JP7124512B2 - Photosensitive CTP flexographic printing original plate - Google Patents

Description

TECHNICAL FIELD The present invention relates to a photosensitive CTP flexographic printing original plate used for producing letterpress printing plates by computer plate making technology. It relates to a flexographic printing original plate.

In recent years, in the field of flexographic printing, computer to plate technology (CTP technology) known as digital image forming technology has become extremely popular. The CTP technique is a method of directly outputting computer-processed information onto an original printing plate to obtain a relief pattern of protrusions and recesses. This technology eliminates the negative film manufacturing process, reducing costs and the time required to make negatives.

In CTP technology, the traditionally used negative film is replaced by a mask that is formed and integrated within the printing plate to cover the areas that should not be photopolymerized. As a method for obtaining this integrated mask, an infrared-sensitive layer opaque to actinic rays (heat-sensitive mask layer) is provided on the photosensitive resin layer, and an infrared laser is used to evaporate this infrared-sensitive layer to form an image mask. is widely used (see Patent Document 1).

The heat-sensitive mask layer is generally composed of carbon black, which is a radiation-opaque material, and a binder. The thermal mask layer is ablated by an infrared laser, and thinner layers are preferred in terms of ablation efficiency. In addition, the thinner the film, the less the influence of wrinkles on the relief. However, the heat-sensitive mask layer is generally required to have a transmission optical density (light-shielding property) of 2.0 or more in order to prevent transmission of radiation through the photopolymerizable layer.

The photosensitive flexo CTP original printing plate of Patent Document 1 is composed of a photosensitive resin layer, a protective layer, and an infrared-sensitive layer, and the protective layer is also called a barrier layer. The barrier layer placed between the photosensitive resin layer and the infrared-sensitive layer has the function of preventing material transfer between the photosensitive resin layer and the infrared-sensitive layer and preventing polymerization inhibition of the photosensitive resin layer by atmospheric oxygen. It has a protective function and plays an important role.

However, when such a water-developable photosensitive resin layer is used as a photosensitive resin layer of a CTP plate, there is a problem that wrinkles occur on the plate surface due to the high flexibility of the photosensitive resin. The wrinkles are generated when the plate is removed from the drum and returned to a flat surface after being attached to the drum during laser processing. The above problem is particularly pronounced when a photosensitive resin layer containing latex as a main component is used. It is believed that this is because latex exists in the form of fine particles and the plate is more flexible.

Regarding the problem of wrinkles, Patent Document 2 describes adding a large amount of a specific plasticizer to polyvinyl alcohol, which is the binder polymer of the protective layer (barrier layer), to soften the protective layer and prevent the occurrence of wrinkles. It is suggested to reduce Moreover, Patent Document 3 proposes to reduce the occurrence of wrinkles by appropriately controlling the Young's modulus and layer thickness of the protective layer.

Recently, the photosensitive CTP flexographic printing original plate is becoming the main platemaking technology, replacing the analog plate using a negative film. As a result, the original CTP printing plate has to be operated under a wide range of environmental conditions, from high temperature and high humidity environments to low temperature and low humidity environments. As a result, the barrier layer of the original CTP printing plate was prone to wrinkles under low humidity conditions, especially under low temperature and low humidity conditions. However, the original printing plates of Patent Documents 2 and 3 cannot effectively prevent the occurrence of wrinkles in a low-temperature, low-humidity environment. Therefore, a photosensitive CTP flexographic printing original plate having a high-performance barrier layer that prevents the occurrence of wrinkles under low-temperature and low-humidity environmental conditions and provides a flat-top shape without thickening of highlight halftone dots is provided. strongly desired.

Japanese Patent Publication No. 7-506201 Patent No. 5573675 Patent No. 4332865

The present invention was invented in view of the current state of the above-mentioned prior art, and the object thereof is to prevent the occurrence of wrinkles during handling of a CTP printing original plate against environmental changes over the course of a year and to provide excellent barrier properties. An object of the present invention is to provide a photosensitive CTP flexographic printing original plate. In particular, it is an object of the present invention to provide a photosensitive flexographic printing original plate free from wrinkles even in a low-temperature and low-humidity environment.

As a result of intensive research to achieve the above object, the present inventors have found that a polymer derived from polyethylene glycol or a polyethylene glycol copolymer in the molecule between (C) the heat-sensitive mask layer and (B) the photosensitive resin layer. By providing a (D) barrier layer made of a polyamide resin containing 15 to 35% by mass of a polyether that The present invention has been completed.

