KR20100073751A - An o-plate and a fabrication method thereof - Google Patents

Abstract

PURPOSE: An O PLATE and a manufacturing method thereof are provided to realize an excellent contrast ratio by adjusting surface direction, retardation, thickness direction retardation, and orientation angle. CONSTITUTION: A base layer(110) has a surface direction retardation of 130-170nm, a thickness direction retardation of 140-180nm, and an orientation angle of 20-40 degree. An orientation layer(120) is located on the base layer. A liquid crystal layer(130) is located on the orientated layer and has a splay orientation property.

Description

O-Plate and its manufacturing method {AN O-PLATE AND A FABRICATION METHOD THEREOF}

The present invention relates to an O-plate and a method for manufacturing the same, and more particularly, by adjusting the surface retardation (R ₀ ), thickness direction retardation (R _th ) and the orientation angle, excellent contrast ratio (contrast ratio: It relates to an O-plate that implements CR) and a method of manufacturing the same.

Flat panel displays (FPDs) have continued to grow since the 1970s, based on state-of-the-art semiconductor technology, and now form a global market and are steadily expanding in size. Among the FPDs, liquid crystal devices (LCDs) using liquid crystals, especially anisotropic materials, are excellent in their characteristics, and are currently receiving the most attention in the FPD market despite the late start compared to other FPDs. The industry base is also quite thick. LCDs are thin and light, and feature low power consumption and low operating voltage. Because of this, it has grown to be the most widely used among the existing FPDs, and its applications range from public welfare to industrial. LCD can be driven for a long time with low power consumption and operates at low voltage, so it is possible to drive IC directly, and it is possible to miniaturize and simplify driving electronic circuit. In addition, the LCD has a thin device, and can be displayed from a large display to a small display. Since the display is easy to colorize, the display function can be expanded and diversified. However, LCDs are often limited in view because display contrast depends on the viewing direction.

On the other hand, it is relatively recent that LCD has been adopted to electronic devices in earnest, and it is only 30 years. In the meantime, LCD technology has evolved from TN-LCD to STN-LCD, MIM-LCD, and TFT-LCD, and the display performance of LCD has been remarkably improved, and it is a new field that is difficult for CRT due to its thinness, light weight, and low power consumption. Has created demand in However, due to the narrow viewing angle problem of the TN mode, it is difficult to use the LCD of a large screen of more than 30˚. Therefore, various liquid crystal modes having wide viewing angle characteristics have recently been developed and commercialized. In particular, LG Philips LCD and Hitachi in In-Plane Switching (IPS) mode, Fujitsu in Multi-domain Vertical Alignment (MVA), and Samsung in Patterned Vertical Alignment (MV). PVA) mode is in production. Nevertheless, due to high process margins and low production costs, TN mode is mostly applied to small and medium-sized displays and large monitors. In order to improve the viewing angle, which is a disadvantage of the TN mode, FUJIFILM's WV (wide view) film is mostly applied. In the conventional TN mode, the viewing angle characteristic is significantly lower than that of IPS or FFS. Therefore, the WV-TN mode, which improves the viewing angle using a compensation film, has been studied, and further improved the viewing angle characteristic by adjusting the characteristics of the compensation film. In particular, the recently developed WV-EA TN has a left and right 80 °, 80 °, 80 °, 75 ° area with a contrast angle of 10: 1 or more, and the existing TN mode is 40 °, 40 °, 15 ° , A significant improvement over the viewing angle of 30 °. In addition, WV film was used to increase the thickness of polarizing plate using two TAC films and adhesives, and reliability problems caused by adhesives occurred. Recently, one TAC film was used to remove adhesives and the thickness direction retardation of TAC films was used. By adjusting, the viewing angle compensation is better and thinner. Nevertheless, the TN mode with WV film still has a lot of weaknesses in the upper and lower viewing angles.

To replace such a WV film, O-plate and biaxial film were used in Patent 10-0757637. The registered patent is characterized in that the biaxial film is located on the panel cell surface, unlike the existing substrate layer on the PVA surface. However, while the registered patent can obtain a contrast ratio characteristic superior to that of the WV film, in order to attach an O-plate having poor adhesion with PVA to PVA, an adhesion process is additionally required.

