JP2023012301A - Rear face moisture-proof paper for decorative sheet - Google Patents

Abstract

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

Description

INDUSTRIAL APPLICABILITY The present invention is applied to decorative panels used for indoor door panels, etc., in order to prevent warping caused by moisture absorption/desorption due to changes in indoor temperature and humidity. Regarding moisture-proof paper.

Conventionally, decorative boards used for the above applications include a solid printing layer for imparting concealment to the surface of plywood, medium density fiberboard (MDF), veneer board, board material, and other multi-layered woody base materials. It is generally known to laminate a decorative sheet on which a pattern pattern layer is printed for improving the design property.
If the moisture content of the wood-based base material is lower than the equilibrium moisture content of the wood-based base material under open air conditions, the surface of the decorative board that is not laminated with the decorative sheet absorbs moisture and the surface expands, causing the wood-based base material to swell. If the moisture content is higher than the equilibrium moisture content of the material, moisture is released and shrinkage occurs. occurs.

In order to prevent this deformation, a method of applying paint to the back surface of a decorative board with a decorative sheet attached to the surface, a method of attaching a synthetic resin sheet such as vinyl chloride, polyethylene, polypropylene, etc., or a method of paper / A method of laminating moisture-proof sheets made of polyethylene/paper is known.
Conventionally, a moisture-proof decorative board is known in which a moisture-proof decorative sheet is attached to the front surface of a plate base material such as plywood, and a moisture-proof back sheet is attached to the back surface thereof via an adhesive (Patent Document 1, paragraph [0007] ], and FIGS. 1-3).

Japanese Patent No. 3206408

However, in the above-described conventional methods, the moisture resistance is insufficient, so when used for a long period of time for doors, sliding doors, partitions, etc. that have a large difference in temperature and humidity environments on both sides, the degree of expansion and contraction of both sides may occur. are different and warping may occur.
SUMMARY OF THE INVENTION The present invention has been made to solve this problem, and an object of the present invention is to provide moisture-proof paper that prevents warping even when used in a place where there is a large difference in temperature and humidity environments on both sides.

The present invention has solved this problem, that is, the back moisture-proof paper for decorative board according to one aspect of the present invention comprises a paper substrate, a carboxyl group, a salt of the carboxyl group, a carboxylic anhydride group and a carboxylic acid. An anchor coat layer containing a first polyolefin having at least one selected from acid esters; a deposited layer; and at least one selected from carboxyl groups, salts of carboxyl groups, carboxylic anhydride groups and carboxylic acid esters. and an overcoat layer containing a second polyolefin, in that order.
The first polyolefin and the second polyolefin may be of the same type or of different types.

Further, the back moisture-proof paper for decorative laminate according to one aspect of the present invention is characterized in that the anchor coat layer has a thickness of 1 μm or more.
A backside moisture-proof paper for a decorative board according to one aspect of the present invention is characterized in that an adhesive primer layer is provided on the exposed surface of an overcoat layer.
The back-side moisture-proof paper for decorative laminate according to one aspect of the present invention is characterized in that the paper substrate is a paper-strengthening paper.

According to one aspect of the present invention, the moisture-proof performance is significantly superior to conventionally used synthetic resin sheets such as vinyl chloride, polyethylene, and polypropylene, or moisture-proof sheets made of paper/polyethylene/paper. , it is possible to provide a moisture-proof backing paper for a decorative board that contributes to a reduction in the amount of plastic material used.

FIG. 2 is an explanatory view showing the cross-sectional shape of one embodiment of the moisture-proof paper of the present invention; FIG. 4 is an explanatory view showing the cross-sectional shape of an example using the adhesion primer layer of the moisture-proof paper of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory diagram of one embodiment in which the moisture-proof paper of the present invention is used as a decorative sheet or a plate substrate;

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a mode for carrying out the present invention will be described with reference to FIGS. 1 to 3. FIG.
However, the present invention is not limited to the following embodiments.

[Back moisture-proof paper 10 for decorative board]
Backside moisture-proof paper 10 for decorative board according to the present invention (hereinafter also referred to as "moisture-proof paper 10") includes a moisture-proof layer 20 on a paper substrate 21, as shown in FIGS. The moisture-proof layer 20 is composed of three layers, an anchor coat layer 22 , a vapor deposition layer 23 and an overcoat layer 24 .
An adhesion primer layer 30 can be provided on the exposed surface of the overcoat layer 24, as shown in FIG.
The anchor coat layer 22 contains a first polyolefin having at least one selected from a carboxyl group, a salt of a carboxyl group, a carboxylic anhydride group and a carboxylic acid ester, and the overcoat layer 24 contains a carboxyl group and a carboxyl group. A second polyolefin having at least one selected from salts, carboxylic anhydride groups and carboxylic acid esters is included.

