Organic EL display device and method for manufacturing the same

Abstract

To provide an organic EL display device of a color filter system, in which fluorescence emitted from a coloring material of a color filter can be used to improve luminance.SOLUTION: An organic EL display device 10 includes, in this order, at least a white organic electroluminescent light-emitting layer 2, a color filter 3 forming red, green, and blue pixels, and an intermediate layer 4 provided adjacent to the color filter, and the intermediate layer is made of a transparent resin that allows a coloring material in the color filter to migrate to the intermediate layer by heating during a manufacturing process of the color filter.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a technique for improving the luminance of an organic EL (Electoluminescence) display device.

Background Art

[0002] An organic EL display device is a self-emitting display device using an organic light-emitting diode (OLED; Organic Light-Emitting Diode), and two emission methods are known. One is the RGB method, and the other is the color filter method.

[0003] The RGB method forms one pixel by each sub-pixel composed of light-emitting diode elements of red (R), green (G), and blue (B). Since no color filter is used, the luminous efficiency is high, and it is also possible to increase the color purity.

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

[0005] The color filter method has a demerit of low luminous efficiency, but has merits of a simple manufacturing process, low cost, and being advantageous for miniaturization. Therefore, in fields such as microdisplays and large TVs, a method of adopting the color filter method and manufacturing the white OLED by vacuum evaporation is adopted.

[0006] In an organic EL display device using a color filter method, there is a problem in principle that the luminous efficiency is low. However, since high luminance is achieved by increasing the output of white OLEDs, there is a problem that the power consumption increases. Therefore, in an organic EL display device using a color filter method, a technology capable of reducing power consumption while maintaining luminance is required.

[0007] As a prior art for solving such a technology, for example, in a color filter type organic EL display device provided with a color filter on a white organic EL light emitting layer in Patent Document 1, when forming a color filter on the white organic EL layer, a low-temperature curing process that does not damage the white organic EL layer is enabled, and a technology that enables the formation of a color filter with a high colorant concentration composed of a thin layer that enables high color reproducibility is disclosed.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0009] However, in this technology, since the color filter is formed with a high colorant concentration, the fluorescence emitted from the colorant is absorbed inside the color filter and cannot be taken out to the outside. Therefore, the fluorescence could not be used to improve the luminance of the organic EL display device.

[0010] In view of the above circumstances, an object of the present invention is to provide an organic EL display device capable of utilizing the fluorescence emitted from the colorant of a color filter to improve luminance in a color filter type organic EL display device.

Means for Solving the Problems

[0011] As a means for solving the above problems, a first aspect of the present invention is an organic electroluminescence display device including, at least, a white organic electroluminescence light-emitting layer, a color filter forming red, green, and blue pixels, and an intermediate layer provided at a position in contact with a surface of the color filter opposite to the white organic electroluminescence light-emitting layer 2, in this order, the intermediate layer contains a colorant of the same type as the colorant contained in at least one pixel of the color filter, the organic electroluminescence display device is characterized in that the colorant concentration of the intermediate layer is lower than the colorant concentration of the color filter.

[0012] A second aspect is the organic electroluminescence display device according to the first aspect, characterized in that the color filter and the intermediate layer contain the same type of polymer.

[0013] A third aspect is a method for manufacturing an organic electroluminescence display device according to the first or second aspect, characterized in that the intermediate layer is formed by the movement of the colorant in the color filter to the intermediate layer side by heating during the manufacturing process of the color filter.

Advantages of the Invention

[0014] According to the organic electroluminescence display device of the present invention, an intermediate layer made of a transparent resin in which the colorant in the color filter can move to the intermediate layer side at the heating temperature during the manufacturing process is provided adjacent to the color filter. Therefore, by heat treatment such as a drying process in the manufacturing process of the color filter, a part of the colorant in the color filter moves to the intermediate layer. As a result, fluorescence is emitted from the colorant that has moved to the intermediate layer by the light from the white organic electroluminescence light-emitting layer, and the luminance of the organic electroluminescence display device is improved by the fluorescence.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

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Figure 6

Embodiments for Carrying Out the Invention

[0016] <Organic EL Display Device> The organic EL display device of the present invention will be described with reference to FIG. 1.

[0017] The organic EL display device 10 of the present invention includes at least a white organic electroluminescence light-emitting layer 2 (hereinafter also referred to as a white organic EL light-emitting layer 2), a color filter 3 that forms red, green, and blue pixels, and an intermediate layer 4 provided adjacent to the color filter, in this order, and is an organic electroluminescence display device. In the organic EL display device 10 of the present invention, the intermediate layer 4 is characterized in that it is made of a transparent resin in which the coloring material in the color filter 3 can move to the intermediate layer 4 side by heating during the manufacturing process of the color filter. The heating temperature is assumed to be, for example, 50°C to 100°C.

