JP6972953B2 - Photosensitive CTP letterpress printing original plate - Google Patents

Description

The present invention relates to a CTP resin letterpress printing original plate (hereinafter referred to as "CTP letterpress printing original plate") used for manufacturing a letterpress printing plate by a computer to plate making technique, particularly while maintaining a high light-shielding property while being a thin film. The present invention relates to a CTP letterpress printing plate having a heat-sensitive mask layer having a higher degree of scratch resistance.

In recent years, in the field of letterpress printing, computer plate making technology (Computer to Plate, CTP technology) known as a digital image forming technology has become extremely common. The CTP technique is a method of directly outputting information processed on a computer onto a printing plate to obtain an uneven pattern as a relief. This technology eliminates the need for a negative film manufacturing process, reducing costs and the time required to create negatives.

In CTP technology, traditionally used negative films are replaced by masks that are formed and integrated within the printing plate to cover areas that should not be photopolymerized. As a method of obtaining this integrated mask, a method of providing an infrared sensitive infrared layer (heat sensitive mask layer) opaque to chemical rays on a photosensitive resin layer and forming an image mask by evaporating the heat sensitive mask with an infrared laser is available. Widely used (see Patent Document 1).

As the heat-sensitive mask layer, a layer made of carbon black, which is a radiation opaque material, and a binder capable of forming a film is generally used. The heat-sensitive mask layer generally requires a transmission optical density (light-shielding property) of 2.0 or more in order to block the transmission of chemical radiation to the photopolymerized layer, and is ablated by an infrared laser. Partially saponified polyvinyl acetate is used as the binder capable of forming a film because of its excellent water solubility. The heat-sensitive mask layer is preferably a thin film in terms of ablation efficiency and wrinkles, but the heat-sensitive mask layer may be used. When the concentration of carbon black was increased in order to make it thinner, the heat-sensitive mask layer became brittle, and there was a problem that the heat-sensitive mask layer was scratched.

As a countermeasure against the above-mentioned problems, Patent Document 2 describes a heat-sensitive mask layer having excellent scratch resistance even in a thin film by using a binder polymer having excellent dispersibility of carbon black. However, also in the heat-sensitive mask layer of Patent Document 2, when another plate is stacked on the surface of the mask layer after ablation, friction may occur between the mask layer and the plate, and the mask layer may be scratched. It was not always satisfactory scratch resistance.

As a method for improving the abrasion resistance of the heat-sensitive mask layer, a flexo containing an acrylic resin having a specific range of storage elastic modulus and glass transition temperature in the heat-sensitive mask layer and a binder polymer having the same structure as the photosensitive resin layer. The CTP version is disclosed in Patent Document 3. However, since the heat-sensitive mask layer contains an acrylic resin, the (meth) acrylate compound used as a photopolymerizable unsaturated compound from the photosensitive resin layer after processing into a CTP plate becomes a heat-sensitive mask layer over time. There was a problem that the scratch resistance was lowered by plasticizing the heat-sensitive mask layer. Further, it is essential that the heat-sensitive mask layer contains a binder polymer having the same structure as the photosensitive resin layer, which causes a problem that the design of the resin composition becomes more complicated.

Recently, there has been a demand for a CTP letterpress printing original plate using a metal support, and even higher scratch resistance is required, but a flexographic CTP plate satisfying high scratch resistance has not yet been obtained.

Special Table No. 7-506201 Gazette Japanese Unexamined Patent Publication No. 2009-300588 Japanese Unexamined Patent Publication No. 2016-188900

The CTP letterpress printing original plate of the present invention was made in view of the current state of the prior art as described above, and the purpose thereof is to specify a polyamide in the heat-sensitive mask layer without designing a complicated resin composition. By containing the above, the scratches generated on the surface of the heat-sensitive mask layer are reduced, and the adhesiveness of the surface of the heat-sensitive mask layer is also reduced. More specifically, it is an object of the present invention to provide a CTP printing original plate having highly excellent handling workability, which reduces the occurrence of scratches due to frictional force on the surface of the heat-sensitive mask layer and further reduces the surface adhesion of the heat-sensitive mask layer.

As a result of diligent studies to achieve the above object, the present inventors have (ii) a tertiary nitrogen atom-containing polyamide as a film-forming polymer in the heat-sensitive mask layer, and an aminocarboxylic acid unit (as a raw material) in the polyamide molecule. Contains 20 to 50 mol% of structural units obtained from cyclohexanedicarboxylic acid with respect to the total of (including the case of lactam), dicarboxylic acid units, and diamine units, and a total of 50 to 95 alicyclic structural units. A CTP letterpress printing original plate having a heat-sensitive mask layer that highly satisfies handling workability while maintaining good dispersibility of carbon black by containing a basic polyamide containing mol% was found, and the present invention was completed. It came to.

That is, the present invention has the following configurations (1) to (7).
A photosensitive CTP relief plate provided with a heat-sensitive mask layer containing (1) (i) partially saponified polyvinyl acetate, (ii) a tertiary nitrogen atom-containing polyamide, and (iii) an infrared absorber on a photosensitive resin layer. In the printing original, (ii) the tertiary nitrogen atom-containing polyamide is cyclo with respect to the total of aminocarboxylic acid units (including the case of lactam as a raw material), dicarboxylic acid units, and diamine units in the polyamide molecule. A photosensitive CTP letterpress printing original plate containing 20 to 50 mol% of structural units obtained from a hexandicarboxylic acid and 50 to 95 mol% of a total of alicyclic structural units.
(2) The photosensitive CTP letterpress printing original plate according to (1), wherein the tertiary nitrogen atom-containing polyamide contains a piperazine ring in the molecule.
(3) Described in (1) or (2), wherein the partially saponified polyvinyl acetate is a modified partially saponified polyvinyl acetate having a photopolymerizable unsaturated group and / or a carboxyl group in the side chain. Photosensitive CTP letterpress printing original plate.
(4) The photosensitive CTP letterpress printing original plate according to any one of (1) to (3), wherein the heat-sensitive mask layer further contains an anionic polymer.
(5) The photosensitive CTP letterpress printing original plate according to any one of (1) to (3), wherein the infrared absorber is carbon black.
(6) The photosensitive CTP letterpress printing original plate according to (1), wherein the photosensitive resin layer contains a modified partially saponified polyvinyl acetate and a 5- to 7-membered heterocyclic compound having a photopolymerizable group.
(7) The photosensitive CTP letterpress printing original plate according to (6), wherein the photosensitive resin layer further contains a basic polyamide.

