JP2009067057A - Method of making flexographic printing plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of making a printing plate capable of converting a so-called analog-type flexographic printing plate (conventional flexographic printing plate) into a digital-type flexographic printing plate (flexographic CTP) which does not use a litho film and can directly output image information from a computer. <P>SOLUTION: The method of making a flexographic printing plate comprises the steps of: forming an image mask on a photosensitive resin layer provided on a support by ejecting an oil-based ink containing colored particles absorbing or reflecting exposure light by an electrostatic inkjet method, thereafter exposing the photosensitive resin layer through the image mask, and developing the photosensitive resin layer, wherein the photosensitive resin layer is at least photo-polymerizable or photo-curable. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for making a flexographic printing plate.

In recent years, the rapid progress of computerized image processing and various high-power lasers has led to the rapid advancement of CTP (computer-to-plate) printing plates. In a flexographic printing plate (in the present invention, abbreviated as “flexographic printing plate”), a high-power IR laser is used to form an image-like mask, and then a flexographic printing plate is obtained by UV overall exposure and development. Flexo CTP systems have been proposed.
However, the current flexo CTP is not different from the conventional flexo plate system in the process after the mask formation from the UV overall exposure, and is not sufficient for improving the productivity, which is the main purpose of CTP.
On the other hand, a commercially available flexo CTP plate is further sensitive to an IR laser on a photosensitive resin (also referred to as “convex flexo plate”) provided on a flexible support such as polyethylene terephthalate (PET). The IR sensitive layer to be formed is provided, and it is a complex sensitive material having a multi-layer structure, which is more expensive than a convex flexo plate. In addition, the proposed system uses an expensive high-power laser with a short lifetime, and there is a problem that the IR-sensitive layer removed at the time of mask formation is generated as waste.
Patent Document 1 discloses a method for producing a relief image by applying a water-based ink image on a printing plate having a photosensitive resin layer, then exposing and developing with a water-based developer. Patent Document 2 discloses a plate material having a transparent topcoat layer on a photosensitive recording layer and forming an image mask on the topcoat layer by an ink jet printer to make a plate. Patent Document 3 discloses a method for making a seamless flexographic plate by forming an inkjet mask on a cylindrical plate material, and performing exposure and development.

JP 63-109052 A German Patent Application Publication No. 417127 JP-A-6-166162

  The problem to be solved by the present invention is to use a lith film as an image mask on a photosensitive resin layer provided on a flexible support such as PET, and to blast the entire surface with UV light to produce a flexographic printing plate. A so-called “analog type flexographic printing plate (convex flexographic plate)” can be converted into a “digital type flexographic printing plate (flexo CTP)” that can output image information directly from a computer without using a lith film. Is to provide.

The above problem has been solved by the following means.
(1) After forming an image mask by discharging oil-based ink containing colored particles that absorb or reflect light to be exposed onto a photosensitive resin layer provided on a support by an electrostatic ink jet method, Exposing the photosensitive resin layer through a mask and developing the flexographic printing plate,
(2) The plate making method according to (1), wherein the oil-based ink is obtained by dispersing charged particles containing a pigment in an insulating organic solvent,
(3) The plate making method according to (2), wherein the pigment is high resistance carbon black,
(4) When the image mask is formed on the photosensitive resin layer, the discharged oil-based ink is landed by overlapping a plurality of times (1) to (3), the plate making method according to any one of the above,
(5) Colored particles that absorb or reflect light exposed by the electrostatic ink jet method on the photosensitive resin layer having a surface resistance of 1 × 10 ¹⁰ Ω / □ or more provided on the support. A method for making a flexographic printing plate, comprising: forming an image mask by ejecting an oil-based ink containing, followed by exposure and development.

  According to the present invention, there is provided a method for making a flexographic printing plate having a low running cost and good mask image density, charging stability and charging uniformity.

The image mask forming process in the present invention will be described below with reference to the drawings.
FIG. 1 is a schematic cross-sectional view showing an example of an electrostatic ink jet apparatus used in the present invention.
In this apparatus, colored particles that absorb or reflect exposure light (light of 200 to 500 nm) are directly applied to a photosensitive resin layer provided on a support of a flexographic plate (flexographic original plate) by an electrostatic ink jet method. An image mask is formed by discharging oil-based ink containing the ink.

  An electrostatic inkjet apparatus 1 shown in FIG. 1 includes a discharge head 10, an ink tank 12 that supplies ink to the discharge head 10, and a head drive driver that drives the discharge head 10 by an image signal from an external device such as a computer (not shown). 14 is provided. The electrostatic ink jet apparatus 1 also includes a charger 16 for charging the surface of the flexographic plate and a static eliminator 18 for removing the charging of the flexographic plate after the mask image formation is completed. Upstream and downstream of the discharge head 10, the flexographic plate is fed to the back electrode 59 from the flexographic plate stocker 26, the ink is fixed on the flexographic plate after forming the mask image, and the masked flexographic plate stocker 28 is provided. A conveying roller 22 and an image fixing roller 24 for conveying are arranged. The image fixing roller 24 volatilizes the solvent in the ink forming the mask image and fixes the ink on the flexographic plate. As the fixing means, known means such as heat fixing, solvent fixing and flash exposure fixing can be used alone or in combination. Further, a solvent recovery means 30 for recovering the solvent vapor volatilized from the oil-based ink is disposed inside the electrostatic ink jet apparatus 1, and the solvent vapor inside the apparatus is recovered by the recovery means and removed from the apparatus outside. Solvented air is discharged.

FIG. 2 is a schematic cross-sectional view showing in detail the structure around the ejection head 10 in FIG.
The ejection head 10 includes an ink chamber 34 in which ink flows in a certain direction, and an ejection unit 36 that ejects ink toward the flexographic plate 32. The ejection unit 36 is provided with an insulating ink guide 38 that guides the ink droplets 80 flying from the ink chamber 34 toward the flexographic plate 32. The gap d between the insulating ink guide 38 and the flexographic plate 32 electrostatically adsorbed on the back electrode 59 is preferably about 200 μm to about 1,000 μm. A first discharge electrode 50 and a second discharge electrode 52 are provided around the discharge portion 36, and a voltage is applied in accordance with an image signal.
The guard electrode 54 is provided in order to prevent an electric field from being affected by the voltage applied to the first ejection electrode 50 and the second ejection electrode 52 in the adjacent ejection section 36.
An electrophoresis electrode 56 is installed in the upper part of the ink chamber, and by applying a predetermined voltage thereto, the electrophoresis of charged particles in the ink in the direction of the ejection position of the insulating ink guide 38 can be controlled. Responsiveness can be improved.
A shield electrode 58 is disposed on the second ejection electrode 52. By applying a voltage to the shield electrode 58, the charged particles in the ink are unevenly distributed in the lower part of the ink chamber 34, and the charged particle concentration in the flying ink droplet 80 can be increased.

  In FIG. 1, a known roller can be used as the feed roller 20 and is arranged so that an unprocessed flexographic plate can be conveyed from the stocker to a mask image forming position. An untreated flexographic plate may have a cover sheet on the surface, and a mask may be formed by a discharge head while the cover sheet is attached, and the cover sheet peeling means may be disposed inside the electrostatic ink jet apparatus. The mask may be formed by an ejection head after peeling. Moreover, since dust etc. may adhere on the flexographic plate, it is desirable to remove them. As the removing means, a known suction removal, a blow-off removal by air (air), a non-contact method such as electrostatic removal, and a contact method using a brush, a roller or the like can be used. In the present invention, preferably, air suction or air is used. It is used either by blowing or by combining them. Further, the feed roller may be composed of a slightly adhesive roller, and the roller cleaner may be provided to remove dust and the like when supplying the flexographic plate.

  In FIG. 1, the flexographic plate conveyed by the feed roller 20 is supplied to the back electrode 59. Further, as shown in FIG. 1, in addition to conveying the flexographic plate using only a roller, a conveying belt can be used. A conveyor belt obtained by coating a metal belt with a fluororesin can be used as the conveyor belt.

  As the charger 16, various methods such as a corotron, a solid charger, and a discharge needle can be applied in addition to a scorotron, and a conductive roller is also preferably used. The surface of the flexographic plate is uniformly charged by the charger 16.

The charged flexographic plate is applied with a recording signal voltage to the ejection electrode with a charging potential as a bias, thereby causing the ink droplet 80 to fly and land on the flexographic plate 32 to form a mask image.
Here, providing a heating means for the flexographic plate and increasing the flexographic plate temperature is also effective for improving the drawing image quality, and further accelerates the fixing of the landed ink droplets 81 on the flexographic plate 32. Is suppressed.

The flexographic plate on which the mask image is formed is neutralized by the static eliminator 18, peeled off from the back electrode 59, and conveyed to the image fixing roller 24 by the conveying roller 22. In FIG. 1, an example of a corona static eliminator is shown as the static eliminator 18, but various methods such as a scorotron, a solid charger, a discharge needle can be applied, and a conductive roller is also preferably used.
The peeled flexographic plate is sent to the image fixing roller 24 by the conveying roller 22 and fixed. As the fixing means, known means such as heat fixing, solvent fixing and flash exposure fixing can be used alone or in combination.

  In heat fixing, infrared or halogen lamp or xenon flash lamp irradiation, hot air fixing using a heater, or heat roll fixing is generally used. In the solvent fixing, a solvent having affinity with the resin component in the ink is sprayed or exposed to vapor, and excess solvent vapor is recovered. Further, flash fixing using a xenon lamp or the like has an advantage that fixing can be performed in a short time. It is desirable that at least the process from the formation of the oil-based ink image by the discharge head 10 to the fixing by the image fixing roller 24 is maintained so that nothing touches the image on the flexographic plate.

  The moving speed of the flexographic plate at the time of fixing can be arbitrarily set. The fixed flexographic plate is accumulated in the mask-formed flexographic plate stocker 28.

  The electrostatic ink jet apparatus 1 used in the present invention has a recovery means 30 for a solvent generated from oil-based ink. The recovery means is made of a solvent vapor absorber, and various activated carbons are preferably used as the solvent vapor adsorbent. After the gas containing the solvent vapor in the machine is introduced into the adsorbent by an exhaust fan and the vapor is adsorbed and recovered, Exhausted outside.

  The present invention is not limited to the above example, and the number, shape, relative arrangement, charging polarity, and the like of constituent devices such as rollers and chargers can be arbitrarily adopted.

An example of the operation of the electrostatic ink jet apparatus according to the present invention will be described. Here, a case where ink containing positively charged pigment particles is used will be described as an example.
In FIG. 2, when forming a mask image, a voltage of +300 V is applied to the migration electrode 56 and a voltage of +100 V is applied to the shield electrode 58, thereby causing charged particles in the ink to be unevenly distributed in the lower portion of the ink chamber 34. At this time, the ink is supplied to the ink flying position at the tip of the insulating ink guide 38 with the charged particle concentration in the ink increased. Here, a pulse voltage of +600 V is applied to the first ejection electrode 50 and the second ejection electrode 52 as a signal voltage corresponding to an image signal, for example, when ON. On the other hand, the flexographic plate 32 is charged to a voltage of −1.5 kV by a scorotron charger. Now, when the discharge voltage is in an ON state (a state where 600 V is applied), the ink droplet 80 is ejected from the ink flying position at the tip of the insulating ink guide 38 and is ejected toward the flexographic plate 32. A mask image is formed by the ink droplets 81 landed on the flexographic plate 32. Note that it is preferable to apply a voltage of +100 V to the guard electrode 54 for suppressing electric field interference in order to precisely control the flying of the ink droplet after flying and improve the landing accuracy on the flexographic plate 32.

  In the electrostatic ink jet method, an electric field directed to the flexographic plate is applied to the ink droplets 80 ejected from the head even during flight, and the landing accuracy of the ink droplets 80 on the flexographic plate is good. A high-density image mask can be formed with high accuracy even when landed multiple times. Usually, an optical density of about 1.3 to 2.2 is obtained by one-time dot drawing, so when oil-based ink is discharged two or three times, 3.0 or more is preferable for dots generated by multiple landings. The optical density is obtained.

