JPH1174084A - Luminescent element and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily form a fine pitch pattering without reducing the characteristic of an element, by dry-etching a cathode or an anode in order to form a picture element for constituting the element. SOLUTION: In a pattern for a stripe electrode, an organic EL element, which is laminated with a transparent anode 2, a luminous organic substance 3, and a cathode 4 on a transparent glass substrate 1, is manufactured, and thereon a shadow mask 5 is placed. Performing dry etching in this condition removes the luminescent organic substance 3 containing the cathode 4 portion, to make only a given region luminous. The shadow mask 5 can perform dry etching accurately by closely fitting to the element as much as possible. It is preferable that, the interelectrode gap has 0.3 mm or less, and the cathode 4 has the main component of aluminium, and is patterned by a dry etching method, moreover a material, for conducting luminescence, contains a biscarbazolyl derivative, and is dry etched by gas containing chlorine.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device capable of converting electric energy into light, and which can be used in fields such as display devices, flat panel displays, backlights, lighting, interiors, and optical signal generators. About.

[0002]

2. Description of the Related Art Recently, research has been actively conducted on organic thin-film light-emitting devices in which electrons injected from a cathode and holes injected from an anode emit light when they recombine in an organic phosphor sandwiched between both electrodes. It has become. This element is thin,
It features high-luminance light emission under low drive voltage and multicolor light emission by selecting a fluorescent material, and is attracting attention.

[0003] This study was carried out by Kodak Corporation. W. Tan
g. et al. showed that the organic laminated thin film element emits light with high luminance (Appl. Phys. Lett. 51 (12)
21, p. 913, 1987), and many research institutions are conducting studies. A typical configuration of an organic laminated thin film light emitting device presented by a research group of Kodak Company is a diamine compound having a hole transporting property and a light emitting layer on an ITO glass substrate.
Aluminum hydroxyquinoline and M as cathode
g: Ag was sequentially provided, and green light emission of 1000 cd / m ² was possible at a driving voltage of about 10 V. The present organic laminated thin-film light-emitting device has a different configuration, such as a device provided with an electron transport layer in addition to the above-described device components, but basically follows the configuration of Kodak Company.

One of the useful applications of the light emitting device is a display using dot matrix display. In the case of this display, it is worth to be able to perform high-definition display.

[0005] For this purpose, it is desirable that the pitch is 0.5 mm or less, preferably 0.3 mm or less. Normal,
In an element in which a transparent electrode / organic material / metal electrode is sequentially laminated, a desired pitch can be realized because a transparent electrode such as ITO can be patterned using a wet process. Then, as a method of patterning a metal electrode formed on a transparent electrode by laminating an organic material, a method of applying a photoresist on a negative electrode, patterning the portion where the resist has been removed through an exposure and development process by etching, and the like. , A method of producing a cathode in that pattern through a shadow mask on a substrate, providing a photosensitive resin or the like on a transparent electrode substrate to form a partition, depositing a luminescent material between them, and then depositing a negative electrode metal in an oblique direction. Forming a cathode stripe so as not to cause a short circuit between the electrodes (Japanese Unexamined Patent Publication No. 5-275172), and by improving the above method, a short circuit between the electrodes does not occur even if metal is not deposited from an oblique direction. To form a negative electrode pattern by forming a partition wall having an overhanging portion projecting in a direction parallel to the substrate on the upper side (Japanese Patent Laid-Open No. 315,981), further methods for patterning by removing the non-light emitting portions by using a laser beam (JP-A 5-3077, JP-A-8-22237
1, JP-A-9-50888) and the like have been devised.

