JP2008078027A - Electrochemiluminescence device and driving method of electrochemiluminescence element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrochemiluminescence device driven by alternating current, having a high response speed, a low driving voltage and a high luminescence intensity, and a method for driving an electrochemiluminescence element.
An electrochemiluminescence element 10 is mainly composed of an electrode 2 and an electrode 4 arranged opposite to each other, and an electrolyte layer 3 arranged between these electrodes. The electrolyte layer 3 is formed of a solution in which a light emitting substance such as [Ru (bpy) ₃ ] (PF ₆ ) ₂ is dissolved in an organic polar solvent. The electrode 2 and the electrode 4 are composed of electrodes 2a and 4 made of a transparent conductive layer such as FTO (tin oxide doped with fluorine) formed on a substrate, and titanium oxide is formed only on one (electrode 2a). A porous electrode 2b is formed. An AC driving voltage having a waveform that causes light emission substantially only in the vicinity of the electrode 2 is applied from the AC power source 7 between these counter electrodes.
[Selection] Figure 1

Description

  The present invention relates to an electrochemiluminescence (ECL) device that can be suitably applied to a display device or a surface light source, and a method for driving an electrochemiluminescence element.

  In recent years, with the progress of high density and high integration of semiconductor circuits, it has become possible to downsize highly functional information terminals and make them portable devices. For this reason, research and development of a thin, lightweight, low power consumption display device that can be used as the display device has been activated.

  A liquid crystal display device (LCD) has been conventionally used as a portable display device for a small portable device or a notebook personal computer. In recent years, performance as a large screen display device has also been improved, and is used in place of a cathode ray tube (CRT) display device. However, the response speed is limited, and it is somewhat unsuitable for high-speed moving image display.

  Thus, organic electroluminescence (EL) elements and the like are attracting attention as next-generation display elements with a high response speed suitable for moving image display. In an organic EL element, electrons and holes from two opposing electrodes are injected into a charge transport layer or an organic light emitting layer by a tunnel process or a Schottky process, respectively, and the injected electrons and holes are regenerated in the organic light emitting layer. Luminescence is obtained by bonding.

  The organic EL element is expected to be applied to a display device and a surface light source because it can display full color, consumes less power, and can emit light in a large area. However, for organic EL elements, conventional electrode materials have insufficient electron and hole injection efficiency, and it is necessary to use lithium or magnesium having a low work function as an electrode material in order to improve charge injection efficiency. However, these materials are extremely reactive with water, oxygen, etc., and it is difficult to maintain their performance, and when driven at a high voltage, microscale peeling occurs at the interface between the electrode and the organic layer, and oxidation of the electrode occurs. As a result, a dark spot is formed due to the deterioration of the device.

  In addition, most of the light emitting layers of organic EL elements already in practical use are formed by a dry process mainly using vacuum deposition. In order to realize an increase in the area of an element and a reduction in manufacturing cost, it is more preferable that the element can be manufactured by a wet process at normal temperature and normal pressure, and problems in the element manufacturing process remain in the organic EL element.

  An electrochemiluminescence (ECL) element has been proposed as a solution to the drawbacks of such organic EL elements. The electrochemiluminescent device is a self-luminous device, like the organic EL device, except that it has an electrolyte layer containing a luminescent substance instead of the light emitting layer and the charge transport layer of the organic EL device.

FIG. 9 is a cross-sectional view showing a general structure of a conventional DC-driven electrochemiluminescence device 100. The electrochemiluminescent device 100 is mainly composed of an anode 102 and a cathode 104 which are arranged to face each other, and an electrolyte layer 103 which is arranged between these electrodes. The electrolyte layer 103 is made of a solution in which a light-emitting substance such as tris (bipyridyl) ruthenium hexafluorophosphate ([Ru (bpy) ₃ ] (PF ₆ ) ₂ ) is dissolved in an organic polar solvent such as acetonitrile. The electrolyte layer 103 is normally liquid, but may be semi-solid or solid.

Light emission in the electrochemiluminescent device 100 occurs through the following three processes. FIG. 9 schematically shows this process from left to right. In the following description, an example in which the luminescent substance is [Ru (bpy) ₃ ] (PF ₆ ) ₂ is shown, and 3+ in the figure represents an oxidized species [Ru (bpy) ₃ ] ³⁺ . + Enclosed in a circle represents a reduced species [Ru (bpy) ₃ ] ⁺ . [Ru (bpy) ₃ ] ²⁺ is abbreviated as Ru ²⁺ (the same applies hereinafter).

First, in the first process, an electrochemical oxidation reaction (1) is performed at the anode 102.
[Ru (bpy) ₃ ] ²⁺ → [Ru (bpy) ₃ ] ³⁺ + e ⁻ (1)
Oxidized species [Ru (bpy) ₃ ] ³⁺ is produced by the electrochemical reduction reaction at the cathode 104 (2)
[Ru (bpy) ₃ ] ²⁺ + e ⁻ → [Ru (bpy) ₃ ] ⁺ (2)
Produces reduced species [Ru (bpy) ₃ ] ⁺ .

Next, in the second process, the generated oxidized species and reduced species move to the counter electrode side in the electrolyte layer 103 by diffusion or the like. When the oxidized species and the reduced species collide during this movement process, the reaction formula (3)
[Ru (bpy) ₃ ] ³⁺ + [Ru (bpy) ₃ ] ⁺ → [Ru (bpy) ₃ ] ^{2+ *} + [Ru (bpy) ₃ ] ²⁺ (3)
As shown in FIG. ² , the excited state [Ru (bpy) ₃ ] ^{2+ *} and the ground state [Ru (bpy) ₃ ] ²⁺ are generated.

Next, in a third step, when the excited state ^{_{[Ru (bpy) 3] 2}} + * transitions to [Ru (bpy) _3] ²⁺ in the ground state, as shown in (4), the excited state And light having a frequency ν corresponding to the energy difference between the ground state and the ground state. In the equation (4), h is a Planck constant.
[Ru (bpy) ₃ ] ^{2+ *} → [Ru (bpy) ₃ ] ²⁺ + hν (4)

  A typical example of the luminescent material of the electrochemiluminescent device is a ruthenium (II) complex as in the above example. A solid-state electrochemiluminescence device using a ruthenium (II) complex was first reported by RWMurray et al. (KMManess, H.Masui, RMWightman, and RWMurray, J.Am.Chem.Soc., 119 3987-3993 (1997)). R.W.Murray et al. Used a tris (bipyridyl) ruthenium complex ester-bonded with polyethylene glycol as the ruthenium (II) complex, but the quantum efficiency was low and the device fabrication process was complicated.

  On the other hand, MFRubner et al. Reported an electrochemiluminescence device with a simple structure that can use the spin cast method (J.-K. Lee, D. Yoo, ESHandy, and MFRubner, Appl. Phys. Lett., 69, 1689-1690 (1996)). The ruthenium (II) complex used by M.F.Rubner et al. Is a tris (phenanthroline) complex.

