JPS6193521A - Membrane keyboard - 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 "Field of Industrial Application" The present invention relates to a membrane keypad 1 in which base films and spacers of upper and lower circuit boards are ultrasonically welded.

``Prior art'' Metsubrene keyboards have the advantage of being simple and robust in structure, and can be lit up by attaching a light source to the back, so they can be used in electronic devices such as office automation equipment, computer computers, calculators, etc. Widely used for equipment operation parts.

FIG. 3 shows an example of the conventional structure of a keyboard, in which both circuits Vi
, l, 2 facing contact points 1c, 2C are exposed through the hole 3a.
The structure is such that a spacer 3 having a spacer 3 is attached using a so-called pressure-sensitive adhesive 5 such as acrylic resin.

"Problems to be Solved by the Invention" However, in such a metsuburen keyboard, since the adhesive 5 generally has tackiness,
It is difficult to handle, requires a lot of labor in the adhesive application process, bonding process, etc., is difficult to automate, and tends to increase manufacturing costs. Furthermore, the adhesive 5 is generally weak against heat and chemicals, so it has problems such as being unsuitable for applications that require high reliability.

The present invention solves the problems mentioned above in terms of cargo movement, and therefore aims to facilitate workability during manufacturing, enable automation, reduce costs, and improve reliability.

``Means for Solving the Problems'' The present invention provides that the base film and spacer of both circuit boards are formed of plastic film, and that the base film and spacer are formed at positions avoiding the circuit conductors of both circuit boards. It is characterized by having a joint part that is integrated by ultrasonic welding, and is made by ultrasonically welding three plastic films into one piece.゛"Embodiment" Hereinafter, an embodiment of the present invention will be described based on FIGS. 1 and 2. A spacer 3 sandwiched between both circuit conductors tb and 2h and allowing the contact IC 22C to face through the hole 3a is formed of a plastic film such as a polyethylene terephthalate film, and the circuit conductors of both circuit boards 1.2 1b, 2
A plurality of spot-shaped joints 4 are formed at positions away from the base films 1a, 2a, for example, at the peripheral edges of the base films 1a, 2a, where the base films 1a, 2a and the spacer 3 are integrated by ultrasonic welding. be. The joint portion 4 has a horn pressure of 19 to 50 kg/cm', for example, 500 to 2000 kg/cm'.
As shown in FIG. 2, the base film 1a of the upper circuit 1iE1 is ultrasonically welded at a frequency of kHz and one side is pressed by the horn H of the ultrasonic welding device.
A recess 4a, which will be the mark of the pawn H, and a raised portion 4b of the base film 1a surrounding the recess 4a are formed on one side of the base film 1a.

The membrane keyboard constructed in this way has three plastic films integrated into one plastic film at the joint 4, so it is difficult to peel off and is resistant to heat, chemicals, etc., as well as under normal usage conditions. It is also strong and highly reliable. In addition, the base film La of both circuit boards 1.2 to be ultrasonically welded,
2a and the spacer 3 do not have a sticky H like the conventional pressure-sensitive adhesive 5, so they are easy to handle, and they can be superposed and ultrasonically welded in a short time, allowing for large quantities. It is possible to automate production. Therefore, a pressure-sensitive adhesive becomes unnecessary, and costs can be significantly reduced.

Next, the results of creating a specific test piece and carrying out a test drive to measure its peel strength will be described.

This test piece was made by sandwiching a 188μ thick polyethylene terephthalate film between two 125μ thick polyethylene terephthalate films, and placing them on an aluminum flat support of an ultrasonic welding machine. death,
Ultrasonic welding was carried out for 0.8 seconds at a frequency of 28.5kHz while pressing with a horn at a pressure of 800kg/am.For comparison, a 125μ A test piece with two sheets of polyethylene terephthalate film of the same thickness attached was prepared and tested in the same manner.

Note that the test piece made with the pressure-sensitive adhesive was formed to a width of ICl11, and the peel strength was measured by peeling off both films in the length direction, but the test piece made with the ultrasonic welding was Since the diameter of the recess formed was approximately II, the strength when this recess was peeled off was defined as the peel strength, and its unit was kg/I. In addition, the symbols in the table indicate the following test conditions.

■: Items left at room temperature■ = Items left at a temperature of 105℃ for 120 hours■
: Items left at a temperature of tOS°C for 240 hours■
: After being left for 240 hours at 40 degrees Celsius and 90% humidity, and then for 2 hours at room temperature: : After being left for 240 hours at 60 degrees Celsius and 90% humidity ■: : Below 25 degrees Celsius for 30 minutes, at room temperature for 5 minutes, and at 70℃ for 3 minutes.
Leave it for 0 minutes and repeat this 5 times.
Stocks]■, MeOH, IPA, and MEK, respectively.

The test results are shown in the table below.The test results are shown in the table below.

Since the results shown in this table differ in peeling conditions, it is not possible to make a simple comparison in terms of peel strength values, but it is clear that the joint formed by ultrasonic welding is 1/10 the width of the test piece adhered with pressure-sensitive adhesive. Therefore, it is estimated that the test pieces made by ultrasonic welding have a peel strength equal to or higher than the test pieces made with pressure-sensitive adhesives in each test result, and are strong against heat and chemicals and maintain excellent adhesion. It is something that can be done.

Incidentally, in the embodiment of the joint joint described in vjI, it is formed in a spot shape, but it can be formed in various shapes, such as a straight shape that avoids the circuit conductor, a curved shape, etc., depending on the shape of the circuit conductor.

"Effects of the Invention" As explained above, the membrane keyboard of the present invention can provide the following effects.

(1) By forming the base film and spacer of both circuit boards from plastic films and performing ultrasonic welding, these plastic films can be easily handled and ultrasonically welded in a short time, facilitating automation in mass production. This makes it possible to eliminate the need for adhesives as in the conventional example, and to achieve a significant cost reduction.

(ii) Since the three plastic films are integrated into one plastic film at the joint, the peel strength between both circuit boards and the spacer is increased, and reliability can be improved.

[Brief explanation of drawings]

FIG. 1 is a front view showing one embodiment of the present invention, and FIG. 2 is a front view showing one embodiment of the present invention.
FIG. 3 is an enlarged cross-sectional view taken along the line ■-■ in the figure, and FIG. 3 is a cross-sectional view showing a conventional membrane keyboard. 1... Upper circuit board, 2... Lower circuit board, 1a
, 2a---Base film, 1b, 2b---
circuit conductor, lc. 2C...Contact, 3...Spacer, 3a...
・Hole, 4...Joint part, 4a...Recess, 4b...
...The exciting part.

Claims (1)

[Claims] The upper circuit board (1) and the lower circuit board (2) are arranged oppositely.
) and a spacer (3) sandwiched between the two circuit boards, the circuit conductors (1b,
2b) A membrane keyboard characterized in that a joint part (4) in which both base films and a spacer are integrated by ultrasonic welding is provided at a position away from 2b).