WO2006057492A1

WO2006057492A1 - Top-emission type organic light emitting display device

Info

Publication number: WO2006057492A1
Application number: PCT/KR2005/003566
Authority: WO
Inventors: Byoungchul Lee
Original assignee: Byoungchul Lee
Priority date: 2004-11-24
Filing date: 2005-10-26
Publication date: 2006-06-01
Also published as: KR20060057944A; KR100656192B1

Abstract

Disclosed is a top-emission type organic light-emitting device (OLED). A transparent en¬ capsulation layer is disposed facing and spaced apart a substrate having a TFT electrode installed on the top surface thereof. A perimeter sealant is provided along the entire edge of a space between the substrate and the encapsulation layer. An organic light-emitting unit having a structure in a way that a light-emitting organic layer is sandwiched between a first electrode layer and a second transparent electrode layer is stacked on the TFT electrode such that the second electrode layer is oriented towards the encapsulation layer. A transparent moisture getter thin film layer is disposed between the second electrode layer and the encapsulation layer to remove moisture from the space. A hydrogen getter is disposed inside the space and/or so as to be extended from the inside to the outside of the space, such that hydrogen inside the space is absorbed and/or absorbed and discharged to outside of the space. As compared with a bottom- emission type OLED, an improved light efficiency can be achieved and defects such as pixel contraction by moisture and hydrogen can be significantly reduced.

Description

TOP-EMISSION TYPE ORGANIC LIGHT EMITTING DISPLAY

DEVICE

Technical Field

[1] The present invention relates to an organic light emitting display device, more specifically, to a top-emission type organic light emitting display device. Background Art

[2] An organic light emitting device (OLED) has advantages of having a high resolution and a good impact resistance and implementing various colors and thus has been employed as a display device for a variety of information industries. Displays using an OLED have various merits such as distinct image, unlimited viewing angle, high speed of operation and low fabrication cost, as compared with a liquid crystal display, a plasma display panel, a field emission display and the like. Therefore, the OLED has drawn attractions as a useful display, for example, a display for TVs, computers and cellular phones, or a display panel for PDAs, computers, TVs and home appliances.

[3] The OLED is generally categorized into a passive type and an active type. The passive type OLED can be fabricated through a simple process, but needs a high operating voltage and thus its power consumption is significant. In addition, due to its limited screen size, its application is limited, for example, to an outside window of cellular phones. In the case of the active type OLED, its operating voltage is low, which leads to reduced power consumption. In addition, the active type can be applied to a medium- and large-scale screen. Fig. 1 shows a structure of a conventional bottom-emission active type OLED. An organic light emitting section 5 is interposed between a transparent electrode 6 and an opaque metallic electrode 4, which are disposed above a TFT layer 7 on a transparent protective layer 8. These are surrounded by an insulation layer 3 and an opaque moisture getter layer 2 is disposed above them. All the above elements are surrounded by a front face protective layer 1. In the OLED having the above configuration, a pair of facing electrodes, i.e., the transparent electrode 6 and the metallic electrode 4 provides electrons and holes to the organic light emitting section 5, which are then combined inside the organic light emitting material layer to thereby emit light.

[4] Referring to Fig. 1, the thin film transistor (TFT) 7 is disposed on a substrate, i.e., the transparent bottom protective layer 8. The organic light emitting section 5 is sandwiched between the metallic electrode 4 and the transparent electrode 6 and thus the transparent electrode 6 is laminated above the TFT layer 7. In the bottom-emission structure, in order to improve light efficiency, a transparent material needs to be placed over the light traveling path from the light emitter (the organic light emitting section 5) to the bottom face. In the OLED configuration of Fig. 1, however, since the TFT layer 7 is disposed to the substrate 8 not emitting light, the light emitted from the organic light emitting section 5 is partly blocked by the TFT layer 7 to thereby degrade light efficiency and opening rate disadvantageously. This disadvantage of degrading light efficiency due to the presence of TFT can be efficiently overcome through adoption of a top-emission mode, in which the light emitted from the organic light emitting section 5 is configured to emit in the opposite side of the substrate 8 with the TFT layer 7 disposed thereon, i.e., towards the front side of the OLED.

[5] On the other hand, an OLED incorporates electric circuit elements inside an airtight case and is sealed using an adhesive polymer having a low moisture permeability. However, moisture and oxygen may be permeated into inside the device during the sealing of device and its use. Hydrogen may be produced during operation of the device. If the moisture inside the OLED is not removed, its performance is degraded, for example, pixel contraction of the OLED device. In addition, if the generated hydrogen remains inside the OLED, the internal pressure of the OLED is increased and the life span of pixels is shortened disadvantageously. Thus, in order to prevent the above problems, moisture getter and hydrogen getter are disposed inside the airtight case of the OLED. In particular, since moisture is adsorbed to the device elements and thus introduced into the OLED in high quantity, it should be removed in the initial stage. The performance of moisture getter and hydrogen getter is determined depending upon the removing rate, the removed amount and the equilibrium con¬ centration at equilibrium state. A good removing agent, that is, a good getter has a high removing rate and a low equilibrium concentration.

