Photosensitive planographic printing plate precursor

A photosensitive planographic printing plate precursor comprising an aluminum substrate surface treated such that the center line surface roughness thereof (Ra) is in a range of from 0.30 .mu.m or more to 0.55 .mu.m or less and a photosensitive layer provided on the substrate and comprised of a photosensitive composition containing (a) a water-soluble or water-dispersible polymer, (b) a monomer or oligomer having at least one ethylenically unsaturated double bond capable of photopolymerization, and (c) a photopolymerization initiation system having .lambda..sub.max in a range of from 330 nm or more to 375 nm or less such that the light absorbance A at .lambda..sub.max and the absorbance B at 400 nm fulfill a relationship of B/A<0.1. A preferred example of (a) the water-soluble polymer is a polymer containing a sulfonic acid (salt) group.

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 The present invention relates to a photosensitive planographic printing
 plate precursor that can be loaded immediately after exposure into a
 printing machine so that printing is started without any special
 processing such as development.
 2. Description of the Related Art
 According to prior art, in order to obtain prints by using a photosensitive
 planographic printing plate precursor (hereinafter referred to as a
 printing plate precursor on occasion), it is necessary to carry out a
 procedure that comprises exposing the printing plate precursor image-wise
 and developing the exposed plate with an appropriate developer so that a
 planographic printing plate precursor having a lipophilic image portion
 and a hydrophilic non-image portion is produced. After that, agum coating
 is applied in order to protect the planographic printing plate precursor.
 Following such wet processing, the planographic printing plate precursor
 is loaded into a printing machine and printing is started.
 For developing processing as a processing step after exposure, a developer,
 which is an alkaline liquid or an alkaline liquid containing an organic
 solvent, is generally used. In this regard, because of environmental
 problems due to waste liquids of the developer or maintenance problems of
 automated developing machines, there is a demand for a system that
 requires no developing step.
 In order to solve these problems, Japanese Patent Application National
 Publication (Laid-Open) No. 6-502,931 proposes a photosensitive
 planographic printing plate precursor having a double-layered
 photosensitive layer comprising a photosensitive hydrophilic layer and a
 photosensitive hydrophobic layer provided thereon. This photosensitive
 planographic printing plate precursor can be loaded immediately after
 exposure into a printing machine so that printing is started without any
 processing after exposure. This photosensitive planographic printing plate
 precursor, however, has a durability problem in printing because the
 adhesion between the upper layer and the lower layer is insufficient.
 WO 96/34316 discloses a photosensitive planographic printing plate
 precursor having a single-layered photosensitive layer composed of a
 polymer comprising a photo-hardenable group and an acid group or an acid
 salt group and a photopolymerization initiator. This photosensitive
 planographic printing plate precursor can also be loaded immediately after
 exposure into a printing machine so that printing is started without any
 processing after exposure. This photosensitive planographic printing plate
 precursor, however, has insufficient durability in printing. Therefore,
 the durability in printing becomes very poor if the pH value of dampening
 water in printing is shifted so as to become alkaline.
 Further, Japanese Patent Application Laid-Open (JP-A) No. 47-8,657
 discloses that a photosensitive planographic printing plate precursor that
 can be loaded immediately after exposure into a printing machine so that
 printing is started without any processing after exposure can be obtained
 by a photosensitive composition comprising polyvinylpyrrolidone, a
 polymeric polycarboxylic acid, an olefinically unsaturated monomer, a
 photopolymerization initiator, and the like. However, the use of the
 photopolymerization initiator disclosed therein presented problems in
 terms of sensitivity and fogging after exposure.
 SUMMARY OF THE INVENTION
 Accordingly, an object of the present invention is to provide a
 photosensitive planographic printing plate precursor which can be loaded
 immediately into a printing machine so that printing is started without
 any post-processing after exposure, which exhibits good durability in
 printing even in low-exposure areas, and which is less liable to fog in
 the period between exposure and printing.
 After intense studies, the present inventors have achieved the present
 invention based on a discovery that a combination of a specific
 photosensitive layer and a specific substrate provides a photosensitive
 planographic printing plate precursor which can be loaded immediately into
 a printing machine so that printing is started without any processing
 after exposure and which always exhibits good durability in printing.
 That is, the photosensitive planographic printing plate precursor of the
 present invention comprises an aluminum substrate surface-treated such
 that the center line surface roughness thereof (Ra) is in a range of from
 0.30 .mu.m or more to 0.55 .mu.m or less and a photosensitive layer
 provided on the substrate and comprised of a photosensitive composition
 containing (a) a water-soluble or water-dispersible polymer, (b) a monomer
 or oligomer having at least one ethylenically unsaturated double bond
 capable of photopolymerization, and (c) a photopolymerization initiation
 system having .lambda..sub.max in a range of from 330 nm or more to 375 nm
 or less such that the light absorbance A at .lambda..sub.max and the
 absorbance B at 400 nm fulfill a relationship of B/A&lt;0.1.
 The above-mentioned (c) photopolymerization initiation system maybe a
 system containing a photopolymerization initiator having .lambda..sub.max
 in a range of from 330 nm or more to 375 nm or less such that the light
 absorbance A at .lambda..sub.max and the absorbance B at 400 nm fulfill
 the relationship of B/A&lt;0.1, or may be a system containing a
 photopolymerization initiator and a sensitizer wherein the system as a
 whole has .lambda..sub.max in a range of from 330 nm or more to 375 nm or
 less such that the light absorbance A at .lambda..sub.max and the
 absorbance B at 400 nm fulfill the relationship of B/A&lt;0.1.
 Generally, although the use of a photopolymerization initiation system like
 the above-mentioned system whose .lambda..sub.max is towards shorter
 wavelengths produces little fogging in the period between exposure and
 printing, a problem with such a system is that the sensitivity is so
 reduced that the durability in printing in low-exposure areas is impaired.
 However, the present inventors found that the use of an aluminum substrate
 surface-treated such that the center line surface roughness thereof (Ra)
 is 0.55 .mu.m or less increases the durability in printing in low-exposure
 areas and therefore two requirements, i.e., prevention of fogging and
 durability in printing in low-exposure areas, can be fulfilled at the same
 time. In a planographic printing plate precursor comprising a substrate
 and an ordinary photosensitive layer provided thereon, a substrate having
 a coarser surface is known to provide better durability in printing due to
 better adhesion between the photosensitive layer and the substrate. In
 contrast, a photosensitive layer according to the present invention
 provides better durability in printing if the photosensitive layer is used
 in a combination with a substrate having a smooth surface. Although not
 fully elucidated, the mechanism is presumably as follows. In a
 photosensitive layer which comprises a water-soluble or water-dispersible
 polymer and a photopolymerization initiation system having
 .lambda..sub.max towards shorter wavelengths, has excellent
 hydrophilicity, and requires no developing processing, the image areas
 become thinner and finally the hydrophilic substrate is exposed after a
 large number of prints are produced. In this case, if the surface of the
 substrate is smooth, the substrate is unlikely to be exposed and therefore
 an image omission due to exposure of the hydrophilic substrate hardly
 occurs even after a required large number of prints are produced, thus
 providing excellent durability in printing.
 DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
 Details of the present invention are given below.
 In the present invention, (a) a water-soluble or water-dispersible polymer
 (hereinafter referred to as water-soluble/water-dispersible polymer on
 occasion) is not particularly limited. Examples of the polymer include
 water-soluble polymers such as polyethylene glycol, polyvinyl alcohol,
 polyvinylpyrrolidone, polyacrylic acid, water-soluble nylon, water-soluble
 urethane, a polymer containing sulfonic acid or a sulfonic acid salt, a
 water-soluble cellulosic derivative, gum arabic, gelatin, and derivatives
 thereof.
 From the standpoint of durability in printing, these
 water-soluble/water-dispersible polymers preferably have in the structures
 thereof a functional group contributing to photopolymerization. Examples
 of such polymers include a water-soluble/water-dispersible polymer
 produced by a polymer reaction between polyvinyl alcohol and glycidyl
 methacrylate so that the polymer obtained has a functional group capable
 of photopolymerization, a water-soluble/water-dispersible polymer produced
 by copolymerization between vinylpyrrolidone and allyl methacrylate so
 that the polymer obtained has a water-soluble skeleton and a
 photo-crosslinkable skeleton, and an ammonium salt of a polymer obtained
 by copolymerization between methacrylic acid and allyl methacrylate.
