JPH05265136A - Production of substrate for photographic printing paper - Google Patents

Abstract

PURPOSE:To obtain a substrate for photographic printing paper excellent in suitability to high-speed coating and having excellent surface smoothness of a resin coating layer. CONSTITUTION:Both sides of base paper are coated with molten polyolefin by extrusion coating to produce a substrate for photographic printing paper with polyolefin resin coating layers on both sides. When the molten polyolefin is solidified by cooling, the surface temp. of at least one of the coating layers is controlled to <25.0 deg.C at the time of exfoliation from a cooling roll. The occurrence of a lateral-stripe pattern which deteriorates quality can be suppressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a support for photographic printing paper.
TECHNICAL FIELD The present invention relates to a production method having a resin coating layer having an excellent surface smoothness and improved high-speed coating property of the resin coating layer.

[0002]

2. Description of the Related Art In recent years, with the speeding up of photographic development processing, a water resistant photographic printing paper support in which both sides of a base paper made of a base paper are coated with a polyolefin resin is used in place of the conventionally used baryta paper. It became so.

Generally, the properties required for a photographic printing paper support are excellent in dimensional stability, moisture resistance, adhesiveness, hiding power, and the like, and do not adversely affect the photographic emulsion layer. In addition, it is necessary that the surface of the photographic emulsion to be coated (surface) is excellent in smoothness. In particular, in a support for photographic printing paper having a high gloss called a mirror surface type, this high surface smoothness is required.

Generally, as a cooling roll used for cooling and solidifying a resin melt layer when the mirror surface type photographic printing paper support is manufactured by melt extrusion coating,
A cooling roll called a super mirror surface roll, which has an extremely smooth (0.2S or less) mirror surface with a hard chrome plating finish, is often used. When a resin melt layer melt-extruded and coated by using such a cooling roll is cooled and solidified, the solidified resin coating layer from the cooling roll has a strong adhesiveness between the cooling roll and the solidified resin coating layer. Peeling failure occurs, which adversely affects the surface of the resin coating layer, and horizontal stripes called horizontal unevenness are formed on the surface of the resin coating layer. The time until the occurrence of the horizontal unevenness varies depending on various manufacturing conditions, but basically it occurs due to poor peeling between the cooling roll and the resin coating layer due to the accumulation of low-molecular-weight polyolefin on the cooling roll surface. It is confirmed to do.

Therefore, such horizontal unevenness is more likely to occur as the operating speed of the melt extrusion coating machine is increased. Therefore, in the conventional technology, in order to prevent the occurrence of horizontal unevenness, it is unavoidable to lower the melt extrusion coating speed, but when dealing with such a method, there is a problem that productivity obviously decreases significantly. Occur.

It is also conceivable to lower the temperature of the molten resin in the melt extrusion coating to reduce the adhesive force of the resin melt layer to the cooling roll in order to prevent the occurrence of horizontal unevenness. However, when the temperature of the molten resin is lowered, the adhesion between the resin coating layer and the paper substrate is deteriorated, and there arises a problem that a photographic printing paper support having a satisfactory quality cannot be obtained.

A method of cooling and solidifying the resin coating layer by applying a cooling roll to the resin melt layer has been practiced conventionally, but conventionally, in order to increase the productivity of the polyolefin resin coated paper, The surface temperature of the cooling roll may be in the range of about 10-32 ° C., especially 1 ° C., as described, for example, in US Pat. No. 3,959,546.
It is common knowledge in the art to adjust to a low temperature such as a temperature within the range of 0 to 15 ° C.

Further, for another purpose, JP-A-58-95733.
As disclosed in Japanese Patent Publication No. JP-A-2004-242242, a method for producing a photographic printing paper support having good cuttability by keeping the surface temperature of the cooling roll in the range of 30 to 100 ° C. without considering productivity is also disclosed. Has been done. However, according to the study of the present inventor, although the cooling and solidifying operation of the polyolefin coating layer at a high temperature of the cooling roll is effective for improving the cutting property, the high-speed coating property is very poor, and the surface It was found that the shape of the resin coating layer formed in 1) had a high occurrence frequency of horizontal unevenness and was not preferable in terms of quality.

