Patent Application
20130303776
The present invention relates to a luminescent material, and an organic light-emitting element, a wavelength-converting light-emitting element (color-converting light-emitting element), a light-converting light-emitting element, an organic laser diode light-emitting element, a dye laser, a display device, and an illumination device using the same.
Priority is claimed on Japanese Patent Application No. 2010-226741, filed Oct. 6, 2010, the content of which is hereby incorporated herein by reference in its entirety.
In order to reduce the power consumption of an organic EL (electroluminescence) element, a highly efficient luminescent material has been developed. A phosphorescent luminescent material using the emission from the triplet excited state can obtain a higher luminous efficiency compared to a fluorescent luminescent material using only the fluorescent emission from the singlet excited state. Therefore, a phosphorescent luminescent material has been developed.
Currently, a phosphorescent material capable of achieving an internal quantum efficiency of approximately 100% at a maximum is used for green pixels and red pixels of an organic EL element. However, a fluorescent material having an internal quantum efficiency of approximately 25% at a maximum is used for blue pixels. The reason is because blue light emission requires a higher energy than that of red light or green light emission; and when it is attempted to obtain high-energy emission from phosphorescent emission at the triplet excited level, portions in a molecular structure which are unstable under high energy are likely to deteriorate.
As a blue phosphorescent material, in order to obtain a high-energy triplet excited state, an iridium (Ir) complex in which an electron-attracting group such as fluorine is introduced into a ligand as a substituent is known (for example, refer to NPLs 1 to 5). However, in a blue phosphorescent material into which an electron-attracting group is introduced, the luminous efficiency is relatively high, whereas the light resistance is low and the lifetime is short.
In addition, it is reported that short-wavelength emission is possible in a complex in which a carbene ligand is used without introducing an electron-attracting group thereinto (refer to NPL 6 and PTL 1).
Luminescent materials disclosed in Non-Patent Document 6 and Patent Document 1 emit blue phosphorescence without introducing an electron-attracting group, which deteriorates light resistance, thereinto. However, the luminous efficiency is low.
Therefore, the development of a luminescent material, which emits blue light with a high luminous efficiency without introducing an electron-attracting group thereinto, is desired.
Various aspects of the present invention have been conceived in consideration of such circumstances of the related art; and are to provide a highly efficient luminescent material, and an organic light-emitting element, a wavelength-converting light-emitting element, a light-converting light-emitting element, an organic laser diode light-emitting element, a dye laser, a display device, and an illumination device using the same.
In order to solve the above-described problems, the present inventors have thoroughly studied and found the following configurations which are aspects of the present invention.
According to an aspect of the present invention, there is provided a luminescent material including a transition metal complex comprising a ligand in which an electron density of a p orbital of a highest occupied molecular orbital level is higher than 0.239 and lower than 0.711 when the electron density is calculated according to quantum chemical calculation (Gaussian09/DFT/RB3LYP/6-31G), the p orbital being the outermost shell of an element coordinated to the metal.
In the luminescent material according to the aspect, the central metal of the transition metal complex may be a metal selected from a group consisting of Ir, Os, Pt, Ru, Rh, and Pd.
In the luminescent material according to the aspect, the ligand may have a structure selected from a group consisting of carbene, silylene, germylene, stannylene, borylene, plumbylene, and nitrene.
In the luminescent material according to the aspect, the ligand may include an element selected from a group consisting of B, Al, Ga, In, and Tl in a structure thereof.
In the luminescent material according to the aspect, the element coordinated to the metal may be a carbon atom, and the electron density of the p orbital of the outermost shell may be a calculated electron density on a 2p orbital which is the highest occupied molecular orbital level according to quantum chemical calculation.
In the luminescent material according to the aspect, the ligand may include a carbene structure.
In the luminescent material according to the aspect, the ligand may be a carbene ligand including a boron atom in a structure thereof.
In the luminescent material according to the aspect, the carbene structure may include an aromatic position.
In the luminescent material according to the aspect, the transition metal complex may be an indium complex.
In the luminescent material according to the aspect, the transition metal complex may be a tris complex in which three bidentate ligands are coordinated, and the amount of a mer (meridional) isomer contained in the transition metal complexes may be greater than that of a fac (facial) isomer.
In the luminescent material according to the aspect, the indium complex comprising a ligand in which an electron density of a p orbital of a highest occupied molecular orbital level is higher than 0.239 and lower than 0.711 when the electron density is calculated according to quantum chemical calculation (Gaussian09/DFT/RB3LYP/6-31G), the p orbital being the outermost shell of an element coordinated to the metal.
According to another aspect of the present invention, there is provided an organic light-emitting element including: at least one organic layer that includes a light-emitting layer; and a pair of electrodes between which the organic layer is interposed, wherein the organic layer includes a luminescent material, and the luminescent material includes a transition metal complex comprising a ligand in which an electron density of a p orbital of a highest occupied molecular orbital level is higher than 0.239 and lower than 0.711 when the electron density is calculated according to quantum chemical calculation (Gaussian09/DFT/RB3LYP/6-31G), the p orbital being the outermost shell of an element coordinated to the metal.
In the organic light-emitting element according to the aspect, the light-emitting layer may include the luminescent material.
According to still another aspect of the present invention, there is provided a wavelength-converting light-emitting element including: an organic light-emitting element; and a fluorescent layer that is disposed on a side of extracting light from the organic light-emitting element, wherein the fluorescent layer absorbs light emitted from the organic light-emitting element and emits light having a different wavelength from that of the absorbed light, wherein the organic light-emitting element includes at least one organic layer that includes a light-emitting layer, and a pair of electrodes between which the organic layer is interposed, wherein the organic layer includes a luminescent material, and wherein the luminescent material includes a transition metal complex comprising a ligand in which an electron density of a p orbital of a highest occupied molecular orbital level is higher than 0.239 and lower than 0.711 when the electron density is calculated according to quantum chemical calculation (Gaussian09/DFT/RB3LYP/6-31G), the p orbital being the outermost shell of an element coordinated to the metal.
According to still another aspect of the present invention there is provided a wavelength-converting light-emitting element including: a light-emitting element; and a fluorescent layer that is disposed on a side of extracting light from the light-emitting element, wherein the fluorescent layer absorbs light emitted from the light-emitting element and emits light having a different wavelength from that of the absorbed light, wherein the fluorescent layer includes a luminescent material, and wherein the luminescent material includes a transition metal complex comprising a ligand in which an electron density of a p orbital of a highest occupied molecular orbital level is higher than 0.239 and lower than 0.711 when the electron density is calculated according to quantum chemical calculation (Gaussian09/DFT/RB3LYP/6-31G), the p orbital being the outermost shell of an element coordinated to the metal.
According to still another aspect of the present invention, there is provided a light-converting light-emitting element including: at least one organic layer that includes a light-emitting layer; a layer for multiplying a current; and a pair of electrodes between which the organic layer and the layer for multiplying a current are interposed, wherein a host material of the light-emitting layer is doped with a luminescent material, and wherein the luminescent material includes a transition metal complex comprising a ligand in which an electron density of a p orbital of a highest occupied molecular orbital level is higher than 0.239 and lower than 0.711 when the electron density is calculated according to quantum chemical calculation (Gaussian09/DFT/RB3LYP/6-31G), the p orbital being the outermost shell of an element coordinated to the metal.
According to still another aspect of the present invention, there is provided an organic laser diode light-emitting element including: an excitation light source; and a resonator structure that is irradiated with light emitted from the excitation light source, wherein the resonator structure includes at least one organic layer that includes a laser-active layer, and a pair of electrodes between which the organic layer is interposed, wherein a host material of the laser-active layer is doped with a luminescent material, and wherein the luminescent material includes a transition metal complex comprising a ligand in which an electron density of a p orbital of a highest occupied molecular orbital level is higher than 0.239 and lower than 0.711 when the electron density is calculated according to quantum chemical calculation (Gaussian09/DFT/RB3LYP/6-31G), the p orbital being the outermost shell of an element coordinated to the metal.
According to still another aspect of the present invention, there is provided a dye laser including: a laser medium that includes a luminescent material; and an excitation light source that stimulates the luminescent material of the laser medium to emit phosphorescence and to perform laser oscillation, wherein the luminescent material includes a transition metal complex comprising a ligand in which an electron density of a p orbital of a highest occupied molecular orbital level is higher than 0.239 and lower than 0.711 when the electron density is calculated according to quantum chemical calculation (Gaussian09/DFT/RB3LYP/6-31G), the p orbital being the outermost shell of an element coordinated to the metal.
According to still another aspect of the present invention, there is provided a display device including: an image signal output portion that outputs an image signal; a drive portion that applies a current or a voltage based on the signal output from the image signal output portion; and an organic light-emitting element that emits light based on the current or the voltage applied from the drive portion, wherein the organic light-emitting element includes at least one organic layer that includes a light-emitting layer, and a pair of electrodes between which the organic layer is interposed, wherein the organic layer includes a luminescent material, wherein the luminescent material includes a transition metal complex comprising a ligand in which an electron density of a p orbital of a highest occupied molecular orbital level is higher than 0.239 and lower than 0.711 when the electron density is calculated according to quantum chemical calculation (Gaussian09/DFT/RB3LYP/6-31G), the p orbital being the outermost shell of an element coordinated to the metal.
According to still another aspect of the present invention, there is provided a display device including: an image signal output portion that outputs an image signal; a drive portion that applies a current or a voltage based on the signal output from the image signal output portion; and a wavelength-converting element that emits light based on the current or the voltage applied from the drive portion, wherein the wavelength-converting element includes an organic light-emitting element, and a fluorescent layer that is disposed on a side of extracting light from the organic light-emitting element, wherein the fluorescent layer absorbs light emitted from the organic light-emitting element and emits light having a different wavelength from that of the absorbed light, wherein the organic light-emitting element includes at least one organic layer that includes a light-emitting layer, and a pair of electrodes between which the organic layer is interposed, wherein the organic layer includes a luminescent material, and wherein the luminescent material includes a transition metal complex comprising a ligand in which an electron density of a p orbital of a highest occupied molecular orbital level is higher than 0.239 and lower than 0.711 when the electron density is calculated according to quantum chemical calculation (Gaussian09/DFT/RB3LYP/6-31G), the p orbital being the outermost shell of an element coordinated to the metal.
According to still another aspect of the present invention, there is provided a display device including: an image signal output portion that outputs an image signal; a drive portion that applies a current or a voltage based on the signal output from the image signal output portion; and a light-converting light-emitting element that emits light based on the current or the voltage applied from the drive portion, wherein the light-converting light-emitting element includes at least one organic layer that includes a light-emitting layer, a layer for multiplying a current, and a pair of electrodes between which the organic layer and the layer for multiplying a current are interposed, wherein a host material of the light-emitting layer is doped with a luminescent material, and wherein the luminescent material includes a transition metal complex comprising a ligand in which an electron density of a p orbital of a highest occupied molecular orbital level is higher than 0.239 and lower than 0.711 when the electron density is calculated according to quantum chemical calculation (Gaussian09/DFT/RB3LYP/6-31G), the p orbital being the outermost shell of an element coordinated to the metal.
According to still another aspect of the present invention, there is provided an electronic apparatus including the above-described display device.
In the display device according to the aspect, an anode and a cathode of the light-emitting portion may be arranged in a matrix shape.
In the display device according to the aspect, the light-emitting portion may be driven by a thin film transistor.
According to still another aspect of the present invention there is provided an illumination device including: a drive portion that applies a current or a voltage; and an organic light-emitting element that emits light based on the current or the voltage applied from the drive portion, wherein the organic light-emitting element includes at least one organic layer that includes a light-emitting layer, and a pair of electrodes between which the organic layer is interposed, wherein the organic layer includes a luminescent material, wherein the luminescent material includes a transition metal complex comprising a ligand in which an electron density of a p orbital of a highest occupied molecular orbital level is higher than 0.239 and lower than 0.711 when the electron density is calculated according to quantum chemical calculation (Gaussian09/DFT/RB3LYP/6-31G), the p orbital being the outermost shell of an element coordinated to the metal.
According to still another aspect of the present invention, there is provided an illumination apparatus including the above-described illumination device.
According to still another aspect of the present invention, there is provided an illumination device including: a drive portion that applies a current or a voltage; and a wavelength-converting light-emitting element that emits light based on the current or the voltage applied from the drive portion, wherein the wavelength-converting element includes an organic light-emitting element, and a fluorescent layer that is disposed on a side of extracting light from the organic light-emitting element, wherein the fluorescent layer absorbs light emitted from the organic light-emitting element and emits light having a different wavelength from that of the absorbed light, wherein the organic light-emitting element includes at least one organic layer that includes a light-emitting layer, and a pair of electrodes between which the organic layer is interposed, wherein the organic layer includes a luminescent material, wherein the luminescent material includes a transition metal complex comprising a ligand in which an electron density of a p orbital of a highest occupied molecular orbital level is higher than 0.239 and lower than 0.711 when the electron density is calculated according to quantum chemical calculation (Gaussian09/DFT/RB3LYP/6-31G), the p orbital being the outermost shell of an element coordinated to the metal.
According to still another aspect of the present invention, there is provided an illumination device including: a drive portion that applies a current or a voltage; and a light-converting light-emitting element that emits light based on the current or the voltage applied from the drive portion, wherein the light-converting light-emitting element includes at least one organic layer that includes a light-emitting layer, a layer for multiplying a current, and a pair of electrodes between which the organic layer and the layer for multiplying a current are interposed, wherein a host material of the light-emitting layer is doped with a luminescent material, and wherein the luminescent material includes a transition metal complex comprising a ligand in which an electron density of a p orbital of a highest occupied molecular orbital level is higher than 0.239 and lower than 0.711 when the electron density is calculated according to quantum chemical calculation (Gaussian09/DFT/RB3LYP/6-31G), the p orbital being the outermost shell of an element coordinated to the metal.
According to the aspects of the present invention, it is possible to provide a highly efficient luminescent material, and an organic light-emitting element, a wavelength-converting light-emitting element, a light-converting light-emitting element, an organic laser diode light-emitting element, a dye laser, a display device, and an illumination device using the same.
As a result of thorough investigation, the present inventors found that a transition metal complex can emit blue phosphorescence with a high efficiency, the transition metal complex including at least a ligand in which an electron density of a p orbital of a highest occupied molecular orbital (HOMO) level is higher than 0.239 and lower than 0.711 when the electron density is calculated according to quantum chemical calculation (Gaussian09/DFT/RB3LYP/6-31G), the p orbital being the outermost shell of an element position coordinated to a metal. In an embodiment of the present invention, a quantum chemical calculation program Gaussian09 (Gaussian09 Revision-A.02-SMP) using density functional theory (DFT) is used for quantum chemical calculation; and the basis function 6-31G is applied to a ligand. In the case of a metal complex, the basis function LanL2DZ is applied to an Ir complex; and the basis function 6-31G* is applied to complexes other than an Ir complex. Information relating to quantum chemical calculation (Gaussian09/DFT/RB3LYP/6-31G) is available from, for example, the website “http://www.gaussian.com/index.htm” (As of Sep. 8, 2011).
