KR100617176B1 - Organic Electroluminescence Display Device - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic electroluminescent device using an organic hygroscopic agent to extend the life of the device, wherein the organic electroluminescent device has a light emitting layer between an anode and a cathode on a substrate, and an absorbent layer for removing moisture in the device is formed. In the moisture absorbent layer, an organic material having an isocyanate group introduced therein is used.

Hygroscopic, Organic Substance, Luminous Life

Description

Organic Electroluminescence Display Device

1 is a cross-sectional view of a general organic electroluminescent device.

2 is a cross-sectional view of an organic electroluminescent device for explaining the problems of the prior art.

3 is a cross-sectional view of an organic electroluminescent device according to a first embodiment of the present invention.

4 is a cross-sectional view of an organic electroluminescent device according to a second embodiment of the present invention.

5 is a cross-sectional view of an organic electroluminescent device according to a third embodiment of the present invention.

* Explanation of symbols on the main parts of the drawings

101: transparent substrate 102: anode

108: cathode 110: organic EL layer

111: packaging plate 112: moisture absorbent layer

112a: absorbent thick film 114: sealing agent

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electroluminescent display device, and more particularly, to an organic electroluminescent device having a hygroscopic agent for extending the life of the organic electroluminescent device.

Recently, researches on flat panel displays have been actively conducted. Among them, liquid crystal displays (LCDs), Feiled Emission Displays (FEDs), electroluminescence devices (ELDs), and plasma display panels (PDPs) have been in the spotlight.

Among them, liquid crystal displays are widely used in personal information terminals including personal communication service (PCS), but organic electroluminescent devices of self-luminous are attracting attention because they have a problem that the viewing angle is narrow and the response speed is slow.

The organic electroluminescent device has the advantage of being able to adapt to various tastes of modern people as it can realize a low voltage driving due to thinness and a fast response speed and excellent brightness. In addition, the device may be formed on a flexible transparent substrate such as plastic.

In addition, the device is suitable for the next-generation flat panel display because it can be driven at a lower voltage than the PDP, has a relatively low power consumption, and can easily realize three colors of green, red, and blue.

On the other hand, the electroluminescent device is applied to the cathode and the anode formed on both ends of the EL layer by injecting and transferring electrons and holes in the EL layer to combine with each other, electroluminescence (EL) phenomenon emitted by the binding energy at this time Will be used.

The materials having electroluminescent properties can be both inorganic and organic. Inorganic electroluminescent devices using inorganic materials have electrons accelerated by a high electric field colliding with the luminescent impurity, excited, and the excited luminescent material falls to the ground state. An organic electroluminescent device that emits light and uses organic materials falls from an excite state to a ground state after pairing electrons and holes respectively injected from an anode electrode and a cathode electrode. It emits light.

Currently, electroluminescent devices using inorganic materials have already been commercialized, but inorganic ELDs are not only difficult to obtain high luminance and high luminance light, but also difficult to obtain various colored lights.

On the contrary, the organic electroluminescent device is driven by a DC voltage of several to several tens of volts, has a high brightness of several hundred to several thousand cd / m ² , and has various advantages in obtaining various emission colors according to molecular structure changes. It becomes the target of.

Hereinafter, an organic electroluminescent device of the prior art will be described with reference to the accompanying drawings.

1 is a cross-sectional view of a general electroluminescent device, and FIG. 2 is a cross-sectional view of an organic electroluminescent device for explaining the problems of the prior art.

In general, the electroluminescent device includes an anode 2 which is a transparent electrode formed on the transparent substrate 1, an organic EL layer 10 formed on the anode 2, and the organic EL layer as shown in FIG. 1. And a packaging plate ("11" in FIG. 2) bonded to the cathode 8 formed on the upper surface 10 and opposed to the transparent substrate 1 above the cathode 8. At this time, the organic EL layer 10 is composed of a laminated film of a hole injection layer 3, a hole transport layer 4, a light emitting layer 5, an electron transport layer 6, an electron injection layer (7).

When an electric field is applied to the anode 2 and the cathode 8 of such an element, electrons are injected from the cathode 8 into the organic EL layer 10, and holes from the anode 2 are injected into the organic EL layer 10. .

