JPH0772788B2 - Resin coated paper for photography - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photographic resin-coated paper in which at least one surface of a paper or synthetic paper substrate is coated with a resin composition containing at least a titanium dioxide pigment and a resin. Relates to a resin-coated paper for photographic use having good surface quality in which no microgrit appears on the coated resin surface of the resin-coated paper.

The term "microgrit" as used herein refers to a photographic resin-coated paper in which at least one surface of a paper or synthetic paper substrate is coated with a resin composition. Refers to a grain.

[0003]

BACKGROUND OF THE INVENTION There are various causes of microgrit. For example, a photographic resin coating produced by melt extrusion coating a photographic thermoplastic resin on at least one surface of a paper or synthetic paper substrate with a melt extruder. The causes of the microgrit appearing on the paper are (1) when the thermoplastic resin itself to be used produces a lot of gel, (2) from the melt extruder through the die,
When the molten resin is extruded into a film and the temperature cannot be maintained at an appropriate temperature and the flow is uneven, (3) If the screen attached to the breaker plate in the melt extruder is dirty, (4) Examples include cracks in the barrel liner in the melt extruder, and (5) insufficient warpage in the melt extruder. These are often relatively easily solved by a skilled engineer.

However, the most difficult countermeasure against microgrit is when the paper or synthetic paper substrate is coated with a resin composition containing at least a thermoplastic resin and a pigment, and microgrit is generated in the photographic resin-coated paper. is there.

In the first place, a method of incorporating a pigment into a thermoplastic resin, preferably a polyolefin resin, is to prepare a so-called masterbatch in which the pigment is contained in the resin in a high concentration in advance, and to prepare them in a desired ratio with a diluting resin. It is usual to use by diluting and mixing, or making a so-called compound in which a desired composition ratio is initially contained in a resin in a resin.

However, especially Banbury mixers,
When preparing a masterbatch or compound by melt-kneading a thermoplastic resin and a pigment using a usual melt-kneader such as a kneader, relatively coarse pigment particles in the thermoplastic resin become fine. It tends to be dispersed as it is, without being dispersed, thus leaving undispersed pigment particles in the masterbatch or compound. As a result, at least one surface of a paper or synthetic paper substrate is coated on a resin surface of a photographic resin-coated paper coated with a resin composition composed of a pigment and a resin produced by using the masterbatch or the compound. Microgrit will be generated.

The generation of microgrit on resin-coated paper as a photographic support causes serious photographic defects.
That is, when a person is copied on a photographic paper having a resin-coated paper in which microgrit is generated as a photographic support, if the microgrit appears on a face or the like, the commercial value of the person is completely lost.

By the way, the pigment contained in the resin layer on the emulsion-coated surface side of the resin-coated paper as a photographic support is usually a titanium dioxide pigment because of its excellent whiteness, hiding power and resolution. It is well known to be done.

Further, photographic resin-coated paper is already known, and for example, as disclosed in US Pat. No. 3,501,298, both sides of a paper substrate are coated with a polyolefin resin, particularly a polyethylene resin, and emulsion coating is carried out. It is well known that the polyolefin resin layer on the surface side contains a titanium dioxide pigment, a coloring pigment, a fluorescent whitening agent and the like. Another type of photographic resin-coated paper is disclosed in JP-A-57-3
There is also known a photographic resin-coated paper in which a paper base as disclosed in Japanese Patent No. 0830 is coated with a resin composition containing a white pigment such as titanium dioxide which is polymerized and cured by electron beam irradiation.

However, a photographic resin-coated paper in which at least one surface of a paper or synthetic paper substrate is coated with a resin composition containing at least a titanium dioxide pigment and a resin is used as a master for the titanium dioxide pigment as described above. When produced using a batch or compound, as described above on the resin surface of the photographic resin-coated paper, there are many occurrences of microgrit due to undispersed pigment, that is, titanium dioxide pigment in this case. There was a serious problem that it tended to be easy to do.

[0011]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a photographic resin-coated paper of good surface quality containing a titanium dioxide pigment in a resin layer, in which the generation of microgrit is completely suppressed or suppressed. To provide. Another object of the present invention is to provide a photographic resin-coated paper which is excellent in light resistance or heat resistance and which has a titanium dioxide pigment in a resin layer and has a good surface quality.

