Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
1 333033
1 TITL~ OF TH~ INVENTION
Recording Paper and Ink Jet Recordng Method by
Use Thereof
5 BACKGROUN~ OF TH~ INV~NTION
Field of the Invention
This invention relates to a recording paper
useful for ink jet recording, particularly to a
recording paper excellent in aqueous-ink absorptivity,
10 resolution of image and color forming characteristic
of the colorant in ink and to an ink jet recording
method by use thereof.
Related Background Art
In the prior art, as the recording paper for
15 ink jet recording, there have been known:
(1) a recording paper which is prepared by
making a paper In general composed mainly of pulp into
a sheet with a low sizing degree such as filter paper,
blotting paper, etc.;
(2) a recording paper prepared by use of a
paper subjected to considerable sizing as the
substrate paper, having an ink absorption layer
provided thereon by coating of a filler which is
porous and large in oil absorption such as silica or
25 zeolite;
(3) a recording paper having a coating layer
- 2 - ~ 333~33
1 provided on a substrate paper-with low sizing degree
as disclosed in Japanese Laid-open Patent Applications
Nos. 53012/1977, 11~29/1980 and 38087/1~84 and U.S.
Patent 4,4~,910, etc.
In the recording paper ~1), although it is
excellent in ink absorptivity, ink is penetrated deep
into the fibrous layer of the paper and therefore
color forming characteristic of the colorant in the
ink is poor. Since the ink is also absorbed along the
10 fibers on the paper surface, there occurs the
phenomenon called feathering, whereby there is the
drawback that dots do not become circular but
staggered or lowering in resolution is brought about
to give no image of good quality.
In the recording paper (2), since the ink
absorbing layer is porous and uniform, good dot shapes
and resolution can be obtained. However, for
imparting sufficient ink ab~orptivity, the ink
absorbing layer must be made thick, and therefore
20 there is also the problem that one coating is
insufficient and a plural number of coatings must be
carried on.
Further, if the ratio of the pigment to the
binder (P/B) in the ink absorbing layer is made too
25 great in order to improve ink absorptivity, the so
called powder drop-off by dropping of the pigment may
1 333033
-- 3 --
1 occur, whereby there are involved the drawbacks such
that the rollers for paper delivery may be slipped or
that clogging of the ink jet nozzle may be caused.
In the recording paper (3), even when a
5 relatively thin coating layer may be provided, there
is the advantage that a recording medium with good ink
absorptivity and excellent color forming
characteristic of the colorant can be obtained as
compared with the recording paper (2). However, as a
10 recording system with higher resolution and higher
attachment density of ink is demanded, the ink
absorptivity may be sufficient when the recording
paper (3) is applied for such a system, but a large
amount of ink will be penetrated into the substrate
15 paper, whereby color forming characteristic of the
colorant and resolution will be lowered. Thus, it is
difficult to satisfy both of ink absorptivity and
these characteristics.
Further, there ensue the problem called
20 cockling in which pulp fibers are swelled with ink and
the printing portion is deformed in wavy form or the
so called back-through problem in which ink reaches
the back surface of the paper. These problems not
only impair quality of recorded image, but cockling
25 will give rise to scraping between the recording paper
and the head to impair images, and also back-through
1 333033
- 4 -
1 may cause back transfer when a recording paper is
superposed on another recording paper. Thus, both
problems are serious.
These phenomena are problems inherent in the
5 recording paper (3) which as a whole receives ink, and
they are problems which have appeared particularly as
the image with high resolution by ink jet recording i~
demanded. However, although the above problems are
inherent in the recording paper (3), no detailed
10 investigation has been made thereabout.
SUMMARY OF THE INVENTION
Accordingly, an object of the present
invention is to provide a recording paper which is
15 little in powder drop-off, can be produced with
relatively low cost and is also excellent in ink
absorptivity and color forming property of the
colorant.
Further, another object of the present
20 invention is to provide a recording paper which is
suitable for providing highly precise image without
causing problems such as cockling or back-through at
the printed portion.