 Examples of the functional group (hereinafter referred to as a
 photopolymerizable functional group on occasion), which can be introduced
 into the structures of these water-soluble/water-dispersible polymers and
 which can contribute to photopolymerization, include a methacrylate group,
 an acrylate group, an allyl group, and the like. These functional groups
 may be introduced by a polymer reaction or by a copolymerization of
 monomers having these functional groups carried out so that these
 functional groups are introduced into the polymer skeleton of the
 water-soluble/water-dispersible polymers. The amount of these
 photopolymerizable functional groups contained in the polymers is
 preferably of 0.7 to 4.0 m eq./g. If the content is less than 0.7 m eq./g,
 durability in printing cannot be improved and the effect of the addition
 is not observed, whereas a content of more than 4.0 m eq./g impairs
 develop ability in a printing machine. A particularly preferred contained
 amount is of from 1.2 to 3.0 m eq./g.
 In order to impart water-solubility or water-dispersibility to a polymer,
 it is necessary to introduce an ionic hydrophilic group or a nonionic
 hydrophilic group into the polymer. Among these groups, a nonionic
 hydrophilic group is preferable from the standpoint of the elimination of
 dependence on pH of dampening water in printing.
 Among the above-mentioned polymers, particularly preferable are
 polyvinylpyrrolidone, a derivative thereof and the polymers containing
 sulfonic acid or a sulfonic acid salt, which are described below in
 detail. The use of such polymers reduces the dependence on pH of dampening
 water and diminishes the loss of paper at the start of printing.
 Examples of the salt in the polymer containing sulfonic acidora sulfonic
 acid salt (hereinafter referred to as a polymer containing a sulfonic acid
 (salt) group on occasion) include an alkali metal salt, an amine salt, a
 quaternary ammonium salt, and the like. Moreover, it is preferable that
 these polymers also have a photopolymerizable functional group such as a
 methacrylate group, an acrylate group, an allyl group, and the like. A
 preferred amount of the sulfonic acid (salt) group contained in the
 polymers is of 0.50 to 4.0 m eq./g. If the contained amount is less than
 0.50 m eq./g, smudging of prints is liable to occur, whereas a contained
 amount of more than 4.0 m eq./g impairs durability in printing. A
 particularly preferred contained amount is of from 0.07 to 2.50 m eq./g. A
 preferred amount of the photopolymerizable functional group contained in
 the polymers is 0 to 6.00 m eq./g. If the contained amount is more than
 6.00 m eq./g, smudging in prints is liable to occur. A particularly
 preferred contained amount is from 0.5 to 3.4 m eq./g. The weight average
 molecular weight of the polymer containing a sulfonic acid (salt) group is
 preferably in a range of from 2,000 to 1,000,000 and is more preferably in
 the range of from 10,000 to 200,000.
 More specifically, a preferred example of the polymer is a polymer having a
 skeleton containing an acrylic based polymerizable group represented by
 the following general formula (1) or (2) and a skeleton containing a
 sulfonic acid (salt) group represented by the following general formula
 (3) or (4).
 ##STR1##
 In the general formula (1), R represents a hydrogen atom or a methyl group;
 R.sub.1, R.sub.2, R.sub.3, R.sub.4, and R.sub.5 each represent a group
 selected from the group consisting of a hydrogen atom, a halogen atom, a
 carboxyl group, a sulfo group, a nitro group, a cyano group, an amido
 group, an amino group, an alkyl group, an aryl group, an alkoxy group, an
 aryloxy group, an alkylamino group, an arylamino group, an alkylsulfonyl
 group, and an arylsulfonyl group; and Z represents oxygen, sulfur, --NH--,
 or --NR'-- (where R' represents an alkyl group). In the general formula
 (2), R.sub.1 and R.sub.2 are the same as R in the general formula (1); Z
 is the same as Z in the general formula (1); and Y.sub.1 and Y.sub.2 each
 represent an alkylene group or an arylene group.
 ##STR2##
 In the general formulae (3) and (4), A represents a hydrogen atom, sodium,
 or NX.sub.4 where each X represents independently a hydrogen atom or an
 alkyl group; and Y.sub.1 and Z are the same as those in the general
 formulae (1) and (2).
 The polymers containing a sulfonic acid (salt) group may contain by
 copolymerization, in addition to the above-mentioned components from
 polymerization, other monomers, such as an alkyl (meth)acrylate, benzyl
 (meth)acrylate, 2-hydroxyethyl (meth)acrylate, acrylonitrile, or the like,
 as a third component.
 The amount added of the polymer in the whole photosensitive composition is
 preferably 20 to 80% by weight and more preferably 30 to 70% by weight. If
 the amount added is less than 20% by weight, smudging in printing occurs,
 whereas durability in printing is liable to become inferior if the amount
 added is more than 80% by weight. Neither is preferable. The
 water-soluble/water-dispersible polymers may be used singly or in a
 combination of two or more.
 In order to improve the durability in printing, an additional polymer,
 i.e., a water-insoluble polymer or a polymer, which by itself cannot be
 dispersed in water, maybe used together with the
 water-soluble/water-dispersible polymer. From the standpoint of further
 enhancing the film strength, it is preferable that the additional polymer
 has a polar group. Preferred examples of the polar group having such a
 property and to be introduced into the polymer include a carboxyl group, a
 phenolic OH group, a sulfonic acid group, a sulfonamide group, a
 phosphoric acid group, and salts of these functional groups. Other
 preferred examples include a hydroxyl group, a cyano group, an amido
 group, an ester group, an ether group, and others. In some cases, these
 may be polymers having a polymerizable group introduced therein.
 Examples of particularly preferred polymers are copolymers comprised
 essentially of acrylic acid, methacrylic acid, crotonic acid, or maleic
 acid. Examples of these polymers include: a multi-component copolymer
 described in Japanese Patent Application Publication (JP-B) No. 52-7,364
 and composed of 2-hydroxyethyl acrylate or 2-hydroxyethyl methacrylate,
 acrylonitrile or methacrylonitrile, acrylic acid or methacrylic acid, and
 optionally other copolymerizable monomers; a multi-component copolymer
 described in JP-A No. 53-120,903 and composed of acrylic acid or
 methacrylic acid esterified with a hydroxy-terminated group containing a
 dicarboxylate residue, acrylic acid or methacrylic acid, and optionally
 other copolymerizable monomers; a multi-component copolymer described in
 JP-B No. 57-43,890 and composed of a monomer terminated with an aromatic
 hydroxy group (e.g., N-(4-hydroxyphenyl)methacrylamide), acrylic acid or
 methacrylic acid, and optionally other copolymerizable monomers; a
 multi-component copolymer described in JP-A No. 56-4,144 and composed of
 an alkyl acrylate, acrylonitrile or methacrylonitrile, and an unsaturated
 carboxylic acid; and modified polyvinyl acetal resins described in JP-A
 Nos. 61-267,042, 61-128,123, and 62-58,242.
 Also useful are polyurethane resins having a substituent group bearing an
 acidic hydrogen atom and described in JP-A Nos. 62-123,452, 62-123,453,
 63-113,450, 63-261,350, 63-287,946, 63-287,947, 1-134,354, 2-146,042,
 2-77,748, and others. When these resins are used in combination with the
 compounds of the present invention, a remarkable improvement in storage
 stability is observed. Therefore, these resins are most desirable as
 polymeric binder resins to be combined with the compounds of the present
 invention.
 The substituent group bearing an acidic hydrogen atom means a group whose
 dissociation constant (pKa) in water is 7 or below. Examples of the group
 include --COOH, --SO.sub.2 NHCOO--, --CONHSO.sub.2 --, --CONHSO.sub.2
 NH--, --NHCONHSO.sub.2 --, and the like. Among these groups, --COOH is
 particularly preferable.
 Further, acidic polyvinyl alcohol derivatives and acidic cellulose
 derivatives are also useful. Also useful is a polyvinyl acetal that is
 rendered alkali-soluble, described in U.K. Patent No. 1,370,316.
