JPH04340968A - Production of flexographic printing board - Google Patents

Abstract

PURPOSE:To obtain the method of producing a water-developing type flexographic printing board which is excellent in water resistance, alcohol resistance, rubber elasticity (elongation and strength) and contains a photosensitive microgel having polymerizable double bonds on the surface of gel particles. CONSTITUTION:The flexographic printing board is manufactured by exposing a photosensitive layer comprising a photosensitive resin comsn., developing the photosensitive layer with water, and then subjecting it to heat treatment. The photosensitive resin compsn. contains such a photosensitive microgel having polymerizable double bonds on the surface of gel particles introduced by the reaction of microgel fine particles (A) with a compd. (B) the molecule of which has at least one polymerizable double bond and a functional group which reacts with quaternary ammonium salt. The microgel fine particles (A) are obtd. by emulsion polymn. of monomers having polymerizable double bonds with a compd. containing quaternary ammonium salt.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a method for producing a flexographic printing plate using a water-developable photocurable resin composition.
More specifically, a method for producing an aqueous-developable flexographic printing plate containing photosensitive microgel having polymerizable double bonds on the surface of gel particles and having excellent water resistance, alcohol resistance, and rubber elasticity (elongation, strength). It is related to.

0002

BACKGROUND OF THE INVENTION In recent years, with the modernization of packaging, flexo printing has come into the spotlight. However, the conventional method of manufacturing flexographic printing plates requires at least three steps, including (a) making a metal plate, b) mold-making, and c) vulcanization of raw rubber, which requires skilled techniques and a long time. As a result, the cost was unavoidably high. Therefore, solvent-developable photosensitive resin plates were introduced, making it easier to print flexographic plates.

However, recently, due to environmental concerns, the appearance of flexographic printing plates that can be developed with water has been eagerly awaited. However, with conventional techniques, it has not been possible to obtain a plate that is water-developable, has the rubber elasticity required for flexographic printing plates, and has ink resistance (water resistance, alcohol resistance) to water-based inks used in flexographic printing plates. Therefore, the present inventors invented a new method for synthesizing photosensitive microgels and attempted to apply them to flexographic printing plates. I couldn't be satisfied with both at the same time.

0004

[Problems to be Solved by the Invention] The present inventor has conducted intensive research to develop a water-developable flexographic printing plate that has the physical properties required for a flexographic printing plate.
By applying heat treatment to a photosensitive layer made of a photosensitive resin composition containing a microgel having a polymerizable double bond on the surface, after manufacturing a printing plate through the steps of exposure and water development,
The present invention was completed by discovering that the water resistance, alcohol resistance, and rubber elasticity were significantly improved compared to before treatment, and that the effects were particularly remarkable when the heat treatment temperature was 60 to 200°C.

[0005]

[Means for Solving the Problems] The present invention emulsion polymerizes a monomer having a polymerizable double bond using a quaternary ammonium salt-containing compound or a quaternary ammonium salt-containing compound and a low-molecular surfactant. The microgel fine particles (A) synthesized by The present invention relates to a method for producing a flexographic printing plate, in which a photosensitive layer made of a photosensitive resin composition containing a photosensitive microgel into which a double bond has been introduced is subjected to heat treatment after exposure and aqueous development.

The microgel particles (A) used in the photosensitive resin composition of the present invention are characterized by emulsion polymerization of a monomer having a polymerizable double bond.

In the present invention, monomers having a polymerizable double bond include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, (
(Meth) such as isopropyl (meth)acrylate, butyl (meth)acrylate, hexyl (meth)acrylate, octyl (meth)acrylate, lauryl (meth)acrylate, etc.
C1-C18 alkyl ester of acrylic acid: glycidyl (meth)acrylate: C2-C20 alkenyl ester of (meth)acrylic acid such as allyl (meth)acrylate: hydroxylethyl (meth)acrylate, hydroxylethyl (meth)acrylate, hydroxypropyl C2-C20 of (meth)acrylic acid such as (meth)acrylate and hydroxypropyl (meth)acrylate
Hydroxyl alkyl ester: C3~ of (meth)acrylic acid such as allyloxylethyl (meth)acrylate
C19 alkenyloxylalkyl ester: (meth)
Acrylic acid, trimethylolpropane tri(meth)acrylic ester, di(meth)acrylic ester of glycols, di(meth)acrylic ester of polyol, di(meth)acrylic ester of polyurethane, di(meth)acrylic ester of polyester Examples include meth)acrylic acid ester, butadiene, isoprene, chloroprene, divinylbenzene, and the like.

These monomers are appropriately selected depending on the desired physical properties, and may be used alone or in combination.
A combination of species or more can be used.

