Background of the Invention
Field of the Invention
[0001] This invention relates to a coating process for preparing polymerizable films.
Description of the Related Art
[0002] The bead coating method of applying fluids to substrates is known. According to this
method, coating fluid is fed via a metering pump to a die which deposits the coating
fluid on the surface of a moving substrate as the substrate moves past the die. As
the coating fluid leaves the die it forms a continuous coating bead between the upstream
die lip, the downstream die lip, and the web. The moving substrate is wetted by the
bead as the substrate moves past the bead to create a layer of coating fluid on the
substrate. To improve the stability of the bead (and thus reduce coating inhomogeneities),
a vacuum may be applied to a vacuum chamber located upstream of the coating bead.
[0003] DE 43 36 365 describes a jet coating apparatus for applying a coating to a moving
web in which a coating mix is propelled through a slot formed by a pair of die lips.
[0004] O'Brien, US 4,445,458 describes a metered bead extrusion coating apparatus adapted
to coat a coating fluid onto the surface of a moving web. The apparatus includes an
upstream portion and a downstream portion separated by an extrusion slot. The downstream
portion has a beveled drawdown surface (see col. 2, lines 9-39).
Summary of the Invention
[0005] The method according to the present invention is defined in the enclosed independent
claims.
[0006] In general, the invention features a method of coating the surface of a substrate
with an essentially solvent-free (i.e., 100% solids) polymerizable fluid by passing
the fluid through a die onto the surface of the substrate as the substrate moves relative
to the die.
[0007] The die includes a channel adapted to receive the fluid and an adjustable width slot
in communication with the channel through which the fluid is passed. The slot is formed
between the downstream bar 66 and the upstream bar 64. The downstream bar lip is formed
as a sharp edge 70 and the upstream bar lip is formed as a land 68 which substantially
corresponds in shape to the shape of the substrate in the immediate area of coating
fluid application. As used herein, "upstream" and "downstream" are relative to the
direction of the moving substrate.
[0008] In preferred embodiments, the edge radius of the sharp edge (as defined in Fig. 3)
measures no more than about 10 microns, and more preferably ranges from about 2 to
about 4 microns. The edge angle A
1 of the sharp edge (as defined in Fig. 3) preferably ranges from about 20° to about
75° and preferably is about 50 - 60°.
[0009] The convergence of the die C (as defined in Fig. 3) preferably ranges from about
0° to about 2.29°, more preferably from about 0° to about 1.5°.
[0010] The sharp edge and the land are preferably configured such that the sharp edge is
displaced towards the surface of the substrate relative to the land. The degree of
displacement is referred to as "overbite" O. Preferably, the overbite is no greater
than about 0.64 mm.
[0011] The sharp edge is substantially straight. For example, along a distance of about
25 cm measured anywhere along the sharp edge, the straightness of the edge does not
vary by more than about 2.5 microns, and preferably no more than about 1 micron.
[0012] The rate at which the fluid passes through the die and the rate at which the substrate
moves relative to the die are adjusted to provide a substantially uniform caliper
coating on the substrate.
[0013] The viscosity of the coating fluid is preferably at least about 10 cps, and may be
100 cps or greater, or even 1000 cps or greater. The method may be adapted to apply
both thin and thick coatings. During coating, a vacuum may be applied to the upstream
side of the die to improve coating quality if desired. The substrate may be a web.
[0014] The invention enables the preparation of solvent-free coatings having uniform caliper
in both the downweb and crossweb directions. Both thick and thin films can be prepared.
The invention is useful in a variety of settings, including the preparation of optical
quality thin films and adhesive films.
[0015] Other features and advantages of the invention will be apparent from the following
description of the preferred embodiments thereof, and from the claims.
Brief Description of the Drawings
[0016] The invention will be more fully understood with reference to the following drawings
in which:
Figure 1 is a cross-sectional view of an extrusion die of the present invention.
Figure 2 is an enlarged cross-sectional view of the slot and lip of the die of Figure
1.
Figure 3 is a cross-sectional view of the slot and lip similar to that of Figure 2.
Figure 4 is a cross-sectional view of an alternative vacuum chamber arrangement.
Figure 5 is a cross-sectional view of another alternative vacuum chamber arrangement.
Figure 6 is a cross-sectional view of an alternative extrusion die of the present
invention.
