EP2850493A1

EP2850493A1 - Method for texturing a substrate having a large surface area

Info

Publication number: EP2850493A1
Application number: EP13727285.2A
Authority: EP
Inventors: Nicolas Chemin; Jérémie TEISSEIRE; Elin Sondergard
Original assignee: Saint Gobain Glass France SAS; Compagnie de Saint Gobain SA
Current assignee: Saint Gobain Glass France SAS; Compagnie de Saint Gobain SA
Priority date: 2012-05-14
Filing date: 2013-05-14
Publication date: 2015-03-25
Also published as: FR2990384A1; EA201492087A1; JP2015522443A; WO2013171420A1; IN2014MN02198A; US9296132B2; KR20150010726A; FR2990384B1; CN104272187A; US20150140837A1; JP6141969B2

Abstract

The invention relates to a method for forming a texture on a substrate, comprising: depositing a deformable layer on the substrate; bringing the deformable layer into contact with the textured surface of a secondary stamp; introducing the covered substrate and the secondary stamp into a bag made from non-permeable material; introducing the bag and the contents thereof into a sealed chamber; removing the air from the chamber until a pressure value of at most 0.5 bar is obtained; sealing the bag before reintroducing air into the chamber; introducing the sealed bag and the contents thereof into an autoclave; applying a pressure of between 0.5 and 8 bar and a temperature of between 25 and 400 °C for a period of between 15 minutes and several hours; opening the bag; and separating the substrate and the secondary stamp. The invention also relates to: a transparent assembly comprising a glass substrate covered with a textured layer, which is obtained using the above method; and the uses of the method in order to obtain a substrate intended for extracting, guiding or redirecting light, or a superhydrophobic or superhydrophilic substrate.

Description

PROCESS FOR TEXTU RATION ON A LARGE SURFACE SUBSTRATE

The invention relates to a method of texturing a substrate of large area (of the order of at least m ² ), based on the transfer of a micro-pattern (5 to 100 μιτι), meso- (1 5 μιτι) and / or nanoscopic (10 to 1000 nm) of a buffer (or mask) in a layer deposited on the surface of the substrate. (Nanoimprint lithography -NIL-, nanoimprint or embossing).

The use of a fluid under pressure to compress the buffer against the substrate makes it possible to overcome the limitations usually observed for the texturing of large substrates with the use of a mechanical press. These limitations come mainly from the lack of flatness of the buffer and the substrate which can not be overcome. When the buffer and the substrate are deposited between the rigid plates of the mechanical press, the flatness defects lead to a variation of the pressure exerted by the buffer on the substrate and thus to a variation in the depth of the transferred patterns. We can have areas without contact between buffer and substrate, so without any transfer of the pattern. This phenomenon increases with the surface to be textured. Insofar as the pressure exerted by a fluid is isostatic, the problem of balance of forces observed with the mechanical press is no longer encountered. This makes it today the preferred technique in the field of NIL printing. The pressure is applied homogeneously over the entire surface of the buffer and allows to deform the layer homogeneously.

Different methods can be used to transmit fluid pressure to the buffer and / or substrate. It may be a pressure vessel, a flexible membrane retranscribing the pressure of the fluid or pressurized fluid streams through openings disposed along the contact surface.

However, this technique was initially and remains mainly developed for the microelectronics industry, it has not been adapted to glass products: • the processes used generally require specific devices dedicated to this use;

• The size of large surface area substrates is small compared to the scales of glass products (several square meters); Contacting the coated substrate and the buffer is critical and requires specific technologies.

The inventors have set themselves the goal of providing a method compatible with the glass industry and making it possible to achieve a perfectly regular texturing in depth, in patterns of a few tens to a few hundred nanometers for example, on a substrate of big surface.

