JP2737565B2 - Method for producing a support for photographic printing paper - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a photographic printing paper support. More specifically, the present invention comprises a paper substrate provided with a resin coating layer made of an unsaturated organic compound curable by electron beam irradiation (hereinafter, referred to as an electron beam-curable unsaturated organic compound). In a photographic paper support, the yellowing of the resin coating layer during development processing is suppressed, the deterioration of the support is reduced, and when stored as photographic paper for a long period of time, the white color resulting from the yellowing of the paper substrate The present invention relates to a production method for obtaining a photographic printing paper support capable of suppressing the occurrence of a decrease in degree.

[0002]

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

[0003] An inorganic white pigment such as titanium dioxide is mixed into the polyolefin resin coating layer of such a support for the purpose of improving the hiding power or the resolving power. In addition, there is a problem that the volatile component contained in the pigment causes foaming in the melt extrusion step to cause film cracking of the coating layer. Therefore, the pigment content in the coating layer cannot be increased to a sufficient level for improving the hiding power or the resolving power. Generally speaking, when using titanium dioxide, it is difficult to incorporate it into the coating layer in an amount of about 20% by weight or more. Therefore, the photographic paper obtained using such a photographic paper support was not sufficiently satisfactory in image sharpness.

In recent years, a so-called electron beam-curable resin composed of a resin composition curable by electron beam irradiation has been applied to a support, and electron beam irradiation has been applied thereto to cure the electron beam-curable resin coating layer. There has been proposed a photographic printing paper support having the following formula (for example, JP-B-60-17104, JP-B-60-17105, JP-A-57-49946). According to this method, the resin composition is not heated to a high temperature when forming the coating layer, so that the pigment content can be increased to 20 to 80% by weight. The image sharpness of photographic printing paper obtained by using photographic printing paper is remarkably improved as compared with photographic printing paper coated with polyolefin resin.

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

[0006] The increase in fog density and yellowing, and the flexibility and yellowing of the coating film, respectively, are mutually inconsistent with respect to the irradiation dose. That is, when a high irradiation dose is used, yellowing due to the developer is suppressed to a low level, but fog increases, and the flexibility of the coating film, the strength of the base paper, and the paper quality tend to deteriorate. On the other hand, at a low irradiation dose, the occurrence of fog is suppressed, and a decrease in the flexibility of the coating film is prevented or reduced, but yellowing is remarkably increased, and the properties of the coating film such as adhesion and film strength tend to deteriorate. There is. In order to solve these problems, a method has been proposed in which the coating layer has a multilayered structure of two or more layers having an inner layer and an outer layer, but the effect is still insufficient depending on the curing conditions. For this reason, setting of more effective curing conditions has been desired.

[0007]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of the prior art, has excellent surface smoothness, maintains high water resistance, and has no decrease in whiteness even after storage aging. The present invention proposes a method for producing a photographic printing paper support which is suitable for efficiently producing photographic printing paper having excellent photographic characteristics without yellowing caused by photographic paper.

[0008]

According to the present invention, there is provided a method for producing a photographic printing paper support, comprising the steps of: providing an unsaturated organic compound curable by electron beam irradiation on one surface of a paper substrate containing natural pulp as a main component. At least one inner coating layer containing a main component is formed, and an outermost coating layer containing an unsaturated organic compound curable by electron beam irradiation as a main component is formed on a molding surface. The outermost cured layer thus cured and the inner coating layer on the paper substrate are overlapped on the molding surface, and the multilayer body is irradiated with a second electron beam to be cured. Is cured and adhered and then released from the molding surface, whereby (1) at least one inner resin coating layer adjacent to the paper substrate, and (2) an outermost resin coating layer adjacent to the photographic emulsion layer. A surface resin coating layer with a laminated structure And forming a back surface resin coating layer containing a film-forming synthetic resin as a main component on the other surface of the paper substrate, the irradiation dose at the time of the first electron beam irradiation, It is characterized by controlling the total amount of the first and second electron beam irradiation doses to 15% or more, and controlling the second electron beam irradiation dose to 2.5 Mrad or less.

[0009]

The structure and operation of the present invention will be described below.
Generally, a support obtained by applying a commercially available electron beam-curable resin composition onto a paper substrate containing natural pulp as a main component and irradiating the paper substrate with an electron beam to form an electron beam-curable resin coating layer. The photographic printing paper containing a yellowish color has a problem of so-called yellowing, which is colored yellow after the development processing. Although the cause of the yellowing is not completely clear, it is considered that the developing agent in the photographic processing chemicals remains adsorbed on the support in the development processing step and is oxidized to cause coloring.

