JPS6282620A - Membrane switch - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a flexible membrane switch.

[Prior Art] A membrane switch is a device in which opposing contacts (electrodes) are arranged on opposing surfaces of two base films with a spacer interposed between them.
The switch function of conduction and insulation can be easily performed.

In recent years, it has been used as a keyboard switch for calculators, personal computers, word processors, etc., as a panel switch for televisions, VTRs, various remote controls, copying machines, facsimiles, etc., as a panel switch for sound W machines, electrical products, etc. communication equipment, measuring equipment,
Membrane switches are also widely used in control systems (I! equipment, etc.).

Due to its structural features, this membrane switch can be made thinner, and since the contact parts are easily sealed, it can also be constructed to be dust-proof and drip-proof.By using this membrane switch, products can be made more compact. This can be expected to improve reliability.

Since this membrane switch performs a switching action by repeatedly pressing the switch, its base film is required to have flexibility. In addition, adhesion between the contact point (conductive electrode) and the base film during repeated pressing, peeling resistance, and adhesion between the printing ink printed for display and the base film are required. Furthermore, the base film is required to be resistant to scratches due to repeated pressing.

In addition, in order to prevent dimensional changes during processing and the resulting deterioration of flatness, a base film that is heat resistant and stable is required.

Conventionally, various flexible synthetic resin films have been used as base films for membrane switches, particularly polyethylene terephthalate films.

However, when these are used as a base film, among the required characteristics, attempting to improve flexibility deteriorates switch resistance and adhesion, and also deteriorates adhesion and scratch resistance. If it is to be maintained well, the flexibility is insufficient.

A membrane switch that has good flexibility, adhesion, and scratch resistance has not yet been obtained.

The present inventor has discovered that each of the above characteristics can be simultaneously satisfied by using a polyethylene naphthalene dicarboxylate film having specific physical properties as a base film, and has arrived at the present invention.

[Object of the invention] The object of the invention is to provide good flexibility and contact points (conductive electrodes).
An object of the present invention is to provide a membrane switch that has good adhesion between the part and the base film, good adhesion between the printing ink and the base film, and scratch resistance.

[Structure of the Invention] The present invention provides a membrane switch in which opposing contacts are arranged on opposing surfaces of two (upper and lower) base films, in which at least one base film serving as the upper or lower base film is F-5. The value is now 11! F/- or more, density is 1,375y/ad or less, and heat shrinkage rate is 1.0 when heated at 120℃ for 30 minutes.
% or less. A membrane switch characterized by using a biaxially oriented polyethylene naphthalene dicarboxylate film.

First, the present invention will be explained with reference to the drawings.

1, 2 and 3 are illustrations of embodiments of membrane switches of the present invention.

1 is a flexible upper base film. 2 is the upper contact (
The electrode is formed of a semiconductor thin film such as indium oxide or copper iodide, or a metal thin film such as gold, palladium, or mesh-like aluminum.

The upper contacts 2 are carried on upper terminals provided at the ends of the upper substrate film 1 for connection to external electronic circuitry.

4 is a lower contact, which is placed in a position opposite to the upper contact, and is made of a semiconductor thin film or metal 7 similar to the upper contact.
It is formed of a membrane. The lower contact 4 is connected to a lower terminal provided at the end of the lower base film 5 for connection to an external electronic circuit.

The lower base film 5 is the same as the base film described above. It is better to use a switch with the same characteristics such as temperature expansion coefficient and humidity expansion coefficient, and the accuracy of the switch action will be better, and the deterioration of flatness and shape change such as warping of the membrane switch due to environmental changes and changes over time will be better. This is because it is difficult to wake up.

Further, as shown in FIG. 2, a reinforcing film 6 may be further formed under the base film described below in order to reinforce mechanical strength.

Polyester film is used as a reinforcing film.

Acrylic resin sheet, hard polyvinyl chloride sheet 1~.

A glass plate or the like is used.

3 is a spacer, which is installed around the membrane switch in a frame-like manner with a constant thickness, and separates a portion of the contact from the lower contact.

The spacer 3 can be installed only around the membrane switch as shown in FIG. 3, or it can be installed between individual contacts as shown in FIG. 1 or 2. Instead of spacers installed between solid contacts, point-like elastic projections of the base film may be formed.

The space between the base film and the lower base film is usually a void, but it may also be filled with a liquid having electrical insulation properties.

Further, the upper base film 1 is printed for normal display.

A protective film (not shown) may be coated roughly on the upper base film.

In addition, when a reinforcing film is used in the lower part as shown in FIG. 3, the lower base film can also be omitted (also used).

In the present invention, the F-5 value (stress at 5% stretching) of the base film is in the longitudinal direction (stretching direction of the film).

It is necessary that the speed in both the lateral direction (width direction of the film) is 11 kg/s or more.