This object has been achieved by the invention which, accordingly, relates to a method of forming a texturing on a substrate, characterized in that it comprises the deposition of a deformable layer on the substrate,

Bringing this deformable layer into contact with the textured face of a daughter pad,

The introduction into a bag of non-permeable material of the coated substrate and the daughter pad, the introduction of the bag and its contents into an airtight enclosure,

• evacuation of the air from the chamber to a pressure not exceeding 0.5 bar, and up to values at most equal to 5 mbar,

• the sealing of the bag before reintroduction of air into the enclosure, · the introduction of the sealed pouch and its contents into an autoclave,

The application of a pressure of between 0.5 and 8 bar and a temperature of between 25 and 400 ° C. for 15 minutes to several hours,

• the opening of the pocket, then • the separation of the substrate and the daughter buffer.

The texturing formed according to the invention is of dimensions between 10 nm and 100 μιτι (depth of the valleys, height of the growths, width / diameter of the growths, width of the valleys ...), or even up to values of several centimeters: "Wall" of 10 μιτι X 10 μιτι X 4 cm.

The texturing is capable of being formed, by this method, on surfaces of the order of at least one square meter, up to the dimensions of the glass sheet called Full Width Float (PLF), that is to say 3m X 6m in particular.

Deposition processes of the deformable layer on the substrate are not limited. A liquid deposit is used (laminar coating, spraying - spray-coating, tempering -dip-coating, and spin coating -spin coating). In a laminar coating, the liquid precursors of the deformable layer form, at rest, a meniscus suspended from a slot from which they are extracted by displacement of this slot in a transverse position above the substrate. The girl pad is so called because it results from the molding of its material compared to a master. Its textured material can be polymer.

The material of the pocket is non-permeable to air.

The air of the chamber is discharged to a pressure at most equal to 0.5 bar or, in order of increasing preference, at 5 mbar, 2 mbar and 1 mbar. For example, the air in the chamber is evacuated for fifteen minutes until a pressure of the order of 0.5 mbar is reached. The pouch is hermetically sealed before reintroducing the air into the enclosure.

The sealed pouch is then placed in an autoclave which will make it possible to apply a pressure of between 0.5 and 8 bar and a temperature of between 25 and 400 ° C. The treatment in the autoclave can be between 15 minutes and several hours. These parameters must be adjusted according to the nature of the deformable layer. The objective here is to press the daughter pad against the initially deformable layer, sol-gel or other, while reticulating to make it indeformable. In this way, we print and freeze the pattern inscribed on the surface of the daughter pad in the layer deposited on the surface of the substrate. step Air sealing and evacuation is required to allow the transmission of fluid pressure to the buffer.

At the outlet of the autoclave, the bag is pierced before it is opened and the daughter pad is removed from the surface of the substrate. The layer can then be subjected to a new heat treatment to densify, crystallize (ΤΊΟ ₂ , ZnO) and improve its mechanical properties and / or to play on the hydrophilic / hydrophobic nature of its surface.

The method of the invention does not require specific equipment (a bagging system and an autoclave). It is compatible with the devices commonly used in the glass industry, particularly for the lamination of windshields or for the manufacture of technical glazing such as laminated incorporating a liquid crystal film, of the type marketed by Saint-Gobain Glass under the registered trademark Privalite®.

Insofar as the process only involves tools already developed on industrial lines, this process appears easily industrializable and compatible with large glazing treatment.

The method is compatible with the use of low cost buffers such as textured polymer sheets (produced by roll-to-roll in particular). Since the buffer is not destroyed during the process, it can be reused several times.

