KR20120035285A - Cellulose acetate film - Google Patents

Abstract

PURPOSE: A cellulose acetate film is provided to have high retardation value along transverse direction, and to have high difference phase value, thereby improving viewing angle and contrast of a VA mode LCD panel. CONSTITUTION: A cellulose acetate film comprises one or more of retardation improvers selected from compounds in chemical formula 1. In chemical formula 1, Z is selected from N-A2-R2 or CR11R12, R1 and R2 is respectively selected from hydrogen, (C1-C10) alkyl, (C6-C20) aryl, ], (C3-C20) cycloalkyl, 5-7 membered heterocycloalkyl, and (C4-C20) heteroaryl, A1 and A2 is respectively a chemical bond, or selected from -CO-, -CS-, -COO-, -COS-, -NHCO-, -NHCS-, -CR3R4-, -POR5-, -SO-, and -SO2-, and n and m is the integer of 0-3.

Description

Cellulose acetate film {CELLULOSE ACETATE FILM}

The present invention relates to a cellulose acetate film used for optical compensation, and a cellulose acetate film having a high thickness retardation (Rth).

The present invention also relates to an optical compensation sheet, a polarizing plate, and a liquid crystal display device using the cellulose acetate film.

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

In VA (Vertical Alignment) mode, transparent electrodes are formed on the upper and lower plates. The polarizing plate is attached to the outer side of the upper and lower plates so that the initial alignment direction is vertical when the electric field is not applied. Therefore, the polarizing plate is completely dark. When the electric field is applied, the liquid crystal directors are rearranged properly to transmit the light. do. The optical compensation film of the liquid crystal display of the VA mode requires high optical anisotropy, that is, high retardation.

The present invention is to provide a cellulose acetate film having a high retardation value in the thickness direction as an optical film. More specifically, the present invention can be used in a VA mode liquid crystal display device, and to provide an optical compensation film that can improve the viewing angle and contrast characteristics of the VA mode LCD panel.

In addition, the present invention is to provide a retardation enhancer for satisfying such optical properties.

In another aspect, the present invention is to provide an optical compensation sheet, a polarizing plate and a liquid crystal display using the cellulose acetate film.

The present invention relates to a cellulose acetate film having excellent optical properties, and relates to a cellulose acetate film having an in-plane retardation value of 0 to 10 nm before stretching and a retardation value of 50 to 250 nm in the thickness direction.

More specifically, in the cellulose acetate film, Re (λ) and Rth (λ) before stretching satisfy the following formulas (I), (II) and (III), and Re (λ) and after stretching 5 to 100 length%. Rth ((lambda)) relates to the cellulose acetate film which satisfy | fills following formula (IV), (V), and (VI).

(I) 0 ≦ Re (550) ≦ 10,

(II) 50 ≦ Rth (550) ≦ 250,

(III) Rth (700) / Rth (450)> 1.0

(IV) 20 ≦ Re (550) ≦ 100,

(V) 70 ≦ Rth (550) ≦ 200,

(VI) Rth (700) / Rth (450)> 1.0

(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.)

The present invention as a retardation additive for satisfying these conditions is characterized in that it comprises at least one retardation enhancer selected from the compound of formula (1).

[Formula 1]

(In Chemical Formula 1, Z is selected from NA ₂ -R ₂ or CR ₁₁ R ₁₂ , wherein R ₁₁ and R ₁₂ are each independently selected from hydrogen, (C 1 -C 10) alkyl, and R ₁ and R ₂ are each independently hydrogen, (C 1 -C 10) alkyl, (C 6 -C 20) aryl, (C 3 -C 20) cyclo One selected from 5- to 7-membered heterocycloalkyl, N, O, S, including one or more elements selected from alkyl, (C2-C7) alkenyl, (C1-C10) alkoxy, N, O, S It is selected from (C4-C20) heteroaryl containing the above element,

Alkyl, aryl, cycloalkyl, alkenyl, alkoxy, heterocycloalkyl, heteroaryl of R ₁ and R ₂ are (C 1 -C 10) alkoxy, (C 1 -C 7) alkyl, halogen, nitro, cyano, hydroxy, 5- to 7-membered heterocycloalkyl or N comprising at least one element selected from amino, (C6-C20) aryl, (C2-C7) alkenyl, (C3-C20) cycloalkyl, N, O, S One or more selected from (C4-C20) heteroaryl including one or more elements selected from O, S may be further substituted, wherein R ₁ and R ₂ are (C3-C20) alkylene or (C3-C20 May be linked to alkenylene to form a fused ring.

A ₁ and A ₂ are each independently a chemical bond, or -CO-, -CS-, -COO-, -COS-, -NHCO-, -NHCS-, -CR ₃ R _4- , -POR _5- , -SO-, -SO _2- , wherein R ₃ and R ₄ are each independently hydrogen, (C1-C10) alkyl, (C6-C20) aryl, (C3-C20) cycloalkyl, (C2-C7 In (C4-C20) heteroaryl comprising at least one element selected from 5- to 7-membered heterocycloalkyl, N, O, S containing at least one element selected from alkenyl, N, O, S is selected, the R ₅ is hydrogen, (C1-C10) alkyloxy, (C6-C20) aryloxy, is selected from -NH-R _6, wherein R ₆ is hydrogen, (C1-C10) alkyl, (C2- C7) alkenyl, (C2-C4) alkynyl, (C6-C20) aryl.

