JPH06175274A - Supporting body for photographic printing paper - Google Patents

Abstract

PURPOSE:To obtain a supporting body suitable for producing a photographic printing paper free from of small in the generation of fogging even in the case of long term preservation by incorporating a magnesium compound aluminum sulfate in a sheet type substrate consisting essentially of natural pulp. CONSTITUTION:The magnesium compound and aluminum sulfate are incorporate in the sheet type substrate consisting essentially of natural pulp. Polyethylene resin such as low density polyethylene, high density polyethylene, linear low density polyethylene and the mixture thereof are mainly used as a polyolefin resin used for coating layers for the surface and rear of the sheet type substrate and a small quantity of another polyolefin resin can be also used. The magnesium compound used in this case is magnesium hydroxide, magnesium carbonate and particularly magnesium sulfate and magnesium hydroxide is preferably used.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a support for photographic printing paper. More specifically, the present invention relates to a support for photographic printing paper that does not cause fog on the photographic printing paper during development processing or has little fog.

[0002]

Conventionally, so-called baryta paper has been used as a support for photographic printing paper. This is manufactured by applying a white pigment such as barium sulfate to both sides of a paper provided with strong size and high strength. However, in recent years, instead of the baryta paper, a polyolefin-coated support produced by coating both sides of a substrate made of paper with a polyolefin resin has been widely used. Since the polyolefin resin coating layer of such a photographic printing paper support is hydrophobic and waterproof, the photographic printing paper support obtained has a processing liquid during the development and fixing process as compared with the baryta paper. Does not easily penetrate into the support, and thus the washing time and the drying time are greatly shortened, and since the treatment liquid does not penetrate into the paper substrate, the expansion and contraction of the support itself is suppressed, and the dimensional stability thereof is reduced. It has advantages such as improvement.

However, when a photographic paper produced by coating a photographic emulsion on the above-mentioned support for photographic printing paper coated with a polyolefin resin is used, it cannot be ignored as a product if it is stored for a long time and then used. There is a problem that fogging occurs to some extent. As a method for preventing this fog, JP-A-55-103549 and the like propose to add water-soluble iodine to a sheet-shaped substrate, but the effect was not sufficient and was not satisfactory. .

[0004]

SUMMARY OF THE INVENTION The present invention solves the above problems of the conventional polyolefin resin coated photographic printing paper support, and does not cause fog even when stored for a long period of time. It is an object of the present invention to provide a photographic paper support suitable for producing photographic paper.

[0005]

A photographic printing paper support of the present invention is formed on a sheet-like substrate and both front and back surfaces thereof,
In addition, the sheet-shaped substrate has a front and back surface coating layer containing a polyolefin resin as a main component, the sheet-shaped substrate contains a natural pulp as a main component, and further contains a magnesium compound and aluminum sulfate.

[0006]

The function of fog that occurs when a conventional photographic printing paper is stored for a long period of time has not been fully clarified yet, but from the sheet-like substrate containing natural pulp as a main component, a substance that affects the occurrence of fog is found. It is considered that, as the storage time elapses, it passes through the polyolefin resin surface coating layer and diffuses into the photographic emulsion layer, which causes fog.

The present inventors have diligently studied means for preventing the transfer of the substance that affects the fog generation to the photographic emulsion layer over time, and as a result, magnesium has been added to the sheet-like substrate containing natural pulp as a main component. It has been found that the inclusion of the compound can prevent the migration of substances that affect the occurrence of fog to the photographic emulsion layer.

Although the mechanism of the effect generation of such a magnesium compound has not been fully clarified yet, the magnesium compound captures (adsorbs) a substance that influences the generation of fog, and this is trapped in the sheet substrate. It is thought to be possible to prevent the movement by fixing it to.

However, when the present inventors measured the whiteness of the sheet-like substrate containing the magnesium compound, the whiteness was lower than that of the sheet-like substrate not containing the magnesium compound, and the white pigment or the fluorescent substance was found on the sheet-like substrate. Even if a polyolefin resin coating layer containing a whitening agent is formed,
It has been found that the effect of improving the whiteness is small and the image formed on the photographic paper feels dull so that the commercial value is lowered.

