KR20170030886A

KR20170030886A - Optical film and display device comprising the same

Info

Publication number: KR20170030886A
Application number: KR1020150128358A
Authority: KR
Inventors: 장준원; 김영진; 이대희; 이은혜; 박문수
Original assignee: 주식회사 엘지화학
Priority date: 2015-09-10
Filing date: 2015-09-10
Publication date: 2017-03-20
Also published as: KR101966818B1

Abstract

The present invention relates to an optical film and a display device including the same, the exemplary optical film of the present application can be used as a reflection-type polarizing plate capable of improving the light utilization efficiency of a display device such as an LCD and brightness. Particularly, since the optical film can reduce a color change at an oblique angle, a display device having excellent image quality can be provided. The optical film includes a first liquid crystal layer and a second liquid crystal layer.

Description

TECHNICAL FIELD [0001] The present invention relates to an optical film and a display device including the same,

The present application relates to an optical film and a display device.

The liquid crystal display (LCD) may include a display panel and a polarizing plate disposed on the upper and lower sides of the display panel, and may include various functional optical films in addition to the polarizing plate.

The LCD can display an image by changing the orientation of the liquid crystal for each pixel of the display panel. Since the LCD is not a self-luminous type device, a light source such as a BLU (Back Light Unit) is usually placed on the back side of the polarizing plate on the lower side of the display panel, and the light emitted from the light source is transmitted through the panel to display an image do. In order to improve the light utilization efficiency of the LCD, a technique of including a reflective polarizer between the lower-side polarizer and the light source is known. As the reflective polarizer, APF (Advanced Polarizer Film) manufactured by 3M Co., for example, is commercially available. Recently, a polarizing film in the form of a cholesteric liquid crystal or a polarizing film in the form of a nanowire grid has been developed as a novel reflective polarizer for replacing the film.

Korea Patent Publication No. 2013-0101327

The present application provides an optical film and a display device.

The present application relates to optical films. An exemplary optical film comprises a liquid crystal layer. The liquid crystal layer may include a liquid crystal compound in a cholesteric orientation. The liquid crystal layer may have a structure of a composite layer including first and second liquid crystal layers. The first and second liquid crystal layers may include different kinds of liquid crystal compounds. In one example, the liquid crystal layer of any one of the first and second liquid crystal layers may include a discotic liquid crystal compound in a cholesteric orientation on the disc, and the other liquid crystal layer may include a nematic liquid crystal The compound may be contained in a cholesteric orientation.

The optical film of the present application can be used as a reflective polarizer capable of improving light utilization efficiency and brightness of a display device such as an LCD. When a cholesteric liquid crystal polarizing film is used as a reflective polarizer, there is a problem in that it exhibits a retardation at an inclination angle due to anisotropy of the liquid crystal, thereby causing a color depending on a viewing angle. In the case of the optical film of the present application, since the retardation generated at the oblique angle can be compensated with each other by the different types of liquid crystal compounds existing in the first and second liquid crystal layers, the color change can be reduced at the oblique angle, A display device having an image quality can be provided.

An exemplary optical film may further comprise a quarter wavelength layer. In one example, the optical film may sequentially include a quarter wavelength layer, a first liquid crystal layer, and a second liquid crystal layer. FIG. 1 is a schematic view of an exemplary optical film of the present application, showing an example of an optical film 10 including a 1/4 wavelength layer 110, a first liquid crystal layer 120 and a second liquid crystal layer 130 in sequence As shown in Fig.

As used herein, the term " quarter wavelength layer " may mean a phase delay element capable of phase-delaying incident light by a quarter of its wavelength. This 1/4 wavelength layer can serve to make circularly polarized light into linearly polarized light. The quarter wavelength layer may have, for example, a phase retardation for a wavelength of 550 nm of 110 nm to 220 nm or 130 nm to 170 nm. In the present specification, " plane phase difference " is a numerical value calculated by (nx-ny) xd, where nx is the refractive index in the plane-phase slow axis direction of the 1/4 wavelength layer, ny is the plane- And d is the thickness of the quarter wavelength layer.

The 1/4 wavelength layer may be a polymer film or a liquid crystal film. Examples of the polymer film include polyolefins such as polycarbonate (PC), norbonene resin, polyvinyl alcohol (PVA), polystyrene (PS), poly (methyl methacrylate) (poly (arylate), PA (polyamide), PET (poly (ethylene terephthalate)) or PS (polysulfone). The polymer film may be stretched or shrunk under appropriate conditions to impart birefringence and used as the 1/4 wavelength layer.

In one example, the 1/4 wavelength layer may be a liquid crystal film formed by orienting and polymerizing a polymerizable liquid crystal compound. The liquid crystal film may contain a polymerizable liquid crystal compound in a polymerized state. In the present specification, the term "polymerizable liquid crystal compound" may mean a compound containing a moiety capable of exhibiting liquid crystallinity, such as a mesogen skeleton, and containing at least one polymerizable functional group. The phrase "the polymerizable liquid crystal compound is contained in a polymerized form" may mean a state in which the liquid crystal compound is polymerized to form a skeleton such as a main chain or side chain of the liquid crystal polymer in the liquid crystal film.

The polymerizable liquid crystal compound may be contained in the liquid crystal film in a horizontally oriented state, for example. As used herein, the term " horizontal alignment " means that the optical axis of the liquid crystal film containing the polymerized liquid crystal compound is in the range of about 0 to about 25 degrees, about 0 to about 15 degrees, about 0 to about 10 degrees , About 0 degrees to about 5 degrees, or about 0 degrees.

