WO2004018539A1 - Dendritic polymer and electronic device element employing the polymer - Google Patents

Abstract

The invention provides a novel dendritic polymer serving as an organic semiconductor material which has high solubility in organic solvent; which is stable (i.e., is not prone to being affected by external inhibitors such as oxygen and water); and which exhibits isotropic, remarkably high carrier conductivity. The invention also provides electronic device elements requiring carrier conductivity and having remarkably high carrier conductivity through a simple production process.The dendritic polymer having a branching structure including a repeating unit having a branch portion, wherein the polymer has an aromatic amine moiety at an end thereof, and the repeating unit is formed of a phenylenevinylene moiety represented by formula (1): which is repeated once or a plurality of times.

Description

Description

Dendritic Polymer and Electronic Device Element Employing the Polymer

Technical Field

The present invention relates to a novel dendritic polymer dendrimer or hyperbranched polymer having carrier conductivity, and to an electronic device employing the dendritic polymer. The dendritic polymer of the present invention attains high carrier conduction at remarkably high efficiency, and thus finds utility particularly in devices requiring carrier conductivity; e.g., switching elements such as organic transistors (organic FETs, organic TFTs , etc.), solar cells, and organic EL devices.

Background Art

Electrically conductive organic polymers have become of scientific and technical interest since the late 1970s. The polymers, which are based on a comparatively new technique, exhibit electronic and magnetic characteristics of metal as well as physical and mechanical characteristics of conventional organic polymers . Known conductive organic polymers include poly (p-phenylene) s , pol (p- phenylenevinylene) s , polyanilines , polythiophenes , polypyrroles, polyazines, polyfurans, polycenophenes, poly (p- phenylene sulfide)s, mixtures thereof, blends thereof with another polymer, and copolymers of monomers of the above- described polymers . These conductive organic polymers are conjugated-system polymers which exhibit electrical conductivity through doping caused by reaction such as oxidation, reduction, or protonization .

In recent years, efforts have been made to fabricate, from these conductive organic polymers, light-emitting elements of organic electroluminescent devices (organic EL, OLED) and active elements of field-effect transistors (organic FET, organic TFT) . In one current practice, an expensive plasma CVD apparatus is used for forming an insulating layer or a semiconductor layer of an amorphous silicon TFT or polysilicon TFT, and an expensive sputtering apparatus is used for forming an electrode. In addition, film formation by CVD must be carried out at a temperature as high as 230 to 350°C, and maintenance operations such as cleaning must be carried out frequently, thereby reducing throughput. In contrast, apparatuses such as a coating apparatus and an ink-j et apparatus for fabricating organic FETs or similar devices are less expensive than the CVD apparatus and sputtering apparatus. In addition, film formation can be performed at lower temperature, and maintenance of the apparatuses is less cumbersome. Therefore, when display devices such as a liquid crystal display and an organic EL are fabricated from an organic FET, a remarkable cost reduction can be expected.

Typical organic EL devices include a transparent • substrate made of material such as glass, a transparent electrode, a hole-injecting layer, a hole-transporting layer, a light-emitting layer, an electron-transporting layer, and a metal electrode. Three separate layers; namely, the hole- transporting layer, the light-emitting layer, and the electron-transporting layer, may be formed into a single hole-transporting and light-emitting layer, or into a single electron-transporting and light-emitting layer. The specific features are disclosed by Japanese Patent Application Laid- Open (kokai) Nos. 7-126616, 8-18125, 10-92576, etc. However, problems such as service life still remain unsolved for organic EL devices, and studies for improvement are under way.

Typical organic TFTs include a transparent substrate made of material such as glass, a gate substrate, a gate insulating film, a source electrode, a drain electrode, and an organic semiconductor film. By modifying gate voltage, electric charge at the interface between the gate insulating layer and the organic semiconductor film is rendered excessive or deficient, whereby the drain current flowing between the source and drain electrodes via the organic semiconductor film is varied, to thereby perform switching. Japanese Patent Application Laid-Open (kokai) No. 63- 076378 discloses that an organic TFT is fabricated from polythiophene or a polythiophene derivative serving as the aforementioned organic semiconductor film. Fabrication of an organic TFT from pentacene is disclosed in Yen-Yi Lin, David J. Gundlach, Shelby F^;. Nelson, and Tomas N. Jackson, IEEE Transaction on Electron Device, Vol. 44, No. 8, p. 1,325 (1997) .

However, use of pentacene raises problems. For example, film formation must be performed through a vapor deposition process, and crystallinity must be elevated for enhancement of device characteristics. Another possible approach is use of a soluble pentacene derivative for enhancing processability . However, in this case, characteristics remain unsatisfactory. Application and development of an organic semiconductor formed of polythiophene, a polythiophene derivative, or a thiophene oligomer are under way, since the organic semiconductor has excellent formability; e.g., is readily formed into thin film through electrolytic polymerization, solution coating, or a similar method. However, in this case, characteristics remain unsatisfactory.

Meanwhile, in recent years, hyperbranched polymer materials in a broad sense such as dendrimers and hyperbranched polymers have become of interest. Characteristic features of dendrimers and hyperbranched polymers include amorphousness, solubility in organic solvent, and presence of a large number of branch ends to which a functional group can be introduced. L. L. Miller et al . describe in J. Am. Chem. Soc. 1997, 119, 1,005 that a polyamide dendrimer having, at branch ends, 1,4,5,8- naphthalenetetracarboxy-diimido residues to which a quaternary pyridinium salt is bonded has isotropic electron conductivity (also referred to as "transportability") , and that the conductivity is provided by interaction of π electrons generated by spatial overlapping of the branch end moieties. Japanese Patent Application Laid-Open (kokai) No. 2000-336171 discloses a dendrimer containing a dendron having hole-conducting moieties at branch ends and no π-electron- conjugated system including a carbonyl group and a benzene ring, as well as a photoelectric conversion device employing the dendrimer. Application of a dendrimer having a phenylenevinylene moiety exhibiting high fluorescent yield to light-emitting elements has also been investigated. Publications (e.g., Mounir Halim, Jonathan N. G. Pillow, Ifor D. W. Samuel, Paul L. Burn, Adv. Mater. 1999, 11, No. 5, 373; John M. Lupton, Ifor D. W. Samuel, Richard Beavington, Paul L. Burn, Heinz

Bassler, Adv. Mater. 2001, 13, No. 4, 258; WO 9921935; and WO 0159030) disclose introduction of phenylenevinylene-based dendrimers having end t-butyl groups in order to enhance solubility of the dendrimers . These publications disclose that solubility and processability can be imparted to the dendrimers through introduction of appropriate end substituents , but do not refer to introduction of end carrier-conductive functional groups. Org. Lett. 2001, Vol. 3, No. 17^", 2645 (Jose L. Segura, Rafael Gomez, Nazario Martin, and Dirk M. Guldi) discloses a phenylenevinylene-based dendrimer having end dibutylamino groups and exhibiting enhanced solubility by virtue of introduction of a long-chain alkyl group .

Meanwhile, in addition to polymers, a low-molecular compound having a phenylenevinylene moiety terminated with an arylamine moiety is employed in organic EL elements (disclosed in Japanese Patent Application Laid-Open (kokai)

Nos. 03-296595 and 06-271848 and Japanese Patent No. 3093796B, etc . ) .

However, in function elements employing semiconductive or conductive polymers such as conjugated polymers, high charge conductivity of the aforementioned organic semiconductor appears along a molecular chain orientation, and varies depending on the molecular structure. In addition, such conjugated-system polymers tend to be affected by oxygen and water, readily leading to deterioration. Therefore, . conventional organic FET elements have drawbacks; i.e., poor stability and electric characteristics and a short service life. In addition, semiconductive or conductive polymers such as conjugated polymers are generally rigid and cannot be dissolved or melted. Most of them cannot be dissolved in solvent. To this end, there are used derivatives of such polymers into which side chains are introduced, and oligomers thereof (see Japanese Patent Application Laid-Open (kokai) Nos. 4-133351, 63-076378, 5-110069, etc.). However, problems also arise. For example, when side chains are introduced, glass transition temperature appears, and thermochromism attributed to micro-Brownian motion is induced, resulting in temperature-dependent variation in characteristics. Use of oligomers may deteriorate reliability. Even when the side- chain-introduced polymer is used, satisfactory mobility cannot be attained. Thus, polymerization degree must be increased, or orientation degree of the conductive organic compound must be enhanced by use of orientation film as described in, for example, Japanese Patent Application Laid- Open (kokai) No. 7-206599.

