[0001] This invention concerns an ink fusion transfer type of paper, and more specifically,
a paper suitable for ink fusion transfer type thermal printers and copiers.
[0002] Smooth, high grade recording paper which has been treated by a Super Calendar or
the like is used in ink fusion transfer type thermal printers or copiers as it is
known to give a clear image. This is particularly true if the recording surface has
a smoothness of 100 seconds or more. By making the paper smoother so that there is
better contact between the paper and the ink ribbon, more ink is transferred to the
paper surface. As a result, reproduction of full tone images is improved, however
reproduction of half tone images is unsatisfactory.
[0003] At present, coated paper having a high smoothness and gloss is generally not used
in ink fusion transfer type thermal printers and copiers. The reason for this is that
although the paper is extremely smooth so that there is uniform contact with the ink
ribbon, which might be expected to give a good ink copy, transfer of ink actually
takes place unevenly and image reproduction is poor.
[0004] Non-uniform transfer of ink is particularly evident in the case of smooth, high gloss
art paper for printing and in the case of cast-coated paper. This is due to the fact
that, as there are very few surface imperfections or cavities, molten ink does not
easily stay on the paper and may be retransferred from the paper back to the ink ribbon.
[0005] Therefore, although coated paper for printing is designed to be adequate for ordinary
printing applications, it is not suitable for ink fusion transfer type thermal printers
and copiers.
[0006] If these problems inherent in coated printing paper could be resolved, it would be
possible to use it for such printers and copiers, and images of higher quality than
ever before might be obtained.
[0007] In general, in order to confer high surface smoothness on coated paper, the surface
is flattened under high pressure using a Super Calendar or similar device. This paper
is not as tough as high grade paper, and since it is very dense, it lacks the feeling
of volume. In addition, the paper has a low gloss so that there is a very poor balance
with the gloss of the image area, and a high image quality comparable to that of ordinary
offset printing cannot be obtained.
[0008] The inventors, after performing various studies aimed at resolving the aforesaid
problems, found that by incorporating a minimum amount of a synthetic silica having
a predetermined specific surface in the paper, good results could be achieved with
coated paper manufactured by cast coating.
[0009] It is therefore an object of this invention to provide a coated paper which not only
gives excellent image reproduction when used in ink fusion transfer type thermal printers
and copiers, but which also has a high gloss in both the non-image and image parts.
[0010] It is a further object of this invention to provide a method of manufacturing a coated
paper that can be used in ink fusion transfer type thermal printing applications.
[0011] The aforesaid objectives of the invention are attained by an ink fusion transfer
paper having a recording layer comprising at least one layer on a support, this paper
being characterized in that the uppermost layer of the recording layer consists of
at least 100 parts by weight of a pigment and 10 - 50 parts by weight of a binder,
the layer being applied to one or both sides of the support at a rate of 5 - 50 g/m²
per side in terms of dry solids, 30 - 100 weight percent of the aforesaid pigment
consists of a synthetic silica having a specific surface of 20 - 600 m²/g, and the
75 degree gloss of the aforesaid uppermost layer of the paper is no less than 50%.
[0012] The synthetic silica used in this invention is generally referred to as non-crystalline
silica, amorphous silica, anhydrous silicic acid, hydrated silicic acid, finely powdered
silica or white carbon. Its structure is based on a Si-O net, and it is a silicic
acid with no fixed crystalline form. From the viewpoint of transferability of molten
ink, it is preferable that the synthetic silica used should have a specific surface
of 20 - 600 m²/g, and particularly preferable that it lies within the range 20 - 300
m²/g. If the specific surface is greater than 600 m²/g or less than 20 m²/g, the reproducibility
of half tone images declines although the reason for this is unclear.
[0013] The synthetic silica used in this invention may be prepared by the wet method, dry
method or aerogel method, there being no particular limitation on the method of preparation.
[0014] In this invention, the blending proportion of synthetic silica in the coating solution
is 30 - 100 parts by weight with respect to 100 parts of pigment. If this blending
proportion is less than 30 parts by weight (i.e. less than 30 weight %), transfer
of molten ink to the recording layer is unsatisfactory and reproducibility of half
tone images is particularly impaired.
