JPH03189626A - Active matrix type liquid crystal display device and its driving method - Google Patents

Abstract

PURPOSE:To accomplish interlaced driving by providing a picture element elec trode and a thin film transistor on the intersection part of a scanning bus line and a data bus line which are orthogonally arranged and driving the picture element electrode by the thin film transistor. CONSTITUTION:The scanning bus line SB and the data bus line DB are arranged to be orthogonally crossed with each other. Then, plural n-channel transistors T1 and T2, p-channel transistors T3 and T4 whose threshold voltages are differ ent from one another, and the picture element electrode E are provided on the intersection part. As to the respective elements, the elements having the large absolute value of the threshold voltage are arranged in the same line and the elements having the small absolute value of the threshold voltage are arranged in the same line, then the elements having the large absolute value are driven first. At such a time, the voltage is impressed in terms of time divi sion through the same line SB and the transistors T1-T4 drive the picture ele ment E in the same line. Thus, the numerical aperture of a panel is enhanced and the number of lines is reduced, then interlaced driving is facilitated.

Description

[Detailed Description of the Invention] [Summary] Regarding an active matrix liquid crystal display device that can achieve high-definition and high-quality display and a method for driving the same, the present invention relates to an active matrix liquid crystal display device that can achieve high-definition, high-quality display, and a method for driving the same. In addition to reducing the number of lines,
In order to enable interlaced driving, a plurality of n-channel thin film transistors with different threshold voltages are installed at each intersection of the scan canvas line and the data bus line, which are arranged orthogonally to each other, and The configuration includes a p-channel thin film transistor and a plurality of pixel electrodes each driven by each thin film transistor, and when scanning each scan canvas line, the voltage applied to each scan canvas line is controlled by each scan canvas line. For each of the n-channel and p-channel "am" transistors connected to the line, after setting all the transistors to a voltage that allows them to conduct, time division is performed such that the transistor with the highest threshold voltage among the conductive transistors becomes non-conductive. It is characterized by changing.

[Industrial Application Field] The present invention relates to an active matrix liquid crystal display device that can achieve high-definition and high-quality display, and a method for driving the same.

In recent years, liquid crystal display panels have been increasingly put to practical use in pocket televisions and the like, and higher definition and higher image quality are also being demanded for use in information terminals and the like.

[Conventional technology]

Conventional active matrix liquid crystal display panels
As shown in the equivalent circuit in the figure, a pixel electrode E and a thin film transistor (TPT) T corresponding to each pixel electrode E are arranged at the intersection of the scan canvas line SB and the data bus line DB.

In order to improve the definition of this active matrix liquid crystal display panel for use in information terminals, the widths of the scan canvas lines SB and data bus lines DB must be made thinner than a certain value in order to keep the pass line resistance below a predetermined value. Therefore, there is a problem that the proportion of the area of the pixel electrode E in the display area, that is, the aperture ratio decreases, and the display becomes dark.

Furthermore, as the number of pass lines increases, problems arise with the pitch of flexible cables and the increase in the number of driver ICs.

[Problem to be solved by the invention]

In order to solve this problem, a plurality of pixel electrodes E and a thin film transistor T corresponding to each pixel electrode are provided at each intersection of the scan bus line SB and the data bus line DB, which are arranged orthogonally to each other, and The present inventors have previously proposed a configuration in which the threshold voltages vth of thin film transistors provided at different positions are made different, and a configuration in which a plurality of thin film transistors provided at each of the above intersection positions are a combination of n-channel and p-channel. Proposed.

In the former configuration, the number of scan canvas lines and/or data bus lines can be reduced, but interlaced driving cannot be performed, and in the latter configuration, the number of lines can be reduced only in scan canvas lines. and data bus line.

As liquid crystal display devices become larger and have higher definition, both the number of scan bus lines and the number of data bus lines are increasing, and there is a strong demand to reduce the number of lines for both. becomes essential.

The present invention has been made based on the above-mentioned requirements, and an object of the present invention is to reduce the number of lines for both scan canvas lines and data bus lines of an active matrix type liquid crystal display device, and also to enable interlaced driving. shall be.

[Means to solve the problem]

In order to solve the above-mentioned problems, the active matrix liquid crystal display device of the present invention includes n-channel thin film transistors having different threshold voltages at each intersection of the scan canvas line and the data bus line, which are arranged orthogonally to each other. The configuration includes p-channel thin film transistors with different voltages and pixel electrodes driven by each of the thin film transistors.

In addition, the driving method is such that when scanning each scan canvas line, the voltage applied to each scan canvas line is
For each of the n-channel and p-channel thin film transistors connected to each scan canvas line, after setting all the elements to a voltage that enables conduction, time division is performed such that the element with the highest threshold voltage among the conductive elements becomes non-conductive. to change.

FIG. 1 (al) is a diagram showing a configuration example of an active matrix liquid crystal display device according to the present invention, in which two cells with different threshold voltages vth are provided at each intersection of a scan canvas line SB and a data bus line DB. This is an example in which an n-channel thin film transistor and two p-channel thin film transistors are provided.

