JPH0443884Y2 - - Google Patents

Description

[Detailed description of the invention] <Industrial application field> The invention relates to a photosensitive resin letterpress plate, and more specifically, the image area is formed by laminating three photosensitive resin layers including an intermediate diffusion layer. It is an object of the present invention to provide a photosensitive resin letterpress printing plate in which the shoulder angle of the convex portions can be adjusted.

<Prior art> Currently, as printing plates used in letterpress printing such as newspaper printing, letterpress printing, business form printing, and flexo printing, photosensitive resin letterpress plates are used instead of conventional etching plates, hand engravings, and molding plates. is widely used. These photosensitive resin letterpress plates are made by casting and drying a photosensitive resin composition into a sheet to form a photosensitive resin layer, and then exposing the resin layer to active light such as ultraviolet rays through a negative film that serves as a manuscript. A relief plate having an embossed image can be obtained by photo-curing the image area and then developing and removing the unexposed area (non-image area) with a suitable solvent or the like.

<Problems that the invention aims to solve> Although these photosensitive resin letterpress plates have considerably improved image reproducibility compared to conventional letterpress plates, they are still not satisfactory compared to other plate types such as lithography or gravure plates. situation. In particular, photosensitive resin letterpress plates use light energy to polymerize and harden to form convex portions, so controlling the light energy, or exposure amount, requires extreme skill, and it is necessary to maintain image fidelity and printing durability. It was extremely difficult to obtain a letterpress with the same characteristics.

Exposure amount control when making a relief plate from a document having highlight areas and shadow areas will be explained with reference to the drawings.

FIG. 1 shows a sectional view of a relief plate made of one photosensitive resin layer after plate making. In FIG. 1, 1 is a resin layer, 2 is a plastic film,
A support body made of a metal plate or the like is shown, and numeral 3 indicates a negative film that will be a document having a highlight part 3a and a shadow part 3b.

Here, in A of FIG. 1, the optimum exposure condition, that is, the shoulder angle is 60~60 in the highlight part 3a.
This is a cross-sectional view of a relief plate when the plate is made by controlling the exposure amount so that the exposure angle is 75°. As shown,
In the highlight part, the desired shoulder angle can be obtained, but in the shadow part 3b, overexposure occurs, the shoulder angle is low, and a shadow part with insufficient relief depth is formed. As a result, in the letterpress in case A, a problem arises in that it is not possible to print faithfully to the original in the shadow areas.

On the other hand, B in FIG. 1 shows the case where the shadow area is exposed to the optimum exposure conditions.
In the shadow areas, the shoulder angle is high and there is sufficient relief depth, but in the highlight areas, the exposure is insufficient, and the base of the highlight area is washed away during the development process, resulting in the highlight area having sufficient printing durability. This results in the problem that it is not formed. As explained above, in a photosensitive resin letterpress plate consisting of a single photosensitive resin layer, it is necessary to control the exposure amount depending on the design, and in reality, masking is done in the shadow areas etc. ,
Multi-stage exposure was performed in stages according to the pattern, and adjustments were made to achieve the optimum exposure conditions for each area. However, this adjustment required skill and also had problems in terms of work efficiency.

Therefore, the present inventor has determined that the lower photosensitive resin layer already consists of two photosensitive resin layers, and the content of the photopolymerization initiator in the lower photosensitive resin layer with respect to the total weight of the polymerizable prepolymer and the polymerizable monomer is determined in the upper photosensitive resin layer. We have proposed a photosensitive resin letterpress printing plate that solves the above-mentioned problems by increasing the thickness by 10 to 1000 times compared to the case of a resin layer. However, in the case of the above proposal, it is necessary to make the photopolymerization rate of the lower photosensitive resin layer extremely higher than that of the upper photosensitive resin layer (the content ratio of the photopolymerization initiator is extremely increased), which If the angle is not sufficient, the desired shoulder angle cannot be obtained. Therefore, when attempting to improve the efficiency of plate-making operations, the content of photopolymerization initiator inevitably increases, leading to an increase in cost.

The present invention attempts to solve these problems.

<Means for Solving the Problem> That is, the present invention provides a photosensitive resin letterpress plate mainly composed of a support and a photosensitive resin layer, in which the photosensitive resin layer includes an upper photosensitive resin layer, an intermediate diffusion layer, and a lower photosensitive resin layer. It is an object of the present invention to provide a photosensitive resin relief printing plate characterized by being composed of three photosensitive resin layers.

The photosensitive resin composition used in the photosensitive resin relief printing plate that is the object of the present invention contains a polymer and/or a polymerizable prepolymer, a polymerizable monomer, and a photopolymerization initiator as main components.

Here, the components used in the photosensitive resin relief printing plate will be exemplified. First of all, as polymers, natural rubber,
Nitrile rubber, chloroprene rubber, polyurethane rubber, polybutadiene rubber, or polybutadiene/styrene copolymer, polyurethane, polyamide, butadiene/acrylonitrile copolymer,
Examples include various conventionally known polymers such as polyester and acrylic copolymers.

