JPH05158186A - Supporting body for photographic paper - Google Patents

Abstract

PURPOSE:To show excellent hiding power and resolving power and also to eliminate a fault based on the undispersed material of pigment by incorporating the specified amount of zinc oxide pigment into inorganic white pigment contained in the surface layer coated with resin which is formed on the surface of the paper base body of a supporting body. CONSTITUTION:A supporting body for photographic paper incorporates a paper base body containing natural pulp as a main component, a surface layer coated with resin and the rear layer coated with resin respectively described below. The surface layer coated with resin consists of the hardened material of electron beam hardenable resin composition containing both an unsaturated organic compound capable of being hardened by irradiation of electron beams and inorganic white pigment as a main component. The rear layer coated with resin is formed on the read of the paper base body and also contains the film formable synthetic resin as a main component. Inorganic white pigment contains zinc oxide 5--75% of the whole amount thereof. Thereby the content of inorganic white pigment in the surface layer coated with resin is increased without violently raising viscosity of the composition of the organic compound for forming the surface layer coated with resin. Moreover, it is prevented that a fault is caused on the surface layer coated with resin by undispersed pigment.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a photographic paper support. More specifically, the present invention relates to an improved photographic paper support material having a smooth surface free of foreign matter protrusions and exhibiting high resolution.

[0002]

Conventionally, so-called baryta paper has been used as a support for photographic printing paper. This is produced by applying a white pigment such as barium sulfate to both sides of paper which is imparted with strong size and high strength. However, in recent years, instead of this, a polyolefin resin-coated support produced by melt-coating a polyolefin resin on both sides of a substrate made of paper, so-called RC paper, has been widely used. Since such a support has a hydrophobic polyolefin resin, compared to baryta paper,
The treatment liquid hardly penetrates into the support during the development and fixing treatment, which has the advantage that the washing time and the drying time are greatly shortened, and since the treatment liquid does not penetrate into the paper substrate,
It has advantages such as expansion and contraction of the support itself and excellent dimensional stability.

An inorganic white pigment such as titanium dioxide is mixed in the polyolefin coating layer of such a support for the purpose of improving the hiding power or the resolution. However, such a pigment is poor in dispersibility in the resin, and when it is coated by the melt extrusion method, there is a problem that foaming occurs due to the volatile component contained in the pigment and a film crack occurs in the coating layer. is there. Therefore, the pigment content in the coating layer,
It cannot be raised to a sufficient level to improve the hiding power or the resolution. Generally speaking, when titanium dioxide is used, it is difficult to mix it in an amount of about 20% by weight or more. Therefore, the photographic printing paper obtained by using such a photographic printing paper support has not been sufficiently satisfactory in image sharpness.

In recent years, an organic compound which is cured by electron beam irradiation, that is, a so-called electron beam curable resin composition is applied to a support, and an electron beam curable resin coating layer which is cured by applying electron beam irradiation is provided. Supports for photographic printing paper have been proposed (for example, Japanese Examined Patent Publication No. 60-17104 and Japanese Examined Patent Publication No. 60-17105).
No., JP-A-57-49946). According to this method, since it is not necessary to heat the organic compound composition to a high temperature when forming the coating layer, the pigment content can be increased to 20 to 80% by weight, and thus such a support can be prepared. The image sharpness of the photographic printing paper obtained by using the photographic printing paper is remarkably improved as compared with the conventional photographic printing paper coated with a polyolefin resin composition.

However, when an inorganic white pigment such as titanium dioxide is added to the electron beam-curable organic compound composition, the viscosity of the resin composition sharply increases as the amount of the compound increases, and it becomes difficult to disperse the pigment. As a result, the amount of undispersed material may increase to cause defects in the coating layer, and further, depending on the type of electron beam-curable unsaturated organic compound used, dispersion of the pigment may not be possible. ..

[0006]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems of the prior art, and an inorganic white color in a surface resin coating layer is obtained without rapidly increasing the viscosity of an organic compound composition for forming a surface resin coating layer. An object of the present invention is to provide a support for photographic printing paper, which has an increased hiding power and a high resolution without increasing defects in the surface resin coating layer due to an increase in the pigment content and the undispersed pigment.

[0007]

According to the present invention, a specific amount of zinc oxide pigment is contained in an inorganic white pigment in a surface resin coating layer formed on the surface of a paper substrate of a photographic printing paper support. As a result, the above problems have been successfully solved.

That is, the support for photographic printing paper of the present invention comprises a paper substrate containing natural pulp as a main component, and at least one unsaturated organic compound formed on the surface of the substrate and curable by electron beam irradiation. And a surface resin coating layer composed of an electron beam cured product of an electron beam curable resin composition containing an inorganic white pigment as a main component, and a film-forming synthetic resin mainly formed on the back surface of the paper substrate. And a backside resin coating layer included as a component, wherein the inorganic white pigment contains zinc oxide in an amount of 5% to 75% based on the total weight of the inorganic white pigment.

