WO1998002774A1 - Dispositif a affichage a cristaux liquides et a eclairage par l'arriere - Google Patents

Dispositif a affichage a cristaux liquides et a eclairage par l'arriere Download PDF

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Publication number
WO1998002774A1
WO1998002774A1 PCT/JP1996/001946 JP9601946W WO9802774A1 WO 1998002774 A1 WO1998002774 A1 WO 1998002774A1 JP 9601946 W JP9601946 W JP 9601946W WO 9802774 A1 WO9802774 A1 WO 9802774A1
Authority
WO
WIPO (PCT)
Prior art keywords
liquid crystal
crystal display
light
optical element
light guide
Prior art date
Application number
PCT/JP1996/001946
Other languages
English (en)
Japanese (ja)
Inventor
Junichi Hirakata
Tatsuhisa Fujii
Tatsuyuki Fumikura
Hitomi Madokoro
Original Assignee
Hitachi, Ltd.
Hitachi Device Engineering Co., Ltd.
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 Hitachi, Ltd., Hitachi Device Engineering Co., Ltd. filed Critical Hitachi, Ltd.
Priority to PCT/JP1996/001946 priority Critical patent/WO1998002774A1/fr
Publication of WO1998002774A1 publication Critical patent/WO1998002774A1/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
    • G02F1/1336—Illuminating devices
    • G02F1/13362—Illuminating devices providing polarized light, e.g. by converting a polarisation component into another one
    • 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
    • G02F1/133528—Polarisers
    • G02F1/133536—Reflective polarizers
    • 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
    • G02F1/133528—Polarisers
    • G02F1/13355—Polarising beam splitters [PBS]

