JP4294796B2 - Printing plate method for photosensitive lithographic printing plate - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming method, and more specifically, an image forming method using a positive photosensitive lithographic printing plate containing a photothermal conversion substance that absorbs light of an image exposure light source and converts it into heat in a photosensitive layer. About.
[0002]
[Prior art]
In recent years, a photosensitive composition obtained by applying a positive photosensitive composition containing at least an alkali-soluble resin (A) and a photothermal conversion substance (B) that absorbs light from an image exposure light source and converts it into heat on the surface of a support. A planographic printing plate has been proposed (for example, JP-A-7-285275, JP-A-9-43847, and JP-A-10-268512). Hereinafter, such a positive photosensitive lithographic printing plate is abbreviated as a thermal positive plate.
[0003]
The thermal positive plate has a very simple composition of the photosensitive layer, can be directly made by laser, does not require post-heat treatment after laser exposure, and can be operated under normal white light including ultraviolet rays. It has the outstanding feature of being. In such a laser exposure process of the thermal positive plate, an outer surface scanning method is preferably employed in which both end surfaces of the photosensitive lithographic printing plate are fixed on the surface of the rotating drum by a pressing jig (for example, a clamp). .
[0004]
[Problems to be solved by the invention]
By the way, in the case of the printing plate method including the laser exposure step by the outer surface scanning method as described above, the unexposed portions on both end surfaces of the thermal positive plate fixed by the holding jig are not melted in the developing step and the image portion Therefore, there are the following problems. That is, for example, when using a vertical offset rotary printing press, both end surfaces in a direction different from the above-described unexposed portion of both end surfaces (direction orthogonal to the above-mentioned image line portion) are pressed by the press. Since it is fixed by the jig, the above-mentioned unexposed portion is solid-printed and an unnecessary image is formed on the printed matter. In addition, even when not using a vertical offset rotary printing press, if the width of the press jig of the printing press is small and the above-mentioned image line portion protrudes, an image that is unnecessary for the printed matter is the same as above. Is formed.
[0005]
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an improved printing plate method in which an unnecessary image is not formed on a printed matter by unexposed portions on both end faces of a photosensitive lithographic printing plate. There is.
[0006]
[Means for Solving the Problems]
That is, the gist of the present invention is that a positive photosensitive composition containing at least an alkali-soluble resin (A) and a photothermal conversion substance (B) that absorbs light from an image exposure light source and converts it into heat on the surface of a support. A method of printing a photosensitive lithographic printing plate by applying an outer surface scanning method in which the opposite end surfaces of the photosensitive lithographic printing plate are fixed on the surface of a rotating drum by a pressing jig. And a developing step, and further includes an end face processing step for removing the unexposed portions on both end faces fixed by a pressing jig. .
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail. First, the thermal positive plate used in the printing plate method of the present invention will be described. In the thermal positive plate, a positive photosensitive composition containing at least an alkali-soluble resin (A) and a photothermal conversion substance (B) that absorbs light from an image exposure light source and converts it into heat is applied to the surface of a support. Configured.
[0008]
As said support body, metal plates, such as aluminum, zinc, copper, steel, a metal plate which plated or vapor-deposited aluminum, zinc, copper, iron, chromium, nickel etc., paper, paper which applied resin, aluminum, etc. Examples include paper with a metal foil attached, a plastic film, a plastic film subjected to a hydrophilic treatment, and a glass plate. Among these, an aluminum plate is preferable, and in particular, surface treatment such as graining treatment by electrolytic etching or brush polishing in hydrochloric acid or nitric acid solution, anodizing treatment in sulfuric acid solution, sealing treatment performed as necessary. Are preferably applied sequentially. The surface roughness of the support is usually about 0.3 to 1.0 μm, preferably about 0.4 to 0.8 μm, as the average roughness (Ra) defined in JIS B0601.
