JPH0451439Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an electroluminescent device that emits light by applying an electric field to a phosphor layer.

[Prior Art] An electroluminescent element has a method in which a phosphor layer and a dielectric layer are interposed between a transparent electrode and a counter electrode, and a voltage is applied between the transparent electrode and the counter electrode. Therefore, since they are configured to emit light, are thin and consume less power, they are widely used as display devices in various devices. Among these electroluminescent elements, in addition to the above-mentioned characteristics, the dispersion type has various advantages such as relatively low cost and easy manufacture, so its use is very popular. It is widespread.

Such a dispersed electroluminescent element is formed by dispersing the aforementioned phosphor layer and dielectric layer in a binder resin, respectively, by dispersing the phosphor powder and the dielectric powder in a binder resin, and then forming the phosphor layer and dielectric layer into a paste. The transparent electrodes are laminated by sequentially applying the transparent electrodes, and a counter electrode is formed on the thus formed laminate. here,
As the binder in the aforementioned phosphor layer and dielectric layer, a synthetic resin having a high dielectric constant, such as cyanoethylated cellulose, is used. However, since this cyanoethylated cellulose has high hygroscopicity, when moisture is absorbed from the outside when configured as an electroluminescent element, it is absorbed by the binder resin.
There is an inconvenience that oxidizing the phosphor powder lowers the brightness. Therefore, in order to prevent this external moisture absorption, binders using resins with good water repellency, such as fluororesin, have recently come to be used.

[Problems to be solved by the invention] Therefore, as mentioned above, if the fluororesin is used as a binder to exhibit a waterproof barrier function, it will be effective in preventing moisture from entering from the outside. However, since the binder resin is formed by applying the paste, it is necessary to dissolve the binder resin in a solvent. Since this solvent may contain water, there is an extremely high possibility that water will be mixed into these pastes before they are formed into dielectric layers or phosphor layers. For this reason, conventionally, after forming these phosphor layers and dielectric layers, the moisture was removed by heating and drying them, but as mentioned above, when using fluororesin as a binder resin, Even if heating is performed, it is not always possible to reliably release the moisture inside. The moisture thus present in the binder resin has the disadvantage that it directly reacts with the phosphor during use as an electroluminescent element, leading to early deterioration of its brightness.

The present invention was developed in view of the above points, and its purpose is to effectively absorb the moisture contained in the binder resin, thereby suppressing the decrease in brightness of the phosphor as much as possible. An object of the present invention is to provide an electroluminescent device that is made of aluminum.

[Means for Solving the Problems] In order to achieve the above-mentioned object, the present invention has a configuration in which a chemically reactive desiccant that reacts with moisture is mixed into the phosphor layer and the dielectric layer. This is a characteristic feature.

[Function] By mixing a chemically reactive desiccant into the paste that forms the phosphor layer and dielectric layer,
The water contained in the paste mentioned above reacts with the desiccant and is chemically changed and does not affect the phosphor, making it possible to suppress the deterioration of its brightness characteristics. Even when using a hygroscopic substance such as cyanoethylated cellulose as a binder resin, it is possible to react with moisture that cannot be completely removed during drying, but especially when using a fluororesin as a binder resin. In this case, the moisture cannot be smoothly released to the outside even if it is heated and dried, so there is a high possibility that moisture will remain inside.
Therefore, such water removal can be effectively carried out, making it extremely effective.

[Example] Hereinafter, an example of the present invention will be described in detail based on the drawings.

The drawing shows a cross section of an electroluminescent element, and in the drawing, 1 indicates a transparent electrode, and 2 indicates a counter electrode. Between the transparent electrode 1 and the counter electrode 2, there is a phosphor layer 3 and a dielectric layer. 4 is interposed. The phosphor layer 3 is located on the transparent electrode 1 side and is formed by dispersing phosphor powder in a binder resin, and the dielectric layer 4 is laminated on the counter electrode 2 side, and is formed by dispersing a high dielectric material in a binder resin. It is formed by dispersing it in resin. These phosphor layer 3 and dielectric layer 4
Calcium oxide is contained in the binder resin that makes up the
A finely divided chemically reactive desiccant such as barium oxide is mixed in.

The electroluminescent element having the above-mentioned structure has a lead part (not shown) connected to the transparent electrode 1 and the counter electrode 2, and a phosphor from the outside, such as by sealing it in a sealing film (not shown). layer 3
They are designed to be protected from moisture infiltration, and are used as display devices for various types of equipment.

