JP6891590B2 - CTP resin 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, and particularly while maintaining a high light-shielding property while being a thin film. The present invention relates to a CTP letter plate printing original 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 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.

CTP technology replaces traditionally used negative films with 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 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).

A heat-sensitive mask 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 prevent the transmission of chemical radiation to the photopolymerization layer, and is ablated by an infrared laser. The thermal mask layer is preferably a thin film from the viewpoint of ablation efficiency and wrinkles, but when the concentration of carbon black is increased in order to make the thermal mask layer thinner, the thermal mask layer becomes brittle and the thermal mask layer is scratched. There was a problem that occurred.

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 storage elastic modulus and a 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 is used as a photopolymerizable unsaturated compound with the passage of time. There is a problem that the scratch resistance is 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 is also a demand for a resin letterpress printing original plate using a metal support, and when the metal support comes into contact with the surface of the mask layer, higher scratch resistance is required.

Special Table No. 7-506201 Japanese Unexamined Patent Publication No. 2009-300588 Japanese Unexamined Patent Publication No. 2012-137515

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 thermal mask layer without designing a complicated resin composition. By containing the binder, the scratches generated on the heat-sensitive mask layer are highly reduced. More specifically, the purpose is to reduce the occurrence of scratches on the surface of the CTP layer due to frictional force.

As a result of diligent studies to achieve the above object, the present inventors contained 25 to 50 mol% of alicyclic structural units obtained from cyclohexanedicarboxylic acid in the molecule as a film-forming polymer in the thermal mask layer. We have found a CTP letter plate printing original plate having a heat-sensitive mask layer that reduces the occurrence of scratches due to frictional force on the surface of the CTP layer by containing a basic nitrogen-containing polyamide, and also achieves good dispersibility of carbon black. Has been completed.

That is, the present invention has the following configurations (1) to (4).
(1) (1) A photosensitive letterpress printing original plate in which at least (A) support, (B) photosensitive resin layer, and (C) heat-sensitive mask layer are sequentially laminated, and (C) heat-sensitive mask layer is Contains at least 25-50 mol% of alicyclic structural units obtained from carbon black, 1,4-cyclohexanedicarboxylic acid and / or 1,3- cyclohexanedicarboxylic acid relative to the total number of moles of all polyamide structural units. A CTP letterpress printing original plate containing a basic nitrogen-containing polyamide.
(2) The CTP letterpress printing according to (1), wherein the heat-sensitive mask layer (C) further contains one or more dispersants selected from the group consisting of butyral resin, polyvinyl alcohol and modified polyvinyl alcohol. Original version.
(3) As the alicyclic structural unit other than the alicyclic structural unit obtained from cyclohexanedicarboxylic acid in the molecule of the basic nitrogen-containing polyamide, the structural unit obtained from isophorone diamine is the total mole of all polyamide structural units. The CTP letterpress printing original plate according to (1) or (2), which is a basic nitrogen-containing polyamide containing 5 to 15 mol% with respect to the number.
(4) The CTP letterpress printing original plate according to any one of claims 1 to 3, wherein the photosensitive resin layer contains a basic nitrogen-containing polyamide.

According to the present invention, it is possible to provide a CTP letterpress printing original plate having a high degree of scratch resistance that reduces the occurrence of scratches due to frictional force on the surface of the CTP 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 CTP letterpress printing original plate of the present invention has a structure in which at least (A) a support, (B) a photosensitive resin layer, and (C) a heat-sensitive mask layer are sequentially laminated. Further, a (D) barrier layer may be provided between (B) the photosensitive resin layer and (C) the heat-sensitive mask layer.

The support (A) used in the original plate of the present invention is preferably a material having flexibility but excellent dimensional stability, for example, a metal support such as steel, aluminum, copper, nickel, or stainless steel, or polyethylene. Examples thereof include a support made of a thermoplastic resin such as a terephthalate film, a polyethylene naphthalate film, a polybutylene terephthalate film, or a polycarbonate film. Among these, a 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 during 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, an adhesive may be provided between the support and the photosensitive resin layer in order to improve the adhesiveness between them.

The (B) photosensitive resin layer used in the original plate of the present invention contains essential components of a synthetic polymer compound, a photopolymerizable unsaturated compound, and a photopolymerization initiator, and a plasticizer, a thermal polymerization inhibitor, a dye, and a pigment. , UV absorbers, fragrances, or any additives such as antioxidants. The photosensitive resin layer is preferably one that can be developed with an aqueous developer.

