JP2011088353A - Method of manufacturing printing plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a printing plate providing a high definition printed matter in a manufacturing technique of the printing plate including a process of pattern formation by means of laser engraving. <P>SOLUTION: Disclosed is a method of manufacturing a printing plate including a process of engraving a printing original plate by laser in such a manner that the height of the vertex of a dot part shows no height difference compared with a solid part. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a printing plate manufacturing method.

In recent years, so-called flexographic printing has been widely used as a printing method for soft packaging materials such as paper and film. For example, various packaging materials such as corrugated cardboard, paper containers, paper bags, and soft packaging films, wallpaper, decorative plates, and the like. As a printing method for building materials and labels, its specific gravity is increasing.
In order to produce a printing plate for flexographic printing, a photosensitive resin (a liquid resin or a solid resin plate formed into a sheet shape) is usually used.

Specifically, after placing a predetermined photomask on the photosensitive resin, irradiating with light through the mask, causing the photosensitive resin to undergo a crosslinking reaction, the unexposed portion that has not undergone the crosslinking reaction is washed away with a developer, A method of producing a printing plate on which a pattern is formed is used.
In recent years, a thin light-absorbing layer called a black layer is provided on the surface of a predetermined photosensitive resin plate, and this is irradiated with laser light to form a mask image directly on the photosensitive resin plate, and light is transmitted through the mask image. A flexo CTP (Computer to Plate) technique, which is an efficient method for producing a printing plate in which a crosslinking reaction is performed by irradiation, and then a non-crosslinked portion is washed away with a developer, has been developed.

However, even in this flexo CTP technology, since a developing process is essential in the printing plate preparation process, further efficiency in the manufacturing process is required.
As a method for producing a printing plate that does not require a development step, there is a method in which a resin layer is directly engraved with a laser to form a pattern.
In this technique, a laser engraving plate is used as a plate material, and there are advantages such as shortening of plate making time and reduction of waste.
In the following Patent Document 1, a printing plate from which engraving debris generated in a laser engraving process is removed, which is a two-point convex part and a concave character, a 30 μm-wide thin line, an independent point of a diameter of 100 μm, and 156 lpi, 1% A laser engraving printing plate in which halftone dots are formed is disclosed.

JP 2008-105429 A

The technique disclosed in Patent Document 1 is a printing plate from which engraving residue generated in a laser engraving process is removed, and has two points of convex portions and concave characters, a thin line of 30 μm width, and an independent point of a diameter of 100 μm. In addition, there is a description of a laser engraving printing plate in which 156 lpi and 1% halftone dots are formed.
However, there are problems such as plate swelling due to ink and mechanical accuracy variations during printing, and these problems have not been studied at all, and there is still much room for improvement. In addition, as the width of the plate cylinder of the printing press increases, the printing pressure fluctuation tends to increase from side to side, and a printing plate having a wide latitude with respect to the printing pressure is desired.
Therefore, in the present invention, in the uneven pattern manufacturing technique including the step of forming a pattern by laser engraving, a printing plate that can easily maintain the printing quality against printing pressure fluctuation, that is, a printing plate having a wide printing pressure latitude is manufactured. It aims to provide a method.

  In order to solve the above-described problems of the prior art, the present inventor has intensively studied a method for manufacturing a concavo-convex pattern, and as a result, has completed the present invention.

  According to the present invention, it is possible to provide a printing plate that can easily maintain printing quality against printing pressure fluctuations.

Cross-sectional view of halftone dot and solid part of conventional printing plate Sectional drawing of the halftone dot and solid part of the printing plate of this Embodiment

  Hereinafter, a mode for carrying out the present invention (hereinafter referred to as the present embodiment) will be described in detail. In addition, this invention is not limited to the following description, In the range of the summary, various deformation | transformation can be implemented.

[Method for producing printing plate of first embodiment]
The method for producing a printing plate according to the first embodiment includes a step of laser engraving a printing original plate so that the height of the top of the halftone dot portion is not different from the height of the solid portion. It is.
As in the technique disclosed in Japanese Patent Application Laid-Open No. 2008-183888, it is known that a conventional printing plate obtained by laser engraving usually has a lower halftone dot top than a solid part. . However, when the printing pressure fluctuates in printing using such a halftone dot, the design value of the halftone dot area ratio on the printing plate and the measured value of the halftone dot area ratio formed on the printing material change significantly, Print quality also tends to fluctuate.

