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WO1998035266A1 - Afficheur par cristaux liquides a plusieurs points d'image - Google Patents

Afficheur par cristaux liquides a plusieurs points d'image Download PDF

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Publication number
WO1998035266A1
WO1998035266A1 PCT/DE1998/000192 DE9800192W WO9835266A1 WO 1998035266 A1 WO1998035266 A1 WO 1998035266A1 DE 9800192 W DE9800192 W DE 9800192W WO 9835266 A1 WO9835266 A1 WO 9835266A1
Authority
WO
WIPO (PCT)
Prior art keywords
liquid crystal
crystal display
display according
layer
delay layer
Prior art date
Application number
PCT/DE1998/000192
Other languages
German (de)
English (en)
Inventor
Christina Heinmueller
Gunther Haas
Original Assignee
Robert Bosch Gmbh
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Robert Bosch Gmbh filed Critical Robert Bosch Gmbh
Priority to JP53353698A priority Critical patent/JP2001510586A/ja
Priority to EP98906830A priority patent/EP0958524A1/fr
Publication of WO1998035266A1 publication Critical patent/WO1998035266A1/fr

Links

Classifications

    • 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

Definitions

  • the invention relates to a liquid crystal display with a plurality of pixels consisting of a liquid crystal cell and polarizers according to the preamble of claim 1.
  • Liquid crystal displays have become known in a wide variety of embodiments. However, STN and TN liquid crystal cells are used most frequently. STN stands for Super Twisted Nematic and TN for Twisted Nematic.
  • Twisted Nemetic is intended to express the fact that a twisted nematic liquid crystal phase is used.
  • FIG. 3 a and 3 b The structure of a conventional TN display is shown in Figure 3 a and 3 b.
  • a liquid crystal is enclosed between two glass plates, each of which is coated with a transparent electrode.
  • the liquid crystal molecules are indicated by elongated rods. With the help of an orientation layer, the liquid crystal molecules are oriented in such a way that they are arranged in a helical manner, twisted by 90 °, between the substrates.
  • Polarizing filters are attached to the outside of the glass plates, the transmissive preferred direction of which is shown in FIG. 3 by a double arrow. Located on the side of the light the polarizer, on the side of the light exit the analyzer. In the voltage-free state of the cell shown in FIG.
  • the angle ⁇ has a value range from 0 to ax. 90 ° and shows how far the viewing angle is inclined out of the normal of the liquid crystal display.
  • the conoscope diagram provides a clear representation of the functions of ⁇ and ⁇ (cf. Fig. 5).
  • ⁇ and ⁇ cf. Fig. 5
  • Inclination angle ⁇ and the angle ⁇ are shown on a circular disk, where ⁇ corresponds to the radial component and ⁇ to the azimuth. Both the results for the grayscale inversion and the contrast values can now be entered in this diagram.
  • a region is generally defined as a suitable viewing angle region (cross-hatched and longitudinally hatched area in FIG. 5) in which a minimum contrast is not undershot (see. Cross-hatched area in FIG. 5) and additionally no grayscale inversion occurs (see FIG. 5, hatched area).
  • the boundary line of the contrast surface is referred to as the ISO contrast curve.
  • a conventional TN liquid crystal display without special measures only has a very narrow suitable viewing angle range (cross-hatched and longitudinally hatched area).
  • a compensation layer is proposed to enlarge the viewing angle range.
  • this comprises a discotic retardation film which is produced from a discotic liquid crystal.
  • Such a film is optically uniaxial, the ordinary refractive index n 0 being greater than the extraordinary one
  • the delay V R d R • (n e - n 0) negative (d R is the thickness of the film).
  • the retardation value of these films is equal in magnitude to the retardation value of the liquid crystal layer, but has the opposite sign.
  • the delay layer described in the application in addition to compensating for the birefringence by the beam material in the liquid crystal, compensates in particular for a birefringence caused by the liquid crystal edge molecules on the substrate surface of the liquid crystal cell, which have a certain angle of attack (pre-tilt) to the substrate surface.
  • the discotic retardation film must always be adapted to the orientation of the liquid crystal for a desired compensation effect. If such a film is applied between the cell and the polarizing filter, the suitable viewing angle range can be significantly improved.
  • Another possibility of improving the suitable viewing angle range is to compensate for the asymmetry in the viewing angle dependency of the contrast and with regard to the viewing angle dependency of the grayscale inversion (cf. FIG. 5).
  • This asymmetry is caused by the non-symmetrical alignment of the liquid crystal molecules.
  • One method of obtaining a symmetrical viewing angle range for the liquid crystal cell is to subdivide each pixel into two subpixels, each with an opposite orientation of the liquid crystal molecules, so that the viewing angle range of the first subpixel is rotated by 180 ° with respect to the viewing angle range of the second subpixel ( Figure 7, 2-domain method, KH Yang: Record 1991 Int. Display Res. Conf., San Diago, California).
