HK1147294A - Method of imaging in crystalline colloidal arrays - Google Patents

Description

Method of imaging in colloidal crystal arrays

Technical Field

The present invention relates to imaging in colloidal crystal arrays, and more particularly to generating images in colloidal crystal arrays by exposure to actinic radiation.

Background

Radiation diffractive materials based on colloidal crystal arrays have been used for a variety of purposes. Colloidal Crystal Arrays (CCAs) are three-dimensional ordered arrays of monodisperse colloidal particles.

Such colloidal dispersion of particles is capable of forming a crystalline structure having a lattice spacing comparable to the wavelength of radiation of ultraviolet, visible or infrared light. These crystal structures have been used to filter narrow bands of selected wavelengths from the broad spectrum of incident radiation and allow transmission of radiation of adjacent wavelengths. Existing devices have been created by dispersing particles in a liquid medium, thereby self-aligning the particles into an ordered array. The particles are fused together by mutual polymerization or by introducing a solvent that expands and fuses the particles together.

In other uses of CCAs, the ordered array is fixed in a matrix and may be used as a colorant when the fixed array diffracts radiation within the visible spectrum. Alternatively, CCAs are fabricated to diffract radiation for use as optical filters, optical switches and optical limiters. While these CCAs use constant inter-particle spacing, the CCAs may function as sensors when the inter-particle spacing changes in response to a stimulus.

In recent years, such sensors have been produced from hydrogels comprising a CCA polymerized within the hydrogel. The polymer of the hydrogel surrounding the CCA changes conformation in response to a specific external stimulus. For example, the volume of the hydrogel can change in response to a stimulus, including the presence of chemical components (e.g., metal ions in solution) and organic molecules (e.g., glucose), making the device useful for chemical analysis. In CCA devices, monodisperse, highly charged colloidal particles are dispersed in a liquid medium of low ionic strength. The particles self-assemble into a CCA due to their electrostatic charge. These ordered structures diffract radiation according to bragg's law, wherein radiation satisfying the bragg condition is reflected and adjacent spectral regions not satisfying the bragg condition are transmitted through the device.

Disclosure of Invention

The invention relates to a method of generating an image, the method comprising: providing an imaging member comprising an array of elements contained within a curable matrix composition; curing the matrix composition within the first portion by projecting laser radiation onto the first portion of the imaging member in an image configuration such that the cured first portion exhibits the first optical property; altering another portion of the imaging member; and curing the other portion of the matrix composition such that the cured other portion exhibits a different optical property than the first portion. The invention also includes a method of generating an image, the method comprising: providing an array of particles contained within a curable matrix composition; curing a first portion of the matrix composition through a grayscale positive or negative mask of the image; and curing another portion of the matrix composition.

The present invention also includes a method of producing a multi-color image in a colloidal crystal matrix, the method comprising providing a plurality of imaging members, each imaging member comprising an ordered array of particles contained within a curable matrix composition; providing each imaging member with an image mask; exposing each imaging member to actinic radiation through one of the image masks to produce a plurality of imaged members, each imaged member having a cured image portion and an uncured background portion; curing the uncured portions of the imaged member such that the cured image portions and the cured background portions diffract radiation of different wavelengths; and stacking the imaged members such that diffraction of radiation from the cured image portions produces a polychromatic image.

Drawings

FIG. 1A is a flow chart of a method of generating an image according to the present invention;

fig. 1B is a schematic diagram of an image generated in a CCA according to one embodiment of the present invention;

FIG. 2 is a flow diagram of another embodiment of generating an image according to a method of the present invention;

FIG. 3A is a schematic diagram of a CCA being imaged with a single laser in accordance with the present invention;

FIG. 3B is a schematic illustration of the use of multiple lasers to produce an image in a CCA according to the present invention;

fig. 4A is a plan view of a CCA image according to one embodiment of the invention;

FIG. 4B is a perspective view of a CCA (as shown in FIG. 4A) containing an image produced in accordance with the present invention; and

FIG. 5 is a flow chart of a method of producing a golden image according to the method of the present invention.

