JP3812144B2 - Manufacturing method of light emitting display - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a light emitting display, and more particularly to a method for manufacturing a light emitting display in which a light emitting layer is formed by discharging a light emitting material using an ejection device.
[0002]
[Prior art]
In recent years, liquid crystal displays have been actively used as display units for word processors, personal computers, and the like. This liquid crystal display is a non-light emitting element, which is problematic in terms of brightness, particularly when used in a reflective display. A light emitting display using an organic light emitting material (hereinafter referred to as an organic EL) having thin and light features has been attracting attention. A cross-sectional view of this light emitting display is shown in FIG. In the figure, 1 is an aluminum electrode, 2 is an organic EL material, 3 is an ITO transparent electrode, 4 is a glass substrate, and 5 is a power source. The method of creating this light emitting display is as follows. First, an ITO transparent electrode is attached on a transparent substrate by sputtering or vapor deposition. Thereafter, an electrode having a desired shape is formed by photolithography. Thereafter, an organic EL material is coated by a spin coating method, a vapor deposition method, a discharge method, or the like to form a light emitting layer.
[0003]
The above-mentioned method is mainly used as a coating method, but recently, a discharge method capable of patterning has attracted attention.
[0004]
A counter electrode is obtained by skipping a metal having a low work function, such as magnesium, aluminum, lithium, calcium, silver, or an alloy thereof by vapor deposition or sputtering on the light emitting layer thus obtained. Although the above is the basic process, in order to increase luminous efficiency, a hole transport material such as N, N′-diphenyl-N, N ′-(2,4-dimethylphenyl) is further added after the ITO transparent electrode is attached. -1,1'-biphenyl-4,4'-diamine may be attached by vapor deposition. Further, after attaching the organic EL material, for example, 2- (4-biphenyl) -5- (4-tert-butylphenyl) -1,3,4-oxydiazole may be attached as the electron transport material.
[0005]
Light can be emitted by applying an electric field to the two types of electrodes facing each other. A characteristic of this light emitting display is that it can be driven at a low voltage of 10 volts or less.
[0006]
By combining this promising technology with an ejection device, patterning of the organic EL material becomes possible, and a full color light emitting display can be obtained. That is, instead of conventional red, green, and blue patterning using a photolithography method, using a discharge device such as a dispenser or an inkjet printing device, a solution in which red, green, and blue organic EL materials are dissolved is used as an appropriate ITO transparent electrode. A full color light-emitting display can be obtained by discharging the upper layer, patterning with the solvent diffused, and then depositing (sputtering) the counter electrode. The concept of this ejection method will be described with reference to FIG. In the figure, 11 is a glass substrate, 12 is a TFT element, 13 is an ITO electrode, and 14 is a nozzle for discharging a solution. With the nozzle shown in the figure, organic EL materials corresponding to red, green and blue are alternately placed on the ITO electrode, for example, on the ITO electrode formed so as to be individually driven by the TFT element shown in the figure, A full color display can be created by discharging so that green and blue organic EL materials are juxtaposed.
[0007]
As a disadvantage of the patterning method by combining the ejection devices, since the solution is ejected from an extremely thin nozzle, there is a disadvantage that the nozzle is clogged due to precipitation of the solute by drying of the solution. In order to overcome this drawback, a hydrophilic solvent having a high boiling point such as glycerin, diethylene glycol, diamine, sugar, or a derivative of these solvents is added.
[0008]
Examples of the organic EL material used for the light emitting display include a low molecular weight organic EL material and a high molecular weight organic EL material. As a polymer material, a polyparaphenylene vinylene (hereinafter abbreviated as PPV) material is attracting attention because of its excellent stability, luminous efficiency, luminance and the like. This material is characterized by the use of a precursor, can handle the raw material in a solution state, and can be thinned by a spin coating method, a dipping method, or the like. By baking the obtained film, the single bond becomes a double bond, becomes insoluble in the solvent, and becomes a stable film. Depending on how double bonds are formed at this time, there are differences in luminous efficiency and luminance.
[0009]
When a solution in which this PPV material is dissolved is used for patterning with a discharge device, it is likely to dry with a general low boiling point solvent such as water or methanol, and nozzle clogging is likely to occur. For this reason, hydrophilic high-boiling solvents such as glycerin and ethylene glycol have been added. This is a conventional example in which a PPV material is used and patterning is performed by a discharge device. When a solution in which a PPV material containing glycerin or the like is dissolved as in the conventional example is discharged by a discharge device and baked, a high boiling point solvent such as glycerin is not easily removed. The phenomenon was observed, and the obtained light-emitting material had drawbacks such as shifting to a shorter wavelength than the light of the target wavelength or hardly emitting light.
