[0001] This invention relates to a versatile ink-jet printing paper, i.e. to paper which
is specially adapted to give good imaging performance when used with an ink jet printer,
but which also exhibits good toner adhesion when imaged by electrophotographic processes
as used in laser printers, xerographic copiers and such like.
[0002] Ink-jet printers will produce an image on most papers, but the print quality varies
markedly in dependence on the nature of the paper used. By "print quality" is meant
factors such as the sharpness, intensity and uniformity of the image produced and
its susceptibility to smudging immediately or shortly after the ink has been applied.
In the case of colour printing, it is important also that the colours should not run
into one another and that they should be vivid, with good brightness.
[0003] Print quality is influenced by a number of factors, but the two most important are
the extent to which the ink droplets spread out after contact with the paper and the
rapidity with which the ink droplets are absorbed into the paper. Excessive droplet
spreading resulting from, for example, flow of ink along the length of the paper fibres,
produces an image which appears blurred, with fuzzy edges, spidery lines and a general
lack of resolution (this is often referred to as feathering or wicking, and the effect
is somewhat analogous to that obtained by writing with a fountain pen on blotting
paper). Slow absorption of the ink into the paper can result in smudging of the image
and in merging of ink from different droplets, giving ragged images and, if the ink
droplets are of different colours, running of the colours into one another, often
termed ink bleed.
[0004] Hitherto, it has generally been found necessary to apply a pigment coating to the
paper in order to achieve top quality colour images, i.e. vivid bright colours which
do not run into one another. The pigment coating makes the paper highly absorptive
to the aqueous ink vehicle, so that the vehicle drains away quickly into the body
of the paper, leaving the coloured dye at the surface and thereby giving bright intense
colours with minimal print bleed. Whilst pigment coating has not been found essential
for good quality black (monochrome) images, it does generally enhance the quality
of those images compared with those obtained on uncoated papers.
[0005] The use of a pigment coating is disadvantageous in certain respects, in that it adds
to raw material and process costs, and tends to give rise to "dusting" problems in
subsequent conversion and printing operations, i.e. pigment particles can become dislodged
from the coating and deposit on reeling, slitting and printing equipment.
[0006] For papers for general office use, the cost of pigment coating is often not justified,
and ordinary uncoated papers have been used. These have generally been hard sized
in order to give good ink "hold-out", which produces bright colours and minimises
strike-through and feathering (regardless of whether colour or monochrome inks are
used). However, hard sizing can adversely affect toner adhesion when the paper is
imaged with laser printers, xerographic copiers and such like. It is important to
appreciate in this regard that the commercial need is for a versatile paper which
offers good performance not just with respect to ink-jet printers but also to laser
printers, xerographic copiers and such like. Many customers utilise a variety of types
of printer, and they seek to obtain paper which works well on all these printers rather
than being forced to use a different paper for each type of printer.
[0007] Good performance with a laser printer or similar requires that the paper should have
a good affinity for the toners used to effect imaging, so that the toner adheres well
to the paper. The adverse effect of hard sizing on toner adhesion can be particularly
pronounced when sizing is achieved by the use of alkyl ketene dimer (AKD) sizing agents,
possibly because AKD sizes are waxy in nature and can produce a release effect. Since
AKD sizing offers the papermaker many benefits compared with traditionally rosin-alum
sizing, it is important that it should be possible to utilise AKD sizing in the production
of papers for office use, and that a solution should be found to the problem of achieving
good ink-jet printing performance and good toner adhesion in the same product.
[0008] Good toner adhesion is particularly difficult to achieve with rough papers which
carry a surface-profile texture, for example a laid line, chain line or other pattern
applied by means of a dandy roll, or a pattern applied by felt marking or wet or dry
embossing. This is probably because toner adhesion is normally achieved by heat- and/or
pressure-fusion of the toner to the paper. With rough or surface-textured papers,
it is difficult to achieve sufficiently good physical contact for this fusion to be
effective.
