JP4548034B2 - Organic EL device - Google Patents

Description

  The present invention relates to an organic EL device and an electronic apparatus.

  As a next-generation display device, an organic electroluminescence device (organic EL device) is expected. An organic EL device is configured by disposing an organic EL element having a light emitting layer sandwiched between upper and lower electrodes on a base, typically on a translucent substrate such as glass, an anode, A structure in which an organic functional layer (a hole transport layer, a light emitting layer, an electron transport layer, or the like) and a cathode are sequentially stacked is employed. The light emitting layer of the organic functional layer is caused to emit light by supplying current to the organic functional layer through the anode and the cathode.

  Organic EL devices are mainly classified into a top emission system that extracts light from the cathode side and a bottom emission system that extracts light from the anode side. Among them, in a bottom emission type organic EL device, an anode is generally formed of a transparent conductive material such as ITO, and a cathode is formed of a metal material such as Al. The light from the light emitting layer is reflected by the cathode and emitted from the anode to display an image.

In the bottom emission type organic EL device, when external light is incident from the anode, the external light is reflected by the cathode, so that the display becomes difficult to visually recognize. In order to solve this problem, a technique of arranging a circularly polarizing plate outside the glass substrate in the organic EL device has been proposed (see, for example, Patent Documents 1 to 4). The circularly polarizing plate is configured by sequentially laminating a retardation film and a polarizing film from the anode side. External light incident on this circularly polarizing plate is first converted into linearly polarized light along the transmission axis of the polarizing film, and further converted into circularly polarized light by the retardation film. When the circularly polarized light enters the organic EL element from the anode and is reflected by the cathode, the circularly polarized light is converted into circularly polarized light whose rotation direction is reversed. The circularly polarized light is absorbed by the polarizing film because it is converted into linearly polarized light orthogonal to the transmission axis of the polarizing film when retransmitting the retardation film. In this way, external light is absorbed by the circularly polarizing plate to ensure the visibility of the display of the organic EL device.
Japanese Patent Laid-Open No. 8-322138 Japanese Patent Laid-Open No. 9-127858 Japanese Patent Laid-Open No. 2001-76865 JP 2002-311239 A

  However, at present, there is no ideal circularly polarizing plate that can absorb all visible light. Although an ideal circularly polarizing plate has been developed, there are many problems such as an increase in thickness and unstable characteristics. Therefore, a general circularly polarizing plate is configured to absorb only green light with high human visibility. In this case, there is a problem that a part of blue light and red light is not absorbed, and the display light of the organic EL device becomes bluish or yellowish.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an organic EL device and an electronic device that can realize high-quality display by reducing coloring of display light. To do.

In order to achieve the above object, an organic EL device according to the present invention includes at least a light emitting layer between a pair of electrodes, and reflects light from the light emitting layer at one electrode and emits light from the other electrode. The apparatus is characterized in that the emission chromaticity in white display and the reflection chromaticity of outside light when not lit are in a complementary color relationship.
A general organic EL device is set so as to perform a blue display or a yellowish white display instead of a pure white display. Therefore, if the reflection chromaticity of the outside light when not lit is set to be yellowish or bluish so as to have a complementary relationship with the emission chromaticity in such white display, coloring of the display light is alleviated. And an ideal white display can be realized. Therefore, it is possible to realize a high-quality display with color balance in a normal environment where there is external light.

Also, an organic EL device that includes at least a light emitting layer between a pair of electrodes, reflects light from the light emitting layer at one electrode and emits light from the other electrode,
C light source in the CIE 1931 color system when the light emission chromaticity (XEL, YEL) in white display is XEL> XC and YEL> YC with respect to the white chromaticity (XC, YC) in the CIE 1931 color system The reflection chromaticity (XR, YR) of the 2-degree visual field is characterized by XR <XC and YR <YC.
According to this configuration, when the organic EL device performs yellowish white display, the reflection chromaticity of external light when not lit is set to be bluish. In this case, since both are in a complementary color relationship, an ideal white display can be realized. Therefore, it is possible to realize a high-quality display with color balance in a normal environment where there is external light.

An organic EL device that includes at least a light emitting layer between a pair of electrodes, reflects light from the light emitting layer at one electrode, and emits light from the other electrode, and is a C light source white in the CIE1931 color system When the emission chromaticity (XEL, YEL) in the white display is XEL <XC and YEL <YC , the reflected chromaticity of the C light source 2 ° field of view when the lamp is not lit (XC, YC) XR, YR) is characterized by XR> XC and YR> YC.
According to this configuration, when the organic EL device performs a bluish white display, the reflection chromaticity of external light when not lit is set to be yellowish. Also in this case, since both are in a complementary color relationship, an ideal white display can be realized. Therefore, it is possible to realize a high-quality display with color balance in a normal environment where there is external light.

Further, it is desirable that a circularly polarizing plate that converts incident external light into circularly polarized light is disposed outside the other electrode.
By tuning this circularly polarizing plate, the reflection chromaticity of external light when not lit can be adjusted.

On the other hand, an electronic apparatus according to the present invention includes the above-described organic EL device.
According to this configuration, it is possible to provide an electronic device that can realize high-quality display.

  Embodiments of the present invention will be described below with reference to the drawings. In each drawing referred to below, in order to make the drawing easy to see, dimensions and the like of each component are appropriately changed and displayed.

(First embodiment)
FIG. 1 is a cross-sectional configuration diagram of an organic electroluminescence device (organic EL device) of the present embodiment. As shown in FIG. 1, the organic EL device 100 of the present embodiment is a bottom emission type organic EL device that extracts output light from the organic EL element 110 from the anode 11 side.

(Basic configuration of organic EL device)
The organic EL device 100 has a configuration in which an organic EL element 110 is disposed on the upper surface of a substrate 10. The organic EL element 110 includes an anode 11 made of a transparent conductive film such as ITO (indium tin oxide), a hole transport layer 12, and a light emitting layer 13 on one side (upper surface in FIG. 1) of the glass substrate 10. The electron transport layer 14 and the cathode 21 made of a light reflective metal film such as Al are sequentially laminated. The hole transport layer 12, the light emitting layer 13, and the electron transport layer 14 form an organic functional layer 15 made of an organic functional material. Further, as will be described in detail later, a retardation film 31 and a polarizing film 32 are sequentially laminated on the other surface (the lower surface in FIG. 1) side of the glass substrate 10 to constitute a circularly polarizing plate 30.

The anode 11 is typically made of ITO, but is not limited to this, and a known light-transmitting conductive material can be used.
For the cathode 21, Al (aluminum) having good light reflectivity can be suitably used. In this case, the cathode 21 has a function of reflecting light generated in the light emitting layer 13 to the anode 11 side. In addition to Al, Au (gold), Ag (silver), Cr (chromium), Cu (copper), Ni (nickel), Ca, Mg (magnesium), Sr, Yb (ytterbium), Er (erbium) ), Tb (terbium), Sm (samarium), and the like, and a structure in which a plurality of thin films of metal materials selected from these are stacked.

  As the light-emitting material that can constitute the light-emitting layer 13, known polymer light-emitting materials capable of emitting fluorescence or phosphorescence are polyfluorene derivatives (PF), polyparaphenylene vinylene derivatives (PPV), polyphenylene derivatives ( PP), polyparaphenylene derivative (PPP), polyvinylcarbazole (PVK), polythiophene derivative, polydialkylfluorene (PDAF), polyfluorenebenzothiadiazole (PFBT), polyalkylthiophene (PAT), polymethylphenylsilane (PMPS) Such as polysilanes can be suitably used. In addition, these light-emitting materials include polymer materials such as perylene dyes, coumarin dyes, rhodamine dyes, rubrene, perylene, 9,10-diphenylanthracene, tetraphenylbutadiene, Nile red, coumarin 6, quinacridone, and the like. It is also possible to use a low molecular weight material doped.

The hole transport layer 12 enhances the charge injection efficiency from the anode 11 to the light emitting layer 13 and has a function of blocking electrons moving in the light emitting layer 13. There is an effect of increasing the coupling probability. For the hole transport layer 12, a material having a low injection barrier from the anode 11 and a high hole mobility is preferably used. As such a material, for example, a polythiophene derivative, a polypyrrole derivative or the like, or a doped body thereof is used. Specifically, a dispersion of 3,4-polyethylenedioxythiophene / polystyrene sulfonic acid (PEDOT / PSS) [trade name; Bytron-p: manufactured by Bayer], that is, polystyrene as a dispersion medium A dispersion obtained by dispersing 3,4-polyethylenedioxythiophene in sulfonic acid and further dispersing it in water is used.
If necessary, the efficiency of electron injection from the cathode 21 to the light emitting layer 13 may be increased, and the electron transport layer 14 having a hole blocking function may be formed. The electron transport layer 14 can be formed of an organic material such as an oxadiazole derivative or Alq ₃ .

In the organic EL device 100 of the present embodiment having the above-described configuration, light is applied in the light emitting layer 13 according to the amount of current flowing through the organic functional layer 15 by applying a predetermined voltage between the anode 11 and the cathode 21. appear. The generated light is extracted directly from the anode 11 and the light reflected by the cathode 21 is indirectly extracted from the glass substrate 10 side.
Note that the light emitting layer 13 can emit light of different colors by appropriately selecting the material of the light emitting layer 13. Therefore, the organic EL device 100 of the present embodiment has a configuration in which a plurality of organic EL elements 110 that emit light in any of the three primary colors of RGB are arranged in a matrix.

By the way, when all the RGB three primary colors of the organic EL elements 110 are turned on, the organic EL device 100 performs white display. As a representative example of white light, the International Commission on Illumination (CIE) defines a C light source. This C light source is light having a color temperature of 6740 degrees K and is considered to be close to daylight.
FIG. 3 is a chromaticity diagram of the CIE 1931 color system. In the CIE 1931 color system, the chromaticity (X _C , Y _C ) of the C light source white is C (0.310, 0.316) in FIG.

However, a general organic EL device is set so as to perform a blue display or a yellowish white display instead of a pure white display. Such white display can be performed by adjusting the driving voltage of the organic EL element of RGB primary colors.
FIG. 4 is a spectral spectrum in white display of the organic EL device of the first embodiment. In the organic EL device according to the first embodiment, the emission intensity of red light in the vicinity of a wavelength of 640 nm is strong, and is set to perform a yellowish white display. Note that in the CIE1931 colorimetric system, emission chromaticity _{(X EL, Y EL)} in the white display of the organic EL device of the first embodiment is E1 (0.3540,0.3717) in FIG. _{3, X EL} > X _C and Y _EL > Y _C

(Circularly polarizing plate)
Returning to FIG. 1, a circularly polarizing plate 30 is disposed on the light emitting surface side of the glass substrate 10. The circularly polarizing plate 30 includes a retardation film 31 disposed on the glass substrate 10 side and a polarizing film 32 disposed on the outside thereof. This polarizing film 32 transmits only the linearly polarized light in the transmission axis direction of the external light incident on the organic EL device 100 from the outside of the glass substrate 10 (the lower side in FIG. 1). The polarizing film 32 is provided with a film of polyvinyl alcohol (PVA) or the like on which a iodine complex or the like is adsorbed on the surface of a support substrate made of triacetyl cellulose (TAC) or the like, and the film is stretched in a predetermined direction to increase the PVA height. It is formed by aligning molecules and iodine complexes.

The retardation film 31 has a so-called birefringence in which the refractive index in the fast axis direction is smaller than the refractive index in the slow axis direction. The retardation film 31 is formed by mounting a film such as polycarbonate on the surface of a support substrate made of triacetylcellulose (TAC) or the like, and stretching the film in a predetermined direction to orient the polycarbonate molecules. Specifically, Nitto Denko SEG1425Du can be used as the retardation film 31. The retardation film 31 made of polycarbonate has a relatively large wavelength dispersion of 1.09. Note that chromatic dispersion is represented by a ratio (R450 / R590) between a phase difference (R450) given to transmitted light having a wavelength of 450 nm and a phase difference (R590) given to transmitted light having a wavelength of 590 nm.
In addition to the polycarbonate retardation film, a norbornene retardation film (wavelength dispersion 1.00) or WRF (wavelength dispersion 0.70) manufactured by Teijin Ltd. may be used.

  FIG. 2 is an explanatory view of the arrangement of the polarizing film and the retardation film, and is a bottom view of FIG. As shown in FIG. 2, the slow axis 31 a of the retardation film 31 is arranged to form 45 ° with the transmission axis 32 a of the polarizing film 32. Thereby, the linearly polarized light transmitted through the polarizing film 32 is converted into elliptically polarized light. Further, the thickness of the retardation film 31 is set so that the retardation of the retardation film 31 is about λ / 4, where λ is the wavelength of light incident on the retardation film 31. That is, a so-called λ / 4 plate is employed as the retardation film 31. And the circularly-polarizing plate 30 which converts incident light into circularly polarized light is comprised by the polarizing film 32 mentioned above and the phase difference film 31 which is (lambda) / 4 board. In addition, it is also possible to comprise a circularly polarizing plate by using a retardation film in which a λ / 4 plate and a λ / 2 plate are combined.

  Then, light incident on the organic EL device 100 from the outside of the glass substrate 10 shown in FIG. 1 (lower side in FIG. 1) is converted into linearly polarized light perpendicular to the paper surface by the polarizing film 32, for example. The linearly polarized light is converted into, for example, counterclockwise circularly polarized light by the retardation film 31, passes through the glass substrate 10, and enters the organic EL element 110. When this counterclockwise circularly polarized light is reflected by the cathode 21 which is a metal electrode, the rotational direction is reversed with respect to the traveling direction, and becomes clockwise circularly polarized light. When the clockwise circularly polarized light is transmitted again through the retardation film 31, it is converted into linearly polarized light parallel to the paper surface. This linearly polarized light is absorbed by the polarizing film 32 having a transmission axis perpendicular to the paper surface. Thus, in the organic EL device 100 of this embodiment, even when used in an environment where external light is incident on the panel, the external light reflected by the light-reflective cathode 21 is absorbed by the polarizing film 32, It is designed not to reach the observer.

  However, the external light absorbed by the polarizing film 32 as described above is limited to external light in the vicinity of the wavelength λ where the retardation film 31 functions as a λ / 4 plate. Although it is ideal to employ a retardation film that functions as a λ / 4 plate for all wavelengths of visible light, there is no such retardation film at present. Although an ideal retardation film has been developed, there are many problems such as an increase in thickness and unstable characteristics. Therefore, a general retardation film is set so as to function as a λ / 4 plate for light in the vicinity of green light (λ = about 550 nm) having the highest human visibility. Note that the R590 value of such a retardation film is about 140 nm.

In contrast, the retardation film 31 of the first embodiment employs a film that functions as a λ / 4 plate for light having a longer wavelength than green light. The retardation film has an R590 value of about 160 nm, and can be tuned by adjusting the thickness.
FIG. 5 is a reflection spectrum when the organic EL device of the first embodiment is not lit. The organic EL device of the first embodiment is set so that reflected light having a wavelength of around 650 nm is absorbed by the polarizing film. Conversely, blue light having a wavelength of about 440 nm is set so as to actively pass through the polarizing film. That is, the reflected light when the organic EL device is not lit is bluish. In the CIE 1931 color system, the reflection chromaticity (X _R , Y _R ) of the C light source 2 ° field of view when the organic EL device is not lit is F1 (0.1615, 0.1477) in FIG. That is, X _R <X _C and Y _R <Y _C for the chromaticity (X _C , Y _C ) of the C light source white described above.

  As described in detail above, the organic EL device according to the first embodiment is set to perform yellowish white display. Further, the reflection chromaticity of external light when not lit is set to be bluish. In this case, since both are in a complementary color relationship, the coloring of the display light can be relaxed, and an ideal white display can be realized. Therefore, it is possible to realize a high-quality display with color balance in a normal environment where there is external light.

  In the present embodiment, the bottom emission type organic EL device has been described as an example. However, the present invention can also be applied to a top emission type organic EL device. In the top emission type organic EL device, the anode is made of a metal material such as Al, and the cathode is made of a transparent conductive material such as ITO. The light from the light emitting layer is reflected by the anode and emitted from the cathode. Therefore, a circularly polarizing plate may be disposed outside the sealing substrate that hermetically seals the entire organic EL element, and the circularly polarizing plate may be configured in the same manner as in this embodiment.

(Second Embodiment)
Next, the organic EL device of the second embodiment will be described. The organic EL device according to the second embodiment is set so as to perform a bluish white display, and the reflection chromaticity of external light when not lit is set to be yellowish. The configuration is the reverse of that of the organic EL device of one embodiment. Note that detailed description of portions having the same configuration as in the first embodiment is omitted.

FIG. 6 is a spectral spectrum in white display of the organic EL device of the second embodiment. In the organic EL device of the second embodiment, the emission intensity of blue light near the wavelength of 440 nm is strong, and is set to perform a bluish white display. Note that in the CIE1931 colorimetric system, emission chromaticity _{(X EL, Y EL)} in the white display of the organic EL device of the second embodiment is E2 (0.2432,0.2641) in FIG. _{3, X EL} <X _C and Y _EL <Y _C.

On the other hand, the retardation film of the second embodiment employs a film that functions as a λ / 4 plate for light having a wavelength shorter than that of green light. The retardation film has an R590 value of about 115 nm.
FIG. 7 is a reflection spectrum when the organic EL device of the second embodiment is not lit. The organic EL device of the second embodiment is set so that reflected light having a wavelength of around 490 nm is absorbed by the polarizing film. Conversely, the red light near the wavelength of 640 nm is set so as to actively pass through the polarizing film. That is, the reflected light when the organic EL device is not lit is yellowish. In the CIE 1931 color system, the reflection chromaticity (X _R , Y _R ) of the C light source 2 ° field of view when the organic EL device is not lit is F2 (0.4902, 0.3403) in FIG. That is, X _R > X _C and Y _R > Y _C with respect to the chromaticity (X _C , Y _C ) of the C light source white described above.

  As described above, the organic EL device according to the second embodiment is set to perform a bluish white display. Further, the reflection chromaticity of the external light when not lit is set to be yellowish. Also in this case, since both are in a complementary color relationship, it is possible to alleviate the coloring of the display light, and an ideal white display can be realized. Therefore, it is possible to realize display with high image quality and excellent visibility in a color balance in a normal environment where external light exists.

(Electronics)
FIG. 8 is a perspective configuration diagram illustrating an example of an electronic apparatus including the organic EL device according to each of the embodiments. A cellular phone 1300 shown in the figure includes a plurality of operation buttons 1302, an earpiece 1303, a mouthpiece 1304, and a display unit 1301 including the organic EL device of the previous embodiment. According to the cellular phone 1300, high-quality display can be performed by the organic EL device provided in the display unit.
The electronic apparatus provided with the organic EL device according to the present invention is not limited to the above-mentioned ones. For example, digital cameras, personal computers, televisions, portable televisions, viewfinder type / monitor direct view type video tape recorders. PDAs, portable game machines, pagers, electronic notebooks, calculators, clocks, word processors, workstations, videophones, POS terminals, devices with touch panels, and the like. In addition, examples of the electronic device including the organic EL device according to the present invention include a vehicle-mounted display such as a vehicle-mounted audio device, a vehicle instrument, and a car navigation device.

It is a section lineblock diagram of the organic EL device of a 1st embodiment. It is explanatory drawing of arrangement | positioning of a polarizing film and retardation film. It is a chromaticity diagram of the CIE 1931 color system. It is a spectrum in the white display of the organic EL device of the first embodiment. It is a reflection spectroscopy spectrum at the time of non-lighting of the organic electroluminescent apparatus of 1st Embodiment. It is a spectrum in the white display of the organic EL device of the second embodiment. It is a reflection spectrum when the organic EL device of the second embodiment is not lit. It is a perspective block diagram of the mobile telephone which is an example of an electronic device.

Explanation of symbols

  C ... C light source white chromaticity E1, E2 ... Light emission chromaticity in white display F1, F2 ... Reflection chromaticity of outside light when not lit

Claims (2)

A pair of electrodes;
A light emitting layer disposed between the pair of electrodes;
A circularly polarizing plate,
In the organic EL device that reflects the light from the light emitting layer at one of the electrodes and transmits the light through the other electrode and the circularly polarizing plate,
The circularly polarizing plate is set to function as a λ / 4 plate for light having a wavelength shorter than 550 nm ,
When light emission chromaticity (X _EL , Y _EL ) in white display is X _EL <X _C and Y _EL <Y _C with respect to C light source white chromaticity (X _C , Y _C ) in the CIE 1931 color system the organic EL device, wherein the reflective chromaticity of illuminant C 2 ° field of view in time of non-lighting _(X R, _{Y R)} is _X R> _{X C} and _Y R> _{Y C.} The organic EL device according to claim 1,
The circularly polarizing plate is set such that the reflection chromaticity (X _R , Y _R ) of the C light source 2 ° field of view when not turned on is X _R > X _C and Y _R > Y _C. An organic EL device.

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