JP7728187B2 - Wood composite material, flooring material, method for manufacturing wood composite material, and method for manufacturing flooring material - Google Patents

Description

The present invention relates to wood composite materials, flooring materials, methods for manufacturing wood composite materials, and methods for manufacturing flooring materials.

Flooring materials used in detached houses, apartment buildings, and other buildings include solid wood flooring, as well as decorative flooring made from the surface of wood substrates such as plywood, MDF, and particle board, or laminated wood substrates (hereinafter, laminated wood substrates will also be referred to simply as "wood substrates") with a decorative material made from fine wood applied to the surface.

Decorative flooring materials use a base material that expands and contracts less due to moisture than solid wood, and the surface is coated with various types of paint to prevent moisture from penetrating into the interior. This means that they are less likely to warp and are easier to handle in the environment in which they are used after installation, and for these reasons, they are becoming more widely used on construction sites.

Flooring, a type of composite material, has a decorative panel placed on the surface (top surface) of a wood base material, with grooves such as V-shaped grooves formed in the decorative panel to enhance the design. The surface of the flooring is then finished with a coating to ensure abrasion resistance, scratch resistance, and smoothness, and to prevent cleaning rag fibers from remaining in the grooves. Finishing coating is done using colorless paint or colored paint, and the flooring surface, including the grooves, is made up of a coating film.

To effectively utilize wood substrates with surface defects, such as softwood plywood and wood substrates made from planted trees, composite materials are used in which wood fiber boards are bonded to the surface of the wood substrate (see, for example, Patent Documents 1 to 4).

Patent No. 5909087 specification Japanese Patent Application Laid-Open No. 2008-50896 Patent No. 5820994 specification Japanese Utility Model Application Laid-Open Publication No. 6-16004

In the configuration described in Patent Document 1, the wood fiberboard directly beneath the decorative surface layer of the flooring is made of hardwood fiber. Because hardwood fiberboards are dark in color, if the decorative surface layer is light in color, the underlying hardwood fiberboard will show through the decorative surface layer, causing the color of the underlying base to show through. This show-through of the underlying color detracts from the light color of the decorative surface layer and reduces the design appeal. However, simply replacing hardwood fiberboards with softwood fiberboards results in significant dimensional change in the softwood fiberboard in response to changes in humidity. This causes significant dimensional change in the flooring due to moisture from the concrete foundation and changes in humidity when underfloor heating is in use and not in use, resulting in significant warping of the flooring.

In the configuration described in Patent Document 2, a surface decorative material is laminated onto a wooden base material, and grooves are formed across the surface decorative material and the wooden base material. A primer containing a scale-like pigment is applied to the inner surface of the grooves, preventing excessive absorption of the colored paint into the wooden base material in the grooves. However, because penetration of the colored paint into the grooves is prevented, there is a risk of paint pooling in the grooves. This paint pooling in the grooves reduces the design appeal.

The wood board described in Patent Document 3 has a structure in which a wood-based thermoplastic resin sheet containing wood flour and inorganic filler is adhered to the surface of a wood-based substrate, and a decorative layer is further provided on that surface. Joint grooves are formed in the decorative layer and the wood-based thermoplastic resin sheet, and the surface of the wood board, including the joint grooves, is covered with a surface protective coating. Even with this structure, as with the structure described in Patent Document 2, the penetration of colored paint into the grooves is suppressed, so there is a risk of paint pooling in the grooves. Paint pooling in the grooves detracts from the design.

The veneer-laminated decorative board described in Patent Document 4 has a structure in which a thin veneer is placed on the front side of the decorative board, and a veneer dyed in a similar color to the thin veneer is sandwiched between the thin veneer and a wood substrate placed on the back side of the decorative board. However, with this structure, it is difficult to ensure sufficient strength for the veneer, and it is difficult to ensure sufficient scratch resistance, such as resistance to dents when a heavy object is dropped.

The present invention was made in consideration of the above-mentioned problems, and aims to provide wood composite materials and flooring materials that can suppress warping caused by dimensional changes due to humidity changes, have excellent design potential, and ensure sufficient scratch resistance, as well as methods for manufacturing these materials.

The present invention relates to the following wood composite materials, flooring materials, and manufacturing methods thereof.

(1) a wood substrate;
a first wood fiber board adhered to the surface of the wood substrate;
a second wood fiber board adhered to the surface of the first wood fiber board;
a decorative material adhered to the surface of the second wood fiber board;
Grooves formed in the decorative material and the second wood fiber board;
Equipped with
A wood composite material, wherein the second wood fiber board is softwood MDF.

(2) The wood composite material described in (1) above, wherein the first wood fiber board is hardwood MDF.

(3) The wood composite material according to (2) above, which satisfies at least one of the following: the density of the softwood MDF is 0.70 g/cm ³ or more; and the density of the hardwood MDF is 0.70 g/cm ³ or more.

(4) The wood composite material described in any one of (1) to (3), wherein the second wood fiber board is thinner than the first wood fiber board.

(5) The wood composite material according to any one of (1) to (4), wherein the decorative material is a light-colored board.

(6) The wood composite material according to any one of (1) to (5), wherein the wood substrate includes a coniferous layer.

(7) The composite wood material according to any one of (1) to (6),
a coating film formed on the surface of the decorative material and the surface of the groove portion;
The flooring is provided with:

(8) a wood substrate;
a first wood fiber board adhered to the surface of the wood substrate;
a second wood fiber board adhered to the surface of the first wood fiber board;
a decorative material adhered to the surface of the second wood fiber board;
Grooves formed in the decorative material and the second wood fiber board;
Equipped with
A method for producing a wood composite material, wherein the second wood fiber board is softwood MDF,
A method for manufacturing a wood composite material, comprising the steps of: preparing the wood base material, the first wood fiber board, the second wood fiber board, and the decorative material separately; and then stacking the wood base material, the first wood fiber board, the second wood fiber board, and the decorative material together.