[0010]
[Problems to be solved by the invention]
The present invention has been made to solve the problem that the emission wavelength shifts to a lower wavelength side and hardly emits light in the manufacture of an organic EL light emitting display using a PPV material by a discharge device. The present invention has been made in order to provide a manufacturing method for producing a full-color light emitting display by ejecting a PPV organic EL material using an ejection device and patterning it without changing the manufacturing method.
[0011]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, a method for manufacturing a light-emitting display according to the first aspect of the present invention is to discharge a solution containing a precursor material of polyphenylene vinylene and a high-boiling solvent onto a substrate by a discharge device, and then fire the substrate. It is characterized by including a step of removing the solvent at room temperature and a step of drying before the step. The drying temperature is preferably 120 ° C. or lower, and it has been found that when the polyparaphenylene vinylene precursor is treated at this temperature or lower, the solvent can be removed without forming double bonds. It has been found that the reaction proceeds and the emission wavelength shifts to a lower wavelength side when the temperature is higher than this temperature, and the luminous efficiency is extremely lowered.
[0012]
The second aspect is characterized in that the high boiling point solvent is glycerin, diethylene glycol, triethanolamine, sugar, a derivative of these solvents, or a mixture of these solvents. By adding these solvents, the inside of the nozzle of the discharge device can always be moistened so that it can be used for a long time without causing clogging of the nozzle.
[0013]
The third aspect is characterized in that the solvent is removed at room temperature under vacuum. Since the reaction is performed at room temperature and under vacuum, a high-boiling solvent can be removed without causing a reaction of the precursor of PPV, and a light-emitting display with high light emission efficiency can be manufactured without a shift in light emission wavelength.
[0014]
The fourth aspect limits the degree of vacuum, and it is more preferable that most high boiling point solvents can be treated at a temperature lower than the boiling point of the high boiling point solvent by processing under a vacuum of 1 mmHg or less.
[0015]
Claim 5 is a step for removing traces of high-boiling solvent after removing the solvent. By including this step, the lifetime and emission intensity of the display can be further increased. If the temperature is too high, the PPV reaction will not proceed well, and if the temperature is low, it will not take much time to remove, which is possible at 120 ° C. or lower, but preferably 70 ° C. or lower.
[0016]
According to a sixth aspect of the present invention, the discharge device is an ink jet printing device. As the discharge device, there are a dispenser, an ink jet printing device, and the like, but an ink jet printing device is preferable in terms of miniaturization and high speed.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
(Example 1) The following solution containing 0.5% by weight of a polymer electrolyte which is a precursor of polyparaphenylene vinylene was taken in a discharge device and discharged onto a substrate with an ITO transparent electrode.
[0018]
Solution water: 90 weight percent glycerin: 10 weight percent After discharging, the substrate was dried at 100 ° C. for 1 hour under a vacuum of 1 mmHg. After drying, the temperature was raised to 170 ° C. under a vacuum of 1 mmHg, followed by baking at 170 ° C. for 4 hours. Thereafter, 2000 angstroms of aluminum metal was vapor-deposited by a vapor deposition machine. When the fluorescence spectrum of the obtained panel was examined, the maximum emission wavelength of the fluorescence spectrum was 535 nm. Further, when this light emitting display was driven, the light emission spectrum, which could be driven at 6 volts, almost coincided with the fluorescence spectrum.
[0019]
(Comparative example) After discharging the precursor solution of polyparaphenylene vinylene onto the electrode substrate with ITO transparent electricity by the same method as in Example 1, it was directly baked at 170 ° C under a vacuum of 1 mmHg. The maximum emission wavelength of the fluorescence spectrum of the panel was 485 nm, and the emission intensity was about an order of magnitude worse than that in Example 1. Also, no luminescence was observed when driven at 20 volts.
