KR102448120B1 - Optical film for improving contrast ratio, polarizing plate comprising the same and liquid crystal display apparatus comprising the same - Google Patents

Abstract

protective layer; and a contrast improvement layer including a second resin layer sequentially stacked from the lower surface of the protective layer and a first resin layer facing the second resin layer, wherein the second resin layer is the first resin layer Higher refractive index, the first resin layer is at least one portion facing the second resin layer, two or more embossed optical patterns and a flat portion between the embossed optical pattern and the embossed optical pattern immediately adjacent to A pattern portion having a pattern portion having a base, the embossed optical pattern has a base angle (θ) of 75° to 90°, the pattern portion satisfies Equation 1, and at least one of the first resin layer and the second resin layer is a metal Provided are a contrast ratio improvement optical film comprising at least one of a complex dye and an organic black dye, a polarizing plate comprising the same, and a liquid crystal display including the same.

Description

Contrast improvement optical film, polarizing plate including same, and liquid crystal display including same

The present invention relates to an optical film for improving contrast ratio, a polarizing plate including the same, and a liquid crystal display including the same.

The present invention relates to an optical film for improving contrast ratio, a polarizing plate including the same, and a liquid crystal display including the same.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a contrast improvement optical film capable of improving the front contrast ratio and lowering the reflectance.

Another object of the present invention is to provide a contrast ratio improvement optical film capable of lowering the degree of lateral color shift (color shift).

Another object of the present invention is to provide an optical film for improving the contrast ratio that can minimize the separation of the dye from the high refractive index layer by allowing the composition for the high refractive index layer to be cured well.

Another object of the present invention is to provide an optical film for improving the contrast ratio that can minimize the separation of the dye from the low-refractive layer by making the composition for the low-refractive layer cured well.

Another object of the present invention is to provide a contrast-ratio improving optical film in which light leakage from the side is reduced by reducing light emitted to the side in the black mode and the contrast ratio is improved in the black mode.

Another object of the present invention is to provide a contrast ratio improvement optical film including a dye in the second resin layer, but improving luminance and comprising a second resin layer having excellent light transmittance.

Another object of the present invention is to provide a polarizing plate and an optical display device including the contrast-ratio improved optical film of the present invention.

Contrast improvement optical film of the present invention is a protective layer; and a contrast improvement layer including a second resin layer sequentially stacked from the lower surface of the protective layer and a first resin layer facing the second resin layer, wherein the second resin layer is the first resin layer Higher refractive index, the first resin layer is at least one portion facing the second resin layer, two or more embossed optical patterns and a flat portion between the embossed optical pattern and the embossed optical pattern immediately adjacent to and a pattern part having a base angle (θ) of 75° to 90° of the embossed optical pattern, and the pattern part satisfies the following formula 1,

<Equation 1>

1 < P/W ≤ 10

(In Equation 1, P is the period of the pattern part (unit: μm),

W is the maximum width of the optical pattern (unit: μm),

At least one of the first resin layer and the second resin layer may include at least one of a metal complex dye and an organic black dye.

The polarizing plate of the present invention may include a polarizing film and the contrast improving optical film of the present invention formed on the polarizing film.

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

The present invention provides a contrast improvement optical film capable of improving the front contrast ratio and lowering the reflectance.

The present invention provides a contrast ratio improvement optical film capable of lowering the degree of lateral color conversion.

The present invention provides an optical film for improving the contrast ratio having an excellent appearance because the composition for the high refractive index layer can be cured well and the dye can be dissolved and mixed in the high refractive resin resin.

The present invention provides an optical film for improving the contrast ratio having an excellent appearance because the composition for the low refractive layer can be cured well and the dye can be dissolved and mixed in the low refractive resin.

The present invention provides an optical film for improving the contrast ratio in which the light leakage from the side is reduced by reducing the light emitted to the side in the black mode and the contrast ratio is improved in the black mode.

The present invention provides a contrast ratio improvement optical film including a dye in the second resin layer, but improving luminance and comprising a second resin layer having excellent light transmittance.

The present invention provides a polarizing plate and an optical display device including an optical film capable of improving side contrast ratio, lowering reflectance, and increasing a sense of black according to the present invention.

1 is a cross-sectional view of a contrast ratio improvement optical film according to an embodiment of the present invention.
Figure 2 shows the first zone and the second zone of the second resin layer of the contrast improvement optical film of the present invention.
3 is a cross-sectional view of a polarizing plate according to an embodiment of the present invention.
4 is a SEM image of a cross-section of the contrast-ratio improved optical film according to Comparative Example 4. Referring to FIG.
5 shows transmittance (TT) according to wavelengths of each dye and organic black dye included in the organic black dye used in Examples.

With reference to the accompanying drawings, the embodiments will be described in detail so that those of ordinary skill in the art to which the present invention pertains can easily implement them. 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.

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 in which 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 adjacent to” means that no other structure is interposed therebetween.

In this specification, "horizontal direction" and "vertical direction" refer to a long direction and a single direction of a rectangular liquid crystal display screen, respectively. In the present specification, "front" and "side" are based on the horizontal direction, when (φ, θ) by a spherical coordinate system, the front is (0°, 0°), and the left end point (180°, 90°) and the right end point (0°, 90°), the side means (0°, 60°) or (0°, 80°).

As used herein, "top part" means the highest part of the embossed optical pattern.

As used herein, "aspect ratio" means a ratio of the maximum height to the maximum width of the optical pattern (maximum height/maximum width).

In the present specification, the term “period” refers to a distance between adjacent optical patterns, for example, the sum of the maximum width of one optical pattern and the width of one flat portion immediately adjacent to the optical pattern.

In the present specification, "plane direction retardation (Re)" is a value at a wavelength of 550 nm, and is expressed by the following formula A:

<Formula A>

Re = (nx - ny) x d

(In the formula A, nx and ny are the refractive indices in the slow axis direction and the fast axis direction of the corresponding protective layer or base layer, respectively, at a wavelength of 550 nm, and d is the thickness (unit: nm) of the corresponding protective layer or base layer.

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

The inventor of the present invention, in the optical film for improving contrast ratio having a pattern part described in detail below, by including one or more of a metal complex dye and an organic black dye in at least one of the first resin layer and the second resin layer, the pattern part The present invention was completed by discovering that it is possible to improve the front contrast ratio without affecting the improvement of the lateral contrast ratio by

Hereinafter, a contrast ratio improvement optical film according to an embodiment of the present invention will be described with reference to FIG. 1 . 1 is a cross-sectional view of a contrast ratio improvement optical film according to an embodiment of the present invention.

Referring to FIG. 1 , in the contrast improvement optical film 10 , the contrast improvement layer 200 is formed on the lower surface of the protective layer 100 .

protective layer

The protective layer 100 may be formed on one surface of the contrast improvement layer 200 to support the contrast improvement layer 200 . The protective layer 100 may be formed directly with the second resin layer 220 of the contrast improvement layer 200 to thin the contrast ratio improvement optical film 10 . The "directly formed" means that any adhesive layer, adhesive layer, or adhesive layer is not interposed between the protective layer 100 and the contrast improvement layer 200 .

