JPH06148799A - Supporting body for photographic printing paper - Google Patents

Abstract

PURPOSE:To provide the supporting body for a photographic printing paper improved in the deterioration of whiteness degree and hinding property resulted from an inferior dispersibility of titanium dioxide in an electron beam curable resin which is the problem which the supporting body for the photographic printing paper having the resin coating layer consisting of an electron beam curable resin has. CONSTITUTION:In the supporting body for the photographic printing paper, the surface side resin coating layer consisting of the electron beam curable unsatd. org. compd. containing titanium dioxide and an anionic high polymer dispersant is formed on one surface of the paper substrate consisting essentially of a natural pulp, and the rear side resin coating layer consisting of a film forming resin coating layer is formed on the other surface of the paper substrate.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a support for photographic printing paper. More specifically, the present invention is
By improving the dispersibility of titanium dioxide contained in an unsaturated organic compound that can be cured by electron beam irradiation on a paper substrate (hereinafter referred to as an electron beam-curable unsaturated organic compound), whiteness and hiding power ( The present invention relates to a photographic printing paper support having improved transparency.

[0002]

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

An inorganic white pigment such as titanium dioxide is mixed in the polyolefin resin coating layer on the side of the support on which the photographic emulsion layer is formed, for the purpose of improving its hiding power or resolution. There is a problem that such a pigment has poor dispersibility in the resin, and that volatile components contained in the pigment cause foaming in the melt extrusion step to cause film cracking in the resin coating layer. Therefore, the pigment content in the resin coating layer cannot be increased to a level necessary for sufficiently improving the hiding power or the resolution. Generally, if titanium dioxide is used, this should be about 2
It is difficult to add it to the resin in an addition amount of 0% by weight or more. Therefore, the photographic printing paper obtained using such a photographic printing paper support is considered to be sufficiently satisfactory in image sharpness. I couldn't say.

In recent years, a so-called electron beam curable resin, which is a resin composition which can be cured by electron beam irradiation, is applied to a support, and this is irradiated with electron beam to be cured by electron beam curable resin coating. A support for a photographic printing paper having a layer has been proposed (for example, JP-B-60-17104, JP-B-60-17105, and JP-A-57-49946). In this photographic printing paper support, it is not necessary to heat and melt the resin composition at a high temperature when forming the resin coating layer, so that the content of the pigment can be increased to 20 to 80% by weight. Therefore, the image sharpness of the photographic printing paper obtained by using such a photographic printing paper support is remarkably improved as compared with the polyolefin resin-coated photographic printing paper.

However, in general, it is difficult to disperse titanium dioxide in an electron beam curable resin having a high viscosity, and the viscosity of a coating solution in which titanium dioxide is dispersed is further increased, resulting in a low coating amount coating or a high speed coating. There is a problem such as not suitable for. Further, it was revealed that the whiteness and the hiding property may be significantly reduced due to the poor dispersibility of titanium dioxide.

In order to solve this problem, for example, in JP-A-61-86747 and JP-A-61-98346, titanium dioxide is surface-treated to improve its dispersibility in an electron beam curable resin. Ways to improve have been proposed.
However, even if the titanium dioxide subjected to the surface treatment proposed here is used, the decrease in paint viscosity is insufficient,
When the coating solution is stored for a long period of time, titanium dioxide reaggregates to increase the viscosity of the coating material. Also, JP-A-61-2012
No. 42 proposes lowering the viscosity of a paint by improving the dispersibility of titanium dioxide by using a nonionic surfactant. However, even if the surfactant proposed here is used, the adsorptivity of the surfactant to the titanium dioxide surface is weak, and the adsorbed surfactant desorbs from the titanium dioxide surface due to the shearing force during dispersion. The increase in viscosity due to the reduction of the dispersion effect or the long-term stability of the coating is still insufficient, and the whiteness and the hiding power and the image sharpness are reduced.

Therefore, it is extremely important to find a method of improving the dispersibility in an electron beam curable resin, realizing a low viscosity of a coating material, realizing long-term storage stability, and improving whiteness and hiding power. It was

[0008]

DISCLOSURE OF THE INVENTION The present invention solves the above problems of a conventional photographic printing paper support having an electron beam curable resin coating layer formed thereon, retains high whiteness and is excellent. An object of the present invention is to provide a support for photographic printing paper suitable for producing photographic printing paper having photographic characteristics.

[0009]

The photographic printing paper support of the present invention comprises a paper base containing natural pulp as a main component, and an electron beam curable unsaturated organic material formed on one surface of the paper base. A front side resin coating layer containing a compound as a main component (a side forming a photographic emulsion layer), and a back side resin coating layer formed on the other surface of the paper substrate and containing a film-forming synthetic resin as a main component. And titanium dioxide and an anionic polymer dispersant are contained in the surface side resin coating layer.