According to the present invention, it is possible to provide a CTP printing original plate having a high degree of handling workability that satisfies scratch resistance and low surface adhesion on the surface of a heat-sensitive mask layer while maintaining good dispersibility of carbon black.

Hereinafter, the CTP letterpress printing original plate of the present invention will be described in detail.

The heat-sensitive mask layer used in the present invention comprises (i) a partially saponified polyvinylacetate, (ii) a tertiary nitrogen atom-containing polyamide, an aminocarboxylic acid unit (including the case of lactam as a raw material) in a polyamide molecule, and a dicarboxylic acid. A basic polyamide containing 20 to 50 mol% of structural units obtained from cyclohexanedicarboxylic acid and 50 to 95 mol% of alicyclic structural units with respect to the total of units and diamine units. iii) Contains an infrared absorber.

(I) The partially saponified polyvinyl acetate preferably has a saponification degree of 60 mol% or more from the viewpoint of water solubility. More preferably, the partially saponified polyvinyl acetate is a partially saponified polyvinyl acetate having a saponification degree of 70% or more and 95% or less. Further, the partially saponified polyvinyl acetate is a modified partially saponified polyvinyl acetate having a photopolymerizable unsaturated group, a polar group and a hydrophilic nonionic group in the side chain in order to improve the dispersibility of the polyamide and the infrared absorber. It may be. As a method for modifying partially saponified polyvinyl acetate, partially saponified polyvinyl acetate having a degree of saponification of 70% or more and 95% or less has a hydroxyl group and can be denatured by reacting with the hydroxyl group. Further, as another modification method, modification is also possible by copolymerizing a polymerizable monomer having a polar group.

(I) The average degree of polymerization of the partially saponified polyvinyl acetate is preferably in the range of 300 to 2,000, more preferably 500 to 1,000. When the average degree of polymerization is 300 or more, a film having sufficient strength can be obtained, and when the average degree of polymerization is 2000 or less, sufficient water solubility can be obtained.

(I) The partially saponified polyvinyl acetate is preferably contained in the heat-sensitive mask layer in an amount of 10 to 70% by mass from the viewpoint of water developability and film formation. If it is less than 10% by mass, the water developability is poor, and if it exceeds 70% by mass, it becomes difficult to form a stable film.

Specific modified partially saponified polyvinyl acetate used in the present invention includes nonions such as partially sausible polyvinyl acetate and ethylene oxide having polar groups such as photopolymerizable unsaturated groups, anionic groups and cationic groups in the molecule. Examples thereof include modified partially saponified polyvinyl acetate having a hydrophilic group. Among them, partially saponified polyvinyl acetate having an anionic group and a photopolymerizable unsaturated group is preferable. Examples of the anionic polar group include a carboxyl group, a sulfonic acid group, and a phosphoric acid group, but the carboxyl group is preferable from the viewpoint of easiness of modification.

As a method of introducing a carboxyl group into partially saponified polyvinyl acetate, it can be modified by reacting with a hydroxyl group in partially saponified polyvinyl acetate. For example, there are a method of reacting with an acid anhydride, a reaction with a carboxylic acid compound having an epoxy group, and a copolymerization with a monomer having a carboxylic acid. Examples of commercially available products include CM-318 manufactured by Kuraray Co., Ltd. and T-350 manufactured by Nippon Synthetic Chemistry Co., Ltd.

On the other hand, examples of the method of introducing a cationic group include a method of copolymerizing a monomer having a cationic group and a reaction with a cationic group-containing compound having an epoxy group, and commercially available products include a cationic group (quaternary ammonium salt). There is Gosenex K-434 of Nippon Synthetic Chemical Co., Ltd., which has introduced the above into the side chain. Examples of the modified partially saponified polyvinyl acetate having a nonionic hydrophilic group include modified partially saponified polyvinyl acetate having a nonionic hydrophilic group of alkylene glycol, and specifically, a hydrophilic ethylene oxide group is added to the side chain. Examples thereof include WO-320R manufactured by Nippon Synthetic Chemical Co., Ltd., which has a nonionic modified partially saponified polyvinyl acetate.

As a method of introducing a photopolymerizable unsaturated group into partially saponified polyvinyl acetate, for example, a hydroxyl group in partially saponified polyvinyl acetate is reacted with an acid anhydride, and a carboxyl group is reacted with respect to the hydroxyl group of partially saponified polyvinyl acetate. Is introduced into the polymer side chain. A photopolymerizable unsaturated group can be introduced by reacting the carboxyl group with an unsaturated epoxy compound. Alternatively, a photopolymerizable unsaturated group can be introduced by copolymerizing vinyl acetate with an unsaturated carboxylic acid or an unsaturated carboxylic acid ester.

The (ii) tertiary nitrogen atom-containing polyamide of the present invention is cyclohexanedicarboxylic with respect to the total of aminocarboxylic acid units (including the case of lactam as a raw material), dicarboxylic acid units, and diamine units in the polyamide molecule. A basic polyamide containing 20 to 50 mol% of structural units obtained from an acid and a total of 50 to 95 mol% of alicyclic structural units functions as a film-forming polymer. In the present invention, a basic polyamide containing 20 to 50 mol% of a structural unit obtained from a cyclohexanedicarboxylic acid and a total of 50 to 95 mol% of alicyclic structural units is blended as a film-forming polymer. It is also possible to overcome the high degree of scratch resistance that can withstand friction when a metal support is used.

(Ii) The tertiary nitrogen atom-containing polyamide has a high Tg because it contains an alicyclic structural unit, and when used in a CTP layer, imparts scratch resistance and low surface adhesiveness to the heat-sensitive mask layer. Can be done. Further, since the heat-sensitive mask layer containing (ii) a tertiary nitrogen atom-containing polyamide is easily dispersed in water, it can be particularly suitably used as a heat-sensitive mask layer for a water-developed plate.

