JP2006107950A - Organic el display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic EL display device in which a display performance deterioration of an organic EL element due to water invading from the interface of a protecting film and a substrate is prevented. <P>SOLUTION: The organic EL element is pinched by two layers of protecting films (11-a, b) of which main components are Si and N, and the two layers of the protecting films mutually contact at the pattern end part. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a display device using an organic EL element that emits light by applying an electric field to a thin film made of an organic compound.

  An organic EL element is an element in which an organic compound existing between both electrodes emits light by a current flowing between a cathode and an anode.

  Organic EL elements are self-luminous and have high visibility, and at the same time can be made thinner and lighter than liquid crystal display elements.

  An example of the cross-sectional structure of the organic EL element is shown in FIG. In the figure, (1) is a substrate, (2) is a metal electrode, (3) is a hole transport layer, (4) is a light emitting layer, (5) is an electron transport layer, and (6) is a transparent electrode. The light emission display is performed from the upper surface side of the substrate. An organic EL element having this structure is generally called a top emission element, and has an advantage that high definition can be realized because the aperture ratio can be increased as compared with a bottom emission element that emits light from the back surface of the substrate.

  On the other hand, in organic EL elements, a very small amount of moisture or oxygen causes alteration of the organic light-emitting material or peeling between the light-emitting layer and the electrode, resulting in a decrease in light emission efficiency and an increase in non-light-emitting regions (dark spots). There is a problem that display performance deterioration occurs. For this reason, conventionally, the entire element is covered with a concave metal or glass sealing cap, and a moisture is sealed by enclosing a desiccant in the element substrate and the empty wall (sealing space) of the sealing cap. In general, a configuration is employed in which the element is trapped and deterioration of the element is prevented. However, in this configuration, it is necessary to secure a space for enclosing the desiccant, which is disadvantageous for reducing the size and thickness of the element, and arranging the desiccant on the light emission extraction surface side, so that the light extraction efficiency of the top emission element is improved. There was a problem of lowering.

  On the other hand, in recent years, efforts have been made to cover and protect the element with a thin film having a high moisture barrier property. For example, Patent Document 1 discloses a method of covering and protecting the entire element with a SiN film or a diamond-like carbon film. However, the penetration of moisture is advantageous not only through the protective film but also through the interface between the protective film and the base substrate. Therefore, even when a protective film is formed on the organic EL element by these methods, there is a problem that the deterioration of the characteristics of the element cannot be prevented because the intrusion of moisture from the end of the protective film pattern cannot be prevented.

  On the other hand, efforts are being made to prevent intrusion of moisture from the pattern edge by increasing the size of the protective film pattern. For example, Patent Document 2 discloses a method of covering and protecting the entire element with a laminated film including a SiON film and designing the area of the SiON film pattern to be the largest. However, even when a protective film is formed on the organic EL element by these methods, the intrusion of moisture through the contact interface between the substrate and the protective film cannot be completely prevented, and thousands of hours required for the organic EL display device are required. There was a problem that good display performance could not be realized. In particular, when a thermal shock is applied to the organic EL display device, there is a problem that moisture permeation from the interface between the protective film and the substrate is accelerated and element deterioration is likely to occur.

JP-A-10-261487 JP 2002-25765 A

  An object of the present invention is to prevent display performance deterioration of an organic EL element due to moisture entering from an interface between a protective film and a substrate.

The organic EL display device of the present invention formed to achieve the above object has an organic EL element sandwiched between two protective films mainly composed of Si and N, and the two protective films are patterned. The ends are in contact with each other.
Further, the two-layer protective films are both SiNx, SiOxNy, or SiHxNy.
Further, the organic EL element is a top emission element that extracts light emission from the upper surface side of the substrate.

