EP2994307A1

EP2994307A1 - A panel comprising a solid surface coating on a thermally deformable support

Info

Publication number: EP2994307A1
Application number: EP13884020.2A
Authority: EP
Inventors: Mikko Tilli
Original assignee: UPM Kymmene Wood Oy
Current assignee: UPM Plywood Oy
Priority date: 2013-05-10
Filing date: 2013-05-10
Publication date: 2016-03-16
Also published as: WO2014181031A1; EP2994307A4

Abstract

A panel having a thickness in a first direction, a length in a second direction, and a width in a third direction, wherein the thickness is smaller than the length and the thickness is smaller than the width. The panel comprises a support layer comprising wood and polymer material and a surface layer that does not comprise wood, wherein at least a part of the surface layer is arranged in the first direction from the support layer. The panel further comprises adhesive in between the support layer and the surface layer, and a thermosensitive area. Because of the thermosensitive area the panel has a strength at a first temperature, the panel can be separated to a first part and a second part at a second temperature using a stress, wherein the second temperature exceeds the first temperature by at least 30 °C and by at most 200 °C, and the stress is at most half of the strength.

Description

A panel comprising a solid surface coating on a thermally deformable support

Field of the Invention The invention relates to a panel. The invention relates to a recyclable panel. The invention relates to a deformable panel. The invention relates to a panel that can be divided to parts, and optionally deformed when heated. The invention relates to stackable panels. The invention relates to panels having a surface of which mechanical, electrical, or optical properties are engineered for the purpose of use. In particular, the invention relates to panels having a wear resistant surface. Such panels can be used in or for furniture. Such panels can be used in buildings. Such panel can be used for flooring or for work surfaces. Background of the Invention

Panels are often used in buildings. Panels can form part of furniture, they can be used as or in flooring, wall, or ceiling elements. In addition, such panels can be used in various desks and in shops as shop fittings. Panels can also be used for working surfaces in buildings. Working surfaces and flooring require good wear resistance of the surface that is exposed to wear. Moreover, in these applications, the surface is preferably moisture resistant, since water is often needed e.g. for cleaning such surfaces. Therefore, panels having a high wear resistance and high moisture resistance are known. For example plaques are used for the purpose. They, however are relatively expensive and fragile. Thereby a lot of labor force is needed for installation. Summary of the Invention

One aspect of the invention is to provide a panel of which materials are more easily recyclable. Another aspect of the invention is to provide a panel having a surface that is resistant to wear, but which panel is at the same time light and less fragile. Other aspects include easy deformation, in particular to a preferred shape. A panel according to an embodiment of the invention has a thickness in a first direction, a length in a second direction, and a width in a third direction, wherein the thickness is smaller than the length and the thickness is smaller than the width. An embodiment of the panel comprises

- a support layer comprising wood and polymer material and

- a surface layer that does not comprise wood, wherein at least a part of the surface layer is arranged in the first direction from the support layer, the panel further comprising

- adhesive in between the support layer and the surface layer, and

- a thermosensitive area, whereby

- the panel has a strength at a first temperature,

- the panel can be separated to a first part and a second part at a second temperature using a stress, wherein

- the second temperature exceeds the first temperature by at least 30 °C and by at most 200 °C, and

- the stress is at most half of the strength.

Description of the Drawings

Figure 1 a shows, in a side view, an embodiment of a panel,

Figure 1 b shows, in a perspective view, the panel of Fig. 1 a,

Figure 1 c shows, in another perspective view, the panel of Fig. 1 a,

Figure 1 d shows, in a perspective view, the panel of Fig. 1 a,

Figure 1 e1 shows, in a side view, an embodiment of a panel at a first temperature, having a tensile strength and a shear strength c_ss, and comprising a thermosensitive area arranged in the support layer,

Figure 1 e2 shows, in a side view, the division of the panel of Fig. 1 e1 at a second temperature using a shear stress σ_δ, wherein the second temperature is higher than the first temperature, and wherein the shear stress σ_δ is less than the shear strength c_ss at the first temperature,

Figure 1 e3 shows, in a side view, the division of the panel of Fig. 1 e1 at a second temperature using a tensile stress wherein the second temperature is higher than the first temperature, and wherein the tensile stress at is less than the tensile strength a_ts at the first temperature,

Figure 1 e4 shows, in a side view, the separated first part of the panel of Fig.

1 e1 and the separated second part of the panel of Fig. 1 e1 , Figure 1 f 1 shows, in a side view, an embodiment of a panel at a first temperature, having a tensile strength a_ts and a shear strength a_ss, and comprising a thermosensitive area arranged on the support layer,

Figure 1f2 shows, in a side view, the division of the panel of Fig. 1 f 1 at a second temperature using a shear stress a_s, wherein the second temperature is higher than the first temperature, and wherein the shear stress a_s is less than the shear strength a_ss at the first temperature,

Figure 1 g 1 shows, in a side view, an embodiment of a panel at a first temperature, having a tensile strength a_ts and a shear strength a_ss, and comprising a thermosensitive area arranged in the adhesive,

Figure 1 g2 shows, in a side view, the division of the panel of Fig. 1 g 1 at a second temperature using a shear stress a_s, wherein the second temperature is higher than the first temperature, and wherein the shear stress a_s is less than the shear strength a_ss at the first temperature,

Figure 1 g3 shows, in a side view, the division of the panel of Fig. 1 g 1 at a second temperature using a tensile stress a_t, wherein the second temperature is higher than the first temperature, and wherein the tensile stress a_t is less than the tensile strength a_ts at the first temperature,

Figure 2a shows, in a top view, an adhesive layer and a surface layer, Figure 2b shows, in a top view, an adhesive layer and a surface layer, Figure 2c shows, in a top view, an adhesive layer and a surface layer,

Figure 3a shows, in a side view, heating of a panel comprising viscous adhesive,

Figure 3b shows, in a side view, heating of a panel comprising solid adhesive,

Figure 4 shows, in a side view, an adhesive layer,

Figure 5 shows, in a side view support layer, Figure 6a shows, in a side view, an essentially planar panel,

Figure 6b shows, in a side view, form pressing the panel of Fig. 6a,

Figure 7a shows, in a side view, a panel having the shape of an open tube, Figure 7b shows, in a side view, a panel having the shape of half a tube, Figure 7c1 shows, in a side view, a panel having a planar central area and curved boundary areas,

Figure 7c2 shows, in another side view, the panel of Fig. 7c1 ,

Figure 7d shows, in a side view, a panel having a curved central area and curved boundary areas, and

Figure 8 shows, in a perspective view, a panel 100 that is curvilinear in two different directions.

Detailed Description of the Invention Panels are often used in buildings. Panels can for part of furniture, they can be used as or in flooring, wall, or ceiling elements. Panels can also be used for working surfaces in buildings. In addition, such panels can be used in various desks and in shops as shop fittings. Working surfaces and flooring require good wear resistance of the surface that is exposed to wear. Moreover, in these applications, the surface is preferably moisture resistant, since water is often needed e.g. for cleaning such surfaces. It is known to use plaques for the purpose.

Some polymer materials are also resistant to moisture and wear. Moreover, the wear resistance can be increased by adding some filler material to a polymer matrix. Filler materials can also be used to engineer other properties of the composite material, such as electrical conductance (related to antistatic properties and EMC protection), resistance to electric discharge, thermal resistance, fire resistance, color, opaqueness, resistance to radiation (e.g. UV radiation), acoustic impedance, and hardness; or to bring some functionality to the surface layer, such as self-cleaning, easy-cleaning, change of color with temperature (thermochromism). In general, the properties can be engineered in either direction, such as increasing or decreasing the thermal conductance, or increasing or decreasing the wavelength that the surface layer emits, reflects, or absorbs, depending on the application. However, typically the material becomes more brittle, when such filler material is added. Moreover, the polymer comprising the filler may be reasonable expensive, since some filler materials are expensive, whereby their addition makes the material more expensive. Some other filler material or materials can be used to reduce cost.

Because of the high cost of such materials, a relatively thin layer is preferably used. However, as discussed, the material is brittle. Handling of sheets of thin, brittle material, is very hard, whereby such materials are not commonly available.

In an embodiment of the present invention, the engineered polymer composite material forms only a surface layer of a panel. Figures 1 a to 1 d show an embodiment of such a panel 100 in a side view and in some perspective views. The panel 100 has a thickness Tp in a first direction Sx, a length Lp in a second direction Sy, and a width Wp in a third direction Sz, wherein the thickness Tp is smaller than the length Lp and the thickness Tp is smaller than the width Wp. In this description the first, the second, and the third directions (Sx, Sy, Sz) are orthogonal, and oriented as in a common right handed coordinate system, as depicted in Figs. 1 b to 1 d. The panel 100 comprises

- a support layer 200,

- a surface layer 400, wherein at least a part of the surface layer 400 is arranged in the first direction Sx from the support layer 200, and

- adhesive 300 in between the support layer 200 and the surface layer 400.

In an embodiment, the surface layer 400 does not comprise wood. In an embodiment, the support layer 200 comprises wood. In an embodiment, the support layer 200 comprises wood and polymer material. In an embodiment, the polymer material of the support layer 200 comprises natural polymer material and/or synthetic polymer material. The support layer 200 comprises different material than the surface layer 400. The support layer 200 may be made of different material than the surface layer 400. In an embodiment, the surface layer 400 comprises materials, whereby these materials form a set of surface materials; and the support layer comprises at least a support material such that the set of surface materials does not comprise the support material. Wood is an example of such support material. The adhesive 300 consists of a different composition of material or materials than the support layer 200. The different composition refers to composition of same materials (in the adhesive 300 and the support layer 200) in different proportional quantities or to a composition (of the adhesive) comprising at least some material that the other material (of the support layer) does not comprise or to a composition (of the adhesive) that does not comprise some material that the other material (of the support layer) comprises. Thus boundary between the adhesive 300 and the support layer 200 is observable. Moreover, the adhesive 300 consists of a different composition of material or materials than the surface layer 400; in the sense discussed above. Thus boundary between the adhesive 300 and the surface layer 400 is observable.

In particular, the material that is comprised by the support layer 200, but is not comprise by the surface layer 400 (i.e. the set of surface materials) may be cheaper, lighter, and stronger than the material(s) of the surface layer 400. In this way the panel 100 is easier to handle, lighter (in weight), and cheaper than a corresponding panel made of only the material of the surface layer 400. Moreover, the panel 100 is more wear resistant than a corresponding panel made of only the material of the surface layer 200, at least from the side of the surface layer. Still further, as discussed, many other properties of the surface layer 400 may be engineered using additional material admixed in the surface layer 400, e.g. to a polymer matrix. The feature "at least part of the surface layer 400 is arranged in the first direction Sx from the support layer 200" expresses two issues. First, adhesive 300 is not necessarily a uniform layer, whereby a part of the surface layer 400 may be in contact with the support layer 200. Moreover, referring to Fig. 7a, the panel 100 may be significantly curvilinear. In this case, even if the panel "has a thickness in a first direction", the thickness and the corresponding direction are necessarily measured in a location, which then defines the direction and the thickness at this location. Thus, the whole surface layer 400 is not necessarily located a distance apart from the support layer 200 in this direction. In some embodiments, the properties of the surface layer 400 are engineered for better mechanical, visual, or other properties, as discussed above. As for wear resistance, in an embodiment, the resistance to surface wear of the panel 100 (i.e. its surface layer 400) is from 58 to 75 lost weight mm³/100 rev according to the standard DIN ISO 4586 T6. In some embodiments, the lost weight is from 58 to 63 mnn³/100 rev; and in some embodiments, the lost weight is from 63 to 75 mm³/100 rev. The resistance to boiling water can be characterized by the increase in weight and/or visual properties of the surface. In an embodiment, the surface layer 400 is resistant to boiling water such that the increase in weight according to standard DIN ISO 4586 T7 is from 0.1 % to 0.7 %; preferably from 0.1 % to 0.3 %. In an embodiment, the surface layer 400 is resistant to boiling water such that the no visible change occurs according to the standard DIN ISO 4586 T7. In an embodiment, the surface layer 400 of the panel 100 belongs to the class B according to its fire behavior or its fire resistance, as classified according to the European classification EN 13501 -1 : Fire Test to Building Material - Classification. In an embodiment, the surface layer 400 of the panel 100 belongs to the class B-s1 according to its fire behavior or its fire resistance (same classification). In an embodiment, the surface layer 400 of the panel 100 belongs to the class B-dO according to its fire behavior or its fire resistance (same classification). In an embodiment, the surface layer 400 of the panel 100 belongs to the class B-s1 -d0 according to its fire behavior or its fire resistance (same classification), As for the standards, the latest version to these standards is referred to on 7^th May 2013.

In an embodiment, the opposing surfaces of the panel 100 have approximately the same size. Referring to Fig. 1 a, the panel 100 comprises a top surface 140, wherein the top surface 140 has a surface normal parallel to the first direction Sx, and the surface layer 400 comprises the top surface 140. The panel 100 further comprises a bottom surface 130, wherein the bottom surface 130 has a surface normal parallel to the first direction Sx, and the support layer 200 comprises the bottom surface 130. The area of the top surface 140 is denoted by Atop. The area of the bottom surface 130 is denoted by Abot. In an embodiment, the ratio Abot/Atop is from 0.25 to 4. In an embodiment, the ratio Abot Atop is from 0.5 to 2. Preferably the ratio Abot/Atop is close to 1 or equal to 1 . The ratio may be e.g. from 0.8 to 1 .25, from 0.9 to 1 .1 , or from 0.95 to 1 .05. Moreover, the support layer 200 may be greater than the surface layer 400, or equal in size. Thus, the ratio Abot/Atop may be from 1 to 4, from 1 to 2, from 1 to 1 .25, from 1 to 1 .1 , or from 1 to 1 .05. This ensures that the support layer 200 protects also the boundaries and edges of the surface layer 400.

After service, the building, furniture, or other structure comprising the panel 100 is preferably recycled. This is particularly true, if the materials are expensive, such as the material of the surface layer 400. However, such a panel 100, while comprising a support layer 200 and a surface layer 400 of different material, is hard to recycle. Therefore, according to an embodiment of the invention, the panel can be separated to two parts using heat. With reference to Figs. 1 e1 to 1 g3, an embodiment of the panel 100 further comprises

- a thermosensitive area 500, whereby

- the panel 100 has a strength (such as shear strength σ₈₈ or tensile strength a_t8; cf. Fig. 1 e1 ) at a first temperature Te1 ,

- the panel 100 can be separated to a first part 101 and to a second part 102 at a second temperature Te2 using a stress (such as a shear stress σ₈ or a tensile stress < _t; cf. Fig. 1 e2 to 1 e4), wherein

- the second temperature Te2 is more than the first temperature Te1 (i.e. Te2>Te1 ), and

- the stress is at most half of the strength (e.g. a_t ≤ ½ σ_ί8 or σ₈ < ½ σ₈₈). As for the first and second temperatures Te1 and Te2, preferably the second temperature exceeds the first temperature by at least 30 °C and by at most 200 °C. The lower limit, 30 °C, allows for reasonably large temperature variations for the operation temperature of the panel. The upper limit 200 °C, indicates that the thermosensitive area 500 is sensitive to temperature, and not only arbitrary material that melts.