[0009]

The structure and operation of the present invention will be described below.
In general, the resin composition constituting the surface resin coating layer of the support for photographic printing paper contains an inorganic white pigment for the purpose of improving the hiding power / resolution. Titanium dioxide is widely used as the pigment, and from the viewpoint of effect, its content is preferably 20% or more of the total weight of the resin composition. However, in the case of containing titanium dioxide, the resin coating layer obtained by increasing the content thereof and rapidly increasing the viscosity of the resin composition and gradually making it difficult to disperse, and increasing the content rate of the undispersed substance In some cases, defects may occur in the resin, and it becomes impossible to disperse the pigment depending on the type of electron beam-curable organic compound used. Therefore, increase the blending amount to the level desired to enhance the hiding power and resolution. You may not be able to

As a result of diligent study on this problem, the present inventors have found that by replacing zinc oxide with a part of the white pigment dispersed in the electron beam curable resin, the viscosity of the electron beam curable organic compound composition can be improved. The inventors have completed the present invention by discovering that the rise can be suppressed and the particles can be dispersed evenly very easily.

That is, in the present invention, zinc oxide contained in the electron beam curable resin composition is a part of titanium dioxide contained as a white inorganic pigment in the surface resin coating layer of a usual photographic paper support. Used in place of The compounding weight ratio of titanium dioxide and zinc oxide is 95: 5-2.
It is optional between 5:75, but 80:20 to 50:50
It is particularly advantageous to be in the range. When the blending weight ratio of zinc oxide to the total weight of the pigment is less than 5%, it becomes difficult to reduce the viscosity of the obtained composition, and the dispersibility cannot be improved. Also it is 75%
If it exceeds, the phenomenon such that the concealing property of the obtained surface resin coating layer is deteriorated or the resolution when used as photographic paper cannot be improved occurs.

The white inorganic pigment contained in the surface resin coating layer of the present invention generally contains titanium dioxide as described above in addition to zinc oxide, but the type of titanium dioxide is not particularly limited, and zinc oxide is not limited. Any material can be used as long as it can be mixed with. In addition to titanium dioxide (anatase type and rutile type), any of barium sulfate, calcium carbonate, aluminum oxide, magnesium oxide and the like can be used.

The content of the total white inorganic pigment containing zinc oxide is 20 to 80% by weight of the total solid content of the surface resin coating layer.
Is preferred. If the content is less than 20% by weight, the sharpness of the photographic image on the photographic printing paper obtained may not be sufficient, and if it exceeds 80% by weight, the flexibility of the resin coating layer obtained may decrease. ..

To disperse the inorganic white pigment in the electron beam-curable unsaturated organic compound 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 or the like can be used.

Examples of the method for applying the organic compound-pigment 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. Any of the coating methods may be used. For this purpose, a fountain coater or slit die coater system can be used.

A casting method is advantageously used for coating the coating composition in order to enhance the surface smoothness of the resulting support and to obtain high gloss.

The weight of the electron beam curable resin coating layer is 2 to 60.
It is preferably g / m ² (solid content).

As an electron beam accelerator used for electron beam irradiation, a curtain beam system, which is relatively inexpensive and has a large output, is effectively used. The accelerating voltage at the time of electron beam irradiation is preferably 100 to 300 kv, and the absorbed dose is preferably 0.1 to 6 Mrad, and 0.1.
2-4.0 Mrad is particularly preferred. Absorbed dose is 0.1Mrad
In the following cases, the double bond in the electron beam curable resin does not complete the reaction and remains in the cured film, which may adversely affect the photographic characteristics. Increasing the absorbed dose above 6 Mrad is not preferable because it is not only wasteful in terms of energy but also causes curling and the coating film may become too hard.

The oxygen concentration in the atmosphere during electron beam irradiation is preferably 500 ppm or less. Oxygen concentration is 5
If it exceeds 00 ppm, oxygen acts as a retarder for the polymerization reaction, and the curing of the electron beam curable organic compound may be insufficient. Formed using an inert gas for the purpose of lowering the oxygen concentration, suppressing the generation of ozone due to electron beam irradiation, or cooling the window that generates heat when the electron beam passes. Of course, there is no problem with electron beam irradiation in the atmosphere.

