JP2003122306A - Active matrix type display device and active matrix type organic electroluminescence display device - Google Patents

Abstract

(57) [Problem] To provide a pixel circuit having a function of compensating variation in characteristics of a TFT, the number of elements is larger than that of a basic pixel circuit of a voltage writing type. SOLUTION: In the active matrix type organic EL display device, the organic EL display device includes two TFTs 21 and 23 and one capacitor 22, and supplies a current corresponding to luminance information to the organic EL device.
The pixel circuit that flows through the element is composed of two pixels vertically adjacent to each other.
The pixel circuits are provided in common to the L elements 11A and 11B, and the organic EL elements 11A and 11B are appropriately selected by the selection TFTs 15A and 15B so that the pixel circuits are vertically adjacent to each other.
The pixels are shared in a time-sharing manner, and the number of elements of the pixel circuit per pixel is reduced.

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 in which an active element is provided for each pixel and display control is performed on a pixel-by-pixel basis by the active element. An active matrix type display device using an optical element as a pixel display element and electroluminescence of an organic material as an electro-optical element (hereinafter, referred to as organic EL (electroluminescence)
Note) Active matrix type organic EL using elements
Regarding display device.

[0002]

2. Description of the Related Art In a display device, for example, a liquid crystal display device using a liquid crystal cell as a display element of a pixel, a large number of pixels are arranged in a matrix and the light intensity of each pixel is changed according to the image information to be displayed. Image display drive is performed by controlling. This display drive is also the same in an organic EL display device using an organic EL element as a display element of a pixel.

However, in the case of an organic EL display device, since it is a so-called self-luminous display device that uses a light emitting element as a display element of a pixel, the backlight has a higher image visibility than a liquid crystal display device. Is unnecessary and has a fast response speed. Further, the brightness of each light emitting element is controlled by the value of the current flowing therein, that is, the organic EL element is a current control type, which is a great difference from a liquid crystal display device in which a liquid crystal cell is a voltage control type.

As with the liquid crystal display device, the organic EL display device can employ a simple (passive) matrix system and an active matrix system as its driving system. However, although the former has a simple structure, it has a problem that it is difficult to realize a large-sized and high-definition display. For this reason, in recent years, active matrix methods have been actively developed in which the current flowing through the light emitting element inside the pixel is controlled by an active element (generally, a thin film transistor (TFT)) similarly provided inside the pixel. There is.

FIG. 8 shows an active matrix organic EL.
A circuit example of a voltage writing type pixel circuit (unit pixel circuit) in a display device is shown (for more details, see US Pat. No. 5,684,365 and JP-A-8-234683).

As is apparent from FIG. 8, the pixel circuit according to this circuit example is an organic EL device having a cathode (cathode) grounded.
Element 101 and anode of organic EL element 101
The drain of which is connected to the positive power supply Vcc, and the source of which is connected to the positive power supply Vcc;
cc and the capacitor 103 connected between cc and
And a TFT 104 having a drain connected to the gate of 02 and a source connected to the data line 105.
A scanning pulse is applied to the gate of No. 4 through the scanning line 106.

Here, since the organic EL element has a rectifying property in many cases, an OLED (Organic Light Emitting Diode) is used.
Sometimes called. Therefore, in FIG. 8 and other drawings, the symbol of the diode is used as the organic EL element. However, in the following description, organic EL
The element does not necessarily require rectification.

The operation of the pixel circuit having the above configuration is as follows. First, the potential of the scanning line 106 is in a selected state (here,
When the write potential Vw is applied to the data line 105, the TFT 104 becomes conductive and the capacitor 103
Are charged or discharged, and the gate potential of the TFT 102 becomes the write potential Vw. Next, when the potential of the scanning line 106 is set to a non-selected state (here, low level), the scanning line 10
6 and the TFT 102 are electrically separated, but the TFT
The gate potential of 102 is stably held by the capacitor 103.

The current flowing through the TFT 102 and the organic EL element 101 has a value according to the gate-source voltage Vgs of the TFT 102, and the organic EL element 101 continues to emit light with a brightness according to the current value. Here, the operation of selecting the scanning line 106 and transmitting the brightness information given to the data line 105 to the inside of the pixel will be hereinafter referred to as “writing”. As described above, in the pixel circuit shown in FIG. 8, once the potential Vw is written, the organic EL element 101 continues to emit light at a constant brightness until the next writing.

A large number of such pixel circuits (hereinafter sometimes simply referred to as pixels) 111 are arranged in a matrix as shown in FIG. 9, and the scanning lines 112-1 to 112n are sequentially selected by the scanning line driving circuit 113. However, from the voltage driving type data line driving circuit 114 to the data lines 115-1 to 115
By repeating writing through -m, an active matrix type display device (organic EL display device) can be constructed. Here, a pixel array of n rows × m columns is shown. In this case, the scan line is, of course, n
There are m and data lines.

