 |
Description  |
|
|
FIELD OF THE INVENTION
The present invention relates to a support for a photographic printing
paper, particularly to a support for a photographic printing paper having
an excellent resolving power, and to a manufacturing process therefor.
BACKGROUND OF THE INVENTION
Up to now, a support for a photographic printing paper comprising a
substrate coated on both sides thereof with a resin has been known. In
such a support, titanium dioxide, a pigment, a blueing agent (including a
blue pigment), and a fluorescent whitening agent are generally contained
in a coating layer on an emulsion-coated side (U.S. Pat. No. 3,501,298).
Titanium dioxide used in such a support has an action to increase a light
reflection coefficient as well as a waterproofing property. It is known
that the larger the content of this titanium dioxide, the higher
improvement in the image resolving power is obtained.
The waterproof resin layer is formed by melt extruding a waterproof resin
containing titanium dioxide from a slit die in a short time. In the case
where 20 weight % or more of titanium oxide is incorporated into a resin
coating and a melt extrusion is carried out at a conventional extrusion
temperature, i.e., 290.degree. to 350.degree. C., cracking of the
waterproof resin layer (hereinafter referred to as film cracking) is
generated or stripes are liable to form at a die lip portion of an
extruder (hereinafter referred to as die lip stripes).
Generation of such film cracking not only damages the appearance of the
product but also spoils the commercial value because of loss of a water
proof property. Further, formation of the die lip stripes generates
continuous stripes on a surface of a film or a laminate in a longitudinal
direction; therefore, not only the appearance of the product is notably
damaged but also unevenness is caused on a transparency of the film during
a secondary processing such as stretching, which results in reduction of
the commercial value.
In addition, in order to completely remove die lip stripes once formed,
there is no way other than disassembling a die lip to rinse it, and a lot
of labor and time is required for assembling and rinsing it, which results
in a notable reduction of productivity. Accordingly, the resolution
thereof is required.
Various methods for preventing formation of die lip stripes have so far
been investigated. There are proposed, for example, from a viewpoint of an
improvement in a resin composition, a method in which zinc oxide and a
specific amount of a metal salt of higher fatty acid are used in
combination (JP-A-53-102947; the term JP-A-as used herein means an
unexamined published Japanese Patent No. Application), a method in which
titanium dioxide dried reducing the weight thereof and a specific amount
of a metal salt of fatty acid are used in combination (JP-A-57-16819), a
method in which an anti-oxidation agent and a specific amount of a metal
salt of fatty acid are used in combination (JP-A-60-11841), and a method
in which the conditions titanium dioxide dried reducing the weight
thereof, a metal salt of fatty acid and a specific melt viscosity of the
composition are selected and used in combination (JP-B-59-42296). Further,
many proposals have been made, such as a method in which, from a viewpoint
that since a significant amount of staining and spots generate as the
amount of titanium dioxide increases, titanium dioxide is required to be
modified, a surface of titanium dioxide is treated with aluminum hydroxide
hydrate (JP-A-57-108849 corresponding to U.S. Pat. No. 4,447,524), a
method in which a treatment with di- to tetrahydrate alcohol is carried
out (JP-A-58-17433 corresponding to U.S. Pat. No. 4,442,200), a method in
which a treatment with alkyltitanate is carried out (JP-A-57-151942), a
method in which a treatment with organic aluminum is carried out
(JP-A-62-141544), a method in which a loss of the amount on drying of
titanium dioxide is controlled to 0.35% or less (JP-A-59-1544,
JP-A-59-121329, and JP-A-59-215234), and a method in which the
conductivity of a suspension of titanium dioxide is controlled to 60
mbo/cm or less (JP-A-58-220140).
However, they are insufficient as a method for preventing formation of the
die lip stripes.
In the case where an extrusion temperature is set to less than 290.degree.
C. in order to improve such defects, the adhering power between a
substrate such as a paper substrate and a waterproof resin markedly
lowers.
Accordingly, a method in which the content of titanium dioxide is
suppressed to 20 weight % or less even at a sacrifice of a resolving power
has so far been employed.
Recently, a support for a high resolution printing paper has been developed
in which an adhesion-providing resin is added to a titanium
dioxide-containing layer and melt-extrusion is carried out at an extrusion
temperature of 175.degree. to 290.degree. C. to increase the content of
titanium dioxide in the layer (International Publication No. WO92/17538).
