DECORATIVE SHEET AND METHOD FOR PRODUCING THE SAME Background The present invention relates to a decorative sheet, and a method for producing the same, particularly, a multi-tone (two-tone) colored decorative sheet having different colors, or different colors and patterns on the same sheet surface, and a method for producing the same. The decorative sheet of the present invention can be used as an interior material or a decorative material used in furniture, housing parts, or the like.

A decorative material having a surface laminated with a thermoplastic resin sheet has been used in interior applications for doors inside a room, cupboard doors, kitchen doors and so on. However, such a sheet has only a single color tone or pattern, and the surface of the decorative material is monotonous and lacks in design property.

To give a more varied design to a decorative material, two kinds of decorative sheets having different colors or patterns can be cut and then attached to the surface of a decorative material. However, an uneven pattern in the design can often be made on the decorative material surface. It is difficult to adhere two kinds of decorative sheets to such a surface and mate them to each other without leaving gaps. To do this, a very high level of skill is required.

In order to make the above-mentioned working technique easy, a method of using a splicing adhesive tape useful for mating the ends of two kinds of decorative films having an adhesive each other and then joining the ends has been disclosed (see, for example, JP-A-8-73823). Joining different decorative films to each other is easier using such a splicing tape. The adhesive tape is effective for making the joints of the decorative films inconspicuous after the films are joined. However, even if this adhesive tape is used, a high-level of skill is still required. Even if no gap is left following the joining of the tapes, the decorative films can shrink over time forming a gap between them. Thus, a problem with the appearance can develop with time.

Another method for producing a laminate sheet having a two-tone colored appearance on its surface is disclosed whereby a laminate sheet comprising two kinds of sheets having different colors is passed between a soft roll and a hard roll so as to press them (see, for example, JP-A-8-323899). According to this method, the laminate is passed between the rolls whereby the side of the laminate having the joint is against

the harder of the two rolls. Therefore, the sheet surface on which the two sheets are exposed is flattened, so that the surfaces of both sheets are flattened and leveled.

However, even if the above-mentioned production method is adopted, when the sheets are thermally laminated to join them by thermally fusing them together, the heat from the rolls is conducted directly to the two different kinds of sheets, and the sheets can rapidly shrink. Thus, distortion can occur at the boundary between the two different kinds of sheets.

When a web of two different kinds of sheet materials are joined to each other using an adhesive layer without the application of heat, passing the web continuously between a pair of rolls it is necessary to use an unwind 10 and a winder 20 as illustrated in Fig. 1. A certain tension is applied to the sheets between the unwind 10 and nip rolls 30, or between the rolls 30 and the winder 20, so that the tension can cause distortion at the joinboundary area of the two different kinds of sheets caused by the tension.

Additionally, when a printed pattern layer is formed on the sheets, the pattern can be distorted by either the heat, the tension or both.

Summary It is desirable to overcome the above-mentioned problems in the prior art and provide a multi-tone (two-tone) colored decorative sheet having, on its surface, different colors or different colors and patterns, where no distortion or entrapment of air bubbles occur in the join boundary area between different colors and between different printed patterns, and further where the printed patterns are not distorted. Additionally, it is desirable to provide a method for producing such a decorative sheet comprising sandwiching a base layer and a decorative layer between two process films, and then laminating them thermally, thereby forming a laminate-structure without causing distortion or air bubble entrapment.

In one embodiment of the present invention there is provided a decorative sheet having a laminate structure, comprising: a base layer comprising a thermoplastic resin film and having a first surface and a second surface opposite the first surface, a decorative layer having a first surface and a second surface opposite the first surface, wherein the decorative layer is colored differently from the base layer and

wherein the decorative layer is provided on the first surface of the base layer so that it shields at least a part of the first surface of the base layer, and a transparent protective layer which is provided so that it covers the first surface of the decorative layer and the rest of the first surface of the base layer which is not shielded with the decorative layer, characterized in that the decorative layer comprises a thermoplastic resin film having a thickness of 10 urn to 80 urn.

