Patent Application
20080001515
The fluorescent complex according to the present invention comprises a rare earth ion and a β-diketone ligand. The rare earth ion can be properly selected so that fluorescence with a wavelength depending upon applications is emitted. However, preferred are lanthanoid ions. More specifically, europium or terbium is preferred. Europium is particularly preferred from the viewpoint of realizing a fluorescent complex having a large spectral intensity in the red region and excellent color rendering properties.
Further, the fluorescent complex according to the present invention has a β-diketone ligand. A fluoroalkyl group is bonded to this β-diketone ligand through an electron donative linking group.
The fluoroalkyl group refers to an alkyl group in which hydrogen has been substituted by fluorine. The luminous intensity increases with increasing the degree of substitution by fluorine. Accordingly, a fluoroalkyl group in which not less than 50% of the alkyl group has been substituted by fluorine is preferred, and a fluoroalkyl group in which all the hydrogen atoms in the alkyl group have been entirely substituted by fluorine, that is, a perfluoroalkyl group, is most preferred. The number of carbon atoms in the fluoroalkyl group is not particularly limited. In general, however, the number of carbon atoms is 1 to 22, preferably 3 to 7. The fluoroalkyl group may be of a straight chain type or a branched chain type.
It is considered that, in the fluorescent complex according to the present invention, the luminous intensity is increased by activating the C—H bond in the β-diketone ligand by taking advantage of an electron withdrawing property of the fluoroalkyl group. When the fluoroalkyl group is bonded directly to the β-diketone ligand, however, the durability of the complex is likely to be lowered. The present invention has succeeded in simultaneously realizing excellent luminous intensity and durability by introducing an electron donative linking group into between the β-diketone skeleton and the fluoroalkyl group.
In the present invention, the linking group for linking the β-diketone ligand skeleton to the fluoroalkyl group is used for keeping the fluoroalkyl group as the electron withdrawing group away from the β-diketone skeleton. To this end, the linking group should be electron donative. This linking group is selected from the group consisting of hydrocarbon chains, siloxane bond, ether bond, thioether bond, and seleno bond. Said hydrocarbon chain can contain unsaturated bond, and may be straight chain or branched chain. Among them, hydrocarbon chains, particularly alkylene groups, are preferred from the viewpoint of easiness on synthesis. The length of the electron donative group is not particularly limited. In the case of the alkylene group, however, the number of carbon atoms is 1 to 22, preferably 1 to 7.
This linking group is generally bonded to the β-diketone ligand skeleton at its 1-position and/or 3-position. Hydrogen is generally bonded to the β-diketone skeleton at its 2-position. Alternatively, deuterium or fluorine may be bonded.
The fluorescent complex according to the present invention may contain an aromatic substituent. When the aromatic substituent is bonded to the β-diketone ligand skeleton at its 1-position or 3-position, the luminous intensity of the fluorescent complex is advantageously increased. The aromatic substituent is not particularly limited so far as the substituent has an aromatic ring. Examples of aromatic substituents include phenyl, biphenyl, naphthyl, and fluorenyl groups. They may be substituted, for example, by an alkyl or alkoxy group. Among them, the fluorenyl group is preferred because luminous intensity increasing effect is large.
A preferred structure of the fluorescent complex may be represented as follows:
wherein m0 and n0 are an integer of 1 or more, preferably m0 is 1 to 22 and n0 is 1 to 22; and Ar represents a substituted or unsubstituted aromatic group.
The fluorescent complex according to the present invention may contain other ligand different from the β-diketone ligand. When such ligands are used, the distortion of the ligand field occurs and the luminous intensity is further increased. Such ligands include phosphine oxide and sulfonylamide. More specifically, ligands having the following structures are preferred.
wherein R1 to R4, which may be the same or different, represent a group selected from the group consisting of alkyl, substituted alkyl, alkoxy, substituted alkoxy, phenyl, substituted phenyl, biphenyl, substituted biphenyl, naphthyl, and substituted naphthyl; and p is an integer of 1 to 7.
Among the fluorescent complexes having ligands other than the β-diketone ligand, fluorescent complexes represented by formulae (2) to (4) may be mentioned as preferred examples.
wherein, m0 and n0 are an integer of 1 or more; Ar represents a substituted or unsubstituted aromatic group; R1 to R6, which may be the same or different, represent a group selected from the group consisting of alkyl, substituted alkyl, alkoxy, substituted alkoxy, phenyl, substituted phenyl, biphenyl, substituted biphenyl, naphthyl, and substituted naphthyl; and p is an integer of 1 to 7.
Further, in the fluorescent complex according to the present invention, crown ether ligands or cyclic multidentate ligands may be used as other ligands. Such cyclic ligands are preferred because they can significantly attain fluorescent complex ligand field distortion effect and can significantly increase the luminous intensity. Such cyclic ligands include cyclic multidentate ligands as described in Japanese Patent Application No. 180421/2005. This type of ligands have the following structure.