When the terms such as vertical, horizontal, orthogonal, or parallel are used in defining the angles in this specification, they mean substantially vertical, horizontal, orthogonal, or parallel in the range not to impair the desired effect. For example, , Manufacturing tolerance (error) or variation, and the like. For example, each of the above cases may include an error within about +/- 15 degrees, an error within about +/- 10 degrees, or an error within about +/- 5 degrees.

The term " liquid crystal layer " used herein means a layer containing a liquid crystal compound, and " cholesteric liquid crystal layer (hereinafter referred to as CLC layer) " means a layer containing a cholesteric liquid crystal compound it means. Referring to FIG. 2, the CLC has a helical structure in which a waveguide (n in FIG. 2) of liquid crystal molecules is layered and aligned along a spiral axis (X in FIG. 2). As used herein, the term " director " may mean an optical axis of a liquid crystal molecule, for example, when the liquid crystal compound is in the discotic state, it may mean an axis in the normal direction of the discotic plane, It can mean the long axis of the liquid crystal molecule. The distance (P in Fig. 2) until the waveguide of the liquid crystal molecules completes the rotation of 360 degrees in the structure of CLC is called " pitch ". As used herein, the term " CLC region " may refer to a CLC region in which a CLC waveguide completes a rotation of 360 degrees. In this specification, each CLC region can be divided, for example, according to the reflection wavelength of each CLC region.

The CLC can selectively reflect only circularly polarized light having the same twisted direction and circular polarization direction as the helical structure and having a wavelength equal to the helical pitch of the liquid crystal. The wavelength of the light reflected by the CLC depends on the refractive index and the pitch of the liquid crystal. The helical twist of the CLC waveguide causes spatially periodic deformation in the dielectric tensor of the material, which causes wavelength selective reflection of the light. Generally, in CLC, Bragg reflections occur when the wavelength λ of the light propagating along the helical axis falls within the category of the following general formula (1).

[Formula 1]

NoP < lambda < NeP

Where P is the pitch of the CLC region, Ne is the refractive index of the CLC for the light polarized parallel to the waveguide of the CLC and No is the refractive index of the CLC for the light vertically polarized in the waveguide of the CLC, .

In addition, the center wavelength? ₀ in the wavelength range of the light reflected by the CLC, that is, the reflected light, can be approximated by the following general formula (2).

[Formula 2]

? ₀ = 0.5 (No + Ne) P

In the general formula (2), P, Ne and No are as defined in the general formula (1).

Further, the spectral width?? ₀ of the light reflected by the CLC can be approximated by the following general formula (3).

[Formula 3]

? ₀ = 2? ₀ (Ne-No) / (No + Ne) = P (Ne-No)

In the above general formula (3), P, Ne and No are the same as defined in the general formula (1).

In the optical film, the liquid crystal layer may be a structure of a composite layer including first and second liquid crystal layers. In the present specification, the first and second liquid crystal layers are composite layers, meaning that the first and second liquid crystal layers are formed by laminating or adhering each other, or formed by continuously coating the first liquid crystal layer composition and the second liquid crystal layer composition Lt; / RTI > In one example, the first or second liquid crystal layer may be laminated or adhered via a pressure-sensitive adhesive layer described later, or an alignment layer or a primer layer may be coated on the first liquid crystal layer, and then the second liquid crystal layer composition may be coated .

In the optical film, any one of the first and second liquid crystal layers may include a discotic liquid crystal compound on the disc, and the other liquid crystal layer may include a nematic liquid crystal compound on the rod. The discotic liquid crystal compound on the disc or the nematic liquid crystal compound on the rod may be included in the first or second liquid crystal layer in a cholesteric orientation. That is, any one of the first and second liquid crystal layers includes a cholesteric discotic discotic liquid crystal compound, and the other liquid crystal layer contains a nematic liquid crystal compound on a cholesteric aligned rod .

As used herein, the term " liquid crystal compound on a disc " means a liquid crystal compound having a core of a molecule and a linear chain alkyl group, alkoxy group, substituted benzoyloxy group or the like substituted radially as a linear chain thereof, &Lt; / RTI > As such a liquid crystal compound on a disc, a liquid crystal compound known to form a so-called discotic phase can be used. In general, the liquid crystal compound on the disk has a negative refractive index anisotropy (monoaxiality), and examples thereof include benzene derivatives described in C. Destrade et al. Mol. Cryst. 71, p. 111 (1981); Cyclohexane derivatives described in B. Köhne et al. Angew. Chem. 96, 70 (1984); And azelaic compounds such as those described in J. Chem. Commun., 1794 (1985), J. Zhang et al., J. Am. Chem. Soc. Vol. 116, 2655 (1994) Acetylenic macrocycles, and the like. In one example, the liquid crystal compound on the disc may have a crosslinkable or polymerizable functional group. Examples of the crosslinkable or polymerizable functional group include, but are not limited to, an alkenyl group, an epoxy group, a cyano group, a carboxyl group, an acryloyl group, a methacryloyl group, an acryloyloxy group or a methacryloyloxy group .

As used herein, the term " liquid crystal compound on a rod " includes a compound that has a liquid crystal property with a film structure substituted with a linear chain alkyl group, alkoxy group, substituted benzoyloxy group, or the like. A liquid crystal compound known to form a so-called nematic phase can be used as the liquid crystal compound on such a rod. As used herein, the term " nematic phase " may refer to a liquid crystal phase arranged in order along the major axis, although there is no regularity for the position of the liquid crystal molecules. In one example, the liquid crystal compound on the rod may have a crosslinkable or polymerizable functional group. Examples of the crosslinkable or polymerizable functional group include, but are not limited to, an alkenyl group, an epoxy group, a cyano group, a carboxyl group, an acryloyl group, a methacryloyl group, an acryloyloxy group or a methacryloyloxy group .

