Sheet decoration method

Abstract

To provide a sheet decoration method that can solving at least one of existing issues.SOLUTION: A sheet decoration method includes a ground layer formation step 220 of forming a ground layer on a sheet, and a decorative layer formation step 230 of discharging a light-transmissible UV ink in liquid state onto the surface of the ground layer and curing the ink to form a decorative layer having an uneven pattern including at least one of a parallel line pattern and a halftone dot pattern.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a sheet decoration method. [Background technology]

[0002] Patent Document 1 discloses a flexographic printing machine. This flexographic printing machine forms a base layer by printing letters, designs, etc. on a sheet using colored inks, and then forms a transparent layer by printing a relief pattern including relief lines on the base layer using transparent ink, thereby producing a printed product. It is said that the glossiness of the transparent layer of the printed product produced by this flexographic printing machine changes subtly depending on the angle from which it is observed, thereby creating a sense of luxury and elegance. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-110782 Summary of the Invention [Problem to be solved by the invention]

[0004] However, flexographic printing is expensive because it requires the creation of elastic plates, and the plates must be replaced when changing the pattern. In addition, the printing equipment tends to be large, and the printing resolution is relatively low.

[0005] The present invention has been made in light of these circumstances, and one exemplary purpose of an embodiment of the present invention is to provide a sheet decoration method that can solve at least one of the above-mentioned problems. [Means for solving the problem]

[0006] In order to solve the above problems, a sheet decoration method according to one aspect of the present invention provides a sheet decoration method comprising: A transparent liquid UV ink is ejected and then hardened, forming a UV ink layer on the surface.The method includes a base layer forming step of forming a base layer, and a decoration layer forming step of ejecting a translucent liquid UV ink onto the surface of the base layer and curing it to form a decoration layer having a concave-convex pattern including at least one of a line pattern and a halftone dot pattern. The base layer forming step is performed by passing the sheet through a sheet decorating device that includes an applicator that applies UV ink to the sheet transported in one direction, and the decorative layer forming step is performed by passing the sheet through a sheet decorating device that includes an applicator that applies UV ink to the sheet transported in one direction. do.

[0007] Any combination of the above components, or mutual substitution of the components or expressions of the present invention between methods, devices, systems, etc., are also valid aspects of the present invention. [Effects of the Invention]

[0008] According to the present invention, at least one of the above-mentioned problems can be solved. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a side view schematically showing a sheet decoration system according to an embodiment. [Figure 2] 1 is a plan view schematically showing a sheet decoration system according to an embodiment; [Figure 3] FIG. 10 is a cross-sectional view of a decorative sheet in which a decoration is applied to a sheet. [Figure 4] 10A to 10C are process diagrams showing the steps of creating a decorative sheet. [Figure 5] FIG. 10 is a diagram illustrating UV ink ejection data for a decorative layer. [Figure 6] FIG. 10 is a diagram illustrating a method for determining wettability. DETAILED DESCRIPTION OF THE INVENTION

[0010] The present invention will be described below based on preferred embodiments with reference to the drawings. The embodiments are illustrative and do not limit the invention, and all features and combinations described in the embodiments are not necessarily essential to the invention. The same or equivalent components, parts, and processes shown in each drawing are designated by the same reference numerals, and redundant descriptions will be omitted where appropriate.

[0011] 1 and 2 are schematic diagrams showing a sheet decoration system 10. FIG. 1 is a side view, and FIG. 2 is a plan view. The sheet decoration system 10 is an apparatus that applies a predetermined decoration to a sheet while transporting the sheet. The sheet may be made of a variety of materials, including paper, cloth, resin, and metal. Hereinafter, the direction in which the sheet is transported (the direction from right to left in FIGS. 1 and 2) will be referred to as the transport direction Y, and the direction perpendicular to the transport direction Y (the direction perpendicular to the paper surface in FIG. 1, and the up-and-down direction in FIG. 2) will be referred to as the width direction X.