In addition, n and m are each independently an integer of 0 to 3).

In particular, the present invention can further increase the phase difference of the cellulose acetate film by using the compounds of the following formula (1-1 to 1-17), it is possible to improve the viewing angle and contrast. The cellulose acetate film according to the present invention is suitable for the liquid crystal display device for VA mode.

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

First, the cellulose acetate film will be described. In the present invention, the cellulose acetate film has a density of about 1.2 to about 1.35 although the density thereof is not limited.

Cellulose acetate is an ester of cellulose and acetic acid, in which all or part of the hydrogen atoms of the hydroxyl groups in the second, third and sixth positions of the glucose units constituting cellulose are substituted with acetyl groups. Although the substitution degree of a cellulose acetate is not restrict | limited, Preferably it is 2.7 or more, More preferably, it is 2.7-3.0. The substitution degree can be measured according to ASTM D-817-91.

In the present invention, the molecular weight range of the cellulose acetate is not limited, but the weight average molecular weight is preferably in the range of 200,000 to 350,000. In addition, the molecular weight distribution of the cellulose acetate 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.

It is preferable to manufacture a cellulose acetate film by the solvent cast method using a cellulose acetate dope solution. In the solvent cast method, a solution (dope) in which cellulose acetate is dissolved in a solvent is cast on a support, and the solvent is evaporated to form a film.

It is preferable to use cellulose acetate particles as a raw material of the cellulose acetate dope solution. In this case, it is preferable to use 90 wt% or more of the cellulose acetate particles having an average particle diameter of 0.5 to 5 mm. Moreover, it is preferable that 50 weight% or more of the cellulose acetate particle | grains to be used are 1-4 mm in average particle diameter.

It is preferable that the cellulose acetate particles have a shape as close as possible to the spherical shape, and the cellulose acetate particles are preferably dried with a water content of 2% by weight or less, more preferably 1% by weight or less, and then prepared as a dope solution.

Next, the additive used for a cellulose acetate film is demonstrated.

In the cellulose acetate solution (dope) used in the solvent cast method, various additives according to the use in each preparation step, for example, plasticizers, ultraviolet light inhibitors, deterioration inhibitors, fine particles, release agents, infrared absorbers, optically anisotropic control agents and the like Can be added. Specific kinds of such additives may be used without limitation as long as it is conventionally used in the art, the content is preferably used in a range that does not lower the physical properties of the film. The timing of adding the additive is determined by the type of the additive. The process of adding an additive at the end of dope preparation can also be performed.

The plasticizer may be used to improve the mechanical strength of the film, and may shorten the drying process time of the film when the plasticizer is used. The plasticizer can be used without limitation as long as it is commonly used, and examples thereof include phosphate esters and carboxylic acid esters selected from phthalic acid esters or citric acid esters. Examples of the phosphate ester include triphenyl phosphate (TPP), biphenyl diphenyl phosphate, tricresyl phosphate (TCP) and the like. Examples of the phthalate esters include dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), dioctyl phthalate (DOP), diphenyl phthalate (DPP) and diethylhexyl phthalate (DEHP). have. Examples of citric acid esters include o-acetyltriethyl citrate (OACTE) and o-acetyltributyl citrate (OACTB). Examples of other carboxylic acid esters include butyl oleate, methyl acetyl lysine oleate, dibutyl sebacate and various trimellitic acid esters. It is preferable to use a phthalate ester (DMP, DEP, DBP, DOP, DPP, DEHP) plasticizer. The content of the plasticizer is 2 to 20 parts by weight, more preferably 5 to 15 parts by weight based on 100 parts by weight of cellulose acetate.

The ultraviolet inhibitor may be a hydroxy benzophenone compound, a benzotriazole compound, a salicylic acid ester compound, a cyanoacrylate compound and the like. The amount of the sunscreen agent is 0.1 to 3 parts by weight, more preferably 0.5 to 2 parts by weight based on 100 parts by weight of cellulose acetate.

As the deterioration inhibitor, for example, an antioxidant, a peroxide decomposing agent, a radical inhibitor, a metal deactivator, a deoxygenating agent, a light stabilizer (hindered amine, etc.) and the like can be used. Particularly preferred deterioration inhibitors 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 cellulose acetate.

The said fine particles are added in order to maintain the curl suppression, conveyance property, the adhesion prevention in a roll form, or a flaw resistance of a film favorably, and you may use any of inorganic compounds and organic compounds. Examples of the inorganic compound include silicon-containing compounds, silicon dioxide, titanium oxide, zinc oxide, aluminum oxide, barium oxide, zirconium oxide, strontium oxide, antimony oxide, tin oxide, tin oxide / antimony, calcium carbonate, talc, Clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate, calcium phosphate and the like are preferred, and more preferably silicon-containing inorganic compounds, zirconium oxide and the like can be 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 retardation improving agent used for this invention is demonstrated.

The retardation enhancer is used to increase the retardation value Rth in the film thickness direction, and is preferably a compound represented by the following formula (1).

