Photosensitive resin letterpress printing original plates and printing plates

Abstract

[Problem] To provide a printing original plate for a photosensitive resin letterpress with which it is possible to achieve both gradation print reproducibility and printing durability in highlighted areas, and plate surface tackiness is low. [Solution] A printing original plate for a photosensitive resin letterpress in which a support, a photosensitive resin layer, and a cover film are laminated in this order, wherein the photosensitive resin layer has a lower layer present on the support side and an upper layer present on the cover film side, the upper layer is a photosensitive resin layer having a thickness of 3−30 μm and containing a water-soluble or water-dispersible resin (A) having a glass transition temperature of 40−90°C measured by a differential scanning calorimeter, the lower layer contains a water-soluble or water-dispersible resin (B) having a glass transition temperature higher than that of the water-soluble or water-dispersible resin (A) by 5°C or more, and the glass transition temperature of the resin (B) measured by a differential scanning calorimeter is 95−135°C.

Description

[Technical Field]

[0001] The present invention relates to a photosensitive resin relief printing original plate and a printing plate. [Background technology]

[0002] Photosensitive resin compositions used in printing plates generally contain a soluble polymer compound, a photopolymerizable unsaturated compound, and a photopolymerization initiator, and may contain additives such as stabilizers and plasticizers as needed.

[0003] It has been widely known that a relief plate for printing can be produced by a platemaking process in which the photosensitive resin composition layer is irradiated with actinic rays through a negative film having a transparent image area, the photosensitive layer in the exposed area is cured, and then the photosensitive layer in the unexposed area is dissolved and removed with an appropriate solvent, followed by drying and post-exposure.

[0004] As the soluble polymer compound for the photosensitive resin composition, it has been proposed to use soluble polyamides, fully saponified or partially saponified polyvinyl acetate, and the like.

[0005] Recently, user demands for letterpress printing plates have been moving in the direction of reproducing ultra-fine patterns, and the minimum highlight area used in printing photographs must be 5% of 200 lines or less, with the ability to reproduce smooth changes in brightness at a print size close to the negative size (gradation of highlight dots).

[0006] Conventional technologies that meet the demand for fine halftone dot printing in highlight areas include a letterpress printing plate (see Patent Document 1) that improves image reproducibility by making the photosensitive resin layer a multi-layer structure with different light transmittances, and a letterpress printing plate (see Patent Document 2) that sharpens the relief shape by making the photosensitive resin layer multi-layered, but neither of these letterpress printing plates can fully satisfy the gradation of halftone dots in highlight areas.

[0007] Furthermore, letterpress printing plates often suffer from the problem of cracks occurring in the plate during printing, resulting in defective printed matter. To improve this printing durability, a method has been proposed in which a partially saponified PVA is used in combination with a polyamide compound and a specific crosslinking agent (see Patent Document 3), and a method has been proposed in which a polyamide copolymerized with an alicyclic dicarboxylic acid and an alicyclic diamine is used (Patent Document 4). [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-23349 [Patent Document 2] Japanese Patent Application Publication No. 06-313966 [Patent Document 3] Japanese Patent Application Laid-Open No. 2014-142622 [Patent Document 4] WO17 / 056692 publication Summary of the Invention [Problem to be solved by the invention]

[0009] The present invention has been made in view of the current state of the prior art as described above, and its object is to provide a photosensitive resin letterpress printing blank and printing plate that can achieve both gradation printing reproducibility in highlight areas and high-level printing durability, and further a photosensitive resin letterpress printing blank and printing plate that have low plate surface adhesion. More specifically, the present invention is to provide a photosensitive resin letterpress printing blank and printing plate that are less likely to crack even when printed under high printing pressure, which was not possible with prior art printing blanks, and that can print a larger number of copies and have low plate surface adhesion. [Means for solving the problem]

[0010] In order to achieve the above-mentioned object, the present inventors conducted extensive research into the resin used in the photosensitive resin composition of a letterpress printing plate and the structure of the printing plate. As a result, they discovered that a photosensitive resin layer having a lower layer located on the support side and an upper layer located on the cover film side, and that by setting the thickness of the upper layer of the photosensitive resin layer and the glass transition temperatures of the resins used in the upper and lower layers within specific ranges, it is possible to achieve both good gradation printing reproducibility in highlight areas and high levels of printing durability, and thus completed the present invention.

[0011] That is, the present invention can have the following configurations (1) to (3). (1) A photosensitive resin relief printing original plate having a support, a photosensitive resin layer, and a cover film laminated in this order, wherein the photosensitive resin layer has a lower layer located on the support side and an upper layer located on the cover film side, and the upper layer contains a water-soluble or water-dispersible resin (A) having a glass transition temperature of 40 to 90°C as measured by a differential scanning calorimeter, and has a thickness 7 a photosensitive resin letterpress printing original plate having a thickness of 1000 to 30 micrometers, wherein the lower layer is a layer containing a water-soluble or water-dispersible resin (B) having a glass transition temperature 5°C or higher than that of the water-soluble or water-dispersible resin (A), and the glass transition temperature of the resin (B) is 95 to 135°C as measured by a differential scanning calorimeter. (2) The photosensitive resin letterpress printing original plate according to (1), wherein the resin (A) is polyamide or polyetherurethaneurea, and the resin (B) is polyamide, polyetherurethaneurea, or polyetheramide. (3) A printing plate obtained by removing the uncured portion of the photosensitive resin layer from the photosensitive resin letterpress printing original plate according to (1) or (2). [Effects of the Invention]

[0012] According to the present invention, it is possible to obtain a photosensitive resin letterpress printing original plate and printing plate that can achieve both 1 to 5% gradation printing reproducibility in highlight areas and high-level printing durability, and further has low plate surface adhesion. DETAILED DESCRIPTION OF THE INVENTION

[0013] The photosensitive resin layer of the present invention has a structure in which the photosensitive resin layer has a lower layer present on the support side and an upper layer present on the cover film side, and the upper layer is a photosensitive resin layer having a thickness of 3 to 30 micrometers and containing a water-soluble or water-dispersible resin (A) having a glass transition temperature of 40 to 90°C, and the lower layer is preferably a layer containing a water-soluble or water-dispersible resin (B) having a glass transition temperature at least 5°C higher than that of the water-soluble or water-dispersible resin (A).In this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits.

[0014] The thickness of the upper layer of the photosensitive resin layer used in the present invention is preferably 3 micrometers or more, more preferably 5 micrometers or more, and even more preferably 7 micrometers or more. If it is too thin, printing durability may decrease when the number of printing shots is increased. Also, it is preferably 30 micrometers or less, more preferably 20 micrometers or less, and even more preferably 10 micrometers or less. If it is too thick, printability in highlight areas may decrease.