That is, the present invention has the following configurations (1) to (4).
(1) A photosensitive CTP flexographic printing original plate comprising at least (A) a support, (B) a photosensitive resin layer, and (C) a heat-sensitive mask layer, which are sequentially laminated, comprising (C) a heat-sensitive mask layer and (B) Water developable, characterized in that (D) a barrier layer made of a polyamide resin containing 15 to 35% by mass of polyether derived from polyethylene glycol or polyethylene glycol copolymer in the molecule is provided between the photosensitive resin layer. A photosensitive CTP flexographic printing original plate.
(2) The water according to (1), wherein the polyether contained in the molecule of the polyamide resin in the barrier layer (D) is polyetheramide or polyetheresteramide having a number average molecular weight of 400 to 1000. A developable photosensitive CTP flexographic printing plate precursor.
(3) The water-developable photosensitive CTP flexographic printing according to (1) or (2), wherein the polyamide resin in the barrier layer (D) is a polyamide containing a piperazine ring in the molecule. Original version.
(4) The photosensitive resin composition used for the photosensitive resin layer (B) contains a polymer obtained from a water-dispersed latex as the synthetic polymer compound. Photosensitive letterpress printing plate.

According to the present invention, it is possible to provide a photosensitive CTP flexographic printing plate which does not cause wrinkles during handling of the CTP printing plate in a low-temperature, low-humidity environment and which has excellent barrier properties.

The flexographic printing original plate of the present invention will be described in detail below.

The flexographic printing original plate of the present invention comprises at least (A) a support, (B) a photosensitive resin layer, (C) a heat-sensitive mask layer, and (D) between (C) the heat-sensitive mask layer and (B) the photosensitive resin layer. ) has a basic structure in which barrier layers are sequentially laminated.

The support used in the flexographic printing original plate of the present invention is preferably a flexible material with excellent dimensional stability. Thermoplastic supports such as polyethylene naphthalate film, polybutylene terephthalate film, or polycarbonate film can be used. Among these, a polyethylene terephthalate film having excellent dimensional stability and sufficiently high viscoelasticity is particularly preferred. The thickness of the support is desirably 50 to 350 μm, preferably 100 to 250 μm, from the viewpoints of mechanical properties, shape stabilization, handleability during printing plate making, and the like. Moreover, if necessary, an adhesive may be provided between the support and the photosensitive resin layer in order to improve the adhesion between them.

The photosensitive resin layer used in the flexographic printing original plate of the present invention comprises a synthetic polymer compound, a photopolymerizable unsaturated compound, essential components of a photopolymerization initiator, a plasticizer, a thermal polymerization inhibitor, a dye, a pigment, It contains optional additives such as UV absorbers, fragrances, or antioxidants.

The barrier layer used in the flexographic printing original plate of the present invention exhibits its effect when the non-photocured photosensitive resin layer has high flexibility. Evaluation of flexibility can be evaluated by the amount of indentation displacement. In the present invention, wrinkles can be reduced even when the amount of indentation displacement of the photosensitive resin layer is 5 μm or more. Examples of the photosensitive resin layer having high flexibility include a photosensitive resin layer containing a water-dispersible polymer obtained from latex as a polymer compound.

Examples of latex from which a water-dispersible polymer can be obtained include polybutadiene latex, natural rubber latex, styrene-butadiene copolymer latex, acrylonitrile-butadiene copolymer latex, polychloroprene latex, polyisoprene latex, polyurethane latex, methyl Water-dispersible latex polymers such as methacrylate-butadiene copolymer latex, vinylpyridine polymer latex, butyl polymer latex, thiocol polymer latex, acrylate polymer latex, and other polymers such as acrylic acid and methacrylic acid added to these polymers. and a polymer obtained by copolymerizing the components of. Among these, a water-dispersible 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 preferred. The polymer obtained from the latex is preferably present in the photopolymerizable unsaturated compound as discrete fine particles.

The photosensitive resin layer used in the flexographic printing original plate of the present invention may contain a synthetic rubber that is solid at room temperature as a synthetic polymer compound within a range that does not reduce water developability. Specific synthetic rubbers are synthetic rubbers selected from butadiene rubbers, nitrile-butadiene rubbers, isoprene rubbers, styrene-isoprene rubbers, and styrene-butadiene rubbers. These may be used alone or in combination of two or more. Among these, butadiene rubber and nitrile-butadiene rubber are preferred, and butadiene rubber is most preferred. Moreover, it is preferable that the hydrophobic polymer obtained from the water-dispersed latex of the conjugated diene rubber component and the rubber have a common skeleton structure. Thereby, the mechanical strength of the photosensitive resin layer is improved, and a printing plate having printing durability can be obtained. Further, in order to improve the mechanical strength of the photosensitive resin layer, the synthetic rubber to be compounded should be a solid high molecular weight polymer and should not contain liquid rubber or low molecular weight oligomers. The amount of the conjugated diene rubber component in the photosensitive resin composition constituting the photosensitive resin layer is preferably 1 to 40% by mass, more preferably 1 to 20% by mass. In particular, in order to reduce the influence of water developability, it is preferably 1 to 10% by mass.

