WO2015061484A1 - Revêtement antireflet à couches multiples - Google Patents

Revêtement antireflet à couches multiples Download PDF

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Publication number
WO2015061484A1
WO2015061484A1 PCT/US2014/061816 US2014061816W WO2015061484A1 WO 2015061484 A1 WO2015061484 A1 WO 2015061484A1 US 2014061816 W US2014061816 W US 2014061816W WO 2015061484 A1 WO2015061484 A1 WO 2015061484A1
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WO
WIPO (PCT)
Prior art keywords
layer
coating
substrate
refractive index
layers
Prior art date
Application number
PCT/US2014/061816
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English (en)
Inventor
Phong Ngo
John E. Madocks
Original Assignee
General Plasma, Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by General Plasma, Inc. filed Critical General Plasma, Inc.
Publication of WO2015061484A1 publication Critical patent/WO2015061484A1/fr

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Classifications

    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements
    • G02B1/10—Optical coatings produced by application to, or surface treatment of, optical elements
    • G02B1/11—Anti-reflection coatings
    • G02B1/113—Anti-reflection coatings using inorganic layer materials only

Definitions

  • the present invention relates in general to antireflection coatings, and in particular to a multiple layer vacuum deposited coatings that are produced by a highly uniform and stable plasma enhanced chemical vapor deposition (PECVD) process.
  • PECVD plasma enhanced chemical vapor deposition
  • AR coatings on optically clear substrates have received both scientific and commercial attention for many years. Such coatings can enhance the performance and efficiency of products such as solar panels and cells, video display screens, automobile windscreens, building windows and touch displays. Unfortunately, AR coatings on such products have met with limited market penetration owing to the technological problems of depositing AR coatings of sufficient quality and performance. Owing to the practical difficulties, even those AR coatings that have been implemented have material attributes that are compromised when the manufacture of large substrates and high quantities is attempted.
  • a transparent substrate with an antireflection coating includes: at least six-layers in overlying contact on the surface, the six layers having at least one layer having a refractive index greater than about 2.15 at 632 nm and at least one layer having a lower refractive index of between 1.44 and 1.52 at 632 nm, where at least one of the lower refractive index layers is Si0 2 containing at least 0.25% hydrogen by atomic concentration.
  • all of the at least one lower refractive index layer are Si0 2 containing at least 0.25% hydrogen by atomic concentration.
  • At least one of the at least one layer has a refractive index greater than about 2.15 is Ti0 2 containing at least 0.25% chlorine by atomic concentration.
  • the substrate has at least one dimension larger than 150mm.
  • the substrate has at least one dimension larger than 300mm.
  • the inventive coating has an optical thickness variation of less than ⁇ 1.5% over the substrate.
  • the inventive coating has an optical thickness variation of less than ⁇ 3% over the substrate.
  • FIG. 1 is a cross-section view schematically illustrating a six layer anti-reflection coating stack in accordance with the present invention with the extent of the individual layers being distorted for visual clarity;
  • FIG. 2 shows graphs of reflectance as a percentage vs. visible wavelength (nm) spectrum for 3 different coated samples. Each sample has a 6 layer AR coating of the present invention applied to both sides.
  • FIG. 3 compares graphs of reflectance as a percentage vs. the visible wavelength (nm) spectrum for a four layer AR coating and the 6 layer AR coating of the present invention.
  • large area in the context of substrates is defined as having at least one dimension larger than 150 mm. This includes substrates that are individually coated as well as substrates that are combined on a carrier and passed through the coating process as, effectively, one larger substrate. These substrates can be flat like window glass or curved like an automotive windshield. They can be of any shape, square, round, etc. and can have holes or other features. They can also be flexible like a polymer film.
  • optical thickness is defined as the physical thickness of a layer multiplied by the refractive index (RI) of that layer at 632 nm. Visible light is generally accepted, and defined herein, as being light within a wavelength range between about 425 and 675 nm.
  • RI refractive index
  • Visible light is generally accepted, and defined herein, as being light within a wavelength range between about 425 and 675 nm.
  • range is intended to encompass not only the end point values of the range but also intermediate values of the range as explicitly being included within the range and varying by the last significant figure of the range.
  • a recited range of from 1 to 4 is intended to include 1-2, 1-3, 2-4, 3-4, and 1-4.
  • the PECVD layers of the present invention are enabled by the AC ion source sold by General Plasma, Inc. in Arlington Arizona and detailed in WO2010077659.
  • This source couples two electrodes across an AC power supply.
  • the electrodes span the width of the substrate (inclusive of carriers holding many small substrates) and the substrate(s) is moved past the electrodes.
  • a plasma and ion beam deposition zone is formed along the length of the source (the width of the substrate) between the substrate and source.
  • Highly uniform coatings are deposited across the substrate width, to within ⁇ 1.5% optical thickness variation, as the substrate passes through this deposition zone. Constant conveyance speed through the deposition zone produces equally uniform coating along the substrate length.
  • Two other aspects of the AC ion source to make the inventive 6 layer AR coating possible 1) highly stable and repeatable deposition process over days and weeks and 2) The deposited films are dense and amorphous and are environmentally durable.
  • a PECVD process with AC ion sources is generally conducted in the sequence and according to the guidelines below. These illustrative steps are for an Si02 coating process. The process steps for other materials are similar other than precursor and gas changes. While helpful as starting points, the process settings given will vary according to product requirements and substrate materials.
