U.S. patent number 3,922,687 [Application Number 05/500,271] was granted by the patent office on 1975-11-25 for means and method for creating a visible display utilizing high sensitivity magnetochemical particles.
This patent grant is currently assigned to Lyne S. Trimble. Invention is credited to Florence A. Ito, Lyne S. Trimble.
United States Patent |
3,922,687 |
Trimble , et al. |
November 25, 1975 |
Means and method for creating a visible display utilizing high
sensitivity magnetochemical particles
Abstract
Improved means and method for creating a visible display
utilizing magnetochemical particles that respond to a magnetic
field by exposing an interface capable of reacting chemically with
a surrounding chemical environment to provide an immediately
visible change in color. Waterphase droplets in a carrier medium
provide an envelope for the chemical and contained particles. The
particles have a high sensitivity to magnetic fields obtained by a
unique structure which utilizes two masses of ferromagnetic
materials usually in spherical form, and in which each has a core
of magnetostrictive material with properties common to hard
magnetic materials. Each core is coated with a metallic material
capable of reacting upon exposure to the chemical environment to
produce a visible color, but which is normally shielded and
prevented from reacting by an overcoating of a brittle material.
The two masses are relatively oriented and physically attached with
their magnetizable axes in parallel relation, whereby upon
subjection to a magnetic field, magnetic poles will be induced
which produce repulsive forces for assisting in the rupture of the
particle. Thus, when the particle is exposed to a magnetic field
pulse, three forces influence its performance. The force generated
by magnetostriction provides motion that acts to loosen the bond
between the brittle frangible coating and the chemically reactive
layer; the induction of adjacent like poles in the attached spheres
generates a force of repulsion which, added to the magnetostrictive
force, ruptures the frangible physical attachment and exposes the
color forming metal to the surrounding chemical environment; the
hard magnetic quality of the mass material results in the formation
of two permanent magnets such that the force of repulsion persists
following induction to complete the rupture started by the
triggering pulse.
Inventors: |
Trimble; Lyne S. (North
Hollywood, CA), Ito; Florence A. (North Hollywood, CA) |
Assignee: |
Trimble; Lyne S. (North
Hollywood, CA)
|
Family
ID: |
26904785 |
Appl.
No.: |
05/500,271 |
Filed: |
August 26, 1974 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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210077 |
Dec 20, 1971 |
3882507 |
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Current U.S.
Class: |
430/84; 148/105;
346/74.6; 360/131; 428/403; 252/62.51R; 29/DIG.95; 346/74.2;
360/55; 428/100; 430/39 |
Current CPC
Class: |
G03G
19/00 (20130101); Y10S 29/095 (20130101); Y10T
428/24017 (20150115); Y10T 428/2991 (20150115) |
Current International
Class: |
G03G
19/00 (20060101); G03G 019/00 (); G11B 005/84 ();
G01D 015/34 () |
Field of
Search: |
;360/131,137,55,114,116,56,113 ;324/43,47 ;346/74.1 ;29/DIG.95
;117/1M ;148/31.5,105 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Eddleman; Alfred H.
Attorney, Agent or Firm: McManigal; Robert M.
Parent Case Text
This is a division of application Ser. No. 210,077, filed Dec. 20,
1971, now U.S. Pat. No. 3,882,507.
Claims
We claim:
1. A supporting medium having a coating containing high sensitivity
magnetochemical particles comprising two anisotropic masses of
magnetic material and means capable of chemical activation in
response to an applied magnetic field to provide a visible pattern
in the area exposed to such magnetic field.
2. A supporting medium having a coating, comprising: a plurality of
distinctly chemically different high sensitivity magnetochemical
particles comprising two anisotropic masses of magnetic material
and including materials adapted to react with a chemical
environment within which the particles are contained to provide
distinct visible colors, each of said particles being capable upon
exposure to a magnetic field to form a visible color of a
multicolor image, and said chemical reactions to form distinctly
different colors being selectively activated by predetermined
characteristics of said magnetic field.
3. A supporting medium according to claim 2, wherein the color
gradations for each color are determined by the intensity of the
magnetic field.
4. A supporting medium according to claim 2, wherein the image
characteristics are dependent upon the magnetic field strength and
its duration.
5. A supporting medium according to claim 2, wherein the multicolor
image is formed in real time.
6. Magnetic field responsive means, comprising:
a. a carrier medium;
b. small water phase droplets in said medium, each containing a
color forming chemical;
c. at least one high sensitivity magnetochemical particle confined
in the chemical of the droplet, said particle comprising: a pair of
attached masses of ferromagnetic materials having their maximum
anisotropic axes parallel;
d. each of said masses being coated with a metal which is reactive
to the droplet chemical; and
e. an overcoating of a protective material normally shielding the
reactive metal coating with respect to the droplet chemical.
Description
BACKGROUND OF THE INVENTION
The present invention is broadly concerned with the creation of a
visible display in response to the magnetic stimulation of
magnetochemical particles.
Heretofore, the use of magnetic fields as a means of triggering
chemical activity to provide a visible change has been generally
known from U.S. Pat. No. 3,281,669. It has been also known from
U.S. Pat. No. 3,512,169 to utilize such means generally for
creating visible displays in color. In both of these patents, the
creation of the visible display was dependent upon magnetostrictive
size change induced in certain materials by a magnetic field. The
material was selected with provision for overplating such that
contact with a colorless chemical environment would bring about a
chemical change to form color, and it was coated with a frangible
protective film that could be severed by sufficient
magnetostrictive size change, so that exposure to a magnetic field
resulted in the formation of a visible color. The change in size of
the magnetostrictive materials in many instances was found to be
insufficient to cause rupture of the frangible protective film,
when the magnetic field strength was reduced substantially below
1000 oersteds. To avoid borderline situations involving control of
very thin frangible films and to increase sensitivity for response
to magnetic field exposure, the present invention takes advantage
of additional forces found to be available from a magnetic field.
