JPH04267097A - Sealing method for organic light emitting element - Google Patents

Abstract

PURPOSE:To carry out sealing of an organic light emitting element which is easily subject to a damage caused by heating or an organic solvent without damaging the element, mechanically protecting the element, and restraining deterioration of light emitting intensity. CONSTITUTION:In a sealing method where a film consisted of at least two layers is formed on an organic light emitting element, a thin film 401 of a first layer is formed by a vapor phase method such as a deposition method or a chemical vapor phase epitaxial method, and a photocuring resin is deposited on the first layer, followed by curing by light irradiation, thus obtaining a second layer 402.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is directed to so-called electroluminescent elements (EL), which are electrical light-emitting elements used in various illuminations such as backlights of liquid crystal displays and various decorations, displays, displays, and light sources for optical communication. This invention relates to a method for sealing an element.

More specifically, the present invention relates to a method for sealing an organic light-emitting device containing an organic compound or an organometallic complex compound in a light-emitting layer, an electron or hole transfer layer, or the like.

0003

2. Description of the Related Art Hitherto, high-brightness organic light-emitting devices have been known as electroluminescent devices. For example, regarding this organic light emitting device, Applied Physics Letter (Appl. Phys. Let.) 5
1 913 (1987) and Japanese Journal of Applied Physics (Jpn
．． J. Appl. Phys. )271269
(1988), etc.

The devices announced in these publications have a structure in which a transparent electrode is formed on a transparent substrate such as glass, and a hole transport layer, a light emitting layer, and in some cases an electron transport layer and an electrode are layered on top of the transparent electrode. , it is a thin film surface emitting device with a total thickness of several μm or less. Therefore, it is expected to be applied to matrix movable displays.

[0005] In this organic light emitting device, an organic compound or an organometallic complex such as a diamine or an aluminum complex is used in the hole transport layer, electron transport layer, or light emitting layer, and the layer is typically composed of vapor-deposited films of these. It is known as an example.

[0006] Such organic light-emitting devices are composed of organic thin films or organic compounds, and because they are thin films on the μm level, they have low mechanical strength, and furthermore, oxygen and water in the atmosphere can reduce the luminescence intensity. known to bring about

For example, the 59th Spring Annual Meeting of the Chemical Society of Japan Abstracts III 2409, 2 Special 606 (1990)
describes that at a practical luminance of 100 cd/m2 or more, the luminance and efficiency rapidly decrease. Although the cause of these deteriorations is not clear, it is presumed that oxygen and water in the atmosphere are one of the causes. 4 (1990), it has been revealed that oxygen causes deterioration of the luminescence of an organic light-emitting layer.

[0008] Therefore, it is necessary to mechanically protect the device and seal it from oxygen and moisture in the atmosphere. However, since organic light-emitting devices are thin films containing organic compounds or organometallic complexes, the method of sealing by forming a sealing film on the thin film requires the use of organic solvents for coating and curing the sealing film. In the film formation process that involves a heating process, the quality of the thin film changes, causing damage to the element, making it impossible to use as a practical sealing method.
There was no practical sealing method.

[0009]

[Problems to be Solved by the Invention] The present invention solves the practical problem of deterioration of luminescence intensity in organic light emitting devices by mechanically protecting them and sealing them from oxygen and moisture in the atmosphere. It's about doing.

0010

[Means for Solving the Problems] In order to solve the above problems, the inventors of the present invention, as a result of intensive studies on sealing materials and methods, have developed a photocurable molding material on a first layer formed in a low-temperature process using at least a vapor phase method. It was discovered that the two-layer structure of the second layer made of resin makes it possible to mechanically protect the organic light-emitting element without causing any damage to the element, and also to suppress the deterioration of the luminescence intensity, and has developed the present invention. completed.

[0011] In an organic light emitting device, the present invention protects and seals the device with a film having at least a two-layer structure, and forms a first layer of the sealing film from the device side by a vapor phase method. This is a method of sealing an organic light-emitting device in which two layers are formed by coating a photocurable resin on the first layer and curing it.

[0012] The organic light-emitting device in the present invention refers to an electroluminescent device in which layers constituting the device, such as a hole transport layer, a light emitting layer, and an electron transport layer, are made of an organic compound or an organometallic complex or contain them. say.

FIG. 1 shows an example of the configuration of the present invention. In this figure, 401 indicates the first sealing layer, and 402 indicates the second sealing layer. The first layer is formed by a vapor phase method. In the present invention, the vapor phase method refers to a vapor deposition method and a chemical vapor deposition method, in which insulating oxides, organic compounds, high-molecular organic compounds, and radicals are vaporized and layered on the surface of the sealant. A method of laminating layers through chemical reaction or polymerization. Regarding these specific methods, see, for example, Japan Society for the Promotion of Science, Thin Film No. 13.
1 Committee, Thin Film Handbook (1983) Ohmsha
etc. are listed. As the first layer of the present invention, a SiO2 film may be formed by ordinary organic vapor deposition or chemical vapor deposition, but a polymer thin film is more preferable from the viewpoint of resistance to photocurable resin and bondability.

[0014] As methods for forming such a polymer thin film, there are known methods in which radicals are created by methods such as plasma polymerization and thermal decomposition, and polymer vacuum evaporation methods. For example, the aforementioned Japan Society for the Promotion of Science, Thin Film No. 1
31 Committee, Thin Film Handbook (1983), Ohmsha, p. 246 and 66th Electrophotography Society Conference Abstracts 68 (1990) describe specific methods for forming polymer thin films by the vapor phase method. For example, a film can be formed by causing glow discharge while introducing a gas such as methane, ethylene, butadiene into the vicinity of the electrode under a pressure of several Torr or less. Further, a polymer film made of polyparaxylene can be formed on the element by thermal decomposition of diparaxylene in the gas phase.

According to the present invention, the first layer can be uniformly formed on the element, the end face of the element, and the substrate by these methods. Before forming the first layer, a primer layer may be applied as a preliminary coat on the substrate or electrode in order to improve the adhesion between the substrate or electrode and the first layer.

[0016] The primer layer is preferably formed by a vapor phase method, and the film thickness may be thin, and is usually formed to a thickness of 10 nm or less. For example, vapor deposition of a silane coupling agent can be cited as a suitable example for improving adhesion to a substrate or electrode made of glass or an inorganic compound.

[0017] The thickness of the first layer is from 0.1 μm to 50 μm.
is preferable, and the first layer may have a multilayer structure formed by a plurality of vapor phase methods, and may be composed of multiple components.

The second layer is formed by coating a photocurable resin on the first layer and curing it by irradiating it with a predetermined light.

The photocurable resin may be one that contains few volatile components such as solvents, has low permeability to atmospheric oxygen and moisture during curing, and has low residual strain.

[0020] In general, a photocurable resin is composed of a photopolymerizable monomer, a photopolymerizable oligomer, a photoinitiator, a solvent, and other additives, and these are prepared and used.

The photocurable resin used in the present invention preferably has a small solvent content, preferably 5%.
The following is preferable, and more preferably, it does not contain. Similarly, it is preferable that the amount of other volatile components is small, and it is even more preferable that they be omitted.

The photopolymerizable monomer used in the present invention is preferably a non-volatile monomer, and preferably has a high boiling point. Therefore, photopolymerizable monomers are selected from those with low volatility and low shrinkage during polymerization, such as branched polyfunctional monomers such as trimethylol acrylates such as trimethylolpropane triacrylate and ditrimethylolpropane tetroacrylate. Long chain acrylates such as 1,6-hexanediol diacrylate, 1,6-hexanediol dimethacrylate,
Preferred examples include monomers with large molecular bulk such as cyclohexyl acrylates such as dicyclopentenyloxyethyl acrylate, dicyclopentenyl acrylate, and cyclohexyl methacrylate, and isobornyl acrylate.

The photopolymerizable oligomer preferably has good insulation properties and water resistance. Preferred examples of such photopolymerizable oligomers include polyester acrylate, epoxy acrylate, urethane acrylate, acrylic acrylate, and polyether acrylate. From the standpoint of insulation and water resistance, epoxy acrylate is a more preferred example.

As photoinitiators, benzoin ethers,
Examples include benzophenones, thioxansones, acetophenones, and ketals, but benzophenones such as benzophenone and Mikhail ketone, and ketals such as benzyl dimethyl ketal are more preferred.

[0025] In addition, fillers such as mica, glass fiber, silica, and inert polymers may be added as additives, and thixotropic agents and modifiers may be added as necessary. Furthermore, an agent for improving adhesion to metals and inorganic substances may be added.

Preferred examples of the method for applying the photocurable resin onto the first layer include a spray method, a screen printing method, a dip coating method, and a spin coating method. After being applied, the photocurable resin applied by such a method is cured by being irradiated with light using a mercury lamp, a xenon lamp, or the like. A heat ray cut filter or the like may be used to avoid heating the irradiation surface of the light emitting element. The thickness of the resin after curing is preferably 30 μm or more in order to obtain a sealing effect.

[0027]

[Examples] The present invention will be specifically explained below with reference to Examples, but the embodiments of the present invention are not limited thereto. Example 1 (1) On a 50 mm x 50 mm regular square blue plate glass with a thickness of 1.8 mm, a 30 mm x 30 square plate was placed in the center of the glass.
Apply a mask so that a film is formed in a square of mm,
A tris(8-hydroxyquinoline) aluminum complex thin film serving as a light emitting layer was formed to a thickness of 20 nm by vacuum evaporation. (2) Diparaxylylene dichloride is vaporized in a preliminary chamber, thermally decomposed at 680°C and 0.5 Torr, and the decomposed radical monomer is applied onto the tris(8-hydroxyquinoline) aluminum complex thin film formed in (1). A first sealing film layer of a polymonochloroparaxylene film having a thickness of 5 μm was formed. (3) Viscoat 540 epoxy acrylate (manufactured by Osaka Organic Chemical Industry) 50 wt%, light acrylate I
20 wt% of B-XA isobornyl methacrylate (manufactured by Kyoeisha Yushi Kagaku Co., Ltd.) and 30 wt% of Aronix M-315 triacryloyloxyethyl isocyanate (manufactured by Toagosei Kagaku Kogyo Co., Ltd.) were mixed, and 3 wt% of the total was added as a photoinitiator. Darocure 1173 (manufactured by Merck & Co., Ltd.) was added to prepare a photocurable resin. This photocurable resin was placed on the first layer formed in (2), and spin coating was performed by rotating at 1000 rpm while keeping the substrate horizontal. Immediately after spin coating, light irradiation with a high-pressure mercury lamp was performed for 15 minutes in a nitrogen atmosphere to cure the second sealing film.
formed a layer. When the film thickness of the photocurable resin layer was measured,
It was 160 μm. (4) When the tris(8-hydroxyquinoline) aluminum thin film serving as the light-emitting layer was excited with excitation light of 400 nm and the emission spectrum was compared before and after the formation of the sealing film, there was almost no change. This indicates that even when the organic thin film itself is sealed, the organic thin film is not damaged by the formation of the sealing film. (5) This sealed tris(8-hydroxyquinoline) aluminum thin film sample was continuously irradiated with 400 nm excitation light using an emission spectrometer (Shimadzu Spectral Photometer RF-5000) with a slit of 10 mm, and the emission spectrum was measured. When a deterioration test was conducted, almost no deterioration of the emission spectrum was observed even after 60 minutes of irradiation. FIG. 2 shows the change in emission intensity at 520 nm (■ in the figure).

Comparative Example 1 When the same deterioration test as in (5) of Example 1 was conducted on the device with only the organic thin film formed in (1) of Example 1 but without sealing, it was found that the luminescence intensity changed over the irradiation time. A phenomenon was observed in which the number decreased with time. From this initial stage, 1 minute, 3 minutes,
Figure 3 shows the change in emission spectrum at 10 minutes, 30 minutes, and 60 minutes.
Figure 2 shows the change in emission intensity at 520 nm (■ in the figure).
) is shown. This shows that in Example 1, the deterioration of the light emission of the organic thin film was suppressed by the sealing method of the present invention.

Comparative Example 2 When the same deterioration test as in Example 2 (5) was performed on the device sealed with only the first layer formed by the vapor phase method formed in Example 1 (2), no deterioration was observed. Ta. Figure 2 shows the change in luminescence intensity (■ in the figure). This indicates that the first layer alone was not able to sufficiently seal off oxygen and moisture in the atmosphere.

Comparative Example 3 A photocurable resin was coated and cured under the same conditions as in Example 1 (3) to the element having only an organic metal thin film formed in Example 1 (1). When the same deterioration test as in Example 1 (5) was conducted, it was found that the emission spectrum hardly changed and deterioration was suppressed. However, when the emission spectra were measured before and after photocuring, the emission intensity was reduced to approximately half. This indicates that a sealing method using only a photocurable resin has a sealing effect, but damages the organometallic complex thin film during formation of the sealing film.

Example 2 (1) A glass substrate (Matsuzaki vacuum (manufactured by) by vacuum evaporation method.
,N,N',N'-tetraphenyl-1,3-diaminobenzene thin film, tris(8-hydroxyquinoline)aluminum, and magnesium in order of 30nm and 20nm.
A light-emitting device was formed by laminating layers with a thickness of 200 nm and 200 nm. (2) Diparaxylylene dichloride was vaporized in a preliminary chamber and thermally decomposed at 680°C and 0.5 Torr, and the decomposed radical monomer was evaporated onto the laminated film formed in (1) to form a film with a thickness of 8 μm. A first sealing film layer of polymonochloroparaxylene film was formed. (3) Viscoat 540 epoxy acrylate (manufactured by Osaka Organic Chemical Industry) 50 wt%, light acrylate I
20 wt% of B-XA isobornyl methacrylate (manufactured by Kyoeisha Yushi Kagaku Co., Ltd.) and 30 wt% of Aronix M-315 triacryloyloxyethyl isocyanate (manufactured by Toagosei Kagaku Kogyo Co., Ltd.) were mixed, and 3 wt% of the total was added as a photoinitiator. Darocure 1173 (manufactured by Merck & Co., Ltd.) was added to prepare a photocurable resin. This photocurable resin was placed on the first layer formed in (2), and spin coating was performed by rotating at 1000 rpm while keeping the substrate horizontal. Immediately after spin coating, light irradiation was performed using a high-pressure mercury lamp in a nitrogen atmosphere for 15 minutes to cure and form a second sealing film layer. (4) The luminance characteristics of the sealed device are 14
There was almost no change even after continuous light emission for 100 hours while applying a voltage of V. In addition, the initial luminance characteristics were almost the same as the initial characteristics of the device obtained in Example 2 (1). Figure 4 shows the brightness-voltage change (■: initial, ■: 1
00 hours later) and FIG. 5 shows the temporal change in brightness (■ in the figure). From this, it can be seen that even in the case of sealing a light emitting element made of a laminated film including an organic thin film, the element is not damaged by the formation of the sealing film and deterioration is suppressed by the sealing.

Comparative Example 4 When the same deterioration test as in (4) of Example 2 was conducted on the device that was not sealed with only the laminated film formed in (1) of Example 2, it was found that the luminance was It decreased with This is shown in FIG. 5 (■ in the figure). This shows that in Example 2, the deterioration of the light emitting element was suppressed by the sealing method of the present invention.

Comparative Example 5 When the same deterioration test as in Example 2 (4) was carried out on the element sealed with only the first layer formed by the vapor phase method prepared in Example 2 (2), the emission intensity was Deterioration was observed. This is shown in FIG. 5 (■ in the figure). This indicates that the first layer alone cannot sufficiently seal the light emitting element from oxygen and moisture in the atmosphere.

Comparative Example 6 A photocurable resin was applied and cured under the same conditions as in Example 2 (3) to the unsealed multilayer film-only device prepared in Example 2 (1). . When the same deterioration test as in (4) of Example 2 was conducted, it was observed that dark speckled areas appeared on the light emitting surface and spread with the emitting time. This shows that, at least in the sealing method using only a photocurable resin, the photocurable resin component passes through the electrode layer during and after formation of the sealing film and damages the organometallic complex thin film.

Example 3 (1) A 50 mm x 50 mm square ITO with a thickness of 1.0 nm was used as a transparent electrode on a glass substrate (manufactured by Matsuzaki Vacuum Co., Ltd.) that had been pattern-etched with a thickness of 200 nm. A light-emitting device was made by laminating N,N,N',N'-tetraphenyl-1,3-diaminobenzene thin film, tris(8-hydroxyquinoline)aluminum, and magnesium to thicknesses of 30 nm, 20 nm, and 200 nm using a vapor deposition method. was formed. (2) 1,3-butadiene gas is introduced near the laminated film formed in (1) using hydrogen as a carrier gas, and the pressure is 1
Glow discharge was performed at Torr to form a polymer film of 0.8 μm, which was used as the first layer of the sealing film. (3) Viscoat 540 epoxy acrylate (manufactured by Osaka Organic Chemical Industry) 50 wt%, light acrylate I
20 wt% of B-XA isobornyl methacrylate (manufactured by Kyoeisha Yushi Kagaku Co., Ltd.) and 30 wt% of Aronix M-315 triacryloyloxyethyl isocyanate (manufactured by Toagosei Kagaku Kogyo Co., Ltd.) were mixed, and 3 wt% of the total was added as a photoinitiator. Darocure 1173 (manufactured by Merck & Co., Ltd.) was added to prepare a photocurable resin. This photocurable resin was placed on the first layer formed in (2), and spin coating was performed by rotating at 1000 rpm while keeping the substrate horizontal. Immediately after spin coating, light irradiation was performed using a high-pressure mercury lamp in a nitrogen atmosphere for 15 minutes to cure and form a second sealing film layer. (4) As in Example 2, the luminance characteristics of the sealed device hardly changed even after continuous light emission for 100 hours. Further, the initial luminance characteristics were almost the same as the initial characteristics of the device before sealing.

[0036]

[Effects of the Invention] The sealing method of the present invention is a very good method for forming a film that protects and seals an organic light-emitting element, thereby suppressing deterioration of the light-emitting element. It is estimated that such effects are obtained for the following reasons. First, there is no heating process and the sealing film is formed at a low temperature, so the organic light emitting device itself is not damaged. In addition, the first layer acts as a protective layer for the photocurable resin of the second layer, and prevents damage to the organic light emitting element due to the resin component itself or the solvent or volatile components contained in the resin. It is believed that due to these factors, a sealing film can be substantially formed without damaging the device. In addition, the film formed by the vapor phase method for the first layer has no residual strain due to film formation, and has the effect of buffering the strain of photocurable resin, which has some volumetric shrinkage due to its characteristics. It is thought that a film with excellent sealing effect is formed because it has good bonding properties with the mold resin.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of the configuration of a sealing film in the present invention.

FIG. 2 is a diagram showing changes in luminescence intensity in a deterioration test, where ■ is the result of Example 1, ■ is the result of Comparative Example 1, and ■ is the result of Comparative Example 2.

FIG. 3 is a diagram showing changes in the emission spectrum of Comparative Example 1 in a deterioration test; Represents the spectrum at 60 minutes.

FIG. 4 is a diagram showing voltage-luminance characteristics in Example 2, where ■ is the initial characteristic and ■ is the characteristic after 100 hours.

FIG. 5 is a diagram showing changes in luminescence intensity in a deterioration test, where ■ indicates the results in Example 2, ■ indicates the results in Comparative Example 4, and ■ indicates the results in Comparative Example 5.

[Explanation of symbols]

000 Transparent substrate 100 Transparent electrode 201 Hole transport layer 202 Luminescent layer 300 electrode 401 Sealing film first layer 402 Sealing film second layer

Claims (1)

[Claims] 1. In an organic light-emitting device, the device is protected and sealed by a film having at least a two-layer structure,
The first layer is formed from the element side of the sealing film by a vapor phase method, and the second layer is formed by coating a photocurable resin on the first layer and curing it. A method of sealing a light emitting element.