The detailed investigations on the above-described support for a high
resolution printing paper made by the present inventors have clarified
that not only is the dispersibility of titanium dioxide not sufficient,
but separation of the titanium dioxide-containing layer from a cooling
roll after extrusion-laminating is inferior, which results in a bad
appearance of the product.
The extensive investigations made by the present inventors in order to more
securely manufacture the support for the high resolution printing paper
have resulted in finding that in the case where a waterproof resin layer
containing a specific material is first provided and the above
adhesion-providing resin and/or adhesive resin is not incorporated into a
titanium dioxide-containing layer, titanium dioxide can readily be
incorporated in an amount of 20 weight % or more and further that even in
the case where extrusion molding is carried out at a melting temperature
of less than 290.degree. C., the adhesive property is sufficiently
maintained, and the present invention was reached.
SUMMARY OF THE INVENTION
A first object of the present invention is to provide a support for a
photographic printing paper provided on both sides of a substrate with a
waterproof resin-coating layer which can be manufactured by high speed
melt-extrusion coating of a waterproof resin containing titanium dioxide
in a sufficient amount on the substrate without causing troubles such as
the forming of film cracking or die lip stripes.
A second object of the present invention is to provide a support for
photographic printing paper having a high resolving power and having an
excellent adhesive power of a waterproof resin layer to a substrate.
A third object of the present invention is to provide a manufacturing
process for the support as described above, without forming any film
cracking or die lip stripes.
The above objects of the present invention have been achieved by a support
for a photographic printing paper comprising a substrate and a waterproof
resin coating layers provided on the both sides of the substrate, wherein
at least the waterproof resin-coating provided on the side of the
substrate on which an emulsion for forming an image is coated comprises i)
a lowermost waterproof resin coating layer contacting the substrate and
ii) at least one upper coating layer containing a waterproof resin capable
of melt-extruded at a temperature of from 170.degree. to 290.degree. C.
and containing uniformly dispersed titanium dioxide, and a method for
manufacturing the support, which comprises coating the waterproof resin
layer containing titanium dioxide by melt-extrusion at 170.degree. to
290.degree. C.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a partial sectional schematic diagram of an embodiment of the
support for a photographic printing paper of the present invention.
FIG. 2 shows a partial sectional schematic diagram of another embodiment of
the support for a photographic printing paper of the present invention in
case of using three waterproof resin layers on an emulsion coating side of
a substrate.
FIG. 3 shows a graph of adhesion strength with respect to the content of
talc.
DETAILED DESCRIPTION OF THE INVENTION
The support for a photographic printing paper of the present invention and
the manufacturing process therefor will be explained below in detail.
A waterproof resin for forming a coating layer in the present invention is
preferably selected from the resins which can be melt-extruded at about
170.degree. to 290.degree. C. Usually, a polyolefin resin such as a
polyethylene, a polypropylene or a polyester copolymer is used, and a
polyethylene is particularly preferably used. The polyethylene may be any
one of a high density polyethylene, a low density polyethylene and a
linear low density polyethylene, which may be used singly or in a mixture
of two or more kinds.
In the present invention, the melt index of the waterproof resin in the
upper layer is preferably higher than the melt index of the waterproof
resin in the lowermost layer.
The melt index (MI) of a waterproof resin is measured according to
condition shown in Table 1 of JISK 7210. In the present invention, the
melt index of the resin before processing is the melt index of a resin
before kneading with additives such as a blueing agent and TiO.sub.2, or
is the melt index of a diluting resin before using as a diluent.
In the present invention, the melt index of the waterproof resin containing
titanium dioxide is preferably falls in a range of 1.2 to 100 g/10
minutes, and the waterproof resin used in the other waterproof resin
coating layer(s) preferably also has a melt index falling in a range of
1.2 to 100 g/10 minutes. The melt index is more preferably within the
range of from 2 to 80 g/10 minutes and particularly preferably from 10 to
50 g/10 minutes. Furthermore, it is preferred that the melt index of the
upper waterproof layer(s) containing titanium dioxide has a higher melt
index than the lowest waterproof resin layer in order to harmonize the
flow properties of these layers to obtain even layers.