The quaternary ammonium salt-containing compound is effective as an emulsifier, and is usually a compound having a tertiary amino group that is quaternized by neutralizing it with an acid. Among such emulsifiers, low molecular weight emulsifiers include C6~ such as dimethyllaurylamine, dimethylmyristylamine, dimethylpalmitylamine, dimethylstearylamine, diethyllaurylamine, diethylmyristylamine, diethylpalmitylamine, diethylstearylamine, etc. Hydrochloric acid, nitric acid, sulfuric acid, reactive monomers with amino groups such as C20 alkyl and alkenyl tertiary amines, 2,2-dimethylaminoethyl (meth)acrylate, 2,2-diethylaminoethyl (meth)acrylate, etc. Acetic acid, propionic acid, butyric acid,
There are reactants with acids such as (meth)acrylic acid, and 2,2-dimethylaminoethyl (meth) is used as a polymer emulsifier.
Acrylate, 2,2-diethylaminoethyl (meth)
Reactive monomers with amino groups such as acrylates and other reactive monomers, such as methyl (meth)acrylate, (
(meth)ethyl acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, hexyl (meth)acrylate, octyl (meth)acrylate, lauryl (meth)acrylate, etc. C1-C18 alkyl ester of meth)acrylic acid: glycidyl (meth)acrylate: C2-C8 alkenyl ester of (meth)acrylic acid such as allyl (meth)acrylate: hydroxylethyl (meth)acrylate, hydroxylethyl (meth)acrylate, C2 to C8 of (meth)acrylic acid such as hydroxypropyl (meth)acrylate and hydroxypropyl (meth)acrylate
Hydroxyl alkyl ester: C3~ of (meth)acrylic acid such as allyloxylethyl (meth)acrylate
C19 alkenyloxylalkyl ester: (meth)
Examples include those obtained by copolymerizing one or more vinyl monomers selected from acrylic acid and the like, followed by neutralization with an acid. Also included are polymers containing amino groups, such as natural polymers such as chitosan and synthetic polymers such as polyethyleneimine, which are neutralized with acid.

[0010] These polymeric emulsifiers can be used as they are, or by reacting a part of the quaternary ammonium salt with a compound containing an epoxy group and a quaternary ammonium salt, such as glycidyl (meth)acrylate, to introduce a polymerizable double bond. It can also be used as a reactive emulsifier.

[0011] The above polymer emulsifier is a preferred emulsifier in applications where water resistance is required because the degree of water solubility can be controlled. These emulsifiers are 0.0% based on the monomer.
It is used in an amount of 1 to 50% by weight, preferably 3 to 20% by weight.

[0012] Also, examples of low-molecular surfactants that can be used in combination with the above-mentioned polymeric emulsifiers include nonionic surfactants and cationic surfactants. Examples of nonionic surfactants include polyoxyethylene lauryl ether, polyoxyethylene stearyl ether,
Polyoxyethylene alkyl ethers such as polyoxyethylene cetyl ether, polyoxyethylene alkyl allyl ethers such as polyoxyethylene octylphenyl ether, polyoxyethylene nonylphenyl ether, polyoxyethylene derivatives, oxyethylene/oxypropylene block copolymers, glycerin fatty acids Examples include ester, polyoxyethylene fatty acid ester, and the like.

Examples of the cationic surfactant include monomethylamine, monoethylamine, stearylamine, etc.
amine hydrochloride, dimethylamine, diethylamine,
Hydrochlorides of secondary amines such as distearylamine, hydrochlorides of tertiary amines such as trimethylamine, triethylamine, and stearyldimethylamine, hydrochlorides of ethanolamines such as monoethanolamine, diethanolamine, and triethanolamine, ethylenediamine, diethylenetriamine, etc. Examples include hydrochloride salts of polyethylene polyamines.

[0014] The above-mentioned low-molecular surfactant is used in combination with a polymeric emulsifier, and is preferably 0.1 to 50%, more preferably 0.1 to 20%, based on the monomer.

[0015] The temperature of emulsion polymerization is 50 to 95°C, preferably 65 to 80°C. In emulsion polymerization, the solid content of the monomer and emulsifier is preferably 10 to 50% by weight, preferably 15%.
~30% by weight. In the present invention, the particle size of the microgel produced by emulsion polymerization is usually 10 to 500 nm as measured by a light scattering method.

[0016] The quaternary ammonium salt present on the surface of the microgel particles (A) thus produced and 1
A compound (B) having a functional group such as an epoxy group and at least one polymerizable double bond in its molecule is reacted with the compound (B) to introduce a polymerizable double bond onto the surface of the microgel particles. Examples of the compound (B) include glycidyl (meth)acrylate, N-glycidyl (meth)acrylamide, glycidyl allyl ether, epoxy compounds having unsaturated double bonds such as 1,2-epoxy-5-hexene, glycidyl cinnamate, etc. can be mentioned. These compounds (B)
are appropriately selected depending on the desired physical properties, and may be used alone or in combination of two or more. The reaction can be carried out in any proportion from 1 to 100 mol % with respect to the quaternary ammonium salt on the surface of the microgel particles. This reaction is completed by simply mixing the epoxy compound into the microgel emulsion and stirring at a temperature of 30 to 90°C, preferably 60 to 80°C, for 2 hours or more. As described above, the present invention has the advantage that the reaction can be carried out even in an aqueous dispersion.

