JPH01251029A - Supporting body for photographic printing paper - Google Patents

Abstract

PURPOSE:To easily make removable a coated layer composed of a polyolefin positioned on the rear of the supporting body from the photographic printing paper by controlling the mean permeating depth of polyvinyl alcohol or its modified compd. positioned on the rear of an original paper in the inside of the original paper to 5-25mu. CONSTITUTION:The supporting body is obtd. by applying the polyvinyl alcohol or its modified compd. on the both surfaces of the original paper, and in this case, the modified compd. of the polyvinyl alcohol is exemplified by a polyvinyl alcohol compd. modified with carboxyl group, a polyvinyl alcohol compd. modified with a silanol or a copolymer of polyvinyl alcohol and acrylamide, etc. In this case, the mean permeating depth of the polyvinyl alcohol or its modified compd. positioned on the rear of the original paper within the original paper is <=25mu, more preferably, 5-20mu. Accordingly, the amount of an original paper pulp which is interacted with the polyvinyl alcohol or its modified compd. by allowing the original paper pulp to contact with the polyvinyl alcohol or its modified compd. is small. Thus, the polyolefin coated layer positioned on the rear of the supporting body for the photographic printing paper can be easily removable.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a support for photographic paper, and more specifically,
This invention relates to a support for photographic paper that is pasted on a panel.

(Prior Art) In recent years, for the purpose of rapid development of photographic paper, water-resistant photographic paper supports in which both sides of the paper are coated with polyolefin such as polyethylene have been preferably used. Among these, glossy photographic paper having a smooth surface of the polyolefin coating layer on the front side, that is, the side to which the photographic emulsion is coated, is preferably used.

In addition, various film-forming polymers are applied to the surface of the base paper for surface size treatment such as increasing the surface strength of the base paper, which is the base material of the polyolefin-coated waterproof support. For example, when starch is used, dot-like blisters are likely to occur due to glabella peeling on the surface of the base paper during polyolefin extrusion coating, and
During the development process, there is a lot of staining of the developer from the cut cross section, making it difficult to obtain excellent photographic paper, so polyvinyl alcohol and its modified products, which have excellent film properties, are often used. In this way, when polyvinyl alcohol and its modified products are used, the surface softening performance is good,
It is known that a support for photographic paper with excellent gloss and smoothness can be obtained.

(Problems to be Solved by the Invention) As described above, after applying polyvinyl alcohol or a modified product thereof to both sides of the base paper, a polyolefin coating layer is laminated, and in particular, a white pigment is contained in the polyolefin coating layer on the front side. The photographic paper obtained by coating the surface of the photographic paper support with a photographic emulsion has excellent surface size processing performance and is suitable for obtaining photographs with good gloss and smoothness through rapid development processing. However, when pasting photographs obtained using such photographic paper onto panels, the adhesive does not adhere well to the polyolefin coating layer when pasting the adhesive on the back of the photographic paper and pasting it onto the panel board. There has been a problem that peeling occurs immediately after wearing or over time. Therefore, conventional practice has been to peel off the polyolefin coating layer on the back side and apply water and glue to the exposed base paper to attach it to the panel board, but in this case, the polyolefin coating layer is difficult to peel off, so the polyolefin coating layer When peeling off the paper, the base paper is torn and the exposed surface of the base paper becomes uneven, so if you apply water and glue to this surface and stick it to a panel board, a pattern-like shadow will appear on the photo surface that follows the unevenness of the base paper. There was a drawback that a good panel could not be obtained due to the following problems.

As a result of intensive studies to solve these conventional drawbacks, the inventors of the present invention have found that by adjusting the amount of polyvinyl alcohol or its modified product applied to the back side of the base paper, the peeling of the polyolefin coating layer on the back side of the panel board can be prevented. The present invention has been achieved based on the discovery that this can be carried out conveniently.

Therefore, an object of the present invention is to provide a support for photographic paper that enables the production of good panel photographs.

