JP3158369B2 - Photocurable resin letterpress and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photocurable resin relief printing plate. More specifically, the present invention relates to a photocurable resin relief plate having a high image reproducibility and a good printing effect, formed by using a negative photosensitive resin of a type in which exposed portions are insolubilized with a solvent.

[0002]

2. Description of the Related Art In recent years, a negative photosensitive resin layer is irradiated with actinic light through a negative film in place of plate making using a conventional lead letterpress casting machine, and a selected portion of the photosensitive resin layer is photocured. Then, a resin relief printing plate is manufactured by removing an uncured portion with a water solvent or high-pressure air.
Since the photocurable resin letterpress obtained in this way is lighter and more excellent in handleability than the lead letterpress, it is rapidly becoming popular in the printing field, including in newspaper printing.

[0003] The quality of the photocurable resin letterpress generally depends largely on the hardness of the photocurable resin layer. For example, in the case of hard photocurable resin letterpress, there is little deformation at the top of the relief due to printing pressure, so print reproducibility of fine line point images is excellent.However, since ink transferability is poor, capital letters, solids, halftones, etc. There is a disadvantage that an image having a large area is blurred. Attempting to print at a high printing pressure in order to solve such a problem of ink transferability causes other problems such as thickening of fine line points and reduction in printing durability due to abrasion of a relief top.

On the other hand, a soft photocurable resin letterpress has an excellent ink transfer property, and a sufficient ink transfer property can be obtained even on a printing medium having a poor surface smoothness such as rough paper or newsprint paper. Because the top of the relief is easily deformed, the image is easily thickened, and it is difficult to obtain sharp printed matter.Particularly when the mechanical accuracy of the printing press is low, excessive printing pressure is applied locally, causing unevenness in fatness. It is difficult to prevent.

In order to remedy such a drawback, in flexographic printing, a method of providing a soft elastic layer under a support of a printing plate has been tried, but in this method, a cushion through a support is provided. The effect of preventing thickening during printing is small because of the effect, and the provision of the cushion layer allows the printing pressure to escape, so that it is not possible to obtain a sufficient effect of improving the print quality, such as fading easily in a solid portion or the like. Was.

Japanese Patent Application Laid-Open No. 54-92402 proposes a photocurable resin relief having two photocurable resin layers having a hardness difference of 10 to 20 degrees in Shore hardness. By making the top layer harder than the lower layer, deformation of the relief top due to printing pressure is reduced, but since the thickness of the relief in the highlight portion and the portion other than the highlight portion is the same, the dot area ratio is particularly 7% or less. Cannot be sufficiently suppressed due to the printing pressure of the highlight portion, and satisfactory printed matter cannot be obtained.

Japanese Patent Application Laid-Open No. 55-6392 (corresponding to British Patent Application No. 2012977A) discloses that the photopolymerization rate of a photosensitive resin layer corresponding to a relief lower layer is 1.5 to 1.5 of that of a photosensitive resin layer corresponding to a top layer. The photocurable resin relief plate is 200 times, and is composed of two photosensitive resin layers such that a difference in modulus of 50 psi or more occurs between both layers after exposure. Furthermore, Japanese Patent Application Laid-Open No. 62-124559 discloses that the minimum light-insolubilizing amount of the photosensitive resin layer corresponding to the relief lower layer is 5 mJ / cm ² or less, and the minimum amount of the photosensitive resin layer corresponding to the relief top layer is minimum. There has been proposed a photosensitive resin relief printing plate having two photosensitive resin layers in which the amount of the insolubilized light is １ ／ or less. By making the difference in sensitivity between these two photosensitive resin layers and lowering the sensitivity of the photosensitive resin corresponding to the relief top layer, the image thickness of the relief surface portion of the obtained printing plate is reduced. It can be thinner than that of the negative film used for exposure, and the print quality can be improved by that much.However, since the thickness of the relief in the highlight part and the part other than the highlight part is the same, the printing The thickening due to pressure could not be prevented, and satisfactory printed matter could not be obtained.

[0008]

Under such circumstances, the present inventors have conducted intensive studies to develop a photocurable resin relief plate having high image reproducibility and excellent printing effect. When the two types of photosensitive resin layers having different photosensitive characteristics to form the base layer and the top layer having different photosensitive characteristics and satisfying a specific relationship are image-exposed for a specific time, the dot area ratio is reduced. Surprisingly, it is possible to make the thickness of the relief layer in the highlight portion which is 7% or less smaller than the thickness of the relief layer in the portion other than the highlight portion, thereby preventing the image in the highlight portion from becoming fat. I also learned. The present invention has been completed based on this finding.

Therefore, one object of the present invention is that the thickness of the relief layer in the highlight portion is smaller than the thickness of the relief layer in the portion other than the highlight portion, and the image reproducibility is high.
An object of the present invention is to provide a photocurable resin letterpress having an excellent printing effect. Another object of the present invention is to provide a method for efficiently and inexpensively producing the above-described photocurable resin relief printing plate. The above and other objects, features and advantages of the present invention will become apparent from the following detailed description and the appended claims, taken in conjunction with the accompanying drawings.

