JPH04320257A - Base material for photographic printing paper - Google Patents

Abstract

PURPOSE:To provide a base material for photographic printing paper not or hardly causing fogging to the printing paper at the time of development. CONSTITUTION:A front side resin coating layer based on the mixture of an electron beam-curing resin with an inorg. white pigment is formed on one side of a paper base and a magnesium compd. is used as a part or the whole of the white pigment. A rear side resin coating layer based on a film forming synthetic resin is formed on the other side.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a support for photographic paper. More specifically, the present invention relates to a support material for photographic paper that does not or suppresses fogging on the photographic paper through development treatment.

0002

[Prior Art] Conventionally, so-called baryta paper has been used as a support for photographic paper, and this paper is coated with a white pigment such as barium sulfate on both sides of the paper to give it strong size and strength. It was manufactured by However, in recent years, instead of baryta paper, polyolefin-coated supports produced by coating both sides of a paper substrate with polyolefin resins have come to be widely used. Because the polyolefin coating layer on such supports is hydrophobic, processing liquids are less likely to penetrate into the support during development and fixing compared to baryta paper, and this significantly reduces washing and drying times. It has the advantage of being shortened, and since the treatment liquid does not permeate into the paper base, expansion and contraction of the support itself is suppressed and it has excellent dimensional stability.

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 hiding power or resolution, but such a pigment cannot be dispersed in a resin. In addition, volatile components contained in the pigment cause problems such as foaming during the melt extrusion process and cracking of the coating layer. For this reason, the pigment content in the coating layer cannot be increased to a level sufficient to improve the hiding power or resolution. Generally speaking, when titanium dioxide is used, it is difficult to incorporate it in a large amount of about 20% by weight or more. Therefore, the photographic paper obtained using such a support for photographic paper cannot be said to be fully satisfactory in terms of image sharpness.

[0004] In recent years, a so-called electron beam curable resin made of a resin composition that can be cured by electron beam irradiation is coated on a substrate, and then electron beam irradiation is performed to form an electron beam curable resin coating layer. Supports for photographic paper have been proposed (for example, Japanese Patent Publication No. 60-17104, Japanese Patent Publication No. 60-1
No. 7105, JP-A-57-49946, etc.). According to this method, there is no need to heat the resin composition to a high temperature when forming the coating layer, and the pigment content can be reduced to 20 to 80% by weight.
Therefore, the image sharpness of photographic paper obtained using such a support is significantly improved compared to polyolefin resin-coated photographic paper.

However, in photographic materials manufactured by coating a photosensitive layer on an electron beam-cured resin coating layer that has been cured by electron beam irradiation, photographic processing chemicals are adsorbed onto the resin coating layer during the development process. In addition, if the product is subjected to development after storage, the density of fog may increase to such an extent that it cannot be ignored as a product. It was found that the sensitivity may change.

Various improvement methods have been proposed to solve this problem. For example, Japanese Patent Publication No. 1-21495 discloses a method of providing a polyethylene coating layer on an electron beam curing resin coating layer as a means for suppressing sensitivity changes during storage. However, with this method, the fog reduction effect cannot be enhanced unless the polyethylene coating layer is made considerably thicker, which means that the greatest advantage of using electron beam curing technology, which is improved image sharpness, must be sacrificed. There are some problems such as:

[0007] Also, in Japanese Patent Application Laid-open No. 124336/1987,
Water-soluble polymers, polyolefins, ethylene polymers and copolymers, acrylate or methacrylate polymers and copolymers,
A method has been proposed for suppressing changes in photographic sensitivity by disposing a blocking layer formed from a dispersion of vinyl acetate copolymer or the like or a mixture of these polymer dispersions. However, the materials disclosed herein as materials for forming a shielding layer are still insufficient in terms of preventing fog during long-term storage.

[0008] In addition, Japanese Patent Application Laid-open Nos. 62-61049 and 61-141543 propose the use of specific polymers or monomers, but even with these methods, the problem still remains unsolved. No solution has been reached.

On the other hand, fog density and yellowing exhibit contradictory tendencies with respect to exposure dose. That is, when a high irradiation dose is used, yellowing caused by the developer can be suppressed to a low level, but fogging increases. On the other hand, in the case of a low irradiation dose, although the occurrence of fogging is suppressed to some extent, yellowing increases markedly and physical properties of the coating film such as adhesion and film strength also deteriorate. Therefore, in order to improve the yellowing resistance of the surface resin coating layer without deteriorating its physical properties, it is necessary to irradiate the surface resin with an appropriate dose of electron beam, which can prevent fogging that occurs depending on the irradiation dose. It has become extremely important to find a way to solve all of the above problems simultaneously and effectively.