Detailed Description

The present invention includes a method of producing an image in an imaging member (i.e., a device in which an image can be produced to produce an imaged member). In one embodiment, the imaging member comprises an array of elements contained within a curable matrix composition. The image is produced by exposing a portion of the imaging member to laser radiation and modifying another portion of the imaging member such that the first portion and the other portion diffract radiation of different wavelengths, rendering the image detectable. In all embodiments described herein, the first portion may correspond to an image having the second or other portion as a background, and vice versa, wherein the first portion is the background of the image generated in the second portion. For example, the image may be detectable to authenticate or identify the article to which it is applied, or the image may be decorative. The image may be detected by exposing the image to radiation and detecting radiation reflected by the image. Each of the exposed radiation and the reflected radiation may be in the visible spectrum or the invisible spectrum. In some embodiments, images produced according to the present invention may be detected by the naked eye. In other embodiments, the image may be detected using optics (e.g., a spectrophotometer) to recover or view the image.

In one embodiment, the array of elements is an ordered periodic array of particles (colloidal crystal array or CCA) contained in a matrix composition. An ordered periodic array of particles refers to an array of particles that diffract radiation. Parallel layers or planes formed by a periodic array of particles interact with incident radiation according to bragg's law. The diffracted light is goniochromatic, i.e. the colour depends on the viewing angle. The diffraction wavelength of light at a given angle is proportional to the distance between the bragg planes formed by the periodic array of particles, which is proportional to the particle diameter of the dense spheres. The diffraction wavelength also depends on the effective refractive index of the imaging member. The effective refractive index of the imaging member is close to a volume average of the refractive indices of the materials of the imaging member (including the particles and the matrix material surrounding the particles). The intensity of the diffracted light depends on the refractive index variation within the imaging member, which is controlled by the arrangement of the particles and the surrounding matrix. The number of layers formed by the array of particles and the matrix, as well as the refractive index contrast between alternating layers, can also affect the diffraction intensity. More particle layers produce greater diffraction intensity. Higher refractive index contrast between alternating layers also produces greater diffraction intensity. Higher refractive index contrast between alternating layers can be obtained by using particles and matrices having relatively large differences in their respective refractive indices. Alternatively, directionally expanding the particles and/or the matrix can change the layered structure and increase the refractive index contrast between the layers.

In one embodiment, the matrix in which the particles are retained is produced from a curable matrix composition, which may be an organic polymer, such as an acrylic polymer, polystyrene, polyurethane, alkyd polymer, polyester, silicone-containing polymer, polysulfide, epoxy-containing polymer, or a polymer derived from an epoxy-containing polymer. Upon curing of the matrix material, the relative positions of the particles may be fixed so that the inter-particle distances may be fixed.

In one embodiment, the particles are composed of a material different from the matrix. Suitable materials for the particles include polystyrene, polyurethane, acrylic polymers, alkyd polymers, polyesters, siloxane-containing polymers, polysulfides, epoxy-containing polymers, and polymers derived from epoxy-containing polymers, as well as inorganic materials, such as metal oxides (e.g., alumina, silica, or titanium dioxide) or semiconductors (e.g., cadmium selenide), or combinations of these materials.

In one embodiment, the particles have a general monolithic structure. Alternatively, the particles may have a core-shell structure in which the core is produced from a different composition than the shell composition. Suitable compositions for the particle core include: organic polymers such as polystyrene, polyurethane, acrylic polymers, alkyd polymers, polyesters, silicone-containing polymers, polysulfides, epoxy-containing polymers, or polymers derived from epoxy-containing polymers; and inorganic materials such as metal oxides (e.g., alumina, silica, or titania) or semiconductors (e.g., cadmium selenide). Suitable compositions of the shell include organic polymers (e.g., polystyrene, polyurethane, acrylic polymers, alkyd polymers, polyesters, siloxane-containing polymers, polysulfides, epoxy-containing polymers, or polymers derived from epoxy-containing polymers), where the composition of the particle shell is different from the matrix material of the particular array of core-shell particles. The shell material may be non-film-forming, i.e., the shell material remains in place surrounding each particle core without forming a film of the shell material, such that the core-shell particles remain as discrete particles within the polymeric matrix. As such, the array includes at least three general regions; namely a matrix, a particle shell and a particle core. Alternatively, the shell material may be film-forming such that the shell material forms a film around the core. The core material and the shell material have different refractive indices. In addition, the refractive index of the shell may vary as a function of the shell thickness in the form of a refractive index gradient through the shell thickness. The refractive index gradient may be caused by a gradient in the composition of the shell material through the thickness of the shell.

