EP0055985B1 - Verfahren zum Verbessern der Uniformität einer Beschichtung - Google Patents

Verfahren zum Verbessern der Uniformität einer Beschichtung Download PDF

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Publication number
EP0055985B1
EP0055985B1 EP19820100014 EP82100014A EP0055985B1 EP 0055985 B1 EP0055985 B1 EP 0055985B1 EP 19820100014 EP19820100014 EP 19820100014 EP 82100014 A EP82100014 A EP 82100014A EP 0055985 B1 EP0055985 B1 EP 0055985B1
Authority
EP
European Patent Office
Prior art keywords
coating
web
applicator
electrode
charge
Prior art date
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.)
Expired
Application number
EP19820100014
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English (en)
French (fr)
Other versions
EP0055985A2 (de
EP0055985A3 (en
Inventor
Semyon Kisler
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Polaroid Corp
Original Assignee
Polaroid Corp
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 Polaroid Corp filed Critical Polaroid Corp
Publication of EP0055985A2 publication Critical patent/EP0055985A2/de
Publication of EP0055985A3 publication Critical patent/EP0055985A3/en
Application granted granted Critical
Publication of EP0055985B1 publication Critical patent/EP0055985B1/de
Expired legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D3/00—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials
    • B05D3/14—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials by electrical means
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05C—APPARATUS FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05C11/00—Component parts, details or accessories not specifically provided for in groups B05C1/00 - B05C9/00
    • B05C11/02—Apparatus for spreading or distributing liquids or other fluent materials already applied to a surface ; Controlling means therefor; Control of the thickness of a coating by spreading or distributing liquids or other fluent materials already applied to the coated surface
    • B05C11/023—Apparatus for spreading or distributing liquids or other fluent materials already applied to a surface
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03C—PHOTOSENSITIVE MATERIALS FOR PHOTOGRAPHIC PURPOSES; PHOTOGRAPHIC PROCESSES, e.g. CINE, X-RAY, COLOUR, STEREO-PHOTOGRAPHIC PROCESSES; AUXILIARY PROCESSES IN PHOTOGRAPHY
    • G03C1/00—Photosensitive materials
    • G03C1/74—Applying photosensitive compositions to the base; Drying processes therefor
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03C—PHOTOSENSITIVE MATERIALS FOR PHOTOGRAPHIC PURPOSES; PHOTOGRAPHIC PROCESSES, e.g. CINE, X-RAY, COLOUR, STEREO-PHOTOGRAPHIC PROCESSES; AUXILIARY PROCESSES IN PHOTOGRAPHY
    • G03C1/00—Photosensitive materials
    • G03C1/76—Photosensitive materials characterised by the base or auxiliary layers
    • G03C1/91—Photosensitive materials characterised by the base or auxiliary layers characterised by subbing layers or subbing means
    • G03C1/915—Photosensitive materials characterised by the base or auxiliary layers characterised by subbing layers or subbing means using mechanical or physical means therefor, e.g. corona

