Stock material or miscellaneous articles – Composite – Of inorganic material
Reexamination Certificate
2000-03-22
2003-03-11
Kelly, Cynthia H. (Department: 1774)
Stock material or miscellaneous articles
Composite
Of inorganic material
C428S917000, C313S502000, C313S503000, C313S506000, C252S301340, C427S069000, C427S601000
Reexamination Certificate
active
06531234
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an organic electroluminescence element (electroluminescence is hereinafter abbreviated as “EL”). More specifically, it relates to an organic EL element which is excellent in a durability without decreasing a luminance even in the driving for a long period of time, and a process for producing the same.
BACKGROUND OF THE INVENTION
An EL element using electroluminescence has characteristics that for its emission, the visibility is high and since it is a complete solid state element, the impact strength is excellent. Accordingly, its use as a luminescence element in various display devices has attracted much interest.
The EL elements include an inorganic EL element obtained by using an inorganic component as a emitting material and an organic EL element obtained by using an organic compound as a emitting material. Especially the organic EL element of these can much reduce an applied voltage, is easy to downsize, reduces consumption power, allows area luminescence and also easily emits luminescence of three primary colors. Accordingly, studies have positively been made to put the same to practical use as a luminescence element in the next generation.
With respect to the construction of this organic EL element, an element based on a construction of anode/organic emitting layer/cathode and provided on this with a hole injecting and transporting layer or an electron injection layer as required, for example, an element having a construction of anode/hole injecting and transporting layer/organic emitting layer/cathode, anode/hole injecting and transporting layer/organic emitting layer/electron injection layer/cathode or the like has been known.
The greatest problem in the studies to put such an organic EL element to practical use is to establish a technology in which an organic EL element can hold the practical quality by controlling the decrease in its luminance accompanied by the driving for a long period of time.
In this respect, according to
Gekkan Display
, September, p. 15 (1995) and
Oyo Butsuri
, vol. 66, No. 2, pp. 114-115 (1997), it is known that the purity of various organic compounds used to produce electric EL elements strongly influences the decrease in a emitting efficiency and a luminance. However, the influence of the structures, qualities and the like of various organic compounds used in organic EL elements on properties of organic EL elements has not been clarified yet, and a method for quantitatively measuring the same has been unknown.
Accordingly, when organic EL elements are used for a long period of time, the details of the reasons for decreasing the luminance have been currently unknown.
Further, especially in recent years, there have been a large number of examples in which an anthracene skeleton, a naphthacene skeleton, a pyrene skeleton or a perylene skeleton is used in a hole transport-injection material, a emitting material and a doping material. However, these skeletons are characterized in that they are easily oxidized, and a technology of controlling the oxidized compound has not been developed yet.
DISCLOSURE OF THE INVENTION
Under these circumstances, the present invention aims to provide a practical organic EL element which is excellent in a durability without decreasing a luminance even in the driving for a long period of time, a process for producing the same, and further an organic electroluminescence film.
The present invention aims to, among others, especially a practical organic EL element which is excellent in a durability without decreasing a luminance even in the driving for a long period of time, when using a material having an anthracene skeleton, a naphthacene skeleton, a pyrene skeleton or a perylene skeleton in an organic EL element, a process for producing the same, and further an organic electroluminescence film.
The present inventors have assiduously conducted investigations to develop an organic EL element excellent in a durability, and have consequently found that when at least one layer of an organic compound layer mounted between a pair of electrodes has a specific mass spectrum, an element is excellent in a durability and that an organic compound layer having a specific mass spectrum is formed by strictly controlling deposition conditions when the organic compound layer is formed by a deposition method. The present invention has been completed on the basis of such findings.
That is, the present invention is an organic electroluminescence element, a process for producing the same, and further an organic electroluminescence film which follow.
1. An organic electroluminescence element in which an organic compound layer having at least an organic emitting layer is held between a pair of electrodes, an anode and a cathode, characterized in that the mass spectrum of at least one layer of the organic compound layer satisfies a relationship of formula (I)
∑
(
I
sn
)
I
M
≤
25
%
(
I
)
(wherein I
M
represents an intensity of a main peak, and I
sn
represents an intensity of an n-th peak of sub-peaks).
2. The organic electroluminescence element as recited in the above 1, wherein the mass spectrum of at least one layer of the organic compound layer satisfies the relationship of formula (I) and a relationship of formula (II)
&Sgr;|M
MW
−S
Mwn
|≦50 (II)
(wherein M
MW
represents a mass of a main peak, and S
Mwn
represents a mass of an n-th peak of sub-peaks).
3. The organic electroluminescence element as recited in the above 1, wherein in at least one of the organic compounds used to form the organic compound layer, a ratio of a main peak area to a total peak area is at least 98% in the analysis by gel permeation chromatography (GPC).
4. A process for producing an organic electroluminescence element in which an organic compound layer having at least an organic emitting layer is held between a pair of electrodes, an anode and a cathode, characterized in that the organic compound layer is formed by deposition such that the mass spectrum of at least one layer of the organic compound layer satisfies a relationship of formula (I)
∑
(
I
sn
)
I
M
≤
25
%
(
I
)
(wherein I
M
represents an intensity of a main peak, and I
sn
represents an intensity of an n-th peak of sub-peaks).
5. The process as recited in the above 4, wherein the organic compound layer is formed such that the mass spectrum of at least one layer of the organic compound layer satisfies the relationship of formula (I) and a relationship of formula (II)
&Sgr;|M
MW
−S
Mwn
|≦50 (II)
(wherein M
MW
represents a mass of a main peak, and S
Mwn
represents a mass of an n-th peak of sub-peaks).
6. The process as recited in the above 4, wherein in at least one of the organic compounds used to form the organic compound layer, a ratio of a main peak area to a total peak area is at least 98% in the analysis by gel permeation chromatography (GPC).
7. The organic electroluminescence element as recited in any of the above 1 to 3, characterized in that the organic compounds are compounds containing at least one of an anthracene structure, a naphthacene structure, a pyrene structure and a perylene structure in the skeleton structure.
8. The process as recited in any of the above 4 to 6, characterized in that the organic compounds are compounds containing at least one of an anthracene structure, a naphthacene structure, a pyrene structure and a perylene structure in the skeleton structure.
9. A process for producing an organic electroluminescence element in which an organic compound layer having at least an organic emitting layer is held between a pair of electrodes, an anode and a cathode, characterized in that the mass spectrum of a powder of an organic compound used to form the organic compound layer satisfies a relationship of formula (I)
∑
(
I
sn
)
I
M
≤
25
%
(
I
)
(wherein I
M
represents an intensity of a main peak, and I
sn
represents an intensity of an n-th peak of sub-peaks), and a relationship of formula (II)
&Sgr;|M
MW
−
Higashi Hisahiro
Hosokawa Chishio
Sakai Toshio
Garrett Dawn
Idemitsu Kosan Co. Ltd.
Kelly Cynthia H.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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