JPH0380292B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to silver halide photographic materials, and more particularly to a method for improving the surface gloss of photographic paper. Photographic paper consists of an opaque support made of paper, baryta paper, polymer-laminated paper, polymer film with an opaque layer, etc., and at least one light-sensitive emulsion layer, a surface protective layer, and, if necessary, a surface protection layer. , an intermediate layer, a filter layer, an undercoat layer, and a backing layer. Since the photographic image formed on the support of photographic paper is observed using reflected light, the quality of the image is greatly influenced by the reflection density of the image. As one means for increasing the reflection density of photographic paper, efforts have been made to increase the surface gloss of photographic paper. For example, a baryta layer, a polymer laminate layer, etc. is provided on the surface of the support, and then a photosensitive emulsion layer is applied thereon to improve the smoothness of the surface of photographic paper, thereby preventing scattering of incident light. , by increasing the surface gloss, or by drying the surface of the photographic paper after the development process by bringing it into contact with a heated metal plate (so-called ferro type), which has a mirror surface. Conventionally, methods of increasing surface gloss by so-called ferrotype coating and methods of combining both methods have been well known. In recent years, photographic paper has become thinner as an energy-saving material, and as supports have become thinner, the light-sensitive emulsion layer, surface protection layer, and other layers coated on the support have been made to withstand high humidity or low humidity. At such times, thinning of the protective layer results in a reduction in surface gloss, where thinning is required due to increased curl. Furthermore, in recent years there has been a demand for faster processing of phenomena.
For this reason, it is necessary to make the coating layer thinner, and maintaining and improving surface gloss has become an extremely important issue from that point of view as well. Japanese Patent Publication No. 56-24253 discloses a technique using lime-treated gelatin with a Delhi strength of 300 g as the top layer, but as the top layer becomes thinner, its effect decreases, resulting in a decrease in gloss and an accompanying decrease in density. This leads to a decline in the commercial value of photographic paper. on the other hand,
In Japanese Patent Publication No. 57-10416, there is a technology in which colloidal silica is contained in the top layer and vinyl polymer is contained in the emulsion layer, but this technique cannot be expected to produce much gloss, and as the top layer becomes thinner, The effect is less, and furthermore, if colloidal silica is added to the top layer, the gloss of the white background of the photographic image decreases, making it undesirable for photographic paper. SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a method for increasing the surface gloss of photographic paper.
Another object of the present invention is to provide photographic paper with increased surface gloss and high reflection density. The object of the present invention can be achieved by incorporating lime-treated ossein gelatin having a jelly strength of 300 g or more and desalted to a calcium content of 1000 PPM or less in the top layer of a silver halide photographic material. I found it. The jelly used in the present invention has a strength of 300 g or more,
Moreover, lime-processed ossein gelatin with a calcium content of 1000 PPM or less has a jelly strength of 300 g.
The above represents the jelly strength measured by the PAGIMETHOD method described in the Photographic Gelatin Test Method (1970 Photographic Gelatin Test Method Joint Council Luminescence), page 5, and the photographic chemistry (1968) published by Kyoritsu Shuppansha. It is distinguished from the jelly strength described in Shinichi Kikuchi (written by Shinichi Kikuchi), page 215. Generally, gelatin is manufactured by solubilizing collagen, the main component of animal skin and bones, in hot water, but it is difficult to extract the raw material immediately into hot water, After treatment with dilute hydrochloric acid, collagen is partially hydrolyzed in advance by pretreatment of soaking it in milk of lime for 1 to 3 months, that is, a long-term pretreatment called lime pickling.
A common method is to extract it after that. Of course, the gelatin of the present invention can also be obtained by such a method. The gelatin according to the present invention is made from bovine bones, and most of the inorganic content, which accounts for more than half of the bovine bones, is calcium phosphate. When this is converted into soluble calcium dihydrogen phosphate and eluted with dilute hydrochloric acid, a substance called ossein whose main component is insoluble collagen remains. Since ossein is partially hydrolyzed by acid and lost, hydrochloric acid treatment is carried out under efficient conditions, and long-term treatment to completely remove calcium phosphate is optimal because the necessary hydrolysis of ossein proceeds. Processing is being carried out locally. For example, the optimum temperature is 5% hydrochloric acid.
