KR101716120B1 - Liquid crystal cellulose ester phase difference film - Google Patents

Abstract

The present invention relates to a liquid crystal cellulosic ester phase difference film, and more particularly, to a liquid crystal cellulose ester phase difference film capable of producing a polarizing plate having improved reliability by including a resin capable of improving high temperature and high humidity reliability and an additive.

Description

[0001] The present invention relates to a liquid crystal cellulose ester phase difference film,

The present invention relates to a cellulose ester phase difference film, and more particularly, to a cellulose ester phase difference film capable of producing a polarizing plate having improved reliability by including a resin capable of improving high temperature and high humidity reliability and an additive.

In recent years, the development of thin and lightweight notebook computers is under way. Accordingly, a protective film of a polarizing plate used in a display device such as a liquid crystal display device has been increasingly demanded for further thinning and higher performance. Since a liquid crystal display device displays a display by polarization control by a liquid crystal, a polarizing plate is required, and a polarizing plate in which a PVA film containing iodine is stretched is usually used. Since the polarizing plate is fragile, a polarizing plate protective film is used to protect the polarizing plate. In general, triacetylcellulose film is widely used for a polarizing plate protective film. In addition to these polarizing plate protective films, a retardation film is also used to control the retardation of the polarized light. These used a retardation film in a liquid crystal display device or the like may be used in order to solve the problems such as color compensation and wide viewing angle by using the phase difference (R _υθ) in the thickness direction by the use in combination with a polarizing plate, and the phase difference in-plane direction (R _ο) May have a function of converting linearly polarized light into circularly polarized light with respect to the wavelength of the visible light region or conversely converting circularly polarized light into linearly polarized light.

The polarizing plate protective film is intended to protect the polarizing plate and it is most preferable to use a film made of cellulose acetate in order to protect the polarizing plate made of PVA containing moisture, considering the production process of the polarizing plate. On the other hand, as a retardation film, materials other than cellulose acetate have been used to exhibit optical performance. That is, conventionally, as a material of the retardation film, for example, there are polycarbonate, polysulfone, polyethersulfone, amorphous polyolefin and the like. These polymer films have such characteristics that the longer the wavelength is, the smaller the retardation, and it is difficult to impart an ideal retardation property to the entire wavelength of the visible light region.

In the case where linearly polarized light is converted into circularly polarized light with respect to the wavelength of the visible light region or conversely circularly polarized light is converted into linearly polarized light, in order to obtain the above effect with one piece of retardation film, the retardation in the wavelength? 4 < / RTI > Such a retardation film can be obtained by using, for example, a retardation film having a phase difference of? / 4 and only one polarizing plate for a reflective liquid crystal display device having a back electrode as a reflective electrode, thereby obtaining a reflective display device having excellent image quality . Further, with respect to the observer of the guest-host type liquid crystal layer, the retardation film is used on the back side, or the circularly polarized light of the reflection type polarizing plate composed of cholesteric liquid crystal or the like that reflects only one of the left and right circularly polarized light is converted into linearly polarized light It is also used as an element.

Further, the retardation film has a function of converting linearly polarized light into elliptically polarized light or circularly polarized light, or converting linearly polarized light in a certain direction into another direction, and therefore, the viewing angle, contrast, etc. of the liquid crystal display device can be improved .

Generally, a retardation film is attached to a pair of polarizing plates, respectively. At present, N-TAC of Konica Minolta Holdings, Inc. of Japan is generally used as a phase difference film for a VA mode liquid crystal display. The NTAC phase difference film was a cellulose acetate propionylate (CAP) having a retardation in the plane of 50 nm (in terms of retardation (R ₀ , λ = 550 nm) and a retardation in the thickness direction (R _υθ , ) Film.