[0006]

However, none of these methods is satisfactory in that a high definition display can be stably manufactured. In other words, in a wet process using a photoresist, the organic substance dissolves, swells, or undergoes a morphological change because contact between the photoresist solvent and the developer and the organic substance is unavoidable. I will. Also, in the production by vapor deposition of a negative electrode through a shadow mask, the mask portion necessary for forming the gap (distance between electrode edges) of the negative electrode must be kept as a shadow mask because it becomes thin like a thread. Can not be done. This is inconspicuous when a very small display is performed, but becomes apparent when, for example, a display having a diagonal size of 4 inches is manufactured. In addition, the method of obliquely vapor-depositing after forming the partition walls is difficult to firstly increase the number of steps for forming the partition walls, and to suppress the short circuit between the electrodes while securing the deposition angle, and to uniformly vapor-deposit the electrodes. is there. Finally, the method of forming a partition having an overhang portion has been improved in that oblique deposition does not need to be performed as compared with the above method, but it is necessary to form this overhang portion with good reproducibility over the entire panel. Has the problem that considerable labor and careful work are required, the number of steps is increased, and the yield is low.

Therefore, the production of a fine pitch electrode (here, the pitch indicates the distance from the center line of an electrode to the center line of an adjacent electrode) is indispensable for high definition of a screen.
It is an object of the present invention to make it possible to easily produce a negative electrode even on a panel having a large area without performing a complicated additional process.

[0008]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above object, and as a result, a substance which emits light exists between an anode and a cathode. It has been found that a desired fine pitch patterning can be easily formed without deteriorating the characteristics of the device by dry etching the cathode, and the present invention has been achieved.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, the anode is made of a conductive metal oxide such as tin oxide, indium oxide, indium tin oxide (ITO), or gold, silver, chromium or osmium, if it is transparent to extract light. Such as metals, copper iodide, inorganic conductive substances such as copper sulfide, and conductive polymers such as polythiophene, polypyrrole, and polyaniline, are not particularly limited, but are usually ITO glasses having both high light transmittance and low resistance characteristics. And Nesa glass can be preferably used. The resistance of the transparent electrode is not limited as long as a current sufficient for light emission of the element can be supplied, but is preferably low from the viewpoint of power consumption of the element. For example, ITO of 300Ω / □ or less
If it is a substrate, it functions as an element electrode.
Since it is possible to supply substrates of about Ω / □,
It is desirable to use a low resistance product from the viewpoint that power consumption and driving voltage can be reduced. The thickness of the ITO can be arbitrarily selected according to the resistance value.
Often used between nm. A thicker ITO electrode requires a certain thickness because the resistance value decreases and the defects in the thin film decrease, but if it is too thick, the light transmittance decreases, and a short-circuit phenomenon with the counter electrode occurs at the edge of the pattern. Since the probability of occurrence is high, it is necessary to determine the optimum film thickness in consideration of these matters. The optimal film thickness is ITO
Although it cannot be determined unequivocally because it depends on the film forming method, device configuration, device constituent material, device manufacturing method, etc., it is usually between 100 and 200 nm. The patterning of the present transparent electrode can usually employ a wet process in which a resist is applied, exposed, developed, and then etched. However, in the case where a light emitting organic layer is formed first after forming a cathode and then a transparent electrode is formed, dry etching by this method is a preferred method. In particular, when the gap between the electrodes is 0.3 mm or less, the vapor deposition pattern processing using a shadow mask is not particularly effective because sufficient precision cannot be obtained.

The glass substrate is made of alkali zinc borosilicate glass, sodium borosilicate glass, soda lime glass, low alkali borosilicate glass, barium borosilicate glass, borosilicate glass, aluminoborosilicate glass, aluminosilicate glass, fused silica glass Since synthetic quartz glass or the like is used, and the thickness only needs to be sufficient to maintain the mechanical strength, 0.5 mm or more is sufficient. The material of the glass is not particularly limited, but alkali-free glass which rarely elutes from the glass or soda-lime glass coated with a barrier coat such as SiO ₂ is used. The method of forming the ITO film is not particularly limited, such as an electron beam method, a sputtering method, and a chemical reaction method.

