CA2118544A1 - Reliability elastomeric keypads and method for making same - Google Patents

Reliability elastomeric keypads and method for making same

Info

Publication number
CA2118544A1
CA2118544A1 CA 2118544 CA2118544A CA2118544A1 CA 2118544 A1 CA2118544 A1 CA 2118544A1 CA 2118544 CA2118544 CA 2118544 CA 2118544 A CA2118544 A CA 2118544A CA 2118544 A1 CA2118544 A1 CA 2118544A1
Authority
CA
Canada
Prior art keywords
elastomeric
keypad
keypads
skin oil
buttons
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Abandoned
Application number
CA 2118544
Other languages
French (fr)
Inventor
Henry W. Krautter
Amy Jean Muller
James Douglas Sinclair
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
AT&T Corp
Original Assignee
American Telephone and Telegraph Co Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority to US17636193A priority Critical
Priority to US176,361 priority
Application filed by American Telephone and Telegraph Co Inc filed Critical American Telephone and Telegraph Co Inc
Publication of CA2118544A1 publication Critical patent/CA2118544A1/en
Abandoned legal-status Critical Current

Links

Classifications

    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01HELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H13/00Switches having rectilinearly-movable operating part or parts adapted for pushing or pulling in one direction only, e.g. push-button switch
    • H01H13/70Switches having rectilinearly-movable operating part or parts adapted for pushing or pulling in one direction only, e.g. push-button switch having a plurality of operating members associated with different sets of contacts, e.g. keyboard
    • H01H13/702Switches having rectilinearly-movable operating part or parts adapted for pushing or pulling in one direction only, e.g. push-button switch having a plurality of operating members associated with different sets of contacts, e.g. keyboard with contacts carried by or formed from layers in a multilayer structure, e.g. membrane switches
    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01HELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H2209/00Layers
    • H01H2209/002Materials

Abstract

Applicants have discovered that coating elastomeric keypads with fluoroaliphatic polymers improves their resistance to skin oil. Specifically, the use of a pentadecafluoroctyl methacrylate polymer coating increases by a factor of 5 the resistance of silicone rubber keypads to skin oil.

Description

211~5~9 IMPROVED RELIABILITY ELASTOMERIC KEYPADS AND
METHOD FOR MAKING SAME

Field of the Invention This invention relates to keypads such as elastomeric keypads used in 5 telephones. The invention is particularly useful for providing a silicone rubber keypad highly resistant to cont~min~tion by human skin oil.
Back~round of the Invention Elastomeric keypads provide easily made highly useful interfaces between human users and a variety of electronic instruments including telephones. A
10 typical elastomeric keypad comprises a molded array of projecting elastomericbuttons each of which includes beneath the button, a concave region containing aconductive region. When the button is pressed, the concave region is flattened, pushing the conductive region into contact with conductors or resistors placed below.
One shortcoming of such devices, however, is the tendency of elastomeric materials to absorb human skin oil. After repeated use the skin oil diffuses through the keypad and into the conductive region, greatly increasing its contact resistance and leading to failure of the keypad.
A variety of steps have been taken to deal with this problem including 20 the development of "oil resistant" silicones and the use of hard plastic caps over the elastomeric buttons. The new materials, however, still suffer the same problem.
Accordingly, there is a need for a way of improving the reliability of elastomeric keypads.
Summary of the Invention Applicants have discovered that coating elastomeric keypads with fluoroaliphatic polymers improves their resistance to skin oil. Specifically, the use of a pentadecafluoroctyl methacrylate polymer coating increases by a factor of 5 the resistance of silicone rubber keypads to skin oil.
Brief Description of the Drawin~s In the drawings:
FIG. 1 is a schematic cross section of an elastomeric keypad in accordance with the invention; and FIG. 2 illustrates the repeat unit of the preferred polymeric coating for the keypad of FIG. 1.

