JPH08234362A - Support body for photographic paper - Google Patents

Abstract

PURPOSE: To provide a photographic paper with good operating property, smoothness and image clarity. CONSTITUTION: In the support body for photographic paper in which at least one surface of a base paper mainly consisting of natural pulp is covered with a polyolefin resin composite containing polyolefin resin and titanium dioxide, the peak radius of hole distribution curve by a mercury press-in porosimeter of the base paper after calendering treatment is not more than 1.0μm, and 40-100wt.% of a high density polyethylene having a density of 0.945g/cm<3> or more is contained in the polyolefin resin. It is particularly preferred that the thickness unevenness index (Rp) of the base paper after calendering treatment is not more than 1.30mV, the central surface average roughness is not more than 1.3μm, and the shearing viscosity at 310 deg.C and a shearing speed of 100 (1/sec) of the polyolefin resin composite is 700-2500 poises. More preferably, 30wt.% or more of SBSP is used in the base paper, the peak radius of the hole distribution curve is not more than 0.80μm, and the shearing viscosity of the polyolefin resin composite is 1200-2500 poises.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photographic printing paper support, and more particularly to a photographic printing paper support which has good operability and is excellent in smoothness and image clarity. Is.

[0002]

2. Description of the Related Art Conventionally, as a support for photographic printing paper,
It is well known that both sides of a base paper are coated with a resin composition mainly composed of a white pigment and a polyolefin resin. Since the support hardly absorbs the developing solution, the washing and drying after the processing can be greatly shortened, and the support has excellent dimensional stability.

However, compared with the conventional baryta paper which can be mirror-finished after development, a photographic printing paper using a polyolefin resin-coated support needs to have a mirror-finished surface at the stage of the polyolefin resin-coated support. The white pigment such as titanium dioxide in the resin used for the shielding effect adversely affects the gloss.

The printing paper has "glossy", "silk-like" and "matte", and in the case of a printing paper using a polyolefin resin-coated support, the base paper is melt-extruded and coated with the polyolefin resin composition. Although it is determined by the shape of the surface of the cooling roll that comes into contact later, the "glossy tone" predominantly occupies the majority and a good mirror surface is required. However, the peelability from the cooling roll is the most "glossy", and peeling is most difficult, and the surface quality such as uneven gloss is likely to be adversely affected.

Various proposals have been made so far for a support for photographic printing paper coated with a polyolefin resin and having good surface smoothness. For example, it is proposed to use a base paper whose center surface average roughness (SRa) measured by a three-dimensional surface roughness meter is below a specific value (Japanese Patent Laid-Open No. 63-291054), and optical surface roughness is below a specific value. Proposal to use base paper of Japanese Patent Application Laid-Open No. Sho 64
No. 80948), the smoothness of the support can be improved, but the effect on the image clarity when used as photographic printing paper after emulsion coating is small. Further, the density is 0.6 to 0.
There is a proposal (Japanese Unexamined Patent Publication No. 64-18145) that uses 7 g / cm ³ of pulp and sets the elastic modulus of the sheet into a specific range. However, the balance between the stiffness (waist) and smoothness of the support is Good, but the effect of improving smoothness is small, and the effect on image clarity of photographic paper after emulsion coating is small.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a photographic printing paper support having good operability, smoothness of printing paper and excellent image clarity.

[0007]

As a result of intensive studies to solve these problems, the present inventors have invented the support for photographic printing paper of the present invention.

That is, the photographic printing paper support of the present invention is a photographic printing paper in which a polyolefin-based resin composition containing a polyolefin resin and titanium dioxide is coated on at least one surface of a paper containing natural pulp as a main component. A support for paper, the base paper is treated with at least one of a machine calendar, a super calendar, or a thermal calendar,
The peak radius of the pore distribution curve measured by the mercury penetration porosimeter is 1.0 μm or less, and the high density polyethylene (A) having a density of 0.945 g / cm ³ or more is 40 to 100% by weight of the polyolefin resin. To do.

Further, in the support for photographic printing paper of the present invention, preferably, the thickness unevenness index Rp of the base paper defined below is 1.3 mV or less on at least one side in the paper making direction of the base paper, Moreover, the center plane average roughness SRa in the papermaking direction at a cutoff of 0.8 mm or more at a wavelength measured using a stylus type three-dimensional average roughness meter is 1.3 μm or less, and the polyolefin resin composition has a temperature of 310 ° C. , Shear rate 100 (1 / sec)
The shear viscosity measured by the capillary rheometer in the above is 700 to 2500 poise.

