EP0395170B1 - Procédé pour développer une image permanente sur une couche comprenant des cristaux liquides - Google Patents

Procédé pour développer une image permanente sur une couche comprenant des cristaux liquides Download PDF

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Publication number
EP0395170B1
EP0395170B1 EP19900201032 EP90201032A EP0395170B1 EP 0395170 B1 EP0395170 B1 EP 0395170B1 EP 19900201032 EP19900201032 EP 19900201032 EP 90201032 A EP90201032 A EP 90201032A EP 0395170 B1 EP0395170 B1 EP 0395170B1
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EP
European Patent Office
Prior art keywords
image
liquid crystalline
crystalline material
optically anisotropic
image layer
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 - Lifetime
Application number
EP19900201032
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German (de)
English (en)
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EP0395170A1 (fr
Inventor
Jürgen Münch
Carl Walter Metzger
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.)
Akzo Nobel NV
Original Assignee
Akzo NV
Akzo Nobel NV
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Publication date
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Publication of EP0395170A1 publication Critical patent/EP0395170A1/fr
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
    • B41M5/00—Duplicating or marking methods; Sheet materials for use therein
    • B41M5/26—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used
    • B41M5/28—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used using thermochromic compounds or layers containing liquid crystals, microcapsules, bleachable dyes or heat- decomposable compounds, e.g. gas- liberating
    • B41M5/281—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used using thermochromic compounds or layers containing liquid crystals, microcapsules, bleachable dyes or heat- decomposable compounds, e.g. gas- liberating using liquid crystals only

