SI25887A - A method for producing polymeric surface modification layers - Google Patents

Abstract

The present invention provides methods of improving surface wetting and in particular reducing the receding contact angle and / or increasing the contact angle hysteresis. The methods presented may include the following steps: a) mixing poly (styrene), poly (methyl methacrylate) and solvent to form a polymer solution; b) applying the polymer solution to the substrate to form a polymer solution; c) drying the coating of the polymer solution to form a polymer layer on the substrate; d) exposing the polymer layer to reactive polar species to form an altered polymer layer on the substrate.

Description

METHOD OF PRODUCING POLYMER LAYERS WITH MODIFIED SURFACE

FIELD OF THE INVENTION

The present invention relates to polymer layers and in particular, although not exclusively, to surface modifying polymer layers suitable for various printing applications.

Background of the invention

Wetting regulation plays an important technological role in many applications, including the printing of functional inks on solid, non-permeable substrates, which are a key part of printed electronics.

This technology enables cost-effective fabrication of electronic components on various substrates (substrates), such as glass, plastic, ceramics and metal foils. In printed electronics, for example, layer-to-layer printing is common, so that each new pattern is printed on an inhomogeneous surface (i.e., a surface that already has the layer (s) applied). This can result in complex and unpredictable wetting, which is characterized by different contact angles on surfaces that have already had structures applied and on surfaces that are the uncoated surface of the substrate. As a result, the resolution or stability of the printed sample may be compromised. There is also a significant risk of short circuit if lines or printed elements are connected where they should not be.

Wetting a specific surface with liquid is described by the advancing and retracting contact angle of the liquid. Progressive contact angle is the maximum possible contact angle; the contact line advances when the current contact angle exceeds the advancing contact angle. Retracting contact angle is the smallest possible contact angle; the contact line retracts when the instantaneous contact angle is less than the retracting contact angle. The difference between the two angles is the hysteresis of the contact angle. This one is ubiquitous. It prevents the droplet from slipping on sloping surfaces, such as raindrops on windows, and plays a key role in the stability of printed patterns and drying.

In inkjet printing, ideally, the interaction between the ink and the substrate would result in a high advancing contact angle and a zero receding contact angle. A high advancing contact angle is ideal for high resolution (resolution), while a retracting contact angle equal to zero is ideal for the stability of the printed pattern. The ideal surface (atomically smooth and chemically homogeneous) in theory shows a hysteresis of the contact angle equal to zero, ie the same advancing and receding contact angles. However, it is well known that surface irregularities such as topographic or chemical variations cause contact angle hysteresis.

In general, smooth and chemically homogeneous surfaces show less contact angle hysteresis compared to rough, chemically inhomogeneous surfaces.

Wetting and spreading of the ink on a particular substrate can be adjusted either by (i) changing the surface properties of the substrates or (ii) by locally limiting the spread of the ink.

(11 Changing the surface properties of the substrate

This approach is based on the production of partial substrate wetting. In doing so, the interaction between the ink and the substrate must be well balanced to maintain the stability and definition of the printed structures. A common approach for adjusting substrate wetting is surface treatment such as wet cleaning, plasma treatment, and UV / ozone treatment. These methods are commonly used to lower the contact angle and prepare the surface for further use in coatings where good wetting (very small contact angle) is desirable. On the other hand, printing requires precise adjustment of the contact angle to ensure partial wetting. This can be achieved by using a wetting control layer before the printing step.

Young et al. (Adv. Electron. Mater., 2015, 1500086) a layer of poly (methyl methacrylate) (PMMA) was used as a wetting control layer.A thin layer was applied to the glass substrate by spin-coating. This process was followed by drying at 200 ° C for 10 minutes, UV / ozone treatment increased the surface energy of the PMMA layer and reduced the contact angle of the functional ink, the PMMA layer was smooth and the ink contact angle hysteresis was small, as indicated by detachment ( angl, de-pinning) contact lines at low substrate temperatures during printing.

