MATERIALS USEFUL IN LITHOGRAPHIC PRINTING PLATES
FIELD OF THE INVENTION
This invention relates to a media-ink jet fluid set used in ink ιet printing to produce a more durable, water-fast image, and more particularly, to a media-mk jet fluid set that provides an economical lithographic printing plate
BACKGROUND OF THE INVENTION
Lithographic printing has long been the most widely used printing technique, especially for short to medium printing run lengths of 1 ,000 to 15,000 The term "lithographic" is meant to include various terms used synonymously, such as offset, offset lithographic, wet lithographic, planographic, and others Most lithographic plates are still produced photographically The disadvantages of this and some ofthe alternative lithographic plate materials and processes are described in U S Patent Nos 4,958,563 and 5,487,338
With the advent ofthe computer in revolutionizing the graphics design process leading to printing, there have been extensive efforts to develop a convenient and inexpensive computer-to-plate system, particularly for use in lithographic pπnting Many of the new computer-to-plate systems are large, complex, and expensive They are designed for use by large pπnting companies as a means to streamline the prepress process of their printing operations and to take advantage ofthe rapid exchange and response to the digital information of graphics designs provided by their customers There remains a strong need for an economical and efficient computer-to-plate system for the many smaller pπnters who utilize lithographic pπnting A number of electronic, non-impact printing systems have been investigated for use in making lithographic pπnting plates to satisfy the needs of these smaller pπnters Foremost among these have been laser pπnting systems, for example as described in U S Patent No 5,304,443 and references therein These have had some limited success, but have not been able to overcome the disadvantages of undesired background toner imaging, limitation to small sizes (approximately 1 1 inches by 18 inches) which
are too small for many applications, and limitation to only those flexible substrates such as paper and plastic films which can transport through the laser printers
Another non-impact printing system which has received attention for economical and convenient computer-to-plate preparation for lithographic printing is thermal transfer printing, for example, as described in U S Patent No 4,958,564 This involves the pπnting of a hydrophobic wax or resin material on to the lithographic pπnting blank This approach has similar size and flexible substrate limitations as described above for laser printing In addition, the nature ofthe thermal transfer process is very demanding on intimate contact ofthe wax or resin donor πbbon to the receiver substrate to obtain consistent image quality For this latter reason especially, the low cost thermal transfer pπnters in wide use for hard copy color output pπnting from computers are not used to prepare lithographic printing plates Instead, more expensive, specially built thermal transfer pπnters have been proposed The only widely used pπnters for hard copy computer output that have seen some use in making lithographic plates are laser pπnters, in spite of their aforementioned disadvantages
In recent years, ink jet pnnters have replaced laser pπnters as the most popular hard copy output pπnters for computers Some ofthe competitive advantages of ink jet printers have been low cost, reliability, and the ability to make color images without significantly increasing the cost ofthe printer Both thermal ink jet and piezoelectnc ink jet printing methods have been widely adopted for desktop computer printing A third conventional type of ink jet pπnting, a continuous flow type method, has found acceptance in high quality color printing and proofing in graphics applications
In spite ofthe very large and rapidly growing installed base of low cost desktop inkjet printers as well as a large number of higher cost, larger size ink jet printers used m prepress proofing and in pπnting output, there has not been use of these ink jet pπnters to make lithographic printing plates There have been some reports in the literature proposing the use of ink jet prr cτs to make lithographic pπnting plates In Japanese Kokai 62-25081, an oleophilic liquid or fluid ink was printed by ink jet printing on to a hydrophilic aluminum surface of a lithographic pπnting plate Titanate or silane coupling agents were present in the ink
An inkjet pπnting apparatus to make lithographic pπnting plates is described m PCT WO 94/11191 It is directed to depositing hydrophobic or hydrophilic substances
on hydrophobic printing plates.
In U.S. Patent No. 5,501,150, a fluid ink and hydrophilic media set containing materials to produce a silver-reducible image by ink jet printing are used to make a metallic silver image which, following wet processing to make the silver image
5 sufficiently hydrophobic, is said to provide a lithographic printing plate.
