DESCRIPTION METHOD FOR PRODUCING MATERIAL FOR LIGHT EMITTING DEVICE, MATERIAL PRECURSOR FOR LIGHT EMITTING DEVICE, AND METHOD FOR PRODUCING LIGHT EMITTING DEVICE

Technical Field

[0001]
The present invention relates to a precursor of a material for light emitting device, a method for producing a material for light emitting device, and a method for producing a light emitting device. The light emitting device can be utilized in the fields of display devices, flat panel displays, backlights, illuminations, interior, signs, signboards, electrophoto-graphic devices and optical signal generators.

Background Art

[0002]
The organic light emitting device is a light emitting device having a structure in which an organic emitting layer is interposed between an anode and a cathode, and electrons injected from a cathode and holes injected from an anode emit light by energy generated when they are recombined in an organic emitting layer. The organic light emitting device is characteristic for a thin and light-weight device with high luminance light emission under a low driving voltage, and multicolor light emission due to selection of a light emitting material, and is paid attention as a next-generation display device.

[0003]
The material used in an emitting layer of an organic light emitting device is preferably a material which has both electrochemical stability and satisfactory light emission characteristics. Derivatives of a polycyclic aromatic hydrocarbon (anthracene, pyrene, naphthacene, etc.) capable of satisfying these conditions are often used as the light emitting material (see Patent Documents 1 to 3).

[0004]
In case of using a polycyclic aromatic hydrocarbon as the light emitting material, the polycyclic aromatic hydrocarbon is commonly converted into derivatives by introducing a substituent so as to adjust an emission wavelength and to improve durability of the device. From the viewpoint of an improvement in durability, suppression of aggregation of the substituent due to steric hindrance is particularly effective. Thus, various substituents have been studied.

[0005]
In polyacene-based materials such as anthracene derivatives and naphthacene derivatives among these materials, the material having substituents existing mutually at cis positions to the plane formed by polyacene skeletons, and the material having substituents existing mutually at trans positions with the same composition largely differ in durability, and the material containing many trans-forms is considered to be excellent in durability (see Patent Document 4).

Prior Art Documents

Patent Documents

[0006]
Patent Document 1: Japanese Unexamined Patent Publication
(Kokai) No. 2007-63501
Patent Document 2: Japanese Unexamined Patent Publication
(Kokai) No. 2009-246354
Patent Document 3: Japanese Unexamined Patent Publication
(Kokai) No. 2002-8867
Patent Document 4: International Publication No. WO
2007/097178 pamphlet

Disclosure of the Invention

Problems to be Solved by the Invention

[0007]
The above-mentioned polyacene derivatives containing

many trans-forms are produced by synthesizing the objective compound and then isomerizing through a treatment at high temperature of 200°C or higher for one or more hours, and thus causing a problem such as degradation of the material due to heat. Particularly, compounds such as naphthacene derivatives and pentacene derivatives, which are likely to be oxidized, are easily oxidized when subjected to a high-temperature treatment in air or under an inert atmosphere in which a trace amount of oxygen remains, and thus the formed oxidized product exerts an adverse influence on characteristics of the device.

[0008]
An object of the present invention is to solve these problems, and thus providing a method for producing a material for light emitting device, which is excellent in durability, under mild conditions.

Means for Solving the Problems

[0009]
Namely, the present invention is directed to a method for producing a material for light emitting device, which includes converting a material precursor for light emitting device represented by the general formula (1) or (2) by heating and/or light irradiation to produce a material for light emitting device, wherein the obtained material for light emitting device includes many trans-forms compared with cis-forms:

[0010]
[Chemical Formula 1]
A.-3

[0011]
wherein Ar1 to Ar4 may be the same or different and are selected from among an alkyl group, a cycloalkyl group, an alkenyl group, a cycloalkenyl group, an alkoxy group, an alkylthio group, an arylether group, an arylthioether group, an aryl group and a heteroaryl group, provided that these substituents have a structure in which cis and trans isomers can be exist on a plane of the benzene ring to which they are attached; R1 to R24 may be the same or different and are selected from among a hydrogen, a hydroxyl group, an alkyl group, a cycloalkyl group, an alkenyl group, a cycloalkenyl group, an alkoxy group, an alkylthioether group, an arylether group, an arylthioether group, an aryl group and a heteroaryl group, and adjacent substituents may be combined with each other to form a ring; and R1 or R2, and R7 or R8 may be combined to form a bicyclo skeleton, and R13 or R14, and R17 or R18 may be combined to form a bicyclo skeleton.

[0012]
The present invention also includes the material precursor for light emitting device.

[0013]
The present invention also includes a method for producing a light emitting device, which includes the steps of forming a layer containing the material precursor for light emitting device on a substrate, and converting the material precursor for light emitting device into a material for light emitting device by heating and/or light irradiation.

Effects of the Invention

[0014]
According to the method for producing a material for light emitting device of the present invention, it is possible to produce an organic light emitting material containing many trans-forms, which is excellent in durability, under mild conditions which can suppress degradation of the material even in case of producing polyacene derivatives which had a problem such as degradation due to heat by a conventional method.

Brief Description of the Drawings

[0015]
Fig. 1 is a cross-sectional view showing an example of a structure of an organic light emitting device.

Mode for Carrying Out the Invention

[0016]
The material precursor for light emitting device of the present invention is represented by the general formula (1) or (2) :

[0017]
[Chemical Formula 2]

[0018]
wherein Ar1 to Ar4 may be the same or different and are selected from among an alkyl group, a cycloalkyl group, an alkenyl group, a cycloalkenyl group, an alkoxy group, an alkylthio group, an arylether group, an arylthioether group, an aryl group and a heteroaryl group, provided that these substituents have a structure in which cis and trans isomers can be exist on a plane of the benzene ring to which they are attached; R1 to R24 may be the same or different and are selected from among a hydrogen, a hydroxyl group, an alkyl group, a cycloalkyl group, an alkenyl group, a cycloalkenyl group, an alkoxy group, an alkylthioether group, an arylether group, an arylthioether group, an aryl group and a heteroaryl group, and a djacent substituents may be combined with each other to form a ring; and R1 or R2, and R7 or R8 may be combined to form a bicyclo skeleton, and R13 or R14, and R17 or R18 may be combined to form a bicyclo skeleton.

[0019]
The alkyl group represents, for example, saturated aliphatic hydrocarbon groups such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group and a tert-butyl group, and the alkyl group may have a substituent or not. In the present invention, the number of carbon atoms of the alkyl group is preferably within a range from 1 to 20. There is no particular limitation on additional substituent when substituted, and examples of the substituent include an alkyl group, an aryl group and a heteroaryl group. This shall be applied to the following description.

[0020]
The cycloalkyl group represents, for example, saturated alicyclic hydrocarbon groups such as a cyclopropyl group, a cyclohexyl group, a norbornyl group and an adamantyl group. In the present invention, the number of carbon atoms of the cycloalkyl group is preferably within a range from 3 to 20. The cycloalkyl group may have a substituent or not.

[0021]
The alkenyl group represents, for example, unsaturated aliphatic hydrocarbon groups containing a double bond, such as a vinyl group, an allyl group and a butadienyl group. In the present invention, the number of carbon atoms of the alkenyl group is preferably within a range from 2 to 20. The alkenyl group may have a substituent or not.

[0022]
The cycloalkenyl group represents, for example, unsaturated alicyclic hydrocarbon groups containing a double bond, such as a cyclopentenyl group, a cyclopentadienyl group and a cyclohexenyl group. In the present invention, the number of carbon atoms of the cycloalkenyl group is preferably within a range from 3 to 20. The cycloalkenyl group may have a substituent or not.

The alkoxy group represents, for example, functional groups to which an aliphatic hydrocarbon group is attached through an ether bond, such as a methoxy group, an ethoxy group and propoxy group. In the present invention, the number of carbon atoms of the alkoxy group is preferably within a range from 1 to 20. The aliphatic hydrocarbon group may have a substituent or not.

