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Description  |
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BACKGROUND OF THE INVENTION
This invention relates to a coated type ink jet recording sheet. More
particularly, it relates to a coated type ink jet recording sheet for use
in an ink jet recording system that employs water-base ink, the sheet
exhibiting a high rate of absorption of the ink deposited on the recording
sheet so as to allow a clear color to develop, providing an image having
circular dots and sharply defined edges, having a high surface strength
and the same touch and feel during use as plain paper, and being able to
record images with high resolution that are water-proof.
The ink jet recording sheet of the present invention may be used in
recording, printing and writing employing water-base ink.
In order for an ink jet recording system to be able to produce high quality
recorded images, it is required that the substrate employed be such that
the ink deposited on the surface of the recording sheet which is composed
mainly of paper spreads to form a true circle and is absorbed quickly in a
controlled manner without becoming irregularly spread on the surface, and
that the surface structure be such as to promote coloration of the
deposited ink. Various proposals have so far put forward with a view to
realizing these requirements.
For example, Japanese Patent Publication (KOKOKU) No. 27588/1985 discloses
an ink jet recording paper wherein coating layer is applied with not less
than 1 to 5 g/cm.sup.2 of a binder to one surface of a substrate paper
having a Stockigt sizing degree of not more than 3 seconds such that ink
droplets deposited on the paper surface are quickly absorbed within the
interior of the sheet and spreading of the ink dots on the paper surface
is prevented.
However, when the Stockigt sizing degree of the substrate sheet is lowered
for this purpose, the water-proof quality of the deposited ink will be
inadequate and such phenomena as strike-through, irregular ink spreading
and inferior coloring will occur. In order that the capacity to absorb ink
may be improved to provide a higher ink absorption rate and that spreading
of the ink may be controlled so as to realize a dot shape close to a true
circle without adversely affecting the water-proof quality and the color
brightness, it is necessary to drastically increase the amount of coating
material coated on the substrate surface to a value not less than 10
g/m.sup.2. With a coating amount of not more than 10 g/m.sup.2, the dot
shape and coloration are not satisfactory and the dot size control that is
necessary for good quality image reproduction cannot be achieved. However,
if the coating amount is increased, the cost is raised and the feel of the
plain paper and its suitability for use and converting.
Non-coated type ink jet paper has recently become popular in view of its
suitability from the standpoint of cost, printing quality and adaptability
to use as office paper. It is known in regard to the production of such
ink jet paper for liquid-absorbing pigments such as silica or heavy
calcium carbonate to be added to the raw materials at the time of making
the paper. However, this type of ink jet paper presents certain problems
in that the ink may not develop sufficient color brightness when applied
to and absorbed by the paper on account of certain optical properties of
the pulp and filler customarily used so that clear coloration of a quality
comparable to that obtained when using coated paper is not attainable.
Furthermore spreading of the ink cannot be prevented and the ink
absorption rate and capacity are low.
For applications in which importance is attached to the brightness of color
images, a coated type of paper is employed which has a coating layer
consisting essentially of white pigments having superior water absorption
properties so that the above-described dot shape and color brightness can
be obtained.
In the absence of a specialized type of processing, it is impossible to
provide water-proof images if water-base ink is used with any of these
types of paper. For this reason, it is necessary to perform a
water-proofing operation using a cationic surfactant or cationic polymer.
However, the conventional water-proofing agents used for ink jet images,
such as polyethyleneimine and copolymers thereof (see, for example,
Japanese Patent Publication Nos. 120486/1982 and 129778/1982), have only
poor water-proofing ability and tend to lower the weatherability qualities
of the images formed. The provision of a coating of a water-soluble
polymer is disclosed in Japanese Patent Publication (KOKAI) No. 8685/1983,
while Japanese Patent Publication (KOKAI) No. 55283/1983 discloses use of
polyvinylpyrrolidone and hydroxyethyl cellulose. However, it has been
pointed out that the dot shape attainable in these cases is poor and the
surface strength inadequate, the weatherability properties also being
adversely affected. Japanese Patent Application (KOKAI) Nos. 20696/1984,
109894/1985 and 74880/1986 discloses the use of water-soluble metal salts
or cationic polymers, such as polydiallyl dimethyl ammonium chloride. This
approach is not satisfactory either, however, in that the degree of
water-proofing is insufficient and the weatherability properties and,
above all, the color fastness, are adversely affected.
