DE102009030303A1 - Process for the preparation of antireflective coating-forming coatings and antireflective coatings - Google Patents

Abstract

The method for the production of a coating having antireflexion layer on a movable substrate (30) by a plasma-enhanced chemical vapor deposition (PECVD), comprises providing a gas mixture having process-, carrier- and/or balance gas through a slit formed between two high-voltage electrodes (20) and producing plasma between a self-moving substrate that is supported by a counter electrode (50), and the high-voltage electrode. The plasma presets a plasma zone with standard, where the plasma is processed at atmospheric pressure and/or approximate atmospheric pressure. The method for the production of a coating having antireflexion layer on a movable substrate (30) by a plasma-enhanced chemical vapor deposition (PECVD), comprises providing a gas mixture having process-, carrier- and/or balance gas through a slit formed between two high-voltage electrodes (20) and producing plasma between a self-moving substrate that is supported by a counter electrode (50), and the high-voltage electrode. The plasma presets a plasma zone with standard, where the plasma is processed at atmospheric pressure and/or approximate atmospheric pressure and a volume dose of the plasma of 2x 10 5>to 2x 10 7>Ws/m 3>is kept in the plasma zone. The plasma zone is worked with dielectric barrier discharge. The gas speed of the gas mixture is selected so that a time spent of the plasma in the plasma zone is 5-500 ms. The PECVD process is carried out so that the plasma zone comprises a pre-ionization area with decreased deposition rate and deposition area and the pre-ionization is partially carried out in gap. A reflection reduction is achieved to 2.5% in a wavelength range of 200 nm per coated substrate surface related to the uncoated substrate. The substrate has a reflexion reduction of 2.5% in the range of 300-1000 nm. A further layer is deposited on a layer that forms antireflexion layer. A layer influencing the wetting of the surface is deposited as a further layer. A layer improving the scraper stability of the surface is deposited as a further layer. The glass is float glass or cast glass. The substrate is optical transparent plastic. An independent claim is included for an antireflexion coating on a substrate.

Description

The The invention relates to a process for the preparation of antireflective coating-forming Coatings on a substrate as well as an antireflective coating on a substrate.

It is known today that transparent plastics and glass are provided with an antireflection coating in order to minimize the losses due to the reflection on the surfaces. For z. As lenses and windows are used mainly layer combinations that contain at least one high refractive index layer. These multilayer films are mainly produced by PVD processes, such as sputtering or vapor deposition ( EP 1 206 715 A1 ) or via PECVD / PICVD methods ( DE 102 50 564 A1 ). However, these multilayer antireflective coatings are only suitable for applications in which the spectral bandwidth of the antireflection coating may be less than one octave ( A. Gombert, M. Rommel, Research Group Solar Energy "Themen 97/98", p. 81 ). For a broadband anti-reflection, as z. B. is required for solar applications, these methods can therefore not be used. In addition, the multilayer systems are too expensive for many applications.

In order to achieve an effective increase in solar transmission, the refractive index of the substrate material (n _S ≅ 1.5) must be adjusted to that of air (n _L = 1) over a very low refractive index thin film system (n _D <1.3). This is not achievable with the classical coating technologies as dense films. However, a number of methods for the broadband transmission enhancement of acrylic glass and float glass have already been investigated ( A. Gombert, M. Rommel, Research Group Solar Energy "Themen 97/98", p. 81 ), which are based on porous or microstructured materials in which a solid is mixed with air. The pores or structures must be fine enough so that they are not dissolved by the incident radiation.

In the field of solar applications, such antireflective properties on glass via sol-gel layers (Centrosolar, EP 1 328 483 B1 . EP 1 181 256 B1 ) and etched surfaces (SUNARC) already offered. Another possibility is the deposition of such porous layers by means of PECVD processes under low pressure conditions as described in US Pat DE 199 12 737 is described.