Definitions

  • Liquid crystal display device and backlight device Liquid crystal display device and backlight device
  • the present invention relates to a liquid crystal display device and a backlight device of a simple matrix type or an active matrix type. In particular, by providing an optical element for improving light use efficiency, a bright and high contrast ratio is obtained.
  • the present invention relates to a liquid crystal display device and a backlight device with low power consumption.
  • Conventional liquid crystal display devices capable of large-capacity display include a super twisted nematic type (STN) and a thin film transistor type (TFT), which control the amount of transmitted light.
  • STN super twisted nematic type
  • TFT thin film transistor type
  • a pair of polarizing plates is provided with a liquid crystal layer interposed therebetween.
  • this polarizing plate was able to transmit only one-way polarized light component due to absorption of a dichroic dye represented by iodine, and was able to use only 50% of the light amount of the backlight. Therefore, there is a problem that the display screen is large, the contrast ratio is low, the power consumption is large, and if the battery is driven, it cannot be used for a long time.
  • a polymer disperse liquid crystal (PDLC) method has been proposed as a display method that does not use a polarizing plate as a means of increasing the light use efficiency of the backlight.
  • PDLC polymer disperse liquid crystal
  • An object of the present invention is to provide a liquid crystal display device and a backlight device that have high light use efficiency, are bright, have a high contrast ratio, and consume less power.
  • a liquid crystal display device of the present invention comprises a pair of substrates, at least one of which is transparent and has an electrode, a liquid crystal layer sandwiched between the pair of substrates,
  • a liquid crystal display device comprising: a liquid crystal display element including voltage control means for applying a voltage to the liquid crystal layer to change the amount of light transmitted through the liquid crystal layer; and a light source device disposed on the side opposite to the viewing direction of the liquid crystal display element.
  • a first optical element between the liquid crystal display element and the light source device for transmitting a single polarization component of light from the light source device and reflecting another polarization component;
  • a second optical element for dispersing an arbitrary polarization component of light into a plurality of polarization components is provided between the first optical element and the light source device.
  • the light source device includes a light guide, a light emitting element provided on an end face of the light guide, and a reflector disposed on a side opposite to the observation direction of the light guide. If the vibration direction of the light of the single polarization component passing through the first optical element is different from the liquid crystal direction at the liquid crystal layer side interface of one of the substrates adjacent to the first optical element, A third optical element (rotatory element) for rotating the light oscillation direction in a direction substantially parallel to the liquid crystal alignment direction is disposed between the first optical element and the liquid crystal display element.
  • the liquid crystal display device is of the STN type, since the display principle is different from that of the TFT type, the angle between the light oscillation direction and the liquid crystal alignment direction is 20. ⁇ 70. In the range of.
  • the light that has passed through the first optical element is light having a single polarization component, so that the light is absorbed by the polarizing plate disposed on the light source device side. Is not in principle. Therefore, when the liquid crystal display element is sandwiched between a pair of polarizing plates, and the oscillation direction of the light of the single polarization component passing through the first optical element is the polarizing plate adjacent to the first optical element. If the polarization axis is different from that of the first optical element and the polarizing plate, an optical rotation element for rotating the oscillation direction of the light in a direction substantially parallel to the polarization axis direction of the polarizing plate. To be placed. In this regard, the STN and TFT types are common.
  • the first optical element may be composed of two or more thin films having different refractive indexes.
  • the ratio of the refractive index of two adjacent thin films among the above thin films is 1.1 or more.
  • the optical pitch of the third optical element be 2 ⁇ m or more, and that the rotation angle be less than 90 °.
  • a backlight device for achieving the above object includes a light guide, a light emitting element provided on an end face of the light guide, a reflector disposed on one of the light guides, and the other of the light guides.
  • a first optical element polarization splitting element
  • a second optical element a depolarizer
  • the polarizing beam splitter also has the function of the polarization separating element.
  • the light source device is a transparent light guide plate, a linear light source arranged on at least one end face of the light guide plate, and a light guide opposite to the observation direction side of the light guide.
  • the light guide plate is formed of an arranged reflector, and the surface on the observation direction side of the light guide plate forms a prism array that transmits a single polarization component of light from inside the light guide and reflects another polarization component.
  • a liquid crystal display device or a backlight device including an optical element between the light guide plate and the reflection plate for dispersing an arbitrary polarization component of light into a plurality of polarization components may be applied.
  • FIG. 1 is a schematic sectional view of the liquid crystal display device according to the present invention.
  • FIG. 2 is a diagram for explaining an optical path of a polarization component of the liquid crystal display device according to the present invention.
  • FIG. 3 is a cross-sectional view of the first polarization separation element of the liquid crystal display device according to the present invention.
  • FIG. 4 is a cross-sectional view of the second polarization separation element of the liquid crystal display device according to the present invention.
  • FIG. 1 is a schematic sectional view of the liquid crystal display device of the present invention.
  • 1a and 1b are polarizing plates
  • 2 is a liquid crystal layer
  • 3a and 3b are substrates sandwiching liquid crystal
  • 4 is an optical rotation element
  • 5 is a polarization separation element
  • 6 is a depolarizer
  • 7 is a backlight
  • 8 is a backlight. Construct a reflector.
  • the viewing direction of the liquid crystal display element is above the polarizing plate 1a on the drawing, and in this specification, for example, the polarizing plate 1a is connected to the polarizing plate on the viewing direction side or the upper polarizing plate and the polarizing plate 1b.
  • the surface 5a of the polarization beam splitter 5 is appropriately defined as the surface on the observation direction side or the upper surface.
