Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B29/00—Layered products comprising a layer of paper or cardboard
  • B32B29/06—Layered products comprising a layer of paper or cardboard specially treated, e.g. surfaced, parchmentised
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
  • D21H17/63—Inorganic compounds
  • D21H17/67—Water-insoluble compounds, e.g. fillers, pigments
  • D21H17/68—Water-insoluble compounds, e.g. fillers, pigments siliceous, e.g. clays
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B17/00—Layered products essentially comprising sheet glass, or glass, slag, or like fibres
  • B32B17/06—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material
  • B32B17/067—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material of fibres or filaments
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B5/00—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts
  • B32B5/02—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by structural features of a fibrous or filamentary layer
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B5/00—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts
  • B32B5/22—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by the presence of two or more layers which are next to each other and are fibrous, filamentary, formed of particles or foamed
  • B32B5/24—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by the presence of two or more layers which are next to each other and are fibrous, filamentary, formed of particles or foamed one layer being a fibrous or filamentary layer
  • B32B5/28—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by the presence of two or more layers which are next to each other and are fibrous, filamentary, formed of particles or foamed one layer being a fibrous or filamentary layer impregnated with or embedded in a plastic substance
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
  • B32B7/04—Interconnection of layers
  • B32B7/12—Interconnection of layers using interposed adhesives or interposed materials with bonding properties
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H13/00—Pulp or paper, comprising synthetic cellulose or non-cellulose fibres or web-forming material
  • D21H13/36—Inorganic fibres or flakes
  • D21H13/38—Inorganic fibres or flakes siliceous
  • D21H13/40—Inorganic fibres or flakes siliceous vitreous, e.g. mineral wool, glass fibres
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H13/00—Pulp or paper, comprising synthetic cellulose or non-cellulose fibres or web-forming material
  • D21H13/36—Inorganic fibres or flakes
  • D21H13/38—Inorganic fibres or flakes siliceous
  • D21H13/44—Flakes, e.g. mica, vermiculite
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H13/00—Pulp or paper, comprising synthetic cellulose or non-cellulose fibres or web-forming material
  • D21H13/36—Inorganic fibres or flakes
  • D21H13/46—Non-siliceous fibres, e.g. from metal oxides
  • D21H13/50—Carbon fibres
• • G—PHYSICS
  • G02—OPTICS
  • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
  • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
  • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
  • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
  • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
  • G02F1/1333—Constructional arrangements; Manufacturing methods
  • G02F1/133305—Flexible substrates, e.g. plastics, organic film
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/24—Structurally defined web or sheet [e.g., overall dimension, etc.]
  • Y10T428/24355—Continuous and nonuniform or irregular surface on layer or component [e.g., roofing, etc.]
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/4935—Impregnated naturally solid product [e.g., leather, stone, etc.]

Definitions

• the present invention relates to an impregnated inorganic material and method for manufacturing the impregnated inorganic material.
• the impregnated inorganic material flexible substrate, impregnated inorganic paper
• the impregnated inorganic material is used to make a flexible display or a flexible electronic.
• the plastic substrates by themselves suffer from poor O 2 and water vapor barrier properties, relatively high CTE, dimensional stability, thermal limits, and chemical durability.
• the metal substrates suffer from surface roughness, non-transparency, and conductivity while, the thin glass substrates are brittle and flaw sensitive, so bending and cutting are problematic.
• One main purpose of this invention is to provide a flexible substrate which has improved physical properties when compared to the properties of plastic substrates, metal substrates and continuous thin glass substrates. This need and other needs are satisfied by the flexible substrate and method of the present invention.
• a flexible substrate is described herein which is made from a freestanding inorganic material (e.g., mica paper) with pores/interstices that have been impregnated with a special impregnating material (e.g., silsesquioxane, alkali silicate glass with weight ratio of Si ⁇ 2 /X 2 ⁇ (where X is alkali Na, K etc.) between 1.6-3.5.
• a freestanding inorganic material e.g., mica paper
• a special impregnating material e.g., silsesquioxane, alkali silicate glass with weight ratio of Si ⁇ 2 /X 2 ⁇ (where X is alkali Na, K etc.) between 1.6-3.5.
• the flexible substrate is made by: (1) providing a freestanding inorganic material; (2) providing an impregnating material; (3) impregnating the pores/interstices within the freestanding inorganic material with the impregnating material; and (4) curing the freestanding inorganic material with the impregnated pores/interstices to form the flexible substrate.
• the flexible substrate is typically used to make a flexible display or a flexible electronic.