  According to the present invention, the organic EL element is sandwiched between two protective films having high moisture barrier properties and similar compositions, and the two protective films are brought into contact with each other at the pattern end, thereby providing a protective film. And the penetration of moisture from the interface between the protective film and the substrate can be prevented, and display performance deterioration of the organic EL element can be prevented.

  According to the present invention, an organic EL display device is characterized in that an organic EL element is sandwiched between two protective films mainly composed of Si and N, and the two protective films are in contact with each other at a pattern end. Since the two-layer protective film having a similar composition has high affinity and extremely high adhesion at the adhesion interface, it is possible to prevent moisture from entering through the interface. In addition, the two-layer protective film having a similar composition has substantially the same thermal expansion coefficient, and even when a thermal shock is applied to the element, the adhesion at the adhesive interface does not deteriorate.

  Furthermore, since the organic EL display device of the present invention has a very high moisture barrier property of the protective film, it is possible to prevent display performance deterioration of the organic EL element without using a sealing cap or a desiccant. It is. Further, in order to further improve the reliability of the device, even when the protective film of the present invention and the sealing cap are used in combination, the amount of the desiccant present in the sealing space may be very small compared to the conventional case. Therefore, the device can be made thin and small by placing a desiccant in a minute space outside the light emitting area of the device, or by arranging a small amount of desiccant into a sealing cap or on the device. A highly reliable small and thin organic EL display device can be realized without impairing performance.

The requirements of the protective film that can be used in the present invention include the following points.
(1) Having high moisture-proof performance. Specifically, the moisture permeability of the membrane is preferably 1.0 × 10 ⁻³ g / m ² / day or less.
(2) Since it is used on the light emission side of the organic EL element, it has a high light transmittance in the visible light region. Specifically, the visible light transmittance is preferably 90% or more from the viewpoint of the luminous efficiency of the device.
(3) In order to prevent element destruction when forming a protective film on the element, the film can be formed at a temperature lower than the heat resistance temperature of the organic EL display portion, that is, at least 100 ° C. or lower.
(4) Do not use UV light during film formation.
(5) Do not use an organic solvent that dissolves the organic EL element during film formation.

  SiNx, SiOxNy, and SiHxNy films can be most suitably used as protective films that satisfy these conditions. Moreover, as a method for forming these inorganic films, vacuum film formation such as sputtering or CVD can be suitably used.

  Furthermore, in order to increase the affinity of the contact interface, it is more preferable to perform activation treatment such as UV irradiation and reverse sputtering treatment on the surface of the first protective film before forming the second protective film.

  Examples of the present invention will be described below with reference to the drawings. However, the present invention is not limited to these examples.

Example 1
A first embodiment according to the present invention will be described with reference to FIG. FIG. 2 schematically shows a cross section of a side end portion of the organic EL display device manufactured in this example.

  First, a SiOxNy film (11-a) is formed to a thickness of 100 nm by sputtering on the substrate (1) on which the TFT (8) is formed, and then a contact hole is formed at the drain electrode portion of the TFT by dry etching. The planarization film (9) was formed by coating, exposing and developing a photocurable resin (acrylic resin (World Rock 815T, manufactured by Kyoritsu Chemical Co., Ltd.)) by spin coating. Next, similarly, using a photocurable resin (acrylic resin (World Lock 815T, manufactured by Kyoritsu Chemical Co., Ltd.)), a pixel separation film (10) was formed so as to cover the TFT and the electrode wiring. Subsequently, a chromium film having a thickness of 200 nm was formed and patterned to obtain a metal electrode (2).

  Thereafter, the substrate was successively subjected to ultrasonic cleaning with acetone and isopropyl alcohol (IPA), then boiled with IPA and dried. Further, UV / ozone cleaning was performed.

Next, using a vacuum deposition apparatus (manufactured by Vacuum Kiko Co., Ltd.), an αNPD represented by the following formula 1 having hole transportability is formed on the washed substrate with a film thickness of 50 nm by a vacuum deposition method. Thus, a hole transport layer (3) was formed. The degree of vacuum during vapor deposition was 1.3 × 10 ⁻⁴ Pa (1.0 × 10 ⁻⁶ Torr), and the film formation rate was 0.2 to 0.3 nm / sec.

