Foil printing method and foil printing apparatus

Abstract

Achieving foil printing without heating. [Solution] Pad printing is performed on the surface of the object to be printed using UV-curable ink (Step S1). Next, UV light is irradiated onto the printed area of ​​the pad print to partially cure the UV-curable ink (Step S2). Next, while the UV-curable ink is still partially cured, a foil sheet is pressed onto the printed area to transfer the foil (Step S3). After that, UV light is irradiated onto the printed area to fully cure the UV-curable ink (Step S4).

Description

Technical Field

[0001] The present invention relates to a foil printing method and a foil printing apparatus using an ultraviolet-curable ink as printing ink.

Background Art

[0002] Foil printing for transferring an aluminum vapor-deposited sheet (metal foil) such as gold or silver to a printing object is known. Patent Document 1 discloses a method of foil printing. In Patent Document 1, after transferring a pattern to the surface of a printing object, a foil sheet is overlaid on the pattern, and pressure and heat are applied to the foil sheet by a heated pad to transfer the foil to the pattern surface.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In Patent Document 1, the foil is transferred by thermocompression bonding. Therefore, a press machine capable of performing thermocompression bonding is required, and it is necessary to sufficiently adjust the heating temperature and heating time of the pad. If this adjustment is insufficient, for example, the gloss is lost due to thermal deterioration of the foil, or transfer failure occurs due to insufficient pressure bonding.

Means for Solving the Problems

[0005] The foil printing method for solving the above problems includes performing predetermined printing on the surface of a printing object using an ultraviolet-curable ink, irradiating ultraviolet rays on the printed portion by the predetermined printing to make the ultraviolet-curable ink in a semi-cured state, and pressing a foil sheet against the printed portion while the ultraviolet-curable ink is in the semi-cured state to transfer the foil.

[0006] A foil printing apparatus that solves the above problems comprises a printing unit that performs a predetermined print on the surface of a printing object using an ultraviolet-curable ink, an irradiation unit that irradiates the printed portion with ultraviolet light, and a transfer unit that presses a foil sheet onto the printed portion to transfer the foil. The irradiation unit irradiates the ultraviolet-curable ink with ultraviolet light so that it becomes semi-cured, and the transfer unit transfers the foil while the ultraviolet-curable ink remains in the semi-cured state. [Effects of the Invention]

[0007] According to the present invention, foil printing can be achieved without heating. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a plan view showing an example of printing on an object. [Figure 2] Figure 2(a) is a cross-sectional view taken along line 2a-2a in Figure 1, and Figure 2(b) is a cross-sectional view taken along line 2b-2b in Figure 1. [Figure 3] Figure 3 is a flowchart showing the foil printing method. [Figure 4] Figure 4 is a schematic block diagram showing an example of a foil printing apparatus. [Modes for carrying out the invention]

[0009] An embodiment of the foil printing method and foil printing apparatus will be described below with reference to Figures 1 to 4. <Explanation of foil printing> Figure 1 shows printed materials P1, P2, and P3 printed on the surface of the printing target 10. The printing target 10 can be a sheet-like object such as a card, sticker, or label, or an object with a curved surface such as the body of a ballpoint pen. Printed materials P1 to P3 include letters (including numbers) and pictures (including symbols and figures). In Figure 1, printed material P1 is shown as the figure "square," printed material P2 as the letter "あ," and printed material P3 as the letter "H." In Figure 1, printed materials P1 and P2 are printed materials after foil printing, while printed material P3 is printed material before foil printing.

[0010] As shown in Figures 1 and 2(a), the printed material P1 after foil printing has a first printing layer M1 and a second printing layer M2 superimposed on the first printing layer M1. Although not shown, the printed material P2 after foil printing also has a first printing layer M1 and a second printing layer M2, similar to printed material P1. The first printing layer M1 is formed by performing a predetermined printing on the surface of the object to be printed 10 to form the printed materials P1 to P3. The predetermined printing is either pad printing or screen printing. The second printing layer M2 is formed by foil printing using, for example, an aluminum vapor-deposited sheet in gold, silver, or metallic colors, or a sheet with various colors and patterns. In this specification, various sheets such as aluminum vapor-deposited sheets used in foil printing are collectively referred to as "foil sheets".