  • the polarization separation element 5 By providing the polarization separation element 5, the light of the knock light is separated into two polarization components, only one polarization component is transmitted, and the other polarization component is reflected. The reflected light returns to the polarization separation element 5 after changing the polarization plane again by the function of the depolarizer 6 and the reflector 6 described later. Therefore, the light from the knock light 7 is not absorbed even by the optical member which is deviated or shifted, and in principle, all the light is directly or regenerated, so that the efficiency of the light can be improved.
  • the polarization component transmitted through the polarization separation element 5 can rotate the polarization plane (polarization axis or transmission axis) by a desired angle by the optical rotation element 4, and the polarization plane can be rotated to the lower polarizing plate of the liquid crystal layer 2. Light is incident almost parallel to the polarization axis of 1b.
  • the polarization plane of the polarization component transmitted through the polarization separation element 5 is incident almost parallel to the liquid crystal molecular axis on the viewing direction plane of the substrate 3b in the case of the TFT type, and 2 in the case of the STN type. 0 to 70.
  • the same efficiency of light can be achieved by shifting the incident light within the range.
  • a retardation film made of a plastic film having birefringence between the liquid crystal layer 2 and the optical rotation element 4 or the polarizing plate 1b.
  • the polarization plane of the emitted light is incident substantially parallel to the optical axis of the retardation film.
  • the retardation film has a product ⁇ nd of a birefringence and a thickness of polyforce-bonate of about 0.4 ⁇ .
  • the polarized light component reflected by the polarization separation element 5 is returned to random polarization by the depolarizer 6, and then reflected by the reflection plate 8 to enter the polarization separation element 5 again.
  • each of the substrates 3a and 3b is about 0.7 mm, and the surface is polished, and a transparent electrode of ITO (indium tin oxide) is formed by a sputtering method.
  • the liquid crystal of the liquid crystal layer 2 has a positive dielectric anisotropy ⁇ of about 4.5 and a birefringence of about 0.13 3 (at a temperature of 20 ° C. and a wavelength of 589 nm). (Measured in (1)).
  • the twist angle of the liquid crystal is around 240 degrees, the maximum value is limited because the lighting state near the threshold value is an orientation that scatters light, and the maximum value is almost 260 degrees, and the lower limit is limited by contrast. Nearly 200 degrees is the limit.
  • a polyimide-based orientation control film is provided on the surface of the substrates 3a and 3b on the liquid crystal layer side, and a pretilt angle of about 3.5 degrees is formed by rubbing. The pretilt angle is measured by a rotating crystal method.
  • a red, blue, or green striped color filter may be arranged on one of the substrates.
  • the optical rotatory element 5 is a transparent glass substrate with a spacing of about 0.7 mm and a liquid crystal material sealed to a twist angle of about 45 degrees and a helical pitch of about 20 ⁇ .
  • the substrate is made of a plastic material such as PET (polyethylene terephthalate) or the liquid crystal layer is made of a high molecular weight liquid crystal film, the thickness becomes thinner, more powerful and lighter. Is desirable for the liquid crystal display device.
  • the depolarizer 6 is obtained by coating a liquid crystal material with PVA (polyvinyl alcohol), forming a capsule having a diameter of about 0.1, and then laminating the film with a PET film.
  • PVA polyvinyl alcohol
  • the knock light 7 prints aluminum on the lower surface of the light guide, It suffices if a process of reflecting light from above is performed on the surface.
  • FIG. 2 is a diagram schematically illustrating the optical path of the polarized light component of the liquid crystal display device of the present invention.
  • the light emitted from the knock light is composed of an s-polarized light component and a p-polarized light component.
  • the angle of the light is random, only the s-polarized light component is transmitted by the polarization splitting element, and the polarization plane (polarization axis or transmission axis) is rotated by the optical rotation element, so that the polarization axis is shifted to the liquid crystal molecular axis of the lower substrate of the liquid crystal layer.
  • the plane of polarization is incident parallel or perpendicular.
  • the p-polarized light component is reflected by the polarization splitter, but is again dispersed by the depolarizer into the s-polarized light component and the p-polarized light component, and is reflected by the reflector and then re-enters the polarization splitter.
  • the polarizing plate 1b of the liquid crystal element By repeating this series of light paths of polarization separation, depolarization, and reflection, only a single polarization component is incident on the polarizing plate 1b of the liquid crystal element, and the polarization axis of the light from the polarizing plate transmission axis and the polarization separator.
  • the planes match, the loss due to light absorption by the polarizing plate is eliminated, and the light use efficiency is high, the brightness is high, the contrast ratio is high, and the power consumption can be further reduced.
  • FIG. 3 is a schematic cross-sectional view of an example of the polarization beam splitter of the liquid crystal display device of the present invention, which is composed of thin film layers having different refractive indexes.
  • the efficiency of polarization separation improves.
  • the refraction of each adjacent thin film layer The efficiency of polarization separation improves as the ratio of the ratios increases.
  • the refractive index ratio be about 1.1 or more.
  • This polarized light separating element is formed of three layers of acrylolate with a refractive index of 1.4, tolyl cyanolate (TAC) with a refractive index of about 1.5, and polycarbonate with a refractive index of about 1.6. The separation rate is almost 95%.
  • FIG. 4 is a schematic cross-sectional view of another example of the polarization beam splitter of the liquid crystal display device of the present invention, which is composed of a microprism.
  • This micro prism has the shape of the surface itself in the observation direction of the light guide described above.
  • the light guide has the function of both the polarization splitting element 5 and the light guide shown in FIG. Will have. Therefore, when the light guide having the function of the polarization splitting element is used, the depolarizer 6 is disposed between the light guide 7 and the reflection plate 8.
  • a liquid crystal display device having high contrast and excellent viewing angle characteristics can be obtained, and the transmittance of the liquid crystal display device, which had been limited to about 5% in the past, can be increased to about twice (about 9%) in the past. Above).
  • the present invention is applied to any liquid crystal display device or backlight device, and particularly provides a means for realizing a bright liquid crystal display device, which has been a problem to be solved for many years.

