CA1305242C - Multicolor liquid crystal display - Google Patents
Multicolor liquid crystal displayInfo
- Publication number
- CA1305242C CA1305242C CA000602241A CA602241A CA1305242C CA 1305242 C CA1305242 C CA 1305242C CA 000602241 A CA000602241 A CA 000602241A CA 602241 A CA602241 A CA 602241A CA 1305242 C CA1305242 C CA 1305242C
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- Canada
- Prior art keywords
- liquid crystal
- color
- cell
- polarizer
- red
- 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.)
- Expired - Fee Related
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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
- G02F1/133528—Polarisers
- G02F1/133533—Colour selective polarisers
-
- 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
- G02F1/133531—Polarisers characterised by the arrangement of polariser or analyser axes
-
- 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
- G02F1/13725—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 guest-host interaction
-
- 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
- G02F1/1393—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 the birefringence of the liquid crystal being electrically controlled, e.g. ECB-, DAP-, HAN-, PI-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
- G02F1/1396—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 the liquid crystal being selectively controlled between a twisted state and a non-twisted state, e.g. TN-LC cell
-
- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- 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
- G02F1/1396—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 the liquid crystal being selectively controlled between a twisted state and a non-twisted state, e.g. TN-LC cell
- G02F1/1397—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 the liquid crystal being selectively controlled between a twisted state and a non-twisted state, e.g. TN-LC cell the twist being substantially higher than 90°, e.g. STN-, SBE-, OMI-LC cells
Abstract
ABSTRACT OF THE INVENTION
MULTICOLOR LIQUID CRYSTAL DISPLAY
A liquid crystal display device is described which includes two transparent sheets separated by a given distance, with liquid crystal material being disposed therebetween. Adjacent one transparent sheet is a stack of at least three pleochroic polarizers which act to separately polarize each incoming primary color wavelength. A second stack of at least three pleochroic polarizers are adjacent the second transparent sheet and are oriented to select the primary color polarizations exiting from the liquid crystal structure.
MULTICOLOR LIQUID CRYSTAL DISPLAY
A liquid crystal display device is described which includes two transparent sheets separated by a given distance, with liquid crystal material being disposed therebetween. Adjacent one transparent sheet is a stack of at least three pleochroic polarizers which act to separately polarize each incoming primary color wavelength. A second stack of at least three pleochroic polarizers are adjacent the second transparent sheet and are oriented to select the primary color polarizations exiting from the liquid crystal structure.
Description
~305242 Yos-88-ool MULTICOLOR LIQU_D C Y TAL DISPLAY
by H. L. Ong, S. W. Depp FIELD OF THE INVENTION
This invention relates to multicolor liquid crystal displays and, more particularly, to a multicolor liquid cry~tal display which exhibits minimum color b 1 eed- thro~gh.
DESCR I PT I ON OF THE DRAWINGS
FIG. 1 is a schematic of a prior art, 90 TN left-handed liquid crystal cell.
FIG. 2a and 2b are plots of transmission vs cell thickness for red, blue and green light wavelengths.
FIG. 3 is a schematic of a 90 TN left-handed liquid crystal cell constructed in accordance with the invention.
FIG. 4 i# a plot of entrance and exit polarization angles for a 90 TN liquid crystal cell which incorporates the invention.
FIG. .5 is a schematic blow-up of a compo~ite polarizing sheet and color filter.
FIG. 6 is a schematic of a color filter sheet usable with the invention.
There are a number of prior art multicolor di~plays which employ twisted nematic (TN) liquid crystal (LC) and polarizers. One of the more commonly proposed TNLC
displays is shown in FIG. 1. In that cell, the liquid crystal layer serves to twist linearly polarized light :
. .
Y09-88-001 la from one orientation to another (e.g., from 0 to 90).
The entrance polarizer enables light having a polarization vector 10 to enter into the TN ~iquid crystal region. If no voltage is applied across the TN
liquid crystal, the polarization vector of the light is rotated by 90 until it is parallel with line 12. If the upper polarizer sheet has its direction of polarization 14 oriented parallel to polarization vector 10, theoretically no light should pass to the viewer. In other words, the cell should be "dark". It is known that this is not the ca~e.
.~
In actuality, the structure of FIG. 1 permits "bleed-through" of various color wavelengths. This results from the fact that linearly polarized light becomes rotationally dispersed as it passes through the TN liquid crystal. In specific, the linear polarization of certain wavelengths is transformed by the liquid crystal material into elliptical polarization and passes, partially, through the second polarizing plate. A
simplified analysis of this phenomenon is found in an article by Gooch and Tarry, J. Phys. D,8, 1575 (1975). A
more generalized and comprehensive treatment of this phenomenon is presented by one of the inventors hereof, H. L. Ong in "Optical Properties of General Twisted Nematic Liquid-Crystal Displays", Applied Physics Letters 5l (18) pages 1398-1400, (1987).
Analysis of both the Gooch, Tarry equation and the more general equation given by Ong, indicates that for each thickness of a TN liquid crystal, there will be a preerred wavelength which will experience maximum transmittance and minimum rotational dispersion. All other wavelength~ will experience differing dispersions and, if subjected to parallel entrance and exit polarizing filters, will "bleed through" when the liquid crystal i8 in the "dark" or "off" state.
