JP2013029739A - Plate making method for flexographic printing plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plate making method for a flexographic printing plate with high removability of an unexposed part.SOLUTION: A plate making method for a flexographic printing plate includes: an exposure step (step a) of exposing a relief forming layer of an original flexographic printing plate in a form of an image; a step (step b) of arranging an absorbent material on an external surface of the exposed relief forming layer; a heating step (step c) of heating the exposed original flexographic printing plate to a temperature enough for an unexposed part thereof to generate a liquefied substance; and a removal step (step d) of removing the liquefied substance by at least partially attaching it to the absorbent material. Before the step d, the method includes a step (step e) of exposing at least the unexposed part of the relief forming layer of the original flexographic printing plate to an active ray from an external surface direction of the relief forming layer.

Description

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

  In order to prepare a flexographic printing plate, a lithographic printing plate precursor (PS plate) in which an oleophilic photosensitive resin layer (photosensitive layer, image forming layer) is provided on a hydrophilic support has been widely used. . Usually, the lithographic printing plate precursor is exposed through an original image such as a lithographic film, and then the portion that becomes the image portion of the image forming layer is left, and the other unnecessary image forming layer is washed with an alkaline developer or organic A lithographic printing plate is obtained by dissolving and removing with a solvent and exposing the surface of the hydrophilic support to form a non-image area.

  As described above, in the plate making process of the conventional flexographic printing plate precursor, after the exposure, a step of dissolving and removing unnecessary image forming layers with a developer or the like is necessary, but it is closer to the neutral range in terms of environment and safety. Treatment with a developing solution and a small amount of waste liquid are cited as problems. In particular, in recent years, the disposal of waste liquid discharged from wet processing due to consideration for the global environment has become a major concern for the entire industry, and the demand for the solution of the above problems has become stronger. 1 to 3 describe a method for producing a flexographic printing plate by a heat development method.

Japanese Patent Laid-Open No. 5-19469 JP 2005-250487 A JP 2007-86781 A

  An object of the present invention is to provide a method for making a flexographic printing plate excellent in removability of an unexposed portion.

The above-described problems of the present invention have been solved by the means described in <1> below. It is described below together with <2> to <9> which are preferred embodiments.
<1> (Step a) An exposure step in which the relief forming layer of the flexographic printing plate precursor is imagewise exposed, (Step b) a step of disposing an absorbent material on the outer surface of the exposed relief forming layer, and (Step c) exposure. A heating step in which the unexposed portion of the flexographic printing plate precursor is heated to a temperature sufficient to generate a liquefied product, and (step d) a removing step in which at least a part of the liquefied product is adhered to the absorbent material and removed. Before the step d, the step (e) includes a step of irradiating at least an unexposed portion of the relief forming layer of the flexographic printing plate precursor with actinic rays from the outer surface direction of the relief forming layer. Plate making method,
<2> The plate making method of a flexographic printing plate according to <1>, wherein the absorbing material is a material that transmits actinic rays.
<3> The plate making method of a flexographic printing plate according to <1> or <2>, wherein the actinic ray in the step e is an ultraviolet ray,
<4> The method for making a flexographic printing plate according to <3>, wherein the step e is a step of uniformly irradiating ultraviolet rays from a light source,
<5> The method for making a flexographic printing plate according to <1> or <2>, wherein the step e is a step of irradiating a laser beam in a reverse image manner,
<6> The plate making method of a flexographic printing plate according to any one of <1> to <5>, which includes step a, step b, step e, step c, and step d in this order,
<7> The plate making method of a flexographic printing plate according to any one of <1> to <5>, which includes step a, step e, step b, step c, and step d in this order,
<8> The plate making method of a flexographic printing plate according to any one of <1> to <7>, including a back irradiation step of irradiating the entire surface with actinic rays from the back before the step a.
<9> The flexographic printing plate according to any one of <1> to <8>, wherein the irradiation amount of active light in the step e is 1 to 20% of the irradiation amount of active light in the step a. Plate making method.

  ADVANTAGE OF THE INVENTION According to this invention, the plate-making method of the flexographic printing plate excellent in the removability of an unexposed part was able to be provided.

It is the conceptual diagram which showed the process of the plate making method of this invention.

The plate making method of the flexographic printing plate of the present invention comprises: (Step a) an exposure step of exposing the relief forming layer of the flexographic printing plate precursor imagewise; (Step b) disposing an absorbent material on the outer surface of the exposed relief forming layer. A step, (step c) a heating step in which the unexposed portion of the exposed flexographic printing plate precursor is heated to a temperature sufficient to generate a liquefied product, and (step d) bonding at least a part of the liquefied product to the absorbent material And a step of irradiating at least an unexposed portion of the relief forming layer of the flexographic printing plate precursor with actinic rays from the outer surface direction of the relief forming layer before the step d. Features.
In the present invention, the description of “lower limit to upper limit” representing a numerical range represents “lower limit or higher and lower limit or lower”, and the description of “upper limit to lower limit” represents “lower limit or higher and lower limit or higher”. That is, it represents a numerical range including an upper limit and a lower limit.
In addition, “(step a) an exposure step in which the relief forming layer of the flexographic printing plate precursor is imagewise exposed” or the like is simply referred to as “step a” or the like.

As a result of intensive studies, the present inventor conducted step e (step of irradiating at least an unexposed portion of the relief forming layer of the flexographic printing plate precursor with an actinic ray from the outer surface direction of the relief forming layer) before the heating step and the removing step. It has been found that the removability of the unexposed portion is improved by having it, and the present invention has been completed. That is, the plate making method of the flexographic printing plate of the present invention adds a step of irradiating actinic rays to an unexposed portion in plate making by so-called dry heat development. Here, the outer surface of the relief forming layer means a surface opposite to the surface in contact with the support.
The reason is not clear, but by irradiating actinic rays from the outer surface direction of the relief forming layer, the adhesion between the absorbent material and the unexposed part (uncured part) is improved, and the unexposed part is easily removed. It is thought that it became easy to remove even fine parts.

In this specification, regarding the description of the flexographic printing plate precursor and the flexographic printing plate, a layer having a flat surface as an image forming layer to be subjected to an exposure step is referred to as a relief forming layer, and the relief forming layer is exposed and developed. A layer having irregularities on the surface is referred to as a relief layer. Further, a flexographic printing plate can be obtained by exposing and developing the flexographic printing plate precursor.
Hereafter, each process of the plate making method of a flexographic printing plate is demonstrated.