The feature "the stress is at most half of the strength" is to be interpreted such that the stress with which the panel can be separated at the second temperature Te2 is less than the corresponding strength at the first temperature Te1 . In particular, the tensile stress at, with which the panel 100 can be divided at the second temperature, is at most half of the tensile strength o_ts of the panel at the first temperature (o_t < ½ ^χ σ_ί8). Or, in terms of shear stress and strain, shear stress σ₈, with which the panel 100 can be divided at the second temperature, is at most half of the shear strength σ₈₈ at the first temperature (σ₈ < ½ ^χ < _SS). Still further, if a combination of shear and tensile stresses is used to determine the strength at the first temperature Te1 , a similar combination of shear and tensile stresses is used to separate the parts 101 and 102 apart from the panel 100 at the second temperature Te2. If the strength values are given for a point force (shear, tensile, or combination), the corresponding stress is also for a point force (shear, tensile, or combination, respectively). If the strength values are given for a distributed force, i.e. stress (shear, tensile, or combination), the corresponding stress is also for a distributed force, i.e. stress (shear, tensile, or combination, respectively). Moreover, if a specific strain rate is used to determine the strength at the temperature Te1 , the same strain rate is used to test the stress (< _t, σ₈, or combination) by which the panel 100 can be separated to (at least) two parts at the second temperature Te2.

Preferably the stress is less than the strength by a reasonably significant amount. This reasonably significant amount may refer, in case of tensile stress and strength to the ratios σι/σ_ί8 ≤ 1/2 (as above), σι/σ_ί8 ≤ 1/4, σι/σ_ΐ8≤ 1/10, or σι/σ_ί8≤ 1/20. This reasonably significant amount may refer, in case of shear stress and strength to the ratios σ₈/σ₈₈ < 1/2 (as above), σ₈/σ₈₈ < 1/4, σ₈/σ₈₈ < 1/10, or σ₈/σ₈₈ < 1/20. These ratios may apply also for a combination of shear and tensile stresses.

Typically, the surface layer 400 comprises most of the valuable materials of the panel 100. Therefore, preferably the surface layer 400 can be recycled as a single piece. Therefore, in an embodiment the surface layer 400 is heat resistant to temperatures from the first temperature Te1 to the second temperature Te2. The term heat resistant to a temperature means that the surface layer 400 does not melt or burn at that temperature. Thus, the surface layer 400 does not melt or burn at the second temperature Te2 and at temperatures below Te2. The surface layer 400 may be heat resistant to temperatures up to a temperature exceeding the second temperature Te2 by at least 10 °C, 20 °C, 30 °C, or more. The surface layer 400 may be heat resistant to temperatures down to a temperature that is below the first temperature Te1 by at least 25 °C, 50 °C, 75 °C, or more. In an embodiment, the surface layer 400 is heat resistant to temperatures from the first temperature to 150 °C, preferably to 180 °C or to 200 °C. The strength of the panel 100 (e.g. the shear strength c_ss or the tensile strength which forms a reference value for the separation stress, can be measured e.g. in a typical use condition. Thus, in an embodiment the strength of the panel is the strength of the panel at the first temperature of 25 °C. In short, in an embodiment the first temperature is 25 °C.

The second temperature may be e.g. at least 50 °C, preferably at least 60 °C, at least 70 °C, at least 100 °C, at least 120 °C, or at least 150 °C. The second temperature Te2 may exceed the first temperature Te1 by at least some value ΔΤ, i.e. Te2-Te1 > ΔΤ. The at least some value ΔΤ be e.g. 10 °C, 20 °C, 30 °C, 40 °C, 50 °C, 60 °C, 70 °C, 80 °C, 90 °C, or 100 °C. Preferably, in order to allow for a reasonably large temperature range for the use of the panel 100, the second temperature Te2 may exceed the first temperature Te1 by at least 60 °C, or by any of the greater values listed above. In an embodiment, the first temperature Te1 correspond to the normal operation temperature, i.e. 20 °C. In this embodiment, the second temperature may be e.g. 50 °C, 70 °C or 90 °C. As for the second temperature Te2, a temperature of at most 100 °C may be preferred in some embodiments, since in that case hot water can be used to heat the panel. In some embodiments, the second temperature may be from 50 °C to 200 °C, such as from 70 °C to 1 10 °C.

As depicted in the Figures 1 e1 to 1 g3, in some embodiments the thermosensitive area 500 forms a layer. The thermosensitive area 500 may be a continuous layer, i.e. a layer without holes, grooves, or channels. Alternatively, the thermosensitive area 500 may be a discontinuous layer. The layer may, for example, comprise holes. In a discontinuous layer, the thermosensitive area may be an arrangement of dots or stripes of thermosensitive material. The layer is not necessarily planar; separation of the panel 100 is possible also when the thermosensitive area 500 is not planar. Moreover, separation of the panel to two parts may be possibly even if the thermosensitive area 500 does not form a layer that extends through the panel 100. Preferably, the area of the termosensitive area 500 is reasonably large compared to the area of the surface layer 400 (e.g. to the area Atop of the top surface 140). In an embodiment,

- the area of the surface layer 400 is Atop, and

- the area of thermosensitive area 500 is Ats, wherein

- the ratio Ats/Atop is at least 25 %, preferably at least 50 %, at least 70 %, or at least 90 %. Here the area of the thermosensitive area, Ats, is measured in a cross section, wherein the cross section has a surface normal parallel to the surface normal of the top surface 140 at the same point. In a planar panel 100 (e.g. Fig. 1 e1 ) this is more or less evident, however, this applies also for the curvilinear panel, such as the panel of Fig. 7a.

When ratio Ats/Atop is less than 100 %, the termosensitive area 500 serves as a seed for dividing the panel 100 to the two parts 101 and 102, if the rest of the weak part of the panel is solid. The term weak part referring to the part of the panel 100 that breaks upon the division, but is not thermosensitive. However, irrespective of the when ratio Ats/Atop, the termosensitive area 500 may be the only solid object that joins the first part 101 to the second part 102.

Less stress is needed for the separation when the termosensitive area 500 forms a layer that extends through the panel. In this case the panel does not comprise a solid weak part as discussed above. In an embodiment, the thermosensitive area 500 extends through the panel 100. In this embodiment,

- the thermosensitive area 500 extends through the panel 100.

In an embodiment, the thermosensitive area 500 extends in a direction parallel to the top surface 140. In this embodiment,

- the surface layer 400 has a top surface 140 having a surface normal parallel to the first direction Sx, and

- the thermosensitive area 500 extends parallel to the top surface 140. In the embodiment of Figs. 1 e1 , 1 f 1 , and 1 g1 , the thermosensitive area 500 extends through the panel 100 and the thermosensitive area 500 extends parallel to the top surface 140. Referring specifically to Figs. 1 e1 to 1 e4, in an embodiment

- the thermosensitive area 500 is arranged in the support layer 200, whereby

- the panel 100 can be separated to the first part 101 (Fig. 1 e4) and the second part 102 such that

- the first part 101 comprises at least a part 201 (in Figs. 1 e2 to 1 e4 only a part) of the support layer 200 and the second part 102 comprises the surface layer 400.

As shown in Fig. 1 e4, in this embodiment the second part 102 further comprises the adhesive 300 and a part 202 of the support layer 200.

Figure 1 e1 shows, in addition to the features discussed above, how the shear strength a_ss can be determined at the first temperature Te1 . The arrows near the symbol for shear strength indicate the direction of shear forces (imposing the shear stresses) in determining the shear strength. Figure 1 e1 shows how the tensile strength a_ts can be determined at the first temperature Te1 . The arrows near the symbol for tensile strength indicate the direction of tensile forces (imposing the tensile stresses) in determining the tensile strength. As discussed, the forces can be point forces or distributed. Even if not discussed before, the forces can be a combination of point and distributed forces.

Figure 1 e2 shows a shear stress a_s used to separate the panel 100 of Fig. 1 e1 to two parts 101 and 102 at the second temperature Te2. Since the thermosensitive area 500 is arranged in the support layer 200 as a thermosensitive layer, the panel 100 separates at this layer 500. Moreover, as depicted in the figure, the support layer 200 separates to a first part 201 and a second part 202.

Figure 1 e3 shows a tensile stress at used to separate the panel 100 of Fig. 1 e1 to the two parts 101 and 102 at the second temperature Te2. Since the thermosensitive area 500 is arranged in the support layer 200, the panel 100 separates at this layer 500. Moreover, as depicted in the figure, the support layer 200 separates to a first part 201 and a second part 202.

Figure 1 e4 shows in more detail the first part 101 separated from the panel 100 and the second part 102 separated from the panel 100. The first part 101 comprises only a part 201 of the support layer 200. The second part 102 comprises the surface layer 400. The second part 102 further comprises the adhesive 300 and a part 202 of the support layer 200. The thermosensitive area 500 can be arranged in the support layer 200, e.g. when the support layer 200 itself is a layered structure comprising thermally sensitive material in between the layers of the structure. The thermally sensitive material may be e.g. thermoplastic polymer. Material selections for the support layer 200 will be discussed in detail later.

Referring specifically to Figs. 1 f 1 and 1f2, in an embodiment

- the thermosensitive area 500 is arranged on the support layer 200, whereby

- the panel 100 can be separated to the first part 101 and the second part 102 such that

- the first part 101 comprises at least a part of the support layer 200 (in Fig. 1f2 the whole support layer) and the second part 102 comprises the surface layer 400.

Referring to Fig. 1f2, in this case the first part 101 separated from the panel 100 comprises the support layer 200 (or a part of the support layer 200, since part of the material of the thermosensitive area 500 may be stuck with the adhesive 300). The second part 102 separated from the panel 100 comprises the surface layer 400 and further comprises the adhesive 300. Referring to Figs. 1 g 1 to 1 g3, in an embodiment

- the adhesive 300 forms the thermosensitive area 500 (or another thermosensitive area), whereby

- the first part 101 comprises the support layer 200 and the second part 102 comprises the surface layer 400. In the figure 1 g 1 the adhesive 300 itself is thermosensitive. Thus, the panel

100 may be separated to the parts 101 and 102 such that both the parts (101 , 102) comprise some of the adhesive 300, as shown in the figures 1 g 1 to 1 g3.

The adhesive 300 may form the thermosensitive area 500 also in combination with the support layer 200 or the surface layer 400. For example, the adhesion between the adhesive 300 and the support layer 200 may be dependent on temperature. The adhesion between the adhesive 300 and the support layer 200 may decrease as the temperature increases. In this case, the panel 100 could be separated to two parts such that the adhesive 300 separates from the support layer 200. In this case, the first part

101 of the separated panel comprises the support layer 200, and the second part 102 of the separated panel comprises the surface layer 400 and the adhesive 300 (cf. Figs. 1 f 1 and 1f2). Alternatively or in addition it is possible that the adhesion between the adhesive 300 and the surface layer 400 decreases as the temperature increases. In this case, the panel 100 could be separated to two parts such that the adhesive 300 separates from the surface layer 200. In this case, the first part 101 of the separated panel comprises the support layer 200 and the adhesive, and the second part 102 of the separated panel comprises the surface layer 400.

It is noted that the panel 100 may comprise multiple thermosensitive areas. E.g. the adhesive 300 may serve as a first thermosensitive area 500, and the support layer 200 may comprise one or more thermosensitive areas 500, e.g. when the support layer 200 is a layered structure comprising thermoplastic material in between the layers. In the above embodiments,

- the panel 100 can be separated to the first part 101 and the second part

102 such that

- the first part 101 comprises at least a part of the support layer 200 and the second part 102 comprises the surface layer 400. Preferably the second part 102 of the panel 100 does not comprise much more material than the surface layer 400. This helps the recyclability of the panel 100. The size of the parts 101 , 102 after the separation can be affected by selecting a proper location for the thermosensitive area 500. For example, the thermosensitive area 500 may be arranged at the intersection of the adhesive 300 and the surface layer 400. This can be done by selecting the adhesive such that the adhesion properties on the material of the surface layer 400 are dependent on temperature. Alternatively or in addition, the adhesive 300 itself may be thermosensitive (e.g. thermoplastic). Alternatively or in addition, the thermosensitive area 500 may be arranged in the support layer 200, close to the intersection of the adhesive 300 and the support layer 200. These and other possibilities for the location of the thermosensitive area 500 were discussed above. In an embodiment,

- the surface layer 400 has a mass,

- the thermosensitive area 500 is arranged in the panel 100 such that

- the panel 100 can be divided to the first part 101 and the second part 102 in such a way that

- the second part 102 comprises the surface layer 400 and

- the mass of the second part 102 is at most 1 .1 times the mass of the surface layer 400, preferably at most 1 .05 times the mass of the surface layer 400. In an embodiment, the thermosensitive area 500 comprises thermoplastic polymer. When the temperature exceeds the melting temperature i.e. the deflection temperature of the thermoplastic polymer, the parts 101 and 102 of the panel 100 become moveable with respect to each other. In this case reasonably low stresses (in comparison to the strength of the panel at the first temperature as discussed above) are needed to separate the parts 101 , 102 of the panel 100. For tensile stress, the ratio ctAj_ts may be e.g. at most 1/50 or 1/100, or higher, as discussed above. For shear stress, the ratio σ₈/σ may be e.g. at most 1/50 or 1/100, or higher, as discussed above. For thermoplastic materials, the terms "melting temperature" and "deflection temperature" are used interchangeable in this description. Alternatively or in addition, the thermosensitive area 500 may comprise thermoset polymer having a reasonably low deflection temperature i.e. glass transition temperature. When the temperature exceeds the deflection temperature or the glass transition temperature, the parts 101 and 102 of the panel 100 become moveable with respect to each other. In this case higher stresses (in comparison to case of thermoplastic material and to the strength of the panel at the first temperature as discussed above) may be needed to separate the parts 101 , 102 of the panel 100. The ratio at/ats may be e.g. at most 1 /2 or 1 /5; or the ratio C_SAJ_ss may be e.g. at most 1 /2 or 1 /5. For thermoset materials, the terms "glass transition temperature" and "deflection temperature" are used interchangeable in this description.

Preferably the thermosensitive area 500 comprises thermoplastic polymer having a melting temperature. In such a case, the surface layer 400 may comprise polymer. In an embodiment,

- the surface layer 400 comprises polymer having a deflection temperature, and

- the melting temperature of the thermoplastic polymer of the thermosensitive area 500 is less than the deflection temperature of the surface layer 400.

In this case, even if the thermoplastic material of the thermosensitive area 500 melts, the surface layer 400 still remains a solid object, and can be reasonably easily be separated from the panel 100. In some embodiments, the deflection temperature of the surface layer 400 exceeds the melting temperature of the thermoplastic polymer of the thermosensitive area 500 by at least 10 °C, 20 °C, 30 °C, 40 °C, 50 °C, 60 °C, 70 °C, 80 °C, 90 °C, 100 °C or more.

Preferably the melting temperature of the thermoplastic polymer of the thermosensitive area is at most 200 °C. More preferably at most 180 °C, 170 °C, 160 °C, 150 °C, 140 °C, 130 °C, or 120 °C.

In general, panels are preferably stored in piles. Therefore, panels - at least in a storage - are preferably planar or substantially planar. However, as discussed, typically the properties of the surface layer 400 and the support layer 200 are different. The difference in the desired properties typically also inevitably leads to difference in thermomechanical properties, particularly in the thermal expansion. Therefore alternating temperature may bend the panel 100. Thus, preferably the surface layer 400 is attached to the support layer 200 at a temperature, that is reasonably close to the temperature at which the panel 100 is later stored. This issue will be discussed in more detail below.

