GB2109704A

GB2109704A - Photographic support

Info

Publication number: GB2109704A
Application number: GB08231488A
Authority: GB
Inventors: Osamu Kitamura
Original assignee: Fuji Photo Film Co Ltd
Current assignee: Fujifilm Holdings Corp
Priority date: 1981-11-10
Filing date: 1982-11-04
Publication date: 1983-06-08
Also published as: JPS5880637A; GB2109704B; JPH0234371B2; DE3241599A1

Abstract

A photographic support comprising a paper sheet provided with a polyolefin coating layer on both surfaces thereof, at least one of said polyolefin coating layer containing a white pigment, in which said paper sheet is impregnated or coated with a mixture of 100 parts by weight of a carboxylated polyvinyl alcohol containing maleic acid and/or itaconic acid comonomer component and 5-200 parts by weight of a divalent metallic salt. The mixture is employed in such an amount that not less than 0.5 g. of the carboxylated polyvinyl alcohol is impregnated into or coated over 1 m<2> of the paper sheet.

Description

SPECIFICATION Photographic support This invention relates to a photographic support. More particularly, this invention relates to a waterproof photographic support comprising a paper sheet provided with a polyolefin coating layer on both surfaces thereof, which is substantially free from being soiled by a developing solution at the edge portion produced by the cutting procedure.

In the art of a photosensitive material comprising a paper sheet as its support medium, especially a photographic material, a water-proof support has been studied for coping with the requirement of a rapid development process. Recently, a water-proof photographic support comprising a paper sheet coated with a hydrophobic polyolefin on both surfaces thereof has been developed. The upper polyolefin coating layer of the water-proof photographic support, on which is to be placed a photographic emulsion layer, usually contains therein a white pigment for increasing sharpness of a photographic image.

A photographic support is provided with a photographic emulsion layer on its upper surface to give a photographic material. The photographic material is exposed to light through a negative image, and then the so-exposed photographic material is developed in a development processing solution (referred to hereinafter as developing solution) to produce a picture with a positive image.

During a developing procedure, the both surfaces of a photographic support comprising a paper sheet coated with a polyolefin have high water-proof characteristics. However, the photographic support is apt to be soiled by a developing solution at the edge portion produced by the cutting procedure, because the hydrophilic wood pulp fibers constituting the paper sheet are liable to draw the developing solution into the paper sheet from the exposed cut edge. When the developing solution permeates the photographic material over 0.2 mm deep from the cut edge thereof, the edge soiling of the paper sheet is observed clearly through both the photographic emulsion layer and the polyolefin coating layer, resulting in deterioration of the value of the photographic material.

Until now, there is known and generally employed a measure for preventing the permeation of a developing solution which involves incorporation of a sizing agent into the paper sheet. However, the result is not considered to be satisfactory.

There is also proposed to employ a measure involving coating a water-repelling agent over the edge portion of the photographic material as disclosed, for instance, in Japanese Provisional Patent Publication No. 53(1978)-i 10,819, or a measure involving coating a carboxylated polyvinyl alcohol over the edge portion as disclosed, for instance, in Japanese Provisional Patent Publication No.

56(1981 )~14,235. However, even in such measures, the results are not satisfactory.

Accordingly, a principal object of the invention is to provide a photographic support which is free from edge soiling produced by permeation of a developing solution.

Other objects of the invention will be apparent from the content of the specification.

These objects are accomplished by the present invention residing in a photographic support comprising a paper sheet provided with a polyolefin coating layer on both surfaces thereof, at least one layer of the polyolefin coating layer containing a white pigment, in which the paper sheet is impregnated or coated with a mixture of 100 parts by weight of a carboxylated polyvinyl alcohol having maleic acid and/or itaconic acid comonomer component and 5-200 parts by weight of a divalent metallic salt, in which the mixture is employed in such an amount that not less than 0.5 g of the carboxylated polyvinyl alcohol is impregnated into or coated over 1 m2 of the paper sheet.

The photographic support of the present invention is, when employed in a photographic material, remarkably resistant to permeation of a developing solution from the cut edge portion. Moreover, the photographic support of the invention is improved in the surface strength. As for the photographic characteristics, the treatment of the paper sheet with the mixture of the carboxylated polyvinyl alcohol and the divalent metallic salt according to the present invention never gives adverse effect to a photographic material.

Preferred embodiments of the invention are now described hereinafter.

A photographic support of this invention has a basic structure comprising a paper sheet and a polyolefin coating layer provided on both surfaces thereof.