Thickness unevenness index Rp: An optical displacement sensor that irradiates red LED light from above the plane and captures the reflected light with a photodetector array to measure the position of the plane. The level meter is about 13 mm between the sensor and the sample. The needle is located in the center, and the lower surface of the sample just below the beam is supported by the ball point needle, and the sample is fixed to the XY stage while preventing vertical displacement, and the XY stage is set to the X axis (main scanning axis). 2 in the direction
The thickness variation in the papermaking direction of the sample is measured by scanning at a constant speed of mm / sec, and the frequency analysis in the frequency range of 0-5Hz by the FFT analyzer of the obtained measurement signal value is performed in the Hanning window and 128 times. The power spectrum (unit: mV ² ) is calculated by adding and averaging
Sum the power spectrum values in the frequency range from Hz to 2Hz to 2
The value obtained by multiplying the value multiplied by / 3 to the power of 1/2 is defined as the film thickness unevenness index Rp (unit: mV).

In the photographic printing paper support of the present invention, the hardwood bleached pulp is preferably 30% by weight or more of the natural pulp.

Further, in the support for photographic printing paper of the present invention, the peak radius of the pore distribution curve measured by the mercury porosimeter is 0.
It is preferably 8 μm or less.

The support for photographic printing paper of the present invention comprises a polyolefin resin composition at 310 ° C. and a shear rate of 100 (1
/ Sec) and the shear viscosity measured by a capillary rheometer is preferably 1200 to 2500 poise.

The support for photographic printing paper of the present invention will be described in detail below.

The center surface average roughness SRa at a cut-off value of 0.8 mm measured by using a stylus type three-dimensional surface roughness meter referred to in the present specification is defined by the following mathematical formula 1. .

[0016]

[Equation 1] In Formula 1, Wx is the X-axis direction of the sample surface area (papermaking direction)
, Wy represents the length of the sample surface area in the Y-axis direction (direction perpendicular to the papermaking direction), and Sa represents the area of the sample surface area.

Specifically, as a stylus type three-dimensional surface roughness meter and three-dimensional roughness analyzer, SE-produced by Kosaka Laboratory Ltd.
Using 3AK type machine and SPA-11 type machine, cutoff value 0.8mm, Wx = 20mm, Wy = 8mm, therefore Sa =
It can be calculated under the condition of 160 mm ² . As the data processing in the X-axis direction, 500 points are sampled,
As the scanning in the Y-axis direction, 17 lines or more are performed.

The peak radius in the pore distribution curve in the mercury porosimetry porosimeter of the present invention is ME of Carlo Erba Co.
RCURY PRESSURE PROSIMETE
It is measured by RMDD220. On the basis of the characteristics of the liquid that does not get wet under normal pressure in the pores, it is necessary to apply pressure from the outside to the liquid having a wetting angle of 90 ° or more in order to put the liquid into the pores due to the surface tension. Using mercury as a liquid, measure the intrusion volume of mercury while applying pressure,
Obtain the void volume distribution curve (HP GRACE, JA
mer. Inst. Chem. Engra. , 2, P.
307 (1956), Onoki et al., Paper and Paper Cooperative Paper, 28, 9
9 (1974) et al.). The pore distribution curve can be obtained from the void distribution curve.

The measurement of the pore size by the mercury porosimetry was carried out by the following equation 2 which was derived assuming that the cross section was circular.

[0020]

## EQU00002 ## Pr = 2.alpha.Cos.theta. Where r is the hole radius and .alpha. Is the surface tension of mercury, which is 482.5.
The contact angle was 36 ° dynes / cm, θ was 141 °, and P was the pressure applied to mercury, and was varied from ¹ to 2000 kg / cm ² . About 1 g of the sample was precisely weighed to measure the cumulative pore volume (ml / g) per unit sample, and this was differentiated by the pore radius to obtain a pore distribution curve as a frequency with respect to the pore radius.

The peak radius of the pore distribution curve of the base paper is 0.5
It is the hole radius of the most frequent peak appearing in the vicinity of ˜5 μm.