Planar panels, even if easy to store in piles, are relatively flexible. This is because the stiffness in general is dependent on the third power of the thickness. However, reasonable rigidity is often needed for panels 100 in use. Thus, in some embodiment, the panel 100 is bent (by from pressing) before use. In effect, bending increases the dimension of the panel that is parallel to the thickness of the panel 100 (cf. e.g. Fig. 7c1 , wherein the boundary area is curved, thereby increasing the dimension in the direction Sx, and the thickness of the central area of the panel is parallel to Sx). In this way, the stiffness of the panel 100 is also increased. Some shapes of a bent panel 100 will be discussed later. In order to enable bending and stiffening of the panel, in an embodiment

- the support layer 200 comprises thermoplastic polymer.

This thermoplastic polymer may also serve as the thermosensitive area 500.

As discussed above, the material of the surface layer 400 is reasonably expensive. Therefore, preferably, the panel 100 comprises only one surface layer 400. In other words, provided that the panel is planar, the panel 100 is not plane symmetric. In other words, no plane that has the surface normal parallel to the first direction Sx is a plane of symmetry for the panel 100. In other directions the panel may be symmetric. As the properties of the surface layer 400 and the support layer 200 are different, the thermal expansion properties are also typically different. Referring to Figs. 1 c and 1 d, in an embodiment,

- the support layer 200 has a first coefficient of thermal expansion k1 in a direction d1 that is perpendicular to the first direction Sx, and a second coefficient of thermal expansion k2 in another direction that d2 is perpendicular to the first direction Sx, wherein the directions are selected such that the second coefficient of thermal expansion k2 is smaller than or equal to the first coefficient of thermal expansion k1 (i.e. k2 < k1 ),

- the surface layer 400 has a third coefficient of thermal expansion k3 in a direction d3 that is perpendicular to the first direction Sx, and a fourth coefficient of thermal expansion k4 in another direction d4 that is perpendicular to the first direction Sx, wherein the directions are selected such that the fourth coefficient of thermal expansion k4 is smaller than or equal to the third coefficient of thermal expansion k3 (i.e. k4 < k3), and

- the third coefficient of thermal expansion k3 is different from the first coefficient of thermal expansion k1 (i.e. k3≠ k1 ).

In an embodiment,

- the third coefficient of thermal expansion k3 is greater than the first coefficient of thermal expansion k1 (i.e. k3 > k1 ).

In Figure 1 d, the white area is only shown for clarity, for the reference signs on the white area to by visible.

In general, the coefficients of thermal expansion (CTE) depend on the temperature. Unless otherwise stated, all the values of the CTEs in this description are given at the temperature 25 °C.

The coefficients of thermal expansion (k1 , k2, k3, and k4) depend on the selection of materials, as will be discussed later. In general, the support layer 200 may be anisotropic, whereby the first k1 and the second k2 coefficients of thermal expansion may be different. In general, the surface layer 400 may be anisotropic, whereby the third k3 and the fourth k4 coefficients of thermal expansion may be different. The expression "coefficient of thermal expansion in a direction" means the coefficient of thermal expansion (CTE) as measured in that particular direction.

From the above discussion, and with reference to Fig. 7a, it is evident that the first, second, third, and fourth CTEs are measured in a tangent plane of a curvilinear panel. In particular in the tangent plane that has the surface normal parallel to the first direction. The difference between the third coefficient of thermal expansion k3 and the first coefficient of thermal expansion k1 is due to the fact that the surface layer 400 should have different properties than the support layer 200. The surface layer 400 is preferably wear and moisture resistant and also typically fragile, while the support layer 200 is preferably light, cheap, and shock resistant.

For the handling of the surface layer 400 during manufacturing, and for the needed wear resistance, in the panel 100, the thickness T2 of the surface layer 400 may reasonable close to the thickness T1 of the support layer 200. In some embodiments, the thickness T2 of the surface layer 400 is less than the thickness T1 of the support layer 200. In some embodiments, the ratio of the thickness T1 of the support layer 200 to the thickness T2 of the surface layer, i.e. T1/T2, is from 1 to 10; preferably from 1 .2 to 5

It is also noted that the thickness of the support layer 200 is not necessarily constant. E.g. the boundary areas of the support layer 200 may be thinned. Alternatively or in addition, the boundary areas of the support layer 200 may be rounded. Moreover, the thickness of the surface layer 400 is not necessarily constant. E.g. the boundary areas of the surface layer 400 may be thinned. Alternatively or in addition, the boundary areas of the surface layer 400 may be rounded.

The difference in the CTEs could result is some difficulties for manufacturing planar panels 100 that are bendable. In particular, the properties of the adhesive 300 should be selected such that excessive temperature changes before form pressing are avoided.

To allow for forming the panel 100 at a high temperature, the support layer 200 may comprise thermoplastic polymer and/or thermoset polymer having low deflection temperature. The panel 100 may be heated to a temperature, in which the thermoplastic polymer of the support layer melts or the thermoset polymer softens. In this temperature, the panel can be deformed. When cooled down, the panel 100 approximately keeps it shape. The term "approximately" here is written, since the different coefficients of thermal expansion bend the panel 100 upon heating or cooling. Even if the surface layer 400 may be brittle and may comprise thermoset polymer, the surface layer 400 may be deformable when reasonably thin, and reasonably supported by the adhesive 300 and the support layer 200. Properties of the adhesive

Such panels, before thermally deformed, are preferably in planar form. Moreover, typically both the surface layer 400 and the support layer 200 are manufactured in planar form. As the coefficients of thermal expansion are different, changes in the temperature would impose thermal stress in the panel, which would bend the panel. Thus, if the surface layer 400 would be attached to the support 200 in a high temperature using an adhesive 300 solidifying, hardening, or drying at that temperature, cooling down to storage temperature would result in curving.

Therefore, in a preferred embodiment,

- the adhesive is selected from a group of adhesives that can be bonded at a temperature from 0 °C to 50 °C.

More preferably, the adhesive is selected from a group of adhesives that can be bonded at a temperature from 10 °C to 30 °C.

Such adhesives include self adhesives, self stick adhesives, and pressure sensitive adhesives in any form. Such adhesives further include adhesives that dry or harden in the described temperature range.

The terms "self adhesive", "pressure sensitive adhesive", and "self stick adhesive" all refer to an adhesive which forms bond when pressure is applied to join the adhesive with the adherend. The expression "can be bonded" refers to bonding in such a way that the adhesion strength between the surface layer 400 and the support layer 200 is reasonably high. The adhesion strength between the surface layer 400 and the support layer 200 is in this sense reasonably high at least when the adhesion strength is such that the adhesive can bear the gravitational load of the surface layer 400. The adhesive 300 can be bonded (to surface layer 400 and support layer 200) at the temperature from 0 °C to 50 °C (preferably from 10 °C to 30 °C) when the adhesion strength is such that when holding the panel 100 from the support layer 200 (in any orientation), the surface layer 400 does not fall from the panel 100 due to the gravitational force only. In addition or alternatively, adhesive 300 can be bonded (to surface layer 400 and support layer 200) when the adhesion strength is such that when holding the panel 100 from the surface layer 400 (in any orientation), the support layer 200 does not fall from the panel 100 due to the gravitational force only. This test can be performed e.g. at the temperature 25 °C. The falling may not occur immediately; in the above, the part that falls off from the panel is considered to fall off from the panel, if and only if it falls off during the first day (24 hours) once the panel has been oriented for the test.

As for absolute value, in an embodiment, the adhesive 300 is selected from a group of such adhesives that, when bonded at a temperature from 0 °C to 50 °C (preferably from 10 °C to 30 °C) to the surface layer 400 and the support layer 200, the adhesion strength between the surface layer and the support layer is at least 100 Pa. This corresponds to the aerial mass of the surface layer 400 or the support layer 200 of about 10 kg/m². Preferably the adhesion strength between the surface layer and the support layer is at least 500 Pa or at least 1 kPa. Naturally the adhesion strength may be also much higher. The adhesion strength may refer to specifically to shear strength (e.g. vertically aligned panel and gravitational stress). The adhesion strength could refer to specifically to tensile strength (e.g. horizontally aligned roof panels and gravitational stress). The absolute values for the adhesion strength may be measured at the temperature 25 °C. The absolute values for the adhesion strength may be measured using a (shear) strain rate of at least 1/s.

Moreover, in a panel 100 the adhesive is selected from a group of such adhesives that, when bonded at a temperature from 0 °C to 50 °C (preferably from 10 °C to 30 °C), the adhesion strength remains stable in a stable environment for at least one year. The expression "remains stable" can be interpreted in such a way, that

- in a first environment and at a first time, the adhesion strength has a first value,

- in the first environment and at a second time, the adhesion strength has a second value, wherein - the second time is at least one year later than the first time, and

- the second value is at least half (and optionally at most twice) the first value. However, alternating environment may deteriorate the properties of the adhesive, whereby in the test, the panel 100 is kept in the first environment between the first time and the second time. Thus, the "stable environment" refers to the stable first environments of the test, from the first time to the second time. The term "environment" refers to properties of the environment, such as at least temperature, humidity, and acceleration, and optionally lightning and pressure.

Moreover, as discussed above, the panel 100 may be deformed, such as bent, in later stages of use. When the panel 100 is bent, it is beneficial that the surface layer - possibly being fragile - is joined to the support essentially in all locations. Preferably the adhesive 300 forms an adhesive layer 300 that completely covers the support layer 200. In this way each location of the surface layer 400 becomes bonded to the support layer 200 with the adhesive 300. In practice, the adhesive 300 needs not to completely cover the support layer 200. Referring to Figs. 2a-2c, in an embodiment

- the panel comprises a top surface, wherein the top surface has a surface normal parallel to the first direction and the surface layer comprises the top surface,

- the surface layer comprises a bottom surface of the surface layer that is opposite to the top surface,

- the area of the bottom surface of the surface layer 400 is As, and

- the area of the contact between the adhesive 300 and the surface layer 400 is Aa, wherein

- the ratio Aa/As is at least 50 %.

More preferably the ratio is at least 75 %, least 90 %, or least 95 %.

The area As may equal the area Atop of the top surface 140.

In an embodiment, the adhesive comprises pressure sensitive adhesive. This has the technical effect that the surface layer 400 can simply be pressed onto the adhesive 300 to form the panel 100. The pressure sensitive adhesive can be supplied in the form of a tape (e.g. on a carrier film, as will be discussed). In this case the tape may be applied only to some locations between the support layer 200 and the surface layer 400. In these cases, the ratio Aa/As may be much less than the values given above. The ratio Aa/As may be e.g. at least 10 %, or at least 25 %. However, the non-bonded areas increase the risk of fracturing the surface layer 400. Therefore, preferably the ratio is high, as discussed above. Pressure sensitive adhesive can be applied onto a surface of the surface layer 400 or onto a surface of the support layer 200 alternatively or in addition without a film. In this case, the adhesive may be e.g. sprayed onto a surface.

In an embodiment, the adhesive 300 comprises viscous adhesive. This has the technical effect that the viscous adhesive allows for the surface layer 400 to slide with respect to the support layer 200 when the temperature of the panel changes. This reduces the thermal stresses in the system. The viscosity of an adhesive depends on temperature and on shear rate. In this sense, a viscous adhesive has a viscosity of at most 1000 Pas for the shear rate 1/s at the temperature 20 °C. Preferably, the adhesive 300 allows for deformations, i.e. is not very viscous. Preferably, the viscosity of the adhesive 300 is at most 100 Pas and more preferably at most 30 Pas; both values for the shear rate 1/s at the temperature 20 °C.

The viscosity of the adhesive 300 can also be tested. The test is relatively simple. Referring to Fig. 3a when heating the panel 100, the surface layer 400 and the support layer 200 tends to expand differently. If the adhesive layer is viscous, it allows for sliding of these layer with respect to each other. Therefore, a stair can be observed in the edge of a heated panel, when the panel 100 comprises viscous adhesive. Some common viscous adhesive comprise acrylate and/or polyacrylate. They may comprise acrylates and/or polyacrylates. Thus, in an embodiment, the adhesive comprises at least one of acrylate and polyacrylate. Other common viscous adhesives may comprise acrylic (or acrylics) and/or polyurethane (or polyurethanes). Referring to Fig. 4, the adhesive 300 may be arranged on a carrier film 310. The carrier film 310 may also be referred to as a liner. In a corresponding embodiment

- the panel 100 further comprises a carrier film 310 having a first side and a second side,

- the adhesive 300 is arranged on a first side of the carrier film 310, and

- the adhesive 300 or another adhesive 320 is arranged on the second side of the carrier film 310. In an embodiment, the melting point (temperature) of the carrier film 310 is higher than the melting point of the adhesive 300. In case two adhesives are used (e.g. on the opposite side of the film 310), the melting point of the carrier film 310 is higher than the melting point of one of the adhesives (300, 320). However, the ordering of the adhesive 300, 320 is arbitrary, whereby the adhesive 300 can be considered the one having the lower melting point. In an embodiment, the carrier film comprises at least one of polypropylene, polyethylene, and polyethylene terephthalate. The adhesive 300 can be selected such that it bonds well to the surface layer 400. If needed, another adhesive 320 be selected such that it bonds well to the support layer 200. Moreover, the carrier film 310 can be engineered in such a way the these adhesives bond well to both sides of the carrier film 310. Thus, the carrier film 310 may be a multilayered structure. In an embodiment

- the carrier film 310 comprises a first carrier layer and a second carrier layer,

- the adhesive 300 is arranged on a first side of the carrier film, on the first carrier layer of the carrier film, and

- other adhesive 320 is arranged on the second side of the carrier film, on the first second layer of the carrier film, wherein the other adhesive 320 is different from the adhesive 300. The carrier film 310 may be solid or foam. Solid carrier films are typically thin, e.g. less than 1 mm. Foam-like carrier films may be thicker, e.g. less than 2 mm. In either case, preferably the thickness of the carrier film 310 is at most 1 mm. The thickness of the carrier film 310 may be e.g. from 40 μηη to 3 mm. Preferably the thickness of the carrier film is from 60 μηη to 100 μηη. In practice a solid film may be deeded for such a thin carrier film 310. The thickness of the adhesive 310, or the other adhesive 320 on the carrier film 310 is preferably from 25 μηη to 50 μηη. If a carrier film 310 is not used, and a pressure sensitive adhesive is used (e.g. sprayed), the thickness of the layer of the adhesive 300 may be e.g. from 10 μηη to 1 mm, preferably from 25 μηη to 0.5 mm; and more preferably from 30 μηη to 100 μηη.