[0010] In order to prevent yellowing, it is only necessary to reduce the amount of developing agent adsorbed. For that purpose, it is effective to increase the crosslink density of the coating film, and for that purpose, it is necessary to cure the resin composition. High irradiation dose of electron dose,
It has been known that measures such as increasing the amount of the polyfunctional monomer in the coating layer are effective. However, all of these methods not only reduce the flexibility of the coating film, but also increase the fog during long-term storage of photographic paper when the irradiation dose of the electron beam is increased, and furthermore, increase the electron emission. There is also a disadvantage that the base paper is deteriorated by the impact of the radiation.

As a result of various studies on this point, the present inventors have found that when forming an electron beam-curable resin layer having a multilayer structure, the curing of the outermost resin layer applied to the molding surface has no effect on the base paper. Therefore, it is not necessary to set an upper limit on the irradiation dose.However, in order to prevent yellowing due to development, the cured resin layer needs to have a crosslink density of a certain value or more. It has been found that a lower limit exists. As a result of repeated studies on this point, the following conclusion was reached. That is, the first irradiation dose is 15% or more of the total amount of the second irradiation dose and the first irradiation dose, which are performed after the outermost layer is superimposed on the resin layer forming the inner layer, and the first irradiation dose. It has been found that this problem can be solved by controlling it.

Further, since the second irradiation cannot avoid the irradiation of the electron beam to the paper base material, the irradiation dose should be as low as possible within a range where the resin for the inner layer is sufficiently cured. There is a need. Therefore, as a result of studying this point, they found that it was necessary to control the second irradiation dose to 2.5 Mrad or less in order to prevent deterioration of the paper base material, and completed the present invention.

In the present invention, of the surface resin coating layer,
The electron beam-curable resin used in the outermost resin coating layer to which the photographic emulsion is applied may be a monomer alone or an oligomer alone, or may be a mixture of them, as long as it can be highly crosslinked. Although there is no particular limitation on the type of the resin, it is usually preferable that the resin is mainly composed of a resin having four or more functional groups. The types of resin that can be used for the resin layer located inside the paper substrate side are:
A wider range can be selected. In this case, it is not necessary to consider yellowing due to the development treatment, so that it is not necessary to increase the crosslink density of the resin layer, and a resin layer having flexibility can be formed.

According to the present invention, since the dose of electron beam irradiation to the base paper can be suppressed to a low level, it is possible to prevent deterioration and discoloration of the base paper due to the electron beam irradiation, and furthermore, to preserve the base paper for a long term due to the electron beam irradiation. It is also possible to prevent fog at the time.

[0015] The surface resin coating layer formed on one surface of the paper substrate of the present invention comprises an electron beam-curable unsaturated organic compound,
It is formed from an electron beam-curable resin composition of a composition containing a mixture with a white pigment and, if necessary, other additives.

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 valent alcohols and polyalkylene glycols (2) Aliphatic, alicyclic, araliphatic, 1 to 6 valent Acrylate compounds of alkylene oxide added to alcohol

(3) Polyacryloyl alkyl phosphates (4) Reaction product of carboxylic acid, polyol and acrylic acid (5) Reaction product of isocyanate, polyol and acrylic acid (6) Epoxy Reaction product of compound and acrylic acid (7) Reaction product of epoxy compound, polyol and acrylic acid

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

In the method of the present invention, these unsaturated compounds can be used alone or in combination of two or more thereof. The unsaturated compounds used for forming the outermost layer include highly crosslinked As described above, unsaturated compounds having four or more functional groups are particularly advantageously used so as to impart properties.

In the method of the present invention, the resin coating layer may contain a white pigment for the purpose of improving the sharpness of an image when used as photographic paper. Titanium dioxide (anatase type and rutile type) is mainly selected as a white pigment used for such a purpose, but any of barium sulfate, calcium carbonate, aluminum oxide, and magnesium oxide can be used. It is.

The content of the white pigment is preferably 20 to 80% by weight based on the total solid weight of the electron beam curable resin coating layer. If the content is less than 20% by weight, the sharpness of the photographic image on the obtained photographic paper may be insufficient,
When the content exceeds 0% by weight, the flexibility of the obtained resin coating layer is reduced, and the film may be cracked.