Therefore, the inventors of the present invention have further earnestly studied means for preventing the time-dependent migration of a substance that affects the occurrence of fog to a photographic emulsion layer when it is stored for a long period of time so as not to reduce the whiteness, and as a result, By containing a magnesium compound and aluminum sulfate in a sheet-like substrate containing natural pulp as a main component, it is possible to prevent the transfer of substances that affect the occurrence of fog to the photographic emulsion layer and prevent the reduction of whiteness. That is, the present invention has been completed.

The sheet-like substrate containing only the magnesium compound shows a decrease in whiteness, whereas the sheet-like substrate containing the magnesium compound and aluminum sulfate does not show a decrease in the whiteness. It is considered that aluminum sulfate suppresses the decrease in whiteness due to the compound. However, of course, the present invention is not bound by this assumption. Regardless of the reason for the above effect, according to the present invention, it is possible to prevent the fog of the photographic printing paper obtained from the photographic printing paper support without deteriorating the whiteness of the photographic printing paper support.

The magnesium compound used in the present invention is magnesium hydroxide, magnesium carbonate, magnesium sulfate or the like, but magnesium hydroxide is preferably used. These magnesium compounds may be used alone as pigments to be incorporated in the sheet-like substrate, or other types of pigments such as calcium carbonate, titanium dioxide, talc, clay, barium sulfate, and aluminum oxide. It can also be used as a mixture with at least one of the above.

The amount of the magnesium compound compounded in the sheet-like substrate is 0.1 to 1 with respect to the total weight of the sheet-like substrate.
It is preferably 0% by weight. When it is less than 0.1% by weight, the fog-preventing effect on the obtained photographic printing paper is small, and when it exceeds 10% by weight, the anti-fogging effect on the obtained photographic printing paper is sufficient.
However, the paper-like strength of the sheet-shaped substrate itself may be deteriorated and may become impractical.

In the present invention, the content of aluminum sulfate in the sheet substrate is preferably 0.05 to 5% by weight based on the total weight of the sheet substrate. This is 0.
When it is less than 05% by weight, the effect of preventing the reduction of the whiteness of the resulting photographic printing paper support is small, and it is 5
When the content is more than 10% by weight, the effect of preventing the decrease in whiteness of the support is sufficient, but the effect of preventing fog in the resulting photographic paper decreases, and it may become impractical.

As a method of incorporating the magnesium compound and aluminum sulfate into the sheet-like substrate, there are a method of internally adding the magnesium compound and aluminum sulfate to the pulp slurry, and a method of applying the same by a size press. .

The sheet-like substrate used in the present invention is usually made of paper, and any of those generally used for photographic printing paper can be used. Examples thereof include natural pulp paper, synthetic pulp paper, mixed paper of natural pulp paper and synthetic pulp, and various other types of laminated paper.
In general, natural pulp mainly composed of softwood pulp, hardwood pulp, softwood mixed hardwood pulp and the like is widely used.

The sheet-shaped substrate of the present invention further comprises a sizing agent, a fixing agent, a paper-strengthening agent, which are generally used for papermaking,
Additives such as antistatic agents, pH adjusters, dyes and the like may be added. Further, a surface sizing agent, a surface paper strength agent, an antistatic agent, etc. may be appropriately applied on the surface.

In the present invention, as the polyolefin resin used for both the front and back surface coating layers, polyethylene resins such as low density polyethylene, high density polyethylene, linear low density polyethylene and mixtures thereof are often used.
It may also contain small amounts of other polyolefin resins.

In the present invention, when a polyethylene resin is used for forming both front and back surface coating layers, the molecular weight thereof is not particularly limited, but is usually 20,000 to 200,000.
It is preferable to use one having a range of 0.