[0012]

As a result of intensive studies conducted by the present inventors, the object of the present invention is to provide a resin composition in which at least one surface of a paper or synthetic paper substrate is composed of at least a titanium dioxide pigment and a resin. In a photographic resin-coated paper coated with a product, the titanium dioxide pigment is pulverized with a steam mill, and the titanium dioxide pigment is 60 μm.
It has a suspension electric conductivity of mho (μΩ ^-1 ) / cm or less, which is defined below, and the total amount of the inorganic surface treating agent is 0.2 to 1.2% by weight with respect to the titanium dioxide pigment. It has been found to be achieved by including in the resin layer a titanium dioxide pigment surface-treated with aluminum hydroxide oxide and silicon hydroxide oxide (calculated in the form of Al ₂ O ₃ and SiO ₂ ).

The suspension electric conductivity of the titanium dioxide pigment as used herein is defined as follows.

That is, electric conductivity of suspension: A rotor of a magnetic stirrer was placed in a beaker having a volume of 100 ml.
100 ml of distilled water (water temperature 21.5 ° C.) was added, and subsequently 10.0 g of titanium dioxide pigment was added. After the addition, a conductivity cell (θ = 0.1) of an electric conductivity meter is installed in the liquid so that the value of the electric conductivity with time can be traced. After installation, the magnetic stirrer was started, the rotor was rotated at a rotation speed of 420 rotations for 1 minute, the contents in the beaker were stirred, and the contents were made into a titanium dioxide pigment suspension. The liquid is stirred for 16 minutes while keeping the liquid temperature at 21.5 ° C ± 0.5 ° C. Sixteen minutes after the start of stirring, the electrical conductivity of the titanium dioxide pigment suspension was adjusted to a liquid temperature of 21.5 ° C.
In (temperature compensation), the suspension is stirred and read and measured.

Specifically, a magnetic stirrer rotor (sold by Universal Co., Ltd., a Teflon-processed rotor having a length of 45 mm and a diameter of 8 mm) was placed in a 100 ml beaker, and 100 ml of distilled water (water temperature 21.5). C.) and subsequently add 10.0 g of titanium dioxide pigment. After the addition, the beaker is placed on a magnetic stirrer (Yamato Scientific Co., Ltd., type MH-61). After that, a conductivity cell (manufactured by Toa Denpa Kogyo Co., Ltd., model CM-5B) (Type CG-2001PL (θ = 0.1) manufactured by Toa Denpa Kogyo Co., Ltd.) was placed under the liquid level of the beaker to remove the liquid. Installed in a liquid so that the electric conductivity of can be measured (without touching the rotor, of course) so that the value of electric conductivity over time can be traced.
The magnetic stirrer was started, the rotor was rotated at a rotation speed of 420 rotations per minute, the contents in the beaker were stirred, and the contents were made into a titanium dioxide pigment suspension. Stir for 16 minutes while maintaining the liquid temperature at 21.5 ° C ± 0.5 ° C. Sixteen minutes after the start of stirring, the titanium dioxide pigment suspension is read and measured at a liquid temperature of 21.5 ° C. while stirring the suspension.

The electric conductivity thus obtained is defined as the suspension electric conductivity of the titanium dioxide pigment as used herein.

In the present invention, a steam mill such as a micronizer is suitable, and it is difficult to sufficiently suppress the generation of microgrit with a commonly used impact crusher such as a hammer mill. . Therefore, like titanium dioxide in the present invention, titanium dioxide having a suspension electric conductivity of 60 μmho (μΩ ⁻¹ ) / cm or less, and by using a steam mill, generation of microgrit is extremely reduced. A small amount of photographic resin-coated paper can be obtained.

As described above, the present invention particularly relates to a photographic thermoplastic resin-coated paper which is produced by using a masterbatch or a compound of a titanium dioxide pigment and which is well prevented from generating microgrit and has good surface quality. It is effective in providing a polyolefin resin-coated paper.

This is a Banbury mixer having a small impact force applied to the titanium dioxide pigment as compared with a conventional masterbatch or compound composed of the titanium dioxide pigment and a thermoplastic resin, that is, a mixer usually used for preparing paints and the like. , A kneader, a masterbatch prepared by an ordinary melt-kneader such as an extruder for kneading, or a photographic thermoplastic resin-coated paper produced by using a compound, particularly a photographic polyolefin resin-coated paper, as a titanium dioxide pigment. In the case of using the conventionally known one, although the occurrence of microgrit, which is considered to be mainly caused by the undispersed substance of the titanium dioxide pigment, when the titanium dioxide pigment of the present invention is used, the generation of microgrit is well prevented. It is well understood from this.

