Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
1998-01-22
2003-09-23
Kim, Robert H. (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S194000, C252S585000, C359S494010
Reexamination Certificate
active
06624859
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a polarizing converter, and a method of manufacturing the same, which increases and extracts luminous light with a specific plane of polarization by rotating and adding luminous flux having a different plane of polarization, when luminous flux with a large component of the specific plane of polarization is extracted by the incident of natural light with a plurality of planes of polarization at the polarizing converter. The present invention further relates to an optical transducer using the polarizing apparatus, and an electronic device using this optical transducer.
PRIOR ART
As one example of an optical transducer using the polarization of light may be cited a liquid crystal display device. As such a device is known, for example, the backlit liquid crystal display device
300
shown in FIG.
23
. In this liquid crystal display device
300
, on the side from which light from a backlight
310
is impinged on a liquid crystal cell
320
, a polarizer
330
is disposed before the liquid crystal cell
320
, and light passing through the liquid crystal cell
320
is passed through an analyzer
340
.
Light emitted from the backlight
310
has planes of polarization in all directions, but this light can be thought of as including, for example, luminous flux having a vector component in the vertical direction and luminous flux having a vector component in the horizontal direction orthogonal to the vertical direction. In optical terms the former could be referred to as the p-polarized light and the latter as the s-polarized light.
The polarizer
330
is an absorbing or reflecting type which for example allows the component of luminous flux in the vertical plane to pass, while not allowing the component of luminous flux in the horizontal plane to pass. In a liquid crystal display device, the absorbing type is normally used. In a normally-white liquid crystal display device, the polarizing plane of light passed through the analyzer
340
lets the light passed through the polarizer
330
coincide with the plane of polarization rotated through the given twist angle of the liquid crystal cell
320
.
For natural light, the vector components in the vertical and horizontal polarizing planes are each 50%. Therefore, in principle 50% of the light is lost when the light is passed through the polarizer
330
. In practice, taking the incident light as 100%, because of other losses the light passed by the polarizer
330
is not more than 35%.
In a reflective liquid crystal display device, the light-transmitting performance of the polarizer disposed on the side of the incident light is similar to that of the above backlit type of liquid crystal display device.
Thus, in a conventional liquid crystal display device
300
using the polarizer
330
, only a portion of the incident light can be used for display, and this is an obstacle to the reduction of power consumption and the increase of luminosity of liquid crystal display devices.
For example, in a backlit type of liquid crystal display device
300
, since the use efficiency of the light at the polarizer
330
is low, a light source capable of providing at least twice the amount of light that can be transmitted by the polarizer
330
is required. For this reason, conventionally, in for example a notebook computer provided with a liquid crystal display device, a large proportion of the required power supply is consumed by the backlighting light source. As a result, unless the power for the backlighting can be reduced, there is a limit to the degree to which the power consumption of the liquid crystal display device can be reduced.
Moreover, since the light from the backlighting is absorbed by the polarizer (polarizing plate), and is converted to heat, the panel surface becomes hotter, exerting a deleterious influence on the elements of the panel, the chemical structure of the liquid crystal, and so forth. Thus, it reduces the optical performance and the reliability of the liquid crystal display device.
The object of the present invention, considering these problems with the prior art, is to provide a polarizing apparatus which significantly eliminates the losses occurring when aligning the direction of polarization of incident light, and allows the optical efficiency to be improved.
Another object of the present invention is the provision of a method of fabricating the polarizing apparatus which can be applied to the manufacture of a polarizing apparatus of the above description.
A further object of the present invention is to construct an optical transducer such as a liquid crystal display device using the above polarizing apparatus, so as to provide an optical transducer such that the optical efficiency can be improved, and a brighter display screen can be achieved, or a substantial reduction in the power consumption of the light source can be attained.
Yet another object of the present invention is to construct an electronic device using the above optical to transducer, so as to provide an electronic device in which the optical efficiency can be improved, and a brighter display screen is achieved, or the power consumption of the light source can be substantially reduced, whereby further as a result of the improved optical efficiency the functional reliability can be improved and the device can be made more compact.
DISCLOSURE OF THE INVENTION
According to one aspect of the present invention, a polarizing apparatus for polarizing incident light having planes of polarization to light having a particular plane of polarization, comprising:
an optically active material disposed so as to exhibit anisotropy with respect to the optical activity; and
wherein the optically active material increases the intensity of luminous flux having the particular plane of polarization and reduces the intensity of luminous flux having a plane of polarization perpendicular to the particular plane of polarization.
The property of optical activity exhibited by the optically active material used in the present invention refers to the phenomenon whereby when plane polarized light passes through a material, the emitted light has a plane of polarization rotated through a particular angle with respect to the incident light. The material exhibits such phenomenon referred to optically active material.
Optically active materials can be broadly divided into two classes: those which exhibit optical activity in a crystalline structure in which the molecules have no chiral center, and organic substances possessing a chiral center such as an asymmetric carbon atom within the molecule. Examples of the former include quartz, cinnabar, lithium-potassium sulfate, LiKSO
4
, sodium perchlorate and sodium bromate. Examples of the latter include lactic acid, tartaric acid, tartrates, sucrose, alanine, grape sugar, ard glucose.
Taking as an example the case of an organic substance in which the molecules include a chiral center, for a single molecule, as shown in
FIG. 1
, a first incident vector component
10
of incident light in a certain plane of polarization, being for example the horizontal plane of polarization as shown in
FIG. 1
, is rotated within the optically active material
1
through an angle &thgr;
1
with respect to the horizontal plane of polarization. Meanwhile a second incident vector component
20
of incident light in the other plane of polarization, being for example the vertical plane of polarization as shown in
FIG. 1
, is rotated within the optically active material
1
through an angle &thgr;
2
with respect to the vertical plane of polarization. The relative magnitudes of the optical rotation angles are for example such that &thgr;
1
<&thgr;
2
. Thus viewing a single molecule it exhibits anisotropy of optically activity.
However, with a large number of molecules in a solid in the amorphous state, in a polymer, or in an aqueous solution, the anisotropy of each individual molecule is unordered, and mutually canceled out ever the number of molecules, so that the optical rotation angle becomes the same in all ori
Fujimori Yuji
Sugiyama Jun
Oliff & Berridg,e PLC
Schechter Andrew
Seiko Epson Corporation
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