JPH10319909A - Display device and driving method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain uniform light emission quantity for each pixel and each panel and to improve picture definition. SOLUTION: A controller 2 stores a binary picture signal in one frame unit. The controller 2 divides one frame into plural sub-frames showing a picture to be displayed in two-level picture data based on values of each digit of a picture signal of stored one frame. This two-level picture data for each sub- frame is written in a capacitor Cp from a drain driver 4 for each line. When the picture data is '1', a transistor for driving 12 is turned on. A common driver 5 applies voltage of the prescribed level for each sub-frame, and controls voltage applied between electrodes of an organic EL element 11. Thereby, the organic EL element 11 emits light with different brightness for each sub-frame. Pictures of each sub-frame are synthesized visibly, and gradation in one frame is expressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device and a driving method thereof, and more particularly to a display device suitable for gradation display of an organic EL display device and a driving method thereof.

[0002]

2. Description of the Related Art With the rise of mobile computing, there is an increasing demand for flat display devices. Conventionally, a liquid crystal display device is generally used as a flat display device. However, liquid crystal display devices have problems such as a narrow viewing angle and poor response characteristics.

On the other hand, an organic EL (electroluminescence) display device has recently attracted attention as a flat display device having a wide viewing angle and good response characteristics.
Each pixel of an organic EL panel used in an organic EL display device that performs dot matrix display includes, for example, an organic EL element 31 and a TFT (Thin Film Tran) as shown in FIG.
a driving transistor 32 composed of
And a selection transistor 33 composed of T. The gate of the selection transistor 33 is connected to a gate line GL connected to a gate driver (not shown), and the drain is connected to a drain line DL connected to a drain driver (not shown). The source of the selecting transistor 33 is connected to the gate of the driving transistor 32. The source of each driving transistor 32 is connected to the cathode of the corresponding organic EL element 31, and the drain is grounded. Then, the anodes of all the organic EL elements 31 include:
The connection is made such that a constant reference voltage Vdd is always applied.

For example, when a full-color image is displayed on the organic EL display device, the voltage applied to the driving transistor 32 from the drain driver via the drain line DL and the selection transistor 32 is controlled, and the source of the driving transistor 32 is controlled. -By controlling the drain-to-drain current, the issued luminance gradation display of each organic EL element 31 was performed.

That is, as shown in the characteristic diagram of FIG.
Assuming that the reference potential Vdd is constant, that is, the source-drain voltage Vsd of the driving transistor 32 is constant,
By changing the gate voltage Vg, the source-drain current Isd changes. As a result, the amount of current flowing through the organic EL element 31 changes, and the energy excited when the holes and electrons are combined in the organic EL layer in the organic EL element 31 changes.
The amount of light emitted by 1 changes.

However, as the number of pixels increases, it is extremely difficult to make the gate voltage-source drain current characteristics of the driving transistors 32 connected to all the organic EL elements 31 in one panel uniform. Therefore, even if the value of the voltage applied to the gate of the driving transistor 32 is the same, the current between the source and the drain varies. Similarly, since the transistor characteristics of the selection transistor 33 also vary, the variation of the characteristics of the transistors 32 and 33 synergistically causes the value of the current flowing through the organic EL element 31, in other words, the hole. The amount of light emitted from the organic EL element 31 varies from pixel to pixel even though the same data signal is output to the drain line DL. However, there is a problem that the quality of the image displayed on the display is deteriorated.

[0007] This problem causes a problem that the yield of the organic EL panel is reduced.

[0008]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and a display device which can obtain a uniform light emission amount for each pixel and each panel and has a good image quality. And a driving method thereof.

[0009]

In order to achieve the above object, a display device according to a first aspect of the present invention includes a plurality of light emitting elements arranged in a matrix and one end of each of the light emitting elements. A plurality of first switches connected to one electrode and having a reference voltage applied to the other end;
A plurality of second switches for writing data for turning on / off the switches to the first switches, and an image of one field according to the gradation of the image in one field. Image processing means for dividing into sub-field images composed of gradation images, selection driving means for sequentially selecting the second switches in the rows of the matrix, and each sub-field divided by the image processing means Data driving means for outputting data for turning on / off the first switch via the second switch selected in each subfield according to an image, and the light emitting element for each row of the matrix The sub-electrode is connected to the other electrode of the light emitting element corresponding to the second switch in the row selected by the selection driving means. Characterized in that it comprises a voltage driving means for applying a predetermined voltage defined for each field, a.

A display device according to a first aspect of the present invention includes a plurality of light emitting elements arranged in a matrix and having a reference potential applied to one of a pair of electrodes; A display comprising: a plurality of first switches connected to the other electrode of each of the elements; and a plurality of second switches for writing data for turning on / off each of the first switches to the first switch. A panel, image processing means for dividing an image of one field into sub-field images each composed of an image of a gradation in accordance with the gradation of the image in one field, and the second line of the matrix. And a second driver selected for each subfield according to an image for each subfield divided by the image processing means.
Data driving means for outputting data for turning on / off the first switch through the switches of the plurality of switches, and the other end of each of the plurality of first switches for each row of the matrix, and A voltage driving means for applying a predetermined voltage determined for each of the subfields may be provided at the other end of the first switch corresponding to the second switch in the row selected by the means.

Here, the first switch is, for example,
A memory transistor in which an impurity is doped into a gate insulating film so that data can be written to a gate can be used. Further, the first switch can be constituted by a transistor and a capacitor (capacitor) for holding data for turning on / off the transistor.

According to these display devices, the data for turning on / off the first switch is based on the light emission / emission of the light emitting element for each subfield according to the gradation in one field.
No light emission is determined. Then, by controlling the voltage applied to the other electrode of the light emitting element by the voltage driving means,
The brightness of the light emitting element that emits light is controlled for each subfield. For this reason, the images divided into subfields are visually combined to form an image of one field, and the brightness of the light emitting element is determined by the sum of the light emission luminance in one field. That is, since the gray scale can be controlled only by turning on and off the first switch and the second switch, in this display device, the brightness of the pixel at the same gray scale can be controlled by the first switch and the second switch in any light emitting element. Since it can be made substantially constant without being substantially influenced by variations in the electrical characteristics, an image with high image quality can be displayed. Further, there is no display variation for each display panel.

Here, the predetermined voltage refers to a voltage at a level at which the light-emitting element emits light at an appropriate light emission luminance in accordance with a subfield when the first switch is turned on. Further, the gradation in this display device means the luminance of an image.

In the above display device, the first switch is constituted by a transistor that is turned on and off in accordance with data, and the on resistance of the transistor is sufficiently smaller than the resistance of the light emitting element. It is preferable that the off-state resistance is sufficiently larger than the resistance of the light-emitting element.

Here, the on-resistance of the transistor is:
For example, when the resistance of the light-emitting element is one-tenth or less, most of the voltage applied to the transistor and the light-emitting element is divided by the light-emitting element, so that the on-resistance of the transistor can be ignored. , Which are sufficiently larger than the resistance of the light emitting element. On the other hand, the off-resistance of the transistor is sufficiently larger than the resistance of the light-emitting element so that the voltage divided into the light-emitting element among the voltages applied to the transistor and the light-emitting element is equal to or lower than the threshold value. Is what you do.

