WO2018230548A1 - Ink for forming functional layer - Google Patents

Abstract

The purpose of the present invention is to provide an ink for forming a functional layer including a functional material, whereby the ink has less unevenness of drying than the prior art. An ink for forming a functional layer, containing a functional material (A), a first solvent or dispersion medium (B), and a second solvent or dispersion medium (C), wherein the ink for forming a functional layer is characterized in that 1) an organic solvent having a Hansen solubility parameter ∆D < 20 and a boiling point of 200-340°C is used as the first solvent or dispersion medium (B), 2) an organic solvent having a boiling point that is 160-300°C and equal to or lower than that of the first solvent or dispersion medium (B) used is used as the second solvent or dispersion medium (C), and 3) the amount of the second solvent or dispersion medium (C) used is equal to or greater than the amount of the first solvent or dispersion medium (B) used.

Description

Functional layer forming ink

The present invention relates to a functional layer forming ink.

In obtaining a coating film containing a functional material, a technique such as mixing the functional material shown on the left with a solvent or a dispersion medium and applying it to an object to be coated such as a support to remove the solvent or the dispersion medium is often used. ing. As the functional material at this time, dyes, pigments, semiconductor materials, organic EL, quantum dots, conductive materials, insulating materials, and the like are appropriately selected and used for the purpose of obtaining a target function. Recently, light-emitting elements using organic EL, quantum dots, and the like are attracting attention as display materials.

For example, various light-emitting elements usually include an anode, a hole transport layer, a light-emitting layer, an electron transport layer, and a cathode. When an electric field is applied to the light emitting element, holes are injected from the anode into the hole transport layer, electrons are injected from the cathode into the electron transport layer, and then holes and electrons are injected into the light emitting layer. In the light emitting layer, the injected holes and electrons are recombined, and the light emitting material in the light emitting layer emits light by the energy generated at this time. Note that the light-emitting element may not have a hole transport layer and / or an electron transport layer depending on circumstances. Moreover, other layers, such as a positive hole injection layer and an electron injection layer, may be included.

Self-luminous elements are suitable and are being put into practical use from the standpoint of display performance such as high visibility and low viewing angle dependence, as well as the ability to make the display lighter and thinner. However, since there is still a demand for improvement in power consumption, research for further improvement in luminous efficiency is ongoing.

Such a functional layer forming ink often uses a single solvent alone. For example, in Patent Documents 1 and 2, a functional layer is formed using a plurality of solvents having different properties. .

In Patent Document 1, excellent storage stability and excellent film quality can be obtained by using diethylene glycol butyl methyl ether and 1,4-dimethylnaphthalene in combination and diethylene glycol dibutyl ether and 1,4-dimethylnaphthalene in combination. It is described that

Patent Document 2 describes that by using diethylene glycol or dipropylene glycol diether and the like in combination with isopropyl naphthalene, a pinning effect is provided and a flat film quality is obtained.

JP 2013-131574 A JP2015-191792A

In recent years, from the viewpoints of high-definition patterning and high material utilization efficiency, it has been studied to form each layer constituting the organic light-emitting element by a wet film forming method, particularly an ink jet method.

In this wet film forming method, a substrate having a bank structure is used to dispose ink at an intended position (pixel). The ink ejected to the pixels located in the peripheral part of the substrate tends to dry faster than the ink ejected to the pixels located in the central part of the substrate. In the substrate, each pixel is adjacent to each other in the center, so there are many ink solvent molecules that evaporate. However, the pixels located around the substrate have fewer ink solvent molecules that evaporate and the evaporation is centered. Because it becomes faster than the part. As described above, when the drying time of the ink filled in the pixel differs depending on the pixel position in the substrate, the film thickness unevenness occurs in the light emitting layer formed based on the ink between the pixels in the substrate. When there is such a film thickness unevenness, a difference occurs in the current flowing through the light emitting layer or the like, which causes display unevenness such as luminance unevenness or light emission color unevenness when the light emitting layer emits light.
For example, even if an attempt is made to form a functional layer such as a light emitting layer by an ink jet method using a plurality of solvents as described in Patent Documents 1 and 2, it does not lead to improvement in drying unevenness between pixels.

Therefore, the present invention provides an ink for forming a functional layer, which has extremely small drying unevenness between pixels as an ink using a functional material, and can fully exhibit the functions inherent to the functional material itself. Objective.

The present inventors have conducted intensive research to solve the above problems. As a result, the present inventors have found that the above problem can be solved by using two or more different solvents or dispersion media in a specific ratio as the solvent or dispersion medium, and have completed the present invention.

That is, the present invention relates to a functional layer forming ink containing the functional material (A), the first solvent or dispersion medium (B), and the second solvent or dispersion medium (C).
1) An organic solvent having a Hansen solubility parameter δD <20 and a boiling point of 200 to 340 ° C. is used as the first solvent or dispersion medium (B).
2) As the second solvent or dispersion medium (C), a low boiling point organic solvent having a boiling point of 160 to 300 ° C. and the first solvent or dispersion medium (B) used is used,
3) The second solvent or dispersion medium (C) is used so that the amount of the first solvent or dispersion medium (B) is not less than the amount used.
It is characterized by that.

According to the present invention, when ink containing a functional material is ejected, it is possible to obtain an ink for forming a functional layer that exhibits extremely small unevenness in drying between pixels and fully exhibits the functions inherent to the functional material itself. it can.

It is a fragmentary sectional view which shows typically the process of forming a coating film by the inkjet printing method.

Hereinafter, embodiments for carrying out the present invention will be described in detail.

[Functional layer forming ink]
The functional layer forming ink according to the present embodiment includes a functional material, an organic solvent having a Hansen solubility parameter δD <20 and a boiling point of 200 to 340 ° C., a second solvent or a first solvent or dispersion medium (B). The greatest feature is that the dispersion medium (C) includes a first solvent used at a boiling point of 160 to 300 ° C. and a low-boiling organic solvent having a boiling point of not higher than the dispersion medium (B). Hereinafter, the first solvent or dispersion medium (B) may be abbreviated as solvent (B), while the second solvent or dispersion medium (C) may be abbreviated as solvent (C).

The functional material will be described in detail later, but when the functional layer forming ink of the present invention is applied to display applications, the functional material contained therein is typically a light emitting material. . The functional material may further contain a light emitting material and other additives as required. In this specification, “emission” includes emission by fluorescence and emission by phosphorescence.

In the ink of the present invention, as the functional material (A), one kind or two or more kinds of known and commonly used ones can be used. Specific examples of such a functional material (A) include the following.

<Functional materials>
Examples of the functional material include dyes, pigments, semiconductor materials, organic EL, quantum dots, conductive materials, and insulating materials.

[dye]
The dye as the functional material is 4-dicyanmethylene-2-methyl-6- (p-dimethylaminostyryl) -4H-pyran (DCM), coumarin, pyrene, perylene, rubrene, derivatives thereof, Or any combination thereof.

[Quantum dots]
Quantum dots as functional materials have a diameter of less than 150 mm. The population of quantum dots has an average diameter in the range of 15 Å to 125 Å. Quantum dots may be spherical, rod-shaped, disc-shaped, or other shapes. The quantum dots can include a core of semiconductor material. The quantum dot can include a core having the formula MX, where M is cadmium, zinc, magnesium, mercury, aluminum, gallium, indium, thallium, or mixtures thereof, where X is oxygen, sulfur, Selenium, tellurium, nitrogen, phosphorus, arsenic, antimony, or mixtures thereof.

[Organic EL]
An organic EL as a functional material includes a light emitting material and a host material.

[Organic EL red light emitting material]
The red light emitting material is not particularly limited, and various red fluorescent materials and red phosphorescent materials can be used alone or in combination of two or more.

The red fluorescent material is not particularly limited as long as it emits red fluorescence. For example, perylene derivatives, europium complexes, benzopyran derivatives, rhodamine derivatives, benzothioxanthene derivatives, porphyrin derivatives, Nile red, 2- (1, 1-dimethylethyl) -6- (2- (2,3,6,7-tetrahydro-1,1,7,7-tetramethyl-1H, 5H-benzo (ij) quinolizin-9-yl) ethenyl)- 4H-pyran-4H-ylidene) propanedinitrile (DCJTB), 4- (dicyanomethylene) -2-methyl-6- (p-dimethylaminostyryl) -4H-pyran (DCM), poly [2-methoxy-5 -(2-Ethylhexyloxy) -1,4- (1-cyanovinylenephenylene)], poly [{9,9-dihexyl-2,7- (1-cyanovinylene) fluorenylene} ortho- co- {2,5-bis (N, N'-diphenylamino) -1,4-phenylene}], poly [{2-methoxy-5- (2-ethylhexyl)] Siloxy) -1,4- (1-cyanovinylenephenylene)}-co- {2,5-bis (N, N′-diphenylamino) -1,4-phenylene}] and the like.