  According to the manufacturing method of the first embodiment of the present invention, which includes the step of laser engraving the printing original plate so that the height of the top of the halftone dot and the height of the top of the halftone dot are not different from the solid part. When the obtained printing plate is compared with a conventional printing plate in which the height of the top of the halftone dot is lower than the solid portion, there is a difference in print quality stability during printing, and the height of the top of the halftone dot, The printing plate of the present embodiment having no level difference in the solid portion has a design value of the halftone dot area ratio on the printing plate and an actual measurement value of the halftone dot area ratio formed on the printing material with respect to printing pressure fluctuation. It was found that the printing plate is easy to maintain the printing quality even when touched by the printing pressure.

In the first embodiment of the present invention, as a method of laser engraving the printing original plate so that the height of the top of the halftone dot portion is not different from the height of the solid portion, for example, the energy irradiated to the shoulder of the halftone dot The method of controlling the amount of light, the method of controlling the gradient of the energy applied to the shoulder of the halftone dot, the method of combining them, the method of engraving the solid part, etc., are not limited thereto.
Here, “there is no difference in height between the top of the halftone dot and the solid portion” means that there is substantially no difference in height between the height of the top of the halftone dot and the solid portion. The allowable range for the substantial height difference is preferably less than 10 μm, more preferably 5 μm or less, and even more preferably 1 μm or less.

In the method for producing a printing plate of the present embodiment, the halftone dot means a conical or cylindrical shape formed with the density of the screen lines, and the top of the halftone dot portion has a conical dot shape. Means the most advanced part, and when the halftone dot is cylindrical, it means a flat part at the tip.
In the printing plate manufacturing method according to the present embodiment, the halftone dot ratio of a halftone dot that does not have a height difference from the solid part is not particularly limited, but a halftone dot having a halftone dot ratio of 5% or more does not appear to have a height difference from the solid part. Laser engraving is preferable.

In the printing plate manufacturing method of the first embodiment of the present invention, the number of screen lines (density of convex patterns) of the halftone dots is preferably 80 lpi or more and 175 lpi or less, more preferably 85 lpi or more and 150 lpi or less, and further preferably 90 lpi. It is 133 lpi or less. Within this range, it can be regarded as a high-quality printed matter.
The resolution of data used for the laser engraving (hereinafter sometimes referred to as “engraving original data”) is preferably 100 dpi (the number of dots per inch) or more and 5000 dpi or less, and more preferably 100 dpi or more and 4000 dpi or less. By setting it in this range, a concavo-convex pattern in which the shadow and highlight are balanced can be obtained.
An AM screen is usually used for the arrangement of dots in the engraving source data pixels, but an FM screen or a hybrid combining them may be used.

In the manufacturing method of the printing plate of the first embodiment of the present invention, the shape of the top of the halftone dot may be sharp, rounded, flat, or other shapes, From the viewpoint of reducing the fluctuation of the halftone dot area ratio of the printed matter with respect to the fluctuation of the printing pressure, it is preferable to be flat.
The printing plate according to the first embodiment of the present invention may use an unengraved portion as a solid portion from the viewpoint of manufacturing efficiency. In the first embodiment, as long as there is no difference in height between the top of the halftone dot and the solid part, the printing plate may be manufactured using the unengraved part as a solid part. May be engraved to produce a printing plate.

[Method for producing printing plate of second embodiment]
Another method for producing a printing plate of the second embodiment is a method for producing a printing plate having a laser engraving process for forming halftone dots so that the tops of the halftone dots are not laser engraved.
As in the technique disclosed in Japanese Patent Application Laid-Open No. 2008-183888, it is known that a conventional printing plate obtained by laser engraving usually has a laser-engraved height at the top of the halftone dot. However, a printing plate in which the top of the halftone dot is laser engraved has a lower height than that of the unengraved part (solid part), and the printing pressure is low in printing using such a halftone dot. When it fluctuates, the design value of the halftone dot area ratio on the printing plate and the actually measured value of the halftone dot area ratio formed on the substrate to be printed tend to fluctuate significantly, and the print quality tends to fluctuate.

  When the second printing plate of the present embodiment in which the top of the halftone dot is not laser engraved is compared with the conventional printing plate in which the height of the top of the halftone dot is laser engraved, printing during printing is performed. The printing plate of the second embodiment of the present embodiment in which there is a difference in quality stability and the top of the halftone dot is not laser-engraved is the design value of the halftone dot area ratio on the printing plate against the fluctuation of the printing pressure. It was found that the fluctuation of the measured value of the halftone dot area ratio formed on the substrate was small.

