JP2839310B2 - Method for producing a support for photographic printing paper - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a photographic printing paper support. More specifically, the present invention relates to a method for producing a photographic paper support having a surface having excellent smoothness.

[Conventional technology]

In recent years, with the speeding up of photographic processing, water-resistant photographic printing paper supports in which both surfaces of a base made of a manuscript are coated with a polyolefin resin have been used in place of the conventionally used baryta paper. I have.

In general, the properties required for a photographic paper support include excellent dimensional stability, moisture resistance, adhesiveness, hiding power, and the like, and that the photographic emulsion layer is not adversely affected. In addition, the surface (surface) on which the photographic emulsion is coated must be excellent in smoothness. In particular, in a support for photographic paper having high gloss called a gloss type, this high surface smoothness is extremely important.

Generally, when this gloss type photographic paper support is manufactured by melt extrusion coating, a cooling roll used to cool and solidify the applied resin melt layer is called a super mirror roll, Rolls with a very smooth (less than 0.2S) mirror finish with hard chrome plating are often used.

When cooling and solidifying a resin melt layer coated and melt-extruded using such a cooling roll, when the solidified resin coating layer is peeled off from the cooling roll due to a strong adhesive force between the cooling roll and the resin, The peeling point is not stable, so flaking occurs on the peeled support, which also has an adverse effect on the surface of the resin coating layer, and uneven coating called step unevenness occurs in the traveling direction of the support. On the other hand, it may occur in the form of tatami in the vertical direction.

Such step unevenness is more likely to occur as the operation speed of the melt extrusion coating machine is increased. For this reason, in the prior art, in order to prevent the occurrence of step unevenness, the melt extrusion coating speed has to be reduced, but this causes a problem that productivity is reduced.

Further, in order to prevent the occurrence of step unevenness, it is conceivable to lower the temperature of the molten resin in the melt extrusion coating to lower the adhesive force of the resin melt layer to the cooling roll. However, when the temperature of the molten resin is lowered, the adhesiveness between the resin coating layer and the sheet-like substrate deteriorates, and a problem arises in that a photographic printing paper support of satisfactory quality cannot be obtained.

[Problems to be solved by the invention]

The present invention solves the above-mentioned drawbacks of the conventional method for producing a photographic paper support, and provides a method for producing a photographic paper support having excellent quality such as surface smoothness with high productivity. What you want to do.

[Means for solving the problem]

The method for producing a photographic printing paper support of the present invention is a method for melt-extrusion coating a resin composition containing a polyolefin resin as a base material on both sides of a sheet-like substrate, and forming a molten resin composition layer formed by super-extrusion. A method of forming a support comprising a sheet-like substrate and a resin coating layer bonded thereto by contacting the mirror-finished cooling roll with a cooling roll to cool and solidify the cooling roll, wherein at least the resin coating layer In the formation of one layer, the resin coating layer cooled and solidified by the cooling roll, and bound to the sheet-like substrate, the cooling roll, a peeling roll arranged with a gap of 5 mm or less,
Alternatively, the resin coating layer is melt-extruded by peeling off from the cooling roll through a peeling roll whose peripheral surface is joined to a circumferential surface of the cooling roll with a support member therebetween. It is formed at a speed of 100 m / min or more.

The method of the present invention will be described with reference to FIGS.
1 and 2, a sheet-like substrate 1 to be coated with a resin is supplied to a melt extrusion coating machine 1a having a T-die 3, a pressure roll 2, a cooling roll 5, and a release roll 6, and the T-die The molten resin stream 4 extruded from 3 is applied on the surface of the sheet-like substrate 1. The sheet-like substrate united with the molten resin layer in this manner is applied to the cooling roll 5 rotating in the direction of the arrow so that the molten resin layer is brought into contact with the peripheral surface of the cooling roll 5 by the pressure roll 2 disposed at the entrance. The molten resin layer is cooled and solidified to form a resin coating layer 8 and bonded to the sheet-like substrate 1 to form a resin coating sheet (support) 7. A peeling roll 6 is disposed at an exit portion of the cooling roll 5. In one embodiment of the peeling roll, the gap 9 between the peripheral surface of the peeling roll 6 and the peripheral surface of the cooling roll 5 is 5 mm or less, and the peeling roll 6 rotates as the support 1 runs. That is, the peeling roll 6
Is separated from the peripheral surface of the cooling roll 5 with the support to be peeled therebetween as shown in FIG. 2, and the gap is 5 mm or less, preferably 2 mm or less. In another embodiment of the peeling roll, as shown in FIG. 1, its peripheral surface is joined to the peripheral surface of the cooling roll with a support thereon.

The resin coating layer 8 bound to the sheet-like substrate 1 is peeled off from the peripheral surface of the cooling roll 5 by the peeling roll 6. Since the peeling roll 6 and the cooling roll 5 are joined via a support or the gap between them is as narrow as 5 mm or less, the peeling point of the resin coating layer 8 from the cooling roll 5 is stable. The support is smoothly peeled off without fluttering.

In the method of the present invention as described above, the peeling position is stable even when using a coating speed at which step unevenness occurs in the resin coating layer due to flapping of the support in the prior art due to the use of the peeling roll. Also does not occur.

In the method of the present invention, the peeling roll may press the support against the cooling roll or may not press it, but it is necessary that both are extremely close to each other with a gap of 5 mm or less.

If this gap is larger than 5 mm, the point of separation of the support from the cooling roll tends to fluctuate, causing flapping of the support and making it difficult to achieve stable and smooth separation.

