JPH0138291B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a photographic resin-coated paper in which at least one side of a paper or synthetic paper base is coated with a resin composition comprising at least a titanium dioxide pigment and a resin, and more particularly to a resin-coated paper for use in photography. Micro grit on the coated resin surface
This invention relates to a photographic resin-coated paper with good image quality in which no appearance of . 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 substrate is coated with a resin composition. There are various causes of microgrit, but for example, the formation of microgrit that appears on photographic resin-coated paper manufactured by melt-extruding photographic thermoplastic resin onto at least one side of a paper or synthetic paper substrate using a melt extruder. This is because (1) the thermoplastic resin itself tends to generate a lot of gel, and (2) the temperature cannot be maintained at an appropriate temperature when the molten resin is extruded from the melt extruder through the die into a film. If the flow is uneven, (3) if the screen attached to the breaker plate in the melt extruder is dirty, (4) if there are cracks in the barrel liner in the melt extruder, (5) if the melt extruder Examples include cases where there is insufficient bending in the machine, but these can often be resolved relatively easily by skilled engineers. However, the most difficult countermeasure against microgrit is when microgrit occurs in photographic resin-coated paper in which the paper or synthetic paper substrate is coated with a resin composition consisting of at least a thermoplastic resin and a pigment. In the first place, the method of incorporating pigments into a thermoplastic resin, preferably a polyolefin resin, is to prepare a so-called master batch in which pigments are contained in a resin at a high concentration in advance, and then dilute and mix them with a diluent resin to a desired ratio. It is usual to prepare a so-called compound in which a desired composition ratio of pigment is contained in a resin from the beginning. However, when preparing a masterbatch or compound by melt-kneading a thermoplastic resin and a pigment using an ordinary melt-kneading machine such as a Banbury mixer or a kneader, relatively coarse pigment particles are mixed in the thermoplastic resin. However, there is a tendency for pigment particles to be dispersed as they are, rather than being dispersed in a fine state, resulting in the presence of undispersed pigment particles in the masterbatch or compound. As a result, microgrids are deposited on the resin side of a photographic resin-coated paper in which at least one side of the paper or synthetic paper substrate is coated with a resin composition comprising a pigment and a resin produced using the masterbatch or the compound. will occur. The occurrence of microgrit in resin-coated papers used as photographic supports causes serious photographic defects. That is, when a person is photographed on a photographic paper having a resin-coated paper containing microgrit as a photographic support, if microgrit appears in areas such as the face, the photograph has no commercial value. By the way, titanium dioxide pigments are usually not used as pigments contained in the resin layer of the emulsion-coated area of resin-coated paper used as a photographic support because they have excellent whiteness, hiding power, resolution, etc. well known. Resin-coated papers for photography are also already known, for example as disclosed in US Pat. It is well known that the resin layer contains a titanium dioxide pigment, a colored pigment, a fluorescent whitening agent, and the like. Another type of photographic resin-coated paper is a resin composition containing a white pigment such as titanium dioxide, whose paper base is polymerized and cured by electron beam irradiation, as disclosed in JP-A-57-30830. Photographic resin-coated papers coated with are also known. However, for photographic resin-coated paper in which at least one side of the paper or synthetic paper substrate is coated with a resin composition comprising at least a titanium dioxide pigment and a resin, a masterbatch or compound of the titanium dioxide pigment as described above may be used. When manufactured by using the resin-coated photographic paper, as mentioned above, there is a tendency for a large number of microgrits to be generated on the resin surface of the photographic resin-coated paper due to undispersed pigment, that is, titanium dioxide pigment in this case. There was a serious problem. SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a photographic resin-coated paper containing a titanium dioxide pigment in the resin layer and having a good surface quality, in which the generation of microgrit is little or significantly suppressed. Another object of the present invention is to provide a photographic resin-coated paper having excellent light resistance or heat resistance and containing a titanium dioxide pigment in the resin layer and having a good surface quality. As a result of intensive research by the present inventors, an object of the present invention is to provide a photographic resin coating in which at least one side of a paper or synthetic paper substrate is coated with a resin composition comprising at least a titanium dioxide pigment and a resin. It has been found that this can be achieved in paper by incorporating in the resin layer a titanium dioxide pigment having a suspension electrical conductivity defined below of 60 μ/cm or less. The electrical conductivity of a suspension of titanium dioxide pigment herein is defined as follows. That is, suspension electrical conductivity: Place the rotor of a magnetic stirrer in a 100ml beaker,
Add 10 g of distilled water (water temperature 21.5°C) and then add 10.0 g of titanium dioxide pigment. After addition, place the conductivity cell (θ = 0.1) of the electrical conductivity meter into the liquid,
Allows you to track electrical conductivity values over time. After installation, start the magnetic stirrer, rotate the rotor at a rotational speed of 420 revolutions for 1 minute, stir the contents in the beaker, make the contents into a titanium dioxide pigment suspension, and dissolve the titanium dioxide pigment. Stir the suspension for 16 minutes while maintaining the liquid temperature at 21.5°C ± 0.5°C. 16 minutes after the start of stirring, the electrical conductivity of the titanium dioxide pigment suspension was measured at a liquid temperature of 21.5°C (temperature compensation).
