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Description  |
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BACKGROUND OF THE INVENTION
This invention relates to inks characterized by opaque properties in light.
More specifically, this invention relates to inks which are opaque in
ordinary light so as to render them particularly suitable as a means for
marking various materials.
Ink jet printing is a recent development in the art of applying identifying
and decorative indicia to a base. In general terms, a fluid ink is forced,
under pressure, through a very small orifice in an orifice block which
contains a piezoelectric crystal vibrating at high frequency (50-100,000
vibrations per second) causing the ink passing through the orifice to be
broken into minute droplets equal in number to the crystal vibrations. The
minute droplets are passed through a charging area where individual
droplets receive an electrical charge in response to a video signal, the
amplitude of the charge being dependent on the amplitude of the video
signal. The droplets then pass through an electrical field of fixed
intensity, causing a varied deflection of the individual droplets
dependent on the intensity of the charge associated therewith, after which
the deflected drops are allowed to impinge to the base medium which is to
receive the decorative or informative printed indicia. Apparatus suitable
for carrying out the ink jet printing process is described in detail in
U.S. Pat. Nos. 3,465,350 and 3,465,351, issued Sept. 2, 1969 and it is in
connection with an apparatus and process such as are described in the
aforementioned patents that the ink of the present invention is designed
to function.
In order to operate satisfactorily in an ink jet printing system, an ink
must display a consistent drop breakup length, drop velocity and drop
charge under set operating conditions.
It has been determined that an ink jet printer, described in U.S. Pat. Nos.
3,465,350 and 3,465,351, inks with viscosity of 25 cps. will perform
satisfactorily depending upon the type of nozzle used. However, inks with
lower viscosities perform much better. Resistivity of ink may range as
high as 10,000 ohm cm. for satisfactory operations.
BRIEF DESCRIPTION OF THE DRAWINGS
The FIGURE shows schematically and greatly enlarged a perspective view of
an ink jet performing the process of the invention.
DESCRIPTION OF THE INVENTION
This invention is a process for information recording comprising producing
a fine jet of liquid, directing a jet of liquid onto a recording medium,
modulating the density of the applied jet by an electric field in
accordance with the information to be recorded, thereby recording said
information, applying moisture to said recorded information, thereafter
rendering said recorded information opaque.
According to another of its aspects, this invention is a process for
information recording comprising producing a fine jet of liquid, directing
said jet of liquid onto a recording medium, modulating the density of said
applied jet by an electric field in accordance with the information to be
recorded, thereby recording said information, and thereafter lowering the
temperature ambient to said recorded information to the dew point, thereby
rendering said recording opaque.
Inks of this invention include three basic components. The first is a
colorant for providing visibility of the printed indicia. The second major
component is the solvent which provides fluidity to the ink and carries in
solution or suspension the resin and colorant. The third component is a
resin or binder which remains on the substrate surface after printing and
serves to adhere and bind the dye or pigment in position on the substrate
surface. In addition to these three components which are found in nearly
all fluid printing inks, various other ingredients may be utilized,
including drying, dispersing and wetting agents, plasticizers, diluents
and the like.
This invention, thus, relates to inks which are opaque. These inks are
organic in nature, also an advantage, in that they do not have the
abrasive wearing quality of many inks based on abrasive, inorganic
pigments.
Inks of this invention contain resin/polymers in concentration of 1 to 80%
alone or in blends, dissolved in solvents. Solvents include aliphatic
alcohol and other solvents can be ketones, aldehydes, ethers, esters,
glycols, glycol ethers, hydrocarbon, lactones. Typical aliphatic
monovalent alcohols are methyl alcohol, ethyl alcohol, etc.
A necessary resin includes at least one member of the group consisting of
cellulose derivatives such as cellulose esters (nitrocellulose, cellulose
acetate and the like), and especially cellulose ethers, for example,
methylcellulose, hydroxyethylcellulose, hydroxypropylcellulose,
propionitrile cellulose, ethyl cellulose and benzylcellulose. The
corresponding derivatives of other polysaccharides can also be used.
Suitable dyeing agents are direct dyes (substantive dyes), acid dyes, base
dyes, and various oil-soluble dyes. The dye type can be chosen depending
on the thinning agent combination and the binding agent type.
Preferred coloring materials are basic dye bases.
The inks can have a viscosity of 1.5 cps to 25 cps at 25.degree. C. The
preferred range is 1.8 cps to 7.5 cps.
The resistivity of ink can be as high as 10,000 ohms-cm. The preferred
range is 1,500 to 4,000 ohms-cm.
Inks of this invention have adhesion on practically all substrates.
The resin component of a jet printing ink suitable for printing on coated
or virgin metal must also meet a variety of requirements. Of primary
importance is the ability of the resin to adhere to the coated or virgin
metal surface on which the ink is printed and to maintain this strong
adhesion under widely varying conditions of humidity and temperature. When
the ink is applied to the metal surface, it must "wet" or adhere to a
coated or virgin metal surface, even in the presence of some moisture, and
must exhibit a high degree of moistureproofness, not only to maintain
adhesion to the metal but also to protect the dye, which may be water
sensitive, from the effects of moisture which may make the dye bleed into
surrounding areas.
