KR20180070169A - Optical film - Google Patents

Abstract

The present invention relates to an optical film, a manufacturing method thereof, and a usage thereof. The optical film has excellent durability by enhancing coherence of a substrate layer and a liquid crystal layer, and has excellent liquid crystal alignment and coating properties. Therefore, the optical film can be used as a viewing angle compensation film or a phase difference film.

Description

Optical film {Optical film}

The present application relates to an optical film, a manufacturing method thereof, and a use thereof.

The optical film can be used as a viewing angle compensation film or a retardation film in a display device, for example, a liquid crystal display device or an OLED display device. The optical film may include a liquid crystal layer. In one example, the optical film may comprise a layer of lyotropic liquid crystal. The liquid crystal refers to a liquid crystal capable of forming a liquid crystal phase at a constant composition or concentration. The optical film can be produced by directly coating a liquid crystalline composition on a base layer. However, when the liquid crystal composition is directly coated on the base layer, the adhesion between the base layer and the liquid crystal layer may be degraded under severe conditions such as high temperature and / or high humidity. The problem of deterioration of the adhesion between the two layers is directly related to the problem of durability of the optical film, which is one of the most important factors determining the performance of the optical film.

US Patent Publication No. 8,580,143

The present application provides an optical film which is excellent in durability by improving adhesion between a substrate layer and a liquid crystal layer, and also has excellent alignment property and coating property of a liquid crystal, a production method thereof, and use thereof.

The present application relates to optical films. The present application may include a base layer, a liquid crystal layer, and an adhesive layer positioned between the base layer and the liquid crystal layer. The liquid crystal layer may include a dichroic dye showing a liquid crystalline phase. The adhesive layer may comprise an acryl styrene copolymer.

 The optical film of the present application not only improves the adhesive force between the base layer and the liquid crystal layer by disposing the adhesive layer between the base layer and the liquid crystal layer but also enhances the adhesion between the base layer and the liquid crystal layer by using an adhesive layer containing an acryl- Orientation and coating properties can be improved. Hereinafter, the optical film of the present application will be specifically described.

The optical film of the present application may have a structure including the base layer 100, the adhesive layer 200, and the liquid crystal layer 300 sequentially as shown in Fig.

The optical film has excellent durability because it has excellent adhesive property between the base layer and the liquid crystal layer. The adhesive property of the optical film can be represented by a cross-cut test in which the exfoliated area is 5% or less of the total area, and in the other examples, the exfoliated area according to the crosscut test measured according to ASTM D3002 / D3359 May be less than 5%, less than 4%, less than 3%, or less than 2% of the total area. The cross-cut test may be performed according to a cross-hatch adhesion force measurement <Experimental Example 1> described later.

The optical film of the present application includes a base layer. The base layer serves as a support for the liquid crystal layer and the adhesive layer. For example, in one example, the base layer may be a polyolefin such as polyethylene or polypropylene; Polyesters such as polyethylene terephthalate and polyethylene naphthalate; Cellulose such as triacetylcellulose, diacetylcellulose, propionylcellulose, butylcellulose or acetylcellulose; Polyamides such as 6-nylon or 6,6-nylon; Acrylic polymers such as polymethyl methacrylate; Polystyrene, polyvinyl chloride, polyimide, polyvinyl alcohol, polycarbonate, or ethylene vinyl alcohol, but the present invention is not limited thereto. The base layer may be formed of a mixture or polymer of one or more of the above-mentioned types, or may be of a structure in which a plurality of layers are laminated.

The base layer may contain known additives such as an antistatic agent, an ultraviolet absorber, an infrared absorber, a plasticizer, a lubricant, a colorant, an antioxidant or a flame retardant.

The base layer may be one whose surface has been modified. The surface modification may employ, for example, a chemical treatment, a corona discharge treatment, a mechanical treatment, an ultraviolet (UV) treatment, an active plasma treatment or a glow discharge treatment.

The thickness of the base layer is not particularly limited, but may be in the range of, for example, 10 탆 to 300 탆.

The base layer may have a refractive index within a range of, for example, 1.0 to 2.5 with respect to light having a wavelength of 550 nm. Within this range, appropriate transparency of the optical film can be ensured and optical characteristics can be applied to a display device.

The optical film of the present application includes a liquid crystal layer. The liquid crystal layer may include a liquid crystalline compound. The liquid crystal layer may include a dichroic dye as the liquid crystalline compound.

The term &quot; LLC (Lyotropic Liquid Crystal) &quot; as used herein means a material exhibiting liquid crystallinity in a constant composition or concentration range, unlike a thermotropic liquid crystal exhibiting properties of liquid crystal at a constant temperature.

