JPS5914744B2 - Method for manufacturing printing plates that prevent background smearing - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention involves applying an ink-repellent substance to a photosensitive resin layer that has been subjected to an image-forming exposure process and a process to remove unexposed areas in order to prevent scumming during printing. The present invention relates to a method for producing a photosensitive resin layer characterized by the following.

Currently, photosensitive resin plate making involves irradiating a photosensitive resin layer molded to a certain thickness or a member combining it with a support layer with actinic rays through a negative film, etc., and performing image-forming exposure. , the unexposed areas are removed by elution with various solutions or solvents, and then dried.

5 The photosensitive resin layer thus created is subjected to letterpress printing.

By the way, in the case of letterpress printing, the relief image, which is the image area, is required to have a considerable height. This is because, in the case of letterpress printing, if the relief image is low, ink will inevitably adhere to non-image areas, causing so-called scumming. In order to prevent such scumming, the height of the relief image is usually required to be 0.5 mm or more. When printing with a plate that has such a relatively high relief image, especially in the case of rotary printing, it is necessary to make the 15th plate into a cylinder and attach it to the plate cylinder. Plates, ie those with thick layers, are disadvantageous.

There are also plate materials that have flexible properties to make them easier to install on rotary printing presses, but it is more convenient for plates to be thinner when they can be installed on a plate cylinder. Another advantage is that the thinner the plate, the lower the cost of the plate material. For this reason, in recent years, a method called the dry offset method, in which printing is performed using a printing plate with a relatively small relief image height of about 0.1 to 0.3 degrees, has been viewed as promising.

However, the printing press used in this method requires considerable precision in order to prevent ink from adhering to non-image areas, and requires great care in maintenance. On the other hand, the 30 lithographic plate used in conventional offset printing is
Although this method does not require the height of the eyelid relief image, there are various problems due to the use of water in printing and the like.

In addition, a lithographic plate that does not use water has recently been proposed, and although it has been used in negative areas, it has not yet been fully put into practical use. 35 Furthermore, in plate making of a photosensitive resin layer, the relief image is made of a photosensitive layer that has been photocured.

Therefore, when a high relief image is required, it is necessary to increase the thickness of the photosensitive layer and to photocure the layer to a thickness corresponding to the height. Therefore, in general, with photosensitive resin plates, it is necessary to pay attention to the exposure settings in order to balance the formation of fine points and detailed relief images with the fogging of characters with a large number of strokes and the dark areas of the halftone plate. The thicker the cured thickness, the more difficult it becomes to maintain the balance. From this point of view as well, if the relief height is lowered, the reproducibility of the plate will be improved and the exposure time can also be shortened.

In view of these points, the present inventors have created a plate that has a relatively low relief, does not require a special printing machine, and can be printed without background smudge using a conventional ordinary letterpress printing machine. Through these studies, we have arrived at the present invention.

That is, the inventors have discovered that scumming can be prevented by a simple operation of applying an ink-repellent substance to the entire surface of a photosensitive resin plate that has been subjected to image-forming exposure processing and removal processing of unexposed areas. On the other hand, regarding printing plates in which the non-image areas are made of an ink-repellent material and only the image areas are made ink receptive, they are widely used as an alternative to conventional planographic plates for offset printing and as planographic plates that do not require dampening water. Proposed.

However, these methods consist of forming only the non-image areas with an ink-repellent material using various methods.
Therefore, in these methods, the printing plate master must be composed of multiple layers, or it is necessary to employ various complicated methods in its preparation. In contrast, the object of the present invention can be achieved by applying an ink-repellent substance to the entire surface of the photosensitive resin plate on which an image has been formed.

Of course, it is more convenient to apply the ink-repellent material only to the non-image areas in order to achieve the purpose of the present invention, but
Such an operation is virtually impossible and impractical.

The photosensitive resin plate used in the method of the present invention is made by forming a layer of a photosensitive resin composition whose solubility in various solvents is significantly reduced compared to that before photocuring or irradiation by irradiation with actinic rays, and then layering the photosensitive resin composition with a support. 4 combinations, image forming exposure and removal treatment of unexposed areas, or a printing plate made by a method in which only the photosensitive resin layer is exposed on both sides as shown in Japanese Patent Publication No. 45-23165. The height of this version of the relief statue is 0.05m7! L or more, preferably 0.1 or more.

Although the mechanism of the present invention, in which only the image area is printed while preventing scumming in the non-image area by applying an ink-repellent substance to the entire plate surface, has not been clarified in detail, the following is It is estimated as follows.

That is, in the method of the present invention, the ink-repellent substance is applied to the entire plate surface, but since the relief image has a height, the width of the ink roller and the markings in the non-printing area and the printing area are limited during printing. Since the pressures are different, ink does not adhere to the non-image areas, or even if it does, it is only a small amount, and since the printing pressure is also small, it is thought that no background stains will occur on the printed matter. Therefore, if the height of the relief image is set to 0.05 degrees or less, scumming will occur, and if the printing pressure is reduced to avoid this, the image area will not be printed clearly, resulting in printed matter with blurred lines. Become.

