JP2008297354A - Blue light-emitting polyimide - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a blue light-emitting polyimide useful as a light-emitting layer material in a polymer type organic EL display element. <P>SOLUTION: The polyimide comprises a repeating unit represented by the general formula (1) and a repeating unit represented by the general formula (2), wherein, when a molar fraction of the repeating unit represented by the general formula (1) is made to X and a molar fraction of the repeating unit represented by the general formula (2) is made to Y, X is in a range of 0.001-1 and Y is in a range of 0.999-0. A is a divalent aliphatic group or an aromatic group, and B is a tetravalent alicyclic group. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a novel polyimide, and more particularly to a blue light emitting polyimide useful as a light emitting layer material in an organic electroluminescence (EL) display element.

  In recent years, electroluminescence (EL) full-color displays have been put into practical use and have come to be installed in sub-panels of mobile phones and digital cameras, etc., but the panel size has also progressed from the 3-inch class to the 5-inch class. In the future, it is expected to expand to a larger screen represented by television. Currently, liquid crystal displays are the mainstream as flat panel displays, but EL displays are superior to liquid crystal displays in terms of power consumption, resolution, and visibility. Furthermore, since there is no need to use a polarizing plate or an optical compensation film used in the liquid crystal display, the EL display has a great advantage that it can be made much thinner and lighter than the liquid crystal display.

The organic EL display basically has a three-layer structure of an electron transport layer, a light-emitting layer, and a hole transport layer, or a two-layer structure in which the light-emitting layer serves as either an electron transport layer or a hole transport layer. In order to drive at a low voltage, highly controlled thinning technology is indispensable.
Organic EL devices are classified into low-molecular types and high-molecular types. The former is manufactured by a dry process such as organic molecular beam evaporation, whereas the latter is a wet process by spin coating or dip coating. It is made with. Therefore, the polymer EL element is advantageous not only in that the production apparatus is simpler, but also in that a uniform and large-area thin film can be produced with high productivity and low cost.

  Recently, as a wet process, an inkjet printing method widely used for printers of personal computers has attracted attention. As a result, high-definition patterning is possible, solution waste is small, and multicoloring is possible.

  Other advantages of the polymer EL element are mechanical strength and flexibility. Further, by using a polymer material instead of glass as a substrate, it is possible to form an EL display that is flexible and has high impact resistance. In addition, polymer type EL elements are less likely to crystallize and aggregate than low molecular type elements, and are expected to be stored and used under high temperature conditions.

  Low molecular dye deposition film forms a uniform amorphous film, but it is often crystallized due to exposure to high temperature conditions for outdoor use or in-vehicle use, or due to Joule heat generated during driving at high temperature or device driving. And aggregation occur, and the stability of the EL element is significantly reduced. In recent years, studies have been made to increase the glass transition temperature of a low molecular dye deposition layer as high as possible in order to improve the heat resistance of an EL element. From this point of view, it is extremely effective to use a polymer layer having high heat resistance instead of a low molecular dye.

  Currently, various blue light emitting polyimides are known (for example, see Non-Patent Document 1). Polyfluorene is one of the most promising polymer blue light-emitting materials among them (see, for example, Non-Patent Document 2). However, the production method of polyfluorene is complicated, and the driving life (durability) of the EL element is remarkably high when applied to the EL light emitting layer unless the catalyst used after polymerization is completely removed and the purity is not extremely high. Serious problems such as decline have been pointed out.

  For example, if an electron and hole transporting group or a light-emitting group is bonded to a heat-resistant polymer and aggregation of these functional groups can be suppressed, there is a possibility that the driving life of the EL element can be greatly extended. Polyimide, polybenzoxazole, polybenzimidazole, polyphenylene, polyfluorene, and the like are known as heat-resistant polymer materials having extremely high glass transition temperatures. From the viewpoint of simplicity of production method, thinning ability, film purity, etc. Polyimide is most suitable.

  Polyimide is a substrate obtained by solution casting of a high molecular weight soluble polyimide precursor (polyamic acid) obtained by equimolar polyaddition reaction of two types of monomers, namely tetracarboxylic dianhydride and diamine, in an amide solvent. After film formation, it can be easily obtained without a catalyst by heating dehydration cyclization reaction (imidation reaction). Moreover, since various commercially available monomers are available, the polyimide system is extremely advantageous from the viewpoint of improving physical properties and precise control. However, few practical polyimides with controlled emission characteristics and the like are known.

