Laser imaged printing plate.

IS 2 138 646 T3

DESCRIPTION

Laser photocomposition plate.

Field of the invention

This invention relates to plates that can be prepared without using a negative. More specifically, it relates to a laser photocomposition plate. Such plates are particularly useful for flexographic printing, but can be used for offset and lithographic printing.

Foundation of the invention

Flexography is a printing method commonly used for high-volume print runs. Flexography is used to print on a variety of substrates such as paper, cardboard or cardboard, corrugated cardboard, films, metal foils and laminates. Newspapers and shopping bags are outstanding examples. Rough or rough surfaces and elastic films can be printed economically only by means of flexography. Flexo plates are raised plates with image elements raised over open areas. One type of flexographic plate resembles a plastic mat, transparent or translucent, when ready for use. The plate is somewhat soft and flexible enough to wrap around a print cylinder and durable enough to print more than a million copies.

Such plates offer a variety of advantages to the printer, based primarily on their durability and the ease with which they can be made. Other improvements, related to the degree of definition (fineness of detail) that can be achieved, as well as cost reductions, extend the usefulness of these plates. The present invention allows to achieve a better definition through the use of laser treatment and cost reductions thanks to the elimination of the use of a negative to make the plate.

A characteristic flexographic plate, as supplied by its manufacturer, is a multi-layered article consisting of a backing, an unexposed photocurable layer, a protective layer or film, and a cover sheet. The support supports the plate. It is characteristically a plastic sheet approximately 127 μm (5 thousandths of an inch) thick, which can be transparent or opaque. The photocurable layer can be about 635-6.985 µm (25-275 thousandths of an inch) thick and can be formulated from a wide variety of known photopolymers, initiators, reactive diluents, fillers, etc. The protective film is a thin sheet (approximately 2.54 - 25.4 μm (0.1 - 1.0 thousandths of an inch)) that is transparent to UV light and that protects the photopolymer from dust and increases its ease of handling. . The covering sheet or lamine is a thick protective layer, characteristically made of polyester, plastics, or paper.

In normal use, the printer peels the backing sheet off the plate and places a negative on the protective film. The plate and negative are then exposed to high intensity UV light and through the negative. The areas exposed to light are cured, or hardened, and the unexposed areas are removed (revealed). Typical methods of development include washing with various solvents or water, frequently using a brush. Other possibilities for development include the use of an air or heat knife plus blotting paper.

Plate exposure is usually carried out by applying a vacuum to ensure good contact between the negative and the plate. Any air gap will lead to image deterioration. Likewise, any foreign matter, for example dirt and dust between the negative and the plate, results in a loss of image quality.

Even when protective films are thin and made of transparent materials, they still produce some light scattering and somewhat limit the definition that can be obtained from a given image. If the protective film is removed, finer and more detailed images can be obtained.

A finer definition would be particularly desirable for the reproduction of complicated print, for example when it comes to Japanese characters and for photographic images.

A negative can be an expensive item. For some reason, any negatives used for printing must be perfect. The minor defect carried over to each printed item. Consequently, every effort would be adequate to ensure that the negative is done accurately. In addition, the negative is usually made with a silver halide compound that is expensive and whose disposal presents environmental difficulties.

IS 2 138 646 T3

Given these considerations, it is clear that any procedure that eliminates the use of negative, or reduces the effects of light scattering and other exposure limitations of protective films, would offer considerable advantages in terms of cost, environmental impact, convenience. and image quality on the present methods.

The inventors have found a means of achieving these advantages by employing an image guided laser stored in an electronic data file to create a negative in situ on a modified protective film and then exposing and developing the plate in the normal manner. Consequently, the printer does not have to rely on the use of negatives and all its supporting equipment and can instead rely on a scanned and stored image. Such images can be easily altered for different purposes, thus offering the printer greater convenience and flexibility. In addition, this method is compatible with current developing and printing equipment, so there is no need to make costly alterations to the rest of the equipment.

Layser engraving of various materials, such as wood and metal, is well known. The layser engraving of hard rubber plates or lithographic plates is also known. If this procedure were applied to a flexographic plate, the plate would first be exposed to non-imaging UV light. Later the líaser would be used to engrave an image on the hardened plate. This procedure has been tried but found to be too slow to be commercially competitive. Flexographic plates require high relief (letters 762-1016 μm (30-40 thousandths of an inch in height)) that take a long time to engrave.

