JPH09114044A - Resin coated paper for photographic printing paper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain photographic printing paper having satisfactory image transferability and fine glossiness. SOLUTION: In this resin coated paper obtd. by coating both sides of base paper of natural pulp based with polyolefin resin, the base paper is multilayered base paper obtd. by a laminated paper making method. The outermost layer contains >=5wt.%, preferably >=20wt.% pigment and this pigment is preferably kaolin, clay, talc, barium sulfate or calcium carbonate and has 0.1-2μm average particle diameter. The outermost layer accounts for 20-60wt.% of the amt. of all the base paper and the SRa of the base paper is most preferably <=1.2μm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin-coated paper for photographic printing paper in which a polyolefin resin is coated on both sides of a base paper mainly composed of natural pulp, and more particularly to a resin-coated paper for photographic printing paper having a highly smooth surface. It is a thing.

[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 development processing solution, washing and drying after the processing can be greatly shortened, and the support is also excellent in dimensional stability.

However, compared to the conventional baryta paper which can be mirror-finished after development, photographic printing paper using a polyolefin resin-coated paper needs to have a mirror surface at the stage of the polyolefin resin-coated paper, but has a light-shielding effect. White pigments such as titanium dioxide in the resins used for adversely affect the gloss.

The printing paper has "glossy", "silk",
There is a "matte tone", and in the case of photographic paper using polyolefin resin-coated paper, it is determined by the shape of the surface of the cooling roll that comes into contact after melt-extruding and coating the polyolefin resin composition on the base paper. "Glossy" 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), both of which can improve the smoothness of the support, but have little effect on the image clarity when used as photographic printing paper after emulsion coating. Further, the density is 0.6 to
Proposal of using 0.7 g / cm ³ of pulp and setting the elastic modulus of a sheet within a specific range (JP-A-64-18145).
However, the effect of improving the smoothness is small, and the effect on the image clarity of the photographic paper after emulsion coating is small.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a resin-coated paper for photographic printing paper which has good operability and is excellent in smoothness, image clarity and glossiness of the printing paper.

[0007]

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

The resin-coated paper for photographic printing paper according to the present invention is a resin-coated paper for photographic printing paper in which both sides of a base paper mainly composed of natural pulp are coated with a polyolefin resin. It is a paper for making paper, and the outermost layer of the multi-layer paper for making paper contains 5% by weight or more of a pigment with respect to the natural pulp constituting the outermost layer.

In the resin-coated paper for photographic printing paper of the present invention, the pigment content in the outermost layer is 20 with respect to natural pulp.
It is more preferable that the content be not less than% by weight.

The average particle size of the pigment contained in the outermost layer of the multi-layer paper is preferably 0.1 to 2 μm.

The pigment contained in the outermost layer is preferably one or more selected from kaolin, clay, talc, aluminum hydroxide, barium sulfate and calcium carbonate.

In the resin coated paper for photographic printing paper of the present invention, the natural pulp forming the outermost layer is 30% by weight.
The above-mentioned hardwood bleached sulfite pulp is preferable.

The absolute dry weight of the outermost layer of the multi-layer paper is preferably 20 to 60% by weight based on the weight of the paper.

In the resin-coated paper for photographic printing paper of the present invention, the surface of the multi-layer paper is preferably center surface average roughness SR measured by a stylus type three-dimensional surface roughness meter.
a is 1.2 μm or less.

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

The base paper of the resin-coated paper for photographic printing paper used in the present invention is a multi-layer paper base paper by a commonly used paper machine such as a Fourdrinier paper machine or a round net paper machine, and preferably a multi-layer paper base paper. A hardwood bleached sulfite pulp (hereinafter abbreviated as LBSP) is used as the outermost natural pulp in an amount of 30% by weight or more.

