JP2638306B2 - 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 paper support. More specifically, the present invention relates to a photographic printing paper support material which is free from fogging or suppressed on photographic printing paper by development processing.

[0002]

2. Description of the Related Art Conventionally, so-called baryta paper has been used as a support for photographic printing paper, which is obtained by coating a white pigment such as barium sulfate on both sides of a paper having strong size and high strength. It was manufactured by However, in recent years, instead of this, a polyolefin-coated support manufactured by coating both surfaces of a paper substrate with a polyolefin resin has been widely used. In such a support, since the polyolefin coating layer is hydrophobic, the processing solution is less likely to penetrate into the support during the development and fixing process than the baryta paper, so that the washing time and the drying time are significantly longer. It has the advantage of being shortened, and has the advantages that the treatment liquid does not penetrate into the paper substrate, so that expansion and contraction of the support itself is suppressed, and excellent dimensional stability is obtained.

However, an inorganic white pigment such as titanium dioxide is mixed into the polyolefin coating layer of such a support for the purpose of improving the hiding power or the resolving power. Such a pigment is dispersed in a resin. However, there are problems such as poor foamability and foaming in the melt extrusion process due to volatile components contained in the pigment to cause film cracking in the coating layer. Therefore, the pigment content in the coating layer, the hiding power,
Or, it cannot be increased to a sufficient level for improving the resolving power. Generally speaking, when using titanium dioxide, it is difficult to incorporate it in an amount of about 20% by weight or more. Therefore, the photographic paper obtained using such a photographic paper support was not sufficiently satisfactory in image sharpness.

In recent years, a so-called electron beam-curable resin composed of a resin composition curable by electron beam irradiation has been applied to a support, and an electron beam-curable resin coating layer cured by electron beam irradiation has been applied thereto. Photographic paper supports have been proposed (for example, JP-B-60-17104, JP-B-60-1710).
No. 5, JP-A-57-49946, etc.). According to this method, it is not necessary to heat the resin composition to a high temperature when forming the coating layer, and it is possible to increase the pigment content to 20 to 80% by weight. The image sharpness of the photographic printing paper thus obtained is remarkably improved as compared with the photographic printing paper coated with a polyolefin resin.

However, in a photographic photosensitive material produced by applying a photosensitive layer on an electron beam-cured resin coating layer cured by electron beam irradiation, a photographic processing chemical is adsorbed on the resin coating layer in a developing step. Phenomenon in which yellowing occurs after development processing, that is, yellowing occurs, and furthermore, after storage aging, if this is subjected to development processing, the density of fog increases to a degree that cannot be ignored as a product, It has been found that the sensitivity may change.

Various improvements have been proposed to solve this problem. For example, Japanese Patent Publication No. 1-2495 discloses a method of providing a polyethylene coating layer on an electron beam curable resin coating layer as means for suppressing a change in sensitivity during storage. However, in this method, the effect cannot be obtained unless the coating layer of polyethylene is thickened, and therefore, it is necessary to sacrifice the improvement of image sharpness which is the greatest advantage when using the electron beam curing technology. Problem.

Also, Japanese Patent Application Laid-Open No. 60-144736 proposes a method of suppressing a change in photographic sensitivity by disposing a blocking layer between a base paper and an electron beam curable resin coating layer. However, the material proposed here as a shielding layer forming material is still insufficient with respect to fog prevention during long-term storage. Also, JP-A-62-161049, and
No. 61-141543 proposes to use specific polymers or monomers, but these methods have not yet sufficiently solved the problem.

[0008] On the other hand, the fog density and the yellowing show a tendency to contradict each other with respect to the irradiation dose. That is, when a high irradiation dose is used, yellowing due to the developer can be suppressed low, but fog increases. On the other hand, at a low irradiation dose, the generation of fog is suppressed to some extent, but the yellowing is remarkably increased, and the physical properties of the coating film such as adhesion and film strength are also deteriorated. Therefore, in order to improve yellowing without deteriorating the film properties, it is necessary to irradiate an appropriate electron dose,
It is extremely important to find a method for removing the fogging generated thereby to simultaneously and effectively eliminate all of the above problems.

[0009]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of the prior art, has excellent surface smoothness, maintains high water resistance, and does not cause an increase in fogging due to development after storage. Another object of the present invention is to provide a photographic paper support suitable for producing photographic paper having excellent photographic properties while suppressing yellowing.

