JP2830474B2 - Organic light emitting device and its substrate - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an organic light-emitting element used for a display element, a communication light-emitting device, an information file read / write head, a printing apparatus, and the like, and a substrate used therefor.

BACKGROUND ART A conventional organic light-emitting element has, for example, a light-emitting body composed of an organic light-emitting body and an electrically insulating binder interposed between a transparent substrate having a transparent electrode such as indium tin oxide, and an anode electrode of the electrode. An organic electroluminescence cell in which a porphyrin-based compound layer is formed between the luminous body region and the luminous body region has been proposed (JP-A-57-51781). The organic electroluminescence cell emits light when holes are injected by a hole injector made of a porphyrin compound based on a signal electric field applied between the two electrodes.

Light-emitting elements using such organic thin films have the advantage that they can be provided at a low cost, but their applications are limited to display panels due to the wide half width of the spectrum, and each material emits only one color light. Therefore, only a single-color display could be manufactured using a single material.

DISCLOSURE OF THE INVENTION An object of the present invention is to provide an organic light emitting device with improved spectral width and light emission characteristics.

Another object of the present invention is to provide a substrate for the organic light emitting device. The gist of the present invention for solving the above problems is as follows.

(1) A micro-optical resonator is composed of a light-emitting layer composed of an organic thin film having a light-emitting function and reflectors provided on both sides of the light-emitting layer, and the micro-optical resonator is configured to emit light. element.

(2) A translucent reflective layer is provided on a transparent substrate, a transparent conductive layer is disposed on the translucent reflective layer, and a light emitting layer composed of an organic thin film is provided on the transparent conductive layer. An organic light-emitting device having electrodes formed thereon, wherein the translucent reflective layer has a reflection function of transmitting a part of light emitted from the light-emitting layer to the transparent substrate side and reflecting a part of light emission to the light-emitting layer side. An organic light-emitting device in which the translucent reflective layer is configured to function as an optical resonator between the translucent reflective layer and an electrode on the back surface of the light-emitting layer.

(3) A translucent reflective layer is provided on a transparent substrate, a transparent conductive layer is disposed on the translucent reflective layer, and a hole injection layer, a light emitting layer composed of an organic thin film, and an electron injection layer are provided on the transparent conductive layer. An organic light-emitting element having an electrode formed thereon, wherein the translucent reflective layer transmits part of the light emitted from the light-emitting layer to the transparent substrate side and transmits part of the light emitted from the light-emitting layer. An organic light-emitting device having a reflection function of reflecting light to the side, wherein the translucent reflection layer is configured to function as an optical resonator with an electrode on the back surface of the light-emitting layer.

(4) When the phase shift of reflected light generated between the translucent reflective layer and the electrode on the back of the light emitting layer is A radian, the optical distance L between the translucent reflective layer and the electrode on the back of the light emitting layer is ( Integer-A / 2π) times [where S <(2L) <T, and S and T are
It indicates a wavelength at which the emission intensity in the emission spectrum of the light emitting element having no translucent reflection layer is 1/2 of the maximum intensity. The organic light-emitting device according to the above.

(5) When the phase shift of the reflected light generated between the translucent reflective layer and the electrode on the back of the light emitting layer is A radian, the optical distance L between the translucent reflective layer and the electrode on the back of the light emitting layer is [ 0.9 of the length of the peak wavelength of the light to be extracted x (integer-A / 2π) / 2]
The organic light-emitting device of the present invention having a magnification of 1.1 times.

For example, the optical distance of the resonator is equal to the emission wavelength of 2
The same resonance effect can be obtained in the case of multiple times, 3 times,... N times and integer times, or in the case of 1/2, 3/2,.

(6) The organic light-emitting device wherein the translucent reflection layer is a dielectric multilayer film.

(7) The sum of the optical distances represented by the product of the thicknesses of the transparent conductive layer, the hole injection layer, the light emitting layer and the electron injection layer and the respective refractive indices is equal to or close to the peak wavelength of light emission. The organic light-emitting device.

(8) The organic light emitting device, wherein the translucent reflection layer is a metal total reflection film having a light emission extraction window by patterning.

(9) The organic light emitting device wherein the translucent reflective layer has a reflectance of 50 to 99.9% or a transmittance of 50 to 0.1%.

(10) a transparent substrate, and a semi-transparent reflective layer made of a dielectric multilayer film that partially transmits light and partially reflects light on the transparent substrate;
An organic light emitting device substrate having a transparent conductive film on the translucent reflective layer.

(11) a transparent substrate, and a semi-transparent reflective layer formed of a dielectric multilayer film on the transparent substrate, and the semi-transparent reflective layer has a reflectance of 50 to 99.9.
% Or a substrate for an organic light emitting device having a transmittance of 50 to 0.1%.