Further, Japanese Patent Application Laid-Open No. 3-200140 discloses a method of peeling from a cooling roll via a peeling roll arranged with a gap of 5 mm or less between the cooling roll and the paper substrate. However, with this method,
I couldn't eliminate the horizontal unevenness enough. Because the main cause of this horizontal unevenness is on the surface of the cooling roll,
This is because the accumulated low-molecular-weight polyolefin causes the surface temperature of the polyolefin-coated resin to be high, which is nothing but manifestation due to the physical hot tack property. Therefore, by adjusting the distance between the peeling rolls, it is possible to improve the peelability up to a certain resin coating speed, but it is not a fundamental solution at all when higher speed coatability is required. ..

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to provide a manufacturing method having a resin coating layer surface having excellent smoothness and improving the high speed coating property of the resin coating layer. More specifically, the present invention relates to a method for producing a support for photographic printing paper having a resin coating layer surface which is free from quality defects such as horizontal stripes and has excellent high-speed coating properties and excellent smoothness.

[0011]

[Means for Solving the Problems] In order to solve the above problems, the inventors of the present invention have earnestly studied, and as a result, the molten polyolefin resin was applied on both sides of the base paper by an extrusion coating method to form a double-sided polyolefin resin coating layer. In the method for producing a support for photographic printing paper having, when the molten polyolefin forming at least one coating amount is cooled and solidified, the surface temperature of the polyolefin resin coating layer immediately after peeling from the cooling roll is 25.0 ° C. It has been found to be achieved by controlling below.

A means for achieving this can be achieved by controlling the cooling water temperature of the cooling roll for cooling and solidifying the polyolefin resin coating layer to be less than 10.0 ° C. Further, the cooling water flow rate of the cooling roll was 300 l per 1 m ² of the contact area between the polyolefin resin coating layer and the cooling roll.
It is also achieved by being / min or more. Furthermore, it is possible to control by combining the cooling and solidifying conditions of these cooling rolls, and it is a condition that is preferably used.

In producing a support for photographic printing paper (polyolefin resin-coated paper) having polyethylene resin coating layers on both sides of the raw paper which is the object of production of the present invention, first, the melted polyolefin is coated on the surface of the raw paper. Is applied by extrusion coating. The extrusion coating method for applying the molten polyolefin can be arbitrarily selected from conventionally used methods. Further, the melting conditions and coating conditions of the polyolefin can be selected from the conditions adopted in the known production method of the polyolefin resin-coated paper.

Cooling and solidification of the molten polyolefin resin body is usually performed by applying the molten polyolefin resin body to the base paper and applying a cooling roll to the molten polyolefin resin coating body at the same time. The method of cooling and solidifying the molten polyolefin resin body by applying a cooling roll to the molten polyolefin resin coated body has been actually carried out in the past, but the conventional technique disclosed in the above-mentioned reference specifies the cooling roll temperature. Is what
It does not define the surface temperature of the resin coating layer immediately after being actually peeled off. As a result, even when the cooling roll temperature is set to a predetermined temperature, when the molten polyolefin resin body is applied to the base paper at a high speed, the surface temperature of the polyolefin resin coating layer immediately after being peeled off is remarkably increased, and peeling failure due to hot tack property may occur. Then, the quality failure of the horizontal striped unevenness occurs.

According to the studies by the present inventors, the cooling and solidifying operation of the polyolefin resin coating layer, which controls the surface temperature of the polyolefin resin coating layer immediately after peeling from the cooling roll to less than 25.0 ° C., has a very high productivity. It is effective in increasing the number, and the occurrence of horizontal unevenness as a quality failure is extremely reduced. The surface temperature range of the more preferable polyolefin resin coating layer of the present invention immediately after peeling from the cooling roll is 10.0 ° C to 22.0 ° C. Further, in order to control the surface temperature to be less than 10 ° C., in consideration of a cooling roll for cooling and solidifying the molten polyolefin resin body and heat exchange efficiency, a special refrigerant is required as cooling water in high speed processing. Therefore, temperature control / management becomes very difficult. Further, the difference between the temperature of the surface of the cooling roll and the room temperature becomes large, the moisture in the air is condensed on the cooling roll, and the condensed moisture has an adverse effect such that the glossiness of the surface of the polyolefin resin coating layer is lowered.

