KR20010046469A - Electroluminescence device - Google Patents

Abstract

PURPOSE: A thick film electroluminescence device is provided to improve brightness and durability of a device by suppressing an air gap from being caused within a fluorescent layer of the thick film electroluminescence device. CONSTITUTION: A transparent electrode is formed by vacuum-depositing a conductor such as ITO or transparent tin metal on an upper side surface of a substrate. Then, fluorescent powder is manufactured by mixing ZnS with CuxS and performing a sintering process. The powder is grinding into a size of 1 to 2μm. An etching is proceeding with cyanide to remove the CuxS deposited on the surface of the fluorescent powder. Accordingly, a light emitted by the CuxS is prevented from being blocked by an energy applied from the outside. A binder is formed by mixing cyano resin with N-Dimetyhlformanide(HCON(CH2)2=73.09) solvent at a predetermined ratio. The above manufactured ZnS:Cu and an insulator are mixed with the binder to be uniformly coated on an upper side surface of the transparent electrode. The coating is dried for 20 minutes at a temperature of 130°C to form a fluorescent layer. The fluorescent material, the insulator and the binder are blended to make a fluorescent paste. The fluorescent paste is coated on the transparent electrode through a screen print process.

Description

Thick Film Electroluminescent Device {ELECTROLUMINESCENCE DEVICE}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electroluminescent device (ELD), and more particularly, to a thick film type electroluminescent device in which voids between the transparent electrode layer (ITO layer) and the fluorescent layer interface of a thick film type electroluminescent device are removed. .

As one of the most direct information transfer means of displaying specific information, the display element is used. The display element is similar to the principle of cathode ray tube (CRT) and cathode ray tube using hot electron emission and phosphor emission, but the electron emission cathode ray is a solid line. (Tungsten wire) and its overall shape is mainly planar fluorescent display panel (VFD), liquid crystal display device (LCD) using the electro-optical properties of the liquid crystal, plasma display device using the gas discharge phenomenon between the charged both electrodes (PDP), an electroluminescent element (ELD) using an electroluminescent effect, and a field emission element (FED) having a structure which emits a fluorescent layer by emitting cold cathode electrons. These display elements have different purposes and uses according to their respective functions and structural characteristics.

Until now, CRTs have been mainly used, but according to the trend of requiring ultra-large to portable display devices, the use of LCDs, PDPs, ELDs, and FEDs, which can be thinned down, is increasing or commercialized.

Among them, ELD is used in display devices, such as low-power consumption, high stability against impact and strong environmental characteristics, such as environmental characteristics evaluation equipment or medical equipment requiring fast response speed.

ELDs are largely classified into thin film electroluminescent devices using a thin film process, thick film type electroluminescent devices in which a phosphor is mixed with a binder and printed in a paste state, and organic electroluminescent devices according to materials and structures of elements.

Thick film type electroluminescent device has advantages such as easy manufacturing and simple structure in production, excellent price competitiveness, thin and flexible device, regardless of installation location, LCD ( It is mainly used for the backlight of Liquid Crystal Device).

The thick film type electroluminescent device is mainly composed of a structure in which a transparent electrode, a fluorescent layer, an insulating layer, and a back electrode are stacked in order. Generally, a cyan resin is formed of N, N-dimethylformamide (N-). Dimetyhlformanide) (HCON (CH ₂ ) ₂ = 73.09) A paste obtained by mixing a phosphor or an insulator in a binder dissolved in a predetermined ratio in a solvent is applied by screen printing to form a phosphor layer or an insulation layer. At this time, the binder and the phosphor or the insulator are mixed in a ratio of 4: 6 or 3: 7.

The structure of a conventional fluorescent layer formed by mixing a binder and a phosphor in this manner is shown in FIG. As shown in Figure 1, the phosphor is widely distributed with a particle size of about 10 to 40㎛.

However, in such a fluorescent layer structure, voids are generated between the fluorescent layer and the transparent electrode or inside the fluorescent layer, and bubbles are generated in the fluorescent layer. In FIG. 2, a fluorescent layer of a conventional thick film type electroluminescent device in which bubbles are generated is enlarged. FIG. 2A shows an enlarged fluorescent layer at a magnification of about 200 times, and FIG. 2B shows an enlarged fluorescent layer at a magnification of about 800 times.

The main cause of bubbles in the phosphor of the conventional thick film type light emitting device is that the volatilization of the N and N-dimethylformamide components, which are solvents of cyan resin, is high. More specifically, while the phosphor and the binder are mixed and printed, for example, while being dried at 130 ° C., the highly volatile solvent is volatilized to generate bubbles as shown in FIG. 2. In particular, since voids are formed in the fluorescent layer structure, bubbles are more easily generated.