Further, the present invention is a resin-coated paper which uses paper or synthetic paper containing a titanium dioxide pigment whose surface is treated with an inorganic surface-treating agent as a substrate, and which is excellent in light resistance and heat resistance. It is particularly effective for providing an excellent photographic resin-coated paper having good surface quality in which generation of microgrit is prevented. This will be apparent from the description in the following specification.

In the first place, commercially available titanium dioxide pigments have an inorganic surface treating agent such as aluminum oxide hydroxide, silicon oxide hydroxide, titanium oxide hydroxide, zirconium oxide hydroxide, zinc hydroxide, magnesium hydroxide, manganese compound, and phosphoric acid compound on the surface of the particles. In particular, most of them are modified by precipitating hydrous aluminum oxide and / or hydrous silicon oxide. As described above, the reason why the titanium dioxide pigment is modified by precipitating the inorganic surface treating agent on the surface of the particles is generally to improve the light resistance of the titanium dioxide pigment and to improve the dispersibility of the titanium dioxide pigment in the resin. It was thought to be because. As a result of examination by the present inventors, the surface treatment is not applied or the inorganic surface treatment agent is extremely mild (the inorganic surface treatment agent is less than 0.2% by weight calculated as an anhydride with respect to titanium dioxide). When a titanium dioxide pigment which is only surface-treated is used in a resin, it may cause a serious defect that the light resistance and heat resistance of the resin layer containing the titanium dioxide pigment are certainly deteriorated. all right. This means that even when a resin-coated paper containing a titanium dioxide pigment in the resin layer is used as a support for photographic paper, the white background of the photograph is discolored over time and the storability of the photograph is deteriorated. Leads to.

However, on the other hand, as a result of examination by the present inventors,
When a titanium dioxide pigment surface-treated with an inorganic surface-treating agent, in particular with hydrous aluminum oxide, in an amount of 0.2% by weight calculated as an anhydride with respect to titanium dioxide is used in the resin layer, Although the light resistance and heat resistance of the resin-coated paper containing the titanium dioxide pigment in the resin layer are improved,
Surprisingly, depending on the degree of surface treatment of the titanium dioxide pigment with an inorganic surface treatment agent, in particular with hydrous aluminum oxide, as the degree increases, the dispersibility of the titanium dioxide pigment in the resin, especially the thermoplastic resin, increases. It becomes worse, and there is a tendency for microgrids to frequently occur on the resin surface of the resin-coated paper.
Furthermore, when the degree of surface treatment of the titanium dioxide pigment with an inorganic surface treating agent, particularly with hydrous aluminum oxide, is 1.2% by weight or more calculated as an anhydride relative to titanium dioxide, the resin of the titanium dioxide pigment is In particular, the dispersibility in a thermoplastic resin becomes very poor, and microgrits are extremely frequently generated on the resin surface of the resin-coated paper.