Definitions

  • the present invention relates to a method and apparatus for coating and improving the uniformity of a coating material after it has been applied to a charge-retaining material, in general, and to such apparatus for improving the uniformity of a coating material that has been applied to a moving web of such material, in particular.
  • a nonuniform thickness coating applied to a moving web of such material would require considerably more drying time for drying the thicker portions of said nonuniform coating than would be required for drying the thinner portions of said nonuniform coating.
  • a temperature gradient that is optimum for drying said thicker coating portions is often excessive for optimum drying of said thinner coating portions. Drying time is usually the major factor limiting maximum production rates of many coated products.
  • many properties of photographic film such as sensitivity to light, color saturation, etc., for example, can be adversely affected when constructed with non- uniformly coated sheet materials.
  • One of the most effective coating thickness control techniques in present day used in the coating industry involves the employment of an electrostatic field to assist in the uniform deposition of coating materials on products to be coated.
  • an electrostatic field is established across the gap between the coating applicator and said backing roller by a high voltage power supply whose output terminals are connected between said applicator and said roller.
  • the electrostatic field in said coating causes a coating of uniform thickness to be deposited on a particular web surface.
  • the magnitude of the voltage established between said applicator and said roller is normally less than that required to generate corona, but often exceeds 3 KV DC.
  • Electrostatic depositing apparatus like this are described in US ⁇ A ⁇ 2 052 131 or US-A-3 335 026.
  • Electrostatic fields utilized in a manner such as those described above can greatly improve the thickness and/or surface uniformity of a layer of coating material.
  • the use of an electrostatic field for coating improvement purposes will often cause changes in coating properties such as surface tension and/or the residual electrostatic charge on the material to be coated, and that can limit the extent to which coating uniformity can be improved with an electrostatic field.
  • Electrostatic charges present on a coated material, or coating fluid on a coating material having an electrostatic field related change in such properties as surface tension, etc., for whatever reason or reasons, can also limit the extent to which the uniformity of a coating material can be improved.
  • electrostatic charges having detrimental effects on coating uniformity can be produced also in other way than by deposition of a coating in an electrostatic field.
  • the technical problem underlying the invention is to remove remaining electrostatic charges on a moving web to improve the uniformity of the coating.
  • Claims 1 and 7 respectively comprise features for solving the technical problem in connection with a coating apparatus using an electrostatic field for deposition and in connection with an apparatus respectively operating without assistance of an electrostatic field.
  • Claim 8 discloses a method for solving said technical problem.
  • numeral 10 generally indicates coating apparatus employing conventional electrostatic coating-gap assist apparatus constructed in accordance with the teaching of the prior art.
  • Web support or backing roller 12 is cylindrically shaped, is electrically conductive and is mounted for rotation about backing roller axis 14.
  • Coating applicator 16 is mounted in a fixed position with respect to backing roller 12 and is spaced from said roller 12 by a distance or gap 18.
  • the coating fluid supplied by applicator 16 is electrically conductive, it often maintains said applicator 16 at or near ground potential through a coating-fluid-supplying conduit (not shown), the high voltage terminal of power supply 20 is necessarily connected to said roller 12 and the low voltage terminal of said supply 20 is connected to said grounded applicator 16.
  • electrostatic field 26 is produced in coating gap 18 between high potential backing roller 12 and grounded applicator 16.
  • charge-retaining web 28 is moved in direction 30 through gap 18 by drive means (not shown)
  • said web 28 is electrostatically charged by orienting its dipoles (such as by orienting dipoles 31) by said electrostatic field 26.
  • Electrostatic charges produced on web 28 by electrostatic field 26 cause fluid 32 flowing from applicator 16 into coating gap 18 to be attracted toward and uniformly deposited on moving web 28.
  • This portion of the coating material 32 is sometimes referred to as a coating fluid bead and is designated numeral 34 in prior art Fig. 1.
  • the surface of web 28 normally moves faster than the rate at which coating fluid 32 flows onto said web 28 surface. This being so, as web 28 and fluid 32 in the form of bead 34 are brought into contact with each other, the faster moving web 28 pulls and thereby stretches said fluid 32 causing the thickness of coating fluid 32 to be reduced to a desired intermediate level.
  • electrostatic field 26 changes properties of coating fluid 32 such as surface tension, thereby allowing said fluid 32 to be stretched to a greater degree and over a larger gap between web 28 and applicator 16 without losing (breaking) bead 34 than would be possible if electrostatic gap-assisting field 26 were not present.
  • gap 18 in Fig. 1 must be large enough to accommodate such things as web splices and foreign matter so that such splices or matter do not come into contact with applicator 16 and thereby adversely affect web coating quality.
