U.S. patent application number 10/922665 was filed with the patent office on 2006-03-09 for bichromal and multicolored balls.
This patent application is currently assigned to Xerox Corporation. Invention is credited to John R. Andrews, Naveen Chopra, Daniel A. Foucher, Peter M. Kazmaier.
Application Number | 20060050363 10/922665 |
Document ID | / |
Family ID | 35995901 |
Filed Date | 2006-03-09 |
United States Patent
Application |
20060050363 |
Kind Code |
A1 |
Chopra; Naveen ; et
al. |
March 9, 2006 |
BICHROMAL AND MULTICOLORED BALLS
Abstract
Various techniques are disclosed for forming bichromal balls or
multicolored balls by laser-based methods. In one method, a laser
and a template are used to form small discrete precursors that are
subsequently spherodized. In another method a laser is used to cut
or otherwise form small discrete precursors that are also
subsequently spherodized. These methods are particularly well
suited for forming balls or other sphere-like bodies having
diameters less than 100 microns.
Inventors: |
Chopra; Naveen; (Oakville,
CA) ; Foucher; Daniel A.; (Toronto, CA) ;
Kazmaier; Peter M.; (Mississauga, CA) ; Andrews; John
R.; (Fairport, NY) |
Correspondence
Address: |
Richard M. Klein, Esq.;FAY, SHARPE, FAGAN, MINNICH & McKEE, LLP
SEVENTH FLOOR
1100 SUPERIOR AVENUE
CLEVELAND
OH
44114-2579
US
|
Assignee: |
Xerox Corporation
|
Family ID: |
35995901 |
Appl. No.: |
10/922665 |
Filed: |
August 20, 2004 |
Current U.S.
Class: |
359/296 ;
345/107 |
Current CPC
Class: |
G09F 9/372 20130101;
G02B 26/026 20130101 |
Class at
Publication: |
359/296 ;
345/107 |
International
Class: |
G02B 26/00 20060101
G02B026/00; G09G 3/34 20060101 G09G003/34 |
Claims
1. A process for forming bichromal balls, said process comprising:
providing a bilayer including (i) a first layer of a wax material
having a first color, and (ii) a second layer of a wax material
having a second color different than said first color; providing a
laser capable of ablating said wax material in said bilayer;
operating said laser and directing light emitted therefrom upon
said bilayer to ablate said bilayer and form a plurality of
precursor particles from said bilayer, each particle having a first
region of said first color and a second region of said second
color; heating said plurality of precursor particles to thereby
form said bichromal balls.
2. The process of claim 1, further comprising: providing a template
defining at least one aperture extending through said template; and
prior to said step of operating said laser, positioning said
template adjacent said bilayer such that said aperture constitutes
a desired line of cutting upon ablation by said laser of said
bilayer.
3. The process of claim 3, wherein said precursor particles are in
the shape of cylinders, squares or rhomboids.
4. The process of claim 1, wherein said heating is performed such
that said plurality of precursor particles are heated to a
temperature greater than the softening temperature of the wax
materials in said first layer and said second layer.
5. The process of claim 1, wherein each of said first layer and
said second layer has a thickness of from about 10 microns to about
45 microns.
6. The process of claim 1, wherein said bichromal balls produced
therefrom have a diameter of from about 20 microns to about 100
microns.
7. The process of claim 1, wherein said laser emits ultraviolet
light.
8. The process of claim 1, wherein said heating is performed by a
technique selected from the group consisting of (i) heating in a
flowing gas stream and (ii) heating in a liquid nonsolvent.
9. The plurality of bichromal balls produced by the process of
claim 1.
10. A process for forming multicolored balls, said process
comprising: providing a layered array of at least two layers, each
said layer comprising a wax material and having a color different
than the other layer; ablating regions of said layered array in a
predetermined pattern to form a plurality of precursor particles
from said layered array, each said precursor particle containing at
least two regions, each region comprising a wax material and having
a color different than the other region; removing said plurality of
precursor particles from said ablated layered array; and heating
said plurality of precursor particles to a temperature sufficient
to cause melting of said wax material in each region of said
precursor particles; whereby said precursor particles are
spherodized.
11. The process of claim 10, further comprising: providing a
template defining at least one aperture; prior to said ablating
step, positioning said template on said layered array.
