GB2626763A

GB2626763A - UV printed automotive interior veneer

Info

Publication number: GB2626763A
Application number: GB2301473.1A
Authority: GB
Inventors: Howard Joseph
Original assignee: Bayerische Motoren Werke AG
Current assignee: Bayerische Motoren Werke AG
Priority date: 2023-02-01
Filing date: 2023-02-01
Publication date: 2024-08-07
Also published as: GB202301473D0

Abstract

An ultraviolet (UV) curable ink 10 is printed, to provide a decorative finish, onto the veneer of an interior part used in car. Preferably a primer is deposited before multiple printed ink layers are applied and crosslinked. The printed layers are preferably covered with a polyurethane sealant and then polyester or polyurethane based lacquer(s). The vehicle’s interior part is preferably a dashboard, door panel, centre console, footplate, armrest, boot floor, floor mat or seat back.

Description

UV Printed Automotive Interior Veneer

Introduction

The present invention relates to a method of applying a decorative finished to an interior veneer for an automobile, as well as to such interior parts with a decorative finish.

Background to the Invention

It is desirable to add an aesthetically pleasing decorative finish to interior veneer for an automobile. As such, a method of applying an aesthetically pleasing decorative finish to a veneer is desired.

Known methods for applying a decorative finish to a car parts include screen-printing and pad printing. Screen-printing can only be used for relatively simple designs with limited complexity. It is not easy to form a textured design via screen-printing, nor is it simple to incorporate a colour gradient into a screen-printed design.

Whilst pad printed designs can be more complex than screen-printed designs, pad printing can only be used for relatively small prints due to limitations on the size of the sponge used.

Applying a printed design or other decorative finish to veneers presents particular challenges due to the relative fragility and lack of rigidity of veneers compared to solid components. In addition, for wood veneers the grain of the veneer can give rise to uneven ink distribution, presenting a further challenge.

Accordingly, it is an aim of the present invention to provide an alternative method of applying a decorative finish to interior parts of automotive vehicles, without the problems noted above. It is a further aim of the invention to provide an interior veneer for an automobile with an aesthetically pleasing decorative finish.

Summary of the Invention

The invention provides a method of applying a decorative finish to an interior veneer for an automobile, the method comprising a UV printing step. -2 -

The decorative finish applied by UV printing comprises at least a single layer applied by UV printing. A layer is considered to be a single thickness of ink, applied in a single pass of the printer and cured. A layer does not have to be a continuous layer. In preferred embodiments, the layer is not a continuous layer such that a design can be added to the interior part by the UV printed layer. Typically, a UV printed layer has a thickness of approximately 20 microns to 40 microns.

The method may comprise applying two or more layers by UV printing (referred to as UV printed layers). Applying multiple layers, enables a textured finish to be achieved. Typically, the method comprises applying 2 or more layers by UV printing, preferably 3 or more layers and most preferably 4 or more layers (for example 5 layers or more). Typically, no more than 20 layers are applied by UV printing, preferably no more than 15 layers, and most preferably no more than 12 layers (for example 10 layers or less).

Applying a layer by UV printing comprises (i) depositing a UV-curable ink onto a substrate, and (ii) curing the layer by exposing it to UV light.

Where more than one layer is deposited by UV printing, the deposition of each layer comprises (i) depositing a UV-curable ink onto a substrate, and 00 curing the layer by exposing it to UV light, i.e. between each layer of ink being deposited, the layer is cured by exposing it to UV light. A single layer can therefore be defined as a layer applied by a single deposition step followed by a single curing step.

In some embodiments the ink colour of the layers may be the same throughout, however in other embodiments the ink colour may be different for some layers. In preferred embodiments, the first layer (or only layer in cases where only a single layer is present) comprises a coloured ink. Preferably, when present, second and subsequent layers may comprise a coloured and/or a clear (i.e. transparent) ink.

