JP7854326B2 - Manufacturing method of composite panels - Google Patents

Description

This invention relates to a method for manufacturing a composite board in which a printed pattern is applied to a metal plate that serves as a base material.

As a conventional technique, for example, Patent Document 1 discloses a method for manufacturing composite boards as described below. In this manufacturing method, first, an ink layer made of a first resin cured by ultraviolet light is formed so that a portion of the surface of the wood-based board is exposed. Next, a visible light-transmitting surface protection layer, mainly composed of a second resin different from the first resin, is hot-pressed to cover the surface of the wood-based board on which the ink layer has been formed.

Japanese Patent Publication No. 2017-075495

However, when using the composite panel manufacturing method described in Patent Document 1, and using a metal plate as the base material for the composite panel, a base layer may be formed to enhance the clarity of the printed pattern when applying a printed design to the metal plate. When a resin sheet is used as this base layer, the heat generated when applying the laminate film causes the resin sheet to expand (stretch) and then contract. If the laminate film is applied while the base layer is expanded (stretched), the laminate film constrains the base layer. Therefore, when the base layer attempts to contract, bending stress may be generated in the metal plate. As a result, the composite panel is more prone to warping, and even slight warping can impair the aesthetic appearance of the laminate film's surface.

This invention has been made in view of the above points, and its objective is to provide a method for manufacturing a composite panel that can reduce warping of the composite panel even when a printing base layer is formed on the surface of a metal plate, a printing pattern is applied to this base layer, and then a laminate film is attached.

In view of the above problems, the present invention provides a method for manufacturing a composite panel in which a printed pattern is applied to a metal plate that serves as a base material, comprising: a base layer formation step of uniformly depositing base ink particles made of an ultraviolet-curable resin onto the surface of the metal plate, and then curing the base ink particles by irradiating them with ultraviolet light to form a base layer for printing on the surface of the metal plate; a printing step of applying a predetermined printed pattern by attaching printing ink particles made of an ultraviolet-curable resin to the base layer, and then curing the printing ink particles by irradiating them with ultraviolet light; and a lamination step of applying a laminate film made of a thermoplastic resin to the base layer with the printed pattern, while applying heat and pressure to the base layer with the printed pattern at a temperature lower than the softening point of the thermoplastic resin, so as to cover the surface with the printed pattern, thereby laminating the surface of the metal plate.

According to the present invention, in the lamination process, a laminate film is heat-pressed onto the printed base layer at a temperature lower than the softening point of the thermoplastic resin. This allows lamination to be performed on the metal plate surface while maintaining the surface condition (texture, smoothness, etc.) of the laminate film and increasing its flexibility. As a result, air trapped between the base layer (or printed layer) and the laminate film during lamination can be suppressed, thereby reducing silvering on the surface of the composite board.

Furthermore, in this invention, during the base layer formation process, the base ink particles are cured by irradiation with ultraviolet light, thereby forming a printing base layer on the surface of the metal plate. As a result, this base layer is more porous than a base layer made of a resin sheet and acts like a buffer. Consequently, the base layer is less likely to expand (stretch) due to the heat generated when the laminate film is applied, and even if the buffer-acting base layer tries to contract slightly, bending stress is less likely to occur in the metal plate. This results in suppressing warping of the composite panel.

In metal sheets obtained through machining processes such as punching and pressing, if residual stress exists in the machined areas, heating the metal sheet during the lamination process can release this residual stress, causing slight deformation of the metal sheet. Therefore, in such cases, even if the back surface of the metal sheet is left unheated and the laminating film is applied using heat and pressure, the underlying layer is porous and has low thermal conductivity, making it difficult for the metal sheet to heat up. Consequently, bending stress is less likely to occur in the metal sheet due to the heat generated during lamination.

However, if the effect of such residual stress is negligible, a more preferable embodiment is to perform the lamination process while heating the back surface of the metal plate to a heating temperature corresponding to the thermal pressure temperature of the laminating film.

In this embodiment, since the base layer is made of a resin material, its coefficient of thermal expansion is greater than that of the metal material of the metal plate. Therefore, during lamination, the base layer is prone to expansion due to heat. However, in this embodiment, the metal plate is also heated by heating from the back during lamination, causing it to expand slightly, thus allowing it to follow the expansion of the base layer. This reduces the difference in thermal expansion between the base layer and the metal plate, thereby suppressing the bending stress acting on the metal plate.

