Classifications

• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
  • C09K11/00—Luminescent, e.g. electroluminescent, chemiluminescent materials
  • C09K11/08—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials
  • C09K11/56—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials containing sulfur
  • C09K11/562—Chalcogenides
  • C09K11/565—Chalcogenides with zinc cadmium
• • 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
  • H05B33/02—Details
  • H05B33/04—Sealing arrangements, e.g. against humidity
• • 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
  • H05B33/10—Apparatus or processes specially adapted to the manufacture of electroluminescent light sources

Definitions

• This invention relates to a dispersion-type electroluminescence (EL) device exhibiting high brightness and excellent color rendering properties.
• An electroluminescence (EL) phosphor is a voltage excitation type phosphor known to be useful in a dispersion-type EL device, in which a phosphor powder is sandwiched between a pair of electrodes to provide a luminescent element, or a thin film type EL device.
• the dispersion-type EL device generally has a structure including two electrodes at least one of which is transparent and a dispersion of a phosphor powder in a high dielectric constant binder sandwiched in between the electrodes. It emits light on applying an alternating electric field between the electrodes.
• the EL device fabricated by using a phosphor powder has many advantages, such as surface emission, small thickness (several millimeters or even smaller), reduced heat generation, and good luminescence efficiency. It is therefore expected to be applicable as road signs, interior and exterior lights, light sources of flat panel displays, such as LCDs, light sources for large area advertisements, and the like.
• Dispersion-type EL devices providing white light emission proposed to date have at least two emitting regions having high emission intensities, a blue-green region and an orange-red region.
• white light emitting EL devices containing a rhodamine compound in their light emitting layer have been proposed as disclosed in many patents including JP 60-25195 A, JP 60- 170194A and JP 2-78188A.
• JP 2005-302693A discloses a dispersion-type EL device having at least two emission peaks, one at a wavelength of 450 to 530 nm, and one at a wavelength of 605 nm or longer.
• JP 2000-230172 A describes a phosphor element having specific absorption wavelengths and specific luminescence wavelengths, which is combined with a blue LED to provide white light emission having three wavelength peaks.
• U.S. Patent 6806642 discloses an EL lamp providing white light emission having three emission peaks.
• luminescence brightness may be increased by using small phosphor particles as proposed in patent JP- A-2002-235080 and JP-A-2004- 265866.
• using small phosphor particles increases the number of phosphor particles per unit volume of the light emitting layer, thereby binging about improved brightness.
• any of the EL devices described in JP 60-25195 A, JP 60-170194A and JP 2- 78188A uses a material emitting light around 580 nm in combination with ZnS:Cu,Cl that emits blue-green light. For this reason, when a transparent medium, such as a transparent positive image, is observed on the EL device, the color reproduction is considerably inferior to the case when it is observed on a conventional surface light source using, for example a fluorescent tube.
• orange luminescence by a rhodamine dye is utilized as red luminescence so that the white light obtained fails to reproduce red when a transparent medium, such as a transparent positive image, is placed thereon to be observed.
• the EL device of JP 2005-302693 A produces white light based on emission in two wavelength ranges and therefore exhibits poor color reproduction in the green range, leaving room for improvement of color rendition.
• patent JP 2000-230172A and U.S. Patent 6806642 are disadvantageous in that the emission intensity is not adequate, resulting in a failure to provide sufficient color rendition.
• An object of the invention is to provide a dispersion-type EL device having excellent color rendering properties.
• a dispersion-type EL device containing a ZnS phosphor and having high color rendering properties based on well-balanced emission of blue, green, and red light is obtained by designing the emission spectrum to have at least one peak in each of at least three wavelength ranges at intensities in a specific descending order.
• the invention has been completed based on this finding.
• a dispersion-type electroluminescence device including: a light emitting layer containing ZnS phosphor particles, wherein the dispersion-type electroluminescence device has at least one emission peak in each of a short wavelength range of 450 to 514 nm, an intermediate wavelength range of 515 to 569 nm, and a long wavelength range of 570 to 650 nm, the intensities of the peaks descending in the order of the short wavelength range, the long wavelength range, and the intermediate wavelength range.
• the dispersion-type electroluminescence device as described in (3) further including: a back electrode, wherein the red conversion material is present in a layer provided between the light emitting layer and the back electrode.
• the dispersion-type electroluminescence device as described in (1) which is sealed by a gas barrier laminate film, wherein the gas barrier laminate film includes at least one inorganic layer and at least one organic layer on or above a base film, the organic layer containing a polymerization product of a monomer composition, the monomer composition containing at least one acrylate having a phosphoester group.
• the EL device of the invention is contemplated to provide white light emission.
• the white light emission spectrum has at least three peaks, the intensities of which descend in the order of short wavelength range, long wavelength range, and intermediate wavelength range.
• white light is produced as a mixture of, for example, two large emission bands, one being based on electroluminescence (blue-green) of ZnS phosphor particles and the other being emission of longer wavelengths (orange to red) by a wavelength converting material having absorbed part of the electroluminescence as with the case of JP 2005- 302693 A. Therefore, it is of concern how the emission is distributed in the vicinities of wavelengths at which blue, green, and red colors are the most perceptible to the human eye.