  The above-mentioned electrochemiluminescence device has a simple structure and has an advantage that a large area can be manufactured at a low cost by a simple process by a wet process, and thus is expected as a display element and a large area surface light emitting device. Yes. However, in practice, the electrochemiluminescence device has a problem that the light emission efficiency is low and a sufficient light emission amount cannot be obtained, and it has been difficult to put it into practical use as a light emitting device.

  On the other hand, in Patent Document 1 described later, an electrochemiluminescence device is proposed in which a porous electrode having a porous structure is used as at least one of the counter electrodes. In Patent Document 1, it is possible to realize an improvement in emission intensity and a reduction in emission start voltage by efficiently performing an electrode reaction by using a porous electrode at least one and increasing the collision probability between an oxidized species and a reduced species. It is stated. An example in which the emission intensity is improved nearly 100 times by using a porous electrode made of titanium oxide on the cathode side is shown. Further, it is described that a normal DC voltage is applied to the electrochemiluminescence device, but light emission can be obtained even with an AC voltage.

Japanese Patent Laying-Open No. 2005-302332 (pages 3 and 4 and FIGS. 1 and 3)

  Although Patent Document 1 describes that light emission can be obtained even with an AC voltage, an example in which AC driving is actually performed is not shown.

FIG. 10 is a cross-sectional view showing an operation state of the AC-driven electrochemiluminescence device 110 using a conventional model (for example, see Toshiba Review, 60, 33-37 (2005)). Similar to the electrochemiluminescent device 100, the electrochemiluminescent device 110 is mainly composed of the electrodes 112 and 114 arranged opposite to each other, a solvent such as acetonitrile, and a luminescent material such as [Ru (bpy) ₃ ] PF _6. And an electrolyte layer 113. The principle of light emission is the same as in the case of direct current drive, but there are characteristics different from direct current drive in the movement of the generated oxidized and reduced species and the region in the electrolyte layer where light emission occurs. Hereinafter, these points will be described.

FIG. 10A shows a change that occurs in a period S in which the electrode 112 is kept at a higher potential than the electrode 114 in one cycle. In this period, the electrode 112 functions as an anode and the electrode 114 functions as a cathode.
[Ru (bpy) ₃ ] ²⁺ → [Ru (bpy) ₃ ] ³⁺ + e ⁻ (1)
Oxidized species [Ru (bpy) ₃ ] ³⁺ is generated by the electrode 114, and the reduction reaction (2) occurs at the electrode 114.
[Ru (bpy) ₃ ] ²⁺ + e ⁻ → [Ru (bpy) ₃ ] ⁺ (2)
Produces reduced species [Ru (bpy) ₃ ] ⁺ . The generated oxidized species and reduced species attempt to move in the electrolyte layer 113 to the counter electrode side by diffusion or the like.

FIG. 10B shows a change that occurs in a period T in which the electrode 112 is kept at a lower potential than the electrode 114 in one cycle. In this period, the electrode 112 functions as a cathode and the electrode 114 functions as an anode.
[Ru (bpy) ₃ ] ²⁺ + e ⁻ → [Ru (bpy) ₃ ] ⁺ (2)
Reduces species [Ru (bpy) ₃ ] ⁺ , and the electrode 114 oxidizes (1).
[Ru (bpy) ₃ ] ²⁺ → [Ru (bpy) ₃ ] ³⁺ + e ⁻ (1)
Produces oxidized species [Ru (bpy) ₃ ] ³⁺ . The generated oxidized species and reduced species attempt to move in the electrolyte layer 113 to the counter electrode side by diffusion or the like.

As described above, the characteristic of AC driving is that oxidation and reduction occur alternately at the same electrode, and the oxidized species and the reduced species are generated with a slight time difference. For example, in the electrode 112, oxidized species are produced by oxidation in the period S, and this oxidized species starts to move toward the electrode 114. When the polarity of the electrode is reversed in the period T, as shown in FIG. In addition, reducing species are produced on the electrode 112 by a reduction reaction, and the moving direction of the oxidized species produced in the period S is reversed, and the oxidized species move toward the electrode 112. For this reason, in the vicinity of the electrode 112, the reducing species produced in the period T and the oxidizing species produced in the period S coexist, and reaction formulas (3) and (4) are caused by collision between the two.
[Ru (bpy) ₃ ] ³⁺ + [Ru (bpy) ₃ ] ⁺ → [Ru (bpy) ₃ ] ^{2+ *} + [Ru (bpy) ₃ ] ²⁺ (3)
[Ru (bpy) ₃ ] ^{2+ *} → [Ru (bpy) ₃ ] ²⁺ + hν (4)
As shown in FIG. 4, the reaction proceeds and light emission occurs. Similarly, in the period S, as shown in FIG. 10A, the oxidized species generated on the electrode 112 and the reduced species produced in the period T coexist, and the reaction ( 3) and (4) occur and light emission occurs.

  The concentration of oxidized species accumulated in the vicinity of the electrode 112 in the period S is maximized when the period S ends and an attempt is made to move to the period T, and the concentration of reducing species accumulated in the vicinity of the electrode 112 in the period T. Is maximized when the period T ends and the period S is about to be shifted to. Therefore, it is expected that the light emission intensity in the vicinity of the electrode 112 takes the maximum value immediately after the polarity of the voltage applied to the counter electrode is reversed twice during one cycle.

  The light emission in the vicinity of the electrode 114 is the same as the light emission in the vicinity of the electrode 112 except that the phase is shifted by a half cycle, and the polarity of the voltage applied to the counter electrode is reversed twice during one cycle. Immediately after that, the luminescence intensity is expected to reach the maximum value. From the above, in the electrochemiluminescence device 110 driven by alternating current, it is expected that the emission intensity takes the maximum value twice in one cycle for each electrode and four times in total for the whole device.

  Comparing the direct current drive and the alternating current drive, in the direct current drive, it is necessary to cut the electrolyte layer 103 until the oxidized species and the reduced species collide to emit light, whereas in the alternating current drive, this is not necessary. Both collide near the electrode and emit light. For this reason, in DC driving, the response speed depends on the thickness of the electrolyte layer 103 and is generally slow, whereas in AC driving, the response speed does not depend on the thickness of the electrolyte layer 113 and is fast. Further, when the lifetime of the oxidized species or reduced species is short, in the direct current drive, the ratio of oxidized species or reduced species that disappear while traversing the electrolyte layer 103 before collision increases. In the AC drive, there is an advantage that the ratio of oxidized species or reduced species lost before the collision is small, and the luminous efficiency is increased.

  Further, in the DC drive, there is a problem that impurities are accumulated in one electrode, whereas in the AC drive, such a problem does not occur.

  As described above, although AC driving is expected to have many advantages over DC driving, there has been no report that has been studied in detail regarding an electrochemiluminescence device for AC driving an electrochemiluminescence element.

  The present invention has been made in view of such a problem, and an object thereof is an electrochemiluminescence device in which an electrochemiluminescence element is driven by alternating current, and an electroluminescence device having a high response speed, a low driving voltage, and a high emission intensity. It is an object to provide a chemiluminescent device and a method for driving an electrochemiluminescent element.

