U.S. patent application number 11/561843 was filed with the patent office on 2007-06-21 for ink jet uv curing.
This patent application is currently assigned to Con-Trol-Cure, Inc.. Invention is credited to Stephen B. Siegel.
Application Number | 20070139504 11/561843 |
Document ID | / |
Family ID | 36602082 |
Filed Date | 2007-06-21 |
United States Patent
Application |
20070139504 |
Kind Code |
A1 |
Siegel; Stephen B. |
June 21, 2007 |
Ink Jet UV Curing
Abstract
A method and apparatus for printing a product, article or other
object at a printing station and for enhancing the application of
UV light to UV photo initiators in a UV curable ink being applied
to a product, article or other object at the printing station,
comprising the steps for: printing a UV-curable ink with a printing
head of a printer on a substrate, product, article or other object
at a printing station; providing a primary light source of UV light
preferably comprising at least one set of UV-LED arrays of UV-LED
chips adjacent the printing head; and partially curing the ink dots
by emitting light on the ink dots from the primary light source to
set and partially polymerize, coalesce, coagulate and/or gel the
ink dots so as to substantially inhibit the growth of the ink dots
and prevent, running or smudging of the ink dots. The curing of the
ink dots are completed by emitting light on the ink dots from a
secondary light source, such as from one or more fluorescent
lamps.
Inventors: |
Siegel; Stephen B.;
(Chicago, IL) |
Correspondence
Address: |
NEAL, GERBER, & EISENBERG
SUITE 2200
2 NORTH LASALLE STREET
CHICAGO
IL
60602
US
|
Assignee: |
Con-Trol-Cure, Inc.
Chicago
IL
|
Family ID: |
36602082 |
Appl. No.: |
11/561843 |
Filed: |
November 20, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11017354 |
Dec 20, 2004 |
7137696 |
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11561843 |
Nov 20, 2006 |
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10789020 |
Feb 20, 2004 |
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11017354 |
Dec 20, 2004 |
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10753947 |
Jan 7, 2004 |
7211299 |
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10789020 |
Feb 20, 2004 |
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10386980 |
Mar 12, 2003 |
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10753947 |
Jan 7, 2004 |
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10339264 |
Jan 9, 2003 |
7175712 |
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10386980 |
Mar 12, 2003 |
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Current U.S.
Class: |
347/102 |
Current CPC
Class: |
B29C 2035/0827 20130101;
B41F 23/0409 20130101; B41J 11/002 20130101; F26B 3/28 20130101;
B41J 3/4071 20130101 |
Class at
Publication: |
347/102 |
International
Class: |
B41J 2/01 20060101
B41J002/01 |
Claims
1. A method for printing on an object at a printing station,
comprising the steps of: printing ink dots comprising a UV-curable
ink on the object with a printer having a printer head, the printer
head having a primary light source emitting substantially constant
intensity UV light from a primary light source, at a printing
station, the primary light source comprising a first plurality of
UV LEDs emitting a UV light at a first wavelength and a second
plurality of UV LEDs emitting UV light at a second distinct
wavelength; and, setting and partially curing the ink dots by
emitting the substantially constant intensity UV light from the
primary light source on the ink dots printed on the object for
partially polymerizing, coalescing, coagulating or gelling the ink
dots to substantially inhibit running, smudging, growing, or
bleeding of the ink dots.
2. The method claim 1 wherein the primary light source comprises
staggered arrays of UV-LED assemblies.
3. The method of claim 1 further comprising the step of positioning
the primary light source above the ink dots.
4. The method of claim 1 wherein the primary light source is a
separate element from the printer head, and wherein the primary
light source is attached to and in a fixed relationship with the
printer head.
5. The method of claim 1 wherein the first and second plurality of
LEDs are first and second LED arrays, respectively.
6. The method of claim 1 further comprising the step of
substantially completing the curing of the partially cured ink dots
by emitting light on the ink dots from a secondary light source to
substantially polymerize, coalesce, gel, or coagulate the ink
dots.
7. The method of claim 6 further comprising the step of positioning
the secondary light source below the ink dots.
8. The method of claim 6 wherein the secondary light source
comprises at least one fluorescent lamp.
9. A method for printing and curing ink dots of ultraviolet (UV)
curable ink dispensed from a printing head of an ink jet printer or
other printer onto an object, comprising the steps of: emitting UV
light from a primary UV light source at a substantially constant
intensity on ink dots printed on the object for partially curing
the ink dots; and, emitting UV light on the ink dots from a
secondary UV light source for completing the curing of the
partially cured ink dots, wherein the step of emitting UV light
from the primary UV light source comprising emitting UV light at a
plurality of distinct UV wavelengths.
10. The method of claim 9 wherein the primary UV light source
comprises staggered arrays of UV-LED assemblies.
11. The method of claim 9 wherein the secondary UV light source is
located adjacent to or downstream of the printer head and above or
below the ink dots.
12. The method of claim 9 wherein the primary light source is
positioned above the ink dots.
13. The method of claim 9 including carrying the primary light
source in fixed relationship with printer head.
14. The method of claim 9 including positioning the secondary light
source below the substrate carrying the ink dots.
15. The method of claim 9 wherein the secondary light source
comprises at least one fluorescent lamp.
16. The method of claim 9 further comprising the steps of: moving
the primary light source relative to the object being printed as
the printing head is printing ink dots on the object for curing the
ink.
17. The method of claim 9 wherein the step of emitting a
substantially constant intensity UV light from the primary UV light
source comprises substantially continuously measuring a sensed
intensity value representative of the UV light intensity from the
primary light source and adjusting the primary UV light source in
response to the sensed intensity value for maintaining
substantially constant UV light intensity.