A contrast improvement layer 200 is formed on the light incident surface of the protective layer 100 . Light passing through the contrast improvement layer 200 may be emitted through the passivation layer 100 .

The protective layer 100 may have a total light transmittance of 90% or more in the visible light region, for example, 90% to 100%. In the above range, incident light can be transmitted without affecting it.

The protective layer 100 may be a protective film or a protective coating layer including a light incident surface and a light output surface opposite to the light incident surface. Preferably, by using a protective film as a protective layer, the degree of support for the contrast improving layer may be excellent.

When the protective layer is a protective film, the protective layer may include a single layer of an optically transparent resin film. However, the protective layer may include a case in which a plurality of resin films are laminated. The protective film may be formed by melting and extruding a resin. If necessary, a further stretching step may be added. The resin is a cellulose ester-based resin including triacetyl cellulose (TAC), a cyclic polyolefin-based resin including an amorphous cyclic polyolefin (COP), etc., a polycarbonate-based resin, polyethylene terephthalate (PET), etc. Polyacrylate-based resins, including polyester-based resins, polyethersulfone-based resins, polysulfone-based resins, polyamide-based resins, polyimide-based resins, acyclic-polyolefin-based resins, polymethyl methacrylate resins, etc. It may include at least one of a vinyl alcohol-based resin, a polyvinyl chloride-based resin, and a polyvinylidene chloride-based resin.

The protective film may be an unstretched film, but may be a retardation film or an isotropic optical film having a retardation within a predetermined range by stretching the resin by a predetermined method. In one embodiment, the protective film may be an isotropic optical film having Re of 0 nm or more and 60 nm or less, specifically 40 nm to 60 nm. The image quality may be improved by compensating the viewing angle within the above range. The “isotropic optical film” refers to a film in which nx, ny, and nz are substantially the same, and the “substantially identical” includes both cases including a slight error as well as cases where they are completely identical. In another embodiment, the protective film may be a retardation film having Re of 60 nm or more. For example, the protective film may have Re of 60 nm to 500 nm, and 60 nm to 300 nm. For example, the protective film may have a Re of 8,000 nm or more, specifically 10,000 nm or more, more specifically 10,000 nm or more, more specifically 10,100 nm to 30,000 nm, and 10,100 nm to 15,000 nm. In the above range, rainbow spots may not be recognized, and the diffusion effect of light diffused through the contrast improvement layer may be greater.

The protective coating layer may be formed of an active energy ray-curable resin composition including an active energy ray-curable compound and a polymerization initiator. The active energy ray-curable compound may include at least one of a cationically polymerizable curable compound, a radical polymerizable curable compound, a urethane resin, and a silicone-based resin. The cationically polymerizable curable compound may be an epoxy compound having at least one epoxy group in the molecule, or an oxetane compound having at least one oxetane ring in the molecule. The epoxy compound may be at least one of a hydrogenated epoxy compound, a chain aliphatic epoxy compound, a cyclic aliphatic epoxy compound, and an aromatic epoxy compound.

The radically polymerizable curable compound can be obtained by reacting two or more types of (meth)acrylate monomers and functional group-containing compounds having at least one (meth)acryloyloxy group in the molecule, and at least two (meth)acryloylox in the molecule The (meth)acrylate oligomer which has a group is mentioned. As the (meth)acrylate monomer, a monofunctional (meth)acrylate monomer having one (meth)acryloyloxy group in the molecule, and a bifunctional (meth)acrylate having two (meth)acryloyloxy groups in the molecule a monomer, and a polyfunctional (meth)acrylate monomer having three or more (meth)acryloyloxy groups in the molecule. The (meth)acrylate oligomer may be a urethane (meth)acrylate oligomer, a polyester (meth)acrylate oligomer, or an epoxy (meth)acrylate oligomer. A polymerization initiator can harden an active-energy-ray-curable compound. The polymerization initiator may include at least one of a photocation initiator and a photosensitizer. A photocationic initiator and a photosensitizer may use those commonly known to those skilled in the art.

The thickness of the protective layer 100 is 5 μm to 200 μm, specifically, 30 μm to 120 μm, 30 μm to 100 μm in the case of a protective film type, preferably 50 μm to 90 μm, 5 μm to 5 μm in the case of the protective coating layer type It can be 50 μm. It can be used for a polarizing plate in the above range.

On at least one surface (at least one of the upper surface and the lower surface) of the protective layer 100, 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, and an ultra-low reflection layer is further formed it might be The hard coating layer, the anti-fingerprint layer, and the anti-reflection layer may provide additional functions to the protective layer, the polarizing film, and the like. The primer layer may improve adhesion between the protective layer and the adherend (eg, a polarizer).

Contrast improvement layer

The contrast improvement layer 200 includes a first resin layer 210 and a second resin layer 220 facing the first resin layer 210 . Preferably, the contrast improvement layer 200 is composed of only the first resin layer 210 and the second resin layer 220, such that the first resin layer 210 and the second resin layer 220 are in direct contact with each other. has been

The first resin layer 210 is formed on the light incident surface of the second resin layer 220 . The light incident from the lower surface of the first resin layer 210 may be emitted to the second resin layer 220 . The first resin layer 210 may diffuse the light by refracting the light incident from the lower surface in various directions according to the incident position and emitting it.

The first resin layer 210 is formed directly on the second resin layer 220 , and the second resin layer 220 (the lower surface of the second resin layer) is in direct contact with the first resin layer 210 . A pattern portion to be described in detail below is formed on the interface. FIG. 1 shows that the pattern part completely contacts the second resin layer 220 . However, contacting the pattern portion with at least a portion of the second resin layer 220 may also be included in the scope of the present invention. A portion not in contact between the second resin layer 220 and the first resin layer 210 may be filled with air or a resin having a predetermined refractive index. Preferably, the pattern part completely contacts the second resin layer 220 .

The pattern portion includes one or more embossed optical patterns 221; and a flat portion 222 between the embossed optical pattern 221 and the immediately adjacent optical pattern 221 . In the pattern portion, a combination of the embossed optical pattern 221 and the flat portion 222 is repeatedly formed.

The optical pattern 221 may be an optical pattern including one or more inclined surfaces 223 having a first surface 224 formed on a top portion and connected to the first surface 224 . The first resin layer 210 includes an upper surface 210a and a lower surface 210b. The upper surface 210a of the first resin layer 210 is an interface between the first resin layer 210 and the second resin layer 220 and may correspond to the pattern portion.