The paper substrate used in the present invention is usually 50-
It preferably has a weight of 300 g / m ² and has a smooth surface. As the paper substrate, any of those generally used for a photographic printing paper support can be used. As the natural pulp forming the paper substrate, generally, those containing, as a main component, softwood pulp, hardwood pulp, mixed softwood hardwood pulp, etc. are widely used. Bleached pulp such as kraft pulp, sulfite pulp and soda pulp can also be used. Further, it may be synthetic pulp or pulp containing synthetic fibers.

Further, the paper substrate may contain additives such as a sizing agent, a fixing agent, a paper strength enhancer, a filler, an antistatic agent, a pH adjusting agent, a pigment and a dye which are generally used in papermaking. Good. Further, it may be a paper substrate on the surface of which a surface sizing agent, a surface paper strength agent, an antistatic agent, etc. are appropriately applied.

The surface resin coating layer formed on the surface of the paper substrate of the present invention comprises a mixture of at least one unsaturated organic compound curable by electron beam irradiation and an inorganic white pigment, and , An electron beam curable organic compound composition containing other additives as required. The electron beam curable unsaturated organic compound used in the present invention can be selected from the following compounds.

(1) Aliphatic, alicyclic, and araliphatic acrylate compounds of 1- to 6-hydric alcohols and polyalkylene glycols. (2) Aliphatic, alicyclic and araliphatic acrylate compounds obtained by adding an alkylene oxide to a monohydric 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.

Specifically, as the electron beam-curable unsaturated organic compound, 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 phenoxyphosphoric 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, neopentyl glycol diacrylate, and neopentyl glycol-modified trimethylol propane diacrylate, and the like.

In the present invention, the film-forming synthetic resin used to form the backside resin coating layer is a polyolefin resin used in the production of conventional photographic paper supports, or the electron beam curable resin described above. A resin composition or the like can be used. As the polyolefin resin for forming the backside resin coating layer, homopolymers of ethylene, α-olefins such as propylene, at least two copolymers of the above olefins, and at least two of these various polymers You can choose from a mixture of. 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 usually 20,000-
Those in the range of 200,000 are advantageously used.

The polyolefin resin, if necessary,
A small amount of antioxidant and a lubricant can be added and used. In order to form the backside resin coating layer using a polyolefin resin, a usual melt extrusion method can be used. When the electron beam curable resin composition is used to form the backside resin coating layer, all the compounds used for forming the above-mentioned frontside resin coating layer can be used.
Further, in this case, the method for forming the back surface resin coating layer can be performed in the same manner as in the case of the front surface resin coating layer. The weight of the backside resin coating layer is not particularly limited, but generally 10 to 40
It is preferably in the range of g / m ² .

[0027]

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

Example 1 A high- quality paper (150 g / m ² square meter, 180 μm thick) was subjected to a surface activation treatment by corona discharge, and then a polyethylene resin (HDPE) melt extrusion coating was applied on the back surface of the high-quality paper. Was applied to form a backside resin coating layer having a coating amount of 30 g / m ² .

Separately, an electron beam curable resin composition having the following composition was prepared. Component content ―――――――――――――――――――――― Urethane acrylate oligomer 36.0 parts by weight (Trademark: BS-550B, manufactured by Arakawa Chemical Industries) Bifunctional acrylate monomer 24.0 parts by weight Part (Trademark: M-220, manufactured by Toagosei) Titanium dioxide 10.0 parts by weight (Trademark: A-220, manufactured by Ishihara Sangyo) Zinc oxide 30.0 parts by weight (Trademark: No. 1 Zinc Hua, Mitsui Metal)

The above composition was mixed and dispersed for 1 hour using a paint conditioner to prepare an electron beam curable resin composition. The viscosity of this composition was measured using a vibrating viscometer (CJV-20
01, manufactured by System Development Co., Ltd.). The results are shown in Table 1.

The above composition was applied onto the surface of the paper substrate using a wire bar so that the coating amount after curing was 20 g / m ² , and the accelerating voltage: 165 Kv.
Then, an electron beam was irradiated under the condition of absorbed dose: 2 Mrad, and this coating liquid layer was cured to form a surface resin coating layer.

The optical transmission density of the support for photographic printing paper thus obtained was measured. The higher the transmission density, the better the hiding power. The measurement results are shown in Table 1. Further, the number of foreign matter-like protrusions due to the undispersed inorganic white pigment per 10 cm ² of the surface of the obtained photographic printing paper support was measured. The result is 0 for the number of abnormal protrusions, ○, 1 to 5 for Δ, 6
Table 1 shows the number of pieces or more as x.

Further, on the obtained support for photographic printing paper,
A black-and-white photographic light-sensitive material (trademark: Art Emulsion (manufactured by Fuji Photo Film)) was applied using a # 60 wire bar and dried to complete black-and-white photographic paper. Exposure was performed using an MTF exposure device, and the resolution was measured at a spatial frequency of 5 lines / mm. The results are shown in Table 1.