• the present invention is contemplated to provide improved color reproduction of green, which is the most perceptible color to human eye, by adding, to the emission peaks of blue-green (450 to 530 run) and of orange-red (605 nm or longer) as proposed in JP 2005-302693 A supra, an additional peak in the range of from 515 to 569 nm.
• the inventor has succeeded in providing well-balanced white light based on at least one peak in a short wavelength range of 450 to 514 nm, at least one peak in an intermediate wavelength range of 515 to 569 nm, and at least one peak in a long wavelength range of 570 to 650 nm.
• the peak in the short wavelength range is preferably in the range of from 460 to 510 nm, more preferably from 470 to 505 nm.
• the peak in the intermediate wavelength range is preferably in the range of from 520 to 565 nm, more preferably from 525 to 560 nm.
• the peak in the long wavelength range is preferably in the range of from 575 to 630 nm, more preferably from 580 to 610 nm.
• White light having emission peaks in these wavelength ranges exhibits good color rendering properties.
• the term "emission peak” or shortly “peak” denotes a profile apparently indicating a maximum emission intensity in an emission spectrum, the emission peak having an emission intensity higher than that at a wavelength 10 nm away from the peak wavelength in both directions.
• the wavelength of the emission peak is designated “emission peak wavelength” or simply "peak wavelength”.
• the emission peak intensities descend in the order of the short wavelength emission peak, the long wavelength emission peak, and the intermediate wavelength emission peak.
• the intensity of the short wavelength peak being taken as 100
• the intensity of the intermediate wavelength peak is 30 to 54, preferably 35 to 52, more preferably 40 to 50
• that of the long wavelength peak is 55 to 90, preferably 59 to 85, more preferably 60 to 80.
• the dispersion-type EL device (inorganic EL device) of the invention having ZnS phosphor particles dispersed in a high dielectric constant binder will be described in detail.
• the EL device of the invention includes at least one light emitting layer containing ZnS phosphor particles between facing two electrodes, a transparent electrode and a back electrode.
• the El device preferably includes a dielectric layer, such as an insulating layer or a blocking layer, between the light emitting layer and each electrode for the purpose of preventing breakdown of the EL device and concentrating a stable electric field in the light emitting layer.
• the material serving for emission in the longest wavelength range may be present at any location between the electrodes but is preferably present in an insulating layer, more preferably in the half of an insulating layer closer to the light emitting layer.
• the ZnS phosphor particles preferably contain a metal ion, such as Cr ion, and a rare earth element (e.g., Ce, Eu, Sm, or Tb) as an activator.
• a metal ion such as Cr ion
• a rare earth element e.g., Ce, Eu, Sm, or Tb
• halogens such as Cl, Br, and I, Al, Ga, and In.
• the ZnS phosphor particles may have its emission wavelengths adjusted by means of an activator and a co-activator.
• the ZnS phosphor particles which have an emission peak in the short wavelength region are preferably those activated with copper and chloride, hereinafter also referred to as ZnS:Cu,Cl phosphor particles.
• the Cu content of the ZnS: Cu 5 Cl phosphor particles is preferably IxIO "4 to IxIO '2 mol, more preferably 5xlO '4 to 5xlO "3 mol, per mole of ZnS.
• the Cl content of the ZnS:Cu,Cl phosphor particles is preferably IxIO "3 to IxIO 2 mol, more preferably IxIO "2 to IxIO 1 mol, per mole of ZnS.
• the color of luminescence of the EL device may also preferably be adjusted by combining the blue-green emitting phosphor with a blue emitting EL phosphor, such as ZnS:Cu,Br or ZnS:Cu,I, or a green emitting EL phosphor, such as ZnS:Cu,Al, or mixing a blue emitting EL phosphor and a green emitting EL phosphor.
• a blue emitting EL phosphor such as ZnS:Cu,Br or ZnS:Cu,I
• a green emitting EL phosphor such as ZnS:Cu,Al
• the above described luminescent materials be combined with a color conversion material that absorbs the light emitted from the blue-green emitting phosphor particles and converts the blue-green light to red light having an emission peak at 570 to 650 nm (hereinafter referred to as a red conversion material) thereby to obtain white emission.
• a color conversion material that converts the blue- green light to green light having a peak at 515 to 569 nm (hereinafter referred to as a green conversion material) may also be used in combination.
• the red conversion material absorbs the luminescence from the ZnS phosphor material to emit red light
• all the peaks of the emission spectrum are decided by subtracting the absorption by the red emitting material from the luminescence of the blue-green emitting ZnS phosphor material and overlapping the residual peak of the blue-green luminescence with the peak of the red luminescence by the color conversion material. Because the absorption by the red emitting material varies with wavelength, i.e., exhibits a maximum and a minimum, it follows that an additional peak appears in the emission spectrum of the combined system, whereby white emission with high color rendering properties is obtained.
• a red emitting phosphor material (red EL material) and a green emitting phosphor material (green EL material) may be used in place of, or in addition to, the red conversion material and the green conversion material.
• red or green emitting phosphor material it is preferably incorporated into the light emitting layer.