The electrons and holes injected into the organic EL layer 10 move to the organic EL layer under an electric field and combine with each other to form an exciton, and the electrons in the exciton excited state transition to the ground state to emit light in the visible region. To me.

The manufacturing process of the organic ELD is a sequential order of the anode (2), hole injection layer (3), hole transport layer (4), light emitting layer (5), electron transport layer (6), electron injection layer (7), cathode (8) By forming, first, the anode 2 is formed by depositing and patterning ITO (Indium Tin Oxide, In 2 O 3 + SnO 2), which is a transparent conductive material on the transparent substrate 1.

Next, copper-phthalocyanine (copper (II) phthalocyanine) is deposited on the anode 2 to form a hole injection layer 3, and NPD (N, N-di (naphthalen-1) is formed thereon. -yl) -N, N'-diphenylbenzidine) is deposited to a thickness of 30 to 60 nm to form a hole transport layer (4).

Next, the light emitting layer 5 emitting green light, red light, and blue light is selectively formed on the hole transport layer 4, and each light emitting material is formed by using a unique light emitting material, or a light emitting material is formed on a host material. Can be formed by doping.

For example, in the case of green light, it is formed by using a light emitting material of Alq3 (tris (8-hydroxyquinolate) aluminium) alone or by doping a material of N-methylquinacridone to a host such as Alq3. can do. At this time, the thickness is about 30 to 60 nm.

Subsequently, the electron transport layer 6 and the electron injection layer 7 are sequentially vacuum deposited on the light emitting layer 5. At this time, the electron transport layer 6 is formed to a thickness of 20 to 50 nm using Alq3, and the electron injection layer 7 is formed to a thickness of 30 to 50 nm using an alkali metal derivative.

Finally, the cathode 8 is formed by depositing a metal material such as aluminum (Al), lithium (Li), or magnesium (Mg) on the upper surface of the electron injection layer 7, and as shown in FIG. 2, an epoxy resin or the like. When the packaging plate 11 is bonded to the transparent substrate 1 via the sealing agent 14 therebetween, the organic electroluminescent device is completed.

However, in spite of various advantages, the organic electroluminescent device has a short lifespan.

That is, the hole injection layer, the hole transport layer, the light emitting layer, the electron transport layer, the electron injection layer is made of an organic material, and the cathode uses a metal having a low work function, these materials are vulnerable to oxygen and moisture . Therefore, when the device is driven for a long time, the organic material and the cathode material react with oxygen and moisture introduced from the inside or the outside of the device, resulting in deterioration, resulting in a decrease in the life of the device.

As described above, since the organic material and the cathode material have low moisture resistance and oxidation resistance, deterioration occurs in the operation of the display, and such deterioration forms a non-light emitting region called a dark spot. Over time, the sunspot region diffuses around and no light emission occurs throughout the device.

In order to solve this problem, as shown in Figure 2, the packaging plate 11 is attached to the moisture absorbent 12 on the transparent substrate (1).

The moisture absorbent 12 is inorganic, such as barium oxide (BaO), calcium carbonate (CaCO3), calcium oxide (CaO), phosphorus oxide (P ₂ O _5), zeolite _, zeolite, silica gel, alumina, or alumina. Compounds are used, and when they come into contact with water, they form a hydroxyl group (-OH) by chemical reaction, which serves to remove water.

In order to maximize the contact area with water, the inorganic moisture absorbent is mainly present in a fine powder state, and is fixed to the recessed portion of the packaging plate 11 by a semipermeable membrane 13 such as paper or Teflon.

However, due to its low reactivity with water, the water removal effect is low, and the moisture absorbent powder scatters inside the device, causing an error in device operation.

In addition, since the encapsulant 14 used to bond the substrate is also an organic polymer material, it does not completely perform a water blocking function from the outside.

The present invention has been made to solve the above problems, and an object of the present invention is to provide an organic electroluminescent device using a moisture absorbent for an organic electroluminescent device reinforcing the disadvantages of the conventional inorganic moisture absorbent.

The organic electroluminescent device according to the present invention for achieving the above object is an organic electroluminescent device having a light emitting layer between the anode and the cathode on the substrate, the moisture absorbent layer for removing moisture in the device is formed, the absorbent layer It is characterized by using an organic material into which isocyanate groups are introduced.

