JPH027454B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a waterless lithographic printing plate for direct printing, and more particularly to a waterless lithographic printing plate for direct printing that has accurate ink transfer and excellent long-term storage stability. A lithographic printing plate that prints without using dampening water (hereinafter referred to as a waterless lithographic plate) usually has a photosensitive resin layer and a silicone rubber layer laminated in sequence on a support layer. After stacking the films and exposing them to light, washing with a solvent will selectively leave only the exposed areas when using a photopolymerizable photosensitive resin, and remove the unexposed areas of the resin layer and silicone rubber layer. . Further, when a photo-solubilized resin is used as the photosensitive resin, only the unexposed portion remains. Since the printing plate thus obtained has a silicone rubber layer on the surface of the remaining area, this area repels ink and does not require conventional dampening water. Such a waterless lithographic plate is known for offset printing, in which the image is once transferred onto a blanket and then printed, or direct printing, in which the image is printed directly onto the printing material. On the other hand, a so-called water-filled lithographic plate that uses dampening water is one in which a photosensitive resin is laminated on a support made of, for example, a metal plate, and is known for use in offset printing and direct printing. Generally speaking, when comparing direct printing and offset printing,
In offset printing, the ink is transferred onto the surface of the printing material using the rubber elasticity of the blanket, whereas in direct printing, the ink is transferred directly from the printing plate to the printing material. It is extremely difficult to print by applying printing pressure uniformly over the entire printing medium for transfer. Also,
When the printing material has a rough surface such as unevenness caused by paper fibers, there is a drawback that ink is preferentially transferred to the convex portions of the printing material. In an attempt to improve this drawback, Japanese Patent Publication No. 51-9323 discloses a water-filled lithographic plate for direct printing in which a printing layer is provided on a rubber elastic layer having a specific hardness and thickness. In this planographic plate with water, the rubber elastic layer plays the role of a blanket in offset printing and has good ink transfer properties. Problems, and even rubber vulcanizing agents,
It was not satisfactory due to problems such as the plasticizer in the plastic. Therefore, the present inventors came up with the idea of using an elastic material for the support layer in a waterless lithographic plate that does not require dampening water, and conducted repeated studies. However, when natural rubber, synthetic rubber, plasticized plastic, etc., as exemplified in the above-mentioned Japanese Patent Publication No. 51-9323, are used as a support, there is a problem that these elastomers and photosensitive substances interact and change over time. For the time being. Although the interaction may be due to absorption of the photosensitive material by the elastomer, it is also believed that additives added to the elastomer react with the photosensitive material. That is, a large amount of additives are usually added to natural rubber or synthetic rubber. For example, vulcanization accelerator,
These include plasticizers, softeners, and anti-aging agents.
Also, large amounts of plasticizers and stabilizers are added to plasticized polyvinyl chloride. These additive components tend to migrate to the surface over time during long-term storage, especially under harsh conditions of high temperature and humidity. In printing base plates made by laminating a photosensitive component on a rubber or elastomer layer containing such additives, the photosensitive component may react with the additive components that have migrated to the rubber or elastomer surface during storage. hand,
This significantly impairs photosensitivity. In addition, if such a compounding agent is mixed into the photosensitive resin layer, especially in the case of a waterless lithographic material having a silicone layer as an upper layer, the adhesion between both layers will change, and the silicone layer will be damaged during the development operation after exposure. may peel off or remain on the entire surface, making it impossible to develop. A further disadvantage is that when printing, naturally ink is used, and after printing is completed there is a step of wiping off the ink with a solvent. Printing plate materials are required to withstand these inks and solvents, but when rubber or elastomer containing plasticizers is used, these additives are extracted by the ink or wiping solvent, and the elasticity increases over time. This results in loss of print quality and makes it impossible to obtain a good printing effect. The inventors of the present invention have made extensive studies to solve the above-mentioned problems, and as a result, have arrived at the following invention. That is, the present invention provides a waterless lithographic printing plate precursor in which a photosensitive resin layer and a silicone layer are successively laminated on an elastic support layer, the support layer comprising:
