JP2013175485A - Organic el element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an organic EL element capable of improving half width and color purity of each emission spectrum considering an emission spectrum distribution of light of three colors emitted at each light-emitting layer.SOLUTION: The organic EL element comprises: a substrate 10a; a positive electrode 12 disposed on the substrate 10a; a three kinds of light-emitting layers 15a to 15c disposed on the positive electrode and emitting light of three colors of red, green, and blue; negative electrodes 18a to 18c disposed respectively on the light-emitting layers 15a to 15c; and characteristic improvement films 11a to 11c disposed respectively on the negative electrodes 18a to 18c, which absorb light in wavelength regions of light of the three colors.

Description

  The present invention relates to an organic EL element having at least three types of light emitting layers each emitting red, green, and blue light, an anode, and a cathode.

  Conventionally, in an organic EL element for realizing an organic EL (organic electroluminescence) display or the like, the element structure shown in FIG. 13 or FIG. 14 is used.

  The organic EL element shown in FIG. 13 or FIG. 14 is divided into three light-emitting regions in order to emit light of three colors of red (R), green (G), and blue (B) (three-color light emission). method).

  Note that the organic EL element having the element structure shown in FIG. 13 is configured such that light of three colors (R, G, B) emitted from the light emitting layers 15a to 15c is extracted from the substrate 10 side.

  On the other hand, the organic EL element having the element structure shown in FIG. 14 is configured such that light of three colors (R, G, B) emitted from the light emitting layers 15a to 15c is extracted from the cathodes 18a to 18c side. Yes (top emission structure).

  In general, in the organic EL element, in order to improve the efficiency of extracting the light emitted from the light emitting layers 15a to 15c to the outside, the structure on the side to extract the light emitted from each of the light emitting layers 15a to 15c (extraction side structure) A material having such a characteristic that the light is not absorbed as much as possible is used.

  For example, the red (R) light extraction side structure in the organic EL element shown in FIG. 13 is formed by the hole transport layer 14 a, the hole injection layer 13 a, the anode 12 a, and the substrate 10.

  FIG. 15 shows an example of an emission spectrum distribution of light of three colors (R, G, B) emitted from the light emitting layers 15a to 15c. In the example of FIG. 15, the emission spectrum distribution of blue (B) light is indicated by a solid line, the emission spectrum distribution of green (G) light is indicated by a broken line, and the emission spectrum distribution of red (R) light is indicated by a one-dot chain line. Show.

  In such an organic EL element, as shown in FIG. 15, the emission spectrum distribution of blue (B) light extends not only to the blue region but also to the green region, and the emission spectrum distribution of green (G) light is green. Since the emission spectrum distribution of red (R) light extends not only to the red region but also to the green region, the mixed color of blue and green, and green and red Color mixing occurs.

Japanese Patent Laid-Open No. 6-092466 JP-A-11-329742

  However, in the conventional organic EL element, as described above, the full width at half maximum of the emission spectrum of the light of three colors (R, G, B) is wide, and the base of each emission spectrum distribution straddles other color regions. Therefore, there is a problem that the color purity is insufficient.

  Therefore, the present invention has been made in view of the above points, and in consideration of the emission spectrum distribution of the three colors of light emitted from each light emitting layer, the half width and color purity of each emission spectrum are improved. It aims at providing the organic EL element which can be manufactured.

  The present invention is characterized in that a substrate, an anode disposed on the substrate, three types of light emitting layers disposed on the anode and emitting light of three colors of red, green, and blue, respectively, and the light emitting layer And a characteristic improving film disposed on each of the cathodes and having a characteristic of absorbing light within the wavelength region of the three colors of light. To do.

  According to this invention, in consideration of the emission spectrum distribution of each light, the half-value width and the color purity of the emission spectrum of each light can be improved by providing the characteristic improving film in the structure on the light extraction side of the three colors. Can do.

  ADVANTAGE OF THE INVENTION According to this invention, the organic EL element which can improve the half value width and color purity of each light emission spectrum can be provided in consideration of the light emission spectrum distribution of the light of three colors emitted by each light emitting layer. .

It is a figure which shows the cross-section of the organic EL element which concerns on the 1st Embodiment of this invention. It is a figure which shows a mode that the emission spectrum distribution of the light of green (G) changes with the characteristic improvement film | membrane of the organic EL element which concerns on the 1st Embodiment of this invention. It is a figure which shows a mode that the emission spectrum distribution of the light of blue (B) changes with the characteristic improvement film | membrane of the organic EL element which concerns on the 1st Embodiment of this invention. In the organic EL element which concerns on the 1st Embodiment of this invention, it is a figure which shows the relationship between the absorption coefficient and wavelength of copper phthalocyanine used as a characteristic improvement film | membrane. It is a figure which shows the relationship between the transmission ratio of a copper phthalocyanine film | membrane with respect to the light of a different wavelength, and a copper phthalocyanine film thickness. It is a figure which shows the cross-section of the organic EL element which concerns on the example of a change of this invention. It is a figure which shows the cross-section of the organic EL element which concerns on the example of a change of this invention. It is a figure which shows the cross-section of the organic EL element which concerns on the example of a change of this invention. It is a figure which shows the cross-section (top emission structure) of the organic EL element which concerns on the example of a change of this invention. It is a figure which shows the cross-section (top emission structure) of the organic EL element which concerns on the example of a change of this invention. It is a figure which shows the cross-section (top emission structure) of the organic EL element which concerns on the example of a change of this invention. It is a figure which shows the cross-section (top emission structure) of the organic EL element which concerns on the example of a change of this invention. It is a figure which shows the cross-section of a general organic EL element. It is a figure which shows the cross-section (top emission structure) of a common organic EL element. It is a figure which shows the emission spectrum distribution of the light light-emitted by the general organic EL element.

(Organic EL device according to the first embodiment of the present invention)
With reference to FIG. 1 thru | or FIG. 5, the organic EL element which concerns on the 1st Embodiment of this invention is demonstrated. FIG. 1 shows a cross-sectional structure of an organic EL element according to this embodiment.

  As shown in FIG. 1, the organic EL device according to this embodiment is divided into three light emitting regions in order to emit light of three colors of red (R), green (G), and blue (B). (Three-color light emission method).

  Specifically, the red (R) light emission region in the organic EL device according to the present embodiment is formed on the substrate 10 with the property improving film 11a, the anode 12a, the hole injection layer 13a, the hole transport layer 14a, The light-emitting layer (R) 15a, the electron transport layer 16a, the electron injection layer 17a, and the cathode 18 common to the three colors (R, G, B) are sequentially stacked.

  In addition, the green (G) light emission region in the organic EL element according to the present embodiment is formed on the substrate 10 on the characteristic improvement film 11b, the anode 12b, the hole injection layer 13b, the hole transport layer 14b, the light emission layer ( G) 15b, an electron transport layer 16b, an electron injection layer 17b, and a cathode 18 common to three colors (R, G, B) are sequentially stacked.

  Furthermore, the configuration of the blue (B) light in the organic EL device according to the present embodiment is such that the characteristic improving film 11bc, the anode 12c, the hole injection layer 13c, the hole transport layer 14c, and the light emitting layer (B ) 15c, an electron transport layer 16c, an electron injection layer 17c, and a common cathode 18 for three colors (R, G, B).

  Here, the organic EL element is manufactured by coating each layer separately for each light emitting region of three colors using a known manufacturing method such as a mask method.

  In the organic EL device according to the present embodiment, at least two extractions among the three color (R, G, B) light extraction side structures emitted from the three types of light emitting layers 15a to 15c described above are extracted. The side structures are configured such that light absorption characteristics in the wavelength regions of light of three colors (R, G, B) are different.

  For example, in the present embodiment, in order to realize such an organic EL element, three colors (R, G, B) are included in at least one of the three light extraction side structures described above. Characteristic improvement films 11a to 11c having a characteristic of absorbing light within a wavelength region of light (for example, a visible light region of 400 nm to 750 nm) are provided.

  Here, as shown in FIG. 1, the red (R) light extraction side structure emitted from the light emitting layer 15 a includes a substrate 10, a characteristic improving film 11 a, an anode 12 a, a hole injection layer 13 a, And the hole transport layer 14a.

  The structure for extracting green (G) light emitted from the light emitting layer 15b is formed by the substrate 10, the property improving film 11b, the anode 12b, the hole injecting layer 13b, and the hole transporting layer 14b. Has been.