[0010]

The present invention solves the above-mentioned problems by disposing a pigment coating layer containing a pigment comprising a magnesium compound on at least one surface of a paper substrate in a photographic paper support. Is a successful one. That is, the photographic printing paper support of the present invention comprises a paper substrate containing natural pulp as a main component, and at least one of the paper substrates.
A sheet-like substrate formed on a surface and comprising a pigment coating layer containing 1 to 50 g / m ² of a pigment comprising a magnesium compound; and a sheet-like substrate formed on one surface of the sheet-like substrate and cured by electron beam irradiation And a surface resin coating layer containing, as a main component, an electron beam irradiation-curable resin of a composition containing an unsaturated organic compound and an inorganic pigment, and a film-forming layer formed on the opposite surface of the sheet-like substrate. And a backside resin coating layer containing a synthetic resin as a main component.

[0011]

The structure and operation of the present invention will be described below.
In general, a commercially available electron beam-curable resin composition is applied to a paper substrate made of natural pulp, and the resulting substrate is irradiated with an electron beam to form an electron beam-curable resin coating layer. However, there is a problem that fogging during storage is remarkable.
Although the cause of fogging is not clear, it is considered that active radicals generated by electron beam irradiation remain in the support and react with the photographic emulsion layer to generate fog. The active radical is generated from cellulose constituting the paper substrate and the electron beam-curable resin, and it is considered that the active radical generated particularly from cellulose has a great effect on fog. The present inventors have conducted various studies on this point, and as a result, as described above, by providing a pigment coating layer containing a pigment made of a magnesium compound on at least one surface of the paper substrate, the prevention of the above fogging has been improved. It was found that the present invention was completed. That is, the pigment coating layer is formed not only on the surface of the paper substrate on which the photographic emulsion is coated but also as an intermediate layer for preventing diffusion of active radicals, but also on the opposite side of the paper substrate on which the photographic emulsion layer is coated. According to the present invention, it has been found that, even when a pigment coating layer is provided on the side surface, the effect of preventing fog is also obtained. Although the mechanism of such fogging prevention is not yet completely clear, the pigment coating layer prevents the radicals generated from cellulose upon electron beam irradiation from migrating to the photographic emulsion layer by some action.
It is considered that the fog was suppressed, thereby improving the fog prevention.

Further, according to the present invention, it is not necessary to keep the irradiation dose of the electron beam extremely low in order to prevent the occurrence of fog, and therefore it is also effective in improving yellowing. FIG. 1 is a sectional explanatory view of an example of the photographic printing paper support of the present invention.
In FIG. 1, on one side or both sides of the paper base layer 1 (FIG.
, On both surfaces), a pigment coating layer 2 is formed, thereby forming a sheet-like substrate 4. On one surface of the sheet-like substrate 4, a surface resin coating layer 3 containing an electron beam curable resin is formed. The back surface resin coating layer 5 is formed on the opposite side surface.

In the present invention, the magnesium compound used as a pigment in the pigment coating layer can be selected from magnesium hydroxide, magnesium carbonate, magnesium oxide, magnesium sulfate and the like. It is preferred to use magnesium. These magnesium compounds may be used alone or as a mixture of two or more thereof, or may optionally contain other types of pigments such as calcium carbonate, titanium dioxide, talc, clay, barium sulfate,
It can also be used as a mixture with aluminum oxide or the like. The amount of the other pigment mixed with the magnesium compound is arbitrary, but preferably does not exceed 40% of the total amount of the pigment.
If this exceeds 40%, the effect of preventing fogging of the resulting pigmented coating layer may be insufficient.

When applying the pigment on a paper substrate,
Generally, a binder is used in combination. Such binders include SBR latex, polyvinyl alcohol,
Any binder selected from ordinary binders used in the production of coated paper, such as gelatin and starch, can be used. The mixing ratio of the pigment and the binder is arbitrary, but as the pigment ratio is increased as much as possible within a range where the pigment can be uniformly dispersed, the antifogging effect increases.

