JPS58220140A - Resin-coated paper for photography - Google Patents

Abstract

PURPOSE:To obtain resin-coated paper for photography with improved resistance to the formation of microgrit, by coating a paper substrate with a resin composition contg. TiO2 pigment having specified electric conductivity in the form of a suspension. CONSTITUTION:At least one side of a paper or synthetic paper substrate is coated with a resin composition consisting of TiO2 pigment and resin to obtain resin coated paper for photography. The TiO2 pigment to be used has <=60/OMEGAcm electric conductivity in the form of a suspension. When the resin coated paper contains TiO2 pigment surface-treated with an inorg. surface treating agent, especially aluminum oxide hydrate in the resin layer, the paper is provided with superior light and heat resistances, prevents the formation of microgrit and has high surface quality. The preferred amount of the surface treating agent to be used is 0.2-1.2wt% of the amount of TiO2.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides that at least one surface of the paper or synthetic paper substrate is
It relates to a photographic resin-coated paper coated with a resin composition comprising at least a titanium dioxide pigment and a resin,
More specifically, the present invention relates to a photographic resin-coated paper with a good surface quality in which no microgrit (m1cro Kr) is observed on the coated resin surface of the resin-coated paper.

Microgrit refers to minute foreign matter or minute particles that appear on the surface of the coated resin in photographic resin-coated paper where at least one side of the paper or synthetic paper base is coated with a resin composition. .

There are various main causes of microgrit, but for example, photographic resin-coated paper produced by melt-extrusion coating photographic thermoplastic resin on at least one side of a paper substrate using a melt-extrusion machine. The main causes of "microgrit" that appear are (1) when the thermoplastic resin used itself generates a lot of gel, (2) when the molten resin is extruded into a film form from the melt extruder through the die,
If the temperature cannot be maintained at the appropriate temperature and the flow becomes uneven, (3
) If the screen attached to the player plate in the melt extruder is dirty, (4) If there are cracks in the barrel liner in the melt extruder, (5) If there is insufficient bending in the melt extruder, etc. However, these problems can often be solved 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 patch 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. Ordinarily, a so-called compound is prepared and used in which a desired composition ratio of pigment is contained in a resin from the beginning.

However, q! fK Panbury Miser, Nieder
When preparing a masterbatch or compound by melt-kneading a thermoplastic resin and a pigment using an ordinary melt-kneading machine such as the There is a tendency for the pigment to remain dispersed without being dispersed, thus resulting in the presence of undispersed pigment particles in the master patch or compound. As a result, 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, and the resin composition is coated on the resin side of the resin-coated photographic paper. Microgrit is generated (rZ).

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 microgrit-generated resin-coated paper as a photographic support, if microgrit appears in areas such as the face, the photograph has no commercial value.

Incidentally, titanium dioxide pigments are usually used as pigments contained in the resin layer on the emulsion-coated side of resin-coated paper used as photographic supports because of their excellent properties such as transparency, whiteness, hiding power, and resolution. is well known.

Furthermore, resin-coated paper for photographs is already known.
For example, as disclosed in U.S. Pat. No. 3,501,298, both sides of a paper substrate are coated with a polyolefin resin, particularly a polyethylene resin, and the polyolefin resin layer on the emulsion-coated side is coated with titanium dioxide pigments, colored pigments, Products containing fluorescent brighteners and the like are well known. Another type of photographic resin-coated paper is JP-A-57-30830.
Photographic resin-coated papers are also known in which a paper substrate is coated with a resin composition containing a white pigment, such as titanium dioxide, which is polymerized and cured by electron beam irradiation, as disclosed in No.

However, 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. As mentioned above, microgrit tends to occur frequently on the resin surface of resin-coated paper for nuclear photography, which is caused by undispersed pigments, that is, titanium dioxide pigment in this case. There was a serious problem.