In the case in which no alkyl group has been introduced to ends of the aforementioned dendrimers having a phenylenevinylene moiety, solutions of such dendrimers are difficult to prepare, because of poor solubility of the dendrimers in organic solvent. Another problem is difficulty in synthesis or purification of higher generation dendrimers. Meanwhile, when long-chain alkyl groups are introduced to ends of the dendrimers, there arises a problem similar to that arising in the aforementioned polymer derivatives having side chains; i.e., the resultant polymers come to have a glass transition temperature, causing a problem of physical properties having a temperature-dependency. When a low- molecular compound is used, the problem of physical properties having a temperature-dependency arises because it^'s glass transition temperature is lower than that of polymers . Furthermore, when these polymers or compounds are employed as organic semiconductor materials, carrier mobility attains a low level which is not suitable for practical use.

Disclosure of the Invention The present invention has been conceived in order to solve the aforementioned problems arising in conventional techniques. Thus, an object of the present invention is to provide a novel dendritic polymer serving as an organic semiconductor material which has high solubility in organic solvent; which is stable (i.e., is not prone to being affected by external inhibitors such as oxygen and water) ; and which exhibits isotropic, remarkably high carrier conductivity. Another object of the invention is to provide an electronic device employing the dendritic polymer. ^■ The present inventors have carried out extensive studies in order to solve the aforementioned problems , and have found that through introduction of an aromatic amine moiety to an end of a dendritic polymer formed of phenylenevinylene serving as a repeating unit of a dendritic structure, solubility of the polymer in organic solvent increases; hole-conductivity is imparted to the ends of the polymer; and the phenylenevinylene skeleton included inside the polymer molecule is protected by the aromatic amine skeleton serving as a molecular surface, enabling provision of an organic semiconductor material which is stable in air and exhibits isotropic, remarkably high carrier conductivity. The present invention has been accomplished on the basis of this finding. Accordingly, a first mode of the present invention to solve the aforementioned problems is drawn to a dendritic polymer having a branching structure including a repeating unit having a branch portion, characterized in that the polymer has an aromatic amine moiety at an end thereof, and that the repeating unit is formed of a phenylenevinylene moiety represented by formula (1) :

which is repeated once or a plurality of times .

A second mode of the present invention is directed to a dendritic polymer mentioned in relation to the first mode, wherein the aromatic amine moiety includes at least one species represented by formula (2) :

wherein Ar^x represents a single bond or a divalent aromatic group, and each of Ari and Ar₂ represents a monovalent aromatic group .

A third mode of the present invention is directed to a dendritic polymer mentioned in relation to the second mode, wherein the divalent aromatic group included in the aromatic amine moiety is a phenylene group or a naphthylene group, and the monovalent aromatic group is independently selected from the groups represented by formula (3) :

wherein each of Ri and R₂ is independently selected from among a hydrogen atom, a C1-C4 alkyl group, and a C1-C4 alkoxy group.

A fourth mode of the present invention is directed to a dendritic polymer mentioned in relation to any one of the first to third modes, wherein the repeating unit serving as a starting point of the branching structure is further bonded to a center moiety serving as a core.

A fifth mode of the present invention is directed to a dendritic polymer mentioned in relation to the fourth mode, wherein the core is selected from- among the moieties represented by formula (4) .

A sixth mode of the present invention is directed to a dendritic polymer mentioned in relation to any one of the first to fifth modes, which is a dendrimer.

A seventh mode of the present invention is directed to a dendritic polymer mentioned in relation to the sixth mode, wherein the dendrimer is of the second generation or of a higher generation.

A eighth mode of the present invention is directed to an electronic deyice element characterized by employing a dendritic polymer as recited in relation to any one of the first to seventh modes .

A ninth mode ^"of the present invention is directed to an electronic device element mentioned in relation to the eighth mode, which is a charge-transporting device element. A tenth mode of the present invention is directed to an electronic device element mentioned in relation to the eighth mode, which is a switching transistor element.

A eleventh mode of the present invention is directed to an electronic device element mentioned in relation to the eighth mode, which is a light-emitting device element.

A twelfth mode of the present invention is directed to an electronic device element mentioned in relation to the eighth mode, which is a photoelectric conversion device element.

Brief Description of the Drawings

FIG. 1 schematically shows a cross-section of an organic thin film switching transistor according to Example 1 of the present invention. FIG. 2 is a schematic view showing a light-emitting element according to Example 2 of the present invention. FIG. 3 is a schematic view showing an organic solar cell element according to Example 3 of the present invention.

FIG. 4 is a schematic view showing an organic solar cell element according to Comparative Example 3.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention will next be described in detail. In the present invention, the term "dendritic polymer" conceptually refers to a polymer species which includes generally defined dendrimers and hyperbranched polymers . Thus, the dendritic polymer encompasses any compounds having a structure in which the aforementioned structural repeating unit represented by formula (1) (i.e., dendritic structural unit) is repeated once or more (i.e., the dendritic polymer contains two or more repeating units) . Notably, a- structure including the aforementioned structural repeating unit represented by formula (1) ; i.e., a structure including the repeating units which have been repeated so as to form a divergent structure, is referred to as a "branching ■ structure . " Dendrimer and hyperbranched polymers are generally represented by the following structural formulas . As shown in the formulas , the dendrimer has a regularly repeated branching structure, while the hyperbranched polymer has an irregularly repeated branching structure. These polymers may have a structure in which the polymer chains are dendritically branched from one focal point, or a structure in which polymer chains are radiated from a plurality of focal points linked to a polyfunctional molecule serving as a core. Although other definitions of these species may also be acceptable, in any case, the dendritic^' polymer of the present invention encompasses dendritic polymers having a regularly repeated branching structure and those having an irregularly repeated branching structure, wherein these two types of dendritic polymers may have a dendritically branching structure or a radially branching structure.

According to a generally accepted definition, when a dendritic structural unit extends from its preceding dendritic structural unit as an exact copy thereof, the extension of the unit is referred to as the subsequent "generation." It should be noted that the definition of a "dendritic polymer" according to the present invention covers those having a structure in which each of the dendritic structural units which are similar to one another with the same basic structure are repeated at least once also fall within the scope of the present invention.

The concepts in relation to dendritic polymer, dendrimer, hyperbranched polymer, etc. are described in, for example, Masaaki KAKIMOTO, Chemistry, Vol. 50, p. 608 (1995) and Kobunshi (High Polymers , Japan) , Vol. 47, p. 804 (1998), and these publications can be referred to and are incorporated herein by reference. However, the descriptions in these publications should not -be construed as limiting the present invention thereto. Dendrimer Hyperbranched polymer

molecule)

The dendritic polymer of the present invention is structurally characterized in that the dendritic structural unit is formed of a phenylenevinylene moiety represented by the aforementioned formula (1) ; a dendritic structural unit of single species is bonded to each bonding hand of the benzene ring serving as a branching portion, the dendritic structural unit being repeated once or a plurality of times; and an end of the dendritic polymer is formed of an aromatic amine moiety. As used herein, the "structure in which the dendritic structural unit is repeated once" refers to a unit represented by a parenthesized structure in the following formula .

