EP0957852A1 - Obturateur a cristaux liquides et dispositif pourvu d'un tel obturateur et servant d'ecran contre la lumiere - Google Patents

Obturateur a cristaux liquides et dispositif pourvu d'un tel obturateur et servant d'ecran contre la lumiere

Info

Publication number
EP0957852A1
EP0957852A1 EP96935760A EP96935760A EP0957852A1 EP 0957852 A1 EP0957852 A1 EP 0957852A1 EP 96935760 A EP96935760 A EP 96935760A EP 96935760 A EP96935760 A EP 96935760A EP 0957852 A1 EP0957852 A1 EP 0957852A1
Authority
EP
European Patent Office
Prior art keywords
liquid crystal
ofthe
crystal cell
cell
shutter
Prior art date
Legal status (The legal status 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 status listed.)
Ceased
Application number
EP96935760A
Other languages
German (de)
English (en)
Inventor
Ake HÖRNELL
Stephen Palmer
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
3M Svenska AB
Original Assignee
Hornell International AB
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 Hornell International AB filed Critical Hornell International AB
Publication of EP0957852A1 publication Critical patent/EP0957852A1/fr
Ceased legal-status Critical Current

Links

Classifications

    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F9/00—Methods or devices for treatment of the eyes; Devices for putting-in contact lenses; Devices to correct squinting; Apparatus to guide the blind; Protective devices for the eyes, carried on the body or in the hand
    • A61F9/04—Eye-masks ; Devices to be worn on the face, not intended for looking through; Eye-pads for sunbathing
    • A61F9/06—Masks, shields or hoods for welders
    • A61F9/065—Masks, shields or hoods for welders use of particular optical filters
    • A61F9/067—Masks, shields or hoods for welders use of particular optical filters with variable transmission
    • 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
    • G02F1/133509—Filters, e.g. light shielding masks
    • 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
    • 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
    • G02F1/1347—Arrangement of liquid crystal layers or cells in which the final condition of one light beam is achieved by the addition of the effects of two or more layers or cells
    • G02F1/13471—Arrangement of liquid crystal layers or cells in which the final condition of one light beam is achieved by the addition of the effects of two or more layers or cells in which all the liquid crystal cells or layers remain transparent, e.g. FLC, ECB, DAP, HAN, TN, STN, SBE-LC cells
    • 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
    • G02F1/137—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 characterised by the electro-optical or magneto-optical effect, e.g. field-induced phase transition, orientation effect, guest-host interaction or dynamic scattering
    • G02F1/139—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 characterised by the electro-optical or magneto-optical effect, e.g. field-induced phase transition, orientation effect, guest-host interaction or dynamic scattering based on orientation effects in which the liquid crystal remains transparent