SUMMARY OF THE INVENTION An object of the present invention is to provide an O-plate and a method of manufacturing the same, which can realize an excellent contrast ratio, improve screen quality, and reduce cost. In addition, another object of the present invention is to provide an O-plate capable of localizing a retardation film for TN-LCD, which relies on current 100% import, and a manufacturing method thereof.

In order to achieve the above object, the present invention provides a substrate having a surface direction retardation (R ₀ ) of 130 to 170nm, a thickness direction retardation (R _th ) of 140 to 180nm, the orientation angle of 20 to 40 degrees layer; An alignment layer positioned on the base layer; And a liquid crystal layer disposed on the alignment layer and provided with spreading orientation.

In the present invention, the base layer is triacetyl cellulose, polyethylene terephthalate, polymethyl methacrylate, polycarbonate, polyethylene, cycloolefin polymer, polyvinyl alcohol, diacetyl cellulose, polyether sulfone film and glass substrate in the group One selected; And one type selected from the group consisting of rod-shaped additives, plate-shaped additives, and mixtures thereof.

The present invention also provides an O-plate, wherein the alignment layer is an O-plate, characterized in that it comprises a discotic compound.

In addition, the present invention provides an O-plate, wherein the liquid crystal layer comprises a rod-like liquid crystal compound having a hybrid orientation.

In addition, the present invention provides a substrate layer having a) surface direction retardation (R ₀ ) is 130 to 170 nm, thickness direction retardation (R _th ) is 140 to 180 nm, and orientation angle is 20 to 40 °. step; b) forming an alignment layer on the substrate layer; And c) forming a liquid crystal layer imparted with spreading orientation on the alignment layer.

In addition, the present invention is the step b) spin-coated the discotic compound on the substrate layer, and heat-treated at 60 to 100 ℃ for 2 to 4 minutes, using a UV light of 18 to 22mJ intensity based on 365nm Painting; And forming the alignment layer by performing orientation treatment on the photocured discotic compound.

In addition, the present invention is the step c) spin-coated the rod-like liquid crystal compound of hybrid orientation on the alignment layer, and heat-treated for 2 to 4 minutes at 60 to 100 ℃, 18 to 22mJ intensity based on 365nm It provides a method for producing an O-plate characterized in that the step of curing using ultraviolet light to form a liquid crystal layer.

In addition, the present invention provides a polarizing plate including the O-plate.

In addition, the present invention provides a liquid crystal display device comprising an O-plate.

O-plate of the present invention implements an excellent contrast ratio, the screen quality is improved, it is possible to reduce the cost. In addition, the O-plate of the present invention has the advantage that the localization of any configuration is possible.

Hereinafter, the present invention will be described in detail.

1 is a cross-sectional view showing an O-plate according to an embodiment of the present invention.

Referring to FIG. 1, an O-plate 10 according to an embodiment of the present invention may be formed on a base layer 110, an alignment layer 120 positioned on the base layer 110, and an alignment layer 120. It includes a liquid crystal layer 130 located.

The substrate layer 110 has a surface direction retardation (R ₀ ) of 130 to 170 nm, a thickness direction retardation (R _th ) of 140 to 180 nm, and an orientation angle of 20 to 40 °. If the base layer satisfies the above-described range, it is possible to secure an excellent side contrast ratio (overall viewing angle of 60: 1 or more) without further processing.

The base layer 110 is a cyclo olefin polymer such as triacetyl cellulose, polyethylene terephthalate, polymethyl methacrylate, polycarbonate, polyethylene, norbornene derivative, polyvinyl alcohol, diacetyl cellulose, polyether sulfone film and glass One selected from the group consisting of substrates; And a rod type additive having a phase difference control function, a plate type additive, and a mixture thereof. The rod additive controls the surface retardation, and the plate-shaped additive controls the thickness retardation.

