JP2001244073A - Organic thin film light emitting display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an organic thin-film light-emitting display in which an upper electrode can be easily patterned into an arbitrary shape by laser processing without damaging an element, and which has low cost and good productivity. I will provide a. A substrate, a lower electrode formed on the substrate, an organic electroluminescence medium layer including at least a light-emitting layer provided on the lower electrode, and formed on the organic electroluminescence medium layer An organic thin-film light-emitting display having an upper electrode, wherein the lower electrode, the organic electroluminescence medium layer, and an overlapping portion of the upper electrode each have a light-emitting pixel, wherein the upper electrode and the organic electroluminescence The media layer is
In an organic thin-film light emitting display that is patterned into a predetermined shape by laser processing, a material having a lower melting point than the upper electrode between the lower electrode and the organic electroluminescent medium layer and at least the laser-processed portion. Is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic electroluminescence (hereinafter, also referred to simply as "EL") element, and more particularly, to an organic thin-film light-emitting display used for a flat panel display or the like.

[0002]

2. Description of the Related Art As shown in FIGS. 2A and 2B, an organic EL device is generally composed of a transparent electrode (lower electrode) 2 of an anode made of ITO or the like and an organic material on a transparent substrate 1 as shown in FIGS. An organic EL medium layer 4 including a hole transport layer 4a and a light emitting layer 4b, and a metal electrode (upper electrode) 5 serving as a cathode are sequentially formed. The organic layer has a two-layer structure (Appl. Ph.
ys. Lett. 51, 913, 1987)
And an electron transport layer 4c between the cathode 5 and the light emitting layer 4b.
Are known, in which the organic layer has a three-layer structure.
Recently, there is also a four-layer structure in which a hole injection layer is formed between the anode 2 and the hole transport layer 4a (for example, SI
D 97 DIGEST, p. 1073, 1997).

[0003] In an organic thin-film light emitting display using the organic EL element shown in FIG. 2, for example, X, as shown in FIG.
There is a Y matrix type (simple matrix type). This organic thin-film light emitting display has an IT
A plurality of transparent electrodes 2 such as O, an organic EL medium layer 4 including a hole transport layer 4a and a light emitting layer 4b, and a metal cathode (upper electrode) 5 in a direction orthogonal to the transparent electrode 2 are sequentially laminated. It is formed. A light-emitting portion serving as an organic EL element is formed by a transparent anode and a metal cathode formed in pairs in directions orthogonal to each other with the hole transport layer, the light-emitting layer, and, if desired, further interposed the electron transport layer. One pixel is formed by using the light emitting portion in the intersection area of each of the transparent anode and the metal cathode as one unit. By driving a panel in which a plurality of such organic EL elements are formed on a single element substrate in accordance with the number of pixels through a transparent anode and a metal cathode protruding from the periphery thereof, a flat panel display device is realized. Be composed.

Generally, the patterning of the anode as the lower electrode is performed by a photolithography method after forming an anode material on a substrate. That is, a photoresist is applied on the anode film, exposed and developed, and after the resist is patterned into a desired shape, the anode material is etched.
The resist is stripped.

On the other hand, it is extremely difficult to pattern the upper electrode by photolithography because of the low heat resistance, solvent resistance and moisture resistance of the organic EL medium used for the charge injection layer and the light emitting layer. There is also a method of patterning using an evaporation mask (see Japanese Patent Application Laid-Open No. 9-320758). In this case, however, poor adhesion between the substrate and the mask causes pattern blurring due to the wraparound of the evaporation material, or a fine and fine If an attempt is made to form a precise pattern, problems such as bending of the mask due to poor strength of the mask occur, and an accurate pattern cannot be formed.

As a method for solving such a problem, laser processing using an excimer laser, a YAG laser, or the like has been proposed (see Japanese Patent Application Laid-Open Nos. 8-222371 and 9-320760). Generally, organic EL
The cathode formed on the medium is a simple substance of a metal such as Al or Mg or an alloy thereof, and has a metallic luster.
Laser light used for processing is reflected at a high reflectance, and a high intensity of laser light is necessary for a portion to be processed to sufficiently absorb heat required for processing from the laser light. However, when such a high-intensity laser is used, heat is dispersed over a wide area, and the organic layer around the laser beam irradiation part is damaged, and the anode under the cathode part to be processed is damaged. Problems arise. In addition, when there is a weak portion of the laser beam due to the intensity distribution of the laser beam to be used, the cathode is not completely removed, and burrs are generated around the processed cathode line edge, which causes a short circuit with the anode. There is a problem. To solve these problems, for example, Japanese Patent Application Laid-Open No. 9-50888 discloses that a laser protective layer having heat resistance is provided between an anode and an organic EL medium layer, and a laser absorbing layer is provided on a cathode. Has been proposed.