The oil-based ink used in the electrostatic ink jet method preferably contains a material that absorbs or reflects the photosensitive wavelength region of the photosensitive resin layer in the wavelength component of light to be exposed. Colored particles are preferably used as such a material, and examples of the colored particles include pigments and dyes. The photosensitive wavelength region is preferably 200 to 500 nm.
Examples of the pigment that absorbs light of 200 to 500 nm include black pigments such as carbon black, and examples of the pigment that reflects light having the wavelength include white pigments such as titanium oxide and zinc oxide.
As the pigment used in the present invention, a black pigment is preferable, and high resistance carbon black having a high resistance value is more preferably used. By using the high resistance carbon black, an effect that the adhesion of particles to the electrode portion of the ejection head is less likely to occur is exhibited. This will be described in detail later.

The oil-based ink used as the ink is preferably one in which charged particles having a particle size of about 0.1 to 5.0 μm are dispersed in a carrier liquid. The carrier liquid is required to be an insulating organic solvent having a high electrical resistivity (1 × 10 ¹⁰ Ωcm or more). If a carrier liquid having a low electrical resistivity is used, the carrier liquid itself is charged by charge injection due to the voltage applied by the ejection electrode, so the concentration of charged particles (charged ink particles) cannot be increased, Concentration does not occur. In addition, a carrier liquid having an extremely low electrical resistivity is not suitable for use in the present invention because there is a concern of causing electrical continuity between adjacent recording electrodes.

  The dielectric constant of the insulating organic solvent is preferably 5 or less, more preferably 4 or less, and still more preferably 3.5 or less. By using an organic solvent having such a relative dielectric constant range, an electric field is effectively applied to the charged particles in the insulating organic solvent, and migration easily occurs.

  The insulating organic solvent used in the present invention is preferably a linear or branched aliphatic hydrocarbon, alicyclic hydrocarbon, or aromatic hydrocarbon, and halogen-substituted products of these hydrocarbons. For example, hexane, heptane, octane, isooctane, decane, isodecane, decalin, nonane, dodecane, isododecane, cyclohexane, cyclooctane, cyclodecane, benzene, toluene, xylene, mesitylene, Isopar C, Isopar E, Isopar G, Isopar H, Isopar L (Isopar: trade name of Exxon), Shellsol 70, Shellsol 71 (Shellsol: trade name of Shell Oil), Amsco OMS, Amsco 460 solvent (Amsco: Trade name of Spirits), silicone oil (for example, Shin-Etsu Silicone KF-96L) or the like is used alone or in combination.

  The image mask must be opaque or reflective to the ultraviolet or visible light component that sensitizes the photosensitive resin layer. Thus, the image mask should contain a radiation opaque material. Any material that blocks the transmission of actinic rays to the photosensitive resin layer can be used as the radiation opaque material for forming the image mask. Examples of suitable radiation opaque materials include dyes that absorb ultraviolet or visible light, dark inorganic pigments, and combinations thereof. Preferred radiation opaque materials are carbon black and graphite. The carbon black concentration as the radiation opaque material is selected so that the required optical density is reached, that is, the image mask prevents the transmission of chemical radiation to the photosensitive resin layer. In general, a transmission optical density (OD) greater than 2.0 is preferable, 3.0 or more is more preferable, and 4.0 or more is particularly preferable.

  Pigments as opaque materials used to form suitable image masks include dark inorganic pigments such as carbon black, graphite, copper chromite, chromium oxide and chromium-cobalt aluminate. Examples of suitable dyes are: poly (substituted) phthalocyanine compounds; cyanine dyes; squarylium dyes; chalcogenopyryl arylidene dyes; bis (chalcogenopyrrillo) -polymethine dyes; oxyindolizine dyes; bis (aminoaryl) -polymethines Examples include dyes; merocyanine dyes; croconium dyes; metal thiolate dyes; and quinoid dyes.

  Dark inorganic pigments generally act as radiation opaque materials. Carbon black, graphite and mixtures thereof are particularly preferred dark inorganic pigments. Metals and alloys also act as radiation opaque materials. Examples of metals include aluminum, copper and zinc, and alloys of bismuth, indium and copper.

  The particles dispersed in the non-aqueous solvent may be dispersed in the dielectric liquid as the dispersed particles as described above or in dispersed resin particles for improving the fixing property. Good. In the case of inclusion, the pigment is generally coated with a resin material of dispersed resin particles to form resin-coated particles, and the dye is generally coated with dispersed resin particles to form colored particles. is there. These particles are preferably contained in the range of 0.5 to 30% by weight, more preferably 1.5 to 25% by weight, still more preferably 3 to 20% by weight, based on the whole ink. It is desirable that

As the pigment used in the present invention, a black pigment is preferable.
Examples of the black pigment include carbon black and graphite, and carbon black is preferably used.
Among carbon blacks, high resistance carbon black is more preferably used. In this case, it can also be used as dispersed in a non-aqueous solvent.
High resistance carbon black refers to carbon black having a volume resistance of 1 × 10 ⁻² Ω · cm or more, preferably 1 × 10 ⁻¹ Ω · cm or more.
The volume resistance of carbon black was measured as follows.
To a cup consisting of a round brass bottom plate with a cross-sectional area of 1.327 cm ^{2 and} a cylinder surrounding the side surface, weigh 0.10 g of carbon black to be measured, and flatten the surface. Then, a brass lid having a bottom area of 1.327 cm ² in cross-sectional area was placed thereon, and a pressure of 300 kg / cm ² was applied for 100 seconds. Thereafter, only the cylinder around the cup was removed, and a current value flowing when a DC voltage of 3 V was applied between the upper and lower brass plates was detected, and a volume resistance value was calculated from the value and the thickness of the carbon black pellet.
By using the high resistance carbon black, an effect that the adhesion of particles to the electrode portion of the ejection head is less likely to occur is exhibited.

  The average particle diameter of the pigment particles dispersed in the insulating solvent of the present invention is preferably 0.1 μm to 5 μm. More preferably, it is 0.2 micrometer-1.5 micrometers, More preferably, it is the range of 0.4 micrometer-1.0 micrometer. This particle size is determined by CAPA-500 (trade name, manufactured by Horiba, Ltd.).

  Further, the viscosity of the ink composition is preferably in the range of 0.5 to 5 mPa · sec, more preferably in the range of 0.6 to 3.0 mPa · sec, and still more preferably in the range of 0.7 to 2.0 mPa · sec. The pigment particles have a charge, and various charge control agents used in electrophotographic liquid developers can be used as necessary. The charge amount is desirably in the range of 5 to 200 μC / g, more preferably 10 The range is ˜150 μC / g, more preferably 15 to 100 μC / g. In addition, the electrical resistance of the dielectric solvent may change due to the addition of the charge control agent, and the distribution ratio P defined below is 50% or more, more preferably 60% or more, and even more preferably 70% or more.

P = 100 × (σ ₁ −σ ₂ ) / σ ₁
Here, σ ₁ is the electrical conductivity of the ink composition, and σ ₂ is the electrical conductivity of the supernatant obtained by subjecting the ink composition to a centrifuge. The electrical conductivity is measured using an LCR meter (AG-4311 manufactured by Ando Electric Co., Ltd.) and an electrode for liquid (LP-05 type manufactured by Kawaguchi Electric Manufacturing Co., Ltd.) under the conditions of applied voltage of 5 V and frequency of 1 kHz. Value. Centrifugation was performed for 30 minutes using a small high-speed cooling centrifuge (Tomy Seiko Co., Ltd. SRX-201) under conditions of a rotational speed of 14,500 rpm and a temperature of 23 ° C.

  By using the ink composition as described above, migration of charged particles is likely to occur, and the ink composition is easily concentrated.

On the other hand, the electrical conductivity σ ₁ of the ink composition is preferably in the range of 100 to 3000 pS / cm, more preferably in the range of 150 to 2500 pS / cm, and still more preferably in the range of 200 to 2000 pS / cm. By setting the electric conductivity in the above range, the voltage applied to the ejection electrode is not extremely high, and there is no fear of causing electrical conduction between adjacent recording electrodes. The surface tension of the ink composition is preferably in the range of 15 to 50 mN / m, more preferably 15.5 to 45 mN / m, and still more preferably 16 to 40 mN / m. By setting the surface tension within this range, the voltage applied to the ejection electrodes does not become extremely high, and the ink does not spread around the head and become contaminated.

The photosensitive flexographic plate includes a support and a photosensitive resin layer provided thereon as an essential component.
The support can be any flexible material suitable for preparing flexographic printing plates. Examples of suitable support materials include polymeric films formed from addition polymerized and linear condensation polymers, transparent foams and weaves, and metals such as aluminum. The support is preferably transparent to actinic radiation (meaning UV and / or visible light throughout this specification) and optionally transparent to infrared light, i.e. the light passes through the support. It is preferably possible to pass through without attenuation or substantially without attenuation. Metal supports are not transparent to radiation, but this is acceptable for certain end uses. A preferred support is a polyester film, and particularly preferred is polyethylene terephthalate (PET). The support typically has a thickness of 0.0051 to 0.025 cm, preferably 0.0076 to 0.020 cm.

  The term “photosensitive resin layer” used herein is meant to include photopolymerizability, photocrosslinkability, or both. This photosensitive resin layer is composed of an elastomeric binder, at least one monomer and a photopolymerization initiator as essential components. The photopolymerization initiator is sensitive to non-infrared actinic radiation. In many cases, the photoinitiator is sensitive to visible and / or ultraviolet light. Any suitable photosensitive resin composition for forming a flexographic printing plate can be used in the present invention. Examples of suitable compositions include, for example, Chen et al. U.S. Pat. No. 4,323,637; Gruetzmacher et al. 4,427,749 and Feinberg et al. 4,894,315. It is shown in

The elastomeric binder can be a single polymer or a polymer mixture, which can be soluble, swellable or dispersible in aqueous, semi-aqueous or organic solvent developers.
Binders that are soluble or dispersible in aqueous or semi-aqueous developers are Alles, U.S. Pat. No. 3,458,311; Pohl, 4,442,302; Pine, 4,361, No. 640; Inoue et al., 3,794,494; Proskow, 4,177,074; 4,431,723; and Worns, 4,517,279, etc. Is shown in
Binders soluble, swellable or dispersible in organic solvent developers include polyisoprene, 1,2-polybutadiene, 1,4-polybutadiene, butadiene / acrylonitrile, butadiene / styrene thermoplastic-elastomeric block copolymers and other copolymers. Natural or synthetic polymers of conjugated diolefin hydrocarbons including are included. Use block polymers as described in Chen US Pat. No. 4,323,636; Heinz et al. 4,430,417; Toda et al. 4,045,231, etc. Can do.
The binder preferably occupies at least 65% by weight of the photosensitive resin layer. Binder terms used herein include core-shell microgels and mixtures of microgels with preformed macromolecular polymers, such as those described in U.S. Pat. No. 4,956,252 to Fryd et al. It is a waste.

  Binders that can be preferably used in the present invention are those that are soluble or dispersible in an aqueous or semi-aqueous developer, and typical examples of such water-soluble binders are described in detail below. (1) A microgel binder comprising a combination of an elastomer disclosed in JP-A-7-84362 and an amphoteric stabilizer having both hydrophobic and hydrophilic parts adsorbed thereto, and (2) JP-A-7- 84369, a core-shell microgel binder having an elastomer as a core and a hydrophilic component as a shell, and (3) a mixture of an elastomer component disclosed in JP-A-7-333830 and a hydrophilic polyamide adsorbed thereto The microgel binder formed will be described below.

The microgel binder (1) will be described.
The microgel binder is prepared from an aqueous dispersion of an elastic polymer. There is at least one polymer stabilizer in the dispersion, which has a hydrophobic portion and a hydrophilic portion. The hydrophobic portion is oriented toward the surface of the dispersed elastic polymer. The hydrophilic part is oriented away from the surface of the elastic polymer and towards the aqueous phase. A solid binder can be obtained by removing water from this aqueous dispersion.

  The binder in the photosensitive resin layer imparts overall properties to the final flexographic printing plate. It should therefore be elastic and must give the printing plate sufficient elasticity, flexibility or flexibility, durability, ink solvent resistance and good ink transfer. Such desirable properties are well known in the field of flexographic technology. A suitable binder for practicing the present invention is a microgel of an elastomeric polymer that can be cross-linked, which has at least one compound having a hydrophobic part and a hydrophilic part adsorbed on its surface. Yes. Such a binder is called a “composite binder”.