Referring to FIGS. 2a and 2b, charts are shown which, for primary colors red, blue and green, plot the percentage transmission T against the thickness (in microns) of a TN
liquid crystal cell. FIG. 2b is an expanded portion of the bottom-mo~t region of FIG. 2a.
- ~30524Z
From an examination of both FIGS. 2a and 2b (and an analysis in accordance with the equation given by Ong), it is apparent that transmission T is strongly dependent on cell thickness and liyht wavelength.
Thus, while the thickness of a LC cell can be optimized for a particular color, other colors will experience undesired bleed through in the dark state. For instance, assuming that a liquid crystal, having ordinary and extraordinary indices of refractions of 1.50 and 1.59 respectively is employed, the optimized cell thicknesses are 4.62 microns, 5.29 microns, and 6.36 microns for wavelengths of 4,800 Angstroms (blue), 5,500 Angstroms (green), and 6,600 Angstroms (red) respectively. If a cell thickness is optimized for 15 green, at 5.29 microns, the off state transmission for blue and red is 2.4$ and 4.5~ respectively.
Conseguently, high contrast ratios are obtained for green, but relatively low contrast ratios are~obtained for blue and red.
Ogawa et al, in U.S. Patent 4,632,514 solved this problem by proposing a liquid crystal display of the TN h type wherein the cell thickness was optimized for each color picture element. Thus, each red cell thickness 25 was optimized for red light; each green cell for green light and each blue cell ~or blue light. While this structure did overcome the rotational dispersion problem above discussed, it requires a very complex structure which is~expensive to implement.
Dir in U.S. Patent 4,506,956 proposed solving the dispersion problem through the use of a dichroic dye added to the liquid crystal material. The dye mixture, Y0988-001 ; ~ 3 -.
~3052~2 - `
together with high extinction ratio polarizers prevented light bleed through and enhanced the liquid crystal's contrast ratio.
Accordingly, it is an object of this invention to provide a color, TN liquid crystal display which exhibits minimum color bleed through.
It is another object of this invention to provide an optimized, color TN liquid crystal display having a constant thickness liquid crystal cell.
It is still a further object of this invention to provide a color TN liquid crystal display of simple planar construction.
SUMMARY OF THE INVENTION
A liquid crystal display device is described which includes two transparent sheets separated by a given distance, with liquid crystal material being disposed therebetween. Ad~acent one transparent sheet is a stack of at least three pleochroic polarizers which act to separately polarize each incoming primary color wavelength. A second stack of at least three pleochroic polarizers are adjacent the second transparent sheet and are oriented to select the primary color polarizations exiting from the liquid crystal structure.-Y0988-OOl 13052~2 -~ Y09-88-001 5 DETAILED DESCRIPTTON_OF THE INVENTION
Prior to describing the invention, definitions are given for LC cell geometry, notations, equations for calculation of off-state transmission and equations for analysis of optimum polarizer orientations.
Entrance and exit polarizers are generally placed respectively before and after the LC layer. An incident optical field, propagating in the +z direction, with polarization defined by the entrance `:i`~p ~05242 polarizer,is normally incident on the LC medium. In the cell, an LC layer of thickness d is confined between the planes at z = o and z = d of a cartesian coordinate system. Both surfaces are treated to give a homogeneous alignment with pretilt angle eS defined with respect to the surface, which is in the xy plane.
The LC director at the entrance surface is directed along the x axis: at the exit surface, the LC is d$rected at an azimuthal anqle 0 with respect to the x axis. p is denoted the LC twist angle, PEnt the entrance polarizer angle, and PExit the exit polarizer angle. All the azimuthal angles ~P~ PEnt' and PExit) are negative for the counter clockwise ~right-handed) d$rection, and positive for the clockwise (left-handed) direction.
Equation notations are as follows:
;~ is the wavelength of the incident light.
Is is the intensity of the incident light.
d is the cell thickness.
The pretilt angle ~s is defined with respect to the surface, p denotes the twist angle, P Ent ~ the entrance polarizer angle, P Exit - the exit polarizer angle, nO and ne are the ordinary and extraordinary indices of refraction.
.
W n l ~ s The formula for calculating off-state transmission is as follows: .
For an uniformly twisted nematic cell, t~e off-state transmitted intensity with normal incidence is J _ Jo[cos~ + ~ ~ sin~t~ ~ ) sin 2(~ - ~e~ s~ 2 + - ~ sin (2~ ~ ) s;n2(~ - ~e~
_ I 15jnl(~ ~ ) cos2(~ - ~e~ ~~ 2~C~]~ (I) For TN LCD's with ~s ' ~ ~Ent 3 ~ PEXit 0~
transmission expression reduces to the Gooch and Tarry formula:
J_ 1O {I-tsin[2~ ~ )~Itl~ ul~}. (2) The formula for calculating optimum polarizer orientation are:
For each LC cell, the optimized exit polarizer angle for wavelength ?~ is given by + ~ i _1 ~ sin(2 4 4 ~n ~~~~~ u oo~
where n = O, 1, 2, 3 ...
