JP2002203676A - Organic electroluminescence display element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain easily an organic electroluminescence element 10 that is capable of multi-color display. SOLUTION: A positive electrode 2, a hole transport layer 3, a pigment dope layer 4 that is arranged in pattern in circular shape in surface direction of the picture element, a luminous layer and concurrently electron transport layer 5, and a negative electrode 6 are provided on a substrate 1, and spontaneous emission of two different colors are generated in one picture element from two places of luminous regions, that are, a luminous region made of only the luminous layer and concurrently electron transport layer 5 and a luminous region overlapped with the pigment dope layer 4 and the luminous layer and concurrently electron transport layer 5. The display color of the picture element when seen from the top becomes a mixed color of two colors of spontaneous emission.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic electroluminescence device (hereinafter, referred to as an organic EL device), and more particularly to an organic EL device for performing multi-color display.

[0002]

2. Description of the Related Art Appl. Phys. Lett. , 5
No. 1,913 (1987) adopts an organic material as a light emitting layer, and laminates a hole transport layer and a light emitting layer and an electron transport layer.
An organic EL device having a layered structure and using tris (8-quinolinolato) aluminum (hereinafter referred to as Alq) for a light emitting layer and an electron transporting layer is disclosed. This organic EL element emits green light at a driving voltage of 10 V or less, has a luminance of 1000 cd / m ² and a luminous efficiency of 1.5 lumen / W.

It is also known to select a luminescent material or perform dye doping in order to obtain color light emission in an organic EL device. For example, using Alq as a host material of the light emitting layer, rubrene is used to convert yellow to a compound of the following formula 4 (hereinafter referred to as DCM1) or a compound of the following formula 5
(Hereinafter referred to as DCM2) can emit red light.

[0004] In order to make an organic EL device multi-colored, it is also known to form films having different types of light emitting layers and dyes individually for each pixel. In JP-A-8-213172, a light emitting layer capable of emitting a certain color is formed between a hole transport layer and an electron transport layer of one pixel, and the electron transport layer is used as a light emitting layer in another pixel. It is disclosed that different emission colors are generated depending on pixels.

[0005] Jpn. J. Appl. Phys
s. , 38, 5274 (1999), only a certain pixel is formed in a laminated structure of a hole transport layer / a hole blocking layer / an electron transport layer. In this pixel, the hole transport layer is used as a light emitting layer, and other pixels are used. Discloses that a different emission color is obtained for each pixel by using an electron transport layer as a light emitting layer without forming a hole blocking layer. It is also known to generate a different color for each pixel by combining an organic EL element having a relatively wide wavelength range of emitted light and a color filter.

[0006]

However, in order to perform a multi-color display in the prior art, a plurality of light-emitting materials are used.
It was necessary to form an element having a complicated structure. For example,
In the case of an organic EL element that directly emits color light, the luminescent color unique to a luminescent material is used, and in the case of an organic EL element using a color filter, the transmission color unique to a pigment is used as a display color for a pixel. Therefore, the number of types of materials is required for the number of colors for color display. Further, the pattern formation for each pixel becomes complicated, and a manufacturing process with low productivity has to be used.

[0007] In addition, by adjusting the mixture ratio by laminating a plurality of luminescent materials or by adjusting the mixing ratio, color adjustment can be performed by combining luminescent colors specific to the materials, but precise control of film thickness and concentration is required. there were. In the prior art, the structure and the manufacturing process of the device are complicated, the manufacturing yield is not improved, and it is difficult to obtain reproducibility of the emission color of the completed device.
Further, the degree of freedom of the obtained shade is limited, and it is difficult to freely perform a desired multi-color display. An object of the present invention is to provide a colorized organic E which can be easily adjusted in color.
An attempt is being made to provide an L element, and further, a multicolored organic EL element.

[0008]

According to the present invention, there is provided an organic electroluminescent display device in which a plurality of pixels are arranged on a display surface and driven by each pixel to generate a luminescent color from a luminescent area. There is provided an organic electroluminescent display element in which two or more light emitting regions capable of generating mutually different light emitting colors are provided, and the light emitting colors are mixed to exhibit a display color of a pixel.

Further, the present invention provides the above-described organic electroluminescent display device, wherein the area ratio of the plurality of light emitting regions in one pixel is different for a plurality of pixels. In addition, the present invention provides the above-described organic electroluminescent display element, wherein the area ratio changes according to a direction in which pixels are spatially arranged.

