JP2000155410A - Photosensitive structure for flexographic printing plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a photosensitive structure for a flexographic printing plate with an easily workable and inexpensive superior adhesive layer having such high stable adhesive strength as to cause no hindrance even under actual printing conditions between a photosensitive resin layer and its polyester film substrate. SOLUTION: A photosensitive resin layer containing a thermoplastic elastomer consisting of a monovinyl substituted aromatic hydrocarbon and conjugated diene, at least one ethylenically unsaturated compound and a photoinitiator system is laminated on a substrate by way of an adhesive layer to obtain the objective photosensitive structure for a flexographic printing plate. The adhesive layer comprises a reaction product of polyol and a multifunctional isocyanate having a polyester structure and/or a polyurethane structure, the substrate is a polyester film and the ethylenically unsaturated compound in the photosensitive resin has two unsaturated bonds in one molecule.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flexographic printing plate photosensitive composition used for making a flexographic printing plate.

[0002]

2. Description of the Related Art A photosensitive composition for a flexographic printing plate generally comprises a support of a polyester film and a photosensitive resin layer provided thereon. The procedure for making a flexographic printing plate is as follows: First, the entire surface is exposed to ultraviolet light (back exposure) through a support, and a thin uniform cured layer is provided.
Next, after performing image exposure (relief exposure) on the surface of the photosensitive resin layer through a negative film, an unexposed portion is washed away with a developing solvent to form a desired image, that is, a relief image to obtain a printing plate. ing.

[0003] The obtained plate is fixed to the plate cylinder of a printing press by a double-sided tape or vacuum evacuation, and is used for printing. Due to the shear stress between the plate cylinder and the impression cylinder during printing, The support and the cured resin layer must not peel off. Also,
After printing is completed, the printing plate is removed from the plate cylinder in order to store it for printing again, even if a large force is applied to the cured resin layer in order to peel off the cured resin layer at that time It is necessary that the printing plate is firmly adhered to the support without being damaged.

[0004] For this purpose, good adhesion between the support and the photosensitive resin layer is required.
When the film is forcibly peeled at an angle of? From such a viewpoint, it is common to provide an adhesive layer between the support and the photosensitive resin layer, thereby strengthening the adhesion between the support and the photocurable resin layer.

[0005] However, generally, there is a large difference in polarity between the polyester film as the support and the photosensitive resin layer, and there are only very limited adhesives having an affinity for both. It is. Moreover, since the adhesive layer having an affinity for the photosensitive resin layer is in direct contact with the photosensitive resin layer, the components in the photosensitive resin migrate into the adhesive layer over time, and as a result, the original adhesive It often happens that the function of is impaired.

When the initiator and the monomer of the photosensitive resin layer migrate into the adhesive layer, these monomers undergo polymerization in the adhesive layer during the exposure step, and due to the residual curing shrinkage stress at that time, the monomer adheres to the support. This causes a problem that interface separation easily occurs with the agent layer.

[0007] Therefore, the adhesives between the polyester film of the support and the photosensitive resin, which have been used so far, are often prepared by first providing a base layer on the surface of the polyester film and then applying the adhesive layer thereon. . For example, such an adhesive having a multilayer structure is also disclosed in JP-A-1-296252 and JP-A-5-94015.

However, these multi-layered adhesives are:
In addition to complicating the process of applying the adhesive, it is disadvantageous in terms of manufacturing cost, and further complicates the problem of component transfer between layers, so that stable adhesive strength cannot be expected. there were.

[0009]

According to the present invention, a photosensitive resin layer and a polyester film as a support thereof have an adhesive strength which is strong enough to cause no trouble even under actual printing conditions and is stable over time. Another object of the present invention is to provide a photosensitive composition for flexographic printing plates having an inexpensive adhesive layer that is easy to process.

[0010]

Means for Solving the Problems As a result of intensive studies on the above problems, the present inventors have found the following photosensitive structure for a flexographic printing plate which has solved the problems and completed the present invention.

That is, the present invention provides (a) a thermoplastic elastomer composed of (b) a support, (c) a monovinyl-substituted aromatic hydrocarbon and a conjugated diene via an adhesive layer, and at least one kind of ethylenically unsaturated compound. In the photosensitive composition for a flexographic printing plate in which a photosensitive resin layer containing a compound and a photoinitiator system is laminated, the adhesive layer of (1) (a) has a polyester structure or a polyurethane structure, or both structures. (2) The support of (b) is a polyester film, and the ethylenically unsaturated compound in the photosensitive resin of (3) and (c) is a reactant of the polyol. The present invention provides a photosensitive composition for flexographic printing plates, characterized by having two unsaturated bonds.

