JP2002190384A - Electroluminescent element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide improved durability of a carrier-injection electroluminescent element, using a substrate made of polymer material with prolonged life time of the electroluminescent element. SOLUTION: The electroluminescent element has an organic luminescent material between electrodes opposing each other, with the oxygen permeability of the substrate made of the polymer material being 1 (ml/m2.24 H.atm) or less, the polymer material formed by laminating the electrodes and thin films of the organic luminescent material (light-emitting part).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electroluminescent device (electroluminescent light emitting device), and more particularly to an electroluminescent device using an organic luminescent material.

[0002]

2. Description of the Related Art In an electroluminescent device, due to a difference in emission excitation mechanism, an intrinsic electroluminescent device which excites a luminous body by local movement of electrons and holes in a luminescent layer and emits light only in an alternating electric field, and an electrode. Injection of electrons and holes from the semiconductor and recombination thereof in the light emitting element layer excites the light emitting body, and is classified into two types of carrier injection type electroluminescent elements which operate by a DC electric field. Intrinsic electroluminescence type light emitting elements are generally ZnS, CaS, Sr
An inorganic compound in which a rare earth metal such as Mn or Ce is added to S is used as the light-emitting body. However, a high AC electric field of about 200 V is required for driving, the manufacturing cost of peripheral circuits is high, and the brightness and durability are high. There is a problem that the properties are insufficient.

On the other hand, carrier-injection type electroluminescent devices have been able to obtain high brightness since a thin film organic compound is used as a light emitting layer. Applied
Physics Letters, Vol. 51 (12),
P. 913 (1987) discloses an electroluminescent device comprising an anode, an organic hole injecting and moving body, an organic electron injecting light emitting body and a cathode. An aromatic tertiary amine is used as the organic hole injecting and moving body material. An electroluminescent device using an aluminum quinolate complex as an organic electron injecting luminescent material has been reported.

[0004] Recently, various proposals have been made for a light emitting material, a hole transporting material, an electron transporting material, and an electrode material, and remarkable improvements in all of luminous efficiency, luminous intensity, luminous color and luminous element life are seen. . In addition, light-emitting elements using an organic polymer material such as polyphenylenevinylene (PPV) as a light-emitting material have been actively developed. In applications where portability is important, such as mobile phones and notebook personal computers, lighter and thinner display devices are required. For this reason, a carrier injection type electroluminescent device using a substrate made of a polymer material instead of a conventional glass substrate has been proposed.

For example, Japanese Patent Application Laid-Open No. 10-144469 discloses an electroluminescent device using a photocurable resin substrate having a smooth surface. In Japanese Patent No. 293111, a plastic sheet subjected to lens processing is used for a substrate. However, polymer materials are more permeable to oxygen and water vapor than glass. Many organic materials and electrode materials used for the carrier injection type electroluminescent device are liable to react with water or oxygen, and it is reported that the luminescent characteristics are significantly deteriorated in the presence of water or oxygen. Therefore, a carrier-injection type electroluminescent device using a substrate made of a polymer material has not yet been put to practical use.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to improve the durability of a carrier-injection type electroluminescent device using a substrate made of a polymer material and extend the life of the device.

[0007]

The above object of the present invention is attained by the following items 1) to 11). 1) In an electroluminescent device having an organic light emitting material between opposing electrodes, the electrode and the organic light emitting material thin film (light emitting portion)
There substrate made of polymeric material to be laminated, electroluminescent device, characterized in that the oxygen permeability is one that is treated to be ^{1 (ml / m 2 · 24H} · atm) or less. 2) The electroluminescent device according to 1), wherein the substrate is formed by laminating a resin material layer or a metal oxide layer having low oxygen permeability. 3) The electroluminescent device according to any one of 1) to 2), wherein the substrate is a film or a sheet. 4) The portion where the light emitting portion is formed has an oxygen permeability of 1 (m
characterized in that the ^{l / m 2 · 24H · atm} ) or less of the polymeric material is coated with a coating material to the substrate 1) -
The electroluminescent device according to any one of 3). 5) The electroluminescent device according to 4), wherein the coating material is in the form of a film or a sheet. 6) The electroluminescent device according to 4) or 5), wherein the substrate on which the light emitting portion is formed and the covering material are adhered with a flexible epoxy adhesive. 7) The electroluminescent device according to any one of 4) to 6), wherein a space formed by the substrate on which the light emitting portion is formed and the coating material is filled with an inert gas. . 8) The electroluminescent device according to 7), wherein the pressure of the inert gas is 1 atm or more. 9) A drying agent (hygroscopic agent) and / or an oxygen absorbing agent is arranged between the substrate on which the light emitting portion is formed and the coating material. Electroluminescent element. 10) The light-emitting portion is separated from the desiccant (hygroscopic agent) and / or oxygen absorber by a film- or sheet-like separator made of a polymer material as a base material 9).
An electroluminescent device according to claim 1. 11) The oxygen permeability of the isolation ^{material, 1 (ml / m 2 ·} 24
H · atm) or more.

