JP7676858B2 - Manufacturing method of decorative sheet - Google Patents

Description

This disclosure relates to a method for producing decorative sheets with high design quality.

In decorative sheets used to impart designs to the surfaces of building materials, fittings, flooring materials, etc., transparent thermoplastic resin layers are widely used as the substrates because the transparent thermoplastic resin layers have excellent abrasion resistance and scratch resistance.
In recent years, there has been a demand for higher design in such decorative sheets. For example, in the case of wood designs, designs closer to natural wood are being demanded. In response to such demands, a combination of an embossed pattern and a picture layer has been used (Patent Document 1), or a picture layer (i.e., a front picture layer and a back picture layer) has been provided on each of the front and back sides of a transparent thermoplastic resin layer.

However, when providing a front pattern layer and a back pattern layer on each side of a transparent thermoplastic resin layer, it is difficult to synchronize the relative positions of the front pattern layer and the back pattern layer in a plan view. Therefore, it has been difficult to manufacture a decorative sheet with high designability in which the relative positions of the front pattern layer and the back pattern layer in a plan view are synchronized. The reasons why it is difficult to synchronize the relative positions of the front pattern layer and the back pattern layer in a plan view are, for example, as follows.
The dimensions of the back design layer also expand and contract vertically and horizontally (i.e., two-dimensionally) due to expansion and contraction caused by the release of residual stress in both layers due to heat applied to both layers when laminating a transparent thermoplastic resin layer to the front side of the colored thermoplastic resin layer on which the back design layer is formed, and expansion and contraction caused by tension applied during transport of both layers. Therefore, even if the printing plate for the back design layer and the printing plate for the front design layer are made with high precision so that the positions of the back design layer and the front design layer are synchronized in plan view (i.e., the front and back are registered), it is difficult to synchronize the positions of the back design layer and the front design layer.

The decorative sheet according to Patent Document 1 has a transparent embossed resin layer with a pitch-like embossed pattern on the front surface of a transparent synthetic resin base sheet, and an inkjet-printed pattern layer on the back surface, with the inkjet-printed pattern layer on the back surface being in sync with the embossed pattern on the front surface.

JP 2020-055211 A

Patent Document 1 synchronizes the inkjet-printed pattern layer on the back side with the embossed pattern on the front side, but does not synchronize the front and back printed pattern layers with each other. The synchronization method involves measuring the pitch of the embossed pattern that has been formed and matching the pitch of the inkjet-printed pattern layer to that pitch. With this method, it is thought that synchronization can be achieved with high precision near the beginning of the pitch of the inkjet-printed pattern layer, which is a repeating pattern, but that the synchronization becomes deviated as the end of the pitch is approached.

In view of the above, the object of the present disclosure is to provide a method for manufacturing a decorative sheet having a front pattern layer on the front side of a transparent thermoplastic resin layer and a back pattern layer on the back side, in which the printed pattern layers on the front and back can be precisely aligned with each other over the entire surface of the repeating pattern.

The manufacturing method for a decorative sheet of the present disclosure is a manufacturing method for a decorative sheet comprising at least three layers, namely, a back pattern layer, a band-shaped transparent thermoplastic resin layer, and a front pattern layer, laminated in this order, and includes the following steps (i) to (iii) in this order.
Step (i): First, one side of the transparent thermoplastic resin layer is selected as the back side. Then, when the direction corresponding to the long side direction of the rectangular strip shape of the transparent thermoplastic resin layer is the longitudinal direction and the short side direction perpendicular to the longitudinal direction is the short side direction, the back side pattern layer is laminated on the back side of the transparent thermoplastic resin layer in a periodic arrangement in the longitudinal direction of the transparent thermoplastic resin layer.
Step (ii): Next, for the backside picture layer, the dimension P ^R _MD of one period of the picture in the longitudinal direction of the transparent thermoplastic resin layer and the dimension P ^R _TD in the lateral direction are measured.
Step (iii): Next, a surface pattern layer is printed on the surface opposite to the back surface of the transparent thermoplastic resin layer by using an inkjet printing method, and the dimension P ^F _MD of one pattern period of the surface pattern layer in the longitudinal direction and the dimension P ^F _TD in the transverse direction are
^PFMD ₌ ^PRMD _{, and} ^PFTD ₌ ^PRTD
With this relationship in mind, the patterns on the back surface pattern layer and the front surface pattern layer are printed in register with each other.

In the method for producing the decorative sheet, the decorative sheet further includes a colored thermoplastic resin layer, and the method for producing the decorative sheet is formed by laminating at least four layers in this order: a colored thermoplastic resin layer, a back design layer, a transparent thermoplastic resin layer, and a front design layer,
Step (i) may also be a method for producing a decorative sheet in which a back pattern layer is laminated on one side of a colored thermoplastic resin layer, and then laminated so that the back surface of a transparent thermoplastic resin layer faces the back surface of the back pattern layer, thereby laminating the back pattern layer on the back surface of the transparent thermoplastic resin layer.

According to the present disclosure, it is possible to provide a method for manufacturing a decorative sheet that can precisely align the printed pattern layers on the front and back of a transparent thermoplastic resin layer over the entire surface of the repeated pattern, in a decorative sheet having a front pattern layer on the front side and a back pattern layer on the back side.

FIG. 1 is a cross-sectional view showing an outline of the layer structure of a first embodiment of a decorative sheet according to the present disclosure. FIG. 1A is a schematic plan view of a decorative sheet according to the present disclosure; FIG. 2 is a cross-sectional view showing an outline of the layer structure of a second embodiment of the decorative sheet of the present disclosure. FIG. 3 is a cross-sectional view showing an outline of the layer structure of a third embodiment of the decorative sheet of the present disclosure. FIG. 1 is a schematic cross-sectional view illustrating a manufacturing method of a decorative sheet according to a first embodiment of the present disclosure. A diagram explaining examples of the shape of the register marks FIG. 1 is a diagram for explaining an outline of the path of the printed material and the arrangement of each device in an inkjet printer according to the decorative sheet manufacturing method of the present disclosure. FIG. 11 is a schematic cross-sectional view illustrating a manufacturing method of a decorative sheet according to a second embodiment of the present disclosure. FIG. 11 is a schematic cross-sectional view illustrating a manufacturing method of a decorative sheet according to a third embodiment of the present disclosure.

[Decorative sheet]
A first embodiment of a decorative sheet according to the manufacturing method of a decorative sheet of the present disclosure will be described below with reference to Fig. 1. Note that each of the figures shown below is a schematic diagram, and the size, shape, decoration, etc. of each part are appropriately exaggerated or simplified to facilitate understanding. Also, configurations that are not directly related to the description are appropriately omitted. Note that in each of the figures below, the same parts are given the same reference numerals, and some detailed descriptions may be omitted.

In the following description, specific numerical values, shapes, materials, etc. are given, but these can be changed as appropriate.
In this specification, the words plate, sheet, film, etc. are used, but in general usage, they are used in the order of thickness, plate, sheet, and film, and this specification follows that order. However, since such distinction has no technical meaning, the essence of this disclosure and the interpretation of the claims will not change even if these words are appropriately replaced. In this disclosure, the word sheet is used in a broad sense that includes the forms of thickness that are usually called so-called plate, sheet, and film.
In addition, although the terms "front side" and "back side" are used in this specification, the distinction between the front side and the back side has no technical meaning, and when one side of the sheet is the front side, the other side is the back side. In this specification, the decorative sheet is described as the side that is normally observed when the decorative sheet is used as the front side, and the opposite side is the back side.