According to the study by the present inventor, when the surface temperature of the polyolefin resin coating layer immediately after peeling from the cooling roll is peeled at a temperature of 25.0 ° C. or higher, the molten polyolefin resin forming the polyolefin resin coating layer is formed. The body adheres to the cooling roll, the cooling roll surface is contaminated with low molecular weight resin components, and the peeling property between the polyolefin resin coating layer and the cooling roll becomes extremely poor, and the surface of the polyolefin resin coating layer is formed. Step unevenness occurs, which is extremely unfavorable in terms of quality. further,
When peeling at a temperature exceeding 30.0 ° C,
Due to the occurrence of stronger horizontal unevenness and, in the worst case, poor peeling, the polyolefin resin may wind around the cooling roll and even the substrate produced may even break, resulting in a marked deterioration in productivity. ..

In the present invention, the cooling efficiency (heat balance) between the cooling roll and the molten polyolefin resin body is taken into consideration, and it is also considered to select an appropriate cooling roll diameter and an appropriate cooling roll metal surface thickness. But,
As a method for controlling the surface temperature of the polyolefin resin coating layer immediately after peeling, the cooling water temperature of the cooling roll is set to 1
It is effective to control the temperature to less than 0.0 ° C., and the cooling roll cooling water flow rate is 3 per 1 m ² of the contact area between the polyolefin resin coating layer and the cooling roll.
Controlling the flow rate to 100 l / min or more also improves the heat exchange between the cooling roll and the molten polyolefin resin body coated on the base paper in the cooling roll, improves the cooling efficiency more effectively, and prevents uneven horizontal stripes. Very few occurrences.

The surface temperature in the present invention may be measured by a contact thermometer or a non-contact thermometer. However, in the present invention, the contact type thermometer is often restricted in order to ensure the quality in manufacturing, and it is preferable to manage the contact type thermometer with the non-contact thermometer. For example, a temperature distribution analyzer Thermoviewer JTG-4000 manufactured by JEOL Ltd. is used. Non-contact temperature measurement is based on temperature measurement using radiant energy (infrared energy) corresponding to the temperature of a substance. When measuring the surface temperature with a contact thermometer, the measured value may fluctuate depending on the contact condition of the detection part,
Alternatively, it is difficult to make an accurate measurement due to the influence of heat disturbance caused by contact.

The cooling roll used in the present invention is not different from the conventionally used cooling rolls. For example, metal such as stainless steel or iron plated with nickel or chrome,
Cooling rolls made of various materials such as ceramic coating can be used.

The surface shape of the cooling roll is not particularly limited. For example, the surface of the cooling roll is a mirror surface, Japanese Patent Publication No. 56-4902, US Pat. No. 3,959,546, Japanese Patent Publication No. 55-5103, and British Patent. As described in Japanese Patent No. 1,466,030, etc., the surface is a silk, a finely rough surface,
It may be formed into a surface shape such as a matte shape, or may have another surface shape, or a surface shape that is imprinted. In particular, a cooling roll having a slightly rough surface is used as a preferred mode.

When the molten polyolefin resin body is cooled and solidified, it is manufactured by a cooling roll and a press roll. The press roll used at this time has a hardness of 80 to 90 (JIS K 6301) and a rubber thickness of 10 ~ 2
It is preferably 5 mm. The nip pressure between the press roll and the cooling roll is 30 to 80 in linear pressure.
kg / cm is preferable, and the material of the surface rubber used for the press roll is preferably ethylene propylene rubber.

As to the peeling roll for peeling the polyolefin resin coating layer from the cooling roll, it is particularly necessary to dispose the peeling roll at a distance of 5 mm or less between the cooling roll and the paper base, as disclosed in the above-mentioned reference. Absent. Further, when the peeling roll is arranged at a position where the peeling angle becomes a low angle, or when the peeling roll is arranged by changing the holding angle of the portion where the paper is in contact with the cooling roll circumference, the effect is slightly recognized, Almost no effect of improving the horizontal row is observed.

In particular, even when the peeling roll is arranged at 5 mm or less, when the molten polyolefin resin is applied at a high speed,
It has no effect. This is because the horizontal unevenness is caused by the surface temperature of the polyolefin resin coating layer immediately after peeling from the cooling roll. However, if the peeling roll is arranged with a space of 50 mm or more between the cooling roll and the paper base,
This time, the effect as a peeling roll is weakened, peeling does not occur uniformly, and peeling failure occurs, so that high-speed processability is significantly deteriorated.

The thickness of the polyolefin resin coating layer is not particularly limited, and can be selected according to the thickness of the coating layer of the conventional polyolefin resin coated paper of the photographic printing paper support. Its thickness is usually chosen in the range from 10 to 100 microns, and especially from 15 to 50 microns.

The photographic printing paper support obtained by the production method of the present invention has a basic structure comprising a base paper and a polyolefin resin coating layer provided on both sides thereof. The base paper is selected from materials commonly used for photographic printing paper. Examples of such materials include natural pulp paper, synthetic pulp paper, mixed paper of natural pulp and synthetic pulp, and various laminated papers.
The base paper is usually used in a thickness of 50 to 500 microns.

In the present invention, as the polyolefin forming the polyolefin resin coating layer, various conventionally used polyolefins can be arbitrarily selected from various conventionally used polyolefins. Examples of such polyolefins include α-olefin homopolymers such as polyethylene and polypropylene, and α-olefin homopolymers thereof.
Mention may be made of olefin copolymers, and mixtures of these various polymers. A particularly preferred polyolefin is polyethylene. These polyolefins have a molecular weight of 2 as long as extrusion coating is possible.
Polyolefins in the range of 20,000 to 200,000 are used.

The polyolefin resin used for forming the resin coating layer of the polyolefin resin coated base paper for photographic printing paper,
It is already known to add various additives such as a white pigment, a coloring pigment, or a fluorescent whitening agent and an antioxidant, and even when the polyolefin resin used in the present invention is prepared, such a matter is naturally required. Various additives are possible and preferred for some purposes. Types of such various additives, the amount added, about the addition method, for example, U.S. Pat.No. 3,833,380, 4,169,188, 3,501,298,
It is described in detail in publications such as 3,449,257 and 3,499,762. Alternatively, those additives can be applied onto the coating layer after formation of the coating layer, as described in US Pat. No. 3,884,692. Alternatively, U.S. Pat.Nos. 2,715,075, 2,846,727, 3,549,406,
As described in publications such as No. 3,590,107,
The surface activation treatment of the resin coating layer can be performed if necessary.

In the present invention, in order to apply a photographic emulsion to a support for photographic printing paper to obtain a photographic printing paper, a method conventionally used for producing photographic printing paper can be used. Further, for the processing such as development and fixing of the photographic printing paper thus manufactured, conventionally used techniques can be used. As for these conventional techniques, for example, “Photochemistry” (written by Shinichi Kikuchi; Kyoritsu Shuppan; 1973),
And "THE THEORY OF PHOTOGRAPHIC PROCESS" (CE
K. Mess; 3rd.ed.) and other publications.

[0029]

EXAMPLES The present invention will be described in detail below with reference to specific examples. Examples 1 to 4 and Comparative Examples 1 to 5 A 1: 1 mixture of a bleached hardwood bleached kraft pulp (LBKP) and a bleached softwood sulphite pulp (NBKP) was beaten to a volume of 300 mlcsf at Kandian standard freeness, and a pulp slurry was obtained. It was adjusted. Alkyl ketene dimer as a sizing agent to pulp 0.5% by weight, and polyacrylamide as a strength agent to pulp 1.0
A weight% cationized starch was added to the pulp in an amount of 2.0% by weight, and a polyamide epichlorohydrin was added to the pulp in an amount of 0.5% by weight, and diluted with water to prepare a 1% slurry. This slurry was made into paper by a Fourdrinier paper machine so as to have a weight of 170 g / m ² , and was used as a base paper for a support for photographic printing paper.

The density of the prepared base paper is 0 at a coating speed, a peeling temperature, a cooling roll cooling water temperature, and a cooling water flow rate shown in Table 1 for 10 hours, respectively, using a cooling roll that is finely roughened. A polyethylene resin composition in which 10% by weight of anatase-type titanium oxide is uniformly dispersed in 100% by weight of low-density polyethylene of 0.918 g / cm ³ is melted at 320 ° C. to have a thickness of 30 μm. Was extrusion coated. At this time, the press pressure between the press roll and the cooling roll is a linear pressure of 40 kg / c.
went in m. For the other surface, a cooling roll having a roughened surface was used, and the cooling water was cooled at a constant temperature of 20 ° C. and the flow rate of the cooling water was set at a constant flow rate of 500 l / min. The same high density polyethylene resin with a density of 0.962 g / cm ³ and the low density polyethylene described above are used in the same ratio of 320: 1.
It was melted at 0 ° C. and extrusion-coated to a thickness of 30 μm to produce a photographic paper support.

