Organic EL display device

Abstract

To provide a color filter type organic EL display device in which fluorescence emitted from a coloring material of a color filter can be used to improve brightness.SOLUTION: An organic EL display device includes at least, a white organic EL light emitting layer 2, a planarizing layer 3 that planarizes the surface of the white organic EL light emitting layer, and a color filter 4 that forms red, green, and blue pixels in this order, and the planarization layer includes at least one or more fluorescent coloring materials, and the concentration of the fluorescent coloring material is lower than the concentration of the coloring material in the color filter.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a technique that enables improvement in the brightness of an organic EL (Electroluminescence) display device. [Background technology]

[0002] An organic EL display device is a self-luminous display device that uses organic light-emitting diodes (OLEDs), and there are two known light-emitting methods: the RGB method and the color filter method.

[0003] In the RGB method, one pixel is formed by sub-pixels made of red (R), green (G), and blue (B) light-emitting diode elements. Because no color filters are used, the light-emitting efficiency is high and it is also possible to increase color purity.

[0004] The color filter method is a method of forming color images by combining red (R), green (G), and blue (B) color filters with a white OLED. Since the emission intensity of the white OLED element corresponding to each color can be controlled independently, it is possible to increase the color purity of dark areas (black) and also to display a high contrast.

[0005] Although the color filter method has the disadvantage of low light-emitting efficiency, it has the advantage of a simple manufacturing process, low cost, and favorable miniaturization. Therefore, in fields such as microdisplays and large TVs, the color filter method is used, and white OLEDs are produced by vacuum deposition.

[0006] In organic EL display devices using the color filter method, the light-emitting efficiency is low in principle, but the power consumption increases because high brightness is achieved by increasing the output of white OLED. Therefore, there is a demand for technology that can reduce power consumption while maintaining brightness in organic EL display devices using the color filter method.

[0007] As a prior art that solves such a problem, for example, Patent Document 1 discloses a technology in which, in a color filter type organic EL display device having a color filter on a white organic EL light-emitting layer, a low-temperature curing process that does not damage the white organic EL layer when forming a color filter on the white organic EL layer can be performed, making it possible to form a color filter with a high color material concentration made of a thin layer that enables high color reproducibility. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] JP 2019-153389 A Summary of the Invention [Problem to be solved by the invention]

[0009] However, in this technology, the color filters are formed with a high concentration of color materials, so the fluorescence emitted from the color materials is absorbed inside the color filters and cannot be extracted to the outside, and therefore the fluorescence cannot be used to improve the brightness of the organic EL display device. In view of the above circumstances, the present invention is directed to improving the brightness of a color filter type organic EL display device. The objective of the present invention is to provide a technology that enables [Means for solving the problem]

[0010] As a means for solving the above problems, a first aspect of the present invention is an organic electroluminescence display device comprising, in this order, at least a white organic electroluminescence light-emitting layer, a planarization layer for planarizing a surface of the white organic electroluminescence light-emitting layer, and color filters for forming red, green, and blue pixels, the planarization layer contains at least one fluorescent color material, The organic electroluminescence display device is characterized in that the concentration of the fluorescent color material is lower than the concentration of the color material in the color filter.

[0011] A second aspect is the organic electroluminescence display device according to the first aspect, wherein the planarizing layer has a light transmittance of 90% or more.

[0012] A third aspect is the organic electroluminescence display device according to the first or second aspect, characterized in that the fluorescent color material contains at least one of Pigment Red 254 and Acid Red 289. Effect of the Invention

[0013] According to the organic EL display device of the present invention, the planarization layer that planarizes the surface of the white organic electroluminescence light-emitting layer contains at least one color material that emits fluorescence. Since the concentration of the fluorescent color material is lower than the concentration of the color material in the color filter, the fluorescence generated by the excitation of the color material in the planarization layer is not absorbed by the color material in the planarization layer, but passes through the color filter and can be observed from outside the organic EL display device. Therefore, the brightness of the organic EL display device can be improved by the fluorescence emitted from the planarization layer. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a cross-sectional view illustrating an organic EL display device of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] The organic EL display device of the present invention will be described with reference to FIG.

[0016] The organic EL display device 10 of the present invention is an organic electroluminescence display device including, in this order, a drive circuit board 1 on which a drive circuit using semiconductor elements is formed, and at least a white organic electroluminescence light-emitting layer 2, a planarization layer 3 for planarizing the surface of the white organic electroluminescence light-emitting layer 2, and a color filter 4 for forming red, green, and blue pixels on the drive circuit board 1. Furthermore, a glass plate 6 is attached to the surface of the color filter 4 opposite to the planarization layer 3 via an adhesive layer 5, for example, to form the organic EL display device 10.

