EP1618967A1

EP1618967A1 - Apparatus for applying varnish onto a film

Info

Publication number: EP1618967A1
Application number: EP05005644A
Authority: EP
Original assignee: DeMaxZ AG; DeMaxz Deutschland GmbH
Current assignee: DeMaxZ AG
Priority date: 2004-02-23
Filing date: 2005-03-15
Publication date: 2006-01-25
Also published as: EP1755791A4; WO2005084823A1; EP1755791A1; CN1942253A

Abstract

An apparatus for applying varnish onto a film, said apparatus comprising:

a coating roller (10) for transferring varnish from the coating roller onto the film (18),
a pressure roller (12) arranged adjacent said coating roller (10),
means for advancing said film (18) at a first velocity through a gap (44) between said coating roller (10) and said pressure roller (12), and
means for rotating said coating roller (10) such that the circumference of the coating roller (10) adjacent said film (18) moves at a second velocity different to said first velocity.

Description

The invention is concerned with an apparatus for applying varnish or lacquer onto a film.
It is well known in the prior art to use a so-called coating roller and a so-called pressure roller (also sometimes called a counter roller) for applying varnish onto a flexible film. Said flexible film may preferably have so-called release properties such that the layer of varnish can be transferred from said film onto an object, e.g. after curing (cross-linking) or partial curing of the varnish, by peeling off the varnish layer.
Films having so-called release properties are well known in the prior art; see for example, EP 1 053 793 A1 and EP 0 573 676 B1. The prior art includes both paper- based films and films made of a resin, the surfaces of which are prepared such that the film comprises release properties. When layers of colour or varnish are applied to such a film having release properties, the layers can be transferred onto an object to be decorated in such a way that the layers of varnish and colour are peeled off from the film.
The prior art according to EP 0 573 676 B1 discloses a process of decorating an object wherein a layer of varnish is applied on a film having release properties. That layer of varnish is partially cured. A layer of colour is applied onto the partially cured varnish layer and a second layer of varnish is applied onto the colour layer. Said second layer of varnish is also partially cured. Thereafter, said layers of varnish and colour, respectively, are transferred onto the object to be decorated (the "substrate"). After said transfer by release, the first and second varnish layers are completely cured. The "curing" referred to herein is also called "cross-linking".
EP 1 053 793 A1 teaches the application of varnish and colour onto an object by means of a release film, wherein a glue is applied on top of the varnish and colour layers of the release film. When transferring said layers onto the object to be decorated, the glue is in direct contact with said object.
The present invention is, in particular, directed to applying a varnish layer onto such a film which, preferably, has release properties. Said film may be printed, before or after applying said varnish layer, with a colour layer.
In the prior art it was very difficult, if not impossible, to apply relatively thick layers of varnish onto a film. The films in question here typically have a width of more than 100 cm, e.g. a width in the range of 160 to 180 cm. The machines according to the prior art were capable of applying varnish layers having a thickness typically less than 60 µm.
The present invention aims at providing an apparatus that is capable to be adapted to apply a variety of varnish layers of different thickness, in particular relatively thick varnish layers.
To this end, the present invention teaches an apparatus for applying varnish onto a film, said apparatus comprising:

a coating roller for transferring varnish from the coating roller onto the film,
a pressure roller arranged adjacent said coating roller,
means for advancing said film at a first velocity through a gap between the coating roller and the pressure roller, and
means for rotating the coating roller such that the circumference of the coating roller adjacent the film moves at a second velocity different to the first velocity.

