JPH0711249A - Thin film electroluminescent element and its production - Google Patents

Abstract

PURPOSE:To produce the subject element which has the electroluminescent layer containing a specific polyoxydlazole derivative and is useful in information display because of its excellent electroluminescent properties, charge injection, transportation and durability. CONSTITUTION:The objective element has the electroluminescent layer comprising polyoxydiazole derivative of the formula (X, Y are difunctional organic groups; n > 2) which is formed by the deposition polymerization between the electrodes at least one of which is transparent. In the element, the electroluminescent layer preferably contains fluorescent dyes or pigments in an amount of 0.01 to 10 mole% per the recurring unit of the compound of the formula in addition.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a thin film electroluminescent device such as a light emitting device and a display device using an organic electroluminescent material used in the field of information display or optical information processing, and a method for manufacturing the same.

[0002]

BACKGROUND OF THE INVENTION Organic electroluminescent materials have recently attracted attention in the fields of information display and optical information processing. When this organic electroluminescent material is sandwiched between electrodes and a voltage is applied,
It emits light with a wavelength and intensity specific to this material.
Such light emission is generally caused by electrons and electrons injected into the organic electroluminescent material from their respective electrodes by applying a voltage.
It is said that these are caused by moving in the organic electroluminescent material and recombining in the organic electroluminescent material. It should be noted that this light substantially matches the fluorescence spectrum unique to this material.

By the way, as the electroluminescent material, there are organic and inorganic materials, and as the organic electroluminescent material, anthracene which causes blue electroluminescence has been known for a long time. Semiconductors are well known as light emitting materials. At present, among the light emitting semiconductors, an LED (light emitting diode) that emits red or yellow light is known as a highly bright and stable light emitting material. In addition, LE that emits red, orange, or green light
D is combined and put into practical use as a three-color display for street display.

Appl. Phys. Lett., Vol. 51, No. 12 (1987) p. 91
3-915 describes a two-layer type electroluminescent device (EL device) using an organic electroluminescent material. This two-layer type electroluminescent device is provided on an ITO (Indium Tin Oxide) electrode,
Hole injection layer, light emitting layer having electron transport function, MgAg
It is formed by sequentially depositing electron injection electrodes made of an alloy. When a voltage of several tens of volts is applied to this electroluminescent device, electrons and holes are injected into the electroluminescent layer of this device to emit light. In this two-layer type electroluminescent device, the emission color can be changed by selecting various electroluminescent materials. As the electroluminescent material, a low molecular weight compound such as aluminum quinolinol complex (Alq ₃ ) is used. When this aluminum quinolinol complex is used as a light emitting material, green light emission is obtained.

However, in this two-layer type electroluminescent device, the above-mentioned low molecular weight compound deposited as a light emitting layer is crystallized and peeling occurs between the organic layer (light emitting layer) and the electrode.
There is a problem that it does not emit light. Further, there is a problem that the two-layer type light emitting element generates heat due to light emission, the temperature of the element remarkably rises, and the element deteriorates.

Saito et al. Have proposed a three-layer type organic electroluminescence (EL) device in order to improve luminous efficiency (Jpn.JA.
ppl.Phys., Vol.27, No.2,1988, pp.L269-L271 and Jpn.
J. Appl. Phys., Vol. 27, No. 4, 1988, pp. L713-L715). This three-layer type organic electroluminescent device has an ITO electrode (positive electrode),
Hole injection layer, electroluminescent layer, electron injection layer and MgAg
An electrode (negative electrode) is sequentially laminated and formed, and among these layers, three layers of a hole injection layer, an electroluminescent layer and an electron injection layer are composed of organic layers. EL like this
In the device, the hole injection layer improves the injection efficiency of holes from the positive electrode to the electroluminescent layer, and the electron injection layer improves the injection efficiency of electrons from the negative electrode to the electroluminescent layer. For this reason, the threshold voltage required for electroluminescence of this three-layer organic electroluminescent device is several V, and blue light emission, which has been difficult with inorganic materials in the past, is also a problem with this three-layer organic electroluminescent device. In the case of the two-layer type electroluminescent device, the threshold voltage is the same as that of the two-layer type electroluminescent device.

However, in this three-layer organic electroluminescent device, an organic low molecular compound such as oxadiazole having a single oxadiazole ring is used as a material having a hole injecting function or an electron transporting function. Has been. The melting point of these organic low molecular weight compounds is 300 ° C.
Many of them have the following low melting points. Therefore, the three-layer organic electroluminescent device using these organic low molecular weight compounds has poor heat resistance, and there is a problem that the performance is deteriorated by heat or the device is crystallized and deteriorated.

Therefore, at least one of the electron injecting (transporting) layer, the light emitting layer, and the hole injecting (transporting) layer is formed of a polymer thin film, so that the above-described electroluminescence device is thermally deteriorated and crystallized. Proposed to prevent. For example,
In JP-A-4-2096, a polymer thin film containing an electroluminescent low molecular weight material or a low molecular weight material having a hole injecting function or an electron transporting function is formed by a wet method such as a spin coating method or a dip coating method. A method of manufacturing a polymer thin film EL device has been proposed. However, the device manufactured by this method needs to apply a voltage of several tens of V in order to provide effective light emission luminance, and even if such a high voltage is applied, it is 200 cd / m ² There is a problem that the efficiency is low because only the following emission brightness is obtained.

In addition, when a polymer thin film containing the above-described low molecular weight electroluminescent material or a low molecular weight material having a hole injecting function and an electron transporting function is formed on an electrode by a spin coating method, a high formed film is formed. There is a problem that pinholes are easily generated in the molecular thin film, and the pinholes cause the device to be easily broken during driving. Further, the wet method has a drawback that impurities are easily mixed in the element and the element mixed with the impurities is easily deteriorated.

The polymer thin film electroluminescent device in which the polymer thin film is formed by the wet method as described above has an advantage that the low molecular weight material contained in the polymer thin film is difficult to crystallize, but it is difficult to crystallize electrons and holes. There is a problem that the injection efficiency is lowered, or it is easily broken. When an organic layer (upper layer) is further formed on the organic layer (lower layer) by a wet method to manufacture an electroluminescent device, when the upper organic layer is formed so that the lower organic layer is not dissolved or eluted. It is necessary to select the solvent of the coating liquid used for. Thus, the materials that can be used when forming the lower layer and the upper layer, or the solvent for dissolving these materials is limited, and as a result, the organic layer of the polymer thin film electroluminescent device can be formed. There is a problem that the types of polymer materials that can be produced or low molecular weight materials that can be contained in the polymer materials are extremely limited.

On the other hand, in JP-A-4-274693, the following formula (V):

[0012]

[Chemical 8]

An acid dianhydride represented by the formula (wherein X represents an organic group containing an aromatic group) and the following formula (VI): H ₂ N—Y—NH ₂ (VI) (wherein Y represents an organic group having EL capability (at least one of charge injection function, charge transport function and electroluminescence function) by a vapor deposition polymerization method to react with a polyamino acid (polyimide precursor). ) Formed by the following formula (VII):

[0014]

[Chemical 9]

It has been proposed to use a thin film of polyimide represented by the formula (wherein X and Y have the above meanings and n is an integer indicating the degree of polymerization) as an electroluminescent layer or a charge injection / transport layer. ing.

In the polyimide represented by the above formula (VII), the nitrogen atom forming the sp ³ hybrid orbital and the carbon atom of the carbonyl group form a σ bond, and this σ bond forms one of the main chains of the polyimide. Forming a part. Since the π-bonded site is restricted by this σ-bonding site, excellent electroconductivity cannot be expected in an electroluminescent device using a thin film made of polyimide as an electroluminescent layer or a charge injection / transport layer. Therefore, it is not possible to expect to obtain an electroluminescent device having high luminous efficiency.