  As a result of intensive studies to solve the above problems, the inventor of the present invention, in an electrochemiluminescence device in which an electrochemiluminescence element is driven by alternating current, twice each cycle for each electrode, the entire element Contrary to the above expectation that the emission intensity has a maximum value four times, the maximum emission intensity is observed only once per cycle for each electrode, or no emission can be obtained. The present invention has been completed while discovering that there is a case where the error occurs and investigating the cause.

That is, the present invention provides an electrolyte layer disposed between the counter electrodes, the oxidized species generated by oxidation of the chemical species included in the electrolyte layer in the counter electrode, and the same type of the chemical species included in the electrolyte layer. Alternatively, in an electrochemiluminescence device in which an electrochemiluminescence element that emits light by a reaction with a reduced species generated by reducing another chemical species at the counter electrode is AC driven,
The present invention relates to an electrochemiluminescence device characterized in that light emission occurs substantially only in the vicinity of one electrode of the counter electrode.

The present invention also provides an electrolyte layer disposed between the counter electrodes, the oxidized species generated by oxidation of the chemical species included in the electrolyte layer in the counter electrode, and the same type of the chemical species included in the electrolyte layer. Alternatively, in the method of driving an electrochemiluminescent device, the electrochemiluminescent device that emits light by a reaction with a reduced species generated by reducing another chemical species at the counter electrode is AC driven.
The present invention relates to a driving method for an electrochemiluminescence device, characterized in that a driving voltage for causing light emission is supplied substantially only in the vicinity of one electrode of the counter electrode.

  Here, “substantially” means that the light emission performance of the electrochemiluminescence device or the electrochemiluminescence element is actually determined by light emission in the vicinity of the one electrode. It means that the light emission intensity in the vicinity of the other electrode is approximately 10% or less and at most 20% or less of the light emission intensity in the vicinity of the one electrode.

  As a result of repeated research, the present inventor has reduced the oxidized species generated by oxidation of the chemical species and the same or different species as the chemical species in an electrochemiluminescent device driven by alternating current. There is a reaction in which the reduced species generated in this manner disappear on the counter electrode due to the reverse reaction of these production reactions, and this becomes an important reaction path for reducing the luminous efficiency of the oxidized species and the reduced species. I found that. In an electrochemiluminescent device driven by direct current, there is no need to consider such a reverse reaction, and therefore the reaction system of the electrochemiluminescent device driven by alternating current is much more complex than in the case of direct current drive.

  Further, in the electrochemical reaction system, the rate of the oxidation reaction at the anode and the rate of the reduction reaction at the cathode are equal, and both cannot be set independently. For this reason, it is impossible to find a condition that can optimize both the light emission in the vicinity of both electrodes of the counter electrode, or even if possible, it is necessary to conduct extremely complicated studies.

Therefore, in the present invention, the method of optimizing both the light emission in the vicinity of both electrodes of the counter electrode is abandoned, and the light emitted by the electrochemiluminescence device is concentrated in the vicinity of the one electrode, and in the vicinity of the one electrode. Select a method to optimize the light emission. That is, the electrochemiluminescence device of the present invention is
The method of driving the electrochemiluminescence device of the present invention is characterized in that light emission occurs substantially only in the vicinity of one of the counter electrodes.
A driving voltage for causing light emission is supplied substantially only in the vicinity of one electrode of the counter electrode.

  This method does not throw away half of the luminescence generated in the vicinity of both poles, but normally concentrates the luminescence scattered in two electrodes in the vicinity of the one electrode. The decrease in the emission intensity due to concentration in the light is slight. In addition, finding conditions for optimizing the light emission that occurs in the vicinity of the one electrode is much easier than finding conditions that optimize both the light emission in the vicinity of both poles. Therefore, according to the present method, as a result, an electrochemiluminescence device having a quick response speed, a low driving voltage, and a high emission intensity, more easily and reliably than the method of emitting light in the vicinity of both electrodes of the counter electrode, and A method for driving an electrochemiluminescence device can be provided.

  In the present invention, it is preferable that an AC power supply for supplying the AC drive voltage is connected between the counter electrodes.

  The one electrode may be a porous electrode having a porous structure. Alternatively, the surface area of the one electrode is preferably larger than the surface area of the other electrode of the counter electrode. In these cases, the surface area of the one electrode is preferably 10 times or more the surface area of the other electrode. Thus, by making the surface area of the one electrode larger than the surface area of the other electrode, it is possible to concentrate light emission that would normally be dispersed in the vicinity of the two electrodes in the vicinity of the one electrode. .

  At this time, the porous electrode is preferably made of a metal and / or a metal oxide, and the metal oxide preferably contains titanium oxide. Titanium oxide is an electrically conductive and chemically stable material.

  In addition, the AC drive is performed by an AC voltage having a duty ratio different from 1 and / or an AC voltage having a DC component, and the oxidation is performed in the vicinity of the one electrode over a long time in one cycle of the AC drive. After the seeds or the reduced species are accumulated and the polarity of the driving voltage is reversed, the accumulated oxidized species or the reduced species may react quickly in a short time to cause light emission.

  The electrochemiluminescence device of the present invention is preferably configured as a surface light source. Alternatively, the counter electrode is preferably provided in a pattern for forming a plurality of light emitting regions, and is preferably configured as a display device.

  Next, a preferred embodiment of the present invention will be specifically described with reference to the drawings.

FIG. 1 is a cross-sectional view showing the structure of an electrochemiluminescence (ECL) apparatus based on this embodiment. As shown in FIG. 1, the electrochemiluminescent device 10 mainly includes an electrode 2 and an electrode 4 that are arranged to face each other, and an electrolyte layer 3 that is arranged between these electrodes. The electrode 2 and the electrode 4 are bonded via a spacer 6 to form a cell. The electrolyte layer 3 is a solution in which a light emitting substance such as tris (bipyridyl) ruthenium hexafluorophosphate ([Ru (bpy) ₃ ] (PF ₆ ) ₂ ) is dissolved in an organic polar solvent such as acetonitrile. The electrolyte layer 3 is normally liquid, but may be semi-solid or solid.

  The electrode 2 includes an electrode 2a and a porous electrode 2b that is the porous electrode. The electrode 2a is made of a transparent conductive layer such as FTO (tin oxide doped with fluorine) formed on a substrate 1 such as a glass substrate by a sputtering method or the like. The porous electrode 2b includes a porous layer of titanium oxide formed by forming a titanium oxide fine particle layer on the electrode 2a by coating or the like and sintering the layer. The counter electrode 4 is made of a transparent conductive layer such as FTO formed on a substrate 5 such as a glass substrate by a sputtering method or the like.

  The feature of the electrochemiluminescence device 10 is that a porous electrode 2b having a porous structure is used as one of the counter electrodes. As shown in Comparative Example 1 of Example 1 described later, when the electrode 2 is not provided with the porous electrode 2b and both the counter electrodes are made of only the FTO conductive layer, the light emission start voltage is large and the light emission amount is small. Similarly, as shown as Comparative Example 2, when porous electrodes are provided on both counter electrodes, light emission cannot be obtained. Therefore, what is important in this case is that the porous electrode is provided not on both of the counter electrodes but on one side.