Hereinafter, the discussion will be made in terms of material science. It is generally known that, when a transition metal complex is expected as a highly efficient phosphorescent luminescent material, MLCT (Metal-to-Ligand Charge Transfer) is used as an emission mechanism.
Therefore, the present inventors thought that, in order to develop a luminescent material having a high luminous efficiency (PL quantum efficiency), it was essential that the molecular design of a metal complex be made so as to obtain a high MLCT ratio for T1 emission (phosphorescent emission). First, in the discussion about a method of increasing the ratio of MLCT transition using quantum chemical calculation, the validity of quantum chemical calculation was verified.
Next, regarding well-known phosphorescent luminescent materials of the related art, the ratio of MLCT transition (MLCT ratio) was calculated according to quantum chemical calculation to verify the correlation with a PL quantum yield φPL (luminous efficiency). Here, MLCT is one of charge transfer transitions (transition processes of transferring electrons between atoms); and refers to charge transfer transition from a central metal to a ligand. In general, a metal complex absorbs energy from outside, which causes electron transition. Electron transition is broadly divided into d-d transition, charge transfer transition (charge transfer transition from a central metal to a ligand (MLCT), charge transfer transition from a ligand to a central metal (LMCT), or intervalence charge transfer used when a metal complex contains plural metal atoms (IVCT), and ligand-ligand transition. In an embodiment of the present invention, the ratio of MLCT to these transition processes is calculated as MLCT ratio. A method of calculating a MLCT ratio will be described in detail using Examples.
Next, in order to increase the MLCT ratio of a transition metal complex, the present inventors thought that the probability of metal-to-ligand charge transfer could be increased by making a central metal electron-rich, and the verification thereof was performed. More specifically, the present inventors conceived a configuration of increasing an electron density of a position coordinated to a metal in order to make a central metal electron-rich. The reason of focusing on the electron density of a position of a ligand coordinated to a metal is as follows.
In a position coordinated to a metal, an orbital in the outermost shell of a coordinated element contributes to a bond with a metal.
Normally, when an electron donor donates an electron, the electron moves from an HOMO having the highest energy. In addition, a p orbital which is the outermost shell of an element bonded to a metal contributes to a bond with a metal. Therefore, in order to make a central metal electron-rich, the present inventors thought that it is important to increase an electron density on an orbital of the outermost shell (p orbital) of an element position bonded to a central metal.
The present inventors focused on a carbene complex which can emit blue light emission without depending on a substituent and shows an electron donating ability to a metal center; and examined the relationship between the MLCT ratio and the electron density of an orbital of the outermost shell (p orbital) of a coordination site in a ligand using the quantum chemical calculation.
Ir was used as the central metal, and a tris complex having three bidentate carbene ligands was used for quantum chemical calculation. The MLCT ratio was calculated with the same method as that of Example 2 described below. In addition, in order to calculate the electron density of the orbital of the outermost shell of the coordination site of a ligand, each structure of the carbene ligands was optimized according to Gaussian09/DFT/RB3LYP/6-31G. Next, the electron density of a p orbital (2p orbital) in the outermost shell of a carbene carbon, which was an element coordinated to a metal, was calculated according to one-point calculation of Gaussian09/DFT/RB3LYP/6-31G<key word: pop=reg>. The results of each compound are plotted in
The basis function 6-31G is called a split valence basis set; and refers to a basis function that takes into consideration two or more basis functions having the same shape (orbital shapes such as s, p, and d) and different sizes. Specifically, it is considered that a hydrogen atom has two 1s orbitals (1s′ and 1s″) having different sizes; and a carbon atom has three 2p orbitals having different sizes (that is, 2PX′, 2PY′, 2PZ′, 2PX″, 2PY″, and 2PZ″). As a result, the basis function 6-31G is more flexible in orbital than a minimal basis set.
In an embodiment of the present invention, the electron density (HOMO level) of a 2p orbital is calculated according to the following expression 1. In the following expression 1, C(2PX′), C(2PY′), C(2PZ′), C(2PX″), C(2PY″), and C(2PZ″) represent orbital coefficients of the respective orbitals. In an embodiment of the present invention, in an actual calculation file, the electron density of a 2p orbital is calculated from coefficient values of 2PX, 2PY, and 2PZ and of 3PX, 3PY, and 3PZ which are different orbitals from the above orbitals.
[Numerical Expression 1]
Electron Density of 2P Orbital=C(2PX′)2+C(2Py′)2+C(2PZ′)2+C(2PX″)2+C(2PY″)2+C(2PZ″)2 (Expression 1)
When Ir complexes having various carbene were examined, as illustrated in FIG. 3, it was found that the higher the electron density of a site of a ligand coordinated to a metal, the higher the MLCT ratio; more specifically, the higher the electron density of a p orbital (in the case of the basis function 6-31G, which is determined based on coefficient orbitals of 2P orbitals (2PX, 2PY, and 2PZ) in an embodiment of the present invention), which is the highest occupied molecular orbital (HOMO), in the outermost shell of a carbon atom coordinated to a metal, the higher the MLCT ratio.
In addition, as illustrated in
The correlation between the MLCT ratio and the electron density of the orbital in the outermost shell can be approximately represented by the regression line “y=110.57x+6.6815”.
Here, the reason why the boron atom was introduced into the carbene structure is that the boron atom has a high Lewis acid strength, an empty p orbital, and a strong electron-accepting property. In addition, it is known that, when N and B are bonded in the carbene structure, similar characteristics to those of a C═C bond are exhibited. Therefore, three N atoms (electron-donating property) and two B atoms (electron-accepting property), which have a larger amount of charge localization compared to a C═C bond, were bonded in a ring to generate an electron-rich state and to form an aromatic ring (in which a ring current effect is obtained and electrons are easily moved). As a result, the design of increasing the electron density of the carbene site was made.
Based on such quantum chemical calculation results, plural Ir complexes in which the carbene ligand including a boron atom in a structure thereof was coordinated were actually synthesized and were applied to organic light-emitting elements as illustrated in Examples 4 to 10 described below. Then, the current efficiency (luminous efficiency) was measured. The actual luminescence property (current efficiency) of each complex measured in Examples 4 to 10; and the electron density, calculated according to quantum chemical calculation, on an orbital in the outermost shell of a carbene site are plotted in
Related-Art Compound 1 Related-Art Compound 2 Related-Art Compound 3
As illustrated in
When the ligand including such carbene structures was used as a metal complex, the results were obtained in which the electron density of the metal center was increased and components which emitted strong light with metal-to-ligand charge transfer (MLCT) were significantly increased. As a result, the luminous efficiency was improved.
In addition, it was found from the results of
In Related-Art Compounds 1 to 3 illustrated in
In addition, it is assumed that, as the electron density of the coordination site of the ligand coordinated to the metal is closer to the ideal value 1.00, the electron-donating property to the metal is higher. However, when the electron density on the orbital in the outermost shell of the coordination site of the element is too high, an electron cloud moves to a region in which electrons are relatively easily accepted. Therefore, ligand-ligand transition is likely to occur. For example, in an Os(CO)2(L)2 complex described in P.-C. Wu et al., Organometallics, 2003, 22, 4938, when a C site of CO having the high electron-donating property is coordinated to a central metal, the electron density of a 2p orbital of the C site of CO is 0.711. This non-patent literature describes that, when CO is used as a ligand, the electron-donating property is high; and, due to the high electron-donating property of CO, fluorescence having a low luminous efficiency is likely to be emitted by π-π* transition caused by L-to-L transition (ligand-to-ligand transition). The reason is considered to be that the electron cloud is moved to the ligand side opposite CO due to the high electron-donating property of CO; and as a result, L-to-L transition is likely to occur.
Therefore, in the embodiment of the present invention, in order to realize highly efficient phosphorescent emission using MLCT, it is preferable that the electron density of the p orbital in the outermost shell of the coordination site of a ligand coordinated to the metal is higher than 0.239 and lower than 0.711. In addition, based on the results of
In addition, it was confirmed from the results of
In the above-described examination examples, the structure of the ligand includes the boron atom. It is generally known that Group 13 elements (B, Al, Ga, In, Tl) have an electron structure of s2p1, the same valence electron number, and similar chemical properties. In addition, a compound having a Group 13 element does not satisfy the octet rule and is likely to become an electron-deficient compound. That is, as in the case of a boron atom, the electron density is reduced in the vicinity of a Group 13 element such as Al, Ga, In, or Tl. As a result, an electron is likely to be donated from a position coordinated to a metal. Therefore, it is preferable that the luminescent material according to the embodiment includes a structure including a Group 13 element such as B, Al, Ga, or In.
In addition, the luminescent material according to the embodiment may have a structure, which can donate an electron to a metal center and does not satisfy the octet rule, as a transition metal complex. When the luminescent material does not satisfy the octet rule, the electron-donating property is high, the electron-donating property to a metal center is increased, and the electron density of an original metal position in MLCT can be increased. As a result, the MLCT ratio can be increased. Therefore, the luminescent material according to the embodiment may includes any one of a silylene (Si) complex, a germylene (Ge) complex, a stannylene (Sn) complex, a borylene (B) complex, a plumbylene (Pb) complex, and a nitrene (N) complex. Among these, it is particularly preferable that the luminescent material includes a carbene complex or a silylene complex from the viewpoint of strong σ donor property.
Furthermore, in the above-described examination example, the case in which a central metal is Ir has been described. However, in the luminescent material according to the embodiment, a central metal may be another transition metal. In a transition metal complex for highly efficient emission, when phosphorescence is emitted using MLCT, the heavy atom effect of the central metal works effectively on the ligand, and intersystem crossing (transition from the first excited state to the triplet excited state, S→T: approximately 100%) occurs rapidly. Then, similarly, when the heavy atom effect is high, the transition rate constant (kr) from T1 to S0 is increased. As a result, the PL quantum yield (φPL=kr/(knr+kr); wherein knr represents the rate constant of being thermally deactivated from T1 to S0) is increased. The increase in PL quantum yield leads to an increase in the luminous efficiency of an organic electronic device.
In order to effectively obtain the above-described heavy atom effect, it is preferable that a luminescent material according the embodiment of the present invention be a transition metal complex in which a central metal is any one of Ir, Os, Pt, Ru, Rh, and Pd. In these metals, the atomic radius is relatively short due to lanthanide contraction, whereas the atomic weight is great and the heavy atom effect is effectively exhibited. Among these, Ir Os, or Pt is preferable and Ir is particularly preferable.
When a transition metal complex which is the luminescent material according to the embodiment is a tris complex having three bidentate ligands, a mer (meridional) isomer or a fac (facial) isomer exist as geometric isomers.
Regarding a compound illustrated in
As a result, it was indicated that, in a carbene complex including a boron atom, which is the luminescent material according to the embodiment, a mer isomer had a higher MLCT ratio and a higher luminous efficiency than that of a fac isomer. In addition, in Example 3 described later, when a luminescent material was actually synthesized and the PL quantum yield thereof is measured, it was confirmed that a complexes containing only a mer isomer had a higher PL quantum yield than that of a mixed complexes containing a fac isomer and a mer isomer; and in the luminescent material according to the embodiment, a mer isomer had a higher PL quantum yield that that of a fac isomer. Therefore, when the luminescent material according to the embodiment is a tris complex, the tris complexes may contain either or both of a mer isomer or a fac isomer. However, it is preferable that the amount of a mer isomer contained in the transition complexes be greater than that of a fac isomer from the viewpoint of improving the PL quantum yield.
The luminescent material according to the embodiment realizes highly efficient blue phosphorescent emission even when the luminescent material does not contain an electron-attracting group.
Hereinafter, a transition metal complex which is preferable as the luminescent material according to the embodiment will be described using specific structure examples.
The luminescent material according to the embodiment is a transition metal complex including at least a ligand in which a central metal is one kind of metal selected from a group consisting of Ir, Os, Pt, Ru, Rh, and Pd; and an electron density of a p orbital of a highest occupied molecular orbital (HOMO) level is higher than 0.239 and lower than 0.711 when the electron density is calculated according to quantum chemical calculation (Gaussian09/DFT/RB3LYP/6-31G), the p orbital being in the outermost shell of an element position coordinated to the metal. It is preferable that the ligand includes a structure selected from a group consisting of carbene, silylene, germylene, stannylene, borylene, plumbylene, and nitrene. A ligand of the luminescent material according to the embodiment may be neutral or monoanionic and may be a monodentate, bidentate, or tridentate ligand.
In a transition metal complex which is the luminescent material according to the embodiment, when a central metal is Ir, Os, Ru or Rh, the transition metal complex has a 6-coordinated octahedral structure; and when a central metal is Pt or Pd, the transition metal complex has a 4-coordinated square planar structure.
For example, it is preferable that the transition metal complex, which is the luminescent material according to the embodiment, includes a partial structure represented by any one of the following formulae (1) to (3).
(In the formulae (1) to (3), M represents Ir, Os, Pt, Ru, Rh or Pd; X represents C, Si, Ge, Sn, B, Pb, or N; Q represents B, Al, Ga, In or Tl; R11, R12, and R13 each independently represent a monovalent organic group; Y represents a divalent hydrocarbon group; Z represents a divalent organic group; and V represents a divalent organic group having a ring structure.)
In addition, for example, it is more preferable that the transition metal complex, which is the luminescent material according to the embodiment, includes a partial structure represented by the following formula (4) or (5).
(In the formulae (4) and (5), M represents Ir, Os, Pt, Ru, Rh or Pd; X represents C, Si, Ge, Sn, B, Pb, or N; R11, R12, and R13 each independently represent a monovalent organic group; Y represents a divalent hydrocarbon group; Z represents a divalent organic group; and V represents a divalent organic group having a ring structure.)
Examples of the monovalent organic group represented by R11, R12, and R13 include an aliphatic hydrocarbon group having 1 to 8 carbon atoms or an aromatic group having 1 to 10 carbon atoms. The aliphatic hydrocarbon group and the aromatic group represented by R11, R12, and R13 may have a substituent.
Examples of the aliphatic hydrocarbon group having 1 to 8 carbon atoms represented by R11, R12, and R13 include a linear, branched, or cyclic aliphatic hydrocarbon group. Specific examples thereof include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a tert-butyl group, an n-pentyl group, an n-hexyl group, an n-heptyl group, an n-octyl group, and a cyclohexyl group. R11 and R12 may be partially bonded and integrated to form a ring structure.
Examples of the aromatic group having 1 to 10 carbon atoms represented by R11, R12, and R13 include a phenyl group and a naphthyl group, and these aromatic groups may have a substituent.
Examples of the divalent hydrocarbon group represented by Y include a divalent hydrocarbon group having 1 to 3 carbon atoms. Specific examples thereof include —CH2—, —CH2—CH2—, and —C(CH3)2—. Among these, —CH2— is preferable.
M represents preferably Ir, Os, Pt, Ru, Rh or Pd; more preferably Ir, Os, or Pt; and particularly preferably Ir, from the viewpoints of increasing the PL quantum yield of the transition metal complex, which is a luminescent material, due to the heavy atom effect and increasing the luminous efficiency.
It is preferable that X does not satisfy the octet rule from the viewpoints of improving the electron-donating property of a ligand, increasing the MLCT ratio of a metal complex, and improving the luminous efficiency. Specifically, C, Si, Ge, Sn, B, Pb, or N is preferable; C or Si is more preferable; and C is particularly preferable.
