WO1993016410A1 - Affichage a cristaux liquides eclaire a l'avant - Google Patents

Affichage a cristaux liquides eclaire a l'avant Download PDF

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Publication number
WO1993016410A1
WO1993016410A1 PCT/US1993/001190 US9301190W WO9316410A1 WO 1993016410 A1 WO1993016410 A1 WO 1993016410A1 US 9301190 W US9301190 W US 9301190W WO 9316410 A1 WO9316410 A1 WO 9316410A1
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WO
WIPO (PCT)
Prior art keywords
display
light
light emitting
liquid crystal
light source
Prior art date
Application number
PCT/US1993/001190
Other languages
English (en)
Inventor
J. Philip Jones
Original Assignee
Raychem Corporation
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 Raychem Corporation filed Critical Raychem Corporation
Publication of WO1993016410A1 publication Critical patent/WO1993016410A1/fr

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Classifications

    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/0001—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems
    • G02B6/0011—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems the light guides being planar or of plate-like form
    • G02B6/0033—Means for improving the coupling-out of light from the light guide
    • G02B6/0035—Means for improving the coupling-out of light from the light guide provided on the surface of the light guide or in the bulk of it
    • G02B6/0045—Means for improving the coupling-out of light from the light guide provided on the surface of the light guide or in the bulk of it by shaping at least a portion of the light guide
    • G02B6/0046—Tapered light guide, e.g. wedge-shaped light guide
    • G02B6/0048—Tapered light guide, e.g. wedge-shaped light guide with stepwise taper
    • 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
    • G02F1/1336—Illuminating devices
    • G02F1/133615—Edge-illuminating devices, i.e. illuminating from the side
    • 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
    • G02F1/133368—Cells having two substrates with different characteristics, e.g. different thickness or material
    • 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
    • G02F1/1334—Constructional arrangements; Manufacturing methods based on polymer dispersed liquid crystals, e.g. microencapsulated liquid crystals
    • 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
    • G02F1/1336—Illuminating devices
    • G02F1/133616—Front illuminating devices
    • 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
    • G02F1/1336—Illuminating devices
    • G02F1/133617—Illumination with ultraviolet light; Luminescent elements or materials associated to the cell

