WO2014040333A1 - 显示装置 - Google Patents

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Publication number
WO2014040333A1
WO2014040333A1 PCT/CN2012/083240 CN2012083240W WO2014040333A1 WO 2014040333 A1 WO2014040333 A1 WO 2014040333A1 CN 2012083240 W CN2012083240 W CN 2012083240W WO 2014040333 A1 WO2014040333 A1 WO 2014040333A1
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WO
WIPO (PCT)
Prior art keywords
front side
film
back side
liquid crystal
display device
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Application number
PCT/CN2012/083240
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English (en)
French (fr)
Inventor
康志聪
海博
Original Assignee
深圳市华星光电技术有限公司
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Priority to US13/703,030 priority Critical patent/US9164323B2/en
Publication of WO2014040333A1 publication Critical patent/WO2014040333A1/zh

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    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/1333—Constructional arrangements; Manufacturing methods
    • G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
    • G02F1/13363—Birefringent elements, e.g. for optical compensation
    • G02F1/133634—Birefringent elements, e.g. for optical compensation the refractive index Nz perpendicular to the element surface being different from in-plane refractive indices Nx and Ny, e.g. biaxial or with normal optical axis
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/30—Polarising elements
    • G02B5/3025—Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state
    • G02B5/3033—Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state in the form of a thin sheet or foil, e.g. Polaroid
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/1333—Constructional arrangements; Manufacturing methods
    • G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
    • G02F1/13363—Birefringent elements, e.g. for optical compensation
    • G02F1/133635—Multifunctional compensators
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F2413/00—Indexing scheme related to G02F1/13363, i.e. to birefringent elements, e.g. for optical compensation, characterised by the number, position, orientation or value of the compensation plates
    • G02F2413/01—Number of plates being 1
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F2413/00—Indexing scheme related to G02F1/13363, i.e. to birefringent elements, e.g. for optical compensation, characterised by the number, position, orientation or value of the compensation plates
    • G02F2413/02—Number of plates being 2
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F2413/00—Indexing scheme related to G02F1/13363, i.e. to birefringent elements, e.g. for optical compensation, characterised by the number, position, orientation or value of the compensation plates
    • G02F2413/05—Single plate on one side of the LC cell
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F2413/00—Indexing scheme related to G02F1/13363, i.e. to birefringent elements, e.g. for optical compensation, characterised by the number, position, orientation or value of the compensation plates
    • G02F2413/12—Biaxial compensators

Definitions

  • the present invention relates to liquid crystal displays, and more particularly to a display device for a VA display mode.
  • the compensation by the wide viewing angle compensation film can effectively reduce the light leakage of the dark state picture, and can greatly improve the contrast of the picture within a certain viewing angle.
  • the compensation principle of the compensation film (or called the retardation film) is generally to correct the phase difference generated by the liquid crystal at different viewing angles, so that the birefringence properties of the liquid crystal molecules are compensated for symmetry. Different compensation modes are used for different liquid crystal display modes.
  • the compensation film used for large-size LCD TVs is mostly for VA display mode.
  • Konica's N-TAC was used in the early days, and later developed into OPOTES's Zeonor, Fujitsu.
  • the display device includes a VA (Vertical).
  • the Alignment, vertically aligning) the liquid crystal cell 300 and the optical compensation structure further include a front side polarizing plate 100 and a back side polarizing plate 200 disposed on both sides of the VA liquid crystal cell 300.
  • the front side polarizing plate setting 100 includes a front side polarizing unit 110 and a front side polarizing unit 110 on a side of a light emitting direction of the VA liquid crystal cell 300 (herein, a light direction is defined as a direction in which the backlight 400 is directed to the observer 500).
  • the second front side TAC film 120 is interposed with the VA liquid crystal cell 300.
  • the back side polarizing plate 200 includes a back side polarizing unit 220 and a back side biaxial film 210 disposed between the back side polarizing unit 220 and the VA liquid crystal cell 300, the back side biaxial compensation film 210 having both a retardation film and The role of the protective film.
  • the viewing angle of a liquid crystal display device (such as a liquid crystal TV) (view Angle) is called the range of angle of view, including the horizontal view angle and the vertical view angle.
  • the horizontal view angle is based on the vertical normal of the liquid crystal cell, and is at a certain angle perpendicular to the left or right of the normal. The display image can still be seen normally, and this angle range is the horizontal viewing angle of the liquid crystal display device.
  • the horizontal normal of the liquid crystal cell is taken as the standard, the viewing angle of the upper and lower sides is called the vertical viewing angle.
  • the horizontal normal 300a of the VA liquid crystal cell is used as a reference to calibrate the direction.
  • the absorption axis 110a of the front side polarization unit 110 is parallel to the horizontal normal 300a
  • the slow axis 120a of the second front side TAC film 120 is perpendicular to the horizontal normal 300a
  • the back front side polarization unit 220 is The absorption axis 220a is perpendicular to the horizontal normal 300a
  • the slow axis 210a of the back side biaxial compensation film 210 is perpendicular to the horizontal normal 300a.
  • the optical compensation structure described above includes a double-axis compensation film (back side double-axis compensation film 210), and thus is also generally referred to as a single-layer two-axis compensation film compensation structure.
  • the currently common solution is to replace the above-described single-layer biaxial compensation film compensation structure with a double-layered biaxial compensation film compensation structure.
  • the original second front side TAC film 120 is replaced with a biaxial compensation film, so that the front side polarizing plate 100 and the back side polarizing plate 200 are both belts.
  • a polarizing plate of a biaxial retardation film is replaced with a biaxial retardation film.
  • the dark angle of these dark states is between the horizontal and vertical angles of view. Generally, the contrast and sharpness of the horizontal viewing angle have the greatest influence on the viewing effect, while the large viewing angle (close to the vertical viewing angle) has less influence on the viewer because it is not easily seen. It can be seen that the double-layer double-axis compensation film compensation structure can improve the viewing effect.
  • FIGS. 4 and 5 respectively show a full-view contrast distribution diagram of the single-layer biaxial compensation film compensation structure and the double-layer biaxial compensation film compensation structure.
  • the double-layer dual-axis in FIG. The contrast of the compensation film compensation structure near the horizontal viewing angle is significantly increased compared with the contrast of the single-layer biaxial compensation film compensation structure in FIG. 4, and the display effect is further improved.
  • the double-layered biaxial compensation film compensation structure improves the display effect
  • the use of the double-layered dual-axis compensation film will increase the cost of the display device, making the display device thus prepared at a disadvantage in the market competition.
  • the technical problem to be solved by the present invention is to provide a display device for the defect that the display device of the prior art has low contrast in the vicinity of the horizontal viewing angle.