Therefore, an object of the present invention is to provide a photographic resin-coated paper containing titanium dioxide in the resin layer and having a good surface quality, in which the generation of microgrit is completely eliminated 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, the purpose of the present invention is to:
In a photographic resin-coated paper 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, the titanium dioxide pigment has a value of 60 μΩ/cI11 or less as defined below. It has been found that this can be achieved by incorporating a titanium dioxide pigment with suspension electrical conductivity into the resin layer.

The electrical conductivity of a suspension of titanium dioxide pigment herein is defined as follows.

Magnetic stirrer rotor in a 100-capacity beaker (released by Universal Co., Ltd., length 45 baits, diameter 8I)
Place the Teflon coated rotor (I11), add distilled water xoo- (water temperature 21.5°C), and then add titanium dioxide pigment 10. Add Of. 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, conductivity cell (manufactured by Toa Denpa Kogyo Co., Ltd., type CG-20) of an electrical conductivity meter (manufactured by Toa Denpa Kogyo Co., Ltd., model CM-sB) was used.
01PL (+!; l=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 as time passed. It is possible to track the associated electrical conductivity values. After installation, start the magnetic stirrer, rotate the rotor IC1C at 0 speed for 4 minutes for 1 minute, stir the contents in the beaker, make the contents into a titanium dioxide pigment suspension, and turn the contents into a titanium dioxide pigment suspension. Stir for 16 minutes while maintaining the liquid temperature at 215°C ± 0.5°C. 16 minutes after the start of stirring, check the electrical conductivity of the titanium dioxide pigment suspension. Stir the suspension at a liquid temperature of 21°C (temperature compensation). Measure while reading.

The electrical conductivity thus obtained is defined as the titanium dioxide pigment suspension electrical conductivity in this specification.

The present invention provides photographic thermoplastic resin-coated paper, particularly polyolefin resin-coated paper, which is produced using a masterbatch or compound of titanium dioxide pigment and which is well prevented from forming microgrit and has good surface quality. It is effective for

This makes it possible to mix titanium dioxide #1 in comparison to a mixer normally used to prepare a typical masterbatch or compound consisting of titanium dioxide pigment and thermoplastic resin, i.e., paints, etc.
Banbury mixer with low impact force applied to i class,
Thermoplastic resin-coated paper for photography, especially polyolefin resin-coated paper for photography, is manufactured using a masterbatch or compound prepared using a conventional melt-kneading machine such as a kneader-1 cross-wire extruder. When conventionally known pigments are used, microgrits occur frequently, which is thought to be mainly caused by undispersed titanium dioxide pigments. However, when the titanium dioxide pigment of the present invention is used, microgrits often occur. It is well understood because it is prevented.

The present invention also provides a resin-treated paper whose substrate is paper or synthetic paper containing a titanium dioxide pigment surface-treated with an inorganic surface treatment agent, particularly hydrous aluminum oxide, in the resin layer,
It is particularly effective in providing excellent photographic resin-coated paper that has excellent light resistance and heat resistance, and also has a good surface quality that prevents the generation of microgrit. This is clear from the ffd description in the following specification.

In the first place, commercially available titanium dioxide pigments have hydrated aluminum oxide, ram, hydrated silicon oxide, hydrated titanium oxide,
Inorganic surface treatment agents such as hydrated zirconium oxide, zinc hydroxide, magnesium hydroxide, manganese compounds, phosphoric acid compounds, etc. (mostly modified by precipitation of hydrated aluminum oxide and/or hydrated silicon oxide).

In this way, the two 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. As a result of the inventors' investigation, it was found that the inorganic surface treatment agent was used to improve Calculated with objects is 0
If a titanium dioxide pigment that has been surface-treated (less than 2% by weight) is used in a resin, there is a serious problem that the light resistance and heat resistance of the resin layer containing the titanium dioxide pigment will certainly deteriorate. It was found that there were some drawbacks.