In the second embodiment, as a method of forming a halftone dot so that the top of the halftone dot is not laser engraved, for example, a method of controlling the amount of energy irradiated to the shoulder of the halftone dot, A method for controlling the gradient of energy applied to the shoulder of the head, a method for combining them, and the like are not limited thereto.
In the printing plate manufacturing method according to the second embodiment, the size of the halftone dot whose top is not laser engraved is not particularly limited, but the top of the halftone dot having a dot area ratio of 5% or more is a laser. Preferably it is not engraved.

In the printing plate manufacturing method of the second embodiment, the screen line number of the halftone dots (density of the convex pattern) is preferably 80 lpi or more and 175 lpi or less, more preferably 85 lpi or more and 150 lpi or less, and further preferably 90 lpi. It is 133 lpi or less. Within this range, it can be regarded as a high-quality printed matter.
An AM screen is usually used for the arrangement of dots in the engraving source data pixels, but an FM screen or a hybrid combining them may be used.

[Laser engraving]
The laser used for laser engraving is not particularly limited as long as the resin layer described below includes a wavelength having absorption.
Specifically, an infrared or infrared emitting solid laser such as a sealed carbon dioxide laser, a flow-through carbon dioxide laser, a YAG laser, or a semiconductor laser can be cited as a suitable laser.
In addition, the second harmonic of a YAG laser having an oscillation wavelength in the visible light region, a copper vapor laser, an ultraviolet laser having an oscillation wavelength in the ultraviolet region, such as an excimer laser, and a YAG laser that has been wavelength-converted to the third or fourth harmonic are: It is a laser capable of ablation processing that cuts the bonds of organic molecules, and is a laser suitable for performing fine processing.
The laser irradiation described above may be continuous irradiation or pulse irradiation.

There is no limitation on the atmosphere for performing laser engraving on the resin layer. For example, laser engraving can be performed in an oxygen-containing gas, generally in the presence of air or in an air stream, but may be performed in the presence of carbon dioxide gas or nitrogen gas.
After completion of laser engraving, the powdered or liquid substance generated uses a predetermined method, for example, a method of cleaning with water containing a solvent or a surfactant, a strong alkaline electrolyzed water, a high-pressure spray, etc. Or by irradiating with high-pressure steam.
In the laser engraving process, a desired image can be set as digital data, and a predetermined image can be used to perform laser engraving using a laser device for engraving to form a relief image on the resin layer.

The laser engraving may be performed in a plurality of times, and the same light source or different light sources may be used for the plurality of times of engraving.
Specifically, the laser engraving can be performed using a known technique, for example, a technique described in JP-A-2001-146064.

Specifically, first, the block data created by a block forming device such as a computer is read into a laser engraving control device via a floppy disk (registered trademark), MO disk, CD, DVD, portable hard disk, LAN, etc. . Subsequently, the control device analyzes the composition data in accordance with the machining control program, creates an execution file, and instructs the resin layer to start engraving. Subsequently, the resin layer is engraved by outputting a laser to a portion corresponding to the concave portion of the printing original plate.
In addition, as a laser used for the laser engraving process, a laser having a plurality of laser heads, a laser having a function of dividing a single laser, an engraving machine having a function of simultaneously engraving a plurality of places with software, and the like are used. This can shorten the number of manufacturing steps of the concavo-convex pattern and improve the manufacturing efficiency.

  The engraving speed of the resin layer during the laser engraving is preferably 2 m / s or more and 18 m / s or less. Here, the engraving speed refers to the scanning speed of the laser in the main scanning direction. More preferably, they are 2 m / s or more and 17 m / s, More preferably, they are 2 m / s or more and 16 m / s. If it is this range, a resin layer can move stably.

  The laser engraving feed pitch is preferably 5 μm or more and 20 μm or less. Here, the engraving feed pitch means that when the original forming the concave / convex pattern is cylindrical or fixed in a cylindrical shape, when the original or the cylindrical original is rotated once, the laser head of the laser is This means the distance moved in the sub-scanning direction. Also, when the original plate is a flat plate or fixed to a flat surface (flat bed), when the laser head moves to the next row after engraving the previous row, the laser head moves in the sub-scanning direction. Means the distance to move. The engraving feed pitch is more preferably 7 μm or more and 18 μm, and still more preferably 10 μm or more and 15 μm. Within this range, dots can be stably formed. In this case, the laser may be either a type of engraving machine in which the workpiece is movable in the sub-scanning direction or the laser head is movable in the sub-scanning direction.

It is preferable that the maximum output of the laser is 60 W or more and 1200 W or less. More preferably, they are 100W or more and 800W or less, More preferably, they are 150W or more and 700W or less. Within this range, the productivity and stability of laser engraving can be maintained.
Regarding the output of the laser, for example, the laser emitted from the laser head, the field mate (trade name, manufactured by Coherent, USA) which is a laser power meter display, and the power sensor PM5K (trade name, manufactured by Coherent, USA) It can be measured by combining them.