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

Examples of the method of applying the resin composition to the surface of a molding surface or the surface of a paper substrate include a bar coating method, a blade coating method, a squeeze coating method, an air knife coating method, a roll coating method, a gravure coating method and a transfer coating method. Any of these may be used. Further, for this purpose, a fountain coater or a slit die coater method can be used. In particular, when the surface of a metal drum is used as a molding surface, a roll coating method using a rubber roll or an offset gravure coating method is used in order to prevent scratches on the molding surface surface. A fountain coater or a slit die coater method is advantageously used.

The total weight of the multilayer type electron beam curable resin surface coating layer is preferably 5 to 60 g / m ² (solid content).

As the film-forming synthetic resin used for forming the backside resin coating layer, a polyolefin resin used in the production of a conventional support for photographic printing paper, or the above-mentioned electron beam-curable resin is used. I can do it.

Examples of the polyolefin resin for forming the backside resin coating layer include homopolymers of ethylene and α-olefins such as propylene, copolymers of at least two kinds of the olefins, and various polymers. It can be selected from at least two kinds of mixtures. Particularly preferred polyolefin resins are low density polyethylene, high density polyethylene, linear low density polyethylene,
And mixtures thereof. Although the molecular weight of the polyolefin resin is not particularly limited, it is usually 20,000 to 20.
Those having a range of 000 are used. If necessary, a small amount of an antioxidant and a lubricant may be added to the polyolefin resin. In order to form a back resin coating layer using a polyolefin resin, ordinary melt extrusion coating can be used.

As the electron beam-curable unsaturated organic compound for forming the backside resin coating layer, any of the compounds used for forming the above-mentioned frontside resin coating layer can be used.
Further, the method of forming the back surface resin coating layer is the same as that of the above-described front surface resin coating layer. No particular restrictions on the weight of the back surface resin coating layer, but generally is preferably in the range of 10 to 40 g / m ^2.

As an electron beam accelerator used for electron beam irradiation, a curtain beam type which is relatively inexpensive and can obtain a large output is effectively used. The acceleration voltage at the time of electron beam irradiation is preferably 100 to 300 kv. Of course, there is no problem in using an inert gas for the purpose of suppressing ozone generation due to electron beam irradiation or for cooling a window that generates heat when the electron beam passes. The paper substrate used in the present invention usually has a weight of 50 to 300 g / m ² and has a smooth surface.

The paper substrate used in the present invention may be any one which is generally used for a photographic paper support. As natural pulp that forms a paper substrate,
Generally, those containing, as a main component, softwood pulp, hardwood pulp, mixed softwood pulp and the like are widely used. In addition, a magnesium compound can be contained in the paper substrate for the purpose of preventing fogging that occurs during long-term storage of photographic paper.

Further, the paper base may contain additives generally used in papermaking, such as sizing agents, fixing agents, paper strength enhancers, fillers, antistatic agents, pH adjusters, pigments, dyes, and the like. Good. Further, a surface sizing agent, a surface strength agent, an antistatic agent and the like may be appropriately applied to the surface.

Next, the method for forming the surface resin coating layer of the present invention will be further described with reference to the accompanying drawings. In the coating liquid coating and curing equipment 1 shown in FIG. 1, an electron beam-curable resin composition 3 for forming the outermost layer is prepared from a coating container 2 by using coaters 4a and 4b such as an offset gravure coater. The outermost coating liquid layer 7a is applied on the molding surface of the molding base 5 formed of a drum-making drum, and is cured by an electron beam irradiated from the first electron beam irradiation device 6 to form a cured outermost layer 7. At this time, the electron beam irradiation in the first electron beam irradiation device 6 is generally performed in an atmosphere having an oxygen concentration of 500 ppm or less. Therefore, it is important that the oxygen concentration be 600 ppm or more, preferably 100 ppm.
In some cases, the treatment is performed in an atmosphere in which the concentration is increased to 0 ppm or more.

On the other hand, the electron beam-curable resin composition 9 in the container 8 is applied onto one surface of the paper substrate 11 using the coaters 10a, 10b, and 10c to form an inner coating liquid layer 12a. Next, the inner coating liquid layer 12a is
Is guided on a molding base 5 made of a metal drum, and is bonded to the cured outermost layer 7, and is cured by the second electron beam irradiation device 14 to form a surface resin coating layer. The substrate-surface resin coating layer laminate 16 is peeled off from the molding substrate 5 via the guide roll 15, and a photographic printing paper support is obtained.