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, it was found that titanium dioxide was surface-treated with an inorganic surface treatment agent, especially hydrated aluminum oxide, to an amount of 0.2% by weight or more based on anhydrous titanium dioxide. When pigments are used in resin,
Although the light resistance and heat resistance of 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, especially hydrous aluminum oxide, As the degree of dispersion increases, the dispersibility of the dichloromethane pigment in resins, especially thermoplastic resins becomes poor, and microgrit tends to occur frequently on the resin surface of the resin-covered paper. Furthermore, the degree of surface treatment of titanium dioxide pigments with inorganic surface treatment agents, especially hydrated aluminum oxide, is 1 when calculated on anhydrous basis with respect to titanium dioxide.
, 2% by weight or more, the dispersibility of the titanium dioxide pigment in resins, especially thermoplastic resins, becomes extremely poor9, and microgrits appear extremely frequently on the resin surface of resin-coated paper. Become.

As mentioned above, there was a fundamental contradiction in the titanium dioxide family IIJ surface treated with an inorganic surface treatment agent contained in the resin layer of photographic resin-coated paper, especially photographic thermoplastic resin-coated paper. . That is, in an attempt to improve the light resistance and heat resistance of photographic resin-coated paper, or photographic thermoplastic resin-coated paper, when a highly surface-treated titanium dioxide pigment is included in the resin layer, microgrit is generated. On the other hand, in an attempt to prevent the occurrence of black grid, if untreated or only lightly surface treated titanium dioxide is included in the resin layer, it will cause damage to photographic resin-coated paper. There was a contradiction that light resistance and heat resistance were poor. Furthermore, although it is certain that the generation of microgrit is caused by undispersed particles of titanium dioxide pigment, and therefore the dispersion properties of the titanium dioxide pigment itself in the resin are involved to some extent, the generation of microgrit is There are many points that cannot be explained solely by the dispersibility of the titanium dioxide S material.

Even more important is the question of how and in what way the dispersibility of titanium dioxide pigments into thermoplastic resins, especially non-polar polyolefin resins, is related to the physical properties of 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 there are still many problems in the photographic industry.
Currently, we are conducting vigorous studies. 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, the resin layer of resin-coated paper, especially thermoplastic resin-coated paper, is surface-treated with an inorganic surface treatment agent, especially hydrated aluminum oxide, and has a suspension electrical conductivity of 60 μΩ/in or less. This new invention enables the provision of 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 by containing titanium dioxide pigments. In fact, the titanium dioxide pigment in the present invention also contains a titanium dioxide pigment in which the treatment amount of the inorganic surface treatment agent is 0.2 to 1.2 weight by weight, calculated on an anhydride basis with respect to titanium dioxide. The new fact is that the generation of microgrit is particularly prevented when the titanium dioxide pigment is surface treated with hydrous aluminum oxide, and this treatment Calculate the shape of 0.2 x ~ 1.2
When containing titanium dioxide (4), which is t% by weight, it is possible to produce photographic resin-coated paper, especially for photographs, which has excellent light resistance and heat resistance, and has a good surface quality that prevents the generation of microgrit. We have discovered a new fact that thermoplastic resin-coated paper can be provided, and have arrived at the present invention.

The titanium dioxide pigment used in the practice of the present invention includes:
As long as the electrical conductivity of the suspension as referred to in this specification is 60 μΩ/elR or less, any one having a rutile structure, an anatase structure, a chlorine method, or a sulfuric acid method can be used. Regarding their specific manufacturing method, in the case of the chlorine method, titanium dioxide particles are formed by gas phase oxidative decomposition of titanium tetrachloride at high temperatures, and those with a rutile structure are generally easily obtained.

In the case of the sulfuric acid process, hydrated titanium oxide is formed by hydrolysis of an aqueous titanyl sulfate solution, which develops its pigmentary properties. Specially fired. In the case of the sulfuric acid method, products with anatase structure and products with rutile structure can be obtained, but when trying to produce products with rutile structure, the firing temperature must be higher than that 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 tarinker is dry-pulverized in a centrifugal row 2 mill (mainly Raymond mill), the pulverized product is made into a titanium dioxide slurry by making it cloudy with water, and then wet-pulverized in a wet ball mill or vibration mill. Wet classification is carried out using a centrifuge and/or passing through a vibrating double deck screen (325 mesh U, 8° standard screen) to produce substantially coarse particles, hereinafter referred to as fines (flnem). The titanium dioxide slurry and eggplant are free of titanium dioxide.