The first and second liquid crystal layers may each include a CLC region in which the central wavelengths of the reflected light are different from each other. Such an optical film can exhibit selective reflection characteristics in a wide band.

One exemplary optical film is shown in Figures 3 and 4. 3 and 4, the optical film includes a first liquid crystal layer 320 and a first liquid crystal layer 420 formed on quarter wave layers 310 and 410, a quarter wavelength layer 310 and 410, 320, and 420, respectively. 3, the first liquid crystal layer 320 includes a discotic liquid crystal compound on the disc in a cholesteric orientation, and the second liquid crystal layer 330 includes a nematic liquid crystal compound on the rod in a cholesteric orientation . 4, the first liquid crystal layer 420 includes a nematic liquid crystal compound on the rod in a cholesteric orientation and the second liquid crystal layer 430 includes a discotic liquid crystal compound on the disc in a cholesteric orientation . In the above embodiments, the first liquid crystal layers 320 and 420 may have reflection wavelengths of blue and B regions. The reflection wavelength of the B region is within the range of 400 nm to 500 nm, for example, 450 nm to 500 nm. In this case, the second liquid crystal layers 330 and 430 may have reflection wavelengths of green, red, and GR regions. The reflection wavelength of the GR region is in the range of 500 nm to 800 nm, for example, 500 nm to 750 nm. The reflection wavelength of the second liquid crystal layer 330 or 430 may continuously increase or decrease. Specifically, when the reflection wavelength of the GR region adjacent to the first liquid crystal layer 320 or 420 is as low as, for example, about 500 nm, the reflection wavelength may be, for example, about 800 nm . On the contrary, when the reflection wavelength of the GR region adjacent to the first liquid crystal layer 320 or 420 is as high as, for example, about 800 nm, the reflection wavelength decreases to about 500 nm, for example, can do.

Other exemplary optical films are shown in Figures 5 and 6. 5 and 6, the optical film includes a first liquid crystal layer 520 and a first liquid crystal layer 620 formed on quarter wave layers 510 and 610, a 1/4 wavelength layer 510 and 610, 520, and 620. The first liquid crystal layer 530, 5, the first liquid crystal layer 520 includes a discotic liquid crystal compound on the disc in a cholesteric orientation, and the second liquid crystal layer 530 includes a nematic liquid crystal compound on the rod in a cholesteric orientation . 6, the first liquid crystal layer 620 includes a nematic liquid crystal compound on the rod in a cholesteric orientation and the second liquid crystal layer 630 includes a discotic liquid crystal compound on the disc in a cholesteric orientation state . In the above embodiments, the first liquid crystal layers 520 and 620 may have reflection wavelengths of red and R regions. The reflection wavelength of the R region is in the range of 650 nm to 800 nm, for example, 650 nm to 750 nm, or 650 nm to 720 nm. In this case, the second liquid crystal layers 530 and 630 may have reflection wavelengths of green, blue, and GB regions. The reflection wavelength of the GB region is in the range of 400 nm to 650 nm, for example, 400 nm to 620 nm. The reflection wavelength of the second liquid crystal layer 530 or 630 may continuously increase or decrease. Specifically, when the reflection wavelength of the GB region adjacent to the first liquid crystal layer 520, 620 is as low as about 400 nm, for example, the reflection wavelength becomes farther away from one liquid crystal layer 520, 620, . Conversely, when the reflection wavelength of the GB region adjacent to the first liquid crystal layer 520, 620 is as high as about 650 nm, for example, the reflection wavelength decreases to about 400 nm as the distance from one liquid crystal layer 520, can do.

The helical axis of the waveguide of the discotic liquid crystal compound on the disc or the waveguide of the nematic liquid crystal compound on the rod may be parallel to the thickness direction of the first or second liquid crystal layer. Typically, the CLC region includes a CLC molecule rotating in a spiral fashion, such that the helical axis of the CLC molecule is parallel to the thickness direction of the liquid crystal layer. In this specification, the CLC region in which the helical axis is oriented parallel to the thickness direction of the liquid crystal layer as described above may be referred to as a planar aligned CLC region.

In this specification, the term " thickness direction of the liquid crystal layer " may refer to a direction parallel to a virtual line connecting the one main surface of the liquid crystal layer and the main surface opposite thereto at the shortest distance. In one example, when the optical film further includes a substrate as described later, and the liquid crystal layer is formed on one surface of the substrate, the thickness direction of the liquid crystal layer is preferably set so that the thickness direction of the substrate And may be a direction parallel to an imaginary line formed in a direction perpendicular to the plane of FIG.

In one example, in the case where the 1/4 wavelength layer is a liquid crystal film, the 1/4 wavelength layer is a discotic liquid crystal compound (31L.51L) on the disc or a nematic And liquid crystal compounds 41L and 61L. In one example, the 1/4 wavelength layer may include a liquid crystal compound having the same kind of shape as the first liquid crystal layer. For example, the 1/4 wavelength layer and the first liquid crystal layer may each include discotic liquid crystal compounds (31L, 32L; and 51L, 52L) on the disc, and the 1/4 wavelength layer and the first liquid crystal layer And nematic liquid crystal compounds (41L, 42L; and 61L, 62L) on the rod.

The thicknesses of the first and second liquid crystal layers can be appropriately selected within a range not to impair the purpose of the present application. In one example, the first liquid crystal layer may have a thickness in the range of 2 占 퐉 to 5 占 퐉, and the second liquid crystal layer may have a thickness in the range of 4 占 퐉 to 7 占 퐉. When the first and second liquid crystal layers satisfy the above thickness range, it is advantageous to provide an optical film having brightness enhancement characteristics in a wide wavelength range and excellent visibility characteristics at an oblique angle. However, in the thickness range of the first and second liquid crystal layers Is not necessarily limited to the above range.