[0017] (flattening layer) The planarization layer 3 of the organic EL display device 10 of the present invention is characterized in that it contains at least one color material that emits fluorescence. This color material generates fluorescence when excited by the white light emitted from the white organic electroluminescence light-emitting layer 2. The concentration of the color material in the planarization layer 3 is lower than the concentration of the color material in the color filter 4. Therefore, the fluorescence generated in the planarization layer 3 is partly absorbed by the color material in the planarization layer 3, but most of it passes through the planarization layer 3 and further passes through the color filter 4, and can be observed from outside the organic EL display device 10. Therefore, the brightness of the organic EL display device 10 can be improved.

[0018] In the organic EL display device 10 of the present invention, the planarization layer 3 preferably has a light transmittance of 90% or more. Such a high light transmittance allows the concentration of the color material in the planarization layer 3 to be sufficiently low, and most of the fluorescence generated in the planarization layer 3 is not absorbed by the color material in the planarization layer 3 and can reach the outside of the planarization layer 3.

[0019] In the organic EL display device 10 of the present invention, the color material contained in the planarizing layer 3 preferably contains at least one of Pigment Red 254 and Acid Red 289. These color materials can emit fluorescent light with high efficiency, and therefore can provide an excellent effect of improving the brightness of the organic EL display device 10.

[0020] (White organic electroluminescent layer) The white organic EL light-emitting layer 2 is made of a laminate in which a plurality of layers including an organic semiconductor light-emitting layer are laminated, and is a light-emitting layer made of a so-called organic light-emitting diode (OLED) that emits white light.

[0021] (Color filter) The color filter 4 is formed with pixels 7 each including at least a red sub-pixel R, a green sub-pixel G, and a blue sub-pixel B as a constituent unit.

[0022] The color filter 4 is usually produced by preparing a black, red, green and blue colored photosensitive composition by uniformly dispersing a coloring composition consisting of black, red, green and blue fine pigments in a photosensitive transparent resin, coating the composition on a substrate, drying the composition, and then patterning the composition by photolithography.

[0023] Specifically, first, a black matrix 8 (see FIG. 1) is formed on a substrate using a black photosensitive composition that serves as a reference pattern. The black matrix 8 defines partitioned regions for forming red, green, and blue sub-pixels R, G, and B. Next, colored layers of, for example, red, green, and blue colors are formed in sequence to form the color filter 4.

[0024] In the organic EL display device 10 shown in FIG. 1, the above-mentioned substrate is a driving circuit board 1 on which a white organic EL light-emitting layer 2 is formed.

[0025] (Drive circuit board) The driving circuit board 1 is a substrate in which a driving circuit for OLED is formed on the surface of a silicon wafer by, for example, processing the silicon wafer. The driving circuit for OLED is a current maintaining circuit. For example, when an organic EL display device displays images at 30 frames per second, after one image is displayed, the next image is displayed 1 / 30th of a second later. That is, since the OLED, which is the light-emitting element of the organic EL display device, is a current-driven light-emitting element, it is necessary to maintain a current value required for emitting one image for 1 / 30th of a second. Since the liquid crystal element used in the liquid crystal display device is a voltage-driven type, one transistor is sufficient as a switching element, but at least two transistors are required for one subpixel in the organic EL display device.

[0026] (Adhesive layer) The adhesive layer 5 is not particularly limited as long as it is an adhesive material capable of adhering the color filter 4 and the glass plate 6 with a sufficiently strong adhesive strength to form an organic EL display device, and is a transparent material with a high light transmittance of 80% or more in the entire visible light range. Any adhesive having optical specifications that is commonly used can be used.

[0027] (Glass plate) The glass plate 6 has a high moisture and oxygen blocking performance and serves as a protective layer for protecting the white organic EL light-emitting layer 2. Any glass plate made of transparent glass having excellent performance as a protective layer and high surface hardness can be suitably used. EXAMPLES

[0028] Next, an embodiment of the present invention will be described.

[0029] (Formation of white organic EL light-emitting layer) Using a silicon wafer on which a drive circuit for an organic EL element was formed, a white organic EL element was formed by deposition on the side of the silicon wafer on which the drive circuit was formed. Finally, a passivation layer made of silicon nitride was formed by plasma CVD (Chemical Vapor Deposition) and the element was sealed to produce a substrate on which a white organic EL light-emitting layer was formed.

[0030] (Preparation of Coloring Composition) Next, the preparation of a coloring composition for producing a planarizing layer and a color filter will be described. (1) Colored composition for flattening layer The coloring materials (coloring materials) used in the colored resin composition were as follows. Red pigment: CI Pigment Red 254 (BASF "Ilgarfor Red B-CF") Purple dye: Asid Red 289 (Tokyo Chemical Industry Co., Ltd.)