Hydrous aluminum oxide for fines still in slurry form from which coarse particles have been removed.

The surface of the titanium dioxide particles is surface-treated with an inorganic surface treatment agent such as aluminum oxide, hydrous silicon oxide, or hydrous titanium oxide, particularly preferably hydrous aluminum oxide, in a treatment tank equipped with a stirrer. After the core treatment, it is filtered with a filter press, dried with a band dryer, and then final pulverized with a fluid energy mill. / titanium dioxide pigments with a titanium dioxide pigment of less than
filtration and subsequent washing of the titanium dioxide cake in a filter press with running water until a titanium dioxide pigment having a suspension electrical conductivity as referred to herein of 60 AΩ/clIM or less is obtained. washing time,
The water washing conditions, such as the amount of water used and the pressure of the water used, were applied to the titanium dioxide cake collected under a series of combinations of experimental conditions.
It can be determined by subjecting the titanium dioxide pigment to a titanium dioxide #i pigment by subsequent pulverization and measuring the electrical conductivity of a suspension of the titanium dioxide pigment. Water washing can be carried out in the filter press by 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 preferably has a suspension electrical conductivity of 55 μΩ/- or less, as referred to herein, and %Kso μΩ/- or less. More preferred.

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, a titanium dioxide slurry, preferably a fine water-soluble aluminum salt and/or one or more other water-soluble metal salts and/or
or surface treated by precipitating a poorly soluble oxide sulfate and/or a poorly soluble metal compound onto the titanium dioxide pigment, optionally by adding a water-soluble silicon compound and subsequently varying the PTI in the slurry. Things 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 the hydrous aluminum oxide, it is useful to use a surface treatment with the addition of a strong acid or an acidic salt, for example sulfur is2 or hydrochloric acid. In this case, among alkali aluminates, sodium aluminate is particularly useful. Furthermore, in addition to aluminum, those whose surfaces have been treated with other inorganic surface treating agents or those whose surfaces have been surface treated with inorganic surface treating agents other than aluminates 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 such as alkali silicate and silicon tetrachloride, titanium compounds such as titanium tetrachloride, SiA/-sium, and zinc. , manesium,
Various compounds such as metal compounds such as manganese and phosphoric acid compounds can be used.

Examples of resins used in the practice of the present invention include polyethylene/fins, polystyrene, polyvinyl chloride, polyacrylic esters, linear polyesters such as TTF polyethylene terephthalate, polycarbonate, polyamides such as nylon, cellulose tespule, and polyacrylonitrile. Homopolymers or copolymers Any resin may be used as long as it is possible to coat a resin film on the base paper, such as ethylene-vinyl acedate copolymers and mixtures thereof, but in particular polyolefins, polyethylene, polyethylene terephthalate, polychlorinated Vinyl thermoplastic resins are preferred, and polyolefin resins are particularly advantageous in terms of extrusion coating properties, good adhesion to the base paper, and cost. In the present invention, the polyolefin resin refers to a homopolymer such as low-density polyethylene, high-density polyethylene, polypropylene, polybutene, polypentene, or a copolymer consisting of two or more of olefins such as ethylene-7" propylene copolymer, and a copolymer thereof. It is a mixture of various densities and melt viscosity indexes (hereinafter simply referred to as MI) that can be used alone or in combination.

If the content of the titanium dioxide pigment contained in the resin layer of the photographic resin-coated paper in the present invention is less than 5% by weight based on the resin, the hiding power is insufficient as a photographic support. On the other hand, if it is more than 40% by weight, the fluidity etc. will be low, which is not preferable, and it is particularly preferable that the content be in the range of 7-5% to 25% by weight.

It is preferable that the resin 1a of the photographic resin-coated paper in the present invention contains a fatty acid metal salt. Other fatty acid metal salts include zinc stearate, calcium stearate, aluminum stearate, and stearate 71M.
Magnesium, zirconium octylate, sodium palmitate, calcium valmitate, lauric acid.

