JPH0437560B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to an electroluminescent device (electroluminescent device), and more particularly to an electroluminescent device that is flexible and has excellent durability. [Prior art] Conventionally, electroluminescent devices have been known that have a high dielectric constant layer, a light emitting layer, a transparent electrode layer, a water trapping layer, etc. laminated on an electrode layer.The light emitting layer is made of copper or aluminum. Fluorescent powders such as doped zinc sulfide dispersed in high dielectric constant binders such as cyanoethyl cellulose are used;
There is a problem in that the luminance of light emission decreases due to moisture absorption. For this reason, a method is known in which the entire electroluminescent device is wrapped in a transparent moisture-proof protective sheet. Heretofore known protective sheets include the following. A method using a plastic film with excellent moisture resistance, such as monochloride trifluoroethylene (hereinafter abbreviated as PCTFE). A vapor-deposited layer of silicon oxide is provided between two layers of polyolefin film (Utility Model Publication No. 61-42319). A transparent resin film with a sputtered film of silicon oxide or silicon nitride (Utility Model Publication No. 62-24959). [Problems to be solved by the invention] However, these moisture-proof films have the following problems.
I had the following problem. When using plastic film,
Due to insufficient moisture resistance, it is necessary to use a thick film, and flexibility is poor. Most moisture-proof
Even in the case of PCTFE film, a thickness of 200 μm or more is required. Furthermore, since plastic film has poor moisture-proofing performance at high temperatures, the life of the electroluminescent device will be shortened if used at high temperatures. Products made of vapor-deposited or sputtered silicon oxide or silicon nitride must be thicker in order to obtain high moisture-proof performance.
It needs to be thicker than 300A, practically 500A or more, and because of this, it tends to crack when bent, has poor adhesion, and lacks flexibility. Also,
As the film thickness of silicon oxide or silicon nitride increases, the transparency decreases, resulting in a decrease in luminance. In order to solve such problems, the present inventors
After extensive research, we developed a new protective sheet with excellent moisture resistance, flexibility, and transparency.
The inventors have discovered that it is possible to obtain an electroluminescent device with high luminance and excellent flexibility and durability, resulting in the present invention. [Means for Solving the Problems] That is, the present invention provides an electroluminescent device comprising a transparent electrode, an electroluminescent layer, a high dielectric constant layer, an electrode, and a protective sheet surrounding these, wherein the protective sheet is
Provided is an electroluminescent device comprising a plastic film laminated with a metal oxide layer of at least one metal selected from the group consisting of In, Sn, Zn, Zr and Ti. The details of the present invention will be explained below with reference to the drawings. FIG. 1 is a cross-sectional view schematically showing one embodiment of the electroluminescent device of the present invention. In FIG. 1, reference numeral 1 denotes an electrode layer formed by adhering aluminum foil, copper foil, etc. to a plastic film such as a polyester film, or by depositing aluminum, copper, indium oxide, etc. in vacuum. 2 is an electrode layer using a paint in which high dielectric constant powder such as barium titanate or strontium titanate is dispersed in a high dielectric constant binder such as cyanoethyl cellulose, sucrose, glycerol pullulan, or glycerose sucrose together with a solvent such as DMF. This is a high dielectric constant layer that is screen printed and dried on top. 3 is a high-permittivity layer using a paint in which a phosphor such as zinc sulfide, zinc selenide, or cadmium sulfide doped with copper, aluminum, or manganese is dispersed together with a solvent in a high-permittivity binder such as cyanoethyl cellulose or sucrose. This is a luminescent layer that is screen printed and dried on top. 4
tin oxide, on one side of polyester film, etc.