  • FIG. 2 Another type of electrostatically assisted coating apparatus is schematically illustrated in Fig. 2.
  • numeral 36 generally indicated web coating apparatus employing a precharged web coating technique.
  • web support or backing roller 38 is cylindrically shaped, is electrically conductive, is mounted for rotation about backing roller axis 40 and for safety purposes is electrically grounded through path 41 to prevent said roller from operating like a high potential producing Van de Graaff generator.
  • Coating applicator 42 is mounted in a fixed position with respect to backing roller 38 and is spaced from said roller 38 by distance or gap 44.
  • Grounded web support or backing roller 46 is cylindrically shaped, is electrically conductive and grounded, and is mounted for rotation about backing roller axis 48.
  • Conductive bristle brush 50 is mounted in a fixed position with respect to and has the free ends of its bristles pointed toward and spaced from said grounded backing roller 46.
  • DC power supply 52 has its high voltage output terminal connected to one end of each of the bristles of said conductive bristle brush 50 through path 54 and has its low voltage output terminal connected to grounded backing roller 46 through path 56 and common ground points 58.
  • FIG. 3 numeral 70 generally indicated web coating apparatus employing coating uniformity improvement means constructed in accordance with the present invention.
  • web support or backing roller 72 is cylindrically shaped, is electrically conductive and is mounted for rotation about backing roller axis 74.
  • Backing roller 72 may or may not be grounded depending upon whether or not an electrostatically assisted coating technique is employed and if employed, the particular type of electrostatic assist technique selected.
  • Coating applicator 76 is electrically grounded through either the coating fluid conduit (not shown) or through path 77, is mounted in a fixed position with respect to backing roller 72 and is spaced from said roller 72 by distance or gap 78.
  • Conductive bristle brush 82 is mounted in a fixed position with respect to, and has the free ends of its bristles spaced from surface 84 of said web 80.
  • DC power supply 86 has its high voltage output terminal connected to one end of each of the bristles of said conductive brush 82 through path 88 and has its low voltage output terminal electrically grounded through path 90.
  • coating fluid 94 is deposited on said web 80 by coating fluid applicator 76.
  • the coating process may or may not be assisted by an electrostatic field. However, under normal conditions a substantially larger residual electrostatic charge and substantially greater change in coating fluid properties will be present in a coated material and its coating, respectively, when an electrostatic field is employed in a web coating process than when a such a field is not so employed.
  • Fig. 4 is an enlarged detail of energized conductive bristle brush 82 and a portion of coated web 80 immediately adjacent said brush 82, said coated web 80 is moved in direction 92 through the electrostatic field established between said brush 82 and coating fluid 94 on said web 80.
  • surface 96 of coating fluid 94 is relatively uneven or nonuniform after it has been applied to web 80 but before coating fluid 94 with its said nonuniform surface 96 is subjected to the electrostatic field of brush 82.
  • the magnitude and polarity of this electrostatic field is normally established empirically and is primarily determined by the type of material to be coated and the type coating material to be applied.
  • the electrostatic field associated with brush 82 in the coating uniformity improvement apparatus of the present invention must be positioned such that it interacts with the charge retaining material having the residual electrostatic charges that adversely affect coating fluid surface uniformity.
  • sheet of charge-retaining material 80 schematically illustrated in Fig. 3
  • the free ends of conductive bristle brush 82 are optimally located adjacent surface 84 of said sheet 80 which is the side that is directly opposite the side on which coating material 94 is located.
  • the electrostatic field established between brush 82 and coating fluid 94 can most effectively change the electrostatic charge level on web 80 and it is believed, change such properties as the surface tension of coating fluid 94.
  • the web coating uniformity improvement apparatus of the present invention employs the electrically conductive coating material itself as a ground or electrically conductive reference member in conjunction with a conductive bristle brush to establish the desired charge-controlling electrostatic field.
  • This use of coating fluid 94 is necessary because the coating fluid is necessarily in its fluid state when it is subjected to the electrostatic field of brush 82 for coating improvement purposes and if an alternate reference or ground member were employed it would adversely effect coating fluid thickness and surface quality if it were placed in contact with the coating fluid while said fluid was still in its said fluid state.
  • brush 82 When a potential difference is established between brush 82 and coating fluid 94 in, for example, Fig. 3, said brush 82 is sometimes referred to herein as an electrode. Also the term "electrostatic field" employed herein means one species of electric field.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Application Of Or Painting With Fluid Materials (AREA)
  • Coating Apparatus (AREA)
  • Electrostatic Spraying Apparatus (AREA)