Direct exposure of a photopolymer using a laser is also known. This procedure uses a precisely guided laser to replace the high intensity UV lamps that are normally used to expose the plate. US Patent No. 4,248,959, issued in the name of Jeffers et al, on February 3, 1981, relates to direct exposure of a photosensitive polymeric plate using a computer-generated image-guided laser. The method described is not suitable for developing flexographic plates, again because the thickness of the plate prevents curing or hardening. Again, the process is too slow to be commercially competitive.

Other efforts have been directed at generating an image directly in contact with the photocurable layer. United States Patent N^° 5,015,553, published in the name of Grandmot et al, on May 14, 1991, refers to a method of preparing a photoresist (photocurable substance) for a printed circuit board, using a phototracer that works by means of assisted design. computer (CAD) that selectively exposes a photocomposition layer without influencing the underlying UV-sensitive photoresist. The image layer is then chemically developed on the plate and used as an in situ masking for the underlying UV resistant layer during UV light exposure. After exposure, the image layer is peeled off to allow the traditional treatment of the photoresist emulsion. The process requires at least two stages of development of the entire plate and also requires the use of a peelable coating film interposed between the image layer and the photocurable layer.

The ablation or abrading of polymers by liquefying relatively insensitive substrates is known. United States Patent N^° 4,020,762, published in the name of Peterson on May 3, 1977, relates to a method of preparing a sensitized aluminum printing plate for offset lithography. An aluminum sheet was coated with a mixture of finely divided carbon, nitrocellulose, an antioxidant alkyd resin, a diazo sensitizer, cellulose acetate, butylacetate, xylene, and ethyl cellosolve. The coating was etched, at least partially, with a YAG laiser. It is not evident that all the coating was removed from the aluminum substrate, yet when the text alludes to this result. The inventor describes that the attacked areas become sensitive to UV light and that the attacked areas, after exposure to UV light and development, accepted the ink, while the areas that had not been attacked accepted the water. No quantitative results were presented. There is no indication that the liquid coating in the reference could be usable as a flexographic plate. There is no indication that laser ablation was accurate enough to allow removal of a polymeric layer exposing a photosensitive polymeric layer directly below.

EP 0 436 320 A2 describes polymers which are erodible by laser at a chosen ultraviolet wavelength and which are suitable as adhesives in high density interconnected (HDI) systems such as integrated circuit chips.

JP A 59 111 608 describes a Si substrate coated, inter alia, with a layer

ES 2 138 646 T3 made of polyglycidylmethacrylate containing UV absorber. The layer absorbs light having a wavelength of less than 400 nm and prevents the fading or attenuation of the light.

Document FR A 2 258 649 refers to planographic printing plates having a mask layer capable of being selectively removed or made transparent to ultraviolet light by means of a laser beam. The mask layer is opaque to ultraviolet light and can be a metallic layer or a dispersion of metallic or carbon particles in an organic binder.

Document EP 0 182 332 A2 relates to a method for manufacturing integrated circuits by photolithography. In this process, an optic mask is formed by photolixidation of a photolixible layer deposited on a photoresist.

Document DE 30 36 710 A1 describes a method for preparing photopaint structures by exposing, with actanic light, a photoresist layer which is applied on a substrate. The photoresist layer is deposited on a layer that is degradable by high intensity radiation or by a dry chemical etching process.

EA Chandross et al., Appl. Phys. Lett., Vol. 24, No. 2, 1974, 72 describes the manufacture of waveguide oaptic circuits. Photochemical reaction is used to fix a dopant on a polymeric film with a lower refractive index and the unreactive dopant is later removed by heat. The dopant absorbs strongly in the 300 to 380 nm region.

Lasers have also been used to physically transfer small amounts of polymer from one layer of a multilayer article to another. United States Patent N^° 5,156,938, published in the name of Foley et al, on October 30, 1992, refers to an image composition method by ablative transfer induced by laser, suitable for the production of masks (negatives) for the arts industries. graphics and printed circuits. In this process, a laser sensitive material is phase-shifted from a donor layer of a multilayer structure to a receptor layer.

It is described as an ablative transfer because some of the materials in the donor layer soften or erode while other materials are deposited on the receptor layer.

The inventors have discovered that if a protective film, of the type already used with flexographic plates, is modified with a powerful UV absorber, a laser can be used to etch the film in place of the photopolymer. The protective film then effectively becomes a negative that is created in situ. There is no need to produce a separate negative, and neither does the final silver halide removal. Likewise, the effects of light scattering from the protective film are eliminated, thereby increasing the definition of the image.

