Laser nanostructuring for highly transparent anti-fog glass

Abstract

Methods are disclosed for the use of lasers to achieve stable superhydrophilicity in solid surfaces (3) transparent to the visible spectrum, coatings, and devices using solids transparent to the visible spectrum and ultrashort laser pulses (2). The laser is used to shape the surface of a transparent solid material (3) and generate desired nanostructured patterns on the surface without adversely affecting or increasing the transparency of the material, resulting in anti-fogging properties in high humidity environments. More specifically, methods and devices for providing stable anti-fogging effects to solids transparent to the visible spectrum (3) and devices using laser nanostructured solids transparent to the visible spectrum (3) are disclosed.

Description

[Technical field]

[0001] Superhydrophilic / antifog coatings on transparent solids have been used to improve visibility in humid environments or to enhance the performance of transparent media for optoelectronic and electrooptical devices. Coatings suitable for this purpose are those that reduce the contact angle of a water droplet formed on the surface by ambient humidity sufficiently to form a thin layer of water. This thin layer of water has a uniform surface morphology compared to a water droplet, thereby reducing blurring over a wide spectral range of light. [Background technology]

[0002] Anti-fog coatings can be formed by coating the surface of a transparent solid of interest by applying a series of chemical compounds to form one or more thin layers on the transparent material. As a result, the coated surface has enhanced wettability due to the hydrophilic chemical groups selected to terminate the surface. The use of hydrophilic chemical coatings can have adverse environmental effects due to chemical waste generated during manufacture or application. Furthermore, chemical coatings lack stability over time, eventually causing a degradation of their performance and even a complete loss of their functionality under harsh environmental conditions. Last but not least, hydrophilic coatings can adversely affect the optical properties of substrates that are transparent to visible light under conditions of no moisture. Adverse effects include, but are not limited to, translucency and coloration. Summary of the Invention

[0003] The objective of the present invention is to provide a simple and efficient method to generate superhydrophilic surfaces on solid materials transparent to the visible spectrum without affecting or even increasing the transparency of the substrate transparent to the visible spectrum. By machining solids transparent to the visible spectrum with a laser, periodic nanostructures can be generated on the surface, resulting in an enhanced surface roughness and a hydrophilic surface with anti-fogging properties. The proposed technology is a single-step process that can be easily integrated into the industry using high-power and highly reproducible industrial laser sources.

[0004] In particular, a method for shaping the surface of a glass-like material to achieve superhydrophilicity and anti-fogging properties is disclosed. The method includes preparing a solid material transparent to the visible spectrum on a holder. The method may employ an additional heat dissipation layer on the surface of the solid transparent to the visible spectrum, which can absorb excess heat generated by a laser beam impinging on the transparent solid. The method includes identifying a desired target nanostructure anti-fogging pattern on a surface of the solid material transparent to the visible spectrum; identifying a desired focus spot distribution on a surface of the solid material transparent to the visible spectrum; identifying a melting point of the solid material transparent to the visible spectrum; selecting a laser fluence value from a range of laser fluence values; selecting a wavelength, pulse duration, and repetition rate of laser pulses from respective ranges of wavelength, repetition rate, and pulse duration; selecting a number of consecutive laser pulses delivered per focal spot on the laser surface; exposing a surface of the solid material transparent to the visible spectrum to focused laser radiation having a selected wavelength, repetition rate, pulse duration, and number of consecutive laser pulses to raise a temperature of the transparent material to near the melting point to shape at least a portion of the surface to generate at least a portion of the desired target nanostructured pattern; and translating the transparent solid material relative to a laser beam to scan the surface with the beam to generate the desired nanostructured pattern across the surface of the transparent solid.

[0005] By processing the transparent solid surface with laser pulses, self-assembled nanostructures can be formed. The formation of these structures increases the surface roughness compared to the initial planar structure, while maintaining transparency to the visible spectrum due to the small scale of the structures. For example, glass surfaces are inherently hydrophilic because the surface is terminated with hydrophilic groups such as hydroxyl and metal oxides. These species interact strongly with water due to their inherent polarity, and when the free energy of the entire system is minimized, water droplets that may come into contact with these surfaces spread out and the droplet contact angle decreases. Therefore, increasing the surface roughness of an inherently hydrophilic material increases its hydrophilicity according to the well-known Wenzel model.

[0006] In some examples, the surface of a solid material transparent to the visible spectrum is exposed to focused polarized laser radiation. Irradiating the transparent solid with a polarized laser beam results in the formation of nanostructures in all directions within a Gaussian focal spot, ultimately resulting in the texturing of the treated surface with nanospikes. The nanostructures can be quasi-periodic and randomly distributed along the surface. Such surface nanotexturing significantly increases the surface area and enhances hydrophilicity, thus providing anti-fog properties. In some examples, it can simultaneously result in improved transparency and anti-reflection properties [PCT / GR2018 / 000010].