As described above, there is a fundamental contradiction in the titanium dioxide pigment surface-treated with the inorganic surface-treating agent contained in the resin layer of the photographic resin-coated paper, particularly the photographic thermoplastic resin-coated paper. there were. That is, in order to improve the light resistance and heat resistance of photographic resin-coated paper, especially photographic thermoplastic resin-coated paper, the inclusion of highly surface-treated titanium dioxide pigment in the resin layer cannot prevent the generation of microgrit. On the other hand, in order to prevent the generation of microgrit, if the resin layer contains a titanium dioxide pigment that is not surface-treated or only slightly surface-treated, the light resistance and heat resistance of the photographic resin-coated paper There was a contradiction that it was bad. Further, even though it is certain that the generation of microgrit is due to the non-dispersibility of the titanium dioxide pigment, and therefore the dispersibility of the titanium dioxide pigment itself in the resin is involved to some extent, the generation of microgrit does not occur. There are many points that cannot be explained only by the dispersibility of titanium pigment. What is more important is that the dispersibility of the titanium dioxide pigment in the thermoplastic resin, especially in the non-polar polyolefin resin, is related to the pigment physical properties of the titanium dioxide pigment itself and how it is involved. It is not clear, let alone the specific method of improving the dispersibility of the titanium dioxide pigment in the thermoplastic resin, especially in the polyolefin resin, and it is still in the photographic industry that vigorous studies are still underway. It is in. Thus, it was extremely difficult to develop a photographic resin-coated paper having excellent light resistance and heat resistance and good surface quality in which generation of microgrit was prevented, and particularly thermoplastic resin coating for photographic use. However, the resin layer of the resin-coated paper, especially the thermoplastic resin-coated paper was surface-treated with the inorganic surface treatment agent of hydrous aluminum oxide and hydrous silicon oxide, and the titanium dioxide pigment was pulverized by the fluid energy pulverizer. In addition, by containing a titanium dioxide pigment having a suspended electric conductivity of 60 μmho (μΩ ⁻¹ ) / cm or less as described herein, excellent light resistance and heat resistance and excellent microgrit A new fact that it is possible to provide a photographic resin-coated paper having good surface quality in which generation is prevented, particularly a photographic thermoplastic resin-coated paper, and as the titanium dioxide pigment in the present invention, the total treatment amount of the inorganic surface-treating agent However, when the titanium dioxide pigment is contained in an amount of 0.2 to 1.2% by weight calculated as an anhydride with respect to the titanium dioxide pigment, generation of microgrit is particularly prevented. We discovered a new fact that that is what has led to the present invention.

The titanium dioxide pigment used in the practice of the present invention has a suspension electrical conductivity of 60 μm as referred to herein.
Any rutile structure, anatase structure, chlorine method, or sulfuric acid method can be used as long as it has a mho (μΩ ⁻¹ ) / cm or less. In the case of the chlorine method, titanium dioxide particles are formed by vapor-phase oxidative decomposition of titanium tetrachloride at a high temperature in the case of the chlorine method, and a rutile structure is generally easily obtained. In the case of the sulfuric acid method, hydrous titanium dioxide is formed by hydrolysis of an aqueous solution of titanyl sulfate and is fired to develop its pigmentary properties. In the case of the sulfuric acid method, both the anatase structure and the rutile structure can be obtained, but in the case of manufacturing the rutile structure, the firing temperature is higher than that of the anatase structure, or the firing is performed. At times, a metal compound such as a zinc compound for promoting the formation of the rutile structure is allowed to coexist. The product formed by calcination or oxidation will be referred to as a titanium dioxide clinker hereinafter. Titanium dioxide clinker is dry pulverized by a centrifugal roller mill (mainly Raymond mill), suspended pulverized product in water to form titanium dioxide slurry, and then wet pulverized by wet ball mill or vibration mill, continuous horizontal centrifugal separation. Machine and / or vibrating double deck screen (325 mesh US
Wet classification is carried out through a standard screen to form a titanium dioxide slurry substantially free of titanium dioxide, hereinafter referred to as fines. For fines from which coarse particles have been removed and which is still in the form of a slurry, the surface of titanium dioxide particles is surface-treated with an inorganic surface-treating agent of hydrous aluminum oxide and hydrous silicon oxide in a reaction treatment tank equipped with a stirrer. After the reaction treatment, it is filtered with a filter press and dried with a band dryer.
The titanium dioxide pigment having a suspension electric conductivity of 60 μmho (μΩ ⁻¹ ) / cm or less, as described herein, is produced by crushing with an impact crusher. The mother liquor is filtered, and the titanium dioxide cake in the filter press is then washed with running water to 60 μmho (μΩ ⁻¹ ) /
It is prepared by washing with water until a titanium dioxide pigment having a suspension electrical conductivity of less than or equal to cm is obtained. Rinsing conditions such as washing time, amount of water, pressure of water, etc., are the titanium dioxide pigment obtained by subjecting the titanium dioxide cake collected under a series of experimental conditions to drying and crushing to obtain a titanium dioxide pigment. Can be determined by measuring the electrical conductivity of the suspension. Washing with water is carried out in the filter press by running the reaction solution containing titanium dioxide after the surface treatment as it is or by resuspending the filter cake in the tank and running water in a form of exchanging the accumulated water or the supernatant solution. It can also be performed together with the water washing or separately. From the viewpoint of further preventing microgrit, the titanium dioxide pigment in the present invention preferably has a suspension electric conductivity of 55 μmho (μΩ ⁻¹ ) / cm or less, particularly 50
It is more preferably μmho (μΩ ⁻¹ ) / cm or less.