[0015] There is no particular limitation on the type of pigment that can be used together
with the aforesaid synthetic silica. Examples of suitable pigments are inorganic pigments,
e.g. kaolin, clay, heavy calcium carbonate, light calcium carbonate, aluminum hydroxide,
satin white, titanium dioxide, fired clay, zinc oxide, barium sulfate, talc, and colloidal
silica, and organic pigments, e.g. fine particles of styrene rest such as polystyrene
or polymethylstyrene, fine particles of acrylic resins such as polymethylmethacrylate
and polyacrylonitrile, and fine particles of polyvinyl chloride or polycarbonates.
These pigments may also be used in conjunction with each other in any desired proportion.
[0016] Of the organic pigments, fine particles of styrene resins, acrylic resins or styrene-acrylic
copolymer resins are preferable from the viewpoint of hardness, elasticity and heat
resistance. In particular, if fine hollow particles of polystyrene or styrene-methylmethacrylate
copolymer are used, it is easier to achieve smoothness of the coated surface and the
density of the coated layer can be effectively reduced.
[0017] The binder may be a resin, emulsion, latex or natural high polymer which gives a
strong adhesion between the pigment and raw paper, and which does not cause blocking
between papers or between the paper and ink ribbon, these materials being used either
alone or in conjunction with one another.
[0018] Examples of such binders are polyvinyl alcohol or starches such as starch oxide,
starch esters, enzyme-modified starch and cationic starch, casein, soy proteins, fiber
derivatives such as carboxymethyl cellulose and hydroxyethyl cellulose, styrene-acrylic
resins, styrene-butadiene resins, vinyl acetate resins and acrylic resins.
[0019] The blending proportion of the binder in the coating solution composition is preferably
10 - 50 parts by weight with respect to 100 parts by weight of pigment. If the blending
proportion of binder is less than 10 parts by weight, the strength of the coating
film declines, and if the proportion is greater than 50 parts by weight, the properties
of the coating are adversely affected.
[0020] To the coating, dyes or colored pigments may also be added to adjust color, and fluorescent
dyes may be added to improve visual whiteness.
[0021] The coating containing the aforesaid components may easily be prepared by any of
the methods known in the art. Also known additives such as dispersing agents, antifoaming
agents, release agents, pH regulating agents, lubricants, water retention agents and
preservatives may also be added to the aforesaid coating to the extent that they do
not impair the advantage of the invention.
[0022] In this invention, the coating solution prepared as described hereintofore is coated
on a support to be used as a recording layer. If the surface of paper coated with
this solution is simply smoothed by a Super Calendar (Tokkai-sho(nonexamined published
Japanese patent application) 62-198876), however, the paper is not tough enough, sufficient
paper gloss is not obtained, and it is difficult to transport the paper inside the
printer or copier due to the paper's lack of toughness. Further, transferability of
ink declines so that a good image is not obtained, and the balance between the gloss
of the paper in the image and non-image parts is extremely poor.
[0023] If a coated layer is formed by cast coating the aforesaid coating solution on the
paper, on the other hand, paper strength is not impaired, extremely high paper gloss
is achieved and the thermal transfer paper of this invention is easily obtained, although
no definite reasons for this have been given.
[0024] The specific surface of the pigment used in paper coatings is generally 2 - 3 g/m²
and no greater than 10 m²/g. On the other hand, the specific surface of the synthetic
silica used in this invention is 20 - 600 m²/g. This is far greater than that of pigments
commonly used, and it leads to the following inferences.
[0025] In a coated layer produced by cast coating, the synthetic silica of high specific
surface is incorporated in the recording layer without undergoing any modification
which thus gives rise to a very large number of cavities. It may be conjectured that
this results in better transferability of ink, absorption of molten ink by the cavities
so that image surface imperfections are reduced, and reduction of surface scattering
reflections so that image gloss is heightened.
[0026] A single or multiple coating is applied by either an on-line or an off-line coater
to one or both sides of the paper such that the dry weight of coating on each side
is 5 - 50 g/m², and preferably 8 - 30 g/m². If the amount of coating is less than
5 g/m², the film on the surface of the raw paper is insufficient so that a high paper
gloss cannot be obtained, while if it is greater than 50 g/m², the paper density increases
so that it becomes less tough, paper transport is problematic and the paper loses
its function as a printing and copying paper.
[0027] The cast coating method used may be any suitable method known in the art such as
solidification, rewetting or wetting, providing using a casting drum having a mirror
surface.