[0015] The water-soluble or water-dispersible resin (B) used in the lower layer of the present invention has a glass transition temperature of 95°C or higher and 135°C or lower. If the glass transition temperature is too low, printability in highlight areas may be reduced. The glass transition temperature is preferably 95°C or higher, more preferably 105°C or higher, and even more preferably 110°C or higher. If the glass transition temperature is too high, printing durability may be reduced. The glass transition temperature is preferably 135°C or lower, more preferably 130°C or lower, and even more preferably 125°C or lower. By making the water-soluble or water-dispersible resin (B) used in the lower layer have a glass transition temperature that is at least 5°C higher than that of the water-soluble or water-dispersible resin (A), satisfactory gradation printing reproducibility in highlight areas can be achieved.

[0016] The water-soluble or water-dispersible resin (B) is, for example, polyamide or polyether urethane urea, and is preferably polyamide from the viewpoint of molecular design that controls the glass transition temperature.

[0017] The polyamide of the present invention can be obtained, for example, by reacting a diamine and a dicarboxylic acid.

[0018] Examples of diamines include diamines that do not contain a tertiary nitrogen atom, diamines that contain a tertiary nitrogen atom, etc. These can be used alone or in combination of two or more.

[0019] Diamines not containing a tertiary nitrogen atom include ethylenediamine, diethylenediamine, trimethylenediamine, tetramethylenediamine, hexamethylenediamine, 1,3-propylenediamine, 2-methylpentamethylenediamine, undecamethylenediamine, dodecamethylenediamine, 2,2,4-trimethylhexamethylenediamine, 2,4,4-trimethylhexamethylenediamine, isophoronediamine, 1,4-cyclohexanediamine, and 1,3-cyclohexanediamine. Examples of suitable alkyl amines include sandiamine, 1,3-bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane, 1-amino-3-aminomethyl-3,5,5-trimethylcyclohexane, bis(4-aminocyclohexyl)methane, bis(3-methyl-4-aminocyclohexyl)methane, 2,2-bis(4-aminocyclohexyl)propane, methylcyclohexanediamine, norbornanediamine, tricyclodecanediamine, polyetheramine JEFFAMINE ED900, meta- or para-xylylenediamine, and meta- or para-phenylenediamine, but isophoronediamine and 1,3-bis(aminomethyl)cyclohexane are preferred.

[0020] On the other hand, diamines containing a tertiary nitrogen atom include diamines having a basic tertiary nitrogen atom in the main chain or side chain, specifically diamines having a piperazine ring and other diamines. Specific examples of diamines having a piperazine ring include diamines having a piperazine ring such as N,N'-bis(aminomethyl)piperazine, N,N'-bis(2-aminoethyl)piperazine, N,N'-bis(2-aminoethyl)methylpiperazine, N-(aminomethyl)-N'-(2-aminoethyl)piperazine, N,N'-bis(3-aminopentyl)piperazine, N-(2-aminoethyl)piperazine, N-(aminopropyl)piperazine, N-(ω-aminohexyl)piperazine, N-(3-aminocyclohexyl)piperazine, N-(2-aminoethyl)-3-methylpiperazine, N-(2-aminoethyl)-2,5-dimethylpiperazine, N-(2-aminopropyl)-3-methylpiperazine, and N-(3-aminopropyl)-2,5-dimethylpiperazine.

[0021] Examples of diamines other than those having a piperazine ring include N,N-di(2-aminoethyl)amine, N,N-di(3-aminopropyl)amine, N,N-di(2-aminoethyl)methylamine, N,N-di(3-aminopropyl)ethylamine, N,N-di(3-aminopropyl)isopropylamine, N,N-di(3-aminopropyl)cyclohexylamine, N,N-di(4-amino-n-butyl)amine, N-methyl-N-(2-aminoethyl)-1,3-propanediamine, N,N'-dimethyl-N,N'-di(3-aminopropyl)ethylenediamine, N,N'-dimethyl-N,N'-di(3-aminopropyl)tetramethylenediamine, N,N'-diisobutyl-N,N'-di-(3-aminopropyl)hexamethylenediamine, N,N'-dicyclohexyl-N,N'-di-( 1,2-bis(3-aminopropyl)hexamethylenediamine, N,N'-dicyclohexyl-N,N'-bis(2-carboxypropyl)hexamethylenediamine, N,N'-di-(3-aminopropyl)-2,2,4-trimethyl-hexamethylenediamine, 1,2-bis(3-aminopropoxy)-2-methyl-2-(N,N-dimethylaminomethyl)propane, 1,2-bis(3-aminopropoxy)-2-methyl-2-(N,N-diethylaminomethyl)propane, 1,2-bis(3-aminopropoxy)-2-ethyl-2-(N,N-dimethylaminomethyl)propane, 1,3-bis(3-aminopropoxy)-2-(N,N-dimethylaminomethyl)propane, etc., but N,N'-bis(3-aminopropyl)piperazine and N-(2-aminoethyl)piperazine are preferred.

[0022] Examples of dicarboxylic acids include aromatic dicarboxylic acids, aliphatic dicarboxylic acids, unsaturated alicyclic dicarboxylic acids, alicyclic dicarboxylic acids, etc. These can be used alone or in combination of two or more.

