Reverse face moisture-proof paper for decorative board

Abstract

To provide reverse face moisture-proof paper for a decorative board capable of preventing warpage of the decorative board by providing high moisture proof performance even when being used in a place with a large difference in temperature and humidity environments between both sides, and considered for environments by reducing a used amount of plastics.SOLUTION: Reverse face moisture-proof paper 100 for a decorative board according to the present embodiment includes a paper substrate 11, an anchor coat layer 12, a vapor-deposited layer 13, and an overcoat layer 14 in this order, where the anchor coat layer 12 and the overcoat layer 14 are directly in contact with the vapor deposit layer 13, and a softening temperature of the anchor coat layer 12 measured on a cross section in a thickness direction of the reverse face moisture-proof paper 100 for the decorative board by a local thermal analysis method is 180°C or higher.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a moisture-proof paper used for a decorative board used for an indoor door panel or the like, and is used by being bonded to the back surface of the decorative board in order to prevent warping of the decorative board caused by moisture absorption and desorption due to changes in temperature and humidity indoors.

Background Art

[0002] Conventionally, as a decorative board used for applications such as indoor door panels, a decorative sheet printed with a solid printing layer for providing concealment or a pattern layer for improving design on the surface of a plywood, medium density fiberboard (MDF), veneer board, board material, or other multi-layered wood-based substrate is generally known. When the moisture content of the wood-based substrate is smaller than the equilibrium moisture content of the wood-based substrate under outside air conditions, the wood-based substrate absorbs moisture from the surface where the decorative sheet of the decorative board is not bonded, and the surface expands. When the moisture content is larger than the equilibrium moisture content of the wood-based substrate, moisture is released from the surface where the decorative sheet of the decorative board is not bonded, and shrinkage occurs. On the other hand, the surface where the decorative sheet is bonded hardly absorbs and releases moisture, so the decorative board is deformed (warped, dimensional change).

[0003] As a method for preventing this deformation, a method of applying a paint to the back surface of a decorative board with a decorative sheet bonded to the surface, a method of bonding a synthetic resin sheet such as vinyl chloride, polyethylene, or polypropylene, or a method of bonding a moisture-proof sheet made of paper / polyethylene / paper is known (for example, Patent Document 1).

[0004] Further, when higher moisture-proof properties are required, as a method for preventing deformation of the decorative board, a method of bonding a moisture-proof sheet provided with a vapor deposition layer on a synthetic resin substrate is known. In order to obtain high moisture-proof performance, since it is necessary to provide a vapor deposition layer on a smooth surface, a synthetic resin substrate is generally selected, and it is technically difficult to obtain high moisture-proof performance using a paper substrate. On the other hand, in recent years, due to the increasing environmental awareness triggered by issues such as marine plastic waste, the movement towards plastic reduction has been growing. From the perspective of reducing the usage amount of plastic materials, in various fields, the use of paper instead of plastic materials has been under consideration.

[0005] For example, Patent Document 2 below discloses a gas barrier laminate in which a barrier layer is laminated on paper, and a paper-made barrier material in which an anchor coat layer, a vapor deposition layer, and an overcoat layer are provided in this order on a paper substrate has been proposed.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] In conventional moisture-proof inner sheets, the moisture-proof property may be insufficient, and when used for a long time on doors, sliding doors, partitions, etc. where there is a large difference in the temperature and humidity environment on both sides, the degree of expansion and contraction on both sides is different, and warping may occur in the decorative board. Furthermore, in all cases, plastic materials are the main materials, and in terms of environmental load, reduction of their usage amount is required.

[0008] In recent years, in consideration of the environment, the development of gas barrier materials based on paper without using synthetic resin films, etc. has been progressing. However, when stretching wrinkles or using a crimping method such as ironing during the handling of such materials, there is a problem that cracks occur in the barrier layer and the gas barrier property deteriorates. In Patent Document 2, paragraph 0021 states that "the anchor coat layer contains a first polyolefin having a polar group. Such an anchor coat layer is excellent in flexibility, can suppress cracking of the vapor deposition layer after bending, and can improve the adhesion between the anchor coat layer and the vapor deposition layer." An attempt has been made to suppress cracking of the vapor deposition layer after bending. However, in Patent Document 2, when an inorganic oxide is vapor-deposited as the vapor deposition film, no consideration has been given to the fact that the barrier property is less stable than when a metal is vapor-deposited.

[0009] The present invention has been made to solve this problem, and by having high moisture-proof performance, it is possible to prevent warping of the decorative board even when used in a place where there is a large difference in the temperature and humidity environment on both sides, and by reducing the amount of plastic used, it is an object of the present invention to provide a moisture-proof paper for the back surface of a decorative board that takes environmental considerations into account.

Means for Solving the Problem

[0010] In order to solve the above problems, one of the typical moisture-proof papers for the back surface of a decorative board according to the present disclosure is a moisture-proof paper for the back surface of a decorative board comprising a paper base material, an anchor coat layer, a silica vapor deposition layer, and an overcoat layer in this order, wherein the anchor coat layer and the overcoat layer are in direct contact with the silica vapor deposition layer, and in the cross-section in the thickness direction of the moisture-proof paper for the back surface of the decorative board, the softening point of the anchor coat layer measured by local thermal analysis is 180°C or higher.