Further, in the polyimide, a carbonyl group having a large dipole moment exists at the imide bond site. This carbonyl group is known to act as a trap for carriers (electrons and / or holes) and reduce carrier mobility. Therefore, excellent electronic conductivity cannot be expected with such a polymer thin film having low carrier mobility.

[0018]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances and provides a polymer thin film having excellent electroluminescence and / or charge injection / transport properties and durability such as heat resistance. An object of the present invention is to provide a thin film electroluminescent device having electrodes and a method for manufacturing the same.

[0019]

SUMMARY OF THE INVENTION A first thin film electroluminescent device according to the present invention is a thin film electroluminescent device having an electroluminescent layer between electrodes, at least one of which is transparent, and the electroluminescent layer is formed by vapor deposition polymerization. Formula (I) given below:

[0020]

[Chemical 10]

[In the formula, X and Y may be the same or different and each represents a divalent organic group, and n is an integer of 2 or more. ] It consists of the polyoxadiazole derivative represented by these.

The second thin film electroluminescent device according to the present invention comprises:
A thin-film electroluminescent device having an electroluminescent layer between at least one transparent electrode and a charge injection / transport layer between the at least one electrode and the electroluminescent layer, the electroluminescent layer comprising: At least one of the charge injecting / transporting layer is composed of a polyoxadiazole derivative thin film represented by the above formula (I) formed by a vapor deposition polymerization method.

A method of manufacturing a thin film electroluminescent device according to the present invention is represented by the following formula (III):

[0024]

[Chemical 11]

[In the formula, X represents a divalent organic group. ]
And a dicarboxylic acid dichloride represented by the following general formula (I
V):

[0026]

[Chemical 12]

[In the formula, Y represents a divalent organic group. ] By vapor deposition polymerization of a dicarbohydrazide compound represented by
Then, heat treatment is performed to obtain the following formula (I):

[0028]

[Chemical 13]

[In the formula (I), X represents a divalent organic group derived from the dicarboxylic acid dichloride represented by the formula (III), and Y represents a dicarbohydrazide compound represented by the formula (IV). It is a derived divalent organic group, and n is an integer of 2 or more. ] The light emitting layer and / or the charge injecting / transporting layer made of the polyoxadiazole derivative represented by the above formula are formed between electrodes, at least one of which is transparent.

[0030]

DETAILED DESCRIPTION OF THE INVENTION The thin-film electroluminescent device and the method for manufacturing the same according to the present invention will be specifically described below with reference to the drawings.

[Thin Film Electroluminescent Device] FIG. 1 shows a first thin film electroluminescent device according to the present invention. The thin film electroluminescent device 10 is basically composed of a laminated body in which an electroluminescent layer 3 is sandwiched between a negative electrode 1 and a positive electrode 2.

As the negative electrode 1, an electrode having a high efficiency of injecting electrons into the electroluminescent layer 3 and capable of repeatedly injecting electrons into the electroluminescent layer 3, for example, Mg, In, Ca, Al, L.
An electrode made of i, Sm, MgAg, or the like is used.

As the positive electrode 2, the efficiency of injecting holes into the electroluminescent layer 3 is high, and the electroluminescent layer 3 is also excellent.
Electrodes that can be repeatedly injected with holes, such as ITO,
An electrode made of Pt, Au or the like is used.

At least one of the negative electrode 1 and the positive electrode 2 is transparent, and light emitted from the electroluminescent layer 3 can be irradiated through this transparent electrode. Further, either the negative electrode 1 or the positive electrode 2 is usually formed on a transparent substrate such as glass or polymer film.

For example, when the positive electrode 2 is an ITO electrode, this ITO electrode is formed in a thin film on a transparent substrate such as glass or polymer film. In the thin film electroluminescent device 10 shown in FIG. 1, the electroluminescent layer 3 is obtained by a vapor deposition polymerization method, and usually has a thickness of 200 to 2000 angstroms, preferably 300 to 800 angstroms, represented by the following formula (I):

[0036]

[Chemical 14]

[In the formula, X and Y may be the same or different and each represents a divalent organic group, and n is an integer of 2 or more. ] It is formed by the polyoxadiazole derivative thin film represented by this.

The polyoxadiazole derivative thin film represented by the formula (I) has an oxadiazole ring, and the oxadiazole ring itself has electroluminescence. Therefore, X and Y in the formula (I) are not particularly limited, except that they are divalent organic groups.

In order to further improve the electroluminescent efficiency of the thin film electroluminescent device 10, either X or Y is a divalent organic group having electroluminescent property, or one of X and Y is electroluminescent property. Is a divalent organic group having
A divalent organic group having transportability, or X, Y
It is desirable that one is a divalent organic group having an electroluminescent property and the other is a divalent organic group having a hole injecting / transporting property.

The types of X and Y in the formula (I) depend on the type of material forming the negative electrode 1 and / or the positive electrode 2 and the wavelength (color) of the light emitted from the electroluminescent layer 3. It is selected appropriately.

The thin film electroluminescent device 10 is considered to emit light in the following manner. When a voltage is applied between the negative electrode 1 and the positive electrode 2 in the thin film electroluminescent device 10, electrons are injected from the negative electrode 1 into the electroluminescent layer 3 and move in the electroluminescent layer 3, and at the same time from the positive electrode 2 to the electroluminescent layer 3. Holes are injected into the electroluminescent layer 3 and move in the electroluminescent layer 3. These electrons and holes are recombined in the electroluminescent layer 2, and the electroluminescent layer 3 emits light in the process of this recombination.

FIG. 2 shows a first example of the second thin film electroluminescent device according to the present invention. In this thin film electroluminescent device 10, the electron injection / transport layer 4 is formed between the negative electrode 1 and the electroluminescent layer 3 of the thin film electroluminescent device 10 shown in FIG. The electron injection / transport layer 4 plays a role of increasing the injection efficiency of the electrons injected from the negative electrode 1 into the electroluminescent layer 3.

In the thin film electroluminescent device 10 shown in FIG. 2, at least one of the electroluminescent layer 3 and the electron injecting / transporting layer 4 is formed of the polyoxadiazole derivative thin film represented by the above formula (I). ing.

The thin film electroluminescent device 10 shown in FIG.
Then, one of the electroluminescent layer 3 and the electron injecting / transporting layer 4 may be formed of the polyoxadiazole derivative thin film represented by the formula (I), and the other layers are formed of known materials. However, both layers are preferably formed of a polyoxadiazole derivative thin film represented by the above formula (I).

As described above, the electroluminescent layer 3 and the electron injection /
When both layers of the transport layer 4 are formed of the polyoxadiazole derivative thin film represented by the formula (I), the electroluminescent layer 3 is formed of a polyoxadiazole derivative having excellent electroluminescent property, and electron injection / transport is performed. The layer 4 is formed of a polyoxadiazole derivative having an excellent electron / injection / transport property.

