JPH05100209A - Active matrix type display device - Google Patents

Abstract

PURPOSE:To reduce the cost of the active matrix type display device and improve the display quantity of the active matrix type display device of an opposite matrix system. CONSTITUTION:The active matrix type display device is equipped with plural scan bus lines 121 and 122 and data bus lines 13, picture element electrodes 151 and 152 which are arranged in a matrix, switching elements 111 and 112 which are connected to the scan bus lines and data bus lines and correspond to picture elements, and an electrooptic element LC which is electrically connected to picture element electrodes and controlled by the switching elements; and two scan bus lines 121 and 122 are provided for each picture element row and the control electrodes G of switching element couples 111 and 112 corresponding to the picture element electrode couples 151 and 152 which adjoin to each other in the direction of the scan bus lines are connected to the two scan bus lines individually.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active matrix type display device, and more particularly to an active matrix type display device having a structure provided with switching elements corresponding to pixels, data bus lines for data input and scan bus lines for line address. Regarding display device. In recent years, active matrix display devices have been used as thin display devices for information terminals together with simple matrix display devices, and liquid crystal is often used as the display medium.

An active matrix type liquid crystal display device is
Compared to a simple matrix type liquid crystal display device, a large number of pixels can be driven independently, so even if the number of lines increases with the increase in display capacity, the duty ratio of the drive like the simple matrix type And the contrast, and the viewing angle is not reduced.

However, the active matrix type display device (active matrix type liquid crystal display device) is inevitably large in scale due to its complicated structure, and requires a complicated process, resulting in a high manufacturing yield. It takes a lot of effort to obtain. Further, as an unavoidable problem in the active matrix type display device, there is a problem that a large number of driver ICs are required as the display capacity increases.
These large capital investments, manufacturing yield issues, and
Due to factors such as an increase in the cost required for the driver IC, the active matrix type display device is inevitably expensive, and the widespread use is currently hindered. Therefore, it is desired to provide an active matrix type display device which has a high production yield and an excellent display quality without causing a large-scale capital investment and cost increase.

[0004]

2. Description of the Related Art Heretofore, in order to simplify the process and increase the yield in the above-mentioned active matrix type display device, there has been proposed an opposed matrix system without a structure in which bus lines intersect (for example, JP-A-61-235815). FIG. 5 is an exploded perspective view showing an example of a conventional counter matrix active matrix liquid crystal display device, and FIG. 6 is a diagram showing an equivalent circuit of the active matrix liquid crystal display device of FIG. These Figure 5
Reference numerals 6 and 6 show a conventional counter matrix type active matrix type liquid crystal display device disclosed in the above-mentioned JP-A-61-235815.

As shown in FIGS. 5 and 6, a conventional active matrix type liquid crystal display device 50 includes a plurality of scan bus lines 52, a plurality of scan bus lines 52, and a plurality of scan bus lines 52 on each of the glass substrates 50a and 50b arranged opposite to each other. A pixel electrode 55 of a liquid crystal cell 54 provided for each pixel and a thin film transistor (TFT) 51 for controlling the pixel electrode 55 are formed, and data extending in a direction orthogonal to the scan bus line 52 is formed on the other glass substrate 50b. The bus line 53 is formed as a counter electrode of the liquid crystal cell 54. Here, reference numeral 56 indicates an earth bus line.

That is, in the counter matrix active matrix liquid crystal display device 50, the pixel electrode 55, which is one electrode of the liquid crystal cell 54, is connected to the source electrode, which is one controlled electrode of the TFT 51, and the liquid crystal cell 54 is connected. The other electrode 57 is connected (also used) to the data bus line 53, and the liquid crystal cell 54 is connected between the TFT 51 and the data bus line 53. The drain electrode, which is the other controlled electrode of the TFT 51, is commonly connected to an earth bus line 56 formed in parallel with the scan bus line 52.

[0007]

As described with reference to FIGS. 5 and 6, the conventional opposed matrix type active matrix type liquid crystal display device 50 includes a scan bus line 52 and a data bus line 52 arranged in a direct array. Since 53 is formed on one glass substrate 50a and the other glass substrate 50b, which are arranged to face each other, the intersection of the bus lines does not occur, and the manufacturing yield can be improved.

