EP1690130A1 - Dispositif d'affichage a ecran de type nematique bistable optimisant le blanc et procede de definition de ce dispositif - Google Patents
Dispositif d'affichage a ecran de type nematique bistable optimisant le blanc et procede de definition de ce dispositifInfo
- Publication number
- EP1690130A1 EP1690130A1 EP04805550A EP04805550A EP1690130A1 EP 1690130 A1 EP1690130 A1 EP 1690130A1 EP 04805550 A EP04805550 A EP 04805550A EP 04805550 A EP04805550 A EP 04805550A EP 1690130 A1 EP1690130 A1 EP 1690130A1
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- European Patent Office
- Prior art keywords
- orientation
- observer
- polarizer
- range
- liquid crystal
- 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.)
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Classifications
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- 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
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- 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
- G02F1/1391—Bistable or multi-stable liquid crystal 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
- G02F1/133—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
Definitions
- the present invention relates to the field of liquid crystal display devices and more precisely to the optical configuration of a nematic display. bistable operating in an optical mode which optimizes the white state of this display.
- the present invention applies in particular to displays of the reflective type. However, it is not strictly limited to this application.
- the invention indeed also relates to transflective type displays.
- OBJECT OF THE INVENTION A general aim of the present invention is to improve the white state of a bistable display device, that is to say more precisely to obtain a reflectance of the white state of very good quality in terms of luminance and colorimetry across the whole viewing angle. STATE OF THE ART Bistable liquid crystal display switching between two textures differing by a twist of 180 °
- the type of bistable liquid crystal display considered in this invention is a display that switches between two textures, stable with no electric field applied (hence its bistability), different from each other by an angle of ⁇ .
- the angle ⁇ u between the directors of the liquid crystal molecules on the two surfaces of the cell is of the order of 0 to ⁇ 30 °.
- the molecules remain almost parallel to each other, and we will call this texture U.
- the molecules in the texture T rotate around 180 ° ( ⁇ 30 °) between the two cell surfaces.
- the nematic liquid crystal is chiralised so as to have a spontaneous pitch p 0 close to four times the thickness d of the cell, for equalize the energies of the two textures.
- the ratio between the thickness d of the cell and the spontaneous step p 0 , ie d / p 0 is therefore approximately equal to 0.25 +/- 0.1, preferably 0.25 ⁇ 0.05. Without an electric field, these are the minimum energy states.
- Document [1] describes a display which switches between the two textures U and T by applying an electric field pulse of precise shape.
- This display is based on a break in the anchoring of the liquid crystal molecule on one of the so-called zenith alignment surfaces (documents [2] and [3]), that is to say that the molecule is lifted by the field electric before falling back on one side or the other, thus allowing the obtaining of the two textures U and T.
- the structure of the electrodes necessary for the application of the field is standard, identical to that used for the TN or STN type liquid crystal displays.
- This display is generally called BiNem ® . "
- Document [4] describes a display which also uses an anchoring break and a particular type of electrode (called “comb shaped electrodes”), making it possible to obtain a component of the lateral electric field, ie parallel to the substrate.
- the switching between the two textures is carried out in this case by an effect qualified by the author as a break in the azimuth anchoring (document [5]).
- the optical mode requiring white optimization is mainly the reflective mode, which uses ambient light as light source. In this case, what is sought is to obtain a screen which most resembles black ink on white paper.
- This mode uses a cell delay of the same order of magnitude as a display operating in a transmitted mode, between ⁇ / 3 and ⁇ / 2.
- a mode using a single polarizer (transmissive) on the observer side and a mirror placed on the back of the cell The advantage of this mode is that one can integrate the mirror inside the cell. In this case the two images coincide, there is no longer a spurious image.
- the reflective mode studied in detail in the literature is the mode operating with a polarizer and a mirror.
- documents [4], [6] and [7] calculate optimal modes for a linear input polarizer.
- Document [8] studies this reflective mode using a circular type input polarizer.
