JPH07285262A - Multicolor wet lap-printing method of cylindrical member - Google Patents

Abstract

PURPOSE:To simply transfer the laminated ink image of a plurality of colors applied to a blanket roller to a cylindrical member to be printed by one operation using one offset printing press in the multicolor wet lap-printing of the cylindrical member. CONSTITUTION:In a process laminating and applying ink images to a blanket roller 16, a plurality of inks Y, M, C are composed of thermosetting inks having different tack values and made much in the contents of UV curable inks as the tack values become low are applied in order high in tack values. After the ink image laminating and applying process, a process irradiating the laminated ink image with UV rays is performed and the reversal of the high and low order of the tack values is performed by the action of the contained UV curable inks. Thereafter, a process transferring the laminated ink image to a cylindrical member is performed to smoothly and accurately perform both of the coating of the blanket roller 16 and the transfer to the cylindrical member.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multicolor wet overlay printing method for cylinders, and more particularly to an offset printing method for transferring ink images of a plurality of colors from a blanket roller onto a cylinder to be printed so as to form a laminated state. The present invention relates to a multicolor wet overlay printing method for a cylinder used.

[0002]

2. Description of the Related Art In recent years, it has been desired that metal cans, which are containers for beer, soft drinks, etc., be printed on the outer surface so as to draw the customer's attention, as with ordinary packaging containers. Also, multicolor printing such as offset printing is performed.

In the case of printing of a so-called two-piece can, in which the can body and the bottom are integrally formed, of such a metal can, since the object to be printed is preliminarily formed in a cylindrical shape, multicolor printing is performed. When performing the printing, if the first color is printed, the print is dried and printed, and the next color is printed again, it becomes very difficult to perform the alignment during the reprinting. Therefore, it is desirable to simultaneously perform multi-color wet overprinting with one offset printing machine.

In the case of performing such multicolor printing, since the material to be printed is preliminarily formed as a cylindrical body, a rotary blanket roller is used in performing the multicolor printing, and an ink image is formed on the blanket roller. It is applied and transferred to a metal can which is a cylindrical body for printing.

When performing multicolor overprinting, a plurality of ink images are applied in a superposed manner on the blanket roller. In such layered coating of ink images, the inks of the respective colors having the highest tack value are sequentially coated. This is in consideration of smooth application to the blanket roller. For example, when the tack value of the ink layer applied first is smaller than the tack value of the ink layer applied later, it is applied later. This is to prevent the problem that the ink layer does not smoothly move to the previously applied ink layer side and that the previously applied ink layer is peeled off.

On the other hand, the ink image in the laminated state applied on the blanket roller is transferred to the cylindrical body which is the object to be printed in the next step. If the tack value is not larger, the cylinder will not move smoothly. That is, it is difficult to transfer to the metal can as it is, and when the transfer is performed, the upper ink layer on the blanket roller is split, and the lower ink layer is transferred to the metal can. Therefore, proper printing cannot be performed.

As described above, in the above-mentioned offset printing method in which the transfer operation is performed twice, that is, the application to the blanket roller and the transfer from the blanket roller to the can, the setting of the stacking order depending on the size of the tack value is a trade-off. It is in.

Therefore, conventionally, when performing multicolor overprinting on a cylindrical body, the wet overprinting method cannot be used.
For example, a film transfer printing method described in Japanese Patent Publication No. 60-46034 is known.

In the above-mentioned conventional publication, a release liquid is applied onto a blanket roller, the release liquid is dried to increase the adhesive force to form a release film, and the liquid first ink is applied onto the release film. By drying, the liquid second ink is further applied onto the dried first ink and dried in the same manner, and a substantially dried ink film is formed on the release film by repeating this step several times. , A method of transferring a film of an ink film for each release film on a cylindrical body is shown. That is, a transfer film in a substantially dry state is formed on the blanket roller, and the transfer film is transferred to the cylindrical body.

[0010]

However, in the above-mentioned conventional method, a film in a substantially dry state must be formed on the blanket roller, and moreover, each time the release liquid or the liquid ink is applied. Since it has to undergo a drying process, it is extremely difficult to increase the printing speed, and there is a problem that it is not suitable for high-speed printing such as drinking cans.

The present invention has been made by paying attention to the above problems, and a single offset printing machine can be used to perform a simple method to print a plurality of colors of laminated ink images applied on a blanket roller once. An object of the present invention is to provide a multicolor wet overlay printing method for a cylindrical body, which can be moved and printed on the side of the cylindrical body which is the object to be printed by operation.