[0012] The sheet decoration system 10 includes a paper feeder 12 that feeds sheets one by one, an applicator 14 that applies UV ink (ultraviolet-curable ink) to the sheets fed one by one, a foil stamping device 16 that transfers foil to the UV ink on the sheets (i.e., foil stamps) by utilizing the tackiness of the UV ink, a stacker 18 that accumulates the sheets, and a control device 20 that provides overall control of the sheet decoration system 10. The paper feeder 12, applicator 14, foil stamping device 16, and stacker 18 are arranged in a line in this order from the upstream side in the conveyance direction Y (the right side in FIGS. 1 and 2). The control device 20 is connected to the paper feeder 12, applicator 14, foil stamping device 16, and stacker 18 via a network 2.

[0013] The sheet feeding device 12 includes a feeder 22, a registration unit 24, and a corona treatment unit 26. The feeder 22 includes a table 28 and a suction head 30. Sheets are loaded on the table 28. The sheets are loaded by abutting against a guide plate provided at one end of the table 28 in the width direction X (in the illustrated example, the right side as viewed from the upstream side in the conveying direction Y). The table 28 is configured to be able to move up and down. The suction head 30 feeds the sheets loaded on the table 28 one by one, starting from the top.

[0014] The registration unit 24 includes a registration reference guide 32 provided on one end side in the width direction X. The registration reference guide 32 has a guide surface 32a that is perpendicular to the width direction X and extends in the conveying direction Y. The registration unit 24 aligns the position of the sheet in the width direction X by abutting the sheet delivered by the feeder 22 against the guide surface 32a.

[0015] The corona treatment unit 26 includes an electrode 36 disposed above the transport path 34 and a dielectric roller 38 disposed below the transport path 34, facing the electrode 36 from above. The corona treatment unit 26 modifies the surface of the sheet delivered by the feeder 22 by corona discharge between the electrode 36 and the dielectric roller 38. When the sheet is transported while being attracted to the transport path 34 by the air suction unit 40, the distance between the electrode 36 and the sheet is constant, stabilizing the corona discharge. The air suction unit 40 generates negative pressure by arranging one of the suction ports of an exhaust blower (not shown). However, a suction fan may also be disposed to generate negative pressure. The dielectric roller 38 may be rotatable or fixed relative to the housing of the corona treatment unit 26. Furthermore, the shape of the dielectric roller 38 is not limited to a roller, as long as it generates corona discharge between the electrode 36 and the corona treatment unit 26. The corona treatment unit 26 may be disposed upstream of the resist unit 24.

[0016] The coating device 14 includes a sheet sensor 42, at least one UV ink discharge unit 46, a semi-curing ultraviolet lamp 48, and a final-curing ultraviolet lamp 50. The UV ink discharge unit 46, the semi-curing ultraviolet lamp 48, and the final-curing ultraviolet lamp 50 are arranged in this order from upstream to downstream. In the illustrated example, the coating device 14 includes three UV ink discharge units 46, but this is not limited thereto. The coating device 14 may include one UV ink discharge unit 46 extending across the entire area required for printing in the width direction X, or may include two or four or more UV ink discharge units 46. The semi-curing ultraviolet lamp 48 and the final-curing ultraviolet lamp 50 use LEDs that emit ultraviolet light, but other light sources that emit ultraviolet light, such as incandescent lamps or fluorescent lamps, may also be used. It is preferable that the light source have adjustable output.

[0017] The sheet sensor 42 detects the sheet fed from the sheet feeder 12 .

[0018] The UV ink ejection unit 46 is a line-type inkjet head. Triggered by detection of the leading edge (downstream edge) of the sheet by the sheet sensor 42, the UV ink ejection unit 46 ejects UV ink according to UV ink ejection data (plate image data) and applies the UV ink to the sheet. The UV ink ejection data indicates where on the sheet the UV ink is to be applied.

[0019] When foil stamping a sheet, the semi-curing ultraviolet lamp 48 irradiates the UV ink on the sheet with ultraviolet light with a relatively reduced output to semi-cure the UV ink. Semi-cure refers to curing the UV ink lightly enough to reduce its fluidity but not completely harden it (for example, to a state where it can be further hardened). The semi-cured UV ink is then fully hardened by the foil stamping ultraviolet lamp 66 of the foil stamping device 16.

[0020] The semi-curing ultraviolet lamp 48 is turned off or its output is set to minimum when the sheet is not being foil stamped. The semi-curing ultraviolet lamp 48 may also be used when foil stamping is not being performed. For example, if the UV ink applied to the sheet is prone to bleeding, turning on the semi-curing ultraviolet lamp 48 and leaving it to semi-cure has the effect of suppressing bleeding.