- This mode when the mirror is integrated in the cell, involves a complication of the manufacturing process because it is necessary to integrate in the cell a reflecting and diffusing function.
- the delay value ⁇ nd giving the best optical results is of the order of ⁇ / 4, ⁇ representing a wavelength of the visible spectrum, which is approximately two times lower than the delay value adapted in the case.
- a mode with two polarizers A reduction of a factor two of the delay can in theory be obtained by decreasing either the value of the ⁇ n of the crystal liquid is the thickness of the cell.
- the thickness recommended for a bistable display as described above is however already small, of the order of 2 microns, compared to that of a standard liquid crystal display of TN or STN type (around 4 to 5 microns) and halving this value would lead to serious complications in the cell manufacturing process.
- a reduction in the optical anisotropy of the liquid crystal mixture while retaining the electrical anisotropy necessary for breaking the zenithal anchoring is also difficult to achieve.
- the objective of the present invention is to optimize a reflective mode with two polarizers, making it possible to use commercial components and not entailing any substantial modification of the manufacturing process and of the optical delay ⁇ nd, compared with a cell operating in transmissive mode.
- a nematic liquid crystal display device having two stable states, without electric field, obtained by anchoring breakage, characterized in that it has two polarizers, one placed on the observer side, the other on the opposite side of the liquid crystal cell and the latter being at least partially reflective to define a reflective or transflective mode, the orientation of the two polarizers being offset by '' a value equal to the rotational power of the cell to within +/- 30 °.
- the two stable states correspond to two textures of liquid crystal molecules whose torsion differs from 150 ° to 180 ° in absolute value. .
- the orientation of the polarizer placed opposite the observer, relative to the nematic director on the associated face of the cell being included in the range comprising the range + or - (10 ° to 80 °) while the orientation of the polarizer placed on the side of the observer, relative to the same nematic director reference, is included in the range comprising the range of + or - (10 ° to 80 °) for an optical delay ⁇ nd of the order of 250+ 70nm. .
- the orientation of the polarizer placed opposite the observer, relative to the nematic director on the associated face of the cell is in the range [-75 °; -30 °] U [10 °; 65 °]
- the orientation of the polarizer placed on the side of the observer, relative to the same reference of nematic director is included in the range [-60 °; -10 °] U [30 °; 80 °]
- the orientation of the polarizer placed opposite the observer, relative to the nematic director on the associated face of the cell is in the range [-65 °; -10 °] U [30 °; 75 °]
- the orientation of the polarizer placed on the side of the observer, with respect to the same nematic director reference is included in the range [-80 °; -30 °
- the orientation of the polarizer placed opposite to the the observer, relative to the nematic director on the associated face of the cell is included in the range [-65 °; -30 °] U [25 °; 65 °] preferentially [-50 °; -40 °] U [40 °; 50 °], while the orientation of the polarizer placed on the side of the observer, with respect to the same nematic director reference, is included in the range [-40 °; - 10 °] U [50 °; 80 °] preferably [-25 °; -10 °] U [64 °; 80 °], and in the case of a dextrorotatory liquid crystal, for brushing directions making between them between -15 ° and -30 °, the orientation of the polarizer placed opposite the observer,
- the orientation of the polarizer placed opposite the the observer, relative to the nematic director on the associated face of the cell is included in the range [-60 °; -30 °] U [25 °; 65 °] preferentially [-50 °; -40 °] U [40 °; 50 °], while the orientation of the polarizer placed on the side of the observer, with respect to the same nematic director reference, is included in the range [-40 °; - 20 °] U [50 °; 70 °] preferably [-35 °; -25 °] U [55 °; 65 °], and in the case of a dextrorotatory liquid crystal, for brushing directions making between them between -10 ° and -20 °, the orientation of the polarizer placed opposite the observer, relative