Example 2 The same operation as in Example 1 was performed. However, the composition of the electron beam curable resin composition applied on the paper substrate was as follows. Component content ―――――――――――――――――――――― Urethane acrylate oligomer 36.0 parts by weight (Trademark: BS-550B, manufactured by Arakawa Chemical Industries) Bifunctional acrylate monomer 24.0 parts by weight Parts (Trademark: M-220, manufactured by Toagosei) Titanium dioxide 20.0 parts by weight (Trademark: A-220, manufactured by Ishihara Sangyo) Zinc oxide 20.0 parts by weight (Trademark: No. 1 Zinc Hua, manufactured by Mitsui Kinzoku) Same as Example 1 Table 1 shows the result of the test performed.

Example 3 The same operation as in Example 1 was performed. However, the composition of the electron beam curable composition applied on the paper substrate was as follows. Component content ―――――――――――――――――――――― Urethane acrylate oligomer 36.0 parts by weight (Trademark: BS-550B, manufactured by Arakawa Chemical Industries) Bifunctional acrylate monomer 24.0 parts by weight Parts (Trademark: M-220, manufactured by Toagosei) Titanium dioxide 36.0 parts by weight (Trademark: A-220, manufactured by Ishihara Sangyo) Zinc oxide 4.0 parts by weight (Trademark: No. 1 Zinc Hua, Mitsui Kinzoku) Same as Example 1 Table 1 shows the result of the test performed.

Comparative Example 1 The same operation as in Example 1 was performed. However, the pigment contained in the electron beam curable resin composition applied on the paper substrate was titanium dioxide only. Its composition was as follows. Component content ―――――――――――――――――――――― Urethane acrylate oligomer 36.0 parts by weight (Trademark: BS-550B, manufactured by Arakawa Chemical Industries) Bifunctional acrylate monomer 24.0 parts by weight Parts (Trademark: M-220, manufactured by Toagosei) Titanium dioxide 40.0 parts by weight (Trademark: A-220, manufactured by Ishihara Sangyo) The results of the tests conducted in the same manner as in Example 1 are shown in Table 1.

Comparative Example 2 The same operation as in Example 1 was performed. However, a resin composition having the following composition was prepared by using only zinc oxide as the pigment contained in the electron beam curable composition coated on the paper substrate. Component content ―――――――――――――――――――――― Urethane acrylate oligomer 36.0 parts by weight (Trademark: BS-550B, manufactured by Arakawa Chemical Industries) Bifunctional acrylate monomer 24.0 parts by weight Parts (Trademark: M-220, manufactured by Toagosei) Zinc oxide 40.0 parts by weight (Trademark: No. 1 Zinhua, manufactured by Mitsui Kinzoku Co., Ltd.) Table 1 shows the results of the test conducted in the same manner as in Example 1.

Reference Example 1 A polyolefin resin composition having the following composition was coated on the surface of a high-quality paper having a backside resin coating layer by the same method as in Example 1 by a usual melt extrusion coating method to prepare a double-sided polyolefin. A resin coated support was prepared. Component content ―――――――――――――――――――――― High-pressure low-density polyethylene 85.0 parts by weight (Trademark: LK-50, Mitsubishi Yuka) Titanium dioxide 15.0 parts by weight Part (Trademark: A-220, manufactured by Ishihara Sangyo) Table 1 shows the results of the test conducted in the same manner as in Example 1.

[0039]

[Table 1]

The supports for photographic printing papers of Examples 1 to 3 of the present invention are the conventional supports for photographic printing papers of Reference Example 1 in which a resin composition in which titanium dioxide is dispersed in a polyolefin resin is applied by a melt extrusion method. Compared to the body, it was superior in transmission density (hiding power) and resolution. Further, as compared with the case where only titanium dioxide was blended as an inorganic white pigment in the electron beam curable resin (Comparative Example 1), the increase in paint viscosity due to the blending amount of titanium dioxide was suppressed, and no foreign matter protrusion due to undispersed matter was generated. Moreover, it was possible to secure high hiding power and resolution. Further, the hiding power and the resolution were superior to those when only zinc oxide was used as the inorganic white pigment (Comparative Example 2).

[0041]

INDUSTRIAL APPLICABILITY The support for photographic printing paper of the present invention can increase the amount of the inorganic white pigment compounded in the electron beam curable resin composition without rapidly increasing the viscosity of the resin composition. In addition, it is possible to prevent the generation of defects due to undispersed pigments, exhibit excellent hiding power and resolution, and are extremely useful in practice.

