KR100703431B1 - Flat panel display by using organic thin film transistor - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flat panel display using an organic thin film transistor. The present invention relates to a flat panel display device comprising: a voltage changer for changing a voltage of a scan control signal, a first data control signal, and a first data signal; A plurality of scan lines, a plurality of data lines for transmitting the data signal and a second data signal corresponding to the first data signal, a plurality of scan lines and a region defined by the plurality of data lines, between the two electrodes A plurality of pixels including an EPD including charged particles and the second data signal swing between a first voltage level and a second voltage level having a voltage higher than the first voltage level, wherein the pixel A first voltage receiving a data signal and a third voltage level having a voltage level between the first voltage level and the second voltage level are input. Claim to provide a flat panel display device having the second electrode.

Therefore, the flat panel display using the EPD can be driven by using the data driver and the scan driver used in the conventional flat panel display.

Organic Thin Film Transistors, Voltage Fluctuations, Flat Panel Displays, EPDs

Description

Flat panel display using organic thin film transistors {FLAT PANEL DISPLAY BY USING ORGANIC THIN FILM TRANSISTOR}

1 is a structural diagram showing a first embodiment of a flat panel display using an organic thin film transistor according to the present invention.

FIG. 2 is a diagram illustrating a cell structure using EPD in the flat panel display of FIG. 1.

3 is a circuit diagram illustrating a first embodiment of a pixel employed in the flat panel display of FIG. 1.

4 is a waveform diagram illustrating an operation of a pixel employed in a flat panel display using the organic thin film transistor of FIG. 3.

FIG. 5 is a circuit diagram illustrating a second embodiment of a pixel employed in the flat panel display of FIG. 1.

6 is a waveform diagram illustrating an operation of a pixel employed in a flat panel display using the organic thin film transistor of FIG. 5.

 7 is a structural diagram illustrating a second embodiment of a flat panel display using an organic thin film transistor according to the present invention.

*** Explanation of symbols on main parts of drawings ***

100: image display unit 110: pixels

200: data driver 300: scan driver

400: timing controller 500: voltage changer

The present invention relates to a flat panel display using an organic thin film transistor, and more particularly, to an organic thin film transistor for driving a pixel formed of an organic thin film transistor by adjusting a voltage range of a signal output from a scan driver and a data driver. It relates to a flat panel display device used.

BACKGROUND ART A thin, lightweight flat panel display is used as a display device of a portable information terminal such as a personal computer, a cellular phone, a PDA, or a monitor of various information devices. Such flat panel displays include LCDs using liquid crystal panels, organic light emitting displays using organic light emitting diodes, and PDPs using plasma panels.

In such a flat panel display, a plurality of pixels are arranged on a substrate to form a display area, and a scan line and a data line are connected to each pixel to selectively apply a data signal to the pixel for display.

The flat panel display is classified into a passive matrix type flat panel display device and an active matrix type flat panel display device according to the pixel driving method. The flat panel display device is an active device that selects and lights each unit pixel in terms of resolution, contrast, and operation speed. Matrix type is the mainstream.

In recent years, the concept of digital paper has been considered as a new display device having advantages of existing display devices and printed paper. Electronic paper is a kind of reflective display that has the highest visual characteristics of display media with high resolution, wide viewing angle, and bright white background like conventional paper and ink, and can be implemented on any substrate such as plastic, metal, and paper. In addition, since the image is maintained even after the power is cut off and there is no back light power, the battery life of the mobile communication device is maintained for a long time, so that cost reduction and light weight can be easily applied. In addition, like conventional paper, it can be implemented in a large area, so it can be applied to a larger area than any other display. It also has a memory function that does not disappear without the power being displayed.

Such electronic paper can be implemented using an electrophoretic display (EPD). The EPD is expressed in white or black by the voltage applied across the display. That is, when there is a first electrode and a second electrode applying a voltage to the EPD and the EPD is positioned therebetween, when + voltage is applied to the first electrode and-voltage is applied to the second electrode, white is expressed and the first electrode is applied. When a negative voltage is applied to the second electrode and a positive voltage is applied to the second electrode, black is displayed to display.