[0018] The pixel 6 of the color filter 3 includes a red sub-pixel R, a green sub-pixel G, and a blue sub-pixel B.

[0019] In the organic EL display device 10 of the present invention, each sub-pixel R, G, B of the color filter 3 is composed of a thin layer having a high colorant concentration as in the conventional case, but an intermediate layer 4 is provided at a position in contact with the surface of the color filter 3 on the side opposite to the white organic electroluminescence emitting layer 2. By this, it becomes possible to increase the luminance of each sub-pixel R, G, B. This is considered to be because a part of the colorant in each sub-pixel R, G, B moves to the intermediate layer 4 respectively. When the colorant that has moved to the intermediate layer 4 is irradiated with light from the white organic electroluminescence emitting layer 2, fluorescence is emitted. Since the colorant concentration in the intermediate layer 4 is lower than the colorant concentration in the color filter 3, the fluorescence can come out to the outside without being absorbed by the colorant. Therefore, it becomes possible to contribute to the improvement of luminance.

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

[0021] (Color filter) The color filter 3 is formed with a pixel 6 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 3 is usually produced by preparing black, red, green, and blue colored photosensitive compositions in which a coloring composition composed of black, red, green, and blue fine pigments is uniformly dispersed in a photosensitive transparent resin, applying it on a substrate, drying it, and then patterning it by a photolithography method.

[0023] Specifically, first, a black matrix 7 (see FIG. 1) is formed on the substrate using a black photosensitive composition as a reference pattern. By the black matrix 7, a partition region for forming each sub-pixel R, G, B of red, green, and blue is formed. Next, for example, colored layers of red, green, and blue are sequentially formed, whereby the color filter 3 is formed.

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

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

[0026] (Intermediate layer) As the intermediate layer 4, a material obtained by removing color materials such as pigments and dyes from the composition of the color filter 3 can be preferably used. Specifically, at a heating temperature in the drying process or the like in the manufacturing process of the color filter 3, for example, at 50°C to 100°C, the color materials in the color filter 3 enter the intermediate layer 4 It is necessary to be made of a transparent resin that can move to the side. If they are of the same resin system, a step-like concentration difference in the colorant concentration is formed at the interface where the color filter 3 and the intermediate layer 4 are joined. With such a concentration difference, since the particulate colorant is in a situation where it is likely to thermally diffuse, for example, by heating at 50°C to 100°C, a part of the colorant can move to the side of the intermediate layer 4 where there is no colorant. To a certain extent, the colorant moves to the intermediate layer side and the colorant concentration increases, but then the colorant no longer moves. However, the colorant concentration in the region near the interface between the intermediate layer 4 and the color filter 3 is lower than the colorant concentration in the color filter 3. In other words, the colorant concentration of the intermediate layer 4 is lower than that of the color filter 3. Therefore, the fluorescence emitted from the colorant can come out to the outside without being absorbed by the colorant.

[0027] Also, it is possible to use a resin material that has a high affinity with the pigment in the coloring composition used in the color filter 3.

[0028] As shown in FIG. 1, the intermediate layer 4 is formed so as to cover the entire surface of the color filter 3, so that the emission luminance of the entire color filter can be improved. On the other hand, depending on the pigment used in the color filter 3, the luminance may be lower than that of other sub-pixels, and the balance of the emission intensities of each color may not be achieved. When aiming to improve the luminance of at least one of the sub-pixels R, G, and B, it is preferable to form the intermediate layer 4 only on the corresponding sub-pixel. In this case, the intermediate layer 4 may be arranged only on a single-color sub-pixel, or may be arranged on any plurality of color sub-pixels.