As the support, a dimensionally stable polyester film having a thickness in the range of 75 μm to 300 μm can be used. If necessary, a corona treatment, a flame treatment, or a chemical treatment with an alkali or the like may be applied to the surface of the film as a pre-treatment before applying the adhesive.

As the adhesive, a reaction product of a polyol having a polyester structure or a polyurethane structure, or both, and a polyfunctional isocyanate is used.

The polyol having a polyester structure is obtained by a polycondensation reaction with a dicarboxylic acid component in excess of a diol component. Examples of the diol component include diols having a straight-chain or branched aliphatic saturated hydrocarbon as a skeleton, bisphenol A and diol having a structure in which ethylene oxide is added to bisphenol A, polyoxyalkylene glycols, and these diol components. Can be used. On the other hand, as the dicarboxylic acid component, dicarboxylic acids, terephthalic acid, isophthalic acid having a skeleton of linear and branched aliphatic saturated hydrocarbons, and a mixture of these dicarboxylic acid components can be used.

The polyol having a polyurethane structure can be obtained by a polyaddition reaction with a diisocyanate compound under the excess of a diol component as described above. Tolylene diisocyanate as a diisocyanate compound,
Examples include 4,4-diphenylmethane diisocyanate, xylylene diisocyanate, hexamethylene diisocyanate, and mixtures of these diisocyanate compounds.

The polyol having both a polyester and a polyurethane structure can be obtained by reacting a polyol having a polyester structure synthesized in advance with an excess amount of a diisocyanate compound.

The adhesive layer interposed between the support and the photosensitive resin layer used in the present invention is prepared by dissolving the above-mentioned reaction product of the polyol and the polyfunctional isocyanate in an appropriate solvent, coating the support on the support, and drying. Can be obtained.

Here, when the molecular weight of the polyol is low,
The tackiness of the reaction product with the polyfunctional isocyanate increases,
The handling property after coating on the support is impaired. On the other hand, from the viewpoint of the reactivity with the polyfunctional isocyanate, there is a problem that if the molecular weight is too large, the urethane-forming reaction becomes slow. From this, it is preferable that the number average molecular weight of the polyol is 10,000 to 100,000 as measured by gel permeation chromatography in terms of polystyrene.

Examples of the polyfunctional isocyanate include tolylene diisocyanate, 4,4-diphenylmethane diisocyanate, xylylene diisocyanate, hexamethylene diisocyanate, and pentaerythritol, trimethylol, Examples include compounds obtained by an addition reaction with a polyfunctional alcohol such as propane.

The application of the adhesive to the support can be performed, for example, by the following procedure. That is, for 100 parts of the polyol component, an adhesive consisting of 1 to 20 parts of a polyfunctional isocyanate is dissolved in an organic solvent such as ethyl acetate, methyl ethyl ketone, tetrahydrofuran, or toluene or a mixture thereof, and supported using a bar coater or a gravure coater. The composition is uniformly coated on a polyester film as a body, and then dried at 80 to 100 ° C. for several tens seconds to several minutes to form an adhesive layer. At this time, an ultraviolet absorber, a dye, or the like can be added to the adhesive layer as needed for the purpose of imparting an antihalation effect. The coating amount of the adhesive after drying is usually 5 to 30 g / m ² . After that, it is left at 40 to 50 ° C. for several days in order to advance the urethane-forming reaction in the adhesive layer.

The relief body obtained by imagewise exposing the photosensitive resin layer must have the characteristics required for a flexographic printing plate. That is, it must exhibit good printing performance even on a printing medium such as a cardboard or a soft plastic film. Examples of the binder polymer of the photosensitive resin layer having such properties include:
Styrene-butadiene-styrene block copolymer,
A thermoplastic elastomer composed of a monovinyl-substituted aromatic compound represented by a styrene-isoprene-styrene block copolymer and a conjugated diene is exemplified.

Further, if necessary, a polyamide or a polyurethane having a hydrophilic functional group can be used in combination. In order for the mechanical properties of the finally obtained flexographic plate to be at a practical level, these binder polymers are usually used in an amount of 50 to 95% based on the entire photosensitive resin.
Accounts for% by weight.

The monomer includes at least one compound having two ethylenically unsaturated bonds in its molecule, such as hexanediol di (meth) acrylate and nonanediol di (meth) acrylate. Among these monomers, from the viewpoint of better adhesive strength, a diacrylate compound is preferable, and a compound having a structure represented by the following formula (1) is more preferable.

