JPH0754657B2 - Thin film switch - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a thin film switch (membrane switch) in which two films having electrode patterns are bonded to each other via an insulating spacer, and particularly to both films. Regarding the bonding structure of.

[Conventional technology]

Heretofore, as the thin film switch of this type, the following has been known regarding the bonding structure thereof.

The first example is as shown in FIG.
A spacer film 5 formed by die-cutting a film with a double-sided adhesive is interposed between a lower film 2 on which is printed and an upper film 4 on which an upper electrode 3 is printed and formed. The lower film 2 and the upper film 4 are adhered to each other via adhesive layers 6 laminated on both front and back surfaces.

As the adhesive constituting the adhesive layer 6, a pressure-sensitive adhesive, a so-called pressure-sensitive adhesive, is used because each member can be bonded at room temperature and a special heating step is not required for bonding. . In addition, the double-sided adhesive film, which is the base of the spacer film 5, is obtained by continuously coating adhesive on both the front and back surfaces of a roll-formed film, and after drying, release paper on the surface of each adhesive layer. It is made by pasting.

As shown in FIG. 4, a second example of a conventionally known thin film switch is to form an insulating space 7 by printing an insulating printing ink on a portion of the lower film 2 excluding the lower electrode 1. The upper surface of the insulating spacer 7 and the surface of the upper film 4 on which the upper electrode 3 is formed are bonded together via an adhesive layer 6.

For the adhesive layer 6 in the second conventional example, an adhesive is used for the same reason as above. However, the first method for forming the adhesive layer 6 is
Unlike the conventional example, first, a method of printing a solvent-drying pressure-sensitive adhesive on the insulating spacer 7 and subsequently volatilizing the solvent by a heating and drying step is adopted.

As shown in FIG. 5, a third example of a conventionally known thin film switch contains a thermoplastic resin as a main component on the electrode forming surface of either one of the lower film 2 and the upper film 4. The insulating paste is printed to form the insulating spacers 8, and the insulating spacers 8 are heated and pressed to integrate the lower film 2, the insulating spacers 8 and the upper film 4 (Shokai 62-53535).
issue).

Each of these thin film switches forms an air gap 9 between the lower electrode 2 and the upper electrode 3 by interposing insulating spacers 5, 7, 8 between the lower film 2 and the upper film 4. The lower electrode 2 and the upper electrode 3 are always kept in a separated state via the gap 9. Therefore, when the forming portion of the upper electrode 3 is pressed downward from above the upper film 4 with a finger or the like, the flexible upper film 4 is elastically deformed, and when the predetermined stroke is lowered, the upper electrode 3 and the lower electrode 3 are lowered. 1 and 1 come into contact with each other, and a switch-on state is established. Also,
Excluding this pressing force, due to the flexibility of the upper film 4,
Each of the states shown in FIGS. 3 to 5 is restored, and the upper electrode 3 and the lower electrode 1 are separated from each other to be in the switch-off state.

[Problems to be Solved by the Invention]

However, the thin film switch of the first conventional example has the following disadvantages because the spacer film 5 is formed of a film with double-sided adhesive.

Since a release paper not used in the product is required in the process, the cost becomes high, and the workability is poor because the release paper must be peeled off each time the members are bonded together.

An expensive cutting die is required to form the spacer film 5 from the roll-shaped original film.

Since the adhesive layer 6 uses a pressure-sensitive adhesive,
Bubbles tend to enter between the films 2, 4 and 5 during bonding. For this reason, depending on the usage conditions, blister may cause performance deterioration such as abnormal appearance.

Further, the thin film switch of the second conventional example has the following inconvenience because the adhesive layer 6 is formed by printing a solvent drying type adhesive.

The solvent having a high boiling point cannot be used for various reasons as the solvent added to adjust the printability of the pressure-sensitive adhesive. Therefore, the solvent is volatilized while printing is continued even at room temperature, and the printability deteriorates with the passage of time.

If the adhesive adheres to an undesired portion, the adhesiveness increases as the solvent volatilizes, making removal difficult.

The resin used for the printing type pressure-sensitive adhesive generally has a smaller molecular weight than the resin of the coating type pressure-sensitive adhesive, and the adhesive strength is inferior to that of the coating type pressure-sensitive adhesive.

Since the printing type adhesive contains a large amount of solvent, an expensive stainless mesh mask is required to obtain a desired dry film thickness.

Since the thin film switch of the third conventional example does not use an adhesive, it does not have the above problems. However, the insulating spacers 8 made of plastisol containing vinyl chloride as a main component printed on the lower film 2 and the upper film 4 or the insulating spacers made of plastisol containing vinyl chloride as a main component formed on the lower film 2 by printing. When the spacer 8 and the upper film 4 are directly pressure-bonded with each other under heating, since the bonding temperature and the thermal deformation temperature of the upper and lower films 2 and 4 are close to each other, the lower film must be adhered to appropriate heating conditions and pressure conditions. 2 and the upper film 4 are easily deformed by heat,
There is a problem when the appearance is spoiled. Further, particularly when the insulating spacers 8 formed by printing on the lower film 2 and the upper film 4 are directly joined, a joining mark is formed at the joining portion of the upper film 4 and the appearance of the product is deteriorated. is there.

Therefore, conventionally, solving such various problems has been one of the important technical problems in the field of thin film switches. An object of the present invention is to solve such technical problems and to provide a thin film switch excellent in assembling workability, durability, switch characteristics, and aesthetics at low cost.

[Means for Solving the Problems]

In order to achieve the above object, the present invention prints and forms an insulating spacer made of plastisol containing vinyl chloride as a main component on the lower electrode forming surface of the lower film and the upper electrode forming surface of the upper film, respectively. It is characterized in that the opposing surface of the insulating spacer is adhered with a plastisol adhesive containing a copolymer of vinyl chloride and vinyl acetate as a main component.

[Action]

The adhesive is a fluid, and an adhesive layer having a desired pattern can be formed on a desired surface by printing.

Further, the adhesive is thermosetting, does not gel before heating, and has no tack after curing.

Further, since the adhesive contains almost no solvent that easily volatilizes, the stability of viscosity is high.

Further, since the adhesive layer is provided between the insulating spacers, the change in shape during the adhesion does not appear on the surfaces of the upper film and the lower film.

In addition, the insulating spacers are made of plastisol containing vinyl chloride as a main component, and these are bonded with a plastisol adhesive containing a copolymer of vinyl chloride and vinyl acetate as the main component. It can be bonded with and has high adhesive strength.

〔Example〕

 An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of a thin film switch according to an embodiment of the present invention, in which 11 is an insulating spacer and 12 is an adhesive layer. Since the other lower electrode 1, lower film 2, upper electrode 3, and upper film 4 are the same as the conventional ones described above, the same reference numerals are given and description thereof is omitted.

In this embodiment, in the upper surface of the lower film 2, the lower electrode 1
The insulating spacers 11 are formed by a printing technique on the portions other than the upper electrode 4 and on the lower surface of the upper film 4 excluding the upper electrode 3, and the opposing surfaces of these insulating spacers 8 are bonded by an adhesive layer 12 to form a thin film switch. Are configured.

The insulating spacer 11 is formed by printing and forming an insulating paste containing a thermoplastic resin as a main component on both the lower film 2 and the upper film 4, and then heating this.

As this insulating paste, for example, a plastisol in which a thermoplastic resin powder such as vinyl chloride resin is dispersed in a liquid plasticizer such as DOP (dioctyl phthalate), and a stabilizer, a thickener, a pigment and the like are further added if necessary. The type is preferable. That is, such a plastisol has a significantly higher film-forming solid content in the liquid than an organosol having an organic solvent as a dispersion medium, so that the film thickness in one printing can be increased and the number of printings can be significantly reduced. can do.

Further, as the adhesive constituting the adhesive layer 12, a plastisol containing a copolymer of vinyl chloride and vinyl acetate as a main component, to which a plasticizer and, if necessary, a stabilizer and a thickener are added. An adhesive is used.

As the vinyl chloride-vinyl acetate copolymer, a paste resin obtained by emulsifying and polymerizing a mixture of vinyl chloride and vinyl acetate in the presence of an emulsifier and a water-soluble polymerization initiator, or a dispersant and an oil-soluble polymerization initiator. It is possible to use a paste resin produced by a fine suspension polymerization method in which the whole or a part of a mixture of vinyl chloride and vinyl acetate is mechanically finely dispersed in the presence of, and then polymerized. In addition, those paste resins mixed with a vinyl chloride resin having a large particle size produced by ordinary suspension polymerization in a range that does not adversely affect the viscosity, fluidity and processability of the paste sol. Can also be used.

Examples of the plasticizer include phthalic acid plasticizers such as DOP, resin acid ester plasticizers such as di-2-ethylhexyl adipate, resin acid polyester plasticizers such as adipic acid polyester, and tributyl phosphate. And phosphate-based plasticizers such as epoxidized soybean oil.

In addition, as the stabilizer, inorganic metal compounds such as lead white and basic silicates, organic compounds such as lauric acid and various metal salts, organic acid liquid composite stabilizers such as calcium-zinc type or barium-zinc type, etc. Can be used.

A specific example of the composition of the plastisol adhesive applicable to the present invention is shown below.

Paste vinyl chloride-vinyl acetate copolymer (number average degree of polymerization = 1350); 100 parts by weight Plasticizer; 50-60 parts by weight Stabilizer; 3-6 parts by weight Thickener; 1-2 parts by weight A method for manufacturing the thin film switch will be described with reference to FIG.
A description will be given based on (b) and (c).

First, as shown in FIG. 2A, a lower film 2 having a lower electrode 1 patterned and an upper film 4 having an upper electrode 3 patterned are prepared. In this embodiment, the lower film 2 and the upper film 4 are described as a single film, but the films 2 and 4 may be separate bodies.

Next, as shown in FIG. 2 (b), insulating pastes 11a and 11b are printed on the portions of the lower film 2 and the upper film 4 excluding the electrodes 1 and 3 by means such as a screen printing method.
This is heated to melt and gelate.

Further, as shown in FIG. 2 (c), the insulating paste
The adhesive layer 12 is laminated on the layers 11a and 11b by a method such as a screen printing method. In this embodiment, the case where the adhesive layer 12 is laminated on both insulating pastes 11a and 11b is shown, but the adhesive layer may be laminated only on one of the insulating pastes.

Next, the connection between the lower film 2 and the upper film 4 is bent, and the electrodes 1 and 3 are accurately positioned by the multiple positioning holes 2a and 4a formed in the lower film 2 and the upper film 4, respectively. Then, both adhesive layers 12 are overlapped.

Then, the laminated body is heated by a heater (not shown) to cure the adhesive layer 12 to obtain the thin film switch shown in FIG.

In the thin film switch of the above-mentioned embodiment, since the thermosetting adhesive of the fluid containing the copolymer of vinyl chloride and vinyl acetate as the main component was used as the adhesive constituting the adhesive layer 12, desired by printing. An adhesive layer having a desired pattern can be formed on the surface. Therefore, it does not require release paper and die,
The cost of the thin film switch can be reduced. Also,
Since the insulating spacer has good wettability, it is difficult for air bubbles to be trapped, resulting in excellent workability and mass productivity.

By adjusting the viscosity of the adhesive to 100 to 1000 poises, more preferably 100 to 500 poises, a coating film having excellent printability and easy to stick can be obtained.

Further, since it is thermosetting, it does not gel before heating, and it is easy to remove the adhesive attached to unnecessary portions. Further, since there is no tack after curing, workability is not deteriorated and it can be easily scraped off.

Further, since the adhesive contains almost no solvent that easily volatilizes, the viscosity is high and the printability is hardly deteriorated even after printing for a long time. For example, when using a solvent-drying type pressure-sensitive adhesive, the viscosity must be adjusted every 100 to 200 shots, whereas in the case of the adhesive of the above example
Continuous printing of 1000 to 2000 shots or more is possible. However, diluents that are relatively difficult to evaporate are 0-5%, usually 1%
The printability can be further improved by adding it below.

Further, as described above, since the adhesive has almost 100% film-forming components, it is possible to obtain a desired film thickness by using an inexpensive Teflon mesh and a lightweight frame, thereby reducing the cost of manufacturing equipment. Can be achieved.

In addition, the insulating spacer is formed of plastisol containing vinyl chloride as the main component, and these are bonded with the plastisol adhesive containing vinyl chloride-vinyl acetate copolymer as the main component. high. That is, it has a T-type peel strength of 2.5 to 5 kg / 25 mm, and has a peel strength of 85 ° C 100
No deterioration of peel strength is observed even after 0 hour or 60 ° C 95% RH 1000 hour weather resistance test.

In addition, since it is possible to bond at a temperature lower than the heat deformation temperature of the upper film and the lower film, and since pressure is not required, the shape change at the time of bonding does not appear on the surface of the upper film and the lower film. That is, it is possible to provide a product with excellent aesthetics.

Further, no special device is required for printing and curing the adhesive layer 12, and the manufacturing equipment for the thin film switch does not become expensive or complicated.

Note that the gist of the above-mentioned Examples is that the opposing surfaces of the insulating spacers are bonded with a plastisol adhesive containing a copolymer of vinyl chloride and vinyl acetate as a main component. The types of the plasticizer and the stabilizer, the materials of the lower film and the upper film, and the method of forming the electrodes, the insulating spacers, and the adhesive layer are not limited to those in the above-mentioned embodiment. About these, an appropriate thing or a method can be used as needed.

〔The invention's effect〕

As described above, according to the present invention, the viscosity is low, the viscosity does not easily change during the printing process, the tack is small,
The initial strength and environmental resistance, and the compatibility with the insulating spacer made of plastisol whose main component is vinyl chloride are good, and the insulating spacer was bonded with an adhesive whose main component was a copolymer of vinyl chloride and vinyl acetate. Therefore, it is possible to provide a long-life thin film switch having excellent workability, switch characteristics, and aesthetics.

Further, since the adhesive layer is formed between the insulating spacers, no adhesion mark is formed on the surface of the thin film switch, and from this point as well, it is possible to provide the thin film switch having an excellent appearance.

[Brief description of drawings]

FIG. 1 is a sectional view of a thin film switch according to an embodiment of the present invention, FIGS. 2 (a) to 2 (c) are explanatory views showing a manufacturing process of the thin film switch, and FIGS. 3 to 5 are thin film switches. FIG. 7 is a cross-sectional view showing a conventional example of FIG. 1 ... Lower electrode, 2 ... Lower film, 3 ... Upper electrode, 4 ... Upper film, 11 ... Insulating spacer, 11a, 11
b ... Insulating paste, 12 ... Adhesive layer.

Claims (1)

[Claims] 1. A thin film switch in which a lower electrode provided on a lower film and an upper electrode provided on an upper film face each other so as to be contactable and separable via an insulating spacer, and a lower electrode formation surface of the lower film and An insulating spacer made of plastisol containing vinyl chloride as a main component is formed by printing on the upper electrode forming surface of the upper film, and the opposite surface of these two insulating spacers is a plastisol containing a copolymer of vinyl chloride and vinyl acetate as a main component. A thin film switch characterized by being bonded with an adhesive.