Figures 7A and 7B are enlarged cross-sectional views of the slot, face, and vacuum
chamber of the die of Figure 6.
Figures 8A and 8B are schematic views of the die of Figure 6.
Description of the Preferred Embodiments
[0017] This invention is a die coating method for coating polymerizable fluids onto substrates
(e.g., webs) the die includes an upstream die lip formed as a sharp edge and a downstream
die lip formed as a land. The shape of the land substantially corresponds to the shape
of the substrate in the immediate area of coating fluid application. The shape of
the substrate may be flat or curved.
[0018] Figure 1 shows an extrusion die 40 with a vacuum chamber 42 useful in the coating
method according to the present invention. Polymerizable fluid 44 is supplied by a
pump 46 to the die 40 for application to a moving substrate 48, supported by a backup
roll 50. Polymerizable fluid 44 is supplied through a channel 52 to a manifold 54
for distribution through a slot 56 and coating onto the moving substrate 48. The height
and width of slot 56 can be controlled by means of a U-shaped shim 41. The shim is
typically made of brass or stainless steel.
[0019] As shown in Figure 2, the polymerizable fluid 44 passes through the slot 56 and forms
a continuous coating bead 58 between the downstream edge 72 of land 68, the lip of
downstream bar 66, and the substrate 48. Vacuum chamber 42 (Figure 1) applies vacuum
upstream of the bead to stabilize the coating bead. If desired, the temperature of
both die 40 and backup roll 50 may be controlled to improve coating rheology.
[0020] The polymerizable fluid can be one of numerous compositions. Polymerization may be
thermally induced or radiation induced (e.g., ultraviolet radiation or electron beam).
Examples of suitable polymerizable fluids include epoxies, acrylates, methacrylates,
vinyl ethers, isocyanates, and mixtures thereof. The resulting coatings are useful
in a variety of applications, including adhesives, optical quality films (e.g., polymer
dispersed liquid crystal or "PDLC" films and optical adhesives), precision caliper
films, and vibration damping materials. The coatings are particularly useful in applications
requiring thin films with uniform caliper control.
[0021] The lip of the upstream bar 64 is formed as a curved land 68 and the lip of the downstream
bar 66 is formed as a sharp edge 70. Sharp edge 70 should be clean and free of nicks
and burrs, and should be straight within 1 micron in 25 cm of length measured anywhere
along the edge. The edge radius should be no greater than 10 microns. The radius of
the curved land 68 should be equal to the radius of the backup roll 50 plus a minimal,
and non-critical, 0.13 mm allowance for coating gap and substrate thickness.
[0022] Figure 3 shows dimensions of geometric operating parameters for single layer extrusion.
The length L
1 of the curved land 68 on the upstream bar 64 can range from 1.6 mm to 25.4 mm. The
preferred length L
1 is 12.7 mm. The edge angle A
1 of the downstream bar 66 can range from 20° to 75°, and is preferably 50-60°. The
die attack angle A
2 between the downstream bar 66 surface of the coating slot 56 and the tangent plane
P through a line on the substrate 48 surface parallel to, and directly opposite, the
sharp edge 70 can range from 60° to 120° and is preferably 90° to 95°. The coating
gap G
1 is the distance between the sharp edge 70 and the substrate 48.
[0023] Slot height H is the distance between upstream bar 64 and downstream bar 66, and
is controlled by controlling the thickness of shim 41 (shown in Figure 1). In general,
the slot height ranges from 0.076 mm to 1.27 mm.
[0024] Overbite O is a positioning of the sharp edge 70 of the downstream bar 66, with respect
to the downstream edge 72 of the curved land 68 on the upstream bar 64, in a direction
toward the substrate 48. Overbite also can be viewed as a retraction of the downstream
edge 72 of the curved land 68 away from the substrate 48, with respect to the sharp
edge 70, for any given coating gap G
1. Overbite can range from 0 mm to 0.64 mm, and the settings at opposite ends of the
die slot should be within 2.5 microns of each other.
[0025] Convergence C is a counterclockwise, as shown in Figure 3, positioning of the curved
land 68 away from a location parallel to the substrate 48, with the downstream edge
72 being the center of rotation. Convergence can range from 0° to 2.29°, and the settings
at opposite ends of the die slot should be within 0.023° of each other.