In another embodiment of the invention, a method for producing a decorative sheet having a laminate structure is provided comprising: thermally laminating together a laminate comprising, in order, a first process film, a base layer having a first surface and a second surface opposite the first surface wherein the base layer comprises a thermoplastic resin film, a decorative layer having a first surface and a second surface opposite the first surface, the decorative layer comprising a thermoplastic resin film wherein the thermoplastic resin film has a thickness of 10 jj. m to 80 llm wherein the decorative layer is provided on the first surface of the base layer so that it shields at least a part of the first surface of the base layer, a transparent protective layer which is provided so that it covers the first surface of the decorative layer and the rest of the first surface of the base layer which is not shielded with the decorative layer, and a second process film; and removing the first and second process films.

In an additional embodiment, a method for producing a decorative sheet having a laminate structure is provided comprising: providing a base layer film on a surface of a first process film, the base layer having a first surface and a second surface opposite the first surface, the base layer comprising a thermoplastic resin, so that the second surface of the base layer faces the surface of the first process film to form a first laminate, providing a transparent protective layer on a surface of a second process film, the protective layer having a first surface and a second surface opposite the first surface, so that the first surface of the protective layer faces the surface of the second process film and providing a decorative layer comprising a thermoplastic resin film

having a thickness of 10 Fm to 80 urn fixedly on the second surface of the transparent protective layer to form a second laminate, providing the first laminate fixedly on the second laminate so that the first surface of the base layer faces a surface of the decorative layer, removing the first and second process films, and optionally embossing the first surface of the transparent protective layer which is exposed after the removal of the second process film.

Brief Description of the Drawings Figure 1 is a schematic view illustrating a device for continuously joining two kinds of sheets; Figure 2 is a sectional view of a laminate-structure decorative sheet according to one embodiment of the present invention; Figure 3 is a sectional view of a sheet having the first process film and a base layer, according to an embodiment of the present invention; Figure 4 is a sectional view of a sheet having the second process film and a transparent protective layer, according to an embodiment of the present invention; and Figure 5 is a sectional view of a decorative sheet according to an embodiment of the present invention.

Detailed Description A decorative sheet of the present invention comprises: (A) a base layer comprising a thermoplastic resin film and having a first surface and a second surface opposite the first surface; (B) a decorative layer having a first surface and a second surface surface, wherein the decorative layer is colored differently from the color of the base layer and provided so that it shields at least a part of the first surface of the base layer; and (C) a transparent protective layer which is provided so that it covers the first surface of the decorative layer and the rest of the first surface of the base layer which is not shielded with the decorative layer;

wherein the decorative layer comprises a thermoplastic resin film having a thickness of 10 um to 80 pm.

According to this structure, a decorative sheet having a laminate-structure can be provided.

Hereinafter, one embodiment of the decorative sheet having a laminate- structure of the present invention will be explained in detail by making reference to Fig.

2.

The laminate-structure decorative sheet illustrated in Fig. 2 has a laminate- structure wherein a base layer 6 comprises a thermoplastic resin film 1 and a printed pattern 2 formed on the surface thereof; a decorative layer 7 comprising a thermoplastic resin film 3 arranged to shield a part of the base layer 6 and a printed pattern 4 formed on the surface thereof ; and a transparent protective layer 5 are laminated in this order.

The printed pattern 2 and the printed pattern 4 are formed with or without the consideration of design of the whole of the decorative sheet.

The thermoplastic resin film 1 can be made of a thermoplastic resin which is widely known in the prior art, for example, polyvinyl chloride resin, vinyl chloride/ vinyl acetate polymer resins, acrylic polymer resins, polypropylene resin, polyethylene resins, polyester resins or polyolefin resins. A plasticizer may be added to the polyvinyl chloride resin to impart flexibility to the resin. As the plasticizer, a phthalate ester, an adipate ester or a polyester may be used. However, the plasticizer is not limited to these compounds. The resin which can be used for the thermoplastic resin film 1 is preferably a resin having a glass transition temperature in the range of 60 to 90°C, and is more preferably a resin having a glass transition temperature in the range of 65 to 80°C. When the glass transition temperature is higher than 90°C, the following production process issue may be caused: the required process temperature may become so high that when the base layer 6 and the decorative layer 7 are thermally laminated by thermal laminating that the adhesion between the base layer 6 and the decorative layer 7 in the resulting sheet may be deteriorated. On the other hand, when the glass transition temperature is lower than 60°C, there can also arise problems in the production process such that the films undergo mutual blocking or the like so that the films cannot be handled with ease.

