JP2018165772A - CTP flexographic printing original plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flexographic printing original plate having a heat-sensitive mask layer with the reduced occurrence of scratches due to friction.SOLUTION: A flexographic printing original plate has (A) a support, (B) a photosensitive resin layer, and (C) a heat-sensitive mask layer which are laminated in this order. The (C) heat-sensitive mask layer at least has carbon black, and a basic nitrogen-containing polyamide containing an alicyclic structural unit derived from cyclohexane dicarboxylate, of 25-50 mol% in the molecule as a coat-forming polymer.SELECTED DRAWING: None

Description

The present invention relates to a CTP flexographic printing original plate (hereinafter referred to as “CTP flexographic printing original plate”) used for producing a flexographic printing plate by computer plate making technology, and in particular, while maintaining a high light-shielding property while being a thin film. The present invention relates to a flexographic printing plate having a heat-sensitive mask layer having high scratch resistance.

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

In CTP technology, a conventionally used negative film is replaced by a mask that is formed and integrated in a printing plate to cover areas that should not be photopolymerized. As a method of obtaining this integrated mask, there is a method of forming an image mask by providing an infrared sensitive layer (thermal mask layer) opaque to actinic radiation on a photosensitive resin layer and evaporating the thermal mask with an infrared laser. Widely used (see Patent Document 1).

 As the heat-sensitive mask layer, a material composed 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 actinic 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 if the carbon black concentration is increased to make the thermal mask layer thinner, the thermal mask layer becomes brittle and the thermal mask layer is damaged. There was a problem that occurred.

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

As a method for improving the friction resistance of the thermal mask layer, a flexographic resin containing a binder polymer having a storage elastic modulus and a glass transition temperature within a specific range in the thermal mask layer and having the same structure as the photosensitive resin layer. A CTP version is disclosed in Patent Document 3. However, since the thermal mask layer contains an acrylic resin, the (meth) acrylate compound used as a photopolymerizable unsaturated compound from the photosensitive resin layer after processing into the flexo CTP plate is a thermal mask over time. There was a problem that the scratch resistance was lowered by shifting to the layer and 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 that of the photosensitive resin layer, and there is a problem that the resin composition design becomes more complicated.

Recently, there is also a demand for a flexographic printing plate using a metal support, and when the metal support is in contact with the mask layer surface, higher scratch resistance is required.

JP 7-506201 A JP 2009-300588 A JP 2012-137515 A

  The present invention has been made in view of the current state of the prior art as described above, and its purpose is to include a specific polyamide binder in the thermal mask layer without designing a complicated resin composition. Thus, scratches generated in the heat-sensitive mask layer are highly reduced. More specifically, it is to reduce the generation of scratches due to frictional force on the surface of the CTP layer.

As a result of intensive studies to achieve the above object, the present inventors have contained 25 to 50 mol% of an alicyclic structural unit obtained from cyclohexanedicarboxylic acid in the molecule as a film-forming polymer in the heat-sensitive mask layer. A photosensitive flexographic printing master having a heat-sensitive mask layer that reduces the generation of scratches due to frictional force on the surface of the CTP layer and also achieves good dispersibility of carbon black by incorporating a basic nitrogen-containing polyamide is found. The invention has been completed.

That is, the present invention has the following configurations (1) to (4).
(1) A photosensitive flexographic printing plate in which at least (A) a support, (B) a photosensitive resin layer, and (C) a thermal mask layer are sequentially laminated, and (C) the thermal mask layer is at least carbon black. And 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. CTP flexographic printing master.
(2) (C) The thermosensitive mask layer further contains one or more dispersants selected from the group consisting of butyral resin, polyvinyl alcohol, and modified polyvinyl alcohol. The CTP flexographic printing plate according to (1), .
(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 isophoronediamine is the total moles of all structural units of the polyamide. The CTP flexographic printing original plate according to (1) or (2), wherein the basic nitrogen-containing polyamide is contained in an amount of 5 to 15 mol% based on the number.
(4) The CTP flexographic printing original plate as described in any one of (1) to (3), wherein the photosensitive resin layer contains a latex.