1. Method for making a flexographic printing plate (step a) An exposure step for imagewise exposure to a relief forming layer of a flexographic printing plate precursor The plate making method for a flexographic printing plate of the present invention comprises (step a) a relief forming layer for a flexographic printing plate precursor. Includes an exposure process for performing imagewise exposure (hereinafter also simply referred to as an exposure process).
The exposure step is a step in which the relief forming layer is irradiated with an actinic ray in an image-like manner, thereby causing crosslinking and / or polymerization of the region irradiated with the actinic ray and curing. The exposed exposed portion of the relief forming layer does not melt in the subsequent heating step, and does not produce a liquefied portion.

An exposure process can be implemented by exposing through the mask provided in the outer surface side of the relief forming layer.
It is also preferable to use a vacuum frame exposure apparatus, and after the air between the relief forming layer and the mask is discharged, exposure with actinic rays is performed.
The exposure may be performed in a state where the oxygen concentration is lowered or may be performed in the atmosphere, and is not particularly limited. However, from the viewpoint of preventing polymerization inhibition by oxygen, it is preferable to perform the exposure at a low oxygen concentration.

Moreover, the said mask can be produced, for example by apply | coating an actinic-light blocking material or an ink in the reverse image form by inkjet application | coating.
An infrared sensitive layer or a laser sensitive layer may be provided on the relief forming layer, which may be removed by exposure with infrared rays or a laser to produce a mask. More specifically, the formation of a digital mask using an actinic radiation opaque layer described in paragraphs 0032 to 0040 of JP-T-2003-533738 or inkjet ink can be exemplified.

<Backside irradiation process>
Prior to the exposure step, it is also preferable to have a backside irradiation step. The back irradiation step is a step of irradiating the entire surface of the relief forming layer with actinic rays through the support from the support side.
The back irradiation process partially cures the relief forming layer. This curing proceeds closer to the support, and the curing level is the lowest on the outer surface (the surface farthest from the support, the surface opposite to the support).
The backside irradiation step is preferably performed in a shorter time than the exposure step (step a) performed thereafter, and is not performed under irradiation conditions (exposure intensity, exposure time) that cure the entire relief forming layer.

In the back irradiation process, it is preferable to irradiate an electron beam, and the electron beam is irradiated toward the support and is irradiated with energy that does not completely pass through the relief forming layer.
It is preferable to adjust the irradiation conditions so that less than 75% of the irradiated actinic light passes through 50% of the thickness of the relief forming layer. Curing is most promoted at the interface portion between the relief forming layer and the support, and curing is incomplete on the outer surface of the relief forming layer (the surface opposite to the support).
In the case of performing electron beam irradiation, the distance of electrons passing through the support and the relief forming layer can be controlled by adjusting the potential energy through which the accelerated electrons pass.

The back irradiation process forms a relatively thin continuous layer of the cured relief forming layer that is firmly bonded onto the support. This thin hardened layer (floor layer) becomes the base or supporting surface of the image portion to be formed later. In particular, with respect to image details, this thin hardened layer physically reinforces the adhesiveness of the details, reduces defects from the support due to wear and hardening failure, and improves printing durability.
In addition, the thin hardened layer (floor layer) formed by the back irradiation process is not removed from the support by development.

The actinic rays used in the back irradiation step and the exposure step can impart energy for generating a starting species in the relief forming layer by the irradiation, α rays, γ rays, X rays, ultraviolet rays, visible rays, Includes electron beams. Among these, ultraviolet rays and electron beams are preferable from the viewpoint of curing sensitivity and device availability, and it is more preferable to use ultraviolet rays in the exposure step.
Actinic ray sources include low-pressure mercury lamps, high-pressure mercury lamps, ultra-high pressure mercury lamps, metal halide lamps, carbon arc lamps, xenon lamps, zirconium lamps, fluorescent lamps for ultraviolet rays, electronic flash units, electron beam units, lasers, and photography. A floodlight lamp, sunlight, etc. are mentioned. Moreover, LED and LD can also be used as an actinic ray source.
Examples of suitable visible and ultraviolet light sources include carbon arcs, mercury vapor arcs, fluorescent lamps. The most suitable UV light source is a mercury vapor lamp, in particular an acid lamp. Examples of industrial standard light sources include Sylvania 350 Blacklight fluorescent lamps (FR48T12 / 350VL / VHO / 180, 115w) and Philips UV-A “TL” series low pressure mercury vapor fluorescent lamps. A mercury vapor arc or sunlamp is preferably used at a distance of 3 to 150 cm from the photosensitive element (relief forming layer), and these light sources emit 310 to 400 nm long wavelength ultraviolet light.

In the exposure step, it is preferable to irradiate ultraviolet rays, and the wavelength of the irradiated ultraviolet rays is more preferably 200 to 600 nm, further preferably 300 to 450 nm, and particularly preferably 300 to 400 nm.
The active rays to be irradiated is preferably at 2,000 mJ / cm ² or less, more preferably 10 to 2,000 mJ / cm ^2, more preferably from 20 to 1,000 mJ / cm ^2.
The exposure surface illuminance is preferably 10 to 2,000 mW / cm ^2, and more preferably 20 to 1,000 mW / cm ^2.
The irradiation time of the actinic ray is not particularly limited and may be appropriately selected within a range in which sufficient exposure area curing can be obtained. However, from the viewpoint of productivity and the like, it is preferably 60 seconds or less, and 40 seconds or less. More preferably, it is more preferably 30 seconds or less.

(Step b) Step of Arranging Absorbing Material on External Surface of Relief-Forming Layer Exposed The plate making method of the flexographic printing plate of the present invention has a step of (step b) arranging an absorbent material on the outer surface of the exposed relief-forming layer.
After the exposure step, the mask is removed from the relief forming layer and, instead, an absorbent material is placed on the outer surface of the relief forming layer.
In addition, although the process b is performed after the process a, it may be performed before the heating process mentioned later, and may be performed simultaneously with a heating process. Further, the absorbing material may be disposed at a stage where the unexposed portion of the relief forming layer is softened to some extent, but it is preferable to dispose the absorbing material before the unexposed portion is sufficiently softened (liquefied) by heating. .