Here, the resin of the base ink particles and the resin of the printing ink particles may be different types of resins, but in a more preferred embodiment, the resin of the base ink particles and the resin of the printing ink particles are made of the same type of resin.

Since both the resin of the base ink particles and the resin of the printing ink particles are made of the same type of resin, the printing layer, made of the resin of the printing ink particles, follows the expansion and contraction of the base layer, made of the resin of the base ink particles, due to the heat generated during lamination. Therefore, even during lamination, the applied print pattern is less likely to change, and the print pattern from the printing process can be maintained.

In a more preferred embodiment, the printing process involves applying a printed pattern in which multiple raised ridges are formed in one direction using the printing ink particles, and the laminating process involves applying the laminate film while applying heat and pressure to the laminate film along the direction in which the raised ridges with the printed pattern extend, from one end of the substrate layer to the other end of the substrate layer.

According to this embodiment, adhesive is pressed between the protrusions, and the laminate film can be heat-pressed from one end of the substrate to the other, while air is released along the protrusions. Therefore, the laminate film can be attached to the substrate while suppressing air trapped within it, covering the printed pattern.

In a more preferred embodiment, in the printing process, a printed layer consisting of the printed pattern is formed, and in the laminating process, the thickness of the adhesive layer formed on the laminate film is greater than the thickness of the printed layer.

According to this embodiment, by making the thickness of the adhesive layer before lamination greater than the thickness of the printed layer, the printed layer can be embedded in the adhesive layer, thereby suppressing the trapping of air between the laminate film and the printed layer. Furthermore, even if the temperature of the laminate film decreases after heat pressing, the adhesive layer is uniformly formed on the laminate film, so it can absorb the shrinkage of the laminate film caused by the adhesive layer.

According to the present invention, even when a printing underlayment is formed on the surface of a metal plate, a printing pattern is applied to this underlayment, and then a laminate film is attached, the warping of the composite panel can be reduced.

(a) is a schematic perspective view of a composite panel manufactured by the manufacturing method according to an embodiment of the present invention, (b) is a perspective view seen from the back side, and (c) is a cross-sectional view of the main part of the composite panel in (a). This is a flowchart illustrating the manufacturing method of the composite panel according to this embodiment. Figure 2 shows a diagram illustrating the main components of the sublayer formation process; (a) is a perspective view thereof, and (b) is a cross-sectional view of the metal plate after the sublayer formation process. Figure 2 shows the main parts illustrating the printing process; (a) is a perspective view thereof, and (b) is a cross-sectional view of the metal plate after the printing layer formation process. Figure 2 shows a perspective view illustrating the lamination process, where (a) is a schematic perspective view of the metal plate during lamination, and (b) is a perspective view of the main part of (a). (a) is a cross-sectional view illustrating the state before the lamination process, and (b) is a cross-sectional view illustrating the state after the lamination process.

Below, an embodiment of a composite panel manufactured by the manufacturing method according to this embodiment will be described in detail with reference to the drawings. Figure 1(a) is a schematic perspective view of a composite panel manufactured by the manufacturing method according to an embodiment of the present invention, Figure 1(b) is a perspective view from the back side, and Figure 1(c) is a cross-sectional view of the main part of the composite panel in Figure 1(a). Note that in Figure 1(c), etc., for convenience, the thickness 26 of the laminate film is depicted as thinner than the thickness of the adhesive layer 25, but the laminate film is actually thicker.

1. About the Composite Panel 10 As shown in Figures 1(a) to (c), the composite panel 10 has a printed pattern 24A applied to it and is equipped with a metal plate 21 that serves as the base material of the composite panel 10. The metal plate 21 is made of, for example, a stainless steel plate, a plated steel plate such as zinc or tin, or an aluminum plate, as will be described later. One surface of the metal plate 21 has a decorative layer 28 formed on it, which consists of a base layer 22, a printed layer 24, an adhesive layer 25, and a laminate film 26, while the other surface is exposed.

