Moisture-proof paper on the back of decorative panels

Abstract

To provide moisture-proof paper to be used, for instance, by bonding onto a rear face of a decorative sheet, in order to prevent a warpage caused by moisture absorption or moisture desorption by a change in a temperature or humidity inside a room in the decorative sheet to be used in a door panel or the like inside a room.SOLUTION: Moisture-proof paper includes a moisture-proof layer 20 including: an anchor coat layer 22 having a first polyolefin having at least one kind selected from a carboxyl group, a salt of a carboxyl group, a carboxylic acid anhydride group and a carboxylic acid ester; a vapor-deposited layer 23; and an overcoat layer 24 having a second polyolefin having at least one kind selected from a carboxyl group, a salt of a carboxyl group, a carboxylic acid anhydride group, and a carboxylic acid ester in this order on a paper substrate 21. The anchor coat layer 22 may be l μm thick or more. The overcoat layer 24 may be provided with a primer layer 30 for adhesion, on a surface thereof. The paper substrate 21 may be interpaper reinforced paper.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a moisture-proof paper that is used, for example, by laminating it to the back surface of decorative panels used in interior door panels, etc., to prevent warping caused by moisture absorption and release due to changes in indoor temperature and humidity. [Background technology]

[0002] Conventionally, decorative boards used for the above-mentioned applications have generally been formed by laminating a decorative sheet printed with a solid print layer to provide hiding properties or a patterned layer to improve design to the surface of a multilayered wood-based substrate such as plywood, medium-density fiberboard (MDF), veneer, board material, or other material. When the moisture content of a wood-based substrate is lower than the equilibrium moisture content of the substrate under ambient conditions, the surface of the decorative board that is not covered with the decorative sheet will absorb moisture and expand, whereas when the moisture content is higher than the equilibrium moisture content of the substrate, the surface that is covered with the decorative sheet will release moisture and shrink, whereas the surface that is covered with the decorative sheet will neither absorb nor release moisture, causing deformation (warping, dimensional changes) of the decorative board.

[0003] To prevent this deformation, methods such as applying paint to the back of a decorative board with a decorative sheet attached to the surface, attaching a synthetic resin sheet such as polyvinyl chloride, polyethylene, or polypropylene, or attaching a moisture-proof sheet made of paper / polyethylene / paper are known. Conventionally, moisture-proof decorative boards have been known which are formed by adhering a moisture-proof decorative sheet to the front surface of a board substrate such as plywood and a moisture-proof back sheet to the back surface via adhesive (see paragraph

[0007] and Figures 1 to 3 of Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 3206408 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the conventional methods described above have insufficient moisture resistance, and when used for a long period of time on doors, sliding doors, partitions, etc. where there is a large difference in temperature and humidity environment between the two sides, the degree of expansion and contraction on both sides may differ, causing warping. The present invention has been made to solve this problem, and aims to provide a moisture-proof paper that prevents warping even when used in a place where there is a large difference in temperature and humidity environment on both sides. [Means for solving the problem]

[0006] The present invention has solved this problem, and in one embodiment of the present invention, the moisture-proof backside paper for decorative panels is characterized by comprising a moisture-proof layer on a paper base, which comprises, in this order: an anchor coat layer containing a first polyolefin having at least one selected from a carboxyl group, a salt of a carboxyl group, a carboxylic acid anhydride group, and a carboxylic acid ester; a vapor-deposited layer; and an overcoat layer containing a second polyolefin having at least one selected from a carboxyl group, a salt of a carboxyl group, a carboxylic acid anhydride group, and a carboxylic acid ester. The first polyolefin and the second polyolefin may be the same or different.