The pattern portion satisfies Equation 1 below, and the optical pattern 221 may have a base angle θ of 75° to 90°. The base angle θ means an angle between the inclined surface 223 of the optical pattern 221 and the line of the maximum width W of the optical pattern 221 from 75° to 90°. In this case, the inclined surface 223 means an inclined surface directly connected to the flat portion 222 of the optical pattern 221 . In the above range, the side contrast ratio can be improved, and the contrast ratio can be increased at the same side viewing angle: specifically, the base angle θ is 80° to 90°, and P/W (ratio of P to W) is 1.2 to 1.2 8 can be:

<Equation 1>

1 < P/W ≤ 10

(In Equation 1, P is the period of the pattern part (unit: μm),

W is the maximum width of the optical pattern (unit: μm).

1 illustrates a case in which both base angles θ of the optical pattern are the same, but optical patterns having different base angles θ may also be included in the scope of the present invention if the base angles are included in the above-mentioned 75° to 90°.

The optical pattern 221 may be a embossed optical pattern including one or more inclined surfaces 223 having a first surface 224 formed at a top portion and connected to the first surface 224 . 1 shows an optical pattern 221 showing a trapezoidal optical pattern in which two adjacent inclined surfaces 223 are connected by a first surface 224, but the present invention is not limited thereto, and the optical pattern has a trapezoidal cross-section. In addition to the phosphor optical pattern, it may be a rectangular or square optical pattern.

The first surface 224 is formed on the top, so that the light reaching the second resin layer 220 in the optical display device is further diffused by the first surface 224, thereby increasing the viewing angle and luminance. Accordingly, it is possible to minimize the loss of luminance by increasing the light diffusion effect. The first surface 224 may be a flat surface to facilitate the manufacturing process of the contrast ratio improvement optical film. However, the first surface 224 may be formed with fine irregularities or may be curved. When the first surface is formed as a curved surface, a lenticular lens pattern may be formed. 1 shows a pattern in which one plane is formed on the top (the first surface) and the inclined plane is flat, and the cross-section is trapezoidal (eg, the upper part of a prism having a triangular cross-section is cut, cut-prism) . However, the embossed pattern has a first surface formed on the top and an embossed pattern with a curved inclined surface (eg, a contrast improvement layer that is a cut-lenticular lens in which the upper part of the lenticular lens pattern is cut, or the upper part of the microlens pattern is cut shape of a cut-micro lens) may also be included in the scope of the present invention. In addition, a pattern having an N-shaped cross-section such as a rectangle or a square (N is an integer of 3 to 20) may also be included.

The first surface 224 is parallel to at least one of the flat portion 222 , the lowest surface of the first resin layer 210 , and the highest surface of the second resin layer 220 (ie, the upper surface of the second resin layer). can be formed. 1 shows a case in which the first surface 224 of the optical pattern 221, the flat portion 222, the lowest surface of the first resin layer 210, and the highest surface of the second resin layer 220 are parallel to each other. will be.

The first surface 224 may have a width A of 0.5 μm to 30 μm, specifically 1 μm to 15 μm. In the above range, it can be used in an optical display device, and an effect of improving the contrast ratio can be expected.

The optical pattern 221 may have an aspect ratio (H1/W) of 0.1 to 10, specifically 0.1 to 7.0, more specifically 0.1 to 5.0, and even more specifically 0.1 to 1.0. Within the above range, it is possible to improve the contrast ratio and the viewing angle at the side of the optical display device.

The maximum height H1 of the optical pattern 221 may be greater than 0 µm and less than or equal to 20 µm, specifically greater than or equal to 0 µm and less than or equal to 15 µm, and more specifically greater than or equal to 0 µm to less than or equal to 10 µm. In the above range, contrast ratio improvement, viewing angle improvement, and luminance improvement may be exhibited, and moiré and the like may not appear.

The maximum width W of the optical pattern 221 may be greater than 0 µm and less than or equal to 20 µm, specifically greater than or equal to 0 µm and less than or equal to 15 µm, and more specifically greater than or equal to 0 µm and less than or equal to 10 µm. In the above range, contrast ratio improvement, viewing angle improvement, and luminance improvement may be exhibited, and moiré and the like may not appear.

1 illustrates a pattern portion in which adjacent optical patterns have optical patterns having the same base angle, first surface width, maximum height, and maximum width, respectively. However, the adjacent optical patterns may have different base angles, first surface widths, maximum heights, and maximum widths, respectively.

The flat part 222 may increase the front luminance by emitting the light passing through the first resin layer 210 to the second resin layer 220 .

The ratio (W/L) of the maximum width (W) of the optical pattern 221 to the width (L) of the flat portion 222 is greater than 0 and less than or equal to 9, specifically 0.1 to 3, more specifically 0.15 to 2 days can In the above range, the difference between the front contrast ratio and the side contrast ratio may be reduced, and the contrast ratio may be increased at the same side viewing angle and the same front viewing angle. In addition, there may be an effect of preventing moiré. The width L of the flat portion 222 may be 1 μm to 50 μm, specifically, 1 μm to 20 μm. In the above range, there may be an effect of increasing the front luminance.

The maximum width W of one optical pattern 221 and the flat portion 222 immediately adjacent to it form one period P. The period P may be 1 μm to 50 μm, specifically 1 μm to 40 μm. It is possible to prevent moiré while having an effect of improving the contrast ratio within the above range.

1 illustrates pattern portions having the same period and maximum width, respectively, the period and maximum width may be different from each other.

The first resin layer 210 may have a refractive index greater than 0 and less than 1.52, specifically 1.35 or more and less than 1.50. In the above range, the light diffusion effect may be large, manufacturing may be easy, and the light diffusion and contrast ratio improvement effect of polarized light may be large.

The first resin layer 210 may be formed of a composition for a first resin layer including a curable resin. The composition for the first resin layer may further include an initiator. The curable resin and the initiator are the same as those described in the composition for the second resin layer described in detail below. The composition for the first resin layer may further include the additives described in the following composition for the second resin layer.

In one embodiment, the first resin layer 210 may be non-adhesive without tackiness. When the first resin layer 210 is non-adhesive, the contrast-ratio improving optical film may be laminated on an adherend (eg, a polarizing film) by an adhesive, an adhesive, or an adhesive.

In another embodiment, the first resin layer 210 may be adhesive. When the first resin layer 210 is adhesive, the contrast-improving optical film may be laminated on an adherend without an additional adhesive, adhesive, or adhesive, thereby obtaining a thinning effect.

In one embodiment, the first resin layer 210 may not include the metal complex dye and the organic black dye described in detail below.

Although not specified in FIG. 1 , FIG. 1 shows that the optical pattern is formed in a stripe-shaped elongated form in the longitudinal direction of the optical pattern, but the optical pattern may be formed in a dot form. The "dot" means that the optical pattern is spaced apart from each other and dispersed. Preferably, the optical pattern is formed to extend in a stripe shape, so that the left and right viewing angles can be enlarged.

