TWI508977B - Va lcd viewing angle compensating optical film using cellulose ester film having acetyl group and butyryl group - Google Patents

Description

Viewing compensation of a vertical alignment type liquid crystal display using a cellulose ester film having an ethyl fluorenyl group and a butyl fluorenyl group Optical film

The present invention relates to a cellulose ester film, in particular to a cellulose ester film having an ethyl ketone group and a butyl sulfonium group, which is a low-substituted one of the functional components of a conventional film. It can be compensated for its viewing angle when applied to a vertical alignment type liquid crystal display.

With the rapid development of the information technology industry, the demand for information equipment, especially for a thinner and lighter display, is increasing. Therefore, attention has been paid to film-based products such as polarizer protective films for liquid crystal displays.

Recently, liquid crystal displays are becoming thinner, lighter, larger in size and higher in fineness. Due to the aforementioned needs, a larger size, thinner and higher quality optical film is used to improve the viewing angle or contrast of liquid crystal displays. Demand has also increased rapidly. In order to properly improve a viewing angle or contrast of a liquid crystal display, for an optical film, the uniformity of the optical path delay in a high-definition control plane to the thickness direction or azimuth and the uniformity of the film thickness are necessary. One method of controlling the optical path delay or the azimuth of the film or the thickness of the film with high definition is generally to achieve sequential biaxial orientation using sequential vertical and horizontal directions.

Usually a cellulose ester film is used as a polarizer protective film. However, such a cellulose ester film usually forms a film type, and thus the film has a dimensional stability problem, and the film expands due to poor water vapor permeability, especially at high temperature and high humidity. The durability in the environment is degraded, and thus has a significant influence on the functional degradation of the liquid crystal display. In addition, another problem is the decrease in the strength and surface hardness of the film due to thinning.

Therefore, Japanese Patent Laid-Open Publication No. 2002-22956 intends to add a polyester or a polyester ether to improve the dimensional stability of the film, but the stability of storage thereof is lowered, in Japanese Patent Laid-Open Publication No. 2007-84692. A cellulose ester film of a plasticizer having a benzene carboxylic acid or a phenol residue at both ends and comprising an ester having an aliphatic cyclic ethylene glycol and an aliphatic cyclic dibasic acid, but exhibiting dimensional stability And can not get satisfactory performance.

In addition, according to a similar technique disclosed in Korean Unexamined Patent Application Publication No. 2006-0042257, a cellulose ester film having a thiol substitution degree of 1 to 3 and an acetylation degree of less than 2.2 is not examined in Korea. Patent Application Publication No. 2007-0022782 discloses that a hydroxyl group in a cellulose is substituted with a mercapto group, the degree of substitution is more than 1.5 and less than 2.3, but the retardation in the plane direction and the thickness direction are delayed in the sodium hydroxide and potassium hydroxide solutions. The performance is not disclosed. In WO Unexamined Patent Application Publication No. 2008-120595, a phosphorus-based compound having a phosphonite structure is included, but there is no description of the degree of substitution of a butyl group with a hydroxyl group, and WO 2006 No. -073064, a part or all of the hydroxyl group in the cellulose ester is substituted with an ethyl hydrazide group and a butyl group.

However, also in the related art, a butyrene group is used in place of the cellulose film, but because of the high degree of substitution, the taste of butyrate remains after the film is produced.

The present invention is directed to a viewing angle compensating optical film of a vertical alignment type liquid crystal display using a cellulose ester film, which is substituted with a butyl group or a propyl group to replace a component in a conventional film by a butyl group or a propyl group. One of the functional groups can improve the characteristics of an optical path delay.

The invention also provides a viewing angle compensating optical film of a vertical alignment type liquid crystal display using a cellulose ester film having an ethyl fluorenyl group and a butyl fluorenyl group, which is one of the conventional films which is low-substituted by a butyl group or a propylene group. One of the components is functional, but the manufacturing method can be simplified because the optical path delay is not used without using an additive, and the practical application to the display can compensate for an excellent viewing angle.

In the same manner as the present invention, there is provided a cellulose ester film having a degree of substitution of a hydroxyl group of one of the optical films substituted with one thiol group of an optical film of more than 1.87 and less than 2.92.

According to an exemplary embodiment of the present invention, the cellulose ester satisfies the following equations (1) to (4): 1.83<Xa+Ya<2.43---------- Equation (1)

0.57<Xa<0.77---------------- Equation (2)

0.04<Xb+Yb<0.49---------- Equation (3)

0.01<Xb<0.16----------------- Equation (4)

(here, Xa is the degree of substitution of an ethyl fluorenyl group at the 6th carbon position of a glucose unit constituting one cellulose, and Ya is the degree of substitution of the ethane group at the 2nd and 3rd carbon positions, Xb is the degree of substitution of a butyl group or a propyl group at the 6th carbon position, and Yb is a butyl group or a propylene group. The degree of substitution at the 2nd and 3rd carbon positions. )

Further, the cellulose ester film has a plane retardation (Ro) of between 10 nm and 150 nm when faced, and has a retardation (Rth) in a thickness direction between 30 nm and 300 nm.