[0031] Using the above coloring materials, the following colored composition for a flattening layer was prepared. The mixture of the following composition was stirred and mixed to be homogeneous, and then filtered through a 5 μm filter to obtain a coloring material for flattening layer (PL-1). Red pigment: CI Pigment Red 254 10 parts by weight Purple dye: Asid Red 289 10 parts by weight Acrylic varnish (20% solids) 67 parts by weight

[0032] Thereafter, a photosensitive coloring composition (PL-1) for a flattening layer was prepared using the coloring material (PL-1) so as to have the composition shown in Table 1.

[0033] (2) Photosensitive black composition Black composition pigment The coloring materials (pigments) used in the colored (resin) compositions were as follows: Blue pigment: CI Pigment Blue 15:6 ("LIONOL BLUE ES" manufactured by Toyo Color Co., Ltd. Purple pigment: CI Pigment violet 23 ("LIONOGEN VIOLET RL" manufactured by Toyo Color Co., Ltd. Yellow Face: CI Pigment Yellow 139 (BASF Blue "Paliotol Yellow 2146HD"

[0034] Preparation of black pigmented composition A black colored composition (black composition) was prepared using the above pigment. Blue pigment: CIPigment Blue 15:6 11 parts by weight Purple pigment: CI Pigment violet 23 11 parts by weight Yellow face: CIPigment Yellow 139 6 parts by weight Acrylic varnish (20% solids) 170 parts by weight

[0035] After that, the above mixture was stirred and mixed uniformly, and then dispersed in a sand mill using glass beads with a diameter of 1 mm for 5 hours, and then filtered through a 5 μm filter to obtain a black pigment black colorant (BLK-1).

[0036] Using this coloring material (BLK-1), a black photosensitive black composition (photosensitive black composition) (BLK-1) was prepared according to the formulation shown in Table 1.

[0037] (3) Photosensitive red composition Red coloring composition pigment Red pigment: CI Pigment Red 254 (BASF "Ilgarfor Red B-CF") Yellow pigment: CIYellow 139 (BASF "PALIOTOL YELLOW L 2146HD")

[0038] Preparation of red coloring composition The mixture of the following composition was stirred and mixed uniformly, then dispersed in a sand mill using glass beads with a diameter of 1 mm, and filtered through a 5 μm filter to prepare a red colorant (R-1). Red pigment: CI Pigment Red 254 78 parts by weight Yellow pigment: CI Pigment Yellow 139 22 parts by weight Acrylic varnish (20% solids) 215 parts by weight Using the coloring material (R-1), a red photosensitive coloring composition (photosensitive red composition) (RR-1) was prepared according to the formulation shown in Table 1.

[0039] (4) Photosensitive green composition Green coloring composition pigment Green pigment: CI Pigment Green 58 (DIC "FASTOGEN GREEN A110" Yellow pigment: CI Pigment Yellow 185 (BASF "Paliotol Yellow L 1155"

[0040] Preparation of green coloring composition The above pigment was used to mix the mixture having the following composition with stirring until it became uniform, and then the mixture was filtered through a 5 μm filter to obtain a green colored composition (G-1). Green pigment: CI Pigment Green 58 65 parts by weight Yellow pigment: CI Pigment Yellow 185 35 parts by weight Acrylic varnish (20% solids) 215 parts by weight Thereafter, a green photosensitive coloring composition (photosensitive green composition) (GR-1) was prepared using the coloring composition (G-1) so as to have the composition shown in Table 1.

[0041] (5) Blue colored composition Blue coloring composition pigment Blue pigment: CI Pigment Blue 15:6 ("LIONOL BLUE ES" manufactured by Toyo Color Co., Ltd.) Purple pigment: CI Pigment Violet 23 ("LIONOGEN VIOLET RL" manufactured by Toyo Color Co., Ltd.)

[0042] Preparation of blue coloring composition A blue colored resin composition was prepared using the above pigment. The mixture having the following composition was stirred and mixed to be homogeneous, and then filtered through a 5 μm filter to obtain a blue colored composition (B-1). Blue pigment: CIPigment Blue 15:6 63 parts by weight Purple pigment: CI Pigment Violet 23 37 parts by weight Acrylic varnish (20% solids) 215 parts by weight Using this coloring composition, a blue photosensitive coloring composition (photosensitive blue composition) (BR-1) was prepared according to the formulation shown in Table 1.

