JPH05150397A - Photographic support - Google Patents

Abstract

PURPOSE:To obtain the photographic support having strong curl on the reverse side of its support side without increasing an polyolefin resin and a high-density polyethylene resin on the reverse side. CONSTITUTION:This photographic support is formed by sizing only the surface of the reverse side of raw paper base with one or a combination of >=2 selected from a group of polyvinyl alcohol derivative and polyacryamide and gelatin, thus permitting the obtained photographic support to have strong curl on the reverse side without increasing the resin and the high-density polyethylene resin on the reverse side.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photographic support having a substrate made of paper and coated on both sides with a polyolefin resin, and more particularly to a photographic support curled on the back side.

[0002]

2. Description of the Related Art Conventionally, as a photographic support, so-called baryta paper has been used in which a baryta layer mainly composed of barium sulfate is coated on one side of the paper. Recently, the development process is automated and accelerated. For this reason, waterproof photographic printing paper, in which both sides of the base paper are coated with a hydrophobic resin, has come to be used, and nowadays, it has come to occupy most of photographic supports.

Originally, the photographic polyolefin resin-coated paper was required not to curl after the emulsion was coated, but since gelatin is used in the emulsion, it may curl to the emulsion side of the photographic emulsion to reduce the flatness. It is necessary to curl the back side of the photographic support so as not to curl after coating the emulsion.
As a method of curling the back side of a photographic support, a method of using a high-density polyolefin resin for the back side polyolefin resin has been proposed. Further, a method is known in which the coating amount of the polyolefin resin on the back side of the emulsion coating is increased.
However, in these methods, the polyolefin resin melt-extruded from the extruder causes a greater neck-in in the high-density polyethylene, which is disadvantageous in the process, and the cost is increased by using the high-density polyethylene. Further, by increasing the coating amount of the polyolefin resin on the back side of the emulsion, the cost is increased and the cooling of the resin is deteriorated, so that it is necessary to greatly reduce the coating speed.

[0004]

SUMMARY OF THE INVENTION In order to obtain a photographic printing paper having high flatness after emulsion coating, the present invention does not increase the polyolefin resin on the back surface side and does not increase the high density polyethylene on the back surface side. The aim is to provide a photographic support having a high degree of curl on the back side.

[0005]

DISCLOSURE OF THE INVENTION As a result of intensive research conducted by the present inventors in order to obtain a photographic printing paper having a high flatness, a high-density polyethylene can be provided on the back side without increasing the polyolefin resin on the back side. The present invention has been completed by finding a method for producing a photographic support having a high degree of curl on the back side without increasing the amount.

That is, the photographic support is characterized in that the back surface of the base paper is coated with a water-soluble resin having a number average molecular weight (Mn) of 30,000 to 300,000 by an osmotic pressure method. The present invention will be described in detail below. Water-soluble resins that can be used in the present application include polyvinyl alcohol, polyvinyl compounds, gelatin, polyacrylamide and the like. The molecular weight of these water-soluble resins is 3
It is preferably from 30,000 to 300,000. Molecular weight is 3
If it is less than 10,000, the back surface curls, but there is little effect and little improvement. Further, when the molecular weight is 300,000 or more, the effect of curling on the back surface is greatly improved, but the viscosity of the coating solution is increased, the workability such as dissolution and liquid feeding is deteriorated, and the uniformity of coating is lost. is not. The coating amount of these water-soluble resins is 0.5 to 5.0 g / m in terms of solid content.
² is preferred. If the solid content is 0.5 g / m ² or less, the back surface curling effect is small. On the other hand, if the solid content is 5.0 g / m ² or more, drying becomes uneven, which causes wrinkles, which is not preferable. Further, these water-soluble resins may be used alone or in combination of two or more kinds of soluble resins. Alternatively, salt, sodium sulfate for coloring, dye or pigment for coloring may be added. These water-soluble resins are applied to the paper prepared by a usual papermaking method, but the application method is not particularly limited as long as the object of the present invention can be achieved.