  • the technical solution adopted by the present invention to solve the technical problem thereof is to provide a display device including a VA liquid crystal display unit and front side polarizing plates and back side polarizing plates respectively disposed on both sides of the VA liquid crystal display unit;
  • the VA liquid crystal display unit has an optical path difference ⁇ nd at a wavelength of 550 nm of 305.8 nm to 324.3 nm;
  • the front side polarizing plate is disposed on a side of a light emitting direction of the VA liquid crystal cell
  • One of the front side polarizing plate and the back side polarizing plate includes a biaxial compensation film having an in-plane retardation Ro of 50.4 to 78 nm at a wavelength of 550 nm and a thickness direction retardation at a wavelength of 550 nm Rth-b is 168 to 260 nm.
  • the front side polarizing plate includes a front side polarizing unit and the biaxial compensation film disposed between the front side polarizing unit and the VA liquid crystal unit;
  • the back side polarizing plate includes a back side polarizing unit and a first back side TAC film disposed between the back side polarizing unit and the VA liquid crystal cell.
  • the minimum value Y1 and the maximum value Y2 of the thickness direction retardation Rth-t of the first back side TAC film at a wavelength of 550 nm are respectively defined by the following formula:
  • the front side polarization unit includes a first front side TAC film and a front side PVA film disposed between the first front side TAC film and the biaxial compensation film; among them,
  • An absorption axis of the front side PVA film is perpendicular to a slow axis of the biaxial compensation film; a slow axis of the first front side TAC film is parallel to a slow axis of the biaxial compensation film; the front side polarization unit The absorption axis is parallel to the horizontal normal of the VA liquid crystal cell.
  • the back side polarization unit includes a second back side TAC film and a back side PVA disposed between the second back side TAC film and the first back side TAC film Membrane;
  • An absorption axis of the back side PVA film is perpendicular to an absorption axis of the front side PVA film; an absorption axis of the back side PVA film is perpendicular to a slow axis of the first back side TAC film, and the second back side TAC film
  • the slow axis is parallel to the slow axis of the first back side TAC film; the absorption axis of the back side polarizing unit is perpendicular to the horizontal normal of the VA liquid crystal cell.
  • the front side polarizing plate includes a front side polarizing unit and a second front side TAC film disposed between the front side polarizing unit and the VA liquid crystal unit; an absorption axis of the front side polarizing unit and the VA liquid crystal The horizontal normal of the unit is vertical;
  • the back side polarizing plate includes a back side polarizing unit and the biaxial compensation film disposed between the back side polarizing unit and the VA liquid crystal cell; an absorption axis of the back side polarizing unit and the horizontal method The lines are parallel.
  • the minimum value Y1 and the maximum value Y2 of the thickness direction retardation Rth-t of the second front side TAC film at a wavelength of 550 nm are respectively defined by the following formula:
  • the front side polarization unit includes a first front side TAC film and a front side PVA disposed between the first front side TAC film and the second front side TAC film Membrane;
  • the absorption axis of the front side PVA film is perpendicular to the slow axis of the second front side TAC film, and the slow axis of the first front side TAC film is parallel to the slow axis of the second front side TAC film.
  • the back side polarization unit includes a second back side TAC film and a back side PVA film disposed between the second back side TAC film and the biaxial compensation film; among them,
  • the absorption axis of the back side PVA film is perpendicular to the slow axis of the biaxial compensation film, and the second back side TAC film is parallel to the slow axis of the biaxial compensation film.
  • the VA liquid crystal cell is a multi-quadrant liquid crystal cell.
  • the beneficial effects produced by the invention are: by setting a suitable delay value of the biaxial compensation film in the display device, the light leakage amount is significantly reduced compared with the existing single layer double-axis compensation film compensation structure, and the contrast close to the horizontal viewing angle is obvious The increase in display has been further improved.
  • Figure 1 shows an exploded view of a display device of the prior art
  • FIG. 2 illustrates an iso-luminance profile depicting a dark state light leakage profile of a single layer dual axis compensation film compensation structure
  • FIG. 3 shows an iso-luminance profile depicting a dark state light leakage distribution of a two-layer biaxial compensation film compensation structure
  • FIG. 4 shows an iso-contrast profile depicting a full view of a single layer dual axis compensation film compensation structure
  • Figure 5 shows an iso-contrast profile depicting a full view of a two-layer dual-axis compensation film compensation structure
  • FIG. 6 is a schematic structural view of a display device according to a first embodiment of the present invention.
  • FIG. 7 shows an exploded view of the front side polarizing plate 400 exemplified in FIG. 6;
  • FIG. 8 shows an exploded view of the back side polarizing plate 500 exemplified in FIG. 6;
  • Figure 9 shows an iso-luminance profile depicting the dark state light leakage distribution of the display device of Figure 6;
  • Figure 10 is a graph showing the amount of light leakage of the display device of Figure 6 as a function of the delay value
  • Figure 11 is a graph showing the amount of light leakage of the display device of Figure 6 as a function of the delay value
  • FIG. 12 is an isometric profile view depicting a dark state light leakage distribution after the display device of FIG. 6 employs a delay value in accordance with an embodiment of the present invention
  • FIG. 13 shows an iso-contrast profile depicting a full viewing angle after the display device of FIG. 6 employs a delay value in accordance with an embodiment of the present invention
  • FIG. 14 is a schematic structural view of a display device according to a second embodiment of the present invention.
  • Figure 15 shows an exploded view of the front side polarizing plate 100 exemplified in Figure 14;
  • FIG. 16 shows an exploded view of the back side polarizing plate 200 exemplified in FIG.
  • back side and front side are used in this application to refer to the nomenclature used for convenience of description, wherein the “back side” refers to being located between the liquid crystal cell and the backlight, “front side” “Side” refers to being located between the liquid crystal cell and the observer, or the other side of the liquid crystal cell relative to the backlight.
  • the direction of light is defined here as the direction in which the backlight is directed at the observer. It is to be understood that the various terms of the above are used for convenience of description and not limitation of the invention.
  • a display device includes a VA liquid crystal display unit and front side polarizing plates and back side polarizing plates respectively disposed on both sides of the VA liquid crystal display unit.
  • the optical path difference ⁇ nd of the VA liquid crystal display unit at a wavelength of 550 nm is 305.8 nm to 324.3 nm; the front side polarizing plate is disposed on the light emitting direction side of the VA liquid crystal cell; and one of the front side polarizing plate and the back side polarizing plate Including the biaxial compensation film, the in-plane retardation Ro of the biaxial compensation film at a wavelength of 550 nm is 50.4 to 78 nm, and the thickness direction retardation Rth-b at a wavelength of 550 nm is 168 to 260 nm.