You can give things like thorium. In addition, the amount added is 0.
The range is preferably from 0.01 to 5.0 weight.

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 alaxin Fatty acid amides such as acid amides, tetrakis [methylene-3 (3,5-di-tert-'7'-thi-4-hydroxy-phenyl)
Antioxidants such as clobionate comethane, 2,6-tert-butyl-4-methyl-phenol, coloring pigments such as cobalt blue, navy blue, ultramarine, cobalt violet, and fluorescent whitening agents may be added. good.

The photographic resin-coated paper in the present invention is a paper 1 that is normally run.
& is manufactured by melt-extruding a resin composition containing heat-melted titanium dioxide pigment onto a synthetic paper substrate (hereinafter simply referred to as base paper) through a slit die into a film. 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. The thickness of the resin layer of the resin-coated paper is not limited, but it is generally advantageous to use extrusion coating to a thickness of about 5 to 50 microns. 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. The back of the side is usually a matte surface,
Activation treatments such as corona discharge treatment and flame treatment can be performed on the front surface or both the front and back surfaces as necessary.゛The base paper used in the practice of the present invention is ordinary natural pulp paper,
Although synthetic fibers or so-called synthetic papers made by bonding synthetic resin films may be used, natural pulp paper containing wood pulp such as softwood pulp, hardwood pulp, or softwood hardwood mixed 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 preferable, and its basis weight is 50 f/ze to 25 (II
F/- is preferred.

The base paper containing natural polymer as a main component, which is advantageously used in the practice of the present invention, can contain various polymeric compounds and additives. For example, as a dry paper strength enhancer,
Sizing agents such as cationized starch, cationized polyacrylamide, anionized polyacrylamide, carboxy-modified polyvinyl alcohol, and Zeraboon, fatty acid salts, rosin derivatives, dialkyl ketene dimer emulsions,
Petroleum resin emulsion 1, ammonium salt of styrene-maleic anhydride copolymer alkyl ester, clay, kaolin, calcium carbonate, barium sulfate, titanium oxide, etc. as pigments, melamine resin, urea resin as wet paper strength agent , epoxidized polyamide 11 resin, as a fixing agent, polyvalent metal salts such as aluminum sulfate and aluminum chloride, cationic modified polymers such as cationized starch, etc., as a pHli moderator, caustic soda, soda carbonate, hydrochloric acid, etc., as an unsubstituted electrolyte. , salt, mirabilite, dyes, fluorescent brighteners, latex, etc. may be contained in appropriate combinations.

The photographic resin-coated paper of the present invention can be provided with various halogenated steel photographic emulsion layers. For example, copper chloride, silver bromide, steel 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 into the halide steel photographic emulsion layer. As the binder for these silver halide emulsion layers, in addition to usual gelatin, hydrophilic polymeric substances such as polyvinylpyrrolidone, polyvinyl alcohol, and polysaccharide sulfate ester compounds can be used. Further, the above-mentioned silver halide emulsion layer can contain various additives. For example, as sensitizing dyes, cyrinine dyes, merocyanine dyes, etc., as chemical sensitizers, water-soluble gold compounds, sulfur compounds, etc., as antifoggants or stabilizers, hydroxy-triazolopyrimidine compounds, mercapto-hetyl compounds, etc. Cyclic compounds, etc., as hardening agents, formalin, vinyl sulfone compounds, aziridine compounds, etc., as coating aids, benzene sulfonate, sulfosuccinate salts, etc., as anti-staining agents, dialkylnohydroquinone compounds, etc., development accelerators. As,
As ultraviolet absorbers such as UV absorbers, benzotriazole compounds, etc., fluorescent whitening agents, sharpness improving dyes, antistatic agents 1, H regulators, and also during the production and dispersion of silver halides. A suitable combination of water-soluble iridium compounds, water-soluble rhodium compounds, etc. can be contained.