Matavž et al. (Langmuir, 2017, 33 (43), 11893-11900) used layers of poly (styrene), poly (methyl methacrylate), poly (vinyl alcohol), or poly (vinyl pyrrolidone) to adjust the surface characteristics of glass substrates. The wetting of the studied inks depended on the chemical nature of the polymer layer. For a more precise wetting adjustment, a method has been proposed that involves the thermal decomposition of a layer of poly (methyl methacrylate) on a glass substrate at 350 ° C. Similar to the approach used by Yang et al. the polymer layers were smooth and exhibited relatively little contact angle hysteresis.

(ii) Local ink spread limitation

An alternative approach to wetting control is to limit the spread of functional ink by creating low surface energy patterns on well-wetted surfaces.

Nguyen et al. (Appl. Mater. Interfaces, 2014, 6, 4011-4016) used surfaces in combination with hydrophilic and hydrophobic patterns that limit fluid propagation. Selective wetting was achieved by two-step hydrophilic-hydrophobic deposition of 3-aminopropyl trimethoxysilane (APTMS) and 3M Novec 1700 and Novec 7100DL Engineered Fluid on PET surfaces; this was followed by selective hydrophilic treatment (either atmospheric 02 / Ar plasma or UV / ozone surface treatment) using metal stencils. Areas with a high water contact angle of 105 ° and areas with a low water contact angle <5 ° were obtained on one basis. This process uses a mechanical template and thus limits the simple pattern changes characteristic of the printing method.

Li et al. (Appl. Mater. Interfaces, 2017, 9, 8194-8200) used areas with different surface energies to limit the spread of functional ink on glass substrates. Surface energy samples were prepared by dropwise application of a thin layer of CYTOP® polymer and subsequent printing of a pure solvent to remove the hydrophobic CYTOP® layer via the “coffee ring” effect. This process retains the digital definition of the printed sample, but the resolution of the template depends on the characteristics of the printer and the contact angle of the solvent to remove the hydrophobic surface.

Godard et al. (Adv. Mater. TechnoL, 2018, 1800168) used low surface energy alcanthiolates that bind to metal surfaces by chemisorption and form self-organized monoplasts. The samples were printed on platinum-coated silicon wafers by inkjet printing to create areas of low surface energy that limited the spread of functional ink. The process retains the digital definition of the printed sample, but the resolution of the template depends on the characteristics of the printer and the wetting of the alkantiolate ink.

US9248686B2 relates to a printing element having at least one polymer layer having photographable components and a chemically functionalized polymer that makes the polymer layer either more hydrophobic or hydrophilic, providing different wetting with hydrophilic inks. The fluorinated polymer layer is selectively altered under light using a photomask. The unexposed polymer can dissolve to leave a patterned surface.

There remains a need to develop a fast, reliable and cost-effective technique that can adjust the wetting of any solid substrate of optical quality, leading to high contact angle hysteresis.

The present invention has been developed based on the above considerations.

Description of the solution to the technical problem

The invention relates to a method for improving the wettability of a surface.

In general, the present surface modification layers provide a more universal and efficient wetting regulation during the application of the multiple overlapping layers required in printed electronics. The wetting control typically follows a two-step process: (i) covering the entire surface with a thin polymer layer and (ii) treating the polymer layer with a surface modification method (UV / O3 or plasma treatment) to adjust the wetting. The problem arises because the known polymer layers are intrinsically smooth (Ra <1 nm) and chemically homogeneous and consequently express a relatively low contact angle hysteresis.

Hysteresis is usually sufficient to print stable samples and provides medium resolution, but printed samples may shrink during drying. Lower contact angle retraction and greater contact angle hysteresis allow for higher print resolution as well as improved stability after drying by limiting contact line detachment. The methods of the present invention may lead to a decrease in the receding contact angle and / or increased contact angle hysteresis. Even in the case where the contact angle hysteresis is not increased, the methods according to the invention allow a significant value of the hysteresis, while the retracting contact angle is reduced, thus improving the wetting properties of the surface.

