JPH0239054B2 - - 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 equipped 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 kind of thin type, conventional printing of silicone rubber as a spacer has difficulty adjusting the thickness during printing, that is, there is large variation in the thickness of the printed coating, and furthermore, after printing, There were problems with printability, including poor adhesion of the silicone rubber, which was largely related to 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, on one side of a flexible synthetic resin film substrate 1 made of polyester or the like having a thickness of 25 to 150 μm, (a) 0.1~60μ graphite powder, particle size 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, chloropyrene rubber, polyester resin, and phenolic resin.
5 to 30% by weight of a rubber-based, thermoplastic resin, or thermosetting resin binder consisting of one or more species, and (c) a solvent such as dimethylformamide, diethyl carbitol, butyl carbitol, isophorone, and turpentine oil. ~80% by weight was mixed (a+b+c) and uniformly dispersed, with an apparent specific gravity of 0.9-1.9 and a viscosity of
A single cut 5 is made approximately in the center of the film substrate 1 using a suspension of 150 to 10,000 poise.
When the film substrate 1 is folded in half about the line shown in FIGS. 3a and 3b, the desired circuit pattern and the contact pattern to be brought into contact with the desired circuit pattern are exactly opposite to each other. Then, a desired circuit pattern and a contact pattern are printed on the film substrate surface on both sides of the cut line 5 using a screen printing method (FIG. 1a,
(Fig. 1b) (for example, drying at a temperature of 95 to 100°C for 5 to 20 minutes) Furthermore, a spacer layer 3 is similarly printed near the periphery of the contact pattern (Fig. 2a,
(Fig. 2b), the film substrate 1 is then folded in half around the line of the notch 5, and a flexible film is formed so that the contact portion and spacer portion Co and the circuit portion Ci overlap and face each other. In the method for manufacturing a thin keyboard switch member (Fig. 4),
Heat treated in advance at a temperature of 50 to 100℃ for 1 to 10 days,
The spacer layer 3 is formed by printing and applying a semi-cured silicone rubber liquid and drying at a temperature of 90 to 180°C for 10 to 30 minutes to form the spacer layer 3 which is thicker than the circuit and contact pattern layer 2. It is characterized by

The silicone rubber liquid used here refers to a varnish-like dimethylpolysiloxane initial condensate (degree of polymerization 5000 to 10000) (viscosity 0.65 to 10000 cst (25
℃)) is heat-treated in advance at a temperature of 50 to 100 degrees Celsius for 1 to 10 days to advance condensation polymerization to 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 (including one partially cross-linked) mainly composed of dimethylpolysiloxane through thermal polymerization,
The silicone rubber has excellent elasticity, stability over time, and weather resistance.

In the present invention, the silicone rubber liquid that has been subjected to the heat treatment is particularly effective in curing the printed coating film as a spacer with little variation in thickness, easy adjustment of the printing thickness, and excellent printability. can.

In this case, when the printed board 1 is folded inward (folded in half), the desired circuit section
Each pattern is formed on the same surface of the board at a position where they can face each other vertically so that Ci and a desired contact point Co are positioned exactly above and below and can operate as a switch (Figs. 1a and 1b). , 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. In particular, if the consistency is below the lower limit, the conductivity of the film will be extremely poor and the properties as a conductor will be impaired, and if it exceeds the upper limit, the adhesive force will be poor and it is not acceptable.

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, since the printability is poor, the conductivity is poor and it is not possible. 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 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. below the lower limit of 5 to 30% by weight, the dispersion stability of the suspension and the "glue" of printing will be poor, but 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
Dry for 5-20 minutes at a temperature of °C.

Next, on the surface of the film substrate on which the circuit and contact patterns were formed as described above, a film was applied at a temperature of 50 to 100°C.
A desired spacer pattern is printed near the periphery of the contact pattern using a semi-cured silicone rubber liquid subjected to heat treatment for ~10 days, and heated at 90 to 180°C.
Dry for 10-30 minutes at a temperature of . That is, the spacer layer 3 is formed (see FIGS. 2a and 2b).

Therefore, if the heat treatment temperature and number of days for the silicone rubber liquid exceed the upper and lower limits of 50 to 100°C and 1 to 10 days, the properties 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 print and form the spacer portion are very important. For example, the product name Toray Silicone manufactured by Toray Silicone Co., Ltd.
SE1700 (white) etc. can be used for this.

Note that the pattern coating film of the silicone rubber spacer portion dried in this step preferably has a thickness of 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 folding the circuit part Ci and the contact part Co (see Figure 4), the thickness of the spacer layer 3 is too large, so even if the contact part is pressed, the circuit part
It becomes difficult to conduct vertically between Ci and the contact part Co, causing a contact failure.If the distance is below the lower limit, the distance between the two is too short, and even a slight distortion of the board may cause spontaneous contact, so each is not allowed. . In other words, it is not possible because it does not function as a spacer portion.