The titanium dioxide pigment thus obtained has a suspension electric conductivity of 60 μmho (μΩ).
If it is ^-1 ) / cm or less, it is somewhat effective in preventing the generation of microgrit, but in order to make it even more effective, use a steam mill such as a micronizer for grinding after drying the titanium dioxide cake in the above process. Can be obtained by doing.

The titanium dioxide pigment used in the practice of the present invention is one which has been surface-treated by a conventionally known method with an inorganic surface-treating agent of hydrous aluminum oxide and hydrous silicon oxide. For example, by adding a water-soluble aluminum salt and a water-soluble silicon compound to a titanium dioxide slurry, preferably fine, and subsequently changing the pH in the slurry, the sparingly soluble oxide hydrate and / or the sparingly soluble metal compound can be added to titanium dioxide. What was surface-treated by precipitating on a pigment can be used. In particular, as the water-soluble aluminum salt, for example, an aluminate such as alkali aluminate is used, and an aluminate is optionally added to a slurry that exhibits an alkaline reaction after addition of a water-soluble alkali such as caustic soda and potassium hydroxide. For reducing the pH value and precipitating hydrous aluminum oxide, those which are surface-treated by adding a strong acid such as sulfuric acid or hydrochloric acid or a salt exhibiting an acidic reaction are useful. In this case, of the alkali aluminates, sodium aluminate is particularly useful. In the case of using other inorganic surface treatment agent in addition to aluminate, before addition of aluminate,
Those added at any stage during addition or after the addition can be used, but especially those added before addition of aluminate are useful. As the inorganic surface treatment agent other than the aluminate used for the surface treatment, various compounds such as alkali silicate and silicon tetrachloride can be used as the silicon compound.

The resin used in the practice of the present invention is
Homopolymers or copolymers of polyolefins, polystyrenes, polyvinyl chlorides, polyacrylic esters, linear polyesters such as polyethylene terephthalate, polycarbonates, polyamides such as nylon, cellulose esters, polyacrylonitrile, such as ethylene-vinyl acetate copolymers and them. Any resin may be used as long as it is a resin capable of coating a resin film on a base paper such as a mixture of polyolefins, polystyrene, polyethylene terephthalate, and thermoplastic resins of polyvinyl chloride are preferable, and among them, a polyolefin resin is extrudable and has a coating property and a base paper. It is particularly advantageous in terms of good adhesion with, cost, etc. The polyolefin resin in the present invention is a homopolymer such as low-density polyethylene, high-density polyethylene, polypropylene, polybutene, polypentene, or a copolymer composed of two or more olefins such as ethylene-propylene copolymer and a mixture thereof. , Various density and melt viscosity index (melt index: hereinafter simply abbreviated as MI) may be used alone or in combination.

The content of the titanium dioxide pigment contained in the resin layer of the photographic resin-coated paper in the present invention is as follows:
If it is 5% by weight or less relative to the resin, the hiding power as a photographic support is insufficient, while if it is 40% by weight or more, the fluidity is lowered, which is not preferable, and particularly preferably 7.5.
-25% by weight.

The resin layer of the photographic resin-coated paper according to 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, sodium laurate and the like. The addition amount thereof is preferably in the range of 0.01% by weight to 5% by weight with respect to the resin composition containing titanium dioxide.

In the resin layer of the photographic resin-coated paper according to the present invention, in addition to the titanium dioxide pigment and, if necessary, a fatty acid metal salt, a white pigment such as zinc oxide, talc or calcium carbonate, stearic acid. Amides, fatty acid amides such as arachidic acid amide, tetrakis (methylene-3
Antioxidants such as (3,5-di-tert-butyl-4-hydroxy-phenyl) propionate) methane, 2,6-di-tert-butyl-4-methyl-phenol, cobalt blue, dark blue, ultramarine blue, cobalt Coloring pigments such as violet and optical brighteners may be added.

