JP2015216095A - Electrochemical light-emitting cell and composition for forming light-emitting layer of electrochemical light-emitting cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrochemical light-emitting cell that can have high durability since sufficiently uniform surface emission can be obtained.SOLUTION: An electrochemical light-emitting cell comprises a light-emitting layer 12, and electrodes 13, 14 disposed on each face of the light-emitting layer 12. The light-emitting layer comprises organic polymer light-emitting material and ionic liquid. The ionic liquid is represented by general formula (1), where M represents N or P, R, R, Rand Rrepresent a saturated aliphatic group, an unsaturated aliphatic group or an aromatic ring-containing group having 20 or less carbon atoms, and Xis an anion.

Description

  The present invention relates to an electrochemiluminescence cell having a light emitting layer containing a light emitting material and an ionic liquid. 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) devices, which are devices that emit light by 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.

  In general, an organic EL element includes a pair of substrates each having an electrode formed on a surface 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.

  In recent years, light-emitting electrochemical cells (LECs) have attracted attention as self-luminous elements that deal 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.

  As a salt used for an electrochemiluminescence cell, lithium salt and potassium salt are common. These salts are used by being dissolved in an organic solvent or the like. However, lithium salts, potassium salts, and the like have a problem that ion mobility is lowered when an organic solvent is volatilized. Considering this problem, an attempt has been made to use an ionic liquid that is a non-volatile salt and has a higher reorientation rate due to an electric field than a solid electrolyte. So far, a plurality of production examples of electrochemiluminescence cells using an ionic liquid have been reported (Patent Documents 1 and 2 and Non-Patent Document 1).

  Conventionally, as for ionic liquids, nitrogen-based cations such as ammonium ions, pyridium ions, and imidazolium ions have been widely studied from the viewpoint of availability of raw materials. For this reason, it is common technical knowledge to use nitrogen-based ionic liquids in electric devices using ionic liquids, including electrochemiluminescent cells. For example, the cations in the ionic liquids described in Patent Documents 1 and 2 and Non-Patent Document 1 are nitrogen-based cations such as ammonium ions and imidazolium ions. In recent years, examples using a quaternary alkylphosphonium cation as a cation of an ionic liquid used in an electrochemiluminescence cell have also been reported (Non-patent Documents 2 and 3).

JP 2011-103234 A Special table 2012-516033 gazette

Qingjiang Sun, “Polymer Light-Emitting Electrochemical Cells for High-Efficiency Low-Voltage Electroluminescent Devices” JOURNAL OF DISPLAY TECHNOLOGY VOL.3 NO.2, JUNE 2007 Hyun Jung Lee “Hybrid organic-inorganic light-emitting electrochemical cells using fluorescent polymer and ionic liquid blend as an active layer”, APPLIED PHYSICS LETTERS 98, 253309 (2011) Tomo Sakanoue, “Optically pumped amplified spontaneous emission in an ionic liquid-based polymer light-emitting electrochemical cell” Applied Physics Letters, 100, 263301 (2012)

  However, as a cation of the ionic liquid, a phosphonium formed by binding nitrogen-based cations described in Patent Documents 1 and 2 and Non-Patent Document 1 or four aliphatic hydrocarbon groups described in Patent Documents 2 and 3 to a phosphorus atom When cations are used, uniform surface light emission may not be obtained due to insufficient solubility in organic polymer light-emitting materials. In this case, there is a problem that the operation life of the electrochemiluminescence cell is shortened and the durability is liable to be lowered because the load is biased to a part of the light emission scheduled portion in the electrochemiluminescence cell.

  Therefore, as a result of the present inventors diligently studying to increase the solubility of the ionic liquid in the organic polymer light-emitting material, the positive charge of the cation portion of the ionic liquid is canceled out, and the charge is reduced to the organic molecule, which is a neutral molecule. It has been found that it is effective to approach a molecular light emitting material.

  As a result of intensive studies on the method of canceling the positive charge of the cation portion of the ionic liquid, the present inventors have found that it is sufficient to enclose the positive charge structurally by increasing the number of side chain carbons of the cation portion and use it as a larger molecule. The present invention has been completed.

That is, the present invention relates to an electrochemiluminescence cell having a light emitting layer and electrodes disposed on each surface thereof.
The light emitting layer includes an organic polymer light emitting material and an ionic liquid;
The ionic liquid provides an electrochemiluminescence cell represented by the following general formula (1).