The base layer 110 preferably has a thickness of 40 μm to 80 μm. Generally, the retardation film used is gradually decreasing to reflect the thickness reduction trend of panel makers, but there is a limit in the value because it is difficult to control the retardation value when the thickness decreases. In the case of VA mode, the thinnest 45 micrometers of all retardation films, and the thickness of about 60 micrometers in IPS mode are used.

The alignment layer 120 positioned on the substrate layer 110 is not particularly limited as long as it is a material used for an O-plate, but it is preferable to use a discotic compound. Examples of the discotic compound include polyimide and the like. The alignment layer 120 may also be formed of a liquid crystal composition containing a discotic compound. In this case, the discotic compound may be an oblique alignment layer, in which the discotic compound is obliquely oriented. By including such an inclined alignment layer, an O-plate having excellent screen contrast can be obtained. Here, the "inclined orientation" may be a state in which the liquid crystal molecules are inclined at a constant angle and arranged in the same orientation (so-called inclined uniaxial orientation), and the inclination angle (tilt angle) of the liquid crystal molecules in the thickness direction is continuous. Alternatively, it may be in an intermittently increasing or decreasing state (so-called hybrid orientation).

As the discotic compound, any appropriate one can be employed as long as it is a molecule having a disc-shaped core and exhibits a disc-like and / or discotic nematic phase. The discotic compound typically refers to a molecule in which 2 to 8 side chains are radially bonded to an annular center core by an ether bond or an ester bond. Examples of the central core include, for example, benzene, triphenylene, toluxene, pyran, and the like described in Baifukan Co., Ltd., "Liquid Crystal Dictionary" (1989) p. Lufigarol (Le Figarole), porphyrins, metal complexes and the like. The discotic compound is preferably a triphenylene compound having triphenylene as the central core.

Meanwhile, the alignment layer 120 includes forming an alignment layer composition and forming an alignment layer by performing alignment treatment on the alignment layer composition. Here, when the alignment layer composition is polyimide or polyvinyl alcohol, the forming of the alignment layer 120 on the base layer 110 may include spin coating polyimide or polyvinyl alcohol on the base layer. Heat curing at 110 to 130 ° C. for 4 to 6 minutes; And aligning the thermoset polyimide or polyvinyl alcohol to form an alignment layer.

In addition, when the alignment layer composition is a discotic compound, the discotic liquid crystal compound is spin-coated on the base layer 110, heat-treated at 60 to 100 ° C. for 2 to 4 minutes, and then, based on 365 nm. It is preferably a step of curing using ultraviolet rays of 18 to 22mJ intensity. In addition, the step of forming the alignment layer by the alignment treatment is preferably a step of rubbing the alignment treatment.

It is preferable that the thickness of the alignment layer 120 is 50 nm to 150 nm. If the thickness is out of the above-described range, pinholes are frequently generated during coating of the alignment layer if the thickness is too low. Dielectric properties reduce the strength of the vertical electric field, increasing the driving voltage.

The liquid crystal layer 130 positioned on the alignment layer 120 is provided with spreading orientation and is aligned in the same direction as the alignment layer 120. The material forming the liquid crystal layer 130 is a rod-shaped liquid crystal compound having a hybrid orientation. The rod-shaped liquid crystal compound of the hybrid orientation may be used as one or more selected from those having an acrylate group attached as a reactor. The reactor is preferably 4- (3-acrylooxyoxypropyloxy) -benzoic acid 2-methyl-1,4-phenylene ester (4- (3-Acryloyoxypropyloxy) -benzoic acid 2-methyl-1,4-phenylene ester)), 4- (6-acrylooxyoxyhexyloxy) -benzoic acid (4-cyanophenyl ester) (4- (6-Acryloyoxyhexyloxy) -benzoic acid (4-cyanophenyl ester)) and 4- (6 -Acrylooxyoxyhexyloxy) -benzoic acid [4-trans-4-propylcyclohexyl] phenyl ester] (4- (6-Acryloyoxyhexyloxy) -benzoic acid [4-trans-4-propylcyclohexyl] phenyl ester) The hybrid rod-like liquid crystal compound may be prepared by adding all of the reactors. In more detail, the rod-shaped liquid crystal compound of the hybrid orientation may be prepared by dissolving the acrylate-attached as a reactor in a solvent and then applying it on an alignment layer, followed by drying and curing.