Definitions

  • the present invention relates to liquid crystal shutters and electro-optical eye-protection devices with variable transmission density, and then more specifically to constructions according to the preamble of claim 1.
  • Liquid crystal shutters are useful in various applications concerning the transmittance of light through an aperture, in which it should be possible to switch the shutter between a transparent, or light low light-absorbing state and a dark high light-absorbing state.
  • the light transmittance of a liquid crystal shutter construction is made variable in response to a change in the electric influence.
  • a state ofthe art liquid crystal cell in this context comprises liquid crystal molecules sandwiched between two glass plates.
  • the plates have mutually facing surfaces, each of which is provided with alignment means for defining a respective molecule alignment direction for molecules in the proximity of said alignment means in the absence of an electric field.
  • the alignment means may include a plate surface portion having a physical surface shape which co ⁇ operates with the shape of a liquid crystal molecule in the absence of the electric field. This may be accomplished by treating the glass plate surfaces in a uniform direction so that the liquid crystal molecules in the proximity of such a surface tend to align parallel with the treatment direction.
  • the surface may for example be grooved.
  • the standard 90° twisted nematic (TN) cell includes two mutually facing surfaces which are formed with a twist angle of 90° between the molecule alignment directions ofthe glass plates. Smaller twist angles have been described in the copending but not yet published patent applications SE 9401423-0 and corresponding PCT/SE95/00455.
  • the molecules of the liquid crystal types being used have an inherent dielectric anisotropy and can therefore be predominantly aligned upon application of an electric field with a voltage higher than a cell specific threshold value.
  • the helical structure in the cell is then dissolved and the crystal molecules are instead oriented according to the electrical field.
  • the transmission density of such a cell assembly can be controlled by varying the applied electrical field.
  • the cell construction has a high transmittance, in the absence of any stimulating voltage and is said to have a normally white mode.
  • positioning ofthe cell between parallel polarisers results in a cell construction having a low transmittance, in the absence of a stimulating voltage and is said to have a normally black mode.
  • a device having a high transmittance means that light may pass through the device with only a small reduction of light intensity
  • a high transmittance may also be referred to as a low optical density or a low shade number.
  • a device having a low transmittance may be described as having a high optical density and a high shade number.
  • the optical density is conventionally defined as
  • the first switching time involves switching the cell from the inactivated state to an activated state upon application of a driving voltage and it takes typically less than a millisecond for the crystal to react.
  • the second switching time occurs in connection with the reverse process where crystal relaxation takes place upon removal ofthe driving voltage and takes about twenty times longer time.
  • the present invention also relates to the problem of achieving a liquid crystal shutter which provides a satisfactorily light state in the absence of intense light, and which still provides a satisfactorily dark state in the presence of intense light.
  • a further problem to be solved by the present invention is to achieve a liquid crystal shutter with an increased optical density value (or shade number) in the inactivated state.
  • Another object ofthe present invention is to provide a glare shielding device and a welding glass construction with an increased transmission density value (or shade number) in the inactivated state for the purpose of achieving an improved level of safety. Another object is to provide a liquid crystal shutter which by its level of transmittance indicates whether it is in a functional state or not.
  • Another object is to provide a liquid crystal shutter that employs at least one liquid crystal element placed between mutually crossed polarisers in order to maintain a fast switching time from the light state to the dark protective state.
  • a further object is to achieve a shutter ofthe mentioned kind with a highly symmetric shade geometry in its dark state and with a broad contrast range in the activated dark state.
  • the objects are achieved by providing a voltage controllable liquid crystal cell, placed between angularly twisted polarisers and having a transmission characteristic that varies in relation to the wavelength of incident light, with a filter having, in the visible wavelength range, a transmission characteristic which is complementary to the transmission characteristic ofthe liquid crystal cell in the absence of a control voltage applied on said cell.
  • a normally white mode liquid crystal cell that in the inactivated state has a high transmittance for specific wavelength ranges, is combined with a band-pass filter that reduces the transmittance in said specific wavelength ranges, so that a darkened state is achieved in said inactivated state.
  • the band pass filter is devised to have a high transmittance for wavelengths that are transmitted with a controllable transmittance by the liquid crystal cell in its activated state.
  • the inventive liquid crystal shutter construction is provided with low transmittance in the inactivated state, high transmittance in a first activated, light, state and low transmittance in a second activated, dark, state, whilst the fast response time from the light to the dark state is maintained.
  • the liquid crystal cell and the band pass filter should be devised and matched such that the wavelength dependency ofthe transmission characteristics ofthe band pass filter in a certain wavelength range is substantially complementary to the wavelength dependency ofthe transmission characteristics ofthe liquid crystal cell in the absence of an electric field.