The photographic resin-coated paper according to the present invention is a paper or synthetic paper substrate that runs normally (hereinafter, simply referred to as base paper).
It is manufactured by melt-extruding a resin composition containing a titanium dioxide pigment heated and melted into a film form from a slit die. When the resin is a polyolefin resin, the melt extrusion temperature is preferably 200 ° C to 350 ° C. Also,
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 treatment or flame treatment. The thickness of the resin layer of the resin-coated paper is not particularly limited,
In general, extrusion coating having a thickness of about 5 to 50 microns is advantageous. In addition, in a normal resin-coated paper in which both sides of the base paper are coated with a resin, the resin surface containing the titanium dioxide pigment has a glossy surface depending on the application,
It has a matte surface, a silky surface, etc., and the back surface on the opposite side is usually a matte surface, and the front surface or both front and back surfaces can be subjected to activation treatment such as corona discharge treatment or flame treatment as required.

The base paper used in the practice of the present invention may be any of ordinary natural pulp paper, synthetic fiber, or so-called synthetic paper obtained by synthesizing synthetic resin film, but softwood pulp, hardwood pulp, mixed softwood and hardwood pulp. Natural pulp paper containing wood pulp as a main component is advantageously used.
The thickness of the base paper is not particularly limited, but base paper having a good surface smoothness is preferable, and the basis weight is 50 to 250.
g / m ² is preferred.

The base paper containing natural pulp as a main component, which is advantageously used in the practice of the present invention, may contain various polymer compounds and additives. For example, as a dry paper strengthening agent, cationized starch, cationized polyacrylamide, anionized polyacrylamide, carboxy-modified polyvinyl alcohol, gelatin and the like, and as a sizing agent, fatty acid salt, rosin derivative, dialkylketene dimer emulsion, petroleum resin emulsion , Styrene-maleic anhydride copolymer alkyl ester ammonium salt, pigments such as clay, kaolin, calcium carbonate,
Wet paper strengthening agents such as barium sulfate and titanium oxide, melamine resins, urea resins, epoxidized polyamide resins, fixing agents, polyvalent metal salts such as aluminum sulfate and aluminum chloride, and cation-modified polymers such as cationized starch. As the pH adjusting agent, caustic soda, sodium carbonate, hydrochloric acid and the like, and as the inorganic electrolyte, salt, mirabilite and the like, as well as dyes, optical brighteners and latex can be appropriately combined and contained.

Various silver halide photographic emulsion layers can be provided on the photographic resin-coated paper of the present invention. For example, silver chloride, silver bromide, silver chlorobromide, silver iodobromide, and silver chloroiodobromide emulsion layers can be provided. Further, a color coupler may be incorporated in the silver halide photographic emulsion layer to provide a multilayer silver halide photographic constituent layer. As a binder for these silver halide emulsion layers, in addition to ordinary gelatin, hydrophilic polymer substances such as polyvinylpyrrolidone, polyvinyl alcohol, and sulfate ester compounds of polysaccharides can be used. Further, the silver halide emulsion layer may contain various additives. For example,
As sensitizing dyes, cyanine dyes, merocyanine dyes, etc., chemical sensitizers, water-soluble gold compounds, sulfur compounds, etc., antifoggants or stabilizers, hydroxy-triazolopyrimidine compounds, mercapto-heterocyclic compounds, etc. As film agents, formalin, vinyl sulfone compounds, aziridine compounds, etc., as coating aids, benzene sulfonates, sulfocuccinate salts, etc., as stain inhibitors, dialkyl hydroquinone compounds, etc., development accelerators, hydroquinone, phenidone As UV absorbers, such as benzotriazole compounds, in addition to fluorescent whitening agents, sharpness improving dyes, antistatic agents, pH adjusting agents, and water-soluble iridium compounds and water-soluble rhodium compounds during the production and dispersion of silver halide. Including a combination of It can be allowed to.

Further, on the back surface of the photographic resin-coated paper in the present invention, that is, on the surface of the support opposite to the surface on which the photographic constituent layers, most of which are silver halide photographic constituent layers, are applied, curl prevention and charging are prevented. A coating layer composed of a hydrophilic colloid layer called a back coat layer can be provided for the purpose of prevention, adhesion prevention, and slip prevention. The back coat layer may contain a binder or protective colloid, a curing agent, an antistatic agent, a surfactant, a matting agent, latex and the like.

[0036]

EXAMPLES Examples will now be described in order to more specifically describe the present invention.

