Method to enhance transmissivity of transparent solids and glasses and devices with transparent solids and glasses

Abstract

The method suggests coating the transparent solid with an additional laser radiation absorptive layer of material and then laser texture the coated solid to attain a nanostructured transparent solid with increased transmissivity while the additional coating 5 is removed. This method is applicable but not limited to a substrate transparent solid like glasses of silicate composition, such as fused silica, borosilicates, aluminosilicates, alkali aluminosilicates, float glasses, crown glass, amorphous sapphire etc., crystals, for example crystalline sapphire, laser active medium crystals etc. and polymers, for example polycarbonate, plexiglass etc. It is also applicable to substrates coated with a thin film of 0 above mentioned materials.

Description

[0001] Method to enhance transmissivity of transparent solids and glasses and devices with transparent solids and glasses.

[0002] The present invention refers to transparent solids.

[0003] Laser nanotexturing on transparent solids is an emerging technology that modifies the surface of the solid in such a way that the nanotextured material gains new functionalities that are attributed to the attained nanotexture.

[0004] In principle, applying laser irradiation to machine transparent solids which are typically brittle materials, suffers from several drawbacks like limited applicability of the method to some glasses of low thermal expansion, abrupt material cracking and low repeatability of the process. Furthermore, extensive parametric investigations are required to identify the laser parameters that are suitable to laser texture each transparent solid.

[0005] The transmissivity of transparent to the visible spectrum solids is a property that is very important for applications in electronic devices, optics and displays. The increase of the transmissivity of such materials is achieved by applying anti-reflective (AR) organic or inorganic coatings on the transparent glasses or crystals which are usually multi-layered with wet or gas deposition technologies. Other methods involve nano-sculpting of the surface of such materials with methods like chemical or dry etching (plasma, reactive ion etc.). All these methods require the use of chemicals and complex processes. As harsh chemical use is phased out and new regulations are introduced, the push for novel, simpler and more environmentally friendly methods is increasing. Prior art disclosures describe methods of shaping the surface of transparent solid material with laser radiation to create patterns to reduce reflectivity, without altering transmissivity.

[0006] The object of the invention is a method to increase the transmissivity of transparent solids.

[0007] The invention suggests coating the transparent solid with an additional laser radiation absorptive layer of material and then laser texture the coated solid to attain a nanostructured transparent solid with increased transmissivity while the additional coating is removed. This method is applicable but not limited to a substrate transparent solid like glasses of silicate composition, such as fused silica, borosilicates, aluminosilicates, alkali aluminosilicates, float glasses, crown glass, amorphous sapphire etc., crystals, for example crystalline sapphire, laser active medium crystals etc. and polymers, for example polycarbonate, plexiglass etc. It is also applicable to substrates coated with a thin film of above mentioned materials.

[0008] In a first aspect, a method of shaping a surface of a transparent solid material to increase the transmissivity and suppress reflectivity in the optical spectrum is proposed. The method comprises coating the transparent solid with an additional coating film consisting of a single or multiple individual layers; identifying the optimum thickness of the coating; selecting the type of the coating; providing the transparent solid material on a holder; identifying a desired target nanostructure two-dimensional anti-reflection pattern array on the surface of the transparent solid material; identifying a desired focus spot distribution on the surface of the transparent solid material; identifying a melting temperature 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; selecting a number of consecutive laser pulses applied per focus spot on the laser surface; exposing the surface of the transparent solid material to a focused laser radiation with the selected wavelength, repetition rate, pulse duration and number of consecutive laser pulses to raise the temperature of the transparent material to around the melting temperature to shape at least a part of the surface and generate at least part of the desired target nanostructure two-dimensional pattern array; relatively translating the transparent solid material to generate the desired nanostructure two-dimensional pattern array.

