JP2009181752A - Organic el device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic EL device for illumination having excellent luminous efficiency and good surface uniformity. <P>SOLUTION: The organic EL device has a substrate, at least one series-connected organic EL element group, and at least one color conversion layer. The series-connected organic EL element group is constructed of a plurality of organic EL elements having a first electrode, an organic EL layer and a second electrode in this order from the substrate side. At least one of the first electrode and the second electrode is a transparent electrode, and the respective first electrode of the organic EL element to constitute the series-connected organic EL element is connected electrically to the second electrode of the adjoining organic EL element. At least one color conversion layer extends to at least a part of the region between the organic EL elements. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a structure of an organic EL device, and more particularly to a structure of an organic EL device used as a light source for illumination.

  In recent years, there has been an increasing interest in global warming issues. Various energy savings are being sought to reduce carbon dioxide emissions and reduce global warming. Among them, one of the important points is to increase the efficiency of energy use of lighting fixtures. Currently, incandescent lamps and fluorescent lamps that are widely used are saturated from the standpoint of luminous efficiency, and research and development of lighting fixtures with higher luminous efficiency are being actively conducted. In particular, regarding organic EL elements, as future technologies, luminous efficiency of 100 to 200 lm / W and lifetime of 60,000 hours are expected, incandescent lamps of 15 lm / W, 1,000 to 2,000 hours, and fluorescent lamps It is considered that the lighting can be friendly to the global environment for 50 to 100 lm / W for 10,000 hours. The subject of future research and development is to realize the above-mentioned performance and reduce the manufacturing cost.

  FIG. 1 is a diagram showing a light source using a light emitting diode (LED) that is expected to be developed as a next-generation illumination and is being developed (see Non-Patent Document 1). The light source in FIG. 1 is obtained by flip-chip mounting a plurality of LEDs 230 on a metal pattern 220 on a ceramic substrate 210 provided with a heat sink 240 on the opposite surface, and providing a fluorescent resin layer 250 thereon. Emits light. Although uneven emission intensity is reduced by high density arrangement of a plurality of LEDs, there is a limit to high density arrangement. In addition, since it is necessary to mount a plurality of LEDs, there are problems in that the assembling cost increases and it is difficult to manufacture a surface-emitting light source having a large area.

  Regarding the above problems, when an organic EL element is used, there is an advantage that a plurality of organic EL elements can be easily formed on the same substrate. Therefore, it is considered that the cost for mounting the element can be reduced as compared with the case where the LED described above is used, and a lower cost surface emitting light source device can be realized. However, when producing a surface emitting light source having a large area, short circuit defects are likely to occur. If there is a short-circuit defect, the current concentrates on the defect and the light emission is significantly degraded. In order to avoid this problem, a large-area surface-emitting light source in which a plurality of organic EL elements are connected in series has been proposed (see Patent Document 1). By adopting a series connection structure, even if a short-circuit defect occurs in some organic EL elements, it is possible to flow current to other organic EL elements, so that deterioration of light emission as a whole light source can be suppressed. .

JP 2004-234868 A Ogata et al., 98. High luminous flux and compact white LED light source, Proceedings of the 40th National Congress of the Illuminating Society of Japan (August 23 and 24, 2007), p183

  However, in a surface-emitting light source using a plurality of organic EL elements, performance variations inevitably occur between the organic EL elements, and light emission luminance variations and color unevenness occur on the light-emitting surface of the light source. There is a problem that lighting is difficult. In addition, a gap in which no light is emitted is inevitably generated between two adjacent organic EL elements, resulting in a problem that luminance variation in a plane increases.

  In order to produce a high-efficiency, low-cost illumination light source using an organic EL element, it is necessary to consider the entire configuration including the organic EL element, a power source, and a control circuit. The organic EL element is a low voltage element that usually emits light at about 5 to 10V. Therefore, it is important to provide a configuration that allows an organic EL element driven at a low voltage to emit light with high efficiency.

  A normal household power supply is an AC voltage of 100V or 200V. If this power supply can be used in a state where the degree of step-down is small, there is little power conversion loss. Therefore, by connecting organic EL elements that emit light at about 5 to 10 V electrically, for example, 20 series or 10 series, light is emitted from the power from the outlet, and there is almost no power conversion loss. Obtainable. It would be advantageous if this could be manufactured inexpensively.

  In order to solve the above problems, the present invention is an organic EL device having a substrate, at least one series-connected organic EL element group, and at least one color conversion layer, wherein the series-connected organic EL element group includes: It is comprised from the some organic EL element which has a 1st electrode, an organic EL layer, and a 2nd electrode in this order from the said substrate side, At least one of a 1st electrode and a 2nd electrode is a transparent electrode, The said series connection organic EL element Each first electrode of the organic EL elements constituting the group is electrically connected to a second electrode of an adjacent organic EL element, and the at least one color conversion layer is at least one of the regions between the organic EL elements. Provided is an organic EL device characterized by extending to a portion.

  In the present invention, at least one color conversion layer may have a thickness of 0.5 μm or more. At least one color conversion layer is disposed between the substrate and the first electrode, on the surface of the substrate opposite to the surface on which the series-connected organic EL element group is disposed, and on the upper surface of the second electrode. May be. At least one color conversion layer is provided on the surface opposite to the first color conversion layer provided on the upper surface of the second electrode and between the substrate and the first electrode or to the group of organic EL elements connected in series on the substrate. And a second color conversion layer disposed thereon. An additional color conversion layer may be disposed in a region between each organic EL element. The additional color conversion layer may be disposed in a region between the organic EL elements on the first color conversion layer provided on the upper surface of the second electrode.

  The substrate can be a transparent substrate. The first electrode may be a transparent electrode. Both the first electrode and the second electrode may be transparent electrodes. Alternatively, the first electrode can be a reflective electrode and the second electrode can be a transparent electrode.

  The organic EL device of the present invention can further have a reflective layer. The reflective layer may be disposed on the upper surface of the second electrode and between the substrate and the first electrode. When the reflective layer is disposed on the upper surface of the second electrode, a transparent passivation layer may be further provided between the second electrode and the reflective layer.

