JP3047495B2 - Film for lamination on metal plate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a film for laminating a metal can material such as a soft drink, beer or canned product, which is used for heat resistance, cosmetics and rust prevention.

[0002]

2. Description of the Related Art Metal plates such as steel and aluminum are mainly used as can materials for various soft drinks, beers, cans, and the like. Printing and coloring are applied. The method of printing and coloring these containers that is currently in practical use is a method in which a metal plate is slit into a predetermined size and then printed by offset printing or the like and then printed.
Alternatively, it is a method of performing bending and processing into a cylindrical shape after slit processing, performing seam welding, and then performing printing and baking by offset printing or the like. Then, a metal container is obtained by performing flange processing, inside coating and baking, seaming processing, and the like.

[0003]

However, in the method of printing directly on a metal material, whether printing is performed in a flat plate shape or in a method of printing after forming into a cylindrical shape, a metal material such as gravure printing is used. A printing method using an intaglio printing cannot be adopted. This is because the metal material is hard and it is extremely difficult to make the metal intaglio uniformly contact the entire printing surface. Therefore, in the past, a plate having elasticity such as a rubber plate or a flexible resin plate has been used, but the printing accuracy when using such an elastic intaglio is poor, and it is difficult to obtain clear printing. In addition, it is difficult to perform complicated printing that requires a wide range of gradation settings such as halftone printing and photographic printing, and in reality, only extremely monotonous printing and coloring are performed.

[0004] In order to enable more beautiful and three-dimensional printing, multiple printing using a large number of paints is required. However, drying and baking of the printing ink takes a long time. When such multiple printing is incorporated into the can-making process, there arises a problem that the drying and baking of the printing ink is rate-limiting and the can-making speed becomes extremely slow. Therefore, the number of overprints that can be practically used on an industrial scale is naturally limited, and printing with satisfactory sharpness and aesthetic design cannot be obtained.

A method of offset printing on a slit-processed metal plate is also known, but it is still difficult to perform halftone printing and the like, and printing with satisfactory sharpness and aesthetic design cannot be obtained. Then, it is the same as the case of the gravure printing.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to solve the above-mentioned problems pointed out when directly printing on a metal plate processed into a plate shape or a cylindrical shape. It provides a completely new technology that can wipe out the points, and is used for laminating a metal plate for seam welding can to obtain a clear, beautiful and high-grade beautiful decorative metal plate. It is intended to provide a film.

[0007]

Means for Solving the Problems The structure of the laminating film according to the present invention which can solve the above problems is as follows.
On one side of a thermoplastic resin film with a printing ink layer,
A transparent or colored film is laminated via an adhesive layer made of a curable resin, and a transparent cured heat-resistant layer is formed on the surface of the laminate, and a heat seal layer is formed on the opposite side. Has a gist where it is. By using this film for laminating a metal plate for seam welding cans made of steel, aluminum, etc., it is possible to obtain a clear and luxurious cosmetic laminate metal plate, and furthermore, a laminating surface of this laminated metal plate. When the can is made in a conventional manner with the side facing outward, a seam welded can with a beautiful body can be obtained.

[0008]

The present inventors believe that the laminating method can be applied as a new cosmetic means that can at once solve the above-mentioned problems pointed out in the prior art of directly printing on a steel sheet. In order to develop a laminating film that meets these objectives, intensive research was conducted.

That is, if a method of printing a laminate film in advance and laminating it on a metal plate is adopted, not only is the can-making process significantly simplified and high-speed production is made possible, but also the printing becomes soft. Since it is performed on film, clear printing using metal intaglio printing is possible, and halftone printing, photographic printing or multicolor printing with three-dimensional appearance can be easily performed, and high quality cosmetic printing We thought that this could be achieved and proceeded with research based on these ideas.

As a result, it has been found that, when the above-mentioned laminating method is employed, not only the above-mentioned effects expected at first are achieved brilliantly, but also various incidental effects can be obtained as will be described later. I saw the completion. Hereinafter, the configuration, operation and effect of the present invention will be described in detail.

The basic structure of the laminating film according to the present invention is, for example, as shown in FIG. 1 (partly enlarged cross-sectional view), in which a printing ink layer 2 is provided on one surface of a thermoplastic resin 1. 2 is a five-layer structure in which a transparent or colored film 4 is further laminated via an adhesive layer 3 made of a curable resin, and a heat seal layer 5 is formed outside the film 4. The heat seal layer 5 side can be laminated to a metal plate Me indicated by a symbol by a dry lamination method, a thermal lamination method, or the like.