[0007]

However, under the cathode (upper electrode), an organic E having a lower melting point than the cathode material is used.
In the portion where the organic film such as the L medium exists (9 in FIG. 4), the evaporation of the organic film at the time of laser irradiation assists the removal of the cathode. The output becomes smaller as compared with the output required for machining the portion (10 shown in FIG. 4) that does not exist. Therefore, when processing the cathode (upper electrode) using a laser, it is necessary to adjust the laser output to a portion where there is no organic film on the base in order to prevent unprocessed defects. At this time, the organic film exists on the base. In some areas, heat builds up around the laser light-irradiated area due to excessive laser output, damaging the organic layer involved in light emission, and forming non-light-emitting areas in the pixels when the display is manufactured. This problem has not been solved by the above technology.

On the other hand, there is a method of processing while changing the laser output in accordance with the base. However, if a function for automatically controlling the adjustment of the laser output and the movement of the processing stage is added at the same time, the processing apparatus is required. There is a drawback that it becomes expensive. It is also conceivable to change the number of times of irradiation repeatedly while keeping the laser output constant.In this case, however, the scanning speed of the laser is reduced or the scanning is performed multiple times in a portion where there is no organic film on the base. There is a problem that the processing time increases and the productivity decreases. That is, although the patterning of the upper electrode of the organic EL display by laser light is an effective means, it still has a problem to be solved.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to easily pattern an upper electrode into an arbitrary shape by laser processing without damaging the element, and to produce the electrode at low cost. An object of the present invention is to provide an organic thin-film light-emitting display having good properties.

[0010]

In order to solve the above problems, an organic thin film light emitting display according to the present invention comprises a substrate, a lower electrode formed on the substrate, and at least a lower electrode provided on the lower electrode. An organic electroluminescence medium layer including a light emitting layer, and an upper electrode formed on the organic electroluminescence medium layer, and a portion where the lower electrode, the organic electroluminescence medium layer, and the upper electrode overlap each other. An organic thin-film light-emitting display, each having a light-emitting pixel, wherein the upper electrode and the organic electroluminescent medium layer are patterned into a predetermined shape by laser processing, wherein the lower electrode and the organic Between the electroluminescent medium layer and at least the laser-processed portion, It is characterized in that the evaporation layer consisting of low melting point material is provided than the electrode.

In the present invention, it is preferable that the evaporating layer is made of an organic compound, particularly, a photosensitive resin. Further, it is preferable that the evaporation layer is provided in a portion where the organic electroluminescence medium layer does not exist below the upper electrode in the laser processing portion.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the organic thin-film light emitting display of the present invention will be described in detail with reference to the drawings. FIG. 1 is a partial perspective view schematically showing an organic thin-film light emitting display of the present invention, in which a lower electrode 2 (anode) arranged in a stripe on a substrate 1 and a lower electrode 2 on the substrate 1 and the lower electrode 2. An organic EL medium layer 4 formed so as to be present at least at an intersection of the lower electrode 2 and the upper electrode 5;
Further, the upper electrode 5 is formed thereon. As shown, the upper electrode 5 is provided with a processed portion by laser light processing, thereby forming a plurality of upper electrode lines 5 '. The portion where the lower electrode 2 and the upper electrode line 5 'intersect and sandwich the organic EL medium layer 4 corresponds to the light emitting portion, and forms one pixel.

In the present invention, it is sufficient that the evaporation layer 3 is formed of a material having a lower melting point than the upper electrode 5 at least in the laser-processed portion between the lower electrode 2 and the organic EL medium layer 4. Can be appropriately set. Thereby, the organic EL is formed under the upper electrode 2.
The medium layer or the evaporation layer 3 always exists, and at the time of laser beam irradiation, in the portion where the organic EL medium layer 4 does not exist, the evaporation layer 3 assists the removal of the upper electrode similarly to the organic EL medium layer 4. , With a constant and smaller laser power, without the need to change the number of partial scans,
Uniform processing of the upper electrode can be performed. Further, since the evaporating layer 3 has a low melting point, it easily absorbs heat of the laser beam and easily evaporates. Therefore, heat is hardly diffused to the surroundings, and the light emitting layer and the lower electrode 2 (anode) may be damaged. Absent.

