WO2016056529A1

WO2016056529A1 - Electrochemical luminescent cell and composition for forming luminescent layer of electrochemical luminescent cell

Info

Publication number: WO2016056529A1
Application number: PCT/JP2015/078277
Authority: WO
Inventors: 文広米川
Original assignee: 日本化学工業株式会社
Priority date: 2014-10-09
Filing date: 2015-10-06
Publication date: 2016-04-14

Abstract

Provided is an electrochemical luminescent cell 10 having a luminescent layer 12 and electrodes 13, 14 provided on each surface of the luminescent layer 12. The luminescent layer 12 comprises an organic polymeric luminescent material and a combination of at least two organic salts. In particular, the luminescent layer preferably comprises a combination of at least two types of ionic liquids represented by formula (1) (wherein R₁, R₂, R₃ and R₄ each represent an optionally-substituted alkyl group, alkoxy alkyl group, trialkylsilylalkyl group, alkenyl group, alkynyl group, aryl group or heterocylic group. R₁, R₂, R₃ and R₄ may be the same or different. M represents N or P. X^- represents an anion.)

Description

Electrochemiluminescence cell and composition for forming luminescent layer of electrochemiluminescence cell

The present invention relates to an electrochemiluminescence cell having a light emitting layer containing a light emitting material and two or more organic salts. The present invention also relates to a composition for forming a light emitting layer of an electrochemiluminescence cell.

In recent years, the development of organic electroluminescence (organic EL) elements, which are self-luminous elements using electrons and holes as carriers, has been rapidly progressing. Organic EL has features such as being thinner and lighter than a liquid crystal element that does not emit light and requires a backlight, and has excellent visibility.

An organic EL element generally includes a pair of substrates on which electrodes are formed on the surfaces facing each other, and a light emitting layer disposed between the pair of substrates. Among these, the light emitting layer is made of an organic thin film containing a light emitting substance that emits light when a voltage is applied. When such an organic EL device emits light, a voltage is applied to the organic thin film from the anode and the cathode to inject holes and electrons. As a result, holes and electrons are recombined in the organic thin film, and the excitons generated by the recombination return to the ground state, whereby light emission is obtained.

In the organic EL device, in addition to the light emitting layer, a hole injection layer and an electron injection layer for increasing the injection efficiency of holes and electrons between the light emitting layer and the electrode, and recombination of holes and electrons. It is necessary to provide a hole transport layer and an electron transport layer for improving efficiency. As a result, the organic EL element has a multi-layered structure, which complicates the structure and increases the manufacturing process. In organic EL, there are many limitations because it is necessary to consider the work function when selecting the electrode material used for the anode and the cathode.

Recently, attention has been paid to light-emitting electrochemical cells (LECs) as a self-luminous element to cope with these problems. Electrochemiluminescent cells generally have a light emitting layer that includes a salt and an organic light emitting material. When a voltage is applied, cations and anions derived from the salt move toward the cathode and the anode, respectively, in the light emitting layer, which results in a large electric field gradient (electric double layer) at the electrode interface. The formed electric double layer facilitates the injection of electrons and holes in the cathode and the anode, respectively. Therefore, the electrochemiluminescence cell does not require a multilayer structure like an organic EL. In addition, since there is no need to consider the work function of the material used as the cathode and anode in the electrochemiluminescence cell, there are few restrictions on the material. For these reasons, the electrochemiluminescence cell is expected as a self-luminous element that can significantly reduce the manufacturing cost as compared with the organic EL.

Attempts have been made to use ionic liquids in addition to lithium salts and potassium salts as salts used in electrochemiluminescence cells. This ionic liquid is a non-volatile salt and has a higher reorientation rate due to an electric field than a solid electrolyte, so that ion mobility is ensured and an electric double layer is easily formed, and holes and electrons can be more easily injected. (See Patent Document 1 and Patent Document 2).

In organic EL, holes and electrons can be easily moved by adding additives to the layers responsible for the injection and transport of holes and electrons, such as the hole injection layer, hole transport layer, electron injection layer, and electron transport layer. Attempts have been made (see, for example, Patent Documents 3 to 6). In addition, attempts have been made to avoid a reduction in light emission luminance by adjusting the injection balance of holes and electrons into the light emitting layer (see Patent Document 7).

On the other hand, in an electrochemiluminescence cell, particularly an electrochemiluminescence cell having an ionic liquid in a light emitting layer, the movement of holes and electrons is already easy, but the thermal stability and electrochemical which affect the operating life Attempts have been made to improve the performance of electrochemiluminescent cells by improving stability or improving the compatibility between ionic liquids and luminescent materials. For example, Patent Document 8 describes that when a plurality of salts are incorporated into a light-emitting polymer layer, the lifetime of the electrochemiluminescent cell is improved. However, the light emission luminance shown in this document has achieved the maximum luminance of 100 cd / m ² or less at the maximum even when a voltage of 10 V or more is applied to the electrode, as high as necessary for practical use. Absent.

JP 2011-103234 A Special table 2012-516033 gazette JP 2013-171968 A Special table 2012-531737 gazette JP 2011-216893 A International Publication No. 2010/98386 Pamphlet International Publication No. 2013/171872 Pamphlet International Publication No. 2011/032010 Pamphlet

In order to increase the luminous efficiency of the electrochemiluminescence cell, it is considered indispensable to increase the transport efficiency of holes and electrons and to adjust the balance between the hole and electron injection ability from each electrode. That is, when holes or electrons are injected from each electrode in a large amount, either holes or electrons will be excessively present in the light emitting layer, which will hinder transport. It is conceivable that the light emission efficiency decreases or the light emission luminance is affected.

In view of the above problems, as a result of intensive studies by the present inventors, it has been found that the ability to inject holes or electrons from each electrode can be controlled by considering the type of cation or anion of the salt used in the light emitting layer. Specifically, it has been found that the ability to inject holes and electrons into the light emitting layer can be made substantially equal by mixing two or more kinds of salts.