The second resin layer 220 has a higher refractive index than the first resin layer 210 . Therefore, the contrast improvement layer 200 can improve the side contrast ratio by diffusing and emitting the light incident from the light incident surface of the first resin layer 210, and minimize the decrease in the front contrast ratio even if the side contrast ratio is increased, The difference between the front contrast ratio and the side contrast ratio can be reduced, and the contrast ratio can be increased at the same side viewing angle and the same front viewing angle. The difference in refractive index between the second resin layer 220 and the first resin layer 210 may be 0.05 or more, specifically 0.05 to 0.3, and more specifically 0.05 to 0.2. Within the above range, the effect of improving the diffusion of light and the contrast ratio may be large.

The second resin layer 220 may have a refractive index of 1.50 or more, specifically, 1.55 to 1.70. In the above range, the light diffusion effect may be excellent.

The second resin layer 220 may include at least one of a metal complex dye and an organic black dye; And it may be formed of a composition for a second resin layer comprising a curable resin.

At least one of the metal complex dye and the organic black dye may have an average particle diameter (D50) per particle after dispersion of greater than 0 nm and less than or equal to 100 nm, preferably 5 nm to 80 nm. Within the above range, the effects of the present invention can be obtained.

The metal complex dye and the organic black dye have significantly lower average particle diameters compared to the maximum width of the optical pattern and the width of the flat portion, respectively. For example, the ratio of the average particle diameter of the metal complex dye or the organic black dye to the maximum width of the optical pattern, the width of the flat portion, or the width of the first surface of the optical pattern (average particle diameter of the metal complex dye or organic black dye: The maximum width of the optical pattern, the width of the flat portion, or the width of the first surface of the optical pattern) may be 1:500 to 1:800, preferably 1:600 to 1:800. Within the above range, the effects of the present invention can be obtained.

The second resin layer 220 may include at least one of the metal complex dye and the organic black dye having the average particle diameter, thereby improving the front contrast ratio, lowering the reflectance, and lowering the degree of color conversion on the side. When there is a metal complex dye or an organic black dye between the optical pattern and the adjacent optical pattern in the average particle diameter range, it does not affect the movement of light emitted from the flat part of the first resin layer, so that the front contrast ratio can be improved, and the pattern Since it does not affect the light emitted to the side of the , the side contrast ratio by the pattern part can also be improved. In addition, by including a metal complex dye or an organic black dye, the front contrast ratio can be improved, and the increased reflectance due to the increase of the layer can be lowered. In addition, it is possible to increase the sense of low black due to light leakage from the side of the LCD panel. For the contrast-improving optical film, the panel reflectance measured in the protective layer may be less than 5%, preferably 0% or more and 4.95% or less, and 0% or more and 4.9% or less. In the above range, it is possible to improve the appearance by lowering the reflectance.

In one embodiment, at least one of the metal complex dye and the organic black dye is 0.01 to 10% by weight, preferably 0.01 to 5.0% by weight, 0.01 to 3.0% by weight, 0.01 to 2.0% by weight of the second resin layer , more preferably 0.01 wt% to 1.0 wt%, and most preferably 0.01 wt% to 0.5 wt%. In the above range, it is possible to improve the front contrast ratio, decrease the reflectance, and improve the black feeling, and may be included in the second resin layer, obtain a good dispersion effect of the dye, and prevent the decrease in the light transmittance of the second resin layer.

The second resin layer may have a light transmittance of 50% to 92%, preferably 75% to 85% at a wavelength of 550 nm. In the above range, both the side contrast ratio by the pattern and the front contrast ratio by the metal complex dye can be improved.

Although not shown in FIG. 1 , at least one of a metal complex dye and an organic black dye may be included in the entire second resin layer. That is, the space between the embossed optical pattern 220 and the immediately adjacent embossed optical pattern 220 in the second resin layer 220 is referred to as a "first zone", and the embossed optical patterns 220 spaced apart from each other ), when the space between the imaginary surface connecting the first surface 224 and the lower surface of the protective layer 100 is referred to as a “second region”, the second resin layer 220 is formed between the first region and the second region. It is composed of zones, the first zone and the second zone are in contact with each other, and at least one of a metal complex dye and an organic black dye may be included in both the first zone and the second zone. In this case, it may be easy to manufacture the second resin layer. In FIG. 2, the first region 220a and the second region 220b of the second resin layer of the above-described contrast-improving optical film are shown.

Hereinafter, the metal complex dye will be described in detail.

The metal complex dye may include a black dye containing a metal.

The metal complex dye may include one or more of a 1:1 metal complex dye and a 1:2 metal complex dye. 1:1 metal complex dye refers to one metal atom bonded to one dye molecule, and 1:2 metal complex salt dye refers to one metal atom bonded to two dye molecules.

The metal may be, but is not limited to, chromium, nickel, cobalt or copper.

The dye molecule may include an azo (eg, monoazo) molecule including at least one of Hydroxyl, Carboxyl, and an amino group. Through this, there may be further effects of improving the side contrast ratio by the pattern and the front contrast ratio by the metal complex dye, lowering the reflectance, and increasing the sense of black.

In one embodiment, the metal complex dye is an azo dye containing a metal and may have a C6 to C20 monocyclic or polycyclic aromatic functional group. Preferably, the monocyclic or polycyclic aromatic functional group may include a C8 to C15 monocyclic or polycyclic aromatic functional group, for example, a phenyl group or a naphthalene group. Through this, when mixed with the UV curable resin forming the second resin layer, the UV curable resin can be cured well, thereby increasing the hardness of the second resin layer and preventing the metal complex dye from being separated from the second resin layer.

In one embodiment, the metal complex dye may be composed of one dye.

In another embodiment, the metal complex dye may be composed of a mixture of a red metal complex dye, a green metal complex dye and a blue metal complex dye.

The metal complex dye may have a refractive index of 1.6 to 2.2, preferably 1.9 to 2.1. In the above range, when included in the second resin layer, the refractive index of the second resin layer may not be lowered.

The metal complex dye is not particularly limited, and commercially available products may be used. For example, at least one of Orasol® Black X55 (BASF) and Orasol® Black X51 (BASF) may be used.

Hereinafter, the organic black dye will be described in detail.

The organic black dye may include a black dye composed only of organic molecules as a non-metal type that does not contain a metal.

The organic black dye has good dispersibility (minimum dispersion unit of 1 to 5 nm) and good transparency and luminance. On the other hand, inorganic black pigments including carbon black have poor dispersibility (minimum dispersion unit of 50 to 400 nm) and are opaque. Since the reduction and transmittance must be high, the organic black dye is superior to the inorganic black pigment, carbon black.

The organic black dye may have a refractive index of 1.6 to 2.2, preferably 1.9 to 2.1. In the above range, when included in the second resin layer, the refractive index of the second resin layer may not be lowered.

