Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
' ~ 914,717
~96~9
I~PROV~D LATENT SEN~ITIZING INK
The present invention relates to the art of
sensitizin~ substrates with color generating components so
that the sensitized areas, or portions of the sensitized
areas, can be subsequently developed, i.e. rendered visible,
by contact with a color-activatin~ material. More
specifically, latent, sensitizing inks which can be applied
to selected areas of substrates by a varlety of conventional
printing methods are disclosed.
"Carbonless" papers and the art Gf applying
undeveloped, color-generating materials to substrates are
known. Previously, the application of these undeveloped or
latent color-generating materials involved the coating of the
complete surface of substrates usin~ aqueous coatin~
compositions and techniques~ These techniques do not lend
themselves to the application of the color-generating
materials in selected, patterned areas. Accordin~ly, in order
to provide a substrate having imaLing capabilities on only a
portion of the substrate, other techniques were developed
such as desensitizing a portion of the substrate by the
application of a desensitizing compound as disclosed in U.S.
Patent 3,809,668.
As the art of providing and developing latent
images has progressed, particularly in the area of
; paper-based feedback systems for educational uses, the need
for conveniently applying color-generating components in
selected areas on substrates such as paper has become more
acute. Vapor and pressure transfer techniques have been
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employed wherein a latent coreactant is applied to selected
areas of a paper sheet to provide a latent sensitized area
which can be subsequently developed by the applicatlon of a
second coreactant from a source such as a wax crayon applied
to the areas of the sheet containing the latent coreactant.
These systems are exemplified by U.S. Patents 3,784,394,
3,725,104, 3,682,673, and 3,617,324. Spirit dupllcation
techniques have also been employed to provide concealed
lmages for subsequent development as exemplified in U.S.
~-~ 10 Patents 3,451,143 and 3,632,364.
U.S. Patent 3,632,364 also discloses the
application of concealed images by lithographic, stencil,
letterpress, gravure, hand stamp, and silk screen techniques.
The disclosed method involves the application of a special
oxidlzing compound, capable of oxidizing an iodide to iodine,
to selected areas of a sheet which contains starch or
polyvlnyl alcohol. Subsequent application of an oxidizable
iodlde compound ln the areas ln whlch the oxldlzlng compound
has been applled to the substrate results ln a vlsible image
~; 20 belng formed.
While the prlor art vapor and pressure transfer and
splrlt dupllcatlng technlques have proven useful in providing ~-
small numbers of copies containing concealed images, a
satisfactory means of providing large quantities of such
copies by conventional printing methods using plain paper has
been sought. The aforementioned U.S. Patent 3,632,364
~' requlres a speclal iodide oxidation system in combination
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~6~9
--3--
with a prepared sheet containing starch or polyvinyl alcohol.
U.S. Patent 3,850,649 relates to printing a latent coreactant
capable of forming colored complexes with metals by
lithographic offset printing techniques. The coreactant is
carried in a special two-phase, quick-set ink vehicle
suitable for lithographic offset printing. U.S. Patents
3,540,909 through 3,540,914 also disclose "colorless"
printing inks containing a phenolic polymeric material
dissolved in a petroleum solvent. After spot printing, the
acidlc polymeric materlal can be contacted with a basic
chromogenic material to form a visible image. U.S. Patent
4,063,754 issued December 20, 1977, discloses compositions
and processes for providing solventless or "hot-melt" imaging
compositions.
15The present invention has overcome the
disabilitles of the prior art by providing latent,
sensitizing inks comprising, based on the weight of the total
ink compositlon, about 5 to 55% by welght vehlcle component
which ls a non-polymerlc, oleophlllc, organic, proton donor
acid anion having a cationlc counter ion, up to about 30% by
weight thinner and up to about 70% by weight particulate
flller and 20 to 30~ `by welght polymeric hydrocarbon,
thermoplastic, terpene resin. The ink also includes as one
~; of the above components, or as an additional component, at
least about 5% by weight of at least one color-generating
~; component. The ratio of filler to the vehicle component is
from about 0.1:1 to 6:1. The polymeric hydrocarbon
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thermoplastic terpene resins useful in the invention are
known, are commercially avallable under the trade name
"Piccolyte" Pennsylvania Industrial Chemical Corp.) and are
composed essentially of polymers of pinene, especially
beta-pinene. These polymeric terpene resins possess the
unique property, in the environment of the present invention,
to crack or "craze" on drying after application so that the
surface of the ink remains open and receptive to
color-forming coreactants. This effect is particularly
surprising in view of the tendency of conventional polymeric
ink vehicles, e.g., varnishes, to form films which seal the
surface of the film and inhibit color-forming reactions.
