JPH02850A - Base for photographic paper - Google Patents

Abstract

PURPOSE:To eliminate a die lip contamination and to prevent the generation of neck-in by using a polyolefin resin having the SR value (the expansion ratio of a molten resin) within a specific range as the base material to be used for a surface resin coating layer. CONSTITUTION:The polyolefin resin contained in the surface resin coating layer has the value, within the 1.4-1.9 range, of the SR which is measured by a melt extrusion test under the conditions of 10mm length of the capillary by a capillary rheometer, 1mm inside diameter of the capillary, 200 deg.C melt resin temp., and 1000 1/sec shearing rate and is calculated by SR=d/D (where SR denotes the expansion ratio of the molten resin; (d) denotes the diameter in the position apart 10mm from the capillary outlet of the molten resin flow extruded from the capillary; D denotes the inside diameter of the capillary). The contamination of the die lip generated in the melt extrusion coating stage is prevented in this way and the hiding property when the resin is made into the photographic paper is enhanced. The sharp photographic image is thus obtd.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a support for photographic paper,
More specifically, the present invention relates to a photographic paper support that is manufactured without producing needle-like or icicle-like deposits or stains on the tip of the die lip in a melt-extrusion lamination process using a melt-extrusion die, and that has fewer defects in surface quality. It is something.

[Conventional technology]

Conventionally, baryta paper has been used as a support for photographic paper, but in recent years, water-resistant supports have been used that have resin coating layers on both sides of a sheet-like substrate made of a composition containing polyolefin resin as the main component. It has become possible to do so. This water-resistant support shortens washing and drying times during development of photographic papers made from it, eliminates the need for ferrotypes, reduces chemical consumption, maintains high levels of stiffness and strength, and It has the advantage of reducing stains caused by chemical penetration.

In addition, to form a resin coating layer on the support (on the surface), which requires the trouble of applying a photographic emulsion, a polyolefin composition containing titanium dioxide dispersed therein is usually used to improve the sharpness of the resulting photograph. Met.

However, when coating a polyolefin resin composition in which titanium dioxide is dispersed, especially a polyethylene resin composition, by melt-extruding it into a film from a slit die, needle-like or icicle-like attachments are formed on the tip of the die lip after a short period of extrusion. Die-lip stains (hereinafter referred to as die-lip stains) tend to occur, and these die-lip stains tend to grow larger with the elapse of melt extrusion time.

When melt extrusion coating a polyolefin resin composition,
When this dye lip stain occurs, vertical streaks may appear on the surface of the photographic paper support produced as is, and sometimes the stain may adhere to the film, resulting in the contamination of foreign matter. do. The surface quality of a support for photographic paper produced in such a state is significantly impaired, so that it has no commercial value at all as a support for photographic paper that requires excellent surface quality.

In addition, in order to completely remove the die lip stains that have occurred, there is no effective method other than stopping production and cleaning the die lip, which requires a great deal of effort and time. This caused a significant drop in productivity in the body manufacturing process.

As mentioned above, in the conventional manufacturing technology for photographic paper supports, die lip stains occur when coating a sheet-like substrate with a polyolefin resin composition in which titanium dioxide is dispersed by melt extrusion, and this causes problems in the support manufacturing process. Productivity was significantly lowered, but it is believed that the occurrence of die lip staining is closely related to the surface condition of the titanium dioxide used.

Titanium dioxide, which has been conventionally used in the coating layer of photographic paper supports, has the following properties:
Hydrous aluminum oxide, or a mixture of hydrated aluminum oxide and hydrated silicon dioxide that is precipitated and fixed.

The reason why such highly surface-treated titanium dioxide is used in manufacturing photographic paper supports is as described in JP-A-52-35625. This is because the use of titanium dioxide, which has been surface-treated only very lightly, has the following drawbacks.

(1) It has an adverse effect on photographic emulsions.

(2) Titanium dioxide has poor dispersibility and pinholes are likely to occur.

(3) Poor adhesion between the coating resin layer and the emulsion layer.

(4) The white background of photographs tends to change over time due to adsorption and residual photographic processing chemicals.