A plasticizer can be added to the photosensitive resin composition for the purpose of imparting flexibility. The blending amount of the plasticizer is preferably 0.1 to 30% by mass. More preferably, it is 5 to 20% by mass. If the blending amount is less than the above lower limit, the effect of imparting flexibility to the photosensitive resin composition may be reduced. If the above upper limit is exceeded, there is a risk that a problem will occur in the strength of the photosensitive resin composition.

The plasticizer is not particularly limited as long as it generally has the property of softening the printing plate material, but those having good compatibility with other components are preferred. Specific examples include polyene compounds which are liquid at room temperature and compounds having an ester bond. Examples of polyene compounds that are liquid at room temperature include liquid polybutadiene and polyisoprene, as well as maleated products and epoxidized products obtained by modifying their terminal groups or side chains. Compounds having an ester bond include phthalates, phosphates, sebacates, adipates, and polyesters having a molecular weight of 1,000 to 3,000.

The photosensitive CTP flexographic printing original plate of the present invention contains 15 to 35 polyethers derived from polyethylene glycol or polyethylene glycol copolymer in the molecule between (C) the heat-sensitive mask layer and (B) the photosensitive resin layer. The greatest feature is the provision of (D) a barrier layer made of a polyamide resin containing % by mass. By providing the (D) barrier layer containing such a specific polyamide resin, excellent image reproducibility without polymerization failure due to oxygen, and wrinkles even when handling a CTP original plate at low temperature. It is possible to provide a flexographic CTP original plate having high performance without any defects.

(D) The polyamide resin used for the barrier layer is a polyamide resin containing 15 to 35% by mass of polyether derived from polyethylene glycol or polyethylene glycol copolymer in the molecule. As the polyether, polyethylene glycol is preferable, but a polyethylene glycol copolymer obtained by copolymerizing alkylene glycol other than polyethylene glycol may be used as long as the water solubility and physical properties are not lowered. Examples of alkylene glycols other than polyethylene glycol include polypropylene glycol and polytetramethylene glycol. The copolymerization ratio is preferably less than 50% by mass, more preferably less than 35% by mass, because of the influence on water solubility and physical properties. As a method of copolymerization, random copolymerization or block copolymerization may be used, but block copolymerization is preferable from the viewpoint of physical properties.

(D) The number average molecular weight of the polyether contained in the molecule of the polyamide resin used for the barrier layer is preferably 400 to 1000, more preferably 400 to 800, from the viewpoint of film properties and glass transition point of the barrier layer. Moreover, in order to improve the water solubility, the polyamide resin (B) may contain a basic nitrogen atom in its molecule. If the content of polyether in the molecule of the polyamide resin used for the barrier layer (D) is less than the above lower limit, the amount of polyether bonds will be too small, so wrinkles will not occur during low-temperature work. This cannot be prevented, and the coatability of the barrier layer may be deteriorated. On the other hand, if the content of the alkylene glycol structural unit exceeds the above upper limit, the oxygen barrier property of the barrier layer may be insufficient, and the edge reproducibility of the top of the relief halftone dot may be deteriorated.

(D) The polyamide resin used for the barrier layer may contain basic nitrogen atoms. Inclusion of a basic nitrogen atom is preferable because the water solubility can be improved. A basic nitrogen atom is a nitrogen atom that constitutes an amino group that is not an amide group. As such a polyamide resin, a polyamide resin having a basic nitrogen atom in the main chain is preferred. A polyamide resin containing a basic nitrogen atom is, for example, a diamine containing a basic nitrogen atom, such as a diamine having a piperazine ring or a diamine containing a basic nitrogen atom such as methyliminobispropylamine, as a diamine component. obtained by (D) As the polyamide resin used for the barrier layer, it is particularly preferable to use a diamine having a piperazine ring from the viewpoint of water solubility. Diamines having a piperazine ring include 1,4-bis(3-aminoethyl)piperazine, 1,4-bis(3-aminopropyl)piperazine, N-(2-aminoethyl)piperazine and the like. In addition, the polyamide resin used for the (D) barrier layer may be copolymerized using raw materials such as diamines, dicarboxylic acids, aminocarboxylic acids, etc. that partially do not contain basic nitrogen atoms in terms of physical properties. A method for obtaining a polyamide resin containing a basic nitrogen atom in the molecule is disclosed, for example, in JP-A-50-7605.

The amount of basic nitrogen atoms contained in the polyamide molecule is preferably 0.3 mol to 2.0 mol per 1000 grams of polyamide resin. If it is less than 0.3 mol, the effect of improving water solubility is small, and if it exceeds 2.0 mol, it is not preferable because it is likely to be affected by the humidity of the working environment.