The forming of the liquid crystal layer 130 on the alignment layer 120 may include spin-coating a rod-like liquid crystal compound having a hybrid orientation and performing heat treatment at 60 to 100 ° C. for 2 to 4 minutes, followed by 365 nm. It is preferable that the step of curing using ultraviolet rays of 18 to 22mJ intensity.

On the other hand, Figure 2 is a liquid crystal layer of the present invention is a hybrid orientation, it is a conceptual diagram to help understand this.

Referring to FIG. 2, it can be seen that the rod-shaped liquid crystal having a hybrid orientation of the liquid crystal layer 130 has a lower tilt toward the base layer, and exhibits a higher tilt as it moves away from the cellulose ester base layer.

Subsequently, the optical axes of the liquid crystal layer 130 may be disposed to be perpendicular to the optical axes of the base layer 110.

It is preferable that the thickness of the liquid crystal layer 130 is 0.8 μm to 1.5 μm. Only when the above-mentioned range is satisfied, considering the Δn range (0.08 to 0.15) of a general rod-shaped liquid crystal, 120 nm, which is a phase difference value necessary for compensating for the liquid crystal of hybrid alignment near the upper and lower substrates of the TN mode, can be obtained. .

The O-plate according to the present invention is preferably included in the polarizing plate.

In addition, the O-plate according to the present invention is preferably included in the liquid crystal display device.

Hereinafter, the present invention will be described in more detail with reference to Preparation Examples, Test Examples, Examples, and the like. However, the production examples, test examples, examples, and the like described below are for illustrating the present invention, and the present invention is not limited thereto and may be variously modified and changed.

Example 1, Comparative Examples 1 and 2: Preparation of Retardation Film

≪ Example 1 >

The solution having a acetyl group substitution degree of 2 and a propionyl group substitution degree of 0.8 was dissolved in an organic solvent composed of methyl chloride and methyl alcohol. Thereafter, 1.3-fold tenter stretching was performed in the width direction while heating at a temperature of 140 ° C. in the state where the residual solvent was 30% to prepare a cellulose ester base layer. Subsequently, the discotic liquid crystal compound was prepared by synthesizing the polyimide polymer represented by the following Chemical Formula 1 with a molecular weight of 50,000, and then dissolving it in an organic solvent having a MEK: NMP ratio of 9: 1. Thereafter, the discotic liquid crystal compound was coated on the cellulose ester base layer, heat-treated at 80 ° C. for 3 minutes, and cured by irradiating 20 mJ intensity ultraviolet rays based on 365 nm. A rubbing alignment treatment was performed on the cured discotic liquid crystal compound to prepare an alignment layer.

<Formula 1>

Subsequently, a rod-shaped liquid crystal of Merck's UV-curable hybrid alignment was coated on the alignment layer, and heat-treated at 80 ° C. for 3 minutes. Irradiated and cured to prepare a liquid crystal layer. At this time, the liquid crystal layer was disposed such that the cellulose ester base layer and the optical axis were perpendicular to each other.

R _th of the cellulose ester base layer of the retardation film has a tilt angle distribution of 160 nm, R ₀ is 150 nm, and the cellulose ester base layer surface is 30 °.

Comparative Example 1

Fuji's WV retardation film was provided in Comparative Example 1.

Comparative Example 2

Retardation film of the Republic of Korea Registration No. 10-0757637 was provided as Comparative Example 2.