[0010]

That is, according to the present invention, basically, a multilayer photosensitive resin comprising a support and at least two photosensitive resin layers having different photosensitive characteristics on the support. The layer is image-exposed to form a photocurable resin relief plate including a relief layer having a base layer A and a top layer B formed by photocuring in this order, and the photosensitive resin layer has a minimum insolubilizing light amount as a lower layer. a multilayer photosensitive resin layer having a liquid photosensitive resin layer of a minimum insolubilization light amount Q _B as liquid photosensitive resin layer and an upper layer of Q _a Q _B is 23 millijoules / cm ² or more and 5 times or more Q _a Wherein the maximum value of the total thickness of the base layer A and the top layer B formed by photocuring from the lower layer and the upper layer, respectively, is 8 mm or less, and the maximum thickness of the top layer is the maximum of the total thickness of the base layer and the top layer. 1/2 of the value
Light having a thickness of not more than 1 mm and having a dot area ratio of not more than 7%, wherein a thickness of a relief layer of a highlight portion constituting a pattern having a dot area ratio of not more than 7% is smaller than a thickness of a relief layer of a portion other than the highlight portion. A cured resin relief is provided.

[0011] According to yet another aspect of the present invention, the support and the minimum insolubilization light amount Q _B as liquid photosensitive resin layer and the upper layer of the minimum insolubilization light amount Q _A of a lower layer on to the support
A photosensitive element including a multilayer photosensitive resin layer comprising at least two photosensitive resin layers having different photosensitive characteristics having a liquid photosensitive resin layer in this order, wherein the photosensitive element is a multilayer photosensitive resin. A light-cured portion and an uncured portion are formed by image exposure from the layer side, and then the uncured portion is washed out with a developer to form a relief layer having a base layer A and a top layer B obtained from the lower layer and the upper layer, respectively. The method for producing a photocurable resin letterpress comprising a highlight portion constituting a pattern having a dot area ratio of 7% or less including forming and a non-highlight portion constituting a pattern having a dot area ratio exceeding 7%. Te, _{Q B} is 23 millijoules / cm ² or more and _{Q A}
And a range from the minimum exposure required to form the minimum highlight of a highlight portion constituting a pattern having a dot area ratio of 7% or less to 1.5 times the minimum exposure. And the thickness of the relief layer of the highlight portion constituting the pattern whose halftone dot area ratio of the obtained photocurable resin letterpress is 7% or less is smaller than the thickness of the relief layer of the portion other than the highlight portion. A method for producing a photocurable resin letterpress is provided.

The photocurable resin letterpress of the present invention will be described with reference to FIG. FIG. 1 is a schematic cross-sectional view of the photocurable resin relief plate of the present invention, wherein 1 indicates a support, S indicates a relief layer composed of a base layer A and a top layer B of a highlight portion, and L indicates a highlight layer. 3 shows a relief layer in a portion other than the portion (shadow portion and halftone portion), and is composed of a base layer A and a top layer B. The total thickness of the photocurable resin relief plate of the present invention, that is, the maximum value of the total thickness of the base layer A and the top layer B (the thickness T _{1 of the} relief L in FIG. ₁ ) depends on the type of printing press and printing conditions. Is appropriately selected in the range up to 8 mm. The lower limit is about 0.3mm
It is.

The maximum thickness of the top layer B constituting the printing surface of the relief layer (thickness of the layer B of the relief L in FIG. 1) is the maximum of the total thickness of the base layer A and the top layer. Value (in FIG. 1, equal to or less than 1/2 of the sum of the layers A and B of the relief L) and 1 mm or less, preferably in the range of 0.03 mm to 0.5 mm. It is. In other words, when producing a photocured resin relief plate of the present invention, the liquid photosensitive resin layer of a minimum insolubilization light amount Q _A of a lower layer and an upper layer and a liquid photosensitive resin layer of a minimum insolubilization light amount Q _B in this order The total thickness of the upper layer and the lower layer in the multilayer photosensitive resin layer having the upper layer and the lower layer must be 8 mm or less, and the thickness of the upper layer must be 以下 or less and 1 mm or less of the total thickness of the upper layer and the lower layer, and preferably 0.03 mm or less. ~ 0.
The range is 5 mm. Or relief of the thickness of the dot percent of 7% or less of the highlight portion (indicated by T ₂ in FIG. 1) is difficult smaller than the thickness of the relief in the portion other than the highlight portion in the printing plate obtained with less than this thickness However, even if it becomes smaller, the degree becomes smaller, and it becomes difficult to obtain a sufficient effect. On the other hand, if the thickness exceeds this range and the printing plate obtained has a halftone dot area ratio of 7% or less, the thickness of the relief in the highlighted portion becomes too smaller than the thickness of the relief in portions other than the highlighted portion. It is not preferable that the highlight portion is hardly printed, and in some cases, the relief of the highlight portion is difficult to be formed.

The thickness (T ₂ ) of the relief layer in the highlight portion where the halftone dot area ratio of the obtained printing plate is 7% or less is _{20 to 1} more than the thickness (T ₁ ) of the relief layer in the portion other than the highlight portion.
It is desirably smaller by 00 μ, more preferably by 20 to 80 μ.

In the printing plate of the present invention, the relief thickness of the minimum highlight of a highlight portion constituting a pattern having a dot area ratio of 7% or less is the thinnest, and is gradually increased toward the dot area ratio of 7%. In a region exceeding 7%, the relief thickness is the same as that of the portion other than the highlight portion.

In the photocurable resin relief printing plate of the present invention, a photosensitive resin layer (shown by 2B in FIG. 2) for forming the top of the relief layer is formed by a TO method (thickn
Minimum insolubilization light amount obtained by the measurement by ess optimization method) _{Q B} (millijoules / ^cm 2)
(Hereinafter referred to as mJ / cm ² ) is at least 23 mJ / cm ² and the minimum insolubilizing light quantity Q _A (m is indicated by 2A in FIG. 2) of the photosensitive resin layer (shown as 2A in FIG. 2) for forming the relief layer base.
J / cm ² ). When this condition is not satisfied, the printing plate according to the present invention, in which the thickness of the relief layer in the highlight portion constituting the pattern having the dot area ratio of 7% or less is smaller than the thickness of the relief layer in the portion other than the highlight portion. The characteristic structure cannot be obtained.