(D) The polyamide resin used for the barrier layer is preferably copolymerized with 6-nylon or 66-nylon in order to improve the physical properties of the polyamide resin, and preferably contains 45 to 75% by mass. If it is less than 45% by mass, there is no effect of improving physical properties, and if it exceeds 75% by mass, water solubility or water dispersibility is lowered, which is not preferable.

Polyether amide or polyether ester amide can be used as the polyamide resin for the (D) barrier layer, but polyether amide is preferred from the viewpoint of hydrolysis resistance. Polyetheramides can be synthesized according to JP-A-55-79437. Specifically, polyetheramide can be synthesized by adding acrylonitrile to both ends of polyethylene glycol and hydrogen-reducing it to obtain α,ω-diaminopolyoxyethylene as a diamine component. On the other hand, polyether ester amide can be synthesized by a general method of using polyethylene glycol as a raw material and introducing polyethylene glycol into the molecule through an ester bond.

In the present invention, the (D) barrier layer made of a polyamide resin containing 15 to 35% by mass of polyether in the molecule has an appropriate degree of water-solubility or water-dispersibility and does not thicken the image on the resulting printing plate. It has a role of imparting oxygen barrier properties. In addition, (D) the barrier layer contains polyether in its molecule, which plays a role in preventing the occurrence of wrinkles during handling of the original CTP printing plate. In particular, it has become possible to prevent the occurrence of wrinkles even during low-temperature work.

Whether the polyamide of the present invention is water-soluble or water-dispersible can be determined by immersing the sheet-shaped polyamide alone in water or acid water at 30° C. and rubbing with a brush or the like. A polyamide is determined to be water-soluble if it is homogeneously mixed with water or acid water after being physically rubbed with a brush or the like. On the other hand, if the polyamide is partially or entirely swollen and dispersed in water after being physically rubbed with a brush or the like, and the polyamide is unevenly mixed, the polyamide is determined to be water-dispersible. .

The barrier layer may contain additives as long as they do not adversely affect performance. Additives include plasticizers and various stabilizers. In particular, when it is desired to improve the water developability of the barrier layer, it is preferable to incorporate a hydrophilic plasticizer or surfactant into the barrier layer. Moreover, in order to reduce the defects of the barrier layer, additives such as antifoaming agents and leveling agents may be added as long as the performance is not adversely affected.

Hydrophilic plasticizers and surfactants for improving the water solubility of polyamides include the following compounds. The hydrophilic plasticizer has good compatibility with the polyamide used for the barrier layer, and examples thereof include glycol compounds such as ethylene glycol, diethylene glycol, triethylene glycol and tetraethylene glycol. The glycol compound may be a modified glycol compound. Further, examples of surfactants include nonionic surfactants, cationic surfactants and anionic surfactants. The amount used is usually 5% by weight or less based on the weight of the barrier layer.

It has generally been thought that barrier layers have two functions. One is an "interlayer barrier property" that prevents substances from moving between adjacent photosensitive resin layers or heat-sensitive mask layers. Another is "oxygen barrier property" which prevents inhibition of polymerization when actinic rays are applied to the entire surface of the photosensitive resin layer through a mask. If there is a problem with the "oxygen barrier property", it may cause troubles such as failure to obtain fine halftone dots in the produced photosensitive printing original plate, or rounded ends of fine halftone dots. Therefore, it is important whether the halftone dot diameter can be obtained in accordance with the predetermined size.

The heat-sensitive mask layer used in the flexographic printing original plate of the present invention comprises 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 its dispersed binder, which can form a film. and a binder polymer. The dispersing binder and the film-forming binder polymer can also be used together. Further, as optional components other than these, a pigment dispersant, 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.

Although the heat-sensitive mask layer used in the flexographic printing original plate of the present invention is not particularly limited, it is preferably water-developable. Specific heat-sensitive mask layers include a heat-sensitive mask layer combining a polar group-containing polyamide and a butyral resin (Japanese Patent No. 4200510), a polymer having the same structure as the polymer in the photosensitive resin layer, and an acrylic resin. A heat-sensitive mask layer (Patent No. 5710961), a heat-sensitive mask layer containing an anionic polymer and a polymer having an ester bond in the side chain and having a degree of saponification of 0% or more and 90% or less (Patent No. 5525074). .

Although the method for producing the flexographic printing original plate of the present invention is not particularly limited, it is generally produced as follows.
First, components such as a binder other than carbon black for the thermal mask layer are dissolved in an appropriate solvent, and carbon black is dispersed therein to prepare a dispersion. Next, such a dispersion is applied onto a heat-sensitive mask layer support (for example, a polyethylene terephthalate film) and the solvent is allowed to evaporate. The barrier layer components are then overcoated to form one laminate. Separately from this, a photosensitive resin layer is formed on the support by coating to form the other laminate. The two laminates thus obtained are laminated under pressure and/or heat such that the photosensitive resin layer is adjacent to the barrier layer. The heat-sensitive mask layer support functions as a protective film for the surface of the original printing plate after completion.