The base layer 22 is a layer formed on the surface of the metal plate 21 by uniformly depositing base ink particles 22d made of UV-curable resin, and then curing the base ink particles 22d by irradiation with ultraviolet light. The printed layer 24 is formed to uniformly cover the surface of the metal plate 21 with the base ink particles 22d.

The surface of the base layer 22 is given a printed pattern 24A by a resin cured by ultraviolet light. Specifically, the printed pattern 24A is formed by a printed layer 24 made of the ultraviolet-curable resin described above. As shown in Figure 1(c), the printed layer 24 may be formed by depositing printing ink particles 24a so that a part of the surface of the base layer 22 is exposed, or it may cover the entire base layer 22. As in this embodiment, a wood-grain-like printed pattern 24A is given, and multiple raised ridges 24b, described later, may be formed along one direction (along the wood grain pattern) by the printing ink particles 24a (see, for example, Figure 5(b)).

A laminate film 26 is attached to the base layer 22 on which the printed layer 24 is formed, via an adhesive layer 25 made of an adhesive. Specifically, when the printed layer 24 covers a portion of the base layer 22, the laminate film 26 is attached to the surface of both the printed layer 24 and the base layer 22 via the adhesive layer 25. On the other hand, when the printed layer 24 covers the entire base layer 22, the laminate film 26 is attached to the surface of the printed layer 24 via the adhesive layer 25. The laminate film 26 is made of a thermoplastic resin, and both the laminate film 26 and the adhesive layer 25 are made of a resin material that allows visible light to pass through.

In this embodiment, it is preferable that the laminate film 26 is rigid relative to the base layer 22 and the printed layer 24. Here, "rigid" refers to a hard surface (Shore hardness or Vickers hardness). More preferably, the Young's modulus (longitudinal elastic modulus) of the thermoplastic resin constituting the laminate film 26 is greater than the Young's modulus (longitudinal elastic modulus) of the thermoplastic resin constituting the base layer 22 and the printed layer 24. This prevents dents or scratches on the surface of the composite panel 10, and allows the flexible base layer 22 and printed layer 24 to act as cushioning material against impacts acting from the surface of the composite panel 10. Furthermore, as will be described later, if an adhesive layer 25 of a predetermined thickness is formed between the laminate film 26 and the printed layer 24, the cushioning effect can be enhanced.

2. Method for Manufacturing the Composite Panel 10 The method for manufacturing the composite panel 10, as described in Figure 1 and the like, will be explained below with reference to Figures 2 to 6. Figure 2 is a flowchart illustrating the method for manufacturing the composite panel according to this embodiment. Figure 3 is a diagram of the main parts illustrating the base layer formation process shown in Figure 2, where (a) is a perspective view thereof and (b) is a cross-sectional view of the composite panel after the base layer formation process.

2-1. Preparation Step S1 First, in this embodiment, a metal plate 21 is prepared as shown in Figure 3(a). The thickness of the metal plate 21 is not particularly limited as long as it acts as a base material for the composite plate 10, but it is preferably 0.15 mm to 3.0 mm, and more preferably 0.5 mm to 2.0 mm. Here, the metal plate 21 can be a stainless steel plate, a tin-plated steel plate, a galvanized steel plate, an aluminum plate, etc. This is effective in the following manufacturing method.

2-2. Underlayer Formation Process S2 The underlayer formation process S2 is performed on the metal plate 21 prepared in preparation process S1. Specifically, as shown in Figures 3(a) and 3(b), underlayer ink particles 22d made of ultraviolet-curable resin are uniformly deposited on the surface of the metal plate 21, and then the underlayer ink particles 22d are cured by irradiation with ultraviolet light, thereby forming a printing underlayer 22 on the surface of the metal plate 21.

The base layer 22 is printed using an inkjet printer. In this embodiment, the inkjet printer ink contains at least a UV-curable resin, which is a reactive oligomer or reactive monomer to which a photopolymerization initiator has been added, and a colorant. For example, an ink containing a white colorant separately in the UV-curable resin is prepared, and this ink is used to print the plain base layer 22. However, similar to the printing of the printed pattern 24A described later, the base layer 22 may be printed using multiple inks.

As shown in Figure 4(a), the inkjet printer 40 comprises a head 41 and an irradiation device 42, and further includes a transport device (not shown) for transporting the metal plate 21 in the transport direction L. However, if the head 41 and irradiation device 42 scan the entire surface of the metal plate 21 while printing the underlay layer 22 and the printing layer 24 (described later), the transport device may be omitted.