  According to the present invention, it is possible to provide a CTP flexographic printing original plate having high scratch resistance in which generation of scratches due to frictional force is reduced on the surface of the CTP layer while maintaining good carbon black dispersibility.

  Hereinafter, the flexographic printing plate precursor of the present invention will be described in detail.

  The flexographic printing plate precursor of the present invention has a configuration in which at least (A) a support, (B) a photosensitive resin layer, and (C) a thermal mask layer are sequentially laminated. Further, a (D) barrier layer may be provided between (B) the photosensitive resin layer and (C) the thermosensitive mask layer.

  The (A) support used in the original plate of the present invention is flexible, but is preferably a material excellent in dimensional stability. For example, a metal support such as steel, aluminum, copper, or nickel, a polyethylene terephthalate film And a thermoplastic resin support such as 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 from 50 to 350 μm, preferably from 100 to 250 μm, from the viewpoint of mechanical properties, shape stability, or handleability during plate making. Moreover, in order to improve the adhesiveness of a support body and the photosensitive resin layer, you may provide an adhesive agent between them as needed.

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

  The photosensitive resin layer (B) of the present invention contains a solid hydrophobic synthetic rubber other than latex in the photosensitive resin composition as long as the water developability does not decrease in order to improve the physical properties of the photosensitive resin layer. Also good. A preferable range is 1 to 10% by mass. Hydrophobic synthetic rubber includes butadiene polymer, isoprene polymer, acrylonitrile-butadiene copolymer, acrylonitrile-isoprene copolymer, acrylonitrile-isoprene copolymer, methyl methacrylate-isoprene copolymer, methyl acrylate-chloroprene. A copolymer, a methyl acrylate-chloroprene copolymer, an acrylonitrile-butadiene-styrene copolymer, and the like can be given. Among these, a butadiene polymer, an isoprene polymer, and an acrylonitrile-butadiene copolymer are preferable from the viewpoint of rubber elasticity, but it is more preferable to have the same skeleton structure as latex.

  Polymers obtained from usable latexes include polybutadiene latex, natural rubber latex, styrene-butadiene copolymer latex, acrylonitrile-butadiene copolymer latex, polychloroprene latex, polyisoprene latex, polyurethane latex, and methyl methacrylate-butadiene. Water-dispersed latex polymers such as copolymer latex, vinylpyridine polymer latex, butyl polymer latex, thiocol polymer latex, and acrylate polymer latex, and other components such as acrylic acid and methacrylic acid are copolymerized with these polymers And the resulting polymer. Among these, an aqueous dispersion latex polymer containing a butadiene skeleton or an isoprene skeleton in the molecular chain is preferably used from the viewpoint of hardness and rubber elasticity. Specifically, polybutadiene latex, styrene-butadiene copolymer latex, acrylonitrile-butadiene copolymer latex, methyl methacrylate-butadiene copolymer latex, and polyisoprene latex are preferable. Latex needs to be confirmed as independent fine particles. Two or more types of latex may be mixed.

  The heat-sensitive mask layer (C) used in the printing original plate of the present invention is obtained from carbon black, which is a material having a function of absorbing infrared laser and converting it into heat, and a function of blocking ultraviolet light, and cyclohexanedicarboxylic acid. And a basic nitrogen-containing polyamide containing 25 to 50 mol% of an alicyclic structural unit. More preferably, it contains a dispersant. Further, as optional components 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. Moreover, as a polyamide, you may contain the polyamide which does not contain the alicyclic structural unit obtained from a cyclohexane dicarboxylic acid.