Definitions

  • This invention relates to front lit liquid crystal displays.
  • Reflective liquid crystal displays comprising a liquid crystal-based electrooptically active element placed in front of a reflector, are well known in the art.
  • the electrooptically active element transitions between a first and a second optical state in response to an input such as an electrical signal.
  • the amount of incident light which reaches the reflector depends on the optical state and accordingly so is the amount of light reflected by the reflector, thereby providing different viewing states to the observer.
  • Reflective liquid crystal displays find many applications, one of the most popular of which is as a computer screen in portable or "laptop" computers, on account of their light weight and low power consumption.
  • a preferred type of liquid crystal display employs an encapsulated liquid crystal structure, in which liquid crystals are encapsulated or dispersed in a matrix (or containment medium) which can be a polymer.
  • a voltage corresponding to a sufficiently strong electric field is applied across the encapsulated liquid crystal material (the "field-on " condition)
  • the alignment of the liquid crystals is re-oriented in accordance with the field, so that incident light is transmitted.
  • the alignment of the liquid crystals is random and/or influenced by the liquid crystal-matrix interface, so that the liquid crystal material scatters incident light.
  • the applied voltage at which the liquid crystal material begins to change from its field-off condition to its field-on condition is called the threshold voltage-
  • Reflective liquid crystal displays generally do not include a light source, but instead rely on ambient lighting. Where such lighting is absent or of the wrong intensity or is incident at the wrong angle, the viewability of the display can be compromised, the viewability of such displays being notoriously sensitive to lighting conditions. It would be desirable to have a self-lit reflective display, but portability and weight considerations exclude many types of light sources. I have invented a self-lit reflective liquid crystal display which is light-weight, so that it is readily portable and usable under all types of ambient lighting conditions.
  • This invention provides a self-lit display comprising: (a) display means having a viewing area switchable from one viewing state to another; (b) backplane reflector means positioned behind the display means; and (c) light source means which is positioned in front of the display means, is substantially coextensive with the viewing area, and directs light towards the viewing area.
  • the light source means preferably is covered with an antireflective coating.
  • the display means comprises: (i ) a front transparent electrode means; (ii) a rear transparent electrode means; (iiiJ an electro-optical display medium comprising an encapsulated liquid crystal structure, positioned between the front and rear transparent electrode means, the optical state of the encapsulated liquid crystal structure being responsive to the application of an electric field across the front and rear electrode means.
  • the display means comprises: (i ) a front, transparent electrode means; (ii) a rear, reflective electrode means which also functions as the backplane reflector means; (iii ) an electro- optical display medium comprising an encapsulated liquid crystal structure, positioned between the front and rear transparent electrode means, the optical state of the encapsulated liquid crystal structure being responsive to the application of an electric field across the front and rear electrode means.
  • Fig. 1-2 illustrate the operation of a display of this invention in which the display means comprises encapsulated liquid crystal material.
  • a preferred display medium comprises an encapsulated liquid crystal structure, which is switchable between a first state in which incident light is scattered and a second state in which the amount of such scattering is reduced.
  • Encapsulated liquid crystal structures and their preparation are disclosed in U.S. Pat. Nos. 4,435,047 (1984), 4,606,611 (1986) .
  • liquid crystal composition denotes a composition having liquid crystalline properties, whether that composition consists of a single discrete liquid crystalline compound, a mixture of different liquid crystalline compounds, or a mixture of liquid crystalline and non-liquid crystalline compounds.
  • the liquid crystal composition is nematic or operationally nematic. More preferably, it also has a positive dielectric anisotropy.
  • liquid crystal compositions typically have elongated shapes, with a tendency to align or orient themselves with their long molecular axes parallel to each other.
  • This alignment causes a liquid crystal composition to be anisotropic, meaning that its measured physical, optical, and other properties are dependent on the direction of measurement (parallel or perpendicular to the direction of alignment).
  • the alignment direction can be influenced by an external stimulus, such as an electrical or magnetic field, causing the liquid crystal composition to exhibit a particular value of a physical characteristic in one direction when the stimulus is absent, but rapidly switching to a different value when the stimulus is applied. It is because of this anisotropy and its ready realign ⁇ ment that liquid crystal compositions are useful as materials for displays.
  • the containment medium for encapsulated liquid crystal structures is preferably a polymeric material.
  • Suitable containment media include but are not limited to poly(vinyl alcohol) and its copolymers, gelatin, poly ⁇ urethane, poly(ethylene oxide), poly(vinyl pyrrolidone), cellulosic polymers. natural gums, acrylic and methacrylic polymers and copolymers, epoxies. polyolefins, vinyl polymers, and the like.
  • Poly(vinyl alcohol) is a preferred containment medium.
  • An encapsulated liquid crystal structure can be formed by deposition from an emulsion containing both the containment medium and the liquid crystal composition or by the evaporation of liquid from a solution contain ⁇ ing both containment medium and the liquid crystal composition. It can also be formed by making an initially homogeneous mixture containing both containment medium and liquid crystal composition at an elevated temperature, then cooling to phase-separate out liquid crystal volumes contained in the containment medium. Further, it can be formed by an m- situ polymerization process, in which the containment medium is poly- merized and simultaneously encapsulates a liquid crystal composition as it phase separates. The liquid crystal composition need not be entirely sur ⁇ rounded by the polymer, and may exist as part of a system with co- continuous phases.
