CA1305242C - Multicolor liquid crystal display - Google Patents

Multicolor liquid crystal display

Info

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
Authority
CA
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
Application number
CA000602241A
Other languages
French (fr)
Inventor
Steven W. Depp
Hiap L. Ong
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.)
International Business Machines Corp
Original Assignee
International Business Machines Corp
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 International Business Machines Corp filed Critical International Business Machines Corp
Application granted granted Critical
Publication of CA1305242C publication Critical patent/CA1305242C/en
Anticipated expiration legal-status Critical
Expired - Fee Related legal-status Critical Current

Links

Classifications

    • GPHYSICS
    • G02OPTICS
    • G02FOPTICAL 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
    • G02F1/00Devices 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
    • G02F1/01Devices 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 
    • G02F1/13Devices 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
    • G02F1/133Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/1333Constructional arrangements; Manufacturing methods
    • G02F1/1335Structural association of cells with optical devices, e.g. polarisers or reflectors
    • G02F1/133528Polarisers
    • G02F1/133533Colour selective polarisers
    • GPHYSICS
    • G02OPTICS
    • G02FOPTICAL 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
    • G02F1/00Devices 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
    • G02F1/01Devices 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 
    • G02F1/13Devices 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
    • G02F1/133Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/1333Constructional arrangements; Manufacturing methods
    • G02F1/1335Structural association of cells with optical devices, e.g. polarisers or reflectors
    • G02F1/133528Polarisers
    • G02F1/133531Polarisers characterised by the arrangement of polariser or analyser axes
    • GPHYSICS
    • G02OPTICS
    • G02FOPTICAL 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
    • G02F1/00Devices 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
    • G02F1/01Devices 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 
    • G02F1/13Devices 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
    • G02F1/137Devices 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
    • G02F1/13725Devices 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
    • GPHYSICS
    • G02OPTICS
    • G02FOPTICAL 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
    • G02F1/00Devices 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
    • G02F1/01Devices 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 
    • G02F1/13Devices 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
    • G02F1/137Devices 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
    • G02F1/139Devices 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
    • G02F1/1393Devices 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
    • GPHYSICS
    • G02OPTICS
    • G02FOPTICAL 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
    • G02F1/00Devices 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
    • G02F1/01Devices 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 
    • G02F1/13Devices 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
    • G02F1/137Devices 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
    • G02F1/139Devices 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
    • G02F1/1396Devices 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
    • GPHYSICS
    • G02OPTICS
    • G02FOPTICAL 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
    • G02F1/00Devices 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
    • G02F1/01Devices 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 
    • G02F1/13Devices 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
    • G02F1/137Devices 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
    • G02F1/139Devices 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
    • G02F1/1396Devices 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
    • G02F1/1397Devices 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.

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~)]
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.

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.
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.
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.
CA000602241A 1988-10-28 1989-06-08 Multicolor liquid crystal display Expired - Fee Related CA1305242C (en)

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)

* Cited by examiner, † Cited by third party
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)

* Cited by examiner, † Cited by third party
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

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

Similar Documents

Publication Publication Date Title
CA1305242C (en) Multicolor liquid crystal display
CA1168489A (en) Color filter
EP0393191B1 (en) Liquid crystal display
US5184237A (en) Super-twisted nematic type liquid crystal display device
US20020021387A1 (en) Polarized display with wide-angle illumination
WO1997028482A9 (en) Twisted type nematic liquid crystal display
KR950029815A (en) Color liquid crystal display device
EP0699938A2 (en) Liquid crystal display
CA2009319C (en) Liquid crystal display device
JP3289386B2 (en) Color liquid crystal display
JPH10239683A (en) Reflective-type liquid crystal; display device
JPH0815691A (en) Color liquid crystal display device
JPH02125224A (en) Electrooptic element
US5745204A (en) Liquid crystal color display device
JPH06308481A (en) Color liquid crystal display device
JP3289385B2 (en) Color liquid crystal display
JP2000347187A (en) Reflective liquid crystal display device
JPH08313899A (en) Reflection type liquid crystal display device
JP3289392B2 (en) Color liquid crystal display
JP3289391B2 (en) Color liquid crystal display
KR940006984B1 (en) Liquid crystal display device
JPH09258214A (en) Color liquid crystal display device
JPH06317792A (en) Color liquid crystal display device
JPH11174497A (en) Color liquid crystal display device
JP3188427B2 (en) Liquid crystal device

Legal Events

Date Code Title Description
MKLA Lapsed