That is, the present invention relates to an electrochemiluminescence cell having a light emitting layer and electrodes disposed on each surface thereof.
In an electrochemiluminescence cell having a light emitting layer and electrodes arranged on each surface thereof,
The above-mentioned problem is solved by providing an electrochemiluminescent cell in which the light emitting layer contains a combination of an organic polymer light emitting material and two or more organic salts.

Moreover, this invention solves the said subject by providing the composition for light emitting layer formation of an electrochemiluminescence cell containing the combination of an organic polymer light emitting material, an organic solvent, and 2 or more types of organic salts. is there.

According to the present invention, an electrochemiluminescence cell having high luminous efficiency and excellent emission luminance is provided.

FIG. 1 is a schematic cross-sectional view of an electrochemiluminescence cell according to an embodiment of the present invention. FIG. 2 is a conceptual diagram showing a light emission mechanism of an electrochemiluminescence cell. FIG. 2 (a) shows an electrochemiluminescence cell before voltage application, and FIG. 2 (b) shows an electrochemiluminescence cell after voltage application. Show. FIG. 3 is a graph showing the measurement results of the emission luminance of the electrochemiluminescence cells obtained in Example 1 and Comparative Example 1. FIG. 4 is a graph showing the measurement results of the light emission luminance of the electrochemiluminescence cells obtained in Example 2 and Comparative Example 2. FIG. 5 is a graph showing the measurement results of the emission luminance of the electrochemiluminescence cells obtained in Example 3 and Comparative Example 3. FIG. 6 is a graph showing the measurement results of the emission luminance of the electrochemiluminescence cells obtained in Example 4 and Comparative Example 4. FIG. 7 is a graph showing the measurement results of the emission luminance of the electrochemiluminescence cells obtained in Example 5 and Comparative Example 5. FIG. 8 is a graph showing the measurement results of the emission luminance of the electrochemiluminescence cells obtained in Example 6 and Comparative Example 6. FIG. 9 is a graph showing the measurement results of the emission luminance of the electrochemiluminescence cells obtained in Example 7 and Comparative Example 7. FIG. 10 is a graph showing the measurement results of the emission luminance of the electrochemiluminescence cells obtained in Example 8 and Comparative Example 8. FIG. 11 is a graph showing the measurement results of the emission luminance of the electrochemiluminescence cells obtained in Example 9 and Comparative Example 9. FIG. 12 is a graph showing the measurement results of the emission luminance of the electrochemiluminescence cells obtained in Example 10 and Comparative Example 10. FIG. 13 is a graph showing the measurement results of the emission luminance of the electrochemiluminescence cells obtained in Example 11 and Comparative Example 11. FIG. 14 is a graph showing the measurement results of the emission luminance of the electrochemiluminescence cells obtained in Example 12 and Comparative Example 12.

Hereinafter, preferred embodiments of the electrochemiluminescence cell of the present invention will be described with reference to the drawings. As shown in FIG. 1, the electrochemiluminescence cell 10 of this embodiment includes a light emitting layer 12 and

electrodes

13 and 14 disposed on each surface thereof. The electrochemiluminescence cell 10 includes a first electrode 13 and a second electrode 14 that are a pair of electrodes facing each other, and a light emitting layer 12 sandwiched between the pair of

electrodes

13 and 14. In the electrochemiluminescence cell 10, the light emitting layer emits light when a voltage is applied. The electrochemiluminescence cell 10 is used as various displays. FIG. 1 shows a state where a DC power source is used as a power source, the first electrode 13 is connected to the anode of the DC power source, and the second electrode 14 is connected to the cathode. However, contrary to the illustration, the first electrode 13 may be connected to the cathode and the second electrode 14 may be connected to the anode. Moreover, it is also possible to use an AC power source as a power source instead of a DC power source.

The first electrode 13 and the second electrode 14 may be transparent electrodes having translucency, or may be translucent or opaque electrodes. Transparent electrodes having translucency include those made of metal oxides such as indium-doped tin oxide (ITO) and fluorine-doped tin oxide (FTO), poly (3,4-ethylenedioxythiophene) with impurities added ( Examples thereof include those made of a polymer having transparency such as PEDOT) and those made of a carbon-based material such as carbon nanotube or graphene. Examples of the translucent or opaque electrode include aluminum (Al), silver (Ag), gold (Au), platinum (Pt), tin (Sn), bismuth (Bi), copper (Cu), and chromium (Cr). Metal materials such as zinc (Zn) and magnesium (Mg).

It is preferable to use at least one of the first electrode 13 and the second electrode 14 as a transparent electrode because light emitted from the light emitting layer 12 can be easily extracted to the outside. Further, when one is a transparent electrode and the other is an opaque metal electrode, it is preferable because light emitted from the light emitting layer 12 can be taken out while being reflected by the metal electrode. Moreover, it is good also as a see-through light-emitting body by making both the 1st electrode 13 and the 2nd electrode 14 into a transparent electrode. Furthermore, both the first electrode 13 and the second electrode 14 are metal electrodes made of Ag or the like having a high reflectivity, and the thickness of the light emitting layer 12 is controlled, so that the electrochemiluminescence cell 10 is laser-oscillated. It can also be an element.

When the first electrode 13 is a transparent electrode and the second electrode 14 is an opaque or translucent metal electrode, the first electrode 13 is, for example, 10 nm or more and 500 nm or less from the viewpoint of realizing appropriate resistivity and light transmittance. It is preferable to have a thickness of The second electrode 14 preferably has a thickness of, for example, 10 nm or more and 500 nm or less from the viewpoint of realizing an appropriate resistivity and light transmittance in the same manner as the first electrode 13.

The light emitting layer 12 is formed by mixing an organic polymer light emitting material and an organic salt. The light emitting layer 12 may be in a solid state or a liquid state. When the light emitting layer 12 is solid, it can maintain a certain shape and can resist the force applied from the outside.

