2. Description of the Related Art.

[0002] The majority of printing with relief plates is accomplished by first creating an image on a plate and next mounting that plate to a foam tape for printing. The initial step in the process is placing a photosensitive photopolymer sheet on a vacuum table. A mylar substrate covers the photopolymer surface that is not adjacent to the vacuum table, the back surface. The mylar substrate stabilizes the photopolymer by resisting shape changes. This back surface covered by a mylar substrate is exposed to ultra violet (UV) light for a few seconds creating a base for the photopolymer. At this point the photopolymer and mylar combination is sent to the customer to continue the plate manufacturing process.

[0003] The customer receives this back-exposed photopolymer sheet and mylar combination and places it so that the front surface, opposite the back-exposed surface, faces a UV light source. A plastic membrane material, kreen, is then rolled over the front surface of the photopolymer and a negative of an image is placed over the sheet and kreen. The kreen provides intimate contact between the photopolymer sheet and the negative.

[0004] Next, this four-layered composite is exposed to UV light and the desired image is formed on the front surface of the photopolymer. After the plate is face-exposed, a wash-out process uses solvents or water to remove the excess, unexposed photopolymer from the sheet. Then the plate is dried to remove any solvent or water the plate may have absorbed during the wash-out process. The next step is a post-exposure to UV light that cures the entire plate bringing it to the proper degree of hardness for printing. The last step of the plate's manufacture is mounting the plate onto a foam base to be used in a printing press. Mounting the plate onto a foam tape is necessary to absorb the shock the printing press exerts on the plate during the printing process.

[0005] One problem with the conventional process is that the customer must laminate the mylar and photopolymer combination before it may be used for imaging. An additional problem with this process is that the plate is mounted onto foam tape that does not hold the plate tightly and damages the foam very quickly. The foam tape does not provide a consistent backing and consequently the plate does not last as long as it could with a layer of reliable compression material integrated into the plate. Also, the use of foam tape is not cost- effective as it must be frequently replaced.

[0006] An alternative design for relief plates starts with a sheet of photopolymer between two protective polyester sheets. The next layer of the plate is a closed cell foam that is smooth without skin. The last layer is a dimensionally stable support layer such as a polyester film or a thin metal backing.

[0007] The photopolymer is back-exposed and then the back protective polyester sheet is removed leaving the front protective sheet. In a separate step, the foam and support layer are laminated into one piece. Next, a film adhesive is used to laminate the exposed surface of the foam to the back-exposed surface of the photopolymer sheet. The foam is covered by a silicone coated polyester release film that must be pulled off the foam before lamination to the photopolymer layer. After the release film is removed, the photopolymer is manually brought into contact with the foam and backing layer. This labor intensive process requires multiple laborers to hold the two sheets, lay down one edge to another and press the layers as they are lowered into contact. Additionally, the removed release film is a waste product.

[0008] What is needed in the art is an efficient and cost-effective laminating system and method for manufacturing high-quality multi-layered printing plates exhibiting better compression recovery rates and high durability.

SUMMARY OF THE INVENTION [0009] The present invention is a laminating system and method that allow a layered plate to be manufactured by mechanically laminating a back-exposed photopolymer sheet to a pre-laminated layer of foam and stable backing.

[0010] During the first step of the process, a photopolymer sheet is conveyed into a light chamber where it is briefly exposed to UV light. This back-exposure creates a base for the photopolymer. Next, the sheet moves to the laminating station where the photopolymer is laminated to the pre-laminated foam and stable backing combination using a hot melt spray adhesive. After the three layers have been laminated together, the laminate is taken to the cutting table, where it is shaped to the necessary size.

[0011] In the disclosed embodiment of the system, the production line has tracks, a cart, an ultraviolet light chamber, an infra red lamp, a laminating station and a cutting table.

The cart conveys the photopolymer sheet along the track during the process.

[0012] This three-layer design for a printing plate provides better quality printed images and eases the customer's work by eliminating the need for laminating before use.

Additionally, the polyurethane, ester based foam used in the above process is a micro cellular, open cell design, which allows for better compression recovery rates and longer life to the plate.

[0013] The design of the apparatus allows for laminating without the need for manual labor such as smoothing and pressing; the lamination is accomplished by the system so that human contact is not required. The only manual work involved is the feeding of the foam and stable backing together into the nip roll down the material guide. Alternatively, the feeding of the foam and stable backing together may be automated, with mechanical feeders supplying the foam and backing into the nip roll. The automatic application of the hot melt adhesive, without the necessity of contact between the layers until they reach the nip roll, allows for a more cost-effective and better controlled lamination process.