[0009] The additional thin layer on transparent solids may be applied before or at the same time in-situ (one step process). The additional coating improves the applicability of the method on all kinds of transparent solids, improves throughput, repeatability and homogeneity, minimizes cracking and material failure. Methods and devices of enhancing the transmissivity while suppressing surface reflection of transparent solids, coatings and devices employing transparent solids are disclosed. Furthermore, the applicant observed that the application of additional sacrificial coatings can be used to enhance glass cutting quality and throughput achieving low edge Chipping Size and low mean Surface Roughness (Ra).

[0010] During shaping, the temperature of the transparent material may be raised around the melting temperature.

[0011] The additional thin coating material type can be an ink dissolved in a solvent, a spray coated colorant, a food colorant, a spray colorant, a screen-printing solvent ink or ceramic ink, a dip coating ink or colorant a digital printing ink or colorant, a polymeric film, an optical adhesive and a paste like thermal paste. Moreover, the sacrificial layer or coating can be consisted of UV or aqueous coating, varnish coating, lamination, thermal lamination, soft touch coating, anti-scratch coating, matte or glossy coating, satin coating and of course metallic or magnetic coating and even granular coating in the form of powder of these materials. Furthermore, the additional coating material can be comprised of multiple layers of different materials and methods of application.

[0012] During shaping the coating is removed. Nanoparticles of the coating may be encapsulated or soldered on the substrate and remain incidentally

[0013] When the coating is hydrophilic (contact angle less or equal 90 deg) the hydrophilicity of the substrate is higher, because it could be enhanced by remnants - residual particles of the coating which incidentally may encapsulated in the substrate and not be removed.

[0014] The application of the thin coating material can be achieved but not limited to, by a pen, marker, brush or airbrush, by screen printing, digital printing, spraying or spray coating, dip coating and vacuum deposition. The thickness of the additional coating film may be selected in a range from 10 nanometers to 5 millimeters. This may depend on the transparent solid to be shaped and on the laser parameters that may be used to texture it.

[0015] The application of the additional layer modifies the transmissivity of the transparent solid material, making it colored, translucent or black. In some other examples, the additional layer does not modify the transmissivity in the visible spectrum of the transparent solid, as in the case of optical adhesives.

[0016] By applying laser radiation on the coated material, the coating is removed and sacrificed in the areas where the laser propagates. This depends on the thickness of the additional layer and on the selected laser parameters.

[0017] In some examples, the additional coating material is applied before laser radiation occurs. In some other examples, the additional coating material is applied in parallel with the laser radiation, i.e. in-situ.

[0018] By processing the coated transparent solid surfaces with laser pulses, self-assembled or Laser Induced Periodic Surface Structures (LIPSS) may be formed while the additional coating is partially or completely removed. The formation of these structures results in the reduction of reflection of the transparent solid surface and in the increase of the transmissivity of the solid surface.

[0019] In another example, the reduced reflection and light scattering can be controlled according to the laser irradiation conditions in order to produce anti-glare effects with variable haze, i.e from 0.0% up to 80% haziness values along with high transmissivity on the glass or crystalline piece or device.

[0020] In another aspect, processing the coated transparent to the visible spectrum solid surface with laser pulses increases the radiation damage threshold of the shaped material's surface. In yet another aspect, a manufacturing configuration to shape a surface of a transparent solid to increase the transmissivity in the optical spectrum is disclosed. The manufacturing configuration may comprise a coating module and an irradiation module. The coating module may include coating material and an integrated application system. The coating system applies the coating material on the transparent solid before or in parallel with the irradiation. This may include a spraying system, air brush system or a screen-printing module. The irradiation module may have a pulsed laser source or multiple sources and an optical system for focusing one or multiple laser beams from the pulsed laser source or sources. The manufacturing configuration may further comprise a holder configured to hold the transparent solid material. The manufacturing configuration may comprise a coating controller to: set the applied volume per area of the coating; set the applied volume rate of the coating; select the coating type or types; set the substrate temperature. The manufacturing configuration may also comprise an irradiation controller to: set a laser fluence value from a range of laser fluence values; set 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; set a number of consecutive laser pulses applied per focus point spot on the laser surface; and set a relative translation sequence of the transparent solid material in a first direction during a laser exposure with a laser beam from the pulsed laser source to generate a desired nanostructure two-dimensional antireflection pattern array.