  • an encapsulated liquid crystal structure is substantially non-transparent in the absence of a sufficient electric field (the "field-off ' state) and substantially transparent in the presence of a sufficient electric field (or "field-on” state).
  • the electric field induces a change in the alignment of the liquid crystal molecules in the liquid crystal composition, in turn causing the encapsulated liquid crystal structure to switch from a highly light-scattering (and/or absorbent) state to a highly non-scattering and substantially transparent state.
  • the liquid crystal composition have a positive dielectric anisotropy and that the ordinary index of refraction of the liquid crystal composition be matched with the index of refraction of the containment medium, while the extra ⁇ ordinary index of refraction is substantially mismatched therewith.
  • the physical principles by which such encapsulated liquid crystal structures operate are described in further detail in the aforementioned references, particularly the patents to Fergason. In those portions of the encapsulated liquid crystal structure to which a sufficient electric field is applied, the transition from a non-transparent state to a transparent state occurs, while adjacent areas to which no electric field has been applied remain non-transparent.
  • Encap ⁇ sulated liquid crystal structure 8 comprises a containment medium 10 having distributed therein plural volumes of liquid crystal composition 11 and is positioned between top and bottom electrodes 12 and 13, made for example of indium tin oxide ("ITO") or a thin metal coating.
  • a voltage source 14 is connected to electrodes 12 and 13, but with switch 15 in the open position ( Figure 1), no voltage is applied across encapsulated liquid crystal material 12.
  • a light source means 16 is positioned in front of the display's viewing area.
  • Light ray A emitted by light source means 16 is scattered, both backward (rays a' and a") and forward (b' and b").
  • switch 15 When switch 15 is closed ( Figure 2), a voltage is applied across encapsulated liquid crystal material 8, causing molecules in liquid crystal composition 11 to align their long molecular axes with the field of the applied voltage. Owing to the match between the index of refraction of containment medium 10 and the ordinary index of refraction of liquid crystal composition 11, ray A is not scattered, but is transmitted through encapsulated liquid crystal structure 8.
  • the light source means should meet several requirements. It should emit or direct light emitted by it in a generally downward direction, toward the display means, and not towards the viewer. It should be substantially transparent, so that the viewer has a largely unimpeded view of the display means' viewing area. Preferably, it has a slim profile so that it is adapted for use in displays for use with compact or portable computers.
  • a preferred light source means comprises (i) substantially planar. transparent, light guide means having a plurality of angular facets on the face thereof away from the display means; (ii) light emitting means: and (iii) reflector means for redirecting light emitted by the light emitting means in the plane of the light guide means; the angular facets redirecting light from the light emitting means towards the display means.
  • Such a light source means is shown in Fig. 3.
  • Light source means 20, sometimes referred to in the art as a wedge shaped light pipe (although the wedge- shaped profile has been greatly exaggerated in the figure for clarity ) comprises a light guide means 21, made for example of a transparent material such as glass or a clear synthetic resin such acrylate or poly- carbonate.
  • Light emitting means 24 (e.g., a fluorescent light) is positioned along one edge of light guide means 21. Light emitted by light emitting means 24 is redirected (if necessary — compare rays c and c ⁇ ) by reflecting means 25 generally along the plane of light guide means 21.
  • the top surface of light guide means 21, the one facing the viewer and facing away from the display means comprises a plurality of planar surfaces 22 and angular facets 23. Angular facets 23 redirect light from light emitting means 24 down towards the display means (not shown). They may do so by total internal reflection. Alternatively, they may be metallized and do so by simple reflection.
  • the total relative areas of surfaces 22 and facets 23 is such that the former is much larger, for example 90:10 or larger (preferably 95:5 or larger), so that from the viewer's perspective light guide means appears to be a highly transparent body, with greater than 90% trans ⁇ parency, and the underlying viewing area of the display means is readily visible.
  • the angular facets preferably cover less than 10% of the surface area of the light guide means.
  • Light source means of this type are available from Display Engineering, Santa Rosa, California, under the tradename WEDGELIGHTTM.
  • Fig. 3a shows an alternative embodiment, in which the reflective means, instead of being distinct from the light emitting means, is integral therewith, in which light emitting means 24 is partially coated with a reflective material which forms reflective means 25'.
  • Another preferred light source means comprises (i) electrolumi ⁇ nescent light emitting means selectively directing light towards the display means and (ii) support means supporting the electroluminescent light emitting means.
  • electrolumi ⁇ nescent light emitting means selectively directing light towards the display means and (ii) support means supporting the electroluminescent light emitting means.
  • Such a light source means is shown in Fig. 4 and 4a.
  • light source means 30 comprises series of electroluminescent stripes 31 supported by substrate 32. The construction of stripes 31 is such that light emitted by them is generally directed downward towards the display means (not shown), with little or no light being directed toward the viewer.
  • Fig. 4a shows a magnified cross-section* of a stripe 31 (like numerals referring to like elements).
  • Stripe 31 comprises an electroluminescent material 33 sandwiched between bottom and top electrodes 34 and 35, respectively.
  • Top electrode 35 is opaque, blocking off any light emitted upwards by electroluminescent material 33.
  • Bottom electrode 34 is transparent, permitting light to reach the display means.
  • the light source means can be switched on and off independently of the display means. This way, where the display is being used in an environment where the ambient lighting is adequate for goo viewing, the light source means need not be switched on, reducing power consumption. This feature is an important consideration in battery- powered devices, to avoid draining the batteries unnecessarily.