This EPD causes the voltage at both ends to swing between + and-. However, the existing data driver or scan driver outputs a + signal or a-signal. For this reason, the conventional data driver or scan driver cannot be used for EPD.

Accordingly, the present invention has been made to solve the problems of the prior art, and an object of the present invention is to implement a pixel as an organic thin film transistor to reduce the manufacturing cost of the flat panel display device and to facilitate manufacturing, and to display a general flat panel display. A flat panel display using an organic thin film transistor to operate a pixel implemented by an organic thin film transistor using a scan driver and a data driver used in an apparatus is provided.

As a technical means for achieving the above object, a first aspect of the present invention provides a voltage change unit for changing a voltage of a scan control signal, a first data control signal and a first data signal, and a scan signal corresponding to the scan control signal. A plurality of electrodes formed on a region defined by the plurality of scan lines to transfer, a plurality of data lines to transfer the data signal and a second data signal corresponding to the first data signal, and the plurality of scan lines and the plurality of data lines A plurality of pixels including an EPD having charged particles therebetween and the second data signal swing between a first voltage level and a second voltage level having a voltage higher than the first voltage level, wherein the pixels A first voltage level having a first electrode receiving a second data signal and a third voltage level having a voltage level between the first voltage level and the second voltage level is input; A flat panel display device having two electrodes is provided.

In addition, the second aspect of the present invention, the voltage control unit for changing the voltage of the scan control signal, the data control signal and the first data signal, the first power supply and the second power supply is operated by the output, the voltage changer A scan driver for forming a scan signal according to the received scan control signal, and is operated by receiving a third power source and a fourth power source, and forming a second data signal according to the data control signal and the first data signal output from the voltage changer A data driver configured to receive a data driver and the scan signal, the second data signal, and a fifth power source to display an image in response to a difference between the second data signal and the fifth power source; The fourth power supply has a voltage level greater than ground, and the fifth power supply provides a flat panel display having an average value of the voltage levels of the second data signal.

Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

1 is a structural diagram showing a first embodiment of a flat panel display using an organic thin film transistor according to the present invention. Referring to FIG. 1, an image display unit 100, a data driver 200, and a scan driver 300 are included.

The image display unit 100 is a means for displaying an image and includes a first substrate (not shown) and a second substrate (not shown). The first substrate and the second substrate may be made of plastic, glass, metal, or the like. The image display unit 100 includes a plurality of pixels 110 composed of a thin film transistor and an EPD, a plurality of scan lines S1, S2,..., Sn-1, Sn, and pixels that transmit scan signals to the pixels 110. And a plurality of data lines D1, D2, ... Dm-1, Dm for transmitting the data signal.

Each pixel of the image display unit 100 includes a thin film transistor and an EPD. The first end of the EPD is connected to the thin film transistor, and the second end is connected to the reference power supply Vref to switch the data signal through the switching operation of the thin film transistor. Receive optional. The reference power supply Vref connected to the second stage of the EPD is preferably a voltage level having an average value of the maximum value and the minimum value of the voltage level of the data signal. The thin film transistor may be implemented as an organic thin film transistor in order to implement the image display part 100 more flexibly and inexpensively. The organic thin film transistor includes an active layer that is an organic material. When the active layer is used as an organic material, the insulating substrate of the first substrate may be used as the plastic substrate. Therefore, the advantages of processing and ease of application can be provided, thereby reducing the cost of the flat panel display device and making the manufacturing easy.

The data driver 200 is a means for transmitting a data signal to the image display unit 100, and the data signal has a value between 15V and 45V.

The scan driver 300 is a means for transmitting a scan signal to the image display unit 100. The scan signal output from the scan driver 300 has a value between 0V and 60V.