The cathode is not particularly limited as long as it can efficiently inject electrons into the organic material layer.
Examples include gold, silver, copper, iron, tin, aluminum, indium, lithium, sodium, potassium, calcium, magnesium, strontium, samarium, and alloys containing these metals. Among them, alloys containing a low work function metal such as lithium or magnesium (Al: Li, Ag:
Mg etc.) can be used. However, since these low work function metals are generally unstable in the air in many cases, for example, an organic layer is doped with a very small amount of lithium or magnesium (less than 1 nm as indicated by a film thickness gauge by vacuum evaporation) and then doped. A method using an electrode such as aluminum having high stability can be cited as a preferred example,
It is not particularly limited to this. The form of the cathode varies in its application. Predetermined symbols, numbers,
In some cases, illustrations and the like are displayed, in some cases segment displays are performed, and in other cases, dot matrix displays used in personal computers, televisions, portable devices, and the like are used. The present invention can be effectively used as a particularly effective method when the gap between electrodes where patterning of the negative electrode using a normal shadow mask is difficult is narrow, but the present method is also applicable in other cases. It is possible to use. As a specific example, a personal computer, a monitor, and an image and character display on a television usually have a side of 0.3 mm.
The following square pixels are used, and in the case of a large display such as a display panel, pixels having one side on the order of mm are used. In the case of monochrome display, pixels of the same color may be arranged, but in the case of color display,
Display red, green, and blue pixels side by side. In this case, there are typically a delta type and a stripe type. In such a case, the gap between the negative electrodes is 0.3 to 0.04 m.
m, and in some cases, 0.03 to 0.01 mm or less. In such a narrow cell gap, patterning by vapor deposition through a shadow mask becomes hopeless. In particular, in the case of a small element, the problem tends to be relatively difficult to become apparent. However, when the diagonal length is 4 inches or more, such patterning becomes almost impossible. You have to rely on things like that. However, this method is also complicated in operation, yield is low, and there is a danger that the stacked structure of the elements is disturbed near the partition and a short circuit occurs between the electrodes. In the case of a matrix structure, the pattern in the direction orthogonal to the partition is also provided. There is no processing other than the processing before the formation of the partition walls. In particular, there is no flexibility in the arrangement of the phosphors and the arrangement of the negative electrodes in each of the typically delta type and stripe type pixels for performing color display. Therefore, if the dry etching method of the present invention is used, the electrode metal is first vapor-deposited on the entire surface and then patterned into a predetermined shape, so that a complicated process can be omitted and the cathode can be accurately patterned. For patterning by dry etching, a shadow mask is arranged on the light-emitting laminated body manufactured up to the negative electrode. However, the shadow mask in this case is very different from that used when depositing and manufacturing the negative electrode because the negative / positive is reversed, and the shape of the shadow mask is stably held because there are very few openings. This is the basis of the reason why the present invention is effective in a narrow gap between electrodes. FIG. 1 illustrates a shadow mask for producing a stripe electrode and an electrode pattern produced by the shadow mask. That is, an organic EL device in which a transparent positive electrode 2, a luminescent material 3, and a negative electrode 4 are laminated on a substrate 1 is produced, and a shadow mask 5 is placed thereon. When dry etching is performed in this state, the luminescent material including the cathode portion is removed, and only a predetermined region emits light. Here, the shadow mask can be dry-etched with high precision if it is as close as possible to the element. Therefore,
One preferable embodiment is that the substrate on which the shadow mask and the element are manufactured is as smooth as possible. However, when the shadow mask can be closely adhered to the substrate with a magnet using a magnetic material or the like (only when the plasma is not affected so much as to hinder the etching), it is not necessary to pay particular attention to smoothness. The material of the shadow mask is not particularly limited as long as it can withstand dry etching and hardly leave a gap with the substrate. The shadow mask usually uses a metal plate provided with an opening, but may be a polymer film or the like. Metallic materials include stainless steel, nickel or alloys containing nickel (such as nickel-cobalt), and polymer films such as polyimide, acrylic, polyethylene terephthalate, and photosensitive resin films, which do not significantly degrade with plasma, and The material is not particularly limited as long as it has excellent adhesion.