The thermoplastic resins may be in a mixture form. In accordance with a desired object, additives may be added to the thermoplastic resin. Examples of

additives include one or more plasticizers, a fillers, reinforcing materials such as glass fibers, flame retardants, antioxidants, and ultraviolet absorbers.

The thickness of the thermoplastic resin film 1 is preferably from 10 to 150 jjm, more preferably from 20 to 100 llm. When the thickness is more than 150 jjm, the flexibility of the film decreases so that the workability of the film deteriorates. When the thickness is less than 10 pm, the shielding ability of the thermoplastic resin film 1 is low so that the color or pattern of the underlying can be seen through the film.

The printed pattern 2 is made of a colorant on the surface of the thermoplastic resin film 1. The printed pattern 2 is formed on the surface of the thermoplastic resin film 1 by any one of gravure printing, electrostatic printing, electrophotographic imaging, screen printing, ink-jet printing, offset printing and other printing methods.

The colorant for forming the printed pattern 2 is usually a toner or an ink.

The thermoplastic resin film 3 can be produced using a thermoplastic resin and optional additives corresponding to predetermined purposes in the same way as the thermoplastic resin film 1.

The thickness of the thermoplastic resin film 3 is preferably from 10 to 80 um, more preferably from 15 to 25 jjm. When the thickness of the thermoplastic resin film 3 is more than 80 lem, air is easily incorporated into the boundary portion obtained by thermally laminating the overlapped base layer 6 and decorative layer 7, so that the appearance of the decorative sheet having a laminate-structure deteriorates. When the thickness is less than 10 pm, the shielding ability of the decorative layer 7 deteriorates so that the color or pattern of the surface of the base layer 6, which is covered with the decorative layer 7, is more easily seen through the film 3. The printed pattern 4 is also formed on the surface of the thermoplastic resin film 3 by one of the same methods as exemplified for those used to form printed pattern 2.

The base layer 6 and the decorative layer 7 are laminated in such a manner that both of the printed pattern 2 and the printed pattern 4 can be seen from either side. For example, the base layer 6 and the decorative layer 7 can be produced by putting the decorative layer 7 (which is narrower than the base layer 6) onto the base layer 6 and then laminating the layers 6 and 7 thermally.

"Thermally laminating"is a method of applying heat to plural thermoplastic resin films to soften or melt the surfaces thereof and passing the plurality of films

between two lamination rolls to press the films together with the applied pressure and heat.

The surface of the decorative sheet of the present invention is protected by a transparent protective layer 5. The kind of a transparent resin for forming the transparent protective layer is not particularly limited, and examples thereof include polyvinyl chloride resin, fluorine-containing resins, polyurethane resins, acrylic polymer resins, epoxy resins and polyester resins. The thickness of the transparent protective layer 5 is from 20 to 200 jjm, preferably from 50 to 150 um. The surface of the transparent protective layer 5 may be subjected to gloss treatment or matte finish in accordance with a desired purpose.

The laminate-structure decorative sheet of the present invention can be adhered to various underlying materials when in the state that an adhesive layer is laid on the second surface of the thermoplastic resin film 1.

The method for producing a laminate-structure decorative sheet of the present invention will be illustrated by making reference to Figs. 3,4 and 5.

Step (A): As shown in Fig. 3, firstly, a thermoplastic resin film 1, which constitutes a base layer 6, is arranged on the surface of the first process film 8 so that the second surface of the thermoplastic resin film 1 faces the front surface of the first process film 8, thereby forming a printed pattern 2 on the first surface of the thermoplastic resin film 1.