  The blue (B) light extraction side structure emitted from the light emitting layer 15c is formed by the substrate 10, the characteristic improving film 11c, the anode 12c, the hole injection layer 13c, and the hole transport layer 14c. Has been.

  Since the substrate 10 is on the side from which the light emitted by the light emitting layers 15a to 15c is extracted, the substrate 10 is constituted by a light-transmitting transparent substrate such as a glass substrate, for example.

  Since the anodes 12a to 12c are on the side from which the light emitted by the light emitting layers 15a to 15c is extracted, the anodes 12a to 12c are made of transparent electrodes such as ITO (Indium Tin Oxide).

  The hole injection layers 13a to 13c are provided in order to improve the injectability of carriers from the anodes 12a to 12c into the hole transport layers 14a to 14c. For example, amine-based or phthalocyanine-based materials with low ionization energy are used for the hole injection layers 13a to 13c.

  The hole transport layers 14a to 14c are provided to improve the injectability of carriers from the hole injection layers 13a to 13c to the light emitting layers 15a to 15c, and contain electrons in the light emitting layers 15a to 15c. Is possible. For example, an amine-based material (for example, naphthel phenyl benzidine (NPB)) having a low ionization energy is used for the hole transport layers 14a to 14c.

  The light emitting layers 15a to 15c are formed by doping a light emitting material (host material) such as an aluminum complex with a fluorescent and phosphorescent dye (guest material).

  Here, the light emitting layer 15a is configured to emit red (R) light having an emission spectrum distribution shown by a one-dot chain line in FIG. 15 when a voltage is applied between the anode 12a and the cathode 18. The light emitting layer 15b is configured to emit green (G) light having an emission spectrum distribution indicated by a dotted line in FIG. 15 when a voltage is applied between the anode 12b and the cathode 18. The light emitting layer 15c is configured to emit blue (B) light having an emission spectrum distribution indicated by a solid line in FIG. 15 when a voltage is applied between the anode 12c and the cathode 18.

  The electron transport layers 16a to 16c are provided in order to improve the injection property of electrons from the electron injection layers 17a to 17c to the light emitting layers 15a to 15c. For example, aluminum complexes or oxadiazoles are used for the electron transport layers 16a to 16c.

  The electron injection layers 17a to 17c are provided in order to improve the injection property of electrons from the cathode 11 to the electron transport layers 16a to 16c. For example, materials such as an alkali metal such as lithium and a lithium complex are used for the electron injection layers 17a to 17c.

  The cathode 18 is configured as an electrode common to the light emitting layers 15a to 15c, and is configured of, for example, a metal such as aluminum.

  The characteristic improving film 11a has a characteristic of absorbing light within the wavelength range of red (R) light, and the characteristic improving film 11b has a characteristic of absorbing light within the wavelength range of green (G) light. The characteristic improving film 11c has a characteristic of absorbing light within the wavelength region of blue (B) light.

  Here, when the green (G) light having the emission spectrum distribution shown in FIG. 2 (a) passes through the characteristic improving film 11b having the absorbance distribution shown in FIG. 2 (b), the light in the vicinity of the peak at 565 nm is sufficient. Therefore, the emission spectrum distribution is as shown by the broken line in FIG.

  Note that green (G) light having an emission spectrum distribution shown in FIG. 2A is emitted by the light emitting layer 15b formed by doping quinacridone into an aluminum complex.

  Further, when the blue (B) light having the emission spectrum distribution shown in FIG. 3 (a) passes through the characteristic improving film 11c having the absorbance distribution shown in FIG. 3 (b), the light near the peak is sufficiently absorbed. Therefore, the emission spectrum distribution is as shown by the one-dot chain line in FIG.

  Note that the blue (B) light having the emission spectrum distribution shown in FIG. 3A is emitted by the light emitting layer 15b formed by doping DPVBi with BCzVBi.

  As a result, the color mixture of blue (B) light (dotted line in FIG. 2C) and green (G) light (dotted line in FIG. 3C) extracted to the outside is reduced.

  For example, the characteristic improvement films 11a to 11c are made of copper phthalocyanine (CuPc) among phthalocyanines, and have a characteristic of absorbing light (that is, a predetermined absorption coefficient) in the visible light region. .

  In FIG. 4, the distribution with respect to each wavelength of the absorption coefficient of the characteristic improvement films 11a to 11c formed of copper phthalocyanine (CuPc) is shown. As shown in FIG. 4, it can be seen that the characteristic improving films 11a to 11c most easily absorb light having a wavelength of 600 nm to 640 nm.

  FIG. 5 shows the transmission ratio “I / I0” and the film thickness (CuPc film thickness) of the characteristic improvement films 11a to 11c formed of copper phthalocyanine (CuPc) in the light of wavelength 528 nm and the light of wavelength 565 nm. The relationship with “t” is shown.

  Here, the absorption coefficient is “α”, the film thicknesses of the characteristic improvement films 11a to 11c are “t”, the incident light intensity to the characteristic improvement films 11a to 11c is “I0”, and the characteristic improvement film 11a. Assuming that the intensity of emitted light from ˜11c is “I”, the relationship “I = I0exp (−αt)” is established.

  As shown in FIG. 5, it can be seen that as the film thickness of CuPc increases, the absorbance with respect to light having a wavelength of 565 nm increases.

  The organic EL device according to the present embodiment has not only the five-layer structure as described above, but also a three-layer structure that does not include the hole injection layers 12a to 12c and the electron injection layers 17a to 17c, and further electron transport. The present invention can also be applied to a two-layer structure that does not include the layers 16a to 16c, or a single-layer structure that does not include the hole transport layers 14a to 14c.

  In addition, the organic EL element according to the present embodiment is not limited to the structure in which the characteristic improvement films 11a to 11c are provided between the substrate 10 and the anodes 12a to 12c, and can be placed at any position on the light extraction side structure. You may have the structure which provides the characteristic improvement films | membranes 11a-11c.

  For example, as shown in FIG. 6, in the organic EL element according to the present embodiment, the characteristic improving films 11a to 11c may be provided between the anodes 12a to 12c and the hole injection layers 13a to 13c.

  Moreover, as shown in FIG. 7, in the organic EL device according to the present embodiment, the characteristic improving films 11a to 11c are provided between the hole injection layers 13a to 13c and the hole transport layers 14a to 14c. Also good.

  As shown in FIG. 8, in the organic EL device according to this embodiment, the characteristic improving films 11a to 11c may be provided between the hole transport layers 14a to 14c and the light emitting layers 15a to 15c. .

  Furthermore, the organic EL element according to the present embodiment can be applied to an organic EL element having a top emission structure.

  For example, as shown in FIG. 9, in the organic EL element according to this embodiment, the characteristic improving films 11a to 11c may be provided outside the cathodes 18a to 18c.

  As shown in FIG. 10, in the organic EL device according to this embodiment, the characteristic improving films 11a to 11c may be provided between the cathodes 18a to 18c and the electron injection layers 17a to 17c.

  As shown in FIG. 11, in the organic EL element according to this embodiment, the characteristic improving films 11a to 11c may be provided between the electron injection layers 17a to 17c and the electron transport layers 16a to 16c. .

  As shown in FIG. 12, in the organic EL device according to this embodiment, the characteristic improving films 11a to 11c may be provided between the electron transport layers 16a to 16c and the light emitting layers 15a to 15c.

  According to the organic EL element according to the present embodiment, the three colors (R, G, B) are considered in consideration of the emission spectrum distribution of the three colors (R, G, B) emitted from the light emitting layers 15a to 15c. ), The half-value width and color purity of the emission spectra of the three colors (R, G, B) can be improved.

  In addition, according to the organic EL element according to the present embodiment, characteristics in the light extraction side structure of the light of the three colors (R, G, B) are taken into account in consideration of the emission spectrum distribution of the three colors (R, G, B). By providing the improvement films 11a to 11c, the half-value width and color purity of the emission spectra of the three colors (R, G, and B) can be improved.

(Organic EL device according to the second embodiment of the present invention)
An organic EL element according to the second embodiment of the present invention will be described with reference to FIGS.

  The organic EL device according to the present embodiment includes at least two extraction side structures among the three color (R, G, B) light extraction side structures emitted from the light emitting layers 15a to 15c. Light absorption characteristics in the wavelength range of light of colors (R, G, B) are different.