[Paper base material 21]
The paper base material 21 is not particularly limited, and may be appropriately selected according to the application of the moisture-proof paper 10 to be applied.
Specific examples of the paper substrate 21 include thin paper, woodfree paper, art paper, cast coated paper, kraft paper, titanium paper, linter paper, paperboard, gypsum board paper, woodfree paper, coated paper, sulfuric acid paper, glassine paper, and parchment paper. , paraffin paper, and Japanese paper.
Preferably, thin paper mixed with a synthetic resin to increase inter-paper strength (so-called inter-paper reinforced paper), or paper impregnated with latex or synthetic resin is preferably used.
^{The basis} weight is not particularly limited. 20 to 200 g/m ² is preferred, 20 to 100 g/m ² is more preferred, and 20 to 50 g/m ² is even more preferred.

Further, these paper substrates 21 may be subjected to surface treatment such as corona treatment, plasma treatment, flame treatment, etc., as required.
The paper base material 21 may be provided with a coat layer at least on the side in contact with the anchor coat layer 22 described later.
By providing the coat layer, it is possible to prevent the anchor coat layer 22 from soaking into the paper, and it can also play a role of a filler filling the unevenness of the paper, and the anchor coat layer 22 can be uniformly formed without defects. be able to.

For the coating layer, for example, various copolymers such as styrene/butadiene, styrene/acrylic, ethylene/vinyl acetate, polyvinyl alcohol resin, cellulose resin, paraffin (WAX), etc. are used as binder resins. , and fillers such as clay, kaolin, calcium carbonate, talc, and mica.
The thickness of the coat layer is not particularly limited, but may be, for example, 1 to 10 μm, or 3 to 8 μm.

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

[Anchor coat layer 22]
The anchor coat layer 22 is provided on the surface of the paper base material 21 to improve the adhesion between the paper base material 21 and the vapor deposition layer 23 described later and to improve the gas barrier properties of the gas barrier laminate. and constitutes the barrier layer.
The barrier layer in the present invention is excellent in oxygen barrier and water vapor barrier. For the back moisture-proof paper 10 for decorative laminate of the present invention, only the water vapor barrier property is required, and the oxygen barrier property does not contribute.

The anchor coat layer 22 contains a first polyolefin having at least one selected from carboxyl groups, salts of carboxyl groups, carboxylic acid anhydride groups and carboxylic acid esters.
Such an anchor coat layer 22 is excellent in flexibility, can suppress cracking of the vapor deposition layer 23 , and can improve adhesion between the anchor coat layer 22 and the vapor deposition layer 23 . Furthermore, by containing the polyolefin described above, it is possible to form a dense film due to the crystallinity of the polyolefin. In addition, since polyolefin has few polar groups, it is excellent in water vapor barrier properties.

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

The thickness of the anchor coat layer 22 may be, for example, 1 μm or more, 2 μm or more, 20 μm or less, 10 μm or less, or 5 μm or less.
If the thickness of the anchor coat layer 22 is 1 μm or more, the unevenness of the paper substrate 21 can be efficiently filled, and the vapor deposition layer 23 described later can be evenly laminated. Further, if the thickness of the anchor coat layer 22 is 20 μm or less, the deposition layer 23 can be uniformly laminated while suppressing the cost.

Solvents contained in the coating liquid of the anchor coat layer 22 include, for example, water, methyl alcohol, ethyl alcohol, isopropyl alcohol, n-propyl alcohol, n-butyl alcohol, n-pentyl alcohol, dimethylsulfoxide, dimethylformamide, and dimethylacetamide. , toluene, hexane, heptane, cyclohexane, acetone, methyl ethyl ketone, diethyl ether, dioxane, tetrahydrofuran, ethyl acetate, butyl acetate. These solvents may be used singly or in combination of two or more.
Among these, methyl alcohol, ethyl alcohol, isopropyl alcohol, toluene, ethyl acetate, methyl ethyl ketone, and water are preferred from the viewpoint of properties. Moreover, from the viewpoint of the environment, methyl alcohol, ethyl alcohol, isopropyl alcohol, and water are preferable.

As a method for providing the anchor coat layer 22, it can be obtained by applying a coating liquid containing at least the above-described first polyolefin and a solvent on the paper base material 21 and drying it. The smaller the average particle size of the first polyolefin in the coating liquid, the better, from the viewpoint of smoothing the coated surface after drying, uniformly laminating the vapor deposition layer 23, and improving barrier properties. Specifically, it may be 1 µm or less, 0.7 µm or less, or 0.5 µm or less. Although the lower limit of the average particle size of the first polyolefin is not particularly limited, it may be lnm or more, for example.