  Next, in the same manner, on the hole transport layer (3), an aluminum chelate complex (Alq3) represented by the following chemical formula 2 and coumarin 6 represented by the following chemical formula 3 are 100: 6. Co-evaporation was performed at a weight ratio to form a light emitting layer (4) with a film thickness of 50 nm.

  Next, as the electron transport layer (5), a phenanthroline compound represented by the following chemical formula 4 was formed to a thickness of 10 nm.

  Subsequently, a transparent electrode (6) (ITO) was formed to a thickness of 150 nm by a sputtering method to obtain an organic EL element.

Further, after performing reverse sputtering treatment on the adhesion interface part (11-c) of the protective film (11-a), a SiOxNy film (11-b) was formed to 800 nm by a sputtering method. The protective film (11-a, b) is formed using a counter target sputtering apparatus (manufactured by Osaka Vacuum Co., Ltd.) and a Si target in order to prevent plasma damage to the organic EL element. The film was formed under the conditions of 45 kw, film forming pressure: 0.7 Pa, Ar flow rate: 30 sccm, N ₂ flow rate: 8 sccm, and O ₂ flow rate: ₂ sccm.

  The organic EL display device thus obtained was subjected to a high-temperature and high-humidity test (60 ° C., 90% humidity, left for 500 hours). However, before and after the test, display quality degradation such as generation of dark spots and reduction in luminous efficiency was observed. Did not occur. In addition, after a heat cycle test (−30 ° C. × 30 minutes + 60 ° C. × 30 minutes, 10 cycles), a high-temperature and high-humidity test (60 ° C., 90% humidity, left for 500 hours) was similarly performed. The display quality did not deteriorate.

(Example 2)
A second embodiment based on the present invention will be described with reference to FIG. FIG. 3 schematically shows a cross section of the side end of the organic EL display device manufactured in this example.

  First, a SiNx film (11-a) is formed to a thickness of 100 nm by sputtering on the substrate (1) on which the TFT (8) is formed, and then a contact hole is formed at the drain electrode portion of the TFT by dry etching. The planarization film (9) was formed by coating, exposing and developing a photocurable resin (acrylic resin (World Rock 815T, manufactured by Kyoritsu Chemical Co., Ltd.)) by spin coating. Next, similarly, using a photocurable resin (acrylic resin (World Lock 815T, manufactured by Kyoritsu Chemical Co., Ltd.)), a pixel separation film (10) was formed so as to cover the TFT and the electrode wiring. Subsequently, a chromium film having a thickness of 200 nm was formed and patterned to obtain a metal electrode (2).

  Thereafter, the substrate was successively subjected to ultrasonic cleaning with acetone and isopropyl alcohol (IPA), then boiled with IPA and dried. Further, UV / ozone cleaning was performed.

  Next, a hole transport layer (3), a light emitting layer (4), an electron transport layer (5), and a transparent electrode (6) (ITO) were formed in the same manner as in Example 1 to obtain an organic EL element. Obtained.

Further, after performing reverse sputtering treatment on the adhesion interface part (11-c) of the protective film (11-a), an SiNx film (11-b) was formed to 800 nm by sputtering. The protective film (11-a, b) is formed using a counter target sputtering apparatus (manufactured by Osaka Vacuum Co., Ltd.) and a Si target in order to prevent plasma damage to the organic EL element. The film was formed under the conditions of 45 kw, film forming pressure: 0.7 Pa, Ar flow rate: 30 sccm, and N ₂ flow rate: 8 sccm.