• the green emitting phosphor material include, but are not limited to, ZnSrCu, Al and ZnS:Cu,Ga.
• the red emitting phosphor materials include, but are not limited to, ZnS: Cu 5 In and CaS: Eu 5 Ce.
• the phosphor materials including the blue-green emitting ZnS phosphors, the red emitting phosphors, and the green emitting phosphors, are not limited in average particle size and coefficient of particle size variation.
• the average particle size is preferably 1 ⁇ m or greater and smaller than 20 ⁇ m, more preferably 2 ⁇ m or greater than smaller than 19 ⁇ m, with the coefficient of size variation being preferably 3% or greater and smaller than 40%.
• the ZnS phosphor particles for use in the invention can be prepared by baking (solid phase process) widely employed in the art irrespective of the color of electroluminescence.
• zinc sulfide powder of 10 to 50 nm in size (crude powder) is prepared in a liquid phase, which is used as a host material (primary particles).
• Zinc sulfide takes on a high temperature stable hexagonal phase and a low temperature stable cubic phase, either of which or a mixture of which is useful.
• An impurity called an activator or a co-activator and a flux are mixed into the host material, and the mixture is baked in a crucible at a high temperature of from 900° to 1300°C for 30 minutes to 10 hours (first baking) to obtain a phosphor precursor powder.
• the first baking is preferably performed at 950° to 125O 0 C, more preferably 1000° to 1200 0 C, for 0.5 to 6 hours, more preferably 1 to 4 hours.
• the amount of the flux to be added is preferably 20% or more, more preferably 30% or more, even more preferably 40% or more, by mass.
• the proportion of the flux here is shown as follows:
• the proportion of the flux (% by mass) the mass of the flux/(the mass of the raw material phosphor primary particles + the mass of the flux).
• the copper as an activator and the raw powder of phosphor are regarded as integral with each other so that the mass of the copper is included in the mass of the phosphor raw material.
• a flux may have its mass varied between room temperature and a baking temperature.
• barium chloride exists in the form of BaCl 2 -2H 2 O at room temperature but loses the water of hydration to become BaCl 2 at a baking temperature.
• amount of the flux indicates the mass of the flux in a stable condition at room temperature.
• the precursor powder obtained by the baking is preferably washed with ion exchanged water to remove excess activator, co-activator, and flux.
• the precursor powder as obtained by the first baking has a spontaneously generated planar stacking fault (twin structure).
• the stacking fault density may be increased greatly without destroying the particles by adding an impact force in a certain range.
• An impact force may be applied by, for example, bringing the precursor powder particles into direct contact with each other, blending the precursor powder with spherical beads of, e.g., alumina (ball milling), or colliding accelerated precursor powder particles against each other.
• spherical beads of, e.g., alumina (ball milling) e.g., alumina (ball milling)
• the former crystal structure is represented by three layers of the closest packed planes ((111) plane) ABCABC, while the latter crystal structure is arranged by repeating every other closest packed plane, represented as ABAB perpendicular to the c-axis.
• ABAB hexagonal structure
• the precursor powder is then subjected to second baking.
• the second baking is conducted at a temperature lower than in the first baking in the range of from 500° to 800°C for a shorter time of from 30 minutes to 3 hours to achieve annealing.
• the activator is thus caused to precipitate concentrically at the stacking faults.
• the phosphor precursor particles are subjected to etching treatment with an acid (e.g., hydrochloric acid) to be cleared of any metal oxide on their surface and washed with, e.g., a KCN solution to remove copper sulfide from their surface, followed by drying to obtain EL phosphor particles.
• an acid e.g., hydrochloric acid
• KCN solution e.g., a KCN solution to remove copper sulfide from their surface
• vapor phase methods such as laser ablation, CVD, plasma assisted method, sputtering, and a combination of resistance heating or electron beam irradiation and vacuum deposition on fluidized oil film
• liquid phase methods such as double decomposition, precursor pyrolysis, reversed micellation, a combination of any of these liquid phase methods with high temperature baking, and freeze drying
• urea melt method such as urea melt method.
• the average particle size and the particle size variation coefficient of the phosphor particles may be determined by the laser scattering method using, for example, a laser diffraction/scattering particle size analyzer LA-920 from Horiba, Ltd.
• the term "average particle size" denotes a median diameter.
• At least one of the phosphor materials used in the EL device of the invention should comprise zinc sulfide as a host material. It is preferred that other phosphor materials also comprise zinc sulfide as a host material. It is preferred that every phosphor material contain at least one metal element belonging to the second transition series of Groups 6 through 10, particularly at least one of molybdenum, platinum, and iridium. These metal elements are preferably present in zinc sulfide in a concentration of Ixl0 "7 to IxIO 3 mol, more preferably IxIO "6 to 5xlO ⁇ 4 mol, per mole of zinc sulfide.
• the metal element is preferably incorporated into the zinc sulfide particles by thoroughly slurring in deionized water together with zinc sulfide powder and a predetermined amount of copper sulfate, drying the slurry, and baking the dry powder with a co-activator and a flux.
• the metal may also be preferably incorporated into the zinc sulfide particles by blending a powder of a complex containing the metal with a flux or a co-activator and baking zinc sulfide powder together with the blend.