FIG. 2 is a diagram illustrating a cell structure using EPD in the flat panel display of FIG. 1. Referring to FIG. 2, the first substrate 111 and the second substrate 118 of the flat panel display device are formed to face each other at a predetermined distance, and the first substrate 111 and the second substrate 118 are made of plastic, It is formed of glass, metal and the like.

A thin film transistor (not shown) that is a switching element is formed on the first substrate 111, and a first electrode 112 connected to the thin film transistor to receive a data signal through the thin film transistor is formed in an island shape. The second substrate 118 is positioned to face the first substrate 111, and the second electrode 118 is disposed on the rear surface of the second substrate 118 so as to face the first electrode 112 of the first substrate 111. 117 is formed. The first electrode 112 and the second electrode 117 may be implemented as a transparent electrode.

The first and second electrodes 112 and 117 may be polarized by signals transmitted from the scan driver 500 and the data driver 400.

The EPD 120 is positioned between the first electrode 112 and the second electrode 117 so that the EPD 120 expresses a color by an electric field formed by the first and second electrodes 112 and 117. The device will present the image.

The EPD 120 is implemented in the form of a plurality of fine cups 113, and the insulating solution 115 and the fine charged particles 116 having a color are present in the cup 113. And the sealing layer 114 for sealing the cup 113 is attached to the upper portion of the cup 113 to prevent the insulating solution and the charged particles from flowing out.

 The charged particles 116 move upward and downward in the insulating solution 115 according to voltages applied to the first electrode 112 and the second electrode 117. If the charged particles 116 have a (+) charge and a (+) signal is applied to the first electrode 112 and a (-) signal is applied to the second electrode 117, the charged particles 116 are charged. It is moved toward the two electrodes 117. In addition, when a negative signal is applied to the first electrode 112 and a positive signal is applied to the second electrode 117, the charged particles 116 move toward the first electrode 112. Therefore, the charged particles 116 move to the upper or lower portion of the cup 113 according to the signals applied to the first electrode 112 and the second electrode 117. At this time, when the upper surface of the cup 114, the insulating solution 115 is blocked by the charged particles 116, so that the insulating solution 115 can not be seen from the outside, the EPD 120 is black, the charged particles When 116 is lowered to the bottom of the cup 114, the insulating solution 115 is exposed to be able to see the color represented by the insulating solution 115 from the outside, so that the EPD 120 expresses the color.

Accordingly, the EPD 120 expresses colors according to voltages applied to the first electrode 112 and the second electrode 117, so that in the flat panel display device, the first electrode 112 and the second electrode 117 are mutually different. The signals having the opposite polarity must be alternately inputted so that the image can be expressed.

3 is a circuit diagram illustrating a first embodiment of a pixel employed in the flat panel display of FIG. 1. Referring to FIG. 3, a pixel includes an EPD 120 and a pixel circuit. The pixel circuit includes a switching transistor M1 and a capacitor Cst. In addition, the switching transistor M1 is implemented as a P-MOS transistor and has a gate, a source, and a drain. In addition, the capacitor Cst includes a first electrode and a second electrode.

In the switching transistor M1, a source and a drain are connected to the data line Dk and the first node A, and a gate thereof is connected to the scan line S1. The data signal is transferred to the first node A according to the scan signal applied to the gate. Where l is an integer between 1 and n and k is an integer between 1 and m.

The EPD 120 is connected between the first node A and the reference power supply Vref, and is connected to the switching transistor M1 through the first node A to receive a data signal and receive a first signal of the EPD 120. The voltage applied to the substrate 111 receives a data signal having a voltage level higher or lower than that of the reference power supply Vref. Therefore, when the voltage of the second substrate 118 of the EPD 120 is fixed by the reference power supply Vref, and receives a data signal having a voltage level higher than the reference power supply Vref to the first substrate 111, the voltage is relatively increased. The voltage applied to the first substrate 111 is higher than the voltage applied to the second substrate 118, and transfers a data signal having a voltage level lower than that of the reference power supply Vref to the first substrate 111. When received, a voltage relatively lower than the voltage applied to the first substrate 111 is applied to the second substrate 118. Therefore, a voltage difference is generated between the first substrate 111 and the second substrate 118 to form an electric field between the first substrate 111 and the second substrate 118.

