JPH08190801A - Electrochemical light emitting device - Google Patents

Abstract

PURPOSE: To provide a new light emitting device by arranging a light emitting medium containing an electrochemical light emitting substance between two confronting electrodes set with a predetermined electrode spacing so as to generate electrochemical light emission efficiently. CONSTITUTION: An inside electrode wiring film 6 whose both ends are composed of an electrode portion 6a and a terminal portion 6b and an outside electrode wiring film 7 composed of partially opened doughnut-like electrode 7a and a terminal portion 7b are formed concentrically on the insulation layer 2 of a board 1. The wiring films 6, 7 are covered by an insulation film 8 so as to expose the electrode portions and the terminal portions thereof, a lid member 18 is arranged on the insulation film 8 via an O ring 16 arranged outside the electrode portion 7a, and the liquid 17 of an electrochemical light emitting substance, such as pyrene or the like is filled in the inside space thereof. Since the shortest time for ions generated at one side electrode to reach the confronting electrode is expressed by t=d<2> /(D: diffusion constant), an electrochemical light emitting efficiency is improved by setting an electrode spacing (d) so that the (t) is less than the mean lifetime of the ions.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a novel light emitting device utilizing an electrochemical reaction.

[0002]

2. Description of the Related Art When a solution of a certain organic substance or metal complex is electrolyzed, the cation and anion generated by the redox reaction react in the solution, and as a result, the electron of the anion moves to the excited level of the cation. Then, it becomes an excited state, and luminescence (electrochemiluminescence) may appear due to the radiative transition. Examples of substances that cause this type of electrochemiluminescence include aromatic hydrocarbons such as anthracene, rubrene, perylene, and pyrene, and heterocyclic compounds such as isobenzofuran, isoindole, carbazole, cyananthrene, and lumigenin, and ruthenium ( (Tris-2,2'-bipyridine) (II)
Metal complexes such as complexes are known (Showa 59, Gihodo Akira Fujishima et al., "Electrochemical measurement method (1)", page 369-
See page 370). Similar light emission phenomenon may appear when a solid electrolyte is formed using an inorganic material such as sodium-β-alumina or silver iodide-silver molybdate or an organic material such as polymer ethylene oxide. However, since the efficiency of electrochemiluminescence is extremely low, no attempt has been made so far to positively utilize it as a light-emitting device.

[0003]

Known light emitting devices that can be used as light sources for displays include light emitting diodes, semiconductor lasers, electroluminescence, plasma displays, cathode ray tubes, and fluorescent display tubes. An object of the present invention is to provide a novel light emitting device whose operation principle is completely different from those of these light emitting devices.

[0004]

Means for Solving the Problems The present inventor experimentally produced a device in which a luminescent medium containing an electrochemiluminescent substance was disposed between two electrodes facing each other, and as a result, an experiment was conducted. It was found that the electrochemiluminescence efficiently occurs when the electrode interval is set so that the shortest time for the ions to diffuse and reach the other electrode is equal to or less than the average life of the ions in the luminescent medium.

The reason why the efficiency of electrochemiluminescence observed in conventional chemical experiments is low is considered as follows.
That is, when an anode and a cathode are placed in a solution of an electrochemiluminescent substance and a DC voltage is applied, cations generated at the anode and anions generated at the cathode diffuse and move toward the counter electrode, but the solution is In the stationary state, the shortest time t for the ions generated at one electrode to reach the other electrode (counter electrode) is given by the following equation (1).

[0006]

## EQU1 ## t = d ² / D (1) where d: electrode spacing D: diffusion constant The diffusion constant D of a normal electrochemiluminescent substance is at most 1 /
Since it is about 10 ⁵ cm ² / s, the electrode spacing d is, for example, 1
The shortest ion arrival time t in the case of cm is at least about 10 ⁵ s (about 30 hours). However, since the cations and anions have the property of moving in opposite directions to each other, it can be said that the time required for them to encounter on average is less than 30 hours, but it is still about 10 ⁴ s (about 3 s). It is impossible in principle to fall below the (time).

On the other hand, the cations and anions in the solution are
It disappears early due to collision with molecules of the non-ionized luminescent substance or reaction with undesired oxidizing or reducing substances present on the electrode surface or in the solvent. When the average lifetime of ions is estimated in consideration of the probability, the value is at most about several ms. Therefore, the probability that the ions in the solution will encounter and react with ions of the opposite polarity during their lifetime is extremely low, which is considered to be the main cause of lowering the luminous efficiency. When a solid electrolyte of an electrochemiluminescent substance is used as the luminescent medium, the diffusion constant of ions becomes smaller, and the luminous efficiency becomes even lower.