[0023]
The alkylthioether group is a group in which oxygen atoms of an ether bond of an alkoxy group are substituted with sulfur atoms. In the present invention, the number of carbon atoms of the alkylthio group is preferably within a range from 1 to 20. The hydrocarbon group of the alkylthio group may have a substituent or not.

[0024]
The aryl group represents, for example, aromatic hydrocarbon groups such as a phenyl group, a naphthyl group, a biphenyl group, a fluorenyl group, a phenanthryl group, a terphenyl group, an anthracenyl group and a pyrenyl group, or a group in which a plurality of these groups are linked. In the present invention, the number of carbon atoms of the aryl group is preferably within a range from 6 to 40. The aryl group may be non-substituted or substituted. Examples of the substituent, with which the aryl group is substituted, include an alkyl group, a cycloalkyl group, an alkenyl group, an alkynyl group, an alkoxy group, an arylether group, an alkylthio group, halogen, a cyano group, an amino group, an silyl group and a boryl group.

[0024]
The arylether group represents, for example, functional groups to which an aromatic hydrocarbon group is attached through an ether bond, such as a phenoxy group. In the present invention, the number of carbon atoms of the arylether group is preferably within a range from 6 to 40. The aromatic hydrocarbon group may have a substituent or not.

[0026]
The arylthioether group represents groups in which oxygen atoms of an ether bond of an arylether group are substituted with sulfur atoms. In the present invention, the number of carbon atoms of the arylthioether group is preferably within a range from 6 to 40. The aromatic hydrocarbon group in the arylthio group may have a substituent or not.

[0026]
The heteroaryl group represents, for example, aromatic groups having atoms other than carbon atoms in the ring, such as a furanyl group, a thiophenyl group, an oxazolyl group, a pyridyl group, a quinolinyl group and a carbazolyl group. In the present invention, the number of carbon atoms of the heteroaryl group is preferably within a range from 2 to 30. The aromatic group may have a substituent or not.

[0028]
The halogen represents fluorine, chlorine, bromine, iodine and the like.

[0029]
The material precursor for light emitting device represented by the general formula (1) or (2) is a precursor which is useful to produce a material for light emitting device, including many trans-forms under mild conditions. Herein, cis and trans isomers in the material precursor for light emitting device represented by the general formula (1) or (2), and polyacene derivatives as the material for light emitting device obtained using the same will be described. Since the following description shall be applied in common to the precursor and polyacene derivatives, a description will be made by the general formula (1) as an example.

[0030]
The case where Ar1 and Ar2 are respectively rotated around a bond with the linked benzene ring, as an axis, in the general formula (1) is examined. At this time, when the structure of Ar1 and Ar2 has a dyad axis to the above bond axis (for example, the case where Ar1 and Ar2 are p-tolyl groups), cis and trans isomers do not exist. On the other hand, when the dyad axis is absent (for example, the case where Ar1 and Ar2 are o-tolyl groups), an asymmetric site exists in the substituent, and structural isomers of cis-forms in which the asymmetric site locates at the same side of the plane formed by a mother skeleton, and trans¬forms in which the asymmetric site locates at the opposite side are defined. However, cis-forms and trans-forms can be detected as different chemical species when the asymmetric site is sterically bulky, and free rotational movement of Ar1 and Ar2 is inhibited.

[0031]
When cis- and trans-forms can be recognized as another chemical species, it is possible to determine an existing ratio thereof by various analytical methods. High performance liquid chromatography (HPLC) and nuclear magnetic resonance spectrum (NMR) are exemplified as influential techniques. Since trans-forms are usually thermodynamically stable, compounds of such a type are isomerized into trans-forms by applying activation energy for isomerization through heating and/or light irradiation. Therefore, isomers whose content was increased by heating or light irradiation can be assigned to trans-form.

[0032]
Polyacene derivatives including many trans-forms can suppress mutual aggregation of molecules, and therefore exhibit satisfactory characteristics as the material for light emitting device. In order to obtain such a material, it was necessary for a conventional method to perform an isomerization reaction by treating a material for light emitting device after synthesis at a high temperature of 200°C or higher by the following reason. That is, in case Ar1 to Ar4 in the general formula (1) or (2) have a substituent capable of forming a structural isomer, when large steric hindrance occurs between a substituent and a polyacene skeleton (namely, the substituent is bulky), an isomerization reaction does not easily proceed because of high barrier in the isomerization reaction. For example, when naphthacene derivatives having a 2,4-diphenylphenyl group are not treated at high temperature of 300°C or higher, the objective trans-form cannot be obtained.

[0033]
On the other hand, polyacene derivatives exert an adverse influence on device characteristics since impurities are by-produced by an undesired reaction such as oxidation during a high-temperature treatment. In order to prevent such a problem, the atmosphere of a high-temperature treatment should be a strict inert atmosphere, and thus it was difficult to produce polyacene derivatives including many trans-forms.

[0034]
Use of a material precursor for light emitting device represented by the general formula (1) or (2) enables the production of a material for light emitting device including many trans-forms under mild conditions without requiring such a high-temperature treatment. The material precursor for light emitting device can be converted into a material for light emitting device by subjecting to a conversion treatment through heating and/or light irradiation, as mentioned below.

[0035]
[Chemical Formula 3]

[0036]
It has been found that even if the material precursor for light emitting device represented by the general formula (1) or (2) is a mixture of isomers, the material for light emitting device obtained by subjecting to a conversion treatment contains many trans-forms compared with cis-forms.

[0037]
Although the details of the mechanism are unclear, a steric structure of the material precursor for light emitting device represented by the general formula (1) or (2) is considered as one of causes. Namely, carbon at the beta-position of carbons to which Ar1 to Ar4 shown in the general formula (1) or (2) are attached (for example, carbons to which R1, R2, R7 and R8 are attached in the general formula (1)) has a sp3 hybrid orbital, and steric hindrance between substituents represented by Ar1 to Ar4 and a mother skeleton is relieved when compared with the case where carbon at the beta-position has a sp2 hybrid orbital. Therefore, it is considered that many trans-forms are formed under mild conditions because of low activation energy of isomerization of a material precursor for light emitting device represented by the general formula (1) or (2) .

[0038]
At least two mechanisms are considered as the mechanism in which trans-forms increase in the material for light emitting device after conversion. One is the mechanism in which transisomers increase under mild conditions at a stage of a precursor and are directly converted into a material for light emitting device. The other one is the mechanism in which it is easy to form thermodynamically stable trans-forms in a transition state where a precursor is converted into a material for light emitting device, and trans-forms increase after conversion. It is considered that both mechanisms cannot be clearly distinguished and also both mechanisms simultaneously occur.

[0039]
The material precursor for light emitting device, which showed a structure of trans-form, can return to cis-forms in the subsequent conversion treatment. However, the proportion thereof is considered to be low. Therefore, the proportion of trans-forms is preferably increased at a stage of a material precursor for light emitting device.

[0040]
Regarding the conditions required to increase the proportion of trans-forms at a stage of a material precursor for light emitting device, heating at a temperature of lower than 200°C is preferable. More preferably, the temperature is between 100 and 190°C. There is no particular limitation on the heating time, and the heating time is preferably from 1 to 50 hours, and more preferably from 10 to 30 hours.

[0041]
When the treatment for conversion of a material precursor for light emitting device into a material for light emitting device is heating, the temperature of the conversion treatment is about 200°C, although it varies depending on the structure of the material precursor for light emitting device. Accordingly, the conversion treatment by heating can also serve as a treatment for isomerization into trans-forms.

[0042]
The treatment for conversion of a material precursor for light emitting device into a material for light emitting device is preferably light irradiation from the viewpoint of imparting no damage to the material. Irradiation light having a peak wavelength within a range from 300 to 550 nm is preferred. It is particularly-preferable to use blue light which can suppress degradation of the material and also can perform efficient conversion. Specifically, it is preferred to use light having a peak wavelength within a range from 430 to 470 nm, and a peak half value width of 50 nm or less. It is possible to use, as a light source for light irradiation, a combination of a high-luminance light source lamp and a band pass filter, a light emitting diode and the like. Examples of the high-luminance light source lamp.include, but are not limited to, a high-pressure mercury lamp, a halogen lamp, a metal halide lamp and the like. It is preferred to use a light emitting diode among these lamps since only light having the objective wavelength can be extracted and irradiated.

