U.S. patent application number 09/792921 was filed with the patent office on 2001-07-19 for low temperature burnout screen printing frit vehicle.
This patent application is currently assigned to AlliedSignal, Inc.. Invention is credited to Piascik, James, Xue, Liang A..
Application Number | 20010008110 09/792921 |
Document ID | / |
Family ID | 23259289 |
Filed Date | 2001-07-19 |
United States Patent
Application |
20010008110 |
Kind Code |
A1 |
Xue, Liang A. ; et
al. |
July 19, 2001 |
Low temperature burnout screen printing frit vehicle
Abstract
A method for making a glass frit paste is provided. First,
nitrocellulose is dissolved in a high vapor pressure solvent of the
nitrocellulose to make a solution. A portion of the solution is
then mixed with alpha-terpineol to form a vehicle. Glass frit is
mixed with the vehicle and then ground to form the paste. During
the grinding step most of the high vapor pressure solvent
evaporates. The resulting paste has a composition comprising about
0.3-12.0 wt. % nitrocellulose, about 0.5-2.0 wt. % of a high vapor
pressure solvent of said nitrocellulose, about 14.0-25.0 wt. %
alpha-terpineol, and the remainder glass frit.
Inventors: |
Xue, Liang A.; (Randolph,
NJ) ; Piascik, James; (Randolph, NJ) |
Correspondence
Address: |
Keith Newbury Esq.
Honeywell International Inc
Patent Services AB-2B
101 Columbia Road P.O. Box 2245
Morristown
NJ
07962-9806
US
|
Assignee: |
AlliedSignal, Inc.
|
Family ID: |
23259289 |
Appl. No.: |
09/792921 |
Filed: |
February 26, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09792921 |
Feb 26, 2001 |
|
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|
09323459 |
Jun 1, 1999 |
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Current U.S.
Class: |
106/169.51 ;
106/169.35; 106/169.49; 106/311; 501/20 |
Current CPC
Class: |
C03C 8/16 20130101 |
Class at
Publication: |
106/169.51 ;
501/20; 106/169.49; 106/169.35; 106/311 |
International
Class: |
C08L 001/18; C03C
008/16; C09J 101/18 |
Claims
What is claimed is:
1. A method for making a glass frit paste comprising the steps of:
dissolving nitrocellulose in a high vapor pressure solvent of said
nitrocellulose to make a solution; mixing at least a portion of
said solution with alpha-terpineol to form a vehicle; and mixing
and grinding at least a portion of said vehicle with glass frit to
form the paste, whereby by the end of this step of mixing and
grinding most of the high vapor pressure solvent evaporates.
2. The method of claim 1 wherein said nitrocellulose is 1 to 15 wt.
% of the solution.
3. The method of claim 1 wherein said mixing step includes mixing
said solution with said alpha-terpineol at a ratio that is between
1 part solution to five parts alpha-terpineol and 6 parts solution
to 1 part alpha-terpineol.
4. The method of claim 1 wherein said solvent is amyl-acetate.
5. The method of claim 1 wherein said solvent is ethylene glycol
monoethyl ether.
6. The method of claim 1 wherein said step of mixing and grinding
includes mixing and grinding the glass frit with the vehicle at a
ratio that ranges from 2 parts vehicle to 1 part frit to 1 part
vehicle to 8 parts frit.
7. The method of claim 1 wherein at the end of the mixing and
grinding step less than 3 wt. % of the solvent is left in the
paste.
8. The method of claim 1 wherein said step of mixing and grinding
includes the step of adding a dispersing agent.
9. The method of claim 8 wherein said dispersing agent is tridecyl
acid phosphate.
10. A glass frit paste comprising: about 0.3-12.0 wt. %
nitrocellulose; about 0.5-2.0 wt. % of a high vapor pressure
solvent of said nitrocellulose; about 14.0-25.0 wt. %
alpha-terpineol; and the remainder glass frit.
11. The glass frit paste of claim 10 wherein said solvent is
amylacetate.