In accordance with the present invention,
25 there is provided a recording paper compri~ing a
fibrous substrate papei on the surface of which a
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- 5 -
1 silicon containing type pigment and a fibrous material
of the substrate paper are present in a mixted state,
said recording paper having a Stockigt sizing degree
ranging from 0 to 15 sec. and a basis weight ranging
5 from 90 to 200 g/m2.
The present invention also provides a
recording paper comprislng a fibrous substrate paper
on the surface of which a coating li~uid containing a
silicon containing type pigment and an aqueous binder
10 at a weight ratio of 1/1-3/1 is coated, and on the
surface of which a silicon containing type pigment and
a fibrous material of the substrate paper are present
in a mixed state, said recording paper having a
Stockigt sizing degree renging from 0 to 15 sec. and a
15 basis weight ranging from 90 to 200 g/m .
Further, the present invention provides an ink
jet recording method, which comoprises impinging
aqueous ink droplets onto a recording medium, said
recording medium comprising a fibrous substrate paper
20 on the surface of which a silicon containing type
pigment and a fibrous material of the substrate paper
are present in a mixed state, said recording medium
having Stockigt sizing degree ranging from 0 to 15
sec. and.a basis weight ranging from 90 to 200 g/m2.
DETAILED DESCRPTION OF THE PREFERRED EMBODIMENTS
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1 Next, to describe in detail about the present
invention, the substrate paper to be used in the
present invention is a sheet containing
fi~rous material and, if necessary, a pigment, having a
5 Stockigt sizing degree according to JIS P~122 in the
range of 0 to 1~ sec. (based on the basis weight of 65
g/m2), and any paper made to a sizing degree of 0 to
15 sec. by a suitable sizing agent according to the
acidic sheet making method or the neutral sheet making
10 method known in the art can be used. In aspect of ink
absorptivity of the recording paper obtained, the
sizing degree of the substrate paper should be
preferably in the range of 0 to 10 ~ec., more
preferably in the range of 0 to 5 sec. Also, in
15 aspect of coating stability of the coating liquid, it
is preferably one sec. or more.
Also, for accomplishing the desired object of
the present invention, the basis weight of the above
paper is also an important factor. More specifically,
20 the basis weight of the substrate paper to be used in
the present invention is required to be within the
range of 80 to 200 g/m2. If the ~asis weight is less
than the above range, the so called stiffness of the
recording paper is weak to pose a problem in carriage
2~ characteristic within the printer during printing, and
also to lack ink absorption capacity as the recording
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1 paper, and therefore the printing portion causes
cockling to pose a problem that sharpness of ~he image
is lowered. Also, when recording is performed by use
of a printer having a plural number of recording
5 heads, the convex portion formed by cockling will
become in contact with the head during recording,
whereby clogging of the head, etc. may be caused to
involve the problem that irregularity may be formed in
the image obtained.
Further, due to low ink receiving capacity,
the ink not received will be subject to back-through,
whereby there may be caused the problem that the ink
image of the upper recording paper may be back
transferred to the image of the lower recording paper
15 when printed matters are placed as superposed on one
another, or there may occur the problem that no
recording can be performed on the back surface, etc.
On the other hand, if the basis weight exceeds
the above range, since the stress applied to the
20 coating layer on the surface becomes stronger during
bending of the recording paper obtained, whereby
problems such as cracking, powder drop-off or peel-
off, etc. of the coating layer may be caused.
More specifically, during the coating step, by
25 repetition of streching and bending along the rolls of
the coating machine, crack may be formed on the
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- 8 --
1 coating layer surface, which will later cause image
irregularity or powder drop-off. Further, during
cutting or storage after manufacturing of the
recording paper, there is al~o the problem that
5 similar drop-off is liable to occur during mounting on
the printer or in the printer carriage system.