[Printing master]
In the present embodiment, the printing original plate is not particularly limited as long as it includes a resin layer capable of forming a recess by irradiation with a laser. Examples of the resin layer include a thermoplastic resin layer and a cured product layer of a curable resin composition, and a cured product layer of a curable resin composition is preferable from the viewpoint of laser engraving. Examples of the cured product layer of the curable resin composition include a thermoset product layer of a thermosetting resin composition and a photocured product layer of a photosensitive resin composition. The thickness of the resin layer can be arbitrarily selected according to the intended use of the concavo-convex pattern, and is preferably 0.1 to 7 mm.

[Thermoplastic resin layer]
The thermoplastic resin layer that is a specific example of the resin layer may be an elastomer or a non-elastomer.
Although it does not specifically limit as a thermoplastic elastomer, SBS (polystyrene-polybutadiene-polystyrene), SIS (polystyrene-polyisoprene-polystyrene), SEBS (polystyrene-polyethylene / polybutylene-polystyrene), SBR which are styrenic thermoplastic elastomers. (Styrene-butadiene rubber) and the like, olefin-based thermoplastic elastomer, urethane-based thermoplastic elastomer, ester-based thermoplastic elastomer, amide-based thermoplastic elastomer, silicone-based thermoplastic elastomer, and the like. The thermoplastic elastomer is a material that flows by heating and can be molded like a normal thermoplastic, and exhibits rubber elasticity at room temperature. The molecular structure consists of soft segments such as polyether or rubber molecules, and hard segments that prevent plastic deformation at around room temperature, as with vulcanized rubber. The hard segments include frozen phase, crystalline phase, hydrogen bonding, and ionic crosslinking. There are various types.

  The type of thermoplastic elastomer can be selected depending on the use of the uneven pattern. For example, urethane, ester, amide, and fluorine thermoplastic elastomers are preferred in fields where solvent resistance is required, and urethane, olefin, ester, and fluorine heat are required in fields where heat resistance is required. A plastic elastomer is preferred. Moreover, hardness can be changed greatly with the kind of thermoplastic elastomer. When the uneven pattern produced in the present embodiment is used as a normal printing plate, the Shore A hardness is preferably in the range of 20 to 75 degrees, and the uneven pattern is formed on the surface of paper, film, building material, etc. When used for embossing to form, a relatively hard material is required, and it is preferable to have a Shore D hardness of 30 to 80 degrees.

  As non-elastomeric, there is no particular limitation, but polyester resin, unsaturated polyester resin, polyamide resin, polyamideimide resin, polyurethane resin, unsaturated polyurethane resin, polysulfone resin, polyethersulfone resin, polyimide resin, polycarbonate Examples thereof include resins and wholly aromatic polyester resins.

  The softening temperature of the thermoplastic resin is preferably 50 ° C. or higher and 500 ° C. or lower, more preferably 80 ° C. or higher and 350 ° C. or lower, and further preferably 100 ° C. or higher and 250 ° C. or lower. If the softening temperature is 50 ° C. or higher, it can be handled as a solid at room temperature, and a sheet or cylinder processed can be handled without deformation. When the softening temperature is 500 ° C. or lower, it is not necessary to heat to a very high temperature when processing into a sheet or cylinder, and it is not necessary to alter or decompose other compounds to be mixed. In this embodiment, the softening temperature is measured by using a dynamic viscoelasticity measuring device. When the temperature is increased from room temperature, the viscosity changes greatly (the slope of the viscosity curve changes). Let temperature be the softening temperature.

[Thermosetting material layer of thermosetting resin composition]
As a thermosetting material of a thermosetting resin composition, the thermosetting material of the resin composition which mixed the polymerizable monomer with the said thermoplastic elastomer is said, for example. Specific examples of the thermoplastic elastomer that can be used here include SBS (polystyrene-polybutadiene-polystyrene), SIS (polystyrene-polyisoprene-polystyrene), and SEBS (polystyrene-polyethylene / polybutylene-polystyrene), which are styrenic thermoplastic elastomers. Olefin-based thermoplastic elastomer, urethane-based thermoplastic elastomer, ester-based thermoplastic elastomer, amide-based thermoplastic elastomer, silicon-based thermoplastic elastomer, fluorine-based thermoplastic elastomer, and the like.