[0029] For example, FIG. 2 shows an example of an organic EL display device 10-1 in which the intermediate layer 4-1 is formed only on the subpixel R. FIG. 3 shows an example of an organic EL display device 10-2 in which the intermediate layer 4-2 is formed only on the subpixel G. FIG. 4 shows an example of an organic EL display device 10-3 in which the intermediate layer 4-3 is formed only on the subpixel B. FIG. 5 shows an example of an organic EL display device 10-4 in which the intermediate layer 4-4 is formed on the subpixels R and G. FIG. 6 shows an example of an organic EL display device 10-5 in which the intermediate layer 4-5 is formed on the subpixels G and B. When the intermediate layer 4 is formed on a plurality of adjacent subpixels as shown in FIGS. 5 and 6, the intermediate layer 4 may be formed independently so as to correspond to each subpixel as shown in FIGS. 5 and 6, or the intermediate layer 4 may be formed continuously without interruption between the subpixels. By forming the intermediate layer 4 independently so as to correspond to each subpixel, the colorant concentration entering the intermediate layer 4 can be adjusted for each subpixel, and it is easy to balance the emission intensity of each color. On the other hand, when the intermediate layer 4 is formed continuously without interruption between the subpixels, the formation of the intermediate layer 4 becomes easy during manufacturing.

[0030] (Overcoat layer) The overcoat layer 5 serves to protect the color filter 3 and to flatten the surface. The overcoat layer 5 is generally formed using a thermosetting or photocurable resin composition such as an acrylic resin, an epoxy resin, or a polyimide resin. In the present invention, however, a thermosetting resin having excellent smoothness is used as the overcoat layer 5. For this overcoat layer 5, a resin material that is smooth, tough, has transparency, has high heat resistance and light resistance, does not deteriorate such as yellowing or whitening over a long period of time, and is excellent in water resistance, solvent resistance, acid resistance, and alkali resistance can be preferably used.

Example

[0031] Next, examples of the present invention will be described. <Example 1> (Formation of organic EL light-emitting layer) Using a silicon wafer on which a driving circuit of an organic EL element is formed, drive the silicon wafer On the circuit formation surface side, a white organic EL element was formed by a vapor deposition method, and finally, a passivation layer made of silicon nitride was formed by plasma CVD (Chemical Vapor Deposition) method to seal it, thereby producing a substrate on which an organic EL light-emitting layer was formed.

[0032] (Production of materials for forming color filters) Next, materials for color filters to be formed on the substrate on which the organic EL light-emitting layer was formed were produced.

[0033] (1) Black resin composition · Pigment of black coloring composition The colorants (pigments) used in the colored resin composition were as follows. Pigment for blue: C.I.Pigment Blue 15:6 (「LIONOL BLUE ES」 manufactured by Toyo Color Co., Ltd. Pigment for purple: C.I.Pigment violet 23 (「LIONOGEN VIOLET RL」 manufactured by Toyo Color Co., Ltd. Pigment for yellow: C.I.Pigment Yellow 139 (「Paliotol Yellow 2146HD」 blue from BASF

[0034] · Production of black coloring composition Black colored resin compositions were produced using each pigment. After uniformly stirring and mixing the mixture with the following composition, it was dispersed with a sand mill for 5 hours using glass beads with a diameter of 1 mm, and then filtered through a 5 μm filter to produce a dispersion of black pigment. Pigment for blue: C.I.Pigment Blue 15:6 11 parts by weight Pigment for purple: C.I.Pigment violet 23 11 parts by weight Pigment for yellow: C.I.Pigment Yellow 139 6 parts by weight 170 parts by weight of acrylic varnish (solid content: 20%)

[0035] Thereafter, the mixture having the following composition was stirred and mixed uniformly, and then filtered through a 5-μm filter to obtain a black coloring material (BLK-1).

[0036] Using the aforementioned coloring material, a black photosensitive coloring composition (black photosensitive resin composition) was prepared (BLK-1) to have the formulation described in Table 1.

[0037] (2) Red coloring composition · Pigment of the red coloring composition Pigment for red: C.I.Pigment Red 254 (「Irgaphor Red B-CF」 manufactured by BASF) Pigment for yellow: C.I.Yellow 139 (「Paliotol Yellow L 2146HD」 manufactured by BASF)

[0038] · Preparation of the red coloring composition The mixture having the following composition was stirred and mixed uniformly, and then dispersed using a sand mill with 1-mm diameter glass beads, and then filtered through a 5-μm filter to prepare a dispersion of the red pigment. Red pigment: C.I.Pigment Red 254 78 parts by weight Yellow pigment: C.I.Pigment Yellow 139 22 parts by weight Acrylic varnish (solid content: 20%) 215 parts by weight Thereafter, the mixture having the following composition was stirred and mixed uniformly, and then filtered through a 5-μm filter to obtain a red coloring composition (R-1). Using the aforementioned coloring material, a blue photosensitive coloring composition was prepared to have the formulation described in Table 1 (RR-1).