The absorbent material used to remove the uncured (unexposed) relief forming layer is preferably a sheet-like member, and the internal strength and tear resistance at a temperature at which the uncured relief forming layer generates a liquefied product. It is preferable that it is a material which has high absorbency with respect to the liquefied uncured relief forming layer. That is, the melting or softening temperature of the absorbent material to be used needs to be higher than the melting or softening temperature of the uncured relief forming layer. In addition, absorptivity is measured by the gram number of the uncured relief forming layer which can be absorbed with respect to 1 ml of the absorbent material.
The absorbent material is preferably selected from non-woven materials, paper materials, textile fabric materials, open cell foam materials, porous sheets, or other sheet materials having voids.
A preferred absorbent material is a brown microfiber nonwoven fabric formed from a high melting polymer material such as polypropylene, polyester, nylon, or other high melting thermoplastic polymer. Moreover, the absorption member refine | purified by various paper manufacturing processes can also be used. In addition, open cell thermoset foams can be used.
The absorbent material preferably has a void volume of at least 50% or more of the sheet volume (measured in an uncompressed state).

Further preferred absorbent materials include spun-bonded nylon nonwoven webs such as SELEX ^™ nonwoven webs manufactured by James River Corporation, inorganic filament webs, particularly A porous filament is mentioned.

In addition, regarding the absorption of the uncured relief forming layer by the absorbent material, the term “absorption” does not particularly limit the absorption phenomenon. The uncured relief-forming layer that has formed the liquefied material does not need to penetrate into the main body of fibers, filaments, fine particles, etc. that constitute the absorbent member, and absorption into the absorbent member is caused only by internal surface wetting. Also good. The uncured relief forming layer may be removed by adhesion to the absorbent material surface.
The driving force for moving the liquefied uncured relief forming layer to the absorbent member is not particularly limited, and for example, surface tension, electric force (for example, van der Waals force), polar attractive force, affinity, and other physical forces Is mentioned.
In addition, “liquefaction” or “generates a liquefied product” means that the unexposed portion (uncured portion) of the relief forming layer is softened and becomes in a reduced viscosity state and can be removed by the absorbent material. . Therefore, it is not necessary to have a completely fluid state, and includes a softened state. The material constituting the relief forming layer is usually a material that does not have a rapid transition between a solid and a liquid. For this reason, the terms “melting”, “liquefaction” and “softening” represent the behavior of a heated unexposed part, regardless of whether there is an abrupt phase transition temperature between the solid state and the liquid state of the composition. It is used for That is, the unexposed portion of the liquefied relief forming layer can be absorbed and removed by the absorbent material side by contact with the absorbent material.

(Step c) Heating step in which the unexposed portion of the exposed flexographic printing plate precursor is heated to a temperature sufficient to generate a liquefied product. The plate making method of the flexographic printing plate of the present invention comprises (step c) an exposed flexographic printing plate precursor. The unexposed portion has a heating step for heating to a temperature sufficient to produce a liquefied product.
In the heating step, the unexposed portion of the relief forming layer is heated to a temperature sufficient to melt and produce a liquefied product.
The heating temperature is not particularly limited as long as it is a temperature at which the unexposed portion is liquefied to such an extent that it is absorbed by the absorbent material, but is preferably 40 ° C to 230 ° C. It is preferable that the temperature is 40 ° C. or higher because liquefaction is suppressed in the storage state and the exposure process. Moreover, since it is 230 degrees C or less, since a deformation | transformation etc. of a support body are suppressed, it is preferable.
The heating temperature is more preferably 50 to 200 ° C, still more preferably 70 to 180 ° C.
In addition, it is preferable to select the types and addition amounts of the binder, the polymerizable compound, and the like contained in the relief forming layer so that liquefaction of the unexposed portion occurs at the above heating temperature.

  In the heating step, heating can be performed by one or a plurality of heat sources. The method for heating the heat source is not particularly limited, and examples thereof include an electric core heater, an electric heating blanket, water vapor, oil, hot air, and the like. A radiant heater can also be used, and an infrared radiant heater provided with a reflector is exemplified.

(Step d) Removal step of removing at least a part of the liquefied material by adhering to the absorbent material The flexographic printing plate making method of the present invention comprises (step d) adhering at least a part of the liquefied material to the absorbent material. And a removing step for removing.
In step d, the uncured part (unexposed part) liquefied by heating and the absorbent material are adhered and removed. Although it is preferable that the uncured portion is absorbed by the absorbent material, as described above, not all of the uncured portion need be absorbed. Further, in order to sufficiently remove the uncured part, it is preferable to repeat the steps b to d a plurality of times.

In step d, 75% by weight or more of the unexposed portion of the relief forming layer is preferably removed, and more preferably removed by being absorbed by the absorbing member. More preferably, 80% by weight or more is removed, and more preferably 90% by weight or more is removed. In addition, when it has a back irradiation process, the thin continuous layer (floor layer) hardened | cured by the back irradiation process is not contained in the unexposed part removed.
The removal of 75% by weight or more of the unexposed portion is preferable because a good relief shape can be obtained.

  In the removing step, for example, as described in JP-A-2008-544326, a method of supporting an absorbent material with an endless belt and bringing it into contact with an unexposed portion of a relief forming layer, or JP-T-2007-531053. As described in Japanese Patent Application Publication No. Gazette, there can be exemplified a method in which an absorbent material is suspended and brought into contact with a heating roll, and the heating step and the removal step are performed simultaneously.

  As an exposure / development apparatus suitably used for the above heat development, reference can be made to apparatuses described in Japanese Utility Model Publication No. 4-89342, Japanese Translations of PCT International Publication No. 2003-508824, and the like. In performing exposure / development, the relief printing plate precursor may be provided on the surface of the drum or on a flat surface.

(Step e) Step of irradiating at least an unexposed portion of the relief forming layer of the flexographic printing plate precursor with actinic rays from the direction of the outer surface of the relief forming layer. The plate making method of the flexographic printing plate of the present invention comprises: (Step e) flexographic printing plate precursor A step of irradiating at least an unexposed portion of the relief forming layer with actinic rays from the outer surface direction of the relief forming layer.
In the present invention, step e is performed before the removal step (step d). The step e may be performed before the exposure step (step a) or simultaneously with the step a, but is preferably performed after the step a. That is, irradiation of actinic rays is performed before the removal step (step d) on the unexposed region (uncured portion, unexposed portion) of the exposed flexographic printing plate precursor in the exposure step (step a). Preferably it is done.
In the present invention, by including the step e, absorption into the absorbent material can be performed quickly, and fine portions of the unexposed portion can also be removed.
Although the mechanism of action is not clear, by including step e, by slightly curing the unexposed area, the tackiness of the unexposed area can be increased, and the adhesive force between the unexposed area and the absorbent material can be increased. it is conceivable that. Furthermore, it is considered that the bonding between the unexposed portions is increased by slightly curing, and even finer portions can be removed.
Note that irradiating actinic rays to at least the unexposed area means that the actinic rays may be irradiated to the unexposed area, and that the exposed area (image area) may be further irradiated.

