TWI408465B - Liquid crystal display - Google Patents

Abstract

A liquid crystal display including a liquid crystal display panel, a first polarizer, a second polarizer, a first optical compensation plate and a second optical compensation plate is provided. The liquid crystal display panel has a twisted nematic (TN) liquid crystal layer. The first polarizer and the second polarizer are respectively disposed on two sides of the liquid crystal display panel. The first optical compensation plate is disposed between the liquid crystal display panel and the first polarizer, wherein the first optical compensation plate is a biaxial phase retarder and has a plurality of main axis refractive index nx1, ny1 and nz1. The main axis refractive index nx1 and ny1 are in-plane main refractive index, and the main axis refractive index nz is thickness-wise refractive index. The plurality of main axis refractive index nx1, ny1 and nz1 satisfy the following relationship: Nz1=(nx1-nz1)/(nx1-ny1), wherein nx1 > nz1, and -0.5 < Nz1 < 1.. The second optical compensation plate is disposed between the liquid crystal display panel and the first optical compensation plate. Therefore, a liquid crystal display is capable of enlarging the viewing angle and enhancing the display quality.

Description

LCD Monitor

The present invention relates to a display device, and more particularly to a liquid crystal display.

The liquid crystal display is limited by its principle of illumination, and there are still some phenomena that need to be improved. For example, if the viewing angle of the liquid crystal display is too narrow, the display quality of the liquid crystal display may decrease when the viewing angle in the reference direction or the vertical direction is too large, such as contrast. Color saturation and brightness are not as good as when facing a liquid crystal display.

FIG. 1A is a schematic structural view of a conventional twisted nematic liquid crystal display. Referring to FIG. 1A, the composition of the twisted nematic liquid crystal display device 100 generally includes a thin film transistor (TFT) array substrate 110, a color filter (CF) substrate 120, and a first polarizer. A polarizer 130, a second polarizing plate 140, and a twisted nematic liquid crystal layer 150. The thin film transistor array substrate 110 is located on the first polarizing plate 130, and the color filter substrate 120 is located on the thin film transistor array substrate 110. The second polarizing plate 140 is located on the color filter substrate 120, and the twisted nematic liquid crystal layer 150 is located between the thin film transistor substrate 110 and the color filter substrate 120. The twisted nematic liquid crystal layer 150 is twisted to different degrees according to the voltage difference between the thin film transistor array substrate 110 and the color filter substrate 120, thereby controlling the transmittance of light, thereby making the twisted nematic liquid crystal display 100 Produce a display effect.

FIG. 1B is a comparative perspective view of a conventional twisted nematic liquid crystal display. Referring to FIG. 1B, in a conventional twisted nematic-liquid crystal display (TN-LCD), since the twist angle of the liquid crystal molecules is small, the range of the viewing angle is also the smallest, and the viewing angle in the reference direction is only about Each 45 degrees still has a lot of room for improvement. Therefore, how to effectively widen the viewing angle of the twisted nematic liquid crystal display and improve the display quality of the twisted nematic liquid crystal display has become a major issue for liquid crystal displays.

The invention provides a liquid crystal display, which effectively improves the viewing angle of the liquid crystal display and improves the display quality by the first optical compensation plate whose spindle refractive index satisfies a specific relationship.

The invention provides a liquid crystal display comprising a liquid crystal display panel, a first polarizing plate and a second polarizing plate, a first optical compensation plate and a second optical compensation plate. The liquid crystal display panel has a twisted nematic liquid crystal layer. The first polarizing plate and the second polarizing plate are respectively located at two sides of the liquid crystal display panel. The first optical compensation plate is located between the liquid crystal display panel and the first polarizing plate, wherein the first optical compensation plate is a dual optical axis compensation plate and has a plurality of spindle refractive indices nx ₁ , ny ₁ and nz ₁ , wherein nx ₁ , Ny ₁ is the plane principal refractive index, nz ₁ is the thickness direction refractive index, and the main axis refractive indices nx ₁ , ny ₁ , nz ₁ satisfy the following relationship: Nz ₁ = (nx _{1 -} nz ₁ ) / (nx _{1 -} ny ₁ ), nx ₁ > nz ₁ , and -0.5 < Nz ₁ <1. The second optical compensation plate is located between the liquid crystal display panel and the first optical compensation plate.