(9) Dividing the first material wood fiber board along the board surface direction at multiple positions in the thickness direction of the first material wood fiber board to form multiple first divided boards;
The method for manufacturing a wood composite material described in (8) above, wherein any one of the plurality of first divided plates is the first wood fiber board.

(10) Dividing the second material wood fiber board along the board surface direction at multiple positions in the thickness direction of the second material wood fiber board to form multiple second divided boards;
A method for manufacturing a wood composite material according to (8) or (9), wherein any one of the plurality of second divided plates is the second wood fiber board.

(11) The method for manufacturing a wood composite material described in (10), wherein the divided boards that become the wood fiber boards include a relatively dense rock layer in the base wood fiber board.

(12) The method for manufacturing a wood composite material described in (11) above, wherein the divided boards that will become the wood fiber boards are positioned with the rock layer facing the decorative material.

(13) A step of forming grooves in the decorative material and the second wood fiber board of the wood composite material according to any one of (8) to (12);
a coating step of coating the wood composite material in which the grooves are formed;
A method for manufacturing a flooring material, comprising:

The present invention makes it possible to provide a wood composite material that can suppress warping caused by dimensional changes due to humidity changes, has excellent design potential, and ensures sufficient scratch resistance.

Fig. 1(A) is a cross-sectional view of a flooring material including a wood composite material according to this embodiment, showing the state of the flooring material cut at a cross section perpendicular to the longitudinal direction. Fig. 1(B) is an enlarged view of a portion of Fig. 1(A). 2A and 2B are schematic diagrams showing the main steps of preparing a first wood fiber board and a second wood fiber board in the (A1) preparation step. FIG. 3 is a schematic diagram showing the (A2) bonding step. FIG. 4(A) is a schematic diagram showing the (A3) groove forming step, and FIG. 4(B) is a schematic diagram showing the (A4) painting step.

The preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

Figure 1(A) is a cross-sectional view of flooring material 1 including wood composite material 2 according to this embodiment, showing the state of the flooring material 1 cut at a cross section perpendicular to the longitudinal direction. Figure 1(B) is an enlarged view of a portion of Figure 1(A). Figures 2(A) and 2(B) are schematic diagrams showing the main steps of preparing a first wood fiber board and a second wood fiber board in the (A1) preparation step. Figure 3 is a schematic diagram showing the (A2) bonding step. Figure 4(A) is a schematic diagram showing the (A3) groove forming step. Figure 4(B) is a schematic diagram showing the (A4) painting step.

1. Wood Composite Material According to the Present Embodiment Referring to FIGS. 1(A) and 1(B), the flooring material 1 according to the present embodiment has a total thickness of approximately 12.0 mm. There are no particular restrictions on the width or length of the flooring material 1. Typically, the width is 150, 300, or 303 mm, and the length is 900, 1800, or 1818 mm. A thin thickness is preferable from the standpoint of workability (e.g., ease of cutting and reduced waste), but from the standpoint of rigidity, a thickness of 5.0 mm or more is preferable, and 6.0 mm or more is more preferable. The flooring material 1 is installed on a base board or a heated floor mat for underfloor heating. Hereinafter, when the flooring material 1 is installed in a building, the surface of the flooring material 1 facing the member on which the flooring material 1 is placed is referred to as the back surface, and the surface facing the ceiling of the building is referred to as the front surface.

The flooring material 1 comprises a wood composite material 2 and a coating film 3.

The wood composite material 2 has a wood substrate 10, a first wood fiber board 11 adhered to the surface of the wood substrate 10, a second wood fiber board 12 adhered to the surface of the first wood fiber board 11, a decorative material 13 adhered to the surface of the second wood fiber board 12, and grooves 14 formed in the decorative material 13 and the second wood fiber board 12.

The structure of the wood substrate 10 is not particularly specified. Examples of wood substrate 10 include plywood, LVL (laminated veneer lumber), particle board, and OSB (oriented strand board). The material of the wood substrate is not particularly limited, but examples include softwood plywood, plywood made from fast-growing trees such as planted trees, hardwood plywood, and plywood made from a combination of multiple of these woods.

Examples of the above-mentioned softwood plywood include larch, Abies sachalinensis, cypress, cedar, spruce, Japanese spruce, red pine, Douglas fir, western hemlock, spruce, and radiata pine, and further examples include plywood made from one or more selected species of these. Examples of fast-growing tree plywood, such as plantation trees, include falcata, eucalyptus, acacia mangium, japonica, samosa, and poplar, and further examples include plywood made from one or more selected species of these. Examples of hardwood plywood include tropical woods such as meranti, and fast-growing tree plywood such as lauan plywood and falcata plywood.

In this embodiment, the wood substrate 10 is a laminated board made of multiple laminated veneers, such as a 5-ply softwood plywood. For example, the first, third, and fifth layers are made of Abies sachalinensis, and the second and fourth layers are made of cedar. In particular, for the first and fifth layers (back boards), it is advisable to select a wood species with a relatively higher specific gravity than the second and fourth layers (core boards). This is because wood species with a higher specific gravity tend to have higher strength and better surface properties, while wood species with a lower specific gravity tend to have lower strength and more defects such as knots. This laminated board may also be a plywood in which the first, third, and fifth layers are made of Meranti wood and the second and fourth layers are made of Falcata wood. The wood species may be selected appropriately depending on the performance desired for the substrate.

Examples of the thickness of each of the first, third, and fifth layers are 1.0 mm or more, 1.2 mm or more, 1.4 mm or more, 1.6 mm or more, or 1.7 mm or more. Examples of the thickness of each of the second and fourth layers are 2.0 mm or more, 2.2 mm or more, 2.4 mm or more, or 2.6 mm or more. It is preferable that the second and fourth layers be made of the same wood species and have the same thickness. The thickness of each layer may be selected appropriately depending on the performance required of the substrate.

The number of plies in the laminated board that makes up the wood substrate 10 may be 3, 7, or more than 7. The laminated board may also be plywood made from a mixture of wood species depending on the required performance.