wherein:
X represents an atom selected from the group consisting of phosphorus, sulfur, and carbon, and, when a plurality of X's are present in the molecule, they may be the same or different,
R represents a substituent selected from the group consisting of a substituted or unsubstituted straight chain or branched chain alkyl having 20 or less carbon atoms, alkoxy having 20 or less carbon atoms, phenyl, biphenyl, naphthyl and a heterocyclic group, and substituted groups thereof when X bonded to R is a phosphorous atom; R is absent when X bonded to R is a carbon atom; R is absent or represents oxygen bonded to a sulfur atom through a double bond when X bonded to R is the sulfur atom; and when a plurality of R's are present in the molecule, they may be the same or different,
Y represents hydrogen or an alkyl or alkoxy group having 20 or less carbon atoms; Y's in the molecule may be the same or different; and Y may be bonded to another Y in the molecule through a carbon chain optionally containing oxygen to form a crosslinked ring structure,
Z represents a divalent group selected from the group consisting of —O—, —NYa—, —S—, and —Se— wherein Ya represents a substituent selected from the group consisting of a substituted or unsubstituted straight chain or branched chain alkyl having 20 or less carbon atoms, alkoxy having 20 or less carbon atoms, phenyl, biphenyl, naphthyl and a heterocyclic group, and substituted groups thereof; Ya may be bonded to another Y or Ya in the molecule through a carbon chain optionally containing oxygen to form a crosslinked ring structure; and when a plurality of Z's are present in the molecule, they may be the same or different;
m1 and m3 are independently an integer including 0 (zero),
m1+m3 is 2 or more, and
m2 is an integer of m1+m3 or more, and wherein:
—X(═O)R—, —CY2—, and —Z— in the formula are arranged randomly and are bonded to one another in a ring form.
The fluorescent complex according to the present invention may be prepared by allowing the rare earth ion-containing salt, for example, chloride, nitrate, or hydroxide, to react with the ligand in a solvent if necessary with heating. For example, water, alcohols, and ester solvents are generally used as the solvent.
The fluorescent complex according to the present invention absorbs light and emits light with a longer wavelength than the absorbed light. When this property is utilized, a combination of the fluorescent complex with a light emitting element which emits light by taking advantage of electric energy or the like can realize the emission of light with a wavelength different from light emitted from the light emitting element. Further, a combination of the fluorescent complex, for example, with a YAG fluorescent substance or a coloring matter can provide a light emitting element having excellent color rendering properties.
One example of this light emitting element is a near ultraviolet red LED element, and
In this light emitting element, a fluororesin is preferably used as a resin constituting the fluorescent layer. This is because the content of the C—H and O—H bonds in the resin is low. Accordingly, resins having a high fluorination degree are more preferred. However, the fluororesin may be properly selected depending, for example, upon the solubility or dispersibility of the fluorescent complex and other components used. Resins usable herein include Cefral Coat FG700X, A402B, and A610X manufactured by Central Glass Co., Ltd., LUMIFLON manufactured by Asahi Glass Co., Ltd., ZEONOR manufactured by Zeon Corporation, KYNAR, KYNAR FLEX manufactured by Atofina Japan, DUFLON manufactured by Nippon Paint Co., Ltd., and Dyneon THV220, 310, and 415 manufactured by Sumitomo 3M Ltd. (all the above products being tradenames). In addition to the fluorescent complex according to the present invention, for example, YAG fluorescent substances, alkaline earth metal silicate fluorescent substances, alkaline earth metal phosphate fluorescent substances, halophosphate fluorescent substances, BAM:Eu,Mn, BAM:Eu,ZnS, SrGa2S4:Eu, oxynitride:Eu, SrAlO4:Eu, alkaline earth apatite:Eu, Ca apatite:Eu,Mn, CaS:Ce, Y2SiO5:Tb, Sr2P2O7:Eu,Mn, and SrAl2O4:Eu may also be used in the fluorescent layer. Further, white luminescence can also be realized by combining some of them.
The above light emitting element as such may be used in a lighting system and further may be applied to a flashlight device utilizing a short luminescence life. In particular, the light emitting element according to the present invention utilizes elements having small electric energy consumption such as LEDs and thus is useful as a flashlight device for cellular phones with a camera. In such applications, the flashlight device can be used in the same manner as in other conventional light emitting elements.
The camera and the cellular phone with a camera each comprise a flashlight device 11, a lens 12, and a shutter button 13 (not shown in
Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.
Although the following Examples further illustrate the present invention, the present invention is not restricted by these Examples.
Europium complexes according to the present invention can be synthesized by any desired method, for example, through a synthetic route shown in
10% by weight of a compound represented by formula (5) was dissolved in a xylene solution of Cefral Coat FG700X (tradename) manufactured by Central Glass Co., Ltd. The solvent was completely removed, and a near ultraviolet excitation (395 nm) red LED element shown in
An LED element was prepared in quite the same manner as in Example 1, except that a europium complex represented by formula (6) was used. The LED element thus prepared was tested. The retention of the luminous flux after the high-temperature, high-humidity test relative to the initial luminous flux was good and 95%.
An LED element was prepared in quite the same manner as in Example 1, except that a europium complex represented by formula (7) was used. The LED element thus prepared was tested. The retention of the luminous flux after the high-temperature, high-humidity test relative to the initial luminous flux was good and 80%.
The luminous flux reduction is seemed to be derived from that, due to the absence of the phosphine oxide ligand, a part of the polymer component is coordinated to europium and vibrational deactivation occurred.
10% by weight of a compound represented by formula (8) was dissolved in a xylene solution of Cefral Coat FG700X (tradename) manufactured by Central Glass Co., Ltd. The solvent was completely removed, and a near ultraviolet excitation (395 nm) red LED element shown in
An LED element was prepared in quite the same manner as in Example 4, except that a europium complex represented by formula (9) was used. The initial luminous flux of this LED element was measured. Next, a high-temperature, high-humidity test was carried out under conditions of temperature 85° C. and humidity 85% for 100 hr. After the test, the luminous flux was measured and was compared with the initial measured value. As a result, a luminous flux reduction was not observed.
An LED element was prepared in quite the same manner as in Example 1, except that a europium complex represented by formula (10) was used. The LED element thus prepared was tested. The retention of the luminous flux after the high-temperature, high-humidity test relative to the initial luminous flux was 20%, that is, it was found that there was a large deterioration in luminous flux.
A white LED element was prepared by using the fluorescent layer in Example 1 as a second fluorescent layer in a white LED element shown in
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-183088 | Jul 2006 | JP | national |