The peak radius of the pore distribution curve measured by the mercury intrusion porosimeter is 1.0 μm or less, preferably the thickness unevenness index of at least one surface is 1.3 mV or less, and the center surface average roughness SRa is 1.3 μm. The following base papers are specifically obtained by using the following methods, preferably using two or more of the following methods, and more preferably using three or more in combination.

(1) As the natural pulp used in the present invention, it is preferable to use a hardwood bleached sulfite pulp (hereinafter abbreviated as LBSP) described or exemplified in JP-A-60-67940, particularly 30 weight. % Or more, but other than that, hardwood bleached kraft pulp (hereinafter referred to as LB
Various pulps used for general paper such as KP) and hardwood dissolving pulp (hereinafter abbreviated as LDP) are used.

When the LBSP is less than 30%, the relative bending rigidity is low even if the film pressure unevenness index Rp of the base paper, the three-dimensional average roughness SRa, and the peak radius of the pore distribution curve are within the range of the present invention. The stiffness of photographic paper tends to be weak.

(2) A pressure press is used during the drying of the wet paper. Specifically, for example, the wet paper web is subjected to a multi-stage pressure press as described or exemplified in JP-A-3-29945.

(3) Various water-soluble polymers, hydrophilic colloids or polymer latices are contained or coated in or on the base paper. Specifically, various water-soluble polymers or hydrophilic colloids or polymer latices are solid-coated in or on the base paper by size press or tab size press or coating such as blade coating or air knife coating. The amount is preferably ² g / m ² or more, or is preferably applied.

(4) After making the base paper, at least two or more series of calendar treatments are performed on the base paper using a machine calender, a super calender, a thermal calender, or the like. Specifically, for example, the base paper was subjected to machine calendering and / or thermal machine calendering as the first series of calendering, and then machine calendering was further carried out as necessary as the second series of calendering. Later JP-A-4
It is preferable to perform the thermal soft calender treatment described or exemplified in Japanese Patent Publication No. 110939.

The base paper of the present invention has a pore distribution curve with a mercury porosimeter having a peak radius of 1.0 μm or less, preferably 30 LBSP as a natural pulp.
It is used in an amount of not less than wt%.

Particularly, if the LBSP is 30% by weight or more,
A base paper having the characteristics of the present invention can be obtained even if it is weakly treated with a machine calender, a super calender or the like, and a photographic paper support having a high specific bending rigidity (waist) can be obtained.

The support for photographic printing paper of the present invention comprises a specific base paper coated on at least one side with a specific polyolefin resin containing titanium dioxide. The polyolefin resin composition is 310 ° C. and the shear rate is 100 (1). / Sec) has a shear viscosity of 7 measured with a capillary rheometer.
00 to 2500 poise, density 0.945 g / cm ³
The above high-density polyethylene resin (A) is 40 to 100% by weight of the polyolefin resin.

Density in polyolefin resin 0.945
If the content of high-density polyethylene (A) of g / cm ³ or more is less than 40% by weight, the effect of improving the smoothness and image clarity of photographic paper cannot be obtained, and the capillary rheometer at 310 ° C and a shear rate of 100 (1 / sec). If the shear viscosity measured by the method is less than 700 poise, the molten resin excessively penetrates into the capillaries of the base paper, and the optical properties such as opacity of titanium dioxide are likely to be impaired, resulting in poor smoothness of the resin surface. Become a trend. In this respect, it is preferable that the pores of the base paper have a specific diameter or less. If the high-density polyethylene resin (A) is more than 40% by weight, the effect of improving the smoothness and image clarity of the photographic paper is exhibited.

On the other hand, when the shear viscosity is more than 2500 poise, the molten resin does not penetrate into the rough recesses on the surface of the base paper, and the film-forming property between the base paper and the resin layer tends to be poor, and the smoothness of the surface of the resin-coated paper becomes poor. Also affects.

Titanium dioxide is contained in the polyolefin resin layer, but a rutile type or anatase type is used, and the average particle size in a directional measurement by an electron microscope is 0.0.
It is preferably 8 to 0.5 μm. Surface-treated products with alumina or silica or with organic substances such as fatty acid metal salts can be preferably used. Generally, 5 to 30% by weight of the polyolefin resin layer is contained as titanium dioxide. It is preferably 10 to 20% by weight. here,
If it is less than 5% by weight, the sharpness of the photographic paper is inferior, and
When it exceeds 30% by weight, the fluidity of the molten polyolefin resin layer becomes poor.