In Japanese Kokai 08-69108, an inkjet ink containing UV polymerizable monomers or oligomers, an UV sensitive initiator, and a dye is deposited on a treated polyester film and exposed to UV radiation to provide a lithographic printing plate. U.S. Patent No. 5,312,654, describes a method for making a lithographic printing plate l o comprising a support having a hydrophilic layer and an ink absorbing layer over the hydrophilic layer and an ink jet fluid marking material having a photopolymerizable ink composition.
Ink jet printing where the ink is a solid or phase change type ink instead of a liquid or fluid type ink is described in U.S. Patent No. 4,833,486 to deposit a hot wax on
15 a surface of an offset plate. Upon cooling ofthe wax, it solidifies, thereby providing a printing plate. Solid inkjet printing has serious disadvantages for lithographic plates in that the wax or resin image has limited durability due to its thermoplastic, chemical, and adhesive properties and the amount and rounded shape ofthe solidified inkjet droplet on the media do not have the intrinsic image resolution properties found in liquid or fluid
20 inkjet printing.
There is also prior art in the use of ink jet printing to apply an opaque image or mask pattern to a photosensitive lithographic printing plate blank, as for example, in Japanese Kokai 63-109,052. The blank is then exposed through the ink jet imaged mask pattern and then processed by conventional means to provide a lithographic printing
25 plate. This approach retains the materials and processing of conventional lithographic printing plates and only uses ink jet printing as an alternative in the photomask through which the conventional plates are exposed. Thus this approach adds to the complexity and expense of the platemaking process and does not depend on the inkjet ink image for the hydrophobic image ofthe plate. U.S. Patent No. 5,495,803 describes a solid or
30 phase change type of ink jet printing to form a photomask for a printing plate.
Much ofthe technical development in inkjet printing has been directed to color and black imaging for computer hard copy output. The need for more archival, durable,
and waterfast imaged media has led to mk jet inks and receiver media that contain chemically reactive components For example, U S Patent No 5,429,860 describes a reactive ink jet ink/media set where the receiver media has a reactive component which reacts with the ink to give a more durable image and reacts in the non-image areas to give a durable coating This patent is directed solely to durable colorant imaging elements and has no teaching on durable oleophilic material imaging elements or production of lithographic pπnting plates, which are the subjects ofthe present invention Other prior art, as for example, U S Patent 5,006,862 describes the use of reactive colorants m the liquid ink jet ink or fluid to provide more durable, waterfast, and bleed resistant images when printed on the media These approaches for archival, more durable color and black inkjet images do not address the requirements for a durable hydrophobic image suitable for a lithographic pπnting plate It would be advantageous to have a liquid ink jet ink or fluid that could be used on the large installed and future base of ink jet printers, now used extensively to pπnt colorants on media, to pπnt a durable oleophilic and water-insoluble image, particularly for use on a suitable lithographic pπnting plate blank to make a lithographic printing plate
Accordingly, it is an object of this invention to provide a liquid inkjet ink or fluid that provides an oleophilic, durable, and water-fast image upon inkjet pπnting Another object of this invention is to provide a liquid inkjet fluid-media set that provides an oleophilic, durable, and water-fast image with a hydrophilic, durable non-image area It is a further object of this invention that this liquid ink jet fluid-media set provides an imaged printing plate suitable for high quality lithographic pπnting
It is a further object of this invention that the liquid inkjet fluid-media set be capable of being printed on conventional, low cost desktop inkjet pπnters to provide an imaged printing plate suitable for high quality lithographic pπnting Yet another object of this invention is that the liquid ink jet fluid-media set is capable of being printed on conventional large format ink jet pπnters with pπnting widths and lengths in excess of 24 inches to provide an imaged printing plate suitable for high quality lithographic pπntmg Still another object of this invention is that the liquid ink jet fluid-media set is capable of being printed on ink jet pπnters of all sizes with a wider choice of πgid and flexible media than with laser and other non-impact pπnters to provide an imaged printing plate suitable for high quality lithographic printing