[0017] In the present invention, _{Q B} is 23mJ / cm ²
Below with reference to FIG. 2 or more and Q mechanism relief thickness of dot percent of 7% or less of the highlight portion when satisfied is smaller than the relief thickness of other parts of 5-fold or more conditions of _A explain. Activated light (U) is applied to a photosensitive element formed by sequentially laminating a photosensitive resin layer 2A and a photosensitive resin layer 2B on the support 1 from the 2B layer side through the negative film 3.
When image exposure is performed according to V), a portion corresponding to the relief 2A layer is first formed in a highlight portion having a dot area ratio of 7% or less. Further, the portion of the 2B layer in contact with the 2A layer is affected by the 2A layer, and the portion of the 2B layer facing the negative film is partially cured as shown in the figure, but is not cured in the entire depth direction of the 2B layer.) . The state is as shown in FIG. At this point, if the image exposure is stopped and the development process is performed, 2
Base layer A in which the lower part of layer 2B is hardened on layer A
And relief consisting of a small top layer (Relief S in FIG. 1)
Is obtained, and the thickness of the relief S is smaller than the relief portion (relief L in FIG. 1) formed by completely curing the 2B layer. Thus, the printing plate of the present invention is obtained.

[0018] _{Q B} for such a mechanism is 23mJ / c
requires much exposure to m ² or more and a light-curing, Q _A is necessary to ensure that cures at 1/5 and less exposure of Q _B. That is, the image exposure to Q _B is the case is less than 5 times or when Q _A of less than 23 mJ / cm ² to form the smallest highlight of a highlight portion constituting a pattern is 7% or less constant dot area When the amount is multiplied, there is no difference in the relief thickness between the highlighted portion and other portions in the obtained printing plate. Further, in such a system, even if the image exposure amount is reduced, no highlight is formed, and a plate having a relief thickness in the highlight portion smaller than the relief in portions other than the highlight portion cannot be obtained.

The minimum light-insolubilizing amount of the photosensitive resin in the present invention can be determined by the TO method shown below. FIG. 3 shows a principle diagram of the TO method. That is, first, horizontal 1
A photopolymerizable photosensitive resin layer having a size of 5 cm, a length of 3 cm and a thickness of 4 mm is formed on a support 1 having an adhesive layer 4 and being transparent to active light.
Provided above. Then, in a state where the outside of the support was covered with light-shielding pieces 5 having a width of 3 cm continuously arranged side by side in advance, the intensity of active light after passing through the support having the adhesive layer was 0.40. Place it on an irradiation table where the intensity of the light source is adjusted in advance so that it becomes milliwatt (mW) / cm ² ,
Irradiation with actinic rays (UV) is performed from the support side. Next, one of the light-shielding pieces at the end (the left end in FIG. 3) is removed, and the light-shielding pieces are sequentially removed every 30 seconds, and the last fifth light-shielding piece (the right end in FIG. 3) is removed. After the removal, the irradiation of the active light is stopped 30 seconds after that. As a result, a section corresponding to the first light-shielding piece is exposed for 150 seconds, and a section corresponding to the last light-shielding piece is exposed for 30 seconds. Next, the photosensitive resin layer is washed out under a constant elution condition, dried and post-exposed, and then the thickness of the photosensitive resin layer formed on the support is measured in 1/100 mm units. The relationship between the exposure time of the test piece obtained in this way and the thickness of the photocurable resin is graphed as a semilogarithmic graph as shown in FIG. T. (Induction t
im) (second), and the minimum insolubilizing light amount (m
J / cm ² ) can be calculated. The details of the measurement of the minimum insolubilizing light amount by the TO method in the present invention will be described later.

The relief layer referred to in the present invention is not limited to a relief layer directly formed on a support (for example, one having the structure shown in FIG. 1).
ckround layer) is provided, and a case where a convex portion is formed on the top is also included. Further, in the present invention, the case where the convex portion is composed of the two layers of the base layer A and the top layer B has been described above, but the minimum insolubilizing light amount below the base layer A is equal to or smaller than that of the base layer A. A layer may be provided.

The relief layer of the photocurable resin relief plate of the present invention is prepared from two types of liquid photosensitive resin liquids having different properties. When two types of solid photosensitive resin layers are previously formed on a support, the temperature at the time of molding the solid photosensitive resin is higher than that of the liquid resin, and the time from production molding to use is longer. Since the length is long, components such as a photopolymerization initiator and a thermal polymerization inhibitor move between the two solid photosensitive resin layers before the image exposure, so that the photosensitive characteristics of both layers are changed. Therefore, the photosensitive resin used in the present invention needs to be in a liquid state.

The liquid photosensitive resin used in the present invention is not particularly restricted but includes, for example, prepolymers such as unsaturated polyesters and unsaturated polyurethanes and addition-polymerizable ethylenically unsaturated monomers, photopolymerization initiators and thermal polymerization inhibitors. Can be mentioned.

The unsaturated polyester has at least one
An alcohol component comprising at least one polyol;
Certain unsaturated polybasic acids or derivatives thereof (eg, acid anhydrides,
Methyl or ethyl esters, acid halides) and, if necessary, a polycondensation reaction with an acid component comprising a saturated polybasic acid. Examples of unsaturated polybasic acids include maleic acid, fumaric acid, citraconic acid,
Mesaconic acid, itaconic acid, glutaconic acid, muconic acid, aconitic acid and the like can be mentioned. Examples of the saturated polybasic acid include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, phthalic acid, isophthalic acid, terephthalic acid, and pyromellitic acid. be able to.