[0014] With the present invention, a printing plate may be manufactured and customer-ready through a mechanical process that avoids steps seen in conventional plate manufacturing.

[0015] One object of the present invention is to eliminate the labor intensive processes and reduce costs associated with manual laminating.

[00161 Another object of the present invention is to increase the quality of printed images.

[0017] A further object of the present invention is to produce more durable printing plates by adding a protected layer of compressible foam within the plate that absorbs the mechanical shock imposed by the printing process.

BRIEF DESCRIPTION OF THE DRAWINGS [0018] The above mentioned and other features and objects of this invention, and the manner of attaining them, will become more apparent and the invention itself will be better understood by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawings, wherein: [0019] Fig. 1 is a cross section of the integrated printing plate of the present invention; [0020] Fig. 2 is a side perspective view of the apparatus, including the cart; [0021] Fig. 3 is a view similar to Fig. 2, but depicts the cart's progression down the track of the present invention; [0022] Fig. 4 is a side perspective view of the lamination station of the present invention ; [0023] Fig. 5 is a view similar to Fig. 4, but depicts a break-away view of lamination of the photopolymer sheet to the pre-laminated foam and stable backing combination of the present invention; [0024] Fig. 6 is a plan view of the material guide of the present invention, taken along the lines 6-6 of Fig. 2.

[0025] Corresponding reference characters indicate corresponding parts throughout the several views. Although the drawings represent embodiments of the present invention, the drawings are not necessarily to scale and certain features may be exaggerated in order to better illustrate and explain the present invention. The exemplification set out herein illustrates an embodiment of the invention, in one form, and such exemplifications are not to be construed as limiting the scope of the invention in any manner.

DESCRIPTION OF THE PRESENT INVENTION [0026] The embodiment disclosed below is not intended to be exhaustive or limit the invention to the precise form disclosed in the following detailed description. Rather, the embodiment is chosen and described so that others skilled in the art may utilize its teachings.

[0027] The apparatus of the present invention is described in relation to the lamination of a photopolymer sheet layer to a foam and support backing combination to create an integrated printing plate. The dimensionally stable backing may be composed of mylar or a thin metal. The backing is not limited to these materials, but the backing must prevent dimensional distortion of the image. The foam and dimensionally stable backing are laminated to one another before reaching the present apparatus where the two layers are laminated to the photopolymer sheet. The process lamination of foam and dimensionally stable backing is accomplished with a slot die coater.

[0028] In accordance with the present invention, Fig. 1 shows integrated printing plate 10, having three separate layers which are laminated together. In a separate previous step, one side of foam layer 12 is laminated to support layer 15. After foam layer 14 and support layer 15 have been laminated together, photopolymer sheet 16 is laminated to the other side of foam layer 14. Printing plate 10 is comprised of one three-layered sheet secured by two independent layers of adhesive.

[0029] Fig. 2 shows transfer cart 18 on which photopolymer sheet 16 is placed.

Photopolymer sheet 16 is secured to the exposed surface of transfer cart 18 with a hermetic seal created by vacuum bed 19. After photopolymer sheet 16 is on transfer cart 18, sheet 16 is conveyed along track 20 into UV light chamber 22.

[0030] Fig. 3 illustrates the progression of cart 18 into UV light chamber 22.

While in UV light chamber 22, photopolymer sheet 16 is exposed to UV light emanating from a plurality of UV lamps 24 for five to sixty seconds. The surface exposed becomes the back surface and creates a base for photopolymer sheet 16. After this back-exposure, transfer cart 18 conveys photopolymer sheet 16 down track 20 to laminating station 26, shown in greater detail in Fig. 4.

[0031] Fig. 4 shows in-line spray head 28 located before and beneath material guide 30. In-line spray head 28 has multiple spray tips 32 that coat photopolymer sheet 16 with a hot melt spray adhesive. Infra red light 34 is located along the interior surface of material guide 30 to maintain the adhesive's sealant qualities. Material guide 30 is comprised of guides 31 and of slots 39 (best shown in Fig. 6) for adjusting material guide 30 to accommodate pre-laminated foam stable support combinations of varied widths. An operator feeds the pre-laminated foam layer 14 and dimensionally stable support layer 15 down material guide 30 and against nip roll 40. It is contemplated that this feeding process could be automated. Nip roll 40 may be adjusted as needed, depending upon the height of transfer cart 18.

