JP2000214594A - Flexographic plate material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid a tacky surface of a flexographic plate material having a water-developable synthetic rubber-containing photosensitive resin layer, to improve adhesion of an original film to the photosensitive layer particularly in exposure and to obtain a photosensitive resin plate for flexographic printing excellent in image reproducibility. SOLUTION: A coating comprising a mixture of a partially saponified polyvinyl acetate and a rubber latex and a coating comprising a partially saponified polyvinyl acetate having 60-90% saponification degree are successively formed in 0.2-20 μm total thickness on the surface of a flexographic plate material having a water-developable synthetic rubber-containing photosensitive resin layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flexographic printing plate having an anti-adhesion film, and more particularly to a flexographic printing plate having an anti-adhesion film on the surface of a water-developable synthetic rubber photosensitive resin layer (hereinafter referred to as a photosensitive layer). It is.

[0002]

2. Description of the Related Art When exposing a photosensitive resin printing plate in an image shape, a method of exposing an original drawing film (negative or positive) to a photosensitive layer of the resin printing plate in vacuum and exposing it with actinic rays is mainly used. Have been.

[0003] However, the surface of the photosensitive layer of the photosensitive resin printing plate is usually tacky in many cases. Due to this tackiness, when the original film is brought into vacuum contact with the photosensitive layer, the original film and the photosensitive layer are adhered to. And uniform adhesion of the image is hindered, so that uniform printing of an image becomes impossible. Also,
When the original film is peeled off from the photosensitive layer after the exposure, the gelatin film of the original film may be transferred to the surface of the photosensitive layer, or the surface of the photosensitive layer may be transferred to the original film to damage the original film.

In particular, in the case of a photosensitive resin printing plate which can be developed with water, since the photosensitive layer itself has a high affinity for water, the humidity (moisture) in the air causes the surface of the photosensitive layer to become extremely sticky,
There are problems such as difficulty in uniform adhesion.

As a method for solving such a problem, for example, sanding is applied to the surface of the photosensitive layer, and the surface is matted by chemical etching or coating of a resin containing a matting agent.

However, when the stickiness of the surface of the photosensitive layer becomes extremely large due to humid conditions such as a photosensitive resin printing original plate which can be developed with water, even if the photosensitive layer is matted, the adhesion of the original film is not sufficient. Therefore, if the surface of the photosensitive layer is strongly matted in order to enhance the adhesion of the original film, there is also a serious problem that the sharpness of the photosensitive image is reduced due to an increase in scattered light.

A method using a matted film on the original film itself is also used. However, in this case, the film cost is high and the production of the original film is more difficult than that of a normal film. . Furthermore, this method has a high possibility of causing poor adhesion when the surface of the photosensitive layer has a strong tackiness, and has a problem that the image is less sharp due to scattered light.

As described above, various means have been used to improve the adhesion between the original film and the photosensitive layer. In any of the methods, when the surface of the photosensitive layer has a high tackiness, the original image on the surface of the photosensitive layer can be improved. Uniform vacuum adhesion of the film is quite difficult.

As another method for improving the poor adhesion of the original film, there has been proposed, for example, a method of coating the surface of a photosensitive layer with a partially saponified polyvinyl acetate layer having a saponification degree of 90 mol% or more. (JP-A-51-49803).

However, this method also has the following problems. (1) When the cover film is attached after the partial saponified polyvinyl acetate coating is provided, or when the plate is bent inward or outward during the plate making operation, cracks often occur in the partially saponified polyvinyl acetate coating. When such a cracked plate material is exposed, light is scattered at the cracked portions, which causes a serious problem that an image larger than the original film is reproduced. (2) In the case of a plate material in which a cover film is mounted on a partially saponified polyvinyl acetate film, a part of the partially saponified polyvinyl acetate film is peeled off from the photosensitive layer surface when the cover film is peeled off during exposure. A transition phenomenon occurs. In this way, the part where the partially saponified polyvinyl acetate coating has fallen off the photosensitive layer surface has poor negative adhesion, and a problem that an image larger than the original film is reproduced occurs.

[0011]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned drawbacks of the prior art, and an object of the present invention is to provide a flexographic printing plate having a water-developable synthetic rubber photosensitive resin layer. An object of the present invention is to prevent sticking, particularly to improve the adhesion between the original film and the photosensitive layer during exposure, and to provide a flexographic printing plate excellent in image reproducibility.