(Means for Solving the Problems) The above-mentioned object of the present invention is to provide a base paper coated with polyvinyl alcohol or a modified product thereof on both sides, and then a polyolefin-coated rN layer laminated thereon, and a polyolefin-coated layer on the front surface. A support for photographic paper whose layer contains a white pigment, characterized in that the average penetration depth of polyvinyl alcohol or its modified substance on the back side of the base paper into the inside of the base paper is 5 to 25μ. achieved.

The present invention will be explained in more detail below.

The base paper used in the support for photographic paper according to the present invention is selected from materials commonly used for photographic paper. That is,
The main raw material is natural pulp selected from conifers, hardwoods, etc., and if necessary, fillers such as clay, talc, calcium carbonate, urea resin fine particles, rosin, alkyl ketene dimer, higher fatty acids, paraffin wax, alkenyl succinic acid, etc. paper strength agents such as polyacrylamide,
Those to which fixing agents such as sulfuric acid and cationic polymers are added are used. Furthermore, a synthetic pulp may be used in place of the above-mentioned natural pulp, or a mixture of natural pulp and synthetic pulp in an arbitrary ratio may be used.

The photographic paper support of the present invention is prepared by coating both sides of base paper with polyvinyl alcohol or a modified product thereof. Examples of polyvinyl alcohol modified products in this case include carboxyl group modified products, silanol modified products, and copolymers with acrylamide.

The support for photographic paper of the present invention has an average penetration depth of polyvinyl alcohol or its modified substance on the back side of the base paper into the inside of the base paper of 25 μm or less, and preferably 5 μm to 20 μm.

(Function) If the average penetration depth of the polyvinyl alcohol or its modified substance applied to the back side of the base paper into the inside of the base paper is less than 5 μm, there will be problems such as a lot of developer solution staining from the cut cross section during development processing. Moreover, if it exceeds 25μ, the above-mentioned problems will occur and a good panel cannot be obtained, making it impossible to achieve the object of the present invention.

On the other hand, when the average penetration depth of polyvinyl alcohol or its modified product into the base paper is in the range of 5 to 25 μm, the amount of base paper pulp that comes into contact with polyvinyl alcohol or its modified product and is affected by its action is small. Therefore, the polyolefin coating layer on the back side of the photographic paper support can be easily peeled off, and the polyolefin-covered F'i! R peels off along with polyvinyl alcohol or a modified product thereof and a small amount of the base paper layer on the back side of the base paper that is affected by this. Therefore, on the back side of the photographic paper support, there will be no unevenness that would impair the beauty of the photograph after the panel is made, and since the pulp fibers of the base paper are exposed, water and glue will adhere well to it. A good panel can be manufactured by peeling off the polyolefin coating layer on the back side and applying glue.

Here, if the average penetration depth into the base paper of polyvinyl alcohol or its modified substance applied to both sides of the base paper is that the penetration depth on the front side is the same as or less than the penetration depth on the back side, The effect of improving the strength between the base paper layers close to the base paper surface will be reduced, and the surface of the base paper will peel off between the eyebrows during polyolefin extrusion coating, causing dotted blisters, and the smoothness of the surface of the water-resistant support will decrease, reducing its commercial value as a glossy photographic paper. There is a problem that will disappear. In order to avoid such inconvenience, the ratio of front side penetration depth/back side penetration depth is 1.5/
It is preferable that the ratio is 1 or more, thereby more reliably forming a glossy photographic paper with excellent smoothness and a back surface suitable for producing the above-mentioned panels, with few irregularities and good adhesion of water and glue. be able to.

Polyvinyl alcohol or a modified product thereof is dissolved in one or two mixed solvents selected from water, alcohols such as methanol and ethanol, and further added with an antistatic agent and a fluorescent whitening agent as necessary. The solution obtained by adding pigments, antifoaming agents, etc. is processed using a gate roller, blade coater,
It can be applied to both sides of the base paper sequentially or simultaneously by various coating methods such as a bar coater, blade size press, spray, etc., and then it penetrates into the base paper during drying and desolvation.

