.

Specifically, A/B in Equation 1 may be 100 to 1800, more specifically 200 to 1800. In the above range, the above-described effect may be better realized and the retardation film may be easily manufactured.

In Formula 1, A may be 500 mg/kg to 15,000 mg/kg, specifically 800 mg/kg to 12,000 mg/kg, and more specifically 900 mg/kg to 8,500 mg/kg. In the above range, Equation 1 may be easily reached, and reliability of the retardation film may be increased.

The positive C plate retardation layer, ie, B in Equation 1, may have a thickness of 15 μm or less, specifically more than 0 μm and 10 μm or less, more specifically 0.5 μm to 10 μm, and 1 μm to 7 μm. In the above range, Equation 1 can be easily reached, and it can be used for the retardation film.

The positive C plate retardation layer is formed directly on the base layer. The above “directly” means that no other adhesive layer, adhesive layer and/or optical layer is formed between the substrate layer and the positive C plate retardation layer.

Hereinafter, each configuration of the retardation film will be described in detail.

base layer

When forming the positive C plate retardation layer, the base layer may support the positive C plate retardation layer as a coating adherend of the composition for the positive C plate retardation layer.

A positive C plate retardation layer is formed on at least one surface of the base layer. In one embodiment, a positive C plate retardation layer may be formed on one surface of the base layer. At this time, at least one of a retardation film, a retardation coating layer, an adhesive layer, and an adhesive layer may be additionally formed on the other surface of the base layer.

In one embodiment, the base layer may be an optically anisotropic film or an optically isotropic film.

In one embodiment, the base layer may have an in-plane retardation of 10 nm or less at a wavelength of 550 nm, for example, 0 nm to 5 nm. In the above range, light incident to the retardation film may not be affected or light emitted from the positive C plate retardation layer may not be affected.

The base layer may have a thickness direction retardation of -10 nm to 10 nm at a wavelength of 550 nm. In the above range, light incident to the retardation film may not be affected or light emitted from the positive C plate retardation layer may not be affected.

The base layer may use a stretched film or may include an unstretched film. The unstretched film may minimize the influence on the shrinkage of the positive C plate retardation layer when the positive C plate retardation layer is formed.

In one embodiment, the base layer may include an optically transparent resin film. For example, the base layer is a cellulose ester-based resin containing triacetyl cellulose, norbornane, a cyclic polyolefin (COP)-based resin containing amorphous cyclic polyolefin, polycarbonate-based resin, polyethylene terephthalate, poly Polyester-based resins including butylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, etc., polyethersulfone-based resins, polysulfone-based resins, polyamide-based resins, polyimide-based resins, acyclic-polyolefin-based resins , A film containing at least one of poly(meth)acrylate-based resins, polyvinyl alcohol-based resins, polyvinyl chloride-based resins, polyvinylidene chloride-based resins including polymethyl (meth)acrylate resins, etc. can do.

Preferably, the base layer may include a cellulose ester-based resin film containing triacetyl cellulose and the like. The cellulose ester-based resin film can easily reach Equation 1 when the positive C plate retardation layer formed of the cellulose ester-based composition described in detail below is formed.

The base layer may have a thickness of 10 μm to 200 μm, specifically 30 μm to 100 μm. In the above range, it may be used for the retardation film.

Positive C plate retardation layer

The positive C plate retardation layer means a layer in which nz > nx ≒ ny (nx, ny, and nz are the refractive indices of the retardation layer in the slow axis direction, the fast axis direction, and the thickness direction at a wavelength of 550 nm, respectively).

The positive C plate retardation layer contains at least one compound of a cellulose ester compound or a polymer thereof, an aromatic compound, or a polymer thereof. The compound may easily implement a positive C plate and may easily satisfy at least one of Equation 2 and Equation 3 detailed below. Hereinafter, a cellulose ester-type compound and an aromatic-type compound are demonstrated.

The cellulose ester-based compound includes at least one of a cellulose ester-based resin, a cellulose ester-based oligomer, and a cellulose ester-based monomer.

The cellulosic ester-based compound may comprise a condensation reaction product from the reaction of a hydroxyl group on cellulose with a carboxylic acid or carboxylic acid anhydride.

The cellulose ester-based compound may be regioselectively or randomly substituted. Regioselectivity can be determined by determining the relative degree of substitution at C6, C3, C2 on the cellulose ester by carbon 13 NMR. Cellulose esters can be prepared by conventional methods by contacting a cellulose solution with one or more C1 to C20 acylating agents for a contact time sufficient to provide a cellulose ester having the desired degree of substitution and polymerization.

Preferred acylating agents are one or more C1 to C20 straight or branched chain alkyl or aryl carboxylic acid anhydrides, carboxylic acid halides, diketones, or acetoacetic acid esters. Examples of anhydrides of carboxylic acids include acetic anhydride, propionic anhydride, butyric anhydride, isobutyric anhydride, valeric anhydride, hexanoic anhydride, 2-ethylhexanoic anhydride, nonanoic anhydride, lauric anhydride, palmitic anhydride, stearic anhydride, benzoic anhydride, substituted benzoic anhydride, phthalic anhydride, isophthalic anhydride. Examples of carboxylic acid halides include acetyl, propionyl, butyryl, hexanoyl, 2-ethylhexanoyl, lauroyl, palmitoyl, benzoyl, substituted benzoyl, and stearoyl chloride. Examples of the acetoacetic acid ester may include methylacetoacetate, ethylacetoacetate, propylacetoacetate, butylacetoacetate, and tert-butylacetoacetate. Most preferred acylating agents are C2 to C9 straight or branched chain alkyl carboxylic acid anhydrides such as acetic anhydride, propionic anhydride, butyric anhydride, 2-ethylhexanoic anhydride, nonanoic anhydride, stearic anhydride and the like.

Preferred examples of the cellulose ester-based compound may include, but are not limited to, cellulose acetate (CA), cellulose acetate propionate (CAP), and cellulose acetate butyrate (CAB).

In one embodiment, the cellulose ester-based compound may have a substituent of two different acyl groups. At least one or more of the acyl groups may include an aromatic substituent, and the cellulose ester-based compound may have a relative degree of substitution (RDS) of C6>C2>C3. C6 is the degree of substitution at carbon 6 of the cellulose ester, C2 is the degree of substitution at carbon 2 of the cellulose ester, and C3 is the degree of substitution at carbon 3 of the cellulose ester. The aromatic compound may include benzoate or substituted benzoate.

