Method for forming a graphic image web

20

25

It is known in the art to fabricate generally planar display devices which include an image sheet and a lenticular lens sheet which, in combination, give the image and appearance of three dimensionality. The lenticular lens sheet and the image sheet must be aligned properly to avoid a distorted image. The components have heretofore been in sheet form because the process of combining them is usually manual to ensure necessary registration.

The illusion of three dimensionality requires the image originally be made with a special three dimensional or stereoscopic camera, photographing the desired object from a plurality of angularly displaced positions. Such a camera 3Q typically uses a photosensitive film disposed behind a lenticular screen. The lenticular screen is positioned adjacent the photosensitive film so the focal point of each lenticule generally coincides with the front surface of the film. Thus, the image of the object is focused into a narrow image band 35 which is exposed in the film. As the camera is shifted to the next angular position, the lenticular screen is also shifted slightly. A subsequent picture image of the object from the new angular position is then exposed into a separate image band in the film adjacent the preceding image band. Each 4Q time the camera is moved to a new angular position, the object is photographed and the image is exposed in the film as a similar, narrow image band adjacent the previously formed image band, until a series of image bands representing different views of the object is created. To avoid overlap 45 of image bands, the lenticular screen is only moved a distance equal to the width of a single lenticule as the camera is moved through its full angular range. This collection of image bands, which is formed under a single lenticule, may be called an image element. Each image element is approxi- 5Q mately the width of a single lenticule and includes all of the condensed views of the object.

Cameras of this type are disclosed in Stockbridge et al., U.S. Pat. No. 3,380,360, issued Apr. 30, 1968 and Bonnet, U.S. Pat. No. 2,508,487, issued May 23,1950. Both of those 55 patents disclose three dimensional or stereoscopic cameras used to photograph objects from numerous angular positions where the photograph taken at each position is exposed on a film as a linear image band.

Once the object is photographed from tile various posi- 60 tions, the film may be developed the same as any other photographic film, but the resulting image is a compilation of the numerous adjacent image bands. Each image band represents the object from a given angle, albeit in a focused or compressed form. This can provide the overall image with 65 a somewhat distorted look to the naked human eye. However, when the developed image is combined with a len

ticular screen or sheet having lenticules of approximately the same size and focal length as the lenticular sheet used to expose the film, the image becomes clear to the human eye as viewed through the screen.

The lenticular sheet must be placed over the image elements so the focal point of each lenticular lens coincides with the front surface of the image sheet. The image will appear to be three-dimensional because the observer is viewing the image through the lenticular sheet from a slightly different angle due to the lateral spacing between his eyes. In effect, this allows each eye to focus on a different image band, representing different views of the photographed object from separate angles, thereby giving the viewer the illusion of a three dimensional image.

In the past, the lenticules and image elements were relatively wide and each lenticule had to be perfectly aligned over each image element to obtain a clearly, defined three dimensional image. It has been difficult to obtain precise alignment and impossible to mass produce three dimensional images efficiently and economically. Typically, the lenticular sheet has beer manually positioned over the image sheet and then carefully adjusted to eliminate moire line or interference. This is a time consuming, inefficient and expensive task.

Further difficulties exist in mass producing three dimensional sheets for use in publications such as magazines due to the size of the lenticules and the consequent thickness of the lenticular lens sheet. However, larger lenticules have longer focal lengths and necessitate a thicker lens overlay so the focal point of the lenticule is approximately adjacent the image elements on the image sheet. This, of course, leads to a relatively thick composite sheet which is not suitable for magazines or other printed media that require a thinner sheet dimension. Making the sheet sufficiently than to be used in magazines requires the lenticules to be extremely small thus making it more difficult to form the lenticular lens sheet and properly align it with the image sheet. The required precision has made the use of efficient, high output machinery difficult.

It has long been desirable but unattainable to make both the image sheet and the lenticular lens sheet in continuous form and then combine them at a rapid pace with precise registry to produce a finished product having photographically acceptable quality. Standard printing methods could then be used to reproduce the images in continuous form. Though techniques have been developed for creating a lenticular lens in continuous form, and certain methods and devices have also been used in an attempt to combine an image web with a continuous lenticular lens, none of these devices is able to produce a thin, flexible lenticular image composite for economical use in the production of, for example, magazines while maintaining the precision necessary to produce quality images having the illusion of three dimensionality without interference lines or distorted appearance.

In three patents to Conley, U.S. Pat. Nos. 4,420,502, issued Dec. 13, 1983, 4,414,316, issued Nov. 8, 1983, and 4,420,527, issued Dec. 13, 1983 an apparatus and method for making a composite sheet material are disclosed. A transparent base web is directed onto the surface of a first roll and advanced along an arcuate path around the first roll and then through a narrow gap disposed between the first roll and a second roll. Before the transparent base web passes between the first and second rolls, a fiowable, uncured actinic radiation-curable thermosetting resin is directed onto the web behind the narrow gap. The second roll includes 3

grooves so that, as the resin covered web passes through the narrow gap and around the second roll, lenticular formations are made in the flowable resin. Ultraviolet radiation is directed through the transparent basis web and into the flowable resin layer while it remains in contact with the 5 second roll. Thus, the flowable resin is cured into a composite lenticular lens sheet.