  Elastic polymers that can be used in the microgel binder have the elasticity, durability, and chemical resistance required for flexographic printing plates, and can be formed or redispersed in aqueous dispersions. Examples of suitable polymers include poly (butadiene); poly (butadiene-styrene); poly (isoprene); poly (isoprene-styrene); natural rubber; neoprene; A preferred elastomeric polymer is a poly (styrene-butadiene) copolymer that does not have more than about 10% by weight styrene. Others that can be used include polyurethane elastomers and polymers of ethylene-propylene-diene monomers. Elastic polymer mixtures are compatible with each other. That is, they can be used as long as they form a photosensitive resin layer that develops with good resolution. In general, a mixture that forms a photosensitive resin layer without cloudiness or haze can be used. Elastic polymers can have some degree of cross-linking. However, the cross-linking must not be too extensive or it will adversely affect the polymer elasticity.

  The elastic polymer is first formed into a latex dispersion by emulsion polymerization. Emulsion polymerization is generally polymerization in an aqueous system, where the monomer is in the dispersed second phase and the polymer is formed as a dispersed solid phase. The solid elastic polymer dispersion in the aqueous solution is variously called rubber latex, elastomer latex, colloidal elastomer, or microgel dispersion. Very small polymer particles are produced, typically submicron. Emulsion polymerization is a well-known technique, for example, I. Piirma and JL Gardon, Emulsion Polymerization, ACS Symposium Series, 24 (1976); and DR Bassett and AE Hamieliec, Emulsion Polymers and Emulsion Polymerization, ACS Symposium Series, Vol. 165 (1981).

  Adsorbed on the surface of the polymer particles in the latex is a polymer stabilizer. This polymer stabilizer is a compound having a hydrophobic part and a hydrophilic part. In the latex, the polymer stabilizer is oriented on the surface of the elastic polymer at the solid-liquid intermediate interface, toward the surface of the elastic polymer in which the hydrophobic portion is dispersed, and at the same time the hydrophilic portion is separated from the polymer surface. Adsorb selectively to extend and orient into the aqueous phase. Types of polymers that can be used as polymer stabilizers include diblock copolymers and graft copolymers. In diblock copolymers, some of the polymer molecules are mostly composed of hydrophobic monomers, while other parts are mostly composed of hydrophilic monomers. In graft copolymers, the backbone of either hydrophobic or hydrophilic monomers has grafted side chains of other types of monomers thereon. Other types of polymers can also be used as long as they have a hydrophobic portion and a hydrophilic portion.

  Examples of suitable monomers for the hydrophobic moiety include C1-C6 alkyl esters of acrylic acid and methacrylic acid; propylene oxide; and combinations thereof. Examples of suitable monomers for the hydrophilic moiety include acrylic acid and methacrylic acid; sodium and potassium salts of acrylic acid and methacrylic acid; ethylene oxide; vinyl pyrrolidone; and combinations thereof. Examples of suitable polymer stabilizers include diblock copolymers of butyl methacrylate and methacrylic acid and their ammonium, sodium or potassium salts; diblock copolymers of propion oxide and ethylene oxide; methyl methacrylate and ethylene oxide Graft copolymers; and graft copolymers of methyl methacrylate and vinyl pyrrolidone. A preferred polymer stabilizer is a diblock copolymer of butyl methacrylate and methacrylic acid.

  The washout rate, as well as the mechanical properties of the printing plate, determines the size of the elastomer particles in the latex; the relative amount of elastic polymer and polymer stabilizer; the relative amount of hydrophobic and hydrophilic parts in the polymer stabilizer. Amount; degree of compatibility between the elastomeric polymer and the hydrophobic part; ease of dissolution or dispersion of the hydrophilic part in water; and depending on the relative combination of variables including others . The final printing plate's elastic properties, i.e., durometer, elasticity, bendability, etc., generally depend on the elastic polymer since the polymer stabilizers are not usually elastic. The washout rate generally depends on the polymer stabilizer since it provides a hydrophilic portion in which the polymer stabilizer is dispersed or dissolved in the aqueous solution. Thus, for a certain latex particle size, the elastic properties are improved as the ratio of elastic polymer to polymer stabilizer increases (decrease durometer, increase elasticity, increase flexibility) and at the same time the washout rate decreases. However, the elastic properties of the final printing plate are also improved by increasing the particle size in the latex. In general, larger particle size latex can be used to increase the ratio of elastic polymer to polymer stabilizer and achieve both good elastic properties and washout rates.

  There must be a sufficient amount of hydrophobic moieties in the polymer stabilizer because it remains adsorbed on the surface of the elastic polymer particles. At the same time, there must be a sufficient amount of hydrophilic portion to obtain water treatability. Generally, the molar ratio of hydrophobic monomer to hydrophilic monomer in the polymer stabilizer is in the range of about 4: 1 to 1: 4. A preferred range is 3: 2 to 2: 3. The compatibility of the hydrophobic part with the elastic polymer and the ease of dissolution or dispersion of the hydrophilic part depends on the chemical nature of the material used. These must be selected so that a photosensitive resin layer and flexographic printing plate having the desired properties are produced.

The composite binder used in the present invention is generally prepared by first producing an elastic polymer latex, adding a polymer stabilizer, and removing water.
In general, the method of making an elastic polymer latex involves the formation of an oil / water emulsion containing a polymerization catalyst and usually an emulsifier to stabilize the emulsion. As used herein, the term “oil” refers to a liquid that is substantially immiscible with water and forms a second phase. Such a liquid is well known in the art of emulsion polymerization, for example Isopearl. The catalyst can be present in either the oil or water phase. In the case of an elastomer or copolymer, one of the monomers can be present in the normal oil phase of the emulsion. A small amount of a crosslinking agent, such as allyl methacrylate or diallyl maleate can also be present. However, the amount of crosslinking in the elastomeric polymer should be fairly low, for example about 10% or less. Others that can be present in the emulsion are described in the above references.

  After the emulsion is stabilized, the elastomeric polymer monomer is added to the emulsion to initiate polymerization. Usually this is achieved by applying heat, typically between 50 ° and 70 ° C. When the polymerization is complete, the polymer stabilizer is usually added to the latex as an aqueous solution. In some cases, the polymer stabilizer is neutralized with an aqueous base to obtain sufficient water solubility. The two components are then mixed for a time sufficient to cause adsorption. Any conventional mixing method can also be used. The mixing time can vary considerably, but 24 hours is generally sufficient.

  A polymer stabilizer can also be added before or during the polymerization step. The polymer stabilizer can act as an emulsifier for the polymerized particles. An elastic latex in which a polymer stabilizer is adsorbed on the surface of the elastic polymer particles can be used as a latex, such as the dewatering extruder described in Kafka et al. US Pat. No. 4,970,037. The photosensitive resin layer can be formed by directly mixing the monomer and the photopolymerization initiator using an apparatus. However, the liquid (ie, water and oil) may be removed using a dehydrating extruder or other known techniques such as coagulation, filtration, washing and drying before mixing the monomer and photoinitiator. It can be removed from the latex and transformed into a solid form. Freeze drying and spray drying are useful methods for practicing the present invention. Thus, the liquid phase can be removed before, simultaneously with, or after mixing the monomer and photoinitiator.

  In addition to the composite binder, one or more additional polymeric polymer binders can also be added. These can be added to improve the mechanical properties of the final flexographic printing plate, such as durability, but should not compromise the desired elasticity. This additional polymeric polymer binder can contain sufficient acidic groups or other groups that allow the binder to be processed in an aqueous developer. Useful aqueous processable binders are disclosed, for example, in U.S. Pat. Nos. 3,458,311; 4,273,857; and 4,293,635. Examples include acid-containing polymers or their salts; and amphoteric polymers such as N-alkyl acrylamides or methacrylamides, acidic film-forming comonomers and interpolymers derived from alkyl acrylates or hydroxyalkyl acrylates, and the like. . In general, the composite binder or mixture of composite binder and polymeric polymer binder is present in an amount of about 40-95% by weight, preferably 70-90% by weight, based on the total weight of the photosensitive resin layer.

  Next, the core-shell type microgel binder will be described.

  The core-shell type microgel binder that can be used in the present invention is a core-shell microgel having a thermoplastic elastomeric core that can be crosslinked and a thermoplastic non-crosslinked shell. The core provides the elastomeric properties of the binder, while the shell provides aqueous developability. The core is composed of a homopolymer or copolymer of an elastomeric monomer, and the shell is composed of a copolymer of an elastomeric monomer and an ethylenically unsaturated monomer or oligomer having acidic functionality.

  As used herein, the term “elastomeric monomer” means an ethylenically unsaturated monomer that forms a homopolymer having a glass transition temperature of 10 ° C. or lower. Suitable elastomeric monomers include butadiene, isoprene, neoprene, urethane, and mixtures thereof. A preferred elastomeric monomer is butadiene.

  Monomers that can be copolymerized with elastomeric monomers to form a core (“core comonomers”) are those that form copolymers that have similar elastic properties to homopolymers of elastomeric monomers. Generally, the core comonomer is added to improve the durability or fastness of the core and to accelerate the emulsion polymerization process. In many cases, the core comonomer has no additional functional groups, ie acidic functionality. Examples of suitable core comonomers include polymerizable alkenyl aromatic hydrocarbons, particularly vinylic monocyclic aromatic hydrocarbons such as styrene and alpha-methylstyrene. The amount of core comonomer present in the core copolymer should be less than 20% by weight, preferably less than 10% by weight, based on the weight of the copolymer.

  Monomers suitable for copolymerization with the elastomeric monomer to form a microgel shell include (1) at least one ethylenically unsaturated group capable of copolymerizing with the elastomeric monomer, and (2) at least one at least one. It has acid functionality. The acidic groups are preferably carboxylic acids, but sulfonic acids and other acidic groups can also be used. Examples of suitable monomers ("acidic monomers") include acrylic and methacrylic acid, crotonic acid and isocrotonic acid, sorbic acid, maleic acid, cinnamic acid, fumaric acid, itaconic acid, and others. Mixtures of acidic monomers can also be used. Acrylic acid and methacrylic acid are preferred.

  When the core is a copolymer, some core comonomer may remain when acidic monomer is added to form a shell. Thus, the shell may contain some amount of elastomeric monomer / core comonomer / acidic monomer terpolymer. However, the amount of such terpolymer will be very small, if any, since the amount of core comonomer is small relative to the elastomeric monomer. Almost all of the core comonomer will be in the core. In the following description, the microgel shell will be referred to as a copolymer of elastomeric monomer and acidic monomer (or acidic monomer mixture), although it may be considered that some small amount of the core comonomer may be polymerized in the shell.

  The amount of acidic monomer that is copolymerized with the elastomeric monomer should be sufficient to give the microgel binder an aqueous processability, but otherwise it should be minimal. That is, the ratio of acidic shell copolymer to elastomeric core homopolymer or copolymer should be as small as possible while maintaining the potential for aqueous processing. This maximizes the amount of elastomeric polymer in the microgel, thus optimizing the elastic properties of the microgel binder. As stated previously, it is preferred that no more than 95% of the elastomeric monomer is polymerized in the core, most preferably 60-90%.

  One preferred core-shell microgel is a core composed of a copolymer of styrene and butadiene having a styrene content of less than 10%, and a shell composed of an ethylenically unsaturated monomer or oligomer having an acidic functionality and a copolymer of butadiene. It is what has. One more preferred core-shell microgel has a core composed of a copolymer of styrene and butadiene having a styrene content of less than 10% and a shell composed of a copolymer of acrylic acid or methacrylic acid and butadiene. Also preferred are polybutadiene cores and shells made of copolymers of acrylic acid or methacrylic acid and butadiene.

  As used herein, the term “microgel” includes cross-linked spherical polymer molecules having a particle size of 0.01 to 1.0 microns in diameter prepared by emulsion polymerization. It is most desirable to use a microgel with a very light shell. Thus, the binder will have a large area of essentially pure elastomeric polymer and will have elastic properties very similar to this polymer. When a basic compound is added to the microgel to neutralize the acidic functionality, the photosensitive material can be processed in tap water. For the following description, butadiene is used as an example of an elastomeric monomer. However, it will be understood that other elastomeric monomers may be used.

  To prepare the core-shell microgel, the core butadiene homopolymer or copolymer is first formed as a latex dispersion by emulsion polymerization. Emulsion polymerization generally refers to polymerization in aqueous systems, where monomers such as butadiene or a mixture of butadiene and core comonomer are present in the dispersed second phase, producing a polymer as a dispersed solid phase. To do. The solid elastomeric polymer dispersion in this aqueous solution is referred to variously as rubber latex, elastomer latex, colloidal elastomer, or microgel dispersion. Very small polymer particles are produced and are typically of sub-micron size. Emulsion polymerization methods are well known to those skilled in the art, and the article is edited by I. Piirma and JL Gardon, Emulsion Polymerization, ACS Symposium Series, Vol. 24, 1976; and DR Bassett and AE Hamieliec, Emulsion Polymers and Emulsion Polymerization. , ACSSymposium Series, Vol. 165, 1981.