[0012]

In order to solve the above problems, the flexographic printing plate of the present invention mainly has the following constitution. That is, a flexographic printing plate material having a water-developable synthetic rubber-based photosensitive resin layer, and the following (a)
And (b) are provided in this order, and the total thickness of both coatings (a) and (b) is 0.2 to 20 μm. (A) A coating comprising a mixture of partially saponified polyvinyl acetate and a rubber-based latex. (B) A coating made of partially saponified polyvinyl acetate having a saponification degree of 60 to 90 mol%.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The water-developable synthetic rubber photosensitive resin layer referred to in the present invention comprises a water-soluble or water-dispersible hydrophilic polymer and a synthetic rubber as resin components, and further comprises a photopolymerizable unsaturated compound and Refers to a layer formed from a composition comprising a photosensitizer, a thermal polymerization inhibitor, and the like, if necessary.The composition can be formed on a support such as steel, aluminum, iron, glass, or a plastic film of any thickness. To form a photosensitive layer. The photosensitive layer thus formed is
After exposure to actinic light using the original film, the unexposed portion is washed out with water.

Next, each component forming the photosensitive layer will be described.

The hydrophilic polymer of the present invention refers to a polymer having the property of dissolving and / or dispersing in water. For example, when a polymer formed into a film is immersed in water or warm water and rubbed with a brush or the like, the polymer is converted. Elution over the entire surface,
Alternatively, the film loses or disintegrates due to partial elution, or when the polymer swells and separates and disperses in water.

Examples of such a hydrophilic polymer include polymers soluble in alcohol and / or water, and polyamides, partially saponified polyvinyl acetates, celluloses and the like can be used. From the viewpoint of compatibility with the photopolymerizable unsaturated compound, it is preferable to mainly use polyamide.

The present invention makes it possible to develop a neutral aqueous development by utilizing such a characteristic property of a hydrophilic polymer, particularly a hydrophilic polyamide, and is applicable to printing with an aqueous ink.

The hydrophilic polyamide used in the present invention includes all conventionally proposed hydrophilic polyamides. For example, polyamides containing a sulfonic acid group or a sulfonate group obtained by copolymerizing sodium 3,5-dicarboxybenzenesulfonate as disclosed in JP-A-48-72250, No. 43465, a polyamide having an ether bond obtained by copolymerizing any one of a dicarboxylic acid, a diamine and a cyclic amide having an ether bond in a molecule;
No. 0-7605, a polyamide containing a basic nitrogen obtained by copolymerizing N, N'-di (γ-aminopropyl) piperazine and the like, and these polyamides are coated with acrylic acid or the like. Graded polyamide, having a molecular weight of 15 as proposed in JP-A-55-74537.
Copolymerized polyamide containing 0 to 1500 polyether segments, and ring-opening polymerization of α- (N, N′-dialkylamino) -ε-caprolactam or α- (N,
N′-dialkylamino) -ε-caprolactam and ε-
Examples include polyamides obtained by ring-opening copolymerization of caprolactam.

Among these hydrophilic polyamides, copolymerized polyamides containing a polyether segment having a molecular weight of 150 to 1500, more specifically, having a terminal amino group and having a polyether segment having a molecular weight of 150 to 1500 are preferred.
A copolymer polyamide containing 1500 to 150% by weight of a structural unit composed of polyoxyethylene and an aliphatic dicarboxylic acid or a diamine is preferably used.

These hydrophilic polyamides may be used alone or in combination of two or more.

In the present invention, the synthetic rubber used for the photosensitive resin layer means unvulcanized rubber, vulcanized rubber or both. The vulcanized rubber is obtained by vulcanizing an unvulcanized rubber. The unvulcanized rubber is not particularly limited, and a so-called solid rubber having a molecular weight of 40,000 or more is preferably used. For example, high-molecular weight isoprene rubber, butadiene rubber, styrene-butadiene rubber, chloroprene rubber, nitrile rubber, butyl rubber, acrylic rubber, epichlorohydrin rubber, silicone rubber, raw rubber or elastomer, styrene-butadiene copolymer, Copolymers of dienes such as styrene-isoprene copolymer, butadiene-acrylic acid copolymer, and copolymers of olefins such as ethylene-propylene copolymer and ethylene-vinyl acetate copolymer. . Among them, copolymers of dienes or olefins are preferably used. As these unvulcanized rubbers, both self-vulcanizable and non-self-vulcanizable rubbers are suitable for the practice of the present invention. Non-self-vulcanizable rubbers require the presence of a vulcanizing agent to vulcanize the rubber at processing temperatures to a rubber gel content of at least about 80% or more. Self-vulcanizable rubber, as the name implies, vulcanizes at processing temperatures to the extent that the gel content of the rubber is at least about 80% or more without a vulcanizing agent.

In the present invention, the vulcanizing agent component of the rubber is not particularly limited, and vulcanizing agents and vulcanizing agents commonly used for vulcanizing diene rubber can be used. All vulcanizing and accelerating vulcanizing systems applicable to the vulcanization of diene rubbers can be used in the practice of the present invention, such as peroxide, azide, quinoid or accelerating sulfur vulcanizing systems. Combinations of maleimide and peroxide or disulfide accelerators can be used. A sufficient amount of vulcanizing agent is used to achieve essentially complete vulcanization of the rubber. Excess vulcanizing agents should be avoided. The reason for this is that much more than is necessary to completely vulcanize the rubber will result in poor properties, such as a loss of the water soluble and / or dispersible properties of the hydrophilic polymer.

