JP2005112975A - Ultraviolet light absorber for use in photosensitive laminated printing original plate for letterpress printing and method for producing the ultraviolet light absorber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultraviolet light absorber for use in photosensitive laminated printing original plates for letterpress printing, capable of forming an ultraviolet-opaque masking layer forming a masked image layer with high contrast through easily forming an ultraviolet-transparent region without roughening a photosensitive resin layer underneath, and to provide a method for producing the ultraviolet light absorber. <P>SOLUTION: The ultraviolet light absorber consists of a compound of specific structure containing an azo methine group(-N=CH-). This compound has the ability to absorb ultraviolet light in an alkaline or neutral atmosphere with the maximum absorption wavelengths of 300 to 400 nm but exhibits no ultraviolet light-absorbing ability in an acidic atmosphere. The method for producing this ultraviolet light absorber is also provided. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an ultraviolet absorber used for a photosensitive laminated original plate for forming relief printing such as a flexographic printing original plate and a method for producing the same.

Flexographic printing, which is a flexible letterpress printing, has been re-evaluated because it is excellent in economic efficiency, versatility, environmental non-contamination, etc. It is a printing technology that has gathered.
Conventionally, printing methods performed in Japan are relatively large in offset printing and gravure printing, and there are silk screen printing and the like with a small amount, and the use of letterpress printing typified by flexographic printing is relatively small. However, flexographic printing has the following advantages over other printing methods.
(1) Since the plate is convex and flexible, it can be printed on a flat and non-smooth printing object such as cardboard, and can be printed at a relatively high speed and at a low cost.
(2) Printing on a small area such as a label can be performed clearly and inexpensively.
(3) Compared to offset printing, printing with a higher ink density enables clearer printing.
(4) Character and image profiles are sharper than in gravure printing.
(5) Since water-based ink can be used, and completely solvent-free ink such as UV ink can be used, environmental pollution is very low.
(6) Since the time required from the start of printing to the stabilization of color is short, waste of printing media such as paper can be reduced, which is economical.
(7) Even if you want to change or modify a part of the version, it is possible to replace only a part of the version without recreating the whole version, and the cost required for maintenance and modification can be kept low.
(8) Small lot multi-product printing is possible.

  Thus, letterpress printing is an old printing technique, and flexographic printing is a conventional printing technique, and it has been well known that it has various advantages as described above. The usage ratio for the entire printed material was not high. However, due to the recent improvement in the quality of materials used such as printing inks and printing plate precursors, and the growing concern about environmental issues, re-evaluation of relief printing and other letterpress printing has been carried out. Currently, research and development are starting to become more active.

The current development status of the original printing plate itself is as follows. Flexographic printing plates have been manufactured for a long time by using rubber as a constituent material and engraving the rubber layer to form negative images of characters and patterns to be printed. Resin has come to be used (Patent Document 1, Patent Document 2).
This photosensitive resin is generally composed of an elastomeric binder, at least one monomer and a photopolymerization initiator. A printing original plate using the photosensitive resin is a plate-like member in which at least the photosensitive resin layer is provided on a support.
In the production of a flexographic printing plate using this printing original plate, first, a film (mask) having a negative pattern of an image such as characters and images to be printed is placed on the photosensitive resin layer of this printing original plate. The photosensitive resin layer is irradiated with ultraviolet rays through a mask. The portion that has been irradiated with ultraviolet rays undergoes a photopolymerization reaction and is cured. Thereafter, when the uncured portion is washed away with a developer, a convex pattern corresponding to the image remains. As a result, a flexographic printing plate is completed. In flexographic printing, a printed matter is obtained by attaching ink to the tip of the convex pattern and pressing it against a printing medium such as paper.

The following problems are pointed out in the printing original plate using this photosensitive resin, and the solution of these problems has been desired.
(1) If the final pattern of the negative mask needs to be corrected, it cannot be partially corrected, so the entire negative mask needs to be recreated, and the correction work takes a relatively large amount of man-hours.
(2) Since the negative mask is composed of a negative film, the dimensions are likely to change due to changes in temperature and humidity. Therefore, even if the same negative mask is used, if the pattern forming process including exposure and development of the photosensitive resin layer is performed at a different time or in another environment, a printing plate with the same accuracy cannot be obtained. Cases arise.
(3) In the pattern formation process, light incidence-inhibiting substances such as dust are likely to enter between the negative mask and the photosensitive resin layer, and if it enters, the pattern image obtained after exposure and development processing will be disturbed, The printing quality of the printing plate will be reduced.