[0009]
As the alkali-soluble resin (A) which is a constituent component of the positive photosensitive composition, various known resins can be used as the alkali-soluble resin of the photosensitive layer of the photosensitive lithographic printing plate, and the kind thereof is not particularly limited. . For example, a novolac resin, a resole resin, a polyvinylphenol resin, a copolymer of an acrylic acid derivative, and the like can be given. Among these, novolak resins or polyvinylphenol resins are preferable, and novolak resins are particularly preferable. The molecular weight of the alkali-soluble resin (A), that is, the polystyrene-reduced weight average molecular weight (Mw) by gel permeation chromatography measurement is usually 1,000 to 15,000, preferably 1,500 to 10,000. is there.
[0010]
As the photothermal conversion substance (B), which is another component of the positive photosensitive composition, any kind of compound can be used as long as it can absorb light from an image exposure light source described later and convert it into heat. . Such compounds include organic or inorganic dyes, organic dyes, metals, metal oxides, metal carbides, metal borides and the like having an absorption band in part or all of the near infrared region in the wavelength range of 650 to 1300 nm. Can be mentioned. Among these, light absorbing dyes are particularly effective. The light-absorbing dye efficiently absorbs light in the above-mentioned wavelength range, but hardly absorbs light in the ultraviolet region or is not substantially sensitive to absorption. Is a compound having no action to modify the positive photosensitive composition.
[0011]
A typical example of the light absorbing dye is a so-called cyanine dye in a broad sense in which a heterocyclic ring containing a nitrogen atom, an oxygen atom or a sulfur atom is bonded with polymethine: (—CH═) n. In other words, quinoline (so-called cyanine-based), indole (so-called indocyanine), benzothiazole (so-called thiocyanine), aminobenzene (so-called polymethine), pyrylium, thiapyrylium, squarylium And dyes such as chromonic, croconium and azulenium. Of these, quinoline, indole, benzothiazole, aminobenzene, pyrylium or thiapyrylium are preferred. Other examples include aminium, imonium, phthalocyanine, and anthraquinone dyes.
[0012]
The positive photosensitive composition used in the present invention has an alkali-soluble resin (A) and a photothermal conversion substance (B) as a basic composition. The proportion of the component (A) is preferably 70 to 99.9% by weight and the component (B) is preferably 0.1 to 30% by weight with respect to the total amount of these two components.
[0013]
The positive photosensitive composition contains a dissolution inhibitor having a function of reducing the solubility of the two components in order to increase the difference in solubility between the exposed portion and the non-exposed portion in the alkaline developer. It may be.
[0014]
Examples of the dissolution inhibitor include sulfonic acid esters, phosphoric acid esters, aromatic carboxylic acid esters, aromatic disulfones, and carboxylic acid anhydrides described in detail in Japanese Patent Application Laid-Open No. 10-268512 filed by the present applicant. , Aromatic ketone, aromatic aldehyde, aromatic amine, aromatic ether, which are also described in detail in Japanese Patent Application No. 9-291880, lactone skeleton, N, N-diarylamide skeleton, diarylmethylimino skeleton And non-ionic surfactants which are described in detail in Japanese Patent Application No. 9-331512. The upper limit of the proportion of the dissolution inhibitor in the positive photosensitive composition is usually 50% by weight, preferably 30% by weight, and more preferably 20% by weight.
[0015]
In addition to the above-described components, for example, a colorant, a coatability improver, a developability improver, an adhesion improver, a sensitivity improver, and a sensitizer are commonly used in the positive photosensitive composition. Various additives may be contained. The upper limit of the content ratio of these additives in the positive photosensitive composition is usually 10% by weight, preferably 5% by weight.