If plastics are to be anti-reflective, structures are often embossed into the surface or the surface is patterned by plasma etching ( DE 103 18 566 ).

More recently, plasmas that operate at ambient pressure are being used more and more frequently. With cold, operated at atmospheric pressure, in technical usage as well. dielectrically impeded discharges ("(dielectric) barrier discharges") called "corona discharges", it is also possible to deposit layers by means of PECVD. In this case, targeted porous layers can also be produced, which can be used as an antireflection layer. In EP 1 342 810 . EP 1 819 843 A . WO 08/045226 A This is achieved through the use of organosiloxanes on plastics. at Jidenko (J. Phys. D: Appl. Phys. 40 (2007) 4155-4163) and Borra (J. Phys. D: Appl. Phys. 39 (2006) R19-R54) describes the formation of porous layers by means of silane as a monomer.

All these layers or porous materials show a very similar, optically almost the same course of the transmission or reflection. You can about the layer thickness and the refractive index in a limited spectral range to a good transmission or low reflection can be optimized. A broadband anti-reflective coating but can not be achieved with it.

outgoing It is the object of the present invention to provide a cost-effective, to enable broadband antireflective of substrates wherein also the refractive indices of the adjacent layers are adjusted should be.

These The object is achieved by the method with the features of the claim 1 solved. Claim 23 relates to an antireflective coating. Further advantageous embodiments are in the dependent claims contain.

According to the invention, a process is provided for producing at least one antireflection coating on a moving substrate by means of a PECVD process, wherein a gas mixture comprising at least one working, carrier and balance gas is passed through at least one gap forming between at least two high voltage electrodes and at least between the moving substrate carried by at least one counterelectrode and the high voltage electrodes, a plasma is generated which provides a plasma zone with the proviso that operating at atmospheric pressure or approximately atmospheric pressure and a volume dose of the plasma from 10 ⁵ to 10 ⁸ Ws / m ^{3 is maintained} in the plasma zone.

Under approximate atmospheric pressure is understood according to the invention a pressure between 0.9 and 1.1 bar. With the method according to the invention, it is possible via a PECVD process at atmo Spherical pressure (or approximate atmospheric pressure) to achieve a very broadband (several 100 nm) anti-reflection or increase in the transmission. For this purpose, the arrangement of an electrode system with a gas inlet and a plurality of high-voltage electrodes has been optimized such that the layer deposited in one step, ie, only one passage of the wafer to be coated by a coating apparatus, contains different refractive indices. It is important that the number of electrodes and the gas supply and gas removal matched exactly to the monomer who the, to obtain the optimum optical properties.

Preferably, the volume dose is in the range of 2 × 10 ⁵ to 2 × 10 ⁷ Ws / m ³ . As a result, an optimum coating of the substrate is made possible. So it is possible to obtain a surface that is coated as evenly as possible. The volume dose is composed of the power per volume and the residence time of the process gas in the plasma zone in the volume. It is a measure of the degree of conversion of the precursor.

Farther can in the inventive method with a dielectric barrier discharge to be worked.

The Gas velocity of the gas mixture can be chosen so be that a residence time of the plasma in the plasma zone of 1 ms to 1000 ms is maintained. This allows a homogeneous coating of the surface in dependence of the substrates used as well as the working, carrier as well as balance gas. An advantage is a residence time of 5 ms to 500 ms.

alternative The PECVD method can be operated so that the plasma zone a Vorionisationsbereich with reduced deposition rate and a Separation area includes.

Prefers the PECVD process is operated so that the pre-ionization at least partially done in the gap. The arrangement for the method of z. B. a gas supply in the middle and at least one or more arbitrarily wide electrodes on each side consist of gas supply, whereby a targeted extraction of the Gases can be realized. By a suitable electrical Arrangement, the preionization can also take place between the electrodes, so that only the deposition takes place on the substrate. In the area The preionization is usually only a minor Layer deposited, whereas in the deposition zone, the actual Deposition takes place.

advantageously, is coated with the method according to the invention pro Substrate surface, based on the uncoated substrate, a Reflection reduction by at least 2.5% in one wavelength range of at least 200 nm. This area can be variable between 200 nm and 1500 nm are set and z. B. between 300 nm and 500 nm, 400 nm and 600 nm or 500 nm and 700 nm.