The formation of nano-textured polymer layers is discussed here. Spontaneous phase separation between poly (methyl methacrylate) (PMMA) and poly (styrene) (PS) leads to a thin layer with a high topographical and chemically inhomogeneous surface (Figure 1 and Figure 2).

Optional further surface treatments with UV / ozone and / or post-heat treatment, as described herein, may further reduce the declining contact angle and / or increase the hysteresis of the contact angle of the layer.

In a first aspect, the invention relates to a method of application to a substrate, wherein the method comprises the following steps: a) mixing poly (styrene), poly (methyl methacrylate) and solvent to form a polymer solution; b) applying the polymer solution to the substrate to form a polymer solution; c) drying the coating of the polymer solution to form a polymer layer on the substrate; d) exposing the polymer layer to reactive polar molecules to form an altered polymer layer on the substrate.

In some embodiments, in step d), the polymer layer is exposed to UV / ozone. This reduces the receding contact angle and increases the hysteresis of the polar solvent contact angle.

In some embodiments, in step d), the polymer layer is exposed to oxygen plasma. This reduces the receding contact angle and increases the hysteresis of the polar solvent contact angle.

In some embodiments, the surface is further altered by heat treatment of the modified polymer layer at 100 to 200 ° C for 5 to 30 seconds. This can further increase the advancing contact angle and the contact angle hysteresis.

In another aspect, the invention relates to a method for making a printed substrate, comprising the steps of: i) preparing a coated substrate by a method according to the first aspect, and ii) printing on a coated substrate.

In some embodiments, step ii) is performed with an ink containing a polar solvent. Polar solvents have a low withdrawal contact angle and high contact angle hysteresis on substrates prepared as described and are particularly useful in printing functional layers.

In some embodiments, the polar solvent is a mixture of 2-ethoxyethanol (2EE), ethylene glycol (EG) and ethanolamine (EA). This solvent system for printing functional inks allows the formation of homogeneous, flat layers.

In some embodiments, the ink contains metal oxide precursors. Inks with metal oxide precursors decompose at high temperatures to form a functional layer.

In some embodiments, the printed substrate is heated to a temperature of 350 ° C or higher to remove the polymer layer. This allows the polymer layer to act as a temporary surface modification that will not be involved in the function of the printed layer.

In some embodiments, the substrate is a silicon wafer.

In some embodiments, the substrate used in step b) of the method according to the first or second aspect has a pre-printed layer on the surface to which the polymer solution is applied in step b). In this way, many functional layers are accurately printed on top of each other by repeating the above method.

In a third aspect, the invention relates to a substrate obtained by a method according to the first or second aspect.

In some embodiments, the polymer layer on the substrate has a thickness of 10 nm or less. This thickness prevents the printed functional layer from cracking during degradation and reduces the amount of carbon in the intermediate layer.

In some embodiments, the distance between the phase-separated islands is less than 1 pm. This ensures that the phase-separated islands are relatively small in terms of the structure or structures to be printed.

The present invention also relates to coated materials (i.e. a substrate with a polymer coating or layer) obtained by the described methods. Substrates having a polymer layer applied are described herein; printed substrates having a polymer layer and a printed pattern on said layer; and printed substrates having a printed pattern and a substrate from which the polymer layer has been removed.

The invention includes combinations of the aspects and preferred features described, except where such combinations are manifestly impermissible or explicitly excluded.

Embodiments and experiments illustrating the principles of the invention will be described below with the aid of the following figures:

Figure 1 shows a schematic representation of the topography of a textured PMMA / PS polymer layer illustrating surface heterogeneity with separate PMMA and PS phases

Figure 2 shows a schematic cross-sectional view of a textured PMMA / PS polymer layer illustrating the separate phases of PMMA and PS

Figure 3 shows the AFM topography of the surface of the 8 nm thick PMMA / PS polymer layer Figure 4 shows the contact angles of ethylene glycol on PMMA and PMMA / PS coated glass as the droplet volume increases (corresponding to the advancing contact angle) and the droplet volume subsequently decreases corresponding to the retracting contact angle). Both polymer films were treated with UV / ozone for 120 seconds and subsequently heat treated at 150 ° C for 15 seconds. the instantaneous diameter of the droplet on the surface is normalized to the maximum diameter reached at the measurement.