The oxygen permeability and the water vapor permeability of a substrate made of a polymer material (hereinafter, referred to as a polymer substrate) vary greatly depending on the type of polymer. However, even with polyethylene terephthalate (PET), which is said to have relatively excellent gas barrier properties, the oxygen permeability is 4 (ml / m2).
⁽ 2.24 H.atm), and it is difficult to obtain a substrate made of a single polymer material having a smaller oxygen transmission rate and a smaller water vapor transmission rate and having little influence on the deterioration over time of the electroluminescent element. As a method for reducing the oxygen transmission rate and the water vapor transmission rate of the polymer substrate, a method of applying a resin material such as polyvinylidene chloride to the polymer substrate as a base material, or a method of depositing a metal oxide on the polymer substrate by vapor deposition, sputtering, etc. And a method in which an organic metal material which is easily thermally decomposed is applied to a polymer substrate and then heated to laminate a metal oxide on the polymer substrate.

The present inventors have developed various oxygen transmission rates and water vapors.
Carrier-injection-type electrode using a polymer substrate with transmittance
A field emission device was prototyped, and electrodes and an organic luminescent material thin film
Below, these layers are collectively referred to as a light-emitting part).
The oxygen permeability of the plate is 1 (ml / m ²・ 24H ・ atm)
By lowering the durability of the electroluminescent device.
It has been found that the service life can be extended. polymer
Light and thin light-emitting elements can be obtained by using a substrate
There is also an advantage. Use in the electroluminescent device of the present invention
The organic luminescent material that can be used is aluminum quinolino
Complex, beryllium quinoline complex, hydroxyphenyl
Luoxazole, hydroxyphenylthiazole, etc.
In addition to low molecular weight materials, polyphenylene vinylene, polyvinyl
Polymer materials such as carbazole can be used.

Regarding the water vapor transmission rate of the polymer substrate,
It is preferable to be as small as possible. In addition, the portion where the light emitting portion is formed has an oxygen permeability of 1 (ml / m ² · 24H ·
It has been found that by coating with a coating material of atm) or less, the durability of the light emitting element can be further improved and the life can be prolonged. Polymer materials preferably used for the substrate and the coating material include polyethylene terephthalate, polycarbonate, polyether sulfone, polyarylate, and the like. The shape of the substrate or the covering material is not particularly limited as long as it is suitable for the electroluminescent element, but is preferably a film or a sheet from the viewpoint of weight reduction and thinning. Film or sheet thickness is 50-5
00 μm.

[0011] Oxygen transmission rate ^{1 (ml / m 2 · 24H} · a
tm) Examples of the resin material applied to the polymer substrate for the purpose of reducing the content to below are polyvinyl alcohol and Saran. Examples of the metal oxide to be laminated on the polymer substrate by vapor deposition, sputtering, or the like for the same purpose include silicon dioxide, aluminum nitride, silicon nitride, and aluminum oxide. As the easily decomposable organometallic material which is laminated on a polymer substrate as a metal oxide by heating for the same purpose, a metal alcoholate may be mentioned.

[0012] Examples of the adhesive for bonding the substrate on which the light emitting portion is formed and the covering material of the light emitting element include an acrylic adhesive and an epoxy adhesive. The use of an agent is particularly preferable because a strong adhesive strength can be obtained in which the adhesive surface is not broken even by the thermal expansion and contraction of the substrate. Examples of the inert gas filled in the space formed by the substrate on which the light emitting portion is formed and the covering material of the light emitting element include nitrogen, argon, and the like. Further, the pressure of the inert gas is preferably at least 1 atm, that is, at least normal atmospheric pressure, and more than 0.1 atm.
It is more preferable to increase the pressure by about 1 kg / cm ² . This is because by keeping the internal pressure of the light emitting element higher than the external pressure, the inflow of outside air into the light emitting element is prevented, and the deterioration of the light emitting element with time is reduced.