Thus, it has been found that the forces of repulsion between two
like magnetic poles generated in two adjacent ferromagnetic
materials by magnetic field exposure can augment the
magnetostrictive forces and assist in triggering chemical activity
in a surrounding chemical environment. The combination of
magnetostrictive action and mutual repulsion of like poles has been
found sufficiently effective to bring about chemical activity at
field strengths in the order of 100 oersteds.
A mathematical estimation can be made to indicate the maximum force
of repulsion that will result from magnetic field induction in
adjacent magnetic materials. In general, the force increases with
the square of the material radius and it increases as the physical
configuration progresses from spheres to plates to rods. The force
can act in tension, bending, or torsion to separate two attached
magnetic materials. However, as the size of the material is
substantially reduced and the performance of very tiny particles is
considered, the occurrence of self demagnetization acts to offset
mathematical estimations. In small magnetic materials, it is of
uncertain and unpredictable magnitude.
For tiny ferromagnetic materials attached together and exposed to
magnetizing pulses of a few micro seconds duration, it has been
found that both magnetostrictive forces and mutual repulsion forces
can be active in bringing about separation. However, inertia
(overcome by the prolonged forces generated during a longer pulse)
can prevent the materials from fully separating during the short
exposure time and can delay the formation of a visible change in a
surrounding chemical environment. To insure a complete break-away,
it has been found desirable to use hard magnetic materials
characterized by the ability to maintain a magnetic field following
magnetization. Thus, the poles established through magnetic
induction will maintain a portion of the strength induced in them
and continue overcoming the inertia of the materials following the
magnetizing pulse. To further enhance performance, the materials
can be treated to bring into being a preferred direction of
orientation with respect to the establishment of permanent magnetic
fields, and these magnetic field directions can be aligned before
material to material attachment.
A variety of substances known generally as hard magnetic materials
may be used for this purpose, and tabulations of suitable materials
and properties are to be found in the C. C. Van Nostrand
publication (1961) "Ferromagnetism" by Dr. R. M. Bozorth,
particularly in the table, pages 872 and 873. Other hard magnetic
alloys and ceramics developed since 1961 are also applicable. A
preferred direction of orientation can be established by heat
treating and annealing in a magnetic field. The subsequent
alignment of heat treated and annealed materials can be
accomplished by suspending them in a directional magnetic field so
that they can freely rotate to bring the preferred directions of
orientation in line with the field direction. Magnetic materials so
aligned can be attached with a suitable adhesive bond. This
structure and its performance, with modifications to be discussed,
is a main feature of the present invention, and although it will be
referred to as the magnetochemical particle, it is understood to be
a high sensitivity magnetochemical particle and a substantial
improvement on the prior art.
SUMMARY OF THE INVENTION
The present invention relates generally to means and method for
creating a visible display by means of magnetochemical particles,
and in particular such particles as will respond to relatively low
strength magnetic fields, and upon exposure thereto are capable of
reacting with a chemical environment to bring about an immediately
visible change.
In its broad concept, the objects of the present invention
include:
a. The provision of means by which magnetic inductions from low
field strength, short duration magnetic pulses are utilized to
trigger a chemical reaction productive of a visual change in the
area of the magnetic field application.
b. Provision of a magnetic field sensitive visual display technique
responding to low field strength magnetic pulses by triggering the
occurance of a chemical reaction to produce a visible change in the
area of magnetic field application.
c. The provision of a magnetochemical particle consisting of
attached magnetic materials capable of detachment when subjected to
a magnetic field.
d. The provision of a magnetochemical particle comprising a pair of
ferromagnetic materials aligned so that their preferred directions
for magnetic field orientation are parallel, then joined together
to preserve the orientation alignment.
e. The provision and use of a magnetochemical particle comprising
magnetostrictive materials having properties characteristic of hard
magnetic materials, each coated with a chemically reactive metal,
suitably attached and suspended in a chemical environment within
which the metal would normally react but from which it is protected
by a brittle relatively nonreactive continuous surface coating
applied over the external surface. This brittle coating is selected
to have the capability of being ruptured or rendered discontinuous
in response to the forces generated by and between the magnetic
materials under the influence of a magnetic field, thus allowing
the chemically reactive metal to react with the chemical
environment.
f. The embodiment of magnetochemical particles and a surrounding
colorless but color-forming environment in droplet form in such a
manner that the droplet size can be controlled to establish image
resolution in an applied coating prepared by dispersing these
droplets in a resinous carrier and applying the carrier to a
surface.
g. Means for obtaining permanent visible images in color following
exposure to a magnetic field substantially less than 1000 oersteds
and in particular below 800 oersteds to improve upon the condition
shown in FIG. 5 of the referenced U.S. Pat. No. 3,281,669.
h. Provision of magnetochemical particles capable of selectively
triggering chemical reactions in response to different magnetic
field pulse times and threshold levels.
i. Provision of unique means for preparing magnetochemical
particles of the character referred to in the previously noted
objectives.
j. The provision of method and means wherein a plurality of
variable parameters can be selectively controlled, either
individually or in combination, in order to obtain a variety of
desirable effects in the creation of color displays.
k. The provision of an additive three color hard copy on film,
paper, or plastic, wherein the colors are stimulated by magnetic
means upon a real time basis.
l. Means for providing a coating that can be applied to a
supporting medium to disclose the presence of a magnetic field
whether present at the time of application or created later.
m. The provision of means for creating a visible discernible area
coincident with a magnetizing action which produces a magnetized
area.
n. Means for providing coatings on thin supporting media that may
be positioned against or bonded to and later removed from surfaces
believed to contain magnetic fields so that a visual image can be
produced on or within the applied coating which, if removed can be
separately inspected by either reflection or transmission
viewing.
o. The provision of a visible image in the areas of magnetic
fields, wherein the visual density or image intensity is
proportional to the intensity of the magnetic field.
p. The provision of a visible image of magnetic fields with a
resolution equal to the magnetic recording resolution.