[0009] It is an object of the present invention to overcome or at least reduce the problems
described above and to provide an improved ink jet printing paper which gives good
colour and monochrome images without the need for a full pigment coating of the conventional
kind, and which, particularly when the paper has a surface-relief texture, is also
capable of good quality imaging by electrophotographic processes as used in laser
printers, xerographic copiers and such like.
[0010] We have now found that the above-stated object can be achieved by treating a suitable
base paper with a composition comprising an admixture of:
(a) a cooked and/or chemically modified starch;
(b) a hydrophilic polymer other than a starch; and
(c) a hydrophobic polymer.
[0011] Accordingly, the present invention provides, in a first aspect, an ink-jet printing
paper of which the print-receiving surface comprises a base paper treated with a composition
comprising an admixture of:
(a) a cooked and/or chemically modified starch;
(b) a hydrophilic polymer other than a starch; and
(c) a hydrophobic polymer.
[0012] In a second aspect, the present invention provides a method of producing ink-jet
printing paper, comprising the step of treating at least the print-receiving surface
of a base paper with a composition comprising an admixture of:
(a) a cooked and/or chemically modified starch;
(b) a hydrophilic polymer other than a starch; and
(c) a hydrophobic polymer.
[0013] The treatment composition is conveniently applied to the paper by means of a size
press, but other techniques can be used, for example spraying or coating. The expression
"size press" in this context includes modified size presses or coating heads as supplied,
for example, by Voith under the name "Speedsizer", Valmet under the name "Sym-sizer",
Jagenberg under the name "Filmpress" and BSG under the name "Twin HSM".
[0014] Cooked and/or chemically modified starches are widely used in the paper industry
and are thus very well-known. They are to be distinguished from particulate starches
as found in plants (such particulate starches are the raw material from which cooked
and/or chemically modified starches are produced). Dextrins, although derived from
starches, are not considered to be "cooked and/or chemically modified starches" in
this context, since the hydrolysis processes involved in their production result in
loss of essential starch character.
[0015] Suitable starches for use in the treatment composition are generally those used in
the paper industry as surface sizes, as coating binders, or as wet-end additives.
Surface-sizing starches are currently preferred. The starches can be anionic, cationic,
amphoteric or non-ionic in character. A preferred surface sizing starch for use in
the present invention is an anionic oxidised potato-based starch. Other suitable surface
sizing starches are oxidised maize or wheat starches.
[0016] The hydrophilic polymer for use in the treatment composition is preferably a polyvinyl
alcohol, more preferably a relatively low molecular weight partially-hydrolysed polyvinyl
alcohol with a degree of hydrolysation of around 88%, or 87-89% as it is often expressed
in manufacturer's product information sheets. Other hydrophilic polymers which can
be used include dextrin, cellulose derivatives such as carboxymethyl cellulose (CMC)
and hydroxyethyl cellulose (HEC) ; gelatin; vegetable gums such as gum arabic; polyvinylpyrrolidones;
and maleic anhydride copolymers, for example copolymers of maleic anhydride with ethylene
(EMA), or vinyl methyl ether (PVMMA).
[0017] The hydrophobic polymer for use in the treatment composition is preferably a latex,
typically a latex of the kind supplied for use as a paper coating binder or as a surface
sizing additive. Suitable latexes include styrene-acrylic copolymer latexes of various
kinds (including acrylonitrile/n-butylacrylate/styrene copolymer latex); styrene-butadiene
copolymer latexes; and polyurethane latexes.
[0018] The relative proportions of the starch, hydrophilic polymer and hydrophobic polymer
can vary quite widely, although the starch is normally the major component of the
composition, usually making up at least 50% of its total weight on a dry basis. The
amount of hydrophobic polymer present can vary quite widely, depending on the degree
of hydrophobicity of the polymer. For example, the amount of hydrophobic polymer required
when the polymer is a polyurethane is much less than when the polymer is a styrene-acrylic
or carboxylated styrene-butadiene material. Detailed guidance as to suitable relative
proportions of the various mix components can be gained from the specific examples
given hereafter, but in general terms, the treatment composition should contain from
about 50 to about 90% by weight starch, from about 5 to about 50%, more preferably
5 to 25%, by weight of a hydrophilic polymer such as polyvinyl alcohol, and from about
2 to about 40% of hydrophobic polymer, all these percentages being on a dry basis.
