Note: Descriptions are shown in the official language in which they were submitted.
CA 02261403 1999-02-10
TITLE. O1BORIDE COATED PRESSING SURFACES FOR ABRASION
RESISTANT LAMINATE AND MAKING PRESSING SURFACES
INVENTOR: MUYUAN M MA AND JAY T. OLIVER
BACKGROUND OF THE INVENTION
1. Field of the invention
This invention relates to coated) abrasion resistant press plates used in
making
abrasion resistant decorative laminate, to the coating of press plates and to
the making
of laminate with these press plates. Grit, e.g., alumina particles, on the
pressing
surface of abrasion resistant decorative laminate can scratch press plates and
reduce
the casual quality of laminate thereafter made with the press plate. Press
plates of this
invention are particularly useful in making abrasion resistant high gloss
decorative
laminate.
2. Description of the Related Art
In the manufacture of decorative laminate, layers of resin impregnated paper
are
pressed against press plates under conditions of temperature and pressure to
cure the
resin and bond the layers together. A high gloss press plate imparts a high
gloss
surface to laminate. A textured surtace imparts a textured surface to
laminate. These
press plates are extremely uniform, with even microscopic discontinuities
being
minimized. The quality of a high gloss polished press plate can be determined
by
viewing reflected images on its surface and scrutinizing the reflected images
for optical
discrepancies. Grit on the surface of laminate causes micro scratching of
stainless
steel press plates normally used in the manufacture of decorative laminate,
thus
destroying the micro finish of the press plate. Press plates can also be
scratched by
press plate handling equipment and by debris from pressing equipment or
materials
used in making laminate. (Lawrence U.S. Patent 5,244,375)
Melamine resin coated decorative laminate is pressed at temperatures of about
230-
310°F (110-155°C) and pressures of about 300-2000 psi (20-136
bar) and preferably
about 750-1500 psi (51-102'bar). Heating to these temperatures and cooling to
room
temperature results in substantial expansion and contraction of the laminate
and of the
0
CA 02261403 1999-02-10
press plate. Expansion and contraction of the laminate and press plate will
not be the
same, resulting in the movement of grit on the pressing surface of laminate
across the
press plate.
It is disclosed m National Electrical Manufacturers Association (NEMA)
Standards
Publication No. LD 3, that gloss finish laminate has a gloss of 70-100+. High
gloss
textured finish laminate is disclosed as having a gloss of 21-40. Black glass
with a
gloss of 9411 degrees. measured at an angle of 60 degrees, is disclosed as the
NEMA
Standard 3.13.2) for calibrating a gloss meter for 60 degree angle gloss
measurements.
Even discontinuities in high gloss press plates that can only be seen with a
microscope
can impart visible surface defects to a high gloss surface of laminate. Any
scratching of
high gloss press plates imparts visible surface defects to high gloss surfaces
of
laminate and reduce gloss level.
Grit on the decorafrve surface of laminate imparts abrasion resistance, a
commercially
desirable characteristic of laminate. Particles of alumina are commonly used
as grit in
making decorative laminate. The Vickers hardness of alumina is disclosed in
'Tribology: Friction and wear of Engineering Materials") I. M. Hutchings) CRC
Press,
24 1992, to be 1800 to 2000. A useful range of particle sizes is about 10 to
about 75
microns. Grit of about 25-60 microns is preferred. Optimum abrasion resistance
is
obtained in the particle size range of about 40 to 60 microns. (Lane et. al.
U.S. Patent
3,798,111 )
Alumina having a maximum particle size of 9 microns is disclosed as being
effective for
imparting a wear resistant surface to glossy decorative laminate. Wear
resistance is
defined as ttie resistance of a glossy laminate to toss of gloss when the
surface of
laminate is exposed to the abrasive effects of sliding objects. It is
acknowledged that
the resulting laminate does not meet NEMA LD 3.01 requirements to be
considered as
~0 abrasion resistant. However, it is disclosed that glossy press plates an:
not scratched
substantially if the grit particle size is maintained at less than 9 micxons.
(Lex et. al.