Further objects and advantages of the invention will be brought out
in the following part of the specification, wherein detailed
description is for the purpose of fully disclosing an embodiment of
the invention without placing limitations thereon.
BRIEF DESCRIPTION OF THE DRAWINGS
Referring to the accompanying drawings, which are for illustrative
purposes only:
FIG. 1 is an enlarged cross-sectional view diagrammatically
illustrating a sphere constructed according to the present
invention;
FIG. 2 is a cross sectional view of a dimpled plate structure as
utilized in the preparation of magnetochemical particles according
to the present invention;
FIG. 3 is a plan view of a dimpled plate showing the distribution
pattern of spheres thereon;
FIG. 4 is a view diagrammatically illustrating successive steps for
the alignment of spheres and their attachment to provide the
respective particles; and
FIG. 5 is an enlarged view diagrammatically disclosing a particle
composed of two joined spheres, according to the present
invention.
DESCRIPTION OF A PREFERRED EMBODIMENT
Referring more specifically to the drawings, there is shown in FIG.
1, a mass of ferromagnetic material in the form of a sphere as
generally indicated by the numeral 10, which forms a basic
component of the present invention. The preparation, treatment, and
use of these spheres according to the present invention will now be
explained in detail.
Magnetic Material Selection
A number of magnetic materials can be employed in the construction
of the spheres 10. Commercially available alloys containing cobalt,
iron, aluminum, nickel and copper and known as Alnico alloys have
been used as have those containing iron, cobalt, and vanadium and
known to the trade as Vicalloy. A particular alloy which has been
used successfully is one known in the trade as Alnico 5, which has
a composition in addition to iron of 24 percent cobalt, 14 percent
nickel, 8 percent aluminum and 3 percent copper. The
characteristics of this alloy as indicated by Dr. Bozorth show that
a coercive force of 600 oersteds is attained following a
magnetizing field of approximately 450 oersteds, and that lower
residual fields suitable for mutual repulsion purposes are attained
with lower magnetic induction levels. Because of self
demagnetization, it is the prevailing belief that these
characteristics are greatly diminished when a small particle of the
alloy is being considered.
Magnetic Material Preparation
Magnetic alloys are often prepared in ingot form. The metal can be
melted and sprayed into an inert atmosphere so that tiny spheres
are formed without substantial change in the alloy composition. The
size of the spheres can be controlled by the several parameters
well known and in use in the metalizing art. Following cooling, the
spheres are mechanically separated to isolate the desired size
range by using known techniques such as vibration, rotation through
tubes, sieving, and the like. For the purpose of the present
invention, spheres in the 20-30 micron diameter size range were
selected for use, and were separated from the metalizing yield by
mechanical sieving. This choice of size is purely optional and
based upon certain tooling as will be hereinafter discussed.
Spheres as small as 5 microns in diameter and as large as 100
microns in size were used. Larger sizes are equally suitable;
however, the AC fields required to erase these larger spheres
become excessive.
The selected spheres are heat treated and annealed in a magnetic
field to create within each a preferred orientation with respect to
magnetic field direction. The exact procedure depends upon the
alloy that is used. If the alloy is ductile, such as the above
mentioned Vicalloy, then physical hot or cold working can be
substituted for heat treating and annealing. In such case, the
spheres are cold rolled to form elliptical plates that display a
preferred direction of orientation to an applied magnetic field,
for example, parallel to the long axis of the ellipse. A suitable
technique for the Alnico 5 alloy involves packing the spheres to
minimize caking, then heating to a temperature of substantially
1200.degree. to 1300.degree.C. for 1-5 minutes in a dry hydrogen
atmopshere. The spheres are then cooled to a temperature of
700.degree.C. in 2 minutes at a rate of approximately 300.degree.C.
per minute. The cooling is conducted in a 1000 oersted magnetic
field having a single direction through the mass of spheres. The
magnetic field application and cooling rate below 700.degree. C. is
not critical. The spheres are then aged for eight hours at a
temperature of approximately 600.degree.C., which may vary by
10.degree.C. in an atmosphere of argon or hydrogen. An evaluation
of heat treated and annealed Alnico 5 spheres showed that in
addition to an improvement in magnetostrictive properties, the
directional orientation increased the residual magnetic field
following induction by a factor between 3 and 4.
Magnetic Material Plating
Although the metals making up these heat treated spheres will react
with a selected chemical environment to form colored products, the
reaction rate tends to be slow unless a strong chemical environment
is used to dissolve metal from the alloy. To increase the rate of
chemical reaction, a thin film, number 11, is formed around each
sphere by electroless plating with any one of several ductile
metals capable of forming colored salts, such as iron, nickel, or
cobalt. These metals are readily dissolved by a dilute suitably
proportioned chemical environment, as described in U.S. Pat. No.
3,281,669. For the purposes of the present invention, iron was
selected as the color forming metal; and a film thickness up to 1
micron was found to be suitable, when deposited from an electroless
plating bath compounded and used as shown in the following Table 1.
Other application techniques, such as vapor deposition and metal
spraying can also be used to provide thin metal films, but
electroless plating is preferred.