In the support for photographic printing paper of the present invention, the polyolefin resin coating layer formed on the surface (on the side where the photographic emulsion is coated) contains the titanium dioxide pigment in an amount of 5 to 30% by weight. Is preferred. This titanium dioxide pigment may be either one produced by the sulfuric acid method or one produced by the chlorine method, and may be either rutile type or anatase type, but anatase type dioxide excellent in whiteness It is advantageous to use titanium.

Further, the surface of titanium dioxide is treated with an inorganic surface treating agent such as hydrous aluminum oxide, an organic surface treating agent such as organopolysiloxane, or an inorganic surface. Any of a combination of a treatment agent and an organic surface treatment agent, which is coated with an appropriate combination, can be used.
It is desirable that it is formed so as to contain at least 0.2 to 2.0% of hydrous aluminum oxide in terms of ₂ O ₃ .

In the present invention, the coating amount of the polyolefin resin coating layer formed on the surface side of the support is 25 to 40 g.
/ M ² is preferable. If this is less than 25 g / m ² , it becomes difficult to make the surface irregularities of the sheet-shaped substrate sufficiently smooth. Moreover, even if the coating amount of the surface side polyolefin resin coating layer exceeds 40 g / m ² and is large,
There is no improvement in the effect due to it, rather the cost increases,
It is not practical because the effect of the present invention is diluted.

In the present invention, the coating amount of the polyolefin resin coating layer on the back side of the support is not particularly limited, but it is generally preferably used in the range of 10 to 40 g / m ² .

In the present invention, the surface-side polyolefin resin coating layer of the support is made of, in addition to titanium dioxide, white pigments such as zinc oxide, talc, calcium carbonate and aluminum hydroxide, glass fibers, whiskers and the like. Fibrous fillers, carbon black, phthalocyanine pigments, yellow lead, titanium yellow, red iron oxide, ultramarine blue and other color pigments, as well as stabilizers, antioxidants, antistatic agents, plasticizers, which are mixed with ordinary resins. Dispersant, lubricant,
And, one or more kinds such as a fluorescent agent may be contained.

In the present invention, the polyolefin resin coating layer on the back surface side of the support may also contain the same additives as those on the front surface side polyolefin resin coating layer, except for a small amount of an antioxidant and a lubricant. It is normal not to add these.

When forming the support of the present invention, the melt extrusion coating slit die used in the polyolefin resin coating step is preferably a flat die such as a T-type die or an L-type die. The hardness of the pressure roll at the time of melt extrusion coating is 85 to 98 (JIS K63
It is preferable to use those of 01-5).

In the support for photographic printing paper of the present invention, in order to improve the adhesiveness with a photographic emulsion, a subcoat (undercoat layer) is formed on the surface side polyolefin resin coating layer,
Alternatively, a back coat layer or the like may be applied on the back surface side polyolefin resin coating layer in order to improve printability and antistatic property.

[0028]

EXAMPLES The present invention will be further described with reference to the following examples, but of course the present invention is not limited to these examples.

Examples 1 and 2 and Comparative Examples 1 to 4 In each of Examples 1 and 2 and Comparative Examples 1 to 4, a support for photographic printing paper was prepared by the following steps. Water temperature 20 ℃
Canadian Standard Freeness (JIS P
-8121-76) beaten softwood sulphate pulp (NBSP) 20% to 250 ml, and freeness bleached bisulfite pulp (LBK) beaten to the above freeness of 280 ml.
P) was mixed with 80% to prepare a pulp slurry having a concentration of 1.0%. To this pulp slurry, the papermaking additive having the following composition was added in the following addition amount based on the absolute dry weight of pulp. Papermaking additive composition Ingredient Weight cationic starch 2.0% alkyl ketene dimer resin 0.4% Anionic polyacrylamide resin 0.1% polyamidepolyamineepichlorohydrin resin 0.7% sodium bicarbonate 1.0%

After sufficiently dispersing this pulp slurry,
Magnesium hydroxide in the amount shown in Table 1 was added to the dry weight of the pulp, and aluminum sulfate in the amount shown in Table 1 was added to the dry weight of the pulp.

