JP2004134243A - El element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an EL element capable of forming in a tertiary curved shape by heating work using a hot press or the like. <P>SOLUTION: A polycarbonate film 1 as an amorphous film is used as a substrate. A transparent electrode layer 2 comprising a material in which needle ITO crystal powder is dispersed in a binder is formed on the top of the polycarbonate film 1. A luminescent layer 3, an insulating layer 4, and a back plate layer 5 are laminated in order on the top of the transparent electrode layer 2. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an EL element used for backlighting, in-mold molding, and the like of a liquid crystal display device.
[0002]
[Prior art]
In a conventional EL device, a transparent electrode layer is formed by depositing indium-tin oxide (hereinafter, referred to as "ITO") or the like on the upper surface of a transparent base film made of polyethylene terephthalate (hereinafter, referred to as "PET"). A light emitting layer, an insulating layer, a back electrode layer, and a protective layer are sequentially formed on the upper surface of the transparent electrode layer (see, for example, Patent Document 1).
[0003]
[Patent Document 1]
JP-A-7-114988
[Problems to be solved by the invention]
The conventional EL element described above is not suitable for processing a cubic curved surface. That is, since the PET film is formed of a crystalline polymer, the PET film has characteristics that the heat shrinkage is large, anisotropic, and the heat shrinkage differs depending on the direction. For this reason, when the EL element is formed into a cubic curved shape by heating such as a hot press, peeling or the like occurs between the light emitting layer and the PET film due to the property of the PET film that the heat shrinkage is large, and the heat shrinkage occurs. There is a problem that the desired cubic curved shape cannot be formed due to the characteristic of the PET film that the ratio varies depending on the direction. In addition, the ITO-deposited transparent electrode layer is inferior in flexibility and easily breaks or cracks when formed into a cubic curved surface. As an example, the diameter of the curved surface is limited to about 6 to 8 mm, and if a curved surface smaller than that is formed, cracks will occur in the transparent electrode layer made of ITO, which will cause inconvenience such as non-lighting during EL lighting due to disconnection of the transparent electrode layer. There was a problem that occurred.
[0005]
Thus, the present invention provides an EL element that can be formed into a cubic curved shape without any inconvenience by heating such as hot pressing.
[0006]
[Means for Solving the Problems]
The EL device of the present invention uses an amorphous film as a base material, and a transparent electrode layer made of a material in which acicular ITO crystal powder is dispersed in a binder is formed on the upper surface of the amorphous film. The light emitting layer, the insulating layer, and the back electrode layer are sequentially formed on the upper surface of the transparent electrode layer. Since the heat shrinkage of the amorphous film used as the base material is smaller than that of PET, the amorphous film is advantageous in forming a cubic curved surface by heating such as hot pressing as compared with the case where PET is used as the base material. That is, when the heat shrinkage ratio of an amorphous film, for example, polycarbonate and PET is compared, the value is slightly less than 0.5% for PET under the condition of a temperature of 100 ° C. and a time of 30 minutes. The value is very close to 0%, which is lower than that. For this reason, even if it heats, a base material hardly shrinks, and even if it forms into a cubic curved surface shape by heat processing, such as a hot press, a base material does not peel by heat shrinkage. In addition, the amorphous film does not have the characteristic that the heat shrinkage differs depending on the direction unlike the PET film, and can be formed into a desired cubic curved surface shape.
[0007]
In addition, since the transparent electrode layer is made of a material in which acicular ITO crystal powder is dispersed in a binder, even if the transparent electrode layer is formed into a cubic curved shape by hot pressing or the like, the transparent electrode layer is not lit due to disconnection. There is no inconvenience such as.
[0008]
The thickness of the amorphous film is preferably 0.1 to 5 mm for the cubic curved surface processing, and the amorphous film may have a moisture-resistant gas barrier layer formed thereon. It is preferable for preventing oxidation of the transparent electrode layer and improving the moisture resistance of the light emitting layer.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described with reference to the drawings.