• any compound containing the metal element to be incorporated may be used as a source of the metal, it is preferred to use a metal complex having oxygen or nitrogen coordinated to a metal or a metal ion.
• the ligand of the complex may be either an organic compound or an inorganic compound.
• the phosphor particles may have a non-luminous shell on their surface as taught in JP 2005-28391 IA, paras. [0028] through [0033].
• Light Emitting Layer
• the light emitting layer is formed by dispersing the above-described phosphor particles in an organic liquid medium and applying the resulting dispersion to a substrate.
• the liquid medium include organic polymers and high boiling organic solvents.
• Organic binders composed mainly of organic polymers are preferred.
• the organic binder is preferably one having a high dielectric constant.
• the organic binder is preferably chosen from fluoropolymers (e.g., those having a fluoroethylene unit or a chlorotrifluoroethylene unit), polysaccharides having cyanoethylated hydroxyl groups (e.g., cyanoethyl pullulan and cyanoethyl cellulose), polyvinyl alcohols (e.g., cyanoethylated polyvinyl alcohol), phenol resins, polyethylene, polypropylene, polystyrene resins, silicone resins, epoxy resins, polyvinylidene fluoride, and so forth.
• the dielectric constant of the binder may be adjusted by appropriately mixing fine particles of high dielectric constant substances, such as BaTiO 3 and SrTiO 3 , into the binder.
• the phosphor particles are dispersed in the binder by means of a homogenizer, a planetary mixer, a roll mixer, an ultrasonic disperser, and so on.
• the amount of the binder to be used is preferably such as to give a phosphor content of 30% to 90%, more preferably 60% to 85%, by mass based on the total solids content of the light emitting layer. With the recited phosphor content, a smooth surface of the light emitting layer is assured.
• phosphor content refers to the total content of all the phosphor particles used.
• a particularly preferred binder system is one containing at least 20%, more preferably 50% or more, by mass of a polymer having cyanoethylated hydroxyl groups relative to the total mass of organic liquid media used in the light emitting layer.
• the thickness of the light emitting layer is preferably at least 20 ⁇ m and less than 80 ⁇ m, more preferably at least 25 ⁇ m and less than 75 ⁇ m. With a light emitting layer thickness of 20 ⁇ m or more, a light emitting layer with a smooth surface is formed. With a thickness less than 80 ⁇ m, an electric field is effectively applied to the phosphor particles.
• a blocking layer is provided as hereinafter described, it is recommended to reduce the thickness of an insulating layer hereinafter described and increase the thickness of the light emitting layer thereby to compensate for the reduction in initial brightness while securing sufficient durability. To further secure good initial brightness, the thickness of the light emitting layer is preferably not more than 70 ⁇ m. Blocking Layer
• the EL device of the invention may have a blocking layer between the transparent electrode and the light emitting layer.
• a blocking layer for the details of the blocking layer, reference is made to, e.g., JP 2007-12466A, paras. [0013] through [0020]. Insulating Layer
• the insulating layer of the EL device of the invention may be of any material having a high dielectric constant, high insulating properties, and a high dielectric breakdown.
• a dielectric material include metal oxides and metal nitrides, such as BaTiO 3 , KNbO 3 , LiNbO 3 , LiTaO 3 , Ta 2 O 3 , BaTa 2 O 6 , Y 2 O 3 , Al 2 O 3 , and AlON.
• the insulating layer may be formed as a homogeneous layer or a particulate layer containing an organic binder. For example, a film formed of BaTiO 3 particles and BaTiO 3 sol may be used as described in Mat. Res. Bull, vol. 36, p. 1065.
• the thickness of the insulating layer is preferably 10 ⁇ m or more and less than 35 ⁇ m, more preferably 12 ⁇ m or more and less than 33 ⁇ m, even more preferably 15 ⁇ m or more and less than 31 ⁇ m. Too thin an insulating layer easily undergoes dielectric breakdown. Too thick an insulating layer lessens the voltage applied to the light emitting layer, resulting in substantial reduction in luminescence efficiency.
• Examples of the organic binder for use in the insulating layer include polymers with a relatively high dielectric constant, such as cyanoethyl pullulan, cyanoethylated polyvinyl alcohol, and cyanoethyl cellulose resins, and other resins, such as polyethylene, polypropylene, polystyrene resins, silicone resins, epoxy resins, and polyvinylidene fluoride.
• the dielectric constant may be adjusted by appropriately mixing fine particles of high dielectric constant substances, such as BaTiO 3 and SrTiO 3 , into the resins.
• the insulating particles can be dispersed by means of a homogenizer, a planetary mixer, a roll mixer, an ultrasonic disperser, and so on. Red Color Material
• the EL device of the invention may contain, in addition to the blue-green emitting ZnS phosphor particles, at least one of a red color conversion material, a green color conversion material, a red emitting EL phosphor, and a green emitting EL phosphor.
• the red or green conversion material is an organic material that absorbs luminescence of zinc sulfide to convert it to red or green light
• the red or green emitting EL phosphors are inorganic materials.
• Organic fluorescent dyes or pigments are preferably used as the color conversion materials.