As the resin contained in the polyolefin resin composition of the present invention, various polyethylene, polypropylene, polybutylene, polyethylene terephthalate, etc., and their copolymers can be used in addition to high density polyethylene (A) having a specific density. It can be used as long as the effects of the invention are not impaired.

The polyolefin resin composition may contain various additives. For example, white pigments such as rutile-type or anatase-type titanium dioxide, zinc oxide, talc, etc., release agents such as fatty acid amides such as stearic acid amide and arachidic acid amide, and fatty acid metals such as zinc stearate and magnesium stearate. salt,
An organosilicon compound such as polyorganosiloxane may be appropriately contained as an antioxidant, a hindered phenol compound or the like may be contained, and a color pigment such as cobalt blue, ultramarine blue or the like and an optical brightener may be appropriately contained.

The polyolefin resin layer in the present invention is
It is manufactured by melt extrusion coating a polyolefin resin composition into a film from a slit die. The melt extrusion temperature at that time is appropriately selected in the range of 200 to 350 ° C. depending on the polyolefin resin composition. As a slit die, T
A die, an L die, a fish-til type die and the like are preferably used. Before applying the resin composition to the base paper, it is preferable that the base paper is subjected to activation treatment such as corona discharge or flame treatment.
The thickness of the polyolefin resin layer is not particularly limited, but 10
It is generally about 50 μm.

In the present invention, in general, immediately after the base resin is coated with the polyolefin resin composition by melt extrusion, the surface of the base paper is 5
10 to 50 between the cooling roll and the pressure roll at about 25 ° C
The resin surface is cooled by adhering the resin surface to the surface of the cooling roll by passing it under a pressure of about kg / cm to improve the smoothness of the resin layer surface and the adhesion between the resin layer and the base paper.

The release property of the polyolefin resin-coated paper from the cooling roll tends to improve as the melt viscosity of the resin composition increases, but the smoothness of the surface of the resin layer deteriorates. However, it has become clear that the combination with the characteristics of the base paper improves both the releasability and the image clarity of the photographic paper. That is, by treating a base paper using a specific pulp with a calendar or the like, the film thickness unevenness index is a specific value or less, the center surface average roughness SRa is a specific value or less, and the peak radius of the pore distribution curve by the mercury penetration porosimeter is By using a base paper having a specific value or less and using a specific resin composition having a shear viscosity at 310 ° C. in a specific range, good releasability and good image clarity of the printing paper can be obtained. It is a thing.

In the photographic printing paper of the present invention, on the polyolefin resin coating layer for the purpose of improving sharpness,
An undercoat layer containing a hydrophilic colloid binder such as gelatin, a latex such as styrene-butadiene, a methyl methacrylate-butadiene copolymer, and a white pigment such as titanium dioxide may be applied. The coating amount is preferably 0.5 g / m ² or more, more preferably 2 g / m ² or more.

Between the polyolefin resin layer or undercoat layer and the silver halide emulsion layer, an intermediate layer is continuously provided with the emulsion layer by a reduced pressure slide bead system or a slide hopper system for the purpose of preventing irradiation and fog. However, the thickness of the coating layer of the intermediate layer is preferably 4 to 5 μm or less, and when the coating layer of the intermediate layer is thicker than 4 to 5 μm, the sharpness becomes poor.

A slide bead method and a reduced pressure slide bead method are used for coating the silver halide emulsion.

The slide bead system is also called a slide hopper system or an E-bar system, and has a slit for discharging the coating liquid on the upper edge of the slanted slide surface, and the slide surface is inclined while forming a coating layer once. Then, the coating is applied onto the surface of the support while being stacked on the lower coating layer one after another to form a predetermined laminate and forming small beads collectively. The method is disclosed in JP-A-52-115214.
The coating method is described in JP-A-54-1350, and various technical disclosures regarding formation of a good photographic layer are made in JP-A-3-269528.