In one embodiment, the organic black dye may be a mixture of three color dyes. For example, the mixture of three color dyes may be a mixture of a first dye (orange dye), a second dye (red dye) and a third dye (blue dye). The first dye, the second dye, and the third dye may have different maximum absorption wavelengths. The "maximum absorption wavelength" is a value measured at a concentration of 5 mg/L (5 wt %) in the solvent methyl ethyl ketone for each dye. In the above range, it can be considered as a concentration suitable for measuring transmittance.

The first dye may include a dye having a maximum absorption wavelength of 430 nm to 450 nm, preferably 440 nm, and an absorption wavelength range of 360 nm to 640 nm.

The second dye may include a dye having a maximum absorption wavelength of 510 nm to 530 nm, preferably 520 nm, and an absorption wavelength range of 360 nm to 740 nm.

The third dye may include a dye having a maximum absorption wavelength of 590 nm to 610 nm, preferably 600 nm, and an absorption wavelength range of 360 nm to 740 nm.

In one embodiment, the organic black dye comprises 30% to 50% by weight of the first dye, preferably 40% to 50% by weight, and 1% to 20% by weight of the second dye, preferably 1% by weight of the total organic black dye % to 10% by weight, 30% to 50% by weight of the third dye, preferably 40% to 50% by weight, may be a mixture. In the above range, a black dye with high luminance can be obtained.

The first dye (orange dye) may be an azo dye, for example, an aromatic azo dye, for example, a dye represented by the following Chemical Formula 1 (for example, Synolon yellow Brown K-2RS manufactured by Gyeongin Corporation), but limited thereto. doesn't happen

<Formula 1>

The second dye (red dye) may be an azo dye, for example, an aromatic azo dye, for example, a dye represented by the following Chemical Formula 2 (for example, Synolon rubine K-GFL, Gyeongin Corporation), but is not limited thereto.

<Formula 2>

The third dye (blue dye) may be an azo-based dye, for example, an aromatic azo-based dye, and a dye represented by the following Chemical Formula 3 (eg, Synolon navy blue K-GLS, Gyeongin) may be used, but is not limited thereto.

<Formula 3>

The organic black dye is not particularly limited, but commercially available products can be used. For example, BS01 (Kyungin Corp.), BS02 (Kyungin Corp.), etc. may be used.

The curable resin may include at least one of a UV curable resin and a thermosetting resin, but preferably, by using a UV curable resin, the second resin layer can be formed in a short period of time, can do. The curable resin may include (meth)acrylic monomers, oligomers, or resins, and is a resin having high refractive properties. may include

After curing, the curable resin may have a refractive index of 1.55 or more, preferably 1.58 to 1.62. Within the above range, the refractive index of the second resin layer may be secured.

The composition for the second resin layer may further include an initiator. The initiator cures the curable resin and may include at least one of a photoinitiator and a thermal initiator. These may be of conventional types known to those skilled in the art. The photoinitiator may include at least one of phosphorus-based, triazine-based, acetophenone-based, benzophenone-based, thioxanthone-based, benzoin-based, oxime-based, and phenylketone-based types. The initiator may be included in an amount of 0.01 wt% or more and 5 wt% or less, for example, more than 0.5 wt% and 5 wt% or less, 2 wt% to 5 wt% of the second resin layer or the composition for the second resin layer based on the solid content. In the above range, the composition for the second resin layer can be sufficiently cured and the light transmittance of the contrast improving layer can be prevented from being lowered with the remaining amount of the initiator.

The composition for the second resin layer is prepared by using a conventional solvent such as ethanol (EtOH), propylene glycol monomethyl ether acetate (PGME), methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), etc. for the applicability of the composition. may include, but are not limited to.

The composition for the second resin layer may further include conventional additives known to those skilled in the art. The additive may include at least one of a leveling agent, a surface control agent, an antioxidant, an antifoaming agent, an ultraviolet absorber, and a light stabilizer.

The maximum thickness of the second resin layer 220 may be greater than 0 µm and less than or equal to 30 µm, for example, greater than or equal to 0 µm and less than or equal to 20 µm. Within the above range, it is possible to prevent the occurrence of warpage such as curl.

The maximum thickness of the second resin layer 220 - the maximum height (also referred to as 'flesh thickness') of the optical pattern 221 is greater than 0 µm and less than or equal to 30 µm, for example, greater than 0 µm and less than or equal to 20 µm, greater than or equal to 0 µm and less than or equal to 10 µm can be the following In the above range, there may be an effect of minimizing the decrease in the side contrast ratio.

In one embodiment, the second resin layer may not include carbon black.

In one embodiment, the first resin layer may not include carbon black.

The contrast improvement layer 200 may have a thickness of 10 μm to 100 μm, specifically 10 μm to 50 μm, and more specifically 10 μm to 40 μm. Within the above range, it can be used for an optical display device.

The contrast improving layer may be prepared by a conventional method known to those skilled in the art. For example, the contrast improvement layer is formed by coating the protective layer with a composition for a second resin layer, applying an optical pattern and a flat part, and curing the second resin layer, and coating and curing the composition for the first resin layer. can be, but is not limited to.

Hereinafter, a contrast ratio improvement optical film according to another embodiment of the present invention will be described.

The contrast improvement optical film of this embodiment does not include the metal complex dye and the organic black dye in the second resin layer, and at least one of the metal complex dye and the organic black dye is included in the first resin layer. It is the same as the contrast ratio improvement optical film of an embodiment of the present invention.

At least one of the metal complex dye and the organic black dye is 0.01 to 10% by weight, preferably 0.01 to 5.0% by weight, 0.01 to 3.0% by weight, 0.01 to 2.0% by weight of the first resin layer; More preferably, it may be included in an amount of 0.01 wt% to 1.0 wt%. Within the above range, it is possible to obtain the effect of improving the front contrast ratio, increasing the black luminance, improving the reflectance, high transmittance, and good dispersion of the metal complex. Details of the metal complex dye and the organic black dye are the same as described above.

In one embodiment, the second resin layer may not include carbon black.

In one embodiment, the first resin layer may not include carbon black.

Hereinafter, a contrast ratio improvement optical film according to another embodiment of the present invention will be described.

The contrast improvement optical film of this embodiment includes at least one of the metal complex dye and the organic black dye in a second resin layer, wherein at least one of the metal complex dye and the organic black dye is in the second resin layer It may be included only in Zone 1 and may not be included in Zone 2. Since the metal complex dye and the organic black dye are included in specific positions, the effect of improving contrast ratio and improving luminance can be further improved, and a decrease in light transmittance of the second resin layer can be prevented.

At least one of the metal complex dye and the organic black dye is 0.01 wt% to 10 wt%, preferably 0.01 wt% to 5.0 wt%, 0.01 wt% to 3.0 wt%, 0.1 to 5.0 wt%, in the second resin layer, More preferably, it may be included in an amount of 0.1 wt% to 1.0 wt%. In the above range, it is possible to obtain a front contrast ratio improvement, an increase in black luminance, a reflectance improvement effect, a high transmittance, and a good dispersion effect of the metal complex, and there may be no difference in refractive index between the first zone and the second zone. Details of the metal complex dye and the organic black dye are the same as described above.