Figure 5 shows a square pattern measuring 500x500 pm ² printed on PMMA coated glass and PMMA / PS coated glass after drying. The white dashed line outlines the initial shape of the printed square, (a) and (c) show the printed pattern immediately after printing, while (b) and (d) show the same pattern after 30 seconds of drying.

Aspects and embodiments of the present invention will be described with reference to the above-mentioned figures. Further aspects and implementation examples will be apparent to one skilled in the art. All documents mentioned in this text are incorporated herein by reference.

In the present invention, a mixture of PMMA and PS is applied to the surface. The layer is phase separated to form uniform topographic characteristics when the layer dries. The resulting layer has a reduced contact angle and / or increased hysteresis of the contact angle.

The present invention also describes techniques for further adjusting the surface energy of the layer to further reduce the withdrawal contact angle and / or increase the contact angle hysteresis by reacting with polar species.

Furthermore, the present invention describes techniques that increase the advancing contact angle and the contact angle hysteresis by heat treatment.

The invention further describes the decomposition of the polymer layer after printing.

Substrate selection

The PMMA / PS layers according to the invention can be successfully used as layers for surface modification on various types of surfaces. A number of optical quality substrates used in electronics can be selected for inkjet printing. Suitable substrates include silicon wafers, various types of glass, polished ceramic substrates, and metal foils and polymers such as polyimide. A particularly useful substrate is a silicon wafer. In cases where silicon wafers are used, the substrate can be suitably passivated by applying an inert layer, such as an AI2O3 layer. The substrate may also be the above-mentioned material with a pre-printed functional layer on the surface.

Substrates suitable for changing wetting are not limited by size, composition or geometry. The present invention is suitable for modifying the wetting of flat, uneven and curved substrates, since the PMMA / PS layer according to the invention can be applied evenly to such substrates.

Application of polymers

In the first step, the raw materials PMMA and PS are dissolved in the solvent. Suitable solvents include, for example, anisole. Suitable molecular weights of PMMA and PS may be independently from about 1 kDa to 1500 kDa, for example 100 to 1000 kDa, for example 400 to 600 kDa, for example 500 kDa.

A suitable PMMA to PS weight ratio (PMMA: PS) is approximately 0.5: 1 to 1: 0.5. A suitable weight ratio is about 1: 1. The topographic characteristics of the layers can be adjusted by the mass ratio of the two polymers, as is known in the art.

In the second step, the surface of the substrate is coated by applying the polymer solution to the substrate by any suitable technique, for example, knowledge of the method of rotation, spraying or any other application technique.

In the third step, the polymer solution is dried. This can be done by any suitable method. For example, it can be carried out by drying the substrate by application under standard conditions or optionally by heating. A suitable heating temperature is 100 to 200 ° C. A suitable heating time is 0.5 to 10 minutes, especially 1 to 5 minutes. Drying conditions can affect the morphology of the polymer layer, as is known in the art. A suitable drying mode can be selected based on the solvent of the polymer solution. This forms a polymer layer on the substrate.

During this time, PMMA and PS present in the polymer solution in the coating are subjected to phase separation. The resulting polymer layer is believed to contain PMMA and PS phase islands (Figures 1 and 2), making it chemically heterogeneous. This creates a surface with increased contact angle hysteresis compared to a chemically homogeneous surface with similar surface roughness. The inventors have found that the polymer films thus prepared have low surface energy and low surface polarity, resulting in a higher contact angle than many polar solvents, for example diols (such as ethylene glycol), polyols (such as glycerol), water, formamide, dimethyl sulfoxide and ethanolamine. Non-polar solvents such as toluene, benzene, octane have a reduced contact angle on the described low-energy polymer films when compared to polar substrates such as glass and non-coated ceramics.