Definitions

  • the present invention relates generally to imaging systems and, more particularly, to imaging systems in which an image is developed onto an image member including an optically anisotropic liquid crystalline material.
  • Optically anisotropic liquid crystalline materials have also been utilized in other reversible imaging systems such as, for example, temperature sensors. See, e.g., US3697297 and GB1249432, both of which are incorporated by reference herein for all purposes.
  • a reusable image member wherein the image can be easily altered or erased is not desirable.
  • the image is a company logo to be placed on an article of manufacture for advertising purposes, an alteration of the image would destroy the usefulness of the article for its intended purpose.
  • the present invention provides an imaging system including an optically anisotropic liquid crystalline material and method for producing an image in conjunction therewith but, in contrast to the systems and methods of the above references, the image so formed is not only essentially permanent but also quite uniform and reproducible.
  • the present invention provides a method for developing an image onto an image member, the image member comprising an image layer applied over a suitable substrate, and the image layer comprising a thin film including an optically anisotropic liquid crystalline material and having at least a first and second selected area, wherein a degrading energy for the optically anisotropic liquid crystalline material is selectively applied to the first selected area of the image layer to at least partially degrade the liquid crystalline material therein, thereby permanently altering an optical property of the liquid crystalline material in the first selected area in contrast to that of the liquid crystalline material in the second selected area, characterized in that the thin film of the image layer is produced from a composition selected from:
  • JP 74020967 discloses what on first glance appears to be a similar permanent imaging system; however, the system of this reference again operates in a totally different manner.
  • This reference teaches to utilize the liquid crystalline material incorporated in a microcapsule with a photosensitive silver halide shell, which shell turns black upon exposure to light. The remaining silver halide from the unexposed microcapsules is removed by development, leaving the liquid crystalline material in the unexposed portion.
  • the system of this reference therefore, is completely distinguishable from that of the present invention since the liquid crystalline material itself is not exposed to the degrading energy and, consequently, not degraded.
  • the optical properties of the liquid crystalline material in the first selected area of the image member are altered in contrast to those of the second and other selected areas, which may be undegraded, degraded to a different extent or even totally degraded.
  • the resulting contrast in the optical properties of the various selected areas of the image member is the basis for the image formation.
  • the first selected area can be, for example, the area of the image member on which the image is to be developed, or the area of the image member which is to be the background for the image.
  • the second selected area can be, for example, the other of the image or background areas. Additionally, as indicated above, more than one selected area can be exposed, each to varying amounts of degrading energy, to thereby produce varying liquid crystal effects at a number of different selected areas of the image member. This allows for the developement of more complex images on the imaging layer.
  • the liquid crystalline material in the image member should be protected from substantial further degradation by, for example, coating the image member with a protective layer containing a UV absorber.
  • liquid crystal images so produced are suitable for a variety of purposes, primarily of a decorative nature.
  • FIG. 1 is a schematic, in partial cross-section, illustrating an image member having an image being developed thereon in accordance with one embodiment of the present invention.
  • FIG. 2 illustrates, in one aspect, an overhead view of a stencil member which may be used for developing an image on the image member and, in another aspect, an overhead view of an image member with an image developed and visible thereon.
  • FIG. 1 there is depicted a schematic of an image member 10 having an image 12 (FIG. 2) being developed thereon in accordance with one embodiment of the present invention.
  • Image member 10 comprises an imaging layer 10a, which includes a liquid crystalline material, applied over a suitable substrate 10b for support.
  • Imaging layer 10a may take the form of thin film, for example, a thin coating film, laminate, sheet or the like, which comprises at least the desired type or types of liquid crystalline material.
  • imaging layer 10a comprises a thin coating film produced from a coating composition including the liquid crystalline material in microencapsulated and/or laminar form.
  • imaging layer 10a may vary widely, but should be thin enough so that the liquid crystals at a selected portion can be substantially evenly degraded throughout by exposure to a degrading energy for the liquid crystals, as further described below.
  • Preferred thicknesses for image layer 10a generally range from about 1 ⁇ m to about 50 ⁇ m, more preferably from about 5 ⁇ m to about 25 ⁇ m.
  • Liquid crystals include a large number of compounds which, in a liquid state, display properties typically observed in crystalline solids.
  • Liquid crystalline materials suitable for use with the present invention are, as indicated before, those that display optical anisotropies, for example, those which undergo an appearance change in response to an external stimulus.
  • Preferred are those liquid crystalline materials which undergo a color change in response to an external stimulus such as, for example, a temperature change.
  • liquid crystalline materials are those formed from precursors comprising a polysiloxane backbone with suitable mesogenic sidechains like, for example, various cholesterol and biphenyl derivatives.
  • suitable mesogenic sidechains like, for example, various cholesterol and biphenyl derivatives.
  • liquid crystalline material chosen must be degradable by exposure to a degrading energy source, most preferably ultraviolet radiation and/or thermal energy.
  • a degrading energy source most preferably ultraviolet radiation and/or thermal energy.
  • the particular type of degrading energy for a particular type of liquid crystalline material is well-known, and such information is readily available, to those skilled in the art.
  • the liquid crystalline material may be incorporated into imaging layer 10a in any well-known fashion.
  • better and more uniform effects are obtained by incorporating the liquid crystals in microencapsulted form in combination with a flop effect pigment, or in laminar form as a laminar particle at least partially coated with a liquid crystalline material, optionally dispersed within an suitable binder composition, such as described in EP-A-0357844 (European Patent Application No. 88201966.4) and European Patent Application No. 90200266.6 (claiming priority from European Patent Application No. 89200324.5), both of which are hereby incorporated by reference for all purposes.
  • EP-A-0357844 teaches a thermochromic effect coating comprising an aqueous dispersion binder component, a flop effect pigment and a microencapsulted liquid crystal pigment.
  • aqueous dispersion binder components may be mentioned acrylic and/or polyurethane dispersion resins, especially those suited for metallic effect coatings.
  • preferred flop effect pigments may be mentioned those selected from various aluminum and mica pigments which are or can be made substantially stable in aqueous systems.
  • the microencapsulted liquid crystal pigment comprises a liquid crystalline material, of the type described above, which has been microencapsulated in any well-known fashion.
  • the resulting liquid crystal solution, with the liquid crystal pigment dispersed therein, may be used directly or in modified form as the coating, or the liquid crystal pigment may be recovered from solution and utilized later, for example, dispersed in a suitable binder in the fashion of a normal pigment.
  • liquid crystalline material can also be incorporated into thermoplastic and similar laminates and sheets in like well-known manners.
  • Substrate 10b may comprise any suitable material such as, for example, metal, wood or plastic, as long as the material chosen is compatible with the other components of imaging layer 10a.
  • the substrate may be transparent, translucent or opaque, but it is preferred that at least the surface of substrate 10b in contact with imaging layer 10a be dark or darkened, preferably black, to obtain the maximum visual effect when the preferred liquid crystals (color variant) are utilized.
  • a mat type of plastic foil such as currently used in the car refinish area for the repair of relatively small areas of topcoat damage. Such a system is typified by one commercially available under the trade designation Transcolor from Kurt Vogelsang GmbH.
  • the image 12 (FIG. 2) is developed on imaging layer 10a by the selective application of a degrading energy, shown generally as 14, to one or more selected areas of imaging layer 10a.
  • the degrading energy can be, for example, ultraviolet light and/or heat from a source 16 (such as a lamp) selectively applied to imaging layer 10a through the use of a stencil member 18.
  • stencil member 18 comprises a transparent sheet 20 with an opaque and/or reflective image 12 applied thereto.
  • stencil member 18 can comprise an opaque sheet 20 with a transparent image 12, or can take any number of other well-known forms such as as die cut sheets, formed images and the like, generally anything capable of forming a positive or negative image on imaging layer 10a.
  • the liquid crystalline material therein is at least partially degraded except at the particular area covered by image 12 of stencil member 18, which reflects or otherwise fully or partially screens the degrading energy (the screened degrading energy is shown as 14a) from image layer 10a.
  • Stencil member 18 should be placed close to, preferably substantially on top of, imaging layer 10a to prevent scattering of the degrading energy into other selected portions of imaging layer 10a which are, for example, to remain unexposed.
  • stencil member 18 and source 16 as depicted in FIG. 1 may be mentioned, for example, lasers, light pens or like devices which can be utilized to draw images onto imaging layer 10a.
  • the use of a system such as depicted in FIG. 1 can, in many instances, provide a more uniform effect, while the options mentioned above can, in many instances, provide better image details. Combinations of these various systems may also be utilized to obtain the advantages of each.
  • the optical properties of the liquid crystalline material in those selected areas are permanently altered.
  • the liquid crystalline material can be "totally” degraded, whereby no optical effect remains, “partially” degraded, whereby the optical effect is altered, or remain substantially undegraded.
  • the result is that, under conditions in which the liquid crystalline material displays its optical properties, the optical effect will be different for the undegraded selected areas as compared with the "partially” degraded selected areas, with no optical effect from the "totally” degraded selected areas. An image 12, therefore, will become visible.
  • the first selected area can be, for example, the area of the image member on which the image is to be developed (positive), or the area in the image member which is to be the background of the image (negative), while the second selected area can be, for example, the other of the image or background areas. Additionally, more than one selected area can be exposed, each to varying amounts of degrading energy, to thereby produce varying liquid crystal effects at a number of different selected areas of the image member. This allows for the developement of complex images on the imaging layer.
  • a protective layer such as a clear topcoat containing a UV absorber, should be applied over imaging layer 10a to protect against physical damage and further degradation of the liquid crystalline material to maintain the image developed thereon.
  • a protective layer such as a clear topcoat containing a UV absorber
  • Any number of topcoats utilizable in the coatings industry should be suitable as long as the components of the topcoat are compatible with the other components of image member 10.
  • a number of suitable topcoats are mentioned in the aforementioned incorporated EP-A-0357844 and European Patent Application No. 90200266.6.
  • thermochromic effect coating as detailed in Example 1 of EP-A-0357844, to a layer thickness of 15-20 ⁇ m onto a Bonder 132 steel panel, which had been precoated with a black primer (commercially available under the trade designation Primer Black 03-59622 from Akzo Coatings GmbH).
  • the thermochromic effect coating was subsequently dried for 10 minutes at 60°C.
  • a stencil was prepared by photcopying an image (12 of Fig. 2) onto a transparent plastic foil ("Tageslicht Transparent für Normalpapierkopieren, Type 688" commercially available from the 3M Company). The resulting stencil was laid onto the image member and the whole illuminated for 12 hours with a 500W UV-lamp (commercially available under the trade designation Type Q700 from Hanau GmbH). The distance between the lamp and the stencil was about 10 cm.
  • thermochromic effect coating was overcoated with a 2-component solvent-based clearcoat (commercially available under the trade designation Autocryl MS from Akzo Coatings GmbH) by spraying to a layer thickness of 40-45 ⁇ m, which was predried for 30 minutes at 60°C then subsequently dried for 7 days at room temperature.
  • a 2-component solvent-based clearcoat commercially available under the trade designation Autocryl MS from Akzo Coatings GmbH
  • the resulting image member had a black metallic appearance at room temperature.
  • the exposed portion began exhibiting typical thermochromic color changes, while the unexposed area (image) remained black.
  • a sharp picture of the image was thereby formed.
  • the background again became black while the image began to exhibit the typical thermochromic color changes.
  • the same sharp picture of the image was again formed, but in reverse.
  • Example 1 was repeated, except that a reverse image was formed on the stencil wherein the image was clear and the background opaque.
  • the resulting image member had a black metallic appearance at room temperature.
  • the exposed portion (image) began exhibiting typical thermochromic color changes, while the unexposed area (background) remained black. A sharp picture of the image was thereby formed.
  • Example 1 was repeated, except that illumination was carried out using a UV-drying plant commercially available as Serial No. 403 from Wallace Knight Ltd., Slough, England.
  • the plant had a rating of 120 watts/cm2 and a conveyor speed through the plant of 150 cm/min.
  • the UV lamp was 8-9 cm above the image member, with the stencil being a brass cut-out profile of the image of Fig. 2.
  • the resulting image member had a black metallic appearace at room temperature.
  • the area covered by the brass cut-out (image) began to exhibit the typical thermochromic effect, while the exposed portion (background) remained black. A sharp picture of the image was thereby formed.
  • Example 2 An image member was formed by the procedure as set forth in Example 2 of European Patent Application No. 90200266.6. Prior to application of the clearcoat, the image member was illuminated as set forth in Example 3, and a clearcoat layer applied and dried as in Example 1.
  • the resulting image member exhibited the image in the unexposed area, while the background (exposed area) remained black (total degradation-no liquid crystal effect remaining).