Example 1 Anatase type titanium dioxide clinker produced by the sulfuric acid method was dry pulverized with a centrifugal roller mill, and the pulverized product was suspended in water in the presence of sodium hydroxide to form a titanium dioxide slurry, which was further subjected to a wet ball mill. Wet pulverization and wet classification using a continuous horizontal centrifuge were performed to obtain about 25% by weight titanium dioxide slurry substantially free of coarse-grained titanium dioxide, and SiO 2 with respect to titanium dioxide on a dry basis. After adding an aqueous sodium silicate solution in an amount of 0.25% by weight calculated in the form of _2, the amount of 0.50% by weight calculated in the form of Al ₂ O ₃ with respect to titanium dioxide on a dry basis. 50 wt% sodium aluminate aqueous solution was added and held for 30 minutes. The pH of the slurry was then lowered to 7.0 by addition of 20% by weight sulfuric acid and the slurry was aged for 2 hours. After aging, the first mother liquor of the titanium dioxide slurry surface-treated with hydrous aluminum oxide and hydrous silicon oxide is filtered with a filter press, and then the titanium dioxide cake in the filter press is run with running water to 50 μmho (μΩ ^-1 ) / cm.
The suspension was washed with water under predetermined washing conditions until a titanium dioxide pigment having an electric conductivity of suspension was obtained.

Thereafter, the titanium dioxide cake is dried, and further, using a steam mill equipped with a constant amount feeder, about 250 ° C.
The powder was pulverized through superheated steam to produce a titanium dioxide pigment having a suspension electric conductivity of 50 μmho (μΩ ⁻¹ ) / cm.

For comparison, the surface treatment amount of titanium dioxide only with hydrous aluminum oxide is 0.15% by weight or 2.0% by weight with respect to titanium dioxide on a dry basis. Suspended liquid conductivity of 50μmho (μ
Titanium dioxide having an Ω ⁻¹ ) / cm was produced, respectively.

Separately, for comparison, the titanium dioxide cake was dried and then shock pulverized with a hammer mill equipped with a quantitative feeder of another series to obtain a suspension electric conductivity of 50 μmho (μΩ ^{−). A} titanium dioxide pigment having a value of ¹ ) / cm was produced.

For each of the titanium dioxide pigments thus obtained, 70 parts by weight of low-density polyethylene (MI = 4, density 0.923 g / cm ³ ), 30 parts by weight of titanium dioxide pigment and 1.5 parts by weight of zinc stearate. The parts were thoroughly kneaded at 150 ° C. using a Banbury mixer to obtain the above master batches of the titanium dioxide pigment.

On the other hand, 50 parts by weight of hardwood bleached kraft pulp and 50 parts by weight of softwood bleached sulfite pulp were mixed with Canadian Standard Freeness 310 m.
The pulp was beaten to give 1 part, and 3 parts by weight of cationized starch and 0.1 part of anionized polyacrylamide were added to 100 parts by weight of pulp.
2 parts by weight, alkyl ketene dimer emulsion (as ketene dimer content) 0.4 part by weight, polyaminopolyamide epichlorohydrin resin 0.4 part by weight were added to give a basis weight of 16
Paper of 0 g / m ² was made. The obtained wet paper is dried at 110 ° C., and subsequently carboxy-modified polyvinyl alcohol 3
Parts by weight, brightening agent 0.05 parts by weight, blue dye 0.00
After impregnating 25 g / m ^{2 of an} impregnating liquid consisting of 2 parts by weight, citric acid 0.2 parts by weight and water 97 parts by weight, drying with hot air at 110 ° C., and further supercalendering at a linear pressure of 90 kg / cm, Both sides were subjected to corona discharge treatment to produce a base paper of photographic resin-coated paper.

Next, a 1: 1 mixture of high density polyethylene (density 0.96 g / cm ³ , MI = 5) and low density polyethylene (density 0.92 g / cm ³ , MI = 5) was applied to the back surface of the base paper. Coating was performed at a resin temperature of 330 ° C. to a thickness of 30 μ using a melt extrusion coating machine. Then, on the surface of the base paper, 30 parts by weight of the above-mentioned master batch of titanium dioxide pigment, 30 parts by weight of high-density polyethylene (density 0.96 g / cm ³ , MI = 5) and low-density polyethylene (density 0.92 g / cm ³ , MI = 5) 4
A resin composition of 0 part by weight was coated at a resin temperature of 330 ° C. to a thickness of 30 μm to produce polyethylene resin-coated paper containing the titanium dioxide pigment. At that time, the surface of polyethylene containing titanium dioxide pigment is
The glossy surface was completely flat, and the surface quality of the back polyethylene was a matte surface such as paper.

