EP0249942A2 - Dünnschicht-Elektrolumineszenzlagenmaterial - Google Patents

Dünnschicht-Elektrolumineszenzlagenmaterial Download PDF

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Publication number
EP0249942A2
EP0249942A2 EP87108638A EP87108638A EP0249942A2 EP 0249942 A2 EP0249942 A2 EP 0249942A2 EP 87108638 A EP87108638 A EP 87108638A EP 87108638 A EP87108638 A EP 87108638A EP 0249942 A2 EP0249942 A2 EP 0249942A2
Authority
EP
European Patent Office
Prior art keywords
thin film
zns
electroluminescent layer
srs
film electroluminescent
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP87108638A
Other languages
English (en)
French (fr)
Other versions
EP0249942A3 (de
Inventor
Koyata Takahashi
Yukio Ohnuki
Akio Kondoh
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Tosoh Corp
Original Assignee
Tosoh Corp
Toyo Soda Manufacturing Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Tosoh Corp, Toyo Soda Manufacturing Co Ltd filed Critical Tosoh Corp
Publication of EP0249942A2 publication Critical patent/EP0249942A2/de
Publication of EP0249942A3 publication Critical patent/EP0249942A3/de
Withdrawn legal-status Critical Current

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    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B33/00—Electroluminescent light sources
    • H05B33/12—Light sources with substantially two-dimensional radiating surfaces
    • H05B33/14—Light sources with substantially two-dimensional radiating surfaces characterised by the chemical or physical composition or the arrangement of the electroluminescent material, or by the simultaneous addition of the electroluminescent material in or onto the light source
    • H05B33/145—Arrangements of the electroluminescent material
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B33/00—Electroluminescent light sources
    • H05B33/12—Light sources with substantially two-dimensional radiating surfaces
    • H05B33/18—Light sources with substantially two-dimensional radiating surfaces characterised by the nature or concentration of the activator