It is made of a polytetramethylene glycol/polybutylene terephthalate/polybutylene isophthalate copolymerized block polyether ester elastomer, and the copolymerization ratio of the block polyether ester elastomer is 85% by weight≧polytetramethylene glycol≧40
The present invention is a waterless lithographic printing plate blank for direct printing, characterized in that the weight% ranges from polybutylene isophthalate≦50% by weight to 35% by weight≧polybutylene terephthalate≧15% by weight. The most characteristic feature of the present invention is the use of a block polyether ester elastomer as part of the support layer, and this elastomer will be explained below. high melting point, such as polybutylene terephthalate,
Block polyether ester elastomer, which is a block copolymerization of a highly crystalline polyester hard segment and a flexible, low Tg polyether soft segment such as polytetramethylene glycol, can be handled in the molten state in the same way as ordinary plastics. It is known as a thermoplastic elastomer that exhibits rubber elasticity when the polyester crystal phase binds the polyether amorphous rubber phase as a type of physical crosslinking point in the solidified state. Polybutylene terephthalate (PBT)/polytetramethylene glycol (PTMG)-based polyester elastomers (hereinafter referred to as polyester elastomers) can be made from hard, plastic-like materials to extremely flexible materials comparable to rubber, depending on the copolymerization ratio. You can, but
Of course, properties such as chemical resistance such as oil resistance and chemical resistance, adhesiveness, and moldability vary greatly depending on the composition. The waterless lithographic printing original plate that is the object of the present invention is particularly required to have mechanical properties such as rebound resilience and surface hardness, and chemical resistance to printing inks and ink cleaning solvents. Storage stability of the plate (for example, no dimensional change, etc.) is required. When using a polyester elastomer as a rubber layer in a waterless planographic printing original plate, it is necessary to select the copolymerization composition ratio of the polyester elastomer from this point of view. The rebound resilience of polyester elastomer is mainly due to
It is controlled by the PTMG content, and the higher the PTMG content, the higher the rebound. If PTMG is less than 40% by weight (line segment in the figure), the rebound modulus will be 55% or less, which is not preferable as a rubber layer. on the other hand,
Even if there is too much PTMG, the polyester hard block will become too short and will no longer be able to play its role as a mesh node, resulting in a sharp drop in rebound, as well as a drop in chemical resistance.
The upper limit of the amount of PTMG can be defined as 85% by weight (line segment in the figure). In the copolymerization composition of the block polyetherester elastomer, copolymerization of polyester components other than PBT is effective in lowering the elastic modulus and surface hardness. Copolymerization of polybutylene isophthalate (PBI) components is particularly useful in that it can be made flexible without impairing chemical resistance or mechanical strength. If something other than PBI, such as an aliphatic polyester, is used as a copolymer component, chemical resistance is poor and a good printing plate cannot be obtained. PBI used as a copolymerization component also works to improve the adhesion of the elastomer rubber layer to the photosensitive resin layer and support layer, and is particularly advantageous in that it can be laminated at once by extrusion lamination without applying an adhesive. It is. However, the copolymerization ratio of the PBI component is limited to within 50% by weight (line segment in the figure) of the total polyester component. If this copolymerization ratio is exceeded, not only will chemical resistance tend to decrease, but the crystallization rate will slow down, resulting in dimensional changes after molding.
In severe cases, the adhesive may even peel off. Thus, the copolymerization composition range of the polyester elastomer used in the present invention is the region surrounded by ABCD in the figure. Strictly speaking, PTMG is not only a PTMG unit, but also a unit containing a paired terephthaloyl or isophthaloyl group.
It should be indicated as (PTMG)T/I, but since it would be complicated, all PTMG content in this specification is an abbreviation of the above-mentioned strict regulations. A particularly preferable range is a range in which the hardness has a flexibility of 35 or less in shore D, and the hardness is approximately PBT.