[0043]
In order to further increase the content of trans-forms, it is preferred to add a heat treatment step at a temperature of lower than 200°C after synthesizing a material precursor for light emitting device.

[0044]
Regarding conversion of the material precursor for light emitting device into a material for light emitting device, the material precursor for light emitting device may be subjected to a conversion treatment while remaining a solid state, or the material precursor for light emitting device may be subjected to a conversion treatment after preparing a solution, followed by removal of a solvent. In any case, it is desired to use a material precursor for light emitting device in which by-products formed during conversion can be removed by vacuum drying since purification can be omitted. When using such a material precursor for light emitting device, for example, the precursor is filled into a boat for deposition and subjected to a conversion treatment in the boat, and then a light emitting device can be directly produced by a vacuum deposition method.

[0045]
When the material precursor for light emitting device represented by the general formula (1) is converted, the material precursor for light emitting device is converted into a material for light emitting device, including a polyacene skeleton by dissociation of either R1 or R2, and either R7 or R8. Similarly, when the material precursor for light emitting device represented by the general formula (2), the material precursor for light emitting device is converted into a material for light emitting device, including a polyacene skeleton by dissociation of either R13 or R14, and either R17 or R18.

[0046]
For example, the compound in which R1 and R7 are phenyl groups, and R2 and R8 are hydroxyl groups can also be converted into objective material for light emitting device by treating with hydrochloric acid-stannic chloride, as mentioned below.

[0047]
[Chemical Formula 4]

[0048]
In the present invention, taking characteristics of the finally obtained material for light emitting device into consideration, regarding polyacene derivatives obtained by converting the material precursor for light emitting device represented by the general formula (1) or (2), portions corresponding to Ar1 to Ar4 in the general formula (1) or (2) of the present invention are preferably included in the above-mentioned range among structures described in Japanese Unexamined Patent Publication (Kokai) No. 2002-8867 and Japanese Unexamined Patent Publication (Kokai) No. 2009-224604. More preferably, Ar1 to Ar4 are aryl groups or heteroaryl groups. Particularly preferably, Ar1 to Ar4 are aryl groups or heteroaryl groups, which have an aryl group or heteroaryl group at the ortho-position or a-position. Particularly preferred examples of Ar1 to Ar4 are shown below.

[0049]
[Chemical Formula 5]

[0050]
R1 to R24 are particularly preferably those having a group selected from hydrogen, an alkyl group, an aryl group and a heteroaryl group. Herein, the alkyl group, aryl group and heteroaryl group are as described above.

[0051]
Preferred material precursor for light emitting device of the present invention is represented by the general formula (3) or (4):

[0052]
[Chemical Formula 6]

[0053]
wherein Ar5 to Ar8 may be the same or different and are selected from among an alkenyl group, a cycloalkenyl group, an aryl group and a heteroaryl group, provided that these substituents have a structure in which cis and trans isomers can be exist on a plane of the benzene ring to which they are attached; and R25 to R44 may be the same or different and are selected from among hydrogen, an alkyl group, a cycloalkyl group, an alkenyl group, a cycloalkenyl group, an alkoxy group, an alkylthioether group, an arylether group, an arylthioether group, an aryl group and a heteroaryl group, and adjacent substituents may be combined with each other to form a ring. Preferred examples of Ar6 to Ar8 and preferred examples of Ar1 to Ar4 are the same. Preferred examples of R25 to R44 and preferred examples of R1 to R24 are the same.

[0054]
X is an atom or atomic group selected from C=0, CH2, 0 and CHR*. R* is a substituent selected from among an alkyl group, an alkenyl group, an alkoxy group and an acyl group, and may be combined with each other to form a ring.

[0055]
Herein, an acyl group is a substituent represented by R-C(=0)- in which a hydroxyl group is removed from carboxylic acid R-C(=0)0H, and R is selected from among an alkyl group, an alkenyl group, an alkynyl group, an aryl group and a heteroaryl group.

[0056]
Herein, the alkyl group, cycloalkyl group, alkenyl group, cycloalkenyl group, alkoxy group, alkylthio group, arylether group, arylthioether group, aryl group and heteroaryl group are as described above.

[0057]
Specific examples of the portion -X-X- with respect to the case where X is CHR* are shown in the following formulas.

[0058]
[Chemical Formula 7]

[0059]
Among these materials, the material is more preferably a material in which by-product formed when converted into a material for light emitting device is a gas, namely a material precursor for light emitting device in which X is C=0, CH2 or 0, and particularly preferably a material precursor for light emitting device in which by¬product formed by a conversion treatment is a gas, and also conversion condition is light irradiation. Specifically, it is a material in which X is C=0 in the general formula (3) or (4) .

[0060]
When X is C=0 in the general formula (3) or (4), the material precursor for light emitting device releases carbon monoxide by a conversion treatment and is converted into a material for light emitting device. Similarly, when X is CH2, the material precursor for light emitting device releases ethylene by a conversion treatment and is converted into a material for light emitting device. When X is 0, the material precursor for light emitting device releases oxygen by a conversion treatment and is converted into a material for light emitting device.

[0061]
The material precursor for light emitting device of the present invention can be produced by a known method. The compound represented by the general formula (1) or (2) can be produced by the method described in Japanese Unexamined Patent Publication (Kokai) No. 2002-8867. The compound represented by the general formula (3) or (4) can be produced by the Diels-Alder reaction using the corresponding material for light emitting device, vinylsulfone, quinone, benzyne and the like. In case of using vinylsulfone, a desulfonylation reaction by a reductive reaction is performed after the Diels-Alder reaction. When X is 0, the compound can be produced by a reaction of the corresponding material for light emitting device with oxygen. When X is C=0, for example, the compound can be synthesized by the method described in Chemistry A Europian Journal, 2005, Vol. 11, 6212-6220 using the material for light emitting device used in the present invention as a raw material. Namely, it is possible to synthesize the objective material precursor for light emitting device by subjecting a material for light emitting device and vinylene carbonate to the Diels-Alder reaction to form an adduct, converting the adduct into a cross-linked diol form through hydrolysis, and further oxidizing the diol form.

[0062]
The material precursor for light emitting device of the present invention may also be used in the form of an ink. Herein, the ink contains the material precursor for light emitting device and a solvent. The ink may further contain an additive such as a dopant.

[0063]
The solvent is preferably a solvent which can dissolve a material precursor for light emitting device in the concentration of 2% by weight or more, and more preferably 3% by weight or more, at room temperature under an atmospheric pressure. The solvent preferable has a boiling point, a viscosity and a surface tension, suited for a coating process. Specific examples of the solvent include, but are not limited to, water, alcohol having a boiling point of 100°C or higher and 250°C or lower (cyclohexanol, benzyl alcohol, octanol, trimethylhexanol, ethylene glycol, etc.), chloroform, chlorobenzene, dichlorobenzene, trichlorobenzene, toluene, xylene, benzoic
acid ester, tetralin (tetrahydronaphthalene), decalin (decahydronaphthalene), propionitrile, benzonitrile, acetophenone, cyclohexanone, phenol, Y~butyrolactone, N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone and the like. It is also possible to use a mixture of plural solvents. Since impurities contained in the solvent may cause deterioration of characteristics of the thus produced device, it is desired to use a high-purity product as possible.

[0064]
The material for light emitting device obtained by the method of the present invention may be used in any layer which forms a light emitting device, and is a material which is preferably used as a light emitting material for use in an emitting layer, as mentioned below. The material is particularly preferably used as a host material.

