Liquid crystal cells – elements and systems – Cell containing liquid crystal of specific composition – In cholesteric phase
Reexamination Certificate
2003-06-02
2004-08-24
Ton, Toan (Department: 2871)
Liquid crystal cells, elements and systems
Cell containing liquid crystal of specific composition
In cholesteric phase
C349S074000, C349S175000
Reexamination Certificate
active
06781666
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention pertains to a liquid crystal display, and more particularly to a liquid crystal display comprising multiple cells stacked together and the manufacturing method therefor.
2. Description of the Related Art
Research and development of displays using liquid crystal has been actively pursued in recent years. In particular, displays using a chiral nematic liquid crystal composition, which exhibits a cholestric phase at room temperature and which is obtained by adding a chiral agent to nematic liquid crystal, as well as guest-host type displays using nematic liquid crystal to which a dichroic pigment is added, have been drawing attention.
In a liquid crystal display including a liquid crystal composition that exhibits a cholesteric phase, display is performed by switching the liquid crystal back and forth between a planar state (selective reflection state) and a focal conic state (light scattering state) by applying a high or low pulse voltage. Where a material comprising liquid crystal to which a multichroic pigment—such as a dichroic pigment—is added is used for the liquid crystal composition, display is performed by changing the direction of the axes of the liquid crystal molecules when voltage is applied and when voltage is not applied, so that the display alternates between a colored state and a non-colored state.
One method to realize multi-color image display on the displays described above involves a construction in which three cells, which display red (R), green (G) and blue (B), respectively, are stacked. In this case, drive ICs that apply different voltages to the three cells, which display R, G and B, respectively, are needed, resulting in the problem of increased cost. Therefore, a liquid crystal display that has a layered construction having display and drive characteristics appropriate for practical use is not yet available.
SUMMARY OF THE INVENTION
The main object of the present invention is to provide an improved liquid crystal display having a that has a layered construction.
Another object of the present invention is to provide a liquid crystal display that is capable of displaying high-quality images.
Still another object of the present invention is to provide a liquid crystal display that is easy to control.
Yet another object of the present invention is to provide a liquid crystal display in which the stacked cells can be driven using a few types of drive ICs so that the cost can be reduced, as well as a method for manufacturing such a liquid crystal display.
To attain at least one of the objects identified above, the liquid crystal display reflecting a first aspect of the present invention comprises a plurality of liquid crystal light modulation layers stacked together, each of said liquid crystal light modulation layers including a liquid crystal composition comprising a liquid crystal compound, wherein at least two of said liquid crystal light modulation layers are substantially have essentially identical maximum drive voltages.
By including at least two liquid crystal light modulation layers that have essentially identical maximum drive voltages, the liquid crystal display can be driven using a few types of drive ICs and its cost may can reduced.
The maximum drive voltages for all of the liquid crystal light modulation layers may be made identical. In this way, the liquid crystal display can be driven using a smaller number of types of drive ICs, which leads to a further reduction in cost.
Moreover, by making the maximum drive voltages for at least two liquid crystal light modulation layers substantially identical, the ranges of drive voltage for these liquid crystal light modulation layers can be made substantially the same, which makes drive control easy.
It is preferred that each liquid crystal light modulation layer be held between a pair of substrates, and that one of the substrates in the pair have scanning electrodes while the other has signal electrodes. The scanning electrodes of at least two liquid crystal light modulation layers may be electrically connected. By electrically connecting the scanning electrodes, the construction of the drive circuit can be simplified.
The same type of signal drive IC may be used for the signal electrodes of at least two liquid crystal light modulation layers. In this way, the construction of the drive circuit can be simplified.
At least one of the substrates may be pliable. By using pliable substrates, the liquid crystal display may be made flexible. In particular, if resin film substrates are used, the liquid crystal display may be made lightweight.
Resin structures may be placed in the light modulation area between the pair of substrates that holds each liquid crystal light modulation layer. By placing resin structures in this way, the distance between the substrates may be accurately maintained and the thickness of the liquid crystal layer may be made uniform. In addition, the substrate distance may be maintained well even if pliable substrates are used, and it is easy to increase the size of the liquid crystal display.
Each liquid crystal light modulation layer may comprise a composite film in which the liquid crystal composition is dispersed in a high-polymer matrix. In this way, the size of the liquid crystal display can be easily increased and a good angle of visibility can be obtained.
The liquid crystal composition may be one that exhibits a cholesteric phase at room temperature. In this case, the liquid crystal display may comprises, as the light modulation layers, three layers, i.e., a liquid crystal layer for blue color that displays blue, a liquid crystal layer for green color that displays green, and a liquid crystal layer for red color that displays red, stacked in that order from the light receiving side (the viewing side).
Each liquid crystal light modulation layer may comprise one that performs display based on the guest-host effect. This type of display can be realized by using a liquid crystal composition comprising nematic liquid crystal to which a multichroic pigment is added as an additive, for example. In this case, by controlling the orientation of the pigment molecules by changing the liquid crystal molecular alignment, the liquid crystal layer may be alternated between a colored state and a non-colored state.
Each liquid crystal light modulation layer may include functional films such as an insulating film and/or an orientation control film, in addition to the liquid crystal layer including the liquid crystal composition. In this case, the maximum drive voltages for at least two liquid crystal light modulation layers may be made substantially identical by adjusting the thickness of the functional films.
In a second aspect of the present invention, a manufacturing method for a liquid crystal display containing a plurality of liquid crystal light modulation layers stacked together, each of said liquid crystal light modulation layers including a liquid, crystal composition comprising a liquid crystal compound, the manufacturing method comprises a step of substantially equalizing maximum drive voltages of at least two of said liquid crystal light modulation layers by adjusting at least one of the following factors:
a thickness of each of said liquid crystal layers contained in the at least two liquid crystal light modulation layers;
a kind of at least one component of each of the liquid crystal compositions included in the at least two liquid crystal light modulation layers;
a dielectric anisotropy of each of the liquid crystal compositions included in the at least two liquid crystal light modulation layers; and
a thickness of each of functional films provided in the at least two liquid crystal light modulation layers.
By appropriately designing at least one of the above mentioned factors, the maximum drive voltages of the at least two liquid crystal layers can be easily made identical, such that the liquid crystal display can be driven using a small number of types of drive ICs, and its cost may be reduced.
According
Iwamatsu Masako
Kobayashi Nobuyuki
Ueda Hideaki
Minolta Co. , Ltd.
Nguyen Hoan
Sidley Austin Brown & Wood LLP
Ton Toan
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