[0011] Foil printing is performed by pressing a foil sheet Q onto the printed portion of a printed material P3 on a printing target object 10, as shown in Figures 1 and 2(b). After the foil sheet Q is removed from the printed portion of the printing target object 10, the foil sheet Q is transferred and remains on the printed portion. As a result, printed materials P1 and P2 decorated with foil sheet Q are printed on the printing target object 10. In this embodiment, the second printing layer M2 is formed using an ultraviolet-curable ink (hereinafter referred to as UV ink).

[0012] <Explanation of foil printing method> The foil printing method in this embodiment will be explained below with reference to Figure 3. In step S1, pad printing is performed on the surface of the object to be printed 10 using UV ink. In pad printing, UV ink is first poured into an intaglio plate on which the print materials P1 to P3 are formed. Next, in pad printing, the UV ink is left only in the recessed parts of the intaglio plate, and then a silicone pad is pressed against the intaglio plate to adhere the UV ink to the transfer surface of the pad. After that, in pad printing, the pad with the UV ink attached is pressed against the object to be printed 10 to print on its surface.

[0013] Next, in step S2, ultraviolet light is irradiated onto the printed area of ​​the pad print. In the diagram, the irradiation of ultraviolet light in step S2 is referred to as primary irradiation. UV ink hardens from a liquid state to a solid state by undergoing a photochemical reaction with the energy of ultraviolet light. In step S2, the energy of the ultraviolet light irradiated onto the UV ink is set so that the UV ink does not harden, but remains in a semi-hardened state. Semi-hardened UV ink has lower fluidity than the liquid state but higher fluidity than the solid state, and is in a gel-like state, with sufficient adhesion for the printed surface to transfer foil. The energy of the ultraviolet light can be set by the intensity of the ultraviolet light and the irradiation time. Then, in step S2, ultraviolet light is irradiated so that the liquid UV ink printed in step S1 remains in a semi-hardened state.

[0014] Next, in step S3, foil printing is performed by pressing the foil sheet Q onto the UV ink while it is still in a semi-cured state. In the diagram, the foil printing performed in step S3 is referred to as foil transfer. In the foil printing of step S3, the portion of the foil sheet Q corresponding to the printed portion of the pad printing is transferred to the printed portion of the pad printing. As a result, printed materials P1 to P3 decorated with foil sheet Q are printed on the object to be printed 10. In this embodiment, the printed portion of UV ink becomes the first printing layer M1, and the foil-printed portion becomes the second printing layer M2. The first printing layer M1, which consists of UV ink, also serves as an adhesive layer to bond the foil sheet Q.

[0015] Next, in step S4, ultraviolet light is irradiated onto the printed materials P1 to P3. In the diagram, the irradiation of ultraviolet light in step S4 is referred to as secondary irradiation. In step S4, ultraviolet light is irradiated so that the UV ink, which was in a semi-cured state in steps S2 and S3, becomes cured. In other words, in step S4, the energy of the ultraviolet light irradiated onto the UV ink is set to cure the UV ink. As a result, the printed materials P1 to P3 after foil printing in step S3 are fixed to the surface of the printing target object 10. The foil sheet Q is transparent. Therefore, the ultraviolet light passes through the foil which becomes the second printing layer M2 and irradiates the UV ink of the first printing layer M1.

[0016] In the foil printing method of the embodiment, after the pad printing in step S1 is completed, the process of step S5 is performed simultaneously with the processes after step S2 to remove the UV ink adhering to the transfer surface of the pad. In step S5, the UV ink adhering to the transfer surface of the pad is cured by irradiating the transfer surface of the pad with ultraviolet rays. Then, the UV ink is removed by pressing the pad against an adhesive material. The adhesive material is, for example, an adhesive sheet coated with an adhesive. The process of step S5 is preferably completed by the time the foil printing in step S3 is completed.