(First embodiment) First, a first embodiment of the decorative sheet according to the manufacturing method of the decorative sheet of the present disclosure will be described. FIG. 1 is a cross-sectional view showing an outline of the layer structure of the decorative sheet 1 according to the first embodiment. The decorative sheet 1 is laminated in the order of a colored thermoplastic resin layer 14, a back pattern layer 13, a transparent thermoplastic resin layer 11, and a front pattern layer 12 from the bottom in FIG. 1. Since the observation surface of the decorative sheet 1 is usually the front pattern layer 12 side, in this specification, the front pattern layer 12 side is the front side, and the colored thermoplastic resin layer 14 side is the back side. Note that, as long as the back pattern layer 13 can be seen from the front side and the above-mentioned layering order is not disturbed, other layers other than those described above may be included. For example, a primer layer may be present between the transparent thermoplastic resin layer 11 and the front pattern layer 12. In this case, the adhesion between the transparent thermoplastic resin layer 11 and the front pattern layer 12 can be increased.

Figure 2(a) shows a schematic plan view of the decorative sheet 1. As shown in Figure 2(a), the decorative sheet 1 is strip-shaped (long) during production. In this specification, the direction corresponding to the long side of the strip-shaped rectangle (illustrated as the shaded portion) is referred to as the longitudinal direction LD, and the direction of the short side perpendicular to the longitudinal direction is referred to as the transverse direction SD. The transverse direction SD is sometimes referred to as the width direction. During production, the decorative sheet 1 is transported in the longitudinal direction LD.

Each of the components of the decorative sheet 1 will now be described.
<Transparent thermoplastic resin layer>
The transparent thermoplastic resin layer 11 has transparency to visible light, and the term "transparent" as used herein includes both colorless transparency and colored transparency.
The material of the transparent thermoplastic resin layer 11 is not particularly limited as long as it has transparency, and examples thereof include thermoplastic ester resins such as polyolefin thermoplastic resins, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyethylene naphthalate-isophthalate copolymers, polycarbonate, and polyarylate, acrylic thermoplastic resins such as polymethyl methacrylate, polyethyl methacrylate, polyethyl acrylate, and polybutyl acrylate, polyamide thermoplastic resins such as nylon-6 and nylon-66, and non-halogen thermoplastic resins such as polyimide, polyurethane, polystyrene, and acrylonitrile-butadiene-styrene resins, etc., because they have excellent processability and do not generate harmful gases when burned. In addition, these thermoplastic resins may be used alone or in combination of two or more types, but polyolefin resin sheets are preferably used in consideration of the suitability for providing a front pattern layer 12 and a back pattern layer 13 as a design, the fact that harmful gases are not generated when burned, which has become a problem recently, and the cost, etc.

Polyolefin resins are not limited, and examples thereof include polyethylene (low density, high density), polypropylene, polybutene, polymethylpentene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-propylene-butene copolymer, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, polyolefin thermoplastic elastomer, etc. Among these, polypropylene, ethylene-propylene-butene copolymer, polyolefin thermoplastic elastomer, etc. are particularly preferred.

Homopolypropylene or copolymers mainly composed of polypropylene are also preferred, such as homopolypropylene resin, random polypropylene resin, block polypropylene resin, and α-olefins other than propylene having 2 to 20 carbon atoms and having polypropylene crystal parts. In addition, propylene-α-olefin copolymers containing 15 mol% or more of ethylene, butene-1, 4-methylpentene-1, hexene-1, or octene-1 comonomers are also preferred.

Representative examples of the polyolefin-based thermoplastic elastomer include: 1) those whose main raw material is either high density polyethylene or polypropylene as a hard segment, to which an elastomer as a soft segment and an inorganic filler are added; 2) those made of a mixture of isotactic polypropylene as a hard segment and atactic polypropylene as a soft segment, as described in JP-B-6-23278; and 3) those made of ethylene-propylene-butene copolymers, as described in JP-A-9-111055, JP-A-5-77371, JP-A-7-316358, etc.
There is no particular limitation on the thickness of the transparent thermoplastic resin layer 11. When used as a decorative material for building materials, the thickness is usually 20 μm or more and 500 μm or less.

<Colored thermoplastic resin layer>
The material of the colored thermoplastic resin layer 14 is not particularly limited as long as it is colored. For example,

Examples of the film include colored thermoplastic resin films made of olefin resins such as polyethylene and polypropylene, polyester resins such as polyethylene terephthalate, acrylic resins such as polymethyl methacrylate, polycarbonate, fluororesins, and the like.
Here, the polyester resin film is a film melt-extruded from a so-called extrusion die, and is usually a film oriented in two axial directions, namely, the longitudinal direction and the transverse direction, and is a polymer obtained by condensation polymerization of dicarboxylic acid and glycol. Examples of the dicarboxylic acid include terephthalic acid, isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, and sebacic acid, and examples of the glycol include ethylene glycol, trimethylene glycol, tetramethylene glycol, and cyclohexanedimethanol. Specific examples include polyethylene terephthalate, polytetramethylene terephthalate, polyethylene-p-oxybenzoate, poly-1,4-cyclohexylene dimethylene terephthalate, and polyethylene-2,6-naphthalenedicarboxylate. In the case of the present disclosure, polyethylene terephthalate is particularly preferred.

The thermoplastic resin film relating to the colored thermoplastic resin layer 14 is a colored film by blending a pigment and/or a dye, and the pigment can be classified into inorganic pigments and organic pigments. Examples of the inorganic pigments include titanium oxide white, zinc oxide, white lead, carbon black, red oxide, vermilion, yellow lead, ultramarine, cobalt blue, cobalt purple, zinc chromate, etc. Examples of the organic pigments include phthalocyanine-based, dioxazine-based, and anthraquinone-based pigments, and representative examples thereof include quinacridone, watch ang red, and dioxazine violet. The dyes can be classified into natural dyes and synthetic dyes, and representative examples of the natural dyes include indigo (indigo blue), etc. Examples of the synthetic dyes include azo dyes, indigoid dyes, sulfide dyes, nitro dyes, and nitroso dyes. These pigments and dyes can be used alone or in combination of two or more kinds, and inorganic pigments are optimal for providing excellent light resistance and hiding properties to the base sheet.
There is no particular limitation on the thickness of the colored thermoplastic resin layer 14. In general, the thickness is 20 to 100 μm, and preferably 30 to 50 μm, from the viewpoints of excellent smoothness, strength, heat resistance, and particularly excellent heat-resistant dimensional stability.

<Back pattern layer>
The backside picture layer 13 is formed on the backside of the transparent thermoplastic resin layer 11 in the decorative sheet 1. In the decorative sheet 1 according to the first embodiment, the backside picture layer 13 is formed on the frontside of the colored thermoplastic resin layer 14, and is laminated so that the frontside of the backside picture layer 13 (the side opposite to the side on which the colored thermoplastic resin layer 14 is present) faces the backside of the transparent thermoplastic resin layer 11, thereby forming the backside picture layer 13 on the backside of the transparent thermoplastic resin layer 11.

In the decorative sheet 1 of the present disclosure, when forming the rear design layer 13, it is necessary to form the register marks 20 at the same time as the design. The details of the register marks 20 will be described later.
The registration marks 20 are necessary when manufacturing the decorative sheet 1, but are unnecessary when used as the decorative sheet 1 and impair the pattern, so they are usually provided outside the pattern. FIG. 2(b) shows a partially enlarged plan view of the decorative sheet 1, and is an enlarged view of the portion surrounded by a dashed line in FIG. 2(a). In the decorative sheet 1 of the present disclosure, the registration marks 20 are provided in the portions near both ends in the width direction of the decorative sheet 1 where no pattern exists, as shown in FIG. 2(b). In the width direction of the decorative sheet 1, the width direction region where the pattern exists is called the pattern region IR, and the width direction regions on both sides where no pattern exists are called the non-pattern regions NIR. The pattern region IR and the non-pattern region NIR are the width direction regions shown in FIG. 2(b). The registration marks 20 are provided in each of the non-pattern regions NIR near both ends. By providing the registration marks 20 near both ends in the width direction, rather than only on one side, stretch correction is also possible in the width direction (described later). In many cases, the non-picture areas NIR of the decorative sheet 1 are removed by the time the decorative sheet 1 is used by an end user. Even if the non-picture areas NIR have been removed from the decorative sheet, the decorative sheet is still within the scope of the present disclosure as long as it is manufactured using the manufacturing method for decorative sheets according to the present disclosure.