Viscous adhesives 300 are particularly suitable for use with support layers 200 that swell also because of other reasons than temperature. For example, if plywood is used as support layer 200, the support layer may swell because of moistening. Viscous adhesive 300 enables the independent swelling on the support layer 200 and the surface layer 400, as discussed for thermal expansion. The swelling is determined by a moisture swelling coefficient, and also by a moisture absorbance. The moisture absorbance of the materials can be characterized e.g. by saturated water content. This means the maximum water content absorbed by the material in a given environment. In an embodiment, the saturated water content of the support layer 200 is more than the saturated water content of the surface layer 400. In an embodiment, the saturated water content of the support layer 200 exceeds the saturated water content of the surface layer 400 by at least 50 % (provided that the saturated water content of the surface layer 400 is not zero). The saturated water content may be measured in given relative humidity (RH), pressure and temperature. The saturated water content may be measured e.g. in 50 % RH, and NTP conditions (in NTP, i.e. normal temperature and pressure, temperature equals 20 °C and pressure equals 101 .325 kPa). More often the saturated water content is measured in 100 % RH, and NTP conditions. Naturally it is assumed that the saturated water content for the surface layer 400 and for the support layer 200 are measured in the same conditions. In an embodiment, the saturated water content of the support layer is more than the saturated water content of the surface layer at 50% relative humidity and normal pressure and temperature. In an embodiment, the saturated water content of the support layer exceeds the saturated water content of the surface layer by at least 50%. Alternatively or in addition to viscous adhesive, the adhesive 300 may comprise material that hardens or dries, to attach the support layer 200 to the surface layer 400. In a preferred embodiment, the adhesive comprises material that hardens or dries at a temperature from 0 °C to 50 °C. More preferably, the adhesive comprises material that hardens or dries at a temperature from 10 °C to 30 °C. Thus, with such adhesive the surface 400 and support 200 layer can be bonded together at the described temperature range.

Such an adhesive may comprise at least one of polyvinyl acetate, ethylene- vinyl acetate (hotmelt), polyurethanes, polyurethane hot-melts, polypyrroline hot melts, moisture curing polyurethanes, epoxies, polyesters, acrylates, phenolics, phenol-formaldehyde, urea-melamine, melamine formaldehyde, resorcinol glue, silicones. Of these adhesives, polyurethanes and silicones may harden due to the presence of moisture in wood. Preferably, such an adhesive comprises polyurethane and/or acrylate. Such an adhesive may comprise polyurethanes and/or acrylates.

The thickness of the adhesive layer is preferably relatively small. This, on one hand increases the mechanical performance and impact properties of the panel 100, and on the other hand reduces the overall weight of the panel 100 and increases the machinability of the panel. In an embodiment,

- the adhesive 300 has a thickness Ta in the first direction Sx (Fig. 1 a), and

- the thickness Ta of the adhesive is from 30 μηη to 5 mm.

Preferably, the thickness Ta of the adhesive is from 30 μηη to 1 mm. More preferably, the thickness Ta of the adhesive is from 30 μηη to 0.5 mm.

Thick adhesive 300 may be applicable, is the adhesive 300 forms a mass (substance). Such a mass can be used to engineer the properties of the panel. Moreover, such mass can be peeled away from the first part 101 of the panel and/or the second part 102 of the panel to improve recyclability of the materials.

In an embodiment comprising the carrier film,

- the adhesive 300 and the carrier film in combination have a thickness Ta in the first direction Sx (Fig. 1 a), and

- the thickness Ta of the adhesive is in the aforementioned range. Moreover, the adhesive 300 may be thin in comparison to the support layer 200, whereby in an embodiment,

- the adhesive 300 has a thickness Ta in the first direction Sx,

- the support layer 200 has a thickness T1 in the first direction Sx, and

- the thickness Ta of the adhesive 300 is less than the thickness T1 of the support layer 200 (i.e. Ta < T1 ).

Moreover, the adhesive 300 may be thin in comparison to the surface layer 400, whereby in an embodiment,

- the adhesive 300 has a thickness Ta in the first direction Sx,

- the surface layer 400 has a thickness T2 in the first direction Sx, and

- the thickness Ta of the adhesive 300 is less than the thickness T2 of the surface layer 400 (i.e. Ta < T2).

As discussed, the support layer 200 may comprise polymer to enable deforming of the panel 100. The adhesive 300 may comprise thermoplastic adhesive. In an embodiment

- the adhesive 300 comprises thermoplastic material and

- the thermoplastic material has a melting point of at most 200 °C.

In this way, the adhesive may serve as the termosensitive area 500, as discussed in connection with Figs. 1 g 1 to 1 g3. In this or another embodiment,

- the polymer material of the support layer 200 has a first deflection temperature, and

- the adhesive 300 comprises thermoplastic material having a melting point (i.e. melting temperature), wherein

- the melting point of the adhesive 300 is lower than the deflection point of the support layer 200.

The thermal expansion properties of the adhesive 300 may also be selected according the thermal expansion properties of the support layer 200. In an embodiment,

- the adhesive 300 has a coefficient of thermal expansion, and - the coefficient of thermal expansion of the adhesive 300 is greater than the second coefficient of thermal expansion.

In an embodiment, the coefficient of thermal expansion of the adhesive 300 is greater than the first coefficient of thermal expansion. These selections reduce the thermal stress in between the adhesive 300 and the support layer 200.

As for the support layer 200, in an embodiment, the adhesive has a CTE of ka. In some of these embodiments, the ratio ka/k1 is from 0.5 to 2, preferably from 0.75 to 1 .3, and more preferably from 0.9 to 1 .1 . In some of these embodiments, the ratio ka/k2 is from 0.5 to 2, preferably from 0.75 to 1 .3, and more preferably from 0.9 to 1 .1 .

The thermal expansion properties of the adhesive 300 may also be selected according the thermal expansion properties of the support layer 400. In an embodiment,

- the adhesive 300 has a coefficient of thermal expansion, and

- the coefficient of thermal expansion of the adhesive 300 is less than the third coefficient of thermal expansion.

In an embodiment, the coefficient of thermal expansion of the adhesive 300 is less than the fourth coefficient of thermal expansion. These selections reduce the thermal stress in between the adhesive 300 and the surface layer 400. As for the surface layer 400, in an embodiment, the adhesive has a CTE of ka. In some of these embodiments, the ratio ka/k3 is from 0.5 to 2, preferably from 0.75 to 1 .3, and more preferably from 0.9 to 1 .1 . In some of these embodiments, the ratio ka/k4 is from 0.5 to 2, preferably from 0.75 to 1 .3, and more preferably from 0.9 to 1 .1 .

Properties of the support layer

Typically the coefficients of thermal expansion can be measured along the second direction Sy and the third direction Sz. In this case, the support layer 200 has the first coefficient of thermal expansion k1 in a direction d1 that is parallel to the length Lp or the width Wp of the panel. By the definition above, the first CTE k1 is greater than or equal to the second CTE k2, whereby either CTE can be parallel to length or width.

Support materials that are specially suitable for a support material of the panel comprise thermoplastic or thermoset material that has a reasonably low deflection temperature, as discussed above. Moreover, the support material is preferably at least one of

- light (low in density), whereby the panel 100 is easier to handle,

- strong,

- not fragile,

- bendable, when heated, but rigid in typical use temperature, and

- cheap.

Unfortunately, in typical materials there properties affect also the coefficient of thermal expansion. Thereby, in a panel 100,

- the first coefficient of thermal expansion is at most 60 ppm/K; such as at most 30 ppm/K; or at most 10 ppm/K.

The support 200 may e.g. comprise plywood. Then, the first coefficient of thermal expansion may be e.g. from 4 ppm/K to 8 ppm/K; such as from

4 ppm/K to 5 ppm/K. The support 200 may e.g. comprise a particle board.

Then, the first coefficient of thermal expansion may be e.g. from 50 ppm/K to

60 ppm/K. The support 200 may e.g. comprise glass fibre reinforced polymer.

Then, the first coefficient of thermal expansion may be e.g. about 30 ppm/K. By using some low CTE filler materials, a polymer support may have a CTE of as low as 15 ppm/K.

The unit of the CTE, ppm/K, is an abbreviation of "parts per million per Kelvin". The unit equals e.g. (μηη/ηη)/Κ. As known, the CTE (e.g. k) relates an absolute thermal expansion ΔΙ_, a dimension L in a reference temperature TO, and a temperature T as ΔΙ_ = k* L χ (T-T0). This applies is the direction of measurement, such as d. With reference to Figs. 1 c and 1 d, four CTEs and four directions characterize some properties of the panel 100. As noted above, In general, the coefficients of thermal expansion (CTE) depend on the temperature. Unless otherwise stated, all the values of the CTEs in this description are given at the temperature 25 °C. The support layer 200 may be isotropic or essentially isotropic. In such a panel 100

- the ratio of the first coefficient of thermal expansion k1 to the second coefficient of thermal expansion k2 is at most 1 .5; preferably at most 1 .2.

In order to avoid excessively hot temperature for deforming the support layer 200, in an embodiment the support layer 200 comprises

- thermoplastic polymer that has a melting temperature of at most 200 °C. In some of these embodiments, the support layer 200 comprises

- thermoplastic polymer that has a melting temperature of at most 180 °C, at most 170 °C, or at most 160 °C, or at most 150 °C.

The melting temperature of a thermoplastic polymer can also be referred to as a deflection temperature, as the thermoplastic polymer can easily be deflected at the melting temperature and above.

In some embodiments, the support layer 200 comprises thermoplastic polymer that has a melting temperature of at least 20 °C, preferably at least 60 °C.

However, to enable to use in reasonably hot environments, too, the melting point of the thermoplastic polymer of the support layer 200 should not be too low. In order to allow for use in hot environments, in an embodiment the support layer 200 comprises

- thermoplastic polymer that has a melting temperature of at least 80 °C. In some of these embodiment the support layer 200 comprises

- thermoplastic polymer that has a melting temperature of at least 120 °C. Preferably the melting point of the thermoplastic material is such that the support layer 200 is bendable at a temperature from 150 °C to 170 °C. Thus, the melting point of the thermoplastic material of the support layer 200 may be e.g. less than 150 °C or less than 170 °C. In order to avoid excessively hot temperature for deforming the support layer 200, in an embodiment the support layer 200 comprises - thermoset polymer that has a deflection temperature of at most 200 °C. In some of these embodiments, the support layer 20 comprises

- thermoset polymer that has a deflection temperature of at most 180 °C, at most 170 °C, or at most 160 °C, or at most 150 °C.

The deflection temperature of a thermoset polymer can also be referred to as a glass transition temperature, as the thermoset polymer can reasonably easily be deflected at the glass transition temperature and above. Moreover, in order to allow for use in hot environments, in an embodiment the support layer 200 comprises

- thermoset polymer that has a deflection temperature of at least 80 °C.

In some of these embodiment the support layer 200 comprises

- thermoset polymer that has a deflection temperature of at least 120 °C.

In order to ensure sufficient support, in some embodiments, the thickness of the support layer 200 is from 3 mm to 25 mm. In some of these embodiments the thickness of the support layer 200 is from 6 mm to 20 mm. In some embodiments, the thickness of the support layer is from 3 mm to 20 mm; preferably from 4 mm to 15 mm, and most preferably from 6 mm to 12 mm.

The thermoplastic polymer of the support layer may be selected from the group comprising at least one of polyurethane, acrylic, polyvinyl alcohol, polyolefin, lignin, polyethylene, polypropylene, ethylene-vinyl acetate, vinyl, polyester, a co-polymer comprising ethylenes and propylenes, and mixtures of any two or more of them.

The thermoplastic polymer, even if deformable, does not provide support for the surface layer 400 when melted. Therefore, to support the panel 100 even during bending in high temperature, the support layer 200 preferably comprises

- in addition to thermoplastic polymer, additional material.

As discussed, preferably the additional material is thermally stable in the melting temperature of the thermoplastic polymer. For example, if the additional material has a melting point, the melting point of the additional material is preferably more than the melting point of the thermoplastic material . It is also possible that the additional material does not have a well- defined melting point, i.e. the additional material does not melt. This could happen e.g. for ceramic particles, which are heat resistant to very high temperatures and e.g. for some polymers not having a melting point (decomposes before melting).

The additional material may take the shape of curvilinear areas, planes, or fibres, whereby the additional material is "long" in at least one direction. The term "curvilinear area" refers to a material that could have been planar, but has been from pressed to a curvilinear shape. This has the effect the additional material mechanically supports the surface layer 400 during bending. In an embodiment,

- the support layer 200 has a thickness T2 in the first direction,

- support layer 200 comprises pieces of additional material wherein

- the pieces of the additional material has the shape of at least one of curvilinear areas, planes, and fibres, wherein

- a piece of the additional material has a dimension in a direction that is in the tangent plane of the panel, such that

- the dimension of the piece of the additional material is greater than the thickness T2 of the support layer 200.

Preferably,

- a piece of the additional material has a dimension in a direction that is perpendicular to the first direction Sx, such that

- the dimension of the piece of the additional material is greater than half of the smaller of the length of the panel Lp and the width of the panel Wp.

It is known that fibrous materials are generally long and strong. Fibres may be e.g. natural fibres. The fibres may be bonded together. For example, in an embodiment, the additional material comprises material that comprises natural fibres. As an example, in an embodiment, the additional material comprises wood.

A preferred embodiment of the support layer 200 comprises plywood that comprises thermoplastic adhesive. As discussed above, such thermoplastic adhesive may serve as the thermosensitive area 500. On one hand, such a plywood panel can be bent, when the thermoplastic material in between the wooden layer is melt. On the other hand, when the thermoplastic material is solidified, the plywood panel is stiff. Moreover, the price of plywood is much less than that of a typical surface layer 400. Moreover, the density of plywood is much less than that of a typical surface layer 400. Moreover, the strength of plywood is much more than that of a typical surface layer 400.

A support layer 200 may comprise plywood made of hardwood. Hardwood is wood from angiosperm trees or from monocotyledons. Hardwood contrasts with softwood (which comes from gymnosperm trees, also called conifers). The list of angiosperm trees (some hardwood) is wide, and includes e.g. alder, apple, aspen, birch, cherry, ebony, elm, eucalyptus, hickory, mahogany, maple, oak, rosewood, teak, walnut, and willow. In particular, the wood of the support layer 200 may comprise birch. Monocotyledons (some other hardwood) are of less importance in plywood industry. Typically, the density of a support layer 200 that comprises plywood comprising hardwood is from 500 kg/m³ to 800 kg/m³.

A support layer 200 may comprise plywood comprising softwood. The list of softwood include cedar, the genus tilia (e.g. linden, lime or basswood), pine (or generally the genus pinus), and spruce (or generally the genus picea). In particular, the wood of the support layer 200 may comprise spruce. Typically, the density of a support layer 200 that comprises plywood comprising softwood is from 300 kg/m³ to 600 kg/m³.

Density wise, a plywood support comprising hardwood may be beneficial, since such a support is light, as compared to plywood comprising hardwood, and having the same thickness. However, in general a plywood support comprising hardwood may be beneficial, since such a support is stronger, as compared to plywood comprising softwood, and having the same thickness.

In general, the adhesive in between wooden veneer layers of plywood may be thermoset or thermoplastic. In such an embodiment, the support layer 200 comprises - at least a first wooden veneer layer and a second wooden veneer layer, and

- polymer in between the first wooden veneer layer and the second wooden veneer layer, wherein

- at least part of the second wooden veneer layer is arranged in the first direction Sx from the first wooden veneer layer.

The term "at least part" here refers e.g. to a curvilinear panel such as the curvilinear panel of Fig. 7a.

However, as discussed above, preferably the adhesive in between wooden veneer layers of plywood comprise thermoplastic polymer.