[Deposition layer 23]
The deposited layer 23 is a layer deposited with a metal or an inorganic compound. The deposited layer may be obtained by vapor deposition of aluminum, or may contain aluminum oxide (AlOx), silicon oxide (SiOx), or the like.
The thickness of the deposited layer 23 may be appropriately set depending on the intended use, preferably 10 to 300 nm, more preferably 30 to 100 nm. By setting the thickness of the vapor deposition layer 23 to 10 nm or more, the continuity of the vapor deposition layer 23 can be easily made sufficient, and by setting the thickness to 300 nm or less, the occurrence of curling and cracking can be sufficiently suppressed, and sufficient gas barrier performance (oxygen barrier performance) can be achieved. water vapor barrier) and flexibility are easy to achieve.

From the viewpoint of film uniformity, the deposited layer 23 is preferably formed by a vacuum film forming means. Film formation means include known methods such as a vacuum deposition method, a sputtering method, and a chemical vapor deposition method (CVD method), but the vacuum deposition method is preferred because of its high film formation speed and high productivity. In addition, among the vacuum evaporation methods, the film formation method using electron beam heating in particular is easy to control the film formation speed by adjusting the irradiation area and the electron beam current, and the heating and cooling of the evaporation material can be performed in a short time. It is valid.

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

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

The thickness of the overcoat layer 24 may be, for example, 0.05 μm or more, 0.5 μm or more, 1 μm or more, 20 μm or less, 10 μm or less, or 5 μm. may be:
If the thickness of the overcoat layer 24 is 0.05 μm or more, the role of the heat seal layer can be fully exhibited.
Moreover, if the thickness of the overcoat layer 24 is 20 μm or less, it is possible to sufficiently exhibit the adhesiveness to the vapor deposition layer 23 and barrier properties (water vapor barrier except oxygen barrier) while suppressing the cost.

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

These solvents may be used alone or in combination of two or more.
Among these, methyl alcohol, ethyl alcohol, isopropyl alcohol, toluene, ethyl acetate, methyl ethyl ketone, and water are preferred from the viewpoint of properties.
Moreover, from the viewpoint of the environment, methyl alcohol, ethyl alcohol, isopropyl alcohol, and water are preferable.

As a method for providing the overcoat layer 24, it can be obtained by applying a coating liquid containing the above-mentioned second polyolefin and a solvent on the deposition layer 23 and drying it.
Although the average particle size of the second polyolefin in the coating liquid is not particularly limited, specifically, it may be 1 µm or less, 0.7 µm or less, or 0.5 µm or less.
The first polyolefin and the second polyolefin contained in the anchor coat layer 22 and the overcoat layer 24, respectively, may be of the same type or of different types. If so, they are preferably of the same type.

[Adhesion primer layer 30]
Adhesion primer 30 is compatible with various lamination adhesives, such as isocyanate-curing urethane resins and modified vinyl acetate resin emulsions, which are used for laminating and adhering to the surface of various substrates to be adhered. It is provided for the purpose of ensuring sufficient adhesiveness.
Materials for the adhesive primer layer 30 include various primers 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. Among these, the one that matches the type of lamination adhesive is selected and used.
For example, when a modified vinyl acetate resin emulsion-based adhesive is used as a laminating adhesive, a urethane-based adhesive primer provides good adhesion.

If an inorganic fine powder such as silica is added to the adhesion moisture-proof layer 20, the surface of the adhesion primer layer 30 is roughened, thereby preventing blocking during winding and storage of the moisture-proof sheet. In addition, it is also possible to improve the adhesiveness with the laminating adhesive due to the anchoring effect. The adhesive primer layer 30 can be formed by using an appropriate coating means such as a roll coating method, a gravure printing method, or the like.

[Manufacturing method of moisture-proof paper 10]
The moisture-proof paper 10 has the structure described above, and the manufacturing method thereof is as follows.
First, a coating liquid containing a salt of a carboxyl group is applied on the surface of the paper base material 21 using, for example, a bar coater, and dried in an oven to form the anchor coat layer 22 .
For the paper base material 21, for example, 50 g/m ² reinforced paper (manufactured by Tenma Tokushu Paper Co., Ltd.) is used.
As the coating liquid, for example, "trade name: Chemipearl S100, ionomer type, particle size: <0.1 μm, solvent: water, IPA, manufactured by Mitsui Chemicals" is used.

