WO2017056763A1

WO2017056763A1 - Photosensitive relief printing original plate

Info

Publication number: WO2017056763A1
Application number: PCT/JP2016/073927
Authority: WO
Inventors: 和也芳本
Original assignee: 東洋紡株式会社
Priority date: 2015-09-28
Filing date: 2016-08-16
Publication date: 2017-04-06
Also published as: JPWO2017056763A1; JP6768217B2

Abstract

Provided is a photosensitive relief printing original plate that is suitable for CTP technology and that makes it possible to obtain a printing plate having excellent water developability, excellent printing durability, and good print quality. At least the following are layered sequentially in this water development-type photosensitive relief printing original plate: a support body (A); a photosensitive resin layer (B); an oxygen-blocking division layer (C); and a water-soluble or water-dispersible photosensitive mask layer (D) containing carbon black. The photosensitive relief printing original plate is characterized in that the photosensitive resin layer (B) contains a synthetic polymer compound, a photopolymerizable unsaturated compound, and a photopolymerization initiator, the synthetic polymer compound contains polyether urea-urethane or a polyamide comprising a tertiary nitrogen atom, and the division layer (C) contains a polyvinyl alcohol having a saponification degree of 60-85 mol% and a degree of polymerization of 200-800.

Description

Photosensitive relief printing original plate

The present invention relates to a photosensitive relief printing original plate used for producing a relief printing plate by computer plate making technology.

In recent years, in the fields of letterpress printing and flexographic printing, computer plate making technology (CTP technology) known as digital image forming technology has become very common. The CTP technique is a method of obtaining an uneven pattern serving as a relief by forming an image mask directly on a printing plate with digital data and then exposing from the image mask side.

In CTP technology, a negative film, which is conventionally used, is replaced with a mask that is formed and integrated in a printing plate in order to cover an area that should not be polymerized. An image mask is obtained by providing an infrared sensitive layer (heat sensitive mask layer) opaque to actinic radiation on a photosensitive resin layer and decomposing and ablating the infrared sensitive layer with an infrared laser as a method for obtaining this integrated mask. The method of forming is widely used (see Patent Document 1).

As a photosensitive letterpress printing original plate in which CTP technology is introduced, a photosensitive letterpress printing original plate composed of a photosensitive resin layer, a divided layer, and a thermal mask layer has been proposed. This split layer needs to have two important functions.

First, it is necessary to minimize the mass transfer between the photosensitive resin layer and the thermal mask layer. In general, when a low molecular weight monomer or plasticizer has an affinity for a component in an adjacent layer, diffusion transfer over time to the adjacent layer increases. When such mass transfer occurs, the infrared sensitivity of the thermal mask layer is affected.

Second, it is necessary to protect the photosensitive resin layer from atmospheric oxygen. When exposed to atmospheric oxygen, the photosensitive resin layer undergoes polymerization inhibition due to radical deactivation. As a result, the printing plate surface is insufficiently cured and the printing durability is remarkably lowered.

Furthermore, in order to develop a sufficient oxygen barrier ability at the time of exposure and curing, it is necessary that the divided layer can withstand laser ablation. When the thermal mask layer is ablated by the infrared laser, the adjacent divided layers are exposed to a high temperature, and the thermal damage particularly at the overlapping portion of the laser light path becomes significant. The damaged divided layer is locally ablated and excavated at the overlapping portion of the laser optical path, resulting in uneven thickness of the divided layer or discontinuity of the divided layer. As a result, the oxygen permeability of the divided layer varies, and local polymerization inhibition is given when the photosensitive resin layer is exposed. A photosensitive resin plate exposed under non-uniform oxygen conditions causes fine roughness such as irregularities, undulations, and wrinkles on the plate surface, resulting in a decrease in print quality.

Patent Document 2 proposes a photosensitive resin relief printing original plate having an oxygen-permeable dividing layer as a photosensitive relief printing original plate in which CTP technology is introduced. However, since this divided layer is permeable to oxygen, when a photosensitive resin layer that is highly sensitive to polymerization inhibition by oxygen is used, the printing plate surface may be insufficiently cured, resulting in poor printing durability.