The first or second liquid crystal layer may comprise, for example, a CLC composition comprising a discotic liquid crystal compound and a chiral agent on the disc or a nematic liquid crystal compound on the rod and a chiral agent The first or second liquid crystal layer may be formed by polymerizing or crosslinking the CLC composition in a state in which the CLC composition is coated and the helical pitch of the liquid crystal molecules is induced by the chiral agent. In this case, And may include a polymer. In the above, the chiral agent may be crosslinkable or polymerizable, or may be non-crosslinkable or non-crosslinkable. The first and second liquid crystal layers may be formed by successively coating each CLC composition or by laminating or adhering the first and second liquid crystal layers respectively formed from the first and second CLC compositions to each other .

The chiral agent contained in the CLC composition is not particularly limited as long as it does not impair the liquid crystallinity of the liquid crystal compound, for example, discotic or nematic regularity, and can induce a desired spiral pitch Can be used. The chiral agent for causing the helical pitch in the liquid crystal needs to include at least the chirality in the molecular structure. Chiral agents include, for example, a compound having one or more asymmetric carbons, a compound having an asymmetric point on a heteroatom such as a chiral amine or a chiral sulfoxide, or a compound having an asymmetric carbon atom such as cumulene ) Or an axially asymmetric (optically active site) having an axial-reducing agent such as binaphthol. The chiral agent may be, for example, a low molecular weight compound having a molecular weight of 1,500 or less. For example, commercially available chiral nematic liquid crystals such as chiral dopant liquid crystal S-811 available from Merck Co., Ltd. or LC756 available from BASF may be used as the chiral agent. The content of the chiral agent in the CLC composition may be suitably selected within a range that does not impair the purpose of use, and may be, for example, 1 part by weight to 10 parts by weight based on 100 parts by weight of the liquid crystal compound.

The CLC composition may further include an initiator or a crosslinking agent for polymerization or crosslinking of the liquid crystal compound. Suitable polymerization initiators may include those capable of generating free radicals to initiate polymerization and crosslinking and to propagate. The free radical initiator may be selected, for example, depending on its stability or half life. Preferably, the free radical initiator does not generate additional color in the CLC layer by absorption or otherwise. Free radical initiators are typically thermal free radical initiators or photoinitiators. Thermally-free radical initiators include, for example, peroxide, persulfate or azonitrile compounds. Free radical initiators generate free radicals upon thermal degradation.

Photoinitiators can be activated by electromagnetic radiation or particle irradiation. Examples of suitable photoinitiators may include onium salt photoinitiators, organometallic photoinitiators, cationic metal salt photoinitiators, photodegradable organosilanes, latent sulfonic acids, phosphine oxides, cyclohexyl phenyl ketones, amine substituted acetophenones, and benzophenones have. In general, ultraviolet (UV) irradiation may be used to activate the photoinitiator, although other light sources may be used. The photoinitiator can be selected based on absorption of a specific wavelength of light.

The CLC composition typically can be part of a coating composition comprising at least one solvent. The coating composition may comprise, for example, dispersants, antioxidants and antiozonants. In addition, the coating composition may include various dyes and pigments to absorb ultraviolet, infrared or visible light, if desired. In some cases, it may be appropriate to add viscosity modifiers such as thickeners and fillers.

The CLC composition can be applied to the substrate by, for example, various liquid coating methods. In some embodiments, after coating, the CLC composition is crosslinked, polymerized, or converted into a CLC layer. This conversion can be accomplished by evaporation of the solvent, heating to align the CLC material, Crosslinking or polymerizing the CLC composition; Or application of heat, such as, for example, actinic irradiation; Irradiation of light such as ultraviolet light, visible light or infrared light and irradiation of an electron beam, or a combination thereof, or curing of a CLC composition using a similar technique.

The CLC composition may further comprise a solvent if desired. Examples of the solvent include halogenated hydrocarbons such as chloroform, dichloromethane, tetrachloroethane, trichlorethylene, tetrachlorethylene and chlorobenzene; Aromatic hydrocarbons such as benzene, toluene, xylene, methoxybenzene, and 1,2-dimethoxybenzene; Alcohols such as methanol, ethanol, propanol, isopropanol, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, and cyclopentanone; Cellosolve such as methyl cellosolve, ethyl cellosolve, and butyl cellosolve; And ethers such as diethylene glycol dimethyl ether (DEGDME) and dipropylene glycol dimethyl ether (DPGDME). The content of the solvent is not particularly limited and may be suitably selected in consideration of coating efficiency, drying efficiency, and the like.

In addition, the CLC composition may further comprise a surfactant. The surfactant is dispersed on the surface of the liquid crystal to make the surface even and stabilizes the liquid crystal alignment so that the surface of the film can be smoothly maintained after the formation of the CLC layer. As a result, the appearance quality can be improved.

As the surfactant, for example, a fluorocarbon surfactant and / or a silicon surfactant may be used. Fluorad FC4430 (TM), Fluorad FC4432 (TM), Fluorad FC4434 (TM) manufactured by 3M Company and Zonyl produced by Dupont Co., Ltd. can be used as the fluorocarbon surfactant, and silicone surfactants BYK 占 manufactured by BYK-Chemie, etc. may be used. The content of the surfactant is not particularly limited and may be suitably selected in consideration of coating efficiency, drying efficiency, and the like.

In one example, the method of forming the CLC layer such that the reflection wavelength continuously increases or decreases like the second liquid crystal layer is not particularly limited and can be formed by applying a method known in the art. For example, the coating layer of the CLC composition may be formed by irradiating ultraviolet rays to form a concentration gradient of the chiral agent in the coating layer, and then curing the coating layer in which the concentration gradient of the chiral agent is formed. However, It is not.

