JP7676859B2 - 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 described in Patent Document 1 has a transparent embossed resin layer with a pitch-shaped 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 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.

In the above-mentioned method for producing a decorative sheet, template matching may be used when measuring P ^R _MD and P ^R _TD , and the templates used for template matching may be set in two or more places within the picture area.

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. 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. A diagram explaining an example of a template design 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 lamination order is not disturbed, other layers other than the 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.

The pattern of the back pattern layer 13 is not particularly limited, but examples include wood grain patterns, stone patterns, patterns imitating partially rusted metal surfaces, 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 the present 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 of them, 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 patterns, cloth patterns, leather patterns, geometric patterns, letters, symbols, line drawings, various abstract patterns, solid monochrome patterns, monochrome gradations, etc. Given the effect of the present disclosure of precisely synchronizing the positions of the surface pattern layer 12 and the back pattern layer 13 over the entire surface of the repeating pattern, it is preferable for the pattern to be one that is preferably synchronized with the back pattern layer 13. For example, by adding another pattern that is synchronized with the pattern of the back pattern layer 13 as the surface pattern layer 12, the overall pattern of the decorative sheet 1 can be made more sophisticated. As an example, if the pattern on the back pattern layer 13 is a wood grain pattern, and there is no front pattern layer 12, the transparent thermoplastic resin layer 11 will result in an unnaturally glossy, cheap-looking appearance. However, if the front pattern layer 12 is used to form a gloss matte pattern that is in sync with the wood grain pattern on the back pattern layer 13, then the decorative sheet 1 can be made to have a highly aesthetic appearance.

The method for forming the surface pattern layer 12 in this disclosure 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 thick thickness does not cause any problems.

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 rear design layer 13 is formed on the colored thermoplastic resin layer 14 and then laminated to the transparent thermoplastic resin layer 11, thereby forming the rear design layer 13 on the rear side of the transparent thermoplastic resin layer 11. In contrast, the rear design layer 13 in the decorative sheet 201 according to the third embodiment is different in that it is formed (printed) directly on the rear side of the transparent thermoplastic resin layer 11.

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 is 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 these, gravure printing is preferable, which has excellent printability for thermoplastic resins such as the colored thermoplastic resin layer 14.

Next, 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. 6. Fig. 6 is a diagram showing an outline of the path of the printed material and the arrangement of each device in an inkjet printer, and parts that are not related to the description are largely omitted. Fig. 6(a) and Fig. 6(b) differ in the roller arrangement near the camera 30 and the position of the camera 30, which will be described later.
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. 6 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. 6, a camera 30 for acquiring an image for template matching is installed upstream of an inkjet printing unit 45 in the inkjet printer, and as far away from the inkjet printing unit 45 as possible.
In the manufacturing method of the decorative sheet 1 according to the present disclosure, the template 20 for template matching is set at two or more locations. 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 broken line in FIG. 2(a). In the width direction of the decorative sheet 1, if the region in the width direction where the pattern exists is the pattern region IR, and the regions on both sides of the pattern in the width direction where the pattern does not exist are 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). In the decorative sheet 1 according to the present disclosure, the templates 20 are provided near both ends in the width direction of the pattern region IR, as shown in FIG. 2(b). By providing the templates 20 not only on one side in the width direction but also near both ends of the pattern region IR, that is, by setting the templates 20 at two or more locations separated in the width direction, it is possible to perform stretch correction in the width direction as well. Hereinafter, the description will be given assuming that the templates 20 are set at two locations.

In most cases, the non-picture areas NIR of the decorative sheet 1 are removed by the time the sheet is used by an end user. Even decorative sheets from which the non-picture areas NIR have been removed, or sheets that did not originally have non-picture areas NIR, are naturally within the scope of the present disclosure as long as they are manufactured using the manufacturing method for decorative sheets according to the present disclosure.
In the manufacturing method of the decorative sheet 1 according to the present disclosure, there is no need to use so-called register marks for positional synchronization of the front and back patterns. Register marks are not necessary when used as the decorative sheet 1 and would detract from the pattern, so they are usually provided in the non-pattern area NIR. In the manufacturing method of the decorative sheet 1 according to the present disclosure, even if the product does not have a non-pattern area NIR at the time of manufacture, no register marks are used for positional synchronization of the front and back patterns, so there is no need to provide register marks, and a decorative sheet can be manufactured in which the front and back patterns are nevertheless synchronized.

As described above, the templates 20 are provided near both ends of the picture area IR in the width direction. Images for the templates 20 are acquired using the camera 30. The following methods can be considered as methods for acquiring images using the camera 30 to provide the templates 20 near both ends of the picture area IR.