In order to solve such problems, several types of printing original plates having a new configuration have recently been developed (Patent Documents 1 to 7). A common characteristic configuration of these recent printing original plates is that at least an infrared sensitive material layer is formed on the photosensitive resin layer, and this infrared sensitive material layer functions as either a conventional negative or a positive mask. It is also possible to fulfill. This infrared sensitive material layer is opaque to ultraviolet rays that photocure the photosensitive resin, but is sensitive to infrared rays. This infrared sensitivity means so-called ablation that evaporates or / and decomposes by exposure with infrared laser light. Therefore, the infrared sensitive layer is also called an infrared ablation layer.
By laminating the infrared ablation layer, printing image information can be directly recorded on an original printing plate for relief printing including a flexographic printing original plate using an infrared laser beam. A mask film made of a positive film can be omitted. The print image information can be produced, stored, modified, and output as digital information by a computer, and when a conventional mask film is used when producing a relief printing plate by a configuration in which an infrared ablation layer is provided. The required image information processing cost can be greatly reduced.

Several types of compositions of the infrared ablation layer have been proposed, but basically the compositions are similar. For example, in the printing original plate described in Patent Document 1, the infrared ablation layer includes (1) at least one infrared absorbing material and (2) an ultraviolet opaque material (where (1) and (2) are the same). And (3) at least one low molecular weight substance in the photosensitive resin layer and at least one binder that is substantially incompatible.
As the ultraviolet opaque material, any material can be used as long as it prevents transmission of ultraviolet rays for exposing the photosensitive resin layer. Specific examples thereof include dyes that absorb ultraviolet light or visible light, dark inorganic pigments, and combinations thereof, with carbon black and graphite being preferred.
The infrared absorbing material is a material having strong absorption in the range of 750 to 20,000 nm, and specifically, carbon black, graphite, copper chromite, chromium oxide, and chromium aluminate-cobalt. Examples include dark inorganic pigments, and other dyes such as poly (substituted) phthalocyanine compounds, cyanine dyes, squalium dyes, and cargoogenpyryl arylidene dyes.

Japanese Patent No. 2916408 JP 2003-35954 A JP 2003-35955 A Japanese Patent Laid-Open No. 11-153865 JP 9-166875 A JP 2001-324815 A Japanese Patent No. 2773981

As described above, printing using a conventional relief printing original plate has a configuration in which an ultraviolet transmissive region of a mask is formed by selectively ablating (burning out) a mask material layer opaque to ultraviolet rays with an infrared laser. It has become. Therefore, in the step of obtaining the mask image layer by ablating the mask material layer, a suction discharge means for removing the ablation waste from the system is essential so that the ablation debris does not remain on or adhere to the photosensitive resin layer. Become. In addition, if even a very small amount of mask material remains in the UV transmissive area of the mask image layer, the transparency to UV light will be reduced accordingly, so the mask material layer must be ablated until the underlying photosensitive resin layer is exposed. is there. Therefore, the exposed surface of the photosensitive resin layer is somewhat roughened by the infrared laser. This exposed portion remains by subsequent development and becomes a surface to which the printing ink is attached, which may adversely affect print quality.
The present invention has been made in view of the circumstances in the prior art described above, and its purpose is a mask material layer opaque to ultraviolet rays, and an ultraviolet transmissive region can be easily formed without roughening the surface of the underlying photosensitive resin layer. It is another object of the present invention to provide an ultraviolet absorber used for a photosensitive laminated printing original for letterpress printing and a method for producing the same, which can form a mask material layer for forming a mask image layer having excellent contrast.

〔式（１）及び（２）において、Ｒ₁ 、Ｒ₂ はそれぞれ水素、アルキル基、アルコキシ基、置換アミノ基、カルボキシル基、置換カルボキシル基、スルホン酸基、及びハロゲンからなる群より選ばれる基を表し、同一であっても異なっていてもよい。また、Ｘ、Ｙはそれぞれ置換基を有していてもよい芳香族基又は複素環基を表し、Ｘ、Ｙは同一であっても異なっていてもよい。〕 The ultraviolet absorber used in the photosensitive laminated printing original plate for letterpress printing of the present invention is an azomethine group (—N═CH —)-containing compound represented by the formula (1) or (2), and has an alkaline or neutral atmosphere. Among them, it has an ability to absorb ultraviolet light, and its maximum absorption wavelength is in the range of 300 to 400 nm, but it has a characteristic that it does not show ultraviolet absorbing ability in an acidic atmosphere.