[0023] Examples of aromatic dicarboxylic acids include terephthalic acid, isophthalic acid, orthophthalic acid, 2,6-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 5-sodium sulfoisophthalic acid, 5-lithium sulfoisophthalic acid, 5-sodium sulfoterephthalic acid, 4,4'-diphenylmethanedicarboxylic acid, 4,4'-diphenyletherdicarboxylic acid, 4,4'-biphenyldicarboxylic acid, 4,4'-stilbenedicarboxylic acid, p-oxybenzoic acid, p-(hydroxyethoxy)benzoic acid, and β-hydroxynaphthoic acid. Examples of aliphatic dicarboxylic acids include adipic acid, glutaric acid, decanedicarboxylic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, and dimer acid. Examples of unsaturated alicyclic dicarboxylic acids include fumaric acid, maleic acid, itaconic acid, hexahydrophthalic acid, and tetrahydrophthalic acid.Alicyclic dicarboxylic acids include isophoronedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 2,3-norbornanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 2-methyl-1,4-cyclohexanedicarboxylic acid, 2-ethyl-1,4-cyclohexanedicarboxylic acid, 2-propyl-1,4-cyclohexanedicarboxylic acid, 2-butyl-1,4-cyclohexanedicarboxylic acid, 2-t-butyl-1,4-cyclohexanedicarboxylic acid, 2,3-dimethyl-1,4-cyclohexanedicarboxylic acid, 2 ,3-Diethyl-1,4-cyclohexanedicarboxylic acid, 2,3-Dipropyl-1,4-cyclohexanedicarboxylic acid, 2,3-Dibutyl-1,4-cyclohexanedicarboxylic acid, 2-Methyl-3-ethyl-1,4-cyclohexanedicarboxylic acid, 2-Methyl-3-propyl-1,4-cyclohexanedicarboxylic acid, 2-Methyl-3-butyl-1,4-cyclohexanedicarboxylic acid, 2-Ethyl-3-propyl-1,4-cyclohexanedicarboxylic acid, 2-Ethyl-3-butyl-1,4-cyclohexanedicarboxylic acid Acid, 2-methyl-3-t-butyl-1,4-cyclohexanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 2,6-decalindicarboxylic acid, 3-methyl-2,6-decalindicarboxylic acid, 3-ethyl-2,6-decalindicarboxylic acid, 3-propyl-2,6-decalindicarboxylic acid, 3-butyl-2,6-decalindicarboxylic acid, 3,4-dimethyl-2,6-decalindicarboxylic acid, 3,4-diethyl-2,6-decalindicarboxylic acid, 3,4-dipropyl-2,6-decalindicarboxylic acid, 3,4-di butyl-2,6-decalindicarboxylic acid, 3,8-dimethyl-2,6-decalindicarboxylic acid, 3,8-diethyl-2,6-decalindicarboxylic acid, 3,8-dipropyl-2,6-decalindicarboxylic acid, 3,8-dibutyl-2,6-decalindicarboxylic acid, 3-methyl-4-ethyl-2,6-decalindicarboxylic acid, 3-methyl-4-propyl-2,6-decalindicarboxylic acid, 3-methyl-4-butyl-2,6-decalindicarboxylic acid, and 3-ethyl-4-butyl-2,6-decalindicarboxylic acid. Among these, adipic acid and 1,4-cyclohexanedicarboxylic acid are preferred in terms of gradation printing reproducibility in highlight areas.

[0024] For example, known aminocarboxylic acids, lactams, or derivatives thereof can be used as the polyamide of the present invention, as long as they do not affect the properties of the polyamide. Examples of aminocarboxylic acids include 4-aminocyclohexanecarboxylic acid, 3-aminocyclohexanecarboxylic acid, 4-(aminomethyl)cyclohexanecarboxylic acid, 3-(aminomethyl)cyclohexanecarboxylic acid, and 2-aminomethylcyclopropanecarboxylic acid, and examples of lactams include ε-caprolactam and ω-laurolactam. These can be used alone or in combination of two or more.

[0025] The polyamide used in the water-soluble or water-dispersible resin (B) can have a glass transition temperature in a specific range by, for example, introducing a ring structure such as an aromatic ring or an alicyclic ring into the molecular chain. A specific example of a method for increasing or decreasing the glass transition temperature is by increasing or decreasing the mole percent content of alicyclic structural units derived from diamines and dicarboxylic acids in the polyamide.

[0026] The polymerization of the polyamide of the present invention can be carried out, for example, by a known method.

[0027] The molar ratio (amino group / carboxyl group) of diamine to dicarboxylic acid for polymerizing the polyamide of the present invention is, for example, 1.0 or more, preferably 1.01 or more. By setting the molar ratio within the above range, it becomes possible to extract the polymer after the polymerization reaches equilibrium, and fluctuations in molecular weight can be suppressed.

[0028] The polyetherurethane urea of ​​the present invention can be obtained, for example, by addition polymerization of a diamine and a polyethylene glycol-containing terminal diisocyanate compound in a solvent. The molecular weight of the obtained polyetherurethane urea can be increased by further reacting it with a diisocyanate compound.

[0029] The diamine is made from the same raw material as that of polyamide, but from the viewpoint of polymerizability, diamines having a piperazine ring such as N,N'-bis(aminoethyl)-piperazine, N,N'-bis(3-aminopropyl)piperazine, and N-(2-aminoethyl)piperazine are preferred.

[0030] The polyethylene glycol-containing terminal diisocyanate compound, which is the other raw material for synthesizing polyether urethane urea, is a diisocyanate compound having isocyanate groups at substantially both ends, which is obtained by reacting a known aliphatic, alicyclic, or aromatic diisocyanate with an equimolar or less amount of polyoxyethylene glycol.

[0031] The diisocyanate used to obtain the polyethylene glycol-containing terminal diisocyanate compound may be any known aliphatic, alicyclic, or aromatic diisocyanate. Examples include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, p-xylylene diisocyanate, 1,3-cyclohexanedimethylisocyanate, p-xylylene diisocyanate, 1,5-naphthalene diisocyanate, 2,6-diisocyanate methylcaproate, diphenylether-4,4'-diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate. From the viewpoints of storage stability and reactivity, aliphatic diisocyanates are preferred, and hexamethylene diisocyanate is particularly preferred.

[0032] The polymerization of the polyetherurethane urea of ​​the present invention can be carried out by, for example, a known method, such as a method of reacting the two components in a solvent-free state while mixing and stirring, or a method of dissolving the two components in an inert solvent and reacting them.

[0033] The molar reaction ratio (amino group / isocyanate group) between the diamine and diisocyanate compound used to polymerize polyether urethane urea is 1.0 or greater, preferably 1.02 or greater. In this case, even if excess terminal amino groups remain unreacted, this is not a problem as long as it does not adversely affect the performance and physical properties of the composition. Furthermore, an amino group / isocyanate group (equivalent ratio) of less than 1.0 is undesirable because it is prone to undesirable reactions such as gelation. Because the reactivity of amines and isocyanates is extremely high, the reaction between the two can be carried out in active solvents such as water, alcohols such as methanol, or mixtures of water and alcohols, and the reaction is completed rapidly. Furthermore, although the reaction between the two should be carried out under optimal conditions suited to the system, the reaction can also proceed rapidly at relatively low temperatures, such as room temperature.

[0034] The method of adjusting the glass transition temperature of the polyetherurethane urea used in the water-soluble or water-dispersible resin (B) to a specific range can be exemplified by adjusting the amount of urea bonds and the amount of alkylene glycol components in the resin.Specific examples of the method of increasing or decreasing the glass transition temperature include increasing or decreasing the mole percent contents of the urea bonds and alkylene glycol components obtained from the terminal diisocyanate compound containing polyethylene glycol and the dicarboxylic acid in the polyetherurethane urea.

[0035] The polyamide or polyether urethane urea used in resin (B) is water-soluble or water-dispersible (water-developable). To satisfy this requirement, a diamine or dicarboxylic acid having a polar group may be selected. The diamine may be selected from aliphatic diamines, aromatic diamines, heterocyclic diamines, and alicyclic diamines. Among these, diamines having a piperazine ring and diamines containing a tertiary nitrogen atom, such as methyliminobispropylamine, are preferred in terms of water-developability. Furthermore, from the viewpoint of the elastic modulus of the polymer, it is particularly preferred to use a diamine having a piperazine ring. Examples of diamines having a piperazine ring include 1,4-bis(3-aminoethyl)piperazine, 1,4-bis(3-aminopropyl)piperazine, and N-(2-aminoethyl)piperazine.

[0036] The water-soluble or water-dispersible resin (A) used in the upper layer is preferably a resin having a glass transition temperature (Tg) measured by a differential scanning calorimeter of 40° C. to 90° C. More preferably, the glass transition temperature is 55° C. to 85° C., and even more preferably, 65° C. to 80° C. If the glass transition temperature is too low, the tackiness of the plate surface may deteriorate, and if the glass transition temperature is too high, the printing durability may decrease.

[0037] The resin used as resin (A) is preferably a resin selected from polyamide, polyetherurethane urea, or polyether amide.

[0038] The polyamide used for resin (A) is a combination of diamine and dicarboxylic acid, and may optionally contain an aminocarboxylic acid. These raw materials are the same as those for the polyamide of resin (B), but by adjusting the content of the ring-structured diamine or dicarboxylic acid to an appropriate level, the glass transition temperature (Tg) can be adjusted to 40°C or higher and 90°C or lower.

[0039] The polyether urethane urea used in resin (A) is a combination of diamine and diisocyanate compounds. These raw materials are the same as those used in the polyether urethane urea of ​​resin (B), but by adjusting the content of the ring-structured diamine to an appropriate level, the glass transition temperature (Tg) can be adjusted to 40°C or higher and 90°C or lower.

[0040] The polyetheramide used in the present invention is, for example, a polyamide having a polyether bond and an amide bond in the main chain, and uses polyethylene glycol as the polyether component. The polyetheramide can be synthesized by polymerization using, for example, the method described in JP-A-55-74537. Specifically, it can be synthesized by a known polymerization method using a structural unit consisting of polyethylene glycol having an amino group at its terminal and an aliphatic dicarboxylic acid, and other polyamide structural units. The polyetheramide may be a polyetheresteramide containing an ester bond in the molecule. Furthermore, the introduction of a tertiary nitrogen atom can be achieved by copolymerizing a structural unit using a diamine or dicarboxylic acid having a tertiary nitrogen atom as the polyamide component used as the hard segment. The introduction of a tertiary nitrogen atom can facilitate the design of the water solubility or water dispersibility of the resin.

[0041] The polyamides used in the polymerization of polyetheramides are homopolymers, copolymers, and mixtures of two or more thereof, synthesized by known methods from diamines and dicarboxylic acids, or ω-amino acids, lactams, or derivatives thereof. Examples of polyamides include various nylons such as nylon 6, nylon 66, nylon 610, nylon 6 / 66 / 610, and nylon 6 / 66 / 612, as well as polyamides obtained from metaxylenediamine and adipic acid, diaminodicyclohexylmethane copolymerized polyamides, basic nitrogen-containing copolymerized polyamides containing structural units such as N,N'-bis(3-aminopropyl)piperazine and adipic acid, polyether-containing polyamides such as polyethylene glycol copolymerized polyamides containing amino groups at both ends and polyethylene glycol copolymerized polyamides containing carboxyl groups at both ends, and N-methylolated and N-alkoxymethylated products of various polyamides. Among these, basic nitrogen-containing copolymerized polyamides and polyether-containing polyamides are preferred.

[0042] A preferred method for introducing basic nitrogen into polyamide is to use a diamine having a basic tertiary nitrogen atom in the main chain or side chain. Specific examples of the diamine include diamines having a piperazine ring, such as N,N'-bis(aminomethyl)piperazine, N,N'-bis(2-aminoethyl)piperazine, and N,N'-bis(3-aminopropyl)piperazine, with N,N'-bis(3-aminopropyl)piperazine being particularly preferred.

[0043] The polyether may be a polyoxyalkylene glycol having a number-average molecular weight of 200 to 4,000. Specific examples of the polyoxyalkylene glycol include polyoxyethylene glycol having a number-average molecular weight of 200 to 4,000, polyoxypropylene glycol having a number-average molecular weight of 200 to 4,000, and polytetramethylene glycol having a number-average molecular weight of 200 to 4,000. From the viewpoint of achieving both impact resilience and flexibility, the polyether is preferably polyethylene glycol having a molecular weight of 400 to 1,500.

[0044] The glass transition temperature (Tg) of the polyether amide can be adjusted to 40°C or higher and 90°C or lower by adjusting the content of the polyether component derived from polyethylene glycol to an appropriate content.

[0045] Whether resin (A) or resin (B) is water-soluble or water-dispersible can be determined by immersing polyamide, polyetheramide, or polyetherurethaneurea alone in water or acidic water at 30°C and rubbing it with a brush or the like. If the photosensitive resin is uniformly mixed in water or acidic water after physical rubbing with a brush or the like, the resin is determined to be water-soluble. On the other hand, if the photosensitive resin is partially or entirely swelled and dispersed in water after physical rubbing with a brush or the like, and the resin is non-uniformly mixed, the resin is determined to be water-dispersible.

[0046] The photosensitive resin compositions used in the upper and lower layers are composed of resin (A), resin (B), a photopolymerizable unsaturated compound, a photopolymerization initiator, and optional additives such as plasticizers, thermal polymerization inhibitors, dyes, pigments, UV absorbers, fragrances, or antioxidants. It is preferable that the photosensitive resin compositions used in the upper and lower layers use the same compounds in terms of storage stability. In particular, it is preferable that resin (A) and resin (B) be the same resin in terms of interlayer adhesion.

[0047] In the photosensitive resin composition for a photosensitive resin layer of the present invention, if the water-soluble or water-dispersible resin contains basic tertiary nitrogen atoms, it is preferable to quaternize at least a portion of the nitrogen atoms with a quaternizing agent. The quaternizing agent may be a protic or aprotic quaternizing agent. Specific examples include maleic acid, itaconic acid, acrylic acid, methacrylic acid, cinnamic acid, glycolic acid, lactic acid, succinic acid, adipic acid, benzoic acid, glycidyl methacrylate, and glycidyl acrylate, with glycidyl methacrylate and glycidyl acrylate being particularly preferred. The quaternizing agent may be contained in an amount of up to 0.70 mol, particularly up to 0.60 mol, per 1000 g of the polymer compound.