Whilst the amount of polyvinyl alcohol used can vary quite widely, as indicated, cost
factors would normally lead to usage in the lower part of the range quoted. The amount
of hydrophobic polymer used will depend in part on its degree of hydrophobicity. In
general the amount used will be in the range 2 to 30% by weight. Typically the treatment
composition is made up at a solids content of about 5 to about 15% by weight, although
this is not believed to be critical.
[0019] If desired, the treatment composition can include a small proportion of pigment such
that the weight of pigment in the composition is less, normally much less, than the
aggregate dry weight of the starch, the hydrophilic polymer and the hydrophobic polymer.
The weight ratio of pigment : aggregate dry weight of starch, hydrophilic and hydrophobic
polymer may be, for example, about 1:20, although the precise ratio is not thought
to be critical. The inclusion of a minor proportion of pigment in this way can in
some cases enhance the ink-jet printing performance of the paper still further. The
use of a minor proportion of pigments to enhance the effect of the present composition
is to be contrasted with the use of conventional pigment coatings, in which the pigment
normally predominates (a typical pigment : binder ratio for such coatings might be
of the order of 4:1 to 8:1).
[0020] The present treatment composition can be used to enhance the ink-jet printing performance
of a wide variety of papers for office or other business use. Typically however, the
base paper is an around 80 to 100 g m
-2 woodfree base which has been conventionally internally sized, for example with alkyl-ketene
dimer or a rosin/alum sizing system. Hard sizing is preferable, for example to a Cobb
value (60 seconds) in the range 15 to 30. The pulps used and their relative proportions
can vary widely, but a typical furnish would comprise 80% hardwood pulp and 20% softwood
pulp. Usual papermaking fillers and other additives can be present.
[0021] The treatment composition is preferably present in an amount of 1 to 5%, more preferably
2 to 4%, by weight of the base paper on a dry basis. Thus for a 100 g m
-2 base paper to which the treatment composition is applied by means of a size press,
the dry pick-up should preferably be from about 2 g m
-2 to 4 g m
-2, on a dry basis (i.e. 1 or 2 g m
-2 per side). Higher pick-up levels are technically acceptable but may be economically
disadvantageous.
[0022] The paper can be preferably calendered after treatment and subsequent drying, for
example to a Bendsten roughness value of 500 ml min
-1 or less. Alternatively the paper can be one which carries a surface-profile texture
as referred to earlier.
[0023] The reasons why the use of the present treating composition gives good results are
not yet fully understood. However, we believe the presence of the hydrophobic polymer
causes the ink, which is normally aqueous in nature, to be better "held out" on the
surface of the paper - if hydrophobic polymer is omitted, the ink penetrates the paper
structure too rapidly and dull and ragged print images are obtained.
[0024] The polyvinyl alcohol or other hydrophilic polymer on the other hand promotes a controlled
penetration of the ink but without much lateral spreading. If hydrophilic polymer
is omitted, penetration is poor and the ink drying time is too long and an undesirable
degree of mottle results. Thus although bright colours may be obtained, differently-coloured
inks remain on the paper surface for sufficient time to run into and merge with one
another, i.e. print bleed occurs. This is not a problem with monochrome inks, but
the tendency of the ink to stay at the paper surface may give rise to smudging of
the image.
[0025] Thus in summary, the benefits of the present invention are thought to accrue from
the presence of a complementary balanced combination of hydrophilic and hydrophobic
elements. The starch component of the composition is thought to contribute primarily
the normal benefits of a starch sizing agent, i.e. it fills in pores and voids at
the sheet surface and thereby provides a physical impediment to liquid penetration,
sticks down loose fibres, and enhances the strength of the final paper.
[0026] The invention will now be illustrated by the following Examples, in which an asterisk
indicates the first occurrence of a proprietary trade mark, all parts and percentages
are by weight unless otherwise stated, and which provide details of additional specific
benefits which have been achieved by the invention with particular types of paper:
EXAMPLE 1
[0027] 55 parts of anionic oxidised potato starch ("Perfectamyl* P 255 SH" supplied by Tunnel
Avebe, of Ulceby, South Humberside, United Kingdom) and 15 parts of an 88 Mol% hydrolysed
relatively low molecular weight polyvinyl alcohol ("Mowiol* 8-88" supplied by Harlow
Chemical Company Limited of Harlow, Essex, United Kingdom) were blended as dry powders.
The blend was then made up into an approximately 10% solids content aqueous solution/dispersion
and cooked at about 90°C for 30 minutes. After allowing the mixture to cool to about
50°C, 60 parts of 50% solids content (i.e. 30 dry parts) of acrylonitrile/n-butylacrylate/styrene
copolymer latex ("Acronal* S 360 D" supplied by BASF) were added with stirring, to
give a treatment composition of a little under 15% solids content and a viscosity
of about 80 cps (measured at 20°C, Brookfield viscometer, Spindle No. 2, speed 100
rpm).
[0028] This treatment composition was then applied to a sheet of 100 g m
-2 white uncoated woodfree general office base paper using a laboratory size press.
The base paper was internally sized with alkyl ketene dimer, but had not previously
been surface sized. The treated sheet was then dried using a laboratory rotary dryer.
The dry pick-up was found to be about 5% (i.e. about 2.5 g m
-2 per side), based on the dry weight of the base paper before treatment. The treated
paper had a 60 second Cobb value of 18. The treated sheet was then laboratory calendered.
After calendering the sheet had a Bendsten roughness of 150 ml min
-1.
[0029] The sheet and a control sheet which had been treated with a conventional starch sizing
composition were then printed by means of a Hewlett Packard* Deskjet* 560C ink jet
printer. The printed images were of a standard test card giving both colour and monochrome
(black) images and specifically designed to evaluate print quality and reveal failings
in intensity, sharpness, wicking, print bleed and such like.
[0030] The paper according to the invention was found to give rapid ink drying (i.e. penetration
into the paper), good colour intensity, low ink bleed, and sharply defined colour
and monochrome characters, with little wicking and low mottle, i.e. non-uniformity
in print intensity in different areas of the paper. There was little or no strike-through
of the ink to the reverse (unprinted) surface of the sheet.
[0031] By comparison, the control sheet showed more print bleed and less bright colours
on colour-printed areas. The monochrome image quality was quite good (probably a consequence
of the internal sizing of the paper) but had a longer "drying time". This would be
likely to give rise to smudging in everyday use.
EXAMPLE 2
[0032] This illustrates the use of three alternative hydrophobic polymers to that used in
Example 1. These were as follows:
- Mix I -
- polyurethane latex supplied at 20% solids content by Akzo Nobel under the name "Cyclopal*
AP"
- Mix II -
- styrene/acrylic copolymer latex supplied at 27% solids content by Akzo Nobel under
the name "Bewopress* AE 27"
- Mix III -
- carboxylated styrene/butadiene copolymer latex supplied at 50% solids content by Dow
Chemical under the name "Dow* DL 950"
[0033] The other mix components were the same starch and polyvinyl alcohol as used in Example
1. The treatment compositions were prepared by the same general procedure as described
in Example 1, but the final solids content was a little lower (about 12%). The % dry
composition of the compositions was as follows:
Component |
Mix I |
Mix II |
Mix III |
Starch |
77.5 |
55 |
55 |
Polyvinyl alcohol |
20.0 |
15 |
15 |
Latex |
2.5 |
30 |
30 |
[0034] The polyurethane has a higher degree of hydrophobicity than the other two polymers,
and so it was used in a much smaller quantity.