  In order to develop strong EL, it is indispensable that the light emitting layer material exhibits strong photoluminescence (PL). However, in the case of wholly aromatic polyimide, the excited state is strongly quenched due to intramolecular and intermolecular charge transfer interactions. Usually, it becomes almost non-fluorescent (for example, see Non-Patent Document 3). Thus, the charge transfer interaction inherent in aromatic polyimide has the effect of strongly quenching the excited state, so even if a specially designed luminescent group is partially introduced into the aromatic polyimide chain, the luminescent group Often no luminescence from is observed.

Anthracene is known as a low molecular weight compound that exhibits strong blue light emission in a dilute solution. A blue light-emitting polyimide represented by the following formula (3) in which an anthracene residue is bonded to a side chain of polyimide has been reported (for example, see Non-Patent Document 4).

  However, in this case, since the anthracene residue is introduced into the side chain through the methylene chain, the anthracene residue is likely to aggregate when the polyimide film is formed. There is a problem of a significant drop.

For example, a polyimide represented by the following formulas (4) and (5) in which a phenylfuran ring residue having strong blue light emission property is bonded to the main chain or side chain of polyimide has also been reported (for example, Non-Patent Document 5 And 6).

  However, in these phenylfuran ring-containing polyimides, the main chain is rigid, so that the polymer chains are easily oriented in the plane and laminated, and as a result, aggregation between the luminescent groups is likely to occur. In addition, since the excited state is strongly quenched by intramolecular and intermolecular charge transfer interactions, these polyimide films have a blue PL intensity higher than that measured in a dilute solution of the light emitting group-containing monomer. Decrease significantly.

  If the anthracene residue is incorporated into the polyimide main chain via a covalent bond, and further, the charge transfer interaction can be prevented, a decrease in PL intensity can be avoided, and a strong blue light-emitting polyimide is expected to be obtained. .

A technique for producing a blue light emitting polyimide using an anthracene residue-containing diamine monomer represented by the following formula (6) in combination with an aromatic tetracarboxylic dianhydride is disclosed (for example, see Non-Patent Document 7). ).

  Moreover, the polyimide combined with this and an alicyclic tetracarboxylic dianhydride is also reported (for example, refer nonpatent literature 8). However, while these polyimides show blue PL in a high yield in solution, there is a problem that the PL yield is remarkably lowered in a film state.

When the anthracene residue is introduced into the tetracarboxylic dianhydride component rather than the diamine component, it is expected that a higher PL yield can be obtained when the polyimide is used due to the electronic conjugation of the anthracene residue and the carbonyl group. From this viewpoint, in order to obtain a higher blue PL intensity, it is expected to be extremely effective to produce a polyimide using, for example, an anthracene tetracarboxylic dianhydride represented by the following formula (7). However, no such polyimide is known.

  In addition, various light-emitting elements (polymer light-emitting elements) using polymer materials such as high-molecular weight light-emitting materials and charge transport materials have been studied. Examples of polymer materials include polyphenylene vinylene derivatives, polyfluorene derivatives, and polyparaffins. In addition to a polymer compound such as a phenylene derivative, a polymer compound of a fencelen derivative is known (for example, see Patent Document 1).

JP 2007-106874 Progress in Polymer Science, 25, p1089 (2000). Macromolecular Rapid Communication, 22, p1365 (2001). Progress in Polymer Science, 26, p259 (2001). J. Phys. Chem., B, 101, p11068 (1997). Macromolecules, 31, p4777 (1998). Polymer, 40, p125 (1998). Polymers for Advanced Technologies, 11, p325 (2000). High Performance Polymers, 18, p749 (2006).

  This invention provides the blue light emitting polyimide useful as a light emitting layer material in a polymer type organic EL display element by solving the above-mentioned problems.

  In view of the above problems, as a result of intensive studies, it was found that a specific anthracene skeleton-containing polyimide is useful, and the present invention has been completed.

（式（１）及び式（２）中、Ａは２価の脂肪族基又は芳香族基であり、式（２）中、Ｂは４価の脂環族基である。） That is, the present invention is a polyimide comprising a repeating unit represented by the following general formula (1) and a repeating unit represented by the general formula (2), the repeating unit represented by the general formula (1). X is in the range of 0.001-1 and Y is in the range of 0.999-0, where X is the mole fraction of X and Y is the mole fraction of the repeating unit represented by the general formula (2). It is a certain polyimide.

(In Formula (1) and Formula (2), A is a divalent aliphatic group or aromatic group, and in Formula (2), B is a tetravalent alicyclic group.)

  Moreover, this invention is a polymer blue light emitting element characterized by having a layer containing the said polyimide between the electrodes which consist of an anode and a cathode.

  When the polyimide of the present invention is formed into a film and applied to an organic EL device, it exhibits strong blue light emission, has a high glass transition temperature and sufficient toughness, etc. The polyimide thin film can be preferably used.

  Hereinafter, embodiments of the present invention will be described in detail.

<Molecular design>
First, the luminescent group-containing monomer used for synthesizing the polyimide of the present invention will be described. The polyimide of the present invention is produced using 2,3,6,7-anthracenetetracarboxylic dianhydride (hereinafter referred to as ANTDA) represented by the above formula (7). ANTDA is a luminescent group-containing tetracarboxylic dianhydride.

The luminescent group-containing tetracarboxylic dianhydride represented by the following formula (8) or (9), which is an ANTDA isomer, has a 6-membered acid anhydride group and is more heat-resistant than the 5-membered ring in ANTDA. It is mechanically stable. For this reason, the polymerization reactivity with diamine is very low, and it becomes difficult to obtain a high molecular weight polyimide. As a result, the film becomes brittle and the film forming ability may be lost at all. Anhydrides are not suitable as monomers.

  In the polyimide of the present invention, the mole fraction of the polyimide comprising the repeating unit represented by the general formula (1) is X, and the mole fraction of the polyimide having the repeating unit represented by the general formula (2) is Y. Then, it is a polyimide in which X is in the range of 0.001-1, preferably 0.01-0.5, and Y is in the range of 0.999-0, preferably 0.99-0.5. This polyimide may be a homopolymer composed of a single repeating unit or a copolymer composed of a plurality of repeating units.

  In formulas (1) and (2), A independently represents a divalent aliphatic group or aromatic group. A is a diamine residue generated from a diamine monomer, and a combination of two amino groups to -A- is a diamine monomer used when a polyimide or a precursor thereof is synthesized. If A has an electron conjugation smaller than that of the anthracene diimide moiety that is a luminescent group, that is, if the lowest excited state is based on the localized excited state of the anthracene diimide moiety, blue light emission can be observed. In order to suppress the charge transfer interaction that occurs between the diimide moiety therein and the diamine residue A and increase the luminous efficiency, a diamine monomer having a fluorine group or a fluorinated alkyl group as a side chain in A (fluorinated) It is preferable to use a diamine).

  Fluorine groups and fluorinated alkyl groups (particularly trifluoromethyl groups) present as substituents in the diamine monomer act as electron-withdrawing groups, reducing the electron donating properties of the diamine residue A in the polyimide, and intermolecular In order to weaken the action, it has the effect of suppressing intramolecular and intermolecular charge transfer interactions. Preferred fluorinated diamines include 2,2′-bis (trifluoromethyl) benzidine, 2,2-bis (4- (4-aminophenoxy) phenyl) hexafluoropropane, 2,2-bis ( 4-aminophenyl) hexafluoropropane and the like are exemplified.

  It is more preferable to use an aliphatic diamine as the diamine monomer component from the viewpoint of completely hindering the charge transfer interaction and maximizing the light emission efficiency. Of the aliphatic diamines, an alicyclic diamine having a cyclic structure is more preferable from the viewpoint of preventing a decrease in the glass transition temperature. In addition, an alicyclic diamine having a folded steric structure and an irregular structure is preferable from the viewpoint of preventing aggregation between luminescent groups. 4,4′-methylenebis (cyclohexylamine), 4,4′-methylenebis (3-methylcyclohexylamine), isophoronediamine, 1,4-cyclohexanediamine (cis form or cis / A trans mixture) and the like.

  Even when the molar fraction X of the polyimide represented by the formula (1) is 1, blue PL can be observed, but the concentration of the anthracene diimide luminescent group is appropriately controlled (diluted), and the molecule From the viewpoint of preventing interaggregation and increasing luminous efficiency, copolymerization is performed using two or more tetracarboxylic dianhydride monomers so that the repeating units represented by formulas (1) and (2) are included. It is more preferable. In formula (2), B is a tetracarboxylic dianhydride residue generated from a tetracarboxylic dianhydride monomer, and a dianhydride formed by bonding four carboxyl groups to B is polyimide or a polyimide precursor. It is a tetracarboxylic dianhydride monomer used to obtain a body.