  Specifically, the organic EL element according to the present embodiment has a structure for extracting light of three colors (R, G, B) emitted from the light emitting layers 15a to 15c in order to realize such an organic EL element. Among these, at least one material or thickness of the electron injection layers 17a to 17c, the electron transport layers 16a to 16c, the hole transport layers 14a to 14c, and the hole injection layers 13a to 13c between at least two extraction-side structures. Are configured to be different.

  Specifically, when the organic EL element according to the present embodiment has the element structure shown in FIG. 13, the light emission distributions of the three colors (R, G, B) emitted from the light emitting layers 15 a to 15 c are considered. Then, at least one material of the hole transport layers 14a to 14c and the hole injection layers 13a to 13c included in the light extraction side structure of the three colors (R, G, and B) emitted from the light emitting layers 15a to 15c. Or the thickness is changed.

  For example, the hole transport layer 14b or the hole injection layer 13b may be formed of copper phthalocyanine (CuPc) having the absorbance distribution shown in FIG. 2B, or the hole transport layer 14c or the hole injection layer 13c. May be formed of copper phthalocyanine (CuPc) having an absorbance distribution shown in FIG.

  In consideration of the relationship shown in FIG. 5, the film thickness of copper phthalocyanine (CuPc) that forms the hole transport layers 14a to 14c or the hole injection layers 13a to 13c may be changed.

  Further, when the organic EL element according to the present embodiment has the element structure (top emission structure) shown in FIG. 14, the light emission distribution of the light of three colors (R, G, B) emitted from the light emitting layers 15 a to 15 c. In consideration of the above, at least one material of the electron transport layers 16a to 16c and the electron injection layers 17a to 17c included in the light extraction side structure of the three colors (R, G, and B) emitted from the light emitting layers 15a to 15c Or the thickness is changed.

  For example, the electron transport layer 16b or the electron injection layer 17b may be formed of copper phthalocyanine (CuPc) having the absorbance distribution shown in FIG. 2B, or the electron transport layer 16c or the electron injection layer 17c may be formed as shown in FIG. You may form by the copper phthalocyanine (CuPc) which has the light absorbency distribution shown in (c).

  In consideration of the relationship shown in FIG. 5, the film thickness of copper phthalocyanine (CuPc) forming the electron transport layers 16a to 16c or the electron injection layers 17a to 17c may be changed.

  The organic EL element according to the present embodiment is included in the light extraction side structure of light of three colors (R, G, B) in consideration of the emission spectrum distribution of light of three colors (R, G, B). By changing at least one material or thickness of the electron injection layers 17a to 17c, the electron transport layers 16a to 16c, the hole transport layers 14a to 14c, and the hole injection layers 13a to 13c, half of the emission spectrum of each light is obtained. The value range and color purity can be improved.

DESCRIPTION OF SYMBOLS 10 ... Substrate 11a, 11b, 11c ... Characteristic improvement film | membrane 12, 12a, 12b, 12c ... Anode 13a, 13b, 13c ... Hole injection layer 14a, 14b, 14c ... Hole transport layer 15a, 15b, 15c ... Light emitting layer 16a 16b, 16c ... Electron transport layers 17a, 17b, 17c ... Electron injection layers 18, 18a, 18b, 18c ... Cathode

Claims (6)

A substrate,
An anode disposed on the substrate;
Three types of light emitting layers disposed on the anode and emitting light of three colors of red, green, and blue,
A cathode disposed on each of the light emitting layers;
An organic EL element, comprising: a characteristic improving film disposed on each of the cathodes and having a characteristic of absorbing light within the wavelength range of the three colors of light.   It is configured such that the film thickness of the characteristic improving film is different between at least two structures out of the structures on the side from which the three colors of light emitted from the three types of light emitting layers are respectively extracted. The organic EL element according to claim 1.   The organic EL device according to claim 1, wherein the cathode and the property improving film are laminated adjacent to each other.   The organic EL element according to claim 1, wherein the characteristic improving film is formed of a copper compound.   The organic EL element according to claim 4, wherein the characteristic improving film is formed of copper phthalocyanine.   At least one material or thickness of the electron injection layer and the electron transport layer is between at least two of the structures on the side from which the three colors of light emitted from the three types of light emitting layers are extracted. The organic EL device according to claim 1, wherein the organic EL devices are configured differently.

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