[0007] Furthermore, the moisture-proof backside paper for decorative boards according to one aspect of the present invention is characterized in that the anchor coat layer has a thickness of 1 μm or more. A moisture-proof backside paper for decorative panels according to one embodiment of the present invention is characterized in that it comprises an adhesive primer layer provided on the exposed surface of an overcoat layer. The moisture-proof backside paper for decorative boards according to one aspect of the present invention is characterized in that the paper base material is a reinforced inter-paper paper. [Effects of the Invention]

[0008] According to one aspect of the present invention, it is possible to provide a moisture-proof paper for the back side of decorative panels that has significantly superior moisture-proof performance compared to the moisture-proof sheets made of synthetic resins such as polyvinyl chloride, polyethylene, polypropylene, etc., or paper / polyethylene / paper that have been used in the past, and that contributes to reducing the amount of plastic materials used. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is an explanatory diagram showing the cross-sectional shape of one embodiment of moisture-proof paper of the present invention. [Figure 2] FIG. 2 is an explanatory diagram showing the cross-sectional shape of an embodiment of the moisture-proof paper of the present invention using an adhesive primer layer. [Figure 3] FIG. 1 is an explanatory diagram of an embodiment in which the moisture-proof paper of the present invention is used as a decorative sheet or board substrate. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment of the present invention will be described with reference to FIGS. However, the present invention is not limited to the following embodiments.

[0011] [Moisture-proof paper backing for decorative panels 10] As shown in Figures 1 and 2, the moisture-proof backside paper 10 for decorative panels according to the present invention (hereinafter also referred to as "moisture-proof paper 10") includes a moisture-proof layer 20 on a paper substrate 21. The moisture-proof layer 20 is composed of three layers: an anchor coat layer 22, a vapor deposition layer 23, and an overcoat layer 24. As shown in FIG. 3, an adhesive primer layer 30 can be provided on the exposed surface of the overcoat layer 24 . The anchor coat layer 22 contains a first polyolefin having at least one selected from a carboxyl group, a salt of a carboxyl group, a carboxylic anhydride group, and a carboxylic acid ester, and the overcoat layer 24 contains a second polyolefin having at least one selected from a carboxyl group, a salt of a carboxyl group, a carboxylic anhydride group, and a carboxylic acid ester.

[0012] [Paper base material 21] The paper substrate 21 is not particularly limited and may be selected appropriately depending on the application of the moisture-proof paper 10 to be used. Specific examples of the paper substrate 21 include tissue paper, fine paper, art paper, cast coated paper, kraft paper, titanium paper, linter paper, paperboard, gypsum board paper, fine paper, coated paper, parchment paper, glassine paper, parchment paper, paraffin paper, and Japanese paper. Preferably, thin paper in which synthetic resin is mixed to increase the strength between the sheets (so-called inter-sheet reinforced paper) or paper impregnated with latex or synthetic resin is used. The basis weight is not particularly limited, but is preferably 20 g / m 2 If it is less than 200g / m, it will be too flexible and wrinkles will easily occur during processing. 2 If it exceeds this, peeling from the paper layer is likely to occur, so it is recommended to use a thickness of 20 to 200 g / m. 2 is preferable, and 20 to 100 g / m 2 More preferably, 20 to 50 g / m 2 is more preferred.

[0013] Furthermore, the paper substrate 21 may be subjected to surface treatment such as corona treatment, plasma treatment, or flame treatment, if necessary. The paper substrate 21 may have a coating layer provided at least on the side that comes into contact with the anchor coating layer 22 described below. By providing the coating layer, it is possible to prevent the anchor coating layer 22 from penetrating into the paper, and also to act as a sealant to fill in unevenness in the paper, allowing the anchor coating layer 22 to be formed uniformly without defects.

[0014] The coating layer may contain, for example, various copolymers such as styrene-butadiene, styrene-acrylic, and ethylene-vinyl acetate copolymers, polyvinyl alcohol resins, cellulose resins, paraffin (wax), etc. as binder resins, and may also contain clay, kaolin, calcium carbonate, talc, mica, etc. as fillers. The thickness of the coating layer is not particularly limited, but may be, for example, 1 to 10 μm, or 3 to 8 μm.

[0015] The weight of the paper substrate 21 is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 80% by mass or more, based on the weight of the moisture-proof layer 20. If the weight of the paper substrate 21 is 50% by mass or more based on the weight of the moisture-proof layer 20, the amount of plastic material used can be sufficiently reduced, and the moisture-proof paper 10 can be said to be made of paper.

[0016] [Anchor coat layer 22] The anchor coat layer 22 is provided on the surface of the paper substrate 21 to improve adhesion between the paper substrate 21 and the vapor deposition layer 23 described later, and to improve the gas barrier properties of the gas barrier laminate, and constitutes a barrier layer. The barrier layer of the present invention has excellent oxygen and water vapor barrier properties. For the moisture-proof backside paper 10 for decorative boards of the present invention, only water vapor barrier properties are required, and oxygen barrier properties are not a factor.

[0017] The anchor coat layer 22 contains a first polyolefin having at least one selected from a carboxyl group, a salt of a carboxyl group, a carboxylic anhydride group, and a carboxylic acid ester. Such an anchor coat layer 22 has excellent flexibility, can suppress cracking of the vapor deposition layer 23, and can improve adhesion between the anchor coat layer 22 and the vapor deposition layer 23. Furthermore, by including the above-mentioned polyolefin, it is possible to form a dense film due to the crystallinity of the polyolefin. Furthermore, polyolefin has few polar groups, and therefore has excellent water vapor barrier properties.

[0018] The anchor coat layer 22 may contain other components in addition to the first polyolefin. Examples of other components include polyolefins other than the first polyolefin, silane coupling agents, organic titanates, polyacrylics, polyesters, polyurethanes, polycarbonates, polyureas, polyamides, polyimides, melamine, and phenols. The content of the first polyolefin in the anchor coat layer 22 may be, for example, 50% by mass or more, 70% by mass or more, 90% by mass or more, or 100% by mass.

[0019] The thickness of the anchor coat layer 22 may be, for example, 1 μm or more, 2 μm or more, 20 μm or less, 10 μm or less, or 5 μm or less. If the thickness of the anchor coat layer 22 is 1 μm or more, the irregularities of the paper substrate 21 can be efficiently filled, and the vapor deposition layer 23 described below can be evenly laminated. If the thickness of the anchor coat layer 22 is 20 μm or less, the vapor deposition layer 23 can be evenly laminated while keeping costs down.

[0020] Examples of solvents contained in the coating liquid for the anchor coat layer 22 include water, methyl alcohol, ethyl alcohol, isopropyl alcohol, n-propyl alcohol, n-butyl alcohol, n-pentyl alcohol, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, toluene, hexane, heptane, cyclohexane, acetone, methyl ethyl lactone, diethyl ether, dioxane, tetrahydrofuran, ethyl acetate, and butyl acetate. These solvents may be used alone or in combination of two or more. Among these, methyl alcohol, ethyl alcohol, isopropyl alcohol, toluene, methyl acetate, methyl ethyl ketone, and water are preferred from the viewpoint of properties, and methyl alcohol, ethyl alcohol, isopropyl alcohol, and water are preferred from the viewpoint of the environment.

[0021] The anchor coat layer 22 can be formed by applying a coating liquid containing at least the first polyolefin and a solvent onto the paper substrate 21 and drying it. The smaller the average particle size of the first polyolefin in the coating liquid, the better, from the viewpoints of smoothing the coating surface after drying, uniformly depositing the vapor deposition layer 23, and improving barrier properties. Specifically, it may be 1 μm or less, 0.7 μm or less, or 0.5 μm or less. The lower limit of the average particle size of the first polyolefin is not particularly limited, but may be, for example, 1 nm or more.

[0022] [Vapour-deposited layer 23] The vapor-deposited layer 23 is a layer formed by vapor-depositing a metal or an inorganic compound. The vapor-deposited layer may be obtained by vapor-depositing aluminum, or may contain aluminum oxide (AlOx), silicon oxide (SiOx), or the like. The thickness of the vapor-deposited layer 23 may be appropriately set depending on the intended use, but is preferably 10 to 300 nm, and more preferably 30 to 100 nm. A thickness of 10 nm or more of the vapor-deposited layer 23 makes it easy to ensure sufficient continuity of the vapor-deposited layer 23, while a thickness of 300 nm or less makes it easy to sufficiently suppress the occurrence of curling and cracking, and to easily achieve sufficient gas barrier performance (water vapor barrier excluding oxygen barrier) and flexibility.