Other natural pulps are disclosed in JP-A-58 / 58
-73642, JP-A-60-67940, JP-A-6-
It is advantageous to use an appropriately selected natural pulp as described or exemplified in each publication such as 0-69649 and JP-A-61-35442. Moreover, you may use a synthetic pulp, a synthetic fiber, or a recycled pulp as needed.

As the natural pulp, for example, ordinary bleaching treatment of chlorine, hypochlorite, chlorine dioxide bleaching, alkali extraction or alkali treatment, and if necessary, oxidative bleaching treatment with hydrogen peroxide, oxygen, etc., Further, wood pulp such as softwood pulp, hardwood pulp and softwood mixed hardwood pulp which have been subjected to a combination treatment thereof are advantageously used, and various kinds such as kraft pulp, soda pulp and softwood sulfite pulp can be used.

A preferred constitution as the outermost layer of the multi-layered base paper of the present invention is to use hardwood sulfite pulp in an amount of 30% by weight or more of the natural pulp together with a pigment, whereby the resin layer coated on the outermost layer. And the glossiness of the photographic paper is improved. The pigment and hardwood sulfite pulp give a smooth multi-layered base paper, and when a resin coating layer is provided, the outermost layer of the multi-layered base paper causes less thermal deformation, resulting in a uniform resin layer and improved gloss. Expected to do.

Examples of the pigment used in the outermost layer of the multi-layer paper for base paper of the present invention include kaolin, clay, talc, aluminum hydroxide, barium sulfate, calcium carbonate, magnesium carbonate, zinc oxide, titanium dioxide and silica. Of these, kaolin, clay, talc, aluminum hydroxide, barium sulfate, and calcium carbonate are preferable, and the pigment having an average particle diameter of 0.1 to 2 μm is preferably used.

The pigment contained in the outermost layer of the multi-layered base paper of the present invention is used in an amount of 5% by weight or more, preferably 20% by weight or more, more preferably 30% by weight or more based on the natural pulp.

It is not clear why the addition of a specific amount of the pigment to the outermost layer of the present invention improves the "image clarity" and the "glossy appearance" of the photographic printing paper, but the voids between pulp fibers are not clear. In addition to being effectively filled with the pigment, when the high temperature resin in a molten state comes into contact with the surface of the base paper during lamination, it is expected that the change in the smoothness of the base paper is small because the pigment is included. On the other hand, when the average particle size is large,
It is expected that the effect will be small due to the poor surface smoothness of the base paper.

As for the average particle diameter of the pigment, a Microtrac particle size distribution meter (manufactured by Nikkiso Co., Ltd.) was used to determine the volume-weighted average particle diameter by light scattering by laser light.

To evaluate the sharpness of photographic paper, "image clarity" is defined in JIS H8686, and "image clarity" is obtained as image clarity from the waveform of the light quantity obtained through the optical comb. In the present invention, a measured value with a slit width of 2 mm was used.

The absolute dry weight of the multi-layered base paper of the present invention is not particularly limited, but is generally 30 to 250 g / m ² , and the absolute dry weight of the outermost layer is 20 to 60 weight of the multi-layered base paper. % Is preferred.

The base paper of the resin-coated paper for photographic printing paper which is preferably used in the practice of the present invention may contain various additives when preparing a stock slurry. As a sizing agent, fatty acid metal salt or fatty acid, JP-B-62-75
No. 34 or an exemplified alkyl ketene dimer emulsion, an epoxidized higher fatty acid amide, an alkenyl or alkyl succinic anhydride emulsion, a rosin derivative, and the like, which are anionic, cationic or amphoteric as a dry paper strength enhancer. Polyacrylamide, polyvinyl alcohol, cationized starch, vegetable galactomannan, etc. as a wet paper strength enhancer, polyamine polyamide epichlorohydrin resin, etc., as a filler, clay, kaolin, calcium carbonate, titanium oxide, etc. as a fixing agent,
As a pH adjusting agent such as aluminum chloride and water-soluble aluminum salt such as vanadium sulfate, caustic soda, sodium carbonate, sulfuric acid, etc. are described or exemplified in JP-A-63-204251 and JP-A-1-266537. It is advantageous to appropriately combine the above-mentioned coloring pigments, coloring dyes, optical brighteners and the like.