The thickness of the wood substrate 10 is not particularly limited, but can be, for example, 8.0 to 12.0 mm. In order to ensure sufficient strength, a thickness of 9.0 mm or more is preferable, for example, approximately 10 mm. The bending Young's modulus of the wood substrate 10 in the width direction is preferably 3.0 GPa or more.

A backing material may be attached to the back surface of the wood substrate 10. Examples of backing materials include veneer, paper, resin film, resin-laminated paper, and polysand paper, which is a resin composite with paper on both sides. From the perspective of preventing water vapor from entering the flooring material 1, the backing material preferably has a water vapor permeability of 5 g/( ^m² ·d) or less, more preferably 4 g/( ^m² ·d) or less, as measured by JIS K 7129B (infrared sensor). When the backing material is veneer, the thickness is preferably 0.1 mm to 0.4 mm. When the backing material is paper or film, the thickness is preferably 5 μm to 100 μm.

The first wood fiber board 11 is not particularly limited as long as it is a wood fiber board. Examples of the first wood fiber board 11 include MDF (medium density fiberboard), HB (hard board), and insulation board. Examples of MDF include softwood MDF and hardwood MDF. Examples of these softwoods and hardwoods include the above-mentioned tree species. The first wood fiber board 11 is preferably made of hardwood MDF, which has excellent hardness and little dimensional change due to humidity changes. The density of the hardwood MDF is preferably 0.70 g/cm ³ or more in order to ensure sufficient scratch resistance when a heavy object is dropped.

The hardwood MDF is a dark-colored MDF primarily composed of hardwood. The thickness of the hardwood MDF constituting the first wood fiber board 11 is preferably 0.7 mm to 2.7 mm. By making the hardwood MDF 0.7 mm or thicker, sufficient strength (hardness) can be ensured. This allows the hardwood MDF to effectively absorb the irregularities of the wood substrate 10, more reliably preventing the irregularities of the wood substrate 10 from lifting up onto the decorative material 13. Furthermore, by making the hardwood MDF 2.7 mm or thinner, excessive dimensional change in the first wood fiber board 11 due to humidity is prevented, more reliably preventing warping of the flooring material 1. Examples of lower limits for the thickness of the hardwood MDF include 0.7 mm, 1.0 mm, and 1.1 mm. Examples of upper limits for the thickness of hardwood MDF include 2.7 mm, 2.2 mm, 1.7 mm, 1.5 mm, 1.4 mm, and 1.3 mm.

1(B) and 2(B), the first wood fiber board 11 can be obtained, for example, by dividing a first material wood fiber board 21 (MDF), which is the material for the first wood fiber board 11, in half thicknesswise using a slicer or the like, and then grinding one of the resulting two first divided boards 31 to a predetermined thickness using a sander or the like. Dividing MDF into the first wood fiber board 11 eliminates the need to adjust the thickness of the MDF (first material wood fiber board 21) to match the thickness of the first wood fiber board 11. Furthermore, grinding reduces thickness variations across the board surface. Furthermore, from the perspective of ensuring the strength of the first wood fiber board 11, it is preferable that the first divided board 31 used as the first wood fiber board 11 be either the top or bottom surface of the MDF in the first material wood fiber board 21, including the high-density rock layer on both sides. Furthermore, the first divided board 31 used as the first wood fiber board 11 is preferably positioned with the cut surface of the first material wood fiber board 21 facing the wood base material 10 (with the rock layer facing the decorative material 13). This allows the high-strength rock layer to absorb impacts from the decorative material 13, further improving the scratch resistance (i.e., the resistance to dents) of the flooring material 1. Note that the number of divisions of the first material wood fiber board 21 when forming the first wood fiber board 11 may be more than two. Alternatively, the first material wood fiber board 21 may be used as the first wood fiber board 11 without being divided. The thickness of the first material wood fiber board 21 is not limited.

The second wood fiber board 12 is made of softwood MDF. Examples of softwood include the above-mentioned tree species. From the viewpoint of ensuring sufficient scratch resistance when a heavy object is dropped, the density of the softwood MDF is preferably 0.70 g/cm ³ or more, more preferably 0.80 g/cm ³ or more, and even more preferably 0.85 g/cm ³ or more. The surface density of the portion of the second wood fiber board 12 where the grooves 14 are formed affects the paint absorption. If the density is too high, paint absorption will be poor, and there is a risk of paint pooling in the grooves 14. From the viewpoint of paint absorption, the surface density of the softwood MDF is preferably 1.1 g/cm ³ or less.

In this specification, both softwood MDF and hardwood MDF include high density MDF with a density of 0.85 g/cm ³ or more.

The softwood MDF is a light-colored MDF primarily composed of softwood. The thickness of the softwood MDF constituting the second wood fiber board 12 is preferably 0.3 mm to 1.0 mm. By making the softwood MDF 0.3 mm or thicker, scratch resistance, such as dents caused by a heavy object being dropped, can be ensured. Furthermore, by making the softwood MDF 1.0 mm or thinner, dimensional changes in the second wood fiber board 12 due to humidity changes are minimized, thereby more reliably preventing warping of the flooring material 1. Furthermore, while wood fiber boards are more susceptible to paint penetration than decorative materials such as veneer, making the softwood MDF 1.0 mm or thinner can prevent excessive paint penetration in the grooves 14, resulting in the coating film 3 not being formed on the surface of the second wood fiber board 12. This allows for a more uniform coating film 3 to be formed on the surface of the second wood fiber board 12 and the surface of the decorative material 13 in the grooves 14. Examples of lower limits for the thickness of softwood MDF include 0.3 mm and 0.4 mm. Examples of upper limits for the thickness of softwood MDF include 1.0 mm, 0.7 mm, and 0.6 mm.