U.S. Patent 4,971,855)
The use of a 410 stainless steel press plate hardened by nitriding is
disclosed for
making high gloss decorative laminate. After pressing 100 sheets of high gloss
laminate with 6 micron and 15 micron grit) the gloss of the pressed laminate
remained
2
CA 02261403 1999-02-10
good to very good. The rntnded press plate exposed to the 6 micron grit was
rebuffed
after 234 cycles and produced acceptable laminate quality for at least another
103
cycles. Nitrided press plates exposed to 30 micron grit offered limited
durability. It is
disclosed that the 410 sta~niess steel press plate used for nitriding had a
Rockwell) "C"
scale hardness of 38-45 and that the rntrided surface had a Rockwell, "C"
scale
hardness of 60-70. The equwalent Vickers hardness of 410 stainless steel is
about
370-440. based on a conversion table published in "Metals Handbook. Mechanical
Testing") Vol. 8, 9th ed.. ASM. 1985. The equivalent Vickers hardness of
nitrided 410
stainless steel is about 500-1000) based on a conversion table published in
"Metals
Handbook) Mechanical Testing", Vol. 8) 9th ed., ASM) 1985. (Lawrence U.S.
Patent
5,244,375)
Laminate with 35 micron average particle size alumina at its surface (PGA 822
overlay,
available commercially from Mead Corporation) has been pressed with high gloss
press
plates coated with titanium rntride. After ten pressings, the titanium nitride
coated press
plates had about 15 scratches per square centimeter. A control 410 stainless
steel
press plate had about 500 scratches per square centimeter. The Vickers
hardness of
titanium nitride is disclosed in 'Tribology: Friction and wear of Engineering
Materials", I.
M. Hutchings, CRC Press. 1992, to be 1200 to 2000.
The control press plate and the press plate on which the titanium nitride was
coated
were cut from the same stainless steel pressing plate. The scratches was
visible under
a light microscope at 40X magrnfication. Titanium nitride was coated onto 410
stainless
steel high gloss press plates m a magnetron sputter coating system. The use of
a
magnetron sputter coating system for applying a titanium nitride coating is
disclosed in
"Multi-Cathode Unbalanced Magnetron Sputtering Systems," Sprout. Surface and
coating Technology, 49 (1991 ). The use of a magnetron sputter coating system
for
cleaning the surface that is to be coated is disclosed in "A New Sputter
Cleaning
System For Metallic Substrates," Schiller et. al., Thin Solid Films, 33
(1976).
Additionally, the color of the laminate pressed with the titanium nitride
coated press
plate was different than the color of the laminate pressed with the control
press plate.
An ASTM D 2244 color difference in comparison to a standard of less than
(t0.5) DE is
considered as an acceptable. color match to the standard. The ASTM D 2244
color
difference between a standard and laminate pressed with the titanium nitride
coated
press plate was greater than (0.5) DE. The titanium nitride coated press plate
and
3
CA 02261403 1999-02-10
laminate pressed therefrom had a bronze appearance. The control press plate
and the
laminate pressed therefrom did not have a bronze appearance. Laminate pressed
with
the control press plate had an ASTM D 2244 color difference when compared with
the
standard of less than (0.5)oE.
Iron-based cutting tools have been sputter coated w'tth 2-6 microns of
titanium diboride.
The sputtering is carried out in an argon or krypton beam of ions accelerated
to 1300-
1800 volts as a broad-beam ion source. A titanium diboride target is arranged
as a
cathode. The tool is heated to about 200°C(392°~. Sputtering is
done under a
vacuum of about 4-6 milli-Torr. Titanium diboride has an extremely high
Vickers micro-
hardness value, typically about 3600, which is not only considerably higher
than other
borides but also substantially higher than other carbides or nitrides.
Titanium diboride
is also particularly noted for its high density, e.g., 88% of theoretical
density) a low
resistivity of 30 micro-ohms centimeters) a high strength of about 40,000 psi,
and a
coefficient of thermal expansion which is about 8.1 x 10'" at the temperature
range of
20°-800°C(68-1472°F). (Moskowitz et al., U.S. Patent
Number 4,820,392)
Control conditions for sputter coating are disdosed in "influence of Apparatus
Geometry
and Deposition Conditions on the Structure and Topography of Thick Sputtered
?0 Coatings" Thomton, Journal of Vacuum Science Technology, Volume 11, Number
4,
(July/August 1974) and "Sputtering" Thomton et al.; Metals Handbook. Ninth
Edition)
American Society for Metals, Metals Park, Ohio) 44073) Volume 5, pp 412-416,
(1982).
