JP2701597B2 - Photographic paper support - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photographic printing paper support. More specifically, the present invention relates to a photographic paper support that produces little or no fog on photographic paper during development processing.

[0002]

2. Description of the Related Art Heretofore, 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 paper having strong size and high strength. However, in recent years, polyolefin-coated supports manufactured by coating both surfaces of a paper substrate with a polyolefin resin have been widely used in place of baryta paper. In such a photographic printing paper support, since the polyolefin resin coating layer is hydrophobic and waterproof, the resulting photographic printing paper support has a processing solution during development and fixing, as compared to baryta paper. Hardly penetrates into the support, so that the washing time and drying time are greatly reduced, and since there is no penetration of the treatment liquid into the paper substrate, the expansion and contraction of the support itself is suppressed, and the dimensional stability is reduced. It has advantages such as improvement.

However, in the case of using a photographic paper produced by applying a photographic emulsion to the above-mentioned polyolefin resin-coated photographic paper support, if the photographic paper is used after being stored for a long time, it cannot be ignored as a product. There is a problem that fog occurs to a certain extent. JP-A-55-103549 and the like have proposed to add water-soluble iodine to a sheet-like substrate as a method for preventing this fog, but the effect has not been satisfactory or satisfactory.

[0004]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of the conventional polyolefin resin-coated photographic printing paper support, and produces no or little photographic printing even after long-term storage. It is an object of the present invention to provide a photographic paper support suitable for producing paper.

[0005]

The present invention comprises a sheet-like substrate and a coating layer formed on both surfaces thereof and containing a polyolefin resin as a main component, wherein the sheet-like substrate mainly comprises natural pulp. And 0.5 to 10% by weight, based on the total weight of the sheet-like substrate, of at least one magnesium compound selected from magnesium hydroxide, magnesium carbonate and magnesium sulfate. It is.

[0006]

The cause of fogging that occurs when conventional photographic printing paper is stored for a long period of time has not been sufficiently clarified, but substances that affect fog generation are produced from sheet-like substrates mainly composed of natural pulp. It is considered that as the storage time elapses, it passes through the polyolefin resin coating layer and diffuses into the photographic emulsion layer, which causes fogging.

The present inventors have intensively studied means for preventing the substance which influences the fog generation from moving to the photographic emulsion layer over time, and as a result, the sheet-like substrate containing natural pulp as a main component has been described. By including a specific amount of the specific magnesium compound, found that it is possible to prevent the migration of a substance affecting fog generation to the photographic emulsion layer,
The present invention has been completed.

Although the mechanism of the effect of the specific magnesium compound has not been sufficiently elucidated, these magnesium compounds capture (adsorb) substances that affect fog generation, and This is presumably because it is fixed in the sheet-like substrate to prevent its movement.

The specific magnesium compound used in the present invention is selected from magnesium hydroxide, magnesium carbonate, and magnesium sulfate, and among them, magnesium hydroxide is preferably used. These magnesium compounds may be used alone as a pigment to be contained in the sheet-like substrate, or may be other types of pigments such as calcium carbonate, titanium dioxide, talc, clay, barium sulfate, and aluminum oxide. And at least one of them.

The amount of the magnesium compound to be added to the sheet substrate is 0.5 to 10% by weight based on the total weight of the sheet substrate. When the amount is less than 0.5% by weight, the antifogging effect is small, and when it exceeds 10% by weight, the antifogging effect is sufficient. Disadvantaged.

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

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

The sheet-like substrate of the present invention includes a sizing agent, a fixing agent, a paper strength enhancer, and a sizing agent generally used for papermaking.
Additives such as an antistatic agent, a pH adjuster, and a dye may be blended. Further, a surface sizing agent, a surface strength agent, an antistatic agent and the like may be appropriately applied to the surface.

In the present invention, polyethylene resins such as low-density polyethylene, high-density polyethylene, linear low-density polyethylene and mixtures thereof are frequently used as the polyolefin resin used for the coating layer. May be included.

In the present invention, when a polyethylene resin is used for forming the coating layer, its molecular weight is not particularly limited, but it is usually preferable to use one having a molecular weight in the range of 20,000 to 200,000.

In the photographic printing paper support of the present invention, it is preferable that the polyolefin resin coating layer formed on the surface (on the photographic emulsion coating side) contains a titanium dioxide pigment. Or any of those produced by the chlorine method, and may be any of rutile type and anatase type, but it is advantageous to use anatase type titanium dioxide having excellent whiteness. is there.

The surface of titanium dioxide may be treated with an inorganic surface treating agent such as, for example, hydrous aluminum hydroxide, treated with an organic surface treating agent such as organopolysiloxane, or may be treated with an inorganic surface. Any of those coated with an appropriate combination of a treating agent and an organic surface treating agent can be used, but it is necessary to include at least 0.2 to 2.0% of hydrous aluminum hydroxide in terms of Al ₂ O _3. It is desirable to use one that has been processed as described above. Further, the polyolefin resin coating layer formed on the surface side of the support,
It is preferable that titanium dioxide is contained therein in a content of 5 to 30% by weight.

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 / m2.
It is preferably ² . If it is less than 25 g / m ² , it is difficult to make the surface of the sheet-like substrate uneven and sufficiently smooth. Further, even if the coating amount of the surface-side polyolefin resin coating layer is increased to more than 40 g / m ² , the effect is not improved, the cost is rather increased, and the effect of the present invention is diluted, so that it is not practical. .