Objects of the invention

Therefore, an object of the present invention is to provide a method for manufacturing a printing plate that does not require the use of a photographic negative.

Another object of this invention is to make a laser photocomposition plate.

Another object of this invention is to provide a protective layer for a photocurable article that can be conveniently and accurately removed from the article by laser ablation.

The objects of this invention can be achieved by providing a protective layer for a photocurable article comprising:

- a polymeric matrix, and

- a UV absorber having a high extinction coefficient in the range of 300-400 nm, the layer responding to a threshold dose of radiation at a wavelength chosen by photoblasting of the polymeric matrix and, preferably, photolixidization of the dopant. The coating is applied to a photosensitive article and then a laser is used to selectively remove the protective layer, exposing the underlying photocurable composition for further exposure to UV light and curing or curing. The cured plaque can be developed later in a normal way.

IS 2 138 646 T3

Other objects and advantages of this invention will become apparent in the course of its description.

Detailed description of the invention

The Exposure and Development Process

The present invention includes a method for producing a laser photocomposition plate. First, a UV absorber is added to the UV transparent protective film that is already adapted for use with the plate and applied in the normal way to the surface of the plate without hardening. The plate with the modified protective film can be stored for a period of time or used immediately, as required by the printer's needs.

When the printing plate is to be used, a laser is used to selectively ablate, or remove, the protective film. The uncured plate is then exposed to high intensity UV light in the normal way. The areas in which the protective film is removed were cured, or hardened, by exposure to UV light. Areas where the protective film has not softened will remain uncured. Uncured areas can be removed later by washing in the normal development process.

This application has been written in terms of a specific embodiment in which the invention was used for the first time, that is, on flexographic plates. Whoever has a normal knowledge of the subject will easily realize that this invention is not limited to being realization. For example, in this invention the protective film is used as a vehicle for the UV absorber. It is a matter of convenience, since the protective film is already available on existing plates for use.

UV Absorber

An important aspect of the present invention is that the protective film, which would normally be transparent to UV light to facilitate the image composition process, is modified with a UV absorber. The presence of the UV absorber causes a protective film, normally transparent to UV light, to become a highly opaque barrier to UV light. It is a crotic factor that UV absorption is virtually complete, at least 97%, preferably more than 99.9% and even more preferably 99.99%, so that all radiation from the exposure lamps is effectively blocked. to high intensity UV light. The spectral range of high intensity exposure lamps, used in most applications, is 300 - 400 nm. Therefore, the UV absorber should be characteristically active in this range. An alternative way of stating this is to state that the UV absorber must have a high extinction coefficient in the spectral range of emission from the developing lamps.

Benzophenone derivatives and strongly absorbent dyes are favorable. The following materials have high extinction coefficients within the characteristic spectral range of developing lamps:

Uvinul D 49^TM (2,2'-dihydroxy-4,4'-dimethoxybenzophenone) available from BASF Corpo., Parsipanny,

NJ;

Uvinul D 50^TM (2,2 ', 4,4'-tetrahydroxybenzophenone) available from BASF Corp., Parsipanny, NJ;

Uvinul N 539 (benzophenone cyanoacrylate) available from BASF Corp., Parsipanny, NJ;

4- (dimethylaminobenzophenone) available from Aldrich Chemical Company, Milwaukee, WI;

Tinuvin P^TM (benzotriazole) available from Ciba-Geigy, Corp., Hawthorne, NY;

Intrawite OB^TM, dye available from Crompton & Knowles Ltd, Reading, PA;

Intraplast Yellow 2GLN, stain available from Crompton & Knowles;

4-phenylazophenol ("2-PAP") available from Aldrich.

The UV absorber must also exhibit a specific response to laser excitation at an appropriate wavelength. It must allow ablation of the protective film. Finally, the UV absorber must be compatible with the protective film and not present significant migration from

ES 2 138 646 T3 the protective film to the photocurable composition.

The preferred UV absorbers, which have been shown to have these characteristics, are Uvinul^TM D 49 and D 50 (BASF) and 4-phenylazophenol. These materials produce the photoblasting of a characteristic protective film when exposed to a threshold level of power (fluence) at the chosen wavelength of 351 nm. Furthermore, they offer the added advantage of photolysis at 351 nm. The UV absorber is characteristically present in the film in amounts on the order of 1-20 PHR (parts percent, or 1/101-20/120%); preferably around 4-8 PHR, when the protective film has a thickness of 2.54 to 25.4 μm (0.1 to 1.0 thousandths of an inch), preferably 7.62 to 19.7 μm (0, 3 to 0.5 thousandths of an inch).