Examples of the polyol include ethylene glycol, 1,2-propylene glycol, 1,3-propanediol, 1,4-butanediol, diethylene glycol, dipropylene glycol, polyethylene glycol (number average molecular weight of 150 or more), polypropylene glycol (Number average molecular weight of 192 or more), polybutylene glycol (number average molecular weight of 162 or more), poly (oxyethyleneoxypropylene) glycol (number average molecular weight of 1)
20 or more), glycerin, erythritol, pentaerythritol, hexit, trimethylolpropane, and the like.

Further, unsaturated polyurethane has 2 in the molecule.
It is obtained by reacting a polyol compound having at least two terminal hydroxyl groups with a polyisocyanate having at least two or more isocyanate groups, and further reacting a compound having a hydroxyl group and an addition polymerizable unsaturated bond.
As the polyol compound, those having a relatively high molecular weight are preferable, and for example, polyether polyol, polyester polyol, polyalkylene polyol and the like are used. As the polyisocyanate, for example, tolylene diisocyanate, xylylene diisocyanate, hexamethylene diisocyanate and the like are used. In this reaction, various products can be obtained depending on the molar ratio of the polyol and the polyisocyanate, the reaction sequence, the reaction conditions, and the like, but the reaction is carried out so as to have at least two terminal isocyanate groups.

Next, a polyurethane having isocyanate groups at both ends is reacted with an addition-polymerizable ethylenically unsaturated monomer having a hydroxyl group. Examples of such a compound include 2-hydroxyethyl methacrylate and 2-hydroxyethyl methacrylate.
Examples thereof include hydroxyethyl acrylate, 2-hydroxypropyl methacrylate, N-hydroxymethyl acrylamide, polyethylene glycol monomethacrylate, aryl alcohol, and hydroxystyrene.

Examples of the addition-polymerizable ethylenically unsaturated monomer include acrylic acid, methacrylic acid, and esters thereof, such as methyl, ethyl, n-propyl, isopropyl, n-hexyl, n-octyl, n-dodecyl, cyclohexyl, and the like. Acrylates and methacrylates of tetrahydrofurfuryl, aryl, glycidyl, 2-hydroxyethyl, 2-hydroxypropyl, 3-chloro-2-hydroxy, 4-hydroxybutyl, or ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, polyethylene glycol , Polypropylene glycol, butylene glycol mono- or diacrylate and methacrylate, or trimethylolpropane triacrylate and methacrylate, pen Erythrit tetraacrylate and methacrylate or N, N-dimethylaminoethyl methacrylate, acrylamide, methacrylamide or derivatives thereof, such as N-methylolacrylamide and methacrylamide, N-methoxyacrylamide and methacrylamide, N, N′-methylenebisacrylamide And methacrylamide, N, N'-hexamethylenebisacrylamide and methacrylamide, diacetone acrylamide and methacrylamide, and styrene, vinyltoluene, divinylbenzene, diarylphthalate, triallyl cyanurate, and vinyl acetate. .

Examples of the photopolymerization initiator include benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin-n-propyl ether, benzoin isopropyl ether, benzoin-n-butyl ether, benzoin isobutyl ether and benzoin-se.
c-butyl ether, α-methylbenzoin, α-ethylbenzoin, α-methylbenzoin methyl ether,
α-phenylbenzoin, α-arylbenzoin,
Known compounds such as 2,2-dimethoxy-2-phenylacetophenone can be mentioned.

Examples of the thermal polymerization inhibitor include hydroquinone, p-methoxyphenol, catechol, tert-
Known compounds such as butylhydroquinone, benzoquinone, p-phenylenediamine, picric acid, and phenothiazine can be mentioned.

The mixing ratio of the prepolymer and the addition-polymerizable ethylenic monomer in such a photosensitive resin is generally in the range of 100: 20 to 100: 200 (weight ratio), and the plate to be obtained is obtained. Of the prepolymer and the type of the addition-polymerizable ethylenic monomer.

The effect of the present invention is that the relief layer in the highlight portion constituting the pattern having the dot area ratio of 7% or less is less than the thickness of the relief layer in the portion other than the highlight portion. And, in the production thereof, is obtained by imagewise exposing a photosensitive element including a multilayer photosensitive resin layer composed of two kinds of photosensitive resin layers having different sensitivity characteristics with an exposure amount in a specific range, The photosensitive resin that can be used is not limited to the above examples because it is not affected by the composition and physical properties of the photosensitive resin.

The photosensitive characteristics of the photosensitive resin can be changed by various methods. For example, it can be arbitrarily changed by changing the type and amount of the photopolymerization initiator, the type and amount of the polymerization inhibitor, or by adding an ultraviolet absorbing substance.
The larger the amount of the photopolymerization initiator added, the smaller the minimum insolubilizing light amount, and the smaller the amount, the larger the amount. In general, a thermal polymerization inhibitor functions to increase the minimum insolubilizing light amount, and the effect increases as the amount of addition increases. Dyes, pigments, and other UV absorbing materials increase the minimum insolubilizing amount.

In order to increase the absolute level of the sensitivity itself, a photopolymerization initiator having high photoinitiation efficiency such as 2,2-dimethoxy-2-phenylacetophenone may be used,
It is effective to use N, N-dimethylaminoethyl methacrylate or a diacrylate monomer having a large molecular weight as the unsaturated ethylenic monomer.