However, according to the current fine processing technology, it is possible to easily set the electrode interval finely so that the shortest ion arrival time t is equal to or shorter than the average life of the ions.
When the electrode interval d is set to, for example, 1 μm, the shortest ion arrival time t is about 1 ms, which is sufficiently shorter than the average life of the ions (several ms), and as a result, cations and anions encounter ions of opposite polarities. The probability can be increased and the electrochemiluminescent efficiency can be significantly improved.

[0009]

The electrochemiluminescent device according to the present invention will be described in more detail below with reference to some embodiments shown in the drawings. The same symbols used in FIGS. 1 to 11 indicate the same or similar items.

Example 1 The electrochemiluminescent device of this example is provided with two concentric electrodes formed on the same substrate. FIGS. 1 and 2 show the manufacturing process thereof, and FIG. 3 shows the final process. The structure of the product is shown. First, as shown in FIG. 1a, the surface of the silicon substrate 1 is oxidized to form an insulating layer 2 having a thickness of 0.5 μm.
Then, a positive electron beam resist was applied on the insulating layer to form a resist layer 3 having a thickness of 1.5 μm (FIG. 1b). Then, the resist layer 3 was exposed to a desired wiring pattern by an electron beam drawing apparatus, and then an appropriate developing process was performed to remove the exposed resist material from the insulating layer 2 (FIG. 1c). Then, after forming the gold vapor deposition film 5 with a thickness of 0.5 μm using the resist layer 3 as a mask (FIG. 1d), the unnecessary vapor deposition film is removed together with the resist by using a resist stripping solution, so that the inner electrode wiring is formed. The film 6 and the outer electrode wiring film 7 were formed (FIG. 1e). As shown in FIG. 3, the inner wiring film 6
Is a strip shape having both ends thereof as an electrode portion 6a and a terminal portion 6b, and the outer wiring film 7 includes a partially-opened donut-shaped electrode portion 7a surrounding the electrode portion 6a of the inner wiring film 6 and the electrode. It is composed of a strip-shaped terminal portion 7b connected to the portion.

FIG. 2 shows the steps after forming the electrode wiring films 6 and 7. First, as shown in FIG. 2A, an insulating film 8 of silicon dioxide having a thickness of 0.5 μm is formed on the entire surfaces of the electrode wiring films 6 and 7 and the insulating layer 2, and then a positive electron beam is applied to the surface of the insulating film. A resist layer 9 was formed (Fig. 2b). Next, a desired electrode pattern is exposed on the resist layer 9 by an electron beam drawing apparatus, and then an appropriate development process is performed, so that portions of the electrode wiring films 6 and 7 that will be electrode portions and terminal portions ( The resist material (see FIG. 3) was removed (FIG. 2c). Then, by selectively etching the insulating film 8 with an aqueous solution of hydrofluoric acid using this resist layer as a mask, the electrode portions 6a, 7a and the terminal portions 6b, 7b (not shown in FIG. 2d) shown in FIG. 2d are exposed. After that, the resist 9 was peeled off to obtain the intermediate structure shown in FIG. 2e.

In this intermediate structure, as shown in FIG. 3, the intermediate region indicated by the alternate long and short dash line (see FIG. 3a) is covered with the insulating film 8, and the electrode portions 6a, 7a and the terminal portions 6b at both ends are 7b has the electrode wiring films 6 and 7 exposed. The electrode portion 6a of the inner electrode wiring film 6
Was formed in a circular shape having a diameter of 2 μm, and the electrode portion 7a of the outer electrode wiring film 7 was formed in a donut shape having an outer diameter of 10 μm and an inner diameter of 6 μm. Both electrode portions 6a. The interval of 7a was 2 μm. Reference numeral 18 is a lid member made of transparent glass, and is placed on the insulating film 8 via an O-ring 16 arranged further outside the outer electrode portion 7a. In the inner space formed by the lid member 18, the solution 1 of the electrochemiluminescent substance composed of pyrene is formed.
Filled 7. In this embodiment, only one light emitting device is shown to avoid complication, but in reality,
A plurality of light emitting devices were manufactured at the same time by applying the semiconductor processing technology, and the O-ring and the lid member were arranged so as to include these plurality of light emitting devices. As the electrode material, platinum, a transparent conductive material, a semiconductor material or the like can be used in addition to gold, depending on the purpose.