12. The process of claim 10, wherein each of said first layer and
said second layer has a thickness of from about 10 microns to about
45 microns.
13. The process of claim 10, wherein said multicolored balls
produced therefrom have a diameter of from about 20 microns to
about 100 microns.
14. The process of claim 10, wherein said ablating step is
performed by an ultraviolet laser operating at a wavelength of from
about 100 to about 500 nm.
15. The process of claim 10, wherein said heating is performed in a
flowing gas stream or in a liquid nonsolvent.
16. The plurality of multicolored balls produced by the process of
claim 10.
17. A process for forming multicolored balls, said process
comprising: forming a body having a plurality of distinct regions,
each region constituting a wax material exhibiting a color
different than the color of the other regions; laser ablating said
body into a plurality of discrete particles, each said particle
having said plurality of distinct regions; heating said plurality
of discrete particles to thereby form a plurality of multicolored
balls.
18. The process of claim 17, wherein each said multicolored ball
has said plurality of distinct regions.
19. The process of claim 17, wherein said discrete particles are in
the shape of cubes.
20. The plurality of multicolored balls produced by the process of
claim 17.
21. The process of claim 17, wherein the wax material further
includes a pigment, a dye or a combination thereof.
22. The process of claim 17, wherein the laser ablation occurs by
an excimer laser.
23. The process of claim 17, wherein the laser ablation occurs by a
scanned focus laser.
Description
BACKGROUND
[0001] The present disclosure relates, in various exemplary
embodiments, to bichromal or multicolored balls and their formation
by laser ablation. The disclosure finds particular application in
conjunction with producing bichromal balls that can be used in
displays and "electric paper" applications, and will be described
with particular reference thereto. However, it is to be appreciated
that the disclosure is also amenable to other like
applications.
[0002] Bichromal balls or beads as sometimes referred to in the
art, are small spherical balls which have an optical and an
electrical anisotropy. These characteristics generally result from
each hemisphere surface having a different color and electrical
charge.
[0003] These spherical particles are imbedded in a solid substrate
and a slight space between each ball. The substrate is then filled
with a liquid (such as an oil) so that the balls are free to rotate
in a changing electrical field, but can not migrate from one
location to another. If one hemisphere is black and the other is
white, each pixel can be turned on and off by the electrical field
applied to that location by software, etc. Each pixel can be
individually addressed, and a full page image can thus be
generated.
[0004] Numerous patents describe bichromal balls, their
manufacture, incorporation in display systems or substrates, and
related uses and applications. Exemplary patents include, but are
not limited to: U.S. Pat. Nos. 5,262,098; 5,344,594; 5,604,027
reissued as Re 37,085; U.S. Pat. Nos. 5,708,525; 5,717,514;
5,739,801; 5,754,332; 5,815,306; 5,900,192; 5,976,428; 6,054,071;
5,989,629; 6,235,395; 6,419,982; 6,235,395; 6,419,982; 6,445,490;
and 6,703,074; all of which are hereby incorporated by reference.
In addition, disclosure is provided by U.S. Pat. Nos. 4,126,854;
and 5,825,529; and N. K. Sheridon et al., "The Gyricon--A twisting
ball display", Proc. SID, Boston, Mass., 289, 1977; T. Pham et al.,
"Electro-optical characteristics of the Gyricon display", SID '02
Digest, 199, 2002; all of which are hereby incorporated by
reference.
[0005] A typical process for making bichromal balls or Gyricon
spheres is the spinning disk method. Black and white heated waxes
are deposited onto a spinning disk, and centrifugal forces drive
the wax to the perimeter of the disk. At the disk edge, the waxes
sputter off into tiny droplets that solidify into beads or small
spheres after being spun off the disk. Controlling the size
distribution and bichromality of the resultant bichromal balls is a
significant issue with this technique.
[0006] Accordingly, there is a need for a technique for forming
bichromal balls which avoids, or at least significantly reduces,
the problems associated with currently known manufacturing
processes. Furthermore, there is a need for a method of producing
bichromal balls having a relatively small size such as, less than
100 microns.
