JP2638310B2 - 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 does not cause or reduce fogging or yellowing of the photographic printing 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. It is manufactured by applying a white pigment such as barium sulfate on both sides of paper having strong size and high strength. However, in recent years, a polyolefin-coated support manufactured by coating a polyolefin resin on both sides of a paper substrate has been widely used instead of baryta paper.
In such a support, since the polyolefin coating layer is hydrophobic, the resulting photographic printing paper support is less likely to penetrate the processing solution into the support during development and fixing compared to baryta paper. Therefore, the washing time and the drying time are greatly reduced, and since there is no permeation of the treatment liquid into the paper substrate, the expansion and contraction of the support itself is suppressed, and the dimensional stability is improved. I have.

However, in such a polyolefin coating layer of a support, an inorganic white pigment such as titanium dioxide mixed for the purpose of improving the hiding power or the resolving power has a poor dispersibility in a resin and has a poor dispersibility in a pigment. The volatile components contained cause foaming during melt extrusion and cause problems such as cracking of the coating layer. For this reason, the pigment content in the coating layer cannot be sufficiently increased. When using titanium, 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 an organic compound composition curable by electron beam irradiation is applied to a support, and the substrate is made of an electron beam-curable resin cured by electron beam irradiation. Photographic paper support having a coating layer (for example, JP-B-60-17104, JP-B-60-171)
No. 05, 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 resin coating layer, and the pigment content can be increased to a large amount of 20 to 80% by weight. Therefore, the image sharpness of photographic printing paper obtained using such a support,
It is significantly improved compared to photographic paper coated with 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. And develop yellowing after development, that is, yellowing occurs.Furthermore, if storage is subjected to development after storage, the fog density will increase to a level that cannot be ignored as a product, and the sensitivity will increase. Or change in some cases.

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 polyethylene coating layer is thickened, and therefore,
There is such a problem that the greatest advantage of using the electron beam curing technique, that is, improvement in sharpness, must be sacrificed. JP-A-60-144736 proposes a method for suppressing a change in photographic sensitivity by disposing a blocking layer between a base paper and an electron beam curable resin coating layer. But,
Even if the material proposed here as the shielding layer is used, it is still insufficient in terms of preventing fog during long-term storage. JP-A-62-61049 and JP-A-61-141543 propose to use a specific polymer or monomer, but this is still insufficient to solve the problem.

On the other hand, the fog density and yellowing of the photographic paper tend to be opposite to each other with respect to the irradiation dose when the resin coating layer is formed. That is, at a high irradiation dose, yellowing of the photographic paper due to the developing solution can be suppressed to a low level, but fog increases. On the other hand, when the irradiation dose is low, the generation of fog on the photographic paper can be suppressed to some extent, but the yellowing is significantly increased. In addition, the physical properties of the coating film such as the adhesiveness and the film strength of the obtained resin coating layer are deteriorated. Therefore, in order to improve yellowing without deteriorating the film physical properties, it is necessary to irradiate an appropriate irradiation dose, and it is also necessary to find a method of removing fog which increases in response to an increase in the irradiation dose. It is extremely important to eliminate or reduce all of the above problems at the same time.

[0008]

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 characteristics while suppressing yellowing at the same time.

[0009]

The present invention has succeeded in solving the above-mentioned problems by adding a magnesium compound to a sheet-like support formed mainly of natural pulp. That is, the photographic printing paper support of the present invention contains natural pulp as a main component and a sheet-like substrate containing a magnesium compound, and is formed on the surface of the sheet-like substrate, and is cured by electron beam irradiation. A surface resin coating layer comprising an electron beam-curable resin having a composition containing at least one unsaturated organic compound and an inorganic white pigment to be obtained; and a synthetic resin formed on the back surface of the sheet-like substrate and having a film-forming ability. And a back surface resin coating layer made of

[0010]