1(B) and 2(A), the second wood fiber board 12 can be obtained, for example, by dividing a second material wood fiber board 22 (MDF), which is the material for the second wood fiber board 12, into four pieces in the thickness direction using a slicer or the like, and then grinding one of the four second divided boards 32 to a predetermined thickness using a sander or the like. Dividing MDF into the second wood fiber boards 12 eliminates the need to adjust the thickness of the MDF (second material wood fiber board 22) to match the thickness of the second wood fiber board 12. Grinding reduces thickness variations across the board surface. Furthermore, from the perspective of ensuring the strength of the second wood fiber board 12, it is preferable that the second divided boards 32 used as the second wood fiber board 12 be either the top or bottom surface of the softwood MDF in the second material wood fiber board 22, including the high-density rock layers on both sides. Additionally, the second divided board 32 used as the second wood fiber board 12 is preferably positioned with the cut surface of the second material wood fiber board 22 facing the wood base material 10 (with the rock layer facing the decorative material 13). This allows the high-strength rock layer to absorb impacts from the decorative material 13, further improving the scratch resistance (i.e., the resistance to dents) of the flooring material 1. Note that the number of divisions into the second material wood fiber board 22 when forming the second wood fiber board 12 may be two, three, or more than four. The thickness of the second material wood fiber board 22 is not limited.

In this embodiment, the second wood fiber board 12 is thinner than the first wood fiber board 11. This prevents the thickness of the second wood fiber board 12 from becoming excessively large. As a result, the paint used to form the coating film 3 does not soak into the second wood fiber board 12 excessively in the grooves 14, making the finish (appearance) of the coating film 3 more uniform in the grooves 14 and the decorative material 13. Furthermore, dimensional change in the second wood fiber board 12, which is made of MDF containing softwood, which experiences greater dimensional change with humidity changes than hardwood, can be reduced. This more reliably suppresses warping of the flooring material 1.

The combined thickness of the first wood fiber board 11 and the second wood fiber board 12 (total thickness) is preferably 1.0 mm to 3.0 mm. By making the combined thickness of the wood fiber boards 11, 12 1.0 mm or more, the strength of the wood fiber boards 11, 12 can be ensured. This allows the wood fiber boards 11, 12, particularly the first wood fiber board 11, to effectively absorb irregularities in the wood substrate 10, more reliably preventing the irregularities in the wood substrate 10 from lifting up onto the decorative material 13. Furthermore, by making the combined thickness of the wood fiber boards 11, 12 3.0 mm or less, dimensional changes in the wood fiber boards 11, 12, particularly the second wood fiber board 12, due to humidity are prevented from becoming too large, more reliably preventing warping of the flooring material 1. Examples of lower limits for the combined thickness of the wood fiber boards 11, 12 include 1.0 mm, 1.2 mm, 1.5 mm, and 1.6 mm. Furthermore, examples of upper limits for the total thickness of the wood fiber boards 11 and 12 include 3.0 mm, 2.5 mm, 2.2 mm, 1.9 mm, and 1.8 mm.

The decorative material 13 can be made of processed wood such as veneer or sawn board, or a decorative sheet with a printed color pattern on a sheet such as resin film or paper. The thickness of the decorative material 13 is generally 0.05 mm to 3.0 mm, but is not limited to this thickness. When attaching the wooden decorative material 13 using heat and pressure (hot pressing), the thickness of the decorative material 13 is preferably 1.0 mm or less to ensure sufficient heat is applied to the adhesive bonding the decorative material 13 to the second wood fiber board 12 to increase the adhesive strength. In this embodiment, the decorative material 13 is preferably composed of a single light-colored board. Examples of wood species for this light-colored board include maple, paulownia, camphor, chestnut, linden, oak, birch, ash, ash, horse chestnut, oak, elm, beech, sycamore, and cherry. Note that the wood species for the light-colored board are not limited to the above-mentioned species. In this way, by forming the decorative material 13 from a single light-colored board, the color difference between the decorative material 13 and the second wood fiber board 12, which is made of softwood MDF and has a light color, can be reduced. This means that the effort required to reduce the color difference between the decorative material 13 and the second wood fiber board 12 in the groove portion 14 using the coating film 3 can be reduced or even eliminated. Furthermore, even if the decorative material 13 is thin, the design is only slightly impaired by the reflection of the second wood fiber board 12, allowing for greater freedom in selecting the thickness of the decorative material 13.

The adhesives used to bond the surface of the wood substrate 10 to the back surface of the first wood fiber board 11, the surface of the first wood fiber board 11 to the back surface of the second wood fiber board 12, and the surface of the second wood fiber board 12 to the decorative material are not particularly limited. When the first wood fiber board 11 is hardwood MDF, a modified vinyl acetate adhesive can be used as the adhesive to bond the wood substrate 10 to the first wood fiber board 11, and a urea-melamine resin adhesive can be used as the adhesive to bond the wood fiber boards 11, 12 together. When the decorative material 13 is wood, a urea-melamine resin adhesive can be used as the adhesive to bond the second wood fiber board 12 to the decorative material 13. On the other hand, when the decorative material 13 is a decorative sheet, a water-based adhesive or a hot-melt adhesive can be used as the adhesive to bond the second wood fiber board 12 to the decorative material 13. The adhesive that bonds the wood fiber boards 11 and 12 together is preferably placed at least in a location on the second wood fiber board 12 that faces vertically the location where the groove 14 is formed, in order to prevent the paint used to form the coating from seeping into the groove 14.

The grooves 14 are formed along the length of the wood composite material 2. The grooves 14 are formed in the decorative material 13 and the second wood fiber board 12, and are, for example, V-shaped in a cross section perpendicular to the length of the wood composite material 2. The cross-sectional shape of the grooves 14 is not particularly limited. For example, the grooves 14 may be R-grooves with curved cross-sections or VR-grooves with cross-sectional shapes that combine straight and curved surfaces. The grooves 14 need only be formed across the decorative material 13 and the second wood fiber board 12; there are no specific limitations on their depth. However, it is preferable that the depth of the grooves 14 be within the thickness of the second wood fiber board 12. If the grooves 14 reach the first wood fiber board 11, the first wood fiber board 11 would be exposed on the surface of the wood composite material 2, and the difference in color between the bottom and the open side of the grooves 14 would detract from the design. The angle formed by the pair of side surfaces of the groove portion 14 is not particularly limited, but can be, for example, approximately 30 to 120 degrees.