(12) A substrate for an organic light-emitting device, comprising a transparent substrate, a translucent reflective layer on which a transparent conductive film and a transparent insulating film are laminated, and having the transparent conductive film on the translucent reflective layer.

The transparent substrate is preferably a transparent substrate selected from transparent quartz, glass or plastic.

In the present invention, a translucent reflective film is provided between the transparent electrode and the substrate, and the optical distance between the reflective film and the back electrode is equal to that of the emission wavelength or an integral multiple thereof. The inside of the device can be a microcavity of light. Thereby, the half width of the emission spectrum is reduced.

In addition, the light emission characteristics can be improved, for example, the light emission efficiency is improved and the ratio of generation of coherent light is increased.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic sectional view showing the structure of a light emitting device according to one embodiment of the present invention.

FIG. 2 is a schematic sectional view showing the structure of a conventional light emitting device.

FIG. 3 is a comparison diagram of the emission spectra of the device of FIG. 1 and the device of FIG.

FIG. 4 is a graph showing a relationship between an optical distance of a resonator portion of a light emitting device having a translucent reflective film according to one embodiment of the present invention and a half width of an emission spectrum.

FIG. 5 is a schematic sectional view showing the structure of a light emitting device according to one embodiment of the present invention.

FIG. 6 is a spectrum diagram showing the relationship between the thickness of the organic fluorescent film (aluminum chelate) and the emission spectrum.

BEST MODE FOR CARRYING OUT THE INVENTION Example 1 FIG. 1 is a schematic sectional view showing the structure of a light emitting device according to an example of the present invention.

On a glass substrate 1, a translucent reflective film 2 in which a TiO ₂ film and a SiO ₂ film are laminated is formed. A transparent conductive film (Indium Tin Oxide: ITO film) 3 is formed on the translucent reflective film 2, and a hole injection layer 4 made of a triphenyldiamine derivative (TAD), a light emitting layer 5 of aluminum chelate, Electron injection layer 6 of diazole derivative (PBD), Ag-Mg metal electrode 7
Are sequentially formed. The sum of the optical distances obtained from the products of the thicknesses of the transparent conductive film 3, the hole injection layer 4, the light emitting layer 5, and the electron injection layer 6 and the refractive index is the electroluminescence (EL) of aluminum chelate. It is made to coincide with 530 nm which is the peak wavelength of light emission. This constitutes the resonator of the present invention.

In FIG. 1, the hole injection layer 4 and the electron injection layer 6
Is not required unless high performance properties are required,
Either or both of them can be omitted. At that time, holes are injected from the transparent conductive film 3 and electrons are injected from the metal electrode 7 to obtain the light emitting device of the present invention. However, it is better to provide the hole injection layer 4 and the electron injection layer 6. More preferred.

The reflectivity of the translucent reflective film 2 is selected depending on the performance of the material of the light emitting layer 5 and the use of the device. The upper limit of the reflectivity is limited by the limit of energy that the optical resonator can store without self-destruction. The transmittance is 50 to 0.1% and the reflectance is 50 to 99.9%. In order to obtain at least 10 μW / cm ² of emitted light, the transmittance of the extracted light cannot be smaller than 0.1%. The limit of the reflectance is 99.9%. If the reflectivity is too small, it loses its properties as an optical resonator,
If the reflectance is lower than, a sufficient reduction in the spectrum width cannot be obtained.

In the above, aluminum chelate was used for the light emitting layer 5, but a perylene derivative, a perinone derivative, a naphthalene derivative, a coumarin derivative, an oxadiazole / bisbenzoxazoline, an aldazine, a pyrazine derivative, a distilbenzene derivative, a polyphenyl derivative, bis Stilanthracene derivatives, chelate metal complexes and the like are used.

The above organic thin film is deposited, coated, grown by chemical reaction,
It can be produced by the Langmuir-Blodgett method or the like. Further, a plurality of organic materials can be mixed and used.

FIG. 2 is a schematic sectional view showing the structure of an organic EL element having a conventional structure. That is, the structure is such that the translucent reflective film 2 is removed from the structure of FIG.

FIG. 3 is a spectrum diagram comparing the emission spectra of the device of FIG. 1 and the device of FIG. The spectrum A of the device of FIG. 1 has a smaller half width than the spectrum B of the device of FIG. This is because the translucent reflection film 2 resonates light emission inside the device, thereby selectively generating an electromagnetic wave having a resonance frequency. By resonating light emission in this manner, effects such as a reduction in the half width of the emission spectrum, an improvement in luminous efficiency, and generation of coherent light can be obtained. By making the optical distance of the resonator portion of the resonator closer to the emission wavelength, a greater effect can be obtained.

FIG. 4 is a graph showing the relationship between the optical distance of the resonator portion and the half width of the emission spectrum. This is a result of a measurement using an element in which only the film thickness of the hole injection layer 4 is changed in the element structure of FIG. 1, and the half width without the translucent reflective film 2 is 100. The half width is the smallest at around 530 nm where the optical distance coincides with the peak wavelength of light emission, and increases rapidly as the wavelength departs from 530 nm. FIG.
In the device without the translucent reflective film 2 (spectrum B), the wavelength at which the emission intensity is about の of the emission intensity at 530 nm is 480 nm and 5 nm.
It turns out that it is 80 nm. This range corresponds to the range in which the half width is reduced in FIG.

The resonance effect is obtained when the optical distance is in the range of 0.9 to 1.1 times the peak wavelength of the emitted light. This range corresponds to the wavelength region where the half width is reduced in FIG.

In this embodiment, aluminum chelate is used alone as a light emitting layer material. However, any organic material that emits light by electron-hole bonding can be used in a mixture or a laminated structure as long as the material is organic.

Further, in order to stabilize the resonated light emission, it is important to provide a mechanism for keeping the temperature of the element constant.

The optimum values of the transmittance and the reflectivity differ depending on the element structure and the constituent material of the translucent reflective film 2, but the absorptivity is preferably as close to 0 as possible.

As the translucent reflection film 2, a metal total reflection film which is patterned and partially has a window for extracting light emission can be used. In addition, by adopting an element structure in which light emission does not easily leak in the lateral direction, light emission characteristics can be further improved.

In the present embodiment, the case where the optical distance as the resonator is the same as the emission wavelength has been described. However, theoretically, when the emission wavelength is an integral multiple of twice, three times,. The same resonance effect can be obtained in the case of a half integral multiple such as 3/2,.

Further, in the present embodiment, a case is shown in which the total phase shift of light due to reflection on the upper and lower mirror surfaces is 0 or 1 wavelength. In the case of an element configuration having no shift, resonance can be achieved when the optical distance is 1/4, 3/4, 5/4,... Times the emission wavelength.

However, in an actual device, the sharpness at which resonance occurs due to the fabrication of the device is blurred. For this reason, the above effect is sharper as the film thickness is smaller, and the resonance becomes less clear as the multiple becomes larger. Therefore, the practical limit is about 10 times.

The device having the structure of this embodiment generates electroluminescence by charge injection and generates fluorescence in the light-emitting layer by light irradiated from the transparent substrate side, thereby producing a light emission spectrum having a narrow half-width similar to that of electroluminescence. Can be caused. In this case, the organic thin film other than the transparent electrode and the light emitting layer can be omitted.

Example 2 FIG. 5 shows a schematic cross-sectional view of a resonator element utilizing light emission by light excitation.

The organic fluorescent thin film 9 was formed in a structure in which an aluminum chelate was sandwiched between the total reflection metal film 8 and the translucent reflection film 2 made of a laminate of TiO ₂ / SiO ₂ . The translucent reflective film 2
By irradiating light with a wavelength of 406 nm from the side, visible light can be extracted from the organic fluorescent thin film 9.

FIG. 6 shows the relationship between the thickness of the organic fluorescent thin film (aluminum chelate) and the emission spectrum. The emission peak position, half width, and intensity can be changed depending on the thickness of the aluminum chelate. The shape of the emission spectrum can also be changed by changing the reflection characteristics of the translucent reflection film.

The organic light emitting device of the present invention can improve the light emission characteristics such as reduction of the half width of the light emission spectrum, improvement of the light emission efficiency and generation of coherent light by the effect of the optical resonator.

The organic light-emitting device can be used as a substitute for a light-emitting diode or a semiconductor laser that has been conventionally manufactured using an inorganic semiconductor such as GaAs, SiC, or ZnSe. It can be used as a writing head and an optical head of a laser printer.

Continuation of the front page (56) References JP-A-2-46695 (JP, A) JP-A-3-69899 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) H05B 33 / twenty two

Claims (15)