The apparatus for dispersing the pigment in a solution containing a binder includes a three-roll mill (three-roll mill), a two-roll mill (two-roll mill), a cowles dissolver, a homomixer, a sand grinder, a dyno mill, and an ultrasonic disperser. Machine can be used. Further, as a method of applying the pigment coating solution to the paper substrate surface, for example, a bar coating method, an air doctor coating method,
Any of a blade coating method, a squeeze coating method, an air knife coating method, a reverse roll coating method, and a transfer coating method may be used. Further, for this purpose, a fountain coater or a slit die coater method can be used. In addition, the method of drying the applied pigment coating liquid layer is also a drying method using a general dryer, but it is possible to use a cast coating method using a cast drum to increase the surface smoothness. It is advantageous. The pigment amount of the pigment coating layer of the present invention is 1 g / m
^{2 to} 50 g / m ² and 5 g / m ^{2 to} 25 g / m ²
It is preferably ² or less. When the amount of the pigment is less than 1 g / m ² , the effect of preventing fogging is small.
If it exceeds g / m ² , the prevention effect is saturated and not only the paint is wasted, but also adverse effects such as curling may occur, which is not preferable.

The paper substrate used in the present invention is usually 50 to 30.
Those having a weight of 0 g / m ² and a smooth surface are used. Any paper substrate can be used as long as it is generally used as a support for photographic printing paper.However, when a pigment coating layer is provided on the surface of the paper substrate on which the photographic emulsion layer is coated, The paper substrate is not particularly limited to that used for photographic paper, and other base papers may be used. As a natural pulp for forming a paper substrate, generally, a pulp mainly containing a softwood pulp, a hardwood pulp, a softwood pulp mixed pulp, or the like is widely used.

The paper substrate may contain additives such as sizing agents, fixing agents, paper strength agents, fillers, antistatic agents, pH regulators, pigments, dyes and the like which are generally used in papermaking. Good. Further, a surface sizing agent, a surface strength agent, an antistatic agent and the like may be appropriately applied to the surface. In the pigment coating layer of the present invention, if necessary, a surfactant, a hardener,
Additives such as a matting agent, an antistatic agent, and an antifoggant may be contained.

The surfactants usable in the pigment coating layer of the present invention include, in addition to natural products such as saponin, shadowing agents such as higher fatty acid alkali salts, alkyl sulfates, alkyl sulfonates and sulfosuccinates. Ion activators, higher amine halides, alkylpyridinium halides,
Examples thereof include cationic activators such as quaternary ammonium salts, nonionic activators such as polyethylene glycol alkyl ethers and polyethylene glycol fatty acid esters, and synthetic activators such as amphoteric activators such as amino acids.

The surface resin coating layer formed on one surface of the sheet-like substrate having the pigment coating layer according to the present invention comprises a mixture of an unsaturated organic compound curable by an electron beam and a white pigment. The composition contains an electron beam-curable resin containing other additives depending on the composition. The unsaturated organic compound curable by an electron beam used in the present invention can be selected from the following compounds. (1) Aliphatic, alicyclic, and araliphatic acrylate compounds of mono- to hexavalent alcohols and polyalkylene glycols. (2) Acrylic compounds obtained by adding alkylene oxide to aliphatic, alicyclic, and araliphatic mono- to hexavalent alcohols. (3) Polyacryloyl alkyl phosphates. (4) A reaction product of a carboxylic acid, a polyol, and acrylic acid. (5) A reaction product of an isocyanate, a polyol, and acrylic acid. (6) A reaction product of an epoxy compound and acrylic acid. (7) A reaction product of an epoxy compound, a polyol, and acrylic acid.

More specifically, as electron beam-curable unsaturated organic compounds, polyoxyethylene epichlorohydrin-modified bisphenol A diacrylate, dicyclohexyl acrylate, epichlorohydrin-modified polyethylene glycol diacrylate, 1,6-hexanediol diacrylate, hydroxy Vivalic acid ester neopentyl glycol diacrylate, nonylphenoxy polyethylene glycol acrylate, ethylene oxide-modified phenoxylated phosphoric acid acrylate, ethylene oxide-modified phthalic acid acrylate, polybutadiene acrylate, caprolactan-modified tetrahydrofurfuryl acrylate, tris (acryloxyethyl) isocyanurate , Trimethylolpropane triacrylate, Pentaery Lithol triacrylate, dipentaerythritol hexaacrylate, polyethylene glycol diacrylate, 1,4-butadiene diol diacrylate, and the like neopentyl glycol diacrylate and neopentyl glycol-modified trimethylolpropane diacrylate.

In the surface resin coating layer of the support of the present invention,
It contains an inorganic white pigment dispersed in an electron beam curable resin. As such an inorganic white pigment, any of titanium dioxide (anatase type and rutile type), barium sulfate, calcium carbonate, aluminum oxide, and magnesium oxide can be used. The surface of the titanium dioxide particles may be treated with a metal oxide such as alumina hydroxide to improve the dispersibility.