The organic salt contained in the light emitting layer 12 is a substance for ensuring ion mobility, forming an electric double layer easily, and facilitating injection of holes and electrons. In the present embodiment, phosphonium salts, ammonium salts, pyridinium salts, imidazolium salts, pyrrolidinium salts, and the like can be used as organic salts. Among these organic salts, as the phosphonium salt and ammonium salt, for example, those represented by the following formula (1) can be used. Examples of the pyridinium salt, imidazolium salt, and pyrrolidinium salt include anions such as halide ions such as fluorine, bromine, iodine and chlorine, tetrafluoroborate (BF ₄ ), benzotriazolate (N ₃ (C ₆ H ₄ ) ), Tetraphenylborate (B (C ₆ H ₅ ) ₄ ), hexafluorophosphate (PF ₆ ), bis (trifluoromethylsulfonyl) imide (N (SO ₂ CF ₃ ) ₂ ), bis (fluorosulfonyl) imide ( N (SO ₂ F) ₂ ), trifluoromethanesulfonate (SO ₃ CF ₃ ), methanesulfonate (SO ₃ CH ₃ ), tris (pentafluoroethyl) trifluorophosphate ((C ₂ H ₅ ) ₃ PF ₃ ), tri trifluoroacetic acid _(CF 3 COO), amino acids, Bisuokisaratobo Over preparative _{_{_{(B (C 2 O 4)}}} 2), p- toluenesulfonate _{_{_{_{(SO 3 C 6 H 4 CH}}}} 3), thiocyanate (SCN), dicyanamide (N _{(CN) 2),} dialkyl phosphate _{((RO) 2} Those which are POO), dialkyldithiophosphoric acid ((RO) ₂ PSS), aliphatic carboxylic acid (RCOO) and the like can be used. The molecular weight of the cation in the organic salt is 270 or more and 900 or less, particularly 300 or more and 850 or less, particularly 330 or more and 800 or less, and the luminous efficiency of the electrochemiluminescence cell is further improved and the emission luminance is further improved. To preferred.

The organic salt may be solid or liquid at normal temperature (25 ° C.). Among organic salts, for example, those represented by the following formula (1) can be used as the solid organic salt.

(Wherein R ₁ , R ₂ , R ₃ and R ₄ are each an alkyl group, an alkoxyalkyl group, a trialkylsilylalkyl group, an alkenyl group, an alkynyl group, an aryl group, which may be substituted with a functional group, or Represents a heterocyclic group, R ₁ , R ₂ , R ₃ and R ₄ may be the same or different from each other, M represents N or P, and X ⁻ represents an anion.)

Among organic salts, examples of liquid organic salts include ionic liquids that maintain a liquid state at room temperature (25 ° C.) while being ionic species. As the liquid organic salt, for example, a substance represented by the above formula (1) can be used. The organic salt represented by the formula (1) is in a solid or liquid state depending on the combination of the selected cation and anion and the structure of R ₁ to R ₄ which are side chains of the cation.

When a plurality of organic salts represented by the formula (1) are used, all of them may be solid at room temperature, or all of them may be liquid at room temperature. Further, at least one of them may be liquid at normal temperature, and at least one of them may be solid at normal temperature.

In the formula (1), R ₁ to R ₄ may be an alkyl group, an alkoxyalkyl group, a trialkylsilylalkyl group, an alkenyl group, an alkynyl group, an aryl group, or a heterocyclic group. R ₁ to R ₄ may be the same as or different from each other.

In the above formula (1), the alkyl group used as any one of R ₁ to R ₄ is a linear or branched saturated aliphatic group having 1 to 20 carbon atoms, 3 to 20 saturated alicyclic groups are mentioned. Specifically, methyl group, ethyl group, propyl group, isopropyl group, butyl group, s-butyl group, t-butyl group, isobutyl group, amyl group, isoamyl group, t-amyl group, hexyl group, heptyl group, Isoheptyl, t-heptyl, n-octyl, isooctyl, 2-ethylhexyl, t-octyl, nonyl, isononyl, decyl, isodecyl, undecyl, dodecyl, tridecyl, isotridecyl, Examples include tetradecyl group, hexadecyl group, octadecyl group, icosyl group, cyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexyl group, cycloheptyl group, cyclooctyl group, cyclononyl group, cyclohexylmethyl group, and cyclodecyl group.

In the above formula (1), examples of the alkoxy group in the alkoxyalkyl group used as any one of R ₁ to R ₄ include the alkoxides of the alkyl groups described above. Examples of the alkyl group in the alkoxyalkyl group include the same alkyl groups as described above.

In the above formula (1), as the alkenyl group used as any one of R ₁ to R ₄ , those having 2 to 20 carbon atoms are preferably used. For example, vinyl, allyl, isopropenyl, 2-butenyl, 2-methylallyl, 1,1-dimethylallyl, 3-methyl-2-butenyl, 3-methyl-3-butenyl, 4-pentenyl And linear or branched alkenyl groups such as a group, a hexenyl group, an octenyl group, a nonenyl group, and a decenyl group.

In the above formula (1), examples of the alkynyl group used as any one of R ₁ to R ₄ include an ethynyl group and a prop-2-yn-1-yl group.

In the above formula (1), examples of the aryl group used as any one of R ₁ to R ₄ include a phenyl group, a naphthyl group, and an anthracenyl group. Examples of the heterocyclic group include monovalent groups derived from pyridine, pyrrole, furan, imidazole, pyrazole, oxazole, imidazoline, pyrazine and the like.

In each of the above groups, one or two or more of the hydrogen atoms contained therein may be substituted with a functional group. Examples of the functional group include an amino group, a nitrile group, a phenyl group, a benzyl group, a carboxyl group, and an alkoxy group having 1 to 12 carbon atoms. For example, a group in which the above-described alkyl group is substituted with a phenyl group as a functional group, that is, an aromatic alkyl group can be used. Specifically, a benzyl group that is a group in which a methyl group as an alkyl group is substituted with a phenyl group as a functional group can be used.