In an organic electroluminescent display element in which a plurality of pixels are arranged on a display surface and are driven pixel by pixel to generate a luminescent color from a luminescent area,
Two or more light-emitting regions capable of producing different light-emitting colors are provided in one pixel, and the area ratio of each light-emitting region differs depending on the position in the pixel. Provided is an organic electroluminescent display element exhibiting a color.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The organic EL device of the present invention is provided with a plurality of light emitting regions which emit light of different colors in one pixel. Then, when the pixel is driven, the display color of the pixel is observed as a mixed color of the spontaneous emission colors generated from each emission region. At this time, the area of each light-emitting region is provided sufficiently small with respect to the size of the pixel, and the color of the pixel is observed as a mixed color of the light-emitting colors of the respective light-emitting regions.

For example, two types of light emitting regions are provided, and the area ratio is preferably set to 1/10 to 9/10. In this case, the color tone as the display color of the pixel can be adjusted by adjusting the area ratio of each light emitting region.

In the present invention, a method for forming a plurality of light emitting regions having a sufficiently small area in one pixel will be described. First, a plurality of light emitting regions are formed in one pixel by using a dopant. For example, dopants having different emission colors may be doped into the emission layer to form emission regions having different emission colors. Alternatively, a doping layer may be formed between a hole transporting layer and a light emitting layer and an electron transporting layer only in a part of a pixel by using a mask evaporation method. In the portion of the pixel where the doping layer is provided, the dopant emits light, and the light emitting layer / electron transport layer functions only as an electron transport layer.

In other portions without the doping layer, the original light emitting layer emits light. In this way, it is possible to obtain different emission colors depending on the spatial position in the pixel. In order for the display color of the pixel to be observed as a mixed color of the emission colors generated from the respective emission regions, the doping layer region must be set to 0.3
It is preferable to form at a pitch of not more than mm.

If the pitch is too coarse, the color of light emitted from each light emitting region may be observed as it is. Further, it is more preferable to form at a pitch of 0.2 mm or less. In the case where the area of the pixel itself is small or the display surface has a fine or complicated shape, it is more preferable to form the pixel at a pitch of 0.1 mm or less.

However, if the pitch is too fine, it is difficult to form and use a vapor deposition mask required in the manufacturing process. The in-plane shape of the doping layer may be circular, elliptical, rectangular, rhomboidal hexagonal or any other shape. It is preferable that the shape be such that it can be easily formed as an evaporation mask and the area ratio can be easily adjusted. A circular mask is preferable in terms of forming a mask for vapor deposition and handling in a manufacturing process.

Another method for forming the light emitting region is as follows. That is, a hole blocking layer is partially formed between the hole transporting layer and the electron transporting layer, the hole transporting layer at that portion is used as a light emitting layer, and electron transporting is performed at other portions without the hole blocking layer. The layer can be used as a light emitting layer. Then, different luminescent colors can be generated depending on the portion of the luminescent region that is separately formed.

In the present invention, when one pixel presents a display color that is almost uniformly mixed, a plurality of pixels provide different display colors, and a multi-color display can be achieved on the entire display surface. When one pixel has multiple display colors,
Multi-color display can be achieved with one pixel.

Hereinafter, the present invention will be described with reference to the drawings. FIGS. 1 and 2 show the basic structure of the present invention, in which a plurality of light-emitting regions which emit light of different colors in one pixel by doping a light-emitting layer with a dopant having a different light-emitting color of an organic EL element. To form

3 and 4 show Example 2 of the present invention, FIG. 5 shows Application Example 1 of the present invention, FIG. 6 shows Application Example 2 of the present invention, and FIG. 7 shows Example 3 of the present invention. Show. In these figures,
1 is a substrate, 2 is an anode, 3 is a hole transport layer, 4 is a dye-doped layer, 5 is a light emitting layer and electron transport layer, 6 is a cathode, and 7 is a hole blocking layer.

In the basic structure of the present invention, the luminescent color of the dye-doped layer 4 and the luminescent color of the luminescent layer / electron transport layer 5 are mixed,
The color tone is determined according to the area ratio of the pixels, and is observed as the display color of this pixel.

In the application example 1 shown in FIG. 5, the dye-doped layer 4 is arranged in stripes in the plane of the pixel, and the arrangement of the dye-doped layer 4 is changed between the pixels, so that the spontaneously emitted light is emitted. Are different depending on the spatial position. That is, a plurality of pixels 11 and 21 having different observed display colors are shown. As shown in FIG.
The arrangement density of the dye-doped layers 4 of the two pixels 11 and 21 is different.