When the electroluminescent device is operated under a high temperature and high humidity environment, voids generated between the transparent electrode and the fluorescent layer or adhesion characteristics between the fluorescent layer and the transparent electrode are inferior, and thus, bubble areas formed between a specific region, for example, the fluorescent layer and the transparent electrode. The electric field is concentrated on the transparent electrode, which causes the bubbles to appear as black spots. Therefore, the light emission luminance and display characteristics of the thick film type electroluminescent device are degraded, and the durability is also degraded.

Therefore, it is an object of the present invention to improve the luminance and durability characteristics of the device by suppressing the generation of voids in the fluorescent layer of the thick film type electroluminescent device.

1 is a view showing the structure of a fluorescent layer of a conventional thick film type electroluminescent device.

2 is an enlarged view of a fluorescent layer in a conventional thick film type electroluminescent device.

3 is a cross-sectional view showing the structure of a thick film electroluminescent device according to an embodiment of the present invention.

4 is a flowchart illustrating a procedure of manufacturing a thick film electroluminescent device according to an embodiment of the present invention.

5 is a cross-sectional view showing a structure of a fluorescent layer of a thick film electroluminescent device according to an embodiment of the present invention.

In order to achieve the object of the present invention, the thick film type electroluminescent device according to the present invention removes voids formed in the fluorescent layer by mixing an insulator having a very fine size with respect to the fluorescent substance in the fluorescent layer material in which the binder and the phosphor are mixed.

According to an aspect of the present invention, a thick film electroluminescent device includes: first and second electrodes to which a voltage is applied from the outside; And a fluorescent layer formed between the first electrode and the second electrode and having a binder, a phosphor and an insulator mixed therein, and an insulating layer formed between the fluorescent layer and the second electrode.

The insulator mixed in the fluorescent layer may have a particle size of 0.1 μm to 3 μm, and the insulator may be made of a material having a color, so that light having an arbitrary color may be generated when the fluorescent layer emits light.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

3 shows a structure of a thick film type EL device according to an embodiment of the present invention, and FIG. 4 shows a procedure of manufacturing a thick film type EL device according to an embodiment of the present invention.

As shown in FIG. 3, the thick-film electroluminescent device according to the embodiment of the present invention has a transparent electrode 2 in which a conductor such as indium tin oxide (ITO) is vacuum deposited on the substrate 1. Is formed, and an insulator is mixed with phosphor (ZnS: Cu) in which zinc sulfide (ZnS) and copper sulfide (Cu _x S) are mixed on the transparent electrode 2, and a phosphor layer 3 coated and dried is formed. . Here, zinc sulfide (ZnS) forms a fluorescent matrix, and copper (Cu) forms an impurity forming a light emitting center in the fluorescent matrix.

On the fluorescent layer 3, an insulating layer 4 coated with an insulator such as barium titanate (BaTiO ₃ ) is formed, and a backside on which the Ag paste or carbon paste material is thick-printed on the insulating layer 4 is formed. The electrode 5 is formed. The protective film 6 surrounds the outside of the thick film type electroluminescent device made as described above, and the protective film 6 may be made of a material that transmits light in the visible region. The board | substrate 1 consists of a glass substrate, a film, etc.

In the present invention, an insulator having a fine size is formed in the phosphor in order to remove voids generated inside the fluorescent layer 3 or between the transparent electrode 2 and the fluorescent layer 3 so as to suppress bubble generation by the voids. Mixed. At this time, when the material used to remove the voids generated in the fluorescent layer is not an insulator, an insulator must be used since malfunction may occur during the operation of the EL device.

As the insulator mixed with the phosphor, an insulator having a particle size of about 0.1 to 3 μm was used, and the binder used here was a binder used in the fluorescent layer of the conventional EL device.

Next, a method of manufacturing a thick film electroluminescent device according to an embodiment of the present invention having such a structure will be described with reference to FIG. 4.

First, a transparent electrode 2 is formed by vacuum depositing a conductor such as ITO (indium tin oxide) or transparent tin metal on the upper surface of the substrate 1 (S10).

Next, copper sulfide (Cu _x S) is mixed with zinc sulfide (ZnS) to grind the phosphor powder produced through a high temperature sintering process to a size of 1 to 20 μm, and then to the surface of the phosphor powder. Etched with cyanide or the like to remove adhered copper sulfide (Cu _x S). Accordingly, light emitted by copper sulfide (Cu _x S) is prevented from being blocked by energy applied from the outside.