The red phosphorescent material is not particularly limited as long as it emits red phosphorescence, and examples thereof include metal complexes such as iridium, ruthenium, platinum, osmium, rhenium, and palladium. Among the ligands of these metal complexes, And those having at least one of phenylpyridine skeleton, bipyridyl skeleton, porphyrin skeleton and the like. More specifically, tris (1-phenylisoquinoline) iridium, bis [2- (2′-benzo [4,5-α] thienyl) pyridinate-N, C3 ′] iridium (acetylacetonate) (btp2Ir (acac )), 2,3,7,8,12,13,17,18-octaethyl-12H, 23H-porphyrin-platinum (II), bis [2- (2′-benzo [4,5-α] thienyl) Pyridinate-N, C3 ′] iridium, bis (2-phenylpyridine) iridium (acetylacetonate).

In addition to the red light emitting material described above, the red light emitting layer may contain a host material to which the red light emitting material is added as a guest material.

The host material recombines holes and electrons to generate excitons, and the exciton energy is transferred to the red light-emitting material (Forster transfer or Dexter transfer) to excite the red light-emitting material. Have In the case of using such a host material, for example, a red light-emitting material that is a guest material can be used as a dopant by doping the host material.

Such a host material is not particularly limited as long as it exhibits the functions described above with respect to the red light emitting material to be used. For example, an acene derivative such as a naphthacene derivative, a naphthalene derivative, or an anthracene derivative (acene derivative) Materials), distyrylarylene derivatives, perylene derivatives, distyrylbenzene derivatives, distyrylamine derivatives, quinolinolato metal complexes such as tris (8-quinolinolato) aluminum complex (Alq3), and triamines such as tetramers of triphenylamine Lilleamine derivatives, oxadiazole derivatives, silole derivatives, carbazole derivatives, biscarbazole derivatives, indolocarbazole derivatives, oligothiophene derivatives, benzopyran derivatives, triazole derivatives, benzoxazole derivatives, benzothiazo Le derivatives, quinoline derivatives, 4,4'-bis (2,2'-diphenylvinyl) biphenyl (DPVBi) and the like, may be used singly or in combination of two or more of them.

[Organic EL blue luminescent material]
Examples of the blue light emitting material include various blue fluorescent materials and blue phosphorescent materials, and one or a combination of two or more of these can be used.

The blue fluorescent material is not particularly limited as long as it emits blue fluorescence. For example, distyrylamine derivatives such as distyryldiamine compounds, fluoranthene derivatives, pyrene derivatives, perylene and perylene derivatives, anthracene derivatives, benzo Oxazole derivatives, benzothiazole derivatives, benzimidazole derivatives, chrysene derivatives, phenanthrene derivatives, distyrylbenzene derivatives, tetraphenylbutadiene, 4,4′-bis (9-ethyl-3-carbazovinylene) -1,1′-biphenyl (BCzVBi) ), Poly [(9.9-dioctylfluorene-2,7-diyl) -co- (2,5-dimethoxybenzene-1,4-diyl)], poly [(9,9-dihexyloxyfluorene-2, 7-Diyl) -ortho-co- (2- Toxi-5- {2-ethoxyhexyloxy} phenylene-1,4-diyl)], poly [(9,9-dioctylfluorene-2,7-diyl) -co- (ethylnylbenzene)] and the like .

The blue phosphorescent material is not particularly limited as long as it emits blue phosphorescence. Examples thereof include metal complexes such as iridium, ruthenium, platinum, osmium, rhenium, and palladium. Specifically, bis [4 , 6-Difluorophenylpyridinate-N, C2 ′]-picolinate-iridium, tris [2- (2,4-difluorophenyl) pyridinate-N, C2 ′] iridium, bis [2- (3,5-tri Fluoromethyl) pyridinate-N, C2 ′]-picolinate-iridium, bis (4,6-difluorophenylpyridinate-N, C2 ′) iridium (acetylacetonate), and the like.

In addition to the blue light emitting material described above, the blue light emitting layer may contain a host material to which the blue light emitting material is added as a guest material.

As such a host material, the same host material as described in the red light emitting layer can be used.

Further, it is preferable to use an acene derivative (acene-based material) as the host material for the blue light-emitting layer, like the host material for the red light-emitting layer. As a result, the blue light emitting layer can emit red light with higher luminance and higher efficiency.

[Organic EL green light emitting material]
It does not specifically limit as a green luminescent material, For example, various green fluorescent material and green phosphorescent material are mentioned, Among these, it can use 1 type or in combination of 2 or more types.

The green fluorescent material is not particularly limited as long as it emits green fluorescence. For example, quinacridone such as coumarin derivatives and quinacridone derivatives and derivatives thereof, 9,10-bis [(9-ethyl-3-carbazole)- Vinylenyl] -anthracene, poly (9,9-dihexyl-2,7-vinylenefluorenylene), poly [(9,9-dioctylfluorene-2,7-diyl) -co- (1,4-diphenylene-vinylene) -2-methoxy-5- {2-ethylhexyloxy} benzene)], poly [(9,9-dioctyl-2,7-divinylenefluorenylene) -ortho-co- (2-methoxy-5- (2 -Ethoxylhexyloxy) -1,4-phenylene)] and the like.

The green phosphorescent material is not particularly limited as long as it emits green phosphorescence, and examples thereof include metal complexes such as iridium, ruthenium, platinum, osmium, rhenium, and palladium. 2-phenylpyridine) iridium (Ir (ppy) 3), bis (2-phenylpyridinate-N, C2 ′) iridium (acetylacetonate), fac-tris [5-fluoro-2- (5-trifluoro Methyl-2-pyridine) phenyl-C, N] iridium and the like.

Further, the green light emitting layer may contain a host material using the green light emitting material as a guest material in addition to the green light emitting material described above.

As such a host material, the same host material as described in the red light emitting layer can be used.

Further, it is preferable to use an acene derivative (acene-based material) as the host material for the green light-emitting layer, like the host material for the red light-emitting layer. Thereby, the green light emitting layer can emit red light with higher luminance and higher efficiency.

Furthermore, the host material of the green light emitting layer is preferably the same as the host material of the blue light emitting layer described above. As a result, both the light emitting layers can emit green light and blue light in a balanced manner.

The molecular weight of the light emitting material is preferably 5000 g / mol or less, more preferably 2000 g / mol or less, and further preferably 300 to 2000 g / mol. It is preferable that the molecular weight of the host material is 5000 g / mol or less because the light emitting material can be easily dissolved in the solvent.

The content of the light emitting material as the functional material is preferably 0.1 to 50% by mass, and more preferably 0.1 to 10% by mass with respect to the mass of the host material. It is preferable that the content of the light emitting material is 0.1% by mass or more because a uniform film can be formed. On the other hand, when the content rate of the light emitting material is 10% by mass or less, it is preferable because a decrease in light emission efficiency due to concentration quenching of the light emitting material can be suppressed.

[Solvent or dispersion medium]
In one embodiment, the solvent or dispersion medium applied to the functional layer forming ink of the present invention is a different solvent of the solvent (B) and the solvent (C). The solvent (B) is an organic solvent having a Hansen solubility parameter δD <20 and a boiling point of 200 to 340 ° C., while the solvent (C) is a first solvent or dispersion medium having a boiling point of 160 to 300 ° C. B) The following low boiling point organic solvents. These solvents or dispersion media are not particularly limited, but are appropriately selected from known ones according to the functional material to be included in the layer to be formed, and the solvent (B) C) is used.

In the functional layer forming ink of the present invention, the solvent (C) is used so that the usage ratio of the solvent (B) and the solvent (C) is equal to or more than the amount of the solvent (B) used. Among them, when the total amount of the solvent (B) and the solvent (C) is 100 parts in terms of mass, the solvent (C) is more preferably 50 parts or more due to the effect of suppressing drying unevenness, especially Solvent (B) / solvent (C) = 40/60 to 15/85 is preferable because it is most effective in suppressing inter-pixel drying unevenness.

