Stock material or miscellaneous articles – Liquid crystal optical display having layer of specified... – With viewing layer of specified composition
Reexamination Certificate
2000-10-23
2003-09-30
Wu, Shean C. (Department: 1756)
Stock material or miscellaneous articles
Liquid crystal optical display having layer of specified...
With viewing layer of specified composition
C252S299010, C428S001100, C349S201000
Reexamination Certificate
active
06627270
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a new liquid crystalline film capable of generating a diffracted light having polarizability.
BACKGROUND OF THE INVENTION
Diffraction gratings are general-purpose optical elements which are in wide use for example in the field of spectro-optics for the purpose of spectralization or flux division. Diffraction gratings are classified into several types according to shapes thereof, usually classified into amplification type diffraction gratings wherein a light transmitting portion and a non-light transmitting portion are arranged in a periodical manner and phase type diffraction gratings wherein periodic grooves are formed in a material of a high transmittance. There also is a case where there are classified into transmission type diffraction gratings and reflection type diffraction gratings according to directions in which diffracted light is generated (Tetsuo Sueda, “How to use Optical Components and Points to be Noted,” Optronics Co., ISBN4-900474-03-7).
In the above conventional diffraction gratings, there can be obtained only a non-polarized light as a diffracted light obtained upon incidence of a natural light (non-polarized light). In such a polarization optical device as an ellipsometer which is often used in the field of spectro-optics, there can be obtained only a non-polarized light as a diffracted light, so when a natural light emitted from a light source is to be spectralized through a diffraction grating or when only a specific polarization component contained therein is to be utilized, there usually is adopted a method wherein the diffracted light is passed through a polarizer and is then used. However, this method involves a problem such that the quantity of light is reduced by half because about 50% or more of the resulting diffracted light is absorbed by the polarizer. Besides, it is necessary to provide a detector of a high sensitivity and a light source capable of emitting a large quantity of light. Thus, it has been demanded to develop a diffraction grating whereby a diffracted light itself is made into such a specific polarized light as a circularly polarized light or a linearly polarized light.
OBJECTS OF THE INVENTION
It is an object of the present invention to solve the above-mentioned problems and provide a liquid crystalline film which functions suitably as a polarization/diffraction grating, as well as an optical element using the liquid crystalline film.
According to the present invention, by precisely controlling the state of orientation of liquid crystal molecules, a region of a high diffraction efficiency can be formed in a cholesteric liquid crystal layer or in a chiral smectic C liquid crystal layer. More particularly, according to the present invention, a liquid crystalline film which functions suitably as a polarization/diffraction grating can be obtained by controlling and fixing a cholesteric orientation or a chiral smectic C orientation in which the helical axis in cholesteric or chiral smectic C phase is not uniformly parallel in the film thickness direction nor is the helix pitch uniformly equal in the film thickness direction.
SUMMARY OF THE INVENTION
The present invention firstly resides in a liquid crystalline film in which a cholesteric orientation or a chiral smectic C orientation, in which helical axis is not uniformly parallel in the film thickness direction nor is the helix pitch uniformly equal in the film thickness direction, is formed in a certain region of the film.
The present invention secondly resides in the above liquid crystalline film, wherein the above cholesteric orientation or chiral smectic C orientation is formed in a surface region of the film and/or an interior region of the film.
The present invention thirdly resides in a process for fabricating the liquid crystalline film referred to firstly above, wherein a diffraction pattern is transferred to a liquid crystal layer to obtain the liquid crystalline film.
The present invention fourthly resides in a process for fabricating the liquid crystalline film referred to thirdly above, wherein the liquid crystal layer is a liquid crystalline polymer layer.
The present invention fifthly resides in the liquid crystalline film fabricating method referred to fourthly above, wherein the diffraction pattern is transferred to the liquid crystalline polymer layer in a temperature range of above a glass transition point of the liquid crystal and below an isotropic phase transition temperature of the liquid crystal and in a pressure range of 0.3 to 500 kgf/cm
2
.
The present invention sixthly resides in an optical element, wherein the liquid crystalline film referred to firstly above is laminated to an optical member through an adhesive free of any difference in refractive index.
The present invention seventhly resides in an optical element obtained by transferring a diffraction pattern to a surface of a liquid crystal layer in the liquid crystalline film referred to firstly above to make the surface uneven in accordance with the diffraction pattern and by subsequently leveling the uneven surface with use of an adhesive free of any difference in refractive index.
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be described in detail hereinunder.
The liquid crystalline film of the present invention has a unique structure of a liquid crystal layer. More specifically, in at least a partial region of the film there is formed an orientation wherein the helical axis is not uniformly parallel in the film thickness direction nor is the helix pitch uniformly equal in the film thickness direction. As an example of such a liquid crystalline film there is mentioned one wherein when a screw axis structure in an ordinary cholesteric orientation or chiral smectic C orientation is regarded as a pseudo-layer structure, part of the layer structure is oriented in a regularly curved or bent state. But the present invention is not limited thereto, nor is limited means for forming such a structure.
The region where such a unique liquid crystal layer structure is formed may be any region in the film; for example, it may be a part of the film surface (a film surface region) or a part of the film interior (a film interior region). The region in question may be plural regions in the liquid crystalline film, e.g., surface and back regions of the film or plural film interior regions. It is not always necessary that the film in question be formed as a layer having a uniform thickness at the film surface or in the interior of the film. It suffices for the region to be formed at least partially of the film surface or the film interior. The region may be in a desired shape. In the case where the region having a cholesteric or chiral smectic C orientation with the helical axis being not uniformly parallel in the film thickness direction nor being the helix pitch uniformly equal in the film thickness direction is present as layer in the liquid crystalline film of the present invention, it is desirable for the layer to have a thickness usually of 50% or less, preferably 30% or less, more preferably 10% or less, relative to the thickness of the liquid crystalline film. If the thickness of the region in question exceeds 50% of the film thickness, such effects as selective reflection characteristic and circular polarization characteristic based on cholesteric liquid crystal phase or chiral smectic C liquid crystal phase will be deteriorated and it may become impossible to attain the effect of the present invention.
In the case where there are plural regions in each of which is formed a cholesteric or chiral smectic C orientation with the helical axis being not uniformly parallel in the film thickness direction nor being the helix pitch uniformly equal in the film thickness direction, it is not necessary for all of the regions to have the same liquid crystal phase structure, but plural regions may have different structures respectively. In the other region of the liquid crystalline film of the invention than the region where there is formed such a
Nippon Mitsubishi Oil Corporation
Scully Scott Murphy & Presser
Wu Shean C.
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