  Patent Document 1 shows an example in which, in the case of direct current drive, a porous electrode is used for both the anode and the cathode, and a light emission intensity equivalent to that obtained when a porous electrode is used only on the cathode side is obtained. Compared to this example, the operation of the electrochemiluminescence device 10 by AC driving is estimated to be much more complicated than the operation at the time of DC driving. Before examining this problem in detail, the configuration of the electrochemiluminescent device 10 other than the above features will be described below.

  Examples of the shapes of the electrode 2 and the electrode 4 include two types of a parallel plate electrode and a comb electrode. The parallel plate electrode is formed by sandwiching a light emitting layer between a pair of parallel electrodes and arranging the light emitting layer in parallel. In this case, at least one of the electrodes needs to be transparent, and the transmittance is preferably 70% or more.

  On the other hand, the comb-shaped electrodes are arranged such that a pair of comb-shaped electrodes alternately enter between the counter electrodes. In this case, it is necessary to dispose a pair of comb-shaped electrodes on the substrate, and light emission can be extracted from the substrate side by using a transparent substrate having a transmittance of 70% or more. preferable.

  As electrode materials, platinum, gold, copper, titanium, palladium, tin, nickel, silver, aluminum and other conductive metals, and alloys containing these metals, indium oxide, titanium oxide, tin oxide, zinc oxide, Examples thereof include oxide semiconductors mainly composed of niobium oxide, ITO (Indium Tin Oxide), and various conductive carbons.

  The electroluminescence of electrochemiluminescence depends on the collision probability between the reduced dye and the oxidized dye. For this reason, in order to promote the oxidation-reduction reaction and increase the collision probability, as described above, it is preferable to make one electrode porous to increase the reaction area. The surface area of the porous electrode is preferably at least 100 times its projected area (installation area).

  This porous electrode can be formed by processing the above-mentioned material by necking by heating fine particles, a sol-gel method using a polymer as a template, a plating method, or the like, and its manufacturing method is not limited at all.

  The electrode 4 which is the other electrode of the counter electrode can be formed by vacuum deposition, sputtering, sol-gel method, plating method, spin coating method, spray method or the like, and the formation method is not particularly limited. Further, the surface may be smooth or uneven, and may be a porous electrode as long as the surface area is 1/10 or less of the surface area of the porous electrode 2b.

  The luminescent substance contained in the electrolyte layer 3 is not particularly limited as long as it is a compound having fluorescence in the visible light region to the ultraviolet light region.

  For example, preferred examples of the luminescent substance include aromatic conjugated compounds, aromatic amine compounds, aromatic enamine compounds, heterocyclic conjugated compounds, and oxazole compounds. Specifically, 9,10-diphenylanthracene, rubrene (5,6,11,12-tetraphenylnaphthacene), triphenylene (9,10-benzophenanthrene), monophenyltriphenylene, 2,3-diphenyltriphenylene, 2 , 6,10-triphenyltriphenylene, 2,6,10-tri (p-cyanophenyl) triphenylene, 9- (α, -dicyanovinyl) anthracene, 9-styrylanthracene, 2,7-diphenylphenanthrene, N, N , N ′, N′-tetraphenylbenzidine, N, N′-di (m-tolyl) benzidine, N, N′-di (α-naphthyl) benzidine, tri (biphenyl-4-yl) amine, etc. .

  In terms of chemical structure, those having two or more aryl groups represented by a phenyl group as the number of substituents such as 2,6,10-triphenyltriphenylene and tri (biphenyl-4-yl) amine are preferable. The larger the number of aryl groups, the better. However, from the viewpoints of synthesis and solubility, meltability, etc., a substitution number of about 4 is suitable. Therefore, as the light-emitting substance, a compound in which the ring-forming carbon of the cyclic hydrocarbon compound or the heterocyclic compound is substituted with at least two substituted or unsubstituted phenyl groups is used. Is particularly preferable.

  In addition, various polymer light-emitting substances are described in JP-A-6-166743, and these can be used. Specific examples include aromatic conjugated polymer compounds composed of arylene: acetylene bonds such as poly (p-phenylene-ethynylene) and poly (p-phenylene-ethynylene-m-phenylene-ethynylene).

  In addition, a metal complex compound containing a nitrogen-containing heterocyclic compound as a multidentate ligand can also be suitably used as the light-emitting substance of the electrochemiluminescence device used in this embodiment. These compounds have recently attracted attention as spectral sensitizing dyes for organic solar cells, and various materials have been obtained (see J. Am. Chem. Soc., 115, 632 (1993)). ). The chemical structures of these compounds include bispyridine as a ligand and a part and all of bispyridine in a cyclic structure such as 2,10-phenanthroline and 1,8-naphthyridine, and ruthenium (II). Metal complexes composed of metal ions are preferred. Specifically, bispyridine-based metal complex compounds such as tris (2,2′-bipyridyl) ruthenium (II) and cis-bis (thiocyanato) -bis (2,2′-bipyridyl) ruthenium (II) are particularly preferable. .

  Since the emission intensity of the electrochemiluminescent device is substantially proportional to the concentration of the luminescent material in the electrolyte layer, the luminescent material preferably has higher solubility in the solvent of the electrolyte layer. Further, the luminescent substance is not necessarily dissolved or dispersed in the electrolyte layer and may be fixed on the electrode surface. Alternatively, dissolution or dispersion and fixation on an electrode may be used in combination.

  The electrolyte layer in which the light-emitting substance is dissolved or dispersed may be in any state such as a gel state or a solid state as well as a liquid state. For example, a highly viscous liquid such as an ionic liquid may be used as the solvent. Alternatively, a conductive polymer or the like may be added, mixed with nanoparticles to be gelled, or a reactive site may be added to the ionic liquid or polymer to be polymerized and solidified. Moreover, there is no problem even if various additives such as a supporting electrolyte, an antioxidant and a light stabilizer are added.

  Next, the operation of the electrochemiluminescence device 10 driven by alternating current is analyzed in detail, and conditions for improving the light emission characteristics are examined. 2A to 2C show a case where a drive voltage (amplitude ± 2 V, frequency 10 Hz) having a square wave waveform is applied between the counter electrodes of the electrochemiluminescence device 10 using the AC power source 7. FIG. 6 is a graph showing changes in driving voltage applied to electrode 2, current flowing from electrode 2 to electrolyte layer 3, and emission intensity over time.

  From FIG. 2, it can be seen that a large current flows immediately after the polarity of the drive voltage is reversed twice in one cycle, however, light emission occurs only once. From the detailed observation of this light emission, the light emission occurs in the vicinity of the electrode 2 provided with the porous electrode 2b, and a large amount immediately after the polarity of the electrode 2 is reversed from the low potential side (negative) to the high potential side (positive). It can be seen that light emission occurs.