According to an exemplary embodiment of the present invention, the film is a retardation compensation film for a vertical alignment type liquid crystal, and when the elongated axis of the film is vertically aligned, in addition to the front view, the film can be observed to have a satisfyability at one viewing angle. The amount of delay variation of the following equations (5) and (6): -45 nm < Ro < 9 nm & 35 nm < Rth < 180 nm, where θ = 45', Φ = 90 ' & 270 '----- Equation (5)

30nm<Ro<160nm & 35nm<Rth<280nm, where θ=45', Φ=0' & 180'------(6)

(where θ and Φ represent the angles of latitude and longitude, respectively.)

As described above, according to the present invention, a vertical alignment type liquid crystal display viewing angle compensating optical film using a cellulose ester film having an ethyl fluorenyl group and a butyl fluorenyl group, which is constituted by a butyl group or a propyl group Low substitution of one of the components of a conventional film can improve the characteristics of an optical path delay, because the use of additives to achieve optical path delay, and practical application on the display has excellent viewing angle compensation performance.

10‧‧‧cellulose membrane

12‧‧‧Surface A

14‧‧‧ basal layer

16‧‧‧Surface layer B

Figure 1 is the result of compensation and improvement of the viewing angles evaluated according to the examples.

Figure 2 is the result of compensation and improvement of the viewing angles evaluated according to the comparative example.

Figure 3 is a conceptual diagram of a cellulose ester film according to the present invention.

Hereby, the exemplary case according to the present invention will be described in detail with reference to the legend of the annex. In addition, the present invention is not limited to the scope of the examples, and the examples are only one of the examples of the present invention, and thus, other methods modified from the technical concept are not deviated from the scope of the present invention.

A vertical alignment type liquid crystal display viewing angle compensating optical film using a cellulose ester film having an ethyl fluorenyl group and a butyl fluorene group, wherein all thiol groups of the optical film replace one of the monohydroxy groups of one cellulose The ratio of substitution ratios greater than 1.87 and less than 2.92 and satisfying the following equations (1) to (4): 1.83<Xa+Ya<2.43---------- Equation (1)

0.57<Xa<0.77---------------- Equation (2)

0.04<Xb+Yb<0.49---------- Equation (3)

0.01<Xb<0.16----------------- Equation (4)

(here, Xa is the degree of substitution of an ethyl fluorenyl group at the 6th carbon position of a glucose unit constituting one cellulose, and Ya is the degree of substitution of the ethane group at the 2nd and 3rd carbon positions, Xb is the degree of substitution of a butyl group or a propyl group at the 6th carbon position, and the degree of substitution of Yb is a butyl group or a propyl group at the 2nd and 3rd carbon positions.)

The cellulose ester used in the cellulose ester film according to the present invention is obtained by using at least one of cellulose pulp, wood pulp, and kenaf pulp, which is derived from anhydrous acetic acid, propionic anhydride or butyric acid and fiber. It is obtained by a conventional method, and preferably at least one of them is derived from cellulose triacetate, cellulose acetate propionate, cellulose acetate butyrate and cellulose acetate propionate butyrate. The vitamin has a degree of substitution of one of the hydroxyl groups of all the mercapto-substituted celluloses greater than 2.0 and less than 2.9.

When the degree of substitution of all thiol groups is less than 2.0, the water vapor transmission rate may decrease, and the contact angle may be difficult to reduce in alkali saponification, and the adhesion to the polarizing plate may also be lowered. Conversely, when the degree of substitution of all thiol groups exceeds 2.9, it is difficult to control the amount of retardation. The aforementioned cellulose ester has a number average molecular weight of between 70,000 and 200,000, and preferably ranges from 80,000 to 150,000, and has a weight average molecular weight of between 150,000 and 500,000, and is preferred. The range is between 200,000 and 350,000, so it is an advantage from the point of view of the strength of the mechanism. In general, cellulose esters are likely to form a sheet-like morphology via the reaction and washing processes, and have an advantage of having a diameter of between 0.05 mm and 2.0 mm and having solubility.

The fatty acid cellulose ester film having an ethyl fluorenyl group and a butyl sulfonium group according to the present invention can be produced by a solvent casting method comprising dissolving a cellulose ester, a retardation inhibitor and other additives in a solvent, and a solution Cast on a carrier and evaporate the solvent.