Thus, the addition of this unlque polymeric component
provides latent inks having improved imaging properties over
latent inks not having this component. When this polymeric
component is used it has been found that the level of filler
can be reduced significantly. Thus, in certain formulations
the ratio of filler to non-polymeric vehicle component can
now be reduced to levels of about 0.1:1, preferably about
;1 20 0.2:1, as the lower limit. Other ingredlents such as
additional tack and viscosity modifiers, antioxidants,
wetting agents, optlcal brlghteners and the llke can be added
as necessary.
The proton donor acld refers to the class of
proton donor compounds which donate protons to water
molecules in water solution.
As used herein, the term "color-generating
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component" refers to any of the materlals known in the
carbonless paper art which will become colored or effect the
visible coloring of a separate material when contacted with a
color-activating component. Thus, the combination of
materials is essential for color-formation. For purpose of
convenience herein the components in the latent, sensitizing
ink will be referred to as the color-generating component,
while the component which is subsequently used to develop the
color will be called the color-activating component, although
the actual components can be interchanged as will be
described hereinafter.
The vehicle components described above are
preferably the aliphatic, aromatic and allcyclic carboxylic
and sulfonic acids containing at least 6 carbon atoms and the
cation contalning salts of these acids. These vehicle
components have sufficiently oleophilic moieties to provide
acceptable inking qualities and promote rapid and intense
development of the sensitized areas when used in the
formulations of thls lnventlon. They are partlcularly
effective wlth the metal complexing color-generating/
- color-activating components such as the metal/dithiooxamide
(DT0)/polyhydrlc phenol combinatlons which require a
cosolvent reaction medium for rapid, lntense development of
the æensitlzed area. Exemplary of these vehicle components
are the rosin, stearic, oleic, 2-ethylhexoic, 2-phenyl-
butyrlc, benzolc, hydrocinnamlc aclds and dinonylnaphthalg~e
, ,,
sulfonlc acids as well as the corresponding cation salts of
,
,., ~
.
.`~6~9
these aclds.
The described vehicle components are generally olly
liqulds or crystalline or~amorphous waxy solids and when
dispersed or dissolved ln a thinner exhlblt the deslrable
blndlng and vlscoslty modifying characteristics of
conventional polymeric binders wlth respect to tack,
adheslon, and the likeJ whlch are essentlal to the
suitabillty of the inks for appllcation by conventional
printing methods.
As noted above the color-generating component can
be one of the recited lnk components or can be an addltlonal
dlstlnct component. For example, the color-generating
component can be the recited vehlcle component or the flller
or both. Alternatlvely the lnk can include a separate
transltlon metal salt as an addltlonal J dlstlnct
color-generatlng component.
In one embodiment, the vehlcle component ls a `
color-generatlng vehlcle component whlch 18 an oleophlllc,
; organlc proton donor acld anlon contalnlng at least 6 carbon
;~. 20 atoms and havlng a transltlon metal counter-lon. The
; "
'~ transition metal counter-ion forms a colored complex when
`~ contacted with a color-actlvatlng metal complexlng agent,
~ such as dlthiooxamide (DT0) and its derivatives and the
c~
.~ polyhydric phenols.
The oleophillc anlon molety alds ln provldlng good
" . .,
~ lnklng quallties and ln promoting the subsequent development
i: '
~X of the latent, sensltized lnk.
.. ..
.
.