The unit is referred to as a "Ist-generation dendron." Accordingly, when aromatic amine moieties serving as end moieties are bonded to bonding hands of branch portions of the lst-generation dendron, or when a bonding hand on the opposite side is also connected to a core, a lst-generation dendritic polymer is produced. When a repeating unit serving as the focal point of the dendron (i.e., a vinyl group) is replaced by another moiety, the structure is represented by the following formula:

wherein Y represents a monovalent substituent such as a hydrogen atom, a halogen atom, or an aldehyde group. In the present invention, the structure is also referred to as a "lst-generation dendron." A similar structure in which dendritic units having the same structure are successively linked to the bonding hands of the branch portions of a lst-generation dendron is referred to as a "2nd-generation dendron. In a similar manner, an nth-generation dendron is created. Such dendrons having at an end an aromatic amine moiety and dendrons to which a desired substituent or substituents are bonded to the ends' or the focal point thereof are referred to as "dendrimers or hyperbranched polymers of dendritically branching structure." When a plurality of dendritically branched dendrimers or hyperbranched polymers, which are identical to or different from one another, are bonded as subunits to a multivalent core, the formed dendritic polymer is called "dendrimer or hyperbranched polymer of radially branching structure." In the present invention, a dendritic polymer in which nth-generation dendrons are linked to an m-valent (m is an integer of 2 or more) core is defined as an nth-generation, m-branched dendrimer. Notably, a dendritic polymer in which nth-generation dendrons are linked to an m-valent (m is an integer of 2 or more) benzene core is defined not only as an nth-generation, m-branched dendrimer, but also as an (n + 1)- generation dendrimer. Examples of dendrimers in which lst- generation dendrons are linked to a core include those represented by the following formula.

lst-generation core: tetravalent core : trivalen dendron moiety anthracene moiety benzene moiety

lst-generation , 4-branched dendrimer lst-generation , 3-branched dendrimer , or 2nd-generation dendrimer

Specifically , a dendritic polymer in which lst- generation dendrons are linked to a tetravalent anthracene core is defined as a lst-generation , 4-branched dendrimer , and a dendritic polymer in which similar lst-generation dendrons are linked to a trivalent benzene core is defined as a lst-generation , 3-branched dendrimer , or a 2nd-generation dendrimer .

The dendritic polymer of the present invention is characterized in that the polymer has an aromatic amine moiety at an end thereof and a dendritic repeating unit formed of phenylenevinylene. Thus, solubility of the polymer in organic solvent increases; hole-conductivity is imparted to ends of the polymer; and the phenylenevinylene skeleton included inside the polymer molecule is protected by the aromatic amine skeleton serving as a molecular surface. Therefore, an organic semiconductor material which is stable in air, and which exhibits isotropic, remarkably high carrier conductivity can be provided. As mentioned above, the dendritic polymer of the present invention having a large number of branches provides a large number of branch ends . Through employment of the ends, the number of carriers can be increased. Furthermore, since the dendritic polymer provides a large number of paths for carrier conduction, carrier mobility can be effectively enhanced without orienting molecules and increasing crystallinity , which have been performed for conventional conjugated polymers and low- molecule organic semiconductor materials. Since non-planar tertiary aromatic amine moieties are introduced to ends of a polymer, the polymer becomes more amorphous than the polymer having only phenylenevinylene moieties , can form thin film without failure,^" and is in a stable form without crystallizing .

No particular limitation is imposed on the branching structure of the dendritic polymer of the present invention, so long as the polymer has a dendritic structure, and the dendrimer does not necessarily have a completely ordered branching structure. However, when the dendritic polymer of the present invention is a dendrimer, the dendritic polymer is preferably of the second generation or of a higher generation, in order to attain high carrier conductivity. The term "generation of dendritic polymer" refers to the expression described above. The number of generations of dendritic polymers including those having a large or long center moiety is generally 1 to 10. However, the number is preferably 2 to 8 , more preferably 2 to 7 , most preferably 2 to 5, from the viewpoints of carrier conductivity, spatial density of end moieties, and easiness of synthesis. No particular limitation is imposed on the structure of the dendritic polymer of the present invention, so long as the polymer has a dendritic repeating unit formed of a phenylenevinylene moiety represented by the aforementioned formula (1) and has an aromatic amine moiety at an end thereof.

As used herein, the term "aromatic amine moiety" refers to a moiety having an aromatic group instead of a hydrogen atom of amino group or a moiety containing a divalent aromatic group at the bonding hand of the moiety. The aromatic amine moiety may have a hydrocarbon group in the side connected to a dendritic repeating unit. In this case, for example, the aromatic amine moiety is linked to the dendritic repeating moiety via an organic group containing a divalent aromatic group. Notably, two or more such aromatic amine moieties may be present on one end of the polymer. In this case, the aromatic amine moiety may be bonded directly to the dendritic repeating unit or may be bonded indirectly to the repeating unit' via another substituent, preferably an aromatic group.

Preferably, the aromatic amine moiety includes a moiety represented by the aforementioned formula (2) . In formula (2) , Ar^x represents a single bond or a divalent aromatic group, and each of Ari and Ar₂ represents a monovalent aromatic group. Examples of the monovalent or divalent aromatic group include substituted or unsubstituted aromatic hydrocarbon groups, aromatic heterocyclic groups, condensed polycyclic aromatic hydrocarbon groups, condensed heterocyclic aromatic groups, and monovalent or divalent aromatic groups formed through ring-condensation of these groups. The monovalent or divalent aromatic group, for example, preferably has 50 carbon atoms or less, and may contain therein a heteroatom such as 0, N, S, P, B, or Si, or may have a substituent such as a alkyl group, alkoxy group, hydroxy group, a carboxyl group, an acyl group, nitro group, cyano group or a halogen (e.g., fluorine, chlorine, bromine, or iodine) atom, in addition to unsubstituted structure. Specific examples include, but are not limited to, benzene, naphthalene, anthracene, naphthacene, pentacene, hexacene , ' phenanthrene, phenalene, pyrene , chrysene, benzoanthracene , perylene, triphenylene, coronene, pentaphene, picene, naphthoanthracene, trinaphthylene, ovalene, biphenyl , terphenyl , quaterphenyl , quinquphenyl , sexiphenyl, septiphenyl, phenylanthracene, phenylnaphthalene , diphenylanthracene, biphenylene, binaphthalenyl , fluorene, acenaphthylene, dibenzoperylene , indene, pentalene, acephenanthrylene , indacene , aceanthrylene, tetraphenylene , fluoranthene, azulene, cyclooctatetraene, octarene, rubrene , thiophene, furan, pyrrole, silole, oxazole, thiazole, imidazole, pyrazole, furazane, oxadiazole, thiadiazole, pyridine, thiopyran, pyrimidine, pyrazine, pyridazine, triazine, benzothiophene, benzofuran, benzosilole, indole, benzoxazole, benzothiazole, benzimidazole , quinoline, thiochromene, quinazoline, carbazole, dibenzosilole, dibenzofuran, dibenzothiophene , phenanthroline, acridine, benzoquinoline, phenanthridine, phenazine, phenothiazine , thianthrene, phenoxathiine , phenoxazine, bithiophene, terthiophene, quaterthiophene, bifuran, terfuran, quaterfuran, bipyrrole, terpyrrole, quaterpyrrole, bisilole, tersilole, quatersilole, bipyridine, terpyridine, quaterpyridine , phenylpyrrole , phenylpyridine , phenylfuran, phenylthiophene , and phenyloxadiazole . These groups may serve as monovalent aromatic groups or divalent aromatic groups and may be substituted or unsubstituted. In the aforementioned formula (2) , Ar^x is preferably a phenylene group or a naphthylene group, and each of Ari and Ar₂ in the aforementioned formula (3) , which may be identical to or different from each other, is independently selected from the groups represented by formula (3) . In formula (3) , each of Ri and R₂ is independently selected from among a hydrogen atom, a C1-C4 alkyl group, and a C1-C4 alkoxy group. When an alkyl group is introduced to an end, the resultant polymers come to have a glass transition temperature, as mentioned above. Therefore, each of Ri and R₂ is more preferably a hydrogen atom, a methyl group, or a methoxy group, with a hydrogen atom being most preferred. In the present invention, the term "end moieties" of the dendritic polymer is used to refer generally to a surface structure in which arbitrary numbers of ends of a dendritically or radially branching structure are bonded thereto to thereby form a molecular surface of the dendritic polymer (i.e., a partial structure excluding the dendritic or radial branches (repeating units)) . However, an aromatic amine moiety including a benzene ring serving as an end point of a repeating unit of the outermost branching structure also falls within the above definition. No particular limitation is imposed on the structure of the end moieties of the dendritic polymer of the present invention, so long as the moieties have at least an end aromatic amine moiety. However, the end moieties having a structure represented by the aforementioned formula (2) are preferably used in order to attain high carrier conductivity. Specific examples of end moieties include, but are not limited to, those represented by the following formula (5) . No particular limitation is imposed on the mode of bonding between these end moieties and dendritic structural units, and examples thereof include the aforementioned aromatic amine moiety including a benzene ring serving as an end point of a repeating unit of the outermost branching structure; bonding via a vinyl group; carbon-carbon bond; carbon- nitrogen bond; amido bond; ether bond; ester bond; and urea bond.

