JP5569522B2 - ORGANIC ELECTROLUMINESCENCE ELEMENT, ITS DRIVING METHOD, AND LIGHTING DEVICE CONTAINING THE SAME - Google Patents

Description

  The present invention relates to an organic electroluminescence element that satisfies the relationship between luminance and color temperature that a person preferably feels, has a low driving voltage, and obtains high luminance, a driving method thereof, and a lighting device having these.

  In recent years, the expectation of the practical use of the illuminating device using an organic electroluminescent element is increasing. It is known that one of important characteristics required for a lighting device satisfies a Kruithof curve (for example, see Non-Patent Document 1). This region is a region that many people feel favorable based on human instinct. When this characteristic is converted into the performance of an organic electroluminescence device, the higher the luminance, the higher the color temperature, and the correlation can be arbitrarily controlled. . On the other hand, a technique for changing chromaticity in a white panel is disclosed (for example, see Patent Document 1). Since chromaticity can be converted into color temperature, the method described in Patent Document 1 means that the emission color can be controlled in a wide range of color temperatures. In this method, the light emitting layer is laminated in the order of blue and orange from the anode side, and light is emitted using pulse driving together. However, in the specific methods described in the examples, there is no description of the light emission efficiency and the luminance, so it cannot be suggested whether the Kruithof curve is satisfied. In addition, since a fluorescent light emitting material is used and the driving voltage is high and the light emission efficiency is low, it is insufficient for practical use. Furthermore, a similar stacking order of the light emitting layers is known (for example, see Patent Document 2). The method described in Patent Document 2 is also a method using a fluorescent light-emitting material, has a problem of low light emission efficiency, and has an objective effect of suppressing a change in color temperature during storage of the device. The purpose effect is very different. Further, a method for improving the color temperature in an LED using an inorganic light emitting material has been disclosed (for example, see Patent Documents 3 and 4).

  Each of these proposed methods is a technique using a blue light emitting diode. The former is to improve variation in luminance and color temperature, and the object and effect are different from those of the present invention. This is a method of changing radiation. All of these are point light sources and have a problem of large variations in luminance with respect to organic electroluminescent devices that are surface light sources.

  Therefore, at present, a technology that realizes the relationship between luminance and color temperature that humans feel favorable with low driving voltage and high efficiency has not been realized yet.

JP 2000-243563 A JP 2008-85363 A JP 2002-134284 A JP 2001-320094 A

30 Medical Welfare Research No. 2 2006

  The present invention has been made in view of the above problems, and an object of the present invention is to satisfy the relationship between brightness and color temperature that humans preferably feel, and to drive an organic electroluminescence element that can obtain high brightness with a low drive voltage. And it is providing the illuminating device which has these.

  The above object of the present invention is achieved by the following configurations.

  1. An organic electroluminescence device having a control mechanism for controlling light emission of the organic electroluminescence device, wherein all the requirements specified in 1) to 4) below are satisfied.

1) It has a characteristic that the color temperature increases as the luminance increases by controlling the energization amount;
2) The light emitting layer unit is composed of two or more light emitting layers having different emission wavelengths.
3) The light emission wavelength of the light emitting layer on the most anode side is the shortest wavelength, the light emission wavelength of the light emitting layer on the most cathode side is the longest wavelength , and the light emitting layer on the most anode side has the maximum light emission peak wavelength of 430 to 480 nm. The blue phosphorescent light emitting metal complex dopant is contained, and the light emitting layer on the most cathode side contains two or more phosphorescent light emitting dopants having a maximum light emission peak wavelength in the range of 500 to 640 nm, and the blue phosphorescence The luminescent metal complex dopant is a compound represented by the following general formula (BD1) ;
4) The Δ color temperature / Δ driving voltage of the organic electroluminescence element is 300 K / V or more and 3,000 K / V or less ,

[In the formula, R ₁ Represents a substituent. Z represents a nonmetallic atom group necessary for forming a 5- to 7-membered ring. n1 represents an integer of 0 to 5. B ₁ To B ₅ Each represents a carbon atom, a nitrogen atom, an oxygen atom or a sulfur atom, and at least one represents a nitrogen atom. M ₁ Represents a group 8 to group 10 metal in the periodic table. X ₁ And X ₂ Each represents a carbon atom, a nitrogen atom or an oxygen atom; ₁ Is X ₁ And X ₂ Together with an atomic group forming a bidentate ligand. m1 represents 1, 2 or 3, m2 represents 0, 1 or 2, and m1 + m2 is 2 or 3. ]

2. 2. The organic electroluminescence device according to 1 above, which satisfies all the requirements specified in 5) to 7) below.

5) The organic electroluminescence device has at least an anode, a hole transport layer, a light emitting layer unit, an electron transport layer, and a cathode on the substrate.
6) The color temperature of the organic electroluminescence element is in the range of 2,000K to 13,000K.
7) All the light emitting layers contain a phosphorescent metal complex dopant.

3. 3. The organic electroluminescence device according to 1 or 2 , wherein the light emitting layer unit composed of the two or more light emitting layers contains a common light emitting host compound.

4). At least 1 layer of the light emitting layer unit comprised from the said 2 or more light emitting layer contains 2 or more types of different phosphorescence-emitting type metal complex dopants in any one of said 1 to 3 characterized by the above-mentioned. The organic electroluminescent element of description.

5). 5. A driving method of an organic electroluminescence element that is driven by a pulse that intermittently turns on / off the organic electroluminescence element according to any one of 1 to 4 , wherein both the amplitude and the width of the pulse are variable, A driving method of an organic electroluminescence element characterized by having a function of controlling.

6). 6. The method of driving an organic electroluminescence element according to 5 above, wherein a frequency of the driving pulse is 60 Hz or more.

7). 5. An illumination device comprising the organic electroluminescence element according to any one of 1 to 4 above.

8). A lighting device, wherein light emission is driven by the driving method of the organic electroluminescence element of 5 or 6 .

  According to the present invention, an organic electroluminescence element improved in that high luminance is realized, driving voltage and light emission efficiency are improved, power consumption is excellent, and color temperature can be widely changed, and a driving method thereof and its use are used. It is possible to provide a lighting device.

It is a figure which shows an example of the amplitude (energization amount) of a drive pulse and the pulse width (energization time) pattern in the drive method of the organic electroluminescent element of this invention. It is a figure which shows the relationship between a brightness | luminance and color temperature. It is a schematic sectional drawing which shows an example of the illuminating device using the organic electroluminescent element of this invention.

  Hereinafter, embodiments for carrying out the present invention will be described in detail.

  As a result of intensive studies in view of the above problems, the inventor of the present invention has all the requirements defined in 1) to 4) shown below in an organic electroluminescent element having a control mechanism for controlling light emission of the organic electroluminescent element. An organic electroluminescent device characterized by satisfying the characteristics that the color temperature increases as the luminance increases, and the organic electroluminescence device can be provided with high luminance and high luminous efficiency at a low driving voltage. As a result of the present invention, the present inventors have found that it is possible to adjust to a desired color temperature at an arbitrary luminance.

1) It has a characteristic that the color temperature increases as the luminance increases by controlling the energization amount;
2) The light emitting layer unit is composed of two or more light emitting layers having different emission wavelengths.
3) The light emission wavelength of the light emitting layer on the most anode side is the shortest wavelength, and the light emission wavelength of the light emitting layer on the most cathode side is the longest wavelength.
4) The Δ color temperature / Δ driving voltage of the organic electroluminescence element is 300 or more and 3,000 or less.

  That is, in the organic electroluminescence element of the present invention (hereinafter also referred to as “organic EL element”), the light emitting layer unit is laminated in the order of the light emission wavelength of the light emitting layer on the most anode side and the light emitting layer on the most cathode side. The emission wavelength is the longest wave, and the variation range of the color temperature with respect to the driving voltage is 300 to 3,000.

  Hereinafter, the details of the organic EL device of the present invention and its components will be described.

<Light emission characteristics>
According to the embodiment of the present invention, it is possible to provide an organic electroluminescence element having a characteristic that the color temperature increases as the illuminance increases. In other words, the characteristic is that the color temperature increases as the luminance increases. The range of this color temperature is 2,000K to 13,000K. It is said that candles, matches, sunrises and sunsets are about 2,000K, incandescent lamps are about 2,800K, white fluorescent lamps are about 4,200K, and sunlight at noon on sunny days is about 6,500K.

  In addition, since short wave light is absorbed in the atmosphere of sunlight, 6,500K feels slightly yellow instead of white. Accordingly, light with a higher color temperature is felt whiter or slightly blue, and a blue sky on a clear day can be cited as a specific example of the highest color temperature, which exceeds 10,000K. That is, in the present invention, it can be said that the practicality is high at the upper limit of the color temperature.

  One feature of the organic EL device of the present invention is that the Δ color temperature / Δ driving voltage is 300 or more and 3,000 or less.

  That is, since the organic EL element of the present invention can reduce the driving voltage, the color temperature can be greatly changed with a change in driving voltage smaller than that of a conventionally known organic layer configuration. This characteristic is an important characteristic in order to satisfy a wide range of areas that humans feel favorable in the Kruithof curve.

  Furthermore, it is possible to adjust the brightness and color temperature to suit each person's preference by simply changing the drive voltage. In the organic EL device of the present invention, when the minimum color temperature Kl, the maximum color temperature Kh, and the driving voltages Vl and Vh necessary for causing each to emit light, the variable ease X is shown according to the following formula (1). To.

Formula (1)
X = (Kh−Kl) / (Vh−Vl)
For example, in the embodiment described in Patent Document 1 (Japanese Patent Laid-Open No. 2000-243563), X is about 250 when calculated according to the equation (1). In this case, the range in which the chromaticity can be changed is small, and it is difficult to widely control the relationship between the luminance and the color temperature. In the organic EL device of the present invention, the variable ease X calculated according to the above equation (1) is obtained by optimizing the design of the organic layer according to the present invention and the pulse driving conditions according to the driving method of the present invention. , 300 or more and 3,000 or less. For example, when the variable ease X is 3,000 or more, the chromaticity is likely to change with a slight voltage fluctuation, and the color temperature control becomes unstable. Therefore, in the organic EL element of the present invention, a desired color temperature can be stably controlled at an arbitrary luminance by setting the above range.

<< Structure of organic electroluminescence element >>
The organic electroluminescence element of the present invention is constituted by components such as a support substrate (substrate), electrodes, and organic layers having various functions. Specific examples of preferred configurations are shown below, but the present invention is not limited thereto.

