JPH01169493A - Active matrix type display device - Google Patents

Abstract

PURPOSE:To solve a problem caused by the dispersion of the thresh-old of a switching element by making the conductive types of the switching element whose gate is connected to an odd numbered scanning line and the switching element whose gate is connected to an even numbered scanning line contrary. CONSTITUTION:The conductive types of the switching element 3 whose gate G is connected to the odd numbered scanning line 1 and the switching element 3 whose gate G is connected to the even numbered scanning line 1 are made contrary so that one is in a p-type and the other is in an n-type. And a data voltage in accordance with display data is impressed on a data line 2 from a data driver 6 and scanning voltage pulses of a polarity corresponding to the conductive type of the switching element 3 are impressed from a scanning driver 5. Even if the dispersion of the threshold of the switching element exists, the switching element can be surely controlled in an off state until next scanning.

Description

[Detailed Description of the Invention] [Summary] The present invention relates to an active matrix display device with a gate-connected facing matrix configuration in which the gate and drain of a switching element are connected between adjacent scanning lines, and the problem caused by variations in the darkness value of the switching element is solved. For the purpose of In an active matrix display device having a gate-connected facing matrix configuration in which the drain of the switching element is connected to the scanning line and the source is connected to the electrode facing the data line, the gate is connected to the odd numbered scanning line. The conductivity types of the switching elements connected to the gates and the switching elements connected to the even-numbered gates were configured to be opposite.

[Industrial application field]

The present invention relates to an active matrix display device having a gate-connected facing matrix configuration in which the gate and drain of a switching element are connected between adjacent scanning lines.

An active matrix display device is one in which switching elements such as transistors are provided for a large number of pixels, and each pixel can be controlled independently. Therefore, even if the number of scanning lines increases with an increase in display capacity, problems such as a decrease in drive duty ratio, which causes a decrease in contrast and a decrease in viewing angle, do not occur as in simple matrix display devices. Due to its advantages, it has been put into practical use as a display device for portable television receivers and small information terminal devices.

[Conventional technology]

Active matrix display devices use liquid crystal as the display medium and thin film transistors (
A configuration using a TFTJ (hereinafter abbreviated as rTFTJ) is common. In addition, it is common to form a scanning line and a data line on the same substrate, and it is necessary to provide an insulating layer to prevent mutual short circuit at the intersection of the scanning line and data line. It was difficult to improve manufacturing yield.

Therefore, a gate-connected facing matrix structure is proposed in which the scanning line and the data line are formed on one substrate and the other substrate, which are placed facing each other, and the insulating layer at the intersection of the scanning line and the data line can be omitted. We first proposed an active matrix display device.

In this active matrix display device having a gate-connected facing matrix configuration, for example, as shown in FIG. 5, scanning lines 81 to Sn are formed on one substrate and data lines D1 to Dm as electrodes are formed on the other substrate. TPT gate G is connected to one adjacent scanning line, and TPT is connected to the other scanning line.
The drain D of the PT is connected, the source S is connected to the electrode P, and a liquid crystal cell is constructed between the electrode P and the data lines D1 to Dm.

The scanning lines 81 to Sn are supplied with a voltage Vgoff for turning off the TPT and a voltage Vgon for turning it on.
and a reference voltage Vr are sequentially applied, and a data voltage Vd whose polarity is inverted every frame is applied to the data lines D1 to Dm.

In that case, the relationship is selected to be Vgon>Vr>Vgo f f and Vr-Vgoff≧2·Vd.

For example, when voltage Vgon is applied to scan line S1,
A reference voltage Vr is applied to the adjacent scan line S2, and a voltage Vgoff is applied to the other scan lines 83 to Sn. Therefore, T with gate G connected to scan line S1
The PT is turned on by applying gon-Vr between the gate and drain, and the data voltage applied to the data lines D1 to Dm is applied to the liquid crystal cell through the TPT in the on state. Since the liquid crystal cell is capacitive, the applied data voltage is held until the next scan.