On the other hand, in Comparative Example 1 mentioned above, light emission occurred in the vicinity of each electrode immediately after the polarity was reversed from the low potential side (negative) to the high potential side (positive). It turns out that it becomes the maximum twice. Summarizing the above findings, light emission occurs in the AC drive in the vicinity of the electrode whose polarity is reversed from the low potential side (negative) to the high potential side (positive)
When no porous electrode is provided on any electrode (Comparative Example 1 described later)
... The emission intensity is maximized once per cycle for each electrode and twice in total. However, the emission start voltage is large and the emission intensity is small.
When a porous electrode is provided on one electrode (this embodiment, Example 1 described later)
... The emission intensity reaches a maximum once per cycle. Light emission occurs in the vicinity of the porous electrode 2b, the light emission start voltage is low, and the light emission intensity is high.
When porous electrodes are provided on both electrodes (Comparative Example 2 described later)
... Does not emit light.

  FIGS. 3 (a) and 3 (b) are graphs showing the time change of current and light emission intensity in one cycle shown by encircled by dotted lines in FIGS. 2 (b) and 2 (c), with the time axis etc. enlarged. is there. From FIG. 3, the current change after the potential of the electrode 2 is reversed from the low potential side (negative) to the high potential side (positive) can be roughly divided into three periods A to C. It can be seen that the current change after the potential is inverted from the high potential side (positive) to the low potential side (negative) can be roughly divided into two periods, period D and period E. Luminescence occurs mainly during period B.

  4 and 5 are cross-sectional views showing the main operating states of the electrochemiluminescence device 10 in the period A to the period E in a model manner with assumptions. In the periods A to C, since the electrode 2 is on the high potential side, the electrode 2 functions as an anode and the electrode 4 functions as a cathode. In the periods D and E, since the electrode 2 is on the low potential side, the electrode 2 functions as a cathode and the electrode 4 functions as an anode. In the reaction formulas attached to the right side of the figure, complex ions are shown with ligands omitted. Other precautions are the same as in FIG.

  There are three possible causes for the current flowing in the periods A and B. One is that immediately after the polarity of the electrode 2 is reversed, a current flows by rearranging the charges in the vicinity of the electrode in response to a change in the drive voltage, as in the case where a stepped voltage is applied to a capacitor or the like. .

As the current due to the electrode reaction, the reduced species [Ru () accumulated in the vicinity of the electrode by the reduction reaction (2) at the electrode 2 and the oxidation reaction (1) at the electrode 4 in the period E (described later) of the previous cycle, respectively. bpy) ₃ ] ⁺ and the oxidized species [Ru (bpy) ₃ ] ³⁺ return to [Ru (bpy) ₃ ] ^{2+ due} to the reverse reaction at the electrode as shown in FIG. Flowing. That is, at the electrode 2, the reverse reaction (-2) of the reduction reaction (2)
[Ru (bpy) ₃ ] ⁺ → [Ru (bpy) ₃ ] ²⁺ + e ⁻ (-2)
As a result, the reduced species [Ru (bpy) ₃ ] ⁺ disappears, and at the electrode 4, the reverse reaction (-1) of the oxidation reaction (1)
[Ru (bpy) ₃ ] ³⁺ + e ⁻ · → [Ru (bpy) ₃ ] ²⁺ (−1)
As a result, the oxidized species [Ru (bpy) ₃ ] ³⁺ disappears.

In addition, [Ru (bpy) ₃ ] ²⁺ reacts on electrode 2 as a current from another electrode reaction (1)
[Ru (bpy) ₃ ] ²⁺ → [Ru (bpy) ₃ ] ³⁺ + e ⁻ (1)
Oxidized to produce oxidized species [Ru (bpy) ₃ ] ³⁺ , and [Ru (bpy) ₃ ] ²⁺ reacts on electrode 4 (2)
[Ru (bpy) ₃ ] ²⁺ + e ⁻ → [Ru (bpy) ₃ ] ⁺ (2)
To generate a reduced species [Ru (bpy) ₃ ] ⁺ .

In period B, light emission occurs as shown in FIG. This is because the oxidized species and the reduced species collide in the vicinity of the porous electrode 2b to react (3) and (4).
[Ru (bpy) ₃ ] ³⁺ + [Ru (bpy) ₃ ] ⁺ → [Ru (bpy) ₃ ] ^{2+ *} + [Ru (bpy) ₃ ] ²⁺ (3)
[Ru (bpy) ₃ ] ^{2+ *} → [Ru (bpy) ₃ ] ²⁺ + hν (4)
Means that is happening. Therefore, in the period B, the oxidized species [Ru (bpy) ₃ ] ³⁺ generated by the oxidation reaction (1) on the electrode 2 reacts with the reducing species present in the vicinity to generate luminescence. Conceivable. There is a time delay of about 1 ms before the light emission starts after the polarity of the electrode is reversed. At present, the cause of this time delay is not exactly clarified, but during the time delay period A, the process of preparing light emission in the period B, that is, the rearrangement of charges in the vicinity of the electrode, and the reaction (− 2), (-1), (1), (2), etc. occur.

  In electrolysis, the magnitude of the current flowing through the anode and the magnitude of the current flowing through the cathode are the same, so the oxidation reaction occurring at the anode and the reduction reaction occurring at the cathode proceed at the same reaction rate. In this case, either the oxidation reaction or the reduction reaction is often a rate-limiting reaction. Since the current in period A decreases exponentially and the surface area of the electrode 4 is significantly smaller than the surface area of the counter electrode 2b, the reaction occurring at the electrode 4 in the period A (−1 ) Is considered to be the rate-limiting reaction. Therefore, the surface area of the electrode 4 should be small in order to reduce the reducing species that disappear on the electrode 2 during the period A and improve the luminous efficiency.

  There is no direct evidence as to what reaction is occurring at the electrode 4 during period B. However, as will be described later, the main reaction at the electrode 4 in the period C is the reaction (2). Considering the difference between the reaction rate in the period B and the reaction rate in the period C, the main reaction (2) in the period C is not likely to be the main reaction in the period B. Therefore, the reaction occurring at the electrode 4 is presumed to be the same reaction (−1) as in the period A. However, since a current curve that is nearly flat in period B is obtained with respect to the current curve in period A that decreases exponentially, the rate-limiting reaction in period B is the reaction (1) that occurs at electrode 2. Conceivable.

In the reaction in the period A and the period B, since almost all of the oxidized species and reduced species accumulated in the vicinity of the electrode in the E period of the previous cycle disappear, the reaction due to these disappears mainly in the period C, and FIG. As shown in FIG. 2, as the main reaction, the oxidation species [Ru (bpy) ₃ ] ³⁺ is generated in the electrode 2 by the oxidation reaction (1) and accumulated in the vicinity of the electrode 2, and the reduction reaction (2) in the electrode 4. Reduced species [Ru (bpy) ₃ ] ⁺ are generated and accumulated in the vicinity of the electrode 4.