In addition, as a polymerizable prepolymer, molecular weight 500
Liquid prepolymers such as polybutadiene, butadiene/styrene copolymer, butadiene/acrylonitrile copolymer, polyurethane copolymer, unsaturated polyester, polyvinyl alcohol, acrylic copolymer, etc. in the range of 5,000 to 5,000 can be used.

In addition, the polymerizable monomer is a monomer having one or more ethylenically unsaturated groups, and specifically, styrene, chlorostyrene, styrene derivatives such as vinyltoluene, acrylic acid, methacrylic acid, etc. α/β ethylenically unsaturated carboxylic acids or their various esters, acrylamide or their N-substituted derivatives such as acrylamide and methacrylamide, vinyl esters of various carboxylic acids, acrylonitrile, divinylbenzene, triethylene glycol diacrylate , tetraethylene glycol methacrylate, diallyl phthalate, etc. can be used.

As a photopolymerization initiator, benzoin, benzoin methyl ether, bonzoin ethyl ether,
2-ethylanthraquinone, methylbenzoin,
Benzyl, diacetyl, diphenyl disulfide, eosin, thionin, etc. can be used.

Among the above-mentioned components, the polymer and/or prepolymer and monomer can be appropriately combined to form a photosensitive resin composition depending on the intended use of the letterpress, but as for the photopolymerization initiator, the prepolymer in the composition , 0.01 to total weight of monomers
It is necessary to use it in a range of 15% by weight. In addition to the above-mentioned components, it is also possible to add a thermal polymerization inhibitor, a plasticizer, a colorant, and other additives, if necessary.

Here, the photosensitive resin letterpress plate according to the present invention is obtained by laminating a photosensitive resin composition obtained by mixing each of the above-mentioned components on a support as upper and lower photosensitive resin layers, and further layering both photosensitive resin layers. It is characterized by providing a diffusion layer between the two. The diffusion layer is laminated above the lower photosensitive resin layer and has the function of diffusing or refracting light to enlarge the photopolymerization area of the lower photosensitive resin layer and reduce the shoulder angle.

Therefore, for the diffusion layer, extender pigments such as barium sulfate, clay, talc, silica, calcium carbonate, etc., or oxidized A composition containing a white pigment such as titanium, zinc white, lithopone, etc. in an amount of 1 to 30% by weight is effective. If it is less than 1% by weight, the diffusivity will be insufficient, and if it is more than 30% by weight, the amount of light to the lower photosensitive resin layer will be restricted during exposure work, resulting in problems.

Regarding the photopolymerization initiator contained in each photosensitive resin layer, the content rate based on the total weight of the polymerizable prepolymer and polymerizable monomer contained in the lower photosensitive resin composition is the same as that of the upper photosensitive resin layer. It is efficient to contain more than that of the upper photosensitive resin layer, preferably 50 to 300 times the amount of the upper photosensitive resin layer. Note that the ratio of this photopolymerization initiator needs to be adjusted depending on the thickness of each photosensitive resin layer. In addition, as a photopolymerization initiator for the intermediate diffusion layer,
The content can be freely adjusted within the range of the content of the upper and lower photosensitive resin layers.

Furthermore, in the photosensitive resin letterpress plate comprising three layers according to the present invention, adjustment of the thickness of each layer is an important factor. In particular, if the thickness of the intermediate diffusion layer is too large, problems will arise in the exposure operation, and the thickness is preferably in the range of 0.005 mm to 0.1 mm. In addition, the thickness of the upper photosensitive resin layer is as follows:
The thickness of the lower photosensitive resin layer is preferably in the range of 0.1 to 10.0 mm, and making the lower photosensitive resin layer thicker than the upper layer improves printing durability. is important above.

<Function> FIG. 2 shows a cross-sectional view of plate making using the photosensitive resin letterpress plate according to the present invention.

In FIG. 2, 1a represents an upper photosensitive resin layer, 1b represents an intermediate diffusion layer, and 1c represents a lower photosensitive resin layer. When exposed to active light through a negative film made of the same original as shown in FIG. 1, photopolymerization progresses in the upper photosensitive resin layer 1a according to the image on the negative film, but 1b When light reaches the intermediate diffusion layer of
Light diffusion or refraction occurs, and the further down the lower photosensitive resin layer is, the more peripheral areas are also photopolymerized.

Here, by increasing the content of the photopolymerization initiator in the lower photosensitive resin layer, the polymerization rate increases, and even under the same exposure conditions, the upper photosensitive resin layer has a higher content as shown in Figure 1. The same effect as when the exposure amount is limited in the shadow part occurs, and relief with a large shoulder angle is formed in the highlight part (the part corresponding to 3a) and the shadow part (the part corresponding to 3b). On the other hand, on the lower photosensitive resin layer side, the photopolymerization rate is faster even at the same exposure amount, so photopolymerization proceeds in areas other than the exposed areas, resulting in a smaller shoulder angle than the upper photosensitive resin layer, i.e. A base having a sufficient extent to the image area is formed.