In this invention, it is preferable that the process a-the process e have the process a, the process b, the process e, the process c, and the process d in this order.
A preferred process sequence will be described in detail with reference to the drawings.
FIG. 1 is a conceptual diagram showing the steps of the plate making method of the present invention. FIG. 1A shows a flexographic printing plate precursor, and a relief forming layer 2 is provided on a support 1. Here, the outer surface 3 is the surface opposite to the surface in contact with the support of the relief forming layer. In the relief printing plate precursor, an adhesive layer (not shown) may be provided between the support and the relief forming layer. Further, a protective layer (not shown) may be provided until the exposure process.
FIG. 1 (b) shows a backside irradiation process. The active light is irradiated through the support 1 from the support 1 side of the flexographic printing plate precursor, and the surface of the relief forming layer 2 in contact with the support 1 is placed on the floor. A layer (thin hardened layer) 4 is formed. As described above, the back irradiation process is not an essential process, but by forming the floor layer, the adhesive printing force between the support 1 and the relief layer is improved and the printing durability is improved in the resulting relief printing plate. Therefore, it is preferable.

FIG. 1C shows an exposure process. The relief forming layer 2 is irradiated with active light through the mask 5 provided on the outer surface of the relief printing plate precursor, and the region irradiated with the active light (exposed portion 6) is cured. On the other hand, the unexposed portion 7 is uncured.
FIG. 1D shows steps b to e. After the exposure process, the mask 5 is removed, and the absorbing material 8 is placed on the outer surface of the relief forming layer 2 instead. Thereafter, at least the unexposed portion 7 of the relief forming layer of the exposed flexographic printing plate precursor is irradiated with actinic rays from the outer surface direction of the relief forming layer. In FIG. 1 (d), the entire surface is irradiated with actinic rays through the absorbent material 8 from the outer surface direction of the relief forming layer 2.
Next, by heating, a liquefied material is generated in the unexposed portion 7, and the liquefied material is removed by the absorbent material 8. In FIG. 1D, for the sake of convenience, the unexposed portion 7 is removed from the relief forming layer while maintaining its shape, but may be absorbed by the absorbent material 8 and is not particularly limited. Moreover, it is preferable to repeat the process b-the process e shown by FIG.1 (d).

  In addition, this invention is not limited to this, After the exposure process (process a), actinic light irradiation (process e) is performed to an unexposed part, and then process b, process c, and process d are performed in this order. The method of having can also be illustrated. In this case, it is preferable to repeat step e and steps c to d.

Examples of the type and the light source of the active light irradiated in the step e can be the same as those in the exposure step.
In step e, at least the unexposed portion of the relief forming layer may be irradiated with actinic rays, and the entire surface may be exposed, or actinic rays are irradiated only on the unexposed portions by irradiating actinic rays in a reverse image manner. There is no particular limitation. That is, the actinic ray irradiation in the step e may be a step of uniformly irradiating actinic rays, or a step of irradiating only an unexposed portion.
When irradiating actinic rays uniformly, it is preferable to irradiate ultraviolet rays as actinic rays. In this case, the same light source as that used in the exposure step can be preferably exemplified as the ultraviolet light source.
Moreover, when irradiating only an unexposed part, with respect to the exposure process which exposes like an image, it will irradiate like a reverse image. In this case, it is preferable to irradiate laser light in a reverse image manner, and the laser light source is preferably an ultraviolet laser, and the ultraviolet laser is preferably a semiconductor laser that emits light of 250 to 420 nm.

  Further, in step e, actinic rays are irradiated from the outer surface direction of the relief forming layer, but it is not excluded to irradiate actinic rays from the support side. Therefore, after the exposure step, at the same time as step e or before and after step e, there is a step of irradiating the unexposed portion of the relief forming layer with actinic rays from the support side through the support. You may do it.

The actinic ray irradiation amount in step e is preferably 1 to 20% of the actinic ray irradiation amount in the exposure step, more preferably 2 to 18%, and even more preferably 5 to 15%. .
Moreover, it is preferable that it is 1-50% of the irradiation amount of the actinic ray in a back surface irradiation process, it is more preferable that it is 2-45%, and it is still more preferable that it is 5-40%.
When the irradiation amount of the actinic ray in the step e is within the above range, slight curing of the unexposed portion occurs, and the removability of the unexposed portion is enhanced.
In addition, said irradiation amount means the irradiation amount in the outermost surface of an unexposed part. When the actinic ray is irradiated through the absorbing material after the absorbing material is disposed, the irradiation amount on the outermost surface of the actual unexposed portion may be reduced due to the actinic ray transmittance of the absorbing material.

When the step e is performed after the step b, the absorptive material is irradiated after the absorptive material is disposed. Therefore, the absorptive material is preferably a material that transmits actinic rays. The phrase “transmitting actinic rays” means that the transmittance is 3% or more.
It is preferable that the absorbing material is a material that transmits actinic rays because step e can be performed after the absorbing material is disposed on the exposed relief forming layer.
The actinic ray transmittance of the absorbing material is preferably 3% or more, more preferably 5 to 95%, and still more preferably 10 to 80%.

2. Flexographic printing plate precursor The flexographic printing plate precursor used in the flexographic printing plate making method of the present invention will be described below.
In the present invention, the flexographic printing plate has a relief forming layer on a support. The “outer surface” of the relief forming layer means a surface opposite to the surface on which the support of the relief forming layer is provided.

(Relief forming layer)
The relief forming layer is cured by the step a (exposure step). It is preferable that the composition is cured by being irradiated with actinic rays to cause polymerization or a crosslinking reaction. The unexposed portion of the relief forming layer is softened and liquefied by heating, absorbed by the absorbent material, and can be removed from the flexographic printing plate precursor.