  In general, the process for making an elastomeric polymer latex involves the formation of an oil / water emulsion, which includes a polymerization catalyst and usually an emulsifier to stabilize the emulsion. As used herein, the term “oil” refers to a liquid that is substantially immiscible with water and forms a second phase. Such liquids are well known in the art, such as Isopearl. The catalyst can be present in either the oil or water phase. A small amount of a cross-linking agent such as allyl methacrylate can also be present. However, it is preferred that the amount of crosslinking in the butadiene homopolymer or copolymer is fairly low, i.e., less than about 10% crosslinking. Excessive crosslinking in the core will detract from the elastic properties of the microgel. Other substances that can be present in the emulsion are indicated in the above-mentioned literature.

  After the emulsion is stabilized, butadiene monomer is added to the emulsion to initiate polymerization. Usually, it is preferable to apply heat of 50 to 70 ° C. The core comonomer can be added to the stabilized emulsion before or simultaneously with the addition of the elastomeric monomer.

  Due to the microgel binder used in the practice of this invention, butadiene is only partially polymerized at this point. Preferably less than about 95% by weight of the butadiene monomer is polymerized, more preferably 60-90% is polymerized. At this point, a monomer with acidic functionality is added to the reaction mixture. This monomer polymerizes with the residual butadiene monomer to form a light shell on the polybutadiene core.

  The elastomeric latex with core-shell microgel particles thus formed is mixed with the other components of the photosensitive composition and is described in Kafka et al., US Pat. No. 4,970,037. An apparatus such as a dehydrating extruder can be used as a latex for forming the photosensitive resin layer. However, the liquid (ie, water and oil) can also be removed from the latex to make a solid binder before mixing with the other ingredients. This can be done by dewatering extrusion or by other well known methods of agglomeration, filtration, washing and drying. Freeze drying and spray drying are also useful methods for the practice of this invention.

  In addition to the core-shell microgel binder, one or several additional macromolecular polymeric binders can also be present. They can be added to improve the mechanical properties of the final flexographic printing plate, such as durability, but should not adversely affect the required elastic properties. This additional macromolecular polymeric binder can contain sufficient acidic or other groups such that the binder can also be processed in aqueous developers. Useful aqueous processable binders are shown, for example, in U.S. Pat. Nos. 3,458,311; 4,273,857; and 4,293,635. Examples include acid-containing polymers or their salts; and amphoteric polymers such as N-alkylacrylamides or methacrylamides, acidic film-forming comonomers, and interpolymers derived from alkyl or hydroxyalkyl acrylates.

  In general, the core-shell microgel binder or a mixture of this and the macromolecular polymeric binder is present in an amount of about 40-95% by weight, preferably 70-90% by weight, based on the total weight of the photosensitive resin layer.

  Next, a microgel binder made of a mixture of an elastomer component and a hydrophilic polyamide adsorbed thereto will be described. The binder comprises A: hydrophilic polymer and B: rubber having a molecular weight of 40,000 or more, or A: hydrophilic polymer and B: solid rubber.

  “Hydrophilicity” characterized by the component A means the property of being dissolved and / or dispersed 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 completely eluted. Or when the film is reduced or disintegrated by partly eluting, or when the polymer is swollen and dispersed and dispersed in water. For the purpose of the present invention, a film having a thickness of 0.5 mm is soaked in water at 25 ° C. for 1 hour and dissolved, or it can swell 200% by weight or more with respect to the polymer without being dissolved. Preferably used.

  Examples of such hydrophilic polymers include polymers that can be dissolved in alcohol and / or water, and examples include polyamides, partially saponified polyvinyl acetates, and celluloses. From the viewpoint of the compatibility between the hydrophilic polymer and the photopolymerizable unsaturated compound and the printing durability of the resulting printing plate, polyamide is preferably used in the present invention.

  As the hydrophilic polyamide used in the present invention, any of a polyamide having a sulfonic acid group or a sulfonate group in the side chain, a polyamide having an ether bond in the molecule, a polyamide having a piperidine skeleton, and a polyamide having an amino group in the side chain. Is preferred.

  As the polyamide having a sulfonic acid group or a sulfonate group in the side chain, as shown in JP-A-48-72250, sodium 3,5-dicarboxybenzenesulfonate and the like, and ordinary polyamide raw materials such as lactam, Examples thereof include polyamides containing sulfonic acid groups or sulfonate groups obtained by copolymerizing aminocarboxylic acid, diamine and dicarboxylic acid. Examples of the polyamide having an ether bond in the molecule include polyamides obtained by copolymerizing at least one of dicarboxylic acid, diamine, aminocarboxylic acid and lactam having an ether bond in the molecule, and JP-A-55. Examples thereof include copolyamides containing polyalkylene ether segments proposed in JP-A-74537. Examples of the polyamide having a piperidine skeleton include N, N′-di (γ-aminopropyl) piperazine as disclosed in JP-A-50-7605, and dicarboxylic acid, diamine, aminocarboxylic acid as necessary. Examples include polyamides obtained by (co) polymerization with acids and lactams. Further, as the polyamide having an amino group in the side chain, a tertiary one is preferably used as the side chain amino group, and a ring-opening polymer of α- (N, N′-dialkylamino) -ε-caprolactam or α- Examples thereof include polyamides obtained by copolymerizing (N, N′-dialkylamino) -ε-caprolactam and at least one of diamine, aminocarboxylic acid and lactam. In addition, in the polyamide having a piperazine skeleton and the polyamide having an amino group in the side chain, those obtained by quaternizing the nitrogen atom with acrylic acid or the like can be used.

Of these hydrophilic polyamides, polyamides having an ether bond in the molecule are preferably used, and those having an ether bond in the polyalkylene ether segment are preferably used. As this polyalkylene ether segment, those having a molecular weight of 150 to 1500 are more preferably used. As a specific polyamide structure, it contains 30 to 70% by weight of structural units composed of polyoxyethylene having an amino group at the terminal and a molecular weight of the polyether segment part of 150 to 1500 and an aliphatic dicarboxylic acid or diamine. However, the copolymerized polyamide is preferably used.
These hydrophilic polymers may be used alone or in combination of two or more.

The rubber or solid rubber having a molecular weight of 40,000 or more as the B component is not particularly limited, and rubbers other than so-called liquid rubber can be used.
The molecular weight of the rubber here means the number average molecular weight.

  Such rubbers include high-molecular-weight isoprene rubber, butadiene rubber, styrene-butadiene rubber, chloroprene rubber, nitrile rubber, butyl rubber, acrylic rubber, epichlorohydrin rubber, silicone rubber, and other raw rubbers or elastomers, and styrene-butadiene copolymer. Copolymers, copolymers of dienes such as styrene-isoprene copolymer, butadiene-acrylic acid copolymer, copolymers of olefins such as ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, etc. Is mentioned. Among these, a diene polymer or an olefin copolymer is preferably used from the viewpoint of the water-based ink resistance of the obtained printing plate.

  In order to achieve both the water developability of the printing plate material and the compatibility of the printing plate with water-based ink, it is preferable that rubber is dispersed in an independent form in the photosensitive resin composition of the present invention. As a method of dispersing the rubber in the photosensitive resin composition, a method of melting the hydrophilic polymer and the rubber to form a molten mixture is preferably used. Melt mixing means that two or more kinds of polymers are usually mixed at a temperature above their softening point. By performing melt mixing, the rubber particles are dispersed in a minute size throughout the continuous polymer matrix. The melt mixing may be performed using a normal kneading apparatus such as a Banbury mixer, a Brabender mixer, a kneader, or a twin screw extruder. Moreover, it is preferable that the temperature of melt mixing exists in the range of 100-250 degreeC.

  In the polyamide binder used in the present invention, the blending ratio of the hydrophilic polymer and the rubber is preferably 1 to 9 to 8 to 2, more preferably 1 to 9 to 5 to 5, as a weight ratio. When the blending amount of the rubber is within the above range, the flexibility and the developability in neutral water are improved when the flexographic printing plate is used.

  The amount of the hydrophilic polymer used is preferably 3 to 40% by weight, more preferably 5 to 20% by weight based on the total photosensitive resin layer. Within the above range, if it is not less than the lower limit, formability in the raw plate when developing and photosensitive resin plate material is improved. Within the above range, the water resistance of the printing plate is improved and the printing plate tends to swell with water-based ink, and the printing durability tends to be good.

  The amount of rubber used is preferably 10 to 80% by weight, more preferably 30 to 70% by weight in the total photosensitive resin layer. Here, the rubber can be blended in the form of fine particles of rubber such as rubber emulsion and rubber latex in addition to the rubber blended in the molten mixture. When the amount of rubber is within the above range, the flexibility and developability of the printing plate are improved.

  The total amount of the hydrophilic polymer of component A and the rubber of component B is preferably 20 to 90% by weight, more preferably 50 to 80% by weight in the total photosensitive resin composition. When the upper limit is exceeded within the above range, the adhesion of the obtained plate surface becomes small, and the form retainability of the original plate when used as a photosensitive resin plate material is improved. Within the above range, the photosensitive property of the plate, particularly the image reproducibility, is improved if it is below the lower limit.

  An unsaturated epoxy compound may be added to the polyamide binder. By adding an unsaturated epoxy compound to a solution of a molten mixture of a hydrophilic polymer and rubber, and adding the unsaturated epoxy compound to the terminal carboxyl group of the hydrophilic polymer and rubber, the polymer and rubber itself are made photopolymerizable. Therefore, a relief network formed by a photopolymerization reaction with a photopolymerizable compound is formed at a higher density, and the resulting relief has good water resistance and can maintain high image reproducibility, and Since the relief is strong, problems such as cracking during printing can be prevented.

Next, the monomer used for the photosensitive resin layer will be described.
The photosensitive resin layer can comprise a single monomer or a mixture of monomers, which must be compatible with the binder so that a transparent, cloudless photosensitive resin layer is produced. Monomers that can be used in the photosensitive resin layer are conventionally well known in the art, and addition-polymerized ethylenically unsaturated compounds having a relatively low molecular weight (generally less than about 30,000) are known. Including, but not limited to. Preferably, the monomer has a relatively low molecular weight of less than about 5000. Unless otherwise stated, throughout this specification molecular weight is weight average molecular weight.

  Examples of suitable monomers include, but are not limited to, mono- and poly-esters of alcohol and polyol acrylates and methacrylates such as t-butyl acrylate, lauryl acrylate, alkanols, such as 1,4-butanediol. , Diacrylate, 2,2,4-trimethyl-1,3-pentanediol dimethacrylate, and 2,2-dimethylolpropane diacrylate; alkylene glycols, tripropylene glycol diacrylate, butylene glycol dimethacrylate, hexa Methylene glycol diacrylate and hexamethylene glycol dimethacrylate; trimethylolpropane; ethoxylated trimethylolpropane; pentaerythritol, for example, pentaerythritol Ritolol triacrylate; dipentaerythritol; others. Other examples of suitable monomers include isocyanates, esters, epoxides, other acrylate and methacrylate derivatives such as decamethylene glycol diacrylate, 2,2-di (p-hydroxyphenyl) propane diacrylate, 2,2-di (p-hydroxyphenyl) propane dimethacrylate, polyoxyethyl-2,2-di (p-hydroxyphenyl) propane dimethacrylate, and 1-phenylethylene-1,2-dimethacrylate, Etc. Examples of further monomers are Chen US Pat. No. 4,323,636; Fryd et al. 4,753,865; 4,726,877; and Feinberg et al. , 894, 315.

  The monomer is preferably added at least 5% by weight of the photosensitive resin layer. Generally, it is 5 to 50% by weight, preferably 5 to 30% by weight, but in some cases, it is preferably in the range of 10 to 80% by weight. In this case, 10 to 60% by weight is more preferable. preferable.

  The ratio of the photopolymerizable unsaturated compound in the photosensitive resin layer is preferably in the range of 10 to 80% by weight. More preferably, it is 10 to 60% by weight. When the ratio of the photopolymerizable unsaturated compound in the photosensitive resin layer is not less than the lower limit within the above range, the density of the crosslinked structure produced by photopolymerization is sufficient, so that the water-based ink diluted with water as a main component is diluted. It becomes difficult to swell with respect to the solvent, and the solid portion is less likely to swell and fail to print during printing. In addition, since the cross-linking density is sufficient even by exposure, desired image reproducibility tends to be obtained.