An image may be produced in an imaging member having a CCA using actinic radiation as described below. Referring to the flow diagram of FIG. 1A, in one embodiment, an array of particles is contained within a curable matrix (step 10) to provide an imaging member. The imaging member may be produced by similarly pre-arranging charged particles in a periodic array on a substrate and coating the array of particles with a curable matrix composition. The periodic array of particles can be coated by applying a curable matrix composition to the array by spraying, brushing, rolling, gravure coating, curtain coating, flow coating, slot die coating, or ink jet coating (as described in U.S. Pat. No.6,894,086, incorporated herein by reference), or by embedding the array of particles in a coating composition on a substrate.

In step 12, a first portion of the imaging member is exposed to actinic radiation to cure the matrix composition within the exposed portion of the imaging member. The remainder of the array of the imaging member that is not exposed to actinic radiation is treated to change the interparticle spacing of the particles in the remainder of the array (in step 14). After the inter-particle spacing of the particles in the array has been altered, the imaging member is exposed to actinic radiation to cure the remainder of the imaging member in step 16. The first exposed portion of the imaging member diffracts radiation having a different wavelength band than the remainder of the imaging member. For example, the first portion of the imaging member may be exposed to actinic radiation through the use of a mask or through focused laser radiation. In one embodiment, when the matrix composition is curable with Ultraviolet (UV) radiation, such as an acrylate-based composition, the actinic radiation used to cure the matrix composition includes UV radiation.

In another embodiment, the first portion of the imaging member is exposed to actinic radiation to cure the curable matrix within the exposed portion of the imaging member. The remaining unexposed portions of the imaging member are altered in a manner that disrupts the array and prevents the remaining portions from diffracting radiation. Ordered periodic arrays of particles can be disrupted by various techniques, including, for example, by applying a solvent to the array that at least partially dissolves the particles, overheating the unexposed portions to destroy the particles, or by mechanically destroying the particles.

Referring to fig. 1B, a mask 20 having openings 22 configured as desired for the image overlies an imaging member 24, the imaging member 24 having an array of particles provided in a curable matrix composition. The imaging member is exposed to actinic radiation (as at 26 a) through the opening 22 in the mask 20 to cure the exposed portion 28. The inter-particle spacing between particles within remaining portion 30 is altered and imaging member 24 is exposed to actinic radiation 26b to cure all remaining portion 30. The openings in the mask may correspond to the image such that the first cured portions exhibit the image. Alternatively, the opening may correspond to a negative of the image, such that the first cured portion of the imaged member constitutes the background of the image. In either case, the imaged member develops an image due to the difference in diffraction wavelength between the first cured portion and the other cured portion. The interparticle spacing of the particles within a first cured portion is different from the interparticle spacing of the other cured portions, thereby causing the first and other portions to diffract radiation of different wavelengths. By different wavelengths, it is meant that there is a discernable difference in the wavelengths or wavelength bands diffracted by the two portions of the imaging member. The difference in diffraction wavelengths may be visible to the human eye or may be detectable by optics, such as a spectrophotometer or the like.

In one embodiment, a highly detailed image is produced in an imaging member containing a CCA by using a transparency carrying a grey-scale negative image. A grayscale negative image can be produced by converting a full-color image to a grayscale negative image, which is then copied onto a transparency. In use, the transparency acts as a mask, as shown in FIG. 1B. Actinic radiation passes through the transparency without the image negative thereon, thereby curing the first portion of the image-patterned substrate composition. The area of the uncured portion of the matrix composition may constitute the background of the image. The inter-particle spacing in the CCA of the uncured portion is changed so that the inter-particle spacing of the CCA of the uncured portion is different from the inter-particle spacing of the first cured portion, and then the other portion is cured.

The change in inter-particle spacing of the particles in the CCA may be obtained by increasing the size of the particles such that the centers of the particles are further separated from each other or by swelling the matrix composition to urge the particles away from each other. The particle size may be increased by allowing monomers or other materials (e.g., solvents) present in the uncured portion of the imaging member to diffuse into the particles, causing the particles to expand, thereby increasing the inter-particle spacing. The core-shell particles (where the shell can allow diffusion of materials therein) or the particles of the monolithic structure can be expanded. Particle expansion to increase particle size can be enhanced by heating the uncured portion to increase the rate of diffusion of material into the particle from the other curable matrix composition. For curable matrix compositions comprising monomers (including the precursor component of the polymer), the monomers (and/or the precursor component of the polymer) may diffuse into the uncured portion of the particles. Alternatively, a diffusible composition (e.g., a solvent) may be applied to the imaging member to diffuse into the particles. The use of a diffusible composition may be used to replace or increase diffusion of a matrix material into particles, for example to increase the concentration of a material diffused into particles. In another embodiment, the matrix may be expanded by the addition of a monomer or solvent (water or organic solvent) to expand the matrix composition (with or without particle expansion) and increase the inter-particle spacing. Changes in inter-particle spacing due to diffusion of material into the particles and/or expansion of the matrix may also affect the refractive index contrast between the particles and the matrix, the refractive index contrast between alternating layers, and/or the effective refractive index of the imaging member.