[0024]

Embedded image

These monomers are used for the entire photosensitive resin.
The desired effect can be obtained by using it in the range of 1 to 10% by weight. In addition to the above monomers, if necessary, alcohols such as t-butyl alcohol and lauryl alcohol and esters of acrylic acid and methacrylic acid, and maleimide derivatives such as laurylmaleimide, cyclohexylmaleimide and benzylmaleimide, or alcohols such as dioctylfumarate And fumaric acid esters.

As the photoinitiator, known radical polymerization initiators such as aromatic ketones and benzoin ethers such as benzophenone, Michler's ketone, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, α-methylol benzoin methyl ether, It can be selected from α-methoxybenzoin methyl ether, 2,2-diethoxyphenylacetophenone and the like, and used in combination.

Further, additives such as a sensitizer, a thermal polymerization inhibitor, a plasticizer, and a coloring agent can be contained according to the characteristics required for the photosensitive resin layer.

The photosensitive composition used in the present invention can be prepared by various methods. For example, the raw materials to be blended are dissolved in a suitable solvent, for example, a solvent such as chloroform, tetrachloroethylene, methyl ethyl ketone, and toluene, mixed and cast into a mold, and the solvent is evaporated to form a plate as it is. be able to. Also, without using a solvent, the mixture can be kneaded by a kneader or a roll mill and formed into a plate having a desired thickness by an extruder, an injection molding machine, a press or the like.

Since the photosensitive resin layer has tackiness depending on its composition, in some cases, it is necessary to improve the contact with a transparent image carrier to be superimposed thereon during plate making, or to reuse the transparent image carrier. A thin film of polyethylene, polypropylene, polyester, polystyrene or the like is laminated on the surface of the resin layer in order to enable the above. The film is peeled off after exposure through the transparent image carrier overlaid thereon.

Instead of film for a similar purpose,
A thin flexible protective layer which is soluble in a developing solution (for example, see Japanese Patent Publication No. 5-13305) may be provided. In this case, when the unexposed portion is washed out after the exposure through the transparent image carrier is completed, the thin flexible protective layer is also removed at the same time.

When a thin flexible protective layer soluble in a developing solution, for example, a layer of a polyamide, partially saponified polyvinyl acetate, cellulose ester or the like soluble in the developing solution is to be provided on the surface of the photosensitive resin layer. May be dissolved in an appropriate solvent and the solution may be directly coated on the photosensitive resin layer, or once coated on a film of polyester, polypropylene, etc. (protective film), and then this protective film is laminated on the photosensitive layer. Alternatively, the protective film may be transferred by press bonding.

The support or the protective film to which the adhesive has been applied is usually adhered to the photosensitive layer by roll lamination after sheet formation of the photosensitive resin composition. When the laminate is heated and pressed after lamination, a photosensitive resin layer having higher thickness accuracy can be obtained.

The ultraviolet light source used for photo-curing the photosensitive resin layer includes a high-pressure mercury lamp, an ultraviolet fluorescent lamp, a carbon arc lamp, a xenon lamp, and sunlight.

A desired relief image can be obtained by exposing the photosensitive resin layer to ultraviolet rays through a transparent image carrier. However, in order to further strengthen the adhesion between the support and the photosensitive resin layer, a relief image is further required. In order to make the image more stable against the stress when the uncured portion is washed out, it is effective to perform the entire surface exposure from the side of the support. Either the exposure from the transparent image carrier side or the exposure from the support side may be performed first, or both may be performed simultaneously, but from the viewpoint of image reproducibility, from the support side. Exposure is preferably performed first. .

After irradiating the photosensitive resin layer with ultraviolet rays through a transparent image carrier to form an image, the developing solvent used to wash out the unexposed portions is, for example, 1,1,1-.
Chlorinated organic solvents such as trichloroethane and tetrachloroethylene, esters such as heptyl acetate and 3-methoxybutyl acetate, petroleum fractions, hydrocarbons such as toluene and decalin, and alcohols such as propanol, butanol and pentanol And mixtures of the same.

Further, as the aqueous developer, a mixed solution of water and alcohol, water to which a surfactant is added, and the like can be used. Unexposed portions are washed out by spraying from a nozzle or by brushing with a brush. The obtained printing plate is rinse-washed, dried and post-exposed to finish.

[0037]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

[0038]

EXAMPLES Example 1 (1) Preparation of support 624 g of neopentyl glycol, 93 g of ethylene glycol, 485 g of sebacic acid, and 382 of isophthalic acid
g in an air atmosphere at a reaction temperature of 180 ° C. under a reduced pressure of 10 mmHg for 6 hours, and then 87 g of tolylene diisocyanate was added, followed by a further reaction at 80 ° C. for 5 hours. When the number average molecular weight of the obtained polyol was measured by gel permeation chromatography, it was about 32,000 in terms of polystyrene.

