JPH0555055B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to photographic resin-coated paper, and more particularly to photographic resin-coated paper with excellent sharpness. Photographic resin-coated papers are already known, for example as disclosed in US Pat. Those containing titanium pigments, colored pigments, optical brighteners, etc. are well known. However, the actual situation is that, in the method of manufacturing resin-coated photographic paper, resin-coated photographic paper with sufficiently satisfactory sharpness has not yet been obtained. In recent years, as the demand for photographic paper has increased, not only professionals but also general consumers are not satisfied with the current quality and are strongly requesting improvements in image clarity, etc. The reality is that the photographic industry is focusing on improving sharpness. Sharpness is related to the titanium dioxide content in the surface layer of a photographic support, and when a photographic resin-coated paper is used as a support, the resin layer on the emulsion-coated side (hereinafter referred to as
The sharpness tends to improve as the titanium dioxide content in the emulsion surface resin layer (sometimes referred to as an emulsion surface resin layer) increases. If the titanium dioxide content in the emulsion side resin layer is less than 5% by weight, the sharpness will be insufficient, and if it is more than 40% by weight, it will be difficult to produce photographic resin-coated paper using, for example, a melt extrusion coating machine. , which is undesirable because it reduces the fluidity of the molten resin composition, and is usually preferably 7.5 to 25% by weight. The above content is also preferred in the present invention, particularly preferably 9 to 20
Weight%. However, unnecessarily increasing the titanium dioxide content in the emulsion surface resin layer in order to improve sharpness will result in deterioration in quality and operation, such as microgrit and die lip stains. The term "microgrit" as used herein refers to minute foreign matter or minute grains that appear on the surface of the coated resin in photographic resin-coated paper in which at least one side of the paper or synthetic paper base is coated with a resin composition. . The occurrence of microgrit in the emulsion resin layer of photographic resin-coated papers causes serious photographic defects. That is, when a person is photographed using resin-coated paper with microgrit as a photographic support,
If microgrit appears on areas such as the face, it will have no commercial value. These microgrits are often generated due to titanium dioxide, and in particular, they tend to occur more easily as the titanium dioxide content in the emulsion surface resin layer increases. On the other hand, die lip stains refer to needle-like or icicle-like adhesion that occurs at the tip of the die lip during a short period of extrusion when a resin composition containing titanium dioxide pigment, especially a polyethylene resin composition, is melt-extruded into a film from a slit die. This refers to stains on kimono, and these die lip stains tend to grow larger and larger as the melt extrusion time progresses. This die lip stain also occurs more easily as the titanium dioxide content in the resin layer increases. If this die lip stain occurs during melt extrusion coating, vertical streaks may appear on the surface of the photographic resin-coated paper manufactured as is, or streak-like unevenness may occur due to uneven coating amount. In addition, dirt sometimes adheres to the film and is coated, causing foreign matter to appear. As a result, the image quality of the produced resin-coated paper is significantly impaired, making it completely unsuitable as a photographic support that requires excellent surface quality and having no commercial value. In addition, the only way to completely remove die lip stains once they have occurred is to stop production and clean the die lip stains, which requires a great deal of effort and time and causes a significant drop in productivity. This led to an urgent need for an immediate solution. Therefore, there has been a strong demand in the industry for a method for producing photographic resin-coated paper that suppresses the titanium dioxide content in the emulsion side resin layer as low as possible and has excellent sharpness. The present inventors have arrived at the present invention as a result of intensive research aimed at improving this point. That is, in the present invention, at least one surface of the base paper is
In a photographic resin-coated paper coated with a resin composition consisting of at least a resin and a titanium dioxide pigment, the base paper is provided with a coating layer containing an adhesive on at least one surface thereof, and the coating layer is heated. The present invention provides a photographic resin-coated paper with excellent sharpness, which is a coated paper that has been pressure-contacted with a mirror-finished mirror drum or a gloss calendar to give a highly smooth finish. The photographic resin-coated paper of the present invention has excellent sharpness, and in particular, extremely good sharpness can be obtained even without containing titanium dioxide pigment in the resin layer to the extent that it causes die lip stains and the like. Further, normally, as a substrate for photographic resin-coated paper, paper etc. with particularly excellent smoothness is used, but according to the present invention, ordinary paper made from acidic, neutral