A frangible protective coating, number 12, is next applied over the
iron layer by using electroless plating techniques. Although
brittle substances like antimony can be used as described in the
above referenced patent, very good results have been obtained also
by applying a thin film of copper and/or copper oxide. The copper
was applied by using the well-known Fehling's reaction which, in
the absence of an oxygen-getter and when used as shown in the
following Table 2, deposits a brittle film that is a mixture of
copper and cuprous oxide. The adhesion of this film to iron and
other metals is poor and it can be substantially destroyed by the
magnetostrictive size change, when the sphere is magnetized. A
film, one to one-and-one-half microns in thickness, provides
resistance to the color forming chemicals contained in the
environment in which the magnetochemical particle is suspended;
however, for the reasons discussed below, an additional protective
layer 13 of tin or nickel-tin is used. This frangible coating,
number 12, will hereinafter be referred to as copper, although it
will be understood that it is actually the metal oxide mixture
obtained by plating as described above. Although specific plating
formulas have been given in Table 1 and Table 2, it is to be
understood that other suitably proportioned electroless plating
baths capable of depositing these metals may be used in accordance
with the broad concepts of the present inventions.
TABLE 1 ______________________________________ ELECTROLESS IRON
______________________________________ Ferrous Sulfate 20 grams
(FeSO.sub.4) Sodium Citrate 60 grams (Na.sub.3 C.sub.6 H.sub.5
O.sub.7.2H.sub.2 O) Water to make 1.0 liter Add just prior to use:
Ammonium Hydroxide 30 ml (NH.sub.4 OH) Sodium Borohydride 2 grams
(Na BH.sub.4) Temperature 60.degree.C. Plating Time 9 minutes
______________________________________
TABLE 2 ______________________________________ ELECTROLESS COPPER
______________________________________ Rochelle Salts 170.00 grams
(KNaC.sub.4 H.sub.4 O.sub.6.4H.sub.2 O) Sodium Hydroxide 50.00
grams (NaOH) Copper Sulfate 37.00 grams (Cu SO.sub.4.5H.sub.2 O)
Formaldehyde 200.0 ml (CH.sub.2 O 37% Volume) Water to make 1200 ml
Temperature 50.degree.C. Plating Time 7 minutes
______________________________________
The copper surface has a red-orange reflection, when viewed in
white light; and since this can impart a tint to a transparent
medium containing the spheres, the coating, number 13, of tin is
contact plated on the copper surfaces to minimize this tint. If the
spheres are immersed in a 2 percent sodium stannate solution with
aluminum at 65.degree. to 80.degree.C. a small amount of tin will
be plated on the copper. This tin film is bright, highly
reflective, and masks the copper tint. The presence of the tin film
does not affect the magnetochemical particle preparation techniques
to be described nor the particle performance characteristics
although it does provide additional resistance to penetration of
color forming chemicals. Films of nickel-tin alloys are equally
effective in brightening the sphere surfaces and these also provide
resistance to penetration of color forming chemicals. As deposited
from the bath of Table 3, nickel-tin films are frangible as well as
resistant and can be used over a very thin layer of copper to
provide equal protection, as indicated in FIG. 1. Brittle plastic
films such as Acryloid A-11 deposited by solvent evaporation will
provide resistance to the penetration of the color forming
chemicals, but unless they are pigment loaded they do not provide
high reflectivity.
TABLE 3 ______________________________________ NICKEL-TIN PLATING
BATH ______________________________________ 1. Sodium Stannate 26.7
grams (Na.sub.2 SnO.sub.3 . 3H.sub.2 O) 2. Water 650 ml (H.sub.2 O)
3. Glycerine 200 ml (C.sub.3 H.sub.8 O.sub.3) 4. Sodium Fluoride
8.4 grams (NaF) 5. Ammonium Bifluoride 11.4 grams (NH.sub.4 F.HF)
6. Nickel Acetate 25 grams (Ni (C.sub.2 H.sub.3 O.sub.2).sub.2 .
4H.sub.2 O) 7. Ammonium Hydroxide 120 ml (NH.sub.4 OH) 58% 8.
Hypophosphorous acid 44 ml (H.sub.3 PO.sub.2) 50% 9. Temperature
65.degree.-70.degree.C. 10. Plating Time 1 minute
______________________________________
Magnetic Material Attachment
In order to properly perform according to the present invention,
two spheres, which have been heat treated and plated in the manner
described above, must be attached together with their preferred
directions of orientation parallel to provide a particle, as
generally indicated at 14, FIG. 5. Several procedures have been
used for attaching the spheres, including semi-random soldering,
and direct joining, either upon an individual two-by two basis or
upon a quantity basis. A satisfactory technique of attachment to be
described below, has been evolved upon a quantity basis.
Tooling
The photoengraving art can be utilized to provide a metal plate,
number 15, FIG. 2, which is equivalent to a halftone screen and
contains a number of equally spaced and accurately sized dimples,
16, in each square inch. The plate is prepared by starting with a
distortion free negative as a basis for exposing a light sensitive
dichromate and gum resist that has been applied to the metal plate
surface. By using suitable controls during an etching step, dimples
of uniform diameter and depth can be formed without undercutting
around the edges. According to the present invention, the dimples
were made substantially 4 mils in diameter and 4 mils deep, where 1
mil is understood to be 0.001 inches. These were then reduced in
size by applying a layer, 17, of suitable material by electroless
plating techniques, since the deposited material will fill in the
sides of the dimple as it elevates the level of the plate surface.
Plating three mils of metal thickness was found to reduce the size
so that each dimple would hold a single 20-30 micron diameter
sphere, 10, as indicated in phantom lines. In the present instance,
a copper photoengraving plate was used, with 6000 dimples per
square inch, and the dimples were reduced to size by electroless
nickel plating. In the following described procedure, a liquid
resin will be applied to the dimpled surface, and when dry the
resulting film is stripped from the surface. To minimize adhesion
of the resin to the nickel surface, the dimples are plated
one-quarter mil oversize and then reduced to size by applying a
layer, 18, of teflon that will cure to one-quarter mil in
thickness. The teflon is applied by spraying, and cured at
approximately 600.degree.F.
