Back face moisture-proof paper for decorative panel

Abstract

To provide a back face moisture-proof paper for a decorative panel that exhibits high moisture resistance, thereby enabling prevention of warping of the decorative panel even when used in environments with significant differences in temperature and humidity on both sides, and that is environmentally conscious through reduced plastic usage, the back face moisture-proof paper for the decorative panel enabling suppressing deterioration of water vapor barrier properties even after a long period has passed since manufactured (at least 12 months).SOLUTION: A back face moisture-proof paper 100 for a decorative panel at least comprises a paper substrate 11, a first resin layer 12, and an aluminum vapor deposition layer 13 in this order. The moisture content of the back face moisture-proof paper 100 for the decorative panel, as measured after being left for 48 hours under an environment of 23°C and 50% RH, is 4.4 mass% or less.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 obtained by laminating a solid printing layer for providing concealment and 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 laminated, and the surface expands. When it 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 laminated, and shrinkage occurs. On the other hand, the surface where the decorative sheet is laminated 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 laminated on the surface, a method of laminating a synthetic resin sheet such as vinyl chloride, polyethylene, or polypropylene, or a method of laminating a moisture-proof sheet made of paper / polyethylene / paper is known (Patent Document 1).

[0004] In addition, when higher moisture-proof properties are required, as a method for preventing deformation of the decorative board, a method of laminating 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 growing environmental awareness triggered by issues such as marine plastic waste, the movement towards plastic reduction has been on the rise. From the perspective of reducing the usage amount of plastic materials, the use of paper instead of plastic materials has been considered in various fields. Also, for example, Patent Document 2 below discloses a laminate in which a barrier layer is laminated on paper.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] In conventional moisture-proof inner sheets, the moisture-proof property may be insufficient. 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 panel. Furthermore, in all cases, plastic materials are the main materials, and in terms of environmental load, a reduction in their usage amount is required. 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 underway. However, the inventors have found that although the laminate with a barrier layer laminated on paper has good water vapor barrier property in the initial stage (immediately after manufacturing), there is a problem that the water vapor barrier property deteriorates after a long period of time since it was manufactured.

[0007] Therefore, the present invention has been made to solve this problem, and by having high moisture-proof performance, it can 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 a moisture-proof paper for the back surface of a decorative board that takes environmental considerations into account, and can suppress a decrease in water vapor barrier properties even when a long period of time (at least 12 months) has passed since production. The purpose is to provide a moisture-proof paper for the back surface of a decorative board.

Means for Solving the Problem

[0008] In order to solve the above problems, one of the typical moisture-proof papers for the back surface of a decorative board of the present disclosure is a moisture-proof paper for the back surface of a decorative board provided with a paper base material, a first resin layer, and an aluminum vapor deposition layer in this order, or a moisture-proof paper for the back surface of a decorative board provided with a paper base material, a first resin layer, an aluminum vapor deposition layer, and a second resin layer in this order, and the moisture content rate of the moisture-proof paper for the back surface of a decorative board measured after leaving it in an environment of 23°C and 50% RH for 48 hours or more is 4.4 mass% or less.

Effect of the Invention

[0009] According to the present disclosure, it is possible to provide a moisture-proof paper for the back surface of a decorative board that uses paper and aluminum vapor deposition, has a high paper component ratio, and can suppress a decrease in water vapor barrier properties even when a long period of time (at least 12 months) has passed since production. 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 a decorative board according to one aspect of the present invention, by having high moisture-proof performance, it can 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 a moisture-proof paper for the back surface of a decorative board that takes environmental considerations into account, and can suppress a decrease in water vapor barrier properties even when a long period of time (at least 12 months) has passed since production. It is possible to provide a moisture-proof paper for the back surface of a decorative board. 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

[0010]

Figure 1

Figure 2

Embodiments for Carrying Out the Invention

[0011] 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 thicknesses of the respective layers, etc. are different from the actual ones. Further, the embodiments shown below are examples of 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 components as the following ones. 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.

[0012] <Moisture-proof paper 100 for the back surface of a decorative board> FIG. 1 is a schematic cross-sectional view showing the structure of the moisture-proof paper 100 for the back surface of a decorative board according to the present embodiment. The moisture-proof paper 100 for the back surface of a decorative board according to the present embodiment is a moisture-proof paper that is used by being bonded to the back surface of a decorative board used for, for example, an indoor door panel (not shown). In the present embodiment, this moisture-proof paper 100 for the back surface of a decorative board is hereinafter also simply referred to as "moisture-proof paper 100". The moisture-proof paper 100 is used to prevent warping of the decorative board caused by moisture absorption and desorption due to changes in temperature and humidity indoors.

[0013] The moisture-proof back paper 100 for decorative panels in this embodiment comprises at least a paper base material 11, a first resin layer 12, and an aluminum vapor deposition layer 13, in that order, and the moisture content of the moisture-proof back paper 100 for decorative panels measured after leaving it in an environment of 23°C and 50% RH for 48 hours or more is 4.4 mass% or less. The moisture-proof backside paper 100 for decorative boards according to this embodiment may further include a second resin layer 14 on the surface of the aluminum vapor deposition layer 13 opposite to the first resin layer 12 .

[0014] According to the moisture-proof back surface paper 100 for decorative boards, the moisture content of the moisture-proof back surface paper 100 for decorative boards (hereinafter simply referred to as "moisture content") measured after leaving (humidity-conditioning) for 48 hours or more in an environment of 23°C and 50% RH is 4.4 mass% or less, which improves the long-term stability of the water vapor barrier properties of the moisture-proof back surface paper 100 for decorative boards, and suppresses deterioration of the water vapor barrier properties even after a long period of time (at least 12 months) has passed since the moisture-proof back surface paper 100 for decorative boards was manufactured. The inventors speculate that the reason for this effect is as follows: When the moisture content of the backside moisture-proof paper for decorative boards is high, the aluminum vapor-deposited layer is easily corroded and defects occur in the aluminum vapor-deposited layer. As a result, it is believed that the water vapor barrier effect of the aluminum vapor-deposited layer is reduced.