The relief forming layer preferably contains at least a polymerizable compound, a polymerization initiator, and a binder. Hereinafter, each component will be described.
<Polymerizable compound>
In the present invention, the relief forming layer preferably contains a polymerizable compound, and the polymerizable compound is preferably a radical polymerizable compound, and more preferably an ethylenically unsaturated compound. The polymerizable compound is polymerized by irradiation with actinic rays in the exposure step, and the exposed portion (cured portion) is not melted by subsequent heating.
The weight average molecular weight of the polymerizable compound is preferably 5,000 or less. When the weight average molecular weight of the polymerizable compound is 5,000 or less, it is easy to produce a relief-forming layer, and it melts during heating. The viscosity at the time is low, and it is preferable because the unexposed portion can be easily removed.

The polymerizable compound can be arbitrarily selected from compounds having at least 1, preferably 2 or more, more preferably 2 to 6 ethylenically unsaturated groups.
The polymerizable compound that can be used in the present invention is preferably a compound having 2 or more (preferably 2 to 6, more preferably 2 or 3, and still more preferably 2) (meth) acryl groups, It is more preferable that the compound has a (meth) acryloxy group of 2 or more (preferably 2 to 6, more preferably 2 or 3, more preferably 2).

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

Examples of radically polymerizable ethylenically unsaturated compounds include unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, crotonic acid, isocrotonic acid, maleic acid and their salts, and anhydrides having an ethylenically unsaturated group. Polymers such as products, (meth) acrylates, (meth) acrylamides, acrylonitrile, styrene, various unsaturated polyesters, unsaturated polyethers, unsaturated polyamides, 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, an oligomer may be used as the polymerizable compound.
The oligomer is generally a polymer in which a finite number of monomers (generally 5 to 100) are bonded, and a known compound called an oligomer can be arbitrarily selected. It is preferable to select a polymer having a molecular weight of 400 to 5,000 (more preferably 500 to 3,000).
The oligomer preferably has an ethylenically unsaturated group, and more preferably a (meth) acryloxy group.

As the oligomer in the present invention, any oligomer may be used. For example, olefin (ethylene oligomer, propylene oligomer butene oligomer, etc.), vinyl (styrene oligomer, vinyl alcohol oligomer, vinyl pyrrolidone oligomer acrylate oligomer, methacrylate oligomer, etc.), diene, etc. System (butadiene oligomer, chloroprene rubber, pentadiene oligomer, etc.), ring-opening polymerization system (di-, tri-, tetraethylene glycol, polyethylene glycol, polyethylimine, etc.), polyaddition system (oligoester acrylate, polyamide oligomer, polyisocyanate) Oligomers), addition condensation oligomers (phenol resins, amino resins, xylene resins, ketone resins, etc.). In this, oligoester (meth) acrylate is preferable, in which urethane (meth) acrylate, polyester (meth) acrylate, and epoxy (meth) acrylate are more preferable, and urethane (meth) acrylate is still more preferable.
Preferred examples of the urethane (meth) acrylate include aliphatic urethane (meth) acrylates and aromatic urethane (meth) acrylates, and more preferred are aliphatic urethane (meth) acrylates.
The urethane (meth) acrylate is preferably a tetrafunctional or lower urethane (meth) acrylate, and more preferably a bifunctional or lower urethane (meth) acrylate. By containing urethane (meth) acrylate, a relief forming layer having excellent curability can be obtained.
Regarding the oligomer, the oligomer handbook (supervised by Junji Furukawa, Chemical Industry Daily Co., Ltd.) can also be referred to.

Moreover, what is shown below can be illustrated as a commercial item of an oligomer.
Examples of the urethane (meth) acrylate include R1204, R1211, R1213, R1217, R1218, R1301, R1302, R1303, R1304, R1306, R1308, R1901, and R1150 manufactured by Daiichi Kogyo Seiyaku Co., Ltd. EBECRYL series (for example, EBECRYL230, 270, 4858, 8402, 8804, 8807, 8803, 9260, 1290, 1290K, 5129, 4842, 8210, 210, 4827, 6700, 4450, 220) manufactured by Co., Ltd. NK oligo U-4HA, U-6HA, U-15HA, U-108A, U200AX, etc. manufactured by Kogyo Co., Ltd., Aronix M-1100, M-1200, M-1210, M-1310 manufactured by Toagosei Co., Ltd. M-1600, M-1960, and the like.
Examples of the polyester (meth) acrylate include EBECRYL series (for example, EBECRYL770, IRR467, 81, 84, 83, 80, 675, 800, 810, 812, 1657, 1810, IRR302, 450, manufactured by Daicel Cytec Co., Ltd. 670, 830, 870, 1830, 1870, 2870, IRR267, 813, IRR483, 811, etc.), Aronix M-6100, M-6200, M-6250, M-6500, M-7100, manufactured by Toagosei Co., Ltd. , M-8030, M-8060, M-8100, M-8530, M-8560, M-9050 and the like.
Moreover, as an epoxy (meth) acrylate, for example, EBECRYL series (for example, EBECRYL600, 860, 2958, 3411, 3600, 3605, 3700, 3701, 3703, 3702, 3708, RDX63182, 6040, manufactured by Daicel Cytec Co., Ltd. Etc.).

The content of the polymerizable compound in the relief forming layer is preferably 2 to 50% by weight, more preferably 5 to 30% by weight, and more preferably 10 to 20% by weight in the total solid content of the relief forming layer. More preferably.
When the content of the polymerizable compound is within the above range, curing is sufficiently performed and stickiness due to unpolymerized products is suppressed, which is preferable.

<Polymerization initiator>
In the present invention, the relief forming layer preferably contains a polymerization initiator. The polymerization initiator is a compound that absorbs external energy such as actinic rays to generate a polymerization initiating species.
The polymerization initiator generates a polymerization initiating species by exposure in the exposure process (light, preferably irradiation with actinic rays or the like), and causes polymerization of the polymerizable compound.
The polymerization initiator that can be used in the present invention is preferably a free radical photoinitiator, and includes aromatic ketones (eg, quinones, acetophenone compounds), acylphosphine compounds, aromatic onium salt compounds, organic compounds. Examples thereof include peroxides, thio compounds, hexaarylbiimidazole compounds, ketoxime ester compounds, borate compounds, azinium compounds, metallocene compounds, active ester compounds, and compounds having a carbon halogen bond. Specific examples of these polymerization initiators include polymerization initiators described in JP 2008-208190 A and JP 2009-096985 A. A polymerization initiator may be used individually by 1 type, and may use 2 or more types together.