After the inter-particle distance, refractive index contrast, and/or effective refractive index changes, the matrix composition is cured. Curing of the matrix composition fixes the relative positions of the particles such that the inter-particle spacing of the particles in the background portion of the imaging member is different from the previously cured image portion of the imaging member.

Embodiments described herein may include an imaged member having a cured portion that reveals an image (or image background) and a second cured portion that corresponds to the image (or image) background. However, referring to FIG. 2, the inter-particle spacing may vary in more than one portion of the imaging member according to another embodiment of the invention. The array of particles is contained within a curable matrix as an imaging member (step 50). In step 52, a first portion of the imaging member is exposed to actinic radiation, followed by step 54, in which step 54 the interparticle spacing of the remaining uncured portion is altered to generate a second portion of the imaging member that diffracts radiation differently than the first portion of the imaging member. A portion of the uncured matrix is exposed to actinic radiation at step 56 and the inter-particle spacing within the remaining uncured matrix portion is further altered at step 58. This process of exposing a portion of the uncured matrix to radiation and changing the inter-particle spacing within the remaining portion, as indicated at step 60, may be repeated a number of times before the final step 62 of curing any remaining uncured portion of the matrix composition. With each subsequent change in the inter-particle spacing (steps 56 and 58), the changed portion diffracts radiation after curing at a different wavelength than the other portions of the imaging member. In this way, radiation of multiple wavelengths may be diffracted by the image in the CCA.

Alternatively, one or more lasers may provide actinic radiation to produce an image in an imaging member comprising a CCA. Referring to fig. 3A, a single laser 70 may be focused on an imaging member of an array of particles provided in a curable matrix composition 72. The movement of the laser across the imaging member (as indicated by arrow a) creates a path of cured matrix composition corresponding to image portion 74 that follows the pattern of movement of laser 70. Alternatively, as shown in fig. 3B, a plurality of lower intensity lasers 80 may be focused at a common location 84 into an array of particles provided within a curable matrix composition 82 to provide sufficient actinic radiation at the location 84 for curing of the matrix composition. A plurality of lasers 80 may be moved across the array of curable matrices in a similar manner as lasers 70.

Alternatively, a laser marking system can be used to place a grating (raster) on a laser that spans a periodic array of particles contained within a polymeric matrix to produce an image in an imaging member. The use of a laser marking system enables rapid changes in the image between imaging members, such as in a production environment. A series of imaging members can be imaged in a uniquely customized image. Alternatively, a Liquid Crystal Display (LCD) that masks actinic radiation may also be used to block radiation in the configuration of the image to cure the image into the imaging member according to the present invention. The LCD may be controlled to customize an image within each imaging member produced in the product line. Similarly, a digital light projector providing actinic radiation may be used to generate a customized image in the imaging member. These examples of the large number of customizations of the image in the imaging member are not meant to be limiting. Other systems may be used to expose a curable matrix composition containing an ordered array of particles in which the configuration of the actinic radiation is readily changeable.

In another embodiment of the invention, a mask may be used to generate an image that is only properly detectable when viewed from an angle relative to the imaging member. Referring to fig. 4A and 4B, the image 90 may be distorted when viewed from the front of the imaging member 92, but the image 90 is suitably detectable when viewed from an angle relative to the imaging member, as in fig. 4B. Such angular imaging may also be accomplished by using a focused laser directed into the interior of the array to similarly produce a distorted image that appears on the front, yet appears sharp at an angle relative to the imaging member.