• FIGURE 1 is a cross-sectional side-view of a flexible substrate (impregnated inorganic material) which is used to make a flexible display or flexible electronic in accordance with the present invention
• FIGURES 2A-2T show multiple photos and graphs that illustrate the results of various experiments which where conducted to evaluate several exemplary flexible substrates that had been made in accordance with the present invention
• FIGURE 3 is a cross-sectional side-view of a flexible substrate (impregnated inorganic material) which is used as a protective coating on a glass substrate in accordance with the present invention.
• FIGURE 4 is a graph that illustrates the results of an experiment which was conducted to evaluate how well an exemplary flexible substrate functions as a protective coating on a glass substrate in accordance with the present invention.
• FIGURE 1 is a cross-sectional side-view of a flexible substrate 100 (impregnated inorganic material 100) in accordance with an embodiment of the present invention.
• the flexible substrate 100 includes a freestanding inorganic material 102 (freestanding inorganic paper 102) with interstices/pores 104 impregnated with a special impregnating material 106. If desired, the flexible substrate 100 could have a barrier coating 108 placed on one or both surfaces to help improve a barrier property.
• the barrier coating 108 could be a deposited inorganic layer (e.g., silica, silicon nitride,...), a multi-layer inorganic/organic layer stack (e.g., BarixTM coating from Vitex Systems, etc, or a continuous thin organic sheet (e.g., Coming's Microsheet, ).
• a deposited inorganic layer e.g., silica, silicon nitride,
• a multi-layer inorganic/organic layer stack e.g., BarixTM coating from Vitex Systems,
• a continuous thin organic sheet e.g., Coming's Microsheet, .
• the freestanding inorganic material 102 is an assembly of particles (or fibers) which is composed of an inorganic material either crystalline or amorphous.
• the freestanding inorganic material 102 could be mica paper 102, graphite paper 102, carbon nanotube paper 102 or glass fiber paper 102.
• the type of freestanding inorganic material 102 which is selected to be used for a particular application is based on certain physical properties including, for example, material composition, mechanical properties, pore volume, particle size, aspect ratio and optical absorption.
• the freestanding inorganic material 102 is selected based on the type of device it is going to help make like a flexible display (e.g., electrophoretic display, cholesteric liquid crystal display, OLED display, LCD display, other active or passive matrix displays and drive circuitry) or a flexible electronic (e.g., photovoltaic, solar cell, RFID, sensors).
• a flexible display e.g., electrophoretic display, cholesteric liquid crystal display, OLED display, LCD display, other active or passive matrix displays and drive circuitry
• a flexible electronic e.g., photovoltaic, solar cell, RFID, sensors.
• the impregnating material 106 is selected based in part on how well it can impregnate the pores/interstices 104 within the freestanding inorganic material 102.
• the two types of impregnating material 106 which are disclosed herein that have been used to impregnate the pores/interstices 104 within the freestanding inorganic material 102 include a sol-gel silsesquioxane material 106 and a potassium silicate glass 106 (where the potassium silicate glass has a weight ratio of SiC ⁇ /K ⁇ O of 2.5).
• other types of impregnating material 106 could be used instead so long as that material can effectively impregnate the pores/interstices 104 within the freestanding inorganic material 102.
• the impregnating material 106 is selected based in part on whether or not it can make a flexible substrate 100 which has desirable physical properties so one can use it to make a flexible display and/or a flexible electronic.
• TABLE 1 contains a list of the desirable physical properties which have been exhibited by an exemplary flexible substrate 100 so it could be used to make a flexible display or flexible electronic.
• a minimum substrate use temperature which is greater than 300 0 C is a property that can not been obtained by traditional commercially available inorganic papers which are impregnated with a polymer or a silicone (for example US Samica 4791-4 silicone bonded mica paper).
• a substrate fabrication temperature of less than 1000 0 C is a property that can not been obtained by traditional inorganic composites through processes such as glass melt processes or typical pyrolization processes.
• the flexible substrate 100 is made from freestanding mica paper 102 and sol-gel silsesquioxane impregnating material 106.
• the silsesquioxane impregnating material 106 was selected to be used for a variety of reasons including (for example):
• the silsesquioxane impregnating material 106 can effectively infiltrate the pores/interstitials 104 of a pre-formed mica paper 102 so one can make a low porosity/ highly inorganic composite flexible substrate 100.
• the silsesquioxane impregnating material 106 can be used to make a flexible substrate 100 which has a denser matrix than if one used a lower temperature silicone or a polymer impregnating material.
• the silsesquioxane impregnating material 106 makes a flexible substrate 100 which has a higher thermal capability than if one used an organic impregnating material.