18. The method of claim 9 wherein the printing head is reciprocated
transversely of the object together with the primary UV light
source.
19. A method for printing and curing ink dots of ultraviolet (UV)
curable ink dispensed from a printing head of an ink jet printer or
other printer onto an object, comprising the steps of: emitting a
substantially constant intensity UV light from a primary light
source on ink dots printed on the object for partially curing the
ink dots, the UV light intensity being maintained substantially
constant by measuring an intensity level representative of the UV
light intensity of the primary light source and cooling the primary
light source as a function of the intensity level to maintain
substantially constant UV light intensity, and, emitting UV light
on the ink dots from a secondary UV light source for completing the
curing of the partially cured ink dots.
20. The method of claim 19 wherein the step of emitting UV light
from a primary UV light source comprising emitting UV light of a
plurality of distinct wavelengths of UV light.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. application Ser.
No. 11/017,354 filed Dec. 20, 2004, issuing as U.S. Pat. No.
7,137,696 for Ink Jet UV Curing, which is a continuation-in-part of
U.S. application Ser. No. 10/789,020 filed Feb. 20, 2004 for UV
Curing for Ink Jet Printer which is a continuation-in-part of U.S.
application Ser. No. 10/753,947 filed Jan. 7, 2004 for a UV Curing
Method and Apparatus, a continuation-in-part of U.S. application
Ser. No. 10/386,980 filed Mar. 12, 2003 for Multiple Wavelength UV
Curing and a continuation-in-part of U.S. application Ser. No.
10/339,264 filed Jan. 9, 2003 for a Light Emitting Apparatus and
Method for Curing Inks, Coatings and Adhesives.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a method and apparatus for
utilizing ultraviolet (UV) light and other light sources for curing
ink on products, articles or other objects as the ink is applied to
the products, articles or other objects.
[0004] 2. Description of the Related Art
[0005] Heretofore, UV-light emitting diode (LED) arrays have been
proposed for curing inks, coatings or adhesives. Thick polymers
require longer wavelengths for curing. Surface curing requires
shorter wavelengths.
[0006] Pigmented coatings are better cured with wavelengths
dissimilar to the absorption wavelength of the pigments. This is
also true for the wavelength absorption characteristics of resins
and additives in an ink, coating or adhesive.
[0007] Also, oftentimes the ink dots are applied so rapidly that
some running, bleeding and/or smudging of ink occurs.
[0008] It is, therefore, desirable to provide an improved method
and apparatus for ink jet printers and other printers wherein
running, bleeding and/or smudging of ink dots is reduced or
altogether inhibited.
SUMMARY OF THE INVENTION
[0009] An improved method and UV curing apparatus for ink jet
printers and other printers, is provided which are economical,
effective, easy-to-use and efficient.
[0010] As will be described in greater detail hereinafter, the
method and device or apparatus of the present invention provide
techniques and structures for applying UV light emitted from
UV-LEDs onto partially UV curable ink dots of a freshly printed
product, article or other object. In particular, UV-LED light is
applied to the partially UV curable ink dots as they are being
applied to paper or another substrate to cause the ink in the dots
to set, partially cure, partially polymerize, partially coalesce,
partially coagulate and/or partially gel to substantially inhibit,
if not altogether prevent running, bleeding and/or smudging of ink
from ink jet printers or other printers.
[0011] The UV light source can be a UV lamp, although one or more
arrays of UV LEDs attached to and/or riding along with the printer
head are preferred to enhance efficiency and decrease the energy
output and curing temperature.
[0012] The time for setting the ink dots and partial curing of the
ink dots with the method of this invention is very quick.
Advantageously, the jet ink dots do not grow, expand, run, bleed
and/or smudge when printed in accordance with the method of this
invention.
[0013] A secondary light source(s), such as one or more fluorescent
lamps, are used to complete and fully cure and fully polymerize the
partially cured ink dots. The secondary light source can be
positioned above or below the ink dots on the paper or other
substrate depending on the particular printing process. For ink jet
printing, the secondary light source can be positioned below the
substrate carrying the ink dots.
[0014] Since the intensity of light emitted by UV-LED chips is
affected or attenuated, by an increase in the temperature of the
UV-LED chips, one embodiment of the present invention contemplates
the provision of a cooling system including heat radiating fins on
a substrate mounting the chips and the blowing of cooling air past
the fins to keep the temperature of the UV-LED chips within a
predetermined range or generally constant.
[0015] Also, the temperature of the substrate or the intensity of
the light emitted can be monitored and used to control current or
voltage to a fan blowing cooling air on the substrate thereby to
increase cooling of the substrate to maintain a constant
temperature of the substrate thereby to maintain generally constant
light intensity as heating of the chips tends to cause light
intensity to diminish.
[0016] Further "forward voltage matching techniques", VF, can be
employed, (selection of chips) to provide strings or rows of LED
chips wherein the current drawn by the chips only varies between
about 5% and about 10%, thereby to minimize "current hogging".
[0017] The distance between the light source and the product,
article or other object being irradiated with light affects the
intensity of the light. However, if the product, article or other
object is too close to the UV-LED arrays, there will not be a
uniform radiance pattern. Accordingly the preferred distance
between the UV-LED chip arrays is a distance, which will provide a
uniform pattern of light from the light diverging from the UV-LED
chips and at 50% of the power output from the UV-LED chip. This
distance is defined as the Viewing Cone Angle of 2.theta.1/2.
[0018] As other UV wavelength emitting diodes become available, a
wide range of UV light can be employed in curing apparatus and
devices.