Definitions

  • the present invention relates to a thin film electroluminescent layer of a thin film electro­luminescent (EL) display device which shows electro­luminescence (EL) under the application of an AC voltage. More particularly, it relates to an improved thin film electroluminescent layer of a thin film EL device which comprises a transparent electrode, a dielectric layer or layers, an electroluminescent layer or layers and a back face electrode.
  • the improved thin film electro­luminescent layer comprises as a light-emitting medium a body of a mixture of ZnS and at least one sulfide selected from MgS, CaS, SrS and BaS, doped with a transition metal or rare earth element which is optically active in the light-emitting medium.
  • the present invention relates to a process for the preparation of a thin film electroluminescent layer of a thin film EL device, which comprises forming a thin film electroluminescent layer from a compound of a transition metal or rare earth element which is optically active in a light-emitting medium, ZnS and at least one sulfide selected from MgS, CaS, SrS and BaS by the vacuum deposition or sputtering method.
  • an EL device having a double dielectric layer structure in which an electroluminescent layer of ZnS or ZnSe doped with Mn is inserted between films of a dielectric material such as Al2O3 , Y2O3 or TiO3 , and the luminescent characteristics of this EL device have been investigated. Research has been carried out into, especially, an electroluminescent layer of ZnS doped with Mn.
  • an electroluminescent layer comprising CaS or SrS instead of ZnS as the light-­emitting medium has attracted attention as a means of realizing a multi-color EL panel.
  • an electroluminescent layer comprising CaS doped with Eu emits a red luminescence
  • an electroluminescent layer comprising SrS doped with Ce emits a greenish blue luminescence.
  • these devices have problems in that the hygroscopicity of the light-emitting medium is higher than that of ZnS and the light-emitting medium is readily hydrolyzed.
  • the crystal form of a IIa-VIb group compound such as CaS or SrS is of the sodium chloride type and the crystal form of a IIb-VIb group compound is of the wurtzite or zinc blend type. It is known that different compounds of the same crystal form relatively easily form a solid solution. However, there have been few reports on the crystallinity or crystal structure of a film formed on a substrate by using a sintered mixture of compounds differing in crystal form, for example, by the vacuum deposition or sputtering method.
  • the IIa-VIb group compounds and IIb-VIb group compounds have quite different crystal forms, but when a mixture of ZnS and SrS containing a dopant is used as the film-forming material and a thin film electroluminescent layer is prepared by the vacuum deposition or sputtering method, the light-emitting medium of the resulting thin film electroluminescent layer can exhibit the light-­emitting medium characteristics of both SrS and ZnS.
  • a thin film EL device having a double dielectric layer structure by using a compound of a transition metal or rare earth element which is optically active in a light-emitting medium, ZnS and at least one sulfide selected from MgS, CaS, SrS and BaS as the vacuum deposition or sputtering material, and examined the electroluminescence characteristics of the thin film EL device. As the result, it has been found that the device has good EL characteristics.
  • a thin film electroluminescent layer of a thin film EL device comprising, as light-emitting medium, a body of a mixture of ZnS and at least one sulfide selected from MgS, CaS, SrS and BaS.
  • the ZnS and the selected sulfide are doped with a transition metal or rare earth element which is optically active in the matrix.
  • This thin film electroluminescent layer of a thin film EL device is prepared by a process which comprises the step of forming a thin film electroluminescent layer from a compound of a transition metal or rare earth element which is optically active in a light-emitting medium, ZnS and at least one member selected from MgS, CaS SrS and BaS by the vacuum deposition or sputtering method.
  • a thin film electroluminescent layer of a thin film EL device comprising ZnS, which is a II-VI group compound, doped with a compound of a transition metal or rare earth element such as Mn, Tb, Sm or Ce, have been studied.
  • ZnS has a low hygroscopicity, is difficult to decompose, and is chemically stable, and ZnS has a sufficiently large band gap. Accordingly, ZnS is suitable as the light-emitting medium of the electro­luminescent layer. Namely, if electroluminescent layers are composed of ZnS doped with various dopants, thin film EL devices emitting various colors can be prepared.
  • thin film electroluminescent layers formed by doping with HoF3 , ErF3 , SmF3 , TbF3 , NdF3 , TmF3 or the like emit colors such as red, blue, or green, but the blue color does not have sufficient luminance, and thus improvement is desired.
  • thin film EL devices emitting the three primary colors that is, red, blue, and green, an increase of brightness and a prologation of life are desired. In order to attain this object, it is necessary to not only modify the dopant but also improve the light-emitting medium.
  • SrS has an inferior chemical stability to ZnS, but a thin film EL device prepared by doping SrS with CeF3 emits a blue color and a brightness of this blue color is higher than the brightness of the blue luminescence of the thin film EL device having an electroluminescent layer of ZnS doped with TmF3.
  • the light-emitting medium per se is chemically stable.
  • the ratio of ZnS to the sulfide selected from MgS, CaS, SrS and BaS is preferably 0.5/99.5 to 99.5/0.5 by mole, and more preferably 90/10 to 95/5 by mole.
  • transition metal or rare earth element which is optically active in the light-emitting medium and contained as a dopant in the composite body of the electroluminescent layer of the present invention
  • cerium, holmium, erbium, samarium, terbium, neodymium, thulium and manganese there can be mentioned, for example, cerium, holmium, erbium, samarium, terbium, neodymium, thulium and manganese.
  • the amount of the transition metal or rare earth element is CeF3 , HoF3 , ErF3 , SmF3 , TbF3 , NdF3 , TmF3 , and MnF3.
  • the electroluminescent layer of the thin film EL device the present invention can be prepared by sub­jecting a mixture of a dopant, ZnS and at least one sulfide selected from MgS, CaS, SrS, and BaS directly to vacuum deposition or other appropriate operation.
  • the electroluminescent layer can be prepared by subjecting a dopant, ZnS, and at least one sulfide selected from MgS, CaS, SrS, and BaS, in­dependently without mixing, to the multiple vacuum depo­sition or a similar operation.
  • a sputtering or vacuum deposition method using as the target a sintered mixture of ZnS and at least one sulfide selected from MgS, CaS, SrS and BaS, which contains a dopant, is adopted.
  • a suitable compound of a transition metal or rare earth element can be used as the dopant.
  • the so-formed body is ordinarily a solid solution consisting of one phase, but sometimes the thin film luminescent layer is composed of two or more phases differing in crystal form.
  • a thin film EL device having a thin film electroluminescent layer having good durability charac­teristics such as moisture resistance and weatherability.
  • thin film EL devices emitting various colors with a high brightness can be prepared by using various dopants. For example, if a thin film electroluminescent layer composed of a body of a mixture of ZnS and SrS, doped with CeF3 , is used, a thin film EL element emitting color close to blue, with a high brightness, can be prepared.
  • a sputtering target for preparing an electroluminescent layer was prepared.
  • SrS powder having a purity of 99.9%, ZnS having a purity of 99.9%, and CeF3 having a purity of 99.99% were mixed for 30 minutues to obtain a powdery mixture.
  • the powdery mixture was formed into a sputtering target by the hot press method.
  • a film layer having a double insulation structure was formed on a transparent electrode in an Ar atmosphere by the sputtering method to prepare a thin film EL device.
  • the EL device prepared in this example is shown in Fig. 1. Namely, this EL device was constructed by forming many band-like transparent electrodes 2 in parallel on a glass substrate 1, forming a first dielectric layer 3 of Al2O3 to a thickness of 2000 to 3000 ⁇ on the transparent electrode 2, laminating an electroluminescent layer 4, composed of a CeF3-­incorporated film of a mixture of SrS and ZnS, to a thickness of 8000 to 10000 ⁇ on the layer 3, forming a second dielectric layer 5 of Al2O3 to a thickness of 2000 to 3000 ⁇ , and vacuum-depositing a back face electrode 6 of Al in the form of bands extending orthogonal to the transparent electrodes 2.
  • the so-constructed thin film EL device was heat-­treated at 500°C in an Ar atmosphere for 1 hour, and the electroluminescence characteristics of the EL device were examined by applying sinusoidal voltage at 5 kHz.
  • the dependence of the luminance on the applied voltage (V rsm ) is shown in Fig. 2.
  • Curve (A) in Fig. 2 is a luminance-voltage curve just after application of the sinusoidal voltage to the EL device.
  • the threshold voltage and the luminence are changed by aging, as is apparent from Fig. 2, the characteristic curve shown a similar feature compared with that before aging.
  • the luminescence spectrum of the luminescent color of this EL device is shown in Fig. 3, and the chromaticity diagram based on this luminescence spectrum is shown in Fig. 4.
  • the luminescence color of this EL device was a bluish green color and was in agreement with the luminescence colour of an SrS thin film electroluminescent layer having CeF3 as the luminescence center.
  • the crystal structure of the electroluminescent layer of this thin film EL device was examined by X-ray diffractometry.
  • the X-ray diffraction pattern is shown in Fig. 5-(A).
  • the X-ray diffraction pattern of the SrS electroluminescent layer doped with CeF3 which emits a bluish green luminescence, is shown in Fig. 5-(B).
  • the latter EL device was prepared in the same manner as described above with respect to the former EL device. It is well-known that the SrS film prepared on a substrate by the vacuum deposition method is the sodium chrolide type crystal.
  • composition of this film layer of the present invention has the sodium chloride type crystal structure as the SrS film, and Sr element in the SrS crystal lattice is partially sub­stituted by Zn.
  • a thin film EL device comprising as the electro­luminescent film a film of a mixture of ZnS and CaS, doped with CeF3 , was prepared according to the process disclosed in Example 1. This EL device emitted a green luminescence with high brightness as the EL device comprising as the electroluminescent layer the film of a mixture of ZnS and SrS, doped with CeF3 , shown in Example 1.

