Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
1999-09-09
2002-01-08
Ton, Toan (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S110000
Reexamination Certificate
active
06337727
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a liquid crystal display device with excellent visibility, which prevents light from leaking out from the periphery of a liquid crystal panel in its negative type display. More particularly, the present invention relates to a liquid crystal display device which prevents light leaking out from each of liquid crystal panels e.g. where a large number of the liquid crystal panels are arranged to constitute a large-scale display, thereby increasing the visibility.
2. Description of the Related Art
A liquid crystal display device is structured so that a liquid crystal layer is sandwiched by two insulating plates and polarization plates are arranged on the outer surfaces of the two insulating plates, respectively. In the liquid crystal display device, a voltage can be applied to the liquid crystal layer through electrode patterns provided on the inner surfaces of the insulating plates so that the display can be made by controlling the voltage to be applied. More specifically, when the voltage is not applied to the liquid crystal layer, using the optical rotation property of the liquid crystal layer, linear polarized light having only a fixed vibrating direction is optically-rotated by the one polarizing plate by a certain angle. In this case, if the direction of the rotated linear polarized light coincides with that of the polarizing axis of the other polarizing plate, light passes through the liquid crystal layer, whereas if not, the light does not pass therethrough. On the other hand, when the voltage is applied to the liquid crystal layer, the linear polarized light is not optically rotated. In this way, whether or not the light passes can be controlled whether or not the voltage is applied. Thus, by controlling the voltage for each pixel, desired display can be realized. “Negative-type display” refers to the case where both polarizing plates are arranged so that light does not pass when the voltage is not applied to the liquid crystal layer. “Positive-type display” refers to the case where the light passes when the voltage is not applied so that only the pixel to which a voltage is applied is displayed in black.
In the negative type display, in the state where the liquid crystal panel is not operated, the entire face of the liquid crystal panel exhibits a black image. However, as shown in
FIG. 11
, in the area of a liquid crystal panel
20
to which sealant
27
is bonded and its outer periphery, liquid crystal is not located. Therefore, epoxy resin which is a sealant and a spacer which is mixed to make the gap uniform transmit light so that the light is not entirely optically rotated even with the provision of the polarizing plates on both sides. Thus, as shown in
FIG. 11
, although the inside of the sealant
27
where the liquid crystal layer is located exhibits a black image (shaded “B” area), light leaks from the periphery. This makes the image very poor. Particularly, in the liquid crystal panel for color display, which is generally in a negative-type display, such a tendency is remarkable.
In a larger-scale display composed of a number of liquid crystal panels, light leaks from the joints therebetween. This makes the image poor in continuous display. In order to overcome such an inconvenience, as shown in
FIG. 12
, a light shielding tape
28
such as a black vinyl tape is bonded to each joint. The problem relative to the joints occurs not only in the negative display but also in the positive display. Namely, the sealant portion which is black becomes white if no polarized plate is located on the outside thereof.
However, where the light shielding tape
28
is bonded to the joint, discrepancy in position is apt to occur. Therefore, on the display portion onto which the tape is bonded, some breaks may be generated. Otherwise, on the peripheral portion, the leakage of light cannot be prevented completely. In addition, after the liquid crystal panels
20
have been arranged, it is difficult to bond the light shielding tape onto the joints. Further, where a single liquid crystal panel is replaced by another one afterwards, the light shielding tape
28
must be peeled off and thereafter a new light shielding tape must be bonded again. This is very troublesome.
SUMMARY OF THE INVENTION
The present invention has been accomplished in order to solve such a problem. The present invention intends to provide a liquid crystal display device which can remove leakage of light from a sealant portion in a negative-type display to improve the appearance of an image. Where a large-scale display is composed of a large number of liquid crystal display devices, the present invention also intends to provide the liquid crystal display device which can surely make light-proof to the joints to constitute such a large-scale display with an excellent display characteristic.
A liquid crystal display device according to the present invention comprises a liquid crystal panel including two insulating base plates with electrode patterns provided on their surfaces, respectively, a sealant which bonds the two insulating base plates to each other at their peripheries with a prescribed gap therebetween so that the electrode patterns are opposite to each other, a liquid crystal layer provided in the prescribed gap between said two insulating base plates, and polarizing plates provided on the outer surfaces of said two insulating base plates, respectively; and a light-shielding mask which is fit in an exterior area from the sealant at an edge of said liquid crystal panel so that it sandwiches said insulating base plates of said liquid crystal panel from both sides.
In this configuration, regardless with the combination of polarizing plates, leakage of light is always eliminated at the portion of the sealant and its exterior, thereby preventing reduction of visibility due to the sealant. As a result, where a plurality of liquid crystal panels are arranged to constitute a large-scale display, it is possible to prevent leakage of light from the joints between the liquid crystal panels without bonding light shielding tapes to the joints.
The light-shielding mask has a U-shape in section formed by bending a metallic plate having a light-shielding property and resiliency and having an opening which has an interval slightly smaller than the thickness of the said liquid crystal panel. In this configuration, the light-shielding mask has only to be fit in order to realize light interruption. Since the light-shielding mask can be formed to have a very small thickness, the interval of each joint can be reduced, thereby realizing continuous display.
If the light-shielding mask is made from a heat-shrinkable tube of color preventing light from being interrupted, a half part cut in an axial direction from the heat-shrinkable tube having a slightly large diameter is covered on the liquid crystal panel and heated to be hardened. This simply realizes light interruption.
A first aspect of the present invention is a liquid crystal display device which comprises:
a liquid crystal panel including two insulating base plates with electrode patterns provided on their surfaces, respectively, a sealant which bonds the two insulating base plates to each other at their peripheries with a prescribed gap therebetween so that the electrode patterns are opposite to each other, and a liquid crystal layer provided in the prescribed gap between said two insulating base plates; and
a light-shielding mask which is fit in an outer periphery of the sealant at an end of said liquid crystal panel so that it sandwiches said insulating base plates of said liquid crystal panel from both sides.
A second aspect of the device is a liquid crystal display device according to the first aspect, wherein the inner edge of said light-shielding mask is substantially aligned with that of the sealant for the liquid crystal panel.
A third aspect of the device is a liquid crystal display device according to the first aspect, wherein said liquid crystal panel further comprises polari
Ono Koichi
Terumoto Koji
Rohm & Co., Ltd.
Ton Toan
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