FIG. 2 shows an example in which a molding film 17 made of a polymer film such as a polyester film is used as a molding base instead of a metal drum. Also in this case, the electron beam irradiation from the first electron beam irradiation device 6 to the outermost coating liquid layer 7a formed on the film 7 is usually performed in an atmosphere having an oxygen concentration of 500 ppm or less, but is preferably 600 ppm or more, preferably. Is 1000ppm
It may be performed in the above atmosphere. In addition, the second electron beam irradiation may be performed through the molding film 17,
Alternatively, the light may be irradiated from the back surface of the paper base 11 opposite to the molding film 17. The film for molding 17 is repeatedly used after being wound up, but may be in the form of an endless belt. Molding film 1
Reference numeral 7 does not necessarily need to be a polymer film, but may be a belt-shaped metal film.

In both cases of FIGS. 1 and 2, the cured resin film forming the outermost layer 7 is irradiated with the electron beam for two times, so that the cross-linking density of the film is increased and the yellowing in the developing process is caused. And water resistance and gloss are imparted.

[0035]

The structure and effects of the present invention will be described in more detail with reference to the following examples. However, the scope of the present invention is not limited by these.

Example 1 A back surface of a paper substrate having a basis weight of 180 g / m ² was subjected to surface activation treatment by corona discharge, followed by extrusion coating with a polyethylene resin to provide a 30 g / m ² back surface resin coating layer.
Then, after preparing a coating composition for forming the inner resin coating layer having the following composition by mixing and dispersing with a paint conditioner for 1 hour, the composition was coated on the surface of the paper substrate,
Using a wire bar, the applied amount after curing is 20 g / m ²
To form an inner coating layer.

The inner resin coating layer forming coating composition Ingredient Blend weight urethane acrylate oligomer 36 parts by weight (trademark: Beam Set 550B, manufactured by Arakawa Chemical Industries) bifunctional acrylate monomer 24 parts by weight (trademark: M-220, Toa 40 parts by weight of titanium dioxide (trademark: A220, manufactured by Ishihara Sangyo)

Separately, a coating composition for forming an outermost resin coating layer having the following composition was prepared by mixing and dispersing with a paint conditioner for 1 hour, and then this composition was subjected to chromium plating for use as a molding surface. Using a wire bar on the surface of the metal plate, the applied amount after curing is 5 g / m
The coating is a ^2, this accelerating voltage: 175 kV, irradiation dose: at 3Mrad conditions by performing a first electron beam irradiation to form a cured outermost layer by curing the coating solution layer, and then this The inner coating layer on the paper substrate was superimposed on the cured layer, and a second electron beam was irradiated from the back of the paper substrate under the conditions of an acceleration voltage of 175 kv and an irradiation dose of 1 Mrad to cure the multilayer body. The obtained surface resin layer laminate was peeled off from the metal plate molding surface to prepare a photographic printing paper support.

The outermost resin coating layer-forming coating composition Ingredient Blend amount dipentaerythritol hexaacrylate 80 parts by weight (trademark: Beam Set 700, manufactured by Arakawa Chemical Industries) Titanium dioxide 20 parts by weight (trademark: A220, manufactured by Ishihara Sangyo Kaisha Made)

The obtained photographic printing paper support was tested and evaluated for yellowing due to development, the degree of deterioration, and fading. Table 1 shows the test results. In addition,
The evaluation method for each item is as follows.

Yellowing: A test support was coated on an automatic processor (trade name:
RCP20, manufactured by Durst Co.), and the b value was measured according to the “Lab measurement method” of TAPPI-T524. From the b value after the development processing, b value before the development processing was determined.
Evaluation was performed using the value obtained by subtracting the value (Δb value) as an index of yellowing. If the Δb value is within 1.0, there is no practical problem.

Degree of deterioration: The tear strength of the test support was measured by the method of JIS P 8116 to evaluate the degree of deterioration. If the tear strength is 110 g or more, there is no practical problem.