- the orientation of the polarizer placed at the opposite of the observer, relative to the nematic director on the associated face of the cell is included in the range [-75 °; -35 °] U [15 °; 55 °] preferably [-60 °; -50 °] U [30 °; 40 °], while the orientation of the polarizer placed on the side of the observer, with respect to the same reference of nematic director, is included in the range [-50 °; - 20 °] U [40 °; 70 °] preferably [-40 °; -30 °] U [50 °; 60 °], and in the case of a dextrorotatory liquid crystal, for brushing directions making between them between 0 ° and +/- 5 °, the orientation of the polarizer placed at the opposite of the observer, relative to the nematic director on the associated face of the cell, is included in the range [-75 °; -35 °] U [15 °; 55 °]
- the orientation of the polarizer placed at the opposite of the observer, relative to the nematic director on the associated face of the cell is included in the range [-65 °; -40 °] U [20 °; 60 °] preferably [-55 °; -45 °] U [35 °; 45 °], while the orientation of the polarizer placed on the side of the observer, relative to the same reference of nematic director, is included in the range [-60 °; - 20 °] U [30 °; 70 °] preferably [-45 °; -35 °] U [45 °; 55 °], and in the case of a dextrorotatory liquid crystal, for brushing directions making between them between 0 ° and +/- 5 °, the orientation of
- the orientation of the polarizer placed at the opposite of the observer, relative to the nematic director on the associated face of the cell is included in the range [-80 °; -50 °] U [10 °; 60 °], while that the orientation of the polarizer placed on the side of the observer, with respect to the same nematic director reference, is included in the range [-50 °; -25 °] U [45 °; 65 °], and in the case of a dextrorotatory liquid crystal, for brushing directions making between them between 0 ° and +/- 5 °, the orientation of the polarizer placed at l the opposite of the observer, relative to the nematic director on the associated face of the cell, is included in the range [-60 °; -10 °] U [50 °;
- the orientation of the polarizer placed opposite the observer, relative to the nematic director on the associated face of the cell is included in the range [-65 °; -40 °] U [25 °; 50 °] preferably [- 60 °; -45 °] U [30 °; 45 °]
- the orientation of the polarizer placed from side of the observer, relative to the same nematic director reference is in the range [-50 °; -20 °] U [40 °; 65 °] preferably [-40 °; -30 °] U [48 °; 60 °]
- a dextrorotatory liquid crystal for brushing directions between them between -5 ° and -15 °, taking into account an elastic
- the present invention also provides a method for optimizing the orientation of two polarizers in a nematic liquid crystal display device having two stable states by anchoring breakage, one of the polarizers being placed on the observer side while the other polarizer is placed on the opposite side of the liquid crystal cell and the latter being at least partially reflective to define a reflective or transflective mode, characterized in that it comprises the steps consisting in:
- FIG. 1 schematically represents a liquid crystal cell according to the present invention and defines the angles used in the rest of the description
- FIG. 2 schematically represents the angles ⁇ and w characteristic of an elliptical polarization
- FIG. 4 schematically represents the brushing directions on the analyzer and polarizer side and the orientations of the liquid crystal molecules on the alignment layers for the case of an infinitely strong azimuth anchoring
- - Figure 6 shows schematically a view similar to Figure 4 for the case of a finished azimuth anchoring on the cell plate located on the side of the analyzer.
- DETAILED DESCRIPTION OF THE INVENTION The inventors propose an approach which makes it possible to obtain an optical mode with two preferentially reflective polarizers, for a cell [ ⁇ u; ⁇ optimized to obtain a very good overall optical quality of the white state and taking into account certain industrial constraints.
- the inventors also propose to apply this approach to a real cell, that is to say taking into account an azimuth anchoring known as “finite” (that is to say not infinitely strong) for example on one of the alignment layers .
- an azimuth anchoring known as “finite” (that is to say not infinitely strong) for example on one of the alignment layers .
- the two textures differ by a different angle from ⁇ .
- the present invention also applies to the case of a display in which the azimuth anchoring is finished on the two alignment layers, that is to say on the two faces of the display.
- the ideal is to approach the quality of black ink on white paper.
- the paramount parameter is therefore the quality of the white, characterized by its luminance and its color on the whole of the half plan of vision of the screen.