(5) The whitening effect of the fluorescent whitening dye is poor.

Therefore, titanium dioxide (without surface treatment), which has the above-mentioned drawbacks, is rarely used as a support for photographic paper.

However, when titanium dioxide is subjected to such a highly surface-treated surface treatment in order to meet the requirements necessary as a support for photographic paper, the problem arises that die lip stains are more likely to occur as the amount of surface coating increases. will occur. Therefore, if titanium dioxide is not contained in the surface resin coating layer formed on the emulsion-coated side (surface) of the photographic paper support, or if its content is small, the occurrence of die lip stains is small, but , the hiding power of the surface resin coating layer becomes smaller,
A problem arises in that the sharpness is low when used as photographic paper.

[Problem that the invention seeks to solve]

The present invention solves the conventional problems, namely, staining of the die lip that occurs in the melt extrusion coating process, and
It is an object of the present invention to provide a support for photographic paper with excellent surface quality, which has high hiding power and can produce sharp photographic images when made into photographic paper.

[However, in the above formula, SR represents the expansion rate of the molten resin, d represents the diameter of the molten resin flow extruded from the capillary at a position 10 times away from the capillary outlet, and D represents the inner diameter of the capillary]

It is characterized in that the value of SR calculated by is within the range of 1.4 to 1.9.

The present inventors have conducted extensive research in order to reduce or prevent the occurrence of gripp stains when coating a sheet-like substrate with a composition containing titanium dioxide and using a polyolefin resin as a base material, and As a result, they discovered that it is important to control the melt extrusion characteristics of the polyolefin resin used as the base material of the resin coating layer to a predetermined value, and completed the present invention.

That is, in the support for photographic paper of the present invention, the polyolefin resin contained in the surface resin coating layer is 1.4 to
It is important that it has an SR value within the range of 1.9.

In the present invention, the above-mentioned SR value is measured and calculated as follows.

That is, the polyolefin resin is subjected to a melt extrusion test using a capillary rheometer.

An outline of the structure of the capillary rheometer is shown in FIGS. 1 and 2.

In FIGS. 1 and 2, a cylinder 5 is formed in the center of the cylinder block 4, and a capillary block 6 disposed below the cylinder block 4 has a cylinder 5 in the center, which is continuous with the cylinder 5. A capillary 7 is formed having a length and an inner diameter. The cylinder block 4 and the capillary block 6 are heated to a predetermined temperature by a constant temperature bath 8 surrounding them. In addition, in order to pressurize the resin charged in the cylinder 5, a pressurizing device is constructed of a vertically movable raised beam 1, a load cell 2 connected to it, and a plunger 3 extending from it. equipment is provided.

In the present invention, in order to measure and calculate the SR value of a polyolefin resin, first, the polyolefin resin is measured with a capillary rheometer using a capillary length L.
= 1 (1 m, internal diameter of capillary D = 1 mm, molten resin temperature 200°C, shear rate = 10001/sec. Melt extrusion test is performed under the following conditions.

That is, in FIGS. 1 and 2, a sample polyolefin resin powder (pellet) is charged into a cylinder 5, and 2
It is heated and melted at 00℃. Next, this melt is pressurized by a plunger 3 of a pressurizing device that descends at a constant speed,
It passes through the capillary 7 and is pushed out of the capillary. The diameter d of the extruded polyolefin resin melt stream IO at a position 9 10 mm away from the capillary exit is measured optically (for example by laser light projection method or by means of a graduated magnifying glass) in a non-contact manner.

Next, calculate the SR value from this measured value d by formula (1) % formula % (1
) is calculated.

This SR value is the expansion of the polyolefin resin melt relative to the inner diameter of the capillary when the polyolefin resin melt is pushed out of the capillary from a state where it is loaded with shear force in the capillary and released to an unloaded state. It represents a percentage.