(Wherein, M represents N or P. _{Further, R 1, R 2, R} 3 and _{R 4} are each independently a saturated aliphatic group having 1 to 20 carbon atoms, having 2 to 20 carbon atoms Represents an unsaturated aliphatic group or an aromatic ring-containing group having 6 to 20 carbon atoms, provided that at least one of R ₁ , R ₂ , R ₃ and R ₄ is an unsaturated aliphatic group or an aromatic ring-containing group; Carbon atoms constituting the saturated aliphatic group, the unsaturated aliphatic group, and the aromatic ring-containing group may be substituted with a hetero atom, and the saturated aliphatic group, the unsaturated aliphatic group And a hydrogen atom in the aromatic ring-containing group may be substituted with a functional group, and X ⁻ is an anion.)

  Moreover, this invention provides the composition for light emitting layer formation of an electrochemiluminescent cell containing the ionic liquid represented by the said General formula (1), an organic polymer light emitting material, and an organic solvent.

  ADVANTAGE OF THE INVENTION According to this invention, the electrochemiluminescence cell which can have high durability by providing sufficiently uniform surface emission 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 the electrochemiluminescence cell. FIG. 2A shows an electrochemiluminescence cell before voltage application, and FIG. 2B shows an electrochemiluminescence cell after voltage application. FIG. 3 shows the light emitting surface of the electrochemiluminescent cell obtained in Example 6. FIG. 4 shows a light emitting surface of the electrochemiluminescent cell obtained in Comparative Example 2.

  Hereinafter, preferred embodiments of the electrochemiluminescence cell of the present invention will be described with reference to the drawings. As will be described below, the electrochemiluminescence cell 10 of the present embodiment has one of the characteristics in that it has a specific type as anions of the ionic liquid.

  As shown in FIG. 1, the electrochemiluminescence cell 10 of this embodiment has a light emitting layer 12 and electrodes 13 and 14 disposed on each surface thereof. Specifically, the electrochemiluminescence cell 10 includes a first electrode 13 and a second electrode 14, each of which is a pair of electrodes facing each other, and a light emitting layer 12 sandwiched between the pair of electrodes 13 and 14. ing. The electrochemiluminescence cell 10 emits light when a voltage is applied, and is used as various displays. In FIG. 1, a DC power source is used as the 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, 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. Examples of the transparent electrode having translucency include those made of metal oxides such as indium-doped tin oxide (ITO) and fluorine-doped tin oxide (FTO). Moreover, what consists of polymer | macromolecule which has transparency, such as poly (3,4-ethylene dioxythiophene) (PEDOT) which added the impurity, can be mentioned. Examples of the translucent or opaque electrode include aluminum (Al), silver (Ag), gold (Au), platinum (Pt), tin (Sn), bismuth (Bi), copper (Cu), chromium ( Examples thereof include metal materials such as Cr).

  For example, 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 extracted outside while being reflected by the metal electrode. Further, for example, both the first electrode 13 and the second electrode 14 may be transparent electrodes, and a see-through light emitter may be used. In addition, for example, both the first electrode 13 and the second electrode 14 are made of metal electrodes made of Ag or the like having a high reflectivity, and the film thickness of the light emitting layer 12 is controlled, so that the electrochemiluminescent cell 10 is made into a laser. An oscillation element can also be used.

  For example, 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 from the viewpoint of realizing appropriate resistivity and light transmittance. It preferably has a thickness of 500 nm or less. Further, like the first electrode 13, 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 appropriate resistivity and light transmittance.

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

  The ionic liquid contained in the light emitting layer is a substance that maintains a liquid state at room temperature (25 ° C.) while being an ionic species. As described above, the electrochemiluminescence cell 10 of the present embodiment uses a specific type of cation as the ionic liquid.

  Specifically, the electrochemiluminescence cell 10 of this embodiment uses an ionic liquid represented by the following general formula (1). As a result, the electrochemiluminescence cell 10 of the present embodiment can obtain sufficiently uniform surface light emission, so that it can be excellent in durability and enable high emission luminance. The electrochemiluminescent cell 10 is also excellent in terms of voltage resistance, heat resistance, durability, discoloration resistance, and the like because a phosphonium cation having excellent chemical stability can be used. Furthermore, since the electrochemiluminescent cell 10 can use an ammonium-based anion having excellent economic efficiency, it is excellent in terms of cost.

(Wherein, M represents N or P. _{Further, R 1, R 2, R} 3 and _{R 4} are each independently a saturated aliphatic group having 1 to 20 carbon atoms, having 2 to 20 carbon atoms Represents an unsaturated aliphatic group or an aromatic ring-containing group having 6 to 20 carbon atoms, provided that at least one of R ₁ , R ₂ , R ₃ and R ₄ is an unsaturated aliphatic group or an aromatic ring-containing group; Carbon atoms constituting the saturated aliphatic group, the unsaturated aliphatic group, and the aromatic ring-containing group may be substituted with a hetero atom, and the saturated aliphatic group, the unsaturated aliphatic group And a hydrogen atom in the aromatic ring-containing group may be substituted with a functional group, and X ⁻ is an anion.)

