JP2878650B2 - Thin film switch and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film switch (membrane switch) in which two films on which electrode patterns are formed are bonded via an insulating spacer, and more particularly, to a bonding structure of both films.

[0002]

2. Description of the Related Art Heretofore, there has been known a thin film switch of this type which employs a bonding structure shown in FIGS.

First, the thin film switch shown in FIG. 5 will be described. This thin film switch is provided between a lower film 2 having a lower electrode 1 printed on the upper surface and an upper film 4 having an upper electrode 3 printed on the lower surface. The lower film 2 and the upper film 4 are bonded together via an adhesive layer 6 laminated on both the front and back surfaces of the spacer film 5 by interposing a spacer film 5 formed by cutting a film with a double-sided adhesive. is there. 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. . The film with a double-sided adhesive, which is the base of the spacer film 5, is formed by continuously coating the adhesive on both the front and back surfaces of a roll-formed film, and after drying, applying a release paper to the surface of each adhesive layer. Affixed.

On the other hand, in the thin film switch shown in FIG. 6, an insulating printing ink is printed on a portion of the lower film 2 excluding the lower electrode 1 to form an insulating spacer 7, and the upper surface of the insulating spacer 7 and the upper film 4 is bonded to the surface on which the upper electrode 3 is formed via an adhesive layer 6. An adhesive is also used for the adhesive layer 6 for the same reason as described above, but the forming method is different. First, an adhesive dry type adhesive is printed on the insulating spacer 7, and then a solvent is dried by a heat drying step. Has been adopted.

In the thin film switch configured as described above,
In each case, a space 9 is formed between the lower electrode 2 and the upper electrode 3 by interposing a spacer film 5 and an insulating spacer 7 between the lower film 2 and the upper film 4. The electrode 1 and the upper electrode 3 are always kept apart. Therefore, when the formation portion of the upper electrode 3 is pressed downward from above the upper film 4 by a finger or the like, the flexible upper film 4 is elastically deformed, and the upper electrode 3 and the lower electrode 1 Comes into contact and the switch is turned on. When the pressing force is removed, the upper film 4 returns to the initial state shown in FIG. 5 or 6 due to the flexibility of the upper film 4, and the upper electrode 3 and the lower electrode 1 are separated from each other to be turned off.

However, these thin-film switches have the following disadvantages because the adhesive layer 6 for bonding the lower film 2 and the upper film 4 is made of an adhesive. That is, in the thin film switch shown in FIG. 5, since an adhesive having low fluidity is used as the adhesive layer 6, air bubbles easily enter between the films 2, 4, and 5 at the time of bonding. In addition, the release paper attached to the surface of the pressure-sensitive adhesive must be peeled off, and since such release paper is not used for products, there is a problem that workability is poor and cost is high. On the other hand, in the thin film switch shown in FIG. 6, since the adhesive layer 6 is formed by printing a solvent-dry adhesive, the adhesive strength of the adhesive is low, and the printability of the adhesive deteriorates with time. In addition, when the adhesive adheres to an undesired portion, there is a problem that the solvent is volatilized and the tackiness of the adhesive increases, which makes it difficult to remove the adhesive.

In order to solve the problems of the conventional thin film switch using an adhesive, the present applicant has proposed a thin film switch which can bond both films without using an adhesive. 62-53535. FIG. 7 is a cross-sectional view showing such a thin-film switch. In this thin-film switch, an insulating paste containing a thermoplastic resin as a main component is printed on an electrode forming surface of one of the lower film 2 and the upper film 4. The lower spacer 2 and the insulating spacer 8 and the upper film 4 are integrated by heating and pressing the insulating spacer 8.

[0008]

As described above, according to the thin-film switch proposed by the present applicant, the insulating spacer 8 previously formed on the lower film 2 or the upper film 4 is heated and pressed. The lower film 2 and the insulating spacer 8 and the upper film 4 can be integrated, and there is an advantage that an adhesive does not need to be used, but this is not without problems.

That is, the insulating spacer 8 is made of a plastisol type mainly composed of a thermoplastic resin such as vinyl chloride, and is an insulating paste having fluidity when printed on the lower film 2 and the upper film 4. When the upper film 4 is overlaid on the lower film 2 with the insulating paste printed on the lower film 2 and the upper film 4, the insulating paste is crushed by the weight of the upper film 4, and The required film thickness cannot be secured. For this reason, after the insulating paste is printed on the lower film 2 and the upper film 4, the insulating paste is heated so as to be melted and gelled by drying.
It is necessary to heat the dried insulating spacer 8 again to cause it to melt and gel. At that time, the insulating spacer 8
Since the two films 2 and 4 cannot be sufficiently joined only by melting and gelling the film, the two films 2 and 4 must be heated and pressurized at the same time. There was a problem that it became complicated.

When the lower film 2 and the upper film 4 are joined by heating under pressure through the insulating spacer 8 as described above, the melting and gelling temperature of the insulating spacer 8, which is the bonding temperature, and the two films 2, 4 Since the thermal deformation temperature of the lower film 2 and the upper film 4 may be thermally deformed unless proper heating and pressing conditions are strictly observed, the insulating spacers 8 formed on the lower film 2 may be particularly deformed.
When the upper film 4 and the upper film 4 are directly bonded, there is a problem that a joining mark is formed at a bonding portion of the upper film 4 and the appearance of the product is deteriorated.

The present invention has been made in view of such problems of the prior art, and has as its object to provide a thin film switch excellent in assembling workability, durability, switch characteristics, and aesthetics at a low cost. It is in.

[0012]

In order to achieve the above object, a thin film switch according to the present invention comprises a lower electrode provided on a lower film and an upper electrode provided on an upper film contacting and separating via an insulating spacer. In the thin film switch, the insulating spacers made of a plastisol containing a thermoplastic resin as a main component are printed and formed on the lower electrode forming surface of the lower film and the upper electrode forming surface of the upper film. The opposing surface of the spacer is made of a resin containing the thermoplastic resin as a main component, and is bonded with a plastisol adhesive having a bondable temperature lower than the thermal deformation temperature of the lower film and the upper film. It is.

In the above structure, the lower film and the upper film may be separate bodies. However, when the lower film and the upper film are formed of a continuous single film, the insulating spacer is formed by the lower film and the upper film. At the same time, the printing process is simplified.

According to another aspect of the present invention, there is provided a method for manufacturing a thin film switch, wherein a lower electrode provided on a lower film and an upper electrode provided on an upper film can be separated from each other via an insulating spacer. In the method of manufacturing a thin film switch facing the, after forming an insulating spacer made of a plastisol containing thermoplastic resin as a main component on each of the lower electrode forming surface of the lower film and the upper electrode forming surface of the upper film, These insulating spacers are heated to melt and gel, and thereafter, on at least one surface of each of the insulating spacers formed on the lower film and the upper film, a resin containing the thermoplastic resin as a main component, and Laminating a plastisol adhesive whose adhesive temperature is lower than the heat deformation temperature of the lower film and the upper film. Then, the lower film and the upper film are overlapped so that the plastisol adhesive is located between the insulating spacers formed on the lower film and the upper film, and then, by heating the adhesive, The insulating spacers are bonded to each other.

[0015]

According to the thin film switch of the present invention, an insulating spacer made of plastisol containing a thermoplastic resin as a main component is printed and formed on the lower electrode forming surface of the lower film and the upper electrode forming surface of the upper film. The opposing surface is mainly composed of a resin containing the thermoplastic resin, and is adhered with a plastisol adhesive having a bondable temperature lower than the thermal deformation temperature of the lower film and the upper film. It has good compatibility with the adhesive and can increase the adhesive strength between the insulating spacers. Further, since the adhesive is a plastisol adhesive containing a resin containing a thermoplastic resin as a main component, it does not gel before heating, and melt gelation occurs by heating, in other words, It is only possible to bond by heating. Since the adhesive temperature, which is the melting and gelling temperature of the adhesive, is lower than the thermal deformation temperature of the lower film and the upper film, there is no possibility that the lower film and the upper film are deformed at the time of bonding. Since it is not required, workability can be improved.

[0016]

Embodiments will be described with reference to the drawings.
FIG. 1 is a cross-sectional view of a thin film switch according to one embodiment of the present invention, in which 11 indicates an insulating spacer, and 12 indicates an adhesive layer. Since the other lower electrode 1, lower film 2, upper electrode 3, and upper film 4 are the same as those of the above-described conventional one, the same numbers are given and the description is omitted.

In this embodiment, insulating spacers 11 are formed on the upper surface of the lower film 2 except for the lower electrode 1 and on the lower surface of the upper film 4 except for the upper electrode 3 by a printing technique. The thin film switch is formed by bonding the opposing surfaces 11 with an adhesive layer 12.

The insulating spacer 11 is formed by printing an insulating paste mainly composed of a thermoplastic resin on both the lower film 2 and the upper film 4 and then heating the insulating paste. As this insulating paste,
For example, a plastisol type obtained by dispersing a thermoplastic resin powder such as a vinyl chloride resin in a liquid plasticizer such as DOP (dioctyl phthalate) and further adding a stabilizer, a thickener, a pigment, and the like as necessary is preferable. is there. That is, such a plastisol has a remarkably high film solid content in a liquid as compared with an organosol or the like using an organic solvent as a dispersion medium.
The film thickness in one printing can be increased, and the number of printings can be significantly reduced.

The adhesive constituting the adhesive layer 12 is mainly composed of a copolymer of vinyl chloride and vinyl acetate, and a plasticizer, and if necessary, a stabilizer and a thickener. The added plastisol adhesive is used. In addition, as a copolymer of vinyl chloride and vinyl acetate, a paste range 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 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 and then polymerized in the presence of a resin is used. In addition, a mixture of these paste resins and a vinyl chloride resin having a large particle size produced by ordinary suspension polymerization, in a range that does not adversely affect the viscosity, flowability, processability, and the like of the paste sol is used. You can also. Further, as the plasticizer, for example, a phthalic acid-based plasticizer such as the DOP,
Examples include fatty acid ester plasticizers such as di-2-ethylhexyl adipate, fatty acid polyester plasticizers such as adipic polyester, phosphate ester plasticizers such as tributyl phosphate, and epoxy plasticizers such as epoxidized soybean oil. be able to. Examples of the stabilizer include inorganic metal compounds such as lead white and basic silicate, organic compounds such as lauric acid and various metal salts, and organic acid liquid composite stabilizers such as calcium-zinc or barium-zinc. Can be used.

The following is a specific example of the composition of the plastisol adhesive applicable to the present invention. Paste vinyl chloride-vinyl acetate copolymer (number average polymerization degree = 1350); 100 parts by weight Plasticizer; 50 to 60 parts by weight Stabilizer; 3 to 6 parts by weight Thickener; A method for manufacturing the thin film switch will be described with reference to FIGS.

First, as shown in FIG. 2, a lower film 2 on which a lower electrode 1 is patterned and an upper film 4 on which an upper electrode 3 is patterned are prepared. Next, as shown in FIG. 3, insulating pastes 11a and 11b are printed on portions of the lower film 2 and the upper film 4 except for the electrodes 1 and 3 by a screen printing method or the like, and the insulating pastes 11a and 11b are heated to form a molten gel. Through an insulating paste 11
a, 11b are dried.

Further, as shown in FIG. 4, an adhesive layer 12 is laminated on the dried insulating pastes (insulating spacers) 11a and 11b by means such as a screen printing method. In this embodiment, the case where the adhesive layer 12 is laminated on both the insulating pastes (insulating spacers) 11a and 11b is shown, but the adhesive layer may be laminated only on one of the insulating pastes.

Next, the connecting portion between the lower film 2 and the upper film 4 was bent, and the electrodes 1 and 3 were accurately positioned by a number of positioning holes 2a and 4a formed in the lower film 2 and the upper film 4, respectively. In this state, both adhesive layers 12 are overlaid. Thereafter, when the laminate is heated at a temperature lower than the thermal deformation temperature of the lower film 2 and the upper film 4 by a heater (not shown), a reaction occurs in the adhesive layer 12 and the adhesive layer 12 is melted and gelled. 12 is cured to obtain the thin film switch shown in FIG.

The thin-film switch of the above embodiment has an adhesive layer 12
Since a fluid plastisol adhesive containing a copolymer of vinyl chloride and vinyl acetate as a main component was used as an adhesive constituting the above, an adhesive layer having a desired pattern can be formed on a desired surface by printing. Therefore, the cost of the thin film switch can be reduced without the need for the release paper and the punching die. In addition, since the wettability to the insulating spacer is good, bubbles are hardly involved, and workability and mass productivity are excellent. In addition, by adjusting the viscosity of the adhesive to 100 to 1000 poise, more preferably 100 to 500 poise, it is possible to obtain a coating film which is excellent in printability and easy to bond.

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

Further, since the adhesive contains almost no volatile solvent, the viscosity is high and the printability hardly deteriorates even after printing for a long time. For example, when a solvent-drying type adhesive is used, the viscosity must be adjusted every 100 to 200 shots, whereas in the case of the adhesive of the above embodiment, continuous printing of 1000 to 2000 shots or more is possible. It is. However, printability can be further improved by adding 0 to 5%, usually 1% or less of a diluent which is relatively difficult to evaporate.

As described above, since the adhesive has a film forming component of almost 100%, a desired film thickness can be obtained by using an inexpensive Teflon mesh and a lightweight frame. The cost can be reduced.

Further, the insulating spacer is formed of a plastisol mainly containing vinyl chloride which is a thermoplastic resin, and these are made of a plastisol mainly containing a copolymer of vinyl chloride and vinyl acetate which is the same vinyl chloride. Since the adhesive is used for bonding, in other words, the copolymer, which is the main component of the adhesive, contains vinyl chloride. Can be. That is, the T-peel strength is 2.5 to 5 k.
It has a peel strength of g 25 mm, and shows no deterioration in peel strength even after a weather resistance test at 58 ° C. for 1000 hours or 60 ° C. and 95% RH for 1,000 hours.