This is a transparent electrode layer in which a transparent conductive layer made of indium oxide, indium oxide-tin oxide composite oxide, etc. is formed, and the transparent conductive surface is laminated with a light emitting layer by a method such as hot pressing. 5 is a protective sheet made of a plastic film laminated with a metal oxide layer of at least one metal selected from the group consisting of In, Sn, Zn, Zr and Ti; The electrode layer, the high dielectric constant layer, the light emitting layer and the transparent electrode layer are adhesively laminated so as to cover the entire electroluminescent body. The interior of the electroluminescent element may contain a water-absorbing layer such as a polyamide film, if necessary. FIG. 2 is a cross-sectional view schematically showing an example of a protective sheet used in the present invention. In FIG. 2, 11 is a plastic film, 12 is a metal oxide layer made of at least one metal selected from the group consisting of In, Sn, Zn, Zr, and Ti, and 13 is a thermoplastic film for bonding the protective sheet. It is an adhesive layer. FIG. 3 is a cross-sectional view schematically showing another example of the protective sheet used in the present invention. In FIG. 3, 14 is a plastic film, 15 is a metal oxide layer made of at least one metal selected from the group consisting of In, Sn, Zn, Zr, and Ti, and 16 is a metal oxide layer on the metal oxide layer. 17 is another metal oxide layer laminated on the organic thin film layer, and 18 is a thermoplastic adhesive layer for bonding the protective sheet. be. The protective sheet of the present invention has a plastic film laminated with a metal oxide layer made of at least one metal selected from the group consisting of In, Sn, Zn, Zr, and Ti. As the plastic film, the following typical organic polymers can be melted or melt-extruded and stretched in the longitudinal direction and/or width direction as necessary. Typical organic polymers include polyolefins such as polyethylene and polypropylene, polyesters such as polyethylene terephthalate and polyethylene-2,6-naphthalate, vinyl chloride, vinylidene chloride, aromatic polyamide, polyamideimide, polyimide, polyetherimide, polysulfone, Polyether sulfone, polyether ether ketone, polyarylate, polyphenylene sulfide, polyphenylene oxide, tetrafluoroethylene, monochloride trifluoroethylene,
Examples include fluorinated ethylene propylene copolymers. Two or more layers of these plastic films may be laminated. Further, it may be a copolymer of these or a copolymer with another organic polymer, or it may contain another organic polymer. Known additives such as antistatic agents, ultraviolet absorbers, plasticizers, and lubricants may be added to these organic polymers. The light transmittance of the plastic film of the present invention is important for increasing the luminance of the electroluminescent device, and the total light transmittance in white light is at least
It is desirable that it be 70% or more, preferably 80% or more. Prior to the formation of the metal oxide layer, the plastic film of the present invention is subjected to surface treatments such as corona discharge treatment, plasma treatment, glow discharge treatment, reverse sputtering treatment, and surface roughening treatment, as well as known anchor coating treatment. Also good. The thickness of the plastic film of the present invention is not particularly limited, but from the viewpoint of flexibility and shape retention of the electroluminescent device, it is preferably in the range of 10 to 200 μm, more preferably in the range of 25 to 100 μm. This is desirable. A metal oxide layer of at least one metal selected from the group consisting of In, Sn, Zn, Zr and Ti is laminated on at least one surface of the plastic film. The metal oxide layer can be laminated using vacuum evaporation,
Physical vapor deposition methods such as reactive vapor deposition, ion plating, and sputtering can be used. Among these, the method using sputtering is most preferable in terms of durability and flexibility of the electroluminescent device. Sputtering as used in the present invention refers to direct current two-pole sputtering, high-frequency two-pole sputtering, direct current magnetron sputtering, high-frequency magnetron sputtering, etc.
All known sputtering methods are included. It also includes so-called reactive sputtering, in which a reactive gas such as oxygen is introduced during sputtering. The metal oxide layer used in the present invention includes:
It is a metal oxide of at least one metal selected from the group consisting of In, Sn, Zn, Zr, and Ti, and may be a mixture of two or more metal oxides or a composite oxide. Among them, In, Sn, Zn oxides, and In−
A composite oxide of Sn is preferred, and most preferably,
In, Sn oxides, and In-Sn composite oxides are desirable. These metal oxide layers are composed of In ₂ O ₃ ,
Stoichiometric oxides such as SnO, SnO ₂ , ZnO, ZrO ₂ and TiO ₂ are preferred, but non-stoichiometric oxides, such as those with a small number or excess of oxygen atoms relative to metal atoms, are preferred. may contain small amounts of oxidized oxides or unoxidized metal atoms. The metal oxide layer contains elements other than the metal atoms mentioned above, such as Fe, Sb, C, Mo, W, Cu, Al,
A trace amount of Si, Ni, etc. may be included. The thickness of the metal oxide layer is preferably in the range of 30 to 250 Å from the viewpoint of moisture resistance and flexibility. These metal oxide layers exhibit moisture-proofing performance at a thickness of 30 Å or more,
Sufficient moisture-proof performance can be obtained with a film thickness of 50 Å or more. Furthermore, even if the film thickness is made thicker than necessary, the moisture-proof performance of these metal oxide layers will not improve;
If it exceeds this value, the transparency and flexibility will deteriorate. More preferably, it is 50 Å to 200 Å. Moreover, when two or more metal oxide layers are laminated on the plastic film, the moisture-proof performance is further improved. In this case, it is preferable that each metal oxide layer is separated by an organic thin film layer. For this purpose, a method is used in which a metal oxide layer is formed on a plastic film, an organic thin film layer is formed on this metal oxide layer, and another metal oxide layer is formed on this organic thin film layer. This is desirable. Resins used for the organic thin film layer include polyester resin, acrylic resin, epoxy resin,
Examples include vinyl resin, melamine resin, urethane resin, ionomer, and polycarbonate. In addition, the thickness of the organic thin film layer is 0.1 to 10 μm.