~ ' ` !
.
~305242 The optimized entrance polarizer angle for wavelength is given by n~ ~ [~ eo-(2~) I;-n 2(~ ) ~ 5;n(2~)]
by H. L. Ong, S. W. Depp FIELD OF THE INVENTION
This invention relates to multicolor liquid crystal displays and, more particularly, to a multicolor liquid cry~tal display which exhibits minimum color b 1 eed- thro~gh.
DESCR I PT I ON OF THE DRAWINGS
FIG. 1 is a schematic of a prior art, 90 TN left-handed liquid crystal cell.
FIG. 2a and 2b are plots of transmission vs cell thickness for red, blue and green light wavelengths.
FIG. 3 is a schematic of a 90 TN left-handed liquid crystal cell constructed in accordance with the invention.
FIG. 4 i# a plot of entrance and exit polarization angles for a 90 TN liquid crystal cell which incorporates the invention.
FIG. .5 is a schematic blow-up of a compo~ite polarizing sheet and color filter.
FIG. 6 is a schematic of a color filter sheet usable with the invention.
There are a number of prior art multicolor di~plays which employ twisted nematic (TN) liquid crystal (LC) and polarizers. One of the more commonly proposed TNLC
displays is shown in FIG. 1. In that cell, the liquid crystal layer serves to twist linearly polarized light :
. .
Y09-88-001 la from one orientation to another (e.g., from 0 to 90).
The entrance polarizer enables light having a polarization vector 10 to enter into the TN ~iquid crystal region. If no voltage is applied across the TN
liquid crystal, the polarization vector of the light is rotated by 90 until it is parallel with line 12. If the upper polarizer sheet has its direction of polarization 14 oriented parallel to polarization vector 10, theoretically no light should pass to the viewer. In other words, the cell should be "dark". It is known that this is not the ca~e.
.~
In actuality, the structure of FIG. 1 permits "bleed-through" of various color wavelengths. This results from the fact that linearly polarized light becomes rotationally dispersed as it passes through the TN liquid crystal. In specific, the linear polarization of certain wavelengths is transformed by the liquid crystal material into elliptical polarization and passes, partially, through the second polarizing plate. A
simplified analysis of this phenomenon is found in an article by Gooch and Tarry, J. Phys. D,8, 1575 (1975). A
more generalized and comprehensive treatment of this phenomenon is presented by one of the inventors hereof, H. L. Ong in "Optical Properties of General Twisted Nematic Liquid-Crystal Displays", Applied Physics Letters 5l (18) pages 1398-1400, (1987).
Analysis of both the Gooch, Tarry equation and the more general equation given by Ong, indicates that for each thickness of a TN liquid crystal, there will be a preerred wavelength which will experience maximum transmittance and minimum rotational dispersion. All other wavelength~ will experience differing dispersions and, if subjected to parallel entrance and exit polarizing filters, will "bleed through" when the liquid crystal i8 in the "dark" or "off" state.
Referring to FIGS. 2a and 2b, charts are shown which, for primary colors red, blue and green, plot the percentage transmission T against the thickness (in microns) of a TN
liquid crystal cell. FIG. 2b is an expanded portion of the bottom-mo~t region of FIG. 2a.
- ~30524Z
From an examination of both FIGS. 2a and 2b (and an analysis in accordance with the equation given by Ong), it is apparent that transmission T is strongly dependent on cell thickness and liyht wavelength.
Thus, while the thickness of a LC cell can be optimized for a particular color, other colors will experience undesired bleed through in the dark state. For instance, assuming that a liquid crystal, having ordinary and extraordinary indices of refractions of 1.50 and 1.59 respectively is employed, the optimized cell thicknesses are 4.62 microns, 5.29 microns, and 6.36 microns for wavelengths of 4,800 Angstroms (blue), 5,500 Angstroms (green), and 6,600 Angstroms (red) respectively. If a cell thickness is optimized for 15 green, at 5.29 microns, the off state transmission for blue and red is 2.4$ and 4.5~ respectively.
Conseguently, high contrast ratios are obtained for green, but relatively low contrast ratios are~obtained for blue and red.
Ogawa et al, in U.S. Patent 4,632,514 solved this problem by proposing a liquid crystal display of the TN h type wherein the cell thickness was optimized for each color picture element. Thus, each red cell thickness 25 was optimized for red light; each green cell for green light and each blue cell ~or blue light. While this structure did overcome the rotational dispersion problem above discussed, it requires a very complex structure which is~expensive to implement.
Dir in U.S. Patent 4,506,956 proposed solving the dispersion problem through the use of a dichroic dye added to the liquid crystal material. The dye mixture, Y0988-001 ; ~ 3 -.
~3052~2 - `
together with high extinction ratio polarizers prevented light bleed through and enhanced the liquid crystal's contrast ratio.
Accordingly, it is an object of this invention to provide a color, TN liquid crystal display which exhibits minimum color bleed through.
It is another object of this invention to provide an optimized, color TN liquid crystal display having a constant thickness liquid crystal cell.