However, in this counter matrix system, since the other electrode 57 of the liquid crystal cell 54 is directly connected (also used) to the data bus line 53, the potential of the pixel electrode 55 is always kept in data during the retention period after addressing. It will change following the signal waveform. Therefore, in the conventional active matrix method in which both the data and scan bus lines are installed on one substrate, the data signal mixed only through the parasitic capacitance between the source and drain of the TFT is different from the one between the source and drain in the opposite matrix method. In addition to the parasitic capacitance, the parasitic capacitance between the source and the gate also mixes in the liquid crystal cell 54, and so-called crosstalk is unavoidable.

Further, the conventional counter matrix active matrix type liquid crystal display device 50 has a problem that the influence of the address pulse waveform appears on the pixel electrode 55 through the parasitic capacitance. That is, as the scan bus line voltage returns from the write voltage to the holding voltage immediately after the address, this voltage fluctuation appears in the pixel electrode 55 through the parasitic capacitance, and this voltage fluctuation is held until the next address. Although it is desirable that the liquid crystal has no DC component in the drive voltage waveform from the viewpoint of its life characteristics, etc., if there is this voltage fluctuation, the signal voltage will shift in one direction even if it has a positive / negative symmetrical AC voltage waveform. The voltage waveform becomes, and as a result, a DC component is generated. The generation of such a DC voltage not only adversely affects the life characteristics of the liquid crystal, but also causes the generation of flicker and an afterimage, which deteriorates the display characteristics.

In view of the problems of the above-mentioned conventional active matrix type display device, the present invention aims to reduce the cost of the active matrix type display device and to improve the display quality of the opposed matrix type active matrix type display device. The purpose is to

[0011]

According to the present invention, a plurality of
Canvas line 12₁, 12₂;twenty two₁,twenty two₂; 32₁, 32₂42₁, 42 ₂
And data bus lines 13; 23; 33; 43 with matrix
The pixel electrode 15 arranged in₁, 15₂;twenty five₁,twenty five₂; 35₁, 35₂; 45₁, 45
₂And the scan bus line and data bus line
Pixel-compatible switching element 11 connected to₁, 11₂;twenty one₁,
twenty one₂; 31₁, 31₂; 41 ₁, 41₂And electrically connected to the pixel electrode
Controlled by the switching element
It is an active matrix type display device equipped with an element LC.
Yes, the scan bus line 12₁, 12₂;twenty two₁,twenty two₂; 32₁,
32₂42₁, 42₂Two pixels are provided for one pixel row, and
Pixel electrode pairs 15 adjacent to each other in the direction of the canvas line₁, 15₂;twenty five
₁,twenty five₂; 35₁, 35₂; 45₁, 45₂Switching element pair corresponding to
11₁, 11₂;twenty one₁,twenty one₂; 31₁, 31₂; 41₁, 41₂Each control electrode of
Connected to two scan bus lines separately
An active matrix type display device characterized by
Be served.

[0012]

According to the active matrix type display device of the present invention, the scan bus lines 12 ₁ , 12 ₂ ; 22 ₁ , 22 ₂ ; 32 ₁ , 32 ₂ ; 42
_{Two 1} and 42 ₂ are provided for one pixel row, and pixel electrode pairs 15 ₁ and 15 ₂ ; 25 ₁ and 25 adjacent to each other in the scan bus line direction are provided.
₂ ; 35 ₁ , 35 ₂ ; 45 ₁ , 45 ₂ switching element pair 11 ₁ , 1
1 _2; 21 _1, 21 _2; 31 _1, 31 _2; 41 _1, 41 ₂ of the control electrode (gate electrode) is the scan bus line 12 ₁ of the two said, 12 _2; 22 _1, 22 _2; 32
It is designed to be connected to ₁ , 32 ₂ ; 42 ₁ , 42 ₂ separately.

As a result, the cost of the active matrix type display device can be reduced and the display quality of the opposed matrix type active matrix type display device can be improved.

[0014]

Embodiments of the active matrix type display device according to the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a first embodiment of an active matrix display device of the present invention, and this embodiment shows a case where the present invention is applied to a conventionally known normal active matrix display device. is there.

