LIGHT EMITTING DEVICE COMPOSITION AND LIGHT EMITTING DEVICE CONTAINING THE SAME

Abstract

A composition which is useful for production of a light emitting device of which initial deterioration is suppressed, and a light emitting device formed using the composition, are provided. The composition contains a host material and a guest material blended therein. The host material contains an aromatic compound having a condensed ring skeleton in which only three or more benzene rings are condensed. The guest material contains an aromatic amine compound. The total amount of sodium atoms contained in the host material and sodium atoms contained in the guest material is 400 ppb by mass or less with respect to the total amount of the host material and the guest material.

Claims

1. A composition for light emitting device containing a host material and a guest material blended therein, wherein said host material contains an aromatic compound having a condensed ring skeleton in which only three or more benzene rings are condensed, said guest material contains an aromatic amine compound, and the total amount of sodium atoms contained in said host material and sodium atoms contained in said guest material is 400 ppb by mass or less with respect to the total amount of said host material and said guest material.

2. The composition for light emitting device according to claim 1, wherein said aromatic compound is a compound represented by the formula (FH): [Chemical Formula 1]
Ar.sup.1HR.sup.1H).sub.n.sub.1H(FH) wherein, n.sup.1H represents an integer of 0 or more, Ar.sup.1H represents a group obtained by removing from an aromatic hydrocarbon having a condensed ring skeleton in which only three or more benzene rings are condensed n.sup.1H or more hydrogen atoms bonding directly to carbon atoms constituting said condensed ring, and this group optionally has a substituent, when a plurality of the substituents are present, they may be the same or different and may be combined together to form a ring together with atoms to which they are attached, R.sup.1H represents an aryl group or a monovalent heterocyclic group, and these groups optionally have a substituent, when a plurality of the substituents are present, they may be the same or different and may be combined together to form a ring together with atoms to which they are attached, when a plurality of R.sup.1H are present, they may be the same or different and may be combined together to form a ring together with atoms to which they are attached.

3. The composition for light emitting device according to claim 1, wherein said condensed ring skeleton is a condensed ring skeleton in which only three or more and five or less benzene rings are condensed.

4. The composition for light emitting device according to claim 3, wherein said condensed ring skeleton is an anthracene skeleton, a phenanthrene skeleton, a benzoanthracene skeleton, a benzophenanthrene skeleton or a pyrene skeleton.

5. The composition for light emitting device according to claim 1, wherein said aromatic amine compound is a compound represented by the formula (FB): [Chemical Formula 2]
Ar.sup.1BR.sup.1B).sub.n.sub.1B(FB) wherein, n.sup.1B represents an integer of 1 or more, Ar.sup.1B represents an aromatic hydrocarbon group or an aromatic heterocyclic group, and these groups optionally have a substituent, when a plurality of the substituents are present, they may be the same or different and may be combined together to form a ring together with atoms to which they are attached, R.sup.1B represents an amino group or a substituted amino group, and these groups optionally have a substituent, when a plurality of the substituents are present, they may be the same or different and may be combined together to form a ring together with atoms to which they are attached, when a plurality of R.sup.1B are present, they may be the same or different and may be combined together to form a ring together with atoms to which they are attached.

6. The composition for light emitting device according to claim 1, further comprising at least one selected from the group consisting of a hole transporting material, a hole injection material, an electron transporting material, an electron injection material, a light emitting material, an antioxidant and a solvent.

7. A light emitting device having an anode, a cathode, and an organic layer disposed between said anode and said cathode, wherein said organic layer is a layer containing the composition for light emitting device as described in claim 1.

8. A method for producing a composition for light emitting device containing a host material and a guest material blended therein, comprising a host material preparation step of preparing a host material containing an aromatic compound having a condensed ring skeleton in which only three or more benzene rings are condensed, a guest material preparation step of preparing a guest material containing an aromatic amine compound, and a production step of mixing said host material and said guest material at a blending ratio such that the total amount of sodium atoms contained in said host material and sodium atoms contained in said guest material is 400 ppb by mass or less to obtain a composition for light emitting device.

9. The production method according to claim 8, wherein said guest material preparation step comprises a preparation step (B-1) of preparing said aromatic amine compound containing sodium atoms mixed therein, and a step (B-2) of purifying at least a part of said aromatic amine compound prepared in said step (B-1) to remove at least a part of said sodium atoms.

10. The production method according to claim 8, wherein said host material preparation step comprises a step (A-1) of preparing said aromatic compound containing sodium atoms mixed therein, and a step (A-2) of purifying at least a part of said aromatic compound prepared in said step (A-1) to remove at least a part of said sodium atoms.