The basic nitrogen-containing polyamide containing 25 to 50 mol% of an alicyclic structural unit obtained from cyclohexanedicarboxylic acid used in the heat-sensitive mask layer (C) of the present invention functions as a film-forming polymer. Furthermore, 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 heat-sensitive mask layer becomes brittle and has poor scratch resistance. Therefore, in the present invention, in order to overcome this high scratch resistance, a basic nitrogen-containing polyamide containing 25 to 50 mol% of a cyclic 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 based on 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 in the molecule is 25 to 50 mol% with respect to the total number of moles of the structural unit obtained from the acid, aminocarboxylic acid or lactam Containing polyamide.

Since the basic nitrogen-containing polyamide obtained from cyclohexanedicarboxylic acid has a high Tg, it is considered that it was possible to impart friction resistance to the heat-sensitive mask layer. In addition, since a heat-sensitive mask layer made of polyamide containing a cyclic structural unit obtained from butyral resin and cyclohexanedicarboxylic acid is easily dispersed in water, it is particularly preferably used as a heat-sensitive mask layer for a water-developed plate. it can.

  When the ratio of the alicyclic structural unit obtained from cyclohexanedicarboxylic acid in the polyamide is less than the above range, scratch resistance is lowered, which is not preferable. On the other hand, if the above range is exceeded, the heat-sensitive mask layer becomes too hard, and cracking tends to occur when bending stress is applied, which is not preferable.

  The mol% of the structural unit in the polyamide of the present invention indicates the number of moles of each structural unit relative to the total number of moles of each unit composed of an aminocarboxylic acid or lactam unit, a diamine and a 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. Analysis by H-NMR is a commonly performed analysis method, in which the mol% of each structural unit is calculated from the integral value.

  The basic nitrogen-containing copolymer polyamide containing 25 to 50 mol% of an alicyclic structural unit obtained from cyclohexanedicarboxylic acid in the molecule is 1,4-cyclohexanedicarboxylic acid or 1.3-cyclohexanedicarboxylic acid. It is preferable to manufacture by the method of using and manufacturing.

  As a partner diamine to be polycondensed with cyclohexanedicarboxylic acid, an alkylenediamine having 4 to 8 carbon atoms is preferable. Specific examples of the alkylene diamine having 4 to 8 carbon atoms include 1,4-tetramethylene diamine, 2-methylpentamethylene diamine, 1,6-hexane diamine, and 1,8-octane diamine.

  The basic nitrogen-containing polyamide used in the present invention includes alicyclic structural units obtained from other alicyclic diamines or dicarboxylic acids in addition to 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-cyclohexane diamine, 1,3-cyclohexane diamine, 1,3-bis (aminomethyl) cyclohexane, 1,4-bis (aminomethyl). Although cyclohexane and norbornyl diamine are mentioned, isophorone diamine is more preferable.

In the case of introducing a structural unit obtained from isophorone diamine, it is preferable from the viewpoint of physical properties that the structural unit obtained from isophorone diamine is contained in an amount of 5 to 15 mol%, 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 alicyclic groups can be used as long as the properties of the polyamide are not affected. Aliphatic diamines include ethylenediamine, diethylenediamine, 1,3-propylenediamine, 1,4-tetramethylenediamine, 2-methylpentamethylenediamine, 1,6-hexanediamine, 1,11-undecamethylenediamine, 1 , 12-dodecanediamine, 2,2,4,2,4,4-trimethylhexamethylenediamine, or polyetheramine JEFFAMINE ED900. Examples of known aliphatic dicarboxylic acids other than alicyclic dicarboxylic acids include glutaric acid, adipic acid, sebacic acid, and decanedicarboxylic 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. By containing the basic nitrogen atom, water solubility or water dispersibility (water developability) ). Examples of the method of containing a basic nitrogen atom include using a basic nitrogen-containing diamine containing a tertiary nitrogen atom such as a diamine having a piperazine ring or methyliminobispropylamine. Furthermore, it is particularly preferable to use a diamine having a piperazine ring from the viewpoint of the elastic modulus of the polymer. Examples of the diamine having a piperazine ring include 1,4-bis (3-aminoethyl) piperazine, 1,4-bis (3-aminopropyl) piperazine, N- (2-aminoethyl) piperazine, and the like.
Thereby, crystallinity can be imparted to the resulting polyamide.

