This invention concerns a decorative panel comprising a decorative layer on the basis of a natural wood layer with a wood structure comprising lighter coloured spring wood and darker coloured summer wood, wherein this decorative layer comprises a first surface on the basis of said wood structure, and comprising a transparent, wear-resistant top layer which substantially covers the first surface of the decorative layer and through which the first surface of the decorative layer is visible, so that this top layer forms a visible side of the decorative panel comprising a first type of segments corresponding to said spring wood and a second type of segments corresponding to said summer wood.

The invention also concerns a method for producing such a panel.

Decorative panels may for example be floor panels, wood panels, furniture panels etc. Wood structures comprising spring wood and summer wood are regarded as attractive by many people. Trees with a wood structure containing spring wood and summer wood develop because the growth of the trees is not constant throughout the year. Under favourable circumstances, namely in the spring, the tree grows quickly and the cells forming in the wood are wide in diameter. This wood forms the spring wood or so-called early wood or early year wood. When the weather is less favourable for growth, namely in the summer, the cells become smaller in diameter. This wood forms the summer wood or the so-called late wood. The lighter coloured part of the wood is the early wood (spring wood) which grows quickly and has broad channels for the sap. The darker coloured part of the wood is the late wood (summer wood), wherein this wood is more rigid because of the thinner channels with thicker cell walls. The porosity of the spring wood is greater than that of the summer wood.

Wood layers in which the wood structure is visible are frequently used in interior decoration. Products with such wood layers are also regarded as high quality products. These wood layers may have different thicknesses. These wood layers may have a thickness of 2.5 mm or more. In the case of floor panels, they are then described as parquet. The wood layers may also be thinner than 2.5 mm and for example have a thickness between for example 0.3 mm and 1.5 mm. These wood layers are known as veneer wood layers or just veneers. In floor panels, they are described as veneer parquet.

Wood layers are obtained with various methods. For thicker wood layers, being wood layers more than 2.5 mm thick, use is made of sawing or cutting methods. Known sawing methods are plain-sawn wood, quartersawn wood and rift cut wood. Veneer wood layers may be obtained for example by cutting. Examples of cutting methods are rotary peeled veneer, quarter slicing, rift cut, plain slicing or flat cut.

Decorative panels comprising wood layers are widely known. WO 2010/122514 describes such panels. In the case of floor panels, these are known as ready-to-lay, prefabricated or composite parquet, or engineered wood parquet, or veneer parquet.

Floor panels with veneer parquet are described for example in US 5,755,068 and normally comprise at least one substrate and a wood veneer less than 2 mm thick glued thereon. Panels with a wood layer of 2.5 millimetres or more may be described as multilayer parquet according to EN 13489 standard, and are not regarded as veneer parquet. For panels for veneer parquet, a wood-based backing layer may also be glued onto the underside of the substrate. The wood layer on the top forms or helps form a decorative layer and is usually made of hardwood.

US 2006/070,325 and US 2005/136,234 describe a method in which a wood top layer of 2 millimetres or more is glued under pressure onto an MDF/HDF substrate, ensuring a degree of impregnation of the applied glue into the wood top layer.

DE 20 2013 012 020 U1 and WO 2015/078434 describe a method in which a wood veneer layer with a thickness between 0.6 mm and 1.2 mm is pressed via a resin intermediate layer onto an MDF/HDF substrate in a hot press. The resin intermediate layer may comprise a thermosetting resin. In order to provide the existing decorative panels with the necessary wear resistance, the necessary water-tightness and/or waterproof properties etc., usually one or more layers are applied on top of the wood layer. Thus for example one or more lacquer layers are applied on top of the wood layer. These lacquer layers provide the necessary wear resistance but also change the appearance. The appearance of a lacquered wood layer is regarded by some people is less aesthetically pleasing. It is also possible to apply one or more layers of oil to the wood layer. This oil penetrates into the wood layer. An oiled floor is regarded as attractive because the wood structure remains clearly visible. An oil however offers less protection than a lacquer. Thus an oiled wood layer is more susceptible to moisture, scratching, dirt and grease than a lacquered wood layer. An oiled wood layer, such as for example oiled parquet or veneer parquet, must usually be re-treated with oil on a regular basis, for example every year.

The present invention primarily concerns an alternative decorative panel comprising a wood layer, wherein the panel has a visible wood structure and wherein, in different embodiments, solutions are offered to the problems of such decorative panels from the prior art.

The invention concerns a decorative panel comprising

• a decorative layer on the basis of a natural wood layer with a wood structure comprising lighter coloured spring wood and darker coloured summer wood, wherein this decorative layer comprises a first surface on the basis of said wood structure,

• a transparent, wear-resistant top layer which substantially covers the first surface of the decorative layer and through which the first surface of the decorative layer is visible, so that this top layer forms a visible side of the decorative panel comprising a first type of segments corresponding to said spring wood and a second type of segments corresponding to said summer wood, wherein the colour contrasts between the first type of segments and the second type of segments correspond to the colour contrasts between the corresponding spring wood and the corresponding summer wood of the natural wood layer. A decorative layer on the basis of a natural wood layer here means a decorative layer comprising a natural wood layer. The feature "a decorative layer on the basis of a natural wood layer with a wood structure comprising lighter coloured spring wood and darker coloured summer wood, wherein this decorative layer comprises a first surface on the basis of said wood structure" may also be described as "a decorative layer comprising a natural wood layer with a wood structure comprising lighter coloured spring wood and darker coloured summer wood, wherein this decorative layer comprises a first surface on the basis of said wood structure".