By using a photosensitive resin letterpress plate having the above structure, a letterpress plate with excellent image reproducibility and printing durability can be formed without controlling the exposure amount depending on the image. Become.

Hereinafter, the photosensitive resin letterpress plate according to the present invention will be explained in more detail using Examples.

<Example> Methyl ethyl ketone as a photosensitive resin composition
120 parts of styrene/butadiene block copolymer (styrene content 45% by weight), 20 parts of styrene/butadiene prepolymer (molecular weight 4500), 40 parts of ethylene glycol dimethacrylate, and 0.01 part of methyl hydroquinone, and benzophenone added to the composition. Mixture 1 was prepared by adding and mixing 0.5 part of benzophenone, Mixture 2 was prepared by adding and mixing 5.0 parts of benzophenone, and Mixture 3 was prepared by adding and mixing 0.5 part of benzophenone and 20 parts of silica gel. The above mixtures 1 and 2 were separately cast onto a support, dried at a temperature of 45°C for 20 hours,
A photosensitive resin master plate with a thickness of 2.5 mm was obtained. Using a chemical lamp (manufactured by Sylvania Co., Ltd.), the manuscript was exposed to light and cured, and the unexposed areas were removed by development to obtain letterpress plates having a relief of 1.0 mm.

Letterpress 1 using Mixture 1 had a shoulder angle of 74° with an exposure time of 10 minutes, and Letterpress 2 with Mixture 2 had a shoulder angle of 56° with an exposure time of 5 minutes.

In relief plate 1, the base of the highlight area was insufficient and lacked printing durability, and in relief plate 2, the relief depth in the shadow area was shallow and lacked reproducibility.

On the other hand, Mixture 2 was cast on a support and dried, Mixture 3 was cast and dried on it, and Mixture 1 was similarly cast on it and dried. The lower photosensitive resin layer consisting of
A photosensitive resin master plate was obtained which consisted of three layers: 2.0 mm, an intermediate diffusion layer made of Mixture 3 of 30 μm, and an upper photosensitive resin layer of Mixture 1 of 0.5 mm. A relief plate 3 was obtained by making a plate in the same manner.

For Letterpress 3, when exposed for 9 minutes, the shoulder angle was 79° in the upper photosensitive resin layer, and a sufficient relief depth was formed in the shadow area, and the shoulder angle was 45° in the lower photosensitive resin layer. As shown, a sufficient base was formed in the highlighted area.

<Effects of the invention> In the photosensitive resin letterpress plate according to the invention, by uniformly exposing the entire surface without considering the type of image on the negative film that is the original, it is possible to It is also possible to obtain a letterpress plate that maintains reproducibility and printing durability very easily, and it is possible to greatly improve the plate-making work.

Furthermore, since the ratio of the content of the photopolymerization initiator in the upper and lower photosensitive resin layers may be relatively small, problems such as requiring a long exposure time and high cost can be solved.

[Brief explanation of the drawing]

Figure 1 shows a cross section of a conventional photosensitive resin letterpress plate made of one layer after plate making while controlling the exposure amount, and Figure 2 shows a photosensitive resin letterpress plate according to the present invention. It shows a cross section after plate making when used. Note that each symbol in the figure indicates the following. 1
...Photosensitive resin layer, 1a... Upper photosensitive resin layer,
1b... Intermediate diffusion layer, 2... Support, 1c... Lower photosensitive resin layer, 3a... Highlight area, 3...
Negative film, 3b...Shadow part.

Claims (1)

[Scope of Claim for Utility Model Registration] (1) In a photosensitive resin letterpress mainly composed of a support and a photosensitive resin layer, the photosensitive resin layer includes an upper photosensitive resin layer, an intermediate diffusion layer, and a lower photosensitive resin layer. A photosensitive resin letterpress plate characterized by being composed of three layers. (2) The photosensitive resin letterpress plate according to claim 1, wherein the intermediate diffusion layer is a photosensitive resin layer containing an extender pigment or a white pigment. (3) The content ratio of the photopolymerization initiator to the total weight of the polymerizable prepolymer and polymerizable monomer contained in the upper and lower photosensitive resin layers is 5 to 5 in the lower photosensitive resin layer relative to the upper photosensitive resin layer. The photosensitive resin letterpress according to claim 1 of the utility model registration claim, which is 500 times larger. (4) Utility model registration requests where the thickness of the upper photosensitive resin layer is in the range of 0.05 to 2.0 mm, the thickness of the intermediate diffusion layer is in the range of 0.005 to 0.1 mm, and the thickness of the lower photosensitive resin layer is in the range of 0.1 to 10.0 mm. A photosensitive resin letterpress as described in Scope 1.