(5)

Ri to R = a hydrogen atom , a C1-C4 alkyl , or a C1-C4 alkoxy group

In the dendritic polymer of the present invention, a starting point of the repeating unit serving as a starting point of the branching structure may be bonded to a center moiety serving as a core. Briefly, the core can be linked to arbitrary numbers of starting points of a dendritically branching structure, and refers to a partial structure other than a branching structure. In other word, the core serves as the center of dendritic polymer molecules , and refers to a portion of a dendritic polymer other than repeating units . Specific examples of the core include C1-C20 alkylene groups, C6-C20 arylene groups, and groups in which these alkylene groups and arylene groups are combined. In addition to unsubstituted alkylene groups, the alkylene groups may contain therein a heteroatom such as 0, NH, N(CH₃) , S , or S0₂, or may have a substituent such as a hydroxyl group, a carboxyl group, an acyl group or a halogen (e.g., fluorine, chlorine, bromine, or iodine) atom. The core may be a multivalent group of any of the above described groups from which a hydrogen atom bonded to a carbon atom is removed; a multivalent heterocyclic group; a group in which the heterocyclic group and any of the above hydrocarbon group are bonded together; a porphyrin; or a porphyrin complex. In addition to the examples of cores having a valence of at least two, a monovalent core formed by bonding hydrogen atom(s) to a multivalent core may also be used. Particularly, moieties represented by the aforementioned formula (4) are preferably employed as a core.

Notably, dendritic polymers having no core(s) also fall within the scope of the present invention. In this case, the starting point of the branching structure of the dendritic polymer of the present invention is determined in accordance with the starting material for producing repeating units forming the branching structure. At starting point of the branching structure, active group of starting material may be substituted by hydrogen.

No particular limitation is imposed on the method for synthesizing the dendritic polymer of the present invention, and the polymer can be formed (i.e., synthesized) from a monomer (or a precursor thereof) containing an aromatic amine moiety and a monomer containing a structure which serves as a precursor for a phenylenevinylene moiety. As used herein, the term "monomer" refers to a class of low-molecular-weight compounds having, as a partial structure, an aromatic amine skeleton or a skeleton serving as a precursor for a phenylenevinylene moiety, the compounds including derivatives thereof to which mutually reactive substituents for forming a phenylenevinylene moiety are introduced, as well as precursors thereof. No particular limitation is imposed on the synthesis method for forming a dendritic polymer structure from a mononer, and methods which may be employed include the "divergent method" in which branches are successively extended from a focal point; the "convergent method" in which branches are extended from branch ends and the thus-connected units are finally bonded to a focal point; and polycondensation of a polyfunctional monomer of AB₂ type (A and B are mutually reactive functional groups) . Among these methods, the "convergent method" is preferred for effectively synthesizing a high-purity dendritic polymer having no defects, from the viewpoint of no requirement for excessive amounts of starting materials and easiness of purification of products . Examples of methods for forming a phenylenevinylene skeleton include those disclosed in publications (see, e.g., S. K. Deb et al . ; J. Am. Chem. Soc.

1997, 119, 9079, J. N. G. Pillow et al . ; Macromolecules 1999, Vol. 32, No. 19, 5985, H. Meier et al . ; Angew. Chem. Int. Ed.

1998, 37, No. 5, 643, M. Hailm et al . ; Adv. Mater. 1999, 11, No. 5, 371, H. Meier et al . ; Chem. Eur . J. 2000, 6, No. 13, 2462, J. M. Lupton et al . ; Adv. Mater. 2001, 13, No. 4, 258, J. L. Segura et al . ; Org. Lett. 2001, Vol. 3, 17, 2645, or E. D. Barra et al . ; J. Org. Chem. 2001, 66, 5664). The dendritic polymer of the present invention can be produced through a method disclosed in the above reference.

For example, a dendritic polymer containing tertiary aromatic amine moieties at the ends thereof and having a structural repeating unit represented by the aforementioned formula (1) can be produced through the "convergent method" including reaction steps represented by scheme (6) :

Reaction

wherein n is an integer of 1 to 5 , each of Ar_x and Ar₂ represents a monovalent aromatic group, and Ar^x represents a single bond or a divalent aromatic group.

The reaction steps represented by scheme (6) include reaction step 1 in which vinyl compound (a) having an aromatic amine moiety W for forming end moieties is reacted with compound (b) , to thereby form compound (c) ; reaction step 2 in which the aldehyde group of the formed compound (c) is converted to a vinyl group, to thereby form compound (d) ; and reaction step 3 in which the product (d) is reacted with the compound (b) , to thereby form a dendron (e) of a subsequent generation. In addition, when the dendron is bonded to a benzene ring core, there is carried out reaction step 4 in which the compound (e) is reacted with compound (f) having substituents for forming vinyl skeletons through reaction with aldehyde groups, to thereby form compound (g) .

Among the above mentioned compounds, compound (c) and compound (d) can be called a lst-generation dendrimer or dendron, whereas compound (e) can be called a 2nd-generation dendrimer or dendron. For the purpose of simple description, only denderimers of the number of generations 1 and 2 are shown in the aforementioned reaction steps 1 to 3 in scheme. (6) . However, dendrimers of further generations can be produced by repeating reaction step 2 and 3. The compound (g) can be defined as a 3rd-generation dendrimer or a 2nd-generation, 3-branched dendrimer. In the above scheme, 2nd-generation dendrimers (e) are bonded to the compound (f) . However, dendrimers of any generation can be bonded to a center structure molecule according to a similar reaction step.

The reaction for converting the compound (c) to the compound (e) can also be performed through reaction step 5 shown in the following scheme (7) . Specifically, the compound (c) is reacted with a branch-source compound (h) , followed by deprotection of the acetal group for forming the aldehyde group, to thereby produce the compound (e) . Through employment of a similar reaction, the compound (c) can be produced from an aromatic amine compound similar to the compound (a) and having, instead of the vinyl group, an aldehyde group. Through repetition of reaction step 5, a dendrimer of higher generation can be produced.

In reaction step 1 or 3 , reaction of compound (a) or (d) with compound (b) can be performed through the Heck reaction (see, for example, R. F. Heck et al . , J. Org. Chem. 1972, 37, 2320; or T. Mizoroki et al . , Bull. Chem. Soc. Jpn . 1971, 44, 581) . A variety of combinations of a palladium catalyst and a base catalyst can be employed as Heck reaction catalysts . Examples of the palladium catalyst include tetrakis (triphenylphosphine) palladium, palladium acetate, palladium chloride, palladium black, bis (triphenylphosphine) palladium dichloride, bis (tri-o- tolylphosphine) palladium dichloride , bis (dibenzylideneacetone) palladium, bis (tricyclohexylphosphine) palladium dichloride , bis (triphenylphosphine) palladium diacetate, [1,2- bis (diphenylphosphino) butane] palladium dichloride, and [1,2- bis (diphenylphosphino) ethane] palladium dichloride. In addition, combination of a ligand compound with these palladium catalysts may be effective. Examples of ligand compounds include triphenylphosphine, 1,1'- bis (diphenylphosphino) ferrocene , 1,2- bis (diphenylphosphino) ethane , 1,3- bis (diphenylphosphino) propane , 1,4- bis (diphenylphosphino) butane , sodium diphenylphosphinobenzene-3-sulfonate , tricyclohexylphosphine , tri (2-furyl) phosphine , tris (2 , 6-dimethoxyphenyl) phosphine , tris (4-methoxyphenyl) phosphine, tris (4-methylphenyl) phosphine, tris (3-methylphenyl) phosphine, and tris (2- methylphenyl) phosphine . Instead of palladium catalysts, a nickel catalyst, [1 , 1 ' -bis (diphenylphosphino) ferrocene] nickel dichloride may also be used. Examples of the base catalyst include potassium acetate, sodium acetate, sodium carbonate, sodium alkoxides such as sodium ethoxide , t-butoxypotassium, barium hydroxide, triethylamine, potassium phosphate, sodium hydroxide, and potassium carbonate. Examples of preferably employed reaction solvents include dimethylformamide, dimethyl sulfoxide, dioxane, benzene, toluene, tetrahydrofuran, dimethoxyethane , dimethylacetamide, xylene, and acetonitrile . The reaction temperature is preferably 25 to 150°C, and the reaction time is preferably 30 minutes to 24 hours, more preferably for one hour to 12 hours. In reaction step 2, transformation of the aldehyde group of compound (c) into a vinyl group for forming compound (d) can be performed through the Wittig reaction. The Wittig reaction is known to be a reaction for effectively producing an alkene through reaction of an aldehdye or a ketone with a phospho-ylide (see, for example, Org. React. 1965, 14, 270) . In the scheme (6) , the reaction for transforming the aldehyde group to a vinyl group through reaction with a phospho-ylide can be performed by use of a phospho-ylide which has been prepared by reacting a methyl halide with triphenylphosphine, to thereby form a phosphonium salt, and deprotonating the phosphonium salt with a base such as alkyllithium or alkoxide, Solvents such as tetrahydrofuran, diethyl ether, and dimethyl sulfoxide are suitably employed. Since phospho-ylide is highly reactive with water, the solvent to be employed is preferably dehydrated sufficiently.