 If desired, a photopolymerizable group may be introduced into a main or
 side chain of these polymers. The photopolymerizable groups that can be
 introduced are as described above and examples of the groups include a
 methacrylate group, an acrylate group, and an allyl group.
 The amount added of these water-insoluble polymers needs to be 60% by
 weight or less in the whole photosensitive composition. If the amount
 added is more than 60% by weight, smudging in printing occurs. More
 preferably, the amount added is 50% by weight or less. These polymers may
 be used singly or in a combination of two or more. In the case where poly
 pyrrolidone or a derivative thereof is used as a water-soluble polymer,
 the use of the polymer having a polar group in combination therewith is
 particularly preferable, because durability in printing is enhanced due to
 a synergistic effect of the combination.
 The photosensitive composition for use in the planographic printing plate
 precursor of the present invention needs to contain (b) a monomer or
 oligomer having at least one ethylenically unsaturated double bond capable
 of photopolymerization. Here, "oligomer" means a compound having a
 molecular weight of 5,000 or less.
 Some illustrative nonlimiting examples of the monomer or oligomer include:
 monofunctional acrylate or methacrylate such as polyethylene glycol mono
 (meth) acrylate (hereinafter acrylate or methacrylate is described as
 (meth)acrylate), propylene glycol mono (meth) acrylate, phenoxyethyl
 (meth)acrylate, and the like; polyfunctional acrylate or methacrylate such
 as polyethylene glycol di(meth)acrylate, trimethylolethane (meth)acrylate,
 neopentyl glycol di(meth)acrylate, pentaerythritol tri(meth)acrylate,
 pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate,
 hexanediol di(meth)acrylate, trimethylolpropane tri(acryloloxypropyl)
 ether, tri(acryloyloxyethyl) isocyanurate, calcium (meth)acrylate, barium
 (meth)acrylate, compounds which are produced by adding ethylene oxide or
 propylene oxide to a polyhydric alcohol such as glycerin or
 trimethylolethane and esterifying the addition product with (meth)acrylic
 acid; urethane acrylates as described in JP-B No. 48-41,708, JP-B No.
 50-6,034, and JP-A No. 51-37,193; polyester acrylates as described in JP-A
 No. 48-64,183, JP-B No. 49-43,191, and JP-B No. 52-30,490; and an epoxy
 acrylate produced by reacting an epoxy resin with (meth)acrylic acid; and
 N-methylolacrylamide described in U.S. Pat. No. 4,540,649. Also usable are
 compounds introduced as photo-curable monomers and oligomers in Journal of
 the Adhesives Society of Japan Vol. 20, No.7, pp. 300.about.308.
 The amount added of the polyfunctional monomer in the whole photosensitive
 composition is preferably from 10 to 70% by weight and most preferably
 from 15 to 60% by weight. If the amount added is more than 70% by weight,
 the photosensitive layer becomes undesirably tacky, whereas the
 sensitivity is reduced if the amount added is less than 10% by weight.
 It is essential for the photosensitive composition for use in the
 photosensitive planographic printing plate precursor of the present
 invention to contain (c) a photopolymerization initiation system having
 .lambda..sub.max in a range of from 330 nm or more to 375 nm or less such
 that the light absorbance A at .lambda..sub.max and the absorbance B at
 400 nm fulfill a relationship of B/A&lt;0.1. This photopolymerization
 initiation system may be a system containing a photopolymerization
 initiator having .lambda..sub.max in the range of from 330 nm or more to
 375 nm or less such that the light absorbance A at .lambda..sub.max and
 the absorbance B at 400 nm fulfill the relationship of B/A&lt;0.1, or may be
 a system containing a photopolymerization initiator and a sensitizer
 wherein the system as a whole has .lambda..sub.max in the range of from
 330 nm or more to 375 nm or less such that the light absorbance A at
 .lambda..sub.max and the absorbance B at 400 nm fulfill the relationship
 of B/A&lt;0.1. That is to say, the photopolymerization initiation system as a
 whole in the composition needs to exhibit .lambda..sub.max falling in the
 range of from 330 nm or more to 375 nm or less such that the light
 absorbance A at .lambda..sub.max and the absorbance B at 400 nm fulfill
 the relationship of B/A&lt;0.1. If B/A is greater than 0.1, fogging occurs
 when the planographic printing plate precursor is placed under a white
 light lamp in the period between exposure and printing and thus causes
 smudging in printing. If .lambda..sub.max is on a shorter-wavelength side
 of 330 nm, image formation is impossible because sensitivity is extremely
 reduced.
 In the photopolymerization system, particularly preferred is a system whose
 .lambda..sub.max in light absorption is in a range of from 350 nm or more
 to 370 nm or less.
 The photopolymerization initiation system is not particularly limited so
 long as the system fulfills the above-mentioned conditions. A particularly
 preferred photopolymerization initiation system is a combination of a
 photopolymerization initiator or a sensitizer having a triazine or
 oxadiazole skeleton, and an onium salt. If an onium salt is used as the
 photopolymerization initiator, the aforementioned .lambda..sub.max
 wavelength and B/A are determined by a mixing ratio of the onium salt and
 the sensitizer.
 In the present invention, the absorption measurement can be performed by
 measuring the ultraviolet absorption of a solution containing 10 mg of a
 corresponding compound dissolved in one liter of 1-methoxy-2-propanol,
 using an ultraviolet spectrometer. In the case where the sensitizer is
 added, the sensitizer in an amount corresponding to 10 mg of the
 photopolymerization initiator, the amount being based on the weight ratio
 between the photopolymerization initiator and the sensitizer, is dissolved
 for the measurement.
 A particularly preferred photopolymerization initiator having a triazine or
 oxadiazole skeleton is a compound having the structure represented by any
 one of the following general formulae (I) to (III).
 ##STR3##
 In these formulae, R.sup.1 and R.sup.2 each represent a hydrogen atom, a
 hydroxyl group, or an alkoxy group. If one of R.sup.1 and R.sup.2 is a
 hydrogen atom, the other substituent group needs to be a hydroxyl group or
 an alkoxy group. If the other substituent group is an alkoxy group,
 R.sup.1 and R.sup.2 may be linked to each other.
 R.sup.3 represents a phenyl group, a naphthyl group, or a heterocyclic
 skeleton, which may have a substituent group. Examples of the substituent
 group include an alkoxy group, a hydroxyl group, a styryl group, and an
 alkoxystyryl group. Examples of R.sup.4 include a hydrogen atom, an alkyl
 group, and a phenyl group.
 R.sup.5 represents a phenyl group, which may have a substituent group.
 Examples of the substituent group include a hydroxy group and an alkoxy
 group.
 Some illustrative nonlimiting examples of compounds having a triazine or
 oxadiazole skeleton and suited as photopolymerization initiators are
 listed in Table 1 together with physical properties of the compounds.
 TABLE 1
 Photopolymerization initiator
 .lambda..sub.max B/A
 No. 1 ##STR4## 334 nm
 0
 No. 2 ##STR5## 357 nm
 0.031
 No. 3 ##STR6## 357 nm
 0.077
 No. 4 ##STR7## 333 nm
 0
 No. 5 ##STR8## 338 nm
 0
 No. 6 ##STR9## 346 nm
 0.015
 No. 7 ##STR10## 338 nm
 0
 No. 8 ##STR11## 334 nm
 0
 No. 9 ##STR12## 341 nm
 0
 Specific examples of onium salts as other preferred photopolymerization
 initiators are diaryl iodonium salts and triaryl sulfonium salts. Specific
 examples of sensitizers to be used in combination with these onium salts
 are 9,10-dimethoxy anthraquinone and9,10-diphenyl anthracene. It must be
 noted, however, that the present invention is not limited by these
 examples.
 The photosensitive composition of the present invention may further contain
 a dye. The purpose of using the dye is to obtain a visible image by
 exposure (exposure-visualized image) and a visible image after developing.
 A dye suited for this purpose is one whose color changes by a reaction with
 a free radical or an acid. The term "color changes" includes a change from
 colorless to colored, a change from colored to colorless, and a change
 from one color to a different color.