[0021] When the sheet is not to be stamped with foil, the main curing ultraviolet lamp 50 irradiates the UV ink applied to the sheet with ultraviolet light to main cure the UV ink. When the sheet is to be stamped with foil, the main curing ultraviolet lamp 50 is turned off.

[0022] The main curing ultraviolet lamp 50 is turned off when foil stamping is performed on the sheet.

[0023] In other words, when foil stamping is performed on a sheet, the UV ink is semi-cured by the semi-curing ultraviolet lamp 48, and the semi-cured UV ink is fully cured by the foil stamping ultraviolet lamp 66 of the foil stamping device 16. In this case, the full-curing ultraviolet lamp 50 is turned off. When the sheet is not foil stamped, that is, when UV ink is only applied to the sheet, the UV ink is fully cured by the full-curing ultraviolet lamp 50. In this case, the output of the semi-curing ultraviolet lamp 48 is set to minimum, and the foil stamping ultraviolet lamp 66 of the foil stamping device 16 is turned off. Note that, as mentioned above, the semi-curing ultraviolet lamp 48 may be turned on when foil stamping is not performed. Furthermore, although an LED that emits ultraviolet light is used as the light source for the foil stamping ultraviolet lamp 66, any other light source that emits ultraviolet light may be used.

[0024] The foil stamping device 16 transports the web 52 roll-to-roll. The web 52 is a foil-holding film in which foil is held by the film. The foil is, for example, a metal foil. The foil stamping device 16 utilizes the tackiness of the semi-cured UV ink on the sheet to adhere the foil held by the web 52 to the UV ink. Then, with the foil held by the web 52 and adhered to the UV ink on the sheet, the foil stamping ultraviolet lamp 66 irradiates the semi-cured UV ink with ultraviolet light to fully cure the UV ink. This results in a state in which the adhesive strength of the fully cured UV ink to the foil is stronger than the strength with which the web 52 holds the foil. By separating the sheet and the web 52 in this state, the foil held by the web 52 can be transferred to the UV ink-coated portion of the sheet.

[0025] The stacker 18 accumulates the sheets discharged from the foil stamping device 16 .

[0026] The control device 20 is, for example, an information processing terminal such as a PC. The control device 20 accepts input regarding the definition of a print job. The control device 20 may display a predetermined job management screen and accept input regarding the job definition via the job management screen. The job definition includes, for example, the number of sheets to be printed (number of copies to be printed), the sheet size of the sheets to be printed, UV ink ejection data, and whether or not foil stamping is performed. The control device 20 controls the paper feed device 12, the coating device 14, and the foil stamping device 16 based on the job definition.

[0027] The above is the basic configuration of the sheet decoration system 10.

[0028] Alternatively, the sheet decoration system 10 may include a printer, instead of the sheet feeder 12, that prints the base image and registration marks on the sheets, and the sheets may be fed one by one from the printer.

[0029] The sheet decoration system 10 may also include, between the foil stamping device 16 and the stacker 18, a post-processing device for cutting and binding the sheets, a second UV ink application device for protecting the foil surface, a paper inserting machine for surface protection, a punching machine for punching the sheets into a predetermined shape to create carton materials, etc., and a post-processing machine for surface protection of the paper inserts, etc.

[0030] A method for producing a decorative sheet using the sheet decoration system 10 will now be described.

[0031] Fig. 3 is a cross-sectional view of a decorative sheet 102 in which a decoration is applied to a sheet (substrate) 100. Fig. 4 is a process diagram showing a production process 200 for producing the decorative sheet 102. The production process 200 for the decorative sheet 102 includes a color layer forming process 210 for forming the color layer 110, a base layer forming process 220 for forming the base layer 120, and a decoration layer forming process 230 for forming the decoration layer 130. The decorative sheet 102 is produced by passing the sheet 100 through the sheet decoration system 10 three times. Specifically, the color layer 110 is formed in the first pass, the base layer 120 is formed in the second pass, and the decoration layer 130 is formed in the third pass.