In such an embodiment, the support layer 200 comprises

- at least a first wooden veneer layer and a second wooden veneer layer, and

- thermoplastic polymer in between the first wooden veneer layer and the second wooden veneer layer, wherein

Preferably the support layer 200 comprises at least three wooden veneer layers. This helps the bendability of the panel 100. Moreover, preferably the support layer 200 has a symmetric structure. In a symmetric structure, a plane parallel to the bottom surface 130 (cf. Fig. 1 a) forms a symmetry plane for the support layer. In such a case, the symmetric structure gives rise to isotropy of the support layer 200. Isotropy may be beneficial for thermal expansion and dimensional stability. The support layer 200 could be substantially symmetric, wherein the term "substantially symmetric" refers to a support layer 200 that is formed from a symmetric structure by removing material and/or bending. Such a symmetric structure can be realized by selecting properly the fibre orientations of the wooden veneer layers of the support layer 200. Preferably, the support layer 200 comprises symmetrical veneer structure in cross direction of the support layer. The support layer 200 may comprise an odd number of wooden veneer layers. This improves the isotropy of the support layer 200. To facilitate a proper number of wooden veneer layers, in an embodiment - the thickness of a wooden veneer layer is from 0.5 mm to 5 mm. In a preferred embodiment the support layer 200 comprises natural fibre composite that comprises lignocellulosic fibers, plant fibers or wood fibers and thermoplastic adhesive comprising chemical groups capable to form covalent bonds between the adhesive and fibers. Preferably these chemical groups are anhydrides.

Another type of support layer 200, comprising natural fibres in a polymer matrix is a particle board, also known as particleboard or chip board. Particle board is a composite material. It is an engineered wood product manufactured from wood chips, sawmill shavings, or even saw dust, and a synthetic resin or other suitable binder. The board may be pressed and/or extruded. In particle boards the wood chips do not form supporting layers. Therefore, the binder is preferably thermoset. However, the binder may comprise thermoplastic, or even consist of thermoplastic. In the latter case, the amount of material pressed out during form pressing depends on the applied pressure. A particle board may have the CTE as high as 60 ppm/K. The CTE of the particle board may be e.g. at least 30 ppm/K, 40 ppm/K, or 50 ppm/K. The properties of the particle board depend on the amount and type of the binder and the material comprising wood. The density of a particle board may vary from 250 kg/m³ to 1300 kg/m³. Particle boards are typically classified as low density particle boards (density from 250 kg/m³ to 450 kg/m³), medium density particle boards (density from 550 kg/m³ to 700 kg/m³), and high density particle boards (density from 750 kg/m³ to 1300 kg/m³). Typically the density is from 650 kg/m³ to 750 kg/m³. In case a particle board is used as the support layer 200, preferably a low density particle board or a medium density particle board is used. The density may be e.g. from 400 kg/m³ to 800 kg/m³.

As discussed, the additional material of the support layer 200 may comprise fibres. The additional material of the support layer may comprise synthetic organic or inorganic fibres. In an embodiment the additional material comprises woven or non-woven fibrous material such as at least one of carbon fibres, glass fibres, aramid fibres, polypropylene fibres, polyamide fibres (Nylon), and polyurethane fibres. The fibres may be arranged unidirectionally or in multiple directions. The fibrous material may form a woven structure, such as cloth, textile, or mat (e.g. glass fibre mat). Preferably the length of the fibre (or average length of the fibres) is at least ten times a width of the fibre.

Preferably the support layer is reasonably light. Therefore, in an embodiment, - the density of the support layer 200 is at most 1600 kg/m³.

When plywood is used as the support layer 200, the density of the support layer may be e.g. from 300 kg/m³ to 1400 kg/m³. Typical values for plywood comprising hardwood or softwood were given above. The higher values (i.e. from 800 kg/m³ to 1400 kg/m³) may occur exceptionally, e.g. when the plywood comprises a lot of adhesive, or is reinforced with heavier material.

Properties of the surface layer

Typically the coefficients of thermal expansion (CTE) can be measured along the second direction Sy and the third direction Sz. In this case, the surface layer 400 has the third CTE k3 in a direction d3 that is parallel to the length Lp or the width Wp of the panel 100. By the definition above, the third CTE k1 is greater than or equal to the fourth CTE k4, whereby either CTE can be parallel to length or width. In an embodiment, the surface layer 400 has the third coefficient of thermal expansion k3 in a direction d3 that is parallel to the length Lp or the width Wp of the panel 100.

The surface layer typically has a high CTE. Therefore, in an embodiment the third coefficient of thermal expansion k3 is at least 20 ppm/K; or at least 25 ppm/K; and it may also be at least 30 ppm/K. In addition to the third CTE, also the fourth CTE may be reasonably large. In an embodiment, the fourth coefficient of thermal expansion is at least 10 ppm/K, or at least 12 ppm/K. It may also be at least 15 ppm/K, or at least 20 ppm/K.

The surface layer 400 may also be isotropic or substantially isotropic. In this case, the ratio of the third coefficient of thermal expansion k3 to the fourth coefficient of thermal expansion k4 (k3/k4) is at most 1 .5; preferably at most 1 .2.

In comparison to the first CTE k1 of the support layer 200, in an embodiment, the ratio of the third coefficient of thermal expansion k3 (of the surface layer 400) to the first coefficient of thermal expansion k1 , i.e. k3/k1 , is at least 1 .5, preferably at least 2, more preferably at least 3. However, with some material selections (e.g. with a glass fibre reinforced support layer 200 or a particle board support layer 200; and a heavily filled surface layer 400), the first CTE may be greater than the third CTE. For example, the ratio of the first coefficient of thermal expansion k1 (of the support layer 200) to the thid coefficient of thermal expansion k3, i.e. k1/k3, may be at least 1 .5, preferably at least 2, more preferably at least 3. In comparison to the first CTE k1 of the support layer 200, in some embodiments, the difference between the third coefficient of thermal expansion k3 (of the surface layer 400) and the first coefficient of thermal expansion k1 , i.e. k3 - k1 , is at least 10 ppm/K, at least 15 ppm/K, or at least 20 ppm/K. In some other embodiments, the difference between the first coefficient of thermal expansion k1 (of the support layer 200) and the third coefficient of thermal expansion k3, i.e. k1 - k3, is at least 10 ppm/K, at least 15 ppm/K, or at least 20 ppm/K

One reason to have a panel as described herein, is to improve the handling of otherwise fragile panels. The brittleness, i.e. fragility, of the panel can be characterized e.g. by impact resistance or by tensile strain at break, often referred to as elongation at break. However, the term elongation commonly refers to absolute measures such as mm, while strain commonly refers to relative measures such as %. However, also the unit of "elongation at break" is commonly proportional, i.e. %. Moreover, the term elongation refers to tensile deformation. Thus, the term tensile strain at break is preferred in this application.

The surface layer 400 can be brittle as such, i.e. when separated from the adhesive 300 and the support layer 200. Thus, the second part 102 of the panel 100, after the division of the panel 100, can be brittle. Moreover, the surface of the panel 100 that comprises the surface layer 400 can be brittle.

In an embodiment,

- the panel 100 is brittle in such a way that the impact resistance of the surface layer 400, when the surface layer 400 has been separated from the adhesive 300 and the support layer 200, is at most 200 cm, wherein

- the impact resistance is defined as in the standard DIN ISO 4586.

In some of these embodiments, the impact resistance is at most 150 cm, at most 120 cm, or at most 100 cm.

In an embodiment,

- the panel 100 can be divided to the first part 101 and the second part 102 such that the second part 102 comprises the surface layer 400,

- the panel 100 is brittle in such a way that the impact resistance of the second part 102, when separated from the panel 100 such that the second part 102 comprises the surface layer 400,

surface layer 400, when the surface layer 400 has been separated from the adhesive 300 and the support layer 200, is at most 200 cm, wherein

- the impact resistance is defined as in the standard DIN ISO 4586.

In an embodiment,

- the panel 100 is brittle in such a way that the impact resistance of the surface of the panel that comprises the surface layer 400, is at most 200 cm, wherein

- the impact resistance is defined as in the standard DIN ISO 4586.

For the impact resistance test, reference is made to the standard DIN ISO 4586 on 13^th Feb, 2013. In the test, a steel ball having the diameter of 42.8 mm ± 0.2 mm and mass of 324 g ± 5.0 g is dropped from a height H onto a horizontal surface being located at the zero height. The impact resistance of the surface is the highest dropping height for the ball that the surface can withstand without cracking.

In an embodiment,

- the panel 100 is brittle in such a way that the impact resistance of the surface layer 400, when the surface layer 400 has been separated from the adhesive 300 and the support layer 200, is less than the impact resistance of the support layer 200, when the support layer 200 has been separated from the adhesive 300 and the surface layer 400.

In an embodiment,

- the panel 100 is brittle in such a way that the impact resistance (according to the drop test DIN ISO 4586) of the surface of the panel that comprises the surface layer 400, is less than the impact resistance of the surface of the panel that comprises the support layer 200.

In an embodiment the surface layer 400 is more brittle than the support layer 400. Also, as has been disclosed, a panel 100 can be separated to a first part 101 and a second part 102, wherein the second part 102 comprises the surface layer 400. In an embodiment the second part 102 comprises the surface layer 400, and the second part 102 (when separated from the panel) is more brittle than the first part 101 (when separated from the panel). As for the feature "more brittle", the impact resistance or the tensile strain at break can be used.

In an embodiment,

- the first part 101 of the panel, after being separated from the panel 100 has a first impact resistance (according to the drop test DIN ISO 4586)

- the second part 102 of the panel, after being separated from the panel 100 comprises the surface layer 400 and has a second impact resistance (according to the drop test DIN ISO 4586), and

- the second impact resistance is less than the first impact resistance. As for the tensile strain at break, a panel 100 can be separated to a first part 101 and a second part 102, wherein the second part 102 comprises the surface layer 400. In an embodiment,

- the first part 101 of the panel, after being separated from the panel 100 has a first tensile strain at break,

- the second part 102 of the panel, after being separated from the panel 100 comprises the surface layer 400 and has a second tensile strain at break, and

- the second tensile strain at break is less than the first tensile strain at break. In an embodiment,

- the tensile strain at break of the surface layer 400 is less than the tensile strain at break of the support layer 200.

Thus, in a tensile stress test, a panel 100 may fracture first on the side of the surface layer 400.

As for the tensile strain at break, in an embodiment,

- the panel 100 is brittle is such a way that the tensile strain at break of the surface layer 400, when surface layer 400 has been separated from the adhesive 300 and the support layer 200, is e.g. at most 1 %, or less than 5 %, at the temperature 25 °C.

The tensile strain at break may depend on the temperature.

As for the tensile strain at break, in an embodiment,

- the panel 100 is brittle is such a way that the tensile strain at break of the surface layer 400, is at most 8 % at the temperature 25 °C, or less than 5 % at the temperature 25 °C.

In an embodiment, the surface layer 400 comprises polymer. However, to engineer the material properties of the surface layer, in an embodiment, the surface layer 400 further comprises filler material. Filler materials be used to engineer e.g. wear resistance, electrical conductance (related to antistatic properties and EMC protection), resistance to electric discharge, thermal resistance, fire resistance, color, opaqueness, resistance to radiation (e.g. UV radiation), acoustic impedance, and hardness; or to bring some functionality to the surface layer, such as self-cleaning, easy-cleaning, change of color with temperature (thermochromism). In general, the properties can be engineered in either direction, such as increasing or decreasing the thermal conductance, or increasing or decreasing the wavelength that the surface layer emits, reflects, or absorbs, depending on the application. Some filler materials can be used to reduce cost; e.g. when the filler material is cheap. The polymer thus forms a polymer matrix for the filler material. In an embodiment the filler material comprises particles or the filler material comprises fibres.

In an embodiment, the polymer of the surface layer 400 comprises thermoset polymer. In some embodiments, the polymer comprises at least one of acrylate, polyester, and epoxy. In some embodiments, the polymer comprises thermoset polymer having the deflection temperature (e.g. the glass transition) temperature less than 170 °C or less than 160 °C. The deflection temperature of the surface layer may also be related to the deflection temperature (e.g. the melting point) of the thermoplastic polymer of the support layer. In an embodiment,

- the support layer 200 comprises polymer,

- the polymer of the support layer 200 has a deflection temperature Tm, and

- the surface layer 400 comprises thermoset polymer having a glass transition temperature Tg, wherein

- the glass transition temperature Tg is at most the deflection temperature Tm, i.e. Tg≤Tm.

In such a configuration, the surface layer 400 becomes deformable at a temperature, wherein the support layer 200 is also deformable. In this way, the heating energy needed is optimized. Preferably the temperature of the panel 100 during form pressing (Figs. 6a and 6b) is not excessively above the deflection temperature of the support layer 200. The temperature of the panel 100 during form pressing may exceed the deflection temperature of the support layer 200 by e.g. at least 10 °C, at least 20 °C, at least 30 °C, at least 40 °C, or at least 50 °C. However, to optimize the heating energy, in some embodiments, The temperature of the panel 100 during form pressing may exceed the deflection temperature of the support layer 200 by e.g. at most 20 °C, at most 30 °C, at most 40 °C, at most 50 °C, or at most 60 °C.

In an embodiment, the polymer of the surface layer 400 comprises thermoplastic polymer. In an embodiment, the polymer of the surface layer 400 comprises at least one of polyurethane, acrylonitrile butadiene styrene (ABS), acrylic (e.g. poly(methyl methacrylate), PMMA), fluoroplastic or fluoropolymer (e.g. polytetrafluoroethylene, PTFE), polyoxymethylene, polycarbonate, polyetheretherketone, cellulose acetate, polystyrene, polyamide-imide, polyphenylene, polyvinyl alcohol, polyolefin, lignin, polyethylene, polypropylene, and a co-polymer comprising ethylenes and propylenes. In addition or alternatively, the surface layer may comprise multiple components of same type of material, such as polyurethanes and/or fluoroplymers.

It is also noted that the polymer of the surface layer 400 affects the CTE of the surface layer 400. CTEs for some of the aforementioned materials include 200 ppm/K for polyethylene, from 100 ppm/K to 200 ppm/K to polypropylene, and 75 ppm/K for ABS. Moreover, filler material may decrease the CTE.

In an embodiment, the polymer of the surface layer 400 has a deflection temperature of at most 200 °C, preferably at most 170 °C. In an embodiment, the polymer of the surface layer 400 has a deflection temperature of at least 80 °C, preferably at least 90 °C.

In an embodiment, the polymer of the surface layer 400 comprises thermoplastic polymer having the melting temperature of at most 200 °C, preferably at most 170 °C. In an embodiment, the polymer of the surface layer 400 comprises thermoplastic polymer having the melting temperature of at least 80 °C, preferably at least 90 °C.

In an embodiment, the polymer of the surface layer 400 comprises thermoset polymer having the glass transition temperature of at most 200 °C, preferably at most 170 °C. In an embodiment, the polymer of the surface layer 400 comprises thermoset polymer having the glass transition temperature of at least 80 °C, preferably at least 90 °C.

In an embodiment, the polymers are selected such that the polymer of the surface layer 400 remains reasonably rigid, even at a temperature, wherein the support layer 200 is deformable. In this way it is assured that the filler particles remain in their polymer matrix also during the deformation. In a corresponding embodiment,

- the thermo polymer of the support layer 200 has a first deflection temperature Tm1 , and

- the surface layer 400 comprises thermoplastic polymer having a melting temperature Tm2, wherein

- the melting temperature Tm2 is higher than the deflection temperature Tm1 , i.e. Tm2>Tm1 .

The surface layer 400 may be e.g. a polymer layer, a composite layer (i.e. polymer with filler material), or a laminate structure (i.e. layered structure). In a laminate structure, a layer of the laminate may be a reinforcing layer. The reinforcing layer may comprise fibrous material. The reinforcing layer may comprise synthetic fibrous material. These fibrous materials were discussed also in connection with the support layer 200.