[0012]

In order to solve the above-mentioned problems, in the invention according to claim 1, the laminated ink image on the blanket roller is irradiated with ultraviolet rays after the step of laminating ink images with a plurality of inks on the blanket roller. It was decided to perform an ultraviolet irradiation step of irradiating the ink layer to reverse the order of high and low tack values of the ink layer.

That is, as shown in the claim correspondence diagram of FIG. 1, a layer coating step a in which a plurality of ink images are coated from an ink supply roller to a blanket roller in a state of at least partially overlapping, and the layered ink image is printed. A multi-color wet overlay printing method for a cylinder including a transfer step b for transferring to a cylinder that is a body, wherein a plurality of inks to be applied are tacked in a stacking step a in which ink images are laminated on the blanket roller. When the values are different and the tack value becomes smaller, the content of the UV curable ink is increased and the order of the tack value is reversed when exposed to UV rays. The laminated coating is performed in the order of higher tack value before irradiation with ultraviolet rays, and after the laminated coating step a of the ink image, the laminated ink image is exposed to ultraviolet rays. Was irradiated with ultraviolet irradiation step c for performing reversal of high and low order of the tack value, then, it is characterized in that to perform the migration step b of the ink image to the cylindrical body.

Further, in the invention according to claim 2, after the step b of transferring the ink image to the cylindrical body is completed, the heating step d of heating and curing the ink image on the cylindrical body is performed. And

[0015]

According to the first aspect of the present invention, a plurality of ink images are applied from the ink supply roller to the blanket roller in a state in which they are at least partially overlapped. The plurality of applied inks have different tack values as in the conventional case, but in the present invention, the content of the ultraviolet curable ink is different. That is, the degree of curing differs when irradiated with ultraviolet rays. This is because when the resin is cured by the irradiation of ultraviolet rays and the viscosity is increased, the tack value thereof increases according to the content ratio of the ultraviolet curable ink. The order of application to the blanket roller side is the order of higher tack value before UV irradiation, but the content of UV curable ink is increased as the tack value becomes lower, and UV irradiation is performed. When received, it is considered to be a content ratio in which the rank of the tack value reverses.

Therefore, when the subsequent ultraviolet irradiation step c is carried out, the viscosity of the contained ultraviolet-curable ink changes due to the curing phenomenon, and the tack value rises in accordance with the content ratio of the ultraviolet-curable ink. Among the inks applied on the roller, the ink of the ink image laminated above has a higher viscosity and a higher tack value. Then, the inks laminated and applied on the blanket roller in the order of higher tack value are relatively reversed in tack value such that the tack value becomes lower from the upper layer to the lower layer.

As a result, the transfer of the ink image from the blanket roller side to the cylindrical body which is the object to be printed is transferred from the side having a higher tack value in the stacking portion, and the transfer is performed in the middle of the stacked ink. It will be a smooth transition that does not cause division. That is, it is possible to perform a transition operation with a favorable trapping rate.

Further, in the step b of applying the ink image to the blanket roller and the step b of transferring the laminated ink image to the cylindrical body, it is not necessary to heat the ink and adjust the temperature at all, and the irradiation degree of the ultraviolet rays is different for each ink image layer. Since it does not need to be changed to, it can be easily performed without making a troublesome fine adjustment of the tack value.

According to the second aspect of the invention, after the ink image transfer step b to the cylindrical body side is completed, the laminated ink images on the cylindrical body are heated to cure and dry the whole satisfactorily and quickly. It is possible to

[0020]

Embodiments of the present invention will be described below with reference to the drawings.

First, the structure will be described.

FIG. 2 is a schematic configuration diagram of an offset printing mechanism 10 for explaining a multicolor wet overlay printing method for a cylindrical body according to the embodiment of the present invention. In this embodiment, the case where the cylinder to be printed is the two-piece can 12 made of metal, and the case where three layers of ink images are laminated and printed with three colors of ink will be described.

As shown in FIG. 2, the two-piece can 12 is
It is preliminarily formed in a bottomed cylindrical shape, and is rotationally moved along the mandrel wheel 14 while being fitted in a rotating cylindrical mandrel (not shown). Then, the blanket roller 16 is brought into contact with the blanket roller 16, and the blanket roller 16 is rotated along with the rotation of the blanket roller 16 to transfer and print the ink image.

In the figure, the rotational movement direction of the two-piece can 12 is the arrow 100 direction (clockwise direction), and the rotation direction of the blanket roller 16 is the arrow 200 direction (counterclockwise direction).

