KR0180070B1 - Organic eletroluminescent device and its manufacturing method - Google Patents

Abstract

The present invention relates to a method for producing a phosphor resistant to moisture, an organic dispersed electroluminescent device using the phosphor, and a method for manufacturing the same, in particular, a surface protective layer made of low melting glass for preventing moisture from penetrating the surface of the phosphor particles. It characterized by covering the.

Accordingly, the electroluminescent device using the phosphor particles having the moisture barrier protective layer formed thereon has an effect that the configuration is simple and the process is simple and the life is long.

Description

Method for producing phosphors resistant to moisture, organic dispersed electroluminescent device using same and method for manufacturing same

1 is a view showing the configuration of a conventional phosphor particle.

2 is a view showing the structure of a conventional electroluminescent device.

3 is a view for explaining a manufacturing method of a conventional electroluminescent device.

4 is a view showing the configuration of the phosphor particles resistant to moisture employed in the present invention.

5 and 6 are views showing the structure of the preferred embodiments of the organic EL device according to the present invention.

7 is a view for explaining a method for manufacturing an organic dispersed electroluminescent device according to the present invention.

8 is a graph comparing the lifespan of the electroluminescent device.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electroluminescent device used as a surface light source, and more particularly to a method for producing a phosphor resistant to moisture, an electroluminescent device having a long life and a simple manufacturing process using the phosphor, and a method for producing the same.

Electroluminescent devices have a very low luminance and short lifespan, so their application as a light source for illumination temporarily declines. However, in recent years, electroluminescent devices, which are surface light sources, have a uniform brightness due to the trend of miniaturization, low power consumption, and high reliability of electronic devices. The light source has a thickness of less than 1 millimeter and is very thin, is easily recognized as a back light source of a liquid crystal display device because of its advantages such as large area, easy to manufacture various shapes, low power consumption, and little heat generation.

There are two types of electroluminescent devices, a thin film type for graphic display and the like, but a distributed type is suitable for a backlight or a back light source of a liquid crystal display device.

As the phosphor used in the distributed electroluminescent device, a product in which ZnS is additionally activated with Cu and Mn is used. Therefore, the lifetime of the distributed electroluminescent device depends on the lifetime of the phosphor. Especially, in the case of an emulsion, it is easy to deteriorate due to moisture and ultraviolet rays. to be.

The present invention has been made to solve the problems of the prior art, and an object thereof is to provide a method for producing a phosphor resistant to moisture.

Another object of the present invention is to provide an organic dispersion type electroluminescent device having a simple structure, long life, no non-light emitting area, and low cost.

It is another object of the present invention to provide a method for manufacturing an organic dispersed electroluminescent device having a simple manufacturing process.

The phosphor manufacturing method for achieving the object of the present invention comprises the steps of heating the phosphor particles of zinc emulsion / copper type for a predetermined time in a concentrated phosphoric acid or silicon fluoride acid for a predetermined time; It is characterized in that it comprises a step of washing and then drying the phosphor particles having a protective layer formed on the surface by a heating process.

The organic dispersed electroluminescent device of the present invention for achieving the above another object is a phosphor layer, an insulator layer, a resin layer, a phosphor layer having a surface protective layer, and a resin layer laminated sequentially thereon using a front electrode layer as a substrate. A back electrode layer and a back treatment layer are provided.

According to another aspect of the present invention, there is provided a method of manufacturing an organic dispersed electroluminescent device, including: covering a resin layer having a predetermined thickness on a substrate using the front electrode layer as a substrate; Coating a phosphor paste formed of a phosphor having a surface protective layer and a binder on the resin layer to form a phosphor layer; Coating an insulating layer paste on the phosphor layer to form an insulating layer; Coating a conductive paste on the insulating layer to form a back electrode layer; And applying a back treatment layer on the resultant product.

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

First, in order to help the understanding of the present invention, the structure of a conventional phosphor particle, a conventional electroluminescent device, and a manufacturing method will be described with reference to FIGS. 1 to 3.

Referring to FIG. 1, since the conventional phosphor particles do not have a protective layer on the surface, the surface is easily hydrated by the following chemical formula when exposed to moisture.

ZnS + 2H ₂ 0 = ZnO + S0 + 2H

In this way, sulfur is released from the zinc emulsion in response to water, and thus the crystallinity of zinc emulsion, which acts as the mother of the phosphor, is lost and the function of the phosphor is lost.

Therefore, in the conventional electroluminescent device, a moisture proof film layer and a moisture absorbing film layer are provided as shown in FIG. 2 to protect the phosphor particles. That is, the conventional electroluminescent device has a thickness of about 75 to 100 micrometers, the aluminum substrate 10 provided as the lower electrode 10, the insulator layer 12, the light emitting layer 14, the transparent electrode film 16 provided as the upper electrode The upper and lower absorbent films 18 and 20 are respectively disposed on the upper and lower surfaces of the laminated structure, and the outside is sealed by the upper and lower moisture absorbing films 22 and 24. Therefore, since the overall device thickness is formed to be about 1 millimeter thick, it is relatively flexible, but there is a limit in flexibility of bending. In addition, since the non-light emitting region is formed at the edge part because it is sealed with a moisture proof film, such a non-light emitting region must be taken into consideration when designing an application, thereby limiting the freedom of design. In addition, the price of the moisture-proof film is so expensive that occupies half of the material cost of the entire device, causing the cost increase.

Referring to FIG. 3, a conventional method of manufacturing an organic dispersion type electroluminescent device is provided with an aluminum substrate and an insulator paste (302 and 304). The insulator paste is applied to the prepared aluminum substrate by silk screen printing or roll coating and dried (306). Phosphor particles and a binder are mixed in a solvent to prepare a light emitting layer paste (308), and the prepared phosphor paste is coated on the insulator by a silk screen printing method or a roll coating method to a predetermined thickness and then dried (310). ). The aluminum substrate is cut (312) and the lower electrode 314 prepared in advance is attached (316). Meanwhile, the transparent electrode film is prepared (318), the prepared transparent electrode film is cut to a predetermined size (320), and the upper electrode 322 provided on the transparent electrode film is attached (324). The transparent electrode film having the upper electrode attached thereto is laminated on the light emitting layer (326). A moisture absorbing film is prepared (328), the prepared moisture absorbing film is cut to a predetermined size (330), and the cut moisture absorbing film is laminated on an aluminum substrate and a transparent electrode film (332). A moisture proof film is prepared (334), the prepared moisture proof film is cut to a predetermined size (336), and the laminated resultant is encapsulated by laminating the cut moisture proof film (338). The result of sealing the resultant sealed with a moisture-proof film is completed (340).

As described above, in the conventional electroluminescent device, the addition of the moisture-proof films 22 and 24 and the moisture absorbing film layers 18 and 20 increases the thickness of the device, thereby lowering the brightness of the device and complicating the manufacturing process. Is raised. In addition, when moisture penetrates through the adhesive part 26 of the moisture proof films 22 and 24, the problem of shortening the lifetime of the phosphor remains.

Since the surface of the phosphor such as ZnS has a very unstable structure, when moisture penetrates into the surface in the electric field, the surface of the phosphor changes due to electrolysis from the surface facing the electrode. As a result of the electrolysis, the surface of the phosphor becomes rough, and the roughly recessed portion continues to extend into the crystal of the particle. This void expansion acts as a diffusion channel, accelerating crystal destruction.

Therefore, in the present invention, as shown in FIG. 4, the protective layer 42 is disposed on the surface of the phosphor particle 40 to block the chemical reaction so that copper does not come out and oxygen does not enter the crystal. It was made by covering. The protective layer 42 is formed of a low melting glass system (180 degree melting point) which has the property of preventing moisture penetration. The low melting point glass system is phosphate glass or As-S-Br glass. Zinc borosilicate may be applied as the protective layer, but since the melting point is high and a high temperature process is required, problems such as thermal expansion must be considered, which may cause another problem.

In the production of the phosphor of the present invention, the phosphor particles of zinc emulsion / copper are heated in a concentrated phosphoric acid or silicon fluoride for a predetermined temperature for a predetermined time, and the phosphor particles having a protective layer formed on the surface are washed by the heating process. Next, it is formed by drying. By the heating process, ZnS is changed to Zinc Phosphate or Zinc Silicate on the surface of the phosphor.

5 and 6, the electroluminescent device of the present invention comprises a resin layer 52 sequentially stacked on the front electrode layer as a substrate, a light emitting layer composed of phosphor particles and a binder having a surface protective layer ( 54), the laminated structure of the insulator layer 56 and the back electrode layer 58 was sealed by the back process layer 60. FIG. The front transparent electrode layer is formed of an ITO film 50 or a PET film 51 coated with a transparent conductive ink. The resin layer 52 is for increasing the adhesion between the electrode layers 50 and 51 and the light emitting layer 54, and is preferably formed to a thickness of several micrometers. As the binder of the light emitting layer 54, CR-V (Cyanoethyl Pullulan) or CR-5 (Cyanoethyl Polyvinylalcohole) is adopted. The insulator layer 56 is formed of BaTiO ₃ and a binder. The back electrode layer 58 is formed of silver paste or graphite paste. The back treatment layer is formed by lamination of SKA 500 and SKA 100. Here, the SKA series is Thermoplastic Saturated Copolyester Resins manufactured by Sun Kyung Chem. The higher the number is, the softer the harder it is. The manufacturing method of a preferred embodiment of the electroluminescent device of the present invention having such a structure is as follows.

Referring to FIG. 7, a transparent electrode film to be used as a substrate is prepared (602), and a light emitting layer paste is prepared (604). The light emitting paste is advantageously composed of DMF solvent: CR-V: CR-S: phosphor particles at a compounding ratio of 25-45: 1-10: 5-20: 30-60% by weight, and preferably DMF solvent: CR -V: CR-S: phosphor particles are blended at 36: 5: 12: 47 weight percent. Here, if the DMF is less than 25% by weight, the viscosity of the paste is so high that the coating is difficult to print, and if the amount of the phosphor particles exceeds 60% by weight, the coated surface is not uniform, resulting in poor luminescence. .

The resin layer is covered with a thickness of about several micrometers on the prepared substrate, and the light emitting layer paste is coated on the substrate by silk screen printing or roll coating, and then dried (606).

An insulating layer paste is prepared (608). The insulating layer paste is DMF solvent: CR-V: CR-S: BaTiO ₃ is advantageously blended in 30-50: 1-10: 5-20: 30-60% by weight, preferably DMF solvent: CR-V : CR-S: BaTiO ₃ is mix | blended by 40: 5: 13: 42 weight%. If the amount of DMF in the blending ratio is less than 30% by weight, the paste viscosity is high, the coating is not good, and even if the amount of BaTiO ₃ exceeds 60% by weight, the coating is difficult because the viscosity is too high. The prepared insulating layer paste is coated on the light emitting layer by silk screen printing and then dried (610). Graphite paste or silver paste is prepared as a back electrode paste (612), and a back electrode layer is formed on the insulating layer by a silk screen printing method (614). ) SKA 500 is coated first, and then SKA 100 is coated to apply a back treatment layer (618), and the resultant is cut (620) and completed (622).

Effects of the present invention are as follows.

The brightness B over time of the electroluminescent device is represented by the following equation.

Here, n_1 and τ represent the time until the erection of the electroluminescent device reaches a level of 1/2 of the initial brightness B ₀ , which is called half-life, and this value is referred to as the lifetime of the device.

Therefore, in the present invention, the life comparison graph shown in FIG. 8 is performed by comparing the conventional device and the device of the present invention with a sinusoidal alternating current of 100 volts / 400 hertz under a measurement condition of 25 degrees Celsius and 60% RH. Could get In the experiment, it can be seen that the device of the present invention has a long life of approximately 3 times or more compared to 3000 hours of the conventional device at 10,000 hours.

Therefore, the electroluminescent device of the present invention manufactured and configured as described above has a lifespan of 3 times or more, and an overall thickness of 0.35 mm can be manufactured to be about 1/3 thinner than the conventional method. Since the thin structure increases flexibility and does not use moisture proof film, firstly, since the non-luminescent area is not formed, the degree of freedom of design of the applied product is increased, and secondly, the cost can be reduced to less than half by removing expensive moisture proof film. And third, since the laminating process of the moisture absorbing film and the moisture-proof film is eliminated, it is possible to improve the production efficiency and reliability by simplifying the process.

Claims (15)

Heating the zinc emulsion / copper phosphor particles at a predetermined temperature in concentrated phosphoric acid or silicon fluoride for a predetermined time; And a step of washing the phosphor particles having a protective layer formed on the surface by the heating step, and then drying the phosphor particles. An organic dispersion type electroluminescent device, comprising: a light emitting layer, an insulating layer, a back electrode layer, and a back treatment layer formed of a binder and phosphor particles having a surface protective layer sequentially formed thereon and a transparent front electrode layer as a substrate. The organic dispersed type electroluminescent device according to claim 2, wherein the front electrode layer is one of an ITO film and a PET film coated with a conductive ink. The organic dispersed type electroluminescent device according to claim 2, further comprising a resin layer having excellent adhesion between the front electrode layer and the light emitting layer. The organic dispersed type electroluminescent device according to claim 4, wherein the resin layer has a thickness of about several micrometers. The organic dispersed electroluminescent device according to claim 2, wherein the binder is CR-V or CR-S. The organic dispersed electroluminescent device according to claim 2, wherein the insulating layer is made of a BaTiO ₃ binder. The organic dispersed type electroluminescent device according to claim 2, wherein the back electrode layer is a silver paste or a graphite paste. The organic dispersed type electroluminescent device according to claim 2, wherein the back treatment layer is formed of a stack of SKA 500 and SKA 100. Covering a resin layer having a predetermined thickness on the substrate using the front electrode layer as a substrate; Coating a phosphor paste formed of a phosphor having a surface protective layer and a binder on the resin layer to form a light emitting layer; Coating an insulating layer paste on the light emitting layer to form an insulating layer; Coating a conductive paste on the insulating layer to form a back electrode layer; And applying a back treatment layer onto the resultant. The method of claim 10, wherein the phosphor paste is coated by screen printing or roll coating. The method of claim 10, wherein the phosphor paste is DMF solvent: CR-V: CR-S: the organic compound, characterized in that the mixing ratio of the phosphor particles is 25-45: 1-10: 5-20: 30-60% by weight Method of manufacturing a distributed electroluminescent device. The method of claim 10, wherein the phosphor paste has a compounding ratio of DMF solvent: CR-V: CR-S: phosphor particles in a range of 36: 5: 12: 47 wt%. . The method of claim 10, wherein the insulator paste is a compounding ratio of DMF solvent: CR-V: CR-S: BaTiO ₃ is 30-50: 1-10: 5-20: 30-60% by weight Method of manufacturing a distributed electroluminescent device. The method of claim 10, wherein the insulator paste has a blending ratio of DMF solvent: CR-V: CR-S: BaTiO ₃ at 40: 5: 13: 42 weight percent. .