  In the basic nitrogen-containing polyamide of the present invention, a known diamine or dicarboxylic acid can be used in addition to the alicyclic diamine or alicyclic dicarboxylic acid as long as the properties of the polyamide are not affected. Aliphatic diamines include ethylenediamine, diethylenediamine, 1,3-propylenediamine, 1,4-tetramethylenediamine, 2-methylpentamethylenediamine, 1,6-hexanediamine, 1,11-undecamethylenediamine, 1 , 12-dodecanediamine, 2,2,4,2,4,4-trimethylhexamethylenediamine, or polyetheramine JEFFAMINE ED900.

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

  Whether 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 30 ° C water or acidic water and rubbing with a brush or the like. can do. When 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, after physically rubbing with a brush or the like, if a part or the whole of the polyamide swells and disperses in water, and the polyamide is mixed inhomogeneously, 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 in a range that does not affect the properties of the polyamide with respect to the total number of moles of all polyamide structural units. can do. Thereby, crystallinity can be imparted to the resulting polyamide.

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

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

  The basic nitrogen-containing polyamide used in the present invention is preferably copolymerized using a diamine, dicarboxylic acid, aminocarboxylic acid or lactam having a basic tertiary nitrogen atom in the molecule. In that case, it is preferable to react with a quaternizing agent to form 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, and lactic acid as aliphatic organic acids, and benzoic acid and isophthalic acid as aromatic organic acids. However, aliphatic organic acids are preferred from the viewpoint of water solubility.

The thermal mask layer (C) of the present invention preferably contains 30 to 60% by mass, more preferably 30%, of a basic nitrogen-containing polyamide containing 25 to 50 mol% of a cyclic structural unit obtained from cyclohexanedicarboxylic acid. -50 mass%. If the content of the basic nitrogen-containing polyamide is not within the above range, the scratch resistance of the heat-sensitive mask layer may not be achieved.

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

  The dispersant contains one or more dispersants selected from the group consisting of a butyral resin, polyvinyl alcohol, and modified polyvinyl alcohol. By containing the dispersant, a heat-sensitive mask layer with little transmission optical density unevenness can be obtained even if the heat-sensitive mask layer is thinned. Butyral resin and modified polyvinyl alcohol are preferred from the dispersibility of carbon black.

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 polyvinyl alcohol modified with 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 modified by reacting with the hydroxyl group. As another modification method, the modification can also be performed by copolymerizing a polymerizable monomer having a polar group.

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 into which an anionic polar group or a cationic polar group has been introduced. The modified polyvinyl alcohol is preferably alcohol-soluble, and is preferable because the coating solution for the heat-sensitive barrier layer can be prepared using a solvent containing alcohol by selecting the alcohol-soluble property. As a method for introducing a carboxyl group into polyvinyl alcohol, there are 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. -318 and Nippon Synthetic Chemical Co., Ltd. T-350. On the other hand, examples of the method for introducing a cation group include a method of copolymerizing a monomer having a cation group, a reaction with a cation group-containing compound having an epoxy group, and a commercially available product is a cation group (quaternary ammonium salt). And Goseinex K-434 manufactured by Nippon Synthetic Chemical Co., Ltd. On the other hand, a modified polyvinyl alcohol having a nonionic hydrophilic group of alkylene glycol as a modified polyvinyl alcohol having a nonionic hydrophilic group, specifically, a nonionic modified polyvinyl alcohol having a hydrophilic ethylene oxide group in the side chain. Chemical-made WO-320R etc. are mentioned.

