JP5393142B2 - Method for producing relief forming layer and relief printing plate precursor - Google Patents

Description

  The present invention relates to a method for producing a relief forming layer and a relief printing plate precursor obtained by using the method.

  As a method for forming a printing plate by forming irregularities on a photosensitive resin layer laminated on a surface area of a support, a relief forming layer formed using a photosensitive composition is exposed to ultraviolet light through an original film. A method of selectively curing an image portion and removing an uncured portion with a developer, so-called “analog plate making” is well known.

  The relief printing plate is a relief printing plate having a relief layer having irregularities, and the relief layer having such irregularities includes, for example, an elastomeric polymer such as synthetic rubber, a resin such as a thermoplastic resin, Alternatively, it is obtained by patterning a relief forming layer containing a photosensitive composition containing a mixture of a resin and a plasticizer to form irregularities. Among such relief printing plates, those having a soft relief layer are sometimes referred to as flexographic plates.

  When producing a relief printing plate by analog plate making, since an original image film using a silver salt material is generally required, the production time and cost of the original image film are required. Furthermore, since chemical processing is required for development of the original image film and processing of the development waste liquid is also required, a simpler plate preparation method, for example, a method that does not use the original image film, and development processing are required. The method of not doing is examined.

In recent years, a method of making a relief forming layer by scanning exposure without using an original film has been studied.
As a technique that does not require an original image film, a relief printing plate precursor provided with a laser-sensitive mask layer element capable of forming an image mask on a relief forming layer has been proposed (see, for example, Patent Documents 1 and 2). . According to these plate making methods, since an image mask having the same function as the original film is formed from the mask layer element by laser irradiation based on the image data, it is referred to as “mask CTP method”. A film is not necessary, but the subsequent plate making process is a process of exposing with ultraviolet light through an image mask to develop and remove an uncured portion, and there is still room for improvement in that a development process is required.

Many so-called “direct engraving CTP methods” in which a relief forming layer is directly engraved with a laser to make a plate as a plate making method that does not require a development step have been proposed. The direct engraving CTP method literally engraves with a laser to form reliefs, and has the advantage that the relief shape can be freely controlled, unlike the relief formation using the original film. For this reason, when an image such as a letter is formed, the area is engraved deeper than other areas, or the fine halftone dot image is engraved with a shoulder in consideration of resistance to printing pressure. Is also possible.
However, high energy is required to form a relief having irregularities that can withstand printing pressure on a relief forming layer having a predetermined thickness, and the speed of laser engraving is slow, so compared to the type that forms an image through a mask, There is a problem of low productivity.

  For this reason, attempts have been made to improve the sensitivity of the relief original plate. For example, a flexographic printing plate precursor for laser engraving including an elastomer foam has been proposed (see, for example, Patent Document 3). In this technology, low-density foam is used for the relief forming layer to improve the engraving sensitivity. However, because it is a low-density material, the strength of the printing plate is insufficient and the printing durability is significantly impaired. There is a problem of being.

For example, a flexographic printing plate precursor for laser engraving containing an elastomer foam has been proposed (see, for example, Patent Document 4). In this technology, the engraving sensitivity is improved by using a foam having a low density. However, since it is a low density material, the strength as a printing plate is insufficient, and the printing durability is remarkably impaired. is there.
For example, a flexographic printing plate precursor for laser engraving that contains a microsphere encapsulating a hydrocarbon-based gas has been proposed (see, for example, Patent Document 5). In this technology, the gas in the microspheres expands due to the heat generated by the laser, and the engraving sensitivity is improved by a system that disintegrates the material to be engraved. There is a problem that the strength tends to be insufficient. In addition, gas is more easily expanded by heat than solids, and even if a microsphere with a high thermal deformation start temperature is selected, volume change due to changes in external temperature cannot be avoided. However, it is not suitable to use a material containing air bubbles in a printing plate that requires the above.
For example, a resin relief printing plate for laser engraving containing a polymer filler having a ceiling temperature of less than 600 degrees K has been proposed (see, for example, Patent Document 6). In this technology, the engraving sensitivity is improved by adding a polymer filler having a low depolymerization temperature. However, when such a polymer filler is used, the surface of the printing plate precursor is uneven, There is a problem of seriously affecting the print quality.

As described above, various techniques have been proposed for the resin composition that can be suitably used for the relief forming layer of a relief printing plate precursor for laser engraving, but relief printing with high engraving sensitivity when subjected to laser engraving. The method for producing the plate original is not yet provided.
Japanese Patent No. 2773847 JP-A-9-171247 JP 2002-357907 A JP 2000-318330 A US Patent Application Publication No. 2003/180636 JP 2000-168253 A

This invention makes it a subject to achieve the following objectives.
That is, an object of the present invention is to provide a method for producing a relief forming layer, in which the occurrence of film surface defects is suppressed and a relief forming layer having high film strength can be produced. Another object of the present invention is to provide a relief printing plate precursor having a good printing durability and comprising a relief forming layer having a good film surface shape and high film strength, which is obtained by the production method of the present invention. It is to provide.

Means for solving the above-mentioned problems are as follows.
<1> (a) a binder resin, (b) a boiling point of 101 ° C. or higher and 200 ° C. or lower , and at least one selected from the group of propylene glycol monomethyl ether acetate, ethyl lactate, and 1-methoxy-2-propanol solvent, a coating step of coating (c) thermal polymerization initiator, and (d) is a relief forming layer resin solution containing a monomer onto the coating object,
And (b) a drying step in which a solvent having a boiling point of 101 ° C. or higher and 200 ° C. or lower is removed and dried.
(B) The boiling point of a solvent having a boiling point of 101 ° C. or more and 200 ° C. or less is A (° C.), the temperature of the drying step is B (° C.), and the (c) 10 h half-life temperature of the thermal polymerization initiator is C A method for producing a relief forming layer satisfying both the following formulas (I) and (II) when (° C.).
(I) ... A> B + 10
(II) ... A> C

<2> before Kiinui temperature of about燥工is at 70 ° C. or higher 0.99 ° C. or less, and a relief according to the (c) 10h half-life temperature of the thermal polymerization initiator is 120 ° C. or less 60 ° C. or higher <1> Manufacturing method of formation layer.

<3> The method for producing a relief forming layer according to <1> or <2>, wherein the thickness of the obtained relief forming layer is from 0.1 mm to 5 mm.
<4> The method for producing a relief forming layer according to any one of <1> to <3>, wherein the thermal polymerization initiator (c) is a peroxide.

< 5 > The method for producing a relief forming layer according to any one of <1> to < 4 >, further including a thermal crosslinking step after the drying step.
< 6 > The method for producing a relief forming layer according to < 5 >, wherein the following formula (III) is satisfied when the temperature of the thermal crosslinking step is D (° C.).
(III) ... A> D + 10
< 7 > A relief printing plate precursor having a relief forming layer obtained by the production method according to any one of <1> to < 6 >.

  In the present invention, a solvent having a relatively high boiling point and a thermal polymerization initiator having a low decomposition temperature are used, the decomposition temperature of the thermal polymerization initiator is made lower than the boiling point of the solvent, and the temperature of the drying step is made lower than the boiling point of the solvent. By controlling and drying, generation | occurrence | production of the film surface defect of the relief forming layer after drying is suppressed. In addition, the film strength of the relief forming layer after drying is high, and the performance is excellent in handling properties in the drying process. This is because the thermal polymerization initiator having a relatively low decomposition temperature is uniformly dissolved in the relief forming layer. In addition, when the coating film is dried, the drying temperature is controlled to be equal to or lower than the boiling point of the solvent, so that the surface of the coating film caused by the evaporation of the solvent does not occur and the relief forming layer has few defects. It is presumed that the effect is due to the formation of.