Also, platinum, gold, silver,
Metals such as copper, iron, tin, aluminum, and indium, or alloys using these metals, and inorganic substances such as silica, titania, and silicon nitride, polyvinyl alcohol, vinyl chloride, fluorine-based polymers, and hydrocarbon-based polymers. Preferable examples include lamination as a protective layer. The method for producing these electrodes is not particularly limited as long as electrical conduction such as resistance heating, electron beam, sputtering, ion plating, and coating can be achieved. Dry etching may be performed after providing these protective layers.

The substances that control light emission include 1) a hole transport layer / a light emitting layer, 2) a hole transport layer / a light emitting layer / an electron transport layer, 3) a light emitting layer / an electron transport layer, and 4) a combination of the above. Any of the forms in which the combined substances are mixed together may be used. That is, as the element configuration, in addition to the multilayer laminated structure of the above 1) to 3), as in 4), a light emitting material alone or a layer containing a light emitting material and a hole transporting material and an electron transporting material, or a light emitting material and an electron transporting Only one layer containing a material may be provided.

The hole transporting layer is formed by a hole transporting substance alone or by laminating and mixing two or more kinds of substances or by a mixture of a hole transporting substance and a polymer binder. N, N'-diphenyl-N, N'-di (3-methylphenyl) -4,4'-diphenyl-1,1'-diamine, N, N'-diphenyl-N, N'-dinaphthyl-
Representatives include triphenylamines such as 4,4'-diphenyl-1,1'-diamine, biscarbazolyl derivatives, carbazole oligomers, pyrazoline derivatives, stilbene compounds, hydrazone compounds, oxadiazole derivatives, phthalocyanine derivatives, and porphyrin derivatives. Heterocyclic compound, in the case of polymer, polycarbonate or styrene derivative having the monomer in the side chain, polyvinyl carbazole, polysilane and the like are preferable, but a thin film required for device fabrication is formed, holes can be injected from the anode, Further, the compound is not particularly limited as long as it is a compound capable of transporting holes. Specific examples of the biscarbazolyl derivative and the carbazole oligomer include the following.

[0015]

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Embedded image The light-emitting layer in the present invention is mainly composed of anthracene or pyrene which has been known as a light-emitting material before, and the above-mentioned tris (8-hydroxyquinolinolato) aluminum or 10-.
Hydroxybenzo [h] quinoline metal complexes and bis (2-
Methyl-8-quinolinolato) phenolato metal complex, for example, bisstyrylanthracene derivative, tetraphenylbutadiene derivative, coumarin derivative, oxadiazole derivative, distyrylbenzene derivative, pyrrolopyridine derivative, perinone derivative, cyclopentadiene derivative, Oxadiazole derivatives, thiadiazolopyridine derivatives, and polymer-based polyphenylenevinylene derivatives, polyparaphenylene derivatives, and polythiophene derivatives can be used. As the dopant to be added to the light emitting layer, the above-mentioned rubrene, quinacridone derivative, diazaindacene derivative, phenoxazone 660,
DCM1, Nile Red, perinone, perylene, coumarin derivatives and the like can be used as they are.

As the electron transporting material, it is necessary to efficiently transport electrons from the negative electrode between the electrodes to which an electric field is applied, and it is desirable to have a high electron injection efficiency and to efficiently transport the injected electrons. For this purpose, it is required that the material has a high electron affinity, a high electron mobility, a high stability, and a small amount of impurities serving as traps during production and use. Materials satisfying such conditions include tris (8-hydroxyquinolinolato) aluminum, bis (10-hydroxybenzo [h] quinolinolato) beryllium, and 2- (4-biphenyl) -5- (4-t-butylphenyl). -1,3,4-
Oxadiazole derivatives such as oxadiazole (t-BuPBD) and oxadiazole dimer derivatives 1,3-bis (4-t-butylphenyl-1,3,4- Oxazizolyl) biphenylene (OXD-1), 1,3-bis (4-t-butylphenyl-1,3,4-oxazizolyl) phenylene (OXD-1)
-7), triazole derivatives, phenanthroline derivatives and the like.