[0026] Overbite, slot height and convergence together affect the ability of the coating
die to hold a steady bead. The interaction between these variables depends upon the
rheology of the polymerizable coating; accordingly, these variables, along with the
substrate speed, are adjusted based upon the particular polymerizable coating being
used.
[0027] Optimum coating quality is achieved when the die coating apparatus is isolated from
ambient sources of vibration and/or other disrupting factors.
[0028] The vacuum chamber 42, as shown in Figure 4, can be an integral part of, or clamped
securely to, the upstream bar 64 to allow precise, repeatable vacuum system gas flow.
The vacuum chamber 42 is formed using a vacuum bar 74 and can be connected through
a vacuum restrictor 76 and a vacuum manifold 78 to a vacuum source channel 80. As
shown in Figure 4, a curved vacuum land 82 is attached directly to the upstream bar
64. The vacuum land 82 has the same radius of curvature as the curved land 68. The
curved land 68 and the vacuum land 82 can be finish-ground together so they are "in
line" with each other. The vacuum land 82 and the curved land 68 then have the same
convergence with respect to the substrate 48.
[0029] The vacuum land gap G
2 is the distance between the vacuum land 82 and the substrate 48, and is the sum total
of the coating gap G
1, the overbite, and the displacement caused by the convergence C of the curved land.
When the vacuum land gap G
2 is large, an excessive inrush of ambient air to the vacuum chamber 42 occurs. Even
though the vacuum source may have sufficient capacity to compensate and maintain the
specified vacuum pressure level at the vacuum chamber 42, the inrush of air can have
undesirable effects.
[0030] In Figure 5, the vacuum land 82 is part of a vacuum bar 74 which is attached to the
upstream bar 64. During fabrication, the curved land 68 is finished with the convergence
"ground in." The vacuum bar 74 is then attached and the vacuum land 82 is finish ground,
using a different grind center, such that the vacuum land 82 is parallel to the substrate
48, and the vacuum land gap G
2 is equal to the coating gap G
1 for one preselected value of the overbite. The vacuum land length L
2 may range from 6.35 mm to 25.4 mm. The preferred length L
2 is 12.7 mm. This embodiment has greater overall coating capability in difficult coating
situations compared to the embodiment of Figure 4, but it is always finish ground
for one specific set of operating conditions. Consequently, as coating gap G
1 or overbite O are changed vacuum land gap G
2 may move away from its optimum value.
[0031] In Figures 6, 7A, and 7B, the die 40 is mounted on an upstream bar positioner 84,
and the vacuum bar 74 is mounted on a vacuum bar positioner 86. The curved land 68
on the upstream bar 64 and the vacuum land 82 on the vacuum bar 74 are not connected
directly to each other. The vacuum chamber 42 is connected to its vacuum source through
the vacuum bar 74 and the positioner 86. The mounting and positioning for the vacuum
bar 74 are separate from those for the upstream bar 64. A flexible vacuum seal strip
88 seals between the upstream bar 64 and the vacuum bar 74.
[0032] The gap G
2 between the vacuum land 82 and the substrate 48 is not affected by coating gap G
1, overbite, or convergence changes, and may be held at its optimum value continuously,
during coating. The vacuum land gap G
2 may be set within the range from 0.076 mm to 0.508 mm. The preferred value for the
gap G
2 is 0.15 mm. The preferred angular position for the vacuum land is parallel to the
substrate 48.
[0033] Figures 8A and 8B show some positioning adjustments and the vacuum chamber closure.
Overbite adjustment OA translates the downstream bar 66 with respect to the upstream
bar 64 such that the sharp edge 70 moves toward or away from the substrate 48 with
respect to the downstream edge 72 of the curved land 68. Convergence adjustment CA
rotates the upstream bar 64 and the downstream bar 66 together around an axis running
through the downstream edge 72, such that the curved land 68 moves counterclockwise
from the position shown in Figures 8A and 8B, away from parallel to the substrate
48, or clockwise back toward parallel. Coating gap adjustment CGA translates the upstream
bar 64 and the downstream bar 66 together to change the distance between the sharp
edge 70 and the substrate 48, while the vacuum bar remains stationary on its mount
86, and the vacuum seal strip 88 flexes to prevent air leakage during adjustments.