BRIEF DESCRIPTION
[0007] In accordance with one aspect of the present disclosure, a
process for forming bichromal or multicolored balls or beads is
provided. The process comprises providing a bilayer including (i) a
first layer of a polymer material, such as a wax, having a first
color, and (ii) a second layer of a polymer material, such as a
wax, having a second color different than the first color. The
process also comprises a step of providing a laser capable of
ablating the polymer material in the bilayer. The process further
comprises operating the laser and directing light emitted therefrom
upon the bilayer to ablate material from the bilayer and form a
plurality of precursor particles from the bilayer. Optionally, a
template can be utilized to assist in the ablation process. Each
particle so formed has a first region of the first color and a
second region of the second color. The process additionally
comprises a step of heating the plurality of precursor particles to
thereby form bichromal balls or beads. Also included in this
disclosure are the bichromal balls or beads produced by this
process.
[0008] In accordance with another aspect of the present disclosure,
a process for forming bichromal balls is provided in which the
process comprises a step of providing a layered array of at least
two layers. Each layer comprises a wax material and has a color
different than the other layer(s). The process also comprises a
step of ablating regions of the layered array in a predetermined
pattern to form a plurality of precursor particles from the layered
array. Each of the precursor particles contains at least two
regions, each region comprising a wax material and having a color
different than the other region(s). The process further comprises a
step of removing the plurality of precursor particles from the
ablated layered array. The process additionally comprises a step of
heating the plurality of precursor particles to a temperature
sufficient to cause melting of the wax material in each region of
the precursor particles, whereby the precursor particles are
spherodized to form bichromal balls or beads upon cooling.
[0009] In accordance with yet another aspect of the present
exemplary embodiment, a process for forming multicolored balls is
provided in which the process comprises forming a body having a
plurality of distinct regions, each region constituting a wax
material exhibiting a color different than the other regions. The
process also comprises a step of laser ablating the body into a
plurality of discrete particles. Each particle includes the
plurality of distinct regions. The process further comprises a step
of heating the plurality of discrete particles to thereby form a
plurality of multicolored balls. This embodiment also includes the
multicolored balls formed by this process.
[0010] These and other non-limiting aspects and/or objects of the
development are more particularly disclosed below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] The following is a brief description of the drawings, which
are presented for the purposes of illustrating one or more of the
exemplary embodiments disclosed herein and not for the purposes of
limiting the same.
[0012] FIG. 1 is a schematic illustration of a method for forming
bichromal balls in accordance with the present disclosure.
[0013] FIG. 2 is a schematic illustration of another method for
forming bichromal balls in accordance with this disclosure.
DETAILED DESCRIPTION
[0014] The present disclosure relates, in various exemplary
embodiments, to processes and/or procedures for forming
monodisperse, perfectly, or nearly so, bichromal or multicolored
balls, or as sometimes referred to as Gyricon spheres. These balls
or spheres are from about 5 to about 200 microns, including about
20 to about 110 microns, such as less than 100 microns in diameter.
Two layers of different colored polymer materials, such as
pigmented waxes, can be spin-coated on top of one another to create
a bilayer of differently colored films. A UV, i.e. ultraviolet,
laser is used to shape or cut out certain configured precursors,
such as dowels, squares, rectangles, rhomboid or cylindrical shaped
precursors. These configured precursors are then formed and removed
from the sheet and spherodized to create bichromal particles. The
laser source is typically an excimer laser such as KrF (operating
at a wavelength from about 100 nm to about 500 nm including from
about 248 nm wavelength). Also described herein is a method of
making multicolored balls or particles using similar methods.
[0015] The term "wax" is utilized herein to refer to a low-melting
organic mixture of compound of high molecular weight, solid at room
temperature, and generally similar in composition to fats and oils
except that it contains no glycerides. Some are hydrocarbons,
others are esters of fatty acids and alcohols. They are classed
among the lipids. Waxes are thermoplastic, but because they are not
high polymers, they are not considered in the family of plastics.