  • Fig. 6 is a view showing the configuration of a display device according to a first embodiment of the present invention, including a front side polarizing plate 400 and a back side polarizing plate 500 which are disposed on both sides of the VA liquid crystal cell 300.
  • the front side polarizing plate 400 is disposed on the side of the light emitting direction of the VA liquid crystal cell 300 (shown by an arrow in FIG. 6), and includes a front side polarizing unit 410 and a front side polarizing unit 410 and a VA liquid crystal unit 300.
  • the front side biaxial compensation film 420 is disposed on the side of the light emitting direction of the VA liquid crystal cell 300 (shown by an arrow in FIG. 6), and includes a front side polarizing unit 410 and a front side polarizing unit 410 and a VA liquid crystal unit 300.
  • the back side polarizing plate 500 includes a back side polarizing unit 520 and a first back side TAC film 510 disposed between the back side polarizing unit 520 and the VA liquid crystal unit 300.
  • the absorption axis 410a of the front side polarization unit 410 is parallel to the horizontal normal line 300a; and the absorption axis 520a of the back front side polarization unit 520 is perpendicular to the horizontal normal line 300a.
  • the slow axis of the front side biaxial compensation film 420 is perpendicular to the absorption axis of the front side polarization unit 410; the slow axis of the first back side TAC film 510 is perpendicular to the absorption axis of the back side polarization unit 520.
  • FIG. 7 shows an exploded view of the front side polarizing plate 400 illustrated in FIG. 6, the front side polarizing unit of the front side polarizing plate 400 including a first front side TAC film 411 and a first front side TAC. a front side PVA film 412 between the film 411 and the front side biaxial compensation film 420; wherein the slow axis 411a of the first front side TAC film 411 is perpendicular to the absorption axis 412a of the front side PVA film 412, and the first front side The slow axis 411a of the TAC film 411 is parallel to the slow axis 420a of the front side biaxial compensation film 420.
  • FIG. 8 shows an exploded view of the back side polarizing plate 500 exemplified in FIG. 6, which includes a second back side TAC film 522 and a second back side TAC film 522 and a first back side TAC film.
  • the back side PVA film 521 between 510.
  • the absorption axis 521a of the back side PVA film 521 is perpendicular to the absorption axis 412a of the front side PVA film 412, and the slow axis 522a of the second back side TAC film 522 is parallel to the slow axis 510a of the first back side TAC film 510, and
  • the absorption axis 521a of the back side PVA film 521 is perpendicular.
  • the display device only needs to use a double-axis compensation film 420 compared with the existing double-layer biaxial compensation film compensation structure; and the existing single-layer double-axis compensation film.
  • the biaxial compensation film 420 employed is disposed between the front side polarization unit and the liquid crystal cell, and is no longer disposed between the liquid crystal cell and the back side polarization unit.
  • the light leakage is serious.
  • the dark region where the light leakage is severe is close to the vertical vertical viewing angle, and the dark state leakage near the horizontal viewing angle is significantly reduced, so that It can effectively improve the contrast and sharpness of the near horizontal view.
  • the cost is not improved.
  • each optical film in the display device will be described below by taking this embodiment as an example.
  • the retardation value of the biaxial compensation film 420 is further adjusted, or the biaxial compensation film 420 and the first back side are further adjusted at the same time.
  • the retardation value of the TAC film 510 In the course of the simulation, the display device is exemplified by the structure in FIGS. 6-8, but it should be understood that the structure is only used as an example and is not a limitation of the present invention. It is confirmed by simulation that the delay value thus obtained is also the same.
  • a corresponding optical film suitable for other display devices for example, the retardation value of the front side biaxial compensation film 420 obtained herein is also applicable to the biaxial compensation film of other display devices according to the present invention
  • the pretilt angle of the VA liquid crystal cell 300 is 85° to 90°, but not including 90°
  • the liquid crystal azimuth pretwist in the four quadrants is 45°, 135°, 225°, and 315°, respectively
  • the optical path difference LC of the liquid crystal cell ⁇ nd is in the (305.8, 342.3) nm range, at this time corresponding to the wavelength of 550nm
  • the light source uses blue-YAG (Yttrium Aluminum) Garnet) LED spectrum, the central brightness is defined as 100 nit, and the light source distribution is the Lambert distribution.
  • the retardation values of the front side biaxial compensation film 420 and the first back side TAC film 510 have a different influence on the dark state light leakage at different pretilt angles. That is, under different pretilt angles, the corresponding delay value range is the same when the dark state light leakage is minimum.
  • the retardation Ro is 50.4 to 78 nm
  • the thickness direction retardation Rth-b at the wavelength of 550 nm is 168 to 260 nm
  • the first back side TAC film 510 is retarded in the thickness direction at the wavelength of 550 nm.
  • the minimum value Y1 and the maximum value Y2 of the Rth-t are respectively Limited by formulas (1) and (2):
  • Nx and Ny are the in-plane refractive indices of the front side biaxial compensation film 420, and Nz is the thickness refraction index.
  • the dark state light leakage of the display device is improved near the vertical viewing angle, and the light leakage range is concentrated in a small viewing angle range.
  • the amount of light leakage is significantly lower than that of the prior art single-layer biaxial compensation film compensation structure.
  • FIG. 13 is a view showing a full-view contrast distribution diagram of the display device (the same display device in FIG. 12) according to an embodiment of the present invention, compared with FIG. 4, the display device has a contrast ratio close to a horizontal viewing angle.
  • the single-layer biaxial compensation film compensation structure has a significant increase in contrast near the horizontal viewing angle, and the display effect is further improved.
  • Fig. 14 shows a display device according to a second embodiment of the present invention, including a front side polarizing plate 100 and a back side polarizing plate 200 which are disposed on both sides of the VA liquid crystal cell 300.
  • the front side polarizing plate 100 is disposed on the side of the light emitting direction of the VA liquid crystal cell 300 (herein, the light direction is defined as the direction in which the backlight 400 is directed to the observer 500), and includes a front side polarizing unit 110 and a front side polarizing unit 110.
  • the second front side TAC film 120 is interposed with the VA liquid crystal cell 300.
  • the back side polarizing plate 200 includes a back side polarizing unit 220 and a back side biaxial compensation film 210 disposed between the back side polarizing unit 220 and the VA liquid crystal unit 300.
  • the slow axis 120a of the second front side TAC film 120 is perpendicular to the absorption axis of the front side polarization unit 110; the slow axis 210a of the biaxial compensation film 210 is perpendicular to the absorption axis of the back side polarization unit 220.