Air leakage at the ends of the die into the vacuum chamber 42 is minimized by end
plates 90 attached to the ends of the vacuum bar 74 which overlap the ends of the
upstream bar 64. The vacuum bar 74 is 0.10 mm to 0.15 mm longer than the upstream
bar 64, so, in a centered condition, the clearance between each end plate 90 and the
upstream bar 64 will range from 0.050 mm to 0.075 mm.
[0034] The width of the coating produced by a given die is reduced where indicated by "deckling"
the die and the vacuum chamber by concurrently incorporating a) shaped plugs to reduce
the widths of the die cavity manifold 54 and vacuum chamber 42 to the deckling width
and b) a shim into the die that has a shim slot width corresponding to the deckling
width.
[0035] During coating, it has been found that, as a consequence of the structure of die
40, bead 58 does not move down to any appreciable extent into the space between curved
land 68 and the moving substrate 48, even as vacuum is increased. This allows the
use of relatively high vacuum levels. Moreover, good results are obtained even in
the absence of vacuum. In addition, the effect of "runout" in back-up roll 50 on downweb
coating weight is minimized.
[0036] The above-described die structure coupled with careful control of (a) the rate at
which the polymerizable composition is delivered to the die (through control of pump
speed) and (b) the substrate speed results in coatings having uniform caliper in both
the downweb and crossweb directions.
[0037] For applications where optical appearance of the article is critical, contamination
resulting from airborne particulates can be reduced by coating substrates in a clean
room environment.
[0038] The invention will now be more fully understood with reference to the following examples
which are not to be construed as limiting the scope of the invention.
EXAMPLES
Test Procedure A
[0039] The electro-optical responses of the PDLC devices were characterized using a computer-controlled
test stand consisting of an IBM personal computer interfaced with Kepco 125-1KVA-3T
power supply, a Dyn-Optics Optical Monitor 590, and a Valhalla Scientific 2300 Series
Digital Power Analyzer. The optics of the Dyn-Optics Optical Monitor were adjusted
such that the specular transmission of photopically-filter light at an approximate
6° collection half angle was measured relative to an open beam.
[0040] A sample of a PDLC film/electrode sandwich measuring several square centimeters was
attached to the leads of the power supply using a connector such as that described
in the aforementioned Engfer et al. application. A 60 Hz voltage ranging from zero
to 120 volts AC (VAC) was applied to the sample in 5 VAC increments and the specular
transmission recorded.
Test Procedure B
[0041] The haze of the powered (120 VAC, 60 Hz) PDLC devices was measured using a Pacific
Scientific Gardner XL-835 Colorimeter according to the manufacturer's instructions.
Examples 1-6
[0042] A series of adhesives were prepared from prepolymer syrups consisting of a mixture
of 90 wt.% isooctyl acrylate and 10 wt.% acrylic acid (Aldrich, Milwaukee, WI) containing
0.04 wt.% photoinitiator 2-phenyl-2,2-dimethoxy acetophenone (KB-1, Sartomer, West
Chester, PA) as described in U.S. Pat. No. 4,330,590 (Vesley), which is incorporated
herein by reference. The syrups were partially photopolymerized to viscosities of
360, 1950 and 5600 cps (as measured on a Brookfield viscometer using a #4 spindle
operating at 60 rpm) by varying the exposure times.
[0043] After the syrups had been advanced to the indicated viscosities, an additional 0.1
wt.% KB-1 photoinitiator and 0.2 wt.% hexanediol diacrylate (Sartomer, West Chester,
PA) were added to the syrups and the mixtures agitated until homogeneous fluids were
obtained. The resulting fluids were coated on the substrates at the thicknesses indicated
in Table 1 using a precision coating die as described above and the lamination apparatus
described in Vesley et al., PCT International application No.
WO9529811 entitled "Lamination Process for Coatings," filed concurrently with the present application
and assigned to the same assignee as the present application.