• the organic fluorescent dye or pigment may be dispersed in the light emitting layer or the insulating layer and may be located between the light emitting layer and the transparent electrode or on the opposite side of the light-emitting layer to the transparent electrode.
• the red or green emitting EL phosphors may be incorporated into the light emitting layer together with the blue-green emitting phosphor particles or disposed between the transparent electrode and the insulating layer as a red or green emitting EL phosphor layer independent of the blue-green emitting layer.
• White light emitted from the EL device of the invention preferably contains a red component having a wavelength of 590 to 650 nm.
• a red conversion material may be incorporated into the light emitting layer or be disposed between the light emitting layer and the transparent electrode or on the opposite side of the light-emitting layer to the transparent electrode but is most preferably incorporated into the insulating layer. It is preferred that all the insulating layers of the EL device contain the color conversion material. It is more preferred that the EL device has two or more divided insulating layers, one or more of which contains the color conversion material.
• the layer containing the color conversion material is preferably located between a red conversion material-free insulating layer and the light emitting layer. It is also preferred that the layer containing the red conversion material be sandwiched between red conversion material-free insulating layers.
• the thickness of the red conversion material-containing layer is preferably 1 to 20 ⁇ m, more preferably 3 to 17 ⁇ m.
• the concentration of the red conversion material in the insulating layer is preferably 1% to 20% by mass, more preferably 3% to 15% by mass, based on the dielectric material typified by BaTiO 3 .
• the thickness of the red conversion material is preferably 1 to 20 ⁇ m, more preferably 3 to 10 ⁇ m.
• the concentration of the red conversion material in the insulating layer is preferably 1% to 30% by mass, more preferably 3% to 20% by mass, based on the dielectric material.
• the red conversion material-containing layer be free of a dielectric material and composed solely of a high dielectric constant binder and the red conversion material.
• organic fluorescent dyes or pigments are preferably used as the red conversion material.
• examples of preferred compounds constituting the luminescent center of the fluorescent pigments or dyes include compounds having rhodamine, lactone, xanthene, quinoline, benzothiazole, triethylindoline, perylene, triphenylene or dicyanomethylene as a skeleton.
• Cyanine dyes, azo dyes, polyphenylene vinylene polymers, disilane oligothienylene polymers, ruthenium complexes, europium complexes, and erbium complexes are also preferred. These compounds may be used either individually or as a mixture of two or more thereof.
• the color conversion material may be used as dispersed in, e.g., a polymer.
• the fluorescent pigment having an emission peak wavelength in the range recited above is exemplified by SEL 1003 available from Shinloihi Co., Ltd.
• the peak wavelength of the fluorescent pigment or dye used may be adjusted to within the range by using a filter, such as a band reflection filter.
• the transparent electrode for use in the invention is obtained by evenly applying a transparent, electrically conductive material, such as indium tin oxide (ITO), tin oxide, antimony-doped tin oxide, zinc-doped tin oxide, or zinc oxide, to a transparent substrate, such as a glass substrate or a transparent film of polyethylene terephthalate or triacetyl cellulose, to form a thin film by vapor deposition, coating, printing, or any other means.
• ITO indium tin oxide
• tin oxide antimony-doped tin oxide
• zinc-doped tin oxide zinc oxide
• a transparent substrate such as a glass substrate or a transparent film of polyethylene terephthalate or triacetyl cellulose
• conductive or “conductivity” means “electrically conductive” or “electrical conductivity” unless otherwise specified.
• the transparent electrode may be a multilayer structure having a thin film of silver sandwiched in between high refractive index layers.
• Conductive polymers including conjugate polymers, such as polyaniline and polypyrrole, are also used to provide a transparent electrode.
• conjugate polymers such as polyaniline and polypyrrole
• the details of the transparent conductive materials reference can be made to DENJIHA SHIELD ZAIRYO NO GENJYO TO SYORAI, Toray Research Center, Inc. and JP 9-147639A.
• a transparent conductive sheet having improved conductivity is also preferred, which is obtained by preparing a transparent conductive sheet or conductive polymer formed of the above described transparent conductive material on the above described transparent film and disposing thereon a wire structure formed by evenly arranging fine strands of metal and/or alloy wire in a network, comb, grid, or a like pattern.
• the fine wire when used in combination, is preferably of copper, silver, nickel, aluminum, or an alloy thereof.
• wire of the transparent conductive material recited above may be used in place of the metal or alloy wire. It is preferred to use wire materials having high electrical and thermal conductivity.
• the width of the wire strand is preferably, but not limited to, about 0.1 ⁇ m to 1000 ⁇ m.
• the pitch of the wire strands i.e., the distance between adjacent wire strands, is preferably 50 ⁇ m to 5 cm, more preferably 100 ⁇ m to 1 cm.
• the height (or thickness) of the wire structure is preferably 0.1 to 10 ⁇ m, more preferably 0.5 to 5 ⁇ m.
• the wire structure may be exposed on the surface of the transparent conductive material or covered with the transparent conductive material.
• the conductive surface of the transparent conductive electrode preferably has a surface roughness of 5 ⁇ m or less. In terms of good adhesion, the surface roughness is more preferably 0.01 to 5 ⁇ m, even more preferably 0.05 to 3 ⁇ m.
