JP2006165271A - Surface emitting device and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic LED element which increases the spectral radiation brightness component to compensate the brightness lowered at high view angles in a wavelength band with a high visibility at the high view angles shifted vertically to the emission surface. <P>SOLUTION: The organic LED element 10 composed of a plurality of combined light emitting units 12, 14 having mutually different emission spectra is constituted by increasing the quantity of light in a wavelength band, with a high visibility to raise the brightness at high view angles shifted vertically to the emission surface in an emission angle distribution. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a surface light emitting element configured by combining a plurality of light emitting units having different emission wavelengths and a method for manufacturing the same.

Conventionally, an organic LED element, which is one of surface emitting elements, is configured as shown in FIG. 10, for example.
That is, in FIG. 10, the organic LED element 1 is formed by sequentially laminating an organic layer 3 composed of a hole transport layer 3a, a light emitting layer 3b, and an electron transport layer 3c on a so-called ITO substrate 2 having an ITO film 2a formed on the surface thereof. Finally, the cathode 4 made of a metal such as Al or a transparent electrode is formed as a counter electrode.
According to the organic LED element 1 having such a configuration, as shown in FIG. 11, the light L is emitted from the light emitting layer 3 b of the organic layer 3 by applying a driving voltage between the ITO film 2 a (anode) and the cathode 4. The light is emitted, passes through the ITO substrate 2, and is emitted downward in FIGS.

By the way, in the organic LED element 1 of such a structure, the material which comprises the single light emitting layer which emits white light has not been found yet. For this reason, when white light is obtained, a light emitting layer that emits a plurality of light emission colors, for example, two light emission colors having a complementary color relationship (blue and yellow, etc.) and general three primary colors of light (red, green and blue) By combining these, white light is emitted.
For example, when white light is obtained from one organic LED element by combining blue light and yellow light, one or two or more organic materials (for example, fluorescent materials or phosphorescent materials) that emit blue light and yellow light, respectively, are included. Light emitting layers are stacked, and white light emission is obtained by controlling the light emission intensity of each light emitting layer by adjusting the film thickness, the doping concentration of impurities, and the like.

On the other hand, Patent Document 1 discloses a so-called MPE (Multi Photon Emission) element in which a plurality of organic LED elements having the above-described configuration are stacked in the vertical direction on one ITO substrate.
For example, as shown in FIG. 12, the MPE element 5 is constructed by laminating two organic layers (light emitting units) 3 in the vertical direction on an ITO substrate 2 via an equipotential surface forming layer 6. Has been.
Here, the equipotential surface forming layer 6 is also called, for example, a charge generation layer or a CGL (Charge Generation Layer) layer.

According to the MPE element 5 having such a configuration, similarly, by applying a driving voltage between the ITO film 2a (anode) and the cathode 4, light is emitted from each of the two light emitting layers 3b, for example, blue light is emitted from the lower light emitting layer 3b. The light L1 is emitted from the upper light emitting layer 3b and the yellow light L2 is emitted through the ITO substrate 2 downward in FIG. 10 and mixed with each other. The light is emitted.
In such an MPE element 5, white light can be obtained by providing two or more light emitting layers in one light emitting unit.

Further, from Patent Document 2, the optical length is obtained from the product of the thickness and refractive index of each organic layer 3 and ITO film 2a of the organic LED element 1 or MPE element 5, and from the relationship between the optical length and the emission wavelength, the optical length is calculated. It is known that a light interference spectrum shape, light emission intensity, and light emission distribution change due to an optical interference effect.
JP 2003-272860 A JP 07-240277 A

  By the way, since the organic LED element 1 or the MPE element 5 described above generally has a so-called Lambertian emission distribution, the organic LED element 1 emits light L downward from the ceiling. When incorporated in a lighting fixture, the light emission intensity does not change even in a so-called high viewing angle direction that is shifted obliquely from the front, that is, from a direction perpendicular to the element light emitting surface in the radiation angle distribution. However, when an attempt is made to increase the light emission luminance in the direction perpendicular to the element light emission surface (directly below the lighting fixture from the ceiling direction) by controlling the film thickness, for example, the light emission distribution in the oblique direction becomes small. On the other hand, when the emission intensity in the oblique direction is increased, the emission intensity in the vertical direction is reduced, so that, for example, the luminance directly below the illumination device (illuminance from the observer) is reduced.