  • Fig 1 is an exploded schematic view of a first embodiment of a device according to the invention.
  • Fig 2 is an exploded schematic view of a second embodiment of device according to the invention.
  • Fig 3 A shows, in full lines, the wavelength dependency ofthe transmission characteristics of a 90° twisted nematic liquid crystal cell in the absence of a control signal and, in dashed lines, fig 3 A also shows the wavelength dependency ofthe transmission characteristics of a band pass filter.
  • Fig 3B shows, in full lines, the wavelength dependency ofthe transmission characteristics of the 90° twisted nematic cell in a first activated state under the influence of a first drive voltage.
  • Fig 3C shows the transmission characteristics for the cell according to Figs 3 A and B in a second activated state under the influence of a second drive voltage.
  • Fig 4 A shows, in full lines, the wavelength dependency ofthe transmission characteristics of a 0° twisted nematic cell in the absence of a control signal, and, in dashed lines, Fig 4A also shows the wavelength dependency ofthe transmission characteristics of a band pass filter.
  • Fig 4B shows the wavelength dependency ofthe cell according to Fig 4 A under the influence of a first control voltage.
  • Fig 4 c shows the wavelength dependency ofthe transmission characteristics ofthe cell under the influence ofthe second control voltage.
  • Fig 5 illustrates the light transmittance properties for a device in accordance with one embodiment ofthe invention as a function of the control voltage applied to the device.
  • Fig 6 illustrates a third embodiment of a device according to the invention including a retardation film.
  • Fig 7 shows the transmission characteristics of a device according to the invention, including a retardation film and the transmission characteristics ofthe device without any compensating retardation film.
  • FIGS 8A and 8B illustrate the shade geometry for different devices according to the invention.
  • Fig 9 shows a shade geometry for a device according to one embodiment ofthe invention.
  • Fig 10 illustrates the light transmittance properties as a function ofthe control voltage applied to a prior art device.
  • FIG 1 shows a schematic view ofthe components of an embodiment of a liquid crystal shutter construction 1 according to the invention.
  • a nematic type liquid crystal cell 2 comprising transparent plates having electrodes which are connectable to a voltage source and provided with means for defining the direction of molecule alignment near the plate surfaces, therewith causing the liquid crystal molecular directions to be aligned in the absence of an electric field between the plates.
  • the angular difference in molecule alignment (also called the twist angle) between the molecule alignment directions can, according to the invention, be for example 0 degrees. Alternatively the angular difference may be substantially 90°, or a value between 90 degrees and zero degrees.
  • the liquid crystal cell 2 is disposed between two polarisers 3 and 4 having mutually orthogonal polarising directions.
  • the construction 1 is also provided with a band pass filter 5, which is positioned in the path of a light beam LB which passes through the construction 1.
  • the shutter construction may comprise an interference filter 6 with a function of eliminating UV-light and ER-light and which also limits the wavelength range.
  • the band pass filter 5 also blocks out UV-light and IR-light.
  • Fig 2 shows a further embodiment ofthe shutter construction comprising a first polariser 3, a first liquid crystal cell 2, a second polariser 4 whose polarisation direction is at right angles to the polarisation direction of the first polariser 3, a second liquid crystal cell 6, a third polariser 7 which has the same direction of polarisation as the first polariser 3, and a band pass filter 5.
  • Fig 3 A, B and C also shows, in dashed lines, the spectral response of a band pass filter.
  • the diagram in Figs 3 a, b and c illustrate the transmission rate plotted as a function ofthe wavelength substantially in the visible wavelength range.
  • the fully drawn curve shows the spectral response of a 90° twisted nematic cell in the electrically inactivated phase with a ⁇ n*d value of 0.78 micrometers placed between crossed polarisers aligned at 45° and 135°, respectively, relative to the entrance molecular direction vector.
  • the cell In this inactivated phase the cell has a transmission maximum in the range of 400 nm and a transmission minimum in the range of 550 nm.
  • the dashed curve shows the spectral response ofthe band pass filter, which has a high optical transmittance ofthe central part of the visible spectrum, i.e. in the wavelength range of 500 to 600 nm.
  • Fig 3B shows the spectral response ofthe same liquid crystal cell and the same band pass filter as in Fig 3 A, in a first activated state when a small driving voltage in the range of 2.5 volts is applied to the liquid crystal cell. It is clear from the diagram that the transmission maximum for the liquid crystal cell and the band pass filter coincide in the visible wavelength range of 500 to 600 nm. Thus, the combined system at this first activated state is in a transparent, high transmittance mode.
  • Fig 3C shows again the spectral responses ofthe system components of Fig 3 a and Fig 3 b, now in a second electrically activated state with an applied voltage in the range of 5 volts.
  • the transmittance ofthe liquid crystal cell is again reduced in the central part ofthe visible wavelength range.
  • the transmittance is controllable in the visible wavelength range by varying the voltage from about 2 volts and upwards until the liquid crystal cell reaches a transmittance minimum.
  • the liquid crystal cell component of such a combined construction operates in a way similar to a normally white mode and therefore the switching time for the device according to the invention is advantageously short. This advantage is achieved in combination with the advantage of having a device which reverts back to a dark, resting state in absence of an electric field between the plates in the cell. This is described in further detail in connection to Fig 5.