The figures illustrate an example in which grooves 14 are formed at the midpoint in the width direction of the wood composite material 2. However, this does not have to be the case. Grooves 14 may be half grooves (parts that function as a single groove when joined with adjacent products when installed as a product) provided on the four sides of the periphery of the surface of the wood composite material 2, or chamfered parts. If the width of the wood composite material 2 is small, grooves 14 may not be formed along the length of the wood composite material 2 at the midpoint in the width direction, and grooves 14 may be formed only on the periphery of the wood composite material 2.

In addition to vertical grooves formed along the length, the grooves 14 may also include horizontal grooves formed along the width. In the case of a wood composite material 2 with a herringbone design, the grooves 14 extend diagonally relative to the length and width. In this way, the orientation and placement of the grooves 14 are determined appropriately based on the design conditions of the wood composite material 2, and are not limited to specific conditions.

The coating film 3 is formed on the surface of the decorative material 13 and the surface of the grooves 14 by applying a transparent paint, a translucent paint, or a colored paint to the surface of the wood composite material 2 and drying it. Examples of the above-mentioned paint include water-based paint, solvent-based paint, and solvent-free paint. There are no particular limitations on the thickness of the coating film 3.

2. Method for Manufacturing Flooring Material 1 According to the Present Embodiment Referring to FIGS. 1(A) to 4(B), flooring material 1 according to the present embodiment can be manufactured by the following steps.
(A1) A preparation step of individually preparing a wood substrate 10, a first wood fiber board 11, a second wood fiber board 12, and a decorative material 13;
(A2) A bonding step of forming a composite material 40 by overlapping and bonding the wood substrate 10, the first wood fiber board 11, the second wood fiber board 12, and the decorative material 13;
(A3) a groove forming step of forming grooves 14 in the decorative material 13 and the second wood fiber board 12 of the composite material 40 to form the wood composite material 2;
(A4) A painting process in which the surface of the decorative material 13 and the groove portion 14 of the wood composite material 2 is painted to form a coating film 3, thereby converting the wood composite material 2 into a flooring material 1.
A more specific explanation will be given below.

<(A1) Preparation step of individually preparing the wood base material 10, the first wood fiber board 11, the second wood fiber board 12, and the decorative material 13>
The wood base material 10, the first wood fiber board 11, the second wood fiber board 12, and the decorative material 13 are each prepared as a single piece of the above-mentioned material.

For the first wood fiber board 11, the first material wood fiber board 21 is divided along the board surface direction at multiple positions in the thickness direction of the first material wood fiber board 21 to form multiple (e.g., two) first divided boards 31, and one of the multiple first divided boards 31 serves as the first wood fiber board 11. The first divided board 31 that will become the first wood fiber board 11 is preferably polished to a predetermined thickness to become the first wood fiber board 11. The first material wood fiber board 21 may be divided into three or more pieces, but it is preferable that the first divided board 31 that will become the first wood fiber board 11 includes a relatively dense rock layer in the first material wood fiber board 21.

For the second wood fiber board 12, the second material wood fiber board 22 is divided along the board surface direction at multiple positions in the thickness direction of the second material wood fiber board 22 to form multiple (e.g., four) second divided boards 32, and one of the multiple second divided boards 32 serves as the second wood fiber board 12. The second divided boards 32 that will become the second wood fiber board 12 are preferably polished to a predetermined thickness. The number of second divided boards 32 (number of divisions) formed from the second material wood fiber board 22 may be two, three, or more than four. For the second divided boards 32 that will become the second wood fiber board 12, it is preferable from a manufacturing and cost perspective to set the thickness when divided from the second material wood fiber board 22 to a value close to the desired final thickness and then adjust to the final thickness by polishing. Additionally, the second divided board 32 that becomes the second wood fiber board 12 preferably contains the relatively dense rock layer in the second material wood fiber board 22.

<(A2) Adhesion step of superimposing and adhering the wood base material 10, the first wood fiber board 11, the second wood fiber board 12, and the decorative material 13 to form the composite material 40>
When forming the composite material 40, various patterns can be considered for the order in which the wood base material 10, the first wood fiber board 11, the second wood fiber board 12, and the decorative material 13 are layered and bonded together. For example, the following patterns 1 to 3 can be exemplified. When bonding the components together, an appropriate bonding method can be selected, such as hot pressing or room temperature pasting.

As an example of pattern 1, as shown in Figure 3, a first wood fiber board 11 is bonded to a wood substrate 10, then a second wood fiber board 12 is bonded to the first wood fiber board 11, and then a decorative material 13 is bonded to form a composite material 40.

As an example of pattern 2, as shown in Figure 3, wood fiber boards 11 and 12 are bonded together, and then a wood base material 10 is bonded to the composite fiber board formed by bonding the wood fiber boards 11 and 12 together, and then a decorative material 13 is bonded to the second wood fiber board 12 to form a composite material 40.

As an example of pattern 3, as shown in Figure 3, wood fiber boards 11 and 12 are bonded together, then a decorative material 13 is bonded to the composite fiber board formed by bonding the wood fiber boards 11 and 12 together, and then a wood base material 10 is bonded to the first wood fiber board 11 to form a composite material 40.

Note that because the second wood fiber board 12 and the decorative material 13 are both extremely thin, it is not practical to bond these second wood fiber boards 12 and decorative material 13 together, but this bonding process is not excluded.

Furthermore, examples of the adhesive used to bond the wood base material 10 and the first wood fiber board 11, the adhesive used to bond the wood fiber boards 11 and 12 together, and the adhesive used to bond the second wood fiber board 12 and the decorative material 13 include those described above.

A more specific example of a method for overlapping and adhering a wood substrate 10, a first wood fiber board 11, a second wood fiber board 12, and a decorative material 13 is to apply a modified vinyl acetate adhesive to the wood substrate 10, attach a first wood fiber board 11 made of hardwood MDF, and heat-pressure bond the two together to form a composite substrate. Next, a urea-melamine resin adhesive is applied to the first wood fiber board 11 of this composite substrate, and a second wood fiber board 12 made of softwood MDF is attached. After temporary pressing, the two are then coated with urea-melamine resin adhesive, and the decorative material 13 is attached to form a heat-pressure bond (simultaneous bonding).