In order to achieve both the water developability of the printing plate material and the compatibility of the printing plate with the aqueous ink, it is preferable that rubber is dispersed in these hydrophilic polymers. As a method of dispersing the rubber in the hydrophilic polymer, there is a method of melting and mixing the hydrophilic polymer and the unvulcanized rubber. afterwards,
In some cases, the unvulcanized rubber is vulcanized.
Melt mixing refers to mixing two or more polymers at a temperature equal to or higher than the softening point. By performing the melt mixing, the rubber particles having a small size are dispersed throughout the continuous hydrophilic polymer matrix, and thereafter, the rubber particles are vulcanized to obtain a desired blend polymer.

The process for producing the blended polymer involves mixing the hydrophilic polymer with the unvulcanized rubber and, if required, a vulcanizing agent and then subjecting the blend to a temperature sufficient to effect vulcanization. The mastication is performed using a mixing extruder such as a Banbury mixer, a Brabender mixer or a twin screw. The hydrophilic polymer and rubber are mixed at a temperature sufficient to soften the hydrophilic polymer, or more usually at a temperature above the melting point if the hydrophilic polymer is normal and crystalline. After intimate mixing of the hydrophilic polymer and the rubber, a vulcanizing agent is added if necessary.
Heating and mastication at the vulcanization temperature is generally sufficient to complete the vulcanization formation in minutes or less. However, higher temperatures can be used if shorter times are desired. The temperature range suitable for the formation of vulcanization is from the melting temperature of the hydrophilic polymer to the decomposition temperature of the rubber, and this range is generally about 100 ° C to 250 ° C, but the maximum temperature depends on the type of rubber and the deterioration inhibitor. Varies somewhat with presence and mixing time. Typically this range is about 130
C. to 250C. The preferred range is about 150 ° C. to 23
0 ° C. In order to obtain a good rubber vulcanized blend polymer, it is preferred to continue mixing until the vulcanization occurs without stopping mixing.

The mixing ratio of the hydrophilic polymer and the rubber is 1: 9
~ 8: 2, more preferably 1: 9-5: 5.

The amount of the hydrophilic polymer used is preferably from 3 to 40% by weight, more preferably from 5 to 20% by weight in the whole photosensitive resin composition. When the amount of the hydrophilic polymer used is within the above range, the developing property is not reduced and the form retention of the raw plate is not reduced, and the water resistance of the printing plate is not reduced and the printing durability is not deteriorated.

The amount of rubber used is 1 in the total photosensitive resin composition.
It is preferably from 0 to 80% by weight, more preferably from 30 to 70% by weight. The rubber includes not only a rubber of a blended polymer but also a rubber emulsion added at the time of preparing the photosensitive resin composition and fine particles of vulcanized rubber. When the amount of the rubber used is within such a range, the flexibility of the printing plate does not decrease, and the developability does not decrease.

The total amount of the hydrophilic polymer and the rubber is preferably 20 to 90% by weight in the whole photosensitive resin composition.
More preferably, it is 50 to 80% by weight. When the total amount is within such a range, the obtained plate surface will not have large adhesion, the form retention of the plate will not be impaired, and the photosensitive characteristics of the plate, particularly image reproducibility will not be reduced.

Examples of the photopolymerizable unsaturated compound having an ethylenic double bond in the molecule, which is a photocrosslinking agent used in the photosensitive layer of the flexographic printing plate material of the present invention, include known compounds. Those having a certain degree of compatibility or more are used.

Specifically, the following are mentioned. 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 2
Monoacrylates and monomethacrylates having a hydroxyl group, such as -hydroxybutyl acrylate, 2-hydroxybutyl methacrylate, 3-chloro-2-hydroxypropyl acrylate, and 3-chloro-2-hydroxypropyl methacrylate. Polyhydric acrylates and methacrylates obtained by reacting a polyhydric alcohol such as ethylene glycol with an unsaturated carboxylic acid such as acrylic acid or methacrylic acid. Unsaturated epoxy compounds such as glycidyl acrylate, glycidyl methacrylate, 3,4-epoxycyclohexyl acrylate and 3,4-epoxycyclohexyl methacrylate; Polyhydric acrylates and polyhydric methacrylates having a hydroxyl group which are synthesized by the reaction of a polyhydric glycidyl ether such as ethylene glycol diglycidyl ether and an unsaturated carboxylic acid such as acrylic acid and methacrylic acid. Polyhydric acrylates and methacrylates having a hydroxyl group, which are synthesized by reacting an unsaturated epoxy compound such as glycidyl methacrylate with an unsaturated carboxylic acid such as acrylic acid or methacrylic acid. Acrylamide, methacrylamide, N-methylol acrylamide, N-methylol methacrylamide, diacetone acrylamide, methylenebisacrylamide, N-methylol acrylamide or polyhydric acrylamide obtained by condensation reaction of polyhydric alcohol with N-methylol methacrylamide and polyhydric acrylamide Acrylamide-based photopolymerizable monomers such as methacrylamide and the like, and preferably, acrylic or methacrylic esters having a hydroxyl group and acrylic or methacrylamides are used.