  As the tetracarboxylic dianhydride used in combination with ANTDA, other aromatic tetracarboxylic dianhydrides may be partially used, but from the viewpoint of maximizing the luminous efficiency, the alicyclic tetracarboxylic acid It is preferred to use dianhydrides. That is, it is preferable to use a tetracarboxylic dianhydride in which B is an alicyclic group. Preferable examples include 1,2,3,4-cyclobutanetetracarboxylic dianhydride, cyclopentanetetracarboxylic dianhydride, 1,2,4,5-cyclohexanetetracarboxylic dianhydride, bicyclo [2. 2.2] octane-2,3,5,6-tetracarboxylic dianhydride and the like, and 1,2,3,4-cyclobutanetetracarboxylic dianhydride from the viewpoint of polymerization reactivity with diamine Is the best.

<Synthesis of polyimide precursor>
The polyimide of the present invention is produced via its precursor. First, an example of a method for producing a polyimide precursor will be described. First, a diamine is dissolved in a polymerization solvent, and a mixed powder of ANTDA and a tetracarboxylic dianhydride component copolymerized therewith is gradually added thereto, followed by stirring at room temperature for 1 to 72 hours using a mechanical stirrer. At this time, the total amount of the diamine monomer and the tetracarboxylic dianhydride monomer is substantially equimolar. The total monomer concentration is 5 to 30% by weight, preferably 10 to 20% by weight. By carrying out polymerization in this monomer concentration range, a polyimide precursor solution having a uniform and high degree of polymerization can be obtained.

  When the polymerization is performed at a concentration lower than the above monomer concentration range, the degree of polymerization of the polyimide precursor is not sufficiently high, and the finally obtained polyimide film may be brittle, which is not preferable. In addition, when an aliphatic diamine is used as a diamine monomer, salt formation occurs in the initial stage of polymerization, but if polymerization is performed at a concentration higher than the above monomer concentration, a longer polymerization time is required until the formed salt dissolves and disappears. This is not preferable because it may cause a decrease in productivity.

  Other diamines other than the diamine that gives A in the repeating unit can be used as long as the polymerization reactivity of the polyimide precursor and the required properties of the polyimide are not significantly impaired. Examples of the aliphatic diamine that gives A include the following diamines.

  4,4′-methylenebis (cyclohexylamine), 4,4′-methylenebis (3-methylcyclohexylamine), isophoronediamine, trans-1,4-cyclohexanediamine, cis-1,4-cyclohexanediamine, 1,4- Cyclohexanediamine (trans / cis mixture), 1,4-bis (aminomethyl) cyclohexane, 2,5-bis (aminomethyl) bicyclo [2.2.1] heptane, 2,6-bis (aminomethyl) bicyclo [ 2.2.1] heptane, 3,8-bis (aminomethyl) tricyclo [5.2.1.0] decane, 1,3-diaminoadamantane, 2,2-bis (4-aminocyclohexyl) propane, 2 , 2-bis (4-aminocyclohexyl) hexafluoropropane, 1,3-propanediamine, 1,4 Tetramethylenediamine, 1,5-pentamethylenediamine, 1,6-hexamethylenediamine, 1,7-heptamethylene diamine, 1,8-octamethylene diamine, 1,9-nonamethylenediamine, and the like. Two or more of these may be used in combination. More preferably, 4,4′-methylenebis (cyclohexylamine), 4,4′-methylenebis (3-methylcyclohexylamine), isophoronediamine, 1,4-cyclohexanediamine (cis form or cis / trans mixture) is used. .

Examples of the aromatic diamine that gives A include the following diamines.
Although it does not specifically limit as aromatic diamine, p-phenylenediamine, m-phenylenediamine, 2,4-diaminotoluene, 2,5-diaminotoluene, 2,4-diaminoxylene, 2,4-diaminodurene, 4 , 4′-diaminodiphenylmethane, 4,4′-methylenebis (2-methylaniline), 4,4′-methylenebis (2-ethylaniline), 4,4′-methylenebis (2,6-dimethylaniline), 4, 4'-methylenebis (2,6-diethylaniline), 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl ether, 2,4'-diaminodiphenyl ether, 4,4'- Diaminodiphenyl sulfone, 3,3′-diaminodiphenyl sulfone, 4,4′-diaminoben Phenone, 3,3'-diaminobenzophenone, 4,4'-diaminobenzanilide, benzidine, 3,3'-dihydroxybenzidine, 3,3'-dimethoxybenzidine, o-tolidine, m-tolidine, 2,2'- Bis (trifluoromethyl) benzidine, 1,4-bis (4-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,3-bis (3-aminophenoxy) benzene, 4,4 '-Bis (4-aminophenoxy) biphenyl, bis (4- (3-aminophenoxy) phenyl) sulfone, bis (4- (4-aminophenoxy) phenyl) sulfone, 2,2-bis (4- (4- Aminophenoxy) phenyl) propane, 2,2-bis (4- (4-aminophenoxy) phenyl) hexafluoropropane, 2,2-bi (4-aminophenyl) hexafluoropropane, p- terphenyl-phenylenediamine and the like can be used. Two or more of these may be used in combination. More preferably, 2,2′-bis (trifluoromethyl) benzidine, 2,2-bis (4- (4-aminophenoxy) phenyl) hexafluoropropane, 2,2-bis (4-aminophenyl) hexafluoro Fluorinated diamines such as propane are used.