In Patent Document 3, a photosensitive resin layer containing a resin that can be dissolved or dispersed in water and a monomer that can be cured by ultraviolet light, an adhesive force adjusting layer, and a water-insoluble thermal mask layer are laminated in this order. In addition, a photosensitive resin printing original plate in which the adhesion adjusting layer contains partially saponified polyvinyl acetate having a saponification degree of 60 mol% or more is disclosed. In Patent Document 3, regarding the first function of the divided layer (that is, minimizing the mass transfer between the photosensitive resin layer and the thermal mask layer), the thermal mask layer is not used by the divided layer. This is realized by containing a water-insoluble resin. Further, the adhesive force adjusting layer of Patent Document 3 does not require the second function of the above-described divided layer (that is, it can withstand laser ablation in order to exhibit oxygen barrier properties), and therefore the adhesive force adjustment. It can be said that the layer has a function different from that of the divided layer. Furthermore, since the heat-sensitive mask layer of the printing original plate is insoluble in water, it is necessary to develop with a strong brush using a relatively high temperature developer. For this reason, there are problems that the surface of the plate is roughened due to the friction and rubbing of the brush during the development, and relief jumps and chipping occur.

On the other hand, in the case of improving the blocking property of oxygen permeation, the shortage of printing durability due to insufficient photocuring can be improved, but conversely the problem is that the area becomes larger than the negative image of the mask layer in order to promote photocuring ( There has been a demand for a printing original plate that satisfies both printing durability and image reproducibility.

Japanese Patent No. 2773847 Japanese Patent No. 3429634 JP 2005-326442 A

The present invention has been developed in view of the current state of the prior art, and its purpose is to obtain a printing plate with good printing quality that is excellent in all of water developability, printing durability, and image reproducibility. It is to obtain a photosensitive relief printing original plate suitable for the CTP technique.

As a result of intensive studies to achieve the above object, the present inventors have determined that an oxygen-blocking dividing layer containing polyvinyl alcohol having a specific saponification degree and a specific polymerization degree is formed between the photosensitive resin layer and the thermal mask layer. It was found that a relief printing original plate excellent in laser tolerance, printing durability and image reproducibility can be obtained.

The present invention has been created based on such knowledge, and has the following configurations (1) to (2).
(1) At least (A) a support, (B) a photosensitive resin layer, (C) an oxygen-barrier dividing layer, and (D) a water-soluble or water-dispersible thermal mask layer containing carbon black are sequentially laminated. A water-developable photosensitive letterpress printing original plate,
(B) Polyamide or polyether urea urethane in which the photosensitive resin layer contains a synthetic polymer compound, a photopolymerizable unsaturated compound, and a photopolymerization initiator, and the synthetic polymer compound contains a tertiary nitrogen atom And (C) an oxygen-barrier dividing layer contains polyvinyl alcohol having a saponification degree of 60 to 85 mol% and a polymerization degree of 200 to 800.
(2) The photosensitive relief printing original plate as described in (1), wherein the thermal mask layer (D) contains the synthetic polymer compound contained in the photosensitive resin layer (B). .

The photosensitive resin relief printing original plate of the present invention resists infrared laser ablation during ablation and suppresses oxygen inhibition by effectively blocking atmospheric oxygen during exposure. The image reproducibility without weight can be expressed with respect to the negative image of the mask layer which can be promoted and laser ablated. As a result, it is possible to provide a printing plate excellent in printability, printing durability and image reproducibility without fine roughness on the exposed plate surface. In addition, since the photosensitive resin relief printing original plate of the present invention has a water-soluble or water-dispersible heat-sensitive mask layer, it is possible to obtain a water-developing printing plate having excellent developability and good print quality.

4 is a micrograph of the plate surface after development in Example 3. 2 is a micrograph of a plate surface after development in Comparative Example 1.

1: Non-image area, that is, a portion where an image is not formed by a laser and the heat-sensitive mask layer remains 2: Image portion, ie, a portion where the heat-sensitive mask layer is removed by a laser and the surface of the divided layer is exposed

Hereinafter, the photosensitive relief printing original plate of the present invention will be described in detail.

In the relief printing original plate of the present invention, at least (A) a support, (B) a photosensitive resin layer, (C) an oxygen-blocking divided layer, and (D) a water-soluble or water-dispersible thermal mask layer are sequentially laminated. It has a configuration and is a water development type.

In the relief printing original plate of the present invention, the water development type means that a non-exposed portion that is unexposed in a developer containing water as a main component can be washed out with a brush to obtain a concavo-convex pattern.

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 thermoplastic resin supports such as polyethylene naphthalate film, polybutylene terephthalate film and 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 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 bond layer among 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, and optional additives such as antioxidants.