As a light beam passes through a disk, the light is reflected at interfaces and absorbed in the materials; for energy conservation reasons, the transmitted intensity, based on an incident intensity of 100%, is given by T = 100% - R - A, where R and A denote the "energy losses" by reflection and absorption. If it is possible to reduce the reflection by x% by antireflecting an interface of the originally uncoated glass, T increases by x%. The theoretically maximum possible antireflection of an interface of a material with the refractive index n _s is [(n _s -1) / (n _s + 1)] ² , in the case of ordinary glass with n _s ≈ 1.5 that is 4.0%.

The Substrate preferably has a reflection reduction in the range of 300 to 1000 nm of at least 2.5%. Consequently, this does not only cover the area of visible light, but also a part of the near infrared range as well as the UV light. Thus, the invention Method for a large spectral bandwidth and related, various requirements can be used.

It can also with the method according to the invention a coating forming an antireflective layer is deposited.

Farther can be on the at least one layer containing an antireflective layer forms, at least one further layer to be deposited.

Advantageously, a layer influencing the wetting of the surface can be deposited as at least one further layer. This may be a hydrophobic layer, the z. B. by hexamethylcyclotrisiloxane, hexamethyldisiloxane or a fluorine compound (cC ₄ F ₈ or CF ₄ ) under inert conditions (Ar, He, N ₂ as a carrier gas) can be deposited and has a water edge angle over 90 °.

Preferably, a layer which improves the scratch resistance of the surface is deposited as at least one further layer. This allows use of the substrates even under extreme environmental conditions, such. B. in the outdoor area. This may be a glassy SiO _x layer, as described in Example 3.

As the working gas is preferably at least a precursor selected from silanes, organosilanes, organosiloxanes, organosilazanes, alkoxysilanes, fluorine-containing monomers and / or mixtures thereof used.

in this connection is the organosilane selected from substances such. B. Tetramethylsilane, trimethylsilane or mixtures thereof. in this connection is the organosiloxane selected from substances such. Hexamethyldisiloxane, octamethyltrisiloxane or mixtures thereof. Here, the organosilazane is selected from substances such as As hexamethyldisilazane, octamethyltrisilazane or mixtures hereof. Here, the alkoxysilane is selected from substances such as For example, tetramethoxysilane, tetraethoxysilane, aminopropyltrimethoxysilane or mixtures thereof.

Of the Term "working gas" includes a reactive one Substance which under standard conditions (room temperature, normal pressure) may be gaseous and is polymerizable, so they can form a coating on the substrate.

ever After Precursor, the hydrophilicity of the surface be increased or hydrophobic layers are applied or the scratch resistance and thus the stability of the layers increase. A measure of the degree of implementation of the precursor in the plasma zone is the volume dose already mentioned.

Preferably, the balance gas is selected from air, CO ₂ , O ₂ , NH ₃ , N ₂ O, He, N ₂ , Ar. The balance gas according to the invention is a reactive or non-reactive gas which is added to the carrier gas and working gas in front of the plasma zone.

The Carrier gas is preferably selected from noble gases or inert gases, in particular helium, argon and nitrogen. carrier gases are gases that carry the working gas into the plasma zone.

advantageously, is used as a substrate glass, in particular float glass or cast glass. Consequently These layers are excellent u. a. for use suitable for glazing and solar applications. With this Methods can be any possible planar substrates, such as foils, plates or discs made of glass, silicon, rubber or plastic be coated. Furthermore, by means of a dynamic coating, d. H. by movement of the substrate or the electrode head, a particularly good coating and thus a broadband anti-reflection coating be achieved.