Thus prepared polymer films, as described herein, have a higher contact angle hysteresis of many polar and nonpolar solvents, for example ethylene glycol, ethanolamine, glycerol, toluene, benzene and octane, due to irregularities on the surface of the films.

PMMA / PS layers prepared by the described method exhibit periodic topographic characteristics less than 1 pm wide, for example about 400 nm wide with a peak-valley height <10 nm, for example about 4 nm (Figure 3). Each feature acts as a topographic irregularity and effectively increases the binding energy of the contact line of the fluid and consequently its hysteresis of the contact angle. The root mean square roughness of the present PMMA / PS layer on the glass substrate measured by atomic force microscopy is about 1.5 nm, which is low enough to avoid negative effects on the printed functional layers.

Polymer layers made by the methods described herein have a thickness that is suitably 10 nm or less, for example 8 nm or less, to prevent cracking and reduce the effects on the adhesion of the functional oxide layer and to reduce the amount of residual carbon on the intermediate layer after decomposition (decomposition). ).

The surface morphology of the PMMA / PS polymer layer according to the invention can be controlled by the ratio of PMMA to PS, the molecular weight of each polymer, the concentration of the polymer in the coating solution, the application parameters and the heat treatment of the layer.

Changing the surface

The surface energy of the polymer layer can be further increased by exposure to reactive polar species (e.g., oxygen or nitrogen). Suitable treatments include exposure to UV / ozone (O3), O2-plasma, nitrogen plasma or other surface modification techniques known in the art. This additional treatment can further reduce the contact angles of the polar solvents, in particular the receding contact angle, and thus can further increase the contact angle hysteresis. Such surface modifications increase the contact angle of non-polar solvents.

The contact angle and hysteresis of the contact angle of the surface can be adjusted with different exposure times to the polar species. Exposure to polar species lowers the contact angles of polar solvents. With this method, suitable exposure times can be selected to achieve the desired characteristics based on the polymer films and solvents used, and the withdrawal contact angle can also be reduced to zero or close to zero.

Suitable exposure times of UV / O3 modification using a commercial UV / O3 cleaning apparatus depend on the polymer film and the contact angle to be achieved. For example, suitable exposure times may be about 5 to 50 seconds or about 15 to 300 seconds. Exposure times may be about 30 to 300 seconds, for example about 30 to 120 seconds, for example about 30, about 60, about 90 or about 120 seconds. Suitable exposure times to 02-plasma using RF oxygen plasma operating at 50 Pa operating pressure and 50 W are, for example, 0.1 to 60 seconds.

Suitable wavelengths for UV radiation are, for example, from about 100 to 350 nm, for example about 150 to 300 nm, suitably from about 175 to 275 nm. Specific examples include 185 nm and 254 nm. Under these UV conditions, molecular O2 dissociates and forms oxygen radicals with molecular O2 to form ozone.

Suitable exposure distances are approximately 10 to 50 mm as specified in the ozone treatment plant specifications.

A suitable exposure power is about 5 to 50 pW / cm ² , for example about 10 to 30 pW / cm ² , for example about 20 pW / cm ² .

The contact angles of the polymer layer can optionally increase with aging at room temperature in a normal environment. However, this is a slow process and the effect is minimal. It is therefore desirable that printing be resumed as soon as possible after exposure to polar species.

Consequently, in some embodiments, the contact angle may be further increased after exposure to polar species by heat treatment at about 100 to 200 ° C, preferably about 150 ° C. A suitable heat treatment time is about 5 to 30 seconds, suitably about 10 to 20 seconds, for example 15 seconds. Said heat treatment would further increase the advancing contact angle and the contact angle hysteresis.