The pattern of the back pattern layer 13 is not particularly limited, but examples include wood grain patterns, stone patterns, cloth patterns, leather patterns, geometric patterns, letters, symbols, line drawings, various abstract patterns, solid monochrome patterns, and solid monochrome gradations. Given the effect of the present disclosure of precisely aligning the front pattern layer 12 and the back pattern layer 13 over the entire surface of the repeating pattern, it is considered that the patterns of the back pattern layer 13 in this disclosure are more appropriate to be other than the above-mentioned exemplified patterns, rather than the above-mentioned solid monochrome patterns and solid monochrome gradations, which are less likely to cause problems with misregistration between the front and back.

The method for forming the backside pattern layer 13 can be selected from various printing methods, such as plate-based printing methods such as gravure printing, offset printing, flexographic printing, and silk screen printing, or plateless printing methods such as inkjet printing and various transfer printing methods. In terms of the manufacturing method of the decorative sheet disclosed herein, a method in which a cylindrical plate is rotated in the circumferential direction to repeatedly print a pattern, that is, the gravure printing, offset printing, flexographic printing, or the like, among the above, is preferred.

The ink used to form (usually print) the backside pattern layer 13 can be obtained by dissolving (or dispersing) a known colorant (dye or pigment) together with a resin, i.e., a binder resin, in a solvent (or dispersion medium). Examples of colorants include inorganic pigments, organic pigments, metal powder pigments, pearlescent pigments, fluorescent pigments, and luminous pigments. For example, inorganic pigments include carbon black, black iron oxide, titanium white, zinc oxide, red iron oxide, iron blue, yellow lead, and cadmium red. Examples of organic pigments include azomethine azo black pigments, perylene black pigments, chromatic azo pigments of various hues, lake pigments, anthraquinone pigments, quinacridone pigments, phthalocyanine pigments, isoindolinone pigments, nickel-azo complexes, and dioxazine pigments. Examples of metal powder pigments include scaly foil flakes such as aluminum powder and bronze powder. Examples of pearlescent pigments include scaly foil flakes such as titanium oxide-coated mica and bismuth oxide chloride. These colorants may be used alone or in combination with two or more other types, or may be used together with fillers such as silica, extender pigments such as organic beads, neutralizers, surfactants, etc.

Resins (binder resins) used in the backside pattern layer 13 include various polyester resins, vinyl chloride resins such as vinyl chloride-vinyl acetate copolymers and vinyl chloride-vinyl acetate-maleic acid copolymers, acrylic resins such as polymethyl (meth)acrylate, polybutyl (meth)acrylate, methyl (meth)acrylate-butyl (meth)acrylate copolymers, styrene-methyl (meth)acrylate copolymers, and styrene-methyl (meth)acrylate-2-hydroxyethyl (meth)acrylate copolymers, two-component curing urethane resins with a polyol compound as the main agent and an isocyanate compound as the curing agent, and chlorinated polypropylene. The above resins may be used alone or in combination of two or more. It is preferable to add a crosslinking agent, a polymerization initiator, or a polymerization accelerator to the above resins to improve the coating strength and durability. Among the above resins, acrylic resins or mixtures of acrylic resins and vinyl chloride-vinyl acetate copolymers are preferable. This is because it is possible to suppress the bleeding of the plasticizer. In the case of a mixture of an acrylic resin and a vinyl chloride-vinyl acetate copolymer, the mass ratio of the mixture, [mass of acrylic resin]/[mass of vinyl chloride-vinyl acetate copolymer], is preferably in the range of 2/8 to 8/2 from the viewpoints of printability and adhesion of the back design layer 13 to the colored thermoplastic resin layer 14, as well as durability such as weather resistance and scratch resistance.
The thickness of the rear design layer 13 is usually from 0.1 μm to 50 μm, and preferably from 1 μm to 25 μm.

<Surface pattern layer>
The front pattern layer 12 is formed on the front side of the transparent thermoplastic resin layer 11 in the decorative sheet 1. The decorative sheet 1 of the present disclosure is characterized in that the front pattern layer 12 and the back pattern layer 13 are repeatedly and precisely aligned over the entire surface of the pattern.

The pattern of the surface pattern layer 12 is not particularly limited, but examples include wood grain patterns, stone grain patterns, fabric patterns, leather patterns, geometric patterns, letters, symbols, line drawings, various abstract patterns, solid monochrome patterns, monochrome gradations, etc.
Considering the effect of the present disclosure of accurately positionally aligning the front picture layer 12 and the back picture layer 13 over the entire surface of the repeating picture, it is preferable that the picture is preferably positionally aligning with the back picture layer 13. For example, by adding another picture that is positionally aligning with the picture of the back picture layer 13 as the front picture layer 12, the overall picture of the decorative sheet 1 can be made more sophisticated. As an example, when the picture of the back picture layer 13 is a wood grain pattern, if the front picture layer 12 is not present, the transparent thermoplastic resin layer 11 will result in an unnaturally glossy and cheap-looking appearance, but if the front picture layer 12 is formed with a gloss matte pattern that is positionally aligning with the wood grain pattern of the back picture layer 13, the decorative sheet 1 can be made to have a highly sophisticated design.

In this disclosure, the method for forming the surface pattern layer 12 is limited to the inkjet printing method. This is because the feature of this disclosure is the method for forming the surface pattern layer 12 by the inkjet printing method, as described below.

The above-mentioned gloss matte pattern is a picture design that visually expresses unevenness without creating physical unevenness on the surface. Gloss matte printing, which forms the gloss matte pattern, is a technique that utilizes the visual illusion of creating a pattern of glossy and matte parts by printing, which makes the glossy parts appear to protrude and the matte parts appear to be recessed, regardless of the physical unevenness.

Methods for forming a glossy matte pattern include printing the parts that are to be seen as protruding with a known glossy ink and printing the parts that are to be seen as recessed with a known matte ink, printing the parts that are to be seen as recessed on a glossy substrate with a matte ink, or printing the parts that are to be seen as protruding on a matte substrate with a glossy ink. For example, if the backside pattern layer 13 is a wood grain pattern, the transparent thermoplastic resin layer 11 is usually highly glossy, so a method for forming a front side pattern layer 12 with a glossy matte pattern is to print the duct groove parts with a matte ink.

If the film thickness of the matte ink is too thick, the physical thickness will cancel out the visual depression effect, so the thinner the better, and usually a thickness of around 100 μm or less is desirable. For glossy ink, the film thickness amplifies the visual protrusion effect, so a thicker film is not a problem.

The matte ink used can be a mixture of a binder selected from thermoplastic resins, thermosetting resins, ionizing radiation curable resins, radiation curable resins, etc., taking into consideration the intended use, required physical properties, printability, etc., and a suitable mixture of pigments, colorants such as dyes, extender pigments, solvents, stabilizers, plasticizers, catalysts, hardeners, etc.