Protective Film

As discussed above, the preferred vehicle for the UV absorber, in some embodiments of the present invention, is protective film, a thin protective film used with a printing plate on which an image is to be composed. These films are made from a wide variety of polyomers that are compatible with the underlying photopolymer and are easily removed during the development (wash) phase. When using a negative, the protective film has to be transparent to the light used for curing or curing. As high intensity UV lamps normally provide the light for curing, normal protective film is transparent in the 300-400nm range. Such films are well known in the field of photomechanics and, in practice, any such film can be modified by adding the UV absorber of the present invention. Examples are: polyacetals, polyacrylics, polyamides, polyimides, polybutylenes, polycarbonates, polyesters, polyethylenes, cellulosic polyomers, polyphenyloethers and polyethylene oxides. The addition of the UV absorber can change the response of the film to the laoser used in the present invention. For example, many films are not normally affected by their exposure to laser radiation at 351 nm, but when Uvinul D 50 is added, these films become vulnerable to laser ablation and are useful in the present process.

The Photohardenable Composition

In principle, any of the known photocurable formulations can be used in the present invention. However, it is particularly useful if the type of photopolymer and initiator employed are compatible with the laoser or with the wavelength chosen for use in the process.

Photopolymers

Of the photopolymers, those that are not altered by laser radiation at the particular wavelength chosen for the practice of the present invention are particularly useful. Of these, mention may be made of polyurethanes, including acrylate polyurethanes, acid-modified acrylate polyurethanes, amine-modified polyurethanes, rubbers, including acrylonitrile rubbers, and diblock and triblock copolymers such as those made from styrene-isoprene and styrene-butadiene. Amine modified acrylate polyurethanes and diblock and triblock copolymers of styrene isoprene or styrene-butadine are preferred. An uncured printing plate produced from such a photopolymer can withstand some exposure to laser energy without suffering thermal damage. Therefore, the photopolymer and the various additives, except the initiator, should have low absorbency at the laoser action wavelength.

Initiator

The initiator may also have a low absorbance at the wavelength of the laoser chosen to be used in the present invention. However, if the initiator is activated in response to the chosen wavelength, curing or hardening of the photopolymer will begin during the ablation phase, without damage to the photopolymer, prior to exposure to high intensity UV lamps. Therefore, the use of the appropriate initiator can speed up the plate development process and help ensure faster and more uniform hardening.

Photoinitiators for the photocurable composition include benzoin alkyl ethers, for example benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether and benzoin isobutyl ether. Other classes of photoinitiators are the dialkoxyacetophenones, exemplified by 2,2-dimethoxy-2-phenylacetophenone, eg, Irgacure® 651 (available from Ciba-Geigy, Hawthorne, NY), and 2,2-diethoxy-2-phenylacetophenone. Another class of photoinitiators is the carbonolic aldehyde and ketone compounds that have at least

ES 2 138 646 T3 an aromatic nucleus linked directly to the carboxyl group. These photoinitiators include, but are not limited to; benzophenone, acetophenone, o-methoxybenzophenone, acenaphthenquinone, methyl ethyl ketone, valerophenone, hexaphenone, alpha-phenylbutyrophenone, p-morpholino-propiophenone, dibenzosuberone, 4-morpholinobenzophenone, 4'-diaxybenzopholine-4'-diaxybenzopholine-diaxenopholine-4'-diaxybenzopholine-4 '' methoxy-acetophenone, benzaldehyde, alpha-tetralone, 9-acetylphenanthrene, 2-acetylphenanthrene, 10-thioxanthenone, 3-acetylphenanthrene, 3-acetylindone, 9-fluorenone, 1-indanone, 1,3,5-triacetylbenzene, thioxanthen-9 -ona, xanthen-9-one, 7-H-benz [de] -anthracen-7-one, 1-naphthaldehyde, 4,4'-bis (dimethylamino) -benzophenone, fluoren-9one, 1'-aceto-naphthone, 2 ' -acetonaphtone, 2,3-butanedione, acetonephthene, benz [a] anthracene 7.12 dione, etc. In this case, phosphines such as triphenylphosphine and tri-o-tolylphosphine can also be used as photoinicators.

Benzophenone-based initiators are preferable. An example, commercially available, is Irgacure 6521.