The visible colour contrasts of the decorative panel here correspond to the colour contrasts of the natural wood layer, whereby the colour contrasts are similar. In other words, the colour contrasts of the decorative panel are of the same order of magnitude as the colour contrasts of the natural wood layer. In natural wood, there has a colour difference between the spring wood and summer wood, but this colour difference is limited. The colour difference expressed in Delta E 2000 is for example less than 3, for example even less than 2. The colour contrast between spring wood and the summer wood in a natural wood layer is then also slight. The visible colour contrasts of the decorative panel here correspond to the colour contrasts of the natural wood layer, whereby these are also slight. The first type of segments or the second type of segments therefore do not stand out as much and hence are not too prominent.

We have found that this is considered aesthetically pleasing, certainly in comparison with treatments in which the spring wood receives a relatively darker colour in comparison with the summer wood, whereby the spring wood stands out greatly. The natural wood layer here refers to the wood layer which is used to form the decorative panel, wherein no layers are yet applied to the wood layer, and/or this wood layer has not undergone any other treatment.

Here, the colour contrasts between the first type of segments and the second type of segments corresponds to the colour contrasts between the corresponding spring wood and the corresponding summer wood of the natural wood layer. This does not exclude that the first type of segments (which correspond to the lighter spring wood) on average have a darker colour than the second type of segments (which correspond to the summer wood). However, the contrast between the first type of segments and the second type of segments corresponds to the contrast between the spring wood and the summer wood, so that the contrast is limited and not considered disruptive. Thus is no undesired dark discolouration of the spring wood. If the visible colours of the decorative panel are different from the colours of the natural wood layer, for example as a result of applying the top layer and/or treating the wood layer, the colour difference between the first type of segments at the corresponding spring wood here corresponds to the colour difference between the second type segments and the corresponding summer wood. The discolouration of the summer wood and the discolouration of the winter wood are thus similar and correspond, whereby the contrast also remains similar.

In existing decorative panels comprising a decorative layer on the basis of a natural wood layer with a wood structure comprising spring wood and summer wood, wherein this decorative layer comprises a first surface on the basis of said wood structure, but wherein these decorative panels are not provided with a wear-resistant top layer, it may occur that the visible colour contrasts on the visible side correspond to the colour contrasts between the corresponding spring wood and the corresponding summer wood of the natural wood layer. This is the case for example in decorative panels comprising a wood layer on which only one or more layers of oil have been applied, such as a UV oil (e.g. an oil mixed with short-chain and long-chain acrylates and a photo-initiator) or a natural hardwood oil (e.g. linseed oil), known as oiled parquet or oiled veneer parquet. The appearance of such oiled parquet or oiled veneer parquet is regarded by many as very attractive, purely because the visible contrast remains limited. A conventional oil layer contributes little to wear resistance, so no wear-resistant top layer can be obtained in this way. In other words, by means of the invention, a decorative panel such as a floor panel is obtained with the necessary wear resistance but for example with the appearance of oiled parquet or oiled veneer parquet. The decorative panel according to the invention thus need not per se have the appearance of a natural wood layer, but the visible colour contrasts of the wood structure must be limited and correspond for example to the visible colour contrasts of oiled parquet or oiled veneer parquet. The first surface of the decorative layer is visible through the top layer. It is possible that on the visible side, the visible colours deviate from the colours of the first surface. The top layer may namely cause a discolouration. It is however also possible that the top layer does not cause any discolouration. This discolouration may also or additionally be caused because the wood layer has undergone treatment prior to application of the top layer, and the decorative layer is thus a treated wood layer.

A wear-resistant layer means the top layer which gives the decorative panel the necessary wear resistance. The wear resistance may be measured for example using the Taber S33 test method. The wear resistance and/or scratch resistance measured using this test method is for example more than 100 rotations, preferably more than 200 rotations, even more preferably more than 300 rotations, and even more than 500 rotations. The wear resistance and/or scratch resistance may also be expressed for example on the basis of 'Deep Scratch'. Here, the Diamond needle DIN 68861-4:2013 test method may be used. For example, preferably, via this test method, a force of more than 3.5 N or even more than 4 N is necessary to be able to apply scratches to the decorative panel in the top layer.

The layer may or may not be a treated wood layer. If the wood layer has undergone no treatment, preferably the natural wood layer forms the decorative layer. The wood layer may also be a treated wood layer, wherein this treated wood layer then forms the decorative layer. A treated wood layer may for example have undergone a sanding or brushing treatment. Also, one or more layers may be applied to the natural layer.

A simple way to establish whether the visible colour contrasts between the first type of segments and the second type of segments correspond to the colour contrasts between the corresponding spring wood and the corresponding summer wood of the natural layer, is to use reference specimens. The reference specimens may for example be wood layers of a same type of wood, wherein these layers have not been treated. These reference specimens then form 'reference specimens type 1'. Also, some reference specimens may be used with wood layers from the same type of wood on which several lacquer layers based on acrylic resin have been applied, and wherein there is a very clear contrast between the strongly, darker discoloured spring wood and the less strongly discoloured summer wood. These reference specimens then form 'reference specimens type 2'. Finally, reference specimens may be used from layers from the same type of tree on which a layer of UV oil has been applied and the appearance of which is regarded by many as attractive. These reference specimens form 'reference specimens type 3'. If the colour contrasts of this decorative panel lie in the range of reference specimens 1 and 3, this means that the visible colour contrasts between the first type of segments and the second type of segments on the visible side correspond to the colour contrasts between the corresponding spring wood and the corresponding summer wood of the natural wood layer. It is very clearly evident with the naked eye whether the colour contrasts correspond to reference specimens type 1 or reference specimens type 3, and thus clearly deviate from reference specimen type 2.