[0010]

The structure and operation of the present invention will be described below.
Generally, when titanium dioxide is dispersed in an electron beam curable resin, the dispersibility of titanium dioxide is poor because the electron beam curable resin itself has a high viscosity, and the prepared coating liquid has a higher viscosity. Deterioration of the dispersibility of titanium dioxide causes a problem that a low coating amount cannot be coated and a high-speed coating cannot be performed due to an increase in viscosity of the coating liquid. Further, it reduces the whiteness and hiding power of photographic printing paper.

As a result of various investigations by the present inventors, it has been found that this problem can be effectively solved by using an anionic polymer dispersant when dispersing titanium dioxide in an electron beam curable resin. It has been found. That is, in the dispersion of titanium dioxide in the electron beam curable resin, the anionic polymer dispersant is electrically adsorbed on titanium dioxide having a positive charge in the electron beam curable resin. Therefore, the anionic polymer dispersant adsorbed on the titanium dioxide is not desorbed due to the elastic force during dispersion. Further, since the adsorbed dispersant has a high molecular weight, the steric hindrance thereof suppresses the aggregation of titanium dioxide, and the stable dispersibility is maintained for a long period of time. Thus, the whiteness and the hiding property were successfully improved by lowering the viscosity of the coating solution, improving the long-term stability during storage of the coating solution, and improving the dispersibility of titanium dioxide.

The support of the present invention as described above is prepared by dispersing an electron beam-curable unsaturated organic compound as the main component on the surface of a paper substrate containing natural pulp as the main component and dispersing it with an anionic polymer dispersant. It is possible to form a resin coating layer by applying at least one coating layer by applying a coating solution containing titanium dioxide, and by irradiating this with an electron beam to cure it. A backside resin coating layer is formed on the opposite surface of the paper substrate before or after the step of forming the resin coating layer.

Examples of the anionic polymer dispersant used in the present invention include high molecular weight carboxylic acids, aliphatic alcohol sulfate salts, sulfuric acid anion salts and the like. Among them, high molecular weight carboxylic acids are particularly preferable. Its content is
It is preferably 0.1 to 5.0 parts by weight with respect to 100 parts by weight of titanium dioxide. When the content is less than 0.1 part by weight, the dispersion effect is low and the viscosity of the coating solution is not sufficiently lowered. When the content exceeds 5.0 parts by weight, the dispersant itself is a polymer substance and the coating viscosity is high. It may increase and cause a decrease in curability.

The crystal form of titanium dioxide used in the present invention may be either anatase type or rutile type. Also,
Inorganic oxides (Al ₂ O ₃ , AlO (OH), SiO
It is possible to use titanium dioxide surface-treated with ₂ etc.) and titanium dioxide which has been subjected to an organic material treatment such as trimethylolethane, triethanolamine acetate, trimethylcyclosilane in addition to these surface treatments. The content of titanium dioxide is 2% of the total solid content of the electron beam curable resin coating layer.
It is preferably from 0 to 80% by weight. Its content is 2
If it is less than 0% by weight, the whiteness on the obtained photographic paper may be lowered and the sharpness of the photographic image may not be sufficient, and if it exceeds 80% by weight, the flexibility of the obtained resin coating layer may be lowered and film cracking may occur. May occur.

In the present invention, the electron beam curable resin used for forming the surface side resin coating layer may be a monomer alone or an oligomer alone, or a mixture thereof, as long as it can form a highly crosslinked resin layer. It may be one.

The electron beam-curable unsaturated organic compound used in the present invention can be selected from the following compounds, for example. (1) Aliphatic, alicyclic and araliphatic 1 to 6 valent alcohol and polyalkylene glycol acrylate compounds (2) Aliphatic, alicyclic and araliphatic 1 to 6 valent Acrylate compounds obtained by adding alkylene oxide to alcohol (3) Polyacryloylalkyl phosphates (4) Reaction product of carboxylic acid, polyol and acrylic acid (5) Isocyanate, polyol and acrylic acid (6) Reaction product of epoxy compound and acrylic acid (7) Reaction product of epoxy compound, polyol and acrylic acid

To specifically describe these compounds,
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, hydroxybivalic acid ester neopentyl glycol diacrylate, nonylphenoxy polyethylene glycol acrylate, ethylene oxide modified phenoxyphosphoric acid acrylate, ethylene oxide modified phthalic acid acrylate, polybutadiene acrylate, caprolactone modified tetrahydrofurfuryl Acrylate, tris (acryloxyethyl) isocyanate, trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate,
Dipentaerythritol hexaacrylate, polyethylene glycol diacrylate, 1,4-butadiene diol diacrylate, neopentyl glycol diacrylate, neopentyl glycol-modified trimethylolpropane diacrylate and the like can be used.