The inventor of the present invention applies a direct current voltage of 4.3 V to the terminal portions 6b and 7b of the light emitting device thus manufactured to cause an electrochemical reaction in the electrochemiluminescent substance solution 17, and A blue emission could be observed. It was confirmed that the smaller the electrode spacing, the higher the luminous efficiency, and the smaller the power consumption per unit luminous flux.

Example 2 The example shown in FIG. 4 is an electrochemiluminescent device using a solid electrolyte instead of a solution electrolyte. The light emitting device of this example is the same as that of Example 1.
In the same procedure as in the above case, the inner electrode portion 6a and the outer electrode portion 7a
After forming, the solid electrolyte membrane 19 is formed by applying an organic solid electrolyte dissolved in an organic solvent across both electrode parts and drying. The solid electrolyte has advantages such as a function as a partition wall, stability at high temperature, and no fear of liquid leakage.

<Embodiment 3> The electrode structure of this embodiment is shown in FIG.
As shown in, short fence-shaped Xs that are orthogonal to each other on the same substrate
The electrode 21 and the Y electrode 22 are arranged so as to cross each other, and an insulating layer 23 is formed at the intersection so that the two electrodes do not come into contact with each other. The electrode interval is formed at the intersection and the vicinity thereof, and the solution of the electrochemiluminescent substance covering the upper surface of the electrode can emit light at the intersection and the vicinity thereof.

FIG. 6 shows the overall structure of this embodiment. The light emitting device of this example was also manufactured using semiconductor processing technology. The manufacturing process will be described with reference to FIG. As in the case of Examples 1 and 2, using the silicon substrate 1 having the insulating layer 2 formed thereon, first, the X electrode 21 having a thickness of 0.5 μm and long in the horizontal direction was formed on the insulating layer 2. Subsequently, silicon nitride was deposited on the entire surface to form an insulating layer having a thickness of 1 μm. The insulating layer 23 at the intersection was left and the insulating layer at the other portion was removed by using the lithography technique, and then the Y electrode 22 having a thickness of 0.5 μm and long in the vertical direction was formed. The width of both electrodes was 2 μm. After forming an insulating film 10 of silicon dioxide having a thickness of 0.5 μm on the surfaces of both electrodes where the terminal portions are left, the insulating film 10 on both electrodes was removed to expose both electrodes.

After forming the electrodes as described above, the lid member 18 and the O-ring 16 are arranged in the same manner as in Example 1 to form the internal space, and the solution 17 of the electrochemiluminescent substance composed of pyrene is formed therein. Filled.

Example 4 The example shown in FIG. 7 is an electrochemiluminescent device using a solid electrolyte instead of the solution electrolyte of Example 3. In the light emitting device of this example, the X electrode 21 and the Y electrode 22 which are orthogonal to each other are formed by the same procedure as in Example 3, and then an organic solid electrolyte dissolved in an organic solvent is applied on both electrodes and dried. Due to
The solid electrolyte membrane 19 is formed.

<Embodiment 5> The embodiment shown in FIG.
An electrochemiluminescent device in which a solution of an electrochemiluminescent substance is filled between a number of (horizontal) scan electrodes 31 and a Y-axis (vertical) scan electrode 32 arranged orthogonal to the scan electrodes is provided. Show. In the figure, 33 is the X-axis scanning electrode 3
1 is a glass substrate for supporting 1, 34 is a glass substrate for supporting the Y-axis scanning electrode 32, and 35 is a solution of an electrochemiluminescent substance. A ruthenium complex was used as the electrochemiluminescent substance. In the case of the present embodiment, a large number of intersections formed between the scanning electrodes 31 and 32 become individual light emitting pixels. In addition, 480 X-axis scanning electrodes 31,
The Y-axis electrode 32 has 640 electrodes. The interval between the scanning electrodes was 100 μm for both the X axis and the Y axis.

The scanning electrodes 31 and 32 are manufactured by using a well-known semiconductor lithography technique. First, the glass substrate 3
A 0.1 μm thick tin oxide thin film (transparent electrode film) is formed on 3, 34, a resist layer is applied thereon with a thickness of 0.5 μm, and then a reduced projection of i-line (wavelength 365 nm) A desired electrode pattern was formed by exposing the resist layer through an exposure device through a predetermined photomask.
By selectively etching the underlying tin oxide thin film using this resist layer as a mask, scan electrodes 31 and 32 in the X-axis direction and the Y-axis direction were formed. Glass substrate 33,3
In No. 4, the periphery was fixed by a support so that the electrode interval was 2 μm, and the formed internal space was filled with the ruthenium complex solution 35 and sealed.