211854~

Detailed Description Referring to the drawings, FIG. 1 is a schematic cross section of an elastomeric keypad comprising a molded array 10 of projecting elastomeric buttons 11, which includes beneath each button a concave region 12 containing a 5 conductive region 13. The array 10 is advantageously disposed over a substrate 14, such as a circuit board, having a pattern of conductors 15 and resistors 16 in registration with conductive regions 13. For example, depression of a button 11 in the structure illustrated would force a conductive region 13 into contact across a resistor 16, reducing the resistance between the pair of adjacent conductors 15. The outer surface of array 10 is provided with a coating 17 of a fluoroaliphatic polymer to enhance resistance of the structure to human skin oil. The polymer is advantageously a pentadecafluoroctyl methacrylate polymer comprised of the repeating unit shown in FIG. 2. A suitable solution of such a polymer is available from 3 M Corporation as Fluorad fluorochemical coating FC-722.
Tests demonstrated that an AT&T 5500 telephone keypad coated with FC-722 exhibited more than 5 times the resistance of an uncoated 5500 keypad to simulated skin oil. (The formulation for synthetic skin oil is that described inD. Downing, "The Role of Sebum and Epidermal Lipids in Cosmetic Properties of Skin", 8 International Journal of Cosmetic Science, pp. 115-123 (1986)).
20 Specifically, the keypads were initially washed with laboratory detergent and tap water then blotted dry with a paper towel. The non-control pads were then given 1-3 coats of FC-722 by brushing, and were air-dried 30 minutes between coats. 30 11ldrops of simulated skin oil were applied to all the keypads. The keypads were then placed in a 50C oven for 5 hours, were again washed and dried, and then were 25 weighed with the results shown in Table 1:
Table 1 Keypad Coating Application Weight Change AT&T 5500 None 1.0 30AT&T 5500 FC-722 1 coat-brush 0.31 AT&T 5500 FC-722 2 coats-brush0.19 AT&T 5500 FC-722 3 coats-brush-0.045 211854~

Thus the application FC-722 reduces the amount of skin oil absorbed, and its effectiveness is proportional to the number of coatings applied. Two coatings reduce the absorption by a factor of 5.
While brushing was the preferred method of application for testing, it is S believed that in commercial production an adequate thickness of polymer can be achieved by spraying an increased concentration of polymer in solution.

Claims (4)

1. In an elastomeric keypad comprising a plurality of elastomeric buttons, each having a conductive region disposed within an associated concave region, and a substrate having conductive or resistive regions in registration with said buttons for sensing the depression of one of said buttons, the improvement wherein:
said keypad is coated with a fluoroaliphatic polymer for reducing absorption of skin oil.
2. The improved keypad of claim 1 wherein said elastomeric keypad comprises an array of silicone rubber buttons.
3. The improved keypad of claim 2 wherein said fluoroaliphatic polymer comprises pentadecafluoroctyl methacrylate.
4. The improved keypad of claim 2 wherein said fluoroaliphatic polymer comprises repeated units of the structure of FIG. 2.
CA 2118544 1993-12-30 1994-10-20 Reliability elastomeric keypads and method for making same Abandoned CA2118544A1 (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
US17636193A true 1993-12-30 1993-12-30
US176,361 1993-12-30

Publications (1)

Publication Number Publication Date
CA2118544A1 true CA2118544A1 (en) 1995-07-01

Family

ID=22644045

Family Applications (1)

Application Number Title Priority Date Filing Date
CA 2118544 Abandoned CA2118544A1 (en) 1993-12-30 1994-10-20 Reliability elastomeric keypads and method for making same

Country Status (5)

Country Link
JP (1) JPH07220553A (en)
KR (1) KR950022553A (en)
CA (1) CA2118544A1 (en)
GB (1) GB2285340A (en)
IL (1) IL112161D0 (en)

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2006038702A1 (en) 2004-10-06 2006-04-13 Daikin Industries, Ltd. Laminated article having excellent stain-proofing property and interlayer adhesion and method of production of same
GB0703172D0 (en) 2007-02-19 2007-03-28 Pa Knowledge Ltd Printed circuit boards
GB2462823A (en) * 2008-08-18 2010-02-24 Crombie 123 Ltd A switch
JP5645821B2 (en) 2008-08-18 2014-12-24 センブラント リミテッド Halohydrocarbon polymer coating
US8995146B2 (en) 2010-02-23 2015-03-31 Semblant Limited Electrical assembly and method

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR93239E (en) * 1967-01-02 1969-02-28 Ugine Kuhlmann New fluorinated organic compounds.
WO1987001235A1 (en) * 1985-08-16 1987-02-26 Fuji Rubber Company Limited Contact rubber

Also Published As

Publication number Publication date
IL112161D0 (en) 1995-03-15
GB9424640D0 (en) 1995-02-01
JPH07220553A (en) 1995-08-18
KR950022553A (en) 1995-07-28
GB2285340A (en) 1995-07-05

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Legal Events

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EEER Examination request
FZDE Dead