The base paper of resin-coated paper for photographic printing paper which is preferably used in the practice of the present invention contains various water-soluble polymers, antistatic agents and additives by spraying or size press or tab size press. It can be done. As a water-soluble polymer, JP-A-1-
As an antistatic agent, an alkali metal salt such as sodium chloride or potassium chloride, calcium chloride, a starch-based polymer, a polyvinyl alcohol-based polymer, a gelatin-based polymer, a cellulose-based polymer, or the like described or exemplified in JP-A-266537. Alkaline earth metal salts such as barium chloride, colloidal metal oxides such as colloidal silica, organic antistatic agents such as polystyrene sulfonate, etc. as emulsions and latexes, petroleum resin emulsion, ethylene-vinyl acetate copolymer , JP-A-55-4027, JP-A-1-1-1
Clay, kaolin, talc, barium sulfate, pigments such as emulsions or latexes of copolymers containing at least ethylene and acrylic acid (or methacrylic acid) described or exemplified in 80538,
Titanium oxide, etc., as a pH adjuster, hydrochloric acid, phosphoric acid, citric acid, caustic soda, etc.
It is advantageous to include an appropriate combination of additives such as coloring dyes and optical brighteners.

The center surface average roughness SRa at a cutoff 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. .

[0029]

(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-3 manufactured by Kosaka Laboratory Ltd.
Using AK type machine and SPA-11 type machine, cutoff value 0.8 mm, Wx = 20 mm, Wy = 8 mm,
It can be obtained under the condition of Sa = 160 mm ² . Note that sampling is performed 50 times as the data processing in the X-axis direction.
Zero points are performed, and 17 or more lines are scanned in the Y-axis direction.

The base paper of the photographic resin-coated paper preferably used in the practice of the present invention is a short fiber which is easy to produce smoothness and has little decrease in rigidity. Preferably, a hardwood sulfite pulp is used in a large amount, and a beater is used. The material beaten so that the long fiber content is reduced as much as possible is used as the outermost layer of the multilayer paper.

Specifically, the beating of the pulp is based on the fiber length of the pulp after the beating of 15 to 45% of the 42 mesh residue,
It is preferable that the freeness is 150 to 400 CSF. Next, regarding the paper stock chiller to which internal additives have been added, JP-A-58-37642 and JP-A-61-260
No. 240, JP-A No. 61-284762 or the like is adopted, and a suitable papermaking method is adopted, and a uniform formation is obtained by a papermaking machine usually used such as a Fourdrinier paper machine and a round net paper machine. As it is made by multi-layer papermaking,
After papermaking, machine calendar, super calendar,
Calendered using a thermal calender to give a three-dimensional roughness SRa of 1.6 μm or less, preferably 1.2 μm.
The following base papers can be manufactured. There is no particular limitation on the thickness of the base paper, but the basis weight is 30 to 250 g /
m ² is preferred.

(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.

(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 in or on the base paper are applied as a solid coating amount of 2 g / by a size press or a tab size press, or a coating such as blade coating or air knife coating.
It is preferable that m ² or more is contained or coated.

(4) After the raw paper is made into paper, at least two series of calender treatments are performed on the raw paper using a machine calendar, a super calendar, a thermal calendar, or the like. Specifically, for example, the base paper is subjected to a machine calendering treatment and / or a thermal machine calendering treatment as a first series calendering treatment, and then a machine calendering treatment is further performed as a second series or subsequent calendering treatment. It is preferable to perform the thermal soft calender treatment described or exemplified in Kaihei 4-110939.

In particular, the outermost LBSP of the base paper is 30% by weight.
As described above, when the pigment content is 20% 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, etc., and a resin coating for photographic paper having a high specific bending rigidity (flexibility). Paper is obtained.