Examples of the divalent organic group having a ring structure represented by V include an aromatic cyclic divalent organic structure. An aromatic hydrocarbon group or an aromatic group including nitrogen and carbon is preferable. It is preferable that the divalent organic group having a ring structure represented by V be represented by any one of the following formulae (V-1) to (V-5).
In the formula (V-1), for example R15, R16, R17, and R18 each independently represent a monovalent organic group. Examples of the monovalent organic group include a hydrogen atom, an aliphatic hydrocarbon group having 1 to 8 carbon atoms and an aromatic group having 1 to 10 carbon atoms. The aliphatic hydrocarbon group and the aromatic group represented by R15, R16, R17, and R18 may have a substituent. Examples of the aliphatic hydrocarbon group and the aromatic group represented by R15, R16, R17, and R18 are the same as those represented by R11, R12, and R13 in the formula (1) or (2). R15 and R16, R16 and R17, and R17 and R18 may be partially bonded and integrated to form a ring structure. Specific examples thereof include a structure in which R15 and R16 are partially bonded and linked with a cyclic group such as adamantane.
In the formula (V-2), R19 and R20 each independently represent a monovalent organic group. Examples of the monovalent organic group include a hydrogen atom, an aliphatic hydrocarbon group having 1 to 8 carbon atoms, or an aromatic group having 1 to 10 carbon atoms. The aliphatic hydrocarbon group and the aromatic group represented by R19 and R20 may have a substituent. Examples of the aliphatic hydrocarbon group and the aromatic group represented by R19 and R20 are the same as those represented by R11, R12, and R13 in the formula (1) or (2). R19 and R20 may be partially bonded and integrated to form a ring structure. Specific examples thereof include a structure in which R19 and R20 are partially bonded and linked with a cyclic group such as adamantane.
In the formula (V-4), R21 represents a monovalent organic group. Examples of the monovalent organic group include a hydrogen atom, an aliphatic hydrocarbon group having 1 to 8 carbon atoms, or an aromatic group having 1 to 10 carbon atoms. The aliphatic hydrocarbon group and the aromatic group represented by R21 may have a substituent. Examples of the aliphatic hydrocarbon group and the aromatic group represented by R21 are the same as those represented by R11, R12, and R13 in the formula (1) or (2).
In the formula (V-5), R22, R23 and R24 each independently represent a monovalent organic group. Examples of the monovalent organic group include a hydrogen atom, an aliphatic hydrocarbon group having 1 to 8 carbon atoms, or an aromatic group having 1 to 10 carbon atoms. The aliphatic hydrocarbon group and the aromatic group represented by R22, R23 and R24 may have a substituent. Examples of the aliphatic hydrocarbon group and the aromatic group represented by R22, R23 and R24 are the same as those represented by R11, R12, and R13 in the formula (1) or (2). R22 and R23; and R23 and R24 may be partially bonded and integrated to form a ring structure. Specific examples thereof include a structure in which R22 and R23 are partially bonded and linked with a cyclic group such as adamantane.
In the formulae (4) and (5), it is preferable that the divalent organic group represented by Z contain an electron-donating atom. That is, it is preferable that the luminescent material according to the embodiment be a transition metal complex including a partial structure represented by the following formula (6) or (7).
(In the formulae (6) and (7), M represents Ir, Os, Pt, Ru, Rh or Pd; X represents C, Si, Ge, Sn, B, Pb, or N; R11, R12, R13, and R14 each independently represent a monovalent organic group; Y represents a divalent hydrocarbon group; D represents an electron-donating atom; and V represents a divalent organic group having a ring structure.)
In the formulae (6) and (7), specific examples of R11, R12, R13, X, M, V, and Y are the same as above.
Examples of the monovalent organic group represented by R14 include an aliphatic hydrocarbon group having 1 to 8 carbon atoms, or an aromatic group having 1 to 10 carbon atoms. The aliphatic hydrocarbon group and the aromatic group represented by R14 may have a substituent.
Examples of the aliphatic hydrocarbon group having 1 to 8 carbon atoms represented by R14 include a linear, branched, or cyclic aliphatic hydrocarbon group. Specific examples thereof include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a tert-butyl group, an n-pentyl group, an n-hexyl group, an n-heptyl group, an n-octyl group, and a cyclohexyl group. R11 and R12 may be partially bonded and integrated to form a ring structure.
Examples of the aromatic group having 1 to 10 carbon atoms represented by R14 include a phenyl group and a naphthyl group, and these aromatic groups may have a substituent.
Specific examples of the electron-donating atom represented by D include C, N, P, O, and S. Among these, C or N is preferable; and N is particularly preferable.
For example, it is preferable that the luminescent material according to the embodiment be a transition metal complex including a partial structure represented by the following formula (8) or (9).
(In the formula (8) and (9), M represents Ir, Os, Pt, Ru, Rh or Pd; X represents C, Si, Ge, Sn, B, Pb, or N; R11, R12, R13, and R14 each independently represent a monovalent organic group; Y represents a divalent hydrocarbon group; and V represents a divalent organic group having a ring structure.)
In the formulae (8) and (9), specific examples of R11, R12, R13, R14, X, M, V, and Y are the same as above.
Furthermore, it is preferable that the luminescent material according to the embodiment be a transition metal complex having a partial structure represented by the following formula (10) or (11).
(In the formulae (10) and (11), M represents Ir, Os, Pt, Ru, Rh or Pd; X represents C, Si, Ge, Sn, B, Pb, or N; R11, R12, R13, R14, R15, R16, R17, and R18 each independently represent a monovalent organic group; and Y represents a divalent hydrocarbon group.)
In the formulae (10) and (11), specific examples of R11, R12, R13, R14, R15, R16, R17, R18, X, M, and Y are the same as above.
In addition, for example, it is particularly preferable that the luminescent material according to the embodiment be an Ir complex having a partial structure represented by the following formula (12).
(In the formula (12), R11, R12, R13, R14, R15, R16, R17, and R18 each independently represent a monovalent organic group.)
In the formula (12), specific examples of R11, R12, R13, R14, R15, R16, R17, and R18 are the same as above.
In addition, it is preferable that, when a central metal is any one of Ir, Os, Ru, and Rh, the luminescent material according to the embodiment be a tris complex in which three bidentate ligands are coordinated. In this case, as geometric isomers, a mer (meridional) isomer or a fac isomer (facial) may be present. In the luminescent material according to the embodiment, either or both of a mer isomer and a fac isomer may be present. Among these, as described below in Examples, it is preferable that the amount of a mer isomer contained in the transition metal complex be greater than that of a fac isomer, from the viewpoint of improving the PL quantum yield.
Hereinafter, preferable specific examples of a transition metal complex which is the luminescent material according to the embodiment are shown below, but the embodiment is not limited thereto. In the following examples, geometric isomers are not particularly distinguished, and the luminescent material according the embodiment may contain both geometric isomers. In addition, in the following structural formulae, Ph represents a phenyl group.
Among the above examples of the transition metal complex, the following compounds are particularly preferable as the luminescent material according to the embodiment.
The luminescent material according to the embodiment realizes highly efficient blue phosphorescent emission even when the luminescent material does not contain an electron-attracting group.
Next, a synthesis method of the transition metal complex which is the luminescent material according to the embodiment will be described. The transition metal complex having a partial structure represented by any one of the formulae (1) to (12) can be synthesized in a combination of well-known methods. For example, a ligand can be synthesized referring to, for example, J. Am. Chem. Soc., 2005, 127, 10182; Eur. J. Inorg. Chem., 1999, 1765; J. Am. Chem. Soc., 2004, 126, 10198; Synthesis, 1986, 4, 288; Chem. Ber., 1992, 125, 389; and J. Organometal. Chem., 11 (1968), 399. A transition metal complex can be synthesized referring to, for example, Dalton Trans., 2008, 916, Angew. Chem. Int. Ed., 2008, 47, 4542.
Hereinafter, as an example of a synthesis method of a metal transition complex which is the luminescent material according to the embodiment, a synthesis method of a transition metal complex including a partial structure of a carbene ligand (X═C, M=Ir) represented by the formula (11) will be described. An Ir complex (Compound (a-5)) including a partial structure of a carbene ligand (X═C) represented by the formula (11) can be synthesized according to the following synthesis route.
Compound (a-4) which is a ligand can be synthesized referring to, for example, J. Am. Chem. Soc., 2005, 127, 10182 and Eur. J. Inorg. Chem., 1999, 1765. First, Compound (−1) and Compound (a-2) are caused to react with each other in a toluene solution at −78° C., followed by heating to room temperature. As a result, Compound (a-3) can be synthesized. Next, an n-butyllithium solution is added dropwise to Compound (a-3) at 0° C., followed by cooling to −100° C. Then, a dibromoborane compound having a desired ligand R13 is added thereto, followed by slow heating to room temperature. As a result, Compound (a-4) can be synthesized.
Compound (a-5) which is a transition metal complex can be synthesized referring to, for example, Dalton Trans., 2008, 916. 6 equivalents of Compound (a-4) are added to 1 equivalent of [IrCl(COD)]2 (COD=1,5-cyclooctadiene) and silver oxide is further added thereto, followed by heating to reflux. As a result, Compound (a-5) can be synthesized. In the case of a trix complex such as Compound (a-5), a mer isomer or a fac isomer which is a geometric isomer may be present. These geometric isomers can be separated with a method such as recrystallization.
In addition, when the luminescent material according to the embodiment includes two different kinds of ligands, a metal transition complex can be synthesized referring to, for example, Angew. Chem. Int. Ed., 2008, 47, 4542. For example, when an Ir complex [Ir(La)2(Lb)] having two bidentate ligands La and one bidentate ligand Lb is synthesized, 1 equivalent of [IrCl(COD)]2 and 4 equivalents of the ligand La are heated to reflux in an alcohol solution in the presence of sodium methoxide according to a method described in, for example, Dalton Trans., 2008, 916. As a result, a chlorine-bridged dinuclear iridium complex [Ir(μ-Cl)(La)2]2 is synthesized. This chlorine bridged dinuclear iridium complex is caused to react with the ligand Lb. As a result, the Ir complex [Ir(La)2(Lb)] can be synthesized. When either the ligand La or the ligand Lb is a carbene ligand or a silylene ligand, or when both the ligand La and the ligand Lb are a carbene ligand or a silylene ligand, this synthesis method can be applied. The synthesized transition metal complex which is a luminescent material can be identified using MS spectrum (FAB-MS), 1H-NMR spectrum, LC-MS spectrum, or the like.
Hereinafter, embodiments of an organic light-emitting element, a wavelength-converting light-emitting element, an organic laser diode element, a dye laser, a display device, and an illumination device according to embodiments of the present invention will be described referring to the drawings. In the respective drawings of
An organic light-emitting element (organic EL element) according to an embodiment of the present invention includes at least one organic layer that includes a light-emitting layer; and a pair of electrodes between which the organic layer is interposed.
The first electrode 12 and the second electrode 16 function as an anode or a cathode of the organic light-emitting element 10 as a pair. That is, when the first electrode 12 is an anode, the second electrode 16 is a cathode; and when the first electrode 12 is a cathode, the second electrode 16 is an anode. In
The organic EL layer (organic layer) 17 may have a single-layer structure including the organic light-emitting layer 14; and may have a multilayer structure such as the lamination structure illustrated in
(1) Organic light-emitting Layer 14
(2) Hole transport layer 13/Organic light-emitting layer 14
(3) Organic light-emitting layer 14/Electron transport layer 15
(4) Hole injection layer/Organic light-emitting layer 14
(5) Hole transport layer 13/Organic light-emitting layer 14/Electron transport layer 15
(6) Hole injection layer/Hole transport layer 13/Organic light-emitting layer 14/Electron transport layer 15
(7) Hole injection layer/Hole transport layer 13/Organic light-emitting layer 14/Electron transport layer 15/Electron injection layer
(8) Hole injection layer/Hole transport layer 13/Organic light-emitting layer 14/Hole blocking layer/Electron transport layer 15
(9) Hole injection layer/Hole transport layer 13/Organic light-emitting layer 14/Hole blocking layer/Electron transport layer 15/Electron injection layer
(10) Hole injection layer/Hole transport layer 13/Electron blocking layer/Organic light-emitting layer 14/Hole blocking layer/Electron transport layer 15/Electron injection layer
Here, each layer of the organic light-emitting layer 14, the hole injection layer, the hole transport layer 13, the hole blocking layer, the electron blocking layer, the electron transport layer 15, and the electron injection layer may have a single-layer structure or a multilayer structure.
The organic light-emitting layer 14 may be formed of only the above-described luminescent material according to the embodiment. The organic light-emitting layer 14 may be formed of a combination of the luminescent material according to the embodiment, which is a dopant, and a host material; may further include a hole transport material, an electron transport material, and an additive (for example, a donor or an acceptor) as necessary; and may have a configuration in which the above-described materials are dispersed in a polymer material (binder resin) or in an inorganic material. From the viewpoints of luminous efficiency and lifetime, it is preferable that the luminescent material according to the embodiment, which is a light-emitting dopant, be dispersed in a host material. The organic light-emitting layer 14 recombines holes injected from the first electrode 12 with electrons injected from the second electrode 16 and discharges (emits) light using phosphorescent emission of the luminescent material according to the embodiment contained in the organic light-emitting layer 14.
When the organic light-emitting layer 14 is formed of a combination of the luminescent material according to the embodiment, which is a light-emitting dopant, and a host material, a well-known host material for organic EL of the related art can be used as the host material. Examples of such a host material include carbazole derivatives such as 4,4′-bis(carbazole)biphenyl, 9,9-di(4-dicarbazole-benzyl)fluorene (CPF), 3,6-bis(triphenylsilyl)carbazole (mCP), and poly(N-octyl-2,7-carbazole-O-9,9-dioctyl-2,7-fluorene) (PCF); aniline derivatives such as 4-(diphenylphosphoryl)-N,N-diphenylaniline (HM-Al); fluorene derivatives such as 1,3-bis(9-phenyl-9H-fluoren-9-yl)benzene (mDPFB), and 1,4-bis(9-phenyl-9H-fluoren-9-yl)benzene (pDPFB); 1,3,5-tris[4-(diphenylamino)phenyl]benzene (TDAPB); and 1,4-bis(triphenylsilyl)benzene (UGH-2).
The hole injection layer and the hole transport layer 13 are provided between the first electrode 12 and the organic light-emitting layer 14 in order to efficiently perform the injection of holes from the first electrode 12, which is the anode, and the transport (injection) of holes to the organic light-emitting layer 14. The electron injection layer and the electron transport layer 15 are provided between the second electrode 16 and the organic light-emitting layer 14 in order to efficiently perform the injection of electrons from the second electrode 16, which is the cathode, and the transport (injection) of electrons to the organic light-emitting layer 14.
Each of the hole injection layer, the hole transport layer 13, the electron injection layer, and the electron transport layer 15 can be formed of a well-known material of the related art. Each of the hole injection layer, the hole transport layer 13, the electron injection layer, and the electron transport layer 15 may be formed of only the following exemplary materials. As necessary, each of the hole injection layer, the hole transport layer 13, the electron injection layer, and the electron transport layer 15 may further include an additive (for example, a donor or an acceptor) as well as the following exemplary compounds. Each of the hole injection layer, the hole transport layer 13, the electron injection layer, and the electron transport layer 15 may have a configuration in which the following exemplary materials are dispersed in a polymer material (binder resin) or in an inorganic material.