In reaction step 4, the reaction of compound (e) with compound (f) for producing compound (g) can be performed through the Horner-Wadsworth-Emmons reaction (see, for example, L. Horner et al . , Chem. Ber . 1962, 95, 581; or W. S. Wadsworth et al . , J. Am. Chem. Soc. 1961, 83, 1733). Bases such as sodium hydride and alkoxides are suitable employed as catalysts. Examples of reaction solvents include methanol, ethanol, benzene, tetrahydrofuran, dimethyl sulfoxide, diethyl ether, and dimethoxyethane.

In reaction step 5, the reaction of compound (c) with compound (h) for producing compound (e) can be performed through the Horner-Wadsworth-Emmons reaction (see, for example, L. Horner et al . , Chem. Ber. 1962, 95, 581; W. S. Wadsworth et al . , J. Am. Chem. Soc. 1961,.83, 1733; E. D. Barra et al . , J. Org. Chem. 2001, 66, 5664; or H. Meier et al . , Chem. Eur . J. 2000, 6, No. 13, 2462). Bases such as sodium hydride and alkoxides are suitable employed as catalysts. Examples of reaction solvents include methanol, ethanol, benzene, tetrahydrofuran, dimethyl sulfoxide, diethyl ether, and. dimethoxyethane . No particular limitation is imposed on the acid employed for deprotection of an acetal group, and acids such as inorganic acids, organic acids, and ion-exchange resins can be employed.

No particular limitation is imposed on the method for synthesizing compound (a) . The compound (a) can readily be synthesized by, for example, synthesizing an aromatic amine compound having an aldehyde substituent and transforming the aldehyde group to a vinyl group. In this case, the transformation to a vinyl group can be performed through the Wittig reaction (see, for example, Org. React. 1965, 14, 270) . The aromatic amine compound having an aldehyde substituent can be synthesized through formylation of an aromatic amine compound with a Vilsmeier reagent. Another possible method include condensing a diarylamine compound and an aryl halide having an aldehyde group protected as its acetal form through Ullmann condensation (see Chem. Lett., 1145, (1989), Synth. Commu . 383, (1987) , etc.) or through the Toso method (disclosed in Japanese Patent Application Laid-Open (kokai) No. 10-310561) and deprotecting the acetal group.

The compound yielded in each reaction step is purified, whereby a high-purity dendritic polymer having few defects is synthesized. No particular limitation is imposed on the purification method, and purification methods such as recrystallization, crystallization, sublimation, and purification by means of a column may be employed.

According to the aforementioned production method, a variety of dendritic polymers having aromatic amine moieties at the ends thereof can be produced by selecting species of compound (a) for forming branch ends and compound (f) for forming a center moiety. Since the production method is based on the "convergent method," in which a purification process in each reaction step is readily performed, a high- purity dendrimer (a type of dendritic polymer) having few defects can be produced.

The dendritic polymer of the present invention, having carrier conductivity, is envisaged to be used in a variety of fields . The dendritic polymer of the present invention can provide hole-transporting (p-type) , electron-transporting (n- type) , and a variety of functional electronic materials, by selecting the molecular structure thereof or by doping or a similar process. Thus, such electronic materials can be used in switching elements such as an organic transistor element, an organic FET element, or an organic TFT element; solar cells; photoelectric conversion elements; capacitors; light- emitting elements; electrochromic elements; polymer secondary batteries, etc. The structure of such elements suited for each purpose will next be described in detail.

The organic transistor element includes a semiconductor layer formed of an organic layer having hole transportability and/or electron transportability; a gate electrode formed of a conductive layer; and an insulating layer inserted between the semiconductor layer and the conductive layer. To the assembly, a source electrode and a drain electrode are attached, to thereby produce the transistor element. The above organic layer is formed from the dendritic polymer of the present invention.

The light-emitting device includes a pair of plate-like electrodes disposed in parallel, and an organic layer containing the material of the present invention between the two electrodes. Generally, the device is formed of a transparent electrode (e.g., ITO), a hole-injecting layer, a hole-transporting layer, a light-emitting layer, an electron- transporting layer, and a metal electrode. Carrier- transporting function and light-emitting function may be combined in a single structure. The above organic layer is formed from the dendritic polymer of the present invention. The photoelectric conversion element or a solar cell generally contains an organic layer sandwiched by plate-like electrodes disposed in parallel. The organic layer may be formed on a comb-like electrode. No particular limitation is imposed on the location of the organic layer. No particular limitation is imposed on the material of electrodes. However, when plate-like electrodes disposed in parallel are employed, at least one electrode is preferably formed of a transparent electrode such as an ITO electrode or a fluorine-doped tin oxide electrode. The organic layer is formed of two sublayers; i.e., a layer formed of the dendritic polymer of the present invention having p-type semiconductivity or hole- transportability, and a layer formed of the dendritic polymer of the present invention having n-type semiconductivity or electron-transportability. Furthermore, when a photosensitizing dye group is introduced to the dendritic polymer contained in one of the two layers, or a polymer or hyperbranched polymer in a broad sense including a specific photosensitizing dye molecule moiety is provided between the two layers, element performance is further enhanced, and high-efficiency power generation can be attained by use of, for example, a solar cell of such a structure. Herein, the photosensitizing dye molecule moiety has a HOMO (highest occupied molecular orbital) level lower than the HOMO level of hole-transporting dendritic polymer and has a LUMO (lowest unoccupied molecular orbital) level higher than the LUMO level of electron-transporting dendritic polymer.

When an ion-conductive polymer or a dendritic polymer which satisfies conditions of photoexcitation of the hole- transporting layer or the electron-transporting layer is provided between the hole-transporting layer and the electron-transporting layer, an electrochemical photoelectric conversion element can be formed. A photosensitizing dye group may be introduced to any one of the layers in accordance with needs .

The capacitor includes a hole-transporting layer and an electron-transporting layer, one serving as a conductive layer and the other serving as a semiconductor layer, and an insulating layer inserted between the conductive layer and the semiconductor layer. Alternatively, both the hole- transporting layer and electron-transporting layer are formed of conductive layers, and an ion-conductive layer is inserted between the two conductive layers. Alternatively, the hole- transporting layer is formed of a p-type semiconductor layer and the electron-transporting layer is formed of an n-type semiconductor layer, and the layers may be stacked, to thereby form a continuously stacked multi-layer. The above semiconductor layer is formed from the dendritic polymer of the present invention.

The electrochromic element includes a hole-transporting layer formed of a polymer layer which can be doped with a p- type dopant and discolors by redox reaction; an electron- transporting layer formed of a polymer layer which can be doped with an n-type dopant and discolors by redox reaction; and a layer containing a supporting electrolyte and disposed between the two layers . The element structure may be used in a polymer secondary battery, whereby a secondary battery of high capacitance and low internal resistance is provided.

As described above, by use of the aforementioned materials according to the present invention, devices requiring carrier conductivity and having remarkably high carrier conductivity can be produced through a simple production process.

Examples The present invention will next be described with reference to the below-described Examples in relation to the dendritic polymer and the function element using the same, which should not be construed as limiting the invention thereto. Apparatus, etc. employed in measurement are as follows.

NMR: FT-NMR, model JNM-AL400 (400 MHz, product of JEOL) , solvent: CDC1₃, room temperature, chemical shift reference (0 ppm) : tetramethylsilane (TMS) .

GPC: HLC-8220 GPC , product of Tosoh Corporation; Column: TSK gel Super HZM-M; Eluent: THF ; Detector: UV 254 nm; Measures (weight average molecular weight (Mw) , number average molecular weight (Mn) , and molecular weight distribution (Mw/Mn) ) are reduced to polystyrene as a standard.