[0015] In contrast, by keeping the moisture content of the back surface moisture-proof paper for decorative panels within the above-mentioned range, the deterioration of the water vapor barrier properties of the aluminum vapor-deposited layer due to the phenomenon described above is suppressed, and it is believed that the water vapor barrier properties of the back surface moisture-proof paper for decorative panels are maintained even after a long period of time (at least 12 months) has passed since the back surface moisture-proof paper for decorative panels was manufactured. By using the moisture-proof paper 100 on the back side of decorative panels, it is possible to provide a moisture-proof paper that responds to the movement away from plastic and the problem of marine littering, has a high ratio of paper components, and has stable and excellent water vapor barrier properties.

[0016] FIG. 1 is a schematic cross-sectional view showing the configuration of the back moisture-proof paper for decorative boards according to an embodiment of the present disclosure. The back moisture-proof paper 100 for decorative boards according to an embodiment of the present disclosure includes, for example, a paper base material 11, a first resin layer 12, an aluminum vapor deposition layer 13, and a second resin layer 14 in this order. Hereinafter, each layer will be described.

[0017] [Moisture permeability of moisture-proof paper 100] The moisture permeability of the moisture-proof paper 100 is preferably 5 g / m 2 ·24 hr or less, and more preferably 3 g / m 2 ·24 h or less. If the moisture permeability is equal to or less than the above-described numerical value, 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 hr, but if it is equal to or less than the upper limit of the moisture permeability of the above-described moisture-proof paper 100, for example, 0.1 g / m 2 ·24 hr or more of moisture permeability may be acceptable, or 0.3 g / m 2 ·24 hr or more of moisture permeability may be acceptable, or 0.5 g / m 2 ·24 hr or more of moisture permeability may be acceptable.

[0018] [Paper base material] The paper base material 11 is not particularly limited and may be appropriately selected according to the use of the back moisture-proof paper 100 for decorative boards to be applied. Specific examples of the paper base material 11 include thin 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, thin paper (so-called paper-interlayer reinforced paper) in which a synthetic resin is mixed 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.

[0019] The basis weight of the paper base material 11 is not particularly limited, but if the basis weight of the paper base material 11 is less than 20 g / m 2 it is too flexible and wrinkles are likely to occur during processing. Also, if the basis weight of the paper base material 11 is 200 g / m 2In the case of excessive [thickness], peeling from the paper layer is likely to occur. Therefore, the basis weight of the paper substrate 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.

[0020] When the basis weight of the paper substrate 11 is within the above range, the moisture-proof paper 100 can obtain better water vapor barrier properties not only initially (immediately after production) but also after a long period of time (at least 12 months after production). When the basis weight is lower, the moisture content of the paper substrate 11 is less, so corrosion of the aluminum vapor deposition layer 13 is less likely to occur. However, if the basis weight is too low, dimensional changes of the paper substrate 11 are likely to occur during the coating and drying of the first resin layer 12, and appearance defects such as wrinkles may occur in the moisture-proof paper 100. The preferable range of the thickness (basis weight) of the paper substrate 11 for achieving both corrosion suppression of the aluminum vapor deposition layer 13 and good appearance of the moisture-proof paper 100 is the above range. Also, for these paper substrates 11, surface treatments such as corona treatment, plasma treatment, or frame treatment may be performed on their surfaces as necessary.

[0021] A coating layer (not shown) may be provided on the side of the paper substrate 11 that contacts the first resin layer 12 described later. When the paper substrate 11 is provided with a coating layer, the paper substrate 11 may include at least a paper layer and a coating layer. The coating layer may be provided on both surfaces (front and back) of the paper substrate 11. By providing the coating layer, it is possible to prevent the resin constituting the first resin layer 12 from penetrating into the paper substrate 11, and it can also serve as a caulking to fill the unevenness of the paper substrate 11. Therefore, for a paper substrate 11 having a coating layer on its surface, the first resin layer 12 can be formed uniformly without defects such as coating unevenness.

[0022] The coating layer may contain, as a binder resin, various copolymers such as styrene-butadiene-based, styrene-acrylic-based, ethylene-vinyl acetate-based, polyvinyl alcohol-based resins, cellulose-based resins, paraffin (WAX), etc. Further, the coating layer may contain, as a filler, for example, clay, kaolin, calcium carbonate, talc, mica, etc. Further, the coating layer may be a clay coating layer containing at least clay as a filler. When the paper base material 11 is provided with a coating layer, the thickness of the coating layer is preferably in the range of 1.5 μm or more and 15 μm or less. Further, the thickness of the coating layer may be 1.8 μm or more, 3 μm or more, 5 μm or more, 6 μm or more. Further, the thickness of the coating layer may be 12 μm or less, 10 μm or less. When the thickness of the coating layer is within the above range, the moisture-proof paper 100 can obtain better water vapor barrier properties.

[0023] The surface roughness (Ra) of the coating layer 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. When the surface roughness (Ra) of the coating layer is within the above numerical range, the adhesiveness between the paper base material 11 and the first resin layer 12 is improved due to the anchoring effect. 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. When 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 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 (indicating that it is "made of paper"), and it has excellent recyclability.