Particularly, powder drop-off which occurs during
recording i5 undesirable, because clogging of the
recording head may be caused. Also, it is not
10 preferable to make thickner the thickness of a
substrate paper with large stretching and shrinkage
degree relative to humidity, because the problem of
curling may be caused.
The various problems as described above can be
15 solved by employment of a substrate paper with a basis
weight of 80 to 200 g/m .
The thickness of the substrate paper to be
used in the present invention may be preferably in the
range of 50 to 250 ~m. If the thickness is less than
20 the above range, the so called stiffness of the
recording paper obtained is weak, posing a problem in
conveying characteristic within the printer during
printing and also lacking ink absorption capacity,
whereby the printing portion causes cockling to ensue
25 the problem that sharpness of the image is lowered.
The fibrous material constituting the above
1 3~30~3
g
1 substrate paper to be used in-the present invention is
composed mainly of wood pulp, typically LBKP and NBKP,
but various synthetic fibers or glass fibers may be
mixed, if necessary.
~he aqueous coating liquid to be used in the
present invention comprises primarily a silicon
containing type pigment and an aqueous binder. The
silicon containing pigment may be preferably one which
is hydrophilic and contains relatively large amount of
10 oil absorption according to JIS K 5101 in aspect of
ink absorptivity and color forming property of the
colorant, including for example silica, calcium
silicate, aluminum silicate, magnesium silicate and
the like. Among them, those with oil absorption of 80
15 to 300 ml/100 g, more preferably 150 to 250 ml/100 g,
are preferred.
The above silicon containing type pigment
should be preferably one in which all the particles
have the above oil absorption, but the pigment is not
20 necessarily constituted of all the particles having
uniform oil absorption, and it may also be a mixture
of pigment with different oil absorptions. In the
case of such a mixture of pigments with different oil
absorptions, 60% by weight or more of the whole
25 pigment may have the oil absorption within the above
range.
- 10 -
1 333~33
1 When the oil absorption of the pigment
according to JIS K5101 is less than 80 ml/100 g, the
ink absorptivity when incorporated into a recording
paper is poor, and the colorant in the ink on the
5 surface of the coated layer cannot be ensured, whereby
there is the tendency such that the ink may be
penetrated deep into the recording paper to make color
formation of the colorant bad. On the other hand,
when it exceeds 300 ml/100 g, powder drop-off will
10 occur at the same level of binder and, if a binder
necessary for prevention of powder drop-off is
employed, lowering in ink absorptivity will be
undesirably brought about.
As the aqueous binder, there may be used, for
15 example, one or a mixture of two or more kinds
selected from water-soluble polymers such as polyvinyl
alcohol, starch, oxidized starch, cationized starch,
casein, carboxymethyl cellulose, gelatin, hydroxyethyl
cellulose, etc. and water-dispersed polymers such as
20 SBR latex, MBR latex, vinyl acetate emulsion, etc.
The present inventors have studied variously
about the characteristics of the aqueous coating
liquid during coating, and consequently found that a
recording paper having good ink jet recording
25 characteristics can always be obtained stably when the
liquid viscosity of the aqueous coating liquid at
- 11 - 1 33 3~3~
1 30C is in the range of 60 to-200 cps.
The viscosity in the present invention is
measured under the condition of 60 r.p.m. by B-type
viscometer, and thixotropic characteristic, dilatant
5 characteristic, etc. can be also evaluated by changing
the rotational number.
If the viscosity of the aqueous coating liquid
is less than 60 cps. the aqueous coating liquid will
be penetrated deep into the substrate paper to fill
10 the voids possessed by the substrate paper for
absorption of ink, with the result that lowering in
ink absorptivity may be brought about.
On the other hand, if the viscosity exceeds
200 cps, coating irregularity may be undesirably
15 caused due to too high a viscosity. Also, only water
in the aqueou~ coating liquid is absorbed by the
substrate paper to lower the strength of the surface
layer, whereby powder drop-off, etc. may be caused.
