Illumination – Light source and modifier – Fluorescent type
Reexamination Certificate
1999-11-26
2001-12-18
Sember, Thomas M. (Department: 2875)
Illumination
Light source and modifier
Fluorescent type
C362S217060, C362S218000, C362S029000, C362S263000, C362S084000, C313S607000, C313S234000, C349S071000
Reexamination Certificate
active
06331064
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an liquid crystal display device. More specifically, the invention relates to a back light unit for a liquid crystal display panel.
A liquid crystal display panel is comprised the pair of opposed substrates and a liquid crystal layer interposed between the pair of substrates, wherein an array of pixels is formed in a horizontal plane of the liquid crystal display panel. In this case, a back light unit is needed, and such a back light unit is arranged in the back of the liquid crystal display panel. Thus, each pixel has only the function to control the amount of light switching by controlling the orientation of the liquid crystal molecules.
This back light includes a lamp tube, a diffusing plate and a reflector for supplying the light and uniformalizing the light irradiation of a liquid crystal display panel. A cold cathode fluorescent tube (CFL), whose length is almost equal to the length in a parallel direction of the liquid crystal display panel and which is supplied with a voltage by electrodes attached at both ends of the tube, is used as the lamp tube.
However, a liquid crystal display unit's life span is determined by a lamp tube's short life span. Although replacement of the lamp tube in the back light unit is not easy, all lamps should be replaced to maintain the brightness of the back light unit.
In addition, an electrode material inside the cold cathode fluorescent tube tends to adhere on the inner wall of the lamp tube due to sputtering which occurs while lighting, and so the lamp tube tends to become dark more and more due to the adhesion materials over time. That is, the adhesion materials become an alloy (amalgam) of the mercury inside the cold cathode fluorescent tube, and so the lamp tube's life span shortens more and more by consuming mercury.
SUMMARY OF THE INVENTION
The present invention was accomplished in recognition of the above problems, and, accordingly, it is an object of the present invention to provide a liquid crystal display panel in which the liquid crystal display unit's life span can be increased without the need to replace the lamp tube or the back light unit.
The above objects are achieved by a liquid crystal display device comprising a liquid crystal display panel for modulating light to form an image, and a back light unit having a lamp tube which is discharged by an electrode and is disposed behind said liquid crystal display panel, wherein said electrode is formed outside of said lamp tube.
Further, the above objects are achieved by a liquid crystal display device comprising a liquid crystal display panel having a pair of substrates, a liquid crystal layer interposed between said pair of substrates, and a back light unit having a lamp tube which is discharged by a pair of electrodes and is disposed behind said liquid crystal display panel, wherein said pair of electrodes are formed outside of said lamp tube and are disposed opposite to each other.
Further, the above objects are achieved by a liquid crystal display device comprising a liquid crystal display panel having a pair of substrates, a liquid crystal layer interposed between said pair of substrates, and a back light unit including a plurality of lamp tubes which are discharged by a pair of electrodes comprising a power supply electrode and a ground electrode which are disposed at a location opposite to a display area of said liquid crystal display panel, wherein said pair of electrodes are formed outside of said lamp tube and are formed opposite to each other.
Further, the above objects are achieved by a liquid crystal display device comprising, a liquid crystal display panel for modulating light to form an image, a back light unit including a plurality of lamp tubes which are discharged by a plurality of electrodes, wherein said electrodes are formed on said lamp tubes, and one of the electrodes is formed between a pair of electrodes.
Further, the above objects are achieved by a liquid crystal display device comprising, a liquid crystal display panel having a pair of substrates, a liquid crystal layer interposed between said pair of substrates, and a back light unit having a lamp tube which is discharged by a power supply electrode and a ground electrode formed outside of said lamp tube, wherein said lamp tube has an elbow-shaped bend and is disposed at a location opposite to a display area of said liquid crystal display panel.
Further, the above objects are achieved by a back light unit to supply light for a liquid crystal display panel, which back light unit comprises a lamp tube which is discharged by a power supply electrode and a ground electrode formed on a surface of the outside of said lamp tube, wherein said power supply electrode is positioned on the central portion of said lamp tube.
Further, the above objects are achieved by a back light unit to supply light for a liquid crystal display panel, which back light unit comprises a lamp tube which is discharged by a power supply electrode and a ground electrode formed on a surface of the outside of said lamp tube, wherein said power supply electrode and said ground electrode are divided into two or more pairs, and said power supply electrode or said around electrode a re disposed side by side with respect to each other.
According to the constitution of this invention, the liquid crystal display unit's life span can be increased without changing the lamp tube or the back light unit.
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Hashimoto Koji
Mikoshiba Shigeo
Nishiyama Seiichi
Shiga Tomokazu
Takaku Shigetake
Antonelli Terry Stout & Kraus LLP
Hitachi , Ltd.
Sember Thomas M.
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