The base paper for photographic printing paper of the present invention is obtained by coating at least one surface of a specific base paper with a specific polyolefin resin containing titanium dioxide.

As the resin contained in the polyolefin resin composition of the present invention, various polyethylene, polypropylene, polybutylene, polyethylene terephthalate, etc. and their copolymers may be used in addition to the high density polyethylene (A) having a specific density. However, especially high density polyethylene with a density of 0.945 g / cm ³ or more is used
It is preferably used in an amount of not less than wt%.

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 and surface-treated products with organic substances such as fatty acid metal salts can be preferably used. Generally, titanium dioxide is contained in the polyolefin resin layer in an amount of 5 to 30% by weight. It is preferably 10 to 20% by weight. Here, if it is less than 5% by weight, the sharpness of the printing paper is inferior, and if it is 3% or less.
If it exceeds 0% by weight, the fluidity of the molten polyolefin resin layer becomes poor.

Further, in the polyolefin resin composition,
Various additives can be contained. For example, as white pigments, in addition to rutile-type or anatase-type titanium dioxide, zinc oxide, talc, etc., as release agents, fatty acid amides such as stearic acid amide and arachidic acid amide, fatty acids such as zinc stearate and magnesium stearate. Metal salts, organosilicon compounds such as polyorganosiloxane, antioxidants, hindered phenol compounds, etc., color pigments, cobalt blue,
A brightening agent such as ultramarine can 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 to subject the base paper to an activation treatment such as corona discharge or flame treatment. The thickness of the polyolefin resin layer is not particularly limited,
It is generally about 10 to 50 μm.

In the present invention, generally, the surface of the base paper is coated with the resin 5 immediately after the polyolefin resin composition is applied by melt extrusion.
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.

Regarding the releasability of the polyolefin resin-coated paper from the cooling roll, the larger the melt viscosity of the resin composition is, the better the tendency is, but the smoothness of the resin layer surface is poor. However, it has become clear that the combination of the characteristics of the base paper improves the releasability and the image clarity of the photographic paper. That is, a resin-coated paper for photographic printing paper having good sharpness of photographic printing paper is obtained by treating a specific multi-layered base paper having an outermost layer containing a pigment with a calendar or the like.

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

Between the polyolefin resin layer or the 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 or a reduced pressure slide bead method is 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 slanting 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 Japanese Patent Application Laid-Open No. 54-1350, and various technical disclosures regarding formation of a good photographic layer are also made in Japanese Patent Application Laid-Open No. 3-269528.

The depressurized slide bead system is a system in which a depressurization 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 the method of uniform stabilization during coating is described in U.S. Pat. No. 3,220,877, JP-A-62-121451.
Japanese Patent Laid-Open No. 1-258772 and the like.

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

The resin-coated paper for photographic printing paper according to the present invention may be provided with various back coat layers in order to prevent static electricity, curl and the like. As the material of the back coat layer, colloidal silica, colloidal synthetic hectorite, sodium chloride, polystyrene sulfonate, hydrophilic binder, latex polymer, pigment, surfactant and the like can be used.

The resin-coated paper for photographic printing paper of the present invention is coated with various photographic constituent layers to produce various types of materials such as color photographic printing paper, black-and-white photographic printing paper, typesetting photographic printing paper, copy photographic printing paper and the like. It can be used for various purposes. For example, an emulsion layer of silver chloride, silver bromide, silver chlorobromide, silver iodobromide, or the like can be provided. Including a color coupler in the silver halide emulsion layer,
Multilayer silver halide color photographic construction layers can also be provided. As the binder, in addition to ordinary gelatin, polyvinylpyrrolidone, polyvinyl alcohol and the like can be used. The photographic constituent layer may contain a sensitizing dye, a chemical sensitizer, an antifoggant, a hardener, 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.