[In the formulas (1) and (2), R ₁ and R ₂ are groups selected from the group consisting of hydrogen, alkyl groups, alkoxy groups, substituted amino groups, carboxyl groups, substituted carboxyl groups, sulfonic acid groups, and halogens, respectively. Which may be the same or different. X and Y each represents an optionally substituted aromatic group or heterocyclic group, and X and Y may be the same or different. ]

〔式（３）において、Ｒ₁ 、Ｒ₂ はそれぞれ水素、アルキル基、アルコキシ基、置換アミノ基、カルボキシル基、置換カルボキシル基、スルホン酸基、及びハロゲンからなる群より選ばれる基を表し、同一であっても異なっていてもよい。また、式（４）及び（５）において、Ｘ、Ｙはそれぞれ置換基を有していてもよい芳香族基又は複素環基を表し、Ｘ、Ｙは同一であっても異なっていてもよい。〕 Examples of the ultraviolet absorber used in the photosensitive laminated printing original plate for letterpress printing of the present invention include, for example, a phenylenediamine derivative represented by formula (3) and an aromatic represented by formula (4) and / or (5) or It can be produced by dehydration condensation with a heterocyclic aldehyde. In the case of this method, an ultraviolet absorber having a structure represented by the formula (1) can be produced.

[In Formula (3), R ₁ and R ₂ each represent a group selected from the group consisting of hydrogen, an alkyl group, an alkoxy group, a substituted amino group, a carboxyl group, a substituted carboxyl group, a sulfonic acid group, and a halogen; Or different. In the formulas (4) and (5), X and Y each represents an aromatic group or a heterocyclic group which may have a substituent, and X and Y may be the same or different. . ]

〔式（６）において、Ｒ₁ 、Ｒ₂ はそれぞれ水素、アルキル基、アルコキシ基、置換アミノ基、カルボキシル基、置換カルボキシル基、スルホン酸基、及びハロゲンからなる群より選ばれる基を表し、同一であっても異なっていてもよい。また、式（７）及び（８）において、Ｘ、Ｙはそれぞれ置換基を有していてもよい芳香族基又は複素環基を表し、Ｘ、Ｙは同一であっても異なっていてもよい。〕 Moreover, the ultraviolet absorber used for the photosensitive laminated printing original plate for relief printing according to the present invention is, for example, a phthalaldehyde derivative represented by the formula (6) and an aroma represented by the formula (7) and / or (8). It can also be produced by dehydration condensation with a primary or heterocyclic primary amine. In the case of this method, an ultraviolet absorber having a structure represented by the formula (2) can be produced.

[In the formula (6), R ₁ and R ₂ each represent a group selected from the group consisting of hydrogen, an alkyl group, an alkoxy group, a substituted amino group, a carboxyl group, a substituted carboxyl group, a sulfonic acid group, and a halogen; Or different. In the formulas (7) and (8), X and Y each represents an aromatic group or a heterocyclic group which may have a substituent, and X and Y may be the same or different. . ]

  The ultraviolet absorbent according to the present invention has a property of deactivating ultraviolet absorbing ability upon contact with an acid. The present inventors have continued research on ultraviolet absorbers having such characteristics, and absorb ultraviolet light in a compound containing an azomethine group (—N═CH—) in the molecular structure, and its maximum absorption. The present inventors have found that there is a compound having a wavelength of 300 to 400 nm and whose absorption ability is deactivated by an acid generated by laser light irradiation.

  In a relief printing original plate in which at least a photosensitive resin layer sensitive to ultraviolet rays and a mask material layer are laminated on a support, the mask material layer is irradiated with a binder resin and infrared light to generate heat. The composition includes an acid generator that generates an acid under the action of heat, and an ultraviolet absorber according to the present invention, thereby having both an absorptivity and an ultraviolet absorptivity. It can be set as the mask material layer which becomes inactive when the function is irradiated with infrared rays.