(Ii) The tertiary nitrogen atom-containing polyamide is a basic polyamide containing 20 to 50 mol% of structural units obtained from cyclohexanedicarboxylic acid and a total of 50 to 95 mol% of alicyclic structural units. However, (ii) if the ratio of the alicyclic structural unit obtained from the cyclohexanedicarboxylic acid in the tertiary nitrogen atom-containing polyamide is less than the above range, the scratch resistance is lowered, which is not preferable. Further, if the ratio of the alicyclic structural unit exceeds the above range, the heat-sensitive mask layer becomes hard, which is not preferable.

The mol% of the structural unit in the (ii) tertiary nitrogen atom-containing polyamide of the present invention is the number of moles of each structural unit with respect to the total number of moles of each unit consisting of aminocarboxylic acid or lactam unit, diamine and dicarboxylic acid. It is shown as a ratio. The mol% of each structural unit can be calculated from the number of moles at the raw material charging stage or the measurement result of 1 H-NMR. The analysis by 1 H-NMR is a generally performed analysis method, and is a method of calculating the mol% of each structural unit from the integrated value.

In order to obtain a basic nitrogen-containing copolymerized polyamide containing 25 to 50 mol% of an alicyclic structural unit obtained from cyclohexanedicarboxylic acid in the molecule, 1,4-cyclohexanedicarboxylic acid or 1 is used as the dicarboxylic acid. . A method for producing using 3-cyclohexanedicarboxylic acid is conceivable.

(Ii) The tertiary nitrogen atom-containing polyamide is an alicyclic structural unit obtained from other alicyclic diamines or dicarboxylic acids in addition to the alicyclic structural unit obtained from cyclohexanedicarboxylic acid as an alicyclic structural unit. May be contained in the molecule. Specific examples of diamines include isophorone diamine, 1,4-cyclohexanediamine, 1,3-cyclohexanediamine, 1,3-bis (aminomethyl) cyclohexane, and 1,4-bis (aminomethyl). Examples thereof include cyclohexane and norbornyldiamine, but isophoronediamine is preferable in terms of physical properties.

(Ii) As the tertiary nitrogen atom-containing polyamide, known diamines and dicarboxylic acids other than the alicyclic group can be used as long as the characteristics of the polyamide are not affected. Examples of the aliphatic diamine include ethylenediamine, diethylenediamine, 1,3-propylenediamine, 1,4-tetramethylenediamine, 2-methylpentamethylenediamine, 1,6-hexanediamine, 1,11-undecamethylenediamine, and 1 , 12-Dodecanediamine, 2,2,4, 2,4,4-trimethylhexamethylenediamine and the like. Further, examples of known aliphatic dicarboxylic acids other than alicyclic dicarboxylic acids include glutaric acid, adipic acid, sebacic acid, decandicarboxylic acid and the like.

(Ii) The tertiary nitrogen atom-containing polyamide is a polyamide containing a basic nitrogen atom in the main chain or side chain in the molecule, and is water-soluble or water-dispersible (water-developed) by containing the basic nitrogen atom. Gender) can be given. As the basic nitrogen atom, a piperazine ring or a methyliminobispropyl structure is preferable. As a method for containing a basic nitrogen atom in the molecule of polyamide, a basic nitrogen-containing diamine containing a tertiary nitrogen atom such as a diamine having a piperazine ring or methylimiminobispropylamine can be used. Further, from the viewpoint of the elastic modulus of the polymer, it is particularly preferable to use a diamine having a piperazine ring. Examples of the diamine having a piperazine ring include 1,4-bis (3-aminoethyl) piperazine, 1,4-bis (3-aminopropyl) piperazine, and N- (2-aminoethyl) piperazine.

(Ii) Whether or not the tertiary nitrogen atom-containing polyamide is water-soluble or water-dispersible (water-developable) can be determined by immersing the polyamide alone in water at 30 ° C. or acidic water and rubbing it with a brush or the like. It can be determined. If the polyamide is uniformly mixed with water or acidic water after being physically rubbed with a brush or the like, the polyamide is determined to be water-soluble. On the other hand, if a part or the entire surface of the polyamide swells and is dispersed in water after being physically rubbed with a brush or the like, and the polyamide is non-uniformly mixed, the polyamide is determined to be water-dispersible. ..

(Ii) The tertiary nitrogen atom-containing polyamide contains 10 to 70 mol of structural units obtained from lactam and / or aminocarboxylic acid with respect to the total number of moles of all the structural units of the polyamide as long as the characteristics of the polyamide are not affected. % Can be contained. This makes it possible to impart crystallinity to the obtained polyamide.

(Ii) Polymerization of the tertiary nitrogen atom-containing polyamide can be carried out by a known method.

(Ii) The molar ratio (amino group / carboxyl group) of diamine and dicarboxylic acid for polymerizing the tertiary nitrogen atom-containing polyamide is 1.0 or more, preferably 1.01 or more. By setting the molar ratio in the above range, the polymer can be taken out after the polymerization is in equilibrium, and the fluctuation of the molecular weight can be suppressed.

(Ii) The tertiary nitrogen atom-containing polyamide is preferably copolymerized with a diamine, a dicarboxylic acid, or an aminocarboxylic acid having a basic tertiary nitrogen atom in the molecule. In that case, it is preferable to react with a quaternizing agent to obtain a soluble polymer compound having an ammonium salt-type nitrogen atom from the viewpoint of water solubility. As the quaternizing agent, known organic acids can be used, and aliphatic organic acids and aromatic organic acids can be used. Specific examples of the organic acid include methacrylic acid, acrylic acid, succinic acid, adipic acid, sebacic acid, glycolic acid, lactic acid and the like as the aliphatic organic acid, and benzoic acid and isophthalic acid as the aromatic organic acid. However, an aliphatic organic acid is preferable from the viewpoint of water solubility.