Effect of the Invention

[0011] According to the present disclosure, it is possible to provide a gas barrier laminate using paper and inorganic oxide vapor deposition (silica vapor deposition), which has a high paper component ratio and a stable and excellent gas barrier property, and a moisture-proof paper for the back surface of a decorative board containing the same. Furthermore, according to the moisture-proof paper for the back surface of a decorative board according to one aspect of the present invention, it is possible to provide a moisture-proof paper for the back surface of a decorative board that contributes to reducing the amount of plastic material used. That is, according to the moisture-proof paper for the back surface of the decorative board according to one aspect of the present invention, by having high moisture-proof performance, even when used in a place where there is a large difference in the temperature and humidity environment on both sides, warping of the decorative board can be prevented, and by reducing the amount of plastic used, a moisture-proof paper for the back surface of the decorative board that takes environmental considerations into account can be provided. Problems, configurations, and effects other than those described above will be clarified by the description in the following embodiments for carrying out the invention.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Embodiments for Carrying Out the Invention

[0013] Hereinafter, embodiments for carrying out the present invention will be described with reference to FIGS. 1 and 2. Here, the drawings are schematic, and the relationship between the thickness and the planar dimensions, the ratio of the thickness of each layer, etc. are different from the actual ones. Further, the following embodiments illustrate configurations for embodying the technical idea of the present invention, and the technical idea of the present invention does not specify the materials, shapes, structures, etc. of the constituent parts as the following. The technical idea of the present invention is within the technical scope defined by the claims described in the claims, and various modifications can be made.

[0014] <Moisture-proof paper 100 for the back surface of the decorative board> FIG. 1 is a schematic cross-sectional view showing the configuration of the moisture-proof paper 100 for the back surface of the decorative board according to the present embodiment. The moisture-proof paper 100 for the back surface of the decorative board according to the present embodiment is a moisture-proof paper that is used, for example, by being bonded to the back surface of a decorative board used for an indoor door panel or the like, although not shown. In the present embodiment, this moisture-proof paper 100 for the back surface of the decorative board is hereinafter also simply referred to as "moisture-proof paper 100". The moisture-proof paper 100 is used to prevent the warping that occurs in the decorative board due to moisture absorption and desorption caused by changes in temperature and humidity indoors.

[0015] As shown in FIG. 1, the moisture-proof paper 100 is roughly divided into two layers: a paper base material 11 and a moisture-proof layer 10 laminated on one surface (for example, the surface) of the paper base material 11. The moisture-proof layer 10 includes an anchor coat layer 12, a vapor deposition layer (silica vapor deposition layer) 13, and an overcoat layer 14 in this order. Further, the anchor coat layer 12 and the overcoat layer 14 may be in direct contact with the vapor deposition layer (silica vapor deposition layer) 13, respectively. The anchor coat layer 12 contains at least one resin selected from the group consisting of, for example, acrylic resin, epoxy resin, acrylic urethane resin, polyester-based polyurethane resin, and polyether-based polyurethane resin. By using the backside moisture-proof paper 100 for decorative boards, it is possible to provide a moisture-proof paper that addresses the issues of plastic reduction and marine waste, has a high ratio of paper components, and stably exhibits excellent water vapor barrier properties.

[0016] [Moisture permeability of the moisture-proof paper 100] The moisture permeability of the moisture-proof paper 100 is preferably 5 g / m 2 ·24 h or less, and more preferably 3 g / m 2 ·24 h or less. If the moisture permeability is below the above-mentioned values, it is generally evaluated as having excellent moisture-proof performance. The lower limit of the moisture permeability of the moisture-proof paper 100 is 0 g / m 2 ·24 h, but if it is below the upper limit of the moisture permeability of the above-mentioned moisture-proof paper 100, for example, a moisture permeability of 0.1 g / m 2 ·24 h or more is also acceptable, or a moisture permeability of 0.3 g / m 2 ·24 h or more is also acceptable, or a moisture permeability of 0.5 g / m 2 ·24 h or more is also acceptable.

[0017] [Paper base material] The paper base material 11 is not particularly limited and may be appropriately selected according to the application of the backside moisture-proof paper 100 for decorative boards to be applied. Specific examples of the paper base material 11 include tissue paper, high-quality paper, art paper, cast-coated paper, kraft paper, titanium paper, linter paper, cardboard, gypsum board paper, high-quality paper, coated paper, sulfuric acid paper, glassine paper, parchment paper, paraffin paper, Japanese paper, and the like. Preferably, tissue paper (so-called paper-strengthened paper) obtained by co-papering a synthetic resin with a paper component (for example, cellulose fiber) to strengthen the inter-paper strength, or paper impregnated with latex or synthetic resin is preferably used.