In the simple matrix type display device, each light emitting element emits light only at the selected moment, whereas in the active matrix type display device, the light emitting element continues to emit light even after writing is completed. Therefore, the active matrix type display device is particularly advantageous for a large-sized and high-definition display in that the peak luminance and the peak current of the light emitting element can be reduced as compared with the simple matrix type display device.

By the way, active matrix type organic E
In the L display device, an insulated gate thin film field effect transistor (TFT) formed on a glass substrate is generally used as an active element. However, amorphous silicon (amorphous silicon) and polysilicon (polycrystalline silicon) used for forming the TFT have poor crystallinity as compared with single crystal silicon and poor controllability of the conduction mechanism. It is well known that the formed TFT has a large variation in characteristics.

In particular, when a polysilicon TFT is formed on a relatively large glass substrate, in order to avoid problems such as thermal deformation of the glass substrate, usually, after the amorphous silicon film is formed, it is crystallized by a laser annealing method. Is done. However, it is difficult to uniformly irradiate a large glass substrate with laser energy, and it is unavoidable that the crystallization state of polysilicon varies depending on the location in the substrate. As a result, the TF formed on the same substrate
Even in T, the threshold voltage Vth is several hundred mV depending on the pixel,
In some cases, it is not uncommon to have variations of 1 V or more.

In this case, for example, even if the same potential Vw is written in different pixels, the threshold voltage Vth of the TFT varies depending on the pixel. This allows organic EL
The current Ids flowing through the element greatly varies from pixel to pixel, resulting in a deviation from a desired value, and high image quality cannot be expected for a display. This applies not only to the threshold voltage Vth but also to variations in carrier mobility μ and the like.

In order to improve such a problem, conventionally, the following two pixel circuits have been proposed. FIG. 10 shows a circuit example of a pixel circuit according to one conventional example (hereinafter referred to as conventional example 1).

As is apparent from FIG. 10, the pixel circuit according to the conventional example 1 has an organic EL element 121 whose cathode is grounded, a TFT 122 whose drain is connected to the anode of the organic EL element 121, and a source of the TFT 122. A drain connected to the positive power source Vcc and a source connected to the TFT 123; a TFT 124 connected between the gate and the drain of the TFT 123; a capacitor 125 having one end connected to the gate of the TFT 123;
25, a capacitor 126 connected between the other end of the capacitor 25 and the positive power source Vcc, and a TFT 12 having a drain connected to the other end of the capacitor 125 and a source connected to the data line 128.
7 and a scanning pulse is applied to the gate of the TFT 127 through the scanning line 129,
The drive pulse is applied through 0, and the reset pulse is applied to the gate of the TFT 124 through the reset line 131.

Next, the circuit operation of the pixel circuit according to the conventional example 1 having the above structure will be described with reference to the timing chart of FIG.

First, prior to the writing of data, the scanning line 129 and the reset line 131 are brought into a selected state (both at a high level), and the switching TFT 124 drives the TF.
The gate and drain of T123 are short-circuited. Next, when the drive line 130 is set to the non-selected state (high level), the drive T
The switching TFT 122 interposed between the FT 123 and the organic EL element 121 is turned off. As a result, the drain potential of the driving TFT 123 rises.

On the other hand, since the switching TFT 124 is in the ON state and the gate and drain of the driving TFT 123 are electrically short-circuited, the gate potential also rises,
When this becomes Vcc- | Vtp |, the stable state is reached (this may be hereinafter referred to as the reset state). Here, | Vtp | is the absolute value of the threshold voltage of the driving TFT 123. When the reset operation is completed, the reset line 13
1 is set to the non-selected state (low level), and the voltage according to the luminance information is applied to the data line 128.

The potential of the data line 128 is set to a constant reference potential during the reset operation, as shown in FIG.
After the reset operation, the voltage decreases by ΔV. In that state, the scan line 129 is brought into a non-selected state, whereby the writing operation to the pixel is completed. Since the data line 128 and the gate of the driving transistor 123 are capacitively coupled by the capacitor 125, the potential of the data line 128 is not directly transmitted to the gate of the driving TFT 123, but the potential change ΔV of the data line 128 is transmitted. To be done. After that, when the drive line 130 is brought into a selected state (low level), a current according to the written data flows through the switching TFT 122 to the organic EL element 121. This allows organic E
The L element 121 emits light with a brightness according to the written data.

By the way, assuming that the driving TFT 123 operates in the saturation region, the current Ids flowing through the driving TFT 123 is expressed by the well-known MOS transistor equation as shown in equation (1). Ids = μCox · W / L / 2 (Vcc−Vg− | Vtp |) ² (1) where μ is carrier mobility, Cox is gate capacitance per unit area, W is channel width, and L is L. The channel length.