It is still a further object of this invention to provide a color TN liquid crystal display of simple planar construction.
SUMMARY OF THE INVENTION
A liquid crystal display device is described which includes two transparent sheets separated by a given distance, with liquid crystal material being disposed therebetween. Ad~acent one transparent sheet is a stack of at least three pleochroic polarizers which act to separately polarize each incoming primary color wavelength. A second stack of at least three pleochroic polarizers are adjacent the second transparent sheet and are oriented to select the primary color polarizations exiting from the liquid crystal structure.-Y0988-OOl 13052~2 -~ Y09-88-001 5 DETAILED DESCRIPTTON_OF THE INVENTION
Prior to describing the invention, definitions are given for LC cell geometry, notations, equations for calculation of off-state transmission and equations for analysis of optimum polarizer orientations.
Entrance and exit polarizers are generally placed respectively before and after the LC layer. An incident optical field, propagating in the +z direction, with polarization defined by the entrance `:i`~p ~05242 polarizer,is normally incident on the LC medium. In the cell, an LC layer of thickness d is confined between the planes at z = o and z = d of a cartesian coordinate system. Both surfaces are treated to give a homogeneous alignment with pretilt angle eS defined with respect to the surface, which is in the xy plane.
The LC director at the entrance surface is directed along the x axis: at the exit surface, the LC is d$rected at an azimuthal anqle 0 with respect to the x axis. p is denoted the LC twist angle, PEnt the entrance polarizer angle, and PExit the exit polarizer angle. All the azimuthal angles ~P~ PEnt' and PExit) are negative for the counter clockwise ~right-handed) d$rection, and positive for the clockwise (left-handed) direction.
Equation notations are as follows:
;~ is the wavelength of the incident light.
Is is the intensity of the incident light.
d is the cell thickness.
The pretilt angle ~s is defined with respect to the surface, p denotes the twist angle, P Ent ~ the entrance polarizer angle, P Exit - the exit polarizer angle, nO and ne are the ordinary and extraordinary indices of refraction.
.
W n l ~ s The formula for calculating off-state transmission is as follows: .
For an uniformly twisted nematic cell, t~e off-state transmitted intensity with normal incidence is J _ Jo[cos~ + ~ ~ sin~t~ ~ ) sin 2(~ - ~e~ s~ 2 + - ~ sin (2~ ~ ) s;n2(~ - ~e~
_ I 15jnl(~ ~ ) cos2(~ - ~e~ ~~ 2~C~]~ (I) For TN LCD's with ~s ' ~ ~Ent 3 ~ PEXit 0~
transmission expression reduces to the Gooch and Tarry formula:
J_ 1O {I-tsin[2~ ~ )~Itl~ ul~}. (2) The formula for calculating optimum polarizer orientation are:
For each LC cell, the optimized exit polarizer angle for wavelength ?~ is given by + ~ i _1 ~ sin(2 4 4 ~n ~~~~~ u oo~
where n = O, 1, 2, 3 ...
~ ' ` !
.
~305242 The optimized entrance polarizer angle for wavelength is given by n~ ~ [~ eo-(2~) I;-n 2(~ ) ~ 5;n(2~)]
2 + 2 l~
. u ~ ~ cos(2~ ~) + ~ ~i~(2~) l~n 2~ ~ <DE"j~ ) ~4) Equations 1-4 enable one to calculate, for any liquid crystal cell, optimum polarizer orientations for light of wavelength to enable minimum off-state light transmission. Those equations were used to derive the curves shown in FIGS. 2a and 2b. As arorestated, those FIGS. illustrate that there is only one practical cell thickness (for a given wavelength), to achieve minimum light transmission. While there are larger thicknesses where minimum tran=mission occurs, cells of those thickness tend to switch too slowly to be practical.
Referring now to FIG. 3, a TN liquid crystal cell is shown wherein the single entrance and exit polarizers shown in FIG. 1 have éach been replaced by composite pleochroic polarizers 20 and 22. Each composite polarizer comprises a series o~ three superimposed polarizing sheets, each one adapted to polar~ze light o a certain wavelength and to pass, unpolarized all other wavelengths. At both entrance and exit surfaces 24 and 26 respectively, there is a composite polarizer which includes three individual sheets for polarizing red, blue and green light wavelengths (i.e., 6600 A, 5500 A and 4800 A). Thus, a green polarizinq sheet polarizes only 5500 A light but no other, etc. Such Y0988-001 ~ _ ~
.
~305242 selective polarizing sheets are available from Sanritsu Electric Co., Ltd., 1-30-13, Narimasu, Itabashi-Ku, Tokyo, Japan 175.