Common properties, are water repellency, smooth texture, low
toxicity, freedom from objectionable odor and color. They are
combustible and have good dielectric properties; soluble in most
organic solvents, insoluble in water. The major types are as
follows:
[0016] I. Natural [0017] 1. Animal (beeswax, lanolin, shellac wax,
Chinese insect wax) [0018] 2. Vegetable (carnauba, candelilla,
bayberry, sugar cane) [0019] 3. Mineral [0020] (a) Fossil or earth
waxes (ozocerite, ceresin, montan) [0021] (b) Petroleum waxes
(paraffin, micro-crystalline)(slack or scale wax)
[0022] II. Synthetic [0023] 1. Ethylenic polymers and polyol
ether-esters ("Carboxwax," sorbitol) [0024] 2. Chlorinated
naphthalenes ("Halowax)" [0025] 3. Hydrocarbon type, such as
Nucrel.TM. (DuPont) and Elvax.TM. (DuPont).
[0026] Examples of such commercially available materials and their
sources include polyethylene and polypropylene waxes and their
modified derivatives. One example of a polyethylene wax is
Polywax.TM. 1000, manufactured by the Baker-Petrolite Corporation.
This material is a nearly crystalline polyethylene wax with a
narrow molecular weight distribution, and, consequently, a narrow
melt distribution. This material retains a low melt viscosity until
just above the melting temperature, a desirable property for the
spherodization of the particles. Other examples include lower
molecular weight Polywax.TM. materials, such as Polywax.TM. 400,
Polywax.TM. 500, Polywax.TM. 600, Polywax.TM. 655, Polywax.TM. 725,
Polywax.TM. 850, as well as higher Mw Polywax.TM. materials such as
Polywax.TM. 2000, and Polywax.TM. 3000. Other examples of
commercially available polyethylene waxes include members of the
Licowax.TM. product line, available from Clariant. Examples of such
materials include: Licowax.TM. PA520 S, Licowax.TM. PE130, and
Licowax.TM. PE520, as well as micronized polyethylene waxes such as
Ceridust.TM. 230, Ceridust.TM. 3615, Ceridust.TM. 3620, and
Ceridust.TM. 6071.
[0027] Examples of commercially available montan waxes include
Licolub.TM. CaW 3, Licowax.TM. E, Licowax.TM. OP, all available
from Clariant.
[0028] A commercially available synthetic form of carnauba wax is
Petronauba.TM. C, available from Baker-Petrolite Corporation.
[0029] Examples of polypropylene waxes include Licomont.TM. AR504,
Licowax.TM. PP230, Ceridust.TM. 6071, Ceridust.TM. 6072,
Ceridust.TM. 6721 (Clariant).
[0030] Examples of modified polyethylene waxes include linear
alcohol waxes such as: [0031] Unilin alcohols including Unilin.TM.
350, Unilin.TM. 425, Unilin.TM. 550 and Unilin.TM. 700
(Baker-Petrolite Corporation); [0032] linear carboxylic acid such
as Unicid carboxylic acid polymers including Unicid.TM. 350,
Unicid.TM. 425, Unicid.TM. 550, and Unicid.TM. 700 (Baker-Petrolite
Corporation); [0033] oxidized polymer materials such as Cardis.TM.
314, Cardis.TM. 36, Cardis.TM. 320 (Baker-Petrolite Corporation)
and [0034] oxidized polyethylene waxes such as Petrolite.TM.
C-8500, Petrolite.TM. C-7500, Petrolite.TM. E-2020, Petrolite.TM.
C-9500, Petrolite.TM. E-1040 (Baker-Petrolite Corporation).
[0035] Furthermore, in addition to waxes, different polymer
materials, including other low polymers, can also be utilized
herein so long as the desired properties and characteristics are
produced thereby. Examples of such additional polymers include, but
are not limited to, maleic anhydride-ethylene copolymers, maleic
anhydride polypropylene copolymers, nylons, polyesters,
polystyrene, poly(chloromethylstyrene), and acrylates such as
polymethylmethacrylate.
[0036] Commercially available examples of maleic anhydride-ethylene
copolymers include Ceramer.TM. polymers such as Ceramer.TM. 1608,
Ceramer.TM. 1251, Ceramer.TM. 67, and Ceramer.TM. 5005
(Baker-Petrolite Corporation).
[0037] Commercially available examples of maleic functional
polypropylene polymers include X-10036 and X-10016 (Baker-Petrolite
Corporation).
[0038] Commercially available examples of propylene-ethylene
copolymers include Petrolite.TM. copolymers such as Petrolite.TM.