• the term "surface roughness" of the conductive surface denotes an average amplitude of surface roughness over a measuring area of 5 mm square as measured with a three dimensional surface roughness meter, e.g., Surfcom 575A-3DF from Tokyo Seimitsu Co., Ltd. Surface roughness below the resolution of a surface roughness meter is determined by the measurement using a scanning tunneling microscope or an electron microscope.
• the strand width is preferably 1/10000 to 1/10 the pitch
• the strand height is preferably 1/100 to 10 times the width.
• the transparent electrode preferably has a surface resistivity of 0.1 to 100 ⁇ /sq, more preferably 1 to 80 ⁇ /sq, as measured in accordance with the method specified in JIS K6911.
• the transparent electrode for use in the invention When in using the fine wire structure of metal and/or alloy, it is desirable to minimize reduction in light transmission. It is desirable to secure a light transmission of at least 90% by limiting the pitch, width, and height of the wire strands within the ranges described. It is preferred for the transparent electrode for use in the invention to have a transmission of at least 70%, more preferably 80% or more, even more preferably 90% or more, at a wavelength of 550 nm.
• the transparent electrode In order to improve the brightness and to provide white light emission, it is preferred for the transparent electrode to have a transmission of at least 80%, more preferably 90% or more, for light of 420 to 650 nm. In order to obtain white light emission, it is more preferred for the transparent electrode to have a transmission of 80% or more for light of 380 to 680 nm. Light transmissions of the transparent electrode are determined using a spectrophotometer.
• the back electrode through which emitted light is not extracted may be of any conductive material selected from among, for example, metals, such as gold, silver, platinum, copper, iron, and aluminum, and graphite as appropriate to the configuration of the EL element, the temperature in the fabrication steps, and the like.
• a transparent electrode made of, e.g., ITO may be used as long as conductivity is secured.
• the method for fabricating the EL device of the invention is not limited. For example, the method described in detail in JP 2007- 12466 A, paras. [0046] through
• a gas barrier laminate film is a preferred sealing film.
• the description hereinafter given about the elements of the present invention may sometimes be based on a representative embodiment of the invention, in which case, it should be understood that the invention is not limited to that particular embodiment.
• the gas barrier laminate film that is preferably used as sealing film preferably includes a base film, at least one inorganic layer, and at least one organic layer.
• the number and the sequence of forming the inorganic layer and the organic layer on the base film are not limited.
• the inorganic layer and the organic layer may be provided on the base film in that order or in the reverse order.
• a laminate film having the organic and inorganic layers alternating on the base film for example, a laminate film having an inorganic layer, an organic layer, and an inorganic layer on the base film in that order is preferred.
• the number of the inorganic layers and that of the organic layers to be laminated are each preferably 1 to 10, more preferably 1 to 5, even more preferably 1 to 3.
• the base film may be laminated with these layers on one or both sides thereof.
• a functional layer may be provided between the base film and the inorganic layer, between the base film and the organic layer, or between the inorganic layer and the organic layer.
• the functional layer include optically functional layers, such as an antireflective layer, a polarizing layer, a color filter, and a light extraction efficiency enhancing layer; mechanically functional layers, such as a hardcoat layer and a stress relaxing layer; electrically functional layers, such as an antistatic layer and a conductive layer; an antifogging layer, an antifouling layer, and a printable layer.
• the organic layer making up the gas barrier laminate film may be a film containing a polymer having a phosphoester group.
• a polymer having a phosphoester group is obtainable by polymerizing a monomer composition containing a polymerizable monomer having at least one phosphoester group.
• a laminate film having an inorganic layer and an organic layer containing a polymer having a phosphoester group on one side of the base film may have, on the opposite side of the based film, a gas barrier laminate composed of an inorganic layer, an organic layer, and an inorganic layer in that order.
• a laminate film having such a gas barrier laminate is capable of preventing invasion of water molecules from the opposite side, thereby to control dimensional change of the gas barrier laminate film and to prevent stress concentration in the inorganic layer or break of the inorganic layer, which leads to further improved durability.
• the monomer having a phosphoester group is preferably represented by the following formula (1).
• Z 1 represents Ac 2 -O-X 2 -, a substituent having no polymerizable group or a hydrogen atom
• Z represents Ac -O-X -, a substituent having no polymerizable group or a hydrogen atom
• Ac 1 , Ac 2 , and Ac each independently represents an acryloyl group or a methacryloyl group
• X 1 , X 2 , and X 3 each independently represents an alkylene group, an alkyleneoxy group, an alkyleneoxycarbonyl group, an alkylenecarbonyloxy group, or a combination thereof.
• the monomer represented by formula (1) may be a monofunctional monomer represented by formula (2) below, a bifunctional monomer represented by formula (3) below, or a trifunctional monomer represented by formula (4) below.
• R 1 and R each independently represent a substituent having no polymerizable group or a hydrogen atom.
• each of X 1 , X 2 , and X 3 preferably contains 1 to 12 carbon atoms, more preferably 1 to 6 carbon atoms, even more preferably 1 to 4 carbon atoms.