[0043] [Table 1]

[0044] (Production of color filters and organic EL displays) Next, the photosensitive coloring composition PL-1 for the flattening layer was applied to the substrate on which the white organic EL light-emitting layer was formed by a spinner so that the film thickness of the cured film was 0.1 μm. Then, the film was cured by heating at 100° C. for 10 minutes in a heating oven, and the formation of the flattening layer was completed.

[0045] Next, a photosensitive black composition was applied onto the flattening layer using a spinner so that the film thickness of the cured finished product was 1.0 μm, and the composition was exposed to ultraviolet light through a pattern mask, developed with an alkali, washed with water, and dried to provisionally form a black layer (black matrix) of a color filter with a pixel size of 2.4 μm × 2.4 μm. After that, the composition was heated in a heating oven at 80 ° C for 10 minutes to be cured, completing the formation of the black layer (black matrix) of the color filter.

[0046] Next, a green photosensitive resin composition was applied onto the black matrix using a spinner so that the film thickness of the cured finished product was 1.0 μm, and the composition was exposed to ultraviolet light through a pattern mask, developed with an alkali, washed with water, and dried to provisionally form a green layer (G) of a color filter with a pixel size of 2.4 μm × 2.4 μm. After that, the composition was heated in a heating oven at 80 ° C for 10 minutes to be cured, and the formation of the green layer (G) of the color filter was completed.

[0047] Next, in the same manner as in the formation method of the green layer (G) of the color filter described above, the red photosensitive resin composition was applied by a spinner so that the film thickness of the cured finished product was 1.0 μm, and the red layer (R) of the color filter with a pixel size of 2.4 μm × 2.4 μm was temporarily formed through the steps of ultraviolet exposure through a pattern mask, alkali development, water washing and drying. After that, it was heated in a heating oven at 80 ° C for 10 minutes to be cured, and the formation of the red layer (R) of the color filter was completed.

[0048] Furthermore, in the same manner as in the formation method of the green layer (G) of the color filter described above, the blue photosensitive resin composition was applied by a spinner so that the film thickness of the cured finished product was 1.0 μm, and the blue layer (B) of the color filter with a pixel size of 2.4 μm × 2.4 μm was provisionally formed through the steps of ultraviolet exposure through a pattern mask, alkali development, water washing and drying. Then, the blue layer (B) of the color filter was heated at 80 ° C for 10 minutes in a heating oven for curing, and the formation of the blue layer (B) of the color filter was completed to produce a color filter.

[0049] After forming the color filter, a cover glass was attached to the color filter using a sealant, Structbond XMF-T107 (manufactured by Mitsui Chemicals), to prepare an organic EL display device.

[0050] <Comparative Example> Next, a comparative example will be described.

[0051] An organic EL display device was produced in the same manner as in the example, except that a color filter was formed on the white organic EL light-emitting layer without forming a planarizing layer.

[0052] (Brightness rating) The organic EL display devices produced in the examples and comparative examples were turned on, and the respective luminance values ​​were A relative comparison was performed. The brightness was measured using a Konica Minolta CS-1000A.

[0053] The measurement results of the luminance of the organic EL device are shown in Table 2. When the luminance of the comparative example was taken as 100%, the luminance of the example was 105%. From the results in Table 2, it can be seen that the brightness of the Examples is relatively improved compared to the Comparative Examples. This result is believed to be due to the fact that the planarizing layer converts the light emitted from the white organic EL light-emitting layer, reducing the loss of light in the wavelength range that would normally be absorbed by the color filter, leading to improved brightness.

[0054] [Table 2] [Industrial Applicability]

[0055] The present invention can be used as an organic EL display device for electronic devices such as smart glasses, head-mounted displays, and electronic viewfinders. [Explanation of symbols]

[0056] 1. Drive circuit board 2. White OLED light-emitting layer 3...Planarization layer 4. Color filter 5...adhesive layer 6. Glass plate 7 pixels 8. Black matrix 10...Organic EL display device R Red subpixel G Green subpixel B Blue subpixel

Claims

1. An organic electroluminescence display device comprising at least a white organic electroluminescence light-emitting layer, a planarization layer for planarizing a surface of the white organic electroluminescence light-emitting layer, and color filters for forming red, green, and blue pixels, in this order, the planarization layer contains at least one coloring material that emits fluorescence, 2. An organic electroluminescence display device, wherein a concentration of the fluorescent color material is lower than a concentration of the color material in the color filter.

2. 2. The organic electroluminescent display device according to claim 1, wherein the planarizing layer has a light transmittance of 90% or more.

3. 3. The organic electroluminescence display device according to claim 1, wherein the fluorescent coloring material contains at least one of Pigment Red 254 and Acid Red 289.

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