- Texture T has a lower wavelength dispersion and greater optical stability in the viewing angle than texture U, and will therefore be chosen for white.
- the approach proposed by the inventors consists in calculating the optimum optical mode giving the best white for several values of delay ⁇ nd.
- the delay value finally chosen will depend on the quality compromise of the desired white-contrast.
- FIG. 1 There is shown schematically in FIG. 1 appended a liquid crystal display cell according to the present invention comprising: an analyzer polarizer 10 on the observer side,
- the arrow 50 schematically represents the path of the light rays
- the section 52 representing the outward part (of Taller optical transmission) of the path of the light rays which passes through the analyzer 10 and the cell materialized by the plates 20, 30 before reaching the polarizer 40
- the section 54 represents the return part (Tretour optical transmission) of the path of the rays reflected on the polarizer 40.
- the anchors on the plates 20 and 30 are adapted to allow switching of the nematic liquid crystal molecules between two respectively stable states U and T, which differ between them by a twist of the order of ⁇ , by application of applied electrical signals on electrodes provided on the plates 20 and 30 according to the known methods described in the aforementioned documents.
- Such a liquid crystal cell is characterized by:
- the light which illuminates the screen is the ambient light situated on the side of the observer.
- the polarizer 40 of FIG. 1 is therefore of the reflective type and the output polarizer 10 (observer side) is of the transmissive type.
- ⁇ and ⁇ The angles which the polarizer 40 and the analyzer 10 make respectively with the director of the liquid crystal located on the same side are called ⁇ and ⁇ .
- the value of the torsion of the liquid crystal cell is obtained by making the difference between the director 22 of the liquid crystal on one of the faces 20 of the cell and the director 32 on the other face 30: ⁇ ⁇ ⁇ A -
- Trs ⁇ , ⁇ ) cos 2 (a + ⁇ ) - cos 2 tan Y + tan2 / [1]
- the formula [1] can also be obtained as a function of A and P instead of ⁇ and ⁇ .
- the inventors use the Poincaré formalism, which describes the different possible polarization states as well as the evolution of this during its propagation in the cell by a trace on a sphere called Pointcaré sphere (documents [9] or [10 ]).
- the output polarization Pout is weakly elliptical (almost linear) and the long axis of this ellipse forms an angle PR with respect to the input polarization.
- the output polarization Pout a priori arbitrary therefore elliptical, can be characterized by 2 angles ⁇ and ⁇ .
- ⁇ is the angle made by the major axis of the ellipse with x 'and ⁇ characterizes the ellipticity of the polarization (see figure 2).
- the cancellation of the ellipticity ⁇ is equivalent to obtaining at the cell output a linear polarization, that is to say a configuration where it is possible to obtain with the analyzer 10 a perfect black or white.
- the optimal configuration is calculated for a cell delay ⁇ nd and a given wavelength ⁇ .
- Table 1 describes the optimal reflective optical configurations for different delay values equal to ⁇ / 2 in the visible spectrum range (400nm for blue to 620nm for red).
- the parameter ⁇ is chosen equal to ⁇ opt for each delay value.
- Table 1 To estimate the performances of these configurations and compare them with each other, also appear in table 1 the value of the normalized luminances of the black state and of the white state calculated on the whole of the visible spectrum, as well as the contrast CR ratio. of the two luminances.
- Standardized luminances are calculated as follows: with T R ( ⁇ ) optical transmission of the liquid crystal cell back and forth, y ( ⁇ ) sensitivity of the eye and s ( ⁇ ) spectrum of the illumination source, which we assume constant and equal to 1 (spectrum called " dish ").
- the x, y color coordinates of white (CIE system) are also calculated, which are very important for the visual rendering of the screen.
- perfectly neutral white has the coordinates (0.333; 0.333).
- the white is very close to 1, because the texture T works optimally, the output polarization being linear for the case ⁇ op .
- the color of the white remains close to the theoretical white (0.333; 0.333) for all cases.
- the values corresponding to a delay ⁇ nd of less than 230nm are preferred.