The capacitor Cst is connected to the first node A and the reference power source Vref in parallel with the EPD 120. Therefore, when the switching transistor M1 is turned off by storing the voltage applied between the EPD 120 by the scan signal and the data signal, the capacitor is in a floating state with the first node A to maintain the stored voltage for a predetermined period of time. The voltage is maintained in the EPD 120 for a predetermined time.

4 is a waveform diagram illustrating an operation of a pixel employed in a flat panel display using the organic thin film transistor of FIG. 3. Referring to FIG. 4, a data signal input through the data driver 200 has a voltage value between 15V and 45V, and a scan signal input through the scan driver 300 has a voltage value between 0V and 60V. do. A voltage of 30 V is connected to the second electrode of the EPD.

First, when the signal transmitted through the data line Dk has a voltage value of 15V, a voltage of 15V is applied to the first substrate 111 of the EPD 120 and a voltage of 30V is applied to the second substrate 118. Thus, a voltage of 15V difference is applied between the first substrate 111 and the second substrate 118 of the EPD 120, and the second substrate 118 has a higher potential than the first substrate 111.

Therefore, the charged particles 116 in the EPD 120 are moved by an electric field formed by the first substrate 111 and the second substrate 118. At this time, assuming that the charged particles 116 have a negative polarity (−), the charged particles move toward the second substrate 118, and if the charged particles 116 have a positive polarity (+), the charged particles 116 ) Moves toward the first substrate 111.

On the other hand, when the signal transmitted through the data line Dk has a voltage value of 45V, a voltage of 15V difference is applied between the first substrate 111 and the second substrate 118 of the EPD 120. The first substrate 111 has a higher potential than the second substrate 118.

Therefore, the charged particles 116 in the EPD 120 are moved by an electric field formed by the first substrate 111 and the second substrate 118. In this case, assuming that the charged particles 116 have a negative polarity (−), the charged particles move toward the first substrate 111, and if the charged particles 116 have a positive polarity (+), the charged particles 116 ) Moves toward the second substrate 118.

Then, when the charged particles 116 move toward the first substrate 111, the insulating particles 115 are blocked from being exposed to the outside by the charged particles 116, so that the color of the insulating solution 115 in the EPD 120 may be changed. When the charge particles 116 move toward the second substrate 118, the charged particles 116 sink to the inside of the cup 113, and the color of the insulating solution 115 in the EPD 120 becomes external. Exposed to make the color of the insulating solution visible from the outside.

Therefore, the color of the insulating solution can be expressed or blackened in accordance with the movement of the charged particles 116 for each pixel to express the image.

In addition, the threshold voltage value of the organic thin film transistor is higher than that of the general thin film transistor, so that the value of the scan signal for allowing the organic thin film transistor to perform the switching operation is increased so that the switching operation can be performed regardless of the threshold voltage of the organic thin film transistor.

In addition, the EPD 120 maintains the voltage for a predetermined period of time due to the voltage across the capacitor Cst.

In addition, as shown in FIG. 5, when the switching transistor M1 is implemented with an N MOS transistor and a signal such as that shown in FIG. 6 is input, the pixel may operate to represent an image.

7 is a structural diagram illustrating a second embodiment of a flat panel display using an organic thin film transistor according to the present invention. Referring to FIG. 7, an image display unit 100, a data driver 200, a scan driver 300, a timing controller 400, and a voltage changer 500 are included.

