RELIEF PRINTING ORIGINAL PLATE FOR ROTARY LETTERPRESS PRINTING

Abstract

A relief printing original plate for rotary letterpress printing wherein at least an adhesive layer, a photosensitive resin layer and a cover film are successively layered on a support, wherein the photosensitive resin layer contains at least a synthetic rubber-based polymer, a photopolymerizable unsaturated compound and a photopolymerization initiator, and Shore A hardness of a surface of the photosensitive resin layer after photo-curing is 80 to 95. Preferably, the synthetic rubber-based polymer is a hydrophobic polymer obtained from a water-dispersible latex having a weight-average gelation degree of 50 to 80%. Preferably, the photosensitive resin layer contains 20 to 70% by mass of the synthetic rubber-based polymer. The relief printing original plate is suitably used for a rotary printing machine of a center drum type.

Claims

1-6. (canceled)

7. A method for conducting a rotary letterpress printing by using a relief printing plate for rotary letterpress printing, the method comprising: providing the relief printing plate for rotary letterpress printing that has been prepared by removing a cover film from a relief printing original plate for rotary letterpress printing, exposing the printing original plate, and developing the exposed printing original plate, wherein the relief printing original plate for rotary letterpress printing comprises at least an adhesive layer, a photosensitive resin layer and the cover film which are successively layered on a support, wherein the photosensitive resin layer contains at least a synthetic rubber-based polymer, a photopolymerizable unsaturated compound and a photopolymerization initiator, wherein Shore A hardness of a surface of the photosensitive resin layer after photo-curing is 80 to 95, and wherein a printing pressure during printing is 50 to 125 m.

8. The method according to claim 1, wherein the method is performed on a rotary printing machine of a center drum type.

9. The method according to claim 1, wherein an ink or a coating agent used for the rotary letterpress printing is a nonaqueous ink selected from any of a UV ink and an oily ink or is a nonaqueous coating agent of a UV varnish.

Description

EXAMPLES

[0044] Advantageous effects of the present invention will now be specifically illustrated by way of the following Examples although the present invention is not limited thereto. Evaluations of each characteristic property data were done in accordance with the following methods.

[0045] (Shore A Hardness of the Surface)

[0046] Each of the resulted printing plates was stored at 20 C. and 65% RH for seven days and then Shore A hardness of a surface of a solid part (fully exposed part) of each printing plate was measured at a room temperature (25 C.) using a Shore type durometer (Shore A type) manufactured by Zwick. As to the Shore type durometer (Shore A type) manufactured by Zwick, a product equipped with a stand exclusively therefor was used. The Shore A hardness was measured by placing the printing plate on a rest made of metal.

[0047] (Curling-In Degree)

[0048] On a polyethylene terephthalate film (support) in 125 m thickness wherein a polyurethane adhesive layer prepared from polyester resin and isocyanate compound was applied thereon with a layer thickness of 20 m, a photosensitive resin layer is formed, so as to prepare photosensitive resin original plates of the Examples and the Comparative Examples. Each of the resulting photosensitive resin original plate was exposed for 10 minutes by using a printer of A2 size (chemical lamp of Mitsubishi) manufactured by Nippon Denshi Seiki and cutting was done thereafter whereupon a sample of 10 cm diameter was prepared. After that, the sample was developed by using a developing apparatus to give a relief wherein whole surface thereof was exposed to light. The resulting relief image of 10 cm diameter was stored at 20 C. and 32% RH for seven days so as to prepare a sample for evaluating a curling-in degree. The resulting evaluation sample was allowed to stand on an experimental stand having a horizontal plane and the curling-in degree was measured. The curling-in degree is the highest position of the relief warped by being deformed to an inner side, and expressed by a height (cm) from the horizontal plane.