[6] Here, in case of providing these moisture getter (dehumidifying agent) and hydrogen getter (hydrogen removing agent) to a top-emission type OLED, they need to be made of transparent materials, otherwise to be disposed so as not to block light- traveling path, in order to improve light efficiency.

[7] In connection with a top-emission OLED, U.S. Patent No. 5,739,545 discloses an

OLED structure where a transparent electrode is disposed frontward to transmit the light emitted from the organic light emitting layer to the front side. However, this patent does not mention the arrangement and construction of a moisture getter that is essential to an OLED. U.S. Patent Nos. 6,515,428, 6,670,772 and 6,608,283 disclose the structure and manufacturing method of an active type OLED, but do not disclose the arrangement and construction of a moisture getter. U.S. Patent Nos. 5,714,838 and 6,420,031 disclose a transparent electrode for a top-emission mode, but not a moisture getter. U.S. Patent Nos. 5,920,080, 6,268,695 and 6,497,598 disclose a method of forming a protective layer, in which an insulation material having a low moisture per¬ meability is coated on a transparent electrode in multiple layers. In these patents, however, the process for forming a multi-layered protective layer is complicated and consumes a long period of time, and measures for preventing moisture from in¬ troducing into the side face of the protective layer is not complete. U.S. Patent No. 6,703,184 discloses a method of protecting an organic light emitting layer and an electrode using a transparent film having a low moisture permeability. In this patent, however, moisture may be adsorbed to materials and introduced inside the OLED. Practically, moisture introduced after sealing can be blocked, but moisture adsorbed during fabrication remains inside the device.

[8] Japanese Laid-Open patent No. 2003-144830 discloses a transparent moisture getter used in a top-emission OLED, which is formed of an organometallic compound composed of the group III metals and organic monomer. However, in order for the transparent moisture getter film to be disposed inside of an OLED, an organic solvent must be used, which leads to inconvenience in the process and easy cracking of the formed moisture getter film to thereby cause light-scattering. In addition, a calcination process for volatizing the solvent is required. These chemical solutions and the calcination process may cause a problem with environmental treatment. In addition, the transparent moisture getter layer should have a smooth surface to achieve uniform permeability on the whole area, but this patent does not mention a complete solution for this purpose. Furthermore, the OLED process needs various other processes such as a solution combination process for the transparent moisture getter, a coating process, a calcination process or the like, thus lengthening the process time. In particular, if the calcination process is not completely finished, gas generated from the internal remaining solvent or the like is more likely to cause a progressive dark spot. Disclosure of Invention Technical Problem

[9] Accordingly, the present invention has been made in order to solve the above problems in the prior art. It is an object of the invention to provide a top-emission type OLED, in which light generated from an organic light-emitting layer is emitted toward the front side of a substrate where a TFT is disposed and thus light-blocking by the TFT is prevented, thereby improving light efficiency as compared with a conventional bottom-emission type OLED and avoiding defects such as pixel contraction due to moisture and hydrogen. Technical Solution

[10] In order to accomplish the above objects, according to one aspect of the invention, there is provided a top-emission type organic light-emitting device comprising: a substrate having a TFT electrode installed on the top surface thereof; a transparent en¬ capsulation layer disposed facing the substrate and spaced apart therefrom; a perimeter sealant sealing provided along the entire edge of a space between the substrate and the encapsulation layer so as to seal the space; an organic light-emitting unit having a structure in a way that a light-emitting organic layer is sandwiched between a first electrode layer and a second transparent electrode layer, the organic light-emitting unit being stacked on the TFT electrode such that the second electrode layer is oriented towards the encapsulation layer; a transparent moisture getter thin film layer disposed between the second electrode layer and the encapsulation layer to remove moisture from the space; and a hydrogen getter disposed inside the space and/or so as to be extended from the inside to the outside of the space, such that hydrogen inside the space is absorbed and/or absorbed and discharged to outside of the space. The hydrogen getter is disposed inside the space in such a way that the hydrogen getter is attached in an inside edge of the space, rather than on the light-travelling path directing from the organic light-emitting unit to the encapsulation layer. Due to the arrangement of the hydrogen getter, the hydrogen getter absorbs and removes hydrogen inside the space. The deposition of the hydrogen getter from the inside to the outside of the space is configured such that the hydrogen getter is coated in a surface of either the substrate or the encapsulation layer and the sealant is applied on the coated hydrogen getter except for both edges thereof so that the hydrogen getter can be exposed to inside and outside of the space. Due to the arrangement of the hydrogen getter, the hydrogen getter absorbs and removes hydrogen inside the space.

[11] According to another aspect of the invention, there is provided a top-emission type organic light-emitting device comprising: a substrate having a TFT electrode installed on the top surface thereof; a transparent encapsulation layer disposed facing the substrate and spaced apart therefrom; a perimeter sealant sealing provided along the entire edge of a space between the substrate and the encapsulation layer so as to seal the space; a hydrogen getter provided along the edge of the space in a form of mixture with the sealant, the hydrogen getter absorbing hydrogen inside the space and discharging to outside of the space; an organic light-emitting unit having a structure in a way that a light-emitting organic layer is sandwiched between a first electrode layer and a second transparent electrode layer, the organic light-emitting unit being stacked on the TFT electrode such that the second electrode layer is oriented towards the en¬ capsulation layer; a transparent moisture getter thin film layer disposed between the second electrode layer and the encapsulation layer to remove moisture from the space. The organic light-emitting device may further include a hydrogen getter for absorbing and removing hydrogen. The hydrogen getter is provided in an inside edge of the space so as not to block a light-travelling path directed towards the encapsulation layer from the organic light-emitting unit.