• Examples of the alkylene group or the alkylene moiety of the alkyleneoxy, alkyleneoxycarbonyl, or alkylenecarbonyloxy group as represented by X 1 , X 2 , and X 3 include methylene, ethylene, propylene, butyl ene, pentylene, and hexylene.
• the alkylene group or moiety may be straight chain or branched but is preferably straight chain.
• Each of X 1 , X 2 , and X 3 is preferably an alkylene group.
• Examples of the substituent having no polymerizable group in formulae (1) to (4) include an alkyl group, an alkoxy group, an aryl group, an aryloxy group, and a combination thereof.
• the substituent having no polymerizable group is preferably an alkyl group or an alkoxy group, more preferably an alkoxy group.
• the alkyl group preferably contains 1 to 12 carbon atoms, more preferably 1 to 9 carbon atoms, even more preferably 1 to 6 carbon atoms.
• Examples of the alkyl group are methyl, ethyl, propyl, butyl, pentyl, and hexyl.
• the alkyl group may be straight chain or branched but is preferably straight chain.
• the alkyl group may be substituted with an alkoxy group, an aryl group, an aryloxy group, etc.
• the aryl group preferably contains 6 to 14 carbon atoms, more preferably 6 to 10 carbon atoms. Examples of the aryl group are phenyl, 1-naphthyl, and 2-naphthyl.
• the aryl group may be substituted with an alkyl group, alkoxy group, an aryloxy group, etc.
• the description of the alkyl group and the aryl group given above applies to the alkyl moiety of the alkoxy group and the aryl moiety of the aryloxy group, respectively.
• the monomers of formula (1) may be used either individually or in combination of two or more thereof. When two or more monomers of formula (1) are used in combination, two ore more monomers among a monofunctional monomer represented by formula (2), a bifunctional monomer represented by formula (3), and a trifunctional monomer represented by formula (4) may be combined.
• the polymerizable monomers having a phosphoester group may be synthesized or may be a commercially available compound, such as those available under the tradename KAYAMER from Nippon Kayaku Co., Ltd. and those available under the tradename PHOSMER from Uni-Chemical Co., Ltd.
• the EL device of the invention is particularly effective in applications where a high luminance, e.g., of 600 cd/m 2 or more, is required, specifically, where the EL device is driven by applying a voltage of 100 to 500 V between the transparent electrode and the back electrode or driven by an alternating current source at a frequency of 800 Hz to 4000 kHz.
• Example 1 The dispersion-type EL device of the invention will now be illustrated with reference to Examples but is not construed as being limited thereto.
• Example 1 The dispersion-type EL device of the invention will now be illustrated with reference to Examples but is not construed as being limited thereto.
• a first layer (an insulating layer, thickness: 30 ⁇ m) and a second layer (light emitting layer, thickness: 55 ⁇ m) shown below were formed in that order on a 70 ⁇ m-thick aluminum electrode (back electrode) by applying the respective coating compositions having the viscosity controlled with dimethylformamide and drying at 11O 0 C for 10 hours.
• the second layer (light emitting layer) and the ITO layer were brought into contact and press bonded using a heat roller at 19O 0 C in a nitrogen atmosphere.
• the compositions of the first and second layers described below are in mass per square meter of an EL device.
• Barium titanate particles (average sphere equivalent diameter: 0.05 ⁇ m)
• Red conversion material (SEL 1003 from Shinloihi Co., Ltd.) 1.0 g
• Second layer (light emitting layer)
• Phosphor particles A (see below) 120.0 g
• the mixture was baked at 1200 0 C for 4 hours to give a phosphor precursor.
• the phosphor precursor was washed 10 times with ion exchanged water, dried, ground in a ball mill, and annealed at 700 0 C for 4 hours.
• the resulting phosphor particles were cleaned with a 10% KCN aqueous solution to remove excess Cu ions (copper sulfide) from the surface, followed by washing five times with water to produce phosphor particles A.
• Phosphor particles A had an average particle size of 24 ⁇ m with a particle size variation coefficient of 36% as measured with a laser diffraction/scattering particle size analyzer LA-920 from Horiba, Ltd.
• An electrode terminal (a 60 ⁇ m-thick aluminum sheet) was attached to each of the aluminum electrode and the transparent electrode.
• the structure was sealed in between a pair of moisture-proof sealing films (GX film from Toppan Printing Co., Ltd.), which were heat sealed together while evacuating.
• the resulting EL device was designated EL device 101.
• EL devices designated 102 and 103, were fabricated in the same manner as for EL device 101, except for replacing SEL 1003 with a red conversion material FA 001 or FA 003 (both from Shinloihi Co., Ltd.), respectively.
• Each of EL devices 101 to 103 was operated by continuously applying a voltage of 300 V using an alternating current source having a frequency of 1000 Hz.
• the emission spectrum of each device was determined to see if it had a peak in each of the specific wavelength ranges and to obtain the peak wavelength in each wavelength range and the relative peak intensity in each wavelength range with the intensity of the peak in the shortest wavelength range being taken as 100. The results obtained are shown in Table 1.
• Table 1 Table 1
• Each EL device was driven at a driving voltage (around 140 V) and a frequency (around 1.1 kHz) both adjusted to provide a luminance of 500 cd/m 2 .