The gate potential Vg is Vcc- | Vtp immediately before data writing due to the reset operation described above.
However, immediately after the end of writing, Vg = Vcc− | Vtp | −ΔV (2) By substituting this into the equation (1), Ids = μCoxW / L / 2ΔV ² (3) is obtained. Since the equation (3) does not include Vtp, the current Ids flowing through the driving TFT 123 is equal to the threshold voltage Vt.
It can be seen that it is not affected by the variation of p.

As a pixel circuit according to another conventional example (hereinafter referred to as conventional example 2), a current writing type pixel circuit shown in FIG. 12 has been proposed by the inventor of the present application (for details, see International Publication No. See WO 01-06484).

In the pixel circuit according to the second conventional example, as is apparent from FIG. 12, an organic EL element 141 whose cathode is grounded, a drain is connected to the anode of the organic EL element 141, and a source is connected to the positive power source Vcc. TFT1 connected
42, a capacitor 143 connected between the gate of the TFT 142 and the ground, a TFT 144 having a drain connected to the gate of the TFT 142, and a TFT 144.
Of the positive power supply V
TFT 145 whose source is connected to cc and TFT14
5 has a TFT 146 connected between the gate / drain and the data line 147, and a scanning pulse is applied to each gate of the TFTs 144 and 146 through the scanning line 148.

The pixel circuit according to the second conventional example is characterized in that the luminance data is given in the form of voltage in the pixel circuits of FIGS. 8 and 10, whereas the luminance data is given in the form of current. Is. The operation is as follows.

First, when writing the brightness data, the scanning line 148 is set to the selected state (high level), and the data line 147 is selected.
A write current Iw corresponding to the brightness data is passed through. This write current Iw passes through the TFT 146 and the TFT 145.
Flow to. At this time, since the TFT 144 is in the ON state, the TFT 142 and the TFT 145 form a current mirror circuit. Here, both transistors 142, 1
Since 45 is arranged close to the inside of a small pixel, it has almost the same characteristics.

As a result, a driving current Id proportional to the write current Iw flows through the TFT 142. Drive current Id
The ratio between the write current Iw and the write current Iw
It can be freely selected by appropriately setting the ratio of the channel width / channel length with respect to 45.
Since it is not affected by the threshold voltage of 5 and the carrier mobility value itself, the organic EL of each pixel can have a desired brightness regardless of variations in the threshold voltage and carrier mobility over the entire screen (all pixel regions). The element 141 can emit light.

[0028]

As is apparent from the above description, the pixel circuit having the compensation function for the characteristic variation of the TFT, that is, the pixel circuit according to the conventional example 1 shown in FIG. 10 or the conventional example 2 shown in FIG. In the pixel circuit according to
Regardless of variations in threshold voltage of T and carrier mobility,
It has a great feature that the light emitting element of each pixel can emit light with desired brightness.
There is a drawback in that the number of elements increases as compared with the basic voltage writing type pixel circuit shown in FIG.

That is, the pixel circuit shown in FIG. 8 is composed of two transistors, whereas each pixel circuit shown in FIGS. 10 and 12 requires four transistors. In this pixel circuit, the number of capacitors is increased by one. As a measure against the image quality deterioration due to the characteristic variation of the TFT, there are proposed pixel circuits which are variously devised in addition to the pixel circuits shown in FIG. 10 and FIG. 12, but in any case, the increase in the number of elements cannot be avoided. . As described above, when the number of elements of the pixel circuit per pixel is large, the manufacturing yield is liable to be lowered, and further, it is difficult to reduce the pixel area. Therefore, it is unavoidable to increase the pixel pitch and increase the resolution. It becomes an obstacle.

The present invention has been made in view of the above problems, and an object of the present invention is to improve the manufacturing yield and further reduce the pixel area by reducing the number of elements of the pixel circuit per pixel. It is an object of the present invention to provide an active matrix type display device and an active matrix type organic EL display device which are capable of downsizing and higher resolution.

[0031]

In an active matrix type display device according to the present invention, pixels having electro-optical elements whose brightness is changed by a flowing current are arranged in a matrix and are provided commonly to a plurality of pixels. A pixel circuit which supplies a current corresponding to the brightness information given through the data line to each electro-optical element of the plurality of pixels, and a selection for selecting the electro-optical element of the pixel to be driven by the pixel circuit from the plurality of pixels And means. Also,
This display device is applied to an active matrix type organic EL display device using an organic EL element as an electro-optical element.

In the active matrix type display device or the active matrix type organic EL display device having the above structure, the pixel circuit is shared by a plurality of pixels, and the driving circuit is time-divided by the selecting means from among the plurality of pixels. A current according to the brightness information given through the data line is passed through the electro-optical element or the organic EL element of the pixel that is selectively selected. Here, by sharing the pixel circuit among a plurality of pixels, the number of elements of the pixel circuit per pixel can be reduced.