Examples of resins constituting the binder include cellulose derivatives such as ethyl cellulose, cellulose nitrate, cellulose acetate, and ethylhydroxyethyl cellulose; styrene resins such as polystyrene and poly-α-methylstyrene; acrylic resins such as styrene copolymers, polymethyl (meth)acrylate, polyethyl (meth)acrylate, and polybutyl (meth)acrylate; vinyl polymers such as polyvinyl acetate, vinyl chloride-vinyl acetate copolymers, and polyvinyl butyral; rosin, rosin-modified maleic acid resins, rosin-modified phenolic resins, and rosin ester resins such as polymerized rosin; thermoplastic resins such as chroman resins and thermoplastic urethane resins; and thermosetting resins such as phenolic resins, urea resins, diallyl phthalate resins, melamine resins, guanamine resins, unsaturated polyester resins, polyurethane resins, epoxy resins, aminoalkyd resins, melamine-urea co-condensation resins, silicon resins, and polysiloxane resins.
Of these, it is preferable to use a thermoplastic urethane resin formed from a polyol and an isocyanate, or a one-component curing type or two-component curing type urethane resin.

Examples of the inorganic substances to be added include yellow lead, yellow iron oxide, cadmium yellow, titanium yellow, antimony yellow, red iron oxide, vermilion, cadmium red, chrome vermilion, iron blue, ultramarine, cobalt blue, carbon black, titanium dioxide, antimony trioxide, aluminum powder, copper powder, brass powder, titanium dioxide-coated mica, fish scale foil, and bismuth trichloride.
Examples of the matte pigment include calcium carbonate, barium carbonate, silica, alumina, glass balloons, polyethylene fine powder, and the like, each having a particle size of about 0.1 to 10 μm.

The coating amount of the surface pattern layer 12 is preferably 40 g/ ^m2 or less, more preferably 25 g/ ^m2 or less. In the decorative sheet of the present disclosure, the surface pattern layer 12 is often present not on the entire surface but only partially, so there is no particular lower limit. If it exceeds 25 g/ ^m2 , there is a concern that the non-flammable performance will be impaired due to the increase in organic content.

Second Embodiment
Next, a second embodiment of the decorative sheet according to the manufacturing method of the decorative sheet of the present disclosure will be described. Fig. 3 is a cross-sectional view showing an outline of the layer structure of the decorative sheet 101 according to the second embodiment. The decorative sheet 101 is laminated in the order of a colored thermoplastic resin layer 14, a back pattern layer 13, a transparent thermoplastic resin layer 11, a front pattern layer 12, and a surface protective coating layer 15 from the bottom in Fig. 3. That is, the surface protective coating layer 15 is laminated on the front side of the front pattern layer 12 of the decorative sheet 1 according to the first embodiment. The surface protective coating layer 15 is provided to adjust the surface gloss and improve the surface physical properties such as scratch resistance.
The decorative sheet 101 according to the second embodiment may also include layers other than those described above, so long as the backside pattern layer 13 can be seen from the front side and the above-mentioned stacking order is not disturbed. For example, a primer layer may be provided between the transparent thermoplastic resin layer 11 and the front side pattern layer 12. In this case, the adhesion between the transparent thermoplastic resin layer 11 and the front side pattern layer 12 can be improved.

<Surface protective coating layer>
The surface protective coating layer 15 may be formed by a known coating method (or printing method) using a coating liquid (or ink). For the resin of the surface protective coating layer 15, it is preferable to use a two-liquid curing type urethane resin or an ionizing radiation curing resin such as an acrylate type, in order to improve surface physical properties such as scratch resistance. Furthermore, when scratch resistance is to be imparted, alumina such as α-alumina or silica may be added as an antifriction agent. Note that colorants, inorganic fillers, or various known additives such as ultraviolet absorbers and light stabilizers may be added to the surface protective coating layer 15.
There is no particular limitation on the thickness of the surface protective coating layer 15. When used as a decorative material for building materials, the thickness is usually 1 μm or more and 50 μm or less.

Third Embodiment
Next, a third embodiment of the decorative sheet according to the manufacturing method of the decorative sheet of the present disclosure will be described. Fig. 4 is a cross-sectional view showing an outline of the layer structure in each form of the decorative sheet 201 according to the third embodiment. The decorative sheet 201 according to Fig. 4(a) is laminated in the order of the back design layer 13, the transparent thermoplastic resin layer 11, and the front design layer 12 from the bottom in Fig. 4(a). That is, this is a form in which the colored thermoplastic resin layer 14 is excluded from the configuration of the decorative sheet 1 according to the first embodiment.

In the decorative sheet 1 according to the first embodiment, the backside pattern layer 13 is formed on the colored thermoplastic resin layer 14 and then laminated to the transparent thermoplastic resin layer 11, thereby forming the backside pattern layer 13 on the backside of the transparent thermoplastic resin layer 11. In contrast, the backside pattern layer 13 in the decorative sheet 201 according to the third embodiment is different in that it is formed (printed) directly on the backside of the transparent thermoplastic resin layer 11. The backside pattern layer 13 in the decorative sheet 201 according to the third embodiment also has a registration mark 20 similar to that of the backside pattern layer 13 in the decorative sheet 1 according to the first embodiment.

The decorative sheet 201 according to the third embodiment may also include layers other than those described above, so long as the backside pattern layer 13 can be seen from the front side and the above-mentioned stacking order is not disturbed. For example, a primer layer may be provided between the transparent thermoplastic resin layer 11 and the front side pattern layer 12. In this case, the adhesion between the transparent thermoplastic resin layer 11 and the front side pattern layer 12 can be improved.
As shown in Fig. 4(b), a surface protective coating layer 15 may be laminated on the surface side of the surface pattern layer 12, as in the decorative sheet 101 according to the second embodiment. A back primer layer 16 may be laminated on the back side of the back pattern layer 13, or, as shown in Fig. 4(c), both the surface protective coating layer 15 and the back primer layer 16 may be provided. The back primer layer 16 is provided mainly to improve the adhesion between the surface of the material to be decorated and the decorative sheet 201.

<Rear primer layer>
To form the back primer layer 16, a resin composition is used in which a binder is appropriately mixed with a curing agent, weathering agents such as ultraviolet absorbers and light stabilizers, antiblocking agents, and other known additives. Examples of the binder include those exemplified as binders that can be used in the back design layer 13, namely, urethane resin, acrylic polyol resin, acrylic resin, ester resin, amide resin, butyral resin, styrene resin, urethane-acrylic copolymer, polycarbonate-based urethane-acrylic copolymer (urethane-acrylic copolymer derived from a polymer (polycarbonate polyol) having a carbonate bond in the polymer main chain and two or more hydroxyl groups at the end and side chain), vinyl chloride-vinyl acetate copolymer resin, vinyl chloride-vinyl acetate-acrylic copolymer resin, chlorinated propylene resin, nitrocellulose resin (nitrocellulose), cellulose acetate resin, and other resins, which can be used alone or in combination. For example, a mixture of a polycarbonate-based urethane-acrylic copolymer and an acrylic polyol resin can be used as the binder.

In addition to one-component curing types, various types of resins can be used, such as two-component curing types that include a curing agent such as an isocyanate compound, such as tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPID), or xylylene diisocyanate (XDI).

The thickness of the primer layer is preferably 1 μm or more, more preferably 2 μm or more, and even more preferably 3 μm or more, from the viewpoint of improving interlayer adhesion and mitigating thermal shrinkage of each layer. The upper limit is preferably 10 μm or less, more preferably 8 μm or less, and even more preferably 6 μm or less.

[Method of manufacturing decorative sheet]
(Manufacturing method of the first embodiment)
Hereinafter, a manufacturing method of the decorative sheet 1 according to the first embodiment will be described with reference to the schematic cross-sectional view of Fig. 5. The decorative sheet 1 and its constituent elements, the transparent thermoplastic resin layer 11 and the colored thermoplastic resin layer 14, are in a band shape, and as shown in Fig. 2, the direction corresponding to the long side direction of the rectangle of the band shape is the longitudinal direction LD, and the direction of the short side perpendicular to the longitudinal direction is the short side direction SD.