As the synthetic polymer compound used in the (B) photosensitive resin layer in the present invention, a conventionally known soluble synthetic polymer compound can be used, for example, polyetheramide (for example, JP-A-55-79437), poly. Ether ester amide (for example, JP-A-58-113537, etc.), tertiary nitrogen-containing polyamide (for example, JP-A-50-76055, etc.), ammonium salt-type tertiary nitrogen atom-containing polyamide (for example, JP-A-53-36555). Publication, etc.), an addition polymer of an amide compound having one or more amide bonds and an organic diisocyanate compound (for example, JP-A-58-140737, etc.), an addition polymer of a diamine and an organic diisocyanate compound having no amide bond (for example, JP-A-58-140737). Japanese Patent Application Laid-Open No. 4-97154, etc.), modified polyvinyl alcohol (WO2014 / 021322 International Publication, etc.) and the like. Among them, a tertiary nitrogen atom-containing polyamide and an ammonium salt-type tertiary nitrogen atom-containing polyamide are preferable.

Examples of the photopolymerizable unsaturated compound include a cycloaddition reaction product of a polyhydric alcohol polyglycidyl ether with methacrylic acid and acrylic acid. Examples of the polyhydric alcohol include dipentaerythritol, pentaerythritol, trimethylolpropane, glycerin, ethylene glycol, diethylene glycol, triethylene glycol, and ethylene oxide adducts of phthalic acid, and among them, trimethylolpropane is preferable.

Examples of the photopolymerization initiator include benzophenones, benzoins, acetophenones, benzyls, benzoin alkyl ethers, benzylalkyl ketals, anthraquinones, thioxanthones and the like. Specifically, benzophenone, chlorobenzophenone, benzoin, acetophenone, benzyl, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, benzyl dimethyl ketal, benzyl diethyl ketal, benzyl diisopropyl ketal, anthraquinone, 2-ethylanthraquinone. , 2-Methylanthraquinone, 2-allylanthraquinone, 2-chloroanthraquinone, thioxanthone, 2-chlorothioxanthone and the like.

The (C) thermal mask layer used in the printing original plate of the present invention is obtained from carbon black, which is a material having a function of absorbing an infrared laser and converting it into heat and a function of blocking ultraviolet light, and cyclohexanedicarboxylic acid. It is composed of a basic nitrogen-containing polyamide containing 25 to 50 mol% of the alicyclic structural unit. More preferably, it contains a dispersant. In addition, as an optional component other than these, a filler, a surfactant, a coating aid, or the like can be contained within a range that does not impair the effects of the present invention. Further, as the polyamide, a polyamide containing no alicyclic structural unit obtained from cyclohexanedicarboxylic acid may be contained.

The basic nitrogen-containing polyamide containing 25 to 50 mol% of alicyclic structural units obtained from the cyclohexanedicarboxylic acid used for the (C) heat-sensitive mask layer of the present invention functions as a film-forming polymer. Further, by using a dispersant in combination, the dispersibility of carbon black can be improved, which can contribute to high light-shielding properties. However, when the dispersant alone is used, the coating of the thermal mask layer becomes brittle and the scratch resistance is inferior. Therefore, in the present invention, in order to overcome this high degree of scratch resistance, a basic nitrogen-containing polyamide containing 25 to 50 mol% of a ring-shaped structural unit obtained from cyclohexanedicarboxylic acid is used as the film-forming polymer.

A basic nitrogen-containing polyamide containing 25 to 50 mol% of an alicyclic structural unit obtained from cyclohexanedicarboxylic acid in the molecule with respect to the total number of moles of all polyamide structural units is a diamine or dicarboxylic acid constituting the polyamide. Basic nitrogen in which the mol% of the alicyclic structural unit obtained from cyclohexanedicarboxylic acid is 25 to 50 mol% in the molecule with respect to the total number of moles of the structural unit obtained from the acid, aminocarboxylic acid or lactam. It is a containing polyamide.

Since the basic nitrogen-containing polyamide obtained from cyclohexanedicarboxylic acid has a high Tg, it is possible to impart wear resistance to the heat-sensitive mask layer.
Further, since the heat-sensitive mask layer made of polyamide containing a ring-shaped structural unit obtained from butyral resin and cyclohexanedicarboxylic acid is easily dispersed in water, it is particularly suitable to be used as a heat-sensitive mask layer for a water-developed plate. it can.