An original plate for letterpress printing in which a mask material layer is formed together with a binder resin, a photothermal conversion agent and an acid generator using the ultraviolet absorber of the present invention, does not cause ablation of the mask material layer in a desired pattern. However, the irradiation pattern having an excellent contrast without damaging the surface of the lower photosensitive resin layer by irradiating the infrared ray of the energy amount that excites the photothermal conversion agent in the mask material layer to generate heat) A mask image layer having a pattern latent image composed of a region where the ultraviolet absorption ability corresponding to the above is deactivated and a region where the ultraviolet absorption capability is maintained can be formed.
Furthermore, a relief printing plate capable of clear printing can be obtained by irradiating the relief printing original plate on which the mask image is formed with ultraviolet rays.

The ultraviolet absorber of the present invention is a compound represented by the formula (1) or (2), and is characterized by containing an azomethine group (—N═CH—) in the molecule.

In the formulas (1) and (2), R ₁ and R ₂ are each a group selected from the group consisting of hydrogen, alkyl group, alkoxy group, substituted amino group, carboxyl group, substituted carboxyl group, sulfonic acid group, and halogen. May be the same or different. Of these groups, hydrogen and sulfonic acid groups are preferred. When X and Y are aromatic groups, sulfonic acid groups are particularly preferable.
X and Y each represents an optionally substituted aromatic group or heterocyclic group, and X and Y may be the same or different. Aromatic groups are preferably monocyclic, and substituents containing sulfonic acid groups are particularly preferred. As the heterocyclic group, those containing an N atom as a ring component are preferred.

The compound represented by the formula (1) or (2) (ultraviolet absorber) can be easily produced, for example, by dehydrating and condensing a compound having an appropriate aldehyde group and a compound having a primary amino group. Can do. At that time, it is preferable to add a small amount of an organic acid such as formic acid, oxalic acid or acetic acid as a dehydration condensation catalyst in order to increase the reaction rate.
Specifically, the compound represented by the formula (1) includes a phenylenediamine derivative represented by the formula (3) and an aromatic or heterocyclic aldehyde represented by the formula (4) and / or (5). Can be produced by dehydration condensation (in formulas (3) to (5), R ₁ , R ₂ , X and Y represent the same meaning as described above).

Further, the compound represented by the formula (2) includes a phthalaldehyde derivative represented by the formula (6) and an aromatic or heterocyclic primary amine represented by the formula (7) and / or (8). It can be produced by dehydration condensation (in formulas (6) to (8), R ₁ , R ₂ , X and Y have the same meaning as described above).

  The ultraviolet absorber of the present invention is an azomethine group (—N═CH —)-containing compound represented by the above formula (1) or (2), and has an ability to absorb ultraviolet light in an alkaline or neutral atmosphere. And has a maximum absorption wavelength in the range of 300 to 400 nm, but does not exhibit ultraviolet absorption ability in an acidic atmosphere. As typical compounds having such properties, the following compounds (I) to (XV) can be exemplified. In any of these compounds, the azomethine group (—N═CH—) present in the molecular structure is decomposed by an acid and loses its ability to absorb ultraviolet rays. Table 1 shows melting points and maximum absorption wavelengths (λm) of these compounds. Compound (XV) is an intermediate product for producing an ultraviolet absorber having different X and Y, such as compound (VI).

FIG. 1 and FIG. 2 illustrate how these compounds deactivate their ultraviolet-absorbing ability by acid with respect to compounds (I) and (XII). FIG. 1 and FIG. 2 show the range of wavelengths from 300 to 500 nm for a solution in which compounds (I) and (XII) are dissolved in a solvent (DMF) so as to have a concentration of 10 ppm, and a solution to which 0.1% of sulfuric acid is added. The graphs are obtained by measuring the absorptance (measurement spectrophotometer: Hitachi U-2010 type). In each figure, curve A is before addition of sulfuric acid and curve B is after addition of sulfuric acid.
The ultraviolet absorber of the present invention utilizes the principle that an azomethine group (—N═CH—) is decomposed by an acid, and includes this azomethine group (—N═CH—) in the chemical structure to absorb ultraviolet light. And as long as the maximum absorption wavelength exists in 300-400 nm, it is not limited to the compound quoted above.