(Example 2)
A solution was prepared by adding 2% by weight of 1,1,4,4-tetraphenylbutadiene and rhodamine B to the precursor content of polyparaphenylene vinylene in the precursor solution of Example 1. This solution and the additive-free solution are combined into an organic EL material of three primary colors and filled in an ink tank of an inkjet printing apparatus. As shown in FIG. 2, red, green, and blue are placed on the ITO electrodes juxtaposed on the TFT substrate. Arranged on the mosaic. Thereafter, the film was dried at 100 ° C. for 1 hour under a vacuum of 1 mmHg. After drying, it was baked in another drier in a nitrogen atmosphere at atmospheric pressure for 4 hours.
[0020]
After firing, lithium-containing aluminum was sputtered with 2000 angstroms to form a counter electrode.
[0021]
(Example 3) The following solution containing 0.5% by weight of a polymer electrolyte, which is a precursor of polyparaphenylene vinylene, was taken in a discharge device and discharged onto a substrate with an ITO transparent electrode.
[0022]
Solution water: 90 weight percent glycerin: 10 weight percent After discharging, the substrate was subjected to solvent removal for 4 hours at room temperature under a vacuum of 0.01 mmHg. After removing the solvent, the temperature was raised to 40 ° C. and drying was performed for 30 minutes. After drying, firing was performed at 170 ° C. for 4 hours in a nitrogen atmosphere. Thereafter, 2000 angstroms of aluminum metal was vapor-deposited by a vapor deposition machine. When the fluorescence spectrum of the obtained panel was examined, the maximum emission wavelength of the fluorescence spectrum was 535 nm. Further, when this light emitting display was driven, the light emission spectrum, which could be driven at 6 volts, almost coincided with the fluorescence spectrum.
[0023]
Example 4 A solution was prepared by adding 2 weight percent of 1,1,4,4-tetraphenylbutadiene and rhodamine B to the precursor solution of Example 1 to the precursor content of polyparaphenylene vinylene. It was. This solution and the additive-free solution are combined into an organic EL material of three primary colors and filled in an ink tank of an inkjet printing apparatus. As shown in FIG. 2, red, green, and blue are placed on the ITO electrodes juxtaposed on the TFT substrate. Arranged on the mosaic. Thereafter, the solvent was removed at room temperature under a vacuum of 0.01 mmHg for 4 hours. After removal, the film was dried at 40 ° C. for 30 minutes under a vacuum of 0.01 mmHg. After drying, calcination was performed in a nitrogen atmosphere at atmospheric pressure for 4 hours.
[0024]
After firing, aluminum was sputtered with 2000 angstroms to form a counter electrode.
[0025]
【The invention's effect】
As described above in the detailed description, according to the present invention, by adding a simple process to the conventional process, the peak of the emission spectrum of the light-emitting display prepared by the conventional method is appropriately moved by the preparation method. In contrast, the emission intensity is low, but the emission intensity can be increased and the shift of the spectrum can be reduced. In addition, this method can provide a full color light emitting display easily and inexpensively.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a light-emitting display using an organic EL.
FIG. 2 is a conceptual diagram when an organic EL material is discharged onto a TFT substrate.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Aluminum electrode 2 ... Organic EL material 3 ... ITO transparent electrode 4 ... Glass substrate 5 ... Power source 11 ... Glass substrate 12 ... TFT element 13 ... ITO electrode 14 ... Nozzle

Claims (6)

In a method for manufacturing a light emitting display comprising a polyparaphenylene vinylene-based light emitting material and an electrode material sandwiching the light emitting material, at least one solution of a polyparaphenylene vinylene precursor and a solution comprising a hydrophilic high boiling point solvent are used. After discharging using a discharge device onto a substrate having a transparent electrode, after removing the solvent at room temperature, the substrate is dried at 120 ° C. or lower, and then heated and baked to form a light emitting layer. A method for manufacturing a light-emitting display, characterized by forming an electrode. The method for producing a light-emitting display, wherein the high boiling point solvent according to claim 1 is ethylene glycol, glycerin, ethanolamine, sugar, or a derivative thereof, or a mixture of these solvents. 2. The method for manufacturing a light-emitting display according to claim 1, wherein the solvent is removed at room temperature and under vacuum, followed by heating and drying under vacuum, followed by heating and firing. 4. The method of manufacturing a light emitting display according to claim 3, wherein the solvent is removed under a vacuum of 1 mmHg or less. 5. The method for manufacturing a light-emitting display according to claim 3, wherein the solvent is removed and then heat-dried at a temperature of 70 ° C. or lower and a vacuum of 1 mmHg or lower. A method of manufacturing a light emitting display, wherein the discharge device according to claim 1 is an ink jet printing device.

Images