While stirring the suspension, read and measure. Specifically, a magnetic stirrer rotor (manufactured by Universal Co., Ltd., 45 mm long, 8 mm diameter Teflon coated rotor) was placed in a 100 ml beaker, and 10 ml of distilled water (water temperature 21.5°C) was poured into the beaker. Then add 10.g of titanium dioxide pigment.
After the addition, the beaker is placed on the stand of a magnetic stirrer (manufactured by Yamato Scientific Co., Ltd., type MH-61). After that, the conductivity cell of the electrical conductivity meter (manufactured by Toa Denpa Kogyo Co., Ltd., model CM-5B) [manufactured by Toa Denpa Kogyo Co., Ltd., type CG-
2001PL (θ=0.1)] was placed in the liquid below the liquid level in a beaker to the extent that the electrical conductivity of the liquid could be measured (of course, without touching the rotor), and the electrical conductivity was measured over time. Allows you to track values. After installation,
Start the magnetic stirrer and turn the rotor to 1.
It rotates at a rotational speed of 420 revolutions per minute to stir the contents in the beaker to form a titanium dioxide pigment suspension.
Stir for 16 minutes while maintaining the temperature at ±0.5°C. Sixteen minutes after the start of stirring, the electrical conductivity of the titanium dioxide pigment suspension is read and measured while stirring the suspension at a liquid temperature of 21.5°C (temperature compensation). The electrical conductivity thus obtained is defined as the titanium dioxide pigment suspension electrical conductivity in this specification. The present invention provides a photographic thermoplastic resin-coated paper, particularly a polyolefin resin-coated paper, which is manufactured using a masterbatch or compound of titanium dioxide pigment and which is well prevented from forming microgrit and has good image quality. It is valid. This is a Banbury mixer, a kneader, and a kneader, which have a lower impact force on the titanium dioxide pigment than the mixers normally used to prepare ordinary masterbatches or compounds consisting of titanium dioxide pigments and thermoplastic resins, such as paints. Photographic thermoplastic resin-coated paper, especially photographic polyolefin resin-coated paper manufactured using a masterbatch or compound prepared using an ordinary melt-kneading machine such as an extruder, contains conventionally known titanium dioxide pigments. It is well understood that when the titanium dioxide pigment of the present invention is used, the generation of microgrit is well prevented when the titanium dioxide pigment of the present invention is used, although microgrit occurs frequently, which is thought to be mainly caused by undispersed particles of titanium dioxide pigment. be done. The present invention also provides an inorganic surface treatment agent in the resin layer.
In particular, it is a paper containing titanium dioxide pigment whose surface has been treated with hydrous aluminum oxide, or a resin-coated paper whose substrate is synthetic paper, which has excellent light resistance and heat resistance, and which has good image quality and is prevented from generating microgrit. To provide photographic resin-coated paper,
Particularly effective. This is clear from the description below. In the first place, commercially available titanium dioxide pigments contain inorganic surface treatment agents such as hydrated aluminum oxide, hydrated silicon oxide, hydrated titanium oxide, hydrated zirconium oxide, Acrylic hydroxide, magnesium hydroxide, manganese compounds, phosphoric acid compounds, etc., especially on the particle surface. Most of them are modified by precipitation of hydrated aluminum oxide and/or hydrated silicon oxide. Thus, the reasons why titanium dioxide pigments are modified by precipitating inorganic surface treatment agents on their particle surfaces are generally to improve the light resistance of titanium dioxide pigments and to improve the dispersibility of titanium dioxide pigments in resins. It was thought to be a treasure. As a result of the inventors' investigation, the surface treatment was not performed or the inorganic surface treatment agent was extremely light (the inorganic surface treatment agent was less than 0.2% by weight based on titanium dioxide, calculated as anhydride).