The (ii) tertiary nitrogen atom-containing polyamide containing 25 to 50 mol% of the ring-shaped structural unit obtained from the cyclohexanedicarboxylic acid of the present invention is preferably contained in the heat-sensitive mask layer in an amount of 5 to 40% by mass, more preferably. Is 5 to 30% by mass. If the content of the basic nitrogen-containing polyamide is not within the above range, the scratch resistance of the coating of the thermal mask layer may not be achieved. Further, if it exceeds 50% by mass, the flexibility of the mask layer is lowered, which is not preferable.

The heat-sensitive mask layer of the present invention contains (iii) an infrared absorber. Further, it may contain an ultraviolet absorbing substance that blocks ultraviolet light, but it may also be a substance that has both ablation efficiency and ultraviolet absorbing performance.

The (iii) infrared absorbing substance contained in the heat-sensitive mask layer of the present invention is not particularly limited as long as the infrared absorbing substance has a strong absorption property at a wavelength in the range of 750 nm to 20000 nm. For example, black pigments such as carbon black, carbon graphite and cyanine black, inorganic pigments such as manganese oxide, iron oxide, chromium oxide and copper chromate, phthalocyanine and substituted phthalocyanine derivatives, cyanine dyes, cyanine dyes, melanin dyes and polymethine. Pigments such as dyes and metal thiolate dyes can be mentioned. Among these, carbon black is particularly preferable from the viewpoint of satisfying both ablation efficiency and ultraviolet absorption performance.

Further, carbon black is preferable because it can be used in a wide range of particle size of 10 nm to 200 nm and the particle size can be selected. It is preferable that the particle size of carbon black can be reduced from the viewpoint of ablation efficiency.

The heat-sensitive mask layer of the present invention contains an ultraviolet absorbing substance in order to block ultraviolet rays. The ultraviolet absorbing substance is not particularly limited, but is preferably a compound having absorption in the region of 300 nm to 400 nm. For example, benzotriazole-based compounds, triazine-based compounds, benzophenone-based compounds, carbon black and the like can be mentioned. Two or more of these may be contained. Among these, carbon black is particularly preferably used because it has absorption characteristics not only in the ultraviolet region but also in the infrared region.

In the present invention, the content of the (iii) infrared absorbing substance in the mask layer element is preferably 2% by mass or more, more preferably 5% by mass or more, based on the total solid content of the mask layer element in order to improve the ablation efficiency. Further, if it is 10% by mass or more, it is not necessary to increase the film thickness of the mask layer in order to secure the light blocking property of ultraviolet rays. On the other hand, in order not to reduce the scratch resistance of the mask layer element, it is preferably 75% by mass or less, more preferably 70% by mass or less.

The heat-sensitive mask layer used in the printing original plate of the present invention may contain an anionic polymer as a component other than (i) to (iii). By containing the anionic polymer, the agglomeration of the constituents of (i) to (iii) can be prevented. In addition, as optional components other than these, fillers, surfactants, coating aids and the like can be contained within a range that does not impair the effects of the present invention. Further, a polyamide other than the (ii) tertiary nitrogen atom-containing polyamide may be contained as long as the effect of the present invention is not impaired.

By containing an anionic polymer in the heat-sensitive mask layer of the present invention, the dispersibility of carbon black becomes good, and even if the heat-sensitive mask layer is made thin, a heat-sensitive mask layer with less unevenness in transmitted optical density can be obtained. (I) When the partially saponified polyvinyl acetate contains an anionic group, (i) the partially saponified polyvinyl acetate may be used in combination with the anionic polymer. When an anionic polymer is contained, the dispersibility with carbon black is improved. As a result, the thickness of the heat-sensitive mask layer can be reduced without lowering the light-shielding property (optical density).

The anionic polymer used for the heat-sensitive mask layer is a polymer having an acidic group capable of forming a salt with a tertiary nitrogen atom in a basic polyamide, and a polymer having an anionic group. Examples of the acidic group capable of neutralizing with the tertiary nitrogen atom include a carboxyl group, a sulfonic acid group, and a phosphoric acid group. Examples of such an anionic polymer include an acrylic polymer obtained by copolymerizing a (meth) acrylic monomer having an anionic group, and a partially saponified polyvinyl acetate obtained by reacting an acid anhydride with a partially saponified polyvinyl acetate. Examples thereof include a polymer in which a carboxyl group is introduced into a polymer side chain by reacting a hydroxyl group in the polymer with an acid-free water substance.

It is preferable that such an anionic polymer is contained in the heat-sensitive mask layer in an amount of 5% by mass or more. By containing 5% by mass to 30% by mass of the anionic polymer, a salt is formed from the (ii) tertiary nitrogen atom-containing polyamide contained in the heat-sensitive mask layer, and (ii) the tertiary nitrogen atom is formed in the heat-sensitive mask layer. It is considered that the dispersibility of the contained polyamide is improved. This is especially noticeable in the case of anionic partially saponified polyvinyl acetate.

The film thickness of the heat-sensitive mask layer of the present invention is preferably 0.1 to 20 μm, more preferably 0.5 to 15 μm, and even more preferably 1 to 10 μm. If the film thickness exceeds 20 μm, the ablation property deteriorates, which is not preferable. If the film thickness is less than 0.1 μm, the ultraviolet light shielding property becomes insufficient, which is not preferable.

The CTP letterpress printing platen original plate of the present invention is a CTP letterpress printing platen original plate having at least a support, a photosensitive resin layer on the support, and a mask layer element in this order. In the CTP letterpress printing plate original plate of the present invention, a barrier layer and an adhesive force adjusting layer can be provided between the photosensitive resin composition layer and the mask layer element. The barrier layer and the adhesive force adjusting layer may be provided independently or may be laminated in two layers. Further, the adhesive force adjusting layer and the barrier layer may be one layer that also serves as the adhesive layer.

In the CTP letterpress printing plate original plate of the present invention, when a barrier layer is provided between the photosensitive resin composition layer and the mask layer element, polymerization damage due to oxygen and low molecular weight components in the photosensitive resin composition move to the heat-sensitive mask layer. It can be suppressed. In particular, by suppressing polymerization damage due to oxygen, it is possible to reproduce sharp edges without rounding the edges (boundary portions) of the image insolubilized by photocuring.