In the present invention, when the SR value of the polyolefin resin contained in the surface resin coating layer is larger than 1.9 under the above conditions, the polyolefin resin composition is applied to a support obtained by melt-extrusion coating on a sheet-like substrate. There are many sushi-like defects due to gui-lip stains, and the SR value is 1.
If it is less than 4, the occurrence of gripp stains will be reduced, but during melt extrusion coating, the film-like flow of the polyolefin resin composition melt extruded from the slit die will reach and contact the surface of the sheet-like substrate. During this period, the melt film flow shrinks, and as a result, the width of the resin coating flow of the obtained polyolefin resin composition becomes narrower than a predetermined value, that is, the neck-in phenomenon increases, which reduces the operational efficiency and production of the support manufacturing process. In the present invention, in which the efficiency is significantly reduced, a resin coating layer containing a polyolefin resin having an SR value within the range of 1.4 to 1.9 has fewer sushi-like defects on the sheet-like substrate due to grip stains, and
A support having good surface quality can be obtained with high production efficiency, very little occurrence of the neck-in phenomenon, and no or no neck-in phenomenon.

The conditions of a shear rate of 20,001/sec used in the melt extrusion test using the capillary rheometer are the most typical conditions in the manufacturing process of photographic paper supports by the melt extrusion coating method.

Additionally, the term "shear rate" used herein is
It represents the gradient of the velocity of the melt flow through the capillary in the direction perpendicular to the inner wall surface of the capillary.

The type of polyolefin resin used in the present invention is not particularly limited as long as it is thermoplastic and can be coated by melt extrusion, but polyethylene is particularly preferred, and has various densities and melt density indexes (melt index of 2 or less). Simply M
(abbreviated as 1) can be used alone or in combination. Further, when preparing the resin composition, an appropriate amount of other polyolefin resin such as polypropylene may be mixed to the extent that it does not interfere with the use as a photographic resin composition.

The titanium dioxide pigment to be contained in the polyolefin resin composition coated on the substrate surface on the side to which the photographic emulsion of the present invention is coated (front side) may be one made by a sulfuric acid method or a chlorine method, or a rutile type pigment. or anatase type, but the anatase type is advantageous in terms of whiteness. Furthermore, titanium dioxide pigments without surface treatment can also be used, and titanium dioxide pigments coated with an inorganic surface treatment agent such as hydrous aluminum oxide can also be used.
Alternatively, those coated with an organic surface treatment agent such as organopolysiloxane, or further coated with an appropriate combination of an inorganic surface treatment agent and an organic surface treatment agent, can also be used, but at least A l 203 minutes. as 0.2~2.0
% hydrous aluminum oxide treatment is preferable.

In addition, the content of titanium dioxide in the surface resin coating layer is 5 to 5.
Preferably it is 30% by weight. If the content of titanium dioxide is less than 5% by weight, the hiding power of the resin coating layer may be insufficient as described above, and the sharpness may be lowered when used as photographic paper. Also, 30% by weight
If the amount is more than 1, foaming of the molten polyolefin resin composition may occur during melt extrusion coating, and the coating layer may not be completely formed, which may make it difficult to manufacture the support.

The polyolefin resin composition used in the present invention may contain a metal salt of a fatty acid.

Such metal salts of fatty acids include zinc stearate, calcium stearate, aluminum stearate, magnesium stearate, zirconyl octylate, sodium palmitate, calcium palmitate,
Examples include sodium laurate.

In addition, the amount added is 0.01 based on the total amount of the resin composition.
It is preferably in the range of ~5% by weight.

In addition to fatty acid metal salts, the polyolefin resin composition used in the present invention further contains white pigments such as zinc oxide, talc, calcium carbonate, aluminum hydroxide, barium sulfate, stearic acid amide, alaxic acid amide, etc. fatty acid amide, tetrakis [methylene-3 (3.
5-di-tert-butyl-4-hydroxy-phenyl)propionate] methane, antioxidants such as 2,6-tert-butyl-4-methylphenol, ultramarine,
Coloring pigments such as red iron, carbon black, and titanium yellow, fibrous substances such as glass, asbestos, and whiskers, and fluorescent whitening agents may also be included.

The substrate used for the support of the present invention may be ordinary natural pulp paper, synthetic resin paper, or so-called synthetic paper made from synthetic resin film, but may include softwood pulp, hardwood pulp, and mixed softwood and hardwood pulp. Natural pulp paper based on pulp wood pulp is advantageously used.