In this case, the electroluminescent layer 3 has the following formula (I):

[0047]

[Chemical 15]

[In the formula, X, Y and n have the same meanings as described above. ] The electron injecting / transporting layer 4 formed of a polyoxadiazole derivative thin film represented by the following formula (I
I):

[0049]

[Chemical 16]

[In the formula, X, Y and n have the same meanings as described above. ] It is formed of a polyoxadiazole derivative thin film represented by. The electroluminescent layer 3 and the electron injecting / transporting layer 4 are made of different materials. From this point, at least one of X and Y in the formula (II) is either X or Y in the formula (I). Is different from

The type of the polyoxadiazole derivative forming the electroluminescent layer 3 is selected in the same manner as the electroluminescent layer 3 of the thin film electroluminescent element 10 shown in FIG.
The type of polyoxadiazole derivative forming the electron injecting / transporting layer 4, that is, the types of X and Y in the formula (II) are selected as follows.

X and Y in the formula (II) are both divalent organic groups, and there is no particular limitation except that either one has an electron injecting / transporting property. It is preferable that the divalent organic group has a transporting property, or one is a divalent organic group having an electroluminescent property and the other is a divalent organic group having an electron injecting / transporting property.

The types of X and Y in the formula (I) and the types of X and Y in the formula (II) are the types of materials forming the negative electrode 1 and / or the positive electrode 2, and light is emitted from the electroluminescent layer 3. It is appropriately selected according to the wavelength (color) of light.

When the electron injecting / transporting layer 4 is formed of the polyoxadiazole derivative thin film represented by the formula (II), the film thickness of the electron injecting / transporting layer 4 is usually 50.
~ 2000 angstrom, preferably 50-500
Angstrom.

FIG. 3 shows a second example of the second thin film electroluminescent device according to the present invention. In this thin film electroluminescent device 10, the hole injecting / transporting layer 5 is formed between the positive electrode 2 and the electroluminescent layer 3 of the thin film electroluminescent device 10 shown in FIG. The hole injecting / transporting layer 5 plays a role of increasing the injection efficiency of holes injected from the positive electrode 2 into the electroluminescent layer 3.

In the thin film electroluminescent device 10 shown in FIG. 3, at least one of the electroluminescent layer 3 and the hole injecting / transporting layer 5 is formed of the polyoxadiazole derivative thin film represented by the formula (I). .

The thin film electroluminescent device 10 shown in FIG.
Then, one of the electroluminescent layer 3 and the hole injecting / transporting layer 5 may be formed of the polyoxadiazole derivative thin film represented by the formula (I), and the other layers may be formed of known materials. However, both layers are preferably formed of a polyoxadiazole derivative thin film represented by the above formula (I).

When both the electroluminescent layer 3 and the hole injecting / transporting layer 5 are formed of the polyoxadiazole derivative thin film represented by the above formula (I), the electroluminescent layer 3 is formed.
Is formed of a polyoxadiazole derivative having excellent electroluminescence, and the hole injecting / transporting layer 5 is formed of a polyoxadiazole derivative having excellent hole / injecting and transporting properties.

In this case, the electroluminescent layer 3 has the following formula (I):

[0060]

[Chemical 17]

[In the formula, X, Y and n have the same meanings as described above. ] The hole injecting / transporting layer 5 formed of a polyoxadiazole derivative thin film represented by the following formula has the following formula (II '):

[0062]

[Chemical 18]

[In the formula, X, Y and n have the same meanings as described above. ] It is formed of a polyoxadiazole derivative thin film represented by. The electroluminescent layer 3 and the hole injecting / transporting layer 5 are made of different materials, and from this point, at least one of X and Y in the formula (II ′) is
It is different from both X and Y in the formula (I).

The kind of the polyoxadiazole derivative forming the electroluminescent layer 3 is selected in the same manner as the electroluminescent layer 3 of the thin film electroluminescent element 10 shown in FIG.
Further, the kind of the polyoxadiazole derivative forming the hole injecting / transporting layer 5, that is, X in the formula (II ′),
The type of Y is selected as follows.

X and Y in the formula (II ') are both divalent organic groups, and either one has a hole injecting / transporting property and is not particularly limited, but both are holes. It is preferable that it is a divalent organic group having injection / transport properties, or one is a divalent organic group having electroluminescence and the other is a divalent organic group having hole injection / transport properties. .

The types of X and Y in the formula (I) and the types of X and Y in the formula (II ′) are the types of materials forming the negative electrode 1 and / or the positive electrode 2 and light emitted from the electroluminescent layer 3. It is appropriately selected according to the wavelength (color) of the light to be emitted.

When the hole / injection / transport layer 5 is formed of the polyoxadiazole derivative thin film represented by the formula (II ′), the thickness of the hole / injection / transport layer 5 is usually 50.
-2000 angstrom, preferably 50-500 angstrom.

FIG. 4 shows a third example of the second thin film electroluminescent device according to the present invention. In this thin film electroluminescent device 10, the electron injecting / transporting layer 4 is formed between the negative electrode 1 and the electroluminescent layer 3 of the thin film electroluminescent device 10 shown in FIG. 1, and the positive electrode 2 and the electroluminescent layer 3 are further formed. Hole injection during
The transport layer 5 is formed.

In the thin film electroluminescent device 10 shown in FIG. 4, the electroluminescent layer 3, the electron injection / transport layer 4, the hole injection /
At least one layer, preferably all layers, of the transport layer 5 is formed of the polyoxadiazole derivative thin film represented by the formula (I).

Thus, all layers of the electroluminescent layer 3, the electron injecting / transporting layer 4 and the hole injecting / transporting layer 5 are represented by the above formula (I).
In the case of forming a polyoxadiazole derivative thin film represented by, the electroluminescent layer 3 is formed of a polyoxadiazole derivative having excellent electroluminescent property, and the electron injecting / transporting layer 4 is made of a polyoxadiazole derivative having excellent electron injecting / transporting property. The hole injecting / transporting layer 5 is formed of an oxadiazole derivative, and the hole injecting / transporting layer 5 is formed of a polyoxadiazole derivative having excellent hole injecting / transporting properties. The types of the polyoxadiazole derivative forming the transport layer 4 and the polyoxadiazole derivative forming the hole injecting / transporting layer 5 are different from each other.

To explain this point in more detail,
The type of these polyoxadiazole derivatives is appropriately selected according to the type of material forming the negative electrode 1 and / or the positive electrode 2, the wavelength (color) of the light emitted from the electroluminescent layer 3, and the like.

The thin film electroluminescent device 10 shown in FIG.
The kind of the polyoxadiazole derivative forming the electroluminescent layer 3 is selected in the same manner as the electroluminescent layer 3 of the thin film electroluminescent element 10 shown in FIG.
The kind of the polyoxadiazole derivative forming the transport layer 4 is selected in the same manner as the electron injecting / transporting layer 4 of the thin film electroluminescent device 10 shown in FIG. 2, and the hole injecting / transporting layer 5 is further selected. The type of polyoxadiazole derivative to be formed is selected in the same manner as the hole injecting / transporting layer 5 of the thin film electroluminescent device 10 shown in FIG.

As described above, each of the thin film electroluminescent devices 10 shown in FIGS. 1 to 4 has the electroluminescent layer 3 between the electrodes 1 and 2.
have. In addition, these thin film electroluminescent devices 10
In either case, one of the negative electrode 1 and the positive electrode 2 is transparent, and when a voltage is applied between the electrodes 1 and 2, the electroluminescent layer 3 emits light, and thus the emitted light is transparent in the electrode 1
And / or 3 for irradiation.

In the thin film electroluminescent device 10 shown in FIGS. 1 to 4, the electroluminescent layer 3 is formed between the electrodes 1 and 2 at least one of which is transparent, or the electrode 1 or 2 and the electroluminescent layer 3 are formed. As the electron / injection / transport layer 4 or the hole / injection / transport layer 5, a polyoxadiazole derivative thin film represented by the above formula (I) formed by a vapor deposition polymerization method is formed therebetween.