[0010]
FIG. 1 shows an embodiment, in which a polycarbonate film as an amorphous film is used as a substrate 1 instead of a conventional PET film. Polycarbonate is preferable because it has a smaller heat shrinkage ratio than PET, but is slightly vulnerable to heat, and thus may be softened or adhered by heating during the EL forming step as described below. Therefore, a release paper or a release film coated with a release agent (not shown) on the surface opposite to the EL forming surface of the polycarbonate film 1, that is, on the lower surface side in FIG. It is provided so that it is peeled off after the formation step.
[0011]
In this example, the thickness of the polycarbonate film 1 with the protective film is formed to about 0.5 mm, but the thickness of the polycarbonate film 1 is desirably 0.1 to 5 mm. This is related to the workability in forming a cubic curved surface. If the thickness is less than 0.1 mm, there is a problem that the cubic curved surface cannot be maintained because the thickness is too thin. On the other hand, if the thickness exceeds 5 mm, inconveniences such as generation of cracks may be caused in forming the cubic curved surface.
[0012]
Further, it is desirable that a gas barrier layer is formed on the surface opposite to the EL forming surface of the polycarbonate film 1, that is, on the lower surface side in FIG. That is, although not shown, a gas barrier layer is provided by silicon oxide or titanium oxide. With this gas barrier layer, the oxidation of the transparent electrode layer 2 can be prevented, and the moisture resistance of the light emitting layer 3 can be improved.
[0013]
On the upper surface side of the polycarbonate film 1, a transparent electrode layer 2 is formed. The transparent electrode layer 2 is formed by applying an ITO ink in which acicular ITO crystal powder is dispersed in a binder such as epoxy. As an example, needle-like ITO crystals are formed in advance by baking ITO fine powder, kneaded into a binder made of, for example, cyanoethyl cellulose, and this mixture is screen-printed on a polycarbonate film 1 by a screen printing method or the like. The transparent electrode layer 2 is formed by coating and drying by a method.
[0014]
Next, the light emitting layer 3 is formed on the transparent electrode layer 2. The light-emitting layer 3 uses Cu-doped zinc sulfide as a phosphor, uses a binder obtained by dissolving a copolymer of vinylidene fluoride and propylene hexafluoride in methyl ethyl ketone as a solvent as a fluororesin binder, and mixes both. The luminescent ink is used as a luminescent ink, and the luminescent ink is printed on the transparent electrode layer 2 by a method such as a screen printing method and then heated and dried.
[0015]
Next, the insulating layer 4 is formed on the light emitting layer 3. The insulating layer 4 is obtained by mixing and stirring a high dielectric substance made of barium titanate and the above-mentioned fluororesin binder as the insulating ink, and printing this insulating ink by the same method as the formation of the light emitting layer 3. , By heating and drying.
[0016]
Next, the back electrode layer 5 is formed on the insulating layer 4. The back electrode layer 5 is formed by using a mixture of carbon powder and polyester as a binder as the carbon ink, printing the carbon ink by the same method as described above, and heating and drying.
[0017]
Next, a protective layer 6 is formed on the back electrode layer 5. The protective layer 6 is formed by using a resin such as polyester, polyimide, epoxy or the like, printing on the back electrode layer 5 by a method such as screen printing similar to the above, and then heating and drying.
[0018]
When heating is performed during each forming step, the heating temperature is set to 120 ° C. or lower to protect the polycarbonate film 1.
[0019]
When the EL element having such a configuration is used, for example, for illuminating a switch, the EL element is processed into a dome-shaped cubic curved shape by a hot press or the like in accordance with the dome shape of the switch, and then the rear surface of the polycarbonate film 1 is formed. The protective film attached to the switch may be peeled off and attached to the front of the switch. When insert-molding an EL element as an outer case of a mobile phone or the like, the protective film is peeled off to expose the polycarbonate film 1, the EL element is inserted with the exposed surface facing the cavity side, and a resin is inserted into the cavity. And injection molding. The injected resin is brought into close contact with the polycarbonate film 1 to form an outer case.