In other words, by setting the on-resistance and the off-resistance of the transistor in this way, even if the characteristics of the transistor have some variation, the amount of light emitted by the light emitting element does not vary much. For this reason, it is possible to display a uniform image with good image quality.

In the above display device, the one-field image is an image of 2 ⁿ gradations, and the image processing means divides the one field into n sub-fields, Applies a predetermined voltage to each of the n sub-fields such that the ratio of the light emission amount of the light emitting element is 2 ⁰ : 2 ¹ :...: 2 ^n-1 to the other electrode of the light emitting element Where n is 1
It can be an integer greater than or equal to.

In this case, the image processing means converts the image of each light emitting element in the one field into data consisting of a plurality of digits corresponding to each of the subfields according to the gradation. Means, and image determining means for supplying data for turning on and off the second switch to the data driving means in each of the subfields according to the value of each digit of the data consisting of the plurality of digits. Things.

When one field is divided into subfields and the predetermined voltage ratio is determined in this way, an image of 2 ⁿ gradations can be displayed most efficiently. Further, when the image processing means is configured as described above, it is possible to easily determine in which subfield each of the light emitting elements emits light.

Here, the predetermined voltage for each subfield is determined by characteristics of the light emitting element. For example, the emission luminance of the light emitting element increases linearly when a voltage equal to or higher than a threshold is applied between the electrodes, and the reference voltage applied to the other end of the first switch is set at the same level as the threshold of the light emitting element. when set to voltages of opposite polarity, the ratio of the predetermined voltage 2 ^0: 2 ^1: ...: can be 2 ^n-1.

In the above display device, the voltage driving means may be provided for each of the other electrodes of the light emitting elements in each row.
The predetermined voltage may be applied until the selection driving unit again selects the second switch in the row corresponding to the light emitting element in the next subfield.

In this case, the light emitting period in each subfield of the light emitting element is substantially one subfield period. Thereby, an image can be displayed efficiently.

In this case, the order of the n subfields in which the light emitting elements are issued at the respective light emission amounts is arbitrary.

In the above display device, it is preferable that the other electrodes of the plurality of light emitting elements are commonly formed with the same width in the row direction for each row of the matrix.

In the above display device, the plurality of light-emitting elements may include three types of light-emitting elements that emit red, green, and blue light, respectively, arranged in a predetermined order in the matrix. it can.

As described above, by arranging the three types of light emitting elements in a predetermined order, a color image can be displayed on the display device.

In the above display device, it is preferable that each of the light emitting elements is constituted by an organic electroluminescence element.

That is, since the organic electroluminescence element has good response characteristics, it can emit light sufficiently even when the period of applying the predetermined voltage in the subfield is short.

According to another aspect of the present invention, there is provided a method of driving a display device according to a second aspect of the present invention, comprising: a plurality of light emitting elements arranged in a matrix; A plurality of first switches connected to the plurality of electrodes, and a plurality of second switches for turning on / off each of the plurality of first switches, and the other electrode of the plurality of light emitting elements or the other A reference voltage is applied to one of the other ends of the plurality of first switches, and the other electrode of the plurality of light emitting elements or the other of the other ends of the plurality of first switches is connected to each row. A method of driving a display device having a display panel, wherein an image of one field displayed on the display panel is composed of images of each gradation according to the gradation of an image in one field. Rusa An image processing step of dividing the field of image, and selection drive step of sequentially selecting the second switch row of said matrix, in response to the divided image in each subfield in the image processing step,
A data driving step of outputting data for turning on / off the first switch to the second switch selected in each subfield, and a data driving step connected to each row;
The other electrode of the plurality of light emitting elements or the plurality of first electrodes
A voltage driving step of applying a predetermined voltage determined for each subfield to the other of the other ends of the switch.

The data for turning on / off the first switch determines the light emission / non-light emission of the light emitting element for each subfield according to the gradation in one field. Then, in the voltage driving step, a predetermined voltage determined for each subfield is applied to the other electrode of the plurality of light emitting elements or the other of the other ends of the plurality of first switches connected to each row. By controlling the applied voltage, the brightness of the light emitting element that emits light for each subfield is controlled. For this reason, the images divided into subfields are visually combined to form an image of one field, and the brightness of the light emitting element is determined by the sum of the light emission luminance in one field. That is, since the gray scale can be controlled only by turning on and off the first switch and the second switch, in this display device driving method, the brightness of the first switch and the second switch of the same gray scale can be obtained for any light emitting element. 2
Since it is possible to make the tenon constant without being substantially influenced by the variation in the electrical characteristics of the switch, it is possible to display an image with high image quality.

[0031]

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

In this embodiment, one field period, which is a period for substantially displaying an image of one frame, is divided into four subfield periods, and the light emission amount in each subfield period is 1: 2: 4. : 8, an organic EL display device displaying 16 gradations will be described as an example.

FIG. 1 is a block diagram showing the configuration of the organic EL display device of this embodiment. 1, the organic EL display device includes an organic EL panel 1, a controller 2, a gate driver 3, a drain driver 4, and a common driver 5.

As shown in the equivalent circuit diagram in the figure, each pixel of the organic EL panel 1 includes an organic EL element 11, a driving transistor 12, a selection transistor 13, and a capacitor Cp. Be composed.

The organic EL element 11 emits light of each color of red (R), green (G), and blue (B).
They are arranged in a matrix on the organic EL panel 1 in a predetermined order. As shown in the characteristic diagram of FIG. 2, when a voltage equal to or higher than the threshold value Vth is applied between the anode and the cathode, a current flowing through an organic EL layer, which will be described later, sharply rises, and the organic EL element 11 It emits light at the appropriate brightness. The applied voltage and light emission luminance are from Vth to (Vth + Vx)
Can be expressed substantially as a linear function in the range, the luminance gradation is controlled by gradation control of the voltage applied to both ends of the organic EL tank in this range. The current flowing through the organic EL layer, that is, the amount of light emitted from the organic EL element 11 is determined by the voltage applied between the anode and the cathode being Vt.
When h + Vx or more, saturation occurs.

The driving transistor 12 is composed of a TFT. The gate of the driving transistor 12 is the source of the selection transistor 13, and the drain is the organic EL element 1.
1, and the source is grounded (0 V). The driving transistor 12 is an organic EL element 1
1 is used as a switch for turning on / off the power supplied to the power supply 1.

When a common signal is applied to the organic EL element 11 from the common driver 5 described later, the ON resistance of the driving transistor 12 becomes sufficiently smaller than the resistance of the organic EL element 11 (for example, 1/10 or less). And the off-resistance is sufficiently higher than the resistance of the organic EL element 11 (for example, 10 times or more). Therefore, when the driving transistor 12 is turned on, most of the voltage output from the common driver 5 is applied to the organic EL element 11.
Is divided. Therefore, in the organic EL display device of this embodiment, the on-resistance of the driving transistor 12 can be substantially ignored. On the other hand, when the driving transistor 12 is off, most of the voltage output from the common driver 5 is divided between the source and the drain of the driving transistor 12.