11. A method for producing a composition for light emitting device containing a host material and a guest material blended therein, comprising a host material preparation step of preparing a host material containing an aromatic compound having a condensed ring skeleton in which only three or more benzene rings are condensed, a determination step of determining the blending ratio of the guest material to said host material, a guest material preparation step of preparing a guest material which contains an aromatic amine compound and with which, when mixed with said host material at said blending ratio, the total amount of sodium atoms contained in said host material and sodium atoms contained in said guest material with respect to the total amount of said host material and said guest material is 400 ppb by mass or less, and a production step of mixing said host material and said guest material at said blending ratio to obtain a composition for light emitting device.

12. A method for producing a composition for light emitting device containing a host material and a guest material blended therein, comprising a guest material preparation step of preparing a guest material containing an aromatic amine compound, a determination step of determining the blending ratio of the host material to said guest material, a host material preparation step of preparing a host material which contains an aromatic compound having a condensed ring skeleton in which only three or more benzene rings are condensed and with which, when mixed with said guest material at said blending ratio, the total amount of sodium atoms contained in said host material and sodium atoms contained in said guest material with respect to the total amount of said host material and said guest material is 400 ppb by mass or less, and a production step of mixing said guest material and said host material at said blending ratio to obtain a composition for light emitting device.

13. A method for producing a composition for light emitting device containing a host material and a guest material blended therein, comprising a host material preparation step of preparing an aromatic compound having a condensed ring skeleton in which only three or more benzene rings are condensed as the host material, a guest material preparation step of preparing an aromatic amine compound as the guest material, a determination step of determining the blending ratio of said host material and said guest material, a purification step of purifying at least a part of said aromatic compound and said aromatic amine compound such that, when said host material and said guest material are mixed at said blending ratio, the total amount of sodium atoms contained in said host material and sodium atoms contained in said guest material with respect to the total amount of said host material and said guest material is 400 ppb by mass or less, and a production step of mixing said host material containing said aromatic compound and said guest material containing said aromatic amine compound at said blending ratio to obtain a composition for light emitting device.

14. The production method according to claim 8, further comprising a host material measurement step of measuring the content of sodium atoms contained in said aromatic compound, and a guest material measurement step of measuring the content of sodium atoms contained in said aromatic amine compound.

15. A method for producing a light emitting device containing an anode, a cathode, and an organic layer disposed between said anode and said cathode, comprising a step of forming said organic layer with the composition for light emitting device produced by the production method according to claim 8.

Description

EXAMPLES

[0322] The present invention will be illustrated further in detain by examples below, but the present invention is not limited to these examples.

[0323] In the present examples, the maximum peak wavelength of the emission spectrum of a compound was measured by a spectrophotometer (manufactured by JASCO Corporation, FP-6500) at room temperature. A compound was dissolved in xylene at a concentration of about 0.8×10.sup.−4% by mass and the resultant xylene solution was used as a sample. As the excitation light, UV light with a wavelength of 325 nm was used.

[0324] In the present examples, the amount of sodium atoms contained in a compound was measured by an ICP/MASS method.

<Compound H1 and Compound EM1>

[0325] A compound H1 was synthesized with reference to a method described in Japanese Unexamined Patent Application Publication (JP-A) No. 2011-105643.

[0326] A compound EM1 was synthesized with reference to a method described in International Publication WO2011/137922.

##STR00011##

[0327] The HPLC area percentage value of the compound H1 was 99.5% or more. The amount (C.sup.H) of sodium atoms contained in the compound H1 was 410 ppb by mass.

[0328] The HPLC area percentage value of the compound EM1 was 99.5% or more. The amount (C.sup.1) of sodium atoms contained in the compound EM1 was 420 ppb by mass.

<Purification of Compound H1 (Synthesis of Compound H2)>

[0329] Sublimation purification of the compound H1 was repeated until the amount of sodium atoms contained in the compound H1 became the detection limit or less (0 ppb by mass), to obtain a compound H2. In sublimation purification, the degree of vacuum was set to 3×10.sup.−3 Pa to 5×10.sup.−′Pa, and the sublimation temperature was set to 250° C. to 300° C.

[0330] The HPLC area percentage value was the compound H2 was 99.5% or more. The amount (C.sup.H) of sodium atoms contained in the compound H2 was below the detection limit (0 ppb by mass).

<Purification of Compound EM1 (Synthesis of Compound EM2)>

[0331] Sublimation purification of the compound EM1 was repeated until the amount of sodium atoms contained in the compound EM1 became the detection limit or less (0 ppb by mass), to obtain a compound EM2. In sublimation purification, the degree of vacuum was set to 3×10.sup.−3 Pa to 5×10.sup.−3 Pa, and the sublimation temperature was set to 250° C. to 300° C.

[0332] The HPLC area percentage value was the compound EM2 was 99.5% or more. The amount (C.sup.1) of sodium atoms contained in the compound EM2 was below the detection limit (0 ppb by mass).

[0333] The maximum peak wavelength of the emission spectrum of the compounds H1 and H2 was 421 nm. The maximum peak wavelength of the emission spectrum of the compounds EM1 and EM2 was 454 nm.