[0035] Each treatment composition was applied to a respective sheet of 95 g m
-2 white uncoated woodfree premium business stationery base paper which had been internally
hard sized with alkyl ketene dimer, but which had not been surface sized. The dry
pick-up was found to be about 4% (i.e. about 2 g m
-2 per side). After drying, the sheets were each laboratory calendered to a Bendsten
roughness of around 150 ml min
-1.
[0036] The various sheets, together with a control sheet which was conventionally starch-sized,
were then printed and evaluated as described in Example 1. All three papers according
to the invention were found to give the same good performance as described in detail
in Example 1, and the same benefits over the control paper.
EXAMPLE 3
[0037] This illustrates the use of the present invention on a full-size papermachine, using
a treatment composition with the same ingredients and relative proportions as set
out in detail in Example 1 (55 parts anionic oxidised potato starch, 15 parts 88 Mol%
hydrolysed low molecular weight polyvinyl alcohol, and 30 parts latex, all on a dry
basis). The solids content of the composition was 12%.
[0038] An 80% hardwood/20% softwood furnish internally sized with alkyl ketene dimer and
containing usual papermaking fibres and additives was used to produce a good quality
very smooth white woodfree general office paper. The treatment composition described
above was applied at the size press and the paper was conventionally calendered after
drying. The final paper had a basis weight of 105 g m
-2, topside and wireside Bendsten roughnesses of 66 and 44 ml min
-1 respectively, a 60 second Cobb value of 25 and a filler content of about 15% (ureaformaldehyde
resin synthetic filler).
[0039] The paper, and a control paper of the same type sized only with a conventional starch
size press formulation were then evaluated for ink jet performance generally as described
in previous Examples.
[0040] Toner adhesion was also evaluated. The toner adhesion test, also known as the tape
pull test, involved printing a solid block of toner onto each sheet by means of a
Hewlett-Packard LASERJET* IV laser printer; measuring the print density by means of
an image intensity measuring instrument; applying adhesive tape to the sheet over
the block-imaged area; carefully removing the tape with the aid of an Instron peel
force tester to ensure an even and reproducible removal force; and re-measuring the
print density. The ratio of the print density after removal of the tape to the print
density before application of the tape is then expressed as a percentage value termed
the "toner adhesion".
[0041] The results of the tests were as follows:-
Property |
Invention |
Control |
Colour appearance |
good |
mottled |
Colour brightness (see note 1) |
10.1 |
14.3 |
Colour intensity (see note 2) |
1.1 |
0.8 |
Colour print bleed |
good |
poor |
Monochrome wicking |
good |
acceptable |
Monochrome optical density (see note 4) |
1.6 |
1.6 |
Monochrome ink drying time (see note 3) |
39 sec |
68 sec |
Toner adhesion (%) |
93 |
74 |
NOTES :
1. Measured according to an optical reflectance test method in which the lower the
number obtained, the better the brightness and for which any value higher than 12
is deemed unacceptable. |
2. Measured according to a Hewlett Packard standard test in relation to a composite
black image derived by printing the same area with several different coloured inks
and for which the higher the number obtained, the better the intensity, with a value
of 0.8 being the threshold of acceptability. |
3. Measured according to a Hewlett Packard standard test. |
4. Measured using a Gretag* optical densitometer, with a value of 1.2 being an approximate
threshold of acceptability. |
[0042] It will be seen that the paper according to the invention was markedly better in
most respects than the control paper.
[0043] In a later repeat making of the same type of paper, the starch used was a mill-cooked
potato-based starch. The same product benefits were obtained.
EXAMPLE 4
[0044] This illustrates the use of the present invention on a full-size papermachine making
a less smooth paper than in the case of Example 3 above.
[0045] The procedure was generally as described in Example 3, except that the refining conditions
were different, the solids content of the treatment composition was 10% and precipitated
calcium carbonate was used as the filler rather than ureaformaldehyde resin synthetic
pigment. The final paper had a basis weight of 101 g m
-2, topside and wireside roughnesses of 195 and 132 ml min
-1 respectively, a 60 second Cobb value of 27 and a filler content of about 11%.