[Formula 1]

(In Chemical Formula 1, Z is selected from NA ₂ -R ₂ or CR ₁₁ R ₁₂ , wherein R ₁₁ and R ₁₂ are each independently selected from hydrogen, (C 1 -C 10) alkyl, and R ₁ and R ₂ are each independently hydrogen, (C 1 -C 10) alkyl, (C 6 -C 20) aryl, (C 3 -C 20) cyclo One selected from 5- to 7-membered heterocycloalkyl, N, O, S, including one or more elements selected from alkyl, (C2-C7) alkenyl, (C1-C10) alkoxy, N, O, S It is selected from (C4-C20) heteroaryl containing the above element,

Alkyl, aryl, cycloalkyl, alkenyl, alkoxy, heterocycloalkyl, heteroaryl of R ₁ and R ₂ are (C 1 -C 10) alkoxy, (C 1 -C 7) alkyl, halogen, nitro, cyano, hydroxy, 5- to 7-membered heterocycloalkyl or N comprising at least one element selected from amino, (C6-C20) aryl, (C2-C7) alkenyl, (C3-C20) cycloalkyl, N, O, S One or more selected from (C4-C20) heteroaryl including one or more elements selected from O, S may be further substituted, wherein R ₁ and R ₂ are (C3-C20) alkylene or (C3-C20 May be linked to alkenylene to form a fused ring.

A ₁ and A ₂ are each independently a chemical bond, or -CO-, -CS-, -COO-, -COS-, -NHCO-, -NHCS-, -CR ₃ R _4- , -POR _5- , -SO-, -SO _2- , wherein R ₃ and R ₄ are each independently hydrogen, (C1-C10) alkyl, (C6-C20) aryl, (C3-C20) cycloalkyl, (C2-C7 In (C4-C20) heteroaryl comprising at least one element selected from 5- to 7-membered heterocycloalkyl, N, O, S containing at least one element selected from alkenyl, N, O, S is selected, the R ₅ is hydrogen, (C1-C10) alkyloxy, (C6-C20) aryloxy, is selected from -NH-R _6, wherein R ₆ is hydrogen, (C1-C10) alkyl, (C2- C7) alkenyl, (C2-C4) alkynyl, (C6-C20) aryl.

In addition, n and m are each independently an integer of 0 to 3).

Specifically, the present invention may use one or more compounds selected from Formula 2 below.

[Formula 2]

In Formula 2, R ₁ and R ₂ are each independently hydrogen, (C 1 -C 10) alkyl, (C 6 -C 20) aryl, (C 3 -C 20) cycloalkyl, (C 2 -C 7) alkenyl, N, O 5 to 7 membered heterocycloalkyl containing at least one element selected from S, (C4-C20) heteroaryl containing at least one element selected from N, O, S,

Alkyl, aryl, cycloalkyl, alkenyl, heterocycloalkyl, heteroaryl of R ₁ and R ₂ are (C 1 -C 10) alkoxy, (C 1 -C 7) alkyl, halogen, nitro, cyano, hydroxy, amino, (C6-C20) aryl, (C2-C7) alkenyl, (C3-C20) cycloalkyl, 5- to 7-membered heterocycloalkyl containing one or more elements selected from N, O, S or N, O At least one selected from (C4-C20) heteroaryl including at least one element selected from S may be further substituted, and R ₁ and R ₂ may be (C3-C20) alkylene or (C3-C20) alke It may be linked with niylene to form a fused ring.

A ₁ and A ₂ are each independently -CO-, -CS-, -COO-, -COS-, -NHCO-, -NHCS-, -CR ₃ R _4- , -POR _5- , -SO-, Is selected from -SO _2- , wherein R ₃ and R ₄ are each independently hydrogen, (C1-C10) alkyl, (C6-C20) aryl, (C3-C20) cycloalkyl, (C2-C7) alkenyl, A 5-7 membered heterocycloalkyl comprising at least one element selected from N, O, and S, and a (C4-C20) heteroaryl comprising at least one element selected from N, O, S, wherein R ₅ is selected from hydrogen, (C 1 -C 10) alkyloxy, (C 6 -C 20) aryloxy, —NH—R ₆ , wherein R ₆ is hydrogen, (C 1 -C 10) alkyl, (C 2 -C 7) alkenyl , (C2-C4) alkynyl, (C6-C20) aryl.

In addition, n and m are each independently an integer of 0 to 3).

More specifically, the present invention may use a compound represented by the following formula (3).

(3)

(In Formula 3, R ₇ and R ₈ are each independently (C1-C10) alkoxy, (C1-C7) alkyl, halogen, nitro, cyano, hydroxy, amino, (C6-C20) aryl, (C2 -C7) alkenyl, (C3-C20) cycloalkyl, 5- to 7-membered heterocycloalkyl comprising at least one element selected from N, O, S or at least one element selected from N, O, S One or more selected from (C4-C20) heteroaryl including may be further substituted, and R ₇ and R ₈ may be linked to (C3-C20) alkylene or (C3-C20) alkenylene to form a fused ring. Can be.

A ₁ and A ₂ are each independently -CO-, -CS-, -COO-, -COS-, -NHCO-, -NHCS-, -CR ₃ R _4- , -POR _5- , -SO-, Is selected from -SO _2- , wherein R ₃ and R ₄ are each independently hydrogen, (C1-C10) alkyl, (C6-C20) aryl, (C3-C20) cycloalkyl, (C2-C7) alkenyl, A 5-7 membered heterocycloalkyl comprising at least one element selected from N, O, and S, and a (C4-C20) heteroaryl comprising at least one element selected from N, O, S, wherein R ₅ is selected from hydrogen, (C 1 -C 10) alkyloxy, (C 6 -C 20) aryloxy, —NH—R ₆ , wherein R ₆ is hydrogen, (C 1 -C 10) alkyl, (C 2 -C 7) alkenyl , (C2-C4) alkynyl, (C6-C20) aryl.