[0019] Further, to achieve a greater variation of wavelengths,
UV-LED chip arrays can be placed next to other sources of light,
such as one or more fluorescent lamps whose phosphors are chosen to
augment the increase of light wavelengths. For example, OSRAM
SYLVANIA, INC. of Danvers Mass. offers a type 2011C fluorescent
lamp that emits 351 nm, a type 2052 that emits 371 nm, a type 2092
that emit 433 nm, and a type 2162 that emits 420 nm.
[0020] It is also contemplated that large junction UV-LED chips
(over 400 microns on a side) can be employed since they emit UV
light at higher light density.
[0021] Still further a spacing offset between adjacent rows of 1/x
can be provided in an array of UV-LED chips, where x equals the
number of rows.
[0022] UV-LED light is applied to the partially UV curable ink dots
as they are being applied to paper or another substrate to cause
the ink in the dots to partially set, partially cure, partially
polymerize, partially coalesce, partially coagulate and/or
partially gel to substantially inhibit, if not altogether prevent
running, bleeding and/or smudging of ink from ink jet printers or
other printers.
[0023] According to the teachings of the present invention there is
provided a method and UV curing apparatus for printing a product,
article or other object at a printing station applying some UV
light to the ink as the printing occurs and for enhancing the
application of UV light at a curing station to UV photo initiators
in a UV curable ink applied to a product, article or other object
at the printing station, comprising the steps of or mechanisms for:
printing a UV-curable ink with a printing head on a product,
article or other object at a printing station and providing sets of
or including sets of UV-LED arrays of UV-LED chips adjacent the
printing head; providing sets of or including sets of UV-LED arrays
of UV-LED chips at a curing station, and causing relative movement
between the sets of UV-LED arrays and the printed product, article
or other object.
[0024] A more detailed explanation of the invention is provided in
the following description and appended claims taken in conjunction
with the accompanying drawings.
DESCRIPTION OF THE DRAWINGS
[0025] FIG. 1 is a top plan view of a prior art UV LED chip
assembly including a pad for a cathode and an anode.
[0026] FIG. 2 is a top plan view of a design of mating building
blocks or substrates, which can be blank, or have an anode and
cathode mounted thereon in accordance with the teachings of the
present invention.
[0027] FIG. 3 is a front elevational view of one array of UV LED
assemblies wherein rows of UV LED assemblies are arranged in the
array with alternate rows of UV LED assemblies in one row being
staggered from the UV LED assemblies in the adjacent rows in
accordance with the teachings of the present invention.
[0028] FIG. 4 is front elevational view of a panel of three arrays,
each with six rows of UV LED assemblies as shown in FIG. 3 in
accordance with the teachings of the present invention and shows
schematically a first eccentric cam which moves against one side
edge of the panel against a spring at the opposite side edge of the
panel so as to move, reciprocate or translate the panel in an X
direction and a second eccentric cam which acts against an upper
edge of the panel and against a spring bearing against a lower edge
of the panel to cause movement of the panel in the Y direction and
thereby cause all the arrays to move in a orbital, circular, or
elliptical path when the first and second cams are rotated.
[0029] FIG. 5 is a block schematic diagram of a web made of, or
carrying products, articles or other objects to be UV cured wherein
the web is trained over rollers to move in a generally vertical
path past the panel of arrays of UV LED assemblies shown in FIG. 4
such that the products, articles or other objects with UV photo
initiators therein can be partially cured as each product, article
or other object moves past the arrays of UV LED assemblies while a
non-oxygen, heavier than air gas is injected from a gas tube
located near the top of the path of movement of the web.
[0030] FIG. 6 is a block schematic view of a web made of, or
carrying, products, articles or other objects to be UV cured
wherein the web is trained over rollers to move in a generally
vertical path past the panel of arrays of UV LED assemblies shown
in FIG. 4 such that each product, article or other object with UV
photo initiators therein can be partially cured as each product,
article or other object moves past the arrays of UV LED assemblies
while a non-oxygen gas is injected from a gas tube located near the
bottom of the path of movement of the web.
[0031] FIG. 7 is a plan view of another way of positioning UV LED
assemblies in at least three rows where the spacing between UV LED
assemblies in each row is increased to establish a three tier
staggering of UV LED assemblies.
[0032] FIG. 8 is a plan view of a staggered array of UV LED
assemblies (UV-LED arrays), which emit UV light at different
wavelengths.
[0033] FIG. 9 is a plan view of one die array of four rows of LED
chips.
[0034] FIG. 10 is an enlarged view of a portion of the array shown
in FIG. 9.
[0035] FIG. 11 is an arrangement or line of three of the arrays
shown in FIG. 9 and a secondary light source comprising two long
fluorescent lamps positioned beside the line of arrays of UV LED
assemblies.
[0036] FIG. 12 is a side elevational view of UV LED arrays mounted
on a porcelain-coated substrate, which in turn is mounted on an
aluminum heat sink having heat-dissipating fins.
[0037] FIG. 13 is a side perspective view of the UV LED arrays
shown in FIG. 12 and shows passages through the heat sink for the
passage of power supply conductors to the UV-LED arrays.
[0038] FIG. 14 is a view similar to FIG. 5 except that it shows
four of the heat sink mounted UV-LED arrays shown in FIGS. 12 and
13 are mounted adjacent the moving web of product and shows four
fans for applying cooling air to the heat dissipating fins of the
heat sinks.
[0039] FIG. 15 is a plan view of four UV-LED arrays of the type
shown in FIG. 11 covered with a sheet of glass or plastic material
to protect the LED arrays from splatter.
[0040] FIG. 16 is a fragmentary sectional view of the UV-LED arrays
shown in FIG. 15 and shows the product, article or other object
located above the glass or plastic protective layer and shows a
layer of nitrogen gas between the product, article or other object
and the glass or plastic protective layer.