  By combining a series-connected organic EL element group and a color conversion media (color conversion media: CCM), a light source having excellent luminous efficiency and low cost can be realized. In addition, by forming the color conversion layer on the entire device including the gap between the organic EL elements constituting the series-connected organic EL element group, the color purity of the light and the light conversion layer can be compared with those having no color conversion layer. An organic EL device excellent in brightness uniformity can be obtained. Uniformity can be designed by setting the film thickness of the color conversion layer.

  Hereinafter, the present invention will be described in detail with reference to the drawings.

  The organic EL device of the present invention includes a substrate 10 and a plurality of organic EL elements arranged in a plane having at least a first electrode 20, an organic EL layer 30, and a second electrode 40 in this order from the substrate 10 side. At least one series-connected organic EL element group and at least one color conversion layer 50 are included. At least one color conversion layer 50 extends in at least a part of a region between adjacent organic EL elements. In the plurality of organic EL elements constituting at least one series-connected organic EL element group, the first electrode 20 and the second electrode 40 of the adjacent organic EL element are electrically connected. Here, at least one of the first electrode 20 and the second electrode 40 is a transparent electrode (20t or 40t).

  FIG. 2 shows one embodiment of the organic EL device of the present invention. The organic EL device of this embodiment includes a substrate 10, a color conversion layer 50, a first passivation layer 62, a transparent first electrode 20t, an organic EL layer 30, a reflective second electrode 40r, and a second passivation layer 64 in this order. In the present embodiment, the substrate 10 is a transparent substrate.

  In the present embodiment, one end of the transparent first electrode 20t of each organic EL element (an end facing the organic EL element connected in series) is covered with the organic EL layer 30, and reflected from the transparent first electrode 20t. A short circuit with the second electrode 40r is prevented. The reflective second electrode 40r is continuously formed from the organic EL layer 30 to the transparent first electrode 20t of the adjacent organic EL element. By adopting such a configuration, the organic EL elements composed of the transparent first electrode 20t, the organic EL layer 30, and the reflective second electrode 40r are connected in series to form a series-connected organic EL element group. In the present embodiment, a plurality of series-connected organic EL element groups may be formed.

  In this embodiment, the voltage applied to each organic EL element is controllable by changing the number of the organic EL elements which comprise a series connection organic EL element group. For example, when a voltage of 100 to 120 V is applied to a series-connected organic EL element group composed of 20 organic EL elements, the voltage applied to each organic EL element is 5 to 6 V. Thus, for example, a home AC power source or the like can be used for driving the device of the present embodiment by converting it into DC by a method with high power conversion efficiency that does not require a voltage drop.

  Further, in the series-connected organic EL element group, even if a short-circuit defect occurs in one organic EL element, other organic EL elements in which the short-circuit defect in the series-connected organic EL element group does not continue to emit light. Can do. This feature is very important in the mass production of the organic EL device of this embodiment.

  Further, the color temperature of the emitted light can be arbitrarily set by changing the material, configuration and design of the organic EL layer 30 and the material and configuration of the color conversion layer 50. Although FIG. 2 shows the case where the single color conversion layer 50 is provided, the organic EL device of the present embodiment may use a laminate of a plurality of color conversion layers (for example, a red conversion layer and a green conversion layer). Good.

  Furthermore, the effective light emitting area of each organic EL element, that is, the width x of the area of the organic EL layer 30 sandwiched between the transparent first electrode 20t and the reflective second electrode 40r is sufficiently larger than the distance y between the light emitting areas. By doing so, light emission with high in-plane uniformity can be obtained. For example, if semiconductor manufacturing technology is utilized, it is not so difficult to set the distance y between light emitting regions to 0.1 mm or less. Therefore, for example, in the organic EL device of the present embodiment, light having high in-plane uniformity can be obtained by setting the width x of the effective light emitting region to 2 mm or more. By disposing a color conversion layer also in a region between each organic EL element, the light emitted from the organic EL element can be effectively color-converted to improve the in-plane uniformity of light emission. In the present specification, “regions between organic EL elements” includes regions between adjacent organic EL elements, and regions above and below them. In addition to this effect, the in-plane uniformity of light emission can be further enhanced by appropriately setting the film thickness z of the color conversion layer 50. For example, by setting the film thickness z of the color conversion layer 50 to 0.5 μm or more, between the effective light emitting region (indicated by the width x) and the region between the light emitting regions (indicated by the distance y) of the organic EL element. Differences in brightness and hue can be reduced.

  The first passivation layer 62 and the second passivation layer 64 in this embodiment are optional layers. However, it is a desirable layer to provide in order to prevent the organic EL layer 30 from being deteriorated by moisture and oxygen. However, it is not necessary to consider the damage of the color conversion layer 50 when the substrate 10 is formed using a material having low moisture and oxygen permeability such as glass, and a layer is formed thereon, and the color conversion layer When 50 does not include moisture and oxygen, the first passivation layer 62 can be omitted.

  FIG. 3 shows a modification of the organic EL device of the above embodiment. In this modification, the transparent first electrode 20t, the organic EL layer 30, the reflective second electrode 40r, and the second passivation layer 64 are laminated in this order on one surface of the substrate 10, and the color is formed on the other surface. The conversion layer 50 and the first passivation layer 62 are stacked in this order.

  FIG. 4A shows a modification of the organic EL device of the above embodiment. In this modification, the reflective first electrode 20r, the organic EL layer 30, the transparent second electrode 40t, the passivation layer 60, and the color conversion layer 50 are laminated on the substrate 10 in this order. By adopting such a configuration, a light source capable of extracting light without going through the substrate 10 can be obtained.

  FIG. 4B shows a further modification of the modification shown in FIG. In this modified example, an additional color conversion layer is added to the step between the regions of the organic EL elements, specifically, the step (dent) on the surface of the color conversion layer 50 caused by the shape of the series-connected organic EL element group. 52 is provided to flatten the surface of the color conversion layer. By adopting a structure in which the surface of the color conversion layer is flattened, highly uniform light can be obtained using a color conversion layer having a thinner thickness.