As described above, the material of the evaporating layer 3 is as follows.
Melting point lower than upper electrode 5, preferably organic EL medium layer 4
There is no particular limitation as long as the material has a melting point close to the melting point of the material used in the above, but it is preferable that the material is made of an organic compound, particularly a photosensitive resin. For example, using a general photoresist material, a film is formed by a spin coating method, and after pre-baking, it can be formed by sequentially performing each step of exposure, development, and post-baking as desired. .

As the substrate 1, besides quartz and a glass plate,
A transparent synthetic resin plate such as polyester, polymethacryl acrylate, polycarbonate, and polysulfone can be used. Further, a metal plate, a metal foil, a plastic film, or the like may be used.

The lower electrode 2 may be either an anode or a cathode. However, when the substrate 1 is a transparent substrate, the lower electrode 2 serves as an anode to play a role of hole injection. When the substrate 1 and the lower electrode are made transparent as described above, light emission is extracted from the substrate 1 side. Conversely, the upper electrode 5 ′ is made of a transparent electrode material, and the light emission is made upper. It can also be taken out from the electrode side. In this case, in order to increase the light extraction efficiency, it is preferable to use a metal for the lower electrode material or to form a reflective film on the surface opposite to the film formation surface of the substrate.
Materials for the anode include ITO (In ₂ O ₃ + SnO ₂ ,
Indium tin oxide), indium zinc oxide (In
₂ O ₃ + ZnO) and the like. Alternatively, a laminate of these transparent conductive films and a metal film may be used.

The method for forming the lower electrode 2 is not particularly limited.
A film can be formed by a conventional method, for example, a sputtering method, and processed into a stripe by a photolithography method. Further, the lower electrode 2 is preferably formed so that the line edge has a tapered shape.

The organic EL medium layer 4 has various structures such as a single layer of a light-emitting layer, a two-layer structure of a hole transport layer and a light-emitting layer, or a three-layer structure of a hole transport layer, a light-emitting layer and an electron transport layer. It can be. Examples of the material of the organic EL medium layer 4 include copper phthalocyanine, N, N′-diphenyl-N, N′-bis (3-methylphenyl) -1,1 ′.
- biphenyl-4,4'-diamine (TPD), tris (8-quinolinol) can be mentioned aluminum (Alq ₃₎ or the like.

The upper electrode 5 is made of, for example, Al-Li
In the present invention, after forming the upper electrode 5, the upper electrode line 5 ′ and the organic EL medium layer 4 are patterned into a predetermined shape using laser processing. Since the laser processing section is provided with the evaporating layer 3 according to the present invention, the upper electrode 5 is uniformly processed by a constant low-intensity laser beam even in a portion where the organic EL medium layer 4 does not exist below. It becomes possible.

Laser processing is performed using an excimer laser (Ar
F, KrF, XeCl) and YAG laser (SHG,
THG, FHG) (including THG), etc., and scans with a laser beam focused to several tens to several hundreds of μm using a lens, or as a surface light source, using a mask that transmits only through the processed part. Irradiation. The intensity of the laser beam needs to be appropriately adjusted so that the evaporation layer 3 is not evaporated and the lower electrode 2 is not damaged.

[0021]

The present invention will be described in more detail with reference to the following examples. The organic thin film light emitting display of the present invention is shown in FIG.
In accordance with the manufacturing process shown in FIG. First, a transparent electrode material made of ITO is formed on a transparent substrate 1 made of glass by a sputtering method and processed into a stripe shape by a photolithography method to form a transparent lower electrode 2 (FIG. 5 ( a)). The lower electrode 2 has a thickness of about 100 nm and a line width of 9 nm.
The thickness was set to 0 μm and the gap was set to 20 μm.

