The present invention relates to surface treatment and printing on machined fiber boards. The surface treatment includes applying a layer of primer for

writing/printing onto such a fiber board before the primer is fully cured. This leads to a reduced consumption of printer ink, a more correct color rendition, improved curing, or reduced curing time with associated lower power consumption. The surface treatment results in a substantially equal surface finish on both the machined and non-machined areas of the fiber boards. Herein, both a system for surface treatment of fiber boards and a method for treatment of the fiber boards are described.

Fiber boards of the above type are typically used on internal building walls, and are delivered fully surface treated from the manufacturer so that the installation process is complete immediately after installation. The invention is also applicable for ceiling boards. In this manner, filling and painting can be avoided during installation of indoor wall and ceiling boards. This makes the surface-treated fiber boards extremely economical to use while at the same time a uniform and predictable surface quality is obtained.

Further, the printing process according to the invention allows full freedom to depict textures or pictures with no restrictions on dimensions or what is depicted. Typical examples of texture prints may include concrete texture, wooden texture, metal surface, rust texture, etc. There are no restrictions on what is printed besides the restrictions imposed by a printer.

The boards may be milled so as to have a surface that resembles painted wooden panel with different profiles and patterns, yielding a finished surface that is considered appealing. Generally, the machining is performed using a CNC controlled mill which allows great freedom in the choice of profile, or using special- purpose mills adapted for a particular texture. The milling may include milling of tongue and groove joints along the fiber board edges so that a number of boards can be joined together with no need for finishing the joint through filling and paining, for example, and doesn't need to include milling of the main surface, so that when several fiber boards are put together, the surface can be level.

As used herein, the term fiber board is intended to include chipboard, medium- density fiber board (MDF), high-density fiber board (HDF) and other types of fiber boards used in buildings, in particular indoors.

Further, in the surface treatment of machined fiber boards, it is a problem that the machined areas absorb primer differently than the non-machined areas. Often, the machined areas have a slightly rougher surface than the non-machined areas. The machined areas, therefore, will absorb or require more primer than the areas that have not been machined. At the same time, it is undesirable to apply more primer than necessary, particularly due to cost considerations.

Applying excessive amounts of primer is uneconomical because an unnecessarily large volume of primer is consumed and because it results in an unnecessarily large energy consumption for curing while at the same time the time required for curing the primer becomes unnecessarily long. A thin layer of UV-curable primer or ink, however, causes problems with the curing, and thin layers of primer or ink require more energy than layers of proper thickness.

In other words, it is a problem that thin layers of UV-curable materials such as primer or ink are unable to cure, or cure more slowly if the layer is too thin. In this case, the primer / ink layer is too thin to cure adequately by itself. Printing onto an uncured primer or partially cured primer results in a combined layer of primer and ink that is sufficiently thick to ensure a proper curing process. As an alternative, more ink could have been used in the printing process, but this is problematic for print-technical reasons and is unnecessarily expensive because printer ink is more expensive than primer. Hence, it is advantageous to print onto a thin layer of uncured primer. Printing onto a cured surface leads to increased problems with ink overflow and thus makes it difficult to obtain a sharp or well-defined print. It has been found that the transfer of ink from the printer to the board becomes significantly better and more accurate when printing onto uncured or partially cured ink. Any larger amounts of ink necessary to achieve a proper curing also increase the ink overflow problem. Printing onto uncured or partially cured primer and the ink overflow problem reduces this problem significantly. It has also been found that the accuracy of the ink drops during the transfer of ink from the printer to the board is improved when printing on uncured or partially cured ink. The above applies to an ink-jet printer.

The primer layer may form a base for the application of graphics or printing, and is well suited for printing using a suitable ink-jet printer or printing machine connected to a unit for entering and processing graphics files. In the application of such printing, it is important that the surface onto which the printing is applied has a uniform roughness or surface finish to obtain a neat result without, for example, light being reflected differently from machined and non-machined areas. When using UV-curable ink, however, it is difficult to get the ink to cure if the ink layer is too thin. However, applying an ink layer that is sufficiently thick to ensure a proper curing is expensive and causes other problems with respect to overflow between the ink colors, with respect to proper chroma, etc. Hence, it is also an object of the invention to provide a process in which the amount of ink used is not dictated by the need for obtaining a sufficient thickness to ensure a proper curing process.

The graphics may be provided with a protective layer of transparent lacquer which is commonly cured by way of ultraviolet light. The transparent lacquer should be over-paintable so that the surface can be treated subsequent to installation of the board should it, for example, be desired to change a print to a uniform color.

The present invention relates to a method for surface treatment of a machined fiber board having a non-machined main surface and machined sections with pores or rough surfaces. The method includes at least one first step of applying at least one layer of a UV-curable primer of a type that must be subject to at least one dedicated curing step in order to cure. The invention further includes at least one step of applying a separate layer of UV-curable primer and printing a decoration with a UV-curable printer ink onto the primed surface using an ink-jet printing unit. The layer of UV-curable primer is at least partially uncured during said printing with a UV-curable printer ink. The UV-curable primer and UV-curable printer ink is then cured in a UV curing unit through irradiation with ultraviolet light in a curing step common for the UV-curable primer and UV-curable printer ink.

The method including at least a first step of applying at least one layer of a primer of a type that must be subject to at least one dedicated curing step in order to cure may further include at least one step of removing an excess amount of primer from at least the main surface using at least one roller. The primer is then cured in a curing unit.

The excess primer removed from at least the main surface using at least one roller may be supplied to a step of applying a primer layer.

Applying at least one layer of primer may include spraying the primer onto the fiber board.

Applying at least one layer of primer may include applying primer mist in a low pressure chamber.

The step of applying at least one layer of primer may include applying the primer using a roller.

The primer may be a UV-curable primer, and curing the primer in a curing unit may then include irradiation with ultraviolet (UV) light.

The method may further include a step of printing a decoration of printer ink onto the primed surface using an ink-jet printing unit. The step of printing onto the primed surface using an ink-jet printing unit may include printing the printer ink onto a thin layer of at least partially uncured primer applied onto the at least one layer of cured primer.

Applying the thin layer of at least partially uncured primer may include applying primer in a priming unit and removing excess primer in a roller unit.

The primer onto which printer ink is applied may be a clear primer.

The printer ink may be cured in a dedicated curing step. Alternatively, both the printer ink and uncured primer layer may be cured in a common curing step.

The printer ink could be UV-curable ink.

The method may further include applying a layer of transparent lacquer, of a type that must be subject to at least one dedicated curing step in order to cure, onto the surface of printer ink, using a lacquer unit, and an excess amount of lacquer can be removed from at least the main surface using at least one roller. The lacquer is then cured in a curing unit.

Typically, the lacquer is also a UV-curable primer, in which case curing the lacquer in a curing unit includes irradiation with ultraviolet light.

The invention further includes a method for manufacturing wall or ceiling boards. The method includes providing a fiber board and machining at least joint sections along the fiber board edges. The joint sections may include a groove and tongue arrangement. A layer of UV-curable primer is then applied in an amount exceeding the amount necessary to fill pores formed in the machining. The UV-curable primer layer is then cured through irradiation with ultraviolet light, and a separate layer of UV-curable primer is applied onto the at least one cured primer layer. A decoration of UV-curable printer ink is printed onto the separate UV-curable primer layer, with the separate UV-curable primer layer being uncured or only partially uncured. The UV-curable printer ink and the separate uncured primer layer are then cured in a common curing step. The method may further include that the groove and tongue joints are machined along the edges of the fiber board, that recesses are machined into the fiber board surfaces, and that an excessive amount of the primer layer applied in an amount exceeding the amount necessary to fill pores formed in the machining is removed using at least one roller and returned to a primer applicator unit.

The invention also includes a system for surface treatment of machined fiber boards. The system includes a first priming unit for applying a primer onto the fiber boards, a first firm roller for removing a portion of the primer, a first curing unit, a first grinding unit, a second priming unit, a second hard roller for removing a portion of the primer, and a second curing unit.

The system may further include a third priming unit, a first soft roller for removing a portion of the primer, a third curing unit, a second grinding unit, a second soft roller for removing a portion of the primer, an ink-jet printer, a fourth curing unit, a lacquer unit, and a fifth curing unit. Also described is a third soft roller for applying transparent lacquer as well as a sixth curing unit.

Brief description of the accompanying drawings

Fig 1 is a principle sketch showing an embodiment of a system according to the invention;

Fig. 2 shows a cross-section of a fiber board that may be treated in accordance with the invention;

Fig. 3 is a schematic representation of a fiber board treated in accordance with the invention, wherein different layers are shown;

Fig. 3a is a schematic representation of a fiber board treated in accordance with a second embodiment of the invention, wherein different layers are shown;

Fig. 4 is a principle sketch showing another embodiment of a system or production line according to the invention;

Fig. 4b is a principle sketch showing still another embodiment of a system or production line in its simplest embodiment in accordance with the invention, ;

Fig. 5 is a principle sketch of a unit for applying agents; and

Fig. 6 is a principle sketch of a unit for applying and removing agents. Detailed description of embodiments of the invention with reference to the accompanying drawings

Fig. 1 shows a system or production line according to the invention that may be used in a surface treatment method according to the invention. In Fig. 1 can be seen a fiber board 1 having machined grooves or sections 2 so that the board resembles a wall panel of profiled plank. After the board 1 has been grinded / brushed to remove irregularities, etc. from the machining process and dust and other foreign matter has been removed, the board enters into a priming unit 3 for applying UV-curable primer in an amount larger than the amount desired on the final primed board. Put in another way, the primer layer applied is thicker than the thickness of primer desired on the end product. The primer is typically applied in an amount of 20 -100 g/m ² , preferably 40 - 80 g/m ² .

Priming unit 3 may be a spray painting unit or a vacuum/mist unit for applying the primer. Alternatively, the unit could use a bath, paint rollers, or other means of application. It must be possible to apply the primer in the amounts indicated above.

Following primer application the board 1 proceeds to a roller unit 4 for removing excess primer. The roller unit includes a rigid roller that removes primer from the board, but in such a manner that the primer still remains in the machined sections, typically in an amount of 40-80 g/m ² .

Roller unit 4 includes rollers 5. Typically, two rollers are provided which rotate against each other to collect excess primer. The surfaces of the rollers are smooth and firm so that the removal action in sections 2 is less than on the surface between sections 2. Excess primer is collected by a unit extending along the length of the rollers and stored in a separate container or directly returned to priming unit 3 via a tube 6. Such recycling results in a significant cost reduction as a very small amount of primer is wasted. Following the removal of primer from the top surface, the primer layer is cured by way of UV rays in a curing unit 7. Generally, curing unit 7 will be a unit which illuminates the primer with high intensity ultraviolet light if UV-curable primer is used.

Fig. 2 shows a machined fiber board 1 having machined grooves 2 which may be surface-treated using a system and method according to the present invention. In Fig. 2 it can be clearly seen how machined sections 2 are recessed from the main surface so that the roller removes less primer therefrom than from the main surface. Also, board 1 is shown provided with a tongue 9 and groove 8 joint.

In the following description, reference numbers 1 , 2, 20, 30a, 30b, 30c, 31 , 32a, and 32b refer to Fig. 3, which is a schematic representation of a fiber board treated in accordance with the invention wherein different layers appear. The remaining reference numbers refer to Fig. 4, which is a principle sketch showing an embodiment of a system or production line according to the invention in which the units for performing the different processes appears. Fiber board 1 comprises milled sections 2 or grooves and a non-machined main surface 20.

The grooves or milled sections 2 can be tongue and groove sections along the edges for being joined with similar laterally positioned boards, or typical decorations in the main surface itself.

Fig. 3a shows the simplest embodiment of the invention in which a fiber board 1 having machined sections 2 and a main surface 20 onto which a first layer of primer 30a, a second layer of primer 30d, and a layer of printing ink 31 has been applied. The second primer layer 30d remains uncured, semi-cured, or is only partially cured before printing ink layer 31 is applied. Preferably, printing ink 31 is printed onto an uncured layer of clear primer 30d.

In the following description, reference numbers 1 , 2, 20, 30a, 30b, 30c, 31 , 32a, and 32b refer to Fig. 3, which is a schematic representation of a fiber board treated in accordance with the invention wherein different layers appear. The remaining reference numbers refer to Fig. 4, which is a principle sketch showing an embodiment of a system or production line according to the invention in which the units for performing the different processes appear.