0010

[Problems to be Solved by 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 increase fogging due to development processing even after storage. It is an object of the present invention to provide a support for photographic paper that simultaneously suppresses yellowing and is suitable for producing photographic paper having excellent photographic properties.

[0011]

[Means for Solving the Problems] The present invention includes a magnesium compound as a white pigment in an electron beam curable surface resin coating layer disposed on one surface of a paper substrate in a support for photographic paper. By doing so, we succeeded in solving the above problem.

That is, the support for photographic paper of the present invention comprises a paper base containing natural pulp as a main component, and at least one unsaturated organic material formed on one surface of the paper base that can be cured by electron beam irradiation. a surface resin coating layer containing as a main component an electron beam irradiation-cured resin of a composition containing a compound and an inorganic white pigment, and a film-forming synthetic resin as a main component formed on the opposite side of the paper substrate. and a back resin coating layer comprising a resin coating layer, and a part or all of the white pigment is a magnesium compound.

[0013]

[Operation] The structure and operation of the present invention will be explained below. In general, photographic prints containing a support obtained by applying a commercially available electron beam curable resin composition to a paper base made of natural pulp and irradiating it with electron beams to form an electron beam curable resin coating layer. Paper has the problem of significant fogging during storage. Although the cause of fog is not clear, it is thought that active radicals generated by electron beam irradiation remain in the support and react with the photographic emulsion layer formed thereon, causing fog. The above-mentioned active radicals are generated from the cellulose that constitutes the paper base and the electron beam curing resin, and it is thought that the active radicals generated from cellulose in particular have a large effect on fogging. As a result of various studies on this point, the present inventors found that, as mentioned above, a magnesium compound pigment was included as an inorganic white pigment in the electron beam-cured surface resin coating layer disposed on one surface of the paper substrate. They discovered that the above-mentioned fogging could be prevented by using the method, and completed the present invention.

That is, when an electron beam-curable resin coating layer containing a magnesium compound pigment is provided as an active radical diffusion-preventing intermediate layer on the surface of the paper base on which the photographic emulsion is coated, it is effective in preventing fogging. Not only in the original state, but also in the rolled up state after coating the photographic emulsion.
It has been discovered that the magnesium compound-containing resin coating layer also exhibits an antifogging effect on the photographic emulsion layer in contact with the back resin coating layer disposed on the opposite side of the paper substrate. Although the mechanism of such fog prevention is still not completely clear, the electron beam curing resin coating layer containing a magnesium compound prevents radicals generated from cellulose during electron beam irradiation from migrating to the photographic emulsion layer. It is thought that this is prevented or suppressed by some action, thereby making it possible to improve the fog prevention. Further, according to the present invention, it is not necessary to suppress the electron beam irradiation dose to an extremely low level in order to prevent fogging, and it is therefore effective in improving yellowing.

In the present invention, the magnesium compound pigment used in the electron beam-cured surface resin coating layer replaces part or all of the titanium dioxide used as a white pigment in ordinary photographic resin coating layers. used. The blending ratio of titanium dioxide and the magnesium compound is arbitrary, and the blending ratio of both pigments to the weight of the surface resin coating layer is also arbitrary, but in order to effectively prevent fogging, the amount of the magnesium compound pigment is 1 g/m2. It is preferable that it is above.

As the magnesium compound used in the present invention, those that can be used as white pigments, such as magnesium oxide, magnesium hydroxide, and magnesium sulfate, can be used.

The other white pigments used in the present invention are not particularly limited as long as they can be used in combination with the magnesium compound. For example, in addition to titanium dioxide (anatase type and rutile type), barium sulfate, calcium carbonate, aluminum oxide, zinc oxide, and the like can also be used.

The content of the total white pigment containing the magnesium compound is 20 to 20% based on the total solid weight of the surface resin coating layer.
Preferably it is 80% by weight. If the content is less than 20% by weight, the sharpness of the resulting photographic image on photographic paper may not be sufficient, and if it exceeds 80% by weight, the flexibility of the resulting resin coating layer will decrease and film cracking may occur. This may occur.

In order to disperse the white pigment in the above electron beam curable unsaturated organic compound, a three-roll mill, a two-roll mill, a two-roll mill,
Cowles dissolvers, homomixers, sand grinders, ultrasonic dispersers, and the like can be used.

Examples of methods for applying the resin composition to the surface of the paper substrate include bar coating, air doctor coating, blade coating, squeeze coating, air knife coating, reverse roll coating, and transfer coating. Either of these may be used. Further, for this purpose, a fountain coater or a slit die coater method can also be used.