In addition, n and m are each independently an integer of 0 to 3).

More specifically, the present invention may use a compound represented by the following formula (4).

[Formula 4]

(In Formula 4, R ₇ and R ₈ are each independently (C1-C10) alkoxy, (C1-C7) alkyl, halogen, nitro, cyano, hydroxy, amino, (C6-C20) aryl, (C2 -C7) alkenyl, (C3-C20) cycloalkyl, 5- to 7-membered heterocycloalkyl comprising at least one element selected from N, O, S or at least one element selected from N, O, S One or more selected from (C4-C20) heteroaryl including may be further substituted, and R ₇ and R ₈ may be linked to (C3-C20) alkylene or (C3-C20) alkenylene to form a fused ring. Can be.

In addition, n and m are each independently an integer of 0 to 3).

Substituents comprising the "alkyl and other" alkyl "moieties described herein include both straight and pulverized forms.

“Aryl” described in the present invention is an organic radical derived from an aromatic hydrocarbon by one hydrogen removal, and is a single or fused ring containing 4 to 7, preferably 5 or 6 ring atoms in each ring as appropriate. It includes the system. Specific examples include, but are not limited to, phenyl, naphthyl, biphenyl, tolyl, and the like.

“Heteroaryl” described in the present invention means an aryl group containing 1 to 3 heteroatoms selected from N, O, and S as an aromatic ring skeleton atom, and the remaining aromatic ring skeleton atoms are carbons. Heteroatoms in the ring include bivalent aryl groups that are oxidized or quaternized to form, for example, N-oxides or quaternary salts. Specific examples include furyl, thiophenyl, pyrrolyl, pyranyl, imidazolyl, pyrazolyl, thiazolyl, thiadiazolyl, isothiazolyl, isoxazolyl, oxazolyl, oxdiazolyl, triazinyl, tetrazinyl, tria Zolyl, tetrazolyl, furazanyl, pyridyl, pyrazinyl, pyrimidinyl, pyridazinyl and the like.

More specifically, the compound of Formula 1 may be any one or more selected from compounds of Formulas 1-1 to 1-17, but is not limited thereto.

In addition, an optically anisotropic regulator, a wavelength dispersion regulator, etc. can be further added as needed. Such additives can be used without limitation as long as they are conventionally used in the art.

Next, the manufacturing method of the cellulose acetate film of this invention is demonstrated.

In order to manufacture the cellulose acetate film in the present invention, the following cellulose acetate composition is prepared, that is, a dope solution.

The cellulose acetate composition includes 1 to 15 parts by weight of a retardation enhancer of the following formula (1) based on 100 parts by weight of cellulose acetate.

[Formula 1]

(In Chemical Formula 1, Z is selected from NA ₂ -R ₂ or CR ₁₁ R ₁₂ , wherein R ₁₁ and R ₁₂ are each independently selected from hydrogen, (C 1 -C 10) alkyl, and R ₁ and R ₂ are each independently hydrogen, (C 1 -C 10) alkyl, (C 6 -C 20) aryl, (C 3 -C 20) cyclo One selected from 5- to 7-membered heterocycloalkyl, N, O, S, including one or more elements selected from alkyl, (C2-C7) alkenyl, (C1-C10) alkoxy, N, O, S It is selected from (C4-C20) heteroaryl containing the above element,

Alkyl, aryl, cycloalkyl, alkenyl, alkoxy, heterocycloalkyl, heteroaryl of R ₁ and R ₂ are (C 1 -C 10) alkoxy, (C 1 -C 7) alkyl, halogen, nitro, cyano, hydroxy, 5- to 7-membered heterocycloalkyl or N comprising at least one element selected from amino, (C6-C20) aryl, (C2-C7) alkenyl, (C3-C20) cycloalkyl, N, O, S One or more selected from (C4-C20) heteroaryl including one or more elements selected from O, S may be further substituted, wherein R ₁ and R ₂ are (C3-C20) alkylene or (C3-C20 May be linked to alkenylene to form a fused ring.

A ₁ and A ₂ are each independently a chemical bond, or -CO-, -CS-, -COO-, -COS-, -NHCO-, -NHCS-, -CR ₃ R _4- , -POR _5- , -SO-, -SO _2- , wherein R ₃ and R ₄ are each independently hydrogen, (C1-C10) alkyl, (C6-C20) aryl, (C3-C20) cycloalkyl, (C2-C7 In (C4-C20) heteroaryl comprising at least one element selected from 5- to 7-membered heterocycloalkyl, N, O, S containing at least one element selected from alkenyl, N, O, S is selected, the R ₅ is hydrogen, (C1-C10) alkyloxy, (C6-C20) aryloxy, is selected from -NH-R _6, wherein R ₆ is hydrogen, (C1-C10) alkyl, (C2- C7) alkenyl, (C2-C4) alkynyl, (C6-C20) aryl.

In addition, n and m are each independently an integer of 0 to 3).