[0033]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[First Embodiment] FIG. 1 is a block diagram showing the configuration of an active matrix display device according to the first embodiment of the present invention. In FIG. 1, as a light emitting element provided for each pixel, an electro-optical element whose brightness changes according to a flowing current, for example, an organic EL element 11 (11A, 1
1B) is used, and the organic EL elements 11 are arranged in a matrix in a pixel unit. Here, a pixel array of 2n rows × m columns is shown as an example.

In this pixel arrangement, a plurality of pixels, for example, organic EL elements 11A, 11 of two vertically adjacent pixels are used.
Pixel circuit 12 that allows a current corresponding to the brightness information to flow to B
Are provided in common. That is, one pixel circuit 1
2 is an organic EL element 11A for two pixels vertically adjacent to each other,
It is configured to be commonly used for driving 11B. Therefore, for the pixel array of 2n rows × m columns, n scanning lines 13-1 to 13-n for selecting the pixel circuit 12 in row units,
M data lines 14-1 to 14-m for supplying luminance data to each pixel circuit 12 are arranged in a matrix.

In addition, each pixel has two vertically adjacent pixels.
A pair of selection switches 15A and 15B for driving and selecting the organic EL elements 11A and 11B for pixels are provided in units of two rows. Accordingly, these selection switches 15
Two lines of selection lines 16A-1 to 16A-n and 16B-1 to 16B-n for sequentially driving A and 15B row by row in a time division manner to select the organic EL element 11A / 11B to be driven.
Are wired in units of two rows.

For the pixel portion in which the organic EL elements 11 are arranged in a matrix, for example, on the left side of the drawing, a scanning line driving circuit 17 for selectively driving n scanning lines 13-1 to 13-n.
However, on the right side of the figure, there are two selection lines 16A-1 to 16A-
A select line drive circuit 18 for selectively driving n, 16B-1 to 16B-n has m data lines 14-1 to 14-1 on the lower side of the drawing.
Data line drive circuits 19 for supplying luminance data to 4-m are arranged respectively.

The scanning line driving circuit 17 is composed of, for example, a shift register of n transfer stages, and one end of each of the scanning lines 13-1 to 13-n is connected to the output end of each transfer stage. The select line drive circuit 18 is composed of, for example, a shift register of 2n transfer stages, and the select line 16A is provided at the first half of the output end of each transfer stage.
One end of each of -1 to 16A-n has a selection line 16B in the latter half.
One end of each of -1 to 16B-n is connected.
That is, the selection line drive circuit 18 drives the selection lines 16A-1 to 16A-n in the odd-numbered rows in order, and then the selection lines 16B-1 to 16B-n in the even-numbered rows in order. Has become.

(First Circuit Example) Next, a specific circuit configuration of the pixel circuit 12 will be described. FIG. 2 shows the pixel circuit 12
2 is a circuit diagram showing a first circuit example of FIG. 1, in which the same parts as in FIG. 1 are designated by the same reference numerals. In addition, in FIG.
A circuit configuration for two pixels vertically adjacent to each other is shown.

In FIG. 2, the cathodes of the organic EL elements 11A and 11B for two pixels vertically adjacent to each other are connected (grounded) to the first power source, for example, the ground. Organic E
Each of the anodes of the L elements 11A and 11B has one end of each of the selection switches 15A and 15B, for example, a Pch TFT 15
The drains of A and 15B are connected. These TF
In T15A and 15B, each source is commonly connected to the node N, and each gate has a selection line 16A (16A-1 to 16A-).
n) and 16B (16B-1 to 16B-n), respectively.

The node N has, for example, a Pch TFT 21.
The drain of is connected. The source of the TFT 21 is
It is connected to a second power supply, for example, a positive power supply Vcc. T
One end of the capacitor 22 is connected to the gate of the FT 21, and the other end is connected to the positive power supply Vcc. TFT
The gate of 21 is further connected to the drain of, for example, an Nch TFT 23. The TFT 23 has a source connected to the data lines 14 (14-1 to 14-m) and a gate connected to the scanning lines 13 (13-1 to 13-n).

Next, the specific operation of the active matrix type display device according to the first embodiment having the above-mentioned structure, that is, the active matrix type organic EL display device, will be described.
This will be described with reference to the timing chart of FIG.

First, at the beginning of a frame, the scanning line driving circuit 17 drives the scanning line 13 which is the first scanning line.
-1 is selected (high level), and the TFT 23 of each pixel circuit 12 in the first row is turned on. Thereby, the brightness data given through the data lines 14-1 to 14-m is written in the capacitor 22 via the TFT 23. At this time, the selection line drive circuit 18 drives the selection line 16A-1 to be in the selected state (low level).
Since 6B-1 is in the non-selected state (high level),
15A is turned on and TFT 15B is turned off.