The viscosity of the aqueous coating liquid as
20 described above can be controlled easily by the kinds
of the above pigment and binder, combination thereof,
their proportions used, the respective concentrations
and the total concentration of the both, etc. In the
present invention, the ratio of the silicon containing
25 pigment to the binder used may be generally in the
range of 3/1 to 1/1 (weight ratio), and an aqueous
1 333033
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1 coating liquid with the total-solid content ranging
from about 3 to 70% by weight is preferred.
If the binder amount is more than the above
range, ink absorptivity, particularly initial
5 absorption speed of ink will be lowered. This problem
is pronounced as the sizing degree of the substrtate
paper is higher even within the sizing degree of O to
15 sec. and the basis weight is lower. On the other
hand, if the content of the pigment is larger than the
10 above range, there ensues the problem of powder drop-
off due to shortage in adhesive force even when a thin
coating layer may be provided. Particularly, in the
present invention where a substrate with low sizing
degree and high basis weight is used, since the binder
15 in the coating liquid will be readily absorbed by the
substrate paper, it is essentially required that the
proportion of the pigment should not exceed the above
range. The problem of powder drop-off is more
pronounced, particularly as the sizing degree of the
20 substrate paper is lower.
Further, the viscosity of the above aqueous
coating liquid is also intimately correlated with the
coating speed. More specifically, the above aqueous
coating liquid comprising a filler which is
25 hydrophilic and has an oil absorption of 80 to 300
ml/100 g according to JIS K5101 and an aqueou~ binder
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1 frequently exhibits thixotropic viscosity like coating
liquids in general.
Accordingly, if the coating speed is too
quick, coating irregularity will be liable to occur
5 even if the viscosity may be lower, while if it is too
slow, the time required for scraping off the coating
liquid to a given coated amount after coating is too
long, whereby the aqueous coating liquid will be
penetrated deep into the substrate to lower
10 undesirably ink ab~orptivity. Therefore, as the
balance between the viscosity of the aqueous coating
liquid and the coating speed, the coating speed may be
preferably 60 to 200 m/min. when the viscosity is 60
to 200 cps. A coating speed quicker or slower than
15 this range is not desirable, because various problems
as described above will occur.
As the coating machine to be used in the
present invention, all known in the art may be u~ed,
but the coater suitably used in the present invention
20 may include an air knife coater and a bar coater, etc.
The amount of the aqueous coating liquid
coated may be suitably within the range of 2 to 10
g/m as the coated amount on drying and, if it is less
than 2 g/m2, the coating will not function as the
25 coated layer. In other words, when the coated amount
is less than 2 g/m , the ink colliding against
1 333033
1 the recording surface will be feathered along the
fibers to be disturbed in dot shape, and at the same
time the dye will be penetrated deep into the inner
portion of the paper, whereby coloring density of the
5 image will be lowered. On other hand, if the coated
amount exceeds 10 g/m2, the merit of making the sizing
degree of the substrate paper O to 15 sec. will be
lost, and also there exists no more fibrous material
of the substrate paper on the recording paper surface,
10 whereby ink absorptivity,color forming
characteristic, etc. become un~atisfactory and also
feeling as the paper is lowered, also with attendant
problem of powder drop-off.
In the present invention, after coating of the
15 aqueous coating liquid under the condition in the
present invention, the recording paper is dried
according to the drying method known in the art such
as drying by hot air drying furnace, drying drum, etc.
to provide a recording paper. As an additional step,
20 surface smoothening by super calendering may be also
performed.
As described above, the recording paper of the
present invention having a Stockigt sizing degree of O
to 15 sec. and a basis weight of gO to 200 g/m2 is
25 obtained, but more preferably the Stockigt sizing
- 15 - l 3 3 3 0 3 3
1 degree is in the range of 0 to 10 sec., optimally 0 to
5 sec. and the preferable range of the basis weight is
in the range of 90 to 160 g/m .