It is thus an object of the present invention to provide a coated type
sheet for ink jet recording in an ink jet recording system employing a
water-base ink which not only allows the water-base ink to be absorbed
quickly within the surface region of the recording sheet, but also
provides for good ink image color brightness, the formation of ink dots
which are truely circular in shape and the diffusion of which is
inhibited, and the formation of sharp-tone images and allowing the
production of high-resolution images at high speeds, thereby overcoming
the deficiencies of the coated or filled type sheets of the prior art.
It is another object of the present invention to overcome the deficiencies
of the water-proofing agent used in the aforementioned prior art and to
provide a coated type ink jet recording sheet that offers superior image
quality and water-proofness.
The recording sheet of the present invention may be used in the same way as
other types of recording sheet with water-base ink employing pen plotters
or the like.
SUMMARY OF THE INVENTION
According to the present invention, there is provided an ink jet recording
sheet comprising a sheet-like substrate composed mainly of 70 to 100 wt%
of wood pulp and 0 to 30 wt% of precipitated calcium carbonate and having
a Stockigt sizing degree of not less than 2 seconds and not more than 25
seconds when formed in a sheet having a basis weight of 64 g/m.sup.2, and
a coating layer composed mainly of white pigment, said coating layer being
formed on at least one side of said substrate at a weight of 1 to 10
g/m.sup.2.
DETAILED DESCRIPTION OF THE INVENTION
Our studies have demonstrated that, in order to achieve a more balanced
capacity to exhibit high-speed absorptivity and color brightness with the
above described coated type of ink jet recording sheet, it is important to
use in combination a substrate sheet having a predetermined compositional
range and a coating layer formed from specific materials.
According to the present invention, the substrate consists essentially of
70 to 100 wt% of wood pulp and 0 to 30 wt% of precipitated calcium
carbonate.
The wood pulp employed in the present invention is preferably bleached pulp
obtained by bleaching the pulp that is produced when digesting natural
wood. The precipitated calcium carbonate to be added to the wood pulp
consists essentially of either calcite having a mean particle size ranging
from 1 to 5 .mu.m, a specific surface area ranging from 1 to 10 m.sup.2
/g, and oil absorption ranging from 30 to 50 ml/100 g, or of calcite not
less than 80% of the particles of which have a particle size as measured
by the natural precipitation method ranging between 0.5 and 1.5 .mu.m,
with a specific surface area of 10 to 30 m.sup.2 /g and oil absorption of
30 to 80 g/100 g.
The wood pulp and the precipitated calcium carbonate are formed into paper
in a ratio of 70 to 100 wt% wood pulp to 0 to 30 wt% precipitated calcium
carbonate. This compositional ratio is adapted in order to maximize the
effects derived from addition of calcium carbonate and to ensure uniform
ink absorption. If the content of wood pulp is lower than 70%, the
properties of the paper sheets such as sheet strength will be impaired. If
the content of precipitated calcium carbonate is more than 30%, the
inclusion of the additional precipitated calcium carbonate would not lead
to any further improvement. In addition, the surface strength of the sheet
and the color concentration would be lowered, the natural feel of the
paper would be lost, and paper dust would be generated to cause a lowering
of the paper quality.
A sheet that is devoid of precipitated calcium carbonate, that is,
consisting of 100 wt% of wood pulp, may also be employed as an ink jet
recording sheet. However, a precipitated calcium carbonate content of 10
to 25 wt% provides the most desirable results and hence is most suitable.
It is noted that synthetic pulp and synthetic fibers having a high degree
of whiteness may also included if used in a minor amount of not more than
about 10%. The same may be said of precipitated calcium carbonate. It is
thus possible to add about 10% of other white pigments, such as ground
calcium carbonate, natural or synthetic zeolex, Kaolin clay, talc,
diatomaceous earth, aluminium hydroxide, titanium dioxide or plastic
pigment, depending upon the properties required such as paper quality and
the overall cost.
It is also possible to use various additives commonly used in paper making,
such as a dry-strength resins agent, retention aid, wet strength resins
and dyestuffs. The sheet preferably has a thickness ranging between 20 and
200 .mu.m, more preferably between 50 and 150 .mu.m, and a basis weight
ranging between 20 and 180 g/m.sup.2, more preferably between 50 and 100
g/m.sup.2.