  • Fig 4 a shows the spectral response of a 0° twisted nematic cell and a band pass filter.
  • the fully drawn curve thus shows the optical response of a 0° birefringent cell in the inactivated phase with a ⁇ n*d value of 0.55 micrometers placed between crossed polarisers oriented at 45° and 135° respectively, relative to the entrance molecule director vector.
  • the dashed curve shows the spectral response of a band pass filter selected to have a high optical transmittance over the central part ofthe visible spectrum, i.e. in the range of 500 to 600 nm.
  • Fig 4 b shows the spectral response ofthe same liquid crystal cell and the band pass filter with an applied voltage of between 2 and 3 volts and, as has been explained above, a transparent state is then achieved.
  • Fig 4 c shows the second activated state with a voltage of 5 volts supplied.
  • the second activated state is a dark state which is attained as has been explained above.
  • a glare shielding device includes a sensor for providing a sensor signal in response to the intensity of a detected light.
  • the sensor signal is provided to a controller including a signal generator.
  • the signal generator is set up to generate a control signal in response to the sensor signal.
  • a liquid crystal construction according to the invention includes a liquid crystal cell having two surfaces provided with electrodes for providing an electric field between these surfaces.
  • the electric field is created by applying the control signal to the electrodes.
  • a certain control signal voltage will create a corresponding electric field in the liquid crystal cell between the electrodes.
  • Fig 5 shows a diagram on the electro-optic properties of a liquid crystal cell combination with the transmission density or shade number plotted against applied voltage.
  • the curve in Fig 5 shows the electro-optic properties of an 8 micrometers 90° twisted nematic cell with, for the purpose of this example, the Merck mic 6096 liquid crystal giving a ⁇ n*d value of about 0.78 micrometers.
  • a cell is placed between crossed polarisers aligned at 45° and 135° respectively relative to the entrance molecular director vector and together with the band pass filter that has a high optical transmittance over the central part ofthe visible spectrum in the range of 500 and 600 nm.
  • the optical density value is just above 5.5.
  • the optical density value decreases to about 3.3 in a first activated state which renders it more transparent than in the inactivated state.
  • the optical density value is variable in the range between the minimum value attained in the first activated state and up to a value of about 1 1.
  • advantageous optical angular properties ofthe 0° birefringent cell with ⁇ n*d in the range of 0.5 micrometers are found to be highly favourable and clearly suitable for both a single cell and a double cell liquid crystal shutter construction.
  • Such advantageous properties allow a wide and symmetrical viewing field.
  • the available cell contrast from such a device is small in comparison to that for a 90° twisted nematic liquid crystal cell.
  • the cell contrast is improved by means of an addition of a compensating retardation film.
  • the retardation film should preferably be aligned such that the fast axis direction is perpendicular to the entrance and exit molecular direction vectors.
  • the compensating retardation layer for the 0° birefringent cell can for example be in the form of a single, uniaxially stretched retardation film, with a value of between 25 to 30 nm.
  • the compensating retardation layer may be implemented by means of retardation films that are aligned such that the net over all retardation generated by these two films is given by the difference between the two values ofthe film sheets. With, for example, a 27 nm compensating retardation film applied in the shutter construction, the optimum ⁇ n*d value ofthe cell combination is increased from 0.55 micrometers to 0.77 micrometers.
  • Fig 6 shows in principle a prepared position of a retardation film 10 in accordance with the invention.
  • the retardation film 10 is positioned on one side ofthe liquid crystal cell 2 between the polarisation filters 3 and 4.
  • the retardation film may be comprised within the liquid crystal cell 2 between the molecular alignment directing plates.
  • Fig 7 shows the electro-optic properties of a liquid crystal construction including a 4 micrometer 0° birefringent cell.
  • the birefringent cell in this instance comprising the Merck ZLI-4246 liquid crystal giving a ⁇ n*d value of about 0.52 micrometers, is placed between crossed polarisers aligned at 45° and 135° relative to the entrance molecular director vector.
  • the cell is, in correspondence with the above embodiments, placed together with a band pass filter that has a high optical transmittance over the central part ofthe visible spectrum, that is in the range of 500 to 600 nm.
  • Curve 20 shows the optical response ofthe cell combination without any compensating retardation film
  • curve 22 shows a cell combination including a 26 nm compensating retardation film oriented such that the fast axis is pe ⁇ endicular to the entrance molecular director. The improvement in cell contrast with the compensation retardation film is clearly seen in this figure.
  • Fig 8a, 8b and Fig 9 show in principle the shade geometry in a central viewing cone for the above described cell combinations. More specifically, Fig 8a shows the shade geometry A of a 90° twisted nematic single cell, and it is clear that the shade geometry a is asymmetric to a fairly large extent although the cell contrast is still high.
  • Fig 8 b shows the shading geometry A and B of a combination of two 90° twisted nematic cells arranged with antisymmetrical polarisers. Shading geometry from each cell is still asymmetric but in combination a resulting symmetric shade geometry with high contrast is obtained. In contrast, a to a large extent symmetric shade geometry, as shown in Fig 9, is obtained by means of a 0° low twist single cell and in combination with a retardation film a substantially symmetric shade geometry together with a high contrast is obtained.