The binder polymer used for the barrier layer preferably contains polyvinyl alcohol, partially saponified vinyl acetate, alkyl cellulose, and a cellulosic polymer. These polymers are not limited to one type of use, and two or more types of polymers can be used in combination. Preferred polymers with oxygen barrier properties are polyvinyl alcohol, partially saponified vinyl acetate, and alkyl cellulose. Image reproducibility can be controlled by selecting a binder polymer having a preferable range of oxygen barrier properties.

The layer thickness of the (C) barrier layer is preferably 0.2 to 3.0 μm, more preferably 0.2 to 1.5 μm. If it is less than the above lower limit, the oxygen barrier property is insufficient, and the relief plate surface may be roughened. If the above upper limit is exceeded, the image may become thick.

The photosensitive resin layer used in the original plate of the present invention comprises essential components of a water-soluble or water-dispersible polymer, a photopolymerizable unsaturated compound, and a photopolymerization initiator, as well as a plasticizer, a thermal polymerization inhibitor, a dye, and a pigment. , UV absorbers, fragrances, or any additives such as antioxidants. As the photosensitive resin layer, a layer that can be developed with an aqueous developer is preferable.

Examples of the water-soluble or water-dispersible polymer used for the photosensitive resin layer of the present invention include a polyamide having an ether bond in the main chain, a polyamide having a basic nitrogen atom or a quaternary ammonium salt in the molecule, and a sulfone in the molecule. Polyamides having acid salts, partially sausified polyvinyl acetate and modified partially sausaged polyvinyl acetate, polyacrylamides, cellulose-based polymers, polyvinyl butyral, polyvinylpyrrolidone, etc., but from the aspect of water solubility, polyamides having an ether bond in the main chain, Polyamides having a basic nitrogen atom or a quaternary ammonium salt in the molecule, partially saponified polyvinyl acetate and derivatives thereof are preferable.

As the photosensitive resin layer, a polymer having a photopolymerizable unsaturated group polymerizable group introduced into the side chain as partially saponified polyvinyl acetate can also be used. The photopolymerizable unsaturated group is a functional group that can be crosslinked by a radical reaction, and examples thereof include a vinyl group and a (meth) acryloyl group.

When partially saponified polyvinyl acetate having a photopolymerizable unsaturated group introduced into the side chain is used, it is preferable because the photopolymerization reactivity is improved and a fine relief image can be formed.

The partially saponified polyvinyl acetate having a photopolymerizable unsaturated group in the side chain can be synthesized, for example, by the following method. The partially saponified polyvinyl acetate is reacted with the acid anhydride, and a carboxyl group is introduced into the polymer side chain with respect to the hydroxyl group of the partially saponified polyvinyl acetate. A photopolymerizable unsaturated group is introduced by reacting the carboxyl group with an unsaturated epoxy compound. Further, as another method, the following method can be mentioned. A polymer is obtained by copolymerizing vinyl acetate with an unsaturated carboxylic acid or an unsaturated carboxylic acid ester. A photopolymerizable unsaturated group can be introduced by reacting a carboxyl group obtained by partially saponifying the polymer with a photopolymerizable unsaturated group-containing epoxy compound. Among them, the partially saponified polyvinyl acetate obtained by the former method is preferable because it is easy to synthesize.

Such a photopolymerizable unsaturated group is preferably present in the compound in an amount of 0.10 to 0.70 mol / kg, more preferably 0.15 to 0.35 mol / kg. When the content is 0.10 mol / kg or more, the reactive group reacts and the crosslink density with the polymer is improved, so that the problem that a fine relief image is chipped during development is improved. By setting the content to 0.70 mol / kg or less, good water developability can be maintained.

When the partially saponified polyvinyl acetate having a photopolymerizable unsaturated group introduced into the side chain is imparted with water developability, the saponification degree is preferably 60 to 99 mol%, more preferably 70 to 95 mol%. When the saponification degree is 60 mol% or more, the water solubility is improved and sufficient water developability can be obtained. The average degree of polymerization is preferably in the range of 300 to 1500, more preferably 500 to 1000. By setting the average degree of polymerization to 300 or more, the water resistance is improved and sufficient water resistance can be obtained. By setting the average degree of polymerization to 1500 or less, the water solubility is improved and sufficient water developability can be obtained.

The water-soluble or water-dispersible polymer is preferably contained in the photosensitive resin composition layer in an amount of 10 to 70% by mass. When it is contained in an amount of 10 to 70% by mass, a photosensitive resin composition layer having high thickness accuracy can be formed.

As the (iii) photopolymerizable unsaturated compound (hereinafter, also referred to as (iii) component), those conventionally used by those skilled in the art can be used, for example, having a 5- to 7-membered ring. It preferably contains a heterocyclic-containing photopolymerizable unsaturated compound. The heterocyclic-containing photopolymerizable unsaturated compound having a 5- to 7-membered ring may have a functional group of a hydroxyl group, a carboxyl group, or an amino group in the heterocycle. Since the heterocycle and the functional group are hydrogen-bonded to the hydroxyl group in the component (i), the compatibility with the component (i) can be enhanced. The heterocyclic-containing photopolymerizable unsaturated compound having a 5- to 7-membered ring preferably has a molecular weight of 300 or less. As the molecular weight increases, the compatibility with the component (i) may decrease.

Examples of the (iii) component include benzyl (meth) acrylate, cyclohexyl (meth) acrylate, phenoxymethyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, phenoxydiethylene glycol (meth) acrylate, and 2- (meth) acryloyl. Loxyethyl hexahydrophthalic acid, 2-hydroxy-3-phenoxypropyl (meth) acrylate, 2- (meth) acryloyl oxyethyl phthalic acid, neopentyl glycol- (meth) acrylic acid-benzoic acid ester, (meth) acryloyl Examples thereof include morpholine and N-phenyl (meth) acrylamide, and (meth) acryloylmorpholine is particularly preferable.