In one embodiment, the absolute value of the difference in refractive index between the first zone and the second zone may be 0.02 to 0.20, preferably 0.08 to 0.20. In the above range, it is possible to prevent a decrease in the light transmittance of the second resin layer, the contrast improvement optical film, and the polarizing plate by lowering the difference in refractive index between the first zone and the second zone.

In one embodiment, the second resin layer may not include carbon black.

In one embodiment, the first resin layer may not include carbon black.

Hereinafter, a polarizing plate according to an embodiment of the present invention will be described with reference to FIG. 3 . 3 is a cross-sectional view of a polarizing plate according to an embodiment of the present invention.

Referring to FIG. 3 , the polarizing plate 20 includes a polarizing film 300 and a contrast improvement optical film, and the contrast improvement optical film may include a contrast improvement optical film according to an embodiment of the present invention. The contrast ratio improvement optical film may be formed on the light exit surface of the polarizing film 300 . The contrast improvement optical film may diffuse the polarized light transmitted through the polarizing film 300 to improve the front contrast ratio and the side contrast ratio, improve the viewing angle, and improve the feeling of black.

The polarizing film 300 may polarize light incident from the liquid crystal panel and transmit it to the contrast improvement layer 200 . The polarizing film 300 is formed on the light incident surface of the contrast improvement layer 200 .

The polarizing film 300 may include a polarizer. Specifically, the polarizer may include a polyvinyl alcohol-based polarizer manufactured by uniaxially stretching a polyvinyl alcohol-based film, or a polyene-based polarizer manufactured by dehydrating a polyvinyl alcohol-based film. The polarizer may have a thickness of 5 μm to 40 μm. Within the above range, it can be used for an optical display device.

The polarizing film 300 may include a polarizer and a protective layer formed on at least one surface of the polarizer. The protective layer may protect the polarizer to increase reliability of the polarizer and increase mechanical strength of the polarizer. The protective layer may include one or more of an optically clear, protective film or protective coating layer. The protective layer is the same as described above.

The polarizing plate may be formed by a conventional method. For example, it may be prepared by preparing the contrast ratio improvement optical film by the above-described method, and adhering the polarizing film to the other surface of the protective layer. The adhesion may be formed using one or more of commonly known water-based and photo-curable adhesives.

The liquid crystal display of the present invention may include the polarizing plate of the present invention. In one embodiment, the liquid crystal panel may be included as a viewing-side polarizing plate. The "viewing-side polarizing plate" is disposed opposite to the screen side, that is, the light source side with respect to the liquid crystal panel.

In one embodiment, in the liquid crystal display, a backlight unit, a first polarizing plate, a liquid crystal panel, and a second polarizing plate are sequentially stacked, and the second polarizing plate may include the polarizing plate of the present invention. The liquid crystal panel may employ a vertical alignment (VA) mode, an IPS mode, a patterned vertical alignment (PVA) mode, or a super-patterned vertical alignment (S-PVA) mode, but is not limited thereto. In another embodiment, it may be included as a light source-side polarizing plate for the liquid crystal panel. The "light source side polarizing plate" is disposed on the light source side with respect to the liquid crystal panel. In another embodiment, for the liquid crystal panel, both the viewing side polarizing plate and the light source side polarizing plate may include the polarizing plate of the present invention.

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 help the understanding of the present invention, and the scope of the present invention is not limited to the following examples.

Example 1

As a UV curable resin, 0.15 parts by weight of the dye Orasol® Black X55 (BASF Corporation, average particle diameter (D50): 10 nm, powder, chromium metal: 1: 2 complex salt of an azo compound) is mixed with 100 parts by weight of SSC5760 (Shinah T&C) and a disperser A composition for a second resin layer was prepared by stirring at 2000 rpm for 2 hours using a .

A composition for a first resin layer was prepared by mixing 100 parts by weight of PL8540 with adhesiveness as an acrylic copolymer with 80 parts by weight of methyl ethyl ketone as a diluting solvent and stirring at 500 rpm for 30 minutes using a stirrer.

As a protective layer, the second resin layer composition prepared above was applied to one surface (light incident surface) of a polyethylene terephthalate (PET) film (Toyobo, TA044, thickness: 80 μm) to form a coating layer. Using a film in which the optical pattern and the flat portion were alternately formed, the optical pattern and the flat portion were applied to the coating layer, and the second resin layer was formed by UV curing with an amount of UV light of 500 mJ/cm ² .

By coating the prepared composition for the first resin layer on one surface of the prepared second resin layer and drying it at 90° C. for 4 minutes in a dry oven to form the first resin layer, a contrast improvement optical film was prepared. The first resin layer has adhesiveness, and the refractive index is lower than that of the second resin layer. In the contrast improvement optical film, the dye is included in the entire second resin layer (both the first zone and the second zone).

Table 1 below shows the specifications of the pattern part of the contrast improvement layer.

A polarizing plate was manufactured by laminating one side of the first resin layer of the contrast improvement film and the PET film side of a polarizing film (product name: AMN-6143CPS(CO)) having a PET/PVA/COP three-layer structure of Samsung SDI.

Example 2

In Example 1, except that 0.3 parts by weight of Orasol® Black X55 was used to form the composition for the second resin layer, a contrast-improving optical film and a polarizing plate were prepared in the same manner. In the contrast improvement optical film, the dye is included in the entire second resin layer (both the first zone and the second zone).

Example 3

In Example 1, when forming the composition for the second resin layer, 100 parts by weight of ECOKOT-H903 (NC Chem) resin was used instead of 100 parts by weight of SSC5760 (Shinah T&C), and Orasol® Black instead of Orasol® Black X55 0.15 parts by weight X51 (BASF, average particle diameter (D50): 10 nm, powder, chromium metal: 1: 2 complex salt of an azo-based compound) 0.15 parts by weight were used, except that 0.15 parts by weight were used to prepare a contrast-improving optical film and a polarizing plate. In the contrast improvement optical film, the dye is included in the entire second resin layer (both the first zone and the second zone).

Example 4

In Example 1, a contrast-improving optical film and a polarizing plate were prepared in the same manner as in Example 1, except that 0.3 parts by weight of Orasol ® Black X51 was used as a black dye instead of 0.15 parts by weight of Orasol® Black X55 when forming the composition for the second resin layer. In the contrast improvement optical film, the dye is included in the entire second resin layer (both the first zone and the second zone).

Example 5

A contrast-improving optical film and a polarizing plate were prepared in the same manner as in Example 1, except that 0.15 parts by weight of an organic black dye (average particle diameter: 10 nm) was used instead of 0.15 parts by weight of Orasol black X55 when the composition for the second resin layer was formed. Organic black dye is a mixture of three primary color organic dyes. Synolon yellow brown K-2RS (Kyungin) 45% by weight in orange color, Synolon rubine K-GFL (Kyungin) in red color by 10% by weight, Synolon in blue color A black dye was prepared by mixing 45% by weight of navy blue K-GLS (Kyungin Corporation). 5 shows the transmittance according to the wavelength of each color dye. In the contrast improvement optical film, the dye is included in the entire second resin layer (both the first and second zones).

