KR20100104381A - Liquid crystal display device having viewing angle controlling sheet - Google Patents

Abstract

PURPOSE: A liquid crystal display having a sheet controlling a view angle is provided to install the sheet controlling a viewing angle which includes a plurality of external light absorbing pattern having concave sidewall, thereby improving a color reproduction characteristic. CONSTITUTION: A first polarizing plate(300) and a second polarizing plate(300') are respectively arranged to front and rear side of a liquid crystal cell(100). A sheet controlling a viewing angle is arranged to a front side of the first polarizing plate. The sheet controlling a viewing angle has a light transmitting part(502) and a plurality of external light absorbing patterns. A plurality of grooves(502a) is formed on the light transmitting part. The plurality of external light absorbing pattern is arranged within the groove. The plurality of external pattern comprises a light absorbing substance. The plurality of external pattern has a concave sidewall.

Description

Liquid crystal display device having a viewing angle control sheet

A liquid crystal display device is disclosed. More specifically, a liquid crystal display device including a viewing angle control sheet including a plurality of external light absorption patterns having a concave sidewall on a front surface thereof is disclosed.

Recently, as a flat panel display device used in notebook computers, televisions, or mobile phones, which require thinning, miniaturization, and low power consumption, a plasma display panel (PDP), a field emission display device (field) An emission display device (FED), a thin film transistor liquid crystal display device (TFT-LCD), and the like have been developed, and among these, a liquid crystal display device having excellent color reproducibility and thinness is most actively studied.

It is often desirable that the liquid crystal display has a wide viewing angle so that the viewer can obtain a good image at any position. The viewing angle means an angle at which the image formed on the monitor of the liquid crystal display device can be visually confirmed. This viewing angle is different from the angle at which color distortion occurs and refers to the angle at which the eye can see the screen on the monitor regardless of whether the color looks or not. The angle at which color distortion occurs is usually much smaller than the viewing angle. For example, in a commercially available liquid crystal display device, the angle at which color distortion occurs in a device whose viewing angle is indicated by 170 ° may be only about 90 °. The degree to which color distortion does not occur is called color reproducibility, and it is important to simultaneously improve the viewing angle and color reproducibility in order to obtain a high quality image.

An embodiment of the present invention provides a liquid crystal display device having a viewing angle control sheet including a plurality of external light absorption patterns having concave sidewalls on a front surface thereof.

One aspect of the invention,

Liquid crystal cell;

A first polarizing plate and a second polarizing plate respectively disposed on the front and rear surfaces of the liquid crystal cell;

A viewing angle control sheet disposed on a front surface of the first polarizing plate and including a light transmitting part having a plurality of grooves formed therein, and a plurality of external light absorption patterns disposed in the grooves, the light absorbing material including concave sidewalls; And

Provided is a liquid crystal display device including a backlight unit disposed on a rear surface of the second polarizing plate.

The groove formed in the light transmitting portion may have a concave sidewall.

The refractive index of the external light absorption pattern may be different from that of the light transmitting part.

The difference n ₅₀₂ -n ₅₀₃ between the refractive index n ₅₀₂ of the light transmitting part and the refractive index n ₅₀₃ of the external light absorption pattern may be 0.001 to 0.500.

The liquid crystal display may further include a phase delay film between at least one of the liquid crystal cell and the first polarizing plate and between the liquid crystal cell and the second polarizing plate.

According to an embodiment of the present invention, by providing a viewing angle control sheet including a plurality of external light absorption patterns having concave sidewalls on the front surface, a liquid crystal display device having improved viewing angle and color reproducibility and reduced occurrence of double phase may be provided. .

Hereinafter, a liquid crystal display according to an exemplary embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 is a cross-sectional view schematically illustrating a liquid crystal display device according to an exemplary embodiment of the present invention.

1, a liquid crystal display according to an exemplary embodiment of the present invention includes a liquid crystal cell 100, a pair of phase delay films 200 and 200 ′, a pair of polarizing plates 300 and 300 ′, and an antireflection film ( 400), the viewing angle control sheet 500 and the backlight unit 600.

The liquid crystal cell 100 serves to control the polarization direction of light by using the principle that the arrangement state of the liquid crystal is changed according to the magnitude of the voltage applied thereto. Although not shown here, a pair of substrates having electrodes formed thereon The liquid crystal layer arrange | positioned in between is provided. The operation modes of the liquid crystal for forming an image in the liquid crystal display include a twisted nematic (TN) mode, an in plane switching (IPS) mode, a vertical alignment (VA) mode, and the like.

The first phase delay film 200 and the second phase delay film 200 'are disposed on the front and rear surfaces of the liquid crystal cell 100, respectively, and have a slow axis and a fast axis. In order to have a fast phase with respect to the light of an axial direction, an extended polymer film or a liquid crystal aligning film is used for the 1st, 2nd phase delay films 200 and 200 ', for example. In the conventional liquid crystal display device, such a phase delay film is used for each of the front and rear surfaces of the liquid crystal cell 100. However, in the liquid crystal display device of the present invention, the viewing angle control sheet 500 to be described later includes phase delay films 200 and 200. Since the role of ') may be substituted, at least one of the phase delay films 200 and 200' may be omitted.

