JPH06286289A - Method of pattern coating - Google Patents

Abstract

PURPOSE:To provide a method wherein embracing of bubbles, imperfect covering and the like upon coating can be prevented effectively and, as a result, a coating layer, having no sensible and/or latent fault of coating, can be formed on a substrate. CONSTITUTION:A gravure roll 4, having a specified cell configuration and size, is employed for the pattern coating 13 of metallic foil and/or sheet, film or the laminated body of these elements made of high viscosity liquid coating material 2. According to this method, formation of a coating, efficiency of drying or the operability of drying can be improved, the problem of environmental contamination can be relieved and a expenditure necessary for the prevention of the environmental contamination can be saved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for pattern-coating a metal foil, a sheet, a film or a laminate thereof with a high-viscosity liquid coating material without coating defects.

[0002]

2. Description of the Related Art In the field of packaging containers and the like, it is often necessary to pattern-coat (partially coat) a high-viscosity liquid coating material on a metal foil or sheet, a film or a laminate thereof. For example, when applying the adhesive polymer only to the flange portion of the flanged container, or a part of the tin plate or the tin foil foil container,
An example of this is the case where the tin is exposed and the other part is covered so as to control the elution amount of tin with respect to the content in terms of the content storability.

Conventionally, roll coating is generally used to coat these packaging materials with a liquid coating material. However, there is a problem that it is difficult to control the pattern with the roll coating. As an alternative to this, gravure is used. Roll coating is used.

The gravure coating has an advantage that coating can be performed according to a set pattern by forming a mesh, that is, a concave cell in a portion of the pattern to be applied.

[0005]

However, in the case of pattern-coating a high-viscosity liquid coating material using a known gravure roll, the coating layer to be formed has coating defects such as pinholes and blisters, and potential defects. It is recognized that various coating defects often occur.

Such a coating defect is not preferable in that the coating is not perfect, and in a container having a structure in which a throttle container with a flange and a flexible lid member are heat-sealed, the container and the lid member are heated. A liquid pool, which is independent of the contents placed inside the container, is formed in the vicinity of the seal, and in this liquid pool, due to the local battery action, the above coating defects are fatal such as metal elution and leakage. There is a possibility that it will be a drawback.

The above-mentioned coating defects are generated by applying a viscous coating material to the gravure roll, or by entrapping air bubbles when the coating material is transferred from the gravure roll to the coating material, or a portion other than the cell (bank portion). This is caused by the fact that the coating material transferred from the cell is cast incompletely and thus only an incomplete coating can be obtained due to its wide area. The present situation is that no effective means has yet been found to prevent such air bubble entrapment and incomplete coating.

On the other hand, from the viewpoint of improving the coating efficiency and reducing the heat energy cost for drying the solvent, etc., or further reducing the air pollution and the environmental pollution as much as possible, the solid content concentration in the coating material can be controlled. It is required to be as high as possible, and accordingly, it is required to use a higher viscosity coating material. Also from the viewpoint of productivity, it is required to increase the coating speed as much as possible, and the improvement of coating defects has become more urgent.

Therefore, an object of the present invention is to prevent air bubbles from being trapped during coating or incomplete coating when pattern coating a high-viscosity liquid coating material onto a substrate, particularly a packaging container substrate, with a gravure roll. It is an object of the present invention to provide a method capable of forming a coating layer on a substrate that is effectively prevented and, as a result, is free of overt or latent coating defects.

[0010]

According to the present invention, a metal foil or sheet, a film, or a laminate thereof is pattern-coated with a high-viscosity liquid coating material by a gravure roll, and the circularity is 90 to 90. Pattern coating characterized in that the solid portion is coated using a gravure roll having a smooth cell opening shape in the range of 99% and a cell area ratio per surface area in the range of 75 to 95%. A method is provided. In the cell, a corroded portion was formed on the gravure cylinder by a net gravure method using a net gravure screen having a hexagonal shape, or a hexagonal corroded portion was directly provided on the gravure cylinder by a laser plate making method. After that, it is particularly desirable that a cell having a smooth opening shape is formed by corrosion.

[0011]

[Function] In pattern coating with a gravure roll, a liquid coating material is applied to the gravure roll surface having a pattern formed by cell aggregates by dipping, and then the gravure roll surface is scraped off with a doctor blade or the like.
Excess coating material on the roller surface is removed so that only the coating material in the cells remains, and the liquid coating material in the cells is transferred to the base material to perform pattern coating on the base material.

According to the present invention, in this pattern coating, the shape and dimensions of the cell have a significant influence on the inclusion of bubbles during application, and the roundness of the cell is smooth in the range of 90 to 99%. Use of a gravure roll having a cell area ratio per surface area of 75 to 95% prevents the inclusion of bubbles during coating and incomplete coating even when the coating material is viscous. It is based on the knowledge that a coating free of coating defects or potential coating defects can be formed.

In order to explain the principle of pattern coating by a gravure roll, in FIG. 1, a pan 1 contains a liquid coating material 2, and a liquid surface 3 of the liquid coating material 2 is contained.
The gravure roll 4 has a shaft 5 so that it can be immersed below
It is rotatably supported around. Gravure roll 4
There is a coated surface 6 and a non-coated surface 7 in the form of patterns, and a large number of cells 8 are arranged on the pattern coated surface 6 (the cell 7 is exaggerated in the drawing). Exist).
A pressure roll 9 made of rubber or the like is arranged on the upper side of the gravure roll 4 and supplies a sheet-shaped base material 10 to be pattern-coated to a nip position 11 between the gravure roll 4 and the pressure roll 9 and also the gravure roll 4 Press on. Between the liquid surface 3 of the liquid coating material and the nip position 11 and on the upward rotation side of the gravure roll 4, a doctor 12 whose tip contacts the surface of the gravure roll 4 is arranged.

The gravure roll 4 rotates and the liquid coating material 2
The liquid coating material 2 is applied to both the pattern-coated surface 6 and the non-coated surface 7 including the cells 8 on the roll surface by being dipped in the inside, but the surface of the gravure roll 4 contacts the doctor 12. Then, the liquid coating material on the non-coated surface 7 and the cell 8
The liquid coating material on the pattern coated surface 6 other than the above is scraped off, and the liquid coating material is placed only inside the cells 8. The liquid coating material in the cells 8 is transferred to the sheet-shaped base material 10 at the nip position 11, and the liquid coating material corresponding to the cells 8 is cast and uniformized to perform pattern coating on the base material 10. 13 is formed.

Gravure roll cell 8 used in the present invention
Must first have a smooth opening shape with a roundness of 90 to 99%. In FIG. 2 for explaining the roundness of the cell opening, the area of the cell opening is S
₁ , where S ₀ is the area of the circumscribed circle circumscribing the cell opening, the roundness is defined by the equation: Roundness = S ₁ / S ₀ × 100.

See Example 1 below. In the case of using a gravure roll having a roundness of 70% and a cell having a square shape (square) (Sample 2), air bubbles are included in the coating material when the suspension of the acid-modified polyethylene is applied, The enamel meter value (ERV) of this coated metal foil is as high as 10 mA, but the cell opening is smooth and the roundness is 90% to 9%.
In the case of the gravure roll equipped with the cell of 9% (Sample 1), no bubbles were entrapped when the same coating material was applied, and the coated metal foil formed had an ERV of 0.1 m.
It is suppressed to a small value of A or less.

In the present invention, the reason why a cell having a high roundness and a smooth opening shape can be used for pattern coating without coating defects is that when the cells of the gravure roll enter the liquid coating material. If the roundness is low and angular, bubbles tend to enter, and once entered bubbles are difficult to escape, whereas in the round shape, cells smoothly enter the liquid and bubbles are less likely to occur, Moreover, it is thought that even if bubbles are formed, it is easy to come off.

However, it is considered that when a perfectly circular cell is formed, the ratio of the cell portion to the total surface area becomes small and a large bank portion is formed between the four cells to form an incomplete film. In the present invention, in order to prevent this, the cell area ratio per surface area is 75 to 9
It is important to set it to 5%, especially 75 to 90%. That is, as shown in an example described later, when the cell area ratio is smaller than the above range, an incomplete film is formed due to insufficient casting even if the circularity is within the range of the present invention. Further, when the cell area ratio is larger than the above range, the cells are connected to each other, and as a result, bubbles are entrained, so that the ERV value also tends to increase. Further, a phenomenon occurs in which the bank portion of the cell is cut off, the scraping by the doctor does not proceed smoothly, the skin becomes rough, and the doctor is severely damaged, which makes uniform coating difficult. When the cell area ratio is in the range of 75 to 95%, both of these defects are effectively eliminated.

In order to make the cell opening as smooth and highly round as possible and to adjust the cell area ratio to the above range, the corroded portion is a hexagonal mesh gravure screen. It is preferable that cells are formed on the gravure cylinder by the gravure method or hexagonal corroded portions are directly provided on the gravure cylinder by the laser plate making method, and then cells having a smooth opening shape are formed by the corrosion. By adopting this means, it is possible to increase the circularity of the cell opening and make it smooth without making the cell area ratio too small or too large.

In the present invention, the linear density of cells in the solid portion (pattern portion) of the gravure roll used is preferably in the range of 45 to 120 cells, particularly 50 to 100 cells per inch, and is less than the above range. A uniform and smooth coating tends to be difficult, and when the amount is larger than the above range, it tends to be difficult to form a uniform coating having a sufficient thickness, although it depends on the cell diameter.

The cell depth also has an important influence on the inclusion of bubbles. Generally, the cell depth (depth from the surface to the deepest part) is 1/10 to 1/1 of the cell diameter.
It is preferably in the range of 2, especially 1/4 to 1/2.
That is, if the ratio of the depth per cell diameter is larger than the above range, the inclusion of bubbles will occur more frequently than that within the above range, while if it is smaller than the above range, The amount is also small, and uneven thickness is likely to occur.

According to the present invention, by using the gravure roll having the above cell shape and dimensions for pattern coating of a metal foil or sheet, a film or a laminate of these with a highly viscous liquid coating material, It is possible to form a coating without potential coating defects, improve the efficiency and workability of coating formation and drying, reduce the problem of environmental pollution, and save the cost required for its prevention. .

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION The gravure roll (intaglio plate) used in the present invention is produced by a plate-making method known per se except that cells (ink receiving portions) having the above-described shapes and dimensions are formed on the plate material. As the plate material, for example, a cylinder of iron or aluminum plated with copper is used.

The cell shape is a spherical shape having a circular opening and a cell surface smaller than a hemisphere, a parabolic rotation surface shape, a hyperbolic rotation surface shape, an elliptic surface shape, or a quadratic curve rotation surface shape, or a small diameter. It is preferable that the flat surface portion and the outer peripheral portion of these curved surfaces are smoothly connected, but the present invention is not limited to this as long as it is smooth without corners.

To form cells on the roll surface, a photosensitive material is applied to a plate material to form a photosensitive layer, and an original plate prepared by a net gravure screen is printed on the plate, or directly printed by a laser to form the above-mentioned cell shape. To form a photoresist that is exposed in the area corresponding to
It is obtained by etching (etching) using I), peeling the resist layer, and then forming chrome plating if necessary to enhance printing durability. As the light-sensitive material, a combination of gelatin or a water-soluble polymer and dichromate, a photodimerization-type photopolymer, a photopolymerization-type polymer, a photodegradation-type photopolymer, or the like, and the original plate is a positive image It is appropriately used depending on whether it is a negative image.

In FIG. 3 for explaining etching, a resist film 21 and an exposed portion 22 are present on the upper surface of the plate material 20 before the etching process A. FIG. 4 is a top view showing the arrangement of the exposed portions in the surface direction. If this exposed portion is hexagonal, the cells can be arranged more densely than in a circular shape.
In addition, its interior angle is maximum compared to a triangle or a quadrangle that can be similarly densely arranged. Corrosion during etching process is 3
Proceed in the dimensional direction. Therefore, after the etching process B, the roundness of the cell opening 23 becomes large and the depth direction also becomes a bowl shape, which is excellent in preventing the inclusion of bubbles.
Furthermore, the area of the opening becomes large, the bank portion is minimized, and it is excellent in preventing incomplete coating.

Of course, the formation of the cell used in the present invention is not limited to the above-mentioned method, and may be an electronic direct engraving method using a scanner system or a laser engraving method.

The method of the present invention can be applied to a base material composed of a metal foil, a sheet, a film, or a laminate thereof. Examples of the metal foil or sheet include light metal foils and sheets such as pure aluminum and aluminum alloys, and surface treated steel foils and sheets. Here, examples of the surface-treated steel include tin-plated steel sheets, nickel-plated steel sheets, electric field chromic acid-treated steel sheets (tain-free steel), and foils thereof.

On the other hand, as the plastic film, any thermoplastic resin such as polypropylene, polyethylene, propylene-ethylene copolymer, propylene-ethylene-butene copolymer, ethylene-1-butene copolymer, ethylene-vinyl alcohol is used. Copolymer, ethylene-
Acrylic copolymer, olefin resin such as polyolefin / ionomer; polyester resin such as polyethylene terephthalate, polytetramethylene terephthalate, polyethylene terephthalate / isophthalate, polyethylene / butylene terephthalate, polyethylene naphthoate; nylon 6, nylon 66, nylon 6 / 6
6 copolymer, nylon 12, nylon 11, nylon 6
A film made of a polyamide resin such as a 6/610 copolymer or a nylon 6/11 copolymer; a polycarbonate; a polysulfone or the like is used.

In the present invention, a laminate of the above metal foil or sheet and a plastic film can be used.
For example, a laminate having a two-layer structure in which the metal foil or sheet is the inner surface side of the container and the plastic film is the outer surface side of the container, or a three-layer structure in which the metal foil or sheet is the intermediate layer and the plastic film is the inner or outer layer. A laminated body of a structure is mentioned. Of course, a laminate of different types of plastic films can also be used. It is useful for the purpose of applying various polymer coating materials to these substrates in a partially fixed pattern. Examples of these applications include the application of an easily peelable heat-sealing material to the portion of the container or lid that is to be heat-sealed, the portion of the container or lid that is subjected to severe processing, such as the double winding portion of a can or neck-in processing. Part, or the rivet processing part or score processing part of the easy-open lid, is used in advance to provide a protective coating layer or a lubricity coating layer, and the tin-plated layer exposed on the inner surface of the container is used to retain the flavor of the contents. The application of a partial coat layer on the inner surface side for the purpose of adjusting the exposed area is mentioned, but the invention is not limited to these examples.

As the liquid coating material, various thermoplastic resins,
Solutions such as thermosetting resins and thermoplastic elastomer rubbers, suspensions, emulsions or latexes are used depending on the application.

For use as a protective coating, for example, thermosetting resin coatings such as phenol-formaldehyde resin, furan-formaldehyde resin, xylene-formaldehyde resin, ketone-formaldehyde resin, urea-formaldehyde resin, melamine-formaldehyde resin,
Alkyd resin, unsaturated polyester resin, epoxy resin, bismaleimide resin, triallyl cyanurate resin, thermosetting acrylic resin, silicone resin, oil resin, or thermoplastic resin paint, such as vinyl chloride-vinyl acetate copolymer, chloride Examples thereof include partially saponified vinyl-vinyl acetate copolymers, vinyl chloride-maleic acid copolymers, vinyl chloride-maleic acid-vinyl acetate copolymers, acrylic polymers, saturated polyester resins and the like. These resin paints may be used alone or in combination of two or more.

As the thermoplastic elastomer, polyester elastomer, polyamide elastomer, acrylic elastomer, styrene-butadiene block copolymer elastomer, hydrogenated styrene-butadiene block copolymer elastomer, etc. are used, and the rubber is ethylene. -Propylene copolymer rubber (EPR), ethylene-propylene-non-conjugated diene copolymer rubber (EPD)
M), styrene-butadiene rubber (SBR), nitrile-butadiene rubber (NBR), chloroprene rubber, butyl rubber and the like are used.

As the heat-sealing coating material, polyethylene, polypropylene, ethylene-vinyl acetate copolymer, acid-modified olefin resin, or a blend of two or more kinds of these is used.

These polymer coating materials can be used in the form of a solution, suspension or organosol dissolved or dispersed in an organic solvent, or in the form of emulsion or latex emulsified and dispersed in an aqueous medium. You can also Further, these may be used in combination of two or more kinds, and for example, those obtained by dispersing an acid-modified olefin resin in various resin paints form a protective coating excellent in heat sealability.

Further, in order to impart various functions to the coating layer, various lubricants, tackifiers, and
A plasticizer, a curing agent or a curing accelerator, a leveling agent, etc. can be blended according to a formulation known per se.

The liquid coating material used in the present invention is 1 at 25 ° C.
It has a viscosity of 00 to 3000 centipoise, and it is an advantage that even if the viscosity is considerably high, an excellent coating layer can be formed without inclusion of bubbles. The solid content concentration of the liquid coating material varies depending on the type of polymer, but is generally in the range of 20 to 80% by weight. The thickness of the coating material layer can be largely changed depending on the size of the cell and the like, but the solid content is 1 to 20 μm, particularly 3 to 15 μm.
It is in the range of μm.

According to the present invention, the base material provided with the pattern coating layer is dried and, if necessary, subjected to a treatment such as baking, cut into an appropriate shape and size, and then drawn or deep-drawn. It can be formed into a container such as a cup or a seamless can body. Press molding again
It can be molded into an open lid or the like.

[0039]

The present invention will be further described in the following examples. Example 1 After degreasing the surface of a copper-plated cylinder and removing an oxide film, polyvinyl cinnamate as a photosensitive solution was coated and dried. A cylinder coated with a sensitizing solution using a mesh positive film with a donut-shaped pattern having an outer diameter of 130 cm and an inner diameter of 50 cm made of a hexagonal screen of the size shown in FIG. Burned on. After washing with water and drying, an asphalt solution was applied to a portion not requiring corrosion, and corrosion was performed with a ferric chloride solution.
After the plate depth reached 140 μm, the plate was washed with water. The resist was stripped with a solvent, the surface was washed, and then chrome plating was applied.

The surface of the cylinder (Sample 1) thus prepared was photographed with a dot checker GT8000 (manufactured by Rokuzai Shoji) to measure the shape and dimensions of the cell. As defined above, the roundness is the ratio of the area of the opening to the area of the circle circumscribing the cell. The photograph taken to determine this ratio was copied, and the circumscribed circle and the cell opening were cut out and weighed. The roundness thus obtained was 96.6%. The number of cells per inch was 65. The diameter of the circumscribed circle is 410 μm
The cell depth was 0.34 times that. The cell open area ratio per surface area obtained from the photograph was 80%.

Using this cylinder, tin foil (75
μm thickness, tin plating amount 11 mg / m ²) To 25 ° C
With a solid content of 28% and a viscosity of 1000 cps.
18m / min of propylene-dispersed epoxy phenol paint
It was gravure coated. 220 ℃ 30 seconds baking
After applying, ER of the coating part to check the state of defects in the coating film
When V was measured, it was 0.01 mA. Coating thickness
Was 10 μm.

A 40 μm polypropylene film was laminated on the opposite surface of the coated foil using a urethane adhesive, and the donut-shaped coated portion was blanked, and then molded into a cup having a depth of 40 cm so that the uncoated portion became the bottom. did. This cup was filled with citrus pulp and syrup, and a laminate consisting of 12 μm PET, 7 μm aluminum foil and 70 μm polypropylene film was heat-sealed and sterilized,
It was stored at 37 ° C. for one month, but no corrosion was found on the coated part of the container, and the contents were stored well.

Comparative Example 1 A 65-line screen normally used in gravure has a substantially square corroded portion having a side of 240 μm. Using this screen, a gravure cylinder was produced in the same manner as in Example 1 (Sample 2). The roundness of the cell is 7
0%, opening area ratio is 71%, cell depth is 150μ
It was 0.34 times the diameter of the circumscribed circle at m. Using this gravure cylinder, coating, molding, filling, and preservation were carried out in the same manner as in Example 1. As a result, foaming was observed in the coated part, and the ERV was 10 mA, corrosion was observed in the coated part and leakage occurred. .

Comparative Example 2 A gravure cylinder was produced in the same manner as in Example 1 using a net gravure special screen in which a circle having a diameter of 240 μm became a corroded portion. Roundness is 100%,
The opening area ratio was 60%, and the cell depth was 150 μm, which was 0.46 times the diameter of the opening. A slight unpainted part was observed in the painted part, and its ERV was 15 mA. Corrosion was observed after the storage test.

Example 2-3 Comparative Example 3-5 Table 1 shows the results of the same test as in Example 1 except that the cell forming conditions were changed by changing the corrosion time.

[0046]

[Table 1]

[0047]

According to the present invention, by using a gravure roll having a specific cell shape and size for pattern coating a metal foil or sheet, a film or a laminate of these with a high-viscosity liquid coating material, To form a coating free of specific or potential coating defects,
The efficiency and workability of coating formation and drying can be improved, the problem of environmental pollution can be reduced, and the cost required for its prevention can be saved.

[Brief description of drawings]

FIG. 1 is an explanatory diagram for explaining the principle of pattern coating with a gravure roll.

FIG. 2 is an explanatory diagram for explaining the roundness of a cell opening.

3A and 3B are explanatory views for explaining etching for forming cells, in which A is a top view and a cross-sectional view before the etching, and B is a top view and a cross-sectional view after the etching.

FIG. 4 is a top view showing an arrangement of exposed portions in FIG. 3 in a surface direction.

[Explanation of symbols]

1 is a pan, 2 is a liquid coating material, 3 is a liquid surface, 4 is a gravure roll, 5 is a shaft, 6 is a patterned coating surface, 7 is a non-coating surface, 8 is a cell, 9 is a pressing roll, 10 is Sheet-shaped substrate, 11 nip position, 12 doctor, 13 pattern coating, 20 plate material, 21 resist film, 22
Is an exposed portion and 23 is a cell opening.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takahata Enshu 2-206, Nishitobe-cho, Nishi-ku, Yokohama-shi, Kanagawa Prefecture (72) Inventor Fumio Ikushima 1-2-6 Minami Sanrokusho, Kanagawa Prefecture Kamiooka Stoke Condominium Room 203 (72) Inventor Teisuke Morita 3028 Noborito, Tama-ku, Kawasaki City, Kanagawa Prefecture (72) Masayasu Koyama 1-2-7 Kotsubo, Zushi City, Kanagawa Prefecture

Claims (4)

[Claims] 1. A method for pattern-coating a metal foil, a sheet, a film, or a laminate thereof with a highly viscous liquid coating material by a gravure roll, wherein a smooth cell opening having a circularity of 90 to 99%. A pattern coating method, wherein a solid portion is coated using a gravure roll having a shape and a cell area ratio per surface area of 75 to 95%. 2. The cell is formed on the gravure cylinder by a net gravure method using a net gravure screen having a hexagonal corroded portion or is directly corroded on the gravure cylinder by a laser plate making method. The pattern coating method according to claim 1, wherein cells having a smooth opening shape are formed by corrosion after the provision of the corresponding portion. 3. A solid portion (pattern portion) of a gravure roll
Cell linear density at 45 to 120 per inch
The pattern coating method according to claim 1, which is in the range of 1. 4. The pattern coating method according to claim 1, wherein the cell depth is in the range of 1/10 to 1/2 of the cell diameter at the deepest portion from the surface.