US20030145879A1 - Cleaning thin polarizing glass devices - Google Patents

Cleaning thin polarizing glass devices Download PDF

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Publication number
US20030145879A1
US20030145879A1 US10379290 US37929003A US2003145879A1 US 20030145879 A1 US20030145879 A1 US 20030145879A1 US 10379290 US10379290 US 10379290 US 37929003 A US37929003 A US 37929003A US 2003145879 A1 US2003145879 A1 US 2003145879A1
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Prior art keywords
glass
cleaning
devices
vessel
polarizing
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Legal status (The legal status 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 status listed.)
Abandoned
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US10379290
Inventor
Jeffrey King
Leroy Morse
Hoa Dempsey
Erika Stapleton
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King Jeffrey M.
Morse Leroy R.
Dempsey Hoa T.
Stapleton Erika L.
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    • BPERFORMING OPERATIONS; TRANSPORTING
    • B08CLEANING
    • B08BCLEANING IN GENERAL; PREVENTION OF FOULING IN GENERAL
    • B08B3/00Cleaning by methods involving the use or presence of liquid or steam
    • B08B3/04Cleaning involving contact with liquid
    • B08B3/08Cleaning involving contact with liquid the liquid having chemical or dissolving effect
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B08CLEANING
    • B08BCLEANING IN GENERAL; PREVENTION OF FOULING IN GENERAL
    • B08B3/00Cleaning by methods involving the use or presence of liquid or steam
    • B08B3/04Cleaning involving contact with liquid
    • CCHEMISTRY; METALLURGY
    • C03GLASS; MINERAL OR SLAG WOOL
    • C03CCHEMICAL COMPOSITION OF GLASSES, GLAZES, OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C23/00Other surface treatment of glass not in the form of fibres or filaments
    • C03C23/0075Cleaning of glass

Abstract

A method for en masse cleaning of thin polarizing glass devices involving the steps of using a cleaning vessel possessing a vertical side wall, and a porous shelf attached to the vertical side wall to form a cavity for receiving a plurality of the thin polarizing glass devices and, exposing the cleaning vessel containing the thin polarizing glass devices to washing, rinsing, drying steps to remove organic and inorganic matter from the surfaces of the polarizing glass devices.

Description

    CLAIM OF PRIORITY
  • [0001]
    This application claims the benefit of priority of U.S. Provisional Application No. 60/159,676, filed Oct. 15, 1999, and U.S. patent application Ser. No. 09/670,372, filed Sep. 26, 2000. The contents of both applications are incorporated herein by reference.
  • TECHNICAL FIELD
  • [0002]
    The present invention pertains to a predominantly non-contact process for cleaning polarizing glass pieces. In particular the invention relates to a method suitable for removing organic and inorganic matter from thin polarizing glass devices in large or multiple numbers simultaneously, or in other words en masse cleaning. The polarizing glass devices are of a small size, each device having a dimension along a linear edge that usually does not exceed about 100 mm and a thickness that does not exceed about 200 μm.
  • BACKGROUND OF THE INVENTION
  • [0003]
    Polarizers or polarizing glass devices of thin and small physical dimensions have been employed in various uses in the optical telecommunications and other industries. Typical thin polarizing glass devices, such as POLARCOR™, available commercially from Corning Incorporated, Corning, N.Y., are available in dimensions as thin as 200 μm or less, and each individual piece has a finished linear dimension along an edge of about 1 mm to 10 mm. Preferably, each polarizing glass piece has a thickness of between about 10 μm to about 85 μm. U.S. patent application Ser. No. 09/142,713, filed in the names of Borrelli et al., discloses a process by which polarizing glass may be further thinned to form an “ultrathin” polarizing glass measuring less than about 50 μm in thickness, preferably between about 10-40 μm. The content of the application by Borrelli et al. is incorporated herein by reference.
  • [0004]
    During the thinning process a sheet of polarizing glass is blocked or bonded to a substrate with a suitable material such as a resin or a wax, or a mixture of resin and wax. The polarizing glass sheet is thinned to a desired thickness, for instance about 30-50 μm, and thereafter may be sliced into wafers of about 1 mm×2 mm. Prior to packaging and delivery to the customer all organic matter, such as rosin, wax, and inorganic matter, such as polishing/grinding media, and glass chips from the slicing process, must be removed from the surface of the polarizing glass wafers.