[0044] During the coating operation, the first substrate was unwound from a first unwind
roll and passed over a free-wheeling, unheated steel backup roll 25.4 cm (10 inches)
in diameter where a 10.2 cm (4 inch) wide strip of the prepolymer syrup, which was
delivered to the precision coating die using a precision gear pump (available from
Zenith Corp.), was coated onto the first surface of the first substrate using a 10.2
cm (4 inch) die with no vacuum applied to the vacuum chamber. In Examples 1-4, a coating
die similar to that illustrated in Figure 4 was configured with a 0.50 mm (20 mil)
shim, a 0° convergence, an overbite of 0.076 mm (3 mil), a coating land L
1 of 12.7 mm, a vacuum land L
2 of 12.7 mm, and a die attack angle A
2 of 90°. In Examples 5-6, a 20.3 cm (8 inch) wide strip of the prepolymer syrup was
coated onto the first surface of the first substrate using a 20.3 cm (8 inch) die
similar to that used for Examples 1-4 except that it was configured with a 0.048 mm
(19 mil) shim and an overbite of 0.254 mm (10 mil). The coating gap was adjusted as
indicated in Table 1 along with the pump speed and substrate speed to produce coatings
having the indicated thicknesses. No vacuum was applied to the vacuum chamber during
the coating operation.
[0045] The second substrate was unwound from a second unwind roll and passed around a 2.54
cm (1 inch) diameter sintered metal laminator bar where it was laminated to the coated
face of the first substrate according to the procedure described in the aforementioned
Vesley et al. application. The laminator bar was located approximately 12 cm (4.7
inches) downstream from the backup roll such that the coated substrate was not in
contact with the backup roll or other idler or takeup roll at the point of lamination,
and positioned so that the uncoated first substrate was depressed approximately 3.8
mm (150 mils) below the plane defined by the first substrate as it passed between
the backup roll and the idler roll; the extent of depression is hereinafter referred
to as "interference." Air pressure (approximately 2.1 bar) through the sintered metal
bar was adjusted to provide a cushion of air between the laminator bar and the second
substrate.
[0046] The thus produced uncured laminate construction was cured to a high performance pressure
sensitive adhesive by passing the construction under a bank of fluorescent black lights
lamps (F20T12-350BL, available from Osram Sylvania, Danvers, MA). The laminate construction
was exposed to 360 mJ/cm
2 of irradiation as measured with a UVIRAD radiometer (model number UR365CH3, available
from Electronic Instrumentation and Technology, Inc., Sterling, VA) equipped with
a glass filter responsive between 300 and 400 nm, with a maximum transmission at 365
nm. The average light intensity in the curing zone was about 2.3 mW/cm
2. Coating speeds were controlled by a vacuum pull roll positioned at the end of the
coating line and were maintained at approximately 5.5 m/min. (11 feet/min).
[0047] Table 1 shows typical coating variations for various coating thicknesses and viscosities.
The cured adhesives of examples 5 and 6 adhered to the polyester when the laminated
construction was peeled apart. Adhesive and shear properties of the cured polymer
syrups of Examples 5-6 were consistent with the properties obtained from similar formulations
cured under the conditions described in U.S. Pat. No. 4,330,590.
Table 1
Example |
First Substrate |
Second Substrate |
Viscosity (cps)1 |
Coating Gap (mm) |
Coating Thickness (mm) |
1 |
PET2 |
PET2 |
365 |
0.175 |
0.223±0.004 |
2 |
PET2 |
PET2 |
365 |
0.175 |
0.154±0.003 |
3 |
PET2 |
PET2 |
1,950 |
0.175 |
0.116±0.001 |
4 |
PET2 |
PET2 |
1,950 |
0.175 |
0.221±0.001 |
5 |
Release Paper3 |
PET2 |
5,600 |
0.127 |
0.150±0.001 |
6 |
Release Paper3 |
PET2 |
5,600 |
0.05 |
0.93±0.08 |
1. Measured on a Brookfield viscometer using a #4 spindle operating at 60 rpm. |
2. Biaxially oriented PET film, 51 microns (2 mils) thick. |
3. Polyethylene-coated paper provided with a silicone release coating. |
Example 7
[0048] A PDLC device was prepared from a fluid containing (a) 55 parts of a mixture consisting
of 30.0 wt.% RCC-15C curable matrix mixture obtained without initiator and with 50%
less thiol (W.R. Grace, Atlanta, GA), 7.5 wt.% acrylic acid, 30.0 wt.% isooctyl acrylate,
15.0 wt.% 2-phenoxyethyl acrylate (Sartomer, West Chester, PA), 15.0 wt.% divinyl
