JPH0882890A - Supporting body for photographic paper - Google Patents

Abstract

PURPOSE: To provide a supporting body for a photographic paper suitable to produce a photographic paper which is soft and excellent in surface smoothness and image sharpness and suppresses curling tendency during storage and curling of the photographic paper generating during development. CONSTITUTION: The supporting body consists of a paper base essentially comprising natural pulp, a surface resin coating hardened layer on the surface where photographic emulsion layers are to be formed, and a back resin coating layer on the back surface of the paper base. The surface resin coating layer essentially consists of an unsatd. org. compd. and TiO2 and can be hardened with irradiation of electron beams. The back resin coating layer essentially consists of a film-forming synthetic resin. The film-forming synthetic resin in the back resin coating layer essentially consists of low density polyethylene and has 0.910-0.945g/cc apparent resin density after mixed. The coating amt. is 18-37g/m<2> .

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a support for photographic printing paper. More specifically, the present invention relates to a photographic printing paper support that suppresses curl curl that occurs during storage and photographic paper curl that occurs during development processing and that maintains sufficient flexibility.

[0002]

2. Description of the Related Art Conventionally, as a support for photographic printing paper, a polyolefin-coated support produced by coating both sides of a paper substrate with a polyolefin resin has been widely used. The photographic printing paper obtained by using the body was not sufficiently satisfactory in image sharpness.

In recent years, Japanese Patent Publication No. 60-17104, Japanese Patent Publication No. 60-17105, and Japanese Unexamined Patent Publication No. 57-49946.
Japanese Unexamined Patent Publication (KOKAI) Publication No. 2003-242242 discloses a support for photographic printing paper in which a composition comprising an unsaturated organic compound curable by electron beam irradiation (hereinafter referred to as electron beam curable resin) is applied to the support.

The image sharpness and smoothness of the photographic printing paper obtained by using such a support are remarkably improved as compared with the photographic printing paper obtained by using the polyolefin resin-coated support.

The photographic printing paper can be roughly packaged and stored in two types, that is, a sheet-shaped material and a roll-shaped material. In recent years, since the exposure and development processing of the photographic printing paper has been automated and speeded up,
The percentage of rolled material is increasing. A major problem in rolls is curl curl that occurs during storage. The curl curl causes problems such as paper jams in the transport unit of the exposure device or the automatic developing device, or jumping up when it is attached to the mount, in practice. The degree of curl curl depends on the thickness of the support for photographic printing paper, the rigidity, the electron beam curable resin coating layer and the backside resin in addition to the size of the winding diameter, environmental factors such as aging in the wound state, temperature and humidity. The characteristics of the photographic paper support itself, such as the viscoelasticity of the coating layer, have a great influence.

Further, the photographic printing paper coated with a photographic emulsion has a problem that curling with the emulsion layer side facing inward (hereinafter referred to as photographic printing paper curl) occurs due to drying of the emulsion after development processing. It has been practiced to curl the back surface of the support for paper beforehand.

Further, when a surface resin coating layer of a conventional photographic printing paper support coated with a polyolefin resin is processed by melt extrusion coating with a polyolefin resin heated and melted at 200 ° C. or higher, the surface resin coating accompanying cooling shrinkage of the polyolefin resin Curling occurs with the layers inside.

As a countermeasure against such curl curl and photographic paper curl of the photographic printing paper support, curling is preliminarily provided on the back surface side, and the resin density of the polyolefin resin used for the back surface resin coating layer. JP-B-48-9963 discloses that the resin density is higher than that of the polyolefin resin used for the surface resin coating layer. Therefore, a mixture of high-density polyethylene (hereinafter referred to as HDPE) and low-density polyethylene (hereinafter referred to as LDPE) is generally used for forming the backside resin coating layer,
The present inventor examined the mixing ratio of HDPE and LDPE in order to improve curl resistance in Japanese Patent Application No. 5-283550.
It has been found that the higher the apparent resin density, the better the curl resistance is, by incorporating a large amount of HDPE.

However, in the support for photographic printing paper coated with an electron beam curable resin, when the surface resin coating cured layer is formed,
Since heating other than the reaction heat generated by the curing reaction due to electron beam irradiation is not performed, curling with the surface resin coating cured layer inside immediately after processing due to cooling shrinkage does not occur, and the surface resin coating cured layer outside As a result, there remains a problem that the curl curl with the surface resin coating cured layer side as the outer side becomes large during storage in the wound state.

