JPS6152791B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing printing plates for offset printing. More specifically, the present invention relates to a manufacturing method in which ultraviolet curable ink is transferred using an offset printing machine and photocured. In recent years, the speed and efficiency of printing has been increasing, and there is a desire for faster and more efficient plate making in the printing process. Under these circumstances, for example, in rotary press printing, efforts are being made to replace lead plates with resin plates in order to improve the working environment and reduce pollution. However, the production of resin plates has a problem in that the cost is higher than that of lead plates. Therefore, an inexpensive plate that does not use lead is desired. In addition, there was a tendency to want to achieve the printing effects of offset printing, and the printing that had been done with rotary letterpress began to be replaced with offset printing, and a new method of manufacturing printing plates for offset printing was created. It is also desired. Conventionally, there are the following methods for making printing plates for offset printing. (1) Direct image transfer method, (2) Photochemical transfer method, (3) Photodirect method, (4) Electrophotographic method, etc., allow plate making to be performed easily and quickly, and the number of sheets to be passed through is too large. There is a method used when high printing effects are not required. In addition, (5) photolithography is a method used when a large number of sheets are to be printed and high-quality printed matter is required, and plate making tends to be complicated, and the plate has poor printing durability and reproduction accuracy. It is needed. The currently widely used plate-making method for offset printing is the lithography method.
This is a process in which a photosensitive layer is provided on a metal or plastic substrate, and a negative or positive film is attached and developed.
There are various types such as plate, Wipon plate, flat intaglio plate, and multilayer metal plate. Among these plates, the egg white plate and the Wipon plate have some difficulty in printing durability, and the other plates have a printing durability that can withstand over 100,000 sheets. The plate is known to have a printing durability that can withstand over 500,000 sheets. However, even with multilayer metal plates, there are concerns about problems such as pollution treatment, and the use of PS plates is becoming more preferred. However, PS plates have inferior printing durability compared to multilayer metal plates, so when printing in large quantities, it is necessary to make many plates, and as a result, plate making costs are higher than resin plates. It was hot. As a method for solving the above-mentioned problems, a method of manufacturing a printing plate has recently been proposed in which an ink having ink receptivity after curing and fixation is transferred onto a rough aluminum surface by an offset printing method. The above method does not require new equipment,
Although it is hoped that printing plates can be produced quickly, easily, and inexpensively without causing pollution or occupational hygiene problems, the ink transferred by this offset printing method is different from ordinary general printing inks. In addition to the same properties, it must also have properties sufficient to become the oil-sensitive portion of the plate when cured and fixed. That is, the ink to be transferred by the offset printing method is required to have the following properties. 1. Good adhesion to substrates including rough metal surfaces such as aluminum and chrome plating. 2. Good suitability for offset printing, especially good dot reproducibility. 3. The ink receptivity should be good after curing and fixation. 4. The printing durability of the part after curing and fixing should be good. Furthermore, as the ink to be transferred by the offset printing method, it was considered that an ultraviolet curing ink with a fast curing speed is preferable from the viewpoint of workability. The present inventor has tried using various ultraviolet curable printing inks for the ink to be transferred by the offset printing method. Ink was not easily obtained. In other words, there are conventional UV-curable printing inks that contain epoxy acrylate, urethane-modified acrylate, alkylated acrylate, etc. as printing ink components, but those that contain epoxy acrylate as a printing ink component do not cure after printing. Although the ink receptivity and printing durability of the fixed area (image area) were improved, the suitability for offset printing and the adhesion to the aluminum substrate were insufficient. Furthermore, ink compositions containing urethane-modified acrylate as a printing ink component lacked ink receptivity in hardened and fixed areas (image areas) after printing. In addition, those containing alkylated acrylate as a printing ink component lacked printing durability in the hardened and fixed areas (image areas) after printing. Therefore, the inventors conducted extensive research and found that 5
An ultraviolet curable printing ink containing a curable resin obtained by esterifying acrylic acid and/or methacrylic acid with a resin having a hydroxyl group using a membered ring compound as a starting material is produced, and is printed on a substrate by an offset printing method. When transferred, we were able to obtain an extremely excellent printing plate for offset printing. That is, the present invention provides (1) a method for manufacturing an offset printing plate in which an ultraviolet curable ink is transferred onto a substrate from an original plate using an offset printing machine, and the transferred ultraviolet curable ink is photocured; The curable ink is (A) a resin having a hydroxyl group obtained by reacting the following (a) and (b), or a resin having a hydroxyl group obtained by hydrogenating the resin as necessary, and acrylic acid and/or methacrylic acid. 30 to 80 parts by weight of a curable resin obtained by esterification reaction, (a) the following general formula

[Formula] (In the formula, R is an organic residue having 1 to 3 carbon atoms,
n represents 0 or an integer of 1 to 6. ) and/or their Diels-Alder reaction products; (b) compounds having both a polymerizable double bond and a hydroxyl group in the same molecule; (B) reaction 5 to 50 parts by weight of a photosensitive diluent, (C) 0.1 to 30 parts by weight of a photosensitizer, (D) 40 parts by weight or less of a pigment as required; This is a method of manufacturing printing plates. In the present invention, a substrate similar to that used in the production of general offset printing plates can be used, but the printing ink transferred by the offset printing method firmly adheres to the substrate, which increases the durability. The surface of the substrate is made of aluminum, zinc, chrome plating, etc., which has been grained to create extremely fine irregularities in order to increase the printing force and improve water retention during printing after being made into a printing plate. Preferably, it consists of In addition, as for the method of graining, use an appropriately sized polishing ball (glass, ceramic, steel, etc.) and an abrasive agent (garnet, carborundum, alundum, etc.)