• the silsesquioxane impregnating material 106 is processable in that one can make a hydrolyzed resin of silsesquioxane which can be thermally cured using a mild thermal treatment with minimal shrinkage and minimal mass loss enabling processing that minimizes shrinkage cracks or open porosity.
• the silsesquioxane impregnating material 106 has an index of refraction which can be varied over a range 1.40 ⁇ n ⁇ 1.60 in the visible spectrum so one can optimize an optical match with the freestanding inorganic material 102 such as a glass fiber paper.
• the silsesquioxane impregnating material 106 is easy to process and has a lower modulus, higher strain tolerance when compared to fully inorganic impregnating materials like glass.
• the silsesquioxane impregnating material 106 has a better thermal durability, and less damp heat vulnerability, when compared to most organic polymer impregnating materials. 8.
• the combination of silsesquioxane impregnating material 106 with a mica paper 102 has a desirable form and desirable physical properties like flexibility, thermal durability, permeation resistance, and a low CTE (see TABLE 1).
• the silesquioxane impregnating material 106 requires a lower processing temperature than other material such as glass (from a melt process), pyrolized carbon or ceramic impregnating materials.
• the inventors have tested the combined mica paper 102/silsesquioxane impregnating material 106 and evaluated the resulting flexible substrate 100 to determine if it can be used as a flexible display. A discussion about these tests and their results is provided next with respect to FIGURES 2A-2O.
• mica papers 102 Two commercially available mica papers 102 (and the silsesquioxane impregnating material 106) where used to make a impregnated mica display material 100.
• Both of the mica papers 102 are made from natural mica sources by USSamica Inc. and Cogebi Inc. and both have been typically used in the past as a dielectric layer in the electronic industry (e.g., capacitor applications).
• Cogebi's Cogecap mica paper is formed from a calcined muscovite natural mica. The baseline characteristics of these two mica papers 102 are provided in TABLE 2.
• the two mica papers 102 differ in mica particulate size and thickness, and consequently in fragility. But, both of the mica papers 102 rapidly disintegrate into constituent mica flakes when they are exposed to water. IB. Sol-Gel Approach and Materials
• a silsesquioxane material 106 was used to impregnate the interstices 104 of the two commercially available mica papers 102.
• the silsesquioxane material 106 is characterized by the general formula, RSi ⁇ 3/2, where R is an organic modifier that can range from simple methyl, ethyl and phenyl groups to more complex and reactive organic groups such as methacrylates, expoxides, and bridged compounds.
• R is an organic modifier that can range from simple methyl, ethyl and phenyl groups to more complex and reactive organic groups such as methacrylates, expoxides, and bridged compounds.
• the choice of reactive organic groups allows one to vary the index of refraction, and optimize the thermal and chemical durability of the impregnated inorganic paper 100.
• the silsesquioxane material 106 fits chemically between silica (SiO 2 ) and silicones (R 2 SiO), and has intermediate properties.
• the density of the silsesquioxane material 106 is relatively high, which leads to better permeation properties than silicone impregnating materials.
• the measured densities of the silsesquioxane material 106 ranged from 1.3 to 1.4g/cm 3 depending on composition. Plus, the silsesquioxane material 106 can be cured with minimal shrinkage/mass loss which means it is suitable for impregnating the small scale pores 104 within the mica papers 102.
• the thermal durability and the refracting index match between the mica papers 102/silesequixane 106 were valued parameters for the resulting flexible substrate 100, where the former parameter offers a fundamental differentiation from polymer impregnating materials while the latter parameter enables transparency in the resulting flexible substrate 100.
• a combination of methyl and phenyl silsesquioxane precursors was chosen, so the thermal durability could exceed 350 0 C for both materials, and the refractive index of the silsesquioxane 106 could be varied from 1.4 to 1.6 by increasing the proportion of the phenyl which is substituted into the composition.
• the synthesis of the silsesquioxane 106 proceeded as follows: about 0.035 moles of total alkoxysilane was mixed with 0.039 moles of water and 0.012 moles of HF (as a 48% solution). If desired, the HF and some of the phenyltriethoxysilane could be replaced with 0.022 moles of phenyltrifluorosilane.
• the mixture of alkoxide, water and HF was shaken at 70 0 C until it became homogeneous and clear and then it was allowed to age for 5 hours total at 70 to 8O 0 C. This process initiated hydrolysis of the precursors, and resulted in a clear fluid solution or sol. A sample of the clear sol was then placed in an open beaker and allowed to dry overnight.
