DE1597571A1 - Method and device for the production of printing plates and relief images - Google Patents

Description

Foxcroft Inventions (Proprietary) Ltd., Johannesburg, Transvaal, South Africa

Method and device for the production of printing plates and relief images

The invention relates to the manufacture of Printing plates and relief images in general, the term "relief images" also including photogravures, lithographs, Include screen prints and similar images target. .

In particular, the invention is directed to a method for producing a relief image that is contained therein consists of having a base and a photographic one Negative of the desired image at a distance and parallel

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to each other, the space between the base and the negative with a light, curable, flowable Plastic material fills, light through the unclouded Sends parts of the negative through to harden the corresponding parts of the plastic material and

finally separating the flowable part of the plastic material from the hardened plastic material.

Process of this type in its application to both flowable as well as strong, light, hardening plastic material are for example in the USA patent 2,791,504.

During such a process in its application to solid, partially polymerized plastic material

it is already being used, has been shown / has been shown in experiments using the method on liquid, photopolymerizable, Ethylene-like, unsaturated compounds that form a higher polymerizate through photo initiation of the polymerization form, not suitable for the production of economically viable printing plates. This goes back to that the inevitable heat generated by the light source becomes undesirable. Polymerization by the action of heat under the black areas of the transparency carrying the image due to the radiation heat absorption and the Reflection in this area resulted.

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Also the use of the recently announced thermal relatively insensitive polymerization initiators, which will later generally also be called catalysts, is not a satisfactory solution this problem because, in general, catalysts with low thermal sensitivity also have low photosensitivity show .. Obviously, such a less sensitive catalyst increases the working time considerable and with it the cost of making a printing block, making it economically impossible is, for example, to produce panels with extremely bright points.

It should also be noted that a convenient method of making panels using of liquid photopolymerizable mixtures, in which the proportions of the mixture between the relief images produced Remaining unpolymerized, significant cost savings yield as the unpolymerized material - averaging about $ 75 or more of that in manufacture of a block of resin used - can then be reused.

The invention provides a process for the preparation $ on Beliefbliäem vorgeBChiägenj wherein a ünterlage-Bchicht and a cloudy, image-bearing transparency at a distance and are arranged parallel to each other,

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the distance between the backing layer and the transparency is filled with a light, hardening, flowable plastic material, a liquid infrared light filter is placed above the transparency, and light from a strong ultraviolet light source through the filter and the non-cloudy parts of the transparency to harden the corresponding parts of the synthetic material sent and then the flowable part of the Plastic is separated from the hardened plastic.

The invention is shown schematically in the drawings. These show in:

]? ig. 1 is a partially sectioned side view of an apparatus for producing Printing plates and in

Fig. 2 is a plan view of the table without the 'image-bearing Transparent and the plastic material on top.

The method of carrying out the invention in its preferred Embodiment basically consists in that a base layer 1 is placed on a block 2 of a table 3. A surrounding seal * [will be around the 3 sides of the base layer are placed in such a way that a flat container is created that can be filled with a liquid,

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viscous, easily hardening plastic material 5 can be filled.

A transparency 6 carrying the image, which is in a frame 7 is mounted, is placed so that it extends over Support 8 extends and with the liquid plastic material 5 and the surrounding seal 4 in contact stands, whereby the flat, formed by the pad and the environment from seal container with the exception of End 9 is closed, over which the seal does not extend.

As will be described in more detail later, the The operation is carried out in such a way that it is ensured that no bubbles get caught in the liquid plastic and that the transparency is exactly parallel as far as possible is arranged with the backing layer and at an exact predetermined distance above it.

Then a hood 10 with a liquid filter 11 and a light source 12 placed above this filter over the transparency. Now it becomes strong ultraviolet light sent through the liquid filter and the non-clouded parts of the transparency 6, from top to bottom antennas harden the corresponding parts of the liquid synthetic material 5.

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The light is sent out until the parts of the Plastic material between the transparency and the; "The support plate is hardened. Then the Light irradiation is interrupted, hood and filter are removed from the transparency and the latter weakly from the transparency adhering hardened plastic material peeled off or otherwise removed. Then the remaining liquid plastic material poured off or with the help a suction nozzle into a container and can again be used. The hardened plastic remains in the form of the desired relief image.

Document layer , _χ

The backing layer used can consist of the most varied Materials exist depending on the requirements placed on them. For example, if the relief images do not form part of a printing plate, for example So there are pictures for raised letters and characters with or without a screen, then you use a base plate Made of polished metal or some other material that the plastic will not adhere to.