At this time, scanning lines S3 to S3 other than scanning lines St and S2
The TPT whose gate G is connected to Sn continues to be in the off state because Vgof f - Vgof f=0 is applied between the gate and the drain. In addition, the TPT whose gate G is connected to the scanning line S2 has Vr-Vg between the gate and drain.
orf is applied, but the voltage value is selected so that the off state continues, and even if it becomes an on state, next, voltage Vgon is applied to the scanning line S2 to maintain this T.
Since the PT is turned on, the effect on the displayed content can be ignored.

As described above, by applying a pulse consisting of the voltage Vr and the voltage Vgon to the scanning lines 81 to Sn, and correspondingly applying a data voltage according to the display data to the data lines D1 to Dm, the display data is changed. It is possible to display one character and one figure according to the following.

[Problems to be Solved by the Invention] As described above, in an active matrix display device having a gate-connected facing matrix configuration, the scanning line 8
TP corresponding to the intersection of 1 to Sn and data lines D1 to Dm
It is not easy to make all T's have the same characteristics.

FIG. 6 is a characteristic diagram of the TPT, where the horizontal axis shows the gate bias voltage Vgd of the TPT, the vertical axis shows the drain current 1 ds, and Ion is the standard current of, for example, 10-''A that flows when the TPT is turned on. 1off is a standard leakage current of, for example, 10-■A that flows when the TPT is turned off.

In the case of a TPT with the characteristics shown in the solid curve a, when the gate bias voltage Vgd is set to Ov and the TPT is turned off, the leakage current is less than the standard leakage current 1off, so it is applied to the liquid crystal cell and held. However, in the case of a TPT with the characteristics shown in the dotted line curve, the gate bias voltage is set to Ov.
Even if it is turned off, a leakage current greater than the standard leakage current Ioff flows, so the data voltage applied to the liquid crystal cell decreases relatively rapidly until the next scan, resulting in a change in the display content.

In an active matrix display device in which TPTs with dark value characteristics such as those shown by the solid line curve a and the dotted line curve S coexist, display quality will deteriorate due to variations in display characteristics between pixels. Become. In addition, when TPTs with different threshold characteristics are connected corresponding to scanning lines, the applied voltage is set for each scanning line according to the difference in dark value characteristics.
Although it is possible to correct variations in the dark value characteristics of TPT, it is practically difficult to apply such a means to accommodate a large number of scanning lines.

The present invention aims to solve problems caused by variations in the dark values of switching elements.

[Means for solving problems]

The active matrix display device of the present invention uses switching elements of different conductivity types corresponding to scanning lines, and will be explained with reference to FIG.

A scanning line 1 and a data line 2 are provided perpendicularly on one and the other substrates arranged to face each other, and a switching element 3 is provided on one scanning line adjacent to the scanning line 1.
A display cell 4 in which the gate G of the cell is connected, the drain D is connected to the other scanning line, the source S is connected to an electrode facing the data line 2, and a display medium is filled between this electrode and the data line 2. In an active matrix display device having a gate-connected facing matrix configuration, electrical conduction between switching elements 3 having gates G connected to odd-numbered scan lines 1 and switching elements 3 having gates G connected to even-numbered scan lines 1 The types are reversed such that one is p type and the other is n type, and a data voltage according to the display data is applied from the data driver 6 to the data line 2, and the scanning driver 5
A scanning voltage pulse having a polarity corresponding to the conductivity type of the switching element 3 is applied from the switching element 3 to the switching element 3.

[Effect]

The dark value characteristics of the switching elements 3 having opposite conductivity types are opposite in positive and negative. For example, if the switching element 3 with the gate G connected to the odd numbered number of the scanning line 1 is p type, the gate G is connected to the even numbered number of the scanning line 1. switching element 3 connected to
is assumed to be n-type. Therefore, by applying a positive voltage to the gate of the p-type switching element and a negative voltage to the gate of the n-type switching element when it is not selected, the gate-drain of the p-type switching element (w gate of the n-type switching element) Since a positive polarity voltage is applied and a negative polarity voltage is applied to the gate-drain of the n-type switching element (<= the gate of the p-type switching element), the p-type and n-type switching elements are respectively turned off reliably.

Even if there are variations in the dark values of p-type and n-type switching elements, or variations in the dark values of switching elements of the same conductivity type, switching elements of different conductivity types are alternately placed between odd and even numbers. By being connected, it is possible to reliably control the off state until the next scan.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 2 is an explanatory diagram of the main part of the present invention, in which the gate G of a p-type thin film transistor (hereinafter abbreviated as "nTFTJ") is connected to the odd numbered scanning lines 81 to Sn formed on one substrate, and the drain thereof is D is connected to the even numbered scan lines 81 to Sn, the source S is connected to the electrode P, and the gate G of an n-type thin film transistor (hereinafter abbreviated as rnTFTJ) is connected to the even numbered line, and its drain D is scanned. Line 81~
The source S is connected to the odd numbered Sn, the source S is connected to the electrode P, data lines D1 to Dm as electrodes facing the electrode P are formed on the other substrate, and the data lines D1 to Dm and the electrode P are connected to each other.
A liquid crystal cell is formed by filling liquid crystal as a display medium between the two.

nTFTs and pTFTs can be formed in the same way as forming conventional TPTs. For example, in a transistor region where an amorphous silicon layer is formed on one substrate, an nTFT is formed between a source S and a drain D. For example, the region is doped with phosphorus (P) to form an n'' region, and the p
In the TFT, for example, boron (
B) is doped to form a p"fiJ region, an insulating layer is formed between the source S and the drain D, and a metal layer is formed on the entire surface, and then the gate G, scanning lines S1 to Sn and the electrode P are formed. and their connection circuits are formed by patterning, and the second
A connection configuration as shown in the figure can be produced.

Figure 3 is an explanatory diagram of the characteristics of TPT, which corresponds to Figure 6, where curve A is the dark value characteristic of n T F T and curve B is the dark value characteristic of p
The threshold characteristics of TFT are shown. Therefore, if +2V is applied to the odd-numbered scanning lines and -2V is applied to the even-numbered scanning lines,
+4v is applied between the gate and drain of pTFT, and n
-4V is applied between the gate and drain of the TFT, and both the pTFT and nTFT have a standard leakage current of 1off or less, which is negligible. That is, it can be reliably turned off. That is, even if there are variations in the dark value characteristics, the display quality can be improved by ensuring that the off-state is maintained except when applying the scanning voltage pulse, and the leakage current is negligible. In other words, manufacturing yield can be improved.

FIG. 4 is an explanatory diagram of drive waveforms in an embodiment of the present invention, (a
) shows a data voltage pulse, and (b) to (e) show examples of pulse waveforms applied to the gates G of pTFT and nTFT connected to the scanning line. Data voltage pulses are +Vd and -Vd (e.g. +4V, -4V) for each frame.
This shows the case where the same data is written all along the scanning line by reversing the polarity, and the gate G of the pTFT,
In other words, the scanning voltage pulses applied to the odd numbered scanning lines are:
As shown in (b) and (d), the voltage VPoff (for example +10■) for turning off the pTFT and the reference voltage V
Pr (for example, OV) and the voltage VPon for turning on (
For example, -TV), and the scanning voltage pulse applied to the gate G of the nTFT, that is, the even numbered scanning line, is (C)
, As shown in (e), the voltage VNoff (e.g. -10v) for turning off the nTFT and the reference voltage VNr
(for example, OV) and a voltage VNon (for example, +7V) for turning on.

For example, the voltage VPon (-7V) is applied to the odd-numbered scanning line S1 in FIG. 2 at time t1, and the reference voltage VNr (OV) is applied to the adjacent scanning line S2.
is applied to the other odd-numbered scanning lines, and the voltage VPo f
f (+I GV), voltage V on even numbered scan lines
When No f f (-10V) is applied, the pTFT whose gate G is connected to the scanning line S1 is turned on by applying VPon-VNr=-7V between the gate and drain. Also, the gate G is connected to the scanning line S2.
FT is between gate and toy L/7.
Since f = -I QV is applied, it is turned off. In addition, the pTFT whose gate G is connected to the other odd-numbered scanning line has a voltage of VPof f−VNoff=+10V−(−10V”
) −+20V is applied to ensure that it is turned off. In addition, the nTFT whose gate G is connected to the other even-numbered scanning line has VNof f-VPof f=-LOV-10V=-
20V is applied to ensure that it is turned off, and the leakage current in the off state can be made negligible.

At time t2, voltage VPoff is applied to odd-numbered scanning lines S1, and at time t3 within that time t2, voltage VNon is applied to even-numbered scanning lines S2, and at the same time, voltage VNon is applied to odd-numbered scanning lines S3. Since the voltage VPr is applied, at time t3, the pTFT whose gate G is connected to the scanning line S1 has VPoff between the gate and the train.
Since -VNon=+10V-7V=+3V is applied, it is surely turned off. In addition, the nTFT whose gate G is connected to the scanning line S2 has VNon-V between the gate and drain.
Pr=+7V is applied and turned on. Also, scanning line S
The pTFT with gate G connected to 3 has VPr-VN between the gate and drain.

ff=+10V is applied and turned off. In addition, +20V is applied between the gate and drain of pTFTs whose gates G are connected to other odd-numbered scan lines, and +20V is applied between the gate and drain of nTFTs whose gates G are connected to other even-numbered scan lines. Since -20V is applied to each, even if there is some variation in the dark value characteristics, it will definitely turn off.
Leakage current can be made negligible.

Thereafter, the above-described operation is similarly repeated at time t4, and the data voltages applied to the data lines D1 to Dm are applied to the liquid crystal cell via the pTFT and nTFT that are in the on state.

Further, as shown in FIG. 1, the scan driver 5 is connected to the scan line 1.
By providing the odd numbered side and the even numbered side separately, when the gate G of the pTFT is connected to the odd numbered scanning line and the gate G of the nTFT is connected to the even numbered scanning line, the odd numbered side (b) of FIG. 4 from the side scanning driver,
VPof f, VPr, VPon as shown in (d)
VNo f f as shown in (C1, (@i) in FIG. 4) from the even-numbered scan driver.

By sequentially outputting scanning voltage pulses consisting of voltages VNr and VNon, switching elements consisting of p-channel and n-channel transistors can be easily controlled.

The present invention is not limited only to the above-mentioned embodiments, but can be modified in various ways, and the interlaced drive can also be performed by using the scanning drivers on the odd-numbered side and the scanning drivers on the even-numbered side in FIG. This can be easily done by switching and operating the scanning driver for each frame.

〔Effect of the invention〕

As described above, the present invention provides an active matrix display device having a gate-connected facing matrix configuration, in which switching elements each having a gate G connected to an odd-numbered scanning line 1 and an even-numbered scanning line 1 are provided. Since the conductivity type of switching element 3 is opposite to that of switching element 3, and the scanning voltage pulse is driven with the opposite polarity, even if there are variations in the threshold characteristics of switching element 3, the leakage current can be ignored during the off period. can be reliably turned off. Therefore, there is an advantage that manufacturing yield can be improved.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the principle of the present invention, Fig. 2 is an explanatory diagram of main parts of an embodiment of the present invention, Fig. 3 is an explanatory diagram of TPT characteristics, and Fig. 4 is an explanatory diagram of drive waveforms of an embodiment of the invention. , FIG. 5 is an explanatory diagram of the main parts of the conventional example, and FIG. 6 is an explanatory diagram of the characteristics of TPT. 1 is a scan line, 2 is a data line, 3 is a switching element, 4 is a display cell, 5 is a scan driver, 6 is a data driver, G is a gate, D is a drain, and S is a source.

Claims (1)

[Claims] A scanning line (1) and a data line (2) are provided on one and the other substrates arranged to be orthogonal to each other, respectively,
The gate (G) of the switching element (3) is connected to one of the adjacent scanning lines (1), and the drain (D) of the switching element (3) is connected to the other scanning line.
), and the source (S) is connected to the electrode facing the data line. 1.) An active matrix type display device characterized in that a switching element (3) having a gate connected thereto and a switching element (3) having an even-numbered gate connected thereto have opposite conductivity types.