[0032] Fig. 5 depicts the pre-laminated foam layer 14 and dimensionally stable support layer 15 being fed into nip roll 40, and being pressed into contact with adhesive coated photopolymer sheet 16, which is still secured by vacuum to transfer cart 18. The foam layer 15 is laminated to photopolymer sheet 16 at the back-exposed surface of photopolymer sheet 16. The pre-laminated foam layer 14 and stable support layer 15 may be manually fed into nip roll 40, or alternatively, a mechanical feeder may direct pre-laminated foam layer 14 and stable support layer 15 into nip roll 40. As the materials roll out of laminating station 26, they are now one three-layered sheet secured by two independent layers of adhesive.

Transfer cart 18 carries the integrated printing plate 10 to cutting table 42 to be sized to customer specifications.

[0033] Sealing a foam layer within the plate provides advantages over conventional plate manufacturing and printing. The foam layer is comprised of a micro cellular, open cell, polyurethane, ester based foam. This foam's qualities allow for the best recovery rate after compression, which in turn provide the plate with the greatest protection from the mechanical stress of the printing process. Additionally, certain qualities advance the foam's compatibility with various imaging processes.

EXAMPLE Experimental Materials and Methods I. Materials : Foam An open cell, micro cellular, ester-based foam was cut into 1 inch by 1 inch (2.54 cm by 2.54 cm) squares.

Machine A MTS servo-hydraulic test machine administered a Dynamic Fatigue and Compression Deflection Test on the sample at room temperature.

II. Methods: An exemplary procedure for performing a Dynamic Fatigue and Compression Deflection Test of foam materials is described below as follows: (1) Compress the foam sample to 75% of its original thickness; (2) record the compressive load required to obtain 75% original thickness; (3) apply a cyclic load and compress the samples between 0.00 and 0.03 inches (0.00 cm and 0.0762 cm) at 10 hertz for 50,000 cycles to the foam sample; (4) remove the foam sample and allow to rest undisturbed for 20 minutes; (5) measure and record the foam sample's thickness; (6) repeat steps (2)- (5) four times.

A Dynamic Fatigue and Compression Deflection Test of the foam sample was conducted. The following results were observed: Table I Observed Results-Compressibility of Foam Thickness Extent of Compressive Number Thickness before round of Compression Load @ 75% of Cycles after 20 compression minutes Static 1 0. 1320 in. 0.0330 in. 19.8 lbs.-- (0.33528 cm.) (0.08382 cm.) (8. 9811 kg.) Fatigue 1 0.1320 in. 0. 0300 in.-50, 000 0.1310 in. (0.33528 cm.) (0.07620 cm.) (0. 33274 cm.) Static 2 0.1310 in. 0.0328 in. 19.3 lbs.-- (0.33274 cm.) (0.08331 cm) (8.7543 kg.) Fatigue 2 0.1310 in. 0.0300 in. - 50,000 0.1310 in. (0.33274 cm.) (0.0762 cm.) (0.33274 cm.) Static 3 0.1310 in. 0.0328 in. 18.9 lbs.-- (0.33274 cm.) (0.08331 cm.) (8.5729 kg.) Fatigue 3 0.1310 in. 0. 0300 in.-50, 000 0.1305 in. (0.33274 cm.) (0.0762 cm.) (0.33275 cm.) Static 4 0.1305 in. 0.0326 in. 19.8 lbs.-- (. 33215 cm.) (0.08280 cm.) (8.9811 kg.) Fatigue 4 0.1305 in. 0. 0300 in.-50, 000 0.1300 in. (0.33215 cm.) (0.07620 cm.) (. 33020 cm.) Static 5 0.1300 in. 0.0325 in. 19. 3 lbs. (0.3302 cm.) (0.08255 cm.) (8.7543 kg.) Fatigue 5 0.1300 in. 0. 0300 in.-50, 000 0.1295 in. (0.3302 cm.) (0.0762 cm.) (0.32893 cm.) [0034] As indicated above, the open cell, ester based, polyurethane foam provides unexpected results, namely dramatic increases in compressibility compared to conventional foams. The recovery rate for a foam is calculated by dividing the foam's thickness 20 minutes after the final compression by the foam's original thickness before any compression. The recovery rate for the open cell, ester based, polyurethane foam is 98%.

[0035] Additionally, the above results reveal that the open cell, polyurethane foam is extremely stable over compression. The first compression to 75% of the foam's thickness required 19.8 pounds (9.9811 kg.) of pressure. The final compression to 75% of the foam's thickness after four previous compressions required 19.3 pounds (8.7543 kg.) of pressure. This small decrease in the compressive load from Static 1 to Static 5 is evidence of the foam's resiliency to compression. After four rounds of compression only one-half of a pound (0.2268 kg.) less pressure was required to reduce the foam by 25% than was needed in the first round. The foam was almost as resilient to compression after four rounds of pressure as before the test began. The unusually high recovery rate and resiliency to compression allow for more durable plates. The customer benefits from a cost-effective product that does not have to be replaced as often as a conventional plate or an integrated plate with a conventional foam.