Fig. 4 shows a first unit, the principle of which appears in Fig. 6. Unit 40 performs steps A, B and includes three rollers (Fig. 6), of which the first two rollers 10, 1 1 (as seen in a direction of movement of a board to be treated from the left to the right in Figs. 4 and 6) applies a primer layer, in step A. The first one, 1 1 , of these two rollers adds primer onto the board to be surface-treated, and the second roller 10 provides for applying an appropriate amount of primer and for spreading primer onto the first roller 1 1 that applies the primer onto the board. The first roller 1 1 is soft so as to apply primer onto the entire surface, including within the grooves. A third roller 12 in unit 40 removes excess primer from the board in step B so that only one layer of primer 30a remains in the sections (sections 2, Fig. 2) of the board because these sections are recessed from the main/top surface of board 1 . The third roller 12 of step B is firm, so as to not remove primer from the grooves.

This is advantageous because the machining of sections 2 causes sections 2 to have a rougher surface than the main surface of board 1 (Fig. 2). Additionally, fibers of the board tend to stand up, resulting in an even rougher surface in sections 2. This is the reason why more primer is needed within the grooves. Steel wipers 13, 14 wipe the primer off of roller 12 (Fig. 6).

The surface is then semi/partially cured in a step C in a curing unit 41 for curing the primer. Curing unit 41 is a unit that subjects the primer to UV rays. In this connection, semi curing means that the primer is only partially cured.

The surface is then grinded in a grinding unit 42 polishing the surface in a step D.

The surface is then primed again in a step E by a primer and removal unit 43 which then removes some of the primer in a step F. Unit 43 is shown

schematically in Fig. 6. In step F, a firm roller is used that leaves more primer in the machined sections than on the main surface (20) (Figs. 3, 3a) between machined sections 2. Units 40 and 43 may be similar and hence the board could simply be run twice through the same unit. This, however, is not efficient in a production line. The process leaves a layer 30b.

The primer is then semi cured once again in a new curing unit 44 in a curing step G. Again, this process could have been carried out in curing unit 41 , but again this would be less efficient.

Another layer of primer is then applied by a priming unit 45 in a step H using a priming unit similar to the unit shown in Fig. 5. Priming unit 45 includes a soft roller adding a thin layer of primer 30c onto the entire surface.

Once again the primer is semi cured by a curing unit 46 in a step I. Curing unit 46, like the other curing units, is a unit that effects the curing by way of UV rays.

The surface is polished or grinded by a grinding unit 47 in a step J. This grinding is also considered an intermediate grinding.

Typically, the primer layers of the previous steps comprise white primer.

Another thin primer layer 30d is applied onto the entire surface by a soft roller priming unit 48 in step K. This primer layer is a clear primer. This layer is intended to be fused with ink in a subsequent printing / writing step.

This layer can be applied in an amount of 2-12g/m ² , preferably 3-6 g/m ² .

The entire surface is printed with a desired image or pattern in a printer unit 49 in a printing step L forming an ink layer 31 .

Alternatively, increasing the time spent in a UV curing unit would help completing the curing of the ink, but this makes the process slower and more energy- intensive. The primer layers and ink layer 31 are then fully cured in a curing unit 50 in a step M. Curing unit 50 is also a unit that irradiates the board with UV rays.

A layer of transparent lacquer 32a is then applied onto the entire surface by a lacquer unit 51 in a step N. Lacquer unit 51 may be of the same type as the priming units.

The transparent lacquer is then semi cured in another curing unit 52 in a step O before the application of still another layer of transparent lacquer 32b in a soft roller lacquer unit 53 in a step P before full curing in a curing unit 54 in a step Q.

The surface is then primed again in another priming unit which may be similar to the primer unit of the first step, or could be run one more time through the first unit for new primer application.

The primer of layer 30c is clear/transparent.

Transparent lacquer is applied in still another layer 32a in a unit and is removed by a rigid roller before semi-curing in a curing unit.

Finally, an final layer 32b of transparent lacquer is applied and then fully cured.

Typically, the total amount of primer is 40-60 g/m ² on the main surface (20) and 100-120 g/m ² in the milled sections.

Fig. 4b shows a first unit in the simplest embodiment of the invention. Unit 40 performs step A, of applying a layer of primer.

The surface is then fully or partially cured in a step C in a curing unit 41 for curing the primer. Curing unit 41 is a unit that exposes the primer to UV radiation. In this connection semi-curing means that the primer is only partially cured.

Typically, the primer layer of the preceding steps is a white primer. Another thin primer layer 30d is applied onto the entire surface by a soft roller priming unit 48 in step K. This primer layer is comprised of a clear primer.

This layer is intended to be fused with ink in the following printing / writing step.

This layer may be applied in an amount of 2-12g/m ² , preferably 3-6 g/m ² .

This layer remains uncured or is only semi or partially cured.

The entire surface is then printed with a desired image or pattern in a printing unit 49 in a writing step L forming an ink layer 31 .

The primer layers and ink layer 31 are then fully cured in a curing unit 50 in a step M. The curing unit 50 is also a unit that irradiates the board with UV rays.

The steps and components shown in Fig. 4a can be combined with any one or more of the components or steps shown in Fig. 4

Fig. 5 is a principle sketch of a priming unit or lacquer unit (applicator unit) that may be used in the present invention. The applicator unit includes a first rotating roller 1 1 onto which the agent to be applied onto the underlying board 2 is applied and a second rotating roller 10 which spreads the agent over the first roller 1 1 . The second roller 10 also assists in controlling the amount of agent applied onto the first roller 1 1 .

Fig. 6 is a principle sketch of a combined applicator and removal unit in which the first roller 1 1 and the second roller 10 has the same function and manner of operation as explained above with reference to Fig. 5. However, the combined priming and removal unit also includes a rotating removal roller 12 for removing agent from surface 2. The agent removed from the surface by the removal roller 12 is wiped off by this roller and scraped off of the removal roller 12 by two wipers 13, 14. The agent scraped off may be reused in an applicator unit somewhere in the production line. As used in the present disclosure, the term 'applicator unit' is intended to encompass 'priming unit' and 'lacquer unit'.

In the embodiment described, the use of UV-curable lacquer and primer and UV ray irradiation units has been indicated. However, other forms of curing surface treatment could also be used. It is important, however, to use agents that don't cure in the production conditions before the agents are subject to a dedicated curing treatment.

When using agents that don't cure, the agents removed as excess amounts can be returned to the process recirculation. At the same time the curing may proceed quickly when curing is desired, which is important to achieve an efficient process. It is also advantageous, with respect to the working environment, that agents which cure without producing large amounts of solvents are used. Finally, the use of such agents significantly facilitates the use in the machinery as they don't cure during the process, and as they don't cure when the machinery is not operating.

The system according to the invention is especially well suited for UV-based curing because the use of UV-curable agents eliminates any risk that the primer/agents cure on the rollers or during the return to priming unit 3. This could change the viscosity of the primer and therefore would potentially cause problems. Controlled curing of the primer also simplifies cleaning, maintenance, operational interruptions, etc. significantly when the primer doesn't dry. Recycling primer is significantly more complicated when not using UV-curable primer.

In Table 1 the various steps of the production line according to the invention are listed schematically. TABLE 1

STEP LAYER PROCESS UNIT

A 30 a Primer 1 (first) Priming unit 40

B Remove all primer from surface (first) Firm roller

C Semi/ Partial / Full curing 1 (first) Curing unit 41

D Intermediate grinding 1 (first) Polishing/grinding unit 42

E 30 b Primer 2 (second) Priming unit 43

F Remove some of the primer from surface (second) Firm roller

G Semi /Partial curing 2 (second) Curing unit 44

H 30 d Primer 3 (third) Priming unit 45

Roll on, leave a thin primer layer (first) Soft roller

1 Semi /Partial curing 3 (third) Curing unit 46

(second) Polishing/Grinding unit

J Intermediate grinding 2 47

K Uncured layer for fusing with printing (second) Soft roller

L 31 Printing/Writing Ink-jet printer 49

M Full curing 4 (fourth) Curing unit 50

N 32 a Application of transparent lacquer Lacquer unit 51

0 Semi /Partial curing 5 (fifth) Curing unit 52

P 32 b Application of transparent lacquer (third) Soft roller 53

Q Full curing 6 (sixth) Curing unit 54