  Among these diamine monomers, aliphatic diamine and aromatic diamine are preferable in this order. Among aliphatic diamines, alicyclic diamine and chain diamine are preferable. And when using aromatic diamine, it is desirable to use together with aliphatic diamine. Further, other diamines can be partially used as long as the polymerization reactivity of the polyimide precursor and the required characteristics of the polyimide are not significantly impaired.

  In the blue light emitting polyimide of the present invention, the light emitting yield can be further increased by controlling the light emitting group concentration and suppressing aggregation between the light emitting groups. As long as the polymerization reactivity of the polyimide precursor and the required characteristics of the polyimide are not significantly impaired, the alicyclic tetracarboxylic dianhydride used in combination with the above ANTDA and giving B in the general formula (2) is not particularly limited. Bicyclo [2.2.2] oct-7-ene-2,3,5,6-tetracarboxylic dianhydride, 5- (dioxotetrahydrofuryl-3-methyl-3-cyclohexene-1,2- Dicarboxylic anhydride, 4- (2,5-dioxotetrahydrofuran-3-yl) -tetralin-1,2-dicarboxylic anhydride, tetrahydrofuran-2,3,4,5-tetracarboxylic dianhydride, bicyclo -3,3 ', 4,4'-tetracarboxylic dianhydride, 3c-carboxymethylcyclopentane-1r, 2c, 4c-tricarboxylic acid 1,4: 2,3-dianhydride, 1,2,4,5-cyclohexanetetracarboxylic dianhydride, 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,2,3,4-cyclopentanetetracarboxylic dianhydride, etc. Two or more of these may be used in combination, more preferably 1,2,3,4-cyclobutanetetracarboxylic dianhydride, cyclopentanetetracarboxylic dianhydride, 1,2,4. , 5-cyclohexanetetracarboxylic dianhydride and bicyclo [2.2.2] octane-2,3,5,6-tetracarboxylic dianhydride are used, more preferably 1,2,3,4. -Cyclobutanetetracarboxylic dianhydride is used.

  In addition, the aromatic tetracarboxylic dianhydride component other than ANTDA and alicyclic tetracarboxylic dianhydride is partially used as long as the polymerization reactivity of the polyimide precursor and the required characteristics of the polyimide are not significantly impaired. Also good. The aromatic tetracarboxylic dianhydride that can be used in combination is not particularly limited, but pyromellitic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 3,3 ′, 4, 4′-benzophenone tetracarboxylic dianhydride, 3,3 ′, 4,4′-biphenyl ether tetracarboxylic dianhydride, 3,3 ′, 4,4′-biphenylsulfone tetracarboxylic dianhydride, 2 , 2′-bis (3,4-dicarboxyphenyl) hexafluoropropanoic acid dianhydride, 2,2′-bis (3,4-dicarboxyphenyl) propanoic acid dianhydride, 1,4,5,8 -Naphthalene tetracarboxylic dianhydride etc. are mentioned. These may be used alone or in combination of two or more.

  By polymerizing using the above monomers, a polyimide precursor is obtained, and by imidizing this, a polyimide is obtained. The imidization of the polyimide precursor can be performed by a known method such as heating to 200 ° C to 400 ° C. Moreover, although the use of this polyimide is not limited, it is useful as a blue light emitting element material. When used for this purpose, if the mole fraction of the repeating unit represented by the general formula (1) in the polyimide is X and the mole fraction of the repeating unit represented by the general formula (2) is Y, X Is 0.001-1, preferably 0.01-0.5, more preferably 0.02-0.1, Y is 0.999-0, preferably 0.99-0.5, More preferably, it exists in the range of 0.98-0.9. And it is good that the sum total of X and Y is 0.1 or more, Preferably it is 0.5 or more, More preferably, it is 0.8 or more.

  The polymerization solvent is not particularly limited, but N, N-dimethylacetamide, N, N-diethylacetamide, N, N-dimethylformamide, N-methyl-2-pyrrolidone, hexamethylphosphoramide, dimethylsulfoxide, γ- Butyrolactone, 1,3-dimethyl-2-imidazolidinone, 1,2-dimethoxyethane-bis (2-methoxyethyl) ether, terahydrofuran, 1,4-dioxane, picoline, pyridine, acetone, chloroform, toluene, Aprotic solvents such as xylene and protic solvents such as phenol, o-cresol, m-cresol, p-cresol, o-chlorophenol, m-chlorophenol, and p-chlorophenol can be used. These solvents may be used alone or in combination of two or more.

  When the blue light-emitting polyimide of the present invention is used as a material for a blue light-emitting element, the precursor solution is applied on a substrate or a hole transport layer and then dried at 40 ° C. to 150 ° C. to form a film. By heat-treating this polyimide precursor film at a temperature of 200 ° C. to 400 ° C., preferably 220 ° C. to 350 ° C., the blue light emitting polyimide film of the present invention is obtained. The thermal imidization reaction is desirably performed in a vacuum or in an inert gas atmosphere such as nitrogen, but can be performed in air unless the temperature is too high. The imidation reaction can also be performed chemically by reacting the polyimide precursor film with a dehydrating cyclization reagent (chemical imidization reagent).

<Required properties of polyimide>
Film characteristics required for applying the polyimide of the present invention to an EL light emitting device include high PL yield, high glass transition temperature, high thermal stability, and sufficient film toughness.

  As long as the polyimide of the present invention has a film forming ability (film forming property), the molecular weight (or intrinsic viscosity value) is not particularly limited, and can be applied to the above-mentioned use. If an index is shown, the intrinsic viscosity value of the polyimide of the present invention or a precursor thereof is preferably 0.5 dL / g or more, more preferably 1.0 dL / g or more from the viewpoint of film strength. When it is less than 0.5 dL / g, the film forming property is remarkably deteriorated, and there is a possibility that the film is cracked.

  From the viewpoint of blue purity, the PL peak wavelength of the polyimide film of the present invention (when used as a blue light-emitting polyimide film) is preferably in the range of 420 to 470 nm, and more preferably in the range of 430 to 460 nm.

  The PL quantum yield of the polyimide film of the present invention is preferably 0.1 or more, and more preferably 0.3 or more.

  The glass transition temperature of the polyimide film of the present invention is preferably 150 ° C. or higher, and more preferably 200 ° C. or higher, from the viewpoint of reducing aggregation and deterioration between luminescent groups. More preferably, it is 250 degreeC or more.

If the thermal stability of the polyimide film of the present invention is 5% weight reduction temperature (T _d ⁵⁾ the indicative, and more is possible that T _d ⁵ in air is 350 ° C. or higher is preferably 400 ° C. or higher preferable.

  In the polyimide of the present invention and its precursor, if necessary, an oxidation stabilizer, a filler, an adhesion promoter, a silane coupling agent, a photosensitizer, a photopolymerization initiator, a sensitizer, a terminal blocking agent, a crosslinking agent, etc. Additives can be added.

  The blue light-emitting device of the present invention has a layer containing the polyimide of the present invention between electrodes composed of an anode and a cathode. This layer is preferably a blue light emitting layer. The device can further include a hole transport layer, an electron transport layer, and other known layers.

  The present invention will be described more specifically with reference to the following examples. The materials, amounts used, ratios, processing details, processing procedures, and the like shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention is not limited to the specific examples shown below.

<Infrared absorption spectrum>
Using a Fourier transform infrared spectrophotometer (FT / IR350), an infrared absorption (FT-IR) spectrum of a polyimide thin film (film thickness: about 5 μm) was measured by a transmission method. Moreover, in order to confirm the molecular structure of the synthesized anthracene group-containing tetracarboxylic dianhydride, an FT-IR spectrum was measured by the KBr method.

^<1 H-NMR spectrum>
In order to confirm the molecular structure of the synthesized anthracene group-containing tetracarboxylic dianhydride, ¹ H-NMR of the synthesized product in deuterated dimethyl sulfoxide was measured using a JEOL NMR spectrophotometer (ECP400). The spectrum was measured.

<Differential scanning calorimetry (melting point and melting curve)>
The melting point and melting curve of the synthesized anthracene group-containing tetracarboxylic dianhydride were measured in a nitrogen atmosphere at a heating rate of 5 ° C./minute using a differential scanning calorimeter (DSC3100) manufactured by Bruker AX.

<Intrinsic viscosity>
The polyimide precursor or polyimide 0.5 wt% solution (solvent: DMAc) was measured at 30 ° C. using an Ostwald viscometer.

<Glass transition temperature: Tg>
The glass transition temperature of the polyimide film was determined from the loss peak at a frequency of 0.1 Hz and a heating rate of 5 ° C./min by dynamic viscoelasticity measurement using a thermomechanical analyzer (TMA4000) manufactured by Bruker Ax.

<5% weight loss temperature: Td5>
Using a thermogravimetric analyzer (TG-DTA2000) manufactured by Bruker Ax, the initial weight of the polyimide film was reduced by 5% in the heating process at a heating rate of 10 ° C./min in nitrogen or air. The temperature was measured. Higher values indicate higher thermal stability.

<Linear thermal expansion coefficient: CTE>
By using a thermomechanical analyzer (TMA4000) manufactured by Bruker Ax, the elongation of the test piece at a heating rate of 5 ° C / min per load of 0.5g / film thickness of 1µm is 100-200 ° C. The linear thermal expansion coefficient of the polyimide film was determined as an average value in the range.

<Ultraviolet-visible absorption spectrum>
The ultraviolet-visible absorption spectrum of the polyimide film (film thickness: about 13 μm) was measured using an ultraviolet-visible spectrophotometer (V-530 manufactured by JASCO Corporation).

<Emission spectrum and quantum yield>
The emission spectrum of the polyimide film (film thickness: about 13 μm) was measured using a fluorescence spectrophotometer (F-4500, manufactured by Hitachi, Ltd.) at an excitation wavelength of 350 nm, bandpass: 5 nm at both excitation and detection sides, and room temperature. The area intensity of the emission spectrum normalized by the absorbance at the excitation wavelength is obtained, and the reference substance dispersed in the polymethyl methacrylate film, N, N-bis (2,5-tert-butylphenyl) 3,4,9, The light emission (PL) quantum yield of the polyimide film was determined by a relative method from comparison with the normalized light emission area intensity of 10-perylenedicarboxyimide (fluorescence quantum yield φ = 0.95).

<Birefringence>
Using an Abbe refractometer (Abbe 4T) manufactured by Atago Co., Ltd., the refractive index in the direction parallel to the polyimide film (nin) and the direction perpendicular to the polyimide film (nout) was measured with an Abbe refractometer (using a sodium lamp, wavelength 589 nm). The birefringence (Δn = nin−nout) was determined from the difference in refractive index.

<Dielectric constant>
Using an Abbe refractometer (Abbe 4T) manufactured by Atago Co., Ltd., the refractive index in the direction parallel to the polyimide film (nin) and the direction perpendicular to the polyimide film (nout) is measured with an Abbe refractometer (using sodium lamp, wavelength 589 nm) Based on the average refractive index [nav = (2nin + nout) / 3] of the film, the dielectric constant (εcal) of the polyimide film at 1 MHz was calculated by the following formula: εcal = 1.1 × nav2.

Synthesis Example 2.3 g of 1,2,4,5-tetramethylbenzene was dissolved in 70 mL of carbon tetrachloride in a 300 mL three-necked flask equipped with a light irradiation port, a condenser, a thermometer, and a dropping funnel. 25 g of bromine dissolved in 11 mL of carbon tetrachloride while irradiating the solution through a quartz test tube tube and refluxing it at 80 ° C. with an ultraviolet irradiation device with quartz optical fiber (Harrison Toshiba Lighting Co., Ltd., Toscure 100) Was dropped from the dropping funnel over 4 hours. Thereafter, stirring was continued for 44 hours under the same conditions. After the reaction, a precipitate was deposited. After cooling to room temperature, carbon tetrachloride was separated by decantation, 30 mL of chloroform was added to the reaction mixture, and the supernatant was removed by decantation. This was repeated several times to wash the precipitate, and 1,2,4,5-tetrakis (dibromomethyl) benzene was obtained. This was taken out from the flask as it was and vacuum-dried at room temperature, and then subjected to the Diels-Alder reaction, a solution dissolved in sodium iodide 28 g DMAc 180 mL was added thereto to make a uniform solution, and 5.8 g of N-phenylmaleimide was still powdered. The mixture was further stirred and refluxed at 90 ° C. for 10 hours to obtain a crude product. This was washed with water, further washed with 1,4-dioxane, and vacuum-dried at 100 ° C. for 12 hours to give N, N′-diphenyl-2,3,6,7-anthracenetetracarbodiimide as a yellow precipitate. Obtained (yield: 35%). This was hydrolyzed with a 20% by weight aqueous sodium hydroxide solution at 150 ° C. for 25 hours to obtain a sodium salt of anthracene tetracarboxylic acid, and aniline and the like in the reaction mixture were extracted and removed with diethyl ether. In addition, the anthracene tetracarboxylic acid was precipitated by neutralization. This was washed with water until neutral, and then vacuum-dried at 100 ° C. for 12 hours. In order to carry out dehydration and ring closure, it was dissolved in acetic anhydride, stirred and refluxed at 90 ° C. for 3 hours, and the solution was cooled to room temperature to obtain the desired ANTDA as crystals. When IR (FIG. 1) and ¹ H-NMR spectrum (FIG. 2) of the product were measured, it was confirmed to be the target ANTDA.

Example 1
2 mmol of 4,4′-methylenebis (cyclohexylamine) was placed in a closed reaction vessel equipped with a stirrer and dissolved in N, N-dimethylacetamide sufficiently dehydrated with molecular sieves 4A. Next, 1.96 mmol of 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA) powder was added, followed by ANTDA 0.04 mmol powder. Polymerization was carried out at a solute concentration of 15% by weight. The mixture was stirred at room temperature for 48 hours to obtain a transparent, uniform and viscous polyimide precursor solution. This polyimide precursor solution did not precipitate or gel at all even when left at room temperature and 20 ° C. for one month, and showed extremely high solution storage stability. The intrinsic viscosity of the polyimide precursor measured at 30 ° C. in N, N-dimethylacetamide was 0.45 dL / g. This polymerization solution was applied to a glass substrate and dried at 80 ° C. for 2 hours to obtain a tough polyimide precursor film. This polyimide precursor film was heated on a substrate at 200 ° C. in vacuum for 30 minutes and further at 320 ° C. for 1 hour to perform thermal imidization to obtain a flexible polyimide film having a thickness of 20 μm. .

  The polyimide film showed toughness with no film breakage observed in a 180 ° bending test. The glass transition temperature was 328 ° C. and the linear thermal expansion coefficient was 64.2 ppm / K. The 5% weight loss temperature in nitrogen was 428 ° C., and 377 ° C. in air. This polyimide film exhibited blue light emission (excitation wavelength: 380 nm) having peaks at 431 nm and 454 nm, and the light emission quantum yield was 0.36. The birefringence was 0.0047 and the dielectric constant was 2.66. FIG. 3 shows an FT-IR spectrum of the polyimide thin film, FIG. 4 shows an ultraviolet-visible absorption spectrum, and FIG. 5 shows a PL spectrum.

Comparative Example 1
Polymerization was performed according to the method described in Example 1 except that ANTDA was not used at all, and 1,4,5,8-naphthalenetetracarboxylic dianhydride (hereinafter referred to as NTDA) was used instead. The film was formed and imidized. However, the obtained polyimide film was almost non-fluorescent. This is because ANTDA was not used as the light-emitting tetracarboxylic dianhydride monomer.

It is an ANTDA FT-IR spectrum. It is a ¹ H-NMR spectrum of ANTDA. 2 is an FT-IR spectrum of the polyimide thin film of Example 1. 2 is an ultraviolet-visible absorption spectrum of the polyimide film of Example 1. 2 is a PL spectrum of the polyimide film of Example 1.

Claims (2)

A polyimide comprising a repeating unit represented by the following general formula (1) and a repeating unit represented by the general formula (2), wherein the mole fraction of the repeating unit represented by the general formula (1) is X And the molar fraction of the repeating unit represented by the general formula (2) is Y, a polyimide in which X is in the range of 0.001-1 and Y is in the range of 0.999-0.

(In Formula (1) and Formula (2), A represents a divalent aliphatic group or aromatic group, and in Formula (2), B represents a tetravalent alicyclic group.)   A polymer blue light-emitting device comprising a layer containing polyimide according to claim 1 between electrodes composed of an anode and a cathode.

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