  • the absorption axis 110a of the front side polarization unit 110 is perpendicular to the horizontal normal 300a of the VA liquid crystal cell 300;
  • the absorption axis 220a of the polarization unit 220 is parallel to the horizontal normal 300a.
  • the absorption axis 110a of the front side polarization unit 110 and the absorption axis 220a of the back side polarization unit 220 of the display device according to the embodiment of the present invention are both deflected with respect to the single-layer biaxial compensation film compensation structure of the prior art. 90°.
  • FIG. 15 shows an exploded view of the front side polarizing plate 100 illustrated in FIG. 14, the front side polarizing unit of the front side polarizing plate 100 includes a first front side TAC film 111 and a first front side TAC. a front side PVA film 112 between the film 111 and the second front side TAC film 120; wherein the absorption axis 112a of the front side PVA film 112 is perpendicular to the horizontal normal 300a, and the slow axis 111a and the front side of the first front side TAC film 111 The absorption axis 112a of the side PVA film 112 is perpendicular, and the slow axis 111a of the first front side TAC film 111 is parallel to the slow axis 120a of the second front side TAC film 120.
  • FIG. 16 shows an exploded view of the back side polarizing plate 200 exemplified in FIG. 14, which includes a second back side TAC film 222 and a second back side TAC film 222 and a back side biaxial compensation film.
  • the back side PVA film 221 between 210.
  • the absorption axis 221a of the back side PVA film 221 is parallel to the horizontal normal line 300a, and the slow axis 222a of the second back side TAC film 222 is parallel to the slow axis 210a of the back side biaxial compensation film 210, and to the back side PVA film 221
  • the absorption axis 221a is vertical.
  • the in-plane retardation Ro of the back side double-axis compensation film 210 at a wavelength of 550 nm is also taken as 50.4 to 78 nm
  • the thickness direction retardation Rth-b at a wavelength of 550 nm is also taken as 168 to 260 nm
  • the minimum value Y1 and the maximum value Y2 of the thickness direction direction retardation Rth-t of the front side TAC film 120 at the wavelength of 550 nm are also defined by the formulas (1) and (2), respectively:
  • the dark state light leakage of the improved display device is concentrated near the vertical viewing angle, the light leakage range is concentrated in a small viewing angle range, and the light leakage amount is significantly lower than that of the prior art single layer double
  • the shaft compensation film compensates for the dark state light leakage caused by the structure.
  • the display device also has a significant increase in contrast near the horizontal viewing angle, and the display effect is further improved.
  • TAC triacetate cellulose
  • PVA polyvinyl alcohol
  • biaxial film used in the present application may be any commercially available products of any type, here No longer listed in detail.