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[Procedure amendment]

[Submission date] February 6, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be amended] Detailed explanation of the invention

[Correction method] Change

[Correction content]

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a photographic paper support. More specifically, the present invention relates to an improved photographic paper support material having a smooth surface free of foreign matter protrusions and exhibiting high resolution.

[0002]

Conventionally, so-called baryta paper has been used as a support for photographic printing paper. This is produced by applying a white pigment such as barium sulfate to both sides of paper which is imparted with strong size and high strength. However, in recent years, instead of this, a polyolefin resin-coated support produced by melt-coating a polyolefin resin on both sides of a paper base, so-called RC paper, has come into wide use. Since such a support has a hydrophobic polyolefin resin, compared to baryta paper,
The treatment liquid hardly penetrates into the support during the development and fixing treatment, which has the advantage that the washing time and the drying time are greatly shortened, and since the treatment liquid does not penetrate into the paper substrate,
It has advantages such as expansion and contraction of the support itself and excellent dimensional stability.

An inorganic white pigment such as titanium dioxide is mixed in the polyolefin coating layer of such a support for the purpose of improving the hiding power or the resolution. However, such a pigment is poor in dispersibility in the resin, and when it is coated by the melt extrusion method, there is a problem that foaming occurs due to the volatile component contained in the pigment and a film crack occurs in the coating layer. is there. Therefore, the pigment content in the coating layer,
It cannot be raised to a sufficient level to improve the hiding power or the resolution. Generally speaking, when titanium dioxide is used, it is difficult to mix it in an amount of about 20% by weight or more. Therefore, the photographic printing paper obtained by using such a photographic printing paper support has not been sufficiently satisfactory in image sharpness.

In recent years, an organic compound which is cured by electron beam irradiation, that is, a so-called electron beam curable resin composition is applied to a support, and an electron beam curable resin coating layer which is cured by applying electron beam irradiation is provided. Supports for photographic printing paper have been proposed (for example, Japanese Examined Patent Publication No. 60-17104 and Japanese Examined Patent Publication No. 60-17105).
No., JP-A-57-49946). According to this method, since it is not necessary to heat the organic compound composition to a high temperature when forming the coating layer, the pigment content can be increased to 20 to 80% by weight, and thus such a support can be prepared. The image sharpness of the photographic printing paper obtained by using the photographic printing paper is remarkably improved as compared with the conventional photographic printing paper coated with a polyolefin resin composition.

However, when an inorganic white pigment such as titanium dioxide is added to the electron beam-curable organic compound composition, the viscosity of the resin composition sharply increases as the amount of the compound increases, and it becomes difficult to disperse the pigment. As a result, the amount of undispersed material may increase to cause defects in the coating layer, and further, depending on the type of electron beam-curable unsaturated organic compound used, dispersion of the pigment may not be possible. ..

[0006]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems of the prior art, and an inorganic white color in a surface resin coating layer is obtained without rapidly increasing the viscosity of an organic compound composition for forming a surface resin coating layer. An object of the present invention is to provide a support for photographic printing paper, which has an increased hiding power and a high resolution without increasing defects in the surface resin coating layer due to an increase in the pigment content and the undispersed pigment.

[0007]

According to the present invention, a specific amount of zinc oxide pigment is contained in an inorganic white pigment in a surface resin coating layer formed on the surface of a paper substrate of a photographic printing paper support. As a result, the above problems have been successfully solved.

That is, the support for photographic printing paper of the present invention comprises a paper substrate containing natural pulp as a main component, and at least one unsaturated organic compound formed on the surface of the substrate and curable by electron beam irradiation. And a surface resin coating layer composed of an electron beam cured product of an electron beam curable resin composition containing an inorganic white pigment as a main component, and a film-forming synthetic resin mainly formed on the back surface of the paper substrate. And a backside resin coating layer included as a component, wherein the inorganic white pigment contains zinc oxide in an amount of 5% to 75% based on the total weight of the inorganic white pigment.

[0009]

The structure and operation of the present invention will be described below.
In general, the resin composition constituting the surface resin coating layer of the support for photographic printing paper contains an inorganic white pigment for the purpose of improving the hiding power / resolution. Titanium dioxide is widely used as the pigment, and from the viewpoint of effect, its content is preferably 20% or more of the total weight of the resin composition. However, in the case of containing titanium dioxide, the resin coating layer obtained by increasing the content thereof and rapidly increasing the viscosity of the resin composition and gradually making it difficult to disperse, and increasing the content rate of the undispersed substance In some cases, defects may occur in the resin, and it becomes impossible to disperse the pigment depending on the type of electron beam-curable organic compound used. Therefore, increase the blending amount to the level desired to enhance the hiding power and resolution. You may not be able to

As a result of diligent study on this problem, the present inventors have found that by replacing zinc oxide with a part of the white pigment dispersed in the electron beam curable resin, the viscosity of the electron beam curable organic compound composition can be improved. The inventors have completed the present invention by discovering that the rise can be suppressed and the particles can be dispersed evenly very easily.