There is a need for a hard coating on a press plates, continuous belt, and
other
pressing surfaces that imparts a color to laminate having an ASTM D 2244 color
difference in comparison to a standard of less than (~5) DE. There is a need
for a
coating that can be applied to a pressing surface without changing the
appearance of
the finish on the pressing surface. There is a need for a pressing surface
that is not
scratched when used in pressing laminate coated with alumina particles of
greater than
10 microns and preferably greater than 25 microns. There is a particular need
for a
pressing surface that is not scratched when used in pressing high gloss
laminate with
an ASTM 2457 60 degree angle gloss of greater than 70, when the surface of the
laminate is coated with 25-60 micron alumina particles.
4
CA 02261403 1999-02-10
SUMMARY OF THE~NVENTinN
It has now been discovered that the color, gloss and surface appearance of
laminate
made with pressing surfaces coated with diborides selected from the group
consisting
of hafnium dibonde, molybdenum diboride, tantalum diboride, titanwm diboride,
tungsten diboride. vanadium diboride, or zirconium dibonde or mixtures thereof
are
substantially the same as the color and gloss of laminate made with the
pressing
surfaces before the coating is applied. The preferred diborides for coating
laminate
pressing surfaces are titanium diboride or zirconium diboride. The most
preferred
diboride for coating laminate pressing surtaces is titanium diboride. It is
believed that
titanium diboride is more commonly used commercially fot coating surfaces than
other
members of the diborides of this invention because it can be sputter coated in
a
magnetron sputtering system at a higher deposition rate.
The diboride coating of this invention can be applied on laminate pressing
surfaces to
have a Vickers hardness of at least 2000 and preferably at least 2200,
suffiaent for
pressing laminate with 25-60 micron or larger alumina particles at the
pressing surface
of the laminate without being scratched. A coating of about 3 microns has
sufficient
hardness to resist scratching by alumina particles on the: pressing surface of
laminate.
The hardness of the coating can be controlled in a planar magnetron sputter
coating
system by those skilled in the use of these systems.
It has been discovered that the diboride coating of this invention can be
coated on a
pressing surface with sufficient bond strength for use in pressing high
pressure
laminate. A minimum bond strength of 1.6 and preferably 1.8 kilogram force
(kgf)
determined by diamond scratching bond testing is believed sufficient. Diboride
coatings
of greater than 6 microns can have lower bond strengths due to stresses
produced
during coating.
Bonding of the diboride coating of this invention to the pressing surface is
enhanced by
thoroughly cleaning the pressing surtace before introducing the pressing
surface into a
magnetron sputter coating system. Bonding is further enhanced by etching the
pressing surtace with the magnetron sputter coating system prior to applying
the
titanwm diboride coating. Cleaning, anodic etching ( cathodic etching and
etching with
radio frequency (RF) can be' accomplished by methods known to those skilled in
the
use of a magnetron sputter coating system. It has been discovered that a layer
of
5
CA 02261403 1999-02-10
titarnum applied directly onto the pressing surface before applying the
diboride coating
of this invention further enhances the bonding of the dibonde. Improving
bonding by
cleaning, etching and the use of an intermediate layer between the coating and
substrate are known to those skilled in the art of using magnetron sputter
coating
systems.
DETAILED DESCRIPTION OF THE INVENTION
Black. high gloss) high pressure laminate was pressed with titanium diboride
coated
press plates shown on Table 1. These press plates had been finished for
imparting an
ASTM D 2457 60 degree angle gloss of about 100 to laminate before being coated
with
titanium diboride. The ASTM O 2244 color difference between a standard and
laminate
pressed with the titanium dibonde coated press plates shown on Table 1 was
less than
(0.5) AE. Gloss and color differences on Table 1, are averages of measurements
made
on 10 laminates.
Table 1
Gloss and olor Diffpr~Pmr~s
Press PIa~ ASTM Glo (a~ 60 A STM Color Diff
er nc . D
3000-1 101 0.20
3000-2 100 0.25
6000-1 101
0.35
6000-2 103 0.40
6000-3 102 0.30
6000-4 102 0.40
6000-5 103 0.45
6000-6 101 0.45
Additionally, high gloss Press Plate 3000-2 and a control press plate have
been used in
the pressing of 760 sheets of high pressure, black) high gloss laminate with
35 micron
average particle size alumina particles on its pressing surface. Laminate was
pressed
with these press plates at about 1000 psi (68 bar) and 280°F
(138°C). The pressing
surface of the laminate is commercially available overlay sheet with 35 micron
alumina
grit (PGA 822 from Mead). Press Plate 3000-2 and the control press plate were
cut
from a high gloss. 410 stainless steel press plate that had been finished for
imparting
an ASTM D 2457 60 degree angle gloss of about 100 to laminate. Press Plate
3000-2
s
CA 02261403 1999-02-10
and the control press plate measure about twelve inches along one side and
eleven
inches along their other side. Press Plate 3000-2 was coated with about five
microns of
titanium diboride in a magnetron sputter coating system. The titanium diboride
coating
was applied in 17 scans, applying about 3000 angstroms of titanium diboride
per scan.
The other was used as a control.
The first sheet of black. high gloss laminate with 35 micron average particle
size
alumina particles on its pressing surface pressed with the control press plate
had an
ASTM D 2244 color difference in comparison to a standard of about (0.25)AE.
The first
sheet of black, high gloss laminate pressed with Press Plate 3000-2 had an
ASTM D
2244 color difference in comparison to a standard of about (0.15) 0E.
The first sheet of black laminate pressed with the control press plate had an
ASTM D
2457 60 degree angle gloss of about 100 to laminate. The 760th sheet of black
laminate pressed with the control press plate had an ASTM D 2457, 60 degree
angle
gloss of less than 70. The control press plate imparted a 60 degree angle
gloss of less
than 90 to black laminate after it had pressed about 160 sheets. It is
believed that
laminate with a 60 degree angle gloss of less than 90 is not commercially
acceptable as
a high gloss laminate.
These 760 sheets of black laminate pressed with Press Plate 3000-2 had an ASTM
D
2457 60 degree angle gloss of about 100. Press Plate 3000-2 has been viewed
under
a microscope for scratches after pressing these 760 sheets of black laminate
and none
have been found. The control press plate is heavily scratched.
No differences were observed in the surface appearance of laminate pressed
with the
Press Plates shown on Table 1 and control press plates.
T'rtanwm diboride was coated onto the high gloss press plate in a magnetron
sputter
coating system under a number of conditions It is also believed that a coating
of at
least 3 microns is necessary for achieving a Vickers hardness of at least 2000
and that
adhesion decreases at coating thicknesses of 6 microns or greater. . Hardness
and
adhesion can be controlled, as known to those skilled in the art, by the
pressure and
temperature under which press plates are coated with the diborides of this
invention
and the power (amperes and volts) used in coating the diborides of this
invention on
press plates.
7
CA 02261403 1999-02-10
A textured press plate coated with titanium dibonde, hereinafter "Press Plate
3000-3",
and a control press plate been used in the pressing of greater than 450 sheets
of high
pressure. black. textured laminate with 35 micron average particle size
alumina
particles on its pressing surface. This laminate was pressed at about 1000 psi
(68 bar)
and 280°F (138°C). Press Plate 3000-3 and the control press
plate were cut from a
textured. 630 stainless steel press plate that had been finished for imparting
an ASTM
0 2457 60 degree angle gloss of about 10 to laminate. Press Plate 3000-3 and
the
control press plate measure about twelve inches along each side. Press Plate
3000:3
was coated with about six microns of titanium diboride in a magnetron sputter
coating
system. The titanium diboride coating was applied in 20 scans, applying about
3000
angstroms of titanium dibonde per scan.
The first sheet of this black, textured laminate pressed with the control
press plate had
an ASTM D 2244 color difference in comparison to a standard of about (0.22)
eE.
Black) high gloss laminate pressed with Press Plate 3000-3 had an ASTM D 2244
color
difference in comparison to a standard of about (0.08) oE.