(I) Anode / hole transport layer / light emitting layer unit / hole blocking layer / electron transport layer / cathode (II) Anode / hole transport layer / light emitting layer unit / hole blocking layer / electron transport layer / cathode buffer layer / Cathode (III) Anode / Anode buffer layer / Hole transport layer / Light emitting layer unit / Hole blocking layer / Electron transport layer / Cathode (IV) Anode / Anode buffer layer / Hole transport layer / Light emitting layer unit / Hole Blocking layer / electron transport layer / cathode buffer layer / cathode Also, if an electron blocking layer is provided between the light emitting layer unit layer and the hole transport layer, electrons leaking to the anode side can be kept in the light emitting layer unit. Luminous efficiency may increase.

  The hole transport layer, the electron blocking layer, the hole blocking layer, the electron transport layer, and the following intermediate layer are collectively referred to as a “carrier control layer”. Further, “carrier” refers to electrons and holes, and the “carrier transport layer” is a layer made of a carrier transport material, but is preferably composed of a p-type or n-type semiconductor layer. Here, the “p-type or n-type semiconductor layer” refers to an organic layer that contains an electron-accepting compound or an electron-donating compound and exhibits semiconductivity.

  The “light emitting layer unit” is a structural unit having two or more light emitting layers, and refers to an organic laminate that is laminated from the light emitting layer on the most anode side to the light emitting layer on the most cathode side. That is, each light emitting layer is composed of an organic layer containing a light emitting compound having a different emission color. The unit may have a non-light emitting intermediate layer between the light emitting layers.

  Although the representative example of the said light emitting layer unit is illustrated below, it is not limited to these examples.

(I) Light emitting layer-1 / Light emitting layer-2
(Ii) Light emitting layer-1 / intermediate layer / light emitting layer-2
(Iii) Light emitting layer-1 / hole blocking layer / light emitting layer-2
(Iv) Light emitting layer-1 / electron blocking layer / light emitting layer-2
(V) Light emitting layer-1 / light emitting layer-2 / light emitting layer-3
(Vi) Light emitting layer-1 / intermediate layer / light emitting layer-2 / intermediate layer / light emitting layer-3
(Vii) Light emitting layer-1 / intermediate layer / light emitting layer-2 / hole blocking layer / light emitting layer-3
(Viii) Light emitting layer-1 / electron blocking layer / light emitting layer-2 / intermediate layer / light emitting layer-3
<Light emitting layer unit>
The light emitting layer unit according to the present invention is a structural unit having a plurality of light emitting layers as described above. Further, the light emitting layer according to the present invention is a layer that emits light by recombination of electrons and holes injected from the electrode, the electron transport layer, or the hole transport layer, and the light emitting portion is within the layer of the light emitting layer. Even the interface between the light emitting layer and the adjacent layer may be used.

  The light emitting layer unit according to the present invention is composed of at least two light emitting layers having different light emission colors. This structure is indispensable for obtaining white. In the present invention, the emission color of the light emitting layer arranged on the most anode side is the shortest wave emission color, and the emission color of the light emitting layer arranged on the most cathode side is the longest wave. By adopting this stacking order, the optimum relationship between the color temperature and the luminance defined in the present invention can be realized. In particular, this is extremely effective when the light emitting layers are stacked in the order shown in (i) and (v) above. This is because there is no organic layer that greatly changes the movement of carriers between the light emitting layers.

Specifically, the different luminescent colors selected in the present invention are combinations of at least two wavelength ranges from the following four wavelength ranges. (1) 430-480 nm, (2) 500-540 nm, (3) 541-560 nm, (4) 580-640 nm
Particularly preferably, it is a combination of (1) and (4) in the above-mentioned wavelength range, and further, a different phosphorescent light-emitting dopant is contained in either one of the light-emitting layers that emit light of the wavelength (1) or (4). It is preferable. This is because it is easy to adjust the emission color to be extracted, and the luminous efficiency may be further increased.

  In addition, it is extremely preferable that at least one of the light emitting layers according to the present invention contains phosphorescent light emitting dopants having different emission colors from the viewpoint of improving luminous efficiency. In the dopant that emits the short-wave emission color, the light energy generated when the excited energy disappears is transferred to the dopant that emits the longer-wave emission color. Therefore, longer wave light can be emitted with the amount of current necessary for exciting the short wave dopant. In particular, a combination of a dopant that emits light (2) or (3) in the above wavelength region and a dopant that emits light (4) is effective.

  Next, a host compound and a light-emitting dopant (hereinafter also referred to as “light-emitting dopant” and “light-emitting dopant compound”) included in the light-emitting layer will be described.

[Host compound]
With the host compound contained in the light emitting layer of the organic EL device according to the present invention, the energy of excitons generated by carrier recombination on the compound is transferred to the light emitting compound (light emitting dopant: guest compound), As a result, a compound that emits the luminescent compound, and a compound that traps the carrier on the host compound in the luminescent compound, generates excitons on the luminescent compound, and consequently emits the luminescent compound. Say. Therefore, the lower the luminous ability of the host compound itself, the better. For example, it is a compound whose phosphorescence quantum yield of phosphorescence emission at room temperature (25 degreeC) is less than 0.1, Preferably it is less than 0.01. Moreover, it is preferable that the ratio of the host compound in the compound contained in a light emitting layer is 20 mass% or more.

  As the host compound, known host compounds may be used alone or in combination of two or more. By using a plurality of types of host compounds, it is possible to adjust the movement of charges, and the organic EL element can be made highly efficient. Moreover, it becomes possible to mix different light emission by using multiple types of phosphorescent compounds etc. which are used as a luminescent dopant mentioned later, Thereby, arbitrary luminescent colors can be obtained. It is possible to adjust the kind of phosphorescent compound and the amount of doping, and it can be applied to illumination and backlight.

  As a host compound which concerns on this invention, the compound represented by the following general formula (H1) is mentioned as an example of the compound used preferably. Moreover, the compound represented by general formula (H1) is preferably used also for the adjacent layer (for example, hole-blocking layer etc.) of a light emitting layer.

In the general formula (H1), Z ₁ represents an aromatic heterocyclic ring which may have a substituent, and Z ₂ represents an aromatic heterocyclic ring or an aromatic hydrocarbon which may each have a substituent. Represents a ring, and Z ₃ represents a divalent linking group or a simple bond. R ₁₀₁ represents a hydrogen atom or a substituent.

  The host compound used in the present invention may be a conventionally known low molecular compound or a high molecular compound having a repeating unit, and a low molecular compound having a polymerizable group such as a vinyl group or an epoxy group (deposition polymerization property). (Light emitting host). As the known host compound, a compound that has a hole transporting ability and an electron transporting ability, prevents the emission of light from being increased in wavelength, and has a high Tg (glass transition temperature) is preferable. Specific examples of known host compounds include compounds described in the following documents. For example, Japanese Patent Application Laid-Open Nos. 2001-257076, 2002-308855, 2001-313179, 2002-319491, 2001-357777, 2002-334786, 2002-8860 Gazette, 2002-334787 gazette, 2002-15871 gazette, 2002-334788 gazette, 2002-43056 gazette, 2002-334789 gazette, 2002-75645 gazette, 2002-338579 gazette. No. 2002-105445, No. 2002-343568, No. 2002-141173, No. 2002-352957, No. 2002-203683, No. 2002-363227, No. 2002-231453. No. 2003-3165, No. 2002-234888, No. 2003-27048, No. 2002-255934, No. 2002-286061, No. 2002-280183, No. 2002-299060. 2002-302516, 2002-305083, 2002-305084, 2002-308837, and the like.

  In the present invention, 50% by mass or more of the host compound is preferably a compound having a phosphorescence emission energy of 2.9 eV or more and a glass transition temperature (Tg) of 90 ° C. or more, more preferably It is a compound of 100 ° C. or higher. Further, from the viewpoint of improving the storage stability (also referred to as durability improvement) of the organic EL element and reducing the uneven distribution of the compound at the interface of the light emitting layer, in all the light emitting layers constituting the light emitting layer unit, the physicochemical properties of the host compound The properties are preferably the same or the molecular structure is the same.

(Glass transition temperature: Tg)
The organic compound in each layer constituting the organic electroluminescent element of the present invention preferably contains at least 80% by mass or more of the material having a glass transition temperature (Tg) of 100 ° C. or higher.

  The glass transition temperature (Tg) as used in the field of this invention is a value calculated | required by the method based on JIS-K-7121 using DSC (Differential Scanning Colorimetry: Differential scanning calorimetry). By using a host compound having the same physical characteristics as described above, and more preferably by using a host compound having the same molecular structure, the entire organic compound layer (also referred to as an organic layer) of the organic EL element is used. And uniform film properties are obtained, and furthermore, adjusting the phosphorescence emission energy of the host compound to be 2.9 eV or more effectively suppresses energy transfer from the dopant and obtains high luminance. I can do it.

(Phosphorescent energy)
The phosphorescence emission energy as used in the field of this invention is the 0-0 transition band of the phosphorescence emission spectrum obtained when measuring the photoluminescence of a 100 nm vapor deposition film on a support substrate (it may be just a board | substrate). It refers to peak energy.

<Measuring method of 0-0 transition band of phosphorescence>
First, a method for measuring a phosphorescence spectrum will be described.

  The host compound to be measured is dissolved in a sufficiently deoxygenated mixed solvent of ethanol / methanol = 4/1 (volume ratio), put into a phosphorescence measurement cell, and then irradiated with excitation light at a liquid nitrogen temperature of 77 ° K. Then, an emission spectrum at 100 ms is measured after the excitation light irradiation. Since phosphorescence has a longer emission lifetime than fluorescence, it can be considered that light remaining after 100 ms is almost phosphorescence. For compounds with a phosphorescence lifetime shorter than 100 ms, measurement may be performed with a short delay time. However, if the delay time is set so short that it cannot be distinguished from fluorescence, phosphorescence and fluorescence cannot be separated. Therefore, it is necessary to select an optimum delay time that can be separated. Moreover, about the compound which cannot be melt | dissolved in the said solvent system, you may use the arbitrary solvent which can melt | dissolve the compound. In this case, the above measurement method has no problem because the solvent effect of the phosphorescence wavelength is negligible. Next, the 0-0 transition band is determined. In the present invention, the 0-0 transition band is defined as having the maximum emission wavelength in the phosphorescence spectrum chart obtained by the above measurement method. Since the intensity of the phosphorescence spectrum is usually low, it may be difficult to distinguish between noise and peak when enlarged. In such a case, an emission spectrum during excitation light irradiation (for convenience, this is referred to as a steady light spectrum) is expanded, and an emission spectrum after 100 ms after excitation light irradiation (for convenience, this is referred to as a phosphorescence spectrum) It can be determined by reading the peak wavelength of the phosphorescence spectrum from the stationary light spectrum portion derived from the superposed phosphorescence spectrum. Further, by performing a smoothing process on the phosphorescence spectrum, it is possible to separate the noise and the peak and read the peak wavelength. As the smoothing process, a smoothing method of Savitzky & Golay can be applied.