[Photocured layer of photosensitive resin composition]
The resin (a) constituting the photosensitive resin composition is not particularly limited as long as it is cured by light irradiation. The range of the number average molecular weight is preferably 1000 or more and 500,000 or less, more preferably 2000 or more and 300,000 or less, and further preferably 5000 or more and 100,000 or less. If the number average molecular weight is 1000 or more, sufficient mechanical strength to withstand use as a printing plate when cured is obtained, and if it is 500,000 or less, it can be sufficiently decomposed by laser beam irradiation. Can do. In the present invention, the number average molecular weight is measured using Gel Permeation Chromatography (GPC) and is evaluated with respect to a polystyrene sample having a known molecular weight.

  From the viewpoint of laser engraving properties, styrene, acrylic esters, methacrylic esters, ester compounds, ether compounds, nitro compounds, aliphatic cyclic compounds, etc. as monomer units that are easily decomposed in the molecular chain of the resin (a) Is preferably included. Especially polyethers such as polyethylene glycol, polypropylene glycol, polytetraethylene glycol, aliphatic polycarbonates, polymethyl methacrylate, polystyrene, nitrocellulose, polyoxyethylene, polynorbornene, polycyclohexadiene hydrogenated, or branched structure Many resins such as dendrimers are representative examples of those that are easily decomposed. As an index for measuring the ease of decomposition of the resin, there is a weight reduction rate measured using thermogravimetric analysis under air. The weight reduction rate of the resin (a) used in the present invention is preferably 50 wt% or more at 500 ° C. If it is 50 wt% or more, the resin can be sufficiently decomposed by irradiation with a laser beam.

The photosensitive resin composition may contain an organic compound having an unsaturated bond that participates in radical polymerization reaction or ring-opening polymerization reaction. Examples of such organic compounds include olefins such as ethylene, propylene, styrene, and divinylbenzene, acetylenes, (meth) acrylic acid and derivatives thereof, haloolefins, unsaturated nitriles such as acrylonitrile, (meth) Acrylamide and its derivatives, allyl compounds such as allyl alcohol and allyl isocyanate, unsaturated dicarboxylic acids such as maleic anhydride, maleic acid, fumaric acid and itaconic acid and their derivatives, vinyl acetates, N-vinylpyrrolidone, N-vinyl Examples thereof include carbazole and cyanate esters.
Moreover, the photosensitive resin composition may contain other additives, such as a photoinitiator and a stabilizer.

[Dye / Pigment]
In general, since the resin material has absorption in the vicinity of 10 μm of the carbon dioxide laser, it is not essential to add a component that assists in the absorption of laser light to the resin layer. However, the YAG laser has a wavelength in the vicinity of 1.06 μm, and there are not many resins having absorption for the laser having such a wavelength. Therefore, when a YAG laser is used for laser engraving, it is preferable to add a dye or a pigment to the resin layer as a component that aids absorption.

Specific examples of dyes include poly (substituted) phthalocyanine compounds, metal-containing phthalocyanine compounds, cyanine compounds, squarylium dyes, chalcogenopyrylarylidene dyes, chloronium dyes, metal thiolate dyes, bis (chalcogenopyrrillo) polymethine dyes, oxyindolizine dyes Bis (aminoaryl) polymethine dyes, merocyanine dyes and quinoid dyes.
Specific examples of pigments include dark inorganic pigments such as carbon black, graphite, copper chromite, chromium oxide, cobalt chrome aluminate, copper oxide and iron oxide; metal powders such as iron, aluminum, copper and zinc; and These metals may be doped with Si, Mg, P, Co, Ni, Y or the like.
The above dyes and pigments may be used alone or in combination of two or more, and when the resin layer is composed of a plurality of photosensitive resin layers, the dye and content contained in each layer May be different.

  However, when there is a step of curing the photosensitive resin composition using light in the production process of the resin layer, addition of organic / inorganic compounds (dyes and pigments) having a large light absorption at the wavelength of light used for photocuring The amount is preferably in a range that does not hinder the production of the resin layer. When the photosensitive resin composition is photocured to form a resin layer, the total addition ratio of the dye and the pigment to the total amount of the photosensitive resin composition is preferably 5% by mass or less, and more preferably 2% by mass or less. Note that this is not the case when the curable resin composition is thermally cured to form a resin layer, or when the resin layer is not cured by light or heat.

