JPH044399Y2 - - Google Patents

Description

[Detailed explanation of the idea]

Industrial Application Field The present invention relates to thin-film EL devices, and more specifically, as a means to prevent dielectric breakdown at the edge-like portions of striped electrodes, an organic resin insulating coating with almost no steps is applied to the surface of the striped electrodes. The present invention relates to the formed thin film EL element. 2. Prior Art A thin film EL element 7 forming a matrix type display panel is, as shown in FIG. The layer 3, the light emitting layer 4, the second insulating layer 5, and the back electrode 6 are sequentially formed.
It is formed by laminating layers. The thus obtained thin film EL element 7 is covered with a concave plate-shaped cover glass 8, and the cover glass 8 is placed on the transparent substrate 1 with an adhesive such as an epoxy resin or a photocurable resin. By fixing them together, a matrix type display panel is formed. In order to improve the moisture resistance of the thin film EL element 7, inside the envelope 10 consisting of the transparent substrate 1 and the cover glass 8,
An insulating protective fluid 11 such as silicone oil is sealed. Here, the stripe electrode 2 is
The transparent electrode layer is formed of indium tein oxide (hereinafter referred to as ITO), an oxide of In, Sn, etc., the back electrode 6 is formed as an electrode layer of Al, etc., and the light emitting layer 4 is formed of Mn, etc. The first and second insulating layers ₃ and 5 are made of _Y2O3 , _{Ta2O5 ,} etc. [Japanese Patent Publication No. 57-47559, Japanese Unexamined Patent Application Publication No. 1986-60] Publication No. 11876]. Problems to be Solved by the Invention In the matrix type display panel as described above, in order to reduce mounting costs, a signal voltage is applied only from one terminal of the striped electrode, for example, an ITO striped electrode, and the signal voltage is applied from the other terminal. It is left open. The electrical resistance value of ITO thin film is approximately 2.5×
Since it is as large as 10 ^-4 Ω·cm, the longer the stripe electrode becomes, the greater the degree of attenuation of the signal voltage applied from one terminal of the stripe electrode becomes.
There is a limit to reducing the electrical resistance of an ITO thin film, so in order to reduce the electrical resistance of a striped electrode, it is necessary to
It is necessary to increase the thickness of the thin film. For these reasons, if the thickness of the ITO thin film is increased, the second
As seen in the figure, the edge-shaped portion of the striped electrode has a steep slope, and the film thickness of the first and second insulating layers 3 and 5 and the light-emitting layer 4 that are laminated after the formation of the striped electrode is reduced to the edge-shaped portion 12. As a result, cracks are likely to occur in this area, increasing the risk of dielectric breakdown at the edge-like portions of the striped electrode. The main purpose of the present invention is to provide a means for improving the insulation performance of the edge-shaped portions of striped electrodes, which can solve the above-mentioned problems observed in conventional thin film EL devices. Means for Solving the Problems In view of this objective, the present invention provides a thin-film EL device in which striped electrodes are formed on a transparent substrate, in which an insulating film of organic resin is applied to the striped electrodes by spin coating. The gist of this invention is a thin film EL element characterized by being formed so as to be in direct contact with the gap and surface of the electrode. Operation A coating layer of an organic resin, such as a ladder-shaped polyimide resin, having a flat surface, which functions as a reinforcing layer for the edge-shaped portion, is formed on the surface of the striped electrode by a spin coating method. Embodiment FIG. 1 is a partial vertical cross-sectional view of a thin film EL device according to the present invention. Incidentally, the members forming the thin film EL element that are the same as those in FIG. 2 are indicated by the same reference numerals, and a detailed explanation will be omitted. The etchback method and the bias sputtering method are known as means for forming a flat insulating film on the surface of the striped electrode 2, but in the present invention, we focused on the fact that the material for forming the insulating film is an organic resin. ,
A spin coating method is used. To explain in more detail, a transparent substrate 1 on which striped electrodes 2 are formed
By dropping liquid organic resin onto the surface of the stripe electrode 2 and using the spreading action of centrifugal force to apply the organic resin thickly to the concave portions of the stripe electrode 2 and thinly to the convex portions of the stripe electrode 2, the stripe electrode 2 is formed. A flat insulating coating 13 with substantially no steps is formed on the surface. Organic resins that can be used in this invention include self-adhesive resins, mainly polyimide resins, taking into consideration insulation, heat resistance, mechanical strength [pressure resistance], and adhesiveness to the surface of the striped electrode 2. Preferred are polyimide silicone resins, photosensitive polyimide resins, and the like. Among the polyimide resins, linear polyimides [e.g. DuPont
Particularly recommended are PYRALIN PI-2545, PI-2555] manufactured by Co., Ltd., or polyimide isoindoquinazolinedione (hereinafter referred to as PIQ) in which a ladder structure is introduced as a modification of the usual polyimide.
Both PYRALIN and PIQ can be obtained with a viscosity and resin concentration that suit the purpose by adjusting the degree of polymerization of their precursor polyamic acid. Table 1 below shows the heat resistance and dielectric breakdown strength of PIQ and PYRALIN. PIQ is coated on the surface of stripe electrode 2 with a thickness of 0.6 to 4 μm by spin coating.
The composition has been adjusted to form a thin film, but by adjusting the viscosity and resin concentration,
It is also possible to form an extremely thin insulating film of 500 Å to 20 μm.