  Conversely, if the ratio of the photopolymerizable unsaturated compound in the photosensitive resin layer is below the upper limit within the above range, the density of the crosslinked structure produced by photopolymerization does not become excessive, so that the strength of the plate-making relief is sufficient. Therefore, problems such as cracks in the relief during printing do not occur.

The photoinitiator used for the photosensitive resin layer of this invention is demonstrated.
The photoinitiator can be either a single compound or a combination of compounds, which is sensitive to actinic radiation and generates free radicals that initiate the polymerization of the monomer or monomers. The photopolymerization initiator is generally sensitive to visible light or ultraviolet light, preferably ultraviolet light. The photopolymerization initiator is preferably thermally insensitive at 185 ° C. or lower. Examples of suitable photoinitiators include substituted and unsubstituted polynuclear quinones, aromatic ketones, benzoin and benzoin ethers and 2,4,5-triarylimidazolyl dimers, benzophenones, benzyls, acetophenone And diacetyls. Examples of suitable systems are shown in Grueetzmacher U.S. Pat. No. 4,460,675 and Feinberg et al. 4,894,315.

  In general, the photopolymerization initiator is preferably used in an amount of 0.001 to 15.0%, more preferably about 0.01 to 10% by weight based on the weight of the photopolymerization composition, and 0.1 to 5. It is particularly preferable to use 0% by weight.

Other additives can be used in the photosensitive resin layer in relation to the desired final properties. Such additives include sensitizers, plasticizers, rheology modifiers, thermal polymerization inhibitors, tackifiers, colorants, antioxidants, antiozonants, antistatic agents, UV absorbers, reinforcing agents, Examples thereof include a compatibility aid, a surfactant, an antifoaming agent, a fragrance, and a filler. The other additives generally constitute 10% by weight or less, preferably 5% by weight or less, based on the total weight of the photosensitive resin layer.
The plasticizer is used to adjust the film forming characteristics of the elastomer. Examples of suitable plasticizers include aliphatic hydrocarbon oils such as naphthene oil and paraffin oil; liquid polydienes such as liquid polybutadiene; liquid polyisoprene. Generally, the plasticizer is a liquid having a molecular weight less than about 5,000, but can have a molecular weight up to about 30,000. Low molecular weight plasticizers will include those with molecular weights less than about 30,000.

Polyhydric alcohols such as ethylene glycol, diethylene glycol, triethylene glycol, glycerin, trimethylolpropane, trimethylolethane, N-ethyl-p-toluenesulfone as a compatibilizer for hydrophilic polymer and photopolymerizable unsaturated compound It is also possible to add amide, N-butylbenzenesulfonamide, N-methylbenzenesulfonamide and the like. These polyhydric alcohols and sulfonamide compounds have an effect of further enhancing the flexibility of the portion cured by photopolymerization and preventing the occurrence of relief cracks. Such polyhydric alcohol and sulfonamide compound can be used in the range of 30% by weight or less based on the photosensitive resin layer.
Examples of the thermal polymerization inhibitor include phenols, hydroquinones, catechols and the like. These thermal polymerization inhibitors can be used in the range of 0.001 to 5% by weight based on the total amount of the photosensitive resin layer.

  A basic compound may be added to the photosensitive resin layer using the core-shell type microgel binder. The basic compound is optional and is added when it is desired to develop the photosensitive flexographic plate with tap water. The basic compound neutralizes the acidic functionality of the microgel shell and makes the microgel binder developable in fresh water. The basic compound can be an inorganic base or a basic organic compound such as an amine. Examples of suitable inorganic bases include Group IA and Group IIA metal hydroxides. Examples of suitable organic bases include primary, secondary and tertiary amines such as C2 to C12 alkyl or aryl amines, C2 to C12 alkyl or aryl di- or triamines, alkanolamines, aminodiols, and the like. Includes.

  One preferred basic compound is a nitrogen-containing compound having at least one ethylenically unsaturated group. Photosensitive compositions in which these types of basic compounds are present provide flexographic printing plates with improved resistance to aqueous based inks. Particularly suitable are (meth) acrylates, (meth) acrylamides or compounds containing both (meth) acryloyl carbamate groups and amino groups. Examples of suitable compounds include dialkylaminoalkyl acrylates and methacrylates, dialkylaminoalkyl acrylamides and methacrylamides, dialkylaminoalkyl acrylic oil carbamates and methacrylic oil carbamates, where each alkyl group has 1 to 6 It has a carbon atom. Combinations of basic compounds can also be used.

  The basic compound can be added almost any time during the preparation of the photosensitive flexographic plate, ie the compound is (a) immediately after the formation of the microgel in the latex and (b) the microgel binder is water in the latex. Or (c) with the addition of other components of the photosensitive resin layer. The amount of basic compound added should be sufficient to neutralize the acidic functionality to the extent that the photosensitive composition is water soluble. The molar ratio of basic compound added to the acidic monomer in the copolymer shell is usually in the range of 1: 2 to 2: 1. Generally, the basic compound is present in an amount of about 1 to 15% by weight based on the total weight of the photosensitive resin layer.

  The following method is preferably used as a method for producing the polyamide binder photosensitive resin layer used in the present invention. First, as described above, a molten mixture of hydrophilic polymer and rubber is prepared. A polymerizable monomer component and a photopolymerization initiator component are further mixed into the molten mixture to obtain a polyamide binder type photosensitive resin layer used in the present invention. The addition time of the polymerizable monomer component and the photopolymerization component may be the same or either one may be first.

  As a method for mixing the molten mixture with other components, for example, a molten mixture of a hydrophilic polymer and rubber is dissolved in a mixed solvent such as water / alcohol while heating. Through this process, part or all of the hydrophilic polymer is dissolved, and the microdispersed rubber is dispersed in the solvent. If necessary, an unsaturated epoxy compound is added to this solution to cause an addition reaction to the polymer. Further, a photopolymerizable unsaturated compound, a photopolymerization initiator, and, if necessary, a heat stabilizer are added, and the mixture is stirred and mixed thoroughly to obtain a solution comprising a photosensitive resin for a printing plate.

  The photosensitive resin layer can be made in a single layer or multiple layers having the same composition, or can be made in two layers or more layers having different compositions. In general, the different layers should have the same or similar binder, but the concentration of each component, the type of monomer and photoinitiator and the additives may be different.

  The thickness of the photosensitive resin layer can vary over a wide range depending on the type of flexographic printing plate desired. For so-called “thin plates”, the photosensitive resin layer can have a thickness of about 0.05 to 0.17 cm. With a thicker plate, the photosensitive resin layer will have a thickness of 0.25 to 0.64 cm or even greater. Generally, the photosensitive resin layer contains one or more compounds that can migrate to the surface of the photopolymer layer and possibly into an adjacent layer. In general, low molecular weight compounds, ie, those having a molecular weight of less than 30,000, are mobile. Mobile low molecular weight compounds are mainly liquids but also include low melting point materials. Examples of such mobile materials include monomers and plasticizers. This mobile material tends to migrate over time when they are compatible with the material in adjacent layers.

The photosensitive resin layer used in the present invention preferably has a surface resistance of 1 × 10 ¹⁰ Ω / □ or more, more preferably 2 × 10 ¹⁰ Ω / □ or more. The upper limit is preferably 1 × 10 ¹⁸ Ω / □ or less. A photosensitive resin layer having a surface resistance of 1 × 10 ¹⁰ Ω / □ or more has high charging efficiency and high charging uniformity, and can form a high-quality mask image.
In the present invention, the surface resistance value refers to a resistance value measured by the following measurement method.
Using an electrometer manufactured by Kawaguchi Electric Co. (Universal Electrometer MMAII-17A) under the environment of temperature 20 ° C / humidity RH 65%, a flexographic plate is set in the measurement chamber, wiring is performed in the surface resistance measurement mode, and the electrometer The measured applied voltage was set to 100 V, and the resistance value 1 minute after the voltage application was taken as the measured value.

  The above-mentioned photosensitive resin composition solution for printing plates is coated on the support as a photosensitive layer to obtain a photosensitive resin plate material. In order to form the photosensitive layer, for example, most of the solvent can be distilled and then heated to be melted and extruded onto a support. In addition, it is also possible to form a photosensitive sheet by a dry film forming method and adhere this sheet on a support to form a photosensitive layer. In addition, the photosensitive layer can also be obtained by dry film formation directly on the support. As the support, a metal plate such as steel, stainless steel, aluminum or copper, a plastic sheet such as a polyester film, or a synthetic rubber sheet such as a styrene-butadiene copolymer is used. The photosensitive layer is preferably formed to a thickness of 0.01 to 10 mm. Thus, the photosensitive resin plate material is obtained by coating the photosensitive resin composition of this invention on a support body.

In the present invention, the step after the mask image is formed on the flexographic plate is the entire surface exposure of the photosensitive flexographic plate with chemical radiation through the mask.
The type of radiation used is related to the type of photopolymerization initiator in the photosensitive resin layer. The mask image formed on the surface of the photosensitive resin layer prevents the underlying material from being exposed to actinic radiation, where the area covered by this radiation opaque material does not polymerize. Areas not covered by the radiation opaque material are exposed to actinic radiation and polymerize. Any ordinary source of actinic radiation can be used for this step. Examples of suitable visible or UV light sources include carbon arcs, mercury vapor arcs, fluorescent lamps, electronic flash units, electron beam units and photographic flood lamps. The most suitable UV light source is a mercury vapor lamp, in particular a sun lamp. A standard light source is a Sylvania 350 black light fluorescent lamp (FR 48T 12/350 VL / VHO / 180, 115w), which has a central emission wavelength around 354 nm.

  The overall exposure to actinic radiation can be performed on a flat table, but may be performed using a drum.

  The exposure time of actinic radiation can vary from a few seconds to a few minutes in relation to the intensity of the radiation and the spectral energy distribution, the distance from the photosensitive flexographic plate, the nature and quantity of the photosensitive resin composition, etc. . Typically, a mercury vapor arc or solar mist is used at a distance of about 1.5 to about 60 inches (3.8 to 153 cm) from the photosensitive flexographic plate. The exposure temperature is preferably ambient or slightly elevated, i.e., from about 20 to about 35 ° C.

  Usually, imagewise exposure of a photosensitive flexographic plate to actinic radiation is performed in a vacuum, eliminating the presence of atmospheric oxygen. Exposure is performed in a vacuum to ensure close contact between the original (eg, negative) and the photopolymerizable surface and to prevent oxygen from adversely affecting the polymerization reaction that occurs in the photopolymer layer. (In the presence of oxygen, the polymerization reaction requires a long exposure time and a high intensity light source, and the result is less reproducible) In the method of the present invention, the entire exposure step can be performed in a vacuum, or It can also be carried out outside the vacuum, i.e. in the presence of atmospheric oxygen. The ability to perform this entire exposure step outside the vacuum is surprising, especially since the photosensitive flexographic plate does not have a barrier layer that prevents the action of oxygen on the polymerization. The overall exposure without vacuum for the photosensitive flexographic plate is one of the product characteristics that the sidewalls of the relief structure of the plate are more linear over a wide range of exposure times, i.e. give a wide exposure latitude. Gave an improvement. Users generally benefit from wide exposure latitude in their processing. Another advantage for performing the entire exposure step when not in vacuum is that it is simpler and quicker because it does not require time to evacuate before exposure.

  The method of the present invention usually includes a back exposure or backflush step. This is a full exposure to actinic radiation through the support. This is used to produce a shallow layer or floor of polymerized material on the support side of the photosensitive resin layer and to sensitize the photosensitive resin layer. This floor improves the adhesion between the photosensitive resin layer and the support, promotes the resolution of highlight dots and also determines the relief depth of the plate. Backflash exposure can occur before, after, or during the imaging process. Any of the aforementioned conventional light sources can be used for the backflash exposure step. The exposure time generally ranges from a few seconds to about 1 minute.

  After full exposure to UV light through a mask formed of actinic radiation opaque material, the image is processed by washing with a suitable developer. This processing step removes at least the photosensitive resin layer in areas not exposed to non-infrared actinic radiation. The developer removes unphotopolymerized areas of the photosensitive resin layer.

