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Planographic printing plate precursorRelated Patent Categories: Radiation Imagery Chemistry: Process, Composition, Or Product Thereof, Imaging Affecting Physical Property Of Radiation Sensitive Material, Or Producing Nonplanar Or Printing Surface - Process, Composition, Or Product, Radiation Sensitive Composition Or Product Or Process Of MakingPlanographic printing plate precursor description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20070122743, Planographic printing plate precursor. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS-REFERENCE TO RELATED APPLICATION [0001] This application is a continuation of U.S. application Ser. No. 10/701,686 filed Nov. 6, 2003, which claims priority under 35 USC 119 from Japanese Patent application Nos. 2002-325280, 2002-325282, 2002-333942, and 2003-25929, the disclosures of which are incorporated herein by reference. BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention relates to a planographic printing plate precursor that can be used as an offset printing master, and more particularly, it relates to a so-called positive-type planographic printing plater precursor for direct plate-making capable of forming a printing plate directly from digital data of a computer or the like. [0004] 2. Description of the Related Art [0005] Advances in laser technology have been remarkable in recent years, and in particular, solid lasers and semiconductor lasers that have near infrared to infrared emitting regions, and that have high power and are compact are readily available. These laser devices are significantly useful as exposure light sources for direct plate-making from digital data of a computer or the like in the field of planographic printing. [0006] A positive-type planographic printing plate precursor used with an infrared laser contains, as essential components, an alkali-soluble binder resin and an IR dye or the like which generates heat through light absorption. The IR dye or the like functions as a development inhibitor, which substantially decrease solubility of the binder resin in a developer through interaction with the binder resin, in an unexposed portion (i.e., an image area), and on the other hand, the interaction between the IR dye or the like and the binder resin is diminished in an exposed portion (i.e., a non-image area) to make the IR dye or the like dissolve in the alkali developer, whereby a planographic printing plate is formed. [0007] Since the image forming ability of the positive-type planographic printing plate precursor used with the infrared laser depends on heat generation caused by irradiation with the infrared laser on a surface of a recording layer, the amount of heat used for forming images, i.e., solubilization of the recording layer, is lowered due to heat diffusion to the support in the vicinity thereof, to thereby lower the sensitivity. Therefore, a problem arises in that an effect for losing development inhibiting function of the recording layer is not sufficiently obtained in the non-image area, and consequently, the difference between the image area and the non-image area decreases to cause insufficient reproducibility in highlight portion. [0008] In order to solve the problem associated with reproducibility in highlight portion, it has been proposed to use a recording layer comprising a material that allows the non-image area to be readily developed, i.e., that exhibits good solubility in an aqueous alkali solution. However, such a recording layer becomes low in chemical ability even in the image area to thereby pose a problem of deteriorated chemical resistance, such as becoming susceptible to damage by the action of the developer as well as an ink cleaner and a plate cleaner used upon printing. Accordingly, there has been a strong demand for a resin material that is excellent in chemical resistance and durability of a film prepared therefrom in the non-exposed area, and excellent in developing ability after having undergone light exposure and thereby losing solubility inhibiting function. [0009] It is difficult to solve the aforementioned problems when a mono-layer type recording layer is adopted by selecting the alkali-soluble resin and other components. Thus, a planographic printing plate precursor is disclosed that has a recording layer having a lower layer which is excellent in alkali-solubility due to inclusion of a polyvinylphenol resin and a upper layer which contains a water-insoluble and alkali-soluble resin and an infrared absorber, and which exhibits enhanced solubility in an aqueous alkali solution through light exposure (see, for example, Japanese Patent Application Laid-Open (JP-A) No. 10-250255). However, this planographic printing plate precursor is still insufficient in chemical resistance, although sensitivity thereof is improved. Furthermore, there remains a problem in that adhesiveness between the support and the recording layer is insufficient, and hence printing durability is poor. [0010] A variety of improved techniques have been proposed in order to attain similar objects, including that of making an image forming material by laminating a lower layer which contains a copolymer having a particular monomer and a photosensitive upper layer on a support (see, for example, JP-A No. 11-218914), and that of a process for producing a printing plate using a planographic printing plate precursor formed by laminating a lower layer which contains an alkali-soluble resin and an infrared sensitive and alkali developable upper layer on a hydrophilic support (see, for example, JP-A No. 11-194483). However, the former has a problem in that the resin used in the lower layer, although having good sensitivity and excellent chemical resistance, is insufficient in film strength to leave room for improvement in printing