In the present invention, these compounds may be used alone or in combination of two or more kinds.

In order to disperse titanium dioxide in the electron beam curable resin as described above, a three roll mill (three roll mill), two roll mill (two roll mill), cowles dissolver, homomixer, sand grinder,
A kneader, planetary mixer, ball mill, paint conditioner, ultrasonic disperser and the like can be used alone or in combination.

Further, if necessary, a bluing pigment, a dye, or an antioxidant may be blended in the electron beam curable resin as an auxiliary agent.

As the method for applying the resin composition to the surface of the paper substrate, any of bar coating method, blade coating method, squeeze coating method, air knife coating method, roll coating method, gravure coating method, transfer coating method and the like can be used. Is also good.

The weight of the surface side resin coating layer of the present invention is 5 to 5.
It is preferably 60 g / m ² (solid content).

The film-forming synthetic resin used for forming the backside resin coating layer of the present invention is a polyolefin resin which has been conventionally used for producing a support for photographic printing paper, or the aforementioned electron beam. A curable resin or the like can be used.

As the polyolefin resin for forming the backside resin coating layer, ethylene, α-olefins,
For example, it can be selected from a homopolymer such as propylene, a copolymer of at least two kinds of the above-mentioned olefins, and a mixture of at least two kinds of these various polymers.
Particularly preferred polyolefin resins include low density polyethylene, high density polyethylene, linear low density polyethylene,
And mixtures thereof. The molecular weight of the polyolefin resin is not particularly limited, but is usually 20,000 to 20.
Those in the range of 10,000 are used. If necessary, a small amount of antioxidant and lubricant may be added to the polyolefin resin. In order to form the backside resin coating layer using a polyolefin resin, ordinary melt extrusion coating can be used.

As the electron beam curable resin for forming the back surface side resin coating layer, all the compounds used for forming the front surface side resin coating layer can be used. Further, the method of forming the back surface side resin coating layer may be the same as the case of the above-mentioned front surface side resin coating layer. The weight of the backside resin coating layer is not particularly limited, but it is generally preferably in the range of 10 to 40 g / m ² .

The electron beam accelerator used for electron beam irradiation is not particularly limited in its system, and for example, an electron beam irradiation device such as a Van de Graaff scanning system, a double scanning system, or a curtain beam system can be used. Among these, the curtain beam type, which is relatively inexpensive and can obtain a large output, is effectively used. The acceleration 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 particularly preferably 0.2 to 4 Mrad.

The oxygen concentration in the atmosphere during electron beam irradiation is preferably 500 ppm or less. When the oxygen concentration exceeds 500 ppm, oxygen acts as a retarder for the polymerization reaction, and the resin composition may be insufficiently cured.
However, in order to obtain the surface smoothness of the electron beam curable photographic printing paper support, when an appropriate molding surface such as a metal drum or a plastic film is pressed against the electron beam curing coating liquid applied on the paper substrate. The electron beam curing coating liquid does not come into direct contact with the air during electron beam irradiation, so it is not necessary to particularly reduce the oxygen concentration in the atmosphere during electron beam irradiation, but ozone generation due to electron beam irradiation is suppressed. Of course, there is no problem in using the inert gas for the purpose of cooling the window that generates heat when the electron beam passes.

The paper substrate used in the present invention is usually 50-
It has a weight of 300 g / m ² and has a smooth surface. Such a paper substrate can be selected from those generally used for manufacturing a support for photographic printing paper.
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. Further, the paper substrate may contain a magnesium compound for the purpose of preventing fog that occurs during long-term storage when used as photographic paper.

If desired, the paper substrate may contain additives such as a sizing agent, a fixing agent, a paper strength enhancer, a filler, an antistatic agent, a regulator, a pigment and a dye, which are generally used in papermaking. It may be done. In addition, surface sizing agent, surface paper strength agent,
An antistatic agent or the like may be applied to the surface as appropriate.

[0030]

The present invention will be described in more detail with reference to the following examples, but the present invention is of course not limited to these embodiments.

Example 1 One surface of a paper substrate having a basis weight of 180 g / m ² was subjected to surface activation treatment by corona discharge, and a polyethylene resin was melt-extruded on the surface of the substrate to apply a coating amount of 30 g / m ² . A backside resin coating layer was formed.

