JPH053088B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a flexible thin keyboard switch member, and particularly to a keyboard formed by printing and applying a spacer portion using a silicone rubber liquid that has been semi-cured by heat treatment. The present invention relates to a method of manufacturing a flexible thin keyboard switch member provided with a flexible substrate for a switch.

Conventional keyboard switches combine a gold-plated circuit board, usually on a copper-clad phenolic resin laminate as a substrate, with conductive rubber as a contact, and a separate spacer layer in between. It is extremely difficult to make a so-called thin type, and if forced to do so, it has the disadvantage that it becomes complicated and precise and extremely expensive. Furthermore, even with this type of thin spacer, conventional printing of silicone rubber as a spacer requires difficulty in adjusting the thickness during printing, in other words, there is large variation in the thickness of the printed film. There were problems with printability, including poor ``glue'' of the rubber, which had a large impact on the defective rate of this product.
The present invention was made in order to eliminate the above-mentioned drawbacks, and by using an extremely simple manufacturing process,
A flexible substrate for keyboard switches that allows adjustment of the thickness of the printed coating film during printing and improves printability without impairing the elasticity of the special silicone rubber coating film used for spacers. It is an object of the present invention to provide a method for manufacturing a flexible thin keyboard switch member.

As an embodiment of the present invention is shown in FIGS. 1a to 4, a flexible synthetic resin film substrate 1 made of polyester or the like having a thickness of 25 to 150 μm is used.
on one side of (a) graphite powder with a particle size of 0.1 to 60μ, a particle size of 0.1μ
Fine powder consisting of one or more of the following carbon black powder and silver powder with a particle size of 0.1 to 60μ 20~
80% by weight, and (b) 1 of polyurethane resin, chloroprene rubber, polyester resin, and phenolic resin.
5 to 30% by weight of a rubber-based, thermoplastic resin, and thermosetting resin-based organic binder consisting of one or more species;
(C) Mix with 15 to 80% by weight of a solvent such as dimethyl sulformamide, diethyl carbitol, butyl carbitol, isophorone, and turpentine oil (a+b+
c) Dissolved and uniformly dispersed apparent specific gravity 0.9~
1.9, using a suspension with a viscosity of 150-10000 poise,
A desired contact pattern 2 is printed by screen printing (FIG. 1a is a view from the back side), and a thicker spacer layer 3 is formed near the periphery of the contact pattern 2 by the same printing method (FIG. 2). (viewed from the back side), on one side of another flexible synthetic resin film substrate, a desired circuit pattern Ci to be overlapped corresponding to the contact point and spacer pattern Co is printed using the same screen printing method. Then, holes 4 for alignment are provided in both film substrates (FIGS. 3a and 3b), and the holes 4 for alignment allow the contact portion and the spacer portion to be aligned.
A flexible thin keyboard switch member (fourth
In the manufacturing method shown in Figure), desired circuit and contact pattern layers are formed on each of the above film substrates,
Each is printed and dried at a temperature of 95 to 150°C for 5 to 20 minutes, and then pre-printed at 50 to 100°C for 1 to 20 minutes.
The spacer part was printed and coated using a silicone rubber liquid that had been heat-treated and semi-cured for 10 days.
It is characterized in that it is dried at a temperature of 90 to 180° C. for 10 to 30 minutes to form a spacer layer 3 having a thickness of 25 to 150 μm, which is thicker than the circuit and contact pattern layer 2.

The silicone rubber liquid used here is a varnish-like dimethylpolysiloxane initial condensate (degree of polymerization 5,000 to 10,000) (viscosity 0.65 to 10,000 cst (25°C)) dispersed in an organic solvent as it is or together with a curing agent.
It refers to a silicone rubber liquid that has been heat-treated in advance at a temperature of 50 to 100°C for 1 to 10 days to advance condensation polymerization and bring it into a semi-cured state. Dimethylpolysiloxane is obtained by polymerizing dimethyldihydroxysilane obtained by hydrolyzing dimethyldichlorosilane [(CH ₃ ) ₂ SiCl ₂ ].

Furthermore, this silicone rubber liquid will eventually have a three-dimensional network structure mainly composed of dimethylpolysiloxane (including one partially cross-linked) through thermal polymerization, and the silicone In addition to its excellent elasticity, rubber
Stable over time and weather resistant.

In the present invention, the silicone rubber liquid that has been subjected to the above heat treatment has the advantage that there is little variation in the thickness of the printed coating film used as the spacer, and the printing thickness can be easily adjusted, resulting in excellent printability. can.

In this case, both printed substrates 1, that is, the contact parts
When Co and the circuit part Ci are overlapped using the positioning hole 4, the desired circuit part Ci and the desired contact part Co are positioned exactly above and below so that they can operate as a switch. They will be in a position where they can face each other vertically (see Figure 4).

Therefore, the composition of the suspension (a+b+c)
If the above-mentioned quantity limitations in the composition of graphite, carbon black, and silver exceed the upper and lower limits of 20 to 80% by weight, the so-called "glue" and "glue" in the stability and printability of the suspension used for printing may be affected. The conductivity of the film deteriorates, especially below the lower limit, and the conductivity of the film deteriorates, impairing its properties as a conductor.
Moreover, if it exceeds the upper limit, the adhesive strength will deteriorate and it will not be possible.

In addition, regarding particle size, in the case of graphite and silver powder
If it exceeds 60μ, the stability of the suspension and the so-called "glue" of printing will deteriorate, and sufficient adhesion will not be obtained.
In addition, printability deteriorates and conductivity deteriorates, making it unsuitable. Further, if the lower limit is less than 0.1μ, it is usually commercially available and is suitable in view of the viscosity, consistency, printability, etc. of the suspension. In the case of carbon black powder, the particle size is 0.1μ or less because particles with a particle size larger than 0.1μ are not normally available, and in the case of carbon black, the particle size is 0.1μ or less because This is because, unlike silver powder, the particles are bonded together like a chain, so even if the particles are fine, they are suitable for printability, etc.

Next, (b) the organic binder includes a polyurethane resin, such as Paraprene 22S (trade name, manufactured by Nippon Polyurethane Co., Ltd.), and chloroprene rubber, such as Neoprene WRT (trade name, manufactured by Showa Neoprene Co., Ltd.).
As a thermoplastic resin binder such as WD, polyester resin such as Hitachi Chemical Co., Ltd., trade name ESPEL 1300, 1311, etc., as a thermosetting resin binder, phenol resin, such as Sumitomo Decorez Co., Ltd. trade name PA-301. etc. can be used.

However, if the quantity of this organic binder is limited, i.e., less than the lower limit of 5 to 30% by weight, the dispersion stability of the suspension and the printing "glue" will be poor, the consistency will be insufficient, and the printability will not be good. Not possible. If the upper limit is exceeded, the consistency is too high, which worsens the printability and significantly deteriorates the conductivity, so it is not acceptable.

To prepare the suspension described above, the composition raw material (a),
(b) and (c) are mixed in predetermined amounts each (a+b+c),
Dissolve and disperse to give an apparent specific gravity of 0.9 to 1.9 and a viscosity of
Adjust the suspension to 150-10,000 poise. In this case, if the apparent specific gravity of the resulting suspension is less than 0.9, the graphite, carbon black, and silver powder components will be insufficient, resulting in poor conductivity.
If it exceeds 1.9, the dispersibility of the liquid will be poor, the stability will be impaired, and the adhesive force will be poor, so it is not acceptable.

Next, as an insulating substrate on which desired circuits and contact patterns are printed using this suspension, various synthetic resin films can be used in addition to a flexible polyester film substrate. Printing of circuits and contact patterns on this insulating substrate can be easily performed by screen printing using the suspension. Next, use this suspension to print the desired circuit and contact patterns, and the printed surface of the formed board is 95 to 150
Drying is carried out at a temperature of 5 to 20 minutes at a temperature of 95°C, but drying at temperatures below 95°C or for less than 5 minutes is not possible as there is a risk of insufficient drying. On the other hand, it is not necessary to exceed 20 minutes, and exceeding 150 degrees Celsius may have an adverse effect on the substrate itself, so it is not possible.

Next, heat treatment is performed on the surface of the film substrate on which the contact pattern has been formed for 1 to 10 days at a temperature of 50 to 100°C, and a desired spacer pattern is formed on the contact pattern using a semi-cured silicone rubber liquid. Print near the periphery, 10-30 at a temperature of 90-180℃
The spacer layer 3 is formed by drying for minutes, but the heat treatment temperature and number of days of the silicone rubber liquid are limited;
That is, if the temperature exceeds the upper and lower limits of 50 to 100°C and the number of days is 1 to 10 days, the characteristics of the semi-curable silicone rubber liquid will be impaired. If the upper limit is exceeded, most of the heat-treated silicone rubber will harden, resulting in poor printing adhesion, insufficient consistency, and poor printability, and below the lower limit, the heat-treated silicone rubber liquid will It hardly cures, and unlike conventional silicone rubbers, it has poor adhesion and difficulty in adjusting printing thickness. Furthermore, the heat treatment conditions for the silicone rubber liquid used to form the spacer portion by printing are very important.
For example, Toray Silicone SE1700 (white) manufactured by Toray Silicone Co., Ltd. can be used.