If the proportion of the alicyclic structural unit obtained from the cyclohexanedicarboxylic acid in the polyamide is less than the above range, the scratch resistance is lowered, which is not preferable. On the other hand, if it exceeds the above range, the thermal mask layer becomes too hard and cracks are likely to occur when bending stress is applied, which is not preferable.

The molar% of structural units in the polyamide of the present invention indicates the number of moles of each structural unit to the total number of moles of each unit consisting of aminocarboxylic acid or lactam unit, diamine and dicarboxylic acid. The mol% of each structural unit can be calculated from the number of moles in the raw material charging stage or the measurement result of 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.

Examples of the basic nitrogen-containing copolymer polyamide containing 25 to 50 mol% of the alicyclic structural unit obtained from cyclohexanedicarboxylic acid in the molecule include 1,4-cyclohexanedicarboxylic acid and 1.3-cyclohexanedicarboxylic acid. A method of manufacturing using it is conceivable.

As the partner diamine that polycondenses with the cyclohexanedicarboxylic acid, an alkylene diamine having 4 to 8 carbon atoms is preferable. Specific examples of the alkylenediamine having 4 to 8 carbon atoms include 1,4-tetramethylenediamine, 2-methylpentamethylenediamine, 1,6-hexanediamine, and 1,8-octanediamine.

The basic nitrogen-containing polyamide used in the present invention contains alicyclic structural units obtained from other alicyclic diamines or dicarboxylic acids in addition to the alicyclic structural units obtained from cyclohexanedicarboxylic acid as alicyclic structural units. It 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). Cyclohexane and norbornyldiamine can be mentioned, but isophoronediamine is preferable from the viewpoint of physical properties.

When a structural unit obtained from isophorone diamine is introduced, it is preferable to contain 5 to 15 mol% of the structural unit obtained from isophorone diamine from the viewpoint of physical properties, and cracking of the thermal mask layer can be reduced.

As the basic nitrogen-containing polyamide of the present invention, 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, polyetheramine JEFFAMINE ED900 and the like. Examples of known aliphatic dicarboxylic acids other than the alicyclic dicarboxylic acid include glutaric acid, adipic acid, sebacic acid, and decandicarboxylic acid.

The basic nitrogen-containing polyamide of the present invention 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-developable) by containing the basic nitrogen atom. ) Can be given. As a method for containing a basic nitrogen atom, a basic nitrogen-containing diamine containing a tertiary nitrogen atom such as a diamine having a piperazine ring or methyliminobispropylamine 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.
Thereby, crystallinity can be imparted to the obtained polyamide.

As the basic nitrogen-containing polyamide of the present invention, known diamines or dicarboxylic acids can be used in addition to the alicyclic diamine or alicyclic dicarboxylic acid 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, polyetheramine JEFFAMINE ED900 and the like.

As the dicarboxylic acid used for the basic nitrogen-containing polyamide of the present invention, a known aliphatic dicarboxylic acid other than the alicyclic dicarboxylic acid can be used. Examples of the aliphatic dicarboxylic acid include glutaric acid, adipic acid, sebacic acid, decandicarboxylic acid and the like.

Whether or not the basic nitrogen-containing polyamide of the present invention is water-soluble or water-dispersible (water-developable) is determined by immersing the polyamide alone in water or acidic water at 30 ° C. and rubbing it with a brush or the like. can do. 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 is swollen and 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. ..

The basic nitrogen-containing polyamide of the present invention contains 10 to 70 mol% of structural units obtained from lactam and / or aminocarboxylic acid within a range that does not affect the characteristics of the polyamide, based on the total number of moles of all the structural units of the polyamide. can do. Thereby, crystallinity can be imparted to the obtained polyamide.

The polymerization of the polyamide of the present invention can be carried out by a known method.

The molar ratio of diamine to dicarboxylic acid (amino group / carboxyl group) for polymerizing the polyamide of the present invention is 1.0 or more, preferably 1.01 or more. By setting the molar ratio in the above range, it is possible to take out the polymer after the polymerization is in equilibrium, and it is possible to suppress fluctuations in the molecular weight.