[0041] FIG. 17 is a top plan view of a printing and curing station
where a product, article or other object is printed, then placed on
a support or a conveyor and an UV-LED array is passed over the
printed product, article or other object or the conveyor is moved
under the UV-LED array to cure the print.
[0042] FIG. 18 is a top plan view of a conveyer carrying printed
compact discs under a UV-LED array.
[0043] FIG. 19 is a top plan view of a turntable carrying compact
discs which is indexed first to move the compact discs under spaced
print heads where a printing of a compact disc takes place followed
by a second indexing to move the freshly printed compact discs past
spaced UV-LED arrays for curing of the print.
[0044] FIG. 20 is a block schematic diagram of a system for
maintaining generally constant light intensity from an UV-LED
assembly mounted on a substrate also mounting a heat sink by
monitoring light intensity with a light sensor and then controlling
the current or voltage to a variable speed cooling fan blowing on
the heat sink dependent on the light intensity sensed for
increasing cooling as UV-LED chips in the UV-LED assembly heat up
thereby to maintain a generally constant temperature which results
in a generally constant light output from the UV-LED chips.
[0045] FIG. 21 is a block schematic diagram, similar to the diagram
of FIG. 20, of a system for maintaining generally constant light
intensity by monitoring temperature of a heat sink on a substrate
that also mounts a UV-LED assembly with a heat/temperature sensor
mounted on the heat sink and then controlling the current or
voltage to a fan dependent on the temperature sensed for increasing
cooling as the UV-LED chips in the assembly heat up thereby to
maintain a generally constant temperature which results in a
generally constant light output from the UV-LED chips.
[0046] FIG. 22 is elevational view of a printing and curing station
constructed according to the teachings of the present invention and
shows UV-LED chips mounted on either side of a printing head.
[0047] FIG. 23 is a top plan view of the printing and curing
station of FIG. 22.
[0048] FIG. 24 is a top plan view of a modified printing curing
station, which also includes a heating station, defined by a heat
lamp.
DETAILED DESCRIPTION OF THE INVENTION
[0049] A detailed description of the preferred embodiments and best
modes for practicing the invention are described herein.
[0050] Referring now to the drawings in greater detail, there is
illustrated in FIG. 1 a prior art ultraviolet light-emitting diode
(UV LED) assembly 10 including a cathode pad 12 and an anode 14
mounting a chip 16, which comprises a UV LED chip 16. Each cathode
pad 12 (FIG. 1) is connected to a wire conductor, as is each anode
14.
[0051] Referring now to FIG. 2, there is illustrated therein a
primary light source comprising a building block 20 having a first
array 21 of the UV LED assemblies 10 thereon, namely, pads 12 and
anodes 14, which provide a plurality of UV LED chips 16. The
building blocks are designed to mate with similar building blocks
to form a group 22 of arrays 21, 23 and 25 as shown in FIGS. 3 and
4. In this way, several of the blocks 20 can matingly engage each
other and be arranged in a pattern (e.g., like tiles on a floor) on
a panel 28 (FIG. 4).
[0052] As shown in FIG. 3, the UV LED assemblies 10 in each array
21, 23 and 25 are spaced apart in a first lower row 36 of UV LED
assemblies 10. Then, in a second adjacent row 38, the UV LED
assemblies 10 are arranged in a staggered manner so that they are
located above the spaces between the UV LED assemblies 10 in the
first row. In the same manner, the next upper row 40 of UV LED
assemblies 10 is staggered and a total of twenty (20) staggered
rows are provided in the UV LED array 21 shown in FIG. 3.
[0053] Also, as shown in FIG. 3 the beginning of the first UV LED
assembly 10 in the lowest row 36 in the first array 21 is aligned
with the end of the last UV LED assembly 10 at the end of the
lowest row 42 in the second, lower left, array 23.
[0054] Then, the beginning of the first UV LED assembly 10 in the
uppermost row 44 in the first array 21 is aligned with the end of
the last UV LED assembly 10 in the uppermost row 46 in the second,
lower left array 23. Next, the end of the last UV LED assembly 10
in the lowest row 36 in the first array 21 is aligned with the
beginning of the first UV LED assembly 10 in the lowest row 48 in
the third, lower right array 25. Finally, the end of the last UV
LED assembly 10 in the uppermost row 44 in the first array 21 is
aligned with the beginning of the first UV LED assembly 10 in the
uppermost row 49 in the third, lower right array 25, as shown in
FIG. 3.
[0055] As shown best in FIG. 4, the three arrays 21, 23 and 25 can
be arranged on the panel 28 in a staggered manner so that the UV
light from each UV LED assembly 10 is not only spaced and staggered
relative to adjacent rows in the array but also spaced and
staggered relative to the rows in the other arrays. Also more than
three arrays 21, 23 and 25 can be provided, such as six arrays, not
shown.
[0056] Also shown in FIG. 4, are mechanisms, preferably eccentric
cams 50 and 52 that can be provided for moving translating or
reciprocating the panel 28 back and forth in the X direction and up
and down in the Y direction, much like in an orbital sander. The
first, x axis, eccentric cam 50 is mounted for rotation about a
shaft 54 to act against one side edge 56 of the panel 28 with a
spring 58, such as a helical tension spring, positioned to act
against the other side edge 60 of the panel 28.
[0057] Then the second, y axis, eccentric cam 52 (FIG. 4) is
mounted for rotation on a shaft 64 to act against an upper edge 66
of the panel 28 against the action of a spring 68, such as a
helical tension spring, positioned to act against a lower edge 70
of the panel 28.