  The rate-limiting reaction in period C is considered to be reaction (2) occurring at electrode 4. The reaction (2) in the period C occurs on the electrode 4 having a small surface area, and the reaction (2) itself is less likely to occur than the reaction (1), and thus is included in the light emission process of the electrochemiluminescence device. It is the slowest reaction process among all reaction processes. Therefore, the amount of oxidized species and reduced species accumulated in the vicinity of the electrode 2 and the electrode 4 in the period C is much smaller than the amounts of oxidized species and reduced species accumulated in the period E described later. This is considered to be one of the factors that cause no light emission in the vicinity of the electrode 4.

  As described above, the rate-limiting reaction is different in each of the periods A to C, and it is considered that the current curves in the periods A to C have a complicated shape. In addition, since other reactions occur in parallel with the main reaction, the current curve has a more complicated shape.

  There are two possible causes for the current flowing in the period D. One is that immediately after the polarity of the electrode 2 is reversed, a current flows by rearranging the charges in the immediate vicinity of the electrode in accordance with the change of the drive voltage, as described above.

As shown in FIG. 5 (d), the current due to the electrode reaction is mainly caused by the oxidation reaction (1) at the electrode 2 and the reduction reaction (2) at the electrode 4 during the period C. A current flows due to the accumulated oxidized and reduced species returning to [Ru (bpy) ₃ ] ^{2+ due} to the reverse reaction at the electrode. That is, in the electrode 2, the reverse reaction (-1) of the oxidation reaction (1).
[Ru (bpy) ₃ ] ³⁺ + e ⁻ · → [Ru (bpy) ₃ ] ²⁺ (−1)
As a result, the oxidized species [Ru (bpy) ₃ ] ³⁺ disappears, and at the electrode 4, the reverse reaction (-2) of the reduction reaction (2)
[Ru (bpy) ₃ ] ⁺ → [Ru (bpy) ₃ ] ²⁺ + e ⁻ (-2)
As a result, the reduced species [Ru (bpy) ₃ ] ⁺ disappears.

In parallel to the above reaction, [Ru (bpy) ₃ ] ²⁺ is reduced by reaction (2) on electrode 2 and [Ru (bpy) ₃ ] ²⁺ is oxidized by reaction (1) on electrode 4. However, since the amount of oxidized and reduced species accumulated in the period C is small, almost all of these oxidized and reduced species are lost during the period D due to the reverse reaction, resulting in light emission. Does not contribute. For this reason, in the period D, there is no light emission period corresponding to the period B in the periods A and B.

In the period E, almost all of the oxidized species and reduced species accumulated in the vicinity of the electrode in the period D disappear, and as a main reaction, as shown in FIG.
[Ru (bpy) ₃ ] ²⁺ + e ⁻ → [Ru (bpy) ₃ ] ⁺ (2)
Reduced species [Ru (bpy) ₃ ] ⁺ is generated and accumulated in the vicinity of the electrode 2, and the oxidation reaction (1) occurs at the electrode 4.
[Ru (bpy) ₃ ] ²⁺ → [Ru (bpy) ₃ ] ³⁺ + e ⁻ (1)
As a result, oxidized species [Ru (bpy) ₃ ] ³⁺ are generated and accumulated in the vicinity of the electrode 4.

In this way, the state at the end of the period E and the state at the start of the period A shown in FIG. In this state, a large amount of reducing species [Ru (bpy) ₃ ] ⁺ is accumulated in the vicinity of the electrode 2, and oxidized species [Ru (bpy) ₃ ] ³⁺ is rapidly generated in the period B, and the reaction ( The main condition for improving the emission intensity is that the excited species [Ru (bpy) ₃ ] ^{2+ *} is efficiently produced by 3).

In [Ru (bpy) ₃ ] (PF ₆ ) ₂ as a luminescent substance, the light emission occurs in the AC-driven electrochemiluminescence device with the polarity reversed from the low potential side (negative) to the high potential side (positive) It has already been described that it is in the vicinity of the electrode. As shown in FIG. 4B, light emission occurs when oxidized species are generated where reduced species are accumulated, but conversely, reduced species are generated where oxidized species are accumulated. Also means no light emission. The reason for this is unknown, but when [Ru (bpy) ₃ ] (PF ₆ ) ₂ is used as the luminescent substance, the oxidized species is +3 valent, so it is easily attracted to the cathode, and the reverse reaction at the electrode (−1 ) Is likely to occur. Therefore, it is considered that depending on the luminescent substance, the behavior of the reducing species and the oxidizing species is reversed, and light emission may occur near the electrode whose polarity is reversed from the high potential side (positive) to the low potential side (negative).

  In addition, as described above, in alternating current driving, if a porous electrode is provided on both counter electrodes, no light is emitted. The reason for this is also unknown, but as described above, it can be understood that the reverse reaction (−1) occurring at the electrode 4 is the rate-limiting reaction during the period A. In this case, if the electrode 4 is provided with a porous electrode, the surface area of the electrode 4 is increased, so that the reverse reaction (−1), that is, the rate-limiting reaction at the electrode 4 is increased. For this reason, the speed | rate of the reverse reaction (-2) of the reduction | restoration seed | species in the electrode 2 limited by rate-limiting reaction also becomes high. As a result, the reduced species that disappear due to the reverse reaction (−2) increase during the period A, and when this becomes significant, almost all of the reduced species disappears in the period A, and light emission does not occur.

  From the above consideration, paying attention to the rate-determining step, the conditions and methods for improving the emission intensity are derived as follows.

1. Increasing the amount of reducing species accumulated in period E.
In order to increase the reaction rate of the reduction reaction (2) at the electrode 2, the surface area of the electrode 2 is increased. In addition, the period E is lengthened to increase the amount of accumulated reduced species, and in order to effectively use the period of one cycle, the period C that does not contribute to light emission is shortened to the minimum necessary length. This can be realized by using a square wave whose duty ratio deviates from 1 when a driving voltage having a square wave waveform is applied.

2. To reduce the amount of reducing species that disappear in period A.
When the rate-limiting reaction in the period A is the reaction (-1) in the electrode 4, the surface area of the electrode 4 is decreased. Further, a period in which a voltage is applied so as to keep the reducing species away from the electrode 2 and cause no electrode reaction is provided between the period E and the period A.

3. Quickly generate oxidized species in period B, and efficiently react oxidized and reduced species.
The surface area of the electrode 2 is increased, and the concentration of the luminescent substance in the electrolyte layer is increased to increase the reaction rate of the oxidation reaction (1) at the electrode 2.

  FIG. 6 is a graph showing the relationship between the duty ratio of the square wave driving the electrochemiluminescent device 10 and the emission intensity. 6A to 6C, the duty ratio increases from 1% to 10%, and the amount of light emission increases corresponding to the increase in period B. Thereafter, until the duty ratio increases from 10% to 50% until FIG. 6D, the light emission amount is substantially constant, but in FIGS. 6D to 6F, the duty ratio is 50% to 90%. Further increase in the emission intensity decreases. This corresponds to the fact that the reduction species cannot be sufficiently accumulated in the vicinity of the electrode 2 due to the shortening of the period E.

  FIG. 7 shows an example in which an ideal drive voltage is formed by superimposing a DC component on a square wave drive voltage having an optimum duty ratio. In one cycle of AC driving, as described above, the period E is made sufficiently long, reducing species are accumulated in the vicinity of the electrode 2 over a long period of time, and after instantaneous reversal of the polarity of the driving voltage, the period Compared to E, it is preferable to quickly generate oxidized species during a short period B and to cause light to react efficiently with the accumulated reduced species.

  At this time, as shown in FIG. 7, the luminous efficiency can be further improved by applying a driving voltage having an offset by superimposing the DC voltage components. Actually, when the voltage (absolute value) applied during the period of keeping the electrode 2 negative (periods D and E) is large, the voltage (absolute value) applied during the period of keeping the electrode 2 positive (periods A to C). Even if is small, light emission occurs. For example, when the applied voltage on the negative side is −2.3 V, light emission occurs even when the applied voltage on the positive side is about 0.4 V. As described above, if a sufficient amount of reducing species is formed by applying a large negative voltage in the period E, it is possible to reduce the voltage to be applied for generating the oxidizing species in the period B. . In this manner, the disappearance of the oxidized species in the period A can be suppressed, and highly efficient light emission can be realized. That is, as shown in FIG. 7, the drive voltage having the short positive voltage application time, the long negative voltage application time, and the negative offset is the drive voltage that causes light emission most efficiently. .

  FIG. 8 is an external view showing an example of an electrochemiluminescence device configured as a passive matrix display device. The electrochemiluminescence device of the present invention can be basically used as a surface light source, but can be used as a display device by forming a plurality of light emitting regions. FIG. 8 is intended to illustrate such a possibility. In the apparatus shown in FIG. 8, each counter electrode is composed of a plurality of strip electrodes, and the strip electrodes are arranged in the vertical direction on one electrode side of the counter electrode, and are arranged in the horizontal direction on the other electrode side. A matrix is formed. When a driving voltage is applied to the counter electrode, a region sandwiched between the vertical electrode and the horizontal electrode selectively emits light. This example shows that a passive matrix display device can be easily manufactured.

  Next, the electrochemiluminescence device of the present invention will be described more specifically with reference to examples and comparative examples. The electrochemiluminescence device of the present invention is not limited to the examples shown below.

Examples 1 and 2
In Examples 1 and 2, the electrochemiluminescence device 10 described in the embodiment with reference to FIG. 1 was produced. A transparent conductive layer made of FTO was formed on the substrate 1 made of a glass substrate by a sputtering method to obtain an electrode 2a. A titanium oxide dispersion P25 (manufactured by Nippon Aerosil Co., Ltd.) is applied thereon, and then heated to 500 ° C. to form a porous electrode 2b made of titanium oxide and having a thickness of 10 μm. The electrode 2 is formed by the electrodes 2a and 2b. I made it up. As the counter electrode 4, a transparent conductive layer made of FTO was formed on a substrate 5 made of a glass substrate by sputtering. Next, the electrode 2 and the electrode 4 were bonded together through a spacer 6 having a thickness of 30 μm to produce a cell. Thereafter, an electrolytic solution in which 5 wt% of tris (bipyridyl) ruthenium hexafluorophosphate (II) ([Ru (bpy) ₃ ] (PF ₆ ) ₂ ) is dissolved in acetonitrile in the gap between the electrodes. The electrolyte layer 3 was formed by pouring. The surface area of the porous electrode 2b of the electrode 2 was about 1000 times the surface area of the electrode 4.

  In Example 1, a drive voltage (frequency 10 Hz) having a square wave waveform was applied between the counter electrodes of the electrochemiluminescence device 10 using the AC power source 7, and the light emission start voltage was measured. Further, the emission luminance when a drive voltage with an amplitude of ± 2 V was applied and the time from when the polarity of the drive voltage was reversed until the maximum emission luminance was obtained, that is, the maximum emission luminance arrival time were measured. The measurement results of these light emission characteristics are shown in Table 1 together with the results of Examples 3 and 4 described later and the results of Comparative Examples 1 and 2.

  In Example 2, a driving voltage (frequency 10 Hz) having a triangular waveform was applied between the counter electrodes of the electrochemiluminescence device 10 using the AC power source 7. Otherwise, the emission characteristics were measured in the same manner as in Example 1. The results are shown in Table 2 together with the results of Comparative Examples 3 and 4 described later. In Tables 1 and 2, the light emission luminance is shown in four stages of ◎, ○, Δ, and × from the best.

Examples 3 and 4
In Example 3, in order to examine the effect of the surface area of the porous electrode 2b, the particle diameter of the titanium oxide and the thickness of the titanium oxide layer were changed to form the porous electrode 2b having a surface area about 100 times the surface area of the electrode 4. did. Other than that, the electrochemiluminescence device 10 was produced in the same manner as in Example 1, and a driving voltage (frequency 10 Hz) having a square wave waveform was applied to this electrochemiluminescence device in the same manner as in Example 1, so that the light emission starting voltage was applied. Was measured. In addition, the emission luminance when applying a drive voltage with an amplitude of ± 2.0 V and the maximum emission luminance arrival time were measured. In Example 4, similarly, a porous electrode 2b having a surface area about 10 times the surface area of the electrode 4 was formed. Other than that, the electrochemiluminescence device 10 was produced in the same manner as in Example 1, and a driving voltage (frequency 10 Hz) having a square wave waveform was applied to this electrochemiluminescence device in the same manner as in Example 1, so that the light emission starting voltage was applied. Was measured. In addition, the emission luminance when applying a drive voltage with an amplitude of ± 3.0 V and the maximum emission luminance arrival time were measured.

Comparative Examples 1 and 2
In Comparative Example 1, an electrochemiluminescence device was fabricated in the same manner as the electrochemiluminescence device 10 except that the porous electrode 2b was not provided on the electrode 2 and both electrodes were made of only the FTO conductive layer. A driving voltage (frequency 10 Hz) having a square wave waveform was applied to the electrochemiluminescence device in the same manner as in Example 1, and the light emission starting voltage was measured. In addition, the emission luminance when applying a drive voltage with an amplitude of ± 3.0 V and the maximum emission luminance arrival time were measured. In Comparative Example 2, a porous electrode was provided on the electrode 4 (FTO conductive layer) in the same manner as in Example 1. Others were the same as those of the electrochemiluminescent device 10, and electrochemiluminescent devices having porous electrodes on both electrodes were produced. A drive voltage (frequency 10 Hz) having a square wave waveform was applied to this electrochemiluminescence device in the same manner as in Example 1, and an attempt was made to measure the light emission start voltage, but no light emission was observed.

Comparative Examples 3 and 4
In Comparative Example 3, a drive voltage (frequency 10 Hz) having a triangular waveform was applied between the counter electrodes of the electrochemiluminescence device produced in Comparative Example 1, and the light emission start voltage was measured. In addition, the emission luminance when applying a drive voltage with an amplitude of ± 3.0 V and the maximum emission luminance arrival time were measured. In Comparative Example 4, a drive voltage (frequency 10 Hz) having a triangular waveform was applied between the counter electrodes of the electrochemiluminescence device fabricated in Comparative Example 2 to measure the light emission starting voltage, but light emission was observed. There wasn't.