Attachment Using The Tooling
The treated and plated spheres are magnetically erased to remove
any residual field, then brushed onto the teflon surface of the
plate 15 to place a sphere 10 within each dimple, as shown in FIG.
3. Any spheres remaining on the surface of the plate are readily
removed by means of a known adhesive material such as a
conventional adhesive tape. A thin film of a suitable resin
solution is next applied to the surface of the plate. Although a
number of thermoplastic resins and resin combinations can be used,
including vinyls, acryloids, certain commercial paints, and even
shellac, it has been found that a mixture of acryloid resins
dispersed by ball milling 10 percent by weight of Acryloid A-11 and
90 percent by weight of Acryloid B-72 to make about 35 percent by
weight in toluene, provides a film that following drying has good
dimensional stability and very satisfactory handling quality for
the procedure to be described. Application of the acryloid to the
surface of the plate is accomplished by conventional techniques;
and a drawdown bar calibrated in mils of applied thickness has been
most satisfactory in providing films that dry to thicknesses from
one to ten mils.
As soon as the resin is applied, the plate is subjected to a
directional magnetic field of a strength in the order of 20 to 150
oersteds. A convenient method resides in the placing of the plate
and resin between the unlike poles of the two directionally
magnetized materials, such as plastoid magnets, so that the field
passes from pole to pole through the spheres and parallel to the
surface of the plate. Field strengths in the above range are
sufficient to cause the spheres contained in the dimples, and
suspended in the resin filling the dimples, to rotate so that the
prealigned or preferred direction of orientation of each sphere is
aligned parallel to the surface of the plate and parallel to the
surface of the thin resin film. The electroless nickel on the plate
has sufficient phosphorous content and is sufficiently thin so that
it does not divert the magnetic field and prevent free orientation.
The resin applied at a thickness of about 5 mils will, upon solvent
evaporation in air over a period of 15 to 20 minutes, leave about 2
mils of hard but flexible transparent film which, when stripped
from the teflon surface to which it has limited adhesion, will
display 6,000 peaks per square inch, each peak containing an Alnico
5 sphere oriented with respect to preferred direction of
magnetization. Any residual field in the spheres can be
magnetically erased by using a conventional AC magnetic field
eraser. Resin films thicker than 2 mils are equally satisfactory,
however as the thickness is reduced below 2 mils there is danger of
tearing the film during stripping.
For the purposes of this invention, two resin films containing
magnetic field oriented spheres are prepared. Spheres in
corresponding positions, that is, cast from the same dimple in the
plate, are to be registered for attachment so that they must be in
identical positions with respect to overall film to film alignment.
One means for establishing and maintaining the positioning embodies
a direct alignment by mechanical positioning devices such as
employed in the registration of color separation negatives in the
printing of color motion picture films. Positioning accuracy of 0.2
to 0.4 mil is common practice at motion picture film printing
rates. Two sets of metal register pins fitting the perforations of
a 70 mm films are accurately mounted at each end of the dimple
containing plate so that the perforations of a length of film
placed along the plate would fall on the pins. A 2 to 3 inch length
of 70 mm film base is attached through two perforation holes to
each set of pins. The drawdown layer of resin as previously
described above is applied and overlapped onto these two 70 mm
films, thus forming a firm bond with the 70 mm plastic base. Using
this technique, two identical sphere containing resin films may be
prepared and stripped from the plate. For convenience in handling,
a width of conventional five ounce per inch paper base adhesive
tape can be applied to the exposed surface of the resin after
drying and prior to stripping it from the plate. This is a
protective measure, and the tape is easily removed at any time.
When the two resin films are assembled by again placing the same
perforation holes of the 70 mm film base on the same register pins,
the tiny spheres will be exactly superimposed, their preferred
directions of orientation will be parallel, and parallel to the
surface of each resin. If two identical mirror image dimple plates
are used, the films of the suspended spheres will be mirror images
of each other. In a practical embodiment of the invention, a single
dimple plate was used and the two resin films were handled in such
a manner that mirror images were prepared and mirror image spheres
could be joined together. This was accomplished by stripping one
film from the plate and turning it over to expose the projected
dimples containing the spheres. The exposed surface was then coated
with about 5 mils of resin solution to cover the dimples and
provide a protective layer over the spheres. When dry, the film was
turned over to expose the original surface and mild sanding was
conducted with a 600 W emery paper or equivalent to abrade this
surface and expose a 10-15 micron diameter area of each sphere.
when viewed under the microscope, the Alnico 5 center, and the
electroless plated metal rings were clearly visible. For mirror
image positioning, the second resin film needs only reversal and
abrasion of the projected dimples. However, to simplify handling
and maintain dimensional stability this film was given a very thin
resin overcoating to strengthen it to withstand the abrasive
action.
A better understanding of this procedure will be obtained from a
consideration of FIG. 4 which shows at (a), a diagrammatic
representation of the two resin films 19a and 19b containing
spheres that have been stripped from the dimple containing plate.
For simplicity these are labeled top and bottom and although this
designation will be followed throughout the description it will be
understood that it relates only to the relative position of the two
when superimposed for joining. Following along, (b) shows these
films with a resin layer 20a and 20b applied over the spheres in
each case, and (c) shows the FIG. 4 (b) films 19a and 20b with the
cross-section of the spheres exposed by sanding 20a and abrading
away 19b.
A step of tinning is indicated at (d), and (e) shows the film just
prior to assembly for joining. The projected areas 21 resulting
from tinning are visible. It will be noted that the two films ready
for sphere cross-section joining are mirror images with respect to
the plate upon which they have been prepared. The assembly for
joining with heat that fuses the alloy 21 with which the metal
surfaces have been tinned, is shown at (f), while the
magnetochemical particles 14 prepared by this joining process after
the supporting resin films have been completely dissolved, are
indicated at (g).