If the Stockigt sizing degree of the recording
5 paper exceeds 15 sec., ink absorptivity, particularly
initial absorptivity will undesirably lowered.
When the basis weight of the recording paper
is less than 90 g/m2, the stiffness of the recording
paper obtained is weak to pose a problem in carriage
10 characteristic and or lack ink absorption capacity as
the recording paper, whereby the printlng portion may
cause cockling or back-through, thu~ causing various
problems as described above.
If the basis weight exceeds 200 g/m2, there is
15 involved the problem of powder drop-off or the problem
of curling in the recording paper obtained.
The recording paper of the present invention,
which contains a large amount of a ~ilicon containing
type pigment with high ink absorbing capacity in the
20 surface layer of the recording paper, has high
probability of the ink droplets being trapped and
ab~orbed by the pigment, and therefore feathering and
diffusion of the ink can be inhibited, whereby it may
be considered that dot shape is improved and also the
25 coloring density enhanced.
Also, since the substrate paper itself has ink
- 16 - l 3 3 3 0 33
1 absorptivity, the ink can be rapidly absorbed into the
recording paper, whereby there i5 no such phenomenon
such as flow-out or feathering of ink even when inks
with different colors may be attached on one site
5 within a short time, and there~ore recorded images
with excellent color forming characteristic can be
obtained.
Further, in the range of the coating amount in
the recording paper of the present invent ion, the
10 fibrous material on the surface of the substrate paper
will not be completely covered with the silicon
containing type pigment in the aqueous coating liquid,
and the recording paper surface is under the state
where the silicon containing type pigment and the
15 fibrous material are mixed with each other. For this
reason, not only the recording paper has the
sufficient characteristics as the ink ~et recording
paper, but also it has a texture approximate to plain
paper with little powder drop-off from the coated layer
20 as additional advantage.
The present invention is described in more
detail by re~erring to ~xamples and Comparative
examples. In the sentences, parts and ~ are based on
weight unless otherwise particularly noted.
25 Examples 1 - 5, Comparative examples 1 - 5
As the substrate paper, a hand-made sheet with
1 333033
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1 low sizing degree was controlled to the basis weight
as shown below, and to the substrate paper was applied
by coating an aqueous coating liquid with the
following composition at the coating amounts on
5 drying, respectively, followed by drying at 120 C for
5 minutes, to obtain recording media of the present
invention and for comparative purpose. The basis
weight of the substrate paper, coating amounts on
drying of coating layers, the basis weights of
10 recording media and St~ckigt sizing degrees of
recording media are shown in Table 1.
(Coating liquid composition)
Synthetic silica (Syloid 620, produced by Fuji
Davison Chemical Ltd.) 10 parts
Polyvinyl alcohol (PVA-117), produced by
Kuraray) 4 parts
Water 100 parts
20 Comparative example 6
As an example of the recording paper (2) as
described in the Description of the Related
Art, a wood free paper with a basis weight of
80 g/m , was coated with the above coating
liquid at a coating amount on drying of 6
~ tR~ R ~-
- 18 - l 33 30 3 3
l g/m , dried similarly as above to obtain a
recording medium K for comparison. The
recording medium obtained had a Stockigt
sizing degree of 2S sec.
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Table 1
Basis Amount of Basis Stockigt
Sample No. weight of Coating on weight of gizing
Substrate Coating Recording Recording
Paper Layer Paper Paper
- 4sec.
A 40g/m2 6g/m2 46g/m2 (Comparative
example 1)
4sec.
B 63 2 65(Comparative
example 2)
4sec.
C 63 6 69(Comparative
example 3)
4sec.
D 85 2 87(Comparative
example 4)
4sec.
E 85 6 91(Example 1)
4sec.
F 110 2 112(Example 2)
5sec.
G 110 6 116(Example 3)
5sec.
H 150 2 152(Example 4)
5sec.
I 150 6 156(Example 5)
6sec.