Claims (9)

1. Appareil pour revetement comprenant: un applicateur (76) pour deposer un revetement humide (94) sur une surface d'une bande (80) de matiere retenant les charges ä mesure qu'on la fait avancer a tavers un champ electrostatique dans un espace (78) entre un rouleau d'appui (72) et ledit applicateur (76), ladite bande (80) ayant une charge residueiie ä la suite du depot dudit revetement, caracterise en ce qu'une electrode (82) est montee en un point situe en aval dudit espace (78), le long du parcours de la bande (80) et de maniere contigue ä la surface opposee de la bande (80), le revetement (94) etant encore humide au niveau dudit point situe en aval, I'electrode (82) creant un autre champ electrostatique qui modifie la charge residuelle de la bande (80) et favorise une nouvelle repartition du revetement (94) encore humide et ameliore gräce ä cela son uniformite.
2. Appareil selon la revendication 1, caracterise en ce que ladite electrode servant a modifier la charge residuelle comporte un balai (82) monte au niveau dudit point situe en aval de maniere contigue a la surface opposee (84) de la bande (80) et en que que des moyens sont prevus pour appliquer ledit autre champ electrostatique entre le balai (82) et le revetement (94).
3. Appareil selon la revendication 1, caracterise en ce que l'applicateur (76) pour le depot comporte un chargement bipolaire de ladite bande avant ou pendant le dépôt du revetement (94), ce qui a pour effet qu'une charge bipolaire residuelle demeure apres de depöt du revetement (94).
4. Appareil selon les revendications 1 et 2, caracterise en ce que le revetement est un revetement conducteur (94), en ce que l'applicateur (76) possede au moins une partie conductrice (77) de celui-ci qui definit la polarite et la charge du revetement lorsqu'il est depose sur la bande (80) et en ce que ledit moyen pour appliquer ledit autre champ electrostatique comporte une source (86) d'alimentation en courant electrique ä tension continue, dont les bornes de sortie sont reliees ä I'electrode (82) et ä la terre alors que l'applicateur electrostatique (76) est relie ä la terre par l'intermédiaire de la partie conductrice (77).
5. Appareil selon la revendication 1, caracterise en ce que le potentiel de I'electrode (82) est plus positif que le potentiel du revetement applique (94).
6. Appareil selon la revendication 1, caracterise en ce que le potentiel de I'electrode (82) est plus negatif que le potentiel du revetement applique (94).
7. Appareil pour ameliorer I'uniformite d'un revetement humide (94) depose par un applicateur (76) sur une surface de la bande (80) en matiere retenant des charges qui retient des charges residuelles apres le depöt lorsqu'elle passe par un espace (78) entre I'applicateur (76) et un rouleau d'appui (72), caracterise en ce qu'une electrode (82) est montee de maniere contigue ä la surface opposee (84) de la bande (80) en un point situe en aval dudit espace (78) ou le revetement demeure encore humide et en ce que des moyens (86) sont prevus pour appliquer un potentiel ä I'electrode (82) pour reduire la charge residuelle de la bande (80) et favoriser gräce ä cela une nouvelle repartition du revetement encore humide afin d'ameliorer son uniformite.
8. Procede pour enduire une surface d'une bande (80) à mesure qu'on la fait avancer ä travers un champ electrostatique dans un espace (78) entre un rouleau d'appui (72) et un applicateur (76) de revetement humide (94), caracterise en ce qu'une electrode (82) est montee au niveau d'un point situe en aval de l'espace (78), sur le parcours de la bande (80) et de maniere contigue ä la surface opposee de la bande (80), le revetement etant encore humide au niveau dudit point situe en aval, I'electrode (82) creant un autre champ electrostatique qui modifie la charge residuelle de la bande (80) et favorise une nouvelle repartition du revetement (94) encore humide et ameliore gräce ä cela son uniformite.
9. Procede selon la revendication 8, caracterise en ce que le revetement (94) est conducteur et est depose au moyen de l'applicateur (76), ledit applicateur (76) ayant une partie conductrice (77) qui definit la polarité et la charge du revetement (94) ä mesure qu'il est depose, et en ce qu'un potentiel est applique entre I'electrode (82) contigue a la surface opposee de la bande en aval de l'espace (78) et la partie conductrice de l'applicateur de fagon que I'electrode (82) cree ledit autre champ electrostatique a travers la bande (80) dans la region de I'electrode (82).
EP19820100014 1981-01-05 1982-01-04 Verfahren zum Verbessern der Uniformität einer Beschichtung Expired EP0055985B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US22233481A 1981-01-05 1981-01-05
US222334 1981-01-05

Publications (3)

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EP0055985A2 EP0055985A2 (de) 1982-07-14
EP0055985A3 EP0055985A3 (en) 1983-02-02
EP0055985B1 true EP0055985B1 (de) 1987-04-15

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EP19820100014 Expired EP0055985B1 (de) 1981-01-05 1982-01-04 Verfahren zum Verbessern der Uniformität einer Beschichtung

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EP (1) EP0055985B1 (de)
JP (1) JPS57167751A (de)
CA (1) CA1193226A (de)
DE (1) DE3276052D1 (de)

Families Citing this family (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4457256A (en) * 1981-01-05 1984-07-03 Polaroid Corporation Precharged web coating apparatus
DE69507497T2 (de) * 1994-09-22 1999-09-16 Minnesota Mining And Mfg. Co., Saint Paul Elektrostatisches system zur steuerung des stromes einer flüssigkeit nach ihrer auftragung auf ein substrat
EP0809152A3 (de) * 1996-03-26 1998-02-04 Mitsubishi Chemical Corporation Verfahren zur Herstellung eines elektrophotographischen Photorezeptors
US6368675B1 (en) 2000-04-06 2002-04-09 3M Innovative Properties Company Electrostatically assisted coating method and apparatus with focused electrode field
US6475572B2 (en) 2000-04-06 2002-11-05 3M Innovative Properties Company Electrostatically assisted coating method with focused web-borne charges
JP4899492B2 (ja) * 2006-01-20 2012-03-21 富士ゼロックス株式会社 無端ベルトの製造方法
CN118417124B (zh) * 2024-07-05 2024-09-13 杭州众能光电科技有限公司 一种狭缝式涂布模头

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS497050B1 (de) * 1965-12-23 1974-02-18
US3671806A (en) * 1970-11-20 1972-06-20 Eastman Kodak Co Method of and apparatus for applying an electrical charge to a moving sheet of flexible material

Also Published As

Publication number Publication date
EP0055985A2 (de) 1982-07-14
CA1193226A (en) 1985-09-10
DE3276052D1 (en) 1987-05-21
JPH0135703B2 (de) 1989-07-26
JPS57167751A (en) 1982-10-15
EP0055985A3 (en) 1983-02-02

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