12. The glass frit paste of claim 10 wherein said solvent is
ethylene glycol monoethyl ether.
13. The glass frit paste of claim 10 wherein said glass frit is
lead borosilicate.
14. The glass frit paste of claim 10 wherein said glass frit is
copper aluminoborate.
15. The glass frit paste of claim 10 wherein said glass frit is
lead aluminosilicate.
16. The glass frit paste of claim 10 wherein said glass frit is
lead zinc borate.
17. The glass frit paste of claim 10 wherein said glass frit is
zinc borosilicate.
18. The glass frit paste of claim 10 wherein said glass frit is
zinc bismuthsilicate.
19. The glass frit paste of claim 10 wherein said glass frit is
alkali zincsilicate.
20. The glass frit paste of claim 10 wherein said glass frit is
alkali titaniumsilicate.
21. The glass frit of claim 10 further comprising at least one drop
of a dispersing agent.
22. The glass frit of claim 21 wherein said dispersing agent is
tridecyl acid phosphate.
23. A vehicle for using in making a glass frit paste for use in a
screen printing process comprising: about 0.1-1 3.0 wt. %
nitrocellulose; about 14.0-85.0 wt. % of a high vapor pressure
solvent of said nitrocellulose; and the remainder
alpha-terpineol.
24. The vehicle of claim 23 wherein said solvent is
amyl-acetate.
25. The vehicle of claim 23 wherein said solvent is ethylene glycol
monoethyl ether.
Description
TECHNICAL FIELD
[0001] This invention relates generally to sealing compositions and
in particular to vehicles and pastes for use in the screen printing
of glass frit.
BACKGROUND OF THE INVENTION
[0002] Bernot et al, U.S. patent application Ser. No. 08/986,253,
filed Dec. 5, 1997, entitled, (as amended), "Capacitive Pressure
Sensor Housing Having a Ceramic Base" which is assigned to the
assignee of this application, discloses a glass ceramic capsule
comprised of a cover and a header also referred to as a base that
together define an interior chamber. A capacitive pressure sensor
is mounted within the chamber. The header is ceramic while the
cover is either ceramic or metallic. The cover and header are
sealed together with glass frit.
[0003] Typically, the glass frit is made into a paste using a
vehicle which is a combination of a solvent and a binder. The paste
is then applied onto the surfaces to be bonded by either brushing
or ink-jetting. A critical requirement for the vehicle is that it
have a low temperature burnout capability. It needs to completely
burn out before the glass frit softens (i.e. melts) which occurs at
about 350.degree. C. (662.degree. F.). One vehicle currently used
is amyl-acetate (a solvent) containing a small amount of
nitrocellulose (a binder). This vehicle meets the temperature
requirement because the nitrocellulose burns out well below
350.degree. C. (662.degree. F.).
[0004] A disadvantage to the brushing or ink-jefting methods is
that with these methods it is difficult to control the thickness
and uniformity of the glass frit as it is applied. Using a
screen-printing method to apply the glass frit paste would provide
both performance and cost advantage over these other methods
because the screen printing method produces a more uniform frit
coating layer with easily controlled thickness and can be
economically applied in large scale batch production. However, the
current vehicle of amyl-acetate and nitrocellulose is not suitable
for a screen-printing method because the evaporation rate of
amyl-acetate is too fast creating an unstable paste whose thickness
is difficult to control. Further, other commercially available
screen-printing vehicles do not burn out completely at temperatures
below 350.degree. C. (662.degree. F.).
[0005] Accordingly, there is a need for a low-evaporation rate, low
temperature burnout vehicle that can be used in the formation of a
glass frit paste that can be used in a screen printing process.
SUMMARY OF THE INVENTION
[0006] An object of the present invention is to provide a glass
frit paste that can be used in a screen printing process and a
method for making the paste.
[0007] Another object of the present invention is to provide a
vehicle that can be used in the formation of the glass frit paste
and a method for making such a vehicle.
