JP2838064B2 - Emission color conversion film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a luminescent color conversion film, and more specifically, to convert a luminescent color into another color by combining with a light emitting element, to improve contrast in a bright place, and to provide an external device. The present invention relates to a luminescent color conversion film capable of preventing a decrease in luminous brightness and fading of a luminescent color due to ultraviolet rays or the like.

[0002]

2. Description of the Related Art In general, electroluminescent elements (hereinafter abbreviated as EL elements) are self-luminous and have high visibility, and since they are completely solid elements, they have excellent impact resistance and are easy to handle. Therefore, utilization as a light-emitting element in various display devices has attracted attention. EL devices include an inorganic EL device using an inorganic compound as a light-emitting material and an organic EL device using an organic compound. Among these, the organic EL device can be used in a practical manner because the applied voltage can be significantly reduced. Chemical research is being actively conducted. This organic EL element emits light by injecting electric charges into a thin film made of an organic compound. When such an organic thin film EL element is put to practical use, it is not limited to a single color, but also to three primary colors of red, green and blue. It is desirable to make each color such as white or white uniform, and conventionally, research on light emitting materials for each color has been made. By combining them, a color display such as a CRT (cathode ray tube) is possible in principle.

However, in such a combination, since the luminance of red is low, it is necessary to suppress the luminance of other tones in order to obtain a good color tone, and as a result, it is impossible to manufacture a bright display with high luminance. There's a problem. In order to solve such a problem, a method of obtaining another color by combining an organic thin film EL element and a fluorescence conversion film has been attempted. However, this fluorescence conversion film is usually made of a material that emits fluorescence with visible light, and therefore reacts to light other than the light from the target light emitting element. Below, the visibility of whether or not the light emitting element is lit is reduced. That is,
In a normal use environment, the fluorescence conversion film is excited even when the light emitting element is not lit, and the brightness ratio between when lit and when not lit is inevitably reduced. This causes a problem that the display quality becomes poor.

Further, when a combination of such an organic thin-film EL element and a fluorescence conversion film is exposed to ultraviolet light from the outside for a long time, the fluorescent material or the EL in the conversion film may be reduced.
The light-emitting material in the device is deteriorated, causing fading of light emission and a decrease in light emission luminance. This phenomenon brings about a disadvantage that predetermined luminance and luminescent color cannot be obtained due to long-term exposure to natural light. On the other hand, a self-luminous element (CRT)
It is well known that in order to improve visibility in bright places, anti-reflection layers are provided on the surface or as close to a plane as possible to reduce the reflection of light sources. I have. It is easily presumed that this antireflection layer is also effective for improving visibility in a bright place in an organic thin film EL device which emits light by injecting charges into the organic thin film. Moreover, this organic thin-film EL element is a CRT
In contrast to this, since it is not necessary to manufacture a curved surface, reflection can be suppressed.

[0005]

Under such circumstances, the present invention combines a light-emitting element which emits light by injecting electric charge into an organic thin film to convert a light-emitting color into another color and to provide a light-emitting element. It is an object of the present invention to provide a luminescent color conversion film capable of improving contrast at a place and preventing a decrease in luminous brightness and fading of a luminescent color due to external ultraviolet rays or the like.

[0006]

The present inventors have conducted intensive studies to develop a luminescent color conversion film having the above-mentioned preferred functions. As a result, the fluorescent layer and the contrast improving layer were made essential constituent layers. It has been found that a luminescent color conversion film, which is combined with an ultraviolet absorbing layer if desired, can be suitable for the purpose.
The present invention has been completed based on such findings.
That is, the present invention provides (1) a conversion film combined with a light-emitting element that emits light by injecting electric charge into an organic thin film, wherein a fluorescent layer that emits light by input light and an external light that causes the fluorescent layer to emit light are provided. It is intended to provide a luminescent color conversion film comprising at least two contrast improving layers that absorb light.

In a preferred aspect of the present invention, (2) the fluorescent layer has a light transmittance of 50 at the maximum emission wavelength of the light emitting element.
% Or less, the luminescent color conversion film according to the above (1),
(3) The luminescent color conversion film according to (1) or (2), wherein the contrast improving layer has a light transmittance of 50% or less at the maximum wavelength of the excitation spectrum of the fluorescent layer, and (4) the rhodamine type fluorescent layer (5) The luminescent color conversion film according to the above (1) to (3), which contains 0.1 to 20% by weight of a fluorescent dye.
(1) a conversion film to be combined with a light emitting element such that the fluorescent layer faces the light emission side of the light emitting element, wherein the ultraviolet absorbing layer is provided on the outer surface of the contrast improving layer or between the contrast improving layer and the fluorescent layer; ) To (4), (6) the luminescent color conversion film described in (5) above, wherein an ultraviolet absorbing layer is provided on the outer surface of the contrast improving layer, and (7) the ultraviolet absorbing layer has an ultraviolet absorbing property. The luminescent color conversion film according to the above (5) or (6), which is a glass layer or a resin layer, and (8) the ultraviolet absorbing resin layer contains an ultraviolet absorber and / or a light stabilizer. (7) The luminescent color conversion film according to (7).

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The luminescent color conversion film of the present invention comprises a fluorescent layer and a contrast improving layer as essential constituent layers, and is combined with a light emitting element which emits light by injecting charges into an organic thin film. Used. The fluorescent layer is a layer that emits light by input light. As a dye used for the fluorescent layer,
There is no particular limitation as long as it is excited by light from the light-emitting element and emits fluorescence. There is no particular limitation, and those having a high fluorescence quantum yield and a high molecular absorption coefficient in the emission wavelength region of the light-emitting element are preferable. Such properties may be achieved with a single fluorescent dye or a combination of two or more fluorescent dyes. Examples of such fluorescent dyes include xanthene dyes having a xanthene ring or a similar structure in the molecule (eosine, erythrosin, fluorescein, rhodamine, sulforhodamine, etc.), acridine dyes, coumarin dyes, and the like. However, it is needless to say that the present invention is not limited to these.