• the color rendering index of the emission was determined.
• the results are shown in Table 2.
• Transparent media G-Color Print, from Fuji Film
• Table 2 Table 2
• Phosphor particles B were prepared in the same manner as for phosphor particles A, except for changing the amounts of the fluxes, BaCl 2 -2H 2 O, MgCl 2 -OH 2 O, and SrCl 2 -OH 2 O, to 4.2 g, 11.2 g, and 9.0 g, respectively.
• Phosphor particles B had an average particle size of 17 ⁇ m with a variation coefficient of 31%.
• EL devices 104 to 106 were fabricated in the same manner as for EL devices 101 to 103, respectively, except for replacing phosphor particles A with phosphor particles B.
• EL devices 104 to 106 were equal to EL devices 101 to 103 in emission peak profile, color rendition, and G-color evaluation results. EL devices 104 to 106 exhibited approximately 1.4 times the luminance of EL devices 101 to 103 owing to the reduced size of the phosphor particles. In the evaluation of G-color, the luminance of 500 cd/m was obtained at a driving voltage of about 120 V, which was about 20 V lower than required in Example 1. It was thus proved that although the color rendering properties do not change with the change of phosphor particle size, the improvement in brightness allows for reduction in driving voltage.
• Example 3 Example 3
• EL devices 107 to 109 were fabricated and evaluated in the same manner as in Example 2, except for changing the layer structure as follows. Both the first and the second layers had a thickness of 14 ⁇ m.
• First layer (insulating layer, containing no red conversion material)
• Barium titanate particles (average sphere equivalent diameter: 0.05 ⁇ m)
• Second layer (insulating layer, containing red conversion material)
• Barium titanate particles (average sphere equivalent diameter: 0.05 ⁇ m)
• EL device 110 was fabricated in the same manner as for EL device 104 of Example 2, except for using no red conversion material and replacing 10% and 30% of the weight of the phosphor particles with ZnS:Cu,Al and ZnS:Cu,In, respectively.
• ZnS:Cu,Al and ZnS:Cu,In were obtained in the same manner as described in Example 2, except for adding 0.70 g Of Al 2 S 3 and 0.15 g Of In 2 S 3 , respectively.
• ZnS:Cu,Al had an average particle size of 18 ⁇ m with a variation coefficient of 33%
• ZnS:Cu,In had an average particle size of 19 ⁇ m with a variation coefficient of 37%.
• the resulting EL device had an emission peak in each of the three wavelength ranges similarly to EL device 104 of Example 2 and exhibited satisfactory results in color rendition and color reproduction in G-color evaluation.
• an EL device excellent in color rendering properties and color reproduction is provided by designing the emission spectrum to have at least one peak in each of three wavelength ranges: (1) 450 to 514 nm, (2) 515 to 569 nm, and (3) 570 to 650 nm, at peak intensities descending in the order of (1), (3), and (2).
• Example 5
• An EL device, designated 201, was fabricated in the same manner as for EL device 101 of Example 1, except for replacing GX film with a polyethylene naphthalate film Teonex Q65FA from Teijin Du Pont Films Japan, Ltd. as a sealing film.
• composition was applied to the smooth side of the same polyethylene naphthalate base film as used above (Teonex Q65FA) using a #6 wire bar and irradiated with UV light at an illuminance of 350 mW/cm 2 to give a total energy of 500 mJ/cm 2 using a 160 W/cm air-cooled metal halide lamp (from Eye Graphics) in an environment purged with nitrogen having an oxygen concentration of not more than 0.1% to form an organic layer with a thickness of about 500 ran.
• An inorganic layer of aluminum oxide (AlO x ) was formed to a thickness of 50 nm on the organic layer by sputtering using Al as a target, argon as a discharge gas, and oxygen as a reactive gas.
• the same coating composition as used above to form the organic layer was applied to the inorganic layer with a #6 wire bar and irradiated with UV light at an illuminance of 350 mW/cm 2 to give a total energy of 500 mJ/cm 2 using a 160 W/cm air-cooled metal halide lamp (from Eye Graphics) in an environment purged with nitrogen having an oxygen concentration of not more than 0.1% to form an organic layer with a thickness of about 500 nm.
• a laminate film having a structure of organic layer/inorganic layer/organic layer on the base film.
• EL devices designated 202A to 202G were fabricated in the same manner as for EL device 201, except for using laminate films 202 A to 202G, respectively, as a sealing film.
• Each of EL devices 201 and 202 A to 202G was continuously operated for more than 2500 hours in an environment of 40 0 C and 85% RH.
• the emission intensity of the device at the peak wavelength of 487 run was measured at the beginning (at 0 hr), after 24 hours, and after 2500 hours.
• the results obtained are shown in Table 4, taking the intensity at 0 hr of EL device 201 as 100.
• the results in Table 4 prove that all of EL devices 202A to 202G undergo little reduction in emission intensity after 24 hour operation. In particular, EL devices 202A to 202C showed little reduction in emission intensity even after continuous operation for 2500 hours.
• the invention provides a dispersion-type EL device that achieves high color rendering properties on light emission.

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