[0024] <The first resin layer 12> The first resin layer 12 is provided on the surface of the paper base material 11, and is provided for improving the adhesion between the paper base material 11 and the aluminum vapor deposition layer 13 described later, and for improving the barrier property of the moisture-proof paper 100. The first resin layer 12 may contain at least one resin selected from the group consisting of a polyolefin resin having a polar group, a polyvinyl alcohol-based resin, an acrylic resin, an epoxy resin, an acrylic urethane-based resin, a polyester-based polyurethane resin, and a polyether-based polyurethane resin. Further, from the viewpoint of further reducing the water content rate of the moisture-proof paper 100 and suppressing the decrease in the water vapor barrier property after a long period (after at least 12 months), the first resin layer 12 may contain at least one resin selected from the group consisting of a polyolefin resin having a polar group, an epoxy resin, and an acrylic urethane-based resin.

[0025] When the first resin layer 12 contains a polyolefin resin having a polar group, the first resin layer 12 is excellent in flexibility, can suppress cracking of the aluminum vapor deposition layer 13 described later after bending (after folding), and can improve the adhesion between the first resin layer 12 and the aluminum vapor deposition layer 13. Furthermore, by containing a polyolefin resin having a polar group, a dense film can be formed due to the crystallinity of the polyolefin resin, and the water vapor barrier property is exhibited. That is, when the first resin layer 12 is formed of a polyolefin resin having a polar group, the water vapor barrier property is exhibited due to the crystallinity of the polyolefin resin, and the adhesion to the aluminum vapor deposition layer 13 is exhibited due to having a polar group. The polyolefin resin 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.

[0026] As the polyolefin resin having a polar group, those obtained by copolymerizing ethylene or propylene with an unsaturated carboxylic acid (an unsaturated compound having a carboxyl group such as acrylic acid, methacrylic acid, maleic anhydride, etc.) or an unsaturated carboxylic acid ester, and salts obtained by neutralizing a carboxylic acid with a basic compound may be used. In addition, those obtained by copolymerizing with vinyl acetate, an epoxy compound, a chlorine compound, a urethane compound, a polyamide compound, etc. may also be used. Specific examples of the polyolefin resin having a polar group include ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, copolymer of an acrylic acid ester and maleic anhydride, ethylene-vinyl acetate copolymer, ethylene-glycidyl methacrylate copolymer, and the like.

[0027] When the first resin layer 12 contains a polyvinyl alcohol-based resin, the polyvinyl alcohol-based resin has a polar group (hydroxyl group), and this polar group easily binds to aluminum oxide on the surface of the aluminum vapor deposition layer, so that the adhesion between the aluminum vapor deposition layer 13 and the first resin layer 12 can be easily improved. Further, such a first resin layer 12 is excellent in flexibility and can suppress cracking of the aluminum vapor deposition layer 13 after bending (after folding). The polyvinyl alcohol-based resin is a resin containing vinyl alcohol as a constituent unit. Examples of the polyvinyl alcohol-based resin include a fully saponified polyvinyl alcohol resin, a partially saponified polyvinyl alcohol resin, a modified polyvinyl alcohol resin, and an ethylene-vinyl alcohol copolymer resin.

[0028] The first resin layer 12 may contain other components in addition to the above-described resins. Examples of the other components include polyolefin resins other than the polyolefin resin having the above polar group, silane coupling agents, organic titanate resins, polyester resins, polycarbonate resins, polyurea resins, polyamide resins, polyimide resins, melamine resins, phenol resins, and the like. The content of at least one resin selected from the group consisting of a polyolefin resin having a polar group, a polyvinyl alcohol-based resin, an acrylic resin, an epoxy resin, an acrylic urethane-based resin, a polyester-based polyurethane resin, and a polyether-based polyurethane resin in the first resin layer 12 may be, for example, 50% by mass or more, 70% by mass or more, 90% by mass or more, or 100% by mass based on the mass of the entire first resin layer 12.

[0029] The thickness of the first resin layer 12 may be, for example, 0.5 μm or more, 0.8 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 first resin layer 12 is 0.5 μm or more, the unevenness of the paper base material 11 described above can be efficiently filled, and the aluminum vapor deposition layer 13 described later can be uniformly laminated. Further, if the thickness of the first resin layer 12 is 20 μm or less, the aluminum vapor deposition layer 13 can be uniformly laminated while suppressing costs.

[0030] Examples of the solvent contained in the coating liquid for forming the first resin 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 properties, methyl alcohol, ethyl alcohol, isopropyl alcohol, toluene, ethyl acetate, methyl ethyl ketone, and water are preferable. Further, from the viewpoint of the environment, methyl alcohol, ethyl alcohol, isopropyl alcohol, and water are preferable. The first resin layer 12 can be obtained, for example, by applying a coating liquid containing the above-described resin and solvent onto the paper base material 11 and drying it. In the first resin layer 12, the above-described resin may be granular.

[0031] The drying temperature of the coating liquid is preferably 105°C to 160°C, more preferably 110°C to 155°C, still more preferably 120°C to 150°C, and particularly preferably 130°C to 145°C. By setting the drying temperature to 105°C or higher, the moisture content rate of the moisture-proof paper 100 can be reduced. Paper has the property that it absorbs or desorbs moisture according to the humidity in the environment, and its moisture content changes according to the humidity. At this time, if the moisture content rapidly decreases due to high-temperature drying such as in an oven, then when the paper is left in a humid environment afterwards, its moisture content will be less than before the high-temperature drying. That is, the moisture absorption amount of the paper dried at a high temperature becomes small (the hysteresis phenomenon of the paper). However, if the drying temperature is too high, the paper may shrink due to a rapid change in the moisture content, and appearance defects such as wrinkles may occur. By setting the drying temperature to 160°C or lower, the occurrence of appearance defects such as wrinkles due to the rapid shrinkage of the paper can be suppressed. Also, the drying time of the coating film may be, for example, 0.1 minute to 2 minutes.