or alkaline paper which does not have excellent smoothness is used. Good sharpness can be obtained when resin-coated photographic paper is used as a base paper, such as art base paper, coated base paper, cast base paper, etc., and even when highly smoothed coated paper is used as the base paper. . In the present invention, the base paper refers to a base material (for example, paper or synthetic paper, etc.) with a coating layer containing an adhesive on at least one side pressed against a heated mirror drum or gloss calender to give a highly smooth finish. Refers to the covering paper. Methods for manufacturing the highly smooth coated paper used as the base paper of the present invention include the wet cast method, in which a wet coating layer is pressed against the surface of a heating drum to achieve a highly smooth finish, and the wet coating layer is made into a gel state. Gelling casting method, in which the wet coating layer is once dried or semi-dried, and then plasticized by re-wetting, and then pressed against the heating drum surface, for a highly smooth finish. etc. can be mentioned. In the present invention, the cast finishing method itself is not particularly limited, but the rewet casting method, which allows for relatively high speed, is advantageously used. The highly smooth coated paper produced by gloss calendering in the present invention may be finished by thermal calendering, which is generally known as gloss calendering. That is, for example, finishing may be carried out by pressing the coated paper against an abrasive finishing drum under temperature conditions that induce a temporary plastic state on the coated surface. Adhesives used in the present invention include casein, soybean protein, proteins such as proteins extracted from single-cell assimilating bacteria such as methanol or acetic acid, gelatins, styrene-butadiene copolymers, methyl methacrylate-butadiene, etc. Conjugated diene polymer latex such as copolymer, acrylic polymer latex such as polymer or copolymer of acrylic acid ester and/or methacrylic acid ester, vinyl polymer latex such as ethylene/vinyl acetate copolymer , or alkali-soluble or alkali-insoluble polymer latexes obtained by modifying these various polymers with functional groups using functional-containing monomers such as carboxyl groups, olefin/maleic anhydride resins,
Synthetic resin adhesives such as melamine resin, positive starch,
General adhesives for coated paper, such as starches such as phosphoric acid esterified starch and oxidized starch, and cellulose derivatives such as carboxymethyl cellulose and hydroxyethyl cellulose, can be used alone or in combination. In the present invention, in addition to the above adhesives, various inorganic and organic pigments such as clay, kaolin, aluminum hydroxide, calcium carbonate, titanium dioxide, barium sulfate, zinc oxide, satin white, plastic pigments, etc. One or more coated paper pigments are used. Further, as auxiliary agents, antifoaming agents, coloring agents, mold release agents, fluidity improving agents, etc. may be used as appropriate. The coating composition containing an adhesive or pigment in the present invention can be applied to a blade coater, an air knife coater, a roll coater, a brush coater, a curtain coater, a chain coater, a bar coater, etc., which are commonly used in the production of coated paper. The base paper is coated in one layer or in multiple layers using an on-machine or off-machine coater equipped with a coating device such as a gravure coater or a size press coater. In addition, the coating amount is approximately 2 to 50 g/ ^m2 in dry weight, and as the coating amount increases, sharpness tends to improve when used as photographic resin-coated paper, but operability and In terms of quality, a range of 5 to 35 g/m ² is suitable. The highly smooth coated paper used in the present invention may be highly glossy like ordinary cast coated paper, but in the present invention, the highly smooth coated paper is used as a base paper and a resin layer is formed on it. Since it is provided, the gloss does not have to be as strong as that shown in the left, and it is sufficient as long as it is highly smooth. As for the degree of high smoothness, it is preferable to use highly smooth coated paper whose coated layer has an average pore radius of 0.07 μm or less when measured with a mercury intrusion porosimeter model 220 (manufactured by Carlo Erba). The thermoplastic resin used in the resin layer of the photographic resin-coated paper in the present invention includes polyolefin,
Homopolymers or copolymers such as polystyrene, polyvinyl chloride, polyacrylic esters, linear polyesters such as polyethylene terephthalate, polycarbonate, polyamides such as nylon, cellulose esters, polyacrylonitrile, etc., such as ethylene-vinyl acetate copolymers and mixtures thereof. Any resin may be used as long as it is capable of coating the base paper with a resin film, but
In particular, thermoplastic resins such as polyolefin, polystyrene, polyethylene terephthalate, and polyvinyl chloride are preferred, and among them, polyolefin resins have good extrusion coating properties and good adhesion to the base paper,
This is particularly advantageous in terms of cost. The polyolefin resin in the present invention includes low density polyethylene, medium density polyethylene, high density polyethylene,
These are copolymers consisting of two or more homopolymers such as polypropylene, polybutene, and polypentene, or olefins such as ethylene-propylene copolymers, and mixtures thereof.
