Transparent component with a functionalised surface

Abstract

The invention relates to a transparent component (1) with a functionalised surface, wherein the surface has dimples (2) and laser-induced periodic surface structures (3), and is functionalised by the dimples (2) and the laser-induced periodic surfaces structures (3), wherein the dimples (2) and the laser-induced periodic surface structures (3) spatially overlap and wherein the dimples (2) have a depth between 100nm und 2000nm.

Description

[0001] Transparent component with a functionalized surface

[0002] Technical area

[0003] The present invention relates to a transparent component with a functionalized surface.

[0004] State of the art

[0005] It is known that laser material processing can remove material from a component by vaporizing the material within the focus zone of the laser beam through a strong light-matter interaction. The resulting structures, called dimples, are called depressions.

[0006] It is also known that so-called laser-induced periodic surface structures (LIPSS) can be generated by successive interaction of the same material region with at least two laser pulses.

[0007] Dimples and LIPSS are suitable for functionalizing the surfaces of components, whereby optical properties, wetting properties and tribological properties in particular can be influenced.

[0008] From DE 10 2017 006 358 A1 a method for producing a structured surface on a substrate is known, in which surface structures with dimensions in the sub-micrometer range are produced by treatment with an intense pulsed laser beam.

[0009] EP 2692 855 B1 discloses a device for cell biological and / or medical applications, wherein the device has at least one surface that at least partially has a surface structure generated by electromagnetic radiation, which has a microstructure superimposed by a nanostructure. Furthermore, C. Kunz, "Selective Production of Multifunctional Surfaces Using Laser-Induced Periodic Surface Structures," dissertation, Friedrich Schiller University Jena, 2021, discloses a laser-based surface modification of a quartz glass by LIPSS.

[0010] Description of the invention

[0011] Based on the known prior art, it is an object of the present invention to provide an improved transparent component with a functionalized surface.

[0012] The problem is solved by a transparent component having the features of claim 1. Advantageous further developments emerge from the subclaims, the description, and the figures.

[0013] Accordingly, a transparent component with a functionalized surface is proposed, wherein the surface has dimples and LIPSS, thereby functionalizing the surface. According to the invention, the dimples and the LIPSS spatially overlap.

[0014] The transparent material of the component can be a material such as a polymer or plastic. The material to be processed can also be a semiconductor, for example, an elementary semiconductor such as silicon or germanium, or a III-V semiconductor such as gallium arsenide, or an organic semiconductor, or any other type of semiconductor.

[0015] For example, the material can be a silicon wafer. In particular, the material can be a layer system, with each layer being selected from the group of metals, polymers, plastics, or semiconductors. In particular, the material can also be a glass, for example, sapphire or quartz glass.

[0016] Transparent can mean that the component is optically transparent, i.e., transparent to wavelengths visible to the human eye. For example, the material can transmit more than 80%, more than 85%, more than 90%, more than 95%, or more than 99% of visible light. Transparent can also mean that the material is transparent to the wavelength of a processing laser.

[0017] The dimples and the LIPSS can be manufactured using a laser processing method. A laser provides the laser pulses of the laser beam, with the individual laser pulses forming the laser beam in the beam propagation direction. The pulse duration of the laser pulses can be between 300 fs and 10 ps, ​​and / or the wavelength of the laser pulses can be between 300 nm and 3000 nm, preferably between 900 nm and 2200 nm.

[0018] This allows a laser wavelength to be selected at which the material is transparent, allowing the dimples and the LIPSS to be introduced into the material via a nonlinear interaction. Furthermore, the short pulse duration prevents unwanted heating of the material, which counteracts the formation of the LIPSS.

[0019] In addition, the laser can have a linear polarization, for example the degree of polarization of the laser beam can be more than 80%, preferably more than 95%.

[0020] Instead of individual laser pulses, the laser can also provide laser bursts, with each burst comprising the emission of several laser pulses. For a specific time interval, the laser pulses can be emitted very closely one after the other, at intervals of a few picoseconds to nanoseconds. Laser bursts can, in particular, be GHz bursts, with the sequence of consecutive laser pulses in the GHz range. For example, a burst can comprise between 2 and 10 laser pulses, with the time interval between the laser pulses being between 10 ns and 50 ns. However, a burst can also comprise between 30 and 300 laser pulses, with the time interval between the laser pulses being between 100 ps and 1000 ps.

[0021] For example, the length of the laser pulses can be between 100ps and 100ns, in particular between 1 ns and 20ns, wherein the wavelength can be between 300nm and 550nm, in particular 355nm, wherein the repetition rate of the laser pulses can be between 10kHz and 100kHz, in particular between 10kHz and 50kHz, wherein the laser pulses can have an energy between 60pJ and 300pJ and 1 to 4 pulses can be emitted per spot.