Example 6

As a UV curable resin, SSC5760 (Shinah T&C) was used as the composition for the second resin layer.

As an acrylic copolymer, 100 parts by weight of adhesive PL8540, 0.038 parts by weight of Orasol® Black X55 (BASF, average particle diameter: 10 nm), and 80 parts by weight of methyl ethyl ketone as a diluting solvent are mixed and stirred at 500 rpm for 30 minutes using a stirrer. A composition for the first resin layer was prepared by stirring.

As a protective layer, the second resin layer composition prepared above was applied to one surface (light incident surface) of a PET film (Toyobo, TA044, thickness: 80 μm) to form a coating layer. Using a film in which the optical pattern and the flat portion were alternately formed, the optical pattern and the flat portion were applied to the coating layer, and the second resin layer was formed by UV curing with an amount of UV light of 500 mJ/cm ² .

By coating the prepared composition for the first resin layer on one surface of the prepared second resin layer and drying it in a dry oven at 90° C. for 4 minutes to form the first resin layer, a contrast improvement optical film was prepared. The first resin layer has adhesiveness, and the refractive index is lower than that of the second resin layer.

A polarizing plate was manufactured in the same manner as in Example 1 using the prepared contrast-improving optical film.

Example 7

In Example 6, a contrast-improving optical film and a polarizing plate were prepared in the same manner as in Example 6, except that 0.076 parts by weight of Orasol® Black X55 was used to form the composition for the first resin layer.

Example 8

A composition for a first resin layer was prepared by mixing 100 parts by weight of PL8540 with adhesiveness as an acrylic copolymer with 80 parts by weight of methyl ethyl ketone as a diluting solvent and stirring at 500 rpm for 30 minutes using a stirrer.

As a UV curable resin, 100 parts by weight of SSC5760 (Shinah T&C) was used as the composition for the second zone of the second resin layer.

A predetermined amount of the dye Orasol® Black X55 (BASF Corporation, average particle diameter (D50): 10 nm, powder, chromium metal: 1: 2 complex salt of an azo compound) is mixed with 100 parts by weight of SSC5760 (Shinah T&C) as a UV curable resin and Using a disperser, the mixture was stirred at 2000 rpm for 2 hours and used as a composition for the first zone of the second resin layer.

A coating layer was formed by applying the composition for the first resin layer prepared above on the PET film side (light exit side) of a polarizing film (product name: AMN-6143CPS(CO)) having a PET/PVA/COP three-layer structure of Samsung SDI. . Using a film in which the optical pattern and the flat portion were alternately formed, the optical pattern and the flat portion were applied to the coating layer, and the first resin layer was formed by UV curing with a light amount of UV 500 mJ/cm ² .

The composition for the first zone of the second resin layer prepared above was applied only between the optical patterns of the first resin layer. The composition for the second zone of the second resin layer prepared above was applied to the coating layer. A polarizing plate was prepared by UV curing with a light amount of UV 500mJ/cm ² .

Table 1 below shows the specifications of the pattern part of the contrast improvement layer. The dye was included only in the first zone of the second resin layer and not in the second zone. When forming the composition for the first zone of the second resin layer, Orasol® Black X55 was added so that the content of Orasol® Black X55 in the second resin layer of the finally manufactured polarizing plate was as shown in Table 2 below.

Example 9

A polarizing plate was manufactured in the same manner as in Example 8, except that the content of Orasol® Black X55 in the second resin layer was added as shown in Table 2 below.

Example 10

A polarizing plate was manufactured in the same manner as in Example 8, except that Orasol® Black X51 was used instead of the dye Orasol® Black X55, and the content of Orasol® Black X51 in the second resin layer was added as shown in Table 2 below.

Comparative Example 1

A polarizing plate (product name: AMN-6143CPS(CO)) having a PET/PVA/COP structure from Samsung SDI that does not include an optical film for improving contrast ratio was used.

Comparative Example 2

In Example 1, a contrast improvement optical film and a polarizing plate were prepared in the same manner except that Orasol® Black X55 was not included in the second resin layer.

Comparative Example 3

In Example 1, instead of 0.15 parts by weight of Orasol® Black X55 used in forming the composition for the second resin layer, a light absorber coated with a light absorption layer containing carbon black having an acrylic light diffuser on the surface (Sekisui, xx-) 2740, an average diameter (D50) R is 6㎛), except that 0.5 parts by weight were used to prepare a contrast-improving optical film and a polarizing plate in the same manner.

Comparative Example 4

In Example 6, instead of 0.15 parts by weight of Orasol® Black X55 used as a light absorber when forming the composition for the first resin layer, a light absorber coated with a light absorption layer containing carbon black having an acrylic light diffuser on the surface (Sekisui Corporation) , xx-2740, average diameter (D50) R is 6㎛), except that 0.5 parts by weight were used to prepare a contrast-improving optical film and a polarizing plate in the same manner.

optical pattern shape Optical pattern maximum height (H1)
(μm) Optical pattern maximum width (W)
(μm) Width (A) of the first surface of the optical pattern
(μm) base angle of optical pattern
(°) Width of flat part (L)
(μm) Cycle (P)
(μm) Cut-prism
(trapezoidal, embossed pattern) 5 8 6.7 86 7 15

The following physical properties were evaluated for the contrast ratio improvement optical films and polarizing plates of Examples and Comparative Examples, and the results are shown in Tables 2, 3, and 4 below.

Panel reflectance : After laminating the contrast-improving optical film laminated to the polarizing films of Examples and Comparative Examples with an adhesive having a refractive index of 1.46 to 1.50 on an LCD VN-type Samsung Electronics SUHD 55-inch liquid crystal panel, a spectrophotometer (Konica Minolta, Inc.) , CM-2600D) in the SCI reflection mode (light source: D65 light source) in a wavelength range of 320 nm to 800 nm, and the Y(D65) value among the measured values was measured.

Manufacture of light source side polarizing plate

A polarizer was prepared by stretching the polyvinyl alcohol film 3 times at 60°C, adsorbing iodine, and then stretching it 2.5 times in an aqueous boric acid solution at 40°C. A polarizing plate was manufactured by adhering a triacetyl cellulose film (thickness 80 μm) as a base layer to both sides of the polarizer with an adhesive for a polarizing plate (Z-200, Nippon Goshei). The prepared polarizing plate was used as a light source-side polarizing plate.

Manufacturing of module for liquid crystal display

A module for a liquid crystal display was manufactured by sequentially assembling the light source-side polarizing plate, the liquid crystal panel (PVA mode), and the polarizing plate prepared in Examples and Comparative Examples. Among the polarizing plates manufactured in Examples and Comparative Examples, the protective layer was assembled so that it came out to the outermost part.