Examples of methods for obtaining the thermoplastic resin film 1 on the front surface of the first process film 8 include methods of applying the thermoplastic resin dissolved in a solvent to the front surface of the first process film and then removing the solvent to form the thermoplastic resin film 1; a method of heating and melting the thermoplastic resin, applying the molten resin to the front surface of the first process film, and then cooling the resin to form the thermoplastic resin film 1 ; and a method of bonding a thermoplastic resin film 1 made beforehand in the form of a film to the first process film under pressure by a thermal lamination method.

First process film is preferably a polyethylene terephthalate film by taking into account the heat resistance of the base layer 6 and the decorative layer 7 at the time of thermal lamination and the peeling ability of the first process film from the base layer 6 after the thermal lamination. The preferred thickness thereof is from 25 to 200 Rm.

When the thickness is more than 200 pm, the conduction of heat through the process film becomes low so that adhesive failure between the base layer 6 and the decorative layer 7 is likely. On the other hand, when the thickness is less than 25 jjm, the process film itself may easily be distorted by tension during the thermal lamination so that the decorative sheet of the present invention, whose front and back surfaces are covered by the process films, is also distorted.

Step (B): As shown in Fig. 4, next, a transparent protective layer 5 is arranged on the surface of a second process film 9, so that the second surface of the film 9 faces the first surface of the protective layer 5. In this way, a thermoplastic resin film 3 having a thickness of 10 to 80 um on which a printed pattern 4 is formed is fixedly arranged on the second surface of the transparent protective layer 5 so that this second surface faces the printed pattern 4.

Examples of methods for arranging the transparent protective layer 5 fixedly on the back surface of the second process film 9 include methods of applying a transparent resin dissolved in a solvent to the second process film and then removing the solvent to form the transparent protective layer 5, methods of heating and melting a transparent resin, applying this resin melt to the second process film, and then cooling the resin to form the transparent protective layer 5, and methods of bonding the transparent protective layer 5 made into a film form in advance to the second process film under pressure by a thermal lamination method.

Examples of methods for arranging the decorative layer 7 fixedly on the second surface of the transparent protective layer 5 include a method of bonding the decorative layer 7 and the transparent protective layer 5 to each other under pressure by thermal lamination, and a method of providing an adhesive layer on the second surface of the transparent protective layer 5 and then bonding the decorative layer 7 and the transparent protective layer 5 to each other using this adhesive layer.

The decorative layer 7 is processed to have a smaller width than the width of the base layer 6 in such a manner that when the decorative layer 7 is arranged on the first surface of the base layer 6, a part of the first surface of the base layer 6 can be seen. Therefore, the width of the decorative layer 6 is narrower than that of the transparent protective layer 5, as illustrated in Fig. 5.

Step (C):

The sheet produced in the step (A) is fixedly arranged on the sheet produced in the step (B) so that the first surface of the base layer 6 faces the second surface of the decorative layer 7. The decorative layer 7 is arranged to shield part of the base layer 6, and is fixed to the base layer by a thermal lamination method.

The conditions for this thermal lamination method include a laminating pressure of preferably from 0.2 to 1.0 MPa, and a laminating temperature of preferably from 150 to 250°C. The tension applied to the sheets is preferably from 5 to 50 kg/1000 mm. When the laminating pressure is larger than 1.0 MPa, the sheets deform so that the appearance as a decorative material may be damaged. When the laminating pressure is less than 0.2 MPa, adhesive failure may be caused. When the laminating temperature is higher than 250°C, the sheets are thermally damaged so that the physical properties thereof may be lowered. When the laminating temperature is lower than 150°C, adhesive failure may be caused. When the tension is higher than 50 kg/1000 mm, the sheets themselves may be distorted. When the tension is lower than 5 kg/1000 mm, wrinkles may easily be generated in the laminate sheet.

The time necessary for the laminating ranges from 10 seconds to 5 minutes.

When the laminating time is too long, the sheet may be thermally damaged. When the laminating time is too short, adhesive failure may be caused.

The first process film 8 and the second process film 9 are then removed from the sheet produced in the step (C), thereby yielding the laminate-structure decorative sheet of the present invention. At this time, embossing work may be applied to the first surface of the transparent protective layer 5, which is exposed by the removal of the second process film 9. In this way, the above-mentioned decorative sheet can also be made into a decorative sheet having further designs.