It is a further object of this invention that no wet processing step, before or after the ink jet printing, is required to provide an imaged printing plate suitable for high quality lithographic pπnting It is another object of this invention that no colorant is required in the liquid inkjet fluid to provide an oleophilic, durable, and waterfast image and to provide an imaged pπnting plate suitable for high quality lithographic pπnting
It is a further object of this invention that no metal precursor is required in the liquid inkjet fluid or the media and no metal is required in the image areas to provide an oleophilic, durable, and water-fast image and to provide an imaged printing plate suitable for high quality lithographic pπnting Still another object of this invention is to provide a convenient and economical method to provide an imaged pπnting plate suitable for high quality lithographic pπnting
These and other objects ofthe present invention will become apparent upon a review ofthe following specification and the claims appended thereto
SUMMARY OF THE INVENTION In accordance with the foregoing objectives, there is provided by the present invention a hydrophilic media and an inkjet liquid or fluid containing a transition metal complex reactive component or an organic reactive component Such a media and fluid composition is, in general, useful as novel mateπals in the preparation of a lithographic printing plate, as well as of durable, waterfast imaged materials In a preferred embodiment, the inkjet fluid contains isocyanates, blocked isocyanates, diketenes, diketene emulsions, polyamide epoxides, acid anhydrides, acid chlorides, or chromium complexes of organic acids as the reactive component Upon ink jet printing on a hydrophilic media and subsequent exposure to an external non-photolytic energy source or another suitable non-photolytic means, an oleophilic, durable, and water-insoluble imaged media with hydrophilic non-image areas is obtained
It is most preferred that the Inkjet fluid contains blocked isocyanates, diketene emulsions, or chromium complexes of organic acids as the reactive component A process for the production of such an imaged lithographic printing plate using ink jet pπnting is also provided herewith
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION
The novel inkjet fluid marking material ofthe present invention comprises a liquid carrier and at least one transition metal complex reactive component or organic reactive component The liquid carrier is water or organic solvents or combinations thereof Choice ofthe specific liquid carrier depends on the specific ink jet pπnter and its compatible ink jet pπnting head and cartridge being used for the ink jet pπnting It also depends on the specific reactive component selected Compatibility with both the inkjet hardware and with the reactive component is important in the selection ofthe liquid carrier The types of liquid carriers suitable for use with the different types of ink jet printheads is known in the art, for example, as described in U S Patent No 5,085,698 In general, the piezoelectric and continuous flow types of ink jet printheads have a wider latitude of acceptable liquid carriers than the thermal or bubble type of ink jet printhead For example, piezoelectπc ink jet printheads work acceptably with various non-aqueous or organic liquid carriers while thermal inkjet printheads typically need a high percentage of water or volatile organic solvent in the liquid earner
Likewise, the reactive components of this invention often have a compatibility with the types of liquid carriers that is known in the art For example, some ofthe reactive components of this invention, such as isocyanates, ketenes, and acid anhydrides, are typically sufficiently reactive with water that they would only be compatible with non-aqueous or organic liquid carriers If the compatibhty is not known, it can be readily estimated by mixing the reactive component in the liquid carrier in the desired amounts and using conventional chemical and physical methods, such as quantitative analysis of any change or decomposition of the reactive component, to measure stability This is not sufficient to insure that the reactive component will be compatible and stable in the ink jet printhead during the conditions of storage and pπnting and in the presence of other materials besides the liquid earner which are typically included in the ink jet fluid composition For this reason, the final selection ofthe suitable liquid carrier for each reactive component needs to be demonstrated in the specific ink jet pnnter to be utilized and with the complete inkjet fluid composition, including other additives, present
The transition metal complex reactive components and organic reactive components of this invention are selected for their capability, in addition to being compatible and stable enough to be utilized in at least one type of ink jet pnnthead with a suitable liquid earner, to form an oleophilic, water-insoluble, and durable image when printed on a hydrophilic receiving surface or layer and subsequently exposed to an external non- photolytic energy source or other suitable non-photolytic means to cause the reaction of the reactive component In the present invention it is preferred that the reactive component is an isocyanate, blocked isocyanate, diketene, diketene emulsion, polyamide epoxide, acid anhydnde, acid chloride, or chromium complex of an organic acid Examples of these reactive components include isocyanates sold under the LUPRANATE trade name by BASF Coφoration, such as LUPRANATE M205, blocked isocyanates sold under the DESMODUR trade name by Bayer Corporation, such as DESMODUR BL3175, diketenes sold under the AQUAPEL trade name by Hercules Corporation, diketene emulsions sold under the HERCON trade name by Hercules
Corporation, such as HERCON 79, polyamide epoxides sold under the POLYCUP trade name by Hercules Corporation, such as POLYCUP 172, acid anhydrides sold under the GANTREZ trade name by ISP Corporation, such as long alkyl chain vinyl ether-maleic anhydride copolymers, palmitoyl chloride from Aldnch Chemical Company, and chromium complexes of organic acids sold under the QUILON trade name by Dupont Corporation, such as QUILON C In a most prefeπed embodiment, the reactive component is a blocked isocyanate, diketene emulsion, or chromium complex of an organic acid
While not wishing to be bound to a particular theory, the inkjet inks or fluids ofthe present invention achieve a unique combination of oleophihcity, water- lnsolubility, and durability upon ink jet pπnting and subsequent reaction which is not present in ink jet inks ofthe pπor art, including those containing colorants with reactive groups or reactive additives and those containing titanate and silane coupling agents This advantageous combination of properties is attributed in part to the supenor film forming properties ofthe reactive components ofthe present invention These film forming properties provide the good mechanical integrity or durability over a range of image thicknesses and the strong bonding to the receiving surface that are needed for
demanding applications such as lithographic printing plates and for other archival, durable applications in general
Another reactive component that can be added to the transition metal complex reactive components and the organic reactive components of this invention is an electron beam, ultraviolet, visible, or infrared radiation curable mateπal In a preferred embodiment, the radiation curable material contains unsaturated acrylic or vinyl groups With the proper selection of radiation-sensitive reactive groups and of oleophilic groups in these radiation curable materials, the unique combination of oleophihcity, durability, and water-insolubility properties descπbed above can be increased with these film forming materials
The media ofthe present invention is for use with the inkjet fluid marking mateπal ofthe present invention and comprises a support that has a receiving surface containing at least one hydrophilic material The selection of this hydrophilic material is made based on its performance in three mam areas receptivity to the inkjet fluid marking material to provide a high quality image with the desired resolution, amount, and uniformity, interaction with the reactive component in the ink jet fluid to provide a durable image, and the hydrophilic properties and water-fastness properties needed for high quality lithographic pπnting For example, most aqueous- based ink jet fluids need a hydrophilic receiving surface for good image quality The hydrophilic properties and water-fastness needed in lithographic printing are well known
Preferred hydrophilic matenals m the present invention are polyvinyl alcohols and copolymers thereof, cellulosic polymers, polyvinyl acetates and copolymers thereof, polyacrylates and copolymers thereof, polymethacrylates and copolymers thereof, poly- maleic anhydrides and derivatives and copolymers thereof, polyvinyl acetals and copolymers thereof, polyvinyl pyrroltdones and copolymers thereof, polyamides, or inorganic polymers In a most prefeπed embodiment, the hydrophilic mateπal contains polyvinyl alcohol or a copolymer thereof, aluminum boehmite, alumina, a silicate, or silica The inorganic polymers are typically formed from a sol gel, colloidal particle deposition, or anodization process to provide a gel or network of inorganic polymer
Although the supports for the media of this invention can be selected from a
wide range of materials commonly used in lithographic printing plates with a basic requirement that the media with this support be capable of transport through the ink jet printing hardware where the media is required to be transported, the preferred supports are paper, plastic polymer film, or aluminum. Aluminum is a particularly advantageous support because the anodizing treatments typically done on aluminum supports for use in lithographic printing has a surface which is suitably hydrophilic and does not require the addition of a coating layer containing a hydrophilic material in order to be useful in the present invention.
