JP2002025763A - Insulating board for organic el element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an insulating base board for organic EL display element, made of an organic compound material for making light emission through electron-hole implantation and recombination, superior in the flexibility, waterproofness, resistance against oxygen, and stability in the light-emitting operation. SOLUTION: The insulating base board of the organic EL element includes a base material made from a metal plate or metal foil, where an insulating layer made of an organic resin having a thickness of 1-40 μm and a surface roughness of Ra<=0.5 μm and Rmax<=1.5 μm is formed on the surface of the base material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display element using electroluminescence (hereinafter abbreviated as organic EL) of an organic compound material which emits light by injection and recombination of electrons and holes. The present invention relates to an organic EL element insulating substrate having excellent water resistance, oxygen resistance and luminescence stability.

[0002]

2. Description of the Related Art An organic EL device has a laminated structure in which a thin film containing a fluorescent organic compound is sandwiched between an anode electrode and a cathode electrode, and electrons and holes are injected into the thin film and recombined. To generate excitons, and emission of light when these excitons are deactivated (fluorescence / phosphorescence)
Is a display element that performs display by utilizing the above. As shown in FIG. 2, the organic EL device usually has an anode electrode (5) formed on a substrate, and an organic layer {a hole transport layer, a light emitting layer, an electron transport layer (4)} and a cathode electrode ( The sealing member is formed on the substrate so as to cover each layer. In this case, light is extracted on the substrate side.
Glass is used for the substrate because it requires insulation and transparency, and since its practical use is for mobile phones and in-vehicle displays, the thickness is about several mm for the purpose of weight reduction and thinning. Glass plate (6) is used.

[0003] The anode electrode also needs to be transparent.
A transparent conductive film such as TO (Indium Tin Oxide) is formed with a thickness of about 100 nm. The organic layer serving as the light emitting portion is formed, for example, of a copper phthalocyanine (CuPc) organic film (4a) as a hole injection layer formed with a thickness of several tens of nm, and a film of several tens of nm on the CuPc organic film. Bis [N- (1-nap) as a hole transport layer
htyl-N-phneyl) benzidine] α-
On the NPD organic film (4b) and the α-NPD organic film,
Tris (8-quinolinolato) aluminum (Alq3) as a light emitting layer and an electron transporting layer formed with a thickness of 0 nm
It has a three-layer structure with the organic film (4c). The cathode electrode is, for example, an Al film having a thickness of several tens to several hundreds of nm.
-Consists of Li. Although not shown, since the light emitting portion of the organic EL element is significantly deteriorated in the presence of moisture and oxygen, the glass is formed so as to cover the above layers in an inert gas (eg, dry nitrogen) atmosphere from which water is removed as much as possible. A sealing member is fixed to the substrate with an adhesive. Thickness 0.1 ~ for sealing member
1 mm stainless steel foil or the like is used.

The organic EL element is a self-luminous element which does not require a backlight such as a liquid crystal display, and has a great advantage that it can be made thin.
The light emitting portion itself is an organic material and therefore has flexibility. For this reason, the use environment is expected to expand.For example, it is considered to be used by winding around a curved surface such as a telephone pole, or to use various shapes of molded members. Use for space,
Improvement in design is expected. If it becomes possible to increase the size in the future, there is also a demand for making the display curved so that the screen can be viewed from various angles, such as the aurora vision of a baseball field. However, the substrate currently used is glass having poor flexibility, and cannot satisfy the above-mentioned requirements. Further, the glass substrate is easily broken, and handling becomes a problem. Therefore, a substrate replacing glass is required also from the viewpoint of safety and flexibility.

As a substrate having flexibility, a film made of an organic material is considered, and has been put to practical use as a substrate for various electronic devices such as solar cells. However, since the organic resin film is inferior to glass in water resistance and oxygen resistance, when used as a substrate in direct contact with the element, moisture and oxygen permeating the film cause deterioration of the organic EL element, resulting in long-term stability. There's a problem. Further, since the organic resin film has poor rigidity for maintaining a certain shape, the yield is reduced due to the fluttering of the substrate when the light emitting portion is formed, and there is also a problem that the heat resistance is poor when soldering when forming the integrated circuit. On the other hand, metal plates and metal foils have flexibility, and are excellent in water resistance, oxygen resistance, rigidity and solder heat resistance, and can be expected as substrates for organic EL devices. Note that a foil having a thickness of several tens of μm also has the advantage of being lighter than glass. However, the contact surface with the element must be insulated for integration.

In performing the insulation treatment, if the surface has irregularities of about 1 μm and the convex parts have an acute angle, the light emitting portion may be cut off and cause a short circuit. Cannot be used as a substrate for an organic EL device. A method such as polishing can be considered as a method for removing unevenness and smoothing. For example, a glass substrate currently used as a substrate for an organic EL element is subjected to a polishing treatment on its surface. Nevertheless, a method of forming an organic coating film on the surface of a glass substrate and smoothing the surface is introduced (Japanese Patent Application Laid-Open No. 2000-21563).

[0007]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above circumstances, and uses a substrate having flexibility, excellent water resistance and excellent oxygen resistance, and excellent luminescence stability. An object of the present invention is to provide an insulating substrate for an organic EL device.

[0008]

The present inventors have conducted various studies to achieve the above object. As a result, the inventors have found that a metal plate or a metal foil as a base material, a film thickness of 1 to 40 μm made of an organic resin, and a surface roughness of Found that an insulating layer having Ra ≦ 0.5 μm and Rmax ≦ 1.5 μm should be formed on the surface of the base material, and the present invention was completed.

[0009]

Embodiments of the present invention will be described below. As a base material of the substrate for an organic EL device of the present invention shown in FIG. 1, a metal plate or metal foil (1) of stainless steel, ordinary steel, various types of plated steel, copper, aluminum, etc. is used. An insulating layer (2) is formed on the substrate. The insulating layer needs to have a smooth contact surface with the upper layer, and is formed using a paint containing an organic resin as a main component. Polyester-based organic resin,
There are acrylic, fluorine, epoxy, urethane, silicone, etc., especially polyimide or polyethersulfone heat-resistant resin, which is not affected by heating during the formation of each layer and has a stable smooth surface. Is obtained.

The above-mentioned paint is applied to the surface of the base material by roll coating, spraying, spin coating, dipping or the like so that the insulating layer (2) has a film thickness of 1 to 40 μm.
It is formed by firing. In order to ensure sufficient electrical insulation, a film thickness of 1 μm or more is required, and if it is less than 1 μm, defects such as pinholes are likely to occur. However, when the thickness of the insulating layer exceeds 40 μm, not only does the consumption of the paint increase, but also the adhesion to the substrate decreases. The surface roughness of the insulating layer is Ra ≦ 0.5 μm, Rmax ≦ 1.5 μm
Adjust to the range. Since the convex portion on the surface of the insulating layer formed of an organic resin has a relatively smooth shape (a convex shape with a wide skirt) as compared with the remaining convex shape when the metal surface is smoothed by mechanical polishing, Even if the unevenness difference on the surface of the insulating layer is as large as 1.5 μm as compared with the thickness of the organic layer forming the light emitting portion (about several tens of nm), the light emitting portion does not break and the short circuit hardly occurs. Even so, when the unevenness difference on the surface of the insulating layer exceeds 1.5 μm, it is presumed that the elongation of the organic layer forming the light emitting portion does not withstand the difference in elevation and the film breaks, resulting in a short circuit.

On the insulating layer (2), a cathode electrode (3) made of a metal thin film is formed. The cathode electrode is, for example, A
It is composed of a single metal material having a small work function such as l, Li, Ag, and In, or an alloy having a small work function such as Mg-Ag and Al-Li. The cathode electrode is formed with a thickness of several 100 nm by, for example, vacuum deposition, sputtering, or the like. On the cathode electrode (3), an organic layer (4) having a light emitting portion made of a thin film of an organic compound material is formed. Organic layer (4)
Is, for example, PVD (Physic
al Vapor Deposition) to form a layer having a thickness of about 20 to 50 nm. The organic layer in FIG. 2 includes, for example, Alq3 (4c) as a light emitting layer and an electron transport layer formed on a cathode electrode, and α-NPD as a hole transport layer.
(4b) CuPc (4a) as a hole injection layer is sequentially laminated with a thickness of several tens nm.

An anode electrode (5) is formed on the organic layer (4) as a transparent conductive material. The anode electrode (5) is made of a material having a large work function, such as ITO, and has a thickness of 100 nm, for example, by vacuum evaporation, sputtering, or the like.
m. Not shown, but organic E
Since the light emitting portion of the L element is significantly deteriorated in the presence of moisture and oxygen, a sealing member is attached to the insulating substrate with an adhesive so as to cover the layers in an inert gas (eg, dry nitrogen) atmosphere from which water has been removed as much as possible. It is fixed. In the organic EL device using the insulating substrate according to the present invention, a transparent material is used to extract light from the sealing member side. For example, thickness 0.1 ~
A 1 mm transparent acrylic plate or the like is used. According to the above aspect, the unevenness of the surface of the metal plate or the metal foil caused by the surface finish is completely filled with the organic resin, and the organic resin itself has relatively high leveling properties. A substrate is obtained. As a result, even when the electrode layer and the light emitting section are stacked on the insulating substrate, the organic layer serving as the light emitting section does not break, and short circuit due to contact between the anode electrode and the cathode electrode can be prevented.

[0013]

EXAMPLE Example 1; plate thickness 0.15 mm, Ra = 0.6
SUS4 with a surface roughness of μm, Rmax = 1.8 μm
A 30 stainless steel plate was degreased and used as a substrate. As a coating for the insulating layer, a transparent coating in which a polyether sulfone resin containing no pigment component was dissolved in N-methyl-2-pyrrolidone was used. This paint was applied to a substrate, dried and fired to form an insulating layer. The thickness of the obtained insulating layer is 6 μm.
And the surface roughness is Ra = 0.1 μm, Rmax = 0.
It was 7 μm.

Example 2 A hot-dip Al-plated steel sheet having a thickness of 0.3 mm was prepared with a surface roughness of Ra = 1.2 μm and Rmax =
After cold rolling to 2.0 μm and degreasing, a coating type chromate treatment was performed to obtain a substrate. As a paint for the insulating layer, a transparent paint in which a polyester resin containing no pigment component was dissolved in xylene was used. This paint was applied to a substrate, dried and fired to form an insulating layer. The thickness of the obtained insulating layer was 20 μm, and the surface roughness was Ra = 0.
3 μm and Rmax = 1.0 μm. Example 3 An insulating substrate was produced in the same manner as in Example 1, except that a paint obtained by dispersing a titania powder having a solid content of 20% by mass in a transparent paint was used. The thickness of the obtained insulating layer is 8 μm.
m, surface roughness Ra = 0.4 μm, Rmax =
It was 1.4 μm.

Comparative Example 1 A coating material in which 50% by mass of a titania powder in a solid content ratio was dispersed in a transparent coating material was used.
An insulating substrate was manufactured in the same manner as in Example 1. The thickness of the obtained insulating layer was 8 μm, the surface roughness was Ra = 0.6 μm,
Rmax = 1.8 μm. Comparative Example 2 Example 1 except that the amount of the transparent paint applied was reduced.
An insulating substrate was produced in the same manner as in the above. The thickness of the obtained insulating layer was 0.3 μm, and the surface roughness was Ra = 0.5 μm, Rm
ax = 1.7 μm.

Using the insulating substrates prepared in Examples 1 to 3 and Comparative Examples 1 and 2, the organic EL was prepared by the method shown in FIG.
100 elements were prepared for each insulating substrate, and for the obtained organic EL element, the insulating property of the insulating layer, the light emission yield of the organic EL element (the degree of short-circuiting between the anode electrode and the cathode electrode due to the breakage of the light emitting portion). ) Was evaluated. The evaluation was performed as shown below. (1) Insulation of Insulating Layer If there is a defect or the like in the insulating layer, the organic EL elements (light emitting dot units) that are arranged in a matrix on the insulating substrate and are electrically independent are formed on a metal plate (or metal) (E.g., foil) and cannot emit light alone. Therefore, a voltage of 10 V was applied between the electrode on the insulating layer side (cathode electrode in this embodiment) of the organic EL element and the metal plate, and the insulating property of the insulating layer was evaluated based on the presence or absence of conduction. The symbol “○” indicates that all 100 elements had no electrical connection, and the symbol “X” indicates that at least one element was electrically conductive. (2) Light emission yield of organic EL element A voltage of 10 V is applied between the anode electrode and the cathode electrode,
Evaluation was made based on the presence or absence of light emission of the organic EL element. All 100 elements that emitted light were marked with a circle, those that did not emit light with less than 5 were marked with Δ, and those that did not emit light with 5 or more were marked with x.

Table 1 shows the evaluation results. In the insulating substrate of Comparative Example 1 in which the pigment concentration in the coating film was high and the surface roughness was rough, some of the formed organic EL elements did not emit light. In the insulating substrate of Comparative Example 2 in which the thickness of the insulating layer was small, a short-circuit portion was observed in the insulating layer. In contrast, in the insulating substrates of Examples 1 to 3, no short circuit was observed in the insulating layer, and the formed organic EL
It was confirmed that the light emission yield of the device was high.

[0018]

[Table 1]

[0019]

As described above, the organic EL of the present invention is used.
The element insulating substrate is made of a metal plate or metal foil as a base material, and has an organic insulating layer having a microscopically smooth surface. An organic EL device which is excellent in water resistance and oxygen resistance, has excellent light emission stability without short circuit between the anode electrode and the cathode electrode due to breakage of the light emitting portion, and can be used sufficiently, has great industrial value. .

[Brief description of the drawings]

FIG. 1 shows an example of a cross section of an organic EL element using an insulating substrate for an organic EL element of the present invention.

FIG. 2 shows an example of a cross section of a conventional organic EL element.

[Explanation of symbols]

 1: base material (metal plate or metal foil) 2: insulating layer (organic resin) 3: cathode electrode 4: light emitting section (organic layer) 5: anode electrode

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3K007 AB11 AB18 BA06 BA07 CA06 CB01 DA01 DB03 EB00 FA01 4D075 CA23 DA04 DA06 DB01 EA05 EB39

Claims (1)

[Claims] 1. A metal plate or metal foil as a base material, a film thickness of 1 to 40 μm made of an organic resin, and a surface roughness Ra ≦ 0.
An insulating substrate for an organic EL device, wherein an insulating layer having a thickness of 5 μm and Rmax ≦ 1.5 μm is formed on a surface of a base material.