KR100712094B1 - Organic electroluminescent display device having good visual angle - Google Patents

Abstract

The present invention relates to an organic electroluminescent device, comprising: a substrate, a first electrode layer formed on the substrate, a hole injection layer formed on the first electrode layer, a first hole transport layer formed on the hole injection layer, and the first agent A second hole transport layer formed on the first hole transport layer and deposited to a thickness of 250 to 470 에 in a red region of the pixel region, a blue and green light emitting layer formed on the first hole transport layer, and the second hole A red light emitting layer formed on the transport layer and a second electrode layer formed on the light emitting layer for each pixel can be provided to ensure the emission of red light at a wide viewing angle of 60 degrees. A top-emitting organic electroluminescent device can be provided.

Active element type organic electroluminescent element, wide viewing angle, light path

Description

Organic electroluminescent device with excellent wide viewing angle {ORGANIC ELECTROLUMINESCENT DISPLAY DEVICE HAVING GOOD VISUAL ANGLE}

1 is a cross-sectional view showing an organic EL device having a conventional bottom emitting structure.

2 is a cross-sectional view showing an organic EL device having a conventional top emission structure.

3 is a cross-sectional view schematically showing the structure of an organic EL device according to an embodiment of the present invention.

4 is a graph of an organic electroluminescent device showing a change in luminance with respect to the wide viewing angle of the present invention manufactured by Example 1. FIG.

5 is a graph showing a change in luminance with respect to the wide viewing angle of the organic EL device manufactured by Comparative Example 1. FIG.

[Industrial use]

The present invention relates to an organic electroluminescent device, and more particularly, to an organic electroluminescent device for securing a wide viewing angle for each pixel.

[Prior art]

2. Description of the Related Art In general, an organic light emitting display device is an active light emitting display device, and has been attracting attention as a next generation display device because of its advantages of wide viewing angle, excellent contrast, and fast response speed.

The organic electroluminescent device is classified into an inorganic EL device and an organic EL device according to a material for forming an emitting layer. Herein, the organic EL device has an advantage of excellent luminance, driving voltage, and response speed characteristics, and multicoloring, in comparison with the inorganic EL device.

1 is a cross-sectional view showing an organic electroluminescent device of a conventional bottom emitting structure, and FIG. 2 is a cross-sectional view showing an organic electroluminescent device of a conventional top emitting structure.

1 and 2, in a general organic EL device, a first electrode layer 12 having a predetermined pattern is formed on a substrate 10. In the case of the bottom emission structure, the first electrode layer 12 is formed of a transparent electrode, and in the case of the front emission structure, the first electrode layer 12 is formed of a metal electrode and is formed of a two-layer structure including the transparent electrode 12 '.

The hole injection layer 14, the hole transport layer 16, the light emitting layer, and the hole are formed on the first electrode layer.

 The suppression layer 18, the electron transport layer 20, and the electron injection layer 22 are sequentially formed, and the upper surface of the electron injection layer 22 has a predetermined pattern in a direction orthogonal to the first electrode layer 12. The second electrode layer 24 is formed. Here, the hole injection layer 14, the hole transport layer 16, the light emitting layer, the hole suppression layer 18, the electron transport layer 20, and the electron injection layer 22 are organic thin films made of an organic compound.

Currently, RGB patterns, which are organic light emitting layers, are independently deposited using a fine metal mask (FMM) in top emission and bottom emission structures, and include hole injection layers, hole transport layers, hole suppression layers, electron transport layers, and electron injection layers. The common layer of is formed using an open mask regardless of the RGB pattern.

For example, when looking at the viewing angle of the 5-inch front emission Active Matrix Organic Light Emitting Device (AMOLED), there is a large difference in luminance and white balance at a viewing angle of 0 degrees and 60 degrees.

In particular, the red color indicates that the luminance difference according to the viewing angle between 0 degrees and 60 degrees is greater than the luminance difference according to the viewing angle of 0 degrees and 60 degrees of the blue color. This causes an imbalance in the display composition according to the viewing angle of the 5-inch full emission AMOLED.

In other words, at 60 degrees, the display will be bluish.

Referring to FIGS. 1 and 2, this indicates that the light emission of the bottom emission and the liquid crystal display device (LCD) is linear due to the light path (d), whereas the front emission is relatively small in the light path (d). In addition to light, it is caused by the emission of light according to the viewing angle.

In addition, since the refractive index and the thickness of the thin film are common depending on the total reflection conditions of the thin film, the wavelength bands are different for each RGB, so the short wavelength blue light is secured at the 60 degree viewing angle, thereby driving a bluish display at the 60 degree viewing angle.

Accordingly, there is a need to overcome the phenomenon in which a display becomes bluish by securing an optimal light path for each RGB at a 60 degree viewing angle in an AMOLED.