  In view of the above, the present invention provides an organic LED element with increased brightness by increasing the spectral radiance component in the wavelength band with high visibility on the high viewing angle side shifted from the direction perpendicular to the light emitting surface. It is an object. Moreover, it aims at providing the lighting fixture and backlight which used the said organic LED.

The object of the present invention is to provide a spectral radiance component in a wavelength band with high visibility in a surface-emitting device configured by combining a plurality of light-emitting layers or light-emitting units having emission wavelengths different from each other according to the configuration of the present invention. By providing a surface light emitting device characterized in that the amount of the component in a direction deviated by a certain angle from the direction perpendicular to the light emitting surface is higher than the amount of the component in the direction perpendicular to the light emitting surface in the radiation angle distribution. Achieved.
In the present invention, a wavelength band with high visibility is a wavelength band (510 to 610 nm) having a relative visibility of 0.5 or more in photopic vision. The high viewing angle side is assumed to be an angle side of 40 degrees to 80 degrees from the direction perpendicular to the light emitting surface, but the distance between the illumination device and the observer, or the distance between each illumination device when a plurality of illumination devices are used. For example, it is set according to the use and arrangement of the lighting device.

  The surface light emitting device of the present invention is preferably an organic LED device in which the light emitting layer or the light emitting unit is composed of an organic layer.

The surface light-emitting device of the present invention is preferably an MPE device in which the light-emitting units are stacked on each other via an equipotential surface forming layer.

According to the said structure, when a drive voltage is applied to each light emitting layer or the organic layer of a light emitting unit, light is each radiate | emitted from a light emitting layer among organic layers, and it is irradiated outside by being mixed with each other.
Then, among each light emitting layer or light emitting unit, the spectral radiance component from the light emitting unit that emits light in a wavelength band with high visual sensitivity (for example, a wavelength range of 510 to 610 nm having a specific visual sensitivity of 0.5 or more) is increased. Thus, the luminance on the high viewing angle side deviated from the direction perpendicular to the light emitting surface is enhanced in the radiation angle distribution of the light irradiated to the outside. In other words, in an organic LED element configured by combining a plurality of light emitting units having different emission spectra, by controlling the radiation angle distribution in the wavelength band with high visibility, the high viewing angle side shifted from the direction perpendicular to the light emitting surface Thus, by increasing the spectral radiance component of the wavelength band with high visibility, an organic LED element with improved luminance on the high viewing angle side can be obtained.

Therefore, when this organic LED element is incorporated in, for example, a lighting device provided on the ceiling, the luminance from the lighting device located in front of the high viewing angle side is increased, and the visibility is improved.
In this case, the light radiated to the high viewing angle side is felt bright because the ratio of the spectral radiance component in the wavelength band with high visibility is increased, and a brighter field of view is provided to an observer in front. Will be obtained.
In addition, since the light irradiated in a direction substantially perpendicular to the light emitting surface, that is, directly under the lighting fixture, is a normal emission spectrum component as in the conventional case, it can be observed as in the conventional case, and the emission color is There will be no problems.

  Increasing the spectral radiance component in the wavelength band with high visibility can be achieved by adjusting the shape of the emission spectrum using the optical interference effect of light from each light emitting layer or light emitting unit. . The shape of the emission spectrum can be changed by adjusting various optical distances. The optical distance here is an actual film thickness × refractive index, and in the case of a plurality of layers, it is a distance obtained by adding the actual film thickness × refractive index for each thin film layer. In the case of an organic material, since the refractive index does not change greatly, it is preferable to adjust the optical distance depending on the film thickness. The refractive index of the organic material can be determined by measurement with an ellipsometer or the like, and is generally about 1.7 to 2.0.

  Also, by controlling the emission angle distribution for each emission spectrum component of each light emitting layer or light emitting unit, a large emission spectrum including wavelengths with high visibility is distributed on the high viewing angle side, so that wavelengths with high visibility are obtained. The spectral radiance component of the band can be increased. Radiation angle distribution can be controlled by adjusting the film thickness and refractive index of the ITO film, which is a transparent conductive film, for example, and a large emission spectrum including wavelengths with high visibility is distributed on the high viewing angle side. Thus, the amount of light in the wavelength band with high visibility can be increased.

  When each light emitting layer or light emitting unit is composed of an organic layer, a plurality of organic light emitting layers are formed in the organic layer of one organic LED element, or at least one organic light emitting layer is provided. An organic LED element can be comprised by laminating | stacking the several light emission unit containing in a perpendicular direction.

  When each of the above light emitting units is an MPE element laminated with each other through an equipotential surface forming layer (or charge generation layer or CGL layer), the light emitting units having different emission spectra are the equipotential surface forming layers. By laminating each other via (or a charge generation layer or CGL layer), it can be configured as an MPE element.

  Thus, according to the present invention, in an organic LED element configured by combining a plurality of conventionally known light emitting units, by increasing the spectral radiance component in the wavelength band with high visibility, in the radiation angle distribution Since the luminance on the high viewing angle side deviated from the direction perpendicular to the light emitting surface is enhanced, the visibility on the high viewing angle side is improved, and an organic LED element optimal for a lighting fixture can be obtained. In particular, even if the emission angle distribution is set so that the emission intensity is increased in the direction perpendicular to the emission surface to increase the emission brightness directly under the lighting fixture, the wavelength band with high visibility is achieved even if the emission intensity on the high viewing angle side decreases. As a result of the increase in the spectral radiance component, it is possible to compensate for a decrease in luminance on the high viewing angle side.

  That is, for example, it is possible to obtain a surface light emitting element with improved apparent luminance in which white light is emitted in a direction substantially perpendicular to the light emitting surface and green light is emitted at an oblique angle to the light emitting surface. In addition, when the light emission distribution is actively controlled and white light is condensed in a direction substantially perpendicular to the light emitting surface, the amount of light on the high viewing angle side is reduced. By doing so, it can be reduced.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to FIGS. In the present embodiment, an organic LED is described as an example as follows, but the present invention may be an inorganic EL element that is common in that it has a thin film laminated structure between both electrodes.
The embodiments described below are preferable specific examples of the present invention, and thus various technically preferable limitations are given. However, the scope of the present invention particularly limits the present invention in the following description. As long as there is no description of the effect, it is not restricted to these aspects.

FIG. 1 shows a configuration of a first embodiment of an organic LED element according to the present invention.
In FIG. 1, an organic LED element 10 has the same configuration as the conventional MPE element shown in FIG. 12, and a hole transport layer, a light emitting layer, and a light emitting layer are sequentially formed on a so-called ITO substrate 11 on which an ITO film 11a is formed. After the first organic layer 12 composed of the electron transport layer, the CGL layer 13 and the second organic layer 14 having the same configuration are stacked, the cathode 15 is finally formed as a counter electrode. ing.
Thus, the organic LED element 10 includes two light emitting units each including the first organic layer 12 and the second organic layer 14.

  The ITO substrate 11 is configured by forming an ITO film 11a on the surface of a flat glass substrate. The ITO film had a thickness of 2100 mm.

The first organic layer 12 has a known configuration and is configured to emit blue light L1. The first organic layer 12 had a thickness of 2700 mm composed of a hole injection layer (1800 mm) / hole transport layer (200 mm) / blue light emitting layer (400 mm) / electron transport layer (300 mm).
The blue light L1 from the first organic layer 12 has an emission spectrum as shown in FIG.
In this case, the peak wavelengths of the emission spectrum are 471 nm and 502 nm, and the peak intensity on the short wavelength (471 nm) side is maximum.

  On the first organic layer 12, 300 CGL of the CGL layer 13 was deposited. The CGL layer 13 has a known configuration and forms an equipotential surface.

Similarly, the second organic layer 14 has a known configuration and is configured to emit yellow light L2. As the second organic layer 14, a hole injection layer (700 （) / hole transport layer (200 層) / yellow light emitting layer (300Å) / electron transport layer (200Å) is deposited, and the first organic layer 12 and the CGL layer are combined. The film thickness was 4400 mm.
The yellow light L2 from the second organic layer 14 has an emission spectrum as shown in FIG.

Accordingly, when the blue light L1 and the yellow light L2 from the first organic layer 12 and the second organic layer 14 are mixed with each other, white light L having an emission spectrum as shown in FIG. 4 is obtained. Become.
Here, the white light is represented by CIE chromaticity coordinates (0.336, 0, 334).
2 to 4 are all measured in the front direction (normal direction) with respect to the light emitting surface, that is, the lower surface of the ITO substrate 11, and the vertical axis indicates the spectral radiance. The value (W / m 2 · sr) normalized by the peak intensity value, and the horizontal axis is the wavelength [nm].

  The cathode 15 is composed of a thin film of metal such as Al.

The above configuration is substantially the same as the conventional MPE element 5, but the organic LED element 10 according to the present invention is different in the following points.
That is, the viewing angle of the emission spectrum of the blue light L1 by the organic layer 12 is adjusted by appropriately adjusting the film thicknesses of the organic layers 12 and 14 and the ITO film 11a of each light emitting unit using a method described later. Dependency is controlled.
Thereby, the emission spectrum of the blue light L1 by the organic layer 12 at a viewing angle of 60 degrees from the normal direction of the ITO substrate 11 is different from that in FIG. 2 and, as shown in FIG. The peak intensity on the (471 nm) side decreases and the peak intensity on the long wavelength (502 nm) side increases to give a maximum value.

  The emission spectrum (60-degree direction) of the mixed light L of the blue light L1 and the yellow light L2 from the second organic layer 14 at the viewing angle of 60 degrees changes as shown in FIG. It is represented by a degree coordinate (0.318, 0.408), and is a color of a region called (greenish) white in JIS (Z8102).

Compared with the emission spectrum in the front direction shown in FIG. 4, the intensity of the spectral radiance component in the wavelength band with high visibility increases as the intensity of the short wavelength side of the blue component decreases. This will improve the relative luminance. In the spectrum diagram 4 in the normal direction of the substrate and the spectrum diagram 6 at 60 degrees, the increase in luminance was obtained and shown in Table 1.
Evaluation of the luminance increase at a certain viewing angle (for example, 60 degrees from the normal direction) was performed according to the following procedure. First, the spectral radiance spectrum of the normal direction was measured with respect to the organic LED element. Next, the measured spectral radiance spectrum was normalized with the value at the maximum peak intensity to obtain an emission spectrum. In this embodiment, the spectrum in the normal direction shown in FIG. 4 corresponds to this. Based on the standard relative luminous sensitivity curve in photopic vision shown in FIG. 13, the region corresponding to a specific visual sensitivity of 0.5 or higher (510 nm to 610 nm) to the region corresponding to 0.8 or higher (526 nm to 586 nm), “Emission spectrum intensity × specific luminous sensitivity” was calculated for each wavelength and integrated over the corresponding wavelength region (corresponding to the calculated value of FIG. 4 shown in Table 1). In this example, the calculation was performed using the emission spectrum intensity at 1 nm intervals and the value of specific luminous efficiency.
Next, the spectral radiance spectrum was measured at an angle of 60 degrees from the normal direction of the organic LED element, the same operation as described above was performed, and “emission spectrum intensity × specific luminous sensitivity” in the wavelength region was calculated (Table 1). (Corresponding to the calculated value of FIG. 6). Using these values, the increase in the intensity of the spectral radiance component was calculated and evaluated by the calculation formula for obtaining the “increase (%)” shown in Equation 1. As a result, it was confirmed that the luminance increased in the wavelength range from 510 nm to 610 nm, which corresponds to a specific visual sensitivity of 0.5 or more.

The organic LED element 10 according to the embodiment of the present invention is configured as described above and is manufactured in the same manner as a conventional MPE element, and the film thickness is adjusted when the ITO film 11a and the organic layer 12 are formed. Or by adjusting the refractive index of the ITO film 11a.
For this reason, it is possible to manufacture using the conventional manufacturing apparatus of the organic LED element 10 as it is, and an additional capital investment etc. are unnecessary.
For example, the film thickness configuration of the surface light emitting element is designed to satisfy the following optical distances for the front direction and the desired angular direction, respectively. As a general rule, the optical distance from each light emitting region to the cathode interface serving as a mirror and the glass / ITO interface having a large refractive index difference (n = 1.52 for general glass and about 1.8 for ITO) The direction and the desired angular direction are set so that light of a desired wavelength in each direction is strengthened by the optical interference effect.
Here, in an arbitrary optical system, light having a wavelength λ (nm) is generally generated from a light emitting region, and the optical distance to the interface due to a substance whose phase is inverted by reflection is an odd multiple of 1/4 × λ. By setting the optical distance to the interface by a substance whose phase does not invert due to reflection to an even multiple of 1/4 × λ, the light emission intensity can be increased by the optical interference effect.
Reflection between the glass / ITO interface having a large refractive index difference and the metal cathode as a mirror is mainly inside a general organic LED element, but reflection is also caused by an organic layer interface made of an organic material having a different refractive index. The element design that takes into account the optical interference effect is complicated due to the occurrence and the existence of the emission intensity distribution in the light emitting layer inherent to the element configuration.
Therefore, in the first embodiment, the optical distances from the light emitting region to the metal cathode interface and the glass / ITO interface in each light emitting unit are set to the above-described conditions for increasing the light emission intensity (odd multiples of 1/4 × λ, And an even multiple of 1/4 × λ) was set as the first standard for adjusting the film thickness of the organic material layer and the like. In the embodiment, the wavelength λ (nm) was examined using the peak wavelength of the emission spectrum of each emission color. In addition, the position where the light emission intensity is assumed to be maximum in the light emitting region was used as the position of the light emitting region to calculate the optical distance.
Furthermore, in the first embodiment, after obtaining the optical distance conditions for strengthening each of the blue wavelength and the yellow wavelength, it is necessary to select a condition for combining both to become white, and the viewing angle near 60 degrees is green. Adjustments were made because it was necessary to select the white color conditions, and because the currents flowed at the same current density in the units of each luminescent color, it was necessary to consider the difference in luminous efficiency of each luminescent material. The adjustment is performed by the film thickness and refractive index from the light emitting region to the ITO side, the film thickness and refractive index from the light emitting region to the metal surface side, the ITO film thickness and refractive index, the reflectance of the metal surface, etc. In some cases, the refractive index did not change greatly, and therefore this was mainly done by the thickness of the organic layer.
Accordingly, since the optical distance can be adjusted from the viewpoint of the number of units and color adjustment, the optical distance is not strictly an integral multiple of 1/4 × λ.
In the first embodiment, the optical film thickness is estimated by a simple simulation using the above parameters, and is obtained by finely adjusting the film thickness in device fabrication. In the normal direction, the blue optical distance is obtained. Is 6.7 / 4 × λ on the glass / ITO interface side, 3.4 / 4 × λ on the metal cathode side, and the yellow optical distance is 7.7 / 4 × λ on the glass / ITO interface side, on the metal cathode side It was 0.5 / 4 × λ.

According to the organic LED element 10 having such a configuration, when a driving voltage is applied between the ITO film 11a and the cathode 15, the organic layers 12 and 14 emit light, and blue light L1 and yellow light L2 are emitted. To do.
Then, the blue light L1 and the yellow light L2 travel downward and are emitted downward from the lower surface of the ITO substrate 11, and the blue light L1 and the yellow light L2 are mixed with each other to produce white light. It becomes L and it will irradiate downward.
At this time, the white light L having the emission spectrum shown in FIG. 4 is irradiated on the lower surface of the ITO substrate 11 in the normal direction as in the conventional case, and a bright field of view is obtained.

On the other hand, with respect to the direction of the high viewing angle side (for example, 60 degrees) with respect to the lower surface of the ITO substrate 11, as described above, the luminance of the blue light L1 is improved by the deformation of the emission spectrum, that is, the peak shape adjustment. Since the intensity of the high wavelength band, that is, the green component is increased, the white light L becomes greenish as a whole, and the luminance of the irradiation light is increased.
Further, with respect to the spectral radiance component amount in the wavelength band where the relative visibility in photopic vision is 0.5 or more, the component amount in the direction perpendicular to the light emitting surface in the radiation angle distribution is more than a certain angle from the direction perpendicular to the light emitting surface. By increasing the component amount in the shifted direction by 10% or more and increasing the luminance in a direction shifted by a certain angle from the direction perpendicular to the light emitting surface by 10% or more, it is possible to provide a lighting device with high visibility for the observer. .
Thus, according to the organic LED element 10 according to the embodiment of the present invention, by appropriately adjusting the film thickness of the ITO film 11a and the organic layers 12 and 14, or by appropriately adjusting the refractive index of the ITO film 11a. By changing the emission spectrum from the organic layer 12 and increasing the intensity of the wavelength band with high visibility on the high viewing angle side shifted from the normal direction of the ITO substrate 11, the luminance in the normal direction remains unchanged. While being held, the luminance on the high viewing angle side of the irradiation light is improved, and irradiation light with high visibility can be obtained.

FIG. 8 shows a radiation angle distribution of luminance of the organic LED element.
That is, FIG. 8 shows the brightness of the white light emitted from the organic LED element 20 from 0 degrees to 80 degrees with the front (normal direction) of the ITO substrate 11 being 0 degrees, and from 0 degrees to − The characteristic curve indicated by the symbol W is drawn up to 80 degrees as being symmetrical with respect to the normal line.

Here, when the emission spectrum of the white light is analytically color-separated and divided into a blue component and a yellow component, the blue component is indicated by a symbol B in FIG. It came to show with the code | symbol Y. Here, the blue component means a light emitting component derived from a blue light emitting material, and the yellow component means a light emitting component derived from a yellow light emitting material. The emission spectrum emitted from the element is peak-separated into two components, a blue component and a yellow component. From the PL spectrum of the blue component shown in FIG. 2, the skirt portion of the long-wavelength side portion is cut out, and then the skirt portion is fitted in the 60-degree emission spectrum to extract the blue component. The yellow component was determined by subtracting the blue component from the emission spectrum at 60 degrees.
The blue component indicated by symbol B shows a radiation angle distribution that is the strongest at a high viewing angle near 50 degrees, and the spectrum changes depending on the viewing angle. Seems to be higher.
On the other hand, the yellow component indicated by the symbol Y has a radiation angle distribution that is substantially similar to the so-called Lambasian emission distribution (represented by I = Io · cos θ) indicated by the symbol D in FIG. The brightness is slightly decreased from 80 degrees to 80 degrees.
And the radiation angle distribution of the white light shown with the code | symbol W is the brightness | luminance which exceeds the said Lambasian light emission distribution at 40 to 80 degree | times.
Therefore, in the present organic LED element 20, the emission angle distribution of the blue component having a spectrum in the wavelength range of 510 nm to 610 nm with high visibility is enhanced at a high viewing angle near 50 degrees to obtain greenish white light. It can be seen that the luminance is improved on the high viewing angle side as compared with the organic LED element having a conventional Lambtian emission distribution. This suggests that the intensity on the high viewing angle side can be increased by controlling the radiation angle distribution for each light emitting unit, that is, each organic layer 12 and 14.
In addition, in the viewing angle of 0 degree to 40 degrees, the luminance of the present organic LED element 20 is slightly lower than that in the case of the Lambertian emission distribution.

In this manner, in the organic LED elements 10 and 20 according to the present invention, the luminance is controlled by controlling the emission spectrum and the emission angle distribution with respect to light (blue light) having a high visibility at a high viewing angle. Since the height is increased, the irradiation light becomes brighter on the high viewing angle side shifted from the normal direction of the substrate.
Therefore, when the present organic LED elements 10 and 20 are incorporated into a lighting fixture, for example, as shown in FIG. 9, light with a high viewing angle from the lighting fixture 30 positioned obliquely with respect to the eyes of the observer P is Since the intensity is increased in the wavelength band with high visibility, the viewer P feels brighter. For example, when a lighting fixture is placed at a position 1.5 m higher than the eye level, light at 40 ° from the normal direction of the fixture is about 1.3 m forward, and light at 80 ° is from 8.5 m forward. The light emitted directly enters the eye.
Moreover, since the irradiation light from the lighting fixture 31 immediately above is white light similarly to the irradiation light from the conventional organic LED element, when the observer P observes an object or the like illuminated by the irradiation light, It is possible to correctly determine the color, and there is no problem in color.

FIG. 7 shows a configuration of a second embodiment of the organic LED element according to the present invention.
In FIG. 7, the organic LED element 20 has substantially the same configuration as the organic LED element 10 shown in FIG. 1, and thus the same components are denoted by the same reference numerals and description thereof is omitted.
As a second embodiment, an organic LED element provided with two light emitting units was produced as in the first embodiment. The film thickness of ITO and the film thickness of an organic layer differ from said 1st embodiment.
First light emission having a blue light emitting layer with a short emission wavelength on the first light emitting unit side having a long optical distance from the light emitting portion position to the metal reflecting surface by the cathode, that is, on the ITO glass substrate (ITO thickness 1800 mm) serving as the anode. The unit was vapor-deposited, and then a second light emitting unit having a yellow light emitting layer was laminated.
The first light emitting unit had a thickness of 1400 mm comprising a hole injection layer (600 mm) / hole transport layer (200 mm) / blue light emitting layer (300 mm) / electron transport layer (300 mm). After depositing a 300 Å CGL layer on the first light emitting unit, a hole injection layer (500 Å) / hole transport layer (200 Å) / yellow luminescent layer (300 Å) / electron transport layer (200 Å) is deposited as the second luminescent unit. And it combined with the 1st light emission unit and the CGL layer, it was set as the film thickness of 2900 mm, and the cathode which consists of metal was vapor-deposited finally. In the normal direction, the blue optical distance is 4.2 / 4 × λ on the glass / ITO interface side, the metal cathode side is 3.1 / 4 × λ, and the yellow optical distance is 5.5 × on the glass / ITO interface side. The ratio was 4/4 × λ and 0.5 / 4 × λ on the metal cathode side.
FIG. 14 shows an emission spectrum (solid line) in the normal direction of the manufactured element and an emission spectrum (broken line) observed at an angle of 60 degrees from the normal direction.
White light from the emission spectrum in the normal direction of the fabricated element is CIE chromaticity coordinates (0.318, 0.338), and in the emission spectrum observed at an angle of 60 degrees from the normal direction, CIE chromaticity coordinates ( 0.305, 0.378).
When the emission spectra of the two were compared, it was found that in the spectrum at a high viewing angle (60 degrees), the spectral component increased in the wavelength region of 480 to 570 nm as compared with the spectrum in the normal direction. Further, when the amount of increase in the spectral radiance component in the region corresponding to the specific luminous sensitivity of 0.5 or more (510 nm to 610 nm) was determined, it was + 17%.

As described above, the spectral radiance component amount in the wavelength region with high visibility is higher than that in the normal direction in both configurations of the first embodiment and the second embodiment having different organic layer thicknesses and emission spectrum shapes. An element having the same effect can be manufactured in that it is large in the direction of the high viewing angle (60 degrees), white is visible from the normal direction, and greenish white is visible from the direction of the high viewing angle.
Further, in these MPE elements, it is preferable to arrange the light emission color unit on the short wavelength side, in which the spectral waveform and the light emission intensity can be easily adjusted by the optical interference effect, as the light emission unit on the side far from the electrode having a high reflectance. Since the refractive index of the material used, such as glass, ITO, and organic materials, has a property of being high on the short wavelength side, the optical distance for short wavelengths is longer than the optical distance for long wavelengths even if the physical film thickness is the same. It is. Further, the longer the optical distance, the more the integral multiple of 1/4 × λ, that is, the points of strengthening and weakening, so that the degree of freedom that can be selected for adjustment to the desired emission spectrum increases.