[0021] Furthermore, in order to improve the surface smoothness and high gloss of the obtained support, a casting method is advantageously used for coating the resin composition. The weight of the surface resin coating layer is preferably 2 to 60 g/m2 (solid content).

As the electron beam accelerator used for electron beam irradiation, a curtain beam type accelerator that is relatively inexpensive and can provide a large output is effectively used. The acceleration voltage during electron beam irradiation is preferably 100 to 300 kV, and the absorbed dose is preferably 0.1 to 6 Mrad, particularly preferably 0.2 to 4.0 Mrad. When the absorbed dose is 0.1 Mrad or less, the double bonds in the electron beam curable resin remain in the cured film without completing the reaction, which may adversely affect photographic properties.

Generally, when the absorbed dose is low, the crosslinking of the coating film tends to be low, which has a negative effect on the yellowing resistance, but in the present invention, since fog generation can be suppressed, the absorbed dose is reduced. can be increased, thus improving yellowing resistance. However, increasing the absorbed dose more than necessary is not only wasteful in terms of energy, but also causes curling and may make the coating film too hard, which is not preferable.

The oxygen concentration in the electron beam irradiation atmosphere is 500
It is preferably less than ppm. Oxygen concentration is 500p
pm, oxygen acts as a retardant for the polymerization reaction,
The curing of the resin composition may become insufficient. However, in the case of drum curing, the electron beam curing paint liquid does not come into direct contact with air during electron beam irradiation, and therefore there is no need to particularly reduce the oxygen concentration in the atmosphere during electron beam irradiation. In order to suppress ozone generation caused by
Alternatively, it is of course possible to use an inert gas for purposes such as cooling a window that generates heat when an electron beam passes through it.

The paper substrate used in the present invention usually has a weight of 50 to 300 g/m 2 and preferably has a smooth surface. Any paper substrate that is generally used as a support for photographic paper can be used. As the natural pulp forming the paper substrate, those whose main components are generally softwood pulp, hardwood pulp, mixed softwood and hardwood pulp, etc. are widely used. The paper base may also contain additives commonly used in paper manufacturing, such as sizing agents, fixing agents, paper strength enhancers, fillers, antistatic agents, pH adjusters, pigments, and dyes. Furthermore, a surface sizing agent, a surface paper strength agent, an antistatic agent, etc. may be appropriately applied to the surface.

In the present invention, the surface resin coating layer formed on one surface of the paper substrate is made of a mixture of an unsaturated organic compound that can be cured by an electron beam, a white pigment, and other additives as necessary. The composition includes an electron beam-cured resin.

The unsaturated organic compound curable by electron beam used in the present invention can be selected from, for example, the following compounds. (1) Acrylate compounds of aliphatic, alicyclic, and araliphatic mono- to hexavalent alcohols and polyalkylene glycols. (2) Acrylate compounds obtained by adding alkylene oxide to an aliphatic, alicyclic, or araliphatic mono- to hexavalent alcohol. (3) Polyacryloyl alkyl phosphate esters. (4) A reaction product of carboxylic acid, polyol, and acrylic acid. (5) Reaction product of isocyanate, polyol, and acrylic acid. (6) A reaction product between an epoxy compound and acrylic acid. (7) A reaction product of an epoxy compound, a polyol, and acrylic acid. etc. can be mentioned.

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 Bivalic acid ester neopentyl glycol diacrylate, nonylphenoxy polyethylene glycol acrylate, ethylene oxide modified phenoxylated phosphoric acid acrylate, ethylene oxide modified phthalic acid acrylate, polybutadiene acrylate, caprolactane modified tetrahydrofurfuryl acrylate, tris(acryloxyethyl) isocyanurate , trimethylolpropane triacrylate, pentaerythritol triacrylate, dipentaerythritol hexaacrylate, polyethylene glycol diacrylate, 1,4-butadiene diol diacrylate, neopentyl glycol diacrylate, and neopentyl glycol modified trimethylol propane diacrylate. I can list them.

The film-forming synthetic resin used to form the back resin coating layer of the present invention includes polyolefin resins used in the production of conventional photographic paper supports, the above-mentioned electron beam curing resins, etc. can be used.

The polyolefin resin for forming the back resin coating layer includes homopolymers of ethylene, α-olefins such as propylene, copolymers of at least two of the above-mentioned olefins, and various polymers of these. It is possible to choose from a mixture of at least two types. Particularly preferred polyolefin resins are low density polyethylene, high density polyethylene, linear low density polyethylene, and mixtures thereof. There is no particular restriction on the molecular weight of polyolefin resin, but it is usually between 20,000 and 20
A range of 0,000 is used. If necessary, a small amount of antioxidant and lubricant may be added to the polyolefin resin. To form the back resin coating layer using polyolefin resin, normal melt extrusion coating can be used.