In an original plate for letterpress printing in which an ultraviolet absorber according to the present invention is used and a masking layer is laminated at least with a photosensitive resin layer that is sensitive to ultraviolet rays on a support, the mask material layer is a binder resin, It contains a photothermal conversion agent, an acid generator and the ultraviolet absorber according to the present invention as constituent components.
As the binder resin, hydroxypropyl cellulose, polyvinyl butyral, polyvinyl acetal, epoxy resin, ethyl cellulose, cellulose acetate, nitrocellulose and the like can be used.
The photothermal conversion agent is a substance that generates heat when irradiated with infrared rays, and a phthalocyanine derivative, a cyanine dye, a squalium dye, a cargoogenpyryl arylidene dye, and the like can be used. Specifically, NK-4432 ( Product name: Nippon Photosensitive Dye Co., Ltd., cyanine dye) can be exemplified.
The acid generator is a substance that generates an acid under the action of heat, and iodonew hexafluorophosphate derivatives, iodonew trifluoromethanesulfonate derivatives, paramethoxystyryltriazine derivatives, and the like can be used. Examples thereof include SIS-001 (trade name: manufactured by Sanwa Chemical Co., Ltd., iodonium hexafluorophosphate derivative).

Although the manufacturing method of the original for relief printing using the ultraviolet absorber of this invention is not specifically limited, For example, it can manufacture by the following methods.
First, a binder resin, a photothermal conversion agent, an acid generator, and an ultraviolet absorbent according to the present invention, which are constituents of the mask material layer, are dissolved in a solvent, and the solution is applied onto a cover sheet such as a PET film and dried. To form a mask material layer. Separately, a photosensitive resin layer is formed on a support (base material) such as a PET sheet by a conventional method. The mask material layer and the photosensitive resin layer of the laminate thus obtained are laminated by a method such as pressure bonding with a pressure roller, and the photosensitive resin layer and the mask material having UV sensitivity on the support. A relief printing original plate having at least a layer laminated thereon can be obtained.

The original plate for letterpress printing does not cause ablation of the mask material layer, but is irradiated with an infrared laser having an energy amount that generates heat by exciting the photothermal conversion agent in the mask material layer. Forming a pattern latent image consisting of a region in which UV is deactivated and a region in which UV absorption ability is maintained, and then irradiating UV to cure the photosensitive resin in accordance with the latent image pattern to form a convex image A relief printing plate can be produced by
The amount of irradiation energy of the infrared laser is appropriately set according to the type of the ultraviolet absorber, the constituent conditions of the mask material layer, etc. For example, when a semiconductor laser having a wavelength of 830 nm and an output of 600 mW is used, 3.0 J / cm ² It is about the following.

  That is, in the area of the mask material layer of the relief printing original plate using the ultraviolet absorbent according to the present invention that is irradiated with the infrared laser, ablation does not occur and only the irradiation energy of the infrared laser is applied. However, the photothermal conversion agent is excited by the applied light energy to generate heat. The acid generator in the irradiated area is excited by the thermal energy to generate an acid in the irradiated area. This acid deactivates the ultraviolet absorbing ability of the ultraviolet absorbent of the present invention in the irradiated region. Therefore, as a result, the infrared laser irradiation region has inactivated ultraviolet absorption ability, and when ultraviolet rays are irradiated from the outside, the ultraviolet rays are easily transmitted. On the other hand, since the original ultraviolet absorbing ability is maintained as it is in the region not irradiated with the infrared laser, when the ultraviolet ray is irradiated from the outside, the ultraviolet ray is absorbed in the region, and the region is Cannot penetrate. As a result, the mask material layer that has received pattern irradiation with an infrared laser has a region in which the ultraviolet absorption ability is deactivated and a region in which the ultraviolet absorption ability is maintained, depending on the pattern of the irradiated infrared laser. Pattern latent image is formed.

  By performing ultraviolet exposure through the mask material layer (mask image layer) on which the pattern latent image is formed in this way, the ultraviolet light pattern according to the latent image pattern of the mask image layer is applied to the photosensitive resin layer. A region irradiated with ultraviolet rays is cured by a crosslinking reaction. Thereafter, it is processed by a conventional method to obtain a relief printing plate in which a convex image made of a cured resin is formed on a support according to a pattern such as a target character image.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.
[Examples 1-4: Production Examples of UV Absorber of the Present Invention]
[Example 1: Production Example of Compound I]
Dissolve 10.8 g of paraphenylenediamine in 200 ml of methanol, add 23.3 g of pyridine-4-aldehyde, and add 0.01 ml of acetic acid as a dehydration condensation catalyst to start the reaction. The temperature rises. Stir at 60 ° C. for several hours, remove a small amount of insoluble matter, allow to cool, add 300 ml of purified water and continue stirring. The precipitated yellow crystals are filtered off, washed thoroughly with purified water and dried. 23.5 g of crude product are obtained. Furthermore, 19.3 g of pure products having a melting point of 186 to 188 ° C. can be obtained by recrystallization with isopropyl alcohol.