The range is preferably from 0.3 to 2 μm, more preferably from 0.3 to 2 μm.
It is desirable that If necessary, a thermoplastic adhesive layer is laminated on one side of such a protective sheet in order to enclose the entire electroluminescent layer in a bag-like manner. The thermoplastic adhesive layer may be formed on the plastic film side or the metal oxide layer side, but is preferably formed on the metal oxide layer side. The thermoplastic adhesive layer in the present invention refers to a polymer layer that can be bonded by heating and pressure, and typical examples thereof include the following. Polyolefins such as polyethylene, polypropylene, ethylene-propylene copolymers, polyesters, polyamides, ionomers, ethylene vinyl acetate copolymers, acrylic resins such as acrylic esters and methacrylic esters, polyvinyl acetals, phenols, modified epoxy resins, etc. , copolymers and mixtures thereof, but are not necessarily limited thereto. Among these, polyolefins, polyesters, polyamides, ionomers, and ethylene vinyl acetate copolymers are preferred. The thickness of the heat-sealable thermoplastic adhesive layer is
In terms of adhesive strength, the range is preferably 10 to 200 μm, more preferably 30 to 100 μm. Methods for laminating the thermoplastic adhesive layer on the metal oxide layer include a method in which the components of the thermoplastic adhesive layer are dissolved in an organic solvent and coated, and a method in which the components of the thermoplastic adhesive layer are melted and extrusion laminated. Alternatively, a known method can be employed, such as a method in which a sheet of a thermoplastic adhesive layer is prepared in advance and the sheets are adhesively laminated by dry lamination or the like. The heat-sealing temperature of the thermoplastic adhesive layer can be appropriately selected depending on the characteristics of the thermoplastic adhesive layer used, but it is desirable that the thermoplastic adhesive layer can be heat-sealed at a temperature of 80°C to 180°C. [Applications] The electroluminescent device of the present invention can be widely used in fields such as planar illumination and display. Among them, LCD display elements, LCD TV backlights, curved displays,
Alternatively, it can be used for panel displays in automobiles, trains, etc. [Effects] The electroluminescent device of the present invention exhibits excellent moisture-proofing performance with an extremely thin metal oxide layer, so it has excellent flexibility, moisture-proofing at high temperatures, and excellent transparency. , The electroluminescent device can be made thinner, and the like. [Action] Conventionally known silicon oxide and silicon nitride
Moisture-proofing performance is achieved only with a film thickness of 300A or more, whereas the metal oxide layer of at least one metal selected from the group consisting of In, Sn, Zn, Zr, and Ti used in the present invention is extremely thin. Although it is not clear why the film exhibits excellent moisture resistance regardless of its thickness, it is presumed that this is because these metal oxides adhere well to the surface of the plastic film, resulting in a uniform film even at a thin film thickness. Examples will be described below. [Example] Examples 1 to 5 (Creation of electroluminescent material) A biaxially stretched polyethylene terephthalate film (thickness:
A mixed solution of cyanoethyl cellulose (40 parts), copper-doped zinc sulfide powder (60 parts), and DMF (100 parts) was applied by screen printing onto a transparent conductive layer of 80 μm diameter. A light emitting layer was formed. A mixed solution of cyanoethyl cellulose (50 parts), barium titanate powder (50 parts), and DMF (100 parts) is applied onto this luminescent layer using a screen printing method and dried to form a 100 μm high dielectric constant layer. did. Next, the aluminum foil surface of the electrode layer in which the aluminum foil (thickness 35 μm) and the extraction electrode were laminated on one side of the biaxially stretched polyethylene terephthalate film (thickness 50 μm) and the above-mentioned high dielectric constant layer surface were stacked at 150 μm. Heat glue at ℃, cut,
An electroluminescent material with a size of 100×100 mm was obtained. (Preparation of protective sheet) An indium oxide film was formed on one side of a biaxially stretched polyethylene terephthalate film (thickness: 50 μm, width: 300 mm, length: 200 m) by a reactive sputtering method. For reactive sputtering, a winding type magnetron sputtering device is used, and an indium plate (thickness 5 mm,
150 x 350 mm), and while supplying oxygen-argon mixed gas (mixing ratio 40-60% by volume), the winding speed was changed to obtain thicknesses of 60 Å, 100 Å, and 150 Å.