When a resin having MI lower than 1.2 g/10 minutes is used, extrusion
lamination tends to be difficult, that is, a thin layer lamination tends
to be difficult because of a high viscosity, on the other hand, when a
resin having MI higher than 100 g/10 minutes is used, the extruded layer
tends to be unstable or a layer is hardly formed because of a low
viscosity.
A form of titanium dioxide used in the present invention may be either an
anatase type or a rutile type. In the case of taking precedence of
whiteness, the anatase type is preferably used, and in the case of taking
precedence of sharpness, the rutile type is preferably used. Further,
titaniumdioxide of the anatase type and the rutile type may be blended and
used taking both of whiteness and sharpness into consideration, or in the
case of composing a titanium dioxide-containing layer of two layers,
titanium dioxide of the anatase type may be added to one of the layers and
titanium dioxide of the rutile type may be added to the other layer.
The average particle size of titanium dioxide falls preferably in a range
of from 0.1 to 0.4 .mu.m. When the average particle size is less than 0.1
.mu.m it is difficult to uniformly mix and disperse the particles into a
resin layer. On the other hand, when the average particle size exceeds 0.4
.mu.m, sufficient whiteness cannot be obtained and in some cases
projections generate on a coated surface to exert an adverse influence on
image quality.
Examples of titanium dioxide having such a form and an average particle
size are titanium dioxide having a brand name KA-10 or KA-20 manufactured
by Titan Ind. Co., Ltd., and a brand name A-220, PF-656, PF-654, PF-671,
PF-715, or CR-63 manufactured by Ishihara Industry Co., Ltd.
In general, in order to restrain the activity of titanium dioxide and to
prevent yellowing, titanium dioxide is subjected to a surface treatment
with an inorganic material such as aluminum oxide hydrate and silicon
oxide hydrate. Also titanium dioxide can be subjected to a surface
treatment with an organic material such as polyhydric alcohol, polyvalent
amine, metallic soap, alkyltitanate, and polysiloxane, and it can be
subjected to a surface treatment with the processing agents of an
inorganic material and an organic material in combination.
These processing agents can be used in a proportion of 0.2 to 2.0 weight %
based on titanium dioxide in the case of the inorganic material and in a
proportion of 0.1 to 1.0 weight % based on titanium dioxide in the case of
the organic material.
Titanium dioxide is kneaded in a waterproof resin with a kneading machine
having two rolls or three rolls, a kneader, or a Bumbury's mixer using a
metal salt of higher fatty acid, higher fatty ester, higher fatty amide,
and higher fatty acid as a dispersing aid. The titanium dioxide-containing
waterproof resin thus obtained is molded in a pellet form and used as a
master batch of titanium dioxide.
The titanium dioxide concentration in a pellets is preferably from about 30
to 75 weight % and a concentration of the dispersing aid is preferably
from about 0.5 to 10 weight % based on the amount of titanium dioxide.
The amount of titanium dioxide in the at least one waterproof resin layer
is generally from 5 to 60 weight %, preferably from 8 to 55 weight %, and
more preferably from 20 to 50 weight % based on the amount of the
composition of the waterproof resin layer.
Titanium dioxide may be incorporated into two or more of upper layers each
generally in an amount of 5 to 60 weight %.
When the support has two waterproof resin layers on the lowermost
waterproof resin layer, the amount of titanium dioxide in the uppermost
layer is preferably 0 to 50 weight % and in the middle waterproof layer is
preferably 0 to 60 weight %. The amount of titanium dioxide in the
lowermost layer is generally 0, but it may be incorporated in an amount of
less than 20 weight %, preferably not more than 15 weight %, and more
preferably not more than 10 weight %. When the total amount of the
titanium dioxide in the support is less than 5 weight %, a photographic
material having a lower resolving power is obtained, and when the amount
in one layer exceeds 60 weight %, the layer is liable to generate cracking
when it is bent. (In the present invention the amount of each of titanium
dioxide and other additives in a waterproof resin layer are indicated
based on the total weight of the components contained in the composition
of the waterproof resin layer.)
In order to further improve adhesion of the lowermost layer to the
substrate, the layer may contain at least one additive selected from a
tackifier (an adhesion-providing resin), an adhesive resin, talc, kaolin
and calcium carbonate.
A tackifier is a resin which is usually an oligomer and which is used to
provide tackiness to other resins, e.g., an elastomer thereby to obtain an
elastomer having a higher adhesiveness. A tackifier cannot be laminated.