In an embodiment of the invention, the aforementioned Nz ₁ is, for example, substantially 0.25.

In an embodiment of the invention, the second optical compensation plate may be a single optical axis compensation plate. Of course, the second optical compensation plate may also be a dual optical compensation plate, and the second optical compensation plate has a plurality of main axis refractive indices nx ₂ , ny ₂ and nz ₂ , where nx ₂ and ny ₂ are planar main refractive indexes. , nz ₂ is a refractive index in the thickness direction, and the refractive index of the main axis satisfies the following relationship: Nz ₂ = (nx _{2 -} nz ₂ ) / (nx _{2 -} ny ₂ ), where nx ₂ > nz ₂ and -0.5 < Nz ₂ <1.

In an embodiment of the invention, the aforementioned Nz ₂ is, for example, substantially 0.25.

In an embodiment of the present invention, the phase retardation amount R2 of the second optical compensation plate is, for example, between 95 nm and 195 nm, and the phase delay amount R2 satisfies the following relationship: R2=(nx ₂ -ny ₂ ) × d ₂ , where d ₂ is the thickness of the second optical compensation plate.

In an embodiment of the present invention, the phase retardation amount R1 of the first optical compensation plate is, for example, between 190 nm and 390 nm, and the phase delay amount R1 satisfies the following relationship: R1=(nx ₁ -ny ₁ ) × d ₁ , where d ₁ is the thickness of the first optical compensation plate.

In an embodiment of the invention, the phase retardation amount of the twisted nematic liquid crystal layer is, for example, between 360 nm and 540 nm.

In an embodiment of the invention, the liquid crystal display panel has a reference direction, and the absorption axis of the first polarizing plate and the reference direction are substantially clamped by 0 degrees, and tolerance of +-5 degrees is allowed, and second The absorption axis of the polarizing plate and the reference direction are, for example, substantially 45 degrees and allow a tolerance of +-5 degrees. For example, the slow axis of the first optical compensation plate and the reference direction are substantially 22.5 degrees and allow +- A tolerance of 5 degrees, and the slow axis of the second optical compensation plate and the reference direction are, for example, substantially 45 degrees and allow a tolerance of +-5 degrees.

Based on the above, the liquid crystal display of the present invention has a first optical compensation plate whose spindle refractive index satisfies a specific relationship, so that the phase and color shift are appropriately adjusted after the incident light passes through the liquid crystal display panel. Therefore, the liquid crystal display of the present invention can widen the viewing angle and effectively adjust the color shift phenomenon, thereby improving the display quality of the liquid crystal display.

The above described features and advantages of the present invention will be more apparent from the following description.

The liquid crystal display of the present invention has a first compensating plate that satisfies a specific relationship, and the optical effect of the augmented viewing angle is obtained by the special relationship between the refractive indices of the main axes when the light passes through the first compensating plate optical sheet. In the following embodiments, the specific relationship satisfied by the first compensation film and how the first compensation film assists the transmission of light when passing through the liquid crystal display panel to increase the viewing angle of the liquid crystal display panel will be described.

First embodiment

2A is a cross-sectional view showing a liquid crystal display device according to a first embodiment of the present invention. Referring to FIG. 2A , the liquid crystal display 200 of the present embodiment includes a liquid crystal display panel 210 , a first polarizing plate 220 and a second polarizing plate 230 , a first optical compensation plate 240 , and a second optical compensation plate 250 . The liquid crystal display panel 210 is composed of, for example, a thin film transistor array substrate 212, a color filter substrate 214, and a twisted nematic liquid crystal layer 216 interposed between the two substrates 212 and 214, wherein the twisted nematic type ( Nematic) The liquid crystal is composed of rod-shaped molecules arranged in such a manner that the long-axis directions of the liquid crystal molecules are parallel and have liquid-like fluidity, and the nematic liquid crystal has optical, electrical, magnetic and the like anisotropy. Anisotropy can therefore be used to control the transmittance of light through the twisted nematic liquid crystal layer 216 by applying an applied electric field or magnetic field thereto, and the amount of phase retardation provided by the twisted nematic liquid crystal layer 216 is, for example, in this embodiment. It is between 360 nm and 540 nm.

As shown in FIG. 2A, the first polarizing plate 220 and the second polarizing plate 230 are respectively located at two sides of the liquid crystal display panel 210, and the first polarizing plate 220 and the second polarizing plate 230 respectively have a polarizing axis (shown in FIG. 4). When the light passes through the first polarizing plate 220 or the second polarizing plate 230, it deflects along the direction of its polarization axis (shown in FIG. 4) to form linearly polarized light. The first optical compensation plate 240 is located between the liquid crystal display panel 210 and the first polarizing plate 220. The linearly polarized light passing through the first polarizing plate 220 is phase-compensated by the first optical compensation plate 240, and then enters the second optical compensation plate 250. The second optical compensation plate 250 is located between the liquid crystal display panel 210 and the first optical compensation plate 240.

In more detail, the first optical compensation plate 240 is, for example, a dual optical axis half wave plate, and the second optical compensation plate 250 is, for example, a quarter wave plate, and the first optical compensation plate 240 and the second optical compensation plate 250 For example, a phase delay amount R1 and a phase delay amount R2 are respectively provided. The phase delay amount R1 is defined as the product of (nx ₁ -ny ₁ ) and d ₁ , and d ₁ is the thickness of the first optical compensation plate 240. Also, the phase delay amount R2 is defined as the product of (nx ₂ -ny ₂ ) and d ₂ , where d ₂ is the thickness of the second optical compensation plate 250. The designer can select different phase delay amounts R1 and phase delay amounts R2 to modulate the polarization direction of the displayed image, thereby increasing the optical quality of the image displayed by the liquid crystal display 200, such as compensating for image chromatic aberration and improving color shift. Specifically, in the present embodiment, the phase retardation amount R1 of the first optical compensation plate 240 is between about 190 nanometers (nm) and 390 nm, and the phase retardation amount R2 of the second optical compensation plate 250 is about Between 95nm and 195nm.

In particular, the first optical compensation plate 240 of the present invention belongs to a dual optical axis compensating plate. In detail, the first optical compensation plate 240 has a plurality of main axis refractive indices nx ₁ , ny ₁ and nz ₁ , wherein nx ₁ and ny ₁ are in-plane main refractive indices, and nz ₁ is a thickness direction. The thickness-wise refractive index, in other words, the rate of travel of the light in the first optical compensation plate 240 varies depending on the direction of the film layer. Further, the major axis refractive indices nx ₁ , ny ₁ , nz ₁ of the first optical compensation plate 240 of the present invention satisfy the following relationship: Nz ₁ = (nx _{1 -} nz ₁ ) / (nx _{1 -} ny ₁ ), where nx ₁ > nz ₁ and -0.5 < Nz ₁ <1. In other words, Nz _{1 is} defined as the ratio of nx ₁ -nz ₁ to nx ₁ -ny ₁ .

Further, the principal refractive indices nx ₁ , ny ₁ and nz _{1 of the} first optical compensation plate 240 satisfy the relationship of nx ₁ ≠nz ₁ and nz ₁ ≠ny ₁ . That is, the first optical compensation plate 240 can be regarded as a dual optical axis compensating plate having birefringence properties. Therefore, the first optical compensation plate 240 has a function of modulating the direction of the polarized light emitted through the polarization axis of the first polarizing plate 220, so that the brightness viewed by the user is not significantly lowered. The designer can adjust the polarization direction of the light by selecting different nx ₁ -nz ₁ and nx ₁ -ny ₁ under the condition that the above relationship is satisfied, thereby increasing the amount of light of the display image of the light passing through the liquid crystal display panel 210.

In practice, when the user observes the displayed image, in addition to the above-mentioned brightness requirement, the designer can adjust the light through the first optics through the first optical compensation plate 240 whose refractive index of the main axis satisfies -0.5<Nz ₁ <1.0. The phase retardation amount R1 of the compensation board 240 further satisfies the user's viewing angle requirement for displaying images, and effectively enhances the viewable viewing angle of the liquid crystal display 200.

2B is a comparative perspective optical view of the structure of the liquid crystal display 200 of FIG. 2A. Referring to FIG. 2B, in the embodiment, the Nz ₁ value of the first optical compensation plate 240 is substantially equal to 0.08. Compared with the comparative viewing angle optical diagram (shown in FIG. 1B) of the conventional liquid crystal display device 100, the liquid crystal display device 200 of the present embodiment can effectively enhance the viewing angles of the top, bottom, left, and right.

It should be noted that, in this embodiment, the second optical compensation plate is exemplified by a single optical compensation plate, that is, the plurality of spindle refractive indices nx ₂ , ny _2, and nz _{2 of the} second optical compensation plate satisfy Nz. ₂ is essentially equal to the relationship of 1. In other words, the liquid crystal display 200 of the present invention can design only the first optical compensation plate 240 as a dual optical axis compensation plate. Of course, in other embodiments, the designer may further design the second optical compensation plate 250 as a dual optical compensation plate to form the structure as shown in FIG. 3A. Compared with the comparative viewing angle optical diagram of the conventional liquid crystal display device 100, the liquid crystal display device 200 of the present embodiment can effectively enhance the viewing angles of the top, bottom, left, and right.

Second embodiment

3A is a cross-sectional view showing a liquid crystal display device according to a second embodiment of the present invention. Referring to FIG. 3A, the liquid crystal display 300 is similar to the liquid crystal display 200 of the first embodiment. However, in the embodiment, the second optical compensation plate 350 is further configured as a dual optical compensation plate, and the second optical compensation plate 350 The refractive index of the main axis satisfies the following relationship: Nz ₂ = (nx _{2 -} nz ₂ ) / (nx _{2 -} ny ₂ ), where nx ₂ > nz ₂ and -0.5 < Nz ₂ < 1, thus, the second optical compensation plate The 350 can further improve lateral light leakage and improve optical quality.

3B is a comparative perspective optical view of the liquid crystal display structure of FIG. 3A. Referring to FIG 3B, in the present embodiment, Nz ₂ value of the first optical compensation plate is Nz ₁ value 240 and the second optical compensation plate 350 is substantially equal to 0.25, as compared to conventional art FIG. 1B of the liquid crystal display 100 Comparing the viewing angle optical map (as shown in FIG. 1B), the liquid crystal display 300 of the present embodiment can greatly enhance the viewing angle in each direction.

Specifically, when a principal refractive index (nx ₁ -nz ₁₎ a first optical compensation plate 240 and the Nz value of _{one (1} -ny ₁ nx) the ratio satisfies a specific range, so that the viewer may be viewing angle distribution wider, and the principal refractive index of the second optical compensation plate 350 (nx ₂ -nz ₂₎ Nz and (nx ₂ -ny ₂₎ the ratio of the value of ₂ is further set to -0.5 <Nz ₂ <1, can be Further increase the suppression of lateral light leakage. For example, when Nz ₁ is substantially equal to 0.25 and Nz ₂ is substantially equal to 0.25, there is a broader viewing angle in one embodiment of the invention.

In order to make the disclosure of the liquid crystal display of the present invention more detailed, FIG. 4 further illustrates a perspective view of the liquid crystal display of FIG. 3, and FIG. 5 lists several comparative viewing angle optical views of the liquid crystal display 300 of the FIG.

Referring first to FIG. 4, the liquid crystal display panel 210 will generally have a long side 210a and a short side 210b. The liquid crystal display panel 210 has a certain direction of the viewing direction as the reference direction B. In the present embodiment, the reference direction B is based on the viewing direction of the observer's three o'clock and nine o'clock lines, that is, The reference direction B of the present invention is not limited to the short side direction or the long side direction of the liquid crystal display panel, but is based on the viewing direction of the observer. And the first polarization axis P1 of the first polarizing plate 220 is substantially parallel to the reference direction B, and tolerance of +-5 degrees is allowed. The second polarizing axis P2 of the second polarizing plate 230 is substantially 45 degrees from the reference direction B and allows a tolerance of +-5 degrees, and the first polarizing axis P1 and the second polarizing axis P2 are absorption axes, first The slow axis S1 of the optical compensation plate 240 is substantially 22.5 degrees from the reference direction B and allows a tolerance of +-5 degrees, and the slow axis S2 of the second optical compensation plate 350 and the reference direction B are substantially sandwiched by 45 degrees. A tolerance of +-5 degrees is tolerated, wherein the slow axis S1 of the first optical compensation plate 240 and the slow axis S2 of the second optical compensation plate 350 are respectively nx ₁ and nx _{2 of the} corresponding major refractive indices. It should be noted that the slow axis between the first polarization axis P1 and the second polarization axis P2 can modulate the polarization direction of the polarized light, so that the polarization direction of the light passing through the first polarizer 220 is after passing through the liquid crystal display panel 210. The second polarization axis P2 of the second polarizing plate 230 is smoothly viewed by the user to increase the display brightness seen by the user and increase the viewable angle of view.

Please refer to FIG. 5, which illustrates a comparative perspective optical view of the liquid crystal display of the present invention, which is not intended to limit the present invention. Please refer to FIG. 5. FIG. 4 illustrates a comparative perspective optical view of several liquid crystal displays that satisfy the above specific relationship. As can be seen from FIG. 5, when the first optical compensation plate satisfies the specific relationship of Nz ₁ = (nx _{1 -} nz ₁ ) / (nx _{1 -} ny ₁ ) and -0.5 < Nz ₁ < 1, compared with the conventional one, It can reduce the viewing angle dependence of the liquid crystal display, greatly improve the viewing angle of the liquid crystal display and increase the contrast.

In summary, the present invention appropriately modulates the polarization direction of the display image of the liquid crystal display panel by the arrangement of the first optical compensation plate having the dual optical axis characteristics, so as to cope with various usage scenarios. Moreover, since the refractive index of the main axis of the first optical compensation plate of the present invention satisfies a specific relationship, the liquid crystal display of the present invention can increase the display brightness and reduce the angle dependence of the user's viewing, and greatly increase the user's viewing. The viewing angle of the liquid crystal display and the use of the first compensation film can further reduce lateral light leakage and improve the display quality of the liquid crystal display.

Although the present invention has been disclosed in the above preferred embodiments, it is not intended to limit the invention, and any one of ordinary skill in the art can make some modifications and refinements without departing from the spirit and scope of the invention. Therefore, the scope of the invention is defined by the scope of the appended claims.

100‧‧‧Twisted nematic liquid crystal display

110, 212‧‧‧ Thin film transistor array substrate

120, 214‧‧‧ color filter substrate

130‧‧‧First polarizer

140‧‧‧Second polarizer

150, 216‧‧‧ twisted nematic liquid crystal layer

200, 300‧‧‧ liquid crystal display

210‧‧‧LCD panel

210a‧‧‧Longside

210b‧‧‧ Short side

220‧‧‧First polarizer

230‧‧‧Second polarizer

240‧‧‧First optical compensation board

250, 350‧‧‧ second optical compensation board

B‧‧‧reference direction

D1‧‧‧The thickness of the first optical compensation plate

D2‧‧‧ Thickness of the second optical compensation plate

Nx ₁ , ny ₁ , nz ₁ , nx ₂ , ny ₂ , nz ₂ ‧‧‧ spindle refractive index

P1‧‧‧first polarization axis

P2‧‧‧second polarizing axis

R1, R2‧‧‧ phase delay

S1, S2‧‧‧ slow axis

FIG. 1A is a schematic structural view of a conventional twisted nematic liquid crystal display.

FIG. 1B is a comparative perspective view of a conventional twisted nematic liquid crystal display.

2A is a cross-sectional view showing a liquid crystal display device according to a first embodiment of the present invention.

2B is a comparative perspective optical view of the structure of the liquid crystal display 200 of FIG. 2A.

3A is a cross-sectional view showing a liquid crystal display device according to a second embodiment of the present invention.

3B is a comparative perspective optical view of the liquid crystal display structure of FIG. 3A.

4 is a perspective view of the liquid crystal display of FIG. 3 further.

FIG. 5 is a comparative perspective optical view of the liquid crystal display of the present invention.

210. . . LCD panel

212. . . Thin film transistor array substrate

214. . . Color filter substrate

216. . . Twisted nematic liquid crystal layer

220. . . First polarizer

230. . . Second polarizer

240. . . First optical compensation plate

300. . . LCD Monitor

350. . . Second optical compensation plate

Claims (8)

A liquid crystal display comprising: a liquid crystal display panel having a twisted nematic liquid crystal layer; a first polarizing plate and a second polarizing plate respectively located on both sides of the liquid crystal display panel; a first optical compensating plate located at Between the liquid crystal display panel and the first polarizing plate, wherein the first optical compensation plate is a dual optical axis compensating plate, and has a plurality of main axis refractive indices nx ₁ , ny ₁ and nz ₁ , wherein nx ₁ and ny ₁ are The plane principal refractive index, nz ₁ is the thickness direction refractive index, and the spindle refractive indices nx ₁ , ny ₁ , nz ₁ satisfy the following relationship: Nz ₁ = (nx _{1 -} nz ₁ ) / (nx _{1 -} ny ₁ ) Wherein, nx ₁ > nz ₁ and -0.5 < Nz ₁ <1; and a second optical compensation plate between the liquid crystal display panel and the first optical compensation plate, wherein the liquid crystal display panel has a reference direction, The absorption axis of the first polarizing plate is substantially 0 degrees between the reference axis and the tolerance of +-5 degrees, and the absorption axis of the second polarizing plate is substantially 45 degrees from the reference direction and allows +-5 degree tolerance, the actual between the slow axis of the first optical compensation plate and the reference direction The upper clamp is 22.5 degrees and tolerance of +-5 degrees is tolerated, and the slow axis of the second optical compensation plate is substantially 45 degrees from the reference direction and tolerance of +-5 degrees is tolerated. The liquid crystal display of claim 1, wherein the Nz ₁ is substantially 0.25. The liquid crystal display of claim 1, wherein the second optical compensation plate is a single optical axis compensation plate. The liquid crystal display according to claim 1, wherein the second optical compensation plate is a dual optical compensation plate and has a plurality of spindle refractive indices nx ₂ , ny ₂ and nz ₂ , wherein nx ₂ and ny ₂ are The plane principal refractive index, nz ₂ is the thickness direction refractive index, and the major axis refractive indices satisfy the following relationship: Nz ₂ = (nx _{2 -} nz ₂ ) / (nx _{2 -} ny ₂ ) where nx ₂ > nz ₂ , And -0.5 < Nz ₂ <1. The liquid crystal display of claim 4, wherein the Nz ₂ is substantially 0.25. The liquid crystal display according to claim 1, wherein the second optical compensation plate has a plurality of spindle refractive indices nx ₂ , ny ₂ and nz ₂ , and the second optical compensation plate has a phase retardation amount R2 of 95 Between meters and 195 nm, and the phase retardation amount R2 satisfies the following relationship: R2 = (nx _{2 -} ny ₂ ) × d ₂ , where d _{2 is} the thickness of the second optical compensation plate. The liquid crystal display according to claim 1, wherein the phase retardation amount R1 of the first optical compensation plate is between 190 nm and 390 nm, and the phase retardation amount R1 satisfies the following relationship: R1=( Nx ₁ -ny ₁ )×d ₁ , where d _{1 is} the thickness of the first optical compensation plate. The liquid crystal display of claim 1, wherein the twisted nematic liquid crystal layer has a phase retardation amount of between 360 nm and 540 nm.