KR101311919B1 - Optical film - Google Patents

Abstract

PURPOSE: An optical film is provided to improve a view angle, a contrast ratio, and a color shift phenomenon of an in-plain switching (IPS) device by having low phase difference. CONSTITUTION: A variation amount of Rth is equal to 5nm or less at the 25degrees and 60% RH atmosphere after 1000 hours. The variation amount of the Rth is equal to 20nm or less at the 85degrees and 90% RH atmosphere after 1000 hours. An optical film includes cellulose acylate resin as base resin.

Description

Optical film {OPTICAL FILM}

The present invention relates to an optical film, and relates to an optical film having a low retardation value in the thickness direction and a small retardation change amount under high temperature and high humidity conditions.

Cellulose acetate films are used in various photographic or optical materials because of their strong strength and flame retardancy. The cellulose acetate film has a lower optical anisotropy compared to other polymer films and provides a relatively low retardation. Therefore, it is used in polarizing plates and the like.

Recently, the demand for high functionalization such as image quality improvement is increasing, and the cellulose acetate film for polarizing plate, which is a material thereof, also needs to satisfy the characteristics thereof. In particular, in the case of IPS (In Plain Switching) mode liquid crystal display, optical anisotropy (Re: retardation value in film plane, Rth: retardation value in film thickness direction) of cellulose acetate film is one way of improving chromaticity variation and contrast ratio. This low value is required.

Korean Patent Publication No. 2008-0051060 (Patent Document 1) discloses a compound capable of reducing the retardation in the thickness direction, but mainly comprises adding a methacrylic acid polymer and a wavelength dispersion regulator, 242989 (Patent Document 2) discloses a technique of improving the moisture resistance by adding a citric acid derivative, but does not describe reduction of the retardation value in the thickness direction.

Recently, as the thickness of the liquid crystal display device has been reduced, there has been a demand for a film which is stable under high temperature and high humidity conditions with a low retardation in the thickness direction and little change in retardation, and a film satisfying such properties is not available .

Korea Patent Publication No. 2008-0051060 Japanese Laid-Open Patent No. 2009-242989

The present invention provides an optical film having a low retardation value in the thickness direction. The present invention also provides an optical film having a low retardation value in the thickness direction, a low rate of retardation change in the thickness direction under high temperature and high humidity conditions, and a low rate of dimensional change.

More particularly, the present invention is to provide an optical compensation film which can be used for an IPS mode liquid crystal display and has improved chromaticity variation and contrast ratio of an IPS mode liquid crystal display.

In addition, the present invention is to provide an additive for satisfying such optical properties.

The present invention also provides an optical structure and a display device using the optical film.

The present invention is characterized in that a change amount (R ₁ ) of Rth after 1000 hours under the atmosphere of 25 ° C and 60% RH satisfies the following formula ( ₁ ) and a change amount (R ₂ ) of Rth after 1000 hours under an atmosphere of 85 ° C and 90% To an optical film satisfying the following formula (2).

[Formula 1]

| R ₁ | ≤ 5 nm

[Formula 2]

| R ₂ | ≤ 20 nm

(R ₁ ) is a value obtained by subtracting Rth (550) before treatment from Rth (550) after 1000 hours of treatment at 25 ° C and 60% RH, and R ₂ is a value after treatment at 85 ° C and 90% RH for 1000 hours Is a value obtained by subtracting Rth (550) before processing from Rth (550), and Rth (?) Is a retardation value (unit: nm) in the film thickness direction at wavelength? Nm.

The optical film according to the present invention has an excellent effect of low retardation in the thickness direction, low rate of retardation change and low dimensional change rate under high temperature and high humidity conditions.

The optical film according to the present invention has a small retardation, which can improve the viewing angle, contrast ratio, and color shift of the IPS mode display device.

Hereinafter, the configuration of the present invention will be described in more detail.

The present invention relates to an optical film having a low retardation in the thickness direction and a low rate of retardation change in the thickness direction under high temperature and high humidity conditions, and relates to an optical film using a cellulose acylate resin as a base resin.

More specifically, one embodiment of the present invention relates to a method for producing a compound of formula ( ₁ ), wherein the change amount (R ₁ ) of Rth after lapse of 1000 hours at 25 ° C and 60% RH satisfies the following formula And the change amount (R ₂ ) satisfies the following formula ( ₂ ).

[Formula 1]

| R ₁ | ≤ 5 nm

[Formula 2]

| R ₂ | ≤ 20 nm

(R ₁ ) is a value obtained by subtracting Rth (550) before treatment from Rth (550) after 1000 hours of treatment at 25 ° C and 60% RH, and R ₂ is a value after treatment at 85 ° C and 90% RH for 1000 hours Is a value obtained by subtracting Rth (550) before processing from Rth (550), and Rth (?) Is a retardation value (unit: nm) in the film thickness direction at wavelength? Nm.

As described above, the present invention simultaneously satisfies the ranges of the formulas (1) and (2), thereby providing a film with little change in retardation under high temperature and high humidity conditions.

Specifically, the film of the present invention may have an absolute value of an Rth value measured at 400 to 700 nm in an atmosphere of 85 ° C and 90% RH, that is, even after 1000 hours of treatment under a high temperature and high humidity atmosphere, of less than 20 nm. Also, when | R ₁ | And | R ₂ | is 0 nm? | R ₁ | ? 5 nm, 0 nm? | R ₂ | ≦ 20 nm. When the film thickness is in excess of the above range, retardation in the thickness direction increases sharply when the film is treated in a high temperature and high humidity condition in a post-treatment process using a film, .