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

(Usage example of plate base material 50)
With reference to FIG. 3, an example of fittings such as wooden doors and doors, or a decorative plate used for these fittings will be described. The decorative sheet 40 is adhered to one side of the plate base material 50 via an adhesive, and the adhesive primer layer 30 of the moisture-proof paper 10 is adhered via an adhesive to the opposite side to which the decorative sheet 40 is adhered. Become. Warpage of the plate base material can be prevented.
The overcoat layer 24 may be directly adhered, although the adhesion primer layer 30 is interposed therebetween.

(Characteristic points and effects according to the embodiment based on the present invention)
Aspects of embodiments in accordance with the present invention are as follows.
(First feature point)
The first characteristic point is the moisture-proof paper 10, which has at least one selected from a carboxyl group, a salt of a carboxyl group, a carboxylic acid anhydride group, and a carboxylic acid ester on the paper base material 21. An anchor coat layer 22 containing polyolefin, a deposited layer 23, and an overcoat layer 24 containing a second polyolefin having at least one selected from a carboxyl group, a salt of a carboxyl group, a carboxylic acid anhydride group and a carboxylic acid ester. , in that order.

(Effect of first feature point)
According to the first characteristic point, since the moisture permeability (JIS Z 0208) is 3.0 g / m ² · 24 hr or less, conventionally used synthetic resin sheets such as vinyl chloride, polyethylene, polypropylene Alternatively, it is possible to provide the moisture-proof paper 10 that has much better moisture-proof performance than a moisture-proof sheet made of paper/polyethylene/paper and contributes to a reduction in the amount of plastic material used.

In addition, the anchor coat layer 22 is excellent in flexibility, so that cracking of the vapor deposition layer 23 can be suppressed, and adhesion between the anchor coat layer 22 and the vapor deposition layer 23 can be improved.
Furthermore, by containing the polyolefin described above, it is possible to form a dense film due to the crystallinity of the polyolefin. Since polyolefin has few polar groups, it has excellent water vapor barrier properties.
Furthermore, the overcoat layer 24 has excellent flexibility and excellent adhesion to the deposition layer 23 . In addition, by including the above-mentioned second polyolefin, it is possible to form a dense film due to the crystallinity of the polyolefin. In addition, since polyolefin has few polar groups, it is excellent in water vapor barrier properties.
On the other hand, the first polyolefin and the second polyolefin may be of the same type or different types. be able to.

(Second feature point)
A second characteristic point is that the thickness of the anchor coat layer 22 is 1 μm or more.
(Effect of second feature point)
According to the second characteristic point, if the thickness of the anchor coat layer 22 is 1 μm or more, the unevenness of the paper substrate 21 can be efficiently filled, and the deposition layer 23 can be evenly laminated.

(Third feature point)
A third characteristic point is that an adhesion primer layer 30 is provided on the exposed surface of the overcoat layer 24 .
(Effect of the third feature point)
According to the third feature, various laminate adhesives such as isocyanate-curing urethane resins and modified vinyl acetate resin emulsions, which are used when laminating and adhering to the surface of various substrates to be adhered Sufficient adhesion to the agent can be ensured.

(Fourth feature point)
A fourth characteristic point is that the paper base material 21 is a paper-strengthening paper.
(Effect of fourth feature point)
By using the inter-paper reinforced paper, it is possible to prevent the paper layers from peeling off from each other when used for a long period of time or when an external force is applied force majeure.
(Fifth feature point)
A fifth characteristic point is that the thickness of the anchor coat layer 22 is 20 μm or less.
(Effect of fifth feature point)
According to the fifth characteristic point, if the thickness of the anchor coat layer 22 is 20 μm or less, the deposition layer 23 can be uniformly laminated while suppressing the cost.

(Sixth feature point)
The sixth feature is the addition of inorganic fine powder to the adhesion primer.
(Effect of sixth feature point)
According to the sixth characteristic point, when inorganic fine powder such as silica is added to the adhesion moisture-proof layer 20, the surface of the adhesion primer layer 30 is roughened, so that the moisture-proof sheet can be rolled up and stored. In addition to preventing time blocking, it is also possible to improve the adhesiveness with the laminating adhesive due to the anchoring effect. The adhesive primer layer 30 can be formed by using a suitable coating method such as roll coating or gravure printing, using a single adhesive composition or a mixture thereof.

(Seventh feature point)
A seventh characteristic point is that the basis weight of the inter-paper reinforcing paper is 20 g/m ² or more and 200 g/m ² or less.
(Effect of seventh feature point)
According to the seventh characteristic point, if the basis weight of the inter-paper reinforcing paper is less than ²⁰ g/m ² , it is too soft and wrinkles are likely to occur during processing. detachment is likely to occur.