[Luminescent dopant]
As the luminescent dopant according to the present invention, a fluorescent compound or a phosphorescent compound (hereinafter, also referred to as “phosphorescent compound”, “phosphorescent material”, or “phosphorescent dopant”) can be used. However, from the viewpoint of obtaining an organic EL element with higher luminous efficiency, as a luminescent dopant (also simply referred to as “light-emitting material”) used in the light-emitting layer or light-emitting unit of the organic EL element of the present invention, It is preferable to contain at least one phosphorescent emitter simultaneously with the host compound. In addition, when using a fluorescent substance together, it is preferable to select blue.

(Phosphorescent compound: phosphorescent emitter)
The phosphorescent compound according to the present invention is a compound in which light emission from an excited triplet is observed. Specifically, the phosphorescent compound emits phosphorescence at room temperature (25 ° C.), and the phosphorescence quantum yield is Although defined as a compound of 0.01 or more at 25 ° C., a preferred phosphorescence quantum yield is 0.1 or more.

  The phosphorescence quantum yield can be measured by the method described in Spectroscopic II, page 398 (1992 edition, Maruzen) of Experimental Chemistry Course 4 of the 4th edition. Although the phosphorescence quantum yield in a solution can be measured using various solvents, the phosphorescence emitter according to the present invention achieves the above phosphorescence quantum yield (0.01 or more) in any solvent. It only has to be done. There are two types of light emission principles of phosphorescent emitters. One is the recombination of carriers on the host compound to which carriers are transported to generate an excited state of the host compound, and this energy is transferred to the phosphorescent emitter. The energy transfer type that emits light from the phosphorescent emitter by moving to the other, the phosphorescent emitter becomes a carrier trap, carrier recombination occurs on the phosphorescent emitter, and from the phosphorescent emitter Although it is a carrier trap type in which light emission can be obtained, in any case, the excited state energy of the phosphorescent emitter is required to be lower than the excited state energy of the host compound.

  The phosphor luminescent material can be appropriately selected from known materials used for the light emitting layer of the organic EL element. The phosphorescent emitter according to the present invention is preferably a complex compound containing a group 8-10 metal in the periodic table of elements, more preferably an iridium compound, an osmium compound, a platinum compound (platinum complex compound). ) Or a rare earth complex, and most preferred is an iridium compound. In the present invention, it is particularly preferable that red is selected from iridium compounds. These compounds are described, for example, in Inorg. Chem. 40, 1704-1711, and the like.

  In the present invention, among the phosphorescent compounds (phosphorescent emitters), the blue luminescent compound (dopant) that is preferably used is preferably a compound represented by the following general formula (BD1).

In the general formula (BD1), R ₁ represents a substituent. Z represents a nonmetallic atom group necessary for forming a 5- to 7-membered ring. n1 represents the integer of 0-5. B _{1 to} B ₅ each represent a carbon atom, a nitrogen atom, an oxygen atom or a sulfur atom, and at least one represents a nitrogen atom. M ₁ represents a group 8 to group 10 metal in the periodic table. X ₁ and X ₂ each represent a carbon atom, a nitrogen atom or an oxygen atom, and L ₁ represents an atomic group which forms a bidentate ligand together with X ₁ and X ₂ . m1 represents 1, 2 or 3, m2 represents 0, 1 or 2, and m1 + m2 is 2 or 3.

  In the phosphorescent compound represented by the general formula (BD1), a compound having a HOMO level of −5.15 to −3.50 eV and a LUMO level of −1.25 to +1.00 eV is preferable. In particular, a compound having a HOMO level of −4.80 to −3.50 eV and a LUMO level of −0.80 to +1.00 eV is preferable.

In the phosphorescent compound represented by the general formula (BD1), examples of the substituent represented by R ₁ include an alkyl group (for example, a methyl group, an ethyl group, a propyl group, an isopropyl group, a tert-butyl group, Pentyl group, hexyl group, octyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, etc.), cycloalkyl group (for example, cyclopentyl group, cyclohexyl group, etc.), alkenyl group (for example, vinyl group, allyl group, etc.), Alkynyl group (for example, ethynyl group, propargyl group, etc.), aromatic hydrocarbon ring group (also called aromatic carbocyclic group, aryl group, etc.), for example, phenyl group, p-chlorophenyl group, mesityl group, tolyl group, xylyl group , Naphthyl group, anthryl group, azulenyl group, acenaphthenyl group, fluorenyl group, phenanthryl group, Indenyl group, pyrenyl group, biphenylyl group, etc.), aromatic heterocyclic group (for example, pyridyl group, pyrimidinyl group, furyl group, pyrrolyl group, imidazolyl group, benzoimidazolyl group, pyrazolyl group, pyrazinyl group, triazolyl group (for example, 1, 2,4-triazol-1-yl group, 1,2,3-triazol-1-yl group, etc.), oxazolyl group, benzoxazolyl group, thiazolyl group, isoxazolyl group, isothiazolyl group, furazanyl group, thienyl group, A quinolyl group, a benzofuryl group, a dibenzofuryl group, a benzothienyl group, a dibenzothienyl group, an indolyl group, a carbazolyl group, a carbolinyl group, a diazacarbazolyl group (one of the carbon atoms constituting the carboline ring of the carbolinyl group is a nitrogen atom) Quinoxalinyl) , Pyridazinyl group, triazinyl group, quinazolinyl group, phthalazinyl group, etc.), heterocyclic group (eg, pyrrolidyl group, imidazolidyl group, morpholyl group, oxazolidyl group, etc.), alkoxy group (eg, methoxy group, ethoxy group, propyloxy group, Pentyloxy group, hexyloxy group, octyloxy group, dodecyloxy group, etc.), cycloalkoxy group (eg, cyclopentyloxy group, cyclohexyloxy group, etc.), aryloxy group (eg, phenoxy group, naphthyloxy group, etc.), alkylthio Groups (for example, methylthio group, ethylthio group, propylthio group, pentylthio group, hexylthio group, octylthio group, dodecylthio group, etc.), cycloalkylthio groups (for example, cyclopentylthio group, cyclohexylthio group, etc.), arylthio (Eg, phenylthio group, naphthylthio group, etc.), alkoxycarbonyl group (eg, methyloxycarbonyl group, ethyloxycarbonyl group, butyloxycarbonyl group, octyloxycarbonyl group, dodecyloxycarbonyl group, etc.), aryloxycarbonyl group (eg, , Phenyloxycarbonyl group, naphthyloxycarbonyl group, etc.), sulfamoyl group (for example, aminosulfonyl group, methylaminosulfonyl group, dimethylaminosulfonyl group, butylaminosulfonyl group, hexylaminosulfonyl group, cyclohexylaminosulfonyl group, octylaminosulfonyl group) Group, dodecylaminosulfonyl group, phenylaminosulfonyl group, naphthylaminosulfonyl group, 2-pyridylaminosulfonyl group, etc.), acyl group (for example, Acetyl group, ethylcarbonyl group, propylcarbonyl group, pentylcarbonyl group, cyclohexylcarbonyl group, octylcarbonyl group, 2-ethylhexylcarbonyl group, dodecylcarbonyl group, phenylcarbonyl group, naphthylcarbonyl group, pyridylcarbonyl group, etc.), acyloxy group ( For example, acetyloxy group, ethylcarbonyloxy group, butylcarbonyloxy group, octylcarbonyloxy group, dodecylcarbonyloxy group, phenylcarbonyloxy group, etc.), amide group (for example, methylcarbonylamino group, ethylcarbonylamino group, dimethylcarbonyl) Amino group, propylcarbonylamino group, pentylcarbonylamino group, cyclohexylcarbonylamino group, 2-ethylhexylcarbonylamino group, octyl Sulfonylamino group, dodecylcarbonylamino group, phenylcarbonylamino group, naphthylcarbonylamino group, etc.), carbamoyl group (for example, aminocarbonyl group, methylaminocarbonyl group, dimethylaminocarbonyl group, propylaminocarbonyl group, pentylaminocarbonyl group, Cyclohexylaminocarbonyl group, octylaminocarbonyl group, 2-ethylhexylaminocarbonyl group, dodecylaminocarbonyl group, phenylaminocarbonyl group, naphthylaminocarbonyl group, 2-pyridylaminocarbonyl group, etc.), ureido group (for example, methylureido group, ethyl) Ureido group, pentylureido group, cyclohexylureido group, octylureido group, dodecylureido group, phenylureido group, naphthylureido group, 2- Lysylaminoureido group, etc.), sulfinyl group (for example, methylsulfinyl group, ethylsulfinyl group, butylsulfinyl group, cyclohexylsulfinyl group, 2-ethylhexylsulfinyl group, dodecylsulfinyl group, phenylsulfinyl group, naphthylsulfinyl group, 2-pyridylsulfinyl group) Group), alkylsulfonyl group (for example, methylsulfonyl group, ethylsulfonyl group, butylsulfonyl group, cyclohexylsulfonyl group, 2-ethylhexylsulfonyl group, dodecylsulfonyl group, etc.), arylsulfonyl group or heteroarylsulfonyl group (for example, phenyl) Sulfonyl group, naphthylsulfonyl group, 2-pyridylsulfonyl group, etc.), amino group (for example, amino group, ethylamino group, dimethylamino group, butyl) Amino group, cyclopentylamino group, 2-ethylhexylamino group, dodecylamino group, anilino group, naphthylamino group, 2-pyridylamino group, etc.), cyano group, nitro group, hydroxy group, mercapto group, silyl group (for example, trimethylsilyl group) , Triisopropylsilyl group, triphenylsilyl group, phenyldiethylsilyl group, etc.). Of these substituents, preferred are an alkyl group and an aryl group.

  Z represents a nonmetallic atom group necessary for forming a 5- to 7-membered ring. Examples of the 5- to 7-membered ring formed by Z include a benzene ring, naphthalene ring, pyridine ring, pyrimidine ring, pyrrole ring, thiophene ring, pyrazole ring, imidazole ring, oxazole ring, and thiazole ring. Of these, a benzene ring is preferred.