【table】

[Table] Hereinafter, embodiments of the present invention will be described based on descriptions of specific examples. After laminating an ITO film with a thickness of about 1800 Å as a stripe electrode 2 on a transparent substrate 1 made of glass, a ladder-shaped polyimide resin [PIQ] was applied onto the stripe electrode by spin coating,
Further, baking was performed at approximately 300° C. to form an insulating coating 13 made of a thin film of PIQ. In this state, the film thickness of the insulating coating 13 was measured using the upper surface of the transparent substrate 1 as a reference, and as a result, an average thickness of 2100 Å was recorded, and the PIQ was measured from the upper surface of the recess between the striped electrodes 2 to the striped electrode. It was confirmed that a flat surface with virtually no difference in level was formed over the upper surface of the sample. Thereafter, the excess ladder-shaped polyimide resin adhered to the periphery of the light-transmitting substrate 1 is peeled off according to a conventional method, and the first insulating layer 3, the light-emitting layer 4, the second insulating layer 5, and the back surface are removed. A thin film EL element 7 was created by sequentially stacking electrodes 6. The embodiments of the present invention have been described above based on examples in which ITO is used as the material for forming the striped electrode 2 and ladder-shaped polyimide resin is used as the material for forming the insulating coating 13. The description of the examples should not be construed as limiting, and can include numerous application examples. For example, by adjusting the thickness of the insulating film 13, it is also possible to omit the provision of the first insulating layer 3. Effects of the Idea As can be understood from the above explanation, an insulating film made of organic resin that functions as a reinforcing layer for the edge-shaped portion can be formed on the surface of the striped electrode by the spin coating method. Since the insulating film has a flat surface with virtually no differences in level, it is possible to eliminate the problem in the insulating layer and light-emitting layer due to the level difference in the edge-like portions, which has been a problem in conventional thin film EL devices. It is extremely effective in preventing dielectric breakdown caused by the step difference in the stripe electrode.

[Brief explanation of the drawing]

FIG. 1 is a partial vertical sectional view of a thin film EL device according to the present invention, and FIG. 2 is a partial vertical sectional view of a conventional thin film EL device. DESCRIPTION OF SYMBOLS 1...Transparent substrate, 2...Stripe electrode [transparent electrode], 3...First insulating layer, 4...Light emitting layer,
5... Second insulating layer, 6... Back electrode, 7... Thin film EL element, 13... Insulating coating made of organic resin.

Claims (1)

[Claims for Utility Model Registration] (1) In a thin film EL device in which striped electrodes are formed on a transparent substrate, an insulating coating of organic resin is applied directly to the gaps and surfaces of the striped electrodes by spin coating. A thin film EL element characterized by being formed so that they are in contact with each other. (2) The thin film EL device according to claim 1, wherein the organic resin is an insulating resin selected from the group of polyimide resins, polyimide silicone resins, and photosensitive polyimide resins. (3) The thin film EL device according to claim 2, wherein the polyimide resin is a linear polyimide or a ladder polyimide.