In one embodiment of the present invention, the optical film may have Rth measured after lapse of 1000 hours under an atmosphere of 85 ° C and 90% RH satisfying the following formula (3).

[Equation 3]

| Rth (400) + Rth (700) / Rth (550) | <1

(Unit: nm) at a wavelength of? Nm and Rth (?) Is a retardation value (unit: nm) in a film thickness direction at a wavelength of? Nm.

More specifically, the Rth according to Formula 3 is preferably 0.1 to 0.99, and when it is more than 1, it is considered that the retardation changes largely at high temperature and high humidity conditions and is not suitable for use as an optical film.

In one embodiment of the present invention, the optical film may have a dimensional change (%) measured after lapse of 1000 hours under an atmosphere of 85 ° C and 90% RH satisfies the following formula (4).

[Formula 4]

-5? (L ₂ -L ₁ ) / L ₁ 100? 5

(Where L ₁ is the inter-coating distance before processing, and L ₂ is the inter-coat distance after processing).

More specifically, it is preferable that the dimensional change rate is from -5 to 0. When the dimensional change rate is less than -5 or more than 5, defects may occur in the post-treatment process using the optical film.

In an embodiment of the present invention, the optical film may satisfy the following formula (5) when the change in total light transmittance (%) measured after lapse of 1000 hours under an atmosphere of 85 ° C and 90%

[Formula 5]

0? (TT ₁ - TT ₂ )? 0.6

(TT ₁ is the total light transmittance (%) before the treatment and TT ₂ is the total light transmittance (%) after 1000 hours of treatment at 85 ° C and 90% RH atmosphere.)

More specifically, the total light transmittance change amount is preferably in the range of 0.15 to 0.55, and when it is more than 0.6, the turbidity of the film may visually increase and the optical function may be lost.

In one embodiment of the present invention, the optical film may satisfy the following formula (6) as the change in ultraviolet transmittance (%) measured after lapse of 1000 hours under an atmosphere of 85 ° C and 90% RH.

[Formula 6]

0? (UVT ₁ - UVT ₂ )? 3

UVT ₁ is the ultraviolet transmittance (%) before treatment, and UVT ₂ is ultraviolet transmittance (%) after 1000 hours treatment at 85 ° C and 90% RH atmosphere.

More specifically, the ultraviolet ray transmittance change amount is preferably in the range of 1 to 2.7, and when it is more than 3, the turbidity of the film may visually increase and the optical function may be lost.

Re (?) And Rth (?) Of the optical film of the present invention can satisfy the following formulas (I) and (II). Specifically, when the optical film of the present invention does not satisfy the following range, it may not be suitable for use as an optical film of an IPS mode liquid crystal display device.

(I) 0? Re (550)? 10

(II) -10? Rth (550)? 10

(In the formula, Re (λ) is the in-plane retardation value (unit: nm) at the wavelength λnm, and Rth (λ) is the retardation value (unit: nm) in the film thickness direction at the wavelength λnm.)

Hereinafter, each configuration of the present invention will be described in more detail.

In one embodiment of the present invention, the optical film may contain 1 to 20 parts by weight of at least one compound selected from the group consisting of formula (1), per 100 parts by weight of the cellulose acylate resin.

In one embodiment of the present invention, the cellulose acylate resin is an ester of cellulose and acetic acid. The cellulose acylate resin is a cellulose acylate resin in which all or a part of the hydrogen atoms of the hydroxyl groups existing at the second, third and sixth positions of the glucose unit constituting cellulose are acetyl, A propionyl group, and a butyryl group. The degree of substitution of cellulose acetate is not limited, but is preferably 2.7 or more, specifically 2.7 to 3.0, more preferably 2.85 to 3.0. The degree of substitution can be measured according to ASTM D-817-91. The molecular weight range of the cellulose acylate resin is not limited, but the weight average molecular weight is preferably in the range of 200,000 to 350,000. The molecular weight distribution of the cellulose acylate resin is preferably Mw / Mn (Mw is weight average molecular weight, Mn is number average molecular weight) is 1.4 to 1.8, more preferably 1.5 to 1.7.

In one embodiment of the present invention, the cellulose acylate film may further include any one or two or more additives selected from sunscreens, microparticles, plasticizers, anti-degradants, release agents, infrared absorbers, optically anisotropic control agents.

In one aspect of the present invention, the cellulose acylate film is preferably produced by a solvent cast method using a cellulose acylate dope solution. In the solvent cast method, a solution (dope) in which cellulose acylate is dissolved in a solvent is cast on a support, and the solvent is evaporated to form a film.

As the raw material of the cellulose acylate doping solution, it is preferable to use cellulose acylate particles. At this time, 90 weight% or more of the cellulose acylate particles preferably have an average particle diameter of 0.5 to 5 mm. It is also preferable that at least 50% by weight of the cellulose acylate particles used has an average particle diameter of 1 to 4 mm.

It is preferable that the cellulose acylate particles have a shape as close to a sphere as possible, and that the cellulose acylate particles are dried to a water content of 2% by weight or less, more preferably 1% by weight or less, Do.

Next, the additive used for the cellulose acylate film of one aspect of the present invention will be described.

The cellulose acylate solution (dope) used in the solvent cast method includes various additives depending on the use in each preparation step, for example, plasticizers, ultraviolet light inhibitors, deterioration inhibitors, fine particles, release agents, infrared absorbers, and optically anisotropic control agents. Additives may be added. The specific kind of such additives can be used without limitation as long as they are commonly used in the field, and the content thereof is preferably used within a range that does not deteriorate the physical properties of the film. The timing of adding the additives depends on the type of additive. A step of adding an additive to the end of the doping treatment may be performed.