 Examples of the dye in which a change from colored to colorless or a change
 from one color to a different color takes place include
 triphenylmethane-based dyes, diphenylmethane-based dyes, oxazine-based
 dyes, xanthene-based dyes, iminonaphthoquinone-based dyes,
 azomethine-based dyes, and anthraquinone-based dyes, which are represented
 by Victoria Pure Blue BOH (trade name, manufactured by Hodogaya Chemical
 Co., Ltd.) and a naphthalenesulfonic acid salt thereof, Oil Blue No. 603
 (trade name, manufactured by Orient Chemical Industries Co., Ltd.), Patent
 Pure Blue (trade name, manufactured by Sumitomo Mikuni Chemical Co.,
 Ltd.), Crystal Violet, Brilliant Green, Ethyl Violet, Methyl Violet,
 Methyl Green, Erythrosine B, Basic Fuchsine, Malachite Green, Oil Red,
 m-Cresol Purple, Rhodamine B, auramine,
 4-p-diphenylaminophenyliminonaphthoquinone,
 cyano-p-diethylaminophenylacetanilide, and others.
 On the other hand, examples of the dye in which a change from colorless to
 colored takes place include leuco dyes and primary or secondary
 arylamine-based dyes represented by, for example, triphenylamine,
 diphenylamine, o-chloroaniline, 1,2,3-triphenylguanidine, naphthylamine,
 diaminodiphenylmethane, p,p'-bis-dimethylaminodiphenylamine,
 1,2-dianilinoethylene, p,p',p"-tris-dimethylaminotriphenylmethane,
 p,p'-bis-dimethylaminodiphenylmethylimine,
 p,p',p"-triamino-o-methyltriphenylmethane,
 p,p'-bis-dimethylaminodiphenyl-4-anilinonaphthylmethane, and
 p,p',p"-triaminotriphenylmethane.
 From the standpoint of ease in examining a printing plate, a leuco dye
 which changes from colorless to colored is preferable for use in the
 present invention, a leuco triphenylmethane-based dye is more preferable,
 and Leuco Crystal Violet is particularly preferable.
 Ordinarily, the amount of the dye contained in the photosensitive
 composition is preferably about 0.5 to about 10% by weight, more
 preferably about 1 to 5% by weight, based on the total solids of the whole
 composition.
 Examples of a surfactant that can be used for improving the coatability of
 the photosensitive composition of the present invention include a
 fluorine-containing surfactant and a nonionic surfactant. Particularly
 preferred are fluorine-containing surfactants (e.g., Megafac F-171, 173,
 177 and Defenser MCF 300, 312, 313 [trade names, all manufactured by
 Dainippon Ink and Chemicals Inc.] and Modiper F-100, 102, 110 [trade
 names, all manufactured by Nippon Oil & Fats Co., Ltd.]) as described in
 JP-A Nos. 62-170,950 and 62-226,143 and U.S. Pat. No. 3,787,351.
 Further, it is preferable to incorporate an inhibitor of thermal
 polymerization into the photosensitive composition. Useful as the
 inhibitor are, for example, hydroquinone, p-methoxyphenol,
 di-t-butyl-p-cresol, pyrogallol, t-butylcatechol, benzoquinone,
 4,4'-thiobis(3-methyl-6-t-butylphenol),
 2,2'-methylenebis(4-methyl-6-t-butylphenol), and 2-mercaptobenzoimidazole.
 Examples of a wax include behenic acid, behenic acid amide, and carboxylic
 acids having a long-chain alkyl group such as stearic acid, and esters and
 amides thereof.
 Examples of a plasticizer, which is used to impart flexibility and abrasion
 resistance to the film of the photosensitive layer, include dibutyl
 phthalate, polyethylene glycol, tributyl citrate, diethyl phthalate,
 dibutyl phthalate, dihexyl phthalate, dioctyl phthalate, tricresyl
 phosphate, tributyl phosphate, trioctyl phosphate, tetrahydrofurfuryl
 oleate, and an oligomer or polymer of acrylic acid or methacrylic acid.
 Among these plasticizers, tricresyl phosphate is particularly preferable.
 Preferred examples of an acidic compound having a low molecular weight,
 which is used to prevent smudging, include phosphoric acid, phosphorous
 acid, pyrophosphoric acid, phenylsulfonic acid, oxalic acid, boric acid,
 p-toluenesulfonic acid, benzenesulfonic acid, p-hydroxybenzenesulfonic
 acid, 2-methoxy-4-hydroxy-5-benzoylbenzenesulfonic acid, 3-sulfophthalic
 acid, 4-sulfophthalic acid, 2-sulfoterephthalic acid, 5-sulfoisophthalic
 acid, isopropylnaphthalenesulfonic acid, t-butylnaphthalenesulfonic acid,
 malicacid, tartaric acid, dipicolinic acid, tricarbazolic acid,
 polyacrylic acid and copolymers thereof, polyvinylphosphonic acid and
 copolymers thereof, polyvinylsulfonic acid and copolymers thereof,
 5-nitronaphthalene-1-phosphonic acid, 4-chlorophenoxymethylphosphonic
 acid, sodium phenyl-methyl-pyrazolonephosphonate, citric acid,
 2-phosphonobutane-1,2,4-tricarboxylicacid,
 1-phosphonoethane-1,2,2-tricarboxylic acid, and
 1-hydroxyethane-1,1-disulfonic acid.
 Preferred examples of a development accelerator include a higher alcohol,
 an acid anhydride, and an anionic surfactant.
 In addition, preferably used are, for example, lipophilicity-sensitizers to
 enhance the lipophilic sensitivity of image portions, which are described
 in JP-A No. 55-527, exemplified by a styrene/maleic anhydride copolymer
 half-esterified with alcohol, a novolac resin such as a
 p-t-butylphenol/formaldehyde resin, and a fatty acid-ester of
 p-hydroxystyrene. Although the amounts of these additives vary depending
 on the compositions in which these additives are used and the purpose of
 addition, the amounts are generally 0.01 to 30% by weight based on the
 whole solids of the composition.
 The photosensitive composition stated above is applied to an aluminum
 substrate surface-treated such that the center line surface roughness
 thereof (Ra) is in a range of from 0.30 .mu.m or more to 0.55 .mu.m or
 less, and the coating is then dried, thus forming a photosensitive layer.
 In this way, a photosensitive planographic printing plate precursor of the
 present invention is prepared.
 From the standpoint of increasing the dimensional accuracy in printing, the
 substrate for use in the present invention needs to be an aluminum
 substrate. The aluminum substrate for use in the present invention
 includes an aluminum alloy substrate.
 The aluminum substrate is preferably of IS material. The surface of the
 aluminum substrate is preferably surface treated in order to enhance water
 retention and to increase the adhesion to the photosensitive layer.
 Examples of the surface-roughening method are generally known methods such
 as brushing, ball-abrasion, electrolytic etching, chemical etching,
 liquid-honing, sand-blasting, and combinations thereof. Among these
 methods, brushing, electrolytic etching, chemical etching, and
 liquid-honing are preferable, and a surface-roughening method including
 the use of electrolytic etching is particularly preferable.
 Further, as described in JP-A No. 54-63,902, a method comprising brushing
 followed by electrolytic etching is also preferable.
 As for an electrolytic bath for use in the electrolytic etching, an aqueous
 solution containing acid, alkali, or a salt thereof or alternatively an
 aqueous solution containing an organic solvent is used. Among these
 solutions, particularly preferable is an electrolytic solution containing
 hydrochloric acid, nitric acid, or a salt thereof. The aluminum plate,
 after being surface-roughened, is subjected, if necessary, to a desmutting
 treatment using an aqueous solution of an acid or alkali. The aluminum
 plate thus obtained is desirably subjected to an anodizing treatment which
 is most preferably performed in a bath containing sulfuric acid or
 phosphoric acid.
 If necessary, the aluminum plate is further subjected to an additional
 treatment. Particularly preferred examples of such additional treatment
 include: a treatment with a silicate (sodium silicate, potassium silicate)
 described in U.S. Pat. Nos. 2,714,066 and 3,181,461; a treatment with a
 potassium fluorozirconate described in U.S. Pat. No. 2,946,638; a
 treatment with phosphomolybdate described in U.S. Pat. No. 3,201,247; a
 treatment with an alkyl titanate described in U.K. Patent No. 1,108,559; a
 treatment with a polyacrylic acid described in German Patent No.