In the application example 2 of FIG. 6, in one pixel 31, the arrangement state of the dye-doped layer 4 differs depending on the position in the plane. That is, in this example, the emission color relative ratio changes depending on the position in one pixel, and as a result, the display color of the pixel is observed to change. That is, in the present invention, the display color of one pixel does not necessarily have a substantially uniform color spectrum, but may be formed so that the display color changes according to the spatial position of the pixel. In the vertical or horizontal direction where pixels are spatially arranged,
If the area ratio is gradually changed in the arrangement order of the pixels, it is observed that the display color is gradually changed as a whole.

Further, the area ratio of each light emitting region is provided to be different depending on the position in the pixel, so that different display colors can be presented according to the position in the pixel. The patterning of two or more light emitting areas is changed according to the position in the plane of the pixel so that the area ratio of the light emitting areas is different, whereby the light emitting colors generated from each light emitting area are mixed and observed as a display color. In this case, different display colors are obtained depending on the positions of the pixels.

Further, two or more light-emitting regions are provided in one pixel, and the pixel is divided into two to form a first pixel region and a second pixel region.
And the area ratio of each light emitting region in the two pixel regions can be set to, for example, 2: 1, 1: 2. Further, the pixel can be divided into three or more, so that the three pixel regions have different area ratios of the light emitting regions.
Further, the area ratio can be configured to change substantially continuously or stepwise according to a predetermined direction in a plane. By changing the combination of the light emitting areas in each pixel area, a more complex color pattern can be achieved. As a result, 1
Two or more mixed colors can be generated per pixel, and a complex color display can be performed.

In the present invention, when a plurality of light emitting regions are spatially formed and display colors are made different within one pixel or among a plurality of pixels, the mixing ratio of each light emitting color is, for example, 1 A range of ~ 99% can be employed. For example, three or more light-emitting regions may be patterned and formed in one pixel in a stripe shape or a spot shape, and the display color may be changed according to the state of the combined light-emitting region.

The dye-doped layer 4 and the light-emitting / electron transport layer 5 can be made of any material that can constitute an organic EL device.
Further, the light emitting layer / electron transport layer 5 itself may be doped with a dye to adjust the color tone and improve the luminous efficiency. The light emitting layer and the electron transporting layer may have a stacked structure in which functions are separated.

When a hole blocking layer is formed partially between the hole transporting layer and the electron transporting layer, the hole transporting layer is used as a light emitting layer at that portion, and the hole blocking layer is not provided. In some parts, the electron transport layer can be used as a light emitting layer. According to this method, an organic EL element in which a display color is observed in one pixel or in a plurality of pixels so as to display a display color from a mixed luminescent color according to a spatially formed structure. Can be realized. Further, by forming the formation pattern of the light emitting region in a complicated manner, it is possible to realize an organic EL element having a larger number of colors and a large range of change in color tone as display colors.

In the present invention, when a plurality of light-emitting regions are spatially formed and display colors differ within one pixel or among a plurality of pixels, the mixing ratio of each light-emitting color is 1 to 99. % Can be set freely. When a plurality of light-emitting regions are spatially formed separately by using a mask deposition method, the ratio of the light-emitting regions to be partially formed is 5 to 95%.
% Is preferable. From the manufacturing accuracy, reproducibility, and yield, it can be arbitrarily set within a range in which a light emitting region with a small area can be formed, and the display color can be adjusted.

The emission color of one pixel can be adjusted by setting the color spectrum of the emission color generated from each emission region and its intensity. For example, the first method is
The purpose is to obtain a desired display color by adjusting the type of light emitting material, the thickness of each layer, and the doping concentration of the light emitting material. The second method is to change the area ratio of each light emitting region. The first method and the second method may be combined. Also, 1
By providing three or more emission colors per pixel, it is possible to realize an organic EL element in which the number of colors and the range of change in color tone are larger.

The luminescent material that can be used in the present invention will be described.
First, Alq was used as the light emitting layer and the electron transporting layer,
And the compound of the following formula 2 can be used. Materials for dye doping include rubrene, coumarin derivatives, quinacridone derivatives, compounds of the following formula 3, DCM1
(Compound of the following formula 4), DCM2 (compound of the following formula 5), perylene derivative, distyryl derivative, benzothioxanthene derivative, oxazole dye, cyanine dye, anthracene derivative, tetraphenylbutadiene,
Stilbene dyes, acridine dyes, rhodamine dyes, rare earth complexes and the like can be used.

[0032]

Embedded image

Further, as the light emitting layer and the hole transporting layer, 4,
4′-bis [N- (1-naphthyl) -N-phenylamino] biphenyl (hereinafter referred to as α-NPD), N,
N'-bis (3-methylphenyl) -4,4'-diaminobiphenyl, poly (N-vinylcarbazole) and the like can be used.