A more specific example of a method for overlapping and adhering a wood substrate 10, a first wood fiber board 11, a second wood fiber board 12, and a decorative material 13 is the use of a decorative sheet as the decorative material 13. In this case, a modified vinyl acetate adhesive is applied to the wood substrate 10, and a first wood fiber board 11 made of hardwood MDF is attached and heat-pressed to form a composite substrate. Next, a urea-melamine resin adhesive is applied to the first wood fiber board 11 of the composite substrate, and a second wood fiber board 12 made of softwood MDF is attached and heat-pressed. Next, a decorative sheet is attached to the composite substrate, including the second wood fiber board 12, using a water-based adhesive or hot-melt adhesive.

<(A3) Groove forming step of forming grooves 14 in the composite material 40 to form the wood composite material 2>
In this process, as shown in Figure 4 (A), grooves are formed in the decorative material 13 of the composite material 40 and the second wood fiber board 12 using a cutter or the like to form grooves 14 in the composite material 40, and the wood composite material 2 is formed.

<(A4) Coating step of forming coating film 3 by coating the surfaces of decorative material 13 and grooves 14 in wood composite material 2, and converting wood composite material 2 into flooring material 1>
In this process, as shown in Figure 4 (B), the above-mentioned paint is applied to the decorative material 13 and the grooves 14 of the wood composite material 2 having the grooves 14 formed therein, and then dried to form a flooring material 1 having a coating film 3 formed on the surface of the wood composite material 2. The method of applying the paint in the painting process is not particularly limited. Examples of application methods include a flow coater (curtain coater), a roll coater, and spray application, which apply the paint thickly. Of these application methods, when using a flow coater to apply the paint thickly, paint absorption into the grooves 14 has a significant impact on the design of the flooring material 1. Note that, even when using a roll coater or spray application, paint absorption into the grooves 14 also affects the design of the flooring material 1.

As described above, in this embodiment, the grooves 14 are formed in the decorative material 13 and the second wood fiber board 12, and the second wood fiber board 12 is made of softwood MDF. The first wood fiber board 11 is bonded to the back surface of the second wood fiber board 12. This configuration allows the second wood fiber board 12 to be made thinner. This reduces dimensional changes in the second wood fiber board 12 in the wood composite material 2, such as those caused by moisture from the building or by drying during underfloor heating. Furthermore, when the decorative material 13 is made of a light-colored board, both the decorative material 13 and the second wood fiber board 12 are light-colored. This reduces the color difference between the decorative material 13 and the second wood fiber board 12 in the grooves 14, preventing the color of the base (the second wood fiber board 12) from showing through. Furthermore, the paint used to form the coating film 3 on the surface of the wood composite material 2 does not need to be a colored paint, and a transparent paint can be used. This allows for a natural finish with excellent design. Furthermore, because an adhesive layer is provided between the second wood fiber board 12 and the first wood fiber board 11, the paint is prevented from seeping below this adhesive layer. Therefore, the paint is absorbed into the second wood fiber board 12, which is formed to be moderately thin, in the grooves 14. As a result, the paint is applied appropriately to the surface of the grooves 14, preventing paint from pooling in the grooves 14. As a result, a natural finish with even better design is achieved. Furthermore, when the decorative material 13 is made of a dark-colored board, a color difference occurs between the decorative material 13 and the light-colored second wood fiber board 12 in the grooves 14, so a colored paint is required as a material for the coating film 3. However, as described above, the second wood fiber board 12 can be made moderately thin, and because an adhesive layer is provided between the second wood fiber board 12 and the first wood fiber board 11, the paint is prevented from seeping below the adhesive layer into the first wood fiber board 11. Therefore, the colored paint is absorbed into the second wood fiber board 12 in the grooves 14 in an appropriate amount. As a result, the paint is applied to the surface of the grooves 14 in an appropriate amount, and the coating film 3 can be reliably formed in the grooves 14. Therefore, even if dirt occurs in the grooves 14, the dirt adheres to the coating film 3, making it easy to wipe off the dirt manually. Furthermore, if the coating film 3 is not formed in the grooves 14, moisture or wax may seep into the second wood fiber board 12, causing swelling or mold. However, this prevents such problems from occurring. Furthermore, because the paint is applied to the grooves 14 in an appropriate amount, the formation of paint pools in the grooves 14 is prevented. As a result, a natural color can be achieved across the decorative material 13 and the second wood fiber board 12 in the grooves 14, resulting in a natural finish with excellent design. Furthermore, because the paint soaks into the second wood fiber board 12 to a certain extent, adhesion between the coating film 3 and the wood composite material 2 is improved, preventing peeling of the coating film 3 from the wood composite material 2 and reducing deterioration of the design. Furthermore, because the second wood fiber board 12, made of MDF, which is stronger than veneer, is placed directly below the decorative material 13, scratch resistance, such as resistance to dents when a heavy object is dropped, is ensured. As a result, warping caused by dimensional changes due to humidity changes and other factors, can be reduced, resulting in a wood composite material 2 that has excellent design and sufficient scratch resistance.

Furthermore, according to this embodiment, when the first wood fiber board 11 is made of hardwood MDF, the first wood fiber board 11 can be formed from a material that undergoes less dimensional change due to humidity changes than softwood. This makes it possible to more reliably suppress warping of the wood composite material 2.

In addition, according to this embodiment, the second wood fiber board 12 is thinner than the first wood fiber board 11, allowing the paint that is the material for the coating film 3 to be absorbed appropriately into the second wood fiber board 12. Furthermore, dimensional changes in the second wood fiber board 12 due to humidity changes are minimal, which allows for less warping of the flooring material 1.

Furthermore, according to this embodiment, even when the decorative material 13 is a light-colored board, the degree to which the second wood fiber board 12 made of softwood MDF is visible through the decorative material 13 can be reduced. Therefore, even when the decorative material 13 is a light-colored board, the natural color of the flooring material 1 can be achieved, and the design of the flooring material 1 can be enhanced.