[0049] (Printing Property of a Highlight Part)

[0050] (a) Evaluation of Rotary Printing Machine

[0051] The printing property of the highlight part was evaluated by using each of the resulting printing plate. A rotary printing machine P-20 (manufactured by Sanjo Kikai) was used as a printing machine, Best Cure Indigo (manufactured by T&K TOKA) was used as an ink, and Gross PW-8K (manufactured by Lintec) was used as a thing to be printed. The evaluation of printing was conducted in such a manner that a printing pressure (a pressure between the plate and the thing to be printed) was gradually raised and a pressure at which a blurring of a solid part disappeared was adopted as a proper pressure. Further, an ink feed amount was adjusted so that an ink concentration of the solid part was made 1.7 abs. A screen dot concentration of 150 lines-3% under the proper pressure was measured using CCDOT 4 (manufactured by SDG). The measurement was conducted at five points for each thing to be printed. A degree of dot gain was judged based on an average value at the five points. Incidentally, the printing pressure is expressed by a distance (in m) between a plate cylinder and a pressure cylinder which has been narrowed by using a kiss touch (the very minimum printing pressure necessary for initiating the printing of the image) as an indicator.

[0052] : a halftone dots area rate is 10% or less

[0053] : the halftone dots area rate is more than 10% and is 15% or less

[0054] : the halftone dots area rate is more than 15% and is 20% or less

[0055] : the halftone dots area rate is more than 20%

[0056] (b) Evaluation of rotary printing machine of a center drum type

[0057] The printing property of the highlight part was evaluated by using each of the resulting printing plate. A rotary printing machine (manufactured by Ko-Pack) was used as a printing machine, Best Cure Indigo (manufactured by T&K TOKA) was used as an ink, and Gross PW-8K (manufactured by Lintec) was used as a thing to be printed. The evaluation of printing was conducted by adopting 50 m as a proper pressure. Further, an ink feed amount was adjusted so that an ink concentration of the solid part was made 1.7 abs. A screen dot concentration of 150 lines-3% under the proper pressure was measured using CCDOT 4 (manufactured by SDG). The measurement was conducted at five points for each thing to be printed. A degree of dot gain was judged based on an average value at the five points. Incidentally, the printing pressure is expressed by a distance (in m) between a plate cylinder and a pressure cylinder which has been narrowed by using a kiss touch (the very minimum printing pressure necessary for initiating the printing of the image) as an indicator.

[0058] : a halftone dots area rate is 10% or less

[0059] : the halftone dots area rate is more than 10% and is 15% or less

[0060] : the halftone dots area rate is more than 15% and is 20% or less

[0061] : the halftone dots area rate is more than 20%

[0062] (Ink transfer)

[0063] A solid part of each printing plate was observed by naked eye and the ink transfer was evaluated according to the following judging criteria.

[0064] : a color was not uneven but uniform

[0065] : an uneven color was partially noted

[0066] : the uneven color was noted as a whole

Example 1

[0067] Preparation of Photosensitive Resin Composition A

[0068] Polybutadiene latex (Nippol LX111NF, manufactured by Nippon Zeon, weight-average gelation degree: 86%) (42.2 parts by mass (solid basis)), 7.2 parts by mass (solid basis) of acrylonitrile-butadiene copolymer latex (Nippol SX1503, manufactured by Nippon Zeon, weight-average gelation degree: 0%) and 80 parts by mass of toluene were heated at 60 C. to prepare a solution in which rubber was dissolved. This solution was allowed to cool down to a room temperature. Then, 5 parts by mass (solid basis) of hydrophilic polymer (PFT-4 manufactured by Kyoeisha Chemical), 20 parts by mass of oligobutadiene acrylate (ABU-4 manufactured by Kyoeisha Chemical), 9 parts by mass of trimethylolpropane trimethacrylate, 9 parts by mass of lauryl methacrylate, 6 parts by mass of a plasticizer (B2000, manufactured by Nippon Petrochemical), 1.5 parts by mass of a photopolymerization initiator (Irgacure 651) and 0.1 part by mass of hydroquinone monomethyl ether as a polymerization inhibitor were added thereto together with 15 parts by mass of toluene. They were mixed in a container and toluene and water were removed in vacuo therefrom together with kneading at 80 C. using a kneader. Details of the resulting photosensitive resin composition A are shown in Table 1.

[0069] Preparation of Relief Printing Original Plate

[0070] Between a support prepared by coating a polyester-based adhesive layer in 20 m thickness on a polyethylene terephthalate film of 125 m thickness and a cover film prepared by coating a protective layer (polyvinyl alcohol) and a heat-sensitive mask layer (butyral resin in which carbon black was dispersed) on a polyethylene terephthalate film in 100 m thickness, the photosensitive resin composition A was inserted in such a manner that the adhesive layer and the protective layer contact with the photosensitive resin composition. Then, the resulting laminate was heated and pressed at 100 C. and 15 MPa using a heating/pressing machine whereupon a photosensitive resin original plate was prepared.