In order to improve the viewing angle characteristics (black display state (black characteristic), etc.) of the liquid crystal display device, wavelength dispersion and control techniques are required. In general, the N-TAC film exhibits an inverse wavelength dispersion characteristic in which the retardation value increases with increasing wavelength, and exhibits an excellent viewing angle characteristic improvement effect as compared with the retardation film having a regular wavelength dispersion characteristic in which the retardation value decreases with increasing wavelength. Further, in order to improve a liquid crystal display device, a retardation film having a specific retardation value and a combination thereof are used.

Conventional retardation films (PC, PSu, PA, etc.) have such characteristics that the longer the wavelength is, the smaller the retardation. It is difficult to impart an ideal retardation characteristic to the entire wavelength of the visible light region. So that necessary performance is obtained. Order in one piece of the retardation film to obtain the same performance as that, at a wavelength (λ) incident on the retardation film in-plane retardation (R _ο) is preferably a λ / 4 but, for him and the characteristics of the opposite The longer the wavelength, the more the in-plane directional phase difference (R _ο ) becomes larger. In the film made of cellulose acetate, if such a retardation property can be given, the polarizing plate protective film and the retardation film can be used together, the retardation film composed of a plurality of retardation films can be omitted, It is possible to improve the total light transmittance.

With respect to this problem, Japanese Patent Laid-Open No. 2000-137116 proposes to use an oriented film of cellulose acetate having a degree of substitution (acetylation degree) of 2.5 to 2.8 as a retardation film. According to this method, the longer the wavelength, the larger the phase difference, and the ideal phase difference characteristic is obtained with respect to the entire wavelength of the visible light region. That is, the above-mentioned patent discloses a phase difference plate in which the phase difference becomes smaller as the measurement wavelength becomes shorter with one film. A retardation film comprising a polymeric orientation film having a longer birefringence (? N) at a wavelength of 400 to 700 nm, wherein the polymeric orientation film is an orientation film of a polymeric film having an average refractive index at the above- And the like. As a means for solving this problem, a technique of orienting cellulose acetate having an acetylation degree of 2.5 to 2.8 by stretching is disclosed.

In the embodiment of the above-mentioned patent, 100 parts by weight of cellulose triacetate having an intrinsic viscosity [?] = 1.335 and an acetylation degree of 2.917 obtained from Wako Junyaku Kogyo Co., Ltd. was dissolved in 500 parts by weight of methylene chloride, Hydrolysis of cellulose triacetate with acetic acid and water at 70 DEG C for 100 minutes while removing methylene chloride by depressurization and the reaction product was precipitated with a large amount of water and washed and dried , And a cellulose acetate having an acetylation degree of 2.661 was obtained. Then, a film was prepared from a solution prepared by dissolving 100 parts by weight of this polymer and 3 parts by weight of dibutyl phthalate as a plasticizer in 700 parts by weight of a mixed solvent of methylene chloride / methanol (weight ratio 9/1) by solvent casting method, And uniaxially stretched at a temperature of 170 캜 at 1.5 times. That is, in Embodiment 1 of the patent, the retardation film having the same wavelength characteristics (wavelength dispersion characteristics) as the latter is obtained by stretching. It is also disclosed that by adjusting the retardation value, it is possible to use? / 4 or another retardation film. In Example 4 of the aforementioned patent, cellulose acetate having an acetylation degree of 2.421 was obtained. When the retardation property of the film using the film is measured, the retardation is insufficient when the film thickness is about 100 mu m (50 to 150 mu m) and when the film thickness is preferable as the self-supporting film. When the thickness of the film is as large as about 200 mu m, a preferable retardation of about 80 to 150 nm is provided. In this case, the thickness direction retardation ( _Rv [ _theta] ) is excessively larger than 350 nm, It did not function as an enlarged film and was not sufficient. Furthermore, the molecular weight distribution of the obtained cellulose acetate is not described, and the control of the retardation characteristics by controlling the molecular weight distribution is not described or suggested.