<Example D1> Fabrication and Evaluation of Light Emitting Device D1

(Formation of Anode and Hole Injection Layer)

[0334] An ITO film was attached with a thickness of 45 nm to a glass substrate by a sputtering method, for form an anode. On the anode, a hole injection material ND-3202 (manufactured by Nissan Chemical Corporation) was spin-coated to form a film with a thickness of 35 nm. The substrate carrying the hole injection layer laminated thereon was placed under an air atmosphere and heated on a hot plate at 50° C. for 3 minutes, and further, heated at 230° C. for 15 minutes, to form a hole injection layer.

(Formation of Hole Transporting Layer)

[0335] A polymer compound HTL-1 was dissolved in xylene at a concentration of 0.7% by mass. The resultant xylene solution was spin-coated on the hole injection layer, to form a film with a thickness of 20 nm which was then placed under a nitrogen gas atmosphere and heated on a hot plate at 180° C. for 60 minutes, to form a hole transporting laver. The polymer compound HTL-1 is a polymer compound of Polymer Example 1 in International Publication WO2014/102543.

(Formation of Light Emitting Layer)

[0336] The compound H2 and the compound EM2 (compound H2/compound EM2=90% by mass/10% by mass) were dissolved at a concentration of 2% by mass in toluene. The resultant toluene solution was spin-coated on the hole transporting layer, to form a film with a thickness of 60 nm which was then placed under a nitrogen gas atmosphere and heated at 130° C. for 10 minutes, to form a light emitting layer.

(Formation of Cathode)

[0337] The substrate carrying the light emitting layer formed thereon was placed in a vapor deposition machine and the internal pressure was reduced to 1.0×10.sup.−4 Pa or less, then, sodium fluoride was vapor-deposited with a thickness of about 4 nm on the light emitting layer, then, aluminum was vapor-deposited with a thickness of about 80 nm on the sodium fluoride layer, as cathodes. After vapor deposition, sealing was performed with a glass substrate, to fabricate a light emitting device D1.

(Evaluation of Light Emitting Device)

[0338] Voltage was applied to the light emitting device D1, to observe EL emission. The current value was set so that the initial luminance was 5000 cd/m.sup.2, then, the device was driven at constant current, and the time until the luminance reached 97% of the initial luminance (hereinafter, referred to also as “LT97”) was measured.

Examples D2 to D10 and Comparative Example CD1

[0339] Fabrication and Evaluation of Light Emitting Devices D2 to D10 and CD1

[0340] Light emitting devices D2 to D10 and CD1 were fabricated in the same manner as in Example D1, except that materials described in Table 1 were used at the material ratio described in Table 1 instead of “the compound H2 and the compound EM2 (compound H2/compound EM2=90% by mass/10% by mass)” in (Formation of light emitting layer) of Example D1.

[0341] Voltage was applied to the light emitting devices D2 to D10 and CD1, to observe EL emission. LT97 of the light emitting devices D2 to D10 and CD1 was measured.

[0342] The results of Examples D1 to D10 and Comparative Example CD1 are shown in Table 1. The relative values of LT97 of the light emitting devices D1 to D10 if LT97 of the light emitting device CD1 is taken as 1.0 are shown.

TABLE-US-00001 TABLE 1 Light emitting layer C.sup.H C.sup.1 Light Material (ppb (ppb C.sup.HW.sup.H + C.sup.1W.sup.1 LT97 emitting ratio (% by by (ppb by (relative device Material by mass) mass) mass) mass) value) Example D1 D1 H2/EM2 90/10   0   0   0 2.1 Example D2 D2 H2/EM2/EM1 90/9/1   1  42.0   4.2 1.7 Example D3 D3 H2/H1/EM2 88/2/10   9.1   0   8.2 1.9 Example D4 D4 H2/EM2/EM1 90/7/3   0 126  12.6 1.9 Example D5 D5 H2/H1/EM2 85.5/4.5/10  20.5  0  18.5 1.7 Example D6 D6 H2/EM2/EM1 90/1/9   1 378  37.8 1.7 Example D7 D7 H2/H1/EM2 72/18/10  82.0  0  73.8 1.8 Example D8 D8 H2/H1/EM2 45/45/10 205  0 185 1.6 Example D9 D9 H2/H1/EM2 18/72/10 328  0 295 1.8 Example D10 D10 H1/EM2 90/10 410  0 369 1.8 Comparative CD1 H1/EM1 90/10 410 420 411 1.0 Example CD1

INDUSTRIAL APPLICABILITY

[0343] According to the present invention, a composition which is useful for production of a light emitting device of which initial deterioration is suppressed is provided. The present invention is industrially useful since production of a light emitting device of which initial deterioration is suppressed has effects such as resource saving, energy saving and the like.