[0028] There is no particular limitation on the coating technique employed to obtain the
recording layer, it being possible to use any ordinary coating technique such as blade
coating, roller coating, air knife coating and bar coating.
[0029] The solidifying agent used in cast coating by solidification is commonly formic acid,
acetic acid, succinic acid, tartaric acid, lactic acid, hydrochloric acid, calcium,
zinc, barium, lead, magnesium, cadmium or aluminum sulfates, potassium sulfate, potassium
succinate, borax or boric acid, however this invention is not limited to only these
substances. Further, the choice of a suitable binder which solidifies well together
with these solidifying agents is effective in improving coating speed and the finish
of the coated surface.
[0030] The raw paper may be an acid or neutral high or medium grade paper. For coating purposes,
however, it is preferable that the paper be prepared by known methods of raw paper
blending, preparation and manufacture (Tokkai Sho 55-47385).
[0031] As described hereintofore, the ink fusion transfer paper of this invention has an
extremely high gloss, allows good ink transfer and gives an excellent image gloss.
It therefore offers a good paper/image gloss balance, a high quality image, and is
particularly suitable as a paper for ink fusion transfer type thermal printers and
copiers.
EXAMPLES
[0032] This invention will now be described in more detail by means of the following examples,
but it is to be understood that it is not limited by them in any way. All parts given
in the examples are parts by weight.
[0033] The measurements in the examples were performed as follows:
(1) Density: Measured according to the method of JIS P8118.
(2) Smoothness: Measured according to the method of JIS P8119.
(3) Gloss: The 75° gloss of the coated surface was measured according to the method
of JIS P8142.
(4) Image gloss: Patterns having a half tone dot surface proportion of 25%, 50% and
100% respectively were recorded using a Mitsubishi Color Thermal Printer M4234-10,
and the gloss of each pattern was measured.
(5) Image reproducibility test: Ink transfer performance in the 25% half tone dot
pattern was judged visually.
[0034] If the pattern was uniformly recorded, it was graded by " ○", if some parts were
missing it was graded by "△", and if practically no ink had been transferred it was
graded by "X". (6) Coating strength: Using an IGT Print Suitability Tester (IGT A-1type
machine manufactured by IGT K.K.), an ink tack of 10, ink volume of 0.025 cc and print
speed of 1.2 m/sec, patterns where none of the ink that had been transferred came
off were graded by "○", patterns where some of the ink came off were graded by "△"
and patterns where all the ink came off were graded by "X".
EXAMPLE 1
[0035] 10 parts heavy calcium carbonate, 1 part cationic starch and 0.1 parts of a sizing
agent (alkyl ketene dimer) were blended with 100 parts of a bleached broadleaf tree
kraftpulp slurry of beating degree 400 cc (L-BKP) so as to make a raw paper of weighting
92 g/m².
[0036] A coating solution containing 43% dry solids was also prepared from 80 parts synthetic
silica (commercial name: Syloid 404, Fuji Davison K.K., specific surface 300 m²/g)
and 20 parts primary grade kaolin (commercial name: Ultrawhite 90, E.M.C. K.K.) as
pigments, 5 parts styrene butadiene latex and 5 parts casein as binders, and 2 parts
calcium stearate as a release agent.
[0037] After applying the coating solution obtained to the aforesaid raw paper by means
of a roll coater at a rate of 10 g/m² in terms of dry solids, the coating was solidified
using a 10% aqueous solution of zinc formate as solidifying agent, and while the coating
film was still wet, it was dried in pressure contact with a casting drum having a
mirror surface heated to 100°C. An ink fusion transfer thermal paper of weighting
102 g/m² was thus obtained.
EXAMPLE 2
[0038] A coating solution containing 42% dry solids was prepared from 80 parts synthetic
silica (commercial name: Syloid 404, Fuji Davison K.K., specific surface 300 m²/g)
and 20 parts primary grade kaolin (commercial name: Ultrawhite 90, manufactured by
E.M.C. K.K.) as pigments, 15 parts styrene butadiene latex and 15 parts casein as
binders, and 2 parts calcium stearate as a release agent.