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  • Physics & Mathematics (AREA)
  • Health & Medical Sciences (AREA)
  • Nonlinear Science (AREA)
  • Ophthalmology & Optometry (AREA)
  • Biomedical Technology (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Chemical & Material Sciences (AREA)
  • Mathematical Physics (AREA)
  • Engineering & Computer Science (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Heart & Thoracic Surgery (AREA)
  • Vascular Medicine (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Animal Behavior & Ethology (AREA)
  • General Health & Medical Sciences (AREA)
  • Public Health (AREA)
  • Veterinary Medicine (AREA)
  • Liquid Crystal (AREA)

Abstract

La présente invention concerne un modèle d'obturateur à cristaux liquides qui convient pour les écrans protecteurs en verre et les verres filtrants de soudage à obscurcissement automatique. On peut faire passer ce modèle d'obturateur d'un premier état, à fort taux de transmission de la lumière, à un deuxième état, à faible taux de transmission, et inversement, en réaction à un signal électrique de commande. L'obturateur a une cellule à cristaux liquides nématiques, placée entre des plaques transparentes pourvues d'électrodes pour fournir un champ électrique en réaction au signal de commande. Les plaques ont des surfaces tournées l'une vers l'autre et dont chacune est pourvue d'un dispositif d'alignement pour définir une direction d'alignement des molécules proches de ce dispositif, en l'absence du champ électrique. La cellule à cristaux liquides est montée entre des polariseurs et elle comprend un filtre passe-bande. La cellule à cristaux liquides et le filtre passe-bande sont adaptés l'un à l'autre, de telle manière que la façon dont les caractéristiques de transmission du filtre sont fonction de la longueur d'onde, pour une certaine plage de longueurs d'onde, est sensiblement complémentaire de la façon dont les caractéristiques de transmission de la cellule à cristaux liquides en l'absence de champ électrique sont fonction de la longueur d'onde.
EP96935760A 1995-10-26 1996-10-25 Obturateur a cristaux liquides et dispositif pourvu d'un tel obturateur et servant d'ecran contre la lumiere Ceased EP0957852A1 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
SE9503785 1995-10-26
SE9503785A SE516183C2 (sv) 1995-10-26 1995-10-26 Vätskekristallslutare
PCT/SE1996/001374 WO1997015256A1 (fr) 1995-10-26 1996-10-25 Obturateur a cristaux liquides et dispositif pourvu d'un tel obturateur et servant d'ecran contre la lumiere

