Stock material or miscellaneous articles – Composite – Of inorganic material
Reexamination Certificate
1998-10-21
2001-02-13
Krynski, William (Department: 1774)
Stock material or miscellaneous articles
Composite
Of inorganic material
C428S469000, C428S472100, C257S100000
Reexamination Certificate
active
06187457
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to an organic electroluminescent light emitting device (which will hereinafter be often called an organic EL device for short) using an organic compound, and more particularly to an organic EL device in which an electron injecting electrode for supplying electrons to a light emitting layer is provided thereon with a sealing film, and its production process.
BACKGROUND TECHNIQUE
In recent years, organic EL devices have been under intensive investigation. One such organic EL device basically includes a transparent electrode (a hole injecting electrode) of tin-doped indium oxide (ITO). A thin film is formed on the transparent electrode by evaporating a hole transporting material such as triphenyldiamine (TPD). A light emitting layer of a fluorescent material such as an aluminum quinolinol complex (Alq
3
) is deposited on the hole transporting thin film. An electrode (an electron injecting electrode) is formed thereon from a metal having a low work function such as magnesium or Mg. This organic EL device attracts attentions because they can achieve a very high luminance ranging from several hundreds to tens of thousands cd/m
2
with a voltage of approximately 10 volts.
An electron injecting electrode considered to be effective for such organic EL devices is made up of a material capable of injecting more electrons into the light emitting layer or electron injecting and transporting layer. In other words, the lower the work function of a material, the more suitable is the material as the electron injecting electrode. Various materials having a low work function are available. Regarding materials used as the electron injecting electrode of organic EL devices, for instance, JP-A 2-15595 discloses an electron injecting electrode comprising a plurality of metals other than an alkali metal, at least one of which has a work function of less than 4 eV, typically MgAg.
A preferable material having a low work function is an alkali metal. U.S. Pat. Nos. 3,173,050 and 3,382,394 disclose NaK as one example of the alkali metal. However, an electron injecting electrode made up of the alkali metal is inferior to that built up of MgAg, etc. in terms of safety and reliability, because the alkali metal has high activity and so is chemically unstable.
To use such a material having a low work function as mentioned above or its alloy, film sealing has been under investigation. To achieve sufficient sealing, however, it is required to make use of costly yet troublesome sealing films such as those of Teflon or SiO
2
because any desired result is unachievable by use of glass sealing or the like. Such film sealing should be carried out immediately after the formation of an electron injecting electrode, thereby preventing corrosion of the electron injecting electrode by oxidation. To this end, however, dedicated film sealing equipment should be provided separately.
In efforts to prevent oxidation, it has been proposed to form an aluminum cap layer on Mg.Al as set forth in JP-A 4-233194 or to use a cap layer formed of an alkaline earth metal, a rare earth metal or the like which have a work function much lower than that of the electron injecting electrode material. However, such cap layers have for its object the prevention of appearance of dark spots, and so serve mainly to absorb moisture at an interface between a cathode (electron injecting electrode) and an organic electroluminescent medium, etc. In other words, these cap layers are less than satisfactory for a sealing film protecting the whole of an organic EL device.
DISCLOSURE OF THE INVENTION
It is therefore an object of the invention to provide an organic EL device including a sealing film which can be relatively easily formed continuously from an electron injecting electrode without recourse to any dedicated equipment for sealing films, and has a high sealing effect as well. Another object of the invention is to provide a process of producing such an organic EL device.
Such objects are achievable by the inventions defined below as (1) to (6).
(1) An organic EL device at least comprising a substrate and a hole injecting electrode, a light emitting layer and an electron injecting electrode containing a constituting material having a work function of up to 4 eV formed on said substrate, wherein:
said electron injecting electrode has a sealing film on a side thereof opposite to said substrate, said sealing film containing one or two or more of an oxide, a nitride and a carbide of a constituting material for said electron injecting electrode.
(2) The organic EL device of (1), wherein said sealing film contains oxygen, nitrogen and carbon in amounts of 1 to 60 at % calculated as 0, 1 to 30 at % calculated as N and 1 to 20 at % calculated as C, respectively.
(3) An organic EL device comprising at least a substrate and a hole injecting electrode, a light emitting layer and an electron injecting electrode containing a constituting material having a work function of up to 4 eV formed on said substrate, wherein:
said electron injecting electrode has an auxiliary electrode thereon, said auxiliary electrode having a sealing film on a side thereof opposite to said substrate, and said sealing film containing one or two or more of an oxide, a nitride and a carbide of a constituting material for said auxiliary electrode.
(4) The organic EL device of (3), wherein said sealing film contains oxygen, nitrogen and carbon in amounts of 1 to 60 at % calculated as 0, 1 to 30 at % calculated as N and 1 to 20 at % calculated as C, respectively.
(5) A process of producing an organic EL device, which comprise steps of forming an electron injecting electrode having a work function of up to 4 eV by a sputtering technique, and then sputtering a constituting material for said electron injecting electrode while a gas containing one or two or more of oxygen, nitrogen and carbon is introduced as a reactive gas to form a sealing film, so that an organic EL device as recited in any one of (1) to (4) is obtained.
(6) A process of producing an organic EL device, which comprises steps of:
forming an electron injecting electrode containing a constituting material having a work function of up to 4 eV by a sputtering technique,
forming an auxiliary electrode by a sputtering technique after formation of said electron injecting electrode, and
sputtering a constituting material for said auxiliary electrode while a gas containing one or two or more of oxygen, nitrogen and carbon is introduced as a reactive gas to form a sealing film.
REFERENCES:
patent: 4885211 (1989-12-01), Tang et al.
patent: 5059861 (1991-10-01), Littman et al.
patent: 5652067 (1997-07-01), Ito et al.
patent: 5776622 (1998-07-01), Hung et al.
Arai Michio
Mori Masami
Nakaya Kenji
Onitsuka Osamu
Garrett Dawn L.
Krynski William
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
TDK Corporation
LandOfFree
Organic EL element and method of producing the same does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Organic EL element and method of producing the same, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Organic EL element and method of producing the same will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2593298