[0071] Preparation of Printing Plate from the Relief Printing Original Plate

[0072] The above photosensitive resin original plate was subjected to a back exposure for 15 seconds by using a fluorescent lamp for an ultraviolet ray (10R manufactured by Philips) wherein an illuminance at 350 nm was 8.0 w/m.sup.2. Then, the cover film was detached. Then, an image containing at least 150 lines and 3% of halftone dots was subjected to abrasion to a resin plate heat sensitive mask layer using an IR laser irradiator. After that, a main exposure was conducted by using the same fluorescent lamp for ultraviolet ray. The plate was developed for seven minutes by using a developing apparatus. Then the developed plate was strained, dried at 60 C. for ten minutes, subjected to an after exposure for five minutes by using the same fluorescent lamp for ultraviolet ray, and subjected to a surface treatment by irradiating with a sterilization lamp for five minutes so as to give a relief for evaluation having a relief image wherein there were reproduced the halftone dots of 150 lines and 3%.

[0073] The resulting printing plate was evaluated. Incidentally, the highlight printing property was evaluated by means of (a) rotary printing machine. Details of the printing plate and of the evaluated result thereof are shown in Table 2.

Examples 2 to 15 and Comparative Examples 1 to 3

[0074] As to Examples 2 to 14 and Comparative Examples 1 to 3, the same operation as in Example 1 was conducted except that ingredients and constitutions were changed as shown in Tables 1 and 2 whereupon the photosensitive resin compositions B to I, relief printing original plates and printing plates were prepared and subjected to evaluations. Details of the photosensitive resin composition are shown in Table 1. Details and evaluation results of the printing plate are shown in Table 2. In Example 15, the printing plate prepared in Example 1 was used and the evaluation for highlight printing property was conducted by means of (b) rotary printing machine of a center drum system. Incidentally, the polybutadiene used in the photosensitive resin compositions H and I was Nipol BR 1220 manufactured by Nippon Zeon and a weight-average gelation degree thereof was 0%. Further, in Examples 2 to 4, the printing evaluation was conducted by increasing the printing pressure. In other Examples, the printing evaluation was conducted under the proper pressure. The printing pressure is expressed by a distance (in m) between a plate cylinder and a pressure cylinder which has been narrowed by using a kiss touch as an indicator.

Comparative Example 4

[0075] Preparation of Photosensitive Resin Composition J

[0076] 68 -Caprolactam (500 parts by mass), 575 parts by mass of Nylon salt of 2.70 parts by mass of N-(2-aminoethyl)piperazine with 305 parts by mass of adipic acid and 40 parts by mass of N-(2-aminoethyl)piperazine as an agent for making the terminal into an amino group (as well as an adjusting agent for polymerization degree) were subjected to a melt polycondensation in an autoclave so as to give a light yellow, transparent and alcohol-soluble copolymerized Nylon oligomer (average molecular weight: ca. 3050) wherein a specific viscosity was 1.40 and both terminals were substantially primary and/or tertiary amino group (s). Separately, 750 parts by mass of polypropylene glycol (average molecular weight: 1000) was reacted with 300 parts by mass of hexamethylene diisocyanate so as to give an urethane oligomer having isocyanate groups substantially in both terminals. After that, 92 parts by mass of the copolymerized Nylon oligomer prepared as shown above was dissolved in 200 parts by mass of methanol and, at 50 C., 18 parts by mass of the above urethane oligomer was gradually poured into a Nylon oligomer solution with stirring. The reaction between the both finished within about 15 minutes. Viscosity of the reaction solution was about 180 poises. This light yellow and transparent solution was cast onto a Petri dish coated with Teflon (registered trademark), and methanol was removed by evaporation so as to give a polymer (water-soluble polyether urea urethaneamide) having an amide bond, an urethane bond and an urea bond in a molecule. The resulting polymer was a light yellow, semitransparent, soft and elastic polymer wherein a softening point was 85 to 95 C. and a specific viscosity was 2.20.