When Substrate can also polymers, in particular optically transparent plastics, are used.

Farther is a producible by one of the methods described so far Antireflection coating on a substrate according to the invention.

Based on the following 1 to 5 as well as Examples 1 to 3, the object according to the application is intended to be explained in more detail, without restricting it to these special variants.

1 shows the calculated reflection of a double-coated with porous SiO ₂ layers float glass.

2A shows the schematic structure for coating substrates.

2 B shows the layer thickness and the refractive index as a function of the measuring position.

3A shows the dependence of the reflection on the wavelength.

3B shows the dependence of the transmission on the wavelength.

4A shows a possible arrangement for the deposition of the broadband antireflection coating, wherein the substrate is wider than the area of the gas supply or the gas outlet and the high voltage electrodes.

4B shows a further possible arrangement for the deposition of the broadband antireflection coating, in which case the substrate is narrower than the sum of high voltage electrodes and gas supply or outlet.

4C shows another possible arrangement for depositing the broadband antireflection coating, wherein the gas supply between the two high-voltage electrodes is carried out and the outlet is arranged to the left or right of the high voltage electrodes.

5A shows the influence of the electrical arrangement on the areas of the preionization and the deposition, wherein the high voltage is connected in phase on both electrodes.

5B shows the influence of the electrical arrangement on the areas of the preionization and the deposition, wherein the high voltage is connected in phase opposition.

1 shows the calculated reflection of a floating SiO ₂ layers coated on both sides with floating SiO ₂ layers. The effective refractive index n = 1.24 and the layer thickness is 150 nm. The calculated reflection increases in the range of 250 to 400 nm to 9% and falls to a wavelength of 700 nm back to 0. Thereafter, the value for the calculated reflection in a wavelength range of 700 to 1,500 nm almost linearly increases and thereafter approaches a maximum of 7%.

In 2A the structure for the coating process according to the invention is shown. The gas inlet 10 occurs between the two high voltage electrodes 20 on the glass substrate 30 , The glass substrate 30 is here on the counter electrode 50 arranged. With the numbers 1 to 5 are different measuring positions that are on the glass substrate 30 are designated.

2 B shows the dependence of the layer thickness and the refractive indices on the measuring position 1 to 5 , The layer thickness is at the measuring position 1 to 3 in the range of 50 nm and at the measuring position 4 and 5 in the range of 350 nm. The refractive index is for measuring position 1 at 1,125 and for measurement position 2 and 3 in the range of 1.05. For the measuring positions 4 and 5 the refractive index is 1.2 or 1.1525. In 2 B the refractive index and layer thickness profile of a static coating with silane is shown.

3A shows the reflection as a function of the wavelength in a two-sided antireflection coating according to the invention on float glass, wherein the substrate or the electrode head is moved. the reflection of the antireflection layer is in the range of 0 to 600 nm at 1% and decreases in a range up to about 800 nm to 0.5%. This is followed by an increase in the reflection, which goes in the range of 2,000 to 2,500 against a maximum, here 5%. The reference (uncoated float glass) has an increase in reflection from 5.5 to 8.5% in the range of 0 to 100 nm. Thereafter, the percentage reflection decreases slightly, but is well above the reflection of the antireflection coating according to the invention over the entire measured wavelength range.

3B shows the transmission of a reference and the anti-reflection coating according to the invention as a function of the wavelength. The curves for the transmission run almost parallel, wherein for the antireflection coating according to the invention the transmission has a higher value over the entire measured wavelength range throughout than for the reference (uncoated float glass).

4A shows a possible arrangement for depositing the broadband antireflection coating. Here are the high voltage electrodes 20 left and right of the gas supply 40 arranged. The substrate 30 lies opposite this arrangement. On the counter electrode 50 is the substrate 30 arranged. The arrow below the counter electrode shows the direction of movement of the counter electrode 50 and the substrate thereon 30 at.

4B shows a further possible arrangement for the deposition of the broadband antireflective coating according to the invention. The substrate 30 is on the counter electrode 50 arranged the gas supply 40 is opposite. The gas supply 40 is between two high voltage electrodes 20 arranged. The arrow below the counter electrode 50 shows the direction of movement of the substrate 30 at.

4C shows a further variant for depositing the antireflection coating. Here is the gas supply 40 between two high voltage electrodes 20 above the substrate 30 arranged. The gas outlet 45 is left or right of the high voltage electrodes 20 arranged. The substrate 30 is located on the counter electrode 50 which is moved in the direction of the arrow.

5A shows another possible arrangement, in which case the influence of the electrical arrangement on the areas of preionization 60 and the deposition 70 is shown. The high voltage is on both high voltage electrodes 20 in-phase switched. Here is the substrate 30 on the counter electrode 50 , Opposite this arrangement is the gas supply 40 between the two high voltage electrodes 20 done, arranged.

In 5B is the high voltage of the high voltage electrodes 20 switched in antiphase. As a result, the plasma also ignites between the electrodes 20 and the preionization 60 is not located directly on the substrate surface 30 , The gas supply 40 occurs between the two high voltage electrodes 20 on the substrate 30 that on the counter electrode 50 is arranged. By the arrow below the counter electrode 50 is the direction of movement of the substrate 30 shown.

These various arrangements can be combined as desired in dependence from the substrates as well as the desired surface properties.

example 1

Antireflective coating of a float glass (dynamic)

A coating system with a central gas inlet and a high voltage electrode on each side is used. The gas velocity is chosen to achieve a residence time of 12 ms with a mixture of helium, carbon dioxide, ammonia and silane. A dielectric barrier discharge is operated, so that a volume dose of 6 · 10 ⁵ W · s / m ^{3 is} achieved. A moving glass substrate is coated on one side at a speed of 1 mm / s. The sample is then rotated and coated with the same parameters on the back. In the case of the UV-VIS spectroscopy measured sample, the reflection in the range of 300 to 1000 nm reduced to about 1%.

Example 2

Antireflective coating of a float glass (static)

A coating reactor with two glass plates (10 × 30 cm ² ) and copper tape as planar electrodes (5 × 25 cm ² ) is rinsed from one side with a gas mixture of helium, nitrous oxide, ammonia and silane. The total residence time in the reactor is 360 ms and the total volume dose 2 × 10 ⁵ Ws / m ³ . It turns out that after a residence time of about 5 ms, the layer deposition of an antireflection layer begins and, due to the selected volume dose, this extends as an antireflection layer up to a residence time of about 140 ms. Thereafter, the precursor is almost completely reacted.

Example 3

Anti-reflective and anti-scratch coating

A float glass is first coated with the antireflective layer using the parameters described in Example 1. However, this layer is deposited at a speed of 2 mm / s. Subsequently, with an identical arrangement with the precursor TMOS (tetramethoxysilane) and nitrogen and ammonia as process gases, the gas velocity is chosen so that a residence time of 10 ms and a volume dose of 5 × 10 ⁵ Ws / m ³ and a speed of 4 mm / s operated. In addition to the antireflection effect, this layer combination also exhibits improved scratch stability.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• EP 1206715 A1 [0002]
• DE 10250564 A1 [0002]
• - EP 1328483 B1 [0004]
• - EP 1181256 B1 [0004]
• - DE 19912737 [0004]
• - DE 10318566 [0005]
• - EP 1342810 [0006]
• - EP 1819843 A [0006]
• - WO 08/045226 A [0006]

Cited non-patent literature

• - A. Gombert, M. Rommel, Solar Energy Research Group "Topics 97/98", p. 81 [0002]
• - A. Gombert, M. Rommel, Solar Energy Research Group "Topics 97/98", p. 81 [0003]
• Jidenko (J. Phys. D: Appl. Phys. 40 (2007) 4155-4163) [0006]
• - Borra (J. Phys. D: Appl. Phys. 39 (2006) R19-R54) [0006]