In the CTP flexographic printing original plate of the present invention, a (D) 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 failure due to oxygen and migration of low molecular weight components in the photosensitive resin composition to the thermal mask layer. Examples of the binder polymer in the barrier layer include polyvinyl alcohol, partially saponified vinyl acetate, alkyl cellulose, and 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 having oxygen barrier properties are polyvinyl alcohol, partially saponified vinyl acetate, and alkyl cellulose. Image reproducibility can be controlled by selecting a binder polymer having an oxygen barrier property in a preferable range.

(D) The thickness of the barrier layer is preferably 0.2 μm to 3.0 μm, more preferably 0.2 μm 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, there is a risk that fine line reproduction failure will occur.

The method for producing the CTP flexographic printing original plate of the present invention is not particularly limited, but is generally produced as follows.
First, components such as a binder other than carbon black of the heat-sensitive mask layer are dissolved in a suitable solvent, and carbon black is dispersed therein to prepare a dispersion. Next, such a dispersion is applied onto a support for a thermal mask layer (for example, a PET film), and the solvent is evaporated. Thereafter, the protective layer component is overcoated to produce one laminate. Further, separately from this, a photosensitive resin layer is formed on the support by coating, and the other laminate is prepared. The two laminates thus obtained are laminated so that the photosensitive resin layer is adjacent to the protective layer under pressure and / or heating. The heat-sensitive mask layer support functions as a protective 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, when a protective film is present, the protective film is first removed from the photosensitive printing plate. Thereafter, the thermal mask layer is irradiated imagewise with an IR laser to form a mask on the photosensitive resin layer. Examples of suitable IR lasers include ND / YAG laser (1064 nm) or diode laser (eg, 830 nm). Laser systems suitable for computer plate making technology are commercially available, and for example, CDI Spark (Esco Graphics) can be used. This laser system includes a rotating cylindrical drum that holds a printing original, an IR laser irradiation device, and a layout computer, and image information is directly transferred 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 actinic rays 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 with a conventional flat irradiation unit is advantageous in that it can cope with non-standard plate sizes. It is general. As the actinic ray, 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, an ultraviolet fluorescent lamp, or the like can be used. Thereafter, the irradiated plate is developed to obtain a printing plate. The development step can be performed with a conventional development unit.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these. In the examples (text), the number of parts represents parts by mass. Moreover, the polyamide composition of Table 1 represents mol%. The mol% of the polyamide composition was determined by H-NMR measurement. In addition, evaluation of the characteristic value in an Example depended on the following method.

<Synthesis of basic nitrogen-containing polyamide>
According to the polyamide composition shown in Table 1, the polyamide used in Example 1 was synthesized. In an autoclave, 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% aqueous hypophosphorous acid solution, and 1000 parts of water After charging and replacing with nitrogen, it 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 reacted at normal pressure for 1 hour. The obtained polyamide had a relative viscosity of 2.05. The composition of the polyamide was measured by H-NMR, and it was confirmed that there was no difference between the charged composition and the polymer composition. The polyamides of Examples 2 to 10 were obtained according to the compositions in Table 1 to obtain a polyamide for a film-forming polymer used for the heat-sensitive mask layer by the same polymerization method as in Example 1.

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

Preparation of thermal mask layer coating liquid Dispersion binder was dissolved in a solvent according to the composition (weight ratio) described in the thermal mask layer composition of Table 1, and carbon black was dispersed therein to prepare a dispersion liquid. A working liquid was used. As the solvent, a mixed solution of 70:30 by weight of methanol and ethanol was used.

Preparation of heat-sensitive mask layer A heat-sensitive mask layer coating solution is applied to a PET film support (Toyobo Co., Ltd., E5000, thickness 100 μm) subjected to release treatment on both sides so that the layer thickness becomes 1.5 μm. Coating was performed using an appropriately selected bar coater, and drying was performed at 120 ° C. for 5 minutes to form a thermal mask layer.