[0016]
The positive photosensitive composition is usually used as a solution in which the above-described components are dissolved in an appropriate solvent. The type of the solvent is not particularly limited as long as it has sufficient solubility for each of the above-described components and gives good coating properties. Examples of such solvents include cellosolv solvents such as methyl cellosolve, ethyl cellosolve, methyl cellosolve acetate, ethyl cellosolve acetate, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monobutyl ether, propylene glycol monomethyl ether acetate, propylene Propylene glycol solvents such as glycol monoethyl ether acetate, propylene glycol monobutyl ether acetate, dipropylene glycol dimethyl ether, butyl acetate, amyl acetate, ethyl butyrate, butyl butyrate, diethyl oxalate, ethyl pyruvate, ethyl-2-hydroxybutyrate , Ethyl acetoacetate, methyl lactate, ethyl lactate, 3-methoxypro Ester solvents such as methyl onate, alcohol solvents such as heptanol, hexanol, diacetone alcohol, furfuryl alcohol, ketone solvents such as cyclohexanone, methyl amyl ketone, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, etc. In addition to the polar solvent, acetic acid, a mixed solvent thereof, a mixed solvent obtained by adding an aromatic hydrocarbon thereto, and the like can be given. The ratio of the solvent used is usually in the range of 1 to 20 (weight ratio) times the total amount of the positive photosensitive composition.
[0017]
The positive photosensitive composition is applied by a conventionally known method such as spin coating, wire bar coating, dip coating, air knife coating, roll coating, blade coating, curtain coating and the like. The coating amount is usually in the range of 0.3 to 7 μm, preferably 0.5 to 5 μm, more preferably 1 to 3 μm as a dry film thickness, and drying after coating is usually 30 to 170 ° C., preferably Is carried out in the range of 40 to 150 ° C.
[0018]
Next, an outline of the printing plate method of the present invention will be described. The printing plate method of the present invention includes a laser exposure step and a development step. Examples of the light source used for laser exposure (image exposure) mainly include HeNe laser, argon ion laser, HeCd laser, semiconductor laser, YAG laser, ruby laser, and LED. In particular, a light source that generates a near infrared laser beam of 650 to 1300 nm, for example, a solid-state laser such as a semiconductor laser, a YAG laser, a ruby laser, or an LED is preferable, and a small-sized and long-life semiconductor laser or a YAG laser is particularly preferable.
[0019]
A laser light source usually scans the surface of a photosensitive layer made of a positive photosensitive composition as a high-intensity light beam (beam) collected by a lens, and the sensitivity characteristic (mJ / cm ² ) of the photosensitive layer sensitive thereto. May depend on the light intensity (mJ / s · cm ² ) of the received laser beam. Here, the light intensity of the laser beam is obtained by dividing the amount of energy (mJ / s) per unit time of the laser beam measured by the optical power meter by the irradiation area (cm ² ) of the laser beam on the photosensitive layer surface. I can do it. The irradiation area of the laser beam is usually defined as the area exceeding the 1 / e ² intensity of the laser peak intensity. For simplicity, it should be measured by exposing a positive photosensitive composition exhibiting a reciprocity law. You can also.
[0020]
The light intensity of the light source is preferably 2.0 × 10 ⁶ mJ / s · cm ² or more, and more preferably 1.0 × 10 ⁷ mJ / s · cm ² or more. When the light intensity is in the above range, the sensitivity characteristic of the photosensitive layer can be improved, and the scanning exposure time can be shortened.
[0021]
As a developer used for development after laser exposure (image exposure), an alkali developer containing about 0.1 to 5% by weight of an alkali component is preferably used. Examples of the alkali component include sodium silicate, potassium silicate, lithium silicate, ammonium silicate, sodium metasilicate, potassium metasilicate, sodium hydroxide, potassium hydroxide, lithium hydroxide, sodium carbonate, sodium bicarbonate, potassium carbonate, Inorganic alkali salts such as sodium diphosphate, sodium triphosphate, dibasic ammonium phosphate, tribasic ammonium phosphate, sodium borate, potassium borate, ammonium borate, monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine, monoisopropyl Such as amine, diisopropylamine, monobutylamine, monoethanolamine, diethanolamine, triethanolamine, monoisopropanolamine, diisopropanolamine Machine amine compound. Of these, alkali metal silicates such as sodium silicate and potassium silicate are preferred. An organic solvent such as various surfactants (anionic surfactant, nonionic surfactant, amphoteric surfactant) and alcohol can be added to the developer as necessary.
[0022]
Next, features of the printing plate method of the present invention will be described. In the case of the present invention, the laser exposure step is performed by an outer surface scanning method in which the opposite end surfaces of the photosensitive lithographic printing plate are fixed on the surface of the rotating drum by a pressing jig (for example, a clamp). As a result, both end surfaces of the thermal positive plate fixed by the holding jig become unexposed portions. The greatest feature of the printing plate method of the present invention resides in that it includes an end surface processing step of removing the unexposed portions on both end surfaces fixed by the pressing jig.
[0023]
End face processing for removing the unexposed portion can be roughly divided into a thermal positive plate cutting method and a non-cutting method. The cutting method is a method of removing the unexposed portions on both end surfaces by cutting the thermal positive plate itself with a saw for precision cutting, a cutter, or the like. The non-cutting method is a method of removing unexposed portions (positive photosensitive composition layers) on both end faces of the thermal positive plate, and is further divided into a heating method, a dissolution method, and a pressure treatment method. The heating method is a method of dissolving and removing the unexposed portions on both end faces of the thermal positive plate after heating, and the dissolution removal after heating of the unexposed portions usually uses a development process performed after the laser exposure process. Done. The dissolution method is a method of dissolving and removing the unexposed portion with, for example, a concentrated developer or a commercially available erasing solution. On the other hand, the pressure treatment method is a method of changing the quality by subjecting an unexposed portion to pressure treatment instead of the above heating. And as a pressurization process, although pressurization may be sufficient, the pressurization process by rubbing (friction) is preferable. In these, the end surface processing process by each said non-cutting method is recommended.
[0024]
Hereinafter, the end surface processing step by each non-cutting method will be described with reference to the accompanying drawings. FIG. 1 is a plan explanatory view of a preferred example of an end surface processing apparatus using a heating method (far infrared heater), FIG. 2 is a cross-sectional explanatory view taken along line II-II of the apparatus shown in FIG. 1, and FIG. FIG. 4 is a cross-sectional explanatory view taken along line IV-IV of the apparatus shown in FIG. 3, and FIG. 5 is an end surface treatment by a melting method. FIG. 6 is a perspective explanatory view of a preferred example of the apparatus, FIG. 6 is a plan explanatory view of a preferred example of a rubbing apparatus for an unexposed portion used when the unexposed portion is changed to a non-image portion, and FIG. It is sectional explanatory drawing along the VII-VII line of the apparatus shown in FIG.
[0025]
1 and 2 basically includes a belt conveyor (2) between the left and right frames (1) and (1), and both end portions of the belt conveyor. The guide plates (3) are respectively arranged on the unexposed portions (B) on both end faces of the thermal positive plate (A) which is guided by the guide plate (3) and conveyed in the direction of the arrow by the belt conveyor (2). The far-infrared heaters (4a) and (4b) are arranged at the corresponding positions, and the far-infrared shielding plate (5) is arranged at the corresponding position of the exposure part.
[0026]
Each guide plate (3) is fixed to each frame (1), and each far-infrared heater (4a) and (4b) and far-infrared shielding plate (5) are respectively fixed to each frame (1). It is attached to the member (1a). As the far-infrared heaters (4a) and (4b), conventionally known plate-shaped ones are used, and as the far-infrared shielding plate (5), a conventionally known aluminum plate or the like is used. In the case of the illustrated apparatus, the far-infrared shielding plate (5) spans two far-infrared heaters (4a) and (4b) arranged at predetermined intervals for each end face of the thermal positive plate (A). Has been placed.