First, a colored thermoplastic resin layer 14 is prepared (FIG. 5(a)), and a back design layer 13 and a registration mark 20 (not shown) are laminated on one side (front surface) of the layer in a periodic arrangement in the longitudinal direction of the colored thermoplastic resin layer 14 (FIG. 5(b)). The method of laminating the back design layer 13 on the colored thermoplastic resin layer 14 is preferably a method of repeatedly printing a design by rotating a cylindrical plate in its circumferential direction, i.e., gravure printing, offset printing, flexographic printing, etc. This is because the back design layer 13 can be laminated (printed) in a periodic arrangement in the longitudinal direction LD of the band-shaped colored thermoplastic resin layer 14 easily, i.e., inexpensively and quickly. Among them, gravure printing is preferable because it has excellent printability for thermoplastic resins such as the colored thermoplastic resin layer 14.
<Registration mark>

In the decorative sheet 1 of the present disclosure, when forming the backside picture layer 13, it is necessary to form the registration marks 20 at the same time as the picture. The registration marks 20 in the present disclosure are not intended to align the colors in multi-color printing, but are provided for the purpose of aligning the positions of the front side picture layer 12 and the back side picture layer 13 by grasping the position of the back side picture layer 13 when printing the front side picture layer 12 later.
The registration marks 20 in the present disclosure are preferably formed simultaneously with the image in the non-image area NIR, which is an area different from the image area IR in the width direction, using a cylindrical plate in the gravure printing method, offset printing method, flexographic printing method, or the like. The registration marks 20 are provided in two locations, one near each end in the width direction of the cylindrical plate, and one on each side in the circumferential direction of the cylindrical plate. Therefore, the repeat pitch of the register marks 20 in the longitudinal direction LD matches the repeat pitch of the repeating image.

When the back design layer 13 is formed by multi-color printing, i.e., when it is formed by combining two or more ink colors, it is preferable that the registration mark 20 is formed in any one of the colors. When formed in one color, the registration mark 20 can be formed with high precision without being affected by misregistration between colors. In addition, the ink color forming the registration mark 20 in the process of forming the back design layer 13 is preferably an ink color that makes the outline of the registration mark 20 easy to see in the process of forming the front design layer 12, that is, an ink color that has a large difference in brightness with the colored thermoplastic resin layer 14. This is because the registration mark 20 is easy to recognize by a photoelectric sensor, an image sensor, etc. in the process of forming the front design layer 12.

There is no particular limitation on the shape of the registration mark 20, but it is preferable that the contours in the short direction SD and the long direction LD are clear. Figure 6 shows examples of the shape of the registration mark 20. Figure 6(a) is a cross shape, and Figure 6(b) is a rectangle. It is preferable that each line constituting the registration mark 20 has a certain thickness. This is because it is necessary to be accurately visually recognized by a photoelectric sensor, an image sensor, etc. In addition, since it is preferable to have a certain amount of contour information, the contour may be increased as in the form of Figure 6(c) or Figure 6(d). In order to prevent erroneous matching in template matching, it is preferable that there are no figures of the same or similar shape in the registration mark 20, and from that point of view, the form of Figure 6(e) or Figure 6(f) may be used. Figure 6(g) is an example of a registration mark 20 that is not suitable for pattern matching. In the example of Figure 6(g), the amount of information on the contour in the vertical direction (longitudinal direction LD) is too small, so it is considered that the accuracy of pattern matching in the horizontal direction (short direction SD) is poor. A registration mark 20 like that shown in FIG. 6(g) can be used when only the registration in the longitudinal direction LD is controlled by detecting the registration mark 20 with a photoelectric sensor.

In the manufacturing process, the front side of the back design layer 13 (the side opposite to the colored thermoplastic resin layer 14) and the back side of the transparent thermoplastic resin layer 11 are laminated so as to face each other (FIG. 5(c)). This lamination can be performed, for example, using a known transparent adhesive. Alternatively, the back design layer 13 and the transparent thermoplastic resin layer 11 may be laminated by extruding a hot-melted transparent resin from a T-die between the two layers to be laminated and cooling it to form a transparent resin layer as a binder between the two layers. In this case, it does not matter if the transparent resin layer as a binder and the transparent thermoplastic resin layer 11 are indistinguishable after cooling. In any of the above lamination methods, a material should be selected that allows the back design layer 13 to be visible from the front side of the transparent thermoplastic resin layer 11.

Next, the front pattern layer 12 is laminated on the front side of the transparent thermoplastic resin layer 11 using an inkjet printer (Figure 5(d)). In laminating the front pattern layer 12, the rear pattern layer 13 and the front pattern layer 12 are precisely aligned over the entire surface of the repeating pattern, i.e., the registration of the two is precisely aligned, which is a feature of this disclosure. The method is described below.

In the present disclosure, it is necessary to measure the amount of expansion and contraction of the back pattern layer 13 laminated on the transparent thermoplastic resin layer 11 before printing by the inkjet printer. The amount of expansion and contraction is preferably measured upstream of the inkjet printing unit in the conveying system of the printer that performs inkjet printing. If the measurement of the amount of expansion and contraction and the inkjet printing are performed in separate processes, there is a concern that the amount of expansion and contraction will differ due to the difference in tension applied to the transparent thermoplastic resin layer 11 when the amount of expansion and contraction is measured and when the inkjet printing is performed, or the amount of expansion and contraction will change during storage between the expansion and contraction measurement process and the inkjet printing process. In such a case, there is a high possibility that the effect of the manufacturing method disclosed herein, in which the amount of expansion and contraction is measured and the pattern data related to the front pattern layer 12 is corrected based on the amount of expansion and contraction, and inkjet printing is performed, will be reduced. On the other hand, when the amount of expansion and contraction is measured upstream of the inkjet printing unit in the conveying system of the printer that performs inkjet printing, it is considered that the change in tension from measurement to printing is small, and the change in the amount of expansion and contraction during that time is also very small.

A method for measuring the amount of expansion and contraction upstream of an inkjet printing unit in an inkjet printer will be described with reference to Fig. 7. Fig. 7 is a diagram showing an overview of the path of the printed material and the arrangement of each device in an inkjet printer, and parts that are not relevant to the description are largely omitted.
In the inkjet printer 40, the transparent thermoplastic resin layer 11 unwound from the unwinding section 41 passes through a nip roll 43, a photoelectric sensor 35, a camera 30, an inkjet printing unit 45, and the nip roll 43, and is wound up in a winding section 42. The inkjet printer 40 illustrated in Fig. 7 is a so-called roll-to-roll printer in which the unwinding is wound up onto a roll, and the surface design layer 12 is laminated (printed) on the transparent thermoplastic resin layer 11 in the inkjet printing unit 45. However, the present invention is not limited to this, and instead of the winding section 42, the surface design layer 12 may be cut after printing and laminated sheet by sheet.

As shown in FIG. 7, a camera (register mark detection means) 30 for capturing an image of the register mark 20 is installed upstream of the inkjet printing unit 45 in the inkjet printer, as far away as possible from the inkjet printing unit 45. In order to capture the image of the register mark 20 printed near both ends of the short side (width direction) of the transparent thermoplastic resin layer 11 being conveyed, the camera 30 is installed near both ends of the short side (width direction) of the inkjet printer. That is, two cameras are installed. Since the width of the decorative sheet 1 (transparent thermoplastic resin layer 11) differs depending on the type of decorative sheet 1, the camera 30 is installed so as to be movable in the short side (width direction). In addition, the field of view of the camera 30 is preferably the part where the conveyed transparent thermoplastic resin layer 11 contacts the roller in the conveying system of the inkjet printer. This is because the transparent thermoplastic resin layer 11 does not flutter in the part where the transparent thermoplastic resin layer 11 contacts the roller, making it possible to obtain a stable image.

The position of each of the two cameras 30 in the short direction (width direction) is adjusted so that the registration mark 20 is located near the center of the field of view of the camera 30 according to the width of the decorative sheet 1 (transparent thermoplastic resin layer 11) to be manufactured.
The inkjet printer is provided with a means 47 for detecting the transport amount of the decorative sheet 1 (transparent thermoplastic resin layer 11). One example of the transport amount detection means 47 is a rotary encoder 47 provided on a roller synchronized with the transport speed of the decorative sheet 1 (transparent thermoplastic resin layer 11), for example, a nip roll 43. If the rotary encoder 47 is provided on the nip roll 43, the transport amount per pulse is fixed regardless of the item of the decorative sheet 1, i.e., the printing pitch of the backside design layer 13, so the transport distance can be grasped by counting the number of pulses.

The timing of capturing the image is also adjusted so that the register mark 20 is located near the center of the field of view of the camera 30 in the conveying direction (longitudinal direction). For example, a photoelectric sensor 35 that detects the register mark 20 can be provided further upstream from the camera 30, and the image can be captured when a predetermined number of pulses of the rotary encoder are counted after the photoelectric sensor 35 detects the register mark 20. The predetermined number of pulses is a fixed value determined by the conveying length (path length) from the photoelectric sensor 35 to the camera 30, and is not dependent on the pitch of the repeating pattern, which differs depending on the item.

When the conveyance of the decorative sheet 1 (transparent thermoplastic resin layer 11) begins, the camera 30 captures the registration mark 20 at a predetermined timing to create a reference image. The expansion/contraction amount detection means registers a rectangular area including the registration mark 20 contained in the reference image as a template (reference image) for template matching, and also registers the position of the template in the reference image as a reference position. The expansion/contraction amount detection means is typically an image processing device that uses a template matching method. Template matching refers to searching for a position in the acquired image that is similar to the registered reference image (template).

The timing of the camera 30 imaging after the template registration in the reference image can be determined by counting the pulses from the rotary encoder 47. The pitch of the back pattern layer 13 (registration mark 20) is a design value determined for each item, and is also the plate cylinder circumference when the back pattern layer 13 and registration mark 20 are printed. The number of pulses corresponding to the repetition pitch of the pattern can be uniquely determined by this design value (plate cylinder circumference). When imaging is performed at the timing of a predetermined number of pulses, if the transparent thermoplastic resin layer 11 does not expand or contract at all after the back pattern layer 13 (registration mark 20) is printed until imaging by the camera 30, the position of the reference image (template) in the captured image should theoretically remain unchanged.

However, in reality, after the back pattern layer 13 (registration mark 20) is printed, the transparent thermoplastic resin layer 11 expands and contracts before it is imaged by the camera 30, and the amount of expansion and contraction differs between when the back pattern layer 13 (registration mark 20) is printed and when it is imaged by the camera 30, and for other reasons, the position of the reference image (template) in the captured image changes each time it is imaged.
The amount of displacement of the template position in the acquired image relative to the template position (reference position) in the reference image can be grasped by the result of template matching. In the image processing device, the amount of displacement (positional deviation) of the acquired image relative to the reference image is grasped in units of the number of pixels, but the actual dimension corresponding to one pixel is a fixed value due to the installation of the camera 30. Therefore, the amount of displacement (positional deviation) of the position of the reference image (template) in the acquired image can be easily grasped as an actual dimension. And the amount of displacement (positional deviation) of the position of the reference image (template) is the amount of expansion and contraction of the decorative sheet 1 (transparent thermoplastic resin layer 11) relative to the design value at the imaging position of the camera 30.

Here, for the transport direction (longitudinal direction LD), the amount of displacement (positional deviation) in the vertical direction (transport direction) of the position of the reference image (template) can be used as the amount of expansion/contraction in the transport direction (longitudinal direction LD). Since two cameras 30 are installed near both ends in the short direction SD, two values for the amount of expansion/contraction in the transport direction (longitudinal direction LD) are obtained, but since the two values are usually nearly the same, it is sufficient to use one of the values. Alternatively, the average value of the two may be used.

The amount of expansion and contraction in the width direction (short direction SD) is calculated and understood from the amount of displacement (amount of misalignment) by the two cameras 30. In other words, the difference between the amounts of displacement (amount of misalignment) in the width direction (short direction SD) by the two cameras 30 is the amount of expansion and contraction of the decorative sheet 1 (transparent thermoplastic resin layer 11) in the width direction (short direction SD) relative to the design value. For example, if the amounts of displacement (amount of misalignment) in the width direction (short direction) by the two cameras 30 are in the same direction and have the same dimensions, the amount of expansion and contraction in the width direction (short direction SD) of the decorative sheet 1 (transparent thermoplastic resin layer 11) is 0. Furthermore, if the displacement (positional deviation) in the width direction (short direction SD) by the camera 30 installed on the right side is Ya to the right, and the displacement (positional deviation) in the width direction (short direction SD) by the camera 30 installed on the left side is Yb to the right, then the amount of expansion and contraction in the width direction (short direction SD) of the decorative sheet 1 (transparent thermoplastic resin layer 11) is Ya-Yb, and if Ya-Yb is positive, it is an expansion, and if it is negative, it is a contraction.

As described above, the amount of expansion and contraction of one period of each pattern after the reference image is captured can be grasped. Here, the design values of the backside pattern layer 13 are defined as the dimension P ^S _MD of one period of the pattern in the longitudinal direction and the dimension P ^S _TD of the transverse direction, and the amount of expansion and contraction of one period of each pattern is defined as ΔP ^R _MD and ΔP ^R _TD . Then, the actual measured values of the backside pattern layer 13 at the position of the camera 30 of the inkjet printer are defined as the dimension P ^R _MD of one period of the pattern in the longitudinal direction and the dimension P ^R _TD of the transverse direction, and P ^R _MD and P ^R _TD can be expressed as follows.
P ^R _MD = P ^S _MD + ΔP ^R _MD
P ^R _TD = P ^S _TD + ΔP ^R _TD

As described above, the surface pattern layer 12 is printed by inkjet printing. Inkjet printing is a plateless printing method that does not use plates. The inkjet printer used in the decorative sheet manufacturing method according to the present disclosure, like a home inkjet printer, forms a pattern by controlling the ink ejection position and amount according to the pattern data using so-called driver software. In this way, inkjet printing does not use plates, but simply controls the ink ejection position and amount using software, so the pattern data can be easily updated even while the printing process is in progress.

In the present disclosure, the above-mentioned characteristics of inkjet printing are utilized to correct the image data of the front design layer 12 for expansion and contraction in accordance with actual measurement data including expansion and contraction of the back design layer 13 measured by an inkjet printer, thereby matching the image data of the front design layer 12 to the actual measurement data of the back design layer 13. In other words, assuming that the longitudinal dimension P ^F _MD of one pattern period of the image data of the front design layer 12 is the dimension P F MD in the lateral direction and the lateral dimension P ^F _TD is the relationship between the longitudinal dimension P ^R _MD of one pattern period of the actual measurement values of the back design layer 13 and the lateral dimension P ^R _TD is as follows:
^PFMD ₌ ^PRMD _{, and} ^PFTD ₌ ^PRTD
The image data of the front design layer 12 is stretched or corrected so that the design of the front design layer 12 is printed in register with the design of the back design layer 13.

Although it has been stated above _{that P FMD} ⁼ _{P RMD} ^and P ^FTD = ^P _RTD , since "= (equal)" does not have a width in the strict mathematical sense, it is not appropriate to interpret _" =" in the strict sense with respect to the dimensions related to _{actual manufacturing. The design values of the backside pattern layer 13, i.e., the dimension P SMD} ^of one pattern period in the longitudinal direction and _the dimension P ^STD in the lateral direction, are in units of 1 mm in the specifications.
Furthermore, the amount of expansion and contraction for one period of the pattern, i.e., the amount of expansion and contraction in the longitudinal direction, ΔP ^R _MD , and the amount of expansion and contraction in the lateral direction, ΔP ^R _TD , depend on the pixel resolution of the camera 30 involved in template matching. For example, if the field of view of the camera 30 is 5 cm and the number of pixels is 1000 x 1000, the pixel size in the field of view of the camera 30 is 50 μm. In this case, if the result of template matching is in pixels, the values of ΔP ^R _MD and ΔP ^R _TD will also be discrete values in units of 50 μm, and if the result of template matching is sub-pixel, they will be discrete values with dimensions smaller than 50 μm. As a result,
P ^R _MD = P ^S _MD + ΔP ^R _MD
P ^R _TD = P ^S _TD + ΔP ^R _TD
P ^R _MD and P ^R _TD calculated by the above are also discrete values in units of 50 μm or less.

Furthermore, since the image data related _to ^PFMD and ^PFTD are also digital data _, ^PFMD and _PFTD after expansion/contraction correction are also discrete values. The discrete values ^{of PRMD} _and ^PRTD do not strictly match the discrete values ^{of PFMD} and ^PFTD . As a _result , _it is almost impossible ^to _make ^PFMD _{= PRMD and} ^PFTD _{= PRTD} in the strict sense ^.
Therefore, the above expression " ^PFMD = ^PRMD and ^PFTD = ^PRTD " means "so that _PFMD is closest _to ^{PRMD and PFTD is} closest to _PRTD when quantizing from the calculated values." _In actual measurements of the decorative sheet 1 _that was actually _manufactured , even taking into consideration the accumulation of various process errors such as ^the _quantization error of each of the digital image data, the resolution of the rotary encoder, and the detection error of _{the photoelectric} sensor ^{, it is considered that the difference between PFMD and PRMD ,} _{and the difference} between ^PFTD and ^PRTD are each within 3 mm.

The photoelectric sensor 35 described above is used to register the front pattern layer 12 in the longitudinal direction. Since the path length from the photoelectric sensor 35 to the inkjet printing unit 45 is a fixed length regardless of the item, the timing of printing the front pattern layer 12 can be controlled by counting a fixed number of pulses of the rotary encoder 47 described above. As described above, if printing of the front pattern layer 12 is started at a predetermined timing using the photoelectric sensor 35 and the rotary encoder 47, the registration of the pattern of the front pattern layer 12 and the pattern of the back pattern layer 13 can be matched at least for the leading part of the pattern. Furthermore, in the present disclosure, the pattern data of the front pattern layer 12 is corrected for expansion and contraction according to the actual measurement data including the expansion and contraction of the back pattern layer 13. As a result, in the decorative sheet 1 according to the present disclosure, the front pattern layer 12 and the back pattern layer 13 can be in a state of being in sync (in register) not only at the leading part of the pattern but also over the entire front surface of one cycle of the pattern in the longitudinal direction up to the trailing end of the pattern.
The decorative sheet 1 according to the first embodiment can be obtained by the above-mentioned manufacturing method.

In the above explanation, the reference image and reference position acquired initially were used without being updated. However, this is not a limitation, and the reference image and reference position may be updated during the progress of inkjet printing. In this case, the acquired image for grasping the amount of displacement (amount of positional deviation) is updated as is as the reference image. When updating the reference image, the amount of displacement (amount of positional deviation) at the time of updating the reference image becomes the new reference, but each time the reference image is updated, the amount of displacement (amount of positional deviation) at that time can be added. The frequency with which the reference image can be updated is arbitrary. It does not have to be updated every time, or every few to several tens of times.

In the above description, the image data of the surface pattern layer 12 is corrected for expansion and contraction every time. However, this is not limited to the above, and it is considered that the accuracy of practical use is sufficient even if the image data of the surface pattern layer 12 is corrected once every several to several hundred times. This is because, from experience, it is almost impossible for the amount of expansion and contraction of the transparent thermoplastic resin layer 11 to suddenly fluctuate significantly, and if it does fluctuate, it is almost always the case that small expansion and contraction that occurs continuously accumulates and becomes an amount of expansion and contraction that requires expansion and contraction correction. When the image data of the surface pattern layer 12 is corrected for expansion and contraction every several to several hundred times, the calculation load of the expansion and contraction correction for the image data can be greatly reduced. This is particularly effective in cases where a sufficient path length cannot be secured from the camera 30 to the inkjet printing unit 45, making it difficult to perform expansion and contraction correction for the image data every time.

The method for producing the decorative sheet 1 according to the first embodiment described above can also be expressed as follows.
The method for producing a decorative sheet 1 is formed by laminating at least three layers, a back design layer 13, a band-shaped transparent thermoplastic resin layer 11, and a front design layer 12, in this order, and includes the following steps (i) to (iii) in this order.
Step (i): First, one surface of the transparent thermoplastic resin layer 11 is selected as the back surface. Then, when the direction corresponding to the long side direction of the strip-shaped rectangle of the transparent thermoplastic resin layer 11 is defined as the longitudinal direction LD and the short side direction perpendicular to the longitudinal direction is defined as the short side direction SD, the back surface pattern layer 13 is laminated (printed) on the back surface of the transparent thermoplastic resin layer 11 in a periodic arrangement in the longitudinal direction of the transparent thermoplastic resin layer 11.
Step (ii): Next, for the rear design layer 13, the dimension P ^R _MD of one period of the design in the longitudinal direction of the transparent thermoplastic resin layer 11 and the dimension P ^R _TD in the lateral direction are measured.
Step (iii): Next, the front surface of the transparent thermoplastic resin layer 11 is printed on the front surface by inkjet printing, so that the dimension P ^F _MD of one period of the pattern in the longitudinal direction of the front surface pattern layer 12 and the dimension P ^F _TD in the lateral direction of the front surface pattern layer 12 are set to
^PFMD ₌ ^PRMD _{, and} ^PFTD ₌ ^PRTD
With this relationship in mind, the patterns on the back design layer 13 and the front design layer 12 are printed in register with each other.

The manufacturing method of the decorative sheet 1 according to the first embodiment can be further limited as follows with respect to the above manufacturing method.
The above-mentioned step (i) can be limited as follows: A method for producing a decorative sheet 1 comprising at least four layers, namely, a colored thermoplastic resin layer 14, a back pattern layer 13, a transparent thermoplastic resin layer 11, and a front pattern layer 12, laminated in this order.
Step (i): After laminating a back surface pattern layer 13 on one side of the colored thermoplastic resin layer 14, the back surface of the transparent thermoplastic resin layer 11 and the back surface pattern layer 13 are laminated so as to face each other, thereby laminating the back surface pattern layer 13 on the back surface of the transparent thermoplastic resin layer 11.

As described above, in the manufacturing method of the decorative sheet disclosed herein, the decorative sheet 1 can be obtained in which the printed pattern layers on the front and back are precisely aligned over the entire surface of the repeated pattern. Therefore, for example, in the case where the pattern on the back pattern layer 13 is a wood grain pattern and the pattern on the front pattern layer 12 is a matte pattern that should be aligned with the wood grain pattern, the wood grain pattern on the back and the matte pattern on the front are precisely aligned, so that a more natural look closer to natural wood can be obtained, that is, a decorative sheet with high design quality can be obtained. In addition, since the inkjet printing method is used to print the front pattern layer 12, there is no need to create a plate for printing the front pattern layer 12, and even when the manufacturing item is changed (so-called changeover), there is no need to replace the plate, and no mechanism is required to change the path length from the photoelectric sensor 35 to the printing unit. In addition, the loss of initial registration at the start of production can be reduced.