[0007] In some examples, specifying a desired number of focused pulses to be received on the surface of the transparent solid material can include specifying a preselected percentage overlap of adjacent focused spots, The preselected overlap percentage can be 99.9% or less.

[0008] In some examples, the method may further include scanning and / or rastering the laser beam on a stationary transparent solid material. By scanning multiple times with a small number of pulses (e.g., 3-5) per pass at high speed, the material melts and resolidifies, resulting in very small surface roughness without the formation of structures. The scanning process may be set to about the spot diameter.

[0009] In some examples, the transparent solid material may include at least a piece of glass. The piece of glass may be present on an electronic device. The electronic device may include a solar cell (SC), an automotive display, an electronic screen, a light emitting diode (LED), and / or a light detection and ranging (LiDAR) sensor.

[0010] In some examples, the wavelength of the incident beam can be selected from 100 nm to 6100 nm, which can depend on the material to be molded and the desired target features of the nano-texture pattern.

[0011] In some examples, the laser fluence or peak fluence is 12 J / cm 2 ~0.2J / cm 2 The repetition rate of the laser pulses can be any value and the pulse duration can be chosen up to 800 ps. The combination of these parameters can depend on the nanostructure features to be formed and the melting point of the material.

[0012] In another aspect, a manufacturing configuration is disclosed for shaping a surface of a solid material transparent to the visible spectrum to achieve anti-fog properties. The manufacturing configuration may integrate a pulsed laser source and an optical system for focusing a beam emitted from the pulsed laser source. The manufacturing configuration may further include a holder configured to hold the transparent solid material. The manufacturing configuration may include a controller for setting a laser fluence value from a range of laser fluence values, setting a laser pulse wavelength, a laser pulse repetition rate, and a laser pulse duration from a range of laser pulse wavelengths, repetition rates, and durations, respectively, setting a number of consecutive laser pulses emitted per focused laser spot on the surface, and setting a relative translation sequence between the transparent solid material and a laser beam from a pulsed laser source to scan the transparent material surface to generate a desired nanostructured pattern.

[0013] In some examples, the optical system may include at least a mirror to direct a laser beam from a pulsed laser source towards the transparent solid material, and a focusing optical element to focus the laser beam on the transparent solid material.

[0014] In some examples, the pulsed laser source may be a picosecond or femtosecond laser source.

[0015] In some examples, the translation module may be used to move the transparent solid material holder while the illumination module remains stationary. In other examples, the optical system may be configured to move the laser beam while the transparent solid material holder remains stationary. In yet other examples, the translation module may be configured to move the illumination module while the transparent solid material holder remains stationary.

[0016] In another aspect, an anti-fog solid material is disclosed that is transparent to the visible spectrum. Also disclosed is the use of an optional additional material layer deposited on the surface of the solid material prior to laser treatment. The additional layer acts as a heat sink and is removed by the laser beam during irradiation, again resulting in nanostructuring of the solid surface. The anti-fog transparent solid material may be molded using the molding method according to the examples disclosed herein, and the additional heat sink layer may be a common paint, ink, dye, metallic paint, etc.

[0017] In yet another aspect, an anti-fog solid material transparent to the visible spectrum may be molded using the molding method according to the examples disclosed herein, further using a secondary heat or optical heating source during irradiation.

[0018] In yet another aspect, a device is disclosed, the device may include an anti-fog transparent solid material according to examples disclosed herein.

[0019] In yet another aspect, a system is disclosed for shaping a surface of a solid material transparent to the visible spectrum to achieve anti-fog properties and simultaneously reduce reflections from the surface of the transparent material. The system may include means for providing a solid material transparent to the visible spectrum on a holder; means for depositing a heat absorption layer on a transparent solid surface; means for specifying a desired target nanostructured anti-fog pattern on a surface of the transparent solid material; means for specifying a desired focal spot distribution on a surface of the transparent solid material; means for specifying a melting point of the transparent solid material; means for setting a laser fluence value from a range of laser fluence values; means for setting a wavelength, a repetition rate, and a pulse duration from respective ranges of wavelengths, repetition rates, and pulse durations; means for setting a number of consecutive laser pulses to be applied per focal spot on the laser surface; means for exposing a surface of the transparent solid material to focused laser radiation having a selected wavelength, repetition rate, pulse duration, and number of consecutive laser pulses to raise a temperature of the transparent material to near its melting point to shape at least a portion of the surface and generate at least a portion of the desired target nanostructured pattern; and means for relatively translating the transparent solid material to generate the desired nanostructured pattern.