If a pressure plate is required on the other side, then it may be necessary for the backing plate to adhere firmly to the relief image. The underlay material, on which this relief image is generated can be can be changed to suit the needs of the particular machine on which the printing is being made

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should be, but it is found in general has that suitably prepared steel, with or without plated chrome, tin or copper surfaces or the like. the best results for long-term production shows. However, the invention is not limited to steel, and relief plates can be up to any one desired depth can be made on any material, to which the resin adheres, either with or without the aid of adhesives. In many cases it has Proven to be useful, paper or cardboard, fiberboard, plastics or elastomers as a base material to be used for flexographic printing.

In those cases where the relief image is very small, in the On the order of 0.075 to 0.150 mm (0.003 to 0.006 ") and there is a risk that the inking rollers paint on the open spaces between letters and other characters transferred, it has proven to be practical if the backing material accepts water, as it does in lithographic plates is known, so that the printing press produce the printing piece by a process lcann, which between lithographic printing and the usual pressing end £ ^ |! g | procedure. A suitable one Material for absorbing water in such open areas Rooms are identical to clean chrome plating, with the Water barrier with the help of a steam roller or through it

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. is generated that one of the plate in a suitable manner Exposes water vapor.

Instead of making the base plates suitable for attachment to the printing block furniture, it is possible and provided according to the invention that the furniture or the mounting plate itself is used as a base plate, the relief image being formed directly on it. If the wood from which the furniture or the Eefe- 'stigungsplatte is made is sufficiently porous, the resin can be sucked into the pores so far that a firm adhesion is guaranteed during hardening, the hardening even by sucking or soaking the The upper surface of the plate or furniture can be accelerated by preparing a preparation with polyester + 1% methyl ethyl ketone peroxide + 1/2 $ xobalt naphthanate. But you can also - as in the case of metal plates - use an adhesive that is compatible with the plastic.

During the adherence of the photopolymerized or hardened plastic relief images on the block no substantial Problems with line blocks or halftone blocks without extreme highlights, it creates a problem with blocks with small tip points, fine hairlines and extreme highlights in halftones. This problem is partially alleviated by common mask

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teehniken solved, whereby point points and similar parts of the transparency are exposed to a longer exposure to the light than the usual parts of the block. Mainly, it is solved by using an adhesive consisting of a mixture of epoxy resin and a beigemengtem in a small proportion, for example 10 $ of the photosensitive Polyesterharzgeraisches, curing agent and using the same mixture as it comes to the preparation of relief images on the application.

The bonding mechanism of such adhesives is not entirely clear, but microscopic examination shows that the polyester resin which has a lower specific weight than the epoxy resin and which is immiscible with it is, to the surface of the applied to the backing layer Position in the form of spheres which do not cure or at least not cure for the short time required for the epoxy to set. It is therefore easily possible that these spheres become mixed with the resin from which the relief images are made. combine or mix and when curing by exposure obstructing formations during the construction of the block form in the epoxy resin structure. _

You can use standard epoxy resins, for example the one below

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the trade name known "Epiglaze" and standard hardener, for example polyamides sold under the same trade name. The epoxy resin between the hardened polyester relief images can be dissolved in the usual solvent not easy to solve.

The exposed, upward-facing surface of the backing plate should not be a good reflector for the incident Be ultraviolet light, since it is inevitable that reflection and scattering of the light cause undesirable settling of the parts of the liquid plastic. On the other hand, the backing plate has a limited reflection Advantages, because this means that it is set off and then thickened around the basic parts of the relief images is produced. This leads to more robust images without compromising their sharpness on the printing surface. the end For this reason, the base plates can be colored in the orange to red area to make them partially reflective Surface. A good example is oxidized electrolytic copper, while silver colors should be avoided, since the latter are highly reflective for ultraviolet light.

Liquid , light-curing plastic A preferred light-sensitive, liquid plastic consists of the following components:

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a) Light stabilized, unsaturated polyester resin solution

in $ 335K to $ 35 styrene; . '-

b) elastic isophthalically unsaturated polyester resin solution in 31% to 33% styrene monomer;

c) catalyst sensitive to ultraviolet light, for example the one under the trade brand name U.V. 50 catalyst sold;

d) styrene monomer.

The proportions of components (a), (b) and (d) can be in can be changed widely, with a larger one Strength and fragility predominate in (a) and a greater flexibility and toughness with a predominance of (b) and the addition of the component (d) to it serves to dissolve the catalyst (c) and, if necessary, reduce the viscosity of the mixture to make it less for retaining trapped bubbles as a result of vigorous mixing in air under normal pressure to keep.

, In cases where the resistance to higher Temperatures is required, an unsaturated polyester resin with a minimum of styrene solvents is used

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and no addition of isophthalic unsaturated polyester resin, Such mixtures are more advantageous in a partially evacuated air conditioner and at slightly elevated levels Produces temperatures to lower the viscosity.