[0036] Not only does a compressible layer increase plate durability, an integrated plate produces a better quality image. The internal layer of foam reduces"dot gain", a problem in which the image loses a degree of precision and becomes blurry from plate to final product. The internal layer of foam furnishes a better cushion for the plate, which results in better resolution in the image. The image is more exact because there is less slip in the plate during the printing process.

[0037] Additionally, the customer benefits from the convenience of an integrated plate. The product of the apparatus is a plate that is ready for face-exposure by a customer.

The customer does not need to laminate the product further, nor does he need to mount the plate onto a foam tape, as a foam layer is already secured within the plate. The customer may now take the unexposed plate and create a relief plate using a negative as in conventional practice. After face-exposure, the integrated plate is washed-out, dried and post exposed as any other plate would be. During the wash-out process, solvents that carry away the unexposed photopolymer are washed over the plate. The foam within the plate does not deteriorate when washed by these solvents. The foam is compatible with the wash-out process because it is ester based and therefore solvent resistant. The foam layer further works with thermal radiation, a process that accomplishes the same purpose as the wash-out process. Thermal radiation uses brief exposure to heat to remove the unexposed photopolymer that remains on the plate after the image is created. In addition to conventional means of imaging that utilize a negative to obtain an image, the present invention produces a plate that is compatible with computer controlled digital imaging.

[0038] The mechanical application of hot melt spray adhesive and lamination has advantages over manual lamination with release film adhesives. This mechanical process reduces the number of laborers required to apply an adhesive and allows a better quality application. Manual lamination using release liner adhesive requires multiple laborers to bring together two layers by hand and press them into place before being sent through a nip roll. The present invention provides an automatic application of a spray adhesive that does not require manual removal of a film. Eliminating film adhesives in lieu of spray adhesives reduces the cost of lamination because spray adhesives require fewer laborers to be applied.

Use of three laborers to apply release liner adhesives may prevent release liners'adoption in the industry. Furthermore, the use of film adhesives produces a wasted release film that adds cost by necessitating disposal. Conversely, the present system utilizes only one laborer during the lamination step and does not yield extra waste products.

[0039] The present invention also provides a better quality lamination through the mechanical process in which all contact between the two layers is carried out by a machine.

By limiting the laborer's role to feeding material down a guided path, the present invention provides a more controlled process that is less susceptible to human error. This cost-effective system allows for regulated lamination that saves customers steps, time and money.

[0040] In the exemplary embodiment, track 20 is about thirty-six and a half feet (11.1252 m.) in length and two feet (0.6096 m.) in width. Transfer cart 18 has a rectangular surface and dimensions of about seven feet (2.1336 m.) in length and three feet and eight inches (1.1156 m.) in width. Alternatively, other shapes and dimensions may be used to accomplish the objectives of the present invention. The photopolymer sheet when vacuum sealed to the surface of transfer cart 18 is conveyed at a height of about three feet (0.9144 m.) from the ground. UV light chamber 22 is a frame with dimensions of about ten feet (3.0480 m.) in height, five feet and two inches (1.5748 m.) in width and seven feet and five inches (2.2860 m.) in depth. Alternatively, other shapes and dimensions may be used to expose transfer cart 18 to UV light. The UV lamps 24 are located on crosspieces parallel to track 20 at a height of four feet and ten inches (1.4732 m.) from the ground. UV lights of varying number may be positioned in other formations within UV light chamber 22.

[0041] The exemplary embodiment of the present invention reveals one in-line spray head 28 with multiple spray tips 32. Alternatively, multiple in-line spray heads 28 may be positioned beneath material guide 30. Material guide 30 of the exemplary embodiment has a height of about two feet and eight inches (0.8128 m.), a length of about two feet and seven inches (0.7874 m.) and width of about three feet and eight inches (1.1176 m.).

Material guide 30 is comprised of slots 39 for adjusting material guide 30 for accommodating sheets of varied widths. Nip roll 40 is adjustable in height so that it may correspond with the height of transfer cart 18, creating the proper opening for laminating the photopolymer and foam combination. In the exemplary embodiment, cutting table 42 has a rectangular surface and dimensions of about three feet in height (0.9144 m.), four feet and eleven inches (1.4986 m.) in width and six feet in depth (1.8288 m.). In the alternative, other shapes and dimensions may be used to accomplish the objectives of cutting table 42.

[0042] While this invention has been described as having an exemplary design, the present invention may be further modified within the spirit and scope of this disclosure.

This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains.