JPH10172766A - Organic electroluminscent element and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an organic electroluminescent(EL) element which can effectively utilize the light advancing in the parallel direction of an organic thin film by forming an end surface of the organic thin film in the shape of having a light reflecting function in the organic EL element formed by laminating the organic thin film on a base board. SOLUTION: A semitransparent film 102 such as a titanium oxide or a silicon oxide is formed on a base board 101 formed of glass or the like, and a transparent electrode 103, a hole transport layer 104, a light emitting layer 105 and a back metallic plate 106 are laminated on it, and an organic EL element is formed. An end surface of this organic thin film is made to function as a semitransparent reflecting mirror by a difference in a refractive index with an external part, and is formed in the shape of reflecting the light on the inside. That is, a conventional film thickness changing area is shortened as much as possible, and the light is shut in, and attenuation and extinction of the light are reduced. It is ideally better that the end surface of the organic thin film is a right angle to the base board, but actually, when a right-angled part of about 40 to 90% exists in a thickness of the film, reflection of the light (shutting-in of the light) can be sufficiently obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic light-emitting device, and more particularly to an organic light-emitting device used for an optical-related product using a display light source, an optical circuit component, an optical switch, an optical array, a communication device, an optical recording head, and the like. It relates to an element.

[0002]

2. Description of the Related Art A conventional organic electroluminescent device having a micro-resonator structure is called "Study of a multicolor light-emitting device using an organic light-emitting device using a micro-resonator structure": Nakayama, Kakuta, Nagae: IEICE Journal, As in J77-C-II, 437 (1994), a resonator structure in which an organic light emitting thin film was sandwiched between two plane reflecting mirrors.

[0003]

In a conventional organic electroluminescent device having a microresonator structure, there is no structure for confining light traveling in a direction parallel to the film surface, and the light is not utilized and is lost. In this regard, the same applies to a normal type organic electroluminescent device having no resonator structure.

Here, the reason why light traveling in the direction parallel to the film surface in the conventional organic light emitting device is attenuated will be described.

First, a method for manufacturing an organic light emitting device will be described with reference to FIG.

Reference numeral A denotes a substrate of an organic light emitting device, and a film B is deposited on the substrate A by using an organic material. In this case, the mask area is masked by the metal mask C, which determines the mask area by the evaporation source D.

In such an apparatus, the gap between the film growth surface and the mask edge is practically observable with an optical microscope due to the unevenness of the substrate A, the warpage of the mask, the roundness of the mask edge, and the like. Has occurred. If the gap is 0.1mm =
When the deposition source is viewed from that position,
Assuming a visual angle of 2 °, a film thickness change length of 100 μm × tan (2 °) = 3.5 μm occurs.

That is, between the portion where the film grows 100% and the portion where the film grows 0%, a film thickness change region of 3.5 μm is formed.

Usually, the thickness of an organic thin film such as an organic light-emitting device is about 0.1 μm, and the area where the film thickness changes is 1:35 in terms of the ratio of the thickness to the lateral length.

Therefore, the edge of the film formed when the film is formed by mask evaporation has an angle of arctan (1/35) = 1.6 °.

Light entering such an edge proceeds without being reflected and returned as shown in FIG. 12, and attenuates and disappears.

An object of the present invention is to provide an element which effectively utilizes light traveling in a parallel direction of an organic thin film which has not been utilized in these organic light emitting elements and has been lost.

[0013]

A feature of the present invention is that, in an organic light emitting device having an organic thin film formed on a substrate, an end surface of the organic thin film has an end surface having a light reflecting function of reflecting light. .

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows a device in which the present invention is applied to an organic electroluminescent device having a microresonator structure. The formation of the film end surface by removing the peripheral portion of the device is performed halfway through the transparent electrode film. Although the device structure is shown using a p / n, two-layer EL device in which a light emitting layer and a hole transport layer are stacked, a stacked structure of one layer or three or more layers due to function sharing or combination of functions of the organic layer. Are reported, and any structure can be used.

[0016] The substrate 10 is made of glass.
1, a semi-transparent film 102 made of titanium oxide or silicon oxide is formed, and a transparent electrode 10 is further formed thereon.
3, a hole transport layer 104, a light emitting layer 105, and a back metal electrode 106 are laminated. For these specific materials and the like, the above-mentioned “Journal of the Institute of Electronics, Information and Communication Engineers, J77-C-II, 437 (1994)” and the like, and other suitable materials can be used. Materials can of course also be used.

The feature of the present invention is that, as can be understood from FIG. 1, the end face of the organic thin film is formed to function as an anti-transparent reflecting mirror by a difference in the refractive index from the outside, so that light is reflected inside. It is. In other words, the conventional film thickness change region is made as short as possible, and light is confined to reduce light attenuation and disappearance.

For reference, FIG. 2 shows aluminum chelate (ALQ) and triphenyldiamine (TAD) as examples of the light emitting layer and the hole transport layer. FIG. 3 shows titanium oxide (54 nm).
9 shows transmission characteristics of a dielectric semi-transparent reflective film in which a total of six thin films of silicon oxide (thickness) and silicon oxide (86 nm thick) are laminated. 40
In a region having a wavelength longer than 0 nm, most of the light other than the transmitted light is reflected.

Next, the fabrication of the element can be realized by a method combining cutting and dry etching. Cutting can be performed by running a sharp tip made of glass or the like along the surface of the electroluminescent element formed up to the back metal electrode. FIG. 4 shows a schematic diagram thereof. FIG. 5 shows an electron micrograph of the element after the cutting. FIG. 6 shows an electron micrograph of the device produced by subjecting the device to dry etching under the conditions shown in Table 1. As can be seen from this, it can be seen that an end face from which the organic thin film has been removed can be formed at the lateral portion of the film.

[0020]

[Table 1] The symbols shown in FIGS. 5 and 6 are, respectively, the glass substrate 101 for Quartz, the transparent electrode 103 for ITO, the hole transport layer 104 for TAD, the light emitting layer 105 for ALQ, and AL: LI10
6 is a back metal electrode.

An advantage of this manufacturing method is that processing can be performed without using a chemical such as a resist on the film.
It is important for an organic electroluminescent element to maintain an organic thin film portion with high purity in order to exhibit sufficient performance, and extremely small deterioration of performance is caused by a small amount of impurities. Since the organic thin film has a thickness of about 100 nm and is extremely small in volume, even a very small amount of impurities diffused in from a resist or the like greatly deteriorates the performance. This creation method solves this problem. In addition, the production cost may be reduced by using a dedicated cutting device corresponding to the production pattern as compared with a processing process using a resist.

The precision of the fine processing is determined by the precision of moving the blade or the substrate during cutting. STM and SE
By applying the precision control technology of the stage position used for the M and the like, it is possible to realize a processing accuracy of micron order or finer.

The end face of the organic thin film ideally has a right angle to the substrate, but in practice, four out of four
If there is a right angle portion of about 0 to 90%, sufficient light reflection (in other words, light confinement) can be obtained.

FIGS. 7A and 7B are cross-sectional views of element structures having different etching depths. FIG. 7A shows an element etched to the organic thin film 104, FIG. 7B shows an element etched to ITO, and FIG. (C) is an element etched to the translucent reflection film. The extent to which the processed element is used is optimized for each application in consideration of the production cost and the effect of side reflection. In order to perform deep etching, it is necessary to increase the film thickness of the back metal electrode, use a material with a low etching rate for the electrode, or stack a material with a low etching rate on the electrode and cut it at the same time.

Further, as shown in FIG.
By forming a reflective film 108 of metal or the like on top of this, the effect of side reflection can be improved.

Next, FIG. 9A is a schematic view of an element having a three-dimensional confinement structure by side processing, and FIG. 9B is a schematic view of an element having a two-dimensional confinement structure. As described above, an optical resonator is formed inside the element by confining the light emitting region, and an element utilizing classical and quantum effects (such as modification of the transition probability structure) due to confinement and resonance can be realized. . In addition, as a matter of course, as the area of the element becomes smaller, the contribution of the end face becomes relatively larger, so that the effect of the present invention also appears more.

Here, it is necessary that the interval between the elements etched in FIGS. 7, 8 and 9A is wider than １ ／ of the emission wavelength λ.

That is, the light leaking from the mutual elements reaches a range of 1/4 of the wavelength, and the interval between these elements is 1 /
If it is smaller than 4, one light will interfere with the other element.

FIG. 10A shows a light emitting panel using an organic electroluminescent device having a three-dimensional confinement structure. In this case, the same pixels as those shown in FIG. 1 are used. 101
101A is a glass substrate, 102 is a translucent reflective film formed by stacking six titanium oxides and silicon oxides, 103 is a transparent electrode ITO (200 nm thick), 104 is a hole transport layer TA
D (thickness 50 nm), 105 is a light emitting layer ALQ (thickness 50 nm).
nm), 106 is a back metal electrode Al: Li alloy (thickness 2)
00 nm). Further, the two substrates 101 and 101A are bonded with an adhesive 302 to seal the element. Dried nitrogen gas is sealed in the gap 301 between the substrates 101 and 101A.

As shown in FIG. 10B, the front transparent electrode 103 and the rear metal electrode 303 form a matrix wiring, and a light emitting portion is selected. FIG. 10 (c)
As shown in, a projection 304 made of a soft metal such as In in the form of a projection is formed on 303, and
Pressure bonding is performed between the front transparent electrode 106 and the rear metal electrode 303. At that time, an insulating section 305 is required to prevent 303 and 103 from coming into contact with each other except at the pixel.

The number of organic electroluminescent elements having a three-dimensional confinement structure, which are arranged at the portions where 303 and 103 cross, does not need to be one per crossed portion.
Any number of two or more can be used. FIG. 10 (c)
In this embodiment, two are arranged.

[0032]

According to the present invention, the loss of light is reduced by the action of returning a certain percentage of light to the inside of the film at the end face of the film, the total amount of effective light emitted to the front surface of the film is increased, and the energy per input energy of the light emitting element is reduced. This has the effect of improving the output light emission amount of. Alternatively, an optical resonator is formed inside the device by confining the light emitting region by the effect of returning light into the film, and classical and quantum effects due to confinement and resonance (such as modification of the transition probability structure) are used. An element can also be realized.

[Brief description of the drawings]

FIG. 1 shows an organic electroluminescent device having a microresonator structure,
It is sectional drawing of the element which performed the film end surface processing.

FIG. 2 is a composition diagram of the organic thin film material shown in FIG.

FIG. 3 is an example of transmission characteristics of a translucent reflective layer used for an element.

FIG. 4 is a conceptual diagram of a cutting process.

FIG. 5 is an SEM of a cleaved organic light emitting device after cutting.
It is a statue.

FIG. 6 is an SEM image after dry etching.

FIGS. 7A and 7B are cross-sectional views of element structures having different etching depths. FIG. 7A shows an element etched to an organic thin film, FIG. 7B shows an element etched to an ITO, and FIG. It is a device which did.

FIG. 8 is a cross-sectional view of an element in which a reflective film made of metal or the like is formed on an insulating film to improve the effect of side reflection.

9A is a diagram showing the structure of an element having a three-dimensional confinement structure, and FIG. 9B is a diagram showing the structure of an element having a two-dimensional confinement structure.

10A and 10B are diagrams showing application examples of the present invention, in which FIG. 10A is a cross-sectional structure diagram, FIG. 10B is a structure of a matrix electrode, and FIG.
Is a view looking down from an angle.

FIG. 11 is a configuration diagram of an apparatus for forming an organic thin film.

FIG. 12 is an enlarged sectional view of a conventional organic thin film.

Claims (12)

[Claims] 1. An organic light emitting device having an organic thin film formed on a substrate, wherein an end surface of the organic thin film has an end surface having a light reflecting function of reflecting light. 2. An organic light-emitting device having an organic thin film formed on a substrate, wherein light in the organic thin film is confined at an end face of the organic thin film by a difference in refractive index from the outside. Organic light emitting device. 3. An organic light-emitting device in which an organic thin film is formed on a substrate, wherein an end surface of the organic thin film has a substantially right angle with the substrate surface for at least about 50 to 90%. An organic light-emitting device comprising: 4. An organic light emitting device having a transparent film, a transparent electrode, a hole transport layer, a light emitting layer, and a metal electrode laminated on a substrate, wherein at least an end face to the metal electrode, the light emitting layer, and the hole transport layer is the substrate. At least 5 for the face
An organic light-emitting device having a substantially right-angle relationship over about 0 to 90%. 5. An organic light emitting device having a transparent film, a transparent electrode, a hole transport layer, a light emitting layer, and a metal electrode laminated on a substrate, wherein at least the hole transport layer, the light emitting layer, and the metal electrode are individually separated. An organic light-emitting device comprising: an organic light-emitting device; An organic light-emitting device having an organic thin film formed on a substrate, wherein an end surface of the organic thin film has an end surface having a light reflecting function of reflecting light. 6. A translucent reflecting mirror made of a dielectric laminated film or a translucent metal film is formed on the film surface side of the light emitting front surface of the organic light emitting film, and a vertical direction of the film surface is provided between the reflecting mirror and the upper electrode. An organic light emitting device, comprising an optical resonator, wherein an end face of the organic thin film has an end face having a light reflecting function of reflecting light. 7. A translucent reflecting mirror made of a dielectric laminated film or a translucent metal film is formed on the film surface side of the light emitting front surface of the organic light emitting film, and a vertical direction of the film surface is provided between the reflecting mirror and the upper electrode. An organic light emitting device, comprising an optical resonator, wherein light in the organic thin film is confined at an end face of the organic thin film by a difference in refractive index from the outside. 8. A translucent reflecting mirror formed of a dielectric laminated film or a translucent metal film is formed on the film surface side of the light emitting front surface of the organic light emitting film, and a vertical direction of the film surface is provided between the reflecting mirror and the upper electrode. An organic light-emitting device, comprising an optical resonator, wherein an end face of the organic thin film has a substantially right-angled relationship with the substrate surface for at least about 50 to 90%. 9. A translucent reflective film, a hole transport layer, a light emitting layer, and a metal electrode are laminated on a substrate, and an optical resonator is formed between the reflective film and the metal electrode in a direction perpendicular to the film surface. , At least an end surface up to the metal electrode, the light emitting layer and the hole transport layer is at least 50 to the substrate surface.
An organic light-emitting device having a substantially right angle relationship over about 90%. 10. A translucent reflective film, a hole transport layer, a light emitting layer, and a metal electrode are laminated on a substrate, and an optical resonator is formed between the reflective film and the metal electrode in a direction perpendicular to the film surface. An organic light-emitting device, wherein at least the hole transport layer, the light-emitting layer, and the metal electrode are separately formed, and an interval between each other is set to １ ／ or more of a light emission wavelength. 11. An organic light-emitting device having an organic thin film formed on a substrate, wherein a metal thin film is formed on the organic thin film, and the metal thin film is mechanically or physically removed to form a mask having a required shape. And then obtaining an organic light emitting device by dry etching. 12. The method according to claim 11, wherein the remaining metal thin film is used as a metal electrode.