Stock material or miscellaneous articles – Structurally defined web or sheet – Discontinuous or differential coating – impregnation or bond
Reexamination Certificate
1999-07-23
2002-07-16
Hess, Bruce H. (Department: 1774)
Stock material or miscellaneous articles
Structurally defined web or sheet
Discontinuous or differential coating, impregnation or bond
C428S212000, C428S478200
Reexamination Certificate
active
06420016
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to recording sheets suitable for use in an ink jet printing process, where inks consisting of at least one dye and an ink liquid are used, and to coating compositions for the preparation of ink receiving layers for this process. It relates especially to recording sheets where the image recorded thereon can be observed by both reflected or transmitted light and where the ink receiving system consists of a support onto which are coated at least two layers.
BACKGROUND OF THE INVENTION
In the ink jet printing process droplets of a recording liquid (ink) are placed on the surface of a recording sheet using different methods. Ink jet printing processes are of two types: continuous stream and drop-on-demand.
In continuous stream ink jet printing systems, ink is emitted in a continuous stream under pressure through a nozzle. The stream disintegrates at a certain distance from the nozzle, due to the effect of surface tension, into individual, microscopically small droplets. The individual droplets are charged electrically and deflected in an electric field according to digital data signals in order to direct them to a specific location on a recording medium or a gutter for recirculation.
In the non-continuous process, or the so called “drop-on-demand” systems, an image signal induces a droplet to be expelled from the nozzle. At present the thermal process (thermal jet or bubble jet) is mostly used. In this process the image signal activates a heating element, a vapor bubble is formed in the aqueous ink that ejects the droplet from the nozzle. Most recently the piezoelectric effect is used again which ejects the droplets mechanically from the nozzle.
Available recording sheets for ink jet printing do not meet all the necessary requirements asked for today. There is a need to further improve their ink absorbency, ink absorption rate, drying speed, image quality as well as their light and water fastness.
Recording sheets for ink jet printing, particularly the so called “photo feel” materials, must meet a number of stringent demands. “Photo feel” means that such an image, printed in an ink jet printing process, feels like a photographic silver halide material when touched. The printed image has to fulfill the following properties:
High resolution
High color density
Good color reproduction
High resistance to rubbing
Good water fastness
“Photo feel”
High light stability
No tackiness
The following conditions have to be met to attain these goals:
1. The ink needs to be absorbed quickly into the recording sheet to attain short drying times.
2. The jetted ink droplets have to spread circularly on the recording sheet and have to form well defined edges.
3. Dye diffusion in the recording sheet has to be low so that the diameter of the color points is not increased more than necessary.
4. An ink droplet is not allowed to interfere with a droplet deposited earlier nor should it blur it.
5. The recording sheet needs to have a surface that gives high color density and brilliance and shows “photo feel”.
6. The recording sheet has to show excellent physical properties before and after printing.
These requirements are partly in contradiction to each other. For example a very rapid ink absorption rate may reduce the resistance to rubbing. A “photo feel” surface may show the problem that printed images stick to overhead transparency protectors. In the case of wet sticking a liquid film consisting of ink components is formed between the surface of the image and the overhead transparency protector. This leads to blots, dye transfer to the foil of the overhead transparency protector and in extreme cases even to a separation of the coated layers from the support when the recording sheet is removed from the overhead transparency protector. In the case of dry sticking, which is relevant only in the absence of wet sticking, adhesion between the image and the overhead transparency protector is increased, leading to a whispering noise during separation of the recording sheet from the overhead transparency protector and layer damages.
The steadily increasing performance of ink jet printers resulting in ever higher recording speeds makes it even more difficult to attain these requirements.
Starting with these requirements for receiving sheets for ink jet printing ways are sought that should result in images showing high color densities combined with high resistance to rubbing at the surface, short drying times and “photo feel” without sticking problems in overhead transparency protectors.
Recording sheets having the “photo feel” property normally consist of a support that can not absorb liquids, as for example polyester films or polyethylene coated papers. This, however, leads to long drying times.
To achieve rapid drying the ink liquid has to be drained away quickly from the surface of the recording sheets and it has to be fixed below the surface of the receiving sheet.
Accordingly an object of the present invention is to provide recording sheets for ink jet printing which show high gloss, “photo feel” without sticking to overhead transparency protectors and short drying times for the ink liquids as well as high color densities and high resolution.
SUMMARY OF THE INVENTION
The invention proposes to achieve these objectives by providing a recording sheet for ink jet printing comprising a support, onto which are coated, in addition to optional auxiliary layers, at least one gelatin containing absorption layer for the fixation of the ink liquid and on top of the absorption layer one or more ink receiving layers, characterized in that the gelatin containing absorption layer comprises micelle forming compounds in a quantity from 10% by weight to 50% by weight relative to gelatin.
The invention is directed towards recording sheets that may be used in both recording processes.
An objective of the invention is to provide recording sheets for ink jet printing showing high ink absorbency, high ink absorption rate, excellent image quality, short drying times and “photo feel”.
A further objective of the invention is the preparation of recording sheets for ink jet printing with the property that the printed sheets do not stick together even under conditions of high humidity, that they may be stored in overhead transparency protectors without wet or dry sticking and that the image quality does not deteriorate even after long periods of storage.
A preferred embodiment of the invention relates to recording sheets for ink jet printing showing excellent image quality, high ink absorbency and short drying times. In particular recording sheets for ink jet printing with “photo feel” are looked for where the printed images show high resistance to rubbing at the surface and where the images are not altered or destroyed even under the influence of water or light.
The invention is explained in detail in the following description.
DETAILED DESCRIPTION OF THE INVENTION
The invention describes recording sheets for ink jet printing comprising a support, onto which are coated, in addition to optional auxiliary layers, at least one gelatin containing absorption layer for the fixation of the ink liquid and on top of the absorption layer one or more ink receiving layers, characterized in that the gelatin containing absorption layer comprises micelle forming compounds.
Salts of branched or unbranched alkyl sulfates of formula C
n
H
2n+1
OSO
3
H, wherein n is from 5 to 25;
salts of branched or unbranched alkyl phosphates of formula C
n
H
2n+1
OPO
3
H
2
, wherein n is from 5 to 25;
substituted phenols of general formula (I)
wherein n is from 18 to 50;
or salts of substituted phenols of general formula (II)
wherein n is from 5 to 55;
are used as micelle forming compounds.
Preferred are salts of unbranched alkyl sulfates of formula C
n
H
2n+1
OSO
3
H, wherein n is from 8 to 16, as well as salts of unbranched alkyl phosphates of formula C
n
H
2n+1
OPO
3
H
2
, wherein n is from 8 to 20.
Especially preferred is the alkyl sulfate of formula C
12
H
25
OSO
3
−
M
+
, wh
Peternell Karl
Steiger Rolf
Grendzynski Michael E.
Hess Bruce H.
Ilford Imaging Switzerland GmbH
Onofrio Law
Onofrio, Esq. Dara L.
LandOfFree
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