In the general formula (1), the saturated aliphatic group having 1 to 20 carbon atoms represented by R ₁ , R ₂ , R ₃ and R ₄ is a linear, branched or cyclic saturated aliphatic hydrocarbon Groups. Specific examples of the saturated aliphatic group having 1 to 20 carbon atoms include 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 group, t-heptyl group, n-octyl group, isooctyl group, 2-ethylhexyl group, t-octyl group, nonyl group, isononyl group, decyl group, isodecyl group Group, undecyl group, dodecyl group, tridecyl group, isotridecyl group, tetradecyl group, hexadecyl group, octadecyl group, icosyl group, cyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexyl group, cycloheptyl group, cyclooctyl group, cyclononyl group, Examples include a cyclohexylmethyl group and a cyclodecyl group.

In the general formula (1), the saturated aliphatic group represented by R ₁ , R ₂ , R ₃ and R ₄ has a viewpoint of lowering the charge density and increasing the solubility in the organic polymer light-emitting material, and the organic polymer. From the viewpoint of doping performance to the light emitting material, the carbon number is preferably 2 or more, 16 or less, more preferably 4 or more and 12 or less, and particularly preferably 5 or more and 12 or less. In particular, as the saturated aliphatic group, it is preferable to use a straight-chain group having the above-mentioned range.

In general formula (1), the unsaturated aliphatic group having 2 to 20 carbon atoms represented by R ₁ , R ₂ , R ₃ and R ₄ is a straight chain having at least one double bond or triple bond. , Branched or cyclic aliphatic hydrocarbon groups. Examples of this unsaturated aliphatic group include groups in which one or more of the carbon-carbon single bonds in each aliphatic group listed above are replaced with double bonds or triple bonds. Specifically, , Vinyl group, allyl group, isopropenyl group, 2-butenyl group, 2-methylallyl group, 1,1-dimethylallyl group, 3-methyl-2-butenyl group, 3-methyl-3-butenyl group, 4-pentenyl Group, hexenyl group, octenyl group, nonenyl group, decenyl group or the like linear or branched alkenyl group; ethynyl group, prop-2-yn-1-yl group or the like alkynyl group; cyclobutenyl group, cyclopentenyl group A cycloalkenyl group such as cyclohexenyl group, cycloheptenyl group, cyclooctenyl group, 4-methylcyclohexenyl group, 4-ethylcyclohexenyl group; And butadiene, and a group consisting of polymers or copolymers of those isopropylene and the like. In addition, when an unsaturated aliphatic group is an alkenyl group, both a trans body and a cis body are included.

In the general formula (1), the unsaturated aliphatic group represented by R ₁ , R ₂ , R ₃ and R ₄ has a viewpoint of decreasing the charge density and increasing the solubility in the organic polymer light-emitting material, From the viewpoint of doping performance into the molecular light emitting material, the number of carbon atoms is preferably 2 or more and 12 or less, and more preferably 2 or more and 6 or less.