The first method is to use multiple cameras (area sensor cameras) having light receiving elements arranged two-dimensionally (planarly). Two area sensor cameras are used corresponding to two templates 20 provided near both ends of the pattern area IR. Of the two cameras, one is for the template near the right end in the width direction, and the other is for the template near the left end in the width direction. With this method, the field of view per camera can be narrowed, so that images with high pixel resolution can be obtained, and therefore the positional accuracy of template matching can be improved. In addition, the installation distance of the cameras can be reduced, making it easier to install the cameras in an inkjet printer. In this method, since the field of view per camera is narrow, the cameras can be installed at a position where the field of view is on or near the roller, and stable images can be obtained (Figure 6 (a)). On the other hand, since the widthwise dimensions of the transparent thermoplastic resin layer 11, which is the printed material, and its pattern area IR vary depending on the item, it is necessary to adjust the widthwise position of the camera when changing items (resetting). Additionally, since the amount of expansion and contraction in the width direction is calculated from the distance between the two cameras and the results of template matching, it is important to know the distance between the two cameras and set it in the image processing device, but this creates a burden in managing the distance between the two cameras.

The second method is to use only one area sensor camera. In this method, it is necessary to provide templates 20 near both ends of the pattern area IR in one image acquired by one camera, so the field of view of the camera needs to be wide enough to include the entire pattern area IR. Normally, the camera is installed so that the pattern area IR fits within the field of view of the camera even for the item with the largest pattern area IR, and the position of the camera is not adjusted even when changing items (re-setting). Since the field of view of the camera is wide, it is necessary to set the camera at a large installation distance. In addition, since the field of view of the camera is wide, the field of view cannot be on the rollers, and it is necessary to set the field of view to a part with a distance between the rollers that is equal to or greater than the distance of the pattern area IR, so there are large restrictions on the installation position of the camera in the inkjet printer (Figure 6 (b)). As described above, since the field of view of the camera is between the rollers, there is a concern that the acquired pattern may be slightly deformed due to the fluttering of the transparent thermoplastic resin layer 11, which is the printed material. On the other hand, by installing the camera according to the item for which the width dimension of the image area IR, which varies depending on the item, is maximum, there is no need to adjust the width position of the camera when changing items (setup).

The third method is to use a camera (line sensor camera) with light receiving elements arranged one-dimensionally (linearly). A line sensor camera uses light receiving elements arranged linearly like the reading unit of a scanner or FAX, continuously acquires one-dimensional information in the width direction in synchronization with the transport of the object to be read, and sequentially arranges the many pieces of one-dimensional information in the width direction acquired in synchronization with the transport in the transport direction (longitudinal direction) to ultimately acquire a two-dimensional image. The field of view of the line sensor must include the entire image area IR, as in the case of one area sensor camera. The line sensor of the line sensor camera may be a proximity type in which the field of view length and the length of the line sensor are approximately the same, and the line sensor and the object to be read are close to each other, or a lens reduction type that reads the object to be read from a distant position like an area sensor camera. In general, a lens reduction type line sensor camera is often used because it is resistant to contamination of the line sensor camera and does not interfere with the paper threading operation in an inkjet printer. Unlike the case where there is only one area sensor camera, the line sensor camera has a field of view that has almost no width in the conveying direction (longitudinal direction), so the field of view can be on the rollers (Figure 6(a)). This makes it possible to obtain stable images that are not affected by fluttering.

In the method using multiple cameras (area sensor cameras) among the above, the position of each of the multiple cameras 30 in the short side direction (width direction) is adjusted according to the width of the decorative sheet 1 (transparent thermoplastic resin layer 11) to be manufactured so that a pattern suitable as a template for template matching is located near the center of the field of view of the camera 30. Hereinafter, the pattern included in the template for template matching may be referred to as the template pattern.

As described above, the template image is used as a template for template matching. In order to perform template matching accurately and without erroneous matching, it is preferable that the template image has the following characteristics: an image with contours in both the vertical and horizontal directions, the contours of the image are clear, and there are no image parts within or near the template image that are similar to the template image or any part of it.

Specific examples of template patterns in the case of wood grain patterns are explained in FIG. 7, showing conceptual example patterns. In each figure, an example of the area set as the template 20 is shown as a rectangle inside the figure. Patterns of knots in wood grain (FIG. 7(a)), cross grain patterns (FIG. 7(b)), and figured grain patterns (FIG. 7(c)) are preferable because they have outlines in both the vertical and horizontal directions. In contrast, among wood grain patterns, straight grain patterns (FIG. 7(d)) and vessel patterns (FIG. 7(e)) are not suitable as patterns to be the subject of template matching, because the outlines of the patterns are biased and do not have outlines in both the vertical and horizontal directions.

The inkjet printer is equipped 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 that is synchronized with the transport speed of the decorative sheet 1 (transparent thermoplastic resin layer 11), such as 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 back pattern layer 13, so the transport distance can be determined by counting the number of pulses.

The timing of capturing images is also adjusted so that the template pattern is located near the center of the field of view of camera 30 in the transport direction (longitudinal direction). For example, an image is captured at any timing using camera 30, and the image capturing position in the transport direction (longitudinal direction) is shifted by inputting the distance from the captured image position to the position of the image to be set as the template pattern, or the number of pulses of rotary encoder 47. The image capturing position is then shifted again by similarly inputting the distance or number of pulses for the newly captured image position. By repeating this procedure several times, the template pattern can be adjusted to be near the center of the field of view of camera 30.