It is usually used as an additive.
Examples of the tackifier used in the present invention include a rosin
compound resin (e.g., methyl ester, glycerine ester and pentaerythritol
ester of a rosin such tall oil rosin), a terpene resin (for example,
poly-.beta.-pinene), a coumarone-indene resin and a petroleum series
hydrocarbon resin. Two or more of these resins may be used in combination.
Specific examples of the petroleum series hydrocarbon resin include an
aliphatic series petroleum resin, an aromatic series petroleum resin, a
cyclopentadiene series petroleum resin, a copolymer series petroleum
resin, a hydrogenation series petroleum resin, and an alicyclic series
petroleum resin. The aliphatic series petroleum resin having 5 carbon
atoms is particularly preferable, and the aromatic series petroleum resin
having 9 carbon atoms is particularly preferable.
The tackifier is incorporated into the waterproof resin preferably in an
amount of from 0.5 to 60 weight %, more preferably 10 to 35 weight % based
on the waterproof resin composition of the waterproof resin layer. When
incorporated amount of the tackifier is less than 0.5 weight % improvement
in adhesion is insufficient, and when the amount exceeds 60 weight % the
layer is liable to generate a neck-in during manufacturing.
The adhesive resin used in the present invention is a resin which is able
to be laminated solely and heat-adhesive with a waterproof resin, for
example, an ionomer (e.g., an ethylene-metharylic acid copolymer cross
linked by metal ions such as Na ions or Zn ions), an adhesive polyolefin
resin, an ethylene copolymer resin such as an ethylene-vinyl acetate
copolymer (EVA), an ethylene-methyl methacrylate copolymer (EMMA), an
ethylene-ethyl acrylate copolymer (EEA), an ethylene-methyl acrylate
copolymer (EMA), an ethylene-acrylic acid copolymer (EAA), an
ethylene-ethyl acrylate-maleic anhydride copolymer (E-EA-MAH), an
ethylene-methacrylic acid copolymer (EMAA), and those obtained by
graft-polymerizing a polyolefin (e.g., polypropylene and polyethylene)
with maleic anhydride (MAH-g-polyolefin), and the metal salts thereof
(such as salts of Na, Zn or Mg). An incorporated amount of this adhesive
resin is preferably in a range of from 5 to 500 weight %, more preferably
from 10 to 200 weight %, even more preferably from 20 to 100 weight %
based on the weight of the composition in the lowermost waterproof resin
layer.
In the case where the tackifier and the adhesive resin are used in
combination, the tackifier is converted to the adhesive resin of an amount
of five times the addition amount of the tackifier.
Talc, kaolin, and calcium carbonate used in the present invention have
preferably an average particle size of from 0.01 .mu.m to 1.0 .mu.m, more
preferably from 0.1 .mu.m to 0.5 .mu.m. An average particle size less than
0.01 .mu.m makes dispersion difficult and an average particle size
exceeding 1.0 .mu.m tends to deteriorate the face condition of a covering
surface. The addition amount of at least one of talc, kaolin and calcium
carbonate is preferably from 0.1 wt % to 30 wt %, more preferably from 1.0
wt % to 20 wt % based on the total weight of the layer composition
containing at least one of these compounds. When the amount is less than
0.1 wt %, sufficient improvement in adhesion of the layer to the support
cannot be attained, and when the amount exceeds 30 wt %, whiteness of the
layer tends to lower. Although any one of talc, kaolin, calcium carbonate
particles and a mixture thereof may be used, talc is preferably used.
Talc, kaolin, and/or calcium carbonate used in the present invention
provides an effect for improving the adhesion of the waterproof layer to a
substrate such as a base paper layer remarkably as compared with other
inorganic particles, for example, BaSO.sub.4, ZnO, TiO.sub.2, ZnS,
MgCO.sub.3, and carbon.
A blueing agent can be incorporated into a waterproof resin layer provided
on the emulsion side of the support. Conventionally known blueing agents
such as ultramarine, cobalt blue, phosphoric oxide cobalt, a quinacridone
series pigment, and a mixture thereof can be used.
The particle size of the blueing agent is not specifically limited and
usually falls preferably in a range of from 0.3 to 10
The blueing agent is incorporated preferably in a range of from 0.2 to 0.4
weight % (based on the amount of the composition of the resin layer) in
case of using it for the uppermost layer and in a range of from 0 to 0.15
weight % in case of using it for a layer other than the uppermost layer.