Since it varies depending on the amount, the PBT content is 15% by weight. , indicating a PBT content of 35% by weight, that is, the area surrounded by points A, E, F, C, and G is recommended as the rubber layer of the waterless lithographic printing plate precursor for direct printing of the present invention. The thickness of the polyester elastomer layer used in the present invention can be selected within an appropriate range depending on the material, surface condition, or printing method of the printing medium, but a thickness of about 0.01 to 1 mm is usually used. In addition, in order to provide the shape retention required for printing plates, a support such as a metal plate such as an aluminum plate or iron plate, or a plastic film or sheet can be provided under the elastomer to form a composite support layer. . In this case, the polyester elastomer is formed into a sheet by melt extrusion processing and then laminated onto a support with or without an adhesive. The most economical manufacturing method is to melt form a polyester elastomer into a sheet and laminate it directly onto a support. In addition, in order to improve processability during melt molding and improve thermal stability, it is possible to add a small amount of additives, which is practically useful. In the photosensitive resin layer used in the present invention, the photosensitive component is preferably made of a polymeric photosensitive substance. The polymeric photosensitive substance referred to here has a molecular weight of
1000 or more and contains a substance that becomes photo-insolubilized or photo-solubilized by irradiation with actinic rays. Examples of such substances are (1) Photosensitive polymers that become photoinsolubilized; Photosensitive polymers obtained by pendanting photosensitive groups to existing polymers, or modified versions thereof; (2) Photo-solubilized polymeric photosensitive substances include complexes of diazo compounds with inorganic acids and organic acids, quinonediazodes, etc. combined with suitable polymer binders; examples of (1) include azidophthal of polyvinyl alcohol; Acid ester, (2) is naphthoquinone-1,2-diazide-5- of phenolic novolak resin.
Typical examples include sulfonic acid esters. Further, the thickness of the photosensitive resin is preferably about 0.1 to 100 μm. The thickness of the silicone rubber layer used as the ink repellent layer in the present invention is preferably in the range of 1 to 100 microns. If it is too thin, problems may occur in terms of printing durability, while if it is too thick, it is not only economically disadvantageous, but also makes it difficult to remove the silicone layer during development, resulting in a decrease in image reproducibility. . As the silicone rubber, those used in known waterless lithographic plates can be used in the present invention, and although there are no particular limitations, room temperature curable (RTV) silicone rubbers that cure rapidly at low temperatures are preferred. Fillers can also be mixed into the silicone rubber to improve its strength and resistance to frictional forces generated during printing operations. Furthermore, if necessary, an adhesive layer can be provided between the photosensitive resin layer and the silicone rubber layer for bonding and adhering both layers. Although various adhesive layers can be used, an aminosilane layer is particularly preferred. A transparent protective film can also be laminated on the surface of the silicone rubber layer forming the surface of the lithographic printing original plate constructed in this manner. Useful protective films include polyethylene, polypropylene, polyethylene terephthalate, and the like. The present invention will be specifically described below with reference to Examples. Note that parts used in the examples are based on parts by weight. Example 1 149.4 parts of terephthalic acid, 16.6 parts of isophthalic acid and 381 parts of polytetramethylene glycol having a number average molecular weight of 1000 were polymerized in the presence of a titanium tetrabutoxide catalyst to obtain a polyester elastomer having the following properties. Melting point 138℃ Glass transition temperature -65℃ Breaking strength 200Kg/cm ² Breaking elongation 850% Tensile modulus 140Kg/cm ² Impact modulus 78% Shore hardness (Shor D) 30 This elastomer contains 75% by weight of PTMG, PBT
It consists of 22.5% by weight of components and 2.5% by weight of PBI components. A sheet with a thickness of 0.3 mm was molded from this elastomer using an extrusion molding machine. A phenol resin-modified chloroprene adhesive was applied onto an aluminum plate having a thickness of 0.3 mm, and the elastomer sheets were laminated using a laminator to obtain a composite support layer. On this composite support layer, a phenol novolak resin with a degree of esterification of 45% (manufactured by Sumitomo Bakelite: Sumiresin PR) is applied.
50235) naphthoquinone-1,2-diazide-5
-A 10% by weight ethyl cellosolve solution of sulfonic acid ester (molecular weight approximately 1300) was applied and dried in hot air at 60°C to form a 3μ thick photosoluble photosensitive resin layer. A 0.5% by weight solution of γ-aminopropyltriethoxysilane (A1100 manufactured by UCC) in n-hexane was applied onto this and dried in hot air at 100°C. Furthermore, a 10% by weight n-hexane solution of a silicone gum composition having the following composition was applied on top of this.
A silicone rubber layer with a thickness of 2μ was provided by drying in hot air at °C. (a) Polydimethylsiloxane (molecular weight approximately 80,000, OH groups at both ends) 100 parts by weight (b) Methyltriacetoxysilane 5 parts by weight (c) Dibutyltin acetate 0.2 parts by weight To the printing plate blank obtained as above A negative film was applied to the lamp, and a 2 kW metal halide lamp (Iwasaki Electric's idle fin was installed).