In another embodiment, the cellulose ester-based compound comprises a regioselective substituted cellulose ester compound having the following (a) and (b),

(a) a plurality of chromophore-acyl substituents;

(b) a plurality of pivaloyl substituents;

The cellulose ester-based compound has a hydroxyl group substitution degree of about 0.1 to about 1.2, the cellulose ester-based compound has a chromophore acyl substitution degree of about 0.4 to about 1.6, and the chromophore at carbon 2 of the cellulose ester-based compound The difference between the sum of the morphophore acyl substitution degree and the chromophore acyl substitution degree at carbon 3 and the chromophore acyl substitution degree at carbon 6 is about 0.1 to about 1.6, and the chromophore-acyl is i), (ii), (iii), (iv):

(i) (C _6-20 )aryl-acyl, wherein aryl is aryl unsubstituted or substituted with ^{1 to 5 R 1 ,}

(ii) heteroaryl, wherein heteroaryl is a 5 to 10 membered ring having 1 to 4 heteroatoms selected from N, O, S, wherein the heteroaryl is unsubstituted or 1 to 5 R replaced by ^1,

(iii)

The aryl is C _1-6 aryl,

said aryl is unsubstituted or substituted with ^{1 to 5 R 1 ,}

(iv)

The heteroaryl is a 5-10 membered ring having 1 to 4 heteroatoms selected from N, O, S, the heteroaryl is unsubstituted or substituted with ^{1 to 5 R 1 ,}

이다.each R ¹ is independently nitro, cyano, (C _1-6 )alkyl, halo(C _1-6 )alkyl, (C _6-20 )aryl-CO ₂ -, (C _6-20 )aryl , (C _1-6 )alkoxy, halo(C _1-6 )alkoxy, halo, 5-10 membered heteroaryl having 1 to 4 heteroatoms selected from N,O,S, or

am.

In one embodiment, the chromophore-acyl may be unsubstituted or substituted benzoyl, or unsubstituted or substituted naphthyl.

In one embodiment, the chromophore-acyl may be selected from the group:

또는

or

In this case, * represents the bonding site of the chromophore-acyl substituent to the oxygen of the cellulose ester.

In another embodiment, the cellulose ester-based compound is an acyl unit in which at least a part of the hydroxyl group [C2 hydroxyl group, C3 hydroxyl group, or C6 hydroxyl group] of the sugar monomer constituting cellulose is unsubstituted or substituted as represented by the following formula (1) It may include an ester polymer having

[Formula 1]

(in Formula 1, n is an integer of 1 or more)

Substituents for the cellulose ester-based polymer or acyl are, respectively, halogen, nitro, alkyl (eg, an alkyl group having 1 to 20 carbon atoms), alkenyl (eg, an alkenyl group having 2 to 20 carbon atoms), cycloalkyl (eg, 3 to carbon atoms). A cycloalkyl group having 10 carbon atoms), aryl (eg, an aryl group having 6 to 20 carbon atoms), heteroaryl (eg, an aryl group having 3 to 10 carbon atoms), alkoxy (eg, an alkoxy group having 1 to 20 carbon atoms), It may include at least one of acyl and halogen-containing functional groups. The substituents may be the same or different.

The "acyl" is, as known to those skilled in the art, RC(=O)-*(* is a connecting symbol, R is an alkyl group having 1 to 20 carbon atoms, cycloalkyl having 3 to 20 carbon atoms, aryl having 6 to 20 carbon atoms, or arylalkyl having 7 to 20 carbon atoms). The "acyl" is attached to the ring of cellulose via an ester bond in the cellulose (via an oxygen atom).

The above “alkyl”, “alkenyl”, “cycloalkyl”, “aryl”, “heteroaryl”, “alkoxy”, and “acyl” are each a non-halogenated non-halogen group for convenience. The composition for the second retardation layer may include the cellulose ester alone or a mixture of the cellulose ester.

The "halogen" means fluorine (F), Cl, Br or I, preferably means F.

The "halogen-containing functional group" is an organic functional group containing at least one halogen, and may include an aromatic, aliphatic or cycloaliphatic functional group. For example, the halogen-containing functional group is a halogen-substituted C1-C20 alkyl group, a halogen-substituted C2-C20 alkenyl group, a halogen-substituted C2-C20 alkynyl group, a halogen-substituted C3-C10 of a cycloalkyl group, a halogen-substituted C1-C20 alkoxy group, a halogen-substituted acyl group, a halogen-substituted C6-C20 aryl group, or a halogen-substituted C7-C20 arylalkyl group. , but not limited thereto.

The "halogen-substituted acyl group" is R'-C(=O)-*(* is a connecting symbol, R' is a halogen-substituted C1-C20 alkyl group, halogen-substituted C3-C20 cycloalkyl , halogen-substituted aryl having 6 to 20 carbon atoms or halogen-substituted arylalkyl having 7 to 20 carbon atoms). The "halogen substituted acyl group" is attached to the ring of cellulose via an ester bond in cellulose (via an oxygen atom).

Preferably, the positive C plate retardation layer composition may include a cellulose ester-based polymer substituted with an acyl, halogen or halogen-containing functional group. More preferably, the halogen may be fluorine. Halogen may be included in an amount of 1 wt% to 10 wt% of the cellulose ester-based polymer. Within the above range, the positive C plate retardation layer having the physical properties of the present invention may be easily manufactured, and the degree of circular polarization (ellipticity) may be further increased.

The cellulose ester-based polymer may be prepared by a conventional method known to those skilled in the art or may be purchased commercially and used to prepare a positive C plate retardation layer. For example, the cellulose ester-based polymer having acyl as a substituent may be prepared by reacting a sugar monomer or a polymer of a sugar monomer constituting the cellulose of Formula 1 with trifluoroacetic acid or trifluoroacetic anhydride, or trifluoroacetic acid, tri After reacting fluoroacetic anhydride, an acylating agent (eg, anhydride of a carboxylic acid, or carboxylic acid) is further reacted, or trifluoroacetic acid or trifluoroacetic anhydride and an acylating agent are reacted together. can be manufactured by

The aromatic compound includes a phenyl group, and may include a polystyrene-based compound, fluorobenzene, or difluorostyrene structure, but is not limited thereto.