[0039] The coating solution obtained was applied to the raw paper of Example 1 (92 g/m²)
by means of a roll coater in the same manner as that of Example 1, excepting that
the application rate was 15 g/m² in terms of dry solids. An ink fusion transfer thermal
paper of weighting 107 g/m² was thus obtained.
EXAMPLE 3
[0040] A coating solution containing 46% dry solids was prepared from 100 parts synthetic
silica (commercial name: Mizukasil P-527, Mizusawa Industrial Chemicals K.K., specific
surface 30 m²/g) as a pigment, 20 parts styrene butadiene latex and 20 parts casein
as binders, and 2 parts calcium stearate as a release agent.
[0041] The coating solution obtained was applied to the raw paper of Example 1 by means
of a roll coater such that the application rate was 10 g/m² in terms of dry solids
in the same manner as that of Example 1. An ink fusion transfer thermal paper of weighting
102 g/m² was thus obtained.
EXAMPLE 4
[0042] The synthetic silica used in Example 3 was replaced by a pigment having a specific
surface of 600 m²/g (commercial name: Syloid 600, Fuji Davison K.K.), 23 parts styrene
butadiene latex and 20 parts casein added as binders, then 2 parts calcium stearate
added as a release agent so as to obtain a coating solution containing 40% solids.
The coating solution obtained was applied to the raw paper of Example 1 by means of
a roll coater in the same manner as that of Example 1 excepting that the application
rate was 5 g/m² in terms of dry solids.
[0043] An ink fusion transfer thermal paper of weighting 97 g/m² was thus obtained.
EXAMPLE 5
[0044] A coating solution containing 54% dry solids was prepared from 30 parts synthetic
silica (commercial name: Syloid 404, Fuji Davison K.K., specific surface 300 m²/g),
40 parts primary grade kaolin (commercial name: Ultrawhite 90, E.M.C. K.K.) and 30
parts calcium carbonate (commercial name: Brilliant 15, Shiraishi K.K.) as pigments,
15 parts styrene butadiene latex and 10 parts casein as binders, and 2 parts calcium
stearate as a release agent.
[0045] The coating solution obtained was applied to the raw paper of Example 1 (92 g/m²)
by means of a roll coater in the same manner as that of Example 1, excepting that
the application rate was 12 g/m² in terms of dry solids. An ink fusion transfer thermal
paper of weighting 104 g/m² was thus obtained.
EXAMPLE 6
[0046] 10 parts heavy calcium carbonate, 1 part cationic starch and 0.1 parts of a sizing
agent (alkyl ketene dimer) were blended with 100 parts of a bleached broadleaf tree
craftpulp slurry of beating degree 400 cc (L-BKP) so as to make a raw paper of weighting
69 g/m².
[0047] A coating solution containing 55% dry solids was also prepared from 30 parts synthetic
silica (commercial name: Syloid 404, Fuji Davison K.K., specific surface 300 m²/g)
40 parts primary grade kaolin (commercial name: Ultrawhite 90, E.M.C. K.K.) and 20
parts calcium carbonate (commercial name: Brilliant 15, Shiraishi K.K.) as pigments
together with 10 parts of an organic pigment (commercial name: Boncoat PP-1100, Dai
Nippon Kagaku K.K.), 15 parts styrene butadiene latex and 15 parts casein as binders,
and 2 parts calcium stearate as a release agent.
[0048] The coating solution obtained was applied to the aforesaid raw paper by means of
a roll coater as in Example 1, excepting that the rate of application was 40 g/m²
in terms of dry solids. An ink fusion transfer thermal paper of weighting 109 g/m²
was thus obtained.
COMPARATIVE EXAMPLE 1
[0049] A coating solution was applied to a raw paper by means of a roll coater exactly as
in Example 1, excepting that the application rate was 3.5 g/m² in terms of dry solids.
An ink fusion transfer thermal paper of weighting 95.5 g/m² was thus obtained.
COMPARATIVE EXAMPLE 2
[0050] A coating solution was prepared exactly as in Example 5 excepting that 2 parts butadiene
styrene latex and 2 parts casein were used as binders, and 2 parts calcium stearate
was used as a release agent. The resulting solution contained 50% of dry solids. This
coating solution was applied to the raw paper of Example 1 by means of a roll coater
exactly as in Example 1, excepting that the rate of application was 12 g/m² in terms
of dry solids. An ink fusion transfer thermal paper of weighting 104 g/m² was thus
obtained.