[0054]

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

Example 1 Hardwood bleached sulfite pulp and hardwood bleached kraft pulp 6: 4 mixed pulp was beaten to 320 ml of Canadian Standard Freeness, and further 100 pulp
1 part by weight of kaolin (average particle size 1.6 μm)
00 parts by weight, 3 parts by weight of chaotic starch, 0.2 parts by weight of anionized polyacrylamide, 0.4 parts by weight of emulsion of alkyl ketene dimer (as ketene dimer content), and 0.4 parts by weight of polyaminopolyamide epichlorohydrin resin were added. Pulp slurry A was prepared. Further, a pulp slurry B was prepared in the same manner as the pulp slurry A except that the hardwood bleached kraft pulp alone was used as the pulp. Using a Fourdrinier paper machine having a plurality of heads, a lower layer was continuously dried with pulp slurry B so as to have a dry layer of 120 g / m ² and an upper layer was dried to have a dry layer thickness of 50 g / m ² . The obtained wet paper is dried at 110 ° C., and subsequently 3 parts by weight of carboxy-modified polyvinyl alcohol, 0.05 part by weight of optical brightener, 0.002 part by weight of blue dye, 4 parts by weight of sodium chloride and 0.2 part of citric acid. 25 g / m ^{2 of} impregnating liquid consisting of 1 part by weight and 93 parts by weight of water, and dried with hot air at 110 ° C.,
Further, a supercalendering treatment was performed at a linear pressure of 90 kg / cm to produce a resin-coated paper base paper for photographic printing paper. The SRa of the base paper at this time was 0.9 μm.

Next, after the base paper surface (back surface) opposite to the side on which the photosensitive layer is coated is subjected to corona discharge treatment, a low density polyethylene resin (density 0.92 g / cm ³ , MFR = 2 g / 10) is used.
Min) 25 parts by weight and high density polyethylene resin (density 0.9
6 g / cm ³ , MFR = 20 g / 10 min) 75 parts by weight of a resin composition was melt-extrusion coated at a resin temperature of 320 ° C. to a thickness of 20 μm at a running speed of the base paper of 140 m / min.

Subsequently, the surface of the base paper was subjected to corona discharge treatment, and then the low density polyethylene resin (density 0.92) was applied to the surface.
07.5 g / cm ³ , MI = 8.5 g / 10 min) 47.5% by weight, hydrous aluminum oxide (A against titanium dioxide)
20 parts by weight of a master batch of a titanium dioxide pigment composed of 50% by weight of anatase type titanium dioxide pigment and 2.5% by weight of zinc stearate surface-treated with 0.75% by weight of 1 ₂ O ₃ ), a low density polyethylene resin ( Density 0.92
55 parts by weight of 0 g / cm ³ , MI = 4.5 g / 10 minutes) and high-density polyethylene resin (density 0.970 g / cm ³ , MI
= 7.0 g / 10 minutes) A resin composition consisting of 25 parts by weight was used to make the running speed of the base paper 1 at a resin temperature of 325 ° C and a thickness of 20 μm.
Melt extrusion coated at 40 m / min. In addition,
The melt extrusion coating of the front and back polyethylene resins was performed by a so-called tandem system in which extrusion coating was sequentially performed. At that time, the surface of the resin layer containing the titanium dioxide pigment of the resin-coated paper was processed into a mirror surface, and the surface quality of the resin layer on the back was processed into a matte surface such as paper.

An emulsion layer and a protective layer were simultaneously provided on the polyolefin resin coating layer on the surface of the raw 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. Contains a neutral silver halide photographic emulsion consisting of [0, 0, 1] surface, and further contains an appropriate amount of a stabilizer, a sensitizing dye, a coating aid, a hardener, in addition to gelatin necessary for film formation. Optical brightener,
2.2g with silver nitrate, including thickener and filter dye
/ m ² , and a coating amount equivalent to 4.4 g / m ² with gelatin, a protective layer and a vacuum slide bead coating device were used to apply a multilayer coating at a vacuum degree of -60 mmH ₂ O in a vacuum chamber at a coating speed of 100 m / min and dried. . The protective layer contains a coating aid and a hardening agent in addition to gelatin equivalent to ² g / m ² .