According to a preferred embodiment of the invention, the means for advancing the film advances the film in a first direction through the gap between the coating roller and the pressure roller, and the means for rotating the coating roller rotates the coating roller such that the circumference of the coating roller adjacent the film moves in a second direction opposite to said first direction.
Preferably, said film before entering said gap defines an angle (α) different from zero with a plane that is tangential to both the coating roller and the pressure roller.
According to another preferred embodiment of the invention, said coating roller comprises a rubber surface.
According to another preferred embodiment of the invention, means are provided for moving at least one of said pressure roller or coating roller in a direction parallel to said plane that is tangential to both the coating roller and the pressure roller.
In the following, an embodiment of the present invention is described in detail with reference to the figure.
The figure shows schematically an apparatus for applying varnish onto a film.
The apparatus comprises a coating roller 10 and a pressure roller 12. Pressure rollers are also sometimes called "counter rollers". The pressure roller 12 is driven. The circumferential speed of the pressure roller 12 defines the speed of the film through the apparatus.
A dosing roller 14 is arranged adjacent the coating roller 10 for transferring varnish from a supply (not shown) onto the coating roller 10.
A plane 16 is tangential to both the coating roller 10 and the pressure roller 12, i.e. the plane 16 passes in-between the rollers, which are adjacent to each other.
A film 18 having release properties is advanced in the figures from the right hand side to the left hand side.
The coating roller 10 is rotated around its axis 20 in an anti-clockwise direction as indicated by arrow 46 in the figure. The drive of the coating roller is conventional and is not shown. Pressure roller 12 rotates about its axis 22. Pressure roller 12 is driven by a drive (not shown) at the speed at which the film 18 is advanced.
The film 18 is guided via rollers 24 and 26 such that, before being advanced between the coating roller and the pressure roller, it is not positioned in the tangential plane 16, but rather defines an angle α between the film 18 and the tangential plane 16, as indicated in the figure. That angle α is acute, and is preferably in the range between about 10° and 30°.
As described above, film 18 is advanced in the figure from right to left. Pulling means for pulling the film in the direction 42 are not shown, but they are typically arranged in the figure to the left of the coating roller 10 and the pressure roller 12. For example, a driven collecting roller would be suitable for pulling the film in the direction 42.
Varnish is transferred by the coating roller 10 onto the film 18, and in particular onto the upper surface of film 18, as shown in the figure. The varnish is, preferably, curable by so-called cross-linking, which as such is well known in the art. For example, curing means (not shown) may be arranged to the left of the coating roller 10 and the pressure roller 12.
A varnish container 28 is arranged underneath the pressure roller 12 to collect excess varnish not used for coating the film 18, e.g. varnish applied at the edges of the film 18.
A support 30, which supports both the pressure roller 12 and the coating roller 10, allows rotation of the coating roller 10 and the pressure roller 12 in the direction of arrows 32, i.e. both the coating roller 10 and the pressure roller 12 can be rotated about an axis A that is passing through the axes 20 and 22 in the middle of both rollers. Since the figure shows a centre cross section through the rollers, said axis A is also in the plane of the drawings. By said rotation about axis A in direction of arrows 32, the relative arrangement and positioning between the rollers and the film 18 can be adjusted so that crinkles are avoided.
Pressure roller 12 always rotates anti-clockwise as indicated by the arrow.
Coating knifes 36, 38 are arranged to control the transfer of varnish from the dosing roller onto the coating roller, as is known in the art as such. The coating roller 10 and the dosing roller 14 rotate typically in opposite directions, as indicated by the arrows 46, 48.
Typical dimensions of the rollers are as follows: The coating roller 10 may have a typical diameter in the range between 180 and 300 mm, preferably about 240 mm. The pressure roller 12 may have the same dimensions. The dosing roller 14 has a diameter in the range of 100 to 200 mm, preferably about 160 mm. The dosing roller 14 is smaller than the coating roller.
The width of the film is typically 160 to 180 cm.
A soft knife 40 is arranged near the varnish collecting container 28 in order to clean the pressure roller 12 from excess or non-used varnish.
As described above, the film 18 is advanced in the direction of arrow 42. The film 18 passes through a gap 44 between the coating roller 10 and the pressure roller 12.
The direction of rotation 46 of coating roller 10 and the speed of rotation are controlled such that the circumference of the coating roller 10 adjacent the film 18, i.e. the circumference of the coating roller actually transferring the varnish onto the film, is moving in the opposite direction with reference to the movement of the film. Therefore, the circumferential surface of the coating roller 10 has a velocity relative to the velocity of the film 18 in the opposite direction. That is, in a (moving) coordinate system in which the film 18 is at rest, the circumferential surface of the coating roller 10, which transfers the varnish onto the film, moves relative to the film with a definite velocity different from zero. Most preferably, in a stationary (non-moving) coordinate system (i.e. the coordinate system of the figure), the coating roller 10 has a circumferential surface that rotates counter-clockwise as indicated by arrow 46 in the figure. The dosing roller 14 rotates in a direction opposite to the direction of rotation of the coating roller 10, i.e. dosing roller 14 rotates clockwise.
Typical examples of the velocities are as follows: The speed of advancement (velocity) of the film 18 in direction 42 may be in a range of 1-50 m/min, preferably 10 to 20 m/min. If the speed of advancement (velocity) of the film 18 is 20 m/min, the preferred rotational speed of the coating roller 10 is such that its surface velocity is 10 m/min. Generally speaking, if the speed of advancement of the film 18 is X, the rotational speed of the coating roller is such that its surface velocity is in a range of 30-70% of X. The afore-mentioned velocities are in the same direction, i.e. the film is advanced in direction 42 and the coating roller rotates clockwise. If, on the other hand, the speed of advancement (velocity) of the film 18 is relatively slow, e.g. in the range of 1-5 m/min, the coating roller may rotate anti-clockwise in direction of arrow 46 with surface velocities in the range of 10-5 m/min. The velocities are adjusted in accordance with the specific requirements of the varnish coating to be applied onto the film, in particular the thickness of the varnish and the properties of the varnish.
Depending on the thickness of the layer of varnish to be applied onto the film 18, the coating roller 10 may also rotate clockwise (i.e. opposite to arrow 46) with a circumferential speed smaller than the speed of advancement of the film 18 in the direction of arrow 42. For example, if the speed of advancement of film 18 in direction of arrow 42 is 10 m/min, the circumferential speed of coating roller 10 in clockwise direction (opposite to arrow 46) can be adjusted to be between 3 m/min and 7 m/min, resulting in a corresponding relative speed between be circumference of the coating roller and the film.
The amount of varnish applied onto the film 18 can be controlled as follows: varnish 50 is fed in between the coating roller 10 and the dosing roller 14 as shown in the drawing. By adjusting the pressure between the dosing roller 14 and the coating roller 10 and/or the relative velocity between coating roller 10 and dosing roller 14, the amount of varnish applied by the coating roller 10 onto the film 18 is variably controllable. If only a very small amount of varnish shall be applied onto the film, i.e. a varnish layer of relatively thin strength is to be applied onto the film 18, the dosing roller 14 may rotate in opposite direction as compared to the coating roller 10. This is indicated by the double-arrow 48.
With the apparatus described above, layers of varnish can be applied onto the film 18 which are much thicker than possible with prior art machines, e.g. it is possible to apply a varnish layer having a thickness in the range of 120 µm to 130 µm with a constant thickness along the width and length of the film 18. A film 18 having release properties and coated with a varnish layer having a thickness in the afore-mentioned range, is very suitable for applying varnish onto an object with a high degree of homogeneity of the varnish layer on the object, especially in the area of edges. Cracks are avoided.

Claims

Apparatus for applying varnish onto a film, said apparatus comprising:
- a coating roller (10) for transferring varnish from the coating roller onto the film (18),

- a pressure roller (12) arranged adjacent said coating roller (10),

- means for advancing said film (18) at a first velocity through a gap (44) between said coating roller (10) and said pressure roller (12), and

- means for rotating said coating roller (10) such that the circumference of the coating roller (10) adjacent said film (18) moves at a second velocity different to said first velocity.
Apparatus according to claim 1, wherein said means for advancing said film (18) advances said film through the gap (44) in a first direction (42), and said means for rotating said coating roller (10) rotates said coating roller such that the circumference of the coating roller (10) adjacent said film (18) moves in a second direction (46) opposite to said first direction (42).
Apparatus according to claim 1 or claim 2, wherein said film (18), before entering said gap (44), defines an angle (α) different from zero with a plane (16) that is tangential to both the coating roller (10) and the pressure roller (12).
Apparatus according to any one of claims 1 to 3, wherein said coating roller (10) comprises a rubber surface.
Apparatus according to any one of claims 1 to 4, wherein means (30, 32) are provided for moving at least one of said pressure roller (12) or coating roller (10) in a direction parallel to a plane (16) that is tangential to both the coating roller (10) and the pressure roller (12).