2000), and was exposed for 60 seconds from a distance of 1 m. When the plate surface is immersed in ethanol and rubbed lightly with a cotton pad, the exposed areas are easily removed and the polyester elastomer layer is exposed, while the silicone rubber layer remains firmly in the unexposed areas, making it difficult to remove the negative film. A faithfully reproduced printed version was obtained. The photosensitive characteristics of this printing plate blank did not practically change even after storage at room temperature for one month or storage at 50° C. for seven days after production. This printing plate was attached to a regular flatbed letterpress printing machine and printed directly onto coated paper using waterless lithographic ink "Alpo G" (manufactured by Toka Shiki Kagaku Kogyo). A printed matter with a good inking state and a sharp image was obtained. Example 2 A polyester elastomer containing 50% by weight of PTMG component, 30% by weight of PBT component, and 20% by weight of PBI component obtained by polymerization in the same manner as in Example 1 was extruded.
A composite support layer was created by laminating a 0.3 mm sheet directly onto a 0.25 mm thick polyethylene terephthalate film ("Lumirror" manufactured by Toray Industries, Ltd.) while molding it. A printing plate was prepared in the same manner as in Example 1, and 0.25
When directly printed on mm aluminum, good prints were obtained. Comparative Examples 1 to 3 Composite support layers made of polyester elastomers having the copolymerization composition ratios (wt%) listed in Table 1 were prepared in the same manner as in Example 1, and changes in photosensitive properties,
Examined print suitability.

[Table] * Polybutylene stearate Example 3 A printing plate precursor was prepared in the same manner as in Example 2, except that the photosensitive resin layer in Example 2 was changed to a photopolymerizable resin as shown below. Created. The photopolymerizable photosensitive resin layer has a polymerization degree of 1400,
A 5% by weight methyl cellosolve acetate solution of polycinnamylidene acetate obtained by esterifying completely saponified polyvinyl alcohol (Nippon Gosei Kagaku's "Gohsenol" NM-14) with cinnamylidene acetic acid was applied onto the polyester elastomer layer. , and dried in hot air at 80°C to form a layer with a thickness of 3μ. Before exposure, a 10μ thick polyester film (Lumirror, manufactured by Toray) was laminated on top of the top silicone rubber layer, a positive film was placed on top of it, and the film was brought into close contact with reduced pressure. (manufactured by Oak Seisakusho) and was exposed for 5 minutes from a distance of 1 m. When the plate surface is lightly rubbed with a cotton pad impregnated with triclene, the unexposed areas are easily removed and the polyester elastomer layer is exposed, while the exposed areas have a strong silicone rubber layer, making it possible to remove the positive film. A faithfully reproduced printed version was obtained. When a direct printing test was conducted using this printing plate in the same manner as in Example 1, good results were obtained. Further, the photosensitive characteristics of this printing plate blank did not practically change even after storage at room temperature for one month or storage at 50° C. for seven days after manufacture. Comparative Example 4 A 0.3 mm thick vulcanized NBR sheet containing a plasticizer, process oil, anti-aging agent, etc. was laminated on an aluminum plate in the same manner as in Example 1. A printing plate original plate was produced on this composite support layer in the same manner as in Example 1. A good printing plate was obtained on the 3rd day after production, but the plate that had been stored at room temperature for 1 month after production had some development defects, and the plate that had been stored at 50°C for 7 days was completely undevelopable.

[Brief explanation of drawings]

The figure is a ternary diagram showing the composition of polyester elastomer. Points A to G... Points indicating each composition, area ABCD...
...Composition range that can be used in the present invention.

Claims (1)

[Scope of Claims] 1. A waterless lithographic printing plate precursor in which a photosensitive resin layer and a silicone layer are sequentially laminated on a support layer having elasticity, wherein the support layer is composed of polytetramethylene glycol/polybutylene terephthalate/ It is made of a polybutylene isophthalate-based copolymerized block polyether ester elastomer, and the copolymerization ratio of the block polyether ester elastomer is 85% by weight ≧ polytetramethylene glycol ≧ 40
A waterless lithographic printing plate blank for direct printing, characterized in that the weight% ranges from polybutylene isophthalate≦50% by weight to 35% by weight≧polybutylene terephthalate≧15% by weight.