If a titanium dioxide pigment that has only been surface-treated is used in a resin, a serious drawback may arise in that the light resistance and heat resistance of the resin layer containing the titanium dioxide pigment will certainly deteriorate. I understand. This means that even when resin-coated paper containing titanium dioxide pigment in the resin layer is used as a support for photographic paper, serious photographic quality defects such as discoloration of the white background of the photograph over time and deterioration of the shelf life of the photograph occur. Leads to. However, as a result of studies conducted by the present inventors, inorganic surface treatment agents, especially hydrated aluminum oxide, have an anhydrous content of 0.2% by weight relative to titanium dioxide.
When a titanium dioxide pigment that has been surface-treated as described above is used in a resin, the light resistance and heat resistance of the resin-coated paper containing the titanium dioxide pigment in the resin layer are improved, but surprisingly, inorganic Depending on the degree of surface treatment of a titanium dioxide pigment with a surface treatment agent, especially hydrous aluminum oxide, as the degree increases, the dispersibility of the titanium dioxide pigment in a resin, especially a thermoplastic resin, becomes worse and the resin coating becomes worse. Microgrit tends to appear frequently on the resin surface of paper. Furthermore, the degree of surface treatment of titanium dioxide pigments with inorganic surface treatment agents, especially hydrated aluminum oxide, is 1.2 compared to titanium dioxide when calculated as anhydrous.
If the concentration exceeds % by weight, the dispersibility of the titanium dioxide pigment in resins, particularly thermoplastic resins, becomes very poor, and microgrits are extremely frequently formed on the resin surface of resin-coated paper. As described above, there has been a fundamental contradiction in titanium dioxide pigments that have been surface-treated with inorganic surface treatment agents that are contained in the resin layer of photographic resin-coated papers, particularly thermoplastic resin-coated papers for photographs. That is, when a highly surface-treated titanium dioxide pigment is included in the resin layer in an attempt to improve the light resistance and heat resistance of photographic resin-coated paper, especially photographic thermoplastic resin-coated paper, the generation of microgrit cannot be prevented. On the other hand, in an attempt to prevent the generation of microgrits, if untreated or only lightly surface treated titanium dioxide pigment is included in the resin layer, the light resistance and heat resistance of the photographic resin-coated paper will deteriorate. There was a contradiction that it was bad. Also,
Although it is certain that the generation of microgrits is caused by the undispersed matter of the titanium dioxide pigment and that the dispersion properties of the titanium dioxide pigment itself in the resin are involved to some extent, the generation of microgrits is caused by the dispersion of the titanium dioxide pigment. There are many things that cannot be explained by gender alone. What is more important is how and in what respects the dispersibility of titanium dioxide pigments into thermoplastic resins, especially non-polar polyolefin resins, is related to the physical properties of the titanium dioxide pigments themselves. It is not clear at all, and even more so, it is not clear at all how to improve the dispersibility of titanium dioxide pigments into thermoplastic resins, especially polyolefin resins, and the photographic industry is still actively investigating this issue. In the current situation. Thus, it has been extremely difficult to develop photographic resin-coated paper, especially photographic thermoplastic resin-coated paper, which has excellent light resistance and heat resistance, and has a good surface quality that prevents the generation of microgrit. However, in the resin layer of resin-coated paper, especially thermoplastic resin coating,
By containing a titanium dioxide pigment that has been surface treated with an inorganic surface treatment agent, especially hydrated aluminum oxide, and has a suspension electrical conductivity of 60 μcm or less, it has excellent light resistance and heat resistance. A new fact that it is possible to provide photographic resin-coated paper, in particular photographic thermoplastic resin-coated paper, which prevents the generation of microgrit and has a good surface quality;
In particular, when the titanium dioxide pigment in the present invention contains a titanium dioxide pigment in which the treatment amount of the inorganic surface treatment agent is 0.2% to 1.2% by weight calculated based on the anhydride based on the titanium dioxide, A new fact that the generation of microgrit is prevented, and furthermore, as a titanium dioxide pigment in the present invention,
_Light fastness _and The present invention was achieved by discovering a new fact that it is possible to provide photographic resin-coated paper, especially photographic thermoplastic resin-coated paper, which has excellent heat resistance and a good surface quality that prevents the generation of microgrit. . The titanium dioxide pigment used in the practice of the present invention has a suspension electrical conductivity of 60μ.