EP-700, Petrolite.TM. EP-1104, Petrolite.TM. EP-1100, Petrolite.TM.
EP-1200 (Baker-Petrolite Corporation).
[0039] The polymer or wax materials can be colored through the
addition of pigments, dyes, light reflective or light blocking
particles, etc., as it is commonly known in the art. Moreover, when
waxes are used, pigments aid in the ablation process by absorbing
the energy from the UV excimer laser. Laser ablation of pure
polyethylene wax films is not possible at this wavelength. Films
made of polymers containing aromatic groups (i.e. polystyrene) can
be ablated in the absence of pigments, due to the absorption of the
laser UV radiation by the aromatic rings.
[0040] In this regard, a "pigment" is defined herein to include any
substance, usually in the form of a dry powder, that imparts color
to another substance or mixture. Most pigments are insoluble in
organic solvents and water; exceptions are the natural organic
pigments, such as chlorophyll, which are generally organosoluble.
To qualify as a pigment, a material must have positive colorant
value. This definition excludes whiting, barytes, clays, and
talc.
[0041] Pigments may be classified as follows:
[0042] I. Inorganic [0043] (a) metallic oxides (iron, titanium,
zinc, cobalt, chromium). [0044] (b) metal powder suspensions (gold,
aluminum). [0045] (c) earth colors (siennas, ochers, umbers).
[0046] (d) lead chromates. [0047] (e) carbon black.
[0048] II. Organic [0049] (a) animal (rhodopsin, melanin). [0050]
(b) vegetable (chlorophyll, xantrophyll, indigo, flavone,
carotene).
[0051] Some pigments (zinc oxide, carbon black) are also
reinforcing agents, but the two terms are not synonymous; in the
parlance of the paint and rubber industries these distinctions are
not always observed.
[0052] "Dyes" include natural and synthetic dyes. A natural dye is
an organic colorant obtained from an animal or plant source. Among
the best-known are madder, cochineal, logwood, and indigo. The
distinction between natural dyes and natural pigments is often
arbitrary.
[0053] A synthetic dye is an organic colorant derived from
coal-tar- and petroleum-based intermediates and applied by a
variety of methods to impart bright, permanent colors to textile
fibers. Some dyes, call "fugitive," are unstable to sunlight, heat,
and acids or bases; others, called "fast," are not. Direct (or
substantive) dyes can be used effectively without "assistants";
indirect dyes require either chemical reduction (vat type) or a
third substance (mordant), usually a metal salt or tannic acid, to
bind the dye to the fiber.
[0054] A "colorant" as used herein is any substance that imparts
color to another material or mixture. Colorants are either dyes or
pigments, and may either be (1) naturally present in a material,
(2) admixed with it mechanically, or (3) applied to it in a
solution.
[0055] There may be no generally accepted distinction between dyes
and pigments. Some have proposed one on the basis of solubility, or
of physical form and method of application. Most pigments, so
called, are insoluble, inorganic powders, the coloring effect being
a result of their dispersion in a solid or liquid medium. Most
dyes, on the other hand, are soluble synthetic organic products
which are chemically bound to and actually become part of the
applied material. Organic dyes are usually brighter and more varied
than pigments, but tend to be less stable to heat, sunlight, and
chemical effects. The term colorant applies to black and white as
well as to actual colors.