The polyamide used in the present invention is preferably copolymerized with a diamine, dicarboxylic acid, or 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 organic acids include methacrylic acid, acrylic acid, succinic acid, adipic acid, sebacic acid, glycolic acid, lactic acid and the like as aliphatic organic acids, and benzoic acid and isophthalic acid as aromatic organic acids. However, an aliphatic organic acid is preferable from the viewpoint of water solubility.

The basic nitrogen-containing polyamide containing 25 to 50 mol% of the cyclic structural unit obtained from the cyclohexanedicarboxylic acid of the present invention preferably contains 25 to 60% by mass, more preferably 30 to 50% by mass in the heat-sensitive mask layer. %. 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.

The dispersant used in the present invention is contained in the heat-sensitive mask layer in order to disperse carbon black. The ratio of the dispersant to carbon black is preferably 25:75 to 25.

The dispersant contains one or more dispersants selected from the group consisting of butyral resin, polyvinyl alcohol and modified polyvinyl alcohol. By containing the dispersant, it is possible to obtain a heat-sensitive mask layer having less unevenness in transmitted optical density even if the heat-sensitive mask layer is thinned. Butyral resin and modified polyvinyl alcohol are preferable from the dispersibility.

The butyral resin used in the dispersant of the present invention is also called polyvinyl butyral, and is a kind of polyvinyl acetal produced by reacting polyvinyl alcohol and butyraldehyde with an acid catalyst.

The modified polyvinyl alcohol used in the dispersant of the present invention is a polyvinyl alcohol modified by using a polyvinyl alcohol having a saponification degree of 70% or more and 90% or less. Polyvinyl alcohol having a saponification degree of 70% or more and 90% or less has a hydroxyl group and can be denatured by reacting with the hydroxyl group. As another modification method, modification is also possible by copolymerizing a polymerizable monomer having a polar group.

The specific modified polyvinyl alcohol used in the dispersant of the present invention is a modified polyvinyl alcohol having a nonionic hydrophilic group such as polyvinyl alcohol or ethylene oxide having an anionic polar group or a cationic polar group introduced therein. The modified polyvinyl alcohol is preferably alcohol-soluble, and by selecting alcohol-soluble, a solvent containing alcohol can be used to prepare a coating liquid for the thermal barrier layer, which is preferable. Methods for introducing a carboxyl group into polyvinyl alcohol include a method of reacting with an acid anhydride, a reaction with a carboxylic acid compound having an epoxy group, and a copolymerization of a monomer having a carboxylic acid. Examples include -318 and T-350 manufactured by Nippon Synthetic Chemical Co., Ltd. On the other hand, as a method for introducing a cation group, a method for copolymerizing a monomer having a cation group, a reaction with a cation group-containing compound having an epoxy group, and the like can be mentioned, and commercially available products include a cation group (quaternary ammonium salt). There is Gosenex K-434 of Nippon Synthetic Chemical Co., Ltd., which has introduced the above into the side chain. On the other hand, the modified polyvinyl alcohol having a nonionic hydrophilic group is a modified polyvinyl alcohol having a nonionic hydrophilic group of alkylene glycol, specifically, a nonionic modified polyvinyl alcohol having a hydrophilic ethylene oxide group in the side chain. Examples thereof include WO-320R manufactured by Kagaku Co., Ltd.

In the CTP letterpress printing original plate of the present invention, a barrier layer may be provided between (B) the photosensitive resin layer and (C) the thermal mask layer. By providing the barrier layer, it is possible to suppress polymerization damage due to oxygen and the movement of low molecular weight components in the photosensitive resin composition to the heat-sensitive mask layer. 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 barrier polymer preferably contains polyvinyl alcohol, partially saponified vinyl acetate, alkyl cellulose, and a cellulosic polymer as the binder polymer. These polymers are not limited to one type of use, and two or more types of polymers can be used in combination. Polymers having a preferable oxygen barrier property 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 thickness of the barrier layer (D) 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, fine line reproduction failure may occur.

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 thermal 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 thermal mask layer functions as a protective film (cover film) on the surface of the printing master 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 plate making techniques are commercially available and, for example, CDI Spark (Esco Graphics) can be used. The laser system includes a rotating cylindrical drum that holds the original 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 thermal 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 irradiation unit is advantageous in that it can handle nonstandard plate sizes. And 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 ultra-high-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.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto. The number of copies in the examples (text) represents parts by mass. The polyamide composition in Table 1 represents mol%. The mol% of the polyamide composition was determined by 1 H-NMR measurement. The evaluation of the characteristic values in the examples was based on the following method.