[0020]
Here, since the heat shrinkage of the polycarbonate film 1 used as the base material of the EL element is smaller than that of the PET film, the EL element is formed into a tertiary curved surface shape by heating such as hot pressing as compared with the case of using the PET film as the base material. It is advantageous to do. That is, when the heat shrinkage ratios of polycarbonate and PET are compared, the value is slightly less than 0.5% for PET under the condition of a temperature of 100 ° C. and a time of 30 minutes, whereas 0% is lower than that for polycarbonate. Is very close to Therefore, the polycarbonate film 1 hardly shrinks even when heated, and the polycarbonate film 1 does not peel off due to heat shrinkage even if it is formed into a cubic curved shape by heating such as hot pressing. Further, the polycarbonate film 1 does not have the property that the heat shrinkage differs depending on the direction unlike the PET film, and can be formed into a desired cubic curved surface shape.
[0021]
Further, since the transparent electrode layer 2 made of a material in which acicular ITO crystal powder is dispersed in a binder is used as the transparent electrode layer, even if the transparent electrode layer 2 is formed into a cubic curved shape by hot pressing or the like, the transparent electrode layer 2 may be broken. There is no inconvenience such as non-lighting.
[0022]
In the above embodiment, a conductive layer made of a material in which acicular ITO crystal powder is dispersed in a binder is used as the transparent electrode layer 2, but this conductive layer is used not only as the transparent electrode layer 2 but also as the back electrode layer 5. When the back electrode layer 5 is formed into a cubic curved shape by hot pressing or the like, disconnection of the back electrode layer 5 can be prevented, and non-lighting due to disconnection of the back electrode layer 5 can also be prevented.
[0023]
In the above embodiment, the polycarbonate film 1 was used as the amorphous film. However, other amorphous films such as a polysulfone (PSF) film, an amorphous polyarylate (PAR) film, and a polyether sulfone (PES) were used. ) Films and polyetherimide (PEI) films may be applied. Each of these films has a glass transition temperature of 175 ° C. or higher, is excellent in thermal dimensional stability, hardly shrinks even when heated in the same manner as the polycarbonate film 1, and has a cubic curved surface by heat processing such as hot press. Even if it is formed into a shape, it does not peel off due to heat shrinkage. In particular, the polyethersulfone film and the polyetherimide film have a glass transition temperature of 200 ° C. or higher, and have extremely high thermal dimensional stability, which is more preferable. In addition, these films do not have the property that the heat shrinkage differs depending on the direction unlike PET, and can be formed into a desired cubic curved surface shape.
[0024]
【The invention's effect】
As described above, since the EL element of the present invention uses the amorphous film as the base material, the base material does not peel off even when formed into a cubic curved shape by heating such as hot pressing. In addition, the amorphous film does not have the characteristic that the heat shrinkage differs depending on the direction unlike the PET film, and can be formed into a desired cubic curved surface shape. In addition, since the transparent electrode layer is made of a material in which acicular ITO crystal powder is dispersed in a binder, even if the transparent electrode layer is formed into a cubic curved shape by hot pressing or the like, the transparent electrode layer is not lit due to disconnection. There is no inconvenience such as. Thereby, it can be formed into a cubic curved surface shape without any inconvenience by a heating process such as a hot press.
[Brief description of the drawings]
FIG. 1 is a sectional view showing an embodiment of the present invention.
[Explanation of symbols]
1 polycarbonate film (amorphous film)
2 Transparent electrode layer 3 Light emitting layer 4 Insulating layer 5 Back electrode layer

Claims (3)

Using an amorphous film as the base material,
On the upper surface of the amorphous film, a transparent electrode layer made of a material in which acicular ITO crystal powder is dispersed in a binder is formed,
An EL element comprising: a light emitting layer, an insulating layer, and a back electrode layer sequentially formed on the upper surface of the transparent electrode layer. 2. The EL device according to claim 1, wherein said amorphous film has a thickness of 0.1 to 5 mm. The EL device according to claim 1 or 2, wherein a gas barrier layer having moisture resistance is formed on the amorphous film.

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