If the threshold voltage characteristics of the four thin film transistors T and -T are selected as indicated by Vthl to Vth4 in FIG. 1 (bl), the configuration of FIG. This is an example in which n-channel elements are arranged on the upper side and p-channel elements on the lower side along the scan canvas line SB.

In the case of the above configuration, depending on the polarity of the scanning voltage applied to the scan canvas line SB, the n-channel elements T r, T
*, or p-channel elements T, , T, are selected, and the other remains unselected regardless of the voltage value.

Furthermore, among the selected element groups T+, Tz (or T s, T −), the threshold voltages V the, V
The absolute value of thz (or V thz, V th4) is the applied scanning voltage V+, V* (or V
Those higher than the absolute value of IV4) are unselected or turned off, and those lower than the absolute value are selected and turned on.

Therefore, when selecting each scan canvas line, select the polarity of the scanning voltage applied to each scan canvas line as positive or negative, turn on all the thin film transistors of the polarity to be driven with that polarity, and then Among the thin film transistors that have been turned on, a voltage is applied that turns on all but the one with the highest absolute value of the threshold, and this is then repeated sequentially.
When the scan canvas line is selected, all of the drive target elements of the polarity among the thin film transistors connected to the scan canvas line are driven. This operation is repeated by changing the polarity of the applied voltage.

Note that when driving one line, elements with the same polarity must complete driving within one field, but elements with different polarities may be driven in two consecutive fields; If used, interlaced driving can be performed.

When driving two polarity elements on the same line within one field, the voltage polarities can be selected in any order. In other words, positive or negative voltages may be applied continuously, or positive and negative voltages may be applied alternately, and the order is not limited. However, between voltages of the same polarity, the voltage values should be applied in the order described above. It requires a choice.

[For production]

With the above configuration, four or more pixels can be driven by time-divisionally applying voltages via the same bus line.

Therefore, by arranging the above-mentioned plurality of pixels (n pixels) in i rows x j columns (where 1Xj=n), one scan canvas line can drive the pixels in the i row, and one data bus Since pixels in j columns can be driven by line, the number of scan canvas lines can be reduced to 1/i, and the number of data bus lines can be reduced to 1/j.

Furthermore, in the above configuration, by arranging only n-channel elements on one of two adjacent pixel electrode lines and arranging only p-channel elements on the other, interlaced driving becomes possible.

By configuring the active matrix liquid crystal display panel as described above, it is possible to reduce the number of scan canvas lines and data bus lines, thereby improving the aperture ratio and reducing the number of driver ICs.

〔Example〕

Embodiments of the present invention will be described below with reference to FIG.

The present invention will be explained below using an example in which four pixels are arranged at each intersection of the scan canvas line SB and the data bus line DB.

One embodiment shown in FIG.
A pixel electrode E,
~E4 and the thin film transistors T1~T that drive them
4 is an example of the arrangement.

The above-mentioned four thin film transistors are two n-chuffle devices whose current-voltage characteristics are shown in FIG. Use.

Thin film transistors having the voltage characteristics (1) to (2) are indicated by T (2) to (T), respectively, and their arrangement locations and driving methods will be explained in order.

In the same figure (C1 is at the position of T, ~T4, respectively,
An example of placing T■ is shown. The four thin film transistors T■ to T■ arranged at the intersections of the respective pass lines are driven by the same scan canvas line and the same data bus line. The driving method will be explained with reference to FIG.

When scanning the scan canvas line SB to which the four thin film transistors are connected, first the n-channel elements T■,
Threshold voltage V of the element T■ with higher threshold voltage among T■
A positive voltage V higher than thl.

Apply. When this voltage is applied, both n-channel elements T■ and T■ are turned on, and the display data applied from the data bus line DB is transferred to the pixel electrodes E+ and Et.
will be written to. The display data written to E2 is originally data to be written to E1 and is unnecessary to E2, but the correct data will be written at the next timing and will not be visually recognizable, causing no problem.

Next, a positive voltage (2) lower than Vthl and higher than vtht is applied. When this voltage is applied, T■ is not conductive, only T■ is turned on, and correct data is written to the pixel electrode E and displayed.

During this time, the two p-channel devices remain off, so
No display data is written.

Next, a negative voltage is applied to drive the p-channel elements T■ and T■.First, the absolute value of the threshold voltage of the element T■ whose absolute value is larger than that of the threshold voltage Vth:+ is applied. Apply negative voltage ■. As a result, p-channel elements T■ and T■ are both turned on, and display data is transferred to pixel electrode E3. Written to E4. The display data written to the pixel electrode E4 here is incorrect.

Then, the absolute value is smaller than the threshold voltage Vth3 of T■,
A negative voltage (4) larger than the threshold voltage Vth4 of T (2) is applied to turn on T (2). At this time, T■ is turned off. As a result, correct display data is written to the pixel electrode E4. The above-mentioned incorrect display data is displayed in an instant, and is not visually recognized at all.

When this negative voltage is applied, the two n-channel elements T2 and T2 remain in the off state, and there is no change in the displayed content.