As described above, in the support for photographic printing paper in which the electron beam curable resin is used for the surface resin coating and curing layer and the mixture of LDPE and HDPE is used for the backside resin coating layer,
Curl curl and photographic paper curl were generated, and it was not possible to suppress the curl when used as photographic printing paper.

[0011]

SUMMARY OF THE INVENTION The object of the present invention is to solve the above problems of the prior art, to suppress curl curl and photographic paper curl during storage, to provide flexibility, surface smoothness and image sharpness. The present invention aims to provide a photographic paper support suitable for producing an excellent photographic paper.

[0012]

DISCLOSURE OF THE INVENTION The inventors of the present invention have made various studies to improve the curl curl and the photographic paper curl, which are the above-mentioned problems, and as a result, have found that the backside resin coating layer is composed mainly of polyethylene. According to the apparent resin density of the resin composition and the coating amount, it is found that the back surface resin coating layer is easily deformed when the roll-shaped product is unwound, thereby suppressing the occurrence of curl curl and photographic paper curl,
The present invention has been completed.

The support for photographic printing paper according to the present invention comprises a paper base containing natural pulp as a main component, a paper base on which a photographic emulsion layer is formed, and which is curable by electron beam irradiation. A surface resin coated and cured layer containing a saturated organic compound as a main component and at least one layer containing titanium dioxide, and a back surface resin formed on the back surface of the paper substrate and containing a film-forming synthetic resin as a main component. In a photographic printing paper support comprising a coating layer, the apparent resin density of the film-forming synthetic resin of the backside resin coating layer is 0.9.
It is a polyethylene resin composition of 10 to 0.945 g / cc, and the coating amount of the polyethylene resin composition is 18 to
It is characterized in that it is 37 g / m ² .

Further, curl curl and photographic paper curl according to the present invention are hardly dependent on a manufacturing method such as a coating method when the surface resin coating layer has a multilayer structure, but the surface resin coating layer is It is also possible to improve flexibility and flexibility by using an electron beam curable resin that shares functions such as developer penetration prevention and interference fringe prevention with a layered structure of two or more layers.

An inorganic white pigment such as titanium dioxide is mixed in the surface resin coating layer of the photographic printing paper support of the present invention for the purpose of improving the hiding property and the image clarity. In general, it is difficult to add 20% by weight or more of titanium dioxide because the conventional polyolefin resin has poor dispersibility, and bubbles are generated in the melt extrusion coating step due to the volatile component contained in the pigment. Is. However, by using an electron beam curable resin for the surface resin coating layer, there is no need to heat and melt,
Since the pigment can be added up to 80% by weight, the hiding property and the image sharpness are remarkably improved. Furthermore, since there is no expansion due to heating or contraction due to cooling, the surface of the surface resin coating layer formed by a casting method in which it is pressed against a highly smooth surface such as a metal drum or polyester film to cure and transfer, is melt extruded and coated with a polyolefin resin. The smoothness is significantly higher than that of the surface of the surface resin coating layer.

In the support for photographic printing paper of the present invention, as the polyethylene for forming the backside resin coating layer, LDPE having a resin density of 0.905 to 0.925 g / cc and resin density of 0.941 to 0. 965 g / cc HDPE
Alternatively, linear low-density polyethylene (hereinafter referred to as L.LDPE) having a resin density of 0.926 to 0.940 g / cc can be used, and these are used alone or as a polyethylene resin composition in which these are mixed. The polyethylene resin composition has an apparent resin density of 0.910 to 0.945 g / cc, preferably 0.915 to 0, in order to exert the function of the backside resin coating layer and suppress curl curl and photographic paper curl. It needs to be 940 g / cc. The apparent resin density of this backside resin coating layer is 0.945 g / c
When it exceeds c, the flexibility is poor and the curling curl becomes large. On the other hand, when the apparent resin density is less than 0.910 g / cc, the surface of the backside resin coating layer is likely to be scratched, and it is difficult to peel from the cooling roll during melt extrusion coating.

In the support of the present invention, the polyethylene resin composition has a coating amount of 18 to 37 g / m ² , in order to exert the function of the backside resin coating layer and suppress curl curl and photographic paper curl. Preferably 20-35 g / m ² ,
More preferably, it is in the range of 23 to 30 g / m ² . When the coating amount of the backside resin coating layer is less than 18 g / m ² ,
If the curl of photographic paper becomes large and exceeds 37 g / m ² ,
Poor flexibility and large curl curl.