  The resin layer may have a single layer structure, or may have a structure in which a plurality of materials having different compositions are stacked. For example, a layer that can be engraved using a laser having an oscillation wavelength in the near infrared region such as a YAG laser, a fiber laser, or a semiconductor laser is formed on the outermost surface, and an infrared laser such as a carbon dioxide laser is formed below the layer. Alternatively, a layer capable of laser engraving using a visible / ultraviolet laser may be formed. By adopting such a laminated structure, a relatively rough pattern is deeply engraved using an extremely high output carbon dioxide laser, and an extremely fine pattern is formed near the surface by a near infrared laser such as a YAG laser or a fiber laser. Can be engraved using. Since the fine pattern in the vicinity of the surface only needs to be relatively shallow and can be engraved, the thickness of the layer sensitive to the near infrared laser is preferably in the range of 0.01 mm to 0.5 mm.

As described above, by stacking the layer sensitive to the near infrared laser and the layer sensitive to the infrared laser, the depth of the pattern engraved using the near infrared laser can be accurately controlled. This is because a phenomenon that makes it difficult to engrave a layer sensitive to an infrared laser with a near infrared laser can be used.
Note that the difference in the fineness of the pattern can be controlled due to the difference in the oscillation wavelength inherent to the laser device, that is, the difference in the diameter of the laser beam that can be reduced.
When performing laser engraving by this method, you may use a laser engraving device equipped with an infrared laser and a near-infrared laser, respectively, or use a laser engraving device equipped with both an infrared laser and a near-infrared laser. May be.
A printing plate having a difference between the height of the top of the halftone dot and the height of the solid portion tends to have a sharp tip of the halftone dot. For example, in dry offset printing, from the viewpoint that damage to the ink roller or the blanket roll may occur, the top of the halftone dot of the present embodiment is preferably flat.

Hereinafter, specific examples and comparative examples will be described in detail.
In the following, “parts” and “%” mean “parts by mass” and “% by mass”, respectively.

[Production Example 1] Production of resin layer A 1 L separable flask equipped with a thermometer, a stirrer, and a reflux condenser was added to a polycarbonate diol “PCDL T4672” (trademark) manufactured by Asahi Kasei Chemicals Corporation (number average molecular weight 2025, OH value 55. 4) Add 402.60 g and 24.01 g of tolylene diisocyanate and stir at 80 rpm while heating at 40 ° C. for about 1 hour, then add 0.2 g of dibutyltin dilaurate as a catalyst and react for 3 hours. It was.
Next, 11.53 g of 2-methacryloyloxyisocyanate is added and further reacted for about 3 hours, and the terminal is a methacrylic group (the average number of polymerizable unsaturated groups in the molecule is about 2.0 per molecule). A resin layer forming resin (a) having a number average molecular weight of about 7500 was prepared.

This resin (a) was in the form of a syrup at 20 ° C., flowed when an external force was applied, and did not recover its original shape even when the external force was removed.
The following organic compound, photopolymerization initiator, stabilizer and the like were mixed with 100 parts by mass of the resin (a) to prepare a resin composition for forming a resin layer.
As organic compounds, 37.3 parts by mass of phenoxyethyl methacrylate “Light Ester PO” (trademark) manufactured by Kyoeisha Chemical Co., Ltd. and diethylene glycol monobutyl ether monomethacrylate “Light Ester BC” (trademark) 11.9 manufactured by Kyoeisha Chemical Co., Ltd. Part by mass was used.
As a photopolymerization initiator, 3.0 parts by mass of 2,2-dimethoxy-2-phenylacetophenone, which is a decay type photopolymerization initiator, and 0.8 parts by mass of benzophenone, which is a hydrogen abstraction type photopolymerization initiator, were used.

As stabilizers, 0.9 parts by mass of 2,6-di-t-butyl-4-methylphenol and 1.5 parts by mass of bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate used.
As additives, 1.5 parts by mass of silicone oil “KF-410” (trademark) manufactured by Shin-Etsu Chemical Co., Ltd., an inorganic porous material “Syrosphere C-1504” (trademark) manufactured by Fuji Silysia Chemical Ltd. (number average) Silo which is a porous spherical silica having a particle diameter of 4.5 μm, a specific surface area of 520 m ² / g, an average pore diameter of 12 nm, a pore volume of 1.5 mL / g, a loss on ignition of 2.5% by mass, an oil absorption of 290 mL / 100 g. The sphericity of Sphere C-1504 was observed with a scanning electron microscope, and almost all particles were 0.9 or more).