Solid content concentration of the dope in the present invention is preferably 15 to 25% by weight, more preferably 16 to 23% by weight. If the solid content concentration of the dope is less than 15% by weight, the fluidity is too high, it is difficult to form a film, when it exceeds 25% by weight it is difficult to be completely dissolved.

In the present invention, the content of cellulose acetate is 70% by weight or more, preferably 70 to 90% by weight, more preferably 80 to 85% by weight of the total solid content. In addition, the cellulose acetate may be used by mixing two or more kinds of cellulose acetates having different degrees of substitution, polymerization degree or molecular weight distribution.

It is preferable to use a retardation improving agent in the range of 1-15 weight part with respect to 100 weight part of cellulose acetates. 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 producing the cellulose acetate composition (dope) is preferably an organic solvent. As the organic solvent, halogenated hydrocarbons are preferably used, and halogenated hydrocarbons include chlorinated hydrocarbons, methylene chloride and chloroform, and methylene chloride is most preferably used.

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 ester, methyl formate, ethyl formate, propyl formate, pentyl formate, methyl acetate, ethyl acetate, pentyl acetate and the like can be used, and as ketone, acetone, methyl ethyl ketone, diethyl ketone, diisobutyl ketone , Cyclopentanone, cyclohexanone, methylcyclohexanone and the like can be used, and ether is diisopropyl ether, dimethoxymethane, dimethoxyethane, 1,4-dioxane, 1,3-dioxolane, tetra Hydrofuran, anisole, phentol, and the like can be used, and alcohols include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, t-butanol, 1-pentanol, 2-methyl- 2-butanol, cyclohexanol, 2-fluoroethanol, 2,2,2-trifluoroethanol, 2,2,3,3-tetrafluoro-1-propanol and the like are used.

More preferably, methylene chloride may be used as the main solvent and alcohol may be used as the subsolvent. Specifically, methylene chloride and alcohol may be used by mixing in a weight ratio of 80:20 to 95: 5.

The cellulose acetate composition can be prepared according to normal temperature, high temperature or low temperature dissolution method.

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

The cellulose acetate film can be prepared according to a conventional solvent casting method. More specifically, the prepared dope (cellulose acetate composition) is stored once in a storage tank, and defoaming the foam contained in the dope. The defoamed dope is sent to the press die through a pressurized metering gear pump that can quantitatively and precisely transfer the dope from the dope outlet to the press die, and the dope is placed on the metal support endlessly running from the slit of the press die. By casting uniformly, the less dry cast film is peeled from the metal support at the peeling point at which the metal support is almost round. Both ends of the produced web are sandwiched by a clip and conveyed by a tenter while maintaining the width, then dried by conveying by a roller of a drying apparatus, and wound to a predetermined length by a odor machine. In addition, when the casting film is manufactured, it is also possible to uniaxially and biaxially stretch in the machine direction and the width direction in a state where the amount of residual solvent is 10 to 40% by weight. Or it is also possible to extend | stretch offline after manufacture of a casting film. The elongation is preferably in the range of 5 to 100%, more preferably in the range of 10 to 80%, most preferably in the range of 20 to 50%.

As for the space temperature at the time of application | coating of a solution, -50 degreeC-50 degreeC are preferable, -30 degreeC-40 degreeC are more preferable, -20 degreeC-30 degreeC are the most preferable. Since the cellulose acetate solution applied at a low space temperature is instantaneously cooled on the support to improve gel strength, a film containing many organic solvents is obtained. Therefore, the film can be peeled off from the support in a short time without evaporating the organic solvent from the cellulose acetate. As the gas for cooling the space, ordinary air, nitrogen, argon or helium may 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 acetate solution, -50 degreeC-130 degreeC is preferable, -30 degreeC-25 degreeC are more preferable, -20 degreeC-15 degreeC are the most preferable. In order to cool the casting part, the gas cooled to the casting part may be introduced. A chiller may be placed in the casting to cool the space. In cooling, it is important to take care that water does not adhere to the casting part. When cooling with gas, it is preferable to dry the gas.

Moreover, surface treatment can be given to a cellulose acetate film as needed. Surface treatment is generally performed in order to improve the adhesiveness of a cellulose acetate film. Surface treatment methods include glow discharge treatment, ultraviolet irradiation treatment, corona treatment, flame treatment and saponification treatment.

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

The cellulose acetate film according to the present invention may be used in a polarizing plate, an optical compensation sheet and a liquid crystal display device, and may be used by laminating one or two or more sheets.

The cellulose acetate film according to the present invention can provide a cellulose acetate film having a high retardation value in the thickness direction.

In addition, the cellulose acetate film according to the present invention has a high retardation, thereby improving the viewing angle and contrast of the VA mode LCD panel.

Hereinafter, the present invention will be described by way of example for specific description of the present invention, but 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 injecting light having a wavelength of 450 nm, 550 nm, and 700 nm in a film normal direction in a birefringence measuring instrument (KOBRA-WPR, trade name, manufactured by Oji Scientific Instrument), respectively. Rth is a retardation measured by injecting light having wavelengths of 450 nm, 550 nm, and 700 nm in a direction inclined at 40 degrees with respect to the film normal direction using the Slow Axis (determined by KOBRA-WPR) in the Re plane. Retardation) values were measured.