Scan electrodes 31, 3 in the X-axis direction and the Y-axis direction
Select drive circuits 37 and 38 are connected to each of the two,
In addition, the X-axis scan electrode 31 is scanned by the vertical component of the signal source 36 of the image information, and the Y-axis scan electrode 32 is scanned by the horizontal component of the signal source, whereby electrochemiluminescence of a desired pixel (intersection point) is obtained. As a result of causing the substance to emit light, a light emitting device (display device) with low power consumption of about 10 W could be realized. Further, when the display performance was verified, it was confirmed that an undesired display defect due to an electrochemical reaction was not found and a good display could be obtained.

Since the present light emitting device has an extremely narrow electrode interval, it can be made thin and lightweight. Further, since the light emitting device at each intersection emits light isotropically, there is an advantage that the viewing angle is wide and it is easy to see from anywhere. Furthermore, the response time of light emission after light is applied after applying a voltage to the electrodes is fast because it is commensurate with the lifetime of the ions, and it can be applied to display of high-speed phenomenon. Further, from the above-described principle of light emission, the place where ions emit light is limited to the electrodes and the vicinity near the electrodes, and there are almost no ions that emit light away from the electrodes. Therefore, even if the electrodes are miniaturized to increase the resolution, light is emitted almost in the shape of the electrodes, and a display device with high resolution can be realized.

Incidentally, in the case of the solution of the electrochemiluminescent substance, an undesired reaction product may be produced due to slight impurities contained in the solution. In order to remove such reaction products, the substrates 33, 34 are optionally used.
A structure was adopted in which a thin tube was passed through a support for fixing the, and an external circulation pump for circulating the ruthenium complex solution was connected to the solution exchange section through the tube.

<Embodiment 6> In order to further enhance the function of the light emitting device of Embodiment 5, as shown in FIG. 9, the intersection of the X-axis scanning electrode 31 and the Y-axis scanning electrode 32 is provided with a large number of fine electrodes 31a. A prototype divided into 32a was manufactured. Fine electrode 3
The formation of 1a and 32a was performed by using a well-known semiconductor lithography technique as in the case of Example 5. The width of each of the fine electrodes 31a and 32a was set to 2 μm, and they were arranged at intervals of 4 μm.

<Embodiment 7> In Embodiments 5 and 6, the X-axis scanning electrode 31 and the Y-axis scanning electrode 32 are provided on different substrates 33 and 3, respectively.
In contrast to this, a light emitting device in which both electrodes are formed on a single substrate was manufactured by way of trial. The shape at the intersection was divided into fine electrodes as shown in FIG. 9, and an insulating layer was interposed at the intersection of the fine electrodes in the same manner as shown in FIG. 5 so as not to contact both electrodes. The overall structure of this embodiment is shown in FIG.

In FIG. 10, reference numerals 41 and 42 respectively denote an X-axis scanning electrode and a Y-axis scanning electrode formed on the glass substrate 44, and 43 denotes an insulating layer at the intersection. Although not shown in detail, both electrodes are divided into fine electrodes at the intersections, and the insulating layer 43 is composed of a large number of insulating layers formed at the respective intersections of the fine electrodes. The electrodes 41 and 42 and the insulating layer 43 were formed using the above-mentioned lithography technique. After that, a support member 45 and a lid member 46 made of transparent glass were installed to form an internal space above the electrodes 41 and 42, and a solution of a ruthenium complex was filled therein and sealed.

Example 5 of the implemented light emitting device
When the display performance was verified by driving in the same manner as above, no display defect due to an electrochemical reaction was found, and it was confirmed that good display was obtained.

<Embodiment 8> The embodiment shown in FIG. 11 is an electrochemiluminescent device using a solid electrolyte instead of the solution electrolyte of Embodiment 7. In the light emitting device of this example, the electrodes 41 and the electrodes 42 orthogonal to each other were formed by the same procedure as in Example 7, and then an organic solid electrolyte dissolved in an organic solvent was applied on both electrodes and dried, The solid electrolyte membrane 19 is formed.