[0077] The above-prepared polymer (55 parts by mass) was dissolved in 100 parts by mass of methanol. To this solution were added 5 parts by mas s of adipic acid (which forms an ammonium salt with terminal amino group and basic tertiary nitrogen of a piperazine ring in a main chain of the above polymer so as to make the above polymer water-soluble) , 25 parts by mass of epoxy ester (200PA), 12 parts by mass of n-butylbenzene sulfonamide, 1 part by mass of photopolymerization initiator (Irgacure 651) and 0.1 part by mass of hydroquinone monomethyl ether so as to give a solution of the photosensitive resin composition. This solution was flown into a Petri dish coated with Teflon (registered trade mark) and methanol was removed therefrom by evaporation in a dark place followed by drying in vacuo at 40 C. for a whole day and night more whereupon a sheet of the photosensitive resin composition J was prepared.

[0078] Preparation of Relief Printing Original Plate

[0079] This sheet was adhered to a support prepared by coating an adhesive composition containing an ultraviolet absorber in a film thickness of 20 m onto a polyester film in 125 m thickness. Further, an upper side of the sheet was applied to a polyester film of 125 m thickness coated with a protective layer (polyvinyl alcohol) and a heat-sensitive mask layer (butyral resin in which carbon black was dispersed), so that a coated side thereof contacts with the photosensitive resin composition J. The resulting laminate was thermally pressed at 100 C. whereupon a crude plate of a sheet-form layered product was prepared.

[0080] Preparation of Printing Plate from the Relief Printing Original Plate

[0081] After detaching the cover film of the photosensitive resin original plate, an image containing at least 150 lines and 3% of halftone dots was subjected to abrasion to a resin plate heat-sensitive mask layer. Next, the above photosensitive resin original plate was subjected to a main exposure by using a fluorescent lamp for an ultraviolet ray (10R manufactured by Philips) wherein an illuminance at 350 nm was 8.0 w/m.sup.2. The plate was developed for two minutes by using a developing apparatus. Then the developed plate was strained, dried at 60 C. for ten minutes, subjected to an after exposure for one and half minutes by using the same fluorescent lamp for ultraviolet ray so as to give a relief for evaluation having a relief image wherein there were reproduced the halftone dots of 150 lines and 3%.

[0082] The resulting printing plate was evaluated. Details of the photosensitive resin composition are shown in Table 1, and details of the printing plate and of the evaluated result thereof are shown in Table 2.

TABLE-US-00001 TABLE 1 A B C (solid basis (solid basis (solid basis % by mass) % by mass) % by mass) Photosensitive synthetic rubber ingredient butadiene latex 42.2 42.2 45.2 resin acrylonitrile-butadiene latex 7.2 7.2 10.2 composition polybutadiene hydrophilic polymer PFT 5.0 5.0 5.0 cross-linking agent oligobutadiene acrylate 20.0 15.0 20.0 dimethyloltricyclodecane diacrylate trimethylolpropane triacrylate 9.0 16.0 9.0 lauryl methacrylate 9.0 8.0 9.0 plasticizer liquid polybutadiene 6.0 5.0 photopolymerization initiator benzyl dimethylketal 1.5 1.5 1.5 hydroquinone monomethyl ether 0.1 0.1 0.1 Total 100.0 100.0 100.0 D E F (solid basis (solid basis (solid basis % by mass) % by mass) % by mass) Photosensitive synthetic rubber ingredient butadiene latex 42.2 42.2 47.2 resin acrylonitrile-butadiene latex 7.2 7.2 8.2 composition polybutadiene hydrophilic polymer PFT 5.0 5.0 5.0 cross-linking agent oligobutadiene acrylate 17.0 13.0 25.0 dimethyloltricyclodecane diacrylate 7.0 trimethylolpropane triacrylate 13.0 20.0 lauryl methacrylate 8.0 6.0 plasticizer liquid polybutadiene 6.0 5.0 6.0 photopolymerization initiator benzyl dimethylketal 1.5 1.5 1.5 hydroquinone monomethyl ether 0.1 0.1 0.1 Total 100.0 100.0 100.0 G H I (solid basis (solid basis (solid basis % by mass) % by mass) % by mass) Photosensitive synthetic rubber ingredient butadiene latex 49.2 39.4 39.4 resin acrylonitrile-butadiene latex 9.2 composition polybutadiene 10.0 10.0 hydrophilic polymer PFT 5.0 5.0 5.0 cross-linking agent oligobutadiene acrylate 22.0 20.0 17.0 dimethyloltricyclodecane diacrylate 8.0 trimethylolpropane triacrylate 9.0 13.0 lauryl methacrylate 9.0 8.0 plasticizer liquid polybutadiene 5.0 6.0 6.0 photopolymerization initiator benzyl dimethylketal 1.5 1.5 1.5 hydroquinone monomethyl ether 0.1 0.1 0.1 Total 100.0 100.0 100.0 J (solid basis % by mass) Photosensitive polymer compound water-soluble polyether urea urethaneamide 55.0 resin composition cross-linking agent epoxy ester 200PA 25.0 plasticizer n-butylbenzene sulfonamide 12.0 quaternizing agent methacrylic acid adipic acid 5.0 photopolymerization initiator Irgacure 651 1.0 hydroquinone monomethyl ether 0.1 Total 98.1