Test Example: Evaluation of characteristics of LCD including Example 1, Comparative Example 1 and Comparative Example 2, respectively

LCDs each having a dielectric anisotropy Δε> 0, a refractive index of liquid crystals of ne = 1.6, no = 1.5, and a liquid crystal panel having a thickness of 4.5 μm, and Examples 1, Comparative Examples 1 and 2, respectively, were prepared. In the LCD, the polarizer is placed at an angle of 45 °, and the polarizer is disposed so that the transmission axis of the polarizer is perpendicular to the optical axis of the LCD panel. In the case of Example 1 of the upper and lower LCD panels, as in FIG. 3, in the case of Comparative Example 1, and in FIG. As a polarizing element, a film stretched five times in the longitudinal direction of an iodine-dyed solution in PVA was used, and after the retardation films of Example 1, Comparative Examples 1 and 2 were attached with a PVA adhesive, an adhesive (Sokken) was used again. It was attached to the LCD panel. Further, the transmission axis of the polarizer and the optical axis of the liquid crystal layer were disposed to be perpendicular to each other, and the transmission axis of the polarizer and the optical axis of the cellulose ester support were arranged in parallel.

4 is a result of measuring the viewing angle of the LCD panel including the O-plate of Example 1. FIG. 6 is a result of measuring the viewing angle of the LCD panel including the retardation film of Comparative Example 1. 8 is a result of measuring the viewing angle of the LCD panel including the retardation film of Comparative Example 2.

6, 6, and 8, it can be seen that the viewing angle of the LCD panel including Example 1 according to the present invention is wider than that of the LCD panel including Comparative Examples 1 and 2. FIG.

1 is a cross-sectional view showing an O-plate according to an embodiment of the present invention.

2 is a conceptual diagram illustrating the hybrid orientation of the O-plate according to the first embodiment of the present invention.

3 is a cross-sectional view of the LCD panel including the O-plate of Example 1. FIG.

4 is a result of measuring the viewing angle of the LCD panel including the O-plate of Example 1. FIG.

5 is a cross-sectional view of an LCD panel including a retardation film of Comparative Example 1. FIG.

6 is a result of measuring the viewing angle of the LCD panel including the retardation film of Comparative Example 1.

7 is a cross-sectional view of an LCD panel including a retardation film of Comparative Example 1. FIG.

8 is a result of measuring the viewing angle of the LCD panel including the retardation film of Comparative Example 2.

Claims (9)

A substrate layer having a surface direction retardation (R ₀ ) of 130 to 170 nm, a thickness direction retardation (R _th ) of 140 to 180 nm, and an orientation angle of 20 to 40 °; An alignment layer positioned on the base layer; And An O-plate, wherein the liquid crystal layer is disposed on the alignment layer and provided with spreading orientation. The method according to claim 1, The base layer is 1 type selected from the group consisting of triacetyl cellulose, polyethylene terephthalate, polymethyl methacrylate, polycarbonate, polyethylene, cycloolefin polymer, polyvinyl alcohol, diacetyl cellulose, polyether sulfone film and glass substrate; And O-plate comprising one selected from the group consisting of rod-shaped additives, plate-like additives and mixtures thereof. The method according to claim 1, The alignment layer is characterized in that it comprises a discotic compound. The method according to claim 1, The liquid crystal layer is an O-plate, characterized in that it comprises a rod-like liquid crystal compound of a hybrid orientation. a) providing a substrate layer having a surface direction retardation (R ₀ ) of 130 to 170 nm, a thickness direction retardation (R _th ) of 140 to 180 nm, and an orientation angle of 20 to 40 °; b) forming an alignment layer on the substrate layer; And c) forming a liquid crystal layer imparted with spreading orientation on the alignment layer. The method according to claim 5, The step b) comprises spin-coating a discotic compound on the substrate layer, heat-treating at 60 to 100 ° C. for 2 to 4 minutes, and photocuring the light using ultraviolet rays of 18 to 22 mJ intensity based on 365 nm; And Orienting the photocured discotic compound to form an alignment layer. The method according to claim 5, In step c), the rod-shaped liquid crystal compound of hybrid orientation is spin-coated on the alignment layer, heat-treated at 60 to 100 ° C. for 2 to 4 minutes, and then cured using ultraviolet rays of 18 to 22 mJ intensity based on 365 nm. Forming a liquid crystal layer. A polarizing plate comprising the O-plate of claim 1. A liquid crystal display device comprising the O-plate of claim 1.

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