The laser

The laser is used to precisely remove the protective film by exposing the underlying photopolymer to high intensity exposure and subsequent hardening. The wavelength and power of the laser should be adequate so that the laser treatment can ablate the protective film without damaging the photopolymer layer located below. Excimer lasers can be used, operating in a pulsed mode with a wavelength of 351 ± 50 nm, preferably around 351 nm. The preferred dosage level is 1-5 joules per cm² (J / cm²).

The following examples illustrate the present invention without limiting or limiting the appended claims.

Example 1

Preparation of Modified Polyamide Protective Film with Uvinul D 50 for Placás Flexograficás

KOR

In this example, the protective film that would normally be used with a commercial flexographic plate is modified by adding a UV absorber to achieve zero transmittance (as demonstrated by protection against hardening after exposure to high intensity UV lamp).

A concentrated solution for molding will be prepared with the following formulation:

Isopropanol 45.6 parts

Hexane 23.9 parts

VM&P Naphtha¹ 21.6 parts

Macromelt 6900^TM 8.3 parts

Uvinul D 50 0.664 parts

Note at the bottom

Aromatic solvent blend available from Ashland Chemical Co., Columbus, OH

Polymeric pellets available from Henkel Corp., Lagrange, IL

Films approximately 127 to 178 μm (5 to 7 mils) thick were hand cast onto Mylar backing sheet^TM transparent using a thickness reduction bar. Once dry, measure the average thickness of the film using an Ono Sokki micrometer, giving a thickness of around 7.62-12.7 µm (0.3-0.5 mils).

The films were laminated onto a commercial photopolymeric composition to prepare a UV absorber modified printing plate, analogous to the KOR® printing plate, available from WR Grace & Co.-Conn., Atlanta, Ga. The plates were exposed through a test negative using commercial high intensity UV lamps. Three different concentrations were used (4 PHR, 6 PHR and 8 PHR based on the percentage of solids), three levels of thicknesses (low, medium and high) and two levels of exposure for the study that is summarized in Table I. The The presence or absence of an image was an indication of the effectiveness of the UV absorber in blocking incident UV radiation. With respect to the 4 and 6 PHR charges, an image would appear when the thickness of the protective layer was

ES 2 138 646 T3 below 10.16 µm (0.4 thousandths of an inch), indicating the lowest threshold concentration of D 50 to effectively block all UV light. With respect to the 8 PHR loads, 7.62-10.16 µm (0.3-0.4 mils) was found to be sufficient to block all observed UV light due to no image. For all three concentrations, a thickness above 12.7-15.25 µm (0.5-0.6 thousandths of an inch) was effective.

The modified liner was then laminated onto a Flex Light KOR® ("KOR") plate having a thickness of approximately 635 to 6985 µm (25 to 275 mils). The rolled plates were annealed at 24^° (75^°F) and were used for laser ablation assays, as indicated in Examples 3-6.

TABLE I

Studies on the Concentration of Uvinul D 50 versus the Thickness of the Protective Film

<td></td><td colspan="4">Thickness</td><td colspan="2">Exposition</td>

<td>Concentration¹</td><td>μm</td><td>Humid (mils. Inch)</td><td>μm</td><td>Dry (mils. Inch)</td><td>3 1/2 min.</td><td>7 min.</td>

<td>4 PHR</td><td> 178</td><td> (7)</td><td> 1-</td><td> (0,1-0,2)</td><td>I²</td><td>I</td>

<td>4 PHR</td><td> 254</td><td> (10)</td><td> 2-</td><td> (0,2-0,3)</td><td>I</td><td>I</td>

<td>4 PHR</td><td> 381</td><td> (15)</td><td> 3-</td><td> (1,4-1,5)</td><td>N³</td><td>N</td>

<td>6 PHR</td><td> 178</td><td> (7)</td><td> 4-</td><td> (0,2-0,3)</td><td>I</td><td>I</td>

<td>6 PHR</td><td> 254</td><td> (10)</td><td> 5-</td><td> (0,4-0,5)</td><td>N</td><td>N</td>

<td>6 PHR</td><td> 381</td><td> (10)</td><td> 6-</td><td> (0,7-0,8)</td><td>N</td><td>N</td>

<td>8 PHR</td><td> 178</td><td> (7)</td><td> 7-</td><td> (0,3-0,4)</td><td>N</td><td>N</td>

<td>8 PHR</td><td> 254</td><td> (10)</td><td> 8-</td><td> (0,4-0,5)</td><td>N</td><td>N</td>