In this embodiment the vehicle component also acts
as the color-generating component. Because of this dual
characteristic of the vehicle component, these inks are
particularly effective to provlde greater concentratlons of
available color-generatlng component per unit area of the
substrate to which the ink ls applied than is possible using
color-generatlng components carrled ln conventlonal
polymeric, film-forming vehicles. Thus, these inks can
provide latent sensitized areas which can be more quickly and
intensely developed by contact with color-activating
components than is possible by formulating inks having
color-generating components in conventional ink vehicles,
such as conventional lithographic inks containing varnish.
The transition metal counter ion of these color-
15 generating vehicle components is preferably selected from
among nickel, copper, lron and cobalt~ Generally nlckel and
;~ iron are preferred because of the dark color these matals
produce with conventional color-activating coreactants such
as DT0 and its derivatives or the polyhydric phenols.
20 Representative color-generating vehicle components which can
`~ be used in the present invention are the nickel, iron, and
copper derlvatlves of aliphatic, aromatic and alicyclic
carboxylic and sulfonic acids containing at least 6 carbon
; atoms and combinations thereof. Thus, nickel rosinate,
25 nickel calcium rosinate, nickel 2-ethylhexoate, nickel
stearate, nickel 2-phenylbutyrate, nickel oleate, nickel
benzoate, nickel hydroclnnamate, nickel dinonylnaphthalene
. . ~ _
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--8--
sulfonate, as well as the corresponding copper and iron salts
of the above compounds, and mixtures of two or more of the
above compounds are useful.
An essential ingredient of the latent, sensitizing
- 5 inks of the present in~ention is a particulate filler which
can be dispersed in the liquid ink vehicle. These fillers
are necessary to maintaln the sensitized area suitably
receptive to the color-activating material used to develop
the latent ink. These fillers can be any of the conventional
pigments and extenders whlch are known in the printing art.
The flllers can be chosen so as to be nearly transparent when
dispersed ln the ink vehicle or can be colored if desired.
Thus, when applled to a substrate, the latent, undeveloped
ink can be transparent so as to be invisible or can have a :~
color which closely matches or which contrasts with the
substrate to which the lnk is applled, depending upon the end
use of the sensltized substrates.
The flller must be chosen with some care dependlng
on the partlcular prlntlng method to be employed ln lts
, 20 application. Thus, for certaln prlntlng technlques, such as
wet offset prlntlng, a hydrophoblc filler should be used to
provlde superior results. Inks formulated in thls manner cani
also be used to advantage ln dry offset prlntlng. A slmple
emulsification test can be used to determlne whether the
fillers are suitably hydrophobic. This test can be performed
by grinding the pigment into the desired oil and mixing the
resulting dispersion with the desired aqueous offset fountain
,
61~
g
solution. After thoroughly mixing the pigment-oil combination
with the ~ountain solution, the fountain solution is decanted
and the remaining pigment-oil component weighed. If the
weight gain is more than 20Z by weight the pigment is
generally unsuitable for use in wet offset printing. For dry
offset printing, a relatively non-hydrophobic ~iller, such as
the colloidal silicas sold commercially under the trade ~ffle
Cab-O-Sil (Cabot Corporation) may be used if desired.
The ultimate particle size of the flller in the
final ink composition should be less than about 10 micro-
meters and preferably less than 5 micrometers in order to be
readily applied by conventional printing presses.
Representatlve flllers which can be used are fumed
alumina, alumlna hydrate, and trihydrate, powdered and fumed
anhydrous and particulate colloidal silica, such as the
s'~
commercially available "Aerosils" and "Cab-O-Sils" (available
from Degussa, Inc. and Cabot Corporation, respectively),
calcium and magnesium carbonate, barium sulfate, kaolin clay,
attapulgite clay, bentonite clay, zeolltes, zinc oxide,
- 20 ureaformaldehyde pigment, and the like.
The filler can comprise up to about 70~ by welght
,: ,.; .
of the lnk compoæitlon. The larger amounts of filler may be
;~l necessary on non-absorptlve, smooth papers, whereas lower
amounts of the fillers can be used where the paper readily
absorbs the lnk or has a rough surface whlch aids ln keeplng
the inked surface receptive to the coreactant. For most
applications, the flller preferably comprises up to about 25
.. - .. :. .. - .. ~. . ..