  • [0005]
    Polarizers or polarizing glass devices of thin and small physical dimensions pose an especially difficult task for thorough cleaning during their manufacture. Due to the small and delicate nature of these thin polarizing glass devices, effective cleaning treatments are limited. Conventional cleaning processes for polarizers primarily have involved manually washing each individual thin polarizing glass wafer one at a time, a process, which is not only labor-intensive and inefficient, but also costly—costs, which are ultimately passed to the end consumer. Further, this manual process is a mechanical or contact process. Each device undergoes extensive manipulation, which increases the potential of in-process damage or breakage and post-process contamination.
  • [0006]
    In view of the above-described disadvantages in the art, there exists an explicit need for a cost-efficient, expedient and high-volume process for cleaning thin polarizing glass devices.
  • SUMMARY OF THE INVENTION
  • [0007]
    Accordingly, one object of the present invention is to eliminate the above-mentioned disadvantages by providing a thorough and highly efficient method for cleaning en masse thin polarizing glass devices. As used herein the term “en masse” means that many or multiple individual polarizing devices are cleaned together, all at once. Further, the present invention provides a cleaning process for thin polarizing glass devices that minimizes in-process (e.g., scratching or breaking) and post-process damage (e.g., re-contamination). Another object of the present invention is to provide a cleaning process that is cost-efficient and transferable to large-scale manufacturing.
  • [0008]
    In general, the present en masse method for cleaning is a predominantly chemical (i.e., non-contact), rather than mechanical (i.e., contact) cleaning process. The method may uses a cleaning vessel of any shape or configuration, as long as the vessel is capable of holding a high-volume or plurality of thin polarizing glass devices. The cleaning vessel should be made from a material resistant to harsh chemicals and tolerant of thermal stresses from a drying oven. The cleaning vessel has a porous shelf or substrate, which can support the devices when they are loaded into the vessel. Each pore in the substrate is of a size that is large enough to permit cleaning media to drain away easily and quickly, while small enough to prevent a glass workpiece from either falling through or having one of its corners caught, which can lead to chipping. Once loaded with the polarizing glass devices, the cleaning vessel is exposed to a series of washing, rinsing, and drying steps to remove organic and inorganic material from the surfaces of the polarizing glass devices.
  • [0009]
    In particular, the inventive method comprises the following specific steps:
  • [0010]
    a) providing a plurality of polarizing glass devices, each of which having a dimension along a linear edge not to exceed about 100 mm, and a thickness not to exceed about 200 μm;
  • [0011]
    b) providing a cleaning vessel having a cavity and a porous support for holding a number of polarizing glass devices;
  • [0012]
    c) loading the glass devices into said vessel;
  • [0013]
    d) washing the glass devices with an organic solvent;
  • [0014]
    e) washing the glass devices with an aqueous detergent;
  • [0015]
    f) rinsing the glass devices with a first rinse of high-purity water;
  • [0016]
    g) rinsing the glass devices with a dilute mineral acid rinse on an order of about 0.005-0.3 N; and
  • [0017]
    h) rinsing the glass devices with a second rinse of high-purity water.
  • [0018]
    After rinsing for the second time, the polarizing glass devices in the cleaning vessel are dried in an oven, and unloaded from the vessel. The method may further comprise the steps of:
  • [0019]
    a) exposing the polarizing glass devices contained in the cleaning vessel to an oxygen-rich atmosphere; and
  • [0020]
    b) exposing the polarizing glass devices contained in said cleaning vessel to a humid environment, wherein the further steps are done preceding the unloading of the polarizing glass devices from the cleaning device.
  • [0021]
    In another aspect, the present invention also includes a cleaning vessel for holding a multiple number of glass devices. The vessel comprises:
  • [0022]
    a vertical side wall; and,
  • [0023]
    a porous shelf or support attached to the vertical side wall, such that a cavity is formed for receiving a plurality of polarizing glass devices.
  • [0024]
    Other objects and advantages of the present invention will be apparent from the following description.
  • BRIEF DESCRIPTION OF THE DRAWINGS
  • [0025]
    The accompanying drawings provide a further understanding of the invention and are incorporated in and constitute a part of this specification to illustrate embodiments of the invention, and together with the description serve to explain the principles of the invention.