Further, by disposing a desiccant (hygroscopic agent) and / or an oxygen absorbent in a space formed by the substrate on which the light emitting section is formed and the covering material of the light emitting element, the length of one layer of the light emitting element can be increased. Life can be extended. Examples of the desiccant (hygroscopic agent) include calcium chloride, silica gel, and calcium oxide. As the oxygen absorbent, iron powder dispersed in a resin is often used. Furthermore, by separating the light-emitting portion from the desiccant (hygroscopic agent) and / or oxygen absorber with a film- or sheet-like separator made of a polymer material as a base material, the manufacturing process of the light-emitting element can be simplified. it can. Examples of the polymer material that can be used for the separator include polyethylene terephthalate, polycarbonate, polyethersulfone, and polyarylate. However, the oxygen permeability of the isolation member ^{1 (ml / m 2 · 24H} · a
Unless it exceeds tm), the effect of the desiccant (hygroscopic agent) and / or the oxygen absorbent is not exhibited due to insufficient gas permeability.

[0014]

The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited to these examples.

Example 1 A uniaxially stretched polyethylene terephthalate (PET) film having a thickness of 100 μm was ultrasonically washed in an aqueous detergent and isopropyl alcohol, and then dried at 100 ° C. On one surface of this substrate, a SiOx film (x: 1.
5 to 2.5) with a thickness of 30 nm to 1 μm. Subsequently, an ITO transparent conductive film having a thickness of 120 nm was formed on the same surface side of the substrate by a sputtering method. The substrate temperature during ITO film formation was set to 100 ° C. in consideration of the heat resistance of PET. Next, N, N'-bis (3-methylphenyl)-was used as a hole injection layer.
N, N'-diphenyl- [1,1'-biphenyl]-
4,4 ′ diamine (TPD) is 30 nm, and tris (8-quinolinolate) aluminum (Al
q ₃₎ was 500nm film formation by vacuum deposition. Subsequently, magnesium and silver were co-evaporated to a thickness of 100 nm so that the composition ratio became 10: 1 to form an upper electrode of the light-emitting element.
Finally, a cover glass having a thickness of 0.05 mm was adhered as a surface protective film using a photocurable resin 3052 manufactured by Three Bond.

Example 2 A 100 μm-thick polycarbonate (PC) film was subjected to ultrasonic cleaning in an aqueous detergent and isopropyl alcohol, and then dried at 100 ° C. An SiOx film (x: 1.5 to 2.5) 200 nm was formed on this substrate by a sputtering method. Subsequently, the ITO transparent conductive film 1 is formed by sputtering.
20 nm was formed into a film. Next, Example 1 was used as a hole injection layer.
The same TPD as in Example 1 was formed into a film having a thickness of 30 nm, and the same light emitting layer as in Example 1 was formed using Alq ₃ in a thickness of 500 nm by vacuum evaporation. Subsequently, magnesium and silver were added in such a manner that the composition ratio became 10: 1.
The upper electrode of the light emitting element was formed by co-evaporation of 00 nm. Finally, a SiOx film (x: 1.5 to
2.5) Thickness 100 formed by sputtering 200 nm
A μm polycarbonate (PC) film was bonded using a photocurable resin 3052 manufactured by Three Bond.

Example 3 A polyethersulfone film having a thickness of 100 μm was ultrasonically washed in an aqueous detergent and isopropyl alcohol, and then dried at 100 ° C. An SiOx film (x: 1.5 to 2.5) 200 nm on both surfaces of this substrate by sputtering.
Was formed. Subsequently, an ITO transparent conductive film having a thickness of 120 nm was formed on only one surface by the same sputtering method. Next, the same TPD as in Example 1 was formed to have a thickness of 30 nm as a hole injection layer, and the same Alq ₃ as in Example 1 was formed to have a thickness of 500 nm as a light emitting layer by vacuum evaporation. Subsequently, magnesium and silver were mixed at a composition ratio of 1
The upper electrode of the light-emitting element was formed by co-evaporation at a ratio of 0: 1 to 100 nm. Further, as shown in FIG. 1, a flexible thermosetting epoxy adhesive 3 (ERS manufactured by Sumitomo Bakelite Co., Ltd.) is applied in a shape surrounding the light emitting portion (organic light emitting material thin film) 2 so as to surround the substrate. Similarly, it was bonded to a 100 μm-thick polyethersulfone film having a 100 nm SiOx film on both sides to form a bag-like structure.
At this time, the surface on which the light emitting layer was formed was located inside the bag. Next, the bag-shaped element member was placed in a closed container, and the pressure in the closed container was reduced to 0.1 Pa.
After standing at 0.1 Pa for 10 minutes, nitrogen gas was introduced into the closed container to increase the pressure in the container to atmospheric pressure (about 1 atm), and the opening 4 was opened in the container with a thermosetting epoxy adhesive. Sealed.