The synthetic polymer compound constituting the (B) photosensitive resin layer of the present invention is a polyamide or polyether urea urethane containing a tertiary nitrogen atom. The polyamide containing a tertiary nitrogen atom includes a tertiary nitrogen-containing polyamide and / or an ammonium salt type tertiary nitrogen atom-containing polyamide (see, for example, JP-A No. 53-36555). The polyether urea urethane containing a tertiary nitrogen atom contains a tertiary nitrogen-containing polyether urea urethane and / or an ammonium salt type tertiary nitrogen atom-containing polyether urea urethane (see, for example, JP-A-4-97154). Is. In addition, a synthetic polymer compound that can be dissolved or dispersed in water or a mixture of water and alcohol is preferable in terms of developability. Polyamide or polyether urea urethane containing a tertiary nitrogen atom is particularly preferable because it can be easily developed with water by using an ammonium salt type.

As the photopolymerizable unsaturated compound constituting the photosensitive resin layer (B) of the present invention, conventionally known compounds can be employed. For example, polyglycidyl ether of polyhydric alcohol, methacrylic acid and acrylic acid Of the ring-opening addition reaction product. Examples of the polyhydric alcohol include dipentaerythritol, pentaerythritol, trimethylolpropane, glycerin, ethylene glycol, diethylene glycol, triethylene glycol, and an ethylene oxide adduct of phthalic acid. Among them, trimethylolpropane is preferable.

As the photopolymerization initiator constituting the photosensitive resin layer (B) of the present invention, conventionally known photopolymerization initiators can be employed. For example, benzophenones, benzoins, acetophenones, benzyls, benzoin alkyl ethers, Examples include benzyl alkyl ketals, anthraquinones, and thioxanthones. 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 Examples include 2-methylanthraquinone, 2-allyl anthraquinone, 2-chloroanthraquinone, thioxanthone, and 2-chlorothioxanthone.

(C) The oxygen-barrier dividing layer used for the original plate of the present invention is characterized by containing polyvinyl alcohol having a low saponification degree and a low polymerization degree. The saponification degree and polymerization degree of polyvinyl alcohol used in the present invention are measured in accordance with JIS K 6726 (polyvinyl alcohol test method). The saponification degree of polyvinyl alcohol is required to be 60 to 85 mol%, and the polymerization degree is 200 to 800, preferably 60 to 80 mol% and the polymerization degree is 250 to 750. If the degree of saponification is higher than the above range or the degree of polymerization is high, the divided layer is thermally damaged by infrared laser ablation, and fine roughness such as irregularities, undulations and wrinkles is generated on the plate surface. On the other hand, if the degree of saponification is lower than the above range, water-solubility is lacking and water development cannot be performed. If the degree of polymerization is lower than the above range, the film forming property is lacking, and a divided layer having a desired film thickness cannot be obtained. Further, with respect to image reproducibility, if the degree of saponification is low, the oxygen barrier property is insufficient, and if the degree of saponification is high, the image becomes thick due to the oxygen barrier effect, resulting in a problem that the image reproducibility is lowered. In the present invention, the thickening of the image means the reproducibility of the printing plate with respect to the image of the mask layer ablated by laser, and the thickening means that the image area of the printing plate is larger than the image of the mask layer. . The reproducibility of the printing plate with respect to the image of the mask layer is preferably 95 to 105% as an image area ratio, and particularly preferably 95 to 100%. If the image area ratio is less than the above range, the image area is too small, and if it exceeds the above range, a problem of fatness occurs, which is not preferable.

The above-mentioned (C) oxygen-barrier dividing layer containing polyvinyl alcohol having a low saponification degree and a low polymerization degree generally exhibits excellent characteristics in a polymer material, in which thermal conductivity and density are proportional to each other. However, the higher the degree of polymerization and the higher the degree of polymerization of polyvinyl alcohol, the higher the density due to intermolecular interaction and the higher the thermal conductivity, so the polyvinyl alcohol has a low degree of saponification and a low molecular weight. It is considered that the use of, results in low thermal conductivity and high thermal stability.

(C) In addition to the low saponification degree and low polymerization degree polyvinyl alcohol described above, addition of a surfactant, a plasticizer, etc. to adjust coating properties and stability as required An agent can be included.