[0021] In some examples, the method may further comprise scanning and / or rastering the laser beam on a stationary coated transparent solid material. By scanning with multiple scans in high-speed using a small number of pulses (e.g. three to five) per pass the coating is totally removed, the material melts and resolidifies creating a very small surface roughness without any other structural formation. During removal it may happen that residues in the form of nanoparticles of the coating may be soldered on the surface. The step may be set near to the spot diameter. In some examples, the wavelength of the incident beam may be selected from a range of

[0022] 200 nm to 2100 nm. This may depend on the material to be shaped.

[0023] In some examples, the laser fluence may be selected in a range of 0.2 J / cm2to 12 J / cm2. The repetition rate may then be selected from a range of 1kHz to 10MHz and the pulse duration may be selected up to 100 ns. The combination may depend on the thickness and type of the additional coating layer, the laser fluence selected, the height of the nanostructures to be formed and the melting point of the surface material.

[0024] In some examples, the surface of the transparent solid material is exposed to a focused polarized laser radiation. By irradiating transparent solids with polarized laser radiation, nano-ripples may be formed in all directions along a focus spot which eventually leads to nano-spike formation on the treated surface. Laser radiation may be polarized or not polarized. Nano-spike structures are pseudo-periodic and randomly distributed along the surface. The nano-ripples may be formed in all directions along a Gaussian focus spot or along any other spot. The advantage of pseudo-periodic structures is that they present antireflection properties in all plane directions unlike nano-ripples which tend to exhibit antireflection properties when the plane of incident is perpendicular to the direction of nanoripple orientation.

[0025] In some examples, the transparent solid material may comprise at least a glass piece. The glass piece may be on an electronic device or an optic. The electronic device may include a solar cell (SC), a display screen, a glass optical window, a smartphone, a camera cover, a light emitting diode (LED) and / or a sensor, eyeglasses and / or eyewear.

[0026] In some examples the glass piece can be of this type or composition: fused silica coated with an ink via dip coating or a metallic coating, aluminosilicate glass coated with an ink or a glass film via vacuum deposition; borosilicate like BK7 coated via spin coating; sapphire crystal or glass coated via screen printing; a non-linear crystal like LBO, BBO, BiBO and KTP coated via spay coating and soda lime or similar float glass coated with an ink or inorganic layer via spin coating. The following table provide some examples of laser proceed according to this method a variety transparent in the visible spectrum amorphous and crystalline materials.

[0027] As it can be seen, in all above cases the average transmission after laser treatment is above 97% and the haze less than 4%.

[0028] In some examples, the transparent solid material may comprise at least a crystal piece. The crystal piece may be on an electronic device or an optic. The electronic device may include, a laser active medium, an optical conversion crystal, a wristwatch and / or smart watch, eyeglasses and / or eyewear.

[0029] In some examples, the transparent solid material may comprise at least a polymer piece. The polymer piece may be on an electronic device. The electronic device may include a wristwatch and / or smart watch, eyeglasses and / or eyewear and a display.

[0030] In yet another aspect, a super-transparent solid material is disclosed. The super- transparent solid material may be shaped using a method of shaping according to examples disclosed herein and may comprise a nanostructure two-dimensional anti-reflection pattern array on a surface that increases transmissivity.

[0031] Embodiments of the invention are described with reference to Figures 1 to 4: Figure 1 is a cross sectional view through the glass pane (1) without the application of the additional coating layer (a) and with the addition of the sacrificial coating (2) on the top of the glass (b).

[0032] Figure 2 is an illustration of a typical scheme for the laser induced production of the nanostructures using the method according to the disclosed invention in the description.

[0033] Figure 3 is an enlarged view of section A from Figure 2 which shows a cross section through an embodiment of a glass pane according to the invention, of the substrate glass surface with increased transmittivity.

[0034] Figure 4 is a glass pane side view that demonstrates a glass pane 1 that is initially coated with an additional coating 8 and then progressively coated with an additional coating 2 which lies on top of the first coating forming a double layer coating on the glass pane. In this case the multi-layered coated glass pane is structured according to the invented method disclosed in the description.

[0035] Figure 1(a) depicts details of a glass pane designed according to the invention. The pane consists of a substrate 1 composed of glass, crystal or polymer, typically with a thickness of between 10pm to several mm. A sacrificial layer or coating 2, typically made, is uniformly applied across the surface of the substrate 1 (b) with a controlled thickness.

[0036] Figure 2 presents the radiation 4 from a laser device 3 is focused onto the coating 2 and substrate 1 using, for example, an f-theta lens as a focusing element 6. The radiation 4 is circular, purely circularly, linearly or tangentially polarized and has a wavelength of, for example, 513 nm. The laser 3 is operated in pulsed mode with a pulse length in the range of 1 fs-800 ps and a repetition frequency of 1Hz up to 10MHz. The radiation 4 can be moved over the coating 2 by means of a movable or rotating mirror 5. For the sake of simplicity, only a box containing movable mirror 5 is shown just to clarify the principle. Conventional laser scanning systems are typically used that have a larger number of movable mirrors. The radiation 4 is now moved repeatedly over the coating 2 in a grid-like manner and continuously. The coating 2 is thereby successively completely or partially removed, the glass piece is concurrently heated and melted in areas and solidifies again until the next pass.

[0037] In Figure 3 the removal of the additional coating / sacrificial layer 2 is depicted and the substrate restructured. This structure is composed of numerous nanostructures 7 induced into substrate 1 via laser radiation. Essentially, the initially flat surface of substrate 1 is structured through this laser treatment while the additional coating / sacrificial layer 2 is completely or partially removed. These nanostructures are evenly and two-dimensionally distributed across substrates l's surface. Typically, their shape can be approximately circular base area, forming a dome shape or ripple like surface reliefs. Their shape closely resembles a segment of a prolate ellipsoid of revolution, particularly resembling a halfellipsoid of revolution. As a result, the nanostructures 7 are directly formed on the glass substrate 1 removing the additional coating / sacrificial layer 2 almost completely.

[0038] In Figure 4(a) the glass substrate of Figure 1(a) is presented but this time it is coated with a different coating material 8 and is applied over the entire surface of the substrate 1 as presented in Figure 4 (b). The glass pane of Figure 4(b) is therefore coated with a sacrificial layer or coating that is composed of a different composition and thickness compared to Figure 1(b). Additionally, the glass pane of Figure 4(b) can be further coated with an additional coating of a different material and thickness, forming a double layered coating presented in Figure 4(c) which presents the glass pane 1 coated with 8 and 2. This can be repeated several times resulting in a three layers or multi-layer coating of different materials of varying thicknesses. These layered coatings will always be on the top as presented in Figure 4(c). The laser nanotexturing method disclosed in the present invention will result in a nanostructure 9 that this time formed on the glass multilayered coating 2 and 8 and the additional sacrificial layer on the glass is completely or partially removed by the laser radiation.

[0039] List of reference symbols: (1) Glass substrate

[0040] (2) Sacrificial coating / layer

[0041] (3) Laser device

[0042] (4) Radiation from laser (5) High reflectors

[0043] (6) focusing element

[0044] (7) Nano-structures

[0045] (8) Thin glass coating

[0046] (9) Nano-structures (A) enlarged area

Claims

Claims1. Method of shaping a surface of a transparent in the visible optical spectrum solid material with an initial transmissivity and initial reflectivity to increase the transmissivity above the initial transmissivity, comprising: applying a coating on the surface of the transparent to the visible solid, consisting of a single or multiple individual layers, whereby each individual layer has at least a pre-defined parameter among the following parameters: type, material, thickness, roughness, homogeneity; providing the transparent solid material on a holder; selecting the parameters of a focused laser radiation, whereby the parameters include at least one of a laser fluence value from a range of laser fluence values; a wavelength, a repetition rate, a pulse duration of a laser pulse from a range of wavelengths, repetition rates and pulse durations, exposing the surface of the transparent solid material to a focused laser radiation with the selected wavelength, repetition rate, pulse duration and generate a nanostructure pattern; relatively translating the transparent solid material with the laser beam to generate the nanostructure pattern by passing the laser beam over the surface of the transparent solid material obtaining the solid material with the nanostructured pattern, whereby the transmissivity of the solid material with the nanostructured pattern is higher than the initial transmissivity.

2. Method according to claim 1, whereby the solid material has one of the following materials: fused silica, aluminosilicate, sapphire.

3. Method according to any of previous claims, whereby the solid material comprises at least a glass or crystal piece.

4. Method according to any of previous claims, whereby the solid material after treatment has a haziness that is below 5%, preferably below 1% .

5. Method according to any of previous claims, whereby the transmissivity after shaping is higher than 97%.

6. Method according to any of previous claims, whereby the coating is radiation absorbing.

7. Method according to any of the previous claims, whereby the coating is heat dissipating.

8. Method according to any of previous claims, whereby the solid material has a radiation damage threshold and radiation damage threshold is increased.

9. Method according to any of previous claims, whereby the coating is applied by spray coating, dip coating, spin coating, screen printing or digital printing.

10. Method according to any of previous claims, whereby a layer of the coating is any of the following: color ink, color spray paint transparent to the visible spectrum, optical adhesive, granular material.

11. Method according to any of previous claims, whereby the coating comprises at least a plastic or polymeric piece.

12. Method according to any of previous claims, whereby the coating has a thickness up to 5 mm.

13. Method according to any of previous claims comprising scanning the laser beam on a stationary coated transparent solid material.

14. Method according to any of previous claims, whereby the wavelength is selected from a range of 200 nm to 2100 nm.

15. Method according to any of previous claims, whereby the pulse duration is selected up to 8 ns.

16. Method according to any of previous claims, whereby the laser fluence is selected from a range of 0.2 J / cm2to 12 J / cm2.

17. Method according to any of previous claims, comprising focusing multiple beams simultaneously on the transparent solid material, whereby the beams can be independently utilized by being focused on different areas of the transparent solid or by being combined before focusing to create a diffraction pattern on the coated transparent solid material.

18. Method according to any of previous claims, whereby shaping the transparent solid material comprises shaping a glass piece on an electronic device, the electronic device including a solar cell (SC), a smartphone, an automotive display, a screen, a light emitting diode (LED) and a light detection and ranging (LIDAR) sensor.

19. Structured substrate, whereby the substrate is made at least of one of the following materials: fused silica, aluminosilicate, sapphire, whereby the transmissivity of the structured substrate has an transmissivity that is higher than 97% and exhibits anti-glare characteristics.

20. Use of the structured substrate of claim 20 as an anti-glare glazing element for monitors, screens, and displays.

21. Antifogging device incorporating a structured substrate according to claim 20.

22. An electronic device incorporating a structured substrate according to claim 20.

23. Method of cutting or dicing a transparent in the visible optical spectrum solid material, comprising:providing the transparent solid material on a holder; selecting a coating with one or more of the following parameters: material, number of layers, thickness, roughness, homogeneity; applying the coating on the surface of the transparent to the visible solid material with a thin layer of additional material, consisting of a single or multiple individual layers; selecting a desired focused laser spot area on the surface of the transparent to the visible solid material; 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 the surface of the transparent solid material to a focused laser radiation with the selected wavelength, repetition rate, pulse duration and generate a nanostructure pattern; relatively translating the transparent solid material with the laser beam to cut or dice the substrate by passing the laser beam over a cutting line.

24. Manufacturing configuration to shape a surface of a transparent solid to increase the transmissivity in the optical spectrum, comprising a holder to hold the solid and integrating a coating module and an irradiation module and further comprising a control unit to perform coating and irradiation.

25. Manufacturing configuration according to claim 25, whereby manufacturing configuration and the control unit are configured to perform coating and irradiation simultaneously.

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