For example, the techniques described herein can achieve a contact angle hysteresis for ethylene glycol higher than 43 ° for PMMA / PS layers as described herein after exposure to UV / ozone for 120 seconds and after heat treatment at 150 ° C for 15 seconds. This is about 200% higher contact angle hysteresis than with conventional PMMA layers (Figure 4).

Printing

The present invention provides a surface with high hysteresis of the contact angle, which has a great influence on the drying of the printed structures. The coating surfaces according to the invention can be used for printing electronic components. The PMMA / PS layer can be used to adjust the wetting of many inks, for example for commercial silver inks, inks containing 40% or more by volume of one of ethylene glycol, ethanolamine, 1,3-propanediol, diethylene glycol or any other solvent with a similar surface tension, or inks containing 10% or more by weight of glycerol.

Printing precursor ink of lanthanum nickel with a ternary solvent with the composition 2ethoxyethanol (2EE), ethylene glycol (EG) and ethanolamine (EA) on PMMA layers treated with UV / ozone for 150 seconds (Matavž et al., Appl. Phys. Lett., 2018 , 113, 012904) results in a 10 ° advancing ink contact angle on such a layer. Despite the low advancing contact angle of the treated PMMA layer, drying causes the contact line to shift (Fig. 5, PMMA), which degrades the pattern definition.

In contrast to these known, smooth UV / ozone-treated PMMA layers, which are characterized by the dynamic behavior of the drying droplet contact line, nano-textured PMMA / PS layers as described here do not show wetting instability (Figure 5, PMMA / PS ) and can be used to apply well-defined structures. The higher hysteresis of the contact angle of the PMMA / PS polymer layer according to the invention enables a higher printing resolution, a better quality of the sample definition and a better morphology of the dried coatings.

Decomposition

When the ink or other functional layer is printed on the polymer layer as described herein, said polymer layer can be removed by thermal decomposition. The polymer layer decomposes immediately at temperatures below the temperatures at which the printed functional layer decomposes. Suitable temperatures are higher than 350 ° C.

The preferred thickness of the polymer layer (suitably 10 nm or less, for example 8 nm or less) prevents cracking or delamination of the printed functional layer during this process and reduces the amount of carbon in the intermediate layer.

It should be noted that the printing and optional removal of the polymer layer by degradation can be performed after drying of the polymer solution coating; or, if present, after surface modification by exposure to reactive polar species; or, if present, after surface modification by heating.

It should also be noted that the procedures as described herein can be repeated to print a larger number of samples on the substrate. For example, a substrate on which a sample has already been printed using the methods described herein (optionally by surface modification and / or degradation as described herein) may be used as an initial substrate for further polymer coatings and printing (optionally by surface modification and / or degradation as described herein).

***

The features disclosed in the description or claims or figures, expressed in specific forms or conditions to perform the described function or method or method to provide the described results, may, if appropriate, individually or in any combination of said features be used to realize the invention in various forms of it.

The invention has been described in connection with the possible embodiments described above, but a number of changes and variations are possible which are obvious to a person skilled in the art on the basis of the disclosed text. Accordingly, the presented examples of the invention are illustrative only and do not limit the invention. Various variations of the described embodiments can be made without departing from the spirit of the invention and its scope.

For the avoidance of any doubt, any theoretical explanations in the text are intended to understand the text. The inventors do not want any limitation with any of the theoretical explanations used.

Any subheading within the text is for text organization only and should not be construed as limiting the invention described.

Throughout the text, including claims, unless the context requires otherwise, the word contain and include as well as variations including, including, include the inclusion of a number or step or group of numbers or steps, and not the exclusion of any other number, step or group of numbers or steps .

The singular forms used in the description of the invention and in the claims also include duality and plural, unless the context clearly indicates otherwise. Ranks can be expressed from about one value and / or to about another value. When such a range is used, the second embodiment includes a range from one specified value and / or to another specified value. Similarly, when values are expressed as approximations with the word approximately, the exact value is considered to be represented in the second embodiment. The word approximately in relation to a numerical value is optional and represents, for example, +/- 10%.