In the preparation of the functional layer forming ink of the present invention, other organics not corresponding to the solvents (B) and (C) are used as long as the technical effects due to the combined use of the solvents (B) and (C) are not impaired. A solvent can be used in combination.

In addition, the solvent (B) and the solvent (C) may be used by selecting one type each, or by selecting two or more types in combination. Further, it is preferable that the solvent (B) and the solvent (C) all have a lower boiling point within the range satisfying the above-described definition since drying becomes easy.

Depending on the functional material (A) used, either or both of the solvent (B) and the solvent (C) may function as a solvent or a dispersion medium. However, as the solvent (B) and the solvent (C), it is possible to select and use any of those solvents that dissolve the functional material (A), thereby reducing the original function of the functional material. Can improve the stability of the ink without using possible surfactants and dispersion stabilizers, etc., and has excellent uniformity of the functional material in the coating film containing the functional material in a finer region And more preferable.

Specific examples of the solvent (B) include aromatic solvents, alkane solvents, aliphatic ester solvents, aliphatic ether solvents, aliphatic ketone solvents, alcohol solvents, amide solvents, and other solvents. Each solvent satisfying the conditions of the solvent (B) selected from the above.

Examples of aromatic solvents include pentylbenzene (δD = 17.2, boiling point 205 ° C.), 1,2,3,4-tetrahydronaphthalene (δD = 19.6, boiling point 207 ° C.), naphthalene (δD = 19.2). , Boiling point 218 ° C.), hexylbenzene (δD = 17.1, boiling point 226 ° C.), heptylbenzene (δD = 17.0, boiling point 235 ° C.), cyclohexylbenzene (δD = 18.7, boiling point 236 ° C.), 1- Methylnaphthalene (δD = 19.7, boiling point 241 ° C.), 2-ethylnaphthalene (δD = 19.0, boiling point 252 ° C.), 1-ethylnaphthalene (δD = 19.0, boiling point 260 ° C.), octylbenzene (δD = 16.9, boiling point 264 ° C.), diphenylmethane (δD = 19.5, boiling point 264 ° C.), 1,4-dimethylnaphthalene (δD = 19.0, boiling point 268 ° C.), nonyl Aromatic hydrocarbon solvents such as benzene (δD = 16.9, boiling point 282 ° C.), 3-ethylbiphenyl (δD = 18.9, boiling point 284 ° C.), dodecylbenzene (δD = 16.7, boiling point 344 ° C.); Phenyl acetate (δD = 19.8, boiling point 195 ° C.), methyl benzoate (δD = 18.9, boiling point 200 ° C.), ethyl benzoate (δD = 17.9, boiling point 212 ° C.), isopropyl benzoate (δD = 17.4, boiling point 218 ° C.), methyl 4-methylbenzoate (δD = 19.0, boiling point 226 ° C.), propyl benzoate (δD = 17.6, boiling point 230 ° C.), butyl benzoate (δD = 18.0. 3, boiling point 250 ° C.), isopentyl benzoate (δD = 17.3, boiling point 262 ° C.), ethyl p-anisate (δD = 18.2, boiling point 263 ° C.), dimethyl phthalate (δD = 18.6, boiling point 284) ℃ Aromatic ester solvents such as butyl phenyl ether (δD = 17.5, boiling point 210 ° C.), p-dimethoxybenzene (δD = 18.6, boiling point 212 ° C.), p-propylanisole (δD = 17.8, Boiling point 215 ° C.), m-dimethoxybenzene (δD = 18.6, boiling point 217 ° C.), methyl 2-methoxybenzoate (δD = 18.4, boiling point 228 ° C.), 1,3-dipropoxybenzene (δD = 18) 0.7, boiling point 251 ° C.), diphenyl ether (δD = 19.4, boiling point 258 ° C.), 1-methoxynaphthalene (δD = 19.6, boiling point 271 ° C.), 3-phenoxytoluene (δD = 19.1, boiling point 272) ° C), 2-ethoxynaphthalene (δD = 19.3, boiling point 282 ° C), 1-ethoxynaphthalene (δD = 19.3, boiling point 282 ° C), and the like; Phenone (δD = 18.8, boiling point 202 ° C.), propiophenone (δD = 18.2, boiling point 216 ° C.), 4′-methylacetophenone (δD = 18.6, boiling point 226 ° C.), 4′-ethylacetophenone (ΔD = 18.3, boiling point 239 ° C.), an organic solvent having a Hansen solubility parameter δD <20 and a boiling point of 200-340 ° C. such as an aromatic ketone solvent such as butyl phenyl ketone (δD = 17.9, boiling point 244 ° C.) Can be mentioned.

Examples of the aliphatic ester solvent include isoamyl lactate (δD = 16.2, boiling point 202 ° C.), amyl valerate (δD = 16.2, boiling point 205 ° C.), ethyl levulate (δD = 16.5, boiling point). 205 ° C.), γ-valerolactone (δD = 16.9, boiling point 207 ° C.), ethyl octoate (δD = 15.9, boiling point 208 ° C.), γ-hexalactone (δD = 16.7, boiling point 220 ° C.) , Isoamyl hexanate (δD = 15.8, boiling point 222 ° C.), amyl hexanate (δD = 16.0, boiling point 226 ° C.), nonyl acetate (δD = 16.0, boiling point 228 ° C.), methyl decanoate (δD =, Boiling point 229 ° C.), diethyl glutarate (δD = 16.0, boiling point 230 ° C.), γ-heptalactone (δD = 16.6, boiling point 236 ° C.), ε-caprolactone (δD = 18.0, boiling point 2) 35 ° C.), octalactone (δD = 16.5, boiling point 239 ° C.), propylene carbonate (δD = 20.0, boiling point 242 ° C.), γ-nonanolactone (δD = 16.5, boiling point 243 ° C.), hexyl hexanoate (ΔD = 16.0, boiling point 244 ° C.), diisopropyl adipate (δD = 16.0, boiling point 253 ° C.), δ-nonanolactone (δD = 16.5, boiling point 253 ° C.), glycerol triacetic acid (δD = 16.6. 5, boiling point 260 ° C., δ-decanolactone (δD = 16.5, boiling point 267 ° C.), dipropyl adipate (δD = 16.1, boiling point 274 ° C.), δ-undecalactone (δD = 16.4, boiling point) An organic solvent having a Hansen solubility parameter δD <20 and a boiling point of 200 to 340 degrees.

Examples of the aliphatic ether solvent include diethylene glycol butyl methyl ether (δD = 15.8, boiling point 205 ° C.), diethylene glycol monoethyl ether acetate (δD = 16.2, boiling point 218 ° C.), dihexyl ether (δD = 16.0). , Boiling point 226 ° C.), diethylene glycol monobutyl ether acetate (δD = 16.0, boiling point 247 ° C.), diethylene glycol dibutyl ether (δD = 15.8, boiling point 255 ° C.), diheptyl ether (δD = 15.8, boiling point 262 ° C.) ), Organic solvents having Hansen solubility parameter δD <20 and boiling point 200 to 340 degrees, such as dioctyl ether (δD = 15.9, boiling point 287 ° C.).

Examples of the aliphatic ketone solvent include diisobutyl ketone (δD = 16.0, boiling point 168 ° C.), cycloheptanone (δD = 17.2, boiling point 180 ° C.), and isophorone (δD = 17.0, boiling point 215 ° C.). And an organic solvent having a Hansen solubility parameter δD <20 and a boiling point of 200 to 340 ° C., such as 6-undecanone (δD = 16.1, boiling point 226 ° C.).

Examples of the alcohol solvent include 1-heptanol (δD = 16.0, boiling point 177 ° C.), 2-ethyl-1-hexanol (δD = 15.9, boiling point 187 ° C.), propylene glycol (δD = 16 , Boiling point 188 ° C.), ethylene glycol (δD = 17.0, boiling point 196 ° C.), diethylene glycol monobutyl ether (δD = 16.0, boiling point 230 ° C.), ethyl 3-hydroxyhexanate (δD = 16.3, Boiling point 242 ° C.), tripropylene glycol monomethyl ether (δD = 16.0, boiling point 243 ° C.), diethylene glycol (δD = 16.6, boiling point 246 ° C.), cyclohexanol (δD = 17.4, boiling point 284 ° C.), etc. Examples include organic solvents having a Hansen solubility parameter δD <20 and a boiling point of 200 to 340 degrees.