A device adopting a structure in which opposing electrodes are formed on one substrate, such as the present light emitting device, is
It has the feature that the distance between the electrodes is almost constant even if a force is applied from the outside. Therefore, when a flexible polymer material is used for the substrate, a light emitting device that can be used even in a bent state can be obtained.

[0030]

According to the present invention, high luminous efficiency can be obtained by setting the electrode interval so that the diffusion time of ions is equal to or shorter than the lifetime of ions, and a novel light emitting device by electrochemiluminescence can be realized. You can In addition, since the light emitting device of the present invention can be manufactured by utilizing the lithography technology which is a semiconductor manufacturing technology, it is possible to manufacture the light emitting device with high reproducibility in a large amount and at a low cost.

[Brief description of drawings]

FIG. 1 is a process drawing for explaining the first half of a process of manufacturing an electrode of an embodiment of an electrochemiluminescent device according to the present invention.

FIG. 2 is a process drawing for explaining a latter half of the process following the process of FIG.

FIG. 3 is a structural diagram for explaining an example of an electrochemiluminescent device according to the present invention.

FIG. 4 is a structural diagram for explaining a second embodiment of the present invention.

FIG. 5 is a structural diagram for explaining a structure of an intersection of orthogonal electrodes.

FIG. 6 is a structural diagram for explaining a third embodiment of the present invention.

FIG. 7 is a structural diagram for explaining a fourth embodiment of the present invention.

FIG. 8 is a structural diagram for explaining a fifth embodiment of the present invention.

FIG. 9 is a structural diagram for explaining a sixth embodiment of the present invention.

FIG. 10 is a structural diagram for explaining a seventh embodiment of the present invention.

FIG. 11 is a structural diagram for explaining an eighth embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Silicon substrate 2, 23, 43 ... Insulating layer 3, 9 ... Resist layer 5 ... Gold vapor deposition film 6 ... Inner electrode wiring film 7 ... Outer electrode wiring film 6a, 7a ... Electrode part 6b, 7b ... Terminal part 8 , 10 ... Insulating film 16 ... O-ring 17, 35 ... Electrochemiluminescent substance solution 18, 46 ... Lid member 19 ... Solid electrolyte film 21 ... X electrode 22 ... Y electrode 31, 41 ... X-axis scanning electrode 32, 42 ... Y-axis scanning electrodes 33, 34, 44 ... Glass substrate 36 ... Signal source 37 ... X-axis selection drive circuit 38 ... Y-axis selection drive circuit 31a, 32a ... Fine electrode 45 ... Support

Claims (12)

[Claims] 1. A luminescent medium containing an electrochemiluminescent substance is disposed between opposing electrodes, and the shortest time for ions generated in one electrode to diffuse and reach the other electrode is an ion in the luminescent medium. An electrochemiluminescent device characterized in that the electrode interval is set so as to be less than or equal to the average life of the device. 2. The electrochemiluminescent device according to claim 1, wherein the counter electrode is two electrodes arranged concentrically. 3. The electrochemiluminescent device according to claim 1, wherein the counter electrodes are two electrodes which are orthogonal to each other with an insulating layer interposed at an intersection so as not to contact each other. 4. The electrochemiluminescent device according to claim 1, wherein the counter electrode is a multiplicity of scanning electrodes arranged orthogonally to the X-axis direction and the Y-axis direction. 5. The electrochemiluminescent device according to claim 3, wherein the scanning electrodes are divided into a plurality of fine electrodes at intersections that intersect each other at right angles. 6. The intersection formed by the fine electrodes is formed with an insulating layer interposed so that the scanning electrodes formed on the same surface of the substrate do not contact each other. The electrochemiluminescent device according to. 7. The electrochemiluminescent device according to claim 1, wherein the luminescent medium is a solution of an electrochemiluminescent substance. 8. The electrochemiluminescent device according to claim 7, wherein the electrochemiluminescent substance is an aromatic hydrocarbon. 9. The electrochemiluminescent device according to claim 7, wherein the electrochemiluminescent substance is a heterocyclic compound. 10. The electrochemiluminescent device according to claim 7, wherein the electrochemiluminescent substance is a metal complex. 11. A means for flowing and exchanging the solution of electrochemiluminescent material.
An electrochemiluminescent device according to claim 10. 12. The electrochemiluminescent device according to claim 1, wherein the luminescent medium is a solid electrolyte of an electrochemiluminescent substance.