That is, the moisture absorbent according to the present invention is an organic material having an isocyanate group (-N = C = O; isocyanate group), and has an excellent moisture removal effect, and is characterized by improving the life of the device by preventing the scattering of powder.

In general, when the isocyanate group is in contact with water, a rapid chemical reaction occurs as shown in the following Reaction Formula 1 and is converted into an amine group (-NH 2) to generate inert carbon dioxide (CO 2).

-N = C = O + H2O-> -NH2 + CO2 (g) ↑

In addition, the isocyanate groups react with water again, as in the group to the resulting amine reacts with moisture scheme 2 ammonium hydroxide to form the salt (salt) such as ^{(- - (NH3) + OH} ).

-NH2 + H2O -> - (NH3 ) + OH - ( salt)

In addition, the ammonium hydroxide is adsorbed with water again, as shown in Scheme 3, to exist in the form of a hydrate. It is well known that salts generally have an excellent ability to absorb moisture.

^- (NH3) ⁺ OH - (salt) + H2O -> - (NH3 ) + OH - (H2O) x

(Where x is an integer of 1 to 10).

That is, isocyanate groups react with water to form salts, such as ammonium hydroxide, and the resulting salts again absorb moisture and are present in the form of hydrates.

Therefore, since one isocyanate group removes three or more water molecules, it is evident that the isocyanate group has an excellent ability as a hygroscopic agent to remove water.

In addition, the carbon dioxide produced by the reaction formula 1 also has a water permeation prevention effect to further prevent deterioration of the device by moisture, and also increases the internal pressure of the device to block the ingress of moisture and oxygen from the outside Will also do.

Organic materials having isocyanate groups include low-molecular materials and high-molecular materials, and low-molecular materials include polymethylene diisocyanate, toluene diisocyanate, and naphthalene-1,5-diisocyanate. diisocyanate, diphenyl diisocyanate, diphenylmethane diisocyanate, dimer of 2,4-tolylene diisocyanate, hexamethylene diisocyanate ( hexamethylene diisocyanate) and triphenylmethane triisocyanate

Representatively, the structure of organics having isocyanate groups is shown below.

In addition to the low molecular weight materials described above, polymer materials having isocyanate groups are also possible. For example, polyacrylate, polyurethane, phenol resin, melamine resin, xylene resin, epoxy resin, alkyd resin, silicon resin, unsaturated Isocyanate groups are introduced in the main chain or side chain to polymer materials such as polyester resins, polycarbonates, polyimides, polyamides, polystyrene resins, and nylon resins to be used as hygroscopic agents.

The method of introducing the isocyanate into the polymer is as follows.

First, a polymer material having an aromatic ring is reacted with a mixture of hydrochloric acid and sulfuric acid to introduce a nitro group (-NO ₂ ) into the aromatic ring, which is then reacted with hydrogen at a high temperature and a high pressure of about 100 ° C. to give an amine group. Reduced to (-NH ₂ ). Next, a polymer in which an isocyanate group is introduced according to the present invention is prepared by reacting an aromatic ring having an amine group introduced therein with phosgene (COCl ₂ ).

In the same manner as described above, a large number of polymers having isocyanate groups can be produced, and typical examples thereof are as follows.

As described above, when a low molecule or a polymer having an isocyanate group introduced therein is used as a moisture absorbent for organic ELD, moisture in the device can be completely removed, thereby increasing the life of the device and increasing reliability.

Hereinafter, the present invention will be described in more detail with reference to Examples.

First embodiment

3 is a cross-sectional view of an organic electroluminescent device according to a first embodiment of the present invention.

The first embodiment of the present invention is characterized in that the organic moisture absorbent is formed on the upper surface of the negative electrode.

First, as shown in FIG. 3, an anode 102 is formed by depositing ITO (Indium Tin Oxide, In 2 O 3 + SnO 2), which is a transparent conductive material, on the transparent substrate 101 and patterning the photolithography.

Next, an organic EL layer 110 is formed on the anode 102.

Although not illustrated, the organic EL layer 110 is formed by laminating in order of a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, and an electron injection layer.

