JP2007157550A - Color conversion membrane, and organic multi-colored light emitting el device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a color conversion membrane capable of attaining a thin membrane thickness and high color conversion efficiency at the same time, and an organic multi-colored light emitting device using the color conversion membrane showing a stable light emission property for a long period of time. <P>SOLUTION: On the color conversion membrane, a dyestuff contains a first dyestuff and a second dyestuff; and has a membrane thickness of not less than 2μm. The first dyestuff absorbs light incident on the color conversion membrane and transfers the energy of the light to the second dyestuff. The second dyestuff receives the energy from the first dyestuff and emits light. The first dyestuff is contained in the color conversion membrane with a quantity capable of sufficiently absorbing the incident light. The second dyestuff is contained with a quantity of not more than 1.0 mol with a total constituent molecule of the color conversion membrane as a reference. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a color conversion film formed by a vapor deposition method and having high conversion efficiency. Furthermore, the present invention relates to a multicolor light emitting organic EL device formed using the color conversion film. The multicolor organic EL device of the present invention can be used in personal computers, word processors, televisions, facsimiles, audio, video, car navigation, electric desk calculators, telephones, portable terminals, industrial measuring instruments, and the like.

  In recent years, organic EL devices have been actively researched for practical use. Organic EL elements are expected to achieve high luminance and luminous efficiency because they can achieve high current density at low voltage, and the practical application of organic multi-color EL displays capable of high-definition multi-color or full-color display is expected. Expected. As an example of a method for making the organic EL display multi-colored or full-colored, there is a method using a plurality of types of color filters that transmit light in a specific wavelength region (color filter method). When applying the color filter method, the organic EL element used emits multicolor light and includes the three primary colors of light (red (R), green (G), and blue (B)) in a balanced manner, so-called “white light”. "Is required to emit light.

  In order to obtain a multicolor light-emitting organic EL element, a method of using a light-emitting layer containing a plurality of light-emitting dyes and simultaneously exciting the plurality of light-emitting dyes (see Patent Documents 1 and 2), a host light-emitting material, and a guest light-emitting material A method of exciting and emitting a host luminescent material at the same time using a luminescent layer containing the material, and transferring energy to the guest material and emitting light (see Patent Document 3), and using a plurality of luminescent layers containing different luminescent dyes, A method for exciting a luminescent dye in the method, using a luminescent layer containing a luminescent dye and a carrier transporting layer containing a luminescent dopant adjacent to the luminescent layer, and from excitons generated by carrier recombination in the luminescent layer, A method of transferring excitation energy to a luminescent dopant (see Patent Documents 4 and 5) has been studied.

  However, the above-described multicolor light-emitting organic EL device relies on either exciting a plurality of types of light-emitting materials at the same time or transferring energy between the plurality of types of light-emitting materials. In such an element, it has been reported that the emission intensity balance between the light emitting materials changes and the obtained hue may change as the driving time elapses or the energization current changes.

  As another method for obtaining a multicolor organic EL element, a color conversion method using a monochromatic organic EL element and a color conversion film has been proposed (see Patent Documents 6 to 8). The color conversion film used is a layer that contains one or more color conversion materials that absorb light of short wavelengths and convert it to light of longer wavelengths. As a method for forming a color conversion film, it has been studied to apply a coating liquid in which a color conversion material is dispersed in a resin, or to deposit the color conversion material by a dry process such as vapor deposition or sputtering. .

Japanese Patent No. 2991450 JP 2000-243563 A US Pat. No. 5,683,823 JP 2002-93583 A JP 2003-86380 A JP 2002-75643 A JP 2003-217859 A JP 2000-230172 A

  However, when the concentration of the color conversion material in the color conversion film increases, a phenomenon called concentration quenching occurs in which the absorbed energy is deactivated without light emission while repeating the movement between the same molecules. In order to suppress this phenomenon, a color conversion substance is dissolved or dispersed in some medium to reduce the density (see Patent Document 8).

  Here, when the concentration of the color conversion substance is lowered, the absorbance of light to be absorbed decreases, and sufficient converted light intensity cannot be obtained. With respect to this problem, it has been practiced to increase the absorbance by increasing the thickness of the color conversion film and to maintain the efficiency of color conversion. When such a thick color conversion film (thickness of about 10 μm) is used, electrode pattern disconnection at the stepped portion, difficulty in achieving high definition, residual moisture or solvent in the film (combined with organic EL elements) In such a case, the organic EL layer may be altered by residual moisture or solvent, resulting in display defects). On the other hand, from the viewpoint of reducing the viewing angle dependency, there is a conflicting demand for making the color conversion film thinner.

  Accordingly, an object of the present invention is to provide a color conversion film capable of maintaining sufficient converted light intensity without increasing the thickness. Another object of the present invention is to provide a multicolor light emitting organic EL device using the color conversion film, which is excellent in viewing angle dependency, and has no hue change with the lapse of driving time or change in energization current. An object of the present invention is to provide a multicolor light-emitting organic EL device that exhibits stable light emission characteristics over a long period of time.