There is no particular restriction on the thickness of the substrate, but a substrate with good surface smoothness is preferred, and its basis weight is 50 to 250.
g/- is preferred.

The paper substrate mainly composed of natural pulp used for the support of the present invention can contain various polymer compound additives. For example, dry paper strength enhancers include cationized starch, cationized polyacrylamide, anionized polyacrylamide, carboxy-modified polyvinyl alcohol, gelatin, etc.; sizing agents include fatty acid salts, rosin derivatives, dialkyl ketene dimer emulsions, alkenyl, are used as pigments such as alkyl succinate emulsions, petroleum resin emulsions, ammonium salts of alkyl esters of styrene-maleic anhydride copolymers, and as wet paper strength agents such as clay, kaolin, calcium carbonate, barium sulfate, titanium oxide, etc. , melamine resin, urea resin,
Epoxidized polyamide resin, fixing agents such as polyvalent metal salts such as aluminum sulfate and aluminum chloride, cationic modified polymers such as cationized starch, pH3N moderation agents such as caustic soda, soda carbonate, and hydrochloric acid, and inorganic electrolytes such as salt, In addition to Glauber's salt, a suitable combination of dyes, fluorescent whitening agents, latex, etc. can be incorporated into the paper base.

In producing the support of the present invention, a polyolefin resin composition is coated on a sheet-like substrate by a melt extrusion method.
The melt extrusion temperature at that time is suitably 200 to 350°C, and the slit die used at that time is preferably a flat die such as a T-shaped die or an L-shaped die.

Further, before coating the resin composition on the substrate, it is preferable to subject the substrate to an activation treatment such as a corona discharge treatment or a fire treatment. The thickness of the resin layer of the resin-coated paper is not particularly limited, but it is generally preferable to extrude coat it to a thickness of about 5 microns to 50 microns. In addition, in a normal resin-coated support in which both sides of the base are coated with resin,
The surface of the resin layer containing titanium dioxide pigment has a glossy surface, a matte surface, a grain surface, etc. depending on its use, and the opposite surface (back surface) is usually a matte surface. Both surfaces may also be subjected to activation treatment such as corona discharge treatment or fire treatment. If necessary, a subcoat may be applied on the front resin coating layer to improve adhesion with the photographic emulsion, or a back coat may be applied on the back resin coating layer to improve printing and writability and antistatic properties. You may.

〔Example〕

The present invention will be further explained below with reference to Examples.

1-4 and 1-3 In each Example and Comparative Example, 50 parts by weight of high-density polyethylene having the melt flow index and density listed in Table 1, 50 parts by weight of alumina-treated anatase titanium dioxide, and 2 parts by weight of zinc stearate. .5 parts by weight were kneaded at 160°C using a Banbury mixer.
A master bunch containing 0% titanium dioxide was prepared.

The following sheet-like substrates made of paper were prepared.

That is, Canadian Standard Freeness (JI)
S P-8121-76) 20% softwood bleached sulfite pulp (NBSP) beaten to a freeness of 250- and hardwood bleached sulfate pulp (LBK) beaten to a freeness of 280-
P) was mixed with 80% to prepare a papermaking raw material. The following paper-making additives were used in the following amounts based on the absolute dry weight of the pulp.

Cationized starch 2.0% alkyl ketene dimer resin 0.4% anionic polyacrylamide resin 0.1% polyamide polyamine epichlorohydrin resin 0.7% caustic soda Adjusted to pH 7.5 Paper was made using the above additives. , dryer, size press, machine calender, rice scale 170g/rtr, tension 1.
A paper substrate with a moisture content of 8% was obtained. The size press chemical was prepared by dissolving carboxyl-modified PVA and sodium chloride in water at a ratio of 2=1, and applying it as a 5% size liquid to both sides of the paper at a coating amount of 25 g/d. The obtained paper substrate was subjected to corona discharge treatment and subjected to a coating test. Next, apply high-density polyethylene (density 0.94 g/c) to the back side of the paper base.
J.

M I = 9.0) and low density polyethylene (density 0
．． 92 g/crl, M I = 4.6):
1 mixture was extrusion coated at a resin temperature of 330° C., and set molding was performed using a cooling roll to form a back resin coating layer with a thickness of 30 mm.

Next, a mixture of 20 parts by weight of the 50% titanium dioxide-containing masterbatch and 80 parts by weight of high-density polyethylene having the MI and density listed in Table 1 as a diluent resin was applied to the surface of the paper substrate using a melt extruder. Sample A was prepared by melt extrusion coating using a coating speed of 14 m/min and a melting temperature of 320°C to a film thickness of 30p. The melt extruder is manufactured by Toyo Seiki Co., Ltd. (trade name Labo Plastomill 50C-150), extrusion opening diameter is 20, L/D =
A melt extruder with a 25 mm screw extruder and a 15 mm wide T-die was used.

In addition, the SR value of the polyolefin resin used in each Example and Comparative Example was measured and the occurrence of Greylip stains in the coating process was evaluated as follows.

SR value: Calculated by formula (1) from the value of d measured under the following measurement conditions using a capillary rheometer (manufactured by Toyo Seiki Co., Ltd., trade name: Cavilograph).

Capillary length: 10m, capillary inner diameter: 1
11. Molten resin temperature: 200°C, shear rate = 10001
/sec Die lip stain: The number of die lip stains in all small samples one hour after the start of melt extrusion was measured (number of stains/150 mm width).

Table 1 shows the relationship between the SR value and the effect of preventing die lip staining and neck-in occurrence.

As is clear from Table 1, in Examples 1 to 4 in which the polyolefin resin of the present invention was used, die lip staining did not occur, and the effect of preventing the neck-in phenomenon was also good.

However, in Comparative Examples 1 and 2 (SR>1.'?), a large number of die lip stains occurred.

In Comparative Example 3 (SR<1.4), no die lip stain was observed, but the neck-in phenomenon was so severe that it could not be put to practical use.

〔Effect of the invention〕

In the present invention, by using a polyolefin resin having an SR value within a specific range as the base material for at least the surface resin coating layer, the support of the present invention is free from die lip stains and has the effect of preventing neck-in phenomenon. can have a good surface quality.

[Brief explanation of the drawing]

FIG. 1 is an explanatory cross-sectional view showing the main part of the structure of the capillary rheometer, and FIG. 2 is an explanatory cross-sectional view showing the state of extrusion of a polyolefin resin composition in a part of the capillary of the capillary rheometer shown in FIG. 1... Lowering beam, 2... Load cell, 3...
... Plunger 4 ... Cylinder block, 5
... Cylinder 6... Capillary block, 7... Capillary 8... Constant temperature bath, 9... Position for optically measuring the diameter d of the extruded polyolefin resin composition.

Claims (1)

[Scope of Claims] 1. A sheet-like substrate, and a surface resin coating layer formed on the surface (photographic emulsion coated surface) of the sheet-like substrate and made of a composition whose base material is a polyolefin resin containing titanium dioxide. and a back resin coating layer formed on the back surface of the sheet-like substrate and made of a composition having a polyolefin resin as a base material, wherein at least the polyolefin resin contained in the front resin coating layer is attached to the capillary. By rheometer, capillary length: 10 mm, capillary inner diameter: 1 mm, melt temperature: 200°C and shear rate: 1000 1/
It was measured by a melt extrusion test under the conditions of seconds, and the following formula (1
): SR=d/D(1) [However, in the above formula, SR represents the expansion ratio of the molten resin, and d
represents the diameter of the molten resin flow extruded from the capillary at a position 10 mm away from the capillary outlet,
and D represents the inner diameter of the capillary.] A support for photographic paper having an SR value within the range of 1.4 to 1.9. 2. The support according to claim 1, wherein the sheet-like substrate is made of paper. 3. The support according to claim 1, wherein the polyolefin resin is selected from polyethylene resins. 4. The support according to claim 1, wherein the polyolefin resin composition contains at least one metal salt of a fatty acid.