The hole injection layer is formed by vacuum deposition of copper phthalocyanine at a thickness of 30 nm, the hole transport layer is formed by vacuum deposition of NPD at a thickness of 50 nm, and the light emitting layer is N-methylquinacridone (N-methylquinacridone) in a host such as Alq3. Is formed by depositing a material doped with a material of 30nm thickness, the electron transport layer is formed by depositing Alq3 to a thickness of 40nm, and the electron injection layer is formed by depositing lithium oxide (LiO2) to a thickness of 25nm.

Subsequently, after applying a shadow mask to the organic EL layer 110, metals such as calcium (Ca), magnesium (Mg), aluminum (Al), copper (Cu), and chromium (Cr), or these A cathode 108 is formed by vacuum depositing an alloy between metals to a thickness of 100 nm and then patterning.

Thereafter, naphthalene-1,5-diisocyanate, which is one of the moisture absorbents of the present invention, is vacuum deposited on the entire surface including the cathode 108 to form a moisture absorbent layer 112 having a thickness of 400 nm. do.

Although not shown, an inorganic layer may be further formed on the moisture absorbent layer 112. The inorganic layer is formed of silicon oxide (SiOx), silicon nitride (SiNx), or the like, and has a thickness of about 400 nm.

Subsequently, the encapsulant 114 is printed on the edge of the packaging plate 111, and then, according to a general encapsulation method in a sealed place with an inert gas such as nitrogen (N) or argon (Ar). The packaging plate 111 and the transparent substrate 101 are bonded to each other. Therefore, an inert gas is filled between the transparent substrate 101 and the packaging plate 111.

At this time, the packaging plate 111 is made of glass, plastic, or a canister having a good warp property.

Applying a direct current electric field to the device manufactured in this way, and checked the life of the device in a temperature of 80 ℃, a constant temperature of 90%, a humidistat, it was stable operation for 5,000 hours.

Compared to the life of the organic ELD device fabricated under the same conditions using CaO, the inorganic moisture absorbent according to the prior art, which was 2,000 hours, it can be seen that the effect of the organic moisture absorbent having an isocyanate group is excellent.

In this case, as a result of using other organic materials under the same conditions in addition to the organic materials, the life data was almost the same, from which it was confirmed that the isocyanate group introduced to any chemical group does not affect the effect of removing water.

On the other hand, instead of naphthalene-1,5-diisocyanate as the moisture absorbent. A polymer material having an isocyanate group may be used. When an epoxy resin having an isocyanate group is formed on a cathode by spin coating or screen printing, the life of the device is checked at a temperature of 60 ° C., 90% of constant temperature, and a humidity chamber. As a result, the operation was stable for 7,000 hours.

This also shows that the effect of the organic moisture absorbent having an isocyanate group is excellent as compared with the life of the organic ELD element fabricated under the same conditions using BaO, the inorganic moisture absorbent according to the prior art, which was 2,000 hours.

Second embodiment

4 is a cross-sectional view of an organic electroluminescent device according to a second embodiment of the present invention.

A second embodiment of the present invention is characterized in that an organic moisture absorbent is formed on the inner surface of the packaging plate.

First, as shown in FIG. 4, an anode 102 is formed by depositing and patterning ITO, which is a transparent conductive material, on the transparent substrate 101, and then forming an organic EL layer 110 thereon. A cathode 108 is formed by depositing and patterning a metal such as magnesium, aluminum, copper, chromium, or an alloy between these metals on the 110.

The organic EL layer 110 is composed of a laminated film of a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, and an electron injection layer, and the formation method is similar to that in the first embodiment.

Subsequently, naphthalene-1,5-diisocyanate, which is one of the moisture absorbents of the present invention, is vacuum-deposited on the inner surface of the packaging plate 111 such as glass, plastic, and canister to form a 400 nm thick moisture absorbent thin film.

Thereafter, the encapsulant 114 is printed on the edge of the packaging plate 111, and then the packaging plate 111 and the transparent substrate 101 are encapsulated in an inert gas atmosphere such as nitrogen and argon. To face each other.

Applying a direct current electric field to the device manufactured in this way, and checked the life of the device in a temperature of 80 ℃, a constant temperature of 90%, a humidistat, it was stable operation for 5,000 hours.