The pressure-reducing slide bead system is a system in which a pressure-reducing chamber is provided immediately before coating a bead on the surface of a support by a slide bead system to reduce the pressure to improve the coating property. US Pat. No. 2,681,294 , Ibid 2,761,419
No. 2,761,791 and the like, and a method for uniformly stabilizing the coating is described in U.S. Pat. No. 3,220,877, JP-A-62-121451, It is disclosed in Japanese Patent Laid-Open No. 1-258772.

As the base paper used in the present invention, in addition to the paper using the LBSP of the present invention, a mixed paper using natural pulp and synthetic fibers is used.

In the base paper, a sizing agent, a wet paper strength enhancer, a filler, a pH adjusting agent, a coloring agent, a coloring dye, a fluorescent agent, etc. used in ordinary papermaking, a starch type, a polyvinyl alcohol type, or a surface size, Properly contains water-soluble polymers such as gelatin, inorganic or organic antistatic agents such as sodium chloride, potassium chloride, sodium polystyrene sulfonate, pigments such as kaolin, clay, calcium carbonate, coloring pigments, dyes, fluorescent agents, etc. can do.

The support of the photographic printing paper according to the present invention includes
Various back coat layers can be provided for the purpose of preventing electrification and curling. The material of the back coat layer is colloidal silica, colloidal synthetic hectorite,
Sodium chloride, polystyrene sulfonate, hydrophilic binder, latex polymer, pigment, surfactant and the like can be used.

In the photographic printing paper of the present invention, various photographic constituent layers are coated to provide color photographic printing paper, black and white photographic printing paper,
It can be used for various purposes such as phototypesetting photographic paper and copy photographic paper. For example, an emulsion layer of silver chloride, silver bromide, silver chlorobromide, silver iodobromide or the like can be provided. It is also possible to provide a color coupler in the silver halide emulsion layer to provide a multilayer silver halide color photographic constituent layer. As the binder, in addition to ordinary gelatin, polyvinylpyrrolidone, polyvinyl alcohol and the like can be used. Photographic layers include sensitizing dyes, chemical sensitizers, antifoggants, hardeners,
It may contain a fluorescent whitening agent, an antistatic agent, a pH adjusting agent and the like.

The photographic printing paper of the present invention is subjected to various treatments such as exposure, development, stopping, fixing, bleaching and stabilizing as described in "Photosensitive Materials and Handling Methods" (Kyoritsu Shuppan, Goro Miyamoto). It is applied to form a photographic image.

[0049]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto.
The parts and% in the examples mean parts by weight and% by weight, respectively.

Example 1 A mixed pulp composed of 80% hardwood bleached sulfite pulp and 20% hardwood bleached kraft pulp was used as JIS P81.
After beating to a Canadian freeness of 300 ml according to No. 21, 3 parts of cationic starch to 100 parts of pulp,
0.2 part of anionized polyacrylamide, 0.4 part of alkyl ketene dimer emulsion as a resin component, 0.4 part of polyamide epichlorohydrin resin, and an appropriate amount of optical brightener, blue dye and red dye were added. A stock slurry was prepared. After forming a web using a fourdrinier paper machine running at 200 m / min while giving an appropriate turbulence, the wet part was used for three-stage wet pressing in the range of 15 to 100 kg / cm. , Smoothing rolls were applied, and in the drying part, two-stage pressure pressing was performed at a linear pressure of 30 to 70 kg / cm, followed by drying. afterwards,
Carboxy-modified polyvinyl alcohol 4 during drying
Part, an optical brightener of 0.05 part, a blue dye of 0.002 part, sodium chloride of 4 parts and water of 92 parts are pressed at a size of 25 g / m ² to remove the water content of the base paper finally obtained. It was dried to 8% with dry water. After that, machine calendering was performed, and then thermal calendering was performed at a temperature of 150 ° C., so that the peak radius of the pore distribution curve measured by the mercury porosimeter was 0.72 μm and the basis weight was 180 g /
m ² , density 1.07 g / cm ³ , surface SRa is 1.0
A base paper having a thickness of 0 μm and a transmembrane pressure index Rp of 1.02 mV was obtained.

