JPH0512808B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a keyboard switch, more specifically, a first plastic sheet forming a contact portion;
a second plastic sheet formed with contact portions corresponding to the contact portions of the first plastic sheet, such that the opposing contact portions of both plastic sheets maintain a non-contact state without being pressed; The present invention relates to a keyboard switch in which an insulating spacer layer is formed on the contact forming surface of at least one of both plastic sheets, except for the contact portion.

[Technical background of the invention]

Keyboard switches of the type described above are known.
Figures 3 to 5 show an example of such a known keyboard switch. This keyboard switch is made up of a first plastic sheet 10a and a second plastic sheet 10b, as shown in FIG.
These are obtained by folding a common plastic sheet 10 at the bending portion 16. The first plastic sheet 10a has an appropriate number of contacts 11 at appropriate intervals and a conductive circuit 15 that leads the contacts 11 to a terminal 13 formed in a terminal portion 10c connected to the first plastic sheet 10a. It is formed.

The second plastic sheet 10b is provided with a contact 12 which faces the contact 11 when the plastic sheet 10 is folded at the folding portion 16. A conductive circuit 14 connecting the contact 12 and the terminal 13 is formed in both plastic sheets 10b and 10a.

The plastic sheet 10 is made of a thermoplastic or thermosetting soft and resilient plastic material, such as polyester resin, and is often about 50 to 300 microns thick.

The contacts 11 and 12, the conductive circuits 14 and 15, and the terminal 13 are formed by applying a conductive paint and then curing it by an appropriate method such as heat curing or ultraviolet curing, and the thickness thereof is usually about 5 to 30 microns. be.

At least one of the two plastic sheets 10a, 10b (in the illustrated case, only the second plastic sheet 10b) has a fourth contact point formed on the surface thereof.
As shown in the figure, an insulating spacer layer 17 is provided. This spacer layer 17 is applied to a portion other than the contact 12 so that the contact 12 is exposed, for example, 50~
It is approximately 500 microns thick and is formed using a paint application method such as screen printing, and then hardened.

The plastic sheet 1 shown in Fig. 4 has each contact point, conductive circuit, terminal, and spacer layer formed in this way.
0 by 180 degrees with the spacer layer 17 inside at the bending portion 16 as shown in FIG.
A keyboard switch is constructed in which contacts 11 and 12 of contacts a and 10b face each other with an insulating distance maintained by a spacer layer 17. Note that the first plastic sheet 10a and the spacer layer 17 can be fixed by chemical means such as adhesion or heat fusion, or mechanical means such as screws.

In the example shown in FIGS. 3 to 5, the first and second plastic sheets 10a, 10b are obtained by folding one plastic sheet 10, but both plastic sheets 10a, 10b are separately formed. It can also be made separately. An example is shown in FIG.

In this keyboard switch, the first plastic sheet 10 is made separately.
A and the second plastic sheet 10b, the contact 11a formed on the first plastic sheet 10a having the terminal portion 10c is separated into two semicircular parts, and each has a contact circuit 15 connected to the terminal 13. In contrast, the contacts 12 formed in the second plastic sheet 10b, when pressed, form two contact parts by bridging the two separated contact parts of the opposing contact 11. It functions to form an electric path between the consecutive contacts 13, and the second plastic sheet 10b is not provided with a contact circuit.
When making a keyboard switch using both plastic sheets 10a and 10b shown in Fig. 7,
A spacer layer is interposed between both plastic sheets as shown in the figure, and the process is completed in the same manner.

When forming the spacer layer 17 on the plastic sheet 10 by screen printing in the keyboard switch made as described above,
Conventionally, as shown in FIG. 6, solid printing is performed on the entire surface except for the contact portion 12. Therefore, not only is it necessary to use a large amount of expensive spacer paste, which is uneconomical, but also the obtained spacer film thickness is unevenly thick at the edge part and thinner at the non-edge part, that is, the center part. There was a tendency. This characteristic causes a significant difference in film thickness, especially due to the difference in the plane size of the film, that is, the difference between a narrow pattern width and a wide pattern width. Despite these circumstances, in order to make the spacer film thickness uniform, craftsmen must pay attention to the squeegee pressure and speed during printing, the hardness of the squeegee material, the emulsion thickness of the silk screen mesh, the paste viscosity, etc. Although highly artistic techniques were required, the product yield was still not very good. In particular, non-uniformity in the spacer film thickness around the contacts will significantly degrade the quality of the keyboard switch.