Examples of the amide solvent include organic solvents having a Hansen solubility parameter δD <20 and a boiling point of 200 to 340 degrees, such as N, N-dimethylacetamide (δD = 16.8, boiling point 165 ° C.).

Among the above-mentioned solvents, organic solvents having Hansen solubility parameter δD <18 and boiling point 200-340 ° C. such as diethylene glycol butyl methyl ether, hexyl benzene, heptyl benzene, diethylene glycol dibutyl ether, octyl benzene, nonyl benzene, etc. This is preferable because the coating film becomes smoother.

On the other hand, as the solvent (C), specifically, aromatic solvents, alkane solvents, aliphatic ester solvents, aliphatic ether solvents, aliphatic ketone solvents, alcohol solvents, amide solvents, etc. Each solvent satisfying the conditions of the solvent (C) selected from the above solvents and the like.

As aromatic solvents, mesitylene (δD = 18.0, boiling point 164 ° C.), tert-butylbenzene (δD = 16.6, boiling point 168 ° C.), indane (δD = 18.8, boiling point 179 ° C.), diethylbenzene (ΔD = 17.4, boiling point 182 ° C.), pentylbenzene (δD = 17.2, boiling point 205 ° C.), 1,2,3,4-tetrahydronaphthalene (δD = 19.6, boiling point 207 ° C.), naphthalene ( δD = 19.2, boiling point 218 ° C., hexylbenzene (δD = 17.1, boiling point 226 ° C.), heptylbenzene (δD = 17.0, boiling point 235 ° C.), cyclohexylbenzene (δD = 18.7, boiling point 236) ° C), 1-methylnaphthalene (δD = 19.7, boiling point 241 ° C), 2-ethylnaphthalene (δD = 19.0, boiling point 252 ° C), 1-ethylnaphthalene (δD 19.0, boiling point 260 ° C.), octylbenzene (δD = 16.9, boiling point 264 ° C.), diphenylmethane (δD = 19.5, boiling point 264 ° C.), 1,4-dimethylnaphthalene (δD = 19.0, boiling point) 268 ° C.), nonylbenzene (δD = 16.9, boiling point 282 ° C.), 3-ethylbiphenyl (δD = 18.9, boiling point 284 ° C.) dodecylbenzene (δD = 16.7, boiling point 344 ° C.) and other aromatics Hydrocarbon solvent: phenyl acetate (δD = 19.8, boiling point 195 ° C.), methyl benzoate (δD = 18.9, boiling point 200 ° C.), ethyl benzoate (δD = 17.9, boiling point 212 ° C.), benzoic acid Isopropyl (δD = 17.4, boiling point 218 ° C.), methyl 4-methylbenzoate (δD = 19.0, boiling point 226 ° C.), propyl benzoate (δD = 17.6, boiling point 230 ° C.), butyrate benzoate (ΔD = 18.3, boiling point 250 ° C.), isopentyl benzoate (δD = 17.3, boiling point 262 ° C.), ethyl p-anisate (δD = 18.2, boiling point 263 ° C.), dimethyl phthalate (δD = Aromatic ester solvents such as 18.6, boiling point 284 ° C .; ethyl phenyl ether (δD = 18.4, boiling point 170 ° C.), 4-methylanisole (δD = 18.2, boiling point 175 ° C.), 2,6- Dimethylanisole (δD = 18.5, boiling point 181 ° C.), 2,5-dimethylanisole (δD = 18.5, boiling point 190 ° C.), 3,5-dimethylanisole (δD = 18.5, boiling point 195 ° C.), 4-ethylanisole (δD = 18.0, boiling point 195 ° C.), 2,3-dimethylanisole (δD = 18.5, boiling point 196 ° C.), butylphenyl ether (δD = 17.5, boiling point 210 ° C.) P-dimethoxybenzene (δD = 18.6, boiling point 212 ° C.), p-propylanisole (δD = 17.8, boiling point 215 ° C.), m-dimethoxybenzene (δD = 18.6, boiling point 217 ° C.), 2 -Methyl methoxybenzoate (δD = 18.4, boiling point 228 ° C.), 1,3-dipropoxybenzene (δD = 18.7, boiling point 251 ° C.), diphenyl ether (δD = 19.4, boiling point 258 ° C.), 1 -Methoxynaphthalene (δD = 19.6, boiling point 271 ° C), 3-phenoxytoluene (δD = 19.1, boiling point 272 ° C), 2-ethoxynaphthalene (δD = 19.3, boiling point 282 ° C), 1-ethoxy Aromatic ether solvents such as naphthalene (δD = 19.3, boiling point 282 ° C.); acetophenone (δD = 18.8, boiling point 202 ° C.), propiophenone (δD = 18.2, boiling point) 216 ° C.), 4′-methylacetophenone (δD = 18.6, boiling point 226 ° C.), 4′-ethylacetophenone (δD = 18.3, boiling point 239 ° C.) butyl phenyl ketone (δD = 17.9, boiling point 244 ° C.) The organic solvent having a boiling point of 160 to 300 ° C., such as an aromatic ketone solvent, and the like and having a boiling point equal to or lower than the specific solvent used in the solvent (B).

Examples of the aliphatic ester solvent include hexyl acetate (δD = 16.4, boiling point 169 ° C.), butyl lactate (δD = 15.8, boiling point 187 ° C.), isoamyl lactate (δD = 16.2, boiling point 202 ° C.). , Amylvalerate (δD = 16.2, boiling point 205 ° C.), ethyl levulinate (δD = 16.5, boiling point 205 ° C.), γ-valerolactone (δD = 16.9, boiling point 207 ° C.), octanoic acid Ethyl (δD = 15.9, boiling point 208 ° C.), γ-hexalactone (δD = 16.7, boiling point 220 ° C.), isoamyl hexanate (δD = 15.8, boiling point 222 ° C.), amyl hexanate (δD = 16.0, boiling point 226 ° C.), nonyl acetate (δD = 16.0, boiling point 228 ° C.), methyl decanoate (δD =, boiling point 229 ° C.), diethyl glutarate (δD = 16.0, boiling point 230 ° C.), γ Heptalactone (δD = 16.6, boiling point 236 ° C.), δ-caprolactone (δD = 18.0, boiling point 235 ° C.), octalactone (δD = 16.5, boiling point 239 ° C.), propylene carbonate (δD = 20. 0, boiling point 242 ° C.), γ-nonanolactone (δD = 16.5, boiling point 243 ° C.), hexyl hexanoate (δD = 16.0, boiling point 244 ° C.), diisopropyl adipate (δD = 16.0, boiling point 253 ° C.) ), Δ-nonanolactone (δD = 16.5, boiling point 253 ° C.), glycerol triacetic acid (δD = 16.5, boiling point 260 ° C.), δ-decanolactone (δD = 16.5, boiling point 267 ° C.), dipropyl adipate (ΔD = 16.1, boiling point 274 ° C.), δ-undecalactone (δD = 16.4, boiling point 292 ° C.) and other boiling points of 160 to 300 ° C. and specific examples used in the solvent (B) The organic solvent can be exemplified with the following boiling solvent.

Examples of the aliphatic ether solvent include diethylene glycol dimethyl ether (δD = 15.7, boiling point 162 ° C.), diethylene glycol ethyl methyl ether (δD = 15.7, boiling point 165 ° C.), diethylene glycol isopropyl methyl ether (δD = 15.8, Boiling point 179 ° C.), diethylene glycol diethyl ether (δD = 15.8, boiling point 188 ° C.), diethylene glycol diacetate (δD = 16.2, boiling point 190 ° C.), diethylene glycol butyl methyl ether (δD = 15.8, boiling point 205 ° C.) Diethylene glycol monoethyl ether acetate (δD = 16.2, boiling point 218 ° C.), dihexyl ether (δD = 16.0, boiling point 226 ° C.), diethylene glycol monobutyl ether acetate (δD = 16.0, boiling point) 247 ° C.), diethylene glycol dibutyl ether (δD = 15.8, boiling point 255 ° C.), diheptyl ether (δD = 15.8, boiling point 262 ° C.), dioctyl ether (δD = 15.9, boiling point 287 ° C.), etc. Examples of the organic solvent include 160 to 300 ° C. and a boiling point equal to or lower than the specific solvent used in the solvent (B).