[12] The transparent moisture getter thin film layer is formed of a mixture of a moisture getter (dehumidifying) material decomposing moisture to produce hydrogen and a polymer binder. The moisture getter material may be provided additionally or inde¬ pendently along the peripheral edge of the space in the form of a mixture mixed with the sealant. The moisture getter material includes at least one selected from the group consisting of metals, metal hydrides, their alloys and a mixture thereof. The metal includes at least one selected from the group consisting of metals having a higher ionization tendency than hydrogen, their alloys and a mixture thereof. The metal hydride includes at least one selected from the group consisting of alkaline metal hydride, alkaline earth metal hydride, alkaline metal hydride containing boron or aluminum and a mixture thereof.

[13] The hydrogen getter includes an opaque hydrogen getter, and includes at least one selected from the group consisting of: a) Nb, Ta, Ti, V, Zr, Pd, PdO; b) an alloy of metal selected from Ti and Al, Co, Cr, Cu, Fe, La, Mn, Ni, Si, Sn, Y, and Zr, or a mixture thereof; c) an alloy of metal selected from Zr and Al, Co, Cr, Cu, Fe, La, Mn, Ni, Si, Sn, Y, and Zr, or a mixture thereof; and d) a mixture of two or more materials selected from a) to c) materials. The hydrogen getter may include a mixture of the opaque hydrogen getter and a polymer binder. Preferably, the polymer binder includes a thermosetting resin or a reactive curable resin having a MVTR (moisture vapor transmission rate) of above lOg-mil/m day at 4O⁰C and 75% RH (relative humidity).

[14] Furthermore, an oxygen getter reacting oxygen for absorbing it inside the space may be provided mixed with at least one of the transparent moisture getter thin film layer, the hydrogen getter and the sealant.

Advantageous Effects

[15] As described above, the OLED according to the present invention adopts a top- emission type and thus light blocking due to thin film transistors can be avoided to provide a higher light efficiency, as compared with a convention bottom-emission type OLED. In addition, a dehumidifying material, that is, a moisture getter that can be made transparent is disposed in the light-transmission path so as to remove a large quantity of moisture. An opaque hydrogen getter is disposed in the edge portion of the OLED in the form of a band so as not to block the light transmission and so as to remove a large quantity of hydrogen. Brief Description of the Drawings

[16] Further objects and advantages of the invention can be more fully understood from the following detailed description taken in conjunction with the accompanying drawings in which: [17] Fig. 1 shows a structure of a conventional bottom-emission active type OLED;

[18] Figs. 2 to 5 illustrate a top-emission type OLED according to the present invention where a hydrogen getter is disposed inside of the OLED in various ways;

[19] Figs. 6 to 8 illustrate a top-emission type OLED according to the present invention where a hydrogen getter is disposed to be extended from the inside of the OLED to the outside thereof in various ways; and

[20] Fig. 9 illustrates a top-emission OLED type according to the present invention where a hydrogen getter is provided along with a sealant mixed with the hydrogen getter. Best Mode for Carrying Out the Invention

[21] The preferred embodiments of the present invention will be hereafter described in detail with reference to the accompanying drawings.

[22] Figs. 2 through 5 illustrate various basic structure of a top-emission OLED according to the present invention. The illustrated structures are different to each other in terms of the installation positions of a hydrogen getter 80. A substrate 10 and an en¬ capsulation layer 40 are spaced apart from each other by a certain desired distance and facing each other in parallel. A perimeter sealant 70 is provided along the entire peripheral edge of a space formed between the substrate 10 and the encapsulation layer 40 and the space is sealed by means of the sealant 70. On top surface of the substrate 10 is installed a TFT electrode layer 28, on which an organic light-emitting unit 25 is stacked. The organic light-emitting unit 25 is structured in such a way that a light- emitting organic layer 23 is sandwiched between a first electrode layer 24 and a transparent second electrode layer 22. As well known, the light-emitting organic layer 23 is formed of a material, which transports holes and electrons supplied from the first electrode layer 24 and the second electrode layer 22 and combines them to thereby emit light. The first electrode layer 24 is stacked on the TFT electrode layer 28 such that the second electrode layer 22 is directed towards the encapsulation layer 40. A top-emission type structure is configured such that, when a voltage is applied to the first electrode layer 24 and the second electrode layer 22, the light generated from the light-emitting organic layer 23 is emitted towards the opposite side of the TFT electrode layer 28 (towards the front side of the device). Thus, dissimilar to a bottom- emission type, the light from the light-emitting organic layer 23 is emitted towards the front side of the substrate 100, i.e., to the outside via the encapsulation layer 40. Therefore, the elements not present in the light-traveling path, i.e., the substrate 10, the TFT electrode layer 28 and the first electrode layer 24 can be opaque. However, the elements present in the light- traveling path, i.e., the second electrode layer 22, the en¬ capsulation layer 40 and a moisture getter thin film layer 30 is to have a good light transmittance. For example, the first electrode layer 24 may be formed of an opaque metallic electrode, and the second electrode layer 22 may be formed of a transparent indium-tin oxide (ITO) electrode.