B _{1 to} B ₅ each represents a carbon atom, a nitrogen atom, an oxygen atom or a sulfur atom, and at least one represents a nitrogen atom. The aromatic nitrogen-containing heterocycle formed by these five atoms is preferably a monocycle. Examples include pyrrole ring, pyrazole ring, imidazole ring, triazole ring, tetrazole ring, oxazole ring, isoxazole ring, thiazole ring, isothiazole ring, oxadiazole ring, and thiadiazole ring. Among these, a pyrazole ring and an imidazole ring are preferable, and an imidazole ring is more preferable. These rings may be further substituted with the above substituents. Preferable substituents are an alkyl group and an aryl group. Preferable substituents are an alkyl group and an aryl group, and more preferably an aryl group.

L ₁ represents an atomic group that forms a bidentate ligand together with X ₁ and X ₂ . Specific examples of the bidentate ligand represented by X ₁ -L ₁ -X ₂ include, for example, substituted or unsubstituted phenylpyridine, phenylpyrazole, phenylimidazole, phenyltriazole, phenyltetrazole, pyrazabol, picolinic acid And acetylacetone. These groups may be further substituted with the above substituents.

  m1 represents 1, 2 or 3, m2 represents 0, 1 or 2, and m1 + m2 is 2 or 3. Especially, the case where m2 is 0 is preferable.

The metal represented by M _1, a transition metal element of Group 8 to 10 of the Periodic Table of the Elements (also referred to simply as a transition metal) is used, inter alia, iridium, platinum, more preferably an iridium. Note that the phosphorescent compound represented by the general formula (BD1) may have a polymerizable group or a reactive group.

  Specific examples of the phosphorescent compound represented by the general formula (BD1) are shown below, but are not limited thereto.

  These metal complexes are described in, for example, Organic Letter, vol. 16, 2579-2581 (2001), Inorganic Chemistry, Vol. 30, No. 8, 1685-1687 (1991), J. Am. Am. Chem. Soc. , 123, 4304 (2001), Inorganic Chemistry, Vol. 40, No. 7, 1704-1711 (2001), Inorganic Chemistry, Vol. 41, No. 12, 3055-3066 (2002) , New Journal of Chemistry. 26, 1171 (2002), European Journal of Organic Chemistry, Vol. 4, pages 695-709 (2004), and further synthesized by applying methods such as references described in these documents. it can.

  Other specific examples of the compound used as the phosphorescent light emitter include the compounds described in paragraphs (0106) to (0109) of JP-A No. 2004-311410.

<Non-light emitting intermediate layer>
In the present invention, it is preferable to provide a non-light emitting intermediate layer as the carrier control layer. The layer thickness of the non-light emitting intermediate layer is preferably in the range of 1.0 to 15 nm, more preferably in the range of 3 to 10 nm, suppressing interaction such as energy transfer between adjacent light emitting layers, Moreover, it is preferable from the viewpoint of not applying a large load to the current-voltage characteristics of the element.

  The material used for the non-light emitting intermediate layer may be the same as or different from the host compound of the light emitting layer, but may be the same as the host material of at least one of the adjacent light emitting layers. preferable.

  The non-light emitting intermediate layer may contain a compound common to each light emitting layer (for example, a host compound). Common host materials (where common host materials are used when the physicochemical properties such as phosphorescence energy and glass transition temperature are the same or when the molecular structure of the host compound is the same) In addition, the injection barrier between the light-emitting layer and the non-light-emitting layer is reduced, and the effect of easily maintaining the injection balance of holes and electrons even when the voltage (current) is changed can be obtained. . Moreover, the effect that the color shift when a voltage (current) is applied is improved.

  Further, as described above, by using a material in which the lowest excited triplet energy level T1 of the common host material is higher than the lowest excited triplet energy level T2 of the phosphorescent emitter, light emission is achieved. Since the triplet exciton of the layer is effectively confined in the light emitting layer, a highly efficient device can be obtained.

  In addition, in the organic EL element of three colors of blue, green, and red, when a phosphorescent light emitter is used for each light emitting material, the excited triplet energy of the blue phosphorescent light emitter is the largest, A host material having an excited triplet energy larger than that of the blue phosphorescent emitter may be included as a common host material in the light emitting layer and the non-light emitting intermediate layer.

  In the organic EL device of the present invention, since the host material is responsible for carrier transport, a material having carrier transport capability is preferable. Although carrier mobility is used as a physical property value representing carrier transport ability, the carrier mobility of an organic material is generally dependent on electric field strength. Since a material with high electric field strength dependency easily breaks the balance of hole and electron injection / transport, it is preferable to use a material with low mobility electric field strength dependency as the intermediate layer material and the host material. On the other hand, in order to optimally adjust the injection balance of holes and electrons, it is also preferable that the non-light emitting intermediate layer functions as a blocking layer, that is, a hole blocking layer and an electron blocking layer. It is done.

<< Layer structure of organic EL element >>
In order to extract white light, the light emitting layer, which is a constituent layer of the organic electroluminescence device of the present invention, is arbitrarily selected from light emission colors emitting blue, green, yellow, and red to extract white light.

  In the present invention, the effect of the present invention can be further obtained when a plurality of dopants emitting different luminescent colors are contained in the same layer. Preferably, among the selected luminescent colors, a luminescent compound having a close emission wavelength is contained in the same layer. As a result, energy transition to the long wave luminescent compound is increased, and luminous efficiency is improved.

  As an example, in the case of blue-green-red, at least one of blue-green or green-red is contained in the same layer. When composed of blue-green-yellow-red, at least one of blue-green, green-yellow, yellow-red is contained in the same layer, and an emission color containing a longer wave luminescent compound is contained in the same layer. Is preferred. Specifically, yellow-red and green-yellow. Furthermore, it is preferable that there are a plurality of light-emitting layers containing a plurality of light-emitting compounds having different emission colors. It is more advantageous to have a plurality of configurations in which energy transition is advantageous. Moreover, it is preferable that the volume concentration of the luminescent compound of a longer wave light is 4% or less among several luminescent compounds from which luminescent color differs. Long wave luminescent compounds often have a lower ionization potential and a higher HOMO energy level. In other words, it is easy to hold holes, and the conductivity is lowered, so the hole holding is relaxed by reducing the content ratio, which is advantageous in terms of conductivity, and as a result, the driving voltage for obtaining a desired luminance is lowered, Power consumption is improved. However, what is important is the energy level of HOMO and the structure of the luminescent compound. For example, this is not the case when a blue light-emitting compound having a high HOMO energy level such as the compound represented by the general formula (BD1) according to the present invention is used. The light emitting layer containing a light emitting compound having a high HOMO energy level is preferably arranged on the most cathode side in the light emitting layer.

  In many cases, the luminescent compound having a high HOMO energy level is a red luminescent compound. For example, among the luminescent colors selected to be white, the blue luminescent compound has the highest HOMO energy level. If it is high, it is possible to dispose the light emitting layer containing the blue light emitting compound closest to the cathode, but in the present invention, the light emitting layer having the shortest emission wavelength is disposed closest to the anode. In addition, two types of luminescent compounds from which the luminescent color contained in the same light emitting layer differs are preferable. This is because it is difficult to control the deposition conditions when the number is 3 or more.

(P-type semiconductor layer, n-type semiconductor layer)
In the present invention, a p-type or n-type semiconductor layer is preferably used. Here, the p-type or n-type semiconductor layer refers to a layer that contains an electron acceptor and an electron donor and exhibits semiconductivity.

《Electron Acceptor》
The electron acceptor in the present invention refers to an electron-donating compound. A function is expressed by forming an organic layer by mixing with a host compound as a dopant, not as a simple substance. In other words, the presence of the host compound oxidized by the electron acceptor in the cation radical state reduces the hole barrier near the layer interface on the anode side, increases the hole supply density, and the effect of lowering the voltage is recognized. . A so-called p-type semiconductor layer is formed. Therefore, the electron acceptor is preferably contained in the hole transport layer. The layer containing the electron acceptor may be a light emitting layer. In this case, as a dopant, an electron acceptor and a luminescent compound will be contained. The luminescent species may be fluorescent or phosphorescent.

《Electron Donor》
The electron donor as referred to in the present invention refers to an electron donating compound. A function is expressed by forming an organic layer by mixing with a host compound as a dopant, not as a simple substance. That is, the presence of the host compound reduced by the electron donor in an anion radical state reduces the electron barrier in the vicinity of the cathode-side layer interface, increases the electron supply density, and an effect of lowering the voltage. A so-called n-type semiconductor layer is formed. Therefore, the electron donor is preferably contained in the electron transport layer.

  The layer containing an electron donor may be a light emitting layer. In this case, as a dopant, an electron donor and a luminescent compound will be contained. The luminescent species may be fluorescent or phosphorescent.

《Hole transport layer》
The hole transport layer is made of a hole transport material having a function of transporting holes, and in the present invention, a hole injection layer and an electron blocking layer are also included in the hole transport layer. The hole transport layer can be provided as a single layer or a plurality of layers.

  In the present invention, the hole transport layer is preferably a so-called p-type semiconductor layer. It is interpreted that the effect of lowering the driving voltage is recognized, and doping of the carrier (electron) acceptor increases the hole density, forms a high HOMO level, and increases the hole mobility by hopping conduction.

  Conventionally, the concentration of impurities to be doped has been studied with a uniform concentration in the hole transport layer. However, if the impurity concentration is not uniform and is locally changed, an effect of improving the light emission efficiency can be obtained in addition to the conventional driving voltage reduction. In particular, when a high concentration region is provided locally than the average acceptor concentration, a remarkable effect can be obtained. Although a slight tendency to increase the driving voltage was observed, it is advantageous in terms of power efficiency. The reason is not clear, but when the acceptor concentration is locally increased, the number of fixed electrons increases and the electron barrier increases, and it is assumed that electrons and excitons are confined in the light emitting layer. In the present invention, the hole transport layer can be provided as a single layer or a plurality of layers.