The above results were the same when the organic moisture absorbent was deposited on the cathode and when sealed on the packaging plate. That is, it can be seen that the characteristic change according to the formation position of the absorbent does not appear.

As a result of using other organic materials under the same conditions in addition to the organic materials, life data were almost the same, and it was confirmed that the isocyanate group introduced into any chemical group did not affect the effect of removing moisture.

On the other hand, instead of naphthalene-1,5-diisocyanate as the moisture absorbent. A polymer material having an isocyanate group may be used. When an epoxy resin having an isocyanate group is formed on the inner surface of the packaging plate by spin coating or screen printing, the life of the device is checked at a temperature of 60 ° C., 90% of constant temperature, and a humidity chamber. As a result, the operation was stable for 7,000 hours.

As a result, even when an organic polymer material is used as the absorbent, it can be seen that the characteristic change does not appear according to the formation position of the absorbent.

Third embodiment

5 is a cross-sectional view of an organic electroluminescent device according to a third embodiment of the present invention.

The third embodiment of the present invention is characterized by not forming a separate package plate by forming a thick absorbent on the upper portion of the negative electrode.

First, as shown in FIG. 5, the anode 102 is formed by depositing and patterning ITO, which is a transparent conductive material, on the transparent substrate 101, and then forming the organic EL layer 110 thereon. A cathode 108 is formed by depositing and patterning a metal such as magnesium, aluminum, copper, chromium, or an alloy between these metals on the 110.

The organic EL layer 110 is formed of a laminated film of a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, and an electron injection layer, and the formation method thereof is similar to that of the first embodiment.

Subsequently, naphthalene-1,5-diisocyanate, which is one of the moisture absorbents of the present invention, is vacuum-deposited on the transparent substrate 101 including the cathode 108 to form a thick absorbent thick film 112a having a thickness of 50 µm.

An inorganic layer such as silicon oxide (SiOx) or silicon nitride (SiNx) may be further formed on the moisture absorbent thick film 112a.

Thus, the organic light emitting element is completed. Therefore, since the absorbent thick film 112a serves as a packaging plate, the packaging plate does not need to be separately formed.

As a result of applying a direct current electric field to the device thus manufactured and checking the life of the device in the atmosphere, the device operated stably for 4,000 hours.

Compared to the life of the organic ELD device fabricated under the same conditions using CaO, the inorganic moisture absorbent according to the prior art, which was 900 hours, it can be seen that the effect of the organic moisture absorbent having an isocyanate group is excellent.

In addition, it can be seen that even if the moisture absorbent layer is thickly formed without using a separate packaging plate, a long life element is possible.

As a result of using other organic materials under the same conditions in addition to the organic materials, life data were almost the same, and it was confirmed that the isocyanate group introduced into any chemical group did not affect the effect of removing moisture.

In addition, even when the polymer material was applied by spin coating or screen printing as a moisture absorbent and then cured to form, the hygroscopicity was excellent.

The organic electroluminescent device of the present invention as described above has the following effects.

In other words, when a polymer or a low molecular material having an isocyanate group is used as the moisture absorbent for the organic electroluminescent device, the life of the device is extended due to its excellent water removal ability, and eventually the reliability of the device is improved.

In addition, moisture permeation and oxygen permeation are prevented by carbon dioxide generated when the moisture absorbent having an isocyanate group reacts with water, thereby further increasing the water removal effect.

Claims (11)

In an organic electroluminescent device having a light emitting layer between an anode and a cathode on a substrate, and an absorbent layer for removing moisture in the device using an organic material having an isocyanate group introduced therein, An organic electroluminescent device, further comprising an inorganic layer on the moisture absorbent layer. delete delete delete The method of claim 1, The inorganic layer is an organic electroluminescent device, characterized in that SiNx or SiOx. In an organic electroluminescent device having a light emitting layer between an anode and a cathode on a substrate and a moisture absorbent layer for removing moisture in the device using an organic material having an isocyanate group introduced therein, the substrate including the cathode, An organic electroluminescent device, further comprising an inorganic layer on the moisture absorbent layer. delete delete delete delete delete

Images