JP2004349088A - Illuminating key top apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve adhering strength of a key top to an EL sheet substrate in an interior illuminating type key top device using the EL sheet. <P>SOLUTION: The key top 20 positioned on a light emitting surface side of the EL sheet 10, on which an EL layer 12 is formed on a transparent substrate 11 such as PET film is adhered and fixed by an adhering layer 30 provided with a 2 layer structure consisting of a first layer 31 on the EL sheet side and a second layer 32 on the key top side. The first layer 31 is constituted by adhesive with high adhering force to the EL sheet substrate (PET film)11, and the second layer 31 is constituted by adhesive provided with high adhering force to the key top material. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an illuminated keytop device used for a key input device of a mobile phone, a portable information device, a home appliance or an industrial device.
[0002]
[Prior art]
The present applicant has proposed an illuminated keytop device using an electroluminescent sheet (hereinafter, referred to as an “EL sheet”) in Japanese Patent Application No. 2002-161867 “Illuminated Switch”. In general, an EL sheet is made of a polyethylene terephthalate film (hereinafter referred to as a “PET film”) as a base material, a translucent polycarbonate resin or a silicone elastomer is used as a key top, and both have a single adhesive layer. Had been stuck through.
[0003]
[Patent Document]
Japanese Patent Application No. 2002-161867
[Problems to be solved by the invention]
Conventionally, although the base material of the EL sheet and the keytop are made of different materials, the adhesive layer for attaching them is a single layer. I was not satisfied. That is, if the material of the adhesive layer is selected with an emphasis on the adhesive force to the EL sheet, the adhesive force with respect to the keytop becomes insufficient. The problem is that the adhesive strength to the sheet must be insufficient. For this reason, the key top is used very frequently and repeatedly for key input, but there is a possibility that the key top will peel off from the EL sheet during repeated use for a long time.
[0005]
[Means for Solving the Problems]
In order to achieve the above object, according to the present invention, an adhesive layer for attaching an EL sheet and a key top has a two-layer structure including a first layer and a second layer, and the first layer on the EL sheet side is an EL layer. The second layer on the keytop side is made of an adhesive having a high adhesive strength to the base material of the sheet, and the second layer on the keytop side is made of an adhesive having a high adhesive strength to the material of the keytop. When the adhesive layer has this two-layer structure, the adhesive layer exhibits sufficient adhesive strength to both the base material of the EL sheet and the key top.
[0006]
When the base material of the EL sheet is a PET film, the first layer is preferably a polyvinyl chloride or polyester resin adhesive, and when the key top material is a polycarbonate resin or a silicone resin, the second layer is a silicone adhesive. Is preferred.
More preferably, the sticking surface of the base material or the key top of the EL sheet is formed as a rough surface having minute irregularities. Thereby, the adhesive strength between the base material or the key top of the EL sheet and the adhesive layer is further increased.
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail with reference to preferred embodiments shown in the accompanying drawings.
As shown in FIG. 1, the illuminated key top device of the present invention includes an EL sheet 10, a key top 20 located on a light emitting surface side thereof, and an adhesive layer 30 for attaching the two.
[0008]
The EL sheet 10 is a flexible sheet that emits surface light, and the base material 11 is formed of a thin transparent PET film having a thickness of about 75 to 100 μm in this embodiment. A transparent electrode (not shown) is formed on the back surface by a method such as vapor deposition, and an EL layer 12 having a well-known structure including a light-emitting layer, an insulating layer, and a back electrode (all not shown) is formed on the back surface. I have.
[0009]
In this embodiment, the key top 20 located on the light emitting surface side (substrate 11 side) of the EL sheet 10 is formed of a transparent polycarbonate resin, and the outer peripheral surface including the lower surface (the adhesive surface of the adhesive layer 30) emits light uniformly. In order to obtain the effect (light scattering effect), it is formed on a rough surface (matte) having minute unevenness, and an upper surface thereof is engraved with alphabets, numerals, and the like (not shown).
[0010]
Next, the adhesive layer 30 for attaching and fixing the key top 20 on the EL sheet 10 will be described. The adhesive layer 30 has a two-layer structure including a first layer 31 on the EL sheet 10 side and a second layer 32 thereon (on the keytop 20 side). An adhesive exhibiting good adhesive strength to the base material 11 of the EL sheet 10 is selected for the first layer 31, and an adhesive exhibiting good adhesive strength to the key top 20 is selected for the second layer 31. Selected. More specifically, in this embodiment in which the base material 10 is a PET film and the key top 20 is a polycarbonate resin, the first layer 31 is made of an adhesive of a polyvinyl chloride resin or a polyester resin, and the second layer 32 is made of an adhesive. Used is a modified silicone resin-based adhesive.