[0008] To make the glass frit paste nitrocellulose is dissolved in
a high vapor pressure solvent of the nitrocellulose to make a
solution. A portion of the solution is then mixed with
alpha-terpineol to form a vehicle. Glass frit is mixed with the
vehicle and then ground to form the paste. During the grinding step
most of the high vapor pressure solvent evaporates. The resulting
paste has a composition comprising about 0.3-12.0 wt. %
nitrocellulose, about 0.5-2.0 wt. % of a high vapor pressure
solvent of said nitrocellulose, about 14.0-25.0 wt. %
alpha-terpineol, and the remainder glass frit.
[0009] These and other objects, features and advantages of the
present invention are specifically set forth in or will become
apparent from the following detailed description of a preferred
embodiment of the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0010] A vehicle for use in a screen printing method in applying a
glass frit paste comprises alpha-terpineol, nitrocellulose and a
solvent of nitrocellulose, such as amyl-acetate or ethylene glycol
monoethyl ether. The solvent is transitional in that it mostly
evaporates during the paste making process where the vehicle is
mixed with glass frit. The use of the solvent is nonetheless
essential because the binder, nitrocellulose, does not dissolve in
alpha-terpineol. Due to its low-evaporation rate, the resulting
paste is stable in open air and suitable for screen-printing. The
vehicle burns out at temperatures below 300.degree. C. (572.degree.
F.).
[0011] The process to make the vehicle and paste consists of the
following steps which preferably occur at room temperature and
pressure. First nitrocellulose is dissolved in a high vapor
pressure solvent such as amyl-acetate or ethylene glycol monoethyl
ether to make a solution. The nitrocellulose preferably constitutes
1 to 15 wt. % of the solution. Next, the solution is mixed with
alpha-terpineol. The ratio of solution to alpha-terpineol can range
from 1 part solution to five parts alpha-terpineol to 6 parts
solution to 1 part alpha-terpineol. The mixing of solution and
alpha-terpineol forms the vehicle. The vehicle is then mixed and
ground with a glass frit at a ratio that ranges from 2 parts
vehicle to 1 part frit to 1 part vehicle to 8 parts frit. A
dispersing agent may also be added at this point in the process.
The result is the paste. In the preferred embodiment the paste is
comprised of about 0.1-18.0 wt. % nitrocellulose; about 0.0-3.0 wt.
% of a high vapor pressure solvent; about 8.0-40.0 wt. %
alpha-terpineol; and the remainder glass frit. In a more preferred
embodiment the paste is comprised of about 0.3-12.0 wt. %
nitrocellulose; about 0.5-1.9 wt. % of a high vapor pressure
solvent; about 14.0-25.0 wt. % alpha-terpineol; and the remainder
glass frit. The particular glass frit used is selected to match the
expansion properties of the components that are to be sealed
together. Examples of such frits are lead borosilicate, copper
aluminoborate, lead aluminosilicate, lead zinc borate, zinc
borosilicate, zinc bismuthsilicate, alkali zincsilicate, alkali
titaniumsilicate and the like. During the mixing and grinding
process, the high vapor pressure solvent, (amyl-acetate or ethylene
glycol monoethyl ether), mostly evaporates, that is less than 3 wt.
% of the solvent is left in the paste after the process is
complete.
[0012] Examples of the vehicle and paste are set forth below.
EXAMPLE 1
[0013] 1.90 grams nitrocellulose was dissolved in 51.23 grams amyl
acetate to make an amyl acetate solution containing about 3.7 wt. %
nitrocellulose. The solution was then mixed with 130.45 grams
alpha-terpineol which is a ratio of about 1:2.5 to make the
vehicle. 21.8 grams of this vehicle was mixed with 65.0 grams of
Corning #2366 glass frit which is a ratio of about 1:4 in a mortar
grinder to make a paste to be used in a screen printing process. 4
drops of tridecyl acid phosphate was also added as a dispersing
agent. During the mixing/grinding process most of the amyl acetate
evaporates. The final paste is composed of about 0.3 wt. %
nitrocellulose, 1.2 wt. % amyl acetate, 19.0 wt. % alpha-terpineol,
and 79.5 wt. % glass frit.
