Stock material or miscellaneous articles – Liquid crystal optical display having layer of specified... – With viewing layer of specified composition
Reexamination Certificate
2000-06-21
2003-03-25
Wu, Shean C. (Department: 1756)
Stock material or miscellaneous articles
Liquid crystal optical display having layer of specified...
With viewing layer of specified composition
C428S001100, C252S299010, C349S064000, C349S098000, C349S171000, C349S175000
Reexamination Certificate
active
06537624
ABSTRACT:
INDUSTRIAL APPLICATION FIELD
The present invention relates to a novel liquid crystalline film and the utilization thereof. Particularly, the invention is concerned with a cholesteric liquid crystalline film and a chiral smectic C liquid crystalline film, with suppressed specular reflection, as well as a novel liquid crystalline film capable of producing a diffracted light having polarizability, and the utilization of those films.
PRIOR ART
In a cholesteric liquid crystal, internal liquid crystal molecules thereof are oriented in a regularly twisted state so as to describe a helix in a film thickness direction, and the cholesteric liquid crystal possesses a unique optical property derived from the fact that the helical axis is parallel to the film thickness direction. This unique optical property is a selective reflection of a specific circularly polarized light in a specific wavelength band. This property may be applicable to an optical use in which only a right or left circularly polarized light is to be taken out from a non-polarized light or to an ornamental use which utilizes coloration of reflected or transmitted light because the above selection of a circularly polarized light is limited to a specific wavelength band. For industrial applications, a cholesteric liquid crystalline film obtained by forming a cholesteric liquid crystal into a thin film is considered to have a wide application range because it is easy to handle and is superior in processability.
As a method for forming a cholesteric liquid crystalline film there is known, for example, the method disclosed in Japanese Patent Laid Open No. 186534/1994. In conventional cholesteric liquid crystalline films, the helical axis is perpendicular to a substrate, and a layer structure corresponding to a helix pitch forms a flat sheet structure on the substrate. In such conventional cholesteric liquid crystalline films, an incident light is specularly reflected, and the luminance of reflected light drops rapidly outside the specular reflection area because of a marked viewing angle dependence of the luminance.
There also is known an example of having realized a linear polarizing plate by laminating a cholesteric liquid crystal layer and a quarter-wave plate to each other so that the helical axis of the cholesteric liquid crystal layer becomes perpendicular to the quarter-wave plate, as is disclosed in Japanese Patent Laid Open No. 133003/1989. In this polarizing plate, however, an incident light is reflected in an outer polarizing plate due to a specular reflection of the cholesteric liquid crystal layer, and the visibility as a polarizing plate is inferior.
In such a conventional liquid crystalline film as referred to above, the surface thereof has a metallic gloss and is in the state of a mirror surface. In case of applying this film to a use in which reflected light from the film is utilized, the direction of the reflected light is limited to a specific direction due to such specular reflection, giving rise to the problem that a sufficient luminance is not obtainable in other directions. Further, since the selectively reflecting wavelength band of this film is greatly dependent on the viewing angle due to a blue shift phenomenon, the color tone of reflected light varies markedly with the viewing angle.
As a method for suppressing a specular reflection there widely is known a method of diffusing incident light and reflected light. For realizing this method, however, it has so far been necessary to dispose a diffuser panel on the surface of an object to be measured. However, the use of a diffuser panel newly gives rise to problems such as an increase of cost and an increase in the number of manufacturing steps. Therefore, it is desired to develop a cholesteric liquid crystalline film not requiring such a diffuser panel, capable of suppressing a specular reflection, superior in visibility, and less dependent on the viewing angle.
The above points can also be said of a chiral smectic C liquid crystalline film, and also in this case it is desired to develop a chiral smectic C liquid crystalline film not requiring a diffuser panel, capable of suppressing a specular reflection, superior in visibility, and less dependent on the viewing angle.
Next, diffraction gratings are general-purpose optical elements used widely for the purpose of splitting a light beam in the field of spectrooptics. Diffraction gratings are classified into several types according to shapes thereof, usually into oscillation type diffraction gratings in which a light transmitting portion and a light non-transmitting portion are arranged periodically and phase type diffraction gratings in which periodical grooves are formed in a material of a high transmittance. Diffraction gratings are sometimes classified 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).
According to the above conventional diffraction gratings, as a diffracted light obtained upon incidence of a natural light (non-polarized light), there can be obtained only a non-polarized light. With use of such a polarizing optical device as an ellipsometer which is used frequently in the field of spectrooptics, there can be obtained only a non-polarized light as a diffracted light, so for splitting a natural light emitted from a light source through a diffraction grating and for utilizing only a specific polarization component contained therein, there usually is adopted a method wherein a diffracted light is used through a polarizer. But this method involves the problem that about 50% or more of the diffracted light obtained is absorbed by the polarizer and that therefore the quantity of light is reduced by half. It is also required to use a detector of a high sensitivity and a light source capable of emitting a large amount of light. Thus, it is desired to develop a diffraction grating through which a diffracted light itself becomes a specific polarized light such as a circularly polarized light or a linearly polarized light.
OBJECT OF THE INVENTION
It is an object of the present invention to solve the above-mentioned problems of the prior art.
The present inventors have succeeded in forming an area which exhibits a high diffusion effect in a cholesteric liquid crystal layer and a chiral smectic liquid crystal layer by controlling the state of orientation of liquid crystal molecules precisely. More particularly, by forming a cholesteric orientation and a chiral smectic C orientation in which the helical axis direction in liquid crystal phase is not uniformly parallel in a film thickness direction, to suppress a specular reflection, we have succeeded in obtaining a cholesteric liquid crystalline film and a chiral smectic C liquid crystlaline film both superior in visibility and having a light diffusing property.
First, by precisely controlling the state of orientation of liquid crystal molecules the present inventors have succeeded in forming an area of a high diffraction efficiency in a cholesteric liquid crystal layer or in a chiral smectic C liquid crystal layer. To be more specific, by controlling and fixing a cholesteric orientation or a chiral smectic C orientation wherein the helical axis direction in cholesteric phase or chiral smectic C phase is not uniformly parallel in a film thickness direction nor is the helix pitch uniformly equal in the film thickness direction, we have succeeded in obtaining a liquid crystalline film which functions suitably as a polarizing diffraction grating.
SUMMARY OF THE INVENTION
The present invention is firstly concerned with a light-diffusible cholesteric or chiral smectic C liquid crystalline film having a fixed cholesteric or chiral smectic C orientation in which the helical axis direction is not uniformly parallel in the film thickness direction.
The present invention is secondly concerned with a circular polarizer comprising the above liquid crystalline film.
The present invention is thirdly concerned with a linear polarizer formed by lami
Komatsu Shin-ichi
Nishimura Suzushi
Suzuki Shinichiro
Nippon Mitsubishi Oil Corporation
Wu Shean C.
LandOfFree
Liquid-crystal film does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Liquid-crystal film, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Liquid-crystal film will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3061214