  • [0026]
    [0026]FIG. 1 is a perspective view of an embodiment of a cleaning vessel of the present invention.
  • [0027]
    [0027]FIG. 2 is a perspective view of another embodiment of a cleaning vessel suitable of the present invention.
  • [0028]
    [0028]FIG. 3 shows schematically an embodiment of the cleaning process of the present invention.
  • [0029]
    [0029]FIG. 4 shows schematically another embodiment of the cleaning process of the present invention.
  • [0030]
    Various elements of the drawings are not intended to be drawn to scale, but may be distorted for the purposes of illustrating the invention.
  • DETAILED DESCRIPTION OF EMBODIMENTS
  • [0031]
    The present method satisfies the need for a more cost-effective process for high-volume, simultaneous cleaning of a multiple number of small, thin polarizer devices. Since each polarizing glass workpiece may be as small as about 1.0 mm×2.0 mm×30-50 μm, conventional manual or mechanical washing is inefficient and time consuming, and costly. The method is a chemical cleaning process that employs a cleaning vessel for holding multiple polarizing glass workpieces. The individual workpieces should be positioned in the vessel in a fashion such that all major surfaces of each workpiece is accessable to the cleaning media. For instance, the workpieces may be loaded in a vertical position, each in a groove or slot.
  • [0032]
    [0032]FIG. 1 illustrates an embodiment of a cleaning vessel suitable for use in the present cleaning process. Cleaning vessel 10 comprises a vertical side wall 12 having a first portion 14 and a second tapered portion 16. Vessel 10 further comprises a shelf 18. Shelf 18 is secured to first portion 14 of vertical side wall 12 to form a cavity 20 for containing a plurality (multiple) of polarizers or polarizing glass wafers. Cleaning vessel 10 has an open top 22 and an open bottom 24. Vertical side wall 12 is made of glass, preferably borosilicate.
  • [0033]
    Shelf 18 is made of a chemically resistant and inert material that is porous. In the embodiment of FIG. 1, shelf 18 is made of partially fused glass frit formed into a disc, about 4 mm thick, via known hot glass-working methods. The porous structure is a result of the fritted glass being fused only partially such that melting of the glass does not occur. The term “porous” as used in the present invention to describe the shelf refers to a structure that will allow cleaning fluids to pass through and flow away after coming into contact with the polarizer devices.
  • [0034]
    As an example of a preferred embodiment, cleaning vessel 10 may be made from a standard commercially available Buchner funnel, as modified by cutting-off the top and bottom ends of the funnel to form vertical side wall 12. The Buchner funnel is preferably made of a borosilicate glass. Porous shelf 18 is secured to a first portion 14 of the vertical side wall 12 by glass fusion during fabrication of the original Buchner funnel.
  • [0035]
    [0035]FIG. 2 illustrates another embodiment of a cleaning vessel suitable for used in the present inventive high-volume cleaning process. Cleaning device 50 comprises a vertical side wall 52 having an inner side 56 and an outer side 58. Cleaning device 50 further comprises porous shelf 54 attached to inner side 56 of vertical side wall 52 to form cavity 60 for containing a plurality or high-volume of polarizing glass devices. Cleaning device 50 has an open top 62 and an open bottom 64. Vertical side wall 52 is made of a metal, preferably stainless steel. Porous shelf 54 is made of a meshed material, preferably polypropylene mesh. The mesh openings are smaller in size than the polarizing glass devices, but large enough to allow the cleaning media to pass through, preferably about 400 or 500 μm to about 800 μm (e.g., ˜710 μm) in size. Handles 66 are attached to outer side 58 of vertical wall 52 to provide ease of handling. Of course other “handling” features, such as recesses, slots, or flanges, adapted for automation may be used.
  • [0036]
    A beneficial aspect of the present invention is that the process is carried out en masse, i.e., all at once and together, with little or no handling or manipulation of individual pieces. Hence the inventive process is non-contact.
  • [0037]
    Another useful aspect of the present invention is that all sides of the polarizer devices are either directly or indirectly accessible to the cleaning media at all steps of the process. More specifically, the porous structure of the shelf allows cleaning solutions and media to reach the tops as well as the bottoms, i.e., all sides, of the polarizer devices.