In Examples 2 to 16 and Comparative Examples 1 to 3, the pulp blending ratio of the base paper and the pigment type and ratio of the outermost layer were changed as shown in Table 1. In Comparative Example 2, the pigment in the outermost layer was removed and the processing pressure of the super calender was increased so that the SRa of the base paper was 1.2 μm. In Comparative Example 3, only the lower layer pulp slurry of Example 1 was used to prepare a base paper with a single layer, and supercalendering was performed so that the SRa of the base paper was 1.3 μm.

Table 2 shows the evaluation results of SRa of the base paper and the photographic paper image clarity of the photographic paper for monochrome photography. The calcium carbonate used in Example 7 was precipitated calcium carbonate, and the calcium carbonate used in Example 13 was heavy calcium carbonate. Example 14 used aluminum hydroxide. In Example 15, synthetic silica having a secondary agglomerated particle diameter of 0.5 μm was used.

<Smoothness> The center surface average roughness SRa (unit: μm, cutoff of 0.8 mm or more) was determined with a three-dimensional stylus roughness meter. The larger the number, the coarser it is.

<Mapping property> The measuring method is JIS H868.
The image clarity was determined as the image clarity from the waveform of the amount of light obtained through the optical comb defined in No. 6. 2mm slit width
Measured value. The larger the number, the better.

<Visual Glossiness> The glossiness visually evaluated was evaluated. ⊚: Very good gloss. ◯: Good glossiness.
Δ: Average glossiness X: Poor gloss.

[0065]

[Table 1]

[0066]

[Table 2]

As is clear from Table 2, the resin-coated paper for photographic printing papers of Examples 1 to 16 of the present invention had excellent image clarity of the obtained printing papers. On the other hand, the resin coated papers for photographic printing papers of Comparative Examples 1 to 3 were inferior in image clarity and appearance glossiness.
In particular, Comparative Examples 2 and 3 have good image clarity even if the SRa of the base paper is good.
It looked badly glossy.

[0068]

INDUSTRIAL APPLICABILITY The photographic printing paper using the resin coated paper for photographic printing paper of the present invention is excellent in image clarity and appearance glossiness of the photographic printing paper.

Claims (7)

[Claims] 1. A resin-coated paper for photographic printing paper, wherein both sides of a base paper mainly composed of natural pulp are coated with a polyolefin resin, wherein the base paper is a multi-layered base paper produced by a combining method, and A resin-coated paper for photographic printing paper, characterized in that the outermost layer of the base paper contains 5% by weight or more of a pigment with respect to the natural pulp constituting the outermost layer. 2. The pigment content in the outermost layer is 20% by weight or more based on the natural pulp.
Resin-coated paper for photographic printing paper as described. 3. The resin-coated paper for photographic printing paper according to claim 1, wherein the pigment contained in the outermost layer of the multi-layered base paper has an average particle size of 0.1 to 2 μm. 4. The pigment contained in the outermost layer is kaolin,
Clay, talc, aluminum hydroxide, barium sulfate,
And at least one selected from calcium carbonate, The resin-coated paper for photographic printing paper according to claim 1, wherein the resin-coated paper is photographic paper. 5. The resin-coated paper for photographic printing paper according to claim 1, wherein the natural pulp forming the outermost layer is 30% by weight or more of hardwood bleached sulfite pulp. 6. The resin-coated paper for photographic printing paper according to claim 1, wherein the absolute dry weight of the outermost layer of the multi-layer paper is 20 to 60% by weight of the base paper. 7. The center-plane average roughness SRa of the surface of the multi-layered raw paper as measured by a stylus-type three-dimensional surface roughness meter is 1.2.
The resin-coated paper for photographic printing paper according to any one of claims 1 to 6, wherein the resin-coated paper is not more than μm.