EXAMPLES

EXAMPLE 1

PMMA (polymethylmethacrylate) and PS (polystyrene) with a molecular weight of 500 kDa were used as starting materials. 0.1 g of PMMA and 0.1 g of PS were mixed with 40 mL of anisole and stirred at room temperature until complete dissolution of the polymers. The polymer layer was prepared by completely covering the glass substrate with the polymer solution and dropping at 3000 rpm for 30 seconds. The polymer layer on the substrate was dried on a hot plate at 150 ° C for 2 min to give an 8 nm thick polymer layer.

Contact angles were measured using a Kruss DSA 20E tensiometer by observing suction droplets in a side view at 22 ° C +/- 2 ° C and a relative humidity of 30% + / 10%. Progressive contact angles were measured by increasing the droplet volume at a rate of 5 pL / min using a thin syringe, while receding contact angles were measured by decreasing the droplet volume using a thin syringe at a rate of -5 pL / min. The advancing and retracting contact angles for different solvents are presented in Table 1.

Table 1

Solvent / ink Progressive contact angle n Retracting contact angle (°) Contact angle hysteresis (°) Ethylene glycol 64 45 19 water 90 72 18 ethanolamine 62 41 21 glycerol 80 65 15 1,2-propanediol 58 15 43 Ink with lanthanum nickel precursors in ethylene glycol (0.1 M) 66 48 18 Ink with precursors of lanthanum nickel in 2-ethoxy ethanol, ethylene glycol, ethanolamine at a ratio of 20:16:64 ratio (0.1 M) 47 23 24

COMPARATIVE EXAMPLE 1

The contact angles of the different solvents were measured for smooth PMMA polymer surfaces prepared in the same manner as in Example 1 using 0.2 g of PMMA alone instead of 0.1 g of PMMA and 0.1 g of PS. The results are shown in Table 2.

Table 2

Solvent / ink Advancing contact angle (°) Retracting contact angle n Contact angle hysteresis (°) Ethylene glycol 55 43 12 water 76 64 12 ethanolamine 56 37 19 glycerol 68 60 8 1,2-propanediol 46 22 24 Ink with precursors of lanthanum nickel in 2-ethoxy ethanol, ethylene glycol, ethanolamine at a ratio of 20:16:64 ratio (0.1 M) 42 25 17

EXAMPLE 2

The PMMA / PS polymer layer was applied to the glass substrate as described in Example 1. The polymer layer was then treated as described in Example 1. The polymer layer was then treated with UV / ozone (simultaneous illumination of 185 nm and 254 nm, dominant wavelength of the ozone cleaner, 20 pW / cm ² for a wavelength of 254 nm at a distance of 10 to 50 mm as specified in the ozone cleaner instructions) at room temperature for different times. Ozone is formed through UV-mediated dissociation of molecular oxygen. The advancing and retracting contact angles of the different solvents are shown in Table 3. Exposure to the PMMA / PS layer of UV / ozone did not cause a significant change in surface roughness and morphology.

Table 3

Solvent / ink UV / ozone exposure time (s) Advancing contact angle (°) Retracting contact angle (°) Contact angle hysteresis (°) Ethylene glycol 30 54 31 23 Ethylene glycol 60 45 19 26 Ethylene glycol 120 27 0 27 water 30 62 12 40 water 60 47 0 ^ 47 water 120 44 0 44 Ink with precursors of lanthanum nickel in 2-ethoxy ethanol, ethylene glycol, ethanolamine at a ratio of 20:16:64 ratio (0.1 M) 30 14 0 14

COMPARATIVE EXAMPLE 2

The contact angles of the different solvents were measured for smooth PMMA polymer surfaces prepared and modified with UV / ozone in the same manner as in Example 2. The results are shown in Table 4.