After the insulation spacer is melted and gelled,
Since the adhesive is laminated on the insulating spacer, when the upper film and the lower film are laminated after the adhesive is laminated, even if a force is applied between both films, the gap between the upper electrode and the lower electrode Is maintained by the insulating spacer that has undergone melt gelation. Furthermore, since the adhesive is not cured, the upper film and the lower film are simply superimposed, and the viscosity of the adhesive itself keeps both films together, so pressurizing to dry the adhesive There is no need to perform this, and the workability of the bonding step can be improved. Thus, the top film, adhesive,
There is no need to heat the lower film laminate, and
Since the plastisol adhesive can be melt-gelled and bonded at a temperature lower than the thermal deformation temperature of the upper film and the lower film, it is possible to prevent the upper and lower films from being thermally deformed during bonding. It is possible to provide a thin film switch with excellent aesthetic appearance.

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

The gist of the above embodiment is that the opposite surface of the insulating spacer is made of the same type (vinyl chloride) resin (vinyl chloride and vinyl acetate) containing a thermoplastic resin (vinyl chloride) as a main component of the insulating spacer. Polymer) as a main component, and the method for producing the copolymer, the type of plasticizer and stabilizer, the material of the lower film and the upper film, and the electrodes, insulation The method for forming the spacer and the adhesive layer is not limited to those in the above embodiment. As for these, appropriate ones or methods can be used as needed.

[0032]

As described above, according to the present invention,
On the lower electrode forming surface of the lower film and the upper electrode forming surface of the upper film, an insulating spacer made of a plastisol containing a thermoplastic resin as a main component is formed by printing, and the opposing surfaces of the two insulating spacers contain the thermoplastic resin. Resin and the adhesive temperature is lower than the thermal deformation temperature of the lower film and the upper film is bonded with a plastisol adhesive. It is possible to increase the bonding strength between each other, and since the bondable temperature, which is the melting and gelling temperature of the adhesive, is lower than the heat deformation temperature of the lower film and the upper film, the lower film and the upper film may be deformed at the time of bonding. There is no need to apply pressure at the time of bonding, so that various effects can be achieved, such as improved workability. Door can be.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a thin-film switch according to one embodiment of the present invention.

FIG. 2 is an explanatory view showing a manufacturing process of the thin film switch of FIG.

FIG. 3 is an explanatory view showing a manufacturing process of the thin-film switch of FIG. 1;

FIG. 4 is an explanatory view showing a manufacturing process of the thin-film switch of FIG. 1;

FIG. 5 is a sectional view showing a conventional example of a thin film switch.

FIG. 6 is a cross-sectional view showing another conventional example of the thin-film switch.

FIG. 7 is a cross-sectional view showing still another conventional example of a thin film switch.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Lower electrode 2 Lower film 3 Upper electrode 4 Upper film 11 Insulating spacer 11a, 11b Insulating paste 12 Adhesive layer

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01H 13/00-13/76 H01H 11/00-11/06

Claims (3)

(57) [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 oppose each other via an insulating spacer so as to be able to contact and separate from each other. An insulating spacer made of a plastisol containing a thermoplastic resin as a main component is printed and formed on the upper electrode forming surface of the upper film, and the opposing surfaces of these two insulating spacers are mainly made of a resin containing the thermoplastic resin, and A thin film switch, wherein the thin film switch is bonded with a plastisol adhesive having a bondable temperature lower than the thermal deformation temperature of the lower film and the upper film. 2. The method according to claim 1, wherein the lower film and the upper film are 1
2. The thin film switch according to claim 1, wherein the thin film switch is formed of a continuous body obtained by folding a film. 3. A method of manufacturing a thin-film switch, comprising: a lower electrode provided on a lower film and an upper electrode provided on an upper film facing each other via an insulating spacer so as to be able to contact and separate from each other. On each of the forming surface and the upper electrode forming surface of the upper film, an insulating spacer made of a plastisol containing a thermoplastic resin as a main component is printed and formed, and then these insulating spacers are heated and melt-gelled, and then the lower film is formed. And on at least one surface of each insulating spacer formed on the upper film,
The resin containing the thermoplastic resin as a main component, and the adhesive temperature is laminated plastisol adhesive lower than the thermal deformation temperature of the lower film and the upper film,
Thereafter, the lower film and the upper film are overlapped so that the plastisol adhesive is located between the insulating spacers formed on the lower film and the upper film, and then, by heating the adhesive,
A method for manufacturing a thin film switch, wherein the insulating spacers are bonded to each other.