Here, the thermoplastic resin 1 comprises a printing ink layer 2
Is a substrate film on which is formed a transparent film having a suitable flexibility to enable sharp and beautiful multiple printing and to easily perform a bending process or the like at the time of can manufacturing after lamination. A plastic resin is used. However, this thermoplastic resin has a melting point of 160 so as to withstand the heat received during seam welding during can making, inside coating after can making, boiling after sealing the contents, or retorting afterwards. If the melting point is too low, pinhole defects may occur due to heating during the inside coating process, etc., or the film may melt or soften and shrink, resulting in loss of smoothness or gloss. Loss, and the film is liable to have defects such as blister-like irregularities, stress cracks, and delamination.

From these viewpoints, the more preferable melting point of the thermoplastic resin is 160 ° C. or more, and preferable specific examples thereof include polyester resin, polypropylene resin, polymethylpentene-1, polymer carbonate, polyimide, PPS, and the like which meet the above melting point. , PEK, PEEK, and the like, or various modified resins thereof. When the printing ink layer 2 is formed inside the resin layer 1 as shown in FIG. 1, the thermoplastic resin layer 1 should be transparent so that the printing ink layer can be seen through from the outer surface side.

Next, the printing ink layer 2 is not particularly special, and any type of printing ink used for a conventional packaging film or the like can be used, and its forming method may be a conventional method.

The adhesive layer 3 is used to join the printing ink layer 2 and the transparent or colored film 4, and any type of adhesive having an adhesive property suitable for the purpose is used. However, the laminating film of the present invention is laminated as a metal plate or a metal container exterior as described above, and is subjected to a baking process after the can making process or the filling of the contents and a subsequent retort process. For example, it is desired to use an adhesive made of a curable resin so that sufficient adhesiveness to such heat can be maintained.

Preferred examples of such curable resins include epoxy resins, polyurethanes, polyesters, polyester polyurethanes, isocyanate resins, and various modified resins thereof.

The transparent or colored film 4 bonded to the adhesive layer 3 increases the strength as a laminating film and is laminated as a support layer for convenience in handling. That is, if the adhesive layer 3 is exposed on one side of the laminating film, the film may cause blocking in the handling process, may stick to unexpected parts, or may tear when subjected to tension in the laminating process. However, if the film 4 is laminated on the adhesive layer 3, such a problem does not occur at all, and handling becomes extremely easy. Moreover, if the film 4 is colored, the colored film 4 has an effect of concealing the ground color of the metal plate Me when laminated on a metal plate, and the printing ink layer appearing on the outer surface side of the laminated metal plate is sharp. This is preferable because the effect of further increasing the degree and coloring effect is also exhibited.

The color given to the film may be selected from the optimum colors that can more effectively enhance the coloring effect according to the color of the printing ink. This is advantageous because a uniformly excellent coloring property improving effect is exhibited even for printing inks of various colors. The material of the transparent or colored film 4 is not particularly limited, but it can withstand heat received in a canning process after lamination on a metal plate or a subsequent boiling process or retort process, preferably having a melting point of about 160 ° C. or more, It is more preferable to use those having a temperature of 200 ° C. or higher, and preferred specific examples are polyester resin, polyamide resin,
Examples thereof include polypropylene resin, polycarbonate, polymethylpentene, polyimide, and various modified resins thereof, and have a thickness of 4 to 180 μm, more generally 7.5 to 100 μm.

Next, the heat seal layer 5 provided on the outside of the transparent or colored film 4 is formed as an adhesive layer when laminating to the metal plate Me. Although the type is not particularly limited, considering that a considerably high-temperature heat is applied after the lamination as described above or after the lamination,
Those with a very low melting point are not preferred, preferably 160
It is desirable to use a heat-sealable resin having a melting point of at least 175 ° C, more preferably at least 175 ° C. Examples of such a high melting point heat-sealable resin include various thermoplastic elastomers such as polyester-based, polyamide-based, and vinyl-based resins, and various modified resins thereof. It is better to make the wall thinner as far as the heat sealing property can be exhibited, and the preferable wall thickness is in the range of 0.1 to 50 μm. A more preferred thickness is in the range of 0.5 to 20 μm, and still more preferably 0.8 to 10 μm.

Although the heat seal layer 5 can be formed as the outermost layer in the final step of manufacturing a laminating film, the most common method is to laminate or coat the transparent or colored film 4 with a laminating method or a coating method. This is a method in which the heat seal layer 5 is bonded in advance by, for example, and then bonded to the adhesive layer 3 to form a film for lamination.