Production of CTP printing original plate The CTP printing original plate of this embodiment comprises, for example, a thermal mask layer formed on a cover film, and the thermal mask layer forming surface side and the photosensitive resin layer side laminated on the support. It can be manufactured by closely contacting and pressing. Specifically, a film having a thermal mask layer is closely laminated on a photosensitive resin composition layer formed on a polyethylene terephthalate support (an adhesive layer having an antihalation effect may be provided if necessary). Thus, it can be formed 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 higher, preferably 2.5 or higher.
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 whose uppermost layer was a thermal mask layer was prepared. A PET film and a metal plate are superposed on the surface of the heat-sensitive mask layer, and the scratches formed on the surface of the heat-sensitive mask layer are 10 times after being rubbed once in the left-right direction without applying force while maintaining the state. Visual evaluation was performed using a loupe. Evaluation was performed according to the following criteria. The PET film was E5000 manufactured by Toyobo Co., Ltd. (thickness: 100 μm), and the metal plate was a stainless steel plate (SUS304) having a thickness of 100 μm.
A: No scratches that can be confirmed.
○: 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.

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited thereto.

Example 1 Acrylonitrile-butadiene latex (Nipol SX1503, nonvolatile content 42%, manufactured by Nippon Zeon Co., Ltd.) 10 parts by weight, butadiene latex (Nipol LX111NF nonvolatile content 55%, manufactured by Nippon Zeon Co., Ltd.) 58 parts by weight, oligobutadiene acrylate (ABU) -2S Kyoeisha Chemical Co., Ltd.) 28 parts by weight, lauryl methacrylate (Light Ester L Kyoeisha Chemical Co., Ltd.) 4 parts by weight, dimethylol tricyclodecane diacrylate 4 parts by weight, photopolymerization initiator 1 part by weight, polymerization 0.1 part by weight of hydroquinone monomethyl ether as an inhibitor and 0.1 part by weight of a nonionic surfactant as another additive were mixed in a container together with 15 parts by weight of toluene, and then at 105 ° C. using a pressure kneader. Knead, then remove toluene and water under reduced pressure. Accordingly, to obtain a photosensitive resin composition.

  Next, a CTP flexographic printing original plate was prepared. 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 copolyester adhesive, and a thermal mask film is overlaid thereon. It was. Lamination was performed at 100 ° C. using a heat press machine to obtain a flexographic printing original plate comprising a PET support, an adhesive layer, a photosensitive resin layer, a barrier layer, a thermal mask layer, and a release-treated PET protective film (cover film). The total thickness of the plate was 1.90 mm.

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

As is apparent 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 an alicyclic structural unit obtained from cyclohexanedicarboxylic acid in the molecule. In Examples 1 to 4, both the light shielding property and the high scratch resistance that can withstand a metal support are excellent. For scratch resistance, the content of basic nitrogen-containing polyamide contained in Example 4 in which the alicyclic structural unit obtained from cyclohexanedicarboxylic acid has a high content and the alicyclic structural unit obtained from cyclohexanedicarboxylic acid In Example 7, which is high, this is particularly excellent. On the other hand, in Comparative Example 1 not containing the basic nitrogen-containing polyamide containing the alicyclic structural unit and Comparative Examples 2 to 3 having a low content, the scratch resistance against the metal support is poor.

Claims (4)

  A photosensitive flexographic printing 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 formed of carbon black and molecules. A CTP flexographic printing plate comprising a basic nitrogen-containing polyamide containing 25 to 50 mol% of an alicyclic structural unit obtained from cyclohexanedicarboxylic acid with respect to the total number of moles of all polyamide structural units. .   The CTP flexographic printing original plate according to claim 1, wherein the (C) 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 isophoronediamine is based on the total number of moles of all structural units of the polyamide. The CTP flexographic printing plate precursor according to claim 1 or 2, wherein the basic nitrogen-containing polyamide is 5 to 15 mol%. (B) The CTP flexographic printing original plate according to any one of claims 1 to 3, wherein the photosensitive resin layer contains a latex.