Example 4 A bag-like structure as shown in FIG. 1 was formed in the same manner as in Example 3. Next, the bag-shaped element member was placed in a closed container, and the pressure in the closed container was reduced to 0.1 Pa. After leaving at 0.1 Pa for 10 minutes, nitrogen gas is introduced into the closed container, and the pressure in the container becomes 0.1 kg below atmospheric pressure.
/ Cm ^2, and the opening was sealed with a thermosetting epoxy adhesive while maintaining the pressure in the container.

Example 5 The same procedure as in Example 3 was performed up to the step of forming the upper electrode of the light emitting element. Next, a flexible thermosetting epoxy adhesive (ERS, manufactured by Sumitomo Bakelite Co., Ltd.) is applied in a shape surrounding the periphery of the light emitting portion, and 100 n on both sides like the substrate.
A 100 μm-thick polyethersulfone film having an m.sup.x SiOx film was bonded to form a bag-like structure. At this time, the surface on which the light emitting layer was formed was located inside the bag, and the particle size was 50 μm as a desiccant (hygroscopic agent).
Of silica gel, ferrous oxide having a particle size of 25 μm as an oxygen absorbent dispersed in low-density polyethylene, and having a thickness of 25 μm.
m, and then inserted into a bag-shaped structure such that the low-density polyethylene-coated surface was on the side opposite to the light-emitting layer. The embodiment is shown in FIG. Then
The bag-shaped element member was placed in a closed container, and the pressure in the closed container was reduced to 0.1 Pa. 1 at 0.1 Pa
After standing for 0 minutes, nitrogen gas was introduced into the closed container, and the pressure was increased until the pressure in the container became 0.1 kg / cm ² higher than the atmospheric pressure. While maintaining the pressure in the container, the opening was sealed with a thermosetting epoxy adhesive.

Comparative Example 1 A carrier-injection type electroluminescent device was manufactured in the same manner as in Example 1, except that a substrate on which an SiOx film as a layer for lowering the oxygen permeability was not formed was used. .

Comparative Example 2 A carrier injection type electroluminescent device was prepared in the same manner as in Example 2 except that a surface protective layer in which a SiOx film as a layer for lowering oxygen permeability was not formed was used. Produced.

Comparative Example 3 The adhesive applied in a shape surrounding the periphery of the light emitting portion was changed from a flexible thermosetting epoxy adhesive to a non-flexible light-curing acrylic adhesive (manufactured by Three Bond Co., Ltd.). 30Y
-296G), except that the carrier injection type electroluminescent device was manufactured in the same manner as in Example 3.

Reference Example The steps up to the step of forming the upper electrode of the light emitting element were performed in the same manner as in Example 5 (that is, in the same manner as Example 3). Next, a flexible thermosetting epoxy adhesive (ERS, manufactured by Sumitomo Bakelite Co., Ltd.) is applied in a shape surrounding the periphery of the light-emitting portion, and a thickness of 1 having a 50 nm SiOx film on both surfaces in the same manner as the substrate
It was bonded to a 00 μm polyethersulfone film to form a bag-like structure. At this time, the surface on which the light-emitting layer was formed was placed inside the bag, and silica gel having a particle size of 50 μm was used as a desiccant (hygroscopic agent), and ferrous oxide having a particle size of 25 μm was used as an oxygen absorbent. The dispersion was applied to a 100 μm-thick polycarbonate film, and inserted into a bag-like structure such that the low-density polyethylene application surface was on the side opposite to the light-emitting layer. Note that a 200 nm SiOx film was formed on the polycarbonate film in advance by a sputtering method. Next, the bag-shaped element member was placed in a closed container, and the pressure in the closed container was reduced to 0.1 Pa. After standing at 0.1 Pa for 10 minutes, nitrogen gas was introduced into the sealed container to increase the pressure until the pressure in the container became 0.1 kg / cm ² higher than the atmospheric pressure. While maintaining the pressure in the container, the opening was sealed with a thermosetting epoxy adhesive.

The emission intensity when the electroluminescent devices of Examples 1 to 5 and Comparative Examples 1 to 4 manufactured as described above were driven in a constant temperature layer at 70 ° C. under the condition that the current density was 10 mA / cm ^2. Was examined for changes. For Example 1, Table 1 summarizes the film thickness of the substrate on which the light-emitting element was manufactured, the oxygen transmittance, and the time (H) until the emission intensity became half of the initial value. As is clear from the table, the oxygen transmission rate of the substrate was 1 (ml / m ^2.
At 24 H.atm or less, the effect of preventing the deterioration of the element is remarkable.