The decorative panel according to the invention, wherein the decorative panel has a top layer with the necessary wear resistance while the colour contrasts between the first type of segments and the second type of segments remain limited and are regarded as attractive, preferably comprises one or more of the following properties, wherein these properties may be combined with one another according to all combinations which are not mutually contradictory:

• the decorative layer comprises a dye and/or pigments applied to the wood layer, selectively or non-selectively on the basis of the wood structure, for example only on the summer wood or on the spring wood;

• the decorative layer comprises a reactive agent applied to the wood layer, selectively or non-selectively on the basis of the wood structure, for example only on the summer wood or on the spring wood, wherein this reactive agent discolours under the influence of the top layer;

• the decorative layer comprises a sealing layer (sealer) which is applied to the wood layer in order to close the wood pores of the wood layer, selectively or non- selectively on the basis of the wood structure, for example only on the summer wood or on the spring wood;

• the decorative layer comprises a pore-opening means applied to the wood layer, selectively or non-selectively on the basis of the wood structure, for example only on the summer wood or on the spring wood; • the top layer comprises one or more lacquer layers; the top layer may comprise at least one lacquer layer which is applied directly onto the first surface, wherein this lacquer layer has no constituents which react with the tannins present in the wood layer so as to cause discolouration;

• the top layer comprises a bottom layer, wherein at most 10% by weight of this bottom layer has penetrated into the decorative layer, preferably at most 5% by weight;

• in order to form the decorative layer, the wood layer has undergone treatment, wherein this treatment has removed the tannins from the wood at least partially and/or changed the chemical structure of at least some of the tannins. Examples of such treatments are exposure to ammonia gas (which for example causes dehydrogenation of tannins) or other gases which are able to bind tannins, or exposure to hydrogen peroxide (which for example causes oxidation of tannins);

• the top layer comprises one or more layers which contain pigments and/or a dye;

• the top layer comprises one or more layers and a print which is applied to one of the above-mentioned layers, wherein this print is applied selectively or non- selectively on the basis of the wood structure, for example only on the summer wood or on the spring wood;

• the decorative layer comprises a mask which is applied selectively on the basis of the wood structure, for example only on the summer wood or the spring wood, wherein, in a specific embodiment, this mask partly forms the first surface of the decorative layer; the mask may comprise a lacquer-repellent agent, an antihardening agent etc.;

• the natural wood layer of the decorative layer is obtained by tangential cutting/ sawing of the wood and the natural wood layer has undergone a sanding or brushing treatment to form the decorative layer. This particular method of sawing/cutting and the sanding/brushing treatment removes a large part of the chemicals which ensure an undesired colour change of the wood. Then one or more layers may or may not be applied onto the brushed/sanded wood layer in order to form the decorative layer; • the decorative layer comprises a sanded/brushed wood layer. The natural wood layer may be subjected to a sanding/brushing treatment during forming of the decorative layer.

In a preferred embodiment, the difference between a first value, being the mean colour difference between the first type of segments and the corresponding spring wood of the natural wood layer, and a second value, being the mean colour difference between the second type of segments and the corresponding summer wood of the natural wood layer, is less than 4, preferably less than 3, preferably at most 2, with the colour difference expressed in Delta E 2000. Here the mean colour difference is used, since the colour of the summer wood is not always the same at every location and since the colour of the spring wood is not always the same at every location. To measure said differences, at specific locations, measurements may be carried out on the present spring wood and summer wood of the original natural wood layer prior to forming the decorative panel with this wood layer, and measurements may then be made on the decorative panel at the corresponding locations so as to obtain a mean colour difference. Preferably, measurements are taken at as many locations as possible so that the first and second values obtained are very accurate. To obtain usable first and second values with which it is measurable and clearly perceptible that the visible colour contrasts between the first type of segments and the second type of segments correspond to the colour contrasts between the corresponding spring wood and the corresponding summer wood of the natural wood layer, for each decorative panel/wood layer, preferably 5 measurement locations are required to obtain the first value and 5 measurement locations to obtain the second value, even more preferably at least 10 measurement locations per value, and most preferably at least 20 per value.

Preferably, in this preferred embodiment, the colour difference between the first type of segments and the corresponding spring wood, and the colour difference between the second type of segments and the corresponding summer wood, are almost the same. This means that the summer wood and the spring wood undergo almost the same discolouration. The difference between said first and second value is then also slight. Preferably, this difference is small, for example less than 2, so that this difference in discolouration is almost imperceptible or not perceptible by the human eye. In concrete terms, this means that the colour changes of the spring wood are almost the same as those of the summer wood, and hence the spring wood does not show any stronger, darker discolouration. The visible contrasts of the decorative panel are then almost not strengthened relative to the original natural wood layer, and are thus regarded as attractive.