[Example 2: Production Example of Compound V]
Dissolve 8.0 g of terephthalaldehyde in 240 ml of methanol. Add 12.3 g of aniline, add 0.01 ml of acetic acid while stirring, raise the temperature to 60 ° C., and continue the reaction at the same temperature for several hours.
After completion of the reaction, the mixture is allowed to cool and the precipitated yellow crystals are filtered off, washed well with water and dried. 15.3 g of crude product is obtained. Furthermore, recrystallization with isopropyl alcohol can obtain 13.2 g of a pure product having a melting point of 161 to 163 ° C.

[Example 3: Production Examples of Compounds VI and XV]
21.6 g of paraphenylenediamine is dissolved in 400 ml of methanol, and 21.4 g of pyridine-4-aldehyde is added dropwise with stirring. After dropwise addition, 0.04 ml of acetic acid is added, and the mixture is stirred at 60 ° C. for several hours. After cooling, the precipitated yellow crystals are filtered off, washed well with methanol, dried, and 33.0 g of compound XV having a melting point of 209 to 211 ° C. Can be obtained.
9.9 g of the obtained compound XV was dispersed in 150 ml of methanol while stirring, 5.8 g of benzaldehyde was added, 0.02 ml of acetic acid was further added, and the mixture was refluxed and stirred for several hours. The yellow crystals were filtered off and washed well with methanol. Then, it is dried and recrystallized from MEK to obtain 8.5 g of a pure product having a melting point of 166 to 168 ° C.

[Example 4: Production Example of Compound XII]
Dissolve 40 g of benzaldehyde-o-sulfonic acid in 350 ml of methanol and filter at 40 ° C. to remove inorganic salts.
Add 1,500 ml of isopropyl alcohol to the filtrate, and add 9.4 g of paraphenylenediamine at 45 ° C. while stirring. Stir at the boiling point for 2-3 hours, then stir overnight at room temperature. The precipitated crystals are filtered, washed with ethyl alcohol and dried. Furthermore, it recrystallizes with the mixed solvent of isopropyl alcohol and methanol, and 29.5g of pure products of compound XII can be obtained.
Other compounds can also be easily produced by using corresponding aldehydes and primary amines.

[Reference Example 1: Letterpress printing original plate using Compound I]
Hydroxypropyl cellulose (manufactured by Nippon Soda Co., Ltd.) used as a binder was dissolved in cyclohexanone to obtain a 10% by mass uniform binder solution. To 50 g of this binder solution, 0.5 g of an acid generator that generates an acid by heat (trade name: SIS-001, manufactured by Sanwa Chemical Co., Ltd.) was added and stirred to make it uniform. Into this mixed solution, 0.75 g of the ultraviolet absorber compound (I) of the present invention whose ultraviolet absorption properties are deactivated by contact with an acid, and a photothermal conversion agent (trade name: NK-4432, manufactured by Nippon Photosensitive Dye Co., Ltd.) 0.25 g was added to prepare a uniform mask material solution.
Next, the mask material solution is applied onto a PET film (cover sheet (D)) having a thickness of 100 μm so that the coating film thickness after drying is 5 to 8 μm, and dried at 80 ° C. for 5 minutes. A mask material layer (C) was formed. When the optical density of this mask material layer (C) with respect to 370 nm (ultraviolet rays) was measured using a spectrophotometer (trade name U-2010 type, manufactured by Hitachi, Ltd.), it was 2.5, and the ultraviolet ray was transmitted. It was confirmed to shut off.