In preferred embodiments where two or more layers are applied by UV printing, a first layer of coloured ink is applied, followed by one or more subsequent layers of coloured or clear ink. Therefore, in preferred embodiments where two or more layers are applied by UV printing, the method may comprise the following steps: -3 - (I) Depositing a first layer of coloured ink on a veneer; (ii) Curing the first layer of ink by exposing it to UV light; (iii) Depositing a second layer of coloured or clear ink onto the veneer; (iv) Curing the second layer of ink by exposing it to UV light; and (v) Optionally repeating steps (iii) and (iv) until the desired number of layers are deposited.

Coloured ink may be any colour, e.g. the coloured ink may be black ink, white ink, red ink, green ink etc. The colour of the coloured ink may vary throughout a single layer, for example the colour may have a gradient. The transparency of the coloured ink may vary, however it is preferred that the coloured ink is substantially opaque.

Clear ink is an uncoloured ink and is preferably substantially transparent.

An example of suitable commercially available inks include the UV-curable inks manufactured by Mimaki0.

The method may include additional steps before or after the UV printing step.

Prior to the UV printing step, the method may comprise mounting the veneer on a backing. This can provide useful structural support for the veneer during the printing process, and prevent the veneer from curling during the printing process. If the veneer curls during the printing process, it is likely that the design will be distorted. Suitable materials for the backing include pre-impregnated glue sheets. These sheets can be applied to the veneer using the pressure and heat of a conventional hydraulic press, without the need for additional adhesive. Typically, the thickness of a backing layer (where present) is approximately 0.2mm to 1.5mm, preferably from 0.3mm to 1mm, most preferably from 0.4mm to 0.8mm.

An alternative or additional way of preventing the design distorting during the printing process is to hold the veneer flat using vacuum suction during the printing process. Therefore, the method may include a step of positioning the veneer on a vacuum table to prevent movement during printing. Suitable vacuum tables are known in the art. -4 -

The printing machine used is conventional in the art. A suitable commercially available printer is the model UJF-6042 from manufacturer Mimaki®.

In embodiments where a smooth finish is desired following the UV printing step, a base layer or primer may be deposited prior to the UV printing step. Deposition of a base layer would prevent the grain of the veneer from affecting the texture of the UV printed layer. In some cases, the grain is desirable and therefore no base layer is used. However, in other cases, a visible grain is undesirable and as such a base layer may be deposited. Suitable base / primer layers are available from manufacturers such as Mimaki®. The thickness of a base layer is typically 20 microns to 40 microns.

After the UV printing step, the method may comprise a step of applying a sealant to the printed veneer. In preferred embodiments, at least a single layer of sealant is applied to the printed veneer. In some embodiments two or more layers of sealant may be applied to the printed veneer. Typically, the sealant is applied as a continuous layer over the entire veneer, and not simply over the UV printed sections. Typically, the sealant is a polyurethane-based sealant. Suitable sealants can be obtained from Votteler®.

Typically, a sealant is applied before a lacquer (see below) to ensure the UV printed design is suitably bonded to the veneer and to reduce the likelihood of the design detaching from the veneer. The presence of a sealant layer additionally promotes adhesion of the subsequent lacquer layers to the veneer.

The method may comprise a step of applying a lacquer. It is preferred that a lacquer layer is applied, since a lacquer layer is believed to assist in preserving the wood of the veneer whilst also leading to the desired wood finish. Typically, a lacquer layer (when present) is the outer layer.

The lacquer may be selected depending on the desired finish of the interior part. Examples of suitable lacquer types include high gloss lacquer and open pore lacquer (also referred to as matt satin finish lacquer). The type of lacquer selected may affect the number of lacquer layers applied to the printed veneer. Typically, a greater number of lacquer layers are applied when using high gloss lacquer (for example 6 layers of -5 -more, preferably 8 layers or more), leading to a greater thickness of the lacquer overall compared to when open pore lacquer is used.

Typically, high gloss lacquer on a printed veneer has a total thickness of 0.5mm to 2mm, preferably 0.7mm to 1.5mm, most preferably 0.8mm to 1.2mm (for example approximately 1mm). Excess layers of lacquer may be applied leading to an initial greater lacquer thickness, before the total lacquer thickness is reduced to the desired range during polishing.

The thickness of individual lacquer layers depends on the material of the lacquer. Typically, individual layers of high gloss polyester lacquer have a thickness of approximately 100 microns to 150 microns. Typically, individual layers of high gloss polyurethane lacquer have a thickness of from 40 microns to 50 microns.

When open pore lacquer is used, typically only a single layer of lacquer is used of negligible thickness. This allows the texture of the wood veneer to be felt through the lacquer. The thickness of a single layer of open pore lacquer is typically negligible.

As for the sealant, the lacquer is typically applied as a continuous layer over the entire veneer, and not simply over the UV printed sections.

Suitable high gloss lacquers include polyester and polyurethane lacquers, and a suitable open pore lacquer is a polyurethane lacquer.

After or during application of the lacquer, there may be additional finishing steps. For example, the lacquered printed veneer may be sanded to produce a smooth finish. Sanding is typically preferred when high gloss lacquer is used to produce a smooth untextured finish, with a sanding step being carried out at least before application of the final lacquer layer, preferably before application of the second and all subsequent lacquer layers. When high gloss lacquer is used, there is typically also a polishing step after the final lacquer layers are applied. However, a sanding step is typically not used with open pore lacquer. Therefore, when open pore lacquer is used, the texture of the printed veneer can typically still be felt through the lacquer. -6 -

In some embodiments, a milling step is carried out as an additional finishing step. This step may be used, for example, to smooth the edges of the veneer. Suitable milling machines are known in the art, and include CNC milling machines from Hamuel Reichenbacher, Kelch GmbH and Maka.

As a final step, the method may include applying the printed veneer onto an interior part of an automobile. Methods of applying veneer onto separate parts are standard in the art. Preferably, the printed veneer is applied to the interior part using a membrane press.

The interior part may be any interior part of an automobile to which a veneer can be applied. Suitable interior parts include the dashboard, the door panels, the centre console, the footplates, armrests, boot floors, floor mats, seat backs and individual panels / sections thereof.

The veneer is typically a thin layer of fine wood that can be applied to a surface to give the appearance that the entire surface is wood. It is envisaged that the method of the invention could be used to apply a decorative coating to any known wood veneer. The veneer may be formed from natural wood (comprising only a single type of wood) or it may be engineered (comprising a mixture of woods). Suitable woods include Ash, Beech, Birch, Bocote, Bubinga, Chestnut, Cherry, Ebony, Elm, Eucalyptus, Mahogany, Maple, Koa, Larch, Lemonwood, Oak, Olive, Paldao, Palm, Rosewood, Santos palisander, Sapele, Sindora, Sycamore, Teak, Tulip, Walnut, Wenge, and Zebrano.

Typically, the thickness of the veneer is from 0.2mm to 1.5mm, preferably from 0.3mm to 1.0mm, most preferably from 0.4mm to 0.75mm (for example approximately 0.5mm).

As noted above, the veneer is a typically a layer that can be applied to a part on the interior of an automobile. The printed design is applied to the veneer according to methods of the invention, before the veneer is applied to the part, i.e. only the veneer is placed in the UV printer, and not the part to which it will be attached. -7 -

In some embodiments, the method of the invention may also be used to apply a decorative finish to an interior veneer also featuring other decorative elements. For example, the interior veneer may have one or more layers of paint or stain applied before a decorative finish is applied according to the methods of the invention.

In alternative embodiments, the method may include an initial step of applying one or more layers of paint or stain to the veneer, prior to the UV printing step.

In preferred embodiments, the invention provides a method of applying a decorative finish to an interior veneer for an automobile, the method comprising the following steps in order: (I) Optionally applying a base layer to a veneer; (H) Applying a first coloured layer via UV printing to a veneer to form a printed veneer; (iii) Applying one or more second coloured or clear layers via UV printing to the printed veneer; (iv) Applying a sealant to the printed veneer; and (v) Applying one or more layers of lacquer to the sealed printed veneer.

The method of preferred embodiments may also be summarised as comprising the following steps in order: (I) Optionally applying a base layer to a veneer; (ii) Depositing a first layer of coloured ink on a veneer; (Hi) Curing the first layer of ink by exposing it to UV light; (iv) Depositing a second layer of coloured or clear ink onto the veneer; (v) Curing the second layer of ink by exposing it to UV light; (vi) Optionally repeating steps (iii) and (iv) until the desired number of layers are deposited; (vii) Applying a sealant to the printed veneer; and (viii) Applying one or more layers of lacquer to the sealed printed veneer.

The invention also provides an interior veneer for an automobile with a UV printed decorative finish. -8 -

All description of optional and preferred layers applied as part of the method of the invention may also be present as layers on the interior veneer.

Typically, the UV printed decorative finish comprises two or more layers deposited by UV printing. Preferably, the first layer comprises a coloured ink and the second and subsequent layers comprise a coloured and/or clear ink.

Brief Description of the Drawings

Fig.1 shows a view from above of a UV printed design on a veneer, Fig.2 shows a view from above and to the side of a second UV printed design on a veneer.

Detailed Description of the Invention

Figure 1 shows a UV printed design on a wood veneer. Before the design was printed, the veneer was sanded, first with grit 120 sandpaper and subsequently with grit 240 sandpaper. Sanding the veneer before applying a UV printed design both smooths the veneer surface and additionally improves adhesion of the UV printed design to the veneer.

The design was printed by applying 5 layers of via UV printing to the veneer. To apply each layer, first a layer of UV-curable clear ink was deposited, and the ink was then cured by exposing it to UV light. The UV curable ink used was LUS-120 from Mimaki®. The MimakiCi model UJF-6042 printer was used for each of the UV printing steps.

This process was repeated 4 times to deposit in total 5 layers via UV printing. Each UV-printed layer was deposited exactly on top of the previous layer, producing a design with straight (i.e. not tapered) edges. Each UV printed layer had an approximate thickness of 30 microns and therefore the total thickness of the resultant printed design was 150 microns.

After the five UV printed layers were applied, a layer of sealant was applied across the whole surface of the veneer. The sealant was applied by spraying this over the UV printed layers using a gravity-fed spray gun. The sealant used was a polyurethane-based sealant from Votteler GmbH. The thickness of the sealant layer was negligible. -9 -

Sealant is used since it improves the adhesion of the UV printed design to the veneer and additionally improves the adhesion of the lacquer to the veneer, improving the long term durability of the printed veneer.

After the sealant layer was applied, a layer of open pore polyurethane lacquer were applied by spraying using a gravity-fed spray gun and this was then left to dry. The use of open pore lacquer enables the grain of the wood 2 to be both seen and felt through the UV printed design. The polyurethane lacquer used to produce the printed design of figure 1 was obtained from Votteler GmbH.

In some cases it is desirable for the design to have a smooth, shinier finish. In these cases a high gloss polyester or high gloss polyurethane lacquer may be used in place of the open pore polyurethane lacquer.

Coloured UV printed designs can be formed in a very similar way to the clear UV printed design of figure 1. However, the first UV printed layer would be applied by depositing a first layer of coloured UV-curable ink. The deposited layer of coloured ink would then be cured by exposing it to UV light. Subsequent layers of coloured and/or clear UV-curable ink would then be applied in the same way.

Figure 2 shows a second UV printed design on a veneer. The UV printed design has been formed in a similar way to that of figure 1. However, 10 UV-printed layers were used, and each layer was applied by depositing black UV-curable ink and then exposing the ink to UV light. The black UV-curable ink used was LUS-150-K-BA from M imakie.