A desired fluorescent layer can be obtained by dispersing these fluorescent dyes in a suitable light transmitting medium. The light-transmitting medium is not particularly limited as long as it has both light-transmitting properties and film-forming properties, and examples thereof include a polymer compound, inorganic glass, and a printing medium. Here, as the polymer compound, for example, polyvinylpyrrolidinone, polyacrylonitrile, poly (N, N-dimethylacrylamide), poly (N, N-
Dimethyl methacrylamide), polyvinyl alcohol,
Examples thereof include polymethyl methacrylate, polystyrene, polycarbonate, polyvinyl acetate, polyvinyl chloride, polybutene, polyethylene glycol, and mixtures and copolymers thereof, and examples of the inorganic glass include borate glass and silica glass. And mixtures thereof.

The thickness of the fluorescent layer is preferably in the range of 0.1 to 1000 μm. If the thickness is less than 0.1 μm, it is necessary to increase the concentration of the fluorescent dye, and as a result, the conversion efficiency decreases. On the other hand, if it exceeds 1000 μm, the thickness of the entire display element increases, which is not preferable. From the viewpoint of the conversion efficiency and the thickness of the entire display element, a more preferable film thickness is 1 to 100 μm.
And a range of 5 to 30 μm is particularly preferable.
The fluorescent layer preferably has a light transmittance of 50% or less at the maximum wavelength of the emission spectrum of the light emitting element. If the light transmittance exceeds 50%, the transmittance of light from the light emitting element is high, so that the ratio of converted light is insufficient. Furthermore, as the fluorescent dye concentration in the fluorescent layer,
It is preferable that the concentration is such that the light from the light emitting layer is sufficiently absorbed and the light transmittance is 50% or less at the maximum wavelength of the light emission spectrum of the light emitting layer for the above-described reason. From such a point, as the fluorescent layer, a rhodamine type fluorescent dye is used in 0.1.
Those containing at a rate of ２０20% by weight are preferred.

In the present invention, there is no particular limitation on the method for manufacturing the fluorescence conversion film used for the fluorescent layer, and various methods can be used. For example, after mixing a desired fluorescent dye in a light-transmitting medium, this is cast, spin-coated, printed, bar-coated,
Extrusion molding, roll molding, pressing, spraying,
By forming the film using a method such as a roll coating method, a desired fluorescence conversion film can be obtained. Among these methods, the printing method is preferable because the production cost is low and the film can be formed with sufficient accuracy, and it can be applied to a large area.
In particular, the screen printing method is preferable because the control of the film thickness is easy. When an organic solvent is used in these film forming methods, examples of the organic solvent include dichloromethane, 1,2-dichloroethane, chloroform, acetone, cyclohexanone, toluene, xylene, and N, N.
Dimethylformamide; dimethylsulfoxide; 1,
2-Dimethoxyethane; diethylene glycol dimethyl ether and the like can be used. These solvents are
Each may be used alone, or two or more kinds may be used in combination.

On the other hand, the contrast improving layer in the luminescent color conversion film of the present invention has a function of absorbing light from the outside which causes the fluorescent layer to emit light, and is obtained by dispersing a dye in a suitable light transmitting medium. It is. The dye used in the contrast improving layer is not particularly limited as long as it has high transmittance in the emission wavelength region of the fluorescent layer and low transmittance in the maximum wavelength region of the excitation spectrum of the fluorescent layer. The thickness of the contrast improving layer is preferably in the range of 1 to 1000 μm. If the thickness is less than 1 μm, the contrast improving effect is insufficient, and if it exceeds 1000 μm, the thickness of the entire display element increases, which is not preferable. From the viewpoint of the contrast improving effect and the thickness of the entire display element, the more preferable film thickness is 1 to 1.
It is in the range of 100 μm, and particularly preferably in the range of 1 to 10 μm. The contrast improving layer preferably has a light transmittance of 50% or less at the maximum wavelength of the excitation spectrum of the fluorescent layer. When the light transmittance exceeds 50%, the transmittance of the light of a fluorescent lamp and sunlight is high, so that the light emission of the fluorescent layer due to the external light when the light emitting element is turned off becomes large, and the effect of improving the contrast becomes insufficient.

Further, from the above-mentioned reasons, the dye concentration in the contrast improving layer is preferably such that the light transmittance is 50% or less at the maximum wavelength of the excitation spectrum of the fluorescent layer. This can be achieved by calculating the required dye concentration from the extinction coefficient of the dye and the thickness of the contrast improving layer, and dispersing one or more dyes in the light transmitting medium. As the light-transmitting medium used for the contrast improving layer, the same light-transmitting medium as exemplified in the description of the light-transmitting medium in the fluorescent layer can be used. The method for manufacturing the contrast improving film used for the contrast improving layer is not particularly limited, and various methods can be used. For example, the same method as the method exemplified as the method for manufacturing the fluorescence conversion film may be used. Can be.

The luminescent color conversion film of the present invention comprises the fluorescent layer and the contrast improving layer as essential constituent layers. When used in combination with a light emitting element, the fluorescent layer faces the light emission side of the light emitting element. Are arranged as follows. FIG. 1 is a structural view of an example in which a luminescent color conversion film of the present invention is combined with a luminescent element. The luminescent color composed of a fluorescent layer 2a and a contrast improving layer 2b is provided on the emission side of the organic thin film EL element 1. This shows a state in which the conversion film 2 is arranged so that the fluorescent layer 2a faces the EL element. A is the EL element emission, B
Indicates converted light. In the luminescent color conversion film of the present invention, in order to further prevent the influence of external ultraviolet light on the fluorescent layer, if necessary, an ultraviolet absorbing layer may be provided between the fluorescent layer and the outer surface of the contrast improving layer or between the fluorescent layer and the contrast improving layer. Although it may be provided, it is advantageous to provide an ultraviolet absorbing layer on the outer surface of the contrast improving layer particularly from the viewpoint of the effect.

As the ultraviolet absorbing layer, for example, an ultraviolet absorbing glass layer or a resin layer can be used.
As the former ultraviolet absorbing glass layer, for example, CeO
A glass plate containing an inorganic ultraviolet absorber such as ₂ or CdS, or a glass plate coated on its surface with zinc oxide fine particles is used. Such a glass plate is available as a commercial product [for example, a sharp cut filter UV39 (manufactured by Osaka Spectacle Glass Co., Ltd.) or the like]. On the other hand, the UV-absorbing resin layer includes, for example, acrylic, methacrylic, epoxy, polyolefin, polyester,
A film is formed by adding an ultraviolet absorber and / or a light stabilizer to a resin such as a polyvinyl alcohol resin.
Here, the ultraviolet absorber is not particularly limited, and examples thereof include known ones, for example, benzotriazole-based, salicylate-based, benzophenone-based, and cyanoacrylate-based ones. The light stabilizer is not particularly limited. For example, a nickel complex such as 2,2'-thiobis (4-t-octylphenolate) alkylamine nickel or bis (2,2,6,6-tetramethyl- Hindered amine-based compounds such as (4-piperidyl) sebacate. These ultraviolet absorbers and light stabilizers may be used alone or in combination of two or more. There is no particular limitation on the method of manufacturing the ultraviolet absorbing film used for the ultraviolet absorbing resin layer. For example, the same method as the method exemplified as the method of manufacturing the fluorescence conversion film can be used. The thickness of the ultraviolet absorbing layer is not particularly limited, but is usually in the range of 1 to 500 μm, preferably 10 to 100 μm.

FIG. 2 is a structural view showing an example in which a luminescent color conversion film of the present invention provided with an ultraviolet absorbing layer is combined with a light emitting element.
This shows a state in which a luminescent color conversion film 2 ′ including a fluorescent layer 2 a, a contrast improving layer 2 b, and an ultraviolet absorbing layer 3 is arranged so that the fluorescent layer 2 a faces the EL element. A and B
Is the same as above. As described above, the luminescent color conversion film of the present invention is disposed so that the fluorescent layer faces the light emission side of the light emitting element. In this case, between the light emitting element and the conversion film, between the layers of the conversion film or A gas barrier layer, an antireflection layer, a mask layer for a display pattern, and the like may be provided on the surface of the conversion film opposite to the fluorescent layer, if desired.

Next, the relationship among the light emitting element, the fluorescent layer, and the contrast improving layer will be described. FIGS. 3A and 3B are diagrams for explaining the effect of improving the contrast by the luminescent color conversion film of the present invention. FIG. 3A shows the luminescent spectrum of the light emitting element, FIG. 3B shows the excitation spectrum of the fluorescent layer and the luminescent spectrum associated therewith. (C) conceptually shows the transmittance of the contrast improving layer. In the absence of the contrast improving layer, external light excites the phosphor of the fluorescent layer even when the light emitting element is not emitting light, and causes the fluorescent layer to emit light having a wavelength in the emission spectrum. On the other hand, if there is a contrast improving layer, the wavelength of the excitation spectrum portion of the phosphor is absorbed by the contrast improving layer, so that the fluorescent layer is not excited by external light to emit light. Therefore, light emission from the fluorescent layer is suppressed, and the contrast can be improved. Light from the light emitting element excites the phosphor of the fluorescent layer (excitation spectrum region), and emits light having a wavelength of the emission spectrum. Since this light emission corresponds to a region of the contrast improving layer where the transmittance is high, light is transmitted well. On the other hand, of the light from the light emitting element, the light that has not been absorbed by the fluorescent layer reaches the contrast improving layer, but the light passes through the contrast improving layer because the transmittance of the light is low in the contrast improving layer. Can not do it. Therefore, since the light inherent in the light emitting element does not escape to the outside, the contrast can be improved. The light-emitting element to which the light-emitting color conversion film of the present invention is applied is an element that emits light by injecting charges into an organic thin film, that is, an organic thin-film EL element.

This organic thin film EL element basically has a structure in which a light emitting layer is sandwiched between a pair of electrodes, and a hole injection layer and an electron injection layer are interposed as necessary. Specifically, (1) anode / light emitting layer / cathode (2) anode / hole injection layer / light emitting layer / cathode (3) anode / light emitting layer / electron injection layer / cathode (4) anode / hole injection layer / Light-emitting layer / electron injection layer / cathode. Such an organic thin film EL device is disclosed in, for example, JP-A-3-47890 and JP-A-3-2319.
No. 70, JP-A-5-17765, JP-A-5-17765
No. 135878, Japanese Patent Application Laid-Open No. 5-140145,
JP-A-5-247458, JP-A-5-24745
9, JP-A-6-100857, JP-A-6-100857
It can be produced according to a method described in, for example, 132080.

The light-emitting layer has the following functions: (1) an injection function capable of injecting holes from an anode or a hole injection layer and injecting electrons from a cathode or an electron injection layer when an electric field is applied; It has a transport function of moving injected charges (electrons and holes) by the force of an electric field, and (3) a light-emitting function of providing a field for recombination of electrons and holes inside the light-emitting layer and connecting it to light emission. ing. However, there may be a difference between the ease of injecting holes and the ease of injecting electrons, and the transport function represented by the mobility of holes and electrons may be large or small. It is preferable to use a material having a function of transferring the charge. There is no particular limitation on the type of light emitting material used in the light emitting layer, and a known light emitting material in an organic EL element can be used. Such a light emitting material is mainly an organic compound, and specific examples thereof include the following compounds according to a desired color tone.

First, in order to obtain emission in an ultraviolet region or a purple region, a para-polyphenylene-based material is preferable. The phenyl or phenylene group of the para-polyphenylene compound has one or two substituents such as an alkoxy group, a hydroxyl group, a sulfonyl group, a carboxyl group, an alkoxycarbonyl group, an amino group, a dimethylamino group, and a diphenylamino group. The above may be introduced. Examples of such para-polyphenylene compounds include p-
Quarter phenyl; 3,5,3 ', 5'-tetra-t
-Butyl-p-quinkphenyl; 3,5,3 ', 5'
-Tetra-t-butyl-p-sexiphenyl and the like. Next, in order to obtain blue to green light emission, for example, benzothiazole-based, benzimidazole-based, benzoxazole-based fluorescent whitening agents, metal-chelated oxinoid compounds, and styrylbenzene-based compounds can be used. Further, aromatic dimethylidin compounds (European Patent No. 388768, JP-A-3-23197)
No. 0) can also be preferably used. Examples of the aromatic dimethylidin compound include:
1,4-phenylenedimethylidin; 4,4′-biphenylenedimethylidin; 2,5-xylylenedimethylidylidine; 2,6-naphthylenedimethylidin; 1,4-p
-Telephenylenedimethylidin; 4,4'-bis (2,2-di-t-butylphenylvinyl) biphenyl (DTBPVBi); 4,4'-bis (2,2-diphenylvinyl) biphenyl (DPVBi) and the like And their derivatives.

Further, general formula (I) (RQ) ₂ -Al-OL (I) described in JP-A-5-258882 (wherein L represents a benzene ring A hydrocarbon group containing 6 to 24 carbon atoms, OL represents a phenolate ligand, Q represents a substituted 8-quinolinolate ligand, and R represents an aluminum atom having more than two substituted 8-quinolinolate ligands bonded thereto. Represents an 8-quinolinolate ring substituent which is selected so as to sterically hinder the reaction. Examples of this compound include bis (2-methyl-8-
(Quinolinolate) (p-phenylphenolate) aluminum (III), bis (2-methyl-8-quinolinolate) (1-naphtholate) aluminum (III), and the like.

In addition, in order to obtain highly efficient mixed light emission of blue and green light, a material obtained by adding a dopant to the above-mentioned light emitting material as a host (Japanese Patent Application Laid-Open No. 6-9953) can be used. Examples of the dopant include fluorescent dyes in a blue region or a green region, specifically, coumarin-based fluorescent dyes or fluorescent dyes similar to those used as the above-mentioned host. In particular, a light emitting material having a distyrylarylene skeleton as a host, preferably DPVBi, and a material having a diphenylaminovinylarylene skeleton as a dopant, preferably 4,4′-bis [4- (N,
N-diphenylamino) styryl] benzene (DPAV
Combinations with B) are preferred. As a method for forming a light emitting layer using the above materials, for example, the light emitting layer can be formed by thinning by a known method such as an evaporation method, a spin coating method, a casting method, and an LB method. Preferably, there is. Here, the molecular deposition film refers to a thin film formed by depositing the compound from a gaseous state or a film formed by solidifying the compound from a molten state or a liquid state. Normally, this molecular deposited film can be distinguished from a thin film (molecule accumulation film) formed by the LB method by a difference in a cohesive structure and a higher-order structure and a functional difference resulting therefrom.

This light emitting layer is disclosed in Japanese Patent Application Laid-Open No. 57-517.
As described in No. 81, after dissolving the luminescent material in a solvent together with a binder such as a resin to form a solution,
This can be formed into a thin film by a spin coating method or the like. The thickness of the light emitting layer formed in this way is not particularly limited and can be appropriately selected depending on the situation, but is usually in the range of 5 nm to 5 μm. As the anode in this EL element, a metal, an alloy, an electrically conductive compound, or a mixture thereof having a large work function (4 eV or more) as an electrode material is preferably used. Specific examples of such an electrode material include metals such as Au, CuI, indium tin oxide (ITO), and Sn.
Conductive transparent materials such as O ₂ and ZnO are mentioned. The anode may be formed by forming a thin film of these electrode materials by a method such as vapor deposition or sputtering, and forming a pattern of a desired shape by a photolithography method, or (100 μm Above), a pattern may be formed via a mask having a desired shape at the time of vapor deposition or sputtering of the electrode material.
When light emission is extracted from this anode, the transmittance is 10%.
It is desirable to make it larger, and the sheet resistance as the anode is preferably several hundred Ω / □ or less.

Further, although the film thickness depends on the material, it is usually 10 n
m to 1 μm, preferably 10 to 200 nm. On the other hand, the cathode has a small work function (4 eV
Hereinafter, a metal (referred to as an electron injecting metal), an alloy, an electrically conductive compound, and a mixture thereof are used as an electrode material. Specific examples of such electrode materials include sodium, sodium-potassium alloy, magnesium,
Lithium, magnesium / copper mixtures, magnesium / silver mixtures, magnesium / aluminum mixtures, magnesium / indium mixtures, aluminum / aluminum oxide (Al ₂ O ₃ ) mixtures, indium, lithium / aluminum mixtures, rare earth metals and the like. Among them, from the viewpoint of electron injecting property and durability against oxidation, etc., a mixture of an electron injecting metal and a second metal which is a stable metal having a large work function value, such as a magnesium / silver mixture, magnesium / Aluminum mixture,
A magnesium / indium mixture, an aluminum / aluminum oxide (Al ₂ O ₃ ) mixture, and a lithium / aluminum mixture are preferred. The cathode can be manufactured by forming a thin film of these electrode substances by a method such as vapor deposition or sputtering. Further, the sheet resistance as a cathode is preferably several hundred Ω / □ or less, and the film thickness is usually 10 nm to 1 μm, preferably 50 to 2 μm.
It is selected in the range of 00 nm. In order to transmit light, if either the anode or the cathode of the organic thin-film EL element is transparent or translucent, the luminous efficiency is advantageously improved.