/ cm or less, those with rutile structure,
Those with anatase structure, those produced by the chlorine method, and those produced by the sulfuric acid method can be used. Regarding their specific manufacturing method, in the case of the chlorine method, titanium dioxide particles are formed by vapor phase oxidative decomposition of titanium tetrachloride at high temperatures, and particles with a rutile structure are generally easily obtained. In the case of the sulfuric acid process, hydrous titanium oxide is formed by hydrolysis of an aqueous titanyl sulfate solution and is calcined to develop its pigmentary properties. In the case of the sulfuric acid method, products with both anatase structure and rutile structure can be obtained, but when attempting to produce products with rutile structure, the firing temperature must be set to a higher temperature than in the case of products with anatase structure. Sometimes a metal compound such as a zinc compound is allowed to coexist to promote the formation of a rutile structure. The product produced by calcination or oxidation will hereinafter be referred to as titanium dioxide linker.
Titanium dioxide linker is dry-pulverized using a centrifugal roller mill (mainly Raymond mill), and the crushed product is suspended in water to form titanium dioxide slurry.
It is then wet-milled by a wet ball mill or vibrating mill, and wet-classified using a continuous horizontal centrifuge or/and passed through a vibrating double deck screen (325 mesh US standard screen). fines
This is a titanium dioxide slurry that is substantially free of coarse particles of titanium dioxide. For fines still in slurry form from which coarse particles have been removed, the surface of the titanium dioxide particles is subjected to a reaction with an inorganic surface treatment agent such as hydrous aluminum oxide, hydrous silicon oxide, or hydrous titanium oxide, particularly preferably hydrous aluminum oxide, with a stirrer. The surface is treated by processing.
After the reaction treatment, it is filtered in a filter press, dried in a band dryer, and further finely pulverized in a fluid energy mill. For some titanium dioxide pigments, after surface treatment, the first mother liquor was filtered in a filter press, and then the titanium dioxide pigment cake in the filter press was washed under running water.
It is produced by washing with water until a titanium dioxide pigment having a suspension electrical conductivity as defined herein of 60 μcm or less is obtained. Washing conditions such as washing time, amount of water, and pressure of water were determined under a series of combinations of experimental conditions.The titanium dioxide cake was then dried and pulverized to produce a titanium dioxide pigment. It can be determined by measuring suspension electrical conductivity. Water washing can be carried out in a filter press using running water such as using the reaction solution containing titanium dioxide after surface treatment as it is, or resuspending the filter cake in the tank and replacing the accumulated water or supernatant liquid. It can be done together with or separately. In addition, from the viewpoint of further preventing microgrit, the titanium dioxide pigment in the present invention has a suspension electrical conductivity as referred to in this specification.