As abraded, the exposed metal surface are level with the resin
surface. To elevate them above the resin, the surfaces can be
chemically displaced with copper or electroless copper plated after
step (c) and prior to step (d). Although this is not an essential
operation, a 3 to 4 micron copper layer can be deposited over the
exposed metal surfaces to provide a space differential permitting
subsequent tinning with minimum deposition of tinning material on
the resin.
A number of adhesives are suitable for joining pairs of spheres,
and substances like sulfur, vinyl suspensions like Wilhold Glue,
cyanoacrylate adhesives like Eastman 910 Cement, acetates like Duco
Cement, Epoxy containing cements and Woods metal have been used.
Rupture occurs in the frangible copper layer at the magnetic metal
surface. The fusible alloys were found most satisfactory. Within
the fusible alloy group, one known as Cerrolow 117, melting at
about 117.degree.F. and containing Indium, Bismuth, Lead, Tin, and
Cadmium, has been found to be very satisfactory. Another known as
Cerrolow 105 differing from Cerrolow 117 in the addition of a small
amount of mercury has also been found to be satisfactory. The
alloys can be used singly or in combination; soldering flux often
productive of corrosion is not required. Tinning is accomplished by
mounting the resin film around a cylinder to expose the abraded
sphere areas and advancing it against a flat surface covered by a
thin layer of molten fusible alloy. The surface can be a smooth
copper sheet, tinned with the alloy and maintained at 60.degree.C.
to 90.degree.C. The friction of the exposed spheres against the
molten metal results in tinning, and a thin layer of fusible alloy,
21, is thus applied to each sphere. The alloy is allowed to cool
and solidify and the tinned sphere interfaces are ready for
joining. Although tinning of exposed metal surfaces in both top and
bottom sphere containing films has been described in connection
with FIG. 4, satisfactory results can be obtained by leaving out
the 3 to 4 mil copper layer described hereinabove and tinning only
one of these films. A rolling contact against the thin layer of
fusible alloy will deposit a tiny droplet of alloy on each exposed
metal surface, and flow during the joining step is sufficient to
bond both surfaces.
The two resin films are superimposed face to face and aligned on
the plate using the same 70 mm perforation holes and register pins
used in preparing them. The assembled films can be viewed under
high magnification to insure that the spheres are superimposed,
then subjected to 60.degree.-80.degree.C. heat from a platen heavy
enough to maintain the two films in contact. A thin teflon sheet on
the surface of the plate and one between the platen and the top
film will prevent sticking. After ten to forty five seconds the
platen is removed, a cool platen of equal weight is substituted,
and the films are allowed to cool. By this action the fusible alloy
layers on adjacent spheres will have melted and joined. Following
cooling, the composite film and joined spheres can be removed from
the plate, the 70 mm perforated base trimmed away the acryloid
resin dissolved in a suitable solvent such as toluene or methylene
chloride. When the solvent is decanted, the magnetochemical
particles remain.
When followed in time sequence, the above described technique
provides a supply of magnetochemical particles. If the sequence is
interrupted by time delays, the acryloid resin films can shrink so
that sphere to sphere alignment for registration is not readily
obtained. Control can be introduced by strengthening the acryloid
layer with a hard film of polyvinyl chloride or other suitable
backing. Polyvinyl chloride thicknesses of 3 to 7 mils have been
found satisfactory and can be applied to the back of the two
acryloid surfaces after preparation and before removal from the 70
mm register pins. A thin draw-down layer of viscous acryloid can be
applied to one surface of the poly vinyl chloride to provide an
adhesive of like character for joining onto the dry acryloid layer
holding the metal spheres. The poly vinyl chloride, like other
suitable plastic strengtheners, will dissolve in the solvents, such
as toluene or methylene chloride, or mixture thereof during the
release of the particles as described above.
As a precautionary measure to prevent color forming chemical
penetration into any magnetochemical particles not completely
sealed by the tinning and joining process or ruptured by rough
handling during preparation, a post sealing treatment can be
applied. A very thin film of nickel-tin deposited from an
electroless plating bath will provide additional sealing against
penetration of chemicals as well as provide a surface readily wet
by the viscous water phase mixture. The film can best be applied
over the several metal exposures by normalizing the surfaces with a
thin copper flash followed by the nickel-tin plating. Although a
number of combinations have been used, the following procedure has
been found effective in depositing a sub micron thickness film
providing sealing without appreciably increasing the strength of
the sphere to sphere bond. The copper flash can be deposited using
the electroless copper bath set forth in Table 2. The formaldehyde
(CH.sub.2 O) is omitted and plating is conducted at
40.degree.-45.degree.C. for about 10 minutes. The bath is poured
off, the particles rinsed with water, then treated for about 5
minutes with a 0.1 percent solution of sodium borohydride
(NaBH.sub.4). This solution is decanted and the particles are
nickel-tin electroless plated as set forth in Table 3. Following
plating, they can be rinsed and added to the water phase
mixture.
The Magnetochemical Particle
Each particle consists of two spheres joined together by about 2
microns of fusible alloy 21 as shown in FIG. 5 such that
satisfactory resistance to the color forming chemicals is provided.
By preparation in this manner, the direction of orientation of the
adjacent magnetic spheres is parallel. When subjected to a magnetic
field, the magnetostrictive forces produce a dimensional change
tending to weaken or destroy the bond between the iron and copper
layers 11 and 12, respectively. Magnetic induction establishes like
poles in adjacent areas of the spheres as shown by the phantom
lines 15' and 15", and these have sufficient force of repulsion to
rupture the protective film and allow the spheres to peel apart.