[0048] For example, a desired amount of basic tertiary nitrogen atoms quaternized with a photopolymerizable group-containing aprotic quaternizing agent can be incorporated into a polymeric compound by determining the amount of basic tertiary nitrogen atoms based on the blend ratio of the basic tertiary nitrogen atom-containing raw material in the water-soluble or water-dispersible resin, and then adjusting the quaternization ratio of the photopolymerizable group-containing quaternizing agent relative to the amount of the introduced basic tertiary nitrogen atoms. The quaternization ratio is the ratio of the number of moles of quaternized basic tertiary nitrogen atoms to the number of moles of basic tertiary nitrogen atoms contained in the polymeric compound, and is expressed as mol%. The quaternization ratio using the quaternizing agent is preferably 0 to 50%, more preferably 20 to 50%. While quaternization can be achieved using only a thermal acid generator without a quaternizing agent, the use of a quaternizing agent in combination improves the stability of resin residue removal, and by keeping the quaternization ratio using the quaternizing agent to 50% or less, damage to the image area during washing with water can be suppressed.

[0049] The amount of the water-soluble or water-dispersible resin used in the present invention is preferably 45 to 65% by weight of the total photosensitive resin composition. If the amount is less than 45% by weight, sufficient physical properties cannot be obtained, and if it exceeds 65% by weight, photocurability may deteriorate and image reproducibility may decrease. To satisfy both physical properties and image reproducibility, the amount is more preferably 50 to 65% by weight.

[0050] The photopolymerizable unsaturated compound used in the present invention is, for example, a compound that contains one or more photopolymerizable unsaturated groups in the molecule, and known compounds can be used. Examples of the compound that contains one photopolymerizable unsaturated group in the molecule include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-chloro-2-hydroxypropyl (meth)acrylate, cyclohexyl (meth)acrylate, benzyl (meth)acrylate, N,N'-dimethylaminoethyl (meth)acrylate, glycidyl (meth)acrylate, (meth)acrylamide, N-methylol (meth)acrylamide, N-methylol (meth)acrylamide-n-butyl ether, diacetacrylamide, N-tert-butyl (meth)acrylamide, the ring-opening addition reaction product of glycidyl (meth)acrylate and monoalcohol, and compounds that have one unsaturated bond such as 2-acrylamido-2-methylpropanesulfonic acid. Examples of compounds containing two or more photopolymerizable unsaturated groups in the molecule include ethylene glycol di(meth)acrylate, 1,3-propanediol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, glycerin dimethacrylate, 2-hydroxy-3-acryloyloxypropyl methacrylate, trimethylolethane di(meth)acrylate, trimethylolethane tri(meth)acrylate, trimethylolpropane di(meth)acrylate, trimethylolpropane tri(meth)acrylate, tetramethylolethane di(meth)acrylate, tetramethylolethane tri ... Tyrolmethane di(meth)acrylate, tetramethylolmethane tri(meth)acrylate, tetramethylolmethane tetra(meth)acrylate, tri(meth)acryloyloxyethyl phosphate, triester of tris(2-hydroxyethyl)isocyanuric acid and (meth)acrylic acid, ring-opening addition reaction products of polyglycidyl ethers of polyhydric alcohols and (meth)acrylic acid, for example, reaction products of (poly)ethylene glycol diglycidyl ether and (meth)acrylic acid, reaction products of diglycidyl ether of (poly)propylene glycol and (meth)acrylic acid, 1,Reaction products of 6-hexamethylene glycol diglycidyl ether and (meth)acrylic acid, reaction products of glycerin diglycidyl ether and (meth)acrylic acid, reaction products of trimethylolethane triglycidyl ether and (meth)acrylic acid, reaction products of trimethylolpropane triglycidyl ether and (meth)acrylic acid, reaction products of isophthalic acid diglycidyl ether and (meth)acrylic acid, reaction products of isoprene oligomer dicarboxylic acid diglycidyl ether and (meth)acrylic acid, etc. ring-opening addition reaction products of the above active hydrogen compounds with glycidyl (meth)acrylate, for example, reaction products of (poly)ethylene glycol and glycidyl (meth)acrylate, reaction products of (poly)propylene glycol and glycidyl (meth)acrylate, reaction products of glycerin and glycidyl (meth)acrylate, reaction products of 2-hydroxyethyl (meth)acrylate and glycidyl (meth)acrylate, reaction products of trimethylolethane and glycidyl (meth)acrylate, reaction products of trimethylolpropane and glycidyl Reaction products of (meth)acrylates, reaction products of (meth)acrylic acid and glycidyl (meth)acrylate, reaction products of aliphatic polycarboxylic acids and glycidyl (meth)acrylate, reaction products of aromatic polycarboxylic acids and glycidyl (meth)acrylate, compounds having two or more unsaturated groups obtained by reacting a compound having a primary or secondary amino group with glycidyl (meth)acrylate, N,N'-methylenebis(meth)acrylamide, N,N'-ethylenebis(meth)acrylamide, N,N'-propyl ethylenebis(meth)acrylamide, N,N'-hexamethylenebis(meth)acrylamide, N,N'-m-phenylenebis(meth)acrylamide, N,N'-m-xylylenebis(meth)acrylamide, di(meth)acrylamide-N-methyl ether, 1,3-bis[(meth)acryloylaminomethyl]urea and its derivatives, 1,3-[bis(meth)acryloylaminomethyl]-1,3-dimethylurea and its derivatives, 1,3-[bis(meth)acryloylaminomethyl]ethyleneurea and its derivatives, 1,Examples of photopolymerizable unsaturated compounds include 3-[bis(meth)acryloylaminomethyl]trimethylene urea and its derivatives, triacrylformal, tri(meth)acrylate of tris(2-hydroxyethyl)isocyanuric acid, and compounds having two or more unsaturated bonds, such as 1,3-diglycidyl 5-methyl 5-ethylhydantoin. Among these photopolymerizable unsaturated compounds, glycerin dimethacrylate, 2-hydroxy-3-acryloyloxypropyl methacrylate, reaction products of trimethylolpropane and glycidyl (meth)acrylate, and reaction products of glycerin and glycidyl (meth)acrylate are preferred.

[0051] The photopolymerizable unsaturated compound may be used alone or in combination of two or more. The amount of the photopolymerizable unsaturated compound used is preferably 25 to 50% by weight of the total photosensitive resin composition. If the amount of the photopolymerizable unsaturated compound used exceeds 50% by weight, sufficient mechanical strength cannot be obtained, and if it is less than 25% by weight, photocurability may be poor, which may reduce image reproducibility.

[0052] Known photopolymerization initiators can be used, including benzophenones, benzoins, acetophenones, benzils, benzoin alkyl ethers, benzyl alkyl ketals, anthraquinones, and thioxanthones. Specific examples include benzophenone, benzoin, acetophenone, benzoin methyl ether, benzoin ethyl ether, benzil dimethyl ketal, anthraquinone, 2-chloroanthraquinone, thioxanthone, and 2-chlorothioxanthone. Among these photopolymerization initiators, benzil dimethyl ketal is preferred, and benzil dimethyl ketal may be combined with benzophenones or acetophenones. The amount of photopolymerization initiator used is preferably 0.05 to 5 wt% of the total photosensitive resin composition. A content of less than 0.05 wt% impairs photopolymerization initiation ability, while a content of more than 5 wt% reduces photocurability in the thickness direction of the photosensitive resin layer of the printing plate precursor when creating a printing relief, making the image more susceptible to chipping.

[0053] If necessary, a known thermal polymerization inhibitor may be added. The thermal polymerization inhibitor is added to prevent unintended thermal polymerization due to heating during preparation, production, molding, or other processes of the photosensitive resin composition, or to prevent dark reactions during storage of the composition. Examples of thermal polymerization inhibitors include hydroquinones such as hydroquinone, mono-tert-butylhydroquinone, 2,5-di-tert-butylhydroquinone, and hydroquinone monomethyl ether; benzoquinones such as benzoquinone and 2,5-diphenyl-p-benzoquinone; phenols; catechols such as catechol and p-tert-butylcatechol; aromatic amine compounds; vicinal acids; phenothiazine, α-naphthoquinones, anthraquinones; nitro compounds; and sulfur compounds. The amount of the thermal polymerization inhibitor used is preferably 0.001 to 2 wt %, and particularly preferably 0.005 to 1 wt %, of the total photosensitive resin composition. Two or more of these compounds may be used in combination.

[0054] The photosensitive resin composition of the present invention may contain a known plasticizer. Preferred plasticizers are hydrophilic plasticizers, such as ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, glycerin, and ethylene oxide adducts and propylene oxide adducts of polyhydric alcohols such as glycerin.

[0055] The photosensitive resin composition of the present invention can be molded into a desired laminate configuration by any known method, such as melt molding, hot pressing, casting, melt extrusion, or solution casting, to obtain a relief printing original plate provided with a photosensitive resin layer.

[0056] A relief printing plate precursor can be used by laminating a sheet-shaped molded product (unexposed resin) onto a support with or without a known adhesive. Supports can be made of any material, including steel, aluminum, glass, and plastic films such as polyester film, with a thickness ranging from 50 to 500 μm. When a laminate is supplied in which the sheet-shaped molded product (unexposed resin) is laminated on a support, it is preferable to further laminate a protective film in contact with the sheet-shaped molded product (unexposed resin). The protective film can be a plastic film, such as a polyester film with a thickness of 125 μm. An anti-adhesion layer, consisting of a non-sticky, transparent polymer that disperses or dissolves in a developer and is applied to a thickness of 0.5 to 3 μm, may be provided between the photosensitive resin layer and the protective film. The provision of the anti-adhesion layer on the surface of the photosensitive resin layer facilitates the peeling of the protective layer during the subsequent exposure operation, even if the surface is highly tacky.

[0057] As a method for obtaining a structure in which the photosensitive resin layer of the present invention has a lower layer located on the support side and an upper layer located on the cover film side, known manufacturing methods can be used. However, from the viewpoint of productivity, a method in which a cover film having a photosensitive resin composition laminated on the uppermost layer is laminated on the lower layer is preferred.

[0058] The relief printing original plate of the present invention can be used to produce a CTP (Computer to Plate) plate without using a negative film by providing a heat-sensitive mask layer on the surface of the photosensitive resin layer. A known heat-sensitive mask layer can be used as the heat-sensitive mask layer.

[0059] A relief printing plate precursor obtained from the photosensitive resin composition of the present invention is prepared, for example, by closely superimposing a negative film having a transparent image area on a photosensitive resin layer and then irradiating it with actinic rays from above to produce a plate precursor in which only the exposed areas through which the actinic rays have penetrated are insolubilized. Actinic rays are typically emitted from light sources such as high-pressure mercury lamps, ultra-high-pressure mercury lamps, metal halide lamps, xenon lamps, and chemical lamps, with wavelengths typically ranging from 300 to 450 nm. In the case of a CTP plate, a heat-sensitive mask layer is irradiated imagewise with an IR laser to form a mask (with the same function as a negative film) on the photosensitive resin layer. After image information is written into the heat-sensitive mask layer, the entire surface of the photosensitive printing plate precursor is irradiated with actinic rays through the mask to produce a plate precursor insolubilized only the exposed areas through which the actinic rays have penetrated.

[0060] Next, the unexposed areas (uncured areas) are dissolved and removed using a suitable solvent, particularly neutral water, and can be dissolved and removed using a developing method such as a spray-type developing device or a brush-type developing device. After that, the printing plate from which the unexposed areas have been dissolved and removed undergoes draining, drying, and post-exposure processes to obtain the final printing plate.

[0061] It has been found that a relief printing precursor obtained from the photosensitive resin composition of the present invention exhibits excellent gradation printing performance and printing durability in highlight areas, and further exhibits very low plate surface tackiness. Therefore, the relief printing precursor of the present invention allows a large number of high-quality prints to be printed with a single plate. Furthermore, the reduced plate surface tackiness reduces adhesion of dust and paper powder before and during printing, significantly reducing the number of times the plate needs to be washed to remove adhesions. [Example]

[0062] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these. In the examples (main text), the number of parts represents parts by mass. The polyamide composition in Table 1 represents mol%. The mol% of the polyamide composition was determined by H-NMR measurement. The property values ​​in the examples were evaluated according to the following methods.

[0063] (1) Highlight printability (highlight gradation print reproducibility) First, a printing evaluation negative containing a solid image (1 cm wide x 5 cm long) with 200 lines of dots (1% to 95%), a minimum independent dot diameter of 50 to 600 μm, and a minimum independent line width of 10 to 150 μm was used on a letterpress printing plate with a photosensitive layer thickness of 685 μm. The optimum exposure time was the minimum exposure time required to reproduce 200 lines of dots (1% to 95%), with an illuminance of 25 W / m 2 The plate was exposed to light from a height of 5 cm above the photosensitive resin surface using a chemical lamp adjusted to 1000 kJ / s. It was then developed with tap water at 25°C using a brush washer (120 μm diameter nylon brush, JW-A2-PD model manufactured by Nippon Denshi Seiki Co., Ltd.) to obtain a relief image. After drying with hot air at 60°C for 10 minutes, the plate was post-exposed to an ultra-high-pressure mercury lamp for 30 seconds to obtain a printing plate. Image reproducibility at 200 lpi-1% was assessed visually using a 10x magnifying glass. The resulting printing plate was used to evaluate highlight printability. A rotary printing press, P-20 (Sanjo Kikai), was used, with Best Cure Ai (T&K Toka) ink and Gloss PW-8K (Lintec) for the printed substrate. The printing pressure (pressure between the plate and the printed substrate) was gradually increased until the point at which the solid areas no longer blurred was considered the optimum pressure. The ink feed rate was also adjusted so that the ink density in solid areas would be 1.7abs. The dot density from 1% to 5% at 200 lpi at the appropriate pressure was measured using a CCDOT4 (manufactured by S.D.G. Corporation), and the results are shown in percentages in Table 1. Highlight printability is rated as excellent when the dot density of the print is close to that of the negative film, and when the dot density of the print decreases smoothly as the dot density of the negative film decreases from 5% to 1%.