~1~96~9
--10--
percent by weight of the ink composition and most preferably
about 5 to 15 percent by weight of the composition.
Within the range of compositions disclosed above,
it has been found that the ratio of filler to the
aforementioned vehicle component is important. In order to
obtain the desired printing characteristics along with
superior imaging speed and image intensity when the
sensitized areas are contacted with a color-activating
component, the ratio of filler to vehicle component should be
from about 0.1:1 to about 6:1 and preferably about 0.2:1 to
; 1:1.
As stated previously, certaln of the filler
components can function as color-generating components. The
acldified clays, e.g., kaolin, attapulgite and bentonite
clays, and the natural and synthetic zeolites can be used to
provlde both the color-generating and filling functlon in the
~- ink compositlon slnce they possess the ablllty to provide an
~` intense color when contacted with the color-activatlng basic
chromogenic materials, i.e. the leuco dyes, which are well
known in the carbonless paper art. Generally when these
fillers are used as color-generating components the welght
percent of the flller should be about 15% by weight or
greater to obtain satisfactory color development in the
sensltized areas.
The thlnners which are used in combination with
the aforementioned vehicle components in the inks of the
present lnventlon are materials whlch are known in the
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printing art. These materials are solvents, diluents, and low
viscosity oils which are added to ink to reduce their
consistency and tack, thereby modifying the rheological
properties of the ink as required for use in a particular
printing method. Typical thinner materials are liquid
hydrocarbons, castor oils, dialkyl phthalates, trialkyl
phosphates such as tributyl phosphate, alkyl carboxylates,
low molecular weight alcohols, fatty alcohols, and the like.
The amount and type of thinner to be used in any particular
composition varies, depending primarily upon vehicle
component and the oil-receptive filler employed. A
sufficient amount of the thinner is incorporated into the
formulation to provide the proper viscosity and tack for the
particular prlnting method employed. Determination of ink
tack values as is conventional in the art can be used to
determine the proper amount of thinner to be added.
Generally up to about 30% by weight of thinner can be used.
Preferably the amount of thlnner is about 10 to about 25% by
:
; welght of the total lnk composltlon.
Although the use ln thls lnventlon of the
aforementloned vehicle components ln combination wlth
thlnners ellmlnates the need for conventlonal varnishes in
` order to obtain satlsfactory lnklng propertles, varnlshes can
be used ln the formulatlons if deslred to modlfy further the
tack, vlscosity and other rheologlcal properties where these
properties are difficult to obtaln with normal comblnatlons
of the vehicle component and thinner. Useful varnishes are
.
~1~96~9
-12-
the drying oils and other naturally occurring and synthetic
polymers known in the art such as the phenolics, linseed
oils, alkyds, and modified alkyds, nitrocellulose, tung oil,
cellulose acetate, ethyl cellulose, and the like. Up to
about 40% by weight of varnish, based on the weight of the
total ink composition, may be used. Preferably the varnish
comprises less than about 10% by weight of the ink
compositlon since these varnishes tend to inhibit subsequent
; development of the latent inks due to thelr fllm-formlng
propertles.
Agents whlch lnhlblt the effect of oxygen on the
components of the ink, i.e. antioxidants, can also be added
to stabllize the ink components and the sensitlzed areas
a~ter development. Useful antioxidants are well known in the
prlnting ink art, and any of the known antioxidants which do
not react with the color-generating component can be used.
If an antioxidant which reacts with the color-generating
component is used, the ink may be undesirably "desensitized"
or a colored reaction product may be formed which causes
undeslrable coloring of the sensitlzed area.
Exemplary of the antioxldants which can be used
are thlourea, hydroquinone, hindered phenols such as
alkylated hydroxytoluene, and the like. Preferably the
antioxidant comprlses less than 10% by welght and most
preferably less than about 2.5% by welght of the total lnk
compositlon.
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6~9
Other conventional ink additives can be added to
the ink formulation if desired, such as lubricants, optical
brighteners, dyes, waxes, buffers, wetting agents and
odorants and the like, to improve the application,
performance and aesthetic qualities of the ink. Generally
these additives comprise less than about 2% by weight of the
ink composition and most preferably comprise less than about
0.5% by weight of the total ink composition.