[0023] From the viewpoint of film uniformity, it is preferable to form the deposition layer 23 by a vacuum deposition method. There are known deposition methods such as vacuum evaporation, sputtering, and chemical vapor deposition (CVD), but vacuum evaporation is preferred due to its fast deposition rate and high productivity. Among the vacuum deposition methods, electron beam heating is particularly effective because it allows for easy control of the deposition rate by adjusting the irradiation area and electron beam current, and allows for rapid heating and cooling of the deposition material.

[0024] [Overcoat layer 24] The overcoat layer 24 is provided on the surface of the vapor-deposited layer 23 so as to be in contact with the vapor-deposited layer 23, and contains a second polyolefin having at least one selected from a carboxyl group, a salt of a carboxyl group, a carboxylic anhydride group, and a carboxylic acid ester. Such an overcoat layer 24 has excellent flexibility and excellent adhesion to the vapor deposition layer 23. Furthermore, by including the second polyolefin described above, it is possible to form a dense film due to the crystallinity of the polyolefin. Furthermore, polyolefin has excellent water vapor barrier properties due to its small number of polar groups.

[0025] The overcoat layer 24 may contain other components in addition to the second polyolefin. Examples of other components include silane coupling agents, organic titanates, polyacrylics, polyesters, polyurethanes, polycarbonates, polyureas, polyamides, polyolefin emulsions, polyimides, melamine, and phenols. The content of the second polyolefin in the overcoat layer 24 may be, for example, 50% by mass or more, 70% by mass or more, 90% by mass or more, or 100% by mass.

[0026] The thickness of the overcoat layer 24 may be, for example, 0.05 μm or more, 0.5 μm or more, 1 μm or more, 20 μm or less, 10 μm or less, or 5 μm or less. If the thickness of the overcoat layer 24 is 0.05 μm or more, it can fully function as a heat seal layer. Furthermore, if the thickness of the overcoat layer 24 is 20 μm or less, it is possible to suppress costs and still sufficiently exhibit adhesion to the vapor deposition layer 23 and barrier properties (water vapor barrier excluding oxygen barrier).

[0027] Examples of solvents contained in the coating liquid for the overcoat layer 24 include water, methyl alcohol, ethyl alcohol, isopropyl alcohol, n-propyl alcohol, n-butyl alcohol, n-pentyl alcohol, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, toluene, hexane, heptane, cyclohexane, acetone, methyl ethyl ketone, diethyl ether, dioxane, tetrahydrofuran, ethyl acetate, and butyl acetate.

[0028] These solvents may be used alone or in combination of two or more. Among these, methyl alcohol, ethyl alcohol, isopropyl alcohol, toluene, ethyl acetate, methyl ethyl ketone, and water are preferred from the viewpoint of properties. From the environmental viewpoint, methyl alcohol, ethyl alcohol, isopropyl alcohol, and water are preferred.

[0029] The overcoat layer 24 can be provided by applying a coating liquid containing the second polyolefin and a solvent onto the vapor deposition layer 23 and drying it. The average particle size of the second polyolefin in the coating liquid is not particularly limited, but specifically may be 1 μm or less, 0.7 μm or less, or 0.5 μm or less. The first polyolefin and the second polyolefin contained in the anchor coat layer 22 and the overcoat layer 24, respectively, may be the same or different, but considering ease of production, it is preferable that they are the same.

[0030] [Adhesion primer layer 30] The adhesive primer 30 is provided for the purpose of ensuring sufficient adhesion with various laminating adhesives, such as isocyanate-curing urethane resins and modified vinyl acetate resin emulsions, which are used when laminating onto the surface of various substrates. As materials for the adhesive primer layer 30, various primer agents such as ester-based resins, urethane-based resins, acrylic-based resins, polycarbonate-based resins, vinyl chloride-vinyl acetate copolymers, polyvinyl butyral-based resins, and nitrocellulose-based resins are known, and one that matches the type of laminating adhesive is selected from these and used. For example, when a modified vinyl acetate resin emulsion adhesive is used as the laminating adhesive, good adhesion can be obtained with a urethane adhesive primer.

[0031] Furthermore, adding an inorganic fine powder such as silica to the adhesive moisture-proof layer 20 roughens the surface of the adhesive primer layer 30, preventing blocking when the moisture-proof sheet is rolled up and stored, and also improving adhesion to the laminating adhesive through its anchoring effect. The adhesive primer layer 30 can be formed by using an adhesive composition, either alone or in combination, and then by using a suitable application method such as roll coating or gravure printing.

[0032] [Method of manufacturing moisture-proof paper 10] The moisture-proof paper 10 has the above-mentioned configuration and is manufactured by the following method. First, a coating liquid containing a salt of a carboxyl group is applied onto the surface of the paper substrate 21 using, for example, a bar coater, and then dried in an oven to form an anchor coat layer 22 . The paper substrate 21 is, for example, 50 g / m 2 The paper used is reinforced paper (manufactured by Tenma Special Paper Co., Ltd.). As the coating liquid, for example, "trade name: Chemipearl S100, ionomer type, particle size: <0.1 μm, solvent: water, IPA, manufactured by Mitsui Chemicals" is used.

[0033] The anchor coat layer 22 has a thickness of, for example, 3 μm. Secondly, aluminum is vapor deposited on the anchor coat layer 22 to form a vapor-deposited layer 23 . The thickness of the deposition layer 23 is, for example, 50 nm. Third, a solution containing a salt of a carboxyl group is applied onto the vapor deposition layer 23 using, for example, a bar coater, and dried in an oven to form an overcoat layer 24, thereby obtaining a gas barrier laminate (water vapor barrier excluding oxygen barrier). The solution containing a salt of a carboxyl group is, for example, "trade name: Chemipearl S100, ionomer type, particle size: <0.1 μm, solvent: water, IPA, manufactured by Mitsui Chemicals." The overcoat layer 24 has a thickness of, for example, 3 μm. The moisture-proof paper 10 is manufactured by the above-described manufacturing method.

[0034] (Example of use of board substrate 50) An example of a wooden door or other fitting, or a decorative board used for such fittings, will be described using Figure 3. A decorative sheet 40 is attached to one side of a board substrate 50 via an adhesive, and an adhesive primer layer 30 for moisture-proof paper 10 is attached to the opposite side via an adhesive. This can prevent warping of the board substrate. Although the adhesive primer layer 30 is used for bonding, the overcoat layer 24 may be directly bonded.

[0035] (Features and Effects of the Embodiments Based on the Present Invention) The features of the embodiment of the present invention are as follows. (First feature) The first feature is that the moisture-proof paper 10 includes a moisture-proof layer 20 having, on a paper substrate 21, an anchor coat layer 22 containing a first polyolefin having at least one selected from a carboxyl group, a salt of a carboxyl group, a carboxylic anhydride group, and a carboxylic acid ester, a vapor-deposited layer 23, and an overcoat layer 24 containing a second polyolefin having at least one selected from a carboxyl group, a salt of a carboxyl group, a carboxylic anhydride group, and a carboxylic acid ester, in this order.

[0036] (Effect of the first feature) According to the first characteristic, the moisture permeability (JIS Z 0208) is 3.0 g / m 2Since the moisture-proofing time is 24 hours or less, the moisture-proof paper 10 has significantly better moisture-proofing performance than conventional moisture-proof sheets made of synthetic resins such as vinyl chloride, polyethylene, or polypropylene, or paper / polyethylene / paper, and also contributes to reducing the amount of plastic material used.

[0037] Furthermore, the anchor coat layer 22 has excellent flexibility, which can suppress cracking of the vapor deposition layer 23 and improve the adhesion between the anchor coat layer 22 and the vapor deposition layer 23 . Furthermore, by including the polyolefin, it is possible to form a dense film due to the crystallinity of the polyolefin.Polyolefin has few polar groups, so it has excellent water vapor barrier properties. Furthermore, the overcoat layer 24 has excellent flexibility and excellent adhesion to the vapor deposition layer 23. In addition, by including the second polyolefin described above, it is possible to form a dense film due to the crystallinity of the polyolefin. Furthermore, polyolefin has excellent water vapor barrier properties due to its small number of polar groups. On the other hand, the first polyolefin and the second polyolefin may be the same or different, but using the same type of polyolefin can facilitate production, etc.

[0038] (Second feature) The second feature is that the thickness of the anchor coat layer 22 is 1 μm or more. (Effect of the second feature) According to the second feature, if the thickness of the anchor coat layer 22 is 1 μm or more, the irregularities of the paper substrate 21 can be efficiently filled, and the vapor deposition layer 23 can be laminated evenly.

[0039] (Third feature) The third feature is that an adhesive primer layer 30 is provided on the exposed surface of the overcoat layer 24 . (Effect of the third feature) According to the third feature, sufficient adhesion can be ensured with various laminating adhesives, such as isocyanate-curing urethane resins and modified vinyl acetate resin emulsions, which are used when laminating onto the surface of various substrates.

[0040] (Fourth feature) The fourth feature is that the paper base material 21 is a reinforced inter-paper paper. (Effect of the fourth feature) The use of inter-layer reinforced paper can prevent the paper layers from peeling from between the layers when used for a long period of time or when an external force is applied unavoidably. (5th feature) A fifth feature is that the thickness of the anchor coat layer 22 is 20 μm or less. (Effect of the fifth feature) According to the fifth feature, if the thickness of the anchor coat layer 22 is 20 μm or less, the vapor deposition layer 23 can be laminated uniformly while keeping costs down.

[0041] (6th feature) The sixth feature is that inorganic fine powder is added to the adhesive primer. (Effect of the 6th feature) According to the sixth feature, adding an inorganic fine powder such as silica to the adhesive moisture-proof layer 20 roughens the surface of the adhesive primer layer 30, thereby preventing blocking when the moisture-proof sheet is rolled up and stored, and also improving adhesion to the laminating adhesive through its anchoring effect. Furthermore, these adhesive primer layers 30 can be formed by using an adhesive composition, either alone or in combination, and then applied using a suitable application method such as roll coating or gravure printing.

[0042] (7th feature) The seventh feature is that the basis weight of the reinforced inter-sheet paper is 20 g / m 2 More than 200g / m 2 The following is the result. (Effect of the seventh feature) According to the seventh characteristic point, the basis weight of the reinforced inter-sheet paper is 20 g / m 2If it is less than 200g / m, it will be too flexible and wrinkles will easily occur during processing. 2 If it exceeds this value, peeling from the paper layer is likely to occur.

[0043] (8th feature) An eighth feature is that the thickness of the overcoat layer 24 is not less than 0.05 μm and not more than 20 μm. (Effect of the 8th feature) According to the eighth feature, if the thickness of the overcoat layer 24 is 0.05 μm or more, the overcoat layer 24 can fully function as the heat seal layer described above. If the thickness of the overcoat layer 24 is 20 μm or less, the overcoat layer 24 can fully exhibit adhesion to the vapor deposition layer 23 and barrier properties while keeping costs down.

[0044] (9th feature) A ninth feature is that the thickness of the deposition layer 23 is 10 nm or more and 300 nm or less. (Effect of the 9th feature point) According to the ninth feature, by making the thickness of the vapor deposition layer 23 10 nm or more, it is easy to ensure sufficient continuity of the vapor deposition layer 23, and by making the thickness 300 nm or less, it is possible to sufficiently suppress the occurrence of curling and cracking, and it is easy to achieve sufficient gas barrier performance and flexibility. (10th feature) The tenth feature is that the basis weight of the paper substrate 21 is 20 to 200 g / m 2 is. (Effect of the 10th feature point) According to the tenth characteristic, 20 g / m 2 If it is less than 200g / m, it will be too flexible and wrinkles will easily occur during processing. 2 If it exceeds this value, peeling from the paper layer is likely to occur. [Example]

[0045] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to the following examples in any way. The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0046] (Example) 50g / m as paper base material 2 A coating solution containing a carboxyl group salt (product name: Chemipearl S100, ionomer type, particle size: <0.1 μm, solvent: water, IPA, manufactured by Mitsui Chemicals) was applied to the surface of the reinforced paper (manufactured by Tenma Special Paper Co., Ltd.) using a bar coater, and then dried in an oven to form an anchor coat layer. The thickness of the anchor coat layer was 3 μm. Subsequently, aluminum was vapor-deposited on the anchor coat layer. The thickness of the vapor-deposited layer was 50 nm. A solution containing a carboxyl salt (product name: Chemipearl S100, ionomer-based, particle size: <0.1 μm, solvent: water, IPA, manufactured by Mitsui Chemicals) was then applied onto the vapor-deposited layer using a bar coater and dried in an oven to form an overcoat layer, yielding a gas barrier laminate. The overcoat layer had a thickness of 3 μm.

[0047] (Comparative Example) As a conventional moisture-proof sheet, a 30g / m2 sheet with corona treatment on one side was used. 2 The corona-treated surfaces of the above-mentioned reinforced inter-paper sheets (manufactured by Tenma Special Paper Co., Ltd.) were sandwich-laminated with 50 μm of molten polyethylene resin extruded from a T-die extruder to produce a moisture-proof sheet (reinforced inter-paper sheets / polyethylene / reinforced inter-paper sheets). (evaluation) The moisture permeability of the moisture-proof sheets of the Examples and Comparative Examples prepared above was calculated in accordance with JIS Z 0208, and the moisture permeabilities were compared. The results are shown in Table 1.

[0048] [Table 1]

[0049] As is clear from the results in Table 1, the moisture-proof sheets of the examples had significantly lower moisture permeability than the moisture-proof sheets of the comparative examples. The moisture-proof sheet of the present invention, which has the moisture-proof layer 20, has been found to have improved moisture permeability, and is expected to have the effect of reducing warping of the decorative panel caused by moisture absorption and release due to changes in indoor temperature and humidity compared to conventional products. This enabled us to verify that it is possible to provide a moisture-proof paper for the back side of decorative panels that can prevent warping even when used in places where there is a large difference in temperature and humidity environments on both sides, which is the objective of this invention. [Explanation of symbols]

[0050] 10 Moisture-proof paper backing for decorative panels 20 Moisture barrier 21 Paper base material 22 Anchor coat layer 23 Deposited layer 24 Overcoat layer 30 Adhesive primer layer 40 decorative sheets 50 Plate base material

Claims

1. The moisture-proof layer includes, on a paper substrate, an anchor coat layer containing a first polyolefin having at least one selected from a carboxyl group, a salt of a carboxyl group, a carboxylic anhydride group, and a carboxylic acid ester, a vapor-deposited layer, and an overcoat layer containing a second polyolefin having at least one selected from a carboxyl group, a salt of a carboxyl group, a carboxylic anhydride group, and a carboxylic acid ester, in this order; the thickness of the vapor deposition layer is in the range of 10 nm or more and 300 nm or less; The vapor-deposited layer is in contact with the anchor coat layer and the overcoat layer, and the moisture-proof backside paper for decorative sheets is characterized in that the vapor-deposited layer is in contact with the anchor coat layer and the overcoat layer.

2. The moisture-proof backside paper for decorative sheets according to claim 1 , wherein the vapor-deposited layer contains aluminum.

3. The thickness of the anchor coat layer is in the range of 1 μm or more and 10 μm or less, 3. The moisture-proof backside paper for decorative sheets according to claim 1, wherein the thickness of the overcoat layer is in the range of 0.05 μm to 10 μm.

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