WE CLAIM:
1. A planographic printing plate precursor which includes a polymer layer on a surface of a
support, comprising:
a back coat layer having an arithmetic average height Sa of 0.5 um or greater due to a surface roughness structure in which thin film portions and thick film portions are continuously formed on a rear surface of the support.
2. The planographic printing plate precursor according to claim 1,
wherein the arithmetic average height Sa of the back coat layer is in a range of 0.5 um to 24 um.
3. The planographic printing plate precursor according to claim 1 or 2,
wherein the arithmetic average height Sa of the rear surface of the support is 0.3 um or less.
4. The planographic printing plate precursor according to any one of claims 1 to 3,
wherein a Bekk smoothness of the back coat layer is 200 seconds or shorter.
5. The planographic printing plate precursor according to any one of claims 1 to 4,
wherein the back coat layer contains at least one non-alkali-soluble resin.
6. The planographic printing plate precursor according to any one of claims 1 to 5,
wherein the surface roughness structure is a stripe coated film in which belt-like thick film portions are arranged on planar thin film portions.
7. The planographic printing plate precursor according to any one of claims 1 to 5,
wherein the surface roughness structure is a dot coated film in which dot-like thick film portions are scattered on planar thin film portions.
8. The planographic printing plate precursor according to any one of claims 1 to 5,
wherein the surface roughness structure is a dashed line coated film in which dashed line thick film portions are arranged on planar thin film portions.

9. The planographic printing plate precursor according to any one of claims 1 to 8,
wherein a width W of the thick film portion is in a range of 0.5 mm to 50 mm.
10. The planographic printing plate precursor according to any one of claims 1 to 9,
wherein a pitch X between the thick film portions is in a range of 0.5 mm to 50 mm.
11. The planographic printing plate precursor according to claim 10,
wherein a ratio ZtA, of a difference Zt in thickness between the thin film portion and the thick film portion which are adjacent to each other to the pitch X is 0.10 or less.
12. The planographic printing plate precursor according to claim 11,
wherein a ratio Zt/W of the difference Zt in thickness to the width W of the thick film portion is 0.10 or less.
13. The planographic printing plate precursor according to any one of claims 1 to 12,
wherein the back coat layer contains at least one non-photocurable resin having an average molecular weight of 3000 or less.
14. The planographic printing plate precursor according to any one of claims 1 to 13,
wherein the back coat layer contains at least one selected from the group consisting of a novolak resin such as a phenol formaldehyde resin, an m-cresol formaldehyde resin, a p-cresol formaldehyde resin, an m-/p-mixed cresol formaldehyde resin, or a phenol/cresol (any of m-, p-, and m-/p-mixed)-mixed formaldehyde resin, a resol resin, pyrogallol, an acetone resin, an epoxy resin, a saturated copolymer polyester resin, a phenoxy resin, a polyvinyl acetal resin, a vinylidene chloride copolymer resin, polybutene, polybutadiene, polyamide, an unsaturated copolymer polyester resin, polyurethane, polyurea, polyimide, polysiloxane, polycarbonate, an epoxy resin, chlorinated polyethylene, an aldehyde condensation resin of alkyl phenol, polyvinyl chloride, polyvinylidene chloride, polystyrene, an acrylic resin copolymer resin, hydroxy cellulose, polyvinyl alcohol, cellulose acetate, and carboxymethyl cellulose.
15. The planographic printing plate precursor according to any one of claims 1 to 14,
wherein the polymer layer is a positive type image recording layer containing an

infrared absorbing agent.
16. The planographic printing plate precursor according to any one of claims 1 to 14,
wherein the polymer layer is a negative type image recording layer containing an infrared absorbing agent, a polymerization initiator, or a polymerizable compound.
17. The planographic printing plate precursor according to any one of claims 1 to 14,
wherein the polymer layer is used for a treated key plate formed of a non-photosensitive layer.
18. The planographic printing plate precursor according to any one of claims 1 to 14,
wherein the polymer layer is used for an untreated plate formed of any of a water-soluble layer or a water-dispersible layer.
19. The planographic printing plate precursor according to any one of claims 1 to 14,
wherein the polymer layer is used for an untreated key plate formed of any of a water-soluble layer or a water-dispersible layer.
20. The planographic printing plate precursor according to claim 18 or 19,
wherein the water-dispersible layer contains polymer fine particles.
21. A laminate which is formed by laminating a plurality of planographic printing plate precursors respectively including a polymer layer on a surface of a support and a back coat layer with an arithmetic average height Sa of 0.5 um or greater due to a surface roughness structure in which thin film portions and thick film portions are continuously formed on a rear surface of the support.
22. A method of producing a planographic printing plate precursor which includes a polymer layer on a surface of a support, the method comprising:
a coating step of performing coating of a rear surface of the support to form a coated film having a surface roughness structure in which thin film portions and thick film portions are continuously formed; and
a drying step of drying the coated film to form a back coat layer having an arithmetic

average height Sa of 0.5 urn or greater due to the surface roughness structure.
23. The method of producing a planographic printing plate precursor according to claim 22,
wherein a difference in thickness between the thin film portion and the thick film portion, which are adjacent to each other in the coating step, is in a range of 1 urn to 50 urn.
24. The method of producing a planographic printing plate precursor according to claim 23,
wherein the support is coated with a coating solution under coating conditions in which a viscosity of the coating solution is in a range of 0.3 mPa-s to 100 mPa-s, a surface tension is 20 mN/m to 40 mN/m, and a contact angle between the coating solution and the support is in a range of 10° to 90° to form the coated film having the surface roughness structure in a wet state in the coating step, and
the formed coated film in the wet state is dried under drying conditions in which a drying point t satisfies inequalities of Formula 1 and Formula 2 in the drying step,
where t represents a time to the drying point and the unit thereof is s, X represents an initial average film thickness and the unit thereof is m, r\ represents a viscosity of a coating solution for a stripe coated film and the unit thereof is Pas, X represents a pitch of a stripe coated film and the unit thereof is m, Z0 represents a difference in initial film thickness and the unit thereof is m, Zt represents a difference in film thickness between dry films and the unit thereof is m, a represents a surface tension of a coating solution for a stripe coated film and the unit thereof is N/m, Pe represents a Peclet number and is a constant of 1.5xl0"6, and W represents a width of a stripe and the unit thereof is m.
25. The method of producing a planographic printing plate precursor according to claim 23 or 24,
wherein the coated film is formed by coating the support using any of a bar coating

system, an ink jet printing system, a gravure printing system, a screen printing system, and a spray coating system in the coating step.
26. The method of producing a planographic printing plate precursor according to any one of
claims 23 to 25,
wherein the coated film having the surface roughness structure is a stripe coated film in which belt-like thin film portions and belt-like thick film portions are alternately and continuously arranged.
27. The method of producing a planographic printing plate precursor according to any one of
claims 23 to 25,
wherein the coated film having the surface roughness structure is a dot coated film in which dot-like thick film portions are scattered on the surface of flat thin film portions.
28. The method of producing a planographic printing plate precursor according to any one of
claims 23 to 25,
wherein the coated film having the surface roughness structure is a dashed line coated film in which dashed line thick film portions are continuously arranged on the surface of flat thin film portions.
29. The method of producing a planographic printing plate precursor according to claim 26,
wherein, in a case of the stripe coated film, the coating solution is applied using a coating bar of a bar coating device in the coating step, and
the coating bar is formed such that grooved portions where grooves are formed and groove-free portions where grooves are not formed are alternately formed in an axial core direction.
30. The method of producing a planographic printing plate precursor according to claim 29,
wherein, in depressions and projections constituting the grooves of the grooved portions in the coating bar, in a case where a pitch length between depressions or projections adjacent to each other is set as P, a depth of a depression is set as h, and an opening width of a depression is set as D, P satisfies 0.25 mm or greater, D/P satisfies 0.49 or less, and h/D satisfies in a range of 0.01 to 0.55.

31. The method of producing a planographic printing plate precursor according to claim 29
or 30, which is a method of continuously coating the support that travels and has a belt shape
using the coating bar that coats the support with the coating solution,
wherein, in a case where a diameter of the coating bar is in a range of 6 mm to 50 mm, a rotation speed of the coating bar is set as r and the unit thereof is rpm, and the viscosity of the coating solution is set as r\ and the unit thereof is mPa-s, a relationship of Formula 3 is satisfied.
r < 65714 x r)"1122 ••• Formula 3
32. The method of producing a planographic printing plate precursor according to any one of
claims 23 to 31,
wherein dry wind is blown to the surface of the coated film in the drying step, and a parallel wind component of the dry wind blown to the coated film surface has a relative wind speed of 30 m/s or less.
33. The method of producing a planographic printing plate precursor according to claim 27,
wherein, in a case of the dot coated film, the coating step includes a first coating step of solid-coating the support with a coating solution to form the flat thin film portions and a second coating step of coating the flat thin film portions with the coating solution in a dot shape using a screen printing device to form the thick film portions.
34. The method of producing a planographic printing plate precursor according to claim 28,
wherein, in a case of the dashed line coated film, the coating step includes a first coating step of solid-coating the support with a coating solution to form the flat thin film portions and a second coating step of coating the flat thin film portions with the coating solution in a dashed line shape using a screen printing device to form the thick film portions.