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 R-slip. The back coat layer may contain a binder, a protective colloid, a curing agent, an antistatic agent, a surfactant, a matting agent, a latex, etc. Next, the present invention will be explained in more detail. For this purpose, 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 7.0. Wet milling is carried out by wet milling, followed by wet classification using a continuous horizontal centrifuge to produce a titanium dioxide slurry with a solid content of about 25% and substantially no coarse titanium dioxide. did. Thereafter, the pH of the slurry was adjusted to about 9.0 with sodium hydroxide.
2, and after heating the slurry to about 70°C, add 50% by weight aqueous sodium aluminate solution in an amount that gives a weight of 0.75% in the form of M2O3 to titanium dioxide on a dry basis. and held for 30 minutes. Then,
The pH of the slurry was brought to 20 by addition of sulfuric acid to 7. 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 was passed through a filter press, and then the titanium dioxide kale in the filter press was washed with running water to obtain the electrical conductivity of the suspension as described below. Each sample was washed with water under predetermined water washing conditions until each titanium dioxide #i material was obtained.

Thereafter, the titanium dioxide cake was dried and further impact-pulverized using a thermometer equipped with a quantitative feeder, and the electrical conductivity of the suspension as used herein was determined to be 110 μm/in, 90 μm/in, 70 μm/17 cm, and 60 μΩ/f , seven types of titanium dioxide pigments were manufactured.

Thus, low density polyethylene (MI=7, density 0.9
23) Thoroughly knead 70 parts by weight, 30 parts by weight of titanium dioxide pigment, and zinc stearate at 150°C using a Banbury mixer to form each of the 8 types of titanium dioxide/S family masterbatches. Obtained.

On the other hand, a mixed paper stock of 150 parts by weight of hardwood heading kraft pal and 50 parts by weight of softwood bleached sulfite pulp was beaten to Canadian Standard Freeness 310- parts by weight, and 3 parts by weight of cationized starch was added to 10 parts by weight of pulp. , 0.2 parts by weight of anionized polyacrylamide, 4 parts by weight of alkyl ketene dimer emulsion (as ketene dimer), and 0.4 parts by weight of polyaminopolyamide shrimp chlorohydrin resin were added, and Tsubofu 160f/W? The name of the name was created. The obtained wet paper paper was dried at 110°C, and then 3 parts by weight of carboxy-modified polyvinyl alcohol, 0.05 parts by weight of a fluorescent brightener, 0.002 parts by weight of a white dye,
Impregnated with 25 f/♂ of impregnating liquid consisting of 0.2 citric acid and 97 ml of water, dried with hot air at 100°C, and supercalendered with ftarE90 Kv/equipment, then corona treatment on both sides. A base paper for photographic resin stock paper was produced by electrical discharge treatment.

Next, apply high-density polyethylene (density (1,9
6f /eta, MI=s ) and low density polyethylene /(
density 0.92 f/cf/l, MI = s):
1 mixture was coated with resin WA3:'IQ°C to a thickness of 30μ using a melt extrusion coater. Next, a masterbatch of t-tanium dioxide pigment 30% was applied to the surface of the base paper.
Part by weight, high density polyethylene/(density Q, 96 t/cd
XMI=5) 20 parts by weight and low density polyethylene l
A resin composition containing 50 parts by weight of iO, 92f/cd, MI=5) was coated to a thickness of 30μ at a resin temperature of 330°C to form a polyethylene resin coating containing titanium dioxide pigments with different suspension conductivities. paper was produced respectively. At that time, the surface of the polyethylene containing the titanium dioxide l14 material 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.

(Note 1) #Mirror liquid electrical conductivity has the same meaning as the symptom in the text.

From Table 1, 70μ in the polyethylene resin layer.

In the resin-coated paper other than the present invention containing titanium dioxide family IIA having a suspension electrical conductivity of Ω/1M or more, a large number of microgrits are generated! It is completely unsuitable as a practical support, and on the other hand, 601s fi'/
Titanium dioxide #i with suspension electrical conductivity below cm
It can be seen that the resin-coated paper of the present invention, which contains the resin-coated paper, is well prevented from producing microgrit and is preferable as a photographic support. In addition, when the titanium dioxide pigment contains one having a suspension electrical conductivity of 55 μl/lyn or less, microgrit is further prevented, and further 50 μl
It can be seen that when the suspension contains a suspension having an electrical conductivity of it/c111 or less, the generation of microgrit is further prevented, which is preferable.