For each selective pair of entrance and exit, red, blue and green polarizing sheets, polarization orientations are chosen such that, for the given color, minimum transmission occurs when the liquid crystal is in the off-state. The optimized polarizer orientations, (0Ent'0Exit)' depend mainly on liquid crystal refractive indices, twist angle, cell thickness, pretilt angle, and wavelength of the light. At the optimized polarizer orientation for each LC cell structure. there are two sets of polarizer 15' (~Ent,0Exit)' such that zero ff-state transmission is obtained. This is true for every color. For a TN LC cell with 90 twist angle and an LC
with nO ~ 1.50, ne = 1.59, Os = 1, and cell thickness of d = 5.5 microns, at zero off-state transmission, 20(PEnt = 6.1 ~ 0Exit = 6.1 ), orO (0Ent 96 ' ~Exit = 83.9) for blue; (0Ent = 1-3 ~ 0Exit )' ~0Ent = 91-3 ~ 0Exit = 88.7 ) for green: and (0Ent =
' 0Exit 5.0 ), or (0Ent ' 85-0~ 0E i = 95 ) for red. Thus, the rotary dispersion in TN LCD's can be minimized by a composite polarizer configuration with each entrance and exit color polarizer set, optimized for the respective color.
FIG. 4 illustrates one set of polarizer orientations as above calculated. Note that the blue and green entrance polarizer5 have their polarizing axes oriented at 6.1 and 1.3 whereas the red entrance polarizing axes is -5Ø Furthermore, while the exit polarizing ..
YO988-OOl ~ ~
.....
. , ::' ' .
13052~2 axes are equal and opposite about the 0 axis, this need not be the case, as it is strictly the outcome of the calculation of equations 1-4 which controls.
Referring now to FIG. 5, an exploded view is shown of a composite pleochroic polarizer which includes red, blue and green polarizing sheets 30, 32 and 34. Each sheet contains an absorber which is color wavelength sensitive and allows only light polarization of the particular color to pass which is orthogonal to the absorber's axis. Other colors pass unpolarized. As can be seen, once incident light 36 has passed through sheets 30, 32 and 34, each of the primary colors is incident upon a color filter sheet 38 with a desired angle of polarization. Filter 38 enables one of the polarized colors (e.g. red) to pass into the liquid crystal material and through to the appropriately polarized, exit composite polarizing sheet (oriented as dictated by equation 3).
While only a single color filter 38 is shown, it is known to those ~Xilled in the art that a full color display require~ a compositQ filter of the type shown in FIG. 6, wherein each section denoted R, B or G
- 25~ passes only red, blue or green light respectively.
Such a filter is contemplated for inclusion in the structure shown in FIG. 3.
.
A full-color,~CD using the above described composite pleochroic polarizer configuration will have equal and complete darkness in the off-state for all colors. But due to different polarizer orientations~ light transmission in the on state may be slightly different.
YO988-001 i /~ _ ,............ . ~ ,. . . . ...... .
Equal transmitted intensity for all colors is obtained through adjusting the spectral distribution of the light source and color filter. For transmissive applications, high contrast ratio rather than high brightness is of primary importance because the brightness can be adjusted, within reasonable limits, by means of back illumination.
A preferred cell geometry is obtained by first choosing the cell thickness so that green color is at zero off-state transmission using parallel polarizers. This can be done with a cell thickness d z 5.29 microns for S500 A. ThiS gives 0gEnt ~ 0 Exit blue and red polarizers are then optimized such that zero transmission is also obtained for blue and red colors. That is, pbEnt a 4.6, 0bExit ~ -4.6 or 94.6 and 85.4 respectively, for blue; and prEnt = -6.5, 0rExit ~ 6.5 or 83.5 and 96.5 respectively for red.
Using this geometry, all three colors have zero off-state transmission, and almost the same transmission in the on-state, with green having the maximum transmission. The relative transmission for blue; green; red colors is 0.97; l; and 0.95.
Consequently little ad~ustment, or even no ad~ustment of the light source and color filter is necessary for equal intensity in the on-state for all colors, It should be understood that while the invention has ; been described with respect to a 90 TN liquid crystal cell, it is applicable to all twisted nematic LCD's having dîfferent cell thickness, pretilt angle, twist angle, and LC materials including twisted guest host LCD, 270 supertwisted guest host LCD, supertwisted Y0988-OOl ;~
, , .
.. , ~ : .
birefringent effect LCD, highly twisted birefringent effect LCD and optical mode interference effect LCD.
The invention can be used with positive and negative LCD's (where the off-state is bright and the on-state is dark); with a TN with dichroic dyes, including 90 twisted nematic guest-host LCD, and 270 twisted nematic guest-host LCD: with transmissive mode, reflective mode and transflective mode LCD's. It can be also used for any color combination (including white), besides the standard blue, green and red colors and for field sequential color displays.
The invention can also be used to optimize a color TN
15 LCD at different LC orientation, (such as a non-uniform TN field-off state and field-on state). This is also important for high pre-tilt, super-twist birefringent effect LCD cells. The polarizer orientation can also be chosen to optimize a color TN LCD at some chosen oblique incidence angle.
It i9 to be understood that the above described embodiments of the invention are illustrative only and that mod~ficationR throughout may occur to those skilled in the art. Accordingly, this invention is not to be regarded as limited to the embodiments disclosed herein, but is to be limited as defined by the appended claims.