In this state, the TFT 21 supplies the organic EL element 11A with a current corresponding to the brightness data written in the capacitor 22 through the TFT 15A in the ON state.
Shed on. As a result, the organic EL element 11A in the first row is in a light emitting state and emits light with a brightness according to the flowing current. On the other hand, since the TFT 15B is in the off state, no current flows in the organic EL element 11B in the second row,
1B is turned off.

Next, the scanning line driving circuit 17 drives the scanning line 13-2. Even when the scanning line 13-2 is selected, the organic EL element 11A in the third row is in a light emitting state by the same circuit operation of the pixel circuit 12 as in the selection of the scanning line 13-1. 11B is turned off. Thereafter, similarly, the scanning lines 13-3, ..., 1
By performing the writing operation of the brightness data while selecting 3-n, the organic EL elements 11A in the odd rows of the screen emit light.

Thereafter, the scanning line driving circuit 17 drives the scanning line 13-1 again, and the brightness data is written in the capacitor 22 via the TFT 23 of each pixel circuit 12 in the first row. At this time, the selection line drive circuit 18 drives the selection line 16A-1 to be in the non-selection state and the selection line 16B-1 to be in the selection state, so that the TFT 15A is turned on and the TFT 15B is turned off. As a result, a current according to the brightness data written in the capacitor 22 flows to the organic EL element 11B through the TFT 21 and the TFT 15B.

As a result, the organic EL element 11B in the second row is in a light emitting state and emits light with a brightness according to the flowing current.
On the other hand, since the TFT 15A is in the off state, no current flows in the organic EL element 11A in the first row, and the organic EL element 11A is turned off. Thereafter, in the same manner, the scan line 1
By performing the write operation of the brightness data while selecting 3-2, ..., 13-n, the organic EL elements 11B in the even rows of the screen emit light, and the write of the brightness data for one frame is completed.

As described above, the two TFTs 21 and 23 and the one capacitor 2 are provided as the pixel circuit 12 that causes the current corresponding to the luminance information to flow through the organic EL elements 11A and 11B.
By using a pixel circuit composed of two pixels and sharing the pixel circuit 12 between two vertically adjacent pixels, for example, although transistors for selection (TFTs 15A and 15B) are added, four TFTs 15A, 15B, 2
A pixel circuit for two pixels can be configured with 1, 23 and one capacitor 22.

That is, when the pixel circuit 12 is arranged for each pixel, a capacitor which tends to occupy a large area compared to the case where two TFTs require four TFTs and two capacitors. Can be reduced by one. Therefore, the manufacturing yield can be improved accordingly. Moreover, since the pixel area can be reduced by the amount of one capacitor that can be reduced, the pixel pitch can be narrowed and the display can have high resolution and high definition.

In particular, since the driving method is adopted in which the writing of the luminance data to all the pixels in the odd-numbered rows and the writing of the luminance data to the whole pixels in the even-numbered rows are adopted alternately, the image signal is interlaced (interlaced) scanning. If it is compatible with the system, it is possible to drive the display by using this image signal as it is, and to display an image signal compatible with interlaced scanning without causing any deterioration in display quality. It will be especially useful.

On the other hand, the image signal is progressive (sequential)
If it corresponds to the scanning method, an image memory is prepared externally and, for example, in the first half of one frame, luminance data of even rows is temporarily stored in the image memory, while luminance data of odd rows is stored first. It is sufficient to adopt a driving method in which the brightness data of even rows is read from the image memory and written in the latter half.

Alternatively, the frame frequency is standard 60
If the value is about Hz, only even rows in a certain frame,
In the next frame, flicker does not occur if writing is performed alternately, such as in odd rows only, so that the driving frequency can be halved while obtaining a practical image quality. In this case, although the resolution of the moving image is lowered, it is possible to obtain an image having a resolution of 2n rows × m columns for a still image.

[Modification of First Embodiment] FIG. 4 is a block diagram showing the structure of an active matrix display device according to a modification of the first embodiment of the present invention. Are denoted by the same reference numerals.

In the active matrix type display device according to the first embodiment, two lines (A, B) of organic EL elements 11 are used.
In contrast to the pixel array in which A and 11B are alternately arranged in each row, in the active matrix display device according to this modification, the organic EL elements 11A and 11B of two systems are arranged in each row and each column. They are different in that they adopt a so-called checkered pattern pixel array arranged alternately with each other, and other than that, the basic configuration is the same. In order to realize a checkered pixel arrangement, two selection lines 16A (16
A-1 to 16A-n), 16B (16B-1 to 16B-
For example, a wiring structure in which n) crosses each row in each row is adopted.

As a result, in the pixels on the first data line (the data lines 14-1, 14-3, ..., 14-m-1 in the odd-numbered columns), the luminance data is written in all the pixels in the odd-numbered rows. And the writing of the luminance data to all the pixels of the even-numbered rows are alternately performed, while the writing of the luminance data to the pixels of the odd-numbered rows on the first data line is performed, the second data line adjacent thereto (Data lines 14-2, 14- of odd columns
4, ..., 14-m), the luminance data is written to the pixels in the even rows on the first data line, while the luminance data is written to the pixels in the even rows on the first data line. Luminance data is written to pixels in odd-numbered rows on the line.