  In the electrochemiluminescent devices of Example 1 and Example 2 using the electrochemiluminescent device having the porous electrode 2b as the electrode 2, the comparative examples 1 and 3 using the electrochemiluminescent device having no porous electrode were used. Compared with the electrochemiluminescence device, light was emitted at a lower driving voltage, the maximum luminance arrival time was shortened, and the luminance was greatly improved. As described above, an electrochemiluminescence device using an electrochemiluminescence device provided with a porous electrode having a porous structure on one electrode and driven by alternating current reduces the emission start voltage, shortens the maximum emission luminance arrival time, Improvement of light emission luminance can be realized.

  On the other hand, as in Comparative Example 2 and Comparative Example 4, the electrochemiluminescence device using an electrochemiluminescence device having porous electrodes on both electrodes and driven by alternating current did not emit light at all. Such a phenomenon is not reported in Patent Document 1, and is a phenomenon peculiar to AC driving. As described above, in the case of AC driving, the reverse reaction of oxidizing species and reducing species on the electrodes is likely to occur, so it is considered that an electrochemiluminescent device having porous electrodes on both electrodes cannot be used.

  The surface area of the porous electrode 2 b of the electrochemiluminescence device produced in Example 1 is about 1000 times the surface area of the electrode 4. In the electrochemiluminescence device of Example 3 using the electrochemiluminescence device in which the surface area of the porous electrode 2b is about 100 times the surface area of the electrode 4, the emission start voltage is higher than that of the electrochemiluminescence device of Example 1. Slightly large. However, in the electrochemiluminescence device of Example 4 using the electrochemiluminescence device in which the surface area of the porous electrode 2b is about 10 times the surface area of the electrode 4, the emission of light starts as compared with the electrochemiluminescence device of Example 1. The voltage is large, the maximum emission luminance arrival time is long, the emission luminance is low, and the emission characteristics are remarkably deteriorated. From these examples, it was found that the surface area of the electrode 2 is desirably 10 times or more the surface area of the electrode 4.

  Although the present invention has been described based on the embodiments and examples, it is needless to say that the present invention is not limited to these examples and can be appropriately changed without departing from the gist of the invention. .

  According to the present invention, it is possible to provide an electrochemiluminescence device that can be driven at a low voltage and has a high luminous efficiency, and includes a variety of display devices, low-cost, large-area planar light-emitting light sources, illumination devices, and laser excitation light sources. Can contribute to the realization of a new light emitting device

It is sectional drawing which shows the structure of the electrochemiluminescence (ECL) apparatus based on embodiment of this invention. It is a graph which shows the time change of the drive voltage, electric current, and light emission intensity of an electrochemiluminescence apparatus similarly. It is a graph which shows the time change of the electric current and luminescence intensity of 1 cycle of an electrochemiluminescence apparatus similarly. It is sectional drawing which shows the operating state of an electrochemiluminescence apparatus in model form with assumption. It is sectional drawing which shows the operating state of an electrochemiluminescence apparatus in model form with assumption. It is a graph which shows the relationship between the duty ratio of the square wave which drives an electrochemical chemiluminescent element, and emitted light intensity. 4 is a graph showing an example of an ideal driving voltage of the electrochemiluminescence device. It is an external view which shows the example of the electrochemiluminescence device comprised as a passive matrix type display apparatus similarly. It is sectional drawing which shows the general structure of the conventional electrochemiluminescent element by which direct current drive is carried out. It is sectional drawing which shows the operation state of the electrochemiluminescent element driven by alternating current by the conventional model.

Explanation of symbols

1 ... substrate (glass substrate, etc.), 2 ... electrode,
2a ... Electrode (transparent conductive layer such as FTO),
2b ... porous electrodes (such as TiO _2), 3 ... electrolyte layer, 4 ... electrode (FTO, etc.),
5 ... Substrate (glass substrate, etc.), 6 ... Spacer, 7 ... AC power supply, 10 ... Electrochemiluminescence device,
DESCRIPTION OF SYMBOLS 100 ... Electrochemiluminescent element, 101, 105 ... Board | substrate, 102 ... Anode, 103 ... Electrolyte layer,
104 ... cathode, 106 ... spacer, 110 ... electrochemiluminescence device, 111, 115 ... substrate,
112, 114 ... electrodes, 113 ... electrolyte layer, 116 ... spacer

Claims (13)

An electrolyte layer is disposed between the counter electrodes, and the oxidized species generated by oxidation of the chemical species contained in the electrolyte layer in the counter electrode, and the same or different species of the chemical species contained in the electrolyte layer are In the electrochemiluminescence device in which the electrochemiluminescence element that emits light by reaction with the reduced species generated by reduction at the counter electrode is driven by alternating current,
An electrochemiluminescent device characterized in that light emission occurs substantially only in the vicinity of one electrode of the counter electrode.   The electrochemiluminescence device according to claim 1, wherein an AC power supply that supplies a driving voltage for the AC driving is connected between the counter electrodes.   The electrochemiluminescence device according to claim 1, wherein the one electrode is a porous electrode having a porous structure.   The electrochemiluminescence device according to claim 1, wherein a surface area of the one electrode is larger than a surface area of the other electrode of the counter electrode.   The electrochemiluminescence device according to claim 3 or 4, wherein the surface area of the one electrode is 10 times or more the surface area of the other electrode of the counter electrode.   The electrochemiluminescence device according to claim 3, wherein the porous electrode is made of a metal and / or a metal oxide.   The electrochemiluminescence device according to claim 6, wherein the metal oxide includes titanium oxide.   The AC driving is performed by an AC voltage having a duty ratio different from 1 and / or an AC voltage having a DC component, and in one cycle of the AC driving, the oxidizing species or The reduced species is accumulated, and after reversal of the polarity of the driving voltage, the accumulated oxidized species or the reduced species reacts quickly in a short time to cause light emission. Electrochemiluminescence device.   The electrochemiluminescence device according to claim 1, which is configured as a surface light source.   The electrochemiluminescence device according to claim 1, wherein the counter electrode is provided in a pattern that forms a plurality of light emitting regions.   The electrochemiluminescence device according to claim 10, which is configured as a display device. An electrolyte layer is disposed between the counter electrodes, and the oxidized species generated by oxidation of the chemical species contained in the electrolyte layer in the counter electrode, and the same or different species of the chemical species contained in the electrolyte layer are In the method of driving an electrochemiluminescence device, wherein the electrochemiluminescence device that emits light by reaction with a reducing species generated by reduction at the counter electrode is AC driven,
A driving method for an electrochemiluminescence device, characterized by supplying a driving voltage that causes light emission substantially only in the vicinity of one electrode of the counter electrode.   The method of driving an electrochemiluminescence device according to claim 12, wherein the AC driving is performed by an AC voltage having a duty ratio different from 1 and / or an AC voltage having a DC component.