In addition, when applying with a surface size press, it is difficult to vary the penetration depth of polyvinyl alcohol or its modified product into the inside of the base paper on both sides of the base paper. In comparison, it is not possible to obtain a support for photographic paper suitable for the present invention which penetrates more into the front surface.

The penetration depth of polyvinyl alcohol or its modified product can be changed by the ratio of the solvent in the solution containing the polyvinyl alcohol, f6I & viscosity, coating conditions such as nip pressure during coating, drying speed, etc.

In addition, base paper is made by making a pulp slurry containing the above-mentioned pulp and additives such as fillers, sizing agents, paper strength reinforcing agents, and fixing agents as necessary using a paper machine such as a Fourdrinier paper machine, and then drying the pulp slurry. It is then rolled up and manufactured. Either before or after this drying, coating and drying of the polyvinyl alcohol or its modified product is performed, and calendering is performed after drying and during winding, resulting in a final basis weight of 80 to 200 g/
m2, and the thickness is adjusted to 80 to 230 μm.

The support for photographic paper of the present invention is obtained by coating both sides of the base paper with polyolefin and containing a white pigment in the polyolefin coating layer on the front side, that is, the side to which the photographic emulsion is applied.

Examples of the polyolefin resin include homopolymers of α-olefins such as polyethylene and polypropylene, and mixtures of these various polymers. Particularly preferred polyolefins are high density polyethylene, low density polyethylene and mixtures thereof. There is no particular restriction on the molecular weight of these polyolefins as long as they can be extrusion coated, but polyolefins having a molecular weight in the range of 20,000 to 200,000 are usually used.

There is no particular restriction on the thickness of the polyolefin coating layer, and it can be determined according to the thickness of the polyolefin coating 5 for conventional photographic paper supports, but it is usually 15 to 50 μm.
is suitable.

The polyolefin coating layer on the front surface, that is, the side to which the photographic emulsion is coated, contains a white pigment, and the type and amount of this white pigment, such as titanium oxide pigment containing 5 to 20% by weight, etc. It is possible to appropriately select and employ known techniques, and further to add known additives such as fluorescent brighteners and antioxidants. Further, the polyolefin coating layer on the back surface may be composed only of the polyolefin resin, and may further include a colored pigment or a white pigment, and the same additives as the polyolefin coating layer on the front surface. You can also do it.

Incidentally, as extrusion coating equipment for extrusion coating polyolefin, a normal extruder and laminator for polyolefin are used.

(Effects of the Invention) As described in detail above, according to the present invention, the polyolefin coating layer on the back side can be easily peeled off from the photographic paper, and when the polyolefin coating layer on the back side is peeled off, the base paper Since the polyolefin coating layer can be peeled off along with a small amount of the base paper layer on the back side, there will be no unevenness that would impair the aesthetic appearance of the photograph after the panel is produced. Also, since the pulp fibers of the base paper are exposed, water and glue adhere well to it.
It is possible to provide a support for photographic paper that has been pasted onto a photographic panel, and therefore a good photographic panel can be prepared by peeling off the polyolefin coating layer on the back side and applying water and glue.

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these Examples.

[Examples 1 to 3, Comparative Example 1] Wood pulp consisting of 80% LBKP and 20% LBSP was beaten using a disc refiner and adjusted to Canadian freeness 250cc, and then stearin was added to this pulp slurry. Sodium acid, anionic polyacrylamide, and aluminum sulfate were added at 1.5%, 0.5%, and 1.0%, respectively, based on the bone dry pulp weight, and paper was made using a fourdrinier machine, dried, and calendered. . The basis weight of the base paper was 170 g/m2, and a base paper with a thickness of 165 um was obtained.