[0064] (2)Tackiness of plate surface A printing plate was produced in the same manner as in (1) for producing the relief for evaluating highlight printability, and the resulting printing plate was used to evaluate the adhesion of the printing plate surface. The adhesion was evaluated by pressing the printing substrate, coated paper (Gloss PW-8K, manufactured by Lintec Corporation), against the plate and evaluating the degree of slippage of the coated paper according to the following criteria. ○: The coated paper slides without resistance. △: The coated paper and plate stick together, but slip when pressure is applied. ×: The coated paper and the plate are adhesive and do not slide.

[0065] (3) Printing durability (solid cracking) A printing plate was produced in the same manner as when the relief for evaluating the printability of the highlight area (1) was produced, and 20,000 shots were printed under a high printing pressure that was increased by 100 μm from the appropriate printing pressure. After 10,000 shots and 20,000 shots, the printed matter and the plate were observed under a microscope magnified 200 times, and evaluated according to the following criteria. ◎: No defects in the print and no cracks in the plate. ○: There are no defects in the print, but there are minor cracks in the plate. △: No defects can be found visually on the printed matter, but defects are found when observed under a microscope at 200x magnification. ×: Defects can be visually confirmed in the printed matter.

[0066] (4) Glass transition temperature (Tg) Measurements were performed using a differential scanning calorimeter, DSC100, manufactured by TA Instruments. 10.0 mg of polyamide resin was placed in an aluminum pan and heated to 230°C at a rate of 10°C / min. After reaching 230°C, the pan was held for 3 minutes and then immediately quenched in liquid nitrogen. The pan was then heated from room temperature to 300°C at a rate of 10°C / min, and the glass transition temperature (Tg) was determined. Tg was determined as the temperature at the intersection of the tangent line at the baseline and the inflection point.

[0067] Polymerization example of polyamide resin A-1 394.9 parts of ε-caprolactam, 469.1 parts of adipic acid, 340.5 parts of 1,4-bis(3-aminopropyl)piperazine, 199.1 parts of 1,3-bis(aminomethyl)cyclohexane, 34.1 parts of isophoronediamine, 5 parts of 50% aqueous hypophosphorous acid solution, and 1000 parts of water were charged into an autoclave, purged with nitrogen, sealed, and gradually heated. When the internal pressure reached 0.4 MPa, water was distilled off until the pressure could no longer be maintained. The pressure was returned to normal over approximately 2 hours, and the reaction was continued at normal pressure for 1 hour. The maximum polymerization reaction temperature was 255°C. This yielded a polyamide with a glass transition temperature of 35°C. The composition of the polyamide was measured by H-NMR, confirming that there was no difference between the charged composition and the polymer composition.

[0068] Polymerization of polyamide resins A-2 to A-4, A-7, B-1 to B-5, and B-8 Polyamide resins A-2 to A-4, A-7, B-1 to B-5, and B-8 were polymerized in the same manner as for polyamide resin A-1, except that the types and blending ratios of raw materials were changed as shown in Table 1. The glass transition temperatures of the resulting resins are shown in Table 1.

[0069] Polymerization of Polyetheramide Resin B-6 Two equivalents (672.8 parts) of hexamethylene diisocyanate were placed in a flask equipped with a dropping funnel and heated to 110°C under a nitrogen atmosphere. One equivalent (1200.0 parts) of polyethylene glycol with a number average molecular weight of 600 was then added dropwise using the dropping funnel with stirring. Stirring was continued for 30 minutes after the addition. The amount of isocyanate in the resulting compound was half of the original amount, and the hydroxyl groups at both ends of the polyethylene glycol had reacted with the isocyanate groups, resulting in a PEG600-both-ends HDI-modified product with isocyanate groups at both ends. 219.2 parts adipic acid, 399.7 parts 1,4-cyclohexanedicarboxylic acid, 139.5 parts 2-methylpentamethylenediamine, 320.5 parts 1,4-bis(3-aminopropyl)piperazine, 204.3 parts isophoronediamine, 5 parts 50% aqueous hypophosphorous acid solution, and 1000 parts water were charged into an autoclave, purged with nitrogen, sealed, and gradually heated. When the internal pressure reached 0.4 MPa, water was distilled off until the pressure could no longer be maintained. The pressure was returned to normal over approximately 2 hours, and the reaction was continued at normal pressure for 1 hour. The maximum polymerization reaction temperature was 255°C. This yielded a polyamide with a glass transition temperature of 135°C. Next, 1288 parts of the resulting polyamide and 120.0 parts of α,ω-diaminopolyoxyethylene, obtained by adding acrylonitrile to both ends of polyoxyethylene glycol with an average molecular weight of 400 and then hydrogenating the resulting mixture, were dissolved in 1690 parts of methanol. Subsequently, 655.9 parts of a modified PEG600-HDI product were gradually added with stirring, and the reaction was allowed to proceed for approximately 45 minutes. The resulting solution was placed in a Teflon®-coated Petri dish, and after evaporating and removing the methanol, the mixture was dried under reduced pressure to obtain a polyetheramide resin containing polyethylene glycol. The glass transition temperature of the resulting resin was 112°C.

[0070] Polymerization example of polyether urethane urea resin A-5 Two equivalents (672.8 parts) of hexamethylene diisocyanate were placed in a flask equipped with a dropping funnel and heated to 110°C under a nitrogen atmosphere. One equivalent (1200.0 parts) of polyethylene glycol with a number average molecular weight of 600 was then added dropwise using the dropping funnel with stirring. Stirring was continued for 30 minutes after the addition. The amount of isocyanate in the resulting compound was half of the original amount, and the hydroxyl groups at both ends of the polyethylene glycol had reacted with the isocyanate groups, resulting in a PEG600-both-ends HDI-modified product with isocyanate groups at both ends. Next, 540.8 parts of 1,4-bis(3-aminopropyl)piperazine, 64.6 parts of N-(2-aminoethyl)piperazine, and 323.5 parts of isophoronediamine were dissolved in 1115.0 parts of methanol, and then 90.0 parts of lactic acid was added and dissolved. Next, 1030.7 parts of PEG600-HDI modified product were gradually added to the diamine solution with stirring, followed by 639.1 parts of hexamethylene diisocyanate (HDI) with stirring. The reaction between the two was completed in approximately 15 minutes. This solution was placed in a Teflon (registered trademark)-coated Petri dish, and the methanol was evaporated off. After drying under reduced pressure, the resulting polymer compound was obtained. The glass transition temperature of the resulting resin was 55°C.