Examples of the anion represented by X ⁻ in the formula (1) include halogen ions such as fluorine, bromine, iodine and chlorine, tetrafluoroborate (BF ₄ ), benzotriazolate (N ₃ (C ₆ H ₄ )). ), Tetraphenylborate (B (C ₆ H ₅ ) ₄ ), hexafluorophosphate (PF ₆ ), bis (trifluoromethylsulfonyl) imide (N (SO ₂ CF ₃ ) ₂ ), bis (fluorosulfonyl) imide ( N (SO ₂ F) ₂ ), trifluoromethanesulfonate (SO ₃ CF ₃ ), methanesulfonate (SO ₃ CH ₃ ), tris (pentafluoroethyl) trifluorophosphate ((C ₂ H ₅ ) ₃ PF ₃ ), tri trifluoroacetic acid _(CF 3 COO), amino acids, Bisuo Kisara oxalatoborate _{_{_{(B (C 2 O 4)}}} 2 , P- toluenesulfonate _{_{_{_{(SO 3 C 6 H 4 CH}}}} 3), thiocyanate (SCN), dicyanamide (N _{(CN) 2),} dialkyl phosphate _((RO) 2 POO), dialkyl dithiophosphates _((RO) 2 PSS ), Aliphatic carboxylic acid (RCOO), dimethyl phosphate (P (OCH ₃ ) ₂ (═O) O ₂ ), dibutyl phosphate (P (OC ₄ H ₉ ) ₂ (═O) O), bis-2-ethylhexyl phosphate (P (O (C ₆ H ₁₂ ) ((C ₂ H ₅ ))) ₂ (═O) O ₂ ) and the like.

The electrochemiluminescence cell 10 of this embodiment is characterized in that two or more different organic salts contained in the light emitting layer 12 are used in combination. By using two or more kinds of organic salts in combination, the ability of injecting holes and electrons into the light-emitting layer 12 becomes substantially equal, thereby increasing the luminous efficiency. As the luminous efficiency is increased, the electrochemiluminescence cell 10 of the present embodiment is excellent in emission luminance.

As a combination of two or more kinds of organic salts, for example, in the case of two kinds of combinations, (a) a combination of organic salts having the same cation and different anions, and (b) anion having different cations and anions And (c) combinations of organic salts in which cations are different and anions are different. In the case of (i), for example, a pyridinium ion that is a cation is common, and a combination of organic salts having different types of anions among the above-mentioned anions such as tetrafluoroborate ion and bis (trifluoromethanesulfonyl) imide ion is used. Can be mentioned. In the case of (b), for example, the aforementioned anions such as tetrafluoroborate ions and bis (trifluoromethanesulfonyl) imide ions are common, and a combination of organic salts in which the cations are imidazolium ions and pyrrolidinium ions can be mentioned. . In the case of (c), for example, a combination of a bis (trifluoromethanesulfonyl) imide salt of a pyridinium ion and a tetrafluoroborate ion salt of a pyrrolidinium ion may be mentioned.

Among the combinations of the above two or more organic salts, (a) a combination of organic salts having the same cation and different anions, or (b) a combination of organic salts having the same cation and different anions. Either of these is preferable because the composition of the light emitting layer can be easily designed. That is, (c) in the case of a combination of organic salts having different cations and different anions, cation A and cation B are present, and anion a and anion b are present. As a combination of anions,
(i) cation A + anion a
(ii) cation A + anion b
(iii) Cation B + anion a
(iv) Cation B + anion b
The following four types of combinations are conceivable, and these exist as organic salt types as they are. In other words, for example, when designing with a plurality of salts of the combination of (i) and (ii) that was originally assumed, there is a possibility that the organic salts of (iii) and (iv) may also be mixed in, and this is the emission luminance. There is no denying the possibility of affecting it.

In view of the above, the combination of organic salts includes (i) a combination of organic salts in which the cation is the same and the anion is different (the above (i) and (ii) or (iii) and (iv) Or (b) a combination of organic salts having different cations and the same anion (a combination of (i) and (iii) or (ii) and (iv)). preferable.

Moreover, it is preferable that two or more organic salts are a combination of liquid organic salts. Alternatively, it is also preferable that two or more organic salts are a combination of solid organic salts. Further, the combination of two or more organic salts may be a combination of a liquid organic salt and a solid organic salt.

Preferred organic salt combinations include those represented by the formula (1). In this case, when combining a plurality of different organic salts represented by the formula (1), it is advantageous to employ a combination in which the ability to inject holes and electrons into the light emitting layer 12 is substantially equal. . As a result of the study of the present inventor, when, for example, two types of combinations are used as the different organic salts represented by the formula (1), the first organic salt and the second organic salt are: It has been found that it is preferable to have the same kind of cation and different anions. It was also found that (b) it is preferable that they have the same type of anion and the cation is different.

In the case of (a), the first organic salt and the second organic salt have the same kind of cation, for example, the same kind of ammonium ion or the same kind of phosphonium ion. The first organic salt and the second organic salt have different anions. On the other hand, in the case of (b), the first organic salt and the second organic salt are the same type of anion, for example, ions of halogen such as bistrifluoromethanesulfonylimide, fluorine, bromine, tetrafluoroborate (BF ₄ ), hexa It has ions of halogen-containing compounds such as fluorophosphate (PF ₆ ). The first organic salt and the second organic salt have different cations. Any of the different cations can be an ammonium ion. Alternatively, any heterogeneous cation can be a phosphonium ion. Furthermore, one of the different cations can be an ammonium ion and the other can be a phosphonium ion.

In both cases (a) and (b), as the cation, _{three of} R ₁ , R ₂ , R ₃ and R _{4 in} the formula (1) are the same alkyl group, and the rest One is preferably an alkyl group different from the alkyl group, or an aromatic alkyl group. This is because _one of R ₁ , R ₂ , R _3, and R ₄ is a heterogeneous group, which is structurally asymmetrical, and the fluidity of the organic salt is easily obtained even when the number of carbons increases. is there. Since the molecular weight of the cation can be increased by increasing the number of carbon atoms, the charge density is structurally reduced, so the polar component required to stabilize the charge can be reduced. Leads to increased compatibility with non-polar organic light emitting materials.