That is, in the present invention, at least one of the electroluminescent layer 3, the electron injecting / transporting layer 4 and the hole injecting / transporting layer 5 is formed of the polyoxadiazole derivative thin film represented by the above formula (I). There is.

The polyoxadiazole derivative forming this thin film has an oxadiazole ring, and the oxadiazole ring itself has electroluminescent properties. Therefore, X and Y in the above formula (I) are not particularly limited except that they are divalent organic groups, but at least one of X and Y is electroluminescent and / or charge injecting / transporting. In the case where the thin film electroluminescent device 10 has a property (at least one of electron injecting / transporting property and hole injecting / transporting property), the electroluminescent efficiency of the thin film electroluminescent element 10 can be further enhanced.
From this point of view, it is preferable that at least one of X and Y has an electroluminescent property and / or a charge injection / transport property.

For example, when the electron injecting / transporting layer 4 is formed of the polyoxadiazole derivative represented by the formula (I), at least one of X and Y in the formula (I) is a divalent organic compound such as the following. It is preferred to select from the groups.

[0078]

[Chemical 19]

[0079]

[Chemical 20]

[0080]

[Chemical 21]

The binding sites for these groups are direct or --CH.
_It may be bonded via a divalent bonding group such as _2- , -SiH2-, -O-, and -S-. Of these divalent bonding group, -CH ₂ - and -SiH ₂ - hydrogen atoms may be each substituted with an alkyl group or an aryl group.

R _{1 to} R ₆ may be the same or different and are selected from the group consisting of hydrogen atom, halogen atom, cyano group, alkyl group, aralkyl group and alkyloxy group. Is.

Among these groups, as the divalent organic group excellent in charge injection / transport properties, the above (E-1) to (E-
3), (E-5), (E-7), (E-8), (E-1)
1), (E-21), (E-31), (E-34),
(E-35), (E-56), (E-58), (E-6
0) and groups represented by (E-70), particularly m-phenylene group, p-phenylene group, 4,4′-biphenyldiyl group or 2,6-pyridyldiyl group, and particularly preferably p-phenylene group.

Further, the electron injecting / transporting layer 4 formed of the polyoxadiazole derivative represented by the above formula (I)
Is, for example, Chem. Mater., Vol. 3 (1991) pp. 70, if desired.
9-714 and J.Imag.Sci., Vol.29, No.2 (1985) pp.69-72, electron injection and transport additives such as diphenoquinone derivatives and fluorenone derivatives are usually added. 0.01 to 80 mol%, preferably 1 to 60 mol per repeating unit of this polyoxadiazole derivative
% May be contained.

When the hole injecting / transporting layer 5 is formed of the polyoxadiazole derivative represented by the formula (I), at least one of X and Y in the formula (I) is derived from the following compounds. It is preferable that the group is

Aromatic tertiary amine or porphyrin compounds disclosed in JP-A-63-295695. JP-A-53-27033, JP-A-54-58
445, JP-A-54-149634, JP-A-54-64299, and JP-A-55-144250.
JP-A-56-119132, JP-A-61
-295558, the aromatic tertiary amine compound etc. which are disclosed by Unexamined-Japanese-Patent No. 61-98303 etc.

Particularly preferred groups for the hole injecting / transporting layer 5 are as follows.

[0088]

[Chemical formula 22]

[0089]

[Chemical formula 23]

The binding sites for these groups are direct or --CH.
_It may be bonded via a divalent bonding group such as _2- , -SiH2-, -O-, and -S-. Of these divalent bonding group, -CH ₂ - and -SiH ₂ - hydrogen atoms may be each substituted with an alkyl group or an aryl group.

R ₇ and R ₈ may be the same or different and each is a group selected from the group consisting of hydrogen atom, halogen atom, cyano group, alkyl group, aralkyl group and alkyloxy group. is there.

Of the groups exemplified above, (H-1), (H
-2), (H-5), (H-6), (H-14), (H
-16), (H-19), (H-22) and (H-2
4) is particularly preferable.

Further, the hole injecting / transporting layer 5 formed of the polyoxadiazole derivative represented by the above formula (I)
Is, for example, 4,4 ′, 4 ″ -tris (N, Ndiphenylamino) triphenylamine or 4,4 ′, 4 ″ disclosed in Chem. Lett., 1989, pp. 1145, if desired. -Tris [N- (3-methylphenyl) -N-phenylamino] triphenylamine and other hole injecting / transporting additives such as triphenylamine derivatives are usually used as repeating units of this polyoxadiazole derivative. It may be contained in an amount of 0.01 to 80 mol%, preferably 1 to 50 mol%.

At least one of the divalent organic groups represented by X and Y in the above formula (I) is an electron injecting / transporting divalent group or a hole injecting / transporting divalent group as described above. When it is a valent group, the polymer thin film formed from the polyoxadiazole derivative represented by the above formula (I) has not only the charge injection / transport ability but also the function of emitting fluorescence by itself. .

For example, when X in the above formula (I) is a 1,4-phenylene group and Y is a 1,3-phenylene group, the polyoxadiazole derivative represented by the above formula (I) The polymer thin film formed in 1) emits blue fluorescence having a maximum value at a wavelength of 410 nm. When both X and Y are 1,4-phenylene groups, the polymer thin film formed of the polyoxadiazole derivative represented by the formula (I) has a blue color with a maximum value at a wavelength of 450 nm. Emits fluorescence.

As described above, the polymer thin film formed of the polyoxadiazole derivative represented by the formula (I) has a wavelength of 400 to 400 nm from the thin film electroluminescent device 10 depending on the combination of X and Y in the formula (I). It is possible to emit fluorescence of 600 nm.

Furthermore, when at least one of X and Y shown in the above formula (I) is a divalent organic group having the electroluminescent property as described below, a polyvalent compound represented by the above formula (I) is used. The electroluminescence efficiency of the oxadiazole derivative is significantly improved.

[0098]

[Chemical formula 24]

Of the divalent organic groups exemplified above, (L
-1) is particularly preferable. Further, the electroluminescent layer 3 formed of the polyoxadiazole derivative represented by the formula (I) may be made of a material such as coumarin 343, NK757, DCM, NK2929, or aluminum quinolinol complex known as a laser dye, if desired. The fluorescent dye or pigment may be contained usually in an amount of 0.01 to 10 mol%, preferably 0.01 to 5 mol%.

Between the electrodes 1 and 3 of the electroluminescent device 10 having the electroluminescent layer 3 formed of the polyoxadiazole derivative represented by the above formula (I) and containing the above-mentioned fluorescent dye or pigment. When a voltage is applied, the fluorescent dye or pigment emits an intrinsic fluorescence. For example, when coumarin 343, aluminum quinolinol complex, NK757, DCM is used as the fluorescent dye or pigment,
The electroluminescent element 10 emits light of blue green, green, yellow, and red, respectively. Thus, according to the present invention, by incorporating a fluorescent dye or pigment into the electroluminescent layer 3 formed of the polyoxadiazole derivative represented by the formula (I), the fluorescent dye or pigment The emission color of the electroluminescent element 10 can be controlled according to the type.

In the polyoxadiazole derivative represented by the above formula (I), an oxadiazole ring which is a π-electron conjugated ring is alternately bonded to X and Y in the molecule. X, Y
When each is a π-electron conjugated organic group, π is continuously formed along the main chain direction of the polyoxadiazole derivative molecule.
It is presumed that the thin film formed of the polyoxadiazole represented by the formula (I) has excellent electron conductivity because it can be electron-conjugated. Therefore, each of X and Y is preferably a π-electron conjugated organic group.