In such an organic EL device, many attempts have been made to obtain maximum efficiency and brightness by controlling the thickness of organic thin films. For example, Japanese Patent Laid-Open No. 4-137485 discloses a technique for improving the efficiency of light emission by setting the film thickness of the electron transporting layer to 30 to 60 nm in a configuration in which an anode, a hole transporting layer, a light emitting layer, an electron transporting layer, and a cathode are sequentially formed. Is disclosed.

In addition, Japanese Patent Laid-Open No. 4-328295 discloses a technique in which the luminance of light is substantially increased when the light generated in the light emitting layer and the light reflected from the cathode interfere with each other by adjusting the film thickness of the electron transport layer. In addition, Japanese Patent Laid-Open No. 7-240277 discloses an organic electroluminescent device in which the brightness is improved by controlling the optical film thickness, and in particular, the color purity of blue light emission is increased.

The organic EL device is set to have different optical thicknesses for each color in order to improve luminance. However, in the mass production process, it is difficult to form such that the optical thickness is different for each color by varying the overall process for each color.

The present invention has been made to solve the problems described above, an object of the present invention is that the emission efficiency of red does not decrease even if the viewing angle is changed from 0 to 60 degrees, the front emission organic light that can expand the wide viewing angle of red It is to provide an electroluminescent device.

The present invention to achieve the above object,

Board,

A first electrode layer comprising a metal formed on the substrate,

A first charge transport layer formed on the first electrode layer,

Blue, green, and red light emitting layers formed on the first charge transport layer and formed for each pixel of RGB, and

It includes a second electrode layer including a transparent conductive layer formed on the light emitting layer,

The distance between the red light emitting layer and the first electrode layer provides an organic electroluminescent device, characterized in that thicker by 250 to 470 비해 than the distance between the blue and green light emitting layer and the first electrode layer.

Hereinafter, with reference to the accompanying drawings of the present invention will be described in more detail.

3 is a cross-sectional view schematically showing the structure of an organic EL device according to an embodiment of the present invention.

Referring to FIG. 3, in the organic electroluminescent device of the present invention, the first electrode layer 12 is first formed on the semiconductor substrate 10.

The first electrode layer 12 includes a transparent electrode and a metal electrode, and as the metal electrode, one selected from the group consisting of Al, Al alloys, Ag, Ca, and Mg / Ag is used. 12 ') is preferably selected from the group having a good transmittance such as ITO and IZO and a good energy balance.

The first charge transport layer 16 is formed on the transparent electrode layer 12 ′.

The first charge transport layer is formed thicker by 16 'in the region corresponding to the red R of the pixel of the first charge transport layer.

As a result, the distance between the red light emitting layer R and the first electrode layer 12 is formed to be thicker by 250 to 470 Å as compared to the distance between the blue and green light emitting layer and the first electrode layer.

In this case, when the distance between the red light emitting layer R and the first electrode layer 12 is 250 mW or less or 470 mW or more, the electrical characteristics of the device are deteriorated, thereby making it impossible to implement a high-efficiency top-emitting organic light emitting device.

As a result, when the light corresponding to red (R) emits light, the light path (d ') is increased by the thickness of the second hole transport layer, so that the light path is larger than the conventional light path (d), and the red (R) The optical optimal light path of is implemented. Therefore, since the red light linearity is secured, light emission is secured even at a viewing angle of 60 degrees, thereby eliminating the phenomenon of bluish color at the viewing angle of 60 degrees.

The method of forming the distance between the red light emitting layer R and the first electrode layer 12 to be 250 to 470 mm thicker than the distance between the blue and green light emitting layers and the first electrode layer is further stacked in the red light emitting layer region. 'Is preferably formed by laminating the film to 250 to 470 mm 3, and in addition, the substrate or the first electrode layer may be formed thicker.

Meanwhile, the layers 16 and 16 ′, which constitute the first charge transport layer, may be the same material or may be different materials.

On the other hand, under or above the first charge transport layer 16, 16 ′, ie, between the first electrode layer 12 and the first charge transport layer 16, 16 ′ or the first charge transport layer 16, 16 ′. And a second charge transport layer 14 between the light emitting layer and the light emitting layer. Referring to FIG. 3, one embodiment of the present invention illustrates an example in which the second charge transport layer 14 is formed under the first charge transport layers 16 and 16 ′.

In the above embodiment, when the second charge transport layer 14 is formed below the first charge transport layer 16, the second charge transport layer 14 is laminated to a thickness of 200 to 300 kPa, and the first charge transport layer 16 are laminated to a thickness of 80 to 120 mm 3.

In addition, when the second charge transport layer 14 is formed on the first charge transport layers 16 and 16 ', 16 of the first charge transport layers are stacked to have a thickness of 200 to 300 kPa, and the second charge transport layer ( 14) is laminated to a thickness of 80 to 120 mm 3.