A Delta E value, more specifically the Delta E 2000 value calculated using for example the CIELAB system (CIELAB colour space) -CIEDE2000-, indicates the extent of change in visual perception of two given colours. On a typical scale, the Delta E value varies from 0 to 100 with

<= 1.0 not perceptible by human eye

1 - 2 perceptible by close observation

2 - 10 perceptible at a glance

11 - 49 colours appear more similar than contrasting 100 colours are clearly contrasting.

As indicated above, the colour difference between the spring wood and summer wood in a natural wood layer is limited. The mean colour difference between the first type of segments and the second type of segments is thus also limited and for example less than 4 expressed in Delta E 2000, less than 3 and preferably at most 2.

Preferably, the wear-resistant top layer comprises one or more lacquer layers. Lacquer layers are used to protect the wood layer against external influences. These influences may for example be the sun, water, friction from e.g. shoes or feet if the panel is a floor panel etc. A lacquer consists of resin and for example a solvent or thinning agent such as benzene or short-chain acrylates or water. The lacquer may for example be a water-based lacquer, wherein the lacquer then contains a resin and water. This resin may for example be an alkyd resin, a polyurethane resin or an acrylic/acrylate resin. The acrylic resins or acrylate resins may for example be modified with polyurethane and/or polyethylene and/or an epoxy functionality in order to adapt the physical properties of the resin as required. These lacquer layers are hardenable using for example heat, air and/or UV light. The lacquer layers may provide the necessary wear resistance and weather resistance to moisture and grease. The thickness of the one or more lacquer layers is preferably limited in order to keep said colour contrasts approximately the same. Thus it may be decided, for each applied lacquer layer or certain lacquer layers, to apply less than 30 g/m ² lacquer, preferably less than 20 g/m ² , even more preferably less than 10 g/m ² . Preferably, the lacquer layer is a UV-hardened lacquer and/or an acrylic lacquer. This lacquer layer may contain additives. Preferably, the additives are silane-based additives, silicon-acrylates and/or fluoro-acrylates. These additives are particularly effective for creating an easy- care surface and may lead to easier cleaning.

With respect to these one or more lacquer layers, in specific embodiments the decorative panel comprises one or more of the following properties, wherein these properties may be combined with one another according to all combinations which are not mutually contradictory:

• the lacquer layer has a viscosity of at least 100 mPa.s at 20°C and 1.013 bar, preferably at least 120 mPa.s at 20°C and 1.013 bar; a high viscosity prevents too deep a penetration into the decorative layer if the first surface of the decorative layer has a degree of porosity;

• the lacquer layer comprises a resin such as an acrylate resin, an alkyd resin or a polyurethane resin, and also a thinning agent, a solvent or a reactive thinning agent, wherein this solvent or (reactive) thinning agent does not react with tannins;

• the lacquer layer comprises a resin such as an acrylic resin, an alkyd resin or a polyurethane resin, and in some cases also a thinning agent, a solvent, water or a reactive thinning agent, wherein a said thinning agent or solvent contains a carbon chain with a chain length of for example at least 12 carbon atoms, for example at least 16 carbon atoms. The lacquer layer may also comprise short-chain acrylate molecules such as acrylate monomers;

• the lacquer layer contains wear-resistant particles such as corundum;

• the lacquer layer contains pigments, wherein these pigments are for example selectively present on the basis of the wood layer. Thus the pigments may be concentrated mainly in places on the lacquer layer which extend in the spring wood or in the summer wood, for example by applying a lacquer layer with pigments selectively or by applying pigments selectively;

• a said lacquer layer is sanded prior to application of the next lacquer layer.

The top layer may be constructed such that prior treatment of the natural wood layer to form the decorative layer is superfluous, or for example only a sanding/brushing treatment is required. The natural wood layer in itself or the brushed/ sanded wood layer here forms the decorative layer, and the top layer is applied directly to this wood layer. Thus for example, a top layer may be used comprising a lacquer layer which is directly present on/applied to the wood layer, wherein this lacquer layer comprises for example one or more of the following properties: the lacquer layer comprises a component which fixes the tannins and thus counters undesired colour changes caused by the tannins; the components of the lacquer layer do not react with the tannins. The natural wood layer of the decorative layer may be obtained by tangentially cutting/sawing the wood. If this wood layer has also undergone a sanding/brushing treatment to form the decorative layer, then at the level of this first surface of the decorative layer, a large part of chemicals which might cause the undesired colour changes of the wood will already have been removed.

The top layer may also comprise one or more varnish layers. A varnish layer is for example based on a resin, or mixed with an oil or a solvent such as alcohol, wherein this varnish is for example an oxidative hardening coating. Varnish also contributes to the wear resistance of the top layer. The one or more layers may for example also comprise a paint layer. A paint consists of a colouring agent, being a pigment or dye, a binder such as resin or oil, a thinning agent such as water or turpentine.