  Development is usually carried out at about ambient temperature. The developer can be an organic solution, water, aqueous or semi-aqueous solution. When water is used as the developer, the water can contain a surfactant. The choice of developer will be related to the chemistry of the photosensitive resin to be removed. Suitable organic solution developers include aromatic or aliphatic hydrocarbons and aliphatic or aromatic halogenated hydrocarbon solutions, or mixtures of such solutions with suitable alcohols. Other organic solution developers are described in published German patent application 38 28 551 and US Pat. No. 5,354,645. Suitable semi-aqueous developers typically include water and water miscible organic solutions and alkaline materials. Suitable aqueous developers usually contain water and an alkaline material. Other suitable aqueous developer combinations are described in US Pat. No. 3,796,602.

  Development times can vary or are preferably in the range of about 2 to 25 minutes. The developer can be applied in any conventional manner including immersion, spraying and brush or roller application. Brushing aids can be used to remove unpolymerized portions of the composition. However, washout is often used in automatic processing units, which removes unexposed portions of the plate and uses a developer and mechanical brushing to leave a relief consisting of the exposed area and floor. Yes.

  After solution development, the relief printing plate is usually blotted or wiped dry and then dried in a forced air or infrared oven. The drying time and temperature vary, but typically the plate is dried at 60 ° C. for 60-120 minutes. High temperatures are not recommended because the support shrinks and positioning problems occur. Most flexographic printing plates have a uniform post-exposure to complete the photopolymerization process and to make the plate stable during printing and storage. In this post-exposure step, the same light source as the main exposure is used.

  Detackification (or photofinishing) is an optional post-development treatment that can be applied when the surface is still tacky and this tack is generally not removed by post-exposure. The tackiness can be removed by a conventionally well-known method such as treatment with bromo water or chlorine water. Such processing is described, for example, in Grueetzmacher US Pat. No. 4,400,459; Fickes et al. 4,400,460 and German Patent 28 23 300. Detackification can also be accomplished by exposure to a light source having a wavelength not longer than 300 nm, as shown in European Patent Application No. 0 017 927 and Gibson US Pat. No. 4,806,506. Achieved.

  These flexographic plates can be used particularly advantageously for the production of seamless, continuous flexographic plates. A photopolymerizable flat sheet-shaped flexographic plate is a continuous, seamless form that is wrapped in a cylindrical shape, usually a printing sleeve or the printing cylinder itself, and is fused together at both ends. Can be reprocessed by using a flexible flexo plate. In a preferred method, the photopolymerizable layer wraps around a cylindrical shape and bonds both ends. One method for joining these ends is shown in German Patent DE 28 44 426. This photopolymerizable layer can then be coated with at least one infrared sensitive layer, for example by spray coating.

Continuous printing flexographic plates have applications in continuous design flexographic printing, such as wallpaper, decoration and gift wrapping paper. Moreover, such continuous printing flexographic plates are optimal for mounting on ordinary laser equipment. A sleeve or cylinder over which it is wrapped with a printing flexographic plate and fused at both ends can be mounted directly into the laser apparatus, where it functions as a rotating drum during the laser exposure step.
Moreover, it has been found that the process of the present invention can be carried out with the plate attached in a cylindrical form, i.e., with the cylindrical body wrapped around. Therefore, image-like ablation, overall exposure, development, and additional steps can be performed while the plate is attached in a cylindrical shape. Other benefits that can be obtained using the present methods include increased processing speed, good plate alignment and reduced or sometimes eliminated loading time.

  Unless otherwise stated, the term “flexographic printing plate or flexographic plate” includes any form of plate, including, but not limited to, flat sheets and continuous forms suitable for flexographic printing. It also includes flexographic plates. All publications / literatures mentioned herein are incorporated by reference unless otherwise indicated.

Examples of the present invention are shown below, but the present invention is not limited thereto.
Using a flexographic printing plate having the following five types of photosensitive resins, a mask pattern was formed on the photosensitive resin layer with a carbon black-containing ink by an electrostatic ink jet method, and then exposed and developed.

(Photosensitive resin 1)
Du Pont's Cyrel (Cyrel (registered trademark)) flexographic plate, type 67HLS cover sheet and release layer were used.

(Photosensitive resin 2)
A Du Pont Cyrel (Cyrel (registered trademark)) flexographic plate, from which the type HOS45 cover sheet was removed, was used.

(Photosensitive resin 3)
A flexographic plate having an aqueous development type photosensitive resin layer prepared as follows was used without a cover sheet.

Abbreviations used in the following description are as follows:
Base 1 Diethylaminoethyl methacrylate BD Butadiene BHT Butylated hydroxytoluene DAM Dialne maleate, MTM Hardwick DDM Dodecyl mercaptan t-DDM Tertiary dodecyl mercaptan HMDA 1,6-hexanediol diacrylate HEC Hydroxyethyl cellulose HPC Hydroxypropyl cellulose Crucell (registered trademark) EF, Hercules initiator 2-phenyl-2,2-dimethoxyacetophenone polymerization inhibitor 2,3-diazabicyclo [3.2.2] non-2-ene,
1,4,4-trimethyl-N, N′-dioxide,
CAS No. 34122-40-2
Isopar V C14-C18 isoparaffinic hydrocarbon, CAS No. 64742-46-7, Exxon Corporation,
Roma PW Naphthalenesulfonic acid formaldehyde polymer, sodium salt, CAS No. 9084-06-4, Henkel MAA Methacrylic acid NaDDBS Sodium dodecylbenzenesulfonate NLA n-lauryl acrylate Piccotex R substituted polystyrene, Hercules PVP-VA poly (vinyl pyrrolidone / vinyl acetate)
Rod No. 0 Mixed oil used as an odor masking agent, R. Tee. Vanderbilt TBP Tributoxyethyl phosphate Tinuvin (registered trademark) 1130 Polyethylene glycol mono (2-2 (2H-benzotriazol-2-yl) -6-tert-butyl-4- (3-methoxy-3-oxypropyl) Phenyl) ether and polyethylene glycol bis (2-2 (2H-benzotriazol-2-yl) -6-tert-butyl-4- (3-methoxy-3-oxypropyl) phenyl) ether, Ciba Geigy TKPP pyrroline Acid tetrapotassium, Monsanto Vazo (registered trademark) 67 2,2 "-azo-bis (2-methylbutyronitrile), DuPont Zapon (registered trademark) 335 red pigment, CAS No. 73297-15-1
A flexographic plate having a photosensitive resin layer developable with water used a microgel binder prepared as follows:

I. Preparation of microgel binder A Preparation of aqueous phase solution The aqueous phase solution was composed of the following components.
Romer PW 56g
NaDDBS 239g
Deionized water 13093g
Romer PW and NaDDBS were added to water under a nitrogen atmosphere. Each ingredient was mixed until they melted.

B. Preparation of oil phase The oil phase solution was composed of the following components.
Styrene 1332g
DDM 56g
Bazo (registered trademark) 67 35 g
Isopar V 2244g
DAM 140g
DDM and DAM were dissolved in styrene under a nitrogen atmosphere. Subsequently, Vazo (registered trademark) 67 was added and dissolved. Isopar V was slowly added to the styrene solution in a nitrogen atmosphere.

C Preparation of oil emulsion Add the oil phase to the aqueous phase under a nitrogen atmosphere and keep the solution mixed. Then, using a Microfluidizer (registered trademark) M210 (Microfluidics), a particle size of 100 to 250 nm (Gaussian distribution, NICOMP submicron particle size analyzer) at 3000 to 6000 psi (211 to 422 kg / cm ² ), Homogenization until model 270, Pacific Scientific).

D Butadiene polymerization The following compositions were used for polymerization:
Deionized water 79.00 pounds Oil emulsion 52.00 pounds FeSO ₄ 0.02 g
TKPP 33.00g
BD 43.18 pounds FeSO ₄ and TKPP were dissolved in deionized water under a nitrogen atmosphere. An oil emulsion was added and placed in an autoclave. BD was added and the oil emulsion droplets were swollen with stirring for 1 hour. Subsequently, the temperature was raised to 60 to 65 ° C. to initiate the polymerization reaction. The polymerization was allowed to proceed until approximately 85% BD was polymerized.

The following components were mixed in advance and injected into the polymer when the polymerization rate of BD reached approximately 85%.
MAA 2.27 lbs t-DDM 0.65 lbs NaDDBS 0.31 lbs Deionized water 22.47 lbs

The reaction was allowed to proceed until approximately 90-95% of the total polymerization was complete. The resulting polymer Mooney viscosity was 65. The final particle size was 144 nm (Gaussian distribution, NICOMP submicron particle size analyzer, model 270, Pacific Scientific).
The emulsion was lyophilized to remove water. As a result, a solid microgel binder having a poly (butadiene / styrene) core and a poly (butadiene / methacrylic acid) shell was obtained. The% of MAA is 3.9%.

II. Preparation of photosensitive element including photosensitive resin layer capable of aqueous development The photosensitive resin layer 3 was prepared from the following components.
Microgel binder (prepared by AD) 65.1 parts by weight HMDA 4.0 parts by weight NLA 4.9 parts by weight Base 1 9.8 parts by weight TBP 4.9 parts by weight Initiator 3.0 parts by weight BHT 2 0.0 part by weight Polymerization inhibitor 0.1 part by weight Piccotex (registered trademark) 5.0 part by weight PVP-VA 1.0 part by weight Zapon (registered trademark) 335 0.01 part by weight Tinuvin (registered trademark) 1130 1 part by weight Rod (registered trademark) No. 1 0 0.1 parts by weight

The cover sheet was prepared by applying a layer of HPC and HEC mixture to a 5 mil (0.013 cm) thickness polyethylene terephthalate sheet at a coating weight of 20 mg / dm ² . The support was a 7 mil (0.018 cm) thick polyethylene terephthalate that was flame treated. Each component of the photosensitive resin layer was supplied into a 30 mm twin screw extruder that performs the functions of mixing, defoaming, and filtration of the composition. The material was extruded through a die at 135 ° C. into a rotating bank of a double roll calender and calendered between the support film and the cover sheet.

When forming a photomask, the above cover sheet was removed before use.
After formation of the photomask, the photosensitive element was exposed through a 3 minute surface exposure without vacuum, ie through the formed radiation opaque mask. The element was developed using a brush in a rotary processor and with tap water at ambient temperature for 10 minutes. The unpolymerized aqueous photosensitive layer was removed as expected. It was rinsed with fresh water and dried in an oven at 60 ° C. for 15 minutes. A good image was obtained.

A flexographic printing plate having an aqueous development type photosensitive resin layer prepared as follows was used without a cover sheet.
Abbreviations used in the following description indicate the following:
(Photosensitive resin 4)
AMA Allyl Metacrete
BD Butadiene
BHT 2,6-dimethyl-4-tert-butylphenol
Blue 3R-RF
90% of Macrolex (registered trademark) Blue RR, CI Solvent Blue 97 and Macrolex (registered trademark) Violet B, C.I. I. A mixture with 10% of Solvent Violet 13, both BMA butyl methacrylate from Mobay Chemical
CP-1216
Latex DDM dodecyl mercaptan with 2.8 parts poly (vinylidene chloride / itaconic acid / methyl acrylate) and 1 part poly (ethyl acrylate)
Day Resinate (registered trademark) 731
A modified resin, sodium soap, CAS No. 61790-51-0 70% aqueous solution, Hercules HEC hydroxyethyl cellulose, HEC WP-09-L, Union Carbide
HMDA 1,6-hexanediol diacrylate HPC hydroxypropylcellulose, Crucell (registered trademark) EF, manufactured by Hercules

Initiator 2-phenyl-2,2-dimethoxyacetophenone inhibitor 2,3-diazabicyclo [3.2.2] non-2-ene 4,4-trimethyl-N, N'-dioxide Isopearl V C14-C18 Isoparaffinic hydrocarbons manufactured by Exxon, CAS No. 64742-46-7
Romar PW Sodium salt of naphthalenesulfonic acid formaldehyde polymer, CAS No. 9084-06-4, 90% sodium sulfate, CAS No. 7757-82-6, 5% water CAS No. 5% of 7732-18-5
MAA Methacrylic acid
MMA methyl methacrylate
NaDDBS sodium dodecylbenzenesulfonate (22.5% aqueous solution)
76RES-P546 Vinylidene chloride / acrylate copolymer latex, manufactured by Unocal Chemical Co., Ltd. Resin 90 tall oil resin, CAS No. 8050-09-7, West Baco TKPP tetrapotassium pyrophosphate, Monsanto Tamol (registered trademark) SN Naphthalene sulfonic acid sodium salt, Rohm and Haas UV absorber 2- [3 ', 5'-bis ( 1-methyl-1-phenylethyl) -2'-hydroxyphenyl] benzotriazole Vazo (registered trademark) 67 2,2'-azo-bis (2-methylbutyronitrile), manufactured by DuPont

(Photosensitive resin 4)
The preparation of the composite binder used for the photosensitive resin 4 is shown below.
A. Preparation of aqueous phase solution The aqueous phase solution was composed of the following components.
Day Reginate 731 1298g
NaOH 38g
Tamor SN 282g
NaDDBS 1279g
69267 g of deionized water
Dayresinate 731 and NaOH were dissolved in water by bubbling nitrogen. NaDDBS and Tamol SN were added to this solution under a nitrogen atmosphere. Each component was mixed until they were dissolved.