The proportion of the photopolymerizable unsaturated compound in the photosensitive resin composition is preferably in the range of 10 to 80% by weight. More preferably, it is 10 to 60% by weight. The ratio of the photopolymerizable unsaturated compound in the photosensitive resin composition is 10% by weight.
If it is less than 1, the density of the crosslinked structure generated by photopolymerization is insufficient, so that it is easily swelled in a diluting solvent of an aqueous ink containing water as a main component, causing swelling destruction of a solid portion during printing and poor printing. It will be easier. In addition, sufficient image reproducibility cannot be obtained due to insufficient crosslinking density. In addition, if a photopolymerizable unsaturated compound having higher crosslinkability is used to obtain high quality image reproducibility, the plate hardness of the printing plate material is increased, and the ink adhesion to a printing material is reduced, and a good printed material is obtained. become unable. Conversely, if the proportion of the photopolymerizable unsaturated compound in the photosensitive resin composition exceeds 80% by weight, the density of the crosslinked structure generated by photopolymerization becomes excessive, so that the relief made by the plate becomes very brittle, Therefore, problems such as cracks occurring in the relief during printing occur.

As the photopolymerization initiator in the present invention, all conventionally known photopolymerization initiators can be used. For example, there are benzoin alkyl ethers, benzophenones, anthraquinones, benzyls, acetophenones, diacetyls and the like. These photopolymerization initiators can be used in the range of 0.01 to 10% by weight based on the total amount of the photosensitive resin composition.

In the photosensitive resin composition of the present invention, various additives such as ethylene glycol, diethylene glycol, triethylene glycol, glycerin, trimethylolpropane, and trimethylolethane may be used as a compatibilizer between the hydrophilic polymer and the photopolymerizable unsaturated compound. Polyhydric alcohols, N-ethyl-p
-Toluenesulfonamide, N-butylbenzenesulfonamide, N-methylbenzenesulfonamide and the like can also be added. These polyhydric alcohols,
The sulfonamide-based compound has the effect of increasing the flexibility of the photopolymerized portion and preventing the occurrence of relief cracks. Such polyhydric alcohols and sulfonamide compounds can be used in a range of 30% by weight or less based on the photosensitive resin composition.

In order to improve the thermal stability of the photosensitive resin composition of the present invention, a conventionally known polymerization inhibitor can be used. Preferred thermal polymerization inhibitors include phenols, hydroquinones, catechols and the like. These thermal polymerization inhibitors are used in an amount of 0.0
It can be used in the range of 01 to 5% by weight. Also,
Dyes, pigments, surfactants, defoamers, ultraviolet absorbers, fragrances and the like can be added.

The coating (a) (hereinafter referred to as the first layer) of the flexographic printing plate material of the present invention having anti-adhesion is formed from a mixture of partially saponified polyvinyl acetate and a rubber-based latex. As the partially saponified polyvinyl acetate used here, any known one can be used irrespective of the synthesis method, but more preferably the saponification degree is in the range of 40 to 90 mol%. It is. Within such a range, water development is easy, and scattering of actinic light due to the high crystallinity of the partially saponified polyvinyl acetate does not occur, and the sharpness of the image is maintained.

The rubber latex used in the first layer of the present invention can be any one. This rubber-based latex is preferably the same as the synthetic rubber used for the photosensitive layer, but even if it is different, the affinity of the synthetic rubber is extremely good, so the delamination of the coating of the first layer. Fully exerts the effect of preventing Here, the synthetic rubber refers to an unvulcanized rubber, a vulcanized rubber, or both. Examples of such a synthetic rubber include the following. The vulcanized rubber is obtained by vulcanizing unvulcanized rubber,
The unvulcanized rubber is not particularly limited,
So-called solid rubber having a molecular weight of 40,000 or more can be preferably used. For example, high-molecular-weight isoprene rubber, butadiene rubber, styrene-butadiene rubber, chloroprene rubber, nitrile rubber, butyl rubber, acrylic rubber, epichlorohydrin rubber, silicone rubber, etc. Raw rubber or elastomer, styrene-butadiene copolymer, styrene-isoprene copolymer, butadiene-acrylic acid copolymer, and other diene copolymers;
Propylene copolymer, ethylene-vinyl acetate copolymer,
And other olefins. Among them, copolymers of dienes or olefins are preferably used. A form in which these synthetic rubber fine particles are dispersed in water is called latex. These rubber latexes may be used alone or in combination of two or more.