  • [0038]
    Still another aspect of the present invention is that the cleaning vessel is itself exposed to all steps of the inventive cleaning process. As such, the cleaning vessel must be constructed of a material that is as resistant to cleaning solutions and media, if not more resistant than the polarizers contained therein. The vessel must be able to withstand a wide variety of chemical and physical exposures including chemical treatments and corrosion, in addition to heating and agitation associated with such treatments. Suitable materials for the cleaning vessel include glass (e.g., borosilicate, boroaluminosilicate, aluminosilicate, or silicate), ceramic (e.g., alumina), ferrous and non-ferrous metals including stainless steels, carbonaceous materials (e.g., graphitic or glassy carbon), and/or noble metals (e.g., platinum, rhodium, and gold), which may be coated onto the other substrate materials.
  • [0039]
    The cleaning vessel containing polarizers may be adapted for automation and passed from station to station during the cleaning process. Alternatively, the vessel containing the polarizing devices to be cleaned can be retained in one single location or station throughout all steps, whereby the different cleaning media are passed through the vessel itself. For example, cleaning fluids can be poured into and drained from or pumped through or drawn though the vessel with a vacuum pump from above or below as desired.
  • [0040]
    As depicted in a flow chart shown in FIG. 3, the cleaning method in an embodiment comprises the following steps.
  • [0041]
    1. Pre-Cleaning
  • [0042]
    In a preliminary and preparatory step, a pallet containing a strip of polarizing glass devices bonded to a glass substrate is immersed and soaked in a aqueous-detergent bath to remove the bulk of dirt from polishing, slicing and handling. Ultrasonic agitation may be used in this step to enhance cleaning.
  • [0043]
    As used herein a “pallet” can contain a strip of thin polarizing glass, such as POLARCOR™ glass. The glass is thinned to a desired thickness, 30-50 μm, and sliced into wafers, having dimensions of 1 mm×2 mm, like that described in U.S. patent application Ser. No. 09/142,713.
  • [0044]
    2. Loading
  • [0045]
    The pallet is immersed in a first soak of organic solvent to release the individual polarizer devices from the pallet. A suitable solvent is one that allows for the dissolution of the bond between the polarizers and the glass substrate. An example of an applicable solvent that is commercially available is EN-SOLVE-CW™ (>95% of 1-bromopropane), manufactured by Enviro Tech International Inc., Melrose Park, Ill. The solvent is used at an elevated temperature, preferably 50° C.
  • [0046]
    This preliminary cleaning step is carried out over the cleaning vessel such that upon release, the polarizers fall directly onto the porous shelf, and thus are loaded into the cleaning vessel. Handling of the polarizers is eliminated, which significantly reduces damage caused by breakage. The cleaning media can substantially access each polarizer device equally on all sides, i.e., top, bottom and edges, at each step of the cleaning process.
  • [0047]
    3. Dissolution/Release of Bulk Organic Matter
  • [0048]
    Next, bulk organic material is dissolved from the surfaces of the polarizers. In this step the vessel and the polarizers are immersed in a second soak of organic solvent that is selected for its ability to dissolve organic matter, such as resin, wax, grease, fingerprints, from the surface of the polarizers, while concurrently releasing any inorganic matter, such as glass chips and polishing/grinding media, which may have become imbedded in the organic material. Suitable organic solvents include, for instance, 1,1,1-trichloroethane and 1-bromopropane, with 1-bromopropane being a preferred choice.
  • [0049]
    This step is carried out at elevated temperatures, of about 40-60° C., preferably about 50° C.
  • [0050]
    Ultrasonic agitation, as known in the art, is preferred for a portion of the soaking to enhance and expedite the desired effects, mainly the release of organic matter from the surfaces of the polarizers and from between any over-lapping polarizers.
  • [0051]
    4. Dissolution/Release of Inorganic Matter
  • [0052]
    To dissolve or release inorganic matter, the polarizers are washed with three successive soaks of an aqueous-based detergent selected for its ability to dissolve and release inorganic matter, such as polishing/grinding media, glass chips, and any remaining traces of organic matter. A suitable detergent has a high pH (about 12) and high alkaline content, such as VALTRON® SP2200, by Valtech Corporation, Pughtown, Pa.