The plasticizer is used to improve the mechanical strength of the film. When a plasticizer is used, the drying time of the film can be shortened. As the plasticizer, any conventionally used plasticizer can be used without limitation, and examples thereof include carboxylic acid esters selected from phosphoric acid esters and phthalic acid esters or citric acid esters. Examples of phosphoric acid esters include triphenyl phosphate (TPP), biphenyl diphenyl phosphate, and tricresyl phosphate (TCP). Examples of phthalic acid esters include dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), dioctyl phthalate (DOP), diphenyl phthalate (DPP) and diethylhexyl phthalate have. Examples of citric acid esters include o-acetyltriethyl citrate (OACTE) and o-acetyl tributyl citrate (OACTB). Examples of other carboxylic acid esters include butyl oleate, methyl acetyl ricinoleate, dibutyl sebacate and various trimellitic acid esters. Preferably, phthalate esters (DMP, DEP, DBP, DOP, DPP, DEHP) plasticizers are used. The plasticizer is used in an amount of 2 to 20 parts by weight, more preferably 5 to 15 parts by weight, based on 100 parts by weight of the cellulose acetate.

The UV inhibitor may be a hydroxybenzophenone compound, a benzotriazole compound, a salicylic ester compound, or a cyanoacrylate compound. The amount of the ultraviolet ray inhibitor is 0.1 to 3 parts by weight, more preferably 0.5 to 2 parts by weight, based on 100 parts by weight of the cellulose acylate.

As the deterioration preventing agent, for example, an antioxidant, a peroxide releasing agent, a radical inhibitor, a metal deactivator, an oxygen scavenger, and a photostabilizer (hindered amine) can be used. Particularly preferred examples of the deterioration inhibitor include butylated hydroxytoluene (BHT) and tribenzylamine (TBA). The amount of the deterioration inhibitor is 0.01 to 5 parts by weight, more preferably 0.1 to 1 part by weight, based on 100 parts by weight of the cellulose acylate.

The fine particles are added in order to keep the film in curl suppression, transportability, prevention of adhesion in a roll form, or good maintenance of the film, and any of inorganic compounds and organic compounds may be used. Examples of the inorganic compound include silicon compounds, silicon dioxide, titanium oxide, zinc oxide, aluminum oxide, barium oxide, zirconium oxide, strontium oxide, antimony oxide, tin oxide, tin antimony, calcium carbonate, talc, Clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate and calcium phosphate are preferable, and an inorganic compound containing silicon and zirconium oxide are more preferably used. The fine particles have an average primary particle diameter of 80 nm or less, preferably 5 to 80 nm, more preferably 5 to 60 nm, and particularly preferably 8 to 50 nm. If the average primary particle diameter exceeds 80 nm, the surface smoothness of the film is impaired.

Next, the additive used for this invention is demonstrated in detail. The additive is preferably added to reduce the retardation value (Rth) in the thickness direction of the optical film, and is preferably a compound represented by the following formula (1). And the content thereof may be 1 to 20 parts by weight of at least one compound selected from the group consisting of formula (1) per 100 parts by weight of the cellulose acylate resin. A desired retardation range can be attained and a film having a low rate of change in thickness direction retardation and a small rate of dimensional change under high temperature and high humidity can be provided.

[Formula 1]

(In Formula 1, X is O, S or NR _5, Y is O, S, NR ₂₅ or a chemical bond, wherein the R _1, R _3, R ₅ and R ₂₅ are each independently hydrogen, (C1- (C1-C10) alkoxy, (C3-C20) cycloalkyl, (C2-C7) alkenyl, (C1-C10) alkyl, (C3-C20) heterocycloalkyl, (C4-C20) heteroaryl, wherein R ₂ and R ₄ are each independently selected from the group consisting of hydrogen, -C20) aryl, (C3-C20) cycloalkyl, carbonyl (C1-C10) alkyl, (C3-C20) heterocycloalkyl, (C4-C20) heteroaryl is selected from the R _1, R _2, R ₃ and R &lt; ₄ &gt; are not simultaneously hydrogen,

Wherein _{R 1, R 2, R 3} , R 4, R 5 , and R ₁₅ alkyl, aryl, alkoxy, cycloalkyl, alkenyl, alkoxycarbonyl alkyl, carbonyl-alkyl, heterocycloalkyl, heteroaryl (C1- (C3-C20) cycloalkyl, (C3-C20) heterocycloalkyl or (C4-C20) cycloalkyl, -C20) heteroaryl. &Lt; / RTI &gt;

Substituents comprising the "alkyl", "alkoxy" and other "alkyl" moieties described herein include both straight and crushed forms, and "alkenyl" has 2 to 8 carbon atoms and has one or more double bonds. Includes both straight chain or ground forms containing.

The "(C3-C20) cycloalkyl" described in the present invention includes both saturated monocyclic or saturated bicyclic ring structure forms having 3 to 20 carbon atoms.

&Quot; Aryl &quot;, as used herein, refers to an organic radical derived from an aromatic hydrocarbon by the removal of one hydrogen, with a single or fused ring containing in each ring suitably 4 to 7, preferably 5 or 6 ring atoms . Specific examples include, but are not limited to, phenyl, naphthyl, biphenyl, tolyl, and the like.