Processing is performed at around 15°C for about 4 to 7 days. After the above-mentioned liming treatment, the first extraction (first extraction) of the several extractions is the one with high physical properties and jelly strength of 300 or more. Such a treatment method is known, for example, from JP-A No. 53-9518 filed by the applicant, but even in this case, calcium and other inorganic salts are present at a fairly high concentration in gelatin extracted after lime treatment. For example, if we focus on calcium, commercially available photographic gelatin contains
Contains 2000PPM to 6000PPM calcium. The present inventors have continued intensive research using gelatin that excludes these calcium salts and other inorganic salts, and as a result, we have found that gelatin with a jelly strength of 300 g or more and a calcium content of 1000 PPM or less is contained in the top layer of a photographic material. discovered a new fact that surface gloss is significantly improved by
This led to the present invention. The silver halide photographic material of the present invention has a jelly strength of 300 g or more in the top layer and a calcium content.
1000PPM or more (preferably 500PPM or less),
For example, it is characterized by containing lime-treated ossein gelatin that has been desalted by a commonly used method using an ion exchange resin. The dry thickness of the top layer is preferably in the range of 0.2 μm to 5 μm, particularly preferably in the range of 0.3 μm to 3 μm. The silver halide photographic material of the present invention is characterized in that the top layer contains lime-treated ossein gelatin having a jelly strength of 300 g or more and a calcium content of 1000 PPM or less. Gelatin may be used alone, or gelatin other than the lime-treated ossein gelatin may be used in combination to the extent possible. Preferably, the lime-treated ossein gelatin is contained in an amount of 60% or more. In addition, gelatin derivatives, oxygen-treated gelatin, hydrophilic synthetic polymer substances (e.g. vinyl polymers, styrene, maleic anhydride copolymers, styrene, condensates of maleic anhydride and polyvinyl alcohol, styrene/maleic acid copolymers) copolymers or blend compositions of acrylamide, acrylic acid copolymers, etc.), natural polymeric substances (e.g. colloidal albumin, casein, cellulose derivatives,
In addition to new aqueous binders such as agar, sodium alginate, dextran, gum arabic, starch derivatives, etc., craft polymers of gelatin and acrylic acid in JP-A-50-11023, and colloidal silica in JP-A-57-10416. It may also include. As a method for lowering the calcium concentration of the lime-treated ossein gelatin, there is a method of using an ion exchange resin. The ossein gelatin used in the present invention is preferably typified by Nitta Gelatin's P2275 type, but is not particularly limited thereto. The uppermost layer containing lime-treated ossein gelatin according to the present invention preferably contains an appropriate amount of hardening agent and surfactant. Specific examples of hardening agents include:
Aldehyde compounds such as formaldehyde and glutaraldehyde, ketone compounds such as diacetyl and cyclopendione, bis(2-chloroethylurea)-2-hydroxy-4,6-dichloro-
1.3.5 triazines, reactive halogen-containing compounds as described in U.S. Pat. No. 3,635,718, divinyl sulfone, reactive olefin compounds as described in U.S. Pat. No. 3,635,718, N-methylol as described in U.S. Pat. No. 2,732,316. Compound, U.S. Patent No.
Isocyanates as described in US Pat. No. 3,017,280, aziridyl compounds as described in US Pat. No. 2,983,611, carbodiside compounds as described in US Pat. No. 3,100,704, US Pat.