There are also methods such as the beading method, which uses water and vibration to make small scratches on the metal surface, the method of blowing wet abrasive onto the metal surface with compressed air, the brush method, the anodizing method, and a combination of these methods. However, in order to improve water retention during printing, adhesion with printing ink transferred by offset printing method, and printing durability associated with it, a method of further anodizing after mechanical polishing such as the dubbing method or brazi method is recommended. Preferably, it is treated with In the present invention, an offset printing machine is used to transfer ultraviolet curable printing ink onto a substrate from an original plate, and the original plate may be a PS plate, a multilayer metal plate, a flat intaglio plate, a Wipon plate, or a synthetic resin plate. , a waterless lithographic plate whose non-image areas are coated with a silicone compound, etc. is used. Although the offset printing machine is not particularly limited, it is preferable to use a metal plate printing machine or an offset printing proofing machine. In the present invention, the ultraviolet curable printing ink transferred onto the substrate with an offset printing machine is (A) curable resin 30
~80 parts by weight, (B) 5 to 50 parts by weight of a reactive diluent, (C) 0.1 to 30 parts by weight of a photosensitizer, and (D) 40 parts by weight or less of a pigment if necessary. Preferred for achieving the purpose of the present invention. In the present invention, the curable resin (A) is selected from the group consisting of cyclopentadiene, dicyclopentadiene, tricyclopentadiene, tetracyclopentadiene, and lower alkyl substituted products thereof having 1 to 3 carbon atoms, as component (a). One or more selected types and component (b) selected from the group of (meth)allyl alcohol, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, butenediol, etc. The molar ratio of component (a)/component (b) is from 30/70 to one or more components.
95/5, preferably between 40/60 and 80/20 in the presence of a radical polymerization catalyst or without a catalyst, if desired in the presence of a solvent such as xylene, 150 to 350
A resin having a hydroxyl group is obtained by heating the reaction at ℃, and if necessary, the resin having a hydroxyl group is hydrogenated to form a so-called resinous polyol, which is mostly composed of diol with a molecular weight of 300 to 500, and then acrylic acid is added to the resin. and/or obtained by esterifying methacrylic acid. In the above process, hydrogenation conditions must be carefully selected, and it is preferable to use a noble metal catalyst such as platinum or palladium.
It is preferable to carry out the hydrogenation under the condition of 100 Kg/cm ² without reducing the amount of hydroxyl groups. The degree of hydrogenation is usually determined by hydrogenating 40% or more, preferably 60% or more of the carbon-carbon double bonds of the resin having hydroxyl groups (resinous polyol), which significantly reduces light shielding for the photosensitizer and What is obtained is something that improves the initiation effect of the reaction. Further, the reaction between the resin having a hydroxyl group and acrylic acid and/or methacrylic acid is carried out under normal esterification reaction conditions in the presence of a catalyst or without a catalyst. At this time, it is preferable to react acrylic acid and/or methacrylic acid in an amount of 0.5 to 1 molar equivalent per hydroxyl group 1 of the resin having a hydroxyl group. In the present invention, vinyl compounds are preferred as the reactive diluent, and (meth)acrylic acid derivatives are preferred in view of the requirements for reactivity, solubility, and low viscosity. Examples of such acrylic acid derivatives include trimethylolpropane tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol(meth)acrylate, 1,4-butanediol di(meth)acrylate, and 1,6- Esterification reaction of acrylic acid or methacrylic acid to hexanediol (meth)acrylate, alkyl (meth)acrylate (alkyl group with 1 to 18 carbon atoms), monohydric phenol or polyhydric phenol with alkylene oxide added to the hydroxyl group. Crosslinkable monomers such as styrene, allyl alcohol ester, glycidyl (meth)acrylate, etc. can be used. In the present invention, photosensitizers include thioxanthone, xanthone and their halogen-substituted products as polycyclic carbonyls, penzophenone as aryl ketones, methyl 0-benzoylbenzoate, acetophenone, etc., dialkylaminoaryl ketones as dialkylaminoaryl ketones. 4,4'-bisdiethylaminopendiphenone, P-dimethylaminobenzoic acid, isoamyl, P-dimethylaminoacetophenone, etc.
It can be used singly or in combination of two or more from the group such as benzoin alkyl ethers as acyloins. In the present invention, the pigment is not particularly limited, and organic pigments and inorganic pigments used in offset inks can be used. Although it is not always necessary to add pigment, it is necessary to check and correct the condition when it is transferred to the substrate, and to check the rheological properties of the ink so that the original image can be transferred with good reproducibility using an offset printing machine. Used for adjustment. In producing an ultraviolet curable printing ink in the present invention, (A) a curable resin is made into a varnish with (B) a reactive diluent, and (C) a photosensitizer and, if necessary, a pigment. At the same time, it is dispersed and kneaded using a three-roll mill.
Then, it is manufactured by adjusting the tack value to 8 to 15 and the flow value to 15 to 18. In addition, other organic solvents,
It goes without saying that fillers, additives, etc. can be added as necessary during the above operations. In the present invention, the ultraviolet curable printing ink is
When irradiated with ultraviolet light using a high-pressure mercury lamp or the like, it quickly hardens and fixes on the substrate onto which it is transferred using an offset printer, and has extremely good adhesion to the substrate. Further, the hardening and fixing part (printing part) produces a printing plate that has good ink receptivity to general oil-based printing inks and general ultraviolet curable printing inks, and provides printed matter with excellent reproducibility of the original plate. Furthermore, in offset rotary printing where printing durability is strongly required, a printing plate having printing durability comparable to that of a multilayer metal plate is produced. According to the invention, a large number of offset printing plates can therefore be manufactured very easily and inexpensively by the offset printing method. The following is a description using comparative examples and examples.
(In the examples, parts indicate parts by weight.) Comparative Example 1 71.7 parts of Epicote 828 (epoxy resin manufactured by Shell Oil Co., Ltd.), 28.3 parts of acrylic acid, hydroquinone
0.1 part of triethylenediamine and 0.1 part of triethylenediamine were charged into a four-necked flask equipped with a reflux tube and a stirrer, and reacted at 90 to 110°C for 15 to 20 hours while blowing air, and pumped out when the acid value reached 1 or less. This is called varnish A. Comparative Example 2 20 parts of oleic acid and 47 parts of trimethylolpropane are reacted in a four-necked flask under a carbon dioxide gas stream at 240°C until the acid value reaches 5 or less. Then phthalic anhydride
Add 33 parts and react at the same temperature to obtain an alkyd resin with an acid value of 5 or less and a hydroxyl equivalent of 180. Next, 71.5 parts of this alkyd resin and 10.0 parts of benzene were charged into a four-neck flask equipped with a reflux device and a stirrer, heated to 90°C, and 28.5 parts of acrylic acid, 1.0 part of P-toluenesulfonic acid, and 0.1 part of hydroquinone were added to Drop the mixture at ~95℃ while blowing air, and gradually raise the temperature after dropping.
The reaction takes place at 100-120°C, and when the acid value reaches 5 or less, benzene is removed and pumped out. This is called varnish B. Example 1 132 parts of dicyclopentadiene with a purity of 97%, 58 parts of allyl alcohol, and 110 parts of commercially available mixed xylene were charged into an autoclave equipped with a stirrer, and the temperature was 260.
The reaction was carried out at ℃ for 5 hours. After the reaction is complete, the autoclave is cooled and the contents are distilled to remove unreacted monomers and
Removal of the low polymer and xylene yielded 152 parts of resin ()-1. This resin ()-1
Dissolve 100 parts in commercially available mixed xylene, add 1 part of palladium carbon with a palladium concentration of 5% (5% PdC standard product manufactured by Nippon Engelhard Co., Ltd.), and conduct a hydrogenation reaction at 150°C for 1 hour at a hydrogen pressure of 30 Kg/cm ² . The solvent was distilled off to obtain water-added resin (2)-1. The properties of Resin ()-1 and Resin ()-1 are as follows.