[0032] Also, the surface roughness (Ra) of the first resin layer 12 is preferably within the range of 0.1 μm or more and 10 μm or less, more preferably within the range of 0.5 μm or more and 5 μm or less, and still more preferably within the range of 1 μm or more and 3 μm or less. If the surface roughness (Ra) of the first resin layer 12 is within the above numerical range, due to the anchoring effect, the adhesiveness between the first resin layer 12 and the aluminum vapor deposition layer 13 is improved. Therefore, the frequency of cracks and the like occurring in the aluminum vapor deposition layer 13 can be reduced, and excellent gas barrier properties can be imparted.

[0033] <Aluminum vapor deposition layer 13> The aluminum vapor deposition layer 13 is a layer formed by vapor-depositing aluminum or an aluminum compound. The aluminum vapor deposition layer 13 may be one obtained by vapor-depositing aluminum, or may contain aluminum oxide (AlOx), silicon oxide (SiOx), etc. The thickness of the aluminum vapor deposition layer 13 may be appropriately set according to the intended use, but is preferably 10 nm to 300 nm, more preferably 20 nm to 100 nm, and still more preferably 30 nm to 100 nm. By setting the thickness of the aluminum vapor deposition layer 13 to 10 nm or more, the continuity of the aluminum vapor deposition layer 13 can be easily made sufficient, and by setting it to 300 nm or less, the occurrence of curling and cracking can be sufficiently suppressed, and sufficient gas barrier performance and flexibility can be easily achieved. Further, by setting the thickness of the aluminum vapor deposition layer 13 to 20 nm or more and 100 nm or less, the aluminum vapor deposition layer 13 becomes less likely to crack, and sufficient water vapor barrier properties can be obtained even after bending.

[0034] The aluminum 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) are available as film forming means, but the vacuum evaporation method is preferred because of its high film forming speed and high 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 controlled by the irradiation area, electron beam current, etc., and the temperature increase and decrease of the evaporation material can be performed in a short time. Further, the surface roughness (Ra) of the aluminum vapor deposition layer 13 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 still more preferably in the range of 1 μm or more and 3 μm or less. If the surface roughness (Ra) of the aluminum vapor deposition layer 13 is within the above numerical range, the adhesion between the aluminum vapor deposition layer 13 and the second resin layer 14 is improved due to the anchoring effect. Therefore, the frequency of cracks and the like occurring in the aluminum vapor deposition layer 13 can be reduced, and excellent gas barrier properties can be imparted.

[0035] <Second resin layer 14> The second resin layer 14 is provided on the surface of the aluminum vapor deposition layer 13 so as to be in contact with the aluminum vapor deposition layer 13. By providing the moisture-proof paper with the second resin layer 14, it is possible to prevent the aluminum vapor deposition layer 13 from being exposed to moisture and the vapor barrier property from deteriorating, and it is possible to suppress the deterioration of the vapor barrier property of the moisture-proof paper after a long period (after at least 12 months). The second resin layer 14 may contain a polyolefin resin having a polar group. The polyolefin resin 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.

[0036] As the polyolefin resin having a polar group, those obtained by copolymerizing ethylene or propylene with an unsaturated carboxylic acid (an unsaturated compound having a carboxyl group such as acrylic acid or methacrylic acid) or an unsaturated carboxylic acid ester, and salts obtained by neutralizing a carboxylic acid with a basic compound may be used. Alternatively, those copolymerized with vinyl acetate, an epoxy compound, a chlorine compound, a urethane compound, a polyamide compound, etc. may also be used. Specific examples of the polyolefin resin having a polar group include ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, copolymer of acrylic acid ester and maleic anhydride, ethylene-vinyl acetate copolymer, ethylene-glycidyl methacrylate copolymer, and the like.

[0037] Since the second resin layer 14 contains a polyolefin resin having a polar group, the second resin layer 14 is excellent in flexibility, can suppress cracking of the aluminum vapor deposition layer 13 after bending (after folding), and has excellent adhesion to the aluminum vapor deposition layer 13. Furthermore, by containing the above-mentioned polyolefin resin having a polar group, a dense film can be formed due to the crystallinity of the polyolefin resin, and a water vapor barrier property is exhibited. Also, having a polar group causes adhesion to the aluminum vapor deposition layer 13 to occur. Furthermore, since the second resin layer 14 contains the above-mentioned polyolefin resin having a polar group, the water content rate of the moisture-proof paper 100 can be reduced, and a decrease in the water vapor barrier property of the moisture-proof paper 100 after a long period (after at least 12 months) can be more sufficiently suppressed.

[0038] The second resin layer 14 may contain other components in addition to the polyolefin resin having the polar group. Examples of other components include silane coupling agents, organic titanate resins, polyacrylic resins, polyester resins, polyurethane resins, polycarbonate resins, polyurea resins, polyamide resins, polyolefin resin-based emulsions, polyimide resins, melamine resins, phenol resins, and the like. The content of the polyolefin resin having a polar group in the second resin layer 14 may be, for example, 50% by mass or more, 70% by mass or more, 90% by mass or more, or 100% by mass with respect to the total mass of the second resin layer 14.

[0039] The thickness of the second resin layer 14 may be, for example, 0.05 μm or more, 0.5 μm or more, 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 second resin layer 14 is 0.05 μm or more, it is possible to more sufficiently suppress a decrease in the water vapor barrier property of the moisture-proof paper 100 after a long period of time (at least after 12 months). Further, if the thickness of the second resin layer 14 is 20 μm or less, it is possible to sufficiently exhibit the adhesiveness and barrier property with the aluminum vapor deposition layer 13 while suppressing costs. Further, by setting the thickness of the second resin layer 14 to 2 μm or more and 10 μm or less, the aluminum vapor deposition layer 13 becomes less likely to crack, and a sufficient water vapor barrier property can be obtained even after folding.