• This step in the process increased the degree of condensation, and left a colorless and clear-to-hazy syrupy product free of solvent.
• the resulting resin had a typical mass loss of between 30 and 50% upon drying.
• the resin was then re-dissolved in isopropanol so it had a known weight fraction, typically 50%.
• the resulting solution of silsesquioxane 106 was fluid and clear.
• the 106 involved two steps: (1) impregnating/filling the porous mica paper 102 with the sol silsesquioxane 106; and (2) curing the sol silsesquioxane 106 to form a dense flexible substrate 100.
• the goal was to avoid entrapment of air pockets while impregnating the mica papers 102, and to achieve a high quality surface texture.
• the various experiments were performed using 2" x 2" samples of mica paper 102.
• nebulizer To uniformly dose the mica paper 102 with sol silsesquioxane 106, a small nebulizer was used which produced a fine mist that was soaked onto both sides of the mica paper 102. To produce a well-metered spray, a mass flow system and syringe pump feeding the nebulizer was set-up to deliver ⁇ 0.2 grams of sol silsesquioxane 106 over about 30 seconds. This allowed for the convenient processing of the 2" x 2" mica paper 102. The first nebulizer used in these experiments was a "Mira mist PEEK" nebulizer which was manufactured by Burgener Inc.
• the dosage of silsesquioxane resin 106 that was needed to impregnate the mica paper 102 was calculated from the ratio of the density of a well-impregnated mica paper 102 to a non-impregnated mica paper 102. It was found that about 30 to 35% by weight of silsesquioxane 106 would be needed to impregnate the pores 104 in both of the USSamica and Cogebi mica papers 102. If a sample mica paper 102 was processed with too little sol silsesquioxane 106, then the resulting flexible substrate 100 would show reduced transparency, flexibility, and toughness. Too much sol silsesquioxane 106, caused surface saturation or flash depending on the particular processing method.
• the impregnated/filled mica paper 102 was then air dried, which left a tacky surface.
• the mica paper 102 can be impregnated by a process in which a siloxane/alcohol solution is first pre-hydrolyzed prior to usage. After that, the following procedure can be used to saturate mica paper without damage:
• Note 1 Continuous processing techniques to impregnate and cure the mica or inorganic paper 102 could be used. For instance, this may include a roll-to-roll process in which the mica or other inorganic paper 102 is first saturated with impregnating material 106 and then pressed followed by a heat treatment (if needed).
• the mica paper 102 could be evacuated to remove gases and then, while still in the vacuum, it could be dipped in a solution of the impregnating material 106. Subsequent venting to atmospheric pressure would further force the impregnating material 106 into the pores 104.
• the cure methods include: (1) pressing an impregnated mica paper 102 between two hot plates; (2) supporting an impregnated mica paper 102 on a single flat plate in a vacuum; and (3) curing a suspended (hanging) impregnated mica paper 102 within a vacuum. These cure methods were all implemented with the same exemplary cure schedule in which the temperature was ramped to 140 0 C for 10 to 30 minutes and then ramped to 250C° and held for 10 to 60 minutes.
• the resin saturated mica paper 102 was placed between two flat plates and pressed at pressures of between 500 and 2700 pounds.
• the application of pressure was useful in two ways, first, the compaction of the sol silsesquioxane 106 within the mica paper 102 could be controlled, and second, the surface quality could, at best, replicate the surface roughness of the plates.
• Both hard press surfaces and soft press surfaces were used in this method.
• the soft press surfaces such as PDMS (e.g., Sylgard 184) could be peeled away from the resin saturated mica paper 102. However, the soft press surfaces could tear, and sometimes did tear, the thinner consolidated mica paper 102b.
• the hard press surfaces needed to have an intrinsically good release surface (e.g., non-stick aluminum foil) so the consolidated mica paper 102 could be removed from between the plates.
• the impregnated mica paper 102 can be pressed by using a heated platen press (Carver) 200 as shown in FIGURE 2A.
• the heated platen press 200 has a pair of presses 202a and 202b which are used to press therebetween the impregnated mica paper 102.
• each press 202a and 202b is made from a stacked kapton film 204a and 204b, aluminum foil 206a and 206b and an aluminum block 208a and 208 (shown separated from one another).
• the heated platen press 200 has been used to press samples of impregnated mica paper 102 while investigating various time, temperatures, and pressure combinations. For instance, two temperatures (200 0 C and 235°C) and times up to 420 seconds have been investigated while pressing samples of impregnated mica paper 102.
• a template was developed to suspend and support the mica paper 102 during the impregnating and curing steps.