It is essential that the Stockigt sizing degree of the substrate sheet
having a basis weight of 64 g/m.sup.2 is 2 to 25 seconds. With a Stockigt
sizing degree lower than 2 seconds, not only are the water-proofing
properties lowered, but also print through will take place and a tendency
for irregular spreading of the ink may result. In order to provide ink
absorptivity with a high ink absorption capacity and rate and to control
the spreading of ink so that the formation of ink dots close in shape and
that of a true circle can be realized, it is necessary to drastically
increase the volume of coating on the substrate sheet surface. However, a
coating weight of not more than 10 g/m.sup.2 leads poor quality in terms
of both dot shape and coloration, and additionally the dot size tends to
become more difficult to control. On the other hand, with a Stockigt
sizing degree (basis weight: 64 g/m.sup.2) of not less than 25 seconds, it
is frequently difficult to provide ink absorptivity at a high ink
absorption capacity and rate and to control the extent to which ink
spreads so as to realize an ink dot shape that is close to a true circle
unless the coating weight is increased to at least 10 g/m.sup.2. It is
therefore essential in the present invention for the Stockigt sizing
degree of the sheet having a basis weight of 64 g/m.sup.2 to be in the
range of from 2 to 25 seconds.
The coating layer consisting essentially of white pigment is applied to one
or both sides of the sheet-like substrate at a weight of 1 to 10
g/m.sup.2, preferably 2 to 8 g/m.sup.2. The coating weight is in the range
of from 1 to 10 g/m.sup.2. In the present invention, the Stockigt sizing
degree of the sheet having the basis weight of 64 g/m.sup.2 is 2 to 25
seconds, and the coating weight may thus be in the range of from 1 to 25
g/m.sup.2. However, in order to provide adequate surface strength and a
satisfactory appearance and at the same time to keep costs low, suitable
results can be achieved by setting the coating weight to be no more than
10 g/m.sup.2 in order to produce a highly adaptable sheet.
A bright white color pigment having high oil-absorption and a high specific
surface area is preferred as the white pigment to be employed in the
coating layer of the present invention. Above all, such preferred pigment
should be composed of fine particles of silica having a specific surface
area in the range of from 200 to 400 m.sup.2 /g and mainly composed of
particles having a secondary particle size in the range of from 2 to 10
microns. Other white pigments may also be employed, depending on the
particular application. Examples of such white color pigments include the
pigments commonly used in coated paper sheets, such as precipitated and
ground calcium carbonates, natural or synthetic zeolex, Kaolin clay,
aluminium hydroxide, titanium dioxide and plastic pigments. These white
pigments are preferably employed in an amount of not more than 50%.
The white pigments are usually contained in an amount consisting of 50 to
80 wt% of the coating layer.
A water-soluble polymer is preferably used to provide at least a portion of
the adhesive properties of the coating layer. Also, a cationic polymer is
preferably used as the image water-proofing agent.
In addition, a silanolated vinylalcohol polymer and/or a cationic
vinylacetate copolymer may also be contained in the coating layer for good
results.
Silanolated vinylalcohol copolymers exhibit excellent film-forming
properties and a coating containing the same is transparent and tough and
acts as a superior barrier, and the thick aqueous solution exhibits
sol-gel thixotropy, depending or the pH and the temperature, and also
exhibits superior adhesion to glass and alumina. The copolymer to be
employed preferably has a polymerization degree of 1,700 and a low
silicate content. Any other silanolated vinylalcohol copolymer, such as
that having a polymerization degree of 500 to 1,500 and a high silicate
content may be employed in accordance with the intended usage. The
silanolated vinylalcohol copolymer is preferably contained in an amount of
10 to 40 wt% of the coating layer since then the adhesive power and the
adsorptivity are counterbalanced with respect to each other.
The cationic vinylacetate copolymer emulsion is a polyvinylacetate emulsion
with cationicity that may be imparted in various ways. This cationic
vinylacetate copolymer emulsion is preferably contained in an amount of 10
to 40 wt% of the coating layer to achieve the ink absorptivity and the
adhesive power.
The water-soluble cationic polymer is preferably added to the coating layer
also for the purpose of water-proofing the image. To this end, transparent
aqueous solution of an acrylamide-dimethyl diallyl ammonium chloride
copolymer, having a mean molecular weight of approximately 140,000 to
160,000 and a pH of 2 to 9, is most preferred. However, other
water-soluble cationic polymers, such as polyethyleneimine and copolymers
thereof, may also be employed.
Acrylamide-dimethyl diallyl ammonium chloride copolymer, which may be
employed as the water-proofing agent in accordance with the present
invention, is a copolymer having the following structural formula:
##STR1##
wherein x is 0.5 to 0.05, y is 0.5 to 0.95 and n is 20 to 2,000.