[0040] In the moisture-proof paper 100, when a polyolefin resin having a polar group is contained in the second resin layer 14, the thickness of the second resin layer 14 is 2 μm or more and 10 μm or less, and the thickness of the aluminum vapor deposition layer 13 is 20 nm or more and 100 nm or less, the effect that the aluminum vapor deposition layer 13 becomes less likely to crack and a sufficient water vapor barrier property can be obtained even after folding is particularly remarkable.

[0041] Examples of the solvent contained in the coating liquid for forming the second resin 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. Further, from the viewpoint of the environment, methyl alcohol, ethyl alcohol, isopropyl alcohol, and water are preferable.

[0042] The second resin layer 14 can be obtained, for example, by applying a coating solution containing a polyolefin resin having the above-described polar group and a solvent or the like onto the aluminum vapor deposition layer 13 and drying it. In the second resin layer 14, the polyolefin resin having a polar group may be in a granular form. The melting point of the polyolefin resin having a polar group in the coating solution is preferably 70°C to 160°C, more preferably 80°C to 120°C. If the melting point of the polyolefin resin having a polar group is high, the risk of blocking increases in a high-temperature environment. From the viewpoint of preventing blocking, the particle size of the polyolefin resin having a polar group is preferably larger so that the contact area becomes smaller. Although not particularly limited, specifically, the particle size of the polyolefin resin having a polar group may be 1 nm or more, 0.1 μm or more, 1 μm or less, 0.7 μm or less, or 0.5 μm or less.

[0043] The drying temperature of the coating solution is preferably 105°C to 160°C, more preferably 110°C to 155°C, still more preferably 120°C to 150°C, and particularly preferably 130°C to 145°C. By setting the drying temperature to 105°C or higher, the moisture content rate of the moisture-proof paper 100 can be reduced. Paper has the property of absorbing and desorbing moisture according to the humidity in the environment, and the moisture content changes according to the humidity. At this time, if the moisture content rapidly decreases due to high-temperature drying in an oven or the like, then when the paper is left in a humid environment, the moisture content will be less than before the high-temperature drying. That is, the moisture absorption amount of the paper dried at a high temperature becomes smaller (hysteresis phenomenon of the paper). However, if the drying temperature is too high, the paper may shrink due to a rapid change in the moisture content, and appearance defects such as wrinkles may occur. By setting the drying temperature to 160°C or lower, the occurrence of appearance defects such as wrinkles due to the rapid shrinkage of the paper can be suppressed. Also, the drying time of the coating film may be, for example, 0.1 minute to 2 minutes.

[0044] Also, the surface roughness (Ra) of the second resin layer 14 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 second resin layer 14 is within the above numerical range, the adhesiveness between the second resin layer 14 and the adhesive primer layer 15 is improved due to the anchoring effect. Therefore, the frequency of peeling of the moisture-proof paper 100 can be reduced. The moisture content rate of the moisture-proof paper 100 is 4.4 mass% or less based on the total amount of the moisture-proof paper 100 (100 mass%). This moisture content rate is a value measured after leaving the moisture-proof paper 100 in an environment of 23°C and 50% RH for 48 hours or more (humidity conditioning). By the moisture content rate of the moisture-proof paper 100 being 4.4 mass% or less, it is possible to suppress a decrease in the water vapor barrier property even when a long period has elapsed (at least 12 months) after the moisture-proof paper 100 is manufactured.

[0045] The method for setting the moisture content rate of the moisture-proof paper 100 within the above range is not particularly limited. For example, there are a method of increasing the drying temperature when forming the first resin layer 12 and the second resin layer 14 to reduce the moisture absorption amount of the paper, a method of using a material that is difficult to absorb moisture as the material of the first resin layer 12 and the second resin layer 14, a method of using a material that is difficult to absorb moisture as the paper base material 11, and the like. From the viewpoint of more sufficiently suppressing a decrease in the water vapor barrier property after a long period has elapsed (after at least 12 months have passed), the moisture content rate of the moisture-proof paper 100 may be 4.3 mass% or less, may be 4.0 mass% or less, or may be 3.9 mass% or less. The lower limit value of the moisture content rate is not particularly limited, but may be, for example, 1.0 mass% or more. Note that the moisture content rate of the moisture-proof paper 100 is a value measured in accordance with JIS P8127:2010 after leaving the moisture-proof paper in an environment of 23°C and 50% RH for 48 hours or more for humidity conditioning in accordance with JIS P8111:1998.

[0046] <Adhesive primer layer 15> In this embodiment, an adhesive primer layer 15 may be provided on the surface side of the aluminum vapor deposition layer 13, or on the surface side of the second resin layer 14 provided on the surface of the aluminum vapor deposition layer 13 opposite to the first resin layer 12 as shown in FIG. 2. The adhesive primer layer 15 is used when laminating and adhering to the surface of various adherend substrates, and is provided for the purpose of sufficiently ensuring adhesiveness with various laminating adhesives such as isocyanate-curing type urethane resin-based and modified vinyl acetate resin emulsion-based adhesives.

[0047] As its material, 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 suitable for the type of laminating adhesive is selected from these and used. For example, when a modified vinyl acetate resin emulsion-based adhesive is used as the laminating adhesive, good adhesion can be obtained with a urethane-based adhesive primer agent. In addition, if inorganic fine powder such as silica is added to the adhesive primer layer 15, the surface of the adhesive primer layer 15 is roughened, so that blocking during winding and storage of the moisture-proof paper 100 can be prevented, and the adhesiveness with the laminating adhesive can be improved by the anchoring effect.