Publications (1)

Publication Number Publication Date
EP0957852A1 true EP0957852A1 (fr) 1999-11-24

Family

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Family Applications (1)

Application Number Title Priority Date Filing Date
EP96935760A Ceased EP0957852A1 (fr) 1995-10-26 1996-10-25 Obturateur a cristaux liquides et dispositif pourvu d'un tel obturateur et servant d'ecran contre la lumiere

Country Status (6)

Country Link
EP (1) EP0957852A1 (fr)
JP (1) JPH11514457A (fr)
CN (1) CN1200661A (fr)
AU (1) AU7356796A (fr)
SE (1) SE516183C2 (fr)
WO (1) WO1997015256A1 (fr)

Cited By (1)

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RU2719306C1 (ru) * 2012-12-13 2020-04-17 3М Инновейтив Пропертиз Компани Изогнутый автоматически затемняющий светофильтр

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ATE297706T1 (de) * 2000-12-21 2005-07-15 Optrel Ag Blendschutzvorrichtung für schweisserschutzmasken
JP4382317B2 (ja) * 2001-12-06 2009-12-09 シチズンホールディングス株式会社 液晶可変波長フィルタ装置
AU2003293483A1 (en) * 2002-12-11 2004-06-30 Optiva, Inc. Liquid crystal shutter
EP1821136A1 (fr) * 2006-02-17 2007-08-22 Optrel Ag Dispositif de protection contre l'éblouissement
GB2498726A (en) 2012-01-25 2013-07-31 3M Innovative Properties Co Automatic welding filter with tunable spectral transmission
CN109154752B (zh) * 2016-03-28 2021-02-05 Lc 显示技术公司 具有宽视角的电子光学宾主液晶可变透射滤波器
AU2017263312B2 (en) 2016-05-12 2019-01-03 3M Innovative Properties Company Protective headgear comprising a curved switchable shutter and comprising multiple antireflective layers

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SE425048B (sv) * 1978-04-24 1982-08-30 Ake Hornell Flerskiktsglas, serskilt skyddsglas i en svetsskerm
SE464264B (sv) * 1984-02-24 1991-03-25 Esab Ab Optiskt filter foer svetsskyddsglas
US5208688A (en) * 1991-02-08 1993-05-04 Osd Envizion Company Eye protection device for welding helmets
SE502868C2 (sv) * 1994-04-26 1996-02-05 Hoernell Elektrooptik Ab Svetssnabbfilter med förbättrade vinkelegenskaper

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
RU2719306C1 (ru) * 2012-12-13 2020-04-17 3М Инновейтив Пропертиз Компани Изогнутый автоматически затемняющий светофильтр

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SE516183C2 (sv) 2001-11-26
SE9503785D0 (sv) 1995-10-26
SE9503785L (sv) 1997-04-27
AU7356796A (en) 1997-05-15
WO1997015256A1 (fr) 1997-05-01
CN1200661A (zh) 1998-12-02
JPH11514457A (ja) 1999-12-07

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