The paper sheet is prepared from materials which are generally employable for a photographic support. Examples of such materials include natural pulp paper, synthetic pulp paper, paper prepared from a mixture of natural pulp and synthetic pulp, and other various composite papers. The paper sheet is generally employed with the thickness of 30-500 Mm.

In the invention, the paper sheet is impregnated or coated with a mixture of 100 parts by weight of a carboxylated polyvinyl alcohol comprising maleic acid and/or itaconic acid comonomer component and 5-200 parts by weight of a divalent metallic salt, for instance, in the form of an aqueous solution.

Preferably employable is a carboxylated polyvinyl alcohol comprising maleic acid and/or itaconic acid comonomer component with the saponification degree of 90-98%, containing carboxyl groups of 1-20 mole %. The carboxylated polyvinyl alcohol preferably shows viscosity in the range of approximately 5-100 cPS when it is measured in the 5 wt. % aqueous solution. The polymerization degree of the carboxylated polyvinyl alcohol preferably ranges from about 1000 to about 3000, more preferably from about 1600 to about 1800.

The above-mentioned carboxylated polyvinyl alcohol comprising maleic acid and/or itaconic acid comonomer component is generally produced by (1) a process comprising saponifying a copolymer of maleic acid and/or itaconic acid and a vinyl monomer, or (2) a process comprising modifying polyvinyl alcohol with maleic acid and/or itaconic acid.

The process (1) comprising saponifying a copolymer of maleic acid and/or itaconic acid and a vinyl monomer is exemplified by a process comprising saponifying a copolymer which is prepared by the reaction between an ester of vinyl alcohol with a lower carboxylic acid such as vinyl acetate, vinyl formate and vinyl propionate, and a comonomer such as maleic anhydride, itaconic acid or maleic acid ester. As the vinyl monomer, there can be employed other vinyl compounds such as acrylamide, methacrylamide and methylol acrylamide in place of the ester of vinyl alcohol and a lower carboxylic acid.

In the process (2) comprising modifying polyvinyl alcohol with maleic acid and/or itaconic acid, the polyvinyl alcohol is esterified with a comonomer such as maleic acid or itaconic acid, or their anhydrides to introduce carboxyl groups into the polyvinyl alcohol.

Preferred examples of the divalent metallic salts employable in the invention include salts of cations such as alkaline earth metal, for instance, calcium and magnesium, and transition metals, for instance, zinc and nickel, and anions such as halogen ions, for instance, chlorine ion and sulfuric ion.

However, the employable divalent metallic salts are not restricted to these salts. Particularly preferred are calcium chloride and magnesium chloride.

In the invention, 5-200 parts by weight of the divalent metallic salt is added to 100 parts by weight of the carboxylated polyvinyl alcohol comprising maleic acid and/or itaconic acid comonomer component to prepare a mixture for the surface treatment. When the amount of the metallic salt is employed in an amount less than 5 parts by weight, it is difficult to effectively reduce the edge soiling of the photographic material. When the amount of the metallic salt exceeds 200 parts by weight, the surface strength of the paper sheet is not increased.

The mixture for the surface treatment according to the invention is, generally, prepared in the form of an aqueous solution, and the paper sheet is impregnated or coated therewith. Into the aqueous mixture so!ution for surface treatment, there may be incorporated various additives such as an antistatic agent (for instance, inorganic salts such as sodium sulfate and potassium chloride, or a surface active agent), a fluorescent dye, and a defoaming agent. Otherwise, these additives can be applied onto the paper sheet independently of the aqueous mixture solution described above.

The mixture for surface treatment is employed in such an amount that not less than 0.5 g (preferably, 5-30 g) of the carboxylated polyvinyl alcohol is impregnated into or coated over 1 m2 of the paper sheet When the amount of impregnation or coating is less than 0.5 g/m2, the surface strength of paper sheet cannot be increased to a satisfactory level. For carrying out the impregnating or coating of the paper sheet with the aqueous mixture solution, the qn-machine size pressing method or the on-machine tub sizing method is preferably employed. The coating can also be carried out using a bar, a photogravure, an air knife or the like in the off-machine method.

The paper sheet impregnated or coated with the mixture for surface treatment of the invention is then provided with polyolefin coating layers in a known way.