Examples of the aliphatic ketone solvent include diisobutyl ketone (δD = 16.0, boiling point 168 ° C.), cycloheptanone (δD = 17.2, boiling point 180 ° C.), and isophorone (δD = 17.0, boiling point 215 ° C.). And the above organic solvents having a boiling point of 160 to 300 ° C. such as 6-undecanone (δD = 16.1, boiling point 226 ° C.) and a boiling point lower than the specific solvent used in the solvent (B).

Examples of the alcohol solvent include 1-heptanol (δD = 16.0, boiling point 177 ° C.), 2-ethyl-1-hexanol (δD = 15.9, boiling point 187 ° C.), propylene glycol (δD = 16 , Boiling point 188 ° C.), ethylene glycol (δD = 17.0, boiling point 196 ° C.), diethylene glycol monobutyl ether (δD = 16.0, boiling point 230 ° C.), ethyl 3-hydroxyhexanate (δD = 16.3, Boiling point 242 ° C.), tripropylene glycol monomethyl ether (δD = 16.0, boiling point 243 ° C.), diethylene glycol (δD = 16.6, boiling point 246 ° C.), cyclohexanol (δD = 17.4, boiling point 284 ° C.), etc. Examples of the organic solvent having a boiling point of 160 to 300 ° C. and a boiling point equal to or lower than the specific solvent used in the solvent (B). It is.

Examples of the amide solvents include the organic compounds having a boiling point of 160 to 300 ° C. such as N, N-dimethylacetamide (δD = 16.8, boiling point 165 ° C.) and less than the specific solvent used in the solvent (B). A solvent is mentioned.

Among the solvents described above, 1,2,3,4-tetrahydronaphthalene, cyclohexylbenzene, 1-methylnaphthalene, 1-ethylnaphthalene, methyl benzoate, ethyl benzoate, propyl benzoate, butyl benzoate, dimethyl phthalate, 3-phenoxytoluene, methyl 4-methylbenzoate, 4'-methylacetophenone, 4'-ethylacetophenone, butylphenylketone, propylene carbonate, γ-nonanolactone, glycerol triacetic acid, diisopropyl adipate, δ-nonanolactone, δ-decanolactone More preferably, diethylene glycol butyl methyl ether, diethylene glycol dibutyl ether, ethylene glycol monobutyl ether acetate, 1,2,3,4-tetrahydronaphthalene, benzoic acid Chill, 4'-methylacetophenone, .gamma. Nonanorakuton, cyclohexylbenzene, 1-methylnaphthalene, .delta. Nonanorakuton, it is particularly preferred that it include a .delta.-decanolactone and 3 phenoxytoluene.

The functional layer forming ink of the present invention can be applied to known and commonly used printing methods and coating methods. Specifically, for example, an offset printing method, a gravure printing method, a flexographic printing method, a screen printing method, a reverse printing method, a dispenser printing method, an ink jet printing method, a micro contact printing method and the like can be mentioned. Especially, it is preferable to apply to the ink jet printing method from the viewpoint that only a necessary amount of ink can be applied to a fine region and there is no waste of ink.

The viscosity of the ink solvent containing the solvent (B) and the solvent (C) is not particularly limited, but is preferably 0 to 6.0 mPa · s, and 1.2 to 5.0 mPa · s. More preferred is 1.5 to 4.5 mPa · s. When the viscosity of the solvent is 1.0 mPa · s or more, when the ink of the present invention is ejected by an ink jet method and a coating film is formed with ink droplets, the nozzle of the ink jet head is less likely to be clogged. preferable. On the other hand, when the viscosity of the solvent is 6.0 mPa · s or less, the viscosity of the obtained ink does not become excessively high, and therefore, it is preferable because the ink droplets can be easily ejected from the inkjet head.

The surface tension of the solvent is preferably 20 to 45 mN / m, more preferably 25 to 43 mN / m, and particularly preferably 28 to 40 mN / m. When the surface tension of the ink is 20 mN / m or more, when the ink of the present invention is ejected by an ink jet method, the wettability of the ink on the nozzle surface is not excessively increased, and the ink is attached around the nozzle. This is preferable because bending in the flying direction of the droplets is difficult to occur. On the other hand, it is preferable that the surface tension of the ink is 45 mN / m or less because the shape of the meniscus at the nozzle tip can be easily stabilized and the control of the ink discharge amount and discharge timing can be facilitated.

In one embodiment of the functional layer forming ink of the present invention, a solvent (B) characterized in that the dispersion term δD in the Hansen solubility parameter is less than 20 is used. The Hansen solubility parameter is one type of method for defining the solubility parameter of the solvent. For example, “INDUSTRIAL SOLVENTSHANDBOOK” (pp.35-68, Marcel Dekker, Inc., 1996) or “DIRECTORYOFSOLVENTS” (pp 22-29, Blackie Academic & Professional, 1996), Hansen's solubility parameter calculation software HSPiP attached e-book etc.

By selecting the solvent (B) such that the dispersion term δD in the Hansen solubility parameter is less than 20, preferably less than 18, the coating film in the pixel becomes smoother. When the dispersion term δD of the Hansen solubility parameter of the solvent (B) is 20 or more, the ink tends to aggregate during the drying process, the smoothness is poor, and the film thickness may be uneven.

[Additive]
The functional layer forming ink of the present invention may contain known and conventional additives as required. When preparing an ink composition for an organic light emitting device, additives such as a leveling agent and a viscosity adjusting agent may be used for the purpose of improving the ink jetting property or improving the smoothness when drying the ink jetting material. May be contained.

[Leveling agent]
The leveling agent is not particularly limited, and silicone compounds, fluorine compounds, siloxane compounds, nonionic surfactants, ionic surfactants, titanate coupling agents, and the like can be used. Of these, silicone compounds and fluorine compounds are preferred.

The silicone compound is not particularly limited, and examples thereof include dimethyl silicone, methyl silicone, phenyl silicone, methyl phenyl silicone, alkyl-modified silicone, alkoxy-modified silicone, and polyether-modified silicone. Of these, dimethyl silicone and methylphenyl silicone are preferred.

The fluorine-based compound is not particularly limited, and examples thereof include polytetrafluoroethylene, polyvinylidene fluoride, fluoroalkyl methacrylate, perfluoropolyether, and perfluoroalkylethylene oxide. Of these, polytetrafluoroethylene is preferred.

The siloxane compound is not particularly limited, and examples thereof include dimethylsiloxane compounds (trade names: KF96L-1, KF96L-5, KF96L-10, KF96L-100, manufactured by Shin-Etsu Silicone Co., Ltd.).

Among the leveling agents described above, it is preferable to use a silicone compound, a fluorine compound, or a siloxane compound, and it is more preferable to use a siloxane compound.

The above leveling agents may be used alone or in combination of two or more.

The addition ratio of the leveling agent varies depending on the desired performance, but is preferably 0.001 to 5% by mass, and preferably 0.001 to 1% by mass with respect to the total mass of the ink composition for an organic light emitting device. It is more preferable that It is preferable that the addition ratio of the leveling agent is 0.001% by mass or more because the smoothness of the coating film can be improved. On the other hand, it is preferable that the addition rate of the leveling agent is 5% by mass or less because the luminous efficiency can be improved.

[Viscosity modifier]
The viscosity modifier is not particularly limited, but poly (α-methylstyrene), polystyrene, styrene / acrylonitrile copolymer, styrene / butadiene / acrylonitrile copolymer, polymethyl methacrylate, methacryl / styrene copolymer, polycarbonate, etc. These thermoplastic resins can be used. Of these, poly (α-methylstyrene), polystyrene, styrene / acrylonitrile copolymer, styrene / butadiene / acrylonitrile copolymer, and polymethyl methacrylate are preferable.

The above-mentioned viscosity modifiers may be used alone or in combination of two or more.

The addition ratio of the viscosity modifier varies depending on the desired performance, but is preferably 0.001 to 5% by mass, and 0.01 to 1% by mass with respect to the total mass of the ink composition for a light emitting device. It is more preferable that It is preferable that the addition ratio of the viscosity modifier is 0.001% by mass or more because aggregation of the light emitting host material can be suppressed and the light emission efficiency can be improved. On the other hand, when the addition rate of the viscosity modifier is 5% by mass or less, it is preferable because the flying shape of the inkjet droplet can be improved.

When the functional material (A) is deactivated by oxygen, water or the like and may not function stably over a long period of time as an ink for forming a functional layer of the present invention, it is dissolved in the preparation of the ink. After using the solvents (B) and (C) from which gas and moisture have been removed as much as possible, or after preparing the ink, the ink is degassed or saturated with an inert gas, heated, or passed through a desiccant. It is preferable to remove dissolved oxygen and moisture as much as possible, such as by dehydration.