The blueing agent is kneaded in a waterproof resin with a kneading machine
having two rolls or three rolls, a kneader, or a Bumbury's mixer. The
blueing agent-containing waterproof resin thus obtained is molded into a
pellet form and used as a master batch of the blueing agent.
A concentration of the blueing agent contained in pellets is preferably
from about 1 to 30 weight %. In forming the pellets of the blueing agent,
the blueing agent and titanium dioxide can be kneaded together. Further,
in order to help dispersion of the blueing agent, there can be used a
dispersing aid such as a waterproof resin of a low molecular weight (such
as a low molecular weight polyolefin), a metal salt of a higher fatty acid
(such as zinc stearate), a higher fatty ester, a higher fatty amide, and a
higher fatty acid. An preferred amount of the dispersing aid is 0.1 to 1
parts by weight per 1 parts by weight of the bluing agent.
An anti-oxidation agent can be incorporated as well into the waterproof
resin layer according to the present invention. The content thereof is
preferably from about than 50 to 1,000 ppm based on the waterproof resin
amount. Examples of the anti-oxidation agent include
2,6-di-t-butyl-p-cresol and
tetrakis[methylene-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate]methane.
The master batch thus prepared containing titanium dioxide and/or the
blueing agent is suitably diluted with the waterproof resin and used for
coating.
The multi-layer waterproof resin layer in the present invention is formed
on a substrate such as a paper or a synthetic paper by mixing the pellets
containing titanium dioxide and/or the blueing agent, diluting with a
waterproof resin if desired, heat-melting, and using a successive laminate
method or a laminate method using a multi-layer extruding die of a feet
block type, a multi-manifold type or a multi-slot type.
The form of the die for a multi-layer extrusion is not specifically
limited. In general, a T die or a coat hanger die are preferably used.
In the manufacturing process of the present invention, the waterproof resin
of the lowermost layer is coated on the surface of the emulsion-coating
side of the substrate by a melt-extruding method, and then or
simultaneously at least one upper layer including a waterproof resin layer
containing titanium dioxide is coated by melt-extruding method on this
layer.
The melt-extrusion temperature of the upper layer(s) containing titanium
dioxide is preferably from 170.degree. to 290.degree. C., more preferably
from 240 to 270.degree. C. The upper layer containing no titanium oxide is
preferably extruded at a temperature of from 170.degree. to 345.degree.
C., more preferably 270.degree. to 335.degree. C.
When the melt-extruding temperature of the layer containing titanium oxide
is lower than 170.degree. C., oxidation of the waterproof resin
insufficient which results in lowering of adhesion between the waterproof
resin layers. On the other hand, when the layer contains more than 20
weight % of titanium oxide and the extrusion temperature exceeds
290.degree. C. a film cracking and die lip stripes occur, which markedly
damage the appearance of the product.
The lowermost layer is preferably extruded at a temperature of from
230.degree. to 345.degree. C., more preferably 270.degree. to 340.degree.
C., and particularly preferably 290.degree. to 335.degree. C.
Before coating a resin on a substrate, the substrate is preferably
subjected to an activation treatment such as a corona discharge treatment,
a flame treatment, a glow discharge treatment or a plasma treatment.
In the case where the multi-layer waterproof resin layer of the present
invention is composed of, for example, two layers, it is preferred that
the upper layer has a layer thickness of from 0.5 to 50 .mu.m, more
preferably from 2 to 40 .mu.m, and most preferably from 10 to 30 .mu.m,
and the lowermost layer has a layer thickness of from 0.5 to 20 .mu.m,
preferably from 5 to 15 .mu.m, and in the case of three layers, it is
preferred that the uppermost layer has a layer thickness of from 0.5 to 50
.mu.m, the intermediate layer has a layer thickness of from 5 to 50 .mu.m
and the lowest layer has a layer thickness of from 0.5 to 10 .mu.m. In the
latter case it is preferred that titanium dioxide is incorporated into the
intermediate layer and is not incorporated into the uppermost layer in
order to prevent the formation of stripes more efficiently.
It is preferred that the total thickness of the waterproof layers on the
substrate (emulsion coated side) is from 10 to 60 .mu.m.
