KR100864758B1 - Full color organic electroluminescence device - Google Patents

Abstract

The present invention relates to a full color organic electroluminescence (EL) device in which white light balance is achieved, and an organic light emitting layer corresponding to each color of red (R), green (G), and blue (B) in a full color organic EL device. The present invention has a feature in that the white light balance is adjusted by adjusting the electron transporting capacity ratio of each light emitting layer by changing the thickness of the electron transporting layer formed on the upper surface or by changing the light emitting area.

Description

Full color organic electroluminescence device

1 is a plan view of a lower substrate of a full color organic EL device;

2 is an enlarged cross-sectional view of a portion of the pixel of FIG. 1.

<Description of Symbols for Major Parts of Drawings>

10: lower substrate 12: positive electrode

14 hole injection layer 16 hole transport layer

18: light emitting layer 20: electron transport layer

22 electron injection layer 24 negative electrode

26: negative electrode wiring 28: power supply

30: positive electrode wiring

e: injected electron h: injected hole

The present invention relates to a full color organic electroluminescence (EL) device in which white light balance is achieved, and more particularly, on an organic emission layer corresponding to each color of red (R), green (G), and blue (B). The present invention relates to an organic EL device having a white light balance by adjusting the electron transport ability ratio of each light emitting layer by varying the thickness of the formed electron transporting layer or by varying the light emitting area.

In recent years, the organic EL device attracting great attention is a device for obtaining an electroluminescence wavelength of a new region which does not appear in each material by stacking two or more organic light emitting materials having different band gaps. In this case, the emission wavelength of the new region is that energy emitted when electrons and holes meet and recombine in an organic layer called an emission layer is converted into light.

The organic EL device began to be studied in the 1960s, and in 1987, Eastman Kodak, in order to balance the injection of electrons and holes into the light emitting organic material layer, lowering the thickness of the organic layer to 2000 Å or less, which is practically 10V or less. After successfully achieving low voltage driving, high efficiency and high brightness (Appl. Phys. Lett., 51, 913 (1987), US Patent Nos. 4,356,429, 4,539,507, 4,720,432, 4,885,211), It began to be reviewed in earnest. Subsequently, in 1993, Japan produced three colors of red (R), green (G), and blue (B) simultaneously, resulting in white light close to natural light, high brightness, low power consumption, and long life of the device. EL devices are greatly expected as next-generation flat panel displays replacing liquid crystals.

FIG. 1 is a schematic view showing a basic configuration of a general organic EL device. The organic EL device generally includes a positive electrode 12, a hole injection electrode, and a hole injection layer 14, on a lower substrate 10 of a transparent material. Layer, Hole Transporting Layer 16, Emitting Material Layer 18, Electron Transporting Layer 20, Electron Injection Layer 22 and Electron Injection The negative electrode 24 as an electrode has a light emitting structure in which the electrodes are sequentially stacked.

In this case, electron and hole injection to the light emitting layer should be easy, and in order to facilitate electron injection, an electron injection layer having a low work function is used between the electron transport layer and the metal layer, which is the negative electrode. Generally, glass, quartz, or a flexible plastic or film is mainly used as the material of the positive electrode 12, and Ca, Mg, Al, or the like, which is a metal having a small work function, is used as the material of the negative electrode 24. As the material of the organic light emitting layer 18, a monomolecular organic compound such as Alq ₃ or anthracene or a high molecular organic compound such as PT (polythiophene) is used. As the electron transport layer 20, an oxidazole derivative or the like is mainly used. Al-Li is used as the electron injection layer, and research results on alkali metals having a low work function have been published. The conditions that the metal doped layer should have are excellent in adhesion with the organic material, and should not penetrate the organic material itself while preventing the negative electrode material aluminum from penetrating into the organic material. All of these materials are deposited using a vacuum deposition method.

Here, referring to the operation of the organic EL device, when a positive voltage is applied to the positive electrode 12 and a negative voltage is applied to the negative electrode 24, holes h are injected from the positive electrode 12, and a negative electrode ( At 24, electrons (e) are injected so that holes (h) pass through the hole injection layer (14) and the hole transport layer (16), and electrons (e) pass through the electron injection layer (22) and the electron transport layer (20). At (18), electrons (e) and holes (h) meet and emit light by recombination, and emit light of different wavelengths depending on the material of the light emitting layer, that is, the position of recombination and the material of the organic material. . At this time, due to the difference in the band gap between the electron and the hole, the hole in the light emitting layer cannot pass over the electron transport layer, and the electron cannot pass over the hole transport layer, thus increasing the recombination efficiency in the light emitting layer, thereby increasing the number of electrons / holes that contribute to light emission. More and uses the principle of increasing external efficiency.