[0065]
The structure of the light emitting device will be described below. Fig. 1 is a cross-sectional view showing an example of a typical structure of an organic light emitting device (display) 10. On a support 11, an active matrix circuit composed of TFT 12, a planarizing layer 13 and the like is formed. The light emitting device portion includes a first electrode 15/hole transporting layer 16/emitting layer 17/electron transporting layer 18/second electrode 19 formed thereon. An insulating layer 14 which prevents the occurrence of short circuit at the electrode edge and defines the emitting region is formed at the end of the first electrode. The constitution of the light emitting device is not restricted to this example. For example, a single emitting layer having both the hole transporting function and the electron transporting function may be formed between the first electrode and the second electrode. The hole transporting layer may have a layered structure of plural layers composed of a hole injection layer and a hole transporting layer. The electron transporting layer may have a layered structure of plural layers composed of an electron transporting layer and an electron injection layer. When the emitting layer has an electron transporting function, the electron transporting layer may be omitted. The first electrode/electron transporting layer/emitting layer/hole transporting layer/second electrode may be laminated in this order. Each of these layers may be composed of either a single layer or plural layers. After formation of the second electrode, formation of a protective layer, formation of a color filter, sealing and the like may be carried out using known technologies (not shown in the drawing).

[0066]
The light emitting material of each layer of the emitting layer may be made of either a single material or a mixture of plural materials. From the viewpoint of the emission efficiency, color purity and durability, the emitting layer preferably has a single layer structure composed of a mixture of a host material and a dopant material. The host material preferably accounts for 90 to 99% by weight of the emitting layer.

[0067]
Examples of the light emitting material (host material) include anthracene derivatives, tetracene derivatives, pyrene derivatives, various metal complexes including quinolinol complexes such as tris(8-quinolinolate)aluminum (Alq3) , and benzothiazolylphenol zinc complexes, bisstyrylanthracene derivatives, tetraphenylbutadiene derivatives, cumarin derivatives, oxadiazole derivatives, benzoxazole derivatives, carbazole derivatives, distyrylbenzene derivatives, pyrrolopyridine derivatives, perinone derivatives, cyclopentadiene derivatives, oxadiazole derivatives, thiadiazolopyridine derivatives, rubrene, quinacridone derivatives, phenoxazone derivatives, perinone derivatives, perylene derivatives, cumarin derivatives, chrysene derivatives, pyrromethene derivatives, low-molecular-weight materials such as iridium

complex-based material called phosphorescent materials, and macromolecular materials including polyphenylenevinylene derivatives, polyparaphenylene derivatives and polythiophene derivatives. It is particularly preferred to use, as the host material, material for light emitting device obtained by converting the material precursor for light emitting device of the present invention.

[0068]
There is no particular limitation on the dopant material, and the dopant material may be preferably dopant materials having an emission peak wavelength of 570 nm or more, such as pyrromethene derivatives, indenoperylene derivatives and pyran-based pigments.

[0069]
The hole transporting layer may be composed of either a single layer or plural layers, and each layer may be made of either a single material or a mixture of plural materials. The layer called the hole injection layer is also included in the hole transporting layer. From the viewpoint of hole transporting properties (low driving voltage) and durability, an acceptor material for enhancement of the hole transportability may be mixed in the hole transporting layer.

[0070]
Examples of the hole transporting material include low-molecular-weight materials such as aromatic amines typified by N,N'-diphenyl-N,N'-dinaphthyl-1,1'-diphenyl-4,4'-diamine (NPD), N,N'-biphenyl-N,N'-biphenyl-1,1'-diphenyl-4,4'-diamine and N,N'-diphenyl-N,N'-(N-phenylcarbazolyl)-1,1' -diphenyl-4,4'-diamine, N-isopropyl carbazol, pyrazoline derivatives, stilbene-based compounds, hydrazone-based compounds, and heterocyclic compounds typified by oxadiazole derivatives and phthalocyanine derivatives; and high-molecular-weight materials such as polycarbonates, styrene derivatives, polyvinyl carbazoles and polysilanes having these low-molecular-weight compounds in their side chains. Examples of the acceptor material include low-molecular-weight materials such as 7,7,8,8-tetra-cyanoquinodimethane (TCNQ), and hexaazatriphenylene (HAT) and cyano group derivatives thereof (HAT-CN6). Further examples of the hole transporting materials and the acceptor materials include metal oxides such as molybdenum oxide and silicon oxide thinly formed on the surface of the first electrode.

[0071]
The electron transporting layer may be composed of either a single layer or plural layers, and each layer may be made of either a single material or a mixture of plural materials. The layers called the hole inhibition layer and the electron injection layer are also included in the electron transporting layer. From the viewpoint of the electron transportability (low driving voltage) and durability, a donor material for enhancement of the electron transportability may be mixed in the electron transporting layer. The layer called the electron injection layer is often regarded as the donor material. The transfer material which forms the electron transporting layer may be made of either a single material or a mixture of plural materials.

[0072]
Examples of the electron transport material include low-molecular-weight materials such as quinolinol complexes including Alq3 and 8-quinolinolato lithium (Liq), fused polycyclic aromatic derivatives including naphthalene and anthracene, styryl aromatic ring derivatives represented by 4,4'-bis(diphenylethenyl)biphenyl, quinone derivatives including anthraquinone and diphenoquinone, phosphorus oxide derivatives, benzoquinolinol complexes, hydroxyazole complexes, azomethine complexes, various metal complexes including tropolone metal complexes and flavonol metal complexes, and compounds having heteroaryl ring structures containing electron-accepting nitrogen; and high-molecular-weight materials having these low-molecular-weight compounds in their side chains.

[0073]
Examples of the donor material include various metal complexes containing alkali metals and alkali earth metals such as lithium, cesium, magnesium and calcium, and quinolinol complexes thereof; and oxides and fluorides thereof such as lithium fluoride and cesium oxide.

[0074]
In order to extract emission from the emitting layer, at least one of the first electrode and the second electrode is preferably transparent. In case of the bottom emission in which light is extracted from the first electrode, the first electrode is transparent, while in case of the top emission in which light is extracted from the second electrode, the second electrode is transparent. As the materials of the transparent electrode and the other electrode, known materials may be used as described in Japanese Unexamined Patent Publication (Kokai) No. 11-214154.

[0075]
It is possible to use, as the organic light emitting device, active-matrix type device in which the second electrode is generally formed as a common electrode, a simple matrix type device which has a stripe electrode wherein the first electrode and the second electrode are crossed with each other, or a segment type device in which the display portion is patterned such that predetermined information is displayed. Examples of uses thereof include televisions, personal computers, monitors, watches, thermometers, audio instruments, display panels for automobiles and the like.

[0076]
The method for producing a light emitting device will be described below. The method for producing a light emitting device of the present invention includes the steps of forming a layer containing the material precursor for light emitting device on a substrate, and converting the material precursor for light emitting device into a material for light emitting device by eating and/or light irradiation

[0077]
The method for producing an organic light emitting device shown in Fig. 1 will be described. On a substrate 11, TFT 12, a planarizing layer 13 and a first electrode 15 are formed using the photolithography method. An insulating layer 14 is formed using a photosensitive polyimide precursor and patterning is carried out by a known technology, followed by whole-surface formation of a hole transporting layer 16 using a known technology by the vacuum deposition method. Using the hole transporting layer 16 as the under layer, a red emitting layer 17R, a green emitting layer 17G and a blue emitting layer 17B are patterned on the under layer. The organic light emitting device can be completed by whole-surface formation of an electron transporting layer 18 and a second electrode 19 thereon using a known technology by the vacuum deposition method. Patterning of the emitting layer may be performed by a dry process, a wet process, or a transfer method using a donor substrate. In case of using the material for light emitting device obtained by the present invention in the layer other than the emitting layer, the layer thereof may be formed by the similar method.

[0078]
Specific method for producing a light emitting device will be described in more detail. A description is made by way of the case of producing an emitting layer as an example.

[0079]
First, in case of using a dry process such as a vacuum deposition method, a material precursor for light emitting device dissolved in any solvent is subjected to a conversion treatment and the material for light emitting device precipitated as a result of being insolubilized is recovered. The material precursor for light emitting device in a solid state may be subjected to a conversion treatment. Using the obtained material for light emitting device, an emitting layer is formed on a device substrate on which layers up to a hole transporting layer have been formed by a known method such as a vacuum deposition method. Although the precipitated material for light emitting device may sometimes contain a material precursor for light emitting device, its weight can be sufficiently reduced by subjecting to sufficient conversion treatment.