In the general formula (1), the aromatic ring-containing group having 6 to 20 carbon atoms represented by R ₁ , R ₂ , R ₃ and R ₄ is an aromatic ring such as a benzene ring, a naphthalene ring or an anthracene ring. It is a hydrocarbon group contained in one or more groups. Examples of the aromatic ring-containing group include a group obtained by removing one hydrogen atom on an aromatic ring in an aromatic compound, that is, an aryl group, and 1 in the aliphatic group or unsaturated aliphatic group mentioned above. A group in which the above hydrogen atom is substituted with an aryl group can be exemplified. Examples of the aryl group include a phenyl group, a tolyl group, a xylyl group, a naphthyl group, and an anthracenyl group. Examples of the group in which one or more hydrogen atoms in the aliphatic group are substituted with an aryl group include a benzyl group, a 1-phenylethyl group, a 2-phenylethyl group, a 2-phenylpropyl group, and a 3-phenylpropyl group. Group, 4-phenylbutyl group, 5-phenylpentyl group, 6-phenylhexyl group and the like. Further, a group in which the hydrogen atom at the ortho position, the meta position and / or the para position of the phenyl moiety in these groups is substituted with an alkyl group, for example, a tolylmethyl group, a 1-tolylethyl group, a 2-tolylethyl group, a 2-tolylpropyl group. 3-tolylpropyl group, 4-tolylbutyl group, 5-tolylpentyl group, 6-tolylhexyl group, xylylmethyl group, 1-xylylethyl group, 2-xylylethyl group, 2-xylylpropyl group, 3-xylylpropyl group Arylalkyl groups such as 4-xylylbutyl group, 5-xylylpentyl group and 6-xylylhexyl group. As the group in which at least one hydrogen atom in the unsaturated aliphatic group is substituted with the aryl group, one or more hydrogen atoms in various alkenyl groups mentioned as the unsaturated aliphatic group are aryl. An arylalkenyl group substituted with a group, an arylalkynyl group in which one or more of the hydrogen atoms in the various alkynyl groups mentioned as the unsaturated aliphatic group are substituted with an aryl group, and the like. In these aromatic ring-containing groups (such as aryl groups), one or more hydrogen atoms bonded to the aromatic ring contained in the aromatic ring-containing group are substituted with the above-described aliphatic group or unsaturated aliphatic group. Is also included. The aromatic ring-containing group preferably has 7 to 14 carbon atoms, preferably 7 to 11 carbon atoms, from the viewpoint of solubility in organic polymer light-emitting materials and doping performance to organic polymer light-emitting materials. More preferred. From the same viewpoint, the aromatic ring-containing group is preferably an arylalkyl group. Specifically, the aromatic ring-containing group is more preferably a phenyl group, a benzyl group, a p-tolylmethyl group, or a phenylethyl group, and particularly preferably a benzyl group.

In the general formula (1), a hetero atom which may substitute a carbon atom in the saturated aliphatic group, unsaturated aliphatic group and aromatic ring-containing group represented by R ₁ , R ₂ , R ₃ and R ₄ Examples thereof include an oxygen atom, a sulfur atom, and a nitrogen atom. As such a group substituted with a heteroatom, an aromatic heterocyclic group such as a furyl group, a thiophene group, a pyrrole group, an imidazole group or a group in which these are bonded to an aliphatic group or an unsaturated aliphatic group, or A group in which one or more methylene groups in the saturated aliphatic group, unsaturated aliphatic group and aromatic ring-containing group exemplified above are substituted with an oxygen or sulfur atom, or a saturated aliphatic group, an unsaturated aliphatic group, and Examples include a group in which one or more CH groups in the aromatic ring-containing group are substituted with a nitrogen atom.

In general formula (1), the functional group which may substitute the hydrogen atom in the saturated aliphatic group, unsaturated aliphatic group, and aromatic ring-containing group represented by R ₁ , R ₂ , R ₃ and R ₄ Examples thereof include a nitrile group, amino group, phenyl group, benzyl group, carboxyl group, and an alkoxy group having 1 to 12 carbon atoms.

In general formula (1), at least one of R ₁ , R ₂ , R ₃ and R ₄ is an unsaturated aliphatic group or an aromatic ring-containing group. That is, in the present invention, an ionic liquid composed of an ammonium cation or a phosphonium cation having at least one unsaturated aliphatic group or aromatic ring-containing group is used. By using an ionic liquid of an ammonium cation or a phosphonium cation having an unsaturated aliphatic group or an aromatic ring-containing group, the electrochemiluminescence cell of the present invention has sufficiently uniform surface emission. In addition, since the electrochemiluminescence cell of the present invention enables uniform surface emission, the luminous efficiency is increased, leading to an improvement in luminance. The reason for this is not clear, but the cation part is neutral by enclosing the charge of the cation part of the ionic liquid with an unsaturated aliphatic group or aromatic ring-containing group which is a group having a relatively large structure. Therefore, the present inventor presumes that the miscibility with the organic polymer light emitting material, which is neutral, is improved.

  In addition, an ionic liquid of an ammonium cation or a phosphonium cation having an unsaturated aliphatic group or an aromatic ring-containing group has excellent voltage resistance due to its structural stability. As a result, the electrochemiluminescence cell of the present invention is excellent in voltage resistance in addition to the above-described uniform light emitting surface, leading to a long life.

Among the ionic liquids represented by the general formula (1), _{three of} R ₁ , R ₂ , R ₃ and R ₄ are the saturated aliphatic groups, and one is an unsaturated aliphatic group or an aromatic ring-containing group. An ionic liquid is preferable because it has a low viscosity and a low melting point and is excellent in chemical stability such as voltage resistance. In particular, an ionic liquid in which three of R ₁ , R ₂ , R ₃ and R ₄ are the saturated aliphatic group and one is an arylalkyl group or an alkenyl group is preferable.