The positive C plate retardation layer may include a cellulose ester compound or an aromatic compound; A solvent is included, and the solvent includes a coating layer formed of a composition including the first solvent. Specifically, the positive C plate retardation layer may be formed by coating the composition on a base layer and drying and/or curing the composition. The coating method may employ a conventional method known to those skilled in the art, for example, may be Mayer bar coating, die coating, and the like.

One or more of the cellulose ester-based compound, the aromatic compound, or a polymer thereof may be included in an amount of 1 wt% to 30 wt%, specifically 5 wt% to 20 wt% of the composition. In the above range, a positive C plate retardation layer can be implemented and Equation 1 can be easily reached.

The first solvent was selected to form a coating layer by applying the composition to a predetermined thickness, and to form a positive C plate retardation layer satisfying Equation 1 by drying and curing the coating layer under predetermined conditions.

In one embodiment, the first solvent may have a boiling point of 60°C to 200°C, specifically 70°C to 150°C. Within the above range, Equation 1 can be easily reached.

In one embodiment, the first solvent may include a solvent that dissolves the base layer. Since the first solvent controls the dissolution of the base layer, the formation of the positive C plate retardation layer may be facilitated.

For example, the first solvent may include at least one organic solvent selected from propylene glycol methyl ether, methyl isopropyl ketone, methyl isobutyl ketone, toluene, and xylene. Preferably, the first solvent may include at least one of propylene glycol methyl ether and methyl isopropyl ketone.

The first solvent may be included in an amount of 30 wt% to 95 wt%, specifically 40 wt% to 90 wt% of the solvent. In the above range, Equation 1 can be easily reached when the first solvent is used.

The solvent may further include a second solvent in addition to the first solvent. The second solvent may facilitate the formation of the positive C plate retardation layer when the first solvent is used in the above content.

The second solvent is a solvent having a lower boiling point than the first solvent, and has a boiling point of 30 °C to 150 °C, specifically 30 °C to 135 °C, 30 °C to 90 °C, 50 °C to 90 °C. Within the above range, Equation 1 can be easily reached.

In one embodiment, the second solvent may include at least one of a solvent that dissolves the substrate layer and a solvent that does not dissolve the substrate layer. Preferably, the second solvent may include a solvent that dissolves the base layer.

For example, the second solvent may include an organic solvent including at least one of methyl ethyl ketone, methanol, ethyl acetate, dichloromethane, cyclopentanone, tetrahydrofuran, and methyl tertiary butyl ether.

The second solvent may be included in an amount of 5 wt% to 70 wt%, specifically 10 wt% to 60 wt% of the solvent. In the above range, Equation 1 can be easily reached when the second solvent is used.

The positive C plate retardation layer may further include the second solvent.

The positive C plate retardation layer may be formed by drying the coating layer.

Formula 1 is the concentration of the cellulose ester compound or aromatic compound in the composition, the selection of the first solvent and/or the second solvent in the solvent, the content of the first solvent and/or the second solvent in the solvent, as well as the drying conditions and coating thickness.

Drying may include treating the coating layer at 40° C. to 200° C., specifically, at 60° C. to 150° C. for 1 minute to 10 minutes. Equation 1 can be easily reached within the above range.

The composition described above may further include a compound having an aromatic fused ring.

The compound having an aromatic fused ring serves to control the expression rate and wavelength dispersion of the thickness direction retardation of the positive C plate retardation layer. The compound having the aromatic fused ring may include naphthalene, anthracene, phenanthrene, pyrene, and Structure 1 or Structure 2 below. The additive having the aromatic fused ring may include 2-naphthyl benzoate, 2,6-naphthalene dicarboxylic acid diester of the following structure 3, naphthalene, abietic acid ester of the following structure 4, etc. Not limited to:

[Structure 1]

[Structure 2]

[Structure 3]

(In Structure 3, R is C1 to C20 alkyl or C6 to C20 aryl, n is an integer from 0 to 6)

[Structure 4]

(In Structure 4, R is C1 to C20 alkyl or C6 to C20 aryl)

Preferably, the compound having an aromatic fused ring may include at least one of naphthalene, anthracene, phenanthrene, pyrene, 2-naphthyl benzoate, and 2,6-naphthalene dicarboxylic acid diester of Structure 3 above. .

The compound having an aromatic fused ring may be included in an amount of 0 to 30% by weight, specifically 0.1% to 30% by weight, preferably 10% to 30% by weight of the positive C plate retardation layer. Within the above range, there may be effects of increasing thermal stability, increasing the retardation expression rate per thickness, and controlling wavelength dispersion.

The composition may further include additives such as plasticizers, stabilizers, UV absorbers, antiblock agents, slip agents, lubricants, dyes, pigments, retardation improvers, and the like.

The positive C plate retardation layer satisfies at least one of Equation 2 and Equation 3 below:

[Equation 2]

Re(450)/Re(550) > Re(650)/Re(550)

(In Equation 2, Re(450), Re(550), and Re(650) are in-plane retardation (unit: nm) at wavelengths of 450 nm, 550 nm, and 650 nm of the positive C plate retardation layer, respectively)

[Equation 3]

｜Rth(450)｜/｜Rth(550)｜ > ｜Rth(650)｜/｜Rth(550)｜

(In Equation 3, Rth(450), Rth(550), and Rth(650) are the thickness direction retardation (unit: nm) of the positive C plate retardation layer at wavelengths of 450 nm, 550 nm, and 650 nm, respectively).

The positive C plate retardation layer satisfies at least one of Re and Rth as in Equation 2 and Equation 3, thereby helping to obtain a front contrast ratio improvement effect, a side color shift improvement effect, and a black luminance improvement effect.

Preferably, the positive C plate retardation layer satisfies Equation 3, thereby further improving the effect of improving the front contrast ratio, the lateral color shift, and the black feeling.

More preferably, the positive C plate retardation layer satisfies both Equations 2 and 3, thereby further improving the effect of improving the front contrast ratio, the lateral color shift, and the black feeling.