The first polarizing plate 300 is disposed on the front surface of the liquid crystal cell 100 and the front phase of the first phase delay film 200 in FIG. 1 and vibrates in a specific direction among light incident while vibrating in various directions (that is, polarization). ) And transmits only the first polarizing plate 300, and the first protective film 311 and the second protective film 312 respectively disposed on both sides of the polarizing film 310 and the polarizing film 310. ). In addition, the first protective film 311 may be omitted. In this case, for example, the polarizing film 310 and the anti-reflection film 400 are disposed to be in close contact with each other so that the anti-reflection film 400 may be formed. 1 acts as a protective film 311. The polarizing film 310 is, for example, after stretching a film of polyvinyl alcohol (polyvinyl alcohol (PVA), and then immersed the stretched film in a solution of iodine (I ₂ ) and dichroic dye, iodine molecules It can be prepared by arranging (I ₂ ) and dye molecules side by side in the stretching direction. The first protective film 311 and the second protective film 312 is to protect the polarizing film 310 from moisture and to prevent damage to the surface of the polarizing film 310 to improve the durability, for example, cellulose tri acetate ( TAC).

The second polarizing plate 300 ′ is disposed on the rear surface of the liquid crystal cell 100 and the rear surface of the second phase delay film 200 ′ in FIG. 1, and the polarizing film 310 ′ and the front surface of the polarizing film 310 ′. And a first protective film 311 ′ and a second protective film 312 ′ respectively disposed on the rear surface. Since the role and material of the second polarizing plate 300 ′ are the same as those of the first polarizing plate 300 described above, detailed description thereof will be omitted.

The anti-reflection film 400 plays a role of minimizing eye fatigue of an observer watching for a long time by adjusting the transmittance of visible light, and is disposed on the front surface of the first polarizing plate 300. By arranging the antireflection film 400 as described above to adjust the visible light transmittance of the liquid crystal display device, in addition to the selective absorption effect of the visible light, the secondary effect of improving the color reproducibility such as contrast ratio can be obtained. The antireflection film 400 may be a mixture of indium tin oxide (ITO) and silicon oxide (SiO ₃ ), a mixture of nickel chromate (NiCr) and silicon oxide (SiO ₂ ), titanium oxide or a special fluorine resin having a low refractive index. It can be prepared using. In addition, the anti-reflection film 400 may be omitted as necessary.

The viewing angle control sheet 500 is disposed on the front surface of the first polarizing plate 300 and the front surface of the anti-reflection film 400 in FIG. 1 to refract / reflect light incident in a direction substantially perpendicular to the smooth surface thereof in the vertical direction. By spreading a predetermined angle to the side, it widens the viewing angle, improves color reproducibility, and reduces the occurrence of double images. The viewing angle control sheet 500 includes a light transmitting part 502 in which a plurality of grooves 502a are disposed to be spaced apart from each other, and a light absorbing material and disposed in the groove 502a to form concave sidewalls. It has a plurality of external light absorption pattern 303 having, they may be disposed on the base film 501.

The base film 501 supports the light transmitting unit 502. The base film 501 is, for example, polyethersulphone (PES), polyacrylate (PAR, polyacrylate), polyether imide (PEI, polyetherimide), polyethylene naphthalate (PEN, polyethyelene naphthalate), Polyethylene terephthalate (PET), polyphenylene sulfide (PPS), polyallylate, polyimide, polycarbonate (PC), cellulose tri acetate (TAC), cellulose acetate propio It may be formed of one or more materials selected from the group consisting of cellulose acetate propionate (CAP). In addition, the base film 501 may be omitted as necessary.

The light transmitting portion 502 is a portion that transmits light. The light transmitting part 502 may be formed of a curable resin. The light transmitting portion 502 may be formed of, for example, an acrylate resin that is cured by ionizing radiation or thermal energy. In addition, the grooves 502a formed in the light transmitting portion 502 may have concave sidewalls, and the external light absorption pattern 503 having the concave sidewalls is formed by filling a light absorbing material into the grooves 502a having the concave sidewalls. can do.

The external light absorption pattern 503 absorbs the external ambient light, thereby improving the contrast ratio in the bright room condition, thereby maintaining a high resolution. The external light absorption pattern 503 may be formed of a material capable of absorbing light, for example, a black inorganic material, a black organic material, and / or a blackened metal. In the case of blackened metal, since the electrical resistance is low, the external light absorption pattern 503 formed therefrom may perform an electromagnetic shielding function because the electrical resistance can be controlled by adjusting the content of the metal powder or the thickness of the metal thin film. . The external light absorption pattern 503 may be formed of, for example, an ultraviolet curable resin containing carbon.