&Quot; Heterocycloalkyl &quot; as used herein refers to a saturated cyclic hydrocarbon skeletal atom containing 1 to 3 heteroatoms selected from N, O, S and the remaining saturated monocyclic or bicyclic ring skeletal atom carbon Alkyl group which may be substituted with at least one substituent selected from the group consisting of pyrrolidinyl, azetidinyl, pyrazolidinyl, oxazolidinyl, piperidinyl, piperazinyl, morpholinyl, thiomorpholinyl, thiazolidinyl, Wherein the substituent is selected from the group consisting of alkyl, alkoxy, alkylthio, alkylthio, alkylthio, alkylthio, alkylthio, alkylthio, alkylthio, alkylthio, alkylthio, Tetrahydropyrimidinyl, tetrahydropyrimidinyl, tetrahydrothiophenyl, tetrahydrothiopyranyl, diazepanyl, and azepanyl.

&Quot; Heteroaryl &quot; as used in the present invention means an aryl group having 1 to 3 hetero atoms selected from N, O, S as an aromatic ring skeletal atom and the remaining aromatic ring skeletal atoms carbon, Include heteroaryl groups in the ring which are oxidized or tanned to form, for example, N-oxides or quaternary salts. Specific examples include furyl, thiophenyl, pyrrolyl, pyranyl, imidazolyl, pyrazolyl, thiazolyl, thiadiazolyl, isothiazolyl, isoxazolyl, oxazolyl, oxadiazolyl, triazinyl, tetrazinyl, tri Pyrimidinyl, pyridazinyl, and the like, including, but not limited to, pyrimidinyl, pyrimidinyl, pyridazinyl, pyridazinyl,

More specifically, the formula (1) may be represented by the following formula (2), (3) or (4)

(2)

(3)

[Formula 4]

Wherein R ₁₁ and R ₂₁ are each independently selected from the group consisting of hydrogen, (C 1 -C 5) alkyl, (C 6 -C 10) aryl, (C 3 -C 20) cycloalkyl, (C 3 -C 10) heterocycloalkyl or is selected from heteroaryl, wherein R ₃₁ is hydrogen, (C1-C5) alkyl, carbonyl (C1-C5) alkyl, (C6-C10) is selected from aryl, wherein R ₄₁ is hydrogen, (C1-C5) alkyl , (C6-C10) aryl, (C1-C10) is selected from alkoxy, wherein R ₃₁ is selected from hydrogen, (C1-C5) alkyl, carbonyl (C1-C5) alkyl, (C6-C10) aryl, Wherein R ₄₁ is selected from hydrogen, (C 1 -C 5) alkyl, (C 6 -C 10) aryl, (C 1 -C 10) alkoxy,

Wherein said alkyl, aryl, cycloalkyl, alkoxy, carbonylalkyl, heterocycloalkyl, heteroaryl of R ₁₁ , R ₂₁ , R ₃₁ and R ₄₁ is (C 1 -C 7) alkyl, halogen, nitro, cyano, Amino may be further substituted.)

In one aspect of the invention, the R _11, R ₂₁ and R ₃₁ is hydrogen, (C1-C5) alkyl, (C3-C20) cycloalkyl, (C3-C10) heterocycloalkyl in the general formula (2) or (3), (C6-C10) aryl or (C4-C10) heteroaryl,

The alkyl, cycloalkyl, heterocycloalkyl, aryl and heteroaryl of R ₁₁ , R ₂₁ and R ₃₁ may be further substituted by one or more substituents selected from (C 1 -C 7) alkyl, halogen, nitro, cyano, Can,

Provided that at least two of R ₁₁ , R ₂₁ and R ₃₁ are selected from (C 3 -C 20) cycloalkyl, (C 6 -C 20) aryl, (C 3 -C 20) heterocycloalkyl and (C 4 -C 20) heteroaryl And may include a cyclic substituent.

In one embodiment of the present invention, the compound of Formula 2 or 3 may be selected from the following formulas.

By including such an additive, the retardation in the thickness direction can be excellently reduced as compared with the case where the conventional plasticizer is added, and the optical properties such as stability and moisture resistance at high temperature and high humidity can be remarkably improved.

In addition, optical anisotropy regulators, wavelength dispersion regulators, and the like may further participate as needed, and these other additives may be used without limitation as long as they are commonly used in the art.

Next, the production method of the optical film of the present invention will be described by taking a cellulose acylate film as an example.

To prepare the cellulose acylate film in the present invention, the following cellulose acylate composition, that is, a dope solution is prepared.

The cellulose acylate composition according to one embodiment of the present invention comprises 1 to 20 parts by weight of the retardation control agent of Formula 1, based on 100 parts by weight of the cellulose acylate resin.

In the present invention, the solid concentration of the dope is preferably 15 to 25% by weight, and more preferably 16 to 23% by weight. When the solid concentration of the dope is less than 15% by weight, the fluidity is too high to form a film, and when it exceeds 25% by weight, complete dissolution is difficult.

In one embodiment of the present invention, the content of the cellulose acylate is 70% by weight or more, preferably 70 to 90% by weight, and more preferably 80 to 85% by weight based on the entire solid content. The cellulose acylate may be a mixture of two or more kinds of cellulose acylates having different degree of substitution, degree of polymerization or molecular weight distribution.

The retardation adjusting agent according to an embodiment of the present invention is preferably used in an amount of 1 to 20 parts by weight based on 100 parts by weight of cellulose acetate. When using in the said range, the target phase difference range can be achieved.

When the film is produced by the solvent casting method, the solvent for preparing the cellulose acylate composition (dope) is preferably an organic solvent. As the organic solvent, it is preferable to use halogenated hydrocarbons, and halogenated hydrocarbons include chlorinated hydrocarbons, methylene chloride and chloroform, among which methylene chloride is most preferred.