[0056] Examples of such colorants (i.e., pigments, dyes, etc.) and
their commercial sources include, but are not limited to, magenta
pigments such as 2,9-dimethyl-substituted quinacridone and
anthraquinone dye, identified in the color index as C1 60710, C1
Dispersed Red 15, a diazo dye identified in the color index as C1
26050, C1 Solvent Red 19, and the like; cyan pigments including
copper tetra-4-(octadecylsulfonamido) phthalocyanine, copper
phthalocyanine pigment, listed in the color index as C1 74160,
Pigment Blue, and Anthradanthrene Blue, identified in the color
index as C1 69810, Special Blue X-2137, and the like; yellow
pigments including diarylide yellow 3,3-dichlorobenzidine
acetoacetanilides, a monoazo pigment identified in the color index
as C1 12700, C1 Solvent Yellow 16, a nitrophenyl amine sulfonamide
identified in the color index as Foron Yellow SE/GLN, C1 Dispersed
Yellow 33, 2,5-dimethoxy acetoacetanilide, Permanent Yellow FGL,
and the like. Other suitable colorants include Normandy Magenta
RD-2400 (Paul Uhlich), Paliogen Violet 5100 (BASF), Paliogen Violet
5890 (BASF), Permanent Violet VT2645 (Paul Uhlich), Heliogen Green
L8730 (BASF), Argyle Green XP-111-S (Paul Uhlich), Brilliant Green
Toner GR 0991 (Paul Uhlich), Heliogen Blue L6900, L7020 (BASF),
Heliogen Blue D6840, D7080 (BASF), Sudan Blue OS (BASF), PV Fast
Blue B2GO (American Hoechst), Irgalite Blue BCA (Ciba-Geigy),
Paliogen Blue 6470 (BASF), Sudan III (Matheson, Coleman, Bell),
Sudan II (Matheson, Coleman, Bell), Sudan IV (Matheson, Coleman,
Bell), Sudan Orange G (Aldrich, Sudan Orange 220 (BASF), Paliogen
Orange 3040 (BASF), Ortho Orange OR 2673 (Paul Uhlich), Paliogen
Yellow 152, 1560 (BASF), Lithol Fast Yellow 0991K (BASF), Paliotol
Yellow 1840 (BASF), Novoperm Yellow FG1 (Hoechst), Permanent Yellow
YE 0305 (Paul Uhlich), Lumogen Yellow D0790 (BASF), Suco-Gelb L1250
(BASF), Suco-Yellow D1355 (BASF), Hostaperm Pink E (American
Hoechst), Fanal Pink D4830 (BASF), Cinquasia Magenta (DuPont),
Lithol Scarlet D3700 (BASF), Tolidine Red (Aldrich), Scarlet for
Thermoplast NSD PS PA (Ugine Kuhlmann of Canada), E.D. Toluidine
Red (Aldrich), Lithol Rubine Toner (Paul Uhlich), Lithol Scarlet
4440 (BASF), Bon Red C (Dominion Color Co.), Royal Brilliant Red
RD-8192 (Paul Uhlich), Oracet Pink RF (Ciba-Geigy), Paliogen Red
3871 K (BASF), Paliogen Red 3340 (BASF), and Lithol Fast Scarlet
L4300 (BASF). Examples of black pigments include carbon black
products from Cabot corporation, such as Black Pearls 2000, Black
Pearls 1400, Black Pearls 1300, Black Pearls 1100, Black Pearls
1000, Black Pearls 900, Black Pearls 880, Black Pearls 800, Black
Pearls 700, Black Pearls 570, Black Pearls 520, Black Pearls 490,
Black Pearls 480, Black Pearls 470, Black Pearls 460, Black Pearls
450, Black Pearls 430, Black Pearls 420, Black Pearls 410, Black
Pearls 280, Black Pearls 170, Black Pearls 160, Black Pearls 130,
Black Pearls 120, Black Pearls L; Vulcan XC72, Vulcan PA90, Vulcan
9A32, Regal 660, Regal 400, Regal 330, Regal 350, Regal 250, Regal
991, Elftex pellets 115, Mogul L.
[0057] Carbon black products from Degussa-Huls such as FW1, Nipex
150, Printex 95, SB4, SB5, SB100, SB250, SB350, SB550; Carbon black
products from Columbian such as Raven 5750; Carbon black products
from Mitsubishi Chemical such as #25, #25B, #44, and MA-100-S can
also be utilized.
[0058] Other black pigments that may also be used include Ferro.TM.
6330, a manganese ferrite pigment available from Ferro Corporation,
and Paliotol Black 0080 (Aniline Black) available from BASF.
[0059] Furthermore, as briefly mentioned above, the addition of
dyes and pigments can also increase laser coupling and therefore
increase the cutting efficiency. Hence, selection of the wax
material and/or the dye/pigment can be made to optimize the cutting
and/or shaping process.
[0060] Moreover, one or more processing aid, such as surface active
agents and dispersants aids like Aerosol.TM. OT-100 (from American
Cynamid Co. of Wayne, N.J.) and aluminum octoate (Witco).