In the ionic liquid used in the present invention, the general formula (1) in the X ^- is not particularly limited on the kind of anions represented as, it can be used anion of the ionic liquid used in the conventional electric device. Examples of such anions include tetrafluoroborate (BF ₄ ), benzotriazolate (N ₃ (C ₆ H ₄ )), tetraphenyl borate (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 ), trifluoroacetic acid (CF ₃ COO), amino acids, bisoxalatoborate (B (C ₂ O _{4) 2} ), p-toluenesulfonate (SO ₃ C ₆ H ₄ CH ₃ ), thiocyanate (SCN), dicyanamide (N (CN) ₂ ), halogen, dialkyl phosphoric acid ((RO) ₂ POO), dialkyldithiophosphoric acid ((RO) ₂ PSS), aliphatic carboxylic acid (RCOO), etc. Can be mentioned. Among these, bis (trifluoromethylsulfonyl) imide (N (SO ₂ CF ₃ ) ₂ ), tetrafluoroborate (BF ₄ ), hexafluorophosphate (PF ₆ ), bisoxalatoborate (B (C ₂ O ₄₎ ) ₂ , thiocyanate (SCN) is preferable in terms of low production cost, low viscosity, and good miscibility with organic polymer light-emitting materials.

The ionic liquid represented by the general formula (1) can be produced, for example, as follows. First, among the above-mentioned phosphonium salts, those in which the anion component is halogen use a quaternary phosphonium halide obtained by reacting a tertiary phosphine compound corresponding to the target phosphonium cation and a halogenated hydrocarbon compound. it can. Those having an anionic component other than halogen can be obtained by reacting the quaternary phosphonium halide with a metal salt of the anionic component to exchange anions. For example, R ₁ , R ₂ , R ₃ and R _{4 in} the general formula (1) have a phosphonium cation in which three are saturated aliphatic groups and the remaining one is an unsaturated aliphatic group or an aromatic ring-containing group. In the ionic liquid in which the anion component is halogen, trialkylphosphine is used as the tertiary phosphine compound, and the unsaturated aliphatic group or aromatic ring-containing group is bonded to halogen as the halogenated hydrocarbon compound. It can be obtained by using a compound. In addition, a phosphonium cation in which three of R ₁ , R ₂ , R ₃ and R _{4 in} the general formula (1) are saturated aliphatic groups and the remaining one is an unsaturated aliphatic group or an aromatic ring-containing group. The ionic liquid having an anionic component other than halogen is an ionic liquid in which the anionic component is halogen as described above: bis (trifluoromethylsulfonyl) imide, tetrafluoroborate (BF ₄ ), hexafluorophosphate (PF ₆ ). , Bisoxalatoborate (B (C ₂ O ₄ ) ₂ , thiocyanate (SCN) and the like can be obtained by anion exchange.

  In the electrochemiluminescence cell 10 of the present embodiment, the ratio of the ionic liquid in the light emitting layer 12 is 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. It is preferable that it is 5 mass% or more and 20 mass% or less. Moreover, it is preferable that content of the ionic liquid in the light emitting layer 12 is 10 to 25 mass parts with respect to 100 mass parts of organic polymer light-emitting materials.

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, [(—CH ₂ CH ₂ O—) _n CH ₃ ] (wherein n is an integer of 1 or more and 10 or less). 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.

  From the viewpoint of sufficiently exhibiting these functions of the organic polymer light emitting material, the ratio of the organic polymer light emitting material 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 is more preferable.

  The light emitting layer 12 may contain other than the organic polymer light emitting material and the ionic liquid. Other components include surfactants, polymer components for improving conductivity (polyethylene oxide, etc.), polymer components for improving film forming properties (polystyrene, polymethyl methacrylate (PMMA), etc.), ionic liquids A salt etc. can be mentioned. The amount of components other than the organic polymer light-emitting material and ionic liquid (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 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, light emission can be obtained sufficiently and efficiently from the light emitting layer 12, and defects in a light emission scheduled portion can be suppressed and a short circuit can be prevented.

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

  Next, an ionic liquid 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 ionic liquid 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 ionic liquid 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. Preparation of the composition for forming the light emitting layer and 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. Can be mentioned.

  Next, the second electrode 14 facing the first electrode 13 is formed on the formed light emitting layer 12. In this case, for example, 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 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 high carrier density pin junction. 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 a desired wavelength, an organic polymer light emitting material in which the energy difference (band gap) between the highest occupied orbital (Highest Occupied Molecular Orbital) and the lowest unoccupied molecular orbital corresponds to the desired wavelength. Should be selected.