[0018] The basis weight of the paper base material 11 is not particularly limited. However, if the basis weight of the paper base material 11 is less than 20 g / m 2 it is too soft and wrinkles are likely to occur during processing. Also, if the basis weight of the paper base material 11 exceeds 200 g / m 2 peeling from the paper layer is likely to occur. Therefore, the basis weight of the paper base material 11 is preferably in the range of 20 g / m 2 or more and 200 g / m 2 or less, more preferably in the range of 20 g / m 2 or more and 100 g / m 2 or less, and even more preferably in the range of 20 g / m 2 or more and 50 g / m 2 or less. Also, for these paper base materials 11, surface treatments such as corona treatment, plasma treatment, and frame treatment may be performed on the surface thereof as necessary.

[0019] A coating layer (not shown) may be provided on the side of the paper base material 11 that contacts the anchor coat layer 12 described later. By providing the coating layer, it is possible to prevent the resin constituting the anchor coat layer 12 from penetrating into the paper base material 11, and it can also serve as a caulking to fill the unevenness of the paper base material 11. Therefore, for the paper base material 11 provided with a coating layer on the surface, the anchor coat layer 12 can be formed uniformly without defects such as coating unevenness. The coating layer may contain, as a binder resin, for example, various copolymers such as styrene-butadiene-based, styrene-acrylic-based, and ethylene-vinyl acetate-based copolymers, polyvinyl alcohol-based resins, cellulose-based resins, paraffin (WAX), and the like. Further, the coating layer may contain, as a filler, for example, clay, kaolin, calcium carbonate, talc, mica, and the like.

[0020] The thickness of the coating layer (for example, a clay coating layer) is not particularly limited, but is preferably in the range of 1 μm or more and 10 μm or less, and more preferably in the range of 3 μm or more and 8 μm or less. Further, the thickness of the coating layer is preferably in the range of 5% or more and 80% or less of the total thickness of the paper base material 11, more preferably in the range of 10% or more and 50% or less, and even more preferably in the range of 20% or more and 30% or less.

[0021] The mass of the paper base material 11, more specifically, the mass of the paper component contained in the paper base material 11, 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 total mass of the back moisture-proof paper 100 for decorative boards. If the mass of the paper base material 11 is 50% by mass or more based on the total mass of the back moisture-proof paper 100 for decorative boards, the amount of the plastic material used can be sufficiently reduced, and it can be stated that the back moisture-proof paper 100 for decorative boards is made of paper (displaying the fact that it is "made of paper"), and it has excellent recyclability.

[0022] <Anchor coating layer> The anchor coating layer 12 is a layer provided on the surface of the paper base material 11 and may contain a resin having at least one kind of polar group, or may contain a polyolefin having at least one kind of polar group. Further, the anchor coating layer 12 may contain a polyvinyl alcohol-based resin. The total content of the resin having a polar group (for example, polyolefin having a polar group) in the anchor coat layer 12 is, for example, 50% by mass or more, more preferably 70% by mass or more, still more preferably 90% by mass or more, and most preferably 100% by mass with respect to the mass of the entire anchor coat layer 12.

[0023] The polyolefin having a polar group may have at least one selected from a carboxyl group, a salt of a carboxyl group, a carboxylic anhydride group, and a carboxylic acid ester. For example, unsaturated carboxylic acids (unsaturated compounds having a carboxyl group such as acrylic acid, methacrylic acid, maleic anhydride, etc.) or unsaturated carboxylic acid esters may be copolymerized with ethylene or propylene, or a salt obtained by neutralizing a carboxylic acid with a basic compound may be used. Alternatively, those copolymerized with vinyl acetate, epoxy compounds, chlorine compounds, urethane compounds, polyamide compounds, etc. may also be used. Specific examples include copolymers of acrylic acid ester and maleic anhydride, ethylene-vinyl acetate copolymers, ethylene-glycidyl methacrylate copolymers, and the like.

[0024] The polyvinyl alcohol-based resin is, for example, a completely saponified polyvinyl alcohol resin, a partially saponified polyvinyl alcohol resin, a modified polyvinyl alcohol resin, or an ethylene-vinyl alcohol copolymer resin. Further, the degree of polymerization of the polyvinyl alcohol-based resin is preferably 300 or more and 1700 or less. If the degree of polymerization is 300 or more, the gas barrier property and bending resistance of the back moisture-proof paper 100 for decorative boards will be good. If the degree of polymerization is 1700 or less, the viscosity of the coating liquid of the polyvinyl alcohol-based resin described later will be low, and the coatability will be good.

[0025] The anchor coat layer 12 may contain other components in addition to the polyolefin having the polar group and the polyvinyl alcohol-based resin. Examples of the other components include resins such as polyolefins other than the polyolefin having the polar group, polyacrylics, polyesters, polyurethanes, polycarbonates, polyureas, melamines, phenols, polyethyleneimines, polylactic acids, polyamides, polyimides, starches and their derivatives, and cellulose derivatives, as well as additives such as silane coupling agents, organic titanates, glycerin, glycols, casein, and waxes.

[0026] The anchor coat layer 12 is provided to improve the adhesion to the paper substrate 11 and to improve the gas barrier property of the back moisture-proof paper 100 for decorative boards. By including a resin having at least one kind of polar group in the anchor coat layer 12, the back moisture-proof paper 100 for decorative boards has excellent gas barrier properties. By including a polyvinyl alcohol-based resin, it is further excellent in water vapor barrier properties and oxygen barrier properties. By including a polyolefin, a dense film can be formed due to the crystallinity of the polyolefin, and water vapor barrier properties are exhibited.