A polymerization initiator may be used individually by 1 type, may use 2 or more types together, and is not specifically limited.
As content of a polymerization initiator, it is preferable that it is 0.01 to 15 weight% with respect to the total solid content of a relief formation layer, It is more preferable that it is 0.05 to 10 weight%, 0.1 to More preferably, it is 5% by weight.
It is preferable that the content of the polymerization initiator is within the above range because an appropriate curing reaction occurs during exposure.

The polymerization initiator may be used in combination with various sensitizers and is not particularly limited. The sensitizer that can be used in combination with the polymerization initiator will be described below.
<Sensitizer>
Examples of the sensitizer include polynuclear aromatics (eg, pyrene, perylene, triphenylene, 2-ethyl-9,10-dimethoxyanthracene), xanthenes (eg, fluorescein, eosin, erythrosine, rhodamine B, Rose Bengal etc.), cyanines (eg thiacarbocyanine, oxacarbocyanine etc.), merocyanines (eg merocyanine, carbomerocyanine etc.), thiazines (eg thionine, methylene blue, toluidine blue etc.), acridines (eg , Acridine orange, chloroflavin, acriflavine, etc.), anthraquinones (eg, anthraquinone, etc.), squaliums (eg, squalium), coumarins (eg, 7-diethylamino-4-methylcoumarin, etc.), thioxanthate Class (e.g., thioxanthone, 2-isopropylthioxanthone, 4-isopropylthioxanthone, etc.) and the like. Moreover, the compound described in Unexamined-Japanese-Patent No. 2010-013574, paragraphs 0082-0115 is mentioned.
Among these, thioxanthones can be preferably exemplified.
Moreover, a sensitizer may be used individually by 1 type and may use 2 or more types together.
When using a sensitizer, the total content of the polymerization initiator is preferably 200: 1 to 1: 200, more preferably a weight ratio of the polymerization initiator to the sensitizer with respect to the content of the sensitizer. Is in the range of 50: 1 to 1:50, more preferably 20: 1 to 1: 5.

<Binder>
As binders, for example, as elastomers, polyalkadienes; alkadiene / acrylonitrile copolymers; ethylene / propylene / alkadiene copolymers; ethylene / (meth) acrylic acid / (meth) acrylate copolymers; and styrene, butadiene, And / or thermoplastic elastomeric block copolymers of isoprene. Preference is given to linear and radial thermoplastic elastomeric block copolymers of styrene and butadiene and / or isoprene.

More preferably, the binder is a thermoplastic elastomer.
The thermoplastic elastomer may be a single polymer or a mixture of polymers. Thermoplastic elastomers include natural or synthetic polymers of conjugated diolefin hydrocarbons, including polyisoprene, 1,2-polybutadiene, 1,4-polybutadiene, and butadiene / acrylonitrile. The thermoplastic elastomer may be an ABA type block copolymer (wherein A represents a non-elastomeric block, preferably a vinyl polymer, most preferably polystyrene, and B represents an elastomeric block, preferably polybutadiene or polyisoprene). The elastomeric block copolymer of
Preferred examples of this type of thermoplastic elastomeric binder include poly (styrene / isoprene / styrene) block copolymers and poly (styrene / butadiene / styrene) block copolymers. The ratio of non-elastomer to elastomer is preferably in the range of 10:90 to 35:65.
Most preferably, the thermoplastic elastomer binder is a mixture of at least two poly (styrene / isoprene / styrene) block copolymers (see US Pat. No. 5,972,565). The binder is preferably present at 60% by weight or more in the solid content of the relief forming layer.

  The binder is intended to include a core-shell microgel, a blend of microgels, and a pre-formed polymer.

  Other suitable binders that can be used include polyurethane elastomers. Examples of suitable polyurethane elastomers are (i) organic diisocyanates, (ii) having at least two free hydrogen groups per molecule that can be polymerized with isocyanate groups, and at least one ethylenically unsaturated addition polymerizable. A reaction product of at least one chain extender having a group and (iii) an organic polyol having a minimum molecular weight of 500 and a group containing at least two free hydrogens capable of polymerizing with an isocyanate group. (See Kaihei No. 5-19469).

A binder may be used individually by 1 type, may use 2 or more types together, and is not specifically limited.
The content of the binder is preferably 5 to 60% by weight, more preferably 10 to 50% by weight, and further preferably 15 to 40% by weight based on the total solid content of the relief forming layer. preferable. It is preferable for the content of the bond amount to be in the above range since a relief layer having excellent flexibility can be obtained.

<Other ingredients>
Depending on the desired final properties, the relief-forming layer can be prepared using conventional additives such as thermal polymerization inhibitors, plasticizers, sensitizers, colorants, antioxidants, antiozonants, fillers, rheology adjustments. Agents, processing aids, and the like.
Processing aids include those such as low molecular weight polymers that are compatible with elastomeric block copolymers, such as low molecular weight α-methylstyrene polymers or copolymers.
Examples of the ozonolysis inhibitor include hydrocarbon wax, norbornene, and vegetable oil. Examples of the antioxidant include alkylated phenol, alkylated bisphenol, trimethyldihydroquinone polymer, and dilauryl thiopropionate. Plasticizers are used to adjust the film-forming properties of the binder, examples of suitable plasticizers include aliphatic hydrocarbon oils such as naphthenic oils and paraffin oils; liquid polydienes such as liquid polybutadiene; Liquid polyisoprene is included. Generally, the plasticizer is a liquid having a molecular weight of less than about 5,000, but can have a molecular weight up to about 30,000. Low molecular weight plasticizers include those having a molecular weight of less than about 30,000.

The thickness of the relief forming layer can be selected according to the desired type of flexographic printing plate, and is not particularly limited. It is preferably 0.01 to 1 cm, more preferably 0.05 to 0.64 cm, still more preferably 0.07 to 0.5 cm, and 0.08 to 0.2 cm. Particularly preferred.
When the thickness of the relief forming layer is within the above range, it is possible to obtain a flexographic printing plate having excellent printing durability and excellent relief shape.

(Support)
The material used for the support of the flexographic printing plate precursor is not particularly limited, but materials having high dimensional stability are preferably used. For example, metals such as steel, stainless steel, and aluminum, polyester (for example, PET (polyethylene terephthalate), PBT ( (Polybutylene terephthalate), PAN (polyacrylonitrile)), polyvinyl chloride, polycarbonate, polyimide and other plastic resins, styrene-butadiene rubber and other synthetic rubber, and glass fiber reinforced plastic resins (such as epoxy resins and phenol resins) Can be mentioned. The support is preferably a PET film or a steel substrate, and more preferably a PET film.
When it has a back irradiation process, it is preferable to have transparency to actinic rays.
The form of the support is determined depending on whether the relief forming layer is a sheet or a sleeve.

(Adhesive layer)
When the relief forming layer is formed on the support, an adhesive layer may be provided between the two for the purpose of enhancing the adhesive strength between the layers.
It is preferable that the adhesive layer enhances the adhesion or bonding force of the relief forming layer and the relief layer to the support by performing an undercoat treatment or an adhesion promotion treatment. Such a treatment is generally performed on the surface of the support before application of the relief forming layer.
Corona discharge treatment, laser treatment described in U.S. Pat. No. 4,822,451, mechanical surface roughening, etc., and application of a chemical primer may be used.
Examples of the material (adhesive) that can be used for the adhesive layer include I.I. Those described in the edition of Skeist, “Handbook of Adhesives”, the second edition (1977) can be used.

(Protective film, slip coat layer)
A protective film may be provided on the surface of the relief forming layer for the purpose of preventing scratches and dents on the surface of the relief forming layer. The thickness of the protective film is preferably 25 to 500 μm, more preferably 50 to 200 μm. As the protective film, for example, a polyester film such as PET, or a polyolefin film such as PE (polyethylene) or PP (polypropylene) can be used. The surface of the film may be matted. The protective film is preferably peelable.

  When the protective film cannot be peeled or when it is difficult to adhere to the relief forming layer, a slip coat layer may be provided between both layers. The material used for the slip coat layer is a resin that can be dissolved or dispersed in water, such as polyvinyl alcohol, polyvinyl acetate, partially saponified polyvinyl alcohol, hydroxyalkyl cellulose, alkyl cellulose, polyamide resin, etc. It is preferable that

(Anti-halation layer)
An antihalation layer may be provided between the support and the relief forming layer. Such antihalation layers disperse finely pulverized dyes or pigments that substantially absorb actinic rays and resins or polymers that adhere to both the support and the relief forming layer in a solution or aqueous dispersion. It can be made by coating it on a support and drying it. Suitable antihalation pigments and dyes include carbon black, manganese dioxide, Acid Blue Black (CI 20470), and Acid Magenta O (CI 42585). Suitable polymer or resin carriers include polyvinyl compounds, such as polyvinyl chloride homopolymers or copolymers, copolymers of acrylic acid and methacrylic acid, and the like.

(Formation method of relief forming layer)
The method for forming the relief forming layer in the flexographic printing plate precursor is not particularly limited. For example, a coating resin composition for a relief forming layer is prepared, and if necessary, from this coating resin composition. The method of melt-extruding on a support body after removing a solvent is mentioned. Alternatively, the resin composition may be cast on a support and dried in an oven to remove the solvent from the resin composition.

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. Thereafter, it is also preferable to press the relief forming layer flatly by applying heat and / or pressure.
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 support body then.
When providing an adhesive layer, it can respond by using the support body which apply | coated the adhesive layer. When providing a slip coat layer, it can respond by using the protective film which apply | coated the slip coat layer.

EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples.
In addition, the weight average molecular weight (Mw) of the polymer in an Example is displaying the value measured by GPC method unless there is particular notice. “Parts” and “%” mean “parts by weight” and “% by weight” unless otherwise specified.

[Example 1]
(Manufacture of relief printing plate precursor)
<Preparation of resin composition for relief forming layer>
10 parts by weight of acrylonitrile-butadiene latex (Nipol SX1503, non-volatile content 42%, manufactured by Nippon Zeon Co., Ltd.), 50 parts by weight of butadiene latex (Nipol LX111NF, non-volatile content 55%, manufactured by Nippon Zeon Co., Ltd.), oligobutadiene acrylate ( 28 parts by weight of ABU-2S, manufactured by Kyoeisha Chemical Co., Ltd., 5 parts by weight of lauryl methacrylate (Light Ester L, manufactured by Kyoeisha Chemical Co., Ltd.), 3 parts by weight of dimethyloltricyclodecane diacrylate, photopolymerization initiator (benzyl) 1 part by weight of methyl ketal (manufactured by Sun Chemical Co., Ltd.) and 0.1 part by weight of hydroquinone monomethyl ether as a polymerization inhibitor were mixed in a container together with 15 parts by weight of toluene, and then 105 parts using a pressure kneader. Knead at ℃, then remove toluene and water under reduced pressure By and to obtain a relief forming layer resin composition.

<Preparation of mask layer coating solution>
For the mask layer coating liquid (mask layer coating liquid), a mixture of a carbon black dispersion (manufactured by Orient Chemical Industry Co., Ltd., AMBK-8) and a polyamide resin (Macromelt 6202, manufactured by Macromelt Co., Ltd.) is used. Using. The mixing ratio of each component in the mixture was carbon black: dispersed resin: polyamide resin = 40: 30: 30 in terms of solid content weight ratio.

<Production of mask film>
After performing mold release treatment on both sides of a PET film (Toyobo Co., Ltd., E5000, thickness 100 μm), apply a thermal mask layer coating solution using a bar coater so that the composition thickness is 10 μm. And dried at 120 ° C. for 5 minutes.

<Preparation of flexographic printing plate A>
A resin composition for a relief forming layer was placed on a PET film support (Toyobo Co., Ltd., E5000, thickness 125 μm) coated with a copolyester adhesive, and a mask film was overlaid thereon. Lamination was performed at 100 ° C. using a heat press to obtain a flexographic printing original plate comprising a PET support, an adhesive layer, a photosensitive resin layer (relief forming layer), a mask layer, and a release-treated PET protective film (cover film). . The total thickness of the plate was 1.90 mm.

<Preparation of relief printing plate>
The printing plate precursor was irradiated with 700 mJ / cm ² of actinic radiation from the PET support side with ECS-4011GX (manufactured by Eye Graphics Co., Ltd.). Subsequently, the release-treated PET film (cover film) was peeled off. This plate was wound around a rotating drum of Digital Imager Spark (manufactured by ESKO) so that the heat-sensitive mask layer was on the front side, and image formation was performed. After ablation, the plate was taken out and returned to the flat surface, and left still for 5 minutes in a horizontal state with a hot air dryer (FLT 1200 DRYER (manufactured by Anderson & Vreland)) at 60 ° C. Thereafter, irradiation with 1,000 mJ / cm ² was performed with actinic radiation ECS-4011GX (manufactured by Eye Graphics Co., Ltd.).
Then, after peeling off the mask film, (1) Place the plate on a 1 mm SUS plate, (2) Place in an oven at 140 ° C. for 15 seconds, (3) Absorbent; Stratec RW2100 Thickness 0.58 mm (Idemitsu Unitech (4) Further, after UV irradiation (UV irradiation machine ECS-4011GX (manufactured by Eye Graphics Co., Ltd.)) described in Table 1 was performed from the nonwoven fabric side, (5) ) The non-woven fabric stuck at a peeling angle of 90 ° was peeled off. When increasing the number of developments, (1) to (5) were repeated.

[Examples 2 and 3, Comparative Examples 1 and 2]
In Examples 2 and 3, a relief printing plate was obtained in the same manner as in Example 1 except that the number of developments was changed to the number shown in the table.
In Comparative Examples 1 and 2, a relief printing plate was obtained in the same manner as in Example 1 except that exposure after placing the nonwoven fabric was not performed and the number of developments was changed to the number shown in the table.

(Evaluation)
The following evaluation was performed on the obtained relief printing plate.
<Relief depth>
The relief depth of the engraved part and the unengraved part was measured with a laser microscope VK-8700 (manufactured by Keyence Corporation).
The relief depth is preferably deeper.

<Clogged halftone dots>
After development at 150 lpi and a dot area ratio of 30%, the plate surface was observed with a microscope VHX-1000 (manufactured by Keyence Corporation), and development residue remaining between the small dots was visually evaluated.
○: No residue left Δ: Partial residue left ×: Waste left over

  The ultraviolet transmittance of Stratec RW2100 (thickness 0.58 mm, manufactured by Idemitsu Unitech Co., Ltd.), which is an absorber, was 15%. Therefore, the ultraviolet irradiation to the plate surface was 150 mJ in Examples 1 to 3.

<Examples 4 and 5>
Before placing the nonwoven fabric on the plate, the irradiation energy of UV irradiation was set to 100 mJ / cm ² to irradiate the unexposed area with ultraviolet light, and the UV irradiation of (4) was not performed. A relief printing plate was prepared in the same manner as in 1. When increasing the number of developments, each step was repeated including irradiation of unexposed areas. The evaluation was performed in the same manner as in Example 1.

<Examples 6 and 7>
A relief printing plate was prepared in the same manner as in Example 1 except that the irradiation energy of UV irradiation after placing the nonwoven fabric on the plate was 2,000 mJ / cm ² . The evaluation was performed in the same manner as in Example 1.

<Example 8>
The printing original plate A was irradiated with 700 mJ / cm ² of actinic radiation from the PET support side with ECS-4011GX (manufactured by Eye Graphics Co., Ltd.). Subsequently, the release-treated PET film (cover film) was peeled off. This plate was wound around a rotating drum of Digital Imager Spark (manufactured by ESKO) so that the heat-sensitive mask layer was on the front side, and image formation was performed. After ablation, the plate was taken out and returned to the flat surface, and left still for 5 minutes in a horizontal state with a hot air dryer (FLT 1200 DRYER (manufactured by Anderson & Vreland)) at 60 ° C. Thereafter, irradiation with 1,000 mJ / cm ² was performed with actinic radiation ECS-4011GX (manufactured by Eye Graphics Co., Ltd.).
Thereafter, after peeling off the mask film, (1) the plate is placed on a 1 mm SUS plate, (2) placed in an oven at 140 ° C. for 15 seconds, and (3) non-woven Stratec RW2100 thickness 0.58 mm (manufactured by Idemitsu Unitech) ) Is placed on the plate at a pressure of 200 gf, and (4) this plate is further applied to the mask film so that the thermal mask layer on which a reverse image is formed on the rotating drum of Digital Imager Spark (manufactured by ESKO) is on the front side. And the reverse image irradiation was performed from the nonwoven fabric side, and (5) the nonwoven fabric adhered at a peeling angle of 90 ° was peeled off. When increasing the number of developments, (1) to (5) were repeated.

1: support, 2: relief forming layer, 3: outer surface, 4: floor layer, 5: mask, 6: exposed part (cured part), 7: unexposed part (uncured part), 8: absorbent material

Claims (9)

(Step a) An exposure step of performing imagewise exposure on the relief forming layer of the flexographic printing plate precursor,
(Step b) A step of disposing an absorbent material on the outer surface of the exposed relief forming layer,
(Step c) A heating step in which the unexposed portion of the exposed flexographic printing plate precursor is heated to a temperature sufficient to produce a liquefied product, and
(Step d) having a removing step of removing at least a part of the liquefied material by adhering it to the absorbent material;
Before the step d, (step e) includes a step of irradiating at least an unexposed portion of the relief forming layer of the flexographic printing plate precursor with actinic rays from the outer surface direction of the relief forming layer, and making the flexographic printing plate Method.   The plate making method of a flexographic printing plate according to claim 1, wherein the absorbing material is a material that transmits actinic rays.   The plate making method of a flexographic printing plate according to claim 1 or 2, wherein the actinic rays in the step e are ultraviolet rays.   The plate making method of a flexographic printing plate according to claim 3, wherein the step e is a step of uniformly irradiating ultraviolet rays from a light source.   The flexographic printing plate making method according to claim 1, wherein the step e is a step of irradiating a laser beam in a reverse image manner.   The method for making a flexographic printing plate according to any one of claims 1 to 5, which comprises a process a, a process b, a process e, a process c, and a process d in this order.   The plate making method of a flexographic printing plate according to any one of claims 1 to 5, comprising a step a, a step e, a step b, a step c, and a step d in this order.   The plate making method of a flexographic printing plate according to any one of claims 1 to 7, further comprising a back irradiation step of irradiating the entire surface with actinic rays from the back before the step a.   The plate making method of a flexographic printing plate according to any one of claims 1 to 8, wherein the irradiation amount of the actinic ray in the step e is 1 to 20% of the irradiation amount of the actinic ray in the step a.

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