J 400 6 406(Comparat ve
1 333033
20 -
1 The ink jet recording-adaptability of each of
the above recording papers A - K was evaluated for ink
absorptivity, resolution and color forming
characteristic by performlng ink jet recording with
5 the use of inks having the compositions shown below.by
means of an ink jet printer having ink jet heads with
four colors of Y, M, C, BK each provided w1th 128
nozzle~ at nozzle interval of 1/16 mm(16 nozzles per
lmm).
Y (yellow) ink composition
C.I. Direct Yellow 86 2 parts
Glycerine 15 parts
Diethylene glycol 15 parts
Water 70 parts
M (magenta) ink composition
C.I. Acid Red 35 2 parts
Glycerine lS parts
Diethylene glycol 15 parts
Water 70 parts
C (cyan) ink composition
C.I. Direct Blue 199 2 parts
Glycerine 15 parts
Diethylene glyaol 15 parts
- 21 -l 33 3 03 3
1 Water -70 parts
BK (black) ink composition
C.I. Food Black 2 2 parts
Glycerine 15 parts
Diethylene glycol 15 parts
Water 70 parts
Evaluation items
~1) Dot density was measured for black dots by
means of Sakura Microdensitometer PDM-5 ~produced by
Konishiroku Photo Industry K.K.) by applying JIS K
~505 to ptinting microdot.
(2) Ink absorptivity was evaluated by means of
15 a bubble jet system printer having ink jet recording
heads of four colors of Y, M, C and BK each provided
with 128 nozzles at nozzle interval of 1/16mm. One
with a line being much bolder at the mixed portion of
two color inks of the recorded image than at the
20 monochromatic portion was rated as X, one with
occurrence of feathering, etc. at the color mixed
portion and unclear edge as A, one with clear edge
also at the mixed color portion simlarly to at the
monochromatic portion as o .
(3) For powder drop-off, one which gave paper
powder attached to finger when the coating layer
~le ~R~C
- 22 - l 3 330 3 3
1 surface was touched with finger and one which gives
rise to paper powder through peel-off or cracking of
the coated layer when the recording paper was folded
were rated as x, and one which is not so as O .
(4) For back-through, one in which back-
through was confirmed during printing by the same
printer as in (2) was rated as x, one which was not so
as O , and the middle range as ~.
(5) For cockling, one having scraping
10 generated on the recording paper surface through
cockling with head was rated as x, one without
generation of scraping but with cockling being
confirmed by visual observation and inferior in image
quality as A, and one without noticeable cockling as
15 o.
The evaluaton results are shown in Table 2.
1 333033
Table 2
(1) (2) (3) (4) (5) (6)
Sample Dot Ink Powder Back- Cockling Overall
No. density tivity drop-off through evaluation
A 1.1 ~ O X X X
B 1.1 f~ O X X X
1.2 O O X A x
D 1.1
E 1.2
F 1.1 O O
1.2 O O O
H 1.1
I 1.2 O
1.2 O X O O x
K 1.0 X O O O x
1 33~033
- 24 -
1 Examples 6 - 9
On the substrate paper used in ~xample 1, the
compositions shown below were used, following
otherwise the same procedure as in Example 1,
5 recording media L and M of the present invention were
obtained. Similarly, according to the same procedure
as in Example 3 except for using the compositions
shown below on the same substrate paper used in
Example 3, recording media N and O of the present
10 invention were obtained. Then, by use of the~e
recording media, recording was performed in the same
manner as in ~xample 1 and evaluation was performed.
The results are shown in Table 3.
~xample 6 Example 7 Example 8 Example g
L - M N O
Silica 8 7 8 7
(Syloid 620
Polyvinyl
alcohol 4 5 4 5
(PVA-117)
Water 100 100 100 100
Sizing
degree 4 6 5
- Z5 - l 33 3 03 3
~ o o o o
U~o o o o
~ . o o o o
al ~ O O O O
E~
~ o o o o
~ . . . .
,~ _, _, _,
., ~ ~ a) a
X X X X