Then, after corona-treating the back surface of the base paper, a mixture of high density polyethylene (density: 0.962 g / cm ³ ) and low density polyethylene (density: 0.926) at a ratio of 50:50 was added to 30 μm. After melt extrusion coating to a thickness of 200 m / min, corona treatment was applied to the surface of the base paper, and high density polyethylene (density:
0.962 g / cm ³ ) and low density polyethylene (density: 0.
926) in a mixture of 80:20 and aluminum-treated anatase titanium dioxide in an amount of 15% by weight of the composition, and a polyolefin resin composition at a speed of 200 m / min to a thickness of 30 μm. Melt extrusion coating at a resin composition melting temperature of 310 ° C at the time of contact, cooling roll at a linear pressure of 30 kg / cm with a pressure roll and a cooling water temperature of 15 ° C.
And then a polyolefin resin coating layer was provided on the surface of the base paper to obtain a support for photographic printing paper of the present invention. The surface of the polyolefin resin composition was 310 ° C. and the shear rate was 1
The shear viscosity with a capillary rheometer at 00 (1 / sec) was 2100 poise.

An emulsion layer and a protective layer were simultaneously provided on the polyolefin resin coating layer on the surface of the base paper by a reduced pressure slide bead system to obtain a black and white photographic printing paper.

The emulsion layer comprises hexachloroiridium (II
I) ArBr / AgCl / AgI = 95 / 4.5 / 0.I manufactured by dispersing and producing 19.2 g of silver halide grains as silver nitrate in the presence of 1.2 × 10 ⁻⁵ g of potassium acid.
It has a silver halide photographic emulsion composition of 5 (mol%) in 14.4 g of gelatin, and is sensitized by sulfur sensitization and gold sensitization to the optimum sensitivity with an average grain size of 0.6 μm. Containing a neutral silver halide photographic emulsion consisting of a [0, 0, 1] surface, and further containing gelatin necessary for film formation, an appropriate amount of a stabilizer, a sensitizing dye, a coating aid, a hardener, Contains optical brighteners, thickeners, filter dyes, etc., 2.2g / m ^{2 with} silver nitrate,
With gelatin, apply a coating amount equivalent to 4.4 g / m ^2, and adjust the degree of vacuum in the vacuum chamber with the vacuum slide bead coating device together with the protective layer.
Multilayer coating was performed at 60 mmH ₂ O and a coating speed of 100 m / min, and the coating was dried. The protective layer contains a coating aid and a hardening agent in addition to gelatin equivalent to ² g / m ² .

Example 2 After calendering in the same manner, except that the blending ratio of the pulp used for producing the base paper of Example 1 was changed to a mixed pulp consisting of 20% hardwood bleached sulfite pulp and 80% hardwood bleached softwood pulp. The base radius is 0.86 μm, the basis weight is 180 g / m ² , the density is 1.05 g / cm ³ , and the SRa of the pore distribution curve of the base paper is 0.86 μm.
Is 1.15 μm and the transmembrane pressure index Rp is 1.20 mV to obtain a base paper, the support for photographic printing paper of the present invention is obtained in the same manner as in Example 1, and the black and white photographic print is obtained in the same manner as in Example 1. Got the paper.

Example 3 In addition to the high-density polyethylene and low-density polyethylene used as the surface polyolefin resin in Example 1, the density was 0.
Using 900 polypropylene, their ratio is 40: 4
A support for photographic printing paper of the present invention was obtained in the same manner as in Example 5 except that it was replaced with 5:15, and a black and white photographic printing paper was obtained in the same manner as in Example 1. The shear viscosity of the polyolefin resin layer at 310 ° C. and a shear rate of 100 (1 / sec) was 1600 poise.

Example 4 The basis weight of the calendered base paper was 180 g / m ² and the density was 1.0 in the same manner as in Example 2 except for the calendering conditions.
A base paper having a surface roughness SRa of ³ g / cm ³ , a surface SRa of 1.26 μm, a membrane pressure unevenness index of 1.28 mV, and a peak radius of a pore distribution curve in a mercury porosimeter of 0.98 μm was obtained.
Others were made in the same manner as in Example 1 to obtain a black-and-white photographic printing paper.

Example 5 The composition of the polyolefin resin layer on the surface of the base paper of Example 1 was the same as that of Example 1 except that the ratio of high density polyethylene to low density polyethylene used in Example 1 was changed to 40:60. A support for photographic printing paper of the invention was obtained, and a black and white photographic printing paper was obtained in the same manner as in Example 1. The shear viscosity of the polyolefin resin layer at 310 ° C. and a shear rate of 100 (1 / sec) was 1500 poise.