The molecular weight of polyethylene used in the polyethylene resin composition used for the backside resin coating layer according to the present invention is not particularly limited, but is usually 20,000 to 200,0.
Those in the range of 00 are used. If necessary, additives such as a white pigment, an antioxidant and a lubricant may be added to the polyethylene resin composition. To form the backside resin coating layer using the polyethylene resin composition, a usual melt extrusion coating method can be used.

The unsaturated organic compound in the electron beam curable resin used to form the surface resin coating / cured layer of the present invention may be a monomer alone, an oligomer alone, or a mixture thereof. There is no particular limitation on the kind of compound. The unsaturated organic compound can be selected from the following compounds, for example. (1) Acrylate compounds of aliphatic, cycloaliphatic and aromatic alcohols and polyalkylene glycols. (2) Acrylate compounds obtained by adding an alkylene oxide to an aliphatic, cycloaliphatic or aromatic alcohol. (3) Polyacryloyl alkyl phosphates. (4) Reaction product of polybasic acid, polyol, and acrylic acid. (5) A reaction product of an isocyanate, a polyol, and acrylic acid. (6) A reaction product of an epoxy compound and acrylic acid. (7) A reaction product of an epoxy compound, a polyol, and acrylic acid.

These compounds may be used alone or in part 2.
A combination of two or more species can be used.

In the present invention, the surface resin coated and cured layer is
The mixture mainly contains an unsaturated organic compound that can be cured by electron beam irradiation and a white pigment, and may contain other additives as necessary. As the white pigment, anatase type and rutile type titanium dioxide is mainly used, but in addition to this, any of barium sulfate, calcium carbonate, aluminum oxide, zinc oxide, magnesium oxide and magnesium hydroxide can be used. . The content of the white pigment is 20 to 80% by weight, preferably 30 to 60% by weight, based on the total solid content of the surface resin coated and cured layer. When the content is less than 20% by weight, the image sharpness of the obtained photographic image on the photographic paper is insufficient, and 8
When the content is more than 0% by weight, the flexibility of the surface resin coated cured layer obtained is lowered and film cracking occurs.

In the present invention, the coating amount of the electron beam curable resin in the surface resin coating / curing layer is 10 to 50 g / cured after curing.
m ² , preferably 15 to 30 g / m ² . 10 g / m
^When the coating amount is less than ^2, the smoothness, whiteness and image clarity of the support surface are poor, and when it exceeds 50 g / m ² , the cost is high.

As the paper substrate used in the present invention, one having a basis weight of 50 to 300 g / m ² and a smooth surface is usually used. The paper substrate can be selected from all those generally used for a photographic printing paper support, and as usable natural pulp, generally, softwood pulp, hardwood pulp, softwood hardwood mixed pulp, etc. are the main components. Those that do are widely used. It is also possible to include a filler in the paper substrate.

When a photographic printing paper is produced from the support of the present invention, a magnesium compound such as magnesium hydroxide, magnesium oxide or magnesium salt is contained in the paper base for the purpose of preventing fog which occurs during long-term storage. That is valid. Further, the paper substrate may be blended with additives such as a sizing agent, a fixing agent, a paper strength enhancer, a filler, an antistatic agent, a pH adjusting agent, a pigment and a dye which are generally used for papermaking. Further, a surface sizing agent, a surface paper strength agent, a pigment, a dye, an antistatic agent or the like may be appropriately applied on the surface.

[0025]

EXAMPLES The constitution and effects of the present invention will be further explained by the following examples, but the present invention is of course not limited to these embodiments.

Example 1 A back surface of a woodfree paper having a basis weight of 180 g / m ² was subjected to a surface activation treatment by corona discharge, and a polyethylene resin composition having the following composition (composition 1) was melt-extrusion coated on the back surface. Then, a backside resin coating layer having a coating amount of 20 g / m ² is provided,
A sheet-like substrate was formed. Composition 1 Ingredient weight LDPE (TM: LK-30, manufactured by Mitsubishi Petrochemical Co., Ltd.) 100 parts by weight (resin density 0.918 g / cc, a melt index 4g / min)

Separately, as an electron beam curable resin, an electron beam curable organic compound-white pigment mixed composition having the following composition (composition 2) was mixed and dispersed for 1 hour with a paint conditioner to obtain an electron beam curable resin. Was prepared. Composition 2 Ingredient weight polyester acrylate 30 parts by weight (trademark: Aronix M7100, manufactured by Toagosei Co., Ltd.) ethoxy diethylene glycol acrylate 20 parts by weight (trademark: EC-A, Kyoeisha Yushi Chemical Co., Ltd.) Titanium dioxide (trademark: TIPAQUE A-220 , Ishihara Sangyo) 50 parts by weight

The electron beam curable resin is applied on the surface of a sheet-like substrate with a wire bar so that the coating amount after curing is 25.
The coating is in g / m ^2, the coating liquid layer superposed on the polyester film molding surface, the acceleration voltage from the surface side of the paper substrate is 175 KV, absorbed dose is irradiated with an electron beam under conditions of 2 Mrad, and cured Then, the polyester film was peeled off to prepare a support for photographic printing paper.