In an embodiment, the filler material has the form of filler particles. In this embodiment, the surface layer 400 comprises filler particles.

The possibilities of thermoset and thermoplastic polymer in the surface layer were discussed. To summarize, in some embodiments,

- the support layer 200 comprises thermo polymer having a deflection temperature Tm1 , and

- the polymer of the surface layer 400 comprises at least one of

- (i) thermoset polymer having a glass transition temperature Tg that is less than the deflection temperature Tm1 , (i.e. Tg<Tm1 ) and

- (ii) thermoplastic polymer having a second melting temperature Tm2 that is greater than the deflection temperature Tm1 (i.e. Tm2>Tm1 ).

As an example, in an embodiment, - the support layer 200 comprises polymer having a first deflection temperature, and

- the surface layer 400 comprises polymer having a second deflection temperature, wherein

- the second deflection temperature is less than the first deflection temperature.

However, in case the surface layer 400 comprises surface polymer material and filler material, and the surface polymer material consist of thermoplastic polymer, the thermoplastic polymer of the surface layer does preferably not melt in the form press process. In such an embodiment

- the support layer 200 comprises polymer having a deflection temperature, and

- the surface layer 400 comprises thermoplastic polymer having a melting temperature, wherein

- the melting temperature is higher than the deflection temperature.

More specifically,

- the surface layer 400 comprises surface polymer material and filler material, - the surface polymer material consist of a thermoplastic polymer or thermoplastic polymers,

- the thermoplastic polymer has a melting temperature, which simultaneously is the highest melting temperature; or the multiple thermoplastic polymers have melting temperatures of which one is the highest melting temperature, - the support layer 200 comprises polymer having a deflection temperature, wherein

- the highest melting temperature is higher than the deflection temperature.

However, even if all the polymer material of the surface layer 400 is thermoplastic, form pressing is possible. Also in this case, the amount of material pressed out during form pressing depends on the applied pressure.

It is also noted that, when the highest melting temperature is higher than the deflection temperature, the surface layer comprises thermoplastic polymer having higher melting temperature than the deflection temperature of the support layer 200. However, the surface layer 400 may comprise both thermoplastic and thermoset polymer, in which case the melting temperature of the thermoplastic polymer(s) of the surface layer may be less than the deflection point of the support layer 200.

For increased wear resistance, hard filler particles may be used. In some embodiments, the surface layer 400 comprises hard filler particles, such as particles comprising rock, clay, brick, ceramic, titanium oxide (ΤΊΟ2), alumina (AI2O3), and/or aluminium hydroxide (AI(OH)₃). The hardness of the material of such filler particles can be can be characterized by the Mohs scale of hardness. In an embodiment, the material of the hard filler particles have the hardness of a least 2.5 on the Mohs scale of hardness. Such particles can be especially used in a matrix material comprising thermoset polymer. Particles can be treated with coupling agent(s), so that they are made compatible with the matrix or they can be bonded to the matrix by chemical bonds. Typically different kind of silanes and titanates are used as coupling agents. Such a surface layer may be referred to as a "solid surface", the CTE of such a solid surface may be e.g. from 25 ppm/K to 35 ppm/K, e.g. 30 ppm/K.

Such filler particles are typically heavy, and may have a small coefficient of thermal expansion. In an embodiment, the coefficient of thermal expansion of the filler particles of the surface layer 400 is less than the coefficient of thermal expansion of the polymer of the surface layer 400. In an embodiment, the density of the filler particles of the surface layer is at least 1800 kg/m³. Such particles have been observed to be resistant to wear. Preferably, to increase the wear resistance, the surface layer comprises at least 50 m-%, preferably at least 65 m-%, and more preferably at least 80 m-% filler particles. Here m-% refers to mass percentage, sometimes called weight percent. Such a large filler material content may increase the density of the surface layer. Depending on the amount of hard filler particles, the density of the surface layer is may be e.g. from 1400 kg/m³ to 1900 kg/m³. In an embodiment, wherein the surface layer 400 comprises hard filler particles, the density of the surface layer is from 1600 kg/m³ to 1800 kg/m³. The filler particles may - in addition or alternatively - have a fibrous inner structure. In an embodiment, the surface layer 400 comprises filler particles (as the filler material), the filler particles comprising multiple smaller fibres, such as natural fibres. In some of such embodiments, the surface layer 400 comprises particles in the form of natural cellulose fibres. Such particles can be especially used in a thermoplastic polymer matrix material. The natural cellulose fibres refer to organic natural fiber material that contain cellulose. The organic natural fiber material may originate from any plant material that contains cellulose. The natural cellulose fibres may comprise wood-based cellulose pulp fibers. The organic natural fiber material may comprise mechanically treated and/or chemically treated fibers and/or fiber-like particles. The treated particles used may comprise at least 30 m-% or at least 40 m-%, more preferably at least 50 m-% or at least 60 m-%, and most preferably at least 80 m-% or at least 90 m-% of mechanically treated organic natural fiber material. Mechanically treated may refer to organic natural fiber material, which is isolated from any organic natural raw material comprising cellulose by a mechanical pulping process. However, mechanical processing does not significantly reduce the amount of lignin in the raw material. Organic natural fibre material comprising lignin, however, is prone to decompose (burn) more easily in high temperatures than fiber material free of lignin. In contrast, chemically treated organic natural fiber material typically comprise less lignin. The chemically treated organic natural fibre material preferably comprises chemical pulp. The chemical pulp may be, for example, from kraft process or sulfite process, but also other chemical processes may be used, such as a soda pulping process. Preferably, the chemical pulp is from the kraft process. Advantageously, lignin content of the chemically treated pulp is under 15 m-%, preferably under 10 m-% or under 5 m-%, more preferably under 3 m-%, under 2 m-% or under 1 m-% and most preferably under 0.5 m-%. Preferably, the alfa cellulose content of the chemically treated pulp is above 50 m-%, preferably above 60 m-%, more preferably above 70 m-% and most preferably above 72 m-% or above 75 m-%. Advantageously, the alfa cellulose content of the chemically treated pulp is below 99 m-%, preferable below 90 m-%, more preferably below 85 m-% and most preferably below 80 m-%.

In some embodiments, the surface layer 400 comprises at least 20 m-% filler particles. Preferably the surface layer 400 comprises at least 25 m-%, and more preferably at least 30 m-% filler particles. The surface layer 400 may comprise at least 40 m-% or at least 50 m-% filler particles. Such a large filler material content may increase the density of the surface layer. Depending on the amount of natural cellulose fibres, the density of the surface layer may be e.g. from 900 kg/m³ to 1200 kg/m³. In an embodiment, wherein the surface layer 400 comprises natural cellulose fibres, the density of the surface layer is from 970 kg/m³ to 1 120 kg/m³.

Preferably, the lignin content of the surface layer 400 is low. With the values given above, the lignin content of the surface layer 400 may be e.g. at most 7.5 m-% (50 m-% filler particles, wherein the lignin content is at most 15 m- %). Some other limits calculated from the values above include a ligning content for the surface layer 400 of at most 6 m-%, at most 5 m-%, at most 4 m-%, at most 2 m-%, and at most 1 m-%. Also other value can be calculated, e.g. at most 0.2 m-%.

In an embodiment, the density of the surface layer 400 is greater than the density of the support layer 200. Regardless of the type of the filler particles are generally small . Small e.g. in comparison to the thickness of the surface layer. This ensures the possibility of a smooth surface. Such a smooth surface is easy to clean and also visually attractive. In an embodiment,

- the surface layer 400 comprises filler particles, wherein the each filler particle has three dimensions, and

- the filler particles have a particle size Dp that is the smallest value of the three dimensions,

- the surface layer 400 has a thickness T2 in the first direction Sx, wherein

- the ratio T2/Dp is at least 2, preferably at least 3, and more preferably at least 5. As is evident, the surface layer 400 comprises a multitude of filler particles, whereby the particle size Dp is a statistical measure of the filler particle size. In the above, the "filler particle size Dp" may refer e.g. to a statistical measure of the smallest dimension of the particles. The statistical measure may be e.g. the average or the median. Moreover, particles can also be characterized by a size different from the smallest of its three dimensions. For example, the (linear) size of the particle can be taken as a diameter of a sphere having the same volume as the particle. Moreover, the median of the three dimension could be used a particle size, in particular, if a sieve is used to determine the particle size. As for an absolute values for the size, in an embodiment,

- the surface layer 400 comprises filler particles, and

- the filler particles have three orthogonal dimensions (i.e. sized measured in different directions),

- for at least 75 % of the filler particles, the smallest of the three orthogonal sizes is at most 1 mm, preferably at most 100 μιτι. In some embodiments, for at least 75 % of the filler particles, the smallest of the three orthogonal sizes is at most 50 μιτι. Instead of the 75 % percentile, the median or the average value can be determined by measurements. In the corresponding embodiments,

- for at least 50 % of the filler particles, the smallest of the three orthogonal sizes is at most 1 mm, preferably at most 100 μιτι or at most 50 μιτι; or

- the average of the smallest of the three orthogonal sizes of the particles sizes is at most 1 mm, preferably at most 100 μιτι or at most 50 μιτι.

As discussed, the material cost of the surface layer 400 may be reasonably high. Moreover, the density of the surface layer can be high. To ensure a cost-effective and light panel, the surface layer 400 is preferably thin. In an embodiment, the thickness of the surface layer 400 is at most 15 mm, preferably at most 9 mm, and more preferably at most 6 mm. In some embodiments, the thickness of the surface layer 400 is at least 3 mm, or at least 4 mm. In addition or alternatively, in an embodiment, the thickness of the surface layer 400 is less than the thickness of the support layer 200. Preferable shapes of the panel

As discussed above, panels are preferably stored in piles. Piles are easy to form when the panels 100 of the pile are planar or essentially planar at an operation temperature. The operation temperature may be e.g. from 0 °C to 50 °C, such as from 10 °C to 30 °C, such as 25 °C. Therefore, in an embodiment,

- the panel 100 has multiple non-meandering lines in a top surface 140 (cf. Figs. 1 a and 1 b) facing away from the support layer 200, and

- the radius of curvature of all non-meandering lines at least 5 m.

A radius of curvature is - by definition - well defined only for a line. A "radius of curvature of a non-meandering line of a surface" here refers to the radius of curvature of the line that belongs to the surface, and that is as straight as possible, i.e. non-meandering. Thus, a non-meandering line between a first point and a second point of the top surface 140 is the shortest line along the top surface 140 from the first point to the second point. Thus, the non- meandering line does not meander in the surface, but may curvilinear with the surface. In other words, the a "non-meandering line of a surface" and the "radius of curvature" are, in combination, defined such that the center of the osculating circle for the definition of the radius of curvature is located a distance apart from the top surface normal; possibly in a the direction of a surface normal of the tangent plane of the surface.

Referring to Figs. 6a and 6b, a panel 100, can be form pressed to a curvilinear shape. Fig. 6a shows, in a side view, a panel 100. The support layer 200 comprises thermoplastic material. When the panel 100 is heated to a temperature that is above the melting point of the thermoplastic material of the support layer 200, the thermoplastic material melts. This melting enables the formation of the panel. The panel can be heated before it is bent in a device, or a bending device can heat the panel 100 before bending. Referring to Fig. 6b, the panel 100 can be form pressed to a desired shape. The from pressing can be done in an apparatus for form pressing 500. The apparatus comprises a first surface 512 and a second surface 522. In between these surfaces, the panel 100 is pressed to a form. The first surface 512 may be the surface of a first body 510. The second surface 522 may be the surface of a second body 520. The surfaces 512, 522 are arranged to be movable towards each other. Thus, by inserting a panel in between these surfaces, and by moving the surfaces towards each other, the panel 100 becomes form pressed (i.e. bent).

The apparatus for form pressing 500 may comprise a cooler arranged to cool the panel 100. Alternatively, the panel 100 may cool in between the surfaces 512, 522 by thermal conduction to these surfaces and/or the bodies 510, 520. When the from pressed panel 100 cool down to a temperature below the melting point of the thermoplastic material of the support layer 200, the thermoplastic material solidifies. In this way, the panel 100 re-gains its rigidity. Moreover, as the panel 100 has been bent, the bending stiffness of the panel increases, because the curvilinear part is hard to be bent. In an embodiment, the panel is straight or substantially straight in at least one direction. In such a case, the top surface 140 of the panel 100 is easy to clean and guides liquids. Therefore, in an embodiment,

- the panel 100 has multiple non-meandering lines in a top surface 140 facing away from the support layer 200, and

- the radius of curvature of a non-meandering line is at least 5 m.

Thus, the radius of curvature of at least one non-meandering line is large. However, as is evident, in that case, the radius of curvature of all parallel non-meandering lines may be large.

With reference to Figs. 7c1 and 7c2, the panel 100 shows therein is straight in one direction, i.e. the third direction Sz, as shown in particular in Fig. 7c2. Therefore, the top surface 140 comprises a non-meandering line that has an essentially infinite radius of curvature. This non meandering line of the top surface 140 is parallel to the third direction Sz. An osculating surface, if imagined on the surface 140 of the panel of Fig. 7c2, would have a large, possibly infinite, radius of curvature.

To increase the bending stiffness of the panel 100, the whole panel may be curved. For example, the panel 100 may have the shape of an U -profile. Such an U -profile is bent only in a central area. However, in addition, or alternatively, a panel may be bent at a boundary area.

A bent panel

- comprises a top surface 140 facing away from the support layer 200, - the top surface 140 has a first non-meandering line, and

- the radius of curvature of the first non-meandering line at most 2.2 m; preferably at most 1 .5 m or at most 1 m.

Referring to Figs. 7a and 7b, the panel 100 may take the shape of a tube. Alternatively, the panel may have the shape of a half of a tube. In these shapes, the whole panel has been bent. Thus, also a boundary of the panel has been bent.

Figures 7c1 , 7c2, and 7d show other embodiment, wherein the panel 100 has been form pressed such that the panel 100 is bent at least in a boundary area. In an embodiment

- the panel 100 comprises a top surface 140 facing away from the support layer 200,

- the top surface 140 comprises a boundary area 142,

- the boundary area 142 has a first non-meandering line, and

The boundary area may also be more curved, whereby the radius of curvature of the first non-meandering line may be at most 50 cm, at most 25 cm, or at most 10 cm. For clarity, the first non-meandering line may be selected such that the projection of the first non-meandering line to a plane having the surface normal parallel to the first direction Sx is perpendicular to the direction of the length Lp or the direction of the width Wp of the panel 100. The direction of the projection may also be parallel to a direction that has been the direction of the width Wp or the length Lp of the essentially planar panel 100 before bending. For example, and referring to Fig. 7c1 , the first non-meandering line may have been straight in the second direction Sy, but after bending the panel 100, this non-meandering line no longer is straight. However, its projection to the plane having the surface normal Sx still is directed in the second direction Sy.

With reference to Fig. 7c1 , the panel 100 shows therein is curvilinear at the boundary area 142 and substantially straight at the center area 144. As clear from the figure, the boundary area 142 comprises a first non-meandering line selected such that the projection of the first non-meandering line to a plane having the surface normal parallel to the first direction Sx is perpendicular to the third direction Sz (i.e. to length Lp; cf. Fig. 1 b). This non-meandering line has the radius of curvature R1 , as depicted in figure 7c1 . With reference to Fig. 7c2, it is also noted, that should another non- meandering line be chosen such that the another non-meandering line was parallel to the third direction Sz, the radius of curvature of the another non- meandering line would be essentially infinite, i.e. at least 5 m, as discussed above.