Alternatively, when printing the backside pattern layer 13, a head alignment mark 25 is printed in the non-pattern area NIR at both ends of the width of the decorative sheet 1 using the same plate cylinder as the pattern. The head alignment mark 25 is printed periodically at the same pitch as the backside pattern. A photoelectric sensor 35 for detecting the head alignment mark 25 is then provided further upstream of the camera 30, and an image is taken when a predetermined number of pulses of the rotary encoder have been counted after the photoelectric sensor 35 detects the head alignment mark 25. The predetermined number of pulses is a fixed value determined by the transport 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 an image including the template pattern at a predetermined timing to create a reference image. Then, the template pattern, which is a partial area of the reference image, is registered in the expansion/contraction amount detection means as a template (reference image) for template matching, and the position of the template in the reference image is simultaneously registered as a reference position. The expansion/contraction amount detection means is usually 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 pulses from the rotary encoder 47. The repetition pitch of the back pattern layer 13 is determined as a design value for each item, and is also the plate cylinder circumference when the back pattern layer 13 (and the cue mark 25) is printed. The number of pulses corresponding to the repetition pitch of the pattern can be uniquely determined by this design value (the 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 is printed until the image is captured by the camera 30, the position of the reference image (template) in the captured image should theoretically remain unchanged.

However, in reality, the position of the reference image (template) in the captured image changes each time it is captured, for reasons such as the transparent thermoplastic resin layer 11 expanding and contracting after the back pattern layer 13 is printed and before it is imaged by the camera 30, and the amount of expansion and contraction differing between when the back pattern layer 13 is printed and when it is imaged by the camera 30.
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 the template 20 is set in two locations near both ends of the short direction SD in the image area IR, two values for the amount of expansion/contraction in the transport direction (longitudinal direction LD) are also 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) caused by the two templates 20. In other words, the difference between the amounts of displacement (amount of misalignment) in the width direction (short direction SD) caused by the two templates 20 is the amount of expansion and contraction of the decorative sheet 1 (transparent thermoplastic resin layer 11) relative to the design value in the width direction (short direction SD). For example, if the amounts of displacement (amount of misalignment) in the width direction (short direction) caused by the two templates 20 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 amount of displacement (misalignment) in the width direction (short direction SD) by the template 20 set on the right side is Ya to the right, and the amount of displacement (misalignment) in the width direction (short direction SD) by the template 20 set 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.

Furthermore, in the manufacturing method of the decorative sheet 1 according to the first embodiment, template matching is used when measuring P ^R _MD and P ^R _TD , and templates used for template matching are set in two or more places within the picture area.

As described above, in the manufacturing method of the decorative sheet of the present disclosure, it is possible to produce a decorative sheet 1 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 a 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 feel closer to that of natural wood can be achieved, i.e., a decorative sheet with a highly decorative feel can be produced.
Furthermore, if the design on the backside design layer 13 is a stone pattern, the dark parts of the stone pattern can be made to align with the dark parts of the design on the front side design layer 12 as matte parts, thereby making it possible to obtain a decorative sheet with a higher design quality. If the design on the backside design layer 13 is a pattern that imitates a partially rusted metal surface, the parts that imitate the rust can be made to align with the parts that imitate the rust as matte parts of the design on the front side design layer 12 as to obtain a decorative sheet with a higher design quality.

Furthermore, in the manufacturing method of the decorative sheet of the present disclosure, so-called registration marks are not required to align the pattern of the front pattern layer 12 with the pattern of the back pattern layer 13. Therefore, even for items that do not have a non-pattern area NIR, the patterns on the front and back can be aligned with high precision.
In addition, since the inkjet printing method is used for printing the front surface design layer 12, there is no need to create a plate for printing the front surface design layer 12, and even when the manufacturing item is changed (so-called changeover), there is no need to replace the plate, and no mechanism for changing the path length from the photoelectric sensor 35 to the printing unit is required. In addition, loss due to 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 pattern layer 13 is laminated on one surface (back surface) 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 pattern layer 13 on the transparent thermoplastic resin layer 11 is preferably a method of repeatedly printing a pattern 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 pattern layer 13 on the colored thermoplastic resin layer 14 in the manufacturing method of the first embodiment. This is because laminating (printing) the back pattern 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 printing suitability 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 Template 25 Heading mark 30 Camera 35 Photoelectric sensor 40 Inkjet printer 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 (3)

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 stripe shape of the transparent thermoplastic resin layer is defined as a longitudinal direction, and the direction of the short side perpendicular to the longitudinal direction is defined as a transverse direction. The back surface pattern layer is 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, template matching is performed using a partial area of the pattern related to the pattern area in the acquired image as a template to measure the longitudinal dimension P ^R _MD of one period of the pattern of the transparent thermoplastic resin layer and the transverse dimension P ^R _TD .
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. The method for manufacturing a decorative sheet according to claim 1 or 2, wherein the partial area corresponding to the template in the acquired image and used for the template matching is set in two or more locations within a picture area.