[0025]

[Table 1]

For Examples 2 to 5, Comparative Examples 1 to 3, and Reference Examples, Table 2 summarizes the time required for the emission intensity to be reduced to half of the initial value. In Example 3, a bag-like structure is formed,
Further, by filling with nitrogen gas, the element life is greatly extended as compared with the case where only the surface protective layer of Example 2 is provided. In the fourth embodiment, since the pressure of the nitrogen gas is higher than the atmospheric pressure, the element life is further extended as compared with the case of the atmospheric pressure in the third embodiment. In the fifth embodiment, the device life is further remarkably extended as compared with the fourth embodiment by arranging the desiccant (hygroscopic agent) and the oxygen absorbent.

In Comparative Example 3, the adhesive layer of the protective layer film was damaged in the early stage of the life test, and the film was peeled off. Further, the reference example is related to claim 10, and when a separator having poor gas permeability is used, the fifth embodiment can be used.
The effect of the desiccant (hygroscopic agent) and the oxygen absorbent as shown in (1) is not exhibited, and the element life is only equivalent to that of Example 4 in which the desiccant (hygroscopic agent) and the oxygen absorbent are not provided. It is shown that.

[0028]

[Table 2]

[0029]

Oxygen permeability according to the present invention is ^{1 (ml / m 2 · 24H} ·
atm) By using a polymer substrate that is:
The life of the electroluminescent element can be extended. The portion where the light emitting portion is formed has an oxygen transmittance of 1 (m
coating the ^{l / m 2 · 24H · atm} ) or less of the polymeric material with a coating material to the substrate, filling an inert gas into the space formed by the substrate and the coating material, the pressure of the inert gas The life can be further prolonged by setting it to 1 atm or more and arranging a desiccant (hygroscopic agent) and / or an oxygen absorbent between the substrate and the covering material. In addition, by forming the substrate and the covering material in a film or sheet shape, a light and thin electroluminescent element can be obtained while maintaining the light emission life. Further, the manufacturing process can be simplified by separating the light-emitting portion from the desiccant (hygroscopic agent) and / or the oxygen absorbent with a film or sheet having a polymer material as a base material. Further, by bonding the substrate and the covering material with a flexible epoxy-based adhesive, it is possible to obtain a strong bonding strength such that the bonding surface does not break even when the substrate expands and contracts due to temperature.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an electroluminescent device shown in Example 3.

FIG. 2 is a sectional view of the electroluminescent device shown in Example 5.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Polymer film substrate 2 Light emitting part 3 Adhesive 4 Opening 5 Protective layer 6 Desiccant (hygroscopic), oxygen absorbent isolating film 7 Desiccant (hygroscopic), oxygen absorbent layer

Claims (11)

[Claims] 1. An electroluminescent device having an organic light emitting material between opposing electrodes, wherein the substrate made of a polymer material on which the electrode and the organic light emitting material thin film (light emitting portion) are laminated is:
Electroluminescent device, characterized in that the oxygen permeability is one that is treated to be ^{1 (ml / m 2 · 24H} · atm) or less. 2. The electroluminescent device according to claim 1, wherein the substrate is formed by laminating a resin material layer or a metal oxide layer having low oxygen permeability. 3. The electroluminescent device according to claim 1, wherein the substrate is in the form of a film or a sheet. 4. characterized in that the portion where the light emitting portion is formed is covered with the bag shape oxygen permeability ^{1 (ml / m 2 · 24H} · atm) or less of the polymeric material with a coating material to the substrate The electroluminescent device according to claim 1. 5. The electroluminescent device according to claim 4, wherein the covering material is in the form of a film or a sheet. 6. The electroluminescent device according to claim 4, wherein the substrate on which the light emitting portion is formed and the covering material are bonded with a flexible epoxy adhesive. . 7. The space according to claim 4, wherein a space formed by the substrate on which the light emitting section is formed and the covering material is filled with an inert gas. Electroluminescent device. 8. The electroluminescent device according to claim 7, wherein the pressure of the inert gas is 1 atm or more. 9. The method according to claim 4, wherein a desiccant (hygroscopic agent) and / or an oxygen absorbent is disposed between the substrate on which the light emitting portion is formed and the covering material. An electroluminescent device according to any one of the above. 10. A light-emitting portion and a desiccant (hygroscopic agent) and / or an oxygen absorbent are separated by a film or sheet-like separator made of a polymer material as a base material. An electroluminescent device according to claim 1. 11. The oxygen permeability of the separator is 1 (ml / m2).
Electroluminescent device of claim 10, wherein a is ² · 24H · atm) or more.