The first layer can have a composition in which two components of partially saponified polyvinyl acetate and rubber latex are mixed at an arbitrary ratio. The preferred ratio is 5 parts by weight of partially saponified polyvinyl acetate and 95 parts by weight of rubber latex.
~ 2 parts by weight. However, when the partially saponified polyvinyl acetate alone is used, the adhesion between the water-developable synthetic rubber photosensitive layer and the first layer is insufficient. Delamination occurs. When the rubber-based latex is used alone, the first layer and (b)
In some cases, the second layer may be detached due to insufficient adhesive force with the film (hereinafter, referred to as a second layer). But,
When the first layer of the present invention, that is, the layer obtained by mixing partially saponified polyvinyl acetate and rubber-based latex, is used, the second layer for preventing adhesion is firmly adhered to the photosensitive layer. Therefore, the falling off of the anti-adhesion film, which is observed in the case of the conventional example in which the partially saponified polyvinyl acetate film is directly provided on the photosensitive layer, is completely prevented.

The partially saponified polyvinyl acetate used in the coating (b) of the present invention (hereinafter referred to as the second layer) is all provided that the degree of saponification is in the range of 60 to 90 mol% regardless of the synthesis method. Are available. 90 degree of saponification
When partially saponified polyvinyl acetate exceeding mol% is used, scattering of actinic rays due to the high crystallinity of the partially saponified polyvinyl acetate occurs, and the sharpness of the image is reduced. When the saponification degree is 60 mol% or less, the partially saponified polyvinyl acetate itself becomes tacky at high humidity, and the effect of improving the adhesion of the original film becomes small. For the above reasons, the degree of saponification of the partially saponified polyvinyl acetate used for the second layer needs to be in the range of 60 to 90 mol%.

The thickness of the anti-adhesion film of the present invention having such a two-layer structure (the total thickness of both coatings (a) and (b)) is
It needs to be in the range of 0.2 to 20 μm. When the thickness is less than 0.2 μm, the surface of the photosensitive layer is affected, and the partially saponified polyvinyl acetate surface of the second layer also becomes tacky. 20 μm thick
In this case, the distance between the original film and the photosensitive layer is increased to cause diffusion of the actinic light, so that the sharpness of the image decreases. For the above reasons, the total thickness of the first layer and the second layer must be in the range of 0.2 to 20 μm.

In the flexographic printing plate material of the present invention, the partially saponified polyvinyl acetate film having a saponification degree of 60 to 90 mol% of the second layer has a function of preventing surface adhesion. The coating of the first layer made of a mixture of partially saponified polyvinyl acetate and rubber-based latex serves to prevent the second layer from detaching from the photosensitive layer. By adopting a two-layer structure having different roles in this way, for example, a portion which is seen when a partially saponified polyvinyl acetate coating is directly provided on the photosensitive layer of a water-developable synthetic rubber photosensitive flexographic printing original plate. It has become possible to prevent the saponified polyvinyl acetate film from being detached. In addition, these two layers are completely eluted and dropped from the photosensitive surface at the time of development with water, and therefore do not remain on the plate surface after development. Therefore, there is no adverse effect at the time of printing.

Various methods are available for providing such a thin film having a two-layer structure on the photosensitive layer.
Using a gravure coater, roll coater, curtain flow coater, spray, etc., apply a solution of a mixture of partially saponified polyvinyl acetate and rubber-based latex to the photosensitive layer on the photosensitive layer, and after drying, apply The partially saponified polyvinyl acetate solution of the second layer can be similarly coated and dried to provide an anti-adhesion film.

The simplest method is to apply a partially saponified polyvinyl acetate solution of the second layer on a film to be used as a cover film for protecting the photosensitive layer, and then to dry the first layer.
Partial layer A solution of a mixture of saponified polyvinyl acetate and rubber latex is applied and dried to form a thin film with a two-layer structure on the film, and the cover film is pressed with this film in contact with the photosensitive layer. How to The plate material with the cover film attached in this manner has a strong adhesion between the photosensitive layer and the first layer and the adhesion between the first and second layers when the cover film is peeled off prior to exposure to actinic rays.
Since the entire coating having a layer structure is transferred to the photosensitive layer side, the second
The layer of partially saponified polyvinyl acetate on the layer becomes the plate surface, and the adhesion to the original film is improved. If a matte cover film is used, the surface of the partially saponified polyvinyl acetate film of the second layer transferred to the photosensitive layer side is also matted, and the adhesion of the original film is extremely good. Become. As such a cover film, a polyester film is most suitable in terms of oxygen permeability, dimensional stability and the like, but a polyethylene film, a polypropylene film, an acetate film, a vinyl chloride film, a cellophane and the like can also be used. As a method for forming these films into a mat, sand blowing, chemical etching, coating of a resin containing a matting agent, and the like can be considered. It is also possible to apply a thin resin to a mat film that has been subjected to sand spraying and chemical etching to adjust the degree of the mat.