The first sheet of this black laminate pressed with the control press plate
had an ASTM
D 2457) 60 degree angle gloss of about 9.5. The 450th sheet of this black
laminate
pressed with the control press plate had an ASTM D 2457) 60 degree angle gloss
of
about 8. This black laminate pressed with Press Plate 3000-3 had an ASTM D
2457,
60 degree angle gloss of about 10.
No differences were observed in the surface appearance of laminate pressed
with the
Press Plate 3000-3 and a control press plate.
The press plates on Table 1 and Press Plate 3000-3 were cleaned and then
etched
under radio frequency conditions in a planar magnetron sputter coating system.
These
press plates were then coated with titanium diboride in the magnetron sputter
coating
system under the following averaged conditions.
Cleaning
~ chemical cleaning wipe with ethanol, trichloroethane and acetone
~ physical cleaning 5 minute nitrogen gas blow over press plate
8
CA 02261403 1999-02-10
Radio Freau _nrh. ~trhing Conditions
gas medium argon
in./ minute (cm.J minute) scan speedi(2.54}
mTorr 10
mA/sq. in. (mA/sq. cm.) 3.5(.54)
kV .75
Titanwm Diboride oatina ('re
diti
n
ons argon
gas medium
in./ minute (cm./ minute) scan speed1(2.54)
mTorr 7
mA/sq. in. (mA/sq. cm.) 83(13)
kV .3
Coating Condition and ProoPrti~Pt
Press Plate Scan RateScans ThicknessAdhesionHardness
/scan microns kgf kgf
3000-1 3000 14 4.2 1.T 2280
3000-2 3000 17 5.1 2.1 2830
3000-3 3000 20 5.5 2.0 2700
6000-1 6000 6 3.7 1.8 1940
6000-2 6000 6 3.7 1.8 2160
6000-3 6000 7 4.4 1.8 2250
6000-4 6000 7 4.3 2.0 2190
6000-5 6000 10 6 2.2 2880
6000-6 6000 10 6 2.0 2850
1
micron
=
10.000
A
units
Three high gloss press plates, measuring about four feet by eight feet, of
this invention
have been made. These press plates are referred to as Press Plates 3-1, 3-2)
and 3-3.
These press plates were sputter coated with titanium diboride under planar
magnetron
discharge conditions.
Press Plates 3-1, 3-1, and 3 ~3 were anodically etched and then coated with
titanium
and titanium diboride in a planar magnetron sputter coating system under the
following
averaged conditions. These press plates were chemically cleaned before they
were
s
CA 02261403 1999-02-10
placed into the sputter coating
system. The temperature of these
press plates during
etching_ and coating was about These press
300F(149C). plates
did not
warp at
this
temperature
Cleanma Press Plat ~ -1 '~ 2 and
3 p
chemical cleaning wipe with ethanol)
trichioroethane and acetone
Anodic Etching Conditions lprecc 3 1 3 3 31
Plafag
gas medium argon argon argon
in.l minute (cm.l minute) scan 3(7.6) 3(7.6)3(7.6)
speed
mTorr 25 24 10
mAlsq. in. (mA/sq. cm.) 4.6(.72) 2.9(.45)2.9(.45)
kV .24 .23 .24
number of scans 1 1 5
~t ium Coating Conditions lPrPCC 3 1 ~ ~ 3 ~
plates
gas medium
argon argon argon
in.l minute (cm.l minute) scan 3(7.6) 3(7.6)3(7.6)
speed
mTorr i .6 1.2 2.7
mAlsq. in. (mAlsq. cm.) 70(11) 70(11)70(11)
kV .52 .52 .43
- number of Ti scans 1 1 1
Titanium piboride Coating iC'~~r~itionstes 3 1 ~~
(Press Pla
3~3~
gas medium argon argon argon
in./ minute (cm./ minute) scan 3(7.6) 3(7.6)3(7.6)
speed
mTorr 1.6 1.2 2.7
mA/sq. in. (mA/sq. cm.) 71(11) 75(12)70(11)
kV .52 .60 .50
number of TiBz scans 8 12 18
deposition rate (A/scan) 4125 5500 3000
Properties of T'id2~ Coating (Pr
cc pl
a~c ~ 1 ~ 9 3 3)
thickness (microns) 3.3 6.6 5.4
adhesion (kgf)
. 1.2'
hardness (kgf)
2000 2500 *'
* TiBz~ coating separated from during
Press Plates 3-1 and 3-2 the
pressing
of
laminate.