ether of triethylene glycol (International Specialty Products, Wayne, NJ), and 2.5
wt.% KB-1 photoinitiator, and (b) 45 parts BL036 liquid crystal mixture (EM Industries,
Hawthorne, NY) having a solution viscosity of 42 cps (measured on a Brookfield viscometer
using a #3 spindle operating at 60 rpm). The fluid, which was degassed under vacuum
for approximately 2 minutes at ambient temperature, was applied as a 15.2 cm (6 inch)
wide strip to the electrode surface of an ITO-coated polyester film (90/10 indium/tin
oxide ratio, 80 ohms/square, 51 microns (2 mil) thick PET, available from Southwall
Technologies, Palo Alto, CA) at a rate of approximately 152.4 cm/min (5 ft/minute)
using the precision coating process described in Examples 1-6 except that a 88.9 cm
die similar to that illustrated in Figure 7a was used. This die was deckled to produce
a narrower coating and configured with a 152 micron shim, a coating land having a
length (L
1) of 12.7 mm, a vacuum land having a length L
2 of 12.7 mm, a 0.57° convergence, a 33 micron overbite, a vacuum land gap G
2 of 0.152 mm, a die attack angle A
2 of 95°, and a coating gap G
1 of 102 microns. The convergence of the vacuum bar was 0° and no vacuum was applied
to the vacuum chamber during coating. Both the die and back-up roll were temperature
controlled at 21°C. A pressure of 1.7 bar was maintained to the sintered metal bar
during lamination and the lamination bar was adjusted to provide an interference of
3.6 mm.
[0049] The uncured laminate construction was cured by passing the construction through a
cooled curing chamber constructed of ultraviolet transparent Acrylite™ OP-4 (available
from Cyro Industries, Mt. Arlington, NJ), extending approximately 61 cm (2 feet) into
a cure chamber equipped with two banks of fluorescent black lights (F20T12-350BL,
available from Osram Sylvania, Danvers, MA), one bank positioned on each side of the
laminate. Air temperature in the cooling chamber was monitored by a thermocouple mounted
in the chamber under the second fluorescent bulb and controlled at the indicated temperature
by introducing temperature controlled air. Each side of the laminate construction
was exposed to approximately 530 mJ/cm
2 of radiation calculated from light intensities of 1.1 mW/cm
2 as measured through the conductive electrode used in the PDLC device by means of
a UVIBRITE radiometer (model number UBM365MO, available from Electronic Instrumentation
and Technology, Inc., Sterling, VA) equipped with a glass filter responsive between
300 and 400 nm, with a maximum transmission at 365 nm. The radiometer was specially
calibrated to read in absolute intensity.
[0050] The backup roll 50 was a pacer roll driven by a Torquer Tachometer precision motor
(available from Inland Motor Division, Bradford, VA).
[0051] The cured coating thickness of the resulting PDLC film was 24±1 microns. The PDLC
device had on- and off-state transmissions of 73.1% and 1.2%, respectively, and a
haze of 5.8%.
Example 8
[0052] A PDLC device was prepared as described in Example 7 except that the coating fluid
had the following composition: (a) 50 parts of a mixture consisting of 20.0 wt.% Vectomer
2020 (Allied-Signal, Inc., Morristown, NJ), 5.0 wt.% acrylic acid, 25.0 wt.% isooctyl
acrylate, 15.0 wt.% 2-phenoxyethyl acrylate, 10 wt.% trimethylolpropane tris (3-mercaptopropionate)
(Aldrich, Milwaukee, WI), 22.5 wt.% cyclohexane dimethanol divinyl ether (International
Specialty Products, Wayne, NJ) and 2.5 wt.% Escacure KB-1, and (b) 50 parts BL036
liquid crystal mixture. The viscosity of the coating fluid was 134 cps (measured on
a Brookfield viscometer using a #3 spindle operating at 60 rpm). The coating temperature
was 21°C and during lamination an air pressure of 2.4 bar was maintained to the laminator
bar which was adjusted to provide an interference of 3.8 mm. The fluid was applied
as a 15.2 cm (6 inch) wide strip to the electrode surface of an ITO-coated polyester
film at a rate of approximately 152.4 cm/min (5 ft/minute) using the precision coating
process described in Example 7 except that the die was configured with a 46 micron
overbite, a coating gap of 102 microns, and a vacuum of 1.9 mm Hg (1 inch of water)
was used to apply the solution at 22°C. The film was cured at 21°C by exposing each
side to approximately 530 mJ/cm
2 at an intensity of 1.0 mW/cm
2 to produce a PDLC film with a thickness of 23±1 microns.