Examples of a material forming the hole transport layer 13 include low-molecular-weight materials including oxides such as vanadium oxide (V2O5) and molybdenum oxide (MoO2), inorganic p-type semiconductor materials, porphyrin compounds, aromatic tertiary amine compounds such as N,N′-bis(3-methylphenyl)-N,N′-bis(phenyl)-benzidine (TPD) and N,N′-di(naphthalene-1-yl)-N,N′-diphenyl-benzidine (NPD), hydrazone compounds, quinacridone compounds, and styrylamine compounds; and polymer materials including polyaniline (PANI), polyaniline-camphorsulfonic acid (PANI-CSA), 3,4-polyethylenedioxithiophene/polystyrenesulfonate (PEDOT/PSS), poly(triphenylamine) derivetives (Poly-TPD), polyvinyl carbazole (PVCz), poly(p-phenylenevinylene) (PPV), and poly(p-naphthalenevinylene) (PNV).
In order to efficiently perform the injection and transport of holes from the first electrode 12, as a material forming the hole injection layer, it is preferable that a material having a smaller energy level of highest occupied molecular orbital (HOMO) than that of a material forming the hole transport layer 13 be used. As the material forming the hole transport layer 13, it is preferable that a material having a higher hole mobility than that of the material forming the hole injection layer be used.
Examples of the material forming the hole injection layer include phthalocyanine derivatives such as copper phthalocyanine; amine compounds such as 4,4′,4″-tris(3-methylphenylphenylamino)triphenylamine, 4,4′,4″-tris(1-naphthylphenylamino)triphenylamine, 4,4′,4″-tris(2-naphthylphenylamino)triphenylamine, 4,4′,4″-tris[biphenyl-2-yl(phenyl)amino]triphenylamine, 4,4′,4″-tris[biphenyl-3-yl(phenyl)amino]triphenylamine, 4,4′,4″-tris[biphenyl-4-yl(3-methylphenyl)amino]triphenylamine, and 4,4′,4″-tris[9,9-dimethyl-2-fluorenyl(phenyl)amino]triphenylamine; and oxides such as vanadium oxide (V2O5) and molybdenum oxide (MoO2). However, the material forming the hole injection layer is not limited thereto.
In addition, in order to improve hole injecting and transporting properties, it is preferable that the hole injection layer and the hole transport layer 13 be doped with an acceptor. As the acceptor, materials which are well-known in the related art as an acceptor material for organic EL can be used.
Examples of the acceptor material include inorganic materials such as Au, Pt, W, Ir, POCl3, AsF6, Cl Br, I, vanadium oxide (V2O5), and molybdenum oxide (MoO2); compounds having a cyano group such as TCNQ (7,7,8,8-tetracyanoquinodimethane), TCNQF4 (tetrafluorotetracyanoquinodimethane), TCNE (tetracyanoethylene), HCNB (hexacyanobutadiene), and DDQ (dicyclodicyanobenzoquinone); compounds having a nitro group such as TNF (trinitrofluorenone) and DNF (dinitrofluorenone); and organic materials such as fluorenyl, chloranil, and bromanil. Among these, compounds having a cyano group such as TCNQ, TCNQF4, TCNE, HCNB, and DDQ are more preferable from the viewpoint of being able to efficiently increasing the carrier density.
As a material forming the electron blocking layer, the above-described examples of the material forming the hole transport layer 13 and the hole injection layer can be used.
Examples of a material forming the electron transport layer 15 include low-molecular-weight materials such as inorganic materials which are n-type semiconductors, oxadiazole derivatives, triazole derivatives, thiopyrazine dioxide derivatives, benzoquinone derivatives, naphthoquinone derivatives, anthraquinone derivatives, diphenoquinone derivatives, fluorenone derivatives, and benzodifuran derivatives; and polymer materials such as poly(oxadiazole) (Poly-OXZ) and polystyrene derivatives (PSS).
Examples of a material forming the electron injection layer include, particularly, fluorides such as lithium fluoride (LiF) and barium fluoride (BaF2); and oxides such as lithium oxide (Li2O).
From the viewpoints of efficiently performing the injection and transport of electrons from the second electrode 16 which is the cathode, as the material forming the electron injection layer, it is preferable that a material having a higher energy level of lowest unoccupied molecular orbital (LUMO) than that of the material forming the electron transport material 15 be used; and as the material forming the electron transport layer 15, it is preferable that a material having a higher electron mobility than that of the material forming the electron injection layer be used.
In addition, in order to improve electron injecting and transporting properties, it is preferable that the electron injection layer and the electron transport layer 15 be doped with a donor. As the donor, materials which are well-known in the related art as a donor material for organic EL can be used.
Examples of the donor material include inorganic materials such as alkali metals, alkaline earth metals, rare earth elements, Al, Ag, Cu and In; and organic materials such as anilines, phenylenediamines, benzidines (for example, N,N,N′,N′-tetraphenylbenzidine, N,N′-bis-(3-methylphenyl)-N,N′-bis-(phenyl)-benzidine, and N,N′-di(naphthalene-1-yl)-N,N′-diphenyl-benzidine), compounds having an aromatic tertiary amine in a structure thereof such as triphenylamines (for example, triphenylamine, 4,4′,4″-tris(N,N-diphenyl-amino)-triphenylamine, 4,4′,4″-tris(N-3-methylphenyl-N-phenyl-amino)-triphenylamine, and 4,4′,4″-tris(N-(1-naphthyl)-N-phenyl-amino)-triphenylamine), and triphenyldiamines (for example, N,N-di-(4-methyl-phenyl)-N,N-diphenyl-1,4-phenylenediamine), condensed polycyclic compounds (which may have a substituent; for example, phenanthrene, pyrene, perylene, anthracene, tetracene, and pentacene), TTF (tetrathiafulvalene), dibenzofuran, phenothiazine, and carbazole. Among these, compounds having an aromatic tertiary amine in a structure thereof, condensed polycyclic compounds, and alkali metals are more preferable from the viewpoint of more efficiently increasing the carrier density.
As a material forming the hole blocking layer, the above-described examples of the material forming the electron transport layer 15 and the electron injection layer can be used.
Examples of a method of forming the organic light-emitting layer 14, the hole transport layer 13, the electron transport layer 15, the hole injection layer, the electron injection layer, the hole blocking layer, the electron blocking layer and the like included in the organic EL layer 17 include methods of forming the layers using an organic EL layer-forming coating solution in which the above-described materials are dissolved and dispersed in a solvent through a well-known wet process including a coating method such as a spin coating method, a dipping method, a doctor blade method, a discharge coating method, and a spray coating method; and a printing method such as an ink jet method, a relief printing method, an intaglio printing method, a screen printing method, or a micro gravure method. Other examples thereof include methods of forming the layers using the above-described materials through a well-known dry process such as a resistance heating deposition method, an electron beam (EB) deposition method, a molecular beam epitaxy (MBE) method, a sputtering method, or an organic vapor-phase deposition (OVPD) method. Alternatively, for example, methods of forming the layers using a laser transfer method can be used. When the organic EL layer 17 is formed through a wet process, the organic EL layer-forming coating solution may contain an additive for adjusting properties of the coating solution such as a leveling agent or a viscosity adjuster.
In general, the thickness of each layer included in the organic EL layer 17 is approximately 1 nm to 1000 nm and more preferably 10 nm to 200 nm. When the thickness of each layer included in the organic EL layer 17 is less than 10 nm, there are concerns that necessary properties (injecting properties, transporting properties, and confinement properties of charge (electron and hole) may not be obtained and images defects may occur due to foreign materials such as dust. In addition, when the thickness of each layer included in the organic EL layer 17 is greater than 200 nm, the drive voltage is increased and there is a concern that the power consumption may increase.
The first electrode 12 is formed on the substrate (not illustrated), and the second electrode 16 is formed on the organic EL layer (organic layer) 17.
As an electrode material forming the first electrode 12 and the second electrode 16, a well-known electrode material can be used. From the viewpoint of efficiently performing the injection of holes to the organic EL layer 17, examples of the material forming the first electrode 12 which is the anode include metals having a work function of 4.5 eV or higher such as gold (Au), platinum (Pt), and nickel (Ni); oxide (ITO) formed of indium (In) and tin (Sn); oxide (SnO2) of tin (Sn); and oxide (IZO) formed of indium (In) and zinc (Zn). From the viewpoint of efficiently performing the injection of electrons to the organic EL layer 17, examples of the material forming the second electrode 16 which is the cathode include metals having a work function of 4.5 eV or lower such as lithium (Li), calcium (Ca), cerium (Ce), barium (Ba), and aluminum (Al); and alloys containing these metals such as Mg:Ag alloy and Li:Al alloy.
The first electrode 12 and the second electrode 16 can be formed on the substrate using the above-described materials according to a well-known method such as an EB (electron beam) deposition method, a sputtering method, an ion plating method, or a resistance heating deposition method. However, the embodiment is not limited to these formation methods. In addition, as necessary, the formed electrode can be patterned using a photolithography method or a laser lift-off method. In this case, by using a shadow mask in combination, the electrode can be directly patterned.
The thicknesses of the first electrode 12 and the second electrode 16 are preferably greater than or equal to 50 nm. When the thicknesses of the first electrode 12 and the second electrode 16 are less than 50 nm, the interconnection resistance is increased, and thus there is a concern that the drive voltage may increase.
The organic light-emitting element 10 illustrated in
The organic light-emitting element according to the embodiment may have a bottom emission type device configuration in which emitted light is discharged through a substrate; or a top emission type device configuration in which emitted light is discharged to the opposite side to a substrate. In addition, a method of driving the organic light-emitting element according to the embodiment is not particularly limited, and an active driving method or a passive driving method may be used. However, it is preferable that the organic light-emitting element be driven using an active driving method. By adopting an active driving method, the light-emitting time of the organic light-emitting element is increased compared to a passive driving method, a drive voltage required for obtaining a desired luminance can be reduced, and the power consumption can be reduced. Therefore, an active driving method is preferable.
The organic light-emitting element 20 illustrated in
The TFT circuits 2 and various interconnections (not illustrated) are formed on the substrate 1. Furthermore, the interlayer dielectric 3 and the planarizing film 4 are sequentially laminated so as to cover an upper surface of the substrate 1 and the TFT circuits 2.
Examples of the substrate 1 include inorganic material substrates formed of glass, quartz, or the like; plastic substrates formed of polyethylene terephthalate, polycarbazole, polyimide, or the like; insulating substrates such as a ceramic substrate formed of alumina or the like; metal substrates formed of aluminum (Al) iron (Fe), or the like; substrates obtained by coating a surface of the above-described substrates with an organic insulating material such as silicon oxide (SiO2); and substrates obtained by performing an insulation treatment on a surface of a metal substrate formed of Al or the like using a method such as anodic oxidation. However, the embodiment is not limited thereto.
The TFT circuits 2 are formed on the substrate 1 in advance before forming the organic light-emitting element 20 and have a switching function and a driving function. As the TFT circuits 2, well-known TFT circuits 2 of the related art can be used. In addition, in the embodiment, for the switching and driving functions, metal-insulator-metal (MIM) diodes can be used instead of TFTs.
The TFT circuits 2 can be formed using a well-known material, structure, and formation method. Examples of a material of an active layer of the TFT circuits 2 include inorganic semiconductor materials such as amorphous silicon, polycrystalline silicon (polysilicon), microcrystalline silicon, and cadmium selenide; oxide semiconductor materials such as zinc oxide and indium oxide-gallium oxide-zinc oxide; and organic semiconductor materials such as polythiophene derivatives, thiophene oligomers, poly(p-phenylenevinylene) derivatives, naphthacene, and pentacene. In addition, examples of a structure of the TFT circuits 2 include a staggered type, an inverted staggered type, a top-gate type, and a coplanar type.
A gate insulator of the TFT circuits 2 used in the embodiment can be formed of a well-known material. Examples of the material include SiO2 which is formed using a plasma-enhanced chemical vapor deposition (PECVD) method, a low pressure chemical vapor deposition (LPCVD), or the like; and SiO2 obtained by thermally oxidizing a polysilicon film. In addition, a signal electrode line, a scanning electrode line, and a common electrode line of the TFT circuits 2, the first electrode, and the second electrode which are used in the embodiment can be formed of a well-known material, and examples thereof include tantalum (Ta), aluminum (Al), and copper (Cu).
The gate insulator 3 can be formed of a well-known material, and examples thereof include inorganic materials such as silicon oxide (SiO2), silicon nitride (SiN or Si2N4), tantalum oxide (TaO or Ta2O5); and organic materials such as acrylic resins and resist materials.
Examples of a method of forming the interlayer dielectric 3 include a dry process such as a chemical vapor deposition (CVD) method and a vacuum deposition method; and a wet process such as a spin coating method. In addition, as necessary, patterning can be performed using a photolithography method or the like.
In the organic light-emitting element 20 according to the embodiment, light emitted from the organic EL element 10 is extracted from the sealing substrate 9 side. Therefore, in order to prevent TFT properties of the TFT circuits 2, formed on the substrate 1, from being changed by light incident from outside, it is preferable that the light-shielding interlayer dielectric 3 (light-shielding insulating film) be used. In addition, in the embodiment, the interlayer dielectric 3 and the light-shielding insulating film can be used in combination. Examples of the light-shielding insulating film include polymer resins such as polyimide in which a pigment or a dye such as phthalocyanine or quinacridone is dispersed; color resists; black matrix materials; and inorganic insulating materials such as and NixZnyFe2O4.
The planarizing film 4 is provided for preventing defects of the organic EL element 10 (for example, a defect of a pixel electrode, a defect of the organic EL layer, disconnection of a counter electrode, short-circuiting between a pixel electrode and a counter electrode, or reduction in withstand voltage) caused by convex and concave portions on a surface of the TFT circuits 2 The planarizing film 4 may not be provided.
The planarizing film 4 can be formed of a well-known material, and examples thereof include inorganic materials such as silicon oxide, silicon nitride, and tantalum oxide; and organic materials such as polyimide, acrylic resins, and resist materials. Examples of a method of forming the planarizing film 4 include a dry process such as a CVD method and a vacuum deposition method; and a wet process such as a spin coating method. However, the embodiment is not limited to these materials and formation methods. In addition the planarizing film 4 may have a single-layer structure or a multilayer structure.
In the organic light-emitting element 20 according to the embodiment, light emitted from the organic light-emitting layer 14 of the organic EL element 10, which is a light source, is extracted from the second electrode 16 side which is the sealing substrate 9 side. Therefore, as the second electrode 16, it is preferable that a semitransparent electrode be used. As a material of the semitransparent electrode, a metal semitransparent electrode may be used alone; or a metal semitransparent electrode and a transparent electrode material may be used in combination. From the viewpoints of reflectance and transparency, silver or silver alloys are preferable.
In the organic light-emitting element 20 according to the embodiment, as the first electrode 12 that is disposed on the opposite side to the side of extracting light from the organic light-emitting layer 14, in order to increase the efficiency of extracting light from the organic light-emitting layer 14, it is preferable that an electrode (reflective electrode) having high light reflectance be used. Examples of an electrode material used at this time include a reflective metal electrode such as aluminum, silver, gold, aluminum-lithium alloys, aluminum-neodymium alloys, or aluminum-silicon alloys; and electrodes obtained by combining a transparent electrode and the above-described reflective metal electrode (reflective electrode).
In addition, in the organic light-emitting element 20 according to the embodiment, plural first electrodes 12 that are arranged on the substrate 1 side (opposite side to the side of extracting light from the organic light-emitting layer 14) are provided so as to correspond to respective pixels; and the edge cover 19 that is formed of an insulating material so as to cover respective edge portions (end portions) of first electrodes 12 and 12 adjacent to each other is formed. This edge cover 19 is provided for preventing leakage between the first electrode 12 and the second electrode 16. The edge cover 19 can be formed of an insulating material with a well-known method such as an EB deposition method, a sputtering method, an ion plating method, or a resistance heating deposition method. In addition, patterning can be performed using a well-known dry or wet photolithography method. However, the embodiment is not limited to these formation methods. In addition, as the insulating material forming the edge cover 19, a well-known material of the related art can be used. The insulating material is not particularly limited in the embodiment, and examples thereof include SiO, SiON, SiN, SiOC, SiC, HfSiON, ZrO, HfO, and LaO.
The thickness of the edge cover 19 is preferably 100 nm to 2000 nm. When the thickness of the edge cover 19 is greater than or equal to 100 nm, sufficient insulating property can be secured. As a result, an increase in power consumption and non-emission, caused by leakage between the first electrode 12 and the second electrode 16, can be prevented. In addition, when the thickness of the edge cover 19 is less than or equal to 2000 nm, deterioration in the productivity of a film-forming process and disconnection of the second electrode 16 in the edge cover 19 can be prevented.
In addition, the reflective electrode 11 and the first electrode 12 are connected to one of the TFT circuits 2 through the interconnection 2b which penetrates the interlayer dielectric 3 and the planarizing film 4. The second electrode 16 is connected to one of the TFT circuits 2 through the interconnection 2a which penetrates the interlayer dielectric 3, the planarizing film 4, and the edge cover 19. The interconnections 2a and 2b are not particularly limited as long as they are formed of a conductive material such as Cr, Mo, Ti, Ta, Al, Al alloys, Cu, or Cu alloys. The interconnections 2a and 2b are formed using a well-known method of the related art such as a sputtering method or CVD method and a mask process.
The inorganic sealing film 5 that is formed of SiO, SiON, SiN, or the like is formed so as to cover the upper surface and side surface of the organic EL element 10 formed on the planarizing film 4. The inorganic sealing film 5 can be formed by forming an inorganic film of SiO, SiON, SiN, or the like with an plasma CVD method, an ion plating method, an ion beam method, a sputtering method, or the like. In order to extract light from the organic EL element 10, it is necessary that the inorganic sealing film 5 be light-transmissive.
The sealing substrate 9 is provided on the inorganic sealing film 5, and the organic light-emitting element 10, formed between the substrate 1 and the sealing substrate 9, is sealed in a sealing region surrounded by the sealing material 6.
By providing the inorganic sealing film 5 and the sealing material 6, oxygen or water can be prevented from being mixed into the organic EL layer 17 from outside. As a result, the lifetime of the organic light-emitting element 20 can be improved.
As a material forming the sealing substrate 9, the same materials as those of the above-described substrate 1 can be used. However, since the organic light-emitting element 20 according to the embodiment extracts light from the sealing substrate 9 side (when the observer observes emission from the outside of the sealing substrate 9), it is necessary that the sealing substrate 9 be light-transmissive. In addition, in order to improve color purity, a color filter may be formed on the sealing substrate 9.
As the sealing material 6, a well-known sealing material of the related art can be used. In addition, as a method of forming the sealing material 6, a well-known sealing method of the related art can be used.
As the sealing material 6, for example, a resin (curing resin) can be used. In this case, the upper surface and/or side surface of the inorganic sealing film 5 of the substrate 1 on which the organic EL element 10 and the inorganic sealing film 5 are formed; or the sealing substrate 9 is coated with a curing resin (photocurable resin, thermosetting resin) using a spin coating method or a laminate method. Then, the substrate 1 and the sealing substrate 9 are bonded to each other through the resin layer to perform photo-curing or thermal curing. As a result, the sealing material 6 can be formed. It is necessary that the sealing material 6 be light-transmissive.
In addition, inactive gas such as nitrogen gas or argon gas may be introduced into a gap between the inorganic sealing film 5 and the sealing substrate 9. For example, a method of sealing inactive gas such as nitrogen gas or argon gas with the sealing substrate 9 such as a glass substrate may be used.
In this case, in order to efficiently reduce deterioration of the organic EL portion caused by water, it is preferable that a moisture absorbent such as barium oxide or the like be mixed into inorganic gas to be sealed.
As in the case of the organic light-emitting element 10 according to the first embodiment, the organic EL layer (organic layer) 17 of the organic light-emitting element 20 according to the embodiment also contains the luminescent material according to the embodiment. Therefore, the organic light-emitting element 20 recombines holes injected from the first electrode 12 with electrons injected from the second electrode 16 and can discharge (emit) blue light with a high efficiency using phosphorescent emission of the luminescent material according to the embodiment contained in the organic layer 17 (organic light-emitting layer 14).
A wavelength-converting light-emitting element according to an embodiment of the present invention includes a light-emitting element; and a fluorescent layer that is disposed on a side of extracting light from the light-emitting element, absorbs light emitted from the light-emitting element, and emits light having a different wavelength from that of the absorbed light.
The wavelength-converting light-emitting element 30 illustrated in
The organic EL light-emitting portion 10 is covered with the inorganic sealing film 5. In the organic EL light-emitting portion 10, the organic EL layer (organic layer) 17 in which a hole transport layer 13, a light-emitting layer 14, and an electron transport layer 15 are laminated is interposed between a first electrode 12 and a second electrode 16. A reflective electrode 11 is formed on a lower surface of the first electrode 12. The reflective electrode 11 and the first electrode 12 are connected to one of the TFT circuits 2 through an interconnection 2b which penetrates the interlayer dielectric 3 and the planarizing film 4. The second electrode 16 is connected to one of the TFT circuits 2 through an interconnection 2a which penetrates the interlayer dielectric 3, the planarizing film 4, and an edge cover 19.
In the wavelength-converting light-emitting element 30 according to the embodiment, light emitted from the organic light-emitting element 10, which is a light source, is incident to the respective fluorescent layers 18R and 18G and the scattering layer 31; this incident layer transmits through the scattering layer 31 without any change; the respective fluorescent layers 18R and 18G converts the incident light into light beams of three colors including red, green, and blue; and the converted three light beams are emitted to the sealing substrate 9 side (observer side).
In
In an example of
The red fluorescent layer 18R absorbs light in a blue wavelength range emitted from the organic light-emitting element 10, which is a light source; converts the light in a blue wavelength range into light in a red wavelength range; and emits the light in a red wavelength range to the sealing substrate 9 side.
The green fluorescent layer 18G absorbs light in a blue wavelength range emitted from the organic light-emitting element 10, which is a light source; converts the light in a blue wavelength range into light in a green wavelength range; and emits the light in a green wavelength range to the sealing substrate 9 side.
The scattering layer 31 is provided for improving the viewing angle characteristic and extraction efficiency of light in a blue wavelength range emitted from the organic light-emitting element 10 which is a light source; and emits the light in a blue wavelength range to the sealing substrate 9 side. The scattering layer 31 may not be provided.
In this way, by providing the red fluorescent layer 18R and the green fluorescent layer 18G (and the scattering layer 31), light emitted from the organic light-emitting element 10 is converted into light beams of three colors including red, green, and blue; and the converted light beams are emitted to the sealing substrate 9 side, thereby making full-color display possible.
The color filters 8R, 8G, and 8B that are disposed between the sealing substrate 9 on the light extraction side (observer side) and the fluorescent layers 18R and 18G and the scattering layer 31 are provided for improving the color purity of red, green, and blue light beams emitted from the wavelength-converting light-emitting element 30; and for enlarging the color reproduction range of the wavelength-converting light-emitting element 30. In addition, the red color filter 8R that is formed on the red fluorescent layer 18R and the green color filter 8G that is formed on the green fluorescent layer 18G absorb blue components and ultraviolet components of outside light. Therefore, the emission of the respective fluorescent layers 8R and 8G caused by outside light can be reduced and prevented; and deterioration in contrast can be reduced and prevented.
The color filters 8R, 8G, and 8B are particularly limited, and well-known color filters of the related art can be used. In addition, likewise, as a method of forming the color filters 8R, 8G, and 8B, a well-known method of the related art can be used. The thickness thereof can also be appropriately adjusted.
The scattering layer 31 has a configuration in which transparent particles are dispersed in a binder resin. The thickness of the scattering layer 31 is normally 10 μm to 100 μm and preferably 20 μn to 50 μm.
As the binder resin used for the scattering layer 31, a well-known resin of the related art can be used. The binder resin is not particularly limited, but a light-transmissive resin is preferable. The transparent particles are not particularly limited as long as light emitted from the organic light-emitting element 10 are scattered by and pass through the transparent particles. For example, polystyrene particles having an average particle size of 25 μm and a standard deviation of particle size distribution of 1 μm can be used. In addition, the content of the transparent particles in the scattering layer 31 can be appropriately changed and is not particularly limited.
The scattering layer 31 can be formed using a well-known method of the related art, and the formation method is not particularly limited. Examples of the formation method include methods of forming the layer using a coating solution in which a binder resin and transparent particles are dissolved and dispersed in a solvent through a well-known wet process including a coating method such as a spin coating method, a dipping method, a doctor blade method, a discharge coating method, and a spray coating method; and a printing method such as an ink jet method, a relief printing method, an intaglio printing method, a screen printing method, or a micro gravure method.
The red fluorescent layer 18R contains a fluorescent material capable of absorbing light in a blue wavelength range emitted from the organic light-emitting element 10 to be excited; and emitting fluorescence in a red wavelength range.
The green fluorescent layer 18G contains a fluorescent material capable of absorbing light in a blue wavelength range emitted from the organic light-emitting element 10 to be excited; and emitting fluorescence in a green wavelength range.
The red fluorescent layer 18R and the green fluorescent layer 18G may be formed of the following exemplary fluorescent materials alone; may further contain an additive or the like as necessary; and may have a configuration in which these materials are dispersed in a polymer material (binder resin) or in an inorganic material.
As the fluorescent material forming the red fluorescent layer 18R and the green fluorescent layer 18G, well-known fluorescent materials of the related art can be used. Such fluorescent materials are divided into organic fluorescent materials and inorganic fluorescent materials. Specific exemplary compounds of these fluorescent materials are described below, but the embodiment is not limited to these materials.
First, examples of the organic fluorescent materials will be described. Examples of fluorescent materials used for the red fluorescent layer 18R include cyanine-based dyes such as 4-dicyanomethylene-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran; pyridine-based dyes such as 1-ethyl-2-[4-(p-dimethylamino phenyl)-1,3-butadienyl]-pyridinium-perchlorate; and rhodamine-based dyes such as rhodamine B, rhodamine 6G, rhodamine 3B, rhodamine 101, rhodamine 110, basic violet 11, and sulforhodamine 101. In addition, examples of fluorescent materials used for the green fluorescent layer 18G include coumarin-based dyes such as 2,3,5,6-1H,4H-tetrahydro-8-trifluomethyl quinolizine(9,9a,1-gh)coumarin (coumarin 153), 3-(2′-benzothiazolyl)-7-diethylamino coumarin (coumarin 6), 3-(2′-benzoimidazolyl)-7-N,N-diethylamino coumarin (coumarin 7); and naphthalimide-based dyes such as basic yellow 51, solvent yellow 11, and solvent yellow 116. In addition, the luminescent material according to the embodiment can be used.
Next, examples of the inorganic fluorescent materials will be described. Examples of fluorescent materials used for the red fluorescent layer 18R include Y2O2S:Eu3+, YAlO3:Eu3+, Ca2Y2(SiO4)6:Eu3+, LiY9(SiO4)6O2:Eu3+, YVO4:Eu3+, CaS:Eu3+, Gd2O3:Eu3+, Gd2O2S:Eu3+, Y(P,V)O4:Eu3+, Mg4GeO5.5F:Mn4+, Mg4GeO6:Mn4+, K5Eu2.5(WO4)6.25, Na5Eu2.5(WO4)6.25, K5Eu2.5(MoO4)6.25, and, Na5Eu2.5(MoO4)6.25. Examples of fluorescent materials used for the green fluorescent layer 18G include (BaMg)Al16O27:Eu2+, Mn2+, Sr4Al14O25:Eu2+, (SrBa)Al12Si2O8:Eu2 (BaMg)2SiO4:Eu2+, Y2SiO5:Ce3+,Tb3+, Sr2P2O7—Sr2B2O5:Eu2+, (BaCaMg)5(PO4)3Cl:Eu2+, Sr2Si3O8-2SrCl2.Eu2+, Zr2SiO4, MgAl11O19:Ce3+,Tb3+, Ba2SiO4:Eu2+, Sr2SiO4:Eu2+, and (BaSr)SiO4:Eu2+.
As necessary, it is preferable that the above-described inorganic fluorescent materials be subjected to a surface reforming treatment. Examples of a method of the surface reforming treatment include a chemical treatment using a silane coupling agent and the like; a physical treatment of adding submicron-order particles and the like; and a combination of the above-described methods. When deterioration caused by excitation light and deterioration caused by emission are taken into consideration, it is preferable that the inorganic fluorescent materials be used from the viewpoint of stability. In addition, when the inorganic fluorescent materials are used, it is preferable that the average particle size (d50) of the materials be 0.5 μm to 50 μm.
In addition, when the red fluorescent layer 18R and the green fluorescent layer 18G have a configuration in which the above-described fluorescent materials are dispersed in a polymer material (binder resin), patterning can be performed with a photolithography method by using a photosensitive resin as the polymer material. Here, as the photosensitive layer, one kind or a mixture of plural kinds selected from photosensitive resins (photocurable resist materials) having a reactive vinyl group such as acrylic acid-based resins, methacrylic acid-based resins, polyvinyl cinnamate-based resins, and vulcanite-based resins can be used.
In addition, the red fluorescent layer 18R and the green fluorescent layer 18G can be formed according to a well-known wet process, dry process, or laser transfer method using a fluorescent layer-forming coating solution in which the above-described fluorescent materials (pigments) and binder resin are dissolved and dispersed in a solvent. Here, examples of the well-known wet process include a coating method such as a spin coating method, a dipping method, a doctor blade method, a discharge coating method, and a spray coating method; and a printing method such as an ink jet method, a relief printing method, an intaglio printing method, a screen printing method, or a micro gravure method. In addition, examples of the well-known dry process include a resistance heating deposition method, an electron beam (EB) deposition method, a molecular beam epitaxy (MBE) method, a sputtering method, or an organic vapor-phase deposition (OVPD) method.
The thicknesses of the red fluorescent layer 18R and the green fluorescent layer 18G are normally 100 nm to 100 μm and preferably 1 μm to 100 μm. When the thickness of each of the red fluorescent layer 18R and the green fluorescent layer 18G is less than 100 nm, it is difficult to sufficiently absorb blue light emitted from the organic light-emitting element 10. Therefore, there are cases in which the luminous efficiency of the light-converting light-emitting element 30 may deteriorate or blue transmitted light may be mixed into light converted by the respective fluorescent layers 18R and 18G; and, as a result, the color purity may deteriorate. In addition, in order to improve the absorption of blue light emitted from the organic light-emitting element 10 and to reduce blue transmitted light to a degree that does not have adverse effects on color purity, it is preferable that the thickness of each of the fluorescent layers 18R and 18G be greater than or equal to 1 μm. Even if the thickness of each of the red fluorescent layer 18R and the green fluorescent layer 18G is greater than 100 μm, the luminous efficiency of the light-converting light-emitting element 30 is not increased because blue light emitted from the organic light-emitting element 10 is already sufficiently absorbed. Therefore, since an increase in material cost can be suppressed, it is preferable that the thickness of each of the red fluorescent layer 18R and the green fluorescent layer 18G be less than or equal to 100 μm.
The inorganic sealing film 5 is formed so as to cover the upper surface and side surface of the organic EL element 10. Furthermore, the red fluorescence-converting layer 8R, the green fluorescence-converting layer 8G, the scattering layer 31, and the respective color filters 8R, 8G, and 8B are partitioned by the black matrix 7 and disposed in parallel on one surface of the sealing substrate 9, and the sealing substrate 9 is disposed on the inorganic sealing film 5 such that the respective fluorescent layers 18R and 18G and the scattering layer 31 are disposed opposite the organic light-emitting element. A gap between the inorganic sealing film 5 and the sealing substrate 9 is filled with a sealing material 6. That is, each of the respective fluorescent layers 18R and 18G and the scattering layer 31 that are disposed opposite the organic light-emitting element 10 is partitioned by being surrounded by the black matrix 7; and is sealed in a sealing region surrounded by the sealing material 6.
When a resin (curing resin) is used as the sealing material 6, the inorganic sealing film 5 of the substrate 1 on which the organic light-emitting element 10 and the inorganic sealing film 5 are formed; or the respective fluorescent layers 18R and 18G and the functional layer 31 of the sealing substrate 9 on which the respective fluorescent layers 18R and 18G, the functional layer 31, and the respective color filters 8R, 8G, and 8B are formed, are coated with a curing resin (photocurable resin, thermosetting resin) using a spin coating method or a laminate method. Then, the substrate 1 and the sealing substrate 9 are bonded to each other through the resin layer to perform photo-curing or thermal curing. As a result, the sealing material 6 can be formed.
It is preferable that opposite surfaces of the respective fluorescence-converting layers 18R and 18G and the scattering layer 31 to the sealing substrate 9 be planarized by the planarizing film (not illustrated) and the like. As a result, when the organic light-emitting element 10 is disposed opposite and comes into close contact with the respective fluorescent layers 18R and 18G and the scattering layer 31 with the sealing material 6 interposed therebetween, a gap between the organic light-emitting element 10 and the respective fluorescent layers 18R and 18G and the functional layer 31 can be prevented. Furthermore, the adhesion between the substrate 1, on which the organic light-emitting element 10 is formed, and the sealing substrate 9 on which the respective fluorescent layers 18R and 18G, the scattering layer 31, and the color filters 8R, 8G, and 8B are formed can be improved. As the planarizing film, for example, the same film as the above-described planarizing film 4 can be used.
A material and a formation method of the black matrix 7 are not particularly limited, and a well-known material and formation method of the related art can be used. Among these, it is preferable that the black matrix 7 be formed of a material which further reflects light, which is incident to and scattered by the respective fluorescent layers 18R and 18G, to the respective fluorescent layers 18R and 18G, for example, a light-reflecting metal.
It is preferable that the organic light-emitting element 10 have a top emission type such that a large amount of light can reach the respective fluorescent layers 18R and 18G and the scattering layer 31. At this time, it is preferable that reflective electrodes be used as the first electrode 12 and the second electrode 16; and the optical distance L between these electrode 12 and 16 be adjusted to form a microresonator structure (microcavity structure). In this case, it is preferable that a reflective electrode be used as the first electrode 12; and a semitransparent electrode be used as the second electrode 16.
As a material of the semitransparent electrode, a semitransparent metal electrode may be used alone; or a combination of a semitransparent metal electrode and a transparent electrode material may be used. In particular, as the material of the semitransparent material, silver or silver alloys are preferable from the viewpoints of reflectance and transparency
It is preferable that the thickness of the second electrode 16 which is the semitransparent electrode be 5 nm to 30 nm. When the thickness of the semitransparent film is less than 5 nm, light is not sufficiently reflected and thus there is a possibility that an interference effect may be insufficiently obtained. In addition, when the thickness of the semitransparent film is greater than 30 nm, the light transmittance rapidly deteriorates and thus there is a concern that luminance and efficiency may deteriorate.
In addition, it is preferable that an electrode having high light reflectance be used as the first electrode 12 which is the reflective electrode. Examples of the reflective electrode include a reflective metal electrode such as aluminum, silver, gold, aluminum-lithium alloys, aluminum-neodymium alloys, or aluminum-silicon alloys. As the reflective electrode, a transparent electrode and the above-described reflective metal electrode may be used in combination. In
When the microresonator structure (microcavity) structure is formed by the first electrode 12 and the second electrode 16, light emitted from the organic EL layer 17 is collected in the front direction (light extraction direction: sealing substrate 9 side) due to an interference effect between the first electrode 12 and the second electrode 16. That is, since directivity can be given to light emitted from the organic EL layer 17, light loss escaping to the vicinity can be reduced, and thus the luminous efficiency can be improved. As a result, the light emission energy emitted from the organic light-emitting element 10 can be propagated to the respective fluorescent layers 18R and 18G with a higher efficiency; and the luminance on the front side of the wavelength-converting light-emitting element 30 can be increased.
In addition, due to the above-described microresonator structure, the emission spectrum of the organic EL layer 17 can be adjusted; and a desired emission peak wavelength and full width at half maximum can be obtained. Therefore, the emission spectrum of the organic EL layer 17 can be adjusted to the spectrum capable of effectively exciting fluorescent materials in the fluorescent layers 18R and 18G
By using a semitransparent electrode as the second electrode 16, light, emitted to the opposite direction to the light extraction direction of the respective fluorescent layers 18R and 18G and the scattering layer 31, can be reused.
In the respective fluorescent layer 18R and 18G, the optical distance from an emission position of converted light to a light extraction surface is set to vary depending on each color of the light-emitting element. In the light-converting light-emitting element 30 according to the embodiment, the above-described “emission position” is set to a surface of the respective fluorescent layers 18R and 18G opposite the organic light-emitting element 10 side.
Here, in the respective fluorescent layer 18R and 18G, the optical distance from an emission position of converted light to a light extraction surface can be adjusted by the thickness of the respective fluorescent layers 18R and 18G. The thickness of the respective fluorescent layers 18R and 18G can be adjusted by changing printing conditions in a screen printing method (attack pressure of squeegee, attack angle of squeegee, squeegee speed, or clearance width), the specification of a screen printing plate (selection of screen printing gauze, thickness of emulsion, tension, or strength of frame), and the specification of a fluorescent layer-forming coating solution (viscosity, fluidity, or mixing ratios of resin, pigment, and solvent).
In the light-converting light-emitting element 30 according to the embodiment, light emitted from the organic light-emitting element 10 can be amplified by the microresonator structure (microcavity structure); and the light extraction efficiency of light converted by the respective fluorescent layers 18R and 18G can be improved by adjusting the above-described optical distance (by adjusting the thickness of the respective fluorescent layers 18R and 18G). As a result, the luminous efficiency of the light-converting light-emitting element 30 can be further improved.
The light-converting light-emitting element 30 according to the embodiment has a configuration in which light, emitted from the organic light-emitting element 10 containing the above-described luminescent material according to the first embodiment, is converted by the fluorescent layers 18R and 18G. Therefore, light can be emitted with a high efficiency.
Hereinabove, the light-converting light-emitting element according to the embodiment has been described. However, the light-converting light-emitting element according to the embodiment is not limited thereto. For example, in the light-converting light-emitting element 30, it is preferable that a polarizer be provided on the light extraction surface (upper surface of the sealing substrate 9). As the polarizer, a well-known linear polarizer and a well-known λ/4 polarizer of the related art can be used in combination. Here, by providing the polarizer, outside light reflection from the first electrode 12 and the second electrode 16; or outside light reflection from a surface of the substrate 1 or the sealing substrate 9 can be prevented; and the contrast of the light-converting light-emitting element 30 can be improved.
In addition, in the above-described embodiment, the organic light-emitting element 10 containing the above-described luminescent material according to the embodiment is used as a light source (light-emitting element). However, the embodiment is not limited thereto. Another configuration can be adopted in which a light source such as an organic EL, an inorganic EL, or an LED (light-emitting diode) containing another luminescent material is used as a light-emitting element; and a layer containing the luminescent material according to the embodiment is provided as a fluorescent layer which absorbs emitted from the light-emitting element (light source) and emits blue light. At this time, it is desirable that the light-emitting element which is the light source emit light (ultraviolet light) having a shorter wavelength than that of the blue light.
In the light-converting light-emitting element 30 according to the embodiment, an example of emitting light beams of three colors including red, green, blue has been described. However, the light-converting light-emitting element according to the embodiment is not limited thereto. The light-converting light-emitting element may be a single-color light-emitting element containing only one kind of fluorescent layer; or can include multi-color light-emitting elements of white, yellow, magenta, cyan and the like in addition to light-emitting elements of red, green, and blue. In this case, a fluorescent layer corresponding to each color may be used. As a result, power consumption can be reduced and color reproduction range can be enlarged. In addition, multi-color fluorescent layers can be easily formed by using a photolithography method using a resist, a printing method, or a wet formation method rather than a shadow mask method.
A light-converting light-emitting element according to an embodiment of the present invention includes at least one organic layer that includes a light-emitting layer containing the above-described luminescent material according to the first embodiment, a layer for multiplying a current, and a pair of electrodes between which the organic layer and the layer for multiplying a current are interposed.
The light-converting light-emitting element 40 illustrated in
The organic EL layer 17 can adopt the same configuration as that of the above-described organic EL layer 17 in the organic light-emitting element according to the first embodiment.
The organic photoelectric material layer 43 exhibits a photoelectric effect of multiplying a current, and may include only one NTCDA (naphthalene tetracarboxylic dianhydride) layer; or may include plural layers capable of selecting a sensitivity wavelength range. For example, the organic photoelectric material layer 43 may include two layers including a Me-PTC (perylene pigment) layer and a NTCDA layer. The thickness of the organic photoelectric material layer 43 is not particularly limited and is, for example, approximately 10 nm to 100 nm. The organic photoelectric material layer 43 is formed using a vacuum deposition method.
The light-converting light-emitting element 40 according to the embodiment applies a predetermined voltage between the bottom electrode 42 and the Au electrode 44. When the Au electrode 44 is irradiated with light from outside, holes generated by the irradiation of light are trapped and accumulate in the vicinity of the Au electrode 44, which is the negative terminal. As a result, an electric field is concentrated on the interface between the organic photoelectric material layer 43 and the Au electrode 44, electrons are injected from the Au electrode 44, and the current multiplication phenomenon occurs. The organic EL layer 17 emits light based on the current multiplied in this way. Therefore, superior luminescence property can be obtained.
Since the light-converting light-emitting element 40 according to the embodiment includes the organic EL layer 17 containing the above-described luminescent material according to the first embodiment, the luminous efficiency can be further improved.
An organic laser diode light-emitting element according to an embodiment of the present invention includes an excitation light source (including a continuous wave excitation light source); and a resonator structure that is irradiated with light emitted from the excitation light source. In the resonator structure, at least one organic layer that includes a laser-active layer is interposed between a pair of electrodes.
The hole transport layer 52, the hole blocking layer, the electron transport layer 55, and the electron injection layer 56 have the same configurations as those of the above-described hole transport layer 13, the hole blocking layer, the electron transport layer 15, and the electron injection layer in the organic light-emitting element according to the first embodiment, respectively. The laser-active layer 53 can adopt the same configuration as that of the above-described organic light-emitting layer 14 in the organic light-emitting element according to the first embodiment. It is preferable that a host material be doped with the luminescent material according to the first embodiment. In
In the organic laser diode light-emitting element 50 according to the embodiment, laser light is emitted by the excitation light source 50a from the ITO substrate 51 side which is the anode. As a result, ASE (edge emission) in which the peak luminance is increased corresponding to the excitation intensity of laser light can be produced from a side surface of the resonator structure 50b.
In the dye laser 60 according to the embodiment, when the excitation light source 61 emits the pump light 67, the pump light 67 is collected to the dye cell 62 by the lens 66 and excites the luminescent material according to the embodiment contained in the laser medium of the dye cell 62 to emit light. The light emitted from the luminescent material is discharged outside the dye cell 62 and is reflected and amplified between the partially reflecting mirror 62 and the diffraction grating 63. The amplified light passes through the partially reflecting mirror 65 and is emitted outside. In this way, the luminescent material according to the first embodiment can also be applied to the dye laser.
The above-described organic light-emitting element, wavelength-converting light-emitting element, and light-converting light-emitting element according to the embodiments can be applied to a display device, an illumination device, and the like.
A display according to an embodiment of the present invention includes an image signal output portion, a drive portion, and a light-emitting portion. The image signal output portion outputs an image signal. The drive portion applies a current or a voltage based on the signal output from the image signal output portion. The light-emitting portion emits light based on the current or the voltage applied from the drive portion. In the display device according to the embodiment, the light-emitting portion is configured as any one of the above-described organic light-emitting element, wavelength-converting light-emitting element, and light-converting light-emitting element according to the embodiments. In the following description, a case in which the light-emitting porting is the organic light-emitting element according to the embodiment will be described as an example. However the embodiment is not limited thereto. In the display device according to the embodiment, the light-emitting portion can be configured as the wavelength-converting light-emitting element or the light-converting light-emitting element.
As illustrated in
The scanning circuit 103 and the image signal drive circuit 104 are electrically connected to a controller 105 through control lines 106, 107, and 108. The operation of the controller 105 is controlled by a central processing unit 109. In addition, the scanning circuit 103 and the image signal drive circuit 104 are separately connected to a power circuit 112 through power distribution lines 110 and 111. The image signal output portion includes the CPU 109 and the controller 105.
The drive portion that drives the organic EL light-emitting portion 10 of the organic light-emitting element 20 includes the scanning circuit 103, the image signal drive circuit 104, and the organic EL power circuit 112. The respective regions which are partitioned by the scanning lines 101 and the signal lines 102 form the TFT circuits 2 of the organic light-emitting element 20 illustrated in
Using the image signal output portion and the drive portion having such configurations, when a voltage is applied to the organic EL layer (organic layer) 17 which is interposed between the first electrode 12 and the second electrode 16 of a desired pixel, the organic light-emitting element 20 corresponding to the pixel emits light; light in a visible wavelength range can be emitted from the corresponding pixel; and as a result, a desired color or image can be displayed.