  • [0053]
    This step is conducted at elevated temperatures of 40-70° C., preferably at about 65-70° C. Again, ultrasonic agitation may be used in the second soak to intensify the cleaning. In a first soak, the glass devices contained in the cleaning vessel are held static in contact with the detergent for about 25 minutes, followed by about 5 minutes of ultrasonic agitation. In the second and third soaks, respectively, the glass devices are maintained in static contact with the detergent for about 5 minutes.
  • [0054]
    5. Initial Rinsing
  • [0055]
    Afterwards, the polarizers in the vessel are rinsed with a first rinse of fresh, deionized, high-purity water (e.g., 15-18 or 19 Mega-Q water) preferably at a temperature of about 40-70° C., preferably about 65-70° C., to remove accumulated cleaning media from the previous steps, especially from the detergent soaks.
  • [0056]
    6. Dilute Mineral Acid Rinse
  • [0057]
    A solution of dilute mineral acid is used in a second rinse. In this step the vessel and polarizers are immersed in the mineral acid rinse to ensure complete removal of the aqueous-based detergent. Suitable acids will include volatile mineral acids, such as hydrochloric acid and/or nitric acid of between about 0.001N to about 0.25 or 0.3N. Preferably, one may use about 0.01 or 0.02N to about 0.17 or 0.2N of hydrochloric acid.
  • [0058]
    7. Final Rinsing
  • [0059]
    The glass devices are given in a final rinsing, a second rinse of de-ionized, high-purity water. In this step the vessel and polarizers are immersed in three successive soaks of de-ionized, high-purity water at elevated temperatures of about 40-70° C., preferably about 65-70° C., to remove the mineral acid solution of the previous step and any remaining residues. In a first soak, the glass devices contained in the cleaning vessel are held static in contact with the detergent for about 10 minutes. Preferably, the first soak is intensified with ultrasonic agitation for about 5 minutes. In the second and third soaks, the glass devices are maintained in static contact with the detergent for about 15 minutes each.
  • [0060]
    8. Drying
  • [0061]
    Still in the vessel, the polarizers are dried in an oven heated to an elevated temperature of about 50-115° C., preferably about 50° C.
  • [0062]
    9. Unloading
  • [0063]
    After drying the polarizing glass devices are unloaded from the cleaning vessel, inspected and packaged in storage containers, accordingly.
  • [0064]
    In another embodiment, as depicted in FIG. 4, the method may further comprise the following steps.
  • [0065]
    First, a “transition” step is added, in which the polarizers in the vessel are exposed to a transition agent after the first washing step in organic solvent. The transition agent may aid in the transition from the organic medium of the “dissolution/release of organic matter” step to the aqueous-detergent medium of the “dissolution/release of inorganic matter” step, by maintaining a smaller contact angle between the polarizers and the aqueous-detergent medium. Examples of suitable transition agents may include acetone and isopropyl alcohol. When using acetone, the glass device is maintained in contact with the acetone at room temperature for about 15 minutes. Treatment with the transition agent may help the polarizers sink into the aqueous-detergent medium, and prevent the polarizers from being suspended near the top of the solution bath because of surface tension.
  • [0066]
    Second, a “pre-drying” step is added, in which the polarizers in the vessel are dipped in a bath of fresh, high-purity alcohol, which may enhance the removal of residual water from the “final rinsing” step. Treatment with alcohol can prevent the possible formation of water-spots on the surfaces of polarizers. In this step, isopropyl alcohol, for example, is used as a drying agent to absorb the water from the surface of the polarizers. Isopropyl alcohol is miscible with water and acts to desiccate the water from the glass surface. The isopropyl alcohol may be warmed for better effects.
  • [0067]
    Third, an “oxidation” step is added to follow the “drying” step. In this step the polarizers are exposed to an oxygen-rich atmosphere, such as by means of an UV-ozone device, or more preferably an oxygen-plasma device, to remove any possible lingering traces of organic residue that may have survived the preceding steps.
  • [0068]
    Fourth, following the “oxidation” step, the polarizers can be exposed to a humid or ionizing environment to disperse any possible electrostatic charges, which may have accumulated on the devices during the preceding oxidation step. Such electrostatic charges could lead to recontamination or cause difficulty in the manipulation of the components during any subsequent inspection, transfer to storage containers, or further processing.
  • [0069]
    The present en masse cleaning method has been successfully employed in laboratory experiments, which are presented in the following non-limiting examples to better illustrate the present invention.