The image display unit 100 is a means for displaying an image and includes a first substrate and a second substrate. The first substrate and the second substrate may be made of plastic, glass, metal, or the like. The image display unit 100 includes a plurality of pixels 110 composed of a thin film transistor and an EPD, a plurality of scan lines S1, S2,... A plurality of data lines D1, D2, ... Dm-1, Dm for transmitting data signals are provided. A reference power supply Vref is connected to the pixel, and the reference power supply Vref has a voltage level of 30V.

The timing controller 400 generates a data control signal DCS and a scan control signal GCS in response to synchronization signals supplied from the outside, and outputs the data control signals DCS and the first data signal to the data driver 200. ) And the scan control signals GCS are supplied to the scan driver 300.

The voltage changing unit 500 is divided into a data driving voltage changing unit 501 and a scan driving voltage changing unit 502, and varies a range of voltage levels input from the scan driving unit 200 and the data driving unit 300.

The operation of the data driving voltage changing unit 501 allows a signal output from the timing controller 200 having a voltage range of 0V to 5V to have a voltage range of 15V to 20V, and the scan driving voltage changing unit 502 The operation causes the signal output from the timing controller 200 having a voltage range of 0V to 5V to have a voltage range of 30V to 35V.

The data driver 200 is a means for transmitting a data signal to the image display unit 100. The data driver 200 generates a second data signal through the data control signal DCS changed by the voltage changer 300.

In addition, the data driver 200 operates by receiving the first power source 1Vdd and the second power source 1Vss, and the first power source 1Vdd has a voltage level higher than that of the second power source 1Vss and the second power source (1Vdd). 1Vss) has a voltage level as high as 15V with respect to ground (GND). Accordingly, the data driving voltage changing unit 501 inputs the signal input from the timing controller 200 to about 15V to allow the data driver 400 to operate by the signal input from the timing controller 200.

The data signal output from the data driver 200 has a voltage range of 15V to 45V by the data control signal DCS input through the data driving voltage changing unit 501.

The scan driver 300 is a means for transmitting a scan signal to the image display unit 100. The scan driver 300 generates a scan signal through the scan control signal GCS changed in the scan driving voltage changing unit 502.

In addition, the scan driver 300 operates by receiving the third power source 2Vdd and the fourth power source 2Vss, and the third power source 2Vdd has a higher voltage level than the fourth power source 2Vss and the second power source (2Vdd). 1Vss) has a voltage level as high as 30V with respect to ground (GND).

Accordingly, the scan driving voltage changing unit 302 inputs the signal input from the timing controller 200 to about 30V to allow the scan driver 500 to operate by the signal input from the timing controller 200.

The scan signal output from the scan driver 500 may have a voltage range of 0V to 60V by the scan control signal GCS input through the scan driving voltage changer 302.

The data driving voltage changing unit 501 and the scan driving voltage changing unit 502 may be configured as photo couplers. The photo coupler has four pins and a signal is input through the first pin, and ground (GND) is connected to the second pin. The light emitting diode is connected between the first pin and the second pin. A signal is output through the third pin, and a voltage having a predetermined magnitude is connected to the fourth pin so that a signal output through the third pin is output corresponding to the magnitude of the voltage connected to the fourth pin.

The operation of the data driving voltage changing unit 501 and the scan driving voltage changing unit 502 will be described in detail. The data driving voltage changing unit 501 has a signal having a voltage level range of 0V to 5V through the first pin. When input, a current value flowing through the diode between the first pin and the second pin is sensed. When a voltage of 15V is connected to the fourth pin, the third pin outputs a signal 15V higher than a signal input through the first pin. Therefore, a signal having a voltage level between 15V and 20V is output. When the signal having a voltage level range of 0V to 5V is input through the first pin, the scan driving voltage change unit voltage change unit 502 may input a current value flowing through the diode between the first pin and the second pin. When sensing and a voltage of 30V is connected to the fourth pin, the third pin outputs a signal 30V higher than the signal input through the first pin. Thus, a signal having a voltage range of 30V to 35V is output.