- Black is obtained with the texture U. It is therefore optimized when it has a delay of ⁇ / 2 for the wavelength where the eye is most sensitive.
- Table 1 the best theoretical contrast value for the 275 nm delay, which corresponds to ⁇ / 2 for 550 nm, peak of sensitivity of the eye.
- the contrast value for 275 nm is very high, due to the double pass through the cell. This double pass also makes it possible to obtain good contrast values (> 50) over a large range of delays.
- a satisfactory configuration for contrast is in theory a delay of 275 nm, but a smaller delay (230 nm or 200 nm) makes it possible to obtain a more neutral colorimetric white and would therefore be preferred, as indicated above.
- the delay chosen will depend on the compromise desired.
- the director 22, 32 of the liquid crystal molecule on each face 20, 30 of the cell is determined by the brushing direction of the alignment layer (of polyimide chemical type for example) used on this face. Indeed for an infinitely strong azimuth anchoring, the director of the liquid crystal aligns parallel to the brushing direction (see Figure 4). In this case, a precise value of ⁇ is obtained by fixing the brushing directions of the two alignment layers on the production machine of the display, such that they make an angle ⁇ between them.
- the brushing directions of the cell can be imposed for example by the industrial process.
- the calculation of the best configuration for the polarizer 40 or P and the analyzer 10 or A according to the best white criterion is carried out as follows: Optimization of the white
- Table 2 describes the optimal reflective optical configurations for different values of the delay close to ⁇ / 2.
- the white is slightly less good (around 5%) because the texture T is not at the optimum, but the output polarization remains very slightly elliptical, which guarantees a good level of white.
- the more the delay decreases the more one approaches the condition ⁇ opt ( ⁇ opt approaches -180 ° when the delay decreases). For 200 nm, the white is very close to 1. We find the yellowing effect again when the delay increases.
- the black is produced by a texture U without twist which acts, as before, like a birefringent blade.
- the maximum value of the contrast corresponds as previously to a delay of 275 nm, but the contrast remains high for the other delays due to the double pass.
- the best configuration for contrast is a delay of 275 nm, but a smaller delay (230nm or 200 nm) makes it possible to obtain a more neutral colorimetric white.
- the delay chosen depends on the compromise desired.
- optical transmissions T R of the white and black states corresponding to the 230 nm delay of table 2 are given in FIG. 5 as a function of the wavelength.
- Improvement of the colorimetric neutrality of the white is to adjust the polarizers 10 or A and 40 or P to angles similar but different from those calculated by the method described previously. In this case, the condition on the rotary power which guarantees the brightest white is no longer strictly observed. In fact we agree to lose on the luminance of white to improve the colorimetry.
- transflective for which the rear polarizer 40 or P is transflective, that is to say partially reflecting: part of the polarized light is transmitted, the other part is thoughtful.
- This allows the screen to operate either in transmissive mode when it is backlit, or in reflective mode using ambient light as a light source when not backlit.
- the optimization of white is identical for the reflective and transflective modes, but for the latter the quality of black is low when it operates in transmissive mode (black is not optimized since the light operates, a "one way” through the cell instead of a "round trip" for the reflective mode).
- the dropout goes in the direction of decreasing the absolute value of the torsion of low value ⁇ u, which becomes for example ⁇ u - DE for ⁇ u> 0, and of decreasing the absolute value of the torsion of high value ⁇ ⁇ , which becomes for example ⁇ ⁇ + DE for ⁇ ⁇ ⁇ 0 (see figure 6).
- a finished azimuth anchor typically has Laz in the range of 100 to
- the parameter DE is a physical parameter measurable experimentally, therefore assumed to be known.
- the optimal optical configurations are calculated for the three delay values 310nm, 275nm and 230nm, and for the 2 values of DE 5 ° and 10 °, respectively in Tables 3, 4 and 5. It is noted on these tables that in the presence elastic stall, it is possible to optimize the brushing directions ( ⁇ *) to obtain good performance of the reflective mode: the white is for all cases very close to 1. The highest contrast corresponds as before to a delay of 275 nm, but it remains acceptable for the other delay values considered. All of these configurations have acceptable performance for a screen in reflective mode. Case where the parameter ⁇ * is imposed
- the brushing direction of the cells ⁇ * can be imposed, typically at 0 ° for example.
- the results for the 3 previous delay values are given respectively in Tables 6, 7 and 8. It can be seen in these tables that in the presence of elastic dropout and with ⁇ * imposed at 0 °, it is possible to obtain good performance of the reflective mode: the white is in all cases very close to 1. The highest contrast corresponds as before to a delay of 275 nm, but it remains acceptable for the other delay values considered. All of these configurations have acceptable performance for a screen in reflective mode.
- Table 2 optimal configurations for different delay values, with ⁇ imposed.
- Table 2 “modified” configuration to improve the colorimetry of white, delay 230 nm and ⁇ imposed.
- VARIANTS OF THE INVENTION The foregoing description relates to a levogyre liquid crystal.
- the invention is of course valid when the liquid crystal is dextrorotatory.
- the equivalent configurations are obtained by reversing the signs of ⁇ U and ⁇ T.
- the optimal orientations of the polarizers 40 and analyzer 10 are obtained by reversing the signs of P and A.
- Table 9 (ex 2 '): “modified” configuration to improve the colorimetry of white, delay 230 nm and ⁇ imposed - case of a dextrorotatory liquid crystal.
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FR0313991A FR2863061B1 (fr) | 2003-11-28 | 2003-11-28 | Dispositif d'affichage a ecran de type nematique optimisant le blanc et procede de definition de ce dispositif |
PCT/FR2004/003021 WO2005054940A1 (fr) | 2003-11-28 | 2004-11-25 | Dispositif d’affichage a ecran de type nematique bistable optimisant le blanc et procede de definition de ce dispositif |
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CN (1) | CN100541303C (fr) |
FR (1) | FR2863061B1 (fr) |
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FR2863062B1 (fr) * | 2003-11-28 | 2006-03-17 | Nemoptic | Dispositif d'affichage a ecran de type nematique bistable optimisant le noir et procede de definition de ce dispositif |
US7106411B2 (en) | 2004-05-05 | 2006-09-12 | Imax Corporation | Conversion of cinema theatre to a super cinema theatre |
EP2178079B1 (fr) | 2008-10-15 | 2014-07-30 | France Brevets | Procédé économique en énergie pour marquer une zone d'un écran à cristal liquide |
US20110065081A1 (en) * | 2009-09-17 | 2011-03-17 | Shengmin Wen | Electrically erasable writable educational flash card |
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US5278684A (en) * | 1986-12-11 | 1994-01-11 | Fujitsu Limited | Parallel aligned chiral nematic liquid crystal display element |
JPH01254990A (ja) * | 1988-04-04 | 1989-10-11 | Matsushita Electric Ind Co Ltd | ホログラム記録装置 |
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JP3634390B2 (ja) * | 1992-07-16 | 2005-03-30 | セイコーエプソン株式会社 | 液晶電気光学素子 |
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FR2740894B1 (fr) * | 1995-11-08 | 1998-01-23 | Centre Nat Rech Scient | Dispositif d'affichage perfectionne a base de cristaux liquides et a effet bistable |
FR2741165B1 (fr) * | 1995-11-10 | 1998-01-30 | Ist Naz Fisica Della Materia | Dispositif d'affichage bistable a base de cristaux liquides nematiques autorisant des teintes de gris |
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US6038001A (en) * | 1996-08-13 | 2000-03-14 | Casio Computer Co., Ltd. | Bistable nematic liquid crystal which remains tilted in first and second states and which is tilted according to driving voltage |