  FIG. 5 shows another embodiment of the organic EL device of the present invention. The organic EL device of the present embodiment includes the transparent first electrode 20t, the organic EL layer 30, the transparent second electrode 40t, the passivation layer 60, and the color conversion layer 50 in this order on one surface of the substrate 10, and the other A second color conversion layer 54 is included on the surface. In the present embodiment, the substrate 10 is a transparent substrate. By adopting such a configuration, a light source that extracts light from both sides of the substrate 10 can be obtained. By using different components for the color conversion layer 50 and the second color conversion layer 54, different light can be extracted from both sides.

  FIG. 6 shows another embodiment of the organic EL device of the present invention. The organic EL device according to the present embodiment further includes a reflective layer 70 on the second passivation layer 64 in the organic EL device according to the embodiment of the present invention shown in FIG. By taking such a structure, the luminous efficiency of the organic EL device can be improved and the luminance can be increased. The second passivation layer 64 can be omitted when the reflective layer 70 is not conductive. However, when the reflective layer 70 is conductive, the second passivation layer 64 is an indispensable layer for avoiding a short circuit of the reflective second electrode 40r. .

  FIG. 7A shows a modification of the organic EL device of the above embodiment. In this modification, the reflective layer 70, the first passivation layer 62, the reflective first electrode 20r, the organic EL layer 30, the transparent second electrode 40t, the second passivation layer 64, and the color conversion layer 50 are formed on the substrate 10. They are stacked in order. The first passivation layer 62 can be omitted when the reflective layer 70 is not conductive. However, when the reflective layer 70 is conductive, the first passivation layer 62 is an essential layer for avoiding a short circuit of the reflective first electrode 20r. .

  FIG. 7B shows a further modification of the modification shown in FIG. In this modified example, as in the modified example shown in FIG. 4B, an additional step (dent) on the surface of the color conversion layer 50 caused by the shape of the series-connected organic EL element group is added. A color conversion layer 52 is provided to flatten the surface of the color conversion layer.

  FIG. 8 shows one embodiment of the organic EL device of the present invention. FIG. 8A shows a schematic diagram of a plurality of series-connected organic EL element groups 100 arranged on the substrate 10. FIG. 8B is an enlarged view of the region IXb. The series-connected organic EL element group 100 is configured by arranging a plurality of organic EL elements each having the first electrode 20, the organic EL layer 30, and the second electrode 40 in this order on the substrate 10 in this order from the substrate 10 side. The In order to realize the in-plane uniformity of light emission of the organic EL device, it is desirable that the areas of the effective light emitting regions of the organic EL elements constituting the series-connected organic EL element group 100 are the same. In the present embodiment, the organic EL elements constituting the series-connected organic EL element group are arranged not in a straight line but in a curved line. In this way, two advantages are found. One is that the light source pattern can be freely designed to some extent. The other one is that it is difficult to see the wrinkles of the arrangement by designing the intervals between the organic EL elements with a random pattern. It seems that it gives a great degree of freedom in creating a space suitable for the place of use, atmosphere, and light source conditions. In FIG. 8B, for the sake of simplicity, only the first electrode, the organic EL layer, and the second electrode are shown, and the display of the color conversion layer 50 and other layers is omitted. In this embodiment, it will be understood that the color conversion layer 50 and other layers are provided as shown in FIGS.

  FIG. 9 is a circuit diagram showing one embodiment of the organic EL device of the present invention. Each organic EL element 102 (a ... z) is connected in series, and the one series connection organic EL element group 100 is comprised. The transistor 110 is connected to the end of the series-connected organic EL element group 100, and thereby the current flowing through the organic EL element is controlled. The current is controlled using a control LSI (not shown) so that the average current of each organic EL element becomes the same based on data of a current sensor provided in the transistor 110. The plurality of series-connected organic EL element groups 100 are electrically connected in parallel by buses (buses) 210 and 220. By doing so, the current value of each column can be optimized in consideration of the data of the previous characteristic test, and the color degree can be adjusted appropriately. Further, even when a short-circuited organic EL element is mixed in the series-connected organic EL element group, by adjusting the gate voltage of the transistor 110, it becomes the same as the other series-connected organic EL element group columns. It is possible to control the current.

  Hereinafter, each layer of the organic EL device of the present invention will be described.

Substrate 10
As the substrate 10 of the organic EL device of the present invention, various substrates having a smooth surface known in the art can be used. For example, a transparent substrate such as a glass substrate can be used. The transparent substrate is excellent in light transmittance (having a transmittance of 80% or more in a wavelength range of 400 to 700 nm), and is used for forming a layer to be laminated such as a transparent electrode, an organic EL layer, a reflective electrode (solvent , Temperature, etc.) and excellent in dimensional stability. Examples of transparent substrates include glass substrates, rigid resins made of various plastics such as polyolefins, acrylic resins (including polymethylmethacrylate), polyester resins (including polyethylene terephthalate), polycarbonate resins, and polyimide resins. A substrate, a flexible film, etc. are mentioned.

Organic EL Element The “organic EL element” of the organic EL device of the present invention is configured to have at least the first electrode 20, the organic EL layer 30, and the second electrode 40 in this order from the substrate 10 side. Are arranged in a plane.

(First electrode 20)
The first electrode 20 of the organic EL element of the present invention is an electrode that functions as either an anode or a cathode. The first electrode 20 may be either the transparent first electrode 20t or the reflective first electrode 20r.

(Second electrode 40)
The second electrode 40 of the organic EL element of the present invention is an electrode that functions as either an anode or a cathode. The second electrode 40 may be a reflective second electrode 40r or a transparent second electrode 40t. However, the first electrode 20 and the second electrode 40 are not simultaneously reflective electrodes, and either one is a transparent electrode.

((Transparent electrodes 20t, 40t))
The transparent electrode 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 material for forming the transparent electrode is ITO (In-Sn oxide), IZO (In-Zn oxide), Al-Sn oxide (ATO), NESA film, Sn oxide, In oxide, Zn oxide Materials, Zn—Al oxide, Zn—Ga oxide, and conductive transparent metal oxides in which dopants such as F and Sb are added to these oxides. The transparent electrode usually has a thickness of 50 nm or more, preferably 50 nm to 1 μm, more preferably 100 to 300 nm. Usually, the transparent electrode is formed by depositing a conductive transparent metal oxide using a sputtering method. Here, in the case of forming a transparent electrode made of a partial electrode having a rectangular shape or other desired shape, it may be formed by a deposition method using a mask giving a desired shape, or before the organic EL layer is formed. If possible, patterning may be performed using photolithography after the entire surface is deposited.

