CA2118544A1 - Reliability elastomeric keypads and method for making same - Google Patents
Reliability elastomeric keypads and method for making sameInfo
- Publication number
- CA2118544A1 CA2118544A1 CA002118544A CA2118544A CA2118544A1 CA 2118544 A1 CA2118544 A1 CA 2118544A1 CA 002118544 A CA002118544 A CA 002118544A CA 2118544 A CA2118544 A CA 2118544A CA 2118544 A1 CA2118544 A1 CA 2118544A1
- Authority
- CA
- Canada
- Prior art keywords
- elastomeric
- keypad
- keypads
- buttons
- skin oil
- 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
Links
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
- H01H13/00—Switches having rectilinearly-movable operating part or parts adapted for pushing or pulling in one direction only, e.g. push-button switch
- H01H13/70—Switches 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
- H01H13/702—Switches 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
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04M—TELEPHONIC COMMUNICATION
- H04M1/00—Substation equipment, e.g. for use by subscribers
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
- H01H2209/00—Layers
- H01H2209/002—Materials
Landscapes
- Engineering & Computer Science (AREA)
- Signal Processing (AREA)
- Manufacture Of Switches (AREA)
- Push-Button Switches (AREA)
- Coating Of Shaped Articles Made Of Macromolecular Substances (AREA)
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.
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.
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.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US17636193A | 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 |
---|---|---|---|
CA002118544A 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) | IL112161A0 (en) |
Families Citing this family (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US9068102B2 (en) | 2004-10-06 | 2015-06-30 | Dow Corning Toray Co., 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 |
EP2327283A2 (en) | 2008-08-18 | 2011-06-01 | Semblant Global Limited | Halo-hydrocarbon polymer coating |
GB2462823A (en) * | 2008-08-18 | 2010-02-24 | Crombie 123 Ltd | A switch |
US8995146B2 (en) | 2010-02-23 | 2015-03-31 | Semblant Limited | Electrical assembly and method |
GB201621177D0 (en) | 2016-12-13 | 2017-01-25 | Semblant Ltd | Protective coating |
Family Cites Families (2)
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 |
-
1994
- 1994-10-20 CA CA002118544A patent/CA2118544A1/en not_active Abandoned
- 1994-12-07 GB GB9424640A patent/GB2285340A/en not_active Withdrawn
- 1994-12-22 KR KR1019940035847A patent/KR950022553A/en not_active Application Discontinuation
- 1994-12-22 JP JP6319741A patent/JPH07220553A/en not_active Withdrawn
- 1994-12-27 IL IL11216194A patent/IL112161A0/en unknown
Also Published As
Publication number | Publication date |
---|---|
JPH07220553A (en) | 1995-08-18 |
KR950022553A (en) | 1995-07-28 |
GB2285340A (en) | 1995-07-05 |
GB9424640D0 (en) | 1995-02-01 |
IL112161A0 (en) | 1995-03-15 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
JP3980300B2 (en) | Membrane pressure sensitive resistor and pressure sensor | |
US4315238A (en) | Bounceless switch apparatus | |
US7695647B2 (en) | Electrically conductive metal impregnated elastomer materials and methods of forming electrically conductive metal impregnated elastomer materials | |
EP0045630A3 (en) | Devices comprising conductive polymers and method of making them | |
HK1063592A1 (en) | Coated oil absorbing wipes | |
CA2118544A1 (en) | Reliability elastomeric keypads and method for making same | |
DE60011078D1 (en) | Structures with variable conductance | |
DE69405496T2 (en) | Copolymers of allyl alcohol propoxylates and vinyl aromatic monomers | |
CA2192363A1 (en) | Electrical devices containing conductive polymers | |
KR840007521A (en) | Electrical Energy Transfer Device for Living Tissues | |
ES2059583T3 (en) | MASS OF CONDUCTIVE COATING OF ELECTRICITY, PROCEDURE FOR ITS PREPARATION AND USE. | |
DE3173010D1 (en) | Switching component with variable resistance | |
TW591143B (en) | Cellulose composite and its use | |
Kumar et al. | A flexible capacitance strain sensor with stitched contact terminals | |
JPS6445877A (en) | Porous sheet material and production thereof | |
EP1321981A3 (en) | Selective ionic implantation of fluoropolymer film to modify the sensitivity of underlying sensing capacitors | |
CN108461624B (en) | Silica gel bionic fingertip touch-pressure sensation sensitive device | |
EP0977096A3 (en) | Conductive roll | |
WO1984003172A1 (en) | Variable control device | |
JP2563308Y2 (en) | Electromagnetic wave shielding packing material | |
Cao et al. | Anti-friction gold-based stretchable electronics enabled by interfacial diffusion-induced cohesion | |
JPS5630442A (en) | Composite permeable membrane | |
EP0240192A3 (en) | Membrane switch | |
KR900019267A (en) | High Sensitivity Triac | |
KR900019218A (en) | Thick film elements |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
EEER | Examination request | ||
FZDE | Discontinued |