The addition amount of the photopolymerization initiator needs to be an effective polymerization amount. However, the minimum amount of insolubilized light varies depending on the addition amount. Therefore, in the photosensitive resin layer 2B corresponding to the relief top layer, 0.03-0.
It is preferable to use it in the range of 5% by weight, and in the range of 0.5 to 4.0% by weight of the resin in the photosensitive resin layer 2A corresponding to the relief base layer.

Since the thermal polymerization inhibitor is generally added for the purpose of preventing deterioration during the production or storage of the photosensitive resin, the thermal polymerization inhibitor is required according to the composition of the photosensitive resin, the production conditions and the storage conditions. It may be added to such an extent that a high thermal stability is obtained.
Generally, it is added in the range of about 0.01 to 0.5% by weight based on the resin. In addition, since the thermal polymerization inhibitor functions to increase the minimum insolubilizing light amount, it is necessary to determine the amount to be added according to the minimum insolubilizing light amount to be obtained. different.

In order to obtain a structure in which the halftone dot area ratio of 7%, which is a basic feature of the present invention, is smaller than the thickness of the relief layer in the portions other than the highlight portion in the following highlight portions. , such that the minimum insolubilization light amount _{Q B} of the upper photosensitive resin layer 2B is 23 mJ / cm ² or more and 5 times the minimum insolubilization light amount _{Q a} of the lower photosensitive resin layer 2A 2
It is necessary to use the kinds of photosensitive resin layers 2A and 2B in combination. If desired, the hardness of the liquid photosensitive resin after photocuring can be changed by a known method. For example, in the case of a liquid photosensitive resin comprising an unsaturated polyurethane, an addition-polymerizable ethylenically unsaturated monomer, a photopolymerization initiator, and a thermal polymerization inhibitor, the molar ratio of the polyisocyanate compound to the polyol compound in the unsaturated polyurethane is set to A method of changing the molar ratio of the addition-polymerizable ethylenically unsaturated monomer to the unsaturated polyurethane, a method of changing the molar ratio of the difunctional or polyfunctional monomer among the addition-polymerizable ethylenically unsaturated monomers, There are combinations of methods.

At this time, when two kinds of liquid photosensitive resins are selected from a similar composition group, the adhesion between the relief top layer and the base layer after plate making and the cleaning of the unexposed resin with a common cleaning liquid after image formation are performed. It is preferable because it can be removed, but is not limited to this. Here, the similar composition group means that the polymer of the liquid photosensitive resin is the same series (for example, unsaturated polyester type, unsaturated polyurethane type, etc.).
A group of compositions belonging to

As the support used in the present invention, for example, a metal plate made of iron, stainless steel, copper, zinc, aluminum or the like, a rubber sheet made of natural rubber, synthetic rubber, or the like, or celluloid, cellulose acetate, polyethylene, polypropylene, Polyvinyl chloride, polymethyl methacrylate, polystyrene, polycarbonate,
Examples include plastic sheets or films of polyethylene terephthalate, polyamide, and the like.
Generally, an adhesive layer is provided on the surface of these supports, and an antihalation agent is put in the adhesive layer, or an antihalation layer is provided between the adhesive layer and the support as necessary. It may be provided.

Next, an example of a preferred method for producing the photocurable resin relief plate of the present invention will be described. First on the support,
After two layers (for example, 2A and 2B in FIG. 2) each composed of a different liquid photosensitive resin are sequentially provided so as to have a predetermined thickness, an image is formed by actinic light through a transparent image carrier from the photosensitive resin layer 2B side. Exposure is performed, and then the photosensitive resin in the unexposed areas is removed to form a relief layer on the support. At this time, as the liquid photosensitive resins 2A and 2B, those whose respective photosensitive characteristics satisfy the above characteristics are selected.

The method of forming and laminating the two kinds of liquid photosensitive resin and the support to a predetermined thickness in order to be subjected to exposure includes, for example, brushing, rolling, or applying the photosensitive resin on a cover film which is closely attached to a negative film. After the liquid photosensitive resin layer 2B is formed by previously extending to a predetermined thickness using a doctor knife or the like, the liquid photosensitive resin layer 2A is formed, and at the same time, the support is laminated. Alternatively, the photosensitive resin is spread to a predetermined thickness in advance using a brush, a roll, a doctor knife, or the like on the support to form the liquid photosensitive resin layer 2A, and the same operation is performed using another liquid photosensitive resin. , The liquid photosensitive resin layer 2B can be formed and laminated.

Examples of the actinic light source used in the exposure include a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, an ultraviolet fluorescent lamp, a carbon arc lamp, a xenon lamp, and a metal halide lamp. Anything can be used. From the viewpoint that the exposure time can be shortened, a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, a metal halide lamp, or the like having a high light source intensity is preferable.

In the image forming exposure, the support and the liquid photosensitive resin layer 2A and the liquid photosensitive resin layer 2
B is passed through the transparent image carrier from the side of the liquid photosensitive resin layer 2B to the photosensitive element in which B is closely attached in this order, using the light source. In the case where the material of the support is substantially transparent to the active light, in addition to the image exposure from the photosensitive resin layer 2B side, the entire surface is irradiated with the active light from the support side as well, so that the support is desired. Thick cured resin layer (background)
d layer), and the height of the relief can be arbitrarily adjusted. In this case, the cured resin layer as the background layer is also provided with the top layer B and the base layer A referred to in the present invention.
Is included in the total thickness of the photosensitive resin layer represented by the total thickness.
Exposure through the transparent image carrier may be performed for a time necessary to form a minimum highlight (minimum dot portion) of a highlight portion constituting a pattern having a halftone dot area ratio of 7% or less. As such, the difference between the highlighted portion and the portion other than the highlighted portion in the relief thickness disappears even at such a point portion, so that it is necessary to form the minimum highlight (minimum point portion). It is necessary to carry out the exposure at a range from the minimum exposure to 1.5 times the minimum exposure.