As a result, when the first selection pulse is output from the selection line drive circuit 18, the first column in the first row,
The third row, ..., The organic EL element 11A in the (m-1) th row and 2
2nd, 4th, ..., m-th row organic EL in the row
When the elements 11A and 11A emit light and then the second selection pulse is output from the selection line drive circuit 18, 1 in the second row is output.
The third, third, ..., m-1th row organic EL elements 11B
, And the organic EL elements 11B in the second, fourth, ..., M columns in the first row emit light, and so on. The driving is performed so that one of the pixels emits light.

The active matrix type display device according to the first embodiment is an interlaced scanning method in which writing is first performed in all pixels in odd-numbered rows of the entire screen and then writing is performed in all pixels in even-numbered rows. like,
If the frame frequency is about 60 Hz, flicker does not occur. However, compared to the case where all pixels are progressively scanned at a frame frequency of 60 Hz, there is a drawback that the scanning lines are visually conspicuous. This is because the pixel is repeatedly turned on (emitted) and turned off for each scanning line.

On the other hand, in the active matrix type display device according to the present modification, the driving is performed so that one of the two pixels adjacent to each other on the left and right on the scanning line emits light in synchronization with the vertical scanning. As a result, the scanning lines are less visible. Note that a single-color display device is modeled for simplicity in FIG. 4, but in the case of a color display device, the configuration of FIG. 4 may be adopted for each color.

In the above-described embodiment and its modification, one pixel circuit 12 is shared by two vertically adjacent pixels, but the invention is not limited to this and it is shared by three or more pixels. Obviously, it can be extended as follows. However, if one pixel circuit 12 is shared by many pixels, each organic E
Since the light emitting time of the L element becomes short, it is necessary to increase the peak luminance of the organic EL element in order to obtain the same time average luminance.

Further, in the above-mentioned embodiment and its modification, the case where the present invention is applied to the active matrix type organic EL display device using the organic EL element as the display element of the pixel has been described, but the present invention is not limited to this. However, the present invention is not limited to the above, and can be applied to all active matrix type display devices using an electro-optical element whose luminance changes according to a flowing current as a display element.

(Second Circuit Example) FIG. 5 is a circuit diagram showing a second circuit example of the pixel circuit 12. In the figure, the same parts as those in FIG. 2 are designated by the same reference numerals. In addition, FIG. 5 also shows a circuit configuration for two vertically adjacent pixels.

In FIG. 5, the cathodes of the organic EL elements 11A and 11B for two pixels vertically adjacent to each other are grounded. Each of the anodes of the organic EL elements 11A and 11B has one end of each of the selection switches 15A and 15B, for example, Pc.
The drains of the TFTs 15A and 15B of h are connected. These TFTs 15A and 15B have their sources commonly connected to the node N and their gates connected to the select line 16A (16A).
-1 to 16A-n), 16B (16B-1 to 16B-)
n), respectively.

At the node N, for example, a Pch TFT 31 is used.
The drain of is connected. The source of the TFT 31 is connected to the positive power source Vcc. An Nch TFT 32, for example, is connected between the gate and drain of the TFT 31. The gate of the TFT 32 is connected to the reset line 36. The gate of the TFT 31 has a capacitor 3
One end of 3 is connected. A capacitor 34 is connected between the other end of the capacitor 33 and the positive power supply Vcc. The drain of the Nch TFT 35, for example, is further connected to the other end of the capacitor 33. TFT35
Has a source connected to the data lines 14 (14-1 to 14-m) and a gate connected to the scanning lines 13 (13-1 to 13-n).

The pixel circuit according to the second circuit example having the above configuration is
The basic function thereof is the same as that of the pixel circuit of FIG. 10 given as the conventional example 1, but the feature of the present example is that it is shared by, for example, two vertically adjacent pixels. . That is, the pixel circuit according to the second circuit example is
Similar to the pixel circuit according to the circuit example, an active matrix type organic EL display device can be configured by arranging them in a matrix as shown in FIG. 1 or 4. In addition,
Regarding the reset line 36, the scanning line 13 and the selection line 16
Similar to A and 16B, one wire is arranged every two rows.

Here, the specific operation will be described with reference to FIG.
This will be described with reference to the timing chart of.

First, with the selection line 16A in the non-selected state (high level) and the selection line 16B in the selected state (low level), the scanning line 13 and the reset line 36 are set in the selected state (both high level), and the switch is turned on. The driving TFT 31 short-circuits the gate and drain of the driving TFT 31. Next, when the selection line 16B is set to the non-selection state (high level), the TFT 15B is turned off.
The reset operation is performed similarly to the case of the pixel circuit of. When the reset operation is completed, the reset line 36 is returned to the non-selected state (low level).