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  • Electroluminescent Light Sources (AREA)
  • Luminescent Compositions (AREA)
EP87108638A 1986-06-19 1987-06-16 Dünnschicht-Elektrolumineszenzlagenmaterial Withdrawn EP0249942A3 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP61141473A JPS63995A (ja) 1986-06-19 1986-06-19 薄膜発光層材料
JP141473/86 1986-06-19

Publications (2)

Publication Number Publication Date
EP0249942A2 true EP0249942A2 (de) 1987-12-23
EP0249942A3 EP0249942A3 (de) 1989-08-09

Family

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Family Applications (1)

Application Number Title Priority Date Filing Date
EP87108638A Withdrawn EP0249942A3 (de) 1986-06-19 1987-06-16 Dünnschicht-Elektrolumineszenzlagenmaterial

Country Status (3)

Country Link
EP (1) EP0249942A3 (de)
JP (1) JPS63995A (de)
FI (1) FI872713A (de)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0298745A2 (de) * 1987-07-08 1989-01-11 Sharp Kabushiki Kaisha Dünnfilm-Elektrolumineszenzgerät
US7538483B2 (en) 2002-08-07 2009-05-26 Sanyo Electric Co., Ltd. Inorganic electroluminescent device and method of fabricating the same

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2011032416A (ja) * 2009-08-04 2011-02-17 Sumitomo Metal Mining Co Ltd 蛍光体とその製造方法

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1469230A (en) * 1974-06-04 1977-04-06 Secr Defence Preparation of chemical c-mpounds
EP0209668A2 (de) * 1985-05-28 1987-01-28 Sharp Kabushiki Kaisha Dünnschicht-Elektrolumineszenz-Vorrichtungen und Verfahren zu deren Herstellung
DE3633311A1 (de) * 1985-09-30 1987-04-02 Ricoh Kk Elektrolumineszenzvorrichtung

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1469230A (en) * 1974-06-04 1977-04-06 Secr Defence Preparation of chemical c-mpounds
EP0209668A2 (de) * 1985-05-28 1987-01-28 Sharp Kabushiki Kaisha Dünnschicht-Elektrolumineszenz-Vorrichtungen und Verfahren zu deren Herstellung
DE3633311A1 (de) * 1985-09-30 1987-04-02 Ricoh Kk Elektrolumineszenzvorrichtung

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0298745A2 (de) * 1987-07-08 1989-01-11 Sharp Kabushiki Kaisha Dünnfilm-Elektrolumineszenzgerät
EP0298745A3 (en) * 1987-07-08 1989-08-30 Sharp Kabushiki Kaisha Thin film electroluminescent device
US7538483B2 (en) 2002-08-07 2009-05-26 Sanyo Electric Co., Ltd. Inorganic electroluminescent device and method of fabricating the same

Also Published As

Publication number Publication date
FI872713A0 (fi) 1987-06-17
FI872713A (fi) 1987-12-20
EP0249942A3 (de) 1989-08-09
JPS63995A (ja) 1988-01-05

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