(Eighth feature point)
An eighth characteristic point is that the thickness of the overcoat layer 24 is 0.05 μm or more and 20 μm or less.
(Effect of eighth feature point)
According to the eighth characteristic point, if the thickness of the overcoat layer 24 is 0.05 μm or more, the role as the heat seal layer described above can be sufficiently exhibited. Moreover, if the thickness of the overcoat layer 24 is 20 μm or less, it is possible to sufficiently exhibit the adhesiveness and barrier properties to the deposition layer 23 while suppressing the cost.

(Ninth feature point)
A ninth characteristic point is that the thickness of the deposition layer 23 is 10 nm or more and 300 nm or less.
(Effect of the ninth feature point)
According to the ninth characteristic point, by setting the thickness of the vapor deposition layer 23 to 10 nm or more, the continuity of the vapor deposition layer 23 can be easily achieved, and by setting the thickness to 300 nm or less, the occurrence of curling and cracking can be sufficiently suppressed. It is easy to achieve sufficient gas barrier performance and flexibility.
(Tenth feature point)
A tenth characteristic point is that the basis weight of the paper base material 21 is 20 to 200 g/m ² .
(Effect of tenth feature point)
According to the tenth characteristic point, if it is less than 20 g/m ² , it is too soft and wrinkles are likely to occur during processing, and if it exceeds 200 g/m ² , peeling from the paper layer is likely to occur.

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited to the following examples.
EXAMPLES The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

(Example)
A coating liquid containing a salt of a carboxyl group (trade name: ^Chemipearl S100, ionomer type, particle size: < 0.1 μm, solvent: water, IPA, manufactured by Mitsui Chemicals) was applied with a bar coater and dried in an oven to form an anchor coat layer.
The thickness of the anchor coat layer was 3 μm. Subsequently, AL vapor deposition was performed on the anchor coat layer.
The thickness of the deposited layer was 50 nm. After that, a solution containing a salt of a carboxyl group (trade name: Chemipearl S100, ionomer type, particle size: <0.1 μm, solvent: water, IPA, manufactured by Mitsui Chemicals) was applied onto the vapor-deposited layer with a bar coater, followed by an oven. to form an overcoat layer to obtain a gas barrier laminate. The thickness of the overcoat layer was 3 μm.

(Comparative example)
As a conventional moisture-proof sheet, 30 g/m ² paper gap reinforced paper (manufactured by Tenma Tokushu Paper Co., Ltd.) with corona treatment on one side was extruded from a T-die extruder to fuse molten polyethylene resin between the corona-treated surfaces. Sand lamination was performed at 50 μm to prepare a moisture-proof sheet (paper reinforced paper/polyethylene/paper reinforced paper).
(evaluation)
Regarding the moisture-proof sheets of Examples and Comparative Examples produced above, the moisture permeability was calculated according to JIS Z 0208, and the moisture permeability was compared. Table 1 shows the results.

As is clear from the results in Table 1, the moisture-proof sheets of the examples had significantly lower moisture permeability than the moisture-proof sheets of the comparative examples. By providing the moisture-proof layer 20 in the moisture-proof sheet of the present invention, it is recognized that the performance of moisture permeability is improved. You can expect the effect of reducing it compared to the product.
As a result, it is verified that it is possible to provide backside moisture-proof paper for decorative boards that can prevent warping even when used in a place where there is a large difference in temperature and humidity environments on both sides, which is the subject of the present invention. I was able to

10 Back moisture-proof paper for decorative plate 20 Moisture-proof layer 21 Paper base material 22 Anchor coat layer 23 Vapor deposition layer 24 Overcoat layer 30 Adhesion primer layer 40 Decorative sheet 50 Board base material

Claims (4)

an anchor coat layer containing a first polyolefin having at least one selected from a carboxyl group, a salt of a carboxyl group, a carboxylic acid anhydride group and a carboxylic acid ester, a deposited layer, a carboxyl group, and An overcoat layer containing a second polyolefin having at least one selected from a salt of a carboxyl group, a carboxylic acid anhydride group and a carboxylic acid ester, and a moisture-proof layer provided in this order. Back moisture-proof paper. 2. The back moisture-proof paper for decorative laminate according to claim 1, wherein the anchor coat layer has a thickness of 1 [mu]m or more. 3. The backside moisture-proof paper for decorative laminate according to claim 1, wherein an adhesion primer layer is provided on the exposed surface of the overcoat layer. 4. The moisture-proof back surface paper for decorative laminate according to any one of claims 1 to 3, wherein the paper substrate is a reinforced paper between the papers.

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