[0071] Polymerization of polyether urethane urea resins A-6 and B-7 Polyetherurethane urea resins A-6 and B-7 were polymerized in the same manner as polyetherurethane urea resin A-5, except that the types and blending ratios (mol%) of raw materials were changed as shown in Table 1. The glass transition temperatures of the resulting resins are shown in Table 1.

[0072] The raw materials used in the examples are as follows: BAPP: N,N'-bis(3-aminopropyl)piperazine AEP: N-(2-aminoethyl)piperazine IPDA: Isophoronediamine 1,3-BAC: 1,3-bis(aminomethyl)cyclohexane MPDA: 2-methylpentamethylenediamine HMDA: 1,6-hexanediamine CHDA: 1,4-cyclohexanedicarboxylic acid HDI: 1,6-hexamethylene diisocyanate IPDI: Isophorone diisocyanate

[0073] Example 1 55.0 parts of polyamide resin (P1) were added to a mixture of 62 parts methanol and 10 parts water, heated to 65°C, dissolved, and then 9.0 parts diethylene glycol, 5.0 parts lactic acid as a quaternizing agent, and 0.1 parts hydroquinone monomethyl ether were added and stirred for another 30 minutes. The polyamide was converted to an ammonium salt and made water-soluble. Then, 2.5 parts of glycidyl methacrylate (GMA), 1.0 parts benzyl dimethyl ketal as a photopolymerization initiator, 13 parts of glycerin dimethacrylate (Light Ester G101P, manufactured by Kyoeisha Chemical Co., Ltd.), and 14.5 parts of 2-hydroxy-3-acryloyloxypropyl methacrylate (Light Ester G201P, manufactured by Kyoeisha Chemical Co., Ltd.) were added and stirred for 30 minutes. The mixture was then gradually heated to distill off methanol and water, and concentrated until the temperature inside the vessel reached 110°C. At this stage, a fluid, viscous photosensitive resin composition was obtained. This photosensitive composition was coated onto a 100 μm polyethylene terephthalate film coated with approximately 1.7 μm of 98% saponified poval, and dried at 100° C. to obtain a cover film laminated with 10 μm of the photosensitive resin composition.

[0074] For the lower layer, 55.0 parts of polyamide resin (P6) were added to a mixture of 62 parts methanol and 10 parts water, which was then heated to 65°C and dissolved. Then, 9.0 parts of diethylene glycol, 5.0 parts of lactic acid as a quaternizing agent, and 0.1 parts of hydroquinone monomethyl ether were added and stirred for another 30 minutes. The polyamide was converted into an ammonium salt and made water-soluble. Then, 2.5 parts of glycidyl methacrylate (GMA), 1.0 parts of benzyl dimethyl ketal as a photopolymerization initiator, 13 parts of glycerin dimethacrylate (Light Ester G101P, manufactured by Kyoeisha Chemical Co., Ltd.), and 14.5 parts of 2-hydroxy-3-acryloyloxypropyl methacrylate (Light Ester G201P, manufactured by Kyoeisha Chemical Co., Ltd.) were added and stirred for 30 minutes. The mixture was then gradually heated to distill off the methanol and water, and the mixture was concentrated until the temperature inside the vessel reached 110°C. At this stage, a fluid, viscous photosensitive resin composition was obtained. This photosensitive composition was cast onto a 250 μm polyethylene terephthalate film coated with a 20 μm thick adhesive composition containing an ultraviolet absorber, and a raw plate of a sheet-like laminate with a total thickness of 1080 μm was formed using a laminator so that the photosensitive resin layer side of the cover film laminated with 10 μm of photosensitive resin composition was in contact with the photosensitive resin composition cast onto the 250 μm polyethylene terephthalate film.

[0075] After storing the raw plates for 7 days or more, the printability of the highlights, the adhesion of the plate surface, and the printing durability were evaluated. The results are shown in Tables 2 and 3.

[0076] Examples 2 to 13, Comparative Examples 1 to 6 A green plate of a sheet laminate having a total thickness of 1080 μm was molded in the same manner as in Example 1. However, the resin (A) and resin (B) of the photosensitive resin layer were changed as shown in Table 2. The evaluation results are shown in Table 2.

[0077] [Table 1] [Table 2] [Table 3]

[0078] As can be seen from Table 2, the photosensitive resin compositions of the present invention in Examples 1 to 13 were good in all of the gradation printing reproducibility, printing durability, and plate surface adhesion in highlight areas. In Comparative Example 1, the water-soluble or water-dispersible resin A-7 contained in the upper layer had a high glass transition temperature, resulting in poor printing durability. In Comparative Example 2, the water-soluble or water-dispersible resin A-1 contained in the upper layer had a low glass transition temperature, resulting in poor plate surface adhesion. In Comparative Example 3, the water-soluble or water-dispersible resin B-1 contained in the lower layer had a low glass transition temperature, resulting in poor highlight area printability. In Comparative Example 4, the water-soluble or water-dispersible resin B-8 contained in the lower layer had a high glass transition temperature, resulting in poor printing durability. In Comparative Example 5, the upper layer was thin, resulting in poor printing durability. In Comparative Example 6, the upper layer was thick, resulting in poor highlight area printability. [Industrial Applicability]

[0079] According to the photosensitive resin composition of the present invention, it is possible to obtain a photosensitive resin letterpress printing original plate and printing plate that can achieve both 1 to 5% gradation printing reproducibility in highlight areas and high-level printing durability.

Claims

1. In a photosensitive resin letterpress printing original plate having a support, a photosensitive resin layer, and a cover film laminated in this order, the photosensitive resin layer has a lower layer located on the support side and an upper layer located on the cover film side, the upper layer is a photosensitive resin layer having a thickness of 7 to 30 micrometers and containing a water-soluble or water-dispersible resin (A) having a glass transition temperature of 40 to 90°C as measured by a differential scanning calorimeter; the lower layer is a layer containing a water-soluble or water-dispersible resin (B) having a glass transition temperature higher by 5°C or more than that of the water-soluble or water-dispersible resin (A), The glass transition temperature of the resin (B) measured by a differential scanning calorimeter is 95 to 135°C. Photosensitive resin letterpress printing plate.

2. 2. The photosensitive resin letterpress printing original plate according to claim 1, wherein the resin (A) is polyamide or polyetherurethaneurea, and the resin (B) is polyamide, polyetherurethaneurea, or polyetheramide.

3. 3. A printing plate obtained by removing uncured portions of the photosensitive resin layer from the photosensitive resin relief printing original plate according to claim 1.

Images