Examples of the photopolymerizable unsaturated compound other than the heterocyclic-containing photopolymerizable unsaturated compound having a 5- to 7-membered ring include a ring-opening addition reaction product of polyglycidyl ether of a polyhydric alcohol and methacrylic acid and acrylic acid. Examples thereof include esterified compounds of polyhydric alcohol and methacrylic acid and acrylic acid. Examples of the polyhydric alcohol include dipentaerythritol, pentaerythritol, trimethylolpropane, glycerin, propylene glycol, ethylene glycol, diethylene glycol, triethylene glycol, and an ethylene oxide adduct of phthalic acid, among which glycerin and propylene glycol are used. Is preferable.

The content of these photopolymerizable unsaturated compounds in the photosensitive resin composition layer is preferably 5 to 200 parts by mass with respect to 100 parts by mass of the polymer. When printing with ink, 5 parts by mass or more is preferable from the viewpoint of suppressing swelling of the printing plate. Further, 200 parts by mass or less is preferable because the photosensitive resin layer can be easily formed.

The photopolymerization initiator used for the photosensitive resin layer of the present invention generates radicals by light absorption, and conventionally known ones can be used. For example, benzoin alkyl ethers, benzophenones, anthraquinones, benzyls, acetophenones, diacetyls and the like can be mentioned. The amount used in the photosensitive resin composition is preferably 0.1 to 5% by mass.

Any component such as a surface active agent, an antifoaming agent, a fragrance, and a polymerization inhibitor can be added to the photosensitive resin layer of the present invention. The plasticizer is for increasing flexibility, and specific examples thereof include ethylene glycol, diethylene glycol, triethylene glycol, glycerin and its derivatives, trimethylolpropane and its derivatives, trimethylolethane and its derivatives, and pentaerythritol. And polyhydric alcohols such as derivatives thereof. The amount of these plasticizers used is preferably 20% by mass or less based on the total mass of the photosensitive resin composition of the present invention. The polymerization inhibitor is for increasing thermal stability, and specific examples thereof include phenols, hydroquinones, catechols, hydroxyamine derivatives and the like. The amount of these polymerization inhibitors used is preferably 0.001 to 5% by mass based on the total mass of the photosensitive resin composition of the present invention.

It is preferable that the CTP letterpress printing plate original plate of the present invention is provided with a support. As the support, a material that is flexible but has excellent dimensional stability is preferable, and for example, a metal support such as steel, aluminum, copper, nickel, and stainless steel, polyethylene terephthalate film, polyethylene naphthalate film, and polybutylene. Examples thereof include a support made of a thermoplastic resin such as a terephthalate film or a polycarbonate film. Among these, polyethylene terephthalate film having excellent dimensional stability and sufficiently high viscoelasticity is particularly preferable. The thickness of the support is preferably 50 to 350 μm, preferably 100 to 250 μm, from the viewpoint of mechanical properties, shape stability, handleability at the time of printing plate making, and the like. On the other hand, in applications where a metal support is required, an aluminum or stainless steel support is preferable, and the thickness of the support is preferably 180 to 320 μm. Further, if necessary, in order to improve the adhesiveness between the support and the photosensitive resin layer, an adhesive may be provided between them.

The method for producing the CTP letterpress printing original plate of the present invention is not particularly limited, but is generally produced as follows.
First, a component such as a binder other than carbon black in the heat-sensitive mask layer is dissolved in an appropriate solvent, and carbon black is dispersed therein to prepare a dispersion liquid. Next, such a dispersion liquid is applied onto a support for a heat-sensitive mask layer (for example, a PET film) to evaporate the solvent. Then, the protective layer component is overcoated to prepare one laminate. Further, separately from this, a photosensitive resin layer is formed on the support by coating to prepare the other laminated body. The two laminates thus obtained are laminated under pressure and / or heating so that the photosensitive resin layer is adjacent to the protective layer. The support for the heat-sensitive mask layer functions as a protective film (cover film) on the surface of the printing original plate after completion.

As a method for producing a printing plate from the printing original plate of the present invention, if a protective film is present, the protective film is first removed from the photosensitive printing plate. Then, the heat-sensitive mask layer is irradiated like an image with an IR laser to form a mask on the photosensitive resin layer. Examples of suitable IR lasers include ND / YAG lasers (1064 nm) or diode lasers (eg, 830 nm). Laser systems suitable for computer to plate technology are commercially available and, for example, CDI Spark (Esco Graphics) can be used. The laser system includes a rotating cylindrical drum holding a printing plate, an IR laser irradiation device, and a layout computer, and image information is transferred directly from the layout computer to the laser device.

After the image information is written on the heat-sensitive mask layer, the photosensitive printing original plate is irradiated with active light on the entire surface through the mask. This can be done with the plate attached to the laser cylinder, but removing the plate from the laser device and irradiating it with a conventional flat plate irradiation unit is advantageous in that it can handle non-standard plate sizes. It is common. As the active light beam, ultraviolet rays having a wavelength of 150 to 500 nm, particularly 300 to 400 nm can be used. As the light source, a low pressure mercury lamp, a high pressure mercury lamp, an ultrahigh pressure mercury lamp, a metal halide lamp, a xenon lamp, a zirconium lamp, a carbon arc lamp, a fluorescent lamp for ultraviolet rays and the like can be used. The irradiated plate is then developed to obtain a print plate. The developing step can be carried out in a conventional developing unit.

[Preparation of thermal mask layer coating liquid]
A dispersion binder was dissolved in a solvent according to the composition (weight ratio) shown in the heat-sensitive mask layer composition in Table 1, and carbon black was dispersed therein to prepare a dispersion liquid, which was used as a heat-sensitive mask layer coating liquid.

[Creation of thermal mask layer]
A bar coater in which a heat-sensitive mask layer coating solution is appropriately selected on a PET film support (Toyobo Co., Ltd., E5000, thickness 100 μm) that has been subjected to mold release treatment on both sides so that the layer thickness is 1.5 μm. Was applied and dried at 120 ° C. for 5 minutes to prepare a heat-sensitive mask film provided with a heat-sensitive mask layer.