In the vicinity of the outer circumference of the blanket roller 16,
Ink supply rollers 18, 20 and 22 for applying inks of respective colors to the blanket roller 16 are installed. The ink supply roller 18 applies yellow ink (ink Y), the ink supply roller 20 applies magenta ink (ink M), and the ink supply roller 22 applies cyan ink (ink C) to the blanket roller 16.

Incidentally, each of these ink supply rollers 18, 2
Ink is supplied to 0 and 22 from each inking device 17.

The coating state is a laminated state in which at least a part thereof overlaps as shown in the drawing. Here, the tack value of each ink of the stacked ink images is such that the ink applied first has a higher tack value because ink is smoothly applied from the ink supply rollers 18, 20, 22 to the blanket roller 16. It is set to be high. That is, in the order of height of the tack value, the ink Y applied first is the highest and the ink Y is lowered in the order of ink Y → ink M → ink C.

The characteristic feature of the present invention is that the respective inks contain different amounts of UV-curable ink, and the content ratio of UV-curable ink is, as will be described later, When receiving the irradiation of
Assuming that the above-mentioned high and low tack values are reversed, in contrast to the above-mentioned high and low tack values, the ink C having the lowest tack value contains the largest amount of ink C, ink M, and ink Y.
Is decreasing in order.

Further, in the rotation direction 200 of the blanket roller 16, on the rear side of the ink supply roller 22,
An ultraviolet irradiator 24 for performing the ultraviolet irradiation step is installed. The installation position of the ultraviolet irradiator 24 is set between the laminating coating process and the transfer process, and the ink image laminated on the blanket roller 16 is irradiated with ultraviolet light from above.

After the step of irradiating the ultraviolet rays, the order of the tack values of the inks stacked on the blanket roller 16 is reversed, and then the transfer operation of the ink image to the two-piece can 12 is performed.

Next, the two-piece can 12 to which the ink image has been transferred is overcoated in the next stage, and then conveyed to the heating step. In this embodiment, the two-piece can 1
In order to heat 2 from the outside, a hot air heating furnace (not shown) is installed in the latter stage. That is, the two-piece can 12 is heated by this hot air heating furnace to heat and dry the transferred ink image. The inks that make up the transferred ink images are thermosetting inks and mixed inks of thermosetting inks and UV-curing inks, so each ink is cured and dried well by this heating step. .

Next, the operation will be described.

Each ink supply roller 18, 20, 22 described above
When the ink is applied from the blanket roller 16 to the blanket roller 16, the tack values of the ink Y, the ink M, and the ink C of the thermosetting ink (polyester) are 15 for the ink Y applied to the first layer and 2 for the second layer. Ink M applied to the eyes is 12
.About.13, and the ink applied to the third layer is 9 to 10. The content ratio of the ultraviolet curing agent is set to 0 without mixing the ink Y of the first layer, the content ratio of the ink M of the second layer is 30%, and the content of the ink C of the third layer is contained. The rate was 40%.

When ultraviolet rays are irradiated in the ultraviolet ray irradiation step, the viscosity changes due to the curing phenomenon of each ink,
The tack value changed depending on the content ratio of the ultraviolet curable ink. The change in the tack value changes depending on the irradiation amount of ultraviolet rays, but the minimum ultraviolet irradiation amount is 120 W / cm and is 0.1.
One second is sufficient, and in this embodiment, 120 W / cm is less than 0.1.
It was set to 25 seconds.

As a result, after the irradiation, the ink C
Has a tack value of 17 to 18, and ink M has a tack value of 15 to 18.
Since the ink Y does not contain the ultraviolet curable ink, the tack value remains 15 without any change, and the ink Y is sequentially transferred from the side closer to the outer surface of the two-piece can 12 before the transfer process to the next two-piece can 12. The tack value is high. As a result, the transition to the two-piece can 12 side, which is the next step, has a good trapping rate (7
5.2% ... See Table 3 described below), and the transfer of the laminated ink image was performed smoothly and satisfactorily.

Then, a transparent clear (polyester type) was applied to the upper layer of the two-piece can, and heating in a hot air drying furnace was performed as the final step of printing, and the ink image of the obtained two-piece can 12 was good. It was

As described above, according to the present embodiment, it is not necessary to dry the blanket roller 16 every time it is applied with ink, and an appropriate amount of ultraviolet curable ink is prepared for each thermosetting ink having different tack values in advance. By including the ink, after the ink application work from the ink supply rollers 18, 20, 22 to the blanket roller 16, a predetermined amount (predetermined irradiation amount) of ultraviolet rays set from above is applied to the entire surface of the laminated ink. Only by doing so, it is possible to smoothly transfer the laminated ink image to the two-piece can 12.