[0022] For example, the length of the laser pulses can be between 200 fs and 1000 fs, in particular between 300 fs and 450 fs, wherein the wavelength can be between 900 nm and 2300 nm, in particular 1030 nm, wherein the repetition rate of the laser pulses can be between 10 kHz and 400 kHz, wherein the laser pulses are emitted in laser bursts, wherein each laser burst can contain between 2 and 4 laser pulses, wherein the laser bursts can have an energy between 100 pJ and 400 pJ and the numerical aperture can be between 0.01 and 0.2, in particular 0.08.

[0023] The laser pulses are introduced into the material, whereby the energy of the laser beam is at least partially absorbed in the material, for example by nonlinear interactions, in particular by multiphoton processes.

[0024] The focus of the laser beam can be located above the surface of the material to be processed in the direction of beam propagation or below the surface within the volume of the material to be processed. The focus position can also be exactly on the surface of the material to be processed. In particular, the focus position can be within ten times the Rayleigh length from the surface, where the Rayleigh length is the distance along the optical axis that a laser beam needs for its cross-sectional area to double, starting from the beam waist or focus.

[0025] In particular, the term "focus" can generally be understood as a targeted intensity increase, whereby the laser energy converges into a "focus region." Therefore, the term "focus" is used below regardless of the actual beam shape used and the methods used to achieve the intensity increase. "Focusing" can also influence the location of the intensity increase along the beam propagation direction. For example, the intensity increase can be point-like, and the focus region can have a Gaussian intensity cross-section, as provided by a Gaussian laser beam. The intensity increase can also be linear, resulting in a Bessel-shaped focus region around the focus position, as can be provided by a non-diffracting beam.Furthermore, other more complex beam shapes are possible whose focus position extends in three dimensions, such as a multi-spot profile of Gaussian laser beams and / or non-Gaussian intensity distributions.

[0026] The absorbed energy of the laser beam heats the material according to the intensity distribution of the laser and / or enters a temporary plasma state due to the electromagnetic interaction of the laser with the material. In particular, in addition to linear absorption processes, non-linear absorption processes can also be used, which become accessible through the use of high laser energies or laser intensities. The material is therefore modified particularly at the focus of the laser, since this is where the intensity of the laser beam is greatest. In particular, this can result in part of the material being released from the composite material, for example by melting or evaporating it. This enables known processing processes regarding the interaction between the laser light and the material to be processed, such as laser drilling, percussion drilling or laser ablation.

[0027] The interaction of the laser pulses with the material to be processed creates dimples on the surface of the transparent component.

[0028] A dimple is created by the evaporation of material on the surface due to the incident laser intensity. The material is evaporated particularly where the intensity of the laser beam exceeds a critical, material-specific processing threshold. Accordingly, the shape and form of the laser beam, in particular the beam profile, are crucial for the shape and form of the dimple. In the simplest case, the laser beam is a Gaussian laser beam with a Gaussian beam profile. Around the focal point there is a certain spatial region in which the laser energy lies above the critical threshold. In other words, there is an isointensity area in the intensity distribution of the laser beam at the focus within which the material can be evaporated. This isointensity area determines the shape and form of the dimple.

[0029] In particular, dimples can have a round or elliptical cross-section in the plane of the material surface, with the dimples increasing in depth from the edge to the center. In particular, the cross-section of the dimples in the plane perpendicular to the surface can also be round or rounded.

[0030] By introducing dimples onto the surface of the material, the optical properties of the material can be determined, for example, by scattering light passed through a transparent material at the dimples, thus making the material appear diffuse and / or matte. In particular, dimples on the surface of the material can suppress reflection from the material.

[0031] The dimples can be randomly arranged on the surface.

[0032] A random arrangement can occur if the spatial distances between the dimples are randomly sized. The spatial distances result, for example, from the center-to-center distances or the minimum distances from dimple edge to dimple edge.

[0033] In particular, the spatial distribution of the dimples, including their size, results in a spatial frequency distribution of the dimples via a Fourier transformation. The more irregular the spacing of the dimples, the wider the bandwidth of the spatial frequency distribution and the more diffusely an incident light beam is reflected by the transparent component.

[0034] In particular, "randomly arranged" can therefore mean that the dimples are randomly distributed in spatial frequency domain. By visualizing the position of the dimples in spatial frequency domain, it is also possible to identify potential spatial directions along which interference of the reflected or transmitted light could occur, thus optimizing the arrangement.