EXAMPLE 2
[0014] 9.86 grams nitrocellulose was dissolved in 161.52 grams amyl
acetate to make an amyl acetate solution containing about 5.8 wt. %
nitrocellulose. A portion (120.40 grams) of the solution was then
mixed with 286.27 grams alpha-terpineol which is a ratio of about
1:2.4 to make the vehicle. 65.42 grams of this vehicle together
with an additional 8.19 grams alpha-terpineol were mixed with
186.69 grams of SEM-COM B-10023 glass frit in a mortar grinder to
make the paste. The ratio of vehicle to frit of about 1:2.5. 3
drops of tridecyl acid phosphate was also added as a dispersing
agent. During the mixing/grinding process most of the amyl acetate
evaporates. The final paste is composed of about 0.5 wt. %
nitrocellulose, 0.8 wt. % amyl acetate, 22.2 wt. % alpha-terpineol,
and 76.5 wt. % the glass frit.
EXAMPLE 3
[0015] 28.8 grams nitrocellulose was dissolved in 410.3 grams amyl
acetate to make an amyl acetate solution containing about 7.0 wt. %
nitrocellulose. The solution was then mixed with 481.6 grams
alpha-terpineol which is at a ratio of about 1:1.1 to make the
vehicle. 34.0 grams of this vehicle together with an additional 8.0
grams alpha-terpineol were mixed with 150.0 grams of SEM-COM
B-10050 glass frit in a mortar grinder to make the paste. The
vehicle to frit ratio of this example being about 1:3.6. 3 drops of
tridecyl acid phosphate was also added as a dispersing agent.
During the mixing/grinding process most of the amyl acetate
evaporates. The final paste is composed of about 0.6 wt. %
nitrocellulose, 0.5 wt. % amyl acetate, 14.5 wt. % alpha-terpineol,
and 84.4 wt. % the glass frit.
EXAMPLE 4
[0016] 2.13 grams nitrocellulose was dissolved in 62.36 grams
ethylene glycol monoethyl ether to make an ethylene glycol
monoethyl ether solution containing about 3.3 wt. % nitrocellulose.
A portion (15.87 grams) of the solution was then mixed with 29.94
grams alpha-terpineol which is a ratio of about 1:1.9 to make the
vehicle. It was then mixed with 93.0 grams of Corning #2366 glass
frit, a ratio of about 1:2, in a mortar grinder to make the paste.
During the mixing/grinding process most of the ethylene glycol
monoethyl ether evaporates. The final paste is composed of about
0.4 wt. % nitrocellulose. 0.8 wt. % ethylene glycol monoether 24.0
wt. % alpha-terpineol, and 74.8 wt. % the glass frit.
EXAMPLE 5
[0017] 11.5 gram nitrocellulose was dissolved in 98.5 grams amyl
acetate to make an amyl acetate solution containing about 10.5 wt.
% nitrocellulose. The solution was then mixed with 20.0 grams
alpha-terpineol, a ratio of about 5.5:1, to make the vehicle. It
was then mixed with 70.0 grams of SEM-COM B-10050 glass frit which
is a ratio of about 1.9:1 in a mortar grinder to make the paste.
During the mixing/grinding process most of the amyl acetate
evaporates. The final paste is composed of about 11.1 wt. %
nitrocellulose, 1.9 wt. % amyl acetate, 19.3 wt. % alpha-terpineol,
and 67.6 wt. % the glass frit.
[0018] Thus a glass frit paste is provided that can be used in a
screen printing process resulting in a more uniform frit coating
layer with easily controlled thickness. A vehicle used in the
formation of this paste is also provided. The vehicle having a low
temperature burnout capability below the melting temperature of the
glass frit.
[0019] Various modifications and alterations to the above-described
preferred embodiment will be apparent to those skilled in the art.
Accordingly, these descriptions of the invention should be
considered exemplary and not as limiting the scope and spirit of
the invention as set forth in the following claims.
* * * * *