[Synthesis Example 1] Synthesis of 3rd-generation dendritic polymer <Synthesis Example 1-1> Synthesis of diphenylaminostyrene a vinyl compound (a) having an aromatic amine moiety serving as an end, represented by the following formula

In a nitrogen atmosphere, dehydrated tetrahydrofuran (160 mL) was added to a mixture of methyltriphenylphosphonium bromide (42.9 g) and t-butoxypotassium (13.5 g) , while the mixture was stirred at room temperature . The resultant mixture was allowed to react for two hours at room temperature. Subsequently, diphenylaminobenzaldehyde (10.9 g) dissolved in dehydrated tetrahydrofuran (120 mL) was added dropwise thereto, and the mixture was allowed to react for two hours at room temperature . The reaction was terminated through addition of acetone (10 mL) to the mixture. The precipitates were removed through filtration and washed with methylene chloride. The wash liquid and the filtrate were combined, and the solvent was distilled off under reduced pressure, to thereby yield a crude product. . The crude product was isolated and purified through column chromatography (packing material: Silicagel 60 (product of Merck) , eluent: methylene chloride/n-hexane) , to thereby yield 10.0 g of the target product (a yellow solid, yield: 92%) . The structure of the obtained product was confirmed through ¹H-NMR spectroscopy. The measurement data are shown below.

¹H NMR (CDC1₃) 57.29-7.22 (m, benzene ring, 6H) , 57.08 (d, J=8.4Hz, benzene ring,4H), 57.03-6.98 (m, benzene ring, 4H) , 56.65 (dd, J=18Hz, 11Hz, vinyl, 1H) , 55.63 (d, J=18Hz, vinyl, 1H) , 55.14 (d, J=llHz, vinyl, 1H)

<Synthesis Example l-2> Synthesis of a lst-generation dendron aldehyde represented by the following formula

In a nitrogen atmosphere, dehydrated dimethylacetamide (220 mL) was added to a mixture of 3 , 5-dibromobenzaldehyde (5.8 g), diphenylaminostyrene produced in Synthesis Example 1-1 (12.0 g) , palladium acetate (1.0 g) , triphenylphosphine (2.3 g) , and sodium carbonate anhydrate (5.1 g) . The resultant mixture was heated at 110°C under stirring overnight. After completion of reaction, the reaction mixture was cooled to room temperature. Methylene chloride and water were added to the reaction mixture under stirring, and the thus-formed organic layer was isolated. The thus- isolated organic layer was washed with water and dried over magnesium sulfate, and the solvent was distilled off under reduced pressure, to thereby yield an oily crude product. The crude product was isolated^' and purified through column chromatography (packing material: Silicagel 60 (product of Merck), eluent: methylene chloride/n-hexane) , to thereby yield 8.9 g of the target product (a yellow solid, yield: 63%) . The structure of the obtained product was confirmed through ¹H-NMR spectroscopy. The measurement data are shown below.

^XH NMR (CDC1₃) 510.01 (s, aldehyde, IH) , 57.85 (d, J=1.6Hz, benzene ring, 2H) , 57.79 (t, J=l .6Hz , benzene ring, IH) , 57.41 (d, J=8.4Hz, benzene ring, 4H) , 57.27 (t, J=7.8Hz, benzene ring, 8H) , 57.18 (d, J=16Hz, vinyl, 2H) , 57.12 (d, J=8.4Hz, benzene ring, 8H) , 57.07-7.02 (m, benzene ring 8H and vinyl, 2H) <Synthesis Example l-3> Synthesis of a lst-generation dendron vinyl compound represented by the following formula

In a nitrogen atmosphere, dehydrated tetrahydrofuran (35 mL) was added to a mixture of methyltriphenylphosphonium bromide (10.0 g) and t-butoxypotassium (3.1 g) , while the mixture was stirred at room temperature. The resultant mixture was allowed to react for two hours at room temperature. Subsequently, the lst-generation dendron aldehyde (4.5 g) produced in Synthesis Example 1-2 was dissolved in dehydrated tetrahydrofuran (22 mL) , and the solution was added dropwise to the above reaction mixture, and the mixture was allowed to react for two hours at room temperature. The reaction was terminated through addition of acetone to the mixture. The precipitates were removed through filtration and washed with methylene chloride. The wash liquid and the filtrate were combined, and the solvent was distilled off under reduced pressure, to thereby yield a crude product. The crude product was isolated and purified through column chromatography (packing material: Silicagel 60 (product of Merck) , eluent: methylene chloride/n-hexane) , to thereby yield 4.5 g of the target product (a yellow solid, yield: 99%) . The structure of the obtained product was confirmed through H-NMR spectroscopy. The measurement data are shown below.

^XH NMR (CDC1₃) 57.48 (s, benzene ring, IH) , 57.39-7.37 (m, benzene ring, 6H) , 57.48 (t, J=7.2Hz, benzene ring, 8H) , 57.11-6.96 (m, benzene ring, 20H) , 56.73 (dd, J=18Hz, 11Hz, vinyl, IH) , 55.81 (d, J=18Hz, vinyl, IH) , 55.28 (d, J=llHz, vinyl, IH) <Synthesis Example l-4> Synthesis of a 2nd-generation dendron aldehyde represented by the following formula

In a nitrogen atmosphere, dehydrated dimethylacetamide (40 mL) was added to a mixture of 3 , 5-dibromobenzaldehyde (0.9 g) , the lst-generation dendron vinyl compound produced in Synthesis Example 1-3 (4.5 g) , palladium acetate (0.16 g) , triphenylphosphine (0.37 g) , and sodium carbonate anhydrate ^' (0.82 g) . The resultant mixture was heated at 110°C under stirring overnight. After completion of reaction, the reaction mixture was cooled to room temperature. Methylene chloride and water were added to the reaction mixture under stirring, and the thus-formed organic layer was isolated. The thus-isolated organic layer was washed with water and dried over magnesium sulfate, and the solvent was distilled off under reduced pressure, to thereby yield an oily crude product. The crude product was isolated and purified through recrystallization from a solvent mixture of methylene chloride/n-hexane, to thereby yield 2.9 g of the target product (a yellow solid, yield: 60%) . The structure of the obtained product was confirmed through ^XH-NMR spectroscopy. The measurement data are shown below. Through GPC, the weight average molecular weight (Mw) , number average molecular weight (Mn) , and molecular weight distribution (Mw/Mn) were found to be 1,660, 1,605, and 1.035, respectively. These values indicate that the target polymer has high purity and assumes a single dispersion state. ¹H NMR (CDC1₃) 510.08 (s, aldehyde, IH) , 57.94 (d, J=1.6Hz, benzene ring, 2H) , 57.91 (t, J=l .6Hz , benzene ring, IH) , 57.54 (s, benzene ring, 6H) , 57.42 (d, J=8.8Hz , benzene ring, 8H) , 57.31-7.17 (m, vinyl, 4H, and benzene ring, 16H) , 57.14-7.11 (m, vinyl, 4H , and benzene ring, 16H) , 57.-08-7.01 (m, benzene ring, 16H, and vinyl, 4H) <Synthesis Example l-5> Synthesis of 1,3,5- benzotriphosphonate serving as a 3-valent core, represented by the following formula

The target product was synthesized in accordance with the procedure described by S. K. Deb et al . (J. Am. Chem. Soc. 1997, 119, 9079). Specifically, mesitylene (1 eq.) was reacted with N-bromosuccinimide (3 eq.) at 35°C in methyl formate in the presence of a catalytic amount of benzoyl peroxide, to thereby produce 1 , 3 , 5-tris (bromomethyl) benzene . Triethyl phosphite (6 eq.) was added to the product (1 eq.) , and the mixture was heated to 120°C. Unreacted triethyl phosphite was removed at under reduced pressure, to thereby yield the target product. The structure of the obtained product was confirmed through ¹H-NMR spectroscopy, and the obtained product was confirmed to be the target product; i.e., 1 , 3 , 5-benzotriphosphonate , from the fact that the spectrum of the product coincides with that described in the above reference. The measurement data are shown below.