The content of the white pigment is preferably 20 to 80% by weight of the total solid weight of the surface resin coating layer. If the content is less than 20% by weight, the sharpness of the photographic image on the obtained photographic paper may not be sufficient, and if it exceeds 80% by weight, the flexibility of the obtained surface resin coating layer decreases. This may cause film cracking. The white pigment is dispersed in the electron beam-curable unsaturated organic compound as described above,
Further, as a method of coating on one surface of the sheet-like substrate, a method similar to the above-described dispersion method and coating method used for forming a pigment coating layer can be used.

In order to enhance the surface smoothness of the obtained support and obtain high gloss, it is advantageous to use a casting method for coating and curing the electron beam-curable composition. The weight of the surface resin coating layer is ^{2 to} 60 g / m ² (solid content)
And more preferably 10 to 30 g / m ² . When forming the surface resin coating layer, a curtain beam type which is relatively inexpensive and can obtain a large output is preferable as an electron beam accelerator used for electron beam irradiation. The acceleration voltage at the time of electron beam irradiation is preferably from 100 to 300 kv, and the absorbed dose is preferably from 0.1 to 6 Mrad, particularly preferably from 0.2 to 4.0 Mrad. Absorbed dose is 0.
If it is less than 1 Mrad, double bonds in the electron beam curable resin may not remain in the reaction but remain in the cured film, adversely affecting photographic properties.

In general, when the absorbed dose is low, the degree of cross-linking in the obtained cured resin tends to be low, which deteriorates yellowing resistance. However, according to the present invention, the occurrence of fog can be suppressed, Higher doses can be used, thus improving yellowing resistance. However, increasing the absorbed dose more than necessary is not only wasteful in terms of energy, but also causes curling of the obtained support, and furthermore, the coating film may be too hard, which is not preferable.

The oxygen concentration in the atmosphere during electron beam irradiation is 50
It is preferably 0 ppm or less. If the oxygen concentration exceeds 500 ppm, oxygen acts as a retarder for the polymerization reaction, and the curing of the electron beam-curable composition may be insufficient. However,
In the case of drum curing, the electron beam-curable composition does not come into direct contact with air during electron beam irradiation. Therefore, it is not necessary to particularly reduce the oxygen concentration in the atmosphere during electron beam irradiation. The use of an inert gas for the purpose of suppressing the generation of ozone due to the inert gas or for the purpose of cooling a window that generates heat when an electron beam passes through does not pose a problem.

Examples of the film-forming synthetic resin used for forming the backside resin coating layer of the present invention include a polyolefin resin used in the production of a conventional support for photographic printing paper, and the aforementioned electron beam-curable resin. Can be used. Examples of the polyolefin resin for forming the backside resin coating layer include homopolymers of ethylene, α-olefins, for example, propylene, at least two copolymers of the olefins, and at least two of these various polymers. And mixtures thereof. Particularly preferred polyolefin resins are low density polyethylene, high density polyethylene, linear low density polyethylene, and mixtures thereof. The molecular weight of the polyolefin resin is not particularly limited, but is usually in the range of 20,000 to 200,000.

In the polyolefin resin, if necessary,
Small amounts of antioxidants and lubricants may be added. In order to form a back resin coating layer using a polyolefin resin, ordinary melt extrusion coating can be used. As the electron beam-curable unsaturated organic compound for forming the backside resin coating layer, all the compounds used for forming the above-mentioned frontside resin coating layer can be used. Further, the method of forming the back surface resin coating layer is the same as that of the above-described front surface resin coating layer.

The weight of the backside resin coating layer is not particularly limited, but is generally preferably in the range of 10 to 40 g / m ² .

[0029]

EXAMPLES The structure and effects of the present invention will be further described with reference to the following examples, but the present invention is not limited to these embodiments. Example 1 A pigment-containing paint having the following composition was prepared.

Ingredients Compounding amount Magnesium hydroxide 80.0 parts by weight SBR latex 20.0 parts by weight (solid content) (trademark: JSR 2287, manufactured by Nippon Synthetic Rubber Co., Ltd.) After dispersing with a dissolver for 1 hour, the latex was mixed.

The above coating material was dried on a single side of a paper substrate having a basis weight of 175 g / m ² by a bar coater to a weight of 5 g / m 2.
^This was applied to form a pigment coating layer. Then
Polyethylene was melt-extruded and coated on the opposite surface of the paper substrate to form a back resin coating layer of 30 g / m ² . Next, an electron beam-curable organic compound-white pigment composition having the following composition was prepared.