[0020] In yet another aspect, a non-transient computer program product is disclosed for causing an irradiation configuration to shape a surface of a transparent solid material, which may include instructions for providing the transparent solid material on a holder, instructions for specifying a desired target nanostructured pattern on a surface of the transparent solid material, instructions for specifying a desired focal spot distribution on a surface of the transparent solid material, instructions for specifying a melting point of the transparent solid material, instructions for selecting a laser fluence value from a range of laser fluence values, instructions for selecting a wavelength, a repetition rate, and a pulse duration from respective ranges of wavelengths, repetition rates, and pulse durations, instructions for selecting a number of consecutive laser pulses to be applied per focal spot on the laser surface, instructions for exposing the surface of the transparent solid material to focused laser radiation having a selected wavelength, repetition rate, pulse duration, and number of consecutive laser pulses to raise a temperature of the transparent material to near its melting point to shape at least a portion of the surface and generate at least a portion of the desired target nanostructured pattern, and instructions for relatively translating the transparent solid material or the laser beam to generate the desired nanostructured pattern.

[0021] In yet another aspect, a computer program product is disclosed that may include program instructions for causing an illumination arrangement to perform a method of shaping a surface of a solid material transparent to the visible spectrum according to examples disclosed herein.

[0022] The computer program product may be embodied on a storage medium (e.g., CD-ROM, DVD, USB stick, on a computer memory or on a read-only memory) or may be transmitted on a carrier signal (e.g., an electrical or optical carrier signal).

[0023] The computer program may be in the form of object code, such as in source code, object code, code intermediate source and partially compiled form, or in any other form suitable for use in the implementation of a process. The carrier may be any object or device capable of carrying a computer program.

[0024] For example, the carrier may comprise a storage medium, such as a ROM, e.g. a CD-ROM or a semiconductor ROM, or a magnetic recording medium, e.g. a hard disk. Further, the carrier may be a transmissible carrier, such as an electric or optical signal, which may be conveyed via electric or optical cable, or by radio or other means.

[0025] When the computer program is embodied in a signal which may be conveyed directly by a cable or other device or means, the carrier may be constituted by such cable or other device or means.

[0026] Alternatively, the carrier may be an integrated circuit in which the computer program is embedded, the integrated circuit being adapted for performing, or for use in the performance of, the subject method.

[0027] Non-limiting examples of the present disclosure are described below with reference to the accompanying drawings. [Brief description of the drawings]

[0028] [Figure 1] FIG. 1 shows, as an example, a schematic diagram of the process of nanostructure formation after laser irradiation by method 1 on bare glass and method 2 with an additional heat-absorbing layer. [Diagram 2] Figure 2 shows a schematic diagram and actual images of the hydrophilic and anti-fogging effects of glass in a foggy environment. [Diagram 3]FIG. 3 shows contact angle measurements over time for two representative glass types, as well as transmittance measurements on bare and laser nanostructured surfaces.

[0029] FIG. 1 shows a schematic representation of the process of nanostructure formation (1) after one or multiple scans according to methods 1 and 2. In the case of method 1, an ultrafast laser pulse (2) is irradiated onto a solid (3) transparent to the visible spectrum. The irradiation conditions may vary depending on the type of material, and the whole process may be achieved in one or multiple laser scans. In the case of method 2, an additional layer (4) may be roughly deposited on the glass surface prior to irradiation, acting as a heat dissipation layer (4) for uniform nanostructuring of the glass surface. The nature of the additional layer can be either metallic or organic (i.e. metallic paint, black matrix, ink, powder), and its thickness is irrelevant for the whole process, considering that it is eventually ablated by the laser pulse. Once the layer is completely removed by the laser, the underlying glass surface is morphologically nanostructured (5). The use of an additional layer is optional and may only be used in the case of certain types of glass.

[0030] Figure 2 shows real images showing a characteristic example of the anti-fogging effect caused by laser nanostructuring using either method 1 or 2 mentioned above. The top schematic is a real illustration of a water droplet (6) in contact with the surface of bare glass (3) and laser nanostructured glass (5). The bottom picture shows the surface state of fused silica glass, half of which (right side) (5) has been laser treated, under water mist spray conditions. Note that the wettability of different types of glass is slightly different. However, the laser nanostructuring always has the same effect.