[23] The substrate 10 may be formed of glass, plastic material and the like. The en¬ capsulation layer 40 provides the internal space of an OLED in corporation with the substrate 10, while protecting the elements disposed inside the space. For example, the encapsulation layer 40 may be formed using a transparent glass material, a transparent polymer film, a transparent plastic material and the like. Of course, flexible glass or plastic materials may be employed. In order to prevent external light from being reflected by the organic light-emitting unit 25, a polarization film or a circular po¬ larization film 50 (a polarization film with a film having a wavelength phase different adhered thereto) may be further provided between the encapsulation layer 40 and the organic light-emitting unit 25.

[24] A moisture getter material needs to be disposed inside of the internal space of

OLED in order to remove moisture permeated into the space. For this purpose, a moisture getter thin film layer 30 is provided between the second electrode layer 22 of the organic light-emitting unit 25 and the encapsulation layer 40. The light generated from the organic light-emitting unit 25 is emitted through the encapsulation layer 40. Since the moisture getter thin film layer 30 is preferably widely disposed in the internal space for efficient removing of moisture, it is to be disposed on the light-traveling path. Thus, the moisture getter thin film layer 30 is to be transparent. In addition, the moisture-removing material includes a material absorbing moisture (moisture absorption type material) and a material decomposing moisture to produce hydrogen to remove the moisture (moisture decomposition type material). The moisture de¬ composition type moisture getter has a higher performance as compared with the moisture absorption type, thereby more efficiently preventing pixel contraction phenomenon. Thus, either material may be employed as a raw material for the moisture getter thin film layer 30, but the moisture decomposition type having a higher efficiency is more preferable.

[25] Typically, the moisture decomposition type moisture getter material includes metal hydrides, its alloys and mixture thereof. Suitable metals include metals having a higher ionization tendency than hydrogen, or its alloys or mixture thereof, for example, lithium (Li), natrium (Na), kalium (K), rubidium (Rb), cesium (Cs), beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), aluminum (Al), zinc (Zn), iron (Fe), nickel (Ni) and the like. Preferably, the metal hydride includes at least one selected from the group consisting of alkaline metal hydride, alkaline earth metal hydride, alkaline metal hydride containing boron or aluminum and the mixture thereof. For example, it includes sodium hydride (NaH), potassium hydride (KH), calcium hydride (CaH ), strontium hydride (SrH ), aluminum hydride (AlH ), lithium boro- hydride (LiBH ), lithium aluminum hydride (LiAlH ), sodium aluminum hydride

4 4

(NaAlH ), potassium aluminum hydride (KaIH ), calcium aluminum hydride (CaAl H ) and the like. In case of a moisture getter material using metal hydrides, moisture is removed according to the following chemical equation 3.

[26] [Chemical equation 3]

[27] MH + nH O → M(OH) + nH n 2 n 2

[28] The moisture getter thin film may be fabricated in a way as to add a moisture absorption type moisture getter material, such as alkaline metal oxides, alkaline earth metal oxides and the likes, to a moisture decomposition moisture getter material as a main ingredient. In order to improve transparency, the moisture getter material is preferred to have a particle size of less than 1 micron. More preferably, if the moisture getter material having no more than about 50 nanometers is dispersed and dissolved in a polymer binder, a good transparency can be achieved. In addition, in case where the refraction index of the moisture getter material is similar to that of the polymer binder, the transparency can be improved.

[29] Transparent moisture getter materials, a raw material for the transparent moisture getter thin film layer 30, are to have a good dehumidifying (moisture-getting) performance, a capability of being formed in a film shape, a transparency after formed in a film shape, and a characteristic of being easily bonded with a circular polarization film. These characteristics are well met by a mixture containing a moisture getter material and a thermosetting resin or a mixture containing a moisture getter material and a reactive curable resin, which are employed to fabricate the transparent moisture getter thin film 30. If the polymer binder such as a thermosetting resin or a reactive curable resin is made to become porous in order to provide a good mass transfer, the light transmittance is degraded. Thus, basically a polymer having a high moisture vapor transmission rate (MVTR) is preferred. In addition, in order to minimize transmittance by light scattering, preferably, the turbidity is to be minimized. Furthermore, it is preferably that the moisture getter material can be inherently adhered to other object (for example, the polarization film 50) through a hot-pressing process without using a separate adhesive.

[30] In order to decrease turbidity of the mixture of a moisture getter material and a polymer binder, it is preferable that the moisture getter material and the polymer binder such as a thermosetting resin or a reactive curable resin have the following properties.