The amount of polyvinyl alcohol having a low saponification degree and a low polymerization degree described above is preferably 50% by weight or more, more preferably 60% by weight or more based on the total solid content constituting the (C) divided layer. This amount can sufficiently withstand thermal damage due to laser ablation. In addition, since a uniform film can be formed, sufficient adhesion with the photosensitive resin layer and the heat-sensitive mask layer can be obtained.

(C) The thickness of the oxygen-barrier dividing layer is preferably 15 μm or less, more preferably 0.1 μm or more and 5 μm or less. If the thickness exceeds the above range, the layer may be bent or scattered when exposed to ultraviolet light, and a sharp relief image may not be obtained. On the other hand, if the amount is less than the above range, the oxygen barrier property is insufficient, and the relief plate surface may be roughened.

The (D) heat-sensitive mask layer used in the original plate of the present invention needs to be water-soluble or water-dispersible because the original plate of the present invention is a water developing type. In the present invention, (D) the heat-sensitive mask layer is water-soluble or water-dispersible. (D) the heat-sensitive mask layer alone is dissolved or dispersed by rubbing with a brush in a developer containing water as a main component. It means having properties.

(D) The heat-sensitive mask layer used in the original plate of the present invention is composed of a binder and carbon black having a function of absorbing infrared laser and converting it into heat and a function of blocking ultraviolet light. Further, as an optional component 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.

(D) The thermal mask layer preferably has an optical density of 2.0 or more with respect to actinic radiation in order to prevent the actinic radiation from reaching the photosensitive resin layer. An optical density of 2.0 to 3.0 is more preferable, and an optical density of 2.2 to 2.5 is particularly preferable.

The optical density is defined by the following formula.
Optical density = log ₁₀ (100 / T) = log ₁₀ (I ₀ / I)
(Here, T is transmittance (unit:%), I ₀ is incident light intensity at the time of measuring transmittance, and I is transmitted light intensity).

For optical density measurement, there are known methods of calculating from the measured value of transmitted light intensity with a constant incident light intensity and calculating from the measured value of incident light intensity required to reach a certain transmitted light intensity. However, the optical density in the present invention is a value calculated from the former transmitted light intensity.

The optical density can be measured by using, for example, a black and white transmission densitometer DM-520 (Dainippon Screen Mfg. Co., Ltd.).

(D) The thickness of the thermal mask layer is preferably 0.5 to 5.0 μm, more preferably 1.0 to 2.0 μm. If the thickness is less than the above range, a high coating technique is required, and it may be difficult to obtain an optical density above a certain level. On the other hand, when the above range is exceeded, high energy is required for evaporation of the thermal mask layer, which may be disadvantageous in terms of cost.

(D) The binder used in the heat-sensitive mask layer is not particularly limited, but a copolymer polyamide having a polar group is preferably used. The polyamide used is preferably appropriately selected from conventionally known cationic polyamides, nonionic polyamides, and anionic polyamides. For example, tertiary amino group-containing polyamides, quaternary ammonium base-containing polyamides, ether group-containing polyamides. And sulfonic acid group-containing polyamide.

(D) The carbon black used in the heat-sensitive mask layer has an infrared absorption function and an actinic radiation blocking function, and has a concentration that can achieve the optical density and the layer thickness as appropriate. ) It is used in an amount of 1 to 60% by weight, preferably 10 to 50% by weight, based on the total weight of the thermal mask layer. If the amount used is less than the lower limit, the optical density is lowered, and there is a possibility that the infrared absorption function and the actinic radiation blocking function are not exhibited. On the other hand, when the above upper limit is exceeded, other components such as a binder are insufficient, and the film-forming property may be lowered.

(D) It is preferable to protect the printing original plate by providing a peelable flexible cover film on the thermal mask layer. Suitable examples of the cover film include a polyethylene terephthalate film, a polyethylene naphthalate film, and a polybutylene terephthalate film. However, such a protective film is not absolutely necessary.

The method for producing the relief printing original plate of the present invention is not particularly limited, but is generally produced as follows.
First, components such as binder other than carbon black constituting the heat-sensitive mask layer are dissolved or dispersed in an appropriate 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. Subsequently, a solution or dispersion of the components constituting the divided layer is applied onto the heat-sensitive mask layer to evaporate the solvent, thereby creating 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 divided layer on the thermal mask layer under pressure and / or heating. The support for the thermal mask layer becomes a peelable flexible cover film after the printing original plate is completed, and functions as a protective film for the surface of the thermal mask layer.