Example 1

Preparation of cellulose acetate composition (dope)

0.5 weight part of silicon dioxide (average particle diameter 16nm) with respect to 100 weight part of cellulose acetate powders of substitution degree 2.87, 2- (2H-Benzotriazol-2-yl) -6- (1-methyl-1-phenylethyl) as an ultraviolet-ray inhibitor 2 parts by weight of -4- (1,1,3,3-tetramethylbutyl) phenol, 440 parts by weight of methylene chloride, 50 parts by weight of methanol and 10 parts by weight of a retardation enhancer of the following Chemical Formula 1-1 were added to a stirrer and dissolved at 30 ° C. It was. After heating the obtained dope to 30 degreeC, it sent by gear pump, filtered with the filter paper of 0.01 mm of absolute filtration accuracy, and filtered further with the cartridge filtration apparatus of 5 micrometers of absolute filtration precision.

Preparation of Cellulose Acetate Film

The dope obtained through the filtration process was cast on the mirror stainless steel support through a casting die and peeled off. The amount of residual solvent at the time of peeling was adjusted to be 30wt%. After peeling, the drawing machine stretches 2% (length%) in the film traveling direction, and then connects it to the tenter, and then 10% (length%), 20% (length%) and 30% (length%) in the film width direction Stretched. After the film emerged from the tenter, the left and right ends of the film were removed by 150 mm. The film from which the end was removed was dried through a drier, and both ends of the film from the drier were cut 3 cm, and a nominal process with a height of 100 µm was further applied to a 10 mm portion from the end, and wound up in a roll shape. The thickness of the produced film is 60 micrometers, the sample before extending | stretching and after extending | stretching were prepared, and the retardation (Rth) value of the thickness direction of the cellulose acetate film was measured by the method mentioned above.

[Examples 2 to 17]

Doping was prepared in the same manner as in Example 1 using the compound 1-2∼1-17 to prepare a cellulose acetate film.

Comparative Example 1

Preparation of cellulose acetate composition (dope)

The following composition was placed in a stirrer and dissolved at 30 ° C.

In the following composition, the sunscreen was used 2- (2H-Benzotriazol-2-yl) -6- (1-methyl-1-phenylethyl) -4- (1,1,3,3-tetramethylbutyl) phenol.

100 parts by weight of cellulose acetate powder having a degree of substitution of 2.87

8 parts by weight of triphenyl phosphate

4 parts by weight of biphenyldiphenyl phosphate

UV protection agent 2 parts by weight

Silicon dioxide, average particle size 16nm 0.5 parts by weight

440 parts by weight of methylene chloride

50 parts by weight of methanol

After heating the obtained dope to 30 degreeC, 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.

Preparation of Cellulose Acetate Film

The dope obtained through the filtration process was cast on the mirror stainless steel support through a casting die and peeled off. The amount of residual solvent at the time of peeling was adjusted to be 30wt%. After peeling, the drawing machine stretches 2% (length%) in the film direction and connects to the tenter again, and stretches 10% (length%), 20% (length%) and 30% (length%) in the film width direction, respectively. It was. After the film emerged from the tenter, the left and right ends of the film were removed by 150 mm. The film from which the end was removed was dried through a drier, and both ends of the film from the drier were cut 3 cm, a knurling process having a height of 100 µm was further applied to a 10 mm portion from the end, and wound up into a roll shape. The thickness of the produced film is 60 micrometers, the sample before extending | stretching and after extending | stretching were prepared, and the retardation (Rth) value of the thickness direction of the cellulose acetate film was measured by the method mentioned above.

The retardation values before stretching of the films prepared by the above Examples and Comparative Examples were measured and shown in Table 1 below.

[Table 1]

As shown in Table 1, unlike the conventional plasticizer it can be seen that when added to the optical anisotropy improver described in the Example shows a high Rth.

In addition, using the films of the above Examples and Comparative Examples, the change in the retardation value according to the draw ratio is measured and shown in Table 2 below.

TABLE 2

As shown in Table 2, it was found that the retardation increased significantly as compared with the comparative example as the draw ratio was increased.

Claims (17)

Cellulose acetate film comprising at least one retardation enhancer selected from the compound of formula (1).
[Formula 1]

(In Chemical Formula 1, Z is selected from NA ₂ -R ₂ or CR ₁₁ R ₁₂ , wherein R ₁₁ and R ₁₂ are each independently selected from hydrogen, (C 1 -C 10) alkyl, and R ₁ and R ₂ are each independently hydrogen, (C 1 -C 10) alkyl, (C 6 -C 20) aryl, (C 3 -C 20) cyclo One selected from 5- to 7-membered heterocycloalkyl, N, O, S, including one or more elements selected from alkyl, (C2-C7) alkenyl, (C1-C10) alkoxy, N, O, S It is selected from (C4-C20) heteroaryl containing the above element,
Alkyl, aryl, cycloalkyl, alkenyl, alkoxy, heterocycloalkyl, heteroaryl of R ₁ and R ₂ are (C 1 -C 10) alkoxy, (C 1 -C 7) alkyl, halogen, nitro, cyano, hydroxy, 5- to 7-membered heterocycloalkyl or N comprising at least one element selected from amino, (C6-C20) aryl, (C2-C7) alkenyl, (C3-C20) cycloalkyl, N, O, S One or more selected from (C4-C20) heteroaryl including one or more elements selected from O, S may be further substituted, wherein R ₁ and R ₂ are (C3-C20) alkylene or (C3-C20 May be linked to alkenylene to form a fused ring.
A ₁ and A ₂ are each independently a chemical bond, or -CO-, -CS-, -COO-, -COS-, -NHCO-, -NHCS-, -CR ₃ R _4- , -POR _5- , -SO-, -SO _2- , wherein R ₃ and R ₄ are each independently hydrogen, (C1-C10) alkyl, (C6-C20) aryl, (C3-C20) cycloalkyl, (C2-C7 In (C4-C20) heteroaryl comprising at least one element selected from 5- to 7-membered heterocycloalkyl, N, O, S containing at least one element selected from alkenyl, N, O, S is selected, the R ₅ is hydrogen, (C1-C10) alkyloxy, (C6-C20) aryloxy, is selected from -NH-R _6, wherein R ₆ is hydrogen, (C1-C10) alkyl, (C2- C7) alkenyl, (C2-C4) alkynyl, (C6-C20) aryl.
In addition, n and m are each independently an integer of 0 to 3). The method of claim 1,
Cellulose acetate film comprising a retardation enhancer represented by the formula (2).
(2)