Table 4

Solvent / ink UV / Ozone exposure time (s) Advancing contact angle (°) Retracting contact angle (°) Contact angle hysteresis (°) Ethylene glycol 30 45 25 20 Ethylene glycol 60 42 17 25 Ethylene glycol 120 0 0 0

water 30 62 36 26 water 60 61 31 30 water 120 47 23 24 ink with precursors of lanthanum nickel in 2-ethoxy ethanol, ethylene glycol, ethanolamine at a ratio of 20:16:64 ratio (0.1 M) 30 0 0 0

EXAMPLE 3

The PMMA / PS polymer layer was applied to the glass substrate as described in Example 1. The polymer layer was then treated with UV / ozone for 120 seconds under the conditions described in Example 2. After UV / ozone treatment, the polymer layer was heated to 150 ° C for 15 s. The advancing and retreating contact angles of the different solvents are shown in Table 5. Exposure to the PMMA / PS layer of UV / ozone and subsequent heating to 150 ° C did not result in a significant change in surface roughness and morphology.

Table 5

Solvent / ink UV / ozone exposure time (s) Advancing contact angle (°) Retracting contact angle (°) Contact angle hysteresis (°) Ethylene glycol 120 53 <10 > 43 water 120 73 10 63 Ink with precursors of lanthanum nickel in 2-ethoxy ethanol, ethylene glycol, ethanolamine at a ratio of 20:16:64 ratio (0.1 M) 120 20 0 20

COMPARATIVE EXAMPLE 3

The contact angles of the different solvents were measured for smooth PMMA polymer surfaces prepared and modified with UV / ozone and heated at 150 ° C for 15 s in the same manner as in Example 3. The results are shown in Table 6.

Table 6

Solvent / ink UV / ozone exposure time (s) Progressive contact angle Retracting contact angle (”) Contact angle hysteresis (°) Ethylene glycol 120 51 36 15 water 120 72 54 18 Ink with precursors of lanthanum nickel in 2-ethoxy ethanol, ethylene glycol, ethanolamine at a ratio of 20:16:64 ratio (0.1 M) 120 26 10 16

Figure 4 shows the results for ethylene glycol compared to those obtained using a similar method, where PMMA itself is used as a polymer layer instead of PMMA / PS as described herein.

REFERENCES

Many of the above-mentioned publications are cited for a better description of the invention and the prior art to which the invention relates. These publications are fully included in this description.

Claims (14)

Patent claims A method of applying a polymer layer to substrates, comprising the following steps; a) mixing poly (styrene), poly (methyl methacrylate) and solvent to form a polymer solution; b) applying the polymer solution to the substrate to form a polymer solution; c) drying the coating of the polymer solution to form a polymer layer on the substrate; d) exposing the polymer layer to reactive polar species to form an altered polymer layer on the substrate. The method of claim 1, wherein in step d) the polymer layer is exposed to UV / ozone. The method of claim 1, wherein in step d) the polymer layer is exposed to O2 plasma. A method according to any one of claims 1 to 3, comprising the further step: (e) heating the modified polymer layer to 100 to 200 ° C for 5 to 30 seconds. 5. A method of forming a printed substrate, comprising the steps of: forming an coated substrate by a method according to any one of claims 1 to 4; and (ii) printing on the coated substrate. The method of claim 5, wherein step ii) is performed with an ink containing a polar solvent. The method of claim 6, wherein the polar solvent is a mixture of 2-ethoxyethanol (2EE), ethylene glycol (EG) and ethanolamine (EA). The method of any one of claims 5 to 7, wherein the ink contains a metal oxide. A method according to any one of claims 5 to 8, comprising the further step: (iii) heating the printed substrate to a temperature of 350 ° C or higher to remove the polymer layer. The method of any one of claims 1 to 9, wherein the substrate is a silicon wafer. The method of any one of claims 1 to 10, wherein the substrate used in step b) has a pre-printed layer on the surface to which the polymer solution is applied in step b). A substrate obtained by a method according to any one of claims 1 to 11. The substrate of claim 12, wherein the polymer layer has a thickness of 10 nm or less. A substrate according to any one of claims 12 to 13, wherein the distance between the phase-separated islands is less than 1 pm.