The invention may also be used to produce a multicoloured image in an imaging element. For example, as shown in FIG. 5, separate imaging components are generated that image corresponding to the red, blue, and green channel images. A full color image of the image to be produced is provided (step 100) and separated into red, blue and green channels, as is conventional in photolithography and digital photography (step 102). For each of the respective red, blue and green channels, a red negative image, a blue negative image and a green negative image are generated on the transparency at steps 104, 106 and 108. Each negative image transparency is used as a mask for exposing the periodic array of particles within the curable matrix to expose the matrix composition to actinic radiation through the negative image at steps 110, 112 and 114. Similar to the process outlined in FIG. 1A, actinic radiation cures a portion of each of the three imaging members. The inter-particle spacing within each uncured portion of each imaging member is changed as in step 116 (by expanding the particles, expanding the matrix, or both the particles and the matrix, as described above). The uncured background of the three imaged members is cured in step 118. In step 120, the resulting three imaged members are stacked together. Upon exposure to light, a full color image is restored in the multi-layer stack of imaged members. The multicolor images described herein are not limited to red, blue, and green images that are overlaid to produce a full-color image. Multicolor images may use a two-color (two-tone) image or an image of more than three colors. Similarly, the image may be a positive or negative of the image.

The imaged members of the present invention can be provided on a support film or can be removed from the support film and divided into individually imaged wafers (large sheets having a planar dimension of about 1-10 mm) or smaller sheets. Alternatively, the imaged member can be produced directly on the article, wherein the surface of the article acts as the substrate on which the imaged member is produced.

Imaged members produced according to the present invention can also be applied to an article or other physical structure by a variety of techniques, such as adhering the imaged member-laden film to the article using an adhesive (e.g., a decal or the like) or by hot stamping the imaged member-laden film or transferring the imaged member to the article. Suitable non-limiting techniques for transferring the imaged member to the article include providing the imaged member in a medium and applying the medium containing the imaged member to the article by brushing, spraying, painting, dipping, spraying, electrodeposition, powder spraying, aerosol spraying, roll coating, and printing (e.g., with a jet printer). The imaged member can be incorporated into the article by soaking the article with a medium (e.g., a solvent or dispersant) containing the imaged member, wherein the imaged member soaks into and is incorporated into the article. The imaged member may be incorporated into a woven article (e.g., currency) by weaving the filaments carrying the imaged member into a woven material. Alternatively, the imaged member may be mixed into a material (e.g., a resin material or a paste-type material) used to produce the article. The article may be molded (including injection molding) or extruded (including hot melt extrusion), whereby the imaged member is co-extruded with the article forming material. The imaged members of the present invention may also be provided on or incorporated into a heat shrinkable sleeve that is wrapped around an article.

Imaged members having images produced in accordance with the present invention may be used in marking devices, including documents of value, articles of manufacture, or their packaging and vouchers. Examples of documents of value include currency, credit cards, certificates of compliance (certificate), collectibles and transaction cards, contracts, titles or certificates of registration (e.g., of automobiles), certified decals, tickets (e.g., for travel, event or parking), tax stamps, coins, stamps, checks and drafts, stationery (standationary), lottery tickets, chips and/or tokens, regulators (e.g., evidence), key cards, keys, tracking and tracking items, and as part of bar codes. Articles of manufacture or packaging for articles of manufacture may include aircraft parts, automotive parts (e.g., vehicle identification codes), medical and personal care products, recording media, clothing and footwear, electronics, batteries, ophthalmic devices, wine, food, printing inks and consumables, writing instruments, luxury items (e.g., luggage and handbags), sporting goods, software and software packaging, tamper seals (sampler seals), art (including creative works of art), building materials, munitions, toys, fuel, industrial equipment, biological materials and living goods, jewelry, books, antiques, security items (e.g., fire extinguishers and filtration devices), carpets and other furniture, chemicals, medical devices, coatings and coatings, and windows and transparencies. Examples of documents that may carry an array of colloidal crystals produced according to the present invention include driver's licenses, identification cards (government, business and educational), passports, visas, marriage certificates, hospital bracelets and diplomas. These examples are not meant to be limiting but merely a sampling of devices that may carry images according to the present invention. These exemplary uses of imaging are not meant to be limiting.

While the invention is described herein in connection with producing images in colloidal crystal arrays, this is not meant to be limiting. Other components may be imaged using actinic radiation. For example, a Liquid Crystal (LC) array provided in a curable matrix composition may be imaged by exposing the LC array to radiation (e.g., through a mask or with a laser, as described above) to cure a first portion of the LC array. The pitch of the LC modules within the remaining (uncured) portion of the LC array is changed, for example by heating the LC array. The remaining portion is then cured, thereby fixing the changed pitch of the LC module. In this manner, the imaged LC array includes a portion having altered LC modules that exhibit optical properties that differ from the optical properties of the LC modules that are not altered.