On the other hand, although the protective film of the polarizer PVA layer of the polarizing plate was produced by using materials such as TAC and acrylic, the raw materials added to the CAP, COP, and TAC at the time of manufacturing the retardation film are expensive, .

In addition, the cellulose-based polarizing plate made of the conventional retardation film has a low resistance to high temperature and high humidity environment, and the water resistance property of the film is deteriorated when exposed to a high temperature and high humidity reliability environment, thereby deteriorating the reliability quality of the polarizing plate and LCD.

Disclosure of Invention Technical Problem [8] Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a liquid crystal cellulosic ester phase difference film capable of improving reliability quality in the production of a polarizing plate by including an additive capable of improving high- .

In order to achieve the above-mentioned object, the present invention provides a cellulose ester having an acetyl group degree of substitution in a range of 2.70 to 2.95, an asymmetric ester compound having an aromatic group represented by the following formula (1) and a terminal symmetry There is provided a liquid crystal cellulosic ester phase difference film characterized by an aliphatic compound.

[Chemical Formula 1]

_{M A - [D O -D A} ] n- D O
In the formula 1, M _A : R ₁ -COOH, D _{2 O} : HO-R ₂ -OH, D _A : HOOC-R ₁ -COOH,

M _A is an aryl having a carbon number of 6 or more monocarboxylic acid residue, D _O represents an alkylene glycol residue, D _A is an aryl dicarboxylic acid residue as a compound having a carbon number of 2 to 6, n represents an integer of 1 or more.

delete

(2)

I - (T) n - I

In Formula 2, I represents an ester group having 1 to 20 carbon atoms, an alkoxycarbonyl group having 1 to 20 carbon atoms, an amide group having 1 to 20 carbon atoms, a carbamoyl group having 1 to 20 carbon atoms, a hydroxyl group, T is a 2,2,4-trimethyl-1,3-pentanylene group, or a divalent saturated bridging group having 0 to 40 carbon atoms and 0 to 20 carbon atoms, and the number of atoms 0 means that the groups at both ends of the linkage form a single bond directly. n represents an integer of 1 or more.

In this case, it is preferable that the range of the Vickers hardness value represented by the following formula (2) is 20 HV or more for both surfaces of the liquid crystal cellulosic ester phase difference film.

&Quot; (2) "

In the above equation (2), F is a test load, and d is an arithmetic average of two diagonal lengths (d1 and d2).

The liquid crystal cellulosic ester phase difference film has an effective retardation Reff defined by the following formula (1) within ± 30 nm under the conditions of 23 ° C. and 55% RH, and after being left for 60 hours in a reliability environment of 60 ° C. and 90% RH, It is preferable that DELTA Reff is within 30 nm.

[Equation 1]

Reff = (nx'-ny ') xd

In the above formula (1), d is the thickness (nm) of the film, nx 'and ny' are formed from nx, ny and nz when observed at the positions of? = 45 ° and? Is an effective surface refractive index value.

The present invention having such a constitution can improve the reliability quality of the cellulose ester phase difference film of the present invention when the polarizing plate is manufactured by including the resin and the additive which can improve the high temperature and high humidity reliability.

Fig. 1 is a view showing an effective surface direction formed from nx, ny and nz when measuring Reff according to the present invention.
2 is a schematic view showing a process for producing a cellulose ester film according to the present invention.

Hereinafter, the present invention will be described in more detail with reference to the following examples, but the scope of the present invention is not limited thereto.

The liquid crystal cellulose ester phase difference film according to the present invention comprises a cellulose ester having an acetyl group degree of substitution in a range of 2.70 to 2.95, an asymmetric ester compound having an aromatic group represented by the following formula (1) and a terminal symmetrical aliphatic compound And a liquid crystal cellulosic ester phase difference film.