[31] (1) The particle size of a moisture getter material is enough small (typically no more than 50 nanometers) relative to the wavelength of visible light to the extent to be within a range of Rayleigh scattering, or

[32] (2) the refraction index of the moisture getter material is similar to that of the polymer binder so as to have a small value of Rayleigh ratio, R(θ), which is defined by the following mathematical equation 1. [33] [Mathematical equation 1]

[34]

^{m θ}^ X^N^

[35]

[36] Here, n is the refraction index of a thermosetting or reactive curable resin, which has a certain range of value depending on materials. C is the concentration of a moisture getter material, which cannot be reduced below a certain value, considering the moisture getter efficiency of the transparent moisture getter. In addition, λ is the wavelength of visible light and has a constant value, and also M and N are the

A molecular weight of a moisture getter material and the Avogadro number respectively, which are constant values. Thus, in order to decrease the Rayleigh ratio, the value of ' dn/dc^y is to be reduced, 'dn/dc¹ is a changing rate of the refraction index of the mixture of a moisture getter material and a polymer binder relative to a change to the con¬ centration.

[37] MVTR may vary with the fabrication process of the transparent moisture getter thin film 30, but depends on the chemical structure of the polymer binder. Therefore, in the present invention, MVTR is a property that can be used as a selection criteria for a polymer binder, which is used a material to be mixed with the moisture getter material. For the polymer binder, it is preferably a thermosetting resin or a reactive curable resin having a MVTR of above 10g-mil/m²day at 4O⁰C and 75% RH (relative humidity). Typical thermosetting resins meeting these properties includes polyolefin, unsaturated polyolefin, substituted polyolefin, substituted unsaturated polyolefin, a random copolymer or block copolymer of these monomers, or the like. Polyolefin can be selected from polyethylene, polypropylene, polybutene, poly (4-methylpenten), or a mixture thereof. Unsaturated polyolefin can be selected from polybutadiene, polyisoprene, or a mixture thereof. Substituted polyolefin can be selected from polystyrene, polyvinyl chloride, polyvinyl fluoride, polyvinylidene chloride, polyvinylidene fluoride, or a mixture thereof. Substituted unsaturated polyolefin may include polychloroprene. Alternative to the thermosetting resin may include polypenyloxide, polypenylsulfide, poly ethersulf one, or a mixture thereof. In addition, typical examples for a reactive curable resin meeting the above MVTR may include a polymerizable resin. Polymerizable resin may include one having a property, by which the fluidity is decreased due to increased molecular weight caused by radiation energy or heat.

[38] The transparent moisture getter thin film layer 30 may be attached directly to the encapsulation layer 40 using the inherent adhesive force of a polymer binder or a pressure sensitive adhesive. As shown in the figures, the transparent moisture getter thin film layer 30 may be coated with a film 50 such as an adhesive film or a po¬ larization film and then attached to the encapsulation layer 40. The organic light- emitting unit 25 is disposed so as to be insulated from the transparent moisture getter thin film layer 30 and the encapsulation layer 40, for example, by spacing apart therefrom or interposing an insulation material in-between, as illustrated in the figures.

[39] On the other hand, if the generated hydrogen remains inside the OLED, problems occur that the internal pressure of the OLED increases or the life span of pixels is degraded. In order to prevent these problems, it is preferable that a hydrogen getter is further disposed in the inner space of the OLED to thereby absorb hydrogen and thus reduce hydrogen concentration therein. It is difficult to prepare a transparent hydrogen getter. Thus, in order to avoid degradation of light efficiency, the hydrogen getter needs to be disposed in a position other than a light-travelling path to the encapsulation layer 40 from the organic light-emitting unit 25. Edge portions of the inner space of the OLED do not block the light-emitting path. More specifically, suitable positions for installing a hydrogen getter 80 includes: i) an inner wall of the substrate 10 between the organic light-emitting unit 25 and the sealant 70 in the inner space (Fig. 2), ii) an inner wall of the encapsulation layer 40 between the transparent moisture getter thin film layer 30 and the sealant 70 in the inner space of the OLED (Fig. 3), iii) an edge portion of the transparent moisture getter thin film layer 30 not overlapping with the organic light-emitting unit 25 (Fig. 4), iv) an edge portion of the organic light-emitting unit 25 not overlapping with the transparent moisture getter thin film layer 30 (Fig. 5), and a combination of the above i) to iv) positions. In addition, preferably, the hydrogen getter is disposed in a band or line form along part of the entire edge portion so as to occupy as narrow an area as possible.

[40] The hydrogen getter 80 is formed of an opaque hydrogen removing material or a mixture of an opaque hydrogen removing material and a polymer binder. Suitable opaque hydrogen removing materials include: a) Nb, Ta, Ti, V, Zr, Pd, PdO; b) an alloy of metal selected from Ti and Al, Co, Cr, Cu, Fe, La, Mn, Ni, Si, Sn, Y, and Zr, or a mixture thereof; c) an alloy of metal selected from Zr and Al, Co, Cr, Cu, Fe, La, Mn, Ni, Si, Sn, Y, and Zr, or a mixture thereof; and d) a mixture of two or more materials selected from a) to c) materials. In addition, the polymer binder used for preparation of the transparent moisture getter thin film 30 may be used as a polymer binder for preparation of the hydrogen getter 80. The hydrogen getter 80 may be attached to a desired position using a pressure sensitive adhesive. [41] On the other hand, in addition to simple absorption of hydrogen generated in the inner space of the OLED, the hydrogen may be discharged to the outside to thereby increase the amount of removed hydrogen. Figs. 6 to 8 shows a modified structure of the top-emission OLED, considering the above matter. Dissimilar to those of Figs. 2 to 5, the hydrogen getter 80 is extended from the inner space of the OLED to the outside thereof. More specifically, as illustrated in Fig. 6, a hydrogen getter 80 is coated on the surface of the substrate 10 along the entire peripheral edge thereof and a sealant 70 is further provided between the coated hydrogen getter 80 and the encapsulation layer 40. Here, in order for the hydrogen getter 80 to be extended from the inside to the outside of the OLED space, the sealant 70 is provided such that both edge portions of the hydrogen getter are exposed to the inner space and the outside of the OLED, not covering the entire hydrogen getter. The hydrogen getter 80 may be coated on the en¬ capsulation layer 40 as shown in Fig. 7, and as illustrated in Fig. 8, may be coated on both the substrate 10 and the encapsulation layer 40. When the hydrogen getter 80 is disposed in the above-described manner, it absorbs hydrogen present in the inner space of the OLED. At the same time, the hydrogen contained in the hydrogen getter 80 is discharged to the outside, due to a difference in hydrogen concentration of the hydrogen getter 80 and of the outside of the OLED. The hydrogen getter may be coated on the substrate 10 and the encapsulation layer 80 through a sputtering process.

[42] Fig. 9 illustrates another modified example for a top-emission OLED. Dissimilar to the previous structures, the space between the substrate 10 and the encapsulation layer 80 is sealed by means of a mixture of a hydrogen getter and a sealant. Since the hydrogen getter is exposed to both the inner space of the OLED and the outside thereof, it absorbs hydrogen of the inner space of the OLED and discharges to the outside of the space, in the same manner as previously described. These structures may be combined with those of Figs. 2 to 5, i.e., a hydrogen getter may be provided mixed with a sealant and simultaneously may be provided to the edge portion of the inner space of the OLED.

[43] On the other hand, a tiny amount of oxygen may be added at the initial state according to processing requirements. At this time, it is preferably that the added oxygen is removed after a certain period of time. In case where oxygen is required to add for the process, the oxygen removing material may be mixed with at least one of the transparent thin film layer 30, the opaque hydrogen getter 80 and the sealant 79. A metallic material is used as the oxygen removing material.

[44] Plural electrodes of the transparent second electrode layer 22 are electrically insulated from one another. At this state, if the transparent moisture getter thin film layer 30 is directly stacked on and contacted with the transparent second electrode layer 22, problems may occur that moisture or the like contained the transparent thin film layer 30 prevents the electrodes of the second electrode layer 22 from being insulated from each other, in an extreme case, the electrodes become a short-circuit. In order to avoid this short-circuit among the transparent electrodes, it is preferable that the organic light-emitting unit 25 is electrically insulated from the moisture getter thin film layer 30. For this insulation, an insulation material may be filled with the organic light-emitting unit 25 and the transparent moisture getter thin film layer 30. It is preferable that the insulation material has a high electric resistance and at the same time a good light transmittance since it is disposed on the light-travelling path. The insulation material may be a solid, liquid, or gaseous state, which may include argon or nitrogen, silicon oil, or polymer or glass materials, respectively.

[45] [46] Examples of the present invention will be hereafter described. [47] (1) Preparation and evaluation of transparent moisture getter thin film [48] 1) Preparation of transparent moisture getter thin film [49] Three specimens were prepared in a glove box, where moisture concentration is maintained within a range of 1-2 ppm. The composition of the specimens is summarized in the following table 1.

[50] Table 1

[51] [52] The specimens were prepared according the following procedures. First, a moisture getter material was introduced into a polymer binder above its melting point and then well mixed using a homogenizer. The melt was spread on a releasable film in a thin form and cooled to result in a solid film of about lmm thickness, which is made of a mixture of the moisture getter material and the polymer binder. The above mixture film of 1 mm thickness was interposed between two releasable films, which were pressed between two heated rollers so as to be made into a thinner film. Resultantly, a thin and transparent moisture getter film of about 50 microns was manufactured.

[53] 2) Evaluation of light transmittance for transparent moisture getter film [54] Light transmittance was measured for the above-prepared transparent moisture getter film. The measurement results are shown in the following table 2.

[55] Table 2

[56] [57] (2) Preparation of hydrogen getter [58] Specimens were prepared to have compositions shown in the following table 3. [59] Table 3

[60] [61] The particle size of the hydrogen removing material was selected to have 10-50 microns. A polymer binder was heated to melt and then mixed with the hydrogen removing material. This was cooled to make a solid form, which can be heated and extruded through a nozzle.

[62] [63] (3) Assembling and functional evaluation [64] 1) Preparation of OLED specimen [65] Assembling of OLED specimens were carried out as shown in the structure of Fig. 2. Five specimens were prepared for each condition. The size of the specimen was 25mm x 20mm. The OLED assembling was performed in a glove box, which was maintained less than 2ppm of moisture and less than lppm of oxygen. When assembling, the pressure of the glove box was maintained at atmospheric pressure (760±5mmHg). The thickness of the transparent moisture getter thin film layer was made into 50 microns. The hydrogen getter was made in the form of a band having a thickness of 50microns and a width of lmm, and disposed in three edges of the OLED. The prepared OLED specimens are summarized in the following table 4.

[66] Table 4

[67] [68] 2) Evaluation method [69] The above-prepared four OLED specimens were placed for 360 hours under a humidity of 90% and a temperature of 65⁰C. Thereafter, pixel contraction occurring in the edge of pixels of the OLED specimens and increase in the internal pressure thereof due to hydrogen production were observed.

[70] 3) Evaluation results [71] The observation and measurements for the pixel contraction occurring in the edge of pixels of the OLED specimens and the increase in the internal pressure thereof due to hydrogen production were shown in the following table 5.

[72] Table 5

[73] [74] As can be seen from the above results, in the case where a transparent moisture getter film and a hydrogen getter are employed together (examples 1 and 2), it has been found that the transparent moisture getter film exhibits sufficient light transmittance of above about 70%. The moisture removing effect was found to be enough to exhibit only a slight pixel contraction under a high temperature and humidity. In addition, due to effectiveness of the hydrogen getter, the internal pressure of the OLED specimen was decreased to significantly improve stability of the devices.

[75] In contrast, the specimen of comparison example 1, where a transparent moisture getter film without disposing a hydrogen getter inside the OLED, exhibited an increase in the pressure beyond the measuring limit (760mmHg) of a instrument, due to hydrogen generated during decomposition of the moisture in the moisture getter film. Thus, the stability of the specimen was found significantly degraded. One of the five specimens was destroyed due to the pressure increase. The specimen of comparison example 2, where both a transparent film and a hydrogen getter was not used, exhibited a significant pixel contraction and a significant increase in the pressure of the OLED.

[76] In view of the above evaluation results, when a transparent moisture getter film and a hydrogen getter are used together, pixel contraction of the device can be minimized and simultaneously pressure of the device can be decreased, thereby significantly improving the performance and service life of devices. Industrial Applicability

[77] As described above, the present invention can be applied to manufacturing of a top- emission type organic light-emitting device. The present invention has a structure such that light blocking due to TFT can be prevented to thereby improve light efficiency of the device. In addition, defects such as pixel contraction due to moisture and hydrogen can be avoided to provide an extended lift span of the devices and improve image quality.

[78] Although the present invention has been described with reference to several preferred embodiments, the description is illustrative of the invention and not to be construed as limiting the invention. Various modifications and variations may occur to those skilled in the art without departing from the scope and spirit of the invention, as defined by the appended claims.

Claims

[1] A top-emission type organic light-emitting device comprising: a substrate having a TFT electrode installed on the top surface thereof; a transparent encapsulation layer disposed facing the substrate and spaced apart therefrom; a perimeter sealant sealing provided along the entire edge of a space between the substrate and the encapsulation layer so as to seal the space; an organic light-emitting unit having a structure in a way that a light-emitting organic layer is sandwiched between a first electrode layer and a second transparent electrode layer, the organic light-emitting unit being stacked on the TFT electrode such that the second electrode layer is oriented towards the en¬ capsulation layer; a transparent moisture getter thin film layer disposed between the second electrode layer and the encapsulation layer to remove moisture from the space; and a hydrogen getter disposed inside the space and/or so as to be extended from the inside to the outside of the space, such that hydrogen inside the space is absorbed and/or absorbed and discharged to outside of the space.

[2] The organic light-emitting device as claimed in claim 1, wherein the hydrogen getter is disposed inside the space in such a way that the hydrogen getter is attached in an inside edge of the space, rather than on the light-travelling path directing from the organic light-emitting unit to the encapsulation layer and, due to the arrangement of the hydrogen getter, the hydrogen getter absorbs and removes hydrogen inside the space.

[3] The organic light-emitting device as claimed in claim 2, wherein the inside edge of the space where the hydrogen getter is disposed includes at least one of: i) an inner wall of the encapsulation layer between the transparent moisture getter thin film layer and the sealant inside the space, ii) an inner wall of the substrate between the organic light-emitting unit and the sealant inside the space, iii) an edge portion of the transparent moisture getter thin film layer not overlapping with the organic light-emitting unit, and iv) an edge portion of the organic light- emitting unit not overlapping with the transparent moisture getter thin film layer.

[4] The organic light-emitting device as claimed in claim 2 or 3, wherein the transparent moisture getter thin film layer and/or the hydrogen getter is attached to a desired position using a pressure sensitive adhesive.

[5] The organic light-emitting device as claimed in claim 1, wherein the hydrogen getter is opaque, the deposition of the hydrogen getter from the inside to the outside of the space is configured such that the hydrogen getter is coated in a surface of either the substrate or the encapsulation layer and the sealant is applied on the coated hydrogen getter except for both edges thereof so that the hydrogen getter can be exposed to inside and outside of the space, and, due to the ar¬ rangement of the hydrogen getter, the hydrogen getter absorbs and removes hydrogen inside the space.

[6] The organic light-emitting device as claimed in claim 5, wherein the coating of the hydrogen getter on the substrate and/or the encapsulation layer is carried out through a sputtering process.