Example 6 The pulp used in the production of the base paper of Example 1 was 100% hardwood bleached sulfite pulp (density 0.76 g / cm 3).
^{The same} as above except that the base paper after calendering had a basis weight of 180 g / m ² , a density of 1.06 g / cm ³ , and an SR.
a is 0.92 μm, the transmembrane pressure index Rp is 1.00 mV,
A base paper having a peak radius of a pore distribution curve of 0.62 μm obtained by a mercury porosimetry porosimeter was obtained, a support for photographic printing paper of the present invention was obtained in the same manner as in Example 1, and a black and white photograph was obtained in the same manner as in Example 1. I got the photographic paper.

Example 7 100% of hardwood bleached kraft pulp (density 0.76 g / cm ³ ) was used as the pulp for producing the base paper of Example 1.
In the same manner, except that the base paper after calendering had a basis weight of 180 g / m ² , a density of 1.09 g / cm ³ , SRa of 1.22 μm, a membrane pressure unevenness index Rp of 1.30 mV, and a mercury press-fitting formula. A base paper having a pore distribution curve peak radius of 0.95 μm by a porosimeter was obtained, a support for photographic printing paper of the present invention was obtained in the same manner as in Example 1, and black and white photographic printing paper was obtained in the same manner as in Example 1. Got

Example 8 Calendering was carried out in the same manner except that the pulp content used in the production of the base paper of Example 1 was changed to a mixed pulp consisting of 40% hardwood bleached sulfite pulp and 60% hardwood bleached kraft pulp. The peak radius of the pore distribution curve measured by the mercury penetration porosimeter of the subsequent base paper was 0.80μ.
m, basis weight 180 g / m ² , density 1.05 g / cm ³ ,
SRa is 1.10 μm and transmembrane pressure index Rp is 1.12
A mV base paper was obtained, a photographic printing paper support of the present invention was obtained in the same manner as in Example 1, and a black and white photographic printing paper was obtained in the same manner as in Example 1.

Example 9 In Example 1, 100 high density polyethylene resin having a density of 0.970 g / cm ³ was used as the polyolefin resin on the surface of the base paper.
% A black-and-white photographic printing paper was obtained in the same manner as in Example 1 except that the same was used. The shear viscosity of the polyolefin resin layer at 310 ° C. and a shear rate of 100 (1 / sec) was 2560 poise.

Example 10 A base paper having a basis weight of 180 g / m ² and a density of 1.06 g / c after being calendered in the same manner as in Example 1 except that only hardwood bleached kraft pulp was used as the pulp for the base paper.
m ³ , SRa is 1.29 μm, and the film thickness unevenness index Rp is 1.
A base paper having a peak radius of a pore distribution curve of 38 mV and a porosimeter of mercury pouring type of 1.00 μm was obtained.
A black and white photographic printing paper was obtained in the same manner as.

Comparative Example 1 In Example 1, the base paper was calendered only by a machine calender, and the base paper after the treatment had a basis weight of 180 g / m ² , a density of 1.02 g / cm ³ , an SRa of 1.30 μm, and a film. A base paper having a pressure unevenness index Rp of 1.25 mV and a peak radius of a pore distribution curve in a mercury porosimeter of 1.15 μm was obtained, and a black-and-white photographic printing paper was obtained in the same manner.

Comparative Example 2 Example 1 except that 100% of the low density polyethylene used as the polyolefin resin on the surface of the base paper in Example 1 was used.
A black-and-white photographic printing paper was obtained in the same manner as in. The polyolefin resin layer was heated at 310 ° C. and a shear rate of 100 (1 / se
The shear viscosity in c) was 550 poise.

Comparative Example 3 In Example 2, the base paper was calendered only by machine calendering, and the base paper after the treatment had a basis weight of 180 g / m ² , a density of 1.03 g / cm ³ , and an SRa of 1.35 μm. A base paper having a membrane pressure unevenness index Rp of 1.45 mV and a peak radius of a pore distribution curve of 1.31 μm measured by a mercury press-fitting porosimeter was obtained. In the same manner as in Example 1, a support for photographic printing paper of the present invention was obtained. A black-and-white photographic printing paper was obtained in the same manner as in Example 1.