The polyoxadiazole derivative represented by the above formula (I) has a carbonyl group which becomes a trap for carriers (electrons and holes) such as the polyimide represented by the above formula (VII). Does not form part of the main chain. Therefore, the thin film formed of the polyoxadiazole represented by the formula (I) is superior in electron conductivity to the thin film formed of the polyimide represented by the conventional formula (VII). Guessed.

Further, the thin film electroluminescent device 10 shown in FIGS. 1 to 4 may be provided with a protective film such as an antioxidant film so as to cover the surface on which the negative electrode 1 or the positive electrode 2 is formed. The entire thin film electroluminescent device 10 may be sealed with these protective films. When such a protective film is formed on the negative electrode 1 or the positive electrode 2, the stability of the negative electrode 1 or the positive electrode 2 is increased, and the practicability and durability of the thin film electroluminescent element 10 are improved. Such a protective film can be formed of a metal having a large work function, amorphous silica, germanium monoxide, silicon monoxide, an epoxy resin, a silicone resin, a fluorine resin, or the like.

[Manufacture of Thin-Film Electroluminescent Device] The thin-film electroluminescent device according to the present invention is usually manufactured by i) the step of forming the electrode 1 or 2 on the substrate, ii) the first electrode on the electrode 1 or 2 if desired. Step of forming charge injection / transport layer 4 or 5 by vapor deposition polymerization method, iii) Forming electroluminescent layer 3 on electrode 1 or 2 or on first charge injection / transport layer 4 or 5 by vapor deposition polymerization method And iv) a second charge injecting / transporting layer 4 or 5 (for example, having the ability to inject / transport charges having a sign opposite to that of the first charge injecting / transporting layer 4 or 5 on the electroluminescent layer 3 if desired (for example, When the first charge injection / transport layer is the electron injection / transport layer 4, the second charge injection / transport layer is the hole injection / transport layer 5)
By a vapor deposition polymerization method, v) the counter electrode 1 or 2 on the electroluminescent layer 3 or the second charge injecting / transporting layer 4 or 5 ((eg, the electrode formed in step i) is the negative electrode 1). In some cases, the counter electrode is the positive electrode 2)
And a step of vi) optionally forming a sealing layer of the electroluminescent element on the counter electrode.

Further, in the present invention, the electroluminescent layer 3 and /
Or a charge injection / transport layer (electron injection / transport layer 4 and / or
Alternatively, the hole injecting / transporting layer 5) is formed of the polyoxadiazole thin film represented by the above formula (I), and this polyoxadiazole thin film is formed by vapor deposition polymerization.

In the present invention, when the polyoxadiazole thin film represented by the above formula (I) is formed by vapor deposition polymerization,
Formula (III) below:

[0107]

[Chemical 25]

[In the formula, X represents a divalent organic group. ]
A dicarboxylic acid dichloride represented by the following formula (I
V):

[0109]

[Chemical formula 26]

[In the formula, Y represents a divalent organic group. ] The dicarbohydrazide compound represented by these is used as a monomer for superposition | polymerization. Specific examples of X in the formula (III) and Y in the formula (IV) include the same groups as X and Y in the formula (I). Is also selected in the same manner as X and Y in the above formula (I).

In the present invention, the polyoxadiazole thin film represented by the above formula (I) is formed, for example, in the following order. a) First, a deposition target substrate 22, for example, a substrate with an ITO electrode is set in the deposition chamber 21 of the vacuum deposition apparatus 20 shown in FIG. 5 so that a deposition film is formed on the ITO electrode (the deposition target surface). To do.

B) The above-mentioned two kinds of polymerization monomers A and B
Of the vapor deposition sources 23a and 23b in the vacuum vapor deposition apparatus 20.
Put in. c) The pressure inside the vapor deposition chamber 21 is usually 10 ⁻² P.
The inside of the vapor deposition chamber 21 is decompressed until it becomes a or less, preferably 10 ⁻³ Pa or less.

D) The temperature of the surface to be vapor-deposited, for example, the ITO electrode surface of the substrate with ITO electrodes, is -50 to 200 ° C., preferably 20 to 100, until the pressure in the vapor deposition chamber 21 reaches a predetermined value. Adjust to a temperature of ° C.

E) After the pressure in the vapor deposition chamber 21 reaches a predetermined pressure, the polymerization monomers A and B are kept under this pressure.
However, the temperatures of the evaporation sources 23a and 23b are controlled so that each of them evaporates at an evaporation rate of 10 ^-10 mol / sec · cm ² or more, preferably 10 ^-8 mol / sec · cm ² or more. The temperature at this time is usually -10 to 500 ° C, preferably 40 to
The temperature is 400 ° C, more preferably 70 to 300 ° C, and particularly preferably 100 to 250 ° C. In addition, when at least one of the monomers for polymerization under a predetermined pressure evaporates at room temperature or lower, for example, at a temperature of −10 ° C., this monomer is used so as not to evaporate before reaching a predetermined pressure. The temperature of the evaporation source that accommodates or the temperature of the place where the vacuum vapor deposition apparatus is installed is cooled in advance before heating the evaporation source to a temperature of less than −10 ° C., for example.

The pressure in the vapor deposition chamber 21 and the heating temperature for vaporizing the polymerization monomers A and B are usually the dicarboxylic acid dichloride represented by the above formula (III) and the above formula (IV). The dicarbohydrazide compound represented is 1: 1 to 1:30, preferably 1: 1.
Evaporated at a molar ratio of ˜1: 20 and 0.1 to 10 Å / sec, preferably 1 to 4 Å / sec.
It is adjusted so that a vapor deposition film is formed at a vapor deposition rate of 2 seconds, and the polymerization simultaneously proceeds on the surface to be vapor deposited.

F) After the vapor-deposited polymer film having a film thickness of about 50 to 2000 angstroms is formed in this manner, the vapor-deposited film is usually at 100 to 400 ° C., preferably 200.
The heat treatment is performed at a temperature of 300 ° C. for usually 1 to 240 minutes, preferably 10 to 120 minutes in vacuum or in an inert gas. As a result, the polycarbohydrazide, which is a precursor from both monomers, is changed to the polyoxadiazole derivative represented by the formula (I), and the thin film thereof is on the surface to be vapor-deposited, for example, on the ITO electrode of the substrate with the ITO electrode. Is formed.

The degree of polymerization of the obtained polyoxadiazole derivative is a value corresponding to n in the above formula (I) and is an integer of 2 or more, preferably an integer of 10 or more, more preferably an integer of 100 or more. Is.

Polycarbohydrazide which is a precursor of the polyoxadiazole represented by the above formula (I) is, for example, dimethylformamide (DMF), dimethylacetamide (DMA), dimethylsulfoxide (DM).
It is soluble in organic polar solvents such as SO), N-methylpyrrolidone and pyridine. On the other hand, the polyoxadiazole represented by the formula (I) is soluble in concentrated sulfuric acid,
It is sparingly soluble in the general organic solvents mentioned above. From this, it is possible to estimate the polymerization degree n of the polyoxadiazole represented by the formula (I) by measuring the polymerization degree of the polycarbohydrazide using the organic solvent as described above.