The solvent may be at least one of the following: methyl acetate, ethyl acetate, amyl acetate, ethyl formate, acetone, cyclohexanone, methyl ethyl acetate, tetrahydrofuran, 1,3-dioxolane, 4 -methyl-1,3-dioxolane, 1,4-two Alkenyl (1,4-dioxane), 2,2,2-trifluoroethanol, 2,2,3,3-hexafluoro-1-propanol, 1,3-difluoro-2-propanol, 1,1, 1,3,3,3-hexafluoro-2methyl-2-propanol, 1,1,1,3,3,3-hexafluoro-2-propanol, 2,2,3,3,3 - pentafluoro-1-propanol, nitric oxide, tetrahydropyrrolidone-[2] (2-pyrrolidone), N-methyl-2-pyrrolidone, 1,3-dimethyl- 2-imidazolidinone, dichloromethane and bromopropane, of which methyl acetate, acetone or dichloromethane is preferred. Further, a solvent in which a lower carbon number alcohol such as methanol, ethanol and butanol are mixed is preferred because the solubility of the cellulose ester in these solvents can be increased or the viscosity of the solution can be lowered.

In particular, according to one aspect of the invention, a one having an ethyl fluorenyl group and a butyl group is used. Vertical alignment type liquid crystal display of cellulose ester film The viewing angle compensation optical film is a cellulose ester film having an ethyl fluorenyl group and a butyl fluorene group, which has a plane retardation between 10 nm and 150 nm when viewed squarely (Ro And having a retardation (Rth) in a thickness direction between 30 nm and 300 nm. The optical film is a retardation compensation film of a vertically aligned liquid crystal, so that when the film's elongation axis is vertically aligned, it is in addition to front view. It can be observed from one viewing angle that the cellulose ester film has a retardation variation satisfying the following equations (5) and (6): -45 nm < Ro < 9 nm & 35 nm < Rth < 180 nm, wherein θ = 45', Φ = 90' & 270'-----Eq. (5)

30nm<Ro<160nm & 35nm<Rth<280nm, where θ=45', Φ=0' & 180'------(6)

(where θ and Φ represent the angles of latitude and longitude, respectively.)

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

Example

In the production of the cellulose film, the first casting raw liquid 4 comprises 17.3% by weight of cellulose acetate butyrate (CAB) as a component of cellulose, 72.5% by weight of dichloromethane, and 8.05% by weight. Methanol, 1.9% by weight of a base plasticizer of an aliphatic polyester as a plasticizer, and a base composition of 0.25% by weight of monobenzotriazole as an ultraviolet light absorber, and a second casting native Liquids 2 and 6 include 17.5% by weight of cellulose acetate butyrate, 72.3% by weight of methylene chloride, 8.05% by weight of methanol, and 1.9% by weight of a base polyester plasticizer of plastic polyester as plasticizer. And 0.002% by weight of cerium oxide particles having a diameter of from 0.1 μm to 1 μm.

A cellulose film 10 is composed of a surface layer A 12, a base layer 14 and another surface layer B 16 which are co-extruded by the first and second casting stock solutions 2, 4 and 6 as shown in Fig. 3. A model on the surface of a sheet metal strip having a thickness of 150 μm and a width of 800 mm was prepared.

As shown in FIG. 3, the cellulose film 10 consisting of a surface layer A 12, a base layer 14 and a surface layer B 16 is evaporating and casting the solvent in the raw liquid by rotating the metal strip and extending The cellulose film was expanded and dried to have a total thickness of 40 μm, and each layer thickness did not exceed 33.3% of the overall thickness.

Test of physical properties:

(1) Pencil hardness test - load 500g, speed 60mm/min, pencil angle 45 degrees, hardness: use 2H pencil.

Evaluation Method - Draw 5 lines to find the number of lines that are not slightly scratched under the fluorescent light. (If the number of lines without scratches exceeds 3/5, it means OK)

(2) Water vapor transmission rate

- Measurement method: Refer to Korean Industrial Standard KSA1013 (a method for testing the water vapor transmission rate of waterproof packaging materials)

(3) Dimensional stability - heat resistance: measurement of the dimensional change of the film after a continuous temperature of 80 ° C for 24 hours

- Humidity resistance: Dimensional change of the film after 24 hours of continuous humidity of 90% RH and 60 °C

The cellulose ester film 10 manufactured through the aforementioned method was tested, the surface hardness of the cellulose ester film 10 was improved and exceeded the standard of 1H, and the water vapor transmission rate was lowered to 800 g/m ^{2 for} 24 hours or even lower. Dimensional stability, as small as 0.1% strain or less. Therefore, it exhibits excellent physical properties with such low strain.