When the anti-adhesion film of the present invention is implemented,
The following points are improved as compared with the conventional method. (1) Since the method is not a method of applying powder or the like, skill of an operator is not required. (2) Even when the photosensitive layer itself has a strong adhesiveness, the original film is easily adhered to the original film because the partially saponified polyvinyl acetate film is formed on the entire surface. (3) Since partially saponified polyvinyl acetate having a saponification degree of 60 to 90 mol% has low crystallinity, scattering of actinic rays hardly occurs, so that an extremely sharp image is reproduced. (4) a first layer composed of a mixture of partially saponified polyvinyl acetate and a rubber latex, a second layer composed of partially saponified polyvinyl acetate having a degree of saponification of 60 to 90 mol%, and a synthetic rubber photosensitive layer Since the adhesive layer functions as an adhesive layer, the phenomenon that the partially saponified polyvinyl acetate film detaches from the photosensitive layer and the phenomenon that cracks occur in the anti-adhesion film can be completely prevented when the cover film is peeled or exposed.

Hereinafter, the present invention will be described in more detail by way of examples.

[0045]

【Example】

Example 1 10 parts by weight of partially saponified polyvinyl acetate (Gohsenol KP-06 manufactured by Nippon Synthetic Chemical Co., Ltd.) having a saponification degree of 71 to 75 mol% as a composition for the first layer, and carboxyl-modified as a rubber latex 90 parts by weight of butadiene / acrylonitrile copolymer latex (Luckstar 1570B, solid content: 42%, manufactured by Dainippon Ink and Chemicals, Inc.) in a mixed solvent of water / ethanol = 50/50 (weight ratio): 15% (weight) At 80 ° C. to prepare a stock solution.

The saponification degree of the second layer composition is 78 to 82.
Mol% of partially saponified polyvinyl acetate (Gohsenol KH
-17 Nippon Synthetic Chemical Co., Ltd.)
Concentration 10% (weight) in 40/60 (weight ratio) mixed solvent
At 80 ° C. to prepare a stock solution.

A polyester film (thickness: 75 μm) made of a sand mat was selected as the cover film, and the stock solution for the second layer was first coated on the mat surface with a gravure coater to a dry film thickness of 1 μm.
m and dried at 120 ° C. for 30 seconds. A first layer stock solution was applied thereon to a dry film thickness of 1.5 μm, and dried at 120 ° C. for 30 seconds. In this manner, the second side is placed on the matted polyester film and on the film side.
A coating having a two-layer structure of a layer and a first layer was performed thereon.

As a water developable synthetic rubber photosensitive flexographic printing plate material, a hydrophilic polyamide (ε-caprolactam / equimolar salt of hexamethylenediamine and adipic acid / α, ω-diaminopropylpolyoxyethylene (number Average molecular weight 1000) and equimolar salt of adipic acid = 2
20 parts of a 0/20/60 (weight ratio) copolymerized polyamide and a carboxylated nitrile butadiene rubber (Nipol 10
72 20 parts of Nippon Zeon Co., Ltd. and 20 parts of partially crosslinked type nitrile butadiene rubber (Nipol DN214 manufactured by Nippon Zeon Co., Ltd.) and butadiene rubber (Nipol BR-122)
0L Nippon Zeon Co., Ltd.) 40 parts of a polymer blend obtained by melt-mixing for 10 minutes and 2 parts by weight of sodium methylenebisnaphthalenesulfonate were mixed in a closed mixer.
At 160 ° C. for 3 minutes, and then 10 parts of butadiene latex (Nipol LX111NF, nonvolatile content 55%, manufactured by Nippon Zeon Co., Ltd.) in terms of solid content, 10 parts, carboxy-modified acrylic butadiene latex (DM811, nonvolatile content 50%)
15 parts by weight of solid content, 20 parts by weight of phenoxy polyethylene glycol acrylate as a polymerizable unsaturated compound and 12 parts by weight of glycerin diglycidyl diacrylate are added, and kneaded at 140 ° C. for 15 minutes. Then, 1 part by weight of dimethylbenzyl ketal as a photoinitiator was added and kneaded at 140 ° C. for 10 minutes. The thus obtained photosensitive flexographic printing plate having a thickness of 3 mm was selected. Since the surface of this plate material had remarkable tackiness, it was extremely difficult to adhere the negative film.

On this photosensitive resin layer, a cover film having a two-layer structure obtained by the above-mentioned coating was thermocompression-bonded at 80 ° C. such that the coated surface was in contact with the photosensitive layer.