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 preferable to use it 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 coated with a white pigment such as zinc oxide, talc, calcium carbonate, aluminum hydroxide, glass fiber, whisker or the like in addition to the above-mentioned titanium dioxide. Fibrous fillers, carbon black, phthalocyanine pigments, color pigments such as graphite, titanium yellow, red bengal, ultramarine blue, and stabilizers mixed with ordinary resins, antioxidants, antistatic agents, plasticizers, Dispersants, lubricants,
And one or more kinds of fluorescent agents and the like.

The polyolefin resin coating layer on the back side of the support may also contain the same additives as the above-mentioned polyolefin resin coating layer on the front side, but a small amount of additives other than the antioxidant and the lubricant may be added. Usually not.

In forming the support of the present invention, a flat die such as a T-type die or an L-type die is preferable as the slit die for melt extrusion coating used in the polyolefin resin coating step. It is preferable to use a pressure roll having a hardness of 85 to 98 (JIS K6301-5) at the time of melt extrusion coating.

In the photographic printing paper support of the present invention, in order to improve the adhesiveness with a photographic emulsion, a subcoat (undercoat 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 printing writability and antistatic property.

[0024]

The present invention will be further described with reference to the following examples, which, of course, are not intended to limit the present invention.

Example 1 Canadian Standard Freeness (JIS P-8121-7)
6) Softwood bleached sulfuric acid pulp (NB
SP) 20% and 80% of hardwood bleached sulfite pulp (LBKP) beaten to 280 ml of the above freeness to prepare a pulp slurry having a concentration of 1.0%. In this pulp slurry,
The following papermaking additives were added in the following amounts based on the absolute dry weight of the pulp.

Cationized starch 2.0% Alkyl ketene dimer resin 0.4% Anionic polyacrylamide resin 0.1% Polyamide polyamine epichlorhydrin resin 0.7% Caustic soda pH 7.5 Adjust this pulp slurry sufficiently After the dispersion, magnesium hydroxide was added to the dispersion so that the final content after papermaking was 5% by weight based on the total solid content, and the mixture was subjected to a dispersion treatment for 5 minutes. The solid content concentration of the obtained mixed slurry was adjusted to 0.5%, and this was again subjected to a dispersion treatment for 5 minutes.

Paper is made from the slurry of the above-mentioned raw material, and passed through a drier, a size press, and a machine calendar, and the rice basis weight is 1
A paper substrate was produced having 70 g / m ² , a strength of 1.0 g / cm ³ and a water content of 8%. The chemical used in the size press was a mixture of carboxyl-modified PVA and sodium chloride at a ratio of 2: 1 and this was dissolved in water to form a 5% size liquid. The coating was performed so as to obtain a dry coating amount of m ² .

After a corona discharge treatment was applied to both the front and back surfaces of the paper substrate, it was subjected to the following polyethylene resin coating test.

That is, a high-density polyethylene [density 0.951 g / cm ³ , melt index (M
I) = 9.0] and low-density polyethylene (density 0.918 g / cm
³ , a 1: 1 mixture of MI = 4) was extruded at 330 ° C. resin temperature, matted with a cooling roll, and a thickness of 30
A μm backside resin coating layer was formed.

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

A corona discharge treatment is applied to the surface of the polyethylene resin coating layer containing titanium dioxide on the surface side of the sample,
A normal black and white photographic emulsion (manufactured by Rockland Colloid Co., Ltd., trade name: Liquid Light) is placed on top of it, 15 μm in total darkness
To produce photographic paper.

The obtained photographic printing paper was subjected to a heating accelerated aging treatment at 50 ° C. for 72 hours in place of long-term storage,
This was developed, stopped, fixed and rinsed under the following conditions, and the color density of the unexposed area was measured using a Macbeth densitometer (trade name: Mode).
lNO.RD-914, manufactured by Kollmorgen Corp.), and the measured value was used to indicate the fog density.

Developing conditions Developing solution Kodak D-72 formulation phenomenon liquid: water = 1: 2 Temperature 20 ° C., developing time 1 minute 30 seconds Stop condition 1.5% glacial acetic acid solution temperature 20 ° C., immersion time 20 seconds Fixing condition Fixing solution Kodak F-5 prescription fixing solution Temperature: 20 ° C, Fixing time: 10 minutes Washing conditions: 15 minutes with running water at a temperature of 20 ° C Table 1 shows the test results.

Example 2 The same operation as in Example 1 was performed. However, the final content of magnesium hydroxide after papermaking was 1% by weight based on the total solid content. Table 1 shows the results of the same test as in Example 1.

Example 3 The same operation as in Example 1 was performed. However, magnesium carbonate was used as a magnesium compound, and its final content was 5% by weight based on the total solid content. Table 1 shows the results of the same test as in Example 1.

Comparative Example 1 The same operation as in Example 1 was performed. However, no magnesium compound was contained in the papermaking. Table 1 shows the results of the same test as in Example 1.

[0037]

[Table 1]

As is clear from Table 1, the fog density of the photographic paper using the photographic paper support of Examples 1 to 3 according to the present invention was sufficiently low for practical use, but Comparative Example 1 was used. In the case of (no magnesium compound), considerable fog generation was observed.

[0039]

The support for photographic printing paper according to the present invention is very practical in practical use with less occurrence of fog after long-term storage. The same effect can be obtained when used for color photographic printing paper.

Claims (1)

(57) [Claims] And 1. A sheet substrate, are formed on both sides, and has a coating layer comprising a polyolefin resin as a main component, wherein the sheet substrate comprises a natural pulp as a main component, further, the sheet 0.5 based on the total weight of the substrate
~ 10% by weight of magnesium hydroxide, magnesium carbonate
And a photographic printing paper support comprising at least one magnesium compound selected from magnesium sulfate .