[0046] The results of the ink jet printing performance evaluation for the product according
to the invention and an approximate control paper were as follows:
[0047]
Property |
Invention |
Control |
Colour appearance |
good |
mottled |
Colour brightness |
9.7 |
8.3 |
Colour intensity |
1.3 |
1.7 |
Colour print bleed |
good |
very poor |
Monochrome wicking |
good |
good |
Monochrome optical density |
1.8 |
1.8 |
Monochrome ink drying time |
8 sec |
23 sec |
Toner adhesion |
73% |
28% |
[0048] It will be seen that the paper according to the invention performed better than the
control paper in terms of colour appearance, colour print bleed and ink drying time.
The control paper was slightly better in terms of colour brightness and intensity,
probably because the control paper was very hard sized, but these marginal benefits
are completely outweighed by the severe print bleed, the mottled appearance and the
high drying time of the control paper.
EXAMPLE 5
[0049] This illustrates the use of a range of different hydrophilic polymers in the treatment
composition (these include an 88 Mol % hydrolysed polyvinyl alcohol as used in previous
Examples). In each case, the treatment composition on a dry basis was as follows:
[0050]
Starch ("Perfectamyl P 255 SH") |
85% |
Hydrophilic polymer (see below) |
9% |
Latex ("Bewopress AE 27") |
6% |
[0051] Four different treatment compositions were prepared, the hydrophilic polymers used
being as follows:
[0052]
- Mix I -
- 88 Mol % hydrolysed polyvinyl alcohol ("Mowiol 8-88")
- Mix II -
- Polyvinylpyrrolidone ("Lumiten* PR 8450") supplied in 30% aqueous solution by BASF)
- Mix II -
- Low molecular weight carboxymethyl cellulose ("Finnfix* 5" supplied by Metsa-Serla,
Finland)
- Mix IV -
- Fully hydrolysed polyvinyl alcohol ("Mowiol 10-98" supplied by Harlow Chemical Company)
[0053] Each treatment composition was applied to respective sheets of test paper as used
in Example 2, and then dried and calendered, also as described in Example 2. The various
sheets, together with a control sheet which was conventionally starch-sized, were
then printed and evaluated as described in Example 3.
[0054] The results were as follows:
Property |
Control |
Mix I |
Mix II |
Mix III |
Mix IV |
Monochrome wicking |
A |
A |
A |
A |
A |
Monochrome optical density |
1.5 |
1.6 |
1.7 |
1.7 |
1.8 |
Monochrome ink drying time (sec) |
15 |
15 |
22 |
15 |
25 |
Colour appearance |
G |
G |
G |
G |
G |
Colour brightness |
6.6 |
6.2 |
6.6 |
7.1 |
6.7 |
Colour print bleed |
A |
E |
E |
G |
G |
Toner adhesion (%) |
58 |
86 |
67 |
74 |
78 |
Key:
A = Acceptable
G = Good
E = Excellent |
[0055] It will be seen that papers according to the invention showed improved colour print
bleed and monochrome optical density performance, and much better toner adhesion compared
with the control paper.
EXAMPLE 6
[0056] This illustrates the use of the present invention for treating a 100 g m
-2 laid premium business stationery paper during its manufacture on a full-sized papermachine.
The paper was internally AKD-sized and incorporated a ca. 15% precipitated calcium
carbonate loading. The procedure was generally described in Example 3, and the final
paper had a 60 second Cobb value of 24.
[0057] The results of the tests were as follows:
[0058]
Property |
Invention |
Control |
Colour appearance |
good |
good |
Colour brightness |
6.6 |
7.2 |
Colour intensity |
1.6 |
1.4 |
Colour print bleed |
good |
poor |
Monochrome wicking |
good |
good |
Monochrome optical density |
1.8 |
1.8 |
Monochrome ink drying time |
13 sec |
24 sec |
Toner adhesion (%) |
92 |
51 |
[0059] It will be seen that the paper according to the invention had improved colour brightness
and colour print bleed, a shorter ink drying time and much improved toner adhesion,
compared with the control paper.