^XH NMR (CDC1₃) 57.14 (s, benzene ring, 3H) , 54.01 (q, methylene, 12H) , 53.12 (d, methylene, 6H) , δl.26 (t, methyl, 18H) <Synthesis Example l-6> Synthesis of a 3rd-generation dendritic polymer, represented by the following formula (8)

In a nitrogen atmosphere, the 2nd-generation dendron aldehyde produced in Synthesis Example 1-4 (1.20 g) and 1 , 3 , 5-benzotriphosphonate produced in Synthesis Example 1-5 (150 mg) were dissolved in dehydrated tetrahydrofuran (28 mL) . Sodium hydride (60% in paraffin liquid, 71 mg) was added thereto, and the mixture was allowed to react at room temperature for one hour. Subsequently, sodium hydride (60% in paraffin liquid, 71 mg) was added three times with intervals of 30 minutes, and the mixture was allowed to react for two hours. After completion of reaction, a small amount of water was added thereto, and the solvent was removed under reduced pressure. The residue was dissolved in methylene chloride, and the solution was washed with water. The obtained organic layer was dried over magnesium sulfate, and the solvent was removed under reduced pressure, to thereby produce a crude product. The crude product was isolated and purified through column chromatography (packing material: Silicagel 60 (product of Merck) , eluent: methylene chloride/n-hexane) , to thereby yield 859 mg of the target product (a yellow solid, yield: 72%) . The structure of the obtained product was confirmed through ¹H-NMR spectroscopy and ¹³C-NMR spectroscopy. The measurement data are shown below. Through GPC, the weight average molecular weight (Mw) , number average molecular weight (Mn) , and molecular weight distribution (Mw/Mn) were found to be 4,636, 4,431, and 1.046, respectively. These values indicate that the target polymer has high purity and assumes a single dispersion state. In addition, it is confirmed that the thus-obtained 3rd- generation dendritic polymer can readily be dissolved in an organic solvent such as methylene chloride, toluene, N- methylpyrrolidone , or γ-butyrolactone at room temperature, at least to a level of 1 g/L.

^Η NMR (CDC1₃) 57.55 (s, benzene ring, 3H) , 57.52 (s, benzene ring, 6H) , 57.43 (s, benzene ring, 3H) , 57.35 (s, benzene ring, 12H) , 57.26 (s, benzene ring, 6H) , 57.23 (d, J=8.4Hz, benzene ring, 24H) , 57.16-7.12 (m, vinyl, 12H, and benzene ring, 48H) , 57.05-6.89 (m, vinyl, 18H, and benzene ring, 96H) , 56.80 (d, J=16Hz, vinyl, 12H)

¹³C NMR (CDC1₃) 5147.4, 147.1, 138.0, 137.7, 137.3, 131.2, 129.2, 128.3, 127.4, 126.6, 124.4, 123.4, 122.9 [Synthesis Example 2] Synthesis of 4th-generation dendritic polymer

<Synthesis Example 2-l> Synthesis of 3,5- bis (diethoxyphosphorylmethyl) benzaldehyde dimethylacetal serving as a compound having a branch portion, represented by the following formula

The target product was synthesized through five reaction steps in accordance with the procedure described by E. D. Barra et al . (J. Org. Chem. 2001, 66, 5664) . Specifically, in reaction step 1, trimethylbenzene-1 , 3 , 5- tricarboxylate was reduced in tetrahydrofuran by use of aluminum lithium hydride, to thereby produce 1,3,5- tris (hydroxymethyl) benzene . In reaction step 2, the hydroxymethyl groups were brominated in acetonitrile by use of carbon tetrabromide and triphenylphosphine, to thereby produce 3 , 5-bis (bromomethyl) benzyl alcohol. In reaction step 3, the methylol group was oxidized by use of manganese dioxide in methylene chloride, to thereby produce 3,5- bis (dibromomethyl) benzaldehyde . In reaction step 4, the dibromomethyl groups were phosphonated by use of triethylphosphonate , to thereby produce 3,5- bis (diethoxyphosphorylmethyl) benzaldehyde . In reaction step 5, the aldehyde group was acetalized by use of methyl orthoformate and Montmorillonite K-10 (trade name) in carbon tetrachloride, to thereby yield the target product, 3,5- bis (diethoxyphosphorylmethyl) enzaldehyde dimethylacetal . The obtained product was confirmed to be the target product; i.e., 3 , 5-bis (diethoxyphosphorylmethyl) benzaldehyde dimethylacetal , through ''^'H-NMR from the fact that the spectrum of the product coincides with that described in the above reference. The measurement data are shown below. ¹H NMR (CDC1₃) 57.28 (brs , benzene ring, 2H) , 57.21 (brs , benzene ring, IH) , 55.37 (s, methin, IH) , 54.05-3.98 (m, methylene, 8H) , 53.31 (s, methyl, 6H) , 53.15 (d, methylene, 4H) , δl.25 (t, methyl, 12H) <Synthesis Example 2-2> Synthesis of a 3rd-generation dendron aldehyde represented by the following formula

In a nitrogen atmosphere, the 2nd-generation dendron aldehyde produced in Synthesis Example 1-4 (628 mg) and 3', 5- bis (diethoxyphosphorylmethyl) benzaldehyde dimethylacetal produced in Synthesis Example 2-1 (102 mg) were dissolved in dehydrated tetrahydrofuran (10 mL) . t-Butoxypotassium (61 mg) was added thereto, and the mixture was allowed to react for two hours at room temperature. Subsequently, concentrated hydrochloric acid (1 mL) was added thereto, and the mixture was allowed to react for 18 hours at room temperature. After completion of reaction, the reaction mixture was neutralized with a saturated aqueous sodium hydrogencarbonate solution. The formed organic layer was washed with saturated brine and dried over magnesium sulfate, and the solvent was removed under reduced pressure, to thereby produce a crude product. The crude product was isolated and purified through column chromatography (packing material: Silicagel 60 (product of Merck), eluent: methylene chloride/n-hexane) , to thereby yield 532 mg of the target product (a yellow solid, yield: 82%) . The structure of the obtained product was confirmed through ¹H-NMR spectroscopy. The measurement data are shown below. Through GPC, the weight average molecular weight (Mw) , number average molecular weight (Mn) , and molecular weight distribution (Mw/Mn) were found to be 3,547, 3,422, and 1.036, respectively. These values indicate that the target polymer has high purity and assumes a single dispersion state.

^XH NMR (CDC1₃) 59.96 (s, aldehyde, IH) , 57.82 (brs, benzene ring, 3H) , 57.55-7.54 (m, benzene ring, 6H) , 57.45 (s, benzene ring, 8H) , 57.40 (s, benzene ring, 4H) , 57.33 (d, J=8.8Hz , benzene ring, 16H) , 57.24-6.97 (m, vinyl and benzene ring, 116H) , 56.92 (d, J=16Hz, vinyl, 8H) <Synthesis Example 2-3> Synthesis of a 4th-generation dendritic polymer, represented by the following formula

In a nitrogen atmosphere, the 3rd-generation dendron aldehyde produced in Synthesis Example 2-2 (318 mg) and 1 , 3 , 5-benzotriphosphonate produced in Synthesis Example 1-5

(20 mg) were dissolved in dehydrated tetrahydrofuran (5 mL) . t-Butoxypotassium (14 mg) was added thereto, and the mixture was allowed to react for two hours at room temperature. After completion of reaction, concentrated hydrochloric acid

(1 mL) was added thereto. Diethyl ether was added thereto, and the formed organic layer was isolated. The organic layer was sequentially washed with saturated sodium hydrogencarbonate and saturated brine and dried over magnesium sulfate, and the solvent was removed under reduced pressure, to thereby produce a crude product. The crude product was isolated and purified through column chromatography (packing material: Silicagel 60 (product of Merck) , eluent: methylene chloride/n-hexane) , to thereby yield 224 mg of the target product (a yellow solid, yield: 70%) . Through ¹H-NMR, a broad peak was observed in a region of 6 to 8 ppm. Through GPC, the weight average molecular weight (Mw) , number average molecular weight (Mn) , and molecular weight distribution (Mw/Mn) were found to be 7,679, 7,161, and 1.072, respectively. These values indicate that the target polymer has high purity and assumes a single dispersion state.

<Example 1> Organic switching transistor element An organic thin film switching transistor of a reverse stagger structure containing the dendritic polymer of the present invention was fabricated. FIG. 1 schematically shows a cross-section of the transistor.