  • Pleochroic dyes have been mixed with liquid crystals to form a solution therewith.
  • the molecules of pleochroic dyes generally align with the molecules of liquid crystals, so that the application of the electric field affects not only the predominant alignment of the liquid crystals, but also of the pleochroic dye.
  • the extent of the absorption of incident light by the pleochroic dye depends on its orientation relative to the incident light, the application of an external stimulus to a liquid crystal-pleochroic dye combination provides an mechanism for the controlled attenuation of light by absorption.
  • liquid crystal composition also means, in context, a liquid crystal composition containing pleochroic dye dissolved therein.
  • Pleochroic dyes may be used in encapsulated liquid crystal structures to form colored displays.
  • a display capable of displaying colored images can be formed by depositing side by side red, blue, and green pixels made from encapsulated liquid crystal structures of the corres ⁇ ponding color.
  • a preferred LCD is of the active matrix type, in which each pixel (or picture element) is driven (switched from one visual state to another) by an active switching element such as a thin film transistor ("TFT"), varistor, diode, or MIM.
  • TFT thin film transistor
  • the switching element helps eliminate cross-talk and maintain an initially applied voltage across the corresponding pixel, even when it is not being actively addressed, so that the pixel stays "on” while other pixels are addressed. The longer the pixels holds the initially applied voltage, the longer it can be maintained in the "on” state until it is next addressed, permitting the construction of displays having a larger number of pixels. If the matrix contains a sufficiently large number of switching elements of sufficiently small size, high resolution displays are possible. Active matrix displays are important for television, computer, and instrument screens.
  • Fig. 5 shows a display containing additional preferred features.
  • Display 39 comprises display means 40 in turn comprising front and rear electrode means 42 and 43 sandwiching an encapsulated liquid crystal structure 44 between them.
  • Front electrode means 42 may be made of ITO (preferably of the antireflective type).
  • Rear electrode means 43 may also be made of ITO.
  • rear electrode means 43 may be an active matrix array of individual electrode elements.
  • a wedge-shaped light pipe 41 such a discussed hereinabove with reference to Fig. 1 is placed over display means 40 and is substantially coextensive with the latter's viewing area.
  • a planarization layer 46 is used to protect the angular facets of light pipe 41 and to provide a smooth, even surface for the deposition of additional layers such as antireflective coating 47.
  • Reflector means 45 positioned behind display means 40, may be o various types, depending on the angular distribution of light emitted by light pipe 41. Where the light has a narrow angular distribution then reflector means 45 is preferably a broad, low gain (diffuse) reflector. Where the light has a broad angular distribution, the reflector means 45 is pre ⁇ ferably a narrow, high gain reflector (e.g., a mirror).
  • a gain reflector which preferentially reflects lights within a preferred range of viewing angles (typically within 35° of perpendicular) may be used. If the light distribution is greater than 20°, preferably greater than 35°, then a specular reflector such as a mirror may be used. This is a useful advantage, as mirror reflectors are easily placed within a display cell as a pixel rear electrode. Electroluminescent light sources intrinsically emit light with broad angular distribution.
  • Fig. 6 shows an alternative embodiment, for an active matrix color display, like numerals referring to like numerals in Fig. 5 and detailed discussion being limited to the differing elements.
  • Positioned above the top electrode 42 is an array of color filters 47, for example in a repeating red- green-blue pattern.
  • an array 43' of active matrix rear electrodes positioned in a one-to-one correspondence to color filters 47.
  • array 43' of rear electrodes are reflective, thereby functioning both as electrodes and as reflectors, in which instance separate reflector means 45 may be omitted.
  • Control of the angular distribution of light emanating from the display is important for comfortable viewing. Generally, it is desired that the light be distributed in a cone centered around 35° from vertical.
  • the light distribution can be controlled by controlling (a) the aperture of the light emitting means (element 24 in Fig. 3), (b) the distance thereof from the reflective facets (element 23 in Fig. 3), (c) the curvature of the reflective facets (concave or convex or a combination of concave and convex curvatures), (d) the reflective distribution of the reflector, (e) the scattering characteristics of the encapsulated liquid crystal structure, or (f> combinations of the foregoing. More specifically, the light distribution becomes narrower as the distance between the reflective facets and the aperture increases.
  • the facet has two radii of curvature, one in the vertical plane and one in the horizontal, both of which can be varied to achieve the best result.
  • Another way to improve light uniformity is to use more than one light emitting means, for example to inject light from 2, 3, or 4 sides.
  • the most uniform light source however is probably a circular light source with a stepped cone as the light guide. with the vertical radius of curvature of the facets increasing towards the center.
  • a real image of the light emitting means is formed either above or below the display image plane.
  • a virtual image is formed above the facet plane. The choice between the two depends on the distance between facet plane and image plane, and whether the degree of collimation required is high or low.
  • Moire fringe patterns may be observed if unwanted reflections interfere with the direct light path. These patterns can be minimized by ⁇ a > using antireflecting interfaces, e.g. at the liquid crystal structure-top electrode interface, (b) randomizing the a small extent the position, angle. and curvature of the reflective facets, (c) introducing a small degree of light diffusion, or (d) combinations of the foregoing.
  • a small degree of light diffusion can be achieved by (i) interposing a diffuser between the light emitting means and the light guide material (e.g., element 21 in Fig.