As a method for producing a printing plate from the CTP printing original plate of the present invention, if a protective film is present, the protective film is first removed from the photosensitive printing plate. The thermal mask layer is then imagewise irradiated 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 engraving techniques are commercially available, for example the CDI Spark (Esco Graphics) can be used. The laser system includes a rotating cylindrical drum that holds the printing master, an IR laser illumination device, and a layout computer, with image information transferred directly from the layout computer to the laser device.

After image information is written on the heat-sensitive mask layer, the entire surface of 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 it is advantageous to remove the plate from the laser device and irradiate with a conventional flat irradiation unit because it can handle non-standard plate sizes. and is common. As actinic rays, ultraviolet rays having a wavelength of 150 to 500 nm, particularly 300 to 400 nm can be used. Low-pressure mercury lamps, high-pressure mercury lamps, extra-high pressure mercury lamps, metal halide lamps, xenon lamps, zirconium lamps, carbon arc lamps, ultraviolet fluorescent lamps, and the like can be used as the light source. The irradiated plate is then developed to obtain a printing plate. The development step can be carried out in a conventional development unit.

EXAMPLES The present invention will be described in more detail below with reference to Examples, but the present invention is not limited to these. Parts in the examples (text) represent parts by mass.

The materials used in each example are described below.

<Synthesis of polyamide resin>
PEA-1: 744 parts by mass of ε-caprolactam, an equimolar amount of α,ω-diaminopolyoxyethylene and adipic acid obtained by adding acrylonitrile to both ends of polyethylene glycol having a number average molecular weight of 600 and hydrogen-reducing it. 264 parts by mass of salt and 1000 parts by mass of water were charged into an autoclave and melt-polymerized under normal conditions. The resulting polyamide was a polyether amide containing 18% by mass of polyethylene glycol structural units in the molecule and having a glass transition point of 46°C.
PEA-2: 671 parts by mass of ε-caprolactam, an equimolar amount of α,ω-diaminopolyoxyethylene and adipic acid obtained by adding acrylonitrile to both ends of polyethylene glycol having a number average molecular weight of 600 and hydrogen-reducing it. 329 parts by mass of salt and 1000 parts by mass of water were charged into an autoclave and melt-polymerized under normal conditions. The resulting polyamide was a polyether amide containing 23% by mass of polyethylene glycol structural units in the molecule and having a glass transition point of 46°C.
PEA-3: 545 parts by mass of ε-caprolactam, an equimolar amount of α,ω-diaminopolyoxyethylene and adipic acid obtained by adding acrylonitrile to both ends of polyethylene glycol having a number average molecular weight of 600 and hydrogen-reducing this. 455 parts by mass of salt and 1000 parts by mass of water were charged into an autoclave and melt-polymerized under normal conditions. The resulting polyamide was a polyether amide containing 31% by mass of polyethylene glycol structural units in the molecule and having a glass transition point of 46°C.
PEA-4: 516 parts by mass of ε-caprolactam, 163 parts by mass of 1,4-bis(3-aminopropyl)piperazine adipate, and acrylonitrile added to both ends of polyethylene glycol having a number average molecular weight of 600, followed by hydrogen reduction. 321 parts by mass of the obtained equimolar salt of α,ω-diaminopolyoxyethylene and adipic acid and 1000 parts by mass of water were melt-polymerized under normal conditions. The resulting polyamide was a polyether amide containing 23% by mass of polyethylene glycol structural units in the molecule and 1.0 mol per 1000 mass grams of tertiary nitrogen atoms.
PEA-5: ε-caprolactam 541 parts by mass, N-(2-aminoethyl)piperazine and adipic acid nylon salt 136 parts by mass, polyethylene glycol having a number average molecular weight of 600, acrylonitrile added to both ends, and hydrogen reduction 323 parts by mass of equimolar salt of α,ω-diaminopolyoxyethylene and adipic acid thus obtained and 1000 parts by mass of water were melt-polymerized under normal conditions. The resulting polyamide was a polyether amide containing 23% by mass of polyethylene glycol structural units in the molecule and 1.0 mol per 1000 mass grams of tertiary nitrogen atoms. Incidentally, the tertiary nitrogen atom weight is the tertiary nitrogen atom weight in the piperazine ring, and contains 2 mol of tertiary nitrogen atoms per 1 mol of piperazine.
PEA-6: 489 parts by mass of ε-caprolactam, an equimolar amount of α,ω-diaminopolyoxyethylene and adipic acid obtained by adding acrylonitrile to both ends of polyethylene glycol having a number average molecular weight of 400 and hydrogen-reducing it. 511 parts by mass of salt and 1000 parts by mass of water were melt-polymerized under normal conditions. The obtained polyamide was a polyether amide containing 33% by mass of polyethylene glycol structural units in the molecule.
PEA-7: 589 parts by mass of ε-caprolactam, an equimolar amount of α,ω-diaminopolyoxyethylene and adipic acid obtained by adding acrylonitrile to both ends of polyethylene glycol having a number average molecular weight of 800 and hydrogen-reducing this. 411 parts by mass of the salt was melt-polymerized under normal conditions. The obtained polyamide was a polyether amide containing 31% by mass of polyethylene glycol structural units in the molecule.
PEA-8: 602 parts by mass of ε-caprolactam, obtained by adding acrylonitrile to both ends of polyethylene glycol having a number average molecular weight of 1,000 and hydrogen-reducing it, and equimolar amounts of α,ω-diaminopolyoxyethylene and adipic acid. 398 parts by mass of the salt was melt-polymerized under normal conditions. The obtained polyamide was a polyether amide containing 32% by mass of polyethylene glycol structural units in the molecule.
PEA-9: 862 parts by mass of ε-caprolactam, an equimolar amount of α,ω-diaminopolyoxyethylene and adipic acid obtained by adding acrylonitrile to both ends of polyethylene glycol having a number average molecular weight of 600 and hydrogen-reducing this. 138 parts by mass of the salt was melt-polymerized under normal conditions. The resulting polyamide was a polyetheramide containing 9% by mass of polyethylene glycol structural units in the molecule.
PEA-10: 409 parts by mass of ε-caprolactam, an equimolar amount of α,ω-diaminopolyoxyethylene and adipic acid obtained by adding acrylonitrile to both ends of polyethylene glycol having a number average molecular weight of 600 and hydrogen-reducing it. 591 parts by mass of the salt was melt-polymerized under normal conditions. The obtained polyamide was a polyether amide containing 43% by mass of polyethylene glycol structural units in the molecule.
PEA-11: 449 parts by mass of ε-caprolactam, an equimolar amount of α,ω-diaminopolyoxyethylene and adipic acid obtained by adding acrylonitrile to both ends of polyethylene glycol having a number average molecular weight of 200 and hydrogen-reducing this. 551 parts by mass of the salt was melt-polymerized under normal conditions. The obtained polyamide was a polyether amide containing 33% by mass of polyethylene glycol structural units in the molecule.
PEA-12: 568 parts by mass of ε-caprolactam, obtained by adding acrylonitrile to both ends of polyethylene glycol having a number average molecular weight of 1200 and hydrogen-reducing it, and equimolar amounts of α,ω-diaminopolyoxyethylene and adipic acid. 432 parts by mass of the salt was melt-polymerized under normal conditions. The obtained polyamide was a polyether amide containing 33% by mass of polyethylene glycol structural units in the molecule.
PEEA: A polyether ester amide composed of the following components was synthesized based on a known formulation (for example, JP-A-58-117537). 260 parts by mass of ε-caprolactam, 319 parts by mass of a salt of hexamethylenediamine and adipic acid, polyethylene glycol having a number average molecular weight of 600 and 420 parts by mole of adipic acid in the presence of a tetrabutyl titanate catalyst at 250°C under reduced pressure. Polyether ester amide was obtained by reacting over time. The resulting amide was a polyetherester containing 33% by mass of alkylene glycol structural units in the molecule.