Next, an example of a method for forming the electroluminescent element described above will be described. In order to form the phosphor layer 3 and the dielectric layer 4, first prepare a phosphor paste and a dielectric paste, and apply each paste one after another on a transparent plate such as a polyester sheet.
A transparent electrode 1 made of O is coated and then a counter electrode 2 made of a thin aluminum plate or the like is laminated and bonded to this laminate.

Here, the phosphor paste is, for example, Fluororesin G501 (manufactured by Daikin) 5 parts by weight Phosphor powder (Zn, CU, Cl type) 6 parts by weight MEK (methyl ethyl ketone) 4 parts by weight CaO (calcium oxide) 0.6 parts by weight The dielectric paste may have a composition of, for example, 5 parts by weight of fluororesin G501, 10 parts by weight of BaTiO ₂ powder, 10 parts by weight of MEK, and 1 part by weight of CaO.

Therefore, since MEK is used as a solvent for the phosphor paste and dielectric paste mentioned above,
Water cannot be avoided in each of these pastes. This moisture is released to the outside to some extent when it is dried after being applied to the transparent electrode 1, but since fluororesin is used as the binder resin, even if it is heated and dried, the moisture is not completely removed. cannot be released. However, since each of these pastes contains finely divided calcium oxide as a chemically reactive desiccant, residual moisture reacts with this calcium oxide to form calcium hydroxide, which results in the formation of phosphors. Layer 3 and dielectric layer 4 are now completely free of moisture. In this case, if the paste is applied to the transparent electrode 1 and then heated and dried, the above-mentioned reaction will be accelerated, so the phosphor layer 3,
Moisture within the dielectric layer 4 can be removed extremely efficiently.

The reaction between calcium oxide and water described above is a reversible reaction, but calcium hydroxide decomposes into calcium oxide and water when the temperature reaches 180° C. or higher. However, since electroluminescent elements are used at temperatures below 100°C, there is no risk of the above-mentioned decomposition reaction occurring under normal usage conditions; If it is kept in a state that prevents water from entering, the brightness life characteristics will be significantly improved.

According to the inventor's experiments, when an electroluminescence element containing calcium oxide is applied with an alternating current of 100V and 50Hz under a high temperature load condition of 70℃, the luminance half-life is 950Hr.
On the other hand, when an electroluminescent element was formed using a paste having the same composition as described above except that no calcium oxide was mixed in, and a brightness change experiment was conducted under the same conditions, it was found that
The brightness was reduced by half.

In the above-mentioned embodiments, the phosphor powder constituting the phosphor layer 3 is Zn, Cu, or Cl-based, but it is also possible to use rare earth elements, monovalent metals, transition metals, etc. In addition, the dielectric material constituting the dielectric layer 4 can be made of a material such as TiO ₄ in addition to the above-mentioned materials, and the binder may be made of the above-mentioned fluororesin, cyanoethylated cellulose, or ionomer resin, etc. Furthermore, in addition to MEK, organic solvents such as acetone and toluene may be used as the solvent.In short, a paste consisting of phosphor powder or dielectric powder made of the desired substance, a binder and a solvent is used. A chemically reactive desiccant that reacts with water, such as calcium oxide or barium oxide, may be mixed into the liquid.

[Effects of the invention] As explained above, according to the invention, a chemically reactive desiccant that chemically reacts with water is mixed into the phosphor layer and the dielectric layer, so that a solvent or the like that dissolves the binder resin is used. It becomes possible to completely remove moisture contained in the electroluminescent element, and the brightness life characteristics of the electroluminescent element can be significantly improved.

[Brief explanation of the drawing]

The drawing is a sectional view of an electroluminescent device showing an embodiment of the present invention. 1... Transparent electrode, 2... Counter electrode, 3... Fluorescent layer, 4... Dielectric layer.

Claims (1)

[Claims for Utility Model Registration] (1) A phosphor layer consisting of a phosphor powder dispersed in a binder resin between a transparent electrode and a counter electrode, and a dielectric layer consisting of a high dielectric powder dispersed in a binder resin. 1. An electroluminescence device comprising: a chemically reactive desiccant that reacts with moisture is mixed into the phosphor layer and the dielectric layer. (2) The electroluminescent device according to claim 1, wherein the chemically reactive desiccant comprises calcium oxide or barium oxide.