An indium oxide film with a thickness of 200 Å was obtained. Next, a solvent solution of a linear saturated polyester resin was applied onto this indium oxide film using a gravure coating method and dried to form an organic coating layer made of a linear saturated polyester resin with a thickness of 0.5 μm. . On this organic coating layer, a second layer of indium oxide film was formed in the same manner as the first layer. Next, an unstretched polypropylene sheet (thickness: 50 μm) was adhered onto this indium oxide using urethane resin to create a protective sheet. Example 1: Both layers of indium oxide have a thickness of 60 Å. Example 2: Both layers have a thickness of 100 Å. Example 3: Both layers have a thickness of 150 Å. Example 4 has a thickness of both 200 Å, and Example 5 has a thickness of 60 Å for the first layer and 100 Å for the second layer. (Creation of electroluminescent layer) Two protective sheets made of indium oxide and polyethylene terephthalate film are stacked with the unstretched polypropylene sheets facing inside each other, and the electroluminescent material is inserted between them. An electroluminescent device was obtained by bonding at 150°C using a hot press.The obtained electroluminescent device was connected to a power source of 400Hz and 100V, and the initial luminescence brightness (LO) was measured. The luminance was measured using a Sony Tektronix digital photometer and detector (model J-
6503) was used. Next, this electroluminescent device was kept flat and exposed to high temperature and humidity at 60°C and 90%RH while applying voltage.
After storage for 1000 hours, the luminance luminance (L1) was measured and the luminance retention rate A (L1/L0) was determined. At the same time, this electroluminescent element was
Bend the emissive layer in a mm cylinder so that it faces outward and store it at 60°C and 90% RH for 1000 hours under high temperature and high humidity with voltage applied.Then the luminescence brightness (L2)
was measured, and the brightness retention rate B (L2/L0) was determined. Measured initial emission brightness (L0), brightness retention rate A
(L1/L0) and brightness retention rate B (L2/L0) in Table 1.
Shown below. Examples 6 to 9 Electroluminescent devices were created in the same manner as Examples 1 to 5 except that the protective sheets were created as follows,
The initial luminescence brightness (L0) was measured. Then, while keeping it flat, bend it to a diameter of 100 mm.
It was stored for 1000 hours at a high temperature and humidity of 60° C. and 90% RH with the voltage applied, and the brightness retention rate A (L1/L0) and brightness retention rate B (L2/L0) were measured. The results are shown in Table 1. (Preparation of protective sheet) A tin oxide film was formed on one side of a biaxially stretched polyethylene phthalate film (thickness: 75 μm, width: 300 mm, length: 200 m) by a reactive sputtering method. For reactive sputtering, a winding type magnetron sputtering device is used, and a tin plate (thickness 5 mm, 150 x 350 mm) is used.
While supplying oxygen-argon mixed gas (mixing ratio 45-55% by volume), the winding speed was changed to obtain thicknesses of 70 Å, 120 Å, 150 Å, and 180 Å.
