Liquid crystal cells – elements and systems – Particular excitation of liquid crystal – Electrical excitation of liquid crystal
Reexamination Certificate
2000-01-28
2001-11-20
Sikes, William L. (Department: 2871)
Liquid crystal cells, elements and systems
Particular excitation of liquid crystal
Electrical excitation of liquid crystal
C349S042000
Reexamination Certificate
active
06320630
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a liquid crystal display device and, more particularly, to an art useful in application to a video signal line driving unit (drain driver) of a liquid crystal display device capable of providing multilevel grayscale display.
2. Description of the Related Art
Active matrix liquid crystal display devices which have active elements (for example, thin-film transistors) for individual pixels and drive the active elements in a switching manner are widely used as display devices for notebook personal computers.
In such an active matrix liquid crystal display device, since video signal voltages (grayscale voltages corresponding to individual display data; hereinafter referred to simply as grayscale voltage(s)) to its pixel electrodes via the respective active elements, no crosstalk occurs between the pixels, and unlike a simple matrix liquid crystal display device, multilevel grayscale display can be provided without the need to use a special driving method for preventing crosstalk.
A TFT type of liquid crystal display module is known as one kind of active matrix liquid crystal display device. The TFT type of liquid crystal display module includes a TFT (
T
hin
F
ilm
T
ransistor) type of liquid crystal display panel (TFT-LCD), a drain driver arranged on the top side of the liquid crystal display panel, and a gate driver and an interface block each of which is arranged on any of the sides of the liquid crystal display panel.
The drain driver included in the TFT type of liquid crystal display module is made of one semiconductor chip, and the semiconductor chip has in its inside a multilevel grayscale voltage generation circuit and a multilevel grayscale voltage selection circuit for selecting one grayscale voltage level corresponding to display data, from the multilevel grayscale voltage generated by the multilevel grayscale voltage generation circuit.
This art is disclosed in, for example, Japanese Patent Application Nos. 86668/1996 and 50699/1998.
SUMMARY OF THE INVENTION
In recent years, the trend in liquid crystal display devices such as a TFT type of liquid crystal display module has been toward larger screen sizes in liquid crystal display panels, higher resolution (a larger number of pixels) and higher image quality. In addition, in order to omit a useless space from the interior of a liquid crystal display device and improve the appearance thereof, it has been demanded that the area other than the display area of the liquid crystal display device, i.e., a frame portion, be made as small as possible (the width of the frame portion be made narrow).
Moreover, to promote far wider use of liquid crystal display devices, it has been strongly demanded to decrease the prices of liquid crystal display devices.
For this reason, it has been necessary to increase the number of output pins of a semiconductor chip which constitutes a drain driver (hereinafter referred to simply as a semiconductor chip) and make the area of the semiconductor chip far smaller, i.e., enlarge the scale of integration of the semiconductor chip.
The semiconductor chip has, on the other hand, a plurality of bump electrodes to be connected to the inner leads of a tape carrier package, and protective diode pairs each of which is disposed for the corresponding one of the bump electrodes to protect its internal circuits from noise which enters from outside the semiconductor chip.
In general, each of the protective diode pairs is disposed in the vicinity of the corresponding one of the bump electrodes because it is necessary to electrically connect each of the protective diode pairs to the corresponding one of the bump electrodes.
However, the bump electrodes need to be spaced apart from one another to some extent because it is necessary to prevent an accident such as a short circuit between adjacent bump electrodes.
Moreover, a region in which each of the protective diode pairs is formed needs to have enough area to absorb noise.
For these reasons, there has been the problem that it is impossible to increase the number of output pins of a semiconductor chip and decrease the area thereof, with the result that it is impossible to meet demands such as narrower frame portions in liquid crystal display devices or reductions in the prices thereof.
The invention has been made to solve the problems of the related art, and an object of the invention is to provide an art which is capable of reducing, in a liquid crystal display device, the area occupied by the bump electrodes and the protective diode pairs of a semiconductor chip in a video signal line driving circuit unit, thereby reducing the chip size of the semiconductor chip.
Another object of the invention is to provide an art which is capable of realizing a liquid crystal display device having a far narrower frame portion and a far lower price.
The above and other objects as well as novel advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings.
Representative aspects of the invention disclosed in the present application will be described below in brief.
The invention provides a liquid crystal display device which comprises: a liquid crystal display element having a plurality of pixels arranged in matrix form; and a video signal line driving unit for supplying a video signal voltage to each of the pixels, the video signal line driving unit including at least one semiconductor chip, the at least one semiconductor chip including: a plurality of bump electrodes; a plurality of protective diode pairs each including a first diode and a second diode; and a plurality of interconnect layers disposed to cover an anode region of the first diode and a cathode region of the second diode of each of the protective diode pairs and connected to the anode region of the first diode and the cathode region of the second diode, the plurality of interconnect layers having connection portions for connection to the respective bump electrodes,
each of the interconnect layers which overlie the anode region of the first diode and the cathode region of the second diode of each of the protective diode pairs having the same shape, at least one of the plurality of bump electrodes being disposed over the anode region of the first diode or the cathode region of the second diode of one of the protective diode pairs and being connected to a corresponding one of the connection portions of the interconnect layers over the anode region of the first diode or the cathode region of the second diode of the one of the protective diode pairs.
The invention also provides a liquid crystal display device which comprises: a liquid crystal display element having a plurality of pixels arranged in matrix form; and
a video signal line driving unit for supplying a video signal voltage to each of the pixels, the video signal line driving unit including at least one semiconductor chip, the at least one semiconductor chip including: a plurality of bump electrodes; a plurality of protective diode pairs each including a first diode and a second diode; and a plurality of interconnect layers disposed to cover an anode region of the first diode and a cathode region of the second diode of each of the protective diode pairs and connected to the anode region of the first diode and the cathode region of the second diode, the plurality of interconnect layers having connection portions for connection to the respective bump electrodes, each of the interconnect layers which overlie the anode region of the first diode and the cathode region of the second diode of each of the protective diode pairs being formed to be wider than the anode region of the first diode and the cathode region of the second diode; at least one of the plurality of bump electrodes being disposed over the anode region of the first diode or the cathode region of the second diode of one of the protective diode pairs and being connected to a corresponding one of the connection portions of the interconnect laye
Agata Kentaro
Goto Mitsuru
Ogura Akira
Saito Masanari
Yamashita Yuji
Hitachi , Ltd.
Ngo Julie
Reed Smith Hazel & Thomas LLP
Sikes William L.
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