[0058] Rotation of the shafts 54 and 64 (FIG. 4) each by a prime
mover such as a variable speed motor (not shown) can cause the
panel 28 to move in a generally orbital, annular, circular, or
elliptical path of movement. This will result in orbital movement
of each UV LED assembly 10 in each of the rows in each of the
arrays 21, 23 and 25 mounted on the panel 28 so as to spread out
the emitted UV light and uniformly apply the UV light to the
products, articles or other objects to be partially UV cured. This
spreading of the UV light also minimizes, if not altogether
eliminates the creation of, so called "hot spots" of UV light.
[0059] As shown in FIG. 5, where a schematic block diagram of one
UV curing apparatus, assembly, mechanism or device is shown where
the panel 28 of UV LED arrays 21, 23 and 25 is positioned generally
vertically and closely adjacent the path of movement of a conveyor
belt comprising a web 74 which is trained over rollers 76, 78 and
80 to move generally upright and vertically past and closely
adjacent and in proximity to the panel of UV LED arrays 21, 23 and
25. For this purpose, at least one of the rollers 76, 78 and/or 80
of a conveyor can be a drive roller.
[0060] UV curable products, articles or other objects, such as
labels, positioned in or on the web 74 (FIG. 5), can have one or
more UV curable inks, coatings and/or adhesives between a plastic
cover layer and the label. The partially UV curable ink, coating,
and/or adhesive can have UV photo initiators therein which will
partially polymerize the monomers in the UV curable ink, coating,
or adhesive when subjected to UV light within a predetermined UV
wavelength range.
[0061] The partially UV curable ink, coating and/or adhesive
preferably is located on the side of the web 74 (FIG. 5) that is
closest to and faces the panel 28. Preferably, the UV LED
assemblies are in close proximity to the ink, coating or adhesive
and no closer than a viewing cone angle, 2.theta.1/2. where the
cone of light that emanates from an UV-LED chip is at least 50% of
the light power output of the chip. Note that the effectiveness of
the UV emitted light dissipates exponentially as the distance to
the product, article or other UV curable object to be treated
increases.
[0062] Preferably, the cams 50 and 52 (FIG. 4) are rotated to cause
orbital movement of the panel 28 and UV LED assemblies as the web
74 containing the product, article or other UV curable object moves
past the panel 28. Such movement also minimizes "hot spots" or
"cold spots" and provide uniform sweeping, distribution, and
application of the UV light from the UV LED assemblies 10.
[0063] The block schematic diagram of the assembly or device, shown
in FIG. 5 is provided to minimize exposure of the products,
articles or other objects during curing to oxygen, which inhibits
UV curing. A gas tube 84 providing an upper gas injection is
provided on the assembly and device for injecting a
heavier-than-air, non-oxygen-containing gas, e.g., carbon dioxide,
near an upper end 86 of a path of downward movement, indicated by
the arrow 88, of the web 74, so that the gas can flow downwardly in
the space between the panel 28 and the web 74 to provide an
anaerobic area between the UV LED assemblies 10 on the panel 28 and
the web 74 having UV curable products, articles or other objects to
be cured.
[0064] A wiper blade 90 (FIG. 5) providing a lower inhibitor can be
positioned adjacent the lower edge 70 of the panel 28 for holding,
compressing, collecting and/or blanketing the gas in the area
between the orbiting UV LED arrays 21, 23 and 25 (FIG. 4) and the
moving web 74 (FIG. 5). Preferably the wiper blade 90 is fixed to
the lower edge 70 of the panel 28 and has an outer edge 92 that is
positioned to wipe close to or against the moving web 74. In this
way, the injected gas can be inhibited from escaping the curing
area.
[0065] FIG. 6 is a block schematic diagram of a UV curing
apparatus, assembly, mechanism or device constructed where the
moving web 74 is trained about rollers 94, 96 and 98, at least one
of which can be a drive roller, to cause the web 74 with the UV
curable products, articles or other objects thereon or therein to
move upwardly, as shown by the arrow 100, past the panel 28
mounting arrays 21, 23 and 25 (FIG. 4) of UV LED assemblies, much
the same as in the UV curing apparatus, assembly and device shown
in FIG. 5.
[0066] In the apparatus, assembly or device shown in FIG. 6, a gas
tube 104 providing a lower gas injector is positioned near a lower
end 106 of the path 100 of movement of the web 74 for injecting an
inert lighter-than-air, non-oxygen-containing gas, e.g., helium, in
the area between the orbiting panel 28 (FIG. 4) and the upwardly
moving web 74 (FIG. 6) to thereby provide an anaerobic area to
enhance and facilitate curing of the UV photo initiators in the UV
curable products, articles or other objects that are carried by the
web 74.
[0067] A wiper blade 108 (FIG. 6) providing an upper inhibitor 108
is positioned near the upper edge 68 of the panel 28 as shown in
FIG. 6 to minimize the escape of the lighter-than-air gas and hold,
compress, collect and/or blanket the injected gas in the curing
area between the orbiting panel 28 (FIG. 4) and the moving web 74
(FIG. 6), much the same as in the UV curing apparatus, assembly and
device shown in FIG. 5. Again, the wiper blade 108 (FIG. 6) can be
fixed to the upper edge 68 and arranged to wipe close to or against
the web 74.
[0068] To avoid overheating the UV LED assemblies 10, i.e., to
control the heat generated by the UV LED assemblies 10, the power
supplied to the UV LED assemblies can be periodically or
sequentially activated and deactivated, i.e. can be turned on and
off, at a relatively high frequency. Also, the duty cycle of the
on-off cycle can be varied to adjust the UV light intensity.
[0069] In FIG. 7 is illustrated another way to position the UV LED
assemblies, namely, the LED chips 16, and achieve the same
uniformity as shown in FIG. 2. This would be to use 3 rows to
achieve the uniformity. That is, to have the LED chips 16 in a
first row 112 arranged at a distance of X, and to have the next row
114 (row 2) start at a distance 1/3 in from the start of the first
row 112 and the next row 116 (row 3) start at a distance 2/3 in
from the start of the first row 112 or at a distance 1/3 in from
the start of the second row 114.