As shown in FIG. 1, the active matrix type display device of this embodiment has a plurality of scan bus lines 12 ₁ and 12 ₂ and a plurality of data buses orthogonal to the scan bus lines 12 ₁ and 12 _2. Lines 13, pixel electrodes 15 ₁ and 15 ₂ arranged in a matrix, switching elements 11 ₁ and 11 ₂ for pixels connected to the scan bus line and the data bus line, and electrically connected to the pixel electrodes. And an electro-optical element (liquid crystal) controlled by the switching element. Here, the active matrix type display device of the present embodiment has scan bus lines 12 ₁ and 12 ₂ , data bus line 13, pixel electrodes 15 ₁ and 15 ₂ , and a switching element (TFT) 11 on one insulating substrate. _1, 11 ₂ is formed, it is configured so as to sandwich liquid crystal between a solid-like electrode formed on the other insulating substrate.

As shown in FIG. 1, the scan bus line is
12₁, 12₂Is one pixel row (in the figure
2 for each pixel row)
12 ₁, 12₂Direction, that is, adjacent to each pixel row.
Pixel electrode pair 15₁, 15₂ Switching element pair corresponding to 11
₁, 11₂ Each control electrode (gate electrode) is provided on both sides of the pixel
Two scan bus lines 12₁, 12₂Separately for
It is connected to the. That is, TFT11₁ Gate electrode
Scan bus line 12₁ Connected to the TFT11
₂The gate electrode of the scan bus line 12₂Connected to
There is. In addition, TFT11₁ The source electrode of the pixel electrode 15₁ 
Connected to the TFT11₂The source electrode of is the pixel electrode
15₂Connected to, and TFT11₁ The drain electrode
And TFT11₂Drain electrodes of the same data bus
Commonly connected to in 13.

Here, an address pulse is applied to the _two scan bus lines 12 ₁ and 12 ₂ provided on both sides of the pixel.
/ 2 scan signals V _s and V _s' with different timings are applied only during the horizontal scanning period (0.5 t _H ), and in synchronization with this, display data (V _D ) corresponding to every other pixel on the data bus line Is applied in two times. That is, in the active matrix display device of this embodiment, two pixel electrodes 15 ₁
By driving (15) and 15 ₂ (V _LC , V _LC '), the number of data bus lines 13 can be reduced to 1/2 of the conventional one.

Here, in a normal active matrix type display device, not only the number of pixels in the row direction (horizontal direction) is larger in the pixel configuration, but also, for example, a square full-color pixel composed of three RGB pixels by vertically long pixels. Therefore, in the conventional device, the number of data-side drivers is about four times that of the scan-side drivers. Specifically, in a 640 × 480 active matrix type liquid crystal display device, since three pixels of RGB are arranged in the row direction, the data bus line in the conventional example is 640
× 3 = 1920 is required, but according to this embodiment, 192
It can be reduced to 0/2 = 960. In this embodiment, the number of scan bus lines needs to be doubled from 480 to 960 in the conventional example, but the total number of bus lines (total number of data bus lines and scan bus lines)
However, it is possible to reduce it from the conventional 2400 to 1920. Further, since the data driver needs to operate at high speed and has a complicated circuit configuration, the cost is higher than that of the scan driver which simply selects and scans pixels, and the data bus line (data driver IC) is halved as in the present embodiment. Reducing the scan bus line (scan driver I
Considering that C) is required twice, the effect of cost reduction is great.

FIG. 2 shows an active matrix type table of the present invention.
The principle of the double scanning opposed matrix system in the display device
It is a figure for explaining. Active matri shown in Figure 2
The box-type display device according to the present invention will be described with reference to FIGS.
The opposite matrix active matrix type described
It shows a case where it is applied to a display device. First, FIG.
With reference to FIG.
Reduction of crosstalk in a live matrix display
The principle of is explained. As shown in the figure, the pixel electrode 25
(twenty five₁,twenty five₂) On either side of the two scan bus lines 22₁,
twenty two₂And two reference voltage bus lines 26₁, 26₂Is provided
The scan bus line 22 ₁And 22₂Has 1/2 water
Flat scan period (0.5t_H) A shifted address pulse is applied.
It is supposed to be. And this 1/2 horizontal scanning period
The data bus line is synchronized with the shifted address pulse.
The display data corresponding to every other pixel is displayed twice in
It is designed to be applied separately. This gives the data
The number of bus lines 23 can be reduced to half of the conventional one.
It Here, the data bus line 23 is connected to the scan bus line.
22₁,twenty two₂, Reference voltage bus line 26₁, 26₂, TFT21 (21₁, 2
1₂), And the pixel electrode 25 (25₁,twenty five₂) Etc.
The other insulating substrate (50a) facing the other side through the liquid crystal LC.
Formed as a stripe transparent electrode on the edge substrate (50b)
Has been done. Then, one formed on one insulating substrate
A pair of pixel electrodes 25₁,twenty five₂ One striped electrode corresponding to
(Data bus line 23) is provided (FIGS. 3 to 5).
reference).