[0048] These adhesive primer layers 15 can be used alone or in combination as an adhesive composition and formed using appropriate coating means such as roll coating method or gravure printing method. Also, the surface roughness (Ra) of the adhesive primer layer 15 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 adhesive primer layer 15 is within the above numerical range, the adhesiveness between the adhesive primer layer 15 and the laminating adhesive is improved by the anchoring effect.

[0049] [Effects of this embodiment] The back moisture-proof paper 100 for decorative boards according to this embodiment has the following effects. (1) The back moisture-proof paper 100 for decorative boards according to this embodiment includes at least a paper base material 11, a first resin layer 12, and an aluminum vapor deposition layer 13 in this order, and the moisture content rate of the back moisture-proof paper for decorative boards measured after being left in an environment of 23°C and 50% RH for 48 hours or more is 4.4% by mass or less. With such a configuration, even when a long period of time (at least 12 months) has passed since manufacturing, a decrease in water vapor barrier properties can be suppressed.

[0050] (2) The first resin layer 12 constituting the back moisture-proof paper 100 for decorative boards according to this embodiment may contain at least one resin selected from the group consisting of a polyolefin resin having a polar group, a polyvinyl alcohol-based resin, an acrylic resin, an epoxy resin, an acrylic urethane-based resin, a polyester-based polyurethane resin, and a polyether-based polyurethane resin. With such a configuration, it is possible to prevent the aluminum vapor deposition layer 13 from being exposed to moisture and the water vapor barrier properties from deteriorating.

[0051] (3) The first resin layer 12 constituting the back moisture-proof paper 100 for decorative boards according to this embodiment may contain at least one resin selected from the group consisting of a polyolefin resin having a polar group, an epoxy resin, and an acrylic urethane-based resin. With such a configuration, it is possible to further prevent the aluminum vapor deposition layer 13 from being exposed to moisture and the water vapor barrier properties from deteriorating.

[0052] (4) The back moisture-proof paper 100 for decorative boards according to this embodiment may further include a second resin layer 14 on the surface of the aluminum vapor deposition layer 13 opposite to the first resin layer 12. With such a configuration, it is possible to prevent the aluminum vapor deposition layer 13 from being exposed to moisture and the water vapor barrier properties from deteriorating.

[0053] (5) The second resin layer 14 constituting the back moisture-proof paper 100 for decorative boards according to this embodiment may contain a polyolefin resin having a polar group. With such a configuration, it is possible to further prevent the aluminum vapor deposition layer 13 from being exposed to moisture and the water vapor barrier property from deteriorating.

[0054] (6) The thickness of the aluminum vapor deposition layer 13 constituting the back moisture-proof paper 100 for decorative boards according to this embodiment may be 20 nm or more and 100 nm or less. With such a configuration, the continuity of the aluminum vapor deposition layer 13 becomes sufficient, and the occurrence of curl in the back moisture-proof paper 100 for decorative boards and cracks in the aluminum vapor deposition layer 13 can be sufficiently suppressed, and sufficient gas barrier performance and flexibility can be achieved.

[0055] (7) The back moisture-proof paper 100 for decorative boards according to this embodiment may be provided with an adhesive primer layer 15 on the front surface side of the aluminum vapor deposition layer 13 or on the front surface side of the second resin layer 14 provided on the surface opposite to the first resin layer 12 of the aluminum vapor deposition layer 13. With such a configuration, the adhesiveness between the back moisture-proof paper 100 for decorative boards and the laminate adhesive can be sufficiently ensured.

[0056] (8) The paper base material 11 constituting the back moisture-proof paper 100 for decorative boards according to this embodiment may be an inter-paper reinforced paper. With such a configuration, the mechanical strength of the paper base material 11 can be increased.

[0057] (9) The mass of the paper component contained in the paper base material 11 constituting the back moisture-proof paper 100 for decorative boards may be 50% by mass or more based on the total mass of the back moisture-proof paper 100 for decorative boards. With such a configuration, the amount of plastic material used can be sufficiently reduced.

[0058] [Examples] Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

[0059] <Manufacture of moisture-proof paper> (Example 1) On the surface of a paper interlayer reinforcing paper (manufactured by Amami Special Paper Co., Ltd.) with a basis weight of 50 g / m 2 a water dispersion of a polyolefin resin (polar group-containing polyolefin) containing a salt of a carboxyl group (Sumitomo Seika Chemicals Co., Ltd., trade name: Zexcen AC, particle size: less than 0.2 μm, solvent: water / IPA = 1 / 1 (mass ratio), solid content concentration: 22.5 mass%) was coated with a bar coater and dried in an oven at 140 °C for 1 minute to form a first resin layer with a thickness of 3 μm. Subsequently, Al vapor deposition was performed on the first resin layer by a vacuum vapor deposition method to form an Al vapor deposition layer (aluminum vapor deposition layer) with a thickness of 50 nm. Next, on the Al vapor deposition layer, a water dispersion of a polyolefin resin (polar group-containing polyolefin) containing a salt of a carboxyl group (Mitsui Chemicals, Inc., trade name: ChemPearl S100, particle size: less than 0.1 μm, solvent: water / IPA = 1 / 1 (mass ratio), solid content concentration: 20.0 mass%) was coated with a bar coater and dried in an oven at 140 °C for 1 minute to form a second resin layer with a thickness of 3 μm. Thus, the moisture-proof paper of Example 1 was obtained.