In Formula 2, R ₁ and R ₂ are each independently hydrogen, (C 1 -C 10) alkyl, (C 6 -C 20) aryl, (C 3 -C 20) cycloalkyl, (C 2 -C 7) alkenyl, N, O 5 to 7 membered heterocycloalkyl containing at least one element selected from S, (C4-C20) heteroaryl containing at least one element selected from N, O, S,
Alkyl, aryl, cycloalkyl, alkenyl, heterocycloalkyl, heteroaryl of R ₁ and R ₂ are (C 1 -C 10) alkoxy, (C 1 -C 7) alkyl, halogen, nitro, cyano, hydroxy, amino, (C6-C20) aryl, (C2-C7) alkenyl, (C3-C20) cycloalkyl, 5- to 7-membered heterocycloalkyl containing one or more elements selected from N, O, S or N, O At least one selected from (C4-C20) heteroaryl including at least one element selected from S may be further substituted, and R ₁ and R ₂ may be (C3-C20) alkylene or (C3-C20) alke It may be linked with niylene to form a fused ring.
A ₁ and A ₂ are each independently -CO-, -CS-, -COO-, -COS-, -NHCO-, -NHCS-, -CR ₃ R _4- , -POR _5- , -SO-, Is selected from -SO _2- , wherein R ₃ and R ₄ are each independently hydrogen, (C1-C10) alkyl, (C6-C20) aryl, (C3-C20) cycloalkyl, (C2-C7) alkenyl, A 5-7 membered heterocycloalkyl comprising at least one element selected from N, O, and S, and a (C4-C20) heteroaryl comprising at least one element selected from N, O, S, wherein R ₅ is selected from hydrogen, (C 1 -C 10) alkyloxy, (C 6 -C 20) aryloxy, —NH—R ₆ , wherein R ₆ is hydrogen, (C 1 -C 10) alkyl, (C 2 -C 7) alkenyl , (C2-C4) alkynyl, (C6-C20) aryl.
In addition, n and m are each independently an integer of 0 to 3). The method of claim 2,
Cellulose acetate film comprising a retardation enhancer represented by the formula (3).
(3)

(In Formula 3, R ₇ and R ₈ are each independently (C1-C10) alkoxy, (C1-C7) alkyl, halogen, nitro, cyano, hydroxy, amino, (C6-C20) aryl, (C2 -C7) alkenyl, (C3-C20) cycloalkyl, 5- to 7-membered heterocycloalkyl comprising at least one element selected from N, O, S or at least one element selected from N, O, S One or more selected from (C4-C20) heteroaryl including may be further substituted, and R ₇ and R ₈ may be linked to (C3-C20) alkylene or (C3-C20) alkenylene to form a fused ring. Can be.
A ₁ and A ₂ are each independently -CO-, -CS-, -COO-, -COS-, -NHCO-, -NHCS-, -CR ₃ R _4- , -POR _5- , -SO-, Is selected from -SO _2- , wherein R ₃ and R ₄ are each independently hydrogen, (C1-C10) alkyl, (C6-C20) aryl, (C3-C20) cycloalkyl, (C2-C7) alkenyl, A 5-7 membered heterocycloalkyl comprising at least one element selected from N, O, and S, and a (C4-C20) heteroaryl comprising at least one element selected from N, O, S, wherein R ₅ is selected from hydrogen, (C 1 -C 10) alkyloxy, (C 6 -C 20) aryloxy, —NH—R ₆ , wherein R ₆ is hydrogen, (C 1 -C 10) alkyl, (C 2 -C 7) alkenyl , (C2-C4) alkynyl, (C6-C20) aryl.
In addition, n and m are each independently an integer of 0 to 3). The method of claim 3,
Cellulose acetate film comprising a retardation enhancer represented by the formula (4).
[Chemical Formula 4]

(In Formula 4, R ₇ and R ₈ are each independently (C1-C10) alkoxy, (C1-C7) alkyl, halogen, nitro, cyano, hydroxy, amino, (C6-C20) aryl, (C2 -C7) alkenyl, (C3-C20) cycloalkyl, 5- to 7-membered heterocycloalkyl comprising at least one element selected from N, O, S or at least one element selected from N, O, S One or more selected from (C4-C20) heteroaryl including may be further substituted, and R ₇ and R ₈ may be linked to (C3-C20) alkylene or (C3-C20) alkenylene to form a fused ring. Can be.
In addition, n and m are each independently an integer of 0 to 3). The method of claim 1,
The compound of Formula 1 is a cellulose acetate film selected from the following compounds.