In the display device according to the embodiment, the example in which the above-described organic light-emitting element 20 according to the second embodiment is included as the light-emitting portion has been described. However, the embodiment is not limited thereto. The display device according to the embodiment can suitably include, as the light-emitting portion, any one of the above-described organic light-emitting element, wavelength-converting light-emitting element, and light-converting light-emitting element according to the embodiments.
When the display device according to the embodiment includes, as the light-emitting portion, any one of the above-described organic light-emitting element, wavelength-converting light-emitting element, and light-converting light-emitting element using the luminescent material according to the embodiment, high luminous efficiency can be obtained.
Needless to say, the display device according to the embodiment can be incorporated into various electronic apparatuses. Hereinafter, electronic apparatuses including the display device according to the embodiment will be described referring to
The display device according to the embodiment can be applied to, for example, a mobile phone illustrated in
The display device according to the embodiment can be applied to, for example, a thin-screen TV illustrated in
Furthermore, the display device according to the embodiment can be applied to, for example, a portable game machine illustrated in
In addition, the display device according to the embodiment can be applied to a laptop computer illustrated in
Hereinabove, preferable examples according to one aspect of the present invention have been described referring to
In the illumination device 70 illustrated in
When the organic light-emitting element according to the embodiment is used as the light-emitting portion 72 of the display device 70, the organic light-emitting layer of the organic light-emitting element may further contain a well-known organic EL material of the related art in addition to the luminescent material according to the embodiment.
In the illumination device according to the embodiment, the example in which the above-described organic light-emitting element 10 according to the first embodiment is included as the light-emitting portion has been described. However, the embodiment is not limited thereto. The illumination device according to the embodiment can suitably include, as the light-emitting portion, any one of the above-described organic light-emitting element, wavelength-converting light-emitting element, and light-converting light-emitting element according to the embodiments.
When the illumination device according to the embodiment includes, as the light-emitting portion, any one of the above-described organic light-emitting element, wavelength-converting light-emitting element, and light-converting light-emitting element using the luminescent material according to the embodiment, high luminous efficiency can be obtained.
Needless to say, the illumination device according to the embodiment can be incorporated into various illumination apparatuses.
The organic light-emitting element, wavelength-converting light-emitting element, and light-converting light-emitting element according to the embodiments can also be applied to, for example, a ceiling light (illumination apparatus) illustrated in
Likewise, the organic light-emitting element, wavelength-converting light-emitting element, and light-converting light-emitting element according to the embodiments can be applied to, for example, an illumination stand (illumination apparatus) illustrated in
For example, in the display device described in the embodiment, it is preferable that a polarizer be provided on a light extraction surface. As the polarizer, a well-known linear polarizer and a well-known λ/4 polarizer of the related art can be used in combination. Here, by providing such a polarizer, outside light reflection from the electrodes of the display device; or outside light reflection from a surface of the substrate or the sealing substrate can be prevented; and the contrast of the display device can be improved. In addition, the specific description relating to the shapes, numbers, arrangements, materials, formation methods, and the like of the respective components of the fluorescent substrate, the display device, and the illumination device are not limited to the above-described embodiments and can be appropriately modified.
Hereinafter, the present invention will be described in detail based on Examples, but the present invention is not limited to these Examples.
Compounds synthesized in Synthesis Examples 1 to 8 will be shown below. In the following structural formulae, Ph represents a phenyl group. In the following synthesis examples, compounds in the respective steps and a final compound (transition metal complex) were identified using MS spectrum (FAB-MS).
Compound 1 was synthesized according to the following route.
Compound A (0.1 mol) was added dropwise to an aqueous methylamine solution (0.5 mol). After stirring for several minutes, a solid material precipitated. Water is added to the reaction solution and the solid material was separated by filtration in a liquid separating treatment, followed by drying. As a result, Compound B was obtained. Yield: 82%
A hexane solution of n-BuLi (10.2 mmol) was slowly added to a solution in which Compound B (10.2 mmol) was dissolved in THF (tetrahydrofuran) at room temperature. After 30 minutes, trimethylsilyl chloride (10.2 mmol) was added thereto. Next, the solvent was removed under reduced pressure, followed by extraction with ether. As a result, Compound C was obtained. Yield: 93%
Sn(CH3)4 (5 mol) was added to BBr3 (10 mol) at −50° C. under stirring, followed by stirring for 1 hour. Next, the solvent was removed under reduced pressure, followed by extraction with ether. As a result, Compound D was obtained. Yield: 80%
n-BuLi (9 mmol) was added dropwise to a hexane solution in which methylamine (10 mmol) was dissolved at −10° C. A hexane solution (50 mL) of dibromomethylborane (Compound D: 9 mmol) was slowly added dropwise to this solution at −20° C. The temperature was returned to room temperature, followed by stirring for 1 day. Next, filtration was performed in order to remove LiCl and excess Li[N(H)CH3]. Then, the solvent was removed under reduced pressure, followed by recrystallization with ether. As a result, Compound E was obtained. Yield: 70%
A solution in which Compound E (10.2 mmol) was dissolved in 20 mL of toluene was added dropwise to a solution in which Compound C (10.2 mmol) was dissolved in 10 mL of toluene at −78° C. under stirring. The temperature was returned to room temperature, followed by stirring for 1 hour. The solvent was removed under reduced pressure, followed by extraction with ether. As a result, Compound F was obtained. Yield: 80%
Dibromophenylborane (Compound D) and Compound F were dissolved in 20 mL of chloroform, followed by reflux for 1.5 days. The temperature was returned to room temperature. The solvent was removed under reduced pressure and a residue was washed with hexane. As a result, Compound G was obtained. Yield: 82%
[IrCl(COD)]2 (COD=1,5-cyclooctadiene) (0.15 mmol), Compound G (0.90 mmol), and silver oxide (0.90 mmol) were added to 2-ethoxyethanol (10 mL), followed by reflux for 24 hours under light-shading conditions. Purification was performed by flash chromatography (silica gel/chloroform). Furthermore, the resultant was dissolved in dichloromethane and hexane was added thereto, followed by recrystallization. As a result, Compound 1 having a desired mer isomer was obtained. Yield: 45%, FAB-MS (+): m/e=832
Compound 2 was synthesized according to the following route.
A mixture of diethoxymethane (0.05 mol), aniline (Compound A′, 0.1 mol), and 0.25 mL of glacial acetic acid was refluxed for 2 hours. By-products and unreacted materials were removed under reduced pressure. As a result, Compound B′ was obtained. Yield: 80%
Compound D and Compound E were the same materials used in the synthesis of Compound 1. Compound C′, Compound F′, and Compound G′ were synthesized under conditions of the same equivalent relationship and the same reaction temperature as those of Compound 1.
Compound 2 was synthesized under conditions of the same equivalent relationship and the same reaction temperature as those of Compound 1. Recrystallization was performed with chloroform. As a result, Compound 2 having a desired mer isomer was obtained as a white solid material. Yield: 80%, FAB-MS (+): m/e=1018
Compound 3 (mer isomer) was obtained with the same synthesis method as that of Synthesis Example 2, except that N-(bromo(methyl)boryl)-2-methylpropan-2-amine was used instead of Compound E. Yield: 60%, FAB-MS (+): m/e=1143 (Synthesis Example 4: Synthesis of Compound 4)
Compound 4 (mer isomer) was obtained with the same synthesis method as that of Synthesis Example 1, except that (E)-N-cyano-N-(2,4-dimethylphenyl) formamidine was used instead of Compound A. Yield: 70%, FAB-MS (+): m/e=915
Compound 5 (mer isomer) was obtained with the same synthesis method as that of Synthesis Example 1, except that (E)-N′-(4-tert-butylphenyl)-N-cyanoformamidine was used instead of Compound A. Yield: 72%, FAB-MS (+): m/e=999
Compound 6 (mer isomer) was obtained with the same synthesis method as that of Synthesis Example 2, except that N-(bromo(phenyl)boryl)methaneamine was used instead of Compound D; and dibromo(phenyl)borane was used instead of Compound E. Yield: 65%, FAB-MS (+): m/e=1516
Compound 7 was synthesized according to the following route.
A 2-ethoxyethanol solution in which 4 equivalents of Compound H and an excess amount of sodium methoxide were mixed with 1 equivalent of [IrCl(COD)]2 (COD=1,5-cyclooctadiene) was heated to reflux for 3 hours, followed by separation by chromatography. As a result, Compound J was obtained. Yield: 50%
A mixed solution of Compound J (0.08 mmol), Compound G (0.16 mmol), silver oxide (1.0 mmol), and 20 mL of THF were heated to reflux for 3 hours. Then, the reaction solution was separated by chromatography. As a result, Compound 7 (mer isomer) was obtained. Yield: 60%, FAB-MS (+): m/e=691
In order to obtain a luminescent material which emits blue phosphorescence with a high efficiency, using density functional calculation (Gaussian09 Revision-A.02-SMP), parameters relating to the luminous efficiency which has a correlation between the phosphorescence emission wavelength (experimental values) of transition metal complexes and the calculated values thereof were searched. As a result, as illustrated in
As a result, it was found that, in order obtain a blue luminescent material, it is necessary that a material having a large value of T1 calculated according to the quantum chemical calculation be designed and, preferably, a material having a calculated value T1 of 2.8 eV or higher be designed.
Regarding the well-known phosphorescent luminescent material of the related art illustrated in
As a result, the MLCT ratio was calculated by subtracting the contribution ratio of unoccupied orbitals (among all of 1S to 8D orbitals) of the iridium atom from the contribution ratio of occupied orbitals (among all of 1S to 8D orbitals) of the iridium atom with respect to transitions pertaining to the T1 level calculated according to quantum chemical calculation (Gaussian09/TD-DFT/LanL2DZ<key word:pop=reg>; and atoms other than Ir were calculated using 6-31G*). Here, 1S-8D refers to orbitals calculated as calculation results of Gaussian when the basis function LanL2DZ is used.
The calculus equations of the MLCT ratio are shown in the following expressions 2 to 4. First, using LCAO approximation, the molecular orbital (ψ) is represented by the expression 2.
In the expression 2, Ci(H) represents the orbital coefficients relating to each hydrogen atom; Cj(C) represents the orbital coefficients relating to each carbon atom; and Ck(Ir) represents the orbital coefficients relating to the iridium atom. In addition, ψ1(H) represents the atom orbitals relating to each hydrogen atom; ψj(C) represents the atom orbitals relating to each carbon atom; and ψk(Ir) represents the atom orbitals relating to iridium atoms.
The square values of the orbital coefficients of each atom represent the electron densities around the corresponding atom. In addition, the orbital coefficients of each atom are divided into the orbital coefficients of the respective orbitals (S, P, D orbitals and the like).
Next, the respective orbital coefficients of the respective 1S to 8D orbitals (basis function: LanL2DZ) in an iridium atom of occupied molecular orbitals or unoccupied molecular orbitals are squared and the square values are added. The contributions (A) of the respective orbitals are calculated according to the following expression 3. In the expression 3, C represents the orbital coefficients of the respective orbitals.
[Numerical Values]
A=C(1S)2+C(2S)2+C(3S)2+C(4PX)2+C(4PY)2+C(4PZ)2+C(5PX)2+C(5PY)2+C(5PZ)2+C(6PX)2+C(6PY)2+C(6PZ)2+C(7D 0)2+C(7D+1)2+C(7D−1)2+C(7D+2)2+C(7D−2)2+C(8D 0)2+C(8D+1)2+C(8D−1)2+C(8D+2)2+C(8D−2)2 (Expression 3)
First, it is assumed that the transition from HOMO to LUMO of an Ir complex occurs as the transition from S0 to T1 (from the ground state to the triplet excited state).
The contribution A values of the respective orbitals are calculated according to the expression 2. In order to represent the intramolecular charge transfer of the transition from S0 to T1, as shown in the following expression 4, the MLCT ratio is calculated by subtracting A (LUMO) from A (HOMO) and multiplying the subtraction result by 100.
[Numerical Expression 4]
MLCT Ratio (%)=<A(HOMO)−A(LUMO)>×100% (Expression 4)
In addition, generally, there are multiple combinations of transitions from HOMO−m (m=0 or more) to LUMO+n (n=0 or more) pertaining to the transition from S0 to T1.
In this example, the orbital information regarding LUMO+4, LUMO+3, LUMO+2, LUMO+1, LUMO, HOMO, HOMO−1, HOMO−2, HOMO−3, and HOMO−4 of an Ir complex is calculated; and the respective transition processes from LUMO+n to HOMO−m are taken into consideration. Therefore, the MLCT ratio representing the intramolecular charge transfer of the transition from S0 to T1 can be represented by the following expression 5.
i: Transitions from HOMO−m to LUMO+n (Total: 25, i=1, 2, . . . , 25)
Bi: Numerical values obtained by subtracting the contribution ratio of LUMO+n from the contribution ratio of HOMO−m in transition i
In the actual calculation, all of 25 transitions are not calculated. Several kinds of transitions having a high transition probability are calculated (mathematically, the total transition probability which has been output is less than 100%). The transitions obtained from the calculation and the transitions from HOMO−m (m=0 to 4) to LUMO+n (n=0 to 4) are used for the calculation of the MLCT ratio. Therefore, the total probability of the transitions used for the actual calculation is set to 100%, and the calculated values of transition probability Pi(%) of the transition i are corrected.
According to the expression 5, the MLCT ratios of the well-known phosphorescent luminescent materials of the related art were calculated and plotted with respect to the experimental values of PL quantum yield (φPL, CH2Cl2) of the respective phosphorescent luminescent materials (in
It was found from the results of
Regarding Compound 1 and Compound 3, the PL quantum yields of a mixed complexes containing a fac isomer and a mer isomer (fac isomer:mer isomer=5:1) and a complexes containing only a mer isomer in a toluene solution were obtained. The PL quantum yields were measured according to the following order. First, the emission spectrum of each compound was measured using a PL measurement device FluoroMax-4 (manufactured by Horiba Ltd., excitation wavelength: 380 nm), and the absorbance was measured using an absorbance measurement device UV-2450 (manufactured by Shimadzu Corporation). Next, the PL quantum yield was calculated by matching the absorbance at the excitation wavelength (380 nm) between the well-known reference material fac-Ir(ppy)3 and each compound and comparing the emission intensities to each other. The results thereof are shown in Table 1.
It was confirmed from the results of Table 1 that the complexes containing only a mer isomer had a higher PL quantum yield than that of a mixed complexes containing a fac isomer and a mer isomer; and in Compounds 1 and 3 which are the luminescent materials according to this example, a mer isomer had a higher PL quantum yield that that of a fac isomer.
A silicon semiconductor film was formed on a glass substrate with a plasma chemical vapor deposition (plasma CVD) method, followed by crystallization. As a result, a polycrystalline semiconductor film (polycrystalline silicon thin film) was formed. Next, the polycrystalline silicon thin film was etched to form plural island-shaped patterns. Next, silicon nitride (SiN) was formed on each island structure of the polycrystalline silicon thin film as a gate insulating film. Next, a laminated film of titanium (Ti)-aluminum (Al)-titanium (Ti) was sequentially formed as a gate electrode, followed by etching and patterning. A source electrode and a drain electrode were formed over the gate electrode using Ti—Al—Ti to prepare plural thin film transistors (TFT).
