JPH11327506A - Driving circuit for el display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To keep the display quality of an EL display device by making luminance of respective pixels uniform even when pixels having different areas are included as a light emitting part in the device. SOLUTION: In an EL display device 8, organic layers are laminated between transparent electrodes and metallic electrodes to form pixels as a light emitting part and pixels having different areas are included in the device. Correction data in accordance with respective areas of the pixels of the device 8 are stored in a luminance correction data storage part 14B. A scan output circuit 15 successively scans the metallic electrodes and an arithmetic control circuit 16 reads out correction data of the respective pixels made to correspond to display data stored in a display data storage part 14A from the luminance correction data storage part 14B. In a data outputting part 17, an input voltage is varied for every transparent electrode in synchronization with the scan output circuit 15 by the read out correction data. Then, current values between the electrodes are varied for every pixel by making the energizing time of the current flowing between the electrodes constant.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of forming an organic layer comprising an organic compound such as a hole transport layer and a light emitting layer in a predetermined display pattern between a pair of electrodes at least one of which is made of a transparent conductive material. And a driving circuit for the electroluminescent display device (hereinafter referred to as an EL display device).

[0002]

2. Description of the Related Art An organic electroluminescence device (hereinafter, referred to as an organic EL device) has a structure in which a thin film containing a fluorescent organic compound is sandwiched between a cathode electrode and an anode electrode, and electrons and holes are formed on the thin film. An exciton is generated by injection and recombination, and the device utilizes light emission (fluorescence / phosphorescence) when the exciton is deactivated.

FIG. 4 is a side sectional view showing a schematic configuration of an EL display device using an organic EL element. In the EL display device shown in FIG. 4, a transparent electrode 32 made of ITO (Indium Tin Oxide) is formed on a glass substrate 31 having an insulating property and a light transmitting property. On the transparent electrode 32, an organic layer 33 of an organic phosphor thin film is laminated. The organic layer 33 has a two-layer structure formed on the transparent electrode 32 in the order of the hole transport layer 33A and the light emitting layer 33B, and forms a pixel 34 forming a light emitting part. Al, Ag, Mg: A on the light emitting layer 33B.
g, a metal electrode 35 of Al: Li or the like is laminated.

In the EL display device, a voltage is applied between the electrodes 32 and 35 using the transparent electrode 32 as an anode electrode to flow a constant current. Thereby, each electrode 3 is applied to the organic layer 33.
Electrons and holes are injected from 2,35. Then, the injected electrons and holes recombine to generate excitons, and a desired display is performed by emission of light when the excitons are deactivated. Light emission at that time is observed from the glass substrate 31 side via the transparent electrode 32.

[0005]

By the way, in the above-mentioned EL display device, in order to obtain a uniform luminance and to compensate for the aging of the element, the EL display device is driven with a constant current of each pixel. However, in a configuration in which display is performed by combining pixels having different areas, when driven at a constant current, the luminance becomes inversely proportional to the light emitting area, and uniform luminance cannot be obtained.
There is a problem that display quality is impaired. Further, the same problem as described above has also occurred when pixels have different emission colors or pixels have different emission efficiencies.

Therefore, the present invention has been made in view of the above problems, and even if the pixel area, light emission color and light emission efficiency are different, the brightness of each pixel can be made uniform and the display quality can be maintained. It is an object of the present invention to provide a driving circuit for an EL display device that can be used.

[0007]

In order to achieve the above object, according to the first aspect of the present invention, at least one of the electrodes is made of a light-transmitting member so that pixels 6A and 6B having different areas are formed as light-emitting portions. An organic layer 5 is formed between the two electrodes 2 and 7, and a voltage is applied using one of the electrodes 2 as an anode, and a constant current flows between the two electrodes 2 and 7 to perform EL. The drive circuit 11 of the display device includes a luminance correction data storage unit 14B in which correction data corresponding to the area of each of the pixels 6A and 6B is stored, and the correction data of each of the pixels 6A and 6B corresponding to the display data is stored in the luminance data. The current value between the electrodes 2 and 7 is variably controlled for each of the pixels 6 based on the correction data read out from the correction data storage unit 14 </ b> B, based on the read correction data, while keeping the current flowing between the electrodes 2 and 7 constant. And wherein the Rukoto.