(Example 2) Instead of the titanium dioxide pigment used in Example 1,
The amount of surface treatment of titanium dioxide with hydrous aluminum oxide is calculated in the form of A/, 03 with respect to dry basis titanium dioxide, 0.0.15% by weight, 0.25% by weight, 0.5
% by weight, 0.75% by weight, 1.0% by weight, 1.25% by weight and 2.0% by weight, and the electrical conductivity of the suspension is 50 μd/l-n and 110 tstX/cm. 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 titanium dioxide pigments were used.

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. Chi dioxide on resin coated paper! The resin surface containing the fat was irradiated for 120 hours using a Fetometer (FAL-25X-HCl model) manufactured by Suga Test Instruments, and then the yellow density (hereinafter abbreviated as Y density) of the irradiated surface of the sample was measured using a Macbeth densitometer (TD). -504 m) for verification. A larger value indicates a higher Y concentration, and a higher Y concentration indicates a poorer light resistance of the sample.

On the other hand, as shown in Table 2, the lower the Y#1 degree, the better the light resistance of the sample.
Titanium dioxide pigments with a suspension conductivity of 50 μn/ctn in the resin layer compared to resin-coated papers outside the invention containing titanium dioxide pigments with a suspension conductivity of 0 tt p/lym. The resin-coated paper in the present invention includes:
This is preferable 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 calculated in the form of At203 with respect to titanium dioxide on a dry basis, and is 0.
．． Those using less than 2% by weight of titanium dioxide pigment have poor light resistance, while those using more than 1.2% by weight of titanium dioxide pigment are insufficient in preventing microgrit. Those using titanium dioxide pigments with a surface treatment amount of 0.2% to 1.2% by weight can significantly prevent the generation of microgrit, have good light resistance, and are more preferred as photographic supports. I understand.

(Example 3) Instead of titanium dioxide used in Example 1,
Calculated in the form of AJ, 203 for titanium dioxide on a dry basis 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. 0.5% by weight of hydrated aluminum oxide and 0.2 calculated in the form of 8sO□
Titanium dioxide jl surface-treated with 5% by weight of hydrous silicon oxide and having a suspension electrical conductivity of 50μ≠/cIR
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 material I was used.

This resin-coated paper was suitable as a photographic support because it significantly prevented the generation of microgrit and had excellent light resistance and heat resistance.

(Example 4) Instead of the resin composition containing titanium dioxide coated on the surface of the base paper used in Example 1, 30 parts by weight of a masterbatch of the same titanium dioxide pigment as in Example 1, and ethylene-propylene copolymer were used. material (propylene content 0.1% by weight, density 0.
945 f/cd.

MI=7) 30 parts by weight and low density polyethylene (density 0
．． The same procedure as in Example 1 was carried out except that a resin composition containing 40 parts by weight of 92 f/edz MI =7) was used.

As a result, the same results as in Example 1 were obtained.

Claims (9)

[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 coating is 60μR a/lX A photographic resin-coated paper characterized in that it has a suspension electrical conductivity as defined in the following specification. (2) The photographic resin-coated paper according to claim 1, wherein the surface of the titanium dioxide pigment is treated with an inorganic surface treatment agent. (3) The photographic resin-coated paper according to claim 2, wherein the inorganic surface treatment agent is hydrous 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) The photograph according to claim 2, wherein the amount of the inorganic surface treatment agent treated is 0.2 to 1.2 weight X (calculated in anhydrous form) based on titanium dioxide. resin-coated paper. (6) The processing amount of hydrous aluminum oxide is 0.2 weight N~ per titanium dioxide! , 2 weight (A4゜03
The photographic resin-coated paper according to claim 3 or 4, which is calculated in the form of ). (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. The photographic resin-coated paper according to claim 7, 8 or 9, wherein the resin composition contains a fatty acid metal salt.