[0032] In the color layer forming step 210, the color layer 110 is formed. The color of the upper surface of the color layer 110 becomes the base color of the decoration. In the example of Figure 3, the color layer 110 is formed on the sheet 100, but another layer may be provided between the sheet 100 and the color layer 110.

[0033] In the example of FIG. 3 , the color layer 110 includes an adhesive layer 112 and a foil layer (typically a metal foil layer) 114 adhered (transferred) to the adhesive layer 112. The color layer forming process 210 includes an adhesive layer forming process 212 for forming the adhesive layer 112 and a foil stamping process 214 for transferring foil to the adhesive layer 112 to form the foil layer 114. In the adhesive layer forming process 212, UV ink is ejected onto the sheet 100 from the UV ink ejection unit 46 of the coating device 14, and the ejected UV ink is semi-cured by the semi-curing ultraviolet lamp 48 to form a UV ink layer serving as the adhesive layer 112. In the foil stamping process 214, foil is transferred onto the UV ink layer serving as the adhesive layer 112 by the foil stamping device 16. Note that the adhesive layer 112 is not limited to a UV ink layer. If the adhesive layer 112 is not a UV ink layer, the adhesive layer 112 may be formed in an apparatus separate from the coating device 14.

[0034] The color layer 110 is not limited to the example in Fig. 3 and may be, for example, a colored ink layer. In this case, the color layer forming step 210 may include a coating step of coating (printing) colored ink onto the sheet 100, instead of the adhesive layer forming step 212 and the foil stamping step 214. The coating step may be performed by a device separate from the coating device 14, or the coating device 14 may further include a coating unit that coats (prints) the colored ink.

[0035] Alternatively, the fabrication process 200 may not include the color layer formation process 210. That is, the color layer 110 may not be formed. In this case, the color of the sheet becomes the base color of the decoration. Alternatively, if the base layer 120 is colored (i.e., opaque), the color of the base layer 120 becomes the base color of the decoration.

[0036] In the base layer forming step 220, the base layer 120 is formed. In this embodiment, the base layer 120 is a UV ink layer. Since a decorative layer will be formed on the surface of the base layer 120, it is desirable that the surface of the base layer 120 be as flat as possible with as few irregularities as possible.

[0037] When the color layer 110 is present, the base layer 120 may be applied to the entire upper surface of the color layer 110, or may be applied to only a portion of the upper surface of the color layer 110. Furthermore, in addition to the entire or a portion of the upper surface of the color layer 110, the base layer 120 may also be formed on a portion where the color layer 110 is not formed (for example, the surface of the sheet 100).

[0038] If the color layer 110 is not present, a base layer 120 is formed on the surface of the sheet 100 .

[0039] The base layer forming step 220 includes a base application step 222 in which a light-transmitting UV ink is applied, and a base curing step 224 in which the UV ink is cured.

[0040] In the base coating process 222, UV ink is ejected onto the sheet 100 from the UV ink ejection unit 46 of the coating device 14. In the base coating process 222, UV ink is ejected onto locations on the sheet (particularly the color layer 110) corresponding to pixels where ejection is "required" in accordance with UV ink ejection data for the base layer, which specifies whether or not UV ink should be ejected for each pixel. In the base curing process 224, the UV ink ejected onto the sheet 100 is fully cured by the full-curing ultraviolet lamp 50. Note that the UV ink may be semi-cured by the semi-curing ultraviolet lamp 48 and then fully cured by the full-curing ultraviolet lamp 50.

[0041] In the decorative layer forming process 230, a decorative layer 130 having a textured pattern is formed using a translucent UV ink. The textured pattern includes at least one of a line pattern and a dot pattern. The lines constituting the line pattern are sufficiently thin compared to the size of the base layer. The lines constituting the line pattern may be straight or curved. The textured pattern may include multiple line patterns that differ from each other in at least one of the line length, direction, thickness, and whether the line is straight or curved. Furthermore, the dots constituting the dot pattern are sufficiently small compared to the size of the base layer. The textured pattern may include multiple dot patterns that differ from each other in at least one of the dot shape, size, and density.

[0042] The decorative layer forming process 230 includes a UV ink ejection process 232 in which light-transmitting UV ink is ejected, and a UV ink curing process 234 in which the UV ink is cured.