In addition, the following examples are merely illustrative of the present invention and are not intended to be limiting.

Examples of the invention

Example 1: UV laser imaging

A curable matrix composition (80% propoxylated neopentyl glycol diacrylate and about 20% butane diol diacrylate with photoinitiator) containing a UV acrylate monomer package was disposed on a black background of an opacity chart (opacity chart) (byko-chart, BYK-Gardner inc., usa). A polyethylene terephthalate (PET) film carrying an ordered array of latex particles was disposed on top of the acrylate composition with the latex particles facing right down. The acrylate is interspersed into the film between the opaque pattern and the array to accommodate the curable acrylic composition within the array. The coated array and chart assembly is placed in the path of the UV laser moving for writing the image, curing the area illuminated by the UV laser. The opaque image and the coated array (supported by the PET film) were heated to expand the particles. The swelling of the particles is evidenced by an increase in the reflectivity of the uncured portion of the coated array and a change in its color. The entire coated array was exposed to a UV lamp to cure any uncured portions of the acrylic composition. The PET film was peeled away leaving behind an array of colloidal crystals fixed in a polymerized acrylic matrix composition on an opaque picture with a laser written image. The laser-written image appears blue and the background appears green when the chart is viewed from the front (perpendicular to the chart). When the chart is viewed at grazing angles, the laser-written image appears black and the background appears bluish-violet.

Example 2: UV laser imaging

Example 1 was repeated except that the array provided on the PET film was arranged so as to face upward and the acrylate composition was applied to the array. A PET cover plate was arranged on top. The assembly (PET/array/PET) was placed in the path of a UV laser to cure a first portion of the substrate in an image configuration. The imaged array was heated to expand the particles within the non-imaged portion, as in example 1. The entire coated array is then exposed to UV radiation to cure the non-imaged portions. When the film disposed over the black background is viewed from the front, the laser-written image appears blue and the background appears green. When the film is viewed at a glancing angle over a black background, the laser-written image appears black and the background appears blue-violet.

Example 3: highly detailed CCA imaging

Adobe photoshop was used to convert full color images to negative grayscale images. A negative image is printed onto the transparency with an ink jet printer to create a mask. A UV curable composition comprising epoxidized trimethylpropane triacrylate and propane diol triacrylate with an initiator was disposed on the PET film. A PET film loaded with a array of latex particles was placed on top of the acrylate mixture. The assembly is exposed to UV radiation through a mask to cure the image portions. The mask is removed and the assembly is heated until the uncured portions of the CCA exhibit increased reflectivity and a change in color within the uncured areas of the coated array. The assembly was then exposed to a UV lamp to cure the uncured areas. An image corresponding to the transparency mask is visible within the CCA. The background color is changed from red to bright green by changing the viewing orientation from a direct to glancing angle. The image color is changed from an orange hue to a dark green hue by changing the viewing orientation from a positive to a glancing angle.

Example 4: full color imaging

Adobe Photoshop was used to create red, green and blue channel images of full color images. Each channel image is converted to a negative gray scale image and the negative is printed separately on a transparency in an ink jet printer. The UV curable acrylate mixture was applied to a PET film carrying a periodic array of latex particles. The coated array was placed on the black part of the opaque picture (acrylate side down) and heated until the desired color (red) was obtained. A red channel image mask was then placed over the PET layer and UV cured through the mask. The mask and PET layer were removed and the remaining image was wiped with isopropyl alcohol to remove the uncured acrylate.

The green channel image in the CCA is placed on top of the red image in the same manner. The array within the UV curable matrix composition was heated until a green color was obtained. A green channel image negative is used to expose the green coated array and cure the exposed matrix composition. A blue color coating array is similarly disposed and imaged on top of the red and green color layers. Three images (red, green and blue) were coated with a UV curable acrylate composition and UV cured. The resultant image shows a highly detailed full-color image. The range of colors (palette) seen in the image changes as the viewing orientation changes from positive to grazing angle.

It will be readily appreciated by those skilled in the art that modifications may be made to the invention without departing from the concepts disclosed in the foregoing description. Such modifications are to be considered as included within the following claims unless the claims, by their language, expressly state otherwise. Accordingly, the particular embodiments described in detail herein are illustrative only and are not limiting to the scope of the invention which is to be given the full breadth of the appended claims and any and all equivalents thereof.