  ADVANTAGE OF THE INVENTION According to this invention, generation | occurrence | production of film surface state defect is suppressed and the manufacturing method of a relief forming layer with high film | membrane intensity | strength can be provided. In addition, according to the present invention, it is possible to provide a relief printing plate precursor having good printing durability and having a relief-forming layer having high film strength, in which the occurrence of film surface defects is suppressed.

Hereinafter, the method for producing a relief forming layer and the relief printing plate precursor of the present invention will be described in detail.
The relief forming layer in the present invention is a photosensitive layer used for relief formation and refers to a layer made of a resin composition that can be engraved with a laser.
In addition, a relief printing plate precursor having such a relief forming layer can be applied to the production of not only a resin relief plate (letter press plate) having a convex relief, a flexographic plate and a stamp, but also an intaglio plate and a stencil plate by laser engraving. However, the application range is not limited to these.

According to the method for producing a relief forming layer of the present invention, a relief forming layer having a high film strength in which the occurrence of film surface defects is suppressed can be obtained, and thus has the relief forming layer obtained by the production method of the present invention. Thus, a printing plate precursor for laser engraving excellent in printing durability can be obtained.
Further, in the present invention, the “relief printing plate precursor” includes a relief forming layer having a crosslinking property made of a resin solution for a laser forming layer, but the relief forming layer is in a state in which a crosslinked structure is formed by heat. And those in which a crosslinked structure has not yet been formed. “Relief printing plate” is produced by laser engraving the relief forming layer of the relief printing plate precursor.

The relief forming layer can be formed by molding the resin solution for the relief forming layer into a sheet shape or a sleeve shape. The relief forming layer is usually provided on a support which will be described later. However, the relief forming layer may be directly formed on the surface of a member such as a cylinder provided in an apparatus for plate making and printing, or may be arranged and fixed there. it can.
Hereinafter, the case where the relief forming layer is formed into a sheet shape will be mainly described as an example.

The present invention relates to a relief comprising (a) a binder resin, (b) a solvent having a boiling point of 101 ° C. to 200 ° C. (hereinafter also referred to as “specific solvent”), (c) a thermal polymerization initiator, and (d) a monomer. An application step of applying a resin solution for a forming layer onto an object to be applied; and (b) a drying step of removing the specific solvent and drying,
When the boiling point of the (b) specific solvent is A (° C.), the temperature of the drying step is B (° C.), and the 10 h half-life temperature of the (c) thermal polymerization initiator is C (° C.) This is a method for producing a relief forming layer satisfying both formula (I) and formula (II).
(I) A> B + 10
(II) A> C

First, the manufacturing method of the relief forming layer of this invention is demonstrated. The formation of the relief forming layer is not particularly limited.
<Application process>
A resin solution for a relief forming layer containing (a) a binder resin, (b) a specific solvent, (c) a thermal polymerization initiator, and (d) a monomer is prepared. This preparation is performed by mixing and stirring each raw material, and if necessary, filtering.
This relief forming layer resin solution is applied in a predetermined manner by a coating method such as spin coating, slit coating, cast coating, roll coating, bar coating or the like on the object to be coated, which will be described later, directly or via another layer. Apply so that the film thickness becomes.

<Drying process>
Next, the coated object on which the resin solution for the relief forming layer is coated is subjected to a drying process, and the solvent is removed to obtain the coated object on which the relief forming layer is formed.
This drying step is usually performed by hot air drying using an oven, a drying furnace, or the like, but if necessary, vacuum processing, high-frequency processing, or the like may be used in combination.
Alternatively, a method may be used in which a resin solution for a relief forming layer is cast on an object to be coated and dried in an oven to remove the solvent from the resin solution for the relief forming layer.

  In this invention, since the resin solution for relief forming layers contains a solvent, the drying process which removes a solvent is essential. The drying step is preferably from 0.2 hours to 10 hours from the viewpoint of productivity, more preferably from 0.5 hours to 8 hours, and particularly preferably from 1 hour to 6 hours.

  Formula (I) shows that the boiling point of the solvent is 10 ° C. or more higher than the drying temperature, more preferably the boiling point of the solvent is 15 ° C. or more higher than the drying temperature, and particularly preferably the boiling point of the solvent is the drying temperature. It is higher than 20 ° C. When this condition is satisfied, a local bumping of the solvent does not occur, and a favorable film surface shape can be obtained, which is preferable.

  In addition, the above formula (II) indicates that the boiling point of the solvent is higher than the 10 h half-life temperature of the thermal polymerization initiator, and more preferably the boiling point of the solvent is 10 ° C. higher than the 10 h half-life temperature of the thermal polymerization initiator. More preferably, the boiling point of the solvent is 20 ° C. or more higher than the 10 h half-life temperature of the thermal polymerization initiator. When this condition is satisfied, the polymerization initiation ability of the thermal polymerization initiator is sufficient, the drying time for obtaining a good quality film can be shortened, and the productivity is improved, which is preferable.

  The drying step has the meaning of volatilization of the solvent. As a drying method, a pass roll is arranged in a drying apparatus, a support in which a relief layer is coated on the pass roll, or a method of drying by hot air blown from a dry air blowing slit while wrapping and transporting a web, a support, Alternatively, air is supplied from the upper and lower surfaces of the web through a nozzle to dry the support or the web while it floats, and a heat medium is conducted inside the roll and heated to heat and heat transfer through contact between the roll and the support or the web. There is a method of drying the plate.

  In any method, in order to dry uniformly, the heating control is performed by hot air or a heating medium depending on the type of support or web, the type of relief layer composition, the coating amount, the type of solvent, the running speed, etc. This is done by appropriately changing the flow rate, temperature, and flow method. Also, a combination of two or more drying methods may be used.

In the present invention, the temperature in the drying step refers to the temperature of the drying air.
The surface temperature of the relief layer in the drying process is a value obtained by connecting the surface temperature measurement sensor U-279E-00-DO-1 to the THERMO PRINTER AP-310 type manufactured by Anritsu Keiki Co., Ltd. and measuring the surface temperature of the relief layer. .

Since the boiling point of the (b) specific solvent used in the present invention is 101 ° C. to 200 ° C., the temperature of the drying step is set so as to satisfy the above-described formulas (1) and (2). As temperature, the temperature range of 40-180 degreeC is preferable, and the temperature range of 50-150 degreeC is more preferable.
The 10h half-life temperature of the thermal polymerization initiator (c) used in the present invention is preferably in the temperature range of 60 to 120 ° C, more preferably in the temperature range of 70 to 115 ° C.

<Thermal crosslinking process>
It is preferable to use a thermal cross-linking step in which a cross-linked structure is formed in the relief forming layer by further heating the coated object on which the dried relief forming layer thus obtained is formed.
“Crosslinking” in the present invention is a concept including (a) a crosslinking reaction for linking binder resins, and (d) polymerization reaction between monomers and (a) reaction between binder resin and (d) monomer. This is a concept including the curing reaction of the relief forming layer.

  By crosslinking the relief forming layer, there is an advantage that the relief formed first after laser engraving becomes sharp, and second, the adhesiveness of engraving residue generated during laser engraving is suppressed. When an uncrosslinked relief-forming layer is laser engraved, unintended portions are likely to melt and deform due to residual heat that has propagated around the laser-irradiated portion, and a sharp relief layer may not be obtained. Further, as a general property of a material, a material having a lower molecular weight tends to be liquid rather than solid, that is, there is a tendency that the adhesiveness becomes stronger. The engraving residue generated when engraving the relief forming layer tends to become more tacky as more low-molecular materials are used. Since the polymerizable compound, which is a low molecular weight compound, is polymerized by crosslinking, the generated engraving residue tends to be less tacky.

Examples of the crosslinking method include a method of crosslinking a dried relief forming layer by heating.
As a method for crosslinking the relief forming layer, crosslinking by heat is preferable from the viewpoint that the relief forming layer can be uniformly cured (crosslinked) from the surface to the inside, but crosslinking by photocuring by irradiation with actinic rays may be used in combination. .
Examples of the heating means include a method of heating the printing plate precursor in a hot air oven or a far infrared oven for a predetermined time, and a method of contacting the heated roll for a predetermined time.

When performing crosslinking by heat, the temperature satisfies the following formula (III) with the boiling point (A ° C.) of the solvent of the relief forming layer resin solution when the temperature of the thermal crosslinking step is D (° C.). It is preferable.
(III) A> D + 10
More preferably, A> D + 20, and by satisfying this condition, the occurrence of film surface defects is suppressed, the film strength after drying in the manufacturing process is strong, and a film having good handling properties can be obtained.

When the relief forming layer contains a photopolymerization initiator in addition to (c) the thermal polymerization initiator, in addition to thermal crosslinking, irradiate the relief forming layer with an actinic ray that triggers the photopolymerization initiator. Thus, the relief forming layer can be crosslinked.
The irradiation with actinic light is generally performed on the entire surface of the relief forming layer. Visible light, ultraviolet light, or an electron beam is mentioned as actinic light, but ultraviolet light is the most common. If the support side of the relief forming layer is the back side, the surface may only be irradiated with actinic rays, but if the support is a transparent film that transmits actinic rays, it is preferable to irradiate the back side with actinic rays. . When the protective film exists, the irradiation from the surface may be performed while the protective film is provided, or may be performed after the protective film is peeled off. Since polymerization inhibition may occur in the presence of oxygen, actinic rays may be irradiated after the relief forming layer is covered with a vinyl chloride sheet and evacuated.

<Coating object>
The material to be coated for providing the relief forming layer is not particularly limited, but those having high dimensional stability are preferably used. For example, metals such as steel, stainless steel, and aluminum, polyester (for example, PET, PBT, PAN), and poly Examples thereof include plastic resins such as vinyl chloride, synthetic rubbers such as styrene-butadiene rubber, and plastic resins reinforced with glass fibers (such as epoxy resins and phenol resins). As an object to be coated, a PET (polyethylene terephthalate) film or a steel substrate is preferably used. The form of the object to be coated is determined depending on whether the relief forming layer has a sheet shape or a sleeve shape. A preferable object to be coated in the case of a sleeve shape will be described in detail below.

When the relief forming layer is formed on the object to be coated, an adhesive layer may be provided between them for the purpose of enhancing the adhesive strength between the layers.
The material that can be used for the adhesive layer may be any material that strengthens the adhesive force after the relief forming layer is crosslinked, and preferably has a strong adhesive force before the relief forming layer is crosslinked. Here, the adhesive force means both the adhesive force between the object to be coated / adhesive layer and the adhesive layer / relief forming layer.

The adhesive force between the object to be coated / adhesive layer is the peel force per 1 cm width of the sample when the adhesive layer and the relief forming layer are peeled from the laminate comprising the object to be coated / adhesive layer / relief forming layer at a rate of 400 mm / min. Is preferably 1.0 N / cm or more or non-peelable, more preferably 3.0 N / cm or more or non-peelable.
The adhesive force of the adhesive layer / relief forming layer is such that when the adhesive layer is peeled from the adhesive layer / relief forming layer at a rate of 400 mm / min, the peel force per 1 cm width of the sample is 1.0 N / cm or more or cannot be peeled off. It is preferable that it is 3.0 N / cm or more, or more preferably non-peelable.
Examples of materials (adhesives) that can be used for the adhesive layer include: Those described in the edition of Skeist, “Handbook of Adhesives”, the second edition (1977) can be used.

  The thickness of the relief forming layer is preferably 0.1 mm or more and 5 mm or less, more preferably 0, from the viewpoint of satisfying various flexographic printing aptitudes such as abrasion resistance and ink transferability after being dried. .2 mm to 4 mm, particularly preferably 0.3 mm to 3 mm.

Next, a case where the relief forming layer is formed in a sleeve shape will be described. In the case of molding into a sleeve shape, a known resin molding method can be applied. For example, a casting method, a method of extruding a resin from a nozzle or a die with a machine such as a pump or an extruder, adjusting the thickness with a blade, and adjusting the thickness by calendaring with a roll can be exemplified. In that case, you may shape | mold, heating at the temperature which does not impair the characteristic of the resin composition which comprises a relief forming layer. Moreover, a rolling process, a grinding process, etc. can also be given as needed.
When the relief forming layer is formed into a sleeve shape, the relief forming layer itself may be formed into a cylindrical shape from the beginning, or first formed into a sheet shape and then fixed onto a cylindrical support or plate cylinder to form a cylinder. It can also be made into a shape. The fixing method to the cylindrical support is not particularly limited, and for example, fixing with an adhesive tape having an adhesive layer, an adhesive layer or the like formed on both surfaces, or fixing via an adhesive layer can be performed.

As adhesive tapes, adhesive layers made of acrylic resin, methacrylic resin, styrene-based thermoplastic elastomer, etc. on both sides of film base materials such as polyester film and polyolefin film, polyolefin resin such as polyethylene And a cushioning adhesive tape having a cushioning property in which a foam of polyurethane resin is used as a base material, and an adhesive layer and an adhesive layer similar to those described above are formed on both surfaces, and a cushion having a commercially available double-sided tape or double-sided adhesive layer A tape or the like can also be used as appropriate.
In addition, the adhesive layer in the case where the object to be coated and the relief forming layer are fixed via the adhesive layer can be formed using a known adhesive. Examples of the adhesive that can be used when the relief forming layer is fixed to a cylindrical object to be coated include rubber adhesives such as styrene butadiene rubber (SBR), chloroprene rubber, and nitrile rubber, and silyl groups. Examples thereof include adhesives that are cured by moisture in the air, such as polyurethane resins and silicone resins.

  When the relief forming layer is formed into a cylindrical shape, it may be formed into a cylindrical shape by a known method, and this may be fixed on a cylindrical coated object or a cylindrical plate cylinder. A relief forming layer may be directly molded on the surface of the material by extrusion or the like to form a sleeve. From the viewpoint of productivity, it is preferable to take the former method. Even when the relief forming layer is formed into a sleeve shape, it can be cross-linked and cured as necessary after being fixed to a cylindrical object to be coated and further subjected to rolling treatment, grinding treatment, etc. as desired. .

Cylindrical objects to be used when the relief forming layer is in the form of a sleeve include metal sleeves made of metals such as nickel, stainless steel, iron and aluminum, plastic sleeves made of resin, glass fibers, carbon fibers, and aramid fibers. An FRP sleeve made of a fiber reinforced plastic using reinforced fibers as a reinforcing fiber, a sleeve formed of a polymer film and maintained in shape by compressed air, or the like can be used.
The thickness of the cylindrical object to be coated is arbitrarily selected according to the purpose. In general, the thickness may be 0.1 mm or more as long as the thickness is not damaged by the pressure during printing. For example, a plastic sleeve of 5 mm or more can be used, and a non-hollow cylindrical article to be fixed to the rotating shaft can also be used.
From the viewpoint of effectively fixing the relief forming layer having elasticity, the inner diameter of the cylindrical workpiece can be expanded with a compressed air pressure of about 6 bar, and after the compressed air pressure is released, the inner diameter returns to the original inner diameter. An object to be coated having such characteristics is preferable. By using a support having such a structure that the diameter can be easily adjusted by compressed air or the like, stress can be applied to the sleeve-shaped relief forming layer from the inside, and the winding-tightening characteristic of the relief forming layer functions. However, since the relief layer can be stably fixed on the cylindrical workpiece or the plate cylinder against stress during printing, it is preferable.

Thereafter, a protective film may be laminated on the relief forming layer as necessary. Lamination can be performed by pressure-bonding the protective film and the relief forming layer with a heated calendar roll or the like, or by bringing the protective film into close contact with the relief forming layer impregnated with a small amount of solvent on the surface.
When using a protective film, you may take the method of laminating | stacking a relief forming layer on a protective film first, and laminating a to-be-coated material next.
When the adhesive layer is provided, it can be dealt with by using an object to which the adhesive layer is applied. When providing a slip coat layer, it can respond by using the protective film which apply | coated the slip coat layer.

<Resin forming layer resin solution>
Next, the resin solution for relief forming layers used in the present invention will be described.
The resin solution for a relief forming layer of the present invention contains (a) a binder resin, (b) a solvent having a boiling point of 101 ° C. or higher and 200 or lower, (c) a thermal polymerization initiator, and (d) a monomer.
Hereinafter, the resin solution for a relief forming layer used in the present invention is also simply referred to as “resin solution of the present invention”.

  Since the resin solution for relief forming layers used in the present invention has high engraving sensitivity when subjected to laser engraving, laser engraving can be performed at high speed, so that engraving time can also be shortened. The resin solution for relief forming layers used in the present invention having such characteristics can be applied to a wide range of applications for forming a resin molded article subjected to laser engraving without any particular limitation. For example, as an application mode of the resin solution of the present invention, specifically, an image forming layer of an image forming material that forms an image by laser engraving, a relief forming layer of a printing plate precursor that forms a convex relief by laser engraving, Examples include, but are not limited to, intaglio plates, stencil plates, and stamps. The resin solution for a relief forming layer used in the present invention can be particularly suitably used for an image forming layer of an image forming material for forming an image by laser engraving and a relief forming layer in a relief printing plate precursor for laser engraving. Hereinafter, components of the resin solution for the relief forming layer will be described.

<(A) Binder resin>
The resin solution for relief forming layers used in the present invention contains (b) a binder polymer.
The binder polymer is a polymer component contained in the resin solution for the relief forming layer, and a general polymer compound can be appropriately selected and used alone or in combination of two or more. In particular, when using the resin solution for a relief forming layer for a printing plate precursor, it is necessary to select it in consideration of various performances such as laser engraving property, ink acceptability, and engraving residue dispersibility.

  As binder polymer, polystyrene resin, polyester resin, polyamide resin, polyurea polyamideimide resin, polyurethane resin, polysulfone resin, polyethersulfone resin, polyimide resin, polycarbonate resin, hydrophilic polymer containing hydroxyethylene unit, acrylic resin, acetal resin , Polycarbonate resin, rubber, thermoplastic elastomer and the like.

  For example, from the viewpoint of laser engraving sensitivity, a polymer containing a partial structure that is thermally decomposed by exposure or heating is preferable. Preferred examples of such a polymer include those described in JP 2008-163081 A [0038]. For example, when the purpose is to form a soft and flexible film, a soft resin or a thermoplastic elastomer is selected. The details are described in JP 2008-163081 A [0039] to [0040]. Furthermore, it is preferable to use a hydrophilic or alcoholic polymer from the viewpoint of easy preparation of the resin solution for the relief forming layer and improvement in resistance to oil-based ink in the obtained relief printing plate. As the hydrophilic polymer, those described in detail in JP 2008-163081 A [0041] can be used.

  In addition, polyesters composed of hydroxyl carboxylic acid units such as polylactic acid can be preferably used. Specific examples of such polyesters include polyhydroxyalkanoate (PHA), lactic acid-based polymer, polyglycolic acid (PGA), polycaprolactone (PCL), poly (butylene succinic acid), and derivatives or mixtures thereof. Those selected from the group consisting of are preferred.

Furthermore, a polymer containing a hydroxyethylene unit can also be preferably used. As the hydrophilic polymer containing a hydroxyethylene unit, polyvinyl alcohol (PVA) and its derivatives are preferably used.
Examples of PVA derivatives include acid-modified PVA in which at least part of the hydroxyl group of the hydroxyethylene unit is modified to an acid group such as a carboxyl group, modified PVA in which part of the hydroxyl group is modified to a (meth) acryloyl group, at least of the hydroxyl group Modified PVA partially modified with an amino group, modified PVA introduced with ethylene glycol, propylene glycol and their multimers into at least a part of the hydroxyl group, polyvinyl acetal obtained by treating polyvinyl alcohol with aldehydes, etc. Is mentioned. Among these, polyvinyl acetal is particularly preferably used. As the aldehydes used for the acetal treatment, acetaldehyde and butyraldehyde are preferably used because they are easy to handle. In particular, polyvinyl butyral is a PVA derivative that is preferably used.

In addition, when used for the purpose of curing by heating or exposure and improving the strength, a polymer having a carbon-carbon unsaturated bond in the molecule is preferably used.
Examples of such a polymer that includes a carbon-carbon unsaturated bond in the main chain include SB (polystyrene-polybutadiene), SBS (polystyrene-polybutadiene-polystyrene), SIS (polystyrene-polyisoprene-polystyrene), and SEBS. (Polystyrene-polyethylene / polybutylene-polystyrene) and the like.

Examples of the polymer having a carbon-carbon unsaturated bond in the side chain include carbon-carbon unsaturated groups such as an allyl group, an acryloyl group, a methacryloyl group, a styryl group, and a vinyl ether group in the skeleton of the binder polymer applicable in the present invention. It is obtained by introducing a saturated bond into the side chain. In the method of introducing a carbon-carbon unsaturated bond into the side chain of the binder resin, a structural unit having a polymerizable group precursor formed by bonding a protective group to a polymerizable group is copolymerized with a polymer, and the protective group is eliminated. A polymer group having a plurality of reactive groups such as a hydroxyl group, an amino group, an epoxy group, and a carboxyl group, and a group that reacts with these reactive groups and a carbon-carbon unsaturated bond A publicly known method such as a method of introducing a compound having a polymer by a polymer reaction can be employed. According to these methods, the amount of unsaturated bond and polymerizable group introduced into the polymer compound can be controlled.
Thus, in consideration of the physical properties according to the application application of the resin solution for the relief forming layer, a binder polymer according to the purpose is selected, and one kind of the binder polymer or a combination of two or more kinds may be used. it can.

  The weight average molecular weight (polystyrene conversion by GPC measurement) of the binder resin in the present invention is preferably from 50,000 to 500,000. If the weight average molecular weight is 50,000 or more, the form retainability as a single resin is excellent, and if it is 500,000 or less, it is easy to dissolve in a solvent such as water, which is convenient for preparing a resin solution for a relief forming layer. is there. The weight average molecular weight of the binder resin is more preferably 10,000 to 400,000, and particularly preferably 15,000 to 300,000.

The total content of the binder resin is preferably 5% by mass to 80% by mass, preferably 15% by mass to 75% by mass, and 20% by mass to 65% by mass with respect to the total mass of the solid content of the resin solution for the relief forming layer. More preferred.
For example, in the resin solution for a relief forming layer of the present invention, the printing durability sufficient to use the obtained relief printing plate as a printing plate can be obtained by setting the content of the binder resin to 15% by mass or more. When the amount is 75% by mass or less, other components are not deficient, and flexibility sufficient for use as a printing plate can be obtained even when the relief printing plate is a flexographic printing plate.

<(B) Solvent having a boiling point of 101 ° C. or higher and 200 ° C. or lower>
The boiling point of the solvent (b) having a boiling point of 101 ° C to 200 ° C used in the present invention is preferably 101 ° C to 200 ° C, more preferably 110 ° C to 180 ° C, and particularly preferably 120 ° C to 160 ° C. It is. When the boiling point of the solvent is 101 ° C. or higher, bumping hardly occurs and a good film surface shape is easily obtained. Conversely, it is preferable that the boiling point of the solvent is 200 ° C. or less because the drying time does not take too long.
The solvent (b) having a boiling point of 101 ° C. or higher and 200 ° C. or lower used in the present invention can be arbitrarily selected as long as the boiling point is 101 ° C. or higher and 200 ° C. or lower. Moreover, if it is a solvent whose boiling point is 101 to 200 degreeC, it can also be used in combination.

Specific examples of the solvent are shown below, and () is the boiling point.
Toluene (: 110.6 ° C), o-xylene (144 ° C), m-xylene (139 ° C), p-xylene (138 ° C), isobutyl alcohol (107 ° C), isopentyl alcohol (130.5 ° C), Isobutyl acetate (118 ° C), butyl acetate (126.3 ° C), methyl isobutyl ketone (116.2 ° C), 1,4-dioxane (101.1 ° C), propylene glycol monomethyl ether (120 ° C), ethylene glycol monomethyl Ether (124.5 ° C), ethylene glycol monomethyl ether acetate (145 ° C), propylene glycol monomethyl ether acetate (146.0 ° C), phenylmethyl ether (153.8 ° C), ethylene glycol monobutyl ether (171.2 ° C) , Ethyl lactate (155 ° C), diethyl Glycol dimethyl ether (162 ° C), dipropylene glycol dimethyl ether (171 ° C), diethylene glycol ethyl methyl ether (176 ° C), diethylene glycol isopropyl methyl ether (179 ° C), dipropylene glycol monomethyl ether (188 ° C), diethylene glycol diethyl ether (189 ° C) ), Diethylene glycol monomethyl ether (194 ° C.), 1-methoxy-2-propanol (121 ° C.), and the like. Particularly preferred are ethyl lactate, ethylene glycol monomethyl ether acetate, and 1-methoxy-2-propanol.

<(C) Thermal polymerization initiator>
The 10-h half-life temperature C ° C of the (c) thermal polymerization initiator used in the present invention is preferably 60 ° C or higher and 120 ° C or lower, more preferably 70 ° C or higher and 115 ° C or lower, and particularly preferably 80 ° C or higher and 110 ° C or lower. . If the kind of thermal polymerization initiator is a relationship of Formula (II), a well-known thing can be used without a restriction | limiting. When the 10h half-life temperature C ° C. of the thermal polymerization initiator is 60 ° C. or higher, the stability during preparation is favorable. When the 10 h half-life temperature C ° C. is 120 ° C. or less, the thermal polymerization initiator is preferable because the polymerization initiating ability is sufficient, the drying time for obtaining a good quality film can be shortened, and the productivity is good.

In the present invention, the 10 h half-life temperature of (A) peroxide is a value measured by the measurement method described below.
Using a solvent inert to radicals (in the present invention, benzene is used), an organic peroxide solution having a concentration of 0.1 mol / L is prepared and sealed in a glass tube subjected to nitrogen substitution. . This is immersed in a thermostat set at a predetermined temperature and thermally decomposed. In addition, in a general-purpose method, there is also a method in which this concentration is adjusted to 0.5 mol / L for measurement.
In general, decomposition of an organic peroxide in a dilute solution can be roughly treated as a primary reaction. Therefore, assuming that the decomposition peroxide amount x, decomposition rate constant k, time t, and initial peroxide concentration a are as follows: The relationship of the formula holds.
Formula (1) dx / dt = k (ax)
Formula (2) ln {a / (ax)} = kx

Since the half-life is the time until the peroxide concentration is reduced to half of the initial value due to decomposition, the half-life is indicated by t1 / 2, and when “a / 2” is substituted for “x” in equation (2), the following equation ( 3) is derived.
Formula (3) kt1 / 2 = ln2
Therefore, thermal decomposition is performed at a certain temperature, the relationship between time t and ln {a / (ac)} is plotted, k is obtained from the slope of the straight line obtained by the plot, and the equation (3) The half-life (t1 / 2) can be determined.

On the other hand, the decomposition rate constant k is expressed by the following equation.
Equation (4) k = Aexp (−ΔE / RT)
Formula (5) lnk = lnA−ΔE / RT
Here, A: Frequency factor (1 / h), ΔE: Activation energy (J / mol), R: Gas constant (8.314 J / mol · K), T: Absolute temperature (K) The activation energy can be obtained from the slope of the straight line obtained by plotting the relationship between lnk and 1 / T by measuring k at several temperatures.
In addition, instead of lnk, from the straight line obtained by plotting the relationship between lnt1 / 2 and 1 / T, the decomposition temperature for obtaining the half-life of the organic peroxide at an arbitrary temperature or the arbitrary half-life can be obtained. .

  In addition, as a numerical value of the 10-h half-life temperature of a peroxide, it can also be obtained by literature and a peroxide manufacturer's catalog etc. can be referred. Specifically, for example, it is possible to refer to catalog values (http://www.nof.co.jp/upload_public/sogo/B0100.pdf) of NOF Corporation.

  Hereinafter, regarding specific examples of preferable thermal polymerization initiators, radicals are generated by heat energy, and a polymerization compound including a monomer and a radical polymerization initiator that is a compound that starts and accelerates a polymerization reaction will be described in detail. The present invention is not limited by these descriptions.

In the present invention, preferred radical polymerization initiators include aromatic ketones, onium salt compounds, organic peroxides, thio compounds, hexaarylbiimidazole compounds, ketoxime ester compounds, borate compounds, azinium compounds, metallocene compounds, activity Examples thereof include an ester compound, a compound having a carbon halogen bond, and an azo compound.
In the present invention, organic peroxides and azo compounds are more preferable, and organic peroxides are particularly preferable from the viewpoint of improving the relief edge shape when applied to the sensitivity and the relief forming layer of the relief printing plate precursor. preferable. Among organic peroxides, a compound having a peroxyl group (R—O—O—R) is preferably used as a thermal polymerization initiator.
Specific examples of the thermal polymerization initiator described above will be given below, but the present invention is not limited thereto. In addition, () is a 10-h half-life temperature.

  Specific examples of the organic peroxide include Parroyl L (61.6 ° C.), Perocta O (65.3 ° C.), Parroyl SA (65.9 ° C.), Perhexa 25O (66.2 ° C.), Perhexyl O (69 .9 ° C.), Nipper BMT (73.1 ° C.), Nipper BW (73.6 ° C.), Perhexa MC (83.2 ° C.), Perhexa TMH (86.7 ° C.), Perhexa HC (87.1 ° C.), Perhexa C (90.7 ° C), Pertetra A (94.7 ° C), Perhexyl I (95.0 ° C), Perbutyl MA (96.1 ° C), Perbutyl 355 (97.1 ° C), Perbutyl L (98. 3 ° C), perbutyl I (98.7 ° C), perbutyl E (99.0 ° C), perhexyl Z (99.4 ° C), perhexa 25Z (99.7 ° C), perbutyl A (101.9 ° C), perhexa 22 (1 3.1 ° C.), perbutyl Z (104.3 ° C.), perhexa V (104.5 ° C.), perbutyl P (119.2 ° C.), park mill D (116.4 ° C.), perhexyl D (116.4 ° C.) , Perhexa 25B (117.9 ° C.), Perbutyl C (119.5 ° C.) (above, manufactured by NOF Corporation) and the like.

  Furthermore, Trigonox 36-C75 (60 ° C.), Laurox (61 ° C.), Parkardox CH-50L (72 ° C.), Kayahexa AD (118 ° C.), Parkardox 12-XL25 (92 ° C.), Trigonox 22-N70 (93 ° C), Trigonox 22-70E (102 ° C), Trigonox D-T50 (64 ° C), Kayaester TMPO-70 (70 ° C), Trigonox 121 (74 ° C), Kayaester 0 (83 ° C), Kayaester HTP- 65 W (95 ° C.), Kaya Ester AN (100 ° C.), Trigonox 42 (103 ° C.), Trigonox F-C50 (105 ° C.), Kayabutyl B (97 ° C.), Kaya Carbon BIC-75 (98 ° C.), Trigonox 117 (97 ° C) (made by Kayaku Akzo Co., Ltd.).

  Further, as preferred azo compounds as thermal polymerization initiators usable in the present invention, 2,2′-azobisisobutyronitrile, 2,2′-azobispropionitrile, 1,1′-azobis (cyclohexane) -1-carbonitrile), 2,2′-azobis (2-methylbutyronitrile), 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2′-azobis (4-methoxy-2) , 4-dimethylvaleronitrile), 4,4′-azobis (4-cyanovaleric acid), dimethyl 2,2′-azobisisobutyrate, 2,2′-azobis (2-methylpropionamidooxime), 2,2 ′ -Azobis [2- (2-imidazolin-2-yl) propane], 2,2'-azobis {2-methyl-N- [1,1-bis (hydroxymethyl) -2-hydroxyethyl] Lopionamide}, 2,2′-azobis [2-methyl-N- (2-hydroxyethyl) propionamide], 2,2′-azobis (N-butyl-2-methylpropionamide), 2,2′- Azobis (N-cyclohexyl-2-methylpropionamide), 2,2′-azobis [N- (2-propenyl) -2-methylpropionamide], 2,2′-azobis (2,4,4-trimethylpentane) And the like.

As the (c) thermal polymerization initiator in the present invention, one kind may be used alone, or two or more kinds may be used in combination.
The thermal polymerization initiator is preferably added in an amount of 0.01 to 10% by mass, more preferably 0.1 to 3% by mass, based on the total solid content of the resin solution for the relief forming layer.

<(D) Monomer>
In the present invention, since it is preferable to have a crosslinked relief forming layer, it is preferable that the resin solution for the relief forming layer contains (d) a monomer so that a crosslinked structure can be formed.
The monomer (d) that can be used here can be arbitrarily selected from compounds having at least 1, preferably 2 or more, more preferably 2 to 6 ethylenically unsaturated double bonds.

  Hereinafter, (d) a monofunctional polymerizable compound having one ethylenically unsaturated double bond in the molecule and a polyfunctional polymerizable compound having two or more same bonds in the molecule will be described. .

Examples of polymerizable compounds having an ethylenically unsaturated double bond in the molecule include unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, crotonic acid, isocrotonic acid, maleic acid and their salts, ethylenic Examples thereof include polymerizable compounds such as anhydrides having unsaturated groups, (meth) acrylates, (meth) acrylamides, acrylonitrile, styrene, various unsaturated polyesters, unsaturated polyethers, unsaturated polyamides, and unsaturated urethanes.
The (meth) acrylate represents acrylate or methacrylate, and (meth) acrylamide represents acrylamide or methacrylamide.

  Monofunctional polymerizable compounds include methyl acrylate, ethyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, butoxyethyl acrylate, carbitol acrylate, cyclohexyl acrylate, benzyl acrylate, N-methylol acrylamide, epoxy Acrylic acid derivatives such as acrylate, methacrylic derivatives such as methyl methacrylate, N-vinyl compounds such as N-vinylpyrrolidone and N-vinylcaprolactam, and derivatives of allyl compounds such as allyl glycidyl ether, diallyl phthalate and triallyl trimellitate. Can be mentioned.

  Polyfunctional polymerizable compounds include ethylene glycol diacrylate, triethylene glycol diacrylate, propylene glycol diacrylate, triethylene glycol dimethacrylate, 1,3-butanediol diitaconate, pentaerythritol dicrotonate, sorbitol tetramaleate , Polyhydric alcohol compounds such as methylene bis-methacrylamide, 1,6-hexamethylene bis-acrylamide, or ester compounds or amide compounds of polyvalent amine compounds and unsaturated carboxylic acids, and JP-A 51-37193 Urethane acrylates such as those described in JP-A-48-64183, JP-B-49-43191, and JP-B-52-30490. Can be mentioned resins and (meth) polyfunctional acrylates or methacrylates such as epoxy acrylates obtained by reacting an acrylic acid. Furthermore, the Japan Adhesion Association Vol. 20, no. 7, 300-308 (1984); Shinzo Yamashita, “Cross-linking agent handbook” (1981, Taiseisha); Kato Kiyomi, “UV / EB curing handbook (raw material)” (1985, Takashi Molecular Publications); Radtech Study Group, “Application and Market of UV / EB Curing Technology”, 79 pages (1989, CMC); Eiichiro Takiyama, “Polyester Resin Handbook”, (1988, Nikkan Kogyo) Commercially available products as described in Shimbunsha etc., or radically polymerizable or crosslinkable monomers and oligomers known in the industry can be used.

  Since the relief forming layer according to the present invention preferably has a crosslinked structure in the film, a polyfunctional polymerizable compound is preferably used. The molecular weight of these polyfunctional polymerizable compounds is preferably 200 to 2,000.

In the present invention, it is preferable to use a polymerizable compound having a sulfur atom in the molecule as the monomer (d) from the viewpoint of improving engraving sensitivity.
Thus, as a polymeric compound which has a sulfur atom in a molecule | numerator, from a viewpoint of engraving sensitivity improvement, it has two or more ethylenically unsaturated bonds especially, and connects between two ethylenically unsaturated bonds among them. It is preferable to use a polymerizable compound having a carbon-sulfur bond at the site (hereinafter appropriately referred to as “sulfur-containing polyfunctional monomer”).

  The functional group containing a carbon-sulfur bond in the sulfur-containing polyfunctional monomer in the present invention includes sulfide, disulfide, sulfoxide, sulfonyl, sulfonamide, thiocarbonyl, thiocarboxylic acid, dithiocarboxylic acid, sulfamic acid, thioamide, and thiocarbamate. , Functional groups containing dithiocarbamate or thiourea.

Further, the number of sulfur atoms contained in the molecule of the sulfur-containing polyfunctional monomer is not particularly limited as long as it is 1 or more, and can be appropriately selected according to the purpose. From the viewpoint of balance, 1 to 10 is preferable, 1 to 5 is more preferable, and 1 to 2 is still more preferable.
On the other hand, the number of ethylenically unsaturated sites contained in the molecule is not particularly limited as long as it is 2 or more, and can be appropriately selected according to the purpose. -10 are preferable, 2-6 are more preferable, and 2-4 are still more preferable.
Specific examples of the sulfur-containing polyfunctional monomer preferably used are shown below (R represents a hydrogen atom or a methyl group).

  The sulfur-containing polyfunctional monomer in the present invention is a reaction between a sulfur atom-containing dicarboxylic acid and an epoxy group-containing (meth) acrylate, a reaction between a sulfur atom-containing diol and an isocyanate-containing (meth) acrylate, a dithiol and an isocyanate-containing (meth) acrylate. It is possible to synthesize the compound by using a reaction with a diisothiocyanate and a hydroxy group-containing (meth) acrylate, a known esterification reaction, or the like. Moreover, you may use a commercial item.

  The molecular weight of the sulfur-containing polyfunctional monomer in the present invention is preferably 120 to 3000, more preferably 120 to 1500, from the viewpoint of the flexibility of the formed film.

Moreover, although the sulfur-containing polyfunctional monomer in this invention may be used independently, you may use it as a mixture with the polyfunctional polymerizable compound and monofunctional polymerizable compound which do not have a sulfur atom in a molecule | numerator.
From the viewpoint of engraving sensitivity, it is preferable to use a sulfur-containing polyfunctional monomer alone or as a mixture of a sulfur-containing polyfunctional monomer and a monofunctional ethylenic monomer, more preferably a sulfur-containing polyfunctional monomer and a monofunctional. This is an embodiment used as a mixture with an ethylenic monomer.

The total content of the monomer (d) including the sulfur-containing polyfunctional monomer in the relief forming layer is 10% by mass to 60% by mass with respect to the nonvolatile component from the viewpoint of flexibility and brittleness of the crosslinked film. The range of 15% by mass to 45% by mass is more preferable.
In addition, when using together a sulfur-containing polyfunctional monomer and another monomer, 5 mass% or more is preferable and, as for the quantity of the sulfur-containing polyfunctional monomer in all the monomers, 10 mass% or more is more preferable.

<Other additives>
The resin solution for relief forming layer used in the present invention preferably contains a plasticizer. The plasticizer has an effect of softening the relief forming layer and needs to be compatible with the binder resin.
As the plasticizer, for example, dioctyl phthalate, didodecyl phthalate and the like, polyethylene glycols, polypropylene glycol (monool type and diol type), and polypropylene glycol (monool type and diol type) are preferably used.

The relief forming layer resin solution used in the present invention is more preferably added with nitrocellulose or a highly heat conductive substance as an additive for improving sensitivity. Since nitrocellulose is a self-reactive compound, it generates heat during laser engraving and assists in thermal decomposition of a binder polymer such as a hydrophilic polymer. As a result, it is estimated that the engraving sensitivity is improved.
The highly heat conductive material is added for the purpose of assisting heat transfer, and examples of the heat conductive material include inorganic compounds such as metal particles and organic compounds such as a conductive polymer. As the metal particles, the conductive polymer is preferably a gold fine particle, a silver fine particle, or a copper fine particle having a particle size of from micrometer order to several nanometer order. It is done.

Moreover, the sensitivity at the time of photocuring a relief forming layer can be further improved by using a co-sensitizer.
Furthermore, it is desirable to add a small amount of a thermal polymerization inhibitor in order to prevent unnecessary thermal polymerization of the polymerizable compound during the production or storage of the resin solution for the relief forming layer.
A colorant such as a dye or a pigment may be added for the purpose of coloring the relief forming layer. Thereby, properties such as the visibility of the image portion and the suitability of the image density measuring device can be improved.
Furthermore, in order to improve the physical properties of the cured film of the relief forming layer, a known additive such as a filler may be added.

<Relief printing plate and its manufacture>
The production mode of the relief printing plate using the relief printing plate precursor of the present invention is preferably a mode in which a relief printing plate is produced by forming a relief layer by crosslinking a relief forming layer and then laser engraving. By crosslinking the relief forming layer, wear of the relief layer during printing can be prevented, and a relief printing plate having a relief layer having a sharp shape after laser engraving can be obtained.

The method for producing a relief printing plate includes (1) the above-mentioned thermal crosslinking step of crosslinking the uncrosslinked relief forming layer in the relief printing plate precursor of the present invention by heating, and (2) laser engraving the crosslinked relief forming layer. And a step of forming a relief layer (hereinafter appropriately referred to as “engraving step”).
Hereinafter, the engraving process will be described.

<Engraving process>
In the method for producing a relief printing plate, the engraving step of forming a relief layer by laser engraving the crosslinked relief forming layer is performed after the thermal crosslinking step. According to the method for producing a relief printing plate of the present invention, a relief printing plate having a relief layer on a support can be produced.

In the method for producing a relief printing plate, following the engraving step, the following steps (1) to (3) may be further included as necessary.
Step (1): A step of rinsing the surface of the engraved relief layer with water or a liquid containing water as a main component (rinsing step).
Step (2): A step of drying the engraved relief layer (drying step).
Step (3): A step of imparting energy to the relief layer after engraving and further crosslinking the relief layer (post-crosslinking step).

In the engraving process, the relief forming layer crosslinked in the thermal crosslinking process is laser engraved to form a relief layer. Specifically, the relief layer is formed by engraving the crosslinked relief forming layer by irradiating a laser beam corresponding to the image to be formed. Preferably, a step of controlling the laser head with a computer based on digital data of an image to be formed and scanning and irradiating the relief forming layer is exemplified.
In this engraving process, an infrared laser is preferably used. When irradiated with an infrared laser, the molecules in the relief forming layer undergo molecular vibrations and generate heat. When a high-power laser such as a carbon dioxide laser or a YAG laser is used as an infrared laser, a large amount of heat is generated in the laser irradiation portion, and molecules in the relief forming layer are selectively removed by molecular cutting or ionization, that is, Sculpture is made. The advantage of laser engraving is that the engraving depth can be set arbitrarily, so that the structure can be controlled three-dimensionally. For example, the portion that prints fine halftone dots can be engraved shallowly or with a shoulder so that the relief does not fall down due to the printing pressure, and the portion of the groove that prints fine punched characters is engraved deeply As a result, the ink is less likely to be buried in the groove, and it is possible to suppress the crushing of the extracted characters.
In particular, when engraving with an infrared laser corresponding to the absorption wavelength of the photothermal conversion agent, the relief forming layer can be selectively removed with higher sensitivity, and a relief layer having a sharp image can be obtained. As the infrared laser used in such an engraving process, a carbon dioxide laser or a semiconductor laser is preferable from the viewpoint of productivity, cost, and the like. In particular, a semiconductor infrared laser with a fiber is preferably used.

When engraving residue is attached to the engraving surface, a step (1) of rinsing the engraving residue by rinsing the engraving surface with water or a liquid containing water as a main component may be added. As a means of rinsing, there is a method of washing with tap water, a method of spraying high-pressure water, and a known batch type or conveying type brush type washing machine as a photosensitive resin relief printing machine. For example, when the engraving residue is not smooth, a rinsing solution to which a surfactant is added may be used.
When the step (1) of rinsing the engraved surface is performed, it is preferable to add a step (2) of drying the engraved relief forming layer and volatilizing the rinse liquid.
Furthermore, you may add the process (3) which further bridge | crosslinks a relief forming layer as needed. By performing the additional crosslinking step (3), the relief formed by engraving can be further strengthened.

As described above, a relief printing plate having a relief layer on an object to be coated is obtained.
The Shore A hardness of the relief layer of the relief printing plate is preferably 50 ° or more and 90 ° or less.
When the Shore A hardness of the relief layer is 50 ° or more, even if the fine halftone dots formed by engraving are subjected to the strong printing pressure of the relief printing press, they do not collapse and can be printed normally. In addition, when the Shore A hardness of the relief layer is 90 ° or less, it is possible to prevent faint printing in a solid portion even in flexographic printing with a kiss touch.
The Shore A hardness in the present specification is a durometer (spring type) in which an indenter (called a push needle or indenter) is pushed and deformed on the surface of the object to be measured, and the amount of deformation (pushing depth) is measured and digitized. It is a value measured by a rubber hardness meter.

  The relief printing plate having a relief forming layer produced by the method of the present invention can be printed with oil-based ink or UV ink by a relief printing press, and can also be printed with UV ink by a flexographic printing press. is there.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples.

Example 1
<Preparation of resin solution for relief forming layer>
In a three-necked flask equipped with a stirring spatula and a cooling tube, Denkabutyral # 3000-2 (polyvinyl butyral, molecular weight 90000, manufactured by Denki Kagaku Kogyo Co., Ltd.) 49.65 parts by mass as a binder resin, as a solvent 66 parts by mass of propylene glycol monomethyl ether acetate was added and heated at 70 ° C. for 120 minutes with stirring to dissolve the binder resin. Next, 15 parts by mass of M1 having the structure shown below as a monomer, 33 parts by mass of Bremer LMA (n-dodecyl methacrylate: manufactured by NOF Corporation), and perbutyl Z (t-butyl peroxobenzoate) as a thermal polymerization initiator: 1.6 parts by mass of NOF Corporation) and 0.75 parts by mass of Asahi # 80 (N-220, carbon black produced by Asahi Carbon Co., Ltd.) as a photothermal conversion agent were added and stirred for 30 minutes. A relief resin layer-forming resin solution was obtained.

Ｍ１

M1

  The resin solution for a relief forming layer obtained above was cast on a PET film having a thickness of 0.2 mm and dried in an oven at 100 ° C. for 1 hour to obtain a relief forming layer. The thickness of the obtained relief forming layer was 0.9 mm.

(Examples 2 to 16, Comparative Examples 1 to 5)
A support provided with relief forming layers of Examples 2 to 16 and Comparative Examples 1 to 5 was obtained in the same manner as in Example 1 except that the solvent, the thermal polymerization initiator, and the drying temperature were changed to the conditions described in Table 1. .
The obtained resin solution for relief forming layer and the relief forming layer were evaluated according to the evaluation methods shown below, and the results are summarized in Table 1.

(Method for measuring liquid stability)
The liquid viscosity when the resin solution for relief forming layers was allowed to stand at 70 ° C. was measured, and the time until the fluctuation range became + 10% was measured. If it is 8 hours or more, it is a level with no practical problem.

(Measurement method of film strength)
After thermal crosslinking, the relief forming layer (thickness 0.9 mm) peeled off from the PET film was punched out using a dumbbell as defined in JIS K 62533, and the tip of one side of the relief forming layer punched out only to a spring (max 1000 g) And the other end on one side was pulled by hand, and the value of the load of only the spring when the relief layer broke was obtained by the following equation. If the film strength is 6 N / cm or more, it is at a level that causes no practical problems.
(Sheet strength [N / cm]) = (Load at break [kg] × 9.8 [m / s ² ]) / 0.5 [cm]

(Measuring method of film surface)
The relief forming layer obtained above was thermally crosslinked using a hot air drying oven under the thermal crosslinking conditions shown in Table 1, cut out into 10 cm × 10 cm, and a film thickness of 20 arbitrary locations using a micrometer. The standard deviation (σ) was calculated based on the measurement. If the standard deviation ([sigma]) is 30 [mu] m or less, the film surface state is at a level that causes no practical problems.

  From Table 1, Examples 1 to 15 satisfying both the formulas (I) and (II) of the present invention are excellent in the storage stability of the resin solution, the film strength of the obtained relief forming layer is high, and the relief layer The film thickness was good and the surface was excellent. On the other hand, Comparative Examples 1, 2 and 5 had a non-uniform relief layer and poor surface, and Comparative Examples 3 and 4 had low film strength.

Claims (7)

(A) a binder resin, (b) a solvent having a boiling point of 101 ° C. or higher and 200 ° C. or lower and at least one selected from the group consisting of propylene glycol monomethyl ether acetate, ethyl lactate, and 1-methoxy-2-propanol , c) thermal polymerization initiator, and a coating step of applying onto a coating object the relief forming layer resin solution containing a monomer (d),
And (b) a drying step in which a solvent having a boiling point of 101 ° C. or higher and 200 ° C. or lower is removed and dried.
(B) The boiling point of a solvent having a boiling point of 101 ° C. or more and 200 ° C. or less is A (° C.), the temperature of the drying step is B (° C.), and the (c) 10 h half-life temperature of the thermal polymerization initiator is C A method for producing a relief forming layer satisfying both the following formulas (I) and (II) when (° C.).
(I) ... A> B + 10
(II) ... A> C Temperature before enough Kiinui燥工is at 70 ° C. or higher 0.99 ° C. or less, and wherein (c) 10h half-life temperature of the thermopolymerization initiator in the relief forming layer according to claim 1 or less 120 ° C. 60 ° C. or higher Production method.   The method for producing a relief forming layer according to claim 1 or 2, wherein the thickness of the obtained relief forming layer is from 0.1 mm to 5 mm.   The method for producing a relief forming layer according to any one of claims 1 to 3, wherein the thermal polymerization initiator (c) is a peroxide. The method for producing a relief forming layer according to any one of claims 1 to 4 , further comprising a thermal crosslinking step after the drying step. The manufacturing method of the relief forming layer of Claim 5 which satisfies following formula (III) when the temperature of the said thermal crosslinking process is set to D (degreeC).
(III) ... A> D + 10 A relief printing plate precursor having a relief forming layer obtained by the production method according to any one of claims 1 to 6 .