The performance of each thermal mask layer obtained as described above was evaluated as follows.
Light-shielding property: The optical density of the heat-sensitive mask layer formed on the PET film support was measured using a black-and-white transmission densitometer DM-520 (Dainippon Screen Mfg. Co., Ltd.).
Scratch resistance: A heat-sensitive mask layer created on a PET film support is cut into a square of 20 cm × 20 cm, and another PET film (Toyobo Co., Ltd., E5000, thickness 100 μm) is superposed on the layer surface, and the state thereof. After rubbing once in each of the left and right directions without applying force, the scratches formed on the surface of the thermal mask layer were inspected using a 10-fold loupe.
◯: No scratches.
Δ: There are 1 to 4 scratches of 50 μm or more.
X: There are 5 or more scratches of 50 μm or more.
Crack resistance: The prepared CTP letterpress printing original plate was cut into a width of 20 cm and a length of 20 cm, and used as an evaluation sample. Samples were prepared by storing the samples on a flat table in a homeothermic room at 5 ° C or 25 ° C for 24 hours. After that, the cover sheet of the sample is peeled off, and as an alternative evaluation of the infrared ablation device, it is wrapped around a cylindrical roll (diameter 200 mm) so that the thermal mask layer is on the outside and fixed for 5 minutes, and then removed and placed on a flat place. It was allowed to stand for 5 minutes. Then, the surface of the heat-sensitive mask layer was visually observed, and the judgment was made according to the following criteria.
×: Cracks were confirmed on the entire surface of the CTP layer Δ: Cracks were confirmed on a part of the CTP layer ○: Cracks were not confirmed on the CTP layer

<Synthesis of basic nitrogen-containing polyamide>
The polyamide used in Example 1 was synthesized according to the composition of the polyamide shown in Table 1. 339 parts of ε-caprolactam, 602 parts of cyclohexanedicarboxylic acid, 501 parts of 1,4-bis (3-aminopropyl) piperazine, 170 parts of isophoronediamine, 5 parts of 50% hypophosphorous acid aqueous solution, and 1000 parts of water in an autoclave. After charging and replacing with nitrogen, the mixture was sealed and gradually heated. 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 2.05. 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 10, according to the composition of Table 1, the polyamide for a film-forming polymer used for the heat-sensitive mask layer was obtained by the same polymerization method as in Example 1.

<Dispersant>
C-1: BM-5 manufactured by Sekisui Chemical Co., Ltd. was used as the butyral resin.
C-2: As the modified polyvinyl alcohol, WO-320R manufactured by Nippon Synthetic Chemistry Co., Ltd. was used as a nonionic special modified polyvinyl alcohol having a hydrophilic ethylene oxide group in the side chain.

Preparation of heat-sensitive mask layer coating liquid According to the composition (weight ratio) described in the heat-sensitive mask layer composition in Table 1, a dispersion binder is dissolved in a solvent, and carbon black is dispersed therein to prepare a dispersion liquid, and the heat-sensitive mask layer coating is performed. It was used as a working solution. As the solvent, a mixed solution of methanol and ethanol in a weight ratio of 70:30 was used.

Creation of a heat-sensitive mask layer A PET film support (Toyobo Co., Ltd., E5000, thickness 100 μm) that has been demolded on both sides is coated with a heat-sensitive mask layer coating solution so that the layer thickness is 1.5 μm. The film was applied using an appropriately selected bar coater and dried at 120 ° C. for 5 minutes to prepare a heat-sensitive mask layer.

Preparation 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 a support are formed. It can be manufactured by bringing them into close contact with each other and crimping them. Specifically, a film having a heat-sensitive mask layer is adhered and laminated on a photosensitive resin composition layer laminated on a polyethylene terephthalate support (an adhesive layer having an antihalation effect may be provided if necessary). As a result, it can be molded into a CTP printing original plate.

The performance of each thermal mask layer obtained as described above was evaluated as follows.
Light-shielding property: The optical density of the heat-sensitive mask layer formed on the PET film support was measured using a black-and-white transmission densitometer DM-520 (Dainippon Screen Mfg. Co., Ltd.). 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 without applying force, the scratches formed on the surface of the heat-sensitive mask layer are multiplied by 10 times. Visual evaluation was performed using a 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.

Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited thereto.

Example 1
Add 520 parts of ε-caprolactam, 400 parts of N, N'-bis (γ-aminopropyl) piperazine adipate, 80 parts of 1,3-bisaminomethylcyclohexane adipate and 1000 parts of water to the reactor and perform sufficient nitrogen substitution. After that, it is sealed and gradually heated, and when the internal pressure reaches 10 kg / cm ² , the water in the reactor is gradually distilled to return to normal pressure in about 1 hour, and then to normal pressure for 0.5 hours. Reacted with. A transparent pale yellow polyamide having a maximum polymerization temperature of 210 ° C., a melting point of 140 ° C. and a specific viscosity of 1.83 was obtained.

55.0 parts of the obtained polymer, 7.7 parts of N-methyltoluenesulfonic acid amide, 0.02 part of 1,4-naphthoquinone, 50.0 parts of methanol and 10 parts of water in a heat-dissolving kettle equipped with a stirrer. After mixing at 60 ° C. for 2 hours to completely dissolve the polymer, 30.1 parts of the acrylic acid adduct of trimethylolpropane triglycidyl ether, 3.1 parts of methacrylic acid and 0.1 parts of hydroquinone monomethyl ether were added. Parts, 0.3 part of ammonium sulfite and 1.0 part of benzyl dimethyl ketal were mixed and dissolved for 30 minutes. Next, the temperature was gradually raised to distill out methanol and water, and the temperature in the kettle was concentrated until the temperature reached 110 ° C. At this stage, a fluid and viscous photosensitive resin composition was obtained.

Next, a CTP letterpress printing original plate was created.
The photosensitive resin composition of the reference example is placed on a PET film support (Toyobo Co., Ltd., E5000, thickness 125 μm) coated with a copolymerized polyester adhesive, and a heat-sensitive mask film is superposed on the photosensitive resin composition. It was. A CTP composed of a PET support, an adhesive layer, a photosensitive resin layer, a barrier layer, a heat-sensitive mask layer, and a PET protective film (cover film) having a thickness of 125 μm, which is 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.

Performance evaluation was performed using the obtained thermal mask layer and CTP letterpress printing original plate. The results of these performance evaluations are shown in Table 1 below.

The results of these performance evaluations are shown in Table 1 below.

As is clear from Table 1, the heat-sensitive mask layer contained at least carbon black and a basic nitrogen-containing polyamide containing 25 to 50 mol% of alicyclic structural units obtained from cyclohexanedicarboxylic acid in the molecule. In Examples 1 to 4, both light-shielding property and high scratch resistance capable of withstanding a metal support are excellent. Regarding scratch resistance, the content of the basic nitrogen-containing polyamide containing the alicyclic structural unit obtained from cyclohexanedicarboxylic acid is high in Example 4 and the alicyclic structural unit obtained from cyclohexanedicarboxylic acid. Is particularly excellent in Example 7. 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 (4)

A photosensitive letterpress printing original plate in which at least (A) a support, (B) a photosensitive resin layer, and (C) a heat-sensitive mask layer are sequentially laminated, and (C) the heat-sensitive mask layer is at least carbon black, 1, A basic nitrogen-containing polyamide containing 25 to 50 mol% of alicyclic structural units obtained from 4-cyclohexanedicarboxylic acid and / or 1,3-cyclohexanedicarboxylic acid with respect to the total number of moles of all polyamide structural units. CTP letterpress printing original plate characterized by containing. (C) The CTP letterpress printing original plate according to claim 1, wherein the heat-sensitive mask layer further contains one or more dispersants selected from the group consisting of butyral resin, polyvinyl alcohol and modified polyvinyl alcohol. As the alicyclic structural unit other than the alicyclic structural unit obtained from cyclohexanedicarboxylic acid in the molecule of the basic nitrogen-containing polyamide, the structural unit obtained from isophorone diamine is added to the total number of moles of all polyamide structural units. The CTP letterpress printing original plate according to claim 1 or 2, wherein the polyamide is a basic nitrogen-containing polyamide containing 5 to 15 mol%. (B) The CTP letterpress printing original plate according to any one of claims 1 to 3, wherein the photosensitive resin layer contains a basic nitrogen-containing polyamide.