The positive C plate retardation layer has Re(450)/Re(550) of 0.1 to 10, specifically 0.5 to 5, 1 to 5, Re(650)/Re(550), 0.1 to 5, specifically, 0.1 to 3, 0.1 to can be 2. Within the above range, Equation 2 can be easily implemented.

In one embodiment, the positive C plate retardation layer has Re (450) of 0 nm to 10 nm, specifically 0 nm to 7 nm, Re (550) 0 nm to 8 nm, specifically 0 nm to 5 nm, Re (650) 0 nm to 6 nm, specifically 0 nm to 3 nm. Within the above range, Equation 2 can be easily implemented.

The positive C plate retardation layer has |Rth(450)|/|Rth(550)| 550)| may be 0.1 to 5, specifically, 0.1 to 3, more specifically, 0.1 to 2. Within the above range, Equation 3 can be easily implemented.

In one embodiment, in the positive C plate retardation layer, Rth (450) is -200 nm to 0 nm, specifically -150 nm to 0 nm, Rth (550) is -180 nm to 0 nm, specifically -150 nm to 0 nm, Rth (650) is -160 nm to 0 nm may be specifically -130 nm to 0 nm. Within the above range, Equation 3 can be easily implemented.

The wavelength dispersion of the positive C plate retardation layer described above is at least one of the type and content of the solvent included in the composition, the coating thickness, the drying conditions, and the selection of the base layer while using the above-mentioned material for the positive C plate retardation layer. can be implemented by

In one embodiment, the retardation film, that is, the laminate of the base layer and the positive C plate retardation layer may satisfy at least one of Equation 4 and Equation 5 below. Through this, it can help to achieve the effect of improving the front contrast ratio and the lateral color shift:

[Equation 4]

Re(450)/Re(550) > Re(650)/Re(550)

(In Equation 4, Re(450), Re(550), and Re(650) are in-plane retardation (unit: nm) at wavelengths of 450 nm, 550 nm, and 650 nm of the retardation film, respectively)

[Equation 5]

｜Rth(450)｜/｜Rth(550)｜ > ｜Rth(650)｜/｜Rth(550)｜

(In Equation 5, Rth(450), Rth(550), and Rth(650) are thickness-direction retardation (unit: nm) of the retardation film at wavelengths of 450 nm, 550 nm, and 650 nm, respectively).

Retardation film is Re (450) / Re (550) 0.1 to 10, specifically 0.5 to 5, 1 to 5, Re (650) / Re (550) is 0.1 to 5, specifically 0.1 to 3, 0.1 to 2 can Within the above range, Equation 4 can be easily implemented.

In one embodiment, the retardation film has Re (450) 0 nm to 10 nm, specifically 0 nm to 7 nm, Re (550) 0 nm to 8 nm, specifically 0 nm to 5 nm, Re (650) 0 nm to 6 nm, specifically 0 nm to 3 nm can be Within the above range, Equation 4 can be easily implemented.

The retardation film has |Rth(450)|/|Rth(550)| Specifically, it may be 0.1 to 3, more specifically 0.1 to 2. Within the above range, Equation 5 can be easily implemented.

In one embodiment, the retardation film is Rth (450) is -200nm to 0nm specifically -150nm to 0nm, Rth (550) is -180nm to 0nm specifically -150nm to 0nm, Rth(650) is -160nm to 0nm specifically It can be -130nm to 0nm. Within the above range, Equation 5 can be easily implemented.

The wavelength dispersibility of the above-described retardation film can be realized by using the above-described material for the positive C plate retardation layer and at least one of the type and content of the solvent included in the composition, the coating thickness, the drying conditions, and the selection of the base layer. can

The polarizing plate of the present invention includes the retardation film of an embodiment of the present invention.

Hereinafter, a polarizing plate according to an embodiment of the present invention will be described with reference to FIGS. 1 and 2 .

Referring to FIG. 1 , the polarizing plate includes a polarizer 300 , a protective layer 100 , and a retardation film 200 . The retardation film 200 includes the retardation film of an embodiment of the present invention.

In the polarizing plate, the protective layer 100 is disposed on the upper surface of the polarizer 300 (the light emitting surface of the polarizer). The retardation film 200 is disposed on the lower surface of the polarizer 300 (the light incident surface of the polarizer).

The polarizing plate includes the retardation film of an embodiment of the present invention. Through this, the polarizing plate has excellent adhesion between the base layer and the positive C plate retardation layer, so that the reliability is excellent and the effect of lowering the warpage can be excellent.

Referring to FIG. 2 , when an axis 310 having a high refractive index in the in-plane direction of the polarizer 300 is referred to as a reference (0°), an angle formed by an axis 110 having a low refractive index in the in-plane direction of the protective layer 100 . (α) is -5° to +5°. In the above angle range, the effect of improving the front contrast ratio, the effect of improving the lateral color shift, and the effect of improving the sense of black may be obtained.

In this way, the polarizing plate controls the angle between the axis of the low refractive index of the protective layer and the axis of the high refractive index of the polarizer on the light exit surface of the polarizer, and at the same time controls the wavelength dispersion of the retardation film on the light incidence surface of the polarizer. Through this, the polarizing plate may have a front contrast ratio improvement effect, a side color shift improvement effect, and a black luminous effect improvement effect.

Accordingly, the polarizing plate may have an in-plane retardation of -10 nm to 10 nm, specifically, -5 nm to 5 nm at a wavelength of 550 nm. In the above range, the polarizing plate has less light leakage from the front and can realize true black in the panel.

When expressing "angle" in this specification, "+" means an angle in the clockwise direction when the reference is 0°, and "-" means an angle in the counterclockwise direction when the reference is 0° .

Specifically, in FIG. 2 , the angle α may be -4° to +4°, -3° to +3°, -2° to +2°, -1° to +1°, and more Specifically, it may be 0°. With the above-described effects in the above range, by enabling the manufacture of a polarizing plate by a roll-to-roll process, it is possible to increase the fairness and economic efficiency of the polarizing plate.

Hereinafter, each component of the polarizing plate will be described in detail.

polarizer

The polarizer 300 is an absorption type polarizer having a function of dividing incident light into two orthogonal polarization components, transmitting one polarization component and absorbing the other polarization component.