  • each sub-pixel is given a different orientation, in which e.g. B. on a substrate side with diagonally adjacent sub-pixel regions, the liquid crystal edge molecules are oriented rotated by 180 ° relative to one another (cf. FIG. 10).
  • the technological effort with the 4-domain method is decidedly higher than with the 2-domain method, but a comparatively larger suitable viewing angle range can be achieved (see FIG. 11).
  • the object of the invention is to provide a liquid crystal display in which the largest possible viewing angle range is available, in which there is no gray level inversion and the contrast is above a minimum value (for example 10). This object is solved by the features of claim 1.
  • the invention is based on a liquid crystal display with several pixels, which consists of a liquid crystal cell and polarizers, which are arranged on the top and bottom of the liquid crystal cell, the liquid crystal cell comprising two substrates with transparent electrodes and a liquid crystal enclosed between them.
  • the essence of the invention lies in the fact that each pixel is divided into at least two subpixels in which the liquid crystal has different orientations and that at least between one polarizer and the liquid crystal there is an optically biaxial retardation layer with different refractive indices n e , n 0 , n 2 Compensation of viewing angle dependencies of optical properties of the liquid crystal display, such as. B. the transmission and contrast, is provided, the refractive index n 2 in a normal to
  • Liquid crystal cell substantially parallel axis occurs in the retardation layer.
  • the advantages of a "multi-domain method” can be combined with the advantages of a layer that compensates for birefringence in the liquid crystal cell. Due to the optical biaxial nature, the refractive behavior of the liquid crystal edge molecules set up in the liquid crystal cell relative to the substrate surface can be compensated in the desired manner, whereby a particularly effective compensation can be achieved.
  • the basic orientation of the liquid crystal molecules must be observed, but an opposite 180 ° orientation of the liquid crystal edge molecules is permissible, which is the last In the end, the possibility of using a delay layer for differently oriented subpixels is permitted.
  • the delay layer according to the invention in combination with the “multi-domain method”, in particular when the liquid crystal molecules are oriented by exposing a photosensitive layer, is an inexpensive alternative to comparatively similarly effective compensation layers (eg discotic delay films).
  • the refractive indices n e , n 0 , n z of the biaxial retardation layer be dimensioned such that n e - n 0 > 0 and n B - n 0 ⁇ 0.
  • the delay layer be arranged on the liquid crystal cell between the polarizer and the liquid crystal cell.
  • the delay layer is arranged in the liquid crystal cell between the liquid crystal and the substrate.
  • a particularly simple and compact structure results if the substrate itself forms a retardation layer (plastic substrate with a suitable retardation).
  • the delay layer In order to ensure a high degree of symmetry, it is also proposed to arrange the delay layer on both sides between the liquid crystal and polarizers. In the case of a delay layer applied on both sides, it is advantageous if the layer fulfills the following dimensioning regulations:
  • one or more plastic films are used as the retardation layer.
  • a retardation layer made of a unidirectional plastic film, but not stretched to saturation can be used. It is also possible to use a retardation layer made of a plastic film that is stretched bidirectionally. Finally, a combination of one or more uniaxial positive and one or more uniaxial negative films is possible. Retardation films have the advantage that they can be applied in a simple manner, for example laminated.
  • the delay layer can also be realized by a holographic element or in the form of a liquid crystal polymer.
  • the liquid crystal is oriented in the sub-pixels of a pixel in such a way that the viewing angle areas of the individual sub-pixels complement one another to form a more symmetrical viewing angle area.
  • this can be done by that the angles of attack of the liquid crystal edge molecules of the subpixels on the base substrate are opposite, that the angles of attack of the liquid crystal edge molecules of the subpixels on the cover substrate are opposite, that the angles of attack of the liquid crystal edge molecules of the subpixels on both substrates are opposite, that the angles of attack of the liquid crystal edge molecules of the subpixels are different on the base substrate are large that the angles of attack of the liquid crystal edge molecules of the sub-pixels on the cover substrate are of different sizes, or that the angles of attack of the liquid crystal molecules of the sub-pixels are different due to the cover substrate.
  • the twisting of the TN cell can be between 80 and 100 o.
  • Liquid metal molecules can be oriented on the substrate surfaces by mechanical rubbing of an orientation layer.
  • a photosensitive layer is used to orient the liquid crystal molecules on the substrate surfaces, in which the preferred direction of the liquid crystal molecules is determined by an exposure process.