As shown in FIG. 1, the organic thin film switching transistor of a reverse stagger structure containing the dendritic polymer of the present invention includes an electrically insulating substrate 1 typically formed of glass; a gate electrode 2 provided on the substrate; a gate insulating layer 3 formed on the gate electrode 2 ; a drain electrode 4 and a source electrode 5 formed on the gate insulating layer; and an organic semiconductor layer 6 covering these members. The gate electrode 2 is formed of Ta, and the drain electrode 4 and source electrode 5 are formed of Au . The organic semiconductor layer 6 is formed from a 3rd-generation dendritic polymer synthesized in Synthesis Example 1-6 and having hole- and electron-conductivity (represented by formula (8) ) :

The organic thin film switching transistor was fabricated in the following manner. Firstly, Ta was vapor- deposited via a mask on the electrically insulating substrate 1, to thereby form the gate electrode 2. The surface of the gate electrode 2 was oxidized, to thereby form the gate insulating layer 3. Subsequently, Au was vapor-deposited via a mask on the gate insulating layer, to thereby form the drain electrode 4 and source electrode 5. The dendritic polymer which had been synthesized in Synthesis Example 1-6 (formula (8)) was applied thereto through ink-j et coating, to thereby form the organic semiconductor layer 6. The channel length was 12 μm. The carrier mobility of the organic thin film switching transistor, as measured through the time-of-flight method, was found to be 6 x 10^"1 cm²V^_1s^_1. The on/off current ratio, obtained through evaluation of current-voltage characteristics, was found to be a level of about 10⁶. The obtained carrier mobility and the on/off current ratio were also equivalent to those of a currently employed, similar transistor containing a-Si. The results, together with those in relation to a transistor of Comparative Example 1 shown below, indicate that performance of an organic thin film switching transistor can be drastically enhanced through employment of the dendritic polymer of the present invention.

<Comparative Example 1>

The procedure of Example 1 was repeated, except that oligothiophene was used to form the organic semiconductor layer, to thereby fabricate an organic thin film switching transistor employing an organic semiconductor layer formed of oligothiophene .

The carrier mobility of the organic thin film switching transistor was found to be 8.5 x 10³ cm²V^~1s^~1, and the on/off current ratio was found to be a level of about 10³. <Example 2> Light-emitting element

A light-emitting element containing the dendritic polymer of the present invention was fabricated. FIG. 2 schematically shows the element.

As shown in FIG. 2, the light-emitting element containing the dendritic polymer of the present invention includes a transparent glass substrate 11 for fabricating an organic light-emitting element; an electrode 12 formed thereon; a hole-injecting layer 13 and a dendritic polymer layer (hole-transporting, electron-transporting, light- emitting) 14; and an electrode 15, the layers 13 and 14 being provided between the electrodes 12 and 15.

The light-emitting element was fabricated in the following manner. Firstly, ITO (indium tin oxide) was formed on the glass substrate 11 for fabricating an light-emitting element, to thereby form the electrode 12 serving as a positive electrode. The hole-injecting layer 13 was provided in the film form from a mixture of poly (ethylenedioxythiophene) and sodium poly (styrenesulfonate) through the spin-coating method at room temperature. The thickness of the film was 50 nm. The dendritic polymer layer (hole-transporting, electron- transporting, light-emitting) 14 was provided in the film form from a solution of the dendritic polymer which had been synthesized in Synthesis Example 1-6 (formula (8)) in tetrahydrofuran through the spin-coating method at room temperature. The thickness of the film was 50 nm. Subsequently, aluminum/lithium (9 : 1) alloy was vapor- deposited, to thereby form the electrode 15 serving as a negative electrode. Thus,^" a light-emitting element was fabricated.

The light-emitting element was activated through application of a predetermined voltage, and initial luminance of emitted light was determined to be 1,500 cd/m². The time required for decreasing the initial luminance to the half value was determined to be 3,000 hours or longer. The emitted light had a peak wavelength of 450 nm. The results, together with those in relation to an element of Comparative Example 2 shown below, indicate that element characteristics can be drastically enhanced through employment of the dendritic polymer of the present invention.

<Comparative Example 2>

The procedure of Example 2 was repeated, except that pol (hexylthiophene) was used to form the light-emitting layer, to thereby fabricate a light-emitting element of the same structure.

The light-emitting element was activated through application of a predetermined voltage, and initial luminance of emitted light was determined to be 800 cd/m². The time required for decreasing the initial luminance to the half value was determined to be 800 hours.

<Example 3> Organic solar cell element

An organic solar cell element containing the dendritic polymer of the present invention was fabricated. FIG. 3 schematically shows the element.

As shown in FIG. 3, the organic solar cell element containing the dendritic polymer of the present invention includes a transparent glass substrate 21; an electrode 22 formed on the substrate; an electrode 24; and a dendritic polymer layer 23 provided between the electrodes 22 and 24.

The organic solar cell element was fabricated in the following manner. Firstly, ITO was formed on the glass substrate 21, to thereby form the electrode 22. The dendritic polymer layer (hole-transporting, electron- transporting, light-emitting) 23 was provided in the film form from a liquid mixture containing copper phthalocyanine and a solution of the dendritic polymer (hole- and electron- conductive) which had been synthesized in Synthesis Example 1-6 (formula (8) ) in tetrahydrofuran through the spin-coating method at room temperature. The thickness of the film was 50 nm. Subsequently, silver was vapor-deposited, to thereby form the electrode 24. Thus, an organic solar cell element shown in FIG. 3 was fabricated.

The organic solar cell element was irradiated with the light which was provided from a tungsten lamp and of which light beams of 400 nm or lower were cut out. Initial energy conversion efficiency was determined to be 2.1 to 2.7%, which are satisfactory.

The results, together with those in relation to an element of Comparative Example 3 shown below, indicate that element characteristics • can be drastically enhanced through employment of the dendritic polymer of the present invention.

<Comparative Example 3>

An organic solar cell element of a structure which is schematically shown in FIG. 4 was fabricated.

As shown in FIG. 4, the organic solar cell element of Comparative Example 3 includes a transparent glass substrate 101; an electrode 102 formed on the substrate; a charge- generating layer 103 formed of copper phthalocyanine; an electron-conductive layer 104 formed of a hexazatriphenylene derivative; a hole-transporting layer 105 formed of a mixture of poly (ethylenedioxythiophene) and sodium poly (styrenesulfonate) ; and an electrode 106, these elements being stacked in this order. The organic solar cell element was irradiated by light which was provided from a tungsten lamp and of which light beams of 400 nm or lower were cut out. Initial energy conversion efficiency was determined to be.1.7 to 2.0%. ***

As described hereinabove, according to the present invention, a novel dendritic polymer serving as an organic semiconductor material which has high solubility in organic solvent; which is stable (i.e., is not prone to being affected by external inhibitors such as oxygen and water) ; and which exhibits isotropic, remarkably high carrier conductivity can be provided. In addition, electronic device elements requiring carrier conductivity and having remarkably high carrier conductivity can be produced through a simple production process.

Claims

Claims

1. A dendritic polymer having a branching structure including a repeating unit having a branch portion, characterized in that the polymer has an aromatic amine moiety at an end thereof, and that the repeating unit is formed of a phenylenevinylene moiety represented by formula (1) :

which is repeated once or a plurality of times .

2. A dendritic polymer according to claim 1, wherein the aromatic amine moiety includes at least one species represented by formula (2) :

wherein Ar^x represents a single bond or a divalent aromatic group, and each of Ari and Ar₂ represents a monovalent aromatic group.

3. A dendritic polymer according to claim 2 , wherein the divalent aromatic group included in the aromatic amine moiety is a phenylene group or a naphthylene group, and the monovalent aromatic group is independently selected from the groups represented by formula (3) :

wherein each of Ri and R₂ is independently selected from among a hydrogen atom, a C1-C4 alkyl group, and a C1-C4 alkoxy group.

4. A dendritic polymer according to any one of claims 1 to 3 , wherein the repeating unit serving as a starting point of the branching structure is further bonded to a center moiety serving as a core.

5. A dendritic polymer according to claim 4, wherein the core is selected from among the moieties represented by formula (4) .

6. A dendritic polymer according to any one of claims 1 to 5, which is a dendrimer.

7. A dendritic polymer according to claim 6 , wherein the dendrimer is of the second generation or of a higher generation.

8. An electronic device element characterized by employing a dendritic polymer as recited in any one claims 1 to 7 .

9. An electronic device element according to claim 8 , which is a charge-transporting device element.

10. An electronic device element according to claim 8, which is a switching transistor element.

11. An electronic device element according to claim 8 , which is a light-emitting device element.

12. An electronic device element according to claim 8 , which is a photoelectric conversion device element.