Stock material or miscellaneous articles – Structurally defined web or sheet – Discontinuous or differential coating – impregnation or bond
Reexamination Certificate
2001-10-10
2003-07-08
Kelly, Cynthia H. (Department: 1774)
Stock material or miscellaneous articles
Structurally defined web or sheet
Discontinuous or differential coating, impregnation or bond
C428S328000, C428S331000, C428S480000, C428S500000, C428S524000, C428S537500
Reexamination Certificate
active
06589637
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to new stabilizers for recording sheets used in ink jet printing, containing porous inorganic oxides.
BACKGROUND OF THE INVENTION
Ink jet printing processes are mainly 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 breaks up into droplets at a certain distance from the nozzle. If a specific location on the recording sheet has to be printed the individual droplets are directed to the recording sheet, otherwise they are directed to a gutter. This is done for example by charging unnecessary droplets in accordance with digital data signals and passing them through an electric static field which adjusts the trajectory of these droplets in order to direct them to the gutter. The inverse procedure may also be used wherein uncharged droplets are directed to the gutter.
In the non-continuous process, or the so-called “drop-on-demand” systems, a droplet is generated in accordance with digital data signals only if it is to be placed onto the recording sheet.
The printing speed of modern ink jet printers is always increasing for economical reasons. Recording sheets that are suitable for these printers therefore need to absorb the inks very quickly. Especially suitable are recording sheets containing porous inorganic oxides.
Such recording sheets available today do not meet all of the required demands. In particular, the storage stability of images printed on these recording sheets has to be improved. These images are not particularly stable when they are in contact with ambient air, which normally contains sulfur dioxide and, especially in summer, photochemically generated impurities such as ozone or nitrogen oxides. The images are strongly altered or even destroyed in a short time when they are in contact with ambient air. These phenomena are described for example in Hardcopy Supplies Journal, 6 (7), 35 (2000).
In patent GB 2,088,777 derivatives of phenols and bisphenols are proposed in order to improve the stability of recording sheets containing inorganic oxides.
In patent application EP 0,685,345 the addition of dithiocarbamates, thiocyanates, thiurams or sterically hindered amines to recording sheets containing porous inorganic oxides is proposed in order to improve their stability.
In patent application EP 0,373,573 derivatives of polyhydroxybenzenes are proposed as stabilizers for recording sheets for ink jet printing.
All of these proposed additives only marginally increase the stability of recording sheets for ink jet printing containing porous inorganic oxides when they are in contact with ambient air.
Stabilizing additives for such recording sheets containing porous inorganic oxides need to be sufficiently soluble and compatible with the other ingredients of the mainly aqueous coating compositions. They need to be colorless or are allowed to be colored only slightly. Furthermore, these additives need to be stable when the recording sheets or the images printed thereon are stored over long periods and they are not allowed to yellow. Additionally they need to be non-toxic and inoffensive.
There is therefore an urgent need to improve, in addition to the ink absorption capacity, the image quality, the water fastness, the light stability etc., in particular the storage stability of recording sheets containing porous inorganic oxides when they are in contact with ambient air containing impurities such as ozone, nitrogen oxides or sulfur dioxide.
SUMMARY OF THE INVENTION
An objective of the invention is to provide recording sheets containing porous inorganic oxides with improved storage stability when in contact with ambient air, where images recorded thereon can be observed by both reflected and transmitted light, and consist of a support having coated thereon at least one ink-receiving layer.
We have surprisingly found that the storage stability of recording sheets according to the invention is considerably improved in contact with ambient air when substituted or unsubstituted 1,3-cyclohexanedione is added to the recording sheets. Images printed onto such recording sheets according to our invention show considerably less change of colors and/or dye losses when in contact with ambient air containing impurities such as ozone, nitrogen oxides or sulfur dioxide in comparison with images printed onto recording sheets not containing these compounds.
The recording sheets for ink jet printing according to the invention contain in the coated layers, besides the porous inorganic oxide and the substituted or unsubstituted 1,3-cyclohexanedione, one or more binders. The substituted or unsubstituted 1,3-cyclohexanedione may be added to the layer containing the inorganic porous oxide or to any other layer of the recording sheet.
Preferred additives are 1,3-cyclohexanedione and 2-methyl-1,3-cyclohexanedione.
Further compounds such as reducing agents, organic thio compounds and inorganic thiocyanates may be added to the recording sheets according to the invention.
Additionally a reduction catalyst may be added together with the substituted or unsubstituted 1,3-cyclohexanedione, the reducing agent and the organic thio compounds or inorganic thiocyanates.
The invention will be described in detail in the following description.
DETAILED DESCRIPTION OF THE INVENTION
The invention describes a recording sheet for ink jet printing consisting of a support having coated thereon one or more layers comprising, besides a porous inorganic oxide and binders in the ink-receiving layer, substituted or unsubstituted 1,3-cyclohexanedione. The porous inorganic oxide and the substituted or unsubstituted 1,3-cyclohexanedione may be contained in the same or in different layers.
These 1,3-cyclohexanediones have already been proposed as heat stabilizers or as additives for polyvinyl chloride in order to prevent yellowing in U.S. Pat. No. 4,252,698 or in patent application JP 51-111,852.
An object of the present invention is the addition of tautomeric compounds of formulas Ia (diketo form) and Ib (enol form) to recording sheets for ink jet printing containing a porous inorganic oxide
wherein in formula Ib (enol form)
M represents a hydrogen cation, a metal cation such as Li, Na or K, a triethanolamine cation or an ammonium cation optionally substituted by one or more alkyl or substituted alkyl groups each having from 1 to 18 C atoms;
R
1
represents hydrogen, alkyl with 1 to 12 C atoms or substituted alkyl with 2 to 6 C atoms, wherein the substituents are selected from the group consisting of CN, COOH, OH and COOR
4
, where R
4
represents alkyl with 1 to 12 C atoms; and
R
2
, R
3
independently represent hydrogen, alkyl with 1 to 6 C atoms or substituted alkyl with 2 to 6 C atoms, wherein the substituents are selected from the group consisting of CN, COOH, OH and COOR
5
, where R
5
represents alkyl with 1 to 12 C atoms.
Especially preferred are compounds of formula Ia and Ib, wherein in formula Ib (enol form)
M represents a hydrogen, a Li, a Na, a K, an ammonium or a triethanolamine cation;
R
1
represents hydrogen, alkyl with 1 to 3 C atoms or alkyl substituted by COOR
4
with 2 to 4 C atoms, where R
4
represents alkyl with 1 or 2 C atoms; and
R
2
, R
3
independently represent hydrogen, alkyl with 1 or 2 C atoms or alkyl with 2 to 4 C atoms substituted by COOR
5
, where R
5
represents alkyl with 1 or 2 C atoms.
Preferred additives are 1,3-cyclohexanedione and 2-methyl-1,3-cyclohexanedione.
Such a recording sheet contains one or more of these compounds. The quantity is from 1 mg/m
2
to 5,000 mg/m
2
, preferably from 50 mg/m
2
to 600 mg/m
2
of these compounds.
In addition to the compounds of formulas Ia and Ib reducing agents may be added to the recording sheet as for example ascorbic acid or benzenephosphonic acid.
In addition to the compounds of formulas Ia and Ib organic thio compounds such as thioglycols or thiocarboxylic acids, in particular thiodiethyleneglycol or thiodipropionic acid, or inorganic thiocyanates such as ammonium thiocy
Baettig Kurt
Peternell Karl
Steiger Rolf
Ilford Imaging Switzerland GmbH
Kelly Cynthia H.
Onofrio Law
Onofrio, Esq. Dara L.
Shewareged B.
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