In a specific embodiment, the top layer comprises one or more layers which almost cover the complete decorative layer, and a print which is applied to one of said one or more layers, wherein this print is preferably applied on the basis of the wood structure, preferably on the basis of the presence of the spring wood and/or the summer wood. The print may be situated above the top layer which covers the complete decorative layer, or the print may extend between two said layers which almost cover the complete decorative layer. It may be chosen to apply the print mainly to the spring wood or to apply the print mainly to the summer wood. These one or more layers may for example be lacquer layers. If one or more lacquer layers are applied on top of the decorative layer, this may cause an undesired discolouration of the summer wood. Thus the spring wood may discolour more strongly than the summer wood, and there is an undesired dark discolouration of the spring wood. With other types of layers too, undesired discolourations may occur. By applying for example a light-coloured and transparent print at the places through which the spring wood is visible, or for example a darker coloured and transparent print at the places through which the summer wood is visible, any undesired discolouration caused by said one or more layers of the top layer may be compensated, and thus the contrast between the first type of segments and the second type of segments limited. This print may be a digital print. The print may then be applied using a camera system which detects the wood structure. For example, first the wood structure of a wood layer may be scanned in and then a specific print may be applied on the basis thereof. The digital print may be water-based. For printing for example, an inkjet printer may be used which is controlled by an electronic processor.

In a preferred embodiment, the decorative layer, at the level of the first surface, comprises one or more treatment layers applied to a surface of the wood layer, wherein this wood layer and the one or more treatment layers form a treated wood layer, wherein this treated wood layer forms the first surface of the decorative layer. This wood layer is here then a natural wood layer or a brushed/sanded layer. By treating the wood layer with one or more treatment layers, the properties of the wood may be changed such that the interaction between the top layer and the decorative layer does not cause any undesired contrast change, and hence the contrast between the first type of segments and the second type of segments remains limited. By treating the wood layer with one or more treatment layers, the properties of the wood may be changed such that any colour changes as a result of the top layer can be compensated.

With respect to these one or more treatment layers, the decorative panel preferably comprises one or more of the following properties, wherein these properties may be combined with one another according to all combinations which are not mutually contradictory: • a said treatment layer comprises and preferably is a primer;

• a said treatment layer comprises and preferably is an oil, a lacquer or a glue;

• a said treatment layer has at least partly or completely penetrated into the wood layer;

• a said treatment layer closes the wood pores present in the wood layer and comprises for example a resin. Thus a UV sealer may be used, which preferably also provides the wear resistance, scratch resistance and robustness;

• a said treatment layer changes the porosity of the wood layer;

• a said treatment layer colours the wood layer;

• a said treatment layer comprises pigments;

• a said treatment layer fixes tannins present in wood layer; these fixed tannins are not or are less able to react with the top layer, whereby undesired colour changes are prevented;

• at least one said wood layer is selectively present on the basis of the wood structure, preferably on the basis of the presence of the spring wood and/or the summer wood.

The wear-resistant top layer may be applied on top of this one or more treatment layers, wherein this wear-resistant top layer for example comprises one or more lacquer layers. For example, first the decorative layer may be formed and then the lacquer layers applied to the decorative layer.

Preferably, a said treatment layer has at least partially penetrated into the wood layer. A wood layer has a degree of porosity. The porosity of the spring wood and of the summer wood differs. Because said treatment layer has at least partially penetrated into the wood layer, it will affect how the spring wood and summer wood, visible through the top layer, are perceived. By working with a said treatment layer which has at least partially penetrated into the wood layer, thus undesired colour changes can be countered and compensated. The treatment layer is applied on top of the wood layer and then partially or even completely penetrates into the wood layer. The percentage of penetration is for example between 20% and 100%. The penetration of the wood layer may be local and extend for example at the level of the said surface of the wood layer on which the treatment layer is applied. The complete wood layer may also be penetrated by the treatment layer. The treatment layer may also penetrate to 10 to 70%, 10 to 50%, 10 to 30% of thickness of the wood layer.

Primers (undercoats) are the first layers, and for example only the first layer, being the base layer. These primers may have different compositions and their purpose is to improve the adhesion and/or interaction between the wood layer and the layers applied on the primer. Primers may for example be a base coat, a powder-coating, a hydro-UV primer (acrylates dissolved in water and containing a photo-initiator), an oil etc.

Further preferably, at least one said treatment layer is selectively present on the basis of the wood structure, preferably on the basis of the presence of the spring wood and/or the summer wood. A said treatment layer is here thus selectively applied on the basis of the wood structure. Here for example it may be decided to treat the summer wood and spring wood differently. Or it may be decided that the treatment layer is present almost only on the summer wood. It may also be decided that the treatment layer is present almost only on the spring wood. It may also be decided to apply more of said treatment layer on the summer wood or spring wood, so that the quantity of treatment layer applied is a function of the type of wood. Selective application may take place using a camera system. This is known for example as target covering. Selective application may also take place in other ways. Thus for example glue may be applied only e.g. to certain places, and thus selectively applied, after which particles, for example in powder form and for example pigments, are applied which only adhere to the glue. Then particles may be removed again, for example with a secondary treatment step such as brushing, suction etc., at the places where particles are not glued. The result is a treatment layer comprising glue and particles present at said specific places. But also, for example, firstly the wood layer may be brushed/sanded and hence the less dense spring wood partly brushed/sanded away. By for example applying a said treatment layer with a hard roller, this is only applied to the summer wood. Also, the wood layer may first be treated with a treatment layer and then the wood layer brushed/sanded and the less dense spring wood partly brushed/ sanded away. The treatment layer is then only present at the places not brushed away. The one or more treatment layers may for example comprise at least two primers, wherein a first primer is applied over the complete surface of the wood layer and a second said primer is applied selectively, mainly on the summer wood or spring wood. However it may also be decided to first apply a primer mainly to the summer wood or spring wood, and then apply a primer over the complete surface.