[0035] Randomly distributed can also mean that the spatial distribution of the dimples follows a random distribution, for example a uniform distribution, a Gaussian distribution, a triangular distribution, or another statistical distribution. This has the advantage that the dimples are introduced into the material at irregular intervals from one another, so that disruptive optical effects such as interference are reduced or avoided. In this case, for example, the at least two laser pulses of a burst can spatially overlap. For example, each laser pulse can generate a dimple on its own, while so-called LIPSS are generated in the overlap. This happens when an excited plasmonic state is present in the first dimple, with which the second laser pulse can interact, causing the heated material to orient itself along the electric field of the laser pulse.

[0036] The combination of dimples and LIPSS leads to a complex functionalization of the surface of the transparent component.

[0037] For example, the type and shape of the dimples, as well as their distribution on the surface of the component, can be used to adjust the feel or roughness. It is also possible to adjust the light scattering and thus the optical properties of the material.

[0038] The size of the LIPSS, however, can be used to further functionalize the surface. For example, LIPSS can adjust the wetting properties of a surface by changing the contact angle between a liquid and the material. Furthermore, tribological properties of the material can be modified, for example, adjusting the lubricity of the material.

[0039] The combination of dimples and LIPS allows the surface of the transparent component to be optically and mechanically functionalized.

[0040] The dimples can have a depth between 100nm and 2000nm, preferably between 200nm and 1000nm.

[0041] This makes it particularly advantageous to adjust the roughness of the surface, while avoiding extensive weakening of the material.

[0042] The dimples can have a diameter between 3pm and 25pm, preferably between 3pm and 10pm.

[0043] This allows the diameter to be adjusted particularly advantageously to the microstructure required for functionalization.

[0044] The dimples can vary in size from 5% to 80% of their diameter. For example, if the size variation is 50% and the dimple diameter is 20 μm, the dimples can have diameters between 10 μm and 30 μm on the surface.

[0045] The LIPSS can have a periodicity between 40nm and 1000nm, preferably between 50nm and 300nm.

[0046] The periodicity is determined by the average distance between two neighboring valleys or peaks in the profile of a LIPSS. The periodicity can be used to particularly advantageously adjust the functionalization of the surface. For example, a LIPSS can have a periodicity of 100nm for the medical field, so that the surface has a particularly hydrophobic effect. A surface treated in this way can therefore be used particularly advantageously in endoscopes or laryngoscopes, for example, so that the correspondingly treated surfaces have a liquid-repellent effect and accordingly, when used inside the body, for example, allow a clear view into the interior of the body. In particular, such a functionalized surface is therefore particularly suitable for use in medical devices that allow optical access to the interior of the body.

[0047] The roughness of the transparent component can be between 0.05pm and 1.5pm.

[0048] This can create a particularly high-quality haptic impression of the surface.

[0049] Surface roughness can be defined as a peak-to-valley value, i.e., the distance from the highest elevation to the lowest depression. However, roughness can also be defined as the standard deviation of the depth of the dimples.

[0050] The area filling of the surface with dimples can be between 20% and 95%.

[0051] The surface fill is determined by the ratio of the surface area processed by the dimples to the total surface area of ​​the transparent component. Depending on the desired roughness or functionalization, the surface fill can be adjusted.

[0052] In particular, when machining the surface, the dimples can also be introduced successively or in several passes, whereby the surface coverage is successively increased, thereby reducing distortion or smearing of the dimples.

[0053] In particular, at least two dimples can spatially overlap. Spatial overlap can mean that the dimples touch at the edge, or that the dimples partially overlap, meaning that a surface intersection of the dimples exists.

[0054] The LIPSS can cover the dimples by less than 90%.

[0055] For example, the LIPSS can be centered in the dimple. For example, a dimple can have a diameter of 10 μm, whereas the LIPSS are only found in a surface area with a diameter of 9 μm.

[0056] However, it is also possible that two or more dimples overlap and LIPSS are formed only in the spatial overlap.

[0057] In a preferred embodiment, the transparent component has dimples, wherein the dimples have a depth between 100 nm and 2000 nm, a diameter between 3 pm and 25 pm and a size variation to the diameter between 5% and 80%, wherein the laser-induced periodic surface structures have a periodicity between 40 nm and 1000 nm and the roughness of the functionalized surface is between 0.05 and 1.5 pm, wherein the area filling with dimples is between 20% and 95% and wherein the laser-induced periodic surface structures cover the dimples to less than 90%.

[0058] In a particularly preferred embodiment, the transparent component has dimples, wherein the dimples have a depth between 200 nm and 1000 nm, a diameter between 3 pm and 10 pm and a size variation to the diameter between 5% and 80%, wherein the laser-induced periodic surface structures have a periodicity between 50 and 300 pm and the roughness of the functionalized surface is between 0.05 and 1.5 pm, wherein the area filling with dimples is between 20% and 95% and the laser-induced periodic surface structures cover the dimples to less than 90%.