In general, a commercially available electron beam-curable resin composition is applied to a sheet-like substrate made of natural pulp and irradiated with an electron beam to form a resin coating layer. Paper is significantly fogged during storage. Although the cause of such fogging is not clear, it is considered that active radicals generated by electron beam irradiation 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. In particular, the active radical generated from cellulose has a great effect on fog. As a result of various studies, the present inventors have found that the generation of the fog can be prevented by adding a magnesium compound to the sheet-like substrate, and have completed the present invention. The mechanism of fogging prevention is not completely clear yet, but the magnesium compound contained in the sheet-like substrate prevents or suppresses the transfer of radicals generated from cellulose during electron beam irradiation to the photographic emulsion layer by some action. Thus, it is considered that the antifogging property can be improved.

Further, according to the present invention, it is not necessary to keep the irradiation dose of the electron beam extremely low when forming the surface resin coating layer in order to prevent the occurrence of fog, and therefore, it is also possible to improve the yellowing resistance of photographic paper. It is valid. Magnesium compound used in the present invention, magnesium hydroxide, magnesium carbonate,
Among them, magnesium oxide, magnesium sulfate and the like, among which magnesium hydroxide and magnesium oxide are preferably used. These magnesium compounds may be used alone as a pigment to be contained in the sheet-like substrate, or may be used together with other kinds of pigments such as calcium carbonate, titanium dioxide, talc, clay, barium sulfate, aluminum oxide and the like. They can be used in combination. 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 the amount of the other pigment exceeds 40%, the effect of preventing fogging decreases, which is not preferable.

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.

As a method of incorporating the magnesium compound into the sheet-like substrate, there are a method of internally adding the magnesium compound to the pulp slurry, a method of applying by a size press, and the like. The amount of the magnesium compound contained in the sheet-like substrate is 0.1 to 70% by weight based on the weight of the sheet-like substrate.
And more preferably 1 to 40% by weight
It is. If the content is less than 0.1% by weight, the effect of reducing fog of the obtained photographic paper is insufficient, and
Even if it is added in a large amount exceeding 70% by weight, the effect of scavenging radicals is unnecessarily increased, so that it is not only futile, but also, in some cases, paper strength deteriorates, powder falls,
The photographic properties of the resulting photographic paper may be adversely affected.

Further, 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, a surface coating layer formed on a sheet-like substrate containing a magnesium compound and made of an electron beam-curable resin comprises at least one organic compound curable by an electron beam, a white inorganic pigment, and It is formed from a composition consisting of other additives as appropriate.

The organic compound which can be cured by an electron beam used in the present invention is an unsaturated organic compound which is polymerized and cured by irradiation with an electron beam. Examples of such organic compounds include: (1) Aliphatic, alicyclic, and araliphatic acrylate compounds of mono- to hexavalent alcohols and polyalkylene glycols. (2) Acrylic compounds obtained by adding an alkylene oxide to an aliphatic, alicyclic, or araliphatic mono- to hexavalent alcohol. (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. And the like.

Specific examples of these organic compounds include polyoxyethylene epichlorohydrin-modified bisphenol A diacrylate, dicyclohexyl acrylate, epichlorohydrin-modified polyethylene glycol diacrylate, 1,6-hexanediol diacrylate, and hydroxybivalic 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, pentaerythritol tri Acrylate, dipentaerythritol hexaacrylate, polyethylene glycol diacrylate, 1,4-butadiene diol diacrylate, neopentyl glycol diacrylate, and neopentyl glycol-modified trimethylol propane diacrylate, and the like.

In the surface resin coating layer of the support of the present invention,
It contains a white inorganic pigment dispersed in an electron beam curable resin. As such a 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 based on 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,
If the content is more than 10% by weight, the flexibility of the obtained surface resin coating layer may be reduced, and the film may be cracked. In order to disperse the white pigment in the electron beam-curable unsaturated organic compound composition as described above, a three-roll mill (three-roll mill), a two-roll mill (two-roll mill), a Cowles dissolver,
A homomixer, a sand grinder, an ultrasonic disperser and the like can be used.