<Preparation of coating liquid composition for barrier layer>
The polyamide resin synthesized in Table 1 was dissolved in ethanol at 60° C. so that the solid content concentration was 10% by mass to prepare a barrier layer coating solution.

<Preparation of thermal mask layer>
A mixture of a carbon black dispersion (AMBK-8, manufactured by Orient Chemical Industry Co., Ltd.) and a copolyamide of PA-1 was used as the coating liquid for the heat-sensitive mask layer. The mixing ratio of each component in the mixture was carbon black:butyral resin:copolyamide=35:28:37 in solid content mass ratio. Then, both sides of a PET film (Toyobo Co., Ltd., E5000, thickness 100 μm) were subjected to release treatment, and then the heat-sensitive mask layer coating solution was applied using a bar coater #12. minutes dried. The optical density at this time was 2.3. This optical density was measured with a black-and-white transmission densitometer DM-520 (Dainippon Screen Mfg. Co., Ltd.).

<Preparation of Film of Thermal Mask Layer Laminate Provided with Barrier Layer>
On the prepared heat-sensitive mask layer, the barrier layer coating solution is applied to a predetermined thickness using an appropriate type of bar coater, dried at 120°C for 5 minutes, and the barrier layer is the uppermost layer. A film of the provided heat-sensitive mask layer laminate was obtained.