COMPARATIVE EXAMPLE 3
[0051] A coating solution was prepared exactly as in Example 5 excepting that 30 parts butadiene
styrene latex and 30 parts casein were used as binders, and 2 parts calcium stearate
was used as a release agent. The resulting solution contained 50% of dry solids. This
coating solution was applied to the raw paper of Example 1 by means of a roll coater
exactly as in Example 1, excepting that the rate of application was 20 g/m² in terms
of dry solids. An ink fusion transfer thermal paper of weighting 112 g/m² was thus
obtained.
COMPARATIVE EXAMPLE 4
[0052] A coating solution containing 58% dry solids was prepared from 5 parts synthetic
silica (commercial name: Syloid 404, Fuji Davison K.K., specific surface 300 m²/g),
40 parts primary grade kaolin (commercial name: Ultrawhite 90, E.M.C. K.K.) and 55
parts calcium carbonate (commercial name: Brilliant 15, Shiraishi K.K.) as pigments,
15 parts styrene butadiene latex and 10 parts casein as binders, and 2 parts calcium
stearate as a release agent.
[0053] This coating solution was applied to the raw paper of EXAMPLE 1 by means of a roll
coater exactly as in EXAMPLE 1, excepting that the rate of application was 15 g/m²
in terms of dry solids. An ink fusion transfer thermal paper of weighting 107 g/m²
was thus obtained.
COMPARATIVE EXAMPLE 5
[0054] A coating solution containing 58% dry solids was prepared from 25 parts synthetic
silica (commercial name: Syloid 404, Fuji Davison K.K., specific surface 300 m²/g),
40 parts primary grade kaolin (commercial name: Ultrawhite 90, E.M.C. K.K.) and 35
parts calcium carbonate (commercial name: Brilliant 15, Shiraishi K.K.) as pigments,
15 parts styrene butadiene latex and 15 parts casein as binders, and 2 parts calcium
stearate as a release agent.
[0055] This coating solution was applied to the raw paper of Example 1 by means of a roll
coater exactly as in Example 1, excepting that the rate of application was 15 g/m²
in terms of dry solids. An ink fusion transfer thermal paper of weighting 107 g/m²
was thus obtained.
COMPARATIVE EXAMPLE 6
[0056] A coating solution was applied to a raw paper by means of a roll coater exactly as
in Example 1, excepting that the application rate was 60 g/m² in terms of dry solids.
An ink fusion transfer thermal paper of weighting 129 g/m² was thus obtained.
COMPARATIVE EXAMPLE 7
[0057] A coating solution containing 60% dry solids was prepared from 30 parts synthetic
silica (commercial name: FK 700, Degusa K.K., specific surface 700 m²/g), 40 parts
primary grade kaolin (commercial name: Ultrawhite 90, E.M.C. K.K.) and 30 parts calcium
carbonate (commercial name: Brilliant 15, Shiraishi K.K.) as pigments, 11 parts styrene
butadiene latex and 11 parts casein as binders, and 2 parts calcium stearate as a
release agent.
[0058] This coating solution was applied to the raw paper of Example 1 by means of a roll
coater exactly as in Example 1, excepting that the rate of application was 11 g/m²
in terms of dry solids. An ink fusion transfer thermal paper of weighting 103 g/m²
was thus obtained.
COMPARATIVE EXAMPLE 8
[0059] A coating solution containing 56% dry solids was prepared from 30 parts synthetic
silica (commercial name: Syloid 404, Fuji Davison K.K., specific surface 300 m²/g)
and 70 parts calcium carbonate (commercial name: Brilliant 15, Shiraishi K.K. ) as
pigments, and 22 parts styrene butadiene latex and 2 parts starch oxide as binders.
[0060] This coating solution was applied to the raw paper of Example 1 by means of a roll
coater such that the rate of application was 10 g/m², and dried to give a coated paper
of weighting 102 g/m². The coated surface was then smoothed by means of a Super Calendar
so as to obtain an ink fusion transfer thermal paper.
[0061] Coating solution compositions, specific surfaces of synthetic silica and coating
amounts used for each of the ink fusion transfer thermal papers in the aforesaid Examples
and Comparative Examples are summarized in Table 1. In this Table, the figures in
the pigment column represent the ratios synthetic silica/kaolin/calcium carbonate/organic
pigment, and the figure in the binder column represents the ratio latex/casein.
