Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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INK-JET PRINTER
2 FIELD OF THE INVENTION
3 The present invention relates generally to printing
4 apparatus and more particularly to ink-jet printing
apparatus.
6 BACXG~OUND OF THE INVENTION
7 Ink- jet and bubble- jet printers are kno~n in the art .
8 In such printers, droplets of hot wax-based lnk or ink in a
. 9 water-based solvent are e jected in image ror~ing
configuration from a print-head onto a sheet of paper or
11 other substrate. The substrate may be heated so as to f ix
12 the image on the su~strate by evaporation of the water
13 solvent or melting of the waxy ink. However, the images
14 formed by such printers are often blurred somewhat, as a
L5 result of the "wicking'l of the ink into the paper, due to
16 flow of the water-based solvent or melted waxy ink.
17 Attempts to correct thls proble~ by increasing the
18 viscosity of the ink have not been particularly successful,
19 since the ink-jet process does not work well with viscous
ink.
21 Japanese Patent publicatioll 1 1467S0 describes an ink-
2~ jet system in which W curable ink is applied to a glass
23 drum utilizing an ink droplet method. The ink is cured
24 using W light before it is transferred to a final
su~strate.
26: SUM~ARY OF THE INVENTION
27~ It is the object of the present invention to pro~ide
8 ink-jet printing apparatus which produces a sharp and
29 un~lurred image on a substrate such as paper using
conventional water-based or waxy in~. It is a further
31 object of the present inventi.on to provide multi-color ink-
32 jqt printing apparatus in which very precise registration
33 of th~ color images is obtained. The present invention
34 accomplishes these objects by in~erposing an intermediate
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3S member between the ink-jet head and the substrate, such
36 that the functions of image-formation and image-transfer
37 are separated into two distinct stages.
38 In the first stage, the ink-jet printing head is
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PBI S05
1 operated in the conventional manner to form the desired
2 image, but instead of the image being formed directly on
3 the substrate, it is ~ormed on the surface of the
a intermediate member. In the second stage, the image is
transferred from the surface of the intermediate member to
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W093/07000 - 2 - PCT/NL91/001gO
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1 the desired final substrate. Interposing the in~ermedl~te
2 member affords ~he possibility of using conventional water-
3 ~ased, non-viscous inks for the initial image formation,
4 and then evaporating a desired amount of the water solvent
while the image is still on the intermediate member, prior
6 to final transfer to the substrate. Heating the water-based
7 and waxy inks allows for good transfer with~ut excessive
8 heating of the substrate, reducing power 'requirements of
9 the sy~tem.
Interposing the intermediat~ member also affords the
11 possibility of applying resins or binders onto the image
12 prior to final transfer, thereby enhancing the fixing of
13 the ink image and its adhesion to the substrate.
14 BRI:E~F DE8CRIPI'ION C)F ~IE DR~WI~
The present invention will be better understood and
16 appreciated from the following detailed description taken
17 in conjunction with the accompanying drawings in which:
18 Fig. 1 is a schematic representation of ink-jet
19 printing apparatus in accordance with an embodiment of the
invention.
21 Fig. 2 is a schematic representation of ink-jet
22 printing apparatus in accordance with another embodiment of
23 the inYention.
24 D~TAI~ED DESCRIPTION OF PREFERRED ENBODINENT~
Reference is now made to Fig~ 1 which provides a
26 schematic representation of ink-j~t printing apparatus in
27 accordance with ~n embodiment of the present invention.
28 Included in the apparatus of Fig. 1 ~s an electronic
29 imaging control assembly 8 which comprises ~ microprocessor
and other standard user operatad hardware and software as
31 are known in the art. Con~rol assembly B is connected to an
32 ink-jet assembly 10 which includes an ink-jet printing
33 head, li~uid ink and other ink-jet apparatus as are known
34 in the art. Slightly spaced from ink-jet assembly 10 is a
drum 12 having a surface 14 which may be rigid but which
36 preferably is comprised of a resilient polymeric material.
37 Surface 14 is preferably coated with a non-sticking layer,
38 such as silicone, silicone rubber or teflon which is
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l abhesive to the ink.
2 When the apparatus is in operation, drum l2 rotates in
3 the direction of arrow ~3, and control assembly 8 is
~ operative to provide appropriate control commands to ink-
jet assembly lO so as to caus~ ink-3et assembly lO to eject
6 droplets of ink in the direction of ~urface l4 such that
7 the drops of înk adhere to ~urface 14 in ~ desired image
8 configura ion. In accordance with a preferred embodiment of
9 the invention, surface 14 may be heated by means of an
internal heater 16, or by means of a blower (not shown)~
ll Heater 16 is operative to evaporate a substantial portion
12 of the liquid carrier of the ink in ~olvent based inks, so
13 as to prevent '~wicking" of the image when it is transferred
l4 to the final substrate, as described below.
After the ink image has been deposited on surface 14,
16 drum 12 continues to rotate and the surface bearing the ink
17 image is brou~ht into contact with a final substrate 18,
18 such as a web or a sheet of paper, which is fed into a nip
l9 l9 between drum 12 and an impression roller 20. If surface
l4 is slightly resilient, i~pxession roller 20 i5
21 preferably rigid. However, if surface l4 is solid,
22 impression roller 20 should have a slightly resilient
23 surface. It will ~e appreciated that as a re~ult of the
24 application of pressure at nip lg between the two surfaces,
the ink image is transferred to final substrate 18 from the
~6 non-stic~ surf~ce l4 as the sub~rate is fed through the
27 nip.
28 The inventor has discovered that the specific
29 configuration of ink-jet printing apparatus described above
produces an im~ge on the final substrate superior to that
31 produced by the conventional ink~jet apparatus known in the
32 art. Because the ink image is first produced on surface 14
33 of drum 12 and only then transferred to the final
34 substratel the ink-~et apparatus of the present invention
effectively prevents "wicking" of the solvent based liquid
36 ink when the image is transferred to the final substrate.
37 Heating of surface l4 causes a substantial portion of the
3% liquid solvent to be evaporated prior to final transfer,
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l such that a very clean, concentrated image is transferred.
2 As a conse~uence, it is also unnecessary to heat the final
3 substrate so as to ~ix and dry the image after transfer
4 thereto.
It will also be appreciated that the apparatus of the
6 present inven~ion af~ords not only single color printing of
7 images but al~o multi~color printing of images. For multi
8 color image printing, ink-jet assembly lO~includes several
9 ink-jet sub-ascemblies, one for each of the process colors
as is known in the art, and each such sub-assembly is
11 connected to control assembly ~. As drum l2 rotates, each
12 of the sub assemblies is operative to deposit an image of a
13 single color on surface 14. The use of drum 12 as an
14 intermediate member facilitates a much more precise
registration of the colored images than direct printing on
16 paper, thereby providing a significantly sharper color
17 image on the final substrate.
18 Reference is now made to Fig. 2 which shows ink-jet
l9 printing apparatus in accordance with another embodiment of
the present invention. The apparatus of Fig. 2 is similar
2l to that of Fig. l except t~at upstream of ink-jet assembly
22 lO there is provided a squeegee roller 24 which engages
23 surface l4 of drum 12. In a spacP 26, between squeegee
24 roller 24 and drum 12, is a quantity of a binder resin,
preferably a polymeric binder with or without solvent. The
26 binder resin in space 26 is rep~enished by a dispenser
27 assembly 28. S~ueegee roller 24 rotates in the direction
28 opposite that of drum 12~ as shown by arrow 25, and is
29 operative to cause a controlled thin layer of the binder
resin to ~e coated on surface 14 prior to the deposition of
31 the ink image thereon by ink-jet assembly lO~ The binder
32 resin acts to improve the fixing of the ink image when the
33 image is transferred to the final substrate. In a prefsrred
34 embodiment of the invention, the polymer binder is chosen
to be reactive either with the ink dye and/or with the
36 final substrate so as to improve the adhesion of the image
37 to the substrate and to protect the image. In an
38 alternative embodiment, squeegee roller 24 may be replaced
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l by ~ squeegee blade or other coating pparatus.
2 A large number of material:~ are; uaeS~ul as polymer
3 binders in the present invention, the choice being made on
4 the basis of ~he characteristics of the ink~ the ~ubstrate
and the transfer member. Examples of suitable materials are
6 marketed by Monsanto under the trade name Scripset.
7 It will ~e appreciated that the present invention is
8 not limited by the embodiments descri~ed above in
9 conjunction with the drawings. Rather, the invention is
limited only by the claims which fo~low:
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