[0031] Figure 3 shows the wetting response plots for bare fused silica and Eagle glass substrates, as well as laser nanostructured surfaces for both glasses. Contact angle measurements were performed with distilled water for 100 days. Specifically, 2 μl water droplets were used. Samples were stored at room temperature between measurements. It is clear that water contact is significantly reduced after laser nanostructuring, with less than 10 degrees for each glass over the 100 days of measurements. As described in the specification, the remarkable superhydrophilicity is the reason why the nanostructured surfaces achieve anti-fogging properties in extremely humid environments. Furthermore, the transmittance of the same glass surfaces that exhibit anti-fogging properties increases steadily over most, if not all, of the visible spectrum. The exact transmittance values ​​are shown in the right figure.

Claims

1. 1. A method of shaping a surface of a transparent solid material to improve its hydrophilicity without affecting its optical transparency in the visible light spectrum, the method comprising the steps of: Providing the transparent solid material on a holder; Identifying a desired target nanostructure anti-fogging pattern on the surface of the transparent solid material; Identifying a desired focused laser spot area on the surface of the transparent solid material; selecting a laser fluence value from a range of laser fluence values; selecting a wavelength, a repetition rate, and a pulse duration of a laser pulse from a range of wavelengths, repetition rates, and pulse durations, respectively; exposing a surface of said transparent solid material to focused laser radiation having a selected wavelength, repetition rate and pulse duration to generate at least a portion of a desired target nanostructured pattern; translating the transparent solid-state material relative to a laser beam and directing the laser beam across the surface of the transparent solid-state material to generate a desired nanostructured pattern; A molding method comprising the steps of:

2. The method of claim 1 further comprising scanning the laser beam over a stationary transparent solid material.

3. The molding method according to claim 1 , wherein the transparent solid material comprises at least a piece of glass or crystal.

4. The molding method of claim 1 , wherein the transparent solid material comprises at least a piece of plastic or polymer.

5. 5. The molding method of claim 4, wherein molding the transparent solid material comprises molding a piece of glass on an electronic device, the electronic device comprising a solar cell (SC), an automobile display, a screen, a light emitting diode (LED), and a light detection and ranging (LIDAR) sensor.

6. The molding method according to claim 1, wherein the wavelength is selected from the range of 100 nm to 6100 nm.

7. The molding method of claim 1 , wherein the pulse duration is selected from up to 800 ps.

8. The laser fluence value is 12 J / cm ２ ~0.2 J / cm ２ The molding method according to claim 1 , wherein the range is selected from the range of

9. A manufacturing arrangement for forming a surface of a transparent solid material with an additional layer of material thereon to improve hydrophilicity without affecting the light transmission of the transparent solid material, comprising: An illumination module; A translation module; means for depositing said additional layer of material on a transparent solid surface; A controller, The illumination module includes: A pulsed laser source; and an optical system for focusing a laser beam from the pulsed laser source. the translation module includes a holder configured to stably hold or translate the transparent solid material; The controller: Set the laser fluence value from the range of laser fluence values, Setting a laser pulse wavelength, a laser pulse repetition rate, and a laser pulse duration from a range of laser pulse wavelengths, repetition rates, and durations, respectively; and configuring a relative translational motion between the transparent solid material and the laser beam during laser beam exposure by the laser beam from the pulsed laser source to generate a desired nanostructured anti-fog pattern.

10. 10. The manufacturing configuration of claim 9, wherein the optical system includes at least a mirror to direct the laser beam from the pulsed laser source to the transparent solid material and at least a focusing optical element to focus the laser beam on the transparent solid material.

11. The manufacturing configuration of claim 9 , wherein the pulsed laser source is a picosecond or femtosecond laser source.

12. 10. The manufacturing arrangement of claim 9, wherein the translation module is configured to move the transparent solid material holder while keeping the irradiation module stationary, and / or the irradiation module is configured to move the laser beam while keeping the transparent solid material holder stationary, and / or the translation module is configured to move the irradiation module while keeping the transparent solid material holder stationary.

13. 13. A computer program comprising instructions for controlling a manufacturing arrangement according to any one of claims 9 and 12 to carry out the steps of the method according to claim 1.

14. 14. A computer program as claimed in claim 13, transmitted on a carrier signal or stored on a computer readable medium.

15. 10. A device comprising a solid material transparent in the visible light spectrum surface-modeled using the method of claim 1 or the manufacturing setup of claim 9, wherein the surface of the solid material has a self-assembled nanostructure that exhibits increased surface roughness compared to before the surface modeling and maintains transparency in the visible spectrum.

16. A method for producing an anti-fogging transparent solid material, comprising forming a surface of a solid material transparent in the visible light spectrum by the forming method of claim 1.

Images