[0027] The lower limit of the thickness of the anchor coat layer 12 is, for example, 1 μm or more, more preferably 2 μm or more. The upper limit is, for example, 20 μm or less, more preferably 10 μm or less, and even more preferably 5 μm or less. If the thickness of the anchor coat layer 12 is 1 μm or more, the vapor deposition layer 13 can be laminated uniformly. The thicker the anchor coat layer 12, the more efficiently the unevenness of the paper substrate 11 can be filled, and the vapor deposition layer 13 can be laminated more uniformly. Also, if the thickness of the anchor coat layer 12 is 20 μm or less, each of the above layers can be laminated uniformly while suppressing costs.

[0028] The softening temperature measured by local thermal analysis in the anchor coat layer 12 is 180 °C or higher, more preferably 185 °C or higher, and even more preferably 190 °C or higher. The upper limit of the softening temperature is not particularly limited. If the softening temperature of the anchor coat layer 12 is 180°C or higher, a decrease in the density of the vapor deposition layer 13 can be suppressed. The higher the softening temperature, the more the heat of the vapor deposition material such as SiOx particles during vapor deposition can reduce the softening and elongation of the anchor coat layer 12, so that macro cracks generated in the vapor deposition layer (silica vapor deposition layer) 13 and a decrease in the density of the vapor deposition layer 13 can be further suppressed. Note that the softening temperature of the anchor coat layer 12 can be adjusted by adjusting the constituent materials of the anchor coat layer 12 and the ratio of the resin to be combined.

[0029] As a method for providing the anchor coat layer 12, for example, there is a method of applying a coating liquid containing the constituent materials and solvent of the anchor coat layer 12 described above onto the paper substrate 11 and drying it. Examples of the solvent contained in the coating liquid for forming the anchor coat layer 12 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. These solvents may be used alone or in combination of two or more. Among these, from the viewpoint of characteristics, methyl alcohol, ethyl alcohol, isopropyl alcohol, toluene, ethyl acetate, methyl ethyl ketone, and water are preferable. Also, from the viewpoint of the environment, methyl alcohol, ethyl alcohol, isopropyl alcohol, and water are preferable.

[0030] <Vapor deposition layer> The vapor deposition layer 13 is a layer formed by vapor depositing silica, which is an inorganic compound, and may contain silicon oxide (SiOx) or the like. The thickness of the vapor deposition layer 13 may be appropriately set according to the intended use. The lower limit is preferably 10 nm or more, more preferably 20 nm or more, and even more preferably 30 nm or more. The upper limit of the thickness of the vapor deposition layer 13 is preferably 100 nm or less, more preferably 80 nm or less. By setting the thickness of the vapor deposition layer 13 to 10 nm or more, it is easy to make the continuity of the vapor deposition layer 13 sufficient. By setting it to 100 nm or less, the occurrence of curl in the back moisture-proof paper for decorative boards and cracks in the vapor deposition layer can be sufficiently suppressed, and sufficient gas barrier performance and flexibility can be easily achieved.

[0031] The vapor deposition layer 13 is preferably formed by a vacuum film-forming means from the viewpoints of water vapor and oxygen gas barrier performance and film uniformity. Known methods such as vacuum evaporation, sputtering, and chemical vapor deposition (CVD) can be used as the film-forming means. However, the vacuum evaporation method is preferred because of its high film-forming speed and productivity. Among the vacuum evaporation methods, in particular, the film-forming means by electron beam heating is effective because the film-forming speed can be easily suppressed by the irradiation area, electron beam current, etc., and the temperature increase and decrease of the vapor deposition material can be performed in a short time.

[0032] <Overcoat layer> The overcoat layer 14 is provided on the surface of the vapor deposition layer 13 so as to be in contact with the vapor deposition layer 13. The overcoat layer 14 may contain, for example, a polyolefin having at least one kind of polar group. The polyolefin having a polar group may have, for example, at least one selected from a carboxyl group, a salt of a carboxyl group, a carboxylic anhydride group, and a carboxylic acid ester. Specifically, a copolymer of an acrylic acid ester and maleic anhydride, an ethylene-vinyl acetate copolymer, an ethylene-glycidyl methacrylate copolymer, etc. may be used.

[0033] By including the polyolefin having the polar group described above in the overcoat layer 14, the overcoat layer 14 is excellent in flexibility, can suppress cracking of the vapor deposition layer 13 after bending, and is excellent in adhesion to the vapor deposition layer 13. Further, by including the polyolefin having the polar group described above in the overcoat layer 14, a moisture-proof paper 100 for the back surface of a decorative board excellent in water vapor barrier properties can be obtained. The content of the polyolefin having a polar group in the overcoat layer 14 is, for example, 50% by mass or more, more preferably 70% by mass or more, still more preferably 90% by mass or more, and most preferably 100% by mass. The overcoat layer 14 may contain other components in addition to the polyolefin having the polar group. Examples of the other components include silane coupling agents, organic titanates, polyacrylics, polyesters, polyurethanes, polycarbonates, polyureas, polyamides, polyolefin-based emulsions, polyimides, melamines, phenols, and the like.

