Patent Application
20080004176
The present invention relates to chromogenic material that may respond and shift in color due to environmental conditions such as heat, light or humidity. The light may include both visible and non-visible light, such as ultraviolet light. The chromogenic material may therefore provide a method to independently develop a latent image on a given substrate, and in particular, to a substrate that includes conventional thermosensitive image forming media. The chromogenic material may therefore be applied to a substrate which may initially contain image forming media that may respond adversely to a given environment and otherwise become illegible. The chromogenic material herein may therefore separately provide the ability to communicate useful information on products such as pharmaceutical labels, retail pricing labels, shelf marking labels, food industry labels, luggage ticketing, manufacturing distribution media, packing and shipping labels, etc. Such information may include historical environmental exposure information and/or other labeling indications that may be appropriate for a given product.
As shown therefore in
As illustrated in
With attention directed to
When an particular environmental condition is therefore experienced, a latent image develops as shown in
With respect to the latent images 14, 16, 18, 20, it should be noted that such images may be designed such that as developed, they assume a color that may be legible and contrast with any colored background, e.g. from a white, gray or even a black background. For example, as shown in
It may therefore be appreciated that the present invention may also utilize a chromogenic material and/or a non-chromogenic material. Accordingly, the latent image, as noted above, may develop into a pattern which contrasts against backgrounds of varying darkness. However, the latent image now may be applied to the substrate as separate side-by-side layers. For example, one layer may be a chromogenic material and one layer may be a non-chromogenic material. In addition, one may include layers that may include mixtures of a chromogenic material with a non-chromogenic material. The non-chromogenic material may be in the form of an ink, dye, paint, and/or pigment. The layers may be applied alongside one another either in abutting relationship or even with some degree of overlap. For example, the side-by-side layers may overlap between 1-99%, including all values and increments therein. It may also be appreciated that the combination of a non-chromogenic material (e.g. white in color) with a chromogenic material (which develops white to black) may then provide a gray scale upon development. However, black, red, or any other color may be used to form a gray scale pattern.
It should now be appreciated that reference to a chromogenic material herein contemplates any image forming material capable of developing a color upon exposure to one or more environmental conditions. The environmental conditions, as alluded to above, include but are not limited to light (photochromism), heat (thermochromism), electrical current (electrochromisn), solvent polarity (solvatochromism), ions (ionochromism), pH (halochromism), mechanical friction (tribochromism), mechanical pressure (piezochromism), or a combination thereof. Thus, the chromogenic material may herein be additionally characterized as photochromic, thermochromic, etc. Further, a chromogenic material herein may change color reversibly or irreversibly.
Expanding upon the above, the second chromogenic material may be tailored to appear when an environmental condition occurs which is adverse to either the chromogenic media responsible for the primary image, and/or the particular product identified by the primary image. For example, in the case of a pharmacy prescription label, the temperature at which the second chromographic material changes color may be selected at a typical threshold for a given medication. This may be the case as various medications typically require specific storage requirements or even refrigeration to remain generally effective. Accordingly, the second chromogenic material may be selected so that it develops in the event that it is exposed to temperatures of greater than about 50° C. (122° F.). In addition, the second chromogenic material may be selected so that it develops in the event that it is exposed to a given temperature for a given length of time. For example, 38° C. )100° F.) for a period of 72 hours.
As noted above, the second chromogenic material may be applied in the form of a localized coating on one or more surfaces of the substrate, including the same surface or surfaces in which the first chromogenic material is located. The localized coating may be applied by a variety of printing methods, including but not limited to flexographic, gravure, or screen printing methods. The localized coating may further be applied in the form of words, pictures, or symbols, including but not limited to warnings, instructions, prices, expiration dates, barcodes, or shipping locations.
