Note: Descriptions are shown in the official language in which they were submitted.
8 Field of the Invention
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9 The present invention is concerned with a ribbon for use
in non-impact printing. In particular, it is concerned with
11 the transfer coating for such a ribbon. Printing is achieved
12 by transferring the transfer coating from a ribbon to paper
13 by means of local heating of the ribbon. Such localized
14 heating may be obtained, for example, by contacting the ribbon
with point electrodes and a broad area contact electrode.
16 The high current densities in the neighborhood of the point
17 electrodes during an applied voltage pulse produce intense
18 local heating which causes transfer of transfer coating from
19 the ribbon to a paper in contact with the ribbon.
Prior Art
21 U. S. Patents 2,713,822 and 3,744,611 both describe non-
22 impact printing processes employing a ribbon containing a
23 transfer coating and a substrate. In the prior ~rt the
24 transfer coating has been a mixture of carbon, dye and
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waxes which melt at from about 85 to about 90C. Such
- 26 transfer coatings-have poor rub resistance. It is an object
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27 of the present invention to provide a transfer coating for
28 non-impact printing which is rub resistant.
29 ~ Summary of the Invention
;30~ A ribbon formulation for use~in~non-impact printing has
- 31 ~ been provided.~;The formulation is rub ~esistant and offers
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1 high resolution, dense printing. The transfer coating
2 comprises coloring material, for example, carbon black, one
3 or more dyes, or both, and a thermoplastic polymeric resin
4 having a melting point between 40C and 160~C. It is also
essential that the Ihermoplastic polymeric resin be soluble
6 in a solvent which does not attack the substrate.
7 Outstandingly good results have been obtained using
8 thermoplastic polymeric resins which are polyamides. Examples
g of such polyamides are Versamid~polyamids produced by General
Mills, Inc. Versamid~polyamides are the reaction products
11 of dibasic acids with diamines. They are based on polymerized
12 fatty acids or dimer acids, made by polymerizing unsaturated
13 fatty acids. These materials are well known to the art and
14 are discussed, for example, in the "Handbook of Adhesives,"
by Skeist, publlshed by Reinhold Publishing Corporation, New
16 York, New Yor~, 1962, beginning at pa~e 425.
17 - Other useful thermoplastic polymeric resins include
18 phenol-formaldehyde type resins such as Amberol~226 and
19 Amberol~ST137 from Rohm & Haas. Also useful thermoplastic
; o polymeric resins are ethylene-vinyl acetate copolymers such
21 as Elvax~from duPont.
22 Other thermoplastic polymeric resins include ætyrene
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23 polymers and copolymers and blends thereof. For example, a
24 blend comprising 65% polystyrene and 35% n-butylmethacrylate.
Polystyrene may also be blended with other polymers, for
~26 example, coumerone-indene resin. Thermoplastic polymeric resins
27 are also made from polyols by forming rosin esters thereof.
28 It is necessary that the thermoplastic polymeric resin
29 used in the transfer medium be soluble in a solvent which
does not harm the substrate of the ribbon. The preferred
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1 subs-trate is a polycarbonate resin containing conductive
2 carbon particles. As examples of solvents which do not
3 attack the substrate, and in which the thermoplastic
4 polymeric resins are soluble, there may be mentioned alcohols,
particularly n-propanol or isopropanol, and also mixtures
6 of one or more alcohol with water. Toluene is also a useful
7 solvent. By the use of such solvents, the transfer media
8 may be applied directly to the ribbon substrate during the
g manufacturin~ process.
Tt is necessary that the transfer coating contain a
11 coloring material. Carbon blaek is generally preferred.
12 When desired, in addition to the earbon blaek, one or more
13 dyes may also be ineorporated. In general, about 30~ by-weight
14 of earbon blaek and about 3% by weight of dye will be ineor-
porated in the transfer eoating.
16 The ribbons obtained aecording to the present invention
17 have excellent handling eharaeteristics. No transfer oeeurs
18 from the ribbon to the hands. When used in non-impaet
19 printing, the eoating transfers at energies equal to or less
than that required for wax-based inks. Furthermore, transfer
21 does not oeeur upon impaet.