A said treatment layer may be able to change the density of the wood. The porosity of the spring wood is greater than that of the summer wood. This difference in porosity explains why spring wood and summer wood react differently with the top layer and undesired discolourations occur. By changing the density of the wood by means of a said treatment layer, e.g. by lowering the density of the summer wood and/or increasing the density of the spring wood, it can be ensured that the spring wood and summer wood interact in approximately the same way with the top layer.

By means of selective application, it may also be decided to paint or colour only the summer wood or only the winter wood.

In a particular embodiment, at least one said treatment layer lowers the density of the summer wood of the wood layer and/or at least one said treatment layer increases the density of the spring wood of the wood layer. Since the top layer is applied on the decorative layer, the interactions of the summer wood and spring wood with the top layer are more similar because the density difference between the spring wood and summer wood is reduced or even eliminated. The result is more corresponding colour contrasts. This treatment layer may be applied selectively on the basis of the wood structure so that this treatment layer is applied for example mainly, and preferably only, on the spring wood or summer wood.

In a specific embodiment, a said treatment layer modifies the chemical composition of the summer wood and/or spring wood of the wood layer.

In a specific embodiment, at least one said treatment layer changes the colour of the summer wood and/or the spring wood, wherein preferably the colour change of the summer wood differs from the colour change of the spring wood. The colour change may differ because this treatment layer is applied e.g. only to the summer wood or the spring wood. The colour change may also differ because the summer wood and spring wood react differently to the treatment layer. This treatment layer may be obtained by staining (wood stain), by application of a paint layer, application of a varnish or by other means of colouring. Thus e.g. the spring wood may be coloured with a lighter colour such as white tints or beige tints. If the top layer then causes a stronger discolouration of the summer wood in comparison with the spring wood, said treatment layer compensates for this, so that a visible side is obtained with the desired colour contrasts.

In a particular embodiment, a said treatment layer, at the level of the first surface, at least partially covers some of the pores of the wood layer. Where the pores are closed, the top layer applied to the decorative layer cannot penetrate into these pores, whereby the result is a decorative panel in which the top layer is not present in these pores. The top layer can then also not cause undesired colour changes at these pores. By partly closing the pores, the penetration of the top layer is prevented and hence limited. Here for example it may be decided to apply this treatment layer only on the spring wood, since spring wood is more susceptible to undesired discolouration. Also however, this treatment layer may be applied to the complete wood layer to ensure that all pores are at least partially closed, preferably completely closed.

Preferably, a said treatment layer comprises a dye and/or a pigment and/or a lacquerrepellent agent and/or an anti-hardening agent and/or a paint-repellent agent and/or a bleach and/or wear-resistant particles. A bleach may be used to remove the tannins from the wood layer. Examples of usable bleaches are hydrogen peroxide, ammonia, salt, alkali and oxalic acid, potassium chloride, sodium hypochlorite and chlorine dioxide. By means of a lacquer-repellent agent, it may be ensured that a lacquer layer applied on top of the treatment layer to form the top layer is at least partially repelled. By means of an anti-hardening agent, it may be ensured that a lacquer layer applied on top of the treatment layer to form the top layer does not harden everywhere. Thus for example, lacquer repellent agent or an anti-hardening agent may be applied only to the summer wood or the spring wood. The lacquer which is repelled or not hardened can then be removed by means of a technique such as brushing. This may ensure that not all lacquer layers applied are present for example at the spring wood or for example at the summer wood, and thus undesired colour changes may be prevented or limited.

The wood layer may optionally be a brushed wood layer and/or a sanded wood layer. Thus the wood layer has for example undergone a brushing treatment and/or a sanding treatment. This brushing treatment and/or sanding treatment may be used for selective application of said one or more treatment layers. Thus by means of brushing treatment and/or sanding treatment, part of an applied treatment layer may be removed again, or before applying a said treatment layer, a brushing treatment and/or a sanding treatment may be carried out to ensure that the treatment layer is not applied (equally) everywhere. Brushing may also be carried out if a decorative panel is desired with the appearance of a brushed wood layer.

In a preferred embodiment, the decorative panel comprises a substrate, wherein the decorative layer is applied directly or indirectly to the substrate. By means of a substrate, a rigid panel is obtained which is suitable for example for a floor, wall or furniture. Thus the decorative panel may be a floor panel. The substrate comprises for example a woodbased panel, such as an MDF panel, an HDF panel, a plywood panel etc. The substrate may also comprise one or more wood layers. The substrate may or may not affect the visible side of the decorative panel. Thus the substrate may be almost invisible through the wood layer and/or not penetrate or insufficiently penetrate into the wood layer, so that the substrate has no influence on the definitive appearance of the panel at the visible side. The substrate may also have a bottom counter-layer, such as for example a veneer layer.

The substrate may be at least partially visible through the wood layer, and/or the substrate may partially penetrate into the wood layer, and/or the binder used to apply the decorative layer on the substrate may partly penetrate into the wood layer, such that the visible colour contrasts of the decorative panel are influenced. If the substrate is at least partially visible through the wood layer, the colour of the substrate at the wood layer may influence the definitive appearance of the visible side of the decorative panel. The panel may comprise at least one intermediate layer applied to the substrate, wherein this intermediate layer has at least partially penetrated into said wood layer. If the intermediate layer has penetrated over almost the complete thickness of the wood layer, it may influence the first surface of the decorative panel. This may be important in particular for thin wood layers such as veneers, since the thickness of veneers is small, for example veneers with a thickness of maximum 1 mm, preferably maximum 0.6 mm, even more preferably maximum 0.3 mm. This intermediate layer may for example be a glue layer comprising for example a cold-hardening resin, a thermosetting resin such as melamine formaldehyde, urea formaldehyde, an isocyanate glue or a polyurethane glue. This intermediate layer may have an influence on the colour contrasts between the first type of segments and the second type of segments. For this, the intermediate layer may be applied to the substrate on the basis of the wood structure, for example on the basis of the presence of the spring wood and/or the summer wood. Thus this intermediate layer may for example be applied only at the level of the spring wood or the summer wood. This intermediate layer may for example penetrate over the entire thickness of the wood layer and thus have an influence on the first surface of the decorative panel.

The invention also concerns a method for producing a decorative panel, wherein a natural wood layer with a wood structure comprising lighter coloured spring wood and darker coloured summer wood is provided, wherein this wood layer is treated or not treated and thus forms a decorative layer, and wherein a transparent wear-resistant top layer is applied on top of the decorative layer to form a visible side of the decorative panel through which a first surface of the decorative layer is visible, wherein the visible colour contrasts in the visible side correspond to the corresponding colour contrasts of the natural wood layer. By means of this method, a decorative panel can be produced according to the invention as described above. The advantages and all said embodiments, including the preferred, specific and particular embodiments as described above, are also applicable to this method.

Preferably, the top layer comprises one or more lacquer layers, and these one or more lacquer layers are applied to the first surface of the decorative layer. This may be achieved by a continuous process or a discontinuous process. Preferably, said one or more lacquer layers, if there are two or more lacquer layers, are applied successively and one on top of the other, wherein these lacquer layers are at least partially or completely hardened prior to application of the following lacquer layer. A sanding treatment may also take place between application of certain lacquer layers.

Further preferably, the top layer comprises a print, wherein this print is applied to one of said one or more lacquer layers, wherein this print is preferably applied on the basis of the wood structure, preferably on the basis of the presence of the spring wood and/or the summer wood. For this, for example, target covering may be used. Thus camera systems or other detection systems may be used to determine the location of the spring wood and/or summer wood. On the basis of these data, the print can then be applied at the desired location.

Preferably, one or more treatment layers are applied to the natural wood layer in order to form the decorative layer.

Further preferably, at least one said treatment layer is selectively applied on the basis of the wood structure, preferably on the basis of the presence of the spring wood and/or the summer wood. The selective application of the treatment layer may take place for example according to one or more of the methods described below if these are not mutually contradictory:

- the provision of a camera system with one or more detection means for scanning the top side of the wood layer and/or detecting the summer wood and/or the spring wood, wherein the treatment layer is applied to the wood layer on the basis of what has been scanned or detected;

- brushing or sanding the wood layer prior to application of said treatment layer, after which the treatment layer is applied by means of a hard roller. A hard roller does not follow any notches, cavities etc. in the surface of the wood layer. During brushing, softer parts, e.g. the softer spring wood, are brushed out of the wood layer at the level of the surface. In this way, only the summer wood is treated. - application of said treatment layer over the complete surface of the wood layer, after which the treated wood layer is brushed or sanded so that certain parts, such as softer parts, are brushed away and the treatment layer is thus not present at the brushed parts;

- application of a glue by means of target covering, for example only on the summer wood or only on the winter wood, after which particles such as pigments or wear-resistant particles are scattered on the wood layer so that these particles only adhere to the glue, after which the other particles, which have not settled on the glue, are removed for example by suction or brushing. Thus for example, the wood layer may then be stained in order to brush away the wood layer afterwards and thus remove part of the wood layer so as to remove staining agent locally.

In a preferred embodiment, a substrate is provided and the decorative layer applied on top of the substrate.

Specifically, for the latter preferred embodiment and prior to application of the decorative layer on the substrate, an intermediate layer is applied to the substrate, and the decorative layer is attached to the substrate at the level of this intermediate layer.

According to an alternative embodiment, the feature "the colour contrasts between the first type of segments and the second type of segments correspond to the colour contrasts between the corresponding spring wood and the corresponding summer wood of the natural wood layer" is optional in both the decorative panel and the method for forming this panel. Thus the above-mentioned features, techniques, methods, embodiments, structure of the panel etc. may also be present in a decorative panel or used to form a decorative panel, wherein there is a relatively great contrast between the first type of segments and the second type of segments.

In order to present the features of the invention better, some preferred embodiments are described below purely as an example with no restrictive character, with reference to the appended drawings in which: - figure 1 shows a perspective illustration of a decorative floor panel according to the invention;

- figure 2 shows a top view of the detail indicated as F2 in figure 1, of the decorative panel according to the invention, wherein the visible wood structure is depicted schematically and wherein a measurement point at the first type of segment and a measurement point at a second type of segment are shown;

- figure 3 shows a top view of a detail of a parquet floor panel which does not form part of the invention, wherein this panel has undergone a conventional lacquer treatment and wherein this panel comprises a natural wood layer with a wood structure, wherein this wood structure is illustrated schematically, and this schematic wood structure corresponds to the schematic wood structure in figure 2, and wherein a measurement point at the level of the first type of segment and a measurement point at the level of the second type of segment are shown;

- figure 4 shows a top view of a detail of a parquet floor panel which does not form part of the invention, wherein this panel has undergone a conventional oil treatment and wherein this panel comprises a natural wood layer with a wood structure, wherein this wood structure is illustrated schematically, and this schematic wood structure corresponds to the schematic wood structure in figure 2, and wherein a measurement point at the level of the first type of segment and a measurement point at the level of the second type of segment are shown;

- figure 5 is a schematic illustration of a cross-section of a decorative floor panel according to the invention, wherein the wood layer is a veneer;

- figure 6 is a schematic illustration of the cross-section of a decorative floor panel according to the invention, wherein the wood layer is thicker than 2.5 mm.