As a preferred combination of the first organic salt and the second organic salt, in the case of (i), the cation is the same kind of tetraalkylammonium ion, the same kind of trialkylbenzylammonium ion, the same kind of tetraalkylphosphonium ion, or It is the same kind of trialkylbenzylphosphonium ion, and different anions are ions of bistrifluoromethanesulfonylimide, halogen ions such as fluorine and bromine, or halogens such as tetrafluoroborate (BF ₄ ) and hexafluorophosphate (PF ₆ ). The combination with the ion of a containing compound is mentioned. In the case of (b), the same type of anion is bistrifluoromethanesulfonylimide, halogen ions such as fluorine and bromine, or halogen-containing compounds such as tetrafluoroborate (BF ₄ ) and hexafluorophosphate (PF ₆ ). A different cation is a combination of different tetraalkylammonium ions, a combination of different trialkylbenzylammonium ions, a combination of different tetraalkylphosphonium ions, a combination of different trialkylbenzylphosphonium ions, tetraalkylammonium Ion and trialkylbenzylammonium ion combination, tetraalkylphosphonium ion and trialkylbenzylphosphonium ion combination, tetraalkylammonium ion A combination of ON, a trialkylbenzylphosphonium ion, a combination of a tetraalkylphosphonium ion and a trialkylbenzylammonium ion, and a combination of a tetraalkylphosphonium ion and a tetraalkylammonium ion.

The ratio between the first organic salt and the second organic salt can be selected from a wide range according to the type of these organic salts. For example, as illustrated in the examples described later, there may be a combination that exhibits the maximum light emission luminance at substantially equal mass ratios, or the first organic salt and the second organic salt are 20:80 or 80. In some cases, the combination shows the maximum luminance when the mass ratio is 20.

As described above, the combination of the first organic salt and the second organic salt is merely an example, and achieves the object of the present invention to make the injection ability of holes and electrons into the light emitting layer 12 substantially equal. Therefore, a combination of a plurality of types of ionic liquids such as three or more types can also be employed.

The organic salt represented by the formula (1) can be produced, for example, as follows. When the cation is a phosphonium ion, a quaternary phosphonium halide obtained by reacting a tertiary phosphine compound corresponding to the target phosphonium cation and a halogenated hydrocarbon compound is used, and an ionic liquid in which the anion is halogen is prepared. Obtainable. An anion component other than halogen can be obtained by reacting the quaternary phosphonium halide with a metal salt of the anion component to exchange anions. For example, an ionic liquid having a phosphonium cation in which three of R ₁ , R ₂ , R ₃ and R ₄ in formula (1) are alkyl groups, and the other is an aromatic alkyl group, and the anion component is halogen Can be obtained by using a trialkylphosphine as the tertiary phosphine compound and a compound in which an aromatic alkyl group is bonded to halogen as the halogenated hydrocarbon compound. Further, among R ₁ , R ₂ , R ₃ and R _{4 in} the formula (1), three have an alkyl group and the other one has a phosphonium cation which is an aromatic alkyl group, and the anion component is other than halogen. The organic salt is a bis (trifluoromethylsulfonyl) imide, tetrafluoroborate (BF ₄ ), hexafluorophosphate (PF ₆ ), or bisoxalato borate (B (C _2). It can be obtained by anion exchange with O ₄ ) ₂ ), thiocyanate (SCN) or the like.

The ratio of the organic salt in the light emitting layer 12 is preferably 1% by mass or more and 30% by mass or less from the viewpoint of securing ion mobility and improving the film forming property of the light emitting layer 12. % Or less is more preferable. The content of the organic salt in the light emitting layer 12 is preferably 10 parts by mass or more and 25 parts by mass or less with respect to 100 parts by mass of the organic polymer light emitting material.

The organic polymer light emitting material contained in the light emitting layer 12 functions as a carrier body of electrons and holes by being doped with anions and cations, and emits light when excited by the combination of electrons and holes. Examples of such organic polymer light emitting materials include various π-conjugated polymers. Specific examples include poly (paraphenylene vinylene), poly (fluorene), poly (1,4-phenylene), polythiophene, polypyrrole, poly (paraphenylene sulfide), polybenzothiadiazole, polybiothiophine and the like. it can. In addition, derivatives obtained by introducing substituents into these and copolymers thereof can also be used as the organic polymer light-emitting material. Examples of such a substituent include an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, an aryl group having 6 to 18 carbon atoms, and [(—CH ₂ CH ₂ O—) _n CH ₃ ]. And a group represented by the formula (where n is an integer of 1 to 10). Examples of the copolymer include those obtained by bonding each repeating unit of two or more kinds of the above-mentioned π-conjugated polymers. Examples of the arrangement of each repeating unit in the copolymer include a random arrangement, an alternating arrangement, a block arrangement, or a combination thereof. Furthermore, a commercial item can also be used as an organic polymer light-emitting material. Examples of such commercially available products include PFO-DMP (Poly (9,9-dioctylfluorenyl-2,7-diyl) end capped with dimethylphenyl) which is a compound available from Luminescence Technology under the name LT-S934, It is a compound available from Aldrich (Poly [(9,9-di-n-octylfluorenyl-2,7-diyl) -alt- (benzo [2,1,3] thiadiazol-4,8-diyl)] ) And the like.

From the viewpoint of sufficiently exhibiting the function of these organic polymer light emitting materials, the ratio in the light emitting layer 12 is preferably 10% by mass or more and 95% by mass or less, and 20% by mass or more and 90% by mass or less. It is more preferable.

The light emitting layer 12 may contain substances other than organic polymer light emitting materials and organic salts. Examples of such substances include surfactants, polymer components for improving conductivity (polyethylene oxide, etc.), polymer components for improving film forming properties (polystyrene, polymethyl methacrylate (PMMA), etc.), organic salts, and the like. Other salts may be mentioned. The amount of components other than the organic polymer light-emitting material and organic salt (excluding the solvent) in the light-emitting layer 12 is preferably 90 parts by mass or less when the entire light-emitting layer 12 is 100 parts by mass, and 60 parts by mass. More preferably, it is more preferably 30 parts by mass or less.

The film thickness of the light emitting layer 12 thus configured is preferably 10 nm or more and 200 nm or less, and more preferably 50 nm or more and 150 nm or less. When the film thickness of the light emitting layer 12 is within this range, it is preferable from the viewpoints that light emission can be sufficiently and efficiently obtained from the light emitting layer 12, defects in a light emission scheduled portion can be suppressed, and short circuit prevention can be achieved.