As shown in FIG. 2, two reference voltage bars are provided.
Sline 26₁, 26₂ Is a binary voltage V_R1,
V_R2Is applied and the data voltage waveform (V_D) Sign
The reference voltage is switched according to the. this
LCD cell 24 (24₁,twenty four₂) For the data voltage
(+ V_dAnd -V_d) And reference voltage (+ V_rAnd -V
_r) Is applied, the voltage waveform of
The amplitude can be compressed. Sanawa
Then, the threshold voltage and the saturation voltage of the liquid crystal cell are respectively set to V
_thAnd V_satThen, V_d= (V_sat-V_th) / 2 V_r= (V_sat+ V_th) / 2, the data voltage V_dValue of the reference voltage
Saturation voltage V without replacement_sat1/4 compared to
It can be compressed each time. Furthermore, the facing matrix method
The crosstalk in the equation is the reference voltage waveform when not addressed.
Part of the pixel electrode-drain bus line (reference voltage bus
Line capacity and liquid crystal cell capacity C_1cResult of capacity division with
It increases by appearing at both ends of the liquid crystal cell,
Reference voltage bus line 26₁, 26₂A binary symmetric wave with respect to
Shape reference voltage is applied, and the capacitance between drain bus lines C
_DS1, C_DS2Two reference voltage waveforms that come in through
By canceling each other, the data voltage
To increase the crosstalk reduction effect by compressing
It has become.

FIG. 3 is a diagram showing a second embodiment of an active matrix type display device of the present invention. The present invention is applied to an opposed matrix type active matrix type display device, and further, an opposed matrix type active matrix type display device. This is intended to reduce crosstalk, which is a disadvantage in the display device. As shown in FIG. 3, the pair of pixels 35 ₁ (LC _{2n-1, m} ), 35 ₂ (LC _{2n, m} ) adjacent in the row direction is
Other reference voltage bus lines 36 ₁ and 36 ₂ provided at positions symmetrical to each pixel are connected via TFTs 31 ₁ and 31 ₂ , respectively. Here, the gate electrodes of the TFTs 31 ₁ and 31 ₂ are connected to the scan bus lines 32 ₁ (V _sm ) and 32 ₂ (V _sm '). Further, the stripe electrode made of ITO provided on the counter substrate (corresponding to the glass substrate 50b in FIG. 5) is also used as the data bus line 33, and the two pixels corresponding to the pixel pair (pixel electrodes 31 ₁ and 31 ₂ ). It is formed as a minute width. As the address pulse, as described with reference to FIG. 1, a 1/2 horizontal scanning period (1/2 t _H ) shifted pulse of approximately 1/2 t _H is sequentially added and synchronized with this. The data signal waveform is applied to the data bus line.

The reference voltage waveforms V _R1 and V _R2 applied to the reference voltage bus lines 36 ₁ and 36 ₂ are binary waveforms as shown in FIG. Then, at the time of writing to the pixel 35 ₁ (LC _{2n-1, m} ), the TFT 31 ₁ is turned on by the address pulse V _{G +} applied to the scan bus line 32 _1, and the reference potential V _{r- of the} reference voltage bus line 36 _{1. Is} written in the pixel electrode 35 ₁ of the pixel LC _{2n-1, m} . As a result, the difference voltage between the data bus line voltage V _Dn and the reference voltage bus line 36 ₁ , that is, a positive data signal is written in the liquid crystal cells V _{LC2n-1, m} of the pixels LC _{2n-1, m} .