[0011]
Next, the step of attaching and fixing the key top 20 on the base material (PET film) 11 of the EL sheet 10 will be described.
First, an ink for a first layer is prepared by dissolving a polyvinyl chloride resin in methyl isobutyl ketone, which is one of ketone solvents. This first layer ink has a high adhesive strength to PET which is a material of the base material 11 of the EL sheet 10. Using this ink, as shown in FIG. 2A, a first layer 31 is formed at a position where the key top 20 of the base material (PET film) 11 of the EL sheet 10 is to be fixed by a screen printing technique. Heat and cure. After the first layer is cured, as shown in FIG. 2 (b), a second layer 32 is formed on the first layer 31 formed on the base material 11 by a modified silicone which is a kind of silicone resin adhesive. It is formed by a screen printing technique using a resin adhesive. The modified silicone resin adhesive as the ink for the second layer has a high adhesive strength to the polycarbonate resin as the material of the key top 20. Then, as shown in FIG. 2C, the key top 20 made of polycarbonate is pressed onto the second layer 32 to cure the adhesive layer 30 including the first layer 31 and the second layer 32. Thereby, as shown in FIG. 1, the key top 20 is completely adhered and fixed to the EL sheet 10, and a desired key top device is completed.
[0012]
The key top device completed in this way can be used even if the base material 11 of the EL sheet 10 and the key top 20 adhered and fixed to the EL sheet 10 are made of different materials via the adhesive layer 30 having a two-layer structure. The key top 20 is firmly joined to the base material 11. That is, the bonding interface of the base material 11 of the EL sheet 10 is bonded to the first layer 31 having high adhesive strength to the material of the base material 11, and the bonding interface of the key top 20 is high to the material of the key top 20. This is because it is bonded to the second layer having an adhesive force.
The bonding interface between the first layer 31 and the second layer 32 of the adhesive layer 30 is necessary and sufficient because the printed surface of the first layer is softened by the solvent of the adhesive during the printing of the second layer and bonded together. It has strong adhesion and does not peel off at this interface. According to the verification results, the bonding strength of the key top 20 to the EL sheet 10 according to the present invention is improved by about 20% as compared with the conventional single-layer bonding layer.
[0013]
[Other embodiments]
In the above embodiment, a polyvinyl chloride resin adhesive is used as the first layer 31 of the adhesive layer 30, but a similar effect can be obtained by using a polyester resin adhesive instead. In the case of using a polyester resin adhesive, a first layer ink prepared by dissolving a polyester resin in methyl isobutyl ketone, which is one of ketone solvents, is prepared.
[0014]
In the above embodiment, the modified silicone adhesive is used as the second layer 32 of the adhesive layer 30. The material of the key top 20 of the modified silicone adhesive is polymethyl methacrylate, a silicone resin, or a silicone elastomer. Sometimes it is effective.
[0015]
In the above embodiment, the key top 20 is formed with a rough surface (matte) treatment on the outer peripheral surface thereof in order to obtain a uniform light emitting effect (light scattering effect). By subjecting the surface of the material 31 to the entire surface or the part to which the key top 20 is stuck to partially roughen (matte) the bonding strength can be further increased.
[0016]
【The invention's effect】
According to the configuration of the present invention, since the EL sheet base material and the key top are adhered and fixed via the two-layered adhesive layer adapted to each material, the adhesive strength between the two is sufficiently increased, and the frequency is increased frequently. It is possible to improve the peeling durability of the keytop in the operated keytop device.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of an illuminated keytop device according to the present invention.
FIG. 2 is a process diagram showing a key top attaching procedure in the illuminated key top device according to the present invention.
[Explanation of symbols]
Reference Signs List 10 EL sheet 11 Base material 12 EL layer 20 Key top 30 Adhesive layer 31 First layer 32 Second layer

Claims (4)

Including an EL sheet, a key top located on the light emitting surface side of the EL sheet, and an adhesive layer for attaching both,
The adhesive layer has a two-layer structure including a first layer on the EL sheet side and a second layer on the keytop side,
The first layer is made of an adhesive having a high adhesive strength to the substrate of the EL sheet, and the second layer is made of an adhesive having a high adhesive strength to the material of the keytop. An illuminated key top device, characterized in that: 2. The illuminated key top device according to claim 1, wherein when the base material of the EL sheet is a PET film, the first layer is an adhesive of a polyvinyl chloride resin or a polyester resin. 2. The illuminated key top device according to claim 1, wherein when the key top material is a polycarbonate resin or a silicone resin, the second layer is a silicone-based adhesive. The illuminated keytop device according to any one of claims 1 to 3, wherein the base material or the keytop attachment surface of the EL sheet is formed with a rough surface.

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