  • [0016] 2 Flow oxygen gas into the deposition zone to the process flow setting.
  • a common flow requirement is 3000 liter 02 per meter of substrate width.
  • the deposition zone process pressure should be in the range of 0.2Pa to 2Pa.
  • PECVD coating chambers can be configured to accommodate different substrate sizes and production quantity requirements. For instance, to coat glass 150mm x 100mm pieces with a six layer AR where the annual production quantity is many millions of pieces, the chamber can be designed with 6 AC ion sources. The glass pieces can be mounted in a carrier so about 150 pieces are on one carrier. In this case, the AC ion source deposition zone spans the width of the carrier such that all the glass pieces are uniformly coated. The carrier is moved past the 6 AC ion sources at a constant speed. The process settings of each AC ion source are adjusted so the layer thickness and film properties are correct for the constant speed shared by all the layers. Many other configurations will be evident to those skilled in the art. These will include roll to roll batch systems, large single sheet glass coating systems and smaller, rotating drum configurations. In all configurations, the substrate is moved past the AC ion source to effect PECVD coating uniformity.
  • FIG. 1 schematically illustrates an anti-reflection coating in accordance with the present invention.
  • Coating 20 is a structure of six layers.
  • a first layer 34, adjacent to the substrate, has an RI greater than 2.15 at a wavelength of about 632 nm.
  • a specific material for layer 34 is titanium oxide (Ti0 2 ).
  • the second layer 32 is a layer of a non- absorbing material having a refractive index between about 1.44 and 1.52.
  • a specific material for this layer is silicon dioxide (Si0 2 ).
  • Additional layers 28 and 24 are formed of materials with the same refractive index as layer 34, namely, greater than 2.15 at a wavelength of about 632 nm; or such layers are each independently formed of a material of a different refractive index to achieve a desired reflectivity coating 20.
  • Layers 26 and 22 are formed of materials with the same refractive index as layer 32, namely, between 1.44 and 1.52. Alternatively, such layers are each independently formed of a material of a different refractive index to achieve a desired reflectivity coating 20.
  • layers 34, 28, and 24 are all Ti0 2 and layers 32, 26, and 22 are all Si0 2 .
  • the precursor used to make the Ti0 2 layer is TiCl 4 .
  • TiCl 4 vapor is delivered to the deposition zone with oxygen during the coating process.
  • a dense, amorphous Ti0 2 layer with an RI of greater than 2.36 measured at 632nm with no measureable absorbsion is deposited on the substrate.
  • the Ti0 2 film is highly durable, passing grid and tape adhesion tests after boiling in water for 10 minutes and after immersion in a heated salt bath for 24 hours.
  • the Ti0 2 film is composed of titanium, oxygen and a small amount of chlorine. The function of the chlorine in the deposition process is not known. However, based upon the final film properties, its presence in the plasma process and the in the layer must be considered important.
  • the precursor used to make the Si0 2 layer 32 is trimethyldisiloxane (TMDSO). This precursor is vaporized and combined with oxygen in the deposition zone during the coating process and a dense, amorphous Si0 2 film is deposited.
  • the film has an RI of about 1.46 and has no measureable absorption.
  • the Si0 2 film is highly durable, passing grid and tape adhesion tests after boiling in water for 10 minutes and after immersion in a heated salt bath for 24 hours.
  • the Si02 film is composed of silicon, oxygen and small amounts of hydrogen and carbon.
  • Silane (SiH 4 ) gas has been used in place of TMDSO to make Si0 2 layers of equally good quality and performance. These films have been made using the same AC ion source. Because good PECVD films can be made without the inclusion of carbon, as is the case with silane, only hydrogen is considered mandatory for correct film formation.
  • a 4 layer AR stack design has a narrower bandwidth than a 6 layer AR stack (reference FIG. 3 and Example 2). With a narrower bandwidth, higher reflectance at the low and high wavelengths are detected by the human eye and the overall perceived reflectance is higher.
  • the advantage of a 4 layer stack over a 6 layer design is variation of the overall perceived reflectance color is reduced for a given layer optical thickness error. If a process is capable of ⁇ 3% optical thickness uniformity in production, the color variation from substrate to substrate will be acceptable for a 4 layer AR stack. If a 6 layer design is attempted with the same process, given the overall wider low reflection bandwidth, the reflectance variations at the high and low wavelengths are much more visible and result in unacceptable color variation to the user.
  • Example 1 The present invention is further detailed with respect to the following examples.
  • Example 1
  • FIG. 3 shows graphs of percent reflectance over the visible light spectrum for each coated piece.
  • the coating process is as follows: One piece is loaded into a single-ended, vertical coater PECVD chamber. It is appreciated that a PECVD apparatus that only has a single AC ion source deposits PECVD layers one at a time. The first Ti0 2 layer is deposited (RI 2.366, physical thickness 13.33 nm). The precursor is TiCl 4 .
  • Oxygen gas is delivered with the precursor vapor to the plasma source as the substrate is moved past the source.
  • the ratio between oxygen and precursor vapor is 2: 1.
  • the precursor is changed to TMDSO and oxygen flow is changed to effect a ratio of 10: 1 02:TMDSO.
  • the substrate is moved past the AC ion source to make Si0 2 (RI 1.465, physical thickness 37.90 nm).
  • SIMS Secondary Ion Mass Spectrometry
  • the sheet is turned over and the second side is coated with the same 6 layer AR stack, and by the same method as above. As is apparent from the overlaying graphs in FIG. 2, the coating repeatability is excellent.
  • a 4 layer AR coating is designed using the same materials as Example 1 (two layers of Ti0 2 and two of Si0 2 ) and a glass sheet is coated on both sides using the same PECVD coating chamber and the AC ion source.
  • the reflectance curve over the visible spectrum for this four layer AR coating and 6 layer AR coating are shown in FIG. 3.
  • a 6 layer AR coating has significantly lower overall reflection and the AR bandwidth is wider.
  • the increase in bandwidth is especially important as the human eye detects light from 425nm to 675nm.