[0080]
In case of using a wet process, an ink containing a material precursor for light emitting device and a solvent is applied to a device substrate on which layers up to a hole transporting layer have been formed, and then dried. Then, the material precursor for light emitting device is converted into a material for light emitting device by subjecting to the conversion treatment, and thus enabling formation of an organic layer having high function as an emitting layer. In this case, a solvent, which causes neither dissolution nor reaction of a layer serving as an under layer, is selected as the solvent to be used.

[0081]
In case of using a transfer method, an ink containing a material precursor for light emitting device and a solvent is applied on a substrate other than the device substrate, and then dried. Then, the material precursor for light emitting device is converted into material for light emitting device by subjecting to a conversion treatment. It is possible to form an organic layer having high function as an emitting layer by transferring the obtained film to a device substrate on which layers up to a hole transporting layer have been formed. Hereinafter, the above another substrate is referred to as a "donor substrate".

[0082]
Use of a donor substrate is preferable because of the following advantages. Namely, even if unevenness of application of the material is generated on the donor substrate before the transfer by subjecting the coating film of the material precursor for light emitting device formed on the donor substrate to a conversion treatment and then transferring to a device substrate to form an emitting layer, the unevenness is eliminated upon the transfer, and thus a uniform organic layer can be formed on the device substrate.

[0083]
A known method can be used in the transfer step. Examples thereof include a method in which heat is applied from the side of a donor substrate in a state where a donor substrate and a device substrate are laid one upon another, or light is irradiated from the side of a donor substrate. In case of transferring by heating, it is possible to reduce the material precursor for light emitting device which remains in the obtained organic layer.

[0084]
The conversion treatment is desirably carried out before the transfer step, and may be carried out simultaneously with the transfer or after the transfer. Herein, "simultaneously with the transfer" means that the material precursor for light emitting device is converted into a material for light emitting device during the transfer step. Furthermore, the conversion step may be carried out before, during and after the transfer. When the material precursor for light emitting device transferred onto the device substrate is further subjected to a conversion treatment after the transfer step, it is possible to further reduce the material precursor for light emitting device which remains after the conversion treatment on the donor substrate, and thus achieving longer lifetime.

[0085]
It depends on solubility of a host material whether or not a coating solution for formation of an emitting layer is prepared. Since the material precursor for light emitting device of the present invention has satisfactory solubility, a precursor serving as a host material after conversion is preferably used. It is possible to form an emitting layer containing a host material and a dopant
material by applying a mixed solution of such a precursor and a dopant material on a donor substrate, and drying the mixed solution, followed by the subsequent conversion step and transfer step.

[0086]
A solution of a precursor and a solution of a dopant material may be separately applied. Even if a precursor or host material and a dopant material are not uniformly mixed on a donor substrate, both may be uniformly mixed at the time when transferred onto an organic light emitting device. It is also possible to vary the concentration of a dopant material in an emitting layer in a film thickness direction by utilizing a difference in vaporizing temperature of a precursor or a host material and a dopant material during transfer.

Examples

[0087]
The present invention will be described below by way of Examples, but the present invention is not limited thereto.

[0088]
Synthesis of compounds and preparation of analytical samples were carried out in a yellow room. H-NMR was measured in a deuterated chloroform solution using superconductive FT-NMR EX-27 0 (manufactured by JEOL Ltd.). An isomer was analyzed by HPLC. Analytical conditions of typical HPLC are shown below.

[0089]
Column: Shiseido Co., Ltd., ODS column CAPCELL PAK C18 MGII
Column temperature: 45°C
Eluent: acetonitrile
The measurement sample was dissolved in chloromethane for spectral analysis and then introduced into a device under shading conditions.

[0090]

A compound 2 was synthesized by the method shown in the following reaction scheme.

[0091]
[Chemical Formula 8]
Compound 1, Intermediate 1, Intermediate 2, Compound 2
[0092]
Synthesis of intermediate 1

The compound 1 (0.48 g, cis:trans = 99:1) shown in the above reaction scheme and vinylene carbonate (0.1 mL) were heated to dryness in orthodichlorobenzene (10 mL) for 15 hours. After cooling the reaction solution to room temperature, large excess of hexane was added, followed by vigorous stirring. The thus formed powdered solid was filtrated and dried to obtain an intermediate 1 as a white powder. The intermediate 1 was a mixture of isomers. Yield: 0.53 g (98%). -NMR (5: ppm) 7.93-6.75(m, 34H), 4.88-4.23(m, 4H).

[0093]
Synthesis of intermediate 2
The intermediate 1 (0.33 g) was dissolved in 1,4-dioxane (20 mL) and an aqueous sodium hydroxide solution (4N, 7.5 mL) was added in a nitrogen atmosphere, and then the mixture was heated at reflux for 6 hours. After completion of the reaction, water (50 mL) was added, followed by stirring, addition of dichloromethane (50 mL) and further stirring. The organic layer was separated, washed with saturated brine and then dried over sodium sulfate. After filtration, the solvent was concentrated to dryness to obtain an intermediate 2 as a white solid. The intermediate 2 was a mixture of isomers. Yield: 0.32 g (99%). -NMR (5: ppm) 7.91-6.94(m, 34H), 4.41-3.97(m, 4H).

[0094]
Synthesis of compound 2
Dimethyl sulfoxide (1.2 mL) was dissolved in dehydrated dichloromethane (10 mL) and the solution was cooled to -78°C. Trifluoroacetic anhydride (2.1 mL) was added dropwise, followed by stirring at -78°C for 15 minutes. To the mixture, a dehydrated dichloromethane solution (10 mL) of the intermediate 2 (0.25 g) was slowly added dropwise, followed by stirring at -78°C for 90 minutes. Triethylamine (2.5 mL) was added dropwise and, after stirring at -78°C for 90 minutes, the temperature of the reaction solution was raised to room temperature. After completion of the reaction, dichloromethane was added, followed by stirring, and the organic layer was washed with water. After separation, the organic layer was dried over sodium sulfate. After filtration, the filtrate was concentrated to dryness. The obtained solid was purified by silica gel chromatography to obtain a compound 2 as a yellow powder. The compound 2 was a mixture of isomers. Yield: 0.08 g (32%). ^-NMR (5: ppm) 7.87-6.95(m, 34H) , 4.98, 4.94, 4.93(sx3, 2H).

[0095]
First, a compound 3 was synthesized as follows.

[0096] [Chemical Formula 9]

Intermediate 3, Intermediate 4, Intermediate 5, Compound 3

[0097]
Synthesis of intermediate 3
Phenylacetylene (manufactured by TOKYO CHEMICAL INDUSTRY CO., LTD.) (10 g) was dissolved in dehydrated tetrahydrofuran (200 mL) and the solution was cooled to 0°C, and then an n-butyllithium solution (1.6M hexane solution, 62 mL) was added dropwise, followed by stirring for 1.5 hours. To the solution, a mixed solution of phenylacetaldehyde (manufactured by Alfa Aser) (6.0 g) and tetrahydrofuran (20 mL) was added dropwise and the temperature was raised to room temperature, followed by stirring for 6 hours. To the reaction solution, distilled water (100 mL) and ethyl acetate (150 mL) were added, followed by stirring. The organic layer was separated, washed with saturated brine and then dried over sodium sulfate. The obtained solution was purified by column chromatography (filler: silica gel, elute: hexane/ethyl acetate) to obtain 8.5 g of an intermediate 3.

[0098]
Synthesis of intermediate 4
The intermediate 3 (8.5 g) and sodium hydrogen carbonate (manufactured by Wako Pure Chemical Industries, Ltd.) (6.4 g) and iodine (manufactured by TOKYO CHEMICAL INDUSTRY CO., LTD.) (29 g) were added to acetonitrile (380 mL), and the mixture was stirred under a nitrogen gas flow at room temperature for 4 hours. An aqueous saturated sodium thiosulfate solution (150 mL) and ethyl acetate (150 mL) were added, followed by stirring. The organic layer was separated, washed with saturated sodium thiosulfate and distilled water and then dried over sodium sulfate. The obtained solution was purified by column chromatography
(filler:silica gel, elute:hexane) to obtain 8.7 g of an intermediate 4.