Charges of the first charge transport layer and the second charge transport layer in one embodiment of the present invention are holes.

The first charge transport layer 16, 16 ′ and the second charge transport layer 14 are formed of different materials, and the lower layer of the first charge transport layer 16. 16 ′ and the second charge transport layer 14 is phthalocyanine. Copper phthalocynine (CuPc) or 4,4 ', 4 "-tris (N- (3-methylphenyl) -N-phenylamino) triphenylamine (4,4', 4" -tris (N- (3- A commonly used material such as methylphenyl) -N-phenylamino) triphenylamine) (MTDATA) can be used, and the upper layer is N, N'-di (1-naphthyl) -N, N'-diphenylbenzidine (NPD). Or a commonly used substance such as PEDOT.

After the first and second charge transport layers are formed, the blue (B) and green (G) light emitting layer forming materials are formed in the upper pixel area of the first charge transport layer. In addition, the red (R) light emitting layer forming material is formed in the pixel area of the upper portion 16 'of the first charge transport layer.

As the light emitting material, a commonly used fluorescent light emitting material may be used, and the dopant may further include a fluorescent dopant or a phosphorescent dopant.

Then, the second electrode layer 24 is formed over the entire surface of the substrate. As the second electrode layer, it is preferable to use an electrode layer composed of a two-layer structure of an electrode layer formed independently or formed as a common layer over the entire substrate.

The electrode layer to be formed independently or formed into a common layer is made of an alloy electrode of Mg / Ag, and the electrode layer formed of the second independent form or formed into a common layer is preferably made of a transparent electrode.

In the organic electroluminescent device of the present invention, the third charge transport layer 26 may be formed as a common layer between the emission layer and the second electrode layer 24. The third charge transport layer 26 may further include one or more layers of the hole suppression layer 18, the electron transport layer 20, and the electron injection layer 22.

As the hole suppression layer 18, the electron transport layer 20, and the electron injection layer 22, a material commonly used is used. As the hole suppression layer 18, a biphenoxy-ratio (8-quinolitora) is used. As the aluminum (Balq), the electron transport layer 20 is a polycyclic hydrocarbon derivative, a heterocyclic compound, tris (8-quinolinolato) aluminum (Alq3), the electron injection layer (22) Materials such as LiF can be used.

Meanwhile, in the present invention, the first charge transport layer 16, the second charge transport layer 14, and the third charge transport layer 26 may be independently stacked and deposited.

In addition, in the present exemplary embodiment, a passivation layer (not shown) may be further included on the second electrode layer 24. As the passivation layer, a material such as SiNx or SiO ₂ may be used.

The organic electroluminescent device of the present invention can manufacture an organic electroluminescent device that implements an optimal light viewing angle by setting an optimal light path for each RGB.

Hereinafter, a preferred embodiment of the present invention. However, the following examples are only presented to better understand the present invention, but the present invention is not limited to the following examples.

Example 1

An IDE 406 (manufactured by Idemitsu Co., Ltd.) was deposited to a thickness of 250 mm 3 with a hole injection layer on a reflective film anode electrode made of Al / ITO, and then IDE 320 (manufactured by Idemitsu Co., Ltd.) was deposited to 100 mW as the first hole transport layer. An IDE 320 (manufactured by Idemitsu Co., Ltd.) 300 mW was deposited on the first hole transport layer on the first hole transport layer of the pixel area in which the red light emitting layer was formed. Then, a red light emitting layer was formed with a light emitting layer having a thickness of 350 를 CBP (UDC) doped with 12% R1 / R7 ( UDC) with a dopant in the red region, and Irppy (UDC) 5% doped with a dopant in the green region. The light emitting layer in which the prepared CBP was drawn to a thickness of 250 mm 3 was formed. Then, a light emitting layer was formed with a dopant of IDE 140 (manufactured by Idemitsu Corporation) 4% doped with IDE 140 (manufactured by Idemitsu Corporation) with a thickness of 150 kHz.

After the emission layer was formed, Balq was deposited to 50 kV as a hole blocking layer, and Alq3 was deposited to a thickness of 250 kPa under vacuum as an electron transport layer. After deposition of the electron transport layer, LiF was deposited to an electron injecting layer with a thickness of 30 μm, and a cathode electrode layer was formed with a double electrode having a thickness of 100 Mg / Ag alloy and IZO 800 μm as a cathode, and then a glass encapsulation substrate and calcium oxide. It was sealed using.