[0034] The lower limit of the thickness of the overcoat layer 14 is, for example, 2 μm or more, more preferably 3 μm or more. The upper limit of the thickness of the overcoat layer 14 is, for example, 10 μm or less, more preferably 8 μm or less, still more preferably 5 μm or less. Also, if the thickness of the overcoat layer 14 is 10 μm or less, the adhesion and barrier properties to the vapor deposition layer 13 can be sufficiently exhibited while suppressing costs. Further, if the thickness of the overcoat layer 14 is 2 μm or more, the continuity of the overcoat layer 14 can be easily made sufficient. The thickness of the overcoat layer 14 is preferably the same as the thickness of the anchor coat layer 12, but may be thinner or thicker than the thickness of the anchor coat layer 12.

[0035] As a method for providing the overcoat layer 14, for example, a coating liquid containing the above-described polyolefin and a solvent is applied onto the vapor deposition layer 13 and dried. Examples of the solvent contained in the coating liquid for forming the overcoat layer 14 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. These solvents may be used alone or in combination of two or more. Among these, from the viewpoint of characteristics, methyl alcohol, ethyl alcohol, isopropyl alcohol, toluene, ethyl acetate, methyl ethyl ketone, and water are preferable. From the viewpoint of the environment, methyl alcohol, ethyl alcohol, isopropyl alcohol, and water are preferable.

[0036] The polyolefins having polar groups contained in the anchor coat layer 12 and the overcoat layer 14 may be of the same type or different types, but considering ease of production and the like, it is preferable that they are of the same type. Further, the anchor coat layer 12 may be formed of a polyolefin having two or more polar groups, and the overcoat layer 14 may be formed of a polyolefin having one polar group. Alternatively, the anchor coat layer 12 may be formed of a polyolefin having one polar group, and the overcoat layer 14 may be formed of a polyolefin having two or more polar groups. Even when the anchor coat layer 12 and the overcoat layer 14 are formed of different polyolefins, the same effects as when they are formed of the same polyolefin can be obtained.

[0037] <Adhesive primer layer> Next, the primer layer 15 is used when laminating and adhering to the surface of various substrates to be adhered. For example, it is provided for the purpose of ensuring sufficient adhesiveness with various laminating adhesives such as isocyanate-curing urethane resin-based and modified vinyl acetate resin emulsion-based adhesives. As its material, various primer agents are known, 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. From these, one suitable for the type of laminating adhesive is selected and used. For example, when using a modified vinyl acetate resin emulsion-based adhesive as the laminating adhesive, good adhesion can be obtained with a urethane-based primer agent for adhesion.

[0038] In addition, if inorganic fine powder such as silica is added to the primer layer 15 for adhesion, the surface of the primer layer 15 for adhesion becomes roughened, so that blocking during winding and storage of the moisture-proof paper 100 can be prevented, and the adhesiveness with the laminating adhesive due to the anchoring effect can also be improved. Moreover, these primer layers 15 for adhesion can be made into an adhesive composition alone or in combination, and can be formed using appropriate coating means such as the roll coating method or the gravure printing method. Also, the surface roughness (Ra) of the primer layer 15 for adhesion is preferably in the range of 0.1 μm or more and 10 μm or less, more preferably in the range of 0.5 μm or more and 5 μm or less, and even more preferably in the range of 1 μm or more and 3 μm or less. If the surface roughness (Ra) of the primer layer 15 for adhesion is within the above numerical range, the adhesiveness between the primer layer 15 for adhesion and the laminating adhesive is improved due to the anchoring effect.

[0039] [Effects of this Embodiment] The moisture-proof paper 100 for the back surface of the decorative board according to this embodiment has the following effects. (1) The back moisture-proof paper 100 for decorative boards according to this embodiment includes a paper base material 11, an anchor coat layer 12, a vapor deposition layer 13, and an overcoat layer 14 in this order. The anchor coat layer 12 and the overcoat layer 14 are in direct contact with the vapor deposition layer 13. In the cross-section of the back moisture-proof paper 100 for decorative boards in the thickness direction, the softening temperature of the anchor coat layer 12 measured by local thermal analysis is 180°C or higher. With such a configuration, the moisture-proof performance is enhanced, warping of the decorative board can be prevented even when used in a place where there is a large difference in the temperature and humidity environment on both sides, and the amount of plastic used can be reduced.

[0040] (2) The back moisture-proof paper 100 for decorative boards according to this embodiment includes a paper base material 11, an anchor coat layer 12, a vapor deposition layer 13, and an overcoat layer 14 in this order. The anchor coat layer 12 contains at least one of an epoxy resin, an acrylic urethane resin, an acrylic resin, a polyester-based polyurethane resin, and a polyether-based polyurethane resin. With such a configuration, the moisture-proof performance is enhanced, warping of the decorative board can be prevented even when used in a place where there is a large difference in the temperature and humidity environment on both sides, and the amount of plastic used can be reduced.