The embossing can be performed by heating an embossing roll and the decorative sheet and pressing an inset pattern made in the embossing roll against the decorative sheet. Conditions for the embossing work are not particularly limited. It is preferable that the temperature of the embossing roll is from 50 to 100°C, the temperature of the decorative sheet is from 150 to 250°C and the pressure of the embossing roll against the decorative sheet is from 0.1 to 0.5 MPa.

When the laminate-structure decorative sheet of the present invention is used as an interior material or a decorative material, the decorative sheet can be bonded to

the surface of the interior material or a decorative material using an adhesive, or the decorative sheet may be laminated onto a surface by thermal bonding under pressure.

Examples The present invention will be explained in detail by the following examples.

However, the present invention is not limited to the examples.

Example 1 Firstly, to form a base layer 6, a red resin paste was prepared which paste comprised methyl ethyl ketone and a vinyl chloride/vinyl acetate copolymer (trade name: VYHH, Tg = 72°C) manufactured by Union Carbide Corporation of Danbury, CT, USA. The concentration of the copolymer in the paste was 25% by weight..

The resin paste was applied onto a polyethylene terephthalate film (TETORON film G2 type, thickness = 50 J. m, width = 1330 mm) manufactured by Teijin Ltd. of Osaka, Japan, the polyethylene terephthalate film (PET film) being used as a first process film. The resin paste was coated onto the PET film with a knife coater, and then the coating was dried to produce a thermoplastic resin film 1 coating having a dry thickness of 25 um on the PET film.

A vinyl chloride/vinyl acetate type ink (trade name: VS INK) manufactured by Dainichiseika Color & Chemicals Mfg. Co. , Ltd. (Tokyo, Japan) was used to gravure- print a pattern onto the surface of this thermoplastic resin film 1 coating to form a printed pattern 2.

Next, to produce a decorative layer 7, a white resin paste made of the same vinyl chloride/vinyl acetate copolymer as the resin paste for the base layer 6 was prepared. The paste was applied onto a polyethylene terephthalate film (TETORON <BR> <BR> film G2 type, thickness = 38, um, width = 1330 mm) manufactured by Teijin Ltd. , the polyethylene terephthalate film (PET film) being used as a process substrate. The white resin paste was coated onto the second PET film, with a knife coater, and then dried to produce a white thermoplastic resin film 3 coating having a thickness of 25 m. The following work was performed without peeling the process substrate from the thermoplastic resin film coating 3.

A vinyl chloride/vinyl acetate type ink (trade name: VS INK) manufactured by Dainichiseika Color & Chemicals Mfg. Co. , Ltd. was used to gravure-print a pattern

onto the surface of this white thermoplastic resin film coating 3 to form a printed pattern 4. This printed pattern 4 was different from that previously formed on the first thermoplastic resin film coating the printed pattern 2. Both ends in the width direction of this white thermoplastic resin film 3 coating were cut to prepare a white thermoplastic resin film 3 having a width of 600 mm.

Then, a polyvinyl chloride film (thickness = 150 lem, width =1300 mm) manufactured by Bando Chemical Industries, Ltd. of Kobe, Japan for forming a transparent protective layer 5 was arranged on the back surface of a polyethylene terephthalate film (TETORON film G2 type, thickness = 38 llm, width= 1330 mm) manufactured by Teijin Ltd. , as the second process film, so that the first surface of the protective layer 5 faced the back surface of the second process film. The white thermoplastic resin film coating 3 having a thickness of 25 jjm and a width of 600 mm, on which the printed pattern 4 was formed, was arranged on the second surface of the transparent protective layer 5 so that the printed pattern 4 faced the second surface of the transparent protective layer 5. Thereafter, the respective layers were bonded to each other under pressure by a thermal lamination method. Conditions for the thermal lamination method were as follows: Laminating pressure: 0.6 MPa, Laminating temperature : 180°C, Tension applied to the sheet: 10 kg/1000 mm.

At this stage, the process substrate was removed from the white thermoplastic resin film coating 3.

Next, the decorative layer 7 was arranged so that the second surface of the decorative layer 7 faced the first surface of the base layer 6 produced by the above- mentioned method. The decorative layer 7 was arranged not to shield the first surface portions of both ends of the base layer 6, and then bonded to the base layer 6 under pressure by a thermal lamination method. Conditions for the thermal lamination method were as follows: Laminating pressure: 0.6 MPa, Laminating temperature: 200°C, Tension applied to the sheet: 15 kg/1000 mm.

Next, the second process film 9 of the sheet obtained by the thermal lamination method was removed, and embossing for giving a satin texture was applied

to the exposed first surface of the transparent protective layer 5. Thereafter, the first process film 8 was removed to yield a laminate-structure decorative sheet.

An acrylic adhesive (AROSET 8580, manufactured by Nippon Shokubai Co., Ltd. of Osaka, Japan) was applied onto a release paper (RHC-l l, manufactured by Sun- A Chemical Co. , Ltd. CITY, COUNTRY?) with a knife coater, and then dried to yield an adhesive layer having a thickness of 40 um. Thereafter, the adhesive layer was laminated on the decorative sheet so that the front surface of the adhesive layer faced the second surface of the base layer of the laminate-structure decorative sheet, thereby yielding a decorative sheet with an adhesive layer.

The release paper was peeled from this decorative sheet having the adhesive layer, and then the decorative sheet was adhered to the front surface of a decorative material (trade name: MM series, ZN/M11-54SMB, manufactured by Shin-Nikkei Company Ltd. of Tokyo, Japan). Thereafter, the appearance thereof was observed with an eye. The results are shown in Table 1.

Comparative Example 1 Two kinds of decorative sheets having different surface colors and different surface patterns (DI-NOC Films FA-688 and LE-367, manufactured by Sumitomo 3M Ltd. , of Tokyo, Japan) were mated each other on the front surface of a decorative material (trade name: MM series, ZN/M11-54SMB, manufactured by Shin Nikkei Company Ltd. ), and then adhered onto the front surface. Thereafter, the appearance thereof was observed with the naked eye. The results are shown in Table 1.

Comparative Example 2 A decorative sheet with an adhesive layer was produced in the same way as in Example 1 except that a polyvinyl chloride film (manufactured by Bando Chemical <BR> <BR> Industries, Ltd. ) having a thickness of 100 um, as the thermoplastic resin film 3 of the decorative layer 7, was thermally laminated on a polyethylene terephthalate film (TETORON film G2 type, thickness = 38 pm, width = 1330 mm) manufactured by Teijin Ltd. , as a process substrate, and then the printed pattern 4 was formed on the front surface of the above-mentioned polyvinyl chloride film. This was adhered to the front surface of a decorative material (trade name: MM series, ZN/M11-54SMB, manufactured by Shin Nikkei Company Ltd. ) in the same way. Thereafter, the appearance thereof was observed with the naked eye. The results are shown in Table 1.

Comparative Example 3

A decorative sheet with an adhesive layer was produced in the same way as in Example 1 except that a polyvinyl chloride film (manufactured by Bando Chemical Industries, Ltd. ) having a thickness of 80 um was used as the thermoplastic resin film 1 of the base layer 6, and the polyvinyl chloride film having no first process film, that is, only the polyvinyl chloride film on which the printed film 2 was formed was thermally laminated on the decorative layer on which the second process film and the transparent protective layer were laminated. This was adhered to the front surface of a decorative material (trade name: MM series, ZN/M11-54SMB, manufactured by Shin Nikkei Company Ltd. ) in the same way. Thereafter, the appearance thereof was observed with the naked eye. The results are shown in Table 1.

Table 1 Example 1 Comparative Comparative Comparative Example 1 Example 2 Example 3 Distortion of Not Not observed Not observed Observed pattern observed Distortion of Not Observed Not observed Observed boundary portion observed Gap in the Not Observed Not observed Not observed boundary portion observed Incorporation of air Not Not observed Observed Not observed bubbles into observed boundary portion