It is preferably 55 μcm or less, and particularly preferably 50 μm or less. The titanium dioxide pigments used in the practice of the invention are advantageously surface-treated with inorganic surface treatment agents, especially hydrous aluminum oxide. Moreover, those that have been surface-treated by a conventionally known method are advantageously used. For example, by adding a water-soluble aluminum salt and/or one or more other water-soluble metal salts and/or optionally a water-soluble silicon compound to a titanium dioxide slurry, preferably fines, and subsequently changing the pH in the slurry. , a titanium dioxide pigment surface-treated by precipitating a poorly soluble oxide hydrate and/or a hardly soluble metal compound can be used. In particular, an aluminate such as an alkali aluminate is used as the water-soluble aluminum salt, and if necessary, the aluminate is made into a slurry that exhibits an alkaline reaction after adding a water-soluble alkali such as caustic soda or potassium hydroxide. In order to reduce the pH value and precipitate hydrous aluminum oxide, it is useful to use a surface treatment with the addition of a strong acid, such as sulfuric acid or hydrochloric acid, or a salt that exhibits an acidic reaction. In this case, among alkali aluminates, sodium aluminate is particularly useful. Further, in addition to the aluminate, those whose surface has been treated with an inorganic surface treating agent other than the aluminate or those whose surface has been surface treated with an inorganic surface treating agent other than the aluminate can also be used. In this case, an inorganic surface treatment agent other than the aluminate may be added at any stage of the surface treatment. In particular, when other inorganic surface treatment agents are used in addition to the aluminate, it can be added at any stage before, during, or after the addition of the aluminate. Particularly useful are those added before the addition of the aluminate. Inorganic surface treatment agents other than aluminate used for these surface treatments include silicon compounds, alkali silicate, silicon tetrachloride, etc., titanium compounds,
In addition to titanium tetrachloride, various metal compounds such as zirconium, zinc, magnesium, and manganese, and phosphoric acid compounds can be used. Resins used in the practice of the present invention include homopolymers or copolymers such as polyolefins, polystyrene, polyvinyl chloride, polyacrylic esters, linear polyesters such as polyethylene terephthalate, polycarbonates, polyamides such as nylon, cellulose esters, polyacrylonitrile, etc. For example, any resin may be used as long as it is capable of coating a resin film on the base paper, such as ethylene-vinyl acetate copolymer and mixtures thereof, but thermoplastic resins such as polyolefin, polystyrene, polyethylene terephthalate, and polyvinyl chloride are particularly preferred. Among these, polyolefin resins are particularly advantageous in terms of extrusion coating properties, good adhesion to base paper, and cost. The polyolefin resin in the present invention includes low density polyethylene, high density polyethylene, polypropylene,
These are copolymers consisting of two or more homopolymers such as polybutene and polypentene, or olefins such as ethylene-propylene copolymers, and mixtures thereof. ) can be used alone or in combination. If the content of titanium dioxide pigment contained in the resin layer of the photographic resin-coated paper in the present invention is 5% by weight or less based on the resin, the hiding power will be insufficient as a photographic support; If it exceeds 40% by weight, the fluidity decreases, which is undesirable, and the range of 7.5% to 2.5% by weight is particularly preferable. It is preferable that a fatty acid metal salt is contained in the resin layer of the photographic resin-coated paper in the present invention.
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 is 0.01 to the resin composition containing titanium dioxide.
A range of % to 5% by weight is preferred. Furthermore, 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, the fatty acid metal salt, white pigments such as zinc oxide, talc, and calcium carbonate, stearic acid amide, and arachidin. Fatty acid amides such as acid amides, tetrakis [methylene-3-(3,5-di-tert-
butyl-4-hydroxyphenyl)propionate] methane, antioxidants such as 2,6-di-tert-butyl-4-methylphenol, coloring pigments such as cobalt blue, deep blue, ultramarine, cobalt violet, and fluorescent enhancers. A whitening agent etc. may be added. The photographic resin-coated paper in the present invention is a paper or a synthetic paper base (hereinafter simply referred to as base paper) that normally runs.
It is manufactured by melt-extruding a resin composition containing a heated and melted titanium dioxide pigment onto a film through a slit die. When the resin is a polyolefin resin, the melt extrusion temperature is preferably 200°C to 350°C. Furthermore, before coating the resin composition on the base paper, 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 5.
Extrusion coatings to a thickness of the order of microns to 50 microns are 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 has a glossy surface, a matte surface, a silky surface, etc. depending on its use.
The opposite back surface is usually a matte surface, and if necessary, the front surface or both the front and back surfaces can be subjected to activation treatment such as corona discharge treatment or flame treatment. The base paper used in the practice of the present invention may be ordinary natural pulp paper, synthetic fiber, or so-called synthetic paper made of artificial paper made of synthetic resin film. Natural pulp paper based on pulp is advantageously used. There is no particular restriction on the thickness of the base paper, but a base paper with good surface smoothness is preferred, and its basis weight is preferably 50 g/m ² to 250 g/m ² . The base paper mainly composed of natural pulp, which is advantageously used in carrying out the present invention, can contain various polymeric compounds and additives. 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, etc.
