WO2020169689A1

WO2020169689A1 - Method for printing a three-dimensional optical component

Info

Publication number: WO2020169689A1
Application number: PCT/EP2020/054402
Authority: WO
Inventors: Christel CLAES; John-John VAN DEN BERGH
Original assignee: Luxexcel Holding B.V.
Priority date: 2019-02-20
Filing date: 2020-02-19
Publication date: 2020-08-27

Abstract

The present invention refers to a method for printing a three-dimensional optical component, wherein the three-dimensional structure is built up from layers of printing ink which are printed at least partially one above the other in consecutive layer printing steps, wherein a first layer is printed in a first layer printing step and a second layer is printed at least partially on top of the first layer in a second layer printing step, characterized in that the second layer encloses the first layer.

Description

DESCRIPTION

TITLE

Method for printing a three-dimensional optical component

BACKGROUND

The present invention relates to a method for printing a three-dimensional optical component, wherein the three-dimensional structure is built up from layers of printing ink which are printed at least partially one above the other in consecutive layer printing steps, wherein a first layer is printed in a first layer printing step and a second layer is printed at least partially on top of the first layer in a second layer printing step.

Printing three-dimensional optical components such as lenses, mirrors and the like is known from the prior art. The optical structures are built up layer by layer through a targeted placement of droplets of printing ink. The droplets are ejected towards a substrate by ejection nozzles of the print head of an inkjet printer. Printing of optical components is particularly demanding due to the high accuracy required. Here, it turned out that printing optical components of convex shape, e.g. convex lenses, is particularly difficult. This is due to the fact that the last printed layers are significantly smaller than the previously deposited layers, resulting in large deviations and defects, particularly of the last printed layer, compromising the quality of the optical component.

SUMMARY

It is a purpose of the present invention to provide a method for printing a three-dimensional optical component which prevents the formation of such deviations and defects, in particular in sections of small diameter compared to the overall diameter of the optical component.

According to the present invention, this object is achieved by a method for printing a three- dimensional optical component, wherein the three-dimensional structure is built up from layers of printing ink which are printed at least partially one above the other in consecutive layer printing steps, wherein a first layer is printed in a first layer printing step and a second layer is printed at least partially on top of the first layer in a second layer printing step, characterized in that the second layer encloses the first layer. Herewith it is advantageously possible to prevent the formation of deviations and defects on the comparatively small, final layers of an optical component. In particular, the layers are printed in reverse order, starting with the layer of smallest diameter and continuing with layers of larger diameter. Accordingly, the final layer printed has a large surface area, reducing the probability of defect formation in that layer. Hence, an optical component of improved quality is obtained.

In the sense of the present invention, each layer printing step preferably comprises a targeted placement of droplets of printing ink at least partially side by side and one above the other.

Preferably, the surface area of the first layer is smaller than the surface area of the second layer. In a preferred embodiment, at least one layer printing step is followed by a curing step.

The presented method is particularly suitable for three-dimensional optical components comprising a section of convex shape, such as a convex lens. According to a preferred embodiment of the present invention, the convex section is built up in consecutive layer printing steps, wherein the surface area of at least one printed layer is larger or equal to the surface area of the previously printed layers. Surface area in the sense of the present invention refers to the area of the top surface of the printed layer in the instant of ejection prior to any droplet flow or droplet melting.

In a preferred embodiment, a third layer is printed in a third layer printing step and a fourth layer is printed in a fourth layer printing step at least partially on top of the third layer such that the fourth layer encloses the third layer or such that the fourth layer does not enclose the third layer, depending on a random algorithm. Hence, the printing order of at least a subset of layers is randomly determined. This advantageously provides a method for canceling out and randomly distributing printing errors.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 schematically illustrates a printing method according to the state of the art.

Figure 2 schematically illustrates a printing method according to an exemplary embodiment of the present invention.

DETAILED DESCRIPTION The present invention will be described with respect to particular embodiments and with target to certain drawings but the invention is not limited thereto but only by the claims. The drawings described are only schematic and are non-limiting. In the drawings, the size of some of the elements may be exaggerated and for illustrative purposes may not be drawn to scale.

Where an indefinite or definite article is used when referring to a singular noun, e.g.“a”,“an”, “the”, this includes a plural of that noun unless something else is specifically stated.

Furthermore, the terms first, second, third and the like in the description and in the claims are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein.