(Manufacturing method of the second embodiment)
A method for producing the decorative sheet 101 according to the second embodiment will be described below with reference to the schematic cross-sectional view of Fig. 8. The decorative sheet 101 according to the second embodiment has a configuration in which a surface protective coating layer 15 is laminated on the surface side of the surface pattern layer 12 of the decorative sheet 1 according to the first embodiment as described above.
The steps up to laminating the surface pattern layer 12, i.e., obtaining the decorative sheet 1 according to the first embodiment, are the same as those in the manufacturing method of the decorative sheet 1 according to the first embodiment, and therefore will not be described.

After obtaining the decorative sheet 1 according to the first embodiment (FIG. 8(a)), a surface protective coating layer 15 is laminated on the surface side of the surface pattern layer 12 to obtain the decorative sheet 101 according to the second embodiment (FIG. 8(b)).
The surface protective coating layer 15 may be laminated on the surface side of the surface design layer 12 by a known coating method (or printing method). Coating may be performed using a coater, or a printing method such as gravure printing.

In addition to the above-mentioned effects of the decorative sheet 1 of the first embodiment, the decorative sheet 101 of the second embodiment has the following effects. For example, if the pattern of the back pattern layer 13 is a wood grain pattern and the pattern of the front pattern layer 12 is a matte pattern that is in sync with the wood grain pattern, the surface protective coating layer 15 can be made of a material with a higher gloss than the back pattern layer 13, resulting in a decorative sheet 101 with a more aesthetically pleasing design.

(Manufacturing method of the third embodiment)
A method for producing a decorative sheet 201 according to the third embodiment will be described below with reference to the schematic cross-sectional view of Fig. 9. The decorative sheet 201 according to the third embodiment has a configuration in which the colored thermoplastic resin layer 14 is excluded from the configuration of the decorative sheet 1 according to the first embodiment, as described above.

First, a transparent thermoplastic resin layer 11 is prepared (FIG. 9(a)), and a back design layer 13 and a registration mark 20 are laminated on one side (back side) of the transparent thermoplastic resin layer 11 in a periodic arrangement in the longitudinal direction of the transparent thermoplastic resin layer 11 (FIG. 9(b)). The method of laminating the back design layer 13 on the transparent thermoplastic resin layer 11 is preferably a method of repeatedly printing a design by rotating a cylindrical plate in its circumferential direction, i.e., a gravure printing method, an offset printing method, a flexographic printing method, etc., similar to the method of laminating the back design layer 13 on the colored thermoplastic resin layer 14 in the manufacturing method of the first embodiment. This is because laminating (printing) the back design layer 13 in a periodic arrangement in the longitudinal direction of the band-shaped transparent thermoplastic resin layer 11 can be easily performed, i.e., inexpensively and quickly. Among them, a gravure printing method is preferable, which has excellent printability for thermoplastic resins such as the transparent thermoplastic resin layer 11.

Next, the surface pattern layer 12 is laminated on the surface side of the transparent thermoplastic resin layer 11 using an inkjet printer (Figure 9 (c)). In laminating the surface pattern layer 12, the back pattern layer 13 and the surface pattern layer 12 are precisely aligned over the entire surface of the repeating pattern, i.e., the registration of the two is precisely aligned, which is a feature of the present disclosure. The method of laminating the surface pattern layer 12 on the surface side of the transparent thermoplastic resin layer 11 using an inkjet printer is the same as in the case of the decorative sheet 1 according to the first embodiment, and therefore will not be described here. Also, in the third embodiment, as in the second embodiment, a surface protective coating layer 15 may be laminated on the surface side of the surface pattern layer 12 of the decorative sheet 201 (Figure 9 (d)).

In the decorative sheet 201 according to the third embodiment, as in the decorative sheet 1 according to the first embodiment, the front and back printed pattern layers are precisely aligned with each other over the entire surface of the repeated pattern, so that the same effect as that of the decorative sheet 1 according to the first embodiment can be obtained. The decorative sheet 201 according to the third embodiment does not include a colored thermoplastic resin layer 14, so the only thermoplastic resin layer included in the layer structure is the transparent thermoplastic resin layer 11. Therefore, the decorative sheet 201 according to the third embodiment can be made thinner than the decorative sheet 1 according to the first embodiment and the decorative sheet 101 according to the second embodiment. Therefore, the decorative sheet 201 according to the third embodiment can be made soft and stiff, and can be attached to the material to be decorated with good conformity to the surface shape of the material to be decorated. In addition, since it does not include a colored thermoplastic resin layer 14, the color of the surface of the material to be decorated can sometimes be observed from the front side of the decorative sheet 201 through the back pattern layer 13, and in such cases, a design can be created that makes use of the color of the surface of the material to be decorated.

REFERENCE SIGNS LIST 1, 101, 201 Decorative sheet 11 Transparent thermoplastic resin layer 12 Front design layer 13 Back design layer 14 Colored thermoplastic resin layer 15 Front protective coating layer 16 Back primer layer 20 Register mark 30 Register mark detection means (camera)
35 Photoelectric sensor 40 Inkjet printing machine 41 Unwinding section 42 Winding section 43 Nip roll 45 Inkjet printing unit 47 Conveyance amount detection means (rotary encoder)
LD Longitudinal direction SD Shortitudinal direction

Claims (2)

A method for producing a decorative sheet comprising laminating at least three layers, a back design layer, a band-shaped transparent thermoplastic resin layer, and a front design layer, in this order, the method comprising the following steps (i) to (iii) in this order:
Step (i): First, one surface of the transparent thermoplastic resin layer is selected as a back surface, and the direction corresponding to the long side direction of the rectangular strip shape of the transparent thermoplastic resin layer is defined as the longitudinal direction, and the direction of the short side perpendicular to the longitudinal direction is defined as the short side direction. The back surface design layer and the register marks are laminated on the back surface of the transparent thermoplastic resin layer in a periodic arrangement in the longitudinal direction of the transparent thermoplastic resin layer.
Step (ii): Next, for the backside pattern layer, the dimension P R MD of one period of the pattern in the longitudinal direction and the dimension P R TD in the transverse direction of the transparent thermoplastic resin layer are measured using template matching, _with ^the _area including the registration mark in the acquired image being used as a ^template .
Step (iii): Next, the surface pattern layer is printed on the surface opposite to the back surface of the transparent thermoplastic resin layer by using an inkjet printing method, and the dimension P ^F _MD of one period of the pattern in the longitudinal direction of the surface pattern layer and the dimension P ^F _TD in the lateral direction are
^PFMD ₌ ^PRMD _{, and} ^PFTD ₌ ^PRTD
With this relationship in mind, the designs on the back design layer and the front design layer are printed in register with each other. The decorative sheet further includes a colored thermoplastic resin layer, and the decorative sheet is manufactured by laminating at least four layers, in this order, the colored thermoplastic resin layer, the back design layer, the transparent thermoplastic resin layer, and the front design layer,
The method for manufacturing a decorative sheet as described in claim 1, wherein the step (i) comprises laminating the back pattern layer on one side of the colored thermoplastic resin layer, and then laminating the back surface of the transparent thermoplastic resin layer so that the back surface of the transparent thermoplastic resin layer and the back pattern layer face each other, thereby laminating the back pattern layer on the back surface of the transparent thermoplastic resin layer.