[0007]

[Function] In order to obtain a photographic support having a high degree of curl without increasing the amount of polyolefin resin on the back side and increasing the amount of high-density polyethylene on the back side, only one side is sized on the back side. It can be obtained. The reason therefor cannot be fully explained, but it is considered that when polyvinyl alcohol and polyacrylamide are applied, they shrink and curl the paper to the back side. The present invention will be described in detail below with reference to examples.

[0008]

EXAMPLE A 1: 1 mixture of hardwood kraft pulp (LBKP) and softwood bleached sulfite pulp (LBSP) was beaten to 300 ml with Canadian standard freeness to prepare a pulp slurry. Alkyl ketene dimer as a sizing agent was added to the pulp in an amount of 0.5% by weight, and polyacrylamide as a strength agent was added to the pulp.
0% by weight, cationized starch to 2.0% by weight of pulp and polyamide epichlorohydrin to 0.5% by weight of pulp were added to form a web. A 3% by weight aqueous solution of carboxyl-modified polyvinyl alcohol having a number average molecular weight (Mn) as shown in Table 1 was applied to the paper sheet obtained as described above by a bar coating method to obtain 1.0 g / m ² as a solid content of the emulsion. One side of the base paper opposite to the side to be coated was applied to obtain a base paper for a photographic support.

Further, as shown in Table 2, the number average molecular weight (Mn) 1
3 of 0,000 carboxyl-modified vinyl alcohol
A weight% aqueous solution was applied to one side of the base paper opposite to the side on which the emulsion was applied by a bar coating method to prepare a base paper for a photographic support. Further, as shown in Table 3, the sizing liquid was changed and applied on one side of the base paper on the back side of the base paper to prepare a base paper for a photographic support.

Density 0.918 g / m on the surface of the paper
A polyethylene resin composition in which 10% by weight of anatase-type titanium oxide was uniformly dispersed in 100% by weight of low-density polyethylene ( ² ) was melted at 320 ° and extrusion-coated to a thickness of 30 μm. Density 0.9 on the back
62 g / m ² of high-density polyethylene resin and the above-mentioned low-density polyethylene were melted in a ratio of 1: 1 at 320 ° C. to obtain a thickness of 3
A photographic support was manufactured by extrusion coating so as to have a thickness of 0 μm. Next, the emulsion was coated at 13 g / m ² and the flatness of the whole without a photographic paper was evaluated. These results are shown in Table 1,
The results are shown in Tables 2 and 3.

[0011]

[Table 1]

[0012]

[Table 2]

[0013]

[Table 3]

Evaluation method Curl: The sample was cut into 3 cm in the flow direction and 10 cm in the width direction, and after 24 hours elapsed at a temperature of 25 ° C. and a humidity of 65% RH, the sample was placed on a horizontal table with its central part grounded. , The lifting length of the edge was measured. The curl to the front surface side is positive (+), and the curl to the back surface side is negative (-).

From Table 1, it can be seen that a PVA molecular weight of 30,000 to 300,000 is preferable on one side of the base paper of the substrate, and the curl performance is good. Further, from Table 2, the solid content is 0.
It is understood that 5 to 5.0 g / m ² is preferable and the curl performance is good.

[0016]

INDUSTRIAL APPLICABILITY In a photographic support in which both sides of paper are coated with a polyolefin resin, the molecular weight is 30,0 only on the back side.
By increasing the surface size from 00 to 300,000 and the solid size from 0.5 to 5.0, it is possible to increase the amount of RC applied on the back side without increasing the RC coating amount on the back side.
Highly flat photographic paper was obtained after emulsion coating without increasing DPE.

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Claims (3)

[Claims] 1. A photographic support comprising paper as a substrate, both surfaces of which are coated with a polyolefin resin by a molten resin coating method, wherein only the back surface of the raw paper is surface-sized. 2. The photographic support according to claim 1, wherein the size liquid is a combination of one or more selected from polyvinyl alcohol compounds, gelatin and polyacrylamide. 3. The photographic support according to claim 1, wherein polyvinyl alcohol and polyacrylamide have a molecular weight of 30,000 to 300,000.