Examples of the polyolefins employable for preparing the polyolefin layers include homopolymers of ctcoiefins such as polyethylene and polypropylene, copolymers of these a-olefins, and mixtures thereof. Particularly preferred is polyethylene. There is no limitation on the molecular weight of the polyolefin, as far as the polyolefin can be coated by the extrusion coating procedure. However, a polyolefin with the molecular weight ranging from 20,000 to 200,000 is generally employed. There is no limitation on the thickness of the polyolefin coating layer, and the thickness thereof can be optionally set according to the thickness of the polyolefin layer of the conventional photographic support. The thickness generally ranges from 10 to 100 ,um, and preferably ranges from 15 to 50 ym.

It is known to incorporate a variety of additives such as a white pigment, a color pigment, a fluorescent whitening agent and an antioxidizing agent into the polyolefin to be coated on the paper sheet. These additives can be also incorporated into the polyolefin layer of the photographic support of the invention, and the additive is employed according to the purpose. The kinds, amount and manner of addition of the additives are described in detail, for instance, in publications such as United States Patents No. 3,833,380, No. 4,169,188, No. 3,501,298, No. 3,449,257, and No. 3,499,762. Otherwise, as described in United States Patent No. 3,884,692, the additives can be coated over the coated resin layer. The surface-activation treatment of the resin layer can be carried out, if necessary, as described in publications such as United States Patent No. 2,715,075, No.2,846,727, No. 3,549,406 and No.

3,590,107.

The photographic support of the invention can be coated with a photographic emulsion in a conventional manner to prepare a photographic material. The so-prepared photographic material can be developed and fixed in a conventional manner. The conventional manner is described in detail in published texts such as PHOTOGRAPHIC CHEMISTRY by Shin-ichi Kikuchi (published by Kyoritsu Syuppan, 1973) and THE THEORY OF THE PHOTOGRAPHIC PROCESS, 3rd ed. by C. E. K. Mees.

The present invention is now illustrated by the following examples, but these examples by no means restrict the invention.

EXAMPLES 1-3 AND COMPARISON EXAMPLES 1-3 (1) Preparation of Samples To a pulp slurry containing beaten wood pulp fibers (LBKP/NBKP = 1/1), a dilute aqueous solution containing sodium stearate and aluminum sulfate was added in such a manner that 5 parts by weight of sodium stearate and 10 parts by weight of aluminum sulfate were introduced into 100 parts by weight of dry wood pulp. The pulp slurry was then processed in a conventional way to give a paper sheet weighing 180 g/m2.

Separately, water was added to a mixture of 100 parts by weight of carboxylated polyvinyl alcohol comprising maleic anhydride comonomer component (PVA, saponification degree: 98%, carboxyl content: 2 mole %, viscosity: 68 cPS in 5% aqueous solution, polymerization degree: 1800) and calcium chloride in the amount set forth in Table 1 to make 2000 parts by weight of an aqueous solution for surface treatment. The so-prepared aqueous solution was coated on the paper sheet in such a manner that the carboxylated polyvinyl alcohol comprising maleic anhydride comonomer component was coated in the amount of 20 g/m2 through a test size-pressing machine (produced by Kumagai Riki Co., Ltd., Japan).

One surface of the so treated paper sheet was provided with a polyethylene coating layer (density: approximately 0.965 g/cm3) with the thickness of about 0.030 mm. On another surface of the paper sheet a polyethylene coating layer containing 5 parts by weight of titanium dioxide (density: approximately 1.03 g/cm3) with the thickness of about 0.035 mm was placed, and then a color photographic emulsion was coated thereon to prepare a photographic material.

(2) Evaluation of Samples The edge soiling liability of the photographic material was evaluated by the following procedure.

The photographic material was cut to produce a test strip of 8.25 cm wide. The test strip was then developed in a color paper automatic development apparatus (RPV-409 type; produced by Nohritsu Koki Co., Ltd., Japan), and subjected to eye measurement through a loupe of the depth of developing solution permeation from the cut edge.

The surface strength of the paper sheet was measured by the paper wax-pick test (according to TAPPI standard T-459 su-65) in advance of the provision of the polyethylene coating layer.

The results are set forth in Table 1.

TABLE 1 Depth of Developing Surface Strength PVA/Calcium Solution Permeation of Paper Sheet Chloride (mm) (A) S#xample 1 5/0.25 0.1 14 2 5/5 0 14 3 3/10 0 14 Comparison Example 1 0/5 0.9 6 2 5/0 1.1 12 3 5/12 0.1 9 Note: Comparison Example 1 shows the result on the paper sheet treated with calcium chloride only.