  Subsequently, a sealing glass cap (12) in which a desiccant (calcium oxide) (13) is formed is applied to a portion corresponding to a non-light emitting region of the organic EL display device with an adhesive (Araldite, manufactured by Ciba Geigy Japan) (14) Was attached to the element substrate to cover and protect the entire element to obtain an organic EL display device.

  The organic EL display device thus obtained was subjected to a high-temperature and high-humidity test (60 ° C., 90% humidity, left for 500 hours). However, before and after the test, display quality degradation such as generation of dark spots and reduction in luminous efficiency was observed. Did not occur. In addition, after a heat cycle test (−30 ° C. × 30 minutes + 60 ° C. × 30 minutes, 10 cycles), a high-temperature and high-humidity test (60 ° C., 90% humidity, left for 500 hours) was similarly performed. The display quality did not deteriorate.

(Comparative example)
In this comparative example, an organic EL display device was produced in the same manner as in Example 1 except that the protective film (11-a) shown in FIG. 2 was not formed.

  First, the substrate (1) on which the TFT (8) is formed is coated with a photo-curing resin (acrylic resin (World Lock 815T, manufactured by Kyoritsu Chemical Co., Ltd.)) by spin coating, and is flattened. A chemical film (9) was formed. Next, similarly, using a photocurable resin (acrylic resin (World Lock 815T, manufactured by Kyoritsu Chemical Co., Ltd.)), a pixel separation film (10) was formed so as to cover the TFT and the electrode wiring. Subsequently, a chromium film having a thickness of 200 nm was formed and patterned to obtain a metal electrode (2).

  Thereafter, the substrate was successively subjected to ultrasonic cleaning with acetone and isopropyl alcohol (IPA), then boiled with IPA and dried. Further, UV / ozone cleaning was performed.

  Next, a hole transport layer (3), a light emitting layer (4), an electron transport layer (5), and a transparent electrode (6) (ITO) were formed in the same manner as in Example 1 to obtain an organic EL element. Obtained.

Further, a SiOxNy film (protective film) having a thickness of 800 nm was formed by sputtering. In addition, in order to prevent the organic EL element from being damaged by plasma, the protective film is formed using a counter target sputtering apparatus (manufactured by Osaka Vacuum Co., Ltd.) and a Si target, DC power: 1.45 kw, film forming pressure: 0 The film was formed under the conditions of 0.7 Pa, Ar flow rate: 30 sccm, N ₂ flow rate: 8 sccm, and O ₂ flow rate: ₂ sccm.

  When the organic EL display device thus obtained was subjected to a high-temperature and high-humidity test (60 ° C., 90% humidity, left for 500 hours), the luminous efficiency of the device was lowered before and after the test. In addition, after performing a heat cycle test (−30 ° C. × 30 minutes + 60 ° C. × 30 minutes, 10 cycles), a high temperature and high humidity test (60 ° C., 90% humidity, left for 500 hours) was performed. The occurrence of dark spots was observed, resulting in a decrease in luminous efficiency.

It is sectional drawing which shows an example of a common organic EL element. It is a schematic diagram of the side end part cross section of the organic electroluminescence display based on Example 1 of this invention. It is a schematic diagram of the side end part cross section of the organic electroluminescence display based on Example 2 of this invention.

Explanation of symbols

1 Substrate 2 Metal electrode 3 Hole transport layer 4 Light emitting layer 5 Electron transport layer 6 Transparent electrode 7 Light emitted 8 TFT
9 flattening film 10 pixel separation film 11-a protective film 11-b protective film 11-c protective film bonding interface 12 sealing cap 13 desiccant 14 adhesive

Claims (3)

  An organic EL display device, wherein an organic EL element is sandwiched between two protective films containing Si and N as main components, and the two protective films are in contact with each other at a pattern end.   2. The organic EL display device according to claim 1, wherein the two protective films are either SiNx, SiOxNy, or SiHxNy.   3. The organic EL display device according to claim 1, wherein the organic EL element is a top emission element that extracts light emission from the upper surface side of the substrate.

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