TW384410B (en) * | 1996-12-17 | 2000-03-11 | Casio Computer Co Ltd | Liquid crystal display device having bistable nematic liquid crystal and method of driving the same |
US6057817A (en) * | 1996-12-17 | 2000-05-02 | Casio Computer Co., Ltd. | Liquid crystal display device having bistable nematic liquid crystal and method of driving the same |
KR100417918B1 (ko) * | 1999-03-12 | 2004-02-11 | 엘지.필립스 엘시디 주식회사 | 셀 구성을 최적화한 반사형 액정표시장치 |
FR2808890B1 (fr) * | 2000-05-12 | 2002-08-09 | Nemoptic | Dispositif bistable d'affichage en reflexion avec contraste inverse |
FR2808891B1 (fr) * | 2000-05-12 | 2003-07-25 | Nemoptic | Dispositif bistable d'affichage en reflexion |
GB2367177A (en) * | 2000-09-23 | 2002-03-27 | Sharp Kk | Operating a bistable liquid crystal display |
JP2003015133A (ja) * | 2001-04-27 | 2003-01-15 | Citizen Watch Co Ltd | 液晶表示装置 |
US7224417B2 (en) * | 2001-05-04 | 2007-05-29 | Nemoptic | Nematic liquid crystal bistable display device with grey level |
FR2825480B1 (fr) * | 2001-05-31 | 2003-12-19 | Nemoptic | Polyimides pour ancrage de cristaux liquides, dispositifs d'affichage les incluant et procede de preparation de ces dispositifs |
FR2829244B1 (fr) * | 2001-08-29 | 2004-09-10 | Nemoptic | Dispositif d'affichage bistable a cristal liquide nematique a masque optique perfectionne |
US6784955B2 (en) * | 2001-10-01 | 2004-08-31 | The Hong Kong University Of Science And Technology | Optically optimized permanently bistable twisted nematic liquid crystal displays |
FR2863062B1 (fr) * | 2003-11-28 | 2006-03-17 | Nemoptic | Dispositif d'affichage a ecran de type nematique bistable optimisant le noir et procede de definition de ce dispositif |
US7327420B2 (en) * | 2004-11-12 | 2008-02-05 | Research Foundation Of The University Of Central Florida, Incorporated | Reflective liquid crystal projection displays with low voltage and high contrast using improved bisector effect |
US7705939B2 (en) * | 2006-05-31 | 2010-04-27 | The Hong Kong University Of Science And Technology | Transflective liquid crystal display |
-
2003
- 2003-11-28 FR FR0313991A patent/FR2863061B1/fr not_active Expired - Fee Related
-
2004
- 2004-11-25 JP JP2006540535A patent/JP5230859B2/ja not_active Expired - Fee Related
- 2004-11-25 CN CNB2004800349619A patent/CN100541303C/zh not_active Expired - Fee Related
- 2004-11-25 US US10/580,320 patent/US7532275B2/en not_active Expired - Fee Related
- 2004-11-25 WO PCT/FR2004/003021 patent/WO2005054940A1/fr active Application Filing
- 2004-11-25 EP EP04805550A patent/EP1690130A1/fr not_active Withdrawn
- 2004-11-26 TW TW093136390A patent/TWI406028B/zh not_active IP Right Cessation
-
2006
- 2006-06-27 KR KR1020067012872A patent/KR101265335B1/ko not_active IP Right Cessation
Non-Patent Citations (1)
Title |
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See references of WO2005054940A1 * |
Also Published As
Publication number | Publication date |
---|---|
JP5230859B2 (ja) | 2013-07-10 |
CN1997934A (zh) | 2007-07-11 |
KR101265335B1 (ko) | 2013-05-20 |
US20070103619A1 (en) | 2007-05-10 |
WO2005054940A1 (fr) | 2005-06-16 |
TW200527039A (en) | 2005-08-16 |
KR20060115906A (ko) | 2006-11-10 |
FR2863061A1 (fr) | 2005-06-03 |
JP2007512561A (ja) | 2007-05-17 |
US7532275B2 (en) | 2009-05-12 |
FR2863061B1 (fr) | 2006-02-24 |
TWI406028B (zh) | 2013-08-21 |
CN100541303C (zh) | 2009-09-16 |
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