[0017] <Description of the Foil Printing Apparatus> Hereinafter, an example of a foil printing apparatus 20 that can realize the above-described foil printing method will be described with reference to FIG. 4.

[0018] The foil printing apparatus 20 includes a printing unit 21 that performs pad printing. The printing unit 21 includes a pad, a driving unit for the pad, a gravure plate, an ink supply unit that supplies UV ink to the gravure plate, and a blade. The foil printing apparatus 20 includes a first irradiation unit 22 that irradiates ultraviolet rays onto the printed portion printed by the printing unit 21. The first irradiation unit 22 includes a UV lamp that irradiates ultraviolet rays. The foil printing apparatus 20 includes a transfer unit 23 that transfers a foil sheet Q onto the printed portion of the UV ink that has been semi-cured by the first irradiation unit 22, and a foil supply unit 24 that supplies the foil sheet Q to the transfer unit 23. The transfer unit 23 includes a pressing unit that presses the foil sheet Q supplied from the foil supply unit 24 against the printed portion. The pressing unit includes, for example, a silicon pad.

[0019] The foil printing apparatus 20 includes a transport mechanism 25 that sequentially transports the printing object 10 to a printing unit 21, a first irradiation unit 22, and a transfer unit 23, and a mounting table 26 on which the printing object 10 transported by the transport mechanism 25 is placed. The printing object 10 is transported while being placed on the mounting table 26. Pad printing is performed in the printing unit 21, then ultraviolet rays are irradiated in the first irradiation unit 22, and then foil printing is performed in the transfer unit 23. The foil printing apparatus 20 includes a control device (not shown). The control device controls the operations of the printing unit 21, the first irradiation unit 22, the transfer unit 23, the foil supply unit 24, and the transport mechanism 25. In the embodiment, the printing unit 21 performs the process of step S1 of the foil printing method, the first irradiation unit 22 performs the process of step S2 of the foil printing method, and the transfer unit 23 and the foil supply unit 24 perform the process of step S3 of the foil printing method.

[0020] The foil printing apparatus 20 includes a second irradiation unit 27 that irradiates ultraviolet rays onto the transfer surface of the pad after pad printing, and a wiping unit 28 that removes the UV ink that adheres to the transfer surface of the pad and is in a cured state. The second irradiation unit 27 includes a UV lamp that irradiates ultraviolet rays. The wiping unit 28 includes an adhesive sheet coated with an adhesive. After pad printing, the pad moves to the second irradiation unit 27 and is irradiated with ultraviolet rays, and then moves to the wiping unit 28, and the UV ink on the transfer surface is removed by the adhesive sheet. The operation of the second irradiation unit 27 and the movement of the pad to the second irradiation unit 27 and the wiping unit 28 are controlled by a control device (not shown) provided in the foil printing apparatus 20. In the embodiment, the second irradiation unit 27 and the wiping unit 28 perform the process of step S5 of the foil printing method.

[0021] Note that the secondary irradiation performed in step S4 of the foil printing method is performed by a third irradiation unit 30. The third irradiation unit 30 includes a UV lamp that irradiates ultraviolet rays. After the printing object 10 is foil printed by the transfer unit 23, it is transported to the third irradiation unit 30 and irradiated with ultraviolet rays. As a result, the UV ink constituting the first printing layer M1 of the printed matters P1 to P3 becomes a cured state. The third irradiation unit 30 may be provided in the foil printing apparatus 20 or may be provided separately and independently of the foil printing apparatus 20.

[0022] <Effects of the Foil Printing Method and the Foil Printing Apparatus> (1) UV ink was used in the first printing layer M1, which functions as an adhesive for transferring the foil. Before transferring the foil, the UV ink was allowed to partially harden, providing sufficient adhesion for foil transfer. Therefore, foil printing can be performed by pressing the foil onto the first printing layer M1, which consists of partially hardened UV ink. In other words, the foil can be transferred without heat pressing.