When the filler is, or contains, one of the
aforementloned acldified clays or zeolites, the filler itself
can be a color-generating component in lieu of or in addition
to a color-generating vehicle component. If both the vehicle
and filler contain a color-generating component, the latent,
sensitizing ink may be developed by a plurality of distinct
color-activating components.
In addition to or in lieu of the above-noted
~, color-generatlng components, an additlonal color-generatlng
component or mixture of color-generating components can be
~; incorporated lnto the ink formulatlon. Thus, the lnk
; 20 formulatlon can comprlse a transltlon metal salt such as the
nltrates, sulfates or hallde of the transltlon metals, DTO
or DTO derivatives, the polyhydrlc phenols or the leuco dyes
all o~ which are known in the art as color-generating/
color-activatlng components.
If more than one color-generatlng component is
used in the lnk formulatlon, care must be taken to see that
the components do not prematurely react with each other.
0
. - ., - ~ ., . .: .~ .
:. .. , . . . .: ~ ,
: . .. ., . ., , .. : . : :.. , ~ ,.... . -
6~ 9
-14-
Thus generally a transltion metal salt and a DT0 derlvative
would not be incorporated in the same formulation. Simllarly
an acidi~ied clay and a leuco dye would not be combined.
Typically, the ink may contain a transition metal ion and an
acidified clay so that the ink can be developed by either a
DT0 or other metal complexing compound or by a leuco dye or
both.
As noted previously, the inks can contain
ingredients, such as varnish, to modlfy further the tack,
viscosity and other rheological properties of the ink.
Additional cnventional lngredlents such as antioxidants,
lubricants, optical brighteners, dyes, waxes, buffers,
wetting agents, odorants and the like can be added as
necessary and generally comprise in total less than about 10%
~-~ 15 by weight of the total composition. For example, the ink may
:.,
requlre up to about 7% by weight antloxldant. However, the
amount is generally about 2.5% by weight or less, with the
remaining additives ranging up to about 2% by weight and
preferably less than about 0.5% by welght.
A preferred improved lnk formulatlon would comprise
about 5 to 55%, and preferably about 30 to 45% by weight
vehicle component which is a non-polymeric, oleophillc,
organic acld anion havlng a catlonic counter ion, such as
nlckel-2-ethylhexoate, 20 to 30% by weight polymeric,
hydrocarbon thermoplastic terpene resin, e.g. Piccolyte
resin, about 5 to 15% by weight particulate filler, up to
about 30Z by weight thinner, and about 1% by weight
- .
" - -,
.~
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-, . ~
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9~ 9
-15-
antioxidant.
The inks of the present invention can be prepared
using conventional ink milling equipment. Generally the ink
is prepared by admixing all of the ingredients and blending
to form a homogeneous mixture of working consistency suitable
for an ink mill. In some cases the amount of particulate
filler may be such that only a portion of the flller can be
added before the ink is milled. The admixture is then run
through an ink mill such as a three-roll ink mill or other
~ 10 conventional ink mill until a homogeneous tacky-viscous fluid
`: i8 formed. Any remaining filler is then added and the
mixture further milled to form a homogeneous dispersion. The
particle size in the final mixture should be about 10
micrometers, or less, for ease of application by conventional
printing methods. Other liquid ingredients as previously
noted can be added to the milled ink to ad~ust the tack,
viscosity and other rheological properties of the ink as
required.
- The inks of this invention can be applied to
selected areas of substrates such as paper by conventional
printing techniques, including lithography, flexography,
letterpress, dry offset, rubber plate, intaglio, silk screen,
rotogravure, and the like. Applylng these ink compositions
wlth conventlonal printing equipment makes it practical to
pattern or spot coat substrates, and thus, selectively
sensitlze paper or other substrates for business forms
appllcatlons where there is a desire to have an lmage appear
... . . ,, ", ., .. - .. , :. , ,, ... ,~ : - .
-16- ~ `9
only on certain portions of a form or on certaln sheets of a
multi-sheet form, such as invoice and purchase order forms
where price or cost information is needed only on certain
sheets of the multi-sheet form.