[Chemical Formula 1]

_{M A - [D O -D A} ] n- D O
In the formula 1, M _A : R ₁ -COOH, D _{2 O} : HO-R ₂ -OH, D _A : HOOC-R ₁ -COOH,

M _A is an aryl having a carbon number of 6 or more monocarboxylic acid residue, D _O represents an alkylene glycol residue, D _A is an aryl dicarboxylic acid residue as a compound having a carbon number of 2 to 6, n represents an integer of 1 or more.

delete

(2)

I - (T) n - I

In Formula 2, I represents an ester group having 1 to 20 carbon atoms, an alkoxycarbonyl group having 1 to 20 carbon atoms, an amide group having 1 to 20 carbon atoms, a carbamoyl group having 1 to 20 carbon atoms, a hydroxyl group, T is a 2,2,4-trimethyl-1,3-pentanylene group, or a divalent saturated bridging group having 0 to 40 carbon atoms and 0 to 20 carbon atoms, and the number of atoms 0 means that the groups at both ends of the linkage form a single bond directly. n represents an integer of 1 or more.

At this time, the liquid crystal cellulose ester phase difference film of the present invention is a plasticizer and includes an asymmetric ester compound having an aromatic group represented by the formula (1) and a terminal symmetrical aliphatic compound represented by a formula (2). It is particularly preferable that the optically reliable characteristics of the cellulose ester film before and after the reliability of the cellulose ester film are kept within a predetermined range by including the aromatic-containing asymmetric ester compound and the terminal symmetric aliphatic compound.

Hereinafter, specific compounds of the asymmetric ester compound and the terminal symmetric aliphatic compound including an aromatic compound according to the present invention are shown, but the present invention is not limited thereto.

(One)

(2)

(3)

(4)

On the other hand, the liquid crystal cellulosic ester phase difference film according to the present invention can be produced by a solution casting method. In the solution film forming method, the cellulose ester is dissolved in an additive such as a plasticizer, a UV absorber, a matting agent, etc. and a mixed solvent such as methylene chloride and methanol to prepare a dope, which can be filtered using a filtration apparatus.

In the present invention, the molecular weight range of the cellulose ester is not limited, but the weight average molecular weight is preferably in the range of 150,000 to 220,000.

By reducing the molecular weight to a certain level or more, the strength of the film can be effectively prevented from being lowered.

Further, by keeping the molecular weight at a certain level or less, the viscosity of the cellulose ester solution (dope) is maintained at a certain level or less, thereby facilitating film production by solution casting method.

The degree of molecular weight dispersion (weight average molecular weight Mw / number average molecular weight Mn) of the cellulose ester is preferably in the range of 2.5 to 4.5.

When a film is produced by a solution film forming method (or a solvent casting method), an organic solvent is preferable as the solvent for preparing the cellulose ester composition (dope). 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. Examples of the ester include methyl formate, ethyl formate, propyl formate, pentyl formate, methyl acylate, ethyl acylate, and pentaacetate. Examples of the ketone include acetone, methyl ethyl ketone, diethyl ketone, di Isobutyl ketone, cyclopentanone, cyclohexanone, methylcyclohexanone and the like can be used. As the ether, diisopropyl ether, dimethoxymethane, dimethoxyethane, 1,4-dioxane, Ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, t-butanol, 1-pentanol, 2-butanol and the like can be used. 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 ester composition can be prepared by room temperature, high temperature or low temperature dissolution.

Next, the additives used in the production of the cellulose ester film will be explained. The cellulose ester solution (dope) used in the solution softening method may contain various additives depending on the application in each preparation step such as a plasticizer, a deterioration inhibitor, a matte fine particle, a stripper, a UV stabilizer, an ultraviolet absorber, An additive such as a dispersing agent, an optical anisotropy adjusting agent and the like 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 liquid crystal cellulose ester phase difference film preferably has a Vickers hardness value represented by the following formula (2): 20HV or more for both surfaces.

&Quot; (2) "

In the above equation (2), F is a test load, and d is an arithmetic average of two diagonal lengths (d1 and d2).

