KR20150140458A - Optically isotropic cellulose-acetate film, and display device comprising the same - Google Patents

Abstract

The present invention relates to a retardation film and a liquid crystal display device. More particularly, the present invention relates to an optically isotropic cellulose acetate film which includes a plasticizer for a hydroxy group-terminal ester-based optical film represented by chemical formula 1, and satisfies mathematical formula 1, and the liquid display device including the optically isotropic cellulose acetate film. The optically isotropic cellulose acetate film is very effective to control a phase difference in a rage of 0 <= Re(550) <= 20 and -30 <= Rth(550) <= 30. In the chemical formula 1: M is isopropyl carbonyloxy having 4-15 carbon atoms, an ester compound thereof, or a hydroxy group; G is a bivalent saturated linking group having 20-40 atoms and 8-16 carbon atoms, which is a 2,2,4-trimethyl-1,3-pentanylene group, or ethylene glycol and dicarboxylic acid; and n is an integer of 1 or more. The mathematical formula 1 is: (1) Re(λ) = (nx - ny) × d; (2) Rth(λ) = ((nx + ny) / 2 - nz) × d; (3) 0 <= Re(550) <= 20, -30 <= Rth(550) <= 30; and (4) ¦Re(450) - Re(550) ¦<= 10, ¦ Rth(450) - Rth(550) ¦ <= 15. In the mathematical formula 1: Re(λ) is a retardation value in the direction of a side in a reference wave length λnm; Rth(λ) is a retardation value in the direction of thickness in the reference wave length λnm; nx is a refractive index in the direction of an x axis in a side of the film; ny is a refractive index in the direction of an y axis; nz is a refractive index in the direction of thickness; and d is the thickness of the film.

Description

TECHNICAL FIELD [0001] The present invention relates to an optically isotropic cellulose acetate film and a liquid crystal display device using the optically isotropic cellulose acetate film.

The present invention relates to an optically isotropic cellulose acetate film and a liquid crystal display.

As the performance and quality of the liquid crystal display device have been improved, a polarizing plate protective film having a performance capable of withstanding severe environmental fluctuations of the dimensional stability of the polarizing plate, the curling characteristics of the polarizing plate, and the surface property of the polarizing plate has been required as the polarizing plate protective film used for the polarizing plate .

As a polarizing plate protective film of a liquid crystal display device currently in general use, a film made of cellulose ester is used. The cellulose ester film generally has a solution casting method in view of ensuring flatness and the like. The film expands in the film thickness direction due to the evaporation of the solvent and has a low refractive index in the thickness direction with respect to the film in-plane refractive index. As a result of considering the display mode of the liquid crystal display device and the retardation of the other retardation film and the member, a film having the same refractive index in the thickness direction and the in-plane direction as the polarizer protective film which is optimal for securing the viewing angle of the liquid crystal display device, A polarizing plate protective film having a high refractive index in the polarizing plate protective film has been required.

A display film such as a liquid crystal panel film is required to have optical isotropy, but usually the plastic film is less optically isotropic than glass.

The cellulose acetate film exhibits relatively good transparency, smoothness and optical isotropy, but in order to realize the optical isotropy of the cellulose acetate film, the orientation in the plane direction and the thickness direction must be suppressed, which is possible through the use of a retardation reducing agent .

However, the retardation reducing agent used in the optically isotropic cellulose acetate film is mostly a compound having a low molecular weight. Such a low-molecular-weight additive has a lowering effect but is somewhat inferior in compatibility with cellulose acetate and is highly volatile at the time of film formation Therefore, as the content increases, the problem of bleed-out of the film may be caused, and the retardation of the retardation can be deteriorated.

Disclosure of the Invention An object of the present invention is to provide an optically isotropic cellulose acetate film which can be used as a retardation film for IPS using a specific retardation inhibitor.

The present invention has been made to solve the problems of the prior art,

A plasticizer for a hydroxy-terminated ester-based optical film represented by the following formula (1)

The isotropic cellulose acetate film satisfying the following formula (1).

[Chemical Formula 1]

M- (G) n-M

Wherein M is isopropylcarbonyloxy or an ester compound thereof having 4 to 14 carbon atoms or a hydroxyl group and G is a divalent saturated linking group having 20 to 40 atoms and 8 to 16 carbon atoms and 2,2,4-trimethyl-1 , 3-pentanylene group or ethylene glycol and dicarboxylic acid, and n is an integer of 1 or more.