The amount of catalyst required can vary between 1% and 6% and the time required for settling to the correct extent then also varies, but not proportionally and in each case must be determined by measurement on representative samples.

In general, the most active catalysts available, for example of the peroxide type, and in Amounts of maximum effectiveness regardless of the fact that they may be heat sensitive if adverse Effects on the heat sensitivity can be regulated by a filter, as explained above. In fact, the Catalyst activity as far as reasonably possible through the use of bottom heating of the backing layer with the aid of the heating elements 13 according to I? ig. 1 increased.

This makes it possible, for example, to use lithographic Obtain plates with exposure times on the order of 3 minutes. Generally the exposure is lying on the order of half a minute for 24/1000 mm throughput, but these periods can be increased,

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when additional exposure is required for extreme halftone peak lights and the like.

An example of a typical light-curing plastic mixture is as follows:

lA parts by weight of polyester resin
2 »isophthalic polyester resin

1 "catalytic converter

2 "styrene monomer.

While the flowable polyester resin mixtures with .in A wide range of fluctuating viscosity can be used, since the process according to the invention is the usual one Avoids etching and similar dissolution processes, with the uncured plastic only from the base plate When pouring, low viscosity materials are preferred. In this regard it is important to point out that where the height of the relief images is very low and an adhesive base on the backing layer is used, the adhesive not detached by the hardened plastic is often detached got to. This is done without difficulty, for example by common solvents, such as thinners, without affecting the hardened plastic in any way Way would be affected. Sa emptying the plate

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if sticky and tougher mixtures are used, the relief plates are usually made with styrene monomer cleaned and washed so that any recovered fluids can be reused.

Filter :

The light used to cure the plastic is strong ultraviolet light and a filter is used which - as far as possible - filters out the infrared components that would otherwise have the effect of the plastic preferably to harden under the dark areas of the negative, where the plastic should remain liquid.

One can use a variety of ultraviolet light sources provided that they are strong enough to prevent the plastic from polymerizing or settling to effect in a usable time. For example, a pair of carbon arcs 14 with an input power of 4000 to 4500 watts Use the manufacture of blocks with an area of 0.2-0.3 m (2-3 s.f.).

When using such strong light sources, the usual ones have become Solid infrared filters have basically not proven to be useful, as they radiate the absorbed heat and thereby an undesired withdrawal of the

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liquid plastic .materials under the dark areas of 'create transparency. '

By using a liquid filter and in particular one with circulation and cooling of the liquid, this problem can be solved. A 205 * 1 ge Copper sulfate solution at a depth of 24.5 mm (1 ") has been found to be an extremely satisfactory filter. The filter container is formed by a trough, whose Bottom is formed by a transparent layer 15 on the lower part of the hood 10, the upper surface the liquid is directly exposed to the light source. The circulation and cooling of the filter liquid takes place by a normal pump 16 driven by a motor and by a cooling unit 17. If desired the layer 15 may itself have the shape of a filter and the circulated liquid be so transparent or colored that this layer has the desired filter effect supplies.

By circulating and cooling the filter liquid can have the heating effect on the polymerizable plastic material be offset to such an extent that controlled floor heating of the base layer can be used.

This heating of the floor not only reduces the hardening time

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of the plastic, as described above, but supported also the thickening of the base parts of the relief images, thereby making them stick to the backing layer and reinforcing them the relief image structure are supported.

Halftone blocks

The procedure described is based on in the same way Line and PIaIb tonb locke araiendbar »shows one particular advantage in the latter case, since it reduces the need to use "make ready". This is achieved due to the fact that there is a slope to the height of the points that are desired To change the direction and in proportion to the dark and light shade of the negative, the Extent of this preferred increase in the case of a non-hardening, liquid plastic of the manner described above by the Henge of the styrene solvent monomer used is adjustable. The more styrene monomer is present, the greater the effect, which much more through Regulation of light intensity and duration of exposure can be changed. A long low exposure at low intensity it increases the difference between sharp lights and dark surfaces.

Fastening of the image bearing e nd s Transparents and

Support plate As already stated, it is necessary to be sure-

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deliver that as far as possible the transparency carrying the image and the backing layer are parallel to one another and run at a precisely predetermined distance.

The backing layer 6 is, as can be seen from the drawing, placed on a smooth, ground surface of a base block 2, whereupon a strip 18 made of porous material under the backing layer like this assumes that he is through a hole 19 through the table 3 ■■ which is connected to a vacuum source 20. The edges of the backing layer and the porous The strips are then sealed by adhesive tape 21 and the area between the base block and the Backing layer is evacuated. This ensures that the backing layer 6 is flat on the surface of the pad 2 is and adapts to him.

