US4965698A
Expired / Lapsed
US
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Capacitance humidity sensor
Assignee: Johnson Controls Technology Co
•
Filing: 1989-09-27
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Granted: 1990-10-23
•
Expires: 2009-09-27
Abstract
Abstract A capacitance humidity sensor according to the invention has a dielectric film core which is in contact with a pair of polymeric conductive layers bonded to opposite faces of the core. The dielectric core is made of a polymeric material having a dielectric constant which varies substantially linearly with humidity, such as a polyimide or polyparabanic acid. The conductive layers are made of a polymeric material having conductive particles, such as carbon particles, dispersed therein. Such conductive layers provide superior performance and corrosion resistance in comparison to the metal films commonly employed in the prior art.
Inventors
- 👤 Paul E. Thoma
- 👤 Jeannine O. Colla
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 22:00
CPC Classifications
H; H01; H01G; H01G4/00; H01G4/002; H01G4/005; H01G4/008; G; G01; G01N; G01N27/00; G01N27/02; G01N27/22; G01M; G01M3/00; G01M3/02; G01M3/04; G01M3/16; G01N27/223; G01N27/225; H01G4/018; H01G4/06; H01G4/14; H01G4/18; H01G7/00; Y; Y10; Y10T; Y10T29/00; Y10T29/43; Y10T29/435
Claims Analysis
Total Claims: 51
Claim 1
Independent Claim
167 words
A humidity sensor element, comprising: a thin, flexible film consisting essentially of a dielectric, water-absorbing first polymer having a dielectric constant which varies substantially linearly as a function of relative humidity, said first polymer comprising backbone chains containing heterocyclic units in which one or more atoms in the heterocyclic unit are nitrogen, and one or more carbon atoms in the heterocyclic unit have an oxygen atom double bonded thereto, said polymer being substantially free of hydroxyl groups, said first polymer having the general formula: --(A--B).sub.n -- wherein A is a unit containing a heterocyclic unit including at least one --N--C═O linkage therein, B is an aromatic, alicyclic, or aliphatic, substituted or unsubstituted hydrocarbon unit, and n is at least about 10; and a pair of thin, water-permeable, conductive layers disposed on opposite sides of said film and integrally bonded thereto, said conductive layers each consisting essentially of a second polymer having electrically conductive particles distributed therein, which conductive particles are effective to render said layers electrically conductive.
Claim 2
Dependent Claim
167 words
A humidity sensor element, comprising: a thin, flexible film consisting essentially of a dielectric, water-absorbing first polymer having a dielectric constant which varies substantially linearly as a function of relative humidity, said first polymer comprising backbone chains containing heterocyclic units in which one or more atoms in the heterocyclic unit are nitrogen, and one or more carbon atoms in the heterocyclic unit have an oxygen atom double bonded thereto, said polymer being substantially free of hydroxyl groups, said first polymer having the general formula: --(A--B).sub.n -- wherein A is a unit containing a heterocyclic unit including at least one --N--C═O linkage therein, B is an aromatic, alicyclic, or aliphatic, substituted or unsubstituted hydrocarbon unit, and n is at least about 10; and a pair of thin, water-permeable, conductive layers disposed on opposite sides of said film and integrally bonded thereto, said conductive layers each consisting essentially of a second polymer having electrically conductive particles distributed therein, which conductive particles are effective to render said layers electrically conductive.
Claim 3
Dependent Claim
40 words
The element of claim 1, wherein said unit A contains at least one phthalimide ring structure, and unit B has the formula: --Ph--X--Ph-- wherein Ph is a phenylene group and X is an oxygen atom or a lower alkylene group.
Claim 4
Dependent Claim
14 words
The element of claim 1, wherein said first polymer is a polyimide or poly(amide-imide).
Claim 5
Dependent Claim
13 words
The element of claim 3, wherein said second polymer is a poly(parabanic acid).
Claim 6
Dependent Claim
12 words
The element of claim 1, wherein said first polymer is a poly(iminoimidazolidinedione).
Claim 7
Dependent Claim
16 words
The element of claim 1, wherein said second polymer is the same as said first polymer.
Claim 8
Dependent Claim
14 words
The element of claim 6, wherein said conductive particles consist essentially of carbon particles.
Claim 9
Dependent Claim
12 words
The element of claim 7, wherein said carbon particles are chain forming.
Claim 10
Dependent Claim
33 words
The element of claim 7, wherein said conductive layers consist essentially of 10 to 80 wt. % of said carbon particles substantially uniformly distributed in 20 to 90 wt.% of said second polymer.
Claim 11
Dependent Claim
13 words
The element of claim 1, wherein said second polymer is a cellulosic polymer.
Claim 12
Dependent Claim
18 words
The element of claim 10, wherein said second polymer is cellulose acetate butyrate cross-linked with urea-formaldehyde or melamine-formaldehyde.
Claim 13
Dependent Claim
14 words
The element of claim 10, wherein said conductive particles consist essentially of carbon particles.