According to a second aspect of the present invention, the organic layer 5 is provided between the two electrodes 2 and 7 of which at least one electrode is made of a light-transmitting member so that the pixels 6A and 6B having different areas are formed as the light emitting portion. In the drive circuit 11 of the EL display device, which is formed by laminating and applying a voltage by using one of the electrodes 2 as an anode and flowing a constant current between the two electrodes 2 and 7 to perform a desired display, the pixels 6A and 6B A brightness correction data storage unit 14B in which correction data corresponding to each area is stored;
The correction data of each of the pixels 6A and 6B corresponding to the display data is read from the brightness correction data storage unit 14B, and based on the read correction data, the current value flowing through each of the pixels 6A and 6B is set to be constant, and the electrodes 2 and 6B are fixed. The current supply time of the current flowing between the pixels 7 is variably controlled for each of the pixels 6A and 6B.

In the driving circuit 11 of the EL display device according to claim 1 or 2, the correction data includes data corresponding to the area of the pixels 6A and 6B, data corresponding to the emission color of the pixels 6A and 6B, and the pixel 6A. , 6B according to luminous efficiency,
Alternatively, it may be data based on a combination of these.

[0010]

FIG. 1 is a plan view showing an example of the configuration of an EL display device employing a drive circuit according to the present invention, FIG. 2 is a partially enlarged side sectional view of FIG. 1, and FIG. FIG. 3 is a block diagram illustrating an embodiment of a drive circuit of the display device.

The EL display device shown in FIG. 1 is based on a rectangular element substrate 1. The element substrate 1 is formed of a glass substrate having an insulating property and a light transmitting property. On the surface of the element substrate 1, a transparent electrode 2 made of a translucent member such as ITO is formed with a substantially uniform thickness by an etching method, a max deposition method, or the like. The transparent electrodes 2 in FIG. 1 are formed in a matrix of two rows and three columns by three transparent electrodes 2A in the upper row and three transparent electrodes 2B in the lower row. Each transparent electrode 2A, 2
B is a data output circuit 17 of the drive circuit 11 which will be described later.
It is connected to the.

As shown in FIGS. 1 and 2, on the transparent electrode 2, a high-resistance insulating layer 3 made of, for example, baked epoxy resin, frit glass, or organic silica compound is laminated in a square shape. . The insulating layer 3 includes the transparent electrodes 2A and 2A.
It is patterned with a penetrating portion 4 cut out in the shape of B.

The insulating layer 3 is formed with a substantially uniform thickness by a printing method, a mask evaporation method, an etching method, or the like. Specifically, in addition to extracting SiN or SiO ₂ into a desired pattern shape by an etching method, frit glass or an organic silica compound is printed in a desired pattern shape and baked, or a heat-resistant photosensitive resin is formed by a photolithography method. The insulating layer 3 is formed by patterning into a predetermined pattern shape.

As shown in FIG. 2, an organic layer 5 is formed on the transparent electrode 2 so as to fill the through portion 4 of the insulating layer 3. The organic layer 5 shown in FIG.
And a light-emitting layer 5B made of an organic compound.
A and the light emitting layer 5B are stacked in this order.

The organic layer 5 in which the penetrating portions 4 of the insulating layer 3 are filled
Form the pixel 6 forming the light emitting portion. In the example of FIG. 1, the three pixels 6A in the upper row are formed in a square shape having a side length a. The three pixels 6B in the lower row are formed in a rectangular shape having an area twice the area of the pixels 6A in the upper row. Then, when the organic layer 5 emits light, the display by the shape of the pixel 6 can be observed from the element substrate 1 side.

In the case where the light emitting layer 5B itself emits light, for example, aluminum quinoline (Alq) or a distilylene-based compound is used as the light emitting material of the light emitting layer 5B. Another light emitting material (dopant) is used for the light emitting layer 5B.
When light is emitted by doping a small amount of quinacridone (Qd), a dye for laser or the like is used as a dopant.

As shown in FIG. 1, a metal electrode 7 (7) is formed on the light emitting layer 5B so as to cover the pixels 6A and 6B of each column.
A, 7B) are laminated. The metal electrode 7 is
1, Ag, Mg: Ag, Al: Li, etc., and is formed with a substantially uniform thickness by an etching method, a mask evaporation method, or the like. Each of the metal electrodes 7A and 7B is connected to a scan output circuit 16 of the drive circuit 11 described later.

A sealing substrate 9 as a sealing member is fixed to the outer peripheral portion of the element substrate 1 with an adhesive in an atmosphere of an inert gas (eg, dry nitrogen) or dry air from which water has been removed as much as possible. Thereby, both the electrodes 2 and 7 and the organic layer 5 are protected, and a high-definition organic EL display device is realized.

As another configuration of the EL display device, a configuration in which the transparent electrode 2 and the metal electrode 7 are reversed may be employed. In that case, since the element substrate 1 does not necessarily need to have a light-transmitting property, the element substrate 1 can be formed using a glass substrate having an insulating property. Further, as the electrodes 2 and 7, at least one of the electrodes may be formed of a translucent member.

In the EL display device having the above configuration, a desired display is performed by applying a voltage with one electrode (for example, a transparent electrode) as an anode and flowing a constant current between each transparent electrode 2 and the metal electrode 7. .

A drive circuit 11 for driving the EL display device at a constant current includes a timing signal generation circuit 12, a data control unit 13, a storage unit 14 including a display data storage unit 14A and a luminance correction data storage unit 14B, and a scan output circuit. 1
5, an arithmetic control circuit 16 and a data output circuit 17.

The timing signal generating circuit 12 sequentially scans the metal electrodes 7 in units of columns, and in synchronization with the scanning, inputs a data signal to each transparent electrode 2 so that a desired display can be performed. , A predetermined timing signal to each of the storage unit 14, the scan output circuit 15, and the arithmetic control circuit 16.

The data control section 13 outputs display data (for example, data for displaying English characters "T", "I", "L", etc.) sequentially input from the outside to the timing generation circuit. The data is chronologically fetched in response to the timing signal from the memory 12 and stored in the display data storage unit 14A.

The luminance correction data storage section 14B stores luminance correction data corresponding to the area of each pixel 6 in a table format. More specifically, a voltage level to be applied to a pixel having a predetermined area is determined in advance as reference data, and correction data based on a voltage level corresponding to the area of each pixel 6 is stored in a table format based on the reference data.

Alternatively, a pulse width of a voltage to be applied to a pixel having a predetermined area is determined in advance as reference data, and correction data based on a voltage level corresponding to the area of each pixel 6 is stored in a table format based on the reference data. ing.

The scan output circuit 15 sequentially scans the metal electrodes 7A and 7B of the EL display device in units of columns in accordance with a timing signal from the timing generation circuit 12. In the example of FIG. 1, the upper row of three metal electrodes 7A and the lower row of three metal electrodes 7B are selectively scanned in this order.

The operation control circuit 16 receives a timing signal from the timing generation circuit 12 and displays the data in the display data storage unit 14.
The correction data for each pixel 6 corresponding to the display data read from A is read from the brightness correction data storage unit 14B and output to the data output circuit 17.

Here, when the configuration in which the correction data based on the voltage level is stored in the luminance correction data storage section 14B is adopted, the level of the input voltage of the driver circuit of the data output circuit 17 is changed by the read correction data. The output current flowing between each transparent electrode 2 and the metal electrode 7 is varied according to the area of each pixel 6. The energization time at that time is constant. For example, if the voltage level of the correction data input when the pixel 6A emits light is used as the reference data and the output current at that time is 5 mA / cm ² , the current is twice as long as the pixel 6A. When the pixel 6B having an area emits light, a voltage having a level twice as high as the reference data is input to the data output circuit 17,
The output current becomes 10 mA / cm ² .

On the other hand, the brightness correction data storage section 14B
When the configuration in which the correction data based on the pulse width is stored is adopted, the pulse width of the input voltage of the driver circuit of the data output circuit 17 is varied by the read correction data, and each transparent pixel is changed according to the area of each pixel 6. Electrode 2 and metal electrode 7
And the duration of the output current flowing between them. For example, the pulse width of the correction data input when the pixel 6A emits light is used as the reference data, and the output current at that time is 5 m.
A / cm ² , a pixel 6B having an area twice as large as the pixel 6A
, A voltage having a pulse width twice as large as the reference data is input to the data output circuit 17, and the output current is 10 mA / cm ² .

The data output circuit 17 outputs a data signal for turning on / off each pixel 6 in synchronization with the scan output circuit 15. More specifically, the data output circuit 17
Is composed of a driver circuit provided with constant current drive transistors by the number of transparent electrodes 2. Then, as described above, the data output circuit 17 controls the input voltage so that an output current corresponding to the correction data from the arithmetic and control circuit 16 is obtained, and a constant current corresponding to the area is applied to each transparent electrode 2 and the metal. It flows between the electrode 7.

As described above, according to the EL display device of the present embodiment, even if the light emitting portion is formed by the pixels 6 having different areas, the average values of the current densities of the pixels 6 are made equal to each other. Brightness can be made uniform and display quality can be maintained.

In the above-described embodiment, the organic layer 5 has a two-layer structure of the hole transport layer 5A and the light emitting layer 5B. However, the organic layer 5 is formed of the light emitting layer and the charge transport layer. It may be constituted by a combination with a layer (a hole transport layer, a hole injection / transport layer, an electron injection layer, an electron injection / transport layer, etc.). Specifically, it is composed of only one light-emitting layer, two layers of a light-emitting layer and a hole transport layer, two layers of a light-emitting layer and an electron injection layer, and three layers of a hole transport layer, a light-emitting layer, and an electron injection layer. You.

The electron injecting layer is preferably made of a single metal material having a small work function, such as Li, Na, Mg, Ca, etc., or Al: L, for example, to facilitate electron injection.
An alloy having a small work function such as i, Mg: In, or Mg: Ag is used.

The pattern of the pixel 6 in the EL display device is not limited to the illustrated one, and the shape, area, and number of the pixel 6 can be arbitrarily formed according to the display mode.

In the above embodiment, an example in which two types of pixels 6A and 6B having different areas are provided as an EL display device has been described. However, an EL display device including pixels having different emission colors and pixels having different luminous efficiencies is described. Even in this case, the same effect as described above can be obtained. In that case, the brightness correction data storage unit 14B
In the table, the luminance correction data for each light emission color or light emission efficiency of each pixel 6 is stored in a table format for each pixel 6.

More specifically, the brightness correction data storage unit 1
In 4B, a voltage of a level or a pulse width to be applied for each emission color or emission efficiency of the pixel 6 is stored as correction data. Then, the pixels 6A and 6B having different areas described above are used.
As in the case of emitting light, the output of the data output circuit 17 is controlled by the correction data corresponding to the display data so that the current density corresponds to the luminance required for each pixel 6. As a result, a constant current corresponding to the required luminance is supplied between each transparent electrode 2 and the metal electrode 7.

In addition, the above-described area, emission color, and voltage level or pulse width to be applied for each luminous efficiency of the pixel 6 are stored in the luminance correction data storage unit 14B as correction data in a table format for each pixel. The output of the data output circuit 17 may be controlled by the correction data corresponding to the display data. Note that the correction data may be data of a voltage level or a pulse width according to a combination of the area of the pixel 6, the emission color, and the emission efficiency.

[0038]

As is apparent from the above description, according to the present invention, even if the pixel area, emission color, and emission efficiency are different,
The average value of the current density of each pixel can be made equal so that the brightness of each pixel can be made uniform and the display quality can be maintained.

[Brief description of the drawings]

FIG. 1 is a plan view showing one configuration example of an EL display device employing a drive circuit according to the present invention.

FIG. 2 is a partially enlarged side sectional view of FIG. 1;

FIG. 3 is a block diagram showing an embodiment of a driving circuit of an EL display device according to the present invention.

FIG. 4 is a side sectional view showing a schematic configuration of an EL display device using an organic EL element.

[Explanation of symbols]

2: transparent electrode, 5: organic layer, 6: pixel, 7: metal electrode,
11 ... Drive circuit, 14A ... Display data storage unit, 14B ...
Brightness correction data storage unit.

Claims (4)

[Claims] An organic layer is formed between two electrodes, at least one of which is made of a light-transmitting member, so that pixels having different areas are formed as a light-emitting portion. A driving circuit of an EL display device for applying and applying a constant current between the two electrodes to perform a desired display, comprising: a luminance correction data storage unit in which correction data corresponding to an area of each of the pixels is stored; The correction data of each pixel corresponding to the display data is read from the brightness correction data storage unit, and based on the read correction data, the current value between the electrodes is set for each of the pixels while keeping the current flowing between the electrodes constant. A driving circuit for an EL display device, wherein the driving circuit is variably controlled. 2. An organic layer is formed by laminating at least one electrode between two electrodes made of a light-transmitting member so that pixels having different areas are formed as light-emitting portions. A driving circuit of an EL display device for applying and applying a constant current between the two electrodes to perform a desired display, comprising: a luminance correction data storage unit in which correction data corresponding to an area of each of the pixels is stored; The correction data of each pixel corresponding to the display data is read from the brightness correction data storage unit, and based on the read correction data, the current flowing through the electrodes is determined by setting a current value flowing through each of the pixels to be constant. A driving circuit for an EL display device, wherein the driving circuit performs variable control for each pixel. 3. The driving circuit for an EL display device according to claim 1, wherein the correction data comprises data corresponding to the emission color of the pixel. 4. The driving circuit for an EL display device according to claim 1, wherein the correction data comprises data corresponding to the luminous efficiency of the pixel.