  • each pixel has a switching element such as a thin film transistor, a thin film diode or a metal-insulator-metal diode.
  • a thin-film transistor and a storage capacitor are arranged in each pixel, at least one electrode of the storage capacitor being realized by a conductive opaque layer which covers the boundary region between the sub-pixels. In this way, with the aperture of the liquid crystal display remaining the same, a cover for the border area between the sub-pixels is realized.
  • Fig. 3 a u. b the schematic structure of a conventional twisted nematic liquid crystal display
  • 4 shows a model to illustrate the coordinates for determining the viewing direction
  • 5 shows the depiction of the viewing angle dependence for contrast and grayscale inversion of a conventional nematic liquid crystal cell
  • Fig. 7 shows the basic orientation of the
  • Liquid crystal edge molecules for a pixel divided into two sub-pixels Liquid crystal edge molecules for a pixel divided into two sub-pixels
  • FIG. 11 shows the diagram belonging to FIG. 10 for the viewing angle dependence of contrast and grayscale inversion without delay film
  • FIG. 12 shows the diagram belonging to FIG. 10 for the viewing angle dependence of contrast and grayscale inversion with an optically biaxial retardation layer according to the invention. Description of the exemplary embodiments:
  • the starting point for the description of the exemplary embodiments is a conventional, twisted nematic (twisted nematic) liquid crystal display according to FIGS. 3a and b.
  • a liquid crystal twisted by 90 ° Between two glass substrates 1, 2 there is a liquid crystal twisted by 90 °, the elongated liquid crystal molecules of which are indicated by rods 3.
  • a polarizer 4, 5 is attached to each of the glass substrates.
  • the transmissive direction of the polarizers (indicated by a double arrow) coincides with the orientation of the longitudinal axis of the liquid crystal edge molecules, but it can also be oriented at 90 ° to it.
  • FIG. 3a shows the voltage-free state in which penetrating light (symbolized by the broad arrow) is rotated by 90 ° due to the liquid crystal helix and can then leave the polarizer 5 unhindered.
  • the cell is translucent and appears bright.
  • the liquid crystal molecules align themselves in the electric field due to their dielectric anisotropy, as a result of which the light penetrating from below (also shown in FIG. 3b by a broad arrow) passes unhindered through the liquid crystal cell and therefore at the polarizer 5 is absorbed. In this state, the liquid crystal cell appears dark.
  • the angle ⁇ lying on the substrate plane S should run from 0 to 360 °, whereas the angle ⁇ indicates the angle of inclination from the liquid crystal normal (z).
  • 6a and 6b should be referred to the introduction to the description.
  • Fig. 5 the longitudinally and transversely hatched area of a conventional TN cell, which can be regarded as a suitable viewing angle area, is in need of improvement.
  • FIG. 1 For this purpose, an inventive structure of a liquid crystal display according to FIG. 1 is used.
  • a liquid crystal is located between a base substrate (GS) and a cover substrate (DS), the longitudinal axes of the liquid crystal edge molecules are aligned on the base or cover substrate in accordance with the arrow shown.
  • a delay layer VI, V2 is arranged on the top and bottom of the liquid crystal cell formed by base and cover substrates.
  • the extraordinary axis (n e ) in the retardation layer is symbolized by arrows, whereby it runs perpendicular to the alignment of the liquid crystal molecules on the correspondingly adjacent substrate (for the position of the further optical axes in the retardation layer, see FIG. 2).
  • a polarizing filter P1 or P2 is applied to the delay layers VI and V2, the absorbing axis of which runs parallel to the alignment of the liquid crystal molecules in the correspondingly adjacent substrate (dashed double arrow).
  • the projection of the extraordinary axis of the liquid crystal edge molecules onto the substrate surface with the absorbing axis of the polarizer can include an angle of 0 ° to 5 ° for the base and top substrates and the extraordinary axis of the retardation layer form an angle of 85 ° to 90 ° with the absorbing axis of the polarizer.
  • a picture element according to FIG. 7 is to be divided into sub-picture elements, with neighboring ones Subpixels 6, 7 are oriented opposite to one another in accordance with the symbolically indicated molecular longitudinal axes 8 by 180 °.
  • Such an orientation results in an essentially point-symmetrical course of the grayscale inversion or the boundary line for an area in which a minimum contrast is not undershot (cf. FIG. 8).
  • the area in which no grayscale inversion occurs is shown in FIG. 8 by the line provided with crosses, whereas the isocontrast curve is defined for a minimum contrast of 10 by square dots.
  • the inclination angle ⁇ of approximately 65 ° does not fall anywhere Contrast below a minimum contrast, in the exemplary embodiment a contrast of 10. Likewise, up to one
  • the biaxial retardation film according to the invention thus offers the possibility of producing liquid crystal displays which, with the additional use of the “multi-domain method”, makes excellent viewing-angle dependencies possible.