By sequentially performing the above operations on each scan line, data voltages can be written to the entire screen of the panel.

The four thin film transistors T■ to T■ may be arranged as shown in FIG. 2(e) or (gl).

(e) T■, T■, T■ at the positions of T+ to Ta.

This is an example in which T■ is arranged. To drive this, the scan voltage applied to the scan canvas line SB to which the four thin film transistors are connected is V +
, V3. This can be done by changing V z and V 4.

In this arrangement example, n-channel devices and p-channel devices with large absolute values of threshold voltages and small threshold voltages are arranged in the same row. It is driven first, and immediately after that, the row in which the absolute value of the threshold voltage is arranged is driven.

In addition, in the same figure (gl is an example in which the n-channel device and p-channel device of (C) explained earlier are reversed. In this case, as shown in the same figure (hl), first apply a negative voltage. to drive the p-channel devices T■ and T■, and then apply a positive voltage to drive the n-channel device T■.

Scan in the order of T■.

In the above embodiment, the scanning is performed from top to bottom.

The three cases mentioned above are all examples of non-interlaced scanning, and as shown in Figs. 3(a) to (d),
An example of interlaced scanning will be explained.

In this case, it is necessary to arrange the n-channel devices and the p-channel devices in the same row.

The figure (al) is an example in which p-channel elements T■ and T■ are arranged in the front row, and n-channel elements T■ and T■ are arranged in the rear row.

To drive this, as shown in the figure (bl), in order to drive the previous pixel row, first, when scanning the scan canvas line, negative voltages V, , V are applied in a time-division manner. As a result, display data is written to the pixel electrodes E3 and E4 via the p-channel elements T■ and T■.

Next, in the next field, positive voltages v1 to v8 are applied in a time-division manner to the n-channel element T■.

Display data is written to the pixel electrodes E+ and Et via T■.

In this way, we divide the l frame into two fields,
Interlaced scanning is possible by driving a p-channel device in one field and an n-channel device in the other field.

To perform interlaced scanning, as shown in FIG. As shown in Td), a positive voltage is applied in the preceding field, and a negative voltage is applied in the subsequent field.

As described above, in the present invention, the same channel elements are driven in order from the one with the largest absolute value of the threshold value. In order to do this, the applied voltage is set to Choose a voltage that turns only one off and the others on.

All of the thin film transistors connected to the intersection of each pass line need only be selected once in each frame, and the driving order of the two channels does not need to be particularly limited.

However, in the case of interlaced driving, the elements of one channel are driven in one of the two fields constituting one frame, and the element of the other channel is driven in the other field. In this case, it is necessary to place the elements of the two channels in separate pixel rows.

In any of the above configurations, it is possible to reduce the number of both the scan canvas lines SB and the data/tabus lines DB, which not only improves the aperture ratio but also reduces the number of driver ICs accordingly.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the configuration of the present invention, FIG. 2 is an explanatory diagram of one embodiment of the present invention, FIG. 3 is a detailed explanatory diagram of the present invention, and FIG. 4 is an explanatory diagram of conventional problems. In the figure, T,'r+~T4 are thin film transistors,
SB is the scan canvas line, DB is the data bus line,
E, E+ "'E4 is a pixel electrode, ■~■ are classifications of current-voltage characteristics, T■~T■ are thin film transistors with characteristics of ■~■, ■1~v4 are applied voltages, V th, V th
+ ~V th* indicates the threshold voltage. [Effects of the Invention] As described above, according to the present invention, the aperture ratio of an active matrix liquid crystal display panel can be improved and the number of driver ICs can be reduced. Furthermore, interlaced driving is also easy. The flag of the EJR is the flag of EJR (eJ (l) ) Original 9d/l history example question Ua Figure 3

Claims (4)

[Claims] (1) Scan canvas lines (SB
) and the data bus line (DB), a plurality of n-channel thin film transistors with mutually different threshold voltages (Vth), a plurality of p-channel thin film transistors with mutually different threshold voltages, and a plurality of thin film transistors each driven by 1. An active matrix liquid crystal display device characterized in that a plurality of pixel electrodes (E) are provided. (2) dividing the pixel electrodes (E) connected to the same scan canvas line (SB) into two groups consisting of pixel electrodes driven by n-channel thin film transistors and pixel electrodes driven by p-channel thin film transistors, Part 2
2. The active matrix liquid crystal display device according to claim 1, wherein the pixel electrodes belonging to two groups are arranged in a line along the scan canvas line. (3) When scanning each scan canvas line (SB), the voltage applied to each scan canvas line can be set to conduct all the n-channel and p-channel thin film transistors connected to each scan canvas line. Claim 1: After the voltage is set, the voltage is changed in a time-division manner so that the transistor with the highest threshold voltage among the conductive transistors becomes non-conductive.
A method for driving the active matrix liquid crystal display device described above. (4) Interlace driving is performed by applying a voltage to the scan canvas line (SB) in a time-divisional manner as a positive voltage in one of two consecutive fields and a negative voltage in the other. A method for driving the active matrix liquid crystal display device described above.