Further, when the effective retardation Reff defined by the following formula (1) is within ± 30 nm under the conditions of 23 ° C. and 55% RH, and after being left in a reliability environment of 60 ° C. and 90% RH for 500 hours, the change amount ΔRff of Reff is within ± 30 nm .

[Equation 1]

Reff = (nx'-ny ') xd

In the above formula (1), d is the thickness (nm) of the film, nx 'and ny' are formed from nx, ny and nz when observed at the positions of? = 45 ° C and? Is an effective surface refractive index value.

On the other hand, the cellulose ester film contains a plasticizer for improving mechanical strength, good castability, imparting water absorbency, and reducing water permeability. Examples of the plasticizer include, but are not limited to, carboxylic acid esters selected from phosphoric acid esters, phthalic acid esters and citric acid esters, and the like. In the present invention, the terminal asymmetric aromatic compounds represented by the following Table 1 and It is preferred to use terminally symmetric aliphatic compounds.

The cellulose ester solution thus obtained is cast on a support through a casting die to form a cellulose ester sheet.

The cellulose ester sheet thus formed is subjected to a stretching step in a tenter. In the preheating step, the glass transition temperature (Tg) of the cellulose ester flake is 185 to 200 ° C, the glass transition temperature (Tg) of the retardation film is 150 to 190 Lt; / RTI >

The cellulose ester film of the present invention may be completed in a drying process in a dryer after removing the left and right ends of a film whose surface is damaged by a clip or pin of a tenter after being subjected to a stretching step in a tenter under the above conditions.

Example  One

≪ Step 1 > Cellulose solution ( Lead juice )

Triacetyl cellulose having an average degree of acetyl substitution (DS) of 2.86 was used for the cellulose ester. The plasticizer was used as described in Table 2.

<Step 2> Preparation of Dilute Solution Containing Metal Oxide

20.0 parts by weight of the cellulose solution prepared in <Step 1>, 1.5 parts by weight of silica (SiO2), and 78.5 parts by weight of a mixed solvent obtained by mixing 9: 1 (by weight) of methylene chloride and methanol were added to a mixing tank, ) Was prepared. &Lt; tb &gt; &lt; TABLE &gt;

&Lt; Step 3 > Preparation of cellulose ester film

100 parts by mass of the main doping solution and 5 parts by mass of the fine particle addition liquid were mixed and thoroughly mixed with an inline mixer to prepare a dope. At this time, the composition of the dope was 72 wt% of methylene chloride, 8 wt% of methanol, 17.95 wt% of cellulose ester, 2.5 kg of plasticizer A, 2.5 kg of plasticizer B and 0.05 wt% of silica. Thereafter, the belt was softened uniformly on a stainless steel band support having a width of 2000 mm by using a flexible machine. The solvent was evaporated on the stainless steel band support and peeled off from the stainless band support. Then, both ends of the web were held with a tenter and stretched so that the stretching magnification in the (TD) direction in the temperature environment of 170 ° C was 1.1 times. After the stretching, the stretching was maintained for a few seconds, the tensile force in the width direction was relaxed, the stretching in the width direction was carried out, the stretching was continued for 35 minutes in the drying section set at 110 DEG C, To prepare a cellulose ester film having a knurling width of 10 mm and a height of 8 占 퐉 and a thickness of 20.4 占 퐉.

Example  2

A cellulose ester film was produced in the same manner as in Example 1, except that the film thickness was adjusted to 30.4 占 퐉.

Example  3

A cellulose ester film was produced in the same manner as in Example 1, except that the film thickness was changed to 40.3 탆.

Example  4

A cellulose ester film was produced in the same manner as in Example 1, except that 5 kg of the plasticizer A and 5 kg of B were used and the film thickness was adjusted to 20.4 탆.

Example  5

A cellulose ester film was prepared in the same manner as in Example 1, except that 5 kg of the plasticizer A and 5 kg of B were used and the film thickness was adjusted to 30.4 탆.