Preferably, y is in the range of from 0.7 to 0.9 and n is in the range of
from 100 to 200. This polymer may be obtained by polymerizing an acrylic
acid amide
##STR2##
and a dimethyl diallyl ammonium chloride having the formula:
##STR3##
using light or using a radical polymerization catalyst. This polymer is
generally a transparent liquid having a mean polymerization degree of
about 140,000 to 160,000 and has a specific gravity of 1.00 to 1.10, a pH
of 2 to 9 and an intrinsic viscosity size at 30.degree. C., N/10 NaCl in
the range of 1.60 to 2.00.
The amount of copolymer contained in the coating layer is preferably in the
range from 3 to 30%, more preferably in the range from 5 to 11%.
It is to be noted that the sheet is preferably smoothed by a machine
calendar or super calendar to a Bekk smoothness of not less than 50
seconds, since a sheet having good surface smoothness is required in ink
jet printers.
The water-base ink recording sheet of the present invention is capable of
imparting water-proofness to the image formed by the aqueous ink and is
superior in regard to both ink absorptivity and dot shape when the ink is
used in an ink jet printer, so that a full-color ink jet printer having
high image resolution and free from the deficiencies of the prior art may
be provided by using the ink of the present invention.
EXAMPLE 1
Calcite in the form of hexagonal prisms (precipitated calcium carbonate,
with not less than 80% of the particles having a particle size in the
range of from 0.5 to 1.5.mu.; a specific surface area of 80 ml/100 g; oil
absorption of 80 ml/100 g (Albafil produced by Pfiser Corporation) was
used as the filler. Fifteen parts of this filler was added to 100 parts of
bleached hardwood kraft pulp (brightness, 91%) with water added thereto
and the mixture was subjected to high speed dispersion and mixing followed
by beating. Additives comprising 1 part cationic starch, 0.05 parts of a
neutral sizing agent (Fibran 81, produced by Oji National Co.), 0.5 parts
of urea formalin resin and 0.002 parts of Methyl Violet Blue were added.
The resulting mixture was diluted with water to produce a paper-making
material having a concentration of 0.03%.
Using a multi-cylinder Fourdrinier paper machine, the material was formed
into high quality paper having a basis weight of 64 g/m.sup.2 to produce a
substrate for ink jet recording having a brightness of 92%, an ash content
of 11.4% and a Stockigt sizing degree of 15 seconds. A layer of Coating 1
(see below) was formed on the substrate at a weight of 2 g/m.sup.2, and
was then dried and smoothed by a super-calendar to produce an ink jet
recording sheet. The Bekk smoothness was 110 seconds.
______________________________________
Pigment: Fine silica particles (Finesil
produced by the Tokuyama Soda Co.,
Ltd.) - 100 parts;
Binder: Polyvinylalcohol (PVA-105, produced
by Kuraray) - 50 parts:
Cationic Polymer:
Polyethyleneimine quaternary ammonium
salts - 20 parts;
Dispersant: Sodium polyacrylate - 1 part
______________________________________
EXAMPLE 2
Following the same procedure as that taken in Example 1 and using the same
paper-making material except for using star-shaped calcite as the
precipitated calcium carbonate, a substrate having a basis weight of 64
g/m.sup.2 and a Stockigt sizing degree of 8 seconds was produced. Coating
1 was applied to the substrate at a weight of 5 g/m.sup.2, in the same way
as in Example 1, and was dried and smoothed by a super calendar to produce
an ink jet recording sheet having a coating layer. The Bekk smoothness was
110 seconds.
EXAMPLE 3
A high quality paper sheet having a basis weight of 65 g/m.sup.2,
brightness of 92% and a Stockigt sizing degree of 15 seconds and
containing calcite-type precipitated calcium carbonate (Albaglos, Pfizer
Inc.) as a filler was used as the substrate paper.
Coating 2 (see below) was applied on this substrate paper at a weight of 2
g/m.sup.2, and then dried and smoothed by a calendering machine to produce
a coated ink jet recording paper sheet without any pigment. The Bekk
smoothness was 55 seconds.