In this embodiment, the print head 41 contains ink used in general printing and sprays the ink (underlay ink particles 22d) so that the underlay layer 22 becomes blank. The irradiation device 42 irradiates ultraviolet light to harden the resin particles attached to the underlay layer 22. The print head 41 and the irradiation device 42 reciprocate in a direction S perpendicular to the transport direction L.

This allows for the printing of a predetermined pattern 24A onto the base layer 22 of the conveyed metal plate 21, and the curing of the ultraviolet-curable resin that forms the pattern 24A. In this embodiment, the head 41 and the irradiation device 42 are provided separately, but they may be configured as an integrated unit, for example.

Here, the UV-curable resin (composition) of the base ink particles 22d contains UV-curable monomers/oligomers (acrylate, epoxy acrylate, urethane acrylate, polyester acrylate), a photopolymerization initiator, a photosensitizer, additives, etc., and further contains a dye or pigment as a colorant. The UV-curable monomer/oligomer may be either radical polymerization type or cationic polymerization type. The thickness of the base layer 22 is not particularly limited, but is preferably thinner than the thickness of the metal plate 21, for example, about 0.01 to 0.1 mm.

2-3. Printing Process S3 Next, the printing process S3 will be explained with reference to Figure 4. Figure 4 is a diagram illustrating the main parts of the printing process shown in Figure 2, where Figure 4(a) is a perspective view thereof, and Figure 4(b) is a cross-sectional view of the metal plate after the printing layer formation process.

In printing step S3, printing ink particles 24a made of UV-curable resin are attached to the base layer 22, and then the printing ink particles 24a are cured by irradiation with UV light to impart a predetermined printing pattern. Since the printing pattern 24A is applied to the base layer 22, a more stable pattern can be applied compared to applying a printing pattern to the metal plate 21. In this embodiment, in printing step S3, a printing pattern 24A is applied in which multiple raised ridges 24b are formed in one direction by the printing ink particles 24a. In this embodiment, a printing layer 24 consisting of the printing pattern 24A may be formed by inkjet printing so that it is exposed from the surface of the base layer 22.

In this embodiment, a wood grain patterned printing layer 24 is formed as the printed pattern 24A. When forming such a wood grain patterned printing layer 24, streaky protrusions are formed on the surface including the printing layer 24 along the pattern of the wood's pores, thereby obtaining the texture of a wood grain pattern. In this way, multiple streaky protrusions, or ridges 24b, are formed on the portion including the printing layer 24 along the wood grain pattern (the direction in which the pores extend). Such printing can be carried out as described in the printing of the base layer 22.

Specifically, the wood grain pattern of the printed layer 24 can be obtained by photographing the surface of wood, such as straight-grained wood, as an image, and then printing a pattern (wood surface pattern) corresponding to the photographed image. The printing of the wood grain pattern is performed using an inkjet printer, similar to the printing of the base layer 22. In this embodiment, the inkjet printer ink contains at least a UV-curable resin, which is a reactive oligomer or reactive monomer to which a photopolymerization initiator has been added, and a colorant. For example, four types of inks are prepared, each containing a separate yellow, magenta, cyan, and black colorant in the UV-curable resin. These inks are then used to form the printed layer 24 on the surface of the base layer 22, thereby printing the wood grain pattern.

As shown in Figure 4(a), in this embodiment, the inkjet printer 40 uses the same equipment as the base layer 22. In this embodiment, the head 41 contains inks used for general printing and individually sprays each ink (printing ink particles 24a) according to the wood grain pattern to be printed based on the image described above. The irradiation device 42 irradiates ultraviolet light to harden the resin particles attached to the base layer 22. The head 41 and the irradiation device 42 reciprocate in a direction S perpendicular to the transport direction L.

This allows for the printing of a wood grain pattern 24A onto the base layer 22 of the conveyed metal plate 21, and the curing of the UV-curable resin that forms the pattern 24A. Here, the resin of the base ink particles 22d and the resin of the printing ink particles 24a are made of the same type of resin. For example, if the resin before curing contains acrylate and the resin after curing becomes acrylic resin, then the resin of the base ink particles 22d and the resin of the printing ink particles 24a are acrylate.

Since both the resin of the base ink particles 22d and the resin of the printing ink particles 24a are made of the same type of resin, not only is the adhesion between the base layer 22 and the printing layer 24 enhanced, but the printing layer 24, made of the resin of the printing ink particles 24a, follows the expansion and contraction of the base layer 22, made of the resin of the base ink particles 22d, due to the heat generated during the lamination process described later. Therefore, even during lamination, the applied printing pattern 24A is less likely to change, and the printing pattern 24A from the printing process can be maintained.

2-4. Lamination Process S4 Next, the lamination process S4 will be explained with reference to Figures 5 and 6. Figure 5 is a perspective view illustrating the lamination process S4 shown in Figure 2, Figure 5(a) is a schematic perspective view of the metal plate during lamination, and Figure 5(b) is a perspective view of the main part of Figure 5(a). Figure 6(a) is a cross-sectional view illustrating the state before the lamination process, and Figure 6(b) is a cross-sectional view illustrating the state after the lamination process.

In lamination process S4, a laminate film 26 is attached to the base layer 22, which has the printed pattern 24A, via an adhesive layer 25 formed with an adhesive agent, so as to cover the surface to which the printed pattern 24A is applied, thereby laminating the surface of the metal plate 21.

The laminate film 26 is a film made of thermoplastic resin and is a film that allows visible light to pass through. During lamination, the laminate film 26 is attached to the base layer 22, which has the printed pattern 24A, by applying heat and pressure at a temperature lower than the softening point of the thermoplastic resin. For example, if the thermoplastic resin of the laminate film 26 is polyvinyl chloride, the temperature during heat and pressure is approximately 40°C, which is lower than the softening point of polyvinyl chloride, which is approximately 65°C to 85°C.

In this way, during the lamination process S4, the laminate film 26 is heat-pressed onto the base layer 22 to which the printed pattern 24A has been applied at a temperature lower than the softening point of the second thermoplastic resin. This allows the lamination process to be performed on the surface of the metal plate 21 while maintaining the surface condition (texture, smoothness, etc.) formed on the laminate film 26 and increasing its flexibility. As a result, air trapped between the base layer 22 (or printed layer 24) and the laminate film 26 during lamination can be suppressed, thereby reducing silvering on the surface of the composite board 10.

In the base layer formation process S2, the base ink particles 22d are cured by irradiation with ultraviolet light, forming a printing base layer 22 on the surface of the metal plate 21. Therefore, the base layer 22 is more porous than a base layer made of resin sheet and acts like a buffer. As a result, the heat generated when the laminate film 26 is applied makes it difficult for the base layer 22 to expand (stretch), and even if the base layer 22 acting as a buffer tries to contract slightly, bending stress is less likely to occur in the metal plate 21. This results in suppressing warping of the composite panel 10.

During the lamination process S4, the laminate film 26 is attached to the base layer 22, which has the printed pattern 24A, while applying heat and pressure to the base layer 22. At this time, the back surface 21a of the metal plate 21 is heated to a heating temperature corresponding to the heat and pressure temperature of the laminate film 26 while lamination is performed. Here, it is preferable that the heating temperature is the same as the heat and pressure temperature.

As a result, since the base layer 22 is made of resin material, its coefficient of thermal expansion is larger than that of the metal material of the metal plate 21. Therefore, during lamination, the base layer 22 is prone to expansion due to heat. However, in this embodiment, the metal plate 21 is also heated by heating from the back surface during lamination, causing it to expand slightly, thus allowing it to follow the expansion of the base layer 22. This reduces the difference in thermal expansion between the base layer 22 and the metal plate 21, thereby suppressing the bending stress acting on the metal plate 21.

Furthermore, in this embodiment, during the lamination process S4, the base layer 22 is rolled while being pressed by a hot-press roller (heated roller) 30, from one end 22a to the other end 22b of the base layer 22, along the direction in which the raised ridges 24b with the printed pattern 24A extend. In this way, the laminate film 26 is attached while being heat-pressed by the hot-press roller 30.