  The hole transport material has any one of hole injection or transport and electron barrier properties, and may be either organic or inorganic. For example, triazole derivatives, oxadiazole derivatives, imidazole derivatives, polyarylalkane derivatives, pyrazoline derivatives and pyrazolone derivatives, phenylenediamine derivatives, arylamine derivatives, amino-substituted chalcone derivatives, oxazole derivatives, styrylanthracene derivatives, fluorenone derivatives, hydrazone derivatives, Examples thereof include stilbene derivatives, silazane derivatives, aniline copolymers, and conductive polymer oligomers, particularly thiophene oligomers. The above-mentioned materials can be used as the hole transport material, but it is preferable to use a porphyrin compound, an aromatic tertiary amine compound and a styrylamine compound, particularly an aromatic tertiary amine compound. Representative examples of aromatic tertiary amine compounds and styrylamine compounds include N, N, N ', N'-tetraphenyl-4,4'-diaminophenyl; N, N'-diphenyl-N, N'- Bis (3-methylphenyl)-[1,1′-biphenyl] -4,4′-diamine (TPD); 2,2-bis (4-di-p-tolylaminophenyl) propane; 1,1-bis (4-di-p-tolylaminophenyl) cyclohexane; N, N, N ′, N′-tetra-p-tolyl-4,4′-diaminobiphenyl; 1,1-bis (4-di-p-tolyl) Aminophenyl) -4-phenylcyclohexane; bis (4-dimethylamino-2-methylphenyl) phenylmethane; bis (4-di-p-tolylaminophenyl) phenylmethane; N, N'-diphenyl-N, N ' − (4-methoxyphenyl) -4,4'-diaminobiphenyl; N, N, N ', N'-tetraphenyl-4,4'-diaminodiphenyl ether; 4,4'-bis (diphenylamino) quadriphenyl; N, N, N-tri (p-tolyl) amine; 4- (di-p-tolylamino) -4 '-[4- (di-p-tolylamino) styryl] stilbene; 4-N, N-diphenylamino- (2-diphenylvinyl) benzene; 3-methoxy-4′-N, N-diphenylaminostilbenzene; N-phenylcarbazole, and two more described in US Pat. No. 5,061,569 Having a condensed aromatic ring of, for example, 4,4'-bis [N- (1-naphthyl) -N-phenylamino] biphenyl (NPD), JP-A-4-308 4,4 ', 4 "-tris [N- (3-methylphenyl) -N-phenylamino] triphenylamine in which three triphenylamine units described in Japanese Patent No. 88 are linked in a starburst type ( MTDATA) etc. Further, a polymer material in which these materials are introduced into a polymer chain or these materials are used as a polymer main chain can also be used. Inorganic compounds such as SiC can also be used.

  In the present invention, a known material can be used as the carrier (electron) acceptor material. For example, Jpn. Huang et. al. Authors (Applied Physics Letters 80 (2002), p. 139), JP-A-4-297076, JP-A-2000-196140, JP-A-2001-102175, JP-A-2004-281371, J. Pat. Appl. Phys. 95, 5773 (2004), and the like. Further, compounds represented by the general formulas (1) to (7) described in JP-A-2006-41020 are also preferably used.

  The hole transport material and the carrier (electron) acceptor are formed by thinning by a known method such as a vacuum deposition method, a spin coating method, a casting method, a printing method including an ink jet method, or an LB method. Can do.

  Although it cannot be specified depending on the type of material, the acceptor-containing average volume concentration is 0.1% to 30%, and there is a region where the concentration differs by at least 3% from the average concentration. The difference between the highest concentration and the lowest concentration is 1% to 30%, preferably 1% to 20%. More preferably, it is 1% to 10%. The layer thickness ratio in the highest concentration region is 1% to 50%, more preferably 2% to 45%.

  The layer thickness is usually about 1 nm to 1 μm, preferably 5 nm to 200 nm. Within 5 nm from the interface between the hole transport layer and the organic layer adjacent to the cathode side of the present invention, the lower the carrier (electron) acceptor concentration is within the range not impairing the conductivity, the more preferable from the viewpoint of continuous drive life.

《Electron transport layer》
The electron transport layer is made of a material having a function of transporting electrons. In the present invention, the electron injection layer and the hole blocking layer are also included in the electron transport layer. The electron transport layer can be provided as a single layer or a plurality of layers.

  In the present invention, the electron transport layer is preferably a so-called n-type semiconductor layer. The effect is recognized in the drive voltage, and it is interpreted that the doping of the carrier (electron) donor increases the electron density, forms a high LUMO level, and increases the electron mobility by hopping conduction.

  Regarding the concentration of impurities to be doped, only a uniform concentration has been studied in the electron transport layer. However, if the concentration of the impurities is not uniform and is locally changed, in addition to the conventional low drive voltage, The effect of improving the luminous efficiency is recognized. In particular, a remarkable effect is obtained when a high concentration region is provided locally than the average donor concentration. Although a slight tendency to increase the driving voltage was observed, it is advantageous in terms of power efficiency. The reason is not clear, but when the donor concentration increases locally, the number of fixed holes increases and the hole barrier increases, so it is assumed that holes and excitons are confined in the light-emitting layer. ing. The electron transport layer can be provided as a single layer or a plurality of layers.

  Any electron transport material may be used as long as it has a function of transmitting electrons injected from the cathode to the light emitting layer. Examples include nitro-substituted fluorene derivatives, diphenylquinone derivatives, thiopyran dioxide derivatives, carbodiimides, fluorenylidenemethane derivatives, anthraquinodimethane and anthrone derivatives, oxadiazole derivatives, and the like. Furthermore, in the above oxadiazole derivative, a thiadiazole derivative in which the oxygen atom of the oxadiazole ring is substituted with a sulfur atom, and a quinoxaline derivative having a quinoxaline ring known as an electron withdrawing group can also be used as an electron transport material. Furthermore, a polymer material in which these materials are introduced into a polymer chain or these materials are used as a polymer main chain can also be used. In addition, metal complexes of 8-quinolinol derivatives such as tris (8-quinolinol) aluminum (Alq), tris (5,7-dichloro-8-quinolinol) aluminum, tris (5,7-dibromo-8-quinolinol) aluminum Tris (2-methyl-8-quinolinol) aluminum, tris (5-methyl-8-quinolinol) aluminum, bis (8-quinolinol) zinc (Znq), and the like, and the central metals of these metal complexes are In, Mg, Metal complexes replaced with Cu, Ca, Sn, Ga or Pb can also be used as the electron transport material. In addition, metal-free or metal phthalocyanine, or those having terminal ends substituted with an alkyl group or a sulfonic acid group can be preferably used as the electron transporting material. Further, the distyrylpyrazine derivatives exemplified as the material for the light emitting layer can also be used as the electron transporting material. Moreover, the compound represented with general formula (H1) as described in a host compound is also preferably applicable.

  In the present invention, a known material can be used as the carrier donor material. For example, JP-A-4-297076, JP-A-10-270172, JP-A-2000-196140, JP-A-2001-102175, J. Pat. Appl. Phys. 95, 5773 (2004), and the like. Moreover, the compounds represented by the general formulas (8) to (10) described in JP-A-2006-41020 are also preferably used. In the present invention, an element having low power consumption can be manufactured by using such an electron transport layer having a high n property together with a p property semiconductor layer.

  The electron transport material and the carrier (electron) donor can be formed by thinning by a known method such as a vacuum deposition method, a spin coating method, a casting method, a printing method including an ink jet method, or an LB method. it can.

  Although it cannot be specified by the kind of preferable donor vapor deposition condition material, the donor-containing average volume concentration is 5% to 95%, and it is preferable that there is a region where the difference between at least the maximum concentration and the minimum concentration is 5% or more. The difference between the highest concentration and the lowest concentration is 20% to 90%, but the preferred highest concentration is 15% to 95%. More preferably, it is 25% to 90%. The film thickness ratio of the highest concentration region in the electron transport layer is 1% to 50%, more preferably 2% to 45%. The layer thickness is usually about 1 nm to 1 μm, preferably 5 nm to 200 nm.

  In the region where the layer thickness is 1/3 of the electron transport layer from the interface between the organic layers adjacent to the anode side, the lower the carrier donor concentration within the range not impairing the conductivity, the more preferable from the viewpoint of continuous driving life. Depending on the material, it is often 5 or less. In the present invention, when there are three or more regions having a donor volume concentration different by 5% or more, the light emission efficiency may be further improved, and one example thereof is a case of continuous change. The term “local” as used in the present invention refers to, for example, a case where film thickness configurations of 1 nm or more having different donor volume concentrations are arbitrarily combined. Even in this case, the difference in the donor volume concentration between the maximum concentration and the minimum concentration is 5% or more.

<< Injection layer: electron injection layer, hole injection layer >>
An injection layer is a layer provided between an electrode and an organic layer in order to reduce drive voltage and improve light emission luminance. “Organic EL element and its forefront of industrialization (issued by NTT Corporation on November 30, 1998) 2), Chapter 2, “Electrode Materials” (pages 123 to 166) in detail, and includes a hole injection layer (anode buffer layer) and an electron injection layer (cathode buffer layer).

  The injection layer may be provided as necessary, and may be present between the anode and the light emitting layer or the hole transport layer and between the cathode and the light emitting layer or the electron transport layer as described above.

  The details of the anode buffer layer (hole injection layer) are described in JP-A-9-45479, JP-A-9-260062, JP-A-8-288069 and the like. As a specific example, copper phthalocyanine is used. Examples thereof include a phthalocyanine buffer layer represented by an oxide, an oxide buffer layer represented by vanadium oxide, an amorphous carbon buffer layer, and a polymer buffer layer using a conductive polymer such as polyaniline (emeraldine) or polythiophene. The details of the cathode buffer layer (electron injection layer) are described in JP-A-6-325871, JP-A-9-17574, JP-A-10-74586, and the like. Specifically, strontium, aluminum, etc. Metal buffer layer typified by lithium, alkali metal compound buffer layer typified by lithium fluoride, alkaline earth metal compound buffer layer typified by magnesium fluoride, oxide buffer layer typified by aluminum oxide, etc. . The buffer layer (injection layer) is preferably a very thin film, and the film thickness is preferably in the range of 0.1 to 5 μm, although it depends on the material.

<Blocking layer: hole blocking layer, electron blocking layer>
The hole blocking layer has a function of an electron transport layer in a broad sense, and is made of a hole blocking material that has a function of transporting electrons and has a remarkably small ability to transport holes. The probability of recombination of electrons and holes can be improved by blocking. Moreover, the structure of the electron carrying layer mentioned above can be used as a hole-blocking layer concerning this invention as needed. The hole blocking layer of the organic EL device of the present invention is preferably provided adjacent to the light emitting layer.

  As described above, the blocking layer is provided as necessary in addition to the basic constituent layer of the organic compound thin film. For example, it is described in JP-A Nos. 11-204258, 11-204359, and “Organic EL elements and their forefront of industrialization” (issued by NTT, Inc. on November 30, 1998). There is a hole blocking (hole blocking) layer.

  In the present invention, it is preferable that 50% by mass or more of the compound contained in the hole blocking layer has an ionization potential of 0.2 eV or more larger than the host compound of the shortest wave emitting layer. When the hole blocking layer of the present invention contains the electron donor, the electron density increases, which is preferable for further lowering the voltage.

  The ionization potential is defined by the energy required to emit electrons at the HOMO (highest occupied molecular orbital) level of the compound to the vacuum level, and can be obtained by the following method, for example.

  (1) Using Gaussian 98 (Gaussian 98, Revision A.11.4, MJ Frisch, et al, Gaussian, Inc., Pittsburgh PA, 2002.), a molecular orbital calculation software manufactured by Gaussian, USA The ionization potential can be obtained as a value obtained by rounding off the second decimal place of the value (eV unit converted value) calculated by performing structural optimization using B3LYP / 6-31G *. This calculation value is effective because the correlation between the calculation value obtained by this method and the experimental value is high.

  (2) The ionization potential can also be obtained by a method of directly measuring by photoelectron spectroscopy. For example, a method known as ultraviolet photoelectron spectroscopy can be suitably used by using a low energy electron spectrometer “Model AC-1” manufactured by Riken Keiki Co., Ltd.

  On the other hand, the electron blocking layer has a function of a hole transport layer in a broad sense, and is made of a material that has a function of transporting holes and has an extremely small ability to transport electrons, and transports electrons while transporting holes. By blocking, the recombination probability of electrons and holes can be improved. The electron blocking layer preferably used in the present invention is a material for the hole transport layer. Further, when the electron acceptor is contained, the effect of further lowering the voltage can be obtained.

  The film thickness of the hole blocking layer and the electron transport layer according to the present invention is preferably 3 nm to 100 nm, and more preferably 5 nm to 30 nm.

《Support substrate》
The support substrate (hereinafter also referred to as a substrate, substrate, substrate, support, etc.) applied to the organic EL element of the present invention is not particularly limited in type, such as glass, plastic, etc., and may be transparent. It may be opaque. When extracting light from the support substrate side, the support substrate is preferably transparent. Examples of the transparent support substrate preferably used include glass, quartz, and a transparent resin film. A particularly preferable support substrate is a resin film capable of giving flexibility to the organic EL element. Examples of the resin film include polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polyethylene, polypropylene, cellophane, cellulose diacetate, cellulose triacetate, cellulose acetate butyrate, cellulose acetate propionate (CAP), Cellulose esters such as cellulose acetate phthalate (TAC) and cellulose nitrate or derivatives thereof, polyvinylidene chloride, polyvinyl alcohol, polyethylene vinyl alcohol, syndiotactic polystyrene, polycarbonate, norbornene resin, polymethylpentene, polyether ketone, polyimide , Polyethersulfone (PES), polyphenylene sulfide, polysulfones, Cycloolefins such as polyetherimide, polyetherketoneimide, polyamide, fluororesin, nylon, polymethylmethacrylate, acrylic or polyarylate, Arton (trade name, manufactured by JSR) or Appel (trade name, manufactured by Mitsui Chemicals) Resin etc. are mentioned. On the surface of the resin film, an inorganic film, an organic film, or a hybrid film of both may be formed. Water vapor permeability measured by a method in accordance with JIS K 7129-1992 (25 ± 0.5 ° C., It is preferable that the relative humidity (90 ± 2)% RH) is a barrier film of 1 × 10 ⁻³ g / (m ² · 24 h) or less, and further measured by a method based on JIS K 7126-1987. The oxygen transmission rate is 1 × 10 ⁻³ ml / m ² · 24 h · atm or less, and the water vapor transmission rate (25 ± 0.5 ° C., relative humidity (90 ± 2)% RH) is 1 × 10 ^−3. It is preferable that it is a highly barrier film of g / (m ² · 24h) or less.

  In order to obtain a high barrier film, the material for forming the barrier film formed on the surface of the resin film may be any material that has a function of suppressing intrusion of organic EL elements such as moisture and oxygen, for example, Silicon oxide, silicon dioxide, silicon nitride, or the like can be used. Furthermore, in order to improve the brittleness of the barrier film, it is more preferable to have a laminated structure of these inorganic layers and layers made of organic materials. Although there is no restriction | limiting in particular about the lamination | stacking order of an inorganic layer and an organic layer, It is preferable to laminate | stack both alternately several times.

[Method of forming barrier film]
The method for forming the barrier film is not particularly limited. For example, the vacuum deposition method, the sputtering method, the reactive sputtering method, the molecular beam epitaxy method, the cluster ion beam method, the ion plating method, the plasma polymerization method, the atmospheric pressure plasma treatment Method, plasma CVD method, laser CVD method, thermal CVD method, coating method and the like can be used, but the method based on the atmospheric pressure plasma treatment method described in JP-A-2004-68143 is particularly preferable. Examples of the opaque support substrate include metal plates / films such as aluminum and stainless steel, opaque resin substrates, ceramic substrates, and the like.

  The external extraction efficiency at room temperature of light emission of the organic EL device of the present invention is preferably 1% or more, more preferably 5% or more. Here, external extraction quantum efficiency (%) = number of photons emitted to the outside of the organic EL element / number of electrons flowed to the organic EL element × 100.

<Sealing>
Examples of the sealing means used for sealing the organic EL element of the present invention include a method of bonding a sealing member, an electrode, and a support substrate with an adhesive. The sealing member may be disposed so as to cover the display area of the organic EL element, and may be concave or flat. Moreover, transparency and electrical insulation are not particularly limited. Specific examples include a glass plate, a polymer plate / film, and a metal plate / film. Examples of the glass plate include soda-lime glass, barium / strontium-containing glass, lead glass, aluminosilicate glass, borosilicate glass, barium borosilicate glass, and quartz.

  Examples of the polymer plate include polycarbonate, acrylic, polyethylene terephthalate, polyether sulfide, and polysulfone. Examples of the metal plate include those made of one or more metals or alloys selected from the group consisting of stainless steel, iron, copper, aluminum, magnesium, nickel, zinc, chromium, titanium, molybdenum, silicon, germanium, and tantalum.

In the present invention, a polymer film and a metal film can be preferably used because the element can be thinned. Further, the polymer film has a water vapor permeability (25 ± 0.5 ° C., relative humidity (90 ± 2)% RH) measured by a method according to JIS K 7129-1992, 1 × 10 ⁻³ g / (M ² · 24 h) It is preferable that the film has a barrier property of not more than 1, and further, the oxygen permeability measured by a method according to JIS K 7126-1987 is 1 × 10 ⁻³ ml / m ² · 24 h ·. It is preferably a high barrier film having atm or less, water vapor transmission rate (25 ± 0.5 ° C., relative humidity (90 ± 2)% RH) of 1 × 10 ⁻³ g / (m ² · 24 h) or less. .

  For processing the sealing member into a concave shape, sandblasting, chemical etching, or the like is used.

  Specific examples of the adhesive include photocuring and thermosetting adhesives having a reactive vinyl group of acrylic acid oligomers and methacrylic acid oligomers, and moisture curing adhesives such as 2-cyanoacrylate. be able to. Moreover, the heat | fever and chemical curing types (two-component mixing), such as an epoxy type, can be mentioned. Moreover, hot-melt type polyamide, polyester, and polyolefin can be mentioned. Moreover, a cationic curing type ultraviolet curing epoxy resin adhesive can be mentioned. In addition, since an organic EL element may deteriorate by heat processing, what can be adhesive-hardened from room temperature to 80 degreeC is preferable. A desiccant may be dispersed in the adhesive. Application | coating of the adhesive agent to a sealing part may use commercially available dispenser, and may print it like screen printing.

  In addition, it is also preferable to coat the electrode and the organic layer on the outside of the electrode facing the support substrate with the organic layer interposed therebetween, and form an inorganic or organic layer in contact with the support substrate to form a sealing film. it can. In this case, the material for forming the film may be any material that has a function of suppressing intrusion of elements that cause deterioration of the element such as moisture and oxygen. For example, silicon oxide, silicon dioxide, silicon nitride, or the like is used. it can. Furthermore, in order to improve the brittleness of the film, it is preferable to have a laminated structure of these inorganic layers and layers made of organic materials.

  The method for forming these films is not particularly limited. For example, vacuum deposition, sputtering, reactive sputtering, molecular beam epitaxy, cluster ion beam, ion plating, plasma polymerization, atmospheric pressure plasma treatment A method, a plasma CVD method, a laser CVD method, a thermal CVD method, a coating method, or the like can be used. In the gap between the sealing member and the display area of the organic EL element, an inert gas such as nitrogen or argon, or an inert liquid such as fluorinated hydrocarbon or silicon oil is injected in the gas phase and the liquid phase. Is preferred. A vacuum can also be used. Moreover, a hygroscopic compound can also be enclosed inside. Examples of the hygroscopic compound include metal oxides (eg, sodium oxide, potassium oxide, calcium oxide, barium oxide, magnesium oxide, aluminum oxide), sulfates (eg, sodium sulfate, calcium sulfate, magnesium sulfate, cobalt sulfate, etc.). Metal halides (eg, calcium chloride, magnesium chloride, cesium fluoride, tantalum fluoride, cerium bromide, magnesium bromide, barium iodide, magnesium iodide, etc.), perchloric acids (eg, barium perchlorate, In particular, anhydrous salts are preferably used in sulfates, metal halides and perchloric acids.

《Protective film, protective plate》
In order to increase the mechanical strength of the element, a protective film or a protective plate may be provided outside the sealing film or sealing film on the side facing the support substrate with the organic layer interposed therebetween. In particular, when sealing is performed by the sealing film, the mechanical strength is not necessarily high, and thus it is preferable to provide such a protective film and a protective plate. As a material that can be used for this, the same glass plate, polymer plate / film, metal plate / film, etc. used for the sealing can be used, but the polymer film is light and thin. Is preferably used.

"anode"
As the anode in the organic EL element, an electrode material made of a metal, an alloy, an electrically conductive compound, or a mixture thereof having a high work function (4 eV or more) is preferably used. Specific examples of such an electrode substance include conductive transparent materials such as metals such as Au, CuI, indium tin oxide (ITO), SnO ₂ , and ZnO. Alternatively, an amorphous material such as IDIXO (In ₂ O ₃ —ZnO) capable of forming a transparent conductive film may be used. For the anode, these electrode materials may be formed into a thin film by a method such as vapor deposition or sputtering, and a pattern having a desired shape may be formed by a photolithography method, or when the pattern accuracy is not required (about 100 μm or more) ), A pattern may be formed through a mask having a desired shape when the electrode material is deposited or sputtered. Or when using the substance which can be apply | coated like an organic electroconductivity compound, wet film forming methods, such as a printing system and a coating system, can also be used. When light emission is extracted from the anode, it is desirable that the transmittance be greater than 10%, and the sheet resistance as the anode is preferably several hundred Ω / □ or less. Further, although the film thickness depends on the material, it is usually selected in the range of 10 to 1000 nm, preferably 10 to 200 nm.

"cathode"
On the other hand, as the cathode, a material having a low work function (4 eV or less) metal (referred to as an electron injecting metal), an alloy, an electrically conductive compound, and a mixture thereof as an electrode material is used. Specific examples of such electrode materials include sodium, sodium-potassium alloy, magnesium, lithium, magnesium / copper mixture, magnesium / silver mixture, magnesium / aluminum mixture, magnesium / indium mixture, aluminum / aluminum oxide (Al ₂ O ₃ ) Mixtures, indium, lithium / aluminum mixtures, rare earth metals and the like. Among these, from the point of durability against electron injection and oxidation, etc., a mixture of an electron injecting metal and a second metal which is a stable metal having a larger work function than this, for example, a magnesium / silver mixture, Magnesium / aluminum mixtures, magnesium / indium mixtures, aluminum / aluminum oxide (Al ₂ O ₃ ) mixtures, lithium / aluminum mixtures, aluminum and the like are preferred. The cathode can be produced by forming a thin film of these electrode materials by a method such as vapor deposition or sputtering. Further, the sheet resistance as a cathode is preferably several hundred Ω / □ or less, and the film thickness is usually 10 to 5 μm, preferably 50 to 200 nm. In order to transmit the emitted light, it is an essential requirement that either one of the anode or the cathode of the organic EL element is transparent or translucent.

  Moreover, after producing the said metal with a film thickness of 1-20 nm on a cathode, a transparent or semi-transparent cathode can be produced by producing the electroconductive transparent material quoted by description of the anode on it, By applying this, an element in which both the anode and the cathode are transmissive can be manufactured.

<< Light extraction and / or condensing sheet >>
In particular, in an organic electroluminescence device for a backlight, it is usually desirable that the light is radiated in all directions and the brightness does not change even if the viewing angle is changed. However, it is desirable to reduce the luminance at a large viewing angle (an angle observed from an oblique direction). Therefore, it is preferable that a diffusion plate, a prism sheet and the like for controlling the radiation angle are combined on the organic electroluminescence element.

  Usually, in an organic electroluminescence device that emits light from a substrate (glass substrate, resin substrate, etc.), part of the light emitted from the light emitting layer causes total reflection at the interface between the substrate and air, and the light is emitted. The problem of loss occurs. In order to solve this problem, the prism surface or lens sheet is processed on the surface of the substrate, or the prism sheet or lens sheet is attached to the surface of the substrate, thereby suppressing total reflection and improving the light extraction efficiency. .

  In the organic EL device using the light extraction and / or condensing sheet as described above, the front luminance amplification factor is increased. The light extracted to the outside can be enhanced in luminance in all directions, and the luminance can be made uniform in all directions.

  Since the blue color is generally rate-determined in the lifetime in continuous driving or the like, when such a light extraction and / or condensing sheet is used, a longer lifetime can be achieved in the organic electroluminescence element. Also, the driving voltage is limited by blue, which has the largest energy gap between HOMO and LUMO. Therefore, the organic EL element with improved light extraction has a design that requires less blue front luminance. Can be lowered.

  In other words, since the blue light emitting layer can be made thin and the driving voltage can be lowered, a longer life can be achieved compared to the case where there is no light extraction and / or light collecting sheet, and this combination provides a total of white light. Can be.

  Here, the amplification factor of the front luminance by the light extraction and / or condensing sheet is determined by using a spectral radiance meter (for example, CS-1000 (manufactured by Konica Minolta Sensing)) or the like, and the emission luminance from the front (2 ° field of view). The visible wavelength range is required so that the optical axis of the spectral radiance meter coincides with the normal from the light-emitting surface, with or without light extraction and / or condensing sheet. Measure and integrate the values and take the ratio.

<< Light emission, front luminance, chromaticity, color temperature of organic electroluminescence elements >>
The luminescent color of the compound applied to the organic electroluminescence device or the organic EL device of the present invention is shown in FIG. 4.16 on page 108 of “New Color Science Handbook” (Edited by the Japan Color Society, University of Tokyo Press, 1985). It is determined by the color when the result measured with the spectral radiance meter CS-1000 (manufactured by Konica Minolta Sensing) is applied to the CIE chromaticity coordinates. The light emission color of the organic electroluminescence device of the present invention is white. The place where light is irradiated is measured with a spectral radiation color illuminance meter CL-200 (manufactured by Konica Minolta Sensing), and the color temperature is from 2,000K to 13,000K. Refers to the range.

<< Method for producing organic EL element >>
As an example of the method for producing the organic EL device of the present invention, a method for producing an organic EL device comprising an anode / hole injection layer / hole transport layer / light emitting layer / hole blocking layer / electron transport layer / cathode will be described.

  First, a desired electrode material, for example, a thin film made of a material for an anode is formed on a suitable support substrate by a method such as vapor deposition or sputtering so as to have a film thickness of 1 μm or less, preferably 10 to 200 nm, thereby producing an anode. To do. Next, an organic compound thin film of a hole injection layer, a hole transport layer, a light emitting layer, a hole blocking layer, and an electron transport layer, which are organic EL element materials, is formed thereon.

  As a method for thinning the organic compound thin film, there are a vapor deposition method and a wet process (spin coating method, casting method, ink jet method, printing method) as described above, but it is easy to obtain a uniform film and a pinhole. From the point of being difficult to form, a vacuum deposition method, a spin coating method, an ink jet method, and a printing method are particularly preferable. Further, different film forming methods may be applied for each layer.

When employing a vapor deposition method for film formation, the vapor deposition conditions vary depending on the type of compound used, but generally a boat heating temperature of 50 to 450 ° C., a degree of vacuum of 10 ⁻⁶ to 10 ⁻² Pa, and a vapor deposition rate of 0.01 to It is desirable to select appropriately within the range of 50 nm / second, substrate temperature −50 to 300 ° C., film thickness 0.1 nm to 5 μm, preferably 5 to 200 nm. After forming these layers, a thin film made of a cathode material is formed thereon by a method such as vapor deposition or sputtering so as to have a film thickness of 1 μm or less, preferably in the range of 50 to 200 nm, and a cathode is provided. Thus, a desired organic EL element can be obtained.

  The organic EL element is preferably produced from the hole injection layer to the cathode consistently by a single evacuation, but may be taken out halfway and subjected to different film forming methods. At that time, it is necessary to consider that the work is performed in a dry inert gas atmosphere. In addition, it is also possible to reverse the production order and produce the cathode, the electron injection layer, the electron transport layer, the light emitting layer, the hole transport layer, the hole injection layer, and the anode in this order. When a DC voltage is applied to the multicolor display device thus obtained, light emission can be observed by applying a voltage of about 2 to 40 V with the positive polarity of the anode and the negative polarity of the cathode. An alternating voltage may be applied. The alternating current waveform to be applied may be arbitrary.

<Pulse drive>
In general, an illumination light source is required to have a characteristic that satisfies a specific region of a Kruithof curve [relationship between illuminance (luminance) and color temperature (chromaticity)] that humans feel instinctively desirable. That is, it is important to set the characteristic that correlates the illuminance and the color temperature such that the color temperature is low in a region where the illuminance is low and the color temperature is high when the illuminance is high.

  The organic electroluminescence element driving method of the present invention is an organic electroluminescence element driving method in which the organic electroluminescence element is driven by a pulse that is intermittently turned ON / OFF, and both the amplitude and width of the pulse are variable. A desired color temperature can be obtained under an arbitrary luminance condition by a driving method characterized by having a control function. In other words, by controlling the amplitude (energization amount) and pulse width (energization time) of the drive pulse, the color temperature can be arbitrarily controlled in a higher direction at each luminance. As a result, dimming according to personal preference Is realized.

  The driving method of the present invention shows the effect of changing the energization amount and the energization time, not the constant energization amount. That is, when the energization amount is increased, the color temperature increases, but the luminance also increases. Therefore, by introducing PWM (Pulse Width Modulation) and shortening the energization time in one pulse, the visual brightness can be felt to be the same. By combining this pulse drive, the higher the brightness, the higher the color temperature, and the more efficient organic EL elements can be adjusted to any Kruifof curve area, providing (Only me) organic EL element illumination according to individual preferences We were able to.

  Hereinafter, the driving method of the organic electroluminescence element of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram showing an example of drive pulse amplitude (energization amount) and pulse width (energization time) patterns in the method for driving an organic electroluminescence element of the present invention.

  FIG. 2 is a diagram showing the relationship between luminance and color temperature.

As shown in FIG. 1, a pulse for driving the organic EL element is to be able to change both the amplitude P _H and its application time P _W to apply an electric field in the forward direction for illuminating an organic EL element. By changing the amplitude P _H of the pulse, the relationship between the luminance and color temperature as shown in Figure 2 to move the actual line. From this state, by changing the pulse width P _W from an arbitrary luminance (color temperature), the luminance can be adjusted, that is, the region below the solid line can be freely controlled without changing the color temperature. If preferred region by Kruithof is above the dashed line, it may be controlled P _H and P _W only in the region sandwiched between the solid line and dotted line.

Since the organic EL element is a carrier injection type device, it is desirable to drive it in the forward direction with a current source. Furthermore, in order to draw out the charge accumulated in the organic layer during the OFF period and to turn it off reliably, it is 0 V or more by the voltage source. it is desirable to apply a reverse bias P _L.

  Further, since the pulse frequency feels as flickering if it is too low, it is desirable that the frequency is 60 Hz or more, preferably 100 Hz or more.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In addition, although the display of "part" or "%" is used in an Example, unless otherwise indicated, "part by mass" or "mass%" is represented.

Example 1
<< Production of Organic EL Element 101 >>
After patterning by depositing ITO (indium tin oxide) at 120 nm as an anode on a 30 mm × 30 mm, 0.4 mm thick glass substrate, the glass substrate having the ITO transparent electrode was ultrasonicated with isopropyl alcohol. Washed, dried with dry nitrogen gas, and UV ozone washed for 5 minutes. The glass substrate having the ITO transparent electrode was fixed to a substrate holder of a commercially available vacuum deposition apparatus. Each of the deposition crucibles in the vacuum deposition apparatus was filled with m-MTDATA, NPD, TPB, DCM, Alq ₃ , and aluminum in amounts optimal for the production of the organic EL element 101. As the evaporation crucible, one made of a resistance heating material made of molybdenum or tungsten was used.