The thickness of the silicone rubber spacer pattern coating film dried in this step is preferably 25 to 150 μm. Items exceeding the upper and lower limits of the thickness limit cannot be used as keyboard switch members for the following reasons. First, if the upper limit is exceeded, when the circuit part (Ci) and the contact part (Co) are stacked downward (see Figure 4),
Because the thickness of the circuit is too large, even if the contact part is pressed, it becomes difficult to pass the circuit Ci and the contact part Co up and down, causing a contact failure. Distortion may also cause natural contact, so each is not allowed.
In other words, it is not possible because it does not function as a spacer portion.

In this way, a flexible substrate for a keyboard switch having integrally the spacer portion 3 printed and coated using the semi-curable silicone rubber liquid described above is obtained.

Note that there is an alignment hole (third
Reliable positioning can be achieved by drilling holes (see reference symbol 4 in Figures 3a and 3b).

As shown in FIG. 4, the keyboard switch according to the present invention operates by pressing the conductive part 2 of the contact part Co from the surface of the substrate film 1 with a finger or the like in the direction of the arrow against the elasticity of the spacer layer 3. Then, the conductive part 2 of the circuit part Ci of the lower substrate film 1 is easily and reliably contacted and conduction is established, and the pressing finger etc. is connected to the contact part.
When separated from Co, it is restored by the elasticity of the spacer layer 3, and the contact between the conductive part 2 of the contact part Co and the conductive part 2 of the circuit part Ci is easily and reliably released, and they are separated and restored.

The flexible thin keyboard switch member having semi-hardened silicone rubber as a spacer according to the present invention extremely satisfies the performance as a normal keyboard switch, and of course passes all practical tests. Because the above-mentioned semi-curable silicone rubber liquid is used, the spacer layer formed by this is highly elastic, allowing precise patterns to be printed using screen printing, and the keyboard is better than conventional methods. There is an advantage that flexible substrates for switches can be manufactured. That is, it is possible to obtain a keyboard switch member that is thin, inexpensive, and has high performance.

Briefly explained below with reference to the drawings, Fig. 1a shows a perspective view from the back side when a predetermined contact pattern is printed and formed on a polyester film substrate 1, and Fig. 1b shows a conductive circuit pattern on another film. It is a perspective view when printing on a board|substrate.

FIG. 2 is a perspective view of the semi-curable silicone rubber liquid printed and formed as a spacer layer 3 on the peripheral surface of the contact portion shown in FIG. 1a, viewed from the back side, and FIGS. 3a and 3b. are the contact parts Co (back side) with alignment holes 4 drilled in the respective boards.
and shows the circuit section (surface). Overlap the contact part
Co and the circuit section Ci are positioned so as to face each other as shown in FIG. In other words, by applying pressure in the direction of the arrow (↓), the spacer layer 3 acts as a sufficient cushion and the contact portion
The conductive parts 2, 2 of Co and circuit part Ci come into contact with each other, and current flows through the circuit.

Hereinafter, the present invention will be further described in detail with reference to Examples.

Example 1 (a) 30% by weight of graphite powder with a particle size of 0.1 to 60μ and particle size
Using a suspension (a+b+c) consisting of 15% by weight of carbon black of 0.1 μ or less, (b) 3% by weight of a polyurethane resin, that is, 3% by weight of Paraprene 22S (trade name, manufactured by Nippon Polyurethane Co., Ltd.), and (c) 27% by weight of isophorone. , as shown in FIGS. 1a and 1b, contact points and circuit patterns are independently formed on each substrate 1 by screen printing to a thickness of
It is printed on one side of a 125μ polyester film substrate 1 and dried at a temperature of 100°C for 15 minutes to form a conductive part 2.
was formed. Next, on the surface of the substrate on which the contact pattern has been printed, heat treatment is performed at a temperature of 90°C for 5 days to make a semi-cured silicone rubber liquid, such as Toray Silicone Co., Ltd. trade name Tray Silicone SE-1700 (white). ), as shown in Figure 2, a pattern of the spacer layer 3 with a thickness of 100 μm is printed using the screen printing method, and the temperature is
It was dried at 150°C for 20 minutes to form a spacer layer 3. Print the conductive circuit 2 as described above and form the circuit part Ci.
and a contact portion on which the spacer layer 3 is formed as described above.
Positioning holes 4 were bored in the Co polyester film substrate as shown in FIGS. 3a and 3b, respectively. Finally, using the alignment hole 4, connect the circuit part Ci and the contact Co.
and fixed in a predetermined position facing each other. This completes the manufacturing process of the present invention.

At this time, the obtained flexible substrate for a keyboard switch, that is, a flexible thin keyboard switch member, exhibited excellent elasticity and exhibited sufficient practicality as a keyboard switch. As shown in FIG. 4, when pressed in the direction of the arrow, the switch closes, and when this pressure is released, the switch opens. Furthermore, as mentioned above, by imparting semi-curing properties to the silicone rubber liquid through heat treatment, the thickness of the spacer can be easily adjusted and the defect rate can be reduced. The manufacturing process of the present invention is extremely simple, suitable for mass production, and inexpensive due to printing technology.

In addition, instead of the polyurethane resin, chloroprene rubber (product name: Neoprene WRT, manufactured by Showa Neoprene Co., Ltd.), polyester resin (product name: ESPEL 1311, manufactured by Hitachi Chemical Co., Ltd.), and phenol resin (product name: PA-, manufactured by Sumitomo Decorez Co., Ltd.)
301), almost the same good results were obtained.
In any case, remarkable hardening achieved by the present invention was observed.

[Brief explanation of the drawing]

Fig. 1a is a perspective view of a contact pattern printed and formed on a transparent film substrate according to an embodiment of the present invention, viewed from the back side, and Fig. 1b is a circuit pattern portion to be superimposed by translating the one in Fig. 1a. FIG. 2 is a perspective view of the substrate with a thicker spacer layer formed around the contact pattern shown in FIG. 1a, as seen from the back, and FIG. FIG. 3b is a perspective view of a substrate with alignment holes formed therein. The substrate contact portion Co shown in FIG. A perspective view of the formed substrate, FIG.
FIG. 4 is an enlarged schematic cross-sectional view showing the thin keyboard switch member aligned and stacked and facing each other on the circuit pattern portion Ci shown in FIG. DESCRIPTION OF SYMBOLS 1...Polyester film, 2...Conductive part, 3...Spacer layer, 4...Positioning hole, Co...Contact part, Ci...Circuit part.

Claims (1)

[Claims] 1. On one side of a single flexible synthetic resin film substrate, one or two types of (a) graphite powder with a particle size of 0.1 to 60μ, carbon black powder with a particle size of 0.1μ or less, and silver powder with a particle size of 0.1 to 60μ are applied. 20 to 80% by weight of fine powder consisting of the above, and (b) a rubber-based, thermoplastic resin, and thermosetting resin-based binder consisting of one or more of polyurethane resin, chloroprene rubber, polyester resin, and phenol resin 5 ~30% by weight and (C) 15~80% by weight of a solvent such as dimethylformamide, diethyl carbitol, butyl carbitol, isophorone, and turpentine are mixed (a+b+c) and uniformly dispersed to give an apparent specific gravity of 0.9. ~1.9, viscosity
A desired contact pattern is printed by screen printing using a suspension of 150 to 10,000 poise, and a spacer layer is formed near the periphery of the contact pattern by the same printing method, and then a spacer layer is printed on another sheet of paper. On one side of a flexible synthetic resin film substrate, a desired circuit pattern to be overlapped corresponding to the contact point and spacer pattern is printed by the same screen printing method, and holes for positioning are provided in both film substrates, respectively. In the method for manufacturing a flexible thin keyboard switch member in which the contact portion and spacer portion and the circuit portion are overlapped and opposed to each other by the positioning holes, desired circuits and the like are formed on each of the film substrates. Contact pattern layers are formed by printing and drying at a temperature of 95 to 150°C for 5 to 20 minutes, and then using a semi-cured silicone rubber liquid that has been heat-treated in advance at 50 to 100°C for 1 to 10 days. Then, print and attach the spacer part 90~
A flexible thin keyboard switch characterized in that it is formed by drying at a temperature of 180°C for 10 to 30 minutes to form a spacer layer with a thickness of 25 to 150μ, which is thicker than the circuit and contact pattern layer. Method of manufacturing parts.