On the other hand, 100 parts by mass of a styrene butadiene copolymer having an average molecular weight of 240,000 (trade name: D-1155, manufactured by JSR Shell Elastomer Co., Ltd.) and liquid 1,2-polybutadiene having an average molecular weight of 1,000 (trade name: 70 parts by mass of Nisso PB-1000 (manufactured by Nippon Soda Co., Ltd.), 10 parts by mass of trimethylolpropane triacrylate, 3 parts by mass of methoxyphenylacetophenone, and 2,6-di-tert-butyl-4-hydroxytoluene 0 .05 parts by mass and 0.002 parts by mass of Oil Blue # 503 (manufactured by Orient Chemical Co., Ltd.) were dissolved in a solvent consisting of 0.2 parts by mass of tetrahydrofuran to prepare a photosensitive resin composition. The photosensitive resin composition was extruded to a thickness of 1.7 mm onto a substrate (support) layer (A) made of a polyethylene terephthalate sheet while kneading in an extruder with a high viscosity pump, and a photosensitive resin layer was obtained. (B) was obtained.
The surfaces of the photosensitive resin layer (B) and the mask material layer (C) obtained as described above are laminated using a pressure roller, and the substrate layer (A) -photosensitive resin layer (B) -mask material is laminated. The flexographic printing original plate (letter printing original plate) which consists of the multilayer photosensitive structure of the structure shown in FIG. 3 in which layer (C) -cover sheet (D) was laminated | stacked and integrated sequentially was obtained.
In FIG. 3, 1 is a substrate (support) layer (A), 2 is a photosensitive resin layer (B), 3 is a mask material layer (C), 4 is a cover sheet (D), and 3 mask material layers (C) becomes a mask image layer (C ′) by irradiation with an infrared laser.

[Reference Example 2: Production of a relief printing plate using the relief printing original plate of Reference Example 1]
The cover sheet (D) of the obtained flexographic printing original plate is peeled off, and the mask pattern is 100 lines / mm at a resolution of 100 lines / mm using a semiconductor infrared laser with a wavelength of 830 nm and an output of 600 mW on the exposed mask material layer (C). Irradiation was performed according to a pattern so that the energy was 3 J / cm ² . This irradiation energy of 3 J / cm ² does not cause ablation of the mask material layer (C), but is an energy setting amount sufficient to excite the photothermal conversion agent in the mask material layer (C) to generate heat. .
In the region of the mask material layer (C) irradiated with the infrared laser, ablation does not occur as described above, but the photothermal conversion agent is excited by the applied light energy to generate heat. The acid generator in the irradiated area is excited by the thermal energy to generate an acid in the irradiated area. This acid deactivates the ultraviolet absorbing ability of the ultraviolet absorber in the irradiated region. As a result, in the mask material layer (C) that has received pattern irradiation with an infrared laser, a region in which the ultraviolet absorption ability is deactivated and a region in which the ultraviolet absorption ability is maintained are formed, thereby forming a pattern latent image. Is done. Therefore, the ultraviolet ray absorbing ability is deactivated in the infrared laser irradiation region, and when the ultraviolet ray is irradiated from the outside, the ultraviolet ray is easily transmitted. On the other hand, since the original ultraviolet absorbing ability is maintained as it is in the region not irradiated with the infrared laser, when the ultraviolet ray is irradiated from the outside, the ultraviolet ray is absorbed in the region, and the region is Cannot penetrate.

  The mask material layer (C) becomes a mask image layer (C ′) having a pattern latent image due to transmission / non-transmission of ultraviolet rays by receiving the pattern irradiation of the infrared laser as described above. The pattern formed on the mask image layer (C ′) is an image such as a character or a picture. In this reference example, a character pattern was formed. Using a spectrophotometer (trade name U-2000 manufactured by Hitachi, Ltd.), the optical density of the mask image layer (C ′) with respect to 370 nm (ultraviolet rays) of the infrared laser irradiation region, that is, the ultraviolet absorbing ability deactivation region, As a result of measurement, it was 0.3, and it was confirmed that ultraviolet rays were easily transmitted.

