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Researchers Submit Patent Application, "Composition Capable of Changing Its Solubility, Hole Transport Material Composition, and Organic Electronic...

September 11, 2014



Researchers Submit Patent Application, "Composition Capable of Changing Its Solubility, Hole Transport Material Composition, and Organic Electronic Element Using the Same", for Approval

By a News Reporter-Staff News Editor at Politics & Government Week -- From Washington, D.C., VerticalNews journalists report that a patent application by the inventors Funyuu, Shigeaki (Tsuchiura-shi, JP); Asano, Naoki (Tsukuba-shi, JP); Ishitsuka, Kenichi (Tsukuba-shi, JP), filed on September 26, 2012, was made available online on August 28, 2014.

The patent's assignee is Hitachi Chemical Company, Ltd.

News editors obtained the following quote from the background information supplied by the inventors: "Organic electronic elements are elements which perform electrical actions using organic matter. It is expected that organic electronic elements will be able to provide advantages such as energy conservation, low prices and superior flexibility, and they are attracting considerable attention as an alternative technology to conventional inorganic semiconductors based mainly on silicon.

"Among organic electronic elements, organic EL elements are attracting attention, for example, as substitutes for incandescent lamps or gas-filled lamps in large-surface area solid state light source applications. Further, they are also attracting attention as the self-luminous display most likely to replace liquid crystal displays (LCD) in the field of flat panel displays (FPD), and commercialization of organic EL elements continues to progress.

"Organic EL elements are broadly classified into two types depending on the organic material used, namely low-molecular weight organic EL elements and polymer organic EL elements. Low-molecular weight materials are used as the organic material for low-molecular weight organic EL elements, and polymer materials are used as the organic material for polymer organic EL elements. Compared with low-molecular weight organic EL elements, for which film formation is mainly performed in a vacuum system, polymer organic EL elements can employ simple film formation methods such as printing or inkjet application. Accordingly, it is expected that polymer organic EL elements will be indispensible elements for future large-screen organic EL displays.

"Both low-molecular weight organic EL elements and polymer organic EL elements have already been researched intensively, but improving properties of the elements such as the luminous efficiency and the lifetime of the element remain problems. Using multiple layers for the organic layer that constitutes the organic EL element is used as one method of addressing these problems.

"In a low-molecular weight organic EL element, because film formation is generally performed by a vapor deposition method, multilayering can be easily achieved by sequentially changing the compound used in the vapor deposition. On the other hand, multilayering is problematic in polymer organic EL elements. The reason for this problem is that, in polymer organic EL elements, because film formation is performed by a wet process such as printing or inkjet application, the previously formed lower layer dissolves during formation of the upper layer. In order to enable multilayering of a polymer organic EL element, a method is required in which the already formed lower layer does not change during formation of the upper layer.

"In order to achieve multilayering, investigations have been conducted into the use of compounds having significantly different solubility levels. One typical example of this method is an element having a 2-layer structure consisting of a hole injection layer composed of polythiophene:polystyrene sulfonic acid (PEDOT:PSS) formed using a water dispersion, and a light-emitting layer formed using an aromatic organic solvent such as toluene. In this case, because the hole injection layer composed of PEDOT:PSS does not dissolve in the aromatic organic solvent, the 2-layer structure can be produced.

"However, in this element, the removal of water is problematic, and water can cause a deterioration in the properties of the organic EL element. Further, because drying at a high temperature and/or for a long period of time is performed to remove the water, preparation of an organic EL element using a resin substrate is difficult. Furthermore, there are considerable limitations associated with processes in which reduced pressure conditions are required for the removal of water.

"Another method for achieving multilayering that is being investigated utilizes reactions between compounds (for example, see Non-Patent Document 1, Patent Document 1, and Patent Document 2). These documents disclose methods of achieving multilayering by reacting a polymerizable substituent that has been introduced into a compound. For example, these methods include multilayering that uses the polymerization reaction of a silyl group, styryl group, oxetane group or acrylic group or the like, and multilayering that uses the dimerization of a trifluorovinyl ether group or a benzocyclobutene group or the like."

As a supplement to the background information on this patent application, VerticalNews correspondents also obtained the inventors' summary information for this patent application: "Technical Problem

"However, in the methods mentioned above, when producing the organic EL elements, the polymerizable substituents must be introduced into the compounds used in forming the organic layers.

"An effective multilayering method is required in general for organic electronic elements in which two adjacent organic layers are formed by application, and for example, is also required for organic photoelectric conversion elements in which two adjacent layers (for example, a buffer layer and a photoelectric conversion layer) are formed by application.

"Accordingly, an object of one embodiment of the present invention is to provide a composition, a hole transport material composition and an ink composition which enable multilayering of organic layers using a coating method. Further, an object of another embodiment of the present invention is to provide an organic layer that can be multilayered using a coating method, and a method for forming the organic layer. Furthermore, an object of yet another embodiment of the present invention is to provide an organic electronic element, an organic EL element and an organic photoelectric conversion element having an organic layer formed by a coating method. Moreover, an object of yet another embodiment of the present invention is to provide a display element and an illumination device which use an organic EL element having an organic layer formed by a coating method.