There are epoxy compounds as described in the above issue, halogencarboxaldehydes such as mucochromic acid, dioxane derivatives such as dihydroxydioxane, inorganic hardeners such as chromium alum, potassium alum, and zirconium sulfate. The above can be used in combination. Specific examples of surfactants include natural surfactants such as saponin,
Nonionic surfactants such as alkylene oxide, glycerin, and glycidol, higher alkylamines, quaternary ammonium salts, pyridine,
Other heterocycles, cationic surfactants such as sulfoniums, anionic surfactants containing acidic groups such as carboxylic acids, phosphoric acids, sulfuric ester groups, phosphoric ester groups, amino acids, aminosulfonic acids, sulfuric acid of aminoalcohols, or There are amphoteric surfactants such as phosphoric acid esters, and these can be used alone or in combination of two or more. The silver halide emulsion used in the practice of the present invention can be prepared by a known or commonly used method. silver, silver chlorobromide, etc.), the size and crystal habit of silver halide grains, the ratio of silver halide to gelatin, the PH and PAg of silver halide emulsions, the type and amount of chemical sensitizers, Kupler, high boiling point solvents, There are no limitations on the types and amounts of other additives, gelatin, and other binders. Examples of the support used in the silver halide photographic material of the present invention include paper laminated with baryta or polyolefin resin, a transparent film made opaque by adding a pigment such as titanium oxide, and a transparent film made opaque by adding a pigment such as titanium oxide. Examples include various films such as tate film, polystyrene film, polyethylene terephthalate film, and polycarbonate film. The present invention will be explained in detail below using examples, but the present invention is not limited to these embodiments. Example 1 Silver chlorobromide (Br:Cl=
60:40) as silver on corona discharge machined double-sided polyethylene laminated paper (glossy side) support.
It was coated simultaneously with a protective layer (gelatin 1.4 g/ ^{m 2} ) using a slide hopper type extrusion coater so that the gelatin concentration was 1.4 g/m 2 and gelatin 3.5 g/m ² . The protective layer has a jelly strength of 310g and calcium content made from cow bone ossein by lime treatment.
260PPM gelatin (made by Nitta Gelatin, P2275)
Sample A consisting of gelatin with a jelly strength of 310 g and a calcium content of 4080 PPM,
Sample C consisting of gelatin with a jelly strength of 230 g and a calcium content of 400 PPM, and a further jelly strength of 220
A sample consisting of lime-processed gelatin with a calcium content of 4100 PPM in 100 g was designated as D. Above A, B, C,
Table 1 shows the surface gloss of each sample of D. These values were measured after each sample was subjected to normal photographic processing and left to dry naturally. The surface gloss value here was measured using a VG-ID type gloss meter (gloss meter) manufactured by Nippon Denshoku Kogyo Co., Ltd. at an incident angle of 60° and a light receiving angle of 60°. At the same time, their maximum reflection densities are shown in the same first table.
Here, the measured value of reflection density is based on the method described in JISM7611.

[Table] Jelly strength 300g by comparing D and B
It can be seen that the above gelatin increases the surface gloss only slightly. Also, by comparing D and C, the calcium content should be reduced (1000PPM).
(below) shows that the surface gloss increases only slightly. On the other hand, it is clear that in A, that is, the sample of the present invention, a remarkable surface gloss improvement effect greater than that obtained by simply adding the effects of B and C is obtained. Furthermore, it can be seen that Sample A is the most effective for obtaining high values of reflection density as well as gloss compared to any of B, C, and D. Example 2 Samples E, F, using the same silver halide emulsion layer and the same gelatin as A, BC, and D of Example 1, but having the top layer with the gelatin coverage changed to 0.8 g/ ^m2 , I made G and H. Table 2 shows their surface gloss and maximum reflection density. However, the measurement method is the same as in Example 1.

[Table] In this case, as in Example 1, it is clear that the method of the present invention provides an unexpectedly significant surface gloss improvement effect, and even when the top layer is made thinner than in Example 1. It is clear that the decrease in surface gloss and reflection density is small, and it can be seen that the gloss is further improved by the lime-treated ossein gelatin protective layer used in the present invention.

Claims (1)

[Claims] 1 Jelly strength 300g or more (according to Paggy method measurement)
Moreover, the silver halide photographic material is characterized in that the uppermost layer contains a lime-treated ossein gelatin layer that has been desalted to have a calcium content of 1000 PPM or less.