The term boundary area refers to a set of points of the surface, wherein the distance of the point from the boundary of the surface is reasonably small . For example, a point r is in the boundary area, if

- the dimension D1 of the panel 100 along the top surface 140 of the panel 100, in a direction d, wherein the direction d parallel to the length Lp or the width Wp of the panel 100 is

- at least three times the

- distance D2 of a point r from a boundary of the top surface 140 along the top surface 140 of the panel 100, in the direction d.

This definition divides the panel, in the direction of length Lp, to three equally long areas, wherein two of the area are boundary areas. This definition divides the panel, in the direction of width Wp, to three equally wide areas, wherein two of the area are boundary areas. The ratio, D2/D1 <3, defines a relatively wide boundary area. Other definitions, such as D2/D1 <5, or D2/D1 <10 are also possible. Different ratios can be applied in the direction of length Lp and the direction of width Wp. A central area is then just the part what is left over. Thus, central area is defined such that the top surface consist of a central area and boundary areas as defined above.

With reference to Figs. 7c1 and 7c2, in an embodiment, the central area 144 is planar or substantially planar. In this embodiment,

- the panel 100 comprises a top surface 140 facing away from the support layer, and

- the top surface 140 comprises a central area 144 (as defined above; cf. Fig. 7c1 ),

- the central area 144 has multiple non-meandering lines, and

- the radius of curvature of all non-meandering lines of the central area 144 is at least 5 m.

Referring to Fig. 7d, in a preferred embodiment, the central area 144 is also curvilinear. However, preferably the central area 144 is concave, while the boundary area 142 is convex. This particularly beneficial, since in this embodiment, liquid is collected in the central area 144 by the fact it being concave. The liquid can be guided to a direction, provided that the panel 100 is slightly turned from horizontal. Moreover, it has been noticed that such a panel is relatively simple to manufacture using a (planar) panel as described. Such a panel may be manufactured by form pressing as discussed above. Moreover, since the CTE of the surface layer 400 is larger than the CTE of the support layer 200, cooling the panel 100 after from pressing may curve the panel 100. Thus, even if only boundary area 142 (or areas 142) are form pressed to a curvilinear shape, the central area may be curved due to manufacturing process. Thus, a planar panel having the material properties as discussed above, may be relatively easily be bent to such a complex shape.

As for the shape, in an embodiment

- the panel 100 comprises a first side and an opposite second side,

- the top surface 140 comprises a boundary area 142, - the boundary area 142 has a first non-meandering line,

- the radius of curvature R1 of the first non-meandering line at most 2.2 m; preferably at most 1 .5 m or at most 1 m, wherein

- the center of the osculating circle 151 for the radius of curvature R1 of the first non-meandering line is arranged on a first side of the panel, and

- the top surface 140 comprises a central area 144,

- the central area 144 has second non-meandering line,

- the second non-meandering line has a (non-infinite) radius of curvature R2,

- the center of the osculating circle 152 for the radius of curvature R2 of the second non-meandering line is arranged on a second side of the panel.

For clarity, the first non-meandering line may be selected such that the projection of the first non-meandering line to a plane having the surface normal parallel to the first direction Sx is perpendicular to direction of the length Lp or direction of the width Wp of the panel 100. Referring to Fig. 7d, the projection of the first non-meandering line to a plane having the surface normal parallel to the first direction Sx is perpendicular to the third direction Sz (i.e. the direction of length Lp). Thus, the first non-meandering line has been straight in the second direction Sy, but after bending the panel 100, this non-meandering line no longer is straight. However, its projection to the plane having the surface normal Sx still is directed in the second direction.

Also, for clarity, the projection of the second non-meandering line to a plane having the surface normal parallel to the first direction Sx may be selected parallel to the projection of the first non-meandering line to a plane having the surface normal parallel to the first direction Sx. Referring to Fig. 7d, the projection of the second non-meandering line to a plane having the surface normal parallel to the first direction Sx selected parallel to the projection of the first non-meandering line to a plane having the surface normal parallel to the first direction Sx (i.e. parallel to the second direction Sy).

In an embodiment,

- the radius of curvature of the second non-meandering line is more than the radius of curvature of the first non-meandering line. In an embodiment, the radius of curvature of the second non-meandering is less than 5 m, preferably less than 2.2 m, 1 .5 m, or 1 m. In an embodiment, line is more than the radius of curvature of the first non-meandering line is less than 2.2 m, preferably less than 1 .5 m, less than 1 m, or less than 50 cm.

Referring to Fig. 7d, still further, in this embodiment, the central area 144 of the top surface 140 of the panel, wherein the top surface 140 is comprised by the surface layer 400 is preferably concave. This ensures that the central area can collect liquids. In such an embodiment,

- the support layer 200 is arranged on the first side of the panel 100 (i.e. on the first side, wherein also the center of the first osculating circle 151 is arranged) and

- the surface layer 400 is arranged on the second side of the panel 100 (i.e. on the second side, wherein also the center of the second osculating circle

152 is arranged).

With reference to Fig. 8, a panel 100 can be bent such that is curvilinear to two different directions. Figure 8 shows a panel having the shape of a hemisphere or half of an egg, depending on the coordinate axes.

In an embodiment, the thickness Tp (Fig. 1 a) of the panel is from 6 mm to 50 mm. Typical examples of thicknesses comprise 7 mm, 9 mm, 10 mm, 15 mm, and 20 mm.

Such a panel 100 can be used to manufacture furniture. Thus, a piece of furniture comprises a panel 100 as disclosed above. The piece of furniture may be a table. Thus, a table comprises a panel 100 as disclosed above. The table may be a kitchen table, i.e. a table for kitchen. Such a table for use in a kitchen comprises a panel 100 as disclosed above.

The panel 100 may be used for a working surface. Such a working surface comprises a panel 100 as disclosed above. Such a panel 100 may be used, in particular, in rooms, wherein water is typically used for everyday operations, such as washing, and making food. Therefore a building may comprise

- a room, such as a kitchen, a toilet, a showering room, or a sauna, the room comprising a water tap, wherein the room further comprises

- a piece of furniture comprising the panel 100 as discussed above, wherein

- the piece of furniture is arranged in the room.

A building may, alternatively or in addition, comprise,

- a working surface comprising the panel 100 as discussed above, wherein

- the working surface is arranged in the room. A building may, alternatively or in addition, comprise,

- a floor, wherein the floor comprises the panel 100 as discussed above.

Claims

Claims:

1 . A panel having a thickness in a first direction, a length in a second direction, and a width in a third direction, wherein the thickness is smaller than the length and the thickness is smaller than the width, the panel comprising

- a support layer comprising wood and polymer material and

- adhesive in between the support layer and the surface layer, and

- a thermosensitive area, whereby

- the panel has a strength at a first temperature,

- the stress is at most half of the strength.

2. The panel of claim 1 , wherein

- the support layer has a first coefficient of thermal expansion in a direction that is perpendicular to the first direction, and a second coefficient of thermal expansion in another direction that is perpendicular to the first direction, wherein the directions are selected such that the second coefficient of thermal expansion is smaller than or equal to the first coefficient of thermal expansion,

- the surface layer has a third coefficient of thermal expansion in a direction that is perpendicular to the first direction, and a fourth coefficient of thermal expansion in another direction that is perpendicular to the first direction, wherein the directions are selected such that the fourth coefficient of thermal expansion is smaller than or equal to the third coefficient of thermal expansion, and

- the third coefficient of thermal expansion is different from the first coefficient of thermal expansion.

3. The panel of claim 1 or 2, wherein

- the surface layer is heat resistant to temperatures from the first temperature to the second temperature; preferably up to a temperature exceeding the second temperature by at least 10 °C.

4. The panel of any of the claims 1 to 3, wherein

- the surface layer is heat resistant to temperatures from the first temperature to 150 °C, preferably to 180 °C or to 200 °C.

5. The panel of any of the claims 1 to 4, wherein

- the first temperature is 25 °C, and

- the second temperature is at least 50 °C, preferably at least 70 °C, at least 100 °C, or at least 150 °C.

6. The panel of any of the claims 1 to 5, wherein

- the thermosensitive area extends through the panel.

7. The panel of any of the claims 1 to 6, wherein

- the surface layer has a top surface having a surface normal parallel to the first direction,

- the thermosensitive area extends parallel to the top surface.

8. The panel of any of the claims 1 to 7, wherein

- the panel can be separated to the first part and the second part such that - the first part comprises at least a part of the support layer and the second part comprises the surface layer.

9. The panel of the claim 8, wherein

- the thermosensitive area is arranged in or on the support layer, whereby - the panel can be separated to the first part and the second part such that

- the first part comprises at least a part of the support layer and the second part comprises the surface layer.

10. The panel of the claim 8 or 9, wherein

- the adhesive forms the thermosensitive area or another thermosensitive area, whereby - the panel can be separated to the first part and the second part such that

- the first part comprises the support layer and the second part comprises the surface layer.

1 1 . The panel of any of the claims 1 to 10, wherein

- the surface layer has a mass,

- the thermosensitive area is arranged in the panel such that the panel can be separated to the first part and the second part in such a way that

- the second part comprises the surface layer and

- the mass of the second part is at most 1 .1 times the mass of the surface layer, preferably at most 1 .05 times the mass of the surface layer.

12. The panel of any of the claims 1 to 1 1 , wherein

- the thermosensitive area comprises thermoplastic polymer.

13. The panel of any of claim 12, wherein

- the surface layer comprises polymer having a deflection temperature, and

- the melting temperature of the thermoplastic polymer of the thermosensitive area is at most the deflection temperature.

14. The panel of claim 12 or 13, wherein

- the melting temperature of the thermoplastic polymer of the thermosensitive area is at most 200 °C.

15. The panel of any of the claims 12 to 14, wherein

- the support layer comprises the thermosensitive area.

16. The panel of any of the claims 1 to 15, wherein

- the area of the surface layer is Atop, and

- the area of thermosensitive area is Ats, wherein

- the ratio Ats/Atop is at least 25 %, preferably at least 50 %, at least 70 %, or at least 90 %.

17. The panel of any of the claims 1 to 16, wherein

- panel comprises a bottom surface, wherein the bottom surface has a surface normal parallel to the first direction and the support layer comprises the bottom surface,

- the area of the top surface of the panel is Atop,

- the area of the bottom surface of the panel is Abot, and

- the ratio Abot/Atop is from 0.25 to 4.

18. The panel of the claim 17, wherein

- the ratio Abot/Atop is at least 1 .

19. The panel of any of the claims 2 to 18, wherein

- the third coefficient of thermal expansion is greater than the first coefficient of thermal expansion.

20. The panel of any of the claims 1 to 19, wherein

- no plane that has the surface normal parallel to the first direction is a plane of symmetry for the panel.

21 . The panel of any of the claims 1 to 20 , wherein

- the adhesive is selected from a group of adhesives that can be bonded at a temperature from 0 °C to 50 °C ; preferably from 10 °C to 30 °C.

22. The panel of the claim 21 , wherein

- the adhesive is selected from a group of such adhesives that, when bonded at a temperature from 0 °C to 50 °C to the surface layer and the support layer, has such an adhesion strength that when holding the panel from the support layer in any orientation, the surface layer does not fall from the panel due to the gravitational force only.

23. The panel of any of the claim 21 or 22, wherein

- the adhesive is selected from a group of such adhesives that, when bonded at a temperature from 0 °C to 50 °C to the surface layer and the support layer, has such an adhesion strength that when holding the panel from the surface layer in any orientation, the support layer does not fall from the panel due to the gravitational force only.

24. The panel of any of the claims 21 to 23, wherein

- the adhesive is selected from a group of such adhesives that, when bonded at a temperature from 0 °C to 50 °C to the surface layer and the support layer, the adhesion strength between the surface layer and the support layer is at least 100 Pa.

25. The panel of any of the claims 21 to 24, wherein

- the adhesive is selected from a group of such adhesives that, when bonded at a temperature from 0 °C to 50 °C, the adhesion strength remains stable in a stable environment for at least one year.

26. The panel of any of the claims 1 to 25, wherein

- the surface layer comprises a bottom surface of the surface layer,

- the area of the bottom surface of the surface layer is As, and

- the area of the contact between the adhesive and the surface layer is Aa, wherein

- the ratio Aa/As is at least 50 % preferably at least 90 %.

27. The panel of any of the claims 1 to 26, wherein

- the adhesive comprises pressure sensitive adhesive.

28. The panel of any of the claims 1 to 27, wherein

- the adhesive comprises material having the viscosity of at most 100 Pas for the shear rate 1/s at the temperature 20 °C.

29. The panel of any of the claims 1 to 28, wherein

- the adhesive comprises at least one of polyurethane, acrylate, and polyacrylate.

30. The panel of any of the claims 1 to 29, wherein

- the panel further comprises a carrier film having a first side and a second side,

- the adhesive is arranged on a first side of the carrier film, and

- the adhesive or another adhesive is arranged on the second side of the carrier film.

31 . The panel of the claim 30, wherein

- the melting point of the carrier film is higher than the melting point of the adhesive.

32. The panel of any of claim 30 or 31 , wherein

- the carrier film comprises at least one of polypropylene, polyethylene, and polyethylene terephthalate.

33. The panel of any of the claims 30 to 32, wherein

- the carrier film comprises a first carrier layer and a second carrier layer,

- the adhesive is arranged on a first side of the carrier film, on the first carrier layer of the carrier film, and

- other adhesive is arranged on the second side of the carrier film, on the first second layer of the carrier film, wherein the other adhesive is different from the adhesive.

34. The panel of any of the claims 1 to 33, wherein

- the adhesive comprises material that hardens or dries, to attach the support layer to the surface layer.

35. The panel of claim 34, wherein

- the adhesive comprises material that hardens or dries at a temperature from 0 °C to 50 °C; preferably from 10 °C to 30 °C.

36. The panel of claim 34 or 35, wherein

- the adhesive comprises at least one of polyvinyl acetate, ethylene-vinyl acetate, polyurethane, polyurethane hot melt, polypyrroline hot melt, moisture curing polyurethane, epoxy, polyester, acrylate, phenolic, phenol- fornnaldehyde, urea-melamine, melamine fornnaldehyde, resorcinol glue, and silicone.

37. The panel of claim 36, wherein

- the adhesive comprises polyurethane or acrylate.

38. The panel of any of the claims 1 to 37, wherein

- the adhesive or, if present, the adhesive and the carrier film in combination, has a thickness in the first direction, and

- the thickness of the adhesive is from 30 μΐτι to 5 mm; preferably from 30 μΐτι to 2 mm.

39. The panel of any of the claims 1 to 38, wherein

- the adhesive or, if present, the adhesive and the carrier film in combination has a thickness in the first direction,

- the support layer has a thickness in the first direction, and

- the thickness of the adhesive is less than the thickness of the support layer.

40. The panel of any of the claims 1 to 39, wherein

- the surface layer has a thickness in the first direction, and

- the thickness of the adhesive is less than the thickness of the surface layer.

41 . The panel of any of the claims 1 to 40, wherein

- the adhesive comprises thermoplastic material and

- the thermoplastic material has a melting point of at most 200 °C.

42. The panel of any of the claims 1 to 41 , wherein

- the support comprises polymer material having a deflection temperature, and

- the adhesive comprises thermoplastic material having a melting point, wherein

- the melting point of the adhesive is lower than the deflection point of the support layer.