  In the embodiment described above, the organic LED elements 10 and 20 include the CGL layer 13 between the organic layers 12 and 14, respectively. However, the present invention is not limited to this, and other configurations, etc. may be used instead of the CGL layer 13. It is obvious that a potential forming layer may be provided. Moreover, in embodiment mentioned above, although the organic LED elements 10 and 20 are each comprised as what is called a MPE element, it is not restricted to this, The organic LED element by which the several light emitting layer was formed in one organic layer Obviously it may be. An ITO film is taken as an example of the anode, but a transparent conductive film such as an IZO film or a ZnO film can also be used.

  Further, in the above-described embodiment, the mixed color light of the blue light and the yellow light from the organic layers 12 and 14 as the two light emitting units is irradiated to the outside. It is obvious that the organic LED element may be provided with three light-emitting units, for example, white light mixed with red light, blue light and green light which are the three primary colors of light. is there.

  In this way, according to the present invention, in the emission angle distribution of the emission luminance in the wavelength band with high visibility, the highest luminance is provided on the high viewing angle side shifted from the direction perpendicular to the light emitting surface, which is extremely excellent. Organic LED elements can be provided. Moreover, the lighting fixture using the said organic LED element and a backlight can also be provided.

It is a schematic sectional drawing which shows the structure of 1st embodiment of the organic LED element by this invention. It is a graph which shows the emission spectrum of the blue light radiate | emitted in the normal line direction from the 1st organic layer in the organic LED element of FIG. It is a graph which shows the emission spectrum of the yellow light radiate | emitted in the normal line direction from the 2nd organic layer in the organic LED element of FIG. It is a graph which shows the emission spectrum of the white light radiate | emitted in the normal line direction from the organic LED element of FIG. It is a graph which shows the emission spectrum of the blue light radiate | emitted with a high viewing angle (60 degree | times) from the 1st organic layer in the organic LED element of FIG. It is a graph which shows the emission spectrum of the white light radiate | emitted with a high viewing angle (60 degree | times) from the 1st organic layer in the organic LED element of FIG. It is a schematic sectional drawing which shows the structure of 2nd embodiment of the organic LED element by this invention. It is a graph which shows the radiation angle characteristic of the emitted light in the organic LED element of FIG. It is the schematic which shows the usage example of the lighting fixture incorporating the organic LED element by FIG. 1 or FIG. It is a schematic sectional drawing which shows the detailed structural example of the conventional organic LED element. It is the schematic sectional drawing which simplified the organic LED element of FIG. It is a schematic sectional drawing which shows the structural example of the conventional MPE element. It is a relative visibility curve in photopic vision. It is a graph which shows the emission spectrum of the white light radiate | emitted at 60 degree | times from the normal line direction and normal line direction of the organic LED element of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10, 20 Organic LED element 11 ITO board | substrate 11a ITO film | membrane 12 1st organic layer 13 CGL layer 14 2nd organic layer 30 Lighting fixture (diagonal front)
31 Lighting equipment (directly above)

Claims (4)

  In a surface light-emitting device configured by combining a plurality of light-emitting layers or light-emitting units having emission spectra having different emission wavelengths, the spectral radiance component amount in the wavelength band with high visibility is perpendicular to the light-emitting surface in the radiation angle distribution. A surface light emitting device characterized in that the component amount in a direction shifted by a certain angle from the direction perpendicular to the light emitting surface is higher than the component amount in the direction.   The surface light-emitting element according to claim 1, wherein the wavelength band having high visibility is 510 nm to 610 nm.   The surface emitting element according to claim 1, wherein the light emitting layer or the light emitting unit is composed of an organic layer. The surface light emitting device according to any one of claims 1 to 3, wherein the light emitting units are MPE devices stacked on each other via an equipotential surface forming layer.

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