[0041] (3) The overcoat layer 14 constituting the back moisture-proof paper 100 for decorative boards according to this embodiment may contain a polyolefin having at least one kind of polar group. With such a configuration, excellent flexibility can be imparted to the overcoat layer 14, so that cracking of the vapor deposition layer 13 after bending can be suppressed. As a result, excellent moisture permeability (water vapor barrier property) can be imparted to the back moisture-proof paper 100 for decorative boards. In addition, the adhesion between the overcoat layer 14 and the vapor deposition layer 13 can be improved.

[0042] (4) The thickness of the vapor deposition layer 13 constituting the back moisture-proof paper 100 for decorative boards according to this embodiment may be in the range of 10 nm or more and 100 nm or less. With such a configuration, the continuity of the vapor deposition layer 13 becomes sufficient, and the occurrence of curling in the back moisture-proof paper 100 for decorative boards and cracks in the vapor deposition layer 13 can be sufficiently suppressed, achieving sufficient gas barrier performance and flexibility.

[0043] (5) The thickness of the overcoat layer 14 constituting the back moisture-proof paper 100 for decorative boards according to the present embodiment may be in the range of 2 μm or more and 10 μm or less. With such a configuration, the continuity of the overcoat layer 14 becomes sufficient, and the adhesion and gas barrier performance between the overcoat layer 14 and the vapor deposition layer 13 can be sufficiently exhibited.

[0044] (6) The mass of the paper component contained in the paper base material 11 constituting the back moisture-proof paper 100 for decorative boards according to the present embodiment may be 50% by mass or more based on the mass of the entire back moisture-proof paper 100 for decorative boards. With such a configuration, the amount of plastic material used can be sufficiently reduced.

[0045] (7) The back moisture-proof paper 100 for decorative boards according to the present embodiment may be provided with an adhesive primer layer 15 on the front surface of the overcoat layer 14. With such a configuration, sufficient adhesiveness between the back moisture-proof paper 100 for decorative boards and the laminating adhesive can be ensured.

[0046] (8) The paper base material 11 constituting the back moisture-proof paper 100 for decorative boards according to the present embodiment may be an inter-paper reinforced paper. With such a configuration, the mechanical strength of the base material 11 can be increased.

[0047] [Examples] Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples.

[0048] <Production of moisture-proof paper> (Example 1) Paper (clay-coated paper, basis weight of paper: 50 g / m 2, on the surface of the clay coat layer (thickness: 5 μm), a solution of a polyepoxy resin was coated with a bar coater and dried in an oven to form an anchor coat layer with a thickness of 3 μm. The solution was prepared by mixing 24 parts by mass of Maxceleb C93AT (manufactured by Mitsubishi Gas Chemical Company) and 2 parts by mass of Maxceleb M-100 (manufactured by Mitsubishi Gas Chemical Company) with 17 parts by mass of a mixed solvent of methanol and ethyl acetate in a 1:1 (mass ratio). Subsequently, SiOx was deposited with a thickness of 30 nm on the anchor coat layer to form a silica deposited layer. On top of that, an aqueous dispersion of a polyolefin containing a salt of a carboxyl group (polar group-containing polyolefin) was coated with a bar coater and dried in an oven to form an overcoat layer with a thickness of 3 μm. Thereby, the moisture-proof paper according to Example 1 was obtained.

[0049] (Example 2) As the anchor coat layer, a urethane-cured acrylic resin (acrylic urethane resin), which is a cured product of an acrylic polyol and a polyisocyanate, was coated with a thickness of 1 μm, and the moisture-proof paper according to Example 2 was obtained by the same operation as in Example 1. (Example 3) As the anchor coat layer, a urethane-cured acrylic resin (acrylic urethane-based resin), which is a cured product of an acrylic polyol and a polyisocyanate, was coated with a thickness of 3 μm, and the moisture-proof paper according to Example 3 was obtained by the same operation as in Example 1.

[0050] (Example 4) The moisture-proof paper according to Example 4 was obtained by the same operation as in Example 1, except that the thickness of the silica deposited layer was 10 nm. (Example 5) The moisture-proof paper according to Example 5 was obtained by the same operation as in Example 1, except that the thickness of the silica deposited layer was 100 nm.

[0051] (Example 6) The moisture-proof paper according to Example 6 was obtained by the same operation as in Example 1, except that the thickness of the silica deposited layer was 10 nm and the thickness of the overcoat layer was 2 μm. (Example 7) A moisture-proof paper according to Example 7 was obtained by the same operation as in Example 1, except that the thickness of the silica vapor deposition layer was 10 nm and the thickness of the overcoat layer was 10 μm.

[0052] (Comparative Example 1) A coating solution in which a polyvinyl alcohol resin (PVA resin) with a saponification degree of 98% and a polymerization degree of 500 was dissolved in a solvent of water / IPA = 8 / 2 (mass ratio) was coated on the clay-coated surface of the paper with a bar coater and dried in an oven to obtain an anchor coat layer with a thickness of 3 μm. The silica vapor deposition layer and the overcoat layer were formed into a moisture-proof paper according to Comparative Example 1 by the same operation as in Example 1. (Comparative Example 2) A moisture-proof paper according to Comparative Example 2 was obtained by the same operation as in Comparative Example 1, except that the thickness of the anchor coat layer was 6 μm.