The method of claim 1,
The retardation enhancer is a cellulose acetate film used in 1 to 15 parts by weight based on 100 parts by weight of cellulose acetate. The method of claim 1,
In the cellulose acetate film, Re (λ) and Rth (λ) before stretching satisfy the following formulas (I), (II) and (III), and Re (λ) and Rth (λ) after stretching 5 to 100% by length. The cellulose acetate film which satisfy | fills following formula (IV), (V), and (VI).
(I) 0 ≦ Re (550) ≦ 10,
(II) 50 ≦ Rth (550) ≦ 250,
(III) Rth (700) / Rth (450)> 1.0

(IV) 20 ≦ Re (550) ≦ 100,
(V) 70 ≦ Rth (550) ≦ 200,
(VI) Rth (700) / Rth (450)> 1.0
(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.) A cellulose acetate composition comprising 1 to 15 parts by weight of one or more retardation enhancers selected from compounds of formula (1) based on 100 parts by weight of cellulose acetate.
[Formula 1]

(In Chemical Formula 1, Z is selected from NA ₂ -R ₂ or CR ₁₁ R ₁₂ , wherein R ₁₁ and R ₁₂ are each independently selected from hydrogen, (C 1 -C 10) alkyl, and R ₁ and R ₂ are each independently hydrogen, (C 1 -C 10) alkyl, (C 6 -C 20) aryl, (C 3 -C 20) cyclo One selected from 5- to 7-membered heterocycloalkyl, N, O, S, including one or more elements selected from alkyl, (C2-C7) alkenyl, (C1-C10) alkoxy, N, O, S It is selected from (C4-C20) heteroaryl containing the above element,
Alkyl, aryl, cycloalkyl, alkenyl, alkoxy, heterocycloalkyl, heteroaryl of R ₁ and R ₂ are (C 1 -C 10) alkoxy, (C 1 -C 7) alkyl, halogen, nitro, cyano, hydroxy, 5- to 7-membered heterocycloalkyl or N comprising at least one element selected from amino, (C6-C20) aryl, (C2-C7) alkenyl, (C3-C20) cycloalkyl, N, O, S One or more selected from (C4-C20) heteroaryl including one or more elements selected from O, S may be further substituted, wherein R ₁ and R ₂ are (C3-C20) alkylene or (C3-C20 May be linked to alkenylene to form a fused ring.
A ₁ and A ₂ are each independently a chemical bond, or -CO-, -CS-, -COO-, -COS-, -NHCO-, -NHCS-, -CR ₃ R _4- , -POR _5- , -SO-, -SO _2- , wherein R ₃ and R ₄ are each independently hydrogen, (C1-C10) alkyl, (C6-C20) aryl, (C3-C20) cycloalkyl, (C2-C7 In (C4-C20) heteroaryl comprising at least one element selected from 5- to 7-membered heterocycloalkyl, N, O, S containing at least one element selected from alkenyl, N, O, S is selected, the R ₅ is hydrogen, (C1-C10) alkyloxy, (C6-C20) aryloxy, is selected from -NH-R _6, wherein R ₆ is hydrogen, (C1-C10) alkyl, (C2- C7) alkenyl, (C2-C4) alkynyl, (C6-C20) aryl.
In addition, n and m are each independently an integer of 0 to 3). The method of claim 8,
The compound of Formula 1 is a cellulose acetate composition selected from the following compounds.

The method of claim 8,
The composition is a cellulose acetate composition is further added any one or two or more additives selected from sunscreens, microparticles, plasticizers, anti-degradants, release agents, infrared absorbers, optically anisotropic control agents. After preparing a film by solution casting the cellulose acetate composition according to any one of claims 8 to 10, the cellulose acetate film prepared by uniaxially or biaxially stretched at an elongation of 5 to 100% by length. 12. The method of claim 11,
The stretching is a cellulose acetate film stretched in the state of 10 to 40% by weight of the residual solvent after casting. 12. The method of claim 11,
In the cellulose acetate film, Re (λ) and Rth (λ) before stretching satisfy the following formulas (I), (II) and (III), and after stretching to 5 to 100% by length, Re (λ) and Rth (λ) ) Relates to a cellulose acetate film satisfying the following formulas (IV), (V) and (VI).
(I) 0 ≦ Re (550) ≦ 10,
(II) 50 ≦ Rth (550) ≦ 250,
(III) Rth (700) / Rth (450)> 1.0

(IV) 20 ≦ Re (550) ≦ 100,
(V) 70 ≦ Rth (550) ≦ 200,
(VI) Rth (700) / Rth (450)> 1.0
(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.) Claims 1 to 7, wherein the optical compensation sheet comprising any one of the cellulose acetate film. The polarizing plate containing the cellulose acetate film of any one of Claims 1-7. A liquid crystal display device comprising the cellulose acetate film of any one of claims 1 to 7. 17. The method of claim 16,
The liquid crystal display device is a VA mode liquid crystal display device.