Since a hard magnetic material has been used, two permanent magnets
have been generated and a force of repulsion exists following the
triggering pulse. The measured rupture strengths of the several
metals involved at the sphere to sphere interface show that the
weakest bond is between the fusible alloy and the Alnico 5. Thus,
peel-off occurs at the smallest of the two interfaces resulting
from joining, and between the alloy and the magnetic material. This
exposes the thin ring of iron to the color forming chemicals
contained in the surrounding environment as described in U.S. Pat.
No. 3,281,669 and a visible change occurs immediately. Instant
separation is available with magnetic fields as low as 100 oersteds
and pulse times as short as 2 microseconds (the limiting time on
available measuring equipment).
Packaging of the Magnetochemical Particle
It has been found desirable to modify the technique described in
U.S. Pat. No. 3,281,669 to more effectively package the above
described somewhat more massive magnetochemical particle. The
modifications include changes in the composition of the water phase
components making up the surrounding chemical environment to permit
formation and suspension of slightly larger droplets in the resin
film. The following technique has been found effective. Mix equal
parts by volume of glycerine and glucose. Stir and blend together
well. To the glycerine-glucose mixture add an equal volume of water
and blend thoroughly. To 100 ml of this solution add 2 grams of
boric acid (H.sub.3 BO.sub.3) and 0.5 grams of 2,2' dipyridine. The
magnetochemical particles are readily wet by this water phase
solution and can be added to it. A dispersion of particle
containing droplets in an acrylic resin is made by stirring one
part of the above prepared water phase solution containing the
magnetochemical particles with three parts of an acryloid solution
comprising 40 percent acryloid resin solids in a suitable solvent
such as toluene, methylene chloride, or a mixture thereof. The
extent of stirring determines the size of the particle containing
droplets that are formed, and with particles made using the 20-30
micron diameter spheres described hereinabove, a few moments of
mild stirring will provide a very uniform dispersion of water phase
droplets averaging about 60 to 80 microns in diameter, each
containing a mobile magnetochemical particle. For smaller particles
made by joining smaller ferromagnetic spheres, smaller droplets are
desirable since the resolution of a pattern will be greater and the
total thickness of the final resin film can be decreased. Smaller
droplets are readily formed by reducing the viscosity of the water
phase or by prolonging the stirring or increasing the stirring rate
or both. The resin solution can be applied to a variety of surfaces
by conventional coating techniques such as rollers, drawdown, knife
edge and the like and the film will dry rapidly by solvent
evaporation. A protective resin topcoat can be applied to
incorporate desired surface characteristics.
Use of Magnetochemical Particles
Since the product is magnetic field sensitive, writing, printing,
or recording can be conducted by any technique that provides a
directional magnetic field of the proper strength and with the
desired resolution. For optimum high speed high resolution
performance, it is desirable to prealign the magnetochemical
particles in the water phase droplets by subjecting the resin film
to a magnetic field parallel to the intended direction of the field
to be used for recording or printing. The field strength should not
exceed 50-60 oersteds and could well be an alignment step just
prior to use. The conventional magnetic recording head provides the
most common source of recording. By selection of gap shape and
size, patterns can be constructed of points, lines, or areas. Line
structure can be tight since the fringe flux from the sides of the
magnetic recording head does not erase a previously recorded
pattern to limit packing density as it does during magnetic tape
recording. A "bit" at a time printing results from using a rotating
metal helix sweeping over a magnetizable bar with the recording
material in between the helix and the bar. If the bar is made the
core of an electromagnet, then when the bar is pulsed the metal of
the helix will concentrate the magnetic field and cause printing at
the intersection of the bar and the helix. One rotation of the
helix will print a line of "bits." As a refinement, the helix can
consist of a sequence of points to effect character generation as
described in U.S. Pat. No. 3,017,234 covering Electromagnetic
Printer. Magnetizable type can be used for printing in several
ways. If the type is pre-magnetized, a print is made upon or just
short of contact. If several sheets of the recording material rest
on a magnetic metal plate, stack printing will occur. If the type
is the core of a solenoid, an electrical pulse will effect
printing. A directional magnetic field can be established at a
level just below that necessary to record so that bringing the
metal type into recording position will concentrate the magnetic
field and cause printing. An area printing source results from the
use of a recording on a magnetic tape or on a magnetic metal drum.
Printing techniques devoid of mechanical motion include an x, y,
matrix of tiny solenoids, where printing occurs on point to point
basis through programmed electrical signals. It is also possible to
use an electron beam by converting the beam energy to magnetic
field energy using the chromium manganese antimonides discussed
below and printing on the paper placed against a special CRT face
plate. By use of the antimonides, laser beam energy can be
converted into magnetic field energy for printing.
While this invention may be applied in the many ways described in
the referenced U.S. Pat. Nos. 3,281,669 and 3,512,169, the
capabilities of magnetochemical particle performance at low
magnetic field levels greatly broadens the scope of application.
For example, a color copying device may consist of a television
camera reading station using a rotating color wheel so arranged
that three primary color aspects of an original are obtained and
transmitted sequentially as electrical signals. The signals thus
generated may be used to trigger current flow into an x, y matrix
writing station of tiny solenoids to form magnetic fields in each
solenoid at the matrix surface. With a magnetic field bias applied
to the solenoids, mild excursions of current will effect writing on
a point-to-point basis upon a film or paper, embodying the
invention and placed against the matrix surface. As a further
example, a transformation from an optical image to a magnetic field
productive of visual patterns through magnetochemical action is
available by utilizing the thermal properties of the chromium
manganese antimonide alloys. These materials undergo a transition
from antiferromagnetic to ferrimagnetic at a temperature dependent
upon alloy composition. The thermal differential resulting from
projecting an optical image upon a thin sheet or mosaic of small
particles of the alloy will cause this transition. Concentration of
magnetic flux in the ferrimagnetic areas will effect
magnetochemical action in a paper embodying the invention and
placed against the unexposed surface of the alloy and between the
alloy and the bias magnetic flux sources to be concentrated. If the
alloy is sandwiched between two hard magnetic materials having
prealigned or preferred directions of orientation aligned parallel
to the longest direction of the composition, then the increase in
permeability of the alloy, following the thermally induced
transition will result in a magnet of length equal to the composite
length, and the extension of field from this longer magnet will
effect magnetochemical action.