The black and white photographic printing papers obtained in Examples 1 to 10 and Comparative Examples 1 to 3 were evaluated by the following methods. Table 1
Table 2 shows the results of the pulp content and base paper characteristics, and Table 2 shows the evaluation results of the cooling roll releasability and photographic paper image clarity.

[Cooling roll releasability] The releasability from the chill roll was evaluated when the base paper used in Examples and Comparative Examples was coated with the polyolefin resin composition. ⊚: Peeling is smooth and there is almost no peeling noise. ◯: Peeling is smooth and peeling sound is slightly present. Δ: Some sticking at the time of peeling, peeling noise, practical lower limit. X: There is sticking at the time of peeling, the peeling noise is loud, and the surface quality is apparent and there is lateral unevenness.

[Mapping property] The measuring method is JIS H8686.
The image clarity is determined as the image clarity from the waveform of the amount of light obtained through the optical comb defined by. Measured value when the slit width is 2 mm.

[Smoothness] SRa by a three-dimensional stylus roughness meter
(Μm, cutoff of 0.8 mm or more) is determined. The larger the number, the coarser it is.

[0070]

[Table 1]

[0071]

[Table 2]

As is clear from Table 2, the photographic printing paper supports of Examples 1 to 10 of the present invention were excellent in various characteristics. On the other hand, the supports for photographic printing papers of Comparative Examples 1 to 3 were inferior in cooling roll peelability and printing paper image clarity. In particular, Comparative Example 3
The photographic printing paper for photographic use had poor cooling roll releasability and image clarity.

[0073]

INDUSTRIAL APPLICABILITY The photographic printing paper using the photographic printing paper support of the present invention is excellent in operability at the time of manufacturing the support and image clarity of the photographic printing paper.

Claims (5)

[Claims] 1. A photographic printing paper support comprising a base paper made of natural pulp as a main component and having at least one surface thereof coated with a polyolefin resin composition containing a polyolefin resin and titanium dioxide. High density polyethylene (A) having a peak radius of 1.0 μm or less and a density of 0.945 g / cm ³ or more by a mercury intrusion porosimeter after being treated with at least one of a super calender and a thermal calender. Is 40 to 100% by weight of the polyolefin resin, a support for photographic paper. 2. The base paper has a film thickness unevenness index Rp specified below of 1.3 mV on at least one side in the paper making direction of the base paper.
And the center plane average roughness SRa in the papermaking direction at a cutoff of 0.8 mm or more at a wavelength measured using a stylus type three-dimensional average roughness meter is 1.3 μm or less, and a polyolefin resin composition 310 ° C, shear rate 100 (1 /
The support for photographic paper according to claim 1, characterized in that the shear viscosity measured with a capillary rheometer in sec) is 700 to 2500 poise. Thickness unevenness index Rp: An optical displacement sensor that irradiates red LED light from above the flat surface and captures the reflected light with a row of light receivers to measure the position of the flat surface. The sample is fixed to the XY stage in a state where it is positioned at the center and supports the lower surface of the sample just below the beam with a ball point needle and prevents vertical displacement.
The thickness variation in the papermaking direction of the sample is measured by scanning the XY stage in the X-axis (main scanning axis) direction at a constant speed of 2 mm / sec.
0 to 5 of the obtained measurement signal value by the FFT analyzer
Perform the frequency analysis in the frequency range of Hz in the Hanning window, calculate the power spectrum (unit: mV ² ) by adding and averaging 128 times of integration, and sum the power spectrum values in the frequency range of 0.175 Hz to ² Hz. Then, the value obtained by multiplying the value obtained by multiplying 2/3 by 1/2 is defined as the film thickness unevenness index Rp (unit: mV). 3. The hardwood bleached pulp is 30% of natural pulp.
The support for photographic printing paper according to claim 1 or 2, wherein the support is at least wt%. 4. The support for photographic printing paper according to claim 1, wherein the base paper has a peak radius of a pore distribution curve measured by a mercury porosimeter of 0.8 μm or less. 5. A polyolefin resin composition at 310 ° C.,
The support for photographic printing paper according to any one of claims 1 to 4, wherein the shear viscosity in a capillary rheometer at a shear rate of 100 (1 / sec) is 1200 to 2500 poise.