Further, since the ink on the side close to the outer surface of the two-piece can 12 before the transfer step to the two-piece can 12 is an ink containing at least a thermosetting ink, it is exposed to ultraviolet rays even after being irradiated with ultraviolet rays. The adhesiveness of this thermosetting ink that is not affected can be maintained and the two-piece can 1
It is not necessary to apply an adhesive such as a base coat agent to the outer surface of No. 2, and the transferability of the ink can be prevented from deteriorating when transferring to a two-piece can.

[Experimental Example 1] Experimental data for two color examples are shown below. First, a thermosetting polyester ink containing no ultraviolet (UV) curable ink is applied to the first layer on a blanket roller, and a UV curable ink is contained on the first layer. Was applied to the second layer, and the laminated ink was transferred to the two-piece can side. In this case, the trapping rate of the ink transferred to the two-piece can side after being irradiated with ultraviolet rays and the one transferred without being irradiated with ultraviolet rays has a trapping rate of the second layer ink (M,
The change in the content of the UV curable ink contained in C) was investigated. The experimental results were as shown in <Table 1> and <Table 2> below.

Table 1 shows combinations in which the ink Y is applied to the first layer and the ink M is applied to the second layer.
Indicates a combination in which the ink Y is applied to the first layer and the ink C is applied to the second layer. Further, the ink tack value before irradiation is the same as that in the above-described embodiment (ink Y is 15, ink M is 12 to 1).
3, ink C is 9 to 10), and the UV irradiation conditions are the same.

The trapping rate (%) is the GATF.
The value calculated by the proposed reflection density measurement was used.

The trapping rate (%) by the method proposed by GATF is expressed by the following equation with reference to FIG. _{P 1 = (A 5 -A 1} ) / A 2 × 100 Here, the reflection density A ₂ · · · of A ₁ · · · first ink (the second layer of the ink on the blanket roller) A ₁ ' Reflection density of 2 inks (first layer of ink on the blanket roller) A ₂ 'A ₅ ... Reflection density of overlapping part (that is, secondary color density) <Omitted below>

[Table 1]

[0043]

[Table 2]

From Tables 1 and 2 above, the higher the UV-curable ink content rate α (β), the higher the trapping rate P _{1 with} and without UV irradiation. Without irradiation, the tack value between inks does not reach the trapping rate of 70%, which is suitable for transfer to the two-piece can 12, no matter how much the content is increased. Rate of 30% or more, content rate of <Table 2> 2
It is understood that the trapping rate P ₁ reaches 70% as early as 0% or more. This is because the tack value of the second layer ink overprinted on the blanket roller due to the irradiation of the ultraviolet rays increased due to the irradiation of the ultraviolet rays, and the UV curing type ink content rate α was 30% or more (β is 20%
From the above, it can be seen that the tack value is reversed between the first layer and the second layer.

[Experimental Example 2] Experimental data for three color examples are shown below. First, ink Y is applied as a first layer, ink M is applied as a second layer, and ink C is applied as a third layer on a blanket roller, and the laminated ink is applied to a two-piece can. It was investigated how the trapping rate changes between the one that was moved to the side, the laminated ink was irradiated with ultraviolet rays, and then transferred to the two-piece can side, and the one that was directly transferred without being irradiated with ultraviolet rays. The experimental results were as shown in Table 3 below.

However, the first layer ink Y ... thermosetting polyester ink (UV curing type ink content is 0), the second layer ink M ... UV curing type ink 30%
Incorporated thermosetting polyester ink-Ink C of the third layer ... UV-curable ink 30-
Thermosetting polyester ink containing 80% The tack value of the ink is the same as that in the above embodiment. U
The V irradiation conditions were also the same.

The trapping rate (%) is also GA
The value calculated by the reflection density measurement proposed by TF was used.

The trapping rate P ₂ (%) is obtained by the following equation with reference to FIG.

P ₂ (%) = (A ₆ −A ₁ −A ₂ ) / A ₃ × 100 where A ₁ ... First ink (third layer ink C on the blanket roller) A ₁ ′ Reflection density of A ₂・ ・ ・ second ink (second layer ink M on the blanket roller) A ₂ ′ reflection density A ₃・ ・ ・ third ink (first layer ink Y on the blanket roller) A the reflection density of the reflection density a ₆ · · · overlapping portion of the ₃ '(ie tertiary color density) <omitted below>

[Table 3]

According to Table 3 above, the trapping rate P ₂ increases as the UV-curable ink content difference (β-α) increases, but no matter how the content difference is increased without irradiation. The trapping rate does not reach 70%, but with irradiation, the content difference is 10% or more, and the trapping rate reaches 70% as early as possible. Therefore, the tack value of the third layer and the first layer is high or low. You can see that it is reversed.