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  • Physics & Mathematics (AREA)
  • Chemical & Material Sciences (AREA)
  • Inorganic Chemistry (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Chemical Vapour Deposition (AREA)

Abstract

La présente invention concerne un substrat transparent pourvu d'un revêtement antireflet qui comprend au moins six couches en contact par superposition sur la surface. Les six couches comportent au moins une couche ayant un indice de réfraction supérieur à environ 2,15 à 632 nm et au moins une couche ayant un indice de réfraction inférieur compris entre 1,44 et 1,52 à 632 nm. Au moins une des couches ayant un indice de réfraction inférieur est constituée d'un SiO2 contenant au moins 0,25 % d'hydrogène en concentration atomique. Dans un mode de réalisation particulier du revêtement, au moins une couche ayant un indice de réfraction supérieur à environ 2,15 à 632 nm est constituée d'un TiO2 contenant au moins 0,25 % de chlore en concentration atomique.
PCT/US2014/061816 2013-10-22 2014-10-22 Revêtement antireflet à couches multiples WO2015061484A1 (fr)

Applications Claiming Priority (2)

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US201361894301P 2013-10-22 2013-10-22
US61/894,301 2013-10-22

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5147125A (en) * 1989-08-24 1992-09-15 Viratec Thin Films, Inc. Multilayer anti-reflection coating using zinc oxide to provide ultraviolet blocking
US5362552A (en) * 1993-09-23 1994-11-08 Austin R Russel Visible-spectrum anti-reflection coating including electrically-conductive metal oxide layers
US6368470B1 (en) * 1999-12-29 2002-04-09 Southwall Technologies, Inc. Hydrogenating a layer of an antireflection coating
US20040137718A1 (en) * 1998-09-03 2004-07-15 Micron Technology, Inc. Anti-reflective coatings and methods for forming and using same
US20080002260A1 (en) * 2006-06-28 2008-01-03 Essilor International Compagnie Generale D'optique Optical Article Having a Temperature-Resistant Anti-Reflection Coating with Optimized Thickness Ratio of Low Index and High Index Layers

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5147125A (en) * 1989-08-24 1992-09-15 Viratec Thin Films, Inc. Multilayer anti-reflection coating using zinc oxide to provide ultraviolet blocking
US5362552A (en) * 1993-09-23 1994-11-08 Austin R Russel Visible-spectrum anti-reflection coating including electrically-conductive metal oxide layers
US20040137718A1 (en) * 1998-09-03 2004-07-15 Micron Technology, Inc. Anti-reflective coatings and methods for forming and using same
US6368470B1 (en) * 1999-12-29 2002-04-09 Southwall Technologies, Inc. Hydrogenating a layer of an antireflection coating
US20080002260A1 (en) * 2006-06-28 2008-01-03 Essilor International Compagnie Generale D'optique Optical Article Having a Temperature-Resistant Anti-Reflection Coating with Optimized Thickness Ratio of Low Index and High Index Layers

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