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

Abstract

Un écran à éclairage automatique comprend: (a) un élément d'affichage comportant une aire de présentation commutable d'un état de visualisation à l'autre; (b) un réflecteur de fond de panier placé derrière l'élément d'affichage; et (c) une source d'éclairage, placée devant l'élément d'affichage, qui présente pratiquement la même étendue que l'aire de présentation, et qui dirige la lumière vers cette dernière.
PCT/US1993/001190 1992-02-14 1993-02-10 Affichage a cristaux liquides eclaire a l'avant WO1993016410A1 (fr)

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US83746392A 1992-02-14 1992-02-14
US07/837,463 1992-02-14

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Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2705484A1 (fr) * 1993-05-18 1994-11-25 Thomson Csf Dispositif d'affichage.
EP0867747A2 (fr) * 1997-03-25 1998-09-30 Sony Corporation Dispositif d'affichage reflechissant
EP0939273A1 (fr) * 1998-02-26 1999-09-01 Nitto Denko Corporation Plaque de guidage de lumière, source de lumière plane et dispositif d'affichage réflectif à cristal liquide
EP0942228A1 (fr) * 1998-03-10 1999-09-15 Sony Corporation Affichage réflectif
EP0957392A1 (fr) * 1998-05-11 1999-11-17 Nitto Denko Corporation Unité d'affichage réflectif à cristal liquide
WO1999063394A1 (fr) * 1998-06-02 1999-12-09 Nissha Printing Co., Ltd. Ecran tactile a eclairage frontal
WO1999063399A1 (fr) * 1998-06-04 1999-12-09 Tyco Electronics Corporation Eclairement d'un affichage a cristaux liquides
US6590625B1 (en) * 1999-05-24 2003-07-08 Nitto Denko Corporation Liquid-crystal display device
DE102022121128A1 (de) 2022-08-22 2024-02-22 Schott Ag Vorrichtung zur Lichtapplikation

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Publication number Priority date Publication date Assignee Title
EP0056843A2 (fr) * 1981-01-27 1982-08-04 Siemens Aktiengesellschaft Dispositif d'affichage électro-optique passif
EP0129867A1 (fr) * 1983-06-21 1985-01-02 Nec Corporation Dispositif d'affichage polychrome plat
GB2162300A (en) * 1984-07-26 1986-01-29 Sharp Kk Lighting means for display device
EP0399506A2 (fr) * 1989-05-25 1990-11-28 Hughes Aircraft Company Dispositifs d'affichage à cristal liquide à éclairage latéral

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0056843A2 (fr) * 1981-01-27 1982-08-04 Siemens Aktiengesellschaft Dispositif d'affichage électro-optique passif
EP0129867A1 (fr) * 1983-06-21 1985-01-02 Nec Corporation Dispositif d'affichage polychrome plat
GB2162300A (en) * 1984-07-26 1986-01-29 Sharp Kk Lighting means for display device
EP0399506A2 (fr) * 1989-05-25 1990-11-28 Hughes Aircraft Company Dispositifs d'affichage à cristal liquide à éclairage latéral

Cited By (13)

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