The lower the F-5 value of the base film, the lower the flexibility, and repeated pressing will cause the shape to change.
A phenomenon occurs in which the upper and lower contacts come into contact even when they are not pressed down. From this point, the F-5 value is 12/(9
/I]lll1 or more is preferable, '+3Kg/
More preferably, it is mtA or more. F of base film
-When the L5 value exceeds 18 kg/-, the adhesion between the contact and the base film becomes low, making it easy to peel off, and the adhesion between the base film and printing ink (printability)
It also gets worse. From this point, the F-5 value is 18! IF/s
It is preferably less than or equal to 16 kg/1ruA, and more preferably 16 Kg/1ruA. In the present invention, the density of the base film is 1,350 g/cm'- or more,
It is necessary that it is 1,375/(g/cm or less).

When the density of the base film exceeds 1.375 g/ci,
The crystallinity becomes too high, the toughness is lost, and the fragility is low when processed into a membrane switch. From this point of view, it is more preferable that the density is 1,370 g/cm' or less. The lower the density of the base film, the better the flexibility, but if it is lower than 1.3509/cm', repeated pressing will cause scratches, making the display difficult to read, and the contact condition of the contacts will be poor. Become. From this point, the density of the base film is 1.353 g/ad
It is preferably at least 1.356 g/cm', and more preferably at least 1.356 g/cm'.

In the present invention, the heat shrinkage rate of the base film when heated at 120°C for 30 minutes must be 1.0% or less in both the longitudinal direction (length direction of the film) and the transverse direction (width direction of the film). be.

Heat shrinkage rate of base film at 120℃ for 30 minutes is 1.0%
Exceeding this value will cause dimensional changes in the culm due to processing including heating, which will impair the accuracy of the switch action, and the flatness of the membrane switch will not only spoil the aesthetics of the product, but also cause repeated pressing. Therefore, even when the button is not pressed down, the upper contact and the lower contact may come into contact with each other, making it easy to cause a problem. From this point, the thermal contraction rate when heated at 120°C for 30 minutes is 0.8 in both the vertical and horizontal directions.
% or less, more preferably 0.6% or less, and particularly preferably 0.4% or less.

In the present invention, as at least one base film,
It is essential to use biaxially oriented polyethylene naphthalene carboxylate, which makes it possible to create a base film that simultaneously satisfies the above properties.

Polyethylene Natsuta Range Rupoxyle-1 of the present invention
means a polymer, copolymer, or mixture containing polyethylene-2,6-naphthalene dicarboxylate at 80 ffl f1% or more, and also includes a polyester composition that does not essentially lose the properties of this polymer. This polymer also contains stabilizers such as phosphoric acid, phosphorous acid and their esters, titanium oxide, and particulate silica.

It may also contain a lubricant such as calcium carbonate. J3, if transparency is required, it is preferable that no lubricant or the like be contained, or that a small amount of camellia be contained.

The preferable intrinsic viscosity of polyethylene naphthalene dicarboxylate is 0.5 to 0.9, more preferably 0.5 to 0.9.
52 to 0.8.

′ of the biaxially oriented film in the present invention! The manufacturing method A is a method of simultaneously stretching in the vertical and horizontal directions using common rolls and stenters. Further, it is possible to adopt a method of sequentially stretching in the longitudinal and lateral directions, or a method of stretching in at least two or more stages in the longitudinal direction in addition to the transverse direction.

The following manufacturing method is exemplified, but is not limited thereto.

After melt extrusion at 280 to 320°C and quenching, the substantially non-oriented unstretched sheet is stretched at a wetness of 110°C to 180°C.
, preferably at 115°C to 150°C and at a stretching ratio of 3 to 5 times, in both the longitudinal and lateral directions. (may be stretched). Heat set at 170°C to 260°C.

In the present invention, the thickness of the base film is not particularly limited, but is usually 12 μm to 350 μm, and from the viewpoint of strength and flexibility, 25 μm to 25 μm (preferably 1 μm, 5 μm).
More preferably, the thickness is from 0 μm to 200 μm.

[Examples] The present invention will be further explained based on Examples below. Note that various physical property values and characteristics in the present invention were measured and defined as follows.

11) Cut the film for measuring F-5 value into 10mm pieces and 15cm in length.
-1 to 1100 a/min. When pulled using an Instron type universal tensile testing device, it is determined from the stress at 5% tension. It is expressed as the force applied per unit cross section of the original film <K'J/'mi).

(2) Density r+-- This is the value measured by the float-sink method in a mixed solvent of heptane and carbon tetrachloride at 25°C.

(3) Heat shrinkage rate: open, no tension, 120℃
It was left to stand for 30 minutes and then measured. If the original length is Qo and the measured length is A, then [(fl o-D > / D o l
! Expressed as x100 (%).

Furthermore, the characteristics of the membrane switch were evaluated as described below.

(4) As a flexible membrane switch, the insulation resistance is 100MΩ or less when not tested by repeatedly pressing ().
That is, the number of repeated presses was determined when the F part contact and the lower contact tend to come into contact with each other even when not pressed, resulting in poor insulation.

Normally, 1 million times or more is considered good.

(5) A test was conducted in which the membrane switch was repeatedly pressed down, and the conduction resistance in the pressed state was measured, and the number of repeated presses at which conductivity deteriorated was determined.

In addition, a case where conduction did not occur two or more times within 10,000 presses was defined as a poor conductivity state.

If the adhesion between the contact and the base film is poor, repeated pressing will cause the contact to crack, and eventually the contact will peel off, resulting in a loss of electrical conductivity.

(6) Scratch resistance As a membrane switch, we conducted a test of repeatedly pressing the switch 1 million times, and then visually evaluated the scratch status on the surface.

◎...The scratches are almost invisible.

0...One scratch is slightly visible, but good.

△: Scratches are visible, but the aesthetic appearance is not bad (not bad), and there is no practical problem. The printed information is also visible.

×: There are many scratches and the appearance is poor, making it unusable for practical use. The printed display is also easy to understand.

(Sword) The processing process for surface-mounted membrane switches after processing includes a process in which various talking body films are heated, and depending on the base film used, deformation may occur during the processing process and the flatness may deteriorate. :b Yes.

After commercialization as a membrane switch, its flatness was visually evaluated as described below.

0...Good flatness.

△...Flatness is a little poor, but it does not impair the aesthetics and can be commercialized.

X: Poor flatness, detracts from aesthetics, and cannot be commercialized.

Example 1 A polyethylene-2,6-naphthalene dicarpoxylate beret having an intrinsic viscosity of 0.65 obtained by a conventional method was dried, then melt-extruded, and after cooling, a substantially non-oriented unstretched film was ! ? Ta.

This unstretched film was stretched to 3.5 times in the machine direction (longitudinal direction of the film) at 120°C, then stretched to 3.7 (8 times) in the transverse direction (film width direction) at 140°C, and then stretched to 24 times
Heat treated at 0°C for 20 seconds to produce 1q of biaxially oriented film with a thickness of 75μ.

This 2@oriented film is used as a base film, and a commercially available conductive contact paste containing metal powder is applied to the surface of the film.
U-40 [Asahi Chemical Research Institute Co., Ltd.! ll] was applied and dried to form contacts and terminals. Furthermore, the J: sea urchin base film with the above contacts facing each other is laminated with an adhesive via a
/child.

The surface of the upper base film is coated with commercially available UV1i! ll
An i-kabo printing ink was applied for display purposes and cured by UV irradiation.

The membrane switch had good flexibility, adhesion, and scratch resistance. (Table-1) Example 2.3 and Comparative Example 1 In Example 1, the stretching ratio in the longitudinal and transverse directions was 63 J
: Biaxially oriented films with different F-5 values were obtained by adjusting the stretching temperature.

This was used as a base film in the same manner as in Example 1, and the characteristics of the membrane switch are shown in Table 1.

1! Table 1 shows the characteristics of the membrane switch. The lower the F-5 value, the worse the flexibility, and the lower the F-5 value, the worse the flexibility.
It can be seen that the higher the −5 value, the worse the adhesion.

Comparative Example 2 Polyethylene terephthalate was used instead of polyethylene-2,6-naphthalene dicarboxylate as a frame film, stretched 3.5 times in the machine direction at 90°C, and then stretched 3.8 times in the transverse direction at 120°C. It was stretched twice and heat treated to obtain a biaxially oriented film with a film thickness of 75 μm.

Table 1 shows the characteristics of a membrane switch obtained using this as a base film in the same manner as in Example 1. It has poor flexibility due to its small F-5 value.

Examples 4-5. Comparative Example 3 Biaxially oriented films having different densities and heat shrinkage rates were obtained by adjusting the heat treatment temperature and the stretching ratio in the longitudinal and transverse directions in accordance with J3 in Example 1. Table 1 shows the characteristics of a membrane switch obtained in the same manner as in Example 1 using this as a base film.
It was shown to.

It can be seen that the higher the density, the worse the flexibility, and the lower the density, the worse the scratch resistance.

Also, if the thermal shrinkage rate increases when heated at 150℃ for 30 minutes, the coating liquid, paste, and ink will dry out during processing.

The base film was deformed due to heating and UV irradiation for curing, resulting in poor processing flatness.

[Brief explanation of drawings]

Figures 1, 2, and 3 show actual membrane switches.
It is a part of a cross-sectional view that does not show the configuration of the M mode. 1. Upper base film 2, -L contact 3, spacer 4, lower contact 5, lower base film 6, reinforcing film drawings (no changes in content) Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] In a membrane switch in which opposing contacts are arranged on opposing surfaces of two base films, at least one base film has an F-5 value (5% elongation stress) of 11 kg/mm^2 or more and a density of 1. 375g/
A membrane switch characterized by using a biaxially oriented polyethylene naphthalene dicarboxylate film having a thermal shrinkage rate of 1.0% or less when heated at 120° C. for 30 minutes.