Claim 14
Dependent Claim
33 words
The element of claim 12, wherein said conductive layers consist essentially of 10 to 80 wt. % of said carbon particles substantially uniformly distributed in 20 to 90 wt.% of said second polymer.
Claim 15
Dependent Claim
11 words
The element of claim 12, wherein said carbon particles are chain-forming.
Claim 16
Dependent Claim
19 words
The element of claim 14, wherein the carbon particles have a particle size of about 10 microns or less.
Claim 17
Dependent Claim
11 words
The element of claim 10, wherein said cellulosic polymer is crosslinked.
Claim 18
Dependent Claim
50 words
The element of claim 1, wherein said second polymer has the general formula: --(A--B).sub.n -- wherein A is a unit containing a heterocyclic unit including at least one --N--C═O linkage therein, B is an aromatic, alicyclic, or aliphatic, substituted or unsubstituted hydrocarbon unit, and n is at least about 10.
Claim 19
Dependent Claim
12 words
The element of claim 17 wherein said second polymer is a polyimide.
Claim 20
Dependent Claim
13 words
The element of claim 17 wherein said second polymer is a poly(parabanic acid).
Claim 21
Dependent Claim
16 words
The element of claim 1, wherein the film has a thickness of 0.01 inch or less.
Claim 22
Dependent Claim
18 words
The element of claim 20, wherein the conductive layers each have a thickness of 0.005 inch or less.
Claim 23
Dependent Claim
37 words
The element of claim 21, wherein the conductive layers have a resistivity of 500,000 ohm-cm or less, and the film has a resistivity of at least about 10 13 ohm-cm at 35° C. and 50% relative humidity.
Claim 24
Dependent Claim
16 words
The element of claim 1, wherein the film has a thickness of 0.001 inch or less.
Claim 25
Dependent Claim
18 words
The element of claim 23 wherein the conductive layers each have a thickness of 0.0005 inch or less.
Claim 26
Dependent Claim
37 words
The element of claim 24, wherein the conductive layers have a resistivity of 125,000 ohm-cm or less, and the film has a resistivity of at least about 10 15 ohm-cm at 35° C. and 50% relative humidity.
Claim 27
Dependent Claim
25 words
The element of claim 25, wherein the conductive particles consist essentially of chain-forming carbon particles having a particle size of about 1 micron or less.
Claim 28
Dependent Claim
17 words
The element of claim 1, wherein the first polymer consists essentially of units of the formula: ##STR5##
Claim 29
Dependent Claim
24 words
The element of claim 1, wherein the first polymer consists essentially of units of the formula: ##STR6## wherein R is aromatic, alicyclic or aliphatic.
Claim 30
Dependent Claim
17 words
The element of claim 1, wherein the first polymer consists essentially of units of the formula: ##STR7##
Claim 31
Dependent Claim
80 words
A humidity sensor element, comprising: a thin, flexible film consisting essentially of a dielectric, water-absorbing first polymer made of poly(parabanic acid) having a dielectric constant which varies substantially linearly as a function of relative humidity; and a pair of water-permeable, conductive layers disposed on opposite sides of said film and integrally bonded thereto, said conductive layers each consisting essentially of a second polymer having electrically conductive particles distributed therein, which conductive particles are effective to render said layers electrically conductive.
Claim 32
Dependent Claim
80 words
A humidity sensor element, comprising: a thin, flexible film consisting essentially of a dielectric, water-absorbing first polymer made of poly(parabanic acid) having a dielectric constant which varies substantially linearly as a function of relative humidity; and a pair of water-permeable, conductive layers disposed on opposite sides of said film and integrally bonded thereto, said conductive layers each consisting essentially of a second polymer having electrically conductive particles distributed therein, which conductive particles are effective to render said layers electrically conductive.
Claim 33
Dependent Claim
14 words
The element of claim 30, wherein said second polymer is a cross-linked cellulosic polymer.
Claim 34
Dependent Claim
28 words
The element of claim 31, wherein said second polymer is cellulose acetate butyrate crosslinked with urea-formaldehyde or melamine-formaldehyde, and said conductive particles consist essentially of chain-forming carbon particles.
Claim 35
Dependent Claim
33 words
The element of claim 32, wherein said conductive layers consist essentially of 10 to 80 wt. % of said carbon particles substantially uniformly distributed in 20 to 90 wt.% of said second polymer.
Claim 36
Dependent Claim
17 words
The element of claim 30, wherein the poly(parabanic acid) consists essentially of units of the formula: ##STR8##
Claim 37
Dependent Claim
169 words
A humidity sensor element, comprising: a flexible film having a thickness of 0.001 inch or less consisting essentially of a dielectric, water-absorbing polyimide made of units having the formula: ##STR9## having a dielectric constant which varies substantially linearly as a function of relative humidity within the range of 5 to 95 percent relative humidity at temperatures in the range of 15 to 50° C., which film has a resistivity of at least about 10 15 ohm-cm at 35° C. and 50% relative humidity; a pair of water-permeable, conductive layers having a thickness of 0.0005 inch or less disposed on opposite sides of said film and integrally bonded thereto, said conductive layers each consisting essentially of about 20 to 90 wt. % of a cross-linked cellulosic polymer and about 10 to 80 wt. % of electrically conductive, chain-forming carbon particles having a particle size of about 1 micron or less, which particles are distributed in said cellulosic polymer so that said layer have a resistivity of 125,000 ohm-cm or less.