To 15 parts of this polyol, 1 part of xylylene diisocyanate was added to 45 parts of ethyl acetate to form a uniform solution, and the coated amount after drying was 10-14 g / m ² on a polyester film having a thickness of 125 μm. Was applied using a knife coater so that 80 ℃
For 2 minutes, and then left in an atmosphere of 40 ° C. for 3 days to obtain a support having an adhesive layer.

(2) Preparation of photosensitive composition for flexographic plate The photosensitive resin composition shown in Table 1 was kneaded with a kneader.
The support obtained in (1) is sandwiched between a 100 μm-thick polyester film having a 4-6 μm-thick polyamide (Macromelt 6900, manufactured by Henkel Hakusui) protective layer so that the protective film and the photosensitive resin are in contact with each other. Using a 3 mm spacer, press machine at 130 ° C. for 4 minutes, 20 minutes
Pressure molding was performed by applying a pressure of 0 kg / cm ² to obtain a photosensitive composition for flexographic printing plates.

[0041]

[Table 1]

A 100 μm polyester film was peeled off from the obtained flexographic printing plate photosensitive composition, and a transparent image carrier was stuck on a polyamide protective film layer on a photosensitive resin layer, and an AFP-1500 exposure machine ( Using an ultraviolet fluorescent lamp having a center wavelength of 370 nm on a surface of the support, the entire surface was first exposed to 300 mJ / cm ² from the support side, and then passed through a transparent image carrier.
Image exposure of 00 mJ / cm ² was performed.

At this time, the exposure intensity was set to U
Using a UV illuminometer MO-2 machine and a UV-35 filter, the intensity of ultraviolet light from the lower lamp, which is the side for back exposure, measured on a glass plate was 4.0 mW / cm ² ,
The measured intensity of ultraviolet light from the upper lamp on the relief exposure side was 7.8 mW / cm ² .

Then, AFP-15 was prepared using tetrachloroethylene / n-butanol (3/1: volume ratio) as a developing solution.
The plate was attached to a rotating cylinder of a No. 00 developing machine (made by Asahi Kasei Kogyo Co., Ltd.) with a double-sided tape, developed at a liquid temperature of 25 ° C. for 5 minutes, dried at 60 ° C. for 1 hour, and post-exposed to prepare a flexographic printing plate. Obtained.

In this flexographic plate, the adhesion between the support and the cured resin layer is strong, and the support is forcibly peeled off from the sample obtained by cutting the cured resin layer into a 1 cm-wide strip, and the support is peeled off using a tensile tester. When the support and the resin layer were peeled off at an angle of 50 mm / min at an angle of 1.1 °, 1.1 to 1.
An adhesion of 4 kg / cm was observed.

When printing was performed on a polyethylene film using an ink containing about 15 vol% of an acetic ester, the support and the cured resin layer peeled off due to the shear stress between the plate cylinder and the impression cylinder. Without such, even if printing is completed and a large force is applied to the cured resin layer to peel off the cured resin layer to remove the printing plate fixed with double-sided tape from the plate cylinder, The printing plate was firmly adhered to the support without being damaged. Subsequently, the flexographic plate was stored for one month under the condition of 40 ° C., and was mounted on the printing press again for printing.
Again, peeling of the cured resin layer from the support was not observed.

Example 2 (1) Preparation of support 410 g of ethylene glycol, Newpol BPE-1
605 g of 00 (manufactured by Sanyo Kasei Corp., ethylene oxide-added bisphenol A, hydroxyl value: 168), 16 g of neopentyl glycol, 395 g of azelaic acid, 249 g of terephthalic acid, and 116 g of isophthalic acid in an air atmosphere at a reaction temperature of 180 ° C. and a reduced pressure of 10 mmHg. Under a condensation reaction for 6 hours, and the number average molecular weight in terms of polystyrene is about 6
1000 polyols (measured by gel permeation chromatography) were obtained.

To 15 parts of this polyol, 1 part of an adduct of tolylene diisocyanate (3 mol) of trimethylolpropane (1 mol) was added to 45 parts of ethyl acetate to form a uniform solution, which was then coated on a polyester film having a thickness of 125 μm. Was applied using a knife coater such that the coating amount after drying was 10-14 g / m ² . 80 ℃
For 2 minutes, and then left at 40 ° C. for 3 days to obtain a support having an adhesive layer.