When the cover film is peeled off from the photosensitive flexographic printing plate thus obtained, the partially saponified polyvinyl acetate coating of the second layer is easily lifted off the surface of the photosensitive layer without detachment. Thus, the cover film could be peeled off. The coating layer on the film was completely transferred onto the photosensitive layer, and no tackiness was observed on the surface.

When a negative film was placed on a plate material having an anti-adhesion film having a two-layer structure and adhered in vacuum, it was found that the negative film adhered without any problem. During the exposure operation, the anti-adhesion film did not detach at all.

The plate material thus exposed was developed with a brush-type washing machine containing water (solution temperature 35 ° C.). The plate surface after development was observed with a microscope to confirm that no anti-adhesion film remained on the plate surface. As a result of evaluating the obtained relief image, it was confirmed that the sharpness of the image did not decrease at all and the depth of the white portion did not decrease at all by providing the anti-adhesion film. Even in a flexographic printing test of 100,000 sheets using an aqueous ink using this printing plate, no adverse effect due to the anti-adhesion film was observed at all, and a good printed matter was obtained.

Comparative Example 1 In Example 1, a one-layer coating cover film was prepared by applying only the partially saponified polyvinyl acetate undiluted solution of the second layer to a sand-matted polyester film (thickness: 75 μm) under the same conditions. Then, thermocompression bonding was similarly performed on the photosensitive layer.

When the cover film was peeled off from the thus obtained photosensitive flexographic printing original plate, a phenomenon in which the partially saponified polyvinyl acetate coating was lifted off the photosensitive layer surface and detached was observed.

Example 2 As a composition for the first layer, 5 parts by weight of partially saponified polyvinyl acetate having a saponification degree of 50 mol% and carboxyl-modified butadiene / acrylonitrile copolymer latex (lac) as the same rubber latex as in Example 1 were used. Star 1570B 95% by weight of a solid concentration of 42% (manufactured by Dainippon Ink and Chemicals, Inc.) is dissolved in a mixed solvent of water / ethanol = 60/40 (weight ratio) at 80 ° C. so as to have a concentration of 15% (weight). Thus, a stock solution was prepared.

The second layer composition has a saponification degree of 78 to 82.
Mol% of partially saponified polyvinyl acetate (Gohsenol KL
−05 Nippon Synthetic Chemical Co., Ltd.)
Concentration 15% (weight) in 40/60 (weight ratio) mixed solvent
At 80 ° C. to prepare a stock solution.

As a cover film, a polyester film (thickness: 100 μm) made into a chemical mat was selected.
This was subjected to two-layer coating in the same manner as in Example 1. The thickness of the second layer was 1.5 μm, the thickness of the first layer was 1.5 μm, and the total thickness was 3 μm.

This cover film was thermocompression bonded at 80 ° C. to the same water-developable synthetic rubber photosensitive flexographic printing plate as in Example 1. No peeling of the anti-adhesion film occurred at the time of exfoliation of the cover film and exposure of this plate material. It was confirmed that vacuum adhesion of the negative film was easy, and that no baking occurred.

The plate material thus exposed was developed with a brush-type washing machine (water temperature: 35 ° C.) containing water. The plate surface after development was observed with a microscope to confirm that no anti-adhesion film remained on the plate surface. As a result of evaluating the obtained relief image, it was confirmed that by providing the anti-adhesion film, the sharpness of the image was not reduced at all and the negative was faithfully reproduced, and the depth of the white portion was not reduced at all. Even in a flexographic printing test of 200,000 sheets using an aqueous ink using this printing plate, no adverse effect due to the anti-adhesion film was observed at all, and good printed matter was obtained.

Comparative Example 2 A partially saponified polyvinyl acetate having a saponification degree of 91 to 94 mol% (Gohsenol AL-06, manufactured by Nippon Synthetic Chemical Co., Ltd.) was used as the second layer in Example 2. ), Except that water-developable synthetic rubber photosensitive flexographic printing plate material was obtained in the same manner as in Example 2. No peeling of the anti-adhesion film occurred during the exfoliation of the cover film and the exposure of the plate material. It was confirmed that vacuum adhesion of the negative film was easy, and that no baking occurred.

The plate material thus exposed was developed with a brush-type washing machine (water temperature 35 ° C.) containing water. The plate surface after development was observed with a microscope to confirm that no anti-adhesion film remained on the plate surface. As a result of evaluating the obtained relief image, it was found that the sharpness of the image was reduced, and a thin line having a width of 200 μm was reproduced at 240 μm on the negative. In addition, it was confirmed that the depth of the white portion was also considerably shallow. It was revealed that the use of a partially saponified polyvinyl acetate having a saponification degree of 90 mol% or more significantly affected the scattering of actinic rays.