[Table] Next, 80 parts of resin ()-1, 20 parts of acrylic acid,
1.0 part of para-toluenesulfonic acid and 0.1 part of hydroquinone were added to a condenser with a side arm and a stirrer 4.
Pour into a neck flask and heat at 100℃ under reflux of benzene/methyl isobutyl ketone (MIBK) mixed solvent.
After reacting for 12 hours, benzene and MIBK were distilled off at 120°C to obtain resin (A)-1. Resin ()-1 was also reacted with methacrylic acid in the same manner as resin ()-1 to obtain resin (A)-2. Next obtained resin (A)−
Varnish C and Varnish D were prepared by dissolving 70 parts each of 1 and (A)-2 in 30 parts of trimethylolpropane triacrylate. Varnish A obtained in Comparative Examples 1 and 2 and Example 1,
B, C, and D are made into ink using three rolls according to the following recipe. Ink A Varnish A 50 parts Bisphenol A ethylene oxide adduct diacrylate 29 parts Carmine 6B (T) (monoazo pigment manufactured by Toyo Ink Manufacturing KK) 13 parts Methyl orthobenzoyl benzoate 6 parts P-dimethylaminobenzophenone 1 part 4. 4′-Bisdiethylaminoacetophenone
1 part organic bentonite 2 parts Tack value 10.5 Flow value 15.4 Ink B Varnish B 47 parts dipentaerythritol hexaacrylate
32 parts Carmine 6B (T) 13 parts Benzyl 6 parts P-dimethylaminoacetophenone 1 part 4,4'-bisdiethylaminoacetophenone
1 part Tack value 10.7 Flow value 16.0 Ink C Varnish C 48 parts Bisphenol A ethylene oxide adduct diacrylate 30 parts Carmine 6B (T) 13 parts Methylorthobenzoylacetophenone 6 parts P-dimethylaminoacetophenone 1 part 4・4′-bisdiethylaminoacetophenone
1 part organic bentonide 1 part Tack value 10.2 Flow value 15.6 Ink D Varnish D 36 parts dipentaerythritol hexaacrylate
28 parts Lionol Blue KL (indigo pigment manufactured by Toyo Ink Mfg. KK) 3 parts Hakuenka-O (extender pigment) 25 parts P-chlorothioxanthone 6 parts P-dimethylaminobenzophenone 2 parts Tack value 10.7 Flow value 16.1 Ink E Varnish C 42 parts Sorbitan triacrylate 34 parts Carmine 6B (T) 13 parts Benzoin methyl ether 10 parts Organic bentonite 1 part Tack value 10.5 Flow value 15.8 PS plate (Positype Co., Ltd.) using inks A to E thus obtained as original plates Printed on a 100μ thick aluminum plate that was grained using an offset printing machine for metal plate printing and then anodized.
A high-pressure mercury lamp H- with an intensity of 80W/cm was applied to the printing surface.
2000L (manufactured by Toshiba KK) was irradiated for 10 seconds at a position 10 cm below the plate to produce plates A to E, respectively. Before irradiating ink C with a high-pressure mercury lamp, pre-heat treatment at 180℃ for 5 minutes, then irradiate it with ultraviolet rays under the same conditions as above, and print plate F.
And so. In addition, in plate C, after UV irradiation, an additional 180
Plate G was obtained by heating and processing at ℃ for 5 minutes. Next, the results of a printing test of the obtained plate using a BB type off-print printing machine manufactured by Mitsubishi Heavy Industries are shown.

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Claims (1)

[Scope of Claims] 1. A method for producing a printing plate for offset printing, in which an ultraviolet curable ink is transferred from an original plate onto a substrate using an offset printing machine, and the transferred ultraviolet curable ink is photocured. The ultraviolet curable ink is made by (A) a resin having a hydroxyl group obtained by reacting the following (a) and (b), or a resin having a hydroxyl group obtained by hydrogenating the resin as necessary, and acrylic acid and/or methacrylic acid. 30 to 80 parts by weight of a curable resin obtained by esterifying an acid (a) The following general formula [Formula] (wherein, R represents an organic residue having 1 to 3 carbon atoms, n
represents 0 or an integer from 1 to 6. ) A five-membered ring compound having a double bond and/or a Diels-Alder reaction product thereof, (b) A compound having both a polymerizable double bond and a hydroxyl group in the same molecule (B) Reaction 5 to 50 parts by weight of a photosensitive diluent, (C) 0.1 to 30 parts by weight of a photosensitizer, and (D) 40 parts by weight or less of a pigment as required. Method of manufacturing printing plates.