[0034]

(Example 1) ITO on a glass substrate 1 having a film thickness of 20
A film was formed to a thickness of 0 nm and patterned to form an anode 2.
At this time, the sheet resistance was 7Ω / □. A metal mask is arranged on the anode 2, and N, N'-diphenyl-N, N, N'-diphenyl-N,
N'-bis (3-methylphenyl) -4,4'-diaminobiphenyl (hereinafter referred to as TPD) is 60 nm thick.
To form a hole transport layer 3.

Next, a dye-doped layer 4 was formed by co-evaporation of Alq and rubrene to a thickness of 10 nm. At this time, the concentration of rubrene was 1.0 mol%. For this deposition, another metal mask was used, and a film having a circular shape having a diameter of 100 μm was continuously formed in a polka dot pattern so as to cover 50% of the area of the light emitting region.

Subsequently, Alq is applied to the entire light emitting region to a thickness of 5
Evaporation was performed so as to have a thickness of 0 nm to form a light-emitting layer / electron transport layer 5. Finally, Mg and Ag are co-deposited on the cathode pattern using a metal mask, and a 200 nm-thick MgAg
The cathode 6 was formed from an alloy having a mass ratio of 10: 1 to form an organic EL device (see FIGS. 1 and 2).

The pixel was driven by applying a voltage between the anode 2 and the cathode 6 of the organic EL device of this example thus formed. When the display state of this organic EL element was observed with the naked eye, it emitted yellow-green light. This is because green, which is the emission color of Alq, and yellow, which is the emission color of rubrene, were mixed at 50%, respectively, and were displayed as yellow-green display colors.

Further, by adjusting the size and density of the holes of the metal mask at the time of depositing the dye-doped layer, the relative ratio between the green and yellow light emitting areas can be adjusted between 90:10 and 40:60. According to the area ratio, the color of the display color that can be visually recognized can be set between green and yellow, and various colors were obtained.

(Example 2) ITO having a film thickness of 2 on a glass substrate 1
A film was formed to a thickness of 00 nm and patterned to form the anode 2. At this time, the sheet resistance was 7Ω / □. A metal mask is arranged on the anode 2, and α-NPD is vapor-deposited on the entire light emitting region by a vacuum vapor deposition method so as to have a film thickness of 60 nm.
It was formed as a hole transport layer / light emitting layer 3.

Next, bathocuproine (hereinafter referred to as BCP) was deposited to a thickness of 10 nm to form a hole blocking layer 7. A different metal mask was used for this deposition, BCP was formed on the entire light emitting region in one pixel, BCP was not formed in another pixel, and a single hole was formed in another pixel. Using a polka dot-shaped mask having a pattern of 100 μm in diameter, a BCP film was formed so as to cover 50% of the area of the light emitting region.

Further, Alq and rubrene are coated to a thickness of 10 nm.
To form a light emitting layer. At this time, the concentration of rubrene was 1.0 mol%. Subsequently, Alq was deposited on the entire light emitting region so as to have a thickness of 30 nm to form the electron transport layer 5. Finally, using a metal mask, Mg and Ag are co-deposited on the cathode pattern to form a film having a thickness of 200 nm.
Alloy made of MgAg (mass ratio is 10: 1)
Was formed to produce an organic EL device (see FIGS. 3 and 4).

A pixel was driven by applying a voltage between the anode 2 and the cathode 6 of the organic EL device of this example thus formed. The display state of this organic EL element was observed. The organic EL element includes a first group of pixels 41 exhibiting a blue emission color of α-NPD, a second group of pixels 42 exhibiting a yellow emission color of rubrene, and a blue and rubrene emission color of α-NPD. Are mixed at a ratio of 50:50 to form a third group of pixels 43 exhibiting a white color.
It was visually observed to have the indicated color.

When a hole blocking layer is used as in this example, the function of each layer changes as follows. The light emitting layer / electron transport layer functions as an electron transport layer, and the hole transport layer functions as a light emitting layer / hole transport layer. In general, the light-emitting layer / electron transport layer is often simply referred to as a light-emitting layer, but basically functions as a layer having both functions of “light emission” and “electron transport”.

When a dye-doped layer is provided, almost all light emission occurs in the dye-doped layer. Therefore, even when the same material is used, it functions only as an electron transport layer. When the hole blocking layer is present, holes are blocked by the hole blocking layer, and the holes do not reach the light emitting layer / electron transport layer, so that "recombination" that causes light emission hardly occurs. Therefore, it can be said that it functions only as an electron transport layer. As described above, even if the same material is disposed in each layer, the function can be changed depending on the entire configuration of the element.