The electrochemiluminescence cell 10 of this embodiment can be manufactured by the following manufacturing method, for example. First, a substrate provided with the first electrode 13 is prepared. In the case where the first electrode 13 is formed from, for example, ITO, by forming a deposited ITO film in a pattern on the surface of a glass substrate or the like by using a photolithography method or a combination of the photolithography method and the lift-off method, A first electrode 13 made of ITO can be formed on the surface.

Next, an organic salt and an organic polymer light-emitting material are dissolved in an organic solvent to prepare a composition for forming a light-emitting layer of an electrochemiluminescence cell. From the viewpoint of efficiently mixing the organic salt and the organic polymer light-emitting material, it is preferable to use toluene, benzene, tetrahydrofuran, dimethyl chloride, chlorobenzene, chloroform, or the like as the organic solvent. These organic solvents can be used individually by 1 type or in combination of 2 or more types. The blending ratio (mass ratio) of the organic salt and the organic polymer light-emitting material in the composition for forming a light-emitting layer is preferably 1: 1 to 20 in the former: latter. This composition for forming a light emitting layer is applied onto the first electrode 13 of the substrate by a spin coating method or the like. Thereafter, the coating film formed by this coating is dried to evaporate the organic solvent, thereby forming the light emitting layer 12. The preparation of the light emitting layer forming composition and the formation of the light emitting layer 12 are preferably performed in an inert gas atmosphere having a moisture content of 100 ppm or less. In this case, examples of the inert gas include argon, nitrogen, helium and the like.

Next, the second electrode 14 is formed on the formed light emitting layer 12. In this case, an electrode having a predetermined pattern is formed on the light emitting layer 12 by evaporating aluminum (Al) into a film shape by, for example, a vacuum evaporation method through a mask. In this way, the second electrode 14 is formed on the light emitting layer 12. Thereby, the electrochemiluminescence cell 10 shown in FIG. 1 is obtained. The obtained electrochemiluminescence cell 10 may be vacuum-dried from the viewpoint of improving the film quality of the light emitting layer 12. This vacuum drying may be performed at room temperature or may be performed under heating.

The electrochemiluminescence cell 10 of the present embodiment emits light by the following light emission mechanism. As shown in FIGS. 2A and 2B, a voltage is applied to the light emitting layer 12 so that the first electrode 13 serves as an anode and the second electrode 14 serves as a cathode. As a result, ions in the light emitting layer 12 move along the electric field, and a layer in which anion species are collected in the vicinity of the interface between the light emitting layer 12 and the first electrode 13 is formed. On the other hand, a layer in which cationic species are collected in the vicinity of the interface with the second electrode 14 in the light emitting layer 12 is formed. In this way, an electric double layer is formed at the interface of each electrode. As a result, the p-doped region 16 is spontaneously formed in the vicinity of the first electrode 13 that is the anode, and the n-doped region 17 is spontaneously formed in the vicinity of the second electrode 14 that is the cathode. These doped regions constitute a pin junction with a high carrier density. Thereafter, holes and electrons are respectively injected from the anode and the cathode into the organic polymer light emitting material of the light emitting layer 12 and recombined in the i layer. Excitons are generated from the recombined holes and electrons, and light is emitted when the excitons return to the ground state. In this way, light emission can be obtained from the light emitting layer 12. In order to obtain light of the desired wavelength, the energy difference (band gap) between the highest occupied orbital (Highest Occupied Molecular Orbital) and the lowest unoccupied orbital (Lowest Unoccupied Molecular Orbital) corresponds to the desired wavelength. What is necessary is just to select a material.

As mentioned above, although this invention was demonstrated based on the preferable embodiment, the range of this invention is not restrict | limited to this embodiment. The present invention further discloses the following electrochemiluminescence cell.
[1]
In an electrochemiluminescence cell having a light emitting layer and electrodes arranged on each surface thereof,
The electrochemiluminescence cell in which the light emitting layer includes a combination of an organic polymer light emitting material and two or more organic salts.
[2]
The electrochemiluminescence cell according to [1], wherein the organic salt is an organic salt selected from a phosphonium salt, an ammonium salt, a pyridinium salt, an imidazolium salt, and a pyrrolidinium salt.
[3]
The electrochemiluminescence cell according to [1] or [2], wherein the organic salt is an ionic liquid.
[4]
The electrochemiluminescence cell according to any one of [1] to [3], wherein the organic salt is an organic salt represented by the following formula (1).

(Wherein R ₁ , R ₂ , R ₃ and R ₄ are each an alkyl group, an alkoxyalkyl group, a trialkylsilylalkyl group, an alkenyl group, an alkynyl group, an aryl group, which may be substituted with a functional group, or Represents a heterocyclic group, R ₁ , R ₂ , R ₃ and R ₄ may be the same or different from each other, M represents N or P, and X ⁻ represents an anion.)
[5]
The electrochemiluminescence cell according to [4], wherein the organic salt is a plurality of organic salts represented by the formula (1), and all of them are solid at room temperature.
[6]
The electrochemiluminescence cell according to [4], wherein the organic salt is a plurality of organic salts represented by the formula (1), and all of them are liquid at room temperature.

[7]
A plurality of organic salts represented by the formula (1) is used as the organic salt, at least one of them is liquid at normal temperature, and at least one of them is solid at normal temperature [4 ] The electrochemiluminescence cell of description.
[8]
The light emitting layer includes a combination of two organic salts represented by the formula (1),
The two organic salts have the same kind of cation, and the anion is different, [4] to [7].
[9]
The electrochemiluminescence cell according to [8], wherein one of the different anions is bistrifluoromethanesulfonylimide and the other is halogen.
[10]
The light emitting layer includes a combination of two organic salts represented by the formula (1),
The two types of organic salts are the electrochemiluminescence cells according to any one of [4] to [7], wherein the two kinds of organic salts have the same kind of anion and the cation is different.
[11]
The electrochemiluminescence cell according to [10], wherein the different cations are all ammonium ions or phosphonium ions.
[12]
The electrochemiluminescence cell according to [10], wherein one of the different cations is an ammonium ion and the other is a phosphonium ion.
[13]
In the formula (1), _{three of} R ₁ , R ₂ , R ₃ and R ₄ are the same alkyl group, and the other one is an alkyl group different from the alkyl group, or an aromatic alkyl group. The electrochemiluminescence cell according to any one of [4] to [12].
[14]
A composition for forming a light emitting layer of an electrochemiluminescent cell, comprising a combination of an organic polymer light emitting material, an organic solvent, and two or more organic salts.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto.