In addition, metal ions, halogen ions, and the like are repeatedly washed or removed through an ion exchange resin, and foreign substances having a large particle diameter are filtered. For example, the functional layer forming ink of the present invention is applied to an ink jet printing method. When using, it is preferable from the viewpoint of nozzle clogging and long-term continuous printability because higher reliability can be secured.

[Organic light emitting device]
When preparing an ink composition for an organic light emitting device as an embodiment of the functional layer forming ink of the present invention, an organic light emitting device can be provided based on the ink composition. In this case, the organic light emitting device includes at least an anode, a light emitting layer, and a cathode. The organic light emitting device may include one or more other layers such as a hole injection layer, a hole transport layer, an electron transport layer, and an electron injection layer. Moreover, you may include well-known things, such as a sealing member.

Hereinafter, each configuration of the light emitting element will be described in detail.

[anode]
The anode is not particularly limited, and metals such as gold (Au), copper iodide (CuI), indium tin oxide (ITO), tin oxide (SnO ₂ ), zinc oxide (ZnO), and the like can be used. These materials may be used alone or in combination of two or more.

The film thickness of the anode is not particularly limited, but is preferably 10 to 1000 nm, and more preferably 10 to 200 nm.

The anode can be formed by a method such as vapor deposition or sputtering. At this time, pattern formation may be performed by a photolithography method or a method using a mask.

[Hole injection layer]
The hole injection layer is an optional component in the light-emitting element and has a function of taking holes from the anode. Normally, holes taken from the anode are transported to the hole transport layer or the light emitting layer.

The hole injection material is not particularly limited, but is a phthalocyanine compound such as copper phthalocyanine; a triphenylamine derivative such as 4,4 ′, 4 ″ -tris [phenyl (m-tolyl) amino] triphenylamine; , 5,8,9,12-hexaazatriphenylenehexacarbonitrile, 2,3,5,6-tetrafluoro-7,7,8,8-tetracyano-quinodimethane and other cyano compounds; vanadium oxide, molybdenum oxide, etc. Oxides; amorphous carbon; conductive polymers such as polyaniline (emeraldine), poly (3,4-ethylenedioxythiophene) -poly (styrenesulfonic acid) (PEDOT-PSS), polypyrrole, etc. The hole injecting material is preferably a conductive polymer, and PEDOT-PSS More preferably.

The thickness of the hole injection layer is not particularly limited, but is preferably 0.1 nm to 5 μm.

The hole injection layer may be a single layer or a laminate of two or more.

[Hole transport layer]
The hole transport layer is an arbitrary component in the light emitting element and has a function of efficiently transporting holes. The hole transport layer may have a function of preventing hole transport. The hole transport layer usually takes holes from the anode or the hole injection layer and transports the holes to the light emitting layer.

The hole transport material that can be used for the hole transport layer is not particularly limited, but TPD (N, N′-diphenyl-N, N′-di (3-methylphenyl) -1,1′-biphenyl-4 , 4′diamine), α-NPD (4,4′-bis [N- (1-naphthyl) -N-phenylamino] biphenyl), m-MTDATA (4,4 ′, 4 ″ -tris (3-methyl) Low molecular triphenylamine derivatives such as phenylphenylamino) triphenylamine), and the like, and polymer compounds such as diamine polymers polymerized by introducing substituents into polyvinylcarbazole and triarylamine derivatives. The transport material is preferably a polymer compound obtained by introducing a substituent into a triphenylamine derivative or triarylamine derivative and polymerizing the fluorene skeleton. And more preferably a diamine polymer.

The film thickness of the hole transport layer is not particularly limited, but is preferably 1 nm to 5 μm, more preferably 5 nm to 1 μm, and further preferably 10 to 500 nm.

[Light emitting layer]
The light emitting layer has a function of causing light emission by using energy generated by recombination of holes and electrons injected into the light emitting layer.

At this time, the light emitting layer contains a known and commonly used material such as the light emitting material and the host material as the functional material (A).

The thickness of the light emitting layer is not particularly limited, but is preferably 2 nm to 30 μm, more preferably 10 nm to 20 μm, further preferably 15 nm to 15 μm, and particularly preferably 15 to 200 nm. preferable. The above range is preferable because the film thickness can be controlled with high accuracy.

[Electron transport layer]
The electron transport layer is an optional component in the organic light emitting device and has a function of efficiently transporting electrons. The electron transport layer can have a function of preventing electron transport. The electron transport layer usually takes electrons from the cathode or the electron injection layer and transports the electrons to the light emitting layer.

The electron transport material that can be used for the electron transport layer is not particularly limited, but tris (8-quinolylato) aluminum (Alq), tris (4-methyl-8-quinolinolato) aluminum (Almq3), bis (10-hydroxybenzo). [H] quinolinato) beryllium (BeBq2), bis (2-methyl-8-quinolinolato) (p-phenylphenolate) aluminum (BAlq), bis (8-quinolinolato) zinc (Znq), 8-hydroxyquinolinolatolithium A metal complex having a quinoline skeleton or a benzoquinoline skeleton such as (Liq); a metal complex having a benzoxazoline skeleton such as bis [2- (2′-hydroxyphenyl) benzoxazolate] zinc (Zn (BOX) 2); Bis [2- (2′-hydroxyphenyl) ben Thiazolate] zinc (Zn (BTZ) 2) metal complex having benzothiazoline skeleton; 2- (4-biphenylyl) -5- (4-tert-butylphenyl) -1,3,4-oxadiazole (PBD), 3- (4-biphenylyl) -4-phenyl-5- (4-tert-butylphenyl) -1,2,4-triazole (TAZ), 1,3-bis [5- (p-tert-butylphenyl) -1,3,4-oxadiazol-2-yl] benzene (OXD-7), 9- [4- (5-phenyl-1,3,4-oxadiazol-2-yl) phenyl] carbazole ( CO11), 2,2 ′, 2 ″-(1,3,5-benzenetriyl) tris (1-phenyl-1H-benzimidazole) (TPBI), 2- [3- (dibenzothiophen-4-yl) Phenyl] -1-phenyl-1H-benzimidazole (mDBTBIm-II) and other polyazole derivatives; benzimidazole derivatives; quinoline derivatives; perylene derivatives; pyridine derivatives; pyrimidine derivatives; triazine derivatives; quinoxaline derivatives; Derivatives and the like. Among these, the electron transport material is preferably a benzimidazole derivative, a pyridine derivative, a pyrimidine derivative, a triazine derivative, or a phenanthroline derivative.

The above-mentioned electron transport materials may be used alone or in combination of two or more.

The thickness of the electron transport layer is not particularly limited, but is preferably 5 nm to 5 μm, and more preferably 5 to 200 nm.

The electron transport layer may be a single layer or a laminate of two or more.

[Electron injection layer]
The electron injection layer is an optional component in the organic light emitting device and has a function of taking electrons from the cathode. Usually, electrons taken from the cathode are transported to the electron transport layer or the light emitting layer.

The electron injecting material that can be used for the electron injecting layer is not particularly limited; however, alkali metals such as lithium and calcium; metals such as strontium and aluminum; alkali metal salts such as lithium fluoride and sodium fluoride; 8-hydroxyquino Examples include alkali metal compounds such as lithium lithium; alkaline earth metal salts such as magnesium fluoride; oxides such as aluminum oxide. Among these, the electron injecting material is preferably an alkali metal, an alkali metal salt, or an alkali metal compound, and more preferably an alkali metal salt or an alkali metal compound.

The above-described electron injection materials may be used alone or in combination of two or more.

The thickness of the electron injection layer is not particularly limited, but is preferably 0.1 nm to 5 μm.

The electron injection layer may be a single layer or a laminate of two or more.

[cathode]
Examples of the cathode include, but are not limited to, lithium, sodium, magnesium, aluminum, sodium-potassium alloy, magnesium / aluminum mixture, magnesium / indium mixture, aluminum / aluminum oxide (Al ₂ O ₃ ) mixture, rare earth metal, and the like. . These materials may be used alone or in combination of two or more.

The cathode can be usually formed by a method such as vapor deposition or sputtering.

The film thickness of the cathode is not particularly limited, but is preferably 10 to 1000 nm, and more preferably 10 to 200 nm.