  The color conversion film according to the first embodiment of the present invention is a color conversion film having a thickness of 2 μm or less including a first dye and a second dye: the first dye emits incident light to the color conversion film. A dye that absorbs and transfers its energy to a second dye; the second dye is a dye that accepts the energy from the first dye and emits light; the first dye transmits the incident light Present in the color conversion film in an amount that can be sufficiently absorbed; the second dye is present in an amount of 10 mol% or less, preferably 0.1 to 5 mol%, based on the total number of constituent molecules of the color conversion film It is characterized by doing. Here, the first dye is preferably present in an amount of 50 to 99.99 mol% based on the total number of constituent molecules of the color conversion film. In addition, the color conversion film of this embodiment is desirably formed by a vapor deposition method.

  The multicolor light-emitting organic EL device of the second embodiment of the present invention is a multicolor having a pair of electrodes, at least one of which is a transparent electrode, an organic EL layer sandwiched between the pair of electrodes, and a color conversion film. A light-emitting organic EL device, wherein: the color conversion film includes a first dye and a second dye; the color conversion film has a thickness of 2 μm or less; the first dye emits light incident on the color conversion film A dye that absorbs and transfers its energy to a second dye; the second dye is a dye that accepts the energy from the first dye and emits light; the first dye transmits the incident light Present in the color conversion film in an amount that can be sufficiently absorbed; the second dye is present in an amount of 10 mol% or less, preferably 0.1 to 5 mol%, based on the total number of constituent molecules of the color conversion film It is characterized by doing. Here, the first dye is preferably present in an amount of 50 to 99.99 mol% based on the total number of constituent molecules of the color conversion film. The color conversion film is preferably formed by a vapor deposition method. Furthermore, the color conversion film and the transparent electrode may be disposed in contact with each other.

  By adopting the configuration as described above, incident light absorption and wavelength distribution conversion are separated into functions, and the respective functions are assigned to the first dye and the second dye, so that high color conversion is achieved without increasing the thickness. A color conversion film that maintains efficiency and can be formed using a vapor deposition method can be provided. In addition, the multicolor light-emitting organic EL device formed using such a color conversion film has little viewing angle dependency, and the hue does not change with the passage of driving time or a change in energization current. Stable light emission characteristics can be exhibited.

  The color conversion film of the first embodiment of the present invention includes a first dye and a second dye, and has a thickness of 2 μm or less. The first dye absorbs incident light to the color conversion film, and A dye that transfers energy to the second dye; the second dye is a dye that receives the energy from the first dye and emits light; the first dye is capable of sufficiently absorbing the incident light The second dye is present in an amount of 10 mol% or less, preferably 0.1 to 5 mol% based on the total number of constituent molecules of the color conversion film. To do. Here, the first dye is preferably present in an amount of 50 to 99.99 mol% based on the total number of constituent molecules of the color conversion film. In addition, the color conversion film of this embodiment is desirably formed by a vapor deposition method.

  When producing independently, the color conversion film of this embodiment can be produced by vapor-depositing the 1st and 2nd pigment | dye on a transparent support body, for example. Alternatively, as described later, the color conversion film may be produced by vapor-depositing the first and second dyes on an appropriate support together with other elements. Materials that can be used as the transparent support are glass, diacetylcellulose, triacetylcellulose (TAC), propionylcellulose, butyrylcellulose, acetylpropionylcellulose, nitrocellulose, and other cellulose esters; polyamides; polycarbonates; polyethylene terephthalate, polyethylenena Polyester such as phthalate, polybutylene terephthalate, poly-1,4-cyclohexanedimethylene terephthalate, polyethylene-1,2-diphenoxyethane-4,4′-dicarboxylate, polybutylene terephthalate, etc .; polystyrene; polyethylene, polypropylene, poly Polyolefin such as methylpentene; Acrylic resin such as polymethyl methacrylate; Polycarbonate; Polysulfone; Poly Terusuruhon; polyether ketone; polyetherimides; may be a polymer material such as norbornene resins; polyoxyethylene. When a polymer material is used, the transparent support may be rigid or flexible. The transparent support preferably has a transmittance of 80% or more with respect to visible light, and more preferably has a transmittance of 86% or more.