[0039] (3) Green coloring composition · Pigment of the green coloring composition Pigment for green: C.I.Pigment Green 58 (Manufactured by DIC Corporation, "FASTOGEN GREEN A110" Pigment for yellow: C.I.Pigment Yellow 185 (Manufactured by BASF Corporation, "Paliotol Yellow L 1155"

[0040] · Preparation of green coloring composition A green-colored resin composition was prepared using each pigment. Green pigment: C.I.Pigment Green 58 65 parts by weight Yellow pigment: C.I.Pigment Yellow 185 35 parts by weight Acrylic varnish (solid content 20%) 215 parts by weight Thereafter, the mixture of the following composition was stirred and mixed to be uniform, and then filtered through a 5 μm filter to obtain a green coloring composition (G-1). Using the aforementioned coloring composition, a blue photosensitive coloring composition was prepared (GR-1) so as to have the formulation described in Table 1.

[0041] (4) Blue coloring composition · Pigments of blue coloring composition Pigment for blue: C.I.Pigment Blue 15:6 (Manufactured by Toyo Color Co., Ltd., "LIONOL BLUE ES")[[]] Pigment for purple: C.I.Pigment Violet 23 (Manufactured by Toyo Color Co., Ltd., "LIONOGEN VIOLET RL")[[]]

[0042] · Preparation of blue coloring composition A blue-colored resin composition was prepared using each pigment. Pigment for blue: C.I.Pigment Blue 15:6 63 parts by weight Pigment for purple: C.I.Pigment Violet 23 37 parts by weight Acrylic varnish (solid content 20%) 215 parts by weight Thereafter, the mixture of the following composition was stirred and mixed to be uniform, and then filtered through a 5 μm filter to obtain a blue coloring composition (B-1). Using the aforementioned coloring material, a blue photosensitive coloring composition was prepared (BR-1) to have the formulation shown in Table 1.

[0043] [Table 1]

[0044] (5) Transparent resin composition · Preparation of transparent resin composition A transparent resin composition was prepared to have the formulation shown in Table 2.

[0045] [Table 2]

[0046] (Fabrication of color filter and organic EL display device) First, a transparent resin composition for a planarization film was applied onto the organic EL light-emitting layer using a spinner so that the cured film thickness became 0.1 μm. Then, it was heated in a heating oven at 100 °C for 10 minutes to cure and complete the formation of the planarization film.

[0047] Next, a black photosensitive resin composition was applied onto the planarization film using a spinner so that the cured film thickness became 1.0 μm. Then, through processes of ultraviolet exposure, alkali development, water washing, and drying via a pattern mask, a black matrix of a color filter with a pixel size of 2.4 μm × 2.4 μm was temporarily formed. After that, it was heated in a heating oven at 80 °C for 10 minutes to cure and complete the formation of the black matrix.

[0048] Next, a green photosensitive resin composition was applied onto the substrate on which the black matrix was formed using a spinner so that the cured film thickness became 1.0 μm, and through ultraviolet exposure, alkali development, water washing, and drying processes via a pattern mask, a green layer (G) of a color filter with a pixel size of 2.4 μm × 2.4 μm was temporarily formed. Thereafter, it was heated at 80°C for 10 minutes using a heating oven to cure, and the formation of the green layer (G) of the color filter was completed.

[0049] Next, in the same manner as the method for forming the green layer (G) of the color filter described above, a red photosensitive resin composition was applied using a spinner so that the cured film thickness became 1.0 μm, and through ultraviolet exposure, alkali development, water washing, and drying processes via a pattern mask, a red layer (R) of a color filter with a pixel size of 2.4 μm × 2.4 μm was temporarily formed. Thereafter, it was heated at 80°C for 10 minutes using a heating oven to cure, and the formation of the red layer (R) of the color filter was completed.

[0050] Furthermore, in the same manner as the method for forming the green layer (G) of the color filter described above, a blue photosensitive resin composition was applied using a spinner so that the cured film thickness became 1.0 μm, and through ultraviolet exposure, alkali development, water washing, and drying processes via a pattern mask, a blue layer (B) of a color filter with a pixel size of 2.4 μm × 2.4 μm was temporarily formed. Thereafter, it was heated at 80°C for 10 minutes using a heating oven to cure, and the formation of the blue layer (B) of the color filter was completed to fabricate a color filter.