It will be readily appreciated by those skilled in the art that modifications may be made to the invention without departing from the concepts disclosed in the foregoing description. Such modifications are to be considered as included within the following claims unless the claims, by their language, expressly state otherwise. Accordingly, the particular embodiments described in detail herein are illustrative only and are not limiting to the scope of the invention which is to be given the full breadth of the appended claims and any and all equivalents thereof.

Claims (22)

1. A method of generating an image, comprising the steps of:

providing an imaging member comprising an array of elements contained within a curable matrix composition;

curing the matrix composition within a first portion of the imaging member by projecting laser radiation onto the first portion in the configuration of an image such that the cured first portion exhibits a first optical property;

altering another portion of the imaging member; and

curing the other portion of the matrix composition such that the cured other portion exhibits a different optical property than the first portion.

2. A method according to claim 1, wherein said array of elements comprises an ordered array of particles, and wherein said first cured portion diffracts radiation of a first wavelength and said other cured portion diffracts radiation of another wavelength.

3. The method according to claim 1, further comprising curing another portion of the matrix composition, wherein each cured portion diffracts radiation at a wavelength different from the wavelengths diffracted by the other cured portions.

4. The method of claim 1, further comprising changing the inter-particle spacing of the other portion prior to curing the other portion.

5. The method according to claim 4, wherein altering the inter-particle distances comprises swelling particles within the other portion or swelling the matrix composition within the other portion or both.

6. The method of claim 1, wherein said laser radiation is generated by a laser device that is moved across said imaging member in said configuration of said image.

7. The method of claim 6, wherein said step of curing said matrix composition within said first portion comprises rastering said laser radiation across said array.

8. The method of claim 1, wherein the step of curing the first portion comprises directing laser radiation onto the first portion at an angle relative to the imaging member to produce an image that is detectable when the array is viewed from the angle.

9. The method of claim 1, wherein the step of curing the first portion comprises directing laser radiation through a mask onto the imaging member.

10. The method of claim 1, wherein the matrix composition is curable with ultraviolet radiation and comprises a plurality of cure initiators, each of the cure initiators being reactive to a different wavelength of ultraviolet radiation, and wherein the step of curing a first portion of the matrix composition comprises projecting laser radiation of a first wavelength onto the matrix composition to cause a first initiator to initiate curing of the first portion, and the step of curing a second portion of the matrix composition comprises projecting laser radiation of a second wavelength onto the matrix composition to cause a second initiator to initiate curing of the second portion.

11. A device bearing an image produced according to claim 1, wherein the device comprises a document of value, an article of manufacture, packaging for an article of manufacture, and/or a document.

12. A method of generating an image, comprising the steps of:

providing an array of elements contained within a curable matrix composition;

curing a first portion of the matrix composition through a grayscale positive or negative mask of an image; and

curing another portion of the matrix composition.

13. The method of claim 12, wherein the mask is configured to produce an image in the array when viewed from an angle and a distorted version of the image when viewed from substantially the front of the array.

14. The method according to claim 12, wherein the matrix composition is cured by ultraviolet radiation.

15. The method according to claim 14, wherein the matrix composition comprises an acrylic polymer.

16. The method of claim 12, wherein the image is detectable upon exposure to visible radiation.

17. The method of claim 12, wherein the image is detectable upon exposure to non-visible light radiation.

18. A device bearing an image in a curable member produced according to claim 12, wherein the device comprises a document of value, an article of manufacture, packaging for an article of manufacture, and/or a document.

19. The device of claim 18, wherein the image is a full color image.

20. A method of producing a multicoloured image in a colloidal crystal array comprising the steps of:

providing a plurality of imaging members, each imaging member comprising an ordered array of particles contained within a curable matrix composition;

providing each imaging member with an image mask;

exposing each imaging member to actinic radiation through one of the image masks to produce a plurality of imaged members, each imaged member having a cured image portion and an uncured background portion;

curing the uncured portions of the imaged member such that the cured image portions and the cured background portions diffract radiation of different wavelengths; and

stacking the imaged members such that diffraction of radiation from the cured image portions produces a full color image.

21. The method of claim 20, further comprising changing the interparticle distance of the uncured background portion prior to curing the uncured background portion.

22. A display member exhibiting a full color image, said display member produced according to the method of claim 20.