[0023] (2) Another method for foil printing without heat-pressing the foil is to form an adhesive layer with ink using screen printing or pad printing, and then press the foil onto the foil before the ink dries. However, in this method, the foil is transferred before the solvent in the ink dries, thus blocking the escape route for the solvent. As a result, there is a risk of wrinkles or blistering occurring on the transferred foil, or the adhesion of the foil being significantly impaired. In contrast, the foil printing method and foil printing apparatus of the embodiment form an adhesive layer with solvent-free UV ink, so wrinkles or blistering are less likely to occur on the transferred foil, and the adhesion of the foil is not impaired. As a result, good foil printing can be provided.

[0024] (3) Another method of foil printing involves creating a mold of the desired image in advance and then heat-pressing a foil sheet with an adhesive layer onto it. However, this method requires an expensive mold, making it less versatile and unsuitable for small-volume printing. In contrast, the foil printing method and foil printing apparatus of the embodiment do not require an expensive mold, making them highly versatile and suitable for small-volume printing.

[0025] (4) Pad printing is used for printing with UV ink. This enables foil printing for a wide range of applications, regardless of the shape of the object being printed on. (5) Since UV ink is liquid when not exposed to ultraviolet light, printing with UV ink is considered more difficult in terms of ink transfer compared to general solvent-based inks. For this reason, in pad printing with UV ink, UV ink tends to remain on the transfer surface of the pad, which may adversely affect subsequent printing. For this reason, the foil printing method and foil printing apparatus of the embodiment are designed to remove UV ink from the transfer surface of the pad after pad printing. However, in order to completely remove liquid UV ink from the transfer surface of the pad, it is necessary to press it against the adhesive sheet multiple times. To solve this, the foil printing method and foil printing apparatus of the embodiment cure the UV ink by irradiating the transfer surface of the pad with ultraviolet light after pad printing before pressing it against the adhesive sheet. This makes it possible to remove UV ink from the transfer surface of the pad with a small number of presses, such as just one press.

[0026] <Variation> The embodiments described above can be implemented with the following modifications. Furthermore, the embodiments described above and the following modifications can be combined with each other to the extent that they do not contradict each other technically.

[0027] The foil printing method of the embodiment can also be realized by performing each process in a separate device. In other words, the printing unit 21, the first irradiation unit 22, and the transfer unit 23 of the foil printing apparatus exemplified in the embodiment may be provided in separate devices.

[0028] The process of removing ink from the transfer surface of the pad after pad printing may be performed after each pad printing cycle, or after every multiple pad printing cycles. [Explanation of Symbols]

[0029] 10…Printable object 20…Foil printing device 21…Printing Department 22...First irradiation section 23...Transfer section 24...Foil supply section 25…Conveying mechanism 26… Mounting platform 27...Second irradiation section 28… Wiping section 30…Third irradiation section P1,P2,P3…Printed material M1…1st printing layer M2...2nd printing layer Q... Foil sheet

Claims

1. The process involves printing a predetermined design onto the surface of an object using an ultraviolet-curing ink, The process involves irradiating the printed portion by the predetermined printing method with ultraviolet light to bring the ultraviolet-curable ink to a semi-cured state, A foil printing method comprising pressing a foil sheet onto the printing area while the ultraviolet-curable ink is in the semi-cured state to transfer the foil.

2. The aforementioned specified printing is pad printing, The foil printing method according to claim 1, further comprising: irradiating the transfer surface of the pad with ultraviolet light to cure the ultraviolet-curable ink adhering to the transfer surface of the pad; and then pressing the pad onto an adhesive material.

3. A printing unit that performs a predetermined print on the surface of the object to be printed using ultraviolet-curing ink, An irradiation unit that irradiates ultraviolet light onto the printed portion by the predetermined printing, The system includes a transfer unit that presses a foil sheet onto the printed portion to transfer the foil, In the irradiation section, ultraviolet light is irradiated so that the ultraviolet-curable ink reaches a semi-cured state. The foil printing apparatus is characterized in that, in the transfer section, the ultraviolet-curable ink is transferred to the foil while it is still in the semi-cured state.

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