JPH06282038A - Production of resin coated paper for photography - Google Patents

Abstract

PURPOSE:To obtain a paper substrate excellent in surface smoothness by specifying the water content of each of a web directly after the wire outlet of a paper machine, after a 1st step pressing and after a final step pressing. CONSTITUTION:Both surface of the paper substrate manufactured by the paper machine is coated with the polyolefin resin. At the time of manufacturing the paper substrate, the paper substrate excellent in surface smoothness is obtained by maintaining the distribution of water content of the web so that the water content of the web directly after the wire outlet of the machine paper is 75-85%, the water content of the web after the 1st step pressing is 65-75% and the water content of the web after the final step pressing is 55-65%. In this case, the paper machine to be used is preferably an on-top wire paper machine in respect of the smoothness of the coating surface of the emulsion layer constituting the photographic printing paper. And the polyolefin layer formed on the paper substrate is formed by using extruding coating method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing photographic resin-coated paper. More specifically, it relates to a method for producing a photographic resin-coated paper having excellent surface smoothness.

[0002]

2. Description of the Related Art In recent years, a water-resistant resin-coated paper in which both sides of a paper substrate are coated with a polyolefin resin has been used for the purpose of rapid processing of photographic printing paper. The surface shape of photographic paper using water resistant resin coated paper includes glossy surface, matte surface,
Alternatively, there is one with a pattern such as silk. These shapes can be obtained by changing the shape of the surface of a chill roll that is cooled and solidified while press-bonding a molten resin film onto a paper substrate during extrusion coating. Among these surface shapes, a smooth glossy surface with no pattern is widely preferred, and a large amount is produced and sold. What is preferable as the glossy surface is that it has a smooth surface such as a mirror with few fine irregularities.

The present invention relates to a method for producing a photographic resin-coated paper having an excellent surface smoothness. With photographic printing paper using conventional baryta paper, it was possible to obtain smoothness close to a mirror surface by applying ferro-type coating in the drying process, but photographic resin-coated paper can be printed without the ferro-type drying process. The smoothness of the paper surface depends on the smoothness of the surface of the resin-coated paper, and by extension, the smoothness of the paper substrate. Therefore, in order to obtain a photographic printing paper having good smoothness, the surface of the paper base must be smooth.

As a method for improving the smoothness of the resin-coated paper for photography, the resin layer to be coated is made thicker and the pressing pressure at the time of resin coating is regulated (Japanese Patent Laid-Open No. 1-30343).
No. 5) is known, but its effect is small. On the other hand, as a method for improving the smoothness of the paper substrate, a method in which the beaten fiber length is specified (JP-A-58-68037 and JP-A-60-69649) has been proposed, but the smoothness is to some extent. Although there is an effect of improving, the strength and the rigidity are lowered, and a sufficiently satisfactory quality cannot be obtained. Further, it is general to increase the pressure of the machine calender to increase the density of the paper substrate, but this method is also disadvantageous in terms of cost because it is likely to cause external defects such as blacking and paper sticks.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing a photographic resin-coated paper which does not have the above-mentioned drawbacks.

[0006]

DISCLOSURE OF THE INVENTION As a result of intensive studies by the present inventors to improve these drawbacks, photographic resin-coated paper in which both sides of a paper substrate produced by using a paper machine are coated with a polyolefin resin In the method for manufacturing a paper substrate, the moisture content of the web immediately after the wire exit of the paper machine is 7
5 to 85%, the moisture content of the web after the first-stage pressing is 65 to 75%, and the moisture content gradient is maintained in the web so that the moisture content of the web after the final-stage pressing is 55 to 65%. It has been found that a paper base material having an excellent surface smoothness can be obtained by doing so, and as a result, a photographic resin-coated paper having an excellent smoothness can be obtained.

The present invention will be described in detail below. Regarding the pulp used in the present invention, even if a natural pulp is used,
Depending on the case, synthetic pulp and synthetic fiber may be mixed or may be used alone. A sizing agent, a strengthening agent, a fluorescent brightening agent, an antistatic agent, etc. are used for the paper substrate, and the presence or absence of the use is selected according to the purpose.

The paper machine used in the present invention is a Fourdrinier paper machine,
Any type of paper machine, such as a twin-wire paper machine, an on-top paper machine that combines a Fourdrinier paper machine and a twin-wire paper machine, can be used, but the smoothness of the coated surface of the emulsion layers that make up photographic paper From this point, an on-top type paper machine is preferable.

Regarding the press used in the present invention, a double felt press, a single felt press alone,
Alternatively, a combination of them is used. For the material of the press roll, granite stone roll,
Although an artificial stone roll in which fine stone particles are mixed with hard rubber is used, it can be appropriately selected depending on the speed of paper making, the width of the paper machine, and the like.

The number of stages of the press is usually three, but in some cases there are more stages. Any number of stages is possible if it suits the purpose. At the time of paper-based papermaking, the water content immediately after the wire exit of the paper machine is 75 to 8
It needs to be 5%.

When the water content immediately after the wire exit is less than 75%, it is necessary to lower the nip pressure in the press stage.
After pressing, the nip balance with the smoother and calender collapses, leading to reduced strength and reduced rigidity. Further, in general, in order to reduce the water content immediately after the wire exits, it is necessary to lengthen the wire part or add foils or suction boxes in order to increase the water squeezing capacity of the wire, which is also disadvantageous in terms of cost. Moisture content immediately after the wire exit is 85
When it exceeds%, the good formation formed on the wire is broken and the smoothness is deteriorated, so that the purpose of improving the smoothness cannot be achieved. Furthermore, in the case of a press that has an open draw, it will be difficult to pass the paper, it will cause paper breakage, and it will also cause shadow marks, and the gloss will be distorted when made into resin-coated paper and photographic paper after that, and other quality and operation It becomes a hindrance.

Moisture content immediately after the wire exit is 75-85%
The wet paper of No. 1 is pressed by the first-stage press, but the moisture content after the first-stage press needs to be 65 to 75%. If it is less than 65%, it is necessary to lower the nip pressure of the press, and the balance of the nip pressure with the smoother and calendar is lost, leading to a decrease in strength and rigidity. As a result, the resin-coated paper for photography has a weak stiffness. This may result in poor transportability in the development processing device or the like. Also,
It causes roll stains and deteriorates operability. Roll dirt also causes dents and molds on the paper substrate surface.

The wet paper having a moisture content of 65 to 75% from the first stage press is pressed by the next stage press. Depending on the paper making system, there are multi-stage presses, but in any case, the water content after the final-stage press must be 55 to 65%. When the water content after the final press is less than 55%, the nip pressure balance between the smoother and calender after the final press is lost as in the case of the previous press, and the waist becomes weak as a resin coated paper for photographic paper, and the paper is conveyed. This may result in poor performance or deterioration of smoothness, and the purpose cannot be achieved. 6
If it exceeds 5%, it may lead to stains on the dryer or stains on the press roll, resulting in dents on the resin-coated paper for photographic use, forming molds, and deteriorating smoothness, making it impossible to achieve the purpose.

As described above, the water content immediately after the wire exit is 75 to 85%, and the water content after the first-stage pressing is 65 to 7%.
5%, the moisture content after the final stage pressing is 55 to 65%, and it is necessary to satisfy the moisture content gradient of each part. Even if the condition is satisfied only in one step or only in two steps. It is not possible to obtain a sufficient effect.

The polyolefin resin coating layer formed on the paper substrate in the present invention is formed by an extrusion coating method. Usually, the polyolefin resin coating layer is produced by a so-called extrusion coating method in which a heated melt of a resin is cast on the surface of a running paper substrate, and both surfaces of the paper substrate are coated with the resin. Further, the paper substrate may be subjected to activation treatment such as corona discharge treatment or flame treatment before being coated with the resin. Generally, the surface of the support for photographic paper (emulsion side)
Has a glossy surface, and its back surface is usually a matte surface, and the front surface or both front and back surfaces may be subjected to activation treatment such as corona discharge treatment or flame treatment as required.

As the paper substrate, one having a weight of 100 to 300 g / m ² is usually used. The thickness of the polyolefin resin coating layer formed on the support of the present invention and the weight thereof are not particularly limited, and may be the same as the thickness of the polyolefin resin coating layer of the conventional photographic paper support. good. For example, its thickness is usually selected from the range of 10 to 100 microns, preferably 15 to 80 microns.

The polyolefin resin used for coating both sides of the paper substrate of the present invention includes polyethylene, α-olefins such as homopolymers of propylene, copolymers of two or more of the above olefins, and these. Can be selected from a mixture of two or more kinds of the various polymers mentioned above. Particularly preferred polyolefin resins are low density polyethylene, high density polyethylene, and mixtures thereof. The molecular weight of the polyolefin resin is not particularly limited, but one having a range of 20,000 to 200,000 is usually used.

The polyolefin resin coating layer formed on the surface (the surface on which the emulsion is applied) of the paper substrate of the present invention may contain the specific polyolefin resin composition of the present invention, or any other desired one. It may have a desired composition.
In addition, this polyolefin resin coating layer, a desired amount of additives, for example, white pigments such as titanium oxide, zinc oxide, talc, calcium carbonate, alumina, fibrous fillers such as glass fiber, asbestos, whiskers, carbon black, phthalocyanine. Pigments, yellow lead, titanium yellow,
Red iron oxide, color pigments such as ultramarine, stabilizers mixed with ordinary resins, antioxidants, antistatic agents, plasticizers, dispersants,
It may contain a lubricant, a fluorescent agent and the like. For the types, amounts, and addition methods of these additives, see US Pat. Nos. 3,833,380 and 4,169,1.
88, No. 3,501,298, No. 3,449,25
No. 7, and No. 3,499,762. Also, as described in U.S. Pat. No. 3,884,692, those additives can be applied thereon after forming the polyolefin resin coating layer.
Further, US Pat. Nos. 2,715,075 and 2,84
6,727, 3,549,406, and 3,
As described in Japanese Patent No. 590,107, etc., the surface activation treatment of the polyolefin resin coating layer can be performed if necessary.

[0019]

The present invention will be described in detail below with reference to examples, but the invention is not limited to the examples.

(Examples 1 to 7 and Comparative Examples 1 to 6) LB
Mixed pulp of 50 parts SP and 50 parts LBKP is 350 at Canadian standard freeness using a disc refiner.
After beating to ml, the alkyl ketene dimer (manufactured by Japan PMC Co., Ltd. A
S-24A) 0.3%, higher fatty acid amide (modern chemistry
NS-715) 0.2%, polyamide polyamine epichlorohydrin resin (WS-2 manufactured by Japan PMC Ltd.)
5) 0.3% was added. As for the paper machine, an on-top wire type bell bond former was used for Examples 1 to 6 and Comparative Examples 1 to 6, and a wire Fourdrinier was used for Example 7.

The press was a four-stage press including a tri-nip, and the first-stage press was a double felt press. Immediately after the wire exit, after each of the first-stage pressing and the final-stage pressing, the level of each moisture content was changed by adjusting the foil, the suction box vacuum pressure, and the press nip pressure as shown in Table 1.

The thickness of the paper base after calendering is 172 μm.
m and water content was 7.5%. In addition, this paper substrate has 2g / m ²
Of polyvinyl alcohol is applied by a size press. This paper substrate has a low-density polyethylene layer containing 10 parts by weight of anatase type titanium oxide on the side on which the emulsion is applied by extrusion coating, when the total amount of the emulsion is 100 parts. On the side surface, low density polyethylene 50 parts, high density polyethylene 5
A polyethylene layer mixed with 0 parts was applied in an amount of 30 g / m ² . A polished mirror roll was used as the chill roll for cooling and solidifying the resin layer on the surface on which the emulsion was applied. The photographic resin-coated paper thus obtained was coated with a photographic emulsion to prepare photographic paper.

(Evaluation method) The photographic printing paper was cut into a small roll of 8.2 cm width and was developed by a processor (Sakura CL-
Development processing was performed by RP500). The surface smoothness of the processed photographic paper was visually graded. The grade is 1 with good smoothness and 5 with poor smoothness.
And graded in 5 stages. Regarding the stiffness of the texture, the waist strength of the texture was graded. The grade was set to 1 for the strong ones and 3 for the weak ones, and there were three grades. The results are shown in Table 1.

[0024]

[Table 1]

[0025]

As in Examples 1 to 7, during paper-based papermaking,
The moisture content immediately after the wire exit of the paper machine is 75-85%, the moisture content after the first-stage pressing is 65-75%, and the moisture content after the final-stage pressing is 55-65%. By maintaining the rate gradient on the web, it was possible to obtain a paper substrate having an excellent surface smoothness, and as a result, a photographic resin-coated paper having an excellent smoothness was obtained.

Claims (2)

[Claims] 1. A method for producing a resin-coated paper for photographic use, comprising a wire part and a paper machine having a plurality of press parts, coated on both sides with a polyolefin resin. Of the wire immediately after exiting the wire is 75 to 85%, and in the order of each press part, the water content after the first-stage pressing is 65 to 75%, and the water content after the final-stage pressing is 55 to 65%. A method for producing a photographic resin-coated paper, which has a water content gradient of 2. The method for producing a photographic resin-coated paper according to claim 1, wherein the paper machine is an on-top wire type.