Subsequently, a potential change of ΔVodd is applied to the data line 14, and then the scanning line 13 is brought into a non-selected state (low level), so that the capacitor 3 passing through the TFT 35.
The writing of the brightness data to 4 is completed. Then, if the selection line 16A is set to the selected state (low level), the TFT 15
A is turned on. At this time, the selection line 16B remains in the non-selected state, and the TFT 15B is in the off state.

In this state, the TFT 31 supplies the organic EL element 11A with a current corresponding to the brightness data written in the capacitor 34 through the TFT 15A in the ON state.
Shed on. As a result, the organic EL element 11A enters a light emitting state, and emits light with a brightness corresponding to the flowing current. On the other hand, TFT
Since 15B is in the off state, no current flows in the organic EL element 11B, and the organic EL element 11B is turned off.

After that, the scanning line 13 (13-1 to 13-
n) are sequentially selected and the writing operation of the luminance data to the pixels is performed, whereby the organic EL elements 1 in the odd rows of the screen are
1A emits light. When the writing operation of the luminance data for the odd rows is completed, the writing operation of the luminance data is performed for the even rows from the first scanning line again,
The organic EL elements 11B in the even rows of the screen emit light, and the writing of the luminance data for one frame is completed.

As described above, the pixel circuit according to the second circuit example is shared by, for example, two vertically adjacent pixels, so that five TFTs 15A, 15B, 31, 32, 35 are formed.
Also, a pixel circuit for two pixels can be configured with the two capacitors 33 and 34. That is, when the pixel circuit of FIG. 10 is arranged for each pixel, eight TFTs and four capacitors are required for two pixels, whereas the transistor 3 is used.
The number of capacitors and two capacitors can be reduced. Therefore, the manufacturing yield can be improved accordingly. In addition, the number of signal lines can be reduced by two, and the pixel area can be significantly reduced by the reduction of two capacitors that tend to occupy a large area. Therefore, it is possible to further reduce the pixel pitch and further increase the display. Higher resolution and higher definition can be achieved.

(Third Circuit Example) FIG. 7 is a circuit diagram showing a third circuit example of the pixel circuit 12. In the figure, the same parts as those in FIG. 2 are designated by the same reference numerals. In addition, FIG. 7 also shows a circuit configuration for two vertically adjacent pixels.

In FIG. 7, the cathodes of the organic EL elements 11A and 11B for two pixels vertically adjacent to each other are grounded. Each of the anodes of the organic EL elements 11A and 11B has one end of each of the selection switches 15A and 15B, for example, Pc.
The drains of the TFTs 15A and 15B of h are connected. These TFTs 15A and 15B have their sources commonly connected to the node N and their gates connected to the select line 16A (16A).
-1 to 16A-n), 16B (16B-1 to 16B-)
n), respectively.

At the node N, for example, a Pch TFT 41 is used.
The drain of is connected. The source of the TFT 41 is connected to the positive power source Vcc. A capacitor 42 is connected between the gate of the TFT 31 and the positive power supply 42.
The gate of the TFT 41 is further provided with, for example, an Nch TFT.
The drain of 43 is connected. The gate of the TFT 43 is connected to the scanning line 13. For example, the gate and drain of the Pch TFT 44 are commonly connected to the source of the TFT 43. The source of the TFT 44 is connected to the positive power source Vcc. A TFT 45 is connected between the gate / drain of the TFT 44 and the data line 14. The gate of the TFT 45 is connected to the scanning line 13.

The pixel circuit according to the third circuit example having the above configuration is
The basic function thereof is the same as that of the pixel circuit of FIG. 12 given as the second conventional example, but the present example is characterized in that, for example, it is shared by two vertically adjacent pixels. . That is, if the pixel circuits according to the third circuit example are arranged in a matrix as shown in FIG. 1 or FIG. 4 like the pixel circuits according to the first and second circuit examples, an active matrix organic EL display device is obtained. Can be configured.

As described above, by sharing the pixel circuit according to the third circuit example between two vertically adjacent pixels, six TFTs 15A, 15B, 41, 42, 44,
A pixel circuit for two pixels can be configured with 45 and one capacitor 42. That is, when the pixel circuit of FIG. 12 is arranged for each pixel, eight TFTs and one capacitor are required for two pixels, whereas two transistors and one capacitor can be reduced. Therefore, the manufacturing yield can be improved accordingly. Further, since the pixel area can be reduced by the amount of one capacitor that tends to occupy a large area, the pixel pitch can be narrowed, and high resolution and high definition of the display can be achieved.