Pigments: clay, kaolin, calcium carbonate, barium sulfate, titanium oxide, etc. Wet paper strength agents: melamine resin, urea resin, epoxidized polyamide resin; Fixing agents: polyvalent metal salts such as aluminum sulfate, aluminum chloride, etc. , cationically modified polymers such as cationized starch, etc.
pH adjusters such as caustic soda, soda carbonate, and hydrochloric acid may be used, and inorganic electrolytes such as common salt and mirabilite, as well as dyes, fluorescent brighteners, latex, and the like may be contained in appropriate combinations. 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,
A silver chloroiodobromide emulsion layer can be provided. Also,
A multilayer silver halide photographic constituent layer can be provided by containing a color coupler in the silver halide photographic emulsion layer. As the binder for these silver halide emulsion layers, in addition to ordinary gelatin, hydrophilic polymeric substances such as polyvinylpyrrolidone, polyvinyl alcohol, and polysaccharide sulfate ester compounds can be used. Further, the silver halide emulsion layer described above can contain various additives. For example, sensitizing dyes include cyanine dyes and merocyanine dyes; chemical sensitizers include water-soluble gold compounds and ionic compounds; antifoggants and stabilizers include hydroxytriazolopyrimidine compounds and mercapto heterocyclic compounds;
As a hardening agent, formalin, vinyl sulfone compound, aziridine compound, etc., as a coating aid,
Benzene sulfonates, sulfosuccinates, etc., as anti-staining agents, dialkylhydroquinone compounds, etc., as development accelerators, hydroquinone, phenidone, etc., as ultraviolet absorbers, benzotriazole compounds, etc., as well as fluorescent brighteners, sharpeners, etc. A power improving dye, an antistatic agent, a pH adjuster, and further a water-soluble rhodium compound, a water-soluble rhodium compound, etc. can be contained in an appropriate combination during the production and dispersion of silver halide. In addition, 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 composition diagram and the silver halide photographic composition layer are coated, anti-curl, antistatic, 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, in order to explain the present invention more specifically,
An example will be described. Example 1 Anatase-type titanium dioxide linker produced by the sulfuric acid method was dry-pulverized using a centrifugal roller mill, and the pulverized product was suspended in water in the presence of sodium hydroxide to obtain a titanium dioxide slurry with a pH of 7. The slurry was further milled using a wet ball mill. Wet milling and wet classification using a continuous horizontal centrifuge produced a titanium dioxide slurry having a solids content of approximately 25% by weight, substantially free of coarse titanium dioxide. Then, after increasing the pH of the slurry to about 9.2 with sodium hydroxide and heating the temperature of the slurry to about 70°C, it becomes 0.75% by weight calculated in the form of Al ₂ O ₃ with respect to titanium dioxide on a dry basis. A 50% by weight aqueous solution of sodium aluminate was added and held for 30 minutes. The pH of the slurry was then adjusted to 7.0 by adding 20% sulfuric acid.
The slurry was further aged for 2 hours. After aging, the initial mother liquor of the titanium dioxide slurry surface-treated with hydrous aluminum oxide is passed through a filter press, and then the titanium dioxide cake in the filter press is washed with running water to obtain a suspension with electrical conductivity as described below. Each was washed with water under predetermined washing conditions until a titanium dioxide pigment was obtained. Thereafter, the titanium dioxide cake was dried and further impact-pulverized in a hammer mill equipped with a metering feeder to obtain a suspension electrical conductivity of 110μ.
/cm, 90μ/cm, 70μ/cm, 60μ/cm,
Seven types of titanium dioxide pigments with values of 55 μ/cm, 50 μ/cm, and 40 μ/cm were produced, respectively. Thus, 7 parts by weight of low density polyethylene (MI = 7, density 0.923 g/cm ³ ), 30 parts by weight of titanium dioxide pigment.
Parts by weight and 1.5 parts by weight of zinc stearate were thoroughly kneaded at 150°C using a Banbury mixer to obtain master batches of the seven types of titanium dioxide pigments. On the other hand, 310 ml of Canadian Standard Freeness mixed stock of 50 parts by weight of hardwood bleached kraft valve and 50 parts by weight of softwood marked sulfite pulp was added.