[0070] It will be understood that the space X can be equal to the
width of 1, 2, 3, 4, 5, etc. of an UV LED assembly 10 to provide a
desired staggering of the light beams from the UV LED assemblies
10. Preferably x equals the number of rows.
[0071] Also, in situations where partially UV curable ink or
adhesive might splatter on the UV LED assemblies 10, a
clear/transparent protective sheet or layer of plastic material can
be placed over the arrays 21, 23 and 25 to protect the UV LED
assemblies 10. Then, the protective sheet or layer is cleaned or
replaced periodically.
[0072] In the array 200 shown in FIG. 8, there are illustrated six
(6) staggered rows 201-206 of UV LED assemblies 216. This array 200
is similar to the array shown in FIG. 2. However, the individual UV
LED assemblies 216 in the array have different wavelengths for
applying UV light having different wavelength emissions which can
be more effective in curing inks, coatings and adhesives having UV
photo initiators therein and having a varying thickness.
[0073] It is to be understood that UV light emitted from an LED or
from a fluorescent lamp is over a range of wavelengths, often
referred as the Spectral Energy Distribution with a peak at one
wavelength which is the identified wavelength, e.g. 370 nm.
[0074] The UV LED assemblies can be positioned in a random, mixed
manner or in sequential rows. For example, in row 201 the first
UV-LED assembly 216A can emit light at 390 nm, the next UV LED
assembly 216B can emit UV light at 370 nm and the following UV LED
assembly 216C can emit UV light at 415 nm, and so on, repeating
this pattern throughout the row. The next row 202, and subsequent
rows 203-206, can have the same pattern or a different pattern.
[0075] Alternatively, all the UV LED assemblies 216 in row 201 can
emit light at 390 nm, all the UV LED assemblies 216 in row 202 can
emit light at 370 nm and all the UV LED assemblies 216 in row 203
can emit light at 415 nm and this pattern can be repeated for the
remaining rows 204-206. The pattern or order also can be changed,
e.g., 370 nm, 390 nm, and 415 nm.
[0076] Another variation would be a random mixture of UV LED
assemblies which emit light at 415 nm, 390 nm and 370 nm or other
wavelengths as such UV wavelength emitting diodes become available,
e.g., 350 nm, 400 nm and 420 nm.
[0077] In FIG. 9 is illustrated a lamp panel array 220 of four rows
221-224 of UV LED assemblies. The panel array 220 can be about four
inches long and has two bus strips 227 and 228.
[0078] As shown in FIG. 10 the first UV LED assembly 221A in the
first row 221 can emit light at 370 nm, the first UV LED assembly
222A in the second row 222 can emit light at 390 nm, the first UV
LED assembly 223A in the third row 223 can emit light at 420 nm,
and the first UV LED assembly 224A in the fourth row 221 can emit
light at 400 nm.
[0079] The second UV LED assembly 221 B in the first row 221 can
emit light at 390 nm, the second UV LED assembly 222B in the second
row 222 can emit light at 400 nm, the second UV LED assembly 223B
in the third row 223 can emit light at 370 nm, and the second UV
LED assembly 224B in the fourth row 224 can emit light at 420
nm.
[0080] The third UV LED assembly 221 C, 222C, 223C and 224C in each
row 221-224 can then emit light at, respectively, 420 nm, 390 nm,
400 nm and 370 nm. It will be understood that the UV LED's emit UV
light in a spectral range and the peak wavelength in the spectral
range is the wavelength identified.
[0081] Further, to achieve the greatest variation of wavelengths,
the panel array 220 can be arranged next to another source of
light, such as a fluorescent lamp (or lamps) whose phosphors are
chosen to augment the increase of light wavelengths. For example,
the OSRAM SYLVANIA, INC. Division of OSRAM GmbH of Danvers Mass.
offers a phosphor type 2011C fluorescent lamp that emits 351 nm, a
phosphor type 2052 lamp that emits 371 nm, a phosphor type 2092
lamp that emits 433 nm, and a phosphor type 2162 lamp that emits
420 nm.
[0082] These are several examples of wavelengths that easily can be
added to a curing mix. Additionally, a germicidal lamp or a Pen Ray
lamp can be used for the addition of 254 nm.
[0083] In FIG. 11, a secondary light source comprising two
fluorescent lamps 231 and 232 are illustrated which can be
positioned adjacent an elongate panel 234 formed by three panel
arrays 220 arranged end-to-end and electrically connected
(soldered) together. A web, similar to the web 74, and carrying a
UV curable product, article or other object can be arranged to move
across the elongate panel 234 as indicated by the arrow 236.
[0084] It will be understood that a number of panel arrays 220,
e.g., three (3)-eight (8) can be arranged end to end to form a UV
light emitting area and that more than one or two fluorescent lamps
or other lamps can be used as a secondary light source in the light
emitting area. The UV curable product, article or other object can
also traverse the two fluorescent lamps 231 and 232 and any
additional secondary light sources employed. The secondary light
source can be positioned above or below the partially cured ink
dots and adjacent to or downstream from the primary light source
defined by the arrays 220. The secondary light source. Lamps 231
and 232 are shown in FIG. 11 above and downstream from the primary
light source arrays 220. For ink jet printing, the secondary lught
source can be located below the substrate carrying the ink dots.
The light emitted from the secondary light source fully completes
the curing and polymerization of the ink dots.
[0085] The panel 234 can be oscillated, such as with cams (see FIG.
4), with a significant sweep to ensure overlapping of the four
different wavelengths.