The curl curl and the photographic paper curl of the obtained photographic printing paper support during storage were evaluated by the following methods,
The evaluation results are shown in Table 1.

1. Curling curl (preparation of sample) A sample of a photographic printing paper support having a size of 89 mm in width direction and 140 mm in flow direction is placed flat at 20 ° C. and 65% R.
Leave in H atmosphere for 1 week. A support for photographic printing paper having a size of 89 mm in the width direction and 300 mm in the flow direction is left in an atmosphere of 20 ° C. and 65% RH for 1 week to be used as a backing paper for measurement.

(Treatment) A curl measurement sample is prepared by wrapping a surface-coated resin-cured layer of a sample on a paper tube having an outer diameter of 88 mm so that the cured layer is on the outside, wrapping a wrapping paper on it, and fixing it with an adhesive tape. In an atmosphere of 20 ° C. and 65% RH, one or two of the above samples are placed in a bag having a barrier property such as a polyester film, sealed, and left in a constant temperature bath at 40 ° C. for 5 hours. Then, it is taken out from the constant temperature bath and left for 30 minutes in an atmosphere of 20 ° C. and 65% RH.

(Measurement) After opening the bag having barrier properties, the patch paper is removed and the sample is taken out. The curl degree of the sample was such that the backside resin coating layer surface was on the lower side, and the TAPPI paper pulp test method No.
According to 16-77 "Paper Curl Test Method II", the following formula was used for measurement. +: Represents curl with the back resin coating layer surface outside-: represents curl with the back resin coating layer surface inside (curl degree = 100 / curl radius (cm)) (curl degree evaluation standard) -17 or more: practical Yes (absolute numerical value is small) -17 or less: Not practical (absolute numerical value is large)

2. Curling of photographic paper (pretreatment) Corona discharge treatment was applied to the surface of the resin-coated cured layer of the sample support, and a photographic emulsion for black and white photography (Rockland Colloid, trademark: Liquid Light) was applied to this surface. A photographic printing paper is prepared by coating so that the thickness after drying is 15 μm.

(Treatment and measurement) A test printing paper having a size of 10 cm × 10 cm was prepared by
After being left in an atmosphere of 65 ° C. and 65% RH for 16 hours, the surface-resin-coated cured layer was placed upward on a horizontal plane, the distances between the four corners and the horizontal plane were measured, and the average value thereof was calculated. The results were evaluated in the following 4 grades. (By the study of the present inventors, the evaluation method of the curl of the printing paper tends to be the same as that of the curl after the development processing.) A: The average distance of the four corners of the printing paper from the horizontal plane is 1 mm.
Less than. B: The average distance from the horizontal plane at the four corners of the photographic paper is 1 mm.
It is less than 2 mm. C: The average distance from the horizontal surface of the four corners of the photographic paper is 2 mm
It is less than 4 mm. D: The average distance from the horizontal plane at the four corners of the photographic paper is 4 mm
that's all.

(Evaluation Criteria) A and B: No practical problems C and D: Not usable

Example 2 Composition 1 was coated at a coating amount of 23 g / m ² to form a backside resin coating layer, and the same evaluation results as in Example 1 are shown in Table 1.

Example 3 The results of evaluations conducted in the same manner as in Example 1 by forming a backside resin coating layer with a coating amount of the composition 1 of 30 g / m ² are shown in Table 1.

Example 4 Composition 1 was coated at a coating amount of 35 g / m ² to form a backside resin coating layer, and the same evaluation results as in Example 1 are shown in Table 1.