In addition, PV is applied to both sides of the base paper between the paper machine and the drying zone.
A-110 (polyvinyl alcohol manufactured by Kuraray Co., Ltd.) was applied with a gate roller while adjusting the concentration, gate roller nip pressure, and rotation speed so that it penetrated into the base paper to the depths shown in Table 1.

After that, this base paper was run at a speed of 50 m/min, and high-density polyethylene (density 0.960 g/cm3, MI = 13 g/10 min) was melted on the back side of the base paper using a melt extruder to a resin thickness of 30 μm. A resin layer with a matte surface was formed by extrusion coating.

The average penetration depth of this polyvinyl alcohol into the base paper can be determined by coloring the PVA in the base paper with an iodine/boric acid solution and using a cross-sectional photograph of a base paper sample obtained by magnifying the base paper at 100x magnification using a microscope. It was determined by measurement.

Next, low-density polyethylene containing 10% by weight of anatase titanium dioxide (density 0.923 g/cm3, MI = 7 g/10 min) was applied to the front surface of the base paper using a melt extruder.
was applied by melt extrusion to a resin thickness of 30 μm to form a resin layer having a glossy surface, thereby producing supports for photographic paper in Examples 1 to 3 and Comparative Example 1.

Using each of the obtained supports for photographic printing paper, photographic paper was prepared by coating with ordinary gelatin and silver halide photographic emulsion, exposed and developed, and the glossiness and smoothness of the photographic paper screen were evaluated. was visually evaluated. In addition, the polyolefin coating layer on the back side of the photographic paper was peeled off, and the degree of peeling, peel strength, and amount of change in thickness of the back side layer of the base paper that adhered to and peeled off from the back side polyolefin coating layer at the time of peeling were measured. The unevenness of the surface was observed as an appearance of the panel after being attached to the board.

As a result, differences were observed in the smoothness of the glossy photographic paper, the removability of the back polyolefin coating layer during the production of panel photographs, and the appearance of panel photographs, and the results are also listed in Table 1.

"Bud" - Table The peelability evaluation in Table 1 above was performed based on the following evaluation criteria.

Good: The polyolefin coating layer on the back side can always be peeled off with good peelability with only a slight amount of base paper attached.

Δ: There are cases where the polyolefin coating layer on the back side can be peeled off with only a slight amount of base paper attached, and cases where it cannot be removed.

×... It is difficult to peel off the polyolefin flit on the back side even if it is slightly attached to the base paper, and strong force is required to peel it off.

In addition, the appearance evaluation of the panel photographs was performed based on the following evaluation criteria.

0: The photographic surface of the panel is smooth and beautiful, with no unevenness caused by peeling of the back surface.

Δ...Although there are some irregularities due to peeling on the back surface in the panel photograph, they are not noticeable and are acceptable when observed from a distance.

×: The unevenness of the panel photo due to peeling on the back surface is noticeable even from a distance, and the appearance is poor and there is no commercial value.

Furthermore, the smoothness of the glossy photographic paper was evaluated using the following evaluation criteria.

○: The surface has shallow fine irregularities and is smooth and almost mirror-like.

△: The surface is deeply uneven and has a cloak-like appearance, and has low commercial value as a glossy photographic paper.

Claims (1)

[Scope of Claims] 1) A support for photographic paper, in which both sides of a base paper are coated with polyvinyl alcohol or a modified product thereof, and a polyolefin coating layer is laminated thereon, and the polyolefin coating layer on the front side contains a white pigment. In the body, the average penetration depth of polyvinyl alcohol or its modified substance on the back side of the base paper into the inside of the base paper is 5.
A support for photographic paper, characterized in that it has a thickness of ~25μ. 2) The average penetration depth of polyvinyl alcohol or its modified product is front side penetration depth / back side penetration depth = 1.5 /
The support for photographic paper according to claim 1, wherein the ratio is 1 or more.