[0053] The PDLC device had on- and off-state transmissions of 71.9% and 1.1%, respectively,
and a haze of 4.8%.
Example 9
[0054] A PDLC device was prepared as described in Example 7 except that the fluid contained
500 parts of BL036 liquid crystal mixture and 333 parts of a mixture having the composition
of 2.5 wt.% Esacure KB-1 photoinitiator, 7.5 wt.% acrylic acid, 30.0 wt.% isooctyl
acrylate, 15.0 wt.% 2-phenoxyethyl acrylate 15.0 wt.% Uralac 3004-102 (DSM Resins,
U.S., Inc., Elgin, IL), and 30.0 wt.% Uralac 3004-300 (DSM Resins, U.S., Inc., Elgin,
IL). The 88.9 cm wide die was configured with a slot width of 88.9 cm, an overbite
of 43 microns, a vacuum land gap G
2 of 24.5 mm and a vacuum of 1.9 mm Hg was applied to the vacuum chamber during coating.
The ITO-coated polyester film used for the electrodes was approximately 130 microns
(5 mils) thick. An air pressure of 3.4 bar was maintained to the laminator bar which
was adjusted to provide an interference of 6.35 mm. The resulting laminate was exposed
UV light having an average intensity of approximately 1.68 mW/cm
2 at about 23°C to produce a PDLC film approximately 18 microns thick.
[0055] The PDLC device had on- and off-state transmissions of 73.4% and 1.7%, respectively,
and a haze of 5.3%.
Example 10
[0056] A PDLC device was prepared as described in Example 7 except that a fluid containing
(a) 57.5 parts of a mixture consisting of 13.7 wt.% lauryl methacrylate (Rhom Tech,
Inc., Malden, MA), 3.9 wt.% methacrylic acid (Aldrich, Milwaukee, WI), 80.4 wt.% RCC-15C
obtained without initiator (W.R. Grace, Atlanta, GA), and 2 wt.% photoinitiator KB-1,
and (b) 42.5 parts of BL036 liquid crystal mixture, with a solution viscosity of 210
cps (measured on a Brookfield viscometer using a #4 spindle operating at 60 rpm),
was used. The die was configured with a 152 mm shim having a slot width of 88.9 cm,
a 76 micron coating gap, and a 51 micron overbite. The coating was applied as a 88.9
cm wide strip of the uncured matrix on the ITO coated PET film at a substrate speed
of 0.91 m/minute (3 feet/minute). During coating, a 3.7 mm Hg (2 inches water) vacuum
was applied to the vacuum chamber. During lamination, an interference of 3.8 mm was
used. The laminate construction was exposed to 330 mJ/cm
2 of UV light having an average intensity of 1.7 mW/cm
2.
[0057] The thickness of the cured coating was 21±0.6 microns. The PDLC device had on- and
off-state transmissions of 74% and 2.7%, respectively, and a haze of 4.5%.
Example 11
[0058] A PDLC device was prepared as described in Example 7 except that a fluid containing
(a) 45 parts of a mixture consisting of 2.5 wt.% KB-1 photoinitiator, 20.0 wt.% 9460
allyl aliphatic urethane (Monomer Polymer & Dajac, Trevose, PA), 35.0 wt.% isooctyl
acrylate, 7.5 wt.% acrylic acid, 20 wt.% 2-phenoxyethyl acrylate, and 15.0 wt.% Uralac
3004-102, and (b) 55 parts of BL036 liquid crystal mixture, with a solution viscosity
of 64 cps (measured on a Brookfield viscometer using a #3 spindle operating at 60
rpm), was used. The die was configured with a 152 micron shim having a slot width
of 88.9 cm, an overbite of 30 microns and the coating applied to the ITO coated PET
substrate at a rate of 3 m/min. at 20°C with a vacuum of 2.8 mm Hg applied to the
vacuum chamber. An air pressure of 3.4 bar was maintained to the lamination bar which
was adjusted to provide an interference of 3.8 mm. The laminate construction was exposed
to 303 mJ/cm
2 of UV light having an average intensity of 1.6 mW/cm
2.