Further, per 100 parts by weight of pulp, 3 parts by weight of cationized starch, 0.2 parts by weight of anionized polyacrylamide, 0.4 parts by weight of alkyl ketene dimer emulsion (as ketene dimer content), and 0.4 parts by weight of polyaminopolyamide epichlorohydrin resin. A paper with a basis weight of 160 g/m ² was made. The obtained wet paper was dried at 110°C, and then added with 3 parts by weight of carboxy-modified polyvinyl alcohol, 0.05 parts by weight of fluorescent brightener, 0.002 parts by weight of blue dye, and citric acid.
5 parts by weight of an impregnating solution consisting of 0.2 parts by weight and 97 parts by weight of water.
After impregnating the paper with g/m ² , drying with hot air at 110° C. and supercalendering at a linear pressure of 90 kg/cm, both sides of the paper were subjected to corona discharge treatment to produce a base paper for photographic resin-coated paper. Next, apply high-density polyethylene (density
A 1:1 mixture of 0.96 g/cm ³ , MI=5) and low density polyethylene (density 0.92 g/cm ³ , MI=5) was coated to a thickness of 30μ using a melt extrusion coater at a resin temperature of 330°C. did. Next, 30 parts by weight of the masterbatch of the titanium dioxide pigment described above and high-density polyethylene (density 0.96 g/cm ³ , MI
=5) 20 parts by weight and low density polyethylene (density
A resin composition containing 50 parts by weight of 0.92 g/cm ³ , MI = 5) was coated at a resin temperature of 330°C to a thickness of 30 μm, and a suspension was obtained using a polyethylene resin containing titanium dioxide pigments with different electrical conductivities. Each coated paper was produced. At that time, the surface of the polyethylene containing the titanium dioxide pigment was processed into a completely flat glossy surface, and the surface quality of the back polyethylene was processed into a paper-like matte surface. The number of microgrits generated on the polyethylene resin surface containing the titanium dioxide pigment of the thus obtained polyethylene resin-coated paper was visually counted. The results obtained are shown in Table 1.

[Table] Same meaning as that given.
From Table 1, 70μ/
Resin-coated papers outside the invention containing titanium dioxide pigments with a suspension electrical conductivity of more than
It can be seen that the resin-coated paper of the present invention containing a titanium dioxide pigment having a suspension electrical conductivity of less than /cm is well-prevented from generating microgrit and is preferred as a photographic support. Furthermore, if titanium dioxide pigments include those having a suspension electrical conductivity of 55 μ/cm or less, microgrits are further prevented; It can be seen that in some cases, the generation of microgrit is further prevented, which is preferable. Example 2 In place of the titanium dioxide pigment used in Example 1, the amount of surface treatment of titanium dioxide with hydrous aluminum oxide was calculated in the form of Al ₂ O ₃ with respect to dry basis titanium dioxide, O, 0.15% by weight, 0.25
wt%, 0.5 wt%, 0.75 wt%, 1.0 wt%,
Titanium dioxide pigments were added in the resin layer in the same manner as in Example 1, except that titanium dioxide pigments were used in amounts of 1.25% by weight and 2.0% by weight and suspension electrical conductivities of 50 μ/cm and 110 μ/cm, respectively. A polyethylene resin-coated paper was produced containing: The results obtained are shown in Table 2. In addition, among the descriptions in the table, the light resistance (Note 2) of the polyethylene resin-coated paper was tested as follows. A feedmeter (FAL-25X manufactured by Suga Test Instruments) was applied to the resin surface containing the titanium dioxide pigment of the resin-coated paper.
-HCL type) for 120 hours, and then the yellow density (hereinafter abbreviated as Y density) on the irradiated surface of the sample was measured and verified using a Macbeth densitometer (TD-504 type). The larger the value, the higher the Y concentration, and the higher the Y concentration, the worse the light resistance of the sample. On the other hand, the lower the Y concentration, the better the light resistance of the sample.