  • the display device by replacing the existing front side TAC film with a biaxial compensation film in the front side polarizing plate, and using the TAC film in the back side polarizing plate, Some biaxial compensation films can shift the dark region with serious light leakage from the near horizontal angle to the near vertical angle. Compared with the existing single layer double-axis compensation film compensation structure, the display effect is improved.
  • the display device by shifting the absorption axis of the front side polarization unit and the absorption axis of the back side polarization unit by 90 degrees, it is possible to shift the dark region where the light leakage is severe from the horizontal angle to the vertical direction.
  • the viewing angle is improved compared to the existing single-layer dual-axis compensation film compensation structure.
  • the number of layers of the biaxial compensation film is not increased, and only a single layer double-axis compensation film is used, which reduces the cost compared with the existing double-layer double-axis compensation film compensation structure.

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  • Physics & Mathematics (AREA)
  • Nonlinear Science (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Mathematical Physics (AREA)
  • Chemical & Material Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Liquid Crystal (AREA)
  • Polarising Elements (AREA)

Abstract

一种显示装置，包括VA液晶显示单元（300）以及分别设置在VA液晶显示单元（300）两侧的正面侧偏振片（400）和背面侧偏振片（500）；其中，VA液晶显示单元（300）在波长550nm处的光程差And为305.8nm至324.3nm；正面侧偏振片（400）设置在VA液晶显示单元（300）的出光方向一侧；正面侧偏振片（400）和背面侧偏振片（500）中的一个包括双轴补偿膜（420），双轴补偿膜（420）在波长550nm处的面内延迟Ro为50.4〜78nm，在波长550nm处的厚度方向延迟Rth-b为168〜260nm。通过在显示装置中设置双轴补偿膜（420）合适的延迟值，较之现有的单层双轴补偿膜补偿结构，漏光量明显降低，接近水平视角的对比度有了明显的增加，显示效果得到了进一步的提高。

Description

显示装置 技术领域
本发明涉及液晶显示，尤其涉及一种用于VA显示模式的显示装置。
背景技术
随着TFT-LCD的观察角度增大，画面的对比度不断降低，画面的清晰度下降。这是液晶层中液晶分子的双折射率随观察角度变化发生改变的结果，采用宽视角补偿膜进行补偿，可以有效降低暗态画面的漏光，在一定视角内能大幅度提高画面的对比度。补偿膜（或称为延迟膜）的补偿原理一般是将液晶在不同视角产生的相位差进行修正，让液晶分子的双折射性质得到对称性的补偿。针对不同的液晶显示模式，使用的补偿膜也不同，大尺寸液晶电视使用的补偿膜大多是针对VA显示模式，早期使用的有Konica公司的N-TAC，后来不断发展形成OPOTES公司的Zeonor，富士通的F-TAC系列，日东电工的X-plate等。
图1示出了现有技术中显示装置的爆炸图，如图1所示，该显示装置包括VA（Vertical Alignment，垂直排列）液晶单元300和光学补偿结构，该光学补偿结构进一步包括设置在VA液晶单元300两侧的正面侧偏振片100和背面侧偏振片200。其中，正面侧偏振片设置100在VA液晶单元300的出光方向（此处定义出光方向为背光源400指向观测者500的方向）一侧，包括正面侧偏振单元110和设置在正面侧偏振单元110与VA液晶单元300之间的第二正面侧TAC膜120。背面侧偏振片200包括背面侧偏振单元220和设置在背面侧偏振单元220与VA液晶单元300之间的背面侧双轴（Biaxial）膜210，该背面侧双轴补偿膜210兼具延迟膜和保护膜的作用。
通常情况下将液晶显示装置（例如液晶电视）的可视角度（view angle）称为视角范围，包括水平可视角度和垂直可视角度两个指标，水平可视角度表示以液晶单元的垂直法线为准，在垂直于法线左或右方一定角度的位置上仍然能够正常的看见显示图像，这个角度范围就是液晶显示装置的水平可视角度。同理如果以液晶单元的水平法线为准，上下的可视角度就称为垂直可视角度。在本申请中为了描述方便，使用VA液晶单元的水平法线300a作为参照来标定方向。
在现有的光学补偿结构中，正面侧偏振单元110的吸收轴110a与水平法线300a平行，第二正面侧TAC膜120的慢轴120a与水平法线300a垂直；背正面侧偏振单元220的吸收轴220a与水平法线300a垂直，背面侧双轴补偿膜210的慢轴210a与水平法线300a垂直。
上述光学补偿结构包括一层双轴补偿膜（背面侧双轴补偿膜210），因此通常也称之为单层双轴补偿膜补偿结构。图2示出了单层双轴补偿膜补偿结构的暗态漏光分布图，从图2可以看出单层双轴补偿膜补偿结构的全视角暗态漏光分布，可知在phi=200-400，phi=1400-1600，phi=2000-2200,phi=3100-3300漏光严重，即接近水平位置的视角暗态漏光严重。然而，观众与液晶显示装置的相对位置决定了接近水平的视角更容易被观众看到，所以水平视角的对比度和清晰度对观看效果的影响最大。
为了解决上述问题，目前常用的解决方案是用双层双轴补偿膜补偿结构来替换上述的单层双轴补偿膜补偿结构。仍如图1所示，在双层双轴补偿膜补偿结构中，采用双轴补偿膜替换原有的第二正面侧TAC膜120，使得正面侧偏振片100和背面侧偏振片200均为带双轴延迟膜的偏振片。