The term &quot; dichroic dye &quot; in the present application means a substance which exhibits anisotropic absorption behavior of an electron beam in a predetermined wavelength range, for example, a molecule capable of absorbing more light in a specific direction than in another direction .

The aforementioned liquid crystalline compound may be, for example, a rod-type liquid crystalline compound or a disk-type liquid crystalline compound.

The mammary liquid crystal compound may be a dichroic dye comprising a dye chromophore core and a salt-type moiety. In one example, the liquid crystalline compound may be represented by the following formula (1).

[Chemical Formula 1]

And Q is a chromophore system of a dye in the formula 1, A represents a single bond, an alkali of 1 to 12 carbon atoms or an alkylene group having 1 to 12 carbon atoms in _{dengi, -SO 2 NH-T-, -SO} 2 -T-, -CONH -T-, -CO-T-, -OT-, -ST- or -NH-T-, wherein T is an alkylene group or an alkylidene group having 1 to 10 carbon atoms, R is a salt- n is the number of AR groups bonded to Q and is 1 to 10;

The dye chromophore system in Formula 1 may be a dye chromophore system having a maximum absorption wavelength in the range of 350 nm to 900 nm, preferably 350 nm to 600 nm, more preferably 440 nm to 500 nm. The dye chromophore system may also be a chromophoric system having a molecular weight of from 300 g / mol to 900 g / mol, preferably from 450 g / mol to 800 g / mol, more preferably from 600 g / mol to 900 g / mol have.

In the formula (1), a single bond means that no atom exists in a portion denoted by A and Q and R are directly connected to each other. A is preferably a single bond, an alkylene group having 1 to 8 carbon atoms or an alkylidene group having 1 to 8 carbon atoms, more preferably a single bond, an alkylene group having 1 to 4 carbon atoms or an alkylene group having 1 to 4 carbon atoms An alkylidene group, and more preferably a single bond.

Further, the residue of a salt form in formula (I) are, for example, the residues contained in the above-described breast liquid crystal compound, for example, -X _i O ^- M ⁺ _i, and the like, and preferably -SO ₃ ^- M ⁺ or -COO ^- M ⁺ , wherein M ⁺ is H ⁺ ; ^{_{NH 4 +, Li +, Na}} +, K +, Cs +, 1 / 2Mg ++, 1 / 2Ca ++, 1 / 2Ba ++, 1 / 3Fe +++, 1 / 2Ni ++ or 1 / 2Co Inorganic cations such as ⁺⁺ ; Alkylpyridinium, N-alkylquinolinium, N-alkylimidazolinium, N-alkylthiazolinium, OH- (CH ₂ -CH ₂ O) _m -CH ₂ CH ₂ -NH ₃ ⁺ in, m is from 1 to ^{_{9), RR'NH 2 +, RR'R}} "NH +, RR'R" R * N +, RR'R "R * P + ( in the above, R, R ', R" , R ^* is _{CH 3, ClC 2 H 4,} C 2 H 5, C 3 H 7, C 4 H 9, C 6 H 5 CH 2 substituted or unsubstituted alkyl group such as, a substituted or unsubstituted phenyl or heteroaryl in Im) or _{YH- (CH 2 -CH 2 Y)} k -CH 2 CH 2 ( wherein, Y is O or NH, k may be a 0 to 10).

The M ⁺ may preferably be an inorganic cation, more preferably Li ⁺ , Na ⁺ , K ⁺ or Cs ⁺ , more preferably Na ⁺ or Li ⁺ .

In Formula 1, n is preferably 1 to 5, more preferably 1 to 3.

The liquid crystalline compound of formula (1) may more preferably be represented by the following formula (2).

(2)

Wherein U is -N = N- or -O- (CH ₂ ) - (CHOH) - (CH ₂ ) - (CH ₂ ) -O- and X is independently selected from the group consisting of aryl R ₁ is a hydroxyl group, an alkoxy group having 1 to 12 carbon atoms, a haloalkyl group having 1 to 12 carbon atoms, an oxo group, or -N═N Ph is an alkoxy group having 1 to 12 carbon atoms or an unsubstituted phenyl group; l and m each independently represent 1 or 2, and p and q is the number of R ₁ substituted on X, and each independently represents a number of 0 to 2;

The hetero atom contained in the heteroaryl group as a ring constituting atom in the above may be, for example, N or O, preferably N. [ The heteroatoms in the ring atoms of the heteroaryl group may be, for example, 1 to 5, preferably 1 to 3, more preferably 1 to 2 heteroatoms.

In the general formula (2), -U- may preferably be -N = N-, and X is preferably an aryl group having 6 to 12 carbon atoms or a heteroaryl group having 6 to 12 ring-constituting atoms, more preferably 6 And R ₁ is preferably a hydroxyl group, an alkoxy group having 1 to 8 carbon atoms, a haloalkyl group having 1 to 8 carbon atoms, an oxo group or -N = N-Ph wherein Ph is at least one carbon number More preferably a hydroxy group, an alkoxy group having 1 to 4 carbon atoms, a haloalkyl group having 1 to 4 carbon atoms, an oxo group or -N = N-Ph (in the above formula Ph is a phenyl group substituted with at least one alkoxy group having 1 to 4 carbon atoms or unsubstituted phenyl group), l and m are more preferably 1, and p and q are each independently 0 or 1 Lt; / RTI &gt;

Examples of the halogen which may be substituted on the haloalkyl group include chlorine and fluorine.

With the above-mentioned mammary liquid crystal compound, it is possible to produce a liquid crystal compound for the purpose of changing the colloid-chemical property including the structure of the composition forming the liquid crystal layer based on the liquid crystal compound and the rheological property of the liquid crystal layer based on the liquid crystal compound It may be possible to control the hydrophobic-hydrophilic balance of the mammary liquid crystal compound which is a very important factor other than the purity of the liquid crystalline compound.

Specifically, the characteristics of the composition for forming the liquid crystalline layer and the liquid crystalline compound can be particularly effectively controlled in the case of a dye having two or more ionic groups. In this case it is possible to use two or more different cations, each cation providing their own properties, or other properties. For example, the combination of Li + cations that provide increased solubility and the tetra-butylammonium cations that stabilize the three ethanol ammonium cations and liquefied liquid crystal phases to reduce the cohesion of dye molecules can be achieved by single molecules and / &Lt; / RTI &gt; to form a liquid crystal layer based on a molecular dye association (complex) having at least one functional group. Further, the liquid crystal compound having a linear molecular structure promotes the formation of a nematic liquid crystal phase and provides a higher degree of orientation by the formation of a liquid crystal layer, and as a result, can provide a more effective selective transmission and reflection of the electron beam .

In addition, 1 / 2Mg ^++, the addition of polyvalent cations such as 1 / 2Ca ^++, or 1 / 2Ba ⁺⁺ are supramolecular having a degree of compaction to increase the degree of compaction in the molecular complex and in excess of the high degree of compaction, for example 50 Resulting in the formation of a mammary liquid crystal phase of the complex, the solubility of which can be increased using surfactant ions.

The liquid crystal layer may contain, for example, not more than 50% by weight of a modifier such as a stabilizer of a different type of light including a liquid crystal, a silicone, a plasticizer, a lacquer, a nonionic system and an ionic surfactant, a hydrophilic and / . &Lt; / RTI &gt;

In one example, the liquid crystal layer may be formed in a multi-layer structure, and in this case, the liquid crystal compound contained in each layer may have a different maximum absorption wavelength. Accordingly, selective transmission and reflection characteristics can be exhibited for light in a broader wavelength range.

The thickness of the liquid crystal layer varies depending on the phase difference to be obtained, Δn (birefringence) × d (thickness of the liquid crystal film), but is generally about 0.1 μm to 10 μm. It is preferable that the thickness of the liquid crystal layer is 0.1 占 퐉 to 10 占 퐉 in order to obtain an appropriate range of phase difference for optical compensation of the display device.

The liquid crystal composition containing the liquid crystalline compound is subjected to a shear force induced upon separation of the liquid crystal composition layer from one surface to another surface, for example, as disclosed in U.S. Patent No. 5,739,296, the liquid crystal layer can be formed by a method based on mechanical ordering that can be realized by a method that imposes a force or wedging forces on the liquid crystal layer.

The optical film of the present application may include an adhesive layer positioned between the base layer and the liquid crystal layer. The base layer and the liquid crystal layer may be attached to each other via the adhesive layer.

The adhesive layer may comprise an acryl styrene copolymer. May mean a copolymer of an acrylic monomer and a styrene-based monomer in the present application. The adhesive layer not only improves the adhesive force between the base layer and the liquid crystal layer but also improves the alignment and coating properties of the liquid crystal by including an acrylic styrene copolymer.

As the acrylic monomer, alkyl (meth) acrylate may be used. (Meth) acrylate having an alkyl group of 1 to 20 carbon atoms, 1 to 16 carbon atoms, 1 to 12 carbon atoms, 1 to 8 carbon atoms, or 1 to 4 carbon atoms in consideration of control of cohesion, glass transition temperature and tackiness, Can be used. The alkyl group may be linear, branched or cyclic. Examples of such monomers include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, (Meth) acrylate, n-butyl (meth) acrylate, sec-butyl (meth) acrylate, pentyl (Meth) acrylate, isooctyl (meth) acrylate, isononyl (meth) acrylate and lauryl (meth) acrylate. Can be selected and used.

Examples of the styrene monomer include styrene, methylstyrene, and the like.

In one example, the copolymer may be a copolymer of alkyl (meth) acrylate and styrene. More specifically, the copolymer may be a copolymer of methyl methacrylate and styrene or a copolymer of butyl methyl methacrylate and styrene.

The copolymer may have a weight average molecular weight ranging from 40,000 to 150,000. It is possible to appropriately secure the desired adhesive property within the above range.

The adhesive may comprise 5% to 20% by weight of the copolymer. It is possible to appropriately secure the desired adhesive property within the above range.

The thickness of the adhesive layer included in the optical film of the present application is not particularly limited, but may be in the range of 0.1 to 100 占 퐉.

Such an adhesive layer may be formed by coating a composition containing the above-mentioned components and then curing. The adhesive layer according to the present application may be, for example, a cured layer of an ultraviolet curing compound.

The adhesive layer of the present application may further include an additive such as a hardening agent. Examples of the curing agent contained in the adhesive layer include an amine curing agent, an imidazole curing agent, a phenol curing agent, an acid anhydride curing agent, and an ultraviolet curing agent.

Specific examples of the curing agent include organic amine compounds, dicyandiamide and derivatives thereof, imidazoles and derivatives thereof such as 2-methylimidazole and 2-ethyl-4-methylimidazole; Divalent phenol compounds such as bisphenol A, bisphenol F, brominated bisphenol A, naphthalene diol and 4,4'-biphenol; A novolak resin or an aralkyl phenol resin obtained by condensation reaction of phenol or naphthol with formaldehyde or xylene glycol; There may be mentioned succinic anhydride, maleic anhydride, dehydrated anhydride, hexahydrophthalic anhydride, methylated hexahydrophthalic anhydride, nadic acid, hydrogenated anhydride, trimellitic anhydride, pyromellitic anhydride and the like. Acid anhydrides; Hydrazide compounds such as adipic acid hydrazide; Benzoins such as benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin-iso-propyl ether and? -Methyl benzoin; benzophenones such as? -hydroxyisobutylphenone, benzophenone, p-methylbenzophenone, p-chlorobenzophenone, and p-diethylaminobenzophenone; Anthraquinones such as acetophenone, 9,10-anthraquinone, 1-chloroanthraquinone, and 2-chloroanthraquinone; Or sulfur-containing compounds such as diphenyl disulfide and tetramethyl thiuram disulfide, and the like, and two or more types may be used if necessary.

The adhesive layer may further include a curing accelerator, a dispersant, a filler, or an antioxidant as an additive.

The optical film of the present application further comprises a hard coat layer. The hard coating layer may be on the opposite side of the surface of the base layer 100 that is in contact with the adhesive layer 200, for example, as shown in FIG. 2, It may exist on both sides. Both sides of the adhesive layer 200 may be in contact with the liquid crystal layer 300 and the hard coat layer 400 when the hard coat layer 400 is included on both sides of the substrate layer 100.

The hard coating layer of the present application is present on one side or both sides of the substrate layer and can prevent the flatness of the substrate layer, the adhesion between the respective layers in the optical film, and the deterioration of optical properties due to the difference in physical properties between the respective layers have.

In one example, the hard coat layer may comprise polymerized units of polyfunctional (meth) acrylate.

The term &quot; polymerized unit &quot; in the present application means a state in which the above compound is polymerized in the skeleton such as a main chain or side chain of a polymer formed by polymerizing a predetermined compound.

In one example, the polyfunctional (meth) acrylate may mean two or more functional groups, for example, a (meth) acrylate monomer, oligomer or polymer having a radically polymerizable functional group. In addition, the term &quot; (meth) acrylate &quot; may mean acrylate or methacrylate.

The functional group of the polyfunctional (meth) acrylate compound may be, for example, acryloyl group or methacryloyl group. The functional groups of the polyfunctional (meth) acrylate compound may be the same as or different from each other.

In one example, the polyfunctional (meth) acrylate is selected from the group consisting of trimethylolpropane tri (meth) acrylate, ethoxylated trimethylolpropane tri (meth) acrylate, propoxylated trimethylolpropane tri (meth) (Meth) acrylates such as 2-hydroxyethyl isocyanurate tri (meth) acrylate, glycerin tri (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol tri (Meth) acrylate, and the like.

The polyfunctional (meth) acrylate may be at least one selected from the group consisting of pentaerythritol tetra (meth) acrylate, ditrimethylol propane tetra (meth) acrylate, dipentaerythritol tetra (meth) acrylate, dipentaerythritol penta (Meth) acrylate compound having three or more functionalities such as acrylate, acrylate, ditrimethylolpropane penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate or ditrimethylolpropane hexa Lt; / RTI &gt;

The hard coating layer may further include a polymerization unit of a monomer having a polar functional group capable of interacting with the base layer or the adhesive layer so as to improve the adhesive strength with the base layer or the adhesive layer.

In one example, the monomer containing a polar functional group includes at least one functional group selected from a diol group, a thiol group, a hydroxyl group, a carboxy group, an amine group, an isocyanate group, a glycidyl group, an ether group and an ester group It may be a monomer.

In one example, the monomer having a hydroxyl group includes 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (Meth) acrylate or 8-hydroxyoctyl (meth) acrylate, and the like.

In one example, the monomer having a carboxy group includes (meth) acrylic acid, 2- (meth) acryloyloxyacetic acid, 3- (meth) acryloyloxypropyl acid, 4- , Acrylic acid dimer, itaconic acid, maleic acid or maleic anhydride.

In one example, the thiol group-bearing monomer of the present application may be a polythiol compound having two or more thiol groups.

Specific polythiol compounds include bis (2-mercaptoethyl) sulfide, 4-mercaptomethyl-1,8-dimercapto-3,6-dithiaoctane, 2,3- ) Propane-1-thiol, 2,2-bis (mercaptomethyl) -1,3-propanedithiol, tetrakis (mercaptomethyl) methane; (2,3-bis (2-mercaptoethylthio) propylthio) ethanethiol, bis (2,3-dimercapto (2-mercaptoethylthio) -3-mercaptopropane, 1,2-bis (2,3-dimercaptopropanel) disulfide, 2-mercaptoethylthio) -3-mercaptopropylthio) ethane, bis (2- (2-mercaptoethylthio) -3-mercaptopropyl) sulfide, 2- 3-mercapto-3- [3-mercapto-2- (2-mercaptoethylthio) -propylthio] propylthio-propane- 1 -thiol, 2,2- Propionyloxymethyl) -butyl ester, 2- (2-mercaptoethylthio) -3- (2- (2- [3-mercapto-2- ) Ethylthio) propane-1-thiol, (4R, 11S) -4,11-bis (mercaptomethyl) -3,6,9,12- tetrathiatetradecane- -3 - ((R-2,3-dimercaptopropyl) thio) propane-1,2-dithiol, (4R, 14R) (S) -3 - ((R-3-mercapto-2 - ((2 (R) -3-mercapto methyl) -3,6,9,12,15-pentatihaheptane- -Mercaptoethyl) thio) propyl) thio) propyl) thio) -2 - ((2-mercaptoethyl) thio) propane- 1 -thiol, 3,3'-dithiobis Dithiol, (7R, 12S) -7,12-t-butoxycarbonylamino- Bis (mercaptomethyl) -3,6,9,10,13,16-hexatiaoctadecane-1,18-dithiol, 5,7-dimercaptomethyl-1,11-dimercapto- 6,9-trithiandecane, 4,7-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiandecane, 4,8-dimercaptomethyl-1,11- Dimercapto-3,6,9-trithiandecane, pentaerythritol tetrakis (3-mercaptopropionate), trimethylolpropane tris (3-mercaptopropionate), pentaerythritol tetra Kiss (2-mercaptoacetate), bispentaerythritol-ether-hexakis (3-mercaptopropionate), 1,1,3,3-tetra (Mercaptomethylthio) propane, 1,1,2,2-tetrakis (mercaptomethylthio) ethane, 4,6-bis (mercaptomethylthio) -1,3-dithiane or 2- , 2-bis (mercaptodimethylthio) ethyl) -1,3-dithiethane, and the like.

In one example, the monomer having the diol group of the present application may be a (meth) acrylate compound having a diol group. Examples of the monomer having a diol group include monomers such as ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, butanediol (meth) acrylate, hexanediol di (meth) (Meth) acrylate, propoxylated hexanediol di (meth) acrylate, diethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, tripropylene glycol di ) Acrylate, polypropylene glycol di (meth) acrylate, acrylate neopentyl glycol di (meth) acrylate, epoxidized neopentyl glycol di (meth) acrylate, tripropylene glycol di (meth) Acrylate, glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, ethoxylated neopentyl glycol di (meth) But are not limited to, dipropylene glycol di (meth) acrylate or hydroxypivalic neopentyl glycol di (meth) acrylate.

The optical film of the present application can have the property that the adhesion between each layer is excellent and the optical properties are maintained even under severe conditions through the above-described structures.

The present application also relates to a method for producing an optical film

The method for producing an optical film according to the present application comprises the steps of coating an adhesive composition comprising an acrylic styrene copolymer and a solvent on a base layer to form an adhesive layer and coating the liquid crystal composition comprising a liquid crystalline compound and a solvent .

The method of manufacturing an optical film according to the present application is characterized in that an adhesive layer containing a specific copolymer is first formed on a base layer in order to overcome the problem of a decrease in adhesive strength that may be caused by coating a liquid crystal composition directly on the base layer , It is possible to provide an optical film excellent in adhesion between the substrate layer and the liquid crystal layer, alignment property of the liquid crystal and coating property through the step of forming the liquid crystal layer.

The method of manufacturing an optical film according to the present application may include forming an adhesive layer by coating an adhesive composition on a base layer.

The adhesive composition may comprise an acrylic styrene copolymer.

The acrylic styrene copolymer may be applied to the optical film in the same manner as described above.

The adhesive composition may further comprise a solvent. The solvent may be, for example, a known organic solvent such as methyl ethyl ketone, ethyl acetate or toluene, but is not limited thereto.

As a method of coating the adhesive composition on the substrate layer, known coating methods such as bar coating, spin coating, microgravure coating, gravure coating, dip coating, or spray coating can be used without limitation.

After the adhesive composition is coated on the base layer, the adhesive layer can be formed by applying appropriate heat and curing. The manner of curing is also not particularly limited, and for example, a method of curing the adhesive layer at a temperature at which a solvent or the like can volatilize can be used.

The method for producing an optical film according to the present application also includes a step of coating a liquid crystal composition comprising a liquid crystalline compound to form a liquid crystal layer.

For the liquid crystalline compound, the same contents as described in the item of the optical film may be applied. Examples of the liquid crystalline compound include the compounds represented by Formula 1 or Formula 2 described above.

The liquid crystal composition can be prepared by, for example, dispersing the concentration of the diluting liquid to a required concentration, for example one of the above-mentioned dye molecules or supramolecular complexes, (DMF), dimethylsulfoxide (DMSO), cellosolve, ethyl acetate and water, or by mixing with water, a water / alcohol, a bipolar aprotic solvent An aqueous solution of a suitable dye, an aqueous-organic solution and an organic solution, by dissolving the dry dye in a suitable solvent such as a mixture of water and an organic solvent or other solvent.

At this concentration, the concentration of the dyestuff, i.e., the liquid crystalline compound in the liquid crystalline composition is 0.5% by weight to 30% by weight, preferably about 0.5% by weight to 20% by weight, more preferably about 0.5% by weight to 15% Lt; / RTI &gt;

In order to control the colloid-chemical properties of the liquid crystalline liquid, the composition may contain, in addition to the solvent, additives and modifiers such as nonionic and ionic surfactants, binders and film forming reactants (polyvinyl alcohol, polyvinylpyrrolidone, Polyacrylic acid and its ethers, polyacrylamides, polyethylene oxide and polyethylene glycols, polypropylene glycols and copolymers thereof, ethyl- and hydroxypropyl ethers of cellulose, sodium salts of carboxymethylcellulose and the like). The composition may further comprise additives from the amide family, such as hydrotropic additives such as dimethylformamide, dimethylsulfoxide, alkylamides of phosphoric acid, carbamides and N-substituted derivatives thereof, N-alkylpyrrolidones, Amides and mixtures thereof, and mixtures of amides and glycols. The use of suitable additives not only increases the stability of the composition but also makes it possible to control the aggregation process of dye molecules and consequently to control the formation process of the mammary liquid crystal phase. Thus, the addition of the hydrotropic additive makes it possible to prepare a composition for forming a liquid crystal layer containing a single mammary liquid crystal compound.

Accordingly, the liquid crystal composition can contain different types of light, hydrophilic and / or hydrophobic polymer stabilizers, including up to 50% by weight of modifiers such as liquid crystals, silicones, plasticizers, lacquers, nonionic, May be further included.

In order to form the liquid crystal layer, a liquid crystal composition is first coated on a base layer on which an adhesive layer is formed, followed by drying to remove the solvent. The coating method is not particularly limited, but it is preferable to coat the liquid crystalline composition by a method capable of coating the liquid crystalline composition at a uniform thickness. For example, spin coating, microgravure coating, gravure coating, dip coating, spray coating may be used, and the coating method is not limited thereto.

Removal of the solvent can be carried out by any method generally known in the art in which most of the solvent can be removed and the coated liquid crystal layer does not flow off or flow so badly. The removal of the solvent is not particularly limited, but can be performed by, for example, drying at room temperature, drying in a drying oven, heating and drying on a heating plate, and drying using infrared rays. The drying time and the drying temperature are not particularly limited as long as they depend on the type and content of the solvent, and more specifically, can be carried out for a time sufficient to remove the solvent at 50 ° C to 100 ° C, specifically about 30 seconds to 300 seconds have. The solvent can be effectively removed without adversely affecting the physical properties of the liquid crystal layer and the liquid crystal layer constituent components by drying during the above-mentioned temperature range.

After the solvent is evaporated and removed, the liquid crystal layer can be cured and fixed by, for example, photo-curing. The liquid crystal material vertically aligned by the curing is polymerized and the vertical alignment is fixed. The curing can be carried out in the presence of a photopolymerization initiator that absorbs the wavelength of the ultraviolet region. On the other hand, ultraviolet irradiation can be carried out in an atmosphere of nitrogen or in an atmosphere to increase the reaction efficiency by blocking oxygen.

As the ultraviolet irradiator, a medium pressure or high pressure mercury ultraviolet lamp or a metal halide lamp having an illuminance of usually about 100 mW / cm ² or more may be used, though it is not limited thereto. Furthermore, a cold mirror or a cooling device may be installed between the substrate and the ultraviolet lamp (irradiator) in order to maintain the surface temperature of the film at an appropriate level during ultraviolet irradiation so as to prevent deformation of the film.

The present application also relates to a use of an optical film, for example a display device comprising an optical film.

Specifically, the optical film of the present application can be applied to a polarizing plate as it is, and can be very usefully used as a retardation film or a viewing angle compensating film in various LCD modes such as an IPS mode. The specific types, structures, and components of the display device are not particularly limited, and as long as the optical film is included, all contents known in the art can be applied.

The present application can provide an optical film having improved durability by improving the adhesive force between the base layer and the liquid crystal layer, and having excellent alignment property and coating property of liquid crystal, and a manufacturing method thereof. The optical film of the present application can be used as a viewing angle compensation film or a retardation film of a display device.

1 to 3 are diagrams showing the structure of the optical film according to the present application.
4 is an image of the appearance of the optical films of Example 1, Comparative Example 1 and Comparative Example 3 after initial and 400 hours of exposure

Hereinafter, the present application will be described in more detail by way of examples according to the present application and comparative examples not complying with the present application, but the scope of the present application is not limited by the following embodiments.

Example  One

Preparation of adhesive composition

B-819 (a copolymer of methyl methacrylate and styrene, DS: Mw: 40,000) was prepared from acrylic styrene copolymer. An adhesive composition was prepared by adding 5 wt% of the copolymer to the propyl acetate solvent.

Preparation of liquid crystal composition

A liquid crystal composition was prepared by dissolving a dichromatic dye in which the cation Na ⁺ of the Direct Yellow 12 dye as a dichroic dye forming a mammary liquid crystal phase was substituted with Li ⁺ at a concentration of about 1 wt% in the distilled water.

Manufacture of optical film

The adhesive composition of Preparation Example 1 was coated on a corona-treated substrate layer (PET, thickness: 125 탆) using a wire bar coater and dried in a drying oven at about 85 캜 for 2 minutes to obtain an adhesive Layer. The liquid crystal composition of Production Example 12 was coated on the adhesive layer using a wire bar coater and dried in a drying oven at about 90 캜 for 2 minutes to form a liquid crystal layer having a thickness of about 1 탆, To prepare an optical film.

Example  2

An optical film was prepared in the same manner as in Example 1, except that a copolymer of butyl methyl methacrylate and styrene was used as the acrylic styrene copolymer.

Example  3

An optical film was prepared in the same manner as in Example 1, except that a copolymer of methyl methacrylate and styrene having a weight average molecular weight of 150,000 was used as the acrylic styrene copolymer.

Comparative Example  One

An optical film was produced in the same manner as in Example 1, except that the adhesive layer was not formed on the base layer and the liquid crystal layer was immediately formed.

Comparative Example  2

An optical film was produced in the same manner as in Example 1 except that an adhesive layer containing an acrylic resin (methyl methacrylate homopolymer) was used as an adhesive layer.

Comparative Example  3

An optical film was produced in the same manner as in Example 1, except that an adhesive layer containing an amine-based resin (an epoxy resin containing an amine group) was used as an adhesive layer.

< Experimental Example  1> Cross-hatch adhesion strength measurement

A cross-cut test of the optical films according to Examples and Comparative was conducted according to the standards of ASTM D3002 / D3359, which is a crosscut test standard. Concretely, immediately after the liquid crystal layer was formed and the optical film was produced, the test pieces were cut with 11 lines in the lateral and longitudinal directions at intervals of 1 mm to form 100 square lattices each having 1 mm in width and 1 mm in length. Thereafter, when the CT-24 adhesive tape of Nichiban Co., Ltd. was attached to the cut surface and then peeled off, the ratio of the falling surface was measured. 100 samples were prepared under the same conditions as above, and the number of samples having a peeled area of 5% or less of the total area after the crosscut test was measured. The results are shown in Table 1. The cross-cut test can be carried out at room temperature immediately after the formation of the optical film by forming the liquid crystalline layer on the adhesive layer.

Example 1 Comparative Example 1 ASTM D3002 / D3359 Samples with a peel area of 5% or less of the total area after the crosscut test 100/100 0/100

< Experimental Example  2> Optical durability evaluation

The optical films of Example 1 and Comparative Examples 1 to 3 were laminated on a glass substrate to evaluate durability. The durability of the optical film was evaluated by measuring the basic transmittance (Ts) and the degree of polarization (DOP) after the optical film was left at a temperature of 60 캜 and a relative humidity of 90% for 400 hours and observing whether or not unevenness occurred in the appearance of the sample. Table 2 shows the results of measurement of the basic transmittance and the degree of polarization after initial and 400 hours of exposure, and Fig. 4 is an image of the appearance of the optical films of Example 1, Comparative Example 1 and Comparative Example 3 after initial and 400 hours of exposure. In the following Table 2, &quot; 400hr &quot; means the value obtained by subtracting the initial measured value from the measured value after leaving for 400 hours.

The optical transmittance and polarization degree of the optical film of Example 1 and Comparative Examples 1 to 3 were cut into a size of 40 mm x 40 mm using a spectrophotometer (n & k spectrometer, manufactured by n & k Technology), and the specimen was fixed , Initial initial transmittance (Ts) and initial polarity (DOP) were measured using an external visible ray spectrometer (V-7100, manufactured by JASCO). The polarization transmittance (Ts) is a measurement value for one optical film, and the degree of polarization is obtained when the two optical films are arranged in a state in which the absorption axes are parallel to each other so that the parallel transmittance (Tp) And is defined by the following equation (1) by the orthogonal transmittance (Tc) obtained after orthogonality.

[Equation 1]

Polarization degree = [(Tp - Tc) / (Tp + Tc)] ^1/2

Comparative Example 1 Comparative Example 3 Example 1 TS (%) DOP (%) TS (%) DOP (%) TS (%) DOP (%) Early 41.9 96.0 39.6 93.2 41.38 96.27 100hr 41.6 97.4 39.6 93.0 41.28 96.55 250hr 41.6 97.5 39.7 92.5 41.2 97.61 400hr 41.6 97.4 39.9 92.5 41.23 97.54 DELTA 400hr -0.30 1.40 0.30 -0.70 -0.15 1.27

100: substrate layer
200: adhesive layer
300: liquid crystal layer
400: hard coat layer

Claims (13)

An optical film comprising a substrate layer, a liquid crystal layer including a liquid crystalline compound, and an adhesive layer disposed between the substrate layer and the liquid crystal layer, wherein the adhesive layer comprises an acrylic styrene copolymer. The method according to claim 1,
Wherein the substrate layer comprises a polyolefin; Polyester; cellulose; Polyamide; Acrylic polymer; Or at least one organic polymer selected from the group consisting of polystyrene, polyvinyl chloride, polyimide, polyvinyl alcohol, polycarbonate, and ethylene vinyl alcohol. The method according to claim 1,
Wherein the mammary liquid crystal compound is a dichroic dye comprising a dye chromophore core and a salt form residue. The method according to claim 1,
Wherein the thickness of the liquid crystal layer is in the range of 0.1 to 10 mu m. The method according to claim 1,
Wherein the base layer and the liquid crystal layer are attached to each other via the adhesive layer. The method according to claim 1,
Wherein the adhesive layer comprises 5 to 20% by weight of the acrylic styrene copolymer. The method according to claim 1,
Wherein the acrylic styrene copolymer comprises a copolymer of alkyl (meth) acrylate and styrene. The method according to claim 1,
Wherein the weight average molecular weight of the copolymer is in the range of 40,000 to 150,000. The method according to claim 1,
Wherein the thickness of the adhesive layer is 0.1 to 100 占 퐉. The method according to claim 1,
An optical film further comprising a hard coating layer on either or both sides of the substrate layer. 11. The method of claim 10,
Wherein the hard coating layer comprises a polymerization unit of a polyfunctional (meth) acrylate. Coating an adhesive composition comprising an acrylic styrene copolymer and a solvent on a base layer to form an adhesive layer; and coating a liquid crystal composition including a liquid crystalline compound and a solvent on the adhesive layer to form a liquid crystal layer &Lt; / RTI &gt; A display device comprising the optical film of claim 1.

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