In an embodiment, an axis having a high refractive index among the in-plane directions of the polarizer may be an absorption axis of the polarizer, and an axis having a low refractive index may be a transmission axis of the polarizer.

In one embodiment, an axis having a high refractive index among in-plane directions of the polarizer may be a machine direction (MD) of the polarizer, and an axis having a low refractive index may be a transverse direction (TD) of the polarizer.

The light transmittance of the polarizer 300 may be 40% or more, specifically, 40% to 45%. The polarization degree of the polarizer 300 may be 95% or more, specifically 95% to 100%, and more specifically 98% to 100%. In the above range, the front contrast ratio can be further improved and durability can be improved.

The polarizer 300 may include a polarizer containing a dichroic dye and uniaxially stretched. Specifically, the polarizer containing a dichroic dye may include a polarizer manufactured by uniaxially stretching a base film for a polarizer by MD and dyeing it with a dichroic dye (eg, iodine or potassium iodide as an iodine-containing material). The base film for a polarizer may include a polyvinyl alcohol-based film or a derivative thereof, but is not limited thereto. The polarizer may be manufactured according to a conventional method known to those skilled in the art.

The polarizer 300 may have a thickness of 1 μm to 40 μm, specifically 5 μm to 30 μm, and more specifically 10 μm to 25 μm. Within the above range, it can be used for a polarizing plate.

protective layer

The protective layer 100 is disposed on the upper surface (light incident surface) of the polarizer 300 to protect the polarizer. The protective layer 100 may provide the effect of improving the front contrast ratio, the effect of improving the side color shift, and the effect of improving the sense of black through the above-described angle adjustment between the axes.

The protective layer 100 includes an axis having a high refractive index and an axis having a low refractive index in an in-plane direction. Here, the "axis with high refractive index" and "axis with low refractive index" are defined by relatively comparing refractive indices among the x-axis and y-axis, which are two axes in the in-plane direction of the protective layer. Although not particularly limited, an axis having a high refractive index and an axis having a low refractive index in the in-plane direction of the protective layer may be formed by stretching during the process of manufacturing the protective layer. For example, an axis having a high refractive index may be a slow axis, and an axis having a low refractive index may be a fast axis.

In one embodiment, an axis having a low refractive index in the in-plane direction of the passivation layer is a mechanical direction (MD, machine direction) of the passivation layer, and an axis having a high refractive index in the in-plane direction of the passivation layer is a transverse direction (TD) of the passivation layer. can be In this case, the protective layer may be a TD uniaxially stretched protective film or a TD uniaxially stretched coating layer, or an MD and TD biaxially stretched film, or an MD and TD biaxially stretched coating layer.

In another embodiment, an axis having a low refractive index in the in-plane direction of the passivation layer may be the width direction (TD) of the first passivation layer, and an axis having a high refractive index in the in-plane direction of the passivation layer may be a longitudinal direction (MD) of the first passivation layer. have. In this case, the protective layer may be an MD uniaxially stretched protective film or an MD uniaxially stretched coating layer, or an MD and TD biaxially stretched film, or an MD and TD biaxially stretched coating layer.

In another embodiment, an axis with a low refractive index among the in-plane directions of the protective layer may be inclined with respect to the width direction of the protective layer, and an axis with a high refractive index may be inclined with respect to the longitudinal direction of the protective layer. In this case, the protective layer may be a MD and TD biaxially oriented film or an MD and TD biaxially oriented coating layer.

In another embodiment, the protective layer may be an isotropic film.

Preferably, an axis with a low refractive index in the in-plane direction of the protective layer is the mechanical direction (MD) of the protective layer, and an axis with a high refractive index in the in-plane direction of the protective layer becomes the width direction (TD) of the protective layer, so that the axis with the above-described polarizer Considering the relationship, fairness and economic feasibility can be improved by enabling a roll-to-roll process when manufacturing a polarizing plate. Accordingly, only the above case will be described below.

The protective layer may include a TD uniaxially stretched protective film to have an axis having a low refractive index and an axis having a high refractive index in the in-plane direction.

In TD uniaxial stretching, the protective film may be manufactured by a protective film manufacturing method comprising the step of stretching the melt-extruded resin for protective film only in the TD direction by 2 to 10 times. In the range of the stretching ratio, an axis having a low refractive index and an axis having a high refractive index according to the present invention may be provided. Specifically, the draw ratio may be 3 to 8 times.

Stretching may be performed by at least one of dry stretching and wet stretching, and the stretching temperature is (Tg - 20)°C to (Tg + 50)°C, specifically 70°C to 150°C, based on the Tg of the resin for the protective layer. 80 °C to 130 °C is preferable, and more specifically, it may be 90 °C to 120 °C. In the above range, there may be uniformly the same stretching effect.

After stretching, the protective film may fix the axis and retardation of the protective film by heat-treating the protective film at a predetermined temperature without a stretching process. The protective film prepared by TD uniaxial stretching can be stably fixed to the axis and retardation by performing the above-described heat treatment. During the heat treatment, the temperature and time may be appropriately adjusted according to the material of the protective film.

The passivation layer may have a retardation within a predetermined range due to the axis having a low refractive index and an axis having a high refractive index. The retardation of the passivation layer may vary depending on the degree of elongation of the passivation layer, the refractive index of the axis having a low refractive index, the refractive index of the axis having a high refractive index, and the like.

In one embodiment, the protective layer may have an in-plane retardation (Re) of 5,000 nm or more at a wavelength of 550 nm, specifically 5,000 nm to 15,000 nm, and more specifically 5,000 nm to 12,000 nm. In the above range, there may be a front contrast ratio improvement effect, a rainbow mura suppression effect, and the like.

In one embodiment, the protective layer may have a thickness direction retardation (Rth) of 6,000 nm or more at a wavelength of 550 nm, specifically 6,000 nm to 15,000 nm, and more specifically 6,000 nm to 12,000 nm. Within the above range, there may be an effect of controlling unevenness due to birefringence, an effect of improving viewing angle characteristics in a liquid crystal display, and the like.

In one embodiment, the protective layer may have a degree of biaxiality (NZ) of 2.5 or less at a wavelength of 550 nm, specifically 1.0 to 2.2, more specifically 1.2 to 2.0, and most specifically 1.4 to 1.8. In the above range, there may be a stain control effect due to birefringence, an effect of maintaining the mechanical strength of the film, and the like.