. u ~ ~ cos(2~ ~) + ~ ~i~(2~) l~n 2~ ~ <DE"j~ ) ~4) Equations 1-4 enable one to calculate, for any liquid crystal cell, optimum polarizer orientations for light of wavelength to enable minimum off-state light transmission. Those equations were used to derive the curves shown in FIGS. 2a and 2b. As arorestated, those FIGS. illustrate that there is only one practical cell thickness (for a given wavelength), to achieve minimum light transmission. While there are larger thicknesses where minimum tran=mission occurs, cells of those thickness tend to switch too slowly to be practical.
Referring now to FIG. 3, a TN liquid crystal cell is shown wherein the single entrance and exit polarizers shown in FIG. 1 have éach been replaced by composite pleochroic polarizers 20 and 22. Each composite polarizer comprises a series o~ three superimposed polarizing sheets, each one adapted to polar~ze light o a certain wavelength and to pass, unpolarized all other wavelengths. At both entrance and exit surfaces 24 and 26 respectively, there is a composite polarizer which includes three individual sheets for polarizing red, blue and green light wavelengths (i.e., 6600 A, 5500 A and 4800 A). Thus, a green polarizinq sheet polarizes only 5500 A light but no other, etc. Such Y0988-001 ~ _ ~
.
~305242 selective polarizing sheets are available from Sanritsu Electric Co., Ltd., 1-30-13, Narimasu, Itabashi-Ku, Tokyo, Japan 175.
For each selective pair of entrance and exit, red, blue and green polarizing sheets, polarization orientations are chosen such that, for the given color, minimum transmission occurs when the liquid crystal is in the off-state. The optimized polarizer orientations, (0Ent'0Exit)' depend mainly on liquid crystal refractive indices, twist angle, cell thickness, pretilt angle, and wavelength of the light. At the optimized polarizer orientation for each LC cell structure. there are two sets of polarizer 15' (~Ent,0Exit)' such that zero ff-state transmission is obtained. This is true for every color. For a TN LC cell with 90 twist angle and an LC
with nO ~ 1.50, ne = 1.59, Os = 1, and cell thickness of d = 5.5 microns, at zero off-state transmission, 20(PEnt = 6.1 ~ 0Exit = 6.1 ), orO (0Ent 96 ' ~Exit = 83.9) for blue; (0Ent = 1-3 ~ 0Exit )' ~0Ent = 91-3 ~ 0Exit = 88.7 ) for green: and (0Ent =
' 0Exit 5.0 ), or (0Ent ' 85-0~ 0E i = 95 ) for red. Thus, the rotary dispersion in TN LCD's can be minimized by a composite polarizer configuration with each entrance and exit color polarizer set, optimized for the respective color.
FIG. 4 illustrates one set of polarizer orientations as above calculated. Note that the blue and green entrance polarizer5 have their polarizing axes oriented at 6.1 and 1.3 whereas the red entrance polarizing axes is -5Ø Furthermore, while the exit polarizing ..
YO988-OOl ~ ~
.....
. , ::' ' .
13052~2 axes are equal and opposite about the 0 axis, this need not be the case, as it is strictly the outcome of the calculation of equations 1-4 which controls.
Referring now to FIG. 5, an exploded view is shown of a composite pleochroic polarizer which includes red, blue and green polarizing sheets 30, 32 and 34. Each sheet contains an absorber which is color wavelength sensitive and allows only light polarization of the particular color to pass which is orthogonal to the absorber's axis. Other colors pass unpolarized. As can be seen, once incident light 36 has passed through sheets 30, 32 and 34, each of the primary colors is incident upon a color filter sheet 38 with a desired angle of polarization. Filter 38 enables one of the polarized colors (e.g. red) to pass into the liquid crystal material and through to the appropriately polarized, exit composite polarizing sheet (oriented as dictated by equation 3).
While only a single color filter 38 is shown, it is known to those ~Xilled in the art that a full color display require~ a compositQ filter of the type shown in FIG. 6, wherein each section denoted R, B or G
- 25~ passes only red, blue or green light respectively.
Such a filter is contemplated for inclusion in the structure shown in FIG. 3.
.
A full-color,~CD using the above described composite pleochroic polarizer configuration will have equal and complete darkness in the off-state for all colors. But due to different polarizer orientations~ light transmission in the on state may be slightly different.
YO988-001 i /~ _ ,............ . ~ ,. . . . ...... .
Equal transmitted intensity for all colors is obtained through adjusting the spectral distribution of the light source and color filter. For transmissive applications, high contrast ratio rather than high brightness is of primary importance because the brightness can be adjusted, within reasonable limits, by means of back illumination.
A preferred cell geometry is obtained by first choosing the cell thickness so that green color is at zero off-state transmission using parallel polarizers. This can be done with a cell thickness d z 5.29 microns for S500 A. ThiS gives 0gEnt ~ 0 Exit blue and red polarizers are then optimized such that zero transmission is also obtained for blue and red colors. That is, pbEnt a 4.6, 0bExit ~ -4.6 or 94.6 and 85.4 respectively, for blue; and prEnt = -6.5, 0rExit ~ 6.5 or 83.5 and 96.5 respectively for red.
Using this geometry, all three colors have zero off-state transmission, and almost the same transmission in the on-state, with green having the maximum transmission. The relative transmission for blue; green; red colors is 0.97; l; and 0.95.