Dispersant aids such as X-5175 (from Baker-Petrolite Corporation),
Unithox.TM. 480 (from Baker-Petrolite Corp.), and Ceramer.TM. 5750
(Baker-Petrolite Corp.) can also be added to the waxy base
material.
[0061] In one technique according to the present discovery, a
layered array is formed as follows. Polywax 1000 available from
Baker-Petrolite is compounded with titanium dioxide (TiO.sub.2) to
create a white wax. This wax is heated to a molten state and is
spin coated or blade coated onto a substrate. A similar copolymer
compounded with a black pigment, such as carbon black, is spin
coated/blade coated onto the first layer. Each layer is about 10
microns to about 45 microns, and generally about 30 microns, in
thickness.
[0062] Next, a laser etching, ablating, or cutting operation is
performed. A UV photomask etched with nearly complete circles,
squares, rectangles, rhomboids, etc., is placed over the top sheet.
A DUV, i.e. deep ultraviolet, laser is allowed to "burn" holes
through the apertures of the mask.
[0063] The laser ablation or cutting process could be accomplished
with an excimer laser. In this process the preferred method would
be to singulate a 2-d array of bilayer elements using an imaging
process, as is known in the art, which defines the cut lines. As an
alternate means to laser imaging, a scanned focused laser could be
used to singulate bilayer elements. In this case, an array of lines
could be cut along one axis and a second array of lines could be
cut at right angles to the first lines, forming square or
rectangular (or in general rhomboid) bilayer elements. The scanning
laser could include, but is not be limited to, diode pumped solid
state lasers (and harmonics), CO.sub.2 lasers, copper vapor lasers,
and noble gas ion lasers.
[0064] Alternative shaping or cutting processes such as embossing,
mechanical punching, or stamping are also included within the scope
of this disclosure. The shape or configuration of the precursor can
vary. For example, it has been found that square or rectangular
shaped precursors are in many instances more efficient from a
material usage standpoint.
[0065] After shaping, gentle pressure is applied to the sheet, and
the resulting dowels or precursor particles of bichromal materials
are removed from the bilayer. The dowels or precursor particles are
heated and spherodized to produce the bichromal beads.
[0066] The precursor particles can be spherodized in a flowing
heated air or gas stream such as in a fluidized bed drying
apparatus, which suspends the particles in a circulating hot air
mass. The temperature used would depend on the polymer. For a low
molecular weight styrene, for example, 150.degree. C. can be the
temperature to use. Alternatively, the precursor particles could be
dispersed in a nonsolvent, i.e. a liquid that the particles do not
dissolve in, with the optional aid of a surfactant, and heated to
the softening point of the polymer, allowing the particles to
spherodize. In another embodiment, the particles could be passed
through an air or gas zone of high temperature to spherodize them,
and dropped directly into a cold liquid bath to `quench` the
particles in their spherical state.
[0067] Alternative processes for transforming the dowels or
precursor particles into spheres include spray coating the
particles with a low-melt polymer or wax that is subsequently
spherodized using the techniques mentioned above, to create a
core-shell type spherical particle.
[0068] In yet another method in accordance with the present
discovery, multi-colored balls are produced from a laser etching or
cutting operation. A plurality, such as four different colored
waxes are prepared in a manner similar to that described. Using two
very fine heated nozzles of from about 10 to about 20 microns in
diameter, two strips of wax are deposited in a line. Directly on
top of these two strips are deposited two more strips of wax of
different colors to create a square rod of wax composed of four
differently colored quadrants.
[0069] The laser is used to cut the rod into small cubes. The cubes
are then spherodized to create bichromal balls of four different
colors.
[0070] This process can also be extended to create three colored
balls or particles in which only one strip of colored wax is laid
down on top of the two strips. Spherodizing is generally performed
by heating, as described herein.