(abbreviated as MI) can be used alone or in combination. Furthermore, linear low-density polyethylene, which is a copolymer of ethylene and α-olefin, and mixtures of these and various polyolefins can also be used. The masterbatch used in the resin layer of the photographic resin-coated paper in the present invention can be made using a commonly used melt-kneading machine, such as a Banbury mixer, kneader, two-roll, three-roll, or kneading extruder. It is particularly advantageous to use a Banbury mixer. Further, if necessary, these kneaders may be used in combination. As the titanium dioxide pigment used in the practice of the present invention, either a rutile type or anatase type can be used, but it is advantageous to use an anatase type from the viewpoint of whiteness. In addition, titanium dioxide may be so-called untreated titanium dioxide, which does not undergo any surface treatment, or may be treated with various organic surface treatment agents such as various alcohols, surfactants, siloxane, etc.
It may be surface treated with a silane coupling agent or the like, or various inorganic surface treatment agents such as hydrated aluminum oxide, hydrated silicon oxide, hydrated titanium oxide, hydrated zirconium oxide, zinc hydroxide, etc.
It may be so-called inorganic surface-treated titanium dioxide which has been surface-treated with magnesium hydroxide, a manganese compound, a phosphoric acid compound, or a combination of several of these. The treatment amount of these inorganic surface treatment agents is preferably 0.2 to 1.2% by weight (calculated in anhydrous form), particularly preferably 0.2 to 0.6% by weight, based on titanium dioxide. Hydrous aluminum oxide is preferred as the inorganic surface treatment agent for titanium dioxide used in the practice of the present invention, and the amount of treatment is relative to titanium dioxide.
Preference is given to 0.2 to 1.2% by weight (calculated in the form of A ₂ O ₃ ), particularly preferably 0.2 to 0.6% by weight. The masterbatch used in the resin layer of the photographic resin-coated paper of the present invention preferably contains a fatty acid metal salt. Examples of these fatty acid metal salts include zinc stearate, calcium stearate, aluminum stearate, magnesium stearate, zirconium octylate, sodium palmitate, calcium palmitate, and sodium laurate. In addition, the amount added to the resin composition containing titanium dioxide is as follows:
A range of 0.01% to 5% by weight is preferred. The masterbatch used in the present invention preferably further contains an antioxidant, particularly a hindered phenolic antioxidant. As a hindered phenolic antioxidant,
For example, 1.3.5-trimethyl-2.4.6-tris (3.5-
di-tert-butyl-4-hydroxybenzyl)benzene, tetrakis[methylene (3.5-di-tert-
butyl-4-hydroxy-hydrocinnamate)]
Methane, octadecyl-3.5-di-tert-butyl-
4-hydroxy-hydrocinnamate, 2.2′.2″ tris[3.5-di-tert-butyl-4-hydroxyphenyl)propionyloxy]ethyl isocyanurate, 1.3.5-tris(4-tert-butyl-3-
Hydroxy-2.6-di-methylbenzine) isocyanurate, tetrakis(2.4-di-tert-butylphenyl) 4.4'-biphenylene diphosphite, 4.4'-thiobis-(6-tert-butyl-O-cresol), 2.2' -thiobis-(6-tert-butyl-4-methylphenol), tris-(2-methyl-4-hydroxy-5-tert-butylphenyl)
Butane, 2,2'-methylene-bis-(4-methyl-
6-tert-butylphenol)4.4'-methylene-
Bis-(2.6-di-tert-butylphenol), 4.4
-Butylidenebis-(3-methyl-6-tert-butylphenol), 2,6-di-tert-butyl-4-
Methylphenol, 4-hydroxy methyl-
2.6-di-tert-butylphenol, 2.6-di-tert
-butylphenol, 2,6-di-tert-butyl-4
-n-butylphenol and the like. or,
Depending on the properties of the antioxidant, two or more antioxidants may be used in combination. The content of antioxidant in the masterbatch is based on the resin composition.