Next, the hole injection layer provided as required has a function of transmitting the holes injected from the anode to the light emitting layer, and this hole injection layer is interposed between the anode and the light emitting layer. By doing so, many holes are injected into the light emitting layer at a lower electric field, and furthermore, electrons injected from the cathode or the electron injection layer into the light emitting layer are generated by electrons existing at the interface between the light emitting layer and the hole injection layer. Due to the barrier, the element is excellent in light emitting performance, for example, accumulated at the interface in the light emitting layer and improving light emitting efficiency. Regarding the material of the hole injection layer (hereinafter, referred to as a hole injection material),
There is no particular limitation as long as it has the above preferable properties. Conventionally, in photoconductive materials, those commonly used as a hole charge injection / transport material and known materials used for a hole injection layer of an EL element are used. Any of them can be selected and used.

The hole injecting material has one of a hole injecting property and an electron blocking property, and may be an organic substance or an inorganic substance. As this hole injection material,
For example, triazole derivatives, oxadiazole derivatives,
Imidazole derivatives, polyarylalkane derivatives, pyrazoline derivatives and pyrazolone derivatives, phenylenediamine derivatives, arylamine derivatives, amino-substituted chalcone derivatives, oxazole derivatives, styrylanthracene derivatives, fluorenone derivatives, hydrazone derivatives, stilbene derivatives, silazane derivatives, aniline-based copolymers Coalescing,
Further, a conductive polymer oligomer, particularly a thiophene oligomer, may be used. As the hole injection material, those described above can be used.
Aromatic tertiary amine compounds and styrylamine compounds,
In particular, it is preferable to use an aromatic tertiary amine compound.

Representative examples of the above aromatic tertiary amine compounds and styrylamine compounds include N, N, N ', N'
N-tetraphenyl-4,4′-diaminophenyl;
N'-diphenyl-N, N'-bis (3-methylphenyl)-[1,1'-biphenyl] -4,4'-diamine (TPD); 2,2-bis (4-di-p-tolyl Aminophenyl) propane; 1,1-bis (4-di-p-tolylaminophenyl) cyclohexane; N, N, N ′,
N'-tetra-p-tolyl-4,4'-diaminobiphenyl; 1,1-bis (4-di-p-tolylaminophenyl) -4-phenylcyclohexane; bis (4-dimethylamino-2-methylphenyl ) Phenylmethane; bis (4-di-p-tolylaminophenyl) phenylmethane; N, N'-diphenyl-N, N'-di (4-methoxyphenyl) -4,4'-diaminobiphenyl;
N, N ', N'-tetraphenyl-4,4'-diaminodiphenyl ether; 4,4'-bis (diphenylamino) quadriphenyl; N, N, N-tri (p-tolyl) amine; 4- ( Di-p-tolylamino) -4'-
[4- (di-p-tolylamino) styryl] stilbene; 4-N, N-diphenylamino- (2-diphenylvinyl) benzene; 3-methoxy-4'-N, N-diphenylaminostilbenzene; N-phenyl Carbazole, and further those having two fused aromatic rings in the molecule described in U.S. Pat. No. 5,061,569, for example, 4,4'-bis [N- (1-naphthyl) -N
-Phenylamino] biphenyl (NPD);
No. 3,068,688, in which three triphenylamine units are linked in a star-burst form.
4 ', 4''-tris [N- (3-methylphenyl) -N
-Phenylamino] triphenylamine (MTDAT
A) and the like.

The above-mentioned aromatic dimethylidin-based compound shown as a material for the light emitting layer, p-type Si, p-type Si
An inorganic compound such as C can also be used as the hole injection material. The hole injection layer can be formed by thinning the hole injection material by a known method such as a vacuum deposition method, a spin coating method, a casting method, and an LB method. The thickness of the hole injection layer is not particularly limited, but is usually about 5 nm to 5 μm. The hole injection layer may have a single-layer structure composed of one or more of the above-mentioned materials, or may have a laminated structure composed of a plurality of layers having the same composition or different compositions. Further, the electron injection layer used as necessary may have a function of transmitting electrons injected from the cathode to the light emitting layer, and any material may be selected from conventionally known compounds. Can be used.

The material used for this electron injection layer (hereinafter referred to as
Examples of the electron injection material) include nitro-substituted fluorene derivatives, diphenylquinone derivatives, thiopyran dioxide derivatives, heterocyclic tetracarboxylic anhydrides such as naphthalene perylene, carbodiimide, fluorenylidene methane derivatives, anthraquinodimethane and Examples include anthrone derivatives and oxadiazole derivatives. Further, a series of electron-transporting compounds described in JP-A-59-194393 are disclosed as materials for forming a light-emitting layer in the publication. It has been found that it can be used as a material. Further, in the oxadiazole derivative, a thiadiazole derivative in which an oxygen atom of the oxadiazole ring is substituted with a sulfur atom, and a quinoxaline derivative having a quinoxaline ring known as an electron withdrawing group can also be used as the electron injecting material.

Metal complexes of 8-quinolinol derivatives, for example, tris (8-quinolinol) aluminum (Alq), tris (5,7-dichloro-8-quinolinol) aluminum, tris (5,7-dibromo-8-
Quinolinol) aluminum, tris (2-methyl-8)
-Quinolinol) aluminum, tris (5-methyl-
8-quinolinol) aluminum, bis (8-quinolinol) zinc, and the like, and the central metal of these metal complexes are I
A metal complex replaced with n, Mg, Cu, Ca, Sn, Ga or Pb can also be used as an electron injection material. In addition, metal-free or metal phthalocyanine, or those whose terminals are substituted with an alkyl group, a sulfonic acid group, or the like, can also be preferably used as an electron injection material. Also, the distyrylpyrazine derivative exemplified as the material of the light emitting layer can be used as the electron injection material, and similarly to the hole injection layer, the n-type -S
An inorganic semiconductor such as i, n-type SiC can also be used as the electron injection material.