[0053] (Comparative Example 3) A moisture-proof paper according to Comparative Example 3 was obtained by the same operation as in Comparative Example 1, except that the constituent resin of the anchor coat layer was a polyolefin containing a carboxyl group salt (polar group-containing polyolefin). (Comparative Example 4) A moisture-proof paper according to Comparative Example 4 was obtained by the same operation as in Comparative Example 1, except that the constituent resin of the anchor coat layer was a polyolefin containing a carboxyl group salt (polar group-containing polyolefin) and its thickness was 6 μm.

[0054] (Measurement of local thermal analysis) [Measurement of softening temperature] The softening temperature of the resin layer (anchor coat layer) was measured by the method shown below. The sample (the moisture-proof paper according to each example and each comparative example) was cut into a strip shape with a bottom of 1.0 mm × a height of 5.0 mm with scissors, embedded with a photocurable resin, and cured with a halogen lamp KTX-100R. D-800 manufactured by Toagosei Co., Ltd. was used as the photocurable resin. The test piece after photocuring was fixed with an insert for an AFM sample holder, and the cross-section of the film (sample) was cut with a glass knife at room temperature (25°C).

[0055] Thereafter, at room temperature, final cross-section cutting was carried out with a diamond knife at a cutting speed of 2.0 mm / s and a cutting film thickness of 200 nm, and the cutting was terminated when a mirror surface was obtained. As the cross-section cutting device, an ultramicrotome (Leica EM UC7) and a cryo system (Leica EM FC7) were used. Also, the cutting direction of the knife was perpendicular to the film thickness direction of the layer (sample). The cross-sectioned test piece was fixed with an insert for an AFM sample holder and used for measuring the softening temperature. The atomic force microscope (AFM) used for measuring the softening temperature was an MFP-3D-SA manufactured by Oxford Instruments Co., Ltd., the local thermal analysis option was a Zterm system, and the cantilever was an AN2-200 manufactured by Anasys Instruments with a spring constant of 0.5 to 3.5 N / m. Using these, the softening temperature and the shape were measured.

[0056] When the contact pressure of the cantilever (the change amount of the deflection amount of the cantilever) was 2.0 V, the voltage application acceleration (heating rate) was 0.5 V / second, and the maximum applied voltage was 7.1 V, and the measurement surface, that is, the cross-section of the anchor coat layer, was heated after Detrend correction, the measurement surface expanded and the height of the cantilever increased. Furthermore, when the measurement surface was heated, when the measurement surface softened and the height position of the cantilever decreased by 20 nm, the measurement was terminated. When the maximum applied voltage was reached without the height position decreasing by 20 nm from the change point, the maximum applied voltages at the time of Detrend correction and measurement were increased by 0.5 V and the measurement was carried out again. The applied voltage at the point where the height position of the cantilever in the vertical direction was the maximum was read as the voltage value (the applied voltage at the softening point) for calculating the softening temperature.

[0057] Next, in order to calculate the softening temperature of the anchor coat layer, a constitutive curve was created. As calibration samples, polycaprolactone (melting point: 60 °C), low-density polyethylene (LDPE, melting point 112 °C), polypropylene (PP, melting point: 166 °C), and polyethylene terephthalate (PET, melting point 250 °C) were used. The contact pressure of the cantilever (change in the amount of deflection of the cantilever) was set to 2.0 V, and the voltage application acceleration (heating rate) was set to 0.5 V / second. The measurement position of the calibration sample was changed and measured 10 times, and a calibration curve was created by approximating the average value of the applied voltage at the softening point and the melting point with a cubic function by the least squares method. At this time, an error of ±10 °C was considered as the softening temperature. Using the constitutive curve of the applied voltage and the melting point (melting peak temperature), the applied voltage at the softening point of the resin layer (anchor coat layer) was converted to temperature, and this was taken as the softening temperature in this example. The results thus obtained are shown in Tables 1 to 3.

[0058] <Evaluation> For the moisture-proof paper (moisture-proof sheet) of each of the examples and comparative examples prepared above, the moisture permeability (water vapor transmission rate) was calculated in accordance with JIS Z 0208, and the moisture permeabilities were compared. The results are shown in Tables 1 to 3.

[0059]

Table 1

[0060]

Table 2

[0061]

Table 3

[0062] Note that the unit of the moisture permeability shown in each table is "g / m 2 ·24 hr". Also, in this example, the moisture permeability of the moisture-proof paper (moisture-proof sheet) is 5.0 g / m 2· If it is less than 24 hours, it is considered "qualified" because it can prevent the warping of the decorative board caused by moisture absorption and desorption due to changes in temperature and humidity in the room when actually used as moisture-proof paper (moisture-proof sheet). On the other hand, the moisture permeability of the moisture-proof paper (moisture-proof sheet) is 5.0 g / m 2 · If it exceeds 24 hours, it is considered "unqualified" because warping may occur in the decorative board due to moisture absorption and desorption caused by changes in temperature and humidity in the room when actually used as moisture-proof paper (moisture-proof sheet).