When irradiating the coating layer of the CLC composition with ultraviolet light having a relatively weak intensity at a predetermined temperature, it is possible to induce a concentration gradient of the chiral agent in the coating layer, that is, a change in the concentration of the chiral agent along the predetermined direction in the coating layer . In one example, the concentration gradient of the chiral agent may be formed along the thickness direction of the coating layer. Irradiation of ultraviolet rays forming a concentration gradient of chiral agent can be carried out at a temperature range of, for example, 40 ° C to 80 ° C, 50 ° C to 70 ° C or about 60 ° C. The irradiation of the ultraviolet ray for forming the concentration gradient may be performed by irradiating the ultraviolet ray of the ultraviolet ray A region with an amount of light of about 10 mJ / cm ² to 500 mJ / cm ² .

Next, a coating layer of the CLC composition, in which the concentration gradient of the chiral agent is formed in the coating layer of the CLC composition or in the same manner as described above, is applied to the coating layer of the CLC composition by irradiating with a sufficient amount of active energy ray, To form a CLC layer. The coating layer is fixed in a state in which the helical pitch of the liquid crystal compound is induced by the chiral agent by the ultraviolet ray irradiation, so that the CLC region can be formed. The irradiation condition of the active energy ray for polymerization or crosslinking, for example, ultraviolet rays is not particularly limited as long as the polymerization or crosslinking of the components of the composition is sufficiently carried out.

The optical film may further include a base layer. The base layer may be formed adjacent to the bottom of the quarter wavelength layer. Fig. 7 exemplarily shows an optical film including a base layer. 7, the optical film 70 may include a base layer 740, a 1/4 wavelength layer 710, a first liquid crystal layer 720, and a second liquid crystal layer 73 in sequence .

As the substrate, various kinds of substrates may be used. In one example, the substrate may be an optically anisotropic substrate, a polarization element, or the like, such as an optically isotropic substrate, a retardation layer, or the like.

As the optically isotropic substrate, a transparent substrate such as glass or a transparent plastic substrate may be used. Plastic substrates include cellulosic substrates such as DAC (diacetyl cellulose) or TAC (triacetyl cellulose) substrates; A cycloolefin copolymer (COP) base material such as a norbornene derivative resin base material; Polyolefin based materials such as polyethylene terephthalate (PBT), polyethylene terephthalate (PBT), polyethylene terephthalate (PBT), polyethylene terephthalate (polyarylate) base material, a fluoro resin base material, or the like may be used as the base material, such as a polyetheretherketone base material, a polyetherimide base material, a PEN (polyethylenenaphthatate) base material, a polyester base material such as a PET (polyethyleneterephthalate) base material, The substrate may be, for example, in the form of a sheet or a film.

Another exemplary film is shown in Fig. Referring to FIG. 8, an alignment layer, a primer layer, or a pressure-sensitive adhesive layer 850 may be additionally provided between the first and second liquid crystal layers 820 and 830. As used herein, the term " alignment film " may refer to a film exhibiting surface alignment properties that improve or provide alignment uniformity in the process of forming a liquid crystal layer, or produce alignment of liquid crystal waveguides. As the alignment film, for example, a known alignment film such as a photo alignment film or a rubbing alignment film can be used. The primer layer may be formed on one or both surfaces of one or more liquid crystal layers of the first and second liquid crystal layers from the viewpoint of improving the adhesion between the first and second liquid crystal layers. The type of the primer layer is not particularly limited, and various kinds of primer layers generally used for improving the adhesiveness can be used. The pressure-sensitive adhesive layer is for adhering the first and second liquid crystal layers, and various types of pressure-sensitive adhesive layers generally used for attaching the optical member can be used.

The optical film may further include a protective layer. This protective layer may be formed on the upper side of the second liquid crystal layer, for example, on the opposite side of the side where the first liquid crystal layer of the second liquid crystal layer is formed. Fig. 9 exemplarily shows an optical film including a protective layer. As shown in Fig. 9, the optical film 90 is formed in the order of a quarter wavelength layer 910, first and second CLC layers 920 and 930, and a protective layer 960 in this order.

As used herein, the term protective layer may include all known layers capable of protecting the liquid crystal layer. As the protective layer, for example, a protective layer having a haze of 50% or less can be used. The protective layer may exhibit the most suitable effect depending on the application to which the optical film is applied. For example, when the optical film is used as a brightness enhancement film of a display device as described later, the protective layer can prevent the color characteristics of the display device, in particular, the color change such as color inversion on the side . In addition, the protective layer can improve the brightness of the display device by appropriately scattering and / or diffusing light. The haze of the protective layer can be measured according to the manufacturer's manual using a hazemeter such as HR-100 or HM-150 of Sephoon Co., The specific kind of the protective layer is not particularly limited as long as it exhibits the haze in the above range while performing the function of protecting the liquid crystal layer.

The optical film may further include a surface treatment layer. Such a surface treatment layer can be disposed on the outermost layer of the optical film. In one example, when the second liquid crystal layer is disposed on the optical film, the surface treatment layer may be formed on the second liquid crystal layer, and the protective layer may be formed on the second liquid crystal layer The surface treatment layer may be formed on the protective layer. Fig. 10 exemplarily shows an optical film including a surface treatment layer. As shown in Fig. 10, when the optical film 100 is formed in the order of the 1/4 wavelength layer 101, the first liquid crystal layer 102, the second liquid crystal layer 103, and the surface treatment layer 107 Respectively. Such a surface treatment layer may include at least one layer of, for example, an anti-glare layer such as an SG (Semi-glare) layer, a layer containing a high refractive material, and a layer containing a low refractive material.