In addition, the external light absorption pattern 503 is configured to have a refractive index different from that of the light transmission unit 502, so that the liquid crystal display device adopts the reflection and reflection of light at the interface between the external light absorption pattern 503 and the light transmission unit 502. Increases the viewing angle of the color and improves color reproducibility. Refractive index (n ₅₀₂₎ and a refractive index difference (n -n _{502 503)} between the (n ₅₀₃₎ of the external light-absorbing patterns 503 of the light transmission portion 502 may be, for example, 0.001 ~ 0.500. If the refractive index difference (n ₅₀₂ -n ₅₀₃ ) is less than 0.001, the total reflection effect is not implemented.

In addition, since the external light absorption pattern 503 has a concave sidewall, the advancing direction of incident light is changed differently according to the position of the sidewall, thereby maintaining a high viewing angle and color reproducibility of the liquid crystal display, and reducing the occurrence of a double image. This may be described later with reference to FIG. 2.

The backlight unit 600 is disposed on the rear surface of the second polarizing plate 300 'and serves to provide light L to the liquid crystal cell 100 through the second polarizing plate 300'. The light source of the backlight unit 600 includes a cold cathode fluorescent lamp (CCFL), an external electrode fluorescent lamp (EEFL), a light emitting diode (LED), and a flat fluorescent lamp (FFL).

Hereinafter, referring to FIG. 2, the traveling direction of incident light is changed differently according to the position of the concave sidewall of the external light absorption pattern in the viewing angle control sheet 500, thereby increasing the viewing angle and color reproducibility and reducing the occurrence of a double phase in detail. do.

FIG. 2 is an enlarged cross-sectional view of the viewing angle control sheet 500 included in the liquid crystal display of FIG. 1.

Referring to FIG. 2, the light L ₁ incident in a direction substantially perpendicular to the smooth surface of the viewing angle control sheet 500 is an interface between the light transmitting part 502 and the external light absorption pattern 503 (position = C ₁ ). Is reflected from the exit angle at a predetermined angle between the front and side of the viewing angle control sheet 500 (ie, L ₁ '). Such light L ₁ ′ contributes to an improvement in viewing angle and color reproducibility of the liquid crystal display. In addition, the light L ₂ incident in a direction substantially perpendicular to the smooth surface of the viewing angle control sheet 500 is refracted at an interface (position = C ₂ ) between the light transmitting part 502 and the external light absorption pattern 503. Incident to the external light absorption pattern 503 (that is, L ₂ ′), and only a part of the light L ₂ is reflected at the interface and is emitted at a predetermined angle between the front and side surfaces of the viewing angle control sheet 500 ( That is, L ₂ ″. The light L ₂ ′ derived from such light L ₁ contributes to the reduction of the dual phase, and some of the light L ₂ ′ penetrates the external light absorption pattern 503 to form a liquid crystal. In other words, the light L ₁ and L ₂ incident in a direction perpendicular to the smooth surface of the viewing angle control sheet 500 may be formed between the light transmission unit 502 and the external light absorption pattern 503. The incident angle varies depending on the position incident on the interface, and the light L ₁ is totally reflected at the interface because the incident angle is smaller than the critical angle, and the light L ₂ is Since the angle of incidence is larger than the critical angle, most of the light is transmitted / absorbed at the interface and only a part of the reflection is reflected, thereby improving the viewing angle / color reproducibility and alleviating the occurrence of the dual phase.

Although the preferred embodiment according to the present invention has been described above with reference to the drawings, this is merely illustrative, and those skilled in the art can understand that various modifications and equivalent other embodiments are possible. There will be. Therefore, the protection scope of the present invention should be defined by the appended claims.

1 is a cross-sectional view schematically illustrating a liquid crystal display device according to an exemplary embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view of a viewing angle control sheet included in the liquid crystal display of FIG. 1.

[Description of Symbols for Main Parts of Drawing]

100: liquid crystal cell 200, 200 ': phase delay film

300, 300 ': polarizing plate 310, 310': polarizing film

311, 311 ', 312, 312': Protective film 400: Antireflection film

500: viewing angle control sheet 501: base film

502: light transmitting portion 502a: groove

600: backlight unit

Claims (5)

Liquid crystal cell; A first polarizing plate and a second polarizing plate respectively disposed on the front and rear surfaces of the liquid crystal cell; A viewing angle control sheet disposed on a front surface of the first polarizing plate and including a light transmitting part having a plurality of grooves formed therein, and a plurality of external light absorption patterns disposed in the grooves, the light absorbing material including concave sidewalls; And And a backlight unit disposed on the rear surface of the second polarizing plate. The method of claim 1, And a groove formed in the light transmitting portion has a concave sidewall. The method of claim 1, The refractive index of the external light absorption pattern is different from the refractive index of the light transmitting portion. The method of claim 3, Refractive index (n ₅₀₂₎ and a refractive index (n ₅₀₃₎ Difference (n ₅₀₂ -n ₅₀₃₎ 0.001 to 0.500 in the liquid crystal display device between the external light absorbing pattern of the light transmission. The method of claim 1, A liquid crystal display further comprising a phase delay film between at least one of the liquid crystal cell and the first polarizing plate and between the liquid crystal cell and the second polarizing plate.

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