The resin component must also be very readily soluble in the solvent
combination to form a stable, low viscosity solution that effective
amounts can be dissolved in the solvent without unduly increasing the
viscosity of the composition.
Synthetic, semi-synthetic and natural resins, which is to say both
polymerization as well as polycondensation and polyaddition products, are
suitable. In principle, all resins customary in the printing ink and paint
industry, such as are, for example, described in the lacquer raw material
tables of Karstne (4th edition, Hanover, 1967) and in Wagner and Sarx's
work on lacquer resins (4th edition, Munich, 1959) are used.
The following, for example, are suitable resins: colophony and derivatives
thereof, hydrogenated colophony, di- or polymerized colophony, as calcium
or zinc salt, with colophony esterified with mono- or polyvalent alcohols;
with resinifiers such as acrylic acid and butane diol or maleic acid and
pentaerythritol modified colophony resin; the soluble phenol resins
modified with colophony and resins based on acrylic compounds, maleinate
resins, oil-free alkyd resins, styrolated alkyd resins, vinyl toluene
modified alkyd resins, alkyd resins with synthetic fatty acids, linseed
oil alkyd resins, ricinene alkyd resins, castor oil alkyd resins, soy oil
alkyd resins, coconut oil alkyd resins, tall oil and fish oil alkyd
resins, acrylated alkyd resins, also oils and oil varnishes. Also suitable
are terpene resins, polyvinyl resins such as polyvinyl acetate, polyvinyl
chloride, polyvinylidene chloride, polyvinyl acetals, polyvinyl alcohol,
polyvinyl ether, copolymers and graft polymers with various vinyl
monomers, polyacrylic resins, acrylate resins, polystyrenes,
polyisobutylenes, polyesters based on phthalic acid, maleic acid, adipic
acid, sebacic acid, etc.; naphthalene formaldehyde resins, furane resins,
ketone resins, aldehyde resins, polyurethanes (especially urethane
primary-products that cure only at elevated temperature), epoxide resins
(especially resin-curer mixtures that cure only at elevated temperature)
and precondensates thereof. Suitable too are primary products of
unsaturated polyester resins, dialkylphthalate-prepolymers, polyolefines
such as polyethylene wax or polypropylene wax, indene and cumaron-indene
resins, carbamide and sulphonamide resins, polyamide and polyester resins,
silicone resins, rubber and derivatives thereof, for example, cyclorubber
and chlorinated rubber.
A further requirement of resin is that it should have sufficient solvent
release so that a desired rate of drying is obtained on a given substrate.
In order to be effective in a formulation of a jet printing ink for a
given substrate, the solvent medium must readily dissolve sufficient
amounts of the resin component, the dye and any desirable optional
components such as to achieve the desired level of adhesiveness,
conductivity and visual impact of the ink composition. Further, since some
degree of evaporation of solvent will occur in the ink supply and ink
return systems, thereby, increasing the solids concentration in ink and
solvent should have sufficient power to prevent precipitation in this
situation.
Although evaporation of the solvent from the ink supply and return systems
is generally undesirable, it is important that the solvent evaporate at
the desired rate from the printed image area in order to leave the printed
image smearproof and moisture-proof in required time after the printing
operation is carried out. The solvent must achieve a satisfactory balance
in evaporative properties between these opposed objectives.
Depending upon type of substrate on which ink is to be printed, it is
advantageous to use a solvent which will penetrate the wax or other
coating on substrates to enhance adhesion and rub resistance of the ink.
The jet ink in accordance with this invention, which contains a mixture of
an aliphatic monovalent alcohol and at least one other solvent component,
is easily deflected and exhibits a high particle stability. The ink in
accordance with the invention also contains at least one resin. Typical
aliphatic monovalent alcohols are methyl alcohol, ethyl alcohol, n-propyl
alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, tert-butyl
alcohol, isobutyl alcohol, n-amyl alcohol, amyl alcohol, isoamyl alcohol,
hexyl alcohol, heptyl alcohol, octyl alcohol, or a mixture of same.
Aliphatic monovalent alcohols with 1 to 8 carbon atoms are particularly
preferred. The weight ratio of aliphatic monovalent alcohol to other
solvents is preferably 1-99:99-1, especially 30-80:70-20, and particularly
40-80:60-20.
Solvents which form the mixture for these inks are ketones, aldehydes,
ethers, esters, hydrocarbons, glycol, glycol ethers and lactones.