<Preparation of photosensitive resin composition for photosensitive resin layer>
Acrylonitrile-butadiene latex (Nipol SX1503 non-volatile content 42% Nippon Zeon Co., Ltd.) 10 parts by mass, butadiene latex (Nipol LX111NF non-volatile content 55% Nippon Zeon Co., Ltd.) 58 parts by mass, oligobutadiene acrylate (ABU-2S Kyoeisha) Kagaku Co., Ltd.) 28 parts by mass, 4 parts by mass of lauryl methacrylate (light ester L manufactured by Kyoeisha Chemical Co., Ltd.), 4 parts by mass of dimethyloltricyclodecane diacrylate, 1 part by mass of benzyl dimethyl ketal as a photopolymerization initiator, 0.1 part by mass of hydroquinone monomethyl ether as a polymerization inhibitor and 0.1 part by mass of a nonionic surfactant as another additive were mixed together with 15 parts by mass of toluene in a vessel, and then heated to 105°C using a pressure kneader. and then toluene and water were removed under reduced pressure to obtain a photosensitive resin composition used for the photosensitive resin layer. When the indentation displacement of this composition was measured, it was 15 μm.

<Preparation of printing plate>
The above photosensitive resin composition was placed on a PET film support (Toyobo Co., Ltd., E5000, thickness 125 μm) coated with a copolymer polyester adhesive, and a barrier layer was provided as the uppermost layer thereon. The films of the thermal mask layer laminate were laminated. A heat press was used to laminate at 100° C. to obtain a flexographic printing original plate comprising a PET support, an adhesive layer, a photosensitive resin layer, a protective layer, a heat-sensitive mask layer and a release-treated PET protective film (cover film). The total plate thickness was 1.90 mm.

<Creating a printing plate from a printing plate>
The original plate was irradiated with ultraviolet rays (light source Philips 10R, illuminance at 365 nm: 8 mW/cm ² ) for 1 minute from the PET support side. Subsequently, the release-treated PET film (cover film) was peeled off. This plate was wound around a rotating drum of Digital Imager Spark (manufactured by Barco) so that the heat-sensitive mask layer was on the front side, and after drawing a vacuum, image formation was carried out. After ablation, the plate was removed, placed back flat and irradiated with actinic radiation (light source Philips 10R, illuminance 8 mW/cm ² at 365 nm) for 6 minutes. Thereafter, development was carried out at 40° C. for 8 minutes using a developing machine (Stuck System) manufactured by A&V Co., Ltd. Tap water to which 1% Cascade dishwashing detergent (manufactured by P&G, USA) was added was used as the developer. After development, it was dried at 60° C. for 10 minutes, irradiated with actinic rays for 10 minutes, and finally irradiated with a germicidal lamp for 5 minutes to remove surface tackiness.

<Evaluation method>
Crease resistance: The prepared flexographic printing plate precursor was cut to a width of 20 cm and a length of 20 cm to prepare an evaluation sample. The sample was stored for 24 hours on a flat table in a constant temperature room at 10° C. or 30° C. under conditions of relative humidity of 25% to adjust the sample. After that, the cover sheet of the sample was peeled off, wrapped around a cylindrical roll (diameter 200 mm) with the barrier layer facing out and fixed for 5 minutes, then removed and left to stand on a flat place for 5 minutes. After that, the surface of the barrier layer was visually observed and evaluated according to the following criteria.

○: No wrinkles were observed in the barrier layer △: Wrinkles were observed in part of the barrier layer ×: Wrinkles were observed in the entire surface of the barrier layer

Coatability of barrier layer: The barrier layer of the present invention was hand-coated on an A4 size PET film using a bar coater. After hand-coating the sample at normal temperature, it was placed in a hot air dryer set at 100° C. and allowed to stand for 10 minutes. After that, the sample was taken out from the hot air dryer, the surface of the barrier layer was visually observed, and judged according to the following criteria.

○: The coating surface of the barrier layer is smooth and the coating layer is not cloudy. △: The coating surface of the barrier layer is smooth but the coating layer is cloudy. ×: The coating surface of the barrier layer has streaks and repellency Defects confirmed

Water developability: The prepared flexographic printing plate precursor was immersed in a developer and rubbed with a brush exclusively for the developing machine using nylon fibers with a diameter of 100 μm and 160 μm at 40° C. for 5 minutes. Judged by the standard.

A: The barrier layer is water-developable by brushing for 60 seconds. B: The barrier layer is water-developable by brushing for 90 seconds. △: The barrier layer is water-developable by brushing for 120 seconds. Impossible to develop barrier layer with water by brushing for 120 seconds

Edge reproducibility of relief halftone dot top: Using a CTP layer equivalent to 150 line 2% halftone dot top of a negative film, the shape of a 150 line 2% halftone dot top was evaluated. For the evaluation, the shape of a 150-line 2% halftone dot top magnified 100 times was observed in cross section using a microscope, and the evaluation was made according to the following criteria.