The selection transistor 13 is composed of a TFT. The gate of the selection transistor 13 is an organic EL
The drain is connected to a gate line GL provided for each row (horizontal direction in the drawing) of the panel 1, and the drain is connected to a drain line DL provided for each column (vertical direction in the drawing) of the organic EL panel 1. The source is connected to the gate of the driving transistor 12. The selection transistor 13 is used as a switch for turning on / off the supply of a drive signal from the drain driver 4 described later to the gate of the drive transistor 12.

The capacitor Cp holds a drive signal supplied from a drain driver 4 described later for a predetermined period. The drive signal held by the capacitor Cp is used to turn on and off the drive transistor 12, and the capacitor Cp
A switch for causing the organic EL element 11 to emit light is formed by p and the driving transistor 12.

Hereinafter, the structure of the organic EL panel 1 will be described in detail. FIG. 3 is a plan view showing a configuration for one pixel of the organic EL panel 1, and FIG. 4 is a cross-sectional view taken along line AA of FIG. As shown in these figures, an organic EL panel 1 is configured by forming an organic EL element 11, a driving transistor 12, and a selecting transistor 13 on a glass substrate 14.

More specifically, a gate line GL composed of a gate metal film made of aluminum on a glass substrate 14, a gate electrode 13a of the selection transistor 13 formed integrally with the gate line GL, The gate electrode 12a of the transistor 12 for use is patterned. An anodic oxide film 14a is formed on the gate electrode GL, the gate electrode 13a, and the gate electrode 12a. Further, the anodic oxide film 1 on the gate electrode 12a
4a, a gate insulating film 14b made of silicon nitride
Are formed.

Gate insulating film 1 above gate electrode 13a
4b, a semiconductor layer 1 made of amorphous silicon
3d is formed. On the semiconductor layer 13d, a blocking layer 13e is formed at the center, and ohmic layers 13f are formed on both sides thereof. And the data line D
The drain electrode 13b of the selection transistor 13 integrally formed with L is formed by being stacked on the ohmic layer 13f. On the other hand, on the other side, a selection transistor 1
The third source electrode 13c is formed on the ohmic layer 13f. Thus, the selection transistor 13 is formed. The source electrode 13c of the selection transistor 13 is connected to the gate electrode 12a of the selection transistor 12 via the contact hole 15b.

Gate insulating film 1 above gate electrode 12a
4a, a semiconductor layer 1 made of amorphous silicon
2d is formed. A blocking layer 12e is formed at the center of the semiconductor layer 12d, and ohmic layers 12f are formed on both sides thereof. And the reference voltage line S
The source electrode 12b of the driving transistor 12, which is formed integrally with L, is formed by being stacked on the ohmic layer 12f. On the other hand, the driving transistor 12
Is formed by laminating on the ohmic layer 13f. Thus, the driving transistor 12 is formed. Note that the reference voltage line SL is grounded.

On the driving transistor 12 and the selection transistor 13 formed as described above, except for the contact hole 15a formed at the end of the drain electrode 12c of the driving transistor 12, an interlayer insulating film is formed. 1
4c is formed. On the interlayer insulating film 14c, M
A visible light reflective cathode electrode 11a made of gIn (Magnesium Indium) is patterned. The cathode electrode 11a is connected to the drain electrode 12c of the driving transistor 12 via the contact hole 15a. On the cathode electrode 11a, an organic EL layer 11b having any one of light emitting layers that emit light of each color of R, G, and B is formed in a predetermined arrangement in a matrix. Then, on the organic EL layer 11b, each pixel line extends over the pixel region in the row direction of the matrix corresponding to each gate line GL, and is separated from each other and has the same width over the pixel region in the column direction. ITO (Indium-Tin Oxid
A plurality of anode electrodes 11c of e) are formed. Thus, the organic EL element 11 is formed.
Further, the reference voltage line SL and the gate insulating film 14 are provided for each pixel.
b and the capacitor Cp constituted by the gate electrode 12a
Is made.

Organic EL layer 11 of R organic EL element 11
b comprises an electron transporting light emitting layer formed on the cathode electrode 11a side and a hole transporting layer formed on the anode electrode 11c side.

The electron transporting light emitting layer is made of Alq3
In this, DCM-1 shown in Chemical Formula 2 is dispersed.

Embedded image

Embedded image

The hole transport layer is composed of α-NPD shown in Chemical formula 3.

Embedded image

The electron-transporting light-emitting layer has a recombination region between electrons and holes in the layer, and when no light-emitting material is contained in addition to the used Alq3, the electron-hole recombination occurs. The energy associated with the bond is absorbed to generate green light by Alq3. However, since DCM-1 is dispersed in the layer, DCM-1 absorbs the energy associated with the recombination of electrons and holes. Emits red light.

Organic EL layer 11 of G organic EL element 11
b comprises an electron transporting light emitting layer formed on the cathode electrode 11a side and a hole transporting layer formed on the anode electrode 11c side.

The electron transporting light emitting layer is made of Bebq shown in Chemical formula 4.
Consists of two.

Embedded image

The hole transport layer is made of the same α-NPD as the hole transport layer of the organic EL layer 11b for R. Organic EL for G
In the element 11, the energy associated with the recombination of electrons and holes is absorbed by Bebq2 of the electron-transporting light-emitting layer, and emits green light.

Organic EL Layer 11 of Organic EL Element 11 for B
b denotes an electron transport layer formed on the cathode electrode 11a side, a hole transport layer formed on the anode electrode 11c side,
A light emitting layer formed between the electron transporting layer and the hole transporting layer.

The electron transport layer is made of an organic EL element 11b for R
Made of Alq3 used for the electron transporting light emitting layer. The hole transport layer is made of the same α-NPD as the hole transport layer of the R and G organic EL elements 11b.

The light emitting layer was composed of 96% by weight of DPV shown in Chemical Formula 5.
Bi and 4% by weight of BCzVBi shown in Chemical Formula 6.

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Incidentally, the organic EL of the organic EL element 11 for B
In the layer 11b, the recombination region of electrons and holes is DP
It becomes a light emitting layer composed of VBi and BCzBi. The energy associated with the recombination of electrons and holes in this light emitting layer is represented by D
PVBi and BCzBi absorb and emit blue light.

FIG. 5 is a block diagram showing the configuration of the controller 2 of FIG. As shown, the controller 2
Are R, G, B extraction circuit 2a, A / D converter 2b, correction circuit 2c, table storage unit 2d, image signal storage unit 2e,
It comprises a light emission signal output section 2f, a synchronization signal extraction circuit 2g, a crystal pulse oscillator 2i, a reference clock generation circuit 2j, a gate control signal generation circuit 2k, a drain control signal generation circuit 21 and a common control signal generation circuit 2m.