(Example 3) ITO (film thickness 2
(00 nm) and patterned to form the anode 2. The sheet resistance was 7Ω / □. On the anode 2, α-NPD was deposited to a film thickness of 60 nm on the entire light emitting region by a vacuum deposition method using a metal mask to form a hole transport layer.

Next, Alq and DCM2 were co-evaporated to a thickness of 10 nm to form a dye-doped layer. At this time, the concentration of DCM2 was 1.0 mol%. A different metal mask was used for this deposition, and no dye-doped layer was formed on the left end of the pixel. Conversely, on the right end of the pixel,
A dye-doped layer is formed over the entire area, and in a region between the left end and the right end, a portion 15 where the dye-doped layer is arranged in a stripe shape having a width of 100 to 300 μm and a portion where the dye-doped layer is not arranged are alternately arranged. And the film was formed such that the ratio of the dye-doped layer increased from left to right in the pixel.

Subsequently, Alq was applied to the entire light emitting region to a thickness of 5
Evaporation was performed to a thickness of 0 nm to form a light emitting layer / electron transport layer 5. Finally, using a metal mask, the pattern of Mg and A was
g of MgAg having a thickness of 200 nm (mass ratio is 1
A cathode 6 made of an alloy of 0: 1) was formed to produce an organic EL device (see FIG. 7). The sectional structure of this example is shown in FIG.
It is similar to that of

A pixel was driven by applying a voltage between the anode 2 and the cathode 6 of the organic EL device of this example thus formed. The display state of this organic EL element is such that the left side of the pixel is Al
The color is green so that the display color changes from green to orange gradually from left to right in the intermediate region between the two. In was observed. According to the pattern of the anode 2 formed in a sagittal shape, the color tone of the display color was observed to change depending on the position.

As described above, it was possible to provide different display colors within the display surface of one pixel. In a plurality of pixel groups spatially arranged vertically or horizontally,
It is also possible to provide such that the area ratio of each pixel gradually changes in a certain direction. For example, ten pixels are arranged in the horizontal direction, the area ratio of the first pixel is 10: 1,
The whole may be configured such that the second pixel is 9: 2 and the tenth pixel is 1:10.

[0050]

According to the present invention, with a relatively simple configuration,
An organic EL element having many display colors can be provided. Further, it is possible to provide an organic EL element in which adjustment of display color and easy manufacture are possible. Further, a desired color and patterning can be freely adjusted, and a multicolor display excellent in design can be achieved.

In the present invention, color display can be easily achieved not only in a dot matrix type in which color display is relatively easy, but also in a fixed display type. In addition, even with a display element having a relatively small number of colors, an organic EL element which is easy to adjust color in color display and has excellent design properties can be obtained without increasing the manufacturing cost.

Further, it is possible to obtain an organic EL element having good color reproducibility and excellent display appearance, and to achieve a display device for a vehicle, a public display, and a display device having good visibility even in a bright environment. . Further, it is possible to display different emission colors in a plurality of pixels, or freely form a color display pattern such that emission colors differ between adjacent pixels.

[Brief description of the drawings]

FIG. 1 is a sectional view taken along line AA of FIG.

FIG. 2 is a plan view of Example 1 of the present invention.

FIG. 3 is a plan view of Example 2 of the present invention.

FIG. 4 is a sectional view of Example 2 of the present invention.

FIG. 5 is a sectional view of an application example 1 of the present invention.

FIG. 6 is a sectional view of an application example 2 of the present invention.

FIG. 7 is a plan view of Example 3 of the present invention.

[Explanation of symbols]

 1: substrate 2: anode 3: hole transport layer 4: dye-doped layer 5: light-emitting layer and electron transport layer 6: cathode 7: hole blocking layer

Claims (4)

[Claims] 1. An organic electroluminescent display device in which a plurality of pixels are arranged on a display surface and are driven pixel by pixel to generate a luminescent color from a luminescent area, wherein different luminescent colors are generated within one pixel. An organic electroluminescent display element provided with two or more light emitting regions, wherein the light emitting colors are mixed to exhibit a display color of a pixel. 2. The organic electroluminescent display device according to claim 1, wherein an area ratio of the plurality of light emitting regions in one pixel is different for a plurality of pixels. 3. The organic electroluminescent display device according to claim 2, wherein said area ratio changes according to a direction in which pixels are spatially arranged. 4. An organic electroluminescent display device in which a plurality of pixels are arranged on a display surface and are driven pixel by pixel to generate a luminescent color from a luminescent area, wherein different luminescent colors are generated within one pixel. An organic electroluminescent display element in which two or more light emitting regions are provided, the area ratio of each light emitting region differs depending on the position in the pixel, and the light emitting colors are mixed to present two or more display colors per pixel.