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 ablated with an IR laser to form an image mask on the photosensitive resin layer. Examples of suitable IR lasers include ND / YAG laser (wavelength 1064 nm) or diode laser (wavelength example, 830 nm). These laser systems are commercially available and include a rotating cylindrical drum that holds a printing original, an IR laser irradiation device, and a layout computer. Image information is transferred directly from the layout computer to the laser device.

After writing the image information 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.

Hereinafter, the effects of the present invention are specifically shown by examples, but the present invention is not limited to these examples.

<Preparation of thermal mask layer coating solution>
ε-caprolactam 53 parts by weight, N, N′-bisaminopropylpiperazine adipate 38 parts by weight, 1,3-bis (aminomethyl) cyclohexane adipate 9 parts by weight were polymerized to have a melting point of 139 ° C. and a specific viscosity of 1.95. A tertiary nitrogen-containing polyamide was obtained. Carbon black dispersion (AMBK-8 manufactured by Orient Chemical Co., Ltd.) and the tertiary nitrogen-containing polyamide obtained as described above in a solid weight ratio of carbon black dispersion: tertiary nitrogen-containing polyamide = 63: 37 The solution was dissolved in a methanol / ethanol / isopropyl alcohol mixed solution to prepare a thermal mask layer coating solution.

<Preparation of split layer coating solution>
Polyvinyl alcohols (PVA505, PVA405, PVA403, PVA205, PVA-1 to 7) having various saponification degrees and polymerization degrees obtained as described below were dissolved in a water / isopropyl alcohol mixed solution, and a divided layer coating solution was prepared. Prepared.

Polyvinyl alcohol PVA505, PVA405, PVA403, and PVA205 used Kuraray Poval manufactured by Kuraray Co., Ltd.

Polyvinyl alcohol PVA-1 was synthesized as follows. 50 parts by weight of vinyl acetate and 60 parts by weight of methanol were polymerized at 60 ° C. under nitrogen substitution, and when the degree of polymerization reached 100, the polymerization was terminated by cooling. Next, unreacted vinyl acetate was removed to obtain a methanol solution of polyvinyl acetate. A NaOH methanol solution (10% concentration) was added to the resulting solution for deacetic acid to obtain polyvinyl alcohol PVA-1 having a saponification degree of 63 mol%.

Polyvinyl alcohol PVA-2 to 5 were synthesized as follows. In the same manner as polyvinyl alcohol PVA-1, 50 parts by weight of vinyl acetate and 60 parts by weight of methanol were polymerized at 60 ° C. under nitrogen substitution, and when the degree of polymerization reached 300, 500, 700, 1000, the polymerization was terminated by cooling. did. Next, unreacted vinyl acetate was removed to obtain a methanol solution of polyvinyl acetate. A NaOH methanol solution (10% concentration) was added to the resulting solution to remove acetic acid, polyvinyl alcohol PVA-2 having a polymerization degree of 300 and a saponification degree of 63 mol%, and a polyvinyl alcohol having a polymerization degree of 500 and a saponification degree of 63 mol%. Alcohol PVA-3, polyvinyl alcohol PVA-4 having a polymerization degree of 700 and a saponification degree of 63 mol%, and polyvinyl alcohol PVA-5 having a polymerization degree of 1000 and a saponification degree of 63 mol% were obtained.

Polyvinyl alcohol PVA-6 was synthesized as follows. 50 parts by weight of vinyl acetate and 60 parts by weight of methanol were polymerized at 60 ° C. under nitrogen substitution, and when the degree of polymerization reached 700, the polymerization was terminated by cooling. Next, unreacted vinyl acetate was removed to obtain a methanol solution of polyvinyl acetate. A NaOH methanol solution (15% concentration) was added to the resulting solution for deacetic acid to obtain polyvinyl alcohol PVA-6 having a saponification degree of 80 mol%.

Polyvinyl alcohol PVA-7 was synthesized as follows. 50 parts by weight of vinyl acetate and 60 parts by weight of methanol were polymerized at 60 ° C. under nitrogen substitution, and when the degree of polymerization reached 500, the polymerization was terminated by cooling. Next, unreacted vinyl acetate was removed to obtain a methanol solution of polyvinyl acetate. A NaOH methanol solution (7% concentration) was added to the resulting solution for deacetic acid to obtain polyvinyl alcohol PVA-7 having a saponification degree of 50 mol%.