To extend the underlay look at a distance from it the support strips 8, which are adjustable in height or in some other way, but in each case on one exact distance above the support block.

The sealing strip in its position * l extends to a desired height above the support strips, and the liquid plastic is now poured into the space that is created by the sealing

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strip is limited, which you can then use in frame 7 mounted transparent.

By using a roller supported on the support strip 8 on each side of the base block the banner pushed down from one end to the other. This squeezes out the sealing strip and excess liquid plastic is pressed out into the hood 22, where it is collected in the container 23 will.

The light transparency is in the middle part through the Layer of liquid plastic on which it rests, carried and shows, provided that it is sufficiently tensioned is, no noticeable tendency to sag in the middle.

The support blocks 8 are at a distance from the basic or Base block 2 arranged so that a gutter is formed between these members. This prevents it from being squeezed out of the sealing strip material in any direction other than that in connection with the support strip standing drainage channel 19. Should an undesired flow occur, this would lead to a flow through capillary action between the transparency and the support strip

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lead and an unacceptable lifting of the banner . have as a consequence. ·

Any material can be used to produce the sealing strip 4 with negligible elasticity and usually one Use grease that is not affected by the plastic.

If the dimensions of the transparency are only small, it may be necessary to use a stretched structure use. In such a case, the banner can be mounted on the bottom of a base glass layer, which can form the bottom of the liquid filter container itself. However, such layers tend to have a take on warp-line curve shape when they are of substantial size, resulting in print blocks, the unacceptably shallow depths of throughput (drive) have in the middle part.

The invention has been applied in the foregoing described on a method in which a liquid Infrared filter is used. But it can also be used ■ in connection with * gas filters such as nitrogen or carbon dioxide filters instead of a liquid filter. While such a gas filter is relatively easy to

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roll and cool, it is necessary to achieve the filter element it requires that it be of substantial depth and under considerable pressure, with with increasing pressure the minimum depth becomes smaller. This leads to the obvious practical drawbacks that make it appear advisable to use a liquid filter.

It must also be used when using a gaseous medium between upper and lower translucent layers be included. Surrender at every intermediate surface undesirable losses of light energy. In the case of a liquid filter, this phenomenon is reduced, because the light hits the surface of the liquid directly can hit.

- Patent claims:

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Claims (12)

- 21 - ■■■■ "'(P at e nt rühe 1. Process for the production of relief images, ■ thereby g e k e η η ζ ei that paves a backing plate and a transparent transparency carrying the image at a distance from and parallel to one another, filling the Space between them with a light-curing, flowable plastic material and under arrangement an infrared light filter are arranged above the transparency, the filter being a coolant forming liquid in substantial depth, and that light from a strong ultraviolet light source through the filter and the non-clouded parts of the transparency is sent through to cure the corresponding parts of the plastic material, and then the flowable component of the plastic material from the hardened Plastic material is separated. 2. The method according to claim 1, characterized in that the liquid in the filter itself to form an infrared filter is colored. 3. The method according to claim 1 or 2, characterized in that the liquid in the filter during the exposure. is circulated. BATH 009 8 33/15 A3. 4. The method according to claim 3, characterized in that the liquid in the filter is cooled during the circulation will. 5. The method according to one or more of the preceding claims, characterized in that the bearing the image Transparent under tension with the flowable plastic material during exposure through the Is kept transparent. 6. The method according to claim 5 » characterized in that that the banner is stretched over support structures, which at a distance from the backing layer and exactly are arranged above the level of the bottom of the backing layer. 7. The method according to one or more of the preceding Claims, characterized in that the backing layer is on a flat block leaving one Distance between the backing layer and the block is mounted, this spacing for producing intimate contact of the backing layer with the Block is evacuated. 8. The method according to one or more of the preceding Claims, characterized in that de coming into contact with the flowable resin surface of the lower 009833 / 1SA3 layer by applying an emulsion of epoxy resin and a light-curing, flowable one. Plastic composition pretreated with a specific gravity less than the specific gravity of the epoxy resin will. · 9. The method according to one or more of the preceding Claims, characterized in that a light-curing, flowable plastic mixture is used, which consists of a mixture of polyester resin, an elastic isophthalic polyester resin and a catalyst ;. 10. The method according to one or more of the preceding Claims, characterized in that the flowable, light-curing plastic on the base plate through a strip of non-elastic material is delimited, 11. The method according to one or more of the preceding claims, characterized in that the base layer consists of a pressure set, 12. Modification of the method according to one or more of the preceding claims, characterized in that that. a gas filter is used as a filter. BAD ORIGINAL 009833/1543; Empty soap