22 The partieular most desirable feature of printing done
23 by a non-impaet process using a ribbon of the present invention
24 eontaining a suitable thermoplastie polymerie resin is that
the printing is both dry and wet rub resistant and offers
26 high resolution and exeellent appearanee.
27 The following examples are given solely for purposes of
28 illustration and are not to be eonsidered ]imitations on the
29 invention, many variations of whieh are possible without
departing from the spirit or seope thereof.
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1 EXAMPLE 1
2 19.2 gms of a polyamide (General Mills Versamid 950)
3 was dissolved in 89 gms of propyl alcohol. Added to the
4 solution was 2.84 gms of carbon (Degussa~Special Black 4)
and 0.28 gms of ~ethyl Violet dye. The mixture was then
6 dispersed by vigorous stirring for 45 minutes.
7 The dispersion was then cast onto a substrate of 70
8 polycarbonate and 30% conductive carbon, said substrate
9 having a sheet resistivity of approximately 400 ohms/sq.
The thermoplastic polymeric resin transfer coating was then
11 dried to remove excess solvent. Dry thickness o~ the ink
12 layer was 5 microns.
13 The ribbon was mounted on a print rohot with the ink
14 surface against the paper. A print head consisting of two mil
tungsten electrodes was engaged against the backside of the
16 ribbon. The printer was operated at a speed of 10 inches/sec.
17 and power of 35 volts, 80 milliamps, and at a pulse duration
18 of one millisecond. On removal from the robot a dense black,
~19 high resolution print on paper was observed~ The print was
2C ~ resistant to mechanical abrasion, both wet and dry.
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22 EXAMPLE 2
23~ The same ribbon configuration as described in Example 1
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24 ~was placed on the robot and operated at 10 inches/sec. without
~ ~ the use of electrical current. Qn removal no print was
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26 ~ observed. Thi~ experiment showed the ribbon to be impact
27 ~ resistant, and also showed that print could be obtained only
28 through the use of current causing the thermoplastic po~ymeric
29~; resin t~ansfer~coating to melt and adhere to paper or another
image receiver.
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1 EXAMPLE 3
2 A transfer coating was prepared in the same manner as
3 Example 1. The dispersion was then cast onto a substrate
4 such as described in Example 1 except that an intermediate
:Layer of 1000 A of evaporated aluminum had been deposited on
6 the substrate, offering a highly conductive ground plane.
7 The ribbon was then mounted on the robot and printed at
8 a speed of 10 inches/sec. With this configuration, print
9 energies of 13 volts and 60 milliamps were sufficient to
obtain a black, rub resistant print on paper.
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12 EXAMPLE 4
13 A transfer coating was prepared in the same manner as
14 Example 1 except the carbon was replaced with a color pigment,
Litho Red. The transfer coating was coated onto a substrate
16 described in Example 1. When printed on the robot, a red,
17 rub resistant print was observed.
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19 ~; EXAMPLE 5
20 ~ A ribbon was prepared in the same manner described in
;2~ Example 1 except the carbon was replaced with a colored pigment
22 known as Victoria Blue. When printed, a blue rub resistant
23~ ~ ima~e was observed.
25~ EXAMPLE 6
26~ A~ribbon~was~prepared in the same manner described in
27 ~ Example 1 except the carbon was replaced with a colored pigment
28~ known`as Elgin;Green.~ When printed, a ~reen rub resistant
29 ~ image was obseFved.
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1 EXAMPLE 7
2 A ribbon was prepared in the same manner described in
3 Example 1 except the Versamid resin was replaced with the
4 thermoplastic polymeric resin known as Amberol ST137, which
is a phenol-formaldehyde from Rohm and Haas, and which has a
6 melt range of 60-70C. Upon printing, a black, rub resistant
7 image was observed.
9 EXAMPLE 8
A ribbon was prepared in the same manner as described
11 in Example 1 except the Versamid was replaced with the
12 thermoplastic polymeric resin known as Elvax, which is
13 copolymer of ethylene and vinyl acetate with a softening
14 point of 130C and whieh is available from duPont. Addi-
tionally, the transfer eoating was coated out of toluene
16 rather than alcohols. Upon printing, a black, rub resistant
17 image was observed.
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