[0060] (Example 2) Using a paper interlayer reinforcing paper (manufactured by Amami Special Paper Co., Ltd.) with a basis weight of 65 g / m 2 as the paper substrate, the moisture-proof paper of Example 2 was produced in the same manner as in Example 1 except for this.

[0061] (Example 3) On the surface of a paper interlayer reinforcing paper (manufactured by Amami Special Paper Co., Ltd.) with a basis weight of 50 g / m 2 a coating solution in which a PVA (polyvinyl alcohol) resin (manufactured by Kuraray Co., Ltd., trade name: Poval 5-98) with a degree of polymerization of 500 and a saponification degree of 98 mol% was dissolved at a solid content concentration of 10 mass% in a solution of water / IPA = 8 / 2 (mass ratio) was coated with a bar coater and dried in an oven at 140 °C for 1 minute to form a first resin layer with a thickness of 3 μm. Next, in the same manner as in Example 1, an Al vapor deposition layer and a second resin layer were formed on the first resin layer to obtain the moisture-proof paper of Example 3.

[0062] (Example 4) On the surface of a paper-based reinforcing paper (manufactured by Amma Special Paper Co., Ltd.) with a basis weight of 50 g / m 2 , a coating solution of a urethane-curable acrylic resin (acrylic urethane resin) containing an acrylic polyol and a polyisocyanate was coated with a bar coater and dried in an oven at 140°C for 1 minute to form a first resin layer with a thickness of 1 μm. Next, in the same manner as in Example 1, an Al vapor deposition layer and a second resin layer were formed on the first resin layer to obtain the moisture-proof paper of Example 4.

[0063] (Example 5) To 17 parts by mass of a mixed solvent of methanol and ethyl acetate in a 1:1 (mass ratio), 24 parts by mass of Maxceleb C93AT (trade name, manufactured by Mitsubishi Gas Chemical Company, Inc.) and 2 parts by mass of Maxceleb M-100 (trade name, manufactured by Mitsubishi Gas Chemical Company, Inc.) were added and mixed to prepare a coating solution of an epoxy resin. On the surface of a paper-based reinforcing paper (manufactured by Amma Special Paper Co., Ltd.) with a basis weight of 50 g / m 2 , the above coating solution of the epoxy resin was coated with a bar coater and dried in an oven at 140°C for 1 minute to form a first resin layer with a thickness of 1 μm. Next, in the same manner as in Example 1, an Al vapor deposition layer and a second resin layer were formed on the first resin layer to obtain the moisture-proof paper of Example 5.

[0064] (Comparative Example 1) A moisture-proof paper of Comparative Example 1 was produced in the same manner as in Example 1, except that the drying condition of the first resin layer was changed to 100°C for 1 minute.

[0065] (Comparative Example 2) A moisture-proof paper of Comparative Example 2 was produced in the same manner as in Example 1, except that the drying conditions of both the first resin layer and the second resin layer were changed to 100°C for 1 minute.

[0066] (Comparative Example 3) A moisture-proof paper of Comparative Example 3 was produced in the same manner as in Example 3, except that the drying condition of the first resin layer was changed to 100°C for 1 minute.

[0067] (Comparative Example 4) A moisture-proof paper of Comparative Example 4 was produced in the same manner as in Example 3, except that the drying conditions for both the first resin layer and the second resin layer were changed to 100°C for 1 minute.

[0068] <Measurement of Moisture Content>[ The moisture-proof papers obtained in the examples and comparative examples were cut into A4 size, and conditioned by leaving them in an environment of 23°C and 50% RH for 48 hours in accordance with JIS P8111:1998. Thereafter, the moisture content of the moisture-proof paper was measured in accordance with JIS P8127:2010. The measurement of the moisture content was also carried out in an environment of 23°C and 50% RH so that the moisture content of the moisture-proof paper did not change during the measurement operation. The measurement results are shown in Tables 1 and 2.

[0069] <Measurement of Water Vapor Permeability (Initial)>[ For the moisture-proof papers obtained in the examples and comparative examples, the water vapor permeability (unit: g / m 2 ·day) under the conditions of 40°C and 90% RH was measured in accordance with JIS Z 0208. The measurement was carried out three times, and the average value was obtained. The results are shown in Tables 1 and 2.

[0070] <Measurement of Water Vapor Permeability (After 12 Months)>[ The moisture-proof papers obtained in the examples and comparative examples were cut into A4 size and left in an environment of 23°C and 50% RH for 12 months. After being left for 12 months, the water vapor permeability (average value measured three times) of the moisture-proof paper was determined in the same manner as the measurement method of the water vapor permeability (initial). In addition, the difference (increase amount) between the water vapor permeability after 12 months of leaving and the initial water vapor permeability was calculated. The results are shown in Tables 1 and 2.

[0071] <Measurement of the Number of Defects in the Al Deposition Layer>[ For the moisture-proof paper after being left for 12 months obtained in the above <Measurement of Water Vapor Permeability (After 12 Months)>, the number of defects in the Al deposition layer was measured by the following method. That is, using an optical microscope (manufactured by Olympus Corporation, product name: BX-51), the maximum amount of light was applied from the paper base material side of the moisture-proof paper, and the light transmitted through the moisture-proof paper was observed. Regarding the obtained transmitted light image, 600μm 2The number of transmitted light with a major axis size of 3.5 μm or less within the range was counted as the number of defects (transmission defect number). The results are shown in Tables 1 and 2.