Next, the adjacent pixel LC_{2n, m}Writing to
Reference voltage bus line 36₂Potential V _r-Is the reference potential
Again, a positive data signal is written. in this way,
In this embodiment, positive data is supplied to each pixel in one frame.
After writing, each reference voltage waveform in the next frame
By inverting and writing negative data
Then, the liquid crystal cell is driven by alternating current. still,
In this embodiment, the symmetrical reference voltage waveform V_R1, V
_R2The data voltage is compressed by the
By canceling out the entry into the electrodes,
It is possible to significantly reduce stalk. Also, the counter substrate side
The line width of the ITO stripe electrode of the normal counter matrix
Since it can be doubled in the case of the system, the IT on the opposite side
It also has the effect of facilitating the production of the O stripe electrode.
It

FIG. 4 is a diagram showing a modification of the active matrix type display device of FIG. The active matrix type display device shown in FIG. 4 is different from the embodiment of FIG. 3 in that the reference voltage waveform and the address pulse are made to have different phases, and the polarity of the data to be written in the adjacent pixel is inverted.
Further, in this embodiment, a negative compensation pulse is added before and after the address pulse to reduce the level shift immediately after the address. By inverting the polarities of the data to be written in the adjacent pixels in this way, it is possible to make the flicker that occurs when the optical characteristics of the liquid crystal differ depending on whether the data voltage is positive or negative. Further, by reducing the level shift, it is possible to reduce the DC component generated in the liquid crystal cell and suppress the deterioration of the display characteristics such as the afterimage.

Although liquid crystal is used as the electro-optical element in the above-mentioned embodiments, various elements such as an electroluminescence element and an electrochromic element can be used as the electro-optical element. Further, it goes without saying that various structures, shapes, materials and the like of the active matrix type display device (panel) other than those described above can be used and can be modified.

As described above, according to the active matrix type display device of this embodiment, the driver I, which has been a major factor of cost of the active matrix type display device up to now.
The number of C can be significantly reduced. Further, the occurrence of crosstalk due to parasitic capacitance, which is a problem in the opposed matrix active matrix display device, can be significantly reduced, and an active matrix display device having excellent display characteristics can be realized. Furthermore, since a level shift of the pixel electrode potential due to parasitic capacitance can be reduced by applying a compensation pulse having a polarity opposite to that of the address pulse to the scan bus line adjacent to the pixel, display defects such as an afterimage and flicker due to the level shift can be reduced. Will be resolved. In addition, in the counter matrix active matrix display device, it is necessary to pattern the stripe-shaped data bus electrodes on the counter substrate side at a pitch equal to the pixel pitch, but it is possible to double the pitch of the data bus electrodes. This also makes it possible to produce the counter substrate easily.

[0027]

As described above in detail, according to the active matrix type display device of the present invention, it is possible to reduce the cost of the active matrix type display device and the counter matrix type active matrix type display device. The display quality can be improved.

[Brief description of drawings]

FIG. 1 is a diagram showing a first embodiment of an active matrix type display device of the present invention.

FIG. 2 is a diagram for explaining the principle of a double scanning counter matrix system in an active matrix display device of the present invention.

FIG. 3 is a diagram showing a second embodiment of the active matrix display device of the present invention.

FIG. 4 is a diagram showing a modification of the active matrix display device of FIG.

FIG. 5 is a perspective view showing an example of a conventional counter matrix active matrix liquid crystal display device.

6 is a diagram showing an equivalent circuit of the active matrix type liquid crystal display device of FIG.

[Explanation of symbols]

11 _1, 11 _2; 21 _1, 21 _2; 31 _1, 31 _2; 41 _1, 41 ₂ ... switching elements (thin film transistor) 12 _1, 12 _2; 22 _1, 22 _2; 32 _1, 32 _2; 42 _1, 42 ₂ ... scan bus line 13; 23; 33; 43 ... data bus line (stripe-shaped counter electrode) 24 ₁ , 24 ₂ ; 34 ₁ , 34 ₂ ; 44 ₁ , 44 ₂ ... liquid crystal cell 15 ₁ , 15 ₂ ; 25 ₁ , 25 ₂ ; 35 ₁ , 35 ₂ ; 45 ₁ , 45 ₂ … Pixel electrode 26 ₁ , 26 ₂ ; 36 ₁ , 36 ₂ ; 46 ₁ , 46 ₂ … Reference voltage bus line