After the ink jet fluid marking material ofthe present invention is printed on the media of this invention, the reactive component needs to be reacted by exposure to an external non-photolytic energy source or other suitable non-photolytic means. For the non-radiation curable reactive components ofthe present invention, the preferred external energy source is heat. For the radiation curable reactive components when added to the non-photolytic curing reactive components ofthe present invention, the preferred external energy source is the radiation, such as ultraviolet radiation, to which the material is most efficiently sensitive. For some non-radiation curable reactive components such as some isocyanates, ambient conditions are other suitable non- photolytic means to provide an effective reaction.
In a preferred embodiment, a catalyst is added to the inkjet fluid marking material to increase the rate of reaction ofthe reactive component after printing and upon exposure to the external non-photolytic energy source or other suitable non- photolytic means to cause reaction. In a most preferred embodiment, the catalyst that is added is a metal complex, such as stannous stearate.
In another preferred embodiment, the receiving surface ofthe media also comprises a catalyst to increase the rate of reaction ofthe reactive component after printing and upon exposure to the external non-photolytic_energy source or other suitable non-photolytic means to cause reaction. In a most preferred embodiment, the catalyst that is added to the receiving surface is an alkaline material. Some of the reactive components react under alkaline conditions, but are stable in acidic conditions. Thus, these reactive components must be in the ink jet fluid ofthe present invention in an acidic environment, but require the presence of an alkaline material in the receiving surface to cause the desired reactivity.
In another embodiment ofthe present invention, the reactive component in the inkjet fluid marking material reacts with the hydrophilic material in the receiving surface ofthe media In a preferred embodiment, the reactive component that reacts with the hydrophilic material in the receiving surface is an isocyanate, blocked isocyanate, diketene, diketene emulsion, polyamide epoxide, acid anhydnde, acid chloride, or chromium complex of an organic acid In a most preferred embodiment, the reactive component that reacts with the hydrophilic material in the receiving surface is a blocked isocyanate, a diketene emulsion, or a chromium complex of an organic acid The novel method of preparing an imaged lithographic printing plate ofthe present invention compπses providing a lithographic plate blank having a support that has a receiving surface containing at least one hydrophilic mateπal An image is formed on this receiving surface using an ink jet printer which prints an inkjet fluid marking material which compπses a liquid earner medium and at least one transition metal complex reactive component or organic reactive component After inkjet printing, the lithographic plate blank with the imaged pattern compπsing the reactive component is exposed to an external non-photolytic energy source or other suitable non-photolytic means to cause the reaction ofthe reactive component This forms an effective amount of an oleophilic and water-insoluble pattern on the lithographic plate blank, thereby prepanng it for high quality lithographic pπnting
In a preferred embodiment ofthe method ofthe present invention, the reactive component is an isocyanate, blocked isocyanate, diketene, diketene emulsion, polyamide epoxide, acid anhydnde, acid chloπde, or chromium complex of an organic acid In a most prefened embodiment ofthe method ofthe present invention, the reactive component is a blocked isocyanate, a diketene emulsion, or a chromium complex of an organic acid
The invention will now be more fully explained by the following examples However, the scope ofthe invention is not intended to be limited to these examples
Example 1
An EPSON (trade name of Epson Corporation) black ink jet cartridge, catalog #5020047, was opened After removing the internal sponge, the cartridge was πnsed