In one embodiment, at a wavelength of 550 nm, in the protective layer, any one of a refractive index nx in an x-axis direction and a refractive index ny in a y-axis direction in an in-plane direction may be 1.65 or more. When both nx and ny are less than 1.65 or both nx and ny are 1.65 or more, rainbow blotches may occur due to birefringence due to a change in retardation value depending on the incident angle and wavelength when used as a protective layer. In one embodiment, nx may be 1.65 or more, specifically 1.67 to 1.75, and ny may be 1.45 to 1.55. In other embodiments, ny can be 1.65 or greater, specifically 1.67 to 1.75, more specifically 1.69 to 1.72, and nx can be 1.45 to 1.55. By setting the absolute value (|nx-ny|) of the difference between nx and ny to be 0.1 to 0.2, specifically 0.12 to 0.18, the viewing angle can be further improved and rainbow spots can be prevented from occurring.

In one embodiment, the protective layer 100 may include a film formed of an optically transparent resin. For example, the first protective layer may include a cellulose ester-based resin including triacetyl cellulose, norbornane, a cyclic polyolefin-based resin including amorphous cyclic polyolefin, polycarbonate-based resin, polyethylene terephthalate, polybutyl Polyester-based resins, polyethersulfone-based resins, polysulfone-based resins, polyamide-based resins, polyimide-based resins, non-cyclic-polyolefin-based resins, It may include a protective film including at least one of polyacrylate-based resin including polymethyl methacrylate resin, polyvinyl alcohol-based resin, polyvinyl chloride-based resin, and polyvinylidene chloride-based resin.

Preferably, the protective layer may include a polyester-based resin film including polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, and the like. Since the polyester-based resin film has low moisture permeability, the reliability of the polarizing plate may be improved.

The protective layer 100 may be a single layer, or when a plurality of single-layered resin films are laminated, or may include a film in which a plurality of laminates are integrally formed by co-extrusion.

In another embodiment, the protective layer 100 may be a protective coating layer. The protective coating layer may be formed of a conventional composition known to those skilled in the art.

The protective layer 100 may have a thickness of 1 μm to 100 μm, specifically 5 μm to 100 μm, 10 μm to 90 μm, and 15 μm to 85 μm. Within the above range, it can be used for a polarizing plate.

Although not shown in FIG. 1 , an additional functional coating layer such as a hard coating layer, an anti-fingerprint layer, and an anti-reflection layer may be further formed on the upper surface of the protective layer 100 . In addition, although not shown in FIG. 1 , the polarizer 300 and the protective layer 100 may be laminated by an adhesive layer and/or an adhesive layer.

retardation film

The retardation film 200 may be disposed on a lower surface (light incident surface) of the polarizer 300 to protect the polarizer. The retardation film 200 may help improve the front contrast ratio improvement effect, the side color shift improvement effect, and the black visual perception improvement effect of the present invention by controlling the light when the light incident from the liquid crystal panel is transmitted through the polarizer.

The retardation film 200 may be stacked in order of a base layer and a positive C plate retardation layer from the lower surface of the polarizer 300 . However, the present invention is not limited thereto. That is, the retardation film 200 may be stacked in the order of the positive C plate retardation layer and the base layer from the lower surface of the polarizer 300 .

Although not shown in FIG. 1 , an adhesive layer or an adhesive layer may be further formed on the lower surface of the retardation film 200 . The adhesive layer or the adhesive layer can fix the polarizing plate to an adherend, for example, a liquid crystal panel.

The optical display device of the present invention includes the retardation film of the present invention or the polarizing plate of the present invention. In one embodiment, the optical display device may include a light emitting device display device including an organic light emitting device display device, and an IPS liquid crystal display device.

In one embodiment, the liquid crystal display device includes a liquid crystal panel, a polarizing plate of the present invention laminated on the light exit surface of the liquid crystal panel (viewer-side polarizing plate), and a polarizing plate (light source-side polarizing plate) disposed on the light incident surface of the liquid crystal panel. The polarizing plate disposed on the light incident surface may include a polarizing plate commonly known to those skilled in the art.

The liquid crystal display includes a light source on a lower surface of a 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, quantum dot) light source, a metal fluoride red phosphor light source, specifically, a KSF (K ₂ SiF ₆ :Mn ⁴⁺ ) phosphor or KTF (K ₂ TiF ₆ : Mn ⁴⁺ ) a phosphor-containing light source and the like. The liquid crystal panel may be in an IPS mode, but is not limited thereto.

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 provided to aid understanding of the present invention, and the scope of the present invention is not limited thereto.

Example 1

Retardation film manufacturing

A composition for a positive C plate retardation layer was prepared by mixing a cellulose ester-based compound (Eastman) and a solvent of Table 1 below. The prepared composition was coated on the lower surface of a triacetyl cellulose (TAC) film (KONICA, KC4CT1W, thickness: 40 μm, wavelength 550 nm, Re: 0.10 nm, Rth: 0.30 nm, NZ: 0.8) to a predetermined thickness, and A retardation film was prepared by drying under the conditions shown in Table 1 below to form a positive C plate retardation layer on the lower surface of the TAC film.

Polarizer manufacturing

A polyvinyl alcohol film (KURARAY, VF-TS#4500, thickness: 45㎛) was uniaxially stretched twice at 30°C with the MD of the polyvinyl alcohol film, adsorbed iodine, and then stretched in an aqueous boric acid solution at 60°C to create a polarizer (thickness: 17 μm) was prepared. The maximum draw ratio is 6.5 times. An axis having a high refractive index among the in-plane directions of the polarizer is the absorption axis (MD) of the polarizer.

The upper surface of the prepared TAC film was adhered to the lower surface (light incident surface) of the prepared polarizer. A polyethylene terephthalate (PET) film (Toyobo Corporation, thickness: 80 μm, wavelength 550 nm, Re: 8,500 nm, Rth: 9,300 nm, NZ: 1.55, TD uniaxial) on the upper surface (light exit surface) of the prepared polarizer stretched film) was adhered. In the PET film, the axis with the low refractive index in the in-plane direction is the fast axis and is the MD of the PET film. When an axis having a high refractive index in the in-plane direction of the polarizer is 0°, an angle formed by an axis having a low refractive index in the in-plane direction of the PET film is 0°.