After irradiating the active image through the transparent image carrier as described above, the unexposed or uncured resin is washed with various washing liquids such as water, alcohol, acetone, benzene, toluene, chloroethane, chloroethylene and the like. The removal is carried out by washing with an aqueous solution, for example, an aqueous solution of sodium hydroxide, sodium carbonate, sodium phosphate, sodium tripolyphosphate, sodium borate, sodium silicate, or a surfactant aqueous solution. If necessary, a surfactant or the like can be added to the aqueous alkali solution.

In the photocurable resin relief printing plate of the present invention, since the thickness of the relief layer in the highlight portion having a halftone dot area ratio of 7% or less is smaller than the thickness of the relief layer in the portion other than the highlight portion, there is a disadvantage of relief printing. Thickening of a thin line point in a certain printing is effectively prevented. In the case of halftone printing in particular, the conventional highlights have thicker halftone dots and cannot be applied with too much printing pressure, so the shadows have poor ink transferability and low print quality with poor gradation. By using the photocurable resin letterpress of the present invention, thickening of highlights can be prevented and printing pressure can be applied. Is obtained.

[0044]

Next, the present invention will be described in more detail by way of examples, which should not be construed as limiting the present invention. In the present invention, the photosensitive characteristics were measured by the TO method as follows, and the minimum insolubilizing light amount was determined. The following description is made with reference to FIG.

(1) Preparation of Test Piece A liquid photosensitive resin layer 2 having a width of 15 cm, a length of 3 cm and a thickness of 4 mm was placed on a support 1 having an adhesive layer 4 and being transparent to active light.
Provided above. That is, on a 5 mm thick plate glass, a thickness of 9 mm
μm polyester film is adhered, and a 4 mm rubber spacer with the above dimensions hollowed out is placed on it,
A liquid photosensitive resin was poured into this, and a urethane-based adhesive was applied to a polyester support sheet having a thickness of 0.1 mm by 10 μm.
After applying a liquid having a thickness of m in advance, the liquid photosensitive resin layer is covered with the liquid photosensitive resin layer so as not to allow air to enter, and then a lid with another 5 mm-thick plate glass is prepared.

(2) Light Source As the light source, a 2 kW ultra-high pressure mercury lamp (manufactured by Oak Manufacturing Co., Ltd., trade name: Jetlight) or a 20 W chemical lamp (manufactured by Mitsubishi Electric Corporation, trade name: FLR-20B)
L) is used in which multiple lamps are arranged in parallel so as not to cause unevenness in the light source illuminance. The latter is more convenient from the viewpoint of the stability of the light source.

The light source (UV) is arranged at a position illuminating the lower side (reversely shown in FIG. 3), and the plate glass having a thickness of 5 mm is positioned on the side of the light source so that the liquid glass to be measured can be measured. The support having the adhesive layer 4 used for providing the resin layer 2 is placed such that the adhesive layer is on the lower side,
It is placed on a UV meter (trade name: UV-M01, manufactured by Oak Manufacturing Co., Ltd.) equipped with a UV-35 filter, and the height of the light source is determined so that the intensity indicated by the UV meter is 0.40 mW.

(3) Measurement A test piece prepared in advance, with the support side facing up, 3c
Five light-shielding pieces made of a 1 mm thick black rubber plate having a size of mx 6 cm are successively arranged horizontally from the top of the glass plate to cover the entire test piece. Next, the test piece is sandwiched between the strength-adjusted positions with a glass plate, and placed with the light-shielding piece arranged. In FIG. 3, the stopwatch is started at the same time as removing the first light-shielding piece at the left end, and thereafter the light-shielding pieces are sequentially removed every 30 seconds. After removing the last light-shielding piece at the right end in FIG. Turn off the light source later. As a result, the section corresponding to the first light-shielding piece is exposed for 150 seconds, the last piece is exposed for 30 seconds, and the small pieces in between are exposed to light in increments of 30 seconds.

(4) Elution, drying, and post-exposure Elution is performed with an eluate that effectively dissolves or disperses the uncured resin layer. Usually, water, alkaline water, or a surfactant solution is used as necessary. The distance from the tip of the nozzle to the test piece was 10 m using a spray with a pressure of 2 kg in the tube at 40 ° C.
The washing is performed so that the washing unevenness does not occur. At this time, the test piece is washed for 120 seconds from the side opposite to the light irradiation, that is, the resin side. Next, after drying in a dryer at 60 ° C. for 10 minutes, post-exposure is performed for 5 minutes from the resin side under the intensity of 2 mW using the light source.

(5) Determination of Minimum Insolubilizing Light Amount The thickness of the cured resin layer formed on the support is 1/100 m
It is measured with a thickness gauge that can be measured in m units. The relationship between the thickness of the obtained photocurable resin layer and the exposure time is graphed in a semilogarithmic graph as shown in FIG. T. (Seconds), and the minimum insolubilizing light quantity Q (mJ / cm ² ) is calculated by the following equation. Minimum insolubilizing light quantity Q (mJ / cm ² ) = light source intensity (mW /
cm ² ) × I. T. (Sec) = 0.40 × I.
T.

Example 1 and Comparative Examples 1-3 Polypropylene glycol adipate (molecular weight: 260
0) 1442 parts by weight and tolylene diisocyanate 18
After reacting 1 part by weight at 85 ° C. for 2 hours, 241 parts by weight of glycerin monomethacrylate and 2,6-di-te
0.1 wt% of rt-butyl-p-cresol was added,
After further reacting for 2 hours, disappearance of NCO was confirmed by infrared absorption spectrum. Next, 134 parts by weight of succinic anhydride was added, and the mixture was further reacted for 3 hours to obtain a polyurethane prepolymer (I). Using the polyurethane prepolymer (I) thus obtained, various photosensitive compositions as shown in Table 1 were prepared, and the photosensitive properties were determined by the TO method. Table 1 shows the results.

[0052]

Next, using the photosensitive composition, a thickness 2 covering a negative film having halftone and line drawing
On a 2 μm polypropylene film, a layer serving as a relief top layer was provided with a doctor to a thickness of 0.10 mm (or 0.2 mm), and then a layer serving as a relief base layer was formed thereon with 0.30 mm ( Or 0.20 mm). Next, a urethane-based adhesive containing an antihalation agent previously applied to a polyester support sheet having a thickness of 0.1 mm to a thickness of 10 μm was covered with the liquid resin layer so that air did not enter. Thereafter, the whole was irradiated with a 20 W chemical lamp from the support sheet side so that the irradiation amount became 80% of the insolubilization starting light amount of the relief base layer composition, and then a 6 kW metal halide lamp (intensity 60 mW) from the negative film side. / C
m ² ) for 5 seconds.

After the exposure was completed, the polypropylene film was peeled off, and a 1% by weight aqueous sodium borate solution was used.
For 2 minutes and further with water for 15 seconds to wash out unexposed portions. Next, the plate was further exposed to light for 10 minutes in air using a 20 W chemical lamp (intensity 2.3 mW / cm ² ). Table 2 shows the performance of the obtained photocurable resin letterpress as letterpress printing plates.

As can be seen from Table 2, when the combination of the compositions was such that the Q value of the relief top layer was 23 mJ / cm ² or more,
In all cases where the Q value of the base layer was 5 times or more, a printing plate in which the thickness of the relief layer in the highlight portion was smaller than the thickness of the relief layer in the solid portion was obtained. On the other hand, Q of the relief top layer
In Comparative Example 1 where the value was 23 mJ / cm ² or less, the thickness of the relief layer in the highlight portion and the solid portion was the same even though the Q value of the top layer was 5 times or more the Q value of the base layer. Edition. In Comparative Examples 2 and 3 in which the Q value of the relief top layer is 5 times or less the Q value of the base layer, the Q portion of the relief top layer is 23 mJ / cm ² or more. The printing plate had the same relief layer thickness in the solid portion. Using the printing plate of the example and printing with a flexographic rotary printing machine under a printing pressure of 4 mils at 10,000 copies, a bright print having a wide gradation range with less thickening and good solidness was obtained.

[0056]

Example 2 and Comparative Example 4 Using the same photosensitive resin composition prepared in Example 1,
As in Example 1, the relief top layer 2B was 0.1 m
m, the relief base layer 2B was 0.3 mm thick, and the combination of the photosensitive resin composition of the relief top layer 2B and the relief base layer 2A produced the following combinations of photosensitive elements. P ₁ (in the present invention): 2B / 2A = (3) / (6) (Q _B
31.6 mJ / cm ² , Q _A = 4.6 mJ / cm ² ) P ₂ (the present invention): 2B / 2A = (4) / (6) (Q _{B
^{= 34.4mJ / cm 2, Q A}} = 4.6mJ / c
m ² ) Comparative Example 4: 2B / 2A = (1) / (5) (Q _B =
19.2 mJ / cm ² , Q _A = 3.6 mJ / cm ² )

Using this photosensitive element, a printing plate was made in the same manner as in Example 1 using a test pattern containing a gradation scale as a transparent image carrier. Using the resulting plate, printing was performed with a flexographic rotary press at a printing pressure of 4 mils.

FIG. 5 shows the relationship between the dot area ratio of a negative film as a transparent image carrier and the dot area ratio of 85 lines / inch on a gradation scale of printed matter. For reference, the ideal case of completely reproducing the negative film of the printed matter is indicated by a straight line R.

Compared to the conventional plate, the plate of the present invention shows a reproduction close to that of a negative film, and particularly, the effect of improving the reproducibility in a highlight portion of about 5% is large. Is a dot area ratio of 23% to 100
%, While the plate of the present invention is greatly improved from about 5% to 100%.

Example 3 and Comparative Examples 5 to 6 Polypropylene glycol (number average molecular weight: 2,000)
1339 parts by weight, tolylene diisocyanate 175.
After mixing 8 parts by weight and 0.042 parts by weight of dibutyltin dilaurate and reacting at 85 ° C. for 2 hours, 153.6 parts by weight of glycerin monomethacrylate was added, and the mixture was further reacted for 2 hours. The disappearance of NCO was confirmed, and a polyurethane prepolymer (II) was obtained.

Using the polyurethane prepolymer (II) thus obtained, various photosensitive compositions as shown in Table 3 were prepared, and the photosensitive characteristics were determined by the TO method. Table 3 shows the results.

Next, Example 1 was prepared using the photosensitive composition.
In the same manner as in the above, a photocurable resin letterpress was prepared. Table 4 shows the performance of the obtained relief printing plate.