The video signal externally supplied to the controller 2 is input to the R, G, B extraction circuit 2a and the synchronization signal extraction circuit 2g. The synchronization signal extraction circuit 2g extracts a horizontal synchronization signal and a vertical synchronization signal from the video signal.
The R, G, and B extraction circuit 2a extracts red (R), green (G), and blue (G) from the luminance signal and the color difference signal in the video signal based on the horizontal synchronization signal and the vertical synchronization signal extracted by the synchronization signal extraction circuit 2g. The image signal of B) is extracted in a predetermined order.
The reference clock generation circuit 2j generates a reference clock signal CLK for measuring one horizontal period of one subframe based on the system clock transmitted from the crystal pulse oscillator 2i.
Generate

The A / D converter 2b converts the image signal extracted by the R, G, B extraction circuit 2a into a digital signal represented by a binary number. The correction circuit 2c includes a table storage unit 2d
With reference to the conversion table stored in the A, according to the light emission amount, the gamma characteristic, etc. of each of the R, G, B organic EL elements, A
The value of the image signal digitally converted by the / D converter 2b is corrected. The image signal storage unit 2e temporarily stores the image signal corrected by the correction circuit 2c. The image signal stored in the image signal storage unit 2e is a signal represented by a 4-digit binary number, and the first row, the second row,.
.., A first subfield corresponding to the first digit of the n-th row emits light for each row in the order of the first row, the second row,..., The n-th row based on the timing of the reference clock generation circuit 2j. The signal is read by the signal output unit 2f. Next, the second subfield corresponding to the second digit of the image signal from the first row to the n-th row is read into the emission signal output unit 2f for each row. Finally, the fourth subfield corresponding to the fourth digit of the image signal from the first row to the nth row is read for each row,
An image signal is read from one frame of data. The larger the value of the image signal, the brighter the image of the pixel is. That is, in this organic EL display device, the gradation is from 0 to 15, and as the gradation changes from 0 to 15, the display changes from dark to bright.

The light emission signal output unit 2f is connected to the image signal storage unit 2
In each sub-frame, it is determined whether or not the organic EL element 11 of the pixel emits light in accordance with the image signal stored in the sub-frame e, and each row is determined at a predetermined timing based on the reference clock supplied from the reference clock generation circuit 2j. A minute light emission signal IMG is output. That is, when the digit corresponding to each subfield of the image signal of each pixel is “0”, the light emission signal IMG is an off signal, and when the corresponding digit is “1”, the light emission signal IMG is drained as an on signal. Output to driver 4.

Table 1 shows the relationship between the gradation determined by the light emission signal output unit 2f and each subframe.

[Table 1] The light emission signal IMG output from the light emission signal output unit 2f is supplied to the drain driver 4.

The gate control signal generation circuit 2k generates a gate control signal GCONT based on the horizontal synchronization signal and the vertical synchronization signal extracted by the synchronization signal extraction circuit 2g and the reference clock generated by the reference clock generation circuit 2j. The gate control signal G generated by the gate control signal generation circuit 2k
CONT is supplied to the gate driver 3.

The drain control signal generation circuit 21 generates a drain control signal DCONT based on the horizontal synchronization signal and the vertical synchronization signal extracted by the synchronization signal extraction circuit 2g and the reference clock generated by the reference clock generation circuit 2j.
The drain control signal DCONT includes a start signal, a switching signal, and an output enable signal described later.
The drain control signal DCONT generated by the drain control signal generation circuit 21 is supplied to the drain driver 4.

The common control signal generation circuit 2m generates a common control signal CCONT based on the horizontal synchronization signal and the vertical synchronization signal extracted by the synchronization signal extraction circuit 2g and the reference clock generated by the reference clock generation circuit 2j. Common control signal C generated by common control signal generation circuit 2m
CONT is supplied to the common driver 5.

The gate driver 3 shown in FIG. 1 has a gate control signal GCON supplied from the gate control signal generation circuit 2k.
According T, and outputs a selection signal X ₁ to X _n. Select signal X
Only one of _{1 to Xn} becomes active at the same timing, and selects one of the gate lines GL of the organic EL panel 1. As a result, the selection signals X _{1 to} X _n are applied to the gates of the selection transistors 13 connected to the selected gate line GL, and the selection transistors 1
3 turns on.

The drain driver 4 comprises a shift register 41, latch circuits 42 and 43, and a level conversion circuit 44, as shown in FIG. Shift register 41
Is set to 1 (high-level signal) in the first bit by a start signal in the drain control signal DCONT supplied from the drain control signal generation circuit 21 and each time a shift signal in the drain control signal DCONT is supplied. Bit shift.

The latch circuit 42 is composed of a number of latch circuits corresponding to the number of bits of the shift register 41, and is supplied from the light emission signal output unit 2f to the latch circuit corresponding to the bit of the shift register 41 corresponding to 1. The light emission signal IMG is latched. When the light emission signal IMG for one row in one subframe is latched by the latch circuit 42, the light emission signal IMG is latched by the next-stage latch circuit 43 in accordance with the switching signal in the drain control signal DCONT. Then, the latch circuit 42 latches the light emission signal IMG of the next row.

The level conversion circuit 44 converts the driving signals Y _{1 to} Y _n of a predetermined voltage level into the organic EL according to the light emission signal IMG latched by the latch circuit 43 based on the output enable signal in the drain control signal DCONT. Output to the drain line DL of panel 1. Level conversion circuit 4
The drive signals Y _{1 to} Y _n output from 4 are stored in the gate 12 a of the drive transistor 12 and turn on the drive transistor 12.

The common driver 5 shown in FIG. 1 includes a common control signal CCON supplied from the common control signal generation circuit 2m.
Based on T, the anode electrode 11c of the organic EL element 11
It is applied to generate a common signal Z ₁ to Z _n. This signal is sent to the organic EL element 11 for each row via the common line CL.
To the anode electrode 11c. The ratio of the light emission luminance according to the voltage applied to the anode electrode 11c for each sub-frame is 1: 2: 4: 8, and is applied to the anode electrode 11c in the fourth sub-frame where the maximum voltage is applied. The voltage is Vdd8 (= Vth + Vx).

Hereinafter, the operation of the organic EL display device of this embodiment in one frame period will be described. R,
In the G and B extraction circuit 2a, R,
The R, G, and B signals from which the G and B signals have been extracted are A / D-converted by an A / D converter 2b and subjected to correction such as gamma correction by a correction circuit 2c, and then stored in an image signal storage unit 2e. It is memorized. The image signal stored in the image signal storage unit 2e is represented by a 4-digit binary number as described above. If the data is digital signal data output from a personal computer or the like instead of the video signal, the data is directly output to the correction circuit 2c.

On the other hand, the gate control signal generation circuit 2k, the drain control signal generation circuit 21 and the common control signal generation circuit 2m include the horizontal synchronization signal and the vertical synchronization signal extracted by the synchronization signal extraction circuit 2g, and the reference clock generation circuit 2j. A gate control signal GCONT, a drain control signal DCONT, and a common control signal CCONT are generated based on the generated reference clock CLK.

In the first sub-frame, the light emission signal output section 2f outputs the first digit (least significant) of the image signal for one frame stored in the image signal storage section 2e according to the reference clock CLK generated by the reference clock generation circuit 2j. ) Are sequentially read and output to the drain driver 4 as a light emission signal IMG. The light emission signal IMG from the light emission signal output unit 2f
The drain control signal generation circuit 21 outputs a start signal to the drain driver 4 in synchronization with the output of the drain driver 4.

In the drain driver 4, when the start signal is supplied to the shift register 41, 1 is set to the first bit of the shift register 41. And
The shift register 41 performs a bit shift every time a shift signal in the drain control signal DCONT is input. While the shift register 41 performs the bit shift, the latch circuit 42 latches the light emission signal IMG of the first subframe from the light emission signal output unit 2f in order from the first row. The light emission signal IMG for one row of the first subframe latched by the latch circuit 42 is a drain control signal DCO
The latch signal is latched in the second-stage latch circuit 43 by the switching signal in NT. Next, the drain driver 4 fetches the light emission signals IMG of the second and subsequent rows by the same operation. When the drain driver 4 finishes capturing the light-emitting signal IMG of the first sub-frame in the n-th row, it sequentially captures the light-emitting signal IMG of the second sub-frame.

Gate driver 3 first outputs selection signal X ₁ to gate line GL of the first row for one period of reference clock signal CLK based on gate control signal GCONT from gate control signal generation circuit 21. . Thereby, the selection transistor 13 connected to the gate line GL of the first row is turned on. At this time, the supplied output enable signal in the drain control signal to the level converting circuit 44 of the drain driver 4, the drive signals Y ₁ to Y _n of the predetermined voltage according to the light emission signal IMG latched in the latch circuit 43 is level converted The signal is output from the circuit 44 to the drain line DL of each column. Then, the drive signals Y _{1 to} Y _n are written to the gate 12 a of the drive transistor 12 in the first row during the period in which the selection signal X ₁ is output.

The driving transistor 12 in the first row is turned on when the driving signals Y _{1 to} Y _n are at a high level, and turned off when the driving signals Y _{1 to} Y _n are at a low level. When the selection of the first gate line GL is completed, the common driver 5
Is based on the common control signal CCONT from the common control signal generation circuit 2m,
dd1 a (= Vth + 1 / 8Vx) common signal Z ₁ of the voltage level of the gate driver 3 is applied to the anode electrode 11c of the organic EL element 11 to select the gate line of the first row in the second sub-frame.

Here, when the driving transistor 12 is turned on, the ON resistance thereof is sufficiently smaller than the resistance of the organic EL element 11, and the organic EL element emits light at a light emission luminance of 1 during the first sub-frame light emission period. A voltage of approximately Vdd1 is applied between the eleven electrodes. As a result, a current according to the voltage level flows through the organic EL layer 11b of the organic EL element 11, and the organic EL element 11 emits light. On the other hand, when the driving transistor 12 is off, its off-resistance is sufficiently higher than the resistance of the organic EL element, and no voltage higher than the threshold is applied between the electrodes of the organic EL element 11. Therefore, the organic EL element 11 does not emit light.

The common signal Z is applied to the common line CL of the first row.
_{While 1} is being output, the gate driver 2 selects the gate line GL in the second row. Then, similarly, the drive signals Y _{1 to} Y _n of the second row are written to the gate 12 a of the drive transistor 12. Hereinafter, the organic EL element 11 emits light in the same manner. Then, upon completion of the output of the common signal Z _n to the common line GL of the last row (n th row), and ends the first sub-frame. As described above, the first
In the sub-frame, the organic EL element 11 in which the first digit of the image signal is "1" emits light at luminance 1, and the organic EL element 11 in which the first digit of the image signal is "0" does not emit light.

The operation in the second sub-frame is almost the same as that in the first sub-frame. However, the light emission signal output unit 2f outputs the second digit (lower second digit) of the image signal stored in the image signal storage unit 2e as the light emission signal IMG. Further, the voltage level of the common signal Z ₁ to Z _n output from the common driver 5 to emit light at light emission luminance 2 in the second sub-frame emission period Vdd 2 (=
Vth + ／ Vx). Therefore, the emission luminance of the organic EL element 11 in the second sub-frame is twice as high as the emission luminance of the organic EL element 11 in the first sub-frame.

Therefore, in the second sub-frame,
The organic EL element 11 in which the second digit of the image signal is "1" emits light at a luminance of 2, and the organic EL element in which the second digit of the image signal is "0".
The L element 11 does not emit light.

The operation in the third sub-frame is almost the same as that in the first sub-frame. However, the light emission signal output unit 2f outputs the third digit (lower third digit) of the image signal stored in the image signal storage unit 2e as the light emission signal IMG. Further, the voltage level of the common signal Z ₁ to Z _n output from the common driver 5 to emit light at light emission luminance 4 in the third sub-frame emission period VDD4 (=
Vth + 1 / 2Vx). For this reason, the light emission luminance of the organic EL element 11 in the third sub-frame is 4 times the light emission luminance of the organic EL element 11 in the first sub-frame.

Therefore, in the third subframe,
The organic EL element 11 in which the third digit of the image signal is "1" emits light at luminance 4, and the organic EL element 11 in which the third digit of the image signal is "0".
The L element 11 does not emit light.

The operation in the fourth sub-frame is almost the same as that in the first sub-frame. However, the light emission signal output unit 2f outputs the fourth digit (most significant digit) of the image signal stored in the image signal storage unit 2e as the light emission signal IMG. The voltage levels of the common signals Z _{1 to} Z _n output from the common driver 5 are set to Vdd8 (= Vd8) so that light is emitted at an emission luminance of 8 during the fourth subframe emission period.
th + Vx). Therefore, the emission luminance of the organic EL element 11 in the fourth sub-frame is eight times the emission luminance of the organic EL element 11 in the first sub-frame.
Becomes

For this reason, in the fourth subframe,
The organic EL element 11 in which the fourth digit of the image signal is "1" emits light at a luminance of 8, and the organic EL element in which the fourth digit of the image signal is "0".
The L element 11 does not emit light. Note the voltage level Vdd1~Vdd8 of the common signal Z ₁ to Z _n may, Vt in all Figure 2
h to (Vth + Vx).
The luminance ratio in the 2, 3, and 4 sub-frames is 1: 2: 4:
If it is set to be 8, it is not necessary to make the ratio of each applied voltage value equal to the ratio of each light emission luminance. Therefore, in an organic EL element having a luminance characteristic in which the emission luminance and the voltage value are not represented by a linear function, a voltage according to the luminance ratio may be applied.

In this driving method, as shown in FIG. 9, the timings of the selection signals X _{1 to} X _n and the common signals Z _{1 to} Z _n output in the sub-frame writing period are shifted for each row. The periods in which the selected pixels in one row and the selected pixels in the n-th row emit light are shifted to the first half and the second half of the first subframe light emission period, respectively. Therefore, the period in which the selected pixel in the n-th row emits light extends over the next sub-frame writing period in the first to (n-1) th rows. The above first to first
The image divided into the fourth sub-frame is visually synthesized as an image of one frame by an afterimage effect.

At this time, the total luminance in one frame of the organic EL element 11 of the pixel having the gradation value of 15 is 1
It becomes 5. The total luminance in one frame of the organic EL element 11 having the gradation value of 0 is 0. The total luminance in one frame of the organic EL element 11 of the pixel having the intermediate gradation value becomes a value corresponding to the gradation value. Thereby, each organic EL element 11 visually appears to emit light at a brightness corresponding to the gradation value in one frame. Also, three kinds of organic EL of R, G, B
The light emitted from the element 11 is visually synthesized, and it looks as if a full-color image is displayed on the organic EL panel 1. In FIG. 8, the common signal Za is output immediately after the selection signal Xa (a is an integer satisfying 1 ≦ a ≦ n). However, as shown in FIG. 9, the common signal Za is synchronized with the selection signal Xa or the selection signal Xa.
The common signal Za may be output at a timing that partially overlaps with the common signal Za.

As described above, in the organic EL display device of this embodiment, the driving transistor 12 is turned on and off.
A gray scale display is performed by controlling the voltage applied to the anode electrode 11c connected to the common driver 5 by using the switch as an off switch. For this reason, even if the characteristics of the driving transistor 12 and / or the selection transistor 13 vary, the organic EL element 11 of each pixel has the same gradation.
Can make the amount of light emitted to the anode electrode 11c side substantially constant. Therefore, this organic EL display device has high quality of the displayed image. Moreover, there is no variation in display for each of the plurality of organic EL panels manufactured in the manufacturing process. As shown in FIGS. 3 and 4, the information of the transistors 12 and 13 is added to the light-reflective cathode electrode 11a,
Since the light emitting layer 11b and the transparent anode electrode 11c are arranged, there is no limitation on the pixel area by the transistor, and a display device having a very high light emitting area ratio of the pixel can be realized.
Further, since the light from the light emitting layer 11b is shielded from light by the cathode electrode 11a, the semiconductor layers of the transistors 12 and 13 are not photoexcited to cause a malfunction.

In the above embodiment, the gate driver 3 selects the gate line GL in one sub-frame,
It writes a driving signal Y ₁ to Y _n from the drain driver 4, in the next sub-frame to the gate driver 3 selects the same gate line GL, has output the common signal Z ₁ to Z _n from the common driver 5 . That is, the light emission period of the organic EL element 11 in each sub-frame is almost one.
It was close to the subframe period. Thereby, an image can be displayed efficiently.

Further, in the organic EL display device of this embodiment, the anode electrode 11c of the organic EL element 11 is formed commonly for each row, and the common signal Z ₁ from the common driver 5 is provided.
Starts emission of the organic EL element 11 for each row by to Z _n ·
Had been terminated. For this reason, compared to a method used for a plasma display panel or the like in which all the pixels are turned on at the same time in one sub-frame, variation in propagation delay is reduced, and the entire organic EL panel 1 can emit light uniformly. . For the anode electrode of the organic EL element, a material having a high resistance value, such as ITO, must be selected from the viewpoint of light transmissivity. In the different anode electrodes,
The luminance was partially varied. On the other hand, in the display device of the present embodiment, since the anode electrode 11c is commonly formed for each row, the variation of the common voltage can be reduced as compared with the related art, and each organic EL element 11c
Can emit light of almost the same brightness.

In this embodiment, an organic EL display device using an organic EL element 11 having good response characteristics as a light emitting element is taken as an example. Since the organic EL element 11 has good response characteristics, one frame is divided into sub-frames,
Even if the period for applying the voltage to the L element 11 is short, a sufficient amount of light can be obtained. That is, the present invention relates to an organic EL
The present invention is preferably applied to a display device.

In the above embodiment, each pixel of the organic EL panel 1 includes an organic EL element 11, a driving transistor 12 composed of a TFT, and a selection transistor 1
3 and the capacitor Cp. However, the configuration of each pixel of the organic EL panel is not limited to this, and a switching element such as an MIM may be applied to the selection transistor and / or the driving transistor.

Further, in this embodiment, the driving transistor 12 and the organic EL element 11 are connected in series, one is connected to the common line CL, and the other is grounded. Alternatively, the minimum value of the gradation voltage other than 0 of the signal Z applied to the common line CL is shifted to the positive side by more than the absolute value of Vth in FIG. May be set so as to be the set potential.

In this embodiment, the image signal unit 2
e, the first row of the image signal for one frame stored in
,..., The first subfield corresponding to the first digit of the n-th row are arranged in the order of the first row, the second row,..., The n-th row based on the timing of the reference clock generation circuit 2j. The image signal is read into the emission signal output unit 2f for each row, and then the second subfield corresponding to the second digit of the image signal from the first row to the nth row is read for each row, and finally the first Nth from row
The fourth subfield corresponding to the fourth digit of the image signal up to the line is read for each line, the data for one frame is set so that the image signal is read, and the light emission signal output unit 2f sequentially reads the image signal. On / off signals were output for each subfield of each row based on a reference clock generation circuit according to the image signal. On the other hand, as shown in FIG. 6, the image signal unit 2e outputs a 4-digit image signal for one frame to the arithmetic circuit 2fc of the emission signal output unit 2f for each row or frame. The digits corresponding to the 1, 2, 3, and 4 subfields are sieved to the corresponding subframe memories 1, 2, 3, and 4, the sieved data is output to the readout circuit 2fr, and the reference clock of the reference clock generation circuit 2j is output. The light emission signal IMG corresponding to each subfield of each row may be set to be sequentially output to the drain driver according to the clock.

FIG. 10 is an equivalent circuit diagram of one pixel of an organic EL panel used in the organic EL display device according to the second embodiment of the present invention, and FIG. 11 is an organic EL panel according to the second embodiment.
6 is a timing chart illustrating an operation in the L display device. In the organic EL element 11, the anode electrode 11c is grounded, and the cathode electrode 11a is connected to the source of the driving transistor 12. Driving transistor 1 in predetermined row
The drains 2 are connected to a common line CL. As shown in FIG. 11, the common driver 5 includes -Vdd1, -Vdd2, -Vdd according to each sub-frame period.
4, one of -Vdd8 is selectively applied.

In this embodiment, the driving transistor 12
And the organic EL element 11 were connected in series, one was grounded, and the other was connected to the common line CL. However, instead of the ground line, a fixed line having a positive potential or a negative potential was set. The minimum value of the gradation voltage other than 0 of the signal Z applied to CL may be set to a potential shifted to the negative side from the fixed line potential by the absolute value of Vth in FIG. 2 or more.

FIG. 12 is an equivalent circuit diagram of one pixel of the organic EL panel used in the organic EL display device according to the third embodiment of the present invention, and FIG. 13 is a circuit diagram of the organic EL panel of FIG. FIG. 3 is a cross-sectional view illustrating a configuration for pixels. As shown in these figures, one pixel of the organic EL panel according to the third embodiment of the present invention includes an organic EL element 51, a driving transistor 52, a data holding capacitor 53, and a selecting transistor 54. You. 54a, 54b, 54 in the figure
c is a gate electrode, a drain electrode, and a source electrode of the selection transistor 54, respectively, 52a, 52b, 52c
Are a gate electrode, a drain electrode, and a source electrode of the driving transistor 52.

In this organic EL panel, the driving signals Y _{1 to} Y _n from the drain driver 4 are held in the data holding capacitor 53. Then, the driving transistor 52 and the data holding capacitor 53 realize the same functions as those of the driving transistor 12 and the capacitor Cp of the above embodiment.

In this organic EL panel, the organic EL panel
The element 51 includes a cathode electrode 51, a light emitting layer 51b, and an anode electrode 51a. For each pixel, a driving transistor 52 on a substrate 55, a data holding capacitor 53
And a portion where the selection transistor 54 is not formed. The anode electrode 51a is not formed for each row as in the organic EL panel of the above embodiment, but is formed independently for each organic EL element 51. The anode electrode 51a of the organic EL element 51 is connected to a common line (not shown) formed on a data line (not shown) via an insulating film. Source electrode 52b of driving transistor 52
, A fixed voltage Vds (= Vth) is constantly applied.