EXAMPLES 4-6 AND COMPARISON EXAMPLES 4-6 The preparation and evaluation of the samples were carried out in the same manner as in Example 1 except that carboxylated polyvinyl alcohol comprising itaconic acid comonomer component (PVA, saponification degree: 98%, carboxyl content: 2 mole %, viscosity: 68 cPS in 5% aqueous solution, polymerization degree: 1 800) was employed in place of the carboxylated polyvinyl alcohol comprising maleic anhydride comonomer component.

The results are set forth in Table 2.

TABLE 2 Depth of Developing Surface Strength PVA/Calcium Solution Permeation of Paper Sheet Chloride (mm) (A) Example 4 5/0.25 0.1 14 5 5/5 0 14 6 5/10 0 14 Comparison Example 4 0/5 0.9 6 5 5/0 1.0 12 6 5/12 0.3 9 Note: Comparison Example 4 is the same as Comparison Example 1.

EXAMPLES 7-9 AND COMPARISON EXAMPLES 7-9 The preparation and evaluation of the samples were carried out in the same manner as in Example 1 except that the paper sheet was prepared to have the basis weight of 1 55 g/m2 and that the carboxylated polyvinyl alcohol comprising maleic anhydride comonomer component was coated on the paper sheet in the amount of 15 g/m2. The carboxylated polyvinyl alcohol employed has saponification degree of 94%, carboxyl content of 6 mole %, viscosity: 50 cPS in 5% aqueous solution and polymerization degree of 1700.

The results are set forth in Table 3.

TABLE 3 Depth of Developing Surface Strength PVA/Calcium Solution Permeation of Paper Sheet Chloride (mm) (A) Example 7 10/0.5 0 14 8 10/10 0 16 9 10/20 0 16 Comparison Example 7 0/10 0.9 6 8 10/0 1.0 12 9 10/25 0.3 8 Note: Comparison Example 7 shows the result on the paper sheet treated with calcium chloride only.

EXAMPLES 10-12 AND COMPARISON EXAMPLES 10-12 The preparation and evaluation of the samples were carried out in the same manner as in Example 1 except that carboxylated polyvinyl alcohol comprising itaconic acid comonomer component (PVA, saponification degree: 94%, carboxyl content: 6 mole %, viscosity: 50 cPS in 5% aqueous solution, polymerization degree: 1700) was employed in place of the carboxylated polyvinyl alcohol comprising maleic anhydride comonomer component.

The results are set forth in Table 4.

TABLE 4 Depth of Developing Surface Strength PVA/Calcium Solution Permeation of Paper Sheet Chloride (mm) (A) Example 10 10/0.5 0 14 11 10/10 0 14 12 10/20 0 16 Comparison Example 10 0/10 0.9 6 11 10/0 1.0 12 12 10/25 0.8 8 Note: Comparison Example 10 is the same as Comparison Example 7.

Claims

1. A photographic support comprising a paper sheet provided with a polyolefin coating layer on both surfaces thereof, at least one of said polyolefin coating layer containing white pigment, in which said paper sheet is impregnated or coated with a mixture of 100 parts by weight of a carboxylated polyvinyl alcohol comprising maleic acid and/or itaconic acid comonomer component and 5-200 parts by weight of a divalent metallic salt in which the mixture is employed in such an amount that not less than 0.5 g of the carboxylated polyvinyl alcohol is impregnated into or coated over 1 m2 of the paper sheet.

2. The photographic support as claimed in Claim 1, in which the mixture of the carboxylated polyvinyl alcohol and the divalent metallic salt is employed in such an amount that 5-30 g of the carboxylated polyvinyl alcohol is impregnated into or coated over 1 m2 of the paper sheet.

3. The photographic support as claimed in Claim 1, in which the carboxylated polyvinyl alcohol has the saponification degree of 90~98% and contains 1-20 mole % of carboxyl groups.

4. The photographic support as claimed in Claim 1, in which the carboxylated polyvinyl alcohol has the viscosity of 5-1 00 cPS in 5% by weight aqueous solution.

5. The photographic support as claimed in Claim 1, in which the carboxylated polyvinyl alcohol has the polymerization degree of 1000-3000.

6. The photographic support as claimed in Claim 1, in which the carboxylated polyvinyl alcohol has the polymerization degree of 1600--1800.

7. The photographic support as claimed in Claim 1, in which the divalent metallic salt is selected from the group consisting of alkaline earth metal halides and transition metal halides.

8. The photographic support as claimed in Claim 1, in which the divalent metallic salt is calcium chloride or magnesium chloride.