Claim 38
Dependent Claim
169 words
A humidity sensor element, comprising: a flexible film having a thickness of 0.001 inch or less consisting essentially of a dielectric, water-absorbing polyimide made of units having the formula: ##STR9## having a dielectric constant which varies substantially linearly as a function of relative humidity within the range of 5 to 95 percent relative humidity at temperatures in the range of 15 to 50° C., which film has a resistivity of at least about 10 15 ohm-cm at 35° C. and 50% relative humidity; a pair of water-permeable, conductive layers having a thickness of 0.0005 inch or less disposed on opposite sides of said film and integrally bonded thereto, said conductive layers each consisting essentially of about 20 to 90 wt. % of a cross-linked cellulosic polymer and about 10 to 80 wt. % of electrically conductive, chain-forming carbon particles having a particle size of about 1 micron or less, which particles are distributed in said cellulosic polymer so that said layer have a resistivity of 125,000 ohm-cm or less.
Claim 39
Dependent Claim
16 words
The element of claim 35, wherein said cellulosic polymer is cellulose acetate butyrate cross-linked with urea-formaldehyde.
Claim 40
Independent Claim
150 words
A method for making a humidity sensor element, comprising: (a) disposing a piece of a thin, flexible film made of a dielectric, water-absorbing first polymer having a dielectric constant which varies as a function of relative humidity on a holder of a screen printing apparatus; (b) applying suction through the holder to the film to temporarily secure the film on the holder; (c) positioning a stencil over the film; (d) screen printing the film through the stencil with a liquid composition comprising an electrically nonconductive second polymer, electrically conductive particles and a carrier liquid; (e) drying the liquid composition under conditions effective to form a water-permeable, first conductive layer on one side of said film and integrally bonded thereto, which conductive layer has a shape corresponding to the stencil; (f) repeating steps (a)-(e) to form a second conductive layer on the face of the film opposite the first conductive layer.
Claim 41
Independent Claim
150 words
A method for making a humidity sensor element, comprising: (a) disposing a piece of a thin, flexible film made of a dielectric, water-absorbing first polymer having a dielectric constant which varies as a function of relative humidity on a holder of a screen printing apparatus; (b) applying suction through the holder to the film to temporarily secure the film on the holder; (c) positioning a stencil over the film; (d) screen printing the film through the stencil with a liquid composition comprising an electrically nonconductive second polymer, electrically conductive particles and a carrier liquid; (e) drying the liquid composition under conditions effective to form a water-permeable, first conductive layer on one side of said film and integrally bonded thereto, which conductive layer has a shape corresponding to the stencil; (f) repeating steps (a)-(e) to form a second conductive layer on the face of the film opposite the first conductive layer.
Claim 42
Dependent Claim
50 words
The method of claim 37 wherein said first polymer has the general formula: --(A--B).sub.n -- wherein A is a unit containing a heterocyclic unit including at least one --N--C═O linkage therein, B is an aromatic, alicyclic, or aliphatic, substituted or unsubstituted hydrocarbon unit, and n is at least about 10.
Claim 43
Dependent Claim
12 words
The method of claim 38, wherein said first polymer is a polyimide.
Claim 44
Dependent Claim
13 words
The method of claim 38, wherein said first polymer is a poly(parabanic acid).
Claim 45
Dependent Claim
33 words
The method of claim 38, wherein the second polymer is a cross-linkable cellulosic polymer, and step (e) further comprises heating said film with said liquid composition printed thereon to cure said second polymer.
Claim 46
Dependent Claim
24 words
The method of claim 41, wherein the liquid composition comprises a mixture of said cross-linkable cellulosic polymer, chain-forming carbon particles, and an organic solvent.
Claim 47
Dependent Claim
27 words
The method of claim 42, wherein said cellulosic polymer is cellulose acetate butyrate with an amount of urea-formamaldehyde or melamine-formaldehyde effective for cross-linking therewith during step (e).
Claim 48
Dependent Claim
16 words
The method of claim 37, wherein the film has a thickness of 0.01 inch or less.
Claim 49
Dependent Claim
18 words
The method of claim 44 wherein the conductive layers each have a thickness of 0.005 inch or less.
Claim 50
Dependent Claim
16 words
The method of claim 37, wherein the film has a thickness of 0.001 inch or less.
Claim 51
Dependent Claim
18 words
The method of claim 46, wherein the conductive layers each have a thickness of 0.0005 inch or less.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
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| 3.5 Years (Year 4) | 1993-10-22 | 1994-04-23 | 1994-10-23 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1997-10-22 | 1998-04-23 | 1998-10-23 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2001-10-22 | 2002-04-23 | 2002-10-23 | $7700.00 | Window Closed / Lapsed |