"' The hardness and adhesiq~n
of Press Plate 3-3 has not been
measured. Hardness
and adhesion testing destroys
the surface of a press plate.
Press Plate 3-3 has been used
in the pressing of greater than
1200 sheets of high
CA 02261403 1999-02-10
pressure. black, high gloss laminate with 35 micron average particle size
alumina
particles on their pressing surfaces. Press Plates 3-3 was viewed for
scratches after
pressing these 1200 sheets of laminate and none have been found. The titanium
dibonde coating on Press Plates 3-1 and 3-2) separated from the stainless
steel
substrate after pressing less than 100 sheets of laminate.
A zirconium diboride coated high gloss press plate of this invention and a
control press
plate have each been used in the pressing of 10 sheets of black) high gloss
laminate.
This laminate had an ASTM 0 2244. color difference in comparison to a standard
of
about (0.26) of and an ASTM D 2457) 60 degree angle gloss of about 100. No
differences were observed in the surface appearance of laminate pressed with
the
zirconium coated and control press plates.
A zirconium diboride coated high gloss press plate of this invention has been
used in
i 5 the pressing of 10 sheets of btadc, high gloss laminate with 35 micron
average partite
size alumina particles on its pressing surface. This laminate was pressed at
about
1000 psi (68 bar) and 280°F (138°C). A commercially available
overlay sheet with 35
micron alumina grit {PGA 822 from Mead) is the pressing surface of the
laminate. No
scratches were observed on this press plate after the pressing of these 10
sheets of
laminate.
This zirconium diboride press plate was cut from a high gloss) 410 stainless
steel press
plate having an ASTM D 2457) that had been finished for imparting a 60 degree
angle
gloss of about 100 to laminate. Two press plates measuring about twelve inches
along
each side were cut from this press plate. One was coated with about five
microns of
zirconium diboride in a planar magnetron sputter coating system. This press
plate was
etched under radio frequency conditions for about 15 minutes before the
titanium
diboride coating was applied. A 6 micron zirconium diboride coating was
applied in 15
scans, applying about 4,000 angstroms of zirconium diboride per scan in a
planar
magnetron sputter coating system under the following averaged condi5ons.
Clef
~ chemical cleaning wipe with ethanol, trichloroethane and acetone
~ physical cleaning 5 minute nitrogen gas blow over press plate
m
CA 02261403 1999-02-10
Radio Freauencyr t hin9 Conditions
gas medium argon
in./ minute (cm./ minute) scan speed1 (2.54}
mTorr 10
mA/sq. in. (mA/sq. cm. ) 3.5(.54)
kV .75
Zirconium Diborid
C
ti
C
it
e
oa argon
ng
on- d
~
gas medium
in.l minute (cm.l minute) scan speed1(2.54)
mTorr 7
mAlsq. in. (mA/sq. cm.) 56(9)
kV .4
Black) laminate has been pressed with press plates, measuring six inches by
six inches
(15.24 cm X 15.24 cm), coated with titanium nitride in a magnetron sputter
coating
system. The test results shown on Table 3 are the average results of pressing
five
sheets of laminate with each press plate.
Table 4
Laminate Pressed With Titani ~m Nitride Coated Press plates
control #8#8 TiN #8 control..l~2
ASTM Gloss @ 60° 100 95 100 95
ASTM Color Difference, AE 0.30 0.75 0.35 0.90
The gloss of the laminate pressed with the titanium nitride coated press plate
was tower
than the gloss of laminate pressed with the control press plate. The color of
the
laminate pressed with the titanium nitride coated press plate was
significantly different
from the color of the laminate pressed with the uncoated control press plate.
The
titanium nitride coated press plates and laminate pressed with the titanium
nitride press
plates had a bronze appearance. .
Black, laminate has been pressed with press plates) measuring six inches by
six inches
(15.24 cm X 15.24 cm)) coated with niobium nitride in a magnetron sputter
coating
system. The test results shown on Table 4 are the average results of pressing
five
sheets of laminate with each press plate.
72