Suitable solvents are hydrocarbons, such as hexane, heptane, octane,
decane, cyclopentane, cyclohexane, benzene, toluol, xylol, and
ethylbenzene; hydrocarbon halides, such as carbon tetrachloride, ethylene
dichloride, trichloroethylene, tetrachloroethane, and dichlorobenzene;
ether-type solvents, such as butyl ether, ethylene glycol-diethyl ether,
ethylene glycol-monoethyl ether, ethylene glycol-monobutyl ether;
ketone-type solvents, such as acetone, methylethyl ketone, methyl propyl
ketone, methyl isobutyl ketone, methylamyl ketone, cyclohexanone;
ester-type solvents, such as ethyl formate, methyl acetate, propyl
acetate, butyl acetate, phenyl acetate, ethylene glycol-monoethyl ether
acetate, methylpropionate; other alcohol solvents, such as diacetone
alcohol or such.
This invention relates to ink jet printing ink which has excellent adhesion
on various substrates. More particularly the invention relates to printing
ink which is an ink vehicle which comprises, as the essential component,
very high weight percent of resin or blend of resin dissolved in a blend
of solvents to give viscosity in range of 1.5 cps to 25 cps at 25.degree.
C. and which is compatible with fatty oils; and various oils, resins,
resinous varnishes, solvents, etc., conventionally used as printing ink
materials and further, if necessary, by milling with and dispersing
pigments, extenders and/or auxiliary agents in the resulting components.
A binding agent and additional additives, such as surface active agents can
be added to the ink. Suitable binding agents (vehicle) are dry oils, such
as linseed oil, tung oil, safflower oil, soya oil, dehydrated castor oil;
semidrying oils, such as cottonseed oil and beet oil; non-drying oils,
such as castor oil and olive oil, aliphatic acids and esters of same, such
as oleic acid, linoleic acid, pelargonic acid, caprinic acid,
ethyltrideanate and methyl laurate; dicarboxylic acid ester, such as
dimethyl phthalate, diethyl phthalate, dibutylphthalate, butylbenzene
phthalate, dioctylphthalate, dioctyladipate, dioctylsebacate,
dibutylsebacate, monomethyladipate and monoethylpimelate; polyvalent
alcohols, such as ethylene glycol, polyethylene glycol, diethylene glycol,
propylene glycol, glycerine, dipropylene glycol and esters and ethers of
the same, such as diethylene glycol monobutyl ether, dipropylene
glycolemonoethyl ester or such.
Liquid resins with a molecular weight under 2000 can also be used, for
example, polyester resins, epoxy resins and polybutadiene resins. The
essential characteristic feature of the ink in accordance with the
invention consists in a content of a mixture of an aliphatic monovalent
alcohol and at least one other solvent. Compared to commercial nonaqueous
ink, such an ink exhibits a considerably improved printing velocity. As a
result of the excellent electrostatic properties deflection is very easy
and the ink particles have an increased stability. The ink in accordance
with the invention is suited for jet printing devices and electrical field
type printers.
The invention is described in the following on the basis of exemplified
embodiments.
While there are disclosed below but a limited number of embodiments of the
invention herein presented, it is possible to produce still other
embodiments without departing from the inventive concepts herein
disclosed. Various other modifications will be readily apparent to those
skilled in the art.
EXAMPLE 1
______________________________________
Nitrocellulose 10.0
Methanol 75.0
Methyl ethyl ketone 50.0
MgCl.sub.2 2.0
Water 5.0
142.0
______________________________________
By using blushing it becomes practical to get opaque prints on dark
substrates without the use of pigments. Inks containing up to 40% solids
have been prepared.
EXAMPLE 2
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Nitrocellulose 35.0
Ethyl cellulose 5.0
Methyl ethyl ketone 20.0
Methanol 431.0
Ammonium formate 5.0
496.0
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By using blushing it becomes practical to get opaque prints on dark
substrates without the use of pigments. Inks containing up to 40% solids
have been prepared.
EXAMPLE 3
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Cellulose acetate butyrate
6.0
Methyl ethyl ketone 24.0
Methanol 58.0
Paratoluene sulphonic acid
2.0
90.0
______________________________________
By using blushing it becomes practical to get opaque prints on dark
substrates without the use of pigments. Inks containing up to 40% solids
have been prepared.
EXAMPLE 4
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Ethyl cellulose 8.5
Nitrocellulose 30.0
MgCl.sub.2 5.0
Methanol 431.5
Auramine base dye 5.0
480.0
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EXAMPLE 5
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Cellulose acetate butyrate
34.0
Acryloid B-66 6.4
Nitrocellulose
18/25 seconds 6.9
Methanol 300.0
Acetone 330.0
Methyl ethyl ketone 57.0
MgCl.sub.2 1.5
Distilled water 14.0
Yellow dye 0.2
750.0
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EXAMPLE 6
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Ethyl cellulose N7 20.0
Arofene 24780 50.0
Methyl ethyl ketone 130.0
Methanol 250.0
methyl Cellosolve 100.0
Auramine base 5.0
555.0
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Various resin and solvent combinations can be used to achieve opaque
prints. Solids can range as high as 75%. Color is obtained by using
various dyes. Drying rate is controlled by a combination of various
solvents.
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Description |
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