5 to 250 ppm in 100 parts by weight, preferably 5
~150 ppm, more preferably 5~100 ppm. In the masterbatch used in the present invention, in addition to fatty acid metal salts, zinc oxide,
White pigments such as talc and calcium carbonate, fatty acid amides such as stearic acid amide and arachidic acid amide, coloring pigments such as cobalt blue, deep blue, ultramarine, and cobalt violet, and optical brighteners may be added. Resin-coated paper for photographs can be made by so-called solvent coating, in which resin is dissolved in a solvent and applied to the base paper surface, or by a lamination method, in which a resin film is bonded to the base paper surface. Resin-coated paper is usually manufactured by melt-extruding a resin composition containing heat-melted titanium dioxide pigment onto a running base paper through a slit die into a film. If the resin is polyolefin resin, the melt extrusion temperature is 200℃
The temperature is preferably from 350°C to 350°C. Furthermore, before applying the resin composition to the base paper by melt extrusion, it is preferable to subject the base paper to an activation treatment such as a corona discharge treatment or a flame treatment. There is no particular limit to the thickness of the resin layer of resin-coated paper, but it is generally between 5 microns and 50 microns.
Extrusion coating to a thickness on the order of microns is advantageous. In addition, in ordinary resin-coated paper in which both sides of the base paper are coated with resin, the resin surface containing titanium dioxide pigment can be a glossy surface or a glossy surface depending on the application.
It has a matte surface, a silky surface, etc., and the opposite back surface is usually a matte surface, and the front surface or both the front and back surfaces can be subjected to activation treatment such as corona discharge treatment or flame treatment if necessary. The substrate used in the practice of the present invention may be ordinary natural pulp paper, synthetic fibers, or so-called synthetic paper made by stiffening synthetic resin film.
Natural pulp paper based on wood pulp of softwood pulp, hardwood pulp, softwood hardwood mixed pulp is advantageously used. Further, there is no particular restriction on the thickness of the base paper, but the basis weight is preferably 50 to 350 g/m ² . In the present invention, these natural pulps contain sizing agents such as rosin, soap, wax, and synthetic sizing agents, bands, fixing agents such as aluminum chloride, and fillers such as clay, talc, and calcium carbonate. Even when a photographic resin-coated paper is produced using base paper, coated base paper, etc. as a base paper and coated paper that has been highly smoothed according to the present invention as a base paper, excellent sharpness can be obtained. Furthermore, when a base paper for photographic printing paper is used as the substrate, a resin-coated photographic paper with even better sharpness can be obtained. Various polymer compounds and additives can be contained in the base paper for photographic paper used in the present invention. For example, dry paper strength enhancers include cationized starch, cationized polyacrylamide, anionized polyacrylamide, carboxy-modified polyvinyl alcohol, gelatin, etc. Sizing agents include fatty acid salts, rosin derivatives, dialkyl ketene dimer emulsions, petroleum resin emulsions, etc. , ammonium salt of styrene-maleic anhydride copolymer alkyl ester, pigments such as clay, kaolin, calcium carbonate, barium sulfate, titanium oxide, etc. Wet paper strength enhancers such as melamine resin,
Urea resins, epoxidized polyamide resins, fixing agents such as polyvalent metal salts such as aluminum sulfate and aluminum chloride, cationic modified polymers such as cationized starch, and pH regulators such as caustic soda,
Inorganic electrolytes such as sodium carbonate and hydrochloric acid, salt, mirabilite, and other suitable combinations of dyes, optical brighteners, latex, and the like may be contained. The photographic resin-coated paper of the present invention can be provided with various silver halide photographic emulsion layers. For example, silver chloride, silver bromide, silver chlorobromide, silver iodobromide, and silver chloroiodobromide emulsion layers can be provided. Furthermore, a multilayer silver halide photographic constituent layer can be provided by incorporating a color coupler in the silver halide photographic emulsion layer. In addition to ordinary gelatin, binders for these silver halide emulsion layers include
polyvinylpyrrolidone, polyvinyl alcohol,
Hydrophilic polymeric substances such as polysaccharide sulfate ester compounds can be used. Further, the above-mentioned silver halide emulsion layer can contain various additives. For example, sensitizing dyes include cyanine dyes and merocyanine dyes, chemical sensitizers include water-soluble gold compounds and sulfur compounds, and antifoggants or stabilizers include hydroxy-triazolopyrimidine compounds and mercapto-heterocyclic compounds. As a hardening agent, formalin, vinyl sulfone compounds, aziridine compounds, etc. As a coating aid, benzene sulfonate, sulfosuccinic acid ester salt, etc. As a stain preventive agent, dialkylhydroquinone, phenidone, etc. as an ultraviolet absorber, benzene In addition to triazole compounds, optical brighteners, sharpness-enhancing dyes, antistatic agents,