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

Abstract

L'invention concerne un affichage à cristaux liquides brillant tel que l'absorption de la lumière de la plaque polarisante et faible. L'affichage à cristaux liquides est constitué d'un élément d'affichage à cristaux liquides pourvu d'une paire de substrats (1a et 1b) qui se font face mutuellement et dont l'un est transparent et comporte une électrode, une couche de cristaux liquides (2) maintenue entre lesdits substrats (1a et 1b), et d'un moyen de réglage de la tension qui modifie la transmittance de la couche (2) par application d'une tension à l'électrode, d'une source de lumière (7 et 8) qui est placée à l'arrière de l'élément d'affichage, dans le sens de visionnement, d'un élément de polarisation et de séparation (5) qui transmet une seule composante de lumière polarisée provenant de la source de lumière, réfléchit d'autres composantes de lumière polarisée et est placé entre l'élément d'affichage et la source de lumière, ainsi que d'un dépolariseur (6) qui disperse une composante de lumière polarisée arbitraire en une pluralité de composantes de lumière polarisée et est placé entre l'élément (5) et la source de lumière.
PCT/JP1996/001946 1996-07-12 1996-07-12 Dispositif a affichage a cristaux liquides et a eclairage par l'arriere WO1998002774A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
PCT/JP1996/001946 WO1998002774A1 (fr) 1996-07-12 1996-07-12 Dispositif a affichage a cristaux liquides et a eclairage par l'arriere

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/JP1996/001946 WO1998002774A1 (fr) 1996-07-12 1996-07-12 Dispositif a affichage a cristaux liquides et a eclairage par l'arriere

Publications (1)

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WO1998002774A1 true WO1998002774A1 (fr) 1998-01-22

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2005029168A1 (fr) * 2003-09-23 2005-03-31 Koninklijke Philips Electronics N.V. Recyclage de la lumiere dans un affichage transflectif a cristaux liquides
KR101006895B1 (ko) 2007-03-21 2011-01-13 허니웰 인터내셔널 인코포레이티드 Ｌｃｄ용 편광 플레이트

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH06265892A (ja) * 1993-03-10 1994-09-22 Asahi Glass Co Ltd 照明装置および液晶表示装置
JPH0764085A (ja) * 1993-08-27 1995-03-10 Asahi Glass Co Ltd 直視型表示素子用照明装置および液晶表示装置
JPH0887011A (ja) * 1994-09-16 1996-04-02 Toshiba Corp 表示装置

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH06265892A (ja) * 1993-03-10 1994-09-22 Asahi Glass Co Ltd 照明装置および液晶表示装置
JPH0764085A (ja) * 1993-08-27 1995-03-10 Asahi Glass Co Ltd 直視型表示素子用照明装置および液晶表示装置
JPH0887011A (ja) * 1994-09-16 1996-04-02 Toshiba Corp 表示装置

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2005029168A1 (fr) * 2003-09-23 2005-03-31 Koninklijke Philips Electronics N.V. Recyclage de la lumiere dans un affichage transflectif a cristaux liquides
JP2007506153A (ja) * 2003-09-23 2007-03-15 コーニンクレッカ フィリップス エレクトロニクス エヌ ヴィ 半透明型ｌｃｄにおける光の再利用
CN100414379C (zh) * 2003-09-23 2008-08-27 统宝香港控股有限公司 透反射式lcd中的光循环利用
US7616276B2 (en) 2003-09-23 2009-11-10 Tpo Hong Kong Holding Limited Light recycling in a transflective LCD
KR101006895B1 (ko) 2007-03-21 2011-01-13 허니웰 인터내셔널 인코포레이티드 Ｌｃｄ용 편광 플레이트

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