Further, the height of the relief image of the present invention is the height from the non-image area of a fairly wide area, and is not the height from the non-image line between adjacent relief images.

Therefore, the halftone dot depth in halftone plates, the depth from the top surface of relief images of non-printing lines in characters and designs, etc. are not necessarily 0.0.
It doesn't have to be 5 dragons or more. Examples of the photosensitive resin composition used in the photosensitive resin layer include those containing a compound having an addition-polymerizable unsaturated group as a main ingredient and a photopolymerization initiator added thereto.

Compounds having addition polymerizable unsaturated groups include acrylic acid, methacrylic acid, or esters thereof, such as alkyl, cycloalkyl, tetrahydrofuryl, glycidyl, hydroxyalkyl acrylates and methacrylates, alkylene glycols, Mono- or diacrylates and methacrylates of polyoxyalkylene glycols, or trimethylolpropane triacrylates and methacrylates, pentaerythritate tetraacrylates and methacrylates, etc., or acrylamide, methacrylamide, or derivatives thereof, such as N-methylol acrylamide and methacrylamide, N - addition-polymerizable unsaturated monomers such as mer-alkylene bisacrylamide and methacrylamide, diacetone acrylamide and methacrylamide, styrene, vinyltoluene, divinylbenzene, diallyl phthalate, triacrylic cyanurate, vinyl acetate, acrylonitrile, and unsaturated polyesters. Examples include alkyd resins, unsaturated polyurethane resins, and polyurethane resins modified with addition-polymerized surrounding monomers having active hydrogen, such as hydroxyalkyl acrylates or methacrylates.

As a photopolymerization initiator, penzoin, benzoin alkyl ether, α-methylbenzoin and alkyl ether, α-phenylbenzoin, α-allylbenzoin, anthraquinone, chloroanthraquinone, methylanthraquinone, ethylanthraquinone, benzyl, diacetyl, acetophenone, ω -bromoacetophenone, α
Examples include naphthalene sulfonyl chloride, diphenyl disulfide, dyes such as eosin, thionine, etc., stannous chloride, uranyl salts, etc.

The photosensitive resin composition is a composition in which one or more of the above-described addition-polymerizable unsaturated group-containing compounds and a photopolymerization initiator are added.

Furthermore, if necessary, thermal polymerization inhibitors such as hydroquinone, p-methoxyphenol, catechol, T
Added are ert-butylhydroquinone, benzoquinone, p-phenylenediamine, picric acid, phenothiazine, and the like. In addition, the addition polymerizable polymer compound may be added to a polymer compound soluble in water or an alkaline aqueous solution, such as polyvinyl alcohol and its derivatives, cellulose derivatives, polyacrylic acid, polymethacrylic acid, polyacrylamide, or alcohol-soluble polyamide. Compositions containing a compound having an unsaturated group, a photopolymerization initiator, and a thermal polymerization inhibitor if necessary, and
As an example, a composition comprising a polyene, a polythiol, and a photosensitizer shown in No. 29525 can be mentioned.

The photosensitive resin composition as exemplified above is made into a layer, and this is used as a photosensitive layer for plate making.

In this case, if the photosensitive resin composition is solid at room temperature,
It is molded using a suitable means such as a calendar roll or press, and then adhered to a support to form an original plate. The support used is
There are aluminum plates, steel plates, plastic sheets, etc., and they are provided with a photosensitive layer, an adhesive layer, an antihalation layer, etc. A negative film is placed in close contact with the original plate thus prepared, and exposed to actinic rays to form an image, and then unexposed areas are eluted and removed with water, aqueous alkaline solution, organic solvent, or the like.

On the other hand, if the photosensitive resin composition is liquid at room temperature,
pouring it onto the support to a certain thickness and placing a negative film thereon, or pouring it onto the negative film;
A support is then placed thereon.

Still another method is to set the support and negative film with a certain gap, mold the composition by injecting the composition into the gap, and then perform image forming exposure by irradiating actinic rays through the negative film. . In this case, it is also effective to use a transparent support such as a plastic sheet and use the method disclosed in Japanese Patent Publication No. 46-42452, which exposes from the support side, in addition to image-forming exposure through a negative film. It is a method.

Furthermore, in the case of a liquid composition, an intermediate layer or a gap is provided between the photosensitive layer and the negative film to avoid adhesion between the photosensitive layer and the negative film after exposure.

Examples of active light sources used include arc lamps, mercury lamps, xenon lamps, ultraviolet fluorescent lamps, and sunlight. When carrying out the image forming exposure process and the unexposed area removal process by the above method, the height of the relief image on the photosensitive resin plate is set to be 0.05 u or more.