This produced the liquid resin composition at 20 degreeC.
Next, a fiber-reinforced plastic sleeve (trade name “Polyflex RUBIN”, manufactured by POLYWEST, Germany) having an inner diameter of 152.905 mm, an outer diameter of 155.880 mm, and a width of 1000 mm was prepared as a support.
Cushion tape (trademark “Duploflex 5.3” manufactured by Lohmann, Germany) is pasted on the support, and the resin composition for forming the resin layer prepared as described above is applied thereon with a doctor blade. did.
Thereafter, the metal halide lamp (trade name “M056-L21” manufactured by Eye Graphics Co., Ltd.) was irradiated with ultraviolet rays of 12000 mJ / cm ² (energy amount integrated using a UV meter and a UV-35-APR filter), and cured. Thus, a resin layer was formed to obtain a printing original plate (a laminate of a support and a resin layer).

The outermost surface of the resin layer was adjusted by grinding and polishing so that the printing peripheral length after curing was 500 mm to obtain a printing original plate for printability evaluation.
Ten printing original plates were produced by the same method.

(1) Engraving image The engraving image was created to include the following shapes.
The halftone data were 1%, 2%, 3%, 5%, 10%, 15%, and a pattern designed so that the unengraved part was a solid part. Each size was 15 mm × 15 mm.
Separately, a gradation pattern from 0% to 100% was created.

(2) Relief depth When the relief depth is set large, the area of the relief surface of the fine halftone dot pattern cannot be secured, and the shape collapses and becomes unclear, so the relief depth is set to 0.5 mm.
“Relief depth” means a difference in height between a printing portion (relief surface) and a non-printing portion (back surface) of a printing plate.

(3) The laser engraving machine engraved the engraving pattern using a Stork AGRIOS 5212M (manufactured by STORK, Austria, maximum output 500 W) to obtain a printing plate.
The engraving conditions are summarized in Table 1. Each parameter described in Table 1 is as follows.
dpi: Resolution lpi: Screen line number screen angle: Angle for arranging the screen line number speed: Speed at which the work moves in the engraving machine power limit: Ratio to the maximum output of the laser of the engraving machine First Step: Irradiated on the shoulder of the halftone dot Amount of energy Angle: gradient of energy applied to shoulder of halftone dot

(4) Evaluation of printing quality Printing was performed using a printing plate subjected to laser engraving, and the printing quality was evaluated.
The printer used was “FlexPress16S” (trademark, manufactured by Fischer & Krecke, Germany).
The ink was prepared using a solvent “XS-812” (trademark, manufactured by Dainippon Ink & Chemicals, Inc.), and the viscosity of the ink was 8.4 seconds using a Zahn cup No. 4 (diameter 4 mm opened in a 45 cc cup). The number of seconds required for the ink to fall to 30 cm below from the hole of the above was used.
A milk white polyethylene film having a thickness of 45 μm was used as the printing material.
The number of wires of the anilox roll was 900 (lpi), and the cell volume of the anilox roll was 4 cc.
The printing speed was 200 m / min.

As for the fluctuation of the printing pressure, the printing pressure was increased by 20 μm from the appropriate printing pressure, and two prints were obtained for each printing plate.
The evaluation of the area ratio of the halftone dots of the printed material was performed using an image analysis apparatus (trademark “LUZEX” manufactured by NIRECO Co., Ltd.). The printed matter was photographed so that about 20 dots could be accommodated in one screen, and the photographed image was binarized by dividing it into ink adhering portions (dots) and non-adhering portions. Based on the binarized data, the area ratio with respect to the entire area where the ink was applied was obtained and was defined as “halftone dot area ratio”.

(5) Evaluation of printed matter The halftone dot area ratio of the printed matter obtained in (4) is measured by the method described in (4) above, and the printed matter with appropriate printing pressure is compared with the printed matter with excessive printing pressure. The increase rate of the point area rate was calculated.
(Formula 1)
Increase rate of halftone dot area ratio = ((halftone dot area ratio of proper printing pressure−halftone dot area ratio when printing pressure is excessive by 20 μm) / (halftone dot area ratio of proper printing pressure)) × 100
If the increase rate of the halftone dot area ratio is 15% or less, it can be considered that the print quality is stable in appearance. Further, “◯” was given when the gradation pattern was smooth, and “x” was given when the change in shading was poor.

(6) Measurement of dot height difference The printing plate produced in (3) is made into a sheet, and using “Digimatic Gauge” (trademark, manufactured by Ono Sokki Co., Ltd.), the dot portion from the solid surface of the printing plate created The height difference was measured. The size of the measuring element was a circle having a diameter of 10 mm, and the pressure was 100 g. The solid part of the printing plate was set to “zero height”, and the plate thickness of 1% to 15% of the printing plate was measured.

(Examples 1-1 to 1-6)
The printed matter was evaluated at 80 lpi. Even when the fluctuation of the printing pressure exceeded 20 μm from the appropriate printing pressure, the increase rate of the dot area ratio of 1% to 15% was 15% or less.