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  • Chemical & Material Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Thermal Transfer Or Thermal Recording In General (AREA)
  • Laminated Bodies (AREA)

Claims (11)

  1. Procédé pour développer une image sur un élément d'image, l'élément d'image comprenant une couche d'image appliquée sur un substrat approprié, et la couche d'image comprenant un film mince contenant un matériau cristallin liquide optiquement anisotrope et ayant au moins une première et une seconde zone choisie, dans lequel une énergie de dégradation pour le matériau cristallin liquide optiquement anisotrope est appliquée sélectivement à la première zone choisie de la couche d'image pour dégrader au moins partiellement le matériau cristallin liquide qu'elle contient, pour modifier de manière permanente une propriété optique du matériau cristallin liquide dans la première zone choisie par contraste avec celle du matériau cristallin liquide de la seconde zone choisie, caractérisé en ce que le film mince de la couche d'image est produit à partir d'une composition choisie parmi :
    (1) une composition comprenant un composant liant en dispersion aqueuse, un pigment à effet d'ondulation et un matériau cristallin liquide thermochrome encapsulé ; et
    (2) une composition comprenant un pigment cristallin liquide comprenant une particule laminaire revêtue au moins partiellement d'un matériau cristallin liquide.
  2. Procédé selon la revendication 1, caractérisé en ce que la couche d'image comprend un film mince de revêtement produit à partir d'une composition de revêtement choisie parmi :
    (1) un revêtement comprenant un composant liant en dispersion aqueuse, un pigment à effet d'ondulation et un matériau cristallin liquide thermochrome encapsulé ; et
    (2) un revêtement comprenant un pigment cristallin liquide comprenant une particule laminaire revêtue au moins partiellement d'un matériau cristallin liquide.
  3. Procédé selon la revendication 1, caractérisé en ce que la couche d'image a une épaisseur située dans la plage d'environ 1 µm à environ 50 µm.
  4. Procédé selon la revendication 1, caractérisé en ce que, l'image ayant été développée, une couche protectrice est appliquée sur l'élément d'image.
  5. Procédé selon la revendication 1, caractérisé en ce que l'énergie de dégradation est un rayonnement UV.
  6. Procédé selon la revendication 1, caractérisé en ce que le matériau cristallin liquide optiquement anisotrope subit une modification de couleur en réponse à une stimulation externe.
  7. Procédé selon la revendication 1, caractérisé en ce que le composant liant en dispersion aqueuse de la composition (1) comprend une résine en dispersion aqueuse à base acrylique et/ou de polyuréthanne.
  8. Procédé selon la revendication 1, caractérisé en ce que le pigment à effet d'ondulation est choisi parmi les pigments à base d'aluminium et de mica.
  9. Procédé selon la revendication 1, caractérisé en ce que la particule laminaire comprend un pigment laminaire.
  10. Procédé selon la revendication 1, caractérisé en ce que la particule laminaire présente un diamètre moyen de particule d'environ 5 µm à environ 500 µm.
  11. Elément d'image comprenant une image développée sur lui selon le procédé selon l'une quelconque des revendications 1 à 10.
EP19900201032 1989-04-28 1990-04-25 Procédé pour développer une image permanente sur une couche comprenant des cristaux liquides Expired - Lifetime EP0395170B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
EP89201106 1989-04-28
EP89201106 1989-04-28

Publications (2)

Publication Number Publication Date
EP0395170A1 EP0395170A1 (fr) 1990-10-31
EP0395170B1 true EP0395170B1 (fr) 1993-12-08

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EP19900201032 Expired - Lifetime EP0395170B1 (fr) 1989-04-28 1990-04-25 Procédé pour développer une image permanente sur une couche comprenant des cristaux liquides

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DE (1) DE69005017T2 (fr)

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DE10328741A1 (de) * 2003-06-25 2005-01-13 Metronic Ag Verfahren und Druckerzeugnis zur Erzeugung frei programmierbarer Druckbilder

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DE69005017D1 (de) 1994-01-20
EP0395170A1 (fr) 1990-10-31
DE69005017T2 (de) 1994-06-01

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