<td>Footnotes:</td><td> 1- =</td><td> 2,54 - 5,08</td>

<td>1 - Percent based on the percentage of solids</td><td> 2- =</td><td> 5,08 - 7,62</td>

<td>2 - I: Image formation. D 50 is not effective in blocking UV light</td><td> 3- =</td><td> 35,56 - 38,1</td>

<td>3 - N: No image. The D 50 is effective</td><td> 4- =</td><td> 5,08 - 7,62</td>

<td></td><td> 5- =</td><td> 10,16 - 12,7</td>

<td></td><td> 6- =</td><td> 17,78 - 20,32</td>

<td></td><td> 7- =</td><td> 7,62 - 10,16</td>

<td></td><td> 8- =</td><td> 10,16 - 12,7</td>

Example 2

Preparation of Protective Film, Washable with Water, Cellulosic Base Modified with Uvinul D 50 for Flexographic Plates, Aqueous Development, Amine Modified Polyurethane (AMPU)

In this example, another type of protective film, a cellulose film adapted for use with a water washable flexographic plate, is modified with a UV absorber. The concentration and thickness indicated in the previous example were used to ensure maximum UV absorption by the film.

A concentrated solution will be prepared using the following formulation:

IS 2 138 646 T3

Isopropanol Water Klucel L¹Uvinul D 50

50.2 parts 39.8 parts 10.0 parts

0.8 parts

Footnote;

1: Hydroxypropylcellulose Polymer Pellets available from Aqualon, Inc., Wilmington, DE

As before, 127 to 178 μm (5 to 7 mils) thick films were cast onto a clear Mylar backing sheet.^TM, dried and laminated onto an experimental amine modified polyurethane flex substrate. The plates were between 635 µm and 6985 µm (25 and 275 mils) thick. The ablation and composition of the laser image was carried out on the modified plates as indicated in Examples 3-6.

Example 3

Ablation and Composition of the Image by Laser Using a Co Laser₂,. Watertight, Solid State (10.6 nm)

A commercial photopolymeric resin sheet of Example 1 was formed and laminated with 22.86 μm (0.9 mils) thick polyamide protective film containing 8 PHRs of Uvinul D 50 to prepare an experimental printer plate (KOR ). The plates for this preliminary study were prepared using a hand-molded protective film. Two different laser systems were used for ablative studies: a CO laser₂ watertight absorbing at 10.6 µm and a YAG at 1.06 µm. The YAG laser proved to be essentially ineffective at producing ablation. The power in the sealed CO2 laser was varied from 8 watts to 15 watts. The digital image programming will allow the creation of a rectangular profile (1cm x 2 cm) and also the labeling. The results of the ablative studies are summarized in Table II.

The presence or absence of the protective polyamide film was investigated by ATR-IR analysis. The ablated plate was then exposed to high intensity light from hot lamps for 6 minutes and developed in Solvil^R , the normal commercial developing solvent available from Polyfibron Divison from WR Grace &amp; Co.-Conn., Atlanta, GA, for 6 minutes. In Table II it will be seen that the depth of attack versus creep (power) was not linear. The difference in depth of attack between 8 to 10 watts is seldom more than the experimental error of 2.54 μm (0.1 mils). At 12 watts, the 12.7 µm (0.5 mil) protective film had completely ablated, along with some of the underlying photopolymer. There was also a jump in attack depth from 17.78 μm to 127 μm (0.7 to 5.0 mils) when the power was increased from 12 watts to 15 watts. As might be expected, only the rectangular profiles exhibiting almost complete ablation of the protective film hardened during exposure to high intensity light and subsequent development. However, even when it comes to these profiles, the surface was very textured and rough. Also, the definition was deficient in the lyrics. Therefore, it was seen that the basic idea of ​​the laser photocomposition printing plate was demonstrated and that the use of the CO2 laser resulted in thermal ablation with consequent loss of definition.

Example 4

Ablated and Photocomposed by laaser using Krypton Fluoride (KrF) Excimer 248 nm laaser

The experimental printing plates, prepared according to Example 1 (KOR) and 2 (AMPU) above, were used for photocomposition as in Example 3 using a kryptonian fluoride Excimer laser controlled by compositional digital programming. The results are summarized in Table III.

The Krypton Fluoride Excimer laser at 248nm will prove to be remarkably efficient in producing photoablation. Like most polymers, including protective film polyamide and Kraton rubber^TM

IS 2 138 646 T3

TABLE II

CO Laser Ablative Image Composition Studies₂ on Modified Protective Film with Uvinul D 50 on KOR

<td></td><td></td><td colspan="2"></td><td colspan="2">Plate Image Composition</td><td></td>

<td>Number</td><td>Power in Watts</td><td colspan="2">Attack Depth μm (mils. Inch)</td><td>Profile Rectangular</td><td>Labeled</td><td>Comments</td>

<td> 2</td><td> 8</td><td> -</td><td> (-)</td><td>washed away</td><td>washed away</td><td>ablation insufficient</td>

<td> 5</td><td> 9</td><td> 1-</td><td> (0.1-0,3)</td><td>washed away</td><td>washed away</td><td>ablation insufficient</td>

<td> 6</td><td> 10</td><td> 2-</td><td> (0,3-04)</td><td>washed away</td><td>washed away</td><td>ablation insufficient</td>

<td> 8</td><td> 12</td><td> 3-</td><td> (0,7)</td><td>hardened t (68 mil.p.)</td><td>washed away</td><td>uneven plate surface</td>

<td> 12</td><td> 15</td><td> 4-</td><td> (5.0)</td><td>hardened t (68 mil.p.)</td><td>cured</td><td>uneven plate surface</td>

1- 2.54 - 7.62 t 1727 gm

2- 7.62-10.16 t 1626 gm

3- 17,78

4- 127 of the photopolymer of Example 1, have very strong absorption at 248 nm, even at low magnitude fluences (&lt;0.5 J / cm²) produced the ablation of the film. The mechanism is believed to consist mainly of photoablation (that is, disintegration of the polyamide's chemical bonds) and some heat ablation due to heat generation. Unfortunately, as the styrene-isoprene rubber used to make the photopolymer is also highly absorbent at this wavelength, some surface damage occurred, especially at higher creeps. When thermal damage occurred, the definition was poor.

TABLE III

KOR and AMPU Laser Ablation Using KrF Excimer Laser (248 nm)

<td>Kind</td><td>Creep J / cm²</td><td>Number of Impulses</td><td>Picture</td><td>Comments</td>

<td>KOR</td><td> 0,4</td><td> 10</td><td>Yes</td><td>Thermal damage.</td>

<td>(Ex. 1)</td><td></td><td> 40</td><td>Yes</td><td>Poor resolution in</td>

<td></td><td></td><td> 70</td><td>Yes</td><td>everything</td>

<td></td><td> 1,2</td><td> 1</td><td>Not</td><td></td>

<td></td><td></td><td> 2</td><td>Not</td><td></td>

<td></td><td></td><td></td><td></td><td>Swelling due to</td>

<td></td><td></td><td> 6</td><td>Yes</td><td>incomplete healing.</td>

<td></td><td></td><td> 8</td><td>Yes</td><td>Poor definition</td>

<td>AMPU</td><td> 0,4</td><td> 10</td><td>Yes</td><td>Thermal damage.</td>

<td>(Ex. 2)</td><td></td><td> 40</td><td>Yes</td><td>Poor definition</td>

<td></td><td></td><td> 20</td><td>Yes</td><td></td>

IS 2 138 646 T3

TABLE III (Continued.)

KOR and AMPU Liaser Ablation Using KrF Liaser Excimer (248 nm)

<td>Kind</td><td>Creep J / cm²</td><td>Number of Impulses</td><td>Picture</td><td>Comments</td>

<td></td><td> 1,2</td><td> 1</td><td>Not</td><td>Incomplete ablation</td>

<td></td><td></td><td> 2</td><td>Not</td><td>Incomplete ablation</td>

<td></td><td></td><td> 6</td><td>Yes</td><td></td>

<td></td><td></td><td> 8</td><td>Yes</td><td>Thermal damage.</td>

<td></td><td></td><td></td><td></td><td>Poor Definition</td>

Example 5

Optimization of Fluences Relating to the Xenon Fluoride (XeF) Excimer Laser at 351 nm

Laser ablation and photocomposition studies and optimization of fluences necessary for ablation were carried out, as before, on KOR (Example 1) and AMPU (Example 2). Similar results were observed in both types of plaque. The consolidated results are summarized in Table IV.

Most polyomers do not absorb at 351 nm. However, the modified protective films (both solvent-based polyamide and water-based cellulosic polyomers) were very sensitive to Excimer laoser at 351 nm due to the high extinction coefficient of D 50 at this wavelength. A combination of photolysis (destruction of D 50 molecules) and photoablative effects (transfer of energy absorbed by D 50 to the polymer producing disintegration of the polymer) was observed.