Examples 2 to 6

A retardation film and a polarizing plate were manufactured in the same manner as in Example 1, except that the retardation film manufacturing configuration in Example 1 was changed as shown in Table 1 below.

Comparative Example 1

A polarizing plate was manufactured in the same manner as in Example 1, except that in Example 1, a polarizing plate in which a PET film, a polarizer, and a TAC film were sequentially laminated without a +C plate retardation layer was manufactured.

Comparative Examples 2 to 3

A retardation film and a polarizing plate were manufactured in the same manner as in Example 1, except that the retardation film manufacturing configuration in Example 1 was changed as shown in Table 1 below.

Preparations of retardation films of Examples and Comparative Examples are shown in Table 1 below.

menstruum
(Solvent 1: Solvent 2) menstruum dry B of solvent 1
Percentage (wt%) of solvent 2
Percentage (wt%) Temperature
(℃) hour
(min) Example 1 PGME:MEK 65 35 80 6 4.5 Example 2 PGME:MEK 60 40 80 6 4.5 Example 3 PGME:MEK 55 45 80 6 1.2 Example 4 PGME:MEK 55 45 80 6 6.5 Example 5 MIPK: MEK 75 25 80 6 2.0 Example 6 MIPK:EA 70 30 80 6 2.0 Comparative Example 1 - - - - - 0 Comparative Example 2 PGME:MEK 20 80 80 6 4.5 Comparative Example 3 MIPK:EA 20 80 80 6 4.5

*In Table 1,

PGME is propylene glycol methyl ether

MEK is methyl ethyl ketone

MIPK is methyl isopropyl ketone

EA is ethyl acetate

B is the thickness of the positive C plate retardation layer (unit: μm)

The retardation films and polarizing plates of Examples and Comparative Examples were evaluated for physical properties in Table 2 below.

(1) Content of PGME or MIPK in the positive C plate retardation layer (unit: mg/kg): The content of PGME and MIPK was measured for the retardation film by gas chromatography. Gas chromatography was performed using SHIMADZU's GC 2010 Plus Series injector, Series Auto sampler. After accurately quantifying 0.2 to 0.3 g of the sample to be measured (positive C plate retardation layer) in a 20 mL vial, add 9 mL of AC (acetone), dissolve it using a shaker for about 2 hours or more, and accurately measure and add 1 mL of the internal standard solution. After stirring well, the solution was filtered through a 0.45 μm filter to prepare a pre-treated solution. The prepared solution is injected into gas chromatography through an injector, the temperature is raised at 40 ° C. for 3 min, the temperature increase rate is 20 ° C./min, and the content (mg) of PGME or MIPK in the sample (kg) at 280 ° C. for 3 min. was measured.

(2) Wavelength dispersibility of retardation film including positive C plate layer: Using Axoscan (Axometry) for retardation film, the in-plane retardation and thickness direction retardation at wavelengths 450 nm, 550 nm and 650 nm were calculated to calculate the wavelength dispersion. .

(3) Adhesion: Adhesiveness was evaluated by a cross-cut method with respect to the retardation film. The retardation film was cut into a square size of width x length (10 cm x 10 cm), and only 100 sections were prepared by cutting only the positive C plate retardation layer with 10 columns and 10 columns. When the adhesive tape (No. 405 Tape, Nichiban Co.) was attached to the positive C plate retardation layer surface and the adhesive tape was peeled off, the number of fragments remaining without peeling was counted. The greater the number of remaining fragments, the better the adhesion.

(4) Warpage value (unit: mm): The polarizing plate with the retardation film prepared in Examples and Comparative Examples was cut to the size of MD of the polarizer x TD of the polarizer (219.8mm x 124.15mm), and the retardation among the cut specimens A pressure-sensitive adhesive was attached to the film side, and a specimen for measuring warpage was prepared by laminating it to a 10.1 inch, 0.5T glass plate using the pressure-sensitive adhesive as a medium. The prepared specimen was placed on a flat bottom surface with the polarizing plate facing upward. The height (H1) at which the polarizing plate floats on the floor at 22°C was measured using a three-dimensional measuring instrument.

Then, after the specimen was left at 60° C. for 240 hours, the height (H2) at which the polarizing plate floats from the bottom was measured at 22° C. in the same manner as above.

The warpage value was evaluated by H2-H1. If the warpage value is 0.5 mm or less, the reliability of the polarizing plate is high and can be used.

(5) Front contrast ratio (CR, unit: %): Liquid crystal display devices using the polarizing plates of Examples and Comparative Examples (Except for using the polarizing plates of Examples and Comparative Examples as a light source side polarizing plate, FULLHD LED TV ADONIS (43 inches) , model name: TS-430) and the same configuration) were prepared. The luminance in each of white mode and black mode in front of the spherical coordinate system (0°, 0°) using a spectroradiometer (TOPCON SR-3A) for the module for the liquid crystal display manufactured above. The values were measured. The front contrast ratio is calculated as the ratio of the luminance in the white mode to the luminance in the black mode. The higher the front contrast ratio, the better, but it is applicable only when it is 1300 or more in IPS mode liquid crystal display for large area TV.

(6) Lateral color shift (Δx,y, no units): The module was assembled in the same way as (5). Using EZCONTRAST X88RC (EZXL-176R-F422A4, ELDIM Co., Ltd.), the color coordinates x and y at (45°, 45°) and (45°, 135°) were measured as (θ, φ), respectively. x,y was calculated as the distance of the x,y coordinates from (45°, 45°), (45°, 135°). Δx,y must be less than 0.1 to reduce the side color difference, so it can be applied to an IPS mode liquid crystal display.

A B A/B Re(450)/
Re(550) Re(650)/
Re(550) |Rth(450)|/ |Rth(550)| |Rth(650) |/|Rth(550)| adhesion deflection value CR △
x, y Example 1 989 4.5 220 3.5 0.8 1.4 0.9 100 0.4 1420 0.04 Example 2 6421 4.5 1427 3.4 1.2 1.6 1.1 100 0.4 1380 0.06 Example 3 1235 1.2 1029 2.2 0.7 1.3 0.8 100 0.5 1410 0.08 Example 4 8240 6.5 1268 4.6 0.9 2.9 0.6 100 0.3 1370 0.02 Example 5 3500 2.0 1750 1.9 1.1 1.5 1.1 100 0.45 1400 0.07 Example 6 1500 2.0 750 1.2 0.3 1.4 0.9 100 0.45 1390 0.07 Comparative Example 1 0 0 0 - - - - - 1.2 1250 0.16 Comparative Example 2 8900 4.5 1978 3.1 0.4 1.8 0.8 80 0.4 1000 0.07 Comparative Example 3 12000 4.5 2667 3.6 1.2 1.4 1.4 40 0.4 700 0.07

* In Table 2 above,

A is the content of the first solvent (PGME or MEK) in the positive C plate retardation layer (unit: mg/kg)

B is the thickness of the positive C plate retardation layer (unit: μm)

As shown in Table 2, the retardation film of the present invention had excellent adhesion between the base layer and the positive C plate retardation layer and the effect of lowering the warpage. In addition, the retardation film of the present invention was excellent in the front contrast ratio improvement effect, the side color shift improvement effect, and the black luminous effect improvement effect.

On the other hand, Comparative Example 1, which does not include a positive C plate retardation layer among the retardation films of the present invention, had a large warpage value and a poor lateral color shift. Comparative Examples 2 to 3 having a positive C plate retardation layer but not satisfying Equation 1 of the present invention did not have good adhesion and had poor front contrast ratio.

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

Claims (22)

base layer; and a positive C plate retardation layer formed on at least one surface of the base layer,
The positive C plate retardation layer will satisfy the following formula 1, retardation film:
[Equation 1]
0 < A/B ≤ 1950
(In Equation 1 above,
A is the content of the first solvent in the positive C plate retardation layer (unit: mg/kg)
B is the thickness of the positive C plate retardation layer (unit: μm).
The retardation film of claim 1, wherein A/B in Formula 1 is 100 to 1800.
The retardation film according to claim 1, wherein in Formula 1, A is 500 mg/kg to 15,000 mg/kg, and B is 15 μm or less.
The retardation film of claim 1, wherein the base layer comprises an optically anisotropic film or an optically isotropic film.
The retardation film of claim 1, wherein the base layer comprises a film including a cellulose ester-based resin.
The retardation film according to claim 1, wherein the positive C plate retardation layer contains at least one of a cellulose ester compound, an aromatic compound, or a polymer thereof.
The retardation film of claim 1, wherein the first solvent comprises a solvent for dissolving the base layer.
The retardation film of claim 1, wherein the first solvent includes a solvent having a boiling point of 60°C to 200°C.
The retardation film according to claim 8, wherein the first solvent comprises at least one of propylene glycol methyl ether, methyl isopropyl ketone, methyl isobutyl ketone, toluene, and xylene.
The retardation film of claim 1, wherein the positive C plate retardation layer further comprises a second solvent having a boiling point of 30 to 150°C.
The retardation film of claim 10 , wherein the second solvent comprises at least one of methyl ethyl ketone, methanol, ethyl acetate, dichloromethane, cyclopentanone, tetrahydrofuran, and methyl tertiary butyl ether.
The retardation film of claim 1 , wherein the positive C plate retardation layer satisfies at least one of Equation 2 and Equation 3 below:
[Equation 2]
Re(450)/Re(550) > Re(650)/Re(550)
(In Equation 2, Re(450), Re(550), and Re(650) are in-plane retardation (unit: nm) at wavelengths of 450 nm, 550 nm, and 650 nm of the positive C plate retardation layer, respectively)
[Equation 3]
｜Rth(450)｜/｜Rth(550)｜ > ｜Rth(650)｜/｜Rth(550)｜
(In Equation 3, Rth(450), Rth(550), and Rth(650) are the thickness direction retardation (unit: nm) of the positive C plate retardation layer at wavelengths of 450 nm, 550 nm, and 650 nm, respectively).
The retardation film according to claim 1, wherein the retardation film satisfies at least one of Equation 4 and Equation 5 below:
[Equation 4]
Re(450)/Re(550) > Re(650)/Re(550)
(In Equation 4, Re(450), Re(550), and Re(650) are in-plane retardation (unit: nm) at wavelengths of 450 nm, 550 nm, and 650 nm of the retardation film, respectively)
[Equation 5]
｜Rth(450)｜/｜Rth(550)｜ > ｜Rth(650)｜/｜Rth(550)｜
(In Equation 5, Rth(450), Rth(550), and Rth(650) are thickness-direction retardation (unit: nm) of the retardation film at wavelengths of 450 nm, 550 nm, and 650 nm, respectively).
According to claim 13, Re (450) / Re (550) in the formula 4 is 0.1 to 10, Re (650) / Re (550) will be 0.1 to 5, the retardation film.
The method according to claim 13, wherein |Rth(450)|/|Rth(550)| in Equation 5 is 0.1 to 10, and |Rth(650)|/|Rth(550)| is 0.1 to 5 , retardation film.
The polarizing plate comprising the retardation film of any one of claims 1 to 15.
The polarizing plate of claim 16 , wherein the polarizing plate includes a polarizer, the retardation film disposed on a lower surface that is a light incident surface of the polarizer, and a protective layer disposed on an upper surface that is a light output surface of the polarizer.
The method according to claim 17, wherein when the axis of the high refractive index in the in-plane direction of the polarizer is referred to as the reference (0°), the angle formed by the axis of the low refractive index in the in-plane direction of the protective layer is -5° to +5° , polarizer.
The axis of claim 18 , wherein the high refractive index axis is a machine direction (MD) of the polarizer, and the low refractive index axis is a mechanical direction, a transverse direction (TD) or an inclination with respect to the width direction of the passivation layer. direction, a polarizing plate.
The polarizing plate according to claim 18, wherein the protective layer has an in-plane retardation of 5000 nm or more at a wavelength of 550 nm.
The method according to claim 17, wherein the base layer and the positive C plate retardation layer are stacked in this order from the lower surface of the polarizer, or the positive C plate retardation layer and the base material layer are stacked in this order from the lower surface of the polarizer Phosphorus, polarizer.
The optical display device comprising the polarizing plate of claim 16.

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