Next, on the substrate 1 on which the lower electrode 2 is formed, a positive type photoresist (OFPR-800, manufactured by Tokyo Ohka) using a novolak resin is formed into a film by a spin coating method. The evaporation layer 3 was formed by patterning by photolithography so that the pixel region 7 was removed (FIG. 5B). That is, the film thickness is about 1.2 μm.
m, a pre-bake is performed in a clean oven, and exposure and development are performed using a line-shaped mask having a line width of 30 μm and a gap of 300 μm.
And

Next, as shown in FIG. 5C, an organic EL medium layer 4 and an upper electrode 5 were sequentially vacuum-deposited on the lower electrode 2 and the evaporating layer 3 by a resistance heating method. The deposition of the organic EL medium layer 4 was performed as follows. First, N, N'-
Diphenyl-N, N'-bis (3-methylphenyl)-
1,1'-biphenyl-4,4'-diamine (TPD)
An organic hole transport layer 4a made of and a light emitting layer 4b made of tris (8-quinolinol) aluminum (Alq ₃ ) are each formed to a thickness of about 50 nm, and further, Al—Li as an upper electrode layer is formed. The alloy was deposited to a thickness of about 100 nm.

Next, as shown in FIG. 5D, a laser beam 8 is applied to the laser processing section 6 from above, thereby evaporating the layer 3, the organic EL medium layer 4, and the upper electrode 5 of the laser processing section 6. Was removed by evaporation, and the upper electrode 5 ′ was separated as shown in FIG. In this way, a good organic thin-film light emitting display in which a plurality of pixels corresponding to the pixel region 7 in FIG. 5B were formed was obtained.

For laser processing, an EX-700 series excimer laser processing apparatus (KrF laser: manufactured by Lumonics, PM-84, manufactured by Sumitomo Heavy Industries, Ltd.)
8K laser oscillator) was used. By using a mask and a lens and scanning with a laser beam focused to a line width of 20 μm, a laser output of 100 mJ / pulse to 450 m
In the range of mJ / pulse, favorable upper electrode processing was obtained without being affected by the lower layer.

[0026]

As described above, according to the organic thin-film light emitting display of the present invention, at least the laser-processed portion between the lower electrode and the organic EL medium layer is made of a material having a lower melting point than the electrode to be processed. By providing the vaporized layer, there is at least the organic EL medium layer or the vaporized layer below the processed portion of the upper electrode. Can be uniformly processed. Further, since the evaporating layer according to the present invention also has a function of preventing damage to the lower electrode during laser processing, it is possible to manufacture with a good yield, improve productivity, and achieve cost reduction. is there.

[Brief description of the drawings]

FIG. 1 is a partially cutaway perspective view showing an example of an organic thin-film light emitting display of the present invention.

FIG. 2 is a partial cross-sectional view showing an organic electroluminescence element.

FIG. 3 is a cutaway perspective view showing a configuration of a general organic thin film light emitting display.

FIG. 4 is a partial perspective view showing a conventional organic thin film light emitting display.

FIG. 5 is an explanatory view showing a manufacturing process of the organic thin film light emitting display of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Lower electrode 3 Evaporation layer 4 Organic EL medium layer 4a Hole transport layer 4b Emission layer 4c Electron transport layer 5 Upper electrode 5 'Upper electrode line 6 Laser processing part 7 Pixel area 8 Laser light 9 Lower layer of upper electrode is organic Part which is a compound layer 10 Part where there is no organic compound in the lower layer of the upper electrode

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H05B 33/14 H05B 33/22 Z 33/22 B23K 101: 36 // B23K 101: 36 H01L 21/302 Z F term (reference) 3K007 AB18 BA06 CA01 CB01 DA01 DB03 EA02 EB00 FA01 4E068 AC00 DA09 5F004 AA01 AA06 BA20 BB03 BB04 DB12 DB26 DB31 EA00 EA01 EB02

Claims (4)

[Claims] 1. A substrate, a lower electrode formed on the substrate, an organic electroluminescence medium layer including at least a light emitting layer provided on the lower electrode, and formed on the organic electroluminescence medium layer An organic thin-film light-emitting display having an upper electrode, wherein the lower electrode, the organic electroluminescence medium layer, and an overlapping portion of the upper electrode each have a light-emitting pixel. The luminescent medium layer
In an organic thin-film light emitting display that is patterned into a predetermined shape by laser processing, between the lower electrode and the organic electroluminescent medium layer and at least the laser-processed portion, from a material having a lower melting point than the upper electrode. An organic thin-film light-emitting display comprising an evaporation layer. 2. The organic thin-film light emitting display according to claim 1, wherein said evaporating layer comprises an organic compound. 3. The organic thin-film light emitting display according to claim 1, wherein said evaporating layer is made of a photosensitive resin. 4. The laser processing unit according to claim 1, wherein the evaporation layer is provided in a portion where the organic electroluminescence medium layer does not exist below the upper electrode. The organic thin-film light-emitting display according to the above.