Comparative Example 3 The thickness of the second layer of the two-layer coating of Example 2 was 0.1 μm.
m, a water-developable synthetic rubber photosensitive flexographic plate material was obtained in the same manner as in Example 2 except that the first layer was changed to 0.05 μm and the total film thickness was changed to 0.15 μm. No peeling of the anti-adhesive film occurred at the time of exfoliation and exposure of the cover film of this plate material, but the anti-adhesive film was so thin that the surface of the photosensitive layer was affected and the partially saponified polyvinyl acetate surface of the second layer was exposed. The film also became tacky, and it was difficult to adhere the negative film in vacuum, causing burning blur.

Comparative Example 4 The thickness of the second layer of the two-layer coating of Example 2 was 10 μm.
m, a water-developable synthetic rubber photosensitive flexographic plate material was obtained in the same manner as in Example 2 except that the first layer was changed to 20 μm and the total film thickness was changed to 30 μm. No peeling of the anti-adhesion film occurred at the time of exfoliation of the cover film and exposure of this plate material. The vacuum adhesion of the negative film was also easy.

The plate material thus exposed was developed with a brush-type washing machine containing water (solution temperature 35 ° C.). The plate surface after development was observed with a microscope to confirm that no anti-adhesion film remained on the plate surface. As a result of evaluating the obtained relief image, it was found that the sharpness of the image was reduced, and a thin line having a width of 200 μm was reproduced at 250 μm on the negative. In addition, it was confirmed that the depth of the white portion was also considerably shallow. Anti-adhesion film thickness of 20
When the thickness is more than μm, the distance between the original film and the photosensitive layer is increased to cause diffusion of actinic light.

Example 3 The same water-developable synthetic rubber photosensitive flexographic printing plate as in Example 1 was selected.

As the first layer, the same saponification degree 5 as in Example 2 was used.
5 parts by weight of a partially saponified polyvinyl acetate of 0 mol% and 95 parts by weight of a carboxyl-modified butadiene / styrene copolymer latex (Lackstar 7310k, solid content concentration 49%, manufactured by Dainippon Ink and Chemicals, Inc.) as a rubber latex A stock solution was prepared by dissolving in a mixed solvent of / ethanol = 60/40 (weight ratio) at 80 ° C. so as to have a concentration of 20% (weight). This solution was applied directly on the photosensitive layer using a curtain flow coater and dried at 80 ° C. for 10 minutes.
On top of this, a second layer was formed, having the same degree of saponification of 78 to 78 as in Example 2.
A 15% solution of 82 mol% of partially saponified polyvinyl acetate (Gohsenol KL-05 manufactured by Nippon Synthetic Chemical Co., Ltd.) is applied with a curtain flow coater, dried at 80 ° C. for 10 minutes, and has a two-layer structure on the photosensitive layer. Was provided. The total thickness of the anti-adhesion film was 10 μm.

While supplying a very small amount of water on the anti-adhesion film, an epoxy resin was previously applied to a sand-matted polyester film (thickness: 100 μm) and cured to obtain a film having a reduced degree of matte.
Thermocompression bonding was performed at 0 ° C. No peeling of the anti-adhesion film occurred at the time of exfoliation of the cover film and exposure of this plate material.
Since the surface of the second layer was matted, vacuum adhesion of the negative film was extremely good.

No adverse effect of the anti-adhesion film was observed on development and image reproducibility. A flexographic printing test of 100,000 sheets using water-based ink was performed using this printing plate. Good prints were obtained without any recognition.

[0069]

The anti-adhesion film on the surface of the water-developable synthetic rubber-based photosensitive resin layer of the present invention provides a high degree of image reproducibility, has good water developability, and is an aqueous ink. It satisfies the compatibility with Therefore, it is possible to provide a flexographic printing plate material having excellent printing resistance in flexographic printing using a water-based ink or other flexographic inks, and a water developable flexographic plate material having good rubber elasticity.

Continued on the front page F term (reference) 2H025 AA00 AA04 AA14 AA15 AA16 AB02 AC01 AD01 BC13 BC31 BC51 BC55 BJ03 CB07 CB23 CB52 DA05 DA06 FA17 2H096 AA02 BA06 CA20 EA02 GA08

Claims (2)

[Claims] 1. A flexographic printing plate material having a water-developable synthetic rubber photosensitive resin layer, the surface of which is provided with the following coatings (a) and (b) in this order: Flexographic plate material characterized in that the total thickness of both coatings (a) and (b) is 0.2 to 20 μm. (A) A coating comprising a mixture of partially saponified polyvinyl acetate and a rubber-based latex. (B) A coating made of partially saponified polyvinyl acetate having a saponification degree of 60 to 90 mol%. 2. A water-developable synthetic rubber photosensitive resin layer of a flexographic printing plate material, wherein a vulcanized rubber and an unvulcanized rubber are dispersed in a hydrophilic polymer. Flexo plate material.