JPH11286161A - Printing method and production of printed body of packaging resin film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a printing method, in particular a method for producing the printed body of a packaging resin film in which elimination of an organic solvent in a gravure printing process is advanced and also deterioration in printing quality due to water-color ink and an increase in cost are inhibited. SOLUTION: Ink for gravure printing having prescribed color tone is held in ink pans 11 of respective printing parts 10A, 10B,...10F. Water-color ink is basically used as ink for gravure printing which is held in the ink pans 11. This water-color ink contains aqueous acrylic resin and urethane resin or the like as a vehicle and contains water as a main component instead of an organic solvent and contains alcohols as a co-solvent. Oily ink (solvent-type ink) using the organic solvent is used in printing of a printed pattern having such a pattern that the printed pattern of deep color, a fine character, a minute pattern such as a bar code, and a clear outline are required among the printed patterns printed in a printing part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printing method and a method for producing a resin film print for packaging.

[0002]

2. Description of the Related Art Conventionally, when performing gravure printing, an oil-based ink using a solvent containing toluene (for example, a mixed solution of toluene, methyl ethyl ketone, isopropyl alcohol, n-propyl alcohol, etc.) is often used. However, based on recent organic solvent movements caused by global environmental problems, aqueous gravure inks that can use industrial alcohol, water, isopropyl alcohol, and the like have been proposed, and some of them have been used. On the other hand, gravure inks that do not use toluene due to a reduction in the control concentration of toluene are also used in some cases. Toluene is said to have excellent solubility in various resins used in gravure inks and is said to be the most suitable for gravure printing in terms of dryness, but poisoning symptoms and residual solvents caused by toluene have been reported. From
Particularly in the food field, it is necessary to use a solvent that does not use toluene (for example, a solvent composed of ethyl acetate, methyl ethyl ketone, isopropyl alcohol, and the like).

[0003]

As described above, in recent years, aqueous gravure inks that do not use organic solvents and gravure inks that do not use toluene have been developed and started to be used. However, the aqueous gravure ink has a problem that the reproducibility of fine characters and the like is poor, especially when printing on a resin film for packaging or the like, since the surface tension is high. This is because the water-based ink spreads around after being transferred onto the film, so that the print pattern is disturbed by thick characters or crushed bar codes, and in some cases, it is difficult to determine the characters. At present, in order to solve such problems, the printing plate has a higher number of lines and a higher line ratio than usual, but in this case, the plate cells become shallower and the banks become thinner, and the plate wears down. It becomes intense and the printing cost increases. In addition, when the water-based ink is used, the lubricating property between the outer peripheral surface of the plate cylinder and the doctor blade is also reduced, so that the blade edge of the doctor blade is greatly worn.

[0004] Due to the above-mentioned drawbacks of water-based inks, gravure inks of the type that does not use toluene as an organic solvent are currently considered most promising. According to this ink, since toluene is not used, toluene does not remain in the printed matter, and the amount of other residual solvents can be greatly reduced as compared with the oil-based ink using normal toluene. However, there is no change in using an organic solvent, and it is naturally impossible to remove the organic solvent.

Accordingly, the present invention is to solve the above-mentioned problems, and an object of the present invention is to make it possible to promote the use of an organic solvent in a gravure printing step and to suppress a decrease in printing quality and an increase in cost due to aqueous ink. Printing method,
In particular, it is an object of the present invention to provide a method for producing a printed resin film for packaging.

[0006]

Means taken by the present invention to solve the above-mentioned problem is to perform gravure printing on the same printing substrate using a plurality of printing plates for forming a predetermined printing pattern. In the printing method, a part of the printing plate is subjected to printing using an aqueous printing ink, and the other printing plate is subjected to printing using an oil-based printing ink.

According to this means, when performing gravure printing on the same printing substrate using a plurality of printing plates, the amount of the organic solvent used can be reduced by using aqueous printing ink for printing on some printing plates. When printing with other printing plates, oil-based printing inks can be used to prevent character bleeding and pattern collapse caused by water-based printing inks. When configuring printed matter using patterns, select whether to use water-based printing ink or oil-based printing ink according to the content of the printing pattern, thereby reducing the amount of organic solvent used and ensuring print quality. Can be.
In addition, by providing a plate using oil-based ink, the required level of printing quality of a plate using water-based ink can be relaxed, so reducing the number of lines of the plate for water-based ink and increasing the plate depth. This makes it possible to improve the durability of the plate, improve the printing speed, share the plate for the water-based ink and the plate for the oil-based ink, etc., and suppress the printing cost as a whole.

[0008] Here, compared with the print pattern formed by some of the plates, the print pattern formed by the other plates is:
It is preferable that the pattern be provided with a dark color tone and / or a fine contour or be a pattern that requires a clear contour, that is, a pattern that requires a high level of print quality. According to this means, dark colors such as black and dark red, small characters,
In printing patterns with fine contours such as fine patterns and barcodes, blurring and crushing of the printing pattern with water-based printing ink are often noticeable, and characters and patterns with many curved parts For print patterns that require a clear outline, such as those that include
As a matter of course, bleeding or crushing of the printing pattern by the aqueous printing ink becomes a problem. Therefore, in such a case, by using the oil-based printing ink, the amount of the organic solvent used can be reduced by printing other printing patterns with the aqueous printing ink without deteriorating the print quality.

In each of the above means, the oil-based printing ink desirably does not contain toluene as an organic solvent. According to this means, by using an oil-based printing ink containing no toluene, poisoning by toluene is prevented,
It is possible to reduce the amount of the residual solvent in the print.

Further, in each of the above means, the printing pattern is formed on a surface of the printing substrate made of a synthetic resin material, and the aqueous printing ink and the oil printing ink have printing characteristics suitable for the synthetic resin. Is desirable. By printing on the surface of a synthetic resin material such as a resin film for packaging and a plastic substrate by using an aqueous printing ink and an oil-based printing ink having printing characteristics suitable for the synthetic resin, particularly formed by the aqueous printing ink. The printing layer and the printing layer formed of the oil-based printing ink do not interfere with each other, and can perform overprinting without any trouble.

It is preferable to use a printing method described in each of the above means to produce a printed resin film for packaging. According to this means, by applying the above printing method to a method for producing a printed resin film for packaging, it is possible to reduce the amount of organic solvent remaining on the printed material, and particularly when forming a packaging material for food. Safety can be improved.

In each of the above means, since the required quality of the printing pattern using the water-based ink can be relaxed by providing the printing step for the oil-based ink, the printing plate for the water-based ink used for forming each printing pattern can be used. Conventional high-frequency plates for aqueous inks (typically 200-350L
/ Inch (lines / inch)) can be used. For example, the printing plate for the aqueous ink can be 125 to 250 L / inch, and particularly preferably 150 to 200 L / inch. Decreasing the number of lines on the plate can reduce the cost by improving the durability of the plate, and can be shared with a plate for oil-based ink (usually 100 to 175 L / inch). Also, the production cost of the plate can be reduced.

In each of the above means, the provision of a printing step for an oil-based ink can reduce the required quality of a printing pattern using a water-based ink.
As a plate for water-based ink used for forming each print pattern, a conventional low-depth plate for water-based ink (usually 15 to 24)
μm) can be used.
For example, for a plate for water-based ink, the plate depth is 18 to 33.
μm, and particularly preferably 24 to 27 μm. Increasing the plate depth leads to an increase in print quality while preventing a print pattern from being blurred or the like, thereby reducing printing costs. In addition, since it can be shared with a plate for oil-based ink (usually 27 to 33 μm), the production cost of the plate can be reduced.

In each of the above means, an aqueous printing ink,
Both oil-based printing inks contain a vehicle, a solvent, a colorant, and if necessary, an appropriate additive suitable for the printing substrate. Here, as a water-based printing ink suitable for a printing substrate made of a synthetic resin material, a water-based ink containing a water-based acrylic resin, a urethane resin, or the like as a vehicle and a solvent containing water and alcohols can be used. The oil-based printing ink is a mixture of a colorant, a vehicle, and an organic solvent, and nitrocellulose, a vinyl chloride acetate copolymer, a chlorinated polypropylene,
Resins such as urethane, acrylic, and polyamide are used. In particular, as the organic solvent, ethyl acetate, isopropyl alcohol, methyl ethyl ketone, or the like is used. Toluene is the most ideal solvent for oil-based printing inks. However, it is preferable that toluene be reduced or not used as much as possible in order to improve the printing environment and reduce the amount of solvent remaining in the printed material.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of a printing method and a method for manufacturing a printed resin film for packaging according to the present invention will be described with reference to the accompanying drawings. The present invention is a printing method by gravure printing in which a plurality of printing patterns are printed using a plurality of printing plates, wherein printing is performed using a water-based ink on a part of the plurality of printing plates, and an oil-based ink (solvent) is printed on another printing plate. Mold ink)
Is printed by using the. FIG. 1 shows a rotary press by a gravure printing method used in the present embodiment, and includes a plurality of printing units 10A, 10B,..., 10F. Although the number of printing sections varies depending on the printing material and the printing content, it is generally 1 to 8. Each printing unit includes an ink pan 11 for storing ink, a plate cylinder 12 having a predetermined plate formed on the outer peripheral surface, a doctor 13 for scraping the ink adhered on the outer peripheral surface of the plate cylinder 12, and a printing unit. The body 20 to the plate cylinder 12
And a hot-air dryer 15 for drying the surface of the printed body after printing in each printing unit.

The ink pan 11 of each printing section contains gravure printing ink of a predetermined color tone. Each printing unit is in charge of a printing pattern having a different color tone and / or a different pattern shape. However, for example, the same color ink may be shared by a plurality of printing units with different printing patterns, or the same pattern may be overprinted with inks of different colors. Usually, as the gravure printing ink contained in the ink pan 11, when performing gravure printing on a resin film for packaging, a coloring agent 3 to 4 such as a dye or pigment for securing a predetermined color tone exhibited by the ink.
0%, 0-20% extender pigment for adjusting ink viscosity
And vehicles 5 to 5 as a binder such as an organic resin.
0%, organic solvent 40-70%, and other additives 1
Either oil-based ink (solvent type ink) consisting of 20% or water-based ink containing water as a main component instead of an organic solvent and water as an auxiliary solvent, using an aqueous acrylic resin or urethane resin as a vehicle. Is used. Here, the ratio of water to alcohols is 2: 8 to 5:
It is about 5. However, in the present embodiment, although water-based ink is basically used, printing is performed using oil-based ink in one or a plurality of printing units as needed.

Conventionally, in printing such as gravure printing,
It has not been practiced to use oil-based ink and water-based ink in a plurality of printing steps for the same printed matter. This is due to the fact that the aqueous ink itself particularly suitable for a resin film for packaging has not been common until recently, and it has been technically insane to overprint an aqueous ink and an oil-based ink. However, as a result of various experiments, in particular, in gravure printing using a packaging resin film as a printing substrate, the inventors of the present application have no problem even if the oil-based ink and the water-based ink are overprinted without any problem. It has been found that some of the printing steps can be performed with an aqueous ink and others can be performed with an oil-based ink. When performing gravure printing on the surface of various synthetic resin materials, not only resin films, oil-based inks and water-based inks suitable for synthetic resin materials such as resin films both have good adhesion properties on the material surface, It was also found that the print layer formed using the oil-based ink and the print layer formed using the aqueous ink hardly interfere with each other.

In this embodiment, gravure printing is performed on a packaging resin film. Examples of the resin film for packaging include polyethylene, polypropylene, polyester, nylon, and polyethylene terephthalate. These packaging resin films are used as materials for various packaging bags such as food packaging bags. In particular, when printing on a resin film for food packaging, the front printing method in which printing is performed only on the surface corresponding to the surface of the bag in the resin film, and the surface on the side opposite to the surface of the bag in the resin film is equivalent. There is a method of printing on the surface and laminating another film on the printed surface (back printing method). This embodiment can be applied irrespective of a front printing system or a back printing system. A polyamide resin or a cellulose derivative is generally used as a vehicle for the ink for the front printing system, and a polyurethane resin or the like is generally used for the ink for the back printing system.

Printing is performed by the plurality of printing units based on the plurality of plates. The plates have different printing patterns and / or different tones. The print patterns include various patterns such as characters, symbols, tables, barcodes, pictures, marks, patterns, and backgrounds depending on the contents thereof, and each print pattern has a specific color tone. Some of these printing patterns have relatively large contours, while others have fine contours. Further, the color tone of the print pattern ranges from a dark color to a light color, and a gradation or the like may exist.
In the present embodiment, a plurality of print patterns are basically printed using an aqueous ink.
From patterns with dark tones (black, red, etc.), patterns with fine outlines (small letters, fine patterns, barcodes, etc.), patterns requiring sharp outlines (characters with various curves, etc.) A printing pattern with a high required printing quality is printed with oil-based ink. The number of print patterns using the water-based ink and the number of print patterns using the oil-based ink are arbitrary, but at least one or more of the print pattern using the water-based ink and the print pattern using the oil-based ink are both set. You.

In the present embodiment, since the organic solvent is used in the printing pattern using the oil-based ink, complete deorganization cannot be achieved. However, the use of the organic solvent can be achieved by having a printing process using the aqueous ink. The amount can be reduced. In particular, basically use water-based ink,
Exceptionally, that is, by using the oil-based ink to the required minimum, the amount of the organic solvent can be significantly reduced as compared with the conventional case. In addition, by using oil-based ink for printing patterns having a dark color tone, printing patterns having fine contours, and printing patterns requiring clear contours, blurring and crushing, which are drawbacks of water-based inks, are made inconspicuous. be able to. In this case, it is preferable to use an ink that does not use toluene as the organic solvent as the oil-based ink in order to reduce the amount of the remaining organic solvent and to prevent poisoning caused by toluene.

Furthermore, in the present embodiment, oil-based ink is used for a print pattern which is sensitive to pattern bleeding or crushing, and high print quality is required. Is used, the number of lines on the plate for water-based ink can be reduced, and the depth of the plate can be increased, so that the durability of the plate can be improved and the printing speed can be increased. In addition, printing costs can be reduced.

[0022]

EXAMPLE Next, an example in which a predetermined design is actually printed on a packaging resin film will be described. As a printing base paper as a printing base material, P2161 # 30 (manufactured by Toyobo, product number) having a thickness of 30 μm as an oriented polypropylene film (OPP) was used. There are 5 printing colors, 5
Printing was sequentially performed in one printing unit as shown in Table 1 below. Some of the printing layers formed by the respective printing steps partially overlap each other.

[0023]

[Table 1] ────────────────────────────────── Printing order Color tone Contents of printing pattern Ink used ─── ─────────────────────────────── Black Small letter, bar code LP fine (oiliness) Blue capital letter Aquaecole (water-based) Red one Background of the part Aqua Ecole (aqueous) yellow Main part of the pattern Aqua Ecole (aqueous) White Some background, white part Aqua Ecole (aqueous) ────────────────

In Table 1 above, LP Fine (oil-based) is LP Fine-NT323 (trade name, product number, manufactured by Toyo Ink), which does not contain toluene, and contains ethyl acetate, methyl ethyl ketone, and isopropyl alcohol. An oil-based ink using an organic solvent mixed with propylene glycol monomethyl ether. Also, what is indicated as Aqua Ecole is Aqua Ecole-AQ602F (manufactured by Toyo Ink, trademark-product number), which is an aqueous ink using a mixture of water and alcohol instead of an organic solvent.

The plate cylinder 12 used in each printing section has a line number of 175 L / inch and a plate depth of 26 μm in both cases using oil-based ink and water-based ink.
And The plate of the plate cylinder 12 was formed as a direct plate. Of course, an electronic engraving plate, a laser plate, or the like can also be used. Generally, the number of lines of a conventional oil-based ink plate is 100 to 175 L / inch, and the plate depth is 27 to 33 μm.
The direct version and the electronic engraving version are used,
The number of lines of the plate for aqueous ink is 200 to 350 L / inc.
h, the plate depth is 15 to 24 μm, and an electronic engraving plate or a laser plate is used.

In the present embodiment, oily ink is used for a print pattern having a high required level of print quality, which causes a problem such as blurring or crushing of the printing pattern, so that bleeding or crushing of the pattern does not cause much problem. Since the water-based ink can be used for a relatively loose print pattern of a required level of print quality, a plate for the water-based ink can have a relatively low number of lines and a large plate depth.
Here, the number of lines of the plate is 125 to 250 L / inc.
h, preferably 150 to 200 L / inch. If it exceeds this range, the durability of the plate will be reduced due to a high number of lines, and if it is below this range, sufficient print quality cannot be obtained. The plate depth can be set to 18 to 30 μm, preferably 24 to 27 μm. Exceeding this range will cause noticeable blurring and crushing of the print pattern, and below this range will cause blurring of the print pattern, and the printing speed must be significantly reduced.

The heating temperature (temperature of hot air) of the dryer 15 is 60 to 8 in the case of ordinary gravure printing using oil-based ink.
It is set at about 5 degrees higher than 0 ° C. to be in the range of 65 to 85 ° C., and the printing speed is 100 to 100 in the case of normal gravure printing.
95 to 12 which is about 5 to 35% lower than 150 m / min
0 m / min. When using water-based ink,
Since the lubricating property between the doctor blade and the outer peripheral surface of the plate cylinder deteriorates, and the doctor blade tends to wear more,
The length of the blade portion of the bladed doctor is increased from the conventional 1.4 mm to 2.2 mm and is increased by about 50 to 60% so that the change of the blade edge due to wear is reduced for a long time. The thickness of the cutting edge is 0.07 mm, and the angle difference between the two opposing surfaces (the surface formed on the front and back of the blade) at the cutting edge is the conventional 12.
It has been reduced to about 3 degrees from the degree. Since the angle difference is reduced, the thickness of the blade hardly changes even when the blade is worn.

In this embodiment, only lowercase letters and barcodes having fine contours and requiring clarity of contours are printed with oil-based ink, and all other capital letters, backgrounds, patterns, etc. are printed with water-based ink. Printing. Therefore, the amount of the organic solvent used is reduced to one fifth or less of the conventional one, and printing can be performed without using toluene at all. Therefore, poisoning in the printing process can be prevented, and the environment of the workplace can be improved. The appearance of the printed matter after printing was not inferior to the conventional one, and the amount of the residual solvent in the printed body was almost nonexistent as compared with the conventional one. Therefore, when applied to printing on a resin film for food packaging, the safety is greatly improved. Further, since the plate for oil-based ink and the plate for water-based ink are set to the same number of lines and the same plate depth, the plate can be shared, and the production cost and operation cost of the plate can be reduced.

The appearance of the printed body (resin film for packaging) formed by printing by the printing method of the above embodiment is good, and the heat resistance test for the packaging material for boiling and retorting is 80, Sufficient heat resistance at 85, 90 and 95 ° C. was confirmed.

In the method shown in Table 1, printing is first performed using oil-based ink, and then printing is performed using water-based ink. However, the order of printing steps using oil-based ink is arbitrary. The number of printing steps using the oil-based ink is not limited to one as described above, but is optional. However, it is basically preferable to use an oil-based ink only when an oil-based ink cannot be used to obtain a sufficient print quality in order to reduce the amount of the organic solvent used.

The printing method according to the present invention can be applied to various printing base materials, but it is particularly effective to apply it to synthetic resin materials. Furthermore, among the synthetic resin materials,
A safe packaging material can be constituted by using the resin film printing material for packaging, for example, a resin film for light packaging, or a food packaging material for boiling or retorting. Further, the present invention can be applied to a bag for a boil, a bag for a retort, a laminate film for a tube container, and the like.

[0032]

As described above, when printing is performed using a part of the printing plates, the amount of the organic solvent used can be reduced by using the aqueous printing ink, and printing can be performed using other printing plates. When performing printing, the use of oil-based printing ink can prevent bleeding of characters and crushing of patterns caused by water-based printing ink. By selecting whether to use water-based printing ink or oil-based printing ink, it is possible to achieve both reduction in the amount of organic solvent used and assurance of print quality. In addition, by providing a plate using oil-based ink, the required level of printing quality of a plate using water-based ink can be relaxed, so reducing the number of lines of the plate for water-based ink and increasing the plate depth. This makes it possible to improve the durability of the plate, improve the printing speed, share the plate for the water-based ink and the plate for the oil-based ink, etc., and suppress the printing cost as a whole.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a structure of a rotary press for gravure printing used in an embodiment of a printing method and a method of manufacturing a resin film print for packaging according to the present invention.

[Explanation of symbols]

10A, 10B, 10C, 10D, 10E, 10F Printing unit 11 Ink pan 12 Plate cylinder 13 Doctor 14 Compression cylinder 15 Dryer 20 Printed body (resin film)

Claims (5)

[Claims] 1. A method of gravure printing on the same printing substrate using a plurality of printing plates for forming a predetermined printing pattern, wherein a part of the printing plates is printed using an aqueous printing ink. And printing the other plate using an oil-based printing ink. 2. The printing method according to claim 1, wherein a printing pattern formed by another printing plate has a higher required level of printing quality than a printing pattern formed by some printing plates. Printing method. 3. The printing method according to claim 1, wherein the oil-based printing ink does not contain toluene as an organic solvent. 4. One of claims 1 to 3
In the paragraph, the printing pattern is formed on the surface of the printing substrate made of a synthetic resin material, wherein the aqueous printing ink and the oil-based printing ink have printing characteristics suitable for a synthetic resin. The printing method you want. 5. The method according to claim 1, wherein:
A method for producing a printed resin film body for packaging using the printing method described in the above section.