[0063] As is clear from the results in Tables 1 to 3, the back moisture-proof paper for decorative boards in each example had a lower moisture permeability (water vapor transmission rate) compared to the back moisture-proof paper for decorative boards in each comparative example. By providing a moisture-proof layer with a vapor deposition layer, the moisture-proof paper in each example showed an improvement in the performance of moisture permeability (water vapor transmission rate), and it was expected to have the effect of reducing the warping of the decorative board caused by moisture absorption and desorption due to changes in temperature and humidity in the room compared to conventional products, as well as the effect of reducing the amount of plastic material used. Thus, it was verified that it is possible to provide a back moisture-proof paper for decorative boards that can prevent the warping of the decorative board even when used in a place where there is a large difference in the temperature and humidity environment on both sides, and that also takes environmental considerations into account, which is the problem of the present invention.

[0064] Also, for example, the present invention can take the following configurations. (1) A back moisture-proof paper for decorative boards comprising a paper base material, an anchor coat layer, a silica vapor deposition layer, and an overcoat layer in this order, wherein the anchor coat layer and the overcoat layer are in direct contact with the silica vapor deposition layer, and the softening temperature of the anchor coat layer measured by local thermal analysis in the cross-section in the thickness direction of the back moisture-proof paper for decorative boards is 180°C or higher. A back moisture-proof paper for decorative boards characterized by this. (2) A back moisture-proof paper for decorative boards comprising a paper base material, an anchor coat layer, a silica vapor deposition layer, and an overcoat layer in this order, The anchor coat layer has at least one of an epoxy resin, an acrylic urethane resin, an acrylic resin, a polyester-based polyurethane resin, and a polyether-based polyurethane resin, and the moisture-proof paper for the back surface of the decorative board is characterized by this. (3) The overcoat layer contains a polyolefin having at least one kind of polar group, and the moisture-proof paper for the back surface of the decorative board according to (1) or (2) above is characterized by this. (4) The thickness of the silica vapor deposition layer is in the range of 10 nm or more and 100 nm or less, and the moisture-proof paper for the back surface of the decorative board according to any one of (1) to (3) above is characterized by this. (5) The thickness of the overcoat layer is in the range of 2 μm or more and 10 μm or less, and the moisture-proof paper for the back surface of the decorative board according to any one of (1) to (4) above is characterized by this. (6) The mass of the paper component contained in the paper base material is 50% by mass or more based on the mass of the entire moisture-proof paper for the back surface of the decorative board, and the moisture-proof paper for the back surface of the decorative board according to any one of (1) to (5) above is characterized by this. (7) An adhesive primer layer is provided on the surface of the overcoat layer, and the moisture-proof paper for the back surface of the decorative board according to any one of (1) to (6) above is characterized by this. (8) The paper base material is an inter-paper reinforced paper, and the moisture-proof paper for the back surface of the decorative board according to any one of (1) to (7) above is characterized by this.

Explanation of symbols

[0065] 10: Moisture-proof layer 11: Paper base material 12: Anchor coat layer 13: Silica vapor deposition layer (vapor deposition layer) 14: Overcoat layer 15: Primer layer (adhesive primer layer) 100: Moisture-proof paper for the back surface of the decorative board (moisture-proof paper)

Claims

1. A moisture-proof paper for the back surface of a decorative board, comprising a paper substrate, an anchor coat layer, a silica vapor deposition layer, and an overcoat layer in this order, wherein the anchor coat layer and the overcoat layer are in direct contact with the silica vapor deposition layer, and in the cross-section in the thickness direction of the moisture-proof paper for the back surface of the decorative board, the softening temperature of the anchor coat layer measured by local thermal analysis is 180°C or higher. The moisture-proof paper for the back surface of the decorative board is characterized by this.

2. A moisture-proof paper for the back surface of a decorative board, comprising a paper substrate, an anchor coat layer, a silica vapor deposition layer, and an overcoat layer in this order, wherein the anchor coat layer has at least one of an epoxy resin, an acrylic urethane resin, an acrylic resin, a polyester-based polyurethane resin, and a polyether-based polyurethane resin. The moisture-proof paper for the back surface of the decorative board is characterized by this.

3. The moisture-proof paper for the back surface of a decorative board according to claim 1 or 2, wherein the overcoat layer contains a polyolefin having at least one kind of polar group.

4. The moisture-proof paper for the back surface of a decorative board according to claim 1 or 2, wherein the thickness of the silica vapor deposition layer is in the range of 10 nm or more and 100 nm or less.

5. The moisture-proof paper for the back surface of a decorative board according to claim 1 or 2, wherein the thickness of the overcoat layer is in the range of 2 μm or more and 10 μm or less.

6. The moisture-proof paper for the back surface of a decorative board according to claim 1 or 2, wherein the mass of the paper component contained in the paper substrate is 50% by mass or more based on the total mass of the moisture-proof paper for the back surface of the decorative board.

7. The moisture-proof paper for the back surface of a decorative board according to claim 1, wherein an adhesive primer layer is provided on the surface of the overcoat layer.

8. The moisture-proof paper for the back surface of a decorative board according to claim 1, wherein the paper substrate is an inter-paper reinforced paper.

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