JPH0512807B2 - - 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 on which a contact portion is formed, and a contact point corresponding to the contact portion of the first plastic sheet. a second plastic sheet on which a contact portion is formed, and a contact portion forming surface of at least one of both plastic sheets is provided so that the opposing contact portions of both plastic sheets maintain a non-contact state without being pressed. , relates to a keyboard switch in which an insulating spacer layer is formed 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.
are obtained by folding a single common plastic sheet 10 at the folding portion 16. The first plastic sheet 10a includes
An appropriate number of contacts 11 at appropriate intervals, and this contact 11
A conductive circuit 15 is formed which leads the terminal to a terminal 13 formed in a terminal portion 10c continuous to the first plastic sheet 10a. 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 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.

Although the keyboard switch shown in FIGS. 3 to 5 described above has a structure in which contact circuits 15 and 14 are formed on both plastic sheets 10a and 10b, respectively, a keyboard switch having a different structure is shown in FIG. In this keyboard switch, among the first plastic sheet 10a and the second plastic sheet 10b which are separately made, the contact points 11 formed on the first plastic sheet 10a having the terminal portions 10c are each semicircular. The contacts 12 formed on the second plastic sheet 10b are separated from the opposing contacts 11 when the second plastic sheet 10b is pressed. The second plastic sheet 10b functions to form an electric path through the contact 13 that connects the two contact parts by bridging the two contact parts, and the second plastic sheet 10b is not provided with a contact circuit. Both plastic sheets 10a in FIG.
When making a keyboard switch using 10b, a spacer layer is interposed between both plastic sheets according to FIGS. 3 to 5, and the same process is completed.

When forming the spacer layer 17 on the plastic sheet 10 by screen printing in the keyboard switch made as described above,
Conventionally, solid printing is used. Therefore, as shown in FIG. 6, the coating film thickness obtained tends to be unevenly thick at the edge portions and thinner at the non-edge portions, that is, the central portion. This characteristic causes a large difference in film thickness, especially due to the difference in the plane size of the film, that is, the difference between a thin pattern width and a wide pattern width. Despite these circumstances, in order to make the spacer film thickness uniform, craftsmen must carefully consider 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 provide a keyboard switch equipped with a means for making the spacer film thickness uniform, especially the spacer film thickness around the contact points.

[Summary of the invention]

In order to achieve the above object, the present invention includes a spacer layer that includes a relatively narrow first spacer region formed to surround the contact portion and a region outside the first spacer region. and a second spacer region formed at a slight distance from the first spacer region.
It is characterized by being constructed by applying and curing a composition containing a micron filler and a synthetic resin binder.

[Embodiments 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 17 in FIGS.
a relatively narrow first spacer region 17a formed at a slight distance from the contact point 12 so as to surround the contact point 12; The feature is that the second spacer region 17b is formed, and the other features are the same as those shown in FIGS. 3 and 4.

Since the first spacer regions 17a can be formed in a relatively thin pattern, it is easy to control the thickness of the spacer layer, especially for each spacer region 17a corresponding to each contact point 12.
By making the pattern width constant, it is easy to form a spacer layer with a constant thickness. Further, the first and second spacer regions 17a,
Since a composition containing a filler having a particle size of 50 to 300 microns is used to form the spacer layer 17b, 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 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 of the composition, etc. Both have the advantage that a spacer layer of a desired thickness can be formed very easily.

In the above-mentioned embodiment, the case where the planar shape of the contact point is circular is illustrated, and therefore the case where the first spacer region 17a is ring-shaped has been described, but the shape thereof is limited to circular. However, it can also be implemented in other shapes, for example square or oval.

Among the compositions that can be used to form the spacer layer 17, the filler is particles of glass, ceramic, synthetic resin (for example, acrylic resin, polyethylene resin, etc.), and it is particularly preferable to use spherical glass particles. preferable. 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, a spacer layer of sufficient thickness will not be formed and it will be difficult to maintain a non-contact state between the opposing contacts when no pressure is applied.If the particle size is larger than 300 microns, the gap between the opposing contacts will be becomes too large, making the pressing operation difficult and causing poor workability during coating.

The synthetic resin binder used in combination with the filler includes polybutadiene resin, phenolic resin, acrylic resin, epoxy resin, polyester resin,
These include silicone resins, urethane resins, melamine resins, modified resins of these resins, etc., and each can be appropriately selected and used in consideration of the adhesion to the plastic sheet to be coated. These synthetic resin binders can be of a solution type dissolved in an organic solvent or an organosol type dispersed, an emulsion type obtained by emulsion polymerization in water, or an ultraviolet curing type combined with a reactive monomer and a photosensitizer. .

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.

Screen printing is preferred for forming the spacer layer 17, but known methods such as spray coating and brush coating may also be used. Further, the composition can be cured by methods such as room temperature curing, heat curing, or ultraviolet curing, depending on the type of synthetic resin binder 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.

Example 1 As a composition for forming a spacer layer, 200 parts by weight of a 50% solution of urethane-modified polybutadiene resin (manufactured by Nippon Soda Co., Ltd., TP-1001), 100 parts by weight of glass beads with a particle size of about 100 microns (manufactured by Toshiba Balloteini Co., Ltd.)
As shown in FIGS. 1 and 2, using a composition consisting of parts by weight and 50 parts by weight of carbitol,
A ring-shaped first spacer region 17a with a width of about 1.5 mm is provided at a slight distance from the contact point 12 so as to surround the contact point 12, and a ring-shaped first spacer region 17a with a width of about 1.5 mm is provided at a distance of about 1 mm from the spacer region 17a so as to cover the outside of this spacer region. Then, screen printing was performed so that a second spacer region 17b was formed, and a curing treatment was performed at 150° C. for 30 minutes to form a spacer layer 17.
The thickness of the spacer layer was measured in the spacer region 17a and was 105 to 135 microns, indicating a uniform thickness of the spacer layer.

Example 2 Screen printing was performed in the same manner as in the above example 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). death,
Irradiate for 10 seconds with a high-pressure mercury lamp of 80W/cm to a thickness of approximately 200mm.
A spacer layer was formed to have a thickness of microns. The thickness of the spacer layer was measured for spacer region 17a and was 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 cold-flow type silicone resin varnish and 25 parts by weight of glass beads with a particle size of about 100 microns (manufactured by Toshiba Balloteini). When a layer was formed and the thickness was measured, it was found to be 95 to 120 microns, indicating that the spacer layer had a highly uniform thickness.

Comparative Example Using the silicone resin varnish of Example 3 (not containing glass beads), spacer layers 17a and 17b were formed in the same manner as in Example 1. The thickness of this spacer layer was measured in the spacer region 17a and was found to be 65 to 115 microns, which was non-uniform as compared to the above embodiment of the present invention.

〔Effect of the invention〕

As described above, according to the present invention, a relatively narrow spacer region surrounding the contact is formed using a composition containing a filler having a specific particle size, thereby forming a spacer layer. The thickness of the layer can be arbitrarily controlled, and the thickness can be easily made uniform, thereby providing 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... First spacer region, 17b... Second spacer region.

Claims (1)

[Claims] 1. A first plastic sheet on which contact portions are formed, and a second plastic sheet on which contact portions corresponding to the contact portions of the first plastic sheet are formed, the opposing contact portions of both plastic sheets having 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 pressed. The layer includes a relatively narrow first spacer region formed to surround the contact portion, and a spaced apart from the first spacer region so as to cover an outer region of the first spacer region. The first and second spacer regions are formed by applying and curing a composition containing a filler and a synthetic resin binder with a particle size of 50 to 300 microns. A keyboard switch characterized in that it is formed by