[Evaluation Method] For measuring the surface temperature of the resin coating layer, the temperature of the surface of the resin coating layer when peeled from the cooling roll was measured using a temperature distribution analyzer Thermoviewer JTG-4000 manufactured by JEOL Ltd. Then, the temperature in the width direction was measured and the average value was shown. For the cooling roll cooling water temperature, install a resistance temperature detector at the outlet of the cooling roll,
The temperature of the cooling roll cooling water at the time of manufacture was measured. For the cooling roll cooling water flow rate, an electromagnetic flow meter was installed at the cooling roll inlet, and the cooling roll cooling water flow rate at the time of manufacturing was measured.

[Horizontal unevenness grade] The lateral unevenness was evaluated by visual observation as follows. Grade 1 ... No horizontal unevenness Grade 2 ... Spot-like extremely weak horizontal unevenness Grade 3 ... Weak horizontal unevenness Grade 4 ... Strong horizontal unevenness Grade 5 ... Very strong horizontal unevenness Up to Grade 2, Although there is no problem even if the emulsion is applied, at the grade 3 level, it is not a level until quality failure, but it is not a relatively preferable level. Further, when grades 4 and 5 are applied, the grades in which horizontal unevenness can be observed even when the emulsion is coated are defective grades that do not become products.

[0033]

[Table 1]

In Examples 1 to 4 according to the present invention, when the surface temperature of the resin coating layer peeled off from the cooling roll was 25.0 ° C. or less, the obtained resin coating layer had a high coating speed. Horizontal unevenness does not occur. On the contrary,
In Comparative Examples 1 to 3, the peeling surface temperature was 25 ° C. or higher and the occurrence of horizontal streaks was observed even though the coating speed was not high. Particularly, in Comparative Example 3, the coating speed was 80 m /
Despite the low speed of min, the peeling surface temperature was 35.0
Since the temperature was as high as ℃, peeling failure occurred and strong horizontal unevenness was generated. Further, in Comparative Example 4, when the coating speed is high and the peeling surface temperature is high, very strong horizontal unevenness occurs, and the quality level as a product cannot be maintained. In Comparative Example 5, the peeling roll was arranged with a gap of 4 mm between the cooling roll and the polyethylene resin coating layer. However, since the surface temperature immediately after peeling the resin coating layer was 30.0 ° C., peeling was performed. Even if the rolls were arranged at intervals of 5 mm or less, horizontal unevenness occurred.

[0035]

According to the method for producing a support for photographic printing paper of the present invention, the resin peeled from the cooling roll is controlled by controlling the surface temperature of the resin coating layer peeled from the cooling roll to be lower than 25.0 ° C. The coating layer is peeled off very stably, quality troubles such as horizontal unevenness do not occur, and it is possible to significantly improve the productivity of a photographic printing paper support with good surface smoothness and to manufacture it. It is a very good one of the above value.

Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location D21H 19/20 27/00

Claims (3)

[Claims] 1. A method for producing a support for photographic printing paper having a double-sided polyolefin resin coating layer by applying molten polyolefin to both sides of a base paper by an extrusion coating method, wherein at least one amount of molten polyolefin is formed. When cooling and solidifying, the surface temperature of the polyolefin resin coating layer immediately after peeling from the cooling roll,
A method for producing a support for photographic printing paper, which comprises controlling the temperature to be lower than 25.0 ° C. 2. The cooling water temperature of a cooling roll for cooling and solidifying the polyolefin resin coating layer is 1
The method for producing a support for photographic printing paper according to claim 1, wherein the temperature is controlled to less than 0.0 ° C. 3. The cooling water flow rate of the cooling roll for cooling and solidifying the polyolefin resin coating layer is 300 l / min or more per 1 m ² of the contact area between the polyolefin resin coating layer and the cooling roll. For producing a support for photographic printing paper.