; 5 The sensitized areas of the substrates can then be
developed by contacting the sensitlzed area, or a portion of
the area, with a color-activating component. Typically, the
color-activating component is contained as an encapsulated
component on a sheet of paper, e.g., a CB (coated back)
sheet, so that when the CB sheet is placed in contact with
; the sensitized sheet and the capsules ruptured, as by writing
or typing on the obverse surface of the CB sheet, the
color-activatlng component contacts the sensitized area, or a
portlon thereof, containing the color-generating component
and a visible image is formed.
Alternatively, the sensitized areas can be
contacted with a crayon, or developing solution contalned in
a marklng pen, which contalns a color-actlvating component
and the sensitized area vlslbly developed.
Buslness forms whlch are multi-sheet forms can
comprlse one or more CB sheets overlylng and in register with
one or more sensitized CF (coated front) sheets. Thus a
multi-sheet form may have a CB sheet as the top sheet
overlying one or more sheets in register which are CB sheets
havlng at least a part of the obverse surface sensltlzed.
Writlng or typing on the obverse surface of the top sheet
causes llke lnformatlon to be recorded in the obverse
l~g6~9
-17-
sensitized portions of the underlying sheets which are in
register with the written or typed information entered on the
; top sheet of the multi-sheet form.
.
In addition to the latent, sensitizing ink applied
to the surface of the sheets, conventional printing can be
; applied to the sheets in the sensitized or unsensitized areas
to provide forms for business entries, paper based feedback
systems for educational use and the like.
The following examples further illustrate the
.~ 10 present invention. In these Examples, all parts and percents
are by welght, unless otherwise lndicated.
~"' -
~ 15
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~ , . . , , - .. . : . , .:-, . ,. .: - . , . , -
-18~ S6~g
..-3
Example 1
An lnk for sensitizing selected areas of paper with r
a latent coreactant was prepared having the following
formulation: -
Weight %
- 5 Nickel-2-ethylhexoate 38.5
Hydrophobic silic~a filler 11.5
(Aerosll R-972, Degussa, Inc.)
Polymeric terpene resin 25.4
(Piccolyte S-135~
Butylated hydroxy toluene 1.0
(antloxidant)
10 Hydrocarbon Oil (Magie Oil #520) 23.6
The nickel-2-ethylhexoate, terpene resin and antioxidant
were dlssolved in the hydrocarbon oil. The filler was then
dispersed in the solution and the final dispersion milled
on a three-roll ink mill to a particle size of about 3
micrometers or less.
The ink was applied to 16 lb. bond paper by a hand
roller in sele¢ted areas of the sheet. After drylng at
room temperature, the sensltized sheets were developed by
placlng a sheet coated wlth an encapsulated dlthlooxamlde
derivatlve ("3M" Brand Carbonless Paper, Type 200 CB
[coated back] sheet) so that the capsule coating and the
inked surfaces were ln direct contact. The sheets were run
through a steel pressure roll to develop uniformly a 1.2 cm
wlde strlp of the sensitlzed sheet. The developed area had
an acceptable blue-purple color as determined by optical
denslty measurements.
96
-19-
:
Sensitied sheets were also developed by placing
~ a sheet coated with an encapsulated dlthiooxamide
;~ derivative (CB sheet described above) so that the capsule
coating and the inked surfaces were in direct contact.
Images were produced on the sensltized sheet by writing on
the obverse surface of the CB sheet with a ball-point pen
:,.
~ using normal hand pressure. Similarly, typing on the
,~ obverse surface o~ the CB sheet produced an image on the
sensitized sheet. In both cases image formation was very
rapid.
Example 2
An lnk for sensitizing selected area~ of paper
wlth a latent coreactant and particularly adapted for
- application by a dry o~fset press was prepared having the
1~ formulation shown ln Example 1 except that a non-hydro-
phoblc slllca filler tCab-O-Sll M-5) was substltuted for
the Aerosll R-972 ~iller. This composltion was satls-
factorlly prlnted on a dry offset press and was
satisfactorily developed by a CB sheet as in Example 1.
)~ c?~`2 ,l~
. :,.,. ` ! ' ' . ;,~