[Equation 1]

(1) Re (?) = (Nx - ny) xd

(2) Rth (?) = ((Nx + ny) / 2 - nz) xd

(3) 0? Re (550)? 20, -30? Rth (550)? 30

(450) -Re (550)? 15,? Rth (450) -Rth (550)? 15

Here, Re (?) Is the retardation value in the plane direction at the reference wavelength? Nm and Rth (?) Is the retardation in the thickness direction at the reference wavelength? Nm. nx is the refractive index in the in-plane x-axis direction of the film, ny is the refractive index in the in-plane y-axis direction of the film, nz is the refractive index in the thickness direction of the film, and d is the thickness of the film.

In the present invention, the plasticizer is an isotropic cellulose acetate film characterized by being a plasticizer for a hydroxy-terminated ester optical film represented by the following general formula (2).

(2)

, 또는

이고, n은 1 이상의 정수이다.Here, M is

, or

And n is an integer of 1 or more.

In the present invention, the plasticizer is an isotropic cellulose acetate film characterized by being a plasticizer for a hydroxyl group-terminated ester optical film represented by the following general formula (3).

(3)

Here, n is an integer of 1 or more.

In the present invention, the plasticizer is contained in an amount of 5 to 15 parts by weight based on 100 parts by weight of the cellulose acetate.

In the present invention, the plasticizer may be at least one selected from the group consisting of a polyhydric alcohol ester plasticizer, a polycarboxylic acid ester plasticizer, a glycolate plasticizer, a phthalate ester plasticizer, a fatty acid ester plasticizer and a polyhydric alcohol ester plasticizer , A polyester-based plasticizer, and an acrylic plasticizer. The present invention also provides an isotropic cellulose acetate film.

The present invention also provides an isotropic cellulose acetate film characterized in that the use of the film is a retardation film for IPS.

In addition, a display device including the isotropic cellulose acetate film of the present invention is provided.

The film of the present invention is very effective for controlling the retardation within a range of 0? Re (550)? 20, -30? | Rth (550) |?? 30, and can be used as an IPS phase shifting film.

Hereinafter, the present invention will be described in detail.

According to an aspect of the present invention,

Is an isotropic cellulose acetate film which contains a plasticizer for a hydroxy-terminated ester optical film represented by the following formula (1) and satisfies the following formula (1).

[Chemical Formula 1]

M- (G) n-M

Wherein M is isopropylcarbonyloxy or an ester compound thereof having 4 to 14 carbon atoms or a hydroxyl group and G is a divalent saturated linking group having 20 to 40 atoms and 8 to 16 carbon atoms and 2,2,4-trimethyl-1 , 3-pentanylene group or ethylene glycol and dicarboxylic acid, and n is an integer of 1 or more.

[Equation 1]

(1) Re (?) = (Nx - ny) xd

(2) Rth (?) = ((Nx + ny) / 2 - nz) xd

(3) 0? Re (550)? 20, -30? Rth (550)? 30

(450) -Re (550)? 15,? Rth (450) -Rth (550)? 15

Here, Re (?) Is the retardation value in the plane direction at the reference wavelength? Nm and Rth (?) Is the retardation in the thickness direction at the reference wavelength? Nm. nx is the refractive index in the in-plane x-axis direction of the film, ny is the refractive index in the in-plane y-axis direction of the film, nz is the refractive index in the thickness direction of the film, and d is the thickness of the film.

The compound of the formula (1) may be a plasticizer for an ester-based optical film represented by the following formula (2) or (3).

(2)

(3)

The plasticizer is preferably contained in an amount of 5 to 15 parts by weight based on 100 parts by weight of the cellulose acetate. If it is less than 5, it may not be sufficient to suppress retardation development, and if it exceeds 15, plasticizer may bleed-out, which may be undesirable.

The isotropic cellulose acetate film of the present invention may further contain other conventional plasticizers other than the above-mentioned plasticizers of the present invention within a range that does not adversely affect the object of the present invention. Examples of the plasticizer include polyvalent alcohol ester plasticizers, polyvalent carboxylic ester plasticizers, glycolate plasticizers, phthalate ester plasticizers, fatty acid ester plasticizers and polyhydric alcohol ester plasticizers, polyester plasticizers, acrylic plasticizers, and the like. .

The polyhydric alcohol ester may be a compound obtained by polymerizing a polyhydric alcohol and a monocarboxylic acid.

The polyhydric alcohol is not particularly limited, and examples of preferable polyhydric alcohols include adonitol, arabitol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propanediol, 1,3-butanediol, 1,4-butanediol, dibutylene glycol, 1,2,4-butanetriol, 1,5-butanediol, Pentanediol, 1,6-hexanediol, hexanetriol, galactitol, mannitol, 3-methylpentane-1,3,5-triol, pinacol, sorbitol, trimethylol propane, trimethylolethane and xylitol For example. Particularly preferred are triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, sorbitol, trimethylol propane and xylitol.

The monocarboxylic acid is not particularly limited and any known aliphatic monocarboxylic acid, alicyclic monocarboxylic acid, aromatic monocarboxylic acid, or the like can be used, and examples of preferred monocarboxylic acids include, for example, .

Preferred aliphatic monocarboxylic acids are acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, ferric acid, capric acid, 2-ethylhexanecarboxylic acid, undecylic acid, But are not limited to, acetic acid, lauric acid, decyl acid, myristic acid, pentadecyl acid, palmitic acid, heptadecyl acid, stearic acid, nonadecanoic acid, arachic acid, behenic acid, lignoceric acid, And unsaturated fatty acids such as saturated fatty acids such as lactic acid, undecylenic acid, oleic acid, sorbic acid, linoleic acid, linolenic acid and arachidonic acid.

Examples of preferred alicyclic monocarboxylic acids include cyclopentanecarboxylic acid, cyclohexanecarboxylic acid, cyclooctanecarboxylic acid, and derivatives thereof.

Examples of preferred aromatic monocarboxylic acids include those obtained by introducing an alkyl group into a benzene ring of benzoic acid such as benzoic acid and toluic acid, those having two or more benzene rings such as biphenylcarboxylic acid, naphthalenecarboxylic acid and tetrainecarboxylic acid Aromatic monocarboxylic acids or derivatives thereof. Particularly preferred is benzoic acid.

The molecular weight of the polyhydric alcohol ester is not particularly limited, but is preferably 300 to 1,500, and more preferably 350 to 750. A large molecular weight is preferable because it is difficult to volatilize, and a small molecular weight is preferable in view of the moisture permeability and compatibility with the cellulose ester.

The carboxylic acid used for the polyhydric alcohol ester may be one kind or a mixture of two or more kinds. In addition, the hydroxy (OH) group in the polyhydric alcohol may be entirely esterified, or a part thereof may be left as it is in the hydroxy (OH) group.

The glycolate-based plasticizer is not particularly limited, but alkyl phthalyl alkyl glycolates can be preferably used. Examples of alkyl phthalyl alkyl glycolates include methyl phthalyl methyl glycolate, ethyl phthalyl ethyl glycolate, propyl phthalyl propyl glycolate, butyl phthalyl butyl glycolate, octyl phthalyl octyl glycolate, Butyl phthalyl ethyl glycolate, butyl phthalyl ethyl glycolate, ethyl phthalyl methyl glycolate, ethyl phthalyl propyl glycolate, methyl phthalyl butyl glycolate, ethyl phthalyl butyl glycolate, butyl phthalyl methyl glycolate, Butyl phthalyl propyl glycolate, methyl phthalyl octyl glycolate, ethyl phthalyl octyl glycolate, octyl phthalyl methyl glycolate, and octyl phthalyl ethyl glycolate.

Examples of the phthalate ester plasticizer include diethyl phthalate, dimethoxyethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate, dioctyl phthalate, dicyclohexyl phthalate, dicyclohexylterephthalate, .

Examples of the citrate ester plasticizer include acetyltrimethyl citrate, acetyltriethyl citrate, and acetyltributyl citrate.

As the fatty acid ester plasticizer, butyl oleate, methyl acetyl ricinoleate, dibutyl sebacate and the like can be given.

Examples of the phosphate ester plasticizer include triphenyl phosphate, tricresyl phosphate, cresyldiphenyl phosphate, octyldiphenyl phosphate, diphenyl biphenyl phosphate, trioctyl phosphate, tributyl phosphate and the like.

The film of the present invention is suitable as an IPS retardation compensation film having a retardation within a range of 0? Re (550)? 20 and -30? Rth (550)? 30.

According to another aspect of the present invention,

And a display device comprising the isotropic cellulose acetate film of the present invention.

The display device of the present invention can be manufactured by assembling the isotropic cellulose acetate film of the present invention into a display device, and other display device configurations and manufacturing methods are conventionally known to those skilled in the art Technology can be used without limit.

The display device of the present invention is a liquid crystal display (LCD) and is a reflection type, transmissive type, transflective type LCD or TN type, STN type, OCB type, HAN type, VA type (PVA type and MVA type) IPS type, and the IPS type is preferable.

In particular, by incorporating the polarizing plate of the present invention into a commercially available IPS (In Plane Switching) mode liquid crystal display device, the liquid crystal display device of the present invention with excellent visibility and widened viewing angle can be manufactured.

In the IPS mode, a fringe-field switching (FFS) mode is also included in the present invention, a polarizing plate of the present invention can be assembled in the same manner as the IPS mode, and a liquid crystal display of the present invention .

Hereinafter, the present invention will be described in more detail by way of examples. It is to be understood that the following embodiments are for the purpose of illustration only and are not intended to limit the scope of the present invention.

Example

Example  One

[Preparation of Dope Solution]

A cellulose ester (acetyl group degree of substitution: 2.86) and a plasticizer compound represented by the following formula (2) in an amount of about 12% by weight based on the weight of the cellulose acetate were mixed in a solvent of methylene chloride: methanol = 9: 1. Mixing was carried out using a mixing tank, and the solids were completely dissolved by stirring.

(2)

, 또는

이고, n은 1 이상의 정수이다.
Here, M is

, or

And n is an integer of 1 or more.

[Production of Film]

A cellulose acetate film was prepared using the dissolved dope solution. And dried at a drying temperature of 150 ° C (40 minutes). The thickness of the film was 40 탆.

Example 2

A film was prepared in the same manner as in Example 1, except that the following compound (3) was used as the plasticizer compound.

(3)

Here, n is an integer of 1 or more.

Comparative Example

A film was prepared in the same manner as in Example 1, except that a plasticizer compound represented by the following formula (A) was used.

(A)

Here, n is an integer of 1 or more.

Experimental Example

Retardation  And Hayes  A measure of beauty

The retardation and haze of the films produced in Examples 1 to 3 and Comparative Examples were measured. The retardation was measured using an Axoscan apparatus, and the haze was measured with a haze meter.

The results are shown in Table 1 below.

As can be seen from Table 1, when the additives mentioned in the present invention are used, it can be seen that the phase difference is very effective in controlling the range of 0? Re (550)? 20 and -30? Rth (550)? 30.

Claims (7)

A plasticizer for a hydroxy-terminated ester-based optical film represented by the following formula (1)
Wherein the isotropic cellulose acetate film satisfies the following formula (1).
[Chemical Formula 1]
M- (G) nM
Wherein M is isopropylcarbonyloxy or an ester compound thereof having 4 to 14 carbon atoms or a hydroxyl group and G is a divalent saturated linking group having 20 to 40 atoms and 8 to 16 carbon atoms and 2,2,4-trimethyl-1 , 3-pentanylene group or ethylene glycol and dicarboxylic acid, and n is an integer of 1 or more.
[Equation 1]
(1) Re (?) = (Nx - ny) xd
(2) Rth (?) = ((Nx + ny) / 2 - nz) xd
(3) 0? Re (550)? 20, -30? Rth (550)? 30
(450) -Re (550)? 15,? Rth (450) -Rth (550)? 15
Here, Re (?) Is the retardation value in the plane direction at the reference wavelength? Nm and Rth (?) Is the retardation in the thickness direction at the reference wavelength? Nm. nx is the refractive index in the in-plane x-axis direction of the film, ny is the refractive index in the in-plane y-axis direction of the film, nz is the refractive index in the thickness direction of the film, and d is the thickness of the film. The isotropic cellulose acetate film according to claim 1, wherein the plasticizer is a plasticizer for a hydroxyl group-terminated ester optical film represented by the following formula (2).
(2)

Here, M is

, or

And n is an integer of 1 or more. The isotropic cellulose acetate film according to claim 1, wherein the plasticizer is a plasticizer for a hydroxyl group-terminated ester optical film represented by the following formula (3).
(3)

Here, n is an integer of 1 or more. The isotropic cellulose acetate film according to claim 1, wherein the plasticizer is contained in an amount of 5 to 15 parts by weight based on 100 parts by weight of the cellulose acetate. The plasticizer according to claim 1, wherein the plasticizer is selected from the group consisting of a polyhydric alcohol ester plasticizer, a polycarboxylic acid ester plasticizer, a glycolate plasticizer, a phthalate ester plasticizer, a fatty acid ester plasticizer and a polyhydric alcohol ester plasticizer, Wherein the isotropic cellulose acetate film further comprises one or more other plasticizers selected from the group consisting of polyester plasticizers, and acrylic plasticizers. The isotropic cellulose acetate film according to claim 1, wherein the film is a retardation film for IPS. A display device comprising the isotropic cellulose acetate film of claim 1.