• An exemplary template was manufactured by tracing an outline of the mica paper 102 onto a folded piece of heavy duty aluminum foil. Then, the traced area was removed, and the mica paper 102 was mounted inside the template with a piece of tape. The template was then sealed along the top and suspended from a ring stand with a binder clip. Thereafter, the mica tape 102 was sprayed with sol silsesquioxane 106 and cured in accordance with the aforementioned thermal treatment schedule. If desired, the heating could be done under vacuum within a vacuum oven to better promote the impregnated quality of the pores 104.
• This method produced the most transparent and uniformly impregnated mica papers 102, even though their edges often needed to be removed because the template covered small areas of the mica paper 102 and these areas were not treated. This particular method was relatively easy to perform and had excellent results.
• the thicker USSamica mica paper 102 produced an impregnated mica paper 100 that was easily wrapped around a tube with a radius of 5 cm, and was quite clear, but had optical scattering that distorted the view of an object through the paper 102.
• the thinner Cogebi mica paper 102 produced a more transparent and flexible product, which had sufficient flexibility to wrap around a 5mm radius of curvature.
• the Cogebi mica paper 102 had significantly less distortion due to optical scattering when compared to USSamica mica paper 102.
• FIGURE 2B shows a comparison of these two mica papers 102 before and after impregnating/filling them with silsesquioxane 106.
• the unimpregnated USSamica mica paper 102a and the impregnated USSamica mica paper 102a' are shown on top of a book cover in the left photo. And, the unimpregnated Cogebi mica paper 102b and the impregnated Cogebi mica paper 102b' are shown on top of the same book cover in the right photo.
• FIGURE 2C impregnated USSamica mica paper 102a'
• FIGURE 2D impregnated Cogebi mica paper 102b'
• the SEM micrographs indicate that the impregnated mica papers 102a' and 102b 1 consist of laminar books of mica largely oriented in parallel sheets (shown in lightest contrast). They also indicate that the sol-gel silsesquioxane 106 occupied several types of pore structures, both large inter-laminar void spaces, as well as smaller inter-laminar spaces.
• the impregnated USSamica mica paper 102a 1 appears to have a coarser structure, larger mica platelets and larger inter-laminar voids than the thinner Cogebi mica paper 102b 1 .
• the SEM micrographs indicate that the cure methods used to impregnate the pores 104 happened to be quite effective, and that the composite structure 102a' and 102b' was dense. In fact, voids which might have arisen from volatilization, offgassing or shrinkage did not appear in the SEM micrographs.
• the impregnated Cogebi mica paper 102b' was a bit more subtle, and the silsesquioxane 106 could be seen gluing the particles together, as well as sitting in islands on the top surface of the mica paper 102b.
• the simple press and cure method used in this test was clearly more efficient at impregnating large spaces between mica flakes than it was at providing a finely planarized surface.
• any display substrate 100 needs to be able to support the postprocessing deposition of electronics on top of the surface.
• a silicon deposition process requires that an electronic component be deposited on a surface with ⁇ 10nm roughness.
• the surface roughness of the impregnated mica papers 102a' and 102b' was measured by WYCO interferometry.
• FIGURES 2G and 2H show surface maps of the USSamica mica paper 102a and 102a' before and after the infiltration and the consolidation which was done by pressing them between two silicone plates.
• FIGURES 21 and 2J respectively compare the surface roughness of non-stick aluminum foil alone, and a impregnated USSamica mica paper 102a' consolidated between two steel plates which used non-stick aluminum foil as a release.
• the surface texture of the impregnated USSamica mica paper 102a' was nearly identical to that of the foil, indicating that the hard press surface can move the mica particles and resin into a conformational surface.
• the embossing was so complete that arrays of 15 micron stamped dots in the foil used to indicate the brand name were replicated in the surface of the impregnated USSamica mica paper 102a'.
• the roughness average in the impregnated USSamica mica paper 102a' was ⁇ 300nm, or thirty times greater than is needed for a-Si deposition.
• This high fidelity embossing capability suggested that there is another way which can be used to satisfy the surface quality issue which is to use a smooth emboss method during consolidation.
• This smoothing process may include an additional silsesquioxane application step followed by a continuous roller, static press, or other embossing/smoothing method. Plus, additional planarization layers of silsesquioxane 106 may be applied to filled mica paper 102 to achieve the required surface roughness for a particular application.
• the deflection of the impregnated mica paper 102 is inversely proportional to the stiffness of the impregnated mica paper 102. This relationship can be represented as follows:
• EI 0 Initial stiffness at time 0.