 1,091,433; a treatment with a polyvinylphosphonic acid described in German
 Patent No. 1,134,093 and U.K. Patent No. 1,230,447; a treatment with a
 phosphonic acid described in JP-B No. 44-6,409; a treatment with aphytic
 acid described in U.S. Pat. No. 3,307,951; a treatment with a salt
 produced from a hydrophilic organic polymer and divalent metal described
 in JP-A Nos. 58-16,893 and 58-18,291; a hydrophilicity imparting treatment
 by providing a subbing layer of a water-soluble polymer having a sulfonic
 acid group described in JP-A No. 59-101,651; and a coloration treatment
 with an acid dye described in JP-A No. 60-64,352. Examples of other
 hydrophilicity imparting treatments include, for example, a silicate
 electrodeposition described in U.S. Pat. No. 3,658,662.
 In addition, also preferable is a sealing treatment after graining and
 anodizing of an aluminum plate. The sealing treatment is performed by, for
 example, immersing the aluminum plate in hot water or in a hot aqueous
 solution containing a salt of an inorganic or organic acid, or by using a
 steam bath.
 Further details of the substrate for use in the present invention are given
 below. Firstly, an IS aluminum plate, which contains iron at a weight
 percentage of 0.1 to 0.5%, silicon at a weight percentage of 0.03 to 0.3%,
 copper at a weight percentage of 0.003 to 0.3%, and titanium at a weight
 percentage of 0.01 to 0.1%, is etched by immersion in an aqueous alkali
 solution, which is preferably a 1 to 30% aqueous solution of sodium
 hydroxide, potassium hydroxide, sodium carbonate, sodium silicate or the
 like, at 20 to 80.degree. C. for 5 to 250 seconds. The etching bath may
 contain aluminum in an amount corresponding to about 1/5 of the alkali.
 Next, neutralization after alkali etching and removal of smut are performed
 by immersing the aluminum plate in a 10 to 30% aqueous solution of nitric
 acid or sulfuric acid, at 20 to 70.degree. C. for 5 to 250 seconds.
 The surface of the aluminum plate is then cleaned and is subjected to a
 surface-roughening treatment of the following procedure. Apreferred
 surface-roughening treatment is brushing or/and electrolytic etching.
 The temperature of the electrolytic solution is normally 10 to 60.degree.
 C. The a.c. current for use in the electrolysis may be rectangular,
 trapezoidal, or sinusoidal so long as the positive and negative polarities
 are alternately exchanged. The electricity may be a commercially available
 single-phase or three-phase current. The current density for the treatment
 is preferably of 5 to 100 A/dm.sup.2 for the treatment period of 10 to 300
 seconds.
 The center line surface roughness (Ra) of the aluminum alloy substrate
 surface in the present invention is adjusted by the brush diameter for
 brushing or the quantity of electricity in the electrolytic etching so
 that the center line surface roughness (Ra) falls in a range of from 0.30
 .mu.m to 0.55 .mu.m and preferably in a range of from 0.35 .mu.m to 0.50
 .mu.m. If the center line surface roughness (Ra) of the surface is less
 than 0.30 .mu.m, water allowance becomes narrower and the glare of the
 plate surface worsens to an extent that it is difficult to see the plate
 surface when printing is performed, whereas durability in printing becomes
 worse if the center line surface roughness (Ra) of the surface is more
 than 0.55 .mu.m.
 After being grained as stated above, it is preferable to remove the smut
 from the aluminum alloy plate by using a 10 to 50% hot sulfuric acid
 solution (40 to 60.degree. C.) or a dilute aqueous solution of alkali
 (e.g., sodium hydroxide). If a solution of alkali is used, the plate is
 subsequently immersed in a solution of an acid (nitric acid or sulfuric
 acid) to clean and neutralize the surface.
 After the removal of the surface smut, the plate is subjected to an
 anodizing treatment. The anodizing may be performed by a traditionally
 known method. A sulfuric acid solution is the most useful electrolytic
 solution. Next to the sulfuric acid, phosphoric acid is also useful as the
 electrolytic solution. In addition, a mixture of sulfuric acid and
 phosphoric acid, as described in JP-A No. 55-28,400, is also useful.
 Although anodizing by a sulfuric acid process is normally performed by
 using a d.c. current, an a.c. current may also be used. The concentration
 of the sulfuric acid is 5 to 30%, and the electrolysis is performed at 20
 to 60.degree. C. for 5 to 250 seconds to thereby form an oxide film of 1
 to 10 g/m.sup.2 on the surface. Preferably, the electrolytic solution
 contains aluminum ions. The current density is preferably of 1 to 20
 A/dm.sup.2. If a phosphoric acid process is employed, the concentration of
 the phosphoric acid is of 5 to 50%, and the electrolysis is performed at
 30 to 60.degree. C. for 10 to 300 seconds at a current density of 1 to 15
 A/dm.sup.2.
 After being treated as stated above, the aluminum substrate is preferably
 subjected to a surface treatment using a silicate as described in U.S.
 Pat. No. 2,714,066.
 In addition, it is also preferable to apply a subbing layer to the
 substrate as described in JP-A No. 59-101,651.
 The above-described photosensitive composition is provided on the substrate
 according to the following procedure. Firstly, a coating liquid of a
 photosensitive composition is prepared by dissolving prescribed amounts of
 a photosensitive diazo resin, a polymeric binder of the present invention,
 a fluorine-containing surfactant of the present invention, and optionally,
 additives are dissolved in an appropriate solvent (such as methyl
 cellosolve, ethyl cellosolve, dimethoxyethane, diethylene glycol
 monomethyl ether, diethylene glycol dimethyl ether, 1-methoxy-2-propanol,
 methylcellosolve acetate, acetone, methyl ethyl ketone, methanol,
 dimethylformamide, dimethylacetamide, cyclohexanone, dioxane,
 tetrahydrofuran, methyl lactate, ethyl lactate, ethylene dichloride,
 dimethyl sulfoxide, water, or the like). Next, the coating liquid is
 applied to the substrate, and the coating is then dried. Although the
 solvents may be used singly, it is preferable to use a mixture of a
 high-boiling solvent, such as methyl cellosolve, 1-methoxy-2-propanol,
 methyl lactate, or the like, and a low-boiling solvent such as methanol,
 methyl ethyl ketone, or the like.
 The concentration of the solids in the coating liquid of the photosensitive
 composition is preferably in a range of from 1 to 50% by weight. The
 weight of the photosensitive composition coated is about preferably of
 from 0.2 to 10 g/m.sup.2 (dry weight) and more preferably of from 0.5 to 3
 g/m.sup.2.
 It is preferable to form a mat layer, which is comprised of protrusions
 formed independently from one another, on the photosensitive layer.
 The purpose of the mat layer is to improve vacuum adhesion between a
 negative image film and a photosensitive planographic printing plate
 precursor in a contact exposure process, thus shortening the
 vacuum-drawing time, and to prevent minute halftone dots from being
 destroyed by insufficient adhesion at the time of exposure.
 Examples of the methods for forming the mat layer include a method wherein
 a surface is powdered with a powder of a solid material and the powder is
 then thermally fused, as described in JP-A No. 55-12,947; and a method
 wherein a surface is sprayed with water containing a polymer and the
 surface is then dried, as described in JP-A No. 58-182,636. Although any
 of such methods may be employed in the present invention, it is preferable
 that the mat layer itself be soluble in or removable by dampening water or
 ink.
 The photosensitive layer, which is coated and formed on the substrate, is
 given a negative relief image either by exposure through a transparent
 original having, for example, line images or halftone dot images, or by
 image-wise exposure using a laser or the like.
 Examples of light sources suited for the exposure include, for example, a
 carbon arc lamp, a mercury lamp, a xenon lamp, a metal halide lamp, a
 strobe, ultraviolet light, and laser light.
 After being exposed as stated above, the photosensitive planographic
 printing plate precursor of the present invention is immediately loaded
 into a printing machine and printing can be started without the employment
 of post-processing such as developing processing.