Discoloration: The whiteness of a test support at a wavelength of 475 nm was measured using a Hunter whiteness meter (D type, manufactured by Toyo Seiki Seisaku-Sho, Ltd.) according to the method of JIS P 8123. The ratio (K / S) between the specific absorption coefficient and the specific scattering coefficient was determined by the equation (1). Next, the sample was placed in a constant-temperature air-drying oven at 105 ° C. for 2 hours to perform forced deterioration treatment. Then, the sample was conditioned at 20 ° C. and 65% RH for 24 hours, and the whiteness was measured again ( K / S) value, and the PC value (PostCol) is calculated by the following equation (2).
or Number) and the degree of fading was evaluated. If the PC value is 1.0 or less, there is no practical problem. K / S = (1-R∞ / 100) 2 / (2R∞ / 100) (1) PC value = 100 [After deterioration treatment (K / S) -Before treatment (K / S)] (2) Where R∞: whiteness K: specific light absorption coefficient S: specific light scattering coefficient

Example 2 In the same manner as in Example 1, a photographic printing paper support was produced. However, the first electron beam irradiation is performed at an acceleration voltage of 175 kv,
Irradiation dose: 2 Mrad, and second electron beam irradiation was performed under the conditions of acceleration voltage: 175 kv, irradiation dose: 2 Mrad. Table 1 shows the results of tests performed in the same manner as in Example 1.

Example 3 A photographic paper support was prepared in the same manner as in Example 1. However, the first electron beam irradiation is performed at an acceleration voltage of 175 kv,
Irradiation dose: 0.5 Mrad, and the second electron beam irradiation was performed under the conditions of acceleration voltage: 175 kv, irradiation dose: 2.5 Mrad. Table 1 shows the results of tests performed in the same manner as in Example 1.

Comparative Example 1 A photographic printing paper support was produced in the same manner as in Example 1.
However, the first electron beam irradiation was performed under the conditions of an acceleration voltage of 175 kv and an irradiation dose of 0.3 Mrad, and the second electron beam irradiation was performed under the conditions of an acceleration voltage of 175 kv and an irradiation dose of 2.5 Mrad. . Table 1 shows the results of tests performed in the same manner as in Example 1.

Comparative Example 2 A photographic printing paper support was produced in the same manner as in Example 1.
However, the first electron beam irradiation was performed under the conditions of an acceleration voltage of 175 kv and an irradiation dose of 1 Mrad, and the second electron beam irradiation was performed under the conditions of an acceleration voltage of 175 kv and an irradiation dose of 3 Mrad. Table 1 shows the results of tests performed in the same manner as in Example 1.
Shown in

[0048]

[Table 1]

[0049]

According to the method for producing a photographic printing paper support of the present invention, the drawback of the photographic printing paper support provided with the electron beam-curable resin coating layer, that is, the yellowing of the resin coating layer during development processing. Thus, it has become possible to produce a photographic printing paper support having no or little deterioration of the base material and no fading property when stored as printing paper for a long time.

[Brief description of the drawings]

FIG. 1 is a process explanatory view showing an example of a method for forming a two-layer surface resin coating layer on a photographic printing paper support of the present invention by using a metal drum as a molding surface.

FIG. 2 is a process explanatory view showing an example of a method for forming a two-layer structure surface resin coating layer on a photographic printing paper support of the present invention by using a film material as a molding surface.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 coating liquid coating and curing equipment 2 paint container 3 composition for electron beam curable resin for outermost layer 4 a, 4 b, 4 c, 10 a, 10 b, 10 c coater 5 molding drum 6 first electron beam irradiation Apparatus 7a: Outermost coating liquid layer 7: Cured outermost layer 8: Paint container 9: Electron beam-curable resin composition for inner layer 11: Paper substrate 12a: Inner coating liquid layer 12: Cured inner layer 13, 13a, 13b ... Guide roll 14 ... Second electron beam irradiation device 15, 15a, 15b ... Guide roll 16 ... Surface resin coating layer laminate 17 ... Forming film

Claims (1)

(57) [Claims] At least one inner coating layer containing, as a main component, an unsaturated organic compound curable by irradiation with an electron beam is formed on one surface of a paper substrate containing, as a main component, natural pulp. Forming an outermost coating layer containing an unsaturated organic compound curable by electron beam irradiation as a main component on the uppermost layer, applying a first electron beam irradiation to the outermost coating layer, and curing the outermost coating layer; The inner coating layer on the paper substrate is superimposed on the molding surface, and the multilayer body is irradiated with a second electron beam to be cured and adhered, and then separated from the molding surface, whereby (1) Forming a surface resin coating layer having a laminated structure comprising at least one inner resin coating layer adjacent to the paper substrate and (2) an outermost resin coating layer adjacent to the photographic emulsion layer; On the other side of
Forming a back surface resin coating layer containing a film-forming synthetic resin as a main component, the irradiation dose at the time of the first electron beam irradiation being adjusted to the total amount of the first and second electron beam irradiation doses. Wherein the second electron beam irradiation dose is controlled to be 2.5 Mrad or less.