[7] A top-emission type organic light-emitting device comprising: a substrate having a TFT electrode installed on the top surface thereof; a transparent encapsulation layer disposed facing the substrate and spaced apart therefrom; a perimeter sealant sealing provided along the entire edge of a space between the substrate and the encapsulation layer so as to seal the space; a hydrogen getter provided along the edge of the space in a form of mixture with the sealant, the hydrogen getter absorbing hydrogen inside the space and discharging to outside of the space; an organic light-emitting unit having a structure in a way that a light-emitting organic layer is sandwiched between a first electrode layer and a second transparent electrode layer, the organic light-emitting unit being stacked on the TFT electrode such that the second electrode layer is oriented towards the en¬ capsulation layer; and a transparent moisture getter thin film layer disposed between the second electrode layer and the encapsulation layer to remove moisture from the space.

[8] The organic light-emitting device as claimed in claim 7, further comprising a hydrogen getter for absorbing and removing hydrogen, the hydrogen getter being provided in an inside edge of the space so as not to block a light-travelling path directed towards the encapsulation layer from the organic light-emitting unit.

[9] The organic light-emitting device as claimed in claim 1 or 7, further comprising a moisture getter material for decomposing moisture to generate hydrogen, the moisture getter material being provided along the edge of the space in the form of mixture with the sealant.

[10] The organic light-emitting device as claimed in claim 1 or 7, wherein the transparent moisture getter thin film layer is formed of a mixture of a moisture getter material decomposing moisture to produce hydrogen and a polymer binder.

[11] The organic light-emitting device as claimed in claim 9 or 10, wherein the moisture getter material includes at least one selected from the group consisting of metals, metal hydrides, their alloys and a mixture thereof.

[12] The organic light-emitting device as claimed in claim 11, wherein the metal includes at least one selected from the group consisting of metals having a higher ionization tendency than hydrogen, their alloys and a mixture thereof.

[13] The organic light-emitting device as claimed in claim 11, wherein the metal includes at least one selected from the group consisting of lithium (Li), natrium (Na), kalium (K), rubidium (Rb), cesium (Cs), beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), aluminum (Al), zinc (Zn), iron (Fe), and nickel (Ni).

[14] The organic light-emitting device as claimed in claim 11, wherein the metal hydride includes at least one selected from the group consisting of alkaline metal hydride, alkaline earth metal hydride, alkaline metal hydride containing boron or aluminum and a mixture thereof.

[15] The organic light-emitting device as claimed in claim 11, wherein the metal or the metal hydride has a particle size no more than 1 micron.

[16] The organic light-emitting device as claimed in claim 11, wherein the metal or the metal hydride has a particle size no more than 50 nanometers.

[17] The organic light-emitting device as claimed in claim 1 or 7, wherein the organic light-emitting unit is insulated from the transparent moisture getter thin film layer.

[18] The organic light-emitting device as claimed in claim 1 or 7, further comprising an oxygen getter for absorbing oxygen inside the space, the oxygen getter being formed of a metallic material in the form of a mixture with at least of the transparent moisture getter thin film layer, the hydrogen getter and the sealant.

[19] The organic light-emitting device as claimed in anyone of claims 1, 2, 7 and 8, wherein the hydrogen getter includes an opaque hydrogen getter, and includes at least one selected from the group consisting of: a) Nb, Ta, Ti, V, Zr, Pd, PdO; b) an alloy of metal selected from Ti and Al, Co, Cr, Cu, Fe, La, Mn, Ni, Si, Sn, Y, and Zr, or a mixture thereof; c) an alloy of metal selected from Zr and Al, Co, Cr, Cu, Fe, La, Mn, Ni, Si, Sn, Y, and Zr, or a mixture thereof; and d) a mixture of two or more materials selected from a) to c) materials.

[20] The organic light-emitting device as claimed in claim 18, wherein the hydrogen getter includes a mixture of the opaque hydrogen getter and a polymer binder.

[21] The organic light-emitting device as claimed in claim 10 or 20, wherein the polymer binder includes a thermosetting resin or a reactive curable resin having a MVTR of above 10g-mil/m²day at 4O⁰C and 75% RH (relative humidity).

[22] The organic light-emitting device as claimed in claim 21, wherein the ther- mosetting resin is selected from polyolefin, unsaturated polyolefin, substituted polyolefin, substituted unsaturated polyolefin, and a random copolymer or block copolymer of these monomers.

[23] The organic light-emitting device as claimed in claim 22, wherein the polyolefin is selected from polyethylene, polypropylene, polybutene, poly (4-methylpenten), or a mixture thereof.

[24] The organic light-emitting device as claimed in claim 22, wherein the un¬ saturated polyolefin is selected from polybutadiene, polyisoprene, or a mixture thereof.

[25] The organic light-emitting device as claimed in claim 22, wherein the substituted polyolefin is selected from polystyrene, polyvinyl chloride, polyvinyl fluoride, polyvinylidene chloride, polyvinylidene fluoride, or a mixture thereof.

[26] The organic light-emitting device as claimed in claim 22, wherein the substituted unsaturated polyolefin includes polychloroprene.

[27] The organic light-emitting device as claimed in claim 21, wherein the ther¬ mosetting resin is selected from polypenyloxide, polypenylsulfide, polyethersulfone, or a mixture thereof.

[28] The organic light-emitting device as claimed in claim 21, wherein the reactive curable resin includes a polymerizable resin.

[29] The organic light-emitting device as claimed in claim 28, wherein the poly¬ merizable resin has a property such that the fluidity thereof is decreased due to increased molecular weight caused by radiation energy or heat.