When the organic EL panel is driven in the same manner as described above, assuming that the organic EL element 51 has the characteristics shown in FIG. 2, the voltage applied to the common line CL is In the first to fourth subframes, they are 1/8 Vx, 1/4 Vx, 1/2 Vx, and Vx, respectively.

In this organic EL panel, as shown in FIG. 13, the cathode electrode 51c is made of a transparent insulating film 56.
And on the glass substrate 55 side. This cathode electrode 51c is made of a transparent ITO layer or a light emitting layer 5
The material of the light emitting layer 51b provided on the interface side with
And a transparent two-layer structure of a layer in which a material having a low work function is dispersed and an ITO layer provided on the glass substrate 55 side. Therefore, light emitted from the organic EL layer 51b passes through the transparent glass substrate 55, and
Is displayed on the side of.

In the organic EL panel 1 of the above embodiment, the cathode electrode 51c is used as the driving transistor 52,
The anode electrode 51a was connected to the common line CL. On the other hand, the connection of the electrodes 51a and 51c may be reversed. In this case, the voltage applied from the common driver to the cathode electrode may be set to be more negative than the fixed voltage Vds. The connection between the common line CL and the line to which the fixed voltage Vds is applied may be reversed.

In the above embodiment, the source electrode 52b of the driving transistor 52 has a positive potential, 0V,
Any of negative potentials may be used as long as the common line CL is shifted to the positive side from the potential.

In the above embodiment, when the voltage applied between the anode and the cathode of the organic EL element 11 exceeds the threshold voltage, the light emission luminance of the organic EL element 11 increases linearly. Therefore, a voltage −Vdd with a negative threshold voltage polarity is applied to the cathode electrode 11a of the organic EL element 11, and the value of the voltage applied to the anode electrode 11c is controlled in proportion to the light emission luminance in each subframe. Thus, the light emission luminance of the organic EL element 11 may be controlled, and the present invention can be applied to an organic EL element in which the increase of the light emission luminance at a voltage higher than the threshold voltage is not linear. In this case, the voltage applied between the anode and the cathode of the organic EL element may be controlled so that the light emission luminance of the organic EL element has a predetermined ratio for each predetermined subframe.

In the above embodiment, one frame is divided into four sub-frames having a light emission luminance ratio of 1: 2: 4: 8, and each sub-frame is selected to display 16 gradations. I was getting it. However, the organic EL display device of the present invention can display an image having an arbitrary number of gradations of three or more. For example, when displaying 2 ⁿ gradations, one frame is divided into n sub-frames, and the ratio of the light emission amount of the organic EL element 11 in each sub-frame is 1: 2: 4:. ^n-1 (n is an integer of 1 or more). In addition, whether to selectively emit light from the pixel in each sub-frame is determined in the same manner as in the above-described embodiment.
What is necessary is just to determine based on the gradation value of the pixel binary-displayed.

In the above embodiment, the organic EL elements 11 are sequentially arranged from the first sub-frame in one frame.
The light emission amount was gradually increased. However, the subframe having the largest light emission amount may be displayed first, or the subframe having the largest light emission amount may be displayed next to the subframe having the smallest light emission amount.

In the above-described embodiment, the common driver 5 supplies the common signal from the end of the writing of the light emission signal IMG to the gate of the driving transistor 12 until the start of the writing of the light emission signal IMG of the next subframe. Z1 to Zn were applied to the anode electrode 11c of the organic EL element 11. That is, the light emission period of the organic EL element 11 in one sub-frame was substantially one sub-frame period. However, the light emission period of the organic EL element 11 can be set arbitrarily. Further, the brightness of the image displayed on the organic EL panel 1 may be adjusted by allowing the user to set the light emission period of the organic EL element 11.

In the above embodiment, one frame is constituted by one field without performing interlaced scanning. However, the present invention can be applied to a case where one frame is composed of a plurality of fields.
In this case, the operation in the above embodiment may be performed by replacing the frame with a field and the subframe with a subfield.

In the above embodiment, an image signal obtained by dividing one frame into subframes is displayed as it is without thinning. However, in the present invention, when the number of gradations of a display image is increased, a period of writing data from the drain driver to the gate of the driving transistor
In addition, the period of selective light emission of the organic EL element by the common driver may not be sufficiently obtained. In such a case, the image signal is thinned out based on a predetermined rule to reduce the organic EL.
It may be displayed on the panel. At this time, one frame may be divided into a plurality of fields.

In the above-described embodiment, the voltage corresponding to the light emission signal IMG for each pixel in each subframe is held in the capacitor Cp or the data holding capacitor 53. On the other hand, a configuration in which a memory transistor in which a gate insulating film is doped with an impurity is used as a driving transistor and a capacitor or a data holding capacitor is not provided may be employed.

In the above embodiment, a full-color image is displayed by arranging the organic EL elements 11 having the light emitting layers of R, G, and B in a predetermined order on the organic EL panel 1. An organic EL display device was configured. Instead of using three types of organic EL elements, an organic EL element having a light emitting layer that emits white light including all of R, G, and B light, and a color filter of three colors of R, G, and B are used. May be used. Further, organic EL elements having light-emitting layers of the same color are arranged in a matrix and can be used for an organic EL display device that displays a monochrome image with light and dark colors. In this case, the image signal may be extracted based on only the luminance signal in the video signal.

In the above embodiment, the case where the present invention is applied to an organic EL display device using an organic EL element as a light emitting element of each pixel has been described. However, the present invention can be applied to all kinds of display devices in which each pixel includes a selection transistor, a driving transistor (and a data holding capacitor), and a light emitting element, such as an inorganic EL display device. . When the light-emitting element is formed of an AC-driven inorganic EL element, the polarity may be inverted for each frame.

[0110]

As described above, according to the present invention,
Light emission / non-light emission of each light emitting element is determined in one subfield, and there is no variation in luminance of the light emitting element that emits light. For this reason, when the images are visually combined to form an image of one field, the light amount of the pixels of the same gradation becomes substantially constant. Therefore, the image quality is improved. Further, there is no variation in display for each of a plurality of display panels produced.

In the present invention, when the writing of data to the data holding means is completed, a predetermined voltage is applied to the light emitting element from the voltage driving means. Therefore, variation in propagation delay in light emission of each light emitting element is reduced, and the entire display panel can emit light uniformly.

The voltage driving means applies a predetermined voltage to the other electrode of the light emitting element until the selection driving means next selects and turns on the second switch of the row corresponding to the light emitting element. The organic EL element can emit light for approximately one sub-frame period. For this reason, an image can be displayed most efficiently on the organic EL panel.

Further, by forming the electrodes on the side to which the voltage from the voltage driving means of the light emitting element is applied in units of each row and having the same width in the row direction, the individual electrodes are connected by wiring. Can also lower the resistance value. For this reason, regardless of the length of the distance from the voltage driving means, a voltage of substantially the same level can be applied to the electrode of the light emitting element, so that each light emitting element can emit light of substantially the same brightness. Become.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an organic EL display device according to an embodiment of the present invention.