<Method for producing organic light-emitting device>
According to an embodiment of the present invention, a method for manufacturing an organic light emitting device is provided. The method for producing an organic light-emitting device comprises using a light-emitting material as a functional material, and preparing an ink for forming a functional layer prepared so as to have a viscosity and surface tension suitable for the ink jet printing method described above. And a step of forming a light emitting layer by applying the product on a support by an ink jet printing method (hereinafter also referred to as “light emitting layer forming step”).

[Light emitting layer forming step]
The light emitting layer forming step is a step of forming a light emitting layer by applying an ink composition for an organic light emitting element onto a support by an ink jet method.

Hereinafter, the light emitting layer forming step in one embodiment will be described with reference to the drawings.

More specifically, FIG. 1 is a partial cross-sectional view schematically showing a process of forming a coating film by an ink jet method. In FIG. 1, it has the board | substrate 1, the anode 2 arrange | positioned on the said board | substrate, and the positive hole transport layer 4 arrange | positioned on the said anode. At this time, a plurality of laminated bodies of the anode 2 and the hole transport layer 3 provided on the substrate are separated by the bank 3. When the ink composition for organic light emitting elements is ejected from the nozzle 6 of the ink jet head 7, a coating film 5 of the ink composition for organic light emitting elements is formed on the hole transport layer 3. A light emitting layer can be formed by drying the obtained coating film.

<Ink composition for organic light emitting device>
As the ink composition for an organic light-emitting element, the above-described one can be used, and thus the description thereof is omitted here.

[Support]
The support is a constituent layer of the organic light emitting device adjacent to the light emitting layer, and varies depending on the organic light emitting device to be manufactured. For example, when producing an organic light emitting device comprising an anode, a light emitting layer, and a cathode, the support is an anode or a cathode. In the case of manufacturing an organic light emitting device comprising an anode, a hole injection layer, a light emitting layer, an electron injection layer, and a cathode, the support is a hole injection layer or an electron transport layer. Thus, the support is an anode, a hole injection layer, a hole transport layer, an electron transport layer, an electron injection layer, or a cathode, preferably an anode, a hole injection layer, a hole transport layer, A hole injection layer or a hole transport layer is more preferable, and a hole transport layer is still more preferable.

Note that a bank may be formed on the support. By having the bank, the light emitting layer can be formed only at a desired location.

The height of the bank is preferably 0.1 to 5.0 μm, more preferably 0.2 to 3.0 μm, and further preferably 0.2 to 2.0 μm.

The width of the bank opening is preferably 10 to 200 μm, more preferably 30 to 200 μm, and further preferably 50 to 100 μm.

Furthermore, the length of the bank opening is preferably 10 to 400 μm, more preferably 20 to 200 μm, and further preferably 50 to 200 μm.

Further, the taper angle of the bank is preferably 10 to 100 degrees, more preferably 10 to 90 degrees, and further preferably 10 to 80 degrees.

[Application]
Application | coating is performed by the inkjet printing method, for example. More specifically, the ink composition for an organic light-emitting element is discharged from the nozzle of the inkjet head to the support.

At this time, the discharge amount of the ink composition for an organic light emitting device is preferably 1 to 50 pL / time, more preferably 1 to 30 pL / time, and further preferably 1 to 20 pL / time.

The opening diameter of the inkjet head is preferably 5 to 50 μm and more preferably 10 to 30 μm from the viewpoint of nozzle clogging and ejection accuracy.

The temperature at which the coating film is formed is not particularly limited, but it is 10 to 50 ° C. from the viewpoint of suppressing crystallization of the light emitting material (host material and / or light emitting material) contained in the ink composition for an organic light emitting device. Preferably, the temperature is 15 to 40 ° C., more preferably 15 to 30 ° C.

The relative humidity when forming the coating film is not particularly limited, but is preferably 0.01 ppm to 80%, more preferably 0.05 ppm to 60%, and more preferably 0.1 ppm to 15%. More preferably, it is 1 ppm to 1%, particularly preferably 5 to 100 ppm. It is preferable that the relative humidity is 0.01 ppm or more because the conditions for forming the coating film can be easily controlled. On the other hand, when the relative humidity is 80% or less, it is preferable because the amount of moisture adsorbed on the coating film that can affect the resulting light emitting layer can be reduced.

[Dry]
A light emitting layer can be formed by drying the obtained coating film.

The drying temperature is not particularly limited, but it may be performed at room temperature (25 ° C.) or by heating. When carried out by heating, the temperature is preferably 40 to 130 ° C, more preferably 40 to 80 ° C.

Further, the drying pressure is preferably performed under reduced pressure, and more preferably under reduced pressure of 0.001 to 100 Pa.

Furthermore, the drying time is preferably 1 to 90 minutes, more preferably 1 to 30 minutes.

[Formation process of other layers]
Other layers constituting the organic light-emitting device, specifically, the anode, the hole injection layer, the hole transport layer, the electron transport layer, the electron injection layer, and the cathode can be appropriately formed by known methods. .

For example, the anode and the cathode can be formed by a method such as vapor deposition or sputtering.

Further, the hole injection layer, the hole transport layer, the electron transport layer, and the electron injection layer can be formed by a vacuum deposition method, a spin coat method, a cast method, an ink jet method, an LB method, or the like.

When the functional layer forming ink of the present invention is used, by selecting and using a more suitable solvent (B), all the pixels are equally dried regardless of the substrate position, and the coating within the pixels is applied. The outstanding technical effect of flattening the film is obtained. Even if the uneven drying between pixels is solved, it may be seen that the smoothness of the coating film in the pixel is low, but such an optimal ink of the present invention eliminates such a drawback.

In particular, when a functional layer such as a light emitting layer of an organic light emitting device is formed, the ink ejected to the pixels located in the peripheral portion of the substrate dries faster than the ink ejected to the pixels located in the central portion of the substrate. Tend. This is because, in the central part, each pixel is adjacent to each other in the central portion, so there are many ink solvent molecules that evaporate.However, the pixels located around the ejection substrate have fewer ink solvent molecules that evaporate, and evaporation occurs. This is because it is faster than the central part. As described above, when the drying time varies depending on the pixel position in the substrate, unevenness in the thickness of the light emitting layer occurs between the pixels in the substrate. When there is such a film thickness unevenness, a difference occurs in the current flowing through the light emitting layer or the like, which causes display unevenness such as luminance unevenness or light emission color unevenness when the light emitting layer emits light.

Therefore, a dummy pixel that has substantially the same area as the pixel located on the ejection substrate and does not contribute to the display is disposed around the display region, and the ink including the constituent material of the light emitting layer formed on the pixel located on the ejection substrate is used. There has been proposed a configuration that prevents or suppresses the occurrence of film thickness unevenness such as a light emitting layer in the central portion and the peripheral portion of the ejection substrate by being arranged in the dummy pixel.

Further, in order to increase the effect of preventing and suppressing the unevenness in the thickness of the light emitting layer due to the arrangement of the dummy pixels, the amount of the solvent per unit area discharged to the dummy pixels is changed to the solvent per unit area discharged to the pixels of the display region. It has been proposed that the amount of ink per unit area discharged to the dummy pixels is greater than the amount of ink per unit area discharged to the pixels of the discharge substrate.

On the other hand, as a method of preventing unevenness in the film thickness of the light emitting layer etc. by devising a drying method using a drying device, the area on the substrate where the ink is arranged is divided into a plurality of areas, and the exhaust amount for each of the divided areas is independent. There are also proposals for a drying apparatus having a controllable member and drying apparatuses for drying the substrate with a uniform temperature distribution using a rectifying plate and a heater.

When the functional layer forming ink of the present invention is used for the purpose of forming a light emitting layer of such an organic light emitting element, dummy pixels as described above are purposely formed, and the amount of ink and drying conditions are set in the region. Without using special conditions / apparatuses such as changing each time, or adjusting, it is a uniform and dried film over the entire display area, both outside and inside the display panel. Since a light emitting layer with extremely small thickness unevenness can be obtained, a highly reliable display device without display unevenness can be easily obtained.

Hereinafter, the present invention will be described using examples, but the present invention is not limited to the description of the examples.

[substrate]
Ink was ejected by an inkjet printing method onto a 4 cm long by 7 cm wide substrate with pixels of 300 μm in length and 100 μm in width. The pixel located on the lower right side of the substrate was defined as a peripheral pixel, and the pixel located at the center of the substrate was defined as a central pixel.