That is, in the present invention, zinc oxide contained in the electron beam curable resin composition is a part of titanium dioxide contained as a white inorganic pigment in the surface resin coating layer of a usual photographic paper support. Used in place of The compounding weight ratio of titanium dioxide and zinc oxide is 95: 5-2.
It is optional between 5:75, but 80:20 to 50:50
It is particularly advantageous to be in the range. When the blending weight ratio of zinc oxide to the total weight of the pigment is less than 5%, it becomes difficult to reduce the viscosity of the obtained composition, and the dispersibility cannot be improved. Also it is 75%
If it exceeds, the phenomenon such that the concealing property of the obtained surface resin coating layer is deteriorated or the resolution when used as photographic paper cannot be improved occurs.

The white inorganic pigment contained in the surface resin coating layer of the present invention generally contains titanium dioxide as described above in addition to zinc oxide, but the type of titanium dioxide is not particularly limited, and zinc oxide is not limited. Any material can be used as long as it can be mixed with. In addition to titanium dioxide (anatase type and rutile type), any of barium sulfate, calcium carbonate, aluminum oxide, magnesium oxide and the like can be used.

The content of the total white inorganic pigment containing zinc oxide is 20 to 80% by weight of the total solid content of the surface resin coating layer.
Is preferred. If the content is less than 20% by weight, the sharpness of the obtained photographic image on the photographic printing paper may not be sufficient, and if it exceeds 80% by weight, the flexibility of the obtained resin coating layer may decrease. ..

To disperse the inorganic white pigment in the electron beam-curable unsaturated organic compound 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 or the like can be used.

Examples of the method for applying the organic compound-pigment 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. Any of the coating methods may be used. For this purpose, a fountain coater or slit die coater system can be used.

A casting method is advantageously used for coating the coating composition in order to enhance the surface smoothness of the resulting support and to obtain high gloss.

The weight of the electron beam curable resin coating layer is 2 to 60.
It is preferably g / m ² (solid content).

As an electron beam accelerator used for electron beam irradiation, a curtain beam system, which is relatively inexpensive and has a large output, is effectively used. The accelerating voltage at the time of electron beam irradiation is preferably 100 to 300 kv, and the absorbed dose is preferably 0.1 to 6 Mrad, and 0.1.
2-4.0 Mrad is particularly preferred. Absorbed dose is 0.1Mrad
In the following cases, the double bond in the electron beam curable resin does not complete the reaction and remains in the cured film, which may adversely affect the photographic characteristics. Increasing the absorbed dose above 6 Mrad is not preferable because it is not only wasteful in terms of energy but also causes curling and the coating film may become too hard.

The oxygen concentration in the atmosphere during electron beam irradiation is preferably 500 ppm or less. Oxygen concentration is 5
If it exceeds 00 ppm, oxygen acts as a retarder for the polymerization reaction, and the curing of the electron beam curable organic compound may be insufficient. Formed using an inert gas for the purpose of lowering the oxygen concentration, suppressing the generation of ozone due to electron beam irradiation, or cooling the window that generates heat when the electron beam passes. Of course, there is no problem with electron beam irradiation in the atmosphere.

The paper substrate used in the present invention is usually 50-
It preferably has a weight of 300 g / m ² and has a smooth surface. As the paper substrate, any of those generally used for a photographic printing paper support can be used. As the natural pulp forming the paper substrate, generally, those containing, as a main component, softwood pulp, hardwood pulp, mixed softwood hardwood pulp, etc. are widely used. Bleached pulp such as kraft pulp, sulfite pulp and soda pulp can also be used. Further, it may be synthetic pulp or pulp containing synthetic fibers.

Further, the paper substrate may contain additives such as a sizing agent, a fixing agent, a paper strength enhancer, a filler, an antistatic agent, a pH adjusting agent, a pigment and a dye which are generally used in papermaking. Good. Further, it may be a paper substrate on the surface of which a surface sizing agent, a surface paper strength agent, an antistatic agent, etc. are appropriately applied.

The surface resin coating layer formed on the surface of the paper substrate of the present invention comprises a mixture of at least one unsaturated organic compound curable by electron beam irradiation and an inorganic white pigment, and , An electron beam curable organic compound composition containing other additives as required. The electron beam curable unsaturated organic compound used in the present invention can be selected from the following compounds.

(1) Aliphatic, alicyclic, and araliphatic acrylate compounds of 1- to 6-hydric alcohols and polyalkylene glycols. (2) Aliphatic, alicyclic and araliphatic acrylate compounds obtained by adding an alkylene oxide to a monohydric 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.

Specifically, as the electron beam-curable unsaturated organic compound, 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 phenoxyphosphoric 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, neopentyl glycol diacrylate, and neopentyl glycol-modified trimethylol propane diacrylate, and the like.

In the present invention, the film-forming synthetic resin used to form the backside resin coating layer is a polyolefin resin used in the production of conventional photographic paper supports, or the electron beam curable resin described above. A resin composition or the like can be used. As the polyolefin resin for forming the backside resin coating layer, homopolymers of ethylene, α-olefins such as propylene, at least two copolymers of the above olefins, and at least two of these various polymers You can choose from a mixture of. 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 usually 20,000-
Those in the range of 200,000 are advantageously used.

The polyolefin resin, if necessary,
A small amount of antioxidant and a lubricant can be added and used. In order to form the backside resin coating layer using a polyolefin resin, a usual melt extrusion method can be used. When the electron beam curable resin composition is used to form the backside resin coating layer, all the compounds used for forming the above-mentioned frontside resin coating layer can be used.
Further, in this case, the method for forming the back surface resin coating layer can be performed in the same manner as in the case of the front surface resin coating layer. The weight of the backside resin coating layer is not particularly limited, but generally 10 to 40
It is preferably in the range of g / m ² .

[0027]

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

[0028] After having been subjected to surface activation treatment by corona discharge in Example 1 quality paper (basis weight 150 g / m ^2, thickness 180 [mu] m), melt extrusion coating of polyethylene resin (HDPE) on the back surface of the quality paper Was applied to form a backside resin coating layer having a coating amount of 30 g / m ² .

Separately, an electron beam curable resin composition having the following composition was prepared. Component content ―――――――――――――――――――――― Urethane acrylate oligomer 36.0 parts by weight (Trademark: BS-550B, manufactured by Arakawa Chemical Industries) Bifunctional acrylate monomer 24.0 parts by weight Part (Trademark: M-220, manufactured by Toagosei) Titanium dioxide 10.0 parts by weight (Trademark: A-220, manufactured by Ishihara Sangyo) Zinc oxide 30.0 parts by weight (Trademark: No. 1 Zinc Hua, Mitsui Metal)

The above composition was mixed and dispersed for 1 hour using a paint conditioner to prepare an electron beam curable resin composition. The viscosity of this composition was measured using a vibrating viscometer (CJV-20
01, manufactured by System Development Co., Ltd.). The results are shown in Table 1.

The above composition was applied onto the surface of the paper substrate using a wire bar so that the coating amount after curing was 20 g / m ² , and the accelerating voltage: 165 Kv.
Then, an electron beam was irradiated under the condition of absorbed dose: 2 Mrad, and this coating liquid layer was cured to form a surface resin coating layer.

The optical transmission density of the support for photographic printing paper thus obtained was measured. The higher the transmission density, the better the hiding power. The measurement results are shown in Table 1. Further, the number of foreign matter-like protrusions due to the undispersed inorganic white pigment per 10 cm ² of the surface of the obtained photographic printing paper support was measured. The result is 0 for the number of abnormal protrusions, ○, 1 to 5 for Δ, 6
Table 1 shows the number of pieces or more as x.

Further, on the obtained support for photographic printing paper,
A black-and-white photographic light-sensitive material (trademark: Art Emulsion (manufactured by Fuji Photo Film)) was applied using a # 60 wire bar and dried to complete black-and-white photographic paper. Exposure was performed using an MTF exposure device, and the resolution was measured at a spatial frequency of 5 lines / mm. The results are shown in Table 1.

Example 2 The same operation as in Example 1 was performed. However, the composition of the electron beam curable resin composition applied on the paper substrate was as follows. Component content ―――――――――――――――――――――― Urethane acrylate oligomer 36.0 parts by weight (Trademark: BS-550B, manufactured by Arakawa Chemical Industries) Bifunctional acrylate monomer 24.0 parts by weight Parts (Trademark: M-220, manufactured by Toagosei) Titanium dioxide 20.0 parts by weight (Trademark: A-220, manufactured by Ishihara Sangyo) Zinc oxide 20.0 parts by weight (Trademark: No. 1 Zinc Hua, manufactured by Mitsui Kinzoku) Same as Example 1 Table 1 shows the result of the test performed.

Example 3 The same operation as in Example 1 was performed. However, the composition of the electron beam curable composition applied on the paper substrate was as follows. Component content ―――――――――――――――――――――― Urethane acrylate oligomer 36.0 parts by weight (Trademark: BS-550B, manufactured by Arakawa Chemical Industries) Bifunctional acrylate monomer 24.0 parts by weight Parts (Trademark: M-220, manufactured by Toagosei) Titanium dioxide 36.0 parts by weight (Trademark: A-220, manufactured by Ishihara Sangyo) Zinc oxide 4.0 parts by weight (Trademark: No. 1 Zinc Hua, Mitsui Kinzoku) Same as Example 1 Table 1 shows the result of the test performed.

Comparative Example 1 The same operation as in Example 1 was performed. However, the pigment contained in the electron beam curable resin composition applied on the paper substrate was titanium dioxide only. Its composition was as follows. Component content ―――――――――――――――――――――― Urethane acrylate oligomer 36.0 parts by weight (Trademark: BS-550B, manufactured by Arakawa Chemical Industries) Bifunctional acrylate monomer 24.0 parts by weight Parts (Trademark: M-220, manufactured by Toagosei) Titanium dioxide 40.0 parts by weight (Trademark: A-220, manufactured by Ishihara Sangyo) The results of the tests conducted in the same manner as in Example 1 are shown in Table 1.

Comparative Example 2 The same operation as in Example 1 was performed. However, a resin composition having the following composition was prepared by using only zinc oxide as the pigment contained in the electron beam curable composition coated on the paper substrate. Component content ―――――――――――――――――――――― Urethane acrylate oligomer 36.0 parts by weight (Trademark: BS-550B, manufactured by Arakawa Chemical Industries) Bifunctional acrylate monomer 24.0 parts by weight Parts (Trademark: M-220, manufactured by Toagosei) Zinc oxide 40.0 parts by weight (Trademark: No. 1 Zinhua, manufactured by Mitsui Kinzoku Co., Ltd.) Table 1 shows the results of the test conducted in the same manner as in Example 1.

[00 38] was carried out in the same manner as Comparative Example 3 Comparative Example 1. However, apply it on the paper substrate.
The composition of the electron beam curable composition to be applied was as follows. Component content ―――――――――――――――――――――― Urethane acrylate oligomer 51.0 parts by weight (Trademark: BS-550B, Arakawa Chemical Industries) Bifunctional acrylate monomer 34.0 parts by weight Parts (Trademark: M-220, manufactured by Toagosei) 15.0 parts by weight (Trademark: A-220, manufactured by Ishihara Sangyo) The results of the test conducted in the same manner as in Example 1 are shown in Table 1.
You

[00 39] on the surface of quality paper having a back surface resin coating layer in the same manner as Reference Example 1 Example 1 process, by coating a polyolefin resin composition having the following composition by conventional melt extrusion coating method, both surfaces A polyolefin resin coated support was prepared. Component content ―――――――――――――――――――――― High-pressure low-density polyethylene 85.0 parts by weight (Trademark: LK-50, Mitsubishi Yuka) Titanium dioxide 15.0 parts by weight Part (Trademark: A-220, manufactured by Ishihara Sangyo) Table 1 shows the results of the test conducted in the same manner as in Example 1.

40

[Table 1]

[00 41] support for photographic paper of Examples 1 to 3 of the present invention, a conventional photographic paper of Reference Example 1 was coated a resin composition obtained by dispersing titanium dioxide in a polyolefin resin by melt extrusion method It was excellent in transmission density (hiding power) and resolution as compared with the support. Further, as compared with the case where only titanium dioxide was blended as an inorganic white pigment in the electron beam curable resin (Comparative Example 1), the increase in paint viscosity due to the blending amount of titanium dioxide was suppressed, and no foreign matter protrusion due to undispersed matter was generated. Moreover, it was possible to secure high hiding power and resolution. Further, the hiding power and the resolution were superior to those when only zinc oxide was used as the inorganic white pigment (Comparative Example 2).

[00 42 ]

INDUSTRIAL APPLICABILITY The support for photographic printing paper of the present invention can increase the amount of the inorganic white pigment compounded in the electron beam curable resin composition without rapidly increasing the viscosity of the resin composition. In addition, it is possible to prevent the generation of defects due to undispersed pigments, exhibit excellent hiding power and resolution, and are extremely useful in practice.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location D21H 19/44 27/00 G03C 1/76 502

Claims (1)

[Claims] 1. A paper substrate containing natural pulp as a main component, at least one unsaturated organic compound formed on its surface and curable by electron beam irradiation, and an inorganic white pigment as a main component. A surface resin coating layer made of an electron beam cured product of an electron beam curable resin composition, and a back surface resin coating layer formed on the back surface of the paper substrate and containing a film-forming synthetic resin as a main component, A support for photographic paper, characterized in that the inorganic white pigment contains zinc oxide in an amount of 5% to 75% of the total weight thereof.