In addition to the PH regulator, a water-soluble iridium compound, a water-soluble rhodium compound, etc. can be contained in an appropriate combination during the production and dispersion of silver halide. Further, on the back side of the photographic resin-coated paper in the present invention, that is, on the support surface opposite to the side on which the photographic constituent layer, in most cases the silver halide photographic constituent layer, is coated, anti-curl, antistatic, etc. A coating layer consisting of a hydrophilic colloid layer called a back coat layer can be provided for the purpose of preventing adhesion and slipping. Such a back coat layer may contain a binder, a protective colloid, a curing agent, an antistatic agent, a surfactant, a matting agent, a latex, and the like. Next, examples will be described in order to explain the present invention more specifically. Example 1 100 parts by weight of pulp, 0.6 parts by weight of rosin size, 8 parts by weight of filler (clay: talc = 4:6),
Styrene-butadiene latex (solid content 40%) with a glass transition temperature of 40°C was added to an art base paper with a basis weight of 100 g/m ² consisting of 1.2 parts by weight of sulfuric acid band and a surface size (oxidized starch solid content 4% liquid) at an appropriate concentration. After adjusting the coating amount using an air knife coater to achieve the coating amount (dry weight) listed in Table 1, 120
Dry through an air cap dryer heated to ~130°C. Next, this coated paper was gloss calendered at a roll nip linear pressure of 35 kg/cm to obtain a highly smooth coated paper. Apart from this, low-density polyethylene (MI7, density
0.92 g/m ² ), 50 parts by weight of hydrous aluminum oxide treated anatase titanium dioxide (0.5% by weight calculated in the form of A ₂ O ₃ vs. titanium dioxide), 2 parts by weight of zinc stearate and 3.5 parts by weight of zinc stearate. -tert-butyl-4-hydroxy-hydrocinnamate
Put 100ppm into a Banbury mixer and heat to 150℃.
Mix well to obtain a master batch. Next, while applying corona discharge treatment to the back side of the above-mentioned highly smooth coated paper, high-density polyethylene (MI7, density
0.96g/cm ³ ) and low density polyethylene (MI3, density
A 1:1 mixture of 0.92 g/cm ³ ) was applied to a thickness of 30 μm using a melt extruder at a resin temperature of 320° C. Next, while applying a corona discharge treatment to the coated surface of the highly smooth coated paper, 20 parts by weight of the masterbatch described above and high density polyethylene (MI7, density 0.96 g/
cm ³ ) 20 parts by weight and low density polyethylene (MI5 density
A resin composition containing 60 parts by weight (0.92 g/cm ³ ) was coated at a resin temperature of 320° C. to a thickness of 30 μm to produce a polyethylene resin-coated paper containing a titanium dioxide pigment. At this time, the surface of the polyethylene containing titanium dioxide pigment was processed into a completely flat glossy surface, and the back surface of the polyethylene was processed into a paper-like matte surface. The titanium dioxide-containing resin surface of the five types of photographic resin-coated papers thus obtained was subjected to corona discharge treatment, coated with a color photographic paper emulsion, dried, and then contact-baked using the same negative. The sharpness of the obtained images was evaluated as excellent ◎, good ◎, poor △, and poor ×. The results obtained are shown in Table 1.

[Table] From Table 1, if the coating amount of highly smooth coated paper, which is the base paper of photographic resin-coated paper, is 5 g/m ² or less, only poor sharpness will be obtained, but if the coating amount is 10 g/m ² (average pore radius of coating layer 0.07μ), almost good sharpness was obtained, and coating amount of 20g/ ^m2 (average pore radius of coating layer 0.05μ) resulted in good sharpness. you get something,
It can be seen that even better sharpness can be obtained with a coating weight of 30 g/m ² (average pore radius of the coating layer 0.02 μm). Example 2 20 parts by weight of an aqueous casein solution (concentration 15%) dissolved using soda carbonate and 20 parts by weight (solid content) of styrene-butadiene latex with a glass transition temperature of 40°C were added to obtain an adhesive-containing coating liquid. . This coating liquid was coated on the same base paper as in Example 1 using a roll coater while adjusting the concentration appropriately so that the coating amount was as shown in Table 2, and then dried in a dryer so that the paper moisture became 6%. After drying, highly smooth coated paper was obtained by the same method as the rewet casting method disclosed in JP-A-61-28097. Thereafter, a photographic resin-coated paper was prepared in the same manner as in Example 1, and its sharpness was determined. The results obtained are shown in Table 2.