As a method, the thickness of the photosensitive layer is at least 0.05 nm.
With the above, the height of the relief statue is 0.05m7! It is necessary to remove the unexposed area so that the height is equal to or higher than L, and when using a method of exposing from the support side, adjust the exposure amount so that the height of the relief image does not fall below 0.05 m. It is necessary to do so. Next, an ink-repellent substance is applied to the entire plate surface, and any method such as spray application, brush application, or dipping may be used, but if the amount of application is too large, the fine patterns will be buried, so it is difficult to apply. The amount is 20μ or less in terms of thickness, preferably 1
It is preferable to set it to 0μ or less.

The ink repellent substance of the present invention is a silicone resin or a fluorine compound, and the silicone resin may be in any form such as silicone oil, silicone rubber, or silicone varnish, and a solution or emulsion of these silicone resins may be used. used.

As fluorine compounds, -CF3v-CF2H, -CF
It is a compound having a fluoroal group such as 2-, and this compound can be used as a solution or emulsion. Even the above-described materials may not necessarily exhibit good ink repellency depending on the type of ink, and it is necessary to select an ink repellent material depending on the type of ink used for printing.

Ink repellency, that is, non-adherence of ink, depends on various factors, but in order to achieve the purpose of the present invention, by coating the photosensitive resin plate with the above-mentioned substance, it can be compared with an uncoated plate. What is necessary is to select a material with a large contact angle. The contact angle of normal ink to the surface of a photosensitive resin plate is 25 to 3
Although it is in the 5th place, it is desirable to increase it to at least 50 in or more, preferably 600 or more, by applying an ink repellent material. If the viscosity of the ink is high, it is not easy to measure the contact angle, but if the viscosity is high, the transferability of the ink will also decrease, so even if the above contact angle is not achieved, the above ink-repellent material can be used. can. Examples will be given below to clarify the embodiments of the present invention.

Note that the following examples are merely illustrative and do not limit the method of the present invention in any way. Example 1 Propylene glycol, diethylene glycol, adipic acid, fumaric acid, and isophthalic acid in a molar ratio of 0630/
To 100 parts by weight of a polyester resin (acid value 35) obtained by condensation in the ratio of 0.20/0.15/0.25/0.10, 10 parts by weight of 2-hydroxy methacrylate, 20 parts by weight of diethylene glycol dimethacrylate, 10 parts by weight of diacetone acrylamide, 1 part by weight of benzoin ethyl ether, and 0.1 part by weight of p-methoxyphenol were added and thoroughly mixed to prepare a photosensitive resin composition.

Next, place a negative film for plate making with the top of a newspaper page on a horizontally placed glass plate, cover it with a 20μ thick polypropylene film, and then apply the above composition to a thickness of 0.2 mm using a doctor knife. expand.

Next, a polyethylene terephthalate film with a thickness of 100μ was coated on one side of the spread composition layer with a polyurethane adhesive (a mixture of Nipporan 3002 manufactured by Nippon Polyurethane Industry Co., Ltd. and Coronate L in a ratio of 5:1) to a thickness of 10μ. Laminate so that the adhesive sides are in contact. Next, from the polyester film side, a light source consisting of 10 20W ultraviolet fluorescent lamps was used for 10 seconds at a distance of 10c1n, and from the negative film side, a high-pressure mercury lamp was used for 5 seconds.
0CT! Expose for 25 seconds from distance L. After exposure,
Remove the negative film and polypropylene film, 1
The unexposed areas were removed by elution with a % borax aqueous solution, dried, and then re-exposed to the ultraviolet fluorescent lamp for 3 minutes to prepare a plate. The relief depth of the obtained plate was 0.15 mm. A gasoline solution of silicone varnish (Shin-Etsu Chemical KR252 with 10% catalyst D-7 added and diluted twice with gasoline) was applied to the plate surface thus obtained, and the mixture was heated to 60°C.
It was dried for 20 minutes. The contact angle with newspaper ink before applying silicone was 26 degrees, but after drying it was 600 degrees. As a result of comparing the level of background smearing between the plates prepared as described above and the plate without silicone coating using newspaper ink using a Panda Tsukku letterpress proofing machine, it was found that the plate without silicone coating had a printing pressure of 4 mils (0.5 mils). 1mm), there was significant background staining, whereas the silicone coated surface was 12mm.
Mils (0.311) did not cause background stains.

Examples 2 to 4 A plate prepared in the same manner as in Example 1 was coated with the following ink repellent instead of the silicone varnish solution in Example 1.
The dried printing plate was printed using newspaper ink using a Vanderkut letterpress proofing machine, and the results were as follows.

ink repellent material

Claims (1)

[Claims] 1. A method for eliminating scumming characterized by applying an ink-repellent substance to the entire plate surface of a photosensitive resin plate having a relief image having a height of 0.05 mm or more, which has been subjected to image-forming exposure treatment and removal treatment of unexposed areas. Method of manufacturing prevented printing plates.