According to the present invention, a die lip stripes and film cracking
generated during coating a waterproof resin containing TiO.sub.2 in a high
concentration by melt-extrusion can be prevented and coating by high
speed.melt-extrusion is enabled.
In the present invention, a detailed mechanism of preventing film cracking
is not clear. The film cracking is considered a phenomenon that during
melt-extruding a waterproof resin containing TiO.sub.2 in a high
concentration at a usual melt-extruding temperature of 290.degree. C. to
340.degree. C, water and a volatile component contained in TiO.sub.2 and a
surface treating agent for TiO.sub.2 are converted to gas when they are
discharged from an extruder or a die lip, and therefore a molten film of
the waterproof resin discharged from the die lip is cracked by the gas.
TiO.sub.2 containing more water and/or volatile matter generates more film
cracking at a low TiO.sub.2 concentration region.
A TiO.sub.2 concentration increased to 20 wt % or more suddenly increases
die lip stripes. It is considered that this is because the presence of
TiO.sub.2 makes a waterproof resin susceptible to oxidation.
In the present invention, the extrusion temperature for coating a
waterproof resin containing TiO.sub.2 in a high concentration is
preferably from 170.degree. C. to 290.degree. C. By conducting extrusion
at such a low temperature conversion of water and a volatile component
contained in TiO.sub.2 and a surface treating agent for TiO.sub.2 to gas
is restrained and extruding of a waterproof resin film free of film
cracking is enabled to obtain a layer containing uniformly dispersed
TiO.sub.2 in a high concentration. Further, reduction of the
melt-extruding temperature can decrease oxidation of the waterproof resin
at the same time and can prevent die lip stripes.
In the present invention, by adjusting the melt index of a waterproof resin
used in the waterproof resin layer containing TiO.sub.2 to 1.2 g/10
minutes to 100 g/10 minutes, melt-extrusion at a low temperature at a high
speed can be more efficiently conducted. An excellent adhesion of the
lowermost waterproof resin layer to a substrate such as paper or a
synthetic paper can be secured by adjusting a melt-extruding temperature
of the lowest layer to a usual temperature of 290.degree. C. to
345.degree. C., or by using an additive for improving the adhesion of the
lowermost waterproof resin layer. Thus, a high speed melt-extrusion
coating for production of a support for photographic printing paper having
a high sharpness can be obtained.
A glossy face, a fine face, a matting face, or a silk face described in
JP-A-55-26507 is generally provided on the outermost surface of the
waterproof resin layer on the emulsion-coated side, and a non-gloss layer
is provided on a back face of the support.
The surface obtained after providing the marking can be subjected to an
activation treatment such as a corona discharge treatment or a flame
treatment and can be subjected as well to a treatment for forming a
subbing layer described in JP-A-61-846443 after the activation treatment.
The substrate used in the present invention may be any one of a natural
pulp paper containing a natural pulp as a primary component, a mixed paper
comprising a natural pulp and a synthetic fiber, a synthetic fiber paper
containing a synthetic fiber as a primary component, and that obtained by
converting a synthetic resin such as polystyrene or polypropylene to a
paper-like material, a so-called synthetic paper. The natural pulp paper
(hereinafter called simply the base paper) is particularly preferably used
as a substrate for a photographic printing paper.
Examples of additives which can be incorporated into the base paper include
a filler such as clay, talc, calcium carbonate, and a urea resin fine
particle, a sizing agent such as rosin, a higher fatty acid salt, paraffin
wax, and alkenylsuccinic acid, a paper strengthening agent such as
polyacrylamide, and a fixing agent such as aluminum sulfate as well as
alkylketene dimer. In addition thereto, a dye, a fluorescent dye, a slime
controller, and a defoaming agent are added, if desired.
Further, the following softening agents can be added, if desired.
The softening agent is described in, for example, "New Paper Processing
Manual" (edited by Shiyaku Time Co., Ltd.), pp. 554 to 555 (published in
1980) can be added. A softening agent having a molecular weight of 200 or
more is particularly preferred. This softening agent has a hydrophobic
group having 10 or more carbon atoms and is in a form of an amine salt or
quaternary ammonium salt self-fixing to cellulose.