After adding additives such as a photopolymerization initiator, other resins, monomers, etc. as necessary to the photosensitive microgel obtained in the above manner, it is crosslinked and cured by radiation such as ultraviolet rays and electron beams. After that, water development is performed to obtain a flexographic printing plate. When the above components added to the photosensitive microgel are uniformly dispersed or dissolved in the photosensitive microgel aqueous dispersion, a photosensitive layer is obtained by a casting method after adding them to the photosensitive microgel aqueous dispersion. Alternatively, after drying, a photosensitive layer can be obtained by pressure molding using a press or the like. In addition, if the components added to the photosensitive microgel do not mix uniformly with the photosensitive microgel aqueous dispersion, after drying the photosensitive microgel aqueous dispersion, apply the above components in two rolls or three rolls. After mixing (dispersion, kneading) using a roll, kneader, etc. to obtain a uniform dispersion, a photosensitive layer can be obtained using a press or the like.

The photopolymerization initiators added to the photosensitive microgel include benzophenone, 2-hydroxy-2-methyl-1-phenylpropane-1-one, and 1-(4-isopropylphenyl)2-hydroxy-2-methylpropane-.
Examples include 1-one, 2-methyl-1-[4-(methylthio)phenyl]2-morpholinopropanone-1, and the like. The amount of these photopolymerization initiators added is in the range of 0.1 to 10 parts by weight per 100 parts by weight of the resin.

Examples of water-based resins include polyvinyl alcohol, carboxymethyl cellulose, methyl cellulose,
Examples include hydroxyethyl cellulose, casein, gelatin, starch, polyvinylpyrrolidone, poly(meth)acrylamide, chitosan, and polymers containing quaternary ammonium salts.

[0020] Hydrophilic monomers include N,N-methylenebis(meth)acrylamide, 1,2-di(meth)acrylamide ethylene glycol, N,N-oxymethylenebisacrylamide, (meth)acrylamide, vinylpyrrolidone, 2 -Hydroxyethyl (meth)acrylate, polyoxyethylene (meth)acrylate, polyoxyethylene di(meth)acrylate, etc.

[0021] Furthermore, in order to impart various functions to the photosensitive resin of the present invention, colorants, extender pigments, lubricants,
Additives such as plasticizers, stabilizers, flame retardants, antifoaming agents, antioxidants, bactericides, conductive materials, and magnetic materials can also be included.

The photosensitive layer made of the photosensitive resin composition containing the photosensitive microgel thus obtained is subjected to the steps of exposure and aqueous development to produce a flexographic printing plate. The resulting flexographic printing plate does not have sufficiently satisfactory water resistance, alcohol resistance, and rubber elasticity, and as a means to solve this problem, heat treatment is applied to the cured film after exposure and aqueous development. In addition, for aqueous development,
In addition to development using only water, an alkali or a surfactant may be used in combination.

The heat treatment is effective in crosslinking unreacted polymerizable double bonds remaining in the cured film and in reducing the amount of residual water in the cured film. Due to this effect, the crosslinked structure in the cured film becomes denser, and the water resistance, alcohol resistance, and rubber elasticity of the cured film can be improved.

[0024] The treatment temperature is preferably about 60 to 200°C, more preferably about 100 to 160°C. If the treatment temperature is too low than 60°C, the above-mentioned effects will not be noticeable, and if it is higher than 200°C, the photosensitive microgel itself will tend to deteriorate, making it impossible to obtain sufficient rubber elasticity. It is not desirable because it is stored away. The processing time is
Under processing temperature conditions of about 60 to 200℃, it takes a few minutes to
A sufficient effect can be exerted in about 30 minutes, and even if the treatment is carried out for more than one hour, no greater effect can be obtained. There are no particular restrictions on the method of applying heat, and a wide variety of methods such as dryers can be used.

By performing heat treatment in this way, it has become possible to produce a water-developable flexographic printing plate with excellent water resistance, alcohol resistance, and rubber elasticity.