According to preferred features of the process of the invention:

the deformable layer is made of a thermally crosslinkable material, in particular a sol-gel material; having the advantage of leading to layers of high inorganic content that can withstand a quenching process of a glass sheet (constituting the substrate); mention may be made of silica, titanium oxide, zinc oxide or aluminum oxide, alone or as a mixture of several of them; a silica sol is advantageously obtained by hydrolysis of a sol-gel precursor, preferably methylethoxysilane; it is important to control the conditions of preparation of the sol-gel solution so that the layer remains deformable during the process; the deformable layer has a thermoplastic polymer matrix; mention may be made of poly (methyl methacrylate) (PMMA), polystyrene (PS), polycarbonate (PC), polyvinyl chloride (PVC), polyamide (PA), polyethylene (PE), polypropylene (PP), alone or in mixtures or copolymers of several of them;

the precursors of the deformable layer comprise nanoparticles such as ΤΊΟ ₂ (in particular photocatalytic) or luminescent nanoparticles, for example CdSe, CdS, and / or organic and / or porogenic molecules of the latex type PMMA, PS, surfactant which, for certain d between them, are possibly intended to be eliminated before the final layer is produced; mention may be made of the incorporation of an inorganic component (nanoparticles) into a thermoplastic polymer matrix, to improve its thermal and mechanical resistance (impact resistance for example), or to adjust the optical properties of the textured layer or to provide it with a function;

the textured face of the daughter pad is permeable to the air; contacting during the sealing step then requires no particular precaution to avoid the trapping of air bubbles between the coated substrate and the buffer; it may consist of an elastomeric polymer (PDMS, EVA, epoxy type) or glassy polymer or a copolymer;

the textured face of the daughter pad is made of polymer or organic (polymer) -inorganic hybrid material, and the temperature in the autoclave is successively brought to a higher temperature, then lower than the glass transition temperature of this polymer material, or conversely ; this arrangement makes it possible to precisely control the mechanical behavior of the buffer and to optimize the contact between the buffer and the coated substrate, as well as the quality of the replication of the structures.

The invention also aims to:

a transparent assembly comprising a glass substrate coated with a textured layer, obtained by a process described above; the glass is in particular mineral, such as silicosodocalcique, float; - An application of a method described above, to obtain a substrate for the extraction, guiding or redirection of light; for example, the fields of photovoltaics, daylighting (redirection of sunlight to the ceiling of a room by the appropriate texturing of a glazing), light extraction for OLED, polarizers;

an application of a method described above, to obtain a substrate intended for micro-fluidics; and

an application of a method described above, to obtain a superhydrophobic or superhydrophilic substrate; a superhydrophobic substrate is in particular feasible by covering the textured layer with a sol-gel overlay, for example consisting of a hydrophobic agent such as fluorinated silane, especially from known perfluoroalkylalkyl-trialkoxysilane precursors; the overlayer is advantageously very thin, of a thickness not exceeding a few nanometers - it is then sometimes referred to as monomolecular qualifier, thus not substantially modifying the geometry of the underlying texturing.

The invention is illustrated by the following examples:

Figure 1 shows a scanning electron microscope image showing the texture of the PET daughter plug used in Example 1 below.

Figures 2a and b show scanning electron microscopy images of the embossed sample obtained in Example 1 below views, with respect to the embossed surface, from above (a) and in cross section (b).

EXAMPLE 1 Transfer of a periodic network of micron-spherical half-spheres in a sol-gel silica layer.

A silica sol is prepared from a methyltriethoxysilane mixture (marketed by Sigma Aldrich) / Acetic Acid (Prolabo) in a 45/55 mass ratio. The solution is stirred at room temperature for 12 hours. A PDMS buffer is produced by molding a periodic array of half-spheres obtained by an interferential lithography process. The diameter of the half-spheres is 3 μιτι, the period is 5.5 μιτι. The molding is carried out by casting a 10: 1 mixture of the two components (elastomer: catalyst) of SYLGARD® 184 SILICONE ELASTOMER KIT sold by Dow Corning by evacuating the residual air bubbles under vacuum and then crosslinking the elastomer at 80 ° C. for 4 hours.

The sol is deposited by spin coating (2000 rpm, 1 min) on a 2 mm glass substrate of 10 × 10 cm ² , marketed by Saint-Gobain Glass under the registered trademark Planilux®, the surface of which has been previously cleaned. by a Cerox® polishing. The layer is dried for 5 minutes at 50 ° C.