Furthermore, according to this embodiment, when the wood substrate 10 includes a coniferous tree layer, tree species that are relatively widely grown in Japan, such as cedar and cypress, can be effectively used as the flooring material 1. In particular, when the wood substrate 10 includes both a coniferous tree layer and a broadleaf tree layer, the use of broadleaf trees, which experience minimal dimensional change due to humidity changes, can more reliably suppress warping of the flooring material 1.

In the above embodiment, the wood composite material 2 is used as a flooring material. However, this does not have to be the case. The wood composite material 2 may also be used for other purposes, such as wall materials.

To confirm the effects of the present invention, flooring materials were produced as Example, Comparative Example 1, Comparative Example 2, and Comparative Example 3.

<Production Method of Example>
A composite substrate was produced by applying a modified vinyl acetate adhesive to the surface of a wood substrate made of softwood plywood, and then bonding a first wood fiberboard made of hardwood MDF to it and thermocompressing it. Next, a urea-melamine resin adhesive was applied to the surface of the first wood fiberboard in the composite substrate, and a second wood fiberboard made of softwood MDF was bonded to it, followed by temporary pressing. A urea-melamine resin adhesive was then applied on top of that, and a decorative board was bonded to it and thermocompressed (simultaneous bonding) to produce a wood composite. Next, grooves were formed in the decorative material and the second wood fiberboard of the wood composite, and then paint was applied to the surface of the wood composite using a flow coater to complete the flooring material.

<Production method of Comparative Example 1>
A composite substrate was produced by applying a modified vinyl acetate adhesive to the surface of a wood substrate made of softwood plywood, and then bonding a wood fiberboard made of hardwood MDF together under heat and pressure. Next, a urea-melamine resin adhesive was applied to the surface of the wood fiberboard in the composite substrate, and a decorative board was then bonded together under heat and pressure to produce a wood composite. Next, grooves were formed in the decorative material and wood fiberboard of the wood composite, and then paint was applied to the surface of the wood composite using a flow coater to complete the flooring material.

<Method for producing Comparative Example 2>
A composite substrate was produced by applying a modified vinyl acetate adhesive to the surface of a wood substrate made of softwood plywood, and then bonding a wood fiberboard made of softwood HB to the substrate and subjecting it to thermal pressure compounding. Next, a urea-melamine resin adhesive was applied to the surface of the wood fiberboard in the composite substrate, and a decorative board was then bonded to the substrate and subjecting it to thermal pressure compounding to produce a wood composite. Next, grooves were formed in the decorative material and wood fiberboard of the wood composite, and then paint was applied to the surface of the wood composite using a flow coater to complete the flooring material.

<Production method of Comparative Example 3>
A flooring material was produced that was constructed in the same manner as in Comparative Example 1, except that softwood MDF was used as the wood fiberboard.

<Materials and thicknesses of the example and comparative examples 1 to 3>
The configuration of the embodiment is as follows.
Wood substrate: 10.0 mm softwood plywood (with backer paper)
First wood fiberboard: 1.2 mm hardwood MDF
Second wood fiberboard: 0.47 mm softwood MDF
Decorative material: 0.3mm veneer (maple)

The configuration of Comparative Example 1 is as follows.
Wood base material: 9.0 mm softwood plywood Wood fiberboard: 2.7 mm hardwood MDF
Decorative material: 0.3mm veneer (maple)

The configuration of Comparative Example 2 is as follows.
Wood substrate: 10.0 mm softwood plywood (with backer paper)
Wood fiberboard: 1.8mm softwood HB
Decorative material: 0.3mm veneer (maple)

The configuration of Comparative Example 3 is as follows.
Wood base material: 9.0 mm softwood plywood Wood fiber board: 2.7 mm softwood MDF
Decorative material: 0.3mm veneer (maple)

As is clear from the above explanation, the Example uses two wood fiber boards, a first and a second, while Comparative Examples 1 to 3 use only one wood fiber board. The dimensions of the Example and Comparative Examples 1 to 3 are all 303 mm wide x 1,818 mm long.

<Test Method>
Test 1 (drying test): The sample was left in a dry environment at a temperature of 40° C. and a humidity of 30% for 2 weeks, and the dimensional change before and after the test was measured.
Test 2 (moisture absorption test): The sample was left in a moisture absorption environment at a temperature of 30° C. and a humidity of 90% for 2 weeks, and the dimensional change before and after the test was measured.
In addition, in Tests 1 and 2, the design of the grooves was visually evaluated.
The results are shown in Table 1

<Evaluation of dimensional change>
The dimensional change rate was evaluated. The dimensional change rate (%/%) is the amount of dimensional change per 1% of moisture content, calculated by dividing the amount of dimensional change (%) due to drying or moisture absorption of the wood by the size before the test, and then dividing this amount by the amount of change (%) in the moisture content of the wood due to drying or moisture absorption. The moisture content was measured using the total dry method, which measures the total dry weight of the product, and the total dry moisture content was used for calculations.

For example, if the original dimension was 1818 mm and it was 1816 mm after the drying test, the change would be 2 mm, and the dimensional change would be 2 mm/1818 mm = 0.11 (%). For example, if the moisture content changed by 4% after the drying test, the dimensional change rate would be 0.11 (%)/4 (%) = 0.0275 (%/%). The larger the dimensional change rate, the larger the amount of dimensional change when the moisture content changes by 1%, and it can be said that warping and gaps are more likely to occur (larger behavior).

In the drying test, the dimensional change rate of the Example was the smallest in both the length and width directions, demonstrating that the degree of dimensional change due to drying is extremely small. Furthermore, in the moisture absorption test, the dimensional change rate of the Example was greater in both the length and width directions than Comparative Examples 1 and 3, but was significantly smaller than the dimensional change rate of the Example in the drying test, demonstrating that the degree of dimensional change due to moisture absorption is extremely small.