As the anti-glare layer such as the SG layer, for example, a resin layer having an uneven surface or a resin layer containing particles can be used as the resin layer, wherein the particles are particles having a refractive index different from that of the resin layer .

The resin layer may include, for example, a room temperature curing type, moisture curing type, thermosetting type or active energy ray curing type resin composition in a cured state. In one example, a thermosetting or active energy ray curable resin composition, Or an active energy ray-curable resin composition in a cured state. As used herein, the term " cured state " may mean that the components contained in each resin composition are converted into a hard state through a cross-linking reaction or a polymerization reaction. The above-mentioned room temperature curing type, moisture curing type, thermosetting type or active energy ray curable type resin composition can be prepared by heating the cured state at room temperature or by heating in the presence of appropriate humidity or irradiation of active energy rays &Lt; / RTI > composition.

In this field, various resin compositions are known which can satisfy the pencil hardness in the above-mentioned range in a cured state, and an average person can easily select a suitable resin composition.

The method of forming the uneven surface on the resin layer is not particularly limited. For example, the resin composition may be cured in a state in which the coating layer of the resin composition is in contact with a mold having a desired concavo-convex structure, or particles having a particle diameter appropriate for the resin composition may be blended, Can be implemented.

The anti-glare layer may be formed using particles having different refractive indices from the resin layer.

In one example, the difference in refractive index between the particles and the resin layer may be 0.03 or less or 0.02 to 0.2, for example. If the difference in refractive index is too small, it is difficult to cause haze. On the contrary, if the refractive index difference is excessively large, scattering in the resin layer occurs a lot and haze increases, but deterioration of light transmittance or contrast characteristics may be induced. And appropriate particles can be selected.

The shape of the particles contained in the resin layer is not particularly limited and may have, for example, spherical, elliptical, polyhedral, amorphous or other shapes. The particles may have an average diameter of 50 nm to 5,000 nm. In one example, as the particles, particles having irregularities on the surface can be used. Such particles may have a mean surface roughness (Rz) of, for example, 10 nm to 50 nm or 20 nm to 40 nm, and / or a maximum height of irregularities formed on the surface of about 100 nm to 500 nm or 200 nm to 400 nm, and the width between the irregularities may be 400 nm to 1,200 nm or 600 nm to 1,000 nm. Such particles are excellent in compatibility with the resin layer and in dispersibility therein.

As the particles, various inorganic or organic particles can be exemplified. Examples of the inorganic particles include silica, amorphous titania, amorphous zirconia, indium oxide, alumina, amorphous zinc oxide, amorphous cerium oxide, barium oxide, calcium carbonate, amorphous barium titanate, barium sulfate, Examples of the organic particles include crosslinked or non-crosslinked particles of an organic material such as an acrylic resin, a styrene resin, a urethane resin, a melamine resin, a benzoguanamine resin, an epoxy resin or a silicone resin, It is not.

The concavo-convex structure or the content of the particles formed on the resin layer is not particularly limited. The shape of the concavo-convex structure or the content of the particles can be adjusted, for example, in the case of the SG layer, such that the haze is about 1% to 3%. The haze can be measured according to the manufacturer's manual using a hazemeter such as HR-100 or HM-150 of Sephiroth Co.,

In addition, when the optical film is used as a brightness enhancement film of a display device as described later, the surface treatment layer may include a refractive index control material, for example, a layer containing a high refractive index material and / or a low refractive index material May be formed by coating. As the high refractive index material, it may mean a material having a refractive index of 1.5 or more, 2.0 or more, 2.5 or more, 2.6 or more, or 2.7 or more, and a low refractive index material may usually mean a material having a refractive index of less than 1.5 or 1.0 But is not limited to. The high refractive index material and the low refractive index material are variously known and can be suitably selected and used for the optical film. In order to form the surface treatment layer, it is also possible to form the surface treatment layer by the method described in Korean Patent Publication Nos. 2007-0101001, 2011-0095464, 2011-0095004, 2011-0095820, 2000-0019116, 2000-0009647, 2000-0018983, 2003-0068335, 2002- 0066505, 2002-0008267, 2001-0111362, 2004-0083916, 2004-0085484, 2008-0005722, 2008- 0063107, 2008-0101801 or 2009-0049557 can also be used.

The surface treatment layer may be formed singly or in combination of two or more. As an example of the combination, there is a case in which an SG coating layer capable of giving a general haze effect is formed on the surface of the substrate layer, and a layer containing a high-refractive-index material and / or a layer containing a low- .

In the optical film, at least one of the first and second liquid crystal layers may further include a haze component. In one example, the haze component may be present in a regular or irregularly dispersed state in at least one of the first and second liquid crystal layers, thereby causing scattering or diffusion of incident light to exhibit haze characteristics . When the first and second liquid crystal layers further contain a haze component, an optical film can be formed without forming a separate protective layer. As the haze component, the above-mentioned anti-glare layer may also be a particle having a refractive index different from that of the resin layer.

The haze component is present in a state of being dispersed in at least one of the first and second liquid crystal layers so as to induce haze, and the liquid crystal compound on the disc and / or the liquid crystal compound on the rod Can be used. As the haze component, for example, an organic substance or an inorganic substance can be used. The organic haze component may be, for example, an acrylic resin, a styrene resin, an olefin resin, a nylon resin, a melamine resin, a formaldehyde resin, a silicone resin, a urethane resin, a polyester resin or a polycarbonate resin. Examples of the inorganic haze component include, but are not limited to, antimony, tin, alumina, silica, zirconia, calcium carbonate, barium sulfate, and titanium oxide.

The present application also relates to a display device. An exemplary display device may include the optical film. The optical film may function as a brightness enhancement film in a display device. The optical film of the present application can provide an optical film not only capable of improving the brightness of a display device but also excellent in visual sensitivity at an inclination angle,

In one example, the display device may further include a display panel and a light source disposed on one side of the display panel, and the optical film may be disposed between the display panel and the light source.