[Creation of CTP printing original plate]
In the CTP printing original plate of the present embodiment, for example, a heat-sensitive mask layer is formed on a cover film, and the heat-sensitive mask layer forming surface side and the photosensitive resin layer side laminated on the support are brought into close contact with each other and pressure-bonded. Can be manufactured by. Specifically, a film having a heat-sensitive mask layer is adhered and laminated on a photosensitive resin composition layer laminated and formed on a polyethylene terephthalate support (an adhesive layer having an anti-halation effect may be provided if necessary). Thereby, it can be molded into a CTP printing original plate.

The performance of each heat-sensitive mask layer obtained as described above was evaluated as follows.
Light-shielding property: Using a black-and-white transmission densitometer DM-520 (Dainippon Screen Mfg. Co., Ltd.), the optical density of the heat-sensitive mask layer prepared on the PET film support was measured. The optical density is required to be 2.3 or more, preferably 2.5 or more.
Scratch resistance: The obtained CTP printing original plate was cut into a square of 20 cm × 20 cm, the cover film was removed, and a CTP printing original plate having a heat-sensitive mask layer as the uppermost layer was prepared. A PET film and a metal plate are superposed on the surface of the heat-sensitive mask layer, and after maintaining the state and rubbing once in the left-right direction under its own weight without applying force, the scratches formed on the surface of the heat-sensitive mask layer are removed. It was visually evaluated using a 10x loupe. The evaluation was performed according to the following criteria. The PET film used was E5000 manufactured by Toyobo Co., Ltd. (thickness 100 μm), and the metal plate used was a stainless steel plate (SUS304) having a thickness of 100 μm.
◎: There are no visible scratches.
◯: There are no scratches of 50 μm or more, but there are 4 or less scratches of less than 50 μm.
Δ: There are 1 to 4 scratches of 50 μm or more.
X: There are 5 or more scratches of 50 μm or more.

[(I) -1 Preparation of partially saponified vinyl acetate]
As the partially saponified polyvinyl acetate, a commercially available partially saponified polyvinyl acetate "KL-03" (polymerization degree: about 300, saponification degree: 80 mol%) (i) -1 manufactured by Nippon Synthetic Chemical Industry Co., Ltd. was prepared.

[(I) -Synthesis of modified partially saponified polyvinyl acetate having a carboxyl group in the side chain]
The prepared partially saponified vinyl acetate "KL-03" (polymerization degree: about 300, saponification degree: 80 mol%) was swollen in acetone, 1.0 mol% anhydrous succinic acid was added, and the mixture was stirred at 60 ° C. for 6 hours. A carboxylic acid-modified partially saponified polyvinyl acetate (i) -2 having a carboxyl group added to the molecular chain was obtained. The polymer was washed with acetone to remove unreacted succinic anhydride and dried. The acid value was measured and found to be 9.8 mgKOH / g.

[(I) -Synthesis of modified partially saponified polyvinyl acetate having a photopolymerizable unsaturated group in the side chain]
(I) 100 parts of the modified partially saponified polyvinyl acetate obtained in -2 was dissolved in 200 parts of a mixed solvent of ethanol / water = 30/70 (mass ratio) at 80 ° C. Six parts of glycidyl methacrylate were added thereto to introduce a reactive group into the partially saponified polyvinyl acetate. From the analysis results by the potential difference drip method, it was confirmed that the carboxyl group in the polymer reacted with the epoxy group of glycidyl methacrylate and the metachloro group was introduced into the side chain of the polymer, and (i) photopolymerization on the side chain which is a component. A modified partially saponified polyvinyl acetate (i) -3 having a sex unsaturated group was obtained.

[(Ii) Synthesis of basic nitrogen-containing polyamide]
According to the composition of the polyamide shown in Table 1, (ii) -1 of the polyamide used in Example 1 was synthesized. 460 parts of ε-caprolactam, 266 parts of cyclohexanedicarboxylic acid, 274 parts of 1,4-bis (3-aminopropyl) piperazine, 5 parts of 50% hypophosphorous acid aqueous solution, and 1000 parts of water were charged in an autoclave, and after nitrogen substitution. , Sealed and heated gradually. From the time when the internal pressure reached 0.4 MPa, water was distilled off until the pressure could not be maintained, the pressure was returned to normal pressure in about 2 hours, and then the reaction was carried out at normal pressure for 1 hour. The relative viscosity of the obtained polyamide was 2.01. The composition of the polyamide was measured by 1 H-NMR, and it was confirmed that there was no difference between the charged composition and the polymer composition. For the polyamides of Examples 2 to 8 and Comparative Examples 1 to 3, the polyamides used for the heat-sensitive mask layer were obtained by the same polymerization method as in Example 1 according to the composition of Table 1. The polyamide composition in Table 1 represents mol%. The mol% of the polyamide composition was determined by 1 H-NMR measurement.

[Anionic polymer]
The carboxylic acid-modified partially saponified polyvinyl acetate of (i) -2 synthesized with carboxylic acid-modified partially saponified polyvinyl acetate was prepared as a polymer that also serves as an anionic polymer.

The anionic polymer is an ethylene-acrylic acid copolymer "SG-2000" (manufactured by Namariichi Co., Ltd., 20% by mass aqueous solution, water absorption rate) as a commercially available anionic polymer other than the synthesized carboxylic acid-modified partially saponified polyvinyl acetate. 1.2%, carboxylic acid content 14 wt%) was prepared and used in Example 4.

Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited thereto. The number of copies in the examples (text) represents parts by mass.

Hereinafter, the present invention will be described in detail with reference to Examples.

Example 1
The components (i) and (ii) of Example 1 shown in Table 2 were added to a three-necked flask equipped with a stirring spatula and a cooling tube, and "Solmix" (registered trademark) H-11 (alcohol) was added. After mixing 50 parts of the mixture, 50 parts of Nippon Alcohol Co., Ltd. and 50 parts of water, the mixture was heated at 90 ° C. for 2 hours with stirring to dissolve the components (i) and (ii). After cooling to 70 ° C., other components were added and stirred for 60 minutes to obtain a photosensitive resin composition solution.