In particular, the organic EL display panel including the organic EL device is expected to be applied to a color display device. To this end, the organic light emitting display device uses white light, red (R), green (G), and blue (B) using the light emission principle. A full color display should be manufactured, and a plan view of the lower substrate of the full color organic EL device is shown in FIG. 1.

Meanwhile, in order to reduce the manufacturing cost when fabricating a full color device, the hole injection layer, the hole transport layer, the electron transport layer, and the metal layer are vacuum deposited in common to RGB, and only the light emitting layer is deposited on RGB, respectively. In the deposition method, a metal shadow mask is used to shift while shifting in steps of RGB. In a full color device, each pixel size of RGB is the same, so that one light emitting organic layer is deposited and then one subpixel distance. Move by to deposit. In this way, each color light emitting layer of RGB can be formed, and a full color device can be manufactured.

However, when the red, green, and blue of the organic light emitting layer are turned on at the same time, if the white standards are 0.30 and 0.32, the luminance should be displayed in a ratio of about 1: 2.5: 1.1. Normally, white in displays such as CRTs and LCDs is represented by 0.281, 0.311 to 0.311, 0.312. At this time, the luminance ratio of red, green, and blue is about 2: 7: 1 or 3: 6: 1, but the luminance ratio is also different because the color purity of each color of the organic phosphor is different from the CRT. However, the difference in RGB luminous efficiency is approximately 0.3: 2.5: 0.6. That is, when the same voltage is applied due to the red luminous efficiency deterioration, the white light is not balanced and does not show the true color. In order to compensate for this, a larger current must be injected into the red light emitting efficiency, and in order to flow a larger current, more voltage must be applied only to the red data line in RGB. This will eventually balance the white light, but will apply a greater voltage to the red, resulting in a shorter lifetime of the red light emitting material than other colors. In other words, since the life of the shortest color becomes the life of the device, the application of a large voltage is fatal to the life of the display device. In addition, since the voltage applied to each of the RGB is different, the price of the driving drive is increased, which increases the manufacturing cost of the display.

On the other hand, since the hole mobility speed and the electron mobility speed are about 100 times faster, it is important to facilitate electron injection into the light emitting layer.

Accordingly, the present inventors completed the present invention by adjusting the electron transport capacity ratio of each RGB to match the white light balance in order to solve the above problems.

An object of the present invention is to adjust the electron transporting capacity ratio of each light emitting layer by varying the thickness of the electron transporting layer formed on the organic light emitting layer corresponding to each of the colors of red, green and blue, or by varying the light emitting area so that white light balance can be achieved. It is to provide a full color organic EL device.

A feature of the present invention for achieving the above object is a plurality of cells are divided by color corresponding to red (R), green (G) and blue (B), the electron formed on the organic light emitting layer corresponding to each color In the thickness of the transport layer, the thickness of the electron transport layer formed on the red organic light emitting layer is formed to be thinner than the thickness of the electron transport layer formed on the green and blue organic light emitting layer.

In addition, a feature of the present invention is a full color organic EL device in which the area of the organic light emitting layer corresponding to red is larger than the area of the organic light emitting layer corresponding to green and blue, and the thickness of the red organic light emitting layer is thinner than the thickness of the green and blue organic light emitting layer. In the provided.

Hereinafter, the present invention will be described in more detail.

In the present invention, in the full-color organic EL device in which a plurality of cells are divided by colors corresponding to red (R), green (G), and blue (B), electrons formed on the organic emission layer corresponding to each color Provided is a full color EL device in which the thickness of the electron transport layer formed on the red organic light emitting layer is thinner than the thickness of the electron transport layer formed on the green and blue organic light emitting layer among the thicknesses of the transport layer. It is preferable that the thickness ratio of the electron carrying layer formed in the upper part of the organic light emitting layer corresponding to this is 2-3-3: 3.5-4.5: 2.5-3.5, and the electron carrying layer formed in the upper part of the said organic light emitting layer corresponding to red color is 200-300 GPa thick. It is preferable to form.