[Table] From Table 2, when the coating amount of highly smooth coated paper is 5 g/m ² (average pore radius of the coating layer is 0.07μ), approximately good sharpness can be obtained, and the coating amount of 10 g/m 2 is obtained. m ² (average pore radius of the coating layer 0.05μ), good sharpness was obtained, and the coating amount was 20g/m ² (average pore radius of the coating layer
It can be seen that even better sharpness can be obtained with 0.03μ). Example 3 70 parts by weight of kaolin, 30 parts by weight of light calcium carbonate, and 0.5 parts by weight of sodium polyacrylate were dispersed in water using a Coles disperser to obtain a solid content concentration of 60%.
A pigment slurry was prepared. Add to this 0.5 parts by weight of tributyl phosphate,
Casein aqueous solution (concentration 10% by weight) dissolved using 1.0 parts by weight of potassium oleate and soda carbonate 10
Add parts by weight and 18 parts (solid content) of butadiene acrylate methyl methacrylate copolymer latex,
Furthermore, water was added to prepare a coating liquid with a solid content concentration of 40%. Using this coating liquid, a highly smooth coated paper was obtained by a rewet cast method. That is, base paper for casting (1) with a basis weight of 100 g/m ² and base paper for photographic paper ( ² ) with a basis weight of 160 g/m 2 were coated with an air knife corner so that the coating amount was 15 g/m ² respectively. Thereafter, the same procedure as in Example 2 was carried out to obtain highly smooth coated paper. At this time, the average pore radius of the coated layer of highly smooth coated paper when using base paper for casting is 0.05μ, and the average pore radius of the coated layer of highly smooth coated paper when using base paper for photographic paper. The pore radius was 0.03μ. The base paper for casting (1) is based on 100 parts by weight of pulp, 0.5 parts by weight of rosin size, 10 parts by weight of filler (clay: talc = 1:1), 1.0 parts by weight of sulfuric acid band, and surface size (solid content of oxidized starch). 3% liquid) with a basis weight of 100 g/m ² was used. In addition, base paper for photographic paper (2) contains 3 parts by weight of cationized starch, 0.2 parts by weight of anionized polyacrylamide, and 0.4 parts by weight of alkyl ketene dimer emulsion (as ketene dimer content) per 100 parts by weight of pulp.
parts by weight, and 0.4 parts by weight of polyaminopolyamide epichlorohydrin resin were added to form paper. Subsequently, 3 parts by weight of carboxy-modified polyvinyl alcohol,
0.05 parts by weight of optical brightener, 0.002 parts by weight of blue dye,
It was obtained by impregnating with an impregnating solution consisting of 0.2 parts by weight of citric acid and 97 parts by weight of water, drying with hot air, and further calendering. The two types of highly smooth coated paper thus obtained and the two types of comparative paper [(1) and (2)] were treated with resin on both sides in the same manner as in Example 1, and A resin-coated paper was prepared and its sharpness was determined. The results obtained are shown in Table 3.