That is, the cellulose ester film according to the present invention is a retardation film which is composed of 85% to 95% of a cellulose ester, and an aromatic or aliphatic polymer having a total weight of 5% to 15% with respect to the total weight of the optical film. It consists of an additive containing 8 to 15 benzene rings, and the substitution range satisfies the following equations (1) to (4): 1.83<Xa+Ya<2.43---------- equation (1) )

0.57<Xa<0.77---------------- Equation (2)

0.04<Xb+Yb<0.49---------- Equation (3)

0.01<Xb<0.16----------------- Equation (4)

(here, Xa is the degree of substitution of an ethyl fluorenyl group at the 6th carbon position of a glucose unit constituting one cellulose, and Ya is the degree of substitution of the ethane group at the 2nd and 3rd carbon positions, Xb is the degree of substitution of a butyl group or a propyl group at the 6th carbon position, and the degree of substitution of Yb is a butyl group or a propyl group at the 2nd and 3rd carbon positions.)

Therefore, the amount of delay is measured in individual directions as follows: the amount of delay is θ = 45', Φ = 90' &270'; Ro = -15nm & Rth = 75nm

The delay amount is θ=45', Φ=0' &180'; Ro=60nm & Rth=120nm

(where θ and Φ represent the angles of latitude and longitude, respectively.)

The foregoing retardation film is measured by first applying a polarizing plate to a polyvinyl alcohol in a press-bonding process, and then attaching the retardation film to a vertical alignment type liquid crystal display. A comparison contour map is obtained by measuring the measurement equipment of EZ Contrast, and the result of the compensation obtained by the measurement and the improvement of the viewing angle are shown in Fig. 1.

Comparative example

For comparison, a retardation film was fabricated and measured as follows: the amount of retardation was θ = 45', Φ = 90' &270'; Ro = -15 nm & Rth = 75 nm

The delay amount is θ=45', Φ=0' &180'; Ro=60nm & Rth=120nm

According to the same method as described in the examples, the retardation film was first formed into a polarizing plate by a process of pressing on polyvinyl alcohol, and then the retardation film was attached to a vertical alignment type liquid crystal display. The comparative contour map is obtained by measuring the measurement equipment of EZ Contrast, and the measurement results are shown in Fig. 2.

Comparing the product characteristics of the foregoing examples and comparative examples, it can be found that the contrast between the center and the edge has a significant increase in the area of 1000:1 or more (e.g., sky blue, to yellow area), representing a wide viewing angle.

Although the present invention has been shown and described in terms of its exemplifying embodiments, it should be understood that the details of the technical modifications and those in the process and the details of the scope of the present invention should be regarded as additional patents. The scope of application.

10‧‧‧cellulose membrane

12‧‧‧Surface A

14‧‧‧ basal layer

16‧‧‧Surface layer B

Claims (1)

A vertical alignment type liquid crystal display viewing angle compensating optical film using a cellulose ester film having an ethyl fluorenyl group and a butyl fluorenyl group, wherein all thiol groups of the optical film are substituted for one degree of substitution of one hydroxyl group of cellulose of one of the optical films, The degree of substitution is greater than 1.87 and less than 2.92, wherein the cellulose ester satisfies the following equations (1) to (4), wherein the cellulose ester has a plane retardation (Ro) between 10 nm and 150 nm, and Having a retardation (Rth) in a thickness direction between 30 nm and 300 nm, wherein the cellulose ester film is one of retardation compensation films for a vertical alignment type liquid crystal, and when the elongation axes of the retardation compensation film are vertically aligned In addition to the front view, it can be observed from one viewing angle that the cellulose ester film has a retardation variation satisfying the following equations (5) and (6): 1.83<Xa+Ya<2.43---------- Equation (1) 0.57<Xa<0.77---------------- Equation (2) 0.04<Xb+Yb<0.49---------- Equation (3) 0.01<Xb<0.16----------------- Equation (4) wherein Xa is an ethylidene group at the 6th carbon position of a glucose unit constituting one cellulose Degree of substitution, Ya is 醯The degree of substitution at the 2nd and 3rd carbon positions, Xb is the degree of substitution of a butyl group or a propyl group at the 6th carbon position, Yb is a butyl group or a propyl group at the 2nd and 3rd Degree of substitution of carbon positions; -45nm<Ro<9nm & <35nm<Rth<180nm, where θ=45', Φ=90' &<270'----- equation (5) 30nm<Ro<160nm &<35 nm<Rth<280 nm, where θ=45', Φ=0' &<180'----- Equation (6) where θ and Φ represent the angles of latitude and longitude, respectively.