As is clear from Comparative Examples 2 and 3, when wood fiberboards are made entirely of softwood, even if they are thin (even if the ratio to plywood is small), dimensional change is greater than with hardwood, resulting in significant warping when humidity changes, especially when drying. In the Examples, dimensional change was suppressed by reducing the thickness ratio of softwood MDF as the second wood fiberboard, demonstrating minimal behavior in response to humidity changes. Dimensional change can be minimized, particularly under dry conditions, which minimizes warping and gaps when using underfloor heating.

<Design evaluation>
For the examples and comparative examples 1 to 3, both electron microscope observation and visual inspection with the naked eye were performed. For the electron microscope observation, a cross section perpendicular to the longitudinal direction was magnified 100 times with an electron microscope, and the magnified image was photographed. Then, in the magnified image, it was determined whether a coating film was formed on the entire surface of the decorative material and the groove portion, and whether there was a problem with the coating film in the groove portion based on the presence of paint pools at the bottom of the groove. The same judgments as those made using the photographed images were also made in the visual inspection with the naked eye.

The presence or absence of paint accumulation was determined primarily by visual inspection with the naked eye, while the presence or absence of a coating film on the entire surface of the decorative material and grooves was determined primarily by images taken using an electron microscope.

The evaluation was as follows:
○: No problem with the design of the groove.
×: There are some grooves where the coating film does not remain.
XX: There are some areas where paint has accumulated in the grooves.
As long as a coating film is formed on the surface of the flooring material, there are no problems with dirt or absorption of water or wax, so the evaluation was based on the presence or absence of a coating film.

In Comparative Examples 1 and 3, the grooves absorbed too much paint, resulting in some areas where the paint film was absent, resulting in a rating of ×. In Comparative Example 2, the high surface density of the HB made it difficult for the paint to penetrate, resulting in areas where paint pooled in the grooves. Therefore, in the electron microscope photograph, the coating film on the grooves had a U-shaped cross section rather than a V-shaped cross section, resulting in a rating of ××. In Comparative Example 2, the grooves appeared to be filled with paint. Note that, as in Comparative Example 2, when the wood fiberboard is a 1.8 mm thick HB with a surface density of 1.1 g/cm ³ , paint pooling may occur. In contrast, in the Example, the wood fiberboard was polished to a thickness of 0.3 to 0.4 mm to leave the relatively dense rock layer, and the measured surface density was an average of 0.85 g/cm ³ (0.83 to 0.88 g/cm ³ ). Even with MDF, a similar wood fiberboard, when the surface density is around 1.1 g/cm ³ , paint pooling may occur, similar to that of HB. In addition, the HB of Comparative Example 2 uses softwood material, but is dark in color due to manufacturing. Therefore, when using light-colored boards as decorative materials, coloring of the grooves is necessary. On the other hand, in the Example, a coating film of appropriate thickness is formed over the entire groove, there is no paint accumulation, and the coating film in the grooves is V-shaped in cross section. There are no problems with the design finish of the grooves, and it was rated ○, demonstrating excellent design.

The present invention provides wood composite materials, flooring materials, and methods for manufacturing these.

REFERENCE SIGNS LIST 1 Flooring material 2 Wood composite material 3 Coating film 10 Wood substrate 11 First wood fiber board 12 Second wood fiber board 13 Decorative material 14 Groove portion 21 First material wood fiber board 22 Second material wood fiber board 31 First divided board 32 Second divided board

Claims (13)

A wood substrate and
a first wood fiber board adhered to the surface of the wood substrate;
a second wood fiber board adhered to the surface of the first wood fiber board;
a decorative material adhered to the surface of the second wood fiber board;
Grooves formed in the decorative material and the second wood fiber board;
Equipped with
A wood composite material, wherein the second wood fiber board is softwood MDF. The wood composite material according to claim 1, wherein the first wood fiber board is hardwood MDF. The wood composite material according to claim 2, wherein the density of the softwood MDF is 0.70 g/cm ³ or more, or the density of the hardwood MDF is 0.70 g/cm ³ or more. The wood composite material described in any one of claims 1 to 3, wherein the second wood fiber board is thinner than the first wood fiber board. The wood composite material according to any one of claims 1 to 4, wherein the decorative material is a light-colored board. The wood composite material according to any one of claims 1 to 5, wherein the wood substrate includes a coniferous wood layer. The composite wood material according to any one of claims 1 to 6,
a coating film formed on the surface of the decorative material and the surface of the groove portion;
The flooring is provided with: A wood substrate and
a first wood fiber board adhered to the surface of the wood substrate;
a second wood fiber board adhered to the surface of the first wood fiber board;
a decorative material adhered to the surface of the second wood fiber board;
Grooves formed in the decorative material and the second wood fiber board;
Equipped with
A method for producing a wood composite material, wherein the second wood fiber board is softwood MDF,
A method for manufacturing a wood composite material, comprising the steps of: preparing the wood base material, the first wood fiber board, the second wood fiber board, and the decorative material separately; and then stacking the wood base material, the first wood fiber board, the second wood fiber board, and the decorative material together. Dividing the first material wood fiber board along the board surface direction at a plurality of positions in the thickness direction of the first material wood fiber board to form a plurality of first divided boards;
The method for manufacturing a wood composite material according to claim 8 , wherein any one of the plurality of first divided plates is the first wood fiber plate. Dividing the second material wood fiber board along the board surface direction at a plurality of positions in the thickness direction of the second material wood fiber board to form a plurality of second divided boards;
The method for manufacturing a wood composite material according to claim 8 or claim 9, wherein any one of the plurality of second divided plates is the second wood fiber plate. The method for manufacturing a wood composite material described in claim 10, wherein the divided boards that become the wood fiber boards include a relatively dense rock layer in the base wood fiber board. The method for manufacturing a wood composite material described in claim 11, wherein the divided boards that will become the wood fiber boards are positioned with the rock layer facing the decorative material. A step of forming grooves in the decorative material and the second wood fiber board of the wood composite material according to any one of claims 8 to 12;
a coating step of coating the wood composite material in which the grooves are formed;
A method for manufacturing a flooring material, comprising: