JP2006236801A - Manufacturing method of light-emitting element and light-emitting element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a light-emitting element capable of changing a light emission wavelength specific to a light-emitting layer. <P>SOLUTION: The manufacturing method of the light-emitting element comprises a process of coating solution with a light-emitting material making up a light-emitting layer 8 dissolved in a solvent, and a process of adjusting light emission wavelengths of the light-emitting layer 8 made of the light-emitting material by drying the above solution and adjusting a residual volume of the solvent. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a light emitting element, and a light emitting element.

As a light-emitting element typified by an organic electroluminescence (hereinafter abbreviated as EL) element, there is one having a functional layer such as a light-emitting layer between a cathode and an anode. In the light emitting device having such a configuration, by injecting electrons and holes from each electrode into the light emitting layer, excitons of the fluorescent compound are generated, and light emitted when the excitons return to the ground state is used. To do. Here, for example, Patent Document 1 discloses a technique that adjusts the emission color of light emitted from the light emitting element by changing the specific emission wavelength of the light emitting layer, thereby allowing desired color light to be emitted. .
JP 2003-297579 A

  In Patent Document 1, a light emission wavelength changing agent is contained in order to change the light emission wavelength. However, the addition of such a light emission wavelength changing agent is costly and inconvenient to handle. An object of the present invention is to provide a method for manufacturing a light emitting device capable of changing the light emission wavelength inherent to the light emitting layer without including a special additive as in Patent Document 1, and a light emitting device. Yes.

  In order to solve the above problems, a method for manufacturing a light-emitting element according to the present invention includes a step of applying a solution in which a light-emitting material constituting a light-emitting layer is dissolved in a solvent, and a residual amount of the solvent when the solution is dried. And adjusting the emission wavelength of the light emitting layer made of the light emitting material by adjusting.

  According to such a manufacturing method, the emission wavelength can be easily changed without adding an emission wavelength changing agent or the like as in the prior art. In other words, it is optimal to use a liquid phase method when forming a light emitting material (particularly a polymer light emitting material) constituting the light emitting layer, but the solvent used in this case is actively left in the light emitting layer and dried. By adjusting the residual amount sometimes, it is possible to suitably adjust the emission wavelength of the light emitting layer.

  Here, as a solvent to be used, it is preferable that the dipole moment is 0.5D or more. Such a solvent is likely to interact with the light-emitting material, so it has high solubility in the light-emitting material, is easy to handle during film formation, and emits light when remaining in the light-emitting layer after film formation. Since the interaction with the material is generated, the emission wavelength of the light emitting material can be suitably changed.

  Next, in order to solve the above problems, the light-emitting element of the present invention is a light-emitting element including a functional layer including at least a light-emitting layer between a first electrode layer and a second electrode layer. The light emitting layer includes a light emitting material and a solvent for dissolving the light emitting material, and the emission wavelength of the light emitting layer is adjusted by the content of the solvent.

  According to such a light emitting element, it is possible to easily change the emission wavelength without adding an emission wavelength changing agent or the like as in the prior art by controlling the amount of the solvent contained in the light emitting layer. . In other words, it is optimal to use the liquid phase method when forming the light emitting material constituting the light emitting layer, but the solvent used in this case is actively left in the light emitting layer, and the remaining amount is adjusted during drying. Thus, the emission wavelength of the light emitting layer can be easily adjusted.

  Here, as a solvent to contain, it is preferable that the dipole moment is 0.5D or more. Since such a solvent is likely to interact with the light emitting material, the emission wavelength of the light emitting material can be suitably changed.

(Organic EL device)
Hereinafter, a first embodiment of an organic EL element which is a light emitting element of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional configuration diagram of the organic EL element of the present embodiment. In FIG. 1, an organic EL element 10 includes a substrate 2, an anode (first electrode) 4, a cathode (second electrode) 7 provided on one surface side of the substrate 2, and these electrodes 4, 7. An organic EL layer (organic functional layer) 3 sandwiched therebetween is provided. An element control unit con is connected to the anode 4 and the cathode 7 so that an arbitrary voltage can be applied to both electrodes. The organic EL layer 3 is mainly composed of a hole injection / transport layer 5 and a light emitting layer 8.

  Here, the organic EL element 10 shown in FIG. 1 has a form in which output light from the light emitting layer 8 is extracted from the substrate 2 side to the outside of the apparatus, and the substrate 2 is made of a transparent or translucent material that can transmit light. Yes. Examples of such materials include transparent glass, quartz, sapphire, or transparent synthetic resins such as polyester, polyacrylate, polycarbonate, polyether ketone, and the like. In particular, an inexpensive soda glass is preferably used as a material for forming the substrate 2. Although not shown in the present embodiment, elements such as wiring and thin film transistors can be formed on the substrate 2.

  Similarly, the anode 4 is made of a transparent or translucent conductive material that can transmit light. Specifically, what consists of indium tin oxide (ITO) is employ | adopted.

  On the other hand, in the case where the emitted light is extracted from the side opposite to the substrate 2, the material constituting the substrate 2 may be opaque. In this case, surface oxidation is performed on a ceramic sheet such as alumina or a metal sheet such as stainless steel. It is possible to use an insulating treatment such as a thermosetting resin or a thermoplastic resin. In this case, the anode 4 can be formed of a light shielding or light reflecting material.

  The hole injection / transport layer 5 provides a function of improving device characteristics such as the light emission efficiency and lifetime of the light emitting layer 8. That is, by providing the hole injection / transport layer 5, electrons moving in the light emitting layer 8 are efficiently blocked, and an effect of increasing the recombination probability of holes and electrons in the light emitting layer 8 can be obtained. As a material (formation material) for forming the hole injection / transport layer, for example, a thiophene compound (polythiophene (PEDOT) or the like), a pyrrole compound (polypyrrole or the like), an aniline compound (polyaniline or the like), an acetylene type, for example. A compound (such as polyacetylene) or a derivative thereof can be used.

  As the material for forming the light emitting layer 8, low molecular organic light emitting dyes and polymer light emitting materials, that is, light emitting materials such as various fluorescent materials and phosphorescent materials, and organic electroluminescent materials such as Alq3 (aluminum chelate complex) can be used. It is. Among the conjugated polymers that serve as the light-emitting substance, those containing an arylene vinylene or polyfluorene structure are particularly preferable. In the low-molecular light emitters, for example, naphthalene derivatives, anthracene derivatives, perylene derivatives, polymethine series, xanthene series, coumarin series, cyanine series pigments, 8-hydroquinoline and its metal complexes, aromatic amines, tetraphenylcyclo Pentadiene derivatives and the like, or known ones described in JP-A-57-51781 and 59-194393 can be used. In the present embodiment, poly (9,9-dioctylflorene-2,7-diyl)-(1,4-vinylenephenylene) copolymer (molecular weight Mw = 110,000 (polystyrene conversion)) is used.

  Here, the light emitting layer 8 contains a solvent for dissolving the light emitting material constituting the light emitting layer 8. Specifically, N, N-dimethylacetamide is contained, and the emission wavelength of the light emitting layer 8 is adjusted by the action of the solvent. That is, the intrinsic emission wavelength of the light emitting material constituting the light emitting layer 8 is changed, and the amount of change is adjusted by the content of the solvent. As the solvent, in addition to N, N-dimethylacetamide, a solvent having a dipole moment of 0.5D or more, such as dichlorobenzene, can be used.

  The cathode 7 is a metal electrode made of aluminum (Al), magnesium (Mg), gold (Au), silver (Ag), or the like. In the organic EL element 10, it is preferable to provide a sealing member that covers the cathode 7. Further, between the anode 4 and the substrate 2, the organic EL layer 3 including the anode 4 and the cathode 7 from the substrate 2 side is provided. On the other hand, a sealing layer for blocking the entry of the atmosphere can also be provided. The sealing layer provided on the light extraction side is formed of a transparent material such as ceramic, silicon nitride, silicon oxynitride, or silicon oxide. Among these, silicon oxynitride is preferable from the viewpoint of transparency and gas barrier properties. The thickness of the sealing layer is preferably smaller than the wavelength of light emitted from the light emitting layer 8 (for example, 0.1 μm).

  The organic EL element 10 of the present embodiment can be applied to either an active matrix type or a passive matrix type as its driving method, and a current is supplied to the organic EL layer 3 through the electrodes 4 and 7 to emit light. 8 is made to emit light, and light can be emitted to the outer surface side of the substrate 2.

(Manufacturing method of organic EL element)
Next, a method for manufacturing the organic EL element 10 of FIG. 1 will be described.
First, a translucent substrate 2 made of glass or the like is prepared, and an anode 4 made of ITO is formed on the substrate 2. Subsequently, the hole injection / transport layer 5 is formed by a spin coating method using the liquid composition containing the hole injection / transport layer forming material.

Subsequently, the light emitting layer 8 is formed on the hole injection / transport layer 5 formed. Here, a liquid composition containing a light-emitting material (polymer light-emitting material) that is a light-emitting layer forming material is used and formed by a spin coating method. Here, a poly (9,9-dioctylflorene-2,7-diyl)-(1,4-vinylenephenylene) copolymer (molecular weight Mw = 110,000 (polystyrene conversion)) as a luminescent material is changed to N, A liquid composition (3 wt%) dissolved in N-dimethylacetamide is applied by spin coating, then vacuum dried (30 minutes at 10 ⁻⁴ Torr) and annealed on a hot plate at 100 ° C. for 60 minutes. The intended light emitting layer 8 is obtained.

  Here, when the applied liquid composition is dried, the emission wavelength of the light emitting layer 8 to be formed is adjusted by adjusting the residual amount of the solvent. That is, by controlling the drying time, the drying temperature, the atmospheric pressure, etc., the amount of the solvent remaining in the light emitting layer 8 after drying is controlled to change the emission wavelength and adjust the amount of change.

  Subsequently, aluminum is formed on the formed light emitting layer 8 to obtain the cathode 7. Thereafter, predetermined wiring is formed with the element control unit con and the like, and the organic EL element 10 shown in FIG. 1 is obtained.

  In order to confirm the effect of the present invention, the following examples were carried out.

Example 1
After forming the hole injection / transport layer 5 at 30 nm on the substrate 2 including the anode 4, poly (9,9-dioctylflorene-2,7-diyl)-(1,4-vinylenephenylene) as a light emitting material A liquid composition in which the copolymer was dissolved in N, N-dimethylacetamide (boiling point 166.1 ° C.) was applied by a spin coating method (thickness 50 nm). On top of that, a cathode material was formed by vapor deposition to produce an organic EL device of Example 1. The initial characteristics of the device and the luminance half-life when driven at a constant current were measured. The results are shown in Table 1.

(Example 2)
After forming the hole injection / transport layer 5 at 30 nm on the substrate 2 including the anode 4, poly (9,9-dioctylflorene-2,7-diyl)-(1,4-vinylenephenylene) as a light emitting material A liquid composition in which the copolymer was dissolved in N, N-dimethylacetamide (boiling point 166.1 ° C.) was applied by a spin coating method (thickness 50 nm). Thereafter, vacuum drying (30 minutes at 10 ⁻¹ Torr) was performed, and a cathode material was formed thereon by vapor deposition to produce an organic EL device of Example 2. The initial characteristics of the device and the luminance half-life when driven at a constant current were measured. The results are shown in Table 1.

(Example 3)
After forming the hole injection / transport layer 5 at 30 nm on the substrate 2 including the anode 4, poly (9,9-dioctylflorene-2,7-diyl)-(1,4-vinylenephenylene) as a light emitting material A liquid composition in which the copolymer was dissolved in N, N-dimethylacetamide (boiling point 166.1 ° C.) was applied by a spin coating method (thickness 50 nm). Thereafter, vacuum drying (30 minutes at 10 ⁻⁴ Torr) was performed, and a cathode material was formed thereon by vapor deposition to produce an organic EL device of Example 3. The initial characteristics of the device and the luminance half-life when driven at a constant current were measured. The results are shown in Table 1.

Example 4
After forming the hole injection / transport layer 5 at 30 nm on the substrate 2 including the anode 4, poly (9,9-dioctylflorene-2,7-diyl)-(1,4-vinylenephenylene) as a light emitting material A liquid composition in which the copolymer was dissolved in N, N-dimethylacetamide (boiling point 166.1 ° C.) was applied by a spin coating method (thickness 50 nm). Then, vacuum drying (30 minutes at 10 ⁻⁴ Torr) was performed, annealing was performed on a hot plate at 100 ° C. for 60 minutes, and a cathode material was formed thereon by vapor deposition to produce an organic EL device of Example 4. The initial characteristics of the device and the luminance half-life when driven at a constant current were measured. The results are shown in Table 1.

(Example 5)
After forming the hole injection / transport layer 5 at 30 nm on the substrate 2 including the anode 4, poly (9,9-dioctylflorene-2,7-diyl)-(1,4-vinylenephenylene) as a light emitting material A liquid composition in which the copolymer was dissolved in N, N-dimethylacetamide (boiling point 166.1 ° C.) was applied by a spin coating method (thickness 50 nm). Thereafter, vacuum drying (30 minutes at 10 ⁻⁶ Torr) was performed, annealing was performed on a hot plate at 130 ° C. for 60 minutes, and a cathode material was deposited thereon to produce an organic EL device of Example 5. The initial characteristics of the device and the luminance half-life when driven at a constant current were measured. The results are shown in Table 1.

(Comparative Example 1)
After forming the hole injection / transport layer 5 at 30 nm on the substrate 2 including the anode 4, poly (9,9-dioctylflorene-2,7-diyl)-(1,4-vinylenephenylene) as a light emitting material A liquid composition in which the copolymer was dissolved in toluene was applied by a spin coating method (thickness 50 nm). Thereafter, vacuum drying (30 minutes at 10 ⁻⁴ Torr) was performed, annealing was performed on a hot plate at 100 ° C. for 60 minutes, and a cathode material was deposited thereon to produce an organic EL device of Comparative Example 1. The initial characteristics of the device and the luminance half-life when driven at a constant current were measured. The results are shown in Table 1.

  In Examples 1 to 5, the luminescent material was dissolved in a highly polar solvent, and an interaction was caused between the luminescent material and the solvent. In such an element, the fluorescence is shifted to the short wavelength side, and the light emission is similarly shifted to the short wavelength side during electroluminescence. In particular, by changing the drying conditions of the membrane in the order of Examples 1 to 5, the amount of the remaining solvent was changed, and the shift amount could be changed. Moreover, the conditions which can shift only the light emission wavelength to the short wavelength side were found without impairing the light emission characteristics. Thereby, light emission with good color purity can be obtained without changing the material, and when used as a full color panel, the required luminance can be reduced and the life can be extended.

(Example 6)
After forming the hole injection / transport layer 5 at 30 nm on the substrate 2 including the anode 4, poly (9,9-dioctylflorene-2,7-diyl)-(1,4-vinylenephenylene) as a light emitting material A liquid composition in which the copolymer was dissolved in dichlorobenzene (boiling point 180 ° C., dipole moment 2.27D) was applied by spin coating (thickness 50 nm). Then, vacuum drying (30 minutes at 10 ⁻⁴ Torr) was performed, annealing was performed on a hot plate at 100 ° C. for 60 minutes, and a cathode material was deposited thereon to produce an organic EL device of Example 6. The initial characteristics of the device and the luminance half-life when driven at a constant current were measured. The results are shown in Table 2.

(Comparative Example 2)
After forming the hole injection / transport layer 5 at 30 nm on the substrate 2 including the anode 4, poly (9,9-dioctylflorene-2,7-diyl)-(1,4-vinylenephenylene) as a light emitting material A liquid composition in which the copolymer was dissolved in dichlorobenzene (boiling point 180 ° C., dipole moment 2.27D) was applied by spin coating (thickness 50 nm). Thereafter, vacuum drying (30 minutes at 10 ⁻⁶ Torr) was performed, annealing was performed on a hot plate at 130 ° C. for 60 minutes, and a cathode material was formed thereon by vapor deposition to produce an organic EL device of Comparative Example 2. The initial characteristics of the device and the luminance half-life when driven at a constant current were measured. The results are shown in Table 2.

Table 2 also shows the results of Comparative Example 1 and Example 4. In Example 6, the fluorescence of the coated film is shifted to the longer wavelength side, and the emission is also shifted to the longer wavelength side during electroluminescence. In Comparative Example 2, there was almost no residual solvent amount due to drying, and the shift amount was not sufficient.
Moreover, the conditions which can shift only the light emission wavelength to the long wavelength side or the short wavelength side without impairing the light emission characteristics were found. As a result, multiple colors can be achieved without changing the material.

The cross-sectional block diagram of the organic EL element of this embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 3 ... Organic EL layer (functional layer), 4 ... Anode (1st electrode), 7 ... Cathode (2nd electrode), 8 ... Light emitting layer, 10 ... Organic EL element (light emitting element)

Claims (8)

Applying a solution in which a luminescent material constituting the luminescent layer is dissolved or dispersed in a solvent;
Adjusting the light emission wavelength of the light emitting layer made of the light emitting material by adjusting the residual amount of the solvent when the solution is dried.   The method for manufacturing a light emitting device according to claim 1, wherein the solvent has a dipole moment of 0.5 D or more.   The method for producing a light-emitting element according to claim 1, wherein drying of the solvent is performed with heating, and the residual amount of the solvent is prepared according to the degree of heating temperature.   The luminescence according to any one of claims 1 to 3, wherein the solvent is dried by vacuum drying, and the residual amount of the solvent is adjusted according to the degree of ultimate vacuum. Device manufacturing method.   5. The method for manufacturing a light-emitting element according to claim 1, wherein the residual amount of the solvent is adjusted by an amount of a solvent in which the light-emitting material is dissolved or dispersed. A light emitting device comprising a functional layer including at least a light emitting layer between a first electrode layer and a second electrode layer,
The light emitting element, wherein the light emitting layer includes a light emitting material and a solvent for dissolving or dispersing the light emitting material, and an emission wavelength of the light emitting layer is adjusted by a content of the solvent.   The light emitting device according to claim 6, wherein the solvent has a dipole moment of 0.5D or more.   The light-emitting element according to claim 6, wherein the solvent is a solvent used when the light-emitting material is formed into a film.

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