Following deposition, the textured face of the PDMS buffer is contacted with the sol-gel silica layer. In order to evacuate these air bubbles which may compromise the contact between the layer and the mask, the samples are placed in a sealing bag and installed in a hermetic enclosure which is evacuated until a vacuum of 0.5 mbar is reached. At the end of the 20 minutes the pouch is sealed by heat sealing.

The samples are then placed in the autoclave in which they simultaneously undergo a temperature rise up to 110.degree. C. and pressure up to 1.75 bar (5 min at 20.degree. C., raised to 60.degree. min, plateau at 60 ° C for 10 min, rise to 1 10 ° C in 5 min, plateau at 1 10 ° C for 20 min and drop to 35 ° C in 15 min, rise from 0 to 1, 75 bar in 5 min min, bearing at 1.75 bar for 40 min, down to 0 bar in 15 min). At the exit of the autoclave the samples are demolded cold. The transfer of the pattern into the sol-gel silica layer is characterized by

AFM. We find the hexagonal network of half-spheres. The patterns obtained are similar to those carried by the buffer: 3 μιτι of width, 1 .5 μιτι of height and a period of 5.5 μιτι.

EXAMPLE 2 Transfer of a periodic network of micron-spherical half-spheres in a layer of poly (methyl methacrylate).

A solution of 10% poly (methyl methacrylate) (PMMA) in methyl ethyl ketone (MEK) is prepared by mixing 20 g of PMMA of average molecular weight Mw = 120000 (Sigma-Aldrich) with 180 g of MEK (Prolabo).

A PDMS buffer is produced by molding a periodic array of half-spheres obtained by an interferential lithography process. The diameter of the half-spheres is 3 μιτι, the period is 5.5 μιτι. The molding is carried out by casting a 10: 1 mixture of the two components (elastomer: catalyst) of SYLGARD® 184 SILICONE ELASTOMER KIT sold by Dow Corning by evacuating the residual air bubbles under vacuum and then crosslinking the elastomer at 80 ° C. for 4 hours. The PMMA solution is deposited by spin coating (2000 rpm, 1 min) on a 2 mm glass substrate 10 × 10 cm ² marketed by Saint-Gobain Glass under the registered trademark Planilux®, the surface of which has been previously cleaned by Cerox® polishing.

Following deposition, the textured face of the PDMS buffer is brought into contact with the PMMA layer. In order to evacuate these air bubbles which may compromise the contact between the layer and the mask, the samples are placed in a sealing bag and installed in a sealed chamber which is evacuated until a vacuum of 0.5mbar is reached. When the desired vacuum is reached, the bag is sealed by heat sealing. The samples are then placed in the autoclave in which they undergo an increase in pressure and temperature (5 min stage at 20 ° C, rise to 168 ° C in 10 min, 15 min plateau to 168 ° C and descent to 40 ° C in 30 min, rise from 0 to 1 bar in 5 min, 10 min to 1 bar, rise to 3 bar in 5 min, 30 min to 3 bar, down to 0 bar in 10 min). The pattern transfer in the PMMA layer is characterized by AFM. We find the hexagonal network of half-spheres. The patterns obtained are similar to those carried by the buffer: 3 μιτι width, 1, 5 μιτι height and a period of 5.5 μιτι.

EXAMPLE 3 Transfer of a periodic network of micron-spherical half-spheres in a poly (methyl methacrylate) -SiO2 hybrid layer.

A solution of 10% poly (methyl methacrylate) (PMMA) in methyl ethyl ketone (MEK) is prepared by mixing 20 g of PMMA of average molecular weight Mw = 120000 (Sigma-Aldrich) with 180 g of MEK (Prolabo). A suspension of silica nanoparticles (Nissan Chemical) in the MEK is added to the PMMA solution at a level of 20% by weight. The mixture is homogenized by magnetic stirring for 10 minutes. A PDMS buffer is produced by molding a periodic array of half-spheres obtained by an interferential lithography process. The diameter of the half-spheres is 3 μιτι, the period is 5.5 μιτι. The molding is carried out by casting a 10: 1 mixture of the two components (elastomer: catalyst) of SYLGARD® 184 SILICONE ELASTOMER KIT sold by Dow Corning by evacuating the residual air bubbles under vacuum and then crosslinking the elastomer at 80 ° C. for 4 hours.

The solution of silica and PMMA particles is deposited by spin coating (2000 rpm, 1 min) on a 2 mm glass substrate 10 × 10 cm ² marketed by Saint-Gobain Glass under the registered trademark Planilux®, whose surface has been previously cleaned by Cerox® polishing.

Following the deposition, the textured face of the PDMS buffer is brought into contact with the PMMA-S102 hybrid layer. In order to evacuate these air bubbles which may compromise the contact between the layer and the mask, the samples are placed in a sealing bag and installed in a sealed chamber which is evacuated until a vacuum of 0.5 is reached. mbar. When the desired vacuum is reached, the bag is sealed by heat sealing.

The samples are then placed in the autoclave in which they undergo an increase in pressure and temperature (5 min stage at 20 ° C, rise to 168 ° C in 10 min, 15 min plateau at 168 ° C, descent to 40 ° C in 30 min, rise from 0 to 1 bar in 5 min, 10 min to 1 bar, rise to 3 bar in 5 min, 30 min to 3 bar and down to 0 bar in 10 min).

The pattern transfer in the PMMA layer is characterized by AFM. We find the hexagonal network of half-spheres. The patterns obtained are similar to those carried by the stamp: 3 μιτι width, 1, 5 μιτι height and a period of 5 ^ m.

EXAMPLE 4 Transfer of a semi-periodic network of nanometric spots in a sol-gel silica layer. A silica sol is prepared from a 50-50 mixture by weight of methyltriethoxy silane (marketed by Sigma Aldrich) and a solution of hydrochloric acid pH = 2. The solution is stirred at room temperature for 2 hours. A PDMS buffer is produced by molding a pseudo periodic array of studs obtained by an electronic lithography method coupled to a "step and repeat" method. The pads have a length of 1 .2 μιτι, a width of 200 nm or 400 nm and a height of 350 nm. The molding is carried out by casting a 10: 1 mixture of the two components (elastomer: catalyst) of SYLGARD® 184 SILICONE ELASTOMER KIT sold by Dow Corning by evacuating the residual air bubbles under vacuum and then crosslinking the elastomer at 80 ° C. for 4 hours.

The silica sol is deposited by spin coating (2000 rpm, 1 min) on a 2 mm glass substrate 10 × 10 cm ² marketed by Saint-Gobain Glass under the registered trademark Planilux®, the surface of which has been previously cleaned by Cerox® polishing. The layer is dried for 5 minutes at 50 ° C.

Following deposition, the textured face of the PDMS buffer is contacted with the sol-gel silica layer. In order to evacuate these air bubbles which may compromise the contact between the layer and the mask, the samples are placed in a sealing bag and installed in a hermetic enclosure which is evacuated until a vacuum of 0.5 mbar is reached. When the desired vacuum is reached, the bag is sealed by heat sealing.

The samples are then placed in the autoclave in which they undergo a cycle of pressure and temperature rise (20 to 60 ° C rise in 5 min, 5 min plateau at 60 ° C, rise to 130 ° C in 5 minutes). min, stage of 25 min at 130 ° C, descent to 40 ° C in 20 min, rise from 0 to 2.5 bar in 5 min, 35 min stage at 2.5 bar, descent to 0 bar in 20 min) .