B. Preparation of oil phase The oil phase solution is composed of the following components: 6711 g of styrene
DDM 282g
Baso 67 176g
Isopearl V 11304g
AMA 706g
DDM and AMA were dissolved in styrene under a nitrogen atmosphere. Subsequently, Vazo 67 was added and dissolved. Isopearl V was slowly added to the styrene solution under a nitrogen atmosphere.

C. Oil emulsion preparation The oil phase is added to the water phase under a nitrogen atmosphere and the solution is maintained in a mixed state. This was then used with a Microfluidizer (registered trademark) M210 (Microfluidics) at 3000 to 6000 pounds per square inch (210.9 to 421.8 kg / cm ² ), and a particle size of 100 to 250 nm (Brook Homogenized until measured).

D. Polymerization of butadiene The following components were used for the polymerization.
Deionized water 276.6 lbs Oil emulsion 201.2 lbs FeSO ₄ 0.06 g
TKPP 130.1g
BD 172.0 pounds FeSO ₄ and TKPP are dissolved in deionized water under a nitrogen atmosphere. An oil emulsion was added and placed in an autoclave. BD was added and the oil emulsion droplets were swollen with stirring for 1 hour. The temperature was raised to 60 ° -65 ° C. to initiate the polymerization reaction. The polymerization was allowed to proceed until approximately 90-95% BD conversion was complete. The resulting polymer had a Mooney viscosity of 69. The final particle size was 196 nm (determined by Gaussian distribution with a Pacific Scientific Nikon particle size analyzer model 270).

B. Polymer Stabilizer The polymer used is a groove transfer polymer composed of BMA (10 molecular units) / MMA (5 molecular units) / MAA (10 molecular units). This polymer was prepared in tetrahydrofuran (THF). To this was added 1-propanol and water to make a mixture of 13 parts polymer, 9 parts THF, 6 parts 1-propanol, and 70 parts water. Then 75% of the acid functionality was neutralized with KOH.

C. Composite Binder 135 g of polymer stabilizer solution (13% solids) was mixed with 1049 g of elastic latex (31.7% solids) for 24 hours. The obtained emulsion was freeze-dried at 0 ° C. or lower to remove water. A solid composite binder of butadiene / styrene copolymer elastomer with adsorbed BMA / MMA / MAA polymer stabilizer was obtained.

The photosensitive resin layer 4 was prepared from the following components.
Composite binder 88.2 parts by weight HMDA 10 parts by weight Initiator 1.2 parts by weight BHT 0.5 part by weight Inhibitor 0.1 part by weight The above components were mixed on a 2-roll mill at 115 to 120 ° C for 8 minutes. The cover sheet was prepared by applying a layer of a mixture of 1 part HEC and 1 part HPC at a coating weight of 20 mg / dm ² on a 5 mil (0.013 cm) thick polyethylene terephthalate sheet.

The support contained 0.24% UV absorbers and 0.57% blue 3R-RF, and a 7 mil (0.018 cm) Cronar R polyethylene terephthalate support sheet coated with CP-1216 in an amount of 0.1%. It was prepared by applying a first layer of 8 mg / dm ^{2 and} a second layer of 76 RES P546 with a coating amount of 70 mg / dm ² . The mixed photosensitive composition is placed between the support and the cover sheet and placed in a hydraulic machine at 140 ° C. and the total thickness (photosensitive layer + support + cover sheet) is 112 mils (0.28 cm). It compression-molded so that it might become.

(Photosensitive resin 5)
The preparation of the hydrophilic binder used for the photosensitive resin 5 is described below.
The number of parts used in the following examples is parts by weight, and the number average molecular weight unless otherwise specified is a value obtained by combining the viscosity measurement method and the GPC method. The relative viscosity [ηr] is measured at 25 ° C. by dissolving the polymer in 98% sulfuric acid at a rate of 1 g / 100 cc.

  Below, the synthesis example of the hydrophilic polymer used for the photosensitive resin 5 is demonstrated.

  Synthesis Example A-1 <Synthesis of Polyamide Having Ether Bond> ε-Caprolactam / hexamethylenediamine and equimolar salt of adipic acid / α, ω-diaminopropyl polyoxyethylene (number average molecular weight 1000) and equimolar of adipic acid Copolymerized polyamide was obtained from the salt (20/20/60 weight ratio).

The terminal groups of the copolymerized polyamide obtained here were quantified to be primary amino groups 4.0 × 10 ⁻⁵ mol / g and carboxyl groups 2.1 × 10 ⁻⁵ mol / g. The number average molecular weight was approximately 33,000. This polymer had the property of dissolving in water at 25 ° C.

  A-2 <Synthesis of polyamide having sulfonic acid group in side chain> 113 g of ε-caprolactam, 17.6 g of hexamethylenediamine and 66 g of α-aminocaproic acid were charged into an autoclave, and after nitrogen substitution, the contents were heated at 230 ° C. The reaction was performed for 3 hours. After cooling, 244 g of 3-hydroxy-butanesulfonic acid lactone and 13.8 g of potassium sulfate were added to the reaction mixture, and after substitution with nitrogen, the mixture was reacted again at a temperature of 230 ° C. for 1 hour to obtain a copolymerized polyamide. This polymer had the property of dissolving in water at 25 ° C.

A-3 <Synthesis of polyamide having piperazine skeleton> N, N'-di (γ-aminopropyl) piperazine adipate 50 parts, ε-caprolactam 30 parts and water 20 parts were charged in an autoclave, purged with nitrogen and sealed. Heat gradually. When the internal pressure reached 10 kg / cm ² , water was distilled off until the pressure could not be maintained, returned to normal pressure in about 2 hours, and then reacted at normal pressure for 1 hour. The maximum polymerization reaction temperature was 255 ° C. The obtained polymer was a transparent light yellow polyamide having a softening point of 90 to 105 ° C. and [ηr] 2.3. This polymer had the property of dissolving in water at 25 ° C.

A-4 <Synthesis of polyamide having amino group in side chain>
90 parts of α-dimethylamino-ε-caprolactam and 10 parts of water are charged into an autoclave, purged with nitrogen, sealed and gradually heated. From the time when the internal pressure reached 3.5 kg / cm ² , water was distilled until the pressure could not be maintained, returned to normal pressure in about 2 hours, and then reacted at normal pressure for 2 hours. The maximum polymerization reaction temperature was 260 ° C. [Ηr] of the obtained polymer was 2.5. This polymer had the property of dissolving in water at 25 ° C.

  Photosensitive resin 5 20 parts of the copolymerized polyamide obtained in Synthesis Example A-1 above and 80 parts of carboxyl group-modified nitrile butadiene rubber (Nipol 1072 number average molecular weight 500000, manufactured by Nippon Zeon Co., Ltd.) are operated at 180 ° C. A molten mixture was obtained using a closed mixer.

  Moreover, the form of this molten mixture was observed with a scanning electron microscope (JEOL JSM-T300, measurement condition: reflected electron composition image). As a result of the observation, it was confirmed that the A-1 polymer had a sea-island dispersion structure in which the carboxylated nitrile butadiene rubber was an island and the diameter was in the range of 0.5 to 4 microns.

  60 parts of this molten mixture was heated and dissolved at 160 ° C. in 160 parts by weight of a mixed solvent of ethanol / water = 60/40 (parts by weight).

  Next, 2 parts by weight of glycidyl methacrylate was added and reacted at 80 ° C. for 1 hour to react the amino group and carboxyl group at the end of the polyamide with the epoxy group of glycidyl methacrylate to introduce a methacryloyl group at the end of the polyamide. Then, 30 parts by weight of β-hydroxyethyl-β′-acryloyloxyethyl phthalate is added as a photopolymerizable unsaturated compound, 2 parts by weight of dimethylbenzyl ketal as a photopolymerization initiator, and a thermal polymerization inhibitor hydroquinone monomethyl ether. 1 part by weight and 6 parts by weight of sodium methylenebisnaphthalene sulfonate were added and sufficiently stirred and mixed.

The solution made of the photosensitive resin composition thus obtained is flowed on a 100 μm thick polyester substrate on which a polyester adhesive has been applied and cured in advance so that the photosensitive layer has a thickness of 1700 μm. The solid flexographic printing plate having a compression strength of 4 kg / cm ² was obtained.

  Moreover, the form of this plate material was observed with the scanning electron microscope (JEOL JSM-T300, measurement conditions: reflection electron composition image). As a result of the observation, it has a sea-island dispersion structure consisting of a sea composed of A-1 polymer and a photopolymerizable unsaturated compound and an island of carboxylated nitrile butadiene rubber, and its diameter is in the range of 0.5 to 4 microns. It was confirmed that there was.

(Photosensitive resin layer 6)
A Du Pont Cyrel (Cyrel (registered trademark)) flexographic printing plate, type HOS45 cover sheet was used without removal.

<Creation of ink composition>
10 g of carbon black pigment (MA-200RB manufactured by Mitsubishi Chemical Corporation) and 20 g of the coating agent [AP-1] are put into a table kneader PBV-0.1 manufactured by Irie Shokai Co., Ltd., and the heater temperature is set to 100 ° C. for 2 hours. Heat mixed. 30 g of the obtained mixture was coarsely pulverized with a trio-brender manufactured by Trio Science Co., Ltd., and further finely pulverized with a SK-M10 type sample mill manufactured by Kyoritsu Riko Co., Ltd. 30 g of the obtained finely pulverized product was predispersed in a paint shaker manufactured by Toyo Seiki Seisakusho together with 7.5 g of the dispersant [BZ-2], 75 g of Isopar G, and glass beads having a diameter of about 3.0 mm. After removing the glass beads, together with zirconia ceramic beads having a diameter of about 6.0 mm, a type KDL dynomill manufactured by Shinmaru Enterprises Co., Ltd. was used for 5 hours while maintaining the internal temperature at 25 ° C., followed by 8 hours at 45 ° C. Dispersion (particle formation) was performed at a rotational speed of 000 rpm. The zirconia ceramic beads were removed from the obtained dispersion, and 316 g of Isopar G and 0.6 g of the charge adjusting agent [CT-1] were added to obtain an ink composition. The physical properties of the ink composition were as follows.

The electrical conductivity at 20 ° C. of the ink composition was determined using an LCR meter (AG-4311 manufactured by Ando Electric Co., Ltd.) and an electrode for liquid (LP-05 type manufactured by Kawaguchi Electric Manufacturing Co., Ltd.) with an applied voltage of 5V. When measured under the condition of a frequency of 1 kHz, it was 100 nS / m.
After the ink composition is centrifuged for 30 minutes at a rotational speed of 14,500 rpm and a temperature of 20 ° C. using a small high-speed cooling centrifuge (Tomy Seiko Co., Ltd. SRX-201), the charged particles are precipitated. The electrical conductivity of the supernatant was measured and found to be 30 nS / m. The electric conductivity of the charged particles was 70 nS / m, which was 70% with respect to the electric conductivity of the ink composition. The charged particles were positively charged.
The volume average diameter of the charged particles was measured with a CAPA-700 manufactured by HORIBA, Ltd. at a rotation speed of 5,000 rpm, and was 2.0 μm. The number average diameter was 0.15 μm.
The viscosity at 20 ° C. of the ink composition was measured with an E-type viscometer manufactured by Tokyo Keiki Co., Ltd. and found to be 1.5 mPa · s. Further, the surface tension of the ink composition at 20 ° C. was measured with a FACE automatic surface tension meter manufactured by Kyowa Interface Science Co., Ltd. and found to be 25 mN / m.
The chemical structural formulas of the coating agent [AP-1], the dispersant [BZ-2] and the charge control agent [CT-1] used for preparing the ink composition are shown below.

Example 1
An image mask having a gradation range of 2 to 95% (120 lines / inch, screen) was formed on the photosensitive resin 1 by an electrostatic ink jet printer using the above-described carbon black-containing oil-based ink.
The resulting masked flexographic plate was removed from the ink jet apparatus and subjected to a 14 second backflash exposure with a Cyrel 3040 light source, followed by a 9 minute surface exposure at 50 mm Hg vacuum through a radiation opaque patterned mask.
The exposed element was developed for 6 minutes in a Cyrel Rotarys processor using a 3: 1 mixture (volume / volume) of parkrene and butanol. After ablation of the image-like mask, the unexposed areas of the photosensitive resin were removed and a relief printing plate was formed. The printing plate was oven-dried at 60 ° C. for 1 hour, and then post-exposure and finishing were simultaneously performed for 5 minutes in a silel light finishing unit to obtain a flexographic printing plate.
Printing was performed using the Mark Andy Press System 830 with this printing plate, and film III Dens Black EC 8630 ink (available from Environmental Ink and Coating Co., Ltd.) was measured using a Zahn No. 2 cup and diluted to a viscosity of 27 seconds. Used. A good printed image was obtained.
The reproducibility of image quality was evaluated.

(Example 2)
The same operation as in Example 1 was performed except that the photosensitive resin 2 was used instead of the photosensitive resin 1.

(Example 3)
An image-like mask having a gradation range of 2 to 95% (120 lines / inch, screen) was formed on the photosensitive resin 3 by an electrostatic ink jet printer.
The resulting masked flexographic printing plate was removed from the ink jet apparatus and given a 14 second backflash exposure with a Siler 3040 light source, followed by a 9 minute surface exposure without vacuum through a radiation opaque patterned mask. .
The exposed element was developed for 10 minutes using tap water in a Cyrel Rotarys processor. After ablation of the mask pattern, it was removed from the unexposed area of the photosensitive resin layer, and a relief printing plate was formed. The printing plate was oven-dried at 60 ° C. for 15 minutes, and then post-exposure and finishing were simultaneously performed for 5 minutes in a silel light finishing unit to obtain a flexographic printing plate.
Using the obtained flexographic printing plate, printing was performed with a flexographic printing machine, and the reproducibility of image quality was evaluated.

Example 4
The same operation as in Example 3 was performed except that the photosensitive resin layer 4 was used instead of the photosensitive resin layer 3.

(Example 5)
The same operation as in Example 3 was performed except that the photosensitive resin layer 5 was used instead of the photosensitive resin layer 3.

(Example 6)
The same operation as in Example 1 was performed except that the photosensitive resin layer 6 was used instead of the photosensitive resin layer 1.

(Comparative Example 1)
As a photosensitive resin layer, using Du Pont's Cyrel (Cyrel (registered trademark)) flexographic plate, type 67HLS, and placing a lith film having a gradation range of 2 to 95% (120 lines / inch, screen), Full surface exposure and development were performed in the same manner as in Example 1 to obtain a flexographic printing plate.

(Comparative Example 2)
As the photosensitive resin layer, Du Pont's Cyrel (Cyrel (registered trademark)) flexographic plate, FAST was used, and the mask layer was ablated with an infrared laser of 830 nm, and the floor was 2 to 95% (120 lines / inch, screen). An image-like mask having an adjustment area was formed, and the entire surface was exposed and developed in the same manner as in Example 1 to obtain a flexographic printing plate.

Using the obtained flexographic printing plate, printing was performed with a flexographic printing machine, and the reproducibility of image quality was confirmed.
Regarding the running cost, the plate material, electricity cost, waste processing fee such as developer when 1000 plate was used were calculated and estimated as relative costs.
Table 1 shows the printing evaluation results of the flexographic printing plates obtained in Examples 1 to 6 and Comparative Examples 1 and 2.
Evaluation was performed as follows.
(image quality)
A: 2 to 95% of gradation similar to the mask can be reproduced.
Δ: A gradation of 3 to 95% can be reproduced.
X: 4 to 95% of gradation can be reproduced (reproducibility is poor).
(running cost)
○: Less expensive than convex flexo system (reduction of squirrel film related processes)
×: Cost more than convex flexo system

以上の結果より、本発明のフレキソ印刷版の製版方法は、コンベフレキソ版をフレキソＣＴＰに変える新しい方法であり、さらにユーザーメリットとして高画質化とランニングコスト低下を両立できるシステムであることが分かった。

From the above results, it was found that the flexographic printing plate making method of the present invention is a new method for changing a convex flexo plate to flexo CTP, and is a system that can achieve both high image quality and low running cost as user merit. .

(Example 7)
<Creation of ink composition>
10 g of the carbon black pigment of Table 2 and 20 g of the coating agent [AP-1] were put into a table kneader PBV-0.1 manufactured by Irie Shokai Co., Ltd., the heater temperature was set to 100 ° C., and the mixture was heated and mixed for 2 hours. 30 g of the obtained mixture was coarsely pulverized with a trio-brender manufactured by Trio Science Co., Ltd., and further finely pulverized with a SK-M10 type sample mill manufactured by Kyoritsu Riko Co., Ltd. 30 g of the obtained finely pulverized product was predispersed in a paint shaker manufactured by Toyo Seiki Seisakusho together with 7.5 g of the dispersant [BZ-2], 75 g of Isopar G, and glass beads having a diameter of about 3.0 mm. After removing the glass beads, together with zirconia ceramic beads having a diameter of about 6.0 mm, a type KDL dynomill manufactured by Shinmaru Enterprises Co., Ltd. was used for 5 hours while maintaining the internal temperature at 25 ° C., followed by 8 hours at 45 ° C. Dispersion (particle formation) was performed at a rotational speed of 000 rpm. The zirconia ceramic beads were removed from the obtained dispersion, and 316 g of Isopar G and 0.6 g of the charge adjusting agent [CT-1] were added to obtain an ink composition. The physical properties of the ink composition were as follows.

The electrical conductivity at 20 ° C. of the ink composition was determined using an LCR meter (AG-4311 manufactured by Ando Electric Co., Ltd.) and an electrode for liquid (LP-05 type manufactured by Kawaguchi Electric Manufacturing Co., Ltd.) with an applied voltage of 5V. When measured under the condition of a frequency of 1 kHz, it was 100 nS / m.
After the ink composition is centrifuged for 30 minutes at a rotational speed of 14,500 rpm and a temperature of 20 ° C. using a small high-speed cooling centrifuge (Tomy Seiko Co., Ltd. SRX-201), the charged particles are precipitated. The electrical conductivity of the supernatant was measured and found to be 30 nS / m. The electric conductivity of the charged particles was 70 nS / m, which was 70% with respect to the electric conductivity of the ink composition. The charged particles were positively charged.
The volume average diameter of the charged particles was measured with a CAPA-700 manufactured by HORIBA, Ltd. at a rotation speed of 5,000 rpm, and was 2.0 μm. The number average diameter was 0.15 μm.
The viscosity at 20 ° C. of the ink composition was measured with an E-type viscometer manufactured by Tokyo Keiki Co., Ltd. and found to be 1.5 mPa · s. Further, the surface tension of the ink composition at 20 ° C. was measured with a FACE automatic surface tension meter manufactured by Kyowa Interface Science Co., Ltd. and found to be 25 mN / m.
The chemical structural formulas of the coating agent [AP-1], the dispersant [BZ-2], and the charge control agent [CT-1] used for preparing the ink composition are as described above.

Using inks using various carbon blacks as pigments, the same operations as in Example 1 were performed to evaluate the mask image formability.
A mask having a sufficiently high optical density could be formed by landing the oil-based ink twice.
The results are shown in Table 2.

表中、マスク形成性とは、１回の描画での画像濃度を意味する。画像濃度としては、２．０以上が好ましく、３．０以上がより好ましく、４．０以上が特に好ましい。
以上の結果より、高抵抗のカーボンブラックを用いたときに、良好なマスク画像濃度が得られることが分かった。また、３００時間描画後でもヘッド電極の洗浄は不要であった。

In the table, the mask forming property means the image density in one drawing. The image density is preferably 2.0 or more, more preferably 3.0 or more, and particularly preferably 4.0 or more.
From the above results, it was found that a good mask image density can be obtained when high resistance carbon black is used. Moreover, it was not necessary to clean the head electrode even after 300 hours of drawing.

(Example 8)
(Resin 1)
When preparing the photosensitive resin layer 1, 5% by weight of betaine (chemical structure is shown below) as an antistatic agent was added to the total amount of the photosensitive resin layer composition.

（樹脂２）
感光性樹脂層１を作成する際に、感光性樹脂層全組成物量に対し、帯電防止剤としてベタインを２重量％添加した。
（樹脂３）
感光性樹脂層１をそのまま用いた。
上記樹脂１〜３を感光性樹脂層として用い、実施例１と同様の操作を行い、感光性樹脂層の表面抵抗値と帯電安定性、帯電均一性及び描画性の関係について評価した。

(Resin 2)
When preparing the photosensitive resin layer 1, 2% by weight of betaine was added as an antistatic agent with respect to the total amount of the photosensitive resin layer composition.
(Resin 3)
The photosensitive resin layer 1 was used as it was.
Using the above resins 1 to 3 as the photosensitive resin layer, the same operation as in Example 1 was performed, and the relationship between the surface resistance value of the photosensitive resin layer, the charging stability, the charging uniformity, and the drawing property was evaluated.

Evaluation was performed as follows.
(Charge stability)
○: Surface potential of flexographic plate after standing for 1 minute after charging / surface potential of flexographic plate immediately after charging × 100 (%) is 90% or more and less than 95% ◎: Flexographic plate after standing for 1 minute after charging Surface potential / surface potential of flexographic plate immediately after charging × 100 (%) is 95% or more (Charging uniformity)
○: Surface potential fluctuation on the entire surface of the flexographic plate is 10% or less ×: Surface potential variation on the entire surface of the flexographic plate exceeds 10% (drawing property)
Good: Unevenness cannot be confirmed by visual observation from a position 30 cm away.

  The results are shown in Table 3.

以上の結果より、感光性樹脂層の表面抵抗値が２×１０¹⁰Ω／□以上であるときに良好な帯電安定性、帯電均一性及び描画性が得られることがわかった。

From the above results, it was found that when the surface resistance value of the photosensitive resin layer is 2 × 10 ¹⁰ Ω / □ or more, good charging stability, charging uniformity and drawing property can be obtained.

It is typical sectional drawing which shows an example of the electrostatic inkjet apparatus used for this invention. FIG. 2 is a cross-sectional view illustrating a detailed structure around an ejection head in FIG. 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electrostatic inkjet apparatus 10 Discharge head 12 Ink tank 14 Head drive driver 16 Charger 18 Static elimination device 20 Feed roller 22 Conveyance roller 24 Image fixing roller 26 Flexo plate stocker 28 Mask-formed flexo plate stocker 30 Solvent recovery means 32 Flexo plate 34 Ink chamber 35 Ink flow direction 36 Discharge portion 38 Insulating ink guide 50 First discharge electrode 52 Second discharge electrode 54 Guard electrode 56 Electrophoresis electrode 58 Shield electrode 59 Back electrode 80 Ink droplet 81 Ink droplet landed on the flexographic plate d Gap between the insulating ink guide 38 and the flexographic plate 32 on the back electrode 59

Claims (7)

  An image mask is formed by discharging oil-based ink containing colored particles that absorb or reflect light to be exposed onto a photosensitive resin layer provided on a support by an electrostatic ink jet method, and then through the image mask. A method for making a flexographic printing plate by exposing and developing the photosensitive resin layer, wherein the photosensitive resin layer is at least one of photopolymerizable and photocrosslinkable.   The plate making method according to claim 1, wherein the oil-based ink is obtained by dispersing charged particles containing a pigment in an insulating organic solvent.   The plate making method according to claim 2, wherein the charged particles have a charge amount of 5 to 200 μC / g.   The plate making method according to claim 2 or 3, wherein the pigment is high-resistance carbon black.   The plate making method according to any one of claims 1 to 4, wherein when forming an image mask on the photosensitive resin layer, the discharged oil-based ink is landed by overlapping a plurality of times. The plate making method according to claim 1, wherein the surface resistance of the photosensitive resin layer is 1 × 10 ¹⁰ Ω / □ or more.   The plate making method according to any one of claims 1 to 6, wherein the photosensitive resin layer has an elastomeric binder, at least one monomer, and a photopolymerization initiator as essential components.

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