[0071] Laser ablation of a laminated two layer, i.e. two color, wax
can be efficiently performed with an excimer laser operating an any
convenient wavelength such as 248 nm or 308 nm depending on the
absorption characteristics of the wax. Additives to the wax such as
aromatic-containing polymers would activate the wax to ablation at
248 nm. Excimer laser ablation using area imaging that images
circles onto the substrate could cut cylinders, or truncated cones
from the wax. For spherical beads that are 30 microns in diameter,
the cylinder would need to be 33 microns in diameter and 16.5
microns high. The thickness would be split nearly evenly between
two colors. To adjust the size and to equalize the two colors, the
true truncated cone shape would adjust the size and lead to a
slightly unequal thickness. Such dimensions and aspect ratios fit
easily within the capability of laser ablation processes. Based
upon this, less than about 50% of the material could be converted
into spheres. The size distribution would also be very narrow due
to the precision of the ablation process. A spread of diameters of
from about 5 to about 10% is a reasonable estimate.
[0072] Alternate processes for optical processing such as scanned
cutouts could also be performed though they may be less efficient
than image-wise ablation using an excimer laser.
[0073] It is believed that particles as small as 20 microns in
diameter can be produced in accordance with the methods described
herein. The limiting factors in making smaller balls are (1) the
intermixing of pigmented waxes during the spherodization (which
would destroy the bichromality of the spheres) and (2) the
interparticle attraction due to static and Van der Waals attractive
forces, which would cause particles to `cluster together` during
the spherodization step. It is believed that the laser ablation
cutting step is not limited to 20 micron spheres. A size limit
associated with the laser operating characteristics is believed to
be about 5 microns.
[0074] FIG. 1 illustrates a first embodiment process 100 for
forming the bichromal balls described herein. In this process, a
bilayer of two wax-based materials illustrated as bilayer 20, is
subjected to ultraviolet radiation 10, such as from a UV laser. The
bilayer can be a two layer member including a first layer of a wax
material having a first color, and a second layer of a wax material
having a second color different than the first color. A template 12
is optionally used to form the desired lines of cutting. The
template generally includes one or more apertures or open regions
across its thickness that, upon exposure to ablating light or other
radiation, form lines of cutting in the material undergoing
ablation. The laser cuts, or rather ablates, the wax material along
the desired lines of cutting. The cylindrically shaped precursor
particles are separated from the uncut portion of the bilayer 20 in
a separation step 30. Although the precursor particles are
described as cylindrical, the process includes particles of any
shape. A collection of bilayer cylindrical precursors 32 are then
subjected to a heating operation shown as step 40. By appropriate
selection of the heating temperatures and other parameters, a
collection of bichromal balls 42 are produced. For a bilayer member
having a first layer of a wax material and a second layer of
another wax material, the precursor particle is heated to a
temperature greater than the maximum melting temperature of the wax
materials.
[0075] FIG. 2 illustrates another preferred embodiment process 200.
In this process, two strips of pigmented wax 210 are provided.
Generally, each strip has a color different than the other strip.
An additional one or more other differently colored layers of
wax-based material are deposited thereon in step 220 to form a
strip of material 230. A severing operation, preferably performed
with an ablation laser is performed in step 240 to produce a
plurality of block-shaped precursor particles 250. Next, the
precursor particles are subjected to a spherodizing operation shown
in the figure as step 260. This is preferably performed by
subjecting the precursors 250 to a heating operation. The
spherodized particles are then in the form of a four-colored ball
shown as 270.
[0076] Although the present discovery has been described in terms
of using a plurality of wax materials differing in color, the
discovery includes selecting other types of materials that can
differ in other aspects besides, or in addition to color.
[0077] The bichromal or multicolored balls produced by the process
disclosed above can be used to form display elements. For example,
the bichromal or multicolored balls can be cast in a transparent
sheet material, covered and immersed in a dielectric fluid such as
oil. The oil is then absorbed by the sheets forming oil filled
pockets around each bichromal or multicolored ball.
[0078] Alternatively, the bichromal or multicolored balls can be
encapsulated and incorporated into a substrate. The display
elements so achieved can then be made to operate as conventionally
known in the art of Gyricon displays, such as by bringing the
display into association with an electronic field that causes the
bichromal or multicolored balls within the Gyricon elements to
appropriately rotate so as to display a desired image.
[0079] While particular embodiments have been described,
alternatives, modifications, variations, improvements, and
substantial equivalents that are or may be presently unforeseen may
arise to applicants or others skilled in the art. Accordingly, the
appended claims as filed and as they may be amended are intended to
embrace all such alternatives, modifications variations,
improvements, and substantial equivalents.
* * * * *