Paper is made from the slurry of the above raw materials, passed through a dryer, size press and machine calender, and the rice basis weight is 1
A paper substrate with 70 g / m ² , a tightness of 1.0 g / cm ³ and a water content of 8% was produced. The chemicals used for the size press are
Carboxyl-modified PVA and sodium chloride were mixed at a ratio of 2: 1 and dissolved in water to prepare a 5% size liquid. The dry coating amount was 1.5 g / m on both sides of the paper.
^It was applied so as to be ² .

After the corona discharge treatment was applied to both the front and back sides of the above paper substrate, it was subjected to the following polyethylene resin coating treatment. That is, on the back surface of the paper base, high density polyethylene (density 0.951 g / cm ³ , melt index (M
I) = 9 g / 10 min) and low density polyethylene (density 0.
A 1: 1 mixture of 918 g / cm ³ and MI = 4 g / 10 min) was extrusion-coated at a resin temperature of 330 ° C. and matted with a cooling roll to form a backside resin coating layer having a thickness of 30 μm.

On the other surface (surface), a polyethylene resin containing 10% by weight of anatase type titanium dioxide (density = 0.926 g / cm ³ , melt index (M
I) = 16 g / 10 min linear low-density polyethylene 50
Parts by weight, density = 0.918 g / cm ³ , MI = 4 g / 1
A mixture of 0 minutes with 50 parts by weight of low density polyethylene),
The resin was extruded and applied at a resin temperature of 320 ° C. to form a surface resin coating layer having a thickness of 30 μm.

Corona discharge treatment was applied to the surface of the titanium dioxide-containing polyethylene resin coating layer on the surface side of the above sample,
Ordinary black-and-white photographic emulsion (Rockland Colloid Co., Ltd., trade name: Liquid Light) was added to the above in a total darkness of 15μ.
A photographic printing paper was manufactured by applying the photographic printing paper to a thickness of m.

The obtained photographic printing paper was subjected to a heating accelerated aging test under the conditions of 50 ° C. and 72 hours in place of the long-term storage test, and was subjected to development, stop, fixing and washing treatments under the following conditions. The color density of the unexposed area was measured using a Macbeth densitometer (trademark: RD-914, manufactured by Kollmorgen Corp.), and the fog density was displayed by the measured value.

Development conditions Developer: Kodak Company, D-72 formulation Developer: water = 1: 2 Temperature: 20 ° C, development time: 1 minute 30 seconds Stopping conditions 1.5% glacial acetic acid solution Temperature: 20 ° C, immersion Time: 20 seconds

Fixing conditions Fixing solution: F-5 prescription fixing solution by Kodak Co., Ltd. Temperature: 20 ° C., fixing time: 10 minutes Washing condition 15 minutes with running water at a temperature of 20 ° C. Whiteness measurement The whiteness of the above paper substrate was measured according to JIS P- It was measured according to the method specified in 8123. The test results are shown in Table 1.

[0038]

[Table 1]

As is clear from Table 1, the fog density of the photographic printing paper using the photographic printing paper supports of Examples 1 and 2 according to the present invention was sufficiently low in practical use and the whiteness was high. However, in the case of Comparative Examples 1 and 2 (containing no aluminum sulfate), the fog density was sufficiently low for practical use, but the whiteness was low, and in the case of Comparative Examples 3 and 4, (containing no magnesium compound). In (), a large amount of fog was observed although the whiteness was high.

[0040]

INDUSTRIAL APPLICABILITY The support for photographic printing paper according to the present invention is extremely useful in practice because it causes little fog after long-term storage. The same effect can be obtained when used for color photographic printing paper.

Claims (1)

[Claims] 1. A sheet-like substrate, and front and back double-sided coating layers formed on both front and back surfaces thereof and containing a polyolefin resin as a main component, wherein the sheet-like substrate contains natural pulp as a main component, and A support for photographic printing paper, which contains a magnesium compound and aluminum sulfate.