[Purpose of the invention]

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to economically provide a keyboard switch that is equipped with a means for forming a constant spacer film thickness especially around the contacts.

[Summary of the invention]

In order to achieve the above object, the present invention provides a spacer layer with a relatively narrow spacer region formed so as to surround the contact portion, and a filler with a particle diameter of 50 to 300 microns and a composite material. It is characterized by being formed by applying and curing a paste containing resin.

[Specific description of the invention]

Hereinafter, the present invention will be explained in more detail with reference to FIGS. 1 and 2.

Fig. 1 and Fig. 2 show an embodiment in which the basic structure of the keyboard switch shown in Figs. 3 to 5 is adopted as is, and the same reference numerals indicate the same components, and the explanation thereof will be omitted. . 1st
The figure corresponds to FIG. 4 already mentioned.
The spacer layer shown in FIGS. 1 and 2 is characterized by a relatively narrow spacer region 17a that is formed at a certain distance from the contact 12 so as to surround the contact 12. The other features are the same as those shown in Figures 3 and 4.

Since the spacer regions 17a can be formed in a relatively thin pattern, the thickness of the spacer layer can be easily controlled and made uniform, and in particular, the pattern width of each spacer region 17a corresponding to each contact point 12 can be made constant. By the way,
It is easy to form a spacer layer with a constant thickness.

In the above-mentioned FIG. 1, the planar shape of the contact point is circular, and therefore the spacer area 1
Although the case where 7a is ring-shaped has been described, the shape thereof is not limited to a circle, and other shapes such as a square or an oval can also be used.

Further, since a paste containing a filler having a particle diameter of 50 to 300 microns is used to form the spacer region 17a, it is extremely easy to form a spacer layer with a desired thickness.

That is, since the spacer layer formed by applying and curing the above composition has a thickness approximately equal to the particle size contained in the composition, the size of the filler particles can be adjusted appropriately. Depending on the selection, the spacer layer can have a thickness that corresponds to the particle size. In particular, when forming the spacer layer by silk screen printing, it is not necessary to strictly control the squeegee pressure and speed during silk screen printing, the hardness of the squeegee material, the emulsion thickness of the silk screen mesh, the paste viscosity, etc.
An advantage is that a spacer layer of a desired thickness can be formed very easily.

To form the spacer layer, a paste containing a filler and a synthetic resin with a particle size of 50 to 300 microns is used. Examples of synthetic resins that can be used in the paste include polybutadiene resin, acrylic resin,
The synthetic resin is appropriately selected from among epoxy resins, polyester resins, silicone resins, urethane resins, etc. in consideration of adhesion to the plastic sheet 10.

A keyboard switch with a uniform spacer thickness can be obtained with the above configuration alone, but a paste containing a filler and synthetic resin with a particle size of 50 to 300 microns (hereinafter referred to as filler-containing paste) is used to form the spacer layer. As a result, a keyboard switch with even higher uniformity in spacer film thickness can be obtained.

Fillers that can be used in the filler-containing paste include glass, ceramics, synthetic resins,
(For example, acrylic resin, polyethylene resin, etc.)
It is particularly preferable to use spherical glass particles. The particle size of these fillers is between 50 and 300 microns, preferably between 70 and 150 microns. If the particle size is smaller than 50 microns, it will be difficult to form a spacer layer of sufficient thickness, and it will be difficult to maintain a sufficient non-contact state between opposing contacts when no pressure is applied.
If the diameter is larger than microns, the gap between opposing contacts becomes too large, making pressing operation difficult and causing poor workability during coating.

The mixing ratio of the filler and the synthetic resin binder is preferably 20 to 500 parts by weight, particularly preferably 30 to 200 parts by weight, per 100 parts by weight of the filler.

The paste containing the filler and synthetic resin is adjusted to have a coating viscosity suitable for forming a spacer layer by adding an appropriate solvent if necessary. Further, the spacer layer 7 is preferably formed by a screen printing method, but a known method such as spray coating or brush coating may also be used.

In the above, an embodiment has been described in which the present invention is applied to a keyboard switch of the type shown in FIGS. It goes without saying that the present invention can be applied in exactly the same way to a keyboard switch of the type shown in Figure 1, in which a contact circuit is formed only on one plastic sheet.