(57) [Claims] 1. A translucent reflective layer is provided on a transparent substrate, a transparent conductive layer is disposed on the translucent reflective layer, and a light emitting layer made of an organic thin film is provided on the transparent conductive layer. An organic light-emitting device having an electrode formed thereon, wherein the translucent reflective layer has a reflection function of transmitting part of the light emitted from the light-emitting layer to the transparent substrate side and reflecting part of the light emitted to the light-emitting layer side. An organic light-emitting device having a translucent reflective layer, wherein the translucent reflective layer is configured to act as an optical resonator between the translucent reflective layer and an electrode on the back surface of the light-emitting layer. 2. A transparent substrate having a translucent reflective layer on a transparent substrate, a transparent conductive layer disposed on the translucent reflective layer, a hole injection layer, a light emitting layer comprising an organic thin film, and an electron injection layer on the transparent conductive layer. An organic light-emitting device in which a layer is provided in order and an electrode is formed thereon, wherein the translucent reflective layer transmits a part of light emitted from the light-emitting layer to the transparent substrate side, and transmits a part of light emitted from the light-emitting layer. An organic light-emitting device having a reflection function of reflecting light toward a light-emitting layer, wherein the translucent reflection layer is configured to function as an optical resonator with an electrode on the rear surface of the light-emitting layer. 3. A translucent reflective layer is provided on a transparent substrate, a transparent conductive layer is disposed on the translucent reflective layer, and a hole injection layer and a light emitting layer comprising an organic thin film are provided on the transparent conductive layer. An organic light-emitting device having an electrode formed thereon,
The translucent reflective layer has a reflection function of transmitting part of the light emitted from the light emitting layer to the transparent substrate side and reflecting part of the light emitted to the light emitting layer side. An organic light-emitting device characterized in that the organic light-emitting device is configured to function as an optical resonator. 4. A translucent reflective layer is provided on a transparent substrate, a transparent conductive layer is disposed on the translucent reflective layer, and a light emitting layer composed of an organic thin film and an electron injection layer are sequentially provided on the transparent conductive layer. Wherein the translucent reflective layer transmits part of the light emitted from the light emitting layer to the transparent substrate side, and transmits part of the light emitted from the light emitting layer to the light emitting layer side. An organic light-emitting device having a reflective function of reflecting light, wherein the translucent reflective layer is configured to function as an optical resonator with an electrode on the back surface of the light-emitting layer. 5. When the phase shift of reflected light generated between the translucent reflective layer and the electrode on the back surface of the light emitting layer is A radian,
Optical distance L between the translucent reflective layer and the electrode on the back of the light emitting layer
Is (integer-A / 2π) times [where S <(2L) <T,
S and T indicate wavelengths at which the emission intensity in the emission spectrum of the light emitting element having no translucent reflective layer is 1/2 of the maximum intensity. The organic light-emitting device according to any one of claims 1 to 4, wherein: 6. An optical system according to claim 1, wherein an optical distance between the translucent reflective layer and the electrode on the back surface of the light emitting layer is 0.9 to 1.1 times the peak wavelength of the light to be extracted or an integral multiple thereof. Item 14. The organic light-emitting device according to any one of the items. 7. When the phase shift of reflected light generated between the translucent reflective layer and the electrode on the back of the light emitting layer is A radian,
Optical distance L between the translucent reflective layer and the electrode on the back of the light emitting layer
5. The organic light-emitting device according to claim 1, wherein the length is 0.9 to 1.1 times the length of [peak wavelength of light to be extracted × (integer−A / 2π) / 2]. 6. 8. The sum of the optical distances represented by the product of the thicknesses of the transparent conductive layer, the hole injection layer, the emission layer and the electron injection layer and the respective refractive indices is equal to the peak wavelength of light emission or The organic light-emitting device according to claim 2, which is similar. 9. The organic light-emitting device according to claim 1, wherein said translucent reflection layer is formed of a dielectric multilayer film. 10. The organic light-emitting device according to claim 1, wherein said translucent reflection layer is formed of a metal total reflection film having a light emission window. 11. The translucent reflection layer has a reflectance of 50 to 99.9%.
The organic light-emitting device according to any one of claims 1 to 9, wherein the transmittance is 50 to 0.1%. 12. A transparent substrate, and a semi-transparent reflective layer made of a dielectric multilayer film that partially transmits light and partially reflects light on the transparent substrate. A transparent conductive film is formed on the semi-transparent reflective layer. A substrate for an organic light emitting device, comprising: 13. A transparent substrate, a semi-transparent reflective layer comprising a dielectric multilayer film thereon, a transparent conductive film on the semi-transparent reflective layer, and the semi-transparent reflective layer has a reflectance of 50%. A substrate for an organic light emitting device, wherein the substrate has a transmittance of up to 99.9% or a transmittance of 50 to 0.1%. 14. An organic light-emitting device comprising a transparent substrate, a translucent reflective layer on which a transparent conductive film and a transparent insulating film are laminated, and a transparent conductive film on the translucent reflective layer. Substrate. 15. The transparent substrate according to claim 12, wherein said transparent substrate is a transparent substrate made of quartz, glass or plastic, and a transparent conductive film is patterned on said translucent reflective layer.
Item 15. The substrate for an organic light-emitting device according to any one of items 14 to 14.