TABLE-US-00002 TABLE 2 Exam- Exam- Exam- Exam- Exam- Exam- Exam- Exam- Exam- Exam- ple 1 ple 2 ple 3 ple 4 ple 5 ple 6 ple 7 ple 8 ple 9 ple 10 Printing plate photosensitive resin A A A A G G G B C D constitution layer composition total thickness of 950 950 950 950 950 730 450 950 950 950 printing plate (m) thickness of 805 805 805 805 830 522 305 805 805 805 photosensitive resin layer (m) thickness of adhesive 20 20 20 20 20 20 20 20 20 20 layer (m) thickness of support 125 125 125 125 100 188 125 125 125 125 (m) Printing plate surface hardness 80 80 80 80 86 89 93 83 82 82 property (Shore A) curling-in degree (cm) 0.1 0.1 0.1 0.1 0.2 0.1 0.1 0.1 0.2 0.2 Printing printing pressure (m) 50 75 100 125 50 50 50 50 50 50 property printing property of highlight part 150 lines-3% ink transfer Compar- Compar- Compar- Compar- ative ative ative ative Exam- Exam- Exam- Exam- Exam- Exam- Exam- Exam- Exam- ple 11 ple 12 ple 13 ple 14 ple 15 ple 1 ple 2 ple 3 ple 4 Printing plate photosensitive resin E F H I A A G G J constitution layer composition total thickness of 950 950 950 950 950 1000 450 450 950 printing plate (m) thickness of 805 805 805 805 805 880 242 180 805 photosensitive resin layer (m) thickness of adhesive 20 20 20 20 20 20 20 20 20 layer (m) thickness of support 125 125 125 125 125 100 188 250 125 (m) Printing plate surface hardness 85 83 80 82 80 77 96 98 83 property (Shore A) curling-in degree (cm) 0.2 0.2 0.2 0.2 0.1 0.1 0.1 0.1 5 Printing printing pressure (m) 50 50 50 50 50 printing 75 75 50 property impossible printing property of printing x highlight part 150 impossible lines-3% ink transfer printing x x x impossible

[0083] As will be apparent from the evaluation result of Table 2, the printing plate obtained from the printing original plates of Examples 1 to 15 satisfying the conditions stipulated by the present invention did not result in a problem of curling-in, showed no thickening by printing pressure, was excellent in an ink transfer and had a high highlight printing property. Particularly in Examples 1 to 3, it was confirmed that the highlight printing property was enhanced when a printing pressure was made lower than a usual pressure for letterpress (150 m). Moreover, in Example 15 wherein the printing was conducted by a rotary printing machine of a center drum type, the highlight printing property was significantly improved as compared with the case wherein the printing was done using a usual rotary printing machine. On the contrary, in Comparative Examples 1 to 4 wherein the condition stipulated by the present invention was not satisfied, there happened a problem in any of the curling-in, the highlight printing property and the ink transfer.

INDUSTRIAL APPLICABILITY

[0084] The relief printing original plate of the present invention solves all of the problems in the rotary letterpress printing which are the mounting on plate cylinder, thickening by printing pressure and ink transfer. Accordingly, it is quite suitable for the case wherein a letterpress printing is conducted using a rotary printing machines of a center drum type.