[Preparation of functional layer forming ink]
First, as a luminescent material, tris [2- (p-tolyl) pyridine] iridium (Ir (mppy) ₃ ) (manufactured by Lumtec), 9,9 ′-(p-tert-butylphenyl) -1,3-bis Carbazole H-1 (manufactured by DIC Corporation) was prepared and dissolved in a solvent so that the content of each of them was 1.5% by mass, thereby forming the light emitting layer of the organic light emitting device of each example. Ink compositions were prepared (Examples 1 to 16). See Table 1 and Table 2.

In preparing these inks, diethylene glycol butyl methyl ether, hexyl benzene, heptyl benzene, diethylene glycol dibutyl ether, and nonyl benzene were prepared as the solvent (B). On the other hand, 1,2,3,4-tetrahydronaphthalene (δD = 19.6, boiling point 207 ° C.), ethyl benzoate (ethyl benzoate, δD = 17.9, boiling point 212 ° C.), 4 ′ -Methylacetophenone (δD = 18.6, boiling point 226 ° C), cyclohexylbenzene (δD = 18.7, boiling point 236 ° C), 1-methylnaphthalene (δD = 19.7, boiling point 241 ° C), γ-nonanolactone (δD = 16.5, boiling point 243 ° C.), δ-nonanolactone (δD = 16.5, boiling point 253 ° C.), δ-decanolactone (δD = 16.5, boiling point 267 ° C.), 3-phenoxytoluene (δD = 19.1) , Boiling point 272 ° C.). These were combined and used as a solvent or dispersion medium so as to have a mass ratio as shown in Table 1.

When preparing the ink composition for forming the light emitting layer of the organic light emitting device of the comparative example, 1,4-dimethylnaphthalene or 2-isopropylnaphthalene as the first solvent, diethylene glycol butyl methyl ether or diethylene glycol as the second solvent Dibutyl ether was prepared. These were combined and used as a solvent or dispersion medium so as to have a mass ratio as shown in Table 1. In the same manner as in the examples, the ink composition for forming a light emitting layer of an organic light emitting device of each comparative example was prepared by dissolving in a solvent such that the content of the light emitting material was 1.5% by mass (comparative). Examples 1 to 4). See Table 3.

<Light emitting device production>
An organic light emitting device was fabricated according to the following. In adopting the ink jet printing method, ink is ejected using a printer DMP2831 and a cartridge box DMC-11610 (manufactured by FUJIFILM Corporation) under the conditions of an ejection amount pl order, an operating temperature of 25 ° C., and a relative humidity of 50%. I made it.

1) An ITO (indium tin oxide) substrate having a bank structure was cleaned in this order using acetone and propanol, and then irradiated with UV / O ₃ .
2) Poly (3,4-ethylenedioxythiophene) -poly (styrenesulfonic acid) (PEDOT-PSS resin, CLEVIOS P JET NV2, Heraeus) was deposited to 45 nm by ejecting ink with an inkjet printer. Then, it was heated in the atmosphere at 180 ° C. for 15 minutes to form a hole injection layer.
3) Next, a 1 wt% tetralin solution of HT-2 (American Dye Source) represented by the following formula was ejected onto the hole injection layer with an ink jet printer to form a film with a thickness of 30 nm, and a nitrogen atmosphere A hole transport layer was formed by drying at 200 ° C. for 30 minutes under the above.
4) The ink for forming the light emitting layer of each organic light emitting device of the examples and comparative examples prepared above was ejected onto the hole transport layer with an ink jet printer, and formed to a thickness of 30 nm. A light emitting layer was formed by drying for 40 minutes under a vacuum condition of 25 ° C. and 0.003 Pa in an atmosphere.
5) Under a vacuum condition of 0.005 Pa, ET-1 represented by the following formula is 45 nm as an electron transport layer, lithium fluoride is 0.5 nm as an electron injection layer, and aluminum is 100 nm as a cathode in order. A film was formed.
6) Finally, the substrate was transferred to a glove box and sealed with a glass substrate to produce an organic light emitting device.

<Evaluation of uneven drying between pixels>
The drying behavior of the peripheral pixel and the central pixel after ejection was observed with a microscope. Specifically, in order to confirm the change over time, the peripheral pixel and the central pixel were observed every other minute, and the drying time was recorded. The time immediately after discharge was set as the measurement start time, and the time completely dried was set as the drying time. Thus, the drying unevenness index was obtained and evaluated according to the following criteria.

Drying unevenness index = (peripheral pixel drying time / central pixel drying time) × 100
◎: Drying unevenness index is 50 or more ○: Drying unevenness index is 40 or more and less than 50 ×: Drying unevenness index is less than 40

<Evaluation of coating film smoothness in pixel>
The ink composition for forming a light emitting layer of an organic light emitting device was applied to a substrate, dried in a nitrogen atmosphere, and then dried under reduced pressure at 25 ° C. and 0.003 Pa. The film thickness of the convex part of the organic thin film in the obtained pixel and the film thickness of the concave part were measured using a light interference surface shape measuring apparatus (manufactured by Ryoka System Co., Ltd.) and evaluated according to the following criteria. In addition, the said convex part means the highest thing on the basis of a horizontal surface among organic thin film surfaces, and the said recessed part means the lowest thing on the basis of a horizontal surface among organic thin film surfaces. Further, the pixel to be observed was the central pixel.

○: The value of the film thickness of the convex part with respect to the film thickness of the concave part (convex film thickness / concave film thickness) is 2.5 or less.
X: The value of the film thickness of the convex part with respect to the film thickness of the concave part (convex film thickness / concave film thickness) is larger than 2.5.

The results obtained by the above evaluation are shown in Tables 1 to 3 below. In the table, bp represents the boiling point of the solvent under atmospheric pressure, δD represents the value of the Hansen solubility parameter of the solvent, and the ratio represents the mass ratio of one solvent when the total of two different solvents is 100.

From the results of Table 1, it can be seen that the ink compositions for organic light-emitting devices produced in Examples 1 to 16 are excellent in both drying unevenness between pixels and coating smoothness in the pixels. Even if a solvent having a Hansen solubility parameter δD <20 and a boiling point of 200 to 340 ° C. is used as the first organic solvent, and a solvent having a boiling point of 160 to 300 ° C. is used as the second organic solvent, the latter solvent is used. It is clear that the technical effect of the present invention cannot be achieved with an organic solvent having a higher boiling point.

1: Substrate 2: Anode 3: Bank 4: Hole transport layer 5: Coating film 6: Nozzle 7: Inkjet head.

The ink for forming a functional layer of the present invention has extremely small drying unevenness between pixels and can fully exhibit the functions inherent to the functional material itself. For example, dyes, pigments, semiconductor materials, organic EL, quantum dots, When a functional layer such as a conductive material and an insulating material is used to form a functional layer by printing or the like on a wide surface, a functional layer without unevenness can be formed at any part of the surface. In particular, it is suitable for obtaining a display device such as a display using a light emitting material as a functional material.

Claims (5)

In the functional layer forming ink containing the functional material (A), the first solvent or dispersion medium (B) and the second solvent or dispersion medium (C),
1) An organic solvent having a Hansen solubility parameter δD <20 and a boiling point of 200 to 340 ° C. is used as the first solvent or dispersion medium (B).
2) As the second solvent or dispersion medium (C), a low boiling point organic solvent having a boiling point of 160 to 300 ° C. and the first solvent or dispersion medium (B) used is used,
3) The second solvent or dispersion medium (C) is used so that the amount of the first solvent or dispersion medium (B) is not less than the amount used.
An ink for forming a functional layer. 2. The functional layer forming ink according to claim 1, wherein an organic solvent having a Hansen solubility parameter δD <18 and a boiling point of 200 to 340 ° C. is used as the first solvent or dispersion medium (B). The second solvent or dispersion medium (C) is at least one selected from the group consisting of tetrahydronaphthalene, ethyl benzoate, methylacetophenone, γ-nonanolactone, cyclohexylbenzene, methylnaphthalene, δ-nonanolactone, δ-decanolactone, and phenoxytoluene. The ink for forming a functional layer according to claim 1, wherein the ink is a solvent or a dispersion medium. When the total amount of the first solvent or dispersion medium (B) and the second solvent or dispersion medium (C) is 100 parts in terms of mass, the second solvent or dispersion medium (C) is 50 parts. The functional layer forming ink according to any one of claims 1 to 3, which is as described above. The functional layer forming ink according to any one of claims 1 to 4, wherein the functional material (A) is a light emitting material.

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