Comparative Example 1

An IDE 406 (manufactured by Idemitsu Co., Ltd.) was deposited to a thickness of 250 mm 3 with a hole injection layer on a reflective film anode electrode made of Al / ITO, and then IDE 320 (manufactured by Idemitsu Co., Ltd.) was deposited to 100 mW as the first hole transport layer. Then, CBP (UDC) doped with R1 / R7 (UDC) 12% with dopant in the red region as a light emitting layer to form a red light emitting layer with a thickness of 400 400, Irppy (UDC) 5% doped with dopant in the green region The light emitting layer in which the prepared CBP was drawn to a thickness of 250 mm 3 was formed. Then, a light emitting layer was formed with a dopant of IDE 140 (manufactured by Idemitsu Corporation) 4% doped with IDE 140 (manufactured by Idemitsu Corporation) with a thickness of 150 kHz.

After the light emitting layer was formed, Balq was deposited to 50 kV as the hole blocking layer, and Alq3 was deposited to a thickness of 250 kPa under vacuum as the electron transport layer. After deposition of the electron transport layer, LiF was deposited to an electron injecting layer with a thickness of 30 μm, and a cathode electrode layer was formed with a double electrode having a thickness of 100 Mg / Ag alloy and IZO 800 μm as a cathode, and then a glass encapsulation substrate and an oxide. It was sealed using calcium.

4 and 5 show graphs showing luminance characteristics according to viewing angles of the organic electroluminescent devices manufactured by Example 1 and Comparative Example 1. FIG. Figure 4 is a graph of the organic electroluminescent device of the present invention prepared by Example 1, Figure 5 is a graph of the organic electroluminescent device manufactured by Comparative Example 1.

4 and 5, the organic electroluminescent device according to Example 1 shows only a change in luminance of red (R) from about 150 to 200 cd / m 2 even though the viewing angle is 0 to 60 degrees. In the organic electroluminescent device according to the present invention, the luminance of red (R) is about 225 cd / m 2 at the viewing angle of 0 degrees, whereas the luminance of red rapidly decreases to about 100 cd / m 2 as the viewing angle approaches 60 degrees. have.

As described above, in the present invention, red light is secured at a wide viewing angle of 60 degrees by securing the length of the red light path of the RGB, thereby suppressing the phenomenon in which the display appears bluish in the case of the front emission organic electroluminescent device. Can be.

Claims (15)

Board; A first electrode layer comprising a metal formed on the substrate; A first charge transport layer formed on the first electrode layer; A blue, green, and red light emitting layer formed on the first charge transport layer and formed for each pixel of RGB; And It includes a second electrode layer including a transparent conductive layer formed on the light emitting layer, The distance between the red light emitting layer and the first electrode layer is an organic electroluminescent device, characterized in that thicker than 250 ~ 470 비해 than the distance between the blue and green light emitting layer and the first electrode layer. The method of claim 1, And the first charge transport layer formed between the red light emitting layer and the first electrode layer is thicker than the first charge transport layer formed between the blue and green light emitting layers and the first electrode layer. The method of claim 1, The first charge transport layer formed under the red light emitting layer is formed of a two-layer structure made of different materials organic electroluminescent device. The method of claim 1, And a second charge transport layer between the first charge transport layer and the first electrode layer or between the first charge transport layer and the light emitting layer. The method of claim 4, wherein When the second charge transport layer is formed between the first charge transport layer and the first electrode layer, the second charge transport layer is N, N'-di (1-naphthyl) -N, N'-diphenylbenzidine ( NPD) or PEDOT, and the first charge transport layer is formed of N, N'-di (1-naphthyl) -N, N'-diphenylbenzidine (NPD) or PEDOT. The method of claim 4, wherein When the second charge transport layer is formed between the first charge transport layer and the light emitting layer, the first charge transport layer is N, N'-di (1-naphthyl) -N, N'-diphenylbenzidine (NPD) Or PEDOT and the second charge transport layer is formed of N, N'-di (1-naphthyl) -N, N'-diphenylbenzidine (NPD) or PEDOT. The method of claim 1, And the charges of the first charge transport layer and the second charge transport layer are holes. The method of claim 1, The metal electrode is an organic electroluminescent device which is one selected from the group consisting of Al, Al alloys, Ag, Ca, and Mg / Ag. The method of claim 1, The second electrode layer is an organic electroluminescent device consisting of a two-layer structure of the electrode layer is formed independently or formed as a common layer over the entire substrate. The method of claim 9, And the electrode layer formed of the independent layer or the common layer is formed of Mg / Ag. The method of claim 9, And the electrode layer formed as the independent layer or the common layer is formed of a transparent electrode. The method of claim 1, An organic electroluminescent device further comprising a third charge layer on the light emitting layer. The method of claim 12, And the first charge transport layer, the second charge transport layer, and the third charge transport layer are each independently formed on a pixel-by-pixel basis. The method of claim 12, And the third charge transport layer comprises at least one of a hole suppression layer, a charge transport layer, and a charge injection layer. The method of claim 1, The organic electroluminescent device further comprising a protective film layer on the second electrode layer.

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