In the present invention, the dimensions such as the diameter of the peeling roll are not particularly limited, but generally about 1/20 to 1/3 of the diameter of the cooling roll (generally 300 to 1500 mm) is appropriate.

The cooling roll used in the method of the present invention is a chrome-plated roll whose peripheral surface is polished to a super mirror. The material and processing method of the peeling roll are not particularly limited, and a metal roll or a rubber roll can be used. Generally, it is preferable to use a rubber roll having a hardness (hardness specified by JIS K6301) of 90 or less, since it can prevent the super mirror roll from being damaged even if foreign matter or the like is mixed. The effect of the present invention may cause a slight difference depending on the type of polyolefin resin used for the resin coating layer, for example, high density polyethylene, or sufficient effect can be obtained even when using a medium density polyethylene, density 0.930 The effect is particularly large when the following polyethylene is used.

In other words, low-density polyethylene generally has better adhesion to sheet-like substrates than high- and medium-density polyethylene, but at the same time has strong adhesion to the cooling roll, so it can be melt-extruded at high speed without using a peeling roll. There is a problem that step unevenness easily occurs when the coating is performed, but even when such a low-density polyethylene is used, the use of the release roll of the present invention can completely prevent the step unevenness.

〔Example〕

 Hereinafter, the present invention will be further described with reference to examples.

Examples 1-4 and Comparative Examples 1-4 In each of Examples 1-4 and Comparative Examples 1-4, high-quality paper having a basis weight of 175 g / m ² was used as a sheet-like substrate, and 60 w / m ² was applied to one surface thereof. / min output corona discharge treatment, 90 parts by weight of polyethylene resin of the composition shown in Table 1 on this surface,
A resin composition obtained by mixing 10 parts by weight of titanium dioxide pigment and 0.5 part by weight of zinc stearate is applied by a melt-extrusion coater having a T-die width of 1700 mm, and the molten resin composition layer is subjected to hard chrome plating and super mirror finish. Cooling roll (diameter: 800mm, cooling roll cooling water: 10 ℃, 300 /
Min) and solidify by cooling, and the resin coating layer thus formed is peeled off with a metal or rubber coating (80 mm diameter)
From the cooling roll. The coating speed, the state of the peeling roll, and the resin temperature were as described in Table 1.

Further, the surface of the resin coating layer was observed to visually evaluate step unevenness due to defective peeling, and the adhesion between the resin coating layer and the substrate was evaluated by the following method.

Adhesion evaluation method A test piece with a width of 25 mm and a length of 200 mm is sampled along the longitudinal direction of the support, and only the coating layer is peeled off from one end face of the test piece in the opposite direction by 180 ° along the longitudinal direction of the test piece. Then, fiber fluffing of the peeled base paper surface was observed. If the paper fibers are fluffed and peeled off from the paper layer, the adhesion is good.If the paper fibers are peeled off at the interface between the paper layer and the coating layer without fluffing, it is judged to be poor bonding. The following five classes were evaluated according to the ratio. Classes 1 and 2 are practical, but classes 3 and below are difficult to practice.

 Class 1 Adhesive area is good in all areas. 2 90% or more is good. 3 3 80 4 5 60 5 6 5

In Examples 1 to 4 according to the present invention, even when the coating speed was high, no unevenness occurred in the obtained resin coating layer, and the adhesiveness was good.

On the other hand, in the case of Comparative Examples 1, 2, and 4, the obtained resin coating layer had unevenness or poor adhesion and was not practical, and Comparative Example 3 in the case of,
The obtained photographic printing paper support was usable, but the productivity was extremely low due to the low coating speed.

〔The invention's effect〕

The method for producing a photographic paper support of the present invention is characterized in that a support having a resin-coated layer cooled using a release roll is stably peeled off without causing flapping, and a photograph having good surface smoothness is obtained. This makes it possible to produce a photographic paper support with high productivity, and has excellent practical value.

[Brief description of the drawings]

FIG. 1 is an explanatory side view of an apparatus used for carrying out the method of the present invention, and FIG. 2 is a partial explanatory view showing an operation of a peeling roll in the apparatus of FIG. 1a: Melt extrusion coating machine, 1: Sheet-like substrate, 2 ... Pressure roll, 3 ... T-die, 4 ... Molten resin flow, 5 ... Cooling roll, 6 ... Peeling roll, 7 ... ... Resin coated sheet (support), 8 ... Resin coated layer, 9 ... Gap.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G03C 1/79

Claims (2)

(57) [Claims] 1. A resin composition containing a polyolefin resin as a base material is melt-extruded and coated on both surfaces of a sheet-like substrate,
The molten resin composition layer thus formed is brought into contact with a cooling roll having a super-mirror finish and cooled and solidified to form a support comprising the sheet-like substrate and a resin coating layer bonded thereto. When forming at least one layer of the resin coating layer, the resin coating layer cooled and solidified by the cooling roll, and bound to the sheet-like substrate, the cooling roll, with a gap of 5 mm or less The resin coating layer is dissolved by peeling from the cooling roll via a peeling roll in which the arranged peeling roll or peripheral surface is joined to the peripheral surface of the cooling roll with a support member sandwiched therebetween. A method for producing a support for photographic printing paper, wherein the support is formed at an extrusion coating speed of 100 m / min or more. 2. The polyolefin resin used in the resin coating layer is polyethylene having a density of 0.930 or less.
3. The method for producing a support for photographic printing paper according to item 1.