In addition, the display device may include upper and lower polarizers disposed on both sides of the display panel. As the upper and lower polarizing plates, a conventional polarizing plate known in the art can be used. In one example, a known absorption line polarizer can be used as the polarizer. For example, as the polarizing plate, a polyvinyl alcohol polarizer may be used.

The polyvinyl alcohol polarizer may be a form in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol-based resin film. The polyvinyl alcohol-based resin can be obtained by, for example, gelling a polyvinyl acetate resin. As the polyvinyl acetate resin, homopolymers of vinyl acetate; And copolymers of vinyl acetate and other monomers copolymerizable therewith. Examples of the monomer copolymerizable with vinyl acetate include, but are not limited to, one or more kinds of monomers such as unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and acrylamides having an ammonium group. The degree of gelation of the polyvinyl alcohol resin may generally be about 85 mol% to 100 mol%, preferably 98 mol% or more. The polyvinyl alcohol resin may be further modified. For example, polyvinyl formal or polyvinyl acetal modified with aldehydes may be used.

A protective film may be formed on one surface or both surfaces of the polarizer. As the protective film, for example, a cellulose-based film such as a TAC film or the like; Polyester films such as PET (poly (ethylene terephthalate)) films; Polycarbonate-based films; Polyethersulfone-based films; A polyolefin film such as an acrylic film and / or a polyethylene film, a polypropylene film, a polyolefin film containing a cyclo or norbornene structure, or an ethylene-propylene copolymer film, but the present invention is not limited thereto. The protective film may be attached to the polarizer via a pressure-sensitive adhesive or an adhesive.

In one example, the display element may include the absorption axes of the upper polarizer and the lower polarizer so as to be perpendicular to each other. Further, the optical film may be disposed such that the second liquid crystal layer is positioned closer to the light source as compared with the 1/4 wavelength layer.

In addition, the absorption axis of the lower polarizer plate and the optical axis of the 1/4 wavelength layer may be arranged to form an angle of about 40 degrees to 50 degrees or about -40 degrees to -50 degrees. The quarter wavelength layer may be attached to the lower polarizer plate via a pressure-sensitive adhesive or an adhesive. As the pressure-sensitive adhesive or the adhesive, any of what is known in the art to be used for adhering an optical film can be used without limitation. In one example, the 1/4 wavelength layer is directly attached to one surface of the polarizer of the lower polarizer, for example, in the case of a polyvinyl alcohol-based polarizer, via a pressure-sensitive adhesive or an adhesive on one side of the polyvinyl alcohol- When a protective film is formed on one surface or both surfaces of the polarizer, the 1/4 wavelength layer can be attached to the opposite side of the protective film on the polarizer side via a pressure-sensitive adhesive or an adhesive. From the viewpoint of producing an optical film having a thinner thickness, the 1/4 wavelength layer is formed in a state in which it is directly attached to one side of a polyvinyl alcohol-based resin film such as a polyvinyl alcohol polarizer in a state in which no protective film is present Can be advantageous.

Fig. 11 exemplarily shows the display device. 11, the display device 110 includes a display panel 1102 in which, for example, an upper polarizer 1101 and a lower polarizer 1103 are disposed on both sides; And a light source 1104 disposed on one side of the lower polarizer plate 1103. The optical film 10 may be disposed between the lower polarizer plate 1103 and the light source 1104. [

In this structure, the optical film 10 includes a 1/4 wavelength layer 110 and first and second liquid crystal layers 120 and 130, and the second liquid crystal layer 130 of the first and second liquid crystal layers Is located closer to the light source 1104 than the quarter wavelength layer 110. [

The first and second liquid crystal layers 120 and 130 of the optical film 10 transmit a part of the light emitted from the light source 1104 to the quarter wavelength layer 110 side, The light source 1104 can be turned back on. The light transmitted to the 1/4 wavelength layer can be converted into linearly polarized light by the 1/4 wavelength layer and transmitted to the lower polarizer plate 1103. In this case, the light reflected by the first and second liquid crystal layers 120 and 130 is reflected again inside the device, the polarization characteristics thereof are changed, and the light is incident on the optical film 10 again. The luminance characteristic can be improved.

As long as the display device includes the optical film, other parts, structures, and the like are not particularly limited, and all contents well known in this field can be appropriately applied.

The optical film of the present application can be used as a reflective polarizer capable of improving light utilization efficiency and brightness of a display device such as an LCD. Particularly, since the optical film can reduce a color change at an oblique angle, a display device having excellent image quality can be provided.

1 is a view showing an exemplary optical film.
2 is an exemplary diagram for explaining CLC.
Figures 3 to 10 are views showing an exemplary optical film.
11 is a view showing an exemplary display device.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. However, the scope of the present application is not limited by the following description.

Example One

A blue discotic liquid crystal (manufactured by Fuji Film) having a reflection center wavelength of 480 nm was coated on the top of a 1/4 wavelength plate made of discotic liquid crystal to a thickness of about 3 탆, and a broadband reflection wavelength of 530 nm to 730 nm (Manufactured by Merck) having a haze value of about 25 占 퐉 was coated in a thickness of about 5 占 퐉, and haze component was dispersed in the nematic liquid crystal in an amount of about 20 parts by weight relative to 100 parts by weight of a nematic liquid crystal, % &Lt; / RTI >

Comparative Example One

An optical film was prepared in the same manner as in Example 1, except that a nematic liquid crystal (manufactured by Merck) having a broad-band reflection wavelength of 450 nm to 700 nm was coated on the top of the 1/4 wavelength plate to a thickness of about 6 μm .