It may further be appreciated herein that reference to a medium that may be capable of developing a latent image includes any substrate which is coated, impregnated, or otherwise contains a chromogenic material. The substrate may be paper or a polymeric material and may have one or more surfaces. One surface may be also coated with an adhesive such that the substrate may be used as a label. The substrate may be coated, impregnated, or otherwise contain a first chromogenic material for printing a visible primary image on the substrate. Where the substrate contains a thermochromic material, it may be fed into a thermal printer. The thermal printer may selectively heat the substrate, develop the thermochromic material, and form a visible primary image. It is this substrate and this primary visible image which may fade or darken beyond a legible state when exposed to one or more degrading influences.
The invention may be further illustrated by the following examples. It should be understood that it is not intended to limit the scope of this invention.
Labels were produced by hand painting warning indicators on white undeveloped thermal paper stock. The ink used was a thermochromic white to black ink with a change temperature of about 90° C. available from TMC under the name KROMAGEN FLEXO INK. In order to achieve a measure of gray scale in the warning indicators, the KROMAGEN ink was blended with TITANIUM WHITE LIQUITEX, a non-chromogenic white acrylic paint available for Liquitex, Piscataway, N.J. Three layers were use: a pure non-chromogenic white acrylic paint; a gray blend of the non-chromogenic white acrylic paint and the thermochromic white to black ink; and a pure thermochromic white to black ink. The word “WARNING” was hand painted on the labels such that each letter of text was painted with each of the three layers. On the white undeveloped thermal paper, prior to exposure to any degrading influence, the latent “WARNING” image was not generally visible.
The white undeveloped thermal paper with latent “WARNING” images of Example 1 was exposed to 50° C. for a period of one hour, after which the pure KROMAGEN ink showed indications of darkening. Upon exposure to 60° C. for a period of one hour, the pure KROMAGEN ink showed further indications of darkening and the gray blend began developing. The black and gray scale portions of the “WARNING” image were legible against the relatively light background. Upon exposure to 95° C. for a period of 15 minutes, the KROMAGEN ink fully developed, and the background of the label turned a dark gray color. Against this relatively dark background, the white and gray scale portions of the “WARNING” image were legible. Example 2 thus illustrates that thermochromic white to black ink, in conjunction with the gray scale mixture of Example 1, may enhance the legibility of a latent image when heat exposure has not yet darkened the thermal paper background. Example 2 further illustrates that non-chromogenic white paint on white thermal paper, in conjunction with the gray scale mixture of Example 1, may enhance the legibility of a latent image when heat exposure darkens the thermal paper background.
The white undeveloped thermal paper with latent “WARNING” images of Example 1 was moistened slightly and exposed to microwave energy for 120 seconds. The background of the label turned black, obscuring the visible image. Against this relatively dark background, the white and gray scale portions of the “WARNING” image were legible. Example 3 thus illustrates that non-chromogenic white paint on white thermal paper, in conjunction with the gray scale mixture of Example 1, may enhance the legibility of a latent image when moisture and microwave energy darken the thermal paper background.
The white undeveloped thermal paper with latent “WARNING” images of Example 1 was exposed to microwave energy for 120 seconds followed by exposure to 60° C. and 85% relative humidity for seven days. Such adverse environmental factors induced patchy fading of the labels, obscuring the visible image. Against this relatively light background, the black and gray scale portions of the “WARNING” image were legible. Example 4 thus illustrates that thermochromic white to black ink, in conjunction with the gray scale mixture of Example 1, may enhance the legibility of a latent image when microwave energy and high humidity fade the thermal paper background.
The white undeveloped thermal paper with latent “WARNING” images of Example 1 was exposed to a simulated one year of direct sunlight and a simulated 17 years of direct sunlight. Labels that had previously been darkened due to heat or microwave energy exhibited background fading in response to the simulated 17 years of direct sunlight. The “WARNING” image developed in the light chamber, possibly due to warmth from the lamps, such that the black ink contrasted prominently against the faded background. Example 5 illustrates that thermochromic white to black ink may enhance the legibility of a latent image when direct sunlight fades the thermal paper background.
The foregoing description is provided to illustrate and explain the present invention. However, the description hereinabove should not be considered to limit the scope of the invention set forth in the claims appended hereto.