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

Abstract

La présente invention a trait à un afficheur par cristaux liquides à plusieurs points d'image, constitué d'une cellule de cristaux liquides et de polariseurs (P1, P2) montés sur les faces supérieure et inférieure de ladite cellule, laquelle comprend deux substrats (DS, GS) avec des électrodes transparentes entre lesquelles est inséré le cristal liquide. Pour compenser le fait que les propriétés optiques de l'afficheur par cristaux liquides, notamment la transmittance et le contraste, sont asservies à un champ angulaire, chaque point d'image est divisé en au moins deux sous points d'image, dans lesquels les cristaux liquides présentent différentes orientations et, insérée entre un polariseur et les cristaux liquides, au moins une couche de retard biaxiale (V1, V2) avec différents indices de réfraction ne, no, nz. L'indice de réfraction nz apparaît dans la couche de retard, dans un axe sensiblement parallèle à la normale de la cellule de cristaux liquides.
PCT/DE1998/000192 1997-02-07 1998-01-22 Afficheur par cristaux liquides a plusieurs points d'image WO1998035266A1 (fr)

Priority Applications (2)

Application Number Priority Date Filing Date Title
JP53353698A JP2001510586A (ja) 1997-02-07 1998-01-22 多数のピクセルを備えた液晶表示装置
EP98906830A EP0958524A1 (fr) 1997-02-07 1998-01-22 Afficheur par cristaux liquides a plusieurs points d'image

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE19704717.3 1997-02-07
DE1997104717 DE19704717A1 (de) 1997-02-07 1997-02-07 Flüssigkristallanzeige mit mehreren Bildpunkten

Publications (1)

Publication Number Publication Date
WO1998035266A1 true WO1998035266A1 (fr) 1998-08-13

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Application Number Title Priority Date Filing Date
PCT/DE1998/000192 WO1998035266A1 (fr) 1997-02-07 1998-01-22 Afficheur par cristaux liquides a plusieurs points d'image

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EP (1) EP0958524A1 (fr)
JP (1) JP2001510586A (fr)
DE (1) DE19704717A1 (fr)
WO (1) WO1998035266A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2011113180A1 (fr) * 2010-03-19 2011-09-22 Nokia Corporation Appareil, procédés et programmes d'ordinateur pour la configuration de la sortie d'un dispositif d'affichage

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2023041293A (ja) * 2021-09-13 2023-03-24 日東電工株式会社 光学積層体およびそれを用いた画像表示装置

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1996010775A1 (fr) * 1994-09-30 1996-04-11 Honeywell Inc. Affichage a cristaux liquides a matrice active en demi-teintes possedant des domaines multiples, un angle de visualisation large et un retard de compensation
US5576863A (en) * 1993-05-26 1996-11-19 Hosiden Corporation Gray scale multi domain liquid crystal display panel having capacitive voltage division characteristics
US5594568A (en) * 1993-12-15 1997-01-14 Ois Optical Imaging Systems, Inc. LCD with a pair of retardation films on one side of normally white liquid crystal layer

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2692693B2 (ja) * 1986-10-22 1997-12-17 富士通株式会社 液晶表示パネル
JP3087193B2 (ja) * 1991-12-20 2000-09-11 富士通株式会社 液晶表示装置
JP2693368B2 (ja) * 1993-06-29 1997-12-24 スタンレー電気株式会社 液晶表示素子とその製造方法
JPH0843833A (ja) * 1994-08-04 1996-02-16 Nec Corp 液晶表示装置

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5576863A (en) * 1993-05-26 1996-11-19 Hosiden Corporation Gray scale multi domain liquid crystal display panel having capacitive voltage division characteristics
US5594568A (en) * 1993-12-15 1997-01-14 Ois Optical Imaging Systems, Inc. LCD with a pair of retardation films on one side of normally white liquid crystal layer
WO1996010775A1 (fr) * 1994-09-30 1996-04-11 Honeywell Inc. Affichage a cristaux liquides a matrice active en demi-teintes possedant des domaines multiples, un angle de visualisation large et un retard de compensation

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2011113180A1 (fr) * 2010-03-19 2011-09-22 Nokia Corporation Appareil, procédés et programmes d'ordinateur pour la configuration de la sortie d'un dispositif d'affichage
US9201255B2 (en) 2010-03-19 2015-12-01 Nokia Technologies Oy Apparatus, methods and computer programs for configuring output of a display

Also Published As

Publication number Publication date
JP2001510586A (ja) 2001-07-31
EP0958524A1 (fr) 1999-11-24
DE19704717A1 (de) 1998-08-13

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