The number of microgrit generated on the polyethylene resin surface containing the titanium dioxide pigment of the polyethylene resin-coated paper thus obtained was visually counted and judged.

The light resistance of the polyethylene resin-coated paper was tested as follows. The resin surface containing the titanium dioxide pigment of the resin-coated paper is irradiated with a Suga Test Instruments Fedometer (FAL-25X-HCL type) for 120 hours, and then the yellow density (hereinafter referred to as Y density) of the irradiated surface of the sample is Macbeth. It was measured and measured with a densitometer (TD-504 type). The larger the value, the higher the Y concentration, and the higher the Y concentration, the poorer the light resistance of the sample. On the other hand, the lower the Y concentration, the better the light resistance of the sample.

As a result, based on titanium dioxide on a dry basis, 0.5% by weight of aluminum hydroxide calculated in the form of Al ₂ O ₃ and 0.25% by weight of water content calculated in the form of SiO _2. Resin according to the present invention, which is surface-treated with silicon oxide, has a suspension electric conductivity of 50 μmho (μΩ ⁻¹ ) / cm, and is a titanium dioxide pigment obtained by grinding the titanium dioxide pigment with a steam mill. The coated paper was excellent in light resistance and heat resistance as well as in which generation of microgrit was remarkably prevented, and was suitable as a photographic support.

On the other hand, the resin-coated paper using the titanium dioxide pigment whose surface treatment amount of titanium dioxide only with hydrous aluminum oxide is 0.15% by weight with respect to titanium dioxide on a dry basis has poor light resistance. Further, resin-coated paper using a titanium dioxide pigment whose surface treatment amount of titanium dioxide only with hydrous aluminum oxide is 2.0% by weight with respect to titanium dioxide on a dry basis is a problem because many microgrit are generated. It was Further, the resin-coated paper using the titanium dioxide pigment crushed by a hammer mill has a problem that many microgrit are generated.

[0048]

EFFECTS OF THE INVENTION According to the present invention, generation of microgrit is remarkably suppressed, surface quality is good, and light resistance is good.
An excellent photographic resin-coated paper containing a titanium dioxide pigment in the resin can be provided.

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Claims (5)

[Claims] 1. A photographic resin coated paper in which at least one surface of a paper or synthetic paper substrate is coated with a resin composition comprising at least a titanium dioxide pigment and a resin, the titanium dioxide pigment being pulverized by a steam mill. And the titanium dioxide pigment is 60 μmho (μΩ ⁻¹ ) / cm
It has a suspension electric conductivity defined below and has a total amount of the inorganic surface-treating agent of 0.2 to 1.2% by weight (Al ₂ O ₃ and SiO _{2) based on the} titanium dioxide pigment. A photographic resin-coated paper, characterized in that it is surface-treated with a hydrous aluminum oxide and a hydrous silicon oxide (calculated in the form of ₂ ). Suspension electric conductivity: A rotor of a magnetic stirrer was placed in a beaker of 100 ml volume, 100 ml of distilled water (water temperature 21.5 ° C.) was added, and subsequently 10.0 g of titanium dioxide pigment.
Is added. After addition, the conductivity cell of the conductivity meter (θ =
0.1) is installed in the liquid so that the value of electric conductivity over time can be traced. After installation, the magnetic stirrer was started, the rotor was rotated at a rotation speed of 420 rotations for 1 minute, the contents in the beaker were stirred, and the contents were made into a titanium dioxide pigment suspension. The liquid is stirred for 16 minutes while keeping the liquid temperature at 21.5 ° C ± 0.5 ° C. Sixteen minutes after the start of stirring, the electrical conductivity of the titanium dioxide pigment suspension is measured at a liquid temperature of 21.5 ° C. (temperature compensation) while stirring the suspension. 2. The photographic resin-coated paper according to claim 1, wherein the resin is a thermoplastic resin. 3. The photographic resin-coated paper according to claim 2, wherein the thermoplastic resin is a polyolefin resin. 4. The photographic resin-coated paper according to claim 3, wherein the polyolefin resin is a polyethylene resin. 5. The photographic resin-coated paper according to claim 2, 3 or 4, wherein the resin composition contains a fatty acid metal salt.