Table 1
Coating Solution |
Specific Surface Silica of Synthetic ( m² /g ) |
Application Rate ( g/ m² ) |
|
Pigment |
Binder |
|
|
Example |
|
|
|
|
1 |
80/20/ 0/ 0 |
5/ 5 |
300 |
10 |
2 |
80/20/ 0/ 0 |
15/ 15 |
300 |
15 |
3 |
100/ 0/ 0/ 0 |
20/ 20 |
30 |
10 |
4 |
100/ 0/ 0/ 0 |
23/ 20 |
600 |
5 |
5 |
30/40/ 30/ 0 |
15/ 10 |
300 |
12 |
6 |
30/40/ 20/10 |
15/ 15 |
300 |
40 |
Comparative Example |
|
|
|
|
1 |
80/20/ 0/ 0 |
15/ 15 |
300 |
3.5 |
2 |
30/40/ 30/ 0 |
2/ 2 |
300 |
12 |
3 |
30/40/ 30/ 0 |
30/ 30 |
300 |
20 |
4 |
5/40/ 55/ 0 |
15/ 10 |
300 |
15 |
5 |
25/40/ 35/ 0 |
15/ 15 |
300 |
15 |
6 |
30/40/ 20/10 |
15/ 15 |
300 |
60 |
7 |
30/40/ 30/ 0 |
11/ 11 |
700 |
11 |
8 |
30/ 0/ 70/ 0 |
22/ 0 |
300 |
10 |
[0062] Paper quality test results and image quality test results for the coated papers obtained
as described hereinbefore are given in Table 2.
[0063] The results shown in Table 2 confirm not only that the ink fusion transfer thermal
paper of this invention has a high paper gloss, is tough and of extremely high quality,
but also that images recorded on this paper have a high gloss and that the quality
of these images is excellent.
1. An ink fusion transfer paper comprising at least one recording layer on a support,
the paper being characterized in that the uppermost layer of the recording layer consists
of at least 100 parts by weight of a pigment and 10-50 parts by weight of a binder,
the layer being present on one or both sides of the support at a coverage of 5-50
g/m² per side in terms of dry solids, 30-100 weight percent of the aforesaid pigment
consists of a synthetic silica having a specific surface of 20-600 m²/g, and the 75
degree gloss of said uppermost layer is no less than 50%.
2. An ink fusion transfer paper as claimed in Claim 1, wherein at least one organic pigment
selected from fine particles of styrene resins, acrylic resins and styrene-acrylic
copolymer resins is used as the pigment other than the synthetic silica.
3. An ink fusion transfer paper as claimed in Claim 2, wherein said organic pigment is
fine hollow particles of polystyrene or a styrene-methylmethacrylate copolymer.
4. An ink fusion transfer paper as claimed in Claim 1, 2 or 3, wherein the binding agent
is selected from a polyvinyl alcohol, starches, casein, soy protein, fiber derivatives,
styrene-acrylic resins, styrene-butadiene resins, vinyl acetate resins and acrylic
resins.
5. An ink fusion transfer paper as claimed in Claim 4, wherein the starches consist of
a starch oxide, a starch ester, an enzyme-modified starch or a cationic starch and
the fiber derivatives consist of a carboxymethyl cellulose or hydroxyethyl cellulose.
6. An ink fusion transfer paper as claimed in any preceding claim, wherein at least one
dye which can be a fluorescent dye and/or colored pigment is also contained in the
uppermost layer.
7. An ink fusion transfer paper as claimed in any preceding claim, wherein the uppermost
layer is present on one or both sides of the support at a coverage of 8-30 g/m² per
side in terms of dry solids.
8. A method of manufacturing an ink fusion transfer paper as claimed in any preceding
claim, characterized in that the uppermost layer is prepared by a cast coating method.
9. A method as claimed in Claim 8, wherein the cast coating is carried out by a solidification
method.
10. A method as claimed in Claim 9, wherein at least one solidifying agent selected from
formic acid, acetic acid, succinic acid, tartaric acid, lactic acid, hydrochloric
acid, a sulfate of calcium, zinc, barium, lead, magnesium, cadmium, aluminum or potassium,
potassium succinate, borax or boric acid is contained in a coating solution for said
layer.