In addition, a low molecular weight compound such as the above-mentioned low molecular weight compound having an electron injecting / transporting ability, a low molecular weight compound having a hole injecting / transporting ability, and a low molecular weight compound having an electroluminescent ability is represented by the above formula (I). When the polyoxadiazole thin film represented by the formula (4) is to be contained in the thin film, these low molecular weight compounds are added in the step b) to the carboxylic acid derivative represented by the formula (III) and the dicarbohydrate represented by the formula (IV). Place it in a vapor deposition source separate from the hydrazide compound, and then in step c) above.
To f) are carried out in the same manner as described above, the respective compounds and these monomers are co-deposited to obtain the polyoxadiazole thin film represented by the formula (I) containing the desired low molecular weight compound.

In the present invention, when manufacturing the thin film electroluminescent device 10 shown in FIGS. 1 to 4, all steps from the step of forming the electrode on the substrate to the formation of the counter electrode (the above step i).
To v) are continuously performed in the same vapor deposition chamber, and outside air is allowed to flow into the vapor deposition chamber after each step (the above steps i) to iv) until the step of forming a counter electrode. It is preferable to carry out the next step without any treatment.

When the thin film electroluminescent element 10 is manufactured in this manner, dust contained in the outside air adheres to the layers formed between the electrodes 1 and 2 or is exposed to the outside air by other methods. Although the thin film electroluminescent device 10 deteriorates due to the oxidation caused by the adsorption of oxygen and moisture, such deterioration of the thin film electroluminescent device 10 is prevented.

The electroluminescent element (EL element) according to the present invention thus obtained can emit light by applying a voltage between the electrodes 1 and 2. The applied voltage is not limited to a direct current (DC) applied voltage, and it is possible to emit light by a driving voltage having a waveform such as a pulse or a triangular wave. Especially when a pulse voltage is applied, DC
The power consumption is remarkably reduced as compared with the voltage application. By thus driving the EL element with a voltage having a specific waveform, the EL element can be used as a display element.

Further, the EL element according to the present invention has the negative electrode 1
A matrix electrode or a thin film transistor (TF) as the (electron injection electrode) and the positive electrode 2 (hole injection electrode).
It is also possible to use it as a display element by applying a pattern such as T) electrode and driving it.

[0124]

According to the present invention, there are provided a thin film electroluminescent device having excellent electroluminescent properties, charge injection / transport properties, high luminous efficiency, and excellent durability such as heat resistance, and a manufacturing method thereof. .

[0125]

The present invention will be described in more detail based on the following examples, but the invention is not intended to be limited to these examples.

[0126]

Example 1 [Vapor-deposition Polymerization] As a substrate, glass with ITO having a thickness of 1000 Å (manufactured by HOYA) was used. This substrate was ultrasonically cleaned in the order of acetone, deionized water, a substrate cleaning agent (Semicoclean EL grade, manufactured by Furuuchi Chemical Co., Ltd.), deionized water, and isopropyl alcohol (IPA), then pulled up from boiling isopropyl alcohol and dried. .

The glass substrate with ITO thus dried was attached to a temperature-controllable substrate holder in a vacuum vapor deposition apparatus. As monomers, 1 g of commercially available terephthalic acid dichloride (manufactured by Tokyo Kasei) and 1 g of terephthalic acid dihydrazide (manufactured by Wako Pure Chemical Industries, Ltd.) were used, and each was placed in another vapor deposition source in a vacuum vapor deposition apparatus.

The pressure inside the vapor deposition apparatus was reduced by an oil diffusion pump until the pressure became 1 × 10 ⁻³ Pa or less. First, the shutter provided on the front surface of the substrate and shutting off the substrate and the vapor deposition source was closed, and the vapor deposition source was heated by a resistance heating method. Then, each monomer is 10 ^-8 to 10 ^-7 mol /
It was set to deposit at a vaporization rate of sec.cm ² , the shutter on the front surface of the substrate was opened, and the above monomer was deposited on a glass substrate with ITO. The film thickness of the vapor deposition film on the substrate was measured by a crystal oscillator film thickness meter, and when the thickness was 800 angstrom, the shutter was closed again.

The temperature of the substrate holder was heated to 300 ° C., and the substrate to which the vapor deposition film was attached was heat-treated for 30 minutes.
By this operation, the polymerization reaction of the above terephthalic acid dichloride and terephthalic acid dihydrazide was completed. [Poly (1,4-phenylene-2,5-oxadiazolylene)]
Confirmation that a thin polymer thin film was formed] thickness 0.5 m
A vapor-deposited polymerized film (sample) having a film thickness of 1 μm was formed on the Al substrate of m by performing the same operation as described above.

[0130] was measured for FT-IR spectrum of the sample by a reflection method, characteristic absorption due to the hydrazide group 3212Cm ^-1 and (N-H stretching vibration), 1666 cm ^-1
The C = O stretching vibration of the carbonyl group of 1 disappeared and 1478, 1536 cm ^-1 (-C =
N- and> C = C <stretching vibration)
Absorption of 2,959 cm ⁻¹ (= C—O—C = stretching vibration) was observed, and it was confirmed that an oxadiazole ring was formed. Further, this thin film was dissolved only in concentrated sulfuric acid and was not dissolved in an organic solvent.

From this, it was confirmed that poly (1,4-phenylene-2,5-oxadiazolylene) was produced by the polymerization reaction of terephthalic acid dichloride and terephthalic acid dihydrazide. [Fabrication of electroluminescent device and confirmation of light emission] Poly (1,4-phenylene-2,5 provided on the glass substrate with ITO
-Oxadiazolylene) polymer thin film (light emitting layer)
An MgAg electrode was co-deposited on the above to prepare an electroluminescent device. The weight composition ratio of MgAg alloy (Mg / Ag)
Was set to 10/1.

The electroluminescent device thus obtained is the thin film electroluminescent device 10 of the type shown in FIG.
When a DC voltage of 7 V was applied between the electrodes 1 and 2 with the positive electrode 2 as the electrode and the MgAg electrode as the negative electrode 1, blue electroluminescence (EL) occurred.

[0133]

Example 2 In the same manner as in Example 1, when a polymer thin film made of poly (1,4-phenylene-2,5-oxadiazolylene) was formed on a glass substrate with ITO by a vapor deposition polymerization method, a laser dye was used. Was co-evaporated by evaporating DCM from a vapor deposition source other than the monomer source. At this time, in order to adjust the amount of DCM contained in the polymer thin film, the deposition rate of DCM was adjusted to be 0.05 mol% with respect to the total amount of monomers to be deposited.

The DCM prepared by the above method was added to 0.05
An MgAg electrode was co-deposited on a polymer thin film made of poly (1,4-phenylene-2,5-oxadiazolylene) containing mol% to manufacture an electroluminescent device.

The electroluminescent device thus obtained is the thin film electroluminescent device 10 of the type shown in FIG.
When a DC voltage of 10 V was applied between the electrodes 1 and 2 with the electrode 2 as the positive electrode 2 and the MgAg electrode as the negative electrode 1, red (wavelength 610 nm) electroluminescence occurred.

[0136]

[Example 3] Poly (1,4-phenylene-2,5-oxadiazolylene) was formed on a glass substrate with ITO in the same manner as in Example 1.
A triphenylamine derivative (4,4 ', 4 "-tris [N- (3-methylphenyl) -N-phenylamino] tri, which has excellent hole transporting properties, is formed by vapor deposition polymerization (Phenylamine) was evaporated from a vapor deposition source other than the monomer source to co-evaporate, and in order to adjust the amount of the triphenylamine derivative contained in the polymer thin film, 7 mol% was added to the total amount of the vapor-deposited monomers. The vapor deposition rate of the triphenylamine derivative was adjusted so that

After confirming with a quartz vibrating film thickness meter that the film thickness of the vapor deposition film containing 7 mol% of the triphenylamine derivative with respect to the total amount of monomers was 300 angstroms,
Deposition of the triphenylamine derivative was stopped.