[Table] As can be seen from Table 2, compared to the resin-coated paper outside the invention containing titanium dioxide pigment with a suspension electrical conductivity of 110 μ/cm in the polyethylene resin layer, The resin-coated paper of the present invention containing a titanium dioxide pigment having a suspension electrical conductivity of /cm is preferred because the generation of microgrit is well prevented. However, even in the resin-coated paper of the present invention, the amount of surface treatment of titanium dioxide with hydrous aluminum oxide is 0.2% by weight or less, calculated in the form of Al ₂ O ₃ with respect to titanium dioxide on a dry basis. Those using titanium pigments have poor light resistance, while those using 1.2% by weight or more of titanium dioxide pigments are insufficient in preventing microgrit. Products using titanium dioxide pigment with a surface treatment amount of 0.2% to 1.2% by weight are
It can be clearly seen that the generation of microgrit is significantly prevented and the light resistance is good, making it more preferable as a photographic support. Example 3 A dry standard obtained in the same manner as in Example 1 by further adding a sodium silicate aqueous solution to the titanium dioxide slurry before adding the sodium aluminate aqueous solution to the titanium dioxide slurry instead of the titanium dioxide pigment used in Example 1. of titanium dioxide, surface treated with 0.5% by weight of hydrous aluminum oxide calculated in the form of Al ₂ O ₃ and 0.25% by weight of hydrous silicon oxide calculated in the form of SiO ₂ and suspension electrolyzed. conductivity
A polyethylene resin-coated paper containing a titanium dioxide pigment in the resin layer was produced in the same manner as in Example 1, except that a titanium dioxide pigment of 50 μ/cm was used. This resin-coated paper significantly prevented the generation of microgrit and had excellent light resistance and heat resistance, and was suitable as a photographic support. Example 4 Instead of the resin composition containing titanium dioxide used in Example 1 to coat the surface of the base paper, 30 parts by weight of the same titanium dioxide pigment masterbatch as in Example 1, ethylene-propylene copolymer (propylene Content 0.1% by weight, density 0.945g/cm ³ , MI=7) 30 parts by weight and low density polyethylene (density 0.92g/cm ³ ,
The same procedure as in Example 1 was carried out except that a resin composition having a composition of 40 parts by weight (MI=7) was used. As a result, the same results as in Example 1 were obtained.

Claims (1)

[Scope of 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 consisting of at least a titanium dioxide pigment and a resin, wherein the titanium dioxide pigment is 60μ/cm or less. A photographic resin-coated paper having a suspension electrical conductivity as defined below. Suspension electrical conductivity: Place the rotor of a magnetic stirrer in a 100ml beaker and add distilled water.
Add 100ml (water temperature 21.5℃) and then add 10.0g of titanium dioxide pigment. After addition, a conductivity cell (θ = 0.1) of an electrical conductivity meter is placed in the liquid so that the electrical conductivity value can be tracked over time. After installation, start the magnetic stirrer and rotate the rotor at a rotation speed of 420 rpm for 1 minute.
The contents in the beaker are stirred to form a titanium dioxide pigment suspension, and the titanium dioxide pigment suspension is stirred for 16 minutes while maintaining 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 read and 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 titanium dioxide pigment is surface-treated with an inorganic surface treatment agent. 3. The photographic resin-coated paper according to claim 2, wherein the inorganic surface treatment agent is hydrated aluminum oxide. 4. The photographic resin-coated paper according to claim 2, wherein the inorganic surface treatment agent comprises hydrated aluminum oxide and an inorganic surface treatment agent other than hydrated aluminum oxide. 5. Photographic resin-coated paper according to claim 2, wherein the treatment amount of the inorganic surface treatment agent is 0.2% to 1.2% by weight (calculated in anhydrous form) based on the titanium dioxide. 6. Photographic material according to claim 3 or 4, wherein the amount of hydrous aluminum oxide treated is 0.2% to 1.2% by weight (calculated in the form of Al ₂ O ₃ ) based on titanium dioxide. Resin coated paper. 7. The photographic resin-coated paper according to claim 1, 2, 3, 4, 5, or 6, wherein the resin is a thermoplastic resin. 8. The photographic resin-coated paper according to claim 7, wherein the thermoplastic resin is a polyolefin resin. 9. The photographic resin-coated paper according to claim 8, wherein the polyolefin resin is a polyethylene resin. 10. The photographic resin-coated paper according to claim 7, 8 or 9, wherein the resin composition contains a fatty acid metal salt.