[0027]
The above-mentioned end surface processing apparatus using a far infrared heater is used as follows. That is, the thermal positive plate (A) is conveyed in the direction of the arrow by the belt conveyor (2), and the unexposed portions (B) on both end surfaces of the thermal positive plate (A) are removed by the far infrared heaters (4a) and (4b). Heat. At this time, the exposed portion is protected by the far-infrared shielding plate (5). Therefore, the unexposed portion (B) can be selectively heated without affecting the exposed portion. Since the heating temperature and heating time by the far-infrared heaters (4a) and (4b) vary depending on the type of the positive photosensitive composition used for forming the photosensitive layer, they are determined in advance.
[0028]
3 and 4 basically includes a belt conveyor mechanism similar to that described above, and is located at a position corresponding to the unexposed portion (B) on both end surfaces of the thermal positive plate (A). Heating rolls (6a) and (6b) are arranged, respectively, and cold air blowing nozzles (7a) and (7b) are arranged at positions corresponding to the exposure parts, respectively, and below the heating rolls (6a) and (6b), respectively. The presser rolls (8a) and (8b) (not shown) are arranged. Reference numerals (2a) and (2b) denote thermal positive plate (A) feed rolls provided as necessary before and after the heating rolls (6a) and (6b), respectively. Each guide plate (3) is fixed to each frame (1), and each heating roll (6a) and (6b) is fixed to each frame (1). The end face processing apparatus using the heating roller is used in the same manner as the end face processing apparatus using the far infrared heater, and can selectively heat the unexposed part (B) without affecting the exposed part.
[0029]
5 basically includes first and second rollers (10) and (11) that rotate along the upper and lower surfaces of the end portion of the thermal positive plate (A). And at least the first roller (10) has a surface portion formed of a sponge, and a developer (or erasing solution) supply pipe (12) whose front end faces the surface of the first roller (10). The developer (or erasing solution) suction pipe (13) whose tip is near the top surface of the thermal positive plate (A) and faces the first roller (10) either before or after the travel locus. It has the composition provided with. And the width | variety of a 1st roller (10) is made into the substantially same width as the unexposed part (B) of the end surface of a thermal positive plate (A).
[0030]
As a preferred embodiment, a guide roller (14) that rotates along the end face of the thermal positive plate (A) is provided, and the tip of the developer (or erasing solution) suction pipe (13) is tubular by the brush member (15). It is configured. The guide roller (14) regulates the traveling positions of the first and second rollers (10) and (11), and the brush member (15) is a developer (or a developer) in which an unexposed portion is dissolved by its bending deformation (or It has a function of enhancing the suction removal effect of the erasing liquid.
[0031]
Each of the above elements is attached to the fixed substrate (16). Reference numeral (17) represents a developer (or erasing liquid) supply conduit, and reference numeral (18) represents a developer (or erasing liquid) suction conduit connected to a decompression mechanism (not shown).
[0032]
The end face processing apparatus shown in FIG. 5 is used as follows. That is, the first roller (10) is disposed in contact with the unexposed portion (B) of the end face of the thermal positive plate (A), and the first roller (10) is supplied from the developer (or erasing solution) supply pipe (12). The end surface processing apparatus is run while supplying the developing solution (or erasing solution) to the surface. Since the concentration of the developer varies depending on the type of the positive photosensitive composition used for forming the photosensitive layer, it is determined in advance. Moreover, a suitable commercial product can be used as the erasing liquid.
[0033]
Then, the developing solution (or erasing solution) in which the unexposed portion (B) is dissolved is sucked and removed by the developing solution (or erasing solution) suction tube (13). Such suction removal of the developing solution (or erasing solution) may be executed only in the return path of the reciprocating traveling process of the end face processing apparatus. Such an embodiment is adopted in consideration of the distance between the developer (or eraser) supply pipe (12) and the developer (or eraser) suction pipe (13), the traveling speed of the end surface processing apparatus, and the like. The That is, it is important to obtain a sufficient retention time of the developer (or erasing solution) for dissolving the unexposed portion (B) on the end face of the thermal positive plate (A).
[0034]
According to the end face processing apparatus as described above, the supply of the developer (or erasing liquid) to the unexposed part (B) on the end face of the thermal positive plate (A) is substantially the same width as the unexposed part (B). Since it is performed via the first roller (10), unnecessary diffusion of the developing solution (or erasing solution) is effectively prevented, and as a result, the unexposed portion (B) without affecting the exposed portion. Can be selectively dissolved and removed.
[0035]
The rubbing apparatus for the unexposed portion shown in FIG. 6 and FIG. 7 basically includes a belt conveyor mechanism similar to the end surface processing apparatus using the far infrared heater, and unexposed both end faces of the thermal positive plate (A). The friction member (9) is disposed at a position corresponding to the part (B), and a presser roll (8a) is disposed at the lower portion of each friction member (9). Reference numerals (2a) and (2b) respectively denote feed rolls of the thermal positive plate (A) provided as necessary before and after the friction member (9). Each guide plate (3) is fixed to each frame (1), and each friction member (9) is fixed to each frame (1). For example, a rubber material is preferably used as the friction member (9).
[0036]
The rubbing apparatus is used as follows. That is, the thermal positive plate (A) is conveyed in the direction of the arrow by the belt conveyor (2), and the unexposed portions (B) on both end faces of the thermal positive plate (A) are pressurized by the friction member (9). The reason why the unexposed part (B) is dissolved and removed by the developer by such pressure treatment is not yet fully elucidated, but some alteration has occurred in the unexposed part (B). Presumed to be based. The pressing force and pressurizing time by the friction member (9) vary depending on the type of the positive photosensitive composition used for forming the photosensitive layer, and thus are obtained in advance.
[0037]
【The invention's effect】
According to the present invention described above, an improved plate method is provided so that an unnecessary image is not formed on a printed matter by the unexposed portions on both end faces of the photosensitive lithographic printing plate, and the practical value of the present invention is great. .
[Brief description of the drawings]
FIG. 1 is an explanatory plan view of a preferred example of an end surface processing apparatus using a heating method (far infrared heater). FIG. 2 is a sectional explanatory view taken along line II-II of the apparatus shown in FIG. FIG. 4 is a cross-sectional explanatory view taken along line IV-IV of the apparatus shown in FIG. 3. FIG. 5 is a preferable end face processing apparatus using a melting method. FIG. 6 is an explanatory perspective view of an example. FIG. 6 is an explanatory plan view of a suitable example of a rubbing apparatus for an unexposed area. FIG. 7 is a sectional explanatory view along the line VII-VII of the apparatus shown in FIG.
A: Thermal positive plate B: Unexposed part 1: Frame 1a: Support member 2: Belt conveyor 2a: Feed roll 2b: Feed roll 3: Guide plate 4a: Far infrared heater 4b: Far infrared heater 5: Far infrared blocking plate 6a : Heating roll 6b: heating roll 7a: cold air blowing nozzle 7b: cold air blowing nozzle 8a: presser roll 8b: presser roll 9: friction member 10: first roller 11: first roller 12: developer (or erasing liquid) supply pipe 13: Developer (or eraser) suction tube 14: Guide roller (14)
15: Brush member 16: Fixed substrate 17: Developer (or eraser) supply conduit 18: Developer (or eraser) suction conduit

Claims (1)

A photosensitive lithographic plate obtained by coating a positive photosensitive composition containing at least an alkali-soluble resin (A) and a photothermal conversion substance (B) that absorbs light from an image exposure light source and converts it into heat on the surface of a support. A printing plate printing method comprising a laser exposure step and a development step by an outer surface scanning method performed by fixing opposite opposite end faces of a photosensitive lithographic printing plate on a surface of a rotating drum with a pressing jig, Further, the unexposed portion on both end faces fixed by the holding jig is a means for dissolving the unexposed portion with the developer in the developing step after selectively heating the unexposed portion or the developing step after pressurizing the unexposed portion. plate method of the photosensitive lithographic printing plate, characterized in that it comprises an end surface processing step of divided by means of dissolving with a developer of.

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