FIG. 2 shows an embodiment of the present invention in which the laminating film having the basic structure shown in FIG. 1 is improved. A cured heat-resistant layer 6 is formed on the outer surface side of the plastic resin layer 1 to further increase the heat resistance of the surface layer. That is, as described above, the thermoplastic resin layer 1 having the high softening point is used as the thermoplastic resin layer 1 on which the printing ink layer 2 is provided, but the thermoplastic resin layer 1 is still softened depending on the seam welding conditions during can manufacturing. In some cases, it may be damaged by heat or heat, or a whitening phenomenon may occur due to heat treatment or retort treatment after the contents are enclosed, thereby deteriorating the aesthetics. However, if the cured heat-resistant layer 6 is formed on the surface of the thermoplastic resin layer 1, the cured heat-resistant layer 6 functions as a heat-resistant protective layer, and is accompanied by thermal degradation and softening of the thermoplastic resin layer 1. Deformation or whitening. Therefore, if protection is performed by the cured heat-resistant layer 6, it is possible to use a resin having a relatively low softening point as the thermoplastic resin layer 1.

In this case, since the hardened heat-resistant layer 6 functions as a protective layer on the outermost surface side, for example, as shown in FIG. 2 can also be formed.

The constituent materials of such a cured heat-resistant layer 6 include:
Softening point or decomposition temperature of 250 ° C or higher, more preferably
It is better to use one at 300 ° C or higher, such as silicone, epoxy, urea, acrylic, urethane,
Various curing reactive resins such as an unsaturated polyester resin can be used, but a transparent resin should be used so as not to impair the aesthetic effect provided by the printing ink layer 2. The thickness thereof is 0.5 to 10 g / m ^2, is more range of 0.5 to 5 g / m ² preferably, the surface protective effect if too thin is difficult to sufficiently exhibit, whereas too thick bending cured heat during processing Cracks easily occur in the layer 6.

The laminating film of the present invention is a laminated film having a six-layer structure as described above, and is laminated on a metal plate by a dry laminating method or a thermal laminating method as described above. At this time, for example, as shown in FIG. 4, a transparent or colored coat layer (or primer layer) is formed on the laminate surface side of the metal plate Me.
It is preferable to adopt a method of laminating after forming 7 in advance, because the laminating adhesiveness can be improved and the laminating speed can be further increased.

In particular, it is preferable to color the coat layer 5 because it conceals the ground color of the metal plate and further improves the sharpness provided by the printing ink layer 2 and also increases the lamination strength. The color of the coat layer 7 formed as a base layer may be appropriately selected according to the coloring of the printing ink layer 2.
It is preferable because the uniformity of the printing ink layer 2 of any color can provide an excellent sharpness improving effect.

When the thus obtained laminating film is laminated on a metal plate or a metal plate on which a coating layer is formed by the above-described method, a beautiful metal plate can be obtained. In this state, not only can it be used as various panel materials and decorative outer panel materials, but if it is made according to a conventional method, a very beautiful and highly designable metal container can be obtained.

The present invention is configured as described above. The features of the present invention are summarized below in comparison with the conventional method of printing and printing directly on a metal plate.

(1) Realization of high-quality printing The method of printing directly on a metal plate lacks sharpness as described above, and it is difficult to perform halftone printing or photographic printing, and only monotonous printing can be obtained. However, in the present invention, since the method is a method in which printing is performed on the flexible thermoplastic resin layer and then laminating, the sharpness of the printing is high, and halftone printing, photographic printing, and the provision of a three-dimensional effect by multiple printing are easy. This makes it possible to print a wide range of colors and tones with a high-quality feel.

(2) Achieving high-speed printing In the conventional method, the time required for drying or curing of the printing ink is the rate-limiting of the can-making process as described above, so that the can-making speed cannot be sufficiently increased. In this case, a printed laminating film is prepared in advance, and can be brought into a can-making line to be continuously laminated on a metal plate, so that the speed of can-making can be significantly increased.

(3) Improvement of glossiness In the conventional method, gloss can be increased to some extent by forming an overcoat layer after printing and baking on a metal plate. However, the overcoat layer has a fine-grained coating. It is difficult to obtain satisfactory gloss because fine irregularities are formed on the surface of the coating layer due to slight shrinkage during drying. In contrast, in the present invention, a film having a high degree of smoothness can be obtained by treating the film with a mirror-finished roll in the manufacturing process of the laminating film. Since the outer surface side is slightly stretched in this process, the smoothness of the outermost surface of the laminated film in a can-making state is further increased, and extremely excellent gloss can be obtained.

(4) Improvement of scratch resistance and antifouling property In the case of the conventional example, the ink layer printed on the hard metal is easily damaged by scratching or the like, and the printing ink tends to fall off. Since the printing ink layer is protected by the cured heat-resistant layer and the thermoplastic resin layer having a high softening point, the ink does not drop off or scratch.
In addition, contamination of the printing ink layer due to spilled contents (liquids such as beverages and soups) and external contaminants does not occur.

(5) Reducing Cost of Beautifully Decorated Metal Plate or Metal Container In the method of printing on a metal plate or its cylindrical molded product, if a printing error occurs, all of the printed metal plate or the cylindrical molded product is removed. It becomes defective. In other words, a loss occurs after reaching a high value-added state. However, in the present invention, it is possible to select the quality at the printing stage on the thermoplastic resin film, and the printing technology on the resin film has been remarkably advanced, the rejection rate is extremely low, and if a printing error occurs Is also in a state of low added value, so that loss can be minimized. In addition, since printing on a film and lamination of the film on a metal plate can be performed at a high speed, high-speed production is possible, and from such a viewpoint, the product price can be reduced.

(6) Support for multi-product production In the conventional example, once printing is performed on a metal plate,
Although it can be used only for the purpose, the laminating film of the present invention can be similarly laminated on other metal plates and molded bodies as long as it is of the same size, and it can be used not only for mass production of the same kind but also for various kinds It is easy to cope with small production.

(7) Improvement of Laminating Adhesive Property By forming the heat seal layer as an adhesive layer, high-speed laminating property can be improved and laminating strength can be increased. Moreover, since the residual solvent does not remain between the metal plate and the film, bubbles are not generated by heating such as retort treatment and boiling treatment, and the beautiful appearance is not impaired. And if you color the film,
By hiding the color of the metal, the original color tone of the printing ink can be more effectively expressed.

Next, the present invention will be described in more detail with reference to examples. However, the present invention is not limited by the following examples and may be modified without departing from the above-mentioned purpose. Are all included in the technical scope of the present invention.

[0036]

EXAMPLE 1 A film having a thickness of 12 μm (shrinkage stress at 100 ° C .: 0.5 kg / mm ² ) obtained by using polyethylene terephthalate having an intrinsic viscosity of 0.65 (glass transition point: 65 ° C.) An epoxy-modified urea resin was coated to a solid content of 2 g / m ² and cured to form a cured heat-resistant layer. Next, after printing is performed on the surface of the film opposite to the cured heat-resistant layer, a heat seal layer (manufactured by Toyobo Co., Ltd.) is applied on the printing ink layer via an adhesive (“Adedo” manufactured by Toyo Ink Co., Ltd.). A polyester film (thickness: 12 μm) on which Byron resin (thickness: 2 μm) was previously laminated was joined to obtain a film for lamination.

The laminating film was laminated on a degreased cold-rolled steel sheet by a thermal laminating method to obtain a laminated steel sheet.

When a metal container for soft drinks was prepared from the laminated steel sheet by a conventional method, the laminated surface of the obtained container body had a clear, glossy, beautiful appearance and excellent gloss. It had the following.

In the above-mentioned can-making process, the heat of 250 ° C. or more is applied to the laminating film, which seems to slightly soften the polyethylene terephthalate layer of the film. Almost no shrinkage deformation, decrease in gloss, and deterioration of the printing ink layer were observed because of the protection by the layer. The container was treated with hot water at 100 ° C. and steam at 125 ° C., but no turbidity or thermal deterioration of the laminating film layer was observed, and the beautiful appearance was not impaired.

[0040]

[0041]

The present invention is constituted as described above, and as described in the above (1) to (6), it is easy to give a three-dimensional effect by halftone, photographic printing, multiplex printing, etc. It is possible to provide a beautiful metal plate or metal container with excellent productivity at a low cost, without dropping or scratching of the printing ink, and with high gloss and stain resistance. It has become possible to provide an excellent decorative metal plate and a decorative metal container.

[Brief description of the drawings]

FIG. 1 is an explanatory sectional view showing a basic structure of a laminating film according to the present invention.

FIG. 2 is an explanatory sectional view showing an example of a laminated structure of the laminating film according to the present invention.

FIG. 3 is an explanatory sectional view showing an example of a laminated structure of another laminating film according to the present invention.

FIG. 4 is an explanatory sectional view showing an example of a laminated structure of still another laminating film according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Thermoplastic resin layer 2 Printing ink layer 3 Adhesive layer 4 Transparent or colored film 5 Heat seal layer 6 Curable heat-resistant layer 7 Coat layer (or primer layer) Me Metal plate

Claims (5)

(57) [Claims] 1. A transparent or colored film is laminated on one side of a thermoplastic resin film provided with a printing ink layer via an adhesive layer made of a curable resin, and the surface of the laminate is
A film for laminating on a metal plate, wherein a transparent cured heat-resistant layer is formed, and a heat seal layer is formed on the opposite surface side . 2. A film according to printing ink layer, to claim 1 is obtained by forming between the thermoplastic resin film layer and the adhesive layer. Wherein, it supplied for laminating to precolored coat layer or a primer layer formed metal plate 請
3. The film according to claim 1 or 2 . 4. The coloring in the colored coating layer is white.
The film according to claim 3 . 5. The film according to claim 1, wherein the cured heat-resistant layer has a softening point or a decomposition temperature of 250 ° C. or higher.