[Table] From Table 3, the sharpness of the photographic resin-coated paper based on casting base paper (experiment number 10) was poor with a poor grade, but the sharpness of the photographic resin-coated paper using high smoothness coated paper as the base paper was poor. It can be seen that good sharpness can be obtained in the case of resin-coated paper (experiment number 8). In addition, the sharpness when using photographic resin-coated paper based on photographic paper base paper (experiment number 11) is as follows:
Slightly worse than good grade, but in the case of photographic resin-coated paper based on highly smooth coated paper (Experiment No. 9)
It can be seen that excellent sharpness can be obtained. Example 4 90 parts by weight of kaolin, 10 parts by weight of precipitated calcium carbonate, and 0.2 parts by weight of sodium pyrophosphate were dispersed in water using a Coles disperser to prepare a pigment slurry with a solid content concentration of 70%. To this was added 1 part by weight of phosphoric acid esterified starch and 15 parts (solid content) of styrene-butadiene latex having a glass transition temperature of 0°C, and after thorough stirring, a coating liquid with a solid content concentration of 62% was obtained. This coating liquid was applied to the photographic paper base paper used in Example 3 using a blade coater so that the dry weight was 20 g/m ² , and then the same method as in Example 1 was used to coat the base paper with a high smoothness. Got paper. At this time, the average pore radius of the coated layer of the highly smooth coated paper was 0.04μ. A photographic resin-coated paper was obtained in exactly the same manner as in Example 1 using the highly smooth coated paper thus obtained and the photographic paper base paper used for this highly smooth coated base paper for comparison. , the sharpness was determined. We also investigated die lip stains that occurred on the die of the melt extruder. However, the resin composition to be melt-extruded coated onto the surface of the base paper for photographic paper is 32 parts by weight of masterbatch, 20 parts by weight of high-density polyethylene (MI7, density 0.96 g/cm ³ ), and low-density polyethylene (MI5, density
A resin composition containing 48 parts by weight (0.92 g/cm ³ ) was used. The results obtained are shown in Table 4. *<Number of Die Lips> A masterbatch containing titanium dioxide pigment etc. was obtained under the following conditions using the resin formulation described in the Examples. Screw type extruder with extrusion diameter 65mm and 750
The number of stains generated on the die lip after melt extrusion for 1 hour at a melting temperature of 320° C. and a screw rotation of 150 rpm using a melt extruder having a mm-wide T-die is shown.

[Table] Table 4 shows that photographic resin-coated paper, in which a resin composition containing 10% titanium dioxide pigment is melt-extruded and coated on the coated surface of highly smooth coated paper, has excellent sharpness and is free from die lip stains. It was extremely small and caused no operational problems. On the other hand, in order to obtain excellent sharpness equivalent to that obtained when the above-mentioned highly smooth coated paper is used as the base paper, titanium dioxide pigment in the surface resin composition is used when the base paper for photographic printing paper is used as the base paper. The content is required to be 16%, and in this case, die lip stains occur significantly, which poses a problem in terms of operation. Example 5 The resin composition provided on the coating layer side of Experiment No. 8 in Example 3 was mixed with 26 parts by weight of masterbatch, 20 parts by weight of high-density polyethylene (MI7, density 0.96 g/cm ³ ) and low-density polyethylene (MI5, density 0.92g/ ^cm3 )
A photographic resin-coated paper was obtained in the same manner as in Example 3, except that 54 parts by weight was used, and the sharpness was determined. As a result, excellent sharpness equivalent to that of Experiment No. 9 in Example 3 was obtained. Furthermore, there was almost no occurrence of die lip stains, and there were no operational problems. Example 6 100 parts by weight of kaolin and 0.2 parts by weight of sodium pyrophosphate were dispersed in water using a Coles disperser to prepare a pigment slurry with a solid content of 60%. To this was added 90 parts (solid content) of styrene-butadiene latex having a glass transition temperature of 40°C, and after thorough stirring, a coating liquid with a solid content concentration of 40% was obtained. This coating liquid was applied to the base paper for photographic printing paper used in Example 3 using an air knife coater so that the dry weight was 10 g/m ² , and then the same method as in Example 1 was used to apply a highly smooth coating. I got the covering paper. At this time, the average pore radius of the coating layer of the highly smooth coated paper was 0.05μ. A photographic resin-coated paper was obtained from this highly smooth coated paper in the same manner as in Example 1. However, at this time, melt extrusion coating was applied to the front and back surfaces at 10, 20, and 30 g/m ² , respectively. Thereafter, the sharpness was determined in the same manner as in Example 1. As a result, excellent sharpness was obtained at all melt extrusion coating weights of 10 to 30 g/m ² .

Claims (1)

[Scope of Claims] 1. A photographic resin-coated paper in which at least one surface of a base paper is coated with a resin composition comprising at least a resin and a titanium dioxide pigment, wherein at least one surface of the base paper is coated with an adhesive. Provide a coating layer containing
1. A photographic resin-coated paper characterized in that it is a coated paper in which the coated layer is pressed against a heated mirror drum or gloss calendar to give a highly smooth finish. 2. The photographic resin-coated paper according to claim 1, wherein the coating layer contains a pigment. 3. The photographic resin-coated paper according to claim 1, wherein the coating layer consists only of an adhesive.