Examples of specific softening agents include a reaction product of a
maleic anhydride copolymer and a polyalkylenepolyamine, a reaction product
of a higher fatty acid and a polyalkylenepolyamine, a reaction product of
a urethane alcohol and an alkylation agent, and a quaternary ammonium salt
of a higher fatty acid. Particularly preferred are the reaction product of
a maleic anhydride copolymer and a polyalkylenepolyamine and the reaction
product of a urethane alcohol and an alkylation agent.
A surface sizing treatment can be provided on a pulp surface with a
film-forming polymer (hydrophilic polymer) such as gelatin, starch,
carboxymethyl cellulose, polyacrylamide, and a modified substance of
polyvinyl alcohol. In this case, a carboxyl group-modified substance, a
silanol-modified substance, and a copolymer with acrylamide can be used as
the polyvinyl alcohol-modified substance. The coated amount of the
film-forming polymer is preferably controlled to 0.1 to 5.0 g/m .sup.2,
more preferably 0.5 to 2.0 g/m.sup.2.
Further, an anti-static agent, a fluorescent whitening agent, a pigment,
and a defoaming agent can be added to the above film-forming polymer, if
desired.
The base paper is manufactured by subjecting a pulp slurry containing pulp
and additives such as a filler, a sizing agent, a paper strengthening
agent, and a fixing agent which are added, if desired, to paper making
with a paper making machine such as a Fort-linear paper machine, drying
and rolling up. The surface sizing treatment described above is carried
out either before or after drying, and a calendering treatment is carried
out during the period of after drying to rolling up.
The above calendering treatment can be carried out at either before or
after the surface sizing treatment in the case where the surface sizing
treatment is carried out after drying. The calendering treatment is
carried out preferably in a final finishing process after carrying out
various treatments. Conventional metal rolls and the elastic rolls usually
used for manufacturing paper may be used for the calendering treatment.
The base paper used for the support for the photographic printing paper of
the present invention is finally controlled to a thickness preferably of
from 50 to 250 m by the calendering treatment described above. The base
paper generally has a density of from 0.8 to 1.3 g/m.sup.3, preferably
from 1.0 to 1.2 g/m.sup.3.
Various back coating layers can be provided on the support for the
photographic printing paper in the present invention for
anti-electrification and anti-curling. Further, there can be suitably
combined and incorporated into the back coating layer, inorganic
anti-static agents, organic anti-static agents, hydrophilic binders,
latexes, hardeners, pigments, and surface active agents described, for
example, in JP-B-52-18020 (U.S. Pat. No. 3,884,692; the term "JP-B" as
used herein means an examined Japanese patent publication), JP-B-57-9059
(U.S. Pat. No. 4,173,480), JP-B-57-53940 (U.S. Pat. No. 4,196,001),
JP-B-58-56859, JP-A-59-21484 and JP-A-58-184144 (U.S. Pat. No. 4,547,445).
The photographic support of the present invention can be provided with
various photographic constitutional layers and used for various
applications such as a color photographic printing paper, a black and
white photographic printing paper, a photocomposition printing paper, a
paper for phototype setting, a reversal photographic material, a negative
or positive material used in a silver salt diffusion transfer process, and
a printing material. For forming an image on the support of the present
invention at least one emulsion layer is provided on the support. Examples
of the emulsion include light-sensitive silver halide emulsion, and
examples of silver halide include silver chloride, silver bromide, silver
chlorobromide, silver iodobromide, and silver chloroiodobromide. The color
couplers can be incorporated into the silver halide photographic emulsion
layers to provide a multi-layer silver halide color photographic
constitutional layer. A physical developing nucleus can be incorporated to
provide a silver salt diffusion transfer image-receiving layer.
The support for a photographic printing paper of the present invention has
no die lip stripes and film cracking while maintaining an excellent
adhesion of a substrate to a waterproof resin-coating layer, and enables
high speed melt-extrusion coating. The support is able to provide a high
sharpness when used as a photographic printing paper.
The present invention will be explained below in further detail with
reference to the examples, but the present invention will not be limited
thereto. Unless otherwise indicated, all parts, percents, ratios and the
like are by weight.
Example 1
At a first laminate station, polyethylene having a density of 0.945
g/m.sup.3 and MI of 8 g/10 minutes was coated on one side of a base paper
having a weight of 170.degree. g/m.sup.2 at a speed of 200 m/minute to
form a polyethylene layer having a film th | | |