Evaluation example 1. Evaluation of luminance characteristics

The film of Example 1 was adhered to the protective film (TAC film or acrylic film) of the PVA polarizing plate through an adhesive such that the optical axis of the 1/4 wavelength layer and the absorption axis of the PVA polarizing plate were about 45 degrees or -45 degrees Then, the luminance characteristics were evaluated while the light source was irradiated to the film side of Example 1. Specifically, the degree of brightness enhancement was evaluated by measuring front luminance and front color coordinates using CA210 and BM7 equipment.

As a result of the evaluation, when the film of Example 1 was adhered to the protective film of the PVA polarizing plate, the brightness of the PVA polarizing plate without the separate optical film was about 140% To the protective film of the PVA-based polarizer, a brightness of 136% versus a brightness of 100%. On the other hand, when the film of Example 1 was directly adhered to the PVA side of the PVA polarizing plate through an adhesive agent, similar results were obtained.

Evaluation example 2 color change rate evaluation

The film of Example 1 was adhered to the protective film (TAC film or acrylic film) of the PVA polarizing plate through an adhesive so that the absorption axis of the 1/4 wavelength layer and the PVA polarizing plate had an absorption axis of about 45 degrees or -45 degrees Then, the rate of change of front color coordinates of light before and after transmission of the film of Example 1 and the PVA-based polarizing plate and the rate of change of the frontal color coordinates at an inclination angle of 70 degrees were evaluated while irradiating the film side of Example 1 with the light source. For the film of Comparative Example 1, the rate of change of front chromaticity coordinates and the rate of change of the frontal chromaticity coordinates at an inclination angle of 70 degrees were evaluated in the same manner as in Example 1. Specifically, the rate of change of the color coordinates was measured using EZ Constant equipment, and the measurement result of the front color coordinate change rate of Comparative Example 1 set at 100% is shown in Table 1 below. Similar results were obtained in the case of directly adhering the films of Example 1 and Comparative Example 1 to the PVA side of the PVA polarizing plate through an adhesive agent.

Front chromaticity percentage change Inclination angle 70 ° color change rate Example 1 100% 130% Comparative Example 1 100% 200%

n: CLC waveguide
P: pitch
X: Spiral axis
10, 30, 40, 50, 60, 70, 80, 90, 100: optical film
110, 310, 410, 510, 610, 710, 810, 910, 101:
120, 320, 420, 520, 620, 720, 820, 920, 102:
130, 330, 430, 530, 630, 730, 830, 930, 103:
740: substrate layer
850: alignment layer, primer layer or adhesive layer
960: Protective layer
107: Surface treatment layer
110: display device
1101: Upper polarizer plate
1102: Display panel
1103: Lower polarizer plate
1104: Light source

Claims

Quarter wavelength layer; A first liquid crystal layer; And a second liquid crystal layer, wherein one of the first and second liquid crystal layers includes a discotic liquid crystal compound on the disc in a cholesteric orientation, and the other liquid crystal layer comprises a rod Wherein the nematic liquid crystal compound is in a cholesteric orientation.

The method according to claim 1,
Wherein the reflection wavelength of the first liquid crystal layer is in the range of 400 nm to 500 nm.

3. The method of claim 2,
And the reflection wavelength of the second liquid crystal layer is in the range of 500 nm to 800 nm.

The method of claim 3,
And the second liquid crystal layer has a continuously increasing or decreasing reflection wavelength.

The method according to claim 1,
Wherein the first liquid crystal layer has a reflection wavelength within a range of 650 nm to 800 nm.

6. The method of claim 5,
And the second liquid crystal layer has a reflection wavelength in the range of 400 nm to 650 nm.

The method according to claim 6,
And the second liquid crystal layer has a continuously increasing or decreasing reflection wavelength.

The method according to claim 1,
Wherein the spiral axis of the waveguide of the discotic liquid crystal compound on the disc or the waveguide of the nematic liquid crystal compound on the rod is parallel to the thickness direction of the first or second liquid crystal layer.

The method according to claim 1,
Wherein the 1/4 wavelength layer comprises a discotic liquid crystal compound on a disc or a nematic liquid crystal compound on a rod.

10. The method of claim 9,
Wherein the 1/4 wavelength layer and the first liquid crystal layer each comprise a discotic liquid crystal compound on the disc, or the 1/4 wavelength layer and the first liquid crystal layer each comprise a nematic liquid crystal compound on a rod.

The method according to claim 1,
Wherein the first liquid crystal layer has a thickness in the range of 2 탆 to 5 탆.

The method according to claim 1,
And the second liquid crystal layer has a thickness in the range of 4 탆 to 7 탆.

The method according to claim 1,
An optical film further comprising an orientation film, a primer layer or a pressure-sensitive adhesive layer between the first and second liquid crystal layers.

The method according to claim 1,
And a protective layer having a haze of 50% or less on the second liquid crystal layer.

The method according to claim 1,
Wherein the surface treatment layer further comprises a surface treatment layer on top of the second liquid crystal layer, wherein the surface treatment layer is made of an optical material including at least one of a semi-glare layer, a layer including a high refractive material, film.

The method according to claim 1,
Wherein at least one liquid crystal layer of the first and second liquid crystal layers further comprises a haze component.

The method according to claim 1,
Wherein the optical film further comprises a base layer under the quarter wavelength layer.

A display device comprising the optical film of claim 1.

19. The method of claim 18,
Wherein the display device includes a display panel and a light source disposed on one side of the display panel, and the optical film is disposed between the display panel and the light source.

20. The method of claim 19,
Wherein the optical film is disposed so that the second liquid crystal layer is positioned adjacent to the light source as compared with the 1/4 wavelength layer.