thoroughly with dimethyl sulfoxide An inkjet fluid consisting of 1 part of a blocked isocyanate, sold under the trade name of DESMODUR BL3175A by Bayer Coφoration, and 4 parts of dimethyl sulfoxide was prepared and used to fill the cartπdge The cartridge was then taped shut and placed in the cartridge holder of an EPSON ink jet printer, a piezoelectric type desktop ink jet pπnter sold under the trade name of STYLUS COLOR IIS
Images were jetted on to pπnting plates sold under the trade name of the GENIE brand The images were heated for 5 minutes with a hot air gun set at 900°F and held at 18 inches from the imaged plate The ink receptivity in the imaged areas only was found to be excellent by soaking the sheet under tap water for 30 seconds and then rubbing a standard black rubber-based offset ink on the imaged surface side followed by a water wash
Example 2 A HEWLETT PACKARD (trade name of Hewlett Packard Coφoration) black inkjet cartπdge, catalog # 51625 A, was emptied by piercing the top plug and withdrawing the liquid ink with a pipette The cartridge was then rinsed twice with a solution consisting of 3 parts of isopropyl alcohol and 2 parts of dimethylsulfoxide An ink jet fluid consisting of 4 parts of a chromium complex of an organic acid, sold as a 25% to 30% solution m isopropyl alcohol under the trade name of QUILON C by Dupont Coφoration, and 1 part of isopropyl alcohol was prepared and used to fill the cartπdge with the aid of a pipette The cartπdge was then placed m the cartπdge holder of a HEWLETT PACKARD ink jet printer, a thermal type desktop ink jet pnnter sold under the trade name of HP540C, and imaged, treated with heat, and tested as descπbed m Example 1 The ink receptivity in the imaged areas only was found to be excellent and similar to the results in Example 1
Example 3 The cartπdge containing QUILON C from Example 2 was placed in the cartridge holder of an ENCAD (trade name of Encad Coφoration) ink jet pπnter, a thermal type 36 inch wide inkjet pπnter sold under the trade name of NOVAJET III Imaging, heat treatment, and testing as descπbed in Example 1 gave results similar to the
results in Example 1.
Example 4 The procedure of Example 2 was followed except that a diketene emulsion, sold as a 10% solids emulsion by Hercules Coφoration under the trade name of
HERCON 79, was substituted for the ink jet fluid containing the QUILON C. The ink receptivity was found to be in the imaged areas only and similar to the results in Example 2.
Example 5
The procedure of Example 1 was followed except that the imaging was done on a coated white opaque polyester film, sold by Epson Corporation under the trade name of EPSON GLOSSY PAPER. Analysis ofthe hydrophilic coating on the polyester film showed it to contain both aluminum boehmite inorganic polymer and a polyvinyl alcohol. The ink receptivity in the imaged areas only was found to be excellent and similar to the results in Example 1.
Example 6 The imaged and heat treated plates from Examples 1 and 2 were printed on a conventional lithographic wet offset press using an oil-based black ink from Van Son Corporation and a fountain solution diluted by a ratio of 1 : 10 from a concentrate sold by Itek Coφoration under the trade name of MEGAPLATE FOUNTAIN CONCENTRATE. Satisfactory image quality was achieved on the printed paper sheets throughout a continuous run of 3,000 impressions
Example 7 Preparation of Aluminum plate. A 5 mil thick Anitec DUPLEX 50 (DUPLEX is a trade name of Anitec Coφoration) negative subtractive lithographic plate was, in a darkroom, washed with GRAPHIC MASTERS GMM series subtractive plate developer to remove the photosensitive coating and then rinsed with tap water to provide a clean anodized aluminum surface.
Ink jet cartridge preparation. A solution consisting of 1 part QUILON C, 2 parts methyl alcohol, and 3 parts water was prepared and injected into a drained and rinsed EPSON S020062 black ink cartridge . The cartridge was inserted into an EPSON STYLUS 1500 ink jet printer which underwent a preprogrammed priming cycle. Imaging. The aluminum plate made as described above was manually fed via the rear of the EPSON printer. It was imaged, treated with heat, and tested as described in Example 1. Ink receptivity was found to be excellent in the imaged areas only and similar to the results in Examples 1 and 2.
While the invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that various changes and modifications can be made without departing from the spirit and scope thereof.