[0043] In the UV ink ejection process 232, UV ink is ejected from the UV ink ejection unit 46 of the coating device 14 onto the base layer 120. In particular, in the UV ink ejection process 232, UV ink is applied to locations on the base layer 120 corresponding to pixels for which ejection is "required" in accordance with the UV ink ejection data for the decorative layer, which specifies whether or not UV ink ejection is required for each pixel. Therefore, UV ink is ejected in a shape corresponding to the area for which ejection is "required" in the UV ink ejection data for the decorative layer.

[0044] In the UV ink curing process 234, the UV ink ejected onto the underlayer 120 is fully cured by the full-curing ultraviolet lamp 50. Note that the UV ink may be semi-cured by the semi-curing ultraviolet lamp 48 and then fully cured by the full-curing ultraviolet lamp 50.

[0045] Next, the decorative UV ink ejection data and the uneven pattern of the decorative layer 103 will be described in detail. Fig. 5 is a diagram illustrating the UV ink ejection data for the decorative layer. Fig. 5 can also be considered as a top view of the decorative sheet 102. The two-dot chain line indicates the area where the base layer 120 is applied.

[0046] In FIG. 5, the hatched areas are pixel groups that "require" application, i.e., areas where UV ink is to be applied (hereinafter referred to as "discharge areas"). A plurality of linear discharge areas 240 form a line pattern PTN1. The width W of the linear discharge areas 240 that form the line pattern PTN1 may be 5 μm or more and 200 μm or less. The interval D between the linear discharge areas 240 may be 600 μm or less. Note that in FIG. 5, the linear discharge areas 242 that form the line pattern PTN1 are exaggerated and drawn thick. A plurality of dot-like discharge areas 242 form a halftone dot pattern PTN2. The width (or diameter) W of the linear discharge areas 242 that form the halftone dot pattern PTN2 may be 5 μm or more and 200 μm or less. The interval D2 between the dot-like discharge areas 242 may be 600 μm or less.

[0047] The decorative application data may include information regarding the application amount (discharge amount) of pixels that require application. The decorative application data may indicate whether application is required based on the application amount, i.e., whether the application amount is zero or not. If the decorative application data includes a linear area that requires application, the amount of UV ink applied may vary along the length of the linear area that requires application.

[0048] Next, the UV ink discharged in the UV ink discharge step 232 and the material of the underlayer 120 will be described.

[0049] In the UV ink ejection process 232, if the UV ink in a liquid state (i.e. before it is semi-cured or fully cured) ejected from the UV ink ejection unit 46 has too good a wetting property with the base layer 120, the UV ink will flow, causing the lines of a parallel line pattern to connect together or the dots of a mesh pattern to connect together, making it impossible to express fine details, and if the wetting property with the base layer 120 is too poor, the UV ink will be repelled and will not adhere to the base layer 120. Therefore, the wetting property between the UV ink and the base layer 120 needs to be appropriate.

[0050] FIG. 6 is a diagram illustrating a method for determining wettability. One known method for determining wettability is to observe the shape of a droplet of liquid 302 that has landed on the surface 300a of a solid 300. If the liquid 302 spreads across the surface 300a of the solid 300, it is determined that the wetting is good; if it curls up, it is determined that the wetting is poor. Wetting is quantitatively determined by the contact angle θ. The contact angle θ is the angle between the free surface 302a of the liquid 302 and the surface 300a of the solid 300 at the point where the free surface 302a of the liquid 302 contacts the surface 300a of the solid 300, and can take values ​​between 0° and 180°. The smaller the contact angle θ, the better the wetting is determined, and the larger the contact angle θ, the worse the wetting is determined.

[0051] If UV ink is applied over cured UV ink, it tends to become more repelled (wet poorly). Therefore, it is not recommended, at least with UV ink, to repaint areas that have not been coated due to nozzle problems, etc. This invention focuses on utilizing this tendency for decoration and has discovered the appropriate conditions through experiments.

[0052] According to experiments conducted by the present inventors, when the temperature of the UV ink ejected from the UV ink ejection unit 46 is between 30° and 40° C. and the sheet 100 and therefore the base layer 120 are at room temperature (e.g., 25° C.), if the contact angle θ between the UV ink and the base layer 120 is between 15° and 45° C. a predetermined time after the ejected UV ink lands on the base layer 120, the UV ink is not repelled by the base layer 120 and does not wet or spread that much, making it possible to express a fine uneven pattern. In other words, it was confirmed that the wettability is appropriate. Furthermore, it was confirmed that when the contact angle θ is between 20° and 40° C., a finer uneven pattern can be expressed, i.e., the wettability is more appropriate, and when the contact angle θ is between 23° and 35° C., an even finer uneven pattern can be expressed, i.e., the wettability is even more appropriate.

[0053] The predetermined time may be the time from when the UV ink lands to when it reaches the irradiation range of the final curing ultraviolet lamp 50, or, in the case of semi-curing followed by final curing, the time may be the time from when the UV ink lands to when it reaches the irradiation range of the semi-curing ultraviolet lamp 48. The predetermined time may be, for example, 3 seconds or less.

[0054] When the base layer 120 is a UV ink layer, i.e., a layer of cured UV ink, it has been confirmed that the contact angle θ between the base layer 120 and the liquid UV ink ejected from the UV ink ejection section 46 in the UV ink ejection process 232 is greater than or equal to 15° and less than or equal to 45°.

[0055] In this case, the UV ink for the base layer 120 and the UV ink for the decoration layer 130 may be the same UV ink. If they are the same UV ink, there is no need to clean the UV ink discharge unit 46 or the path for supplying the UV ink to the UV ink discharge unit 46 between the base layer forming process 220 and the decoration layer forming process 230.

[0056] Alternatively, the UV ink for the base layer 120 and the UV ink for the decorative layer 130 may be different UV inks. In the case of different UV inks, the UV ink cartridge may be replaced between the base layer forming process 220 and the decorative layer forming process 230, or the coating device 14 may be capable of holding multiple types of ink cartridges. In these cases, the UV ink discharge unit 46 and the path for supplying UV ink to the UV ink discharge unit 46 are cleaned between the base layer forming process 220 and the decorative layer forming process 230. As a variant, the base layer forming process 220 and the decorative layer forming process 230 may each be performed using separate coating devices 14 each equipped with a different UV ink cartridge. Cleaning of the UV ink discharge unit 46 and the path to it is not necessary.

[0057] Here, the contact angle θ is determined by the surface tension of the solid 300, the surface tension of the liquid 302, and the interfacial tension between the solid 300 and the liquid 302 at the location where the free surface 302a of the liquid 302 contacts the surface 300a of the solid 300, and the relationship between them is expressed by the following equation (1). Equation (1) is called Young's equation. gamma S =γ L ×cosθ+γ SL ···(1) where: gamma S : Surface tension of a solid gamma L : Surface tension of the liquid gamma SL :Interfacial tension between solid and liquid is.

[0058] Equation (1) can be rewritten as the following equation (2). cosθ=(γ S -γ SL ) / γ L ···(2)

[0059] From equation (2), the surface tension of the liquid (γ L ) and / or reduce the surface tension (γ S ) increases, cosθ increases, that is, the contact angle θ decreases, in other words, the wetting improves.

[0060] Furthermore, from equation (2), the surface tension of the liquid (γ L ) and / or increase the surface tension (γ S ) is reduced, cosθ is reduced, i.e., the contact angle θ is increased, in other words, the wetting becomes poor.

[0061] In other words, the liquid contact angle θ can be adjusted by adjusting the surface tension of the liquid. In the case of this embodiment, by adjusting the surface tension of the UV ink discharged in the UV ink discharge step 232, the contact angle θ between the discharged UV ink liquid and the underlayer 120, and therefore the wettability, can be adjusted.

[0062] The surface tension of the liquid UV ink can be adjusted, for example, by the content of the monomer. The higher the content of the monomer with low surface tension, the lower the surface tension of the UV ink (liquid). The monomer can be, for example, a monofunctional acrylate or a difunctional acrylate.

[0063] The surface tension of the liquid UV ink can be adjusted by the amount of surface tension modifier added. The more surface tension modifier added, the lower the surface tension of the UV ink. Examples of surface tension modifiers include organic solvents such as alcohols and glycol ethers, ionic surfactants, nonionic surfactants, and modified silicone oils.