  • EXAMPLE 1
  • [0070]
    A pallet containing about 1000 polarizing glass devices was placed over the cleaning vessel of FIGS. 2 and 2A. The cleaning vessel was placed in a laboratory beaker a little larger than the cleaning vessel. The beaker contains a solvent solution of EN-SOLVE-CW™, at 50° C. The pallet was soaked for 5 minutes to release the polarizers from its backing. As the bond between the polarizers and the glass substrate was disrupted, the devices fell onto the shelf of the cleaning vessel.
  • [0071]
    Thereafter, the cleaning vessel containing the polarizers was immersed in a second, fresh soak of EN-SOLVE-CW™ organic solvent to dissolve and remove organic matter from the surface of the glass polarizers. The soak was in a beaker containing about 700 ml of fluid at a temperature of 50° C., held static for 10 minutes, and then followed by 5 minutes of a conventional ultrasonic agitation cycle.
  • [0072]
    Next, the cleaning vessel and the polarizers were immersed in three successive soaks of 2% v/v VALTRON® SP2200 detergent to dissolve and remove inorganic matter. The first soak was in 700 ml of fluid at 65-70° C., held static for 5 minutes. The second soak was in 700 ml of fluid at 65-70° C., held static for 25 minutes, followed by 5 minutes of ultrasonic agitation. The third soak was in 350 ml of fluid at 65-70° C., held static for 5 minutes.
  • [0073]
    Next, the vessel and the polarizers are rinsed in about 700 ml of de-ionized, high-purity water at 65-70° C., held static for 5 minutes. Transfer is then made to a bath of 200 ml of 0.02N hydrochloric acid where the vessel and the polarizers are soaked statically for 5 minutes.
  • [0074]
    Next, the vessel and the polarizers are immersed in three successive soaks of deionized, high-purity water. The first soak was in 700 ml of fluid at 65-70° C., held static for 10 minutes followed by a 5 minute ultrasonic cycle. The second soak was in 700 ml of fluid at 65-70° C., held static for 15 minutes. The third soak was in 700 ml of fluid at 65-70° C., held static for 15 minutes.
  • [0075]
    Transfer was then made to an oven heated at 50° C., where the polarizers are dried for one hour.
  • [0076]
    Inspection of the polarizing glass devices resulted in about 98% selects, an increase of about 30% over processes that involve physical or manual contact with the glass devices.
  • EXAMPLE 2
  • [0077]
    About 450 polarizing glass optical components, having dimensions of 1.0 mm×2.0 mm×30-50 μm were placed in a cleaning vessel as shown in FIGS. 1 and 1A.
  • [0078]
    The vessel with the polarizers (hereinafter referred to as the vessel) were placed into and filled with isopropyl alcohol, and allowed to soak at room temperature in a static condition, i.e., there was no agitation, for about 30 minutes. Thereafter, the vessel was removed from the isopropyl alcohol and drained by gravity.
  • [0079]
    Next, the vessel was placed into and filled with 1,1,1-trichloroethane at 50° C., soaked statically for 10 minutes, followed by ultrasonic agitation for 5 minutes. A static soaking in acetone at room temperature for about 15 minutes followed.
  • [0080]
    After the vessel was removed from and drained of the acetone, it was placed into and filled with a 2% solution of CA-05, an alkaline pH detergent (manufactured by SPC Electronics America, Inc., Norcross, Ga.) at 50° C., soaked statically for 10 minutes, followed by ultrasonic agitation for 5 minutes. Thereafter, the vessel was removed from the detergent solution, drained and placed into and filled with deionized water at 50° C., soaked statically for 10 minutes, followed by ultrasonic agitation for 5 minutes. The same procedure was repeated with a second charge of de-ionized water.
  • [0081]
    Thereafter, the vessel was removed from and drained of the de-ionized water and placed into and filled with 0.02N hydrochloric acid (i.e., 1% hydrochloric acid) at room temperature and soaked statically. After 5 minutes the vessel was removed from and drained of the hydrochloric acid, placed into de-ionized water at 50° C., and agitated ultrasonically for 5 minutes.
  • [0082]
    Next, the vessel was placed into and filled with isopropyl alcohol at 50° C. and allowed to soak at about 50° C. in static condition for about 15 minutes. After this soaking the vessel was removed from and drained of the isopropyl alcohol and a vacuum was drawn on the vessel to remove any remaining alcohol.