Next, paint a mixture having the composition shown below.
Mix and disperse with a conditioner for 1 hour, and
A coating composition for forming a cover layer (composition 1) was prepared, and this composition
On the other side of the paper substrate, using a wire bar,
Application amount after curing is 25g / m ²So that it becomes
Coating layer, acceleration voltage: 175kV, absorbed dose: 2Mr
Surface side after electron beam irradiation to cure coating layer under ad condition
A resin coating layer was formed to prepare a support for photographic printing paper.

The surface resin coating layer-forming coating composition (composition 1) Ingredient weight urethane acrylate oligomer 30 parts by weight (trademark: R-1301, manufactured by Dai-ichi Kogyo Seiyaku Co.) monofunctional acrylate monomer 20 parts by weight (trademark : NP-2, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) 50 parts by weight of rutile titanium dioxide (trademark: CR-58, manufactured by Ishihara Sangyo) 0.5 parts by weight of anionic polymer dispersant (trademark: Texahol 3098, manufactured by San Nopco)

The resulting photographic printing paper support was evaluated for whiteness and opacity. The evaluation results are shown in Table 1.

[0035]

[Table 1]

The whiteness and opacity are determined by JIS
According to the method of P8123, it measured at the wavelength of 475 nm using the Hunter whiteness meter (Toyo Seiki Seisakusho make, D type). If the whiteness value is 90% or more and the opacity value is 95% or more, there is no practical problem.

Example 2 The same operation as in Example 1 was performed. However, anatase type titanium dioxide (trademark: A-220, manufactured by Ishihara Sangyo) was used in place of the rutile type titanium dioxide of the composition 1. Table 1 shows the result of the test conducted in the same manner as in Example 1.

Example 3 The same operation as in Example 1 was performed. However, the amount of the anionic polymer dispersant added to Composition 1 was 2.5 parts by weight.
Table 1 shows the result of the test conducted in the same manner as in Example 1.

Example 4 The same operation as in Example 1 was performed. However, the following composition 2 was used as the coating composition for forming the surface side resin coating layer. Surface-side resin coating layer-forming coating composition (composition 2) Ingredient weight dipentaerythritol hexaacrylate 50 parts by weight (trademark: DPCA-20, manufactured by Nippon Kayaku) rutile titanium dioxide 50 parts by weight (trademark: CR -58, manufactured by Ishihara Sangyo) 0.5 part by weight of anionic polymer dispersant (trademark: Texahol 3098, manufactured by San Nopco) The results of the test conducted in the same manner as in Example 1 are shown in Table 1.

Comparative Example 1 The same operation as in Example 1 was performed. However, a nonionic ethylene oxide dispersant (trademark: Product 100, manufactured by San Nopco) was used in place of the anionic polymer dispersant of the composition 1. Table 1 shows the result of the test conducted in the same manner as in Example 1.

Comparative Example 2 The same operation as in Example 1 was performed. However, instead of the anionic polymer dispersant of the composition 1, an organic acid salt dispersant of a cationic special amine (trademark: Texahol 277, manufactured by San Nopco) was used. Table 1 shows the result of the test conducted in the same manner as in Example 1.

Comparative Example 3 The same operation as in Example 1 was performed. However, the anionic polymer dispersant was not added to the composition 1. Table 1 shows the result of the test conducted in the same manner as in Example 1.

Comparative Example 4 The same operation as in Example 1 was performed. However, the amount of the anionic polymer dispersant added to Composition 1 was 6 parts by weight. Table 1 shows the result of the test conducted in the same manner as in Example 1.

[0044]

INDUSTRIAL APPLICABILITY The photographic printing paper support of the present invention has a general drawback in dispersing titanium dioxide in an electron beam curable resin, namely, the presence of titanium dioxide in a high viscosity electron beam curable resin. Solves the problems of difficulty in dispersion, difficulty in controlling coating amount due to increased viscosity of the prepared coating liquid, and difficulty in high-speed coating, and lowers whiteness and hiding power due to undispersed titanium dioxide. It is an improved one and is extremely effective in practice.

Claims (1)

[Claims] 1. A paper substrate containing natural pulp as a main component, and a front surface side (photographic emulsion layer) containing an unsaturated organic compound formed on one surface of the paper substrate and curable by electron beam irradiation as a main component. Forming a) a resin coating layer and a back surface resin coating layer formed on the other surface of the paper substrate and containing a film-forming synthetic resin as a main component, wherein the front surface resin coating layer has A photographic paper support comprising titanium dioxide and an anionic polymer dispersant.