EXAMPLE 7
[0060] This illustrates the use of a different type of starch in the treatment composition,
namely a wheat (carbohydrate extract) starch supplied as "Abrastarch*" (at 9% solids
content) by ABR Foods Limited, Corby, England, in place of the "Perfectamyl P 255
SH" starch used in previous Examples.
[0061] The procedure was generally as described in Example 3, except that the treatment
composition was as follows:
[0062]
Starch |
85% |
Polyvinyl alcohol ("Mowiol 8-88") |
9% |
Latex ("Bewopress AE 27") |
6% |
[0063] The total dry pick up of the composition was ca. 4 g m
-2 (4%) and the 60 second Cobb value was 24. The Bendsten roughness of both surfaces
of the paper was in the range 50 - 60 ml min
-1.
[0064] The test results were as follows (no colour intensity measurements were made for
this and subsequent Examples):
[0065]
Property |
Invention |
Control |
Colour appearance |
no mottle |
mottled |
Colour brightness |
13 |
13 |
Colour print bleed |
good |
poor |
Monochrome wicking |
good |
good |
Monochrome optical density |
1.7 |
1.7 |
Monochrome ink drying time |
17 sec |
20 sec |
Toner adhesion (%) |
99 |
57 |
[0066] It will be seen that the paper according to the invention had improved colour appearance,
improved colour print bleed and much improved toner adhesion compared with the control
paper.
EXAMPLE 8
[0067] This illustrates the effect of omitting the hydrophilic polymer from the treatment
composition. Three treatment compositions were evaluated, as follows (dry basis):
[0068]
Invention : |
Starch ("Abrastarch") |
85% |
|
Polyvinyl alcohol ("Mowiol 8-88") |
9% |
|
Latex ("Bewopress AE 27") |
6% |
|
Control I : |
Starch (as above) |
94% |
|
Polyvinyl alcohol (as above) |
6% |
|
Control II : |
Starch (as above) |
100% |
[0069] These compositions were each applied to a relatively rough flecked 100 g m
-2 decorative text and cover paper during its production on a full-size papermachine.
The resulting papers were tested as in Example 7, and the results obtained were as
follows:
[0070]
Property |
Invention |
Control I |
Control II |
Colour appearance |
acceptable |
acceptable |
acceptable |
Colour brightness |
11 |
10 |
10 |
Colour print bleed |
excellent |
acceptable |
acceptable |
Monochrome wicking |
acceptable |
acceptable |
acceptable |
Monochrome optical density |
1.5 |
1.6 |
1.6 |
Monochrome ink drying time |
12 sec |
14 sec |
11 sec |
Toner adhesion (%) |
77 |
36 |
23 |
[0071] It will be seen that the paper according to the invention had improved colour print
bleed and much improved toner adhesion compared with the control paper. Accurate comparison
of properties such as appearance (mottle) and colour brightness was hindered by the
decorative flecked appearance of the paper.
EXAMPLE 9
[0072] This illustrates the use of a minor proportion of pigment in the treatment composition.
The pigment used was calcium carbonate ("Hydrocarb* 90", supplied by Croxton & Garry,
Dorking, England) and was present in the treatment composition in an amount of 5%
calculated as dry weight of pigment to aggregate dry weight of starch, hydrophilic
polymer and hydrophobic polymer. This treatment composition and general procedure
were otherwise as in Example 3. Additionally, paper was produced using the same treatment
composition without pigment and, separately, with a 100% starch treatment composition.