[0051] After forming the color filter, a transparent resin composition OC-1 was applied using a spinner so that the cured film thickness became 1 μm, and through ultraviolet exposure, alkali development, water washing, and drying processes on the red pixels, and thereafter, it was heated at 80°C for 10 minutes using a heating oven to cure, and an overcoat layer 1 was formed on the red pixels. Thereafter, a transparent resin composition OC-2 was applied using a spinner so that the cured film thickness became 1 μm, and through ultraviolet exposure, alkali development, water washing, and drying processes on the green and blue pixels, and thereafter, it was heated at 80°C for 10 minutes using a heating oven to cure, and an overcoat layer 2 was formed on the green and blue pixels.

[0052] After forming the overcoat layer 2, it was bonded to the cover glass using the sealant Struct Bond XMF-T107 (manufactured by Mitsui Chemicals, Inc.) to fabricate an organic EL display device. Note that the overcoat layer 1 and the overcoat layer 2 correspond to the intermediate layer 4 and the overcoat layer 5, respectively, in FIG. 1.

[0053] <Example 2> Similar to Example 1, after forming the color filter and the overcoat layers 1 and 2, the microlens material was applied with a spinner so that the cured film thickness became 2.4 μm, and the entire coating film was exposed to ultraviolet light. Then, it was cured by heating in a heating oven at 80°C for 10 minutes to form a microlens layer. Thereafter, lenses with a planarization film thickness of 1.2 μm and a lens height of 1.2 μm were formed on the aforementioned red, green, and blue pixels by an etch-back method.

[0054] After forming the microlenses, it was bonded to the cover glass using the sealant Struct Bond XMF-T107 (manufactured by Mitsui Chemicals, Inc.) to fabricate an organic EL display device.

[0055] <Example 3> An organic EL display device was fabricated in the same manner as in Example 1, except that the overcoat layer 1 was formed on the blue pixels and the overcoat layer 2 was formed on the red and green pixels.

[0056] <Comparative Example 1> An organic EL display device was fabricated in the same manner as in Example 1, except that the overcoat layer 1 was not used and the overcoat layer 2 was formed on the red, blue, and green pixels.

[0057] <Comparative Example 2> An organic EL display device was fabricated by forming only the overcoat layer 2 in the same manner as in Comparative Example 1 and then forming microlenses in the same manner as in Example 2.

[0058] <Luminance Evaluation> The organic EL display devices fabricated in Examples 1 to 3 and Comparative Examples 1 to 2 were turned on, and relative comparisons of their respective luminances were made. The luminance was measured using a CS-1000A manufactured by Konica Minolta.

[0059] The relative luminances calculated from the luminance measurement results are shown in Tables 3 and 4. In Tables 3 and 4, the luminances of Comparative Example 1 and Comparative Example 2 were set to 100%, respectively. From the results, it was found that Examples 1 to 2 without micro-lenses had relatively improved luminance compared to Comparative Example 1 without an intermediate layer. Similarly, when comparing Example 3 with micro-lenses and Comparative Example 2, it was found that the relative luminance was improved when the intermediate layer was formed.

[0060]

Table 3

Table 4

Explanation of Reference Signs

[0061] 1 ··· Driving circuit board 2 ··· White organic EL light-emitting layer 3 ··· Color filter 4, 4-1, 4-2, 4-3, 4-4, 4-5 ··· Intermediate layer 5 ··· Overcoat layer 6 ··· Pixel 7 ··· Black matrix 10, 10-1, 10-2, 10-3, 10-4, 10-5 ··· Organic EL display device R ··· Red sub-pixel G ··· Green sub-pixel B ··· Blue sub-pixel

Claims

1. An organic electroluminescence display device comprising at least a white organic electroluminescent light-emitting layer, a color filter including a red pixel, a green pixel, and a blue pixel, and an intermediate layer formed at a position in contact with a surface of the color filter opposite to the white organic electroluminescent light-emitting layer, in this order, wherein a region of the intermediate layer in contact with the pixel contains a colorant of the same type as the colorant contained in the pixel, and the organic electroluminescence display device is characterized in that a colorant concentration of the intermediate layer in contact with the pixel is lower than a colorant concentration of the pixel.

2. The organic electroluminescence display device according to claim 1, wherein in a bonding region between the intermediate layer and the pixel, the intermediate layer and the pixel have a stepwise concentration difference in colorant concentration, and in a region other than the bonding region of the pixel, the colorant in the pixel is uniformly dispersed.

3. The organic electroluminescence display device according to claim 1 or 2, characterized in that the color filter and the intermediate layer contain the same type of polymer.

4. A method for manufacturing an organic electroluminescence display device according to any one of claims 1 to 3, characterized in that the intermediate layer is formed by the movement of a colorant in the color filter to the intermediate layer side by heating during a manufacturing process of the color filter.

Images