FIG. 2 is a characteristic diagram of an organic EL element used for an organic EL panel of the organic EL display device of FIG.

FIG. 3 is a plan view showing a structure of one pixel of the organic EL panel of FIG. 1;

FIG. 4 is a sectional view taken along line AA of FIG. 3;

FIG. 5 is a block diagram illustrating a configuration of a controller of the organic EL display device of FIG. 1;

FIG. 6 is a block diagram illustrating a configuration of a controller of the organic EL display device of FIG. 1;

FIG. 7 is a block diagram illustrating a configuration of a drain driver of the organic EL display device of FIG. 1;

FIG. 8 is a timing chart showing an operation in the organic EL display device according to the embodiment of the present invention.

FIG. 9 is a timing chart showing an operation in the organic EL display device according to the embodiment of the present invention.

FIG. 10 is an equivalent circuit diagram of an organic EL panel used in an organic EL display device according to a second embodiment of the present invention.

FIG. 11 is a timing chart showing an operation in the organic EL display device according to the second embodiment of the present invention.

FIG. 12 is an equivalent circuit for one pixel of an organic EL panel used in an organic EL display device according to a third embodiment of the present invention.

13 is a cross-sectional view illustrating a configuration for one pixel of the organic EL panel in FIG.

FIG. 14 is a cross-sectional view showing a configuration for one pixel of a conventional organic EL panel.

15 is a characteristic diagram of a driving transistor used in the organic EL panel of FIG.

[Explanation of symbols]

1 ... organic EL panel, 2 ... controller, 2a ...
R, G, B extraction circuit, 2b A / D converter, 2c correction circuit, 2d table storage unit, 2e image signal storage unit, 2f emission light output unit .., 2g... Synchronization signal extraction circuit, 2i... Crystal pulse oscillator, 2j... Reference clock generation circuit, 2k... Gate control signal generation circuit, 21... Drain control signal generation circuit, 2m.・ Common control signal generation circuit, 3 ・ ・ ・ Gate driver, 4 ・ ・ ・ Drain driver, 5
... Common driver, 11 ... Organic EL element, 11a ...
Cathode electrode, 11b: organic EL layer, 11c: anode electrode, 12: driving transistor, 12a: gate electrode, 12b: source electrode, 12c: drain electrode,
13 ... selection transistor, 13a ... gate electrode, 1
3b ... drain electrode, 13c ... source electrode, 41 ...
Shift register, 42 latch circuit, 43 latch circuit, 44 level conversion circuit, 51 organic EL element, 5
1a: anode electrode, 51b: organic EL layer, 51c ...
.Cathode electrode, 52... Driving transistor, 53.
Data holding capacitor, 54 ... selection transistor,
Cp: capacitor, GL: gate line, DL: drain line, CL: common line, SL: reference voltage line

Claims (11)

[Claims] 1. A plurality of light-emitting elements arranged in a matrix and a plurality of first light-emitting elements each having one end connected to one electrode of each of the light-emitting elements and a reference voltage applied to the other end.
And a display panel including a plurality of second switches for writing data for turning on / off each of the first switches to the first switch. An image of one field is displayed on a floor of an image in one field. An image processing unit that divides the image into sub-field images each composed of a gradation image according to a tone, a selection driving unit that sequentially selects the second switches in a row of the matrix, and the image processing unit. Data driving means for outputting data for turning on / off the first switch via the second switch selected in each subfield in accordance with an image for each divided subfield; and the matrix The other of the light emitting elements connected to the other electrode of the light emitting element for each row and corresponding to the second switch of the row selected by the selection driving means A voltage driving means for applying a predetermined voltage determined for each of the sub-fields to the electrodes of the display device. 2. A plurality of light emitting elements arranged in a matrix and having a reference potential applied to one of a pair of electrodes, and a plurality of light emitting elements having one end connected to each other electrode of the light emitting element. A first switch, a plurality of second switches for writing data for turning on / off each first switch into the first switch, and an image of one field in one field. Image processing means for dividing the image into sub-field images each composed of a gradation image according to the gradation of the image; selection driving means for sequentially selecting the second switches in the rows of the matrix; A data for turning on / off the first switch via the second switch selected for each subfield according to the image for each subfield divided by the processing means. Data drive means for outputting data, and the first drive means connected to the other end of each of the plurality of first switches for each row of the matrix and corresponding to the second switch of the row selected by the selection drive means. A display device comprising, at the other end of the switch, voltage driving means for applying a predetermined voltage determined for each subfield. 3. The first switch comprises a transistor which is turned on / off in accordance with data, wherein the on resistance of the transistor is sufficiently smaller than the resistance of the light emitting element, and the off resistance of the transistor is: The display device according to claim 1, wherein the display device is sufficiently larger than a resistance of the light emitting element. 4. The image of one field is an image of 2 ⁿ gradations, the image processing means divides the one field into n sub-fields, and the voltage driving means is In each of the n subfields, the ratio of the light emission amount of the light emitting element is 2 ⁰ : 2 ¹ : ·.
..: Applying a predetermined voltage of 2 ^n-1 to the other electrode of the light emitting element, wherein n is an integer of 1 or more. The display device according to claim 1. 5. An image conversion means for converting an image of each light emitting element in one field into data comprising a plurality of digits corresponding to each of the subfields, according to a gradation. And an image determination unit that supplies data for turning on and off the second switch to the data driving unit in each of the subfields according to a value of each digit of the data including the plurality of digits. The display device according to any one of claims 1 to 4, wherein: 6. The display device according to claim 5, wherein the data composed of a plurality of digits converted by the image conversion means is a binary number. 7. The display device according to claim 5, wherein the data supplied by said image determining means is supplied to said data driving means for each row for each subfield. 8. The voltage driving means, wherein for each of the other electrodes of the light emitting elements in each row, the selection driving means again selects the second switch in the row corresponding to the light emitting elements in the next subfield. The display device according to any one of claims 1 to 7, wherein the predetermined voltage is applied until the operation is performed. 9. The device according to claim 1, wherein the other electrode of each of the plurality of light emitting elements is formed in common with the same width in the row direction for each row of the matrix. 9. The display device according to any one of claims 1 to 8. 10. The display device according to claim 1, wherein each of said light emitting elements is constituted by an organic electroluminescence element. 11. A plurality of light emitting elements arranged in a matrix, a plurality of first switches each having one end connected to one electrode of each of the light emitting elements, and a plurality of first switches. A plurality of second switches for turning on / off each of the plurality of light emitting elements, a reference voltage is applied to one of the other electrodes of the plurality of light emitting elements or the other end of the plurality of first switches, A driving method of a display device having a display panel in which the other electrode of the light emitting element or the other end of the plurality of first switches is connected to each row, and is displayed on the display panel. 1 field image
An image processing step of dividing the image into sub-field images composed of images of the respective gradations according to the gradation of the image in the field; and a selection driving step of sequentially selecting the second switches in the rows of the matrix. And the second selected for each subfield according to the image for each subfield divided in the image processing step.
A data drive step of outputting data for turning on / off the first switch to the other switches, and the other electrodes of the plurality of light emitting elements or the first electrodes of the plurality of first switches connected for each row. A voltage driving step of applying a predetermined voltage determined for each of the sub-fields to the other of the other ends.