[0026]

[Example] In the examples, parts and % are parts by weight and % by weight, respectively.
shows. Example 1 (a) Preparation of cationic polymer emulsifier 140 parts of lauryl methacrylate, 60 parts of 2-dimethylaminoethyl methacrylate, and 200 parts of 2-propanol were heated to 80°C in a nitrogen atmosphere while stirring in a 2-liter reaction vessel. . Azobisisobutyronitrile (hereinafter referred to as AIBN)
Add 1.6 parts of AIBN and hold for 2 hours, then add 0.4 parts of AIBN.
After that, the reaction mixture was maintained at 80° C. for 4 hours to complete the polymerization. After cooling to room temperature, a mixture of 38.2 parts of acetic acid and 1000 parts of water was added and heated to remove 2-propanol and water by azeotropic distillation. Thereafter, 9.0 parts of glycidyl methacrylate was added, and the mixture was heated to 70° C. in an air atmosphere and maintained for 2 hours to obtain a cationic polymer emulsifier having pendant methacrylic groups. (b) Synthesis of photosensitive microgel 50 parts of R-45ACR-LC (dimethacrylate modified polybutadiene manufactured by Idemitsu Petrochemical Co., Ltd.), 5 parts of Emulgen 810 (polyoxyethylene octylphenyl ether manufactured by Kao Corporation), 50 parts of the aqueous cationic polymer emulsifier solution synthesized in (a) (solid content 20%) and 160 parts of deionized water were heated to 80° C. in a nitrogen atmosphere while stirring in a 500 ml reaction vessel. 3% azobisamidinopropane dihydrochloride (hereinafter AAPD
8 parts of an aqueous solution (denoted as ) were added and held for 2 hours. Then 3
% AAPD aqueous solution was added. After the addition was completed, the reaction mixture was maintained at 80° C. for 4 hours to complete the polymerization. The particle size was measured using a light scattering method and was about 200 nm. After this microgel aqueous dispersion was left to stand overnight, 2.7 parts of glycidyl methacrylate was added and heated to 70° C. in an air atmosphere and maintained for 2 hours to obtain a photosensitive microgel aqueous dispersion. To this photosensitive microgel aqueous dispersion, 0.5 part of Tairocure 2959 (manufactured by Merck & Co., Ltd.) was added, a resin film with a thickness of about 3 mm was produced by a casting method, and then a resin film of 2000 mJ/cm2 was applied through a negative film. An image was formed by irradiating it with ultraviolet light. Furthermore, brush development was performed with warm water at 40°C, and the uncured portion was approximately 1.5 m from the surface.
It was removed to a depth of m. After that, 2000mJ from the back side
A flexographic printing plate was obtained by irradiating the entire surface with ultraviolet light of /cm2. This flexographic printing plate was left in an oven at 100° C. for 10 minutes for the purpose of heat treatment, thereby obtaining a heat-treated flexographic printing plate.

Examples 2 and 3 Flexographic printing plates obtained in exactly the same manner as in Example 1 except that the heat treatment time in Example 1 was changed to 20 and 30 minutes are referred to as Examples 2 and 3, respectively.

Examples 4 and 5 Flexographic printing plates obtained in exactly the same manner as in Example 1 except that the heat treatment temperatures in Example 1 were changed to 130 and 160° C. are referred to as Examples 4 and 5, respectively.

Comparative Example 1 Comparative Example 1 is a flexographic printing plate in which no heat treatment was performed after the exposure and development steps in Example 1.

(Evaluation of Physical Properties) The following physical properties of the flexographic printing plates obtained in Examples 1 to 5 and Comparative Example 1 were compared. (a) Evaluation of rubber elasticity Cut the flexographic printing plate into a size of 10 mm x 50 mm x 1 mm, and use a tensile tester at a tensile speed of 50 mm/mi.
Elongation and breaking strength were measured under conditions of n. (b) Evaluation of water resistance and alcohol resistance Cut the flexographic printing plate into a size of 10 mm x 50 mm x 1 mm, add ion exchange water, isopropyl alcohol (
IPA) for 24 hours and the swelling rate was examined. The swelling rate is
((Weight after 24 hours immersion/Weight before immersion)-1)×1
Obtained at 00. Table 1 shows the results of elongation, breaking strength, water resistance, and IPA resistance.

[0031]

[Table 1]

[0032] By performing the heat treatment in this manner, a flexographic printing plate excellent in rubber elasticity (elongation, breaking strength), water resistance, and IPA resistance could be obtained. As described above, the flexographic printing plate produced by the method of the present invention is water-based developable, resistant to water-based ink, and has excellent rubber elasticity.

Claims (2)

[Claims] [Claim 1] A monomer having a polymerizable double bond,
Microgel fine particles (A) synthesized by emulsion polymerization using a quaternary ammonium salt-containing compound or a quaternary ammonium salt-containing compound and a low molecular weight surfactant;
Compound (B) having at least one polymerizable double bond and a functional group that reacts with the quaternary ammonium salt in the molecule
A flexographic printing plate characterized in that a photosensitive layer made of a photosensitive resin composition containing a photosensitive microgel having polymerizable double bonds introduced onto the surface by reacting with Production method. 2. The method for producing a flexographic printing plate according to claim 1, wherein the heat treatment is carried out at a temperature of 60 to 200°C.