______________________________________
Coating 2
______________________________________
Polyvinylalcohol (PVA-217, produced by Kuraray
Co.) - 100 parts of a copolymer of 50 mol % of
acrylamide and 50 mol % of diallyl dimethyl
ammonium chloride (PAS-J-11, produced by Nittobo
Co.) - 20 parts
______________________________________
EXAMPLE 4
Calcite based precipitated calcium carbonate having a mean particle size
ranging from 1 to 5 microns, a specific surface area ranging from 1 to 10
g/m.sup.2 and oil absorption 30 to 50 ml/100 g (produced by Shiraishi
Kogyo Co.) was added as a filler to 100 parts of bleached hardwood kraft
pulp (brightness, 91%). To the resulting mixture were added 1 part of
cationic starch, 0.05 parts of a neutral sizing agent (Fibran 81, produced
by Oji National Co.), 0.5 parts of a urea formalin resin and 0.002 parts
of Methye Violet Blue, and the resulting mass was formed into a high
quality paper sheet having a basis weight of 64 g/m.sup.2, using a
multi-cylinder Fourdrinier paper machine in the conventional manner to
produce a substrate 1 having a whiteness degree of 92%, an ash content of
15.0% in the form of calcium carbonate and a Stockigt sizing degree of 5
seconds. Coating 3 (see below) was applied to the substrate at a weight of
5 g/m.sup.2, and was dried and smoothed by a super calender to a Bekk
smoothness degree of 110 seconds to produce an ink jet recording sheet.
______________________________________
Coating 3
______________________________________
Fine particles of silica (Finesil, produced by
Tokuyama Soda Co.) - 100 parts;
Polyvinylalcohol (PVA - 117, produced by Kuraray
Co.) - 30 parts;
Dispersant: Sodium polyacrylate - 1 part
______________________________________
EXAMPLE 5
Coating 4 was applied on the substrate of the preceding Example 4 at a
weight of 5 g/m.sup.2, and was dried and smoothed by a super calender to
produce a coated ink jet recording sheet. The Bekk smoothness degree was
110 seconds.
______________________________________
Coating 4
______________________________________
Fine particles of silica (Finesil, produced by
Tokuyama Soda Co.) - 100 parts;
Vinylalcohol copolymer (R-1130, produced by
Kuraray Co.) - 20 parts;
Cationic vinylacetate copolymer (IE 501 K-4) -
30 parts;
Cationic water-soluble polymer (polyethyleneimine
quaternary ammonium salt) - 20 parts;
Dispersant: Sodium polyacrylate - 1 part
______________________________________
EXAMPLE 6
A substrate was formed using the same procedure as that employed in Example
4 and using the same paper-making material except that the calcite used as
the precipitated calcium carbonate was such that not less than 80% of the
particles ranged in size from 0.5 to 1.5 .mu.m and the specific surface
area thereof was 1 to 20 g/m.sup.2 and the oil absorption 10 to 80 ml/100
g (Albafil, produced by Pfizer Inc.). In this way a substrate having a
Stockigt sizing degree of 10 seconds was obtained. Coating 5 was applied
to this substrate at a weight of 5 g/m.sup.2, and was dried and smoothed
by a super calender to produce a coated ink jet recording sheet. The Bekk
smoothness was 110 seconds.
______________________________________
Coating 5
______________________________________
Pigment: Fine particles of silica (Mizukasil,
produced by Mizusawa Kagaku Co.) -
100 parts;
Binder: Polyvinylalcohol copolymers (R-1130,
produced by Kuraray Co. - 30 parts and
PVA-217, produced by Kuraray Co. -
10 parts);
Cationic with vinylacetate copolymer (Yodozol,
Kanebo NSC) - 30 parts;
Water-soluble cationic polymer (acrylamide -
dimethyl diallyl ammonium chloride
copolymer) - 20 parts;
Dispersant:
Sodium polyacrylate - 1 part
______________________________________
COMPARATIVE EXAMPLE 1
Using the same material and procedure as in Example 1, except that 0.02
parts of a neutral sizing agent (Fibran 81, Oji National Co.) was added as
the additive at the time of adding the filler to the ordinary bleached
hardwood kraft pulp, which was subjected to high speed dispersion and
mixing followed by beating, an ink jet recording substrate having a basis
weight of 64 g/m.sup.2 was produced. The substrate had a whiteness degree
of 92%, an ash content of 11.6% and a Stockigt sizing degree of not more
than one second. Coating 1 was applied to this substrate at a weight of 2
g/m.sup.2, and was dried and smoothed by a super calender to produce an
ink jet recording sheet. The Bekk smoothness degree was 100 seconds.