Such a process can produce small, well defined lenticular lenses. However, the difficulty remains in properly joining such a lenticular lens with a corresponding image web in a 10 manner that avoids distortion of the image. Typically, the lenticular lens will still need to be cut in sheets and then carefully aligned by hand with a corresponding image sheet. It would be advantageous, and meet the long-felt need summarized above, if such a lenticular lens could be precisely aligned and combined with the corresponding images 15 while the image sheet and the lenticular lens both remained in continuous form. This would greatly increase the efficiency and volume of the finished web resulting in a very economical product.

20

Other patents disclose methods and devices for making lenticular lens products but none with the accuracy or precision that would allow the finished product to be used in typical publications such as magazines. For instance, Jerothe etal., U.S. Pat. No. 3,264,164, issued Aug. 2,1966, discloses 25 a device which makes a laminated, flexible fabric-like material having interesting characteristics of color and depth. However, precise accuracy is not necessary since one of the purposes of the patented device is to produce images having a moire effect. Additionally, that approach uses 3Q colored lines and various colored shapes placed at different depths between cumulative flexible sheets. In the Jerothe et al. device, a relatively thick sheet is used for the formation of the lenticular lens. The lenticular lens sheet is laminated with various films and the resulting laminate passes between 35 a pressure roll and a gravure roll where surface ribs or lenticular lens type ribs are formed by pressing the relatively thick lens forming sheet against the gravure roll. That device, however, cannot be accurately controlled to make extremely small accurate lenses in alignment with the image 4Q bands of an image web to yield photographically acceptable image quality.

Leach, U.S. Pat. No. 3,565,733, issued Feb. 23, 1971 discloses an apparatus for making a composite web from paper web combined with melted plastic. In Leach, a paper 45 web, which can include an image, is passed between a pressure roll and a coating roll and then around a chilled embossing cylinder. A melted plastic is poured onto the coating roll which brings the melted plastic into contact with the paper web. This combined paper web and melted plastic 50 is immediately brought into contact with the surface of the chilled embossing cylinder which solidifies the melted plastic leaving lenticular lens-type formations in plastic. A problem with the Leach apparatus is that it does not provide for the precision alignment of the lenticular lens formations 55 with the image elements on the image web. This prevents the constant replication of high quality images having the appearance of three dimensionality without distortion. Additionally, meltable plastic will not retain its proper shape under the rigors of magazine use and shipping which can 60 tend to place the lenticular lens formations under harsh conditions of pressure and heat. Once the lenticular lenses degrade, the three dimensional effect is lost. See also U.S. Pat. No. 3,607,340 to Stroupe issued Sep. 21, 1971.

In Lemelson, U.S. Pat. No. 3,146,492, issued Sep. 1, 65 1964, an apparatus is disclosed which produces a multiple image sheet display on a continuous basis. In Lemelson, an

4

impressionable sheet is laminated with a plurality of sheets and then passed through a pair of rolls. One of the rolls is an embossing roll which creates lenticular formations in a face of the impressionable sheet. The apparatus is similar to those mentioned above in that it is difficult to form precision lenticules in the solid web without which an image of photographically acceptable quality cannot be reliably and repeatedly reproduced. Additionally, there is no way for the machine to provide precise alignment of the image elements with the lenticules.

The present invention addresses the foregoing drawbacks involved in making a precision lenticular lens image web having three dimensional image characteristics with photographic quality.

SUMMARY OF THE INVENTION

The invention provides a method of forming a graphic image having the appearance of three-dimensionality, the method comprising the steps of providing a preformed lenticular film having a flat side and having a side with lenticules opposite the flat side; and printing an image on the flat side of the lenticular film using web fed printing to produce a graphic image web in which the perceptible image possesses photographically acceptable quality, wherein the image elements are printed on the lenticular film at an angle which corresponds to the pitch of the lenticules of the lenticular film.

One embodiment of the invention provides a method for forming a graphic image web to produce the illusion of three dimensionality in a visually perceptible image, the method comprising the steps of defining an image field including an object to be viewed; imagewise exposing the object onto a photographically sensitive element over a plurality of spatially disparate views through a lenticular lens having a prescribed optical geometry; developing the latent image on the photographically sensitive element; providing a lenticular lens web; and printing the developed image on the lenticular lens web while the lenticular lens web is translating in a machine direction to create the graphic image web with the illusion of three dimensionality.

Other features and advantages of the invention will become apparent to those of ordinary skill in the art upon review of the following detailed description, claims, and drawings.

BRIEF DESCRIPTION OF THE DRAWING

The invention will now be described with reference to the accompanying drawing, wherein like numerals denote like elements, and:

FIG. 1 is a schematic view of an object being exposed on photographic film through a lenticular sheet;

FIG. 2 is a front elevation view showing the formation of a graphic image web by combining a precursor image web with a lenticular lens web;

FIG. 3 is a schematic perspective view showing the paths of travel of the precursor image web and the lenticular lens web as they are combined;

FIG. 4 is a schematic side view of the relief cut roll which forms the lenticules in the lenticular lens web;

FIG. 5 is a schematic perspective view of a printing unit used in a web offset press;

FIG. 6 is a schematic perspective view of a printing plate;

FIG. 7 is a side view of the graphic image web which