(2) Preparation of photosensitive composition for flexographic printing plate Next, using the above-mentioned support and the photosensitive resin composition shown in Table 2, the photosensitive composition for flexographic printing was operated in the same manner as in Example 1. Was prepared, and a flexographic plate was made through exposure-to-post-exposure steps. In this flexographic plate, the adhesion between the support and the cured resin layer was strong. The adhesion was measured with a tensile tester while the support was forcibly peeled off from the cured resin layer and peeled at an angle of 180 °. 0.2 to 1.6 kg /
cm adhesion was observed.

The same printing as in Example 1 was carried out.
In this case as well, the support and the cured resin layer do not peel off due to the shear stress between the plate cylinder and the impression cylinder, and further, printing is completed and the printing plate fixed with double-sided tape is removed from the plate cylinder. Even when a large force was applied to the cured resin layer to remove the cured resin layer in order to remove it, the printing plate was not damaged and was firmly adhered to the support. Subsequently, the flexographic plate was stored at 40 ° C. for one month, and mounted on a printing machine again for printing. However, it was not found that the cured resin layer and the support were separated from each other.

[0051]

[Table 2]

Comparative Examples 1 and 2 Using the supports used in Examples 1 and 2 and the photosensitive resin compositions shown in Table 3, photosensitive compositions for flexographic printing plates were prepared in the same manner as in Example 1. It was prepared and then made into a plate under the same conditions as in Example 1 to obtain a flexographic plate.

[0053]

[Table 3]

With respect to this flexographic plate, when the support was forcibly peeled off from the cured resin layer and the adhesion was measured while being peeled at an angle of 180 °, as shown in Table 4, the results were all 1.0 kg / cm. Was observed, which was significantly lower than. Further, when the plate fixed to the plate cylinder of the printing press with the double-sided tape was to be peeled off with the cured resin layer portion, a phenomenon that the cured resin layer and the support were easily separated was observed.

[0055]

[Table 4]

Comparative Example 3 A solution (solid content: about 20%) of the adhesive composition shown in Table 5 was prepared using toluene as a solvent, and was placed on a polyester film having a thickness of 125 μm so that the dry film thickness was 8-10 μm. Applied. Using this as a support, the photosensitive resin compositions shown in Table 1 were combined, and a flexographic plate was produced in the same procedure as in Example 1.

[0057]

[Table 5]

For this flexographic printing plate, the support was forcibly peeled off from the cured resin layer, and the adhesion was measured while peeling the support at an angle of 180 °. As a result, the flexo plate was easily peeled between the adhesive layer and the polyester film as the support. Occurred, and the adhesive strength was as low as 0.2 kg / cm.

[0059]

According to the present invention, the adhesive strength between the photosensitive resin layer for the flexographic printing plate and the polyester film as its support is strong, stable over time, and is easy and inexpensive to process. Thus, a photosensitive composition for flexographic printing plates having an excellent adhesive layer can be obtained.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G03F 7/028 G03F 7/028 7/033 7/033 7/09 501 7/09 501 7/11 503 7 / 11 503 F term (reference) 2H025 AA14 AB02 AC01 AD01 BC14 BC32 BC42 BC43 CA01 CB11 CB16 CB58 DA19 DA35 FA04 FA15 2H096 AA02 BA05 BA20 BA05 CA05 CA20 EA02 EA13 EA15 GA03 GA08 4J011 AC04 CA01 PA79 PB40 SA19 SA22 SA54 UA01 VA01 WA01 4J100 AL03Q AL05Q AL62P AL79Q AM45Q AM47Q BC04Q BC43Q CA01 CA04 JA37

Claims (3)

[Claims] 1. A thermoplastic elastomer comprising (a) a support, (c) a monovinyl-substituted aromatic hydrocarbon and a conjugated diene, (a) an adhesive layer, at least one ethylenically unsaturated compound, and In a photosensitive composition for a flexographic printing plate on which a photosensitive resin layer containing a photoinitiator system is laminated, (1) a polyol in which the adhesive layer (a) has a polyester structure or a polyurethane structure, or both of them With a polyfunctional isocyanate,
(2) The support of (b) is a polyester film,
(3) The photosensitive composition for flexographic printing plates according to (c), wherein the ethylenically unsaturated compound in the photosensitive resin has two unsaturated bonds in its molecule. 2. The photosensitive composition for a flexographic printing plate according to claim 1, wherein the at least one ethylenically unsaturated compound contained in the photosensitive resin layer (c) is a diacrylate compound. . 3. The method according to claim 1, wherein the at least one ethylenically unsaturated compound contained in the photosensitive resin layer (c) is a compound represented by the following formula (1). Photosensitive composition for flexographic printing plates. Embedded image