Consequently little ad~ustment, or even no ad~ustment of the light source and color filter is necessary for equal intensity in the on-state for all colors, It should be understood that while the invention has ; been described with respect to a 90 TN liquid crystal cell, it is applicable to all twisted nematic LCD's having dîfferent cell thickness, pretilt angle, twist angle, and LC materials including twisted guest host LCD, 270 supertwisted guest host LCD, supertwisted Y0988-OOl ;~
, , .
.. , ~ : .
birefringent effect LCD, highly twisted birefringent effect LCD and optical mode interference effect LCD.
The invention can be used with positive and negative LCD's (where the off-state is bright and the on-state is dark); with a TN with dichroic dyes, including 90 twisted nematic guest-host LCD, and 270 twisted nematic guest-host LCD: with transmissive mode, reflective mode and transflective mode LCD's. It can be also used for any color combination (including white), besides the standard blue, green and red colors and for field sequential color displays.
The invention can also be used to optimize a color TN
15 LCD at different LC orientation, (such as a non-uniform TN field-off state and field-on state). This is also important for high pre-tilt, super-twist birefringent effect LCD cells. The polarizer orientation can also be chosen to optimize a color TN LCD at some chosen oblique incidence angle.
It i9 to be understood that the above described embodiments of the invention are illustrative only and that mod~ficationR throughout may occur to those skilled in the art. Accordingly, this invention is not to be regarded as limited to the embodiments disclosed herein, but is to be limited as defined by the appended claims.
Claims (6)
1. A liquid crystal display device comprising:
a cell having two transparent sheets separated by a constant predetermined distance;
TN liquid crystal material disposed between said transparent sheets, said TN liquid crystal means acting to rotate the polarization vector of different light colors by different amounts for a given distance of travel by a light color through said TN liquid crystal material;
at least three color-specific polarizer plates in sandwich relationship with one said transparent sheet, each said polarizer plate oriented to provide light of a specific color with a known entry polarization, so that said TN liquid crystal material causes the polarization vector of each said light color to rotate by a known amount over said predetermined distance; and output polarizer means adjacent said second transparent sheet and having an absorption axis parallel to each said rotated color polarization vector.
a cell having two transparent sheets separated by a constant predetermined distance;
TN liquid crystal material disposed between said transparent sheets, said TN liquid crystal means acting to rotate the polarization vector of different light colors by different amounts for a given distance of travel by a light color through said TN liquid crystal material;
at least three color-specific polarizer plates in sandwich relationship with one said transparent sheet, each said polarizer plate oriented to provide light of a specific color with a known entry polarization, so that said TN liquid crystal material causes the polarization vector of each said light color to rotate by a known amount over said predetermined distance; and output polarizer means adjacent said second transparent sheet and having an absorption axis parallel to each said rotated color polarization vector.
2, The invention as defined in Claim 1 wherein said output polarizer means comprises three color specific polarizer plates.
3. The invention of Claim 2 further comprising:
color filter means associated with at least one said transparent sheet.
color filter means associated with at least one said transparent sheet.
4. The invention as defined in Claim 3 wherein said color filter means comprises a plurality of red, blue, green filter areas.
5. The invention as defined in Claim 4 further comprising means for applying across said TN liquid crystal means, a voltage which causes said TN liquid crystal means to orient along the field lines created by said applied voltage.
6. A liquid crystal cell of planar form and constant thickness comprising:
first red, blue and green superimposed polarizing plates adjacent one side of said cell; and second red, blue and green superimposed polarizing plates adjacent the other side of said cell, each of said second plates having a direction of polarization perpendicular to a rotated polarization direction created by said liquid crystal cell for its respective color.