[0059] The cured coating thickness was 17.4±0.6 microns. The PDLC device had on- and off-state
transmissions of 70.0% and 0.8%, respectively, and a haze of 8.6%.
Example 12
[0060] An adhesive composition was prepared as described in Example 5 except that the prepolymer
syrup was prepared from a solution containing 90 wt.% isooctyl acrylate, 10 wt.% acrylic
acid, and 0.04 wt.% KB-1 photoinitiator that had been advanced to a viscosity of 430
cps (measured on a Brookfield viscometer using a #4 spindle operating at 60 rpm) and
to which an additional 0.1 wt.% KB-1 had been added was used as the coating fluid.
The die was configured with a 0.25 mm shim, an overbite of 76 microns and a coating
gap of 76 microns. The polymer syrup was cured in a N
2 atmosphere without a second substrate being applied to the coating by exposure to
UV lights having an average intensity of 1.2 mW/cm
2 to produce a pressure sensitive adhesive having a thickness of 21.5±0.5 microns.
1. Verfahren zur Beschichtung der Oberfläche eines Substrats (48) mit einer Flüssigkeit
(44), umfassend das Leiten der Flüssigkeit durch eine Düse (40) auf die Oberfläche
des Substrats, während sich das Substrat (48) relativ zu der Düse (40) bewegt, wobei
die Düse (40) einen Kanal (52), der zur Aufnahme der Flüssigkeit angepaßt ist, sowie
einen mit dem Kanal in Verbindung stehenden Schlitz mit einstellbarer Breite umfaßt,
durch den die Flüssigkeit geleitet wird und der zwischen einem hinteren Schaber (66)
und einem vorderen Schaber (64) gebildet ist, wobei der hintere Schaber (66) eine
Düsenlippe aufweist, die als scharfe Kante (70) ausgebildet ist, und die vordere Kante
eine Düsenlippe aufweist, die als Steg ausgebildet ist, dadurch gekennzeichnet, daß
die Flüssigkeit (44) eine im wesentlichen lösungsmittelfreie polymerisierbare Flüssigkeit
(44) umfaßt, der vordere Schaber (64) eine als Steg ausgebildete Düsenlippe aufweist,
in einer Form, die im wesentlichen der Form des Substrats (48) im unmittelbaren Bereich
des Auftrags von Beschichtungsflüssigkeit auf das Substrat entspricht, und die durch
den Schlitz (56) tretende Flüssigkeit (44) so gesteuert wird, daß sie einen kontinuierlichen
Beschichtungswulst (58) zwischen der hinteren Kante (72) des Steges (68), der Lippe
des hinteren Schabers (66) und dem Substrat (48) bildet.
2. Verfahren gemäß Anspruch 1, das weiterhin das Einstellen der Geschwindigkeit, mit
der die Flüssigkeit (44) durch die Düse (40) tritt, und der Geschwindigkeit, mit der
sich das Substrat (48) relativ zu der Düse (40) bewegt, umfaßt, so daß eine Beschichtung
mit im wesentlichen gleichmäßiger Dicke auf dem Substrat entsteht.
3. Verfahren gemäß Anspruch 1, das das Konfigurieren der scharfen Kante (70) und des
Steges (68) in einer solchen Weise umfaßt, daß die scharfe Kante (70) relativ zu dem
Steg (68) zur Oberfläche des Substrats (48) hin verschoben ist.
4. Verfahren gemäß Anspruch 1, das das Bereitstellen einer im wesentlichen geraden scharfen
Kante (70) umfaßt, wobei die entlang eines Abstands von etwa 25 cm an irgendeinem
Punkt entlang der scharfen Kante gemessene Geradheit der Kante um nicht mehr als etwa
2,5 µm variiert.
5. Verfahren gemäß Anspruch 1, das das Bereitstellen des Steges (68) in Form eines gekrümmten
Steges umfaßt.
6. Verfahren gemäß Anspruch 1, das das Bereitstellen der Düse (40) mit einer Konvergenz
im Bereich von etwa 0° bis etwa 2,29° umfaßt.
7. Verfahren gemäß Anspruch 1, das das Bereitstellen des Substrats (48) in Form einer
Bahn umfaßt.
8. Verfahren gemäß Anspruch 1, das das Bereitstellen einer polymerisierbaren Flüssigkeit
(44) mit einer Viskosität von wenigstens 10 cP umfaßt.