[0076]

As described above, according to the present invention,
By sharing the pixel circuit among a plurality of pixels in a time division manner, the number of elements of the pixel circuit per pixel can be reduced. In particular, in order to have a compensation function for TFT characteristic variations,
When using a pixel circuit with a complicated circuit configuration,
By sharing the pixel circuit among a plurality of pixels, 1
Since it is possible to effectively reduce the number of transistors and capacitors per pixel, it is possible to improve the manufacturing yield and facilitate realization of a high-definition display.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration example of an active matrix type display device according to a first embodiment of the invention.

FIG. 2 is a circuit diagram showing a first circuit example of a pixel circuit.

FIG. 3 is a timing chart of the circuit operation of the pixel circuit according to the first circuit example.

FIG. 4 is a block diagram showing a configuration example of an active matrix type display device according to a modification of the first embodiment.

FIG. 5 is a circuit diagram showing a second circuit example of a pixel circuit.

FIG. 6 is a timing chart of the circuit operation of the pixel circuit according to the second circuit example.

FIG. 7 is a circuit diagram showing a third circuit example of the pixel circuit.

FIG. 8 is a circuit diagram showing a circuit configuration of a basic voltage writing type pixel circuit.

FIG. 9 is a block diagram illustrating a configuration example of an active matrix display device.

FIG. 10 is a circuit diagram showing a pixel circuit according to Conventional Example 1.

FIG. 11 is a timing chart of the circuit operation of the pixel circuit according to Conventional Example 1.

FIG. 12 is a circuit diagram showing a pixel circuit according to Conventional Example 2.

[Explanation of symbols]

11A, 11B ... Organic EL element, 12 ... Pixel circuit, 1
3, 13-1 to 13-n ... Scan line, 14, 14-1 to 1
4-m ... Data line, 15A, 15B ... Selection switch, 1
6A, 16A-1 to 16A-n, 16B, 16B-1 to
16B-n ... Select line, 17 ... Scan line drive circuit, 18 ... Select line drive circuit, 19 ... Data line drive circuit

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G09G 3/20 624 G09G 3/20 624B 641 641D H05B 33/14 H05B 33/14 A F term (reference) 3K007 AB02 AB06 AB17 AB18 BA06 BB07 DB03 EB00 GA04 5C080 AA06 BB05 DD05 DD22 DD27 EE28 FF11 JJ02 JJ03 JJ04 5C094 AA05 AA07 AA15 AA43 AA44 AA45 AA51 AA55 BA03 BA27 CA19 DA09 DA13 DB01 DB01 FB20 GA04 GA04

Claims (6)

[Claims] 1. An active matrix display device in which pixels having electro-optical elements whose brightness is changed by a flowing current are arranged in a matrix, which is provided commonly to a plurality of pixels and is provided through a data line. A pixel circuit that causes a current corresponding to the luminance information to flow in each electro-optical element of the plurality of pixels; and a selection unit that selects an electro-optical element of a pixel to be driven by the pixel circuit from the plurality of pixels. An active matrix type display device characterized by being provided. 2. The pixel circuit is commonly provided for pixels in two adjacent rows, and writes brightness information to all pixels in odd rows and writes brightness information to all pixels in even rows. 2. The active matrix type display device according to claim 1, wherein the steps are alternately performed. 3. The pixel circuit is provided in common for each pixel in two adjacent rows, and in the pixels on the first data line, writing of luminance information to all pixels in odd rows and writing in even rows. While writing the luminance information to all the pixels alternately, while writing the luminance information to the pixels in the odd rows on the first data line, the pixels in the even rows on the second data line adjacent thereto Luminance information is written to the pixels of even rows on the first data line, while the luminance information is written to pixels of odd rows on the second data line. The active matrix display device according to claim 1, which is performed. 4. An active matrix type organic electroluminescence display in which pixels having organic electroluminescence elements having first and second electrodes and an organic layer including a light emitting layer between these electrodes as display elements are arranged in a matrix. A pixel circuit provided in common to a plurality of pixels, wherein a current corresponding to luminance information given through a data line is passed through each organic electroluminescence element of the plurality of pixels; To a selection means for selecting an organic electroluminescence element of a pixel which is a driving target of the pixel circuit, from the active matrix type organic electroluminescence display device. 5. The pixel circuit is commonly provided for each pixel in two adjacent rows, and writes the brightness information to all the pixels in the odd rows and writes the brightness information to all the pixels in the even rows. 5. The active matrix type organic electroluminescence display device according to claim 4, wherein the steps are alternately performed. 6. The pixel circuit is commonly provided for pixels in two adjacent rows, and in the pixels on the first data line, writing of luminance information to all the pixels in odd rows and writing in the even rows. While writing the luminance information to all the pixels alternately, while writing the luminance information to the pixels in the odd rows on the first data line, the pixels in the even rows on the second data line adjacent thereto Luminance information is written to the pixels of even rows on the first data line, while the luminance information is written to pixels of odd rows on the second data line. The active matrix organic electroluminescence display device according to claim 4, which is performed.