[Example 1 and Comparative Example 1]
A commercially available glass substrate with an ITO film (manufactured by Geomatic Co., Ltd., ITO film thickness 200 nm) was used as the first electrode. PFO-DMP (Poly (9,9-dioctylfluorenyl-2,7-diyl) end capped with dimethylphenyl, manufactured by Luminescencetechnology, LT-S934, average molecular weight (Mn) = 50,000-150,000) is used as the organic polymer light-emitting material. It was. A combination of ionic liquid tributyloctylammonium bistrifluoromethanesulfonylimide (N4448TFSI) and ionic liquid tributyloctylammonium bromide (N4448Br) was used as an organic salt. The mass ratio between the two was as shown in FIG. 3 (a) (in FIG. 3 (a), x on the horizontal axis represents the mass fraction. The same applies to the horizontal axes in FIGS. 4 to 12 below. .)

Organic polymer light-emitting material in a volume ratio of a toluene solution (concentration: 9 g / L) of an organic polymer light-emitting material and a mixed ionic liquid toluene solution (concentration: 9 g / L) in a glove box under an argon atmosphere at room temperature The composition for light emitting layer formation was prepared by mixing with solution: ionic liquid solution = 4: 1. Next, the composition for forming a light-emitting layer prepared above is applied by spin coating on the first electrode of the glass substrate at room temperature in a glove box in an argon atmosphere, and further, 30% on a hot plate at 50 ° C. The organic solvent was evaporated by heating for minutes. In this way, a solid light emitting layer having a thickness of 100 nm was formed. Further, a second electrode made of aluminum (Al) having a thickness of 30 nm was formed on the formed light emitting layer by the method described above. In this way, an electrochemiluminescence cell having an area of a 2 mm × 2 mm square of a planned emission portion was produced.

In the obtained electrochemiluminescence cell, the first electrode was connected to the direct current anode, the second electrode was connected to the cathode, a voltage was applied up to 20 V, and the maximum luminance during this period was defined as the emission luminance. The luminance was measured using CS-2000 (manufactured by Konica Minolta). The results are shown in FIG.

[Example 2 and Comparative Example 2]
A combination of an ionic liquid tributyloctylammonium bistrifluoromethanesulfonylimide (N4448TFSI) and an ionic liquid trioctylmethylammonium bistrifluoromethanesulfonylimide (N8881TFSI) was used as an organic salt. The mass ratio between the two was as shown in FIG. 4 (in FIG. 4, x on the horizontal axis represents the mass fraction). Except this, an electrochemiluminescence cell was produced in the same manner as in Example 1. About the obtained electrochemiluminescence cell, the same measurement as Example 1 was performed. The result is shown in FIG.

[Example 3 and Comparative Example 3]
A combination of ionic liquid trioctylbenzylphosphonium bistrifluoromethanesulfonylimide (P888BzTFSI) and ionic liquid trioctylbenzylphosphonium bromide (P888BzBr) was used as an organic salt. The mass ratio between the two was as shown in FIG. Except this, an electrochemiluminescence cell was produced in the same manner as in Example 1. About the obtained electrochemiluminescence cell, the same measurement as Example 1 was performed. The result is shown in FIG.

Example 4 and Comparative Example 4
A combination of ionic liquid trioctylbenzylphosphonium bistrifluoromethanesulfonylimide (P888BzTFSI) and ionic liquid triethylpentylphosphonium bistrifluoromethanesulfonylimide (P2225TFSI) was used as an organic salt. The mass ratio between the two was as shown in FIG. Except this, an electrochemiluminescence cell was produced in the same manner as in Example 1. About the obtained electrochemiluminescence cell, the same measurement as Example 1 was performed. The result is shown in FIG.

[Example 5 and Comparative Example 5]
A commercially available glass substrate with an ITO film (manufactured by Geomatic Co., Ltd., ITO film thickness 200 nm) was used as the first electrode. F8BT (Poly [(9,9-di-n-octylfluorenyl-2,7-diyl) -alt- (benzo [2,1,3] thiadiazol-4,8-diyl)]) as an organic polymer light-emitting material Aldrich's average molecular weight (Mn) = 10000 to 20000) was used. As an organic salt, a combination of ionic liquid tributyloctylammonium bistrifluoromethanesulfonylimide (N4448TFSI) and ionic liquid tributyloctylammonium bromide (N4448Br) was used. The mass ratio between the two was as shown in FIG. Except this, an electrochemiluminescence cell was produced in the same manner as in Example 1. About the obtained electrochemiluminescence cell, the same measurement as Example 1 was performed. The result is shown in FIG.

[Example 6 and Comparative Example 6]
A combination of ionic liquid trioctylmethylammonium bistrifluoromethanesulfonylimide (N8881TFSI) and ionic liquid trioctylhexadecammonium bistrifluoromethanesulfonylimide (N888 (16) TFSI) was used as an organic salt. The mass ratio between the two was as shown in FIG. Other than this, an electrochemiluminescence cell was produced in the same manner as in Example 5. About the obtained electrochemiluminescence cell, the same measurement as Example 5 was performed. The result is shown in FIG.

[Example 7 and Comparative Example 7]
A combination of ionic liquid trioctylbenzylphosphonium bistrifluoromethanesulfonylimide (P888BzTFSI) and ionic liquid triethylpentylphosphonium bistrifluoromethanesulfonylimide (P2225TFSI) was used as an organic salt. The mass ratio between the two was as shown in FIG. Other than this, an electrochemiluminescence cell was produced in the same manner as in Example 5. About the obtained electrochemiluminescence cell, the same measurement as Example 5 was performed. The result is shown in FIG.

[Example 8 and Comparative Example 8]
A combination of an ionic liquid trioctylmethylammonium bistrifluoromethanesulfonylimide (N8881TFSI) and an ionic liquid trioctylbenzylphosphonium bistrifluoromethanesulfonylimide (P888BzTFSI) was used as an organic salt. The mass ratio between the two was as shown in FIG. Other than this, an electrochemiluminescence cell was produced in the same manner as in Example 5. About the obtained electrochemiluminescence cell, the same measurement as Example 5 was performed. The result is shown in FIG.

[Example 9 and Comparative Example 9]
A combination of ionic liquid tributyloctylammonium bistrifluoromethanesulfonylimide (N4448TFSI) and solid tributyloctylammonium tetrafluoroborate (N4448BF ₄ ) was used as an organic salt. The mass ratio between the two was as shown in FIG. Except this, an electrochemiluminescence cell was produced in the same manner as in Example 1. About the obtained electrochemiluminescence cell, the same measurement as Example 1 was performed. The result is shown in FIG.

[Example 10 and Comparative Example 10]
A combination of ionic liquid tributyloctylammonium bistrifluoromethanesulfonylimide (N4448TFSI) and solid tributyloctylammonium hexafluorophosphate (N4448PF ₆ ) was used as an organic salt. The mass ratio between the two was as shown in FIG. Except this, an electrochemiluminescence cell was produced in the same manner as in Example 1. About the obtained electrochemiluminescence cell, the same measurement as Example 1 was performed. The result is shown in FIG.

[Example 11 and Comparative Example 11]
A commercially available glass substrate with an ITO film (manufactured by Geomatic Co., Ltd., ITO film thickness 200 nm) was used as the first electrode. PFO-Spiro (Poly [(9,9-dioctylfluorenyl-2,7-diyl) -alt-co- (9,9'-spirobifluorene-2,7-diyl)]], Solaris Chem Manufactured by SOL2412). As an organic salt, a combination of solid tetraoctylphosphonium bromide (P8888Br) and solid tetraoctylphosphonium p-toluenesulfonate (P8888TS) was used. The mass ratio between the two was as shown in FIG. Except this, an electrochemiluminescence cell was produced in the same manner as in Example 1. About the obtained electrochemiluminescence cell, the same measurement as Example 1 was performed. The result is shown in FIG.

[Example 12 and Comparative Example 12]
A commercially available glass substrate with an ITO film (manufactured by Geomatic Co., Ltd., ITO film thickness 200 nm) was used as the first electrode. PFO-Spiro (Poly [(9,9-dioctylfluorenyl-2,7-diyl) -alt-co- (9,9'-spirobifluorene-2,7-diyl)]], Solaris Chem Manufactured by SOL2412). As an organic salt, a combination of solid tetrabutylphosphonium dibutyl phosphate (P4P4) and liquid tetrabutylphosphonium dimethyl phosphate (P4P1) was used. The mass ratio between the two was as shown in FIG. Except this, an electrochemiluminescence cell was produced in the same manner as in Example 1. About the obtained electrochemiluminescence cell, the same measurement as Example 1 was performed. The result is shown in FIG.

As is clear from the results shown in FIGS. 3 to 14, it can be seen that the emission luminance is increased by using a combination of two organic salts rather than using a single organic salt.

DESCRIPTION OF SYMBOLS 10 Electrochemiluminescence cell 12 Light emitting layer 13 1st electrode 14 2nd electrode 16 p doped area | region 17 n doped area | region

Claims

In an electrochemiluminescence cell having a light emitting layer and electrodes arranged on each surface thereof,
The electrochemiluminescence cell in which the light emitting layer includes a combination of an organic polymer light emitting material and two or more organic salts.
The electrochemiluminescence cell according to claim 1, wherein the organic salt is an organic salt selected from a phosphonium salt, an ammonium salt, a pyridinium salt, an imidazolium salt, and a pyrrolidinium salt.
The electrochemiluminescence cell according to claim 1 or 2, wherein the organic salt is an organic salt represented by the following formula (1).

(Wherein R 1 , R 2 , R 3 and R 4 are each an alkyl group, an alkoxyalkyl group, a trialkylsilylalkyl group, an alkenyl group, an alkynyl group, an aryl group, which may be substituted with a functional group, or Represents a heterocyclic group, R 1 , R 2 , R 3 and R 4 may be the same or different from each other, M represents N or P, and X − represents an anion.)
The electrochemiluminescence cell according to any one of claims 1 to 3, wherein the two or more organic salts are a combination of liquid organic salts.
The electrochemiluminescence cell according to any one of claims 1 to 3, wherein the two or more organic salts are a combination of solid organic salts.
The electrochemiluminescence cell according to any one of claims 1 to 3, wherein the combination of two or more organic salts is a combination of a liquid organic salt and a solid organic salt.
A composition for forming a light emitting layer of an electrochemiluminescent cell, comprising a combination of an organic polymer light emitting material, an organic solvent, and two or more organic salts.
The composition according to claim 7, wherein the organic salt is an organic salt selected from a phosphonium salt, an ammonium salt, a pyridinium salt, an imidazolium salt, and a pyrrolidinium salt.
The composition according to claim 7 or 8, wherein the organic salt is an organic salt represented by the following formula (1).

(Wherein R 1 , R 2 , R 3 and R 4 are each an alkyl group, an alkoxyalkyl group, a trialkylsilylalkyl group, an alkenyl group, an alkynyl group, an aryl group, which may be substituted with a functional group, or Represents a heterocyclic group, R 1 , R 2 , R 3 and R 4 may be the same or different from each other, M represents N or P, and X − represents an anion.)
The composition according to any one of claims 7 to 9, wherein the two or more organic salts are a combination of liquid organic salts.
The composition according to any one of claims 7 to 9, wherein the two or more organic salts are a combination of solid organic salts.
The composition according to any one of claims 7 to 9, wherein the combination of two or more organic salts is a combination of a liquid organic salt and a solid organic salt.
The composition according to any one of claims 7 to 12, wherein the organic solvent is toluene, benzene, tetrahydrofuran, dimethyl chloride, chlorobenzene or chloroform.
An electrochemiluminescence cell using the composition according to any one of claims 7 to 13 as a material for forming a light emitting layer.