  The first dye absorbs light incident on the color conversion film, preferably blue to blue-green light emitted from the organic EL element, and transfers the absorbed energy to the second dye. Therefore, it is desirable that the absorption spectrum of the first dye overlaps with the emission spectrum of the organic EL element, and the absorption maximum of the first dye overlaps with the maximum of the emission spectrum of the organic EL element. Is more desirable. In addition, it is desirable that the emission spectrum of the first dye overlaps with the absorption spectrum of the second dye, and the maximum of the emission spectrum of the first dye and the absorption maximum of the second dye overlap (match). Is more desirable. Dyes that can be suitably used as the first dye in the present invention include 3- (2-benzothiazolyl) -7-diethylaminocoumarin (coumarin 6), 3- (2-benzimidazolyl) -7-diethylaminocoumarin (coumarin 7), Contains coumarin dyes such as coumarin 135. Alternatively, naphthalimide dyes such as Solvent Yellow 43 and Solvent Yellow 44 may be used as the first dye. The first dye is desirably present in an amount of 50 to 99.99 mol% based on the total number of constituent molecules of the color conversion film. By existing in such a concentration range, it is possible to sufficiently absorb the incident light of the color conversion film and transfer the absorbed light energy to the second dye.

  The second dye is a dye that receives energy transferred from the first dye and emits light. Here, as described above, it is desirable that the emission spectrum of the first dye overlaps with the absorption spectrum of the second dye, and the maximum of the emission spectrum of the first dye and the absorption maximum of the second dye overlap ( Is more desirable). Therefore, the light emitted by the second dye has a longer wavelength than the light absorbed by the first dye. Dyes that can be suitably used as the second dye in the present invention are 4-dicyanomethylene-2-methyl-6- (p-dimethylaminostyryl) -4H-pyran (DCM-1, (I)), DCM- Cyanine dyes such as 2 (II) and DCJTB (III); 4,4-difluoro-1,3,5,7-tetraphenyl-4-bora-3a, 4a-diaza-s-indacene (IV), lumogen F red, Nile red (V), etc. are included. Alternatively, xanthene dyes such as rhodamine B and rhodamine 6G, or pyridine dyes such as pyridine 1 may be used.

  In the color conversion film of the present invention, since the dye that emits light is the second dye, it is important that the second dye does not cause concentration quenching. This is because when the second dye undergoes concentration quenching, the efficiency of color conversion decreases. The upper limit of the density | concentration of the 2nd pigment | dye in the color conversion film of this invention can change depending on the kind of 1st and 2nd pigment | dye, on the condition that concentration quenching does not raise | generate. Further, the lower limit of the concentration of the second dye can be changed depending on the types of the first and second dyes or the intended application, provided that sufficient converted light intensity is obtained. In general, the preferred concentration of the second dye in the color conversion film of the present invention is 10 mol% or less, preferably 0.01 to 10 mol%, more preferably based on the total number of constituent molecules of the color conversion film. Is in the range of 0.1 to 5 mol%. By using the second dye at a concentration within such a range, it is possible to prevent concentration quenching and at the same time obtain a sufficient converted light intensity.

  As described above, by adopting a configuration in which absorption of incident light and color conversion are realized by another type of dye, the absorption peak wavelength of incident light by the first dye and the emission peak wavelength of color conversion by the second dye are calculated. The difference can be increased. Furthermore, by separating the functions, it is possible to expand the choices of materials used as the first dye and the second dye.

  The color conversion film of the present invention is preferably formed by a vapor deposition method (including resistance heating type and electron beam heating type), more preferably by co-evaporation of the first dye and the second dye. This is because it is necessary to disperse the second dye in the first dye in order to prevent concentration quenching. A preliminary mixture in which the first pigment and the second pigment are mixed at a predetermined ratio may be formed in advance, and co-evaporation may be performed using the preliminary mixture. Or a 1st pigment | dye and a 2nd pigment | dye may be arrange | positioned in a separate heating site | part, and each may be heated separately and co-evaporation may be performed. In particular, the latter method is effective when there is a large difference in characteristics (evaporation rate, vapor pressure, etc.) between the first dye and the second dye.

  The color conversion film of the present invention has a film thickness of 2000 nm (2 μm) or less, preferably 100 to 2000 nm, more preferably 200 to 1000 nm. In the color conversion film of the present invention, the first dye constituting most of the color conversion film has a function of absorbing incident light, and thus has sufficient absorbance even in such a thin film thickness. Although not intending to be bound by any theory, when the first dye in the color conversion film of the present invention absorbs light and enters an excited state, it is more than energy transfer between the first dyes. The energy transfer from the first dye to the second dye is considered to occur more easily. Therefore, it is considered that most of the excitation energy of the first dye moves to the second dye without being lost (concentration quenching) due to movement between the first dyes, and can contribute to the emission of the second dye. It is done. Since the second dye is present at a low concentration that does not cause concentration quenching as described above, color conversion is performed by efficiently using the transferred excitation energy, and light having a desired wavelength distribution is emitted. Can do. Thus, in the color conversion film of the present invention, it is possible to achieve both a thin film thickness and high color conversion efficiency.

  The multicolor light-emitting organic EL device according to the second embodiment of the present invention includes an organic EL element and the color conversion film according to the first embodiment, and at least one of the organic EL elements is transparent. And an organic EL layer sandwiched between the pair of electrodes.

  1A to 1D show exemplary structures of the multicolor light-emitting organic EL device of the present invention. The device of FIG. 1A has a configuration of transparent substrate 10 / color conversion film 20 / organic EL element 30a, where the organic EL element 30a includes a transparent electrode 31, an organic EL layer 32, and a reflective electrode 33. . The device of FIG. 1A is a so-called bottom emission type device that has a configuration in which the color conversion film 20 and the transparent electrode 31 are in contact with each other and emits light toward the transparent substrate 10. The device of FIG. 1B has a configuration of substrate 11 / organic EL element 30b / color conversion film 20. Here, the organic EL element 30b includes the transparent electrode 31, the organic EL layer 32, and the reflective electrode 33 similarly to the element 30a, but the stacking order thereof is opposite. The device of FIG. 1B is a so-called top emission type device that has a configuration in which the color conversion film 20 and the transparent electrode 31 are in contact with each other and emits light to the opposite side of the substrate 11.

  In the devices of FIGS. 1A and 1B, one of the pair of electrodes is the transparent electrode 31, and the light (EL light) emitted from the organic EL layer 32 is reflected directly or by reflection at the reflective electrode 33. The light is emitted in the direction of the transparent electrode 31 and enters the color conversion film 20. Part of the EL light is absorbed by the first dye, passes through energy transfer to the second dye, and is emitted as light having different wavelength distributions (photoluminescence light, PL light). Then, it functions as an organic EL device that emits multicolor light by EL light and PL light that are not absorbed by the color conversion film 20.

  On the other hand, the device of FIG. 1C has a configuration of transparent substrate 10 / organic EL element 30a / color conversion film 20 / reflection layer 40, where organic EL element 30c includes first transparent electrode 31a, organic EL element. The layer 32 and the second transparent electrode 31b are included. The device shown in FIG. 1C is a bottom emission type device. The device of FIG. 1D has a configuration of substrate 11 / reflection layer 40 / color conversion film 20 / organic EL element 30c. The device shown in FIG. 1D is a top emission type device.

  In the devices of FIGS. 1C and 1D, both of the pair of electrodes are the transparent electrodes 31 (a, b), and part of the EL light emitted from the organic EL layer 32 passes through the color conversion film 20. Without going through, the light is emitted to the outside (in the direction of the transparent substrate 10 in FIG. 1C and in the direction of the second transparent electrode 31b in FIG. 1D). Of the EL light, part of the light directed toward the color conversion film 20 is absorbed by the color conversion film 20 and converted into PL light. Further, the light that has passed through the color conversion film 20 is reflected by the reflection layer 40, is incident on the color conversion film 20 again, undergoes wavelength distribution conversion, and further passes through the organic EL element 30c and is emitted to the outside.

  In any of the devices of FIGS. 1A to 1D, the color conversion film 20 is disposed in contact with the transparent electrode 31 (including the first and second transparent electrodes 31a and 31b). This arrangement is effective for minimizing the distance between the organic EL layer 32 and the color conversion film 20 and improving the incident efficiency of the EL light to the color conversion film 20 and at the same time reducing the viewing angle dependency. is there.

  Which of the above configurations is adopted is determined depending on a desired use of the device, a hue required for the device, and the like. Below, each of the component of the multicolor light emission organic EL device of this invention is described.

  The transparent substrate 10 and the substrate 11 should be able to withstand the conditions (solvent, temperature, etc.) used for forming the laminated layers, and are preferably excellent in dimensional stability. The material of the transparent substrate 10 used in the bottom emission type structure of FIGS. 1A and 1C may be an inorganic material such as glass, diacetyl cellulose, triacetyl cellulose (TAC), propionyl cellulose, buty Cellulose esters such as rilcellulose, acetylpropionylcellulose, nitrocellulose; polyamides; polycarbonates; polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, poly-1,4-cyclohexanedimethylene terephthalate, polyethylene-1,2-diphenoxyethane Polyesters such as 4,4′-dicarboxylate and polybutylene terephthalate; polystyrenes; polyolefins such as polyethylene, polypropylene and polymethylpentene; Acrylic resins such as chill methacrylate; polycarbonates; polysulfones; polyethersulfones; polyether ketone; polyetherimides; may be a polymer material such as norbornene resins; polyoxyethylene. When a polymer material is used, the transparent substrate 10 may be rigid or flexible. The transparent substrate 10 preferably has a transmittance of 80% or more with respect to visible light, and more preferably has a transmittance of 86% or more.

  On the other hand, since the substrate 11 used in the top emission type configuration of FIGS. 1B and 1D does not require transparency, in addition to the materials that can be used for the transparent substrate 10 described above, metal or ceramic is used. Can be used.

  The transparent electrode 31 (including the first and second transparent electrodes 31a and 31b) preferably has a transmittance of 50% or more, more preferably 85% or more with respect to light having a wavelength of 400 to 800 nm. The transparent electrode 31 is made of ITO (In—Sn oxide), Sn oxide, In oxide, IZO (In—Zn oxide), Zn oxide, Zn—Al oxide, Zn—Ga oxide, or these It can be formed using a conductive transparent metal oxide in which a dopant such as F or Sb is added to the oxide. The transparent electrode 31 is formed using a vapor deposition method, a sputtering method, or a chemical vapor deposition (CVD) method, and preferably formed using a sputtering method. Further, when a transparent electrode 31 composed of a plurality of partial electrodes is required as will be described later, a conductive transparent metal oxide is uniformly formed over the entire surface, and then etched so as to give a desired pattern. The transparent electrode 31 composed of a plurality of partial electrodes may be formed. Or you may form the transparent electrode 31 which consists of a some partial electrode using the mask which gives a desired shape. Alternatively, patterning can be performed by applying a lift-off method.

  The transparent electrode 31 formed from the aforementioned material is suitable for use as an anode. On the other hand, when the transparent electrode 31 is used as a cathode, it is desirable to improve the electron injection efficiency by providing a cathode buffer layer at the interface with the organic EL layer 32. As a material for the cathode buffer layer, an alkali metal such as Li, Na, K, or Cs, an alkaline earth metal such as Ba or Sr, an alloy containing them, a rare earth metal, or a fluoride of these metals may be used. Yes, but not limited to them. The thickness of the cathode buffer layer can be appropriately selected in consideration of the driving voltage, transparency, and the like, but in a normal case, the thickness is preferably 10 nm or less.

The organic EL layer 32 includes at least an organic light emitting layer and has a structure in which a hole injection layer, a hole transport layer, an electron transport layer, and / or an electron injection layer are interposed as necessary. Alternatively, a hole injection / transport layer having both hole injection and transport functions and an electron injection / transport layer having both electron injection and transport functions may be used. Specifically, an organic EL element having the following layer structure is employed.
(1) Anode / organic light emitting layer / cathode (2) Anode / hole injection layer / organic light emitting layer / cathode (3) Anode / organic light emitting layer / electron injection layer / cathode (4) Anode / hole injection layer / organic Light emitting layer / electron injection layer / cathode (5) Anode / hole transport layer / organic light emitting layer / electron injection layer / cathode (6) Anode / hole injection layer / hole transport layer / organic light emitting layer / electron injection layer / Cathode (7) Anode / hole injection layer / hole transport layer / organic light emitting layer / electron transport layer / electron injection layer / cathode In the above layer configuration, the anode and the cathode are respectively transparent electrodes 31 (first and second). Including the transparent electrodes 31a and 31b) or the reflective electrode 33.

  As the material of each layer constituting the organic EL layer 32, known materials are used. For example, organic light-emitting layer materials for obtaining blue to blue-green light emission include fluorescent brighteners such as benzothiazole, benzimidazole, and benzoxazole, metal chelated oxonium compounds, and styrylbenzene. Materials such as compounds and aromatic dimethylidin compounds are preferably used.

Examples of the material for the electron transport layer include 2- (4-biphenyl) -5- (pt-butylphenyl) -1,3,4-oxadiazole (PBD), oxadiazole derivatives, triazole derivatives, and triazines Derivatives, phenylquinoxalines, aluminum quinolinol complexes (eg, Alq ₃ ), and the like can be used. As a material for the electron injection layer, an aluminum quinolinol complex doped with an alkali metal or an alkaline earth metal can be used in addition to the material for the electron transport layer.

  As a material for the hole transport layer, TPD, N, N′-bis (1-naphthyl) -N, N′-diphenylbiphenylamine (α-NPD), 4,4 ′, 4 ″ -tris (N-3) Known materials including triarylamine-based materials such as -tolyl-N-phenylamino) triphenylamine (m-MTDATA) can be used as the material for the hole injection layer, such as phthalocyanines (copper phthalocyanine, etc.) Alternatively, indanthrene compounds can be used.

  The reflective electrode 33 is preferably formed using a highly reflective metal, amorphous alloy, or microcrystalline alloy. High reflectivity metals include Al, Ag, Mo, W, Ni, Cr, and the like. High reflectivity amorphous alloys include NiP, NiB, CrP, CrB, and the like. The highly reflective microcrystalline alloy includes NiAl and the like. The reflective electrode 33 may be used as a cathode or an anode. When the reflective electrode 33 is used as a cathode, the above-described cathode buffer layer may be provided at the interface between the reflective electrode 33 and the organic EL layer 32 to improve the efficiency of electron injection into the organic EL layer 32. Alternatively, when the reflective electrode 33 is used as a cathode, an alkali metal such as lithium, sodium, or potassium, which is a material having a low work function, calcium, magnesium, or the like, which is a material having a low work function compared to the above-described high reflectivity metal, amorphous alloy, or microcrystalline alloy Further, an alkaline earth metal such as strontium can be added and alloyed to improve electron injection efficiency. When the reflective electrode 33 is used as the anode, the conductive transparent metal oxide layer described above is provided at the interface between the reflective electrode 33 and the organic EL layer 32 to improve the efficiency of hole injection into the organic EL layer 32. May be.

  The reflective electrode 33 can be formed using any means known in the art such as vapor deposition (resistance heating or electron beam heating), sputtering, ion plating, laser ablation, etc., depending on the material used. . As will be described later, when a reflective electrode 33 composed of a plurality of partial electrodes is required, the reflective electrode 33 composed of a plurality of partial electrodes may be formed using a mask giving a desired shape.

  1A to 1D, in order to form a plurality of independent light emitting portions in the organic EL element 30 (ac), each of the pair of electrodes is formed from a plurality of parallel striped portions. In the example, the stripes forming one electrode and the stripes forming the other electrode intersect with each other (preferably orthogonally). Therefore, these organic EL elements can perform matrix driving, that is, when a voltage is applied to a specific stripe on one electrode and a specific stripe on the other electrode, The organic EL layer 32 emits light. Alternatively, one electrode may be a uniform flat electrode having no stripe pattern, and the other electrode may be patterned into a plurality of partial electrodes corresponding to each light emitting portion. In that case, a plurality of switching elements corresponding to each light emitting portion are provided and connected to the partial electrodes corresponding to each light emitting portion in a one-to-one manner, so that so-called active matrix driving can be performed. Alternatively, when an organic EL device that emits light uniformly over the entire surface is desired, each of the pair of electrodes can be a uniform planar electrode.

The reflective layer 40 uses the above-described highly reflective metals (Al, Ag, Mo, W, Ni, Cr, etc.), amorphous alloys (NiP, NiB, CrP, CrB, etc.), and microcrystalline alloys (NiAl, etc.). It is preferable to be formed. Since the color conversion film 20 in the present invention is a thin film, a short circuit may be caused between the lower electrodes (between 31a) or between the upper electrodes (between 31b) via the reflective layer 40. In order to prevent this, an insulating layer may be provided between the reflective layer 40 and the color conversion film 20 or between the color conversion film 20 and the electrodes (between the lower electrode 31a or the upper electrode 31b). The insulating layer is formed using a transparent insulating inorganic material such as TiO ₂ , ZrO ₂ , AlO _x , AlN, SiN _x having a refractive index close to that of the color conversion film 20 (preferably about 1.5 to 2.0). be able to.

  In the multicolor light-emitting organic EL device of the present invention, the EL light in the color conversion layer 20 is changed by changing the type of the first dye in the color conversion layer 20 or adjusting the film thickness of the color conversion layer 20. The amount of absorbed light can be adjusted. Further, the amount of PL light emitted from the color conversion layer 20 can be adjusted by adjusting the concentration of the second dye in the color conversion layer 20. In addition to the adjustment of the light absorption amount of EL light and the light emission amount of PL light by these methods, the arrangement of the color conversion layer 20 as shown in FIGS. The multicolor light-emitting organic EL device can emit light of any hue including white light.

  Further, regarding a series of processes of absorption by the first dye, energy transfer from the first dye to the second dye, and light emission from the second dye, the efficiency in each process is constant. That is, the amount of radiation from the second dye changes in proportion to the intensity of the EL light. Therefore, even if the intensity of EL light from the light emitting layer changes with a change in driving voltage or energization time, the multicolor light emitting organic EL device of the present invention follows the change and emits PL light. Since the intensity also changes, it is possible to stably emit light having a desired hue over a long period of time.

  The multicolor light-emitting organic EL device of the present invention is used as a surface light source (backlight) for forming a display (monochrome or multicolor using a color filter in combination) by integrally forming a pair of electrodes. be able to. Alternatively, as described above, a pair of electrodes can be formed so as to be capable of matrix driving, and can be used as a monochrome display or a multi-color display using a color filter together.

[Color conversion film]
Example 1
As the transparent glass substrate, 1737 glass made by Corning, which was washed with pure water and dried and was 50 × 50 × 0.7 mm was used. The transparent glass substrate was conveyed into the vapor deposition apparatus, and a color conversion film composed of coumarin 6 and DCM-2 was produced. A color conversion film having a thickness of 200 nm was prepared by co-evaporation in which coumarin 6 and DCM-2 were heated in separate crucibles in the vapor deposition apparatus. At this time, the heating temperature of each crucible was controlled so that the deposition rate of coumarin 6 was 0.3 nm / s and the deposition rate of DCM-2 was 0.005 nm / s. The color conversion film of this example contained 2 mol% of DCM-2 based on the total number of constituent molecules of the color conversion film (in this case, the number of moles of all dyes) (coumarin 6: mole of DCM-2). The ratio is 49: 1).

(Comparative Example 1)
This comparative example provides a color conversion film in which the ratio between the first dye and the second dye is outside the scope of the present invention. A color conversion film was produced in the same manner as in Example 1 except that the deposition rate of DCM-2 was changed to 0.087 nm / s. The obtained color conversion film contained 25 mol% of DCM-2 based on the total number of constituent molecules of the color conversion film (the molar ratio of coumarin 6: DCM-2 was 3: 1).

(Comparative Example 2)
This comparative example provides a color conversion film in which a first dye and a second dye are dispersed in a transparent medium. As a transparent medium, m-MTDATA was used. A 200 nm thick color conversion film was produced by ternary co-evaporation in which m-MTDATA, coumarin 6 and DCM-2 were heated in separate crucibles in a vapor deposition apparatus. At this time, m = MTDATA is deposited at a rate of 0.3 nm / s, Coumarin 6 is deposited at a rate of 0.007 nm / s, and DCM-2 is deposited at a rate of 0.006 nm / s. The heating temperature was controlled. The color conversion film of this example contained 5 mol% of coumarin 6 and 5 mol% of DCM-2 based on the total number of constituent molecules of the color conversion film (m-MTDATA: coumarin 6: mol of DCM-2). The ratio is 18: 1: 1).

(Evaluation)
A photoluminescence (PL) spectrum was measured when the color conversion films prepared in Example 1 and Comparative Examples 1 and 2 were irradiated with monochromatic light having a constant intensity (wavelength 480 nm). The obtained spectrum is shown in FIG. In FIG. 2, the spectra of Comparative Examples 1 and 2 show the emission intensity axis (vertical axis) enlarged 10 times.

  As is clear from FIG. 2, the PL intensity of the color conversion film of Example 1 is one digit or more stronger than Comparative Examples 1 and 2 at the peak. Even if the color conversion film of Example 1 is a thin film having a thickness of 200 nm, it has a practical color conversion ability. On the other hand, regarding the color conversion film of Comparative Example 1, it is considered that sufficient PL intensity could not be obtained because the concentration of DCM-2 in the color conversion film was high and concentration quenching occurred. Furthermore, in Comparative Example 2, it was considered that the concentration of coumarin 6 was lowered and the absorbance was decreased because of being dispersed in a transparent medium, resulting in insufficient PL intensity.

  In these examples, the peak wavelength of the PL spectrum is different because the concentration of DCM-2 is different in each color conversion film. When the dye concentration changes, the interaction between the same dyes that causes concentration quenching and / or the local electric field in the vicinity of the dye changes, and the energy difference between the ground state and the excited state of the dye molecule changes. Changes.

  From the above, the color conversion film of Example 1 that is within the scope of the present invention has a low concentration of the second dye dispersed in the first dye, thereby suppressing the concentration quenching and reducing the necessary incident light. It can be seen that it has practical performance by realizing absorbance and color conversion ability.

[Organic EL device]
(Example 2)
In this example, a top emission type device shown in FIG. 1B is manufactured.

  As the transparent glass substrate, 1737 glass made by Corning, which was washed with pure water and dried and was 50 × 50 × 0.7 mm was used. The transparent glass substrate was transferred into a sputtering apparatus, and a 200 nm thick CrB film was formed by DC magnetron sputtering. The film-formed substrate was taken out from the sputtering apparatus, and four striped electrodes having a line width of 2 mm were formed at intervals of 2 mm using a photolithography method to obtain a reflective electrode. In patterning by the photolithography method, a commercially available photoresist AZ-1500 (AZ Electronic Materials Co., Ltd.) and a commercially available etching solution Cr-01N (Kanto Chemical Co., Inc.) were used.

  The substrate on which the reflective electrode was formed was transported into a vacuum deposition apparatus. First, a mask having a stripe-shaped opening having a width of 2 mm was provided only on the reflective electrode, which was an area of 25 × 25 mm at the center of the substrate. Then, 1.5 nm of Li was deposited on the interface with the reflective electrode through the mask to obtain a cathode buffer layer.

Next, without breaking the vacuum, the mask was replaced with a mask having an opening in an area of 25 × 25 mm at the center of the substrate. Through the mask, four layers of an electron transport layer / a light emitting layer / a hole transport layer / a hole injection layer were sequentially deposited to obtain an organic EL layer. Each layer is deposited at a deposition rate of 0.1 nm / s, tris (8-hydroxyquinolinato) aluminum (Alq ₃ ) with a thickness of 20 nm as an electron transport layer, and 4,4′- with a thickness of 30 nm as a light emitting layer. Bis (2,2′-diphenylvinyl) biphenyl (DPVBi), 4,4′-bis [N- (1-naphthyl) -N-phenylamino] biphenyl (α-NPD) having a thickness of 10 nm as a hole transport layer As the hole injection layer, copper phthalocyanine (CuPc) having a film thickness of 100 nm was used.

  Furthermore, the substrate on which the organic EL layer was formed was moved to the counter sputtering apparatus without breaking the vacuum. Then, a mask in which stripe-shaped openings having a width of 2 mm perpendicular to the reflective electrode are arranged at intervals of 2 mm was disposed. Through the mask, indium-tin oxide (ITO) with a thickness of 200 nm was deposited to obtain a transparent electrode.

  Next, the substrate on which the reflective electrode was formed was conveyed into a vacuum deposition apparatus. First, a mask having a stripe-shaped opening having a width of 2 mm was provided only on the reflective electrode, which was an area of 25 × 25 mm at the center of the substrate. Then, co-evaporation was performed through the mask under the same conditions as in Example 1 to produce a color conversion film having a thickness of 200 nm. At this time, the heating temperature of each crucible was controlled so that the deposition rate of coumarin 6 was 0.3 nm / s and the deposition rate of DCM-2 was 0.005 nm / s. The color conversion film of this example contained 2 mol% of DCM-2 based on the total number of constituent molecules of the color conversion film.

  Finally, the substrate on which the color conversion film was formed was taken out into a dry atmosphere (water concentration 1 ppm or less, oxygen concentration 1 ppm or less). A 40 × 40 × 0.7 mm sealing glass substrate in which an ultraviolet curable adhesive is applied to a region having a width of 3 mm on each side is bonded to the substrate, and the structure below the color conversion film is sealed. A color light emitting organic EL device was obtained.

When a current was passed through the obtained multicolor light-emitting organic EL device at a current density of 0.3 A / cm ² , (x, y) = (0.30, 0.29) in CIE chromaticity coordinates. Emitted white light. From this, it can be seen that the 200 nm-thick color conversion film of this example absorbs part of the blue-green light emitted from the light emitting layer and emits red light with sufficient intensity.

Subsequently, the continuous lighting test by the constant current drive which fixed the current density to 0.3 A / cm < ² > was done with respect to the obtained multicolor light emission organic EL device. In the organic EL device of this example, no change in hue with the passage of driving time was observed over 100 hours of continuous driving. Therefore, it can be seen that the organic EL device of this example emits very stable white light.

It is a figure which shows the structural example of the multicolor light emission organic EL device of this invention, (a)-(d) is a figure which shows each structural example. 3 is a graph showing PL spectra of Example 1, Comparative Example 1 and Comparative Example 2.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Transparent substrate 11 Substrate 20 Color conversion film 30 (ac) Organic EL element 31 (a, b) Transparent electrode 32 Organic EL layer 33 Reflective electrode 40 Reflective layer

Claims (9)

  A color conversion film having a film thickness of 2 μm or less including a first dye and a second dye: the first dye absorbs incident light to the color conversion film and transfers its energy to the second dye A second dye is a dye that receives the energy from the first dye and emits light; and the first dye is present in the color conversion film in an amount capable of sufficiently absorbing the incident light. A color conversion film characterized in that the second dye is present in an amount of 10 mol% or less based on the total number of molecules constituting the color conversion film;   The color conversion film according to claim 1, wherein the second dye is present in an amount of 0.1 to 5 mol% based on the total number of constituent molecules of the color conversion film.   The color conversion film according to claim 1, wherein the first dye is present in an amount of 50 to 99.99 mol% based on the total number of constituent molecules of the color conversion film.   The color conversion film according to claim 1, wherein the color conversion film is formed by a vapor deposition method.   A multicolor light emitting organic EL device having a pair of electrodes, at least one of which is a transparent electrode, an organic EL layer sandwiched between the pair of electrodes, and a color conversion film, wherein the color conversion film is a first dye The color conversion film has a thickness of 2 μm or less; the first dye absorbs light incident on the color conversion film and transfers the energy to the second dye. A second dye is a dye that receives the energy from the first dye and emits light; the first dye is present in the color conversion film in an amount capable of sufficiently absorbing the incident light; The multicolor light-emitting organic EL device, wherein the dye is present in an amount of 10 mol% or less based on the total number of molecules constituting the color conversion film.   The multicolor light-emitting organic EL device according to claim 5, wherein the second dye is present in an amount of 0.1 to 5 mol% based on the total number of molecules constituting the color conversion film.   The multicolor light-emitting organic EL device according to claim 5, wherein the first dye is present in an amount of 50 to 99.99 mol% based on the total number of molecules constituting the color conversion film.   The multicolor light-emitting organic EL device according to claim 5, wherein the color conversion film is formed by a vapor deposition method. The multicolor light-emitting organic EL device according to claim 5, wherein the color conversion film and the transparent electrode are disposed in contact with each other.

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