<Preparation of laminated film X>
A heat-sensitive mask layer coating solution was applied onto a 100 μm PET film subjected to a release treatment on both sides using a suitable type of bar coater, dried at 120 ° C. for 5 minutes, and a film thickness of 1. A 5 μm thermal mask layer was laminated. 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.).
Next, a split layer coating solution is applied onto the thermal mask layer using an appropriate type of bar coater, dried at 120 ° C. for 5 minutes, and a thermal mask layer having a thickness of 1.5 μm on the PET film and A laminated film X in which divided layers having a thickness of 3.0 μm were laminated in this order was obtained.

<Preparation of photosensitive letterpress printing original plate having photosensitive resin layer A>
ε-caprolactam 53 parts by weight, N, N′-bisaminopropylpiperazine adipate 38 parts by weight, 1,3-bis (aminomethyl) cyclohexane adipate 9 parts by weight were polymerized to have a melting point of 139 ° C. and a specific viscosity of 1.95. A tertiary nitrogen-containing polyamide was obtained. 55 parts of the obtained polyamide was dissolved in 200 parts by weight of methanol and 24 parts by weight of water. In this solution, 3 parts by weight of methacrylic acid, 35 mol% of trimethylolpropane triglycidyl ether, 35 mol% of acrylic acid and 65 mol% of methacrylic acid were added. 36 parts of the reaction product, 5 parts by weight of N-ethyl-p-toluenesulfonamide, 0.1 part by weight of hydroquinone monomethyl ether, and 1 part by weight of benzyldimethyl ketal were added to obtain a photosensitive resin composition solution. This photosensitive resin solution was sent to a concentrator and concentrated at 110 ° C. to obtain a photosensitive resin composition A. Next, the photosensitive resin composition A is sandwiched between the adhesive-coated surface side of the support film obtained by coating the adhesive film on the 250 μm PET film to 20 μm and the divided layer side of the laminated film X at 110 ° C. Was heated and pressed to prepare a photosensitive relief printing original plate having a total thickness of 950 μm.

<Preparation of photosensitive letterpress printing original plate having photosensitive resin layer B>
80 parts of N, N'-bis (3-aminopropyl) piperazine and 20 parts of 2-methylpentamethylenediamine are dissolved in 1000 parts of methanol, and then 600 parts of polyethylene glycol (average molecular weight 600) and hexamethylene diisocyanate are added to the diamine solution. 450 parts of a urethane oligomer having isocyanate groups at substantially both ends obtained by reacting 369 parts was gradually added with stirring. Both reactions were completed in about 15 minutes, and a tertiary nitrogen-containing polyether urea urethane having a specific viscosity of 1.75 was obtained. 55.0 parts of the obtained polyetherureaurethane was dissolved in 100 parts of methanol by heating at 65 ° C., and 5.0 parts of N-ethyltoluenesulfonic acid amide, 0.03 part of 1,4-naphthoquinone, hydroquinone monomethyl ether 0 .1 part was added and stirred and dissolved for another 30 minutes. Thereafter, 3.6 parts of lactic acid, 2.5 parts of glycidyl methacrylate (GMA), 18 parts of water, 0.3 part of ammonium sulfite, 0.1 part of oxalic acid, 1.0 part of benzyl dimethyl ketal as a photopolymerization initiator, 32.5 parts of -hydroxy-3-acryloyloxypropyl methacrylate (Nippon Yushi Co., Ltd. cross-linking agent Blemmer GAM) was added and dissolved by stirring for 30 minutes. This photosensitive resin solution was sent to a concentrator and concentrated at 110 ° C. to obtain a photosensitive resin composition B. Subsequently, the photosensitive resin composition B is sandwiched between the adhesive-coated surface side of the support film obtained by coating the 250 μm PET film with 20 μm of adhesive and the divided layer side of the laminated film X at 110 ° C. Was heated and pressed to prepare a photosensitive relief printing original plate having a total thickness of 950 μm.

<Preparation of photosensitive letterpress printing original plate having photosensitive resin layer C>
The protective film was peeled off from a commercially available relief printing plate capable of being developed on water placed on a film base of nyloprint (registered trademark) WF95H (manufactured by BASF). Next, using a mixture of n-propanol and water in a mixing ratio of 9: 1, the laminated film X was laminated on the surface from which the protective film was peeled off to obtain a photosensitive relief printing original plate.