[0072]

Table 1

[0073]

Table 2

[0074] Note that the unit of the moisture permeability (water vapor transmission rate) shown in each table is "g / m" 2 ·24 hr". Also, in this example, if the moisture permeability of the moisture-proof paper after 12 months is 5.0 g / m 2 ·24 hr or less, when actually used as a moisture-proof paper for a long time, warping of the decorative board caused by moisture absorption and desorption due to changes in indoor temperature and humidity can be prevented, so it is regarded as "qualified". On the other hand, if the moisture permeability of the moisture-proof paper is more than 5.0 g / m 2 ·24 hr, when actually used as a moisture-proof paper, warping may occur in the decorative board due to moisture absorption and desorption caused by changes in indoor temperature and humidity, so it is regarded as "unqualified".

[0075] As is clear from the results in Tables 1 to 2, the back moisture-proof paper for the decorative board of each example had a lower moisture permeability after 12 months compared to the moisture-proof paper of each comparative example. The moisture-proof paper of this example was provided with a moisture-proof layer having a vapor deposition layer, and an improvement in the moisture permeability performance was recognized. The effect of reducing the warping of the decorative board caused by moisture absorption and desorption due to changes in indoor temperature and humidity and the effect of reducing the amount of plastic material used can be expected compared to conventional products. Thus, it was verified that it is possible to provide a back moisture-proof paper for a decorative board that can prevent warping of the decorative board even when used in a place where there is a large difference in temperature and humidity environments on both sides and that also takes environmental considerations into account, which is the problem of the present invention.

[0076] Further, for example, the present invention can be configured as follows. (1) A moisture-proof paper for the back surface of a decorative board, comprising at least a paper base material, a first resin layer, and an aluminum vapor deposition layer in this order, wherein the moisture content rate of the moisture-proof paper for the back surface of the decorative board measured after being left for 48 hours or more in an environment of 23°C and 50% RH is 4.4% by mass or less. (2) The moisture-proof paper for the back surface of a decorative board according to (1) above, wherein the first resin layer contains at least one resin selected from the group consisting of a polyolefin resin having a polar group, a polyvinyl alcohol-based resin, an acrylic resin, an epoxy resin, an acrylic urethane-based resin, a polyester-based polyurethane resin, and a polyether-based polyurethane resin. (3) The moisture-proof paper for the back surface of a decorative board according to (1) above, wherein the first resin layer contains at least one resin selected from the group consisting of a polyolefin resin having a polar group, an epoxy resin, and an acrylic urethane-based resin. (4) The moisture-proof paper for the back surface of a decorative board according to any one of (1) to (3) above, further comprising a second resin layer on the surface of the aluminum vapor deposition layer opposite to the first resin layer. (5) The moisture-proof paper for the back surface of a decorative board according to (4) above, wherein the second resin layer contains a polyolefin resin having a polar group. (6) The moisture-proof paper for the back surface of a decorative board according to any one of (1) to (5) above, wherein the thickness of the aluminum vapor deposition layer is 20 nm or more and 100 nm or less. (7) The moisture-proof paper for the back surface of a decorative board according to any one of (1) to (6) above, wherein an adhesive primer layer is provided on the surface side of the aluminum vapor deposition layer or on the surface side of the second resin layer provided on the surface of the aluminum vapor deposition layer opposite to the first resin layer. (8) The moisture-proof paper for the back surface of a decorative board according to any one of (1) to (7) above, wherein the paper base material is an inter-paper reinforced paper. (9) The mass of the paper component contained in the paper base material is 50% by mass or more based on the total mass of the back moisture-proof paper for decorative boards, and the back moisture-proof paper for decorative boards according to any one of the above (1) to (8).

Explanation of reference signs

[0077] 11: Paper base material 12: First resin layer 13: Aluminum vapor deposition layer (vapor deposition layer) 14: Second resin layer 15: Adhesive primer layer 100: Back moisture-proof paper for decorative boards (moisture-proof paper)

Claims

1. A moisture-proof paper for the back surface of a decorative board, comprising at least a paper base material, a first resin layer, and an aluminum vapor deposition layer in this order, wherein the moisture content rate of the moisture-proof paper for the back surface of the decorative board measured after being left standing in an environment of 23°C and 50% RH for 48 hours or more is 4.4% by mass or less. The moisture-proof paper for the back surface of the decorative board.

2. The moisture-proof paper for the back surface of a decorative board according to claim 1, wherein the first resin layer contains at least one resin selected from the group consisting of a polyolefin resin having a polar group, a polyvinyl alcohol-based resin, an acrylic resin, an epoxy resin, an acrylic urethane-based resin, a polyester-based polyurethane resin, and a polyether-based polyurethane resin.

3. The moisture-proof paper for the back surface of a decorative board according to claim 1, wherein the first resin layer contains at least one resin selected from the group consisting of a polyolefin resin having a polar group, an epoxy resin, and an acrylic urethane-based resin.

4. The moisture-proof paper for the back surface of a decorative board according to claim 1, further comprising a second resin layer on the surface of the aluminum vapor deposition layer opposite to the first resin layer.

5. The moisture-proof paper for the back surface of a decorative board according to claim 4, wherein the second resin layer contains a polyolefin resin having a polar group.

6. The moisture-proof paper for the back surface of a decorative board according to claim 1, wherein the thickness of the aluminum vapor deposition layer is 20 nm or more and 100 nm or less.

7. The moisture-proof paper for the back surface of a decorative board according to any one of claims 1 to 6, wherein an adhesive primer layer is provided on the surface side of the aluminum vapor deposition layer or on the surface side of the second resin layer provided on the surface of the aluminum vapor deposition layer opposite to the first resin layer.

8. The moisture-proof paper for the back surface of a decorative board according to any one of claims 1 to 6, wherein the paper base material is a paper interlayer reinforced paper.

9. The moisture-proof paper for the back surface of a decorative board according to any one of claims 1 to 6, wherein the mass of the paper component contained in the paper base material is 50% by mass or more based on the total mass of the moisture-proof paper for the back surface of the decorative board.

Images