◯: The diameter of the flat portion at the top of the halftone dot reproduces a negative film 150 line 2% equivalent, and the shape of the end portion is not rounded.
Δ: The diameter of the flat portion at the top of the halftone dot is smaller than that of the negative film 150 line 2%, and the edges are rounded.
x: No flat portion was observed at the top of the halftone dot, and the shape of the end portion was rounded.

Measurement of indentation displacement: A disk-shaped indenter with a diameter of 10 mm was applied to a printing plate having a photosensitive resin layer having a thickness of 1.70 mm on a support for 60 seconds with a load of 120 g. The amount of displacement was measured using ONO SOKKI LINEAR SENSOR (GS-112). The greater the indentation displacement, the more flexible the plate.

Example 1
A heat-sensitive mask layer prepared in <Preparation of heat-sensitive mask layer> was prepared. Next, a coating liquid composition was prepared according to <Preparation of coating liquid composition for barrier layer> with the barrier layer composition ratio of Example 1 shown in Table 1. Next, according to <Preparation of Film of Thermal Mask Layer Laminate Provided with Barrier Layer>, a barrier layer was coated on the thermal mask layer to a thickness of 1.5 μm and dried, and the barrier layer was provided as the uppermost layer. A film of a heat-sensitive mask layer laminate was obtained. The obtained film of the heat-sensitive mask layer laminate is laminated with a photosensitive resin layer according to <preparation of printing original plate> to form a PET support, an adhesive layer, a photosensitive resin layer, a protective layer, a heat-sensitive mask layer and a release-treated PET protective film. A flexographic printing original plate consisting of (cover film) was obtained. The total plate thickness was 1.90 mm. The photosensitive resin layer used in Example 1 was prepared in <Preparation of photosensitive resin composition for photosensitive resin layer>.

Examples 2-9, Comparative Examples 1-5
According to the manufacturing method of Example 1, the photosensitive resin layer of Example 1 was provided using a film provided with a heat-sensitive mask layer prepared with the heat-sensitive mask layer composition (mass ratio) shown in Table 1. A flexographic printing original plate comprising a layer, a photosensitive resin layer, a barrier layer, a heat-sensitive mask layer and a release-treated PET protective film (cover film) was obtained. The total plate thickness was 1.90 mm. Performance evaluation was performed using the obtained heat-sensitive mask layer and the original CTP flexographic printing plate. The results of these performance evaluations are shown in Table 1 below.

As can be seen from Table 1, Examples 1 to 9, which satisfy the constituent requirements of the present invention, are excellent in wrinkle resistance, barrier layer coatability, water developability, and edge reproducibility of relief halftone dot tops. On the other hand, Comparative Example 1, in which the content of polyethylene glycol in the polyamide resin is small, is inferior in wrinkle resistance. Content of Polyamide Resin (B) Comparative Example 2, in which the content of polyethylene glycol in the polyamide resin is large, is inferior in edge reproducibility of the top of the relief halftone dot. Polyamide resins containing polyethylene glycol having a number average molecular weight of less than 400 and having a number average molecular weight of more than 1,000 are inferior in coatability.

According to the present invention, a photosensitive CTP having a high-performance barrier layer that achieves both prevention of wrinkles in a low-temperature, low-humidity environment and a flat-top shape without thickening of highlight halftone dots. A flexographic printing master can be provided. Therefore, the present invention is extremely useful.

Claims (3)

A photosensitive CTP flexographic printing original plate comprising at least (A) a support, (B) a photosensitive resin layer, and (C) a heat-sensitive mask layer, which are sequentially laminated,
(D) Barrier made of polyamide resin containing 15 to 35% by mass of polyether derived from polyethylene glycol or polyethylene glycol copolymer in the molecule between (C) the heat-sensitive mask layer and (B) the photosensitive resin layer. layer,
Water -developable photosensitive CTP flexographic printing, wherein the polyether contained in the molecule of the polyamide resin in the barrier layer (D) is polyetheramide or polyetheresteramide having a number average molecular weight of 400 to 1000. Original version. A photosensitive CTP flexographic printing original plate comprising at least (A) a support, (B) a photosensitive resin layer, and (C) a heat-sensitive mask layer, which are sequentially laminated,
(D) Barrier made of polyamide resin containing 15 to 35% by mass of polyether derived from polyethylene glycol or polyethylene glycol copolymer in the molecule between (C) the heat-sensitive mask layer and (B) the photosensitive resin layer. layer,
A water -developable photosensitive CTP flexographic printing original plate, wherein the polyamide resin in the barrier layer (D) is a polyamide containing a piperazine ring in its molecule. 3. The water-developable photosensitive material according to claim 1, wherein the photosensitive resin composition used in the photosensitive resin layer (B) contains, as the synthetic polymer compound, a polymer obtained from a water-dispersed latex. CTP flexographic printing original plate.