In this embodiment, the laminate film 26 can be heat-pressed from one end 22a of the base layer 22 toward the other end 22b of the base layer 22, while releasing air A along the convex ridge 24b in the direction of the arrow in Figure 5(b). As a result, the laminate film 26 can be attached to the base layer 22 while suppressing air trapped within it.

Examples of adhesives that can constitute the adhesive layer 25 include acrylic resin-based adhesives, synthetic rubber-based adhesives, natural rubber-based adhesives, vinyl ether-based adhesives, silicone-based adhesives, and urethane-based adhesives.

Here, the thickness of the laminate film 26 is not particularly limited, but is, for example, in the range of 30 to 350 μm (for example, a thickness of 100 μm), and it is preferable that the thickness of the adhesive layer 25 is greater than the thickness of the printed layer 24. For example, the thickness of the printed layer 24 is preferably 10 to 30 μm, and the thickness of the adhesive layer 25 is preferably 35 μm or more, and more preferably 100 μm or less. Furthermore, if the entire base layer 22 is covered by the printed layer 24, it is preferable that the thickness of the adhesive layer 25 is greater than the difference (height difference) between the lowest position of the printed layer 24 and the highest position of the printed layer 24 in the thickness direction of the metal plate 21.

In this embodiment, as shown in Figures 6(a) and 6(b), by making the thickness T2 of the adhesive layer 25 before lamination thicker than the thickness T1 of the printed layer 24, the printed layer 24 can be embedded in the adhesive layer 25 after lamination. This suppresses the trapping of air between the laminate film 26 and the printed layer 24.

In addition, even if the temperature of the laminate film 26 decreases after heat pressing, the adhesive layer 25 is uniformly formed on the laminate film 26 without being divided by the raised ridges 24b of the printed layer 24. Therefore, the shrinkage of the laminate film 26 due to the adhesive layer 25 can be absorbed.

Although one embodiment of the present invention has been described in detail above, the present invention is not limited to the above-described embodiment, and various design modifications can be made without departing from the spirit of the invention as described in the claims. The present invention allows for adding the configuration of one embodiment to the configuration of another embodiment, replacing the configuration of one embodiment with that of another embodiment, or deleting a part of the configuration of one embodiment.

10: Composite panel, 21: Metal plate, 22: Underlayment layer, 22d: Underlayment ink particles, 24: Printed layer, 24A: Printed pattern, 24a: Printing ink particles, 24b: Raised stripes, 25: Adhesive layer, 26: Laminating film

Claims (4)

A method for manufacturing a composite board in which a printed pattern is applied to a metal plate that serves as a base material,
A base layer formation step is performed in which base ink particles made of an ultraviolet-curable resin are uniformly deposited on the surface of the metal plate, and then the base ink particles are cured by irradiation with ultraviolet light to form a base layer for printing on the surface of the metal plate.
A printing process in which printing ink particles made of UV-curable resin are attached to the aforementioned base layer, and then the printing ink particles are cured by irradiation with UV light to impart a predetermined printing pattern,
The process includes a lamination step in which a laminate film made of thermoplastic resin is attached to the base layer on which the printed pattern is applied, via an adhesive layer formed of an adhesive, so as to cover the surface on which the printed pattern is applied, at a temperature lower than the softening point of the thermoplastic resin, while applying heat and pressure to the base layer on which the printed pattern is applied, thereby laminating the surface of the metal plate .
In the printing process described above, the printing ink particles are used to create the printed pattern in which a plurality of raised stripes are formed in one direction.
A method for manufacturing a composite panel, characterized in that, in the lamination process, the laminate film is attached to the base layer from one end to the other end of the base layer while applying heat pressure to the laminate film along the direction in which the raised ridges on which the printed pattern is applied extend. The method for manufacturing a composite panel according to claim 1, characterized in that, during the lamination process, the back surface of the metal plate is heated to a heating temperature corresponding to the thermal pressure temperature of the laminating film while the lamination process is performed. The method for manufacturing a composite board according to claim 1 or 2, characterized in that the resin of the undercoat ink particles and the resin of the printing ink particles are made of the same type of resin. In the printing process described above, a printed layer consisting of the printed pattern is formed.
A method for manufacturing a composite board according to any one of claims 1 to 3 , characterized in that, in the lamination process, the thickness of the adhesive layer formed on the laminate film is greater than the thickness of the printed layer.