[0073]
Property |
Invention (without Pigment) |
Invention (with Pigment) |
Control |
Colour appearance |
no mottle |
no mottle |
slight mottle |
Colour brightness |
11.2 |
12.0 |
11.6 |
Colour print bleed |
good |
acceptable |
poor |
Monochrome wicking |
good |
good |
good |
Monochrome optical density |
1.7 |
1.6 |
1.6 |
Monochrome ink drying time (sec) |
23 |
36 |
43 |
Toner adhesion (%) |
90 |
90 |
60 |
[0074] It will be seen that both papers according to the invention had improved colour appearance,
improved colour print bleed, shorter ink drying time and much improved toner adhesion
compared with the control paper.
EXAMPLE 10
[0075] This illustrates the use of the invention with an acid sized (rosin/polyaluminium
chloride) paper produced on a full-sized papermachine. The paper was a very smooth
high quality white 100 g m
-2 woodfree business stationery paper containing a ca. 15% precipitated calcium carbonate
loading. The treatment composition, made up at 8% solids content, was as follows:
[0076]
Cationic etherified starch ("Amylopak* 15", supplied by Tunnel Avebe Limited, England) |
82% |
Polyvinyl alcohol ("Mowiol 8-88") |
10% |
Styrene-acrylic latex ("Bewopress AE 27") |
8% |
[0077] The final paper had a 60 second Cobb value of 26, and topside and wireside smoothness
values of 60 ml min
-1 and 50 ml min
-1 respectively (Bendsten). The dry pick up of the treatment composition was ca. 4%,
i.e. ca. 2 g m
-2 per side.
1. Ink-jet printing paper of which the print-receiving surface comprises a base paper
treated with a composition comprising an admixture of:
(a) a cooked and/or chemically modified starch;
(b) a hydrophilic polymer other than a starch; and
(c) a hydrophobic polymer.
2. Ink-jet printing paper as claimed in Claim 1 wherein the starch makes up at least
50% by weight of said composition on a dry basis.
3. Ink-jet printing paper as claimed in Claim 2, wherein the treatment composition contains,
on a dry basis, from 50 to 90% by weight, preferably 50 to 80% by weight, starch;
from 5 to 50% by weight, preferably 5 to 25% by weight, of hydrophilic polymer; and
from 2 to 40% by weight, preferably 2 to 30% by weight, of hydrophobic polymer.
4. Ink-jet printing paper as claimed in any preceding claim wherein the treatment composition
is present in an amount of 1 to 5% by weight, preferably 2 to 4% by weight, of the
base paper on a dry basis.
5. Ink-jet printing paper as claimed in any preceding claim, wherein the starch is a
surface-sizing starch.
6. Ink-jet printing paper as claimed in any preceding claim, wherein the hydrophilic
polymer other than starch is a polyvinyl alcohol.
7. Ink-jet printing paper as claimed in Claim 6, wherein the polyvinyl alcohol is a relatively
low molecular weight polyvinyl alcohol with a degree of hydrolysation of 87 to 89
Mol %.
8. Ink-jet printing paper as claimed in any preceding claim wherein the hydrophobic polymer
is a latex.
9. Ink-jet printing paper as claimed in Claim 5 wherein the latex comprises an acrylonitrile/n-butylacrylate/styrene
copolymer latex; a styrene/acrylic copolymer latex other than the foregoing; a styrene-butadiene
copolymer latex; or a polyurethane latex.
10. Ink-jet printing paper as claimed in any preceding claim wherein the composition includes
a pigment in a small proportion relative to the aggregate dry weight of the starch,
the hydrophilic polymer and the hydrophobic polymer.
11. A method of producing ink-jet printing paper, comprising the step of treating at least
the print-receiving surface of a base paper with a composition comprising an admixture
of:
(a) a cooked and/or chemically modified starch;
(b) a hydrophilic polymer other than a starch; and
(c) a hydrophobic polymer.
12. The use, for the purpose of enhancing the print quality obtained when printing paper
by ink-jet printing processes, and also electrophotographic processes, of a treatment
composition comprising an admixture of:
(a) a cooked and/or chemically modified starch;
(b) a hydrophilic polymer other than a starch; and
(c) a hydrophobic polymer.