This electron injection layer can be formed by forming the above compound by a known thinning method such as a vacuum evaporation method, a spin coating method, a casting method, and an LB method. The thickness of the electron injection layer is not particularly limited, but is usually selected in the range of 5 nm to 5 μm. The electron injection layer may have a single-layer structure composed of one or two or more of these electron injection materials, or may have a laminated structure composed of a plurality of layers having the same composition or different compositions. next,
A preferred example of manufacturing the organic thin film EL device will be described. As an example, a method for manufacturing an EL device composed of the above-described anode / hole injection layer / light-emitting layer / electron injection layer / cathode will be described.
First, a thin film made of a desired electrode material, for example, a material for an anode, is formed on a suitable substrate in a thickness of 1 μm or less, preferably 10 to 20 μm.
An anode is formed so as to have a thickness of 0 nm by a method such as evaporation or sputtering. next,
On this, a thin film made of a material for a hole injection layer, a light emitting layer, and an electron injection layer, which are element materials, is formed.

As a method of thinning, there are spin coating method, casting method, vapor deposition method and the like as described above. However, from the viewpoint that a uniform film is easily obtained and pinholes are hardly formed, vacuum deposition is used. The method is preferred. When this vapor deposition method is employed for thinning the film, the vapor deposition conditions vary depending on the type of compound used, the target crystal structure of the molecular deposition film, the association structure, and the like.
50 ° C., degree of vacuum 10 ^-6 to 10 ^-3 Pa, deposition rate 0.01 to
50 nm / sec, substrate temperature -50 to 300 ° C, film thickness 5 nm
It is desirable to select an appropriate value within a range of from 5 μm to 5 μm.

After forming these layers, a thin film made of a material for a cathode is formed thereon with a thickness of 1 μm or less, preferably 50 to 200 nm.
A desired EL element can be obtained by forming a film having a thickness in the range of m by, for example, a method such as vapor deposition or sputtering and providing a cathode. In the production of this organic thin-film EL element, it is preferable to produce from the hole injection layer to the cathode consistently by one evacuation, but the production order is reversed.
A cathode, an electron injection layer, a light emitting layer, a hole injection layer, and an anode can be formed in this order. EL obtained in this way
When a DC voltage is applied to the element, light emission can be observed by applying a voltage of about 5 to 40 V with the positive polarity of the anode and the negative polarity of the cathode. Also, even if a voltage is applied with the opposite polarity, no current flows and no light emission occurs. Further, when an AC voltage is applied, light is emitted only when the anode is in the + state and the cathode is in the-state. The waveform of the applied alternating current may be arbitrary.

[0034]

EXAMPLES Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. Production Example 1 Production of Organic Thin Film EL Element ITO on a 25 mm × 75 mm × 1.1 mm glass substrate
An electrode formed with a thickness of 100 nm was used as a transparent support substrate. The transparent support substrate was ultrasonically cleaned with isopropyl alcohol for 5 minutes, then with pure water for 5 minutes, and again with isopropyl alcohol for 5 minutes. Next, this transparent support substrate was fixed to a substrate holder of a vacuum evaporation apparatus, and 4,4′-bis (N-phenyl-N- (3-methylphenyl) amino) was placed in a molybdenum resistance heating boat.
200 mg of biphenyl (TPD) was put, and 200 mg of 4,4′-bis (2,2-diphenylvinyl) biphenyl (DPVBi) was placed in another molybdenum resistance heating boat.
The pressure inside the vacuum chamber was reduced to 1 × 10 ⁻⁴ Pa. The boat containing TPD was heated to 215 to 220 ° C., TPD was deposited on the substrate at a deposition rate of 0.1 to 0.3 nm / sec, and a hole injection layer having a thickness of 60 nm was formed. At this time, the substrate temperature was room temperature. Without removing the obtained hole injection layer from the vacuum chamber, a DPV was
Bi at a boat temperature of 250 ° C and a deposition rate of 0.1 to 0.2 nm /
A light emitting layer having a thickness of 40 nm was deposited on the substrate in seconds. This was taken out of the vacuum chamber, and a stainless steel mask was placed on the light emitting layer side, and fixed again to the substrate holder. Next, 0.5 g of silver (Ag) wire is put in a tungsten basket, 1 g of magnesium (Mg) ribbon is put in a boat made of molybdenum, the pressure in the vacuum chamber is reduced to 1 × 10 ⁻⁴ Pa, and Mg (deposition rate, 1.
8 nm / sec) and Ag (evaporation rate, 0.1 nm / sec) were simultaneously deposited, and a negative electrode was formed to produce an organic thin film EL device. The maximum wavelength of the emission spectrum of this EL device is 460
nm.

Example 1 (1) Preparation of Emission Color Conversion Film A red fluorescent dye, 6G1g, was added to 4.4g of a printing ink medium (manufactured by Toyo Ink Co., Ltd.), kneaded well and dissolved. Next, this solution was 25 mm × 75 mm
Cast on a × 1mm glass substrate, air-dry for 12 hours,
Vacuum drying was performed at 50 ° C. to produce a fluorescence conversion film. The thickness of this fluorescence conversion film was 50 μm as measured by a micrometer, and the transmittance at a wavelength of 460 nm was 2%. When the fluorescence excitation spectrum of this film was measured, the maximum wavelength was 576 nm. on the other hand,
4-dicyanomethylene-2-methyl-6- (p-dimethylaminostyryl) -4H-pyran (DCM) 16 mg
Was added to 1 g of polyvinylpyrrolidinone (manufactured by Kanto Kagaku) and dissolved in 10 ml of dichloromethane. Next, it was cast on a glass substrate of 25 mm × 75 mm × 1 mm, air-dried for 12 hours, and then vacuum-dried at 50 ° C. to produce a contrast improving film. The thickness of this contrast improving film was 20 μm when measured with a micrometer.
Met. The transmittance of this film at a wavelength of 576 nm was 50%. Next, the thus-obtained fluorescence conversion film and the contrast improving film were overlapped to produce a luminescent color conversion film comprising a fluorescent layer and a contrast improving layer.

(2) Evaluation of Emission Color Conversion Film On the transparent substrate side of the organic thin film EL device obtained in Production Example 1,
The luminescent color conversion films obtained in the above (1) were overlaid as shown in FIG. 1, the luminescent luminance and the CIE chromaticity coordinates were measured when the EL element was turned on and off, and the contrast was obtained and evaluated by the following equation. . Contrast = luminance when EL element is lit /
Luminance when EL element was turned off The measurement was performed just under 2 m of the fluorescent lamp. Table 1 shows the results.

Comparative Example 1 (1) Preparation of Emission Color Conversion Film A fluorescence conversion film was prepared in the same manner as in Example 1- (1), and this fluorescence conversion film was used as a light emission color conversion film. That is, it is a luminescent color conversion film composed of only a fluorescent layer. (2) Evaluation of emission color conversion film Evaluation was performed in the same manner as in Example 1- (2). The results are shown in Table 1.

Example 2 (1) Preparation of Emission Color Conversion Film Coumarin 6 (manufactured by Kanto Chemical Co., Ltd.), 10 m, which is a green fluorescent dye
g was added to 2 g of a printing ink medium (manufactured by Toyo Ink Co., Ltd.), kneaded well and dissolved. The solution was then added to 25
cast on a glass substrate of
After air drying for 2 hours, vacuum drying was performed at 50 ° C. to produce a fluorescence conversion film. The thickness of this fluorescence conversion film was 40 μm as measured by a micrometer, and the transmittance at a wavelength of 460 nm was 5%. When the fluorescence excitation spectrum of this film was measured, the maximum wavelength was 470 nm. On the other hand, green printing was performed on a polyethylene terephthalate film using a color printer (manufactured by Apple Inc.) to produce a contrast improving film. The thickness of this contrast improving film was 3 μm as measured by a micrometer. The wavelength of this film is 470 nm.
Was 40%. Next, the thus-obtained fluorescence conversion film and the contrast improving film were overlapped to produce a luminescent color conversion film comprising a fluorescent layer and a contrast improving layer. (2) Evaluation of emission color conversion film Evaluation was performed in the same manner as in Example 1- (2). The results are shown in Table 1.

Comparative Example 2 (1) Production of Emission Color Conversion Film A fluorescence conversion film was produced in the same manner as in Example 2- (1), and this fluorescence conversion film was used as an emission color conversion film. That is, it is a luminescent color conversion film composed of only a fluorescent layer. (2) Evaluation of emission color conversion film Evaluation was performed in the same manner as in Example 1- (2). The results are shown in Table 1.

[0040]

[Table 1]

It is apparent from Table 1 that the luminescent color conversion film of the present invention has a large contrast improving effect.

Example 3 (1) Production of Emission Color Conversion Film In the same manner as in Example 1- (1), a fluorescence conversion film and a contrast improving film were produced. On the other hand, 2,4-dihydroxybenzophenone 1 was added to a solution of 1 g of polyvinylpyrrolidinone (manufactured by Kanto Kagaku) in 20 g of dichloromethane.
Dissolve 0mg, form a cast film on a glass plate,
An ultraviolet absorbing film having a thickness of 80 μm was prepared. next,
The fluorescent conversion film, the contrast improving film, and the ultraviolet absorbing film were sequentially superposed on each other to produce a luminescent color converting film including a fluorescent layer, a contrast improving layer, and an ultraviolet absorbing layer.

(2) Evaluation of Emission Color Conversion Film On the transparent substrate side of the organic thin film EL device obtained in Production Example 1,
The luminescent color conversion film obtained in the above (1) is overlaid as shown in FIG. 2, and a 313 nm peak wavelength and an energy intensity of about 100 μW / cm are placed on the luminescent color conversion film from the side of the ultraviolet absorbing layer.
² was irradiated for 10 minutes. Next, the emission color, emission luminance, and CIE when a DC voltage of 10 V was applied to the EL element.
The chromaticity coordinates were determined. The results are shown in Table 2.

Example 4 (1) Production of Emission Color Conversion Film On the contrast improving layer of the emission color conversion film produced in Example 2- (1), a film was obtained in the same manner as in Example 3- (1). The ultraviolet absorbing films were superposed on each other to produce a luminescent color conversion film comprising a fluorescent layer, a contrast improving layer and an ultraviolet absorbing layer. (2) Evaluation of Emission Color Conversion Film Evaluation was performed in the same manner as in Example 3- (2). The results are shown in Table 2.

Reference Examples 1 and 2 As the emission color conversion films, the emission color conversion films obtained in Example 1- (1) (Reference Example 1) and the emission color conversion films obtained in Example 2- (1) Using (Reference Example 2), evaluation was made in the same manner as in Example 3- (2). The results are shown in Table 2.

[0046]

[Table 2]

The same test was performed on the organic thin film EL element alone and on the organic thin film EL element with the ultraviolet absorbing film superimposed thereon.
When only the element is used, the emission color: blue, emission luminance: 180 cd
/ M ² , CIE chromaticity coordinates: x = 0.15, y = 0.17, and an organic thin-film EL element with an ultraviolet absorbing film superposed thereon has an emission color: blue, emission luminance: 190 cd / m ² , CI
E chromaticity coordinates: x = 0.15, y = 0.16. As can be seen from Table 2, the provision of the ultraviolet absorbing film in the luminescent color conversion film could prevent a decrease in luminous brightness as compared with the case where the film was not provided.

Examples 5 to 8 (1) Preparation of luminescent color conversion film 1.2 g of polymethacrylate (PMMA, manufactured by Wako Pure Chemical Industries, Ltd.)
Is dissolved in 11 g of dichloromethane, and a UV absorber and optionally a light stabilizer shown in Table 3 are dispersed in PMMA so as to be 1.0% by weight and 0.5% by weight, respectively. Was applied to a glass plate to produce each ultraviolet absorbing film having a film thickness shown in Table 3. Next, each of the above-mentioned ultraviolet absorbing films was superimposed on the contrast improving layer of the luminescent color conversion film produced in Example 1- (1),
A luminescent color conversion film comprising a fluorescent layer, a contrast improving layer and an ultraviolet absorbing layer was produced. (2) Evaluation of emission color conversion film A test was performed in the same manner as in Example 3- (2), and emission luminance was obtained. The results are shown in Table 4. For comparison, the emission luminance of Reference Example 1 is also shown.

Examples 9 to 12 (1) Preparation of Emission Color Conversion Film Each of the ultraviolet absorbing films prepared in Examples 5 to 8 (1) was replaced with the emission color conversion film prepared in Example 2- (1). A luminescent color conversion film composed of a fluorescent layer, a contrast improving layer, and an ultraviolet absorbing layer was formed on the contrast improving layer. (2) Evaluation of emission color conversion film A test was performed in the same manner as in Example 3- (2), and emission luminance was obtained. The results are shown in Table 4. For comparison, the emission luminance of Reference Example 2 is also shown.

[0050]

[Table 3]

[0051]

[Table 4]

As can be seen from Table 4, when the luminescent color conversion film was provided with the ultraviolet absorbing film, the emission luminance was able to be prevented from lowering as compared with the case where the luminescent color conversion film was not provided.

Example 13 (1) Preparation of Emission Color Conversion Film On the contrast improving layer of the emission color conversion film obtained in Example 1- (1), an ultraviolet glass filter (sharp cut filter UV39, Osaka Glasses Glass Co., Ltd.) was used. (Manufactured by the company) were superposed to produce a luminescent color conversion film comprising a fluorescent layer, a contrast improving layer and an ultraviolet absorbing layer. (2) Evaluation of Emission Color Conversion Film Evaluation was performed in the same manner as in Example 3- (2). The results are shown in Table 5. For comparison, Reference Example 1 is also shown.

Example 14 (1) Preparation of Emission Color Conversion Film On the contrast improving layer of the emission color conversion film obtained in Example 2- (1), an ultraviolet glass filter (sharp cut filter UV39, Osaka Glasses Glass Co., Ltd.) was used. (Manufactured by the company) were superposed to produce a luminescent color conversion film comprising a fluorescent layer, a contrast improving layer and an ultraviolet absorbing layer. (2) Evaluation of Emission Color Conversion Film Evaluation was performed in the same manner as in Example 3- (2). The results are shown in Table 5. For comparison, Reference Example 2 is also shown.

[0055]

[Table 5]

A similar test was conducted for the organic thin film EL element alone and the organic thin film EL element with the ultraviolet glass filter superimposed thereon. Emission luminance: 180
cd / m ² , CIE chromaticity coordinates: x = 0.15, y = 0.17
In the case where the organic thin film EL element is overlaid with an ultraviolet glass filter, the emission color is blue and the emission luminance is 186 cd / m.
² , CIE chromaticity coordinates: x = 0.15, y = 0.16. As can be seen from Table 5, the provision of the ultraviolet color glass filter in the luminescent color conversion film prevented the reduction of the luminous brightness and the fading of the colors as compared with the case where the filter was not provided.

[0057]

The luminescent color conversion film of the present invention is an organic thin film EL.
By combining the device with an element, the emitted color can be converted into another color, the contrast in a bright place can be improved, and the emission luminance can be prevented from being lowered or the emitted color can be prevented from fading due to external ultraviolet rays or the like. The luminescent color conversion film of the present invention is suitably used, for example, for self-luminous displays such as dot matrices and segments, or for lighting (particularly backlights) of OA equipment, watches, exhibition displays, and the like.

[Brief description of the drawings]

FIG. 1 shows an example of the present invention in which a luminescent color conversion film is an organic thin film EL.
It is a block diagram in the case of combining with an element.

FIG. 2 is a configuration diagram of a case where a different emission color conversion film of the present invention is combined with an organic thin film EL element.

FIG. 3 is a diagram for explaining a contrast improving effect by a luminescent color conversion film of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Organic thin film EL element 2 Emission color conversion film 2 'Emission color conversion film 2a Fluorescent layer 2b Contrast improvement layer 3 Ultraviolet absorption layer A EL element emission B Conversion light

Continuation of the front page (56) References JP-A-2-112195 (JP, A) JP-A-3-297090 (JP, A) JP-A-6-5367 (JP, A) JP-A-4-298989 (JP JP-A-8-8665 (JP, A) JP-A-8-222374 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H05B 33/22

Claims (8)

(57) [Claims] 1. A conversion film combined with a light emitting element that emits light by injecting electric charge into an organic thin film, comprising: a fluorescent layer that emits light by input light; and a contrast improvement that absorbs external light that causes the fluorescent layer to emit light. A luminescent color conversion film comprising at least two layers. 2. The luminescent color conversion film according to claim 1, wherein the fluorescent layer has a light transmittance of 50% or less at the maximum emission wavelength of the light emitting device. 3. The luminescent color conversion film according to claim 1, wherein the contrast improving layer has a light transmittance of 50% or less at the maximum wavelength of the excitation spectrum of the fluorescent layer. 4. The fluorescent layer according to claim 1, wherein said rhodamine type fluorescent dye is 0.1 to 0.1.
The luminescent color conversion film according to claim 1, which contains 20% by weight. 5. A conversion film in which a fluorescent layer is combined with a light emitting element so as to face a light emission extraction side of the light emitting element, wherein an ultraviolet absorbing layer is provided between an outer surface of the contrast improving layer or between the contrast improving layer and the fluorescent layer. The luminescent color conversion film according to claim 1, further comprising: 6. The luminescent color conversion film according to claim 5, wherein an ultraviolet absorbing layer is provided on the outer surface of the contrast improving layer. 7. The luminescent color conversion film according to claim 5, wherein the ultraviolet absorbing layer is a glass layer or a resin layer having an ultraviolet absorbing property. 8. The luminescent color conversion film according to claim 7, wherein the ultraviolet absorbent resin layer contains an ultraviolet absorbent and / or a light stabilizer.