(Examples 2-1 to 2-6)
The printed matter was evaluated at 100 lpi. Even when the fluctuation of the printing pressure exceeded 20 μm from the appropriate printing pressure, the increase rate of the dot area ratio of 1% to 15% was 15% or less.

(Examples 3-1 to 3-6)
The printed matter was evaluated at 120 lpi. Even when the fluctuation of the printing pressure exceeded 20 μm from the appropriate printing pressure, the increase rate of the dot area ratio of 1% to 15% was 15% or less.

(Examples 4-1 to 4-6)
The printed matter was evaluated at 133 lpi. Even when the fluctuation of the printing pressure exceeded 20 μm from the appropriate printing pressure, the increase rate of the dot area ratio of 1% to 15% was 15% or less.

(Examples 5-1 to 5-6)
The printed matter was evaluated at 150 lpi. Even when the fluctuation of the printing pressure exceeded 20 μm from the appropriate printing pressure, the increase rate of the dot area ratio of 1% to 15% was 15% or less.

(Comparative Examples 1-1 to 1-6)
The printed matter was evaluated at 80 lpi. When the fluctuation of the printing pressure exceeded the appropriate printing pressure by 20 μm, the increase rate of the dot area ratio of 1% to 15% exceeded 15%, and the gradation was not smooth.

(Comparative Examples 2-1 to 2-6)
The printed matter was evaluated at 100 lpi. When the fluctuation of the printing pressure exceeded the appropriate printing pressure by 20 μm, the increase rate of the dot area ratio of 1% to 15% exceeded 15%, and the gradation was not smooth.

(Comparative Examples 3-1 to 3-6)
The printed matter was evaluated at 120 lpi. When the fluctuation of the printing pressure exceeded the appropriate printing pressure by 20 μm, the increase rate of the dot area ratio of 1% to 15% exceeded 15%, and the gradation was not smooth.

(Comparative Examples 4-1 to 4-6)
The printed matter was evaluated at 133 lpi. When the fluctuation of the printing pressure exceeded the appropriate printing pressure by 20 μm, the increase rate of the dot area ratio of 1% to 15% exceeded 15%, and the gradation was not smooth.

(Comparative Examples 5-1 to 5-6)
The printed matter was evaluated at 150 lpi. When the fluctuation of the printing pressure exceeded the appropriate printing pressure by 20 μm, the increase rate of the dot area ratio of 1% to 15% exceeded 15%, and the gradation was not smooth.
In Examples 1-1 to 5-6, the number of lines, halftone dot data, height difference between halftone dots and a solid portion, halftone dot increase rate (%) when printing pressure is excessive 20 μm, gradation smoothness, relief depth It was described in Table 2.
In Comparative Examples 1-1 to 5-6, the number of lines, halftone dot data, height difference between halftone dots and solid portions, halftone dot increase rate (%) when printing pressure is excessive 20 μm, gradation smoothness, relief depth It was described in Table 3.

Summarizing the above results, in Examples 1-1 to 5-6, in which there is no difference in height between the halftone dot portion and the solid portion, a stable print quality was realized with respect to fluctuations in printing pressure for each number of lines.
In contrast, Comparative Example 1-1 to Comparative Example 5-6, in which the halftone dot portion and the solid portion have a height difference, cannot maintain the print quality against the printing pressure fluctuation, and the gradation is not smooth. It was.

  The present invention is suitable as a method for producing various printing plates such as flexographic printing, gravure printing, and dry offset printing. Also, surface pattern formation such as embossing, relief image formation for printing such as tiles, conductors for electronic components, semiconductors, insulators, pattern formation, antireflection films for optical components, color filters, (near) infrared cut filters, etc. Used for pattern formation of functional materials, and for coating film / pattern formation of alignment films, underlayers, light-emitting layers, electron transport layers, and encapsulant layers in the production of display elements such as liquid crystal displays or organic electroluminescence displays it can.

Claims (4)

  A method for producing a printing plate, comprising a step of laser engraving a printing original plate so that a height of a top portion of a halftone dot portion is not different from a height of a solid portion.   A method for producing a printing plate, comprising a laser engraving step for forming a halftone dot so that the top of the halftone dot is not laser engraved.   3. The method for producing a printing plate according to claim 1, wherein the printing original plate is laser-engraved so that the height of the top of the halftone dot portion of at least 5% or more is not different from the height of the solid portion.   The method for producing a printing plate according to any one of claims 1 to 3, wherein halftone dot laser engraving is performed with a screen line number of 80 lpi or more and 175 lpi or less.