 Printing may be performed with any type of printing machine. Examples of
 the printing methods include (1) a method wherein dampening water is
 applied to a printing plate and thereafter ink is applied to the plate to
 start printing; (2) a method wherein ink is applied to a printing plate
 and thereafter dampening water is applied to the plate to start printing;
 (3) a method wherein dampening water and ink are applied at the same time
 to a printing plate to start printing; and (4) a method wherein the
 non-image portion is wiped with water or a cleaner and thereafter printing
 is started by any of (1), (2) and (3) methods. According to the present
 invention, prints free of remnant non-image portions are obtained and
 durability in printing is good.

EXAMPLES
 In order that those skilled in the art will be better able to practice the
 present invention, the following examples are given by way of illustration
 and not by way of limitation.
 Examples 1 to 6
 A 0.24 mm thick rolled plate of aluminum, containing aluminum at a weight
 percentage of 99.5%, copper at a weight percentage of 0.01%, titanium at a
 weight percentage of 0.03%, iron at a weight percentage of 0.3%, and
 silicon at a weight percentage of 0.1%, was grained by using a 20% by
 weight aqueous suspension of 400-mesh pumice stone powder (manufactured by
 Kyoritsu Yogyo Co., Ltd.) and a rotating nylon (6-10 nylon) brush having a
 brush (hair) diameter of 0.30 mm, and the surface was then washed well
 with water.
 The aluminum plate was etched by immersion in a 15% by weight sodium
 hydroxide aqueous solution (containing 5% by weight of aluminum) so that
 the amount of dissolved aluminum was 5 g/m.sup.2, and the aluminum plate
 was then washed with flowing water. After that, the aluminum plate was
 neutralized with a 1% by weight nitric acid aqueous solution, and was
 thereafter subjected to an electrolytic surface-roughening treatment in a
 0.7% by weight nitric acid aqueous solution (containing 0.5% by weight of
 aluminum as ions) by using a rectangular alternating wave voltage (current
 ratio r=0.90, a current wave shape described in examples of JP-B No.
 58-5,796) at a cathode voltage of 9.3 volts, an anode voltage of 10.5
 volts and by a quantity of electricity at anode of 160 coulombs g/m.sup.2.
 After being washed with water, the aluminum plate was etched by immersion
 in a 10% by weight sodium hydroxide aqueous solution at 40.degree. C. so
 that the amount of dissolved aluminum was 1 g/m.sup.2, and the aluminum
 plate was then washed with water. Next, a desmutting treatment of the
 aluminum plate was performed by immersion in a 30% by weight sulfuric acid
 aqueous solution at 50.degree. C., and the aluminum plate was then washed
 with water.
 Next, the aluminum plate was treated to produce a porous anodized film on
 the surface in a 20% by weight sulfuric acid aqueous solution (containing
 0.8% by weight of aluminum as ions) by using a d.c. current. That is, by
 carrying out an electrolysis at a current density of 13 A/dm.sup.2 and by
 adjusting the electrolysis time, a substrate having an anodized film of
 2.0 g/m.sup.2 was prepared. The substrate was then washed with water.
 The surface of the aluminum substrate obtained in the above procedure was
 measured by using a Macbeth RD920 reflection densitometer. The reflection
 density was 0.28 and the center line surface roughness (Ra) of the surface
 was 0.45 .mu.m. The center line surface roughness (Ra) was measured by
 using a SURFCOM contact needle meter manufactured by Tokyo Seimitsu Kikai
 Co., Ltd. (contact needle : 10 .mu.m R).
 A subbing solution 1 of the following composition was applied to the
 aluminum plate thus obtained, and the coating was dried at 80.degree. C.
 for 30 seconds. The weight of the dried coating was 2 mg/m.sup.2.

Subbing solution 1 in grams
 Sodium salt of a methyl methacrylate/ethyl 0.02
 acrylate/sodium 2-acrylamide-2-
 methylpropanesulfonic acid copolymer
 (60/25/15 in molar ratio of the copolymer)
 Methanol 100
 Next, a photosensitive solution 1 (containing a photopolymerization
 initiator according to the type and amount as shown in Table 2) having the
 following composition was applied by using a bar coater. The coating was
 dried at 120.degree. C. for 30 seconds. The weight of the dried coating
 was 1.5 mg/m.sup.2. Photosensitive solution 1 in parts by weight
 Polyvinylpyrrolidone 0.6 Aronix M-305 (polymerizable acrylate monomer
 having many functional groups; trade name, manufactured by Toa Gosei Co.,
 Ltd.) 0.4 Photopolymerization initiator (as shown in Table 2)

Behenic acid 0.004
 Fluorine-containing surfactant F-176 PF 0.01
 (20% methyl isobutyl ketone solution,
 trade name, manufactured by Dainippon Ink
 and Chemicals Inc.)
 Leuco Crystal Violet 0.04
 1-methoxy-2-propanol 25
 The photosensitive layer was subjected to a matting treatment comprising
 electrostatically spraying the photosensitive layer with a spray solution
 of the following composition and then drying the coating in an atmosphere
 of 80.degree. C. for 5 seconds.

Spray solution in grams
 Sodium salt of a methyl methacrylate/ethyl 0.5
 acrylate/sodium 2-acrylamide-2-
 methylpropanesulfonic acid copolymer
 (60/25/15 in molar ratio of the copolymer)
 Tartrazine 0.01
 Water 100
 TABLE 2
 Photopolymerization initiator
 Amount added
 Example 1 ##STR13##
 0.1 parts by weight
 Example 2 ##STR14##
 0.1 parts by weight
 Example 3 ##STR15##
 0.1 parts by weight
 Example 4 ##STR16##
 0.1 parts by weight
 Example 5 ##STR17##
 0.1 parts by weight
 Example 6 ##STR18##
 0.1 parts by weight/ 0.1 parts by weight
 The heights and widths of the constituent mats were of 2 to 6 .mu.m and of
 20 to 150 .mu.m, respectively, and the total numbers of the mats was 100
 units/m.sup.2. The coating weight was 0.1 g/m.sup.2.
 These photosensitive planographic printing plate precursors were exposed
 image-wise at a distance of 1 m from a lamp, using a PS Light manufactured
 by Fuji Film Co., Ltd. for 1 minute. Then, the plates were each loaded
 into an SOR printing machine manufactured by Hidelberg Co., Ltd. In this
 way, printing was started, and examination was conducted by counting the
 number of complete prints obtainable (durability in printing).
 In addition, the plates, after being exposed to the PS Light, were left to
 stand under a white light lamp of 500 Lux for 4 hours, and thereafter were
 each loaded into the SOR printing machine manufactured by Hidelberg Co.,
 Ltd. In this way, printing was started, and examination was conducted to
 assess the degree of freedom from smudging in prints.
 The results are shown in Table 3.
 TABLE 3
 Freedom from smudging
 Number of in prints by using
 sheets that plates after being placed
 could be printed under a white light lamp
 Example 1 50,000 sheets good
 Example 2 80,000 sheets good
 Example 3 70,000 sheets good
 Example 4 40,000 sheets good
 Example 5 40,000 sheets good
 Example 6 40,000 sheets good
 Comparative Example 1 5,000 sheets good
 Comparative Example 2 40,000 sheets poor
 Comparative Example 3 50,000 sheets poor
 Comparative Examples 1 to 3
 Aluminum plates were surface-treated and coated with the subbing solution
 as in Example 1. The substrates thus obtained were each coated with the
 photosensitive solution as in Examples 1 to 6, except that the
 photopolymerization initiator and the amount added thereof in the
 photosensitive solution were changed. The coating weight was 1.5
 mg/M.sup.2. The types of the photopolymerization initiators and the
 amounts added thereof are shown in Table 4. Then, as in Examples 1 to 6,
 mats were provided on each of the photosensitive layers and the
 planographic printing plate precursors thus prepared were tested in the
 same way. The results are shown in Table 3.
 TABLE 4
 Photopolymerization initiator
 Amount added
 Comparative example 1 ##STR19##
 0.1 parts by weight
 Comparative example 2 ##STR20##
 0.1 parts by weight
 Comparative example 3 ##STR21##
 0.1 parts by weight
 Comparative Examples 4 to 12
 Aluminum plates were surface-treated and coated with the subbing layer as
 in Example 1, except that the nylon brush had a brush (hair) diameter of
 0.48 mm and the center line surface roughness (Ra) of the aluminum plates
 after brushing was 0.64 .mu.m. The substrates thus obtained were coated
 with the photosensitive solutions of Examples 1 to 6 and of Comparative
 Examples 1 to 3, respectively. The coating weight was 1.5 mg/m.sup.2.
 The planographic printing plate precursors thus prepared were tested in the
 same way.
 The results are shown in Table 5.
 TABLE 5
 Freedom from smudging
 Number of in prints by using
 sheets that plates after being placed
 could be printed under a white light lamp
 Comparative Example 4 1,000 sheets good
 or less
 Comparative Example 5 5,000 sheets good
 Comparative Example 6 5,000 sheets good
 Comparative Example 7 1,000 sheets good
 Comparative Example 8 1,000 sheets good
 Comparative Example 9 1,000 sheets good
 Comparative Example 10 1,000 sheets good
 Comparative Example 11 10,000 sheets poor
 Comparative Example 12 10,000 sheets poor
 As stated above, the photosensitive planographic printing plate precursors
 of the present invention, comprising a photopolymerization initiation
 system having .lambda..sub.max in a range of from 330 nm to 375 nm such
 that the light absorbance A at .lambda..sub.max and the absorbance B at
 400 nm fulfill a relationship of B/A&lt;0.1 and the aluminum substrate
 surface-treated such that the center line surface roughness thereof (Ra)
 is 0.45 .mu.m, exhibit excellent durability in printing and hardly produce
 smudges in prints. By contrast, all of the photosensitive planographic
 printing plate precursors of Comparative Examples 1 to 3, comprising the
 photosensitive composition outside the scope of the present invention, and
 of the photosensitive planographic printing plate precursors of
 Comparative Examples 4 to 12, comprising the aluminum substrate having a
 larger center line surface roughness (Ra), exhibit inferior performances
 in terms of smudges in prints or durability in printing.
 Examples 7 to 16
 Aluminum plates were surface-treated as in Examples 1 to 6. The substrates
 thus obtained were each coated with the following photosensitive solution
 2 (containing a water-soluble/water-dispersible polymer in an amount as
 shown in Tables 6 to 8). Then, as in Examples 1 to 6, mats were provided
 on each of the photosensitive layers. In this way, planographic printing
 plate precursors were prepared.

Photosensitive solution 2 in parts by weight
 Water-soluble/water-dispersible polymer (as in Tables 6 to 8)
 Pentaerythritol tetraacrylate 0.4
 Photopolymerization initiator represented 0.01
 by the following formula
 Behenic acid 0.004
 Leuco Crystal Violet 0.04
 1-methoxy-2-propanol 25
 Water 2
 ##STR22##
 TABLE 6
 Polymer
 Amount added
 Example 7 Polyvinylpyrrolidone
 0.6 parts by weight
 Example 8 ##STR23##
 0.5 parts by weight 0.1 parts by weight
 Example 9 ##STR24##
 0.5 parts by weight 0.1 parts by weight
 Example 10 ##STR25##
 0.5 parts by weight 0.1 parts by weight
 TABLE 7
 Polymer
 Amount added
 Ex- am- ple 11 ##STR26##
 0.5 parts by weight 0.1 parts by weight
 Ex- am- ple 12 ##STR27##
 0.4 parts by weight 0.2 parts by weight
 Ex- am- ple 13 ##STR28##
 0.6 parts by weight
 TABLE 8
 Polymer Amount
 added
 Example 14 ##STR29## 0.6
 parts by weight
 Example 15 ##STR30## 0.6
 parts by weight
 Example 16 ##STR31## 0.6
 parts by weight
 These photosensitive planographic printing plate precursors were exposed
 image-wise at a distance of 1 m from a lamp by using a PS Light
 manufactured by Fuji Film Co., Ltd. for 1 minute. Then, the plates were
 each loaded into an SOR printing machine manufactured by Hidelberg Co.,
 Ltd. In this way, printing was started, and examination was conducted by
 counting the number of complete prints obtainable (durability in printing)
 using alkaline dampening water.
 In addition, the plates, after being exposed to the PS Light, were left to
 stand under a white light lamp of 500 Lux for 4 hours, and thereafter were
 each loaded into the SOR printing machine SOR manufactured by Hidelberg
 Co., Ltd. In this way, printing was started, and examination was conducted
 to assess the degree of freedom from smudging in prints. The results are
 shown in Table 9.
 TABLE 9
 Freedom from smudging
 Number of in prints by using
 sheets that plates after being placed
 could be printed under a white light lamp
 Example 7 70,000 sheets good
 Example 8 100,000 sheets good
 Example 9 100,000 sheets good
 Example 10 90,000 sheets good
 Example 11 90,000 sheets good
 Example 12 90,000 sheets good
 Example 13 90,000 sheets good
 Example 14 80,000 sheets good
 Example 15 120,000 sheets good
 Example 16 120,000 sheets good
 As is apparent from Table 9, all of the photosensitive planographic
 printing plate precursors of the present invention do not produce smudges
 in prints in printing after being placed under the white light lamp and
 exhibit excellent durability in printing.
 Comparative Examples 13 and 14
 For the purpose of comparison with the present invention, aluminum plates
 were surface-treated as in Examples 1 to 6 and as in Comparative Examples
 4 to 12, respectively. The substrates thus obtained were each coated with
 the following photosensitive solution 3 (at a coating weight of 1.5
 mg/m.sup.2). In this way, planographic printing plate precursors, which
 required developing processing with an alkali solution, were prepared.

Photosensitive solution 3 in parts by weight
 Polymer represented by the following formula 1.0
 Pentaerythritol tetraacrylate 0.3
 Photopolymerization initiator represented 0.1
 by the following formula
 Leuco crystal Violet 0.03
 Behenic acidamide 0.005
 1-methoxy-2-propanol 25
 Water 1
 Polymer
 ##STR32##
 Photopolymerization initiator
 ##STR33##
 These photosensitive planographic printing plate precursors were exposed
 image-wise at a distance of 1 m from a lamp by using a PS Light
 manufactured by Fuji Film Co., Ltd. for 1 minute. After the exposure, the
 plates were developed by using a developer solution prepared by diluting
 developer agent DC-3C (trade name, manufactured by Fuji Film Co., Ltd.)
 with the same amount of water and were thereafter subjected to gum
 treatment. Then, the plates were each loaded into an SOR printing machine
 manufactured by Hidelberg Co., Ltd. In this way, printing was started, and
 examination was conducted by counting the number of complete prints
 obtainable. The results are shown in Table 10.
 TABLE 10
 Brush diameter Center line
 used for surface- surface rough- Number of
 treating aluminum ness of sub- sheets that
 substrate strate (Ra) could be printed
 Comparative 0.30 mm 0.45 .mu.m 100,000 sheets
 Example 13
 Comparative 0.48 mm 0.64 .mu.m 150,000 sheets
 Example 14
 As is apparent from Table 10, known planographic printing plate precursors
 requiring developing processing with an alkali solution exhibit better
 durability in printing if the center line surface roughness of substrate
 (Ra) is larger.
 Next, examples, wherein a polymer containing a sulfonic acid (salt) group
 is used as (a) the water-soluble or water-dispersible polymer, are given
 below. Synthesis of polymer containing sulfonic acid (salt) group
 Synthesis Example 1
 70.0 g of methyl methacrylate, 15.0 g of ethyl acrylate, 31.0 g of
 2-acrylamide-2-methylpropanesulfonic acid, 290 g of isopropanol as a
 solvent, and 28 g of water were placed in a 1L three-neck flask, and a
 solution was produced.
 Then, while being stirred under a nitrogen stream, the temperature of the
 solution was raised to 70.degree. C. At this temperature, 2.0 g of V-65
 (trade name, manufactured by Wako Pure Chemical Industries, Ltd.) was
 added to the solution, and a polymerization reaction was effected for 4
 hours.