Claims (23)

A process for producing at least one coating which forms an antireflection coating on a moving substrate by means of a PECVD process, wherein a gas mixture comprising at least one working, carrier and balance gas is passed through at least one gap forming between at least two high voltage electrodes and at least between them moving substrate supported by at least one counter electrode, and generating a plasma defining a plasma zone with the proviso that: a) operating at atmospheric pressure and approximate atmospheric pressure; and b) a volume dose of the plasma from 10 ⁵ to 10 ⁸ Ws / m ^{3 is maintained} in the plasma zone. A method according to claim 1, characterized in that the volume dose in the range of 2 × 10 ⁵ to 2 × 10 ⁷ Ws / m ³ . Method according to claim 1 or 2, characterized that works with a dielectric barrier discharge. Method according to at least one of the claims 1 to 3, characterized in that the gas velocity of Gas mixture is chosen so that a residence time of Plasma is maintained in the plasma zone from 1 ms to 1000 ms. Method according to claim 4, characterized in that that a residence time of 5 ms to 500 ms is maintained. Method according to at least one of the claims 1 to 5, characterized in that the PECVD method so operated is that the plasma zone with a Vorionisationsbereich with reduced From a rate and a separation area includes. Method according to at least one of the claims 1 to 5, characterized in that the PECVD method so operated is that the pre-ionization takes place at least partially in the gap. Method according to at least one of the claims 1 to 7, characterized in that per coated substrate surface based on the uncoated substrate, a reflection reduction by at least 2.5% in a wavelength range of at least 200 nm is achieved. Method according to claim 8, characterized in that that the substrate in the range of 300 to 1000 nm, a reflection reduction of at least 2.5%. Method according to at least one of the claims 1 to 9, characterized in that one an antireflection layer forming coating is deposited. Method according to at least one of the claims 1 to 9, characterized in that on the at least one layer, which forms an antireflex, at least one further layer is deposited. Method according to claim 11, characterized in that that as at least one further layer, the wetting of the Surface influencing layer is deposited. Method according to claim 11 or 12, characterized that as at least one further layer, the scratch resistance the surface improving layer is deposited. Method according to at least one of the claims 1 to 13, characterized in that at least as working gas a precursor selected from silanes, organosilanes, organosiloxanes, Organosilazanes, alkoxysilanes, fluorine-containing monomers and / or Mixtures thereof is used. Method according to claim 14, characterized in that that the organosilane is selected from substances such as z. Tetramethylsilane, trimethylsilane or mixtures thereof. Method according to claim 14, characterized in that that the organosiloxane is selected from substances such as z. As hexamethyldisiloxane, octamethyltrisiloxane or mixtures hereof. Method according to claim 14, characterized in that that the organosilazane is selected from substances such as z. As hexamethyldisilazane, octamethyltrisilazane or mixtures hereof. Method according to claim 14, characterized in that that the alkoxysilane is selected from substances such as z. For example, tetramethoxysilane, tetraethoxysilane, aminopropyltrimethoxysilane or mixtures thereof. Method according to at least one of claims 1 to 18, characterized in that the balance gas is selected from air, CO ₂ , O ₂ , NH ₃ , N ₂ O, He, N ₂ , Ar. Method according to at least one of the claims 1 to 19, characterized in that the carrier gas is selected is from noble gases or inert gases, in particular helium, argon and Nitrogen. Method according to at least one of Claims 1 to 20, characterized in that as the substrate glass, in particular float glass or cast glass, is used. Method according to at least one of the claims 1 to 20, characterized in that as a substrate polymers, in particular optically transparent plastics are used. Antireflection coating on a substrate, manufacturable by a method according to at least one of the claims 1 to 22.