Example  6

A cellulose ester film was produced in the same manner as in Example 1 except that 5 kg of the plasticizer A and 5 kg of B were used and the film thickness was made to be 40.3 탆.

Example  7

A cellulose ester film was produced in the same manner as in Example 1 except that 5 kg of the plasticizer A and 5 kg of B were used and the film thickness was 25.3 탆.

Comparative Example  One

Except that 5 kg of plasticizer C and 5 kg of B were used and the film thickness was made to be 40.2 占 퐉, the same procedures as in Example 1 were carried out to prepare a cellulose ester film.

Comparative Example  2

Except that 5 kg of the plasticizer D and 5 kg of B were used and the film thickness was made to be 40.2 탆, a cellulose ester film was prepared.

Comparative Example  3

Except that 5 kg of plasticizer E and 5 kg of B were used and that the film thickness was made to be 40.1 탆, a cellulose ester film was prepared.

Experimental Example

Optical properties of the cellulose ester films prepared in Examples 1 to 7 and Comparative Examples 1 to 3 were measured by the following methods, and the results are shown in Table 2 below.

A cellulose ester film was prepared in the same manner as described above, except that the plasticizer was changed to the dope (cellulose ester, plasticizer) as shown in Table 1, and the kind of plasticizer was changed.

 The cellulose ester film thus obtained was irradiated with light having a wavelength of 590 nm as a reference wavelength under the conditions of 23 ° C. and 55% RH using an optical instrument of AxoScan (OPMF-1, Axometrics), and at a position of θ = 45 ° and Φ = 45 ° And the effective planar phase difference value Reff was measured. The cellulose ester film prepared above was subjected to a reliability treatment for 500 hours at 60 ° C and 90% RH using a high temperature and high humidity chamber, and the Reff after the reliability treatment was measured using the same measuring equipment.

In addition, Vickers hardness was measured on both air and belt surfaces using a Micro Vickers Hardness Tester (Mitutoyo HM-122) Vickers hardness tester.

In order to confirm the surface coating property and the orientation property, 2.5 wt% of a photo-orientable polymer of poly [4- (1-phenylperfluoroheptyloxy) -cinnamate-5-norbornene] was used and a polyhydric acrylate- (PETA) was used so that the weight ratio of the photo-orientable polymer to the binder compound was 2: 1, and with the photo-orientable polymer and the binder compound, a photoinitiator (Ciba-irgacure 907) 0.1% by weight was dissolved in toluene solvent, and the solution was coated on the surface of the cellulose ester film Belt by a thickness of about 100 nm to be bar coated. Then, after drying at 80 DEG C for 2 minutes, the polarized UV of the UV-B region was irradiated at 1 J / cm &lt; 2 &gt; Subsequently, the liquid crystal for the A-plate was coated, dried at 60 ° C for 2 minutes, and irradiated with ultraviolet light of 50 mJ to cure the liquid crystal. Then, a film was inserted between the polarizing plates to confirm the degree of alignment. The degree of orientation is shown by the following standard, and the results of the orientation evaluation are summarized in Table 2 below.

◎. The degree of orientation is very good;

○. Excellent orientation;

△. Although orientation is observed, it is insufficient to be actually used;

X. Almost no orientation was observed;

Plasticizer Type Compound structure A
(Terminal asymmetric aromatic Plasticizer 1 )

B
(Terminal symmetrical aliphatic Plasticizer 1 )

C
(Terminal symmetry Plasticizer 1 )

D
(Terminal symmetry Plasticizer 2 )

E
(Terminal symmetry Plasticizer 3 )

cellulose
ester Plasticizer Type Film thickness
(um) Vickers hardness (HV) Reliability Before / After Reff (nm) Orientation Kinds 2* Kinds 2* Air plane Belt name Before processing After processing Variation Example 1 TAC 100 A + B 2.5 + 2.5 20.3 22.3 22.9 14.2 11.7 -2.5 ◎ Example 2 TAC 100 A + B 2.5 + 2.5 30.4 21.4 21.8 21.5 16.4 -5.1 ◎ Example 3 TAC 100 A + B 2.5 + 2.5 40.3 22.1 21.0 22.4 23.8 1.4 ○ Example 4 TAC 100 A + B 5 + 5 20.4 22.3 22.7 11.9 8.5 -3.4 ◎ Example 5 TAC 100 A + B 5 + 5 30.5 21.7 22.1 19.4 16.4 -3.0 ◎ Example 6 TAC 100 A + B 5 + 5 40.3 21.5 22.1 25.2 20.9 -4.3 ◎ Example 7 TAC 100 A + B 5 + 5 25.3 21.1 21.2 13.8 12.7 -1.1 ○ Comparative Example 1 TAC 100 C + B 5 + 5 40.2 19.1 18.9 39.9 26.1 -13.8 △ Comparative Example 2 TAC 100 D + B 5 + 5 40.2 18.8 18.5 29.6 14.3 -15.3 △ Comparative Example 3 TAC 100 E + B 5 + 5 40.1 19.0 19.2 24.3 11.7 -12.6 X

As shown in Table 2, when the plasticizer proposed in the present invention was included, the cellulose ester film had excellent ΔReff characteristics before and after the reliability treatment, so that the optical reliability and the Vickers hardness of the film surface were excellent, Is excellent.

While the present invention has been particularly shown and described with reference to specific embodiments thereof, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the appended claims. It will be easy for anyone to know.

Claims (3)

1. A liquid crystal cellulose ester phase difference film characterized by an asymmetric ester compound containing an aromatic group represented by the following formula (1) and a terminal symmetrical aliphatic compound represented by the following formula (2), wherein the cellulose ester has an acetyl group degree of substitution in the range of 2.70 to 2.95, The liquid crystal cellulose ester phase difference film has an effective retardation value Reff of 11.9 to 25.2 nm, which is defined by the following formula (1) measured under conditions of 23 캜 and 55% RH, and has a film thickness of 20.3 to 40.3 탆, Deg.] C and 90% RH for 500 hours, and the Reff variation amount [Delta] Reff before and after being left standing is -5.1 to 1.4 nm.
[Chemical Formula 1]
_{M A - [D O - D} A] n- D O
In the formula 1, M _A : R ₁ -COOH, D _{2 O} : HO-R ₂ -OH, D _A : HOOC-R ₁ -COOH,
M _A is an aryl having a carbon number of 6 or more monocarboxylic acid residue, D _O represents an alkylene glycol residue, D _A is an aryl dicarboxylic acid residue as a compound having a carbon number of 2 to 6, n represents an integer of 1 or more.
(2)
I - (T) n - I
In Formula 2, I represents an ester group having 1 to 20 carbon atoms, an alkoxycarbonyl group having 1 to 20 carbon atoms, an amide group having 1 to 20 carbon atoms, a carbamoyl group having 1 to 20 carbon atoms, a hydroxyl group, T is a 2,2,4-trimethyl-1,3-pentanylene group, or a divalent saturated bridging group having 0 to 40 carbon atoms and 0 to 20 carbon atoms, and the number of atoms 0 means that the groups at both ends of the linkage form a single bond directly. n represents an integer of 1 or more.
[Equation 1]
Reff = (nx'-ny ') xd
In the above formula (1), d is the thickness (nm) of the film, nx 'and ny' are formed from nx, ny and nz when observed at the positions of? = 45 ° and? Is an effective surface refractive index value. The method according to claim 1,
Wherein the liquid crystal cellulosic ester phase difference film has a Vickers hardness value range expressed by the following formula (2): 21.1 to 22.9 HV for both surfaces.
&Quot; (2) &quot;

In the above equation (2), F is a test load, and d is an arithmetic average of two diagonal lengths (d1 and d2). delete

Images