This application process was repeated 9 times to deposit in total 10 UV-printed layers. To form the design shown in figure 2, each UV-printed layer was not exactly the same as the previous. The first layer deposited a number of discrete sections of ink. The second layer again deposited a number of discrete sections of ink, in the same locations as the first ink sections. However, each section of ink was smaller in the second layer than the first. This continued for layers 3 to 10. As such, the resultant UV-printed design features a series of raised "pyramid" type structures 10.

-10 -No sealant or lacquer has been applied over the UV printed design of figure 2.

As seen for the grain of the wood in figure 1, the texture of the printed design of figure 2 would likely still be felt through a layer of sealant and a few layers of open pore lacquer. If a large number (for example five layers) of high gloss lacquers were to be applied, it is likely that the texture of the design would no longer be felt.

However, the raised profile of the design in figure 2 would still be visible through the lacquer and would therefore provide a desirable visual effect, even if the texture could not be felt.

UV printing enables a heavily textured finish (such as that shown in figure 2) to be applied to the interior veneer with a high degree of control and repeatability. Additionally, UV printing can be used to impart a design over a large area of the interior part, subject to the size of the printer.

Examples

Testing Samples Samples of three dimensional parts with UV printed veneer formed according to the method of the invention have undergone and successfully completed standard adhesion testing.

Samples have similarly undergone and successfully completed an alternating climate test.

Claims

CLAIMS1. A method of applying a decorative finish to an interior veneer for an automobile, the method comprising a UV printing step.
2 A method according to claim 1, wherein the method comprises applying two or more layers by UV printing.
3. A method according to claim 2, wherein the first layer applied via UV printing comprises a coloured ink and the second and subsequent layers comprise a coloured and/or a clear ink.
4. A method according to any preceding claim, wherein a base layer or primer is deposited onto the interior veneer prior to the UV printing step.
5. A method according to any preceding claim, wherein a sealant is applied after the UV printing step.
6. A method according to claim 5, wherein the sealant is polyurethane-based sealant.
7. A method according to any preceding claim, wherein a lacquer layer is applied after the UV printing step and, when present, after a sealant has been applied.
8 A method according to claim 7, wherein two or more lacquer layers are applied.
9 A method according to claim 7 or 8, wherein the lacquer is selected from a polyester or polyurethane lacquer.
10.A method according to any preceding claim, wherein the printed veneer is applied to an interior part of an automobile.-12 -
11.A method according to claim 10, wherein the interior part is selected from the list comprising the dashboard, the door panels, the centre console, the footplates armrests, boot floors, floor mats, seat backs and individual panels / sections thereof
12.A method of applying a decorative finish to an interior veneer for an automobile, the method comprising (i) Optionally applying a base layer to a veneer; (ii) Applying a first coloured layer via UV printing to a veneer to form a printed veneer; (iii) Applying one or more second coloured or clear layers via UV printing to the printed veneer; (iv) Applying a sealant to the printed veneer; and (v) Applying one or more layers of lacquer to the sealed printed veneer.
13.A method of applying a decorative finish to an interior veneer for an automobile, the method comprising (0 Optionally applying a base layer to a veneer; (ii) Depositing a first layer of coloured ink on a veneer; (iii) Curing the first layer of ink by exposing it to UV light; (iv) Depositing a second layer of coloured or clear ink onto the veneer; (v) Curing the second layer of ink by exposing it to UV light; (vi) Optionally repeating steps (iii) and (iv) until the desired number of layers are deposited; (vii) Applying a sealant to the printed veneer; and (viii) Applying one or more layers of lacquer to the sealed printed veneer.
14. An interior veneer for an automobile with a UV printed decorative finish.
15. An interior veneer for an automobile, wherein the UV printed decorative finish comprises two or more layers deposited by UV printing.-13 -
16. An interior veneer for an automobile according to claim 15, wherein the first layer comprises a coloured ink and the second and subsequent layers comprise a coloured and/or clear ink.
17. An interior veneer for an automobile according to any of claims 14-16, wherein the decorative finish is applied using the method of any of claims 1 to 13.