Claims (6)

[Claims] 1. A plurality of scan bus lines (12 ₁ , 12 ₂ ; 2
2 ₁ , 22 ₂ ; 32 ₁ , 32 ₂ ; 42 ₁ , 42 ₂ ) and data bus line (13;
23; 33; 43) and the pixel electrodes (1
5 ₁ , 15 ₂ ; 25 ₁ , 25 ₂ ; 35 ₁ , 35 ₂ ; 45 ₁ , 45 ₂ ) and switching elements (11 ₁ , 11 ₂ ;) corresponding to the pixels connected to the scan bus line and the data bus line. 21 ₁ , 21 ₂ ; 31 ₁ , 31 ₂ ; 41 ₁ , 4
1 ₂ ) and an electro-optical element (LC) electrically connected to the pixel electrode and controlled by the switching element, wherein the scan bus line (12 ₁ , 12 ₂ ; 22 ₁ , 22 ₂ ; 32 ₁ , 32 ₂ ; 4
2 ₁ , 42 ₂ ) are provided for one pixel row, and pixel electrode pairs (15 ₁ , 15 ₂ ; 25 ₁ , 2) adjacent to each other in the direction of the scan bus line are provided.
5 ₂ ; 35 ₁ , 35 ₂ ; 45 ₁ , 45 ₂ ) corresponding switching element pair (1
1 ₁ , 11 ₂ ; 21 ₁ , 21 ₂ ; 31 ₁ , 31 ₂ ; 41 ₁ , 41 ₂ ). Each active control electrode is separately connected to the two scan bus lines. Matrix display device. 2. The two scan bus lines (12 ₁ , 1)
2 ₂ ; 22 ₁ , 22 ₂ ; 32 ₁ , 32 ₂ ; 42 ₁ , 42 ₂ ), the address pulse is applied at a timing shifted by 1/2 horizontal scanning period. The active matrix display device according to claim 1. 3. One of the controlled electrodes (S) of the switching element pair (11 ₁ , 11 ₂ ; 21 ₁ , 21 ₂ ; 31 ₁ , 31 ₂ ; 41 ₁ , 41 ₂ ) corresponding to the pixel electrode pair is Connected to the pixel electrode and the other controlled electrode
2. An active matrix type display device according to claim 1, wherein (D) is connected to the same data bus line. 4. The plurality of scan bus lines (22 ₁ , 2
2 ₂ ; 32 ₁ , 32 ₂ ; 42 ₁ , 42 ₂ ), a reference voltage bus line (26 ₁ , 26 ₂ ; 36 ₁ , 36 ₂ ; 46 ₁ , 4 provided parallel to the scan bus line).
6 ₂ ), the pixel electrodes (25 ₁ , 2
5 ₂ ; 35 ₁ , 35 ₂ ; 45 ₁ , 45 ₂ ), and the switching element (21 ₁ , 21 ₂ ; 31 ₁ , 31 ₂ ; 41 ₁ , 41 ₂ ) corresponding to the pixel on one insulating substrate. And a counter electrode (33, 43) common to the pixel electrode pair, which is opposed to the pixel electrode pair with the electro-optical element interposed therebetween on the other insulating substrate, and a data bus connected to the counter electrode. The active matrix type display device according to claim 1, wherein lines (33, 43) are provided. 5. The two types of the reference voltage bus lines (36 ₁ , 3
6 ₂ ; 46 ₁ , 46 ₂ ) are provided, and the two types of reference voltage bus lines are alternately arranged in the gap between the pixel rows, one of which is controlled by one of the switching element pair corresponding to the pixel electrode pair. The active matrix type display device according to claim 5, wherein an electrode is connected to the pixel electrode and the other controlled electrode is connected to the two types of reference voltage bus lines separately. 6. The two types of reference voltage bus lines (36 ₁ , 3)
6 ₂ ; 46 ₁ , 46 ₂ ) is applied with two kinds of reference voltage waveforms whose voltage changes are symmetrical with each other with an amplitude smaller than the amplitude of the drive voltage of the electro-optical element. 5. Active matrix type display device.