The modified protective film was partially ablated at lower doses (&lt;1 J / cm²) resulting in either no hardening (and therefore no image) or incomplete hardening (and therefore poor image and definition). Complete ablation was observed at higher doses (&gt; 1.5 J / cm²). There was no damage to the surface of the plate. Exposure to high intensity light and subsequent development gave a very sharp image of the ablated area with good definition.

TABLE IV

Fluence Optimization for Compositing by Líaser Using Líaser Excimer of Xenoin Fluoride at 351 nm for KOR and AMPU

<td>Creep J / cm²</td><td>Number of Impulses</td><td>Picture</td><td>Comments</td>

<td> 0,14</td><td> 50</td><td>Not</td><td>The creep is below the</td>

<td></td><td> 100</td><td>Not</td><td>threshold and therefore ablation</td>

<td></td><td> 200</td><td>Not</td><td>it was incomplete.</td>

<td> 0,4</td><td> 5</td><td>Not</td><td>Creep below threshold,</td>

<td></td><td> 10</td><td>Not</td><td>it did not harden.</td>

<td></td><td> 15</td><td>Not</td><td></td>

<td></td><td> 30</td><td>Not</td><td></td>

<td> 0,9</td><td> 1</td><td>Not</td><td>Insufficient ablation.</td>

<td></td><td> 2</td><td>Not</td><td>Insufficient ablation.</td>

<td></td><td> 6</td><td>Yes</td><td>Incomplete hardening,</td>

<td></td><td> 10</td><td>Yes</td><td>the image was swollen in solvent. Poor definition.</td>

IS 2 138 646 T3

TABLE IV (Continued.)

Fluencing Optimization for Laser Composition Using Xenoan Fluoride Excimer Laser at 351 nm for KOR and AMPU

<td>Creep J / cm²</td><td>Number of Impulses</td><td>Picture</td><td>Comments</td>

<td> 1,6</td><td> 1</td><td>Not</td><td>Insufficient ablation.</td>

<td></td><td> 3</td><td>Yes</td><td>Good definition, good image.</td>

<td></td><td> 5</td><td>Yes</td><td>No surface damage observed</td>

Example 6

Photocomposition Studies on KOR Laminated with Protective Film Modified with D 50 and Impresioan Test with Image Plate

Photocomposition of D 50 modified protective sheet on KOR was carried out using a Xenoan fluoride Excimer laser at 351 nm. The composition of labels or printed characters will be achieved using a CAD file. The following pulse numbers and intensities were used:

<td>Creep J / cm²</td><td>N ° of Impulses</td>

<td> 1,5</td><td> 8</td>

<td> 2,0</td><td> 6</td>

<td> 3,1</td><td> 4</td>

The ablated / imaged plates were exposed to high intensity light under hot lamps for 5 1/2 minutes and washed in Solvit® for 6 minutes to obtain an embossed image of 908-635 μm (20-25 mils). .

The microscope examination confirmed that the quality of the image corresponding to all fluences was good, presenting natid profiles. However, the edges were rounded due to insufficient doses in those areas. There was no indication of superficial dermal damage and the surface of the plate was smooth and uniform in all cases.

Example 7

Laser Ablation and Photocomposition on a Protective Film Modified with 4 PHR D 50 and 4 PHR 4-phenylazophenol (4-PAP)

In this example, a mixture of UV absorber will be used with a protective film similar to that of Example 1. A molding solution for the modified film was prepared using the following formulation:

Isopropanol Hexane VM&amp;P Naphtha Macrometl 6900^TM* Uvinul D 50

4-phenylazophenol

45.6 parts 23.9 parts

21.6 parts 8.3 parts 0.332 parts 0.332 parts

A 1127 to 178 µm (5 to 7 mils) thick film was cast onto a clear Mylar backing sheet. After drying, the film had an average thickness of 7.62 - 12.7 μm (0.3 - 0.5 mils). The modified liner was then laminated onto a KOR plate having a thickness of approximately 1702 µm (67 mils). Laser ablation and photocomposition were carried out as in Example 6. Again, the image quality was excellent with respect to all fluences.

IS 2 138 646 T3

Example 8

The printing plates of Examples 6 and 7 were tested for print quality on glossy paper using aqueous blue ink. The ink deposit was good. The printed letters were naive and without deformations.