JP2749008B2 - Method for manufacturing electroluminescent device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to a method for manufacturing an electroluminescent element used as a display element or a backlight in various display devices and the like. 2. Description of the Related Art In a conventional electroluminescent device, as shown in FIG. 2, a light emitting layer 13 is interposed between a counter electrode 11 and a transparent electrode 12, and The light-emitting layer 13 emits light by applying an AC electric field between the transparent electrode 12 and the light-emitting layer 13. The light-emitting layer 13 is widely used as a display element or a backlight in various display devices and the like. [0003] Here, the above-described electroluminescent element comprises a transparent electrode 12 on a transparent base film 14.
Is formed by means such as sputtering, and the light emitting layer 13 composed of the phosphor layer 13a and the dielectric layer 13b is sequentially laminated on the transparent electrode 12 by means such as screen printing so that the phosphor layer 13a is on the transparent electrode 12 side. The light emitting layer 13 is manufactured by forming a counter electrode 14 on the light emitting layer 13. [0004] Incidentally, the above-described electroluminescent element has a predetermined voltage even if the thickness of the phosphor layer and the dielectric layer is strictly controlled. When is applied, the luminance at the time of light emission varies, and depending on the product, the luminance is remarkably inferior. For this reason, the quality of the product is not constant and the yield is not good. Therefore, the present inventor has investigated the cause of the above-mentioned variation in luminance, and as a result, when the distribution of the phosphor powder constituting the phosphor layer is not uniform, the luminance during light emission decreases. That is, the variation in the distribution of the phosphor powder is caused by poor wettability of the phosphor layer with respect to the transparent electrode, and particularly, the phosphor layer is formed on the transparent electrode by screen printing. In some cases, depending on various conditions, attention is paid to the fact that the conformation of the phosphor layer to the transparent electrode is significantly deteriorated, and therefore, the phosphor layer may not be formed uniformly on the transparent electrode. The invention has been completed. An object of the present invention is to improve the wettability of the phosphor layer with respect to the transparent electrode so that the phosphor powder constituting the phosphor layer can be uniformly dispersed on the transparent electrode. An object of the present invention is to provide a method for manufacturing an electroluminescent device having good luminance. SUMMARY OF THE INVENTION The object of the present invention is to provide a light emitting layer comprising a phosphor layer and a dielectric layer interposed between a counter electrode and a transparent electrode. In an electroluminescent device that emits light from the phosphor layer by applying an AC electric field between the electrodes, an undercoat layer made of cyanoethyl pullulan is formed on the transparent electrode, and then the phosphor layer is coated with an undercoat layer. This is achieved by means of printing on top. [0008] In the above means, by forming an undercoat layer on the surface of the transparent electrode in advance, when forming the phosphor layer on the undercoat layer by printing , the phosphor layer is formed. It can be formed uniformly on the transparent electrode, and the phosphor powder in the phosphor layer is uniformly dispersed, so that the brightness as an electroluminescent device is extremely good. Further, as described above, as a result of the phosphor layer being uniformly dispersed, when a dielectric layer is formed on the phosphor layer, pinholes are generated as shown by P in FIG. No inconveniences occur. Since the undercoat layer is mainly for improving the wettability of the phosphor layer, the undercoat layer may have a small thickness. The thickness does not become particularly large. Here, the undercoat layer must have good compatibility with the phosphor layer as described above, but it is preferable that the undercoat layer itself be compatible with the transparent electrode. However, considering the fact that the phosphor layer is formed by screen printing as described above and the means for forming the undercoat layer is not limited, it is preferable to use cyanoethyl pullulan as the material of the undercoat layer. Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows a cross section of an electroluminescent device obtained by a method for manufacturing an electroluminescent device according to the present invention. In the drawing, 1 is a base film, 2 is a transparent electrode, Denotes a light-emitting layer composed of a phosphor layer 3a and a dielectric layer 3b. The phosphor layer 3a is formed by dispersing a phosphor powder 4 in a binder resin 5. An undercoat layer 6 is interposed between the phosphor layer 3a and the transparent electrode 2 in the light emitting layer 3. Further, a counter electrode 7 is further laminated on the dielectric layer 3b in the laminate formed as described above. Here, the base film 1 is made of polyethylene terephthalate or the like, and the transparent electrode 2 is made of a member such as indium tin oxide. The phosphor powder 4 in the phosphor layer 3a is formed of zinc sulfide or the like, the binder resin 5 is formed of a fluorine resin or the like, and the dielectric layer 3b is preferably formed of the same member as the binder resin 5 of the phosphor layer 3a. Have been. Further, the undercoat layer 6 is formed by mixing a solvent such as γ-butyrolactone with cyanoethyl pullulan, which has good compatibility with the phosphor layer 3a and has high transparency and high dielectric constant. Furthermore, the counter electrode 7 is made of aluminum foil or the like. Next, in manufacturing the above-described electroluminescent device, first, the base film 1
A transparent electrode 2 is formed thereon by coating, and an undercoat layer 6 is formed on the transparent electrode 2. This undercoat layer 6
In order to be able to be uniformly dispersed on the transparent electrode 2, it is formed by, for example, means such as coating. The undercoat layer 6 improves the dispersibility of the phosphor layer 3a when the phosphor layer 3a is formed.
Since it is for improving the wettability of the film, it may be formed into a thin film of, for example, about 1 to 3 μm. On the undercoat layer 6 thus formed, a phosphor layer 3a is formed by means such as screen printing. Here, since the undercoat layer 6 is made of a member that is familiar to the phosphor layer 3a, the dispersibility on the undercoat layer 6 is improved, and the phosphor powder 4 contained in the phosphor layer 3a is removed. As shown in FIG. 1, the particles are uniformly dispersed, and the film thickness is also uniform. Then, a dielectric layer 3b is formed on the phosphor layer 3a. The dielectric layer 3b is made of the same material as the binder resin 5 in the phosphor layer 3a, and the adaptability of both is extremely good. It is. Therefore, there is no possibility that a pinhole or the like is generated between the dielectric layer 3b and the phosphor layer 3a. Further, by laminating the counter electrode 7 on the dielectric layer 3b, an electroluminescent element can be manufactured. In the electroluminescent device manufactured as described above, since the phosphor powder 4 of the phosphor layer 3a in the light emitting layer 3 is extremely uniformly dispersed, the transparent electrode 2 and the counter electrode 7 are formed. The uniformity of the luminance when an AC electric field is applied is extremely good, and the quality of the product can be remarkably improved without pinholes or the like. According to the present invention, to form an undercoat layer made of cyanoethyl pullulan on transparency electrode, the
After, since the printing form fluorescent material layer on the undercoat layer, to improve the wettability when printing form the phosphor layer
Therefore, the dispersibility of the phosphor layer is extremely improved, and the phosphor layer can be formed uniformly.
You. In addition, since the undercoat layer has high transparency and a high dielectric constant, the undercoat layer has good luminance and can significantly improve the quality of a device as a product.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of an electroluminescent device obtained by a manufacturing method according to the present invention. FIG. 2 is a cross-sectional view of an electroluminescent device showing a conventional technique. [Description of Signs] 2 Transparent electrode 3 Light emitting layer 3a Phosphor layer 3b Dielectric layer 4 Phosphor powder 5 Binder resin 6 Undercoat layer 7 Counter electrode

Claims (1)

(57) [Claims] A light emitting layer including a phosphor layer and a dielectric layer is interposed between the counter electrode and the transparent electrode, and an AC electric field is applied between the counter electrode and the transparent electrode to emit light from the phosphor layer. In the electroluminescent device, an undercoat layer made of cyanoethyl pullulan is formed on the transparent electrode, and then the phosphor layer is formed by printing on the undercoat layer. Production method.