  According to the electrochemiluminescence cell 10 of the present embodiment, the entire light emission scheduled portion can be easily made to emit light. Moreover, it is easy to emit light so that the entire light emission scheduled portion emits light, and an arbitrary portion of the light emission scheduled portion has uniform luminance. Therefore, since the load is uniformly applied over the entire area of the light emission scheduled portion, the durability is improved as compared with the conventional case. The light emission scheduled portion refers to a planar region where the first electrode 13, the light emitting layer 12, and the second electrode 14 all overlap when the electrochemiluminescence cell 10 is viewed in plan. According to the electrochemiluminescence cell 10 of the present embodiment, the area of the portion that does not emit light is small, and the portion that does not emit light is dispersed in a scattered manner within the portion that is scheduled to emit light. When the ratio of the area is approximately the same, there is an advantage that a uniform load is less likely to be applied, and a lack of a portion that does not emit light is less visible than a state in which the portion that does not emit light is concentrated in one place.

  Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto. The characteristics in the following examples were measured by the following methods.

<Luminescent characteristics>
In the electrochemiluminescence cell, the first electrode is connected to the anode of the direct current, the second electrode is connected to the cathode, a voltage is applied up to 12 V at a sweep rate of 1 V / sec, and light emission is visually checked while The maximum value of the luminance was defined as the light emission luminance. The emission luminance was measured using CS-2000 (manufactured by Konica Minolta).

<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 13.

  F8BT (Poly [(9,9-di-n-octylfluorenyl-2,7-diyl) -alt- (benzo [2,1,3] thiadiazole-4,8-diyl) as an organic polymer light-emitting material ], A product of Aldrich, average molecular weight (Mn) = 10,000 to 20,000), and a mixed solution of these using trioctylbenzylphosphonium bistrifluoromethanesulfonylimide as an ionic liquid. Specifically, a toluene solution (concentration: 9 g / L) of an organic polymer light emitting material and an ionic liquid toluene solution (concentration: 9 g / L) are organically mixed at a room temperature in a glove box under an argon atmosphere. Polymer light emitting material solution: ionic liquid solution = 4: 1 was mixed to prepare a composition for forming a light emitting layer.

  Next, the light emitting layer forming composition prepared above is applied by spin coating on the first electrode 13 of the glass substrate at room temperature in a glove box in an argon atmosphere and dried, and then a hot plate at 50 ° C. The organic solvent was evaporated by heating for 30 minutes above. Thus, the solid light emitting layer 12 having a thickness of 100 nm was formed. Further, the second electrode 14 made of aluminum (Al) with a thickness of 30 nm was formed on the formed light emitting layer 12 by the method described above. In this manner, an electrochemiluminescence cell 10 having an area of 2 mm × 2 mm square of a light emission scheduled portion was produced. Table 1 shows the results of measuring the light emission characteristics of the obtained electrochemiluminescence cell 10.

<Example 2>
An electrochemiluminescence cell 10 was produced in the same manner as in Example 1 except that triethylbenzylphosphonium bistrifluoromethanesulfonylimide was used as the ionic liquid. Table 1 shows the results of measuring the light emission characteristics of the obtained electrochemiluminescence cell 10.

<Example 3>
An electrochemiluminescence cell 10 was produced in the same manner as in Example 1 except that tributylbenzylphosphonium bistrifluoromethanesulfonylimide was used as the ionic liquid. Table 1 shows the results of measuring the light emission characteristics of the obtained electrochemiluminescence cell 10.

<Example 4>
PFO-DMP (Poly (9,9-dioctylfluorenyl-2,7-diyl) end capped with dimethylphenyl), manufactured by Luminescence Technology) is used as the organic polymer light-emitting material, and trioctylbenzylphosphonium bistrifluoro is used as the ionic liquid. These mixed solutions were prepared using methanesulfonylimide. Specifically, a toluene solution (concentration: 9 g / L) of an organic polymer light emitting material and an ionic liquid toluene solution (concentration: 9 g / L) are organically mixed at a room temperature in a glove box under an argon atmosphere. Polymer light emitting material solution: ionic liquid solution = 4: 1 was mixed to prepare a composition for forming a light emitting layer.
Subsequent operations were the same as those in Example 1, and the electrochemiluminescence cell 10 was produced. Table 1 shows the results of measuring the light emission characteristics of the obtained electrochemiluminescence cell 10.

<Example 5>
An electrochemiluminescence cell 10 was produced in the same manner as in Example 4 except that trioctylallylphosphonium bistrifluoromethanesulfonylimide was used as the ionic liquid. Table 1 shows the results of measuring the light emission characteristics of the obtained electrochemiluminescence cell 10.

<Comparative Example 1>
An electrochemiluminescence cell 10 was produced in the same manner as in Example 1 except that trioctylbutylphosphonium bisfluoromethanesulfonylimide was used as the ionic liquid. Table 1 shows the results of measuring the light emission characteristics of the obtained electrochemiluminescence cell 10.

  From the above results, the electrochemiluminescence cell 10 of each example using an ionic liquid having a phosphonium cation having an unsaturated bond was able to obtain sufficiently uniform surface emission, but a phosphonium cation having no unsaturated bond. Uniform light emission was not obtained from the electrochemiluminescence cell 10 of each comparative example using an ionic liquid having the following.

<Example 6>
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 13.

  Super Yellow (manufactured by Merck, product name: PDY-132) is used as the organic polymer light-emitting material, and trioctylbenzylammonium bistrifluoromethanesulfonylimide (manufactured by Nippon Chemical Industry Co., Ltd.) is used as the ionic liquid. A mixed solution was prepared. Specifically, a toluene solution (concentration: 9 g / L) of an organic polymer light emitting material and an ionic liquid toluene solution (concentration: 9 g / L) are organically mixed at a room temperature in a glove box under an argon atmosphere. Polymer light-emitting material solution: ionic liquid solution = 4: 1 was mixed to prepare a composition for forming a light-emitting layer.

  Next, the light emitting layer forming composition prepared above is applied by spin coating on the first electrode 13 of the glass substrate at room temperature in a glove box in an argon atmosphere and dried, and then a hot plate at 50 ° C. The organic solvent was evaporated by heating for 30 minutes above. Thus, the solid light emitting layer 12 having a thickness of 100 nm was formed. Further, the second electrode 14 made of aluminum (Al) with a thickness of 30 nm was formed on the formed light emitting layer 12 by the method described above. In this manner, an electrochemiluminescence cell 10 having an area of 2 mm × 2 mm square of a light emission scheduled portion was produced. Table 2 shows the results of measuring the light emission characteristics of the obtained electrochemiluminescence cell 10. A photograph of the light emitting surface is shown in FIG.

<Example 7>
The electrochemiluminescence cell 10 was produced in the same manner as in Example 6 except that trioctylphenylethylammonium bistrifluoromethanesulfonylimide (manufactured by Nippon Chemical Industry Co., Ltd.) was used as the ionic liquid. Table 2 shows the results of measuring the light emission characteristics of the obtained electrochemiluminescence cell 10.

<Example 8>
An electrochemiluminescence cell 10 was produced in the same manner as in Example 6 except that trioctyl (4-methylphenyl) methylammonium bistrifluoromethanesulfonylimide (manufactured by Nippon Chemical Industry Co., Ltd.) was used as the ionic liquid. Table 2 shows the results of measuring the light emission characteristics of the obtained electrochemiluminescence cell 10.

<Example 9>
An electrochemiluminescence cell 10 was produced in the same manner as in Example 6 except that trioctylallylammonium bistrifluoromethanesulfonylimide (manufactured by Nippon Chemical Industry Co., Ltd.) was used as the ionic liquid. Table 2 shows the results of measuring the light emission characteristics of the obtained electrochemiluminescence cell 10.

<Comparative Example 2>
An electrochemiluminescence cell 10 was produced in the same manner as in Example 6 except that trioctylmethylammonium bistrifluoromethanesulfonylimide (manufactured by iolitec) was used as the ionic liquid. Table 2 shows the results of measuring the light emission characteristics of the obtained electrochemiluminescence cell 10. Further, a photograph of the light emitting surface is shown in FIG.

<Comparative Example 3>
An electrochemiluminescence cell 10 was produced in the same manner as in Example 6 except that tributyloctylammonium bistrifluoromethanesulfonylimide (manufactured by Nippon Chemical Industry Co., Ltd.) was used as the ionic liquid. Table 2 shows the results of measuring the light emission characteristics of the obtained electrochemiluminescence cell 10.

  From the results shown in Table 2, the electrochemiluminescence cell 10 of Example 1 using an ionic liquid having an ammonium-based cation having an aromatic ring-containing group has sufficiently uniform surface emission as shown in FIG. Moreover, the electrochemiluminescence cell 10 of each Example can obtain sufficient light emission luminance. In contrast, in the electrochemiluminescence cell 10 of Comparative Example 2 using an ionic liquid having an ammonium-based cation having no aromatic ring-containing group, uniform light emission cannot be obtained as shown in FIG. The electrochemiluminescence cell 10 of each comparative example also had a low emission luminance.

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 (14)

In an electrochemiluminescence cell having a light emitting layer and electrodes arranged on each surface thereof,
The light emitting layer includes an organic polymer light emitting material and an ionic liquid;
The electrochemiluminescence cell in which the ionic liquid is represented by the following general formula (1).
(Wherein, M represents N or P. _{Further, R 1, R 2, R} 3 and _{R 4} are each independently a saturated aliphatic group having 1 to 20 carbon atoms, having 2 to 20 carbon atoms Represents an unsaturated aliphatic group or an aromatic ring-containing group having 6 to 20 carbon atoms, provided that at least one of R ₁ , R ₂ , R ₃ and R ₄ is an unsaturated aliphatic group or an aromatic ring-containing group; Carbon atoms constituting the saturated aliphatic group, the unsaturated aliphatic group, and the aromatic ring-containing group may be substituted with a hetero atom, and the saturated aliphatic group, the unsaturated aliphatic group And a hydrogen atom in the aromatic ring-containing group may be substituted with a functional group, and X ⁻ is an anion.) The electrochemiluminescence cell according to claim 1, wherein, in the general formula (1), at least one of R ₁ , R ₂ , R ₃ and R ₄ is the aromatic ring-containing group.   3. In the general formula (1), the unsaturated aliphatic group is a linear, branched or cyclic aliphatic hydrocarbon group having at least one double bond or triple bond. The electrochemiluminescence cell as described.   In the said General formula (1), the said functional group is an amino group, a nitrile group, a phenyl group, a benzyl group, a carboxyl group, or a C1-C12 alkoxy group. Electrochemiluminescence cell.   The organic polymer light-emitting material is poly (paraphenylene vinylene), poly (fluorene), poly (1,4-phenylene), polythiophene, polypyrrole, poly (paraphenylene sulfide), polybenzothiadiazole, polybiothiophine or these The electrochemiluminescence cell according to any one of claims 1 to 4, which is a derivative or a copolymer. In the said General formula (1), _three of R < ₁ >, R < ₂ >, R < ₃ > and R < ₄ > are the said saturated aliphatic groups, and one is an arylalkyl group or an alkenyl group, Any one of Claims 1-5 The electrochemiluminescence cell according to one item. A composition for forming a light emitting layer of an electrochemiluminescent cell, comprising an ionic liquid represented by the following general formula (1), an organic polymer light emitting material and an organic solvent.
(Wherein, M represents N or P. _{Further, R 1, R 2, R} 3 and _{R 4} are each independently a saturated aliphatic group having 1 to 20 carbon atoms, having 2 to 20 carbon atoms Represents an unsaturated aliphatic group or an aromatic ring-containing group having 6 to 20 carbon atoms, provided that at least one of R ₁ , R ₂ , R ₃ and R ₄ is an unsaturated aliphatic group or an aromatic ring-containing group; Carbon atoms constituting the saturated aliphatic group, the unsaturated aliphatic group, and the aromatic ring-containing group may be substituted with a hetero atom, and the saturated aliphatic group, the unsaturated aliphatic group And a hydrogen atom in the aromatic ring-containing group may be substituted with a functional group, and X ⁻ is an anion.) The composition according to claim 7, wherein in the general formula (1), at least one of R ₁ , R ₂ , R ₃ and R ₄ is the aromatic ring-containing group.   In the general formula (1), the unsaturated aliphatic group is a linear, branched or cyclic aliphatic hydrocarbon group having at least one double bond or triple bond. The composition as described.   In the said General formula (1), the said functional group is an amino group, a nitrile group, a phenyl group, a benzyl group, a carboxyl group, or a C1-C12 alkoxy group, It is any one of Claims 7-9. Composition.   The organic polymer light-emitting material is poly (paraphenylene vinylene), poly (fluorene), poly (1,4-phenylene), polythiophene, polypyrrole, poly (paraphenylene sulfide), polybenzothiadiazole, polybiothiophine or these The composition according to any one of claims 7 to 10, which is a derivative or a copolymer.   The composition according to any one of claims 7 to 11, wherein the organic solvent is toluene, benzene, tetrahydrofuran, dimethyl chloride, chlorobenzene or chloroform. In Formula _(1), three of R _1, R 2, _{R 3} and _{R 4} is a said saturated aliphatic groups, one is an aryl alkyl group or alkenyl group any of claims 7 to 12 The composition according to one item.   The electrochemiluminescence cell which used the composition as described in any one of Claims 7-13 as a light emitting layer forming material.