The transfer of the pattern into the sol-gel silica layer is characterized by AFM. We find the network of pads characterized by a variable period. The patterns obtained are similar to those carried by the buffer. Plots of 200 nm and 400 nm in width are found, the length is 1 .2 μιτι and the height of 350 nm. Example 5: Transfer of a semi-periodic network of lines in a silica layer from a PET buffer.

A silica sol is prepared from a 50-50 mixture by weight of methyltriethoxy silane (marketed by Sigma Aldrich) and a solution of hydrochloric acid pH = 2. The solution is stirred at room temperature for 2 hours.

The used dams are PET polymer films on which a coating has been deposited and then textured by roll-to-roll. The polymer films have a size of about 10 x 10 cm ² (Figure 1). The motive of these films was determined with the aim of giving them a "day ligthing" property while retaining the transparency of the PET. The pattern consists of a 200 nm wide array of lines at 350 nm depth (aspect ratio = 1.75) and a 400 nm period. Some noise is introduced at the periodicity of the structure to limit the effects of diffraction (Figure 1).

The surface of the PET film is thoroughly cleaned with alcohol and using sticky rollers (marketed by Teknek) to remove all traces of dust.

The silica sol is deposited by spin-coating (2000 rpm, 1 min) on a 2 mm glass substrate 10 × 10 cm ² marketed by Saint-Gobain Glass under the registered trademark Planilux®, the surface of which has been previously cleaned. by a Cerox® polishing. The layer is dried for 5 minutes at 50 ° C.

Following deposition, the textured face of the PET pad is contacted with the sol-gel silica layer. In order to evacuate these air bubbles which may compromise the contact between the layer and the mask, the samples are placed in a sealing bag and installed in a sealed chamber which is evacuated until a vacuum of 0.5mbar is reached. When the desired vacuum is reached, the bag is sealed by heat sealing.

The samples are then placed in the autoclave in which they undergo a cycle of rise in pressure and temperature (rise of 20 to 60 ° C in 5 min, step 5 min at 60 ° C, raised to 1 10 ° C in 5 min, level of 25 min at 1 10 ° C, descent to 40 ° C in 20 min; rise from 0 to 2 bar in 5 min, step of 35 min to 2 bar, descent to 0 bar in 20 min).

The transfer of the pattern into the sol-gel silica layer is characterized by scanning electron microscopy. We find the network of pseudo-periodic lines with a period of 400 nm. The patterns obtained are similar to those carried by the buffer: 200 nm wide and 400 nm high.

Claims

Method of forming a texturing on a substrate, characterized in that it comprises

depositing a deformable layer on the substrate,

the introduction into a bag of non-permeable material of the coated substrate and the daughter buffer,

the introduction of the bag and its contents into an airtight enclosure,

- the evacuation of the air from the enclosure to a pressure at most equal to 0.5 bar,

the sealing of the bag before reintroduction of the air into the enclosure,

the introduction of the sealed pouch and its contents into an autoclave,

- the opening of the pocket, then

the separation of the substrate and the daughter buffer.

Process according to Claim 1, characterized in that the deformable layer is made of a thermally crosslinkable material.

Process according to claim 1, characterized in that the deformable layer has a thermoplastic polymer matrix.

Method according to one of the preceding claims, characterized in that the precursors of the deformable layer comprise nanoparticles and / or organic and / or porogenic molecules.

Method according to one of the preceding claims, characterized in that the textured face of the daughter plug is permeable to air.

6. Method according to one of the preceding claims, characterized in that the textured face of the daughter pad is made of polymer material or organic hybrid (polymer) - inorganic, and in that the temperature in the autoclave is successively brought to a temperature higher, then lower than the glass transition temperature of this polymeric material, or vice versa.

7. Application of a method according to one of claims 1 to 6, for obtaining a substrate for the extraction, guiding or redirection of light.

8. Application of a method according to one of claims 1 to 6, to obtain a substrate for the microfluidic.

9. Application of a method according to one of claims 1 to 6, for obtaining a superhydrophobic or superhydrophilic substrate.