图3示出了双层双轴补偿膜补偿结构的暗态漏光分布图，从图3可以看出双层双轴补偿膜补偿结构的全视角暗态漏光分布，可知在phi=300-600，phi=1200-1500，phi=2100-2400，phi=3000-3300漏光较为严重，这些暗态漏光严重的视角介于水平与垂直视角之间。通常水平视角的对比度和清晰度对观看效果的影响最大，而大视角（接近垂直视角）因为不容易被看到，对观众的影响较小。由此可以看出，采用双层双轴补偿膜补偿结构可以提高观看效果。
另外，图4和5分别示出了单层双轴补偿膜补偿结构和双层双轴补偿膜补偿结构的全视角对比度分布图，从图4和5可以看出，图5中双层双轴补偿膜补偿结构在接近水平视角的对比度较之图4中单层双轴补偿膜补偿结构在接近水平视角的对比度有了明显的增加，显示效果得到了进一步的提高。
然而，双层双轴补偿膜补偿结构虽然提高了显示效果，但是采用双层双轴补偿膜将提高显示装置的成本，使得由此制备的显示装置在市场竞争中处于劣势。
发明内容
本发明要解决的技术问题在于针对现有技术中显示装置在水平视角附近对比度不高的缺陷，提供一种显示装置。
本发明解决其技术问题所采用的技术方案是：提供一种显示装置，包括VA液晶显示单元以及分别设置在所述VA液晶显示单元两侧的正面侧偏振片和背面侧偏振片；其中，
所述VA液晶显示单元在波长550nm处的光程差△nd为305.8nm至324.3nm；
所述正面侧偏振片设置在所述VA液晶单元的出光方向一侧；
所述正面侧偏振片和所述背面侧偏振片中的一个包括双轴补偿膜，所述双轴补偿膜在波长550nm处的面内延迟Ro为50.4～78nm，在波长550nm处的厚度方向延迟Rth-b为168～260nm。
在依据本发明实施例的显示装置中，
所述正面侧偏振片包括正面侧偏振单元和设置在所述正面侧偏振单元与所述VA液晶单元之间的所述双轴补偿膜；
所述背面侧偏振片包括背面侧偏振单元和设置在所述背面侧偏振单元与所述VA液晶单元之间的第一背面侧TAC膜。
在依据本发明实施例的显示装置中，所述第一背面侧TAC膜在波长550nm处的厚度方向延迟Rth-t的最小值Y1和最大值Y2分别通过以下公式限定：
Y1=0.0041×Rth-b2 - 2.6179×Rth-b + 408.46，
Y2=-0.0009×Rth-b2 - 0.5472×Rth-b + 244.95。
在依据本发明实施例的显示装置中，所述正面侧偏振单元包括第一正面侧TAC膜和设置在所述第一正面侧TAC膜与所述双轴补偿膜之间的正面侧PVA膜；其中，
所述正面侧PVA膜的吸收轴与所述双轴补偿膜的慢轴垂直；所述第一正面侧TAC膜的慢轴与所述双轴补偿膜的慢轴平行；所述正面侧偏振单元的吸收轴与所述VA液晶单元的水平法线平行。
在依据本发明实施例的显示装置中，所述背面侧偏振单元包括第二背面侧TAC膜和设置在所述第二背面侧TAC膜与所述第一背面侧TAC膜之间的背面侧PVA膜；其中，
所述背面侧PVA膜的吸收轴与所述正面侧PVA膜的吸收轴垂直；所述背面侧PVA膜的吸收轴与第一背面侧TAC膜的慢轴垂直，所述第二背面侧TAC膜的慢轴与所述第一背面侧TAC膜的慢轴平行；所述背面侧偏振单元的吸收轴与所述VA液晶单元的水平法线垂直。
在依据本发明实施例的显示装置中，
所述正面侧偏振片包括正面侧偏振单元和设置在所述正面侧偏振单元与所述VA液晶单元之间的第二正面侧TAC膜；所述正面侧偏振单元的吸收轴与所述VA液晶单元的水平法线垂直；
所述背面侧偏振片包括背面侧偏振单元和设置在所述背面侧偏振单元与所述VA液晶单元之间的所述双轴补偿膜；所述背面侧偏振单元的吸收轴与所述水平法线平行。
在依据本发明实施例的显示装置中，所述第二正面侧TAC膜在波长550nm处的厚度方向延迟Rth-t的最小值Y1和最大值Y2分别通过以下公式限定：
Y1=0.0041×Rth-b2 - 2.6179×Rth-b + 408.46，
Y2=-0.0009×Rth-b2 - 0.5472×Rth-b + 244.95。
在依据本发明实施例的显示装置中，所述正面侧偏振单元包括第一正面侧TAC膜和设置在所述第一正面侧TAC膜与所述第二正面侧TAC膜之间的正面侧PVA膜；其中，
所述正面侧PVA膜的吸收轴与所述第二正面侧TAC膜的慢轴垂直，所述第一正面侧TAC膜的慢轴与所述第二正面侧TAC膜的慢轴平行。
在依据本发明实施例的显示装置中，所述背面侧偏振单元包括第二背面侧TAC膜和设置在所述第二背面侧TAC膜与所述双轴补偿膜之间的背面侧PVA膜；其中，
所述背面侧PVA膜的吸收轴与所述双轴补偿膜的慢轴垂直，所述第二背面侧TAC膜与所述双轴补偿膜的慢轴平行。
在依据本发明实施例的显示装置中，所述VA液晶单元是多象限的液晶单元。
本发明产生的有益效果是：通过在显示装置中设置双轴补偿膜合适的延迟值，较之现有的单层双轴补偿膜补偿结构，漏光量明显降低，接近水平视角的对比度有了明显的增加，显示效果得到了进一步的提高。
附图说明
下面将结合附图及实施例对本发明作进一步说明，附图中：
图1示出了现有技术中显示装置的爆炸图；
图2示出了描绘单层双轴补偿膜补偿结构的暗态漏光分布的等亮度轮廓图；
图3示出了描绘双层双轴补偿膜补偿结构的暗态漏光分布的等亮度轮廓图；
图4示出了描绘单层双轴补偿膜补偿结构的全视角的等对比度轮廓图；
图5示出了描述双层双轴补偿膜补偿结构的全视角的等对比度轮廓图；
图6示出了依据本发明第一实施例的显示装置的结构示意图；
图7示出了图6中示例的正面侧偏振片400的爆炸图；
图8示出了图6中示例的背面侧偏振片500的爆炸图；
图9示出了描绘图6中显示装置的暗态漏光分布的等亮度轮廓图；
图10示出了图6中显示装置的漏光量随延迟值的变化曲线；
图11示出了图6中显示装置的漏光量随延迟值的变化曲线；
图12示出了描绘图6中的显示装置采用了依据本发明实施例的延迟值后的暗态漏光分布的等亮度轮廓图；
图13示出了描绘图6中的显示装置采用了依据本发明实施例的延迟值后的全视角的等对比度轮廓图；
图14示出了依据本发明第二实施例的显示装置的结构示意图；
图15示出了图14中示例的正面侧偏振片100的爆炸图；
图16示出了图14中示例的背面侧偏振片200的爆炸图。
具体实施方式
为了使本发明的目的、技术方案及优点更加清楚明白，以下结合附图及实施例，对本发明进行进一步详细说明。应当理解，此处所描述的具体实施例仅用以解释本发明，并不用于限定本发明。
在本申请中用到了术语“背面侧”和“正面侧”，其是为了描述方便所采用的方位名词，其中所述的“背面侧”指的是位于液晶单元和背光源之间，“正面侧”指的是位于液晶单元和观测者之间，或者是液晶单元相对背光源的另一侧。另外，此处定义出光方向为背光源指向观测者的方向。应当理解的是，以上所采用的各个术语仅仅是为了描述方便，并不是对发明的限制。
依据本发明实施例的显示装置包括VA液晶显示单元以及分别设置在VA液晶显示单元两侧的正面侧偏振片和背面侧偏振片。其中，VA液晶显示单元在波长550nm处的光程差△nd为305.8nm至324.3nm；正面侧偏振片设置在VA液晶单元的出光方向一侧；正面侧偏振片和背面侧偏振片中的一个包括双轴补偿膜，双轴补偿膜在波长550nm处的面内延迟Ro为50.4～78nm，在波长550nm处的厚度方向延迟Rth-b为168～260nm。
图6示出了依据本发明第一实施例的显示装置的结构示意图，包括设置在VA液晶单元300两侧的正面侧偏振片400和背面侧偏振片500。其中，正面侧偏振片400设置在VA液晶单元300的出光方向（如图6中箭头所示）一侧，包括正面侧偏振单元410和设置在正面侧偏振单元410与VA液晶单元300之间的正面侧双轴补偿膜420。背面侧偏振片500包括背面侧偏振单元520和设置在背面侧偏振单元520与VA液晶单元300之间的第一背面侧TAC膜510。其中，正面侧偏振单元410的吸收轴410a与水平法线300a平行；背正面侧偏振单元520的吸收轴520a与水平法线300a垂直。
优选地，正面侧双轴补偿膜420的慢轴与正面侧偏振单元410的吸收轴垂直；第一背面侧TAC膜510的慢轴与背面侧偏振单元520的吸收轴垂直。
具体而言，图7示出了图6中示例的正面侧偏振片400的爆炸图，该正面侧偏振片400的正面侧偏振单元包括第一正面侧TAC膜411和设置在第一正面侧TAC膜411与正面侧双轴补偿膜420之间的正面侧PVA膜412；其中，第一正面侧TAC膜411的慢轴411a与正面侧PVA膜412的吸收轴412a垂直，并且，第一正面侧TAC膜411的慢轴411a与正面侧双轴补偿膜420的慢轴420a平行。
图8示出了图6中示例的背面侧偏振片500的爆炸图，该背面侧偏振单元520包括第二背面侧TAC膜522和设置在第二背面侧TAC膜522与第一背面侧TAC膜510之间的背面侧PVA膜521。其中，背面侧PVA膜521的吸收轴521a与正面侧PVA膜412的吸收轴412a垂直，第二背面侧TAC膜522的慢轴522a与第一背面侧TAC膜510的慢轴510a平行，且与背面侧PVA膜521的吸收轴521a垂直。
从以上可以看出，依据本发明实施例的显示装置与现有的双层双轴补偿膜补偿结构相比，只需要采用一层双轴补偿膜420；与现有的单层双轴补偿膜补偿结构相比，所采用的双轴补偿膜420设置在正面侧偏振单元与液晶单元之间，而不再设置在液晶单元与背面侧偏振单元之间。图9示出了依据本发明实施例的该显示装置的暗态漏光分布图，从图9可以看出单层双轴补偿膜补偿结构的全视角暗态漏光分布，可知在phi=500-700，phi=1100-1300，phi=2300-2500，phi=2900-3100漏光严重。相比于图2中现有技术的单层双轴补偿膜补偿结构的暗态漏光分布图，暗态漏光严重的区域已经接近上下垂直视角，而接近水平视角的暗态漏光明显降低，这样就可以有效的提高接近水平视角的对比度和清晰度。与此同时，因为只需要一层双轴补偿膜420，因此成本并没有提高。
下面将以该实施例为例，描述显示装置中各光学膜片的延迟。在显示装置中，为了保证漏光集中在上下垂直视角附近，并且漏光量和漏光范围要尽量小，进一步调节双轴补偿膜420的延迟值，或者进一步同时调节双轴补偿膜420和第一背面侧TAC膜510的延迟值。在模拟的过程中，显示装置以图6-8中的结构为例，但是应当知晓的是，该结构仅用作举例，并不是对本发明的限制，通过模拟证实，由此获得的延迟值同样适用于其它显示装置的对应光学膜片，例如此处所获得的正面侧双轴补偿膜420的延迟值同样适用于依据本发明的其它显示装置的双轴补偿膜；VA液晶单元300的预倾角为85°到90°，但是不包括90°，在四个象限内的液晶方位角pretwist分别为45°、135°、225°以及315°，液晶单元的光程差LC △nd在（305.8, 342.3）nm区间，此时对应波长550nm处；光源使用蓝光-YAG（Yttrium Aluminum Garnet）LED光谱，中央亮度定义为100nit，光源分布为朗伯（Lambert）分布。
模拟结果例如如图10和11中的漏光量随延迟值的变化曲线所示，其中图10为LC △ND=305.8nm，预倾角为89°时，正面侧双轴补偿膜420的面内延迟Ro和厚度方向延迟Rth-b、以及第一背面侧TAC膜510的厚度方向延迟Rth-t取不同值时的漏光量变化曲线；图11为LC △ND=342.3nm，预倾角为89°时，正面侧双轴补偿膜420的面内延迟Ro和厚度方向延迟Rth-b、以及第一背面侧TAC膜510的厚度方向延迟Rth-t取不同值时的漏光量变化曲线。其中，图中的Biaxial Ro指代正面侧双轴补偿膜420的面内延迟Ro，Biaxial Rth指代双轴补偿膜420的厚度方向延迟Rth-b，TAC Rth指代第一背面侧TAC膜510的厚度方向延迟Rth-t。
在模拟中，发现不同预倾角下，正面侧双轴补偿膜420和第一背面侧TAC膜510的延迟值对暗态漏光的影响趋势是一致的。即不同预倾角下，暗态漏光最小时对应的延迟值范围是一样的。根据模拟结果可以获得LC △ND在（305.8, 342.3）nm区间，预倾角在（850-900）区间（不包括900），暗态漏光小于0.2nit（预倾角=890 时模拟出的暗态漏光值，非实测值）时对应的正面侧双轴补偿膜420和第一背面侧TAC膜510的延迟值范围：正面侧双轴补偿膜420在波长550nm处的面内延迟Ro为50.4～78nm，在波长550nm处的厚度方向延迟Rth-b为168～260nm；第一背面侧TAC膜510在波长550nm处的厚度方向延迟Rth-t的最小值Y1和最大值Y2分别通过公式（1）和（2）限定：
Y1=0.0041×Rth-b2 - 2.6179×Rth-b + 408.46 （1）
Y2=-0.0009×Rth-b2 - 0.5472×Rth-b + 244.95 （2）。
已知的，正面侧双轴补偿膜420的面内延迟Ro和厚度方向延迟Rth-b与其折射率和厚度d的关系满足公式（3）和（4）：
Ro=(Nx-Ny)×d （3）
Rth-b=[(Nx+Ny)/2-Nz]×d （4）
其中，Nx和Ny为正面侧双轴补偿膜420的平面内折射率，Nz为厚度折射率。这样，我们可以通过以下三种方法来改变延迟值：改变厚度d来改变延迟值；在厚度d不变的情况下，改变折射率来改变延迟值；同时改变厚度d和折射率来调节延迟值。
图12示出了依据本发明实施例的显示装置采用了依据本发明实施例的延迟值后的暗态漏光分布图，其中，LC △ND=315nm，预倾角为89°，双轴补偿膜的补偿值Ro为66nm，Rth-b为220nm，第一背面侧TAC膜510的补偿值Rth-t为59nm。相比于图2中现有技术的单层双轴补偿膜补偿结构的暗态漏光分布图，改善后显示装置的暗态漏光集中在垂直视角附近，漏光范围集中在较小的视角范围内，且漏光量明显低于现有技术的单层双轴补偿膜补偿结构造成的暗态漏光。
图13示出了示出了依据本发明实施例的该显示装置（图12中同样的显示装置）的全视角对比度分布图，与图4相比，该显示装置在接近水平视角的对比度较之图4中单层双轴补偿膜补偿结构在接近水平视角的对比度有了明显的增加，显示效果得到了进一步的提高。
图14示出了依据本发明第二实施例的显示装置，包括设置在VA液晶单元300两侧的正面侧偏振片100和背面侧偏振片200。其中，正面侧偏振片100设置在VA液晶单元300的出光方向（此处定义出光方向为背光源400指向观测者500的方向）一侧，包括正面侧偏振单元110和设置在正面侧偏振单元110与VA液晶单元300之间的第二正面侧TAC膜120。背面侧偏振片200包括背面侧偏振单元220和设置在背面侧偏振单元220与VA液晶单元300之间的背面侧双轴补偿膜210。优选地，第二正面侧TAC膜120的慢轴120a与正面侧偏振单元110的吸收轴垂直；双轴补偿膜210的慢轴210a与背面侧偏振单元220的吸收轴垂直。
不同于现有技术中的单层双轴补偿膜补偿结构，在依据本发明实施例的显示装置中，正面侧偏振单元110的吸收轴110a与VA液晶单元300的水平法线300a垂直；背面侧偏振单元220的吸收轴220a与水平法线300a平行。换句话说，相对于现有技术中的单层双轴补偿膜补偿结构，依据本发明实施例的显示装置的正面侧偏振单元110的吸收轴110a以及背面侧偏振单元220的吸收轴220a均偏转了90°。
具体而言，图15示出了图14中示例的正面侧偏振片100的爆炸图，该正面侧偏振片100的正面侧偏振单元包括第一正面侧TAC膜111和设置在第一正面侧TAC膜111与第二正面侧TAC膜120之间的正面侧PVA膜112；其中，正面侧PVA膜112的吸收轴112a与水平法线300a垂直，第一正面侧TAC膜111的慢轴111a与正面侧PVA膜112的吸收轴112a垂直，并且，第一正面侧TAC膜111的慢轴111a与第二正面侧TAC膜120的慢轴120a平行。
图16示出了图14中示例的背面侧偏振片200的爆炸图，该背面侧偏振单元220包括第二背面侧TAC膜222和设置在第二背面侧TAC膜222与背面侧双轴补偿膜210之间的背面侧PVA膜221。其中，背面侧PVA膜221的吸收轴221a与水平法线300a平行，第二背面侧TAC膜222的慢轴222a与背面双轴补偿膜210的慢轴210a平行，且与背面侧PVA膜221的吸收轴221a垂直。
另外，在本实施例中，背面侧双轴补偿膜210在波长550nm处的面内延迟Ro同样取为50.4～78nm，在波长550nm处的厚度方向延迟Rth-b同样取为168～260nm；第二正面侧TAC膜120在波长550nm处的厚度方向延迟Rth-t的最小值Y1和最大值Y2同样分别通过公式（1）和（2）限定：
Y1=0.0041×Rth-b2 - 2.6179×Rth-b + 408.46 （1）
Y2=-0.0009×Rth-b2 - 0.5472×Rth-b + 244.95 （2）。
同样经过模拟证实，在本实施例中，改善后的显示装置的暗态漏光集中在垂直视角附近，漏光范围集中在较小的视角范围内，且漏光量明显低于现有技术的单层双轴补偿膜补偿结构造成的暗态漏光。而且该显示装置同样在接近水平视角的对比度有了明显的增加，显示效果得到了进一步的提高。
应当理解的是，本申请中使用的TAC（三醋酸纤维素）膜、PVA（聚乙烯醇）膜、双轴（Biaxial）膜可采用现有的市面上可售的任意型号的产品，此处不再详细列举。
从以上可以看出，通过在显示装置中设置合适的延迟值，较之现有的单层双轴补偿膜补偿结构，漏光量明显降低，接近水平视角的对比度有了明显的增加，显示效果得到了进一步的提高。
具体而言，在依据本发明第一实施例的显示装置中，通过在正面侧偏振片中采用双轴补偿膜替代现有的正面侧TAC膜，以及在背面侧偏振片中采用TAC膜替代现有的双轴补偿膜，可以将暗态漏光严重的区域从接近水平的视角转移至接近垂直的视角，较之现有的单层双轴补偿膜补偿结构，提高了显示效果。在依据本发明第二实施例的显示装置中，通过将正面侧偏振单元的吸收轴以及背面侧偏振单元的吸收轴均偏转了90°，可以将暗态漏光严重的区域从水平视角转移至垂直视角，较之现有的单层双轴补偿膜补偿结构，提高了显示效果。与此同时，并没有增加双轴补偿膜的层数，仅采用单层双轴补偿膜，较之现有的双层双轴补偿膜补偿结构，降低了成本。
应当理解的是，对本领域普通技术人员来说，可以根据上述说明加以改进或变换，而所有这些改进和变换都应属于本发明所附权利要求的保护范围。

Claims (10)

  1. 一种显示装置，其特征在于，包括VA液晶显示单元以及分别设置在所述VA液晶显示单元两侧的正面侧偏振片和背面侧偏振片；其中，
    所述VA液晶显示单元在波长550nm处的光程差△nd为305.8nm至324.3nm；
    所述正面侧偏振片设置在所述VA液晶单元的出光方向一侧；
    所述正面侧偏振片和所述背面侧偏振片中的一个包括双轴补偿膜，所述双轴补偿膜在波长550nm处的面内延迟Ro为50.4～78nm，在波长550nm处的厚度方向延迟Rth-b为168～260nm。
  2. 根据权利要求1所述的显示装置，其特征在于，
    所述正面侧偏振片包括正面侧偏振单元和设置在所述正面侧偏振单元与所述VA液晶单元之间的所述双轴补偿膜；
    所述背面侧偏振片包括背面侧偏振单元和设置在所述背面侧偏振单元与所述VA液晶单元之间的第一背面侧TAC膜。
  3. 根据权利要求2所述的显示装置，其特征在于，所述第一背面侧TAC膜在波长550nm处的厚度方向延迟Rth-t的最小值Y1和最大值Y2分别通过以下公式限定：
    Y1=0.0041×Rth-b2 - 2.6179×Rth-b + 408.46，
    Y2=-0.0009×Rth-b2 - 0.5472×Rth-b + 244.95。
  4. 根据权利要求2所述的显示装置，其特征在于，所述正面侧偏振单元包括第一正面侧TAC膜和设置在所述第一正面侧TAC膜与所述双轴补偿膜之间的正面侧PVA膜；其中，
    所述正面侧PVA膜的吸收轴与所述双轴补偿膜的慢轴垂直；所述第一正面侧TAC膜的慢轴与所述双轴补偿膜的慢轴平行；所述正面侧偏振单元的吸收轴与所述VA液晶单元的水平法线平行。
  5. 根据权利要求2所述的显示装置，其特征在于，所述背面侧偏振单元包括第二背面侧TAC膜和设置在所述第二背面侧TAC膜与所述第一背面侧TAC膜之间的背面侧PVA膜；其中，所述背面侧PVA膜的吸收轴与所述正面侧PVA膜的吸收轴垂直；所述背面侧PVA膜的吸收轴与第一背面侧TAC膜的慢轴垂直，所述第二背面侧TAC膜的慢轴与所述第一背面侧TAC膜的慢轴平行；所述背面侧偏振单元的吸收轴与所述VA液晶单元的水平法线垂直。
  6. 根据权利要求1所述的显示装置，其特征在于，
    所述正面侧偏振片包括正面侧偏振单元和设置在所述正面侧偏振单元与所述VA液晶单元之间的第二正面侧TAC膜；所述正面侧偏振单元的吸收轴与所述VA液晶单元的水平法线垂直；
    所述背面侧偏振片包括背面侧偏振单元和设置在所述背面侧偏振单元与所述VA液晶单元之间的所述双轴补偿膜；所述背面侧偏振单元的吸收轴与所述水平法线平行。
  7. 根据权利要求6所述的显示装置，其特征在于，所述第二正面侧TAC膜在波长550nm处的厚度方向延迟Rth-t的最小值Y1和最大值Y2分别通过以下公式限定：
    Y1=0.0041×Rth-b2 - 2.6179×Rth-b + 408.46，
    Y2=-0.0009×Rth-b2 - 0.5472×Rth-b + 244.95。
  8. 根据权利要求6所述的显示装置，其特征在于，所述正面侧偏振单元包括第一正面侧TAC膜和设置在所述第一正面侧TAC膜与所述第二正面侧TAC膜之间的正面侧PVA膜；其中，
    所述正面侧PVA膜的吸收轴与所述第二正面侧TAC膜的慢轴垂直，所述第一正面侧TAC膜的慢轴与所述第二正面侧TAC膜的慢轴平行。
  9. 根据权利要求6所述的显示装置，其特征在于，所述背面侧偏振单元包括第二背面侧TAC膜和设置在所述第二背面侧TAC膜与所述双轴补偿膜之间的背面侧PVA膜；其中，
    所述背面侧PVA膜的吸收轴与所述双轴补偿膜的慢轴垂直，所述第二背面侧TAC膜与所述双轴补偿膜的慢轴平行。
  10. 根据权利要求1所述的显示装置，其特征在于，所述VA液晶单元是多象限的液晶单元。
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CN102798923A (zh) * 2012-08-23 2012-11-28 深圳市华星光电技术有限公司 光学补偿结构及显示装置

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