[0064] The surface tension of the UV ink in its liquid state is preferably 19 to 33 mN / m, and more preferably 19 to 25 mN / m. By having a surface tension of 33 mN / m or less, and preferably 25 mN / m or less, the UV ink is not repelled and is placed on the underlayer 120. Furthermore, by having a surface tension of 19 mN / m or more, the UV ink does not flow too much.

[0065] According to this embodiment, UV ink is ejected by the UV ink ejection unit 46, i.e., the inkjet head, and an elastic printing plate as in flexographic printing is not required, which reduces costs, and also makes it easy to change the pattern since it is only necessary to change the UV ink ejection data, and the device can be made relatively small and the printing resolution can be made relatively high.

[0066] Furthermore, according to this embodiment, the uneven pattern of the translucent decorative layer 130 includes a fine line pattern and a halftone dot pattern, and the glossiness of the decorative layer 130 changes subtly depending on the angle from which it is observed, giving it a sense of luxury and elegance.

[0067] Furthermore, according to this embodiment, the base layer 120 is a UV ink layer, and in this case, the contact angle θ between the UV ink ejected onto the base layer 120 in the decorative layer forming process 230 and the base layer 120 is greater than or equal to 15° and less than or equal to 45°.In other words, the ejected UV ink has an appropriate degree of wetting with the base layer 120, so that the ejected UV ink can be used to create a detailed uneven pattern.

[0068] The present invention has been described above based on an embodiment. This embodiment is merely an example, and it will be understood by those skilled in the art that various modifications are possible in the combination of each component and each treatment process, and that such modifications are also within the scope of the present invention. These modifications will be described below.

[0069] In the embodiment, the case where the base layer 120 is a UV ink layer has been described, but the base layer 120 is not limited to a UV ink layer and may be any solid layer having a contact angle θ with liquid UV ink of 15° or more and 45° or less. The base layer 120 may include, for example, an adhesive layer (e.g., a UV ink layer) and a foil layer (e.g., a metal foil layer) adhered to the adhesive layer. In other words, the surface of the base layer 120 may be formed by the surface of the foil layer. In this case, the base layer 120 also serves as a color layer. This modification can achieve the same effects as the embodiment.

[0070] Any combination of the above-described embodiments and modifications is also useful as an embodiment of the present invention. A new embodiment resulting from a combination will have the combined effects of the combined embodiments and modifications. It will also be understood by those skilled in the art that the functions to be performed by each component recited in the claims can be realized by each component shown in the embodiments and modifications, either alone or in combination. [Explanation of symbols]

[0071] 10 Sheet decoration system, 100 Sheet, 120 Base layer, 130 Decorative layer, 220 Base layer formation process, 230 Decorative layer formation process, PTN1 Line pattern, PTN2 Halftone dot pattern, θ Contact angle.

Claims

1. a base layer forming step of ejecting a liquid UV ink having translucency onto a sheet and curing it to form a base layer on the surface of the sheet, the base layer being formed by a UV ink layer; a decorative layer forming step of ejecting a translucent liquid UV ink onto the surface of the base layer and curing the ink to form a decorative layer having a relief pattern including at least one of a line pattern and a halftone dot pattern; Equipped with the base layer forming step is performed by passing the sheet through a sheet decoration device that includes an application device that applies UV ink to the sheet that is transported in one direction; The decorative layer forming step is performed by passing the sheet through a sheet decoration device that includes an application device that applies UV ink to the sheet being transported in one direction. Sheet decoration methods.

2. a color layer forming step, which forms a color layer whose upper surface color becomes a base color of the decoration, before the base layer forming step; In the base layer forming step, the base layer is formed on at least a part of the upper surface of the color layer. The sheet decoration method according to claim 1.

3. The color layer includes a UV ink layer and a foil layer adhered to the UV ink layer, The color layer forming step is performed by passing the sheet through a sheet decoration device that includes an applicator that applies UV ink to the sheet transported in one direction and a foil stamping device that transfers foil to the UV ink layer applied by the applicator. The sheet decoration method according to claim 2.

4. The color layer forming process, the base layer forming process, and the decorative layer forming process are each performed by passing the sheet through the same sheet decorating device once each. The sheet decoration method according to claim 3.

5. 5. The sheet decoration method according to claim 1, wherein a contact angle between the underlayer and the liquid UV ink discharged in the decoration layer forming step is 15[deg.] or more and 45[deg.] or less.

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