• fBo Initial deflection at time 0.
• fBt Deflection at time t.
• Optical Absorption Spectroscopy [0045] The impregnated mica paper 102a' and 102b' where evaluated for optical absorption over the spectral range of 300-1 100 ⁇ m using a Hewlett Packard 8453 spectrometer.
• the Hewlett Packard 8453 spectrometer works by probing the electronic transitions of molecules as they absorb light in the UV and visible regions of the electromagnetic spectrum. This test was performed because with transmissive display components it is desirable to minimize any color imparted by a particular absorption peak within the visible range, as well as maximize the total transmission. However, some degree of optical scattering within a substrate may be beneficial for OLED light extraction purposes or other purposes.
• the spectra show an absorption tail from the UV into the blue, as well as small absorptions near 600 and 800nm. More significant, is the fact that the overall attenuation was quite high, with transmission below 15% for the thinner Cogebi mica paper 102b', and below 3% for the USSamica mica paper 102a'. And, when normalized for thickness, the attenuation was nearly equal between the two samples of impregnated mica paper 102a' and 102b'.
• FIGURE 20 shows the impact of light scattering off of the textured samples 102a' and 102b' which was measured by repeating the absorption experiments on the impregnated Cogebi mica paper 102b' using a Hitachi UV/VIS spectrometer equipped with an integrating sphere detector.
• the top measurement in the plot was obtained with an integrating sphere detector and the bottom measurement in the plot was obtained with a standard transmittance detector setup.
• This test was designed to capture the light scattered behind the impregnated Cogebi mica paper 102b 1 , so the attenuation would be due to absorption, forward scattering and reflection losses.
• the strong absorbance from the UV tail impacted the transmission in the blue, but the total transmission was still near 80%.
• FIGURE 2P is a graph that shows the expansion behavior of impregnated USSamica mica paper 102a 1 , as measured by a Dynamic Mechanical analyzer.
• a 2x2 cm piece of impregnated USSamica mica paper 102a' was measured for dimensional change over a temperature range of 20 0 C to 300 0 C.
• a linear response in both the heating curve 214 and the cooling curve 216 was observed and no hysteresis was observed. This indicated that the impregnated USSamica mica paper 102a' did not compact during the measurement, which indicates dimensional stability. From the slope of the curves 202 and 204, a value for the expansion coefficient was calculated to be 7ppm/°C.
• FIGURE 2Q shows the helium flux measured for several types of materials of interest which could be used in a flexible display.
• the traditional Topaz polymer substrate is a high temperature polymer that was found to provide a rather low diffusivity when compared to other polymeric systems.
• the Helium flux measurements for a total of four samples of USSamica mica paper 102a 1 and Cogebi mica paper 102b 1 were plotted, along with a measurement made using a traditional Corning 0211 Microsheet glass substrate with a thickness of 75 microns. In this type of diffusivity measurement, it should be appreciated that the flux is proportional to the diffusivity, and is reciprocal to thickness.
• the two Cogebi mica papers 102b' where by far the thinnest @15 microns, while the other samples ranged in thickness from 80 microns (the USSamica mica papers 102a'), up to 500 microns (the Topaz polymer substrate).
• Two aspects of this measurement are of particular importance, the rate at which the helium diffuses through the thin sample (as indicted by the initial slope of the helium signal per time) and the steady state flux.
• these values correlated to one another, but for dissimilar samples each of these values needed to be qualitatively examined.
• the results showed that the impregnated mica papers 102a 1 and 102b 1 occupied a middle ground between the low diffusivity Microsheet glass substrate and the rather permeable polymer substrate.
• the sample USSamica mica paper 102a' (composite A) showed very low helium flux, which closely approximated the Microsheet glass substrate.
• the USSamica mica paper 102a' (composite B) and the two Cogebi mica papers 102b 1 each had a helium flux that was more substantial, although it was not more than 1/10 th of the Topaz polymer's flux, in spite of the sample mica papers 102a' and 102b' being 6 to 33 times thinner than the Topaz polymer substrate.
• FIGURE 2R is a plot of relative He permeation of several impregnated mica papers 102a' and 102b' as a function of time.
• the performance of the pressed mica papers 102a' and 102b' (which were 5X thinner) was similar to the high permeability USSamica mica paper 102b' (composite B shown in FIGURE 2Q).
• the aging of one of the Cogebi impregnated mica papers 102b' for 10 hours at 300 0 C increased the flux by a factor of about 6. Note: if one were to replace a lower index silsesquioxane 106 used in this test with a higher index silsesquioxane 106 then it is believed the flux could be reduced further by a factor of 2.