After that, the vapor deposition was continued using only the monomer, and the vapor deposition was stopped when the total vapor deposition film thickness reached 800 angstroms. Next, heat treatment was performed under the same conditions as in Example 1 to complete the polymerization reaction, and a MgAg electrode was co-deposited on the polymer thin film obtained to manufacture an electroluminescent device.

The electroluminescent device thus obtained is the thin film electroluminescent device 10 of the type shown in FIG.
When a DC voltage was applied between the electrodes 1 and 2 using the electrode 2 as the positive electrode 2 and the MgAg electrode as the negative electrode 1, blue electroluminescence was generated. At this time, the voltage at which light emission started decreased as compared with the case where the triphenylamine derivative was not contained. In addition, the emission brightness at the same voltage is increased and the efficiency of electroluminescence is improved.

[0140]

Example 4 [Vaporization Polymerization] The cleaned glass substrate with ITO as in Example 1 was attached to a temperature-controllable substrate holder in a vacuum vapor deposition apparatus.

As monomers, 1 g of 4,4′-biphenyldicarboxylic acid dichloride and 1 g of commercially available terephthalic acid dihydrazide (manufactured by Wako Pure Chemical Industries, Ltd.) were used, and each was placed in another vapor deposition source in a vacuum vapor deposition apparatus.

The inside of the vapor deposition apparatus was depressurized by an oil diffusion pump until the pressure became 1 × 10 ⁻³ Pa or less. First, the shutter provided on the front surface of the substrate and shutting off the substrate and the vapor deposition source was closed, and the vapor deposition source was heated by a resistance heating method. Then, each monomer is 10 ^-8 to 10 ^-7 mol /
It was set to evaporate at a speed of sec.cm ² , the shutter on the front surface of the substrate was opened, and the above monomer was vapor-deposited on the glass substrate with ITO. The film thickness of the vapor deposition film on the substrate was measured by a crystal oscillator film thickness meter, and when the thickness was 800 angstrom, the shutter was closed again.

The temperature of the substrate holder was heated to 300 ° C., and the substrate having the vapor deposition film attached was heat-treated for 30 minutes.
By this operation, the polymerization reaction of the above 4,4′-biphenyldicarboxylic acid dichloride and terephthalic acid dihydrazide was completed. [Poly (4,4'-biphenylene-2,5-oxadiazolylene
Confirmation that a polymer thin film composed of -1,4-phenylene-2,5-oxadiazolylene) was formed] A with a thickness of 0.5 mm
l By performing the same operation as above on the substrate, the film thickness of 1μ
m vapor-deposited polymerized film (sample) was formed.

[0144] was measured for FT-IR spectrum of the sample by a reflection method, characteristic absorption due to the hydrazide group 3212Cm ^-1 and (N-H stretching vibration), 1666 cm ^-1
The C═O stretching vibration of the carbonyl group of the above disappeared, and absorption due to the oxadiazole ring (1478, 1536, 100
2,959 cm ⁻¹ ) appeared, and it was confirmed that an oxadiazole ring was formed. The FT-IR spectrum of the thin film obtained by the vapor deposition polymerization was in agreement with the FT-IR spectrum of the thin film obtained by the solution polymerization method.

From this, it was confirmed that poly (1,4-phenylene-2,5-oxadiazolylene) was produced by the polymerization reaction of 4,4′-biphenyldicarboxylic acid dichloride and terephthalic acid dihydrazide. Was done. [Fabrication of electroluminescent device and confirmation of light emission] Poly (4,4'-biphenylene) provided on the glass substrate with ITO
-2,5-oxadiazolylene-1,4-phenylene-2,5-oxadiazolylene) on the polymer thin film (light emitting layer)
A gAg electrode was co-evaporated to prepare an electroluminescent device. The weight composition ratio (Mg / Ag) of the MgAg alloy is 10 /
It was set to 1.

The electroluminescent device thus obtained is a thin film electroluminescent device 10 of the type shown in FIG.
When a DC voltage of 7 V was applied between the electrodes 1 and 2 with the positive electrode 2 as the electrode and the MgAg electrode as the negative electrode 1, blue electroluminescence (EL) occurred.

[0147]

Example 5 Instead of poly (1,4-phenylene-2,5-oxadiazolylene), poly (4,4′-biphenylene-2,5-oxadiazolylene-1,4-phenylene-2,5 is used. -Oxadiazolylene) was used to manufacture an electroluminescent device in the same manner as in Example 2.

The electroluminescent device thus obtained is the thin film electroluminescent device 10 of the type shown in FIG.
When a DC voltage of 10 V was applied between the electrodes 1 and 2 with the electrode 2 as the positive electrode 2 and the MgAg electrode as the negative electrode 1, red (wavelength 610 nm) electroluminescence occurred.

[0149]

Example 6 Instead of poly (1,4-phenylene-2,5-oxadiazolylene), poly (4,4′-biphenylene-2,5-oxadiazolylene-1,4-phenylene-2,5 was used. An electroluminescent device was manufactured in the same manner as in Example 3 except that (oxadiazolylene) was used.

The electroluminescent device thus obtained is the thin film electroluminescent device 10 of the type shown in FIG.
When a DC voltage was applied between the electrodes 1 and 2 using the electrode 2 as the positive electrode 2 and the MgAg electrode as the negative electrode 1, blue electroluminescence was generated. At this time, the voltage at which light emission started decreased as compared with the case where the triphenylamine derivative was not contained. In addition, the emission brightness at the same voltage is increased and the efficiency of electroluminescence is improved.

[0151]

Example 7 [Vaporization Polymerization] The cleaned glass substrate with ITO as in Example 1 was attached to a temperature-controllable substrate holder in a vacuum vapor deposition apparatus.

As monomers, 1 g of 3,5-triphenylamine dicarbonyl dichloride, 1 g of 5-tert-butylisophthalic acid dichloride and 1 g of terephthalic acid dihydrazide (manufactured by Wako Pure Chemical Industries, Ltd.) were used. It was placed in a vapor deposition source.

Next, the pressure inside the vapor deposition apparatus was reduced by an oil diffusion pump until the pressure became 1 × 10 ⁻³ Pa or less. First, the shutter provided on the front surface of the substrate and shutting off the substrate and the vapor deposition source was closed, and the vapor deposition source was heated by a resistance heating method. First, set so that 3,5-triphenylamine dicarboxylic acid dichloride and terephthalic acid dihydrazide are evaporated at a rate of 10 ^-8 to 10 ^-7 mol / sec ・ cm ² , respectively, and open the shutter on the front surface of the substrate. The above monomer was deposited on a glass substrate with ITO. The film thickness of the vapor deposition film on the substrate was measured by a crystal oscillator film thickness meter to obtain a thickness of 500.
When it showed Angstrom, the shutter was closed again.

Then, 5-tert-butylisophthalic acid dichloride and terephthalic acid dihydrazide were respectively added to 10 ^-8
It was set to evaporate at a rate of -10 ⁻⁷ mol / sec · cm ² , the shutter on the front surface of the substrate was opened, and the above monomer was deposited on the glass substrate with ITO. The film thickness of the vapor deposition film on the substrate was measured by a crystal oscillator film thickness meter, and when the thickness was 300 angstrom, the shutter was closed again.