Next, since the polyester film substrate 1 on which the spacer layer has been formed as described above must be folded in half for use, appropriate cuts 5 are required in this case. Without this notch, the contact between the circuit and the contacts would be poor and would not be possible.

That is, in the film substrate on which the spacer layer 3 is formed, a notch is formed between the contact part and the spacer part and the circuit part for folding and overlapping both parts (see FIGS. 3a and 3b).
(see figure).

Finally, the film substrate is folded along the notch 5 so that the contact portion and spacer portion and the circuit portion are overlapped and opposed to each other.

In this way, the method of manufacturing the flexible thin keyboard switch member of the present invention is completed. That is, a flexible substrate for a keyboard switch is obtained which integrally has a spacer portion printed and coated using a semi-curing silicone rubber liquid.

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.

As mentioned above, a flexible substrate for a keyboard switch, that is, a flexible thin keyboard switch member having a spacer obtained using semi-curing silicone rubber is shown in FIGS. 3a, 3b and 4 as an example. Complete as shown in the diagram. The flexible thin keyboard switch member according to the present invention satisfies its performance as a normal keyboard switch, and of course passes all practical tests. Because a semi-curing silicone rubber liquid is used, the spacer layer formed is highly elastic, allowing precise patterns to be printed using screen printing, and is more flexible for keyboard switches than conventional methods. This method has the advantage that a flexible substrate 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 of a polyester film substrate 1 on which a predetermined conductive circuit and contacts, that is, conductive portions 2 are printed and formed, and FIG. 1b is an enlarged sectional view ( between A and B).

In FIGS. 2a and 2b, a semi-curing silicone rubber liquid is printed as a spacer layer 3 on the peripheral surface of the contact portion in FIG. 1a.
Figure a is a perspective view thereof, and figure 2b is an enlarged sectional view along A'-B'. In the first step, circuits and contacts as shown in FIGS. 1a and 1b are formed, and in the next step, the circuits and contacts as shown in FIGS.
A spacer layer 3 is formed as seen in Figures a and 2b.

Next, FIGS. 3a and 3b show the substrate obtained in the next step, in which a cut 5 is formed in the middle part. Finally, fold this board 1 in half and overlap it with the notch 5 as the center, and then
and the circuit section Ci are positioned so as to face each other as shown in FIG. In other words, in the direction of the arrow (↓)
By applying pressure to the spacer layer 3, the spacer layer 3 acts as a sufficient cushion, and the conductive parts 2, 2 of the contact part Co and the circuit part Ci come into contact with each other, and a current flows in 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
A suspension (a+b+
c), as shown in Figures 1a and 1b, a conductive circuit and contact pattern 2 was printed on one side of a 100μ thick polyester film substrate 1 by screen printing method, and the temperature was 100°C. The conductive portion 2 was formed by drying for 15 minutes. Next, the contact pattern conductive portion 2 on the surface of the polyester film substrate 1 on which this circuit and contact pattern are printed
Near the periphery, a silicone rubber liquid heat-treated at a temperature of 75° C. for 7 days to make it semi-curable, such as Toray Silicone SE1700 (trade name) manufactured by Toray Silicone Co., Ltd., is placed near the periphery, as shown in Figures 2a and 2b. As shown in Figure 3, three desired spacer layer patterns having a thickness of 125μ were printed using a screen printing method, and dried at a temperature of 150°C for 20 minutes to form spacer layer 3. As shown in FIGS. 3a and 3b, a notch 5 was formed in the polyester film substrate printed in this manner at the center between the contact portion and spacer portion and the circuit portion.

Next, the film substrate 1 is folded in half along the notch 5, and the contact portion and spacer portion, that is, the contact portion Co and the circuit portion Ci are stacked and facing each other, as shown in FIG. let At this time, an alignment hole 4 for overlapping the substrates in a fixed position can be formed at a desired position of the substrate 1, as shown in FIGS. 3a and 3b. 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, by making the silicone rubber liquid semi-curable through heat treatment, the thickness of the spacer could be easily adjusted, resulting in a reduction in the defective rate. The manufacturing process of the present invention is extremely simple and inexpensive due to printing technology and is suitable for mass production.

In addition, instead of the above polyurethane resin, chloroprene rubber (trade name: Neoprene WRT, manufactured by Showa Neoprene Co., Ltd.), polyester resin (trade name, Espel 1311, manufactured by Hitachi Chemical Co., Ltd.), and phenol resin (trade name, manufactured by Sumitomo Decorez Co., Ltd.) are used.
Almost the same good results were obtained using PA-301). In any case, the remarkable effects of the present invention were recognized.

Example 2 (a) 20% by weight of graphite powder with a particle size of 0.1 to 60μ and particle size
Suspension (a+b+c) consisting of 40% by weight of silver powder of 0.1 to 60μ, (b) 25% by weight of polyurethane resin, i.e., 25% by weight of Paraprene 22S manufactured by Nippon Polyurethane Co., Ltd., and (c) 20% by weight of butyl carbitol.
As shown in Figures 1a and 1b, using
A conductive circuit and contact pattern 2 was printed on one side of a 75 μm thick polyester film substrate 1 by screen printing, and dried at a temperature of 120° C. for 10 minutes to form a conductive portion 2. Next, the vicinity of the periphery of the contact pattern conductive portion 2 on the surface of the polyester film substrate 1 on which the circuit and contact pattern were printed in this step was heat treated at a temperature of 100° C. for 2 days,
Semi-curable silicone rubber liquid, such as Toray Silicone Co., Ltd. (trade name: Toray Silicone Co., Ltd.)
Silicone SE1700 (white) is used as an example.
As shown in FIGS. a and 2b, three desired spacer layer patterns having a thickness of 75 μm were printed using a screen printing method and dried at a temperature of 135° C. for 15 minutes to form a spacer layer 3. In the polyester film substrate printed in this step, as shown in FIGS. 3a and 3b, a notch 5 was formed between the contact portion and spacer portion and the circuit portion. At this time, the contact portion Co,
An alignment hole 4 for overlapping the circuit portion Ci in a fixed position can also be formed at a desired position of the substrate 1, as shown in FIGS. 3a and 3b.

Next, the film substrate 1 is folded in half along the notch 5, and the contact portion and spacer portion, that is, the contact portion Co and the circuit portion Ci are stacked and facing each other, as shown in FIG. let

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 Figure 4, press in the direction of the arrow to close the switch.
When this pressure is released, the switch opens. In addition, by heat-treating the silicone rubber liquid to make it semi-curable, 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 and inexpensive due to printing technology and is suitable for mass production.

In addition, instead of the above polyurethane resin, chloropyrene rubber (trade name: Neoprene WRT, manufactured by Showa Neoprene Co., Ltd.), polyester resin (trade name, Espel 1311, manufactured by Hitachi Chemical Co., Ltd.), and phenol resin (trade name, manufactured by Sumitomo Decorez Co., Ltd.) are used.
Almost the same good results were obtained using PA-301). In any case, the remarkable effects of the present invention were recognized.

[Brief explanation of drawings]

Figure 1a is a perspective view showing a desired circuit and contact pattern formed on a substrate in an embodiment of the present invention, Figure 1b is an enlarged sectional view taken along line A-B in Figure 1a, and Figure 2a is Similarly, FIG. 2b is a partial perspective view of a substrate having a spacer layer printed near the periphery surrounding a desired contact pattern on the same side of the substrate in the next step in an embodiment of the present invention, and FIG. Enlarged sectional view along line '-B', No. 3a
The figure is also a perspective view of a substrate in which a notch is provided approximately in the middle of the substrate in the next step in an embodiment of the present invention, and Figure 3b is an enlarged view of Figure 3a along the line A''-B''. The cross-sectional view, FIG. 4, is a schematic cross-sectional view of one embodiment of the present invention in which the board is folded in two along the notch so that the contact portion, the spacer portion, and the circuit are overlapped and opposed to each other. DESCRIPTION OF SYMBOLS 1...Polyester film, 2...Circuit and contact pattern, ie, conductive part, 3...Spacer layer, 4...Positioning hole, 5...Notch, Co...Contact part, Ci...Circuit part.

Claims (1)

[Claims] 1. On one side of a single flexible synthetic resin film substrate, (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 20 to 80% by weight of fine powder consisting of one or more of the following: (b) rubber-based, thermoplastic resin and thermoplastic resin consisting of one or more of polyurethane resin, chloropyrene rubber, polyester resin and phenolic resin 5 to 30% by weight of a curable resin binder and (c) 15 to 80% by weight of a solvent such as dimethylformamide, diethyl carbitol, butyl carbitol, isophorone and turpentine oil are mixed (a+b+c) and dissolved uniformly. Dispersed apparent specific gravity 0.9-1.9, viscosity
Using a suspension of 150 to 10,000 poise, the film substrate is folded in half around a single notch line provided approximately in the center of the film substrate, resulting in a desired circuit pattern. Print the desired circuit pattern and contact pattern on the film substrate surface on both sides of the notch line by screen printing so that the contact pattern and the contact pattern to be brought into contact with each other face each other exactly. Further, a spacer layer is formed near the periphery of the contact pattern by printing, and then the film substrate is folded in half around the cut line to form the contact and spacer layers. In a method for manufacturing a flexible thin keyboard switch member in which the circuit portion is overlapped and faces each other, heat treatment is performed in advance at a temperature of 50 to 100°C for 1 to 10 days,
It is characterized by being constructed by printing and applying a semi-cured silicone rubber liquid and drying at a temperature of 90 to 180°C for 10 to 30 minutes to form the spacer layer which is thicker than the circuit and contact pattern layer. A method for manufacturing a flexible thin keyboard switch member.