[0059] In a further particularly preferred embodiment, the dimples have a diameter between 13 pm and 20 pm, wherein the laser-induced periodic surface structures have a periodicity between 650 nm and 1000 nm.

[0060] Short description of the characters

[0061] Preferred further embodiments of the invention are described in the following

[0062] Description of the figures explained in more detail. Showing:

[0063] Figure 1 shows a scanning electron microscope image of a dimple with LIPSS; Figure 2 shows a scanning electron microscope image of two overlapping dimples with LIPSS; and

[0064] Figure 3 shows a schematic representation of the spatial overlap of two dimples using LIPSS; and

[0065] Figure 4 shows a schematic representation of the spatial overlap of two dimples with LIPSS in the overlap.

[0066] Detailed description of preferred embodiments

[0067] Preferred embodiments are described below with reference to the figures. Identical, similar, or equivalent elements in the different figures are provided with identical reference numerals, and a repeated description of these elements is partially omitted to avoid redundancies.

[0068] Figure 1 shows a scanning electron microscope image of a dimple 2 with LIPSS 3 on a transparent component 1. The dimple 2 has a diameter of 25 μm and a depth of 200 nm. Furthermore, the dimple 2 contains LIPSS 3, which can be seen as a wave-like pattern. Such dimples 2 can be created, for example, by applying at least two laser pulses, for example, two laser pulses from a Burt, consecutively to the same location on the component 1.

[0069] Figure 2 shows a scanning electron microscope image of two overlapping dimples 2, each of which already has LIPSS 3. In the overlap 30 of the two dimples 2, the dimples 2 intensify, resulting in a variation in depth. Furthermore, the LIPSS 3 also overlap, resulting in a variation in the LIPSS through the spatial addition of the wave-like pattern. This allows for a particularly fine adjustment of the surface's functionalization.

[0070] Figure 3 shows a schematic representation of two dimples 2. The dimples 2 have different sizes, for example, 25 pm and 15 pm. Both dimples 2 are generated, for example, with two laser pulses from a laser burst, so that LIPSS 3 are generated inside the dimples 2 (see Figure 2). The LIPSS overlap in the spatial overlap 30 of the dimples 2 and can thus amplify each other.

[0071] Figure 4 shows a schematic representation of two dimples 2, each generated from a single laser pulse. A first laser pulse has thus generated a first dimple 2, while a second laser pulse has generated a second dimple 2. In the spatial overlap of the dimples 2, the second laser pulse can then interact with the plasmonic state created by the first laser pulse. Accordingly, corresponding LIPSSs can only be formed in the overlap. Dimples 2 and LIPSSs 3, for example, generate advantageous optical and tribological properties of the surface of the transparent component.

[0072] Where applicable, all individual features presented in the embodiments may be combined and / or exchanged without departing from the scope of the invention.

[0073] List of reference symbols

[0074] 1 transparent component

[0075] 2 dimples

[0076] 3 LIPSS 30 Overlap

Claims

Claims 1. Transparent component (1) with a functionalized surface, wherein the surface has dimples (2) and laser-induced periodic surface structures (3) and is functionalized by the dimples (2) and the laser-induced periodic surface structures (3), characterized in that the dimples (2) and the laser-induced periodic surface structures (3) spatially overlap and that the dimples (2) have a depth between 100 nm and 2000 nm.

2. Transparent component according to claim 1, characterized in that the dimples (2) have a depth between 200nm and 1000nm.

3. Transparent component according to one of claims 1 or 2, characterized in that the dimples (2) have a diameter between 3pm and 30pm, preferably a diameter between 3pm and 10pm.

4. Transparent component according to one of the preceding claims, characterized in that the dimples (2) have a size variation to the diameter between 5% and 80%.

5. Transparent component according to one of the preceding claims, characterized in that the laser-induced periodic surface structures (3) have a periodicity between 40 nm and 1000 nm, preferably a periodicity between 50 nm and 300 nm.

6. Transparent component according to one of the preceding claims, characterized in that the roughness of the functionalized surface is between 0.05 and 1.5 pm.

7. Transparent component according to the preceding claim, characterized in that the surface filling with dimples (2) is between 20% and 95%.

8. Transparent component according to one of the preceding claims, characterized in that the dimples (2) are arranged randomly on the surface.

9. Transparent component according to one of the preceding claims, characterized in that at least two dimples spatially overlap. Transparent component according to one of the preceding claims, characterized in that the laser-induced periodic surface structures (3) cover the dimples (2) to less than 90%.

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