[0099]
Synthesis of intermediate 5
The intermediate 4 (5.3 g) was dissolved in a mixed solution of toluene (34 mL) and diethylether (11 mL) and the mixture was cooled to -80°C. To the mixture, 10 mL of an n-butyllithium solution (1.6M hexane solution) was added dropwise, followed by stirring for 3 hours. After raising the temperature to -40°C, 5,12-naphthacenequinone (1.5 g) was added and the temperature was raised to room temperature, followed by stirring for 15 hours. To the reaction solution, methanol (60 mL) was added and the precipitated solid was recovered by filtration to obtain
2.4 g of an intermediate 5.

[0100]
Synthesis of compound 3
The intermediate 5 (2.4 g) was added to dry tetrahydrofuran (36 mL) and the temperature was raised to 40°C under a nitrogen gas flow. To the mixture, 19 mL of a 35% hydrochloric acid solution of tin(II) chloride dehydrate (8.14 g) was added dropwise. After completion of the dropwise addition, the temperature was raised to 70°C and the mixture was heated at reflux with stirring for 4.5 hours. The reaction solution was poured into 150 mL of distilled water and the precipitated solid was recovered by filtration. Furthermore, the solid was washed with distilled water and methanol to obtain 2.3 g of a compound 3. The compound 3 was a 100% cis-form.
-NMR (CDC13 (d = ppm)): 6 . 70-7 . 74 (m, 26H) , 8 . 04-9. 09 (t, 4H) , 8.19(s,2H). [0101]
Furthermore, a compound 4 was synthesized by the method shown in the following reaction scheme.

[0102]

[Chemical Formula 10]
Compound 3, Intermediate 6, Intermediate 7, Compound 4

[0103]
Synthesis of intermediate 6
The compound 3 (0.77 g, 100% cis-form) and vinylene carbonate (1.73 mL) were heated at reflux in orthodichlorobenzene (11 mL) for 13 hours. After the reaction solution was cooled to room temperature, hexane (30 mL) was added, followed by stirring. The obtained solution was purified by column chromatography (filler: silica gel, elute: hexane/dichloromethane) to obtain 0.92 g of an intermediate 6.

[0104]
Synthesis of intermediate 7
The intermediate 6 (0.92 g) was dissolved in 1,4-dioxane (28 mL) and an aqueous sodium hydroxide solution (4N, 14 mL) was added in a nitrogen atmosphere, and then the mixture was heated at reflux for 4.5 hours. After completion of the reaction, water (50 mL) was added, followed by stirring, addition of dichloromethane (50 mL) and further stirring. The organic layer was separated, washed with saturated brine and then dried over sodium sulfate. The obtained solution was purified by column chromatography (filler:silica gel, elute:ethyl acetate) to obtain 0.77 g of an intermediate 7.

[0105] Synthesis of compound 4
Dehydrated dichloromethane (32 mL) and dehydrated dimethyl sulfoxide (3.2 mL) were cooled to -80°C and trifluoroacetic anhydride (4.3 mL) was added dropwise. After stirring for 20 minute, dehydrated dimethyl sulfoxide (15 mL) containing the intermediate 7 (0.75 g) dissolved therein was added dropwise and the mixture was stirred for 2 hours while maintaining at -80°C. N,N-
diisopropylethylamine (16 mL) was slowly added dropwise and then stirring was continued for 3 hours. The temperature of the reaction solution was returned to room temperature, and an aqueous 10% hydrochloric acid solution (24 mL) and dichloromethane (30 mL) were added, followed by stirring for 30 minutes. The organic layer was separated, washed with saturated brine and then dried over magnesium sulfate. The obtained solution was concentrated by a rotary evaporator and then purified by column chromatography (filler:silica gel, elute:ethyl acetate/toluene) to obtain 400 mg of a compound 4. XH-NMR (CDC13 (d = ppm)):

5.15(s,2H), 6.93-7.68(m,26H).

[0106]
In addition, abbreviations and structure of the compounds used in the following Examples are shown below.

[0107] [Chemical Formula 11]

[0108] Example 1
A toluene solution (1% by weight) of the compound 2 obtained in Synthesis Example 1 was spin-coated (800 rpm, 30 seconds) on a glass substrate to form a thin film. The obtained thin film was sufficiently dried by a vacuum dryer and placed in a vacuum chamber, and then the atmosphere in the chamber was replaced by a vacuum (10~4 Pa) atmosphere. The compound 2 was converted into the compound 1 by irradiating with light of a blue light emitting diode through an observation window of the vacuum chamber for 12 hour. The temperature in the chamber was identical to room temperature.

[0109]
After irradiation with light, the glass substrate was removed from the chamber and a ratio of a cis-form to a trans-form of the thus formed compound 1 was analyzed by HPLC. As a result, cis:trans = 1:2.

[0110] Example 2
A toluene solution (1% by weight) of the compound 2 obtained in Synthesis Example 1 was charged in a pressure-resistant glass tube, sealed and then heated at 180°C for 12 hours. The solution was cooled by being left to stand at room temperature and then spin-coated (800 rpm, 30 seconds) on a glass substrate to form a thin film. The obtained thin film was sufficiently dried by a vacuum dryer and placed in a vacuum chamber, and then the atmosphere in the chamber was replaced by a vacuum (10~4 Pa) atmosphere. The compound 2 was converted into the compound 1 by irradiating with light of a blue light emitting diode through an observation window of the vacuum chamber for 12 hour. The temperature in the chamber was identical to room temperature.

[0111]
After irradiation with light, the glass substrate was removed from the chamber and a ratio of a cis-form to a trans-form of the thus formed compound 1 was analyzed by HPLC. As a result, cisrtrans = 1:5.

[0112] Example 3
A toluene solution (1% by weight) of the compound 4 obtained in Synthesis Example 2 was spin-coated (800 rpm, 30 seconds) on a glass substrate to form a thin film. The obtained thin film was sufficiently dried by a vacuum dryer and placed in a vacuum chamber, and then the atmosphere in the chamber was replaced by a vacuum (10~4 Pa) atmosphere. The compound 4 was converted into the compound 3 by irradiating with light of a blue light emitting diode through an observation window of the vacuum chamber for 12 hour. The temperature in the chamber was identical to room temperature.

[0113]
After irradiation with light, the glass substrate was removed from the chamber and a ratio of a cis-form to a trans-form of the thus formed compound 3 was analyzed by HPLC. As a result, the compound was a 100% cis-form.

[0114] Example 4
A toluene solution (1% by weight) of the compound 4 obtained in Synthesis Example 2 was charged in a pressure-resistant glass tube, sealed and then heated at 180°C for 12 hours. The solution was cooled by being left to stand at room temperature and then spin-coated (800 rpm, 30 seconds) on a glass substrate to form a thin film. The obtained thin film was sufficiently dried by a vacuum dryer and placed in a vacuum chamber, and then the atmosphere in the chamber was replaced by a vacuum (10~4 Pa) atmosphere. The compound 4 was converted into the compound 3 by irradiating with light of a blue light emitting diode through an observation window of the vacuum chamber for 12 hour. The temperature in the chamber was identical to room temperature.

[0115]
After irradiation with light, the glass substrate was removed from the chamber and a ratio of a cis-form to a trans-form of the thus formed compound 3 was analyzed by HPLC. As a result, cisrtrans = 2:3.

[0116] Example 5
A toluene solution (0.1% by weight) of the compound 2 obtained in Synthesis Example 1 was irradiated with light of a blue light emitting diode under an argon atmosphere for 3 hours, and a ratio of a cis-form to a trans-form of the thus formed compound 1 was analyzed by HPLC. As a result, cisrtrans = 1:2. The compound 1 precipitated at this time was filtered and dried, and then used in the below-mentioned production of a light emitting device (Example 7).