 After the reaction, 80 g of a 1N sodium hydroxide aqueous solution was
 added to the solution and the resulting solution was stirred. By removing
 the isopropanol and water from the solution under a reduced pressure, 110
 g of a water-soluble polymer 1 was obtained (the structure of the polymer
 is given in Table 11 in the column of Example 17 which is described later)
 Synthesis Example 2
 400 g of N-t-butylmethacrylamide, 171 g of
 2-acrylamide-2-methylpropanesulfonic acid, and 1142 g of
 N,N-dimethylformamide were placed in a 2L three-neck flask, and a solution
 was produced. Then, while being stirred under a nitrogen stream, the
 temperature of the solution was raised to 65.degree. C. At this
 temperature, 8 g of V-65 (manufactured by Wako Pure Chemical Industries,
 Ltd.) was added to the solution, and a polymerization reaction was
 effected for 3 hours.
 After the reaction, the solution was added dropwise to 38 L of ethyl
 acetate to produce a precipitate, which was then collected and dried. In
 this way, 550 g of a water-soluble polymer 2 was obtained (the structure
 of the polymer is given in Table 11 in the column of Example 18 which is
 described later).
 Synthesis Example 3
 68.4 g of 2-hydroxyethyl methacrylate, 77.6 g of
 2-acrylamide-2-methylpropanesulfonic acid, and 440 g of
 N,N-dimethylacetamide as a solvent were placed in a 2L three-neck flask,
 and a solution was produced. Then, while being stirred under a nitrogen
 stream, the temperature of the solution was raised to 65.degree. C. At
 this temperature, 2 g of V-65 (manufactured by Wako Pure Chemical
 Industries, Ltd.) was added to the solution, and a polymerization reaction
 was effected for 4 hours.
 Next, 0.1 g of dibutyltin dilaurate was added to the solution and
 thereafter 93 g of 2-isocyanateethyl methacrylate was added to the
 solution. The solution was stirred at 100.degree. C. for 5 hours. After
 the reaction, the solution was cooled and was added dropwise to 10 L of
 ethyl acetate to produce a precipitate, which was then collected and
 dried. In this way, 210 g of a water-soluble polymer 3 was obtained (the
 structure of the polymer is given in Table 12 in the column of Example 22
 which is described later).
 Examples 17 to 22
 A 0.24 mm thick rolled plate of aluminum, containing aluminum at a weight
 percentage of 99.5%, copper at a weight percentage of 0.01%, titanium at a
 weight percentage of 0.03%, iron at a weight percentage of 0.3%, and
 silicon at a weight percentage of 0.1% was grained by using a 20% by
 weight aqueous suspension of 400-mesh pumice stone powder (trade name,
 manufactured by Kyoritsu Yogyo Co., Ltd.) and a rotating nylon (6-10
 nylon) brush having a brush (hair) diameter of 0.30 mm, and the surface
 was then washed well with water.
 The aluminum plate was etched by immersion in a 15% by weight sodium
 hydroxide aqueous solution (containing 5% by weight of aluminum) so that
 the amount of dissolved aluminum was 5 g/m.sup.2, and the aluminum plate
 was then washed with flowing water. After that, the aluminum plate was
 neutralized with a 1% by weight nitric acid aqueous solution, and was
 thereafter subjected to an electrolytic surface-roughening treatment in a
 0.7% by weight nitric acid aqueous solution (containing 0.5% by weight of
 aluminum as ions) by using a rectangular alternating wave voltage (current
 ratio r=0.90, a current wave shape described in examples of JP-B No.
 58-5,796) at a cathode voltage of 9.3 volts and an anode voltage of 10.5
 volts and by a quantity of electricity at anode of 160 coulombs g/m.sup.2.
 After being washed with water, the aluminum plate was etched by immersion
 in a 10% by weight sodium hydroxide aqueous solution at 40.degree. C. so
 that the amount of dissolved aluminum was 1 g/m.sup.2, and the aluminum
 plate was then washed with water. Next, a desmutting treatment of the
 aluminum plate was performed by immersion in a 30% by weight sulfuric acid
 aqueous solution at 50.degree. C., and the aluminum plate was then washed
 with water.
 Next, the aluminum plate was treated to produce a porous anodized film on
 the surface in a 20% by weight sulfuric acid aqueous solution (containing
 0.8% by weight of aluminum as ions) by using a d.c. current. That is, by
 carrying out an electrolysis at a current density of 13 A/dm.sup.2 and by
 adjusting the electrolysis time, a substrate having an anodized film of
 2.0 g/m.sup.2 was prepared. The substrate was then washed with water.
 The surface of the aluminum substrate obtained in the above procedure was
 measured by using a Macbeth RD920 reflection densitometer. The reflection
 density was 0.28 and the center line surface roughness (Ra) of the surface
 was 0.45 .mu.m. The center line surface roughness (Ra) was measured by
 using a SURFCOM contact needle meter manufactured by Tokyo Seimitsu Kikai
 Co., Ltd. (contact needle: 10 .mu.m R).
 Next, a photosensitive solution 4 having the following composition was
 applied to the substrate by using a bar coater. The coating was dried at
 120.degree. C. for 30 seconds. The weight of the dried coating was 1.2
 mg/m.sup.2. Photosensitive solution 4 in parts by weight Water-soluble
 polymer shown in Tables 12 and 13 0.6 Sartomer 399 (trade name,
 manufactured by SARTOMER Corp.) 0.4

Photopolymerization initiator represented
 by the following formula 0.1
 Fluorine-containing surfactant F-176 PF 0.01
 (20% methyl isobutyl ketone solution,
 trade name, manufactured by Dainippon Ink and
 Chemicals Inc.)
 Phosphoric acid (85% aqueous solution) 0.02
 Leuco Crystal Violet 0.04
 The photosensitive layer was subjected to a matting treatment comprising
 electrostatically spraying the photosensitive layer with a spray solution
 of the following composition and then drying the coating in an atmosphere
 of 80.degree. C. for 5 seconds.
 Photopolymerization initiator
 ##STR34##
 TABLE 11

Content of

sulfonic acid Content of

Content of Content of

Spray solution in grams
 Sodium salt of a methyl methacrylate/ethyl 0.5
 acrylate/sodium 2-acrylamide-2-
 methylpropanesulfoninc acid copolymer
 (60/25/15 in molar ratio of the copolymer)
 Tartrazine 0.01
 Water 100
 The heights and widths of the constituent mats were of 2 to 6 .mu.m and of
 20 to 150 .mu.m, respectively, and the total numbers of the mats was 100
 units/m.sup.2. The coating weight was 0.1 g/m.sup.2.
 These photosensitive planographic printing plate precursors were exposed
 image-wise at a distance of 1 m from a lamp by using a PS Light
 manufactured by Fuji Film Co., Ltd. for 1 minute. Then, the plates were
 each loaded into an SOR printing machine manufactured by Hidelberg Co.,
 Ltd. In this way, printing was started, and examination of develop ability
 in a printing machine was conducted by counting the number of prints at
 and after which printing faults were no longer found and the number of
 complete prints obtainable (durability in printing). The results are shown
 in Table 13.
 TABLE 13
 Developability in a printing Durability in
 machine printing
 Example 17 10th sheet 90,000 sheets
 Example 18 15th sheet 100,000 sheets
 Example 19 15th sheet 130,000 sheets
 Example 20 20th sheet 120,000 sheets
 Example 21 20th sheet 100,000 sheets
 Example 22 15th sheet 120,000 sheets
 Example 17 10th sheet 90,000 sheets
 Example 7 20th sheet 70,000 sheets
 Example 13 100th sheet 90,000 sheets
 As described above, the use of a water-soluble polymer containing sulfonic
 acid or a sulfonic acid salt makes it possible to provide a better balance
 between develop ability in a printing machine and durability in printing.
 For example, in contrast with the case where polyvinylpyrrolidone is used
 as in Example 7 shown in Table 13 or a water-soluble polymer containing a
 carboxyl group is used as in Example 12, develop ability in a printing
 machine in particular is enhanced and the balance between develop ability
 in a printing machine and durability in printing becomes better if a
 water-soluble polymer containing sulfonic acid or a sulfonic acid salt is
 used.
 As stated above, the photosensitive planographic printing plate precursors
 of the present invention could be loaded immediately into a printing
 machine so that printing was started without any post-processing after
 exposure, and exhibited good durability in printing even in low-exposure
 areas. As an additional excellent property, the plates hardly produced
 fogging even when the plates were left to stand under a white light lamp
 in the period between exposure and printing.