  • [0083]
    Thereafter, the vessel was transferred to an oven heated to a temperature of about 100-115° C. The oven was vented and slowly raised to the desired temperature to preclude ignition of any lingering isopropyl alcohol.
  • [0084]
    Next, an oxidation step was performed in an oxygen-plasma chamber and where the vessel was treated at 200 watts for 10 minutes. Then, the vessel was placed in a humidor at 53% relative humidity for several hours to disperse any electrostatic changes.
  • [0085]
    In laboratory experiments surprisingly smooth surfaces, i.e., average roughness of <1 nm, were obtained. While not intending to be limited by theory, this may be a result of the absence of hard contact between the polarizers and the surface of the shelf. It is believed that due to the small mass of the polarizers, and the fact that cleaning solutions can reach all sides of the devices, a thin fluid film separates each polarizer from coming into intimate contact with the porous, pressed, fritted glass. Hence, the polarizers remain in a suspended state, wherein little or no scratches or damage occurs to the glass surface. Advantages of the present invention include short processing times and exceptionally good selects. The inventive cleaning process was at least 3 times as fast as the manual contact process that was previously used. Further, quality of the selects improved about 30% over the prior manual contact process.
  • [0086]
    Although the present invention has been fully described by way of examples with reference to the accompanying drawings, it is to be noted that various changes and modifications will be apparent to those skilled in the art. In particular, the treatment conditions of time, temperature and agitation are mutually related in that, comparable good cleaning can be attained by, for example, decreasing time while increasing temperature and/or agitation. Therefore, unless otherwise such changes and modifications depart from the scope of the present invention, they should be construed as included therein.

Claims (40)

    We claim:
  1. 1. A method for removing organic and inorganic material from glass devices en masse, the method comprising the steps of:
    a) providing a plurality of polarizing glass devices, each of which having a dimension along a linear edge up to about 100 mm, and a thickness up to about 200 μm;
    b) providing a vessel having a cavity and a porous support for holding said glass devices;
    c) loading said glass devices into said vessel;
    d) washing said glass devices with an organic solvent;
    e) washing said glass devices with an aqueous detergent;
    f) rinsing said glass devices with a first rinse of high-purity water;
    g) rinsing said glass devices with a dilute mineral acid rinse on an order of about 0.005-0.3 N; and
    h) rinsing said glass devices with a second rinse of high-purity water.
  2. 2. The method according to claim 34, wherein said method further comprises drying said glass devices at an elevated temperature; and, unloading said glass devices from said cleaning vessel.
  3. 3. The method according to claim 34, wherein said method further comprises exposing said glass devices to a transition agent after said washing step in organic solvent.
  4. 4. The method according to claim 34, wherein said method further comprises dipping said glass devices in a bath of a drying agent to absorb water from a surface of said glass devices.
  5. 5. The method according to claim 34, wherein said method further comprises exposing said glass devices to an oxidizing atmosphere.
  6. 6. The method according to claim 34, wherein said method further comprises exposing said glass devices to either a humid or ionizing environment prior to said unloading step.
  7. 7. The method according to claim 34, wherein said glass devices have a linear dimension of not to exceed about 55 mm, and a thickness not to exceed about 70 μm.
  8. 8. The method according to claim 34, wherein said organic solvent includes 1,1,1 trichloroethane and 1-bromopropane.
  9. 9. The method according to claim 34, wherein said organic solvent is at an elevated temperature.
  10. 10. The method according to claim 42, wherein said organic solvent is at a temperature of about 40-60° C.
  11. 11. The method according to claim 34, wherein said organic solvent is subject to ultrasonic agitation for a portion of said washing step.
  12. 12. The method according to claim 34, wherein said aqueous detergent has an alkaline pH.
  13. 13. The method according to claim 45, wherein said aqueous detergent has a pH of about 12.
  14. 14. The method according to claim 34, wherein said washing step with said aqueous detergent is accomplished with three successive detergent soaks.
  15. 15. The method according to claim 47, wherein said detergent soaks are at an elevated temperature of about 40-70° C.
  16. 16. The method according to claim 48, wherein said detergent soaks are at an elevated temperature of about 65-70° C.