In addition, the data driving voltage changing unit 501 and the scan driving voltage changing unit 502 may be configured as a comparator to compare the input signals to determine the output signals.

The comparator is well known to those skilled in the art, and thus a detailed description thereof will be omitted.

While preferred embodiments of the present invention have been described using specific terms, such descriptions are for illustrative purposes only and it is understood that various changes and modifications may be made without departing from the spirit and scope of the following claims. You must lose.

In the flat panel display using the EPD according to the present invention, by applying a predetermined voltage to the image display unit, an existing data driver may be used to express an image by simply controlling the operation of the EPD without implementing a separate data driver.

In addition, as the organic thin film transistor is used, manufacturing advantages such as compatibility with a plastic substrate and ease of application may be provided, thereby facilitating the fabrication of a flat panel display and reducing manufacturing costs.

Claims (12)

A voltage changer which changes a voltage of the scan control signal, the data control signal and the first data signal; A plurality of scan lines transferring a scan signal corresponding to the scan control signal; A plurality of data lines transferring the first data signal and a second data signal corresponding to the first data signal; A plurality of pixels including an EPD formed in an area defined by the plurality of scan lines and the plurality of data lines and having charged particles between two electrodes; And The second data signal swings between a first voltage level and a second voltage level having a voltage higher than the first voltage level, And the pixel includes a first electrode receiving the second data signal and a second electrode to which a third voltage level having a voltage level between the first voltage level and the second voltage level is input. The method of claim 1, And the third voltage level has an average value of the first voltage level and the second voltage level. The method of claim 1, wherein the pixel, A thin film transistor which is turned on by the scan signal and transfers the second data signal; The EPD connected to the thin film transistor and receiving the second data signal and the third voltage level; And And a capacitor connected to the EPD to maintain a voltage applied to the EPD. The method of claim 3, wherein And the thin film transistor is an organic thin film transistor. The method of claim 1, wherein the EPD, A lower electrode formed on the first substrate; An upper electrode formed to face the first substrate and formed on a rear surface of the second substrate; And A plurality of fine particles including an insulating solution disposed between the upper electrode and the lower electrode to express colors and a plurality of charged particles to block colors represented by the insulating solution according to an electric field formed in the lower electrode and the upper electrode; Flat panel display comprising a cup. The method of claim 5, The charged particles include a plurality of microparticles having a charge of at least one of a positive charge and a negative charge, and the microparticles move according to a voltage applied to both ends of the charged particles to block the insulation from being exposed to the outside. Flat panel display. The method of claim 1, The scan signal includes a flat panel display having a low signal having a voltage level lower than a voltage level of the first voltage of the second data signal and a high signal having a voltage level higher than the voltage level of the second voltage of the second data signal. . The method of claim 1, A scan driver for transmitting the scan signal to the scan line; And And a data driver for transmitting the second data signal to the data line. A voltage changer which changes a voltage of the scan control signal, the data control signal and the first data signal; A scan driver configured to receive and operate a first power source and a second power source to form a scan signal according to the scan control signal output from the voltage changer; A data driver configured to receive a third power source and a fourth power source and to form a second data signal according to the data control signal and the first data signal output from the voltage changer; And An image display unit including an EPD receiving the scan signal, the second data signal, and a fifth power source to display an image corresponding to a difference between the second data signal and the fifth power source and having charged particles between two electrodes; Including; And the second power supply and the fourth power supply have a voltage level greater than ground, and the fifth power supply has an average value of the voltage levels of the second data signal. The method of claim 9, And a timing controller configured to transfer the scan control signal, the data control signal, and the first data signal to the voltage change unit. The method of claim 9, And the voltage changer further includes a data drive voltage changer for changing the voltage level of the first data signal and a scan drive voltage changer for changing the voltage level of the scan control signal. The method of claim 9, And the voltage changer comprises one of a photocoupler and a comparator.

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