The temperature of the substrate holder was heated to 300 ° C., and the substrate to which the vapor deposition film was attached was heat-treated for 30 minutes.
By this operation, the polymerization reaction of 3,5-triphenylamine dicarboxylic acid dichloride and terephthalic acid dihydrazide and the polymerization reaction of 4,4′-biphenyldicarboxylic acid dichloride and terephthalic acid dihydrazide were completed.

In this way, the IT of the glass substrate with ITO
Two different polyoxadiazole thin films were formed on O. [Confirmation that two different layers of polyoxadiazole thin film were formed] 3,5-triphenylamine dicarboxylic acid dichloride and terephthalic acid dihydrazide were vapor-deposited and polymerized on a 0.5 mm thick Al substrate. A 1 μm thin polymer film was formed. Similarly, on an Al substrate with a thickness of 0.5 mm
5-tert-Butylisophthalic acid dichloride and terephthalic acid dihydrazide were vapor-deposited and polymerized to form a polymer thin film having a thickness of 1 μm.

The FT-IR spectra of the above two samples were
When measured by the reflection method, 3212 cm^-1Hydrazide
Characteristic absorption (N-H stretching vibration) caused by the base, and 1666
cm ^-1The C = O stretching vibration of the carbonyl group of
Absorption due to the thiadiazole ring appears and
It was confirmed that the ring was generated. Also, the above vapor deposition
FT-IR spectrum of these thin films obtained by polymerization
Is the FT-IR spectrum of the thin film obtained by the solution polymerization method.
Matched with Le.[Production of electroluminescent device and confirmation of light emission] as mentioned above
And two different polyoxadiazole thin films
Polio of glass substrate with ITO formed on TO
Co-depositing a MgAg electrode on the oxadiazole thin film,
An electroluminescent device was manufactured. In addition, the weight group of MgAg alloy
The composition ratio (Mg / Ag) was set to 10/1.

The electroluminescent device thus obtained is the thin film electroluminescent device 10 of the type shown in FIG.
When a DC voltage of 10 V was applied between the electrodes 1 and 2 with the electrode serving as the positive electrode 2 and the MgAg electrode serving as the negative electrode 1, blue-green electroluminescence (EL) occurred.

[Brief description of drawings]

FIG. 1 is a cross-sectional view schematically showing the configuration of a first thin film electroluminescent device according to the present invention.

FIG. 2 is a cross-sectional view schematically showing a first example of a second thin film electroluminescent device according to the present invention.

FIG. 3 is a cross-sectional view schematically showing a second example of the second thin film electroluminescent device according to the present invention.

FIG. 4 is a cross-sectional view schematically showing a third example of the second thin film electroluminescent element according to the present invention.

FIG. 5 is a drawing for explaining a method of manufacturing a thin film electroluminescent device according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Thin film electroluminescent element 1 ... Negative electrode 2 ... Positive electrode 3 ... Electroluminescent layer 4 ... Electron injection / transport layer 5 ... Hole injection / transport layer 20 ... Vacuum deposition apparatus 21 ... Deposition chamber 22 ... Deposition substrate 23a, 23b ... Evaporation source A, B ... Monomer

Claims (9)

[Claims] 1. A thin film electroluminescent device having an electroluminescent layer between electrodes, at least one of which is transparent, wherein the electroluminescent layer is formed by a vapor deposition polymerization method represented by the following formula (I): [In the formula, X and Y, which may be the same or different, each represents a divalent organic group, and n is an integer of 2 or more. ] A thin film electroluminescent device comprising a polyoxadiazole derivative represented by: 2. A thin film electroluminescent device comprising an electroluminescent layer between electrodes, at least one of which is transparent, and a charge injection / transport layer between the at least one electrode and the electroluminescent layer, At least one of the electroluminescent layer and the charge injecting / transporting layer is formed by a vapor deposition polymerization method and has the following formula (I): [In the formula, X, Y and n represent the same meaning as described above. ] A thin film electroluminescent device comprising a polyoxadiazole derivative represented by: 3. The following formula (I) in which the electroluminescent layer is formed by a vapor deposition polymerization method: [In the formula, X, Y and n represent the same meaning as described above. ] A polyoxadiazole derivative represented by the above formula and the charge injection / transport layer formed by a vapor deposition polymerization method, represented by the following formula (II): [In the formula, X, Y and n represent the same meaning as described above. ] The polyoxadiazole derivative represented by the formula (1), wherein at least one of X and Y in the formula (I) is different from both X and Y in the formula (II). Thin film electroluminescent device. 4. The thin film electroluminescent device according to claim 1, which emits fluorescence having a wavelength of 400 to 600 nm. 5. The electroluminescent layer comprises a polyoxadiazole derivative represented by the formula (I), and a fluorescent dye or pigment in the electroluminescent layer is 0 per repeating unit of the polyoxadiazole derivative. 0.01 to 10 mol
The thin film electroluminescent device according to claim 1, wherein the thin film electroluminescent device is contained in an amount of%. 6. The charge injecting / transporting layer comprises a polyoxadiazole derivative represented by the formula (I), and the additive having charge injecting / transporting ability in the charge injecting / transporting layer is the polyoxadiazole derivative. The thin film electroluminescent device according to claim 2, wherein the diazole derivative is contained in an amount of 0.01 to 80 mol% per repeating unit. 7. The following formula (III): [In the formula, X represents a divalent organic group. ] And a dicarboxylic acid dichloride represented by the following general formula (IV): [In the formula, Y represents a divalent organic group. ] A dicarbohydrazide compound represented by the following formula is vapor-deposited and then heat treated to obtain a compound represented by the following formula (I): [In the formula (I), X is a divalent organic group derived from the dicarboxylic acid dichloride represented by the formula (III), and Y is
Is a divalent organic group derived from the dicarbohydrazide compound represented by the above formula (IV), and n is an integer of 2 or more. ] The manufacturing method of the thin film electroluminescent element characterized by forming the light emitting layer and / or charge injecting / transporting layer which consist of a polyoxadiazole derivative represented by these between electrodes which at least one is transparent. 8. In a vapor deposition chamber, i) a step of forming an electrode on a substrate by a vapor deposition method, ii) a step of optionally forming a first charge injection / transport layer on the electrode by a vapor deposition polymerization method, iii ) A step of forming an electroluminescent layer on the electrode or the first charge injecting / transporting layer by a vapor deposition polymerization method, iv) Opposite the first charge injecting / transporting layer on the electroluminescent layer, if desired. A step of forming a second charge injecting / transporting layer having the ability to inject / transport the charges of the code by a vapor deposition polymerization method, v) forming a counter electrode on the electroluminescent layer or on the second charge injecting / transporting layer And the steps i) to v) are continuously performed in the same vapor deposition chamber, and after each step i) to iv),
The next step is performed without inflowing outside air into the deposition chamber, and at least one of the first charge injection / transport layer, the electroluminescent layer, and the second charge injection / transport layer has the above formula. A polyoxadiazole represented by the above formula (I) formed by subjecting a dicarboxylic acid dichloride represented by the (III) and a dicarbohydrazide compound represented by the above general formula (IV) to vapor deposition polymerization and then heat treatment. 8. The method for manufacturing a thin film electroluminescent device according to claim 7, wherein the thin film electroluminescent device is made of a derivative. 9. In a vapor deposition chamber, i) a step of forming an electrode on a substrate by a vapor deposition method, ii) a step of forming a first charge injection / transport layer on the electrode by a vapor deposition polymerization method, iii) 9. The method according to claim 8, further comprising: a step of forming an electroluminescent layer on the first charge injecting / transporting layer by a vapor deposition polymerization method; and v) forming a counter electrode on the electroluminescent layer. Method for manufacturing thin film electroluminescent device.