The phosphor (ZnS: Cu) and the insulator thus prepared are binders, for example, cyan resin (cyano resin) in general, N, N- dimethylfomanide (N-Dimetyhlformanide) (HCON (CH ₂ ) ₂ = 73.09) The mixture is mixed in a solvent at a predetermined ratio, mixed in a melted binder, uniformly applied to the upper side of the transparent electrode 2, and dried at about 130 ° C. for 20 minutes to form the fluorescent layer 3 (S20 to S40). At this time, the phosphor, an insulator, and a binder may be blended to form a phosphor flake, and may be applied onto the transparent electrode 2 by a screen printing process.

Here, the insulator is to fill the pores generated when mixed with the phosphor and the binder is applied to the upper side of the transparent electrode 2, in the embodiment of the present invention is used an insulator having a size of about 0.1 ㎛ to 3 ㎛ to fill the void Decorated. Insulators of one of AsTiO ₃ , MgO, and SiO ₂ have been used, but are not limited thereto.

The structure of the fluorescent layer in which the insulators are mixed as shown above in FIG. 5 is shown. As shown in FIG. 5, as the insulator is mixed with the phosphor and coated on the transparent electrode 2, the insulator is inserted into the gap generated between the transparent electrode 2 and the fluorescent layer 3 so that the void disappears. In addition, the voids generated inside the fluorescent layer 3 are also removed. Therefore, no bubbles are generated in the fluorescent layer even when a binder having volatility is used because there is no place where voids are generated (voids). At this time, as the voids between the transparent electrode 2 and the fluorescent layer 3 are removed, the adhesion between the transparent electrode 2 and the fluorescent layer 3 becomes stronger.

Next, an insulator made of barium titanate (BaTiO ₃ ) is applied to the upper side of the fluorescent layer 2, and dried at about 130 ° C. for 20 minutes to form an insulating layer 4 (S50 to S60). The back electrode 5 is formed by thick-film printing conductive material such as Ag paste or carbon (C) paste on the upper side of (4) (S70).

Next, in order to align the elements and prevent moisture penetration, the outside of the thick film type electroluminescent element manufactured as described above is sealed with a protective film 6 having light transmittance (S80).

In the thick film type electroluminescent device having such a structure, when a voltage is applied to the back electrode 5 and the transparent electrode 2 from an external driving circuit, it is trapped at the interface between the insulating layer 4 and the fluorescent layer 3. Electrons are injected into the fluorescent layer 3 by a tunneling phenomenon, and electrons injected into the fluorescent layer 3 ionize and excite electrons distributed at the base level of the emission center of the fluorescent matrix (ZnS) to generate light. To be generated. That is, electrons distributed in the valuation band of the luminescent center of the fluorescent matrix are energized by electrons injected from the interface of the insulating layer 4, excited to the conduction band, and fall back to the base level, Ionized electrons fall from the conduction band to the ground level of the emission center and emit light.

At this time, since no bubbles are generated in the fluorescent layer 3, black spots are not displayed on the display surface.

Therefore, a thick film type electroluminescent element can be obtained in which the luminance characteristic and the display characteristic are remarkably improved.

Unlike the above embodiment, in the case of manufacturing an electroluminescent device having a structure in which a substrate, a back electrode, an insulating layer, a fluorescent layer, and a transparent electrode are sequentially stacked, the same as the above-described embodiment, the fluorescent layer The insulator having a fine size may be mixed with the binder to be mixed with the binder to remove voids generated during the formation of the fluorescent layer.

In addition, by using an insulator having a color as an insulator mixed when forming the fluorescent layer, the light generated from the fluorescent layer when the electroluminescent element is generated may have an arbitrary color.

In addition, various implementations are possible without departing from the gist of the invention according to the embodiment of the present invention.

As described above, by removing the voids generated during the formation of the fluorescent layer, bubbles are not generated inside the fluorescent layer or between the fluorescent layer and the transparent electrode. Therefore, black spots caused by bubbles are not displayed when the EL device emits light.

Therefore, the luminance characteristics and display characteristics of the thick film light emitting element are improved.

In addition, as the voids between the transparent electrode and the fluorescent layer are removed, the adhesion between the transparent electrode and the fluorescent layer becomes stronger, and the durability characteristics are improved.

Claims (3)

First and second electrodes to which voltage is applied from the outside; A phosphor layer formed between the first electrode and the second electrode and having a phosphor, a binder, and an insulator mixed therein; And An insulating layer formed between the fluorescent layer and the second electrode Thick film electroluminescent device comprising a. In claim 1, The insulator mixed in the fluorescent layer has a particle size of 0.1㎛ ~ 3㎛. In claim 1, The insulator mixed in the fluorescent layer is made of a material having a color.