Further, as the electron beam curable unsaturated organic compound for forming the back resin coating layer, all the compounds used for forming the front resin coating layer described above can be used. Furthermore, the method for forming the back resin coating layer is the same as that for the front resin coating layer described above.

[0032] The weight of the back resin coating layer is not particularly limited, but it is generally preferably in the range of 10 to 40 g/m2.

[0033]

[Examples] The structure and effects of the present invention will be further explained with reference to the following examples, but the present invention is not limited to these embodiments.

Example 1 One side of a paper substrate containing natural pulp as a main component with a basis weight of 175 g/m 2 was coated with polyethylene by extrusion, and a backlaminate layer of 30 g/m 2 was provided to form a sheet-like substrate.

Next, an electron beam curable organic compound-white pigment composition having the following composition was prepared. Mix the above ingredients with paint conditioner.
An electron beam curable composition was prepared by mixing and dispersing for a period of time.

This composition was applied onto the surface of the paper substrate on the non-backlaminated side of the sheet-like substrate described above using a wire bar so that the coating amount after curing was 20 g/m2. The coating layer was irradiated with an electron beam under the conditions of acceleration voltage: 165 Kv and absorbed dose: 2 Mrad, and this coating layer was cured to form a surface resin coating layer, and the surface of this surface resin coating layer was bonded to the face surface of the support. did.

In order to test the antifogging effect of the obtained support for photographic paper, the surface resin coating layer of the test support was superimposed closely on the emulsion surface of a commercially available color photographic paper, and the entire surface was Temperature 70℃, relative humidity 50% in darkness
After being left for 3 days under these conditions, the color photographic paper was peeled off from the surface resin coating layer of the test support, and this photographic paper was developed using a Durst automatic processor (trademark: RCP20, manufactured by Durst Corporation). provided. The fog density of the developed photographic paper was measured using a Macbeth densitometer (trademark: Model No.
RD-914, Kollmorgen Corp. (manufactured by). The test results are shown in Table 1.

Example 2 The same operation as in Example 1 was carried out. However, the composition of the electron beam curable composition applied onto the paper substrate was as follows. Table 1 shows the results of a test conducted in the same manner as in Example 1.

Example 3 The same operation as in Example 1 was carried out. However, the composition of the electron beam curable composition applied onto the paper substrate was as follows. The test results are shown in Table 1.

Example 4 The same operation as in Example 2 was carried out. However, magnesium hydroxide was used instead of magnesium oxide. Example 1
Table 1 shows the results of a test conducted in the same manner as above.

Example 5 The same operation as in Example 1 was carried out. However, in order to test the antifogging effect, the side of the commercially available color photographic paper that was brought into close contact with the emulsion side was the side opposite to the electron beam curable resin coating layer, which was the side to which polyethylene backlamina was applied. Table 1 shows the results of the fog density of the color photographic paper that was peeled from the backlaminated surface of the test support and developed.

Comparative Example 1 The same operation as in Example 1 was carried out. However, the pigment contained in the electron beam curable composition applied onto the paper substrate was only titanium dioxide. The composition was as follows. Table 1 shows the results of a test conducted in the same manner as in Example 1.

Example 6 The same operation as in Example 1 was carried out. However, the composition of the electron beam curable composition applied onto the paper substrate was as follows. Table 1 shows the results of a test conducted in the same manner as in Example 1.

Comparative Example 2 The same operation as in Example 2 was carried out. However, light calcium carbonate (trademark: Brilliant-15, manufactured by Shiraishi Kogyo) was used instead of magnesium oxide. Table 1 shows the results of a test conducted in the same manner as in Example 1.

Reference Example 1 A photographic RC paper base material obtained by laminating both sides of a base paper with polyethylene resin was tested in the same manner as in Example 1. The results are shown in Table 1.

[Table 1]

[0046]

Effects of the Invention The support for photographic paper of the present invention can significantly reduce the common drawback when an electron beam curing resin layer is provided, that is, the occurrence of fog due to development processing after storage. , and is extremely effective in practice.

Claims (1)

[Claims] 1. A composition comprising a paper substrate containing natural pulp as a main component, at least one unsaturated organic compound formed on one surface thereof and curable by electron beam irradiation, and an inorganic white pigment. and a back resin coating layer formed on the opposite side of the paper substrate and containing a film-forming synthetic resin as a main component, A support for photographic paper, characterized in that part or all of the white pigment is a magnesium compound.