The materials used for the above-described hole transport layer, light-emitting layer, and electron transport layer can be used alone to form the respective layers. As the polymer binder, polyvinyl chloride, polycarbonate, polystyrene, poly (N- Vinyl carbazole), polymethyl methacrylate, polybutyl methacrylate, polyester, polysulfone, polyphenylene oxide, polybutadiene, hydrocarbon resin, ketone resin, phenoxy resin, polysulfone, polyamide,
Solvent-soluble resins such as ethyl cellulose, vinyl acetate, ABS resin, polyurethane resin, phenolic resin, xylene resin, petroleum resin, urea resin, melamine resin, unsaturated polyester resin, alkyd resin, epoxy resin,
It is also possible to use the resin dispersed in a curable resin such as a silicone resin.

The method for forming the substance which controls light emission is not particularly limited, such as resistance heating evaporation, electron beam evaporation, sputtering, molecular lamination, and coating method. Preferred in terms of surface. The thickness of the layer cannot be limited because it depends on the resistance value of the substance that controls light emission.
nm.

The patterning of the present invention can be used for patterning not only the electrodes but also these organic substances. This has beneficial results, especially in making multicolor display panels. First, an element of a predetermined first emission color (for example, blue) is manufactured on the entire panel. Next, the portion that is to emit only blue light is covered with a shadow mask so that only the portion that is to emit light is shaded, and the other portions are dry-etched. Then, an element of the second emission color (for example, green) is formed again on the entire surface, and the first emission color portion and the second emission color portion are covered with a shadow mask so as to be shaded, and the other portions are dry-etched. . Finally, an element of a third emission color (for example, red) is formed on the entire surface, and the remaining unnecessary portion (for example, a black matrix portion) is covered with a shadow mask so as to be dry-etched and etched. What is important at this time is that only the target substance can be etched during dry etching, and in the case of the above example, the cathode or organic substance is etched but the anode is not etched, or is very little is important. And if it is possible to form a metal for black matrix such as chromium through the insulating layer in the last remaining part,
A high-definition display can be manufactured.

The dry etching method according to the present invention includes:
Electrodes installed in the depressurized etching chamber (for example,
A substrate on which a target substance (electrode or organic substance) is formed is placed on one of the parallel plate electrodes), a plasma generating gas composed of a specific component is introduced into the etching chamber, and high frequency power is applied to the electrode to generate plasma. Then, the target material is etched by the plasma. As a typical example, a mixed gas of Cl ₂ and BCl ₃ is used for etching aluminum, and CF ₄ , CHF ₃ or the like is used for etching SiO ₂ .
In the organic thin film, a gas containing a reactive species such as O ₂ and other fluorine, chlorine, and bromine is used.
The combination of mixing and the ratio are not limited. In addition, it goes without saying that power specifications such as frequency and voltage, substrate temperature, and the like can be adjusted in order to pattern into a desired shape or state.

The electric energy for driving the present element mainly refers to a direct current, but it is also possible to use a pulse current or an alternating current. The current value and the voltage value are not particularly limited. However, in consideration of the power consumption and life of the device, it is general to select the device material and the configuration so that the maximum brightness can be obtained with the lowest possible energy.

The matrix can be driven by either a line-sequential driving method or an active matrix. The line-sequential driving has the advantage that the structure is simpler. However, in consideration of the operation characteristics, the active matrix is sometimes superior, and therefore it is necessary to use the same depending on the application.

The present invention can also be applied to segment type display, in which a pattern is formed so as to display predetermined information, and a predetermined area emits light. For example, there are a time display and a temperature display on a digital clock or a thermometer, an operation state display of an audio device, an electromagnetic cooker, or the like, and a panel display of an automobile. The matrix display and the segment display may coexist in the same panel.

Further, the present invention can be applied to a planar light-emitting body such as a backlight if necessary. This is mainly used for the purpose of improving the visibility of a display device that does not emit light, and is used for a liquid crystal display device, a clock, an audio device, an automobile panel, a display panel, and the like. In particular, as a backlight for a liquid crystal display device, especially a personal computer application in which thinning is an issue, considering that it is difficult to reduce the thickness because the conventional type is made of a fluorescent lamp or a light guide plate, the present invention The backlight is thin and lightweight.