COMPARATIVE EXAMPLE 2
Using the same method as in Comparative Example 1, except that 0.15 parts
of the neutral sizing agent (Fibran 81, produced by Oji National Co.) was
added, a substrate for ink jet recording having a basis weight of 64
g/m.sup.2, a brightness of 92%, an ash content of 11.0% and a Stockigt
sizing degree of 30 seconds was produced. Coating 1 was applied to this
substrate at a weight of 2 g/m.sup.2, and was dried and smoothed by a
super calender to produce a sheet for ink jet recording. The Bekk
smoothness was 120 seconds.
COMPARATIVE EXAMPLE 3
Coating 6 was applied on the high quality paper of Example 3, which acted
as the substrate paper, at a weight of 12 g/m.sup.2, and was dried and
smoothed by a super calender to produce a sheet for ink jet recording. The
Bekk smoothness was 100 seconds.
______________________________________
Coating 6
______________________________________
Pigment: Fine particles of Silica (Finesil,
produced by Tokuyama Soda Co.) -
100 parts;
Binder: Polyvinylalcohol (R-2105 produced by
Kuraray Co. - 10 parts and PVA-105
produced by Kuraray Co. - 50 parts);
Water-proofing agent:
Polyethyleneimine -
10 parts;
______________________________________
COMPARATIVE EXAMPLE 4
Coating 7 was applied on the high quality paper of Example 3, and was dried
and smoothed by a super calender to produce a sheet for ink jet recording.
The Bekk smoothness was 100 seconds.
______________________________________
Coating 7
______________________________________
Pigment: Fine particles of silica (Fine Seal
produced by Tokuyama Soda Co.) -
100 parts;
Binder: Polyvinylalcohol (R-2105, produced by
Kuraray Co. - 10 parts and PVA-105,
produced by Kuraray Co. - 50 parts);
Water-proofing agent:
Dimethyl diallyl ammonium
chloride (PAS-H-35S, produced by
Nittobo Co.) - 10 parts
______________________________________
COMPARATIVE EXAMPLE 5
Following the same procedure as in Example 4 except for using 0.20 parts of
neutral sizing agent, a substrate having a basis weight of 64 g/m.sup.2
and a Stockigt sizing degree of 30 seconds was produced. Coating 4 was
applied in the same way as in Example 4 at a weight of 5 g/m.sup.2, and
was dried and smoothed by a super calender to produce a coated ink jet
recording sheet. The Bekk smoothness was 110 seconds.
The results of evaluation of the ink jet recording sheets for all these
cases are shown in Table 1, wherein the symbols .circleincircle., o,
.DELTA. and x indicate the quality in decreasing order. x stands for the
worst case in which the sheets were found to be unusable.
TABLE 1
______________________________________
Coating Ink Color Water
amount absorp- bright-
Dot proof-
Surface
No. (g/m.sup.2)
tivity ness shape ness strength
______________________________________
Ex. 1 2 .circle. .circleincircle.
.circleincircle.
.circleincircle.
2 5 .circleincircle.
.circle.
.circle. .circleincircle.
3 2 .circle. .circle.
.DELTA.
.circleincircle.
4 5 .circle. .circle.
.circle. .circle.
5 5 .circleincircle.
.circle.
.circleincircle.
.circleincircle.
6 5 .circleincircle.
.circleincircle.
.circleincircle.
.circleincircle.
Comp.
Ex. 1 2 .DELTA. X .DELTA. .circle.
2 2 X X X .circle.
3 12 .DELTA. .DELTA.
.DELTA.
.DELTA.
4 .uparw. .circle. .circle.
.DELTA.
.circle.
5 5 X .DELTA.
.DELTA. .circle.
______________________________________
Method of Evaluation of Recording Properties
The ink jet recording properties of the above-described coatings were
evaluated by practical use in a commercially available ink jet printer and
with respect to ink absorptivity, color brightness and the shape of the
recording dots formed.
In evaluating ink absorptivity, the time in seconds taken for ink smudging
on the printed portion to dry was measured and compared.
In evaluating the dot shape, printed dots formed on the paper sheet being
tested by an ink jet printer were measured and observed through a
microscope. The marks .circleincircle., o, .DELTA. and x indicate how
close to a true circle the observed dot shapes were in decreasing order of
quality.
In evaluating water-proofness, the printed images were dipped in flowing
water for five minutes and then dried. The marks .circleincircle., o,
.DELTA. and x denote the degree to which the printed image disappeared,
with the marks .circleincircle. and x respectively indicating images which
remain unchanged after drying and those which almost completely disappear.
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