first red, blue and green superimposed polarizing plates adjacent one side of said cell; and second red, blue and green superimposed polarizing plates adjacent the other side of said cell, each of said second plates having a direction of polarization perpendicular to a rotated polarization direction created by said liquid crystal cell for its respective color.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US07/263,822 | 1988-10-28 | ||
US07/263,822 US4968120A (en) | 1988-10-28 | 1988-10-28 | Multicolor liquid crystal display |
Publications (1)
Publication Number | Publication Date |
---|---|
CA1305242C true CA1305242C (en) | 1992-07-14 |
Family
ID=23003368
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
CA000602241A Expired - Fee Related CA1305242C (en) | 1988-10-28 | 1989-06-08 | Multicolor liquid crystal display |
Country Status (4)
Country | Link |
---|---|
US (1) | US4968120A (en) |
EP (1) | EP0365778A3 (en) |
JP (1) | JPH02150821A (en) |
CA (1) | CA1305242C (en) |
Families Citing this family (22)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5237437A (en) * | 1989-12-18 | 1993-08-17 | Honeywell Inc. | Apparatus and method for a high contrast, wide angle, color, flat panel, liquid crystal display |
US5264951A (en) * | 1990-04-09 | 1993-11-23 | Victor Company Of Japan, Ltd. | Spatial light modulator system |
US5233458A (en) * | 1991-07-01 | 1993-08-03 | Kaiser Aerospace And Electronics Corporation | Method and apparatus to reduce binocular rivalry in a partial overlap binocular display |
WO1993004393A1 (en) * | 1991-08-19 | 1993-03-04 | Smiths Industries, Inc. | Improved lighting technique for color displays |
US5760860A (en) * | 1994-02-25 | 1998-06-02 | The Secretary Of State For Defense In Her Britannic Majesty's Government Of The United Kingdom Of Great Britain And Northern Ireland | Electro-optic scattering type devices with color polariser for switchable color |
SG47360A1 (en) * | 1994-11-14 | 1998-04-17 | Hoffmann La Roche | Colour display with serially-connected lc filters |
JPH10170905A (en) * | 1996-12-09 | 1998-06-26 | Alps Electric Co Ltd | Color polarization filter for reflection and reflection-type color liquid crystal display device using the filter |
US5825451A (en) * | 1997-10-17 | 1998-10-20 | Advanced Display Systems, Inc. | Methods of manufacturing multi-color liquid crystal displays using in situ mixing techniques |
US5982464A (en) * | 1998-12-16 | 1999-11-09 | Technoloogy Resource International Corporation | Multi-twist color liquid crystal display |
US7170679B2 (en) * | 2002-09-18 | 2007-01-30 | Vision Quest Lighting, Inc. | Optically active color filter |
TWI398705B (en) | 2005-11-04 | 2013-06-11 | Semiconductor Energy Lab | Display device |
WO2007063782A1 (en) * | 2005-11-30 | 2007-06-07 | Semiconductor Energy Laboratory Co., Ltd. | Display device |
EP1793264A1 (en) * | 2005-12-05 | 2007-06-06 | Semiconductor Energy Laboratory Co., Ltd. | Liquid crystal display device |
WO2007072766A1 (en) * | 2005-12-22 | 2007-06-28 | Semiconductor Energy Laboratory Co., Ltd. | Display device |
EP1804114B1 (en) * | 2005-12-28 | 2014-03-05 | Semiconductor Energy Laboratory Co., Ltd. | Display device |
EP1804115A1 (en) * | 2005-12-28 | 2007-07-04 | Semiconductor Energy Laboratory Co., Ltd. | Display device |
EP1832915B1 (en) * | 2006-01-31 | 2012-04-18 | Semiconductor Energy Laboratory Co., Ltd. | Display device with improved contrast |
EP1826604B1 (en) * | 2006-01-31 | 2015-12-23 | Semiconductor Energy Laboratory Co., Ltd. | Display device |
KR20080092466A (en) * | 2006-02-02 | 2008-10-15 | 가부시키가이샤 한도오따이 에네루기 켄큐쇼 | Display device |
EP1816508A1 (en) * | 2006-02-02 | 2007-08-08 | Semiconductor Energy Laboratory Co., Ltd. | Display device |
EP1826606B1 (en) | 2006-02-24 | 2012-12-26 | Semiconductor Energy Laboratory Co., Ltd. | Display device |
EP1826605A1 (en) | 2006-02-24 | 2007-08-29 | Semiconductor Energy Laboratory Co., Ltd. | Display device |
Family Cites Families (9)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS5493394A (en) * | 1977-12-30 | 1979-07-24 | Seiko Epson Corp | Liquid crystal display unit |
EP0097384B1 (en) * | 1982-06-18 | 1987-01-28 | Koninklijke Philips Electronics N.V. | Liquid-crystal display device |
US4506956A (en) * | 1983-03-29 | 1985-03-26 | Xerox Corporation | Multicolor liquid crystal display with a dead front |
JPS59219719A (en) * | 1983-05-27 | 1984-12-11 | Seiko Instr & Electronics Ltd | Display device of color liquid crystal |
US4632514A (en) * | 1984-01-31 | 1986-12-30 | Matsushita Electric Industrial Co., Ltd. | Color liquid crystal display apparatus |
JPS6139642A (en) * | 1984-07-28 | 1986-02-25 | Sumitomo Electric Ind Ltd | Light transmitting device |
JPS62206524A (en) * | 1986-03-07 | 1987-09-11 | Stanley Electric Co Ltd | Liquid crystal display |
JPS63274920A (en) * | 1987-05-06 | 1988-11-11 | Jeco Co Ltd | Liquid crystal stereoscopic display device |
JPS6482014A (en) * | 1987-09-25 | 1989-03-28 | Fujitsu Ltd | Liquid crystal display element |
-
1988
- 1988-10-28 US US07/263,822 patent/US4968120A/en not_active Expired - Fee Related
-
1989
- 1989-06-08 CA CA000602241A patent/CA1305242C/en not_active Expired - Fee Related
- 1989-08-18 EP EP19890115241 patent/EP0365778A3/en not_active Withdrawn
- 1989-10-06 JP JP1260390A patent/JPH02150821A/en active Pending
Also Published As
Publication number | Publication date |
---|---|
EP0365778A3 (en) | 1990-12-05 |
JPH02150821A (en) | 1990-06-11 |
US4968120A (en) | 1990-11-06 |
EP0365778A2 (en) | 1990-05-02 |
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