((Reflective electrodes 20r, 40r))
As a material for forming the reflective electrode, a highly reflective metal, amorphous alloy, or microcrystalline alloy is preferably used. 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 usually has a thickness of 50 nm or more, preferably 50 nm to 1 μm, more preferably 100 to 300 nm. When the reflective electrode is used as a cathode, an alkali metal such as lithium, sodium, and potassium, which is a material having a low work function, calcium, magnesium, Electron injection efficiency can be improved by adding an alkaline earth metal such as strontium to form an alloy. When the reflective electrode is used as an anode, the conductive transparent metal oxide layer described above is provided at the interface between the reflective electrode and the organic EL layer 30 to improve the efficiency of hole injection into the organic EL layer 30. Also good. Depending on the material forming the reflective electrode, the reflective electrode may be any known in the art such as vapor deposition (resistance heating vapor deposition or electron beam vapor deposition), sputtering, ion plating, laser ablation, etc. It can form using the method of. Here, in the case of forming a reflective electrode composed of a partial electrode having a rectangular shape or other desired shape, it may be formed by a deposition method using a mask giving a desired shape, or before the organic EL layer is formed. If possible, patterning may be performed using photolithography after the entire surface is deposited.

(Organic EL layer 30)
The organic EL layer 30 of the organic EL element of the present invention is a layer for emitting light having a desired wavelength distribution by recombining carriers injected from the first electrode 20 and the second electrode 40. The organic EL layer 30 of the present invention includes at least an organic light emitting layer, and includes a hole transport layer, a hole injection layer, an electron transport layer, and / or an electron injection layer as necessary.

Specifically, the organic EL layer 30 may have a layer structure as described below. The anode and the cathode are either the first electrode 20 or the second electrode 40. Each layer included in the organic EL layer 30 is formed with a film thickness sufficient to realize desired characteristics in each layer. Each of these layers can be formed using any method known in the art such as vapor deposition.
(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 injection layer / hole transport layer / organic light emitting layer / electron injection layer / cathode
(6) Anode / hole injection layer / organic light emitting layer / electron transport layer / electron injection layer / cathode
(7) Anode / hole injection layer / hole transport layer / organic light emitting layer / electron transport layer / electron injection layer / cathode

The organic EL layer can be formed using any known material. As a material of the organic light emitting layer, in order to obtain light emission from blue to blue green, for example, a fluorescent whitening agent such as benzothiazole, benzimidazole, benzoxazole, porphyrin compound, condensed aromatic ring compound, ring assembly Compounds, metal complexes (such as aluminum complexes such as tris (8-hydroxyquinoline) aluminum complex (Alq ₃ )), metal chelated oxonium compounds, styrylbenzene compounds (4,4′-bis (diphenylvinyl) biphenyl (DPVBi) Etc.), aromatic dimethylidin compounds and the like are preferably used. Or you may form the organic light emitting layer which emits the light of the desired wavelength range containing a blue component and a green component by adding a dopant to a host compound. If necessary, the light emission color of the organic light emitting layer may be white. In that case, a known red dopant is additionally used.

Passivation layers 60, 62, 64
The passivation layer is a layer having high transparency in the visible region (transmittance of 50% or more in the range of 400 to 700 nm), a Tg of 100 ° C. or more, and a surface hardness of 2H or more in pencil hardness. When provided at a position in contact with either the first electrode 20 or the second electrode 40, the passivation layer is required to be insulative. The material of the passivation layer is, for example, an imide-modified silicone resin, an inorganic metal compound (TiO, Al ₂ O ₃ , SiO ₂ or the like) dispersed in acrylic, polyimide, silicon resin, or the like, an ultraviolet curable resin As an epoxy-modified acrylate resin, a resin having a reactive vinyl group of acrylate monomer / oligomer / polymer, a resist resin, an inorganic compound formed by a sol-gel method, a fluorine resin, and the like. As a method for forming a passivation layer using the above-described materials, for example, a conventional method such as a wet method (spin coating method, roll coating method, casting method, etc.) or a sol-gel method can be used. Further, the passivation layer has a barrier property against gas and organic solvent, and has high transparency in the visible range (transmittance of 50% or more in the range of 400 to 700 nm). The passivation layer preferably has a film hardness of 2H or more. You may use the inorganic material which provides. For example, inorganic oxides such as SiOx, SiNx, SiNxOy, AlOx, TiOx, TaOx, ZnOx, and inorganic nitrides can be used. As a method for forming a passivation layer using these inorganic oxides or inorganic nitrides, a conventional method such as a sputtering method, a CVD method, or a vacuum deposition method can be used. The passivation layer described above may be a single layer or a stack of a plurality of layers.

Color conversion layers 50, 52, 54
The color conversion layer of the present invention contains at least one fluorescent material. Fluorescent materials that can be suitably used in the present invention include aluminum chelate dyes such as Alq ₃ (Tris (8-quinolinolato) aluminum complex), 3- (2-benzothiazolyl) -7-diethylaminocoumarin (coumarin 6), 3 -(2-Benzimidazolyl) -7-diethylaminocoumarin (coumarin 7), coumarin dyes such as coumarin 135, and low molecular organic fluorescent dyes such as naphthalimide dyes such as solvent yellow 43 and solvent yellow 44. Further, as the fluorescent material, various polymer light emitting materials represented by polyphenylene, polyarylene, and polyfluorene may be used. Alternatively, the color conversion layer may be formed using a mixture of two fluorescent materials obtained by adding the second fluorescent material to the fluorescent material described above. In this configuration, the above-described fluorescent material absorbs light incident on the color conversion layer, preferably blue to blue-green light emitted from the organic EL element, and the absorbed energy is transferred to the second fluorescent material, whereby the second fluorescence The material emits light of the desired wavelength. The fluorescent material that can be suitably used as the second fluorescent material in the present invention is a quinacridone derivative such as diethylquinacridone (DEQ); 4-dicyanomethylene-2-methyl-6- (p-dimethylaminostyryl) -4H-pyran. Cyanine dyes such as (DCM-1, following formula (I)), DCM-2 (following formula (II)), and DCJTB (following formula (III)); xanthene dyes such as rhodamine B and rhodamine 6G; pyridine 1 Pyridine dyes such as 4,4-difluoro-1,3,5,7-tetraphenyl-4-bora-3a, 4a-diaza-s-indacene (formula (IV) below); lumogen F red; Nile red A low molecular organic fluorescent dye such as (Formula (V) below) is included. Alternatively, various low molecular light emitting materials and various polymer EL light emitting materials can also be applied.

  When using the second fluorescent material, it is important that the second fluorescent material does not cause concentration quenching. This is because the second fluorescent material is a material that emits desired light, and its concentration quenching causes a decrease in the efficiency of color conversion. The upper limit of the concentration of the second fluorescent material in the color conversion layer of the present invention can vary depending on the material used. In general, the preferred concentration of the second fluorescent material in the color conversion layer 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 layer. Is in the range of 0.1 to 5 mol%. By using the second fluorescent material at a concentration within such a range, concentration quenching can be prevented and sufficient converted light intensity can be obtained. The configuration in which the second fluorescent material is added can increase the difference between the absorption peak wavelength of incident light and the emission peak wavelength of color conversion, and is therefore effective when the wavelength shift width is large, such as when converting from blue to red. It is. Furthermore, since the functions are separated, the choice of fluorescent materials can be expanded.

  The color conversion layer of the present invention can be formed using any method known in the art. For example, an evaporation method, an inkjet method, or the like can be used. When the vapor deposition method is used, the color conversion layer can be formed by co-evaporation of the above-described fluorescent material. When the ink jet method is used, first, the above-described fluorescent material is dissolved in an appropriate solvent to form a color conversion layer forming ink. The color conversion layer forming ink may contain an additive for adjusting the viscosity and the like. The color conversion layer can be formed by attaching the electrochromic conversion layer forming ink using an appropriate ink jet device (including a thermal ink jet method and a piezo ink jet method).

  The color conversion layer may be a single layer or a stack of a plurality of layers. The surface of the color conversion layer may be flattened. The flattening may be realized by adding an additional color conversion layer to a step (dent) portion of the color conversion layer by using an ink jet method or the like. The film thickness of the color conversion layer of the present invention is 2 μm or less, preferably 1 μm or less. The film thickness of the color conversion layer of the present invention is preferably 0.3 μm or more, more preferably 0.5 μm or more. By using such a film thickness of the color conversion layer, good luminance variation and chromaticity variation can be obtained in the organic EL device of the present invention.

Reflective layer 70
The reflective layer of the present invention can be formed using any method known in the art. For example, the metal may be laminated by vapor deposition or sputtering. Alternatively, a highly reflective film containing metal may be attached to the passivation layer or the substrate. For the reflective layer, for example, a material such as Ag or Al can be used. The reflective layer has a thickness of 0.1 μm or more.

Example 1
The organic EL device of the present invention was produced according to the following steps (see FIG. 2).
<Example 1-1>
(A) As the substrate 10, a transparent substrate (1737 glass, manufactured by Corning) was prepared.
(B) The color conversion layer 50 was formed on the substrate 10 by vapor deposition. Specifically, the red conversion layer 50R was formed using a mixture of the first fluorescent material: coumarin 6 and the second fluorescent material: DCM-2 (molar ratio was coumarin 6: DCM-2 = 48: 2). The film thickness of the red conversion layer 50R was varied in the range of 0.1 to 2 μm.
(C) On the color conversion layer 50 obtained in the step (b), silicon nitride (SiN) was laminated to a thickness of 100 nm to form the first passivation layer 62. For the lamination, plasma CVD was used (monosilane (SiH ₄ ), ammonia (NH ₃ ), and nitrogen (N ₂ ) were used as source gases). At this time, the substrate temperature was kept at 100 ° C. or lower.
(D) IZO (In-Zn oxide, manufactured by Idemitsu Kosan Co., Ltd.) having a thickness of 200 nm was deposited on the entire surface of the first passivation layer 62 obtained in the step (c) by a sputtering method. Next, a transparent first electrode 20t having a predetermined pattern was formed from the IZO using a photolithographic method. Here, the predetermined pattern is a pattern in which 20 squares of 10 mm square are linearly arranged at intervals of 100 μm.
(E) One end of the transparent first electrode 20t is covered with the organic EL layer 30 and has an opening with a predetermined pattern so as to prevent a short circuit between the first electrode 20 and the second electrode 40 provided later. The transparent first electrode 20t was covered in a pattern using a vapor deposition method using a metal mask to form an organic EL layer 30 having a multilayer structure. The organic EL layer 30 includes a 100 nm thick hole injection layer made of copper phthalocyanine (CuPc), a 20 nm thick hole transport layer made of α-NPD, DPVBi, and rubrene (by volume ratio, DPVBi: rubrene = 95: 5) an organic light emitting layer having a thickness of 20 nm, an electron transport layer having a thickness of 20 nm made of Alq ₃ , and an electron injection layer having a thickness of 0.5 nm made of LiF.
(F) Using a vapor deposition method using a metal mask having an opening with a predetermined pattern, Al is laminated so as to cover the layers below the organic EL layer 30 in a pattern, and a reflective second layer having a thickness of 100 nm. An electrode 40r was obtained. At this time, the reflective second electrodes 40r of the plurality of organic EL elements were continuously formed from the organic EL layer 30 to the transparent first electrodes 20t of the adjacent organic EL elements.
(G) A second passivation layer 64 was formed by stacking silicon nitride (SiN) to a thickness of 100 nm so as to cover the layers below the reflective second electrode 40r entirely. For the lamination, plasma CVD was used (monosilane (SiH ₄ ), ammonia (NH ₃ ), and nitrogen (N ₂ ) were used as source gases). At this time, the substrate temperature was kept at 100 ° C. or lower.

  The organic EL device of the present invention including the series-connected organic EL element group in which the organic EL elements composed of the transparent first electrode 20t, the organic EL layer 30, and the reflective second electrode 40r are connected in series by the above-described steps is obtained. It was. The width x of each effective light emitting area in this organic EL device was 9.7 mm, and the distance y between the light emitting areas was 0.4 mm.

<Example 1-2>
An organic EL device was produced in the same manner as in Example 1-1 except that the green conversion layer 50G was formed instead of the red conversion layer 50R in the step (b). The green conversion layer 50G is formed on the substrate 10 by vapor deposition using a mixture of the first fluorescent material: coumarin 6 and the second fluorescent material: DEQ (molar ratio is coumarin 6: DEQ = 48: 2). did. The film thickness of the green conversion layer 50G was varied in the range of 0.1 to 2 μm.

(Example 2)
The organic EL device of the present invention was produced according to the following steps (see FIG. 4A).
<Example 2-1>
(A) As the substrate 10, a transparent substrate (1737 glass, manufactured by Corning) was prepared.
(B) Al was laminated by using a vapor deposition method using a metal mask having openings with a predetermined pattern to form a reflective first electrode 20r having a thickness of 100 nm. Here, the predetermined pattern is a pattern in which 20 squares of 10 mm square are linearly arranged at intervals of 100 μm.
(C) One end of the reflective first electrode 20r is covered with the organic EL layer 30, and has an opening with a predetermined pattern so as to prevent a short circuit between the first electrode 20 and the second electrode 40 provided later. The reflective first electrode 20r was covered in a pattern using a vapor deposition method using a metal mask to form an organic EL layer 30 having a multilayer structure. The organic EL layer 30 is an electron injection layer made of LiF having a thickness of 0.5 nm, an electron transport layer made of Alq _{3 having a} thickness of 20 nm, DPVBi, and rubrene (by volume ratio, DPVBi: rubrene = 95: 5). It was composed of a 20 nm thick organic light emitting layer, a 20 nm thick hole transport layer made of α-NPD, and a 100 nm thick hole injection layer made of CuPc.
(D) On the organic EL layer 30 obtained in the step (c), IZO (In-Zn oxide, manufactured by Idemitsu Kosan Co., Ltd.) is laminated by a sputtering method using a metal mask having openings with a predetermined pattern. Thus, a transparent second electrode 40t having a predetermined pattern and a film thickness of 200 nm was formed. At this time, the transparent second electrodes 40t of the plurality of organic EL elements were continuously formed from the organic EL layer 30 to the reflective first electrodes 20r of the adjacent organic EL elements.
(E) The passivation layer 60 was formed by laminating silicon nitride (SiN) with a thickness of 100 nm so as to cover the entire layer below the transparent second electrode 40t. For the lamination, plasma CVD was used (monosilane (SiH ₄ ), ammonia (NH ₃ ), and nitrogen (N ₂ ) were used as source gases). At this time, the substrate temperature was kept at 100 ° C. or lower.
(F) The color conversion layer 50 was formed on the passivation layer 60 obtained in the step (e) by a vapor deposition method. Specifically, the red conversion layer 50R was formed using a mixture of the first fluorescent material: coumarin 6 and the second fluorescent material: DCM-2 (molar ratio was coumarin 6: DCM-2 = 48: 2). The film thickness of the red conversion layer 50R was varied in the range of 0.1 to 2 μm.

<Example 2-2>
An organic EL device was produced in the same manner as in Example 2-1, except that the green conversion layer 50G was formed instead of the red conversion layer 50R in the step (f). The green conversion layer 50G is formed on the passivation layer 60 using a mixture of the first fluorescent material: coumarin 6 and the second fluorescent material: DEQ (molar ratio is coumarin 6: DEQ = 48: 2) by vapor deposition. Formed. The film thickness of the green conversion layer 50G was varied in the range of 0.1 to 2 μm.

  The organic EL device of the present invention including the series-connected organic EL element group in which the organic EL elements composed of the reflective first electrode 20r, the organic EL layer 30, and the transparent second electrode 40t are connected in series by the above steps is obtained. It was. The width x of each effective light emitting area in this organic EL device was 9.7 mm, and the distance y between the light emitting areas was 0.4 mm.

(Example 3)
Next to the step (f) for forming the color conversion layer 50, an organic EL device was produced in the same manner as in Example 2-1, except that the step (g) shown below was performed (FIG. 4B). reference).
(G) A film (additional color conversion layer 52) was formed on the step (indentation) portion of the color conversion layer 50 by an inkjet method, and the surface of the color conversion layer 50 was flattened. Specifically, an ink comprising 1000 parts by weight of toluene and 50 parts by weight of a mixture of the first fluorescent material: coumarin 6 and the second fluorescent material: DCM-2 (molar ratio is coumarin 6: DCM-2 = 48: 2). Adjust: Use an inkjet device (UniJet UJ200) in a nitrogen atmosphere to drop ink in a quantity of 60 drops (one drop: about 14 pl) per step (dent) in the red conversion layer 50R using a multi-nozzle. The ink is dried at a vacuum degree of 1.0 × 10 ⁻³ Pa and a temperature of 100 ° C. using a vacuum drying furnace without breaking the nitrogen atmosphere, and the film thickness is 0.2 μm as an additional color conversion layer 52. An additional red color conversion layer 52R (0.4 mm × 10 mm) was formed. The film thickness of the additional red color conversion layer 52R was varied in the range of 0.2 to 0.4 μm by adjusting the conditions (amount and number of drops) of the ink to be dropped.

Example 4
The organic EL device of the present invention was produced according to the following steps (see FIG. 5).
<Example 4-1>
(A) As the substrate 10, a transparent substrate (1737 glass, manufactured by Corning) was prepared.
(B) IZO (In-Zn oxide, manufactured by Idemitsu Kosan Co., Ltd.) is laminated on one surface of the substrate 10 by a sputtering method using a metal mask having openings with a predetermined pattern, and a predetermined pattern is obtained. A transparent first electrode 20t having a thickness of 200 nm was formed. Here, the predetermined pattern is a pattern in which 20 squares of 10 mm square are linearly arranged at intervals of 100 μm.
(C) One end of the transparent first electrode 20t is covered with the organic EL layer 30 and has an opening with a predetermined pattern so as to prevent a short circuit between the first electrode 20 and the second electrode 40 provided later. The transparent first electrode 20t was covered in a pattern using a vapor deposition method using a metal mask to form an organic EL layer 30 having a multilayer structure. The organic EL layer 30 is an electron injection layer made of LiF having a thickness of 0.5 nm, an electron transport layer made of Alq _{3 having a} thickness of 20 nm, DPVBi, and rubrene (by volume ratio, DPVBi: rubrene = 95: 5). It was composed of a 20 nm thick organic light emitting layer, a 20 nm thick hole transport layer made of α-NPD, and a 100 nm thick hole injection layer made of CuPc.
(D) On the organic EL layer 30 obtained in the step (c), IZO (In-Zn oxide, manufactured by Idemitsu Kosan Co., Ltd.) is laminated by a sputtering method using a metal mask having openings with a predetermined pattern. Thus, a transparent second electrode 40t having a predetermined pattern and a film thickness of 200 nm was formed. At this time, the transparent second electrodes 40t of the plurality of organic EL elements were continuously formed from the organic EL layer 30 to the reflective first electrodes 20r of the adjacent organic EL elements.
(E) The passivation layer 60 was formed by laminating silicon nitride (SiN) with a thickness of 100 nm so as to cover the entire layer below the transparent second electrode 40t. For the lamination, plasma CVD was used (monosilane (SiH ₄ ), ammonia (NH ₃ ), and nitrogen (N ₂ ) were used as source gases). At this time, the substrate temperature was kept at 100 ° C. or lower.
(F) The color conversion layer 50 was formed on the passivation layer 60 obtained in the step (e) by a vapor deposition method. Specifically, the red conversion layer 50R was formed using a mixture of the first fluorescent material: coumarin 6 and the second fluorescent material: DCM-2 (molar ratio was coumarin 6: DCM-2 = 48: 2). The film thickness of the red conversion layer 50R was 0.5 μm.
(G) The color conversion layer 54 was formed on the other surface of the substrate 10 by vapor deposition. Specifically, the green conversion layer 54G was formed using a mixture of the first fluorescent material: coumarin 6 and the second fluorescent material: DEQ (molar ratio was coumarin 6: DEQ = 48: 2). The film thickness of the green conversion layer 54G was 0.5 μm.

  The organic EL device of the present invention including the series-connected organic EL element group in which the organic EL elements composed of the transparent first electrode 20t, the organic EL layer 30, and the transparent second electrode 40t are connected in series by the above-described steps is obtained. It was. The width x of each effective light emitting area in this organic EL device was 9.7 mm, and the distance y between the light emitting areas was 0.4 mm.

<Example 4-2>
Example 4-1 except that in step (f), green conversion layer 50G was formed instead of red conversion layer 50R, and in step (g), red conversion layer 54R was formed instead of green conversion layer 54G. Similarly, an organic EL device was produced. The material of the green conversion layer 50G is a mixture of the first fluorescent material: coumarin 6 and the second fluorescent material: DEQ (molar ratio is coumarin 6: DEQ = 48: 2), and the material of the red conversion layer 54R is the first It was a mixture of 1 fluorescent material: coumarin 6 and second fluorescent material: DCM-2 (molar ratio was coumarin 6: DCM-2 = 48: 2).

<Example 4-3>
Next to the step (f) for forming the color conversion layer 50, a step similar to the step (g) shown in Example 3 was performed, and the film thickness of 0.3 μm was obtained in the same manner as in Example 4-1. An organic EL device having an additional red conversion layer 52R was produced.

(Example 5)
Following the step (g), the organic EL device of the present invention was produced in the same manner as in Example 1-1 except that the reflective layer 70 was formed by performing the following step (h) (see FIG. 6). ).
(H) Al was laminated on the second passivation layer 64 obtained in the step (g) by a vapor deposition method to form the reflective layer 70. The thickness of the reflective layer was varied in the range of 0.1 to 0.5 μm.

(Example 6)
An organic EL device of the present invention was produced in the same manner as in Example 3 except that the following steps (x) and (y) were performed in this order between steps (a) and (b). (Refer FIG.7 (b)).
(X) A reflective layer 70 was formed on the substrate 10 by laminating Al by vapor deposition. The thickness of the reflective layer was varied in the range of 0.1 to 0.5 μm.
(Y) On the reflective layer 70 obtained in the step (x), silicon nitride (SiN) was laminated to a thickness of 100 nm to form a passivation layer 62. For the lamination, plasma CVD was used (monosilane (SiH ₄ ), ammonia (NH ₃ ), and nitrogen (N ₂ ) were used as source gases). At this time, the substrate temperature was kept at 100 ° C. or lower.

(Evaluation item)
A voltage of 120 V was applied to the organic EL device of the example, and the following items were evaluated.
(1) Variation in chromaticity:
The spectrum was measured with an Otsuka Electronics multi-channel photo detector (MCPD-3000). Regarding red light emission, chromaticity variation on the entire surface of the organic EL device was evaluated with respect to x = 0.67 and y = 0.33 in the chromaticity diagram (CIE-xy). For green light emission, chromaticity variation on the entire surface of the organic EL device with respect to x = 0.21 and y = 0.71 was evaluated in a chromaticity diagram (CIE-xy). It was confirmed that the collected chromaticity data was within ± 0.02 or ± 0.01 for both x and y.
(2) Luminance and luminance variation:
The luminance was measured with a luminance meter (BM-9) manufactured by Topcon Corporation. The luminance on the entire surface of the organic EL device was evaluated, and variation was obtained from the average value, maximum value, and minimum value.
(3) Conversion efficiency (%):
Using an integrating sphere (manufactured by Spectrometer), count the number of photons emitted from the backlight (organic EL layer before film formation of the color conversion layer), and count the number of photons after film formation of the color conversion layer. The conversion efficiency was evaluated.
(4) Increase in emission luminance (%):
With respect to the light emission luminance of the organic EL device not having the reflective layer 70, an increase in the light emission luminance of the organic EL device provided with the light emitting layer 70 was evaluated.

(Evaluation results)
The organic EL devices of Examples 1-1 and 2-1 have the basic configuration of the present invention. Example 1-1 has a red conversion layer 50R between the substrate and the organic EL layer, and Example 2-1 has a red conversion layer 50R on the upper surface of the organic EL layer. In Example 1-1, the red conversion layer 50R has a film thickness of 0.5 μm or more, and the chromaticity variation of red emission of the organic EL device is within ± 0.01 and the luminance variation is within ± 5%. It was. As for Example 1-2, the green conversion layer was 0.5 μm or more, and the chromaticity variation of green light emission of the organic EL device was within ± 0.01, and the luminance variation was within ± 5%. In Examples 2-1 and 2-2, chromaticity variations were within ± 0.02 and luminance variations were within ± 5%.

  The organic EL device of Example 3 has a configuration in which an additional red conversion layer 52R is further provided on the upper surface of the red conversion layer 50R with respect to the organic EL device of Example 2-1. Table 1 below shows the relationship between the film thickness of the color conversion layer and the variation in chromaticity of red light emission of the organic EL device.

  By providing the additional red color conversion layer 52, the film thickness of the red color conversion layer 50 was 0.3 μm or more, and the uniformity of red light emission was good. Even when the thickness of the stepped portion is increased by the formation of the additional red color conversion layer 52R and rises more than the thickness of the surrounding red color conversion layer 50R, there is no problem in the uniformity of the color of the red light emission. It was.

  Moreover, the relationship between the film thickness (micrometer) of the color conversion layer 50 of the organic EL device of Example 1-1 and 3 and conversion efficiency (%) is shown in FIG. The conversion efficiency of the color conversion layer was saturated at a film thickness of 0.5 μm or more. Therefore, it was found that when the color conversion layer 50 is formed thicker than this film thickness, an organic EL device having uniform emission luminance and chromaticity within the surface can be obtained.

  The organic EL devices of Examples 4-1 and 4-2 are the same as the organic EL devices of Examples 2-1 and 2-2 on the surface of the substrate opposite to the series-connected organic EL element group. The two-color conversion layer 54 is provided. In addition, Example 4-3 has a configuration in which an additional red conversion layer 52R is further provided on the upper surface of the red conversion layer 50R with respect to the organic EL device of Example 4-1. The film thicknesses of the color conversion layer 50 and the second color conversion layer 54 are both 0.5 μm, and the film thickness of the additional red conversion layer 52R is 0.3 μm. The variations in luminance and chromaticity of light emission of the organic EL devices of the respective examples are shown in Table 2 below.

  The organic EL devices of Examples 5 and 6 have a configuration in which a reflective layer 70 is provided. In Example 5, the organic EL device of Example 1-1 is used as a basic configuration, and a reflective layer 70 is further provided on the upper surface of the passivation layer 64. Further, Example 6 has the organic EL device of Example 3 as a basic configuration, and further includes a reflective electrode 70 and a passivation layer 62 in this order from the substrate 10 side between the substrate 10 and the organic EL layer. For each example, the increase in emission intensity when compared with the organic EL device of each basic configuration is shown in Table 3 below.

  In Example 6, the chromaticity variation was the same as in Example 3.

It is a figure which shows the light source using the conventional light emitting diode. It is a figure which shows one Embodiment of the organic EL device of this invention. It is a figure which shows another embodiment of the organic EL device of this invention. (A) And (b) is a figure which shows another embodiment of the organic EL device of this invention. It is a figure which shows another embodiment of the organic EL device of this invention. It is a figure which shows another embodiment of the organic EL device of this invention. (A) And (b) is a figure which shows another embodiment of the organic EL device of this invention. (A) And (b) is the schematic which shows one Embodiment of the organic EL device and series connection organic EL element group of this invention. It is a schematic circuit diagram of one embodiment of an organic EL device of the present invention. It is a figure which shows the effect of the Example of this invention.

Explanation of symbols

10 substrate 20 first electrode 20t transparent first electrode 20r reflective first electrode 30 organic EL layer 40 second electrode 40t transparent second electrode 40r reflective second electrode 50, 52, 54 color conversion layer 50R, 52R, 54R red conversion layer 50G, 52G, 54G Green conversion layer 60, 62, 64 Passivation layer 70 Reflective layer 100 Series connection organic EL element group 210 Ceramic substrate 220 Metal pattern 230 LED
240 Heat sink 250 Fluorescent resin layer x Effective light emitting part y Invalid light emitting part (inter-element connection)
z Color conversion layer thickness

Claims (13)

An organic EL device having a substrate, at least one series-connected organic EL element group, and at least one color conversion layer,
The series-connected organic EL element group is composed of a plurality of organic EL elements having a first electrode, an organic EL layer, and a second electrode in this order from the substrate side,
At least one of the first electrode and the second electrode is a transparent electrode,
Each first electrode of the organic EL elements constituting the series-connected organic EL element group is electrically connected to a second electrode of an adjacent organic EL element,
The organic EL device, wherein the at least one color conversion layer extends in at least a part of a region between the organic EL elements.   The organic EL device according to claim 1, wherein the at least one color conversion layer has a thickness of 0.5 μm or more.   The organic EL device according to claim 1, comprising a plurality of series-connected organic EL element groups.   The organic EL device according to claim 1, wherein the substrate is a transparent substrate and the first electrode is a transparent electrode.   The organic EL device according to claim 4, wherein the at least one color conversion layer is disposed between the substrate and the first electrode.   The organic EL device according to claim 4, wherein the at least one color conversion layer is disposed on a surface of the substrate opposite to the series-connected organic EL element group.   The organic EL device according to claim 5, further comprising a reflective layer on an upper surface of the second electrode.   The organic EL device according to claim 7, further comprising a passivation layer between the second electrode and the reflective layer.   The first electrode is a reflective electrode, the second electrode is a transparent electrode, and the at least one color conversion layer is formed on an upper surface of the second electrode. The organic EL device according to any one of the above.   The organic EL device according to claim 9, further comprising a reflective layer between the substrate and the first electrode.   The organic EL device according to claim 10, wherein an additional color conversion layer is formed in a region between the organic EL elements.   The substrate is a transparent substrate, both the first electrode and the second electrode are transparent electrodes, and the at least one color conversion layer includes a first color conversion layer provided on an upper surface of the second electrode; 4. A second color conversion layer disposed between a substrate and the first electrode or on a surface of the substrate opposite to the series-connected organic EL element group. The organic EL device according to any one of the above.   The organic EL device according to claim 12, wherein an additional conversion layer is formed on an upper surface of the first color conversion layer in a region between the organic EL elements.

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