[0086] In some embodiments of the product, the ink, coating or
adhesive can have two or more photo initiated monomers which are
activated at two or more frequencies, such as for example, 365 nm
and 385 nm and the light rays directed onto the product, article or
other object will include light at those wavelengths.
[0087] Also, as provided in the structures shown in FIGS. 5 and 6
and described above, an inert gas can be injected into the space
between the panel 234 and the moving web having a UV curable
product therein or thereon.
[0088] Empirical tests show that LED chips with a larger area can
emit higher intensity UV light. This feature can be important where
the space between the panel 234 and the web is a factor in the
curing. In this respect a large junction area LED chip emits more
light than a small junction LED chip. A large junction chip can
have 400 or more microns per side and a small junction chip can
have less than 400 microns on a side. The larger chips are referred
to as large junction LED's and provide a higher light density than
small junction LED chips.
[0089] In FIG. 12 there is illustrated a linear UV LED array
assembly 250 which includes an aluminum heat sink 252 having heat
dissipating fins 254 extending therefrom. On top of the heat sink
252 are two porcelain coated steel substrates 260 on which are
mounted UV LED chip arrays 256 and 258 which are similar to the
arrays shown in FIG. 9. Beneath the porcelain coated steel
substrate 260 of the arrays 256 and 258 there is provided a heat
sink compound 270 for securing the porcelain coated steel
substrates 260 to an upper surface of the heat sink 252. It will be
understood that the heat sink compound 270 not only holds the UV
LED chip arrays 256 and 258 to the upper surface of the heat sink
252 but also conducts heat from the UV LED arrays 256 and 258 to
the heat sink 252.
[0090] FIG. 13 is a perspective view of the UV LED array assembly
250 shown in FIG. 12. Here it will be seen that a second UV LED
chip array 274 is positioned behind UV LED chip array 256 and they
are connected together with wire conductors 280 and 282. Also, it
will be seen that the heat sink 252 is provided with a passageway
284 which extends generally parallel to the heat fins 254 and is
located to receive a pair of power supply wire conductors 288 and
290 from the UV LED chip array 274. Additionally, another
passageway 292 is provided in the heat sink 252 extending generally
parallel to the heat dissipating fins 254 adjacent the UV LED chip
array 258 for receiving a pair of power supply wire conductors 294
and 296 extending from the UV LED chip array 258.
[0091] FIG. 14 is a block diagram of a UV curing apparatus 300 that
includes a plurality, e.g., four, UV LED chip array assemblies 250.
The assemblies 250 can be fixed together and can be oscillated,
such as by cams, similar to the oscillation of the panel 28 shown
in FIG. 5.
[0092] A web 301 (FIG. 5) is trained over rollers 302, 304, and 306
to pass closely adjacent and in close proximity to the bank of UV
LED chip array assemblies 250. One of the rollers 302, 303 or 304
can be driven roller of a conveyor.
[0093] In the embodiment of FIG. 5, heat dissipation is provided by
the heat dissipating fins 254 of the bank of UV chip array
assemblies 250. This is important since the intensity of light from
the UV LED chips in the arrays 256, 258 and 274 can be attenuated
by the heating up of the UV LED chip arrays 256, 258 and 274.
Accordingly, in this embodiment the temperature of UV LED chip
arrays 256, 258 and 274 is kept within a predetermined temperature
range by dissipating heat through the heat dissipating fins
254.
[0094] Temperature control of the temperature of the UV-LED arrays
256, 258, and 274 in FIG. 5 can be enhanced further by the
provision of fans such as the fans 312, 314, 316 and 318 shown in
FIG. 14. It will be understood that temperature sensors can be
provided on the heat sink 252 for indicating, to a control circuit
(not shown) for the fans 312-318, the temperature of the arrays.
The control circuit can cause the fans 312-318 to turn on when the
sensors sense a temperature above a certain value and to turn off
when the sensors sense a temperature below a certain value. In this
way, the light density of the light rays from the UV LED chips can
be maintained at a high level.
[0095] FIG. 15 shows a plurality of four arrays 220 similar to the
arrays shown in FIG. 9 mounted on a substrate and covered with a
protective sheet of glass or plastic 320 providing a cover or
envelope to protect the LED arrays 220 from splatter.
[0096] FIG. 16 is a sectional view of a portion of the covered UV
LED chip array panels 220 shown in FIG. 15. Here a product, article
or other object 324 to be cured is shown above the glass or plastic
cover sheet 320 and nitrogen gas is supplied to the area between
the product, article or other object 324 and the cover sheet 320.
Then, of course, below the cover sheet 320 are the UV LED chip
array panels 220.
[0097] In FIG. 17 there is shown a printing and curing station 400
where a product, article or other object 402 (shown on an adjacent
support 404) is printed at a printing station 406 and then placed
on the support 404 (which can be a support conveyor as shown in
FIG. 18) where an assembly 408 of UV-LED arrays 408 is moved or
reciprocated over the freshly printed product, article or other
object (or the support conveyor is moved under the assembly 408 of
UV-LED arrays) to cure the print. The product, article or other
object 402 can be planar or have a curved shape, such as a cell
phone housing.
[0098] In FIG. 18 there is shown a curing station 420 where a
conveyor 422 carrying printed compact discs 424 is moved under an
assembly 426 of UV-LED arrays.
[0099] In FIG. 19 there is shown a turntable 430 for carrying
compact discs 432 beneath print heads 434 and assemblies 436 of
UV-LED arrays. The turntable is first indexed to move the compact
discs 432 under the spaced apart print heads 434 where printing of
compact discs 432 takes place followed by a second indexing of the
turntable to move the freshly printed compact discs 432 past the
spaced apart assemblies of UV-LED arrays for curing of the
print.