"Solution to Problem

"As a result of intensive investigation, the inventors of the present invention discovered that by applying heat and/or light to a thin film formed using a composition containing a polymer or oligomer having a repeating unit with hole transport properties and also having a thienyl group, and an initiator, the solubility of the thin film in solvents changed, and they were therefore able to complete the present invention.

"In other words, one embodiment of the present invention relates to a composition comprising a polymer or oligomer (A) having a repeating unit with hole transport properties and also having a thienyl group which may have a substituent, and an initiator (B), wherein solubility of the composition is capable of being changed by applying heat, light, or both heat and light, and further relates to a hole transport material composition and an ink composition comprising the composition.

"Further, other embodiments of the present invention relate to an organic layer (I) formed by applying the composition capable of changing its solubility, the hole transport material composition, or the ink composition; a method for changing the solubility of the organic layer (I), the method comprising a step of applying heat, light, or both heat and light to the organic layer (I); and an organic layer (II) obtained by applying heat, light, or both heat and light to the organic layer (I).

"Furthermore, yet other embodiments of the present invention relate to an organic electronic element, an organic electroluminescent element and an organic photoelectric conversion element comprising the organic layer (II).

"Moreover, yet other embodiments of the present invention relate to a display element and an illumination device using the organic electroluminescent element.

"Examples of the above embodiments are described below.

"Examples of the aforementioned composition capable of changing its solubility include compositions in which the repeating unit with hole transport properties comprises at least one type of repeating unit selected from the group consisting of a repeating unit containing an aromatic amine structure and a repeating unit containing a carbazole structure; compositions in which the polymer or oligomer (A) has at least one type of structure selected from the group consisting of a structure represented by formula (Ia) shown below, and a structure represented by formula (Ib) shown below; compositions in which the polymer or oligomer (A) has the thienyl group at a terminal thereof; compositions in which the polymer or oligomer (A) has a branched structure and 3 or more terminals, and has a thienyl group at each of 3 or more of all of the terminals; compositions in which the polymer or oligomer (A) has at least one type of structure selected from the group consisting of a structure represented by formula (IIa), a structure represented by formula (IIb), a structure represented by formula (IIIa), and a structure represented by formula (IIIb), all of which are shown below; compositions in which the initiator (B) is an oxidizing agent; compositions in which the initiator (B) is an onium salt; compositions in which the weight-average molecular weight of the polymer or oligomer (A) is from 1,000 to 1,000,000; and compositions further comprising a solvent (C).

"Furthermore, examples of the aforementioned organic electronic element include elements comprising at least two electrodes, and the organic layer (II) positioned between the electrodes; examples of the aforementioned organic electroluminescent element include elements comprising an anode, the organic layer (II), a light-emitting layer and a cathode; and examples of the aforementioned organic photoelectric conversion element include elements comprising an anode, the organic layer (II), a photoelectric conversion layer and a cathode.

"This application is related to the subject matter disclosed in Japanese Application 2011-209610 filed on Sep. 26, 2011, the entire contents of which are incorporated herein by reference.

"Advantageous Effects of Invention

"Embodiments of the present invention can provide a composition, a hole transport material composition and an ink composition which enable multilayering of organic layers using a coating method. Further, other embodiments of the present invention can provide an organic layer that can be multilayered using a coating method, and a method for forming the organic layer. Furthermore, yet other embodiments of the present invention can provide an organic electronic element, an organic EL element and an organic photoelectric conversion element having an organic layer formed by a coating method. Moreover, yet other embodiments of the present invention can provide a display element and an illumination device which use an organic EL element having an organic layer formed by a coating method.

BRIEF DESCRIPTION OF THE DRAWINGS

"FIG. 1 is a graph illustrating the current-voltage characteristics of elements obtained in Example 5 and Comparative Example 5.

"FIG. 2 is a graph illustrating the change in luminance over time of elements obtained in Example 6 and Comparative Example 6."

For additional information on this patent application, see: Funyuu, Shigeaki; Asano, Naoki; Ishitsuka, Kenichi. Composition Capable of Changing Its Solubility, Hole Transport Material Composition, and Organic Electronic Element Using the Same. Filed September 26, 2012 and posted August 28, 2014. Patent URL: http://appft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&u=%2Fnetahtml%2FPTO%2Fsearch-adv.html&r=5904&p=119&f=G&l=50&d=PG01&S1=20140821.PD.&OS=PD/20140821&RS=PD/20140821

Keywords for this news article include: Emerging Technologies, Hitachi Chemical Company, Hitachi Chemical Company Ltd., Nanotechnology, Organic Electronic.

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