Examples of the method of applying the electron beam curable resin composition to the sheet-like substrate surface include a bar coating method, an air doctor coating method, a blade coating method, a squeeze coating method, an air knife coating method, a reverse roll coating method, and the like. Any of transfer coating and transfer coating may be used. Further, for this purpose, a fountain coater or a slit die coater method can be used.

In order to enhance the surface smoothness of the obtained support and increase the gloss, it is advantageous to use a casting method for applying the electron beam-curable resin composition. In the support of the present invention, the weight of the surface resin coating layer,
It is preferably ^{2 to} 60 g / m ² (solid content). As an electron beam accelerator used for electron beam irradiation, a curtain beam type which is relatively inexpensive and can obtain a large output is effectively used. Acceleration voltage for electron beam irradiation is 100 ~ 300kv
It is preferable that the absorbed dose is 0.1 to 6 Mr.
ad is preferable, and 0.2 to 4.0 Mrad is particularly preferable. When the absorbed dose is less than 0.1 Mrad, the double bond in the electron beam-curable organic compound does not complete the reaction and remains in the cured resin layer, which may adversely affect photographic properties. . In general, when the absorbed dose is low, the degree of crosslinking of the cured resin tends to be low, which adversely affects the yellowing resistance of the obtained photographic paper. However, according to the present invention, the generation of fog is suppressed, so that the absorbed dose can be made higher than before, and therefore the yellowing resistance is improved. However, increasing the absorbed dose higher than necessary is not only wasteful in terms of energy, but also causes curling, and the coating film may be too hard, which is not preferable.

In forming the surface resin coating layer, the oxygen concentration in the atmosphere at the time of electron beam irradiation is preferably 500 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 organic compound composition may be insufficient. However, in the case of the drum cure, the electron beam curing coating liquid does not come into direct contact with air during electron beam irradiation, and thus it is not necessary to particularly reduce the oxygen concentration in the atmosphere during electron beam irradiation. In order to suppress the generation of ozone due to the above, or to cool a window that generates heat when an electron beam passes, it is a matter of course to use an inert gas.

In the present invention, examples of the synthetic resin having a film forming ability used for forming the backside resin coating layer include polyolefin resins used in the production of ordinary photographic supports, and the above-mentioned electron beam curable resins. Can be used. As the polyolefin resin, ethylene,
α-olefins, for example, homopolymers such as propylene, at least two types of copolymers of the olefins, and mixtures of at least two types of these various polymers. Particularly preferred polyolefin resins are low density polyethylene, high density polyethylene, linear low density polyethylene, and mixtures thereof. Although the molecular weight of the polyolefin resin used in the present invention is not particularly limited, it is usually preferable to use one having a molecular weight in the range of 20,000 to 200,000.

In the polyolefin resin, if necessary,
Small amounts of antioxidants and lubricants may be added. To form a backside resin coating layer with a polyolefin resin,
Normal melt extrusion coating can be used. Further, as the electron beam-curable organic compound composition for forming the backside resin coating layer, any of the compositions used for forming the above-mentioned frontside resin coating layer can be used. Further, the same method as the above-described front surface resin coating layer can be used for forming the back surface resin coating layer.

Although the weight of the resin coating layer is not particularly limited, it is generally used in the range of 10 to 40 g / m ² .

[0025]

EXAMPLES The structure and effects of the present invention will be further described below with reference to examples, but the present invention is not limited to these examples. Example 1 Canadian Standard Freeness (JIS P-8121-76)
Softwood bleached pulp (NBSP) 20% beaten to 250 ml,
The pulp slurry having a concentration of 1.0% was prepared by mixing 80% of the hardwood bleached sulfite pulp (LBKP) beaten to the freeness of 280 ml. The following papermaking additives were added to the pulp slurry in the following amounts based on the absolute pulp weight.

Cationized starch 2.0% Alkyl ketene dimer resin 0.4% Anionic polyacrylamide resin 0.1% Polyamide polyamine epichlor hydrin resin 0.7% Caustic soda Adjusted to pH 7.5 Fully disperse this pulp slurry After that, magnesium hydroxide was added to this so that the final content after papermaking was 5% by weight based on the total solid content, and dispersion treatment was performed for 5 minutes. After adjusting the solid content concentration of the obtained mixed slurry to 0.05% and dispersing again for 5 minutes, the pulp slurry was subjected to a basis weight of 1 using a hand mill for experiments (Toyo Seiki Co., Ltd.).
A sheet-like substrate having a density of 80 g / m ² and a density of 1.0 g / m ³ was prepared. Next, one surface (back surface) of the sheet-like substrate was subjected to extrusion coating with polyethylene to form a 30 g / m ² back surface resin coating layer.

Next, an electron beam-curable resin composition having the following composition was prepared. The above components were mixed and dispersed for 1 hour with a paint conditioner to prepare an electron beam-curable composition. This composition was applied to the opposite side (surface) of the above-mentioned sheet-like substrate using a wire bar so that the applied amount became 25 g / m ² , and the absorbed dose was applied to this applied layer at an acceleration voltage of 165 kv. An electron beam was irradiated to 3 Mrad, and this was cured to form a surface resin coating layer.

In order to test the antifogging effect of the obtained photographic paper support, the surface of the surface resin coating layer of the test support was stuck so as to be in close contact with the photographic emulsion surface of a commercially available color photographic paper. After the laminated body was left under the condition of 70 ° C. and 50% relative humidity for 3 days under total darkness, the color photographic paper was peeled off from the surface resin coating layer of the test support, and the photographic paper was removed. , Durst automatic developing machine (trademark: RCP20
, Manufactured by Durst Co., Ltd.).

The fog density of the developed photographic paper is
Macbeth densitometer (trademark: Model No.RD-914, Kollmorgen
 Corp.). Table 1 shows the test results
You. Example 2 The same operation as in Example 1 was performed. However, hydroxyl after papermaking
60% final content of magnesium oxide based on total weight of solids
And The results of the test performed in the same manner as in Example 1
It is shown in Table 1.Comparative Example 1 The same operation as in Example 1 was performed. However, in sheet-like substrates
No magnesium hydroxide was added. Same as Example 1
Table 1 shows the results of the tests performed as described above. Reference example 1 Polyethylene on both sides of paper base that does not contain magnesium compound
RC paper base material obtained by laminating ren resin
Was tested in the same manner as in Example 1. So
Table 1 shows the results.

[0030]

[Table 1]

[0031]

As is clear from Table 1, since the support for photographic printing paper of the present invention contains a magnesium compound in its sheet-like substrate, the surface resin coating layer is made of an electron beam-curable resin. Can be significantly reduced, that is, the occurrence of fogging in the development processing after storage for a long time. Further, the photographic printing paper support of the present invention can produce photographic printing paper having excellent yellowing resistance, and is extremely useful in practice.

──────────────────────────────────────────────────の Continuation of front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical display location D21H 27/36 D21H 3/78 G03C 1/76 502 5/00 Z (56) References JP 61-86747 (JP, A) JP-A-56-43637 (JP, A) JP-A-1-191139 (JP, A)

Claims (1)

(57) [Claims] 1. A sheet-like substrate containing natural pulp as a main component and containing a magnesium compound, and at least one unsaturated organic compound formed on the surface of the sheet-like substrate and curable by electron beam irradiation. A surface resin coating layer composed of an electron beam-curable resin of a composition containing a compound and an inorganic white pigment, and a back resin coating layer formed of a synthetic resin having a film-forming ability formed on the back surface of the sheet-like substrate. Support for photographic printing paper.