durability, while the latter has a problem in that, due to low chemical resistance of the alkali-soluble resin used, the recording layer is eluted with a solvent component included in a plate cleaner, and the solvent component penetrates into the interface between the lower layer and the support to thereby impair adhesiveness between the recording layer and the substrate, facilitating peelability of the recording layer. Thus, it has been difficult to satisfy both printing durability, which depends on the film strength of the lower layer, and chemical resistance. SUMMARY OF THE INVENTION [0011] The present invention has been made in view of the aforementioned problems associated with the conventional art, and an object thereof is to provide a positive-type planographic printing plate precursor that can directly form a printing plate by scanning exposure based on digital data and is excellent both in printing durability and chemical resistance. [0012] The inventor conducted extensive research and found that the above object may be achieved by providing, as a recording layer of a planographic printing plate precursor, a lower layer containing a polyurethane resin. The inventor also found that the above object may be achieved by selecting, as a component of the recording layer of the planographic printing plate precursor, a polyimide precursor resin having a particular structure, a water-insoluble and alkali-soluble resin having a urea bond in the polymer main chain, or a water-insoluble and alkali-soluble resin having an amide bond in the polymer main chain, and thereby accomplished the present invention. [0013] A first aspect of the invention is a planographic printing plate precursor which comprises a support having disposed thereon a recording layer that includes a lower layer containing a water-insoluble and alkali-soluble polyurethane resin, and an upper layer containing a water-insoluble and alkali-soluble resin and a development inhibitor and exhibiting enhanced solubility in an aqueous alkali solution through light exposure, wherein at least one of the lower layer and the upper layer of the recording layer contains an infrared absorber. [0014] A second aspect of the invention is a planographic printing plate precursor which comprises a support having disposed thereon a recording layer that contains a polyimide precursor resin containing a structural unit represented by the following formula (1) and exerting water-insolubility and alkali-solubility, a development inhibitor and an infrared absorber, and exhibits enhanced solubility in an aqueous alkali solution through light exposure: [0015] wherein R.sup.1 represents a linking group containing at least one aromatic ring to which a --COOH group directly bonds; and R.sup.2 represents an alkylene group, an arylene group or an aralkylene group. [0016] A third aspect of the invention is a planographic printing plate precursor which comprises a support having disposed thereon a recording layer that includes a lower layer containing a polyimide precursor resin having a structural unit represented by formula (1) and exerting water-insolubility and alkali-solubility, and an upper layer containing a water-insoluble and alkali-soluble resin and a development inhibitor and exhibiting enhanced solubility in an aqueous alkali solution through light exposure, wherein at least one of the lower layer and the upper layer of the recording layer contains an infrared absorber. [0017] A fourth aspect of the invention is a planographic printing plate precursor which comprises a support having disposed thereon a recording layer that contains a water-insoluble and alkali-soluble resin having a urea bond in a polymer main chain, a development inhibitor and an infrared absorber, and exhibits enhanced solubility in an aqueous alkali solution through light exposure. [0018] A fifth aspect of the invention is a planographic printing plate precursor which comprises a support having disposed thereon a recording layer that includes a lower layer containing a water-insoluble and alkali-soluble resin having a urea bond in a polymer main chain, and an upper layer containing a water-insoluble and alkali-soluble resin and a development inhibitor and exhibiting enhanced solubility in an aqueous alkali solution through light exposure, wherein at least one of the lower layer and the upper layer of the recording layer contains an infrared absorber. [0019] A sixth aspect of the invention is a planographic printing plate precursor which comprises a support having disposed thereon a recording layer that contains a water-insoluble and alkali-soluble resin having an amine bond in a polymer main chain, a development inhibitor and an infrared absorber, and exhibits enhanced solubility in an aqueous alkali solution through light exposure. [0020] A seventh aspect of the invention is a planographic printing plate precursor which comprises a support having disposed thereon a recording layer that includes a lower layer containing a water-insoluble and alkali-soluble resin having an amide bond in a polymer main chain, and an upper layer containing a water-insoluble and alkali-soluble resin and a development inhibitor and exhibiting enhanced solubility in an aqueous alkali solution through light exposure, wherein at least one of the lower layer and the upper layer of the recording layer contains an infrared absorber. [0021] While the exact mechanism by which the invention functions is not completely understood, it is presumed to be as follows. Continue reading about Planographic printing plate precursor... Full patent description for Planographic printing plate precursor Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Planographic printing plate precursor patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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