If necessary, organic solvents other than halogenated hydrocarbons may be mixed and used. Organic solvents other than halogenated hydrocarbons include esters, ketones, ethers, alcohols and hydrocarbons. As the ester, methyl formate, ethyl formate, propyl formate, pentyl formate, methyl acetate, ethyl acetate, pentyl acetate and the like can be used. As the ketone, acetone, methyl ethyl ketone, diethyl ketone, diisobutyl ketone , Cyclopentanone, cyclohexanone, methylcyclohexanone and the like can be used. As the ether, diisopropyl ether, dimethoxymethane, dimethoxyethane, 1,4-dioxane, 1,3-dioxolane, tetra Ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, t-butanol, 1-pentanol, 2-methyl- 2-butanol, cyclohexanol, 2-fluoroethanol, 2,2,2-trifluoroethanol and 2,2,3,3-tetrafluoro-1-propanol.

More preferably, methylene chloride may be used as the main solvent, and alcohol may be used as the minor solvent. Specifically, methylene chloride and alcohol may be mixed at a weight ratio of 80:20 to 95: 5.

The cellulose acylate composition can be prepared by room temperature, high temperature or low temperature dissolution.

The viscosity of the cellulose acylate composition is preferably 1 to 400 Pa · s at 40 ° C., more preferably 10 to 200 Pa · s.

The cellulose acylate film can be produced by a conventional solvent casting method. More specifically, the prepared dope (cellulose acylate composition) is once stored in a storage tank and defoamed in the foam contained in the dope. The defoamed dope is sent from a dope discharge port to a pressurized die through a pressurized metering gear pump capable of precisely pumping it at a high accuracy in accordance with the number of revolutions. The dope is transferred onto a metal support which is running from the slit of the pressurized die The casting film is uniformly cast so that the less-dried casting film is peeled off from the metal support at the peeling point at which the metal support almost rises. At this time, the temperature of the die is preferably maintained at the same temperature as the temperature of the dope. Both ends of the manufactured web are held in a clip and conveyed in a tenter while being held in a width, dried, conveyed to a roller of a drying device, dried and winded to a predetermined length by a winder. It is also possible to uniaxially and biaxially stretch in the machine direction and the width direction with the residual solvent amount in the casting film being 10 to 40% by weight. Or it may be stretched off-line after production of the casting film. The machine direction elongation is preferably in the range of -20 to 100% (wherein% is the length%), more preferably in the range of -20 to 50%, and most preferably in the range of -20 to 30%. The elongation in the width direction is preferably in the range of -10 to 100%, more preferably in the range of -10 to 50%, and most preferably in the range of -10 to 30%. In the stretching degree,% means length%. For example, 100% stretching with respect to a film having a length of 1 m before stretching means stretching to 2 m.

As for the space temperature at the time of application | coating of a solution, -50 degreeC-60 degreeC is preferable, -30 degreeC-50 degreeC is more preferable, -20 degreeC-40 degreeC is the most preferable. The cellulose acetate solution coated at a low space temperature is instantaneously cooled on the support to improve the gel strength, and thus a film in which a large amount of organic solvent remains can be obtained. Therefore, the film can be peeled off from the support in a short time without evaporating the organic solvent from the cellulose acylate. As the gas which cools the space, ordinary air, nitrogen, argon or helium can be used. The relative humidity is preferably 0 to 70%, more preferably 0 to 50%.

As for the temperature of the support body (casting part) which apply | coats a cellulose acylate solution, -50-130 degreeC is preferable, -30 degreeC-70 degreeC are more preferable, -20 degreeC-50 degreeC are the most preferable. In order to cool the casting portion, a gas cooled by the casting portion can be introduced. The cooling device may be disposed in the casting portion to cool the space. In cooling, it is important to be careful not to let water stick to the casting part. In the case of cooling with a gas, it is preferable to dry the gas.

In addition, after stretching in the tenter may further comprise the step of removing the left and right ends of the film, the end of the film is dried through a dryer so that the amount of residual solvent in the film to 10% by weight or less, more specifically 5% by weight or less After making it anneal, it can wind up after performing a knurling process.

Further, if necessary, the cellulose acylate film can be subjected to a surface treatment. The surface treatment is generally carried out in order to improve the adhesiveness of the cellulose acylate film. Examples of the surface treatment method include a glow discharge treatment, an ultraviolet ray irradiation treatment, a corona treatment, a flame treatment, and a saponification treatment.

The thickness of the cellulose acylate film is preferably in the range of 20 to 140 μm, more preferably in the range of 40 to 100 μm.

The cellulose acylate film according to the present invention can be used for a polarizing plate, an optical compensatory sheet, an optical filter for stereoscopic image, and a liquid crystal display device, and can be used in one or two or more laminated layers. desirable.

The cellulose acylate film according to the present invention can be used in a polarizing plate, an optical compensatory sheet, an optical filter for stereoscopic image, and a liquid crystal display device, and can be used as one or two or more sheets.

More specifically, the cellulose acylate film of the present invention can be used as a protective film of the polarizing plate. One example of the polarizing plate of the present invention consists of a polarizing film and two polarizing plate protective film to protect both sides thereof, at least one of the protective film may be a cellulose acylate film of the present invention.

When the cellulose acylate film of the present invention is used as the polarizing plate protective film, the surface of the cellulose acylate film may be subjected to a surface treatment. The surface treatment may be a hydrophilic treatment, a glow discharge treatment, a corona discharge treatment, . &Lt; / RTI &gt;

Generally, since a liquid crystal cell is located between two polarizing plates, a liquid crystal display device has two polarizing plate protective films. The cellulose acylate film of the present invention may be used for any of the four polarizing plate protective films, but is suitable for use as a protective film positioned between the polarizing film of the liquid crystal display and the liquid crystal cell. The protective film located on the opposite side of the cellulose acylate film of the present invention may form a transparent hard coating layer, anti-glare coating layer, anti-reflective coating layer and the like.

The optical compensation film containing the cellulose acylate film of this invention, or the liquid crystal display device which has a polarizing plate is also included in the scope of this invention. The cellulose acylate film of the present invention can be used in liquid crystal displays of various display modes, and specifically, can be used in modes such as TN, IPS, FLC, AFLC, OCB, STN, ECB, VA, and HAN. The cellulose acylate film of the present invention is particularly preferably applied to an IPS mode liquid crystal display device and has excellent contrast and viewing angle compensation effect.

Hereinafter, the present invention will be described in detail with reference to the following examples. However, the present invention is not limited to the following examples.

Hereinafter, the physical properties of the film were measured by the following measuring method.

1) optical anisotropy

Re was measured by using a birefringence meter (Axoscan, trade name, manufactured by Axometrics, Inc.) with wavelengths of 400 nm, 450 nm, 550 nm, 650 nm and 700 nm entering the normal direction of the film. Rth is a refractive index ellipsoid obtained by measuring light of 400 nm, 450 nm, 550 nm, 650 nm, and 700 nm, respectively, on the slow axis in the Re plane as oblique axes at intervals of 10 degrees from 0 degree to 50 degrees with respect to the film normal direction And the refractive index of the first lens is given by the following equation.

Rth = [(nx + ny) / 2-nz] × d

   nx: the refractive index of the direction of the larger refractive index of the two refractive indices

   ny: The refractive index of the direction of the smaller refractive index of the two refractive indices

   nz: refractive index in the thickness direction

d: thickness of the film

2) substitution degree

The degree of substitution was measured according to ASTM D-817-91.

3) Rate of change in retardation (%)

The films prepared in Examples and Comparative Examples were cut to a size of 50 mm in width and 50 mm in length, and two samples were prepared and Rth was measured to obtain the value before processing.

Thereafter, one of the samples was maintained at 25 DEG C and 60% RH for 1000 hours, and Rth was measured to calculate a change amount (R ₁ ) of Rth.

The other was kept at 85 캜 and 90% RH for 1000 hours, and Rth was measured to calculate a change amount (R ₂ ) of Rth.

At this time, Rth was calculated on the basis of the measured value at 550 nm, and the rate of change was calculated according to the following equation, and the absolute value of this value was used.

The change amount (R ₁ ) = Rth | before Rth treatment after 1000-hour treatment in 25 degreeC and 60% RH atmosphere.

The change amount (R ₂ ) = Rth | before Rth treatment after 1000-hour treatment in 85 degreeC and 90% RH atmosphere.

In the present invention, | R ₁ | ? 5, | R ₂ | &Lt; / = 20.

4) Dimensional change rate

The films prepared in Examples and Comparative Examples were cut to a size of 50 mm in width and 50 mm in length and samples were measured and the dimensional change rate was measured after lapse of 1000 hours under an atmosphere of 85 ° C and 90% RH.

The rate of dimensional change was plotted in the form of a cross in two directions at intervals of 100 mm in the longitudinal direction of the sample. These films were measured by an optical microscope for the inter-coating distance L _{1 in the} width direction before processing. And subjected to high-temperature and high-humidity treatment (1000 hours elapse in an atmosphere of 85 ° C and 90% RH) in a warm bath. Thereafter, the distance between coatings (L ₂ ) in the width direction after the treatment of the sample with an optical microscope was measured again.

From this, the change ratio (%) in the width direction was calculated.

Dimensional change ratio (%) = (L ₂ -L ₁ ) / L ₁ 100

5) Film thickness

The films prepared in Examples and Comparative Examples were cut to a size of 50 mm in width and 50 mm in length and samples were prepared and measured by a thickness gauge (TESA-μHITE Height Gauge, manufactured by Tesa technology). The thicknesses of the five points including the center of the film specimen were each measured and then averaged.

6) Total light transmittance

The total light transmittance was measured by a transmittance meter (Haze Meter HM-150, manufactured by Murakami Color Research Laboratory) according to ASTM D1003 Haze and Luminous Transmittance of Transparent Plastics.

The amount of change in total light transmittance was measured by measuring the Rth before and after the lapse of 1000 hours under the atmosphere of 85 ° C and 90% RH, and calculating the difference value according to the following formula.

Total light transmittance variation = TT ₁ - TT ₂

(TT ₁ is the total light transmittance (%) before the treatment and TT ₂ is the total light transmittance (%) after 1000 hours of treatment at 85 ° C and 90% RH atmosphere.)

7) Ultraviolet transmittance

The ultraviolet transmittance was measured at a wavelength of 380 nm using a UV-Vis meter (Shimadzu UV-Vis Spectrophotometer UV-1601) according to JIS B 7113 Photographic Sharp-Cut Glass Filters standard.

The ultraviolet ray transmittance change amount was calculated by measuring the Rth before and after 1000 hours under the atmosphere of 85 ° C and 90% RH, and calculating the difference value according to the following formula.

UV transmittance variation = UVT ₁ - UVT ₂

UVT ₁ is the ultraviolet transmittance (%) before treatment, and UVT ₂ is ultraviolet transmittance (%) after 1000 hours treatment at 85 ° C and 90% RH atmosphere.

Example 1

1) Preparation of Cellulose Acetate Composition (Dope)

[Table 1] The composition was put in a stirrer and dissolved at a temperature of 35 ° C.

[Table 1]

The obtained dope was heated to 35 degreeC, and it sent by gear pump, filtered with the filter paper of 0.01 mm of absolute filtration accuracy, and filtered by the cartridge filtration apparatus of 5 micrometers of absolute filtration accuracy.

2) Preparation of Cellulose Acetate Film

The dope obtained through the filtration process was cast on a mirror-surface stainless steel support through a casting die and peeled off. The temperature of the casting die was maintained at 35 degreeC similarly to the temperature of dope, and it adjusted so that the amount of residual solvent at the time of peeling might be 40 wt%. After peeling, it was connected to the tenter and stretched by -1% in the machine direction and 6% in the transverse direction of the film. The thickness of the film after extending | stretching was 60 micrometers. After the film emerged from the tenter, the left and right ends of the film were removed by 150 mm. After removing the film from the end by drying the film for 1 hour so that the amount of residual solvent in the film to 5wt% or less under a hot air condition of 140 ℃ through a dryer, and cut both ends of the film from the dryer 3cm, and the height 10mm from the end A 100 micrometers knurling process was performed and it wound up in roll shape. The thickness of the produced film was 60 μm.

The physical properties of the cellulose acetate film were measured in the manner described above, and are shown in Tables 4 and 5 below.

[Examples 2 to 5]

The additives described in the following Table 2 were added to the composition of Example 1 in place of the additives, and the film thickness was adjusted as shown in Table 2 by adjusting the degree of drawing.

The physical properties of the cellulose acetate film were measured in the manner described above, and are shown in Tables 4 and 5 below.

 [Table 2]

Comparative Example 1

1) Preparation of Cellulose Acetate Composition (Dope)

The composition shown below was placed in a stirrer and dissolved at a temperature of 30 占 폚.

In the composition below, Bis (ethane-2,1-diyl) dipentanoate was used as the ultraviolet light stabilizer and 2- (2H-Benzotriazol-2-yl) -6- 1-methyl-1-phenylethyl) -4- (1,1,3,3-tetramethylbutyl) phenol.

[Table 3]

The resultant dope was heated to 30 DEG C and then sent to a gear pump. The resultant was filtered through a filter paper having an absolute filtration accuracy of 0.01 mm, and then filtered through a cartridge filtration apparatus having an absolute filtration accuracy of 5 mu m.

2) Preparation of Cellulose Acetate Film

The dope obtained through the filtration process was cast on a mirror-surface stainless steel support through a casting die and peeled off. The temperature of the casting die was maintained at 35 degreeC similarly to the temperature of dope, and it adjusted so that the amount of residual solvent at the time of peeling might be 40 wt%. After peeling, it was connected to a tenter and stretched by -1% in the longitudinal direction of the film and by 6.5% in the transverse direction. The thickness of the film after extending | stretching was 60 micrometers. After the film emerged from the tenter, the left and right ends of the film were removed by 150 mm. The film having the terminal removed thereon was dried for one hour through a drier in a hot air condition of 140 ° C so that the amount of the residual solvent in the film was 5 wt% or less, and then dried. The ends of the film from the dryer were cut to 3 cm, And then wound in a roll shape. The thickness of the produced film was 60 μm.

The physical properties of the cellulose acetate film were measured in the manner described above, and are shown in Tables 4 and 5 below.

 [Table 4]

As can be seen from the results of Table 4, in Examples 1 to 5 of the present invention, the rate of change of retardation was low even when 1000 hours were maintained at 85 ° C / 90RH%. However, in Comparative Example 1, it was found that the change amount (R ₂ ) of Rth greatly increased after 1000 hours under the atmosphere of 85 ° C and 90% RH.

Rth (400) + Rth (700) / Rth (550) | Rth from the Rth measured after 1000 hours in an atmosphere of 85 占 폚 and 90% It was found that the values of Example 1 were 0.91, that of Example 2 was 0.84, that of Example 3 was 0.37, that of Example 4 was 0.74, and that of Example 5 was 0.99. However, it was found that Comparative Example 1 was 1.74, exceeding 1.

[Table 5]

As shown in Table 5, the embodiment of the present invention is not limited to the condition that the retardation change amount in the thickness direction is 1000 hours at 25 ° C / 60RH%, but is lower than 1000 hours at 85 ° C / 90RH% Respectively.

Also, it was confirmed that the total light transmittance, ultraviolet transmittance and dimensional change rate did not significantly increase at high temperature and high humidity conditions measured after 1000 hours at 85 ° C / 90RH%.

Claims (12)

The change amount of Rth (R ₁ ) after 1000 hours at 25 ° C. and 60% RH atmosphere satisfies Equation 1 below, and the change amount of Rth (R ₂ ) after 1000 hours at 85 ° C. and 90% RH atmosphere is shown below Equation 2 Satisfies and includes a cellulose acylate resin as a base resin, and an optical film including any one or more compounds selected from Chemical Formula 1.
[Formula 1]
| R ₁ | ≤ 5 nm
[Formula 2]
| R ₂ | ≤ 20 nm
(R ₁ ) is a value obtained by subtracting Rth (550) before treatment from Rth (550) after 1000 hours of treatment at 25 ° C and 60% RH, and R ₂ is a value after treatment at 85 ° C and 90% RH for 1000 hours Is a value obtained by subtracting Rth (550) before processing from Rth (550), and Rth (?) Is a retardation value (unit: nm) in the film thickness direction at wavelength? Nm.
[Formula 1]