• FIGURE 2S is a graph that shows the thermo-gravimetric results over a temperature range of 20 to 1000 0 C where the mass loss events were centered at 260 0 C, 537°C and >600°C. As can be seen, the partially cured mica papers 102b' showed a 10% weight loss over the entire run.
• the silsesquioxane 106 makes up about 30% of the total sample's weight, this correlated to about 30% mass loss in the impregnating material 106 based on the assumption that all of the lost weight was from the buming-off of the organic groups.
• the differential trace in the graph indicated that the mass loss events occurred in three areas:
• [ ⁇ J ⁇ jggjA chemical durability test was performed on both types of impregnated mica papers 102a' and 102b 1 by first curing them at 150 0 C for 45 minutes and 180 0 C for 30 minutes, and then subjecting the cured impregnated mica papers 102a' and 102b 1 to a series of chemical exposures.
• the different exposures had been chosen to simulate the different types of processing environments that one might experience in a semiconductor application.
• porous forms may be used as starting materials for silsesquioxane based composites.
• the following example illustrates that the aforementioned process for forming a flexible material 100 can broadly encompass porous inorganic forms, both in inorganic composition and in amount and form of the porosity.
• a flexible tape 100 was prepared by impregnating silsesquioxane 106 into commercially available Nippon Sheet Glass paper (TGP-OlO). This experiment was conducted to demonstrate a generality in the processing capability from a rather dense mica paper 102 (discussed above) to a very porous glass fiber paper 102 (discussed next).
• the experiment also demonstrated how the properties of the filled porous glass fiber paper 100 are impacted by parameters such as inorganic fill, and form.
• the TGPOlO paper 102 used was extruded chopped fiber which had a porosity of >90%.
• a sample of the paper 102 was cut and weighed to set up a target impregnation volume of the silsesquioxane resin 106.
• the target weight of the final cured composite 100 was 8.2 times the mat weight of the original fiber paper 102 which indicated how much silsesquioxane resin 106 was needed to fill the pores 104 within paper 102.
• the required amount of silsesquioxane resin 106 was prepared as formulation 2 from Table 3.
• the silsesquioxane resin 106 was dried overnight, and weighed. Then, the silsesquioxane resin 106 was diluted to 0.914 times the as-prepared mass of the formulation.
• the paper 102 was dosed with 19.4g of the diluted silsesquioxane resin per gram of the fiber mat to provide the proper resin to glass fiber ratio. Because of the extreme fragility of the paper, the sol 106 was soaked into the paper 102, while the paper 102 was supported on a setter. Two dosing procedures were needed, each using about half of the prescribed volume of diluted resin 106, followed by drying at room temperature for 12 hours. The filled paper 102 was then pre-cured in a vacuum oven at 200 0 C for 10 minutes which left a tacky flexible tape.
• a hot pressing method was used in which the filled tape 102 was placed between two layers in a release package where each of the layers included one layer of aluminum foil tape and one layer of polyimide film. The assembled package was then placed between parallel hot platens in a Carver hydraulic press and allowed to equilibrate at 250 0 C for 1 to 2 minutes. Then, about 100 to 1000 pounds or typically about 100 to 200 psi was applied to the platens and the package was held under pressure at 250 0 C for 30 minutes. The pressure was then released and the release package was cooled. The glass fiber filled resin 100 (which was a colorless slightly translucent tape 100) was peeled from the Al foil and Kapton film.
• FIG. 2T illustrates a SEM of the resulting filled tape 100 in cross-section which shows the well dispersed low glass fiber fraction.
• the glass fibers show up as white features in the darker matrix of silsesquioxane 106.
• the composite tape 100 was flexible, and able to withstand multiple bends over 7 mm cylinder.
• the optical absorption test showed a spectrally neutral color, with scattering loss arising from an index of refraction mismatch of the silsesquioxane 106 with the glass fiber 102.
• the CTE was measured to be between 25 and 30 ppm/°C, reflecting the expansion of the silsesquioxane 106, with little composite effect from the chopped fiber.
• a carbon nanotube paper 102 was used to demonstrate another form of flexible filled composite 100.
• a silsesquioxane 106 composition was prepared as formulation 2 from Table 3. After drying overnight, the silsesquioxane resin 106 was heated to 140 0 C for 10 minutes, along with the carbon paper. The carbon nanotube paper disc 102 was then floated on the sol 106 for 5 minutes under vacuum, and then after venting the system the paper 102 was turned over and the vacuum treatment was repeated. After venting the system the paper 102 was held vertically in the vacuum oven while it was heated to 250 0 C for one hour under vacuum to complete the curing of the silsesquioxane 106.