In Figure 1 a method for printing a three-dimensional optical component 1 according to the state of the art is schematically illustrated. The optical component 1 preferably comprises a section of convex shape. In the described embodiment, the optical component 1 is a convex lens. The optical component 1 is built up through a deposition of layers of printing ink 2, 3, 4 in layer printing steps. The layers result from a targeted placement of droplets 6 of printing ink. These are ejected from the nozzles 8 of a print head 7 towards a substrate or printing plate 5. The droplets 6 of printing ink are deposited at least partially side by side, forming a layer 2, 3, 4 of printing ink. Volume and placement of the droplets 6 is determined from printing data which are conveyed to the print head 7 prior to or during the printing process. Conventionally, printing starts with the section of the optical component 1 with largest surface area. In case of an optical component 1 of convex shape, the first printed layer 2 is the layer with the largest surface area. After the first layer printing step, a first curing step is preferably carried out. During the curing step, the printed structure 1 is irradiated with light, preferably ultra-violet light, from a curing unit 9, which usually forms part of the print head 7. Through curing, the deposited printing ink is at least partially polymerised, at least partially fixing the deposited droplets in their place and shape. The first layer printing step is followed by a second layer printing step, during which the second printed layer 3 is deposited through a targeted placement of droplets 6 of printing ink on the first printed layer 2. The second printed layer 3 has a smaller surface area than the first printed layer 2. The second layer printing step is preferably followed by another curing step. Preferably, a time interval elapses between the last droplet deposition and the curing, so that the deposited droplets can melt with each other and flow, resulting in a particularly smooth surface of the printed layer. Printing is continued in this way, until during the last layer printing step, the layer with smallest surface area is printed. The deposition of the last, small layers at the end of the print introduce large defects and errors in the optical component 1 , compromising its quality and hence its suitability of optical applications. Building up the optical component 1 from layers 2, 3, 4 of decreasing surface area according to the state of the art results in an optical component 1 wherein the top surface shows steps and terraces which are difficult to smooth out. Here and in the following, “top” and “bottom” are defined by the droplet depositing process, i.e. ejected droplets move from top to bottom.

In Figure 2 a method for printing a three-dimensional optical component 1 according to an exemplary embodiment of the present invention is schematically illustrated. According to the present invention, the optical component 1 is built up from layers 2, 3, 4 of printing ink. These are, as described above, deposited through a targeted placement of droplets 6 of printing ink. The droplets 6 are ejected from the ejection nozzles 8 of the print head 7 of an inkjet or droplet-on-demand printer. The droplets 6 are places at least partially side by side so as to form a layer 2, 3, 4 of printing ink. In an exemplary embodiment, the optical component 1 comprises a section of convex shape, in particular the optical component 1 is a convex lens. As opposed to the state of the art, the optical component 1 is built up from layer 2, 3, 4 of printing ink in successive layer printing steps such that at least a second printed layer 3 is printed at least partially on top a first printed layer 2 in such a way that the first printed layer 2 is enclosed by the second printed layer 3. This is preferably achieved by printing at least one layer of larger surface area on top of a layer of smaller surface area. As a consequence, printing ink of the layer of larger surface area flows over the layer of smaller surface area, surrounding the latter. This is preferably done for all layers. In particular, the order of the printed layers is preferably reversed as compared to the state of the art described in Figure 1 for all layers 2, 3, 4. In an alternative embodiment, the order is reversed only for a subset of layers. Preferably, the layer printing steps are followed by a curing step during which the deposited layer is at least partially cured by a curing unit 9. The curing unit 9 preferably comprises a UV light source for irradiating the printed layer with UV light. It is preferred to let a time interval elapse between deposition of the last droplets 6 of a printed layer 2, 3, 4 and curing. During this time interval, the deposited printing ink can flow, resulting in a particularly smooth surface. According to a preferred embodiment, the first printed layer 2 is the layer of smallest diameter and the last printed layer is the layer of largest diameter. The printing ink from the layers flows, resulting in a particularly smooth surface of the resulting optical component 1. As opposed to the state of the art, no terraces and steps form on the surface. In this way, a method is provided that allows printing of optical components, in particular those comprising convex sections, of improved quality and accuracy. In particular, the top surface of the optical components 1 printed according to the presented method have an improved smoothness as compared to those printed by the state of the art.

KEY TO FIGURES

1 Printed optical component

2 First printed layer 3 Second printed layer

4 N-th printed layer

5 Printing plate

6 Droplet of printing ink

7 Print head

8 Ejection nozzle

9 Curing unit

Claims

PATENT CLAIMS

1. Method for printing a three-dimensional optical component, wherein the three- dimensional structure is built up from layers of printing ink which are printed at least partially one above the other in consecutive layer printing steps, wherein a first layer is printed in a first layer printing step and a second layer is printed at least partially on top of the first layer in a second layer printing step, characterized in that the second layer encloses the first layer.

2. Method according to claim 1 , wherein the surface area of the first layer is smaller than the surface area of the second layer.

3. Method according to one of the preceding claims, wherein each layer printing step comprises a targeted placement of droplets of printing ink at least partially side by side and one above the other.

4. Method according to one of the preceding steps, wherein at least one layer printing step is followed by a curing step.

5. Method according to one of the preceding claims, wherein the three-dimensional optical component comprises a section of convex shape.

6. Method according to claim 5, wherein the convex section is built up in consecutive layer printing steps, wherein the surface area of a printed layer is larger or equal to the surface area of the previously printed layers.

7. Method according to one of the preceding claims, wherein the three-dimensional optical component comprises a convex lens.

8. Method according to one of the preceding claims, wherein a third layer is printed in a third layer printing step and a fourth layer is printed in a fourth layer printing step at least partially on top of the third layer such that the fourth layer encloses the third layer or such that the fourth layer does not enclose the third layer, depending on a random algorithm.