Next, an interlayer dielectric having a through-hole was formed on each of the formed thin film transistors, followed by planarizing. Then, indium tin oxide (ITO) was formed as an anode through the through-hole. A single layer of polyimide-based resin was patterned so as to surround the ITO electrode. Then, a substrate on which the ITO electrode was formed was washed with ultrasonic waves, followed by baking at 200° C. under reduced pressure for 3 hours.
Next, 4,4′-bis[N-(1-naphthyl)-N-phenyl-amino]biphenyl(α-NPD) was deposited on the anode using a vacuum deposition method at a deposition rate of 1 angstrom/sec. Then, a hole injection layer with a thickness of 45 nm was formed on the anode.
Next, N,N-dicarbazolyl-3,5-benzene (mCP) was deposited on the hole injection layer using a vacuum deposition method at a deposition rate of 1 angstrom/sec to form a hole transport layer with a thickness of 15 nm on the hole injection layer.
Next, 2,8-bis(diphenylphosphoryl)dibenzothiophene (PPT) (thickness: 50 nm) was deposited on the hole transport layer.
Next, UGH 2 (1,4-bis(triphenylsilyl)benzene) and Compound 1 (mer isomer) were codeposited on the hole transport layer using a vacuum deposition method to form an organic light-emitting layer. At this time, UGH 2 which was the host material was doped with approximately 7.5% of Compound 1. Next, UGH 2 with a thickness of 5 nm was formed on the organic light-emitting layer as a hole blocking layer. Furthermore, 1,3,5-tris(N-phenylbenzimidazol-2-yl)benzene (TPBI) was deposited on the hole blocking layer using a vacuum deposition method. As a result, an electron transport layer with a thickness of 30 nm was formed on the hole blocking layer.
Next, lithium fluoride (LiF) was deposited on the electron transport layer using a vacuum deposition method at a deposition rate of 1 angstrom/sec. As a result, a LiF film with thickness of 0.5 nm was formed. Next, an aluminum (Al) film with a thickness of 100 nm was formed on the LiF film. In this way, the laminated film of LiF and Al was formed as a cathode. As a result, an organic EL element (organic light-emitting element) was prepared.
The current efficiency (luminous efficiency) of the obtained organic EL at 1000 cd/m2 was measured. As a result, the current efficiency was 12.2 cd/A and the emission wavelength was 2.8 eV (440 nm), and highly efficient blue light emission was exhibited.
Organic EL elements (organic light-emitting elements) were prepared with the same preparation method as that of Example 2, except that dopants (luminescent materials) with which the organic light-emitting layers were doped were changed to compounds shown in Table 2. The current efficiency (luminous efficiency) and emission wavelength of each of the obtained organic EL element at 1000 cd/m2 were measured.
The results are shown in Table 2. In Examples 4 to 10, mer isomers were used, and in Comparative Examples 1 and 2, the following mer isomers were used. In the following structural formula, Ph represents a phenyl group.
In the results of Table 2, the organic EL elements using Compounds 1 to 7 which are the luminescent materials according to Examples had a higher luminous efficiency (current efficiency) than that of the organic EL elements using Related-Art Compounds 1 and 2 as the luminescent material. In addition, the other compounds except Compound 6 had an emission wavelength of 460 nm or lower (2.69 eV or higher) and exhibited highly efficient blue light emission.
In this example, using the organic blue light-emitting elements (organic EL elements) containing the luminescent materials according to Examples, a wavelength-converting light-emitting element which converted light emitted from the organic light-emitting element into light in a red wavelength and a wavelength-converting light-emitting element which converted light emitted from the organic light-emitting element into light in a green wavelength were prepared, respectively.
A silver film with a thickness of 100 nm was formed on a glass substrate with a thickness of 0.7 mm using a sputtering method to form a reflective electrode. An indium-tin oxide (ITO) film with a thickness of 20 nm was formed on the silver film using a sputtering method to form a reflective electrode (anode) as a first electrode. Then, the first electrode was patterned using a well-known photolithography method so as to have 90 stripe patterns having a width of 2 mm.
Next, a SiO2 layer with a thickness of 200 nm was laminated on the first electrode (reflective electrode) using a sputtering method and then was patterned using a well-known photolithography method so as to cover edge portions of the first electrode (reflective electrode). As a result, an edge cover was formed. The edge cover had a structure in which short sides of the reflective electrode were covered with SiO2 by 10 μm from the edges. The resultant was washed with water, followed by washing with pure water and ultrasonic waves for 10 minutes, washing with acetone and ultrasonic waves for 10 minutes, washing with isopropyl alcohol steam for 5 minutes, and drying at 100° C. for 1 hour.
Next, the dried substrate was fixed to a substrate holder in an inline type resistance heating deposition device. The pressure was reduced to a vacuum of 1×10−4 Pa or lower, and respective organic layers of the organic EL layer were formed.
First, using 1,1-bis-di-4-tolylamino-phenyl-cyclohexane (TAPC) as a hole injection material, a hole injection layer with a thickness of 100 nm was formed with a resistance heating deposition method.
Next, using N,N′-di-[(1-naphthyl)-N,N′-diphenyl]-1,1′-biphenyl-1,1′-biphenyl-4,4′-diamine (NPD) as a hole transport material, a hole transport layer with a thickness of 40 nm was formed on the hole injection layer with a resistance heating deposition method.
Next, an organic blue light-emitting layer (thickness: 30 nm) was formed at a desired pixel position on the hole transport layer. This organic blue light-emitting layer was prepared by coevaporating 1,4-bis(triphenylsilyl)benzene (UGH-2; host material) and Compound 1 at deposition rates of 1.5 angstrom/sec and 0.2 angstrom/sec, respectively.
Next, using 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP), a hole blocking layer (thickness: 10 nm) was formed on the organic light-emitting layer.
Next, using tris(8-hydroxyquinoline)aluminum (Alq3), an electron transport layer (thickness: 30 nm) was formed on the hole blocking material.
Next, using lithium fluoride (LiF), an electron injection layer (thickness: 0.5 nm) was formed on the electron transport layer.
Through the above-described processes, the respective organic layers of the organic EL layer were formed.
Next, a semitransparent electrode was formed on the electron injection layer as a second electrode. In order to form the second electrode, first, the substrate on which the electron injection layer was formed in the above-described process was fixed to a metal deposition chamber. Then, a shadow mask for forming the semitransparent electrode (second electrode) and the substrate were aligned. As the shadow mask, a mask having openings is used so as to form the semitransparent electrodes (second electrodes) in a stripe shape having a width of 2 mm in a direction opposite the reflective electrodes (first electrodes) in a stripe shape. Next, magnesium and silver were coevaporated on a surface of the electron injection layer of the organic EL layer at deposition rates of 0.1 angstrom/sec and 0.9 angstrom/sec to form desired patterns of magnesium and silver (thickness: 1 nm). Furthermore, a desired pattern of silver (thickness: 19 nm) was formed thereon at a deposition rate of 1 angstrom/sec in order to enhance the interference effect and to prevent voltage drop due to interconnection resistance in the second electrode. Through the above-described processes, the semitransparent electrode (second electrode) was formed. Here, the microcavity effect (interference effect) was exhibited between the reflective electrode (first electrode) and the semitransparent electrode (second electrode), which can improve the luminance on the front side.
Through the above-described processes, the organic EL substrate on which the organic EL portion is formed is prepared.
Next, a red fluorescent layer was formed on a glass substrate equipped with a red color filter having a thickness of 0.7 mm, and a green fluorescent layer was formed on a glass substrate equipped with a green color filter having a thickness of 0.7 mm.
The red fluorescent layer was formed according to the following order. First, 15 g of ethanol and 0.22 g of γ-glycidoxypropyl triethoxysilane were added to 0.16 g of aerosol having an average particle size of 5 nm, followed by stirring for 1 hour at room temperature in open system. This mixture and 20 g of red fluorescent material (pigment) K5Eu2.5(WO4)6.25 were put into a mortar and pounded, followed by heating with an oven at 70° C. for 2 hours and heating with an oven at 120° C. for 2 hours. As a result, a surface-modified K5Eu25(WO4)6.25 was obtained. Next, 30 g of polyvinyl alcohol in which a mixed solution (300 g; water/dimethylsulfoxide=1/1) was dissolved was added to 10 g of the surface-modified K5Eu2.5(WO4)6.25, followed by stirring with a disperser. As a result, a red fluorescent layer-forming coating solution was prepared. The red fluorescent layer-forming coating solution was coated at a red pixel position on a CF-equipped glass substrate using a screen printing method so as to have a width of 3 mm. Next, the resultant was heated and dried with a vacuum oven (under conditions of 200° C. and 10 mmHg) for 4 hours. As a result, a red fluorescent layer with a thickness of 90 μm was formed.
The green fluorescent layer was formed according to the following order. First, 15 g of ethanol and 0.22 g of γ-glycidoxypropyl triethoxysilane were added to 0.16 g of aerosol having an average particle size of 5 nm, followed by stirring for 1 hour at room temperature in open system. This mixture and 20 g of green fluorescent material (pigment) Ba2SiO4:Eu2+ were put into a mortar and pounded, followed by heating with an oven at 70° C. for 2 hours and heating with an oven at 120° C. for 2 hours. As a result, a surface-modified Ba2SiO4:Eu2+ was obtained. Next, 30 g of polyvinyl alcohol (resin) in which a mixed solution (300 g, solvent; water/dimethylsulfoxide=1/1) was dissolved was added to 10 g of the surface-modified Ba2SiO4:Eu2+, followed by stirring with a disperser. As a result, a green fluorescent layer-forming coating solution was prepared. The green fluorescent layer-forming coating solution was coated at a green pixel position on a CF-equipped glass substrate 16 using a screen printing method so as to have a width of 3 mm. Next, the resultant was heated and dried with a vacuum oven (under conditions of 200° C. and 10 mmHg) for 4 hours. As a result, a green fluorescent layer with a thickness of 60 μm was formed.
Through the above-described processes, a fluorescent substrate on which the red fluorescent layer was formed and a fluorescent substrate on which the green fluorescent layer was formed were prepared, respectively.
Regarding the wavelength-converting red light-emitting element and the wavelength-converting green light-emitting element, the organic EL substrate and each of the fluorescent substrates prepared as described above were aligned according to alignment markers which were formed outside a pixel arrangement position. Each of the fluorescent substrates was coated with a thermosetting resin before the alignment.
After the alignment, both substrates are bonded to each other through the thermosetting resin, followed heating at 90° C. for 2 hours to perform curing. The bonding process of both substrates are performed in a dry air environment (water content: −80° C.) in order to prevent the organic EL layer from deteriorating due to water.
A peripheral terminal of each of the obtained wavelength-converting light-emitting elements is connected to an external power supply. As a result, superior green light emission and red light emission can be obtained.
Display devices in which the organic light-emitting elements (organic EL elements) prepared in Examples 4 to 10 were respectively arranged in a 100×100 matrix shape were prepared, and a moving image was displayed thereon. Each of the display devices includes an image signal output portion that outputs an image signal; a drive portion that includes a scanning electrode drive circuit and a signal drive circuit which output the image signal from the image signal output portion; and a light-emitting portion that includes organic light-emitting elements (organic EL element) which are arranged in a 100×100 matrix shape. In all the display devices, an image having a high color purity was obtained. In addition, even when plural display devices were prepared, there were no variations between the devices and the in-plane uniformity was superior.
An illumination device including a drive portion that applies a current; and a light emitting portion that emits light based on the current applied from the drive portion was prepared. In this example, organic light-emitting elements (organic EL elements) were respectively prepared with the same preparation methods as those of Examples 4 to 10, except that the organic light-emitting elements (organic EL elements) were formed on a film substrate. Each of the organic light-emitting elements was used as the light-emitting portion. When a voltage is applied to this organic light-emitting device for lighting, a surface-emitting illumination device having a uniform lighting surface was obtained without using indirect illumination resulting in luminance loss. In addition, the prepared illumination device can be used as a backlight of a liquid crystal display panel.
The light-converting light-emitting element illustrated in
A voltage was applied to the light-converting light-emitting element prepared through the above-described processes using the ITO electrode as the anode. When the Au electrode was irradiated with monochromatic light having a wavelength of 335 nm, the photoelectric current and the illuminance (wavelength: 442 nm) of light emitted from Compound 1 were measured with respect to the applied voltage, respectively. When the measurement was performed with respect to the applied voltage, the photocurrent multiplication effect was observed at 20 V.
The dye laser illustrated in
The dye laser having a configuration in which Compound 1 (in a deaerated acetonitrile solution; concentration 1×10−4M) was used as a laser dye in an XeCl excimer (excitation wavelength: 308 nm) was prepared. The emission wavelength was 430 nm to 450 nm, and a phenomenon in which the intensity was increased in the vicinity of 440 nm was observed.
Referring to H. Yamamoto et al., Appl. Phys. Lett., 2004, 84, 1401, an organic laser diode light-emitting element having the configuration illustrated in
The organic laser diode light-emitting element was prepared according to the following order. First, the same processes as those of Example 1 were performed until the formation of the anode.
Next, 4,4′-bis[N-(1-naphthyl)-N-phenyl-amino]biphenyl (α-NPD) was deposited on the anode using a vacuum deposition method at a deposition rate of 1 angstrom/sec. Then, a hole injection layer with a thickness of 20 nm was formed on the anode.
Next, N,N-dicarbazolyl-3,5-benzene (mCP) and Compound 1 (mer isomer) were coevaporated on the hole injection layer using a vacuum deposition method to form an organic light-emitting layer. At this time, mCP which was the host material was doped with approximately 5.0% of Compound 1. Next, 1,4-bis(triphenylsilyl)benzene (UGH-2) with a thickness of 5 nm was formed on the organic light-emitting layer as a hole blocking layer. Furthermore, 1,3,5-tris(N-phenylbenzimidazol-2-yl)benzene (TPBI) was deposited on the hole blocking layer using a vacuum deposition method. As a result, an electron transport layer with a thickness of 30 nm was formed on the hole blocking layer.
Next, MgAg (9:1, thickness: 2.5 nm) was deposited on the electron transport layer using a vacuum deposition method. Then, an ITO layer with a thickness of 20 nm was formed using a sputtering method. As a result, the organic laser diode light-emitting element was prepared.
The prepared organic laser diode light-emitting element was irradiated with laser beams (Nd:YAG laser SHG, 532 nm, 10 Hz, 0.5 ns) from the anode side to investigate ASE oscillation characteristics. When the laser beam irradiation is performed while changing the excitation intensity, the oscillation starts at 1.0 μJ/cm2 and ASE in which the peak intensity is increased in proportion to the excitation intensity was observed.
The luminescent material according to the Examples is applicable to an organic electroluminescence element (organic EL element), a wavelength-converting light-emitting element, a light-converting light-emitting element, a photoelectric converting element, a laser dye, an organic laser diode element, and the like; and is also applicable to a display device and an illumination device using the respective light-emitting elements.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2010-226741 | Oct 2010 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2011/072832 | 10/4/2011 | WO | 00 | 7/30/2013 |