[01107]
Example 6 (Preparation of ink)
After weighing a solvent and the compound 2 obtained in Synthesis Example 1 in a sample bottle so that the content of the compound 2 becomes 1% by weight, and RD1 was weighed therein in the proportion of 0.5% by weight based on the compound 2. The mixture was subjected to an ultrasonic treatment for 15 minutes by an ultrasonic washer. The obtained solution was left standing to cool up to room temperature, and it was visually confirmed that the solution is a uniform solution.

[0118] Comparative Example 1
The compound 1 in which cis:trans = 99:1 was subjected to sublimation by heating to 300°C under vacuum atmosphere (10~4 Pa), and a ratio of a cis-form to a transform of the sublimed compound 1 was analyzed by HPLC. As a result, cis:trans = 1:1.

[0119] Comparative Example 2
The compound 3 of a 100% cis-form was subjected to sublimation by heating to 270°C under vacuum atmosphere (10~4 Pa), and a ratio of a cis-form to a trans-form of the sublimed compound 3 was analyzed by HPLC. As a result, cis:trans = 10:1.

[0120]
Comparative Example 3
The compound 1 in which cis:trans = 99:1 was subjected to a heat treatment at 90°C for 2 hours under vacuum atmosphere (10~4 Pa) . A ratio of a cis-form to a trans-form of the compound 1 was analyzed by HPLC. As a result, cis:trans = 99:1 and no change was observed compared with the ratio before heating.

[0121] Comparative Example 4
The compound 3 of a 100% cis-form was subjected to a heat treatment at 190°C for 2 hours under vacuum atmosphere (10~4 Pa) . A ratio of a cis-form to a trans-form of the compound 3 was analyzed by HPLC. As a result, the compound was a 100% cis-form.

[0122] Example 7 (Production of light emitting device)
A glass substrate (manufactured by Asahi Glass Co., Ltd., 15Q/D, electron beam vapor-deposited product) on which an ITO transparent conductive film had been vapor-deposited in a thickness of 150 nm was cut into a piece having a size of 30 * 40 mm, and the ITO conductive film was patterned by a photolithography method to form a light emitting portion and an electrode extracting portion. The obtained substrate was ultrasonic-washed with acetone and "SEMICOCLEAN 56" (registered trademark, manufactured by Furuuchi Chemical Corporation) for 15 minutes and then washed with ultrapure water. Subsequently, the substrate was ultrasonic-washed with isopropyl alcohol for 15 minutes, dipped in hot methanol for 15 minutes and then dried. The substrate was subjected to a UV-ozone treatment for 1 hour immediately before the production of a light emitting device and placed in a vacuum evaporation apparatus, and then the air was evacuated until the vacuum degree in the apparatus became 5 * 1CT4 Pa or less. First, HIL1 was vapor-deposited in a thickness of 47 nm as a hole injection layer by a resistance heating method, and then 4,4'-bis(N-(1-naphthyl)-N-phenylamino)biphenyl was vapor-deposited in a thickness of 10 nm as a hole transporting layer. Then, the compound 1 obtained in Example 5 as a host material, and RD1 as a dopant material were vapor-deposited as an emitting layer in a thickness of 30 nm so that the doping concentration became 0.5% by weight. Then, E-l was laminated in a thickness of 30 nm as an electron transporting material. On the thus formed organic layer, lithium fluoride was vapor-deposited in a thickness of 0.5 nm and then aluminum was vapor-deposited in a thickness of 60 nm to form a cathode, and thus a device measuring 5 * 5 mm was produced. As used herein, the film thickness is an indicated value of an oscillation quartz crystal film thickness monitor.

[0123]
Comparative Example 5
In the same manner as in Example 7, except that the compound 1 (cis:trans = 99:1) was used as the host material, an device was produced.

[0124]
Example 8 (Production of light emitting device by transfer method)
A donor substrate was prepared as follows. As a support, an alkali-free glass substrate was used. After washing and a UV-ozone treatment of the substrate, a tantalum film having a thickness of 0.4 urn was formed as a light-to-heat conversion layer by the sputtering method over the whole surface. Subsequently, the light-to-heat conversion layer was subjected to a UV-ozone treatment. On this layer, a positive-type polyimide photosensitive coating agent (DL-1000, manufactured by TORAY INDUSTRIES, INC.) was spin-coated after concentration adjustment. The obtained polyimide precursor film was subjected to prebaking and pattern exposure by UV light, and then the exposed portion was dissolved and removed by a developing solution (ELM-D, manufactured by TORAY INDUSTRIES, INC.). The thus patterned polyimide precursor film was baked by a hot plate at 300°C for 10 minutes to form a polyimide compartment pattern. The height of the compartment pattern was 7 urn and its cross section had a forward tapered shape. In the compartment pattern, apertural areas each having a width of 80 urn and a length of 280 um for exposure of the light-to-heat conversion layer were arranged at pitches of 100 um in a width direction and 300 um in a length direction. On the substrate, a chloroform solution containing the compound 2 obtained in Synthesis Example 1 as a host material in the amount of 1% by weight relative to the solvent, and RD1 as a dopant material in the amount of 0.5% by weight relative to compound 2 was spin-coated and then dried. The donor substrate was sufficiently dried by a vacuum dryer, placed in a vacuum chamber, and then the atmosphere in the chamber was replaced by a vacuum (10~4 Pa) atmosphere. The compound 2 was converted into the compound 1 by irradiating with light of a blue light emitting diode through an observation window of the vacuum chamber for 12 hours. The temperature in the chamber was identical to room temperature.

[0125]
A device substrate was prepared as follows. An alkali-free glass substrate on which ITO transparent conductive coating having a thickness of 140 nm was vapor-deposited (manufactured by Geomatec Co., Ltd., sputter-deposited product) was cut into a piece having a size of 38 x 46 mm, and the ITO was etched into a desired shape by photolithography. Then, a polyimide precursor film patterned in the same manner as in case of the donor substrate was baked at 300°C for 10 minutes to form a polyimide insulating layer. The height of the insulating layer was 1.8 pm and its cross section had a forward tapered shape. In the pattern of the insulating layer, apertural areas (exposing ITO) each having a width of 70 urn and a length of 270 urn were arranged at pitches of 100 urn in a width direction and 100 um in a length direction. The substrate was subjected to an UV ozone treatment and placed in a vacuum deposition apparatus, and then the air was evacuated until the vacuum degree in the apparatus became 3 x 10-4 Pa or less. By a resistance heating method, HIL1 was laminated as a hole injection layer in a thickness of 50 nm and NPD was laminated as a hole transporting layer in a thickness of 10 nm, over the whole emitting region by vapor deposition.

[0126]
Then, the position of the compartment pattern of the donor substrate and the position of the insulating layer of the device substrate were aligned and made to face each other, and the substrates were maintained in vacuum of 3 * 10~4 Pa or less and then removed into air. The transfer space partitioned by the insulating layer and the compartment pattern was maintained in vacuum. For the transfer, light having a center wavelength of 940 nm whose irradiation shape was formed into a rectangle of 340 urn * 50 urn (light source: semiconductor laser diode) was used. The light was irradiated from the glass substrate side of the donor substrate such that the longitudinal direction of the compartment pattern and the insulating layer agree with the longitudinal direction of the light, and scanning was performed in the longitudinal direction such that the transfer material and the compartment pattern were heated at the same time, thereby transferring the co-deposited film as the transfer material onto the hole transporting layer, which is the under layer of the device substrate. The light intensity was adjusted within a range from 140 to 180 W/mm2, and the scanning rate was 0.6 m/s. The scan was repeatedly carried out such that the transfer material is transferred over the whole emitting region while allowing light to shift in the transverse direction at a pitch of about 300 urn so as to partially overlap the scan region.