A film of tin oxide was obtained. Next, on top of this tin oxide film, an unstretched polypropylene sheet (thickness
50 μm) to create a protective sheet. Example 6 has a tin oxide film with a thickness of 70 Å, Example 7 has a thickness of 120 Å, Example 8 has a thickness of 150 Å, and Example 9 has a tin oxide film with a thickness of 180 Å. Comparative Examples 1 to 3 Electroluminescent elements were created in the same manner as Examples 1 to 5 except that the protective sheet was created as follows,
The initial luminance (L0) was measured. Then, while keeping it flat, bend it to a diameter of 100 mm.
Apply voltage and under high temperature and high humidity at 60℃ and 90%RH.
It was stored for 1000 hours and the brightness retention rate A (L1/L0) and brightness retention rate B (L2/L0) were measured. The results are shown in Table 1. (Preparation of protective sheet) A silicon oxide film was formed on one side of a biaxially stretched polyethylene terephthalate film (thickness: 75 μm, width: 200 mm, length: 200 mm) using a high-frequency sputtering method. High-frequency sputtering connects a high-frequency (13.56MHz) power source to a batch-type magnetron sputtering device.
A silicon oxide plate (6 mm thick, 8 inch diameter) was used as a target, and argon gas was supplied. The film thickness is 100Å, 400Å by controlling the sputtering time.
A silicon oxide film with a thickness of 800 Å was obtained. Next, on top of this silicon oxide film, an unstretched polypropylene sheet (thickness
50 μm) to create a protective sheet. Comparative example 1 has a silicon oxide film with a thickness of 100 Å.
Comparative Example 2 has a thickness of 400 Å, and Comparative Example 3 has a thickness of 800 Å. Comparative Examples 4-5 Electroluminescent elements were created in the same manner as Examples 1-5 except that the protective sheet was created as follows,
The initial luminance (L0) was measured. Then, while keeping it flat, bend it to a diameter of 100 mm.
Apply voltage and under high temperature and high humidity at 60℃ and 90%RH.
It was stored for 1000 hours and the brightness retention rate A (L1/L0) and brightness retention rate B (L2/L0) were measured. The results are shown in Table 1. (Creation of protective sheet) An unstretched polypropylene sheet (thickness 50 μm) is adhered to one side of a biaxially stretched polyethylene terephthalate film (thickness 75 μm, width 200 mm, length 200 mm) using urethane resin, and a protective sheet is formed. Created. Comparative Example 4 is an electroluminescent device using this protective sheet. After performing glow discharge treatment on one side of the monochloride trifluoride ethylene film (thickness 100 μm) obtained by melt extrusion, an unstretched polypropylene sheet (thickness 50 μm) was adhered using urethane resin, and a protective sheet was attached. Created. Comparative Example 5 is an electroluminescent device using this protective sheet. As shown in Table 1, the electroluminescent device according to the present invention has characteristics such as high luminance due to its excellent transparency, excellent durability even under high temperature and high humidity, and little decrease in luminance even when folded. show.

【table】

【table】 [Brief explanation of drawings]

FIG. 1 is a sectional view schematically showing one embodiment of an electroluminescent device according to the present invention. In Figure 1,
1 is an electrode layer, 2 is a high dielectric constant layer, 3 is a light emitting layer, 4 is a transparent electrode layer, and 5 is a protective sheet. FIG. 2 is a cross-sectional view schematically showing an example of a protective sheet used in the present invention. In FIG. 2, 11 is a plastic film, 12 is a metal oxide layer, and 13 is a thermoplastic adhesive layer. FIG. 3 is a cross-sectional view schematically showing another example of the protective sheet used in the present invention. In FIG. 3, 14 is a plastic film, 15 is a metal oxide layer, 16 is an organic thin film layer, 17 is a metal oxide layer, and 18 is a thermoplastic adhesive layer.

Claims (1)

[Claims] 1. An electroluminescent device comprising an electrode layer, a high dielectric constant layer, a light-emitting layer, a transparent electrode layer, and a protective sheet surrounding these, wherein the protective sheet includes In, Sn, Zn,
1. An electroluminescent device comprising a plastic film laminated with a metal oxide layer of at least one metal selected from the group consisting of Zr and Ti. 2. A patent claim characterized in that the protective sheet is made of a plastic film laminated with at least two or more metal oxide layers of at least one metal selected from the group consisting of In, Sn, Zn, Zr, and Ti. The electroluminescent device according to item 1.