Next, back exposure of 75 mJ / cm ² from the support plate layer (A) side is performed with ultraviolet rays having a central wavelength of 370 nm through the mask image layer (C ′), and then the mask image layer (C ′) side. To 2500 mJ / cm ² main exposure.
By this ultraviolet main exposure, the photosensitive resin layer (B) is irradiated with ultraviolet pattern light in accordance with the latent image pattern of the mask image layer (C ′), and the region irradiated with the ultraviolet rays undergoes a crosslinking reaction. , Cure. Therefore, in order to remove the non-crosslinked region of the photosensitive resin layer (B), an aromatic hydrocarbon developer (trade name FDO-S2, manufactured by Tokyo Ohka Kogyo Co., Ltd.) is used as the developer, and the liquid temperature is 25. Development processing was carried out at 4 ° C. for 4 minutes. As a result, the photosensitive resin was cured according to the target character image, and a convex image made of the cured resin was formed on the support plate layer (A).
No adhesion of development residue or the like was observed on the obtained plate surface. After development, after drying at 55 ° C. for 50 minutes, post-processing is performed using an ultraviolet fluorescent lamp having a central wavelength at 250 nm, and further, post-exposure is performed with ultraviolet light having a central wavelength at 370 nm of 3000 mJ / cm ² . A flexographic printing plate (letter printing plate) was obtained.
When the flexographic printing plate thus obtained was used for printing on a coated paper, a printed matter having clear characters was printed.

[Reference Example 3: Production of relief printing plate using compound I and production of relief printing plate using it]
Instead of the compound I used in Reference Example 1, 1.0 g of Compound (XII) was dissolved in a small amount of water and added, and a flexographic printing plate precursor was prepared in the same manner as in Reference Example 1. The obtained flexographic printing original plate was irradiated with pattern light using an infrared laser in the same manner as in Reference Example 2 to form a mask image layer (C ′), and then ultraviolet rays were passed through the mask image layer (C ′). Was irradiated to the photosensitive resin layer (B) and further developed to form a character image to obtain a flexographic printing plate. When the obtained flexographic printing plate was used for printing in the same manner as in Reference Example 2, a printed matter having clear characters was printed.

  The ultraviolet absorbent according to the present invention, a relief printing original plate using the same, and a relief printing plate exhibit excellent performance in the field of relief printing.

The graph which shows the relationship between the measurement wavelength and absorption rate before and after addition of an acid about the compound I. The graph which shows the relationship between the measurement wavelength and absorption rate before and after addition of an acid about compound XII. FIG. 3 is an explanatory diagram showing a configuration of a relief printing original plate produced in Reference Example 1.

Explanation of symbols

1 Substrate layer (support) (A)
2 Photosensitive resin layer (B)
3 Mask material layer (C)
4 Cover sheet (D)

Claims (3)

An azomethine group (—N═CH —)-containing compound represented by the formula (1) or (2), having an ability to absorb ultraviolet light in an alkaline or neutral atmosphere, and having a maximum absorption wavelength An ultraviolet absorber for use in a photosensitive laminate printing original plate for letterpress printing, which has a characteristic of being present in 300 to 400 nm but not exhibiting an ultraviolet absorbing ability in an acidic atmosphere.

[In the formulas (1) and (2), R ₁ and R ₂ are groups selected from the group consisting of hydrogen, alkyl groups, alkoxy groups, substituted amino groups, carboxyl groups, substituted carboxyl groups, sulfonic acid groups, and halogens, respectively. Which may be the same or different. X and Y each represents an optionally substituted aromatic group or heterocyclic group, and X and Y may be the same or different. ] The relief printing plate according to claim 1, wherein the phenylenediamine derivative represented by the formula (3) and the aromatic or heterocyclic aldehyde represented by the formula (4) and / or (5) are subjected to dehydration condensation. A method for producing an ultraviolet absorber for use in a photosensitive laminated printing original plate for printing.

[In Formula (3), R ₁ and R ₂ each represent a group selected from the group consisting of hydrogen, an alkyl group, an alkoxy group, a substituted amino group, a carboxyl group, a substituted carboxyl group, a sulfonic acid group, and a halogen; Or different. In the formulas (4) and (5), X and Y each represents an aromatic group or a heterocyclic group which may have a substituent, and X and Y may be the same or different. . ] The phthalaldehyde derivative represented by the formula (6) and the aromatic or heterocyclic primary amine represented by the formula (7) and / or (8) are subjected to dehydration condensation. For producing an ultraviolet absorbent for use in a photosensitive laminated printing original plate for letterpress printing.

[In the formula (6), R ₁ and R ₂ each represent a group selected from the group consisting of hydrogen, an alkyl group, an alkoxy group, a substituted amino group, a carboxyl group, a substituted carboxyl group, a sulfonic acid group, and a halogen; Or different. In the formulas (7) and (8), X and Y each represents an aromatic group or a heterocyclic group which may have a substituent, and X and Y may be the same or different. . ]

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