[0025]

The present invention will be described below with reference to examples and comparative examples, but the present invention is not limited to these examples.

Example 1 A glass substrate (15 Ω / □, electron beam deposited) on which an ITO transparent conductive film was deposited to a thickness of 150 nm was cut into a predetermined size, etched, and washed. UV before use
-Immediately after washing with ozone, the apparatus was installed in a vacuum evaporation apparatus and evacuated until the degree of vacuum in the apparatus became 5 × 10 ⁻⁶ Torr or less. Bis (N-ethylcarbazole), which is a hole transport material, is heated at a rate of 0.3 nm / sec by a resistance heating method.
Deposited 30 nm followed by tris (8-quinolinolato) aluminum to a thickness of 100 nm. Next, after mounting a mask so as to form a 5 × 5 mm square element in a vacuum, lithium was vapor-deposited at 1 nm at a rate of 0.1 nm / sec and finally aluminum was vapor-deposited at 150 nm at a rate of 0.5 nm / sec. A 5 mm square device was produced.

This device was manufactured by Plasma System DES-
3104E (parallel plate type dry etching equipment, Φ8 ″
In the RIE mode (lower electrode power supply) with the aluminum electrode face up, a shadow mask (N
i-Co, 0.3 mm pitch, opening width 0.2 mm stripe shape) was placed, and the pressure was reduced. Cl ₂ gas 10
sccm, BCl ₃ gas 30 sccm, processing pressure 40 m
Torr, RF power 100 Watt, distance between electrodes 70
Etching was performed for 120 seconds under the conditions of mm and stage temperature of 50 ° C. The etching rate was about 0.1 μm / min.

The device was etched in a mask pattern shape, and a stripe-shaped device pattern having a width of 0.1 mm remained. When a direct current was applied to the device pattern, the same region as the pattern emitted green light.

Example 2 Patterning was performed in the same manner as in Example 1 except that a mask was fixed to the electrode side of the substrate by placing a permanent magnet on the back surface of the substrate and the etching time was changed to 180 seconds. Although the etching rate was lowered by the magnetic field, a clear edge was formed because the mask was in close contact with the substrate.

Comparative Example 1 Photosensitive polyimide (UR-3100 manufactured by Toray Industries, Inc.) was spin-coated on the aluminum electrode side of the device manufactured in Example 1, and a phenomenon of solvent penetration into the device was observed. Subsequently, a predetermined stripe pattern (0.3 mm pitch, line width 0.25 mm) was formed using a high-pressure mercury lamp.
When light exposure was performed at mJ / cm2 and development was performed, elementary luminescence was no longer observed.

[0031]

The present invention provides an organic EL panel patterned with high definition and a method for manufacturing the same. In particular, when an electrode is dry-etched, desired characteristics can be easily obtained without deteriorating the characteristics of the device. Fine pitch patterning can be formed.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a dry etching method according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Transparent glass substrate 2 Transparent positive electrode 3 Luminescent organic substance 4 Negative electrode 5 Shadow mask

Claims (7)

[Claims] 1. A light emitting device wherein a cathode or an anode is patterned by a dry etching method to form a pixel constituting the device. 2. The light emitting device according to claim 1, wherein a gap between the electrodes is 0.3 mm or less. 3. The light emitting device according to claim 1, wherein the electrode is a negative electrode containing aluminum as a main component, and is patterned by a dry etching method. 4. The light-emitting device according to claim 1, wherein the substance that controls light emission includes a biscarbazolyl derivative. 5. A method for manufacturing a light-emitting element, wherein a substance responsible for light emission is present between an anode and a cathode, and the element emits light by electric energy, wherein the cathode or the anode is patterned by a dry etching method. . 6. The method according to claim 5, wherein dry etching is performed through a shadow mask. 7. The method according to claim 5, wherein dry etching is performed using a gas containing chlorine.