(In Formula 1, X is O, S or NR _5, Y is O, S, NR ₂₅ or a chemical bond, wherein the R _1, R _3, R ₅ and R ₂₅ are each independently hydrogen, (C1- (C1-C10) alkoxy, (C3-C20) cycloalkyl, (C2-C7) alkenyl, (C1-C10) alkyl, (C3-C20) heterocycloalkyl, (C4-C20) heteroaryl, wherein R ₂ and R ₄ are each independently selected from the group consisting of hydrogen, -C20) aryl, (C3-C20) cycloalkyl, carbonyl (C1-C10) alkyl, (C3-C20) heterocycloalkyl, (C4-C20) heteroaryl is selected from the R _1, R _2, R ₃ and R &lt; ₄ &gt; are not simultaneously hydrogen,
Wherein _{R 1, R 2, R 3} , R 4, R 5 , and R ₁₅ alkyl, aryl, alkoxy, cycloalkyl, alkenyl, alkoxycarbonyl alkyl, carbonyl-alkyl, heterocycloalkyl, heteroaryl (C1- (C3-C20) cycloalkyl, (C3-C20) heterocycloalkyl or (C4-C20) cycloalkyl, -C20) heteroaryl. &Lt; / RTI &gt; The method of claim 1,
Wherein the optical film satisfies the following formula (3): Rth measured after lapse of 1000 hours under an atmosphere of 85 deg. C and 90% RH.
[Formula 3]
| Rth (400) + Rth (700) / Rth (550) | <1
(Rth (?) Is the retardation value (unit: nm) in the film thickness direction at the wavelength? Nm). The method of claim 1,
Wherein the optical film satisfies the following formula (4) as a dimensional change (%) measured after lapse of 1000 hours under an atmosphere of 85 캜 and 90% RH.
[Formula 4]
-5? (L ₂ -L ₁ ) / L ₁ 100? 5
(Where L ₁ is the inter-coating distance before processing, and L ₂ is the inter-coat distance after processing). The method of claim 1,
Wherein the optical film satisfies the following expression (5) when the change in total light transmittance (%) measured after lapse of 1000 hours under an atmosphere of 85 캜 and 90% RH satisfies the following expression (5).
[Formula 5]
0? (TT ₁ - TT ₂ )? 0.6
(TT ₁ is the total light transmittance (%) before the treatment and TT ₂ is the total light transmittance (%) after 1000 hours of treatment at 85 ° C and 90% RH atmosphere.) The method of claim 1,
Wherein the optical film has a change in ultraviolet transmittance (%) measured after lapse of 1000 hours under an atmosphere of 85 캜 and 90% RH satisfies the following formula (6).
[Formula 6]
0? (UVT ₁ - UVT ₂ )? 3
UVT ₁ is the ultraviolet transmittance (%) before treatment, and UVT ₂ is ultraviolet transmittance (%) after 1000 hours treatment at 85 ° C and 90% RH atmosphere. The method of claim 1,
The optical film is an optical film containing 1 to 20 parts by weight of one or more compounds selected from Formula 1 based on 100 parts by weight of cellulose acylate resin. The method according to claim 6,
Wherein the compound of Formula 1 is selected from the following Formula 2, Formula 3 or Formula 4.
(2)

(3)

[Chemical Formula 4]

(C 1 -C 10) aryl, (C 3 -C 20) cycloalkyl, (C 3 -C 10) heterocycloalkyl or (C 4 -C 10) cycloalkyl, wherein R ₁₁ and R ₂₁ are each independently hydrogen, a is selected from heteroaryl, wherein R ₃₁ is hydrogen, (C1-C5) alkyl, carbonyl (C1-C5) is selected from alkyl, (C6-C10) aryl, wherein R ₄₁ is hydrogen, (C1-C5) alkyl, (C6-C10) aryl, (C1-C10) is selected from alkoxy, wherein R ₃₁ is hydrogen, (C1-C5) alkyl, carbonyl (C1-C5) alkyl, (C6-C10) is selected from aryl , Wherein R ₄₁ is selected from hydrogen, (C 1 -C 5) alkyl, (C 6 -C 10) aryl, (C 1 -C 10) alkoxy,
Wherein said alkyl, aryl, cycloalkyl, alkoxy, carbonylalkyl, heterocycloalkyl, heteroaryl of R ₁₁ , R ₂₁ , R ₃₁ and R ₄₁ is (C 1 -C 7) alkyl, halogen, nitro, cyano, Amino may be further substituted.) 8. The method of claim 7,
Wherein R ₁₁ , R ₂₁ and R ₃₁ are independently selected from the group consisting of hydrogen, (C 1 -C 5) alkyl, (C 3 -C 20) cycloalkyl, (C 3 -C 10) heterocycloalkyl, (C4-C10) &lt; / RTI &gt; heteroaryl,
The alkyl, cycloalkyl, heterocycloalkyl, aryl and heteroaryl of R ₁₁ , R ₂₁ and R ₃₁ may be further substituted by one or more substituents selected from (C 1 -C 7) alkyl, halogen, nitro, cyano, Can,
Provided that at least two of R ₁₁ , R ₂₁ and R ₃₁ are selected from (C 3 -C 20) cycloalkyl, (C 6 -C 20) aryl, (C 3 -C 20) heterocycloalkyl and (C 4 -C 20) heteroaryl An optical film comprising a cyclic substituent. 8. The method of claim 7,
Wherein the compound of formula (2) or (3) is selected from the following formulas.

8. The method of claim 7,
Wherein the compound of formula (2) or (3) is selected from the following formulas.

11. The compound according to any one of claims 1 to 10,
Wherein the optical film is used in an optical compensation sheet, an optical filter for stereoscopic images, a polarizing plate, and a liquid crystal display device. A display device comprising an optical film according to any one of claims 1 to 10.