Component Compounding amount Epoxy acrylate oligomer 70.0 parts by weight (trade name: Viscoat 540, manufactured by Osaka Organic Chemical) Bifunctional acrylate monomer (trade name: HDDA, manufactured by Nippon Kayaku) 30.0 parts by weight Titanium dioxide (trade name: A220, Ishihara Sangyo) 25.0 parts by weight The mixture of the above components was mixed and dispersed with a paint conditioner for 1 hour to prepare an electron beam-curable composition. This composition was applied on the above-mentioned pigment coating layer using a wire bar so that the applied amount after curing was 25 g / m ² ,
An electron beam was irradiated under the conditions of an acceleration voltage of 165 kv and an absorbed dose of 3 Mrad, and the coating layer was cured to form a surface resin coating layer. The surface of the surface resin coating layer was used as the face surface of the support.

In order to test the antifogging effect of the obtained photographic printing paper support, the surface resin coating layer of the test support was stuck so as to be in intimate contact with the emulsion surface of a commercially available color photographic printing paper. The color photographic printing paper was peeled off from the surface resin coating layer of the test support after leaving for 3 days under the conditions of a temperature of 70 ° C. and a relative humidity of 50% under the following conditions. : RCP20, manufactured by Durst Co.).

The fog density of the developed photographic paper was measured using a Macbeth densitometer (trade name: Model No. RD-914, Kollmorgen Co., Ltd.).
rp.). Table 1 shows the test results. Example 2 The same operation as in Example 1 was performed. However, the coating amount of the pigment coating layer was adjusted to 20 g / m ² .

Table 1 shows the results of tests performed in the same manner as in Example 1. Example 3 The same operation as in Example 1 was performed. However, the pigment coating layer was provided on the surface (back surface) of the paper substrate on which the back resin coating layer was formed, so that the coating amount was 20 g / m ² .

Table 1 shows the results of tests performed in the same manner as in Example 1. Example 4 The same operation as in Example 1 was performed. However, the pigment coating layers were formed on both sides of the paper substrate. Table 1 shows the results of tests performed in the same manner as in Example 1. Comparative Example 1 The same operation as in Example 1 was performed. However, the surface resin coating layer was formed directly on the base paper without providing the pigment coating layer.

Table 1 shows the results of tests performed in the same manner as in Example 1. Comparative Example 2 The same operation as in Example 1 was performed. However, the coating amount of the pigment coating layer was adjusted to 0.5 g / m ² . Table 1 shows the results of tests performed in the same manner as in Example 1. Comparative Example 3 The same operation as in Example 1 was performed. However, only the SBR latex containing no pigment was applied instead of the pigment coating layer.

Table 1 shows the results of tests performed in the same manner as in Example 1. Comparative Example 4 The same operation as in Example 1 was performed. However, light calcium carbonate (trademark: Brilliant-15, manufactured by Shiroishi Kogyo) was used as the pigment for the pigment coating layer. Table 1 shows the results of tests performed in the same manner as in Example 1. Reference Example 1 A photographic RC paper base material obtained by laminating a base paper with a polyethylene resin was tested in the same manner as in Example 1. Table 1 shows the results.

[0039]

[Table 1]

[0040]

EFFECT OF THE INVENTION The photographic printing paper support of the present invention is capable of greatly reducing the general drawback when an electron beam-curable resin layer is provided, that is, the occurrence of fog due to the development after storage over time. Therefore, it is extremely effective in practical use.

[Brief description of the drawings]

FIG. 1 is an explanatory cross-sectional view showing a configuration of an example of a photographic printing paper support of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Paper base material 2 ... Pigment coating layer 3 ... Surface resin coating layer 4 ... Sheet-like substrate 5 ... Backside resin coating layer

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location D21H 19/38 D21H 1/22 B

Claims (1)

(57) [Claims] 1. A paper substrate containing natural pulp as a main component,
A sheet-like substrate formed on at least one surface of the paper substrate and comprising a pigment coating layer containing 1 to 50 g / m ² of a pigment comprising a magnesium compound; and a sheet-like substrate formed on one surface of the sheet-like substrate. A surface resin coating layer containing, as a main component, an electron beam irradiation-curable resin of a composition containing at least one unsaturated organic compound curable by electron beam irradiation, and an inorganic white pigment; and the sheet-like substrate. And a backside resin coating layer formed on the opposite side of the above and containing a film-forming synthetic resin as a main component.