In addition, in the keyboard switch constructed according to the present invention, the insulating spacer layer is not printed solidly as shown in FIGS. 4 to 6, but is formed only in the area surrounding the contact area. , most of the conductive circuit 14 or 15 formed on the plastic sheet 10 is exposed. For this purpose, a first plastic sheet 1 as shown in FIG.
In a type of keyboard switch in which contact circuits are formed on both the plastic sheet 0a and the second plastic sheet 10b, a short circuit between the contact circuits 14 and 15 tends to occur when the plastic sheets 10a and 10b are opposed to each other. In such a case, an insulating coating should be applied to the entire surface of at least one side of the plastic sheets 10a and 10b except for the contact points, or a spacer layer should be formed not only on the spacer area but also on the contact circuit. In this way, the drawback of short circuit can be prevented.

[Embodiments of the invention]

Comparative example: Using a commercially available room temperature vulcanizable silicone resin varnish,
As shown in Figure 4, screen printing was performed to form a film thickness of 100 microns in the area surrounding the contact 12 except for the 12 mm diameter hole, and the film was heated at 150°C.
The spacer layer 17 was formed by curing for 30 minutes. The thickness of the formed spacer layer 17 was measured at the periphery of the contact 12 (the edge of the spacer layer) and was found to be 85 to 175 microns, which was non-uniform. In addition, a large amount of paste was consumed in forming the spacer layer.

Example 1 A 50% solution of urethane-modified polybutadiene resin (manufactured by Nippon Soda Co., Ltd.) was used as a spacer layer forming composition.
Using a paste consisting of 200 parts by weight of TP-1001), 100 parts by weight of glass beads with a particle size of approximately 100 microns (manufactured by Toshiba Balloteini), and 50 parts by weight of carbitol, the contacts were made as shown in Figures 1 and 2. A ring-shaped spacer region 17 with a width of about 1.5 mm is placed at a slight distance from the contact point 12 so as to surround the contact point 12.
Screen print to form a, 150℃
After curing for 30 minutes, the spacer layer 17a
was formed. When the thickness of the spacer layer was measured, it was 105 to 135 microns, and the spacer layer had a highly uniform thickness.

Example 2 A screen was prepared in the same manner as in Example 1 using a composition consisting of 116 parts by weight of polyester acrylate, 84 parts by weight of pentaerythritol triacrylate, 2 parts by weight of benzophenone, and 100 parts by weight of glass beads (particle size of about 150 microns). This was printed and irradiated with a high-pressure mercury lamp of 80 W/cm for 10 seconds to form a spacer layer 17a. The thickness of the spacer layer was measured to be 170-210 microns.

Example 3 A spacer was prepared in the same manner as in Example 1 using a composition consisting of 75 parts by weight of a commercially available room temperature vulcanizable silicone resin varnish and 2.5 parts by weight of glass beads with a particle size of about 100 microns (manufactured by Toshiba Balloteini). A layer was formed and its thickness was measured to be 95-120 microns.

〔Effect of the invention〕

As described above, according to the present invention, by forming a relatively narrow spacer region surrounding the contact, the spacer film thickness around the contact can be easily made constant; By using a paste containing a filler with a specific particle size to form the spacer layer, a more uniform spacer film thickness can be obtained, resulting in an extremely high quality keyboard switch.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing an example of the manufacturing process of the keyboard switch of the present invention, FIG. 2 is a sectional view of the device shown in FIG. 1, and FIGS. 3 and 4 are different manufacturing steps of the conventional keyboard switch. FIG. 5 is a side view showing the completed state of the keyboard switch shown in FIGS. 3 and 4; FIG. 6 is a sectional view of the main parts of the keyboard switch shown in FIG. 5; FIG. 3 is a plan view showing a manufacturing process of a conventional keyboard switch, which is different from that shown in FIG. 3. FIG. 10a...first plastic sheet, 10b
...Second plastic sheet, 11, 12...
Contact, 13... terminal, 14, 15... conductive circuit,
17... Spacer layer, 17a... Spacer region of the present invention.

Claims (1)

[Claims] 1 A first plastic sheet having a contact portion formed thereon, and a second plastic sheet having a contact portion corresponding to the contact portion of the first plastic sheet formed thereon, wherein the opposing contacts of both said plastic sheets are pressed against each other. In a keyboard switch, an insulating spacer layer is formed on the contact portion forming surface of at least one of both plastic sheets except for the contact portion so as to maintain a non-contact state when not operated. consists of a relatively narrow spacer region formed to surround the contact portion, and the spacer region is formed by applying and curing a paste containing a filler and synthetic resin with a particle size of 50 to 300 microns. A keyboard switch characterized in that it is formed by