A PET film support (Toyobo Co., Ltd., E5000, thickness 125 μm) coated with a polymerized polyester adhesive was prepared. The support having the adhesive layer was obtained by coating an adhesive composition containing an ultraviolet absorber on a polyester film having a thickness of 250 μm so as to have a coating film thickness of 20 μm.

Next, a heat-sensitive mask layer film provided with a heat-sensitive mask layer was prepared.
According to the composition (weight ratio) described in the heat-sensitive mask layer composition of Table 1, 35 parts by mass of (i) -1 partially saponified vinyl acetate and 30 parts by mass of polyamide (ii) -1 of Example 1 were dispersed in a solvent. As the solvent, a mixed solution of water, ethanol and n-propanol in a weight ratio of 30:40:30 was used. 35 parts by mass of carbon black was dispersed in the solution to obtain a thermal mask layer coating liquid used in Example 1.

A bar coater in which a heat-sensitive mask layer coating solution is appropriately selected on a PET film support (Toyobo Co., Ltd., E5000, thickness 100 μm) that has been subjected to mold release treatment on both sides so that the layer thickness is 1.5 μm. Was applied and dried at 120 ° C. for 5 minutes to prepare a heat-sensitive mask layer film.

Next, a CTP letterpress printing original plate was created.
A photosensitive resin composition solution prepared in the composition ratio of Example 1 in Table 2 was flowed onto a PET film support (Toyobo Co., Ltd., E5000, thickness 125 μm) coated with a copolymerized polyester adhesive. A laminated body of the photosensitive resin layer C1 from which the solvent was removed by rolling and heating was obtained. A heat-sensitive mask film was superposed on the heat-sensitive mask layer so that the heat-sensitive mask layer was in contact with the photosensitive resin layer. A CTP composed of a PET support, an adhesive layer, a photosensitive resin layer, a barrier layer, a heat-sensitive mask layer, and a release-treated PET protective film (cover film) having a thickness of 125 μm, laminated at 100 ° C. using a heat press machine. Toppan printing original plate was obtained. The total thickness of the plate was 1.08 mm.

Examples 2-11, Comparative Examples 1-3
A photosensitive resin composition was prepared in the same manner as in Example 1 except that the composition of the heat-sensitive mask layer and the photosensitive resin layer were changed to those shown in Table 3, and a printing original plate was obtained. The obtained printing plate was evaluated in the same manner as in Example 1. These evaluation results are shown in Table 2 together with the compositions of the photosensitive resin compositions of Examples 2 to 11 and Comparative Examples 1 to 3.

The details of the (iii) photopolymerizable unsaturated compound (iii-1 to iii-4), the photopolymerization initiator, the plasticizer, and the thermal polymerization inhibitor shown in Table 2 are as follows.
iii-1: 4-acryloylmorpholin manufactured by KJ Chemicals Co., Ltd. iii-2: 2-acryloyloxyethyl-phthalate HOA-MPL (N) manufactured by Kyoeisha Chemical Co., Ltd. iii-3: 2-hydroxy-3-acryloyloxypropyl Methacrylate NK Ester 701A Shin-Nakamura Chemical Co., Ltd. iii-4: Propylene glycol Diepoxy acrylate Epoxy ester 70PA Kyoeisha Chemical Co., Ltd. Plasticity agent: Diethylene glycol Thermal polymerization initiator: Hydroquinone monomethyl ether Photopolymerization initiator: Benzyldimethylketal

Performance evaluation was performed using the obtained heat-sensitive mask layer and CTP letterpress printing original plate. The results of these performance evaluations are shown in Table 3 below.

As is clear from Table 1, the heat-sensitive mask layer is a basic nitrogen-containing polyamide containing at least carbon black, partially saponified vinyl acetate, and 25 to 50 mol% of alicyclic structural units obtained from cyclohexanedicarboxylic acid in the molecule. In Examples 1 to 11 containing the above, both light-shielding property and high scratch resistance capable of withstanding a metal support are excellent. Regarding scratch resistance, the alicyclic structural unit obtained from cyclohexanedicarboxylic acid is particularly excellent in Examples 5 to 9 having a high content. Further, when the heat-sensitive mask layer contains an anionic polymer, the optical density is high even if the coat thickness is the same, indicating that the dispersibility of carbon black is improved.
On the other hand, Comparative Example 1 which does not contain the basic nitrogen-containing polyamide containing the alicyclic structural unit and Comparative Examples 2 and 3 having a low content are inferior in scratch resistance to the metal support.

Claims (7)

A photosensitive CTP letterpress printing original plate in which a heat-sensitive mask layer containing (i) partially saponified polyvinyl acetate, (ii) a tertiary nitrogen atom-containing polyamide, and (iii) an infrared absorber is provided on a photosensitive resin layer. Therefore, (ii) the tertiary nitrogen atom-containing polyamide is cyclohexanedicarboxylic with respect to the total of aminocarboxylic acid units (including the case of lactam as a raw material), dicarboxylic acid units, and diamine units in the polyamide molecule. A photosensitive CTP letterpress printing original plate containing 20 to 50 mol% of structural units obtained from an acid and 50 to 95 mol% of a total of alicyclic structural units. (Ii) The photosensitive CTP letterpress printing original plate according to claim 1, wherein the tertiary nitrogen atom-containing polyamide contains a piperazine ring in the molecule. (I) The photosensitive of claim 1 or claim 2, wherein the partially saponified polyvinyl acetate is a modified partially saponified polyvinyl acetate having a photopolymerizable unsaturated group and / or a carboxyl group in the side chain. CTP letterpress printing original plate. The photosensitive CTP letterpress printing original plate according to any one of claims 1 to 3, wherein the heat-sensitive mask layer further contains an anionic polymer. (Iii) The photosensitive CTP letterpress printing original plate according to any one of claims 1 to 3, wherein the infrared absorber is carbon black. A photosensitive CTP letterpress printing original plate in which the photosensitive resin composition layer contains partially saponified polyvinyl acetate and a 5- to 7-membered heterocyclic compound having a photopolymerizable group. The photosensitive CTP letterpress printing original plate according to claim 6, wherein the photosensitive resin composition layer further contains a basic polyamide.