<Preparation of photosensitive letterpress printing original plate having photosensitive resin layer D>
The protective film was peeled off from a commercially available relief printing plate capable of being developed with water on a film base of TORELIEF (registered trademark) WF95DT IV (manufactured by Toray Industries, Inc.). Next, using a mixture of n-propanol and water having a mixing ratio of 18: 1, the laminated film X was laminated on the surface from which the protective film was peeled off to obtain a photosensitive relief printing original plate.

<Preparation of printing plate>
The protective film was peeled off from the photosensitive relief printing original plate, and then drawn on the (C) thermal mask layer with an external drum IR laser device. As the IR laser device, CDI Spark 2530 (Esco Graphics Co., Ltd.) and ThermoFlex Narrow (manufactured by Kodak Co., Ltd.) were used. The ablation conditions were set such that the thermal mask layer was substantially decomposed and evaporated by laser irradiation in each laser device. The drawn original is exposed to UV rays for 75 seconds (Philips 10R, illuminance 8 mW / cm ^{2 at} 365 nm), and then exposed to a brush-type washing machine / dryer integrated device (JEWA2 SD JOWA2 SD) for 2 minutes. It was washed out for 30 seconds and dried at 60 ° C. for 10 minutes. Thereafter, as a post-exposure, UV exposure was performed for 75 seconds (Philips 10R, illuminance 8 mW / cm ^{2 at} 365 nm) to obtain a printing plate.

Examples 1-8, Comparative Examples 1-7
According to the conditions described in Table 1 or Table 2, printing plates of Examples 1 to 8 and Comparative Examples 1 to 7 were obtained by the above method. The obtained printing plates were evaluated as follows. The evaluation results are shown in Table 1 or Table 2.

Evaluation of Laser Acceptability A laser system suitable for computer plate making technology includes a rotating cylindrical drum that holds a printing original plate, an infrared laser irradiation device, and a layout computer. Ablation conditions are set such that the thermal mask layer is substantially decomposed and evaporated by laser irradiation. The ablation condition is specifically set by the number of rotations of the rotating cylindrical drum (laser irradiation time) and the laser irradiation output value (laser energy). Various laser apparatuses are commercially available as suitable laser systems, but the ablation conditions and the appropriate ablation range that gives good relief differ depending on the laser apparatus. Therefore, mask drawing was performed under various ablation conditions using CDI Spark 2530 (Esco Graphics Co., Ltd.). The surface of the plate after drawing the mask was observed with an ultra-deep laser microscope to confirm the presence or absence of fine roughness such as irregularities, undulations, and wrinkles. The determination was performed as follows.
○: Roughness such as irregularities, undulations, wrinkles, etc. on the plate surface. Δ: Minor irregularities, undulations, wrinkles on part of the plate surface.
X: Roughness such as irregularities, undulations, wrinkles, etc. occurred on the plate surface As examples of the state of the plate surface after drawing the mask, micrographs in Example 3 and Comparative Example 1 are shown in FIGS.
Ablation conditions: CDI Spark 2530, 200 rpm, 9W
Ultra-deep laser microscope: KEYENCE VK-9500, observation magnification 100 times

Evaluation of image reproducibility The area reproducibility of the relief surface was calculated by the following method using a negative image of a mask layer of 150% 1% (diameter 19 μm) obtained by laser ablation. The halftone dot area was measured by enlarging the relief surface 50 times with a microscope and measuring the area using commercially available image analysis software. Although commercially available image software can be used, the area of the halftone dot surface was measured by image analysis using image analysis software A Image-kun (manufactured by Asahi Kasei Engineering).
Relief area reproduction ratio (%) = (B / A) × 100 for a negative mask layer image of 150% 1%
A: Halftone dot area of negative image of mask layer B: Halftone dot area of relief

Evaluation of printing durability If the surface of the printing plate is weak, fine cracks occur as the number of printed copies increases. The occurrence of cracks was evaluated by a printing durability acceleration test described below. The operating environment of the printing press was 20 to 25 ° C. and humidity 30 to 40% RH. The printing press uses a convex rotary printing press (Mitsugi Machine P-20) to place the printing plate on the plate cylinder in a state where printing pressure is applied to all the images. The shape of the printing plate image was a star shape having a diameter of 16 mm. The printing pressure was usually applied to a printed material having a thickness of 150 to 250 μm, but the load was excessively applied by pressing 450 μm. The printing speed at this time was 20 to 30 m / min. As the ink, UV ink (T & K TOKA Best Cure UV Color Indigo B) was used, and the ink density was adjusted to 0.6 or more and 2.0 or less with a reflection densitometer (Dainippon Screen Manufacturing DM-800). Mirror-coated tack paper (Lintec gloss PW 8K) was used as printing paper. Printing was performed up to 8000 shots, and the occurrence of cracks was judged as impossible. The evaluation of the occurrence of cracks was determined by visually observing the presence of crack marks appearing on the printed matter with a loupe.