• a potassium silicate was used as an impregnating material 106 to fill mica paper 102.
• USSamica mica paper 102 was impregnated with a 29% solids solution in water of a potassium silicate with SiO 2 ZK 2 O weight ratio of 2.5 (note: PQ Corporation provides a variety of potassium silicates in their Kasil® product line). The solution was applied to the surface of the sample USSamica mica paper 102a' and allowed to soak in. The sample USSamica mica paper 102a 1 was then air dried at room temperature overnight and then dried in an oven at 150 0 C.
• the potassium silicate solution 106 was applied as a thin film to the glass via brushing followed by sticking the mica paper 102 to the glass on the side to which the potassium silicate solution 106 was applied. Then, the sample USSamica mica paper 102a' was dryed and cured.
• This serves as an example of another method and material system capable of impregnating an inorganic material that contains interstices or voids.
• the processing steps required to fabricate this type of composite are at temperatures ⁇ 1000°C and provide a composite capable of surviving temperatures >300°C and having a bend radii ⁇ 5cm. If desired, several additional steps can be performed to chemically set, alter the impregnating material's mechanical, alter the chemical durability, or alter it's local composition.
• impregnating material is sold under the brand name of HardSilTM AP from Gelest. This impregnating material is a curable polysilsesquioxane T-resin with a thermal capability of up to 360 0 C.
• flexible substrates 100 (1) flexibility to allow repeated bending to ⁇ 30, ⁇ 5, ⁇ 1, or ⁇ 0.5 cm radius; (2) thermal durability to allow a-Si processing or other electronic >300°C, >35O°C, or >400°C; (3) transparency; (4) low permeability to gases and water; (5) low expansion ⁇ 20, ⁇ 10, or ⁇ 7ppm/°C; (6) chemical durability to semiconductor processing fluids; (7) stability in difficult use conditions such as 85°C/85% RH; (8) surface roughness (Ra) values ⁇ 0.5, ⁇ 0.3m or ⁇ 0.1 microns; (9) composite fabrication temperatures ⁇ 1000°C, ⁇ 600°C, or ⁇ 300°C; (10) density >1.3g/cm 3 , >1.6g/cm 3 , >2g/cm 3 ; (11) tensile strength >200MPa; (12) oxygen transmission rate ⁇ 1 cc/m2/day, ⁇
• FIGURE 3 is a cross-sectional side-view of the flexible substrate 100 (impregnated inorganic material 100) being used as a protective coating on a glass substrate 300 in accordance with another embodiment of the present invention.
• the glass substrate 300 could be 50-100 microns thick and have an electronic device (e.g., OLED, semiconductor, RFID) formed on the non-protected surface.
• the glass substrate 300 would provide the overall barrier performance, and the flexible substrate 100 would provide the scratch resistance.
• the inorganic particles in the flexible substrate 100 could inhibit a defect from propagating to the surface of the glass substrate 300.
• the inorganic particles in the flexible substrate 100 could protect the glass substrate 300 by distributing the force of a puncturing object.
• FIGURE 4 is a plot which compares the average load (force) required to break each of these sample sets 300 and 100/300. Testing of the abraded and non-abraded laminated samples 100/300 resulted in similar failure loads. However, testing of the bare abraded glass 300 resulted in a much lower failure load.
• the flexible substrate 100 offers improved CTE, thermal capability, O 2 and water barrier properties, mechanical stability over traditional polymer substrates that are being used today. All of these properties offer advantages in both the final application as well as the manufacturing process. Plus, the fact that the substrate materials in these designs have lower O 2 and water permeation values when compared to other polymer substrates potentially allows the use of a lower performance/lower cost barrier layer 108.
• the flexible substrate 100 has an increased dimensional stability which effectively improves the substrate's durability, lifetime, resistance to barrier layer micro- cracking, and manufacturability (via photolithography).
• Laminating the flexible substrate 100 to a thin glass substrate 300 improves the durability and scratch resistance when compared to un-protected thin glass substrates.
• the flexible substrate 100 has improved mechanical durability and is particularly resistant to breakage due to propagation of any surface and edge defects possibly present.
• One result of this is potentially low cost cutting methods to be used without a substantial decrease in mechanical durability or achievable bend radius.

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• 2006
  • 2006-07-26 US US11/493,741 patent/US20080026180A1/en not_active Abandoned
• 2007
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  • 2007-07-18 CN CNA2007800287353A patent/CN101495301A/zh active Pending
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