GB2260025A

GB2260025A - Illuminated membrane switch

Info

Publication number: GB2260025A
Application number: GB9120367A
Authority: GB
Inventors: Tutomu Midorikawa; Shinya Kikuchi
Original assignee: TOKYO SHIMODA INDUSTRY Ltd
Current assignee: TOKYO SHIMODA INDUSTRY Ltd
Priority date: 1991-09-25
Filing date: 1991-09-25
Publication date: 1993-03-31
Also published as: GB9120367D0

Abstract

An illuminated membrane switch includes a display sheet 10; an upper sheet 14 located below the display sheet 10 and having upper contacts 12 on the back side; spring members 16 in a semicircular or other desired form located just above the upper contacts 12 on the upper sheet 14; an array of electroluminescent elements 20 located between the display sheet 10 and the upper sheet 14 except in the locations receiving the spring members 16 and sealingly enclosed in a protecting sheet 18; a lower sheet 24 located below the upper sheet 14 and having lower contacts 22 provided on the upper side in face-to-face relation to the upper contacts 12 and a spacer 28 interposed between the upper sheet 14 and the lower sheet 24 and having a number of through-holes in which the contacts 12, 22 can engage with or disengage from each other. Push buttons may be located between the display sheet 10 and the spring members 16 and a metal film for electromagnetic shielding may be applied to the lower side of the lower sheet 24. The switch enables letters, etc. on the display sheet 10 to be visually read even in the dark, and enables a correct response to be fed back to the user. <IMAGE>

Description

TITLE OF THE INVENTION ILLUMINATED TYPE OF MEMBRANE SWITCH ARRANGEMENT BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to an illuminated type of membrane switch which enable letters, etc. on the display sheet to be visua'ly read even in the dark. This type of membrane switch can be put on cr off at a minute stroke and enables letters, etc. on the display sheet to be visually read even in the dark, and so finds application in conjunctlon with the control panels of various electronics for portable telephones, measuring instruments and automotive trims.

Statement of the Prior Art As set forth in Japanese Utility Model Kokai Publication No. 64-31630, this type of membrane switch uses as light emitter means electroluminescent elements - hereinafter simply referred to as ELDs.

As disclosed therein, this membrane switch includes a upper sheet having upper electrodes and a lower sheet having lower electrodes, between which an ELD unit sealed and covered with a package film is located as a spacer to illuminate a display sheet provided over the upper sheet wth the light emanating therefrom.

In order to make the upper and lower electrodes on the upper and lower sheets engage with o disengage from each other, the spacer located between both the sheets is formed with a thickness of usually about 50-200 pm.

According to the above-mentioned, conventional membrane switch in which the ELD unit sealed and covered with the package fi3m is so located below the upper sheet that the display sheet is irradiated with the light emanating from the ELDs through the upper sheet, however, the it is likely to be reflected off or absorbed in the upper sheet before reaching the display sheet; it is impossible te tak full advantage cf the performance that the ELDs have.

For the conventional switch arrangement, it is required to reduce the thickness of the ELD unit covered with the package film to a certain level or less, because it also serves as a spacer between the upper and lower sheets.

However, mass-producing ELD Units with package films applied on them at a total thickness of 200 pm or less involves much difficulty, and needs much development cost as well.

With the conventional membrane switch, it is thus unfeasible to limit the spacing between the upper end lower sheets to a certain level cr less, often causing the user to make a mistake in operating the switch due to difficulty iD determining whether the switch is working well.

Alsc, the conventional membrane switch offers a problem that the built-in mai circuit, etc. are likely to make noise or mallucntion under the influence of an a.. power source for enabling the ELDs to emit light.

In view of the above-mentioned problems of the prior art, the present invention seeks to provide an Illuminated type of membrane switch which enables the display sheet to be illuminated more brightly and can be accurately put on or off because a determination of whether it is working well easily achievable, or can have no adverse influence on the built-in main circuit, etc.

SUMMARY GF THE INVENTION According to one aspect of this invention, there is provided an illuminated type of membrane switch arrangement, including: a display sheet, an upper sheet located below said display sheet and having upper electrodes on the back side, spring members in a semicircular or other desired form, which are located just above said upper electrodes on said upper sheet, units, each having an array of electroluminescent elements, which are located between said display sheet and said upper sheet but except spaces to receive said spring members and sealingly enclosed in a protecting sheet, a lower sheet located below said upper sheet and having lower electrodes provided on the upper side in face-to-face relation to said upper electrodes, and a spacer interposed between said upper sheet and said lower sheet and having a number of through-holes in which both said electrodes engage with or disengage from each other.

According to another aspect of this invention, there is provided an illuminated type of membrane switch as recited in the first aspect, which further includes push buttons located in spaces between said display sheet and said spring members to transmit force applied by the finger on said display sheet to said spring members.

According to the 3rd aspect of this invention, there is provide an illuminated type of membrane switch as recited in the first aspect of tis invention, which further includes a metal-containing film for electromagnetic shielding purposes, which is applied over the back side of said lower sheet.

According to the 4th aspect of this invention, there is provided an illuminated type of membrane switch as recited in the 3rd aspect, which further includes push buttons located in spaces between said display sheet and said spring members to transmit force applied by the finger on said display sheet to said spring members.

BRIEF DESCRIPTION OF THE DRAWINGS The above-mentioned and other objects and features of this invention and the manner of attaining them will become apparent, and the invention itself will be best understood by reference to the following description of the embodiment of the invention in conjunction with the accompanying drawings, wherein:: FIGURE 1 is a partly sectioned, perspective view of a general arrangement of the membrane switch according to the 1st aspect of this invention, FIGURE 2 is a partly sectioned, perspective view of a general arrangement of one embodiment of the membrane switch according to the 2nd aspect of this invention, FIGURE 3 is a partly sectioned, perspective view of a general arrangement of another embodiment of the membrane switch according to the 2nd aspect of this invention, FIGURE 4 is a partly sectioned, perspective view of a general arrangement of the membrane switch according to the 3rd aspect of this invention, FIGURE 5 is sectional view showing an ELD unit at great length, FIGURE 6 is a sectional view of an ELD unit punched out to form a hole, FIGURE 7 is a plan view of an ELD unit punched out to form a hole, and, FIGURE 8 is a sectional view of sealing the hole in the ELD unit.

ILLUSTRATIVE EXPLANATION OF THE INVENTION Referring first to Fig. 1, there is generally shown an embodiment of the membrane switch according to the 1st aspect of this invention. A display sheet 10 is covered on an upper sheet 14 having upper electrodes 12 on its back side, and spring members 16 in a semicircular or other desired form are located on the positions of the surface of the upper sheet 14 just below the upper electrodes 12.

Between the display sheet 10 and the upper sheet 14, but except locations in which the spring members 16 are disposed, an array of ELDs 20 sealed and covered with a protecting sheet 18 are provided to illuminate the display sheet 10 with the light emanating therefrom. Below the upper sheet 14 there is is a lower sheet 24 having on its upper side lower electrodes 22 located in face-to-face relation to the upper electrodes 12. A spacer 28 is then interposed between the upper and lower sheets 14 and 24, and includes a number of through-holes 26 to make both the electrodes 12 and 22 engage with or disengage from each other.

Referring to Fig. 2, there is shown an embodiment of the membrane switch according to the 2nd aspect of this invention. A display sheet 10 is covered on an upper sheet 14 having upper electrodes 12 on its back side, and spring members ifl a semicircuiar or other desired form are located on the positions of the surface of the upper sheet 14 just below the upper electrodes 12. Between the display sheet 10 and the spring members 16 there are locations adapted to receive push buttons 30 for transmitting force applied thereon by the finger to the spring members 16.

Between the display sheet 10 and the upper sheet 14, but except locations in which the spring members 16 are disposed, an array of ELDs 20 sealed and covered with a protecting sheet 18 are provided to illuminate the display sheet 10 with the light emanating therefrom. Below the upper sheet 14 there is a lower sheet 24 having on its upper side lower electrodes 22 located in face-to-face relation to the upper electrodes 12. A spacer 28 is then interposed between the upper and lower sheets 14 and 24, and includes a number of through-holes 26 to make both the electrodes 12 and 22 engage with or disengage from each other.

Referring to Fig. 4, there is shown a general arrangement of the membrane switch according to the 3rd aspect of this invention. As illustrated, a display sheet 10 is covered on an upper sheet 14 having upper electrodes 12 on its back side, and spring members 16 in a semicircular or other desired form are located on the positions of the surface of the upper sheet 14 just below the upper electrodes 12. Between the display sheet 10 and the upper sheet 14, but except locations in which the spring members 16 are disposed, an array of ELDs 20 sealed and covered with a protecting sheet 18 are provided to illuminate the display sheet 10 with the light emanating therefrom. Below the upper sheet 14 there is a lower sheet 24 having on its upper side lower electrodes 22 located in face-to-face relation to the upper electrodes 12.A spacer 28 is then interposed between the upper and lower sheets 14 and 24, and includes a number of through-holes 26 to make both the electrodes 12 and 22 engage with or disengage from each other. In this embodiment, a metal-containing film 32 for electromagnetic shielding purposes is additionally applied over the back side of the lower sheet 24.

Referring to a general arrangement of the membrane switch according to the 4th aspect of this invention, a display sheet 10 is covered on an upper sheet 14 having upper electrodes 12 on its back side, and spring members 16 in a semicircular or other desired form are located on the positions of the surface of the upper sheet 14 just below the upper electrodes 12. Between the display sheet 10 and the spring members 16 there are spaces adapted to receive buttons 30 for transmitting force applied thereon by the finger to the spring members 16. Between the display sheet 10 and the upper sheet 14, but except locations in which the spring members 16 are disposed, an array of ELDs 2C sealed and covered with a protecting sheets are provided to illuminate the display sheet 10 with the light emanating therefrom.Below the upper sheet 14 there is a lower sheet 24 having on its upper side lower electrodes 22 located in face-to-face relation to the upper electrodes i2. A spacer 28 is then interposed between the upper and lower sheets 14 and 24, and includes a number of through-holes 26 to make both the electrodes 12 and 22 detachable from each other. In this embodiment, a metal-containing film 32 for electromagnetic shielding purposes is additionally applied over the back side of the lower sheet 24.

According to this invention wherein the display sheet 10 is illuminated directly by the light emanating from the ELDs 20 located just below the display sheet 10, it is possible to take full advantage of the performance that the ELDs have.

As a push is given on the display sheet 10 by the finger, the spring members 16 are depressed to force the upper sheet 14 down, so that the upper electrodes 12 come into contact with the lower electrodes 22, holding the switch on.

As the finger is put back from the display sheet 10, the upper electrodes 12 disengage from the lower electrodes 11 due to the self-restoring force of the upper sheet 14, and the spring members 16 are restored to the original shape due to their own restoring force as well.

It is thus possible to feed a correct response back to the user, even thought the ELDs are incorporated between the display sheet 10 and the upper sheet 14.

The present invention will now be explained more illustratively but not exclusively with reference to the drawings.

Fig. 1 illustrates a general arrangement of one embodiment of the first aspect of this invention The upper sheet 14 has a number of upper electrodes 12 on its back side, and is provided therebelow with the lower sheet 24. This lower sheet 24 is reinforced on its lower side with a reinforcing sheet 36.

The lower sheet 24 is provided thereon with the lower electrodes 22 in face-to-face relation to the upper electrodes 11 on the upper sheet 14, and the spacer 28 is interposed between the upper and lower sheets 14 and 24.

The spacer 28 has a number of through-holes 26, in which both the electrodes 12 and 22 can engage with or disengage from each other.

Provided just above each upper electrode 12 on the upper sheet 14 is a restorable spring member 16 in a semoircular form, which is fixed at the lower periphery on the upper sheet 14 with a fixing sheet 34.

The upper sheet 14 is covered thereon with the display sheet 10 including regions 10a to be illuminated, on which letters, symbols, patterns, etc. have been previously given.

Between the display sheet 10 and the fixing sheets 34 but except zones in which the spring members 16 are located, there are ELD units 38.

As can be best seen from Fig. 5, each ELD unit 38 is built up of a transparent electrode 42, a back electrode 44 and ELDs 20 with luminous layers 46 located therebetween, which are all sealingly enclosed in a protecting sheet 18 rich in moistureproofness. Application of voltage between the electrodes 42 and 44 causes the luminous layers 46 to emit light.

Between the luminous layers 46 and the back electrode 44 there is an insulating layer 48.

When a vertically separable type of protecting sheet 18 is used, an adhesive layer 50 may be additionally provided between the ELDs 20 and the protecting sheet 18 to bond them together.

It is noted that according to the first embodiment, the regions 10a of the display sheet 10 to be illuminated are formed of a transparent material and the rest - behaving as a background region 10b - is formed of a semitransparent material.

Reference will now be made to the action of the first embodiment.

According to this embodiment wherein the display sheet 10 is directly illuminated by light emanating from the ELD units 38 located just below it, it is possible to take full advantage of the performance the ELD units 38 have.

As the regions 10a of the display sheet 10 are pushed down, the spring members 16 are depressed to push the upper sheet 14 down, so that the upper electrodes 12, just below it, come into contact with the lower electrodes 22, enabling the switch to be held on.

As the finger is put back from the regions iOa, the upper electrodes 12 disengage frsm the lower electrodes 22 due to the self-restoring force of the upper sheet 14, holding the switch off, and the spring members 16 are restored to the original shape due to their own restoring force as well.

Therefore, even though the ELDs are incorporated between the display sheet 10 and the upper sheet 14, a correct response can be fed back to the user, because the spring members 16 are depressed.

According to the first embodiment described above, the regions 10a of the display sheet 10 can be illuminated at an intensity higher than achieved so far, because the ELD units 30 are located just below the display sheet 10 and the light from it is reflected off the spring members 16 and diffused.

Even though the ELD units 38 are incorporated between the display sheet 10 and the upper sheet 14, it is also possible to place the switch under correct on-off control, because a correct response can be fed back to the user.

In addition, the switch can be made much thinner, because the thickness of the spacer 28 interposed between the upper and lower sheets 14 and 24 is not critical and may be on the order of, say, 200 pm or less.

Figure 2 illustrates one embodiment of the membrane switch according to the second aspect of this invention.

According to this embodiment, between the display sheet 10 and the spring members 16 there are spaces in which push buttons 30, T-shaped in section, are receive.

As the display sheet 10 is pushed down with the finger, the push buttons 30 are so forced down to depress the spring members 16 that the upper electrodes 12 come Into contact with the lower electrodes 22, holding the switch on.

According to this embodiment wherein the push buttons 30 are located in the spaces between the display sheet 10 and the spring members 16, it is possible to place the switch under correct on-off control and feed a correct response back to the user, even when the ELD units 38 are increased in thickness to increase the intensity of the light emanating therefrom or the spring members 16 used are of decreased curvature.

Fig. 3 illustrates another embodiment of the membrane switch according to the 2nd aspect of this invention.

As illustrated, the display sheet 10 is provided with a hole 40, from which the head of a push button 30 proJects.

The push button 30 is fitted, fixed and sealed in the hole 40 in the display sheet 40 with the use of, e.g. an adhesive material.

Fig. 4 illustrates a general arrangement of one embodiment of the membrane switch according to the 3rd aspect of this invention.

This embodiment is similar to that shown in Fig. 1, with the exception that an electromagnetic shielding film 32 is applied over the back side of the lower sheet 24. This film 32 may be formed by the hybridization of a film material with a metal foil or the metallization of a film material.

This embodiment - wherein an a.c. power source for making the ELD units 38 luminous is unlikely to produce electric and magnetic influences on the main circuit, etc located below the membrane switch - assures that it is possible to prevent a glitch of the main circuit, etc. or the occurrence of noise.

According to the 4th aspect of this invention, an electromagnetic shielding film 32 is applied over the back side of the lower sheet 24 of the membrane switch shown in Fig. 2 or 3.

As shown in Figs. 6 and 7, the ELD unit 38 is punched out at 51.

If the ELD unit 38 is punched out to form a space (hole) to receive the spring member 16 (and the push button 30), the ELDs 20 incorporated in it are then so exposed to iew that they cannot be used as such. Thus, that space (hole) must be sealed up.

This sealing may be achieved by fitting into the hole 51 a sleeve 52 having an adhesive layer 53 thereon, as can be best seen from Fig. 8. For instance, the sleeve 52 may be fitted under pressure into the hole by a press cylinder 56, while its internal face is heated by a heating cylinder 54.

The sleeve 52, for instance, may be formed of ethylene trifluoride or ethylene tetrafluoride, and the adhesive layer 53, for instance, may be made of a modified polyolefin.

As will be appreciated from what has been described, the present invention has the following merits.

Since the ELDs are located just below the display sheet and the light therefrom is reflected off the spring members and diffused, the regions 10a of the display panel can be illuminated at an intensity higher than achieved so far.

Since the depression of the spring members assures that a correct response is fed back to the user during operation, the switch can be placed under correct on-off control, even though the ELDs are incorporated between the display and upper sheets.

It is possible to make the space between the upper and lower sheets narrower, when comparing with conventional arrangements.

The provision of the push buttons between the display sheet and the spring members further assures that the switch can be placed under correct on-off control even when the ELDs increase in thickness, thus enabling a correct response to be fed back to the user.

Since the electromagnetic shielding film applied over the back side of the lower sheet prevents an a.c. power source for making the ELDs luminous from having electrical and magnetic influences on the main circuit, etc. located below the membrane switch, it is possible to prevent a glitch of the main circuit, etc.

Claims

WHAT IS CLAIMED IS

1. An illuminated type of membrane switch arrangement, including: a display sheet, an upper sheet located below said display sheet and having upper electrodes on the back side, spring members in a semicircular or other desired form, which are located just above said upper electrodes on said upper sheet, units, each having an array of electroluminescent elements, which are located between said display sheet and sald upper sheet but except locations te receive said spring members and sealingly enclosed in a protecting sheet, a lower sheet located below said upper sheet and having lower electrodes provided on the upper side in face-to-face relation to said upper electrodes, and a spacer interposed between said upper sheet and said lower sheet and having a number of through-holes in which both said electrodes engage with or disengage from each other.

2. An illuminated type of membrane switch arrangement, including: a display sheet, an upper sheet located below said display sheet and having upper electrodes cn the back side, spring members in a semicircular or other desired form, which are located just above said upper electrodes on said upper sheet, units, each having an array of electroluminescent elements, which are located between said display sheet and said upper sheet but except locations to receive said spring members and sealingly enclosed in a protecting sheet, a lower sheet located below said upper sheet and having lower electrodes provided on the upper side in face-to-face relation to said upper electrodes, a spacer interposed between said upper sheet and said lower sheet and having a number of through-holes in which both said electrodes engage with or disengage from each other, and push buttons located in spaces between said display sheet and said spring members to transmit force applied by the finger on said display sheet to said spring members.

3. An illuminated type of membrane switch arrangement, including: a display sheet, an upper sheet located below said display sheet and having upper electrodes on the back side, spring members in a semicircular or other desired form, which are located just above said upper electrodes on said upper sheet, units, each having an array of electroluminescent elements, which are located between said display sheet and said upper sheet but except locations to receive said spring members and sealingly enclosed in a protecting sheet, a lower sheet located below said upper sheet and having lower electrodes provided on the upper side in face-to-face relation to said upper electrodes, a metal-containing film for electromagentic shielding purposes, which is applied over the back side cf said lower sheet, and a spacer interposed between said upper sheet and said lower sheet and having a number of through-holes in which both said electrodes engage with or disengage from each other.

4. An illuminated type of membrane switch arrangement, including: a display sheet, an upper sheet located below said display sheet and having upper electrodes on the back side, spring members in a semicircular or other desired form, which are located just above said upper electrodes on said upper sheet, units, each having an array of electroluminescent elements, which are located between said display sheet and said upper sheet but except locations to receive said spring members and sealingly enclosed in a protecting sheet a lower sheet located below sad upper sheet and having lower electrodes provided on the upper side in face-to-face relation to said upper electrodes, a metal-containing film for electromagentic shielding purposes, which is applied over the back side of said lower sheet, a spacer interposed between said upper sheet and said lower sheet and having a number of through-holes in which both said electrodes engage with or disengage from each other.

push buttons located in spaces between said display sheet and said spring members to transmit force applied by the finger on said display sheet to said spring members.

5. An illuminated membrane switch comprising: a switch panel having oppositely disposed contacts which are resiliently spaced apart; a keypad extending over one surface of the switch panel; and an electroluminescent unit disposed between the keypad and the switch panel.

6. An illuminated membrane switch substantially as described herein with reference to, and as shown in, the accompanying drawings.