Next, after reducing the pressure to 4 × 10 ⁻⁴ Pa, the energization crucible containing m-MTDATA was energized and heated, and m-MTDATA was deposited at a deposition rate of 0.2 nm / second, and a glass having an ITO transparent electrode Vapor deposition was performed on the ITO electrode side of the substrate to form a 100 nm hole injection layer.

  Subsequently, in the same manner, NPD was deposited on the hole injection layer at a deposition rate of 0.2 nm / second to provide a 100 nm hole transport layer.

  Next, in the same manner, TPB was deposited on the hole transport layer at a deposition rate of 0.2 nm / second to provide an 80 nm blue light emitting layer (light emitting layer 1).

Next, in the same manner, a 20 nm orange light emitting layer (light emitting layer 2) was provided on the blue light emitting layer. That is, DCM was vapor-deposited at 0.01 nm / second, and at the same time, Alq ₃ was vapor-deposited at a vapor deposition rate of 0.2 nm / second, and Alq ₃ was doped with 5% by mass of a fluorescent light-emitting dopant DCM.

Then, Similarly, by depositing Alq ₃ at a deposition rate of 0.2 nm / sec on the orange emission layer, an electron transporting layer of 100 nm.

  Finally, aluminum 110 nm was vapor-deposited to form a cathode, and an organic EL device 101 was produced.

  Next, the vapor deposition surface side formed above is covered with a glass case, and the organic electroluminescence device 101 is sealed with a glove box in a nitrogen atmosphere (in an atmosphere of high-purity nitrogen gas with a purity of 99.999% or more) without contacting the air. I stopped. FIG. 3 shows a cross-sectional view of the organic EL element 101 which is a lighting device. In FIG. 3, 105 is a cathode, 106 is an organic EL layer, 107 is an ITO transparent electrode, and 101 is a glass substrate. The glass cover 102 is filled with nitrogen gas 108 and a water catching agent 109 is provided.

<< Production of Organic EL Elements 102 to 109 >>
In the production of the organic EL element 101, organic EL elements 102 to 109 were produced in the same manner except that the material type and the formed film thickness of the constituent layers were changed as shown in Table 1.

  Note that all of the luminescent compounds used in the organic EL elements 102 to 109 are phosphorescent compounds.

  Moreover, the maximum peak emission wavelength (nm) of each phosphorescence emission type metal complex dopant used for formation of each light emitting layer of the said organic EL elements 101-109 is as follows.

Ir (ppy) ₃ : 520 nm (phosphorescent metal complex dopant B having a maximum peak wavelength at 500 to 540 nm)
Ir (pic) ₃ : 619 nm (phosphorescent metal complex dopant D having a maximum peak wavelength at 580 to 640 nm)
TPB: 460 nm (phosphorescent metal complex dopant A having a maximum peak wavelength at 430 to 480 nm)
Fir (pic): 460 nm (phosphorescent metal complex dopant A having a maximum peak wavelength at 430 to 480 nm)
BDI-5: 475 nm (phosphorescent metal complex dopant A having a maximum peak wavelength at 430 to 480 nm)
BDI-20: 470 nm (phosphorescent metal complex dopant A having a maximum peak wavelength at 430 to 480 nm)
BDI-23: 460 nm (phosphorescent metal complex dopant A having a maximum peak wavelength at 430 to 480 nm)
DCM: 650 nm (phosphorescent metal complex dopant of comparative example)
In addition, the maximum peak light emission wavelength (nm) of the said dopant applied the produced said organic EL element using the spectral radiance meter CS-1000 (made by Konica Minolta Sensing), and made it light-emit at 1000 cd / cm < ² >. It was determined from the emission intensity distribution spectrum obtained occasionally.

<< Evaluation of display element >>
[Evaluation of luminance dependence of color temperature]
When the drive voltage of each organic EL element is changed and the relationship between the luminance and the color temperature shows the proportional relationship shown in FIG. 2, “◯” is shown, and conversely, the case where the inverse relationship is shown is “×”. Judged.

[Measurement of illuminance]
For each organic EL element, the driving voltage is changed with a direct current, the illuminance is monitored using a color illuminance meter CL-200 manufactured by Konica Minolta Sensing Co., Ltd., and the illuminance 10 (lx) is defined as the minimum illuminance. The illuminance when the illuminance stopped increasing and became a constant value was determined as the maximum illuminance.

(Measurement of color temperature)
In the same manner as the above illuminance measurement, the color illuminance meter CL-200 manufactured by Konica Minolta Sensing Co., Ltd. is used, the color temperature at the minimum illuminance (10 (lx)) is set to the minimum value of the color temperature, and the color at the maximum illuminance. The temperature was determined as the maximum color temperature.

[Measurement of drive voltage]
In the above illuminance measurement, the drive voltage required to obtain an illuminance of 10 (lx) is defined as the minimum drive voltage (V), and the drive voltage required to obtain the maximum illuminance is the maximum drive voltage ( V).

[Calculation of variable ease X]
The difference ΔK between the maximum value and the minimum value of the measured color temperature and the difference ΔV between the maximum value and the minimum value of the drive voltage were calculated, and the variable ease X was determined from ΔK / ΔV.

  The results obtained as described above are shown in Table 2.

  As is clear from the results shown in Table 2, since the organic EL element 101 as a comparative example has low luminance and a high driving voltage for causing light emission, ΔK / ΔV has a low value. The organic EL element 102 in which all the light emitting compounds are changed to phosphorescent dopants and the film thickness of the non-light emitting layer is adjusted can lower the minimum color temperature to 2,000 K, and is improved to high luminance and low voltage. , ΔK / ΔV, a high value could be obtained. Hereinafter, it can be seen that the organic EL elements 103 to 108 sequentially changed to the embodiment of the present invention have higher luminance and lower driving voltage, and thus the efficiency is dramatically improved. Therefore, ΔK / ΔV also gradually increases. On the other hand, in the same organic layer configuration as that of the organic EL device 107, the organic EL device 109 having a configuration other than the present invention by exchanging the order of the light emitting layers is greatly improved in efficiency and voltage, but changes according to the luminance. It turned out that the direction of the color temperature to be reversed is not preferable.

  Further, in the organic EL device of the present invention, all the color-developing layers are light emitting layers (light emitting layer 2) formed by using two types of dopants in combination with the organic EL devices 102 and 103 each composed of one type of dopant. It can be seen that the organic EL elements 104 to 108 having () have a lower driving voltage, and thus the efficiency is further improved.

Example 2
Using the organic EL element 107 produced in Example 1, the effect of the pulse driving method of the present invention was evaluated.

The organic EL element 107 is driven according to a conventional method, by setting the variable current source P _H and the pulse width P _W the like, respectively Table 3, it was measured brightness and color temperature at that time. The frequency of the pulse was 100 Hz (repetition cycle = 10 ms). The color temperature and luminance were measured using a color luminance meter CS-200 manufactured by Konica Minolta Sensing.

As is apparent from the results shown in Table 3, by varying the variable current power P _H and the pulse width P _W, it can be seen that it is possible to control the arbitrary luminance and color temperature.

DESCRIPTION OF SYMBOLS 101 Glass substrate 102 Glass cover 105 Cathode 106 Organic electroluminescent layer 107 ITO transparent electrode 108 Nitrogen gas 109 Water catching agent

Claims (8)

An organic electroluminescence device having a control mechanism for controlling light emission of the organic electroluminescence device, wherein all the requirements specified in 1) to 4) below are satisfied.
1) It has a characteristic that the color temperature increases as the luminance increases by controlling the energization amount;
2) The light emitting layer unit is composed of two or more light emitting layers having different emission wavelengths.
3) The light emission wavelength of the light emitting layer on the most anode side is the shortest wavelength, the light emission wavelength of the light emitting layer on the most cathode side is the longest wavelength, and the light emitting layer on the most anode side has the maximum light emission peak wavelength of 430 to 480 nm. The blue phosphorescent light emitting metal complex dopant is contained, and the light emitting layer on the most cathode side contains two or more phosphorescent light emitting dopants having a maximum light emission peak wavelength in the range of 500 to 640 nm, and the blue phosphorescence The luminescent metal complex dopant is a compound represented by the following general formula (BD1);
4) The Δ color temperature / Δ driving voltage of the organic electroluminescence element is 300 K / V or more and 3,000 K / V or less,
[Wherein R ₁ represents a substituent. Z represents a nonmetallic atom group necessary for forming a 5- to 7-membered ring. n1 represents an integer of 0 to 5. B ₁ to B ₅ each represents a carbon atom, a nitrogen atom, an oxygen atom or a sulfur atom, and at least one represents a nitrogen atom. M ₁ represents a group 8 to group 10 metal in the periodic table. X ₁ and X ₂ each represent a carbon atom, a nitrogen atom or an oxygen atom, and L ₁ represents an atomic group which forms a bidentate ligand together with X ₁ and X ₂ . m1 represents 1, 2 or 3, m2 represents 0, 1 or 2, and m1 + m2 is 2 or 3. ] The organic electroluminescent device according to claim 1, wherein all the requirements specified in 5) to 7) below are satisfied.
5) The organic electroluminescence device has at least an anode, a hole transport layer, a light emitting layer unit, an electron transport layer, and a cathode on the substrate.
6) The color temperature of the organic electroluminescence element is in the range of 2,000K to 13,000K.
7) All the light emitting layers contain a phosphorescent metal complex dopant. The light-emitting layer unit composed of two or more layers of the light-emitting layer, the organic electroluminescent device according to claim 1 or claim 2, characterized in that it contains a common light-emitting host compound. The at least 1 layer of the light emitting layer unit comprised from the said 2 or more light emitting layer contains 2 or more types of different phosphorescence-emitting type metal complex dopants, The any one of Claim 1 to 3 characterized by the above-mentioned. The organic electroluminescent element of description. 5. A driving method of an organic electroluminescence element, wherein the organic electroluminescence element according to any one of claims 1 to 4 is driven by a pulse that is intermittently turned ON / OFF, wherein both the amplitude and width of the pulse are variable. A method for driving an organic electroluminescence element, which has a function of controlling. 6. The method for driving an organic electroluminescence element according to claim 5 , wherein the frequency of the driving pulse is 60 Hz or more. Lighting apparatus characterized by having an organic electroluminescent element of any one of claims 1 4. 7. An illuminating device that is driven to emit light by the method for driving an organic electroluminescence element according to claim 5 or 6 .