[0127]
The device substrate after the transfer was placed in the vacuum deposition apparatus again, and then the air was evacuated until the vacuum degree in the apparatus became 3 x 10-4 Pa or less. By resistance heating, the compound E-l was vapor-deposited as an electron transporting layer in a thickness of 25 nm over the whole emitting region. Subsequently, lithium fluoride as a donor material (electron injection layer) was vapor-deposited in a thickness of 0.5 nm and aluminum as a second electrode was vapor-deposited in a thickness of 65 nm to produce an organic light emitting device having an emitting region measuring 5 mm * 5 mm. It was confirmed that the obtained organic light emitting device emits clear green light.

[0128]
After sealing the organic light emitting devices produced in Examples 7 and Comparative Example 5, respectively, a constant current of 2.5 mA/cm2 was applied thereto. Measurement was carried out by defining the luminance immediately after initiating the application of current as the initial luminance, and the time required for the luminance to decrease to the half of the initial luminance by continuously applying the constant current as the luminance half-life. Regarding the relative ratio of the measured value of Comparative Example 5 calculated assuming the measurement value for Example 7 as 1.0, the initial luminance was 0.4 and luminance half-life was 0.2.

I Similarly, regarding the relative ratio of the measured value of Example 8 calculated assuming the measurement value for Example 7 as 1.0, the initial luminance was 1.9 and luminance half-life was 0.8.

[0129]
As described above, according to the present invention, it was possible to obtain the compound 1 or 3 including many trans-forms without exposing to high temperature conditions of 200°C or higher in the process of producing the compound 1 or 3 from the compound 2 or 4. As is apparent from Example 7 and Comparative Example 5, device characteristics of the material including many trans-forms exhibited high luminance and long lifetime compared with the material which does not include many trans-forms.

[Description of Symbols]

10: Organic light emitting device (Device substrate) 11: Support
12: TFT (including extraction electrode) 13: Planarizing layer 14: Insulating layer 15: First electrode 16: Hole transporting layer 17: Emitting layer 18: Electron transporting layer 19:

Second electrode

Industrial Applicability

[0131]
According to the method for producing a material for light emitting device of the present invention, it is possible to produce a material containing many trans-forms, which is excellent in durability, without causing degradation of an organic light emitting device under mild conditions which can suppress degradation of the material even in case of producing polyacene derivatives which had a problem such as degradation due to heat by a conventional method.

[0132]
The light emitting device obtained by using the material for light emitting device of the present invention can be utilized in the fields of display devices, flat panel displays, backlights, illuminations, interior, signs, signboards, electrophoto-graphic devices and optical signal generators.

CLAIMS

1. A method for producing a material for light emitting device, which comprises converting a material precursor for light emitting device represented by the general formula (1) or (2) by heating and/or light irradiation to produce a material for light emitting device, wherein the obtained material for light emitting device includes many trans¬forms compared with cis-forms:

[Chemical Formula 1]

wherein Ar1 to Ar4 may be the same or different and are selected from among an alkyl group, a cycloalkyl group, an alkenyl group, a cycloalkenyl group, an alkoxy group, an alkylthio group, an arylether group, an arylthioether group, an aryl group and a heteroaryl group, provided that these substituents have a structure in which cis and trans isomers can be exist on a plane of the benzene ring to which they are attached; R1 to R24 may be the same or different and are selected from among a hydrogen, a hydroxyl group, an alkyl group, a cycloalkyl group, an alkenyl group, a cycloalkenyl group, an alkoxy group, an alkylthioether group, an arylether group, an arylthioether group, an aryl group and a heteroaryl group, and adjacent substituents may be combined with each other to form a ring; and R1 or R2, and R7 or R8 may be combined to form a bicyclo skeleton, and R13 or R14, and R17 or R18 may be combined to form a bicyclo skeleton.

2. The method for producing a material for light emitting device according to claim 1, wherein the material precursor for light emitting device is represented by the general formula (3) or (4):

[Chemical Formula 2]

wherein Ar5 to Ar8 may be the same or different and are selected from among an alkenyl group, a cycloalkenyl group, an aryl group and a heteroaryl group, provided that these substituents have a structure in which cis and trans isomers can be exist on a plane of the benzene ring to which they are attached; R25 to R44 may be the same or different and are selected from among a hydrogen, an alkyl group, a cycloalkyl group, an alkenyl group, a cycloalkenyl

group, an alkoxy group, an alkylthioether group, an arylether group, an arylthioether group, an aryl group and a heteroaryl group, and adjacent substituents may be combined with each other to form a ring; X is an atom or atomic group selected from C=0, CH2, 0 and CHR*; and R* is a substituent selected from an alkyl group, an alkenyl group and an alkoxy group, and may be combined with each other to form a ring.

3. The method for producing a material for light emitting device according to claim 2, wherein X in the general formula (3) or (4) is C=0.

4. The method for producing a material for light emitting device according to any one of claims 1 to 3, wherein Ar1 to Ar8 in the general formula (1) to (4) are selected from structures shown in the following formulas:

5. The method for producing a material for light emitting device according to any one of claims 1 to 4, wherein the conversion method is light irradiation.

6. A material precursor for light emitting device represented by the general formula (1) or (2): [Chemical Formula 4]

wherein Ar1 to Ar4 may be the same or different and are selected from among an alkyl group, a cycloalkyl group, an alkenyl group, a cycloalkenyl group, an alkoxy group, an alkylthio group, an arylether group, an arylthioether group, an aryl group and a heteroaryl group, provided that these substituents have a structure in which cis and trans isomers can be exist on a plane of the benzene ring to which they are attached; R1 to R24 may be the same or different and are selected from among a hydrogen, a hydroxyl group, an alkyl group, a cycloalkyl group, an alkenyl group, a cycloalkenyl group, an alkoxy group, an alkylthioether group, an arylether group, an arylthioether group, an aryl group and a heteroaryl group, and adjacent substituents may be combined with each other to form a ring; R1 or R2, and R7 or R8 may be combined to form a bicyclo skeleton, and R13 or R14, and R17 or R18 may be combined to form a bicyclo skeleton.

7. The material precursor for light emitting device according to claim 6, wherein the material precursor for light emitting device is represented by the general formula
(3) or (4) :

[Chemical Formula 5]

wherein Ar5 to Ar8 may be the same or different and are selected from among an alkenyl group, a cycloalkenyl group, an aryl group and a heteroaryl group, provided that these substituents have a structure in which cis and trans isomers can be exist on a plane of the benzene ring to which they are attached; R25 to R44 may be the same or different and are selected from among hydrogen, an alkyl group, a cycloalkyl group, an alkenyl group, a cycloalkenyl group, an alkoxy group, an alkylthioether group, an arylether group, an arylthioether group, an aryl group and a heteroaryl group, and adjacent substituents may be combined with each other to form a ring; X is an atom or atomic group selected from C=0, CH2, 0 and CHR*; and R* is a substituent selected from an alkyl group, an alkenyl group and an alkoxy group, and may be combined with each other to form a ring.

8. The material precursor for light emitting device according to claim 7, wherein X in the general formula (3) or (4) is C=0.

9. The material precursor for light emitting device according to claim 8, wherein Ar1 to Ar8 in the general formula (1) to (4) are selected from structures shown in the following formulas:
[Chemical Formula 6]

10. An ink comprising the material precursor for light emitting device according to any one of claims 6 to 9.

11. A method for producing a light emitting device, which comprises the steps of forming a layer containing the material precursor for light emitting device according to any one of claims 6 to 9 on a substrate, and converting the material precursor for light emitting device into a material for light emitting device by heating and/or light irradiation.

12. The method for producing a light emitting device according to claim 11, which comprises the steps of forming a layer containing the material precursor for light emitting device according to any one of claims 6 to 9 on a substrate of a light emitting device, and converting the material precursor for light emitting device into a material for light emitting device.

13. The method for producing a light emitting device according to claim 11, which comprises the steps of forming a layer containing the material precursor for light emitting device according to any one of claims 6 to 9 on the donor substrate, and transferring a layer containing the material precursor for light emitting device on the donor substrate onto a substrate of a light emitting device, and also comprises the step of converting the material precursor for light emitting device into a material for light emitting device before, during or after the transfer.

14. The method for producing a light emitting device according to any one of claims 11 to 13, wherein the obtained material for light emitting device includes many trans-forms compared with cis-forms