Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
2001-11-19
2004-02-03
Awad, Amr (Department: 2675)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C345S092000, C327S333000, C326S081000
Reexamination Certificate
active
06686899
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a display device, and in particular to an active matrix type display device having a driver circuit for driving pixels, fabricated on its substrate of its display panel.
A display panel has an electrooptical material layer sandwiched between a pair of substrates. In this specification, the term “electrooptical material” refers to material which changes its optical properties such as transmission, emission, refractive index and absorption of light under the influence of an electric field or current. The electrooptical material includes liquid crystal material and electroluminescent material, for example.
By way of example, an active matrix type liquid crystal display device shall be considered.
In the active matrix type liquid crystal display device, each pixel area is surrounded by two adjacent ones of a plurality of gate signal lines extending in the x direction and arranged in the y direction and two adjacent ones of a plurality of drain signal lines extending in the y direction and arranged in the x direction which are fabricated on a liquid-crystal-layer-side surface of one of a pair of substrates sandwiching a liquid crystal layer. Each pixel area is provided with a thin film transistor operated by a scanning signal supplied from one of the gate signal lines and a pixel electrode supplied with a video signal from one of the drain signal lines via the thin film transistor.
The pixel electrode generates an electric field between it and a counter electrode fabricated on the other of the pair of substrates, for example, so that the electric field control the light transmission through the liquid crystal layer between the two electrodes. The liquid crystal display device is provided with a scanning signal driving circuit for supplying a scanning signal to each of the gate signal lines and a video signal line driving circuit for supplying a video signal to each of the drain signal lines.
These scanning signal driving circuit and video signal line driving circuit are formed of a large number of MIS (Metal Insulator Semiconductor) transistors having configurations similar to thin film transistors fabricated in the pixel areas, and therefore a technique is known in which semiconductor layers of the thin film transistors in the pixel areas are made of polycrystalline silicon (p-Si), and the scanning signal driving circuit and the video signal line driving circuit are fabricated on the one of the pair of substrates simultaneously with the pixels. These circuits are composed of transistors made of polycrystalline silicon, therefore their output signal levels are low, and consequently, their output signal themselves are sometimes insufficient for driving the pixels. To solve this problem, voltage level converters are incorporated into the liquid crystal display devices for converting voltages such as pulses from a low level to a higher level. Generally, the voltage level converters as shown in
FIG. 16
or
FIG. 17
, for example.
SUMMARY OF THE INVENTION
The basic operating principle of the above-mentioned voltage level converters is that ON-OFF of a current in one of a pair of MOS transistors of the opposite conductivity types is controlled by an external input pulse, and by using a resultant change in voltage, ON-OFF of a current in the other of the pair of MOS transistors is controlled so as to provide a pulse having an amplitude greater than that of the external input pulse. As a result, ON-OFF of the current in the other of the pair of MOS transistors is controlled by using as an input a large voltage change close to an amplitude of the level-converted voltage. Consequently, some current (hereinafter the through current) flows through the pair of MOS transistors before the voltage for controlling ON-OFF of the current in the other of the pair of MOS transistors reaches a voltage sufficient to control the ON-Off of the current.
When the voltage level converter is composed of polysilicon MOS transistors, it has been pointed out that its current supply capability is decreased further when it is gate-controlled with an external small-voltage input pulse because charge-carrier mobility in the polysilicon MOS transistors is smaller than that in single-crystal MOS transistors, therefore a time is increased which is required for a voltage to reach a value sufficient to control ON-OFF of a current of the MOS transistor, and as a result the above-explained through current is increased.
The present invention has been made so as to solve the above problems, and it is an object of the present invention to provide a display device having a voltage level converter with the above-explained through current sufficiently suppressed.
The following explains the representative ones of the present inventions briefly.
In accordance with an embodiment of the present invention, there is provided a display device including a pair of substrates, an electrooptical material layer sandwiched between the pair of substrates, a plurality of pixels formed between the pair of substrates and a driver circuit for driving the plurality of pixels provided on one of the pair of substrates, the driver circuit including a level converter circuit comprised of MISTFTs (Metal Insulator Semiconductor Thin Film Transistors) having semiconductor layers made of polysilicon, the level converter circuit comprising: a pair of a first NMISTFT (N-channel type Metal Insulator Semiconductor Thin Film Transistor) and a first PMISTFT (P-channel type Metal Insulator Semiconductor Thin Film Transistor), each of the first NMISTFT and the first PMISTFT having both a gate terminal thereof and a first terminal thereof coupled to an input terminal for receiving an input pulse via a first capacitance; a pair of a second NMISTFT and a second PMISTFT, each of the second NMISTFT and the second PMISTFT having a second terminal thereof coupled to the input terminal via a second capacitance; a third PMISTFT having a gate terminal thereof coupled to the gate terminals and the first terminals of the first NMISTFT and the first PMISTFT; a third NMISTFT having a gate terminal thereof coupled to the second terminals of the second NMISTFT and the second PMISTFT, a first terminal of the third PMISTFT, a second terminal of the first NMISTFT, and a second terminal of the first PMISTFT being coupled to a high-voltage power supply line, a second terminal of the third NMISTFT, a gate terminal and a first terminal of the second NMISTFT, a gate terminal and a first terminal of the second PMISTFT being coupled to a low-voltage power supply line, and a first junction point between a second terminal of the third PMISTFT and a first terminal of the third NMISTFT being connected to an output terminal of the level converter circuit.
In accordance with another embodiment of the present invention, there is provided a display device including a pair of substrates, an electrooptical material layer sandwiched between the pair of substrates, a plurality of pixels formed between the pair of substrates and a driver circuit for driving the plurality of pixels provided on one of the pair of substrates, the driver circuit including a level converter circuit comprised of MISTFTs (Metal Insulator Semiconductor Thin Film Transistors) having semiconductor layers made of polysilicon, the level converter circuit having a plurality of stages arranged in series, each of the plurality of stages comprising: a pair of a first NMISTFT (N-channel type Metal Insulator Semiconductor Thin Film Transistor) and a first PMISTFT (P-channel type Metal Insulator Semiconductor Thin Film Transistor), each of the first NMISTFT and the first PMISTFT having both a gate terminal thereof and a first terminal thereof coupled to an input terminal for receiving an input pulse via a first capacitance; a pair of a second NMISTFT and a second PMISTFT, each of the second NMISTFT and the second PMISTFT having a second terminal thereof coupled to the input terminal via a second capacitance; a third PMISTFT having a gate terminal thereof coupled to the gate t
Maki Masahiro
Miyazawa Toshio
Satou Hideo
Satou Tomohiko
Antonelli Terry Stout & Kraus LLP
Awad Amr
Hitachi , Ltd.
LandOfFree
Display device having an improved voltage level converter... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Display device having an improved voltage level converter..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Display device having an improved voltage level converter... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3353429