  17. 17. The method according to claim 47, wherein in a first detergent soak, said glass devices contained in said cleaning vessel are maintained in static contact with said detergent for about 25 minutes, followed by about 5 minutes of ultrasonic agitation.
  18. 18. The method according to claim 47, wherein in a second and a third detergent soak, respectively, said glass devices contained in said cleaning vessel are maintained in static contact with said detergent for about 5 minutes.
  19. 19. The method according to claim 34, wherein said dilute mineral acid rinse includes hydrochloric acid.
  20. 20. The method according to claim 34, wherein said dilute mineral acid rinse includes nitric acid.
  21. 21. The method according to claim 34, wherein said rinsing step with said second rinse of high-purity water is accomplished with three successive soaks of high-purity water.
  22. 22. The method according to claim 54, wherein said soaks of high-purity water soaks are at an elevated temperature of about 40-70° C.
  23. 23. The method according to claim 55, wherein said soaks of high-purity water soaks are at an elevated temperature of about 65-70° C.
  24. 24. The method according to claim 54, wherein in a first soak of high-purity water, said glass devices contained in said cleaning vessel are maintained in static contact with said high-purity water for about 10 minutes, followed by 5 minutes of ultrasonic agitation.
  25. 25. The method according to claim 54, wherein in a second and a third soak of high purity water, said glass devices contained in said cleaning vessel are maintained in static contact with said detergent for about 15 minutes, each.
  26. 26. The method according to claim 35, where said drying step is carried out in an oven at a temperature of about 50-115° C. for 1 hour.
  27. 27. The method according to claim 36, wherein said transition agent is acetone, and said glass devices contained in said cleaning vessel are maintained in contact with said acetone for about 15 minutes.
  28. 28. The method according to claim 34, wherein said cleaning vessel is made of a glass or ceramic.
  29. 29. The method according to claim 34, wherein said cleaning vessel is made of a metal or carbonaceous materials.
  30. 30. The method according to claim 34, wherein said porous support is made of a meshed material.
  31. 31. The method according to claim 34, wherein openings in said porous support are smaller in size than the glass devices, but large enough to allow cleaning media to pass through.
  32. 32. The method according to claim 64, wherein said openings have a size of about 710 μm.
  33. 33. The method according to claim 34, wherein said porous support is made of partially fused glass frit.
  34. 34. A method for simultaneously cleaning a plurality of polarizing glass devices by a predominantly chemical mechanism, the method comprising the steps of:
    providing a holding vessel for containing a plurality of polarizing glass devices, wherein said vessel is defined in part by a sidewall and a porous substrate to support the polarizing glass devices;
    loading said polarizing glass devices into said cleaning vessel, wherein each glass device has a dimension along a linear edge not to exceed about 85 mm, and a thickness of less than or equal to about 180 μm;
    washing said polarizing glass devices in an organic solvent;
    washing said polarizing glass devices in aqueous-based detergent;
    rinsing said polarizing glass devices in a first rinse of high-purity water;
    rinsing said polarizing glass devices in a dilute mineral acid rinse on an order of about 0.01-0.25 N;
    rinsing said polarizing glass devices in a second rinse of high-purity water;
    drying said polarizing glass devices in an oven; and,
    unloading said polarizing glass devices from said holding vessel.
  35. 35. The method of claim 3, further comprising the step of exposing said polarizing glass devices in said cleaning vessel to a transition agent after said washing step in said organic solvent.
  36. 36. The method of claim 3, further comprising the steps of:
    exposing said polarizing glass devices contained in said cleaning vessel to an oxygen-rich atmosphere, and
    exposing said polarizing glass devices contained in said cleaning vessel to a humid environment,
    wherein said further steps are done preceding said unloading of said polarizing glass devices from said cleaning device.
  37. 37. The method of claim 3, wherein said washing step with said organic solvent is accomplished with an organic solvent soak.
  38. 38. The method of claim 6, wherein said organic solvent is 1-bromopropane.
  39. 39. The method of claim 6, wherein said organic solvent soak is at a temperature of about 50° C.
  40. 40. The method of claim 8, wherein in a second organic solvent soak, said polarizing glass devices contained in said cleaning vessel are maintained in contact with said organic solvent for about 10 minutes, followed by about 5 minutes of ultrasonic agitation.
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