MODIFICATIONS AND COMBINATIONS
The heretofore mentioned patents relate to magnetochemical
particles where performance is based upon magnetostrictive action.
This present invention describes a magnetochemical particle wherein
the forces generated through magnetostriction and the forces
generated through induction of like magnetic poles in adjacent
metals or metal alloys combine to bring about a triggering action
for color formation not available through either force alone.
Similarly, the invention includes a magnetochemical particle
capable of triggering a chemical reaction when subjected to a
magnetic field wherein the forces of magnetostriction may be small
in comparison with the forces generated by like magnetic poles such
as, for example, but not limited to, the best permanent magnetic
materials. Conversely, the invention also includes particles
wherein the forces of magnetostriction are large in comparison with
the forces generated by like magnetic poles such as for example,
but not limited to, ferrite materials. Performance within this
scope is available with a variety of combinations.
For magnetochemical particles of the same composition but different
sizes, the induced forces of repulsion vary with the spherical
radius so that different size particles will respond at different
applied field strengths. For example, 60 micron diameter spheres
will respond by rupturing a 20 micron diameter interface at the 100
oersted level, and 10 micron diameter sphere will respond by
rupturing a 5 micron diameter interface at the 1000 oersted level.
The spheres making up the magnetochemical particle may be of
different magnetic materials. For example, a highly
magnetostrictive material combined with one of lower
magnetostriction can result in a preferred cross section of
rupture. Thus, there are many combinations of materials and
physical properties permitting the formation of magnetochemical
particles falling within the scope of this invention. Although iron
has been selected as the preferred color forming metal, very good
results have been obtained with electroless deposits or
displacement films of metals such as cobalt, nickel, zinc, cadmium,
lead, vanadium, silver, copper and tin. Thus, the magnetochemical
particles described herein have a variety of parameters that can
determine performance and are applicable to selective triggering to
form a multi-colored system as described in U.S. Pat. No.
3,512,169. Particles made from spheres have been described
throughout this invention, but it will be understood that plates,
rods, and other shapes are equally applicable according to the
invention.
Although the descriptive techniques have covered the use of
magnetic material and metal films plated onto the magnetic material
as components for color forming purposes, it will be understood
that color forming components can be introduced by other means. The
several sphere to sphere bonding materials discussed hereinabove
are equally applicable, if each contains a small quantity of metal
powder or water soluble or insoluble salts dispersed therein. This
does not alter the adhesive character, bond strength, or ease of
handling and has the advantage that rupture of a sphere to sphere
junction made up of such a loaded adhesive or alloy will expose
enough of the loading material to bring about dissolving and color
formation. Sulfur, for example, has been loaded with cobalt
chloride salt such that upon particle rupture the soluble cobalt
salt is immediately dissolved to react with a nitroso R indicator
in the surrounding environment to generate a red color. The fusible
alloys have been loaded with iron, cobalt, and the like metal
powders that are sealed over during the above described joining
process, but are exposed to chemical action in the surrounding
environment by magnetic field induced rupture. Similar results have
been obtained by incorporating small quantities of water soluble
salts such as ferrous sulfate into the fusible alloys. Upon
rupture, they are immediately available for color formation.
Throughout the description, emphasis has been placed upon the
capability of forming a visual pattern in a clear film by
application of a magnetic field. It will be realized that the
invention is equally applicable to forming a visual differential in
whole or in part by bleaching an existing pattern or changing the
color of an existing area. Exposure of a number of dyes and
pigments to the reducing activity of zinc metal in a slightly acid
medium will result in decolorization. The formation of colorless
leuco bodies by dyes of the triphenylmethane class such as,
malachite green and the reduction of prussian blue pigment to
ferrous ferrocyanide are examples. The complexing activity of
soluble sulfites on dyes of the fuchsine class, for example, will
cause immediate bleaching of color in a water phase droplet
containing the colored substance.
The described techniques have covered the use of the
magnetochemical particle to generate a visible change in a water
system and on a small droplet basis. It will be understood,
however, that the invention is equally applicable to situations
involving large liquid volumes. It is also equally applicable to
organic solvent systems where it may be employed upon a small
droplet or large liquid volume basis. For example, the
magnetochemical particle actuated by a magnetic field can expose
appropriate metal surfaces, salts, or traces of compounds
sufficient to catalyze changes in organic based systems and by
employing the techniques and controls discussed hereinabove, the
changes can be made selective for more than one release. Although
packaging has been described in terms of a suspension of water
phase droplets, it will be understood that conventional
encapsulation techniques are applicable to contain the particle and
a suitable chemical environment in permeable, semi-permeable or
non-permeable shells to permit handling in solid form.
While it is realized that the invention is applicable to pressure
sensitive pattern formation, and this has been demonstrated by
suspending the water phase droplets in a resin that has been
plasticized with conventional substances like castor oil, di butyl
phthalate, or tri cresyl phosphate, for the intended purpose of the
invention, this has been avoided. A moderately hard resin has been
employed so that cutting in shear would not result in breaking
particles and forming color at the sheared edges of a product.
From the foregoing description, the uses, advantages, and operation
of the present invention will be readily understood by those
skilled in the art to which the invention appertains. While certain
forms of the invention have been described, which are now
considered to be the best embodiments thereof, it is to be
understood that the forms shown are merely illustrative and that
the invention is not to be limited to the details disclosed herein,
but is to be accorded the full scope of the appended claims.
* * * * *