In addition, the present invention provides a full-color organic EL device in which the area of the organic light emitting layer corresponding to red is larger than the area of the organic light emitting layer corresponding to green and blue, wherein the light emitting area ratio of red: green: blue is 1.2 to 2.2. It is preferable that it is 1: 1.

Further, in the present invention, in the full-color organic EL device in which the area of the organic light emitting layer corresponding to red is larger than the area of the organic light emitting layer corresponding to green and blue as described above, the organic light emitting layer corresponding to red: green: blue A full color organic EL device having a thickness ratio of 1: 1: 1 is provided.

In addition, the present invention provides a full-color organic electroluminescent device, characterized in that the thickness of the red organic light emitting layer itself is thinner than the thickness of the green and blue organic light emitting layers.

It is preferable that the thickness ratio of the organic light emitting layer corresponding to the red, green, and blue is 2 to 3: 3.5 to 4.5: 2.5 to 3.5, and the organic light emitting layer corresponding to the red is preferably formed to have a thickness of 200 to 300 GPa.

On the other hand, in the present invention, the above-described structure, that is, a structure in which the thickness of the electron transport layer formed on the upper portion of the organic light emitting layer corresponding to each RGB color; A structure in which the area of the organic light emitting layer corresponding to each RGB color is changed; And a structure in which the thickness of the organic light emitting layer itself corresponding to each color of RGB may be separately included, or a combination thereof may be included.

As described above, the luminance ratio of RGB for representing white coordinates in a display is generally known to be about 2: 7: 1, or 3: 6: 1. However, the luminous efficiency of the RGB organic light emitting layer developed so far is about 0.4 lm / W in red, 3.5 lm / W in green, and 0.8 lm / W in blue, between 12 to 15V, which is the panel operating voltage range. Compared with this other color, it is very low and it is very difficult to match white.

According to the present invention, in order to match the white light balance due to the difference in external light emission efficiency, that is, the difference in luminance ratio to the outside, the thickness of the electron transport layer on each of the light emitting layers of the RGB, the light emitting area, or the RGB organic light is different. By manufacturing the organic EL element of the structure which varied the thickness of the light emitting layer itself, or combined them, red light emission efficiency is improved and white light balance is matched. That is, the present invention adopts the above structure in order to improve the red light emission characteristics in consideration of the red light emission characteristics of the band gap is smaller than the green and blue, the red band gap is adopted when the above structure is adopted. By increasing to the same level as the green and blue band gap, the luminous efficiency of RGB is improved to a similar level, and ultimately white light balance can be achieved.

As described above, according to the present invention, in the full color organic EL device configuration, by adjusting the band gap of each organic light emitting layer such as varying the thickness of the electron transporting layer laminated on each of the RGB light emitting layers, By matching the external luminance ratio, it was possible to eventually balance the white light.

Meanwhile, the present invention is not limited to the above-described embodiments, but may be modified and modified within the scope not departing from the gist of the present invention, and the technical idea due to such modifications and variations is within the scope of the following claims. Should be seen.

Claims (10)

A plurality of cells are divided according to colors corresponding to red (R), green (G), and blue (B), and formed on the red organic light emitting layer above the thickness of the electron transport layer formed on the organic light emitting layer corresponding to each color. Full thickness organic electroluminescence device, characterized in that the thickness of the electron transport layer is formed thinner than the thickness of the electron transport layer formed on top of the green and blue organic light emitting layer. The method of claim 1, The thickness ratio of the electron transport layer formed on the organic light emitting layer corresponding to the red, green, and blue is 2 to 3: 3.5 to 4.5: 2.5 to 3.5 characterized in that the full-color organic electroluminescent device. The method of claim 1, Full-color organic electroluminescent device, characterized in that the electron transport layer formed on the organic light emitting layer corresponding to the red is formed to a thickness of 200 ~ 300 Å. The method of claim 1, In addition to the above structure, the area of the organic light emitting layer corresponding to red is formed to be larger than the area of the organic light emitting layer corresponding to green and blue. The method of claim 4, wherein The red: green: blue light emitting area ratio is 1.2 to 2.2: 1: 1, characterized in that the full-color organic electroluminescent device. delete delete delete delete delete

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