43. The panel of any of the claims 2 to 42, wherein

- the adhesive has a coefficient of thermal expansion, and

- the coefficient of thermal expansion of the adhesive is greater than the second coefficient of thermal expansion.

44. The panel of any of the claims 2 to 43, wherein

- the adhesive has a coefficient of thermal expansion, and

- the coefficient of thermal expansion of the adhesive is less than the third coefficient of thermal expansion.

45. The panel of any of the claims 2 to 44, wherein

- the adhesive has a coefficient of thermal expansion of ka,

- the first coefficient of thermal expansion is k1 ,

- the second coefficient of thermal expansion is k2,

- the third coefficient of thermal expansion is k3,

- the fourth coefficient of thermal expansion is k4, and

- (i) the ratio ka/k1 is from 0.5 to 2,

- (ii) the ratio ka/k2 is from 0.5 to 2,

- (iii) the ratio ka/k3 is from 0.5 to 2, or

- (iv) ratio ka/k4 is from 0.5 to 2.

46. The panel of any of the claims 2 to 45, wherein

- the first coefficient of thermal expansion is at most 60 ppm/K; preferably at most 10 ppm/K at the temperature 25 °C.

47. The panel of any of the claims 2 to 46, wherein

- the ratio of the first coefficient of thermal expansion to the second coefficient of thermal expansion is at most 1 .5; preferably at most 1 .2.

48. The panel of any of the claims 1 to 47, wherein the support layer comprises

- polymer that has a deflection temperature of at most 200 °C, preferably at most 180 °C.

49. The panel of any of the claims 1 to 48, wherein the support layer comprises - polymer that has a deflection temperature of at least 80 °C, preferably at least 120 °C.

50. The panel of any of the claims 1 to 49, wherein the support layer comprises

- thermoplastic polymer that has a melting temperature of at most 200 °C, preferably at most 180 °C; optionally at least 20 °C.

51 . The panel of any of the claims 1 to 50, wherein the support layer comprises

- thermoplastic polymer that has a melting temperature of at least 20 °C, preferably at least 60 °C

52. The panel of any of the claims 1 to 51 , wherein

- the thickness of the support layer is from 3 mm to 20 mm; preferably from 4 mm to 15 mm, and most preferably from 6 mm to 12 mm.

53. The panel of any of the claims 1 or 52, wherein

- the support layer comprises thermoplastic polymer, and

- the thermoplastic polymer is selected from the group comprising at least one of polyurethane, acrylic, polyvinyl alcohol, polyolefin, lignin, polyethylene, polypropylene, and a co-polymer comprising ethylenes and propylenes.

54. The panel of any of the claims 1 to 53, wherein the support layer comprises

- thermoplastic or thermoset polymer and

- additional material.

55. The panel of claim 54, wherein

- the support layer has a thickness in the first direction,

- support layer comprises pieces of additional material wherein

- the dimension is greater than the thickness of the support layer.

56. The panel of claim 54 or 55, wherein

- the additional material comprises material that comprises natural fibres.

57. The panel of any of the claims 54 to 56, wherein

- the additional material comprises wood.

58. The panel of any of the claims 54 to 57, wherein the support layer comprises

- at least a first wooden veneer layer and a second wooden veneer layer, and

- at least part of the second wooden veneer layer is arranged in the first direction from the first wooden veneer layer.

59. The panel of any of the claims 54 to 58, wherein the support layer comprises

- at least a first wooden veneer layer and a second wooden veneer layer, and

60. The panel of claim 58 or 59, wherein

- the thickness of a wooden veneer layer is from 0.5 mm to 5 mm.

61 . The panel of any of the claims 54 to 60, wherein

- the additional material of the support layer comprises synthetic organic or inorganic fibres.

62. The panel of claim 54, wherein

- the additional material comprises at least one of carbon fibres, glass fibres, aramid fibres, polypropylene fibres, polyamide fibres, and polyurethane fibres.

63. The panel of claim 62, wherein

- the fibres form a woven structure such as cloth, textile, or mat.

64. The panel of any of the claims 1 to 63, wherein

- the density of the support layer is at most 1600 kg/m³.

65. The panel of any of the claims 2 to 64, wherein

- the third coefficient of thermal expansion is at least 20 ppm/K; preferably at least 25 ppm/K.

66. The panel of any of the claims 2 to 65, wherein

- the fourth coefficient of thermal expansion is at least 10 ppm/K, preferably a least 12 ppm/K.

67. The panel on any of the claims 2 to 66, wherein

- the ratio of the third coefficient of thermal expansion to the fourth coefficient of thermal expansion is at most 1 .5; preferably at most 1 .2.

68. The panel of any of the claims 1 to 67, wherein

- the panel is brittle in such a way that the impact resistance of the surface of the panel that comprises the surface layer, is at most 200 cm.

69. The panel of any of the claims 1 to 68, wherein

- the panel is brittle in such a way that the impact resistance of the surface layer, when the surface layer has been separated from the adhesive and the support layer, is at most 200 cm.

70. The panel of any of the claims 1 to 69, wherein

- the panel is brittle is such a way that the tensile strain at break of the surface layer is at most 8 % at the temperature 25 °C.

71 . The panel of any of the claims 1 to 70, wherein

- the panel is brittle is such a way that the tensile strain at break of the surface layer, when surface layer has been separated from the adhesive and the support layer, is less than 5 % at the temperature 25 °C.

72. The panel of any of the claims 1 to 71 , wherein

- the surface layer comprises polymer.

73. The panel of claim 72, wherein

- the surface layer further comprises filler material in a matrix, wherein the matrix comprises the polymer of the surface layer.

74. The panel of claim 73, wherein

- the filler material comprises particles or the filler material comprises fibres.

75. The panel of any of the claims 72 to 74, wherein

- the polymer of the surface layer comprises thermoset polymer.

76. The panel of any of the claims 72 to 75, wherein

- the polymer of the surface layer comprises at least one of acrylate, polyester, and epoxy.

77. The panel of any of the claims 72 or 76, wherein

- the polymer of the surface layer comprises polymer having a deflection temperature less than 170 °C.

78. The panel of claim 77, wherein

- the polymer of the surface layer comprises thermoset polymer having the glass transition temperature of at most 200 °C, preferably at most 180 °C.

79. The panel of claim 77 or 78, wherein

- the polymer of the surface layer comprises thermoset polymer having the glass transition temperature of at least 80 °C, preferably at least 90 °C.

80. The panel of any of the claims 72 to 79, wherein

- the polymer of the surface layer comprises thermoplastic polymer.

81 . The panel of any claim 80, wherein

- the polymer of the surface layer comprises thermoplastic polymer having the melting temperature of at most 200 °C, preferably at most 180 °C.

82. The panel of claim 80 or 81 , wherein

- the polymer of the surface layer comprises thermoplastic polymer having the melting temperature of at least 80 °C, preferably at least 90 °C.

83. The panel of any of the claims 72 to 82, wherein

- the polymer of the surface layer comprises at least one of polyurethane, acrylonitrile butadiene styrene (ABS), acrylic (e.g. poly(methyl methacrylate), PMMA), fluoroplastics or fluoropolymers (e.g. polytetrafluoroethylene, PTFE), polyoxymethylene, polycarbonate, polyetheretherketone, cellulose acetate, polystyrene, polyamide-imide, polyphenylene, polyvinyl alcohol, polyolefin, lignin, polyethylene, polypropylene, and a co-polymer comprising ethylenes and propylenes.

84. The panel of any of the claims 1 to 83, wherein

- the surface layer comprises filler particles.

85. The panel of claim 84, wherein

- the surface layer comprises hard filler particles, such as particles comprising rock, clay, brick, ceramic, titanium oxide (T1O2), alumina (AI2O3), and/or aluminium hydroxide (AI(OH)₃).

86. The panel of claim 84 or 85, wherein

- the coefficient of thermal expansion of the filler particles of the surface layer is less than the coefficient of thermal expansion of the polymer of the surface layer.

87. The panel of any of the claims 84 to 86, wherein

- the surface layer comprises at least 50 m-%, preferably at least 65 m-%, and more preferably at least 80 m-%, filler particles.

88. The panel of any of the claims 84 to 87, wherein

- the material of the hard filler particles has the hardness of a least 2.5 on the Mohs Scale of Hardness.

89. The panel of any of the claims 84 to 88, wherein

- the density of the filler particles of the surface layer is at least 1800 kg/m³.

90. The panel of the claim 84, wherein

- the surface layer comprises filler particles, the filler particles comprising multiple smaller fibres, such as natural fibres.

91 . The panel of claim 90, wherein

- the surface layer comprises natural cellulose fibres.

92. The panel of claim 91 , wherein

- the surface layer comprises at least 20 m-%, preferably at least 25 m-%, and more preferably at least 30 m-% filler particles.

93. The panel of claim 91 or 92, wherein

- the surface layer comprises at most 7.5 m-%, preferably at most 5 m-% lignin.

94. The panel of any of the claims 84 to 93, wherein

- the surface layer comprises filler particles, wherein the each filler particle has three dimensions, and

- the surface layer has a thickness T2 in the first direction, wherein

- the ratio T2/Dp is at least 2, preferably at least 3, and more preferably at least 5.

95. The panel of any of the claims 84 to 94, wherein

- the surface layer comprises filler particles, and

- the filler particles have three orthogonal dimensions,

- for at least 75 % of the filler particles, the smallest of the three orthogonal sizes is at most 1 mm, preferably at most 100 μιτι.

96. The panel of any of the claims 1 to 95, wherein

- the thickness of the surface layer is at most 15 mm, preferably at most 9 mm, and more preferably at most 6 mm.

97. The panel of any of the claims 1 to 96, wherein

- the density of the surface layer is from 900 kg/m³ to 1900 kg/m³.

98. The panel of the claim 97, wherein

- the surface layer comprises hard filler particles and

- the density of the surface layer is from 1400 kg/m³ to 1900 kg/m³.

99. The panel of any of the claim 97, wherein

- the surface layer comprises natural cellulose fibres and

- the density of the surface layer is from 900 kg/m³ to 1200 kg/m³.

100. The panel of any of the claims 1 to 99, wherein

- the surface layer has a thickness T2,

- the support layer has a thickness T1 ,

- the ratio T1/T2 is from 1 to 5.

101 . The panel of any of the claims 2 to 100, wherein

- the ratio of the third coefficient of thermal expansion to the first coefficient of thermal expansion is at least 1 .5, preferably at least 2, more preferably at least 3.

102. The panel of any of the claims 2 to 101 , wherein

- the ratio of the first coefficient of thermal expansion to the third coefficient of thermal expansion is at least 1 .5, preferably at least 2, more preferably at least 3.

103. The panel of any of the claims 1 to 102, wherein

- the support layer comprises polymer having a first deflection temperature, and

- the surface layer comprises polymer having a second deflection temperature, wherein

104. The panel of any of the claims 1 to 103, wherein

- the support layer comprises polymer having a deflection temperature, and

- the surface layer comprises thermoplastic polymer having a melting temperature, wherein

- the melting temperature is higher than the deflection temperature.

105. The panel of any of the claim 1 to 104, wherein

- the saturated water content of the support layer is more than the saturated water content of the surface layer.

106. The panel of any of the claims 1 to 105, wherein

- the thickness of the surface layer is less than the thickness of the support layer.

107. The panel of any of the claims 1 to 106, wherein

- the panel has multiple non-meandering lines in a top surface facing away from the support layer, and

- the radius of curvature of all non-meandering lines at least 5 m.

108. The panel of any of the claims 1 to 107, wherein

- the radius of curvature of a non-meandering line is at least 5 m.

109. The panel of the claim 108, wherein

- the panel comprises a top surface facing away from the support layer,

- the top surface has a first non-meandering line, and

- the radius of curvature of the first non-meandering line at most 2.2 m.

1 10. The panel of any of the claim 109, wherein

- the panel comprises a top surface facing away from the support layer,

- the top surface comprises a boundary area,

- the boundary area has a first non-meandering line, and

- the radius of curvature of the first non-meandering line at most 2.2 m.

1 1 1 . The panel of claim 1 10, wherein

- the panel comprises a top surface facing away from the support layer,

- the top surface comprises a central area,

- the central area has multiple non-meandering lines, and

- the radius of curvature of all non-meandering lines of the central area is at least 5 m.

1 12. The panel of claim 109 or 1 10, wherein

- the panel comprises a first side and an opposite second side,

- the panel comprises a top surface facing away from the support layer,

- the top surface comprises a boundary area,

- the boundary area has a first non-meandering line,

- the radius of curvature of the first non-meandering line at most 2.2 m, wherein

- the center of the osculating circle for the radius of curvature of the first non- meandering line is arranged on a first side of the panel, and

- the top surface of the panel comprises a central area,

- the central area has second non-meandering line,

- the second non-meandering line has a radius of curvature,

- the center of the osculating circle for the radius of curvature of the second non-meandering line is arranged on a second side of the panel.

1 13. The panel of the claim 1 12, wherein

- the radius of curvature of the second non-meandering line is more than the radius of curvature of the first non-meandering line.

1 14. The panel of the claim 1 12 or 1 13, wherein

- the radius of curvature of the second non-meandering is less than 5 m, preferably less than 2.2 m, and

- the radius of curvature of the first non-meandering line is less than 2.2 m, preferably less than 1 .5 m.

1 15. The panel of the any of the claims 1 12 to 1 14, wherein

- the support layer is arranged on the first side of the panel and

- the surface layer is arranged on the second side of the panel.

1 16. The panel of any of the claims 1 to 1 15, wherein

- the thickness of the panel is from 6 mm to 50 mm.

1 17. The panel of any of the claims 1 to 1 16, wherein

- the density of the surface layer is greater than the density of the support layer.

1 18. The panel of the claim 1 17, wherein

- the ratio of the density of the surface layer to the density of the support layer is at least 1 .2, preferably at least 1 .5, and more preferably at least 2.

1 19. The panel of any of the claims 1 to 1 18, wherein

- the surface layer is more brittle than the support layer.

120. The panel of any of the claims 1 to 1 19, wherein

- the panel can be separated to a first part and a second part, such that the second part comprises the surface layer, and

- the separated second part is more brittle than the separated first part.

121 . The panel of any of the claims 1 to 120, wherein

- the panel is brittle in such a way that the impact resistance of the surface of the panel that comprises the surface layer, is less than impact resistance of the surface of the panel that comprises the support layer.

122. The panel of any of the claims 1 to 121 , wherein

- the tensile strain at break of the surface layer is less than the tensile strain at break of the support layer.

123. A piece of furniture comprising,

- the panel of any of the claims 1 to 122.

124. A table comprising,

- the panel of any of the claims 1 to 122.

125. A table for use in a kitchen comprising,

- the panel of any of the claims 1 to 122.

126. A working surface comprising,

- the panel of any of the claims 1 to 122.

127. A building comprising,

- a room, such as a kitchen, a toilet, a showering room, or a sauna, the room comprising a water tap, wherein the room further comprises - a piece of furniture comprising the panel of any of the claims 1 to 122, wherein

- the piece of furniture is arranged in the room.

128. A building comprising,

- a working surface comprising the panel of any of the claims 1 to 122, wherein

- the working surface is arranged in the room.

129. A building comprising,

- a floor, wherein the floor comprises the panel of any of the claims 1 to 122.

130. A desk comprising the panel of any of the claims 1 to 122.

131 . A shop fitting comprising the panel of any of the claims 1 to 122.