Although the embodiments have been described above with reference to the drawings, the specific structure is not limited to the embodiments, and modifications and additions within the scope of the present invention are included in the present invention. Be done.

In the above embodiment, ink Y, ink M,
Although the case of three colors of ink C is shown, the number and type of ink images can be changed depending on the pattern to be printed.
It may be two colors or four or more colors, and the laminated state is not limited to the state where all layers are always overlapped.
It is also possible to make the types the same plane and form the upper layer ink over both of them. That is, as long as it is a thermosetting ink and the content of the UV curable ink is increased in the order of decreasing tack value, and the order of tack value is reversed when irradiated with ultraviolet rays, the same as in the present embodiment. The effect of can be obtained.

Since the curability (degree) of the UV curable ink varies depending on the color (pigment) of the ink, depending on the combination of the inks to be overprinted, even if the content ratio is less than 30% and the tack value is 10%, There is also a combination in which the high and low ranks can be reversed (the ink M is selected for the first layer and the ink Y is selected for the second layer), and the content of the UV curable ink can be appropriately selected. However, if it is less than 10%, the tack-up amount of the overprinted ink will be small, and even if it is irradiated with ultraviolet rays, the rank order of the tack value will not be reversed, but it will be 70%.
If the content exceeds the range, the UV-cured portion is increased, so that the tackiness of the ink after irradiation with ultraviolet rays is reduced and the transferability of the ink is deteriorated. Therefore, the content rate of ultraviolet rays is preferably selected from 10 to 70%.

In this embodiment, the metal two-piece can is used as the material to be printed, but it can be applied to paper cups, plastic cups, plastic tubes, and the like.

[0055]

As described above, according to the multicolor wet overprinting method for a cylindrical body of the present invention, the following effects can be obtained.

(1) According to the first aspect of the present invention, both the application to the blanket roller and the transfer to the printing cylinder while at least a part of the ink images on the printing cylinder are superimposed. It is possible to perform smoothly and accurately, and as a result, it is possible to print complicated patterns and colors.
It can be applied to the cylinder to be printed in a single operation, and the printing operation can be speeded up.

(2) According to the invention of claim 2, after the step of transferring the ink image to the cylinder to be printed is completed, a special means is required when heating and drying the ink image on the cylinder. Instead, since the heating process which has been conventionally used can be utilized, the ink image can be dried and cured satisfactorily and quickly without making a large change in the equipment.

[Brief description of drawings]

FIG. 1 is a diagram corresponding to a claim of the present invention.

FIG. 2 is a schematic configuration diagram of an offset printing mechanism for explaining a printing method according to an embodiment of the present invention.

FIG. 3 is an explanatory diagram of a method of calculating a wet trapping rate in Experimental Example 1.

FIG. 4 is an explanatory diagram of a method of calculating a wet trapping rate in Experimental Example 2.

[Explanation of Codes] 10 Offset Printing Mechanism 12 Two-piece Can 14 Mandrel Wheel 16 Blanket Roller 18, 20, 22 Ink Supply Roller 24 Ultraviolet Irradiator Y, M, C Ink

Claims (2)

[Claims] 1. A laminated coating step of applying a plurality of ink images from an ink supply roller to a blanket roller in a state of at least partially overlapping, and a transfer step of transferring the laminated ink image to a cylinder which is a printing medium. A method for multi-layer wet overlay printing of a cylindrical body containing a plurality of inks to be applied in the step of stacking ink images on the blanket roller, wherein the tack values are different from each other and the UV values become smaller as the tack value becomes smaller. When the content of the curable ink is increased and the order of tack value is reversed when it is irradiated with ultraviolet rays, it is a thermosetting ink, and the layered coating is applied in the order of higher tack value in those inks before irradiation with ultraviolet rays. After the layered application step of the ink image, the layered ink image is irradiated with ultraviolet rays to reverse the order of the tack value. A multicolor wet overlay printing method for a cylindrical body, comprising performing an outside-irradiation step and then performing a step of transferring an ink image to the cylindrical body. 2. The heating step of heating and curing the ink image on the cylindrical body after the step of transferring the ink image to the cylindrical body is completed. Multicolor wet overlay printing method.