As is apparent from Table 1, the synthetic polymer compound in the photosensitive resin layer contains a polyamide or polyether urea urethane containing a tertiary nitrogen atom, and the dividing layer has a low saponification degree and a low polymerization degree within the scope of the present invention. It can be said that Examples 1 to 8 made of polyvinyl alcohol give a good printing plate free from roughness such as irregularities, undulations, wrinkles and the like, and are excellent in laser tolerance under any ablation condition. As for the image reproducibility, the image reproducibility of Examples 1 to 8 is almost 95% to 103%, and the image reproducibility is 95% especially when the saponification degree of polyvinyl alcohol is in the range of 60 to 80 mol%. It can be seen that the image reproducibility is excellent at ˜100%.

On the other hand, in Comparative Example 3 in which the degree of saponification of polyvinyl alcohol is less than the range of the present invention, the image reproduction rate is too low at 92%, and in Comparative Example 2 in which the degree of saponification of polyvinyl alcohol exceeds the range of the present invention, the image reproduction rate is low. Since it becomes too large with 107%, it is not preferable. In Comparative Example 1 in which the degree of polymerization of polyvinyl alcohol exceeds the range of the present invention and Comparative Example 2 in which the degree of saponification of polyvinyl alcohol exceeds the range of the present invention, roughness of the plate surface such as irregularities, undulations, wrinkles, etc. is caused by ablation conditions. occured. These roughnesses were also observed on the relief after the plate making and had an influence on the printability. In Comparative Example 3 in which the degree of saponification of polyvinyl alcohol was less than the range of the present invention, roughness such as irregularities, undulations and wrinkles was not observed under any ablation condition. However, since the degree of saponification is too low, water development cannot be performed and a relief cannot be obtained. In Comparative Example 4 in which the degree of polymerization of the polyvinyl alcohol was less than the range of the present invention, the film forming property of the divided layer coating liquid was lacking, and a divided layer could not be prepared. Therefore, evaluation was impossible. Since the comparative example 5 does not have a divided layer, the curing reaction of the photosensitive resin layer proceeds while receiving moderate polymerization inhibition under uniform atmospheric oxygen conditions. Therefore, a good printing plate having no rough surface is provided. However, due to insufficient exposure and curing of the printing plate surface, cracks are likely to occur in the solid portion of the printing plate surface during printing, resulting in poor printing durability. In addition, Comparative Examples 6 to 7 in which the synthetic polymer compound in the photosensitive resin layer does not contain a polyamide or polyether urea urethane containing a tertiary nitrogen atom are minor, but the surface of the plate is slightly affected by ablation conditions. Caused rough storms. The printing durability was slightly inferior to the evaluation of the examples.

Since the photosensitive resin relief printing original plate of the present invention has a wide range of appropriate ablation, it can be made by various CTP plate making apparatuses, and there is little fine roughness such as irregularities, undulations, wrinkles, etc. on the exposed plate surface, and a printed product. Can provide a printing plate having excellent printing durability and printing durability.

Claims

Water development in which at least (A) a support, (B) a photosensitive resin layer, (C) an oxygen-barrier dividing layer, and (D) a water-soluble or water-dispersible thermal mask layer containing carbon black are sequentially laminated. Type photosensitive letterpress printing original plate,
(B) Polyamide or polyether urea urethane in which the photosensitive resin layer contains a synthetic polymer compound, a photopolymerizable unsaturated compound, and a photopolymerization initiator, and the synthetic polymer compound contains a tertiary nitrogen atom And (C) an oxygen-barrier dividing layer contains polyvinyl alcohol having a saponification degree of 60 to 85 mol% and a polymerization degree of 200 to 800.
2. The photosensitive letterpress printing original plate according to claim 1, wherein the (D) heat-sensitive mask layer contains the synthetic polymer compound contained in the photosensitive resin layer (B).