Example 5 A polyethylene resin composition having the following composition (composition 3) was prepared and then melt-extrusion coated to a coating amount of 20 g / m ^2.
Table 1 shows the evaluation results obtained by forming a backside resin coating layer as above and performing the same procedure as in Example 1. Composition 3 Ingredient weight LDPE (TM: LK-30, manufactured by Mitsubishi Petrochemical Co., Ltd.) 65 parts by weight (resin density: 0.918 g / cc, a melt index 4g / min) HDPE (TM: EX10S, Mitsubishi Petrochemical Co. 35 parts by weight (resin density: 0.964 g / cc, melt index 2 g / min) (apparent resin density after compounding: 0.934 g / cc)

Example 6 Table 1 shows the evaluation results obtained by the same procedure as in Example 1 except that the backside resin coating layer was formed with the composition 3 having a coating amount of 23 g / m ² .

Example 7 The results of evaluation conducted in the same manner as in Example 1 except that the backside resin coating layer was formed with the coating amount of the composition 3 being 30 g / m ² are shown in Table 1.

Example 8 The results of evaluations conducted in the same manner as in Example 1 by forming a backside resin coating layer with a coating amount of the composition 3 of 35 g / m ² are shown in Table 1.

Comparative Example 1 Composition 1 was coated with a coating amount of 17 g / m ² to form a backside resin coating layer, and the same evaluation results as in Example 1 are shown in Table 1.

Comparative Example 2 Table 1 shows the evaluation results obtained in the same manner as in Example 1 except that the backside resin coating layer was formed with the coating amount of the composition 1 being 40 g / m ² .

Comparative Example 3 A backside resin coating layer was formed with a coating amount of the composition 3 of 17 g / m ² and the evaluation results obtained in the same manner as in Example 1 are shown in Table 1.

Comparative Example 4 Table 1 shows the evaluation results obtained in the same manner as in Example 1 except that the backside resin coating layer was formed with the coating amount of the composition 3 being 40 g / m ² .

Comparative Example 5 A polyethylene resin composition having the following composition (composition 4) was prepared and melt-extruded to a coating amount of 17 g / m ^2.
Table 1 shows the evaluation results obtained by forming a backside resin coating layer as above and performing the same procedure as in Example 1. Composition 4 Ingredient weight LDPE (TM: LK-30, manufactured by Mitsubishi Petrochemical Co., Ltd.) 30 parts by weight (resin density: 0.918 g / cc, a melt index 4g / min) HDPE (TM: EX10S, Mitsubishi Petrochemical Co. 70 parts by weight (resin density: 0.964 g / cc, melt index 2 g / min) (apparent resin density after compounding: 0.950 g / cc)

Comparative Example 6 A backside resin coating layer was formed with a coating amount of the composition 4 of 20 g / m ² and the evaluation results obtained in the same manner as in Example 1 are shown in Table 1.

COMPARATIVE EXAMPLE 7 Composition 1 was coated with a coating amount of 23 g / m ² to form a backside resin coating layer, and the same evaluation results as in Example 1 are shown in Table 1.

Comparative Example 8 A backside resin coating layer was formed with a coating amount of the composition 4 of 30 g / m ² and the evaluation results obtained in the same manner as in Example 1 are shown in Table 1.

Comparative Example 9 A backside resin coating layer was formed at a coating amount of the composition 4 of 35 g / m ² and the evaluation results obtained in the same manner as in Example 1 are shown in Table 1.

[0052]

[Table 1]

From the results shown in Table 1, the photographic printing paper supports having a backside resin coating layer that can be used for both curl curl and printing paper curl are Examples 1 to 8 satisfying the claims.
It has an apparent resin density and a coating amount of the polyethylene resin composition shown in.

[0054]

INDUSTRIAL APPLICABILITY The support for photographic printing paper of the present invention has problems of curling curl which occurs during storage, which is a problem when an electron beam curable resin is used to form a surface resin coating cured layer, and printing which occurs during development processing. It has become possible to obtain a photographic printing paper support suitable for producing a photographic printing paper that suppresses paper curl, is flexible, and has excellent surface smoothness and image sharpness.

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Claims (1)

[Claims] 1. A paper substrate containing natural pulp as a main component, and an unsaturated organic compound which is formed on the side of the paper substrate on which a photographic emulsion layer is formed and is curable by electron beam irradiation as a main component, and A support for photographic printing paper comprising a surface resin coated and cured layer comprising at least one layer containing titanium dioxide and a back surface resin coating layer formed on the back surface of the paper substrate and containing a film-forming synthetic resin as a main component. In the above, the film-forming synthetic resin of the backside resin coating layer contains low density polyethylene as a main component, and the apparent resin density of the film-forming synthetic resin is 0.910 to 0.945 g / c.
A support for photographic printing paper, characterized in that it is the polyethylene resin composition of c and the coating amount of the polyethylene resin composition is 18 to 37 g / m ² .