Using this plate, printing was performed with a flexographic printing machine at 5,000 copies under a printing pressure of 4 mils. As in Example 1, a bright print with a small thickness and good solidness was obtained, and a wide gradation range was obtained. .

[0065]

[0066]

Example 4 A photosensitive element was prepared by using the photosensitive compositions (2) and (6) in Example 1 as a relief top layer and a relief base layer, respectively, and used as a light source with an intensity of 30 m.
A printing plate was prepared in the same manner as in Example 1, except that the exposure time was changed from 5 to 13 seconds using a w / cm ² metal halide lamp.

The obtained version of 85 LPI (line pe
r inch) The difference between the thickness of the relief layer of the highlight portion of 5% and the thickness of the relief layer of the solid portion in the vicinity was measured. The results are shown in Table 5.

From these results, the exposure time for obtaining a printing plate having a desired constitution is in the range from the minimum exposure required for forming the minimum highlight in the photosensitive element to 1.5 times the minimum exposure. It is 7 to 10 seconds corresponding to the exposure amount, and it can be seen that if the exposure is excessively performed, the thickness of the highlight portion is not different from the thickness of the other portions.

[0069]

According to the present invention, the relief curable resin plate of the present invention is used in which the thickness of the relief layer in the highlight portion constituting the pattern having the dot area ratio of 7% or less is smaller than the thickness of the relief layer in the portion other than the highlight portion. And, it is possible to effectively prevent thickening of thin line points in printing which is a drawback of letterpress printing, especially in halftone printing, in the conventional highlight portion, halftone dots are easily thickened,
Because the printing pressure cannot be applied so much, the shadow portion is inferior in ink transferability and only low-grade printing quality with poor gradation can be obtained, but by using the photosensitive resin relief plate of the present invention, Since the thickening of the highlight portion can be prevented and the printing pressure can be applied, a high-quality print with high brightness and rich gradation can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a photocurable resin relief plate of the present invention;

FIG. 2 is a view for explaining a mechanism for forming a relief structure in which a relief thickness of a highlight portion is smaller than a relief thickness of a portion other than the highlight in the present invention;

FIG. 3 is a principle diagram of a TO method used for measuring a photosensitive characteristic for obtaining a minimum insolubilizing light amount Q of a photosensitive resin used in the present invention;

FIG. 4 is a semilogarithmic graph showing an example of a relationship between an exposure time and a thickness of a photocurable resin layer;

FIG. 5 shows a relationship between a dot area ratio of a negative film and a dot area ratio of a printed matter. 1 to 5, the same parts are denoted by the same reference numerals and symbols, 1 is a support layer, 2 is a photosensitive resin layer, 2A and 2B are photosensitive layers corresponding to the base layer A and the top layer B of the relief. The lower and upper layers of the resin layer, 3 is a negative film, 4 is an adhesive layer, and 5 is a light shielding piece.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G03F 7/00 502 G03F 7/095

Claims (4)

(57) [Claims] 1. A support, and a base layer A and a top formed by photo-curing a multilayer photosensitive resin layer comprising at least two layers of photosensitive resin layers having different photosensitive characteristics on the support by image exposure. and the photocurable resin relief plate comprising encompass relief layer having a layer B in this order, the minimum insolubilization light amount Q _B as liquid photosensitive resin layer and the upper layer of the minimum insolubilization light amount Q _a of the photosensitive resin layer as the lower layer of a multilayer photosensitive resin layer having a liquid photosensitive resin layer Q _B is not less 23 millijoules / cm ² or more and 5 times or more of Q _a, base layer formed in each photocurable from the lower and upper The maximum value of the total thickness of A and the top layer B is 8 mm or less, the maximum thickness of the top layer is 以下 or less of the maximum value of the total thickness of the base layer and the top layer, and 1 mm or less. High that constitutes a symbol that is 7% or less Photocured resin relief plate thickness of the relief layer of the site portion is smaller than a thickness of the relief layer of the portion other than the highlight portion. Wherein at least having a support and a liquid photosensitive resin layer of a minimum insolubilization light amount Q _B as liquid photosensitive resin layer and the upper layer of the minimum insolubilization light amount Q _A of a lower layer on to the support in this order two Provided is a photosensitive element including a multilayer photosensitive resin layer comprising photosensitive resin layers having different photosensitive characteristics, and the photosensitive element is subjected to image exposure from the multilayer photosensitive resin layer side to a light-cured portion and an uncured portion. And then washing out the uncured portion with a developing solution to form a relief layer having a base layer A and a top layer B obtained from the lower layer and the upper layer, respectively. A method for producing a photocurable resin relief plate comprising a highlight portion constituting a certain design and a non-highlight portion constituting a design having a halftone dot area ratio of more than 7%, wherein Q _B is 23 mJ / cm ² or more and Q _A is 5 times or more of _A , and the image exposure is performed from the minimum exposure amount required to form the minimum highlight of a highlight portion constituting a pattern having a dot area ratio of 7% or less to 1.5 times the minimum exposure amount. The thickness of the relief layer in the highlight portion constituting the pattern whose halftone dot area ratio of the resulting photocurable resin letterpress is 7% or less is obtained from the thickness of the relief layer in the portion other than the highlight portion. A method for producing a photocurable resin letterpress, characterized in that it is made smaller. 3. The method according to claim 2, wherein the total thickness of the upper layer and the lower layer is 8 mm or less, and the thickness of the upper layer is １ ／ or less and 1 mm or less of the total thickness of the upper layer and the lower layer. 4. A high-pressure mercury lamp, an ultra-high-pressure mercury lamp,
4. The method according to claim 2, wherein a metal halide lamp is used.