A liquid crystal display device including a one-sided edge-type LED light source by assembling an LED light source, a light guide plate, and a module for a liquid crystal display device Model name: UN55KS8000F) and the same configuration) were manufactured.

Using EZCONTRAST X88RC (EZXL-176R-F422A4, ELDIM Co., Ltd.), in the front (0°, 0°) and side (0°, 80°) The luminance value was measured.

The front contrast ratio was calculated as the ratio of the luminance value of the white mode to the luminance value of the black mode in the spherical coordinate system (0°, 0°). The side contrast ratio was calculated as the ratio of the luminance value of the white mode to the luminance value of the black mode in the spherical coordinate system (0°, 80°).

The front relative luminance in the front white mode was calculated as a ratio of the luminance of the corresponding Example or Comparative Example to the luminance of Comparative Example 1 in the white mode. The front relative luminance in the black mode was calculated as a ratio of the luminance of the corresponding Example or Comparative Example to the luminance of Comparative Example 1 in the white mode.

Skin color shift was evaluated using EZCONTRAST X88RC (EZXL-176R-F422A4, ELDIM). The lower the number, the better.

Appearance was evaluated as good when there were no streaks and unusual features on the appearance of the optical film for improving the contrast ratio with the naked eye. If a stripe pattern or a convex surface occurred, it was evaluated as defective.

The light transmittance of the polarizing plate was evaluated with Jasco's V7100.

[Table 2]

comparative example One 2 3 4 No. 1 Resin
(low refractive layer) refractive index - 1.481 1.481 1.481 Carbon Black Content
(weight%) - 0 0 0.5 2nd resin
(high refractive layer) refractive index - 1.5729 1.572 1.572 Carbon Black Content
(weight%) - 0 0.5 0 Front Relative Luminance (%) white mode 100 95 91 92 black mode 100 136 130 132 Contrast (%) (0°, 0°) 100 69.9 70.0 69.7 (0°, 80°) 100 140 141 140 Panel reflectance (%) 4.95 5.18 5.11 5.12 skin color shift
(△xy@45°) Right and left 0.0161 0.010 0.010 0.011 up and down 0.009 0.009 0.008 0.009 Exterior Good Good error
(Protrusion and streaking) error
(Protrusion and streaking) Light transmittance (%) 43.877 43.237 39.231 39.512

As shown in Table 2, the contrast-improving optical film of the present invention can improve the front contrast ratio and the side contrast ratio, lower the reflectivity, and lower the degree of side color conversion. In particular, the contrast improvement optical film of the present invention may have a front contrast ratio of more than 70% and a reflectance of less than 5%. The contrast improvement optical film of the present invention was excellent in appearance because curing of each layer was well and the dye could be dissolved and mixed well.

On the other hand, Comparative Examples 3 and 4 including carbon black did not have good appearance, had a high degree of side color conversion, and had a high panel reflectance, resulting in a low sense of black. In addition, referring to FIG. 4 , when carbon black (shown as a circle in FIG. 4 ) is included, the effect of the present invention cannot be reached because the pattern size does not fit.

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 (17)

protective layer; and a contrast improvement layer comprising a second resin layer sequentially stacked from the lower surface of the protective layer and a first resin layer facing the second resin layer,
The second resin layer has a higher refractive index than the first resin layer,
The first resin layer is provided with a pattern portion having two or more embossed optical patterns and a flat portion between the embossed optical pattern and the embossed optical pattern immediately adjacent to at least one portion facing the second resin layer, , The embossed optical pattern has a light diffusion surface, the embossed optical pattern has a base angle θ of 75° to 90°, and the pattern part satisfies the following formula 1,
<Equation 1>
1 < P/W ≤ 10
(In Equation 1, P is the period of the pattern part (unit: μm),
W is the maximum width of the optical pattern (unit: μm),
The second resin layer contains at least one of a metal complex dye and an organic black dye in an amount of 0.01 wt% to 0.5 wt% of the second resin layer, and the second resin layer does not contain carbon black What is not, the contrast ratio improvement optical film.
The optical film of claim 1 , wherein the metal complex dye and the organic black dye have an average particle diameter (D50) of 100 nm or less per particle.
The optical film of claim 1, wherein the second resin layer has a light transmittance of 50% to 92% at a wavelength of 550 nm.
The optical film of claim 1 , wherein the metal complex dye comprises a black dye containing chromium, nickel, cobalt or copper.
The optical film of claim 4 , wherein the metal complex dye comprises a black dye containing chromium.
The optical film of claim 1 , wherein the metal complex dye is a metal azo dye.
The optical film of claim 1 , wherein the metal complex dye comprises an azo dye having a C6 to C20 monocyclic or polycyclic aromatic functional group.
The optical film of claim 1, wherein the metal complex dye is an azo dye having chromium and a C6 to C20 monocyclic or polycyclic aromatic functional group, and an average particle diameter (D50) of 100 nm or less.
According to claim 1, wherein the organic black dye is a mixture of a first dye having a maximum absorption wavelength of 430 nm to 450 nm, a second dye having a maximum absorption wavelength of 510 nm to 530 nm, and a third dye having a maximum absorption wavelength of 590 nm to 610 nm. Including, the contrast ratio improvement optical film.
The optical film of claim 9 , wherein the first dye, the second dye, and the third dye each include an azo dye.
The optical film of claim 9, wherein the first dye is represented by the following Chemical Formula 1, the second dye is represented by the following Chemical Formula 2, and the third dye is represented by the following Chemical Formula 3.
<Formula 1>

<Formula 2>

<Formula 3>

.
The optical film of claim 1, wherein the first resin layer is adhesive.
The optical film of claim 1 , wherein the optical pattern comprises a pattern having a trapezoidal, rectangular or square cross-section.
According to claim 1, wherein a space between the embossed optical pattern and the immediately adjacent embossed optical pattern of the second resin layer is referred to as a first zone, and the first portion that is the apex of the embossed optical pattern spaced apart from each other When the space between the imaginary surface connecting the surfaces and the lower surface of the protective layer is referred to as the second zone,
wherein at least one of the metal complex dye and the organic black dye is included in both the first zone and the second zone.
According to claim 1, wherein a space between the embossed optical pattern and the immediately adjacent embossed optical pattern of the second resin layer is referred to as a first zone, and the first portion that is the apex of the embossed optical pattern spaced apart from each other When the space between the imaginary surface connecting the surfaces and the lower surface of the protective layer is referred to as the second zone,
At least one of the metal complex dye and the organic black dye is included in the first zone and not included in the second zone.
polarizing film; and a polarizing plate comprising the optical film of any one of claims 1 to 15 formed on the light emitting surface of the polarizing film.
A liquid crystal display comprising the polarizing plate of claim 16 .

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