[0100] Since heat is generated by UV-LED chips when they are
emitting light, and the light intensity decreases as the
temperature increases, it is desirable to maintain a generally
constant temperature of the UV-LED chips to maintain a generally
constant light intensity/output. This can be accomplished with
several different systems. As shown in FIG. 20, one system 500 for
maintaining generally constant light intensity is graphically
illustrated. Here, the system 500 includes a light sensor 502 for
monitoring light intensity from the UV-LED chips in the UV-LED
arrays 504 in an assembly 506 of UV-LED arrays 504 that is directed
toward a printed product, article or other object 507, e.g., a
compact disc (CD). The intensity of the light sensed is used by a
control circuit 508 to control the current or voltage to a variable
speed fan 510 blowing cooling air on a heat sink 512 mounted on a
substrate 514 that also mounts the assembly 506 of the UV-LED
arrays 504. As the UV-LED chips heat up, the speed of the fan 510
is increased to increase the cooling of the heat sink 512 to cool
the heat sink 512 and the UV-LED chips mounted on the substrate
514, thereby to maintain the UV-LED chips at a generally constant
temperature which results in a generally constant light output from
the UV-LED chips.
[0101] Another system 600 is graphically illustrated in FIG. 21.
Here the system 600 for maintaining generally constant light
intensity includes a heat/temperature sensor 602 which monitors the
temperature of a heat sink 604 on a substrate 606 that also mounts
an assembly 608 of UV-LED arrays 610 containing a plurality of
UV-LED chips. The temperature sensed is used by a control circuit
612 to control the current or voltage to a variable speed fan 614
blowing cooling air on the heat sink 604 mounted on the substrate
606 mounting the assembly 608 of the UV-LED arrays 610. As the
UV-LED chips heat up, the speed of the fan 614 is increased to
increase the cooling of the heat sink 604 to cool the heat sink 604
and the UV-LED chips mounted on the substrate 606, thereby to
maintain the UV-LED chips at a generally constant temperature which
results in a generally constant light output from the UV-LED
chips.
[0102] In both systems 500 and 600, the heat sink 512 or 604 is
shown spaced from the UV-LED arrays 504 or 610 on the underside of
the substrate 514 or 606. In actual practice, the heat sink 512 or
604 is preferably located on the substrate 514 or 606 directly
above the UV-LED arrays 504 or 610.
[0103] According to the teachings of the present invention the
UV-LED arrays can be used in ink printing and curing systems such
as the system 620 shown in FIG. 22. Here, a printing head 622 is
arranged for reciprocating transverse movement across a piece 624
of material or product, article or other object, e.g. paper, to
print thereon with an UV curable ink. A first set of two UV-LED
arrays 626 and 628 are arranged to move with the printing head 622
on either side of the printing head 622. The two arrays 626 and 628
serve a very important function in that they apply UV light to the
ink dots as they are applied to the object being printed. This
causes the ink in the dots to at least partially cure, partially
coalesce, partially coagulate or partially gel, thereby to inhibit
if not altogether prevent running or smudging of the ink.
[0104] Then, the piece 622 of paper is indexed in a non-transverse
direction (see arrow in FIG. 23) under another set 630 of one or
more UV-LED arrays which can have LED chips which emit UV light at
one or more other wavelengths.
[0105] If desired and as shown in FIG. 23, the piece 622 of paper
can be indexed further or moved past a fluorescent lamp 632, which
emits light at still another wavelength.
[0106] As shown in FIG. 24, at least one heat lamp 640 can be
included at a curing station 642. In one preferred embodiment, the
heat lamp 640 is an IR, infra-red, lamp. In some circumstances,
other types of heat lamps can be used.
[0107] Here, a printed product, article or other object 644, such
as a compact disc (CD), computer disk, bottle cap or cell phone
housing part, is first moved on a conveyor 645 under the heat lamp
640 for UV curable inks which cure better or faster when heated.
Then the product, article or other object 644 is moved under a set
646 of UV-LED arrays.
[0108] It will be understood that, if desired to provide more
uniform light, the sets 630 and 646 can be reciprocated or
oscillated as described earlier herein.
[0109] Also, the sets 630 and 646 of UV-LED arrays can incorporate
the system 500 or 600 for maintaining the temperature of the UV-LED
chips therein generally constant.
[0110] The primary light source comprises a UV light source, such
as one or more UV lamps, but preferably comprises one or more
arrays of UV LEDs that can be secured by bolts or other fasteners
to the printer head so as to be carried and ride along in fixed
relationship with the printer head of a printer, such as an ink jet
printer, which dispenses and prints UV curable ink on paper or
another substrate, article, or object. The primary UV light source
quickly sets the ink dots dispensed and printed on the paper,
substrate, article, and/or other object and partially cures and
partially polymerizes the ink dots so that the ink dots rapidly
partially gel, coalesce and/or coagulate to prevent the ink dots
from growing, expanding, running, bleeding and/or smudging. The
secondary light source, such as one or more fluorescent lamps can
be placed below the ink dots and emit light on the ink dots to
complete the curing and polymerization of the ink dots. This method
is efficient, effective and economical.
[0111] From the foregoing description it will be apparent that the
method and device or apparatus of the present invention have a
number of advantages, some of which have been described above and
others of which are inherent in the invention.
[0112] Although embodiments of the invention have been shown and
described, it will be understood that various modifications and
substitutions, as well as rearrangements of components, parts,
equipment, apparatus, process (method) steps, and uses thereof on
other products, articles, and/or objects can be made by those
skilled in the art without departing from the teachings of the
invention. Accordingly, the scope of the invention is only to be
limited as necessitated by the accompanying claims.
* * * * *