Figure 1 shows a perspective illustration of a decorative floor panel (1). This panel (1) comprises, from top to bottom: a top layer (3), a decorative layer (2) and a substrate (6). The decorative layer (2) comprises a natural wood layer, wherein this natural wood layer is treated or not treated to form the decorative layer (2). This natural wood layer has a wood structure comprising lighter coloured spring wood and darker coloured summer wood. If the wood layer is thicker than 2.5 mm, it is described as parquet; if the wood layer is thinner than 2.5 mm, it is described as veneer parquet. Figure 5 indicates schematically the cross-section of the floor panel (1) as shown in figure 1 (cross-section VV), in the case of veneer. Figure 6 indicates schematically the cross-section of a floor panel (1) as shown in figure 1 (cross-section VV) in the case of parquet.

This top layer (3) is here shown in one piece, but may consist of one or more layers, which may or may not be visible as separate layers in a cross-section. Thus this top layer (3) may consist for example of 2, 3, 4, 5, 6, 7, 8 or more lacquer layers and/or paint layers and/or varnish layers. The top layer (3) is a wear-resistant top layer (3) with a wear resistance which is greater than 200 rotations when measured using the Taber S33 test method, and which is greater than 3.5 N when measured using ‘Deep Scratch’ with the Diamond needle DIN 68861-4:2013 test method. The top layer (3) is transparent and covers the first surface of the decorative layer (2). The first surface is thus visible through the top layer (3), so that this top layer (3) forms a visible side of the panel (1) comprising a first type of segments (4) corresponding to said spring wood and a second type of segments (5) corresponding to said summer wood.

The decorative layer (2) may be an untreated natural wood layer or a treated wood layer, comprising a natural wood layer on which none, one or more treatment layers have been applied to the wood layer and/or which has undergone one or more other treatment steps such as brushing, sanding, exposure to a gas etc.

The substrate (6) may be integral and for example comprise a wood-based panel such as an MDF panel, and HDF panel or a plywood panel. The substrate (6) may also comprise several layers and for example comprise a wood-based panel and underneath a veneer of lower quality, such as for example spruce veneer.

The unique feature of the panel (1) according to the invention is that the colour contrasts between the first type of segments (4) and a second type of segments (5) correspond to the colour contrasts between the corresponding spring wood and the corresponding summer wood of the natural wood layer, while providing the necessary wear resistance. Two possible ways of checking whether said colour contrasts in fact correspond are described below.

A first way is to use reference specimens. By means of these reference specimens, it is possible to check visually, e.g. with the naked eye, whether the colour contrasts correspond. Preferably, three types of reference specimen are used: first type: untreated wood layer, i.e. a natural wood layer (not shown here) second type: a wood layer which has been given a conventional lacquer treatment, or a 'lacquered wood layer' (see figure 3)

- third type: a wood layer which has been given a conventional oil treatment, or an 'oiled wood layer' (see figure 4).

The panel (1) according to the invention is compared with these three types of reference specimen. As visible in figures 2 and 3, the colour contrasts of the panel (1) according to the invention deviate greatly from the colour contrasts of the lacquered wood layer shown in figure 3. These visible colour contrasts of the lacquered wood layer differ greatly from the colour contrasts of natural wood. As visible in figures 2 and 4, the colour contrasts of the panel (1) according to the invention greatly resemble the colour contrasts of the oiled wood layer shown in figure 4. These visible colour contrasts of the oiled wood layer correspond to the colour contrasts of natural wood. To establish whether a floor panel (1) has colour contrasts which correspond to the colour contrasts of natural wood, this floor panel (1) can simply be compared with the three types of reference specimen. If the colour contrasts are similar to those of reference specimens 1 and 3, they in fact correspond to those of natural wood; if however they are closer to those of the second type of reference specimen, the colour contrasts do not correspond to those of natural wood.

It is very clearly visible with the naked eye whether the colour contrasts correspond to the first type or third type of reference specimens, and thus clearly deviate from the second type of reference specimen.

Corresponding colour contrasts are also measurable. Thus firstly measurements can be carried out on the natural wood layer, prior to use of this wood layer to form the decorative panel (1). At various locations, being a number of locations in the summer wood and a number of locations in the spring wood, colour measurements may be made. After the decorative panel (1) has been formed, colour measurements may also be made at locations which correspond to said different locations. On the basis thereof, the difference can be determined between a first value, being the mean colour difference between the first type of segments (4) and the corresponding spring wood of the natural wood layer, and a second value, being the mean colour difference between the second type of segments (5) and the corresponding summer wood of the natural wood layer. This value should be lower than 4 with the colour difference expressed in Delta E 2000, in the case of corresponding colour contrasts. Here a mean colour difference is used, since the colour of the summer wood is not always the same at every place and since the colour of the spring wood is not always the same at every place.