DE2845754A1 - IMAGE REPRODUCTION PROCESS AND MATERIALS FOR IT - Google Patents

Description

Charles Cowan Tibbetts, 800 Inverness Drive, Flintridge, California 91101, V. St. A..

Image reproduction methods and materials therefor

In the production of stencils, printing plates and other image reproductions, layers usually have to be formed one after the other, dried and further processed, which requires considerable time, care and sometimes special equipment. In the production of screen printing stencils, for example, a number of coatings are successively made from a photoresist applied, each of which are completely dried by themselves until the layer has the desired thickness and uniformity. As these photosensitive materials work on most Respond to wavelengths of light and because they generally have poor storage stability, they and those to be exposed must Surfaces are handled with care. The storage stability of the photosensitive material is even in the refrigerated State limited, which increases the difficulty of its use and the problem of waste.

In addition, such image reproduction methods are known to present a number of specific problems relating to the Cost and image quality. For example, a sensitizer-containing colloidal must be used for screen printing stencils Solution are applied to the sieve in such a way that all meshes of the

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Sieves are filled without fine holes forming, why it is necessary to apply a number of coatings evenly and to dry each of these coatings before the next is applied. Some sensitizers, such as the frequently used dichromates, are also effective because of their toxicity the risk of occupational illnesses occurring. Other sensitizers bring this problem with them because they contain significant amounts of solvents that will evaporate and thereby pollute the air in closed rooms.

In the screen printing process, the screen, which currently usually consists of polyamide or polyester monofilaments or polyamide in ultifilaments or silk , can be specified in terms of mesh size and material, which then largely determines the fidelity of reproduction, the sharpness of the contours, the accuracy of registration and the service life of the stencil are. In graphics there are many areas of application in which stencils are used to reproduce fine to coarse patterns with different thicknesses of the applied layer of paint or paste or other variations in order to achieve special decorative effects.

Both direct and indirect photo templates are currently used. In the former case, the slide is placed directly on the screen on which a resist emulsion has been applied and dried. Usually, an emulsion coating is applied to the front and back of the stencil. In order to achieve optimal contour sharpness, however, experts in this field recommend the application of several coatings in order to prevent concavities in the areas between the threads as far as possible by forming a thicker and more uniform layer. However, this in turn has disadvantages. The application

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Applying multiple layers of emulsion requires complete drying of the emulsion before applying each additional layer, thus increasing not only the number of steps but also the time required to produce the finished coating. The exposure time must also be increased, so during development curing takes place over the entire depth of the coating. Since the exposure time is pretty much even with normal coatings large (e.g. 8 to 30 minutes) is a further increase rarely desired. In order to achieve good registration accuracy, print media and vacuum frames are usually used; however, the sharpness of reproduction that can be achieved with current direct playback techniques is limited. With indirect reproduction techniques Although better sharpness of reproduction can be achieved; however, the coatings are less durable and have a proportionate nature short lifespan.

A number of other considerations must be taken into account when achieving high quality prints or image reproductions because not only the sharpness of the contours, but also the resolution of the lines and the durability and adhesion of the image are essential properties. In screen printing, for example, the mesh size can range from 6.5 to 200 threads / cm (16.6 to 5θ8 strands per inch) or more, and the material must both pass through the mesh and adhere firmly to the screen after curing. The light sensitive Material that is to form the screen image must, on the one hand, fill the mesh and, on the other hand, must after exposure the unexposed part can be easily washed out so that the mesh openings are completely exposed.

Even if the sharpness of the contours is satisfactory, resolution problems can still arise, which are of great concern to the person skilled in the art show as undercuts and bridging and both are annoying with fine lines and halftone prints. the

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Disregard is mainly a diffusion or reflection the radiation through the sieve threads, which has the consequence that the areas of the coating which are not to be exposed are exposed, attained, attributed. The undercut is preferred limited to about 0.1 ram; however, it is difficult to avoid them when the hardened material is of considerable thickness having.

Good image reproduction obtained with a screen printing stencil is also said to have a "bridging" effect. Underneath is to understand that where the edge of a template intersects a mesh opening, it does not follow the stitch thread or depends on the relative angle between the image edge and the mesh, but the part of the mesh opening that is to be covered in exact correspondence with the segment of the original, bridged. Typically, a screen made by the direct technique is expected to be used several thousand times becomes common before the image quality drops noticeably, while with screens made by the indirect technique only a limited number of prints can be obtained. The relevant field of technology is so far developed that with regard to certain properties, excellent results can be achieved. However, it is still very difficult to find a combination of properties of such quality to obtain.

Problems encountered with the screen printing process discussed above are comparable, there are also other image reproduction methods, such as images that are produced by printing and / or etching are formed on carriers. It is also particularly useful for images that are produced on solid supports required that they have good adhesion and durability.

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The invention relates to a method for reproducing an image on a transparent part for printing purposes or other image reproduction purposes, which consists in applying a wet layer of photocurable material from high solids content in the direct, the transparent part facing Contact with this applies to this part and exposed for a sufficient time by means of a suitable radiation source practically harden it in the image parts, peel the transparent part from the hardened image without adverse effects, and washes out the uncured parts so that an accurate image is obtained in a short time without extensive preparatory process steps or the use of toxic materials are required.

The invention relates in particular to the use of a light-sensitized polymeric substance into which a dimensional stabilizer is incorporated. The dimensional stabilizer can be a finely dispersed material introduced into the substance or an opacifier that has the effect of undercuts to restrict and / or close fine lines. The sensitized polymeric substance is a flowable mass, which is preferably free of acrylate and a small proportion of a diluent to modify the flow properties according to the requirements of a particular substrate. A layer of the sensitized material is in direct wetting contact with a photographic original whose image is to be reproduced. For screen printing for example, the original is placed under the screen and the material adheres to the original and fills the mesh openings. Then the material is passed through the photographic original for a short time (from fractions of a second to 12 minutes or above, depending on the intensity of the light source, the thickness

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of the material, the type of sensitized material and the properties of the dimensional stabilizer) exposed so that the Parts of the original image are practically hardened. Though that If the photographic original is held precisely in its position by the material, it can after hardening The material can be easily peeled off without damage, and uncured parts are then removed using conventional solvents washed away. Post-curing can be carried out to ensure full curing over the entire image. A The screen image produced in this way has a high resolution and can produce lines down to 0.1 mm without visible undercuts reproduce. The bridging properties and durability of the stencil are those of conventional methods produced stencils are superior, and images with a comparable resolution can be produced on solid substrates and have special properties, such as extremely thin layers or resistance for certain purposes.

It has been found that according to the invention by utilizing the light transmission capacity of the polymeric material and the receiving system, including the sieve or the fixed one Substrate and the adjacent background, a superior one Fidelity can be achieved. The dimensional stabilizer present in the material can, for example, be a finely dispersed, light attenuating solid such as a pigment or an opacifying agent such as a dye. Both require an increase in Exposure time, but reduce the undercut effect when used appropriately. The finely dispersed solid is preferred, because it can stabilize the polymer during its transition from the uncured to the cured state and thus to leads to an extremely high resolution. Presumably the presence of the light attenuating fine particles hinders the transmission

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port free radicals that occur during hardening by light excitation can be generated so that a sharp interface between exposed and non-exposed areas is created. An undercut can be further reduced by using a screen that absorbs radiation of the active wavelengths, and preferably a non-reflective background is used to avoid the occurrence of radiation interfering with that of the Primary source coming coincides, restrict.

The image reproduction method according to the invention can be continuous provided that light sources of suitable intensity are used at the required wavelengths. However, it is also advantageous when using lighting systems and lamps as they are currently widely used. I.e. for Most of the organizations currently equipped for such work do not require a considerable amount of equipment, and the stability of the chemicals both in storage and when exposed to dim light, enables its use under a wide variety of conditions.

The procedure can be applied in many and different areas, including the production of coatings on solid substrates and other elements, as well as in lithography, the Printed circuit board fabrication, chemical etching, and other examples of graphics can be used. According to the invention Materials used for image reproduction can be characterized as flowable substances with high levels of pesticides and good curability and low toxicity, which contain a dimensional stabilizer and limited adhesiveness of photo originals from the polyester group and some acetates.

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In the drawings is:

FIG. 1 shows a schematic representation of the sequence of process stages in the method according to the invention;

FIG. 2 shows a section through part of a template produced by the method according to the invention, the serves to explain the undercut effect;

Figure 3 is an enlarged plan view of a screen with a Template made by the method according to the invention, which has the bridging capacity illustrates;

Figure 4 is a simplified perspective view of a Apparatus for forming a layer on a photocurable material on a solid support;

Figure 5 is a simplified perspective view of a System for producing layers of photo-curable materials on screens according to the invention; and

FIG. 6 shows a section through part of a template produced according to the invention, which shows the dimensional shrinkage effects.

The method according to the invention illustrated by FIG. 1 can be used to produce reproduced image layers on various surfaces or substrates for photomechanical reproduction purposes. Ie it can be used for the

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provision of images for lithographic printing, for printed Circuits, can be used for chemical milling and for printing forms for screen printing. It can be made of a carrier for example superficially saponified cellulose acetate, as is the case with photomechanical Production of planographic and offset printing forms is used. For the latter purpose it is it is desirable that the oleophilic properties of the hardened surfaces are increased.

Regardless of the field of application, an essential feature of the method according to the invention is the use of a through Light curable material. Furthermore, an adhesive layer of the material is distributed on a substrate, the photographic Original is arranged so that it is in direct contact with the uncured and wet surface of the material with this stands. The vast majority of photographic originals used for professional reproduction and similar processes has a backing made of polyester or cellulose material and adheres easily, but can be removed from materials of the type such as they are used according to the invention without any chemical interaction occurring between the materials.

Radiation curable materials that can be used in accordance with the invention include monomers and oligomers as well as compounds that are curable when exposed to light, preferably a light energy in the ultraviolet part of the spectrum, exposed to wavelengths from J55O - 380 nm of particular Are interested. In contrast, with the conventional methods, the sensitivity in an area that is closer to the visible part of the spectrum is used. Furthermore, the light-curable material is preferably free of acrylate or the monomer in the material is preferably not an acrylate. A

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Material which can be used with advantage is that marketed by the Polychrome Corporation of New York under the designation "Uvimer 778". This material has a high viscosity and is a clear liquid that is extremely stable even at ambient temperatures and therefore has a long shelf life without degradation of its properties. It has low toxicity and can be used in large quantities in closed rooms without adverse effects. According to the invention, the light-curable material can be used in "essentially solvent-free" form, which is to be understood as having only a small proportion (less than $ 20) of a vaporizable solvent which is advantageously added for certain purposes, in order to achieve certain handling options, contains. The addition of 5 to 10 $ of a solvent such as methyl ethyl ketone reduces the viscosity of the material considerably. The curable material, on the other hand, may contain (or may be added) a substantial amount of a reactive diluent which reduces viscosity but increases solids content. In any case, the amount and type of evaporable solvent added must not be such that they affect the properties of the photographic original,. with which the material is to be brought into contact. Usually the material should have a viscosity in the following:
5000 centipoise).

a viscosity in the range of 2500 to 5000 cm ² / s (2500 to

Other suitable photocurable materials which have been used with success in the method according to the invention, are "UR-2279" from Polychrome Corporation and "Dynacure" GA72 from Dynachem. Corp., a division of Thiokol Corporation. However, these photocurable materials are cited here only as examples, and it will be apparent to those skilled in the art that there are many photocurable materials that can be used.

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In most cases a significant amount ( e.g. 20 to 10%) of a reactive diluent is incorporated into the radiation curable material (initially or by addition) to improve stability and handling. If the curable material contains a diluent, this must be taken into account when determining the total amount to be used. Vinyl pyrrolidone is an example of a suitable diluent in the form of a reactive monomer; however, other diluents will suggest themselves to those skilled in the art. While it is possible to use an acrylate as a diluent, consideration must be given to toxicity and handling problems. The presence of a small amount of solvent can help reduce the amount of diluent to be used.

The photohardenable material also contains a small amount (typically $ 1 to $ 4 but less than $ 10) of a sensitizer or photocuring agents such as "irgacure 65I" der Ciba Geigy, New York, or "DEAP" (diethoxyaeetophenone) of the Union Carbide Corp., New York. The former is preferred because it is low in toxicity and otherwise excellent in properties Has.

A proportion of a dimensional stabilizer is also added to the light-curable material, which increases the stability of the polymeric material controls during curing and also the inspection of a prepared coating compound before and after hardening with the eye is facilitated.

The dimensional stability is essential for an accurate image reproduction. The polymeric materials

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lie during exposure to a chemical reaction that defines the interfaces between exposed and non-exposed areas can cross and thus close fine lines that should be open. This dimensional change or interface shift is not completely independent of the undercut effect, which also affects the quality of the image reproduction limited. The use of a dimensional stabilizer, such as a one-part solid, that provides spatially distributed damping of the radiation results, however, both the interfacial shift as a result of the spread of the chemical reaction as well as the undercut effects that result from unwanted light transmission result, restrict. It is currently also believed that the actual reaction mechanism is responsible for the undercut effect results in the transport of free radicals, which are generated by light excitation, into the non-exposed areas, in which hardening progresses is. This transport presumably also takes place when there are reflection and halation effects can be reduced by the optical properties of the screen. The presence of a light damper in the form of a Finely dispersed solids limit the transmission of light energy and thereby increase the exposure time; however it was found that the tolerance of the exposure time is increased considerably. A properly chosen dimensional stabilizer can at the same time also cause an increase in flexibility and thus the durability of the hardened image.

A particularly suitable dimensional stabilizer is carbon black, for example "Special Black No. 4" from De Gussa Corp. It can but other light-attenuating fine particles with other properties can also be used. For stencils it depends on the Layer thickness, the intensity of the light source and the time available, a soot concentration of about $ 0.5 is preferred; however,

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can be used up to about 6%. Considerable percentage amounts of finely divided solids can also be used for special applications. If full hardening can be achieved (for example with a thin film of material and a high intensity light source), the concentration of a finely dispersed pesticide, which is not as light-attenuating as soot, can be up to approximately $ 50.

Alternatively or together with this, an opacifier, such as a dye, which tints or colors the material, can also be present to limit undercut effects. The presence of a dye facilitates visual inspection of the material as it is subsequently spread and dispersed or when the hardened image is retouched. Typically less than about $ 2 of the dye is used, and preferably the dye is present at a concentration of only 0.5 to λ% . Suitable opacifiers are, for example, “Neozapon” green 3G dye from BASF Wyandotte, New Jersey, “Normandy magenta 2400” red dye from Paul Uhlich Co., “Orasol” blue GN dye from Ciba Geigy and “Orasol” brown GR from Ciba Geigy. The dye is mixed thoroughly into the material in a commercially available mixer until a uniform color is achieved. The presence of the dye can slow down curing somewhat and, although the effect is not significant, the amount and type of dye used must be taken into account in the subsequent exposure. In the case of UV-sensitive materials, it has been found that orange-red or red-pink dyes have the least effect in terms of increasing the exposure time. When a finely-dispersed solid is used as a means of attenuating UV light but which is transparent in the visible spectrum, a dye can be used at the same time to facilitate visual inspection.

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The photocurable material thus produced is then spread on the printing surface, substrate or screen to be used. The thickness of the applied layer can define within wide ^G vary and is usually in the range of 0.06 to 0.2 mm (2-1 / 2 to 8 mils), but can also be on the order of up to about 0.5 mm (about 20 mils). If the layer is applied to a screen, its thickness need only be so great that the mesh openings of the screen are completely penetrated and the openings in the pesticide parts of the developed image are completely blocked. For stencils, a layer thickness in the range of 0.06 to 0.2 mm (2-1 / 2 to 8 mils) is usually suitable. On a solid substrate, the layer can be very thin, and the thickness of the layer on a fabric depends on the thickness of the fabric. Even layers of the desired thickness can be applied with little practice using a roller or squeegee. If a substrate made of glass or metal or another flat substrate is to be used, in the presence of the finely divided pesticide or the dye it is also possible for the inexperienced to produce a uniform surface using a doctor blade or a leveling action. If greater accuracy is desired, a cutting edge fixed in a holder can be guided over the substrate at a selected constant distance so that the material spreads over the entire surface at the desired depth. Roller application machines, coating machines with an air knife, etc. can also be used.

If a screen is to be used to receive the material, the photographic original will generally be on a flat surface is placed under the sieve, and the material is deposited on the surface of the Sj & es and through the mesh of the Sieves brought into direct contact with the slide. Advantage-

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It is advisable to first use a squeegee through which the Material is pressed into the mesh, and then leveling the surface with a hard squeegee. It can also be two Coats of material can be applied from opposite sides or from the same side for better distribution on the substrates, especially in the case of printing screens. A thick layer of a certain depth can also be applied, by spreading the material between two foils, one of which consists of the slide, over the sieve.

If a solid substrate is used, the coating can be evenly spread over it and the slide then in contact with the coated substrate to adhere and be retained. Alternatively, the Coating can be applied to the slide itself, and the coated side can then be applied to the substrate will. Layering can be done with high speed and accuracy by using the original with the processed by light-curable material and the substrate between a pair of rollers to form a laminate.

The photographic transparency used can have an influence on the reproduction process, which depends on differences in the UV absorption is based. Triacetate and polyester films have been used with good results; however, it was found that triacetate films are more permeable to UV and therefore require shorter curing times. However, some acetates can be absorbed by light hardenable materials adhere and can be damaged during separation, so that for the production of slides Films that do not adhere firmly must be used. When the material is fully cured, any type of original (usually a positive) that can be stripped off manually without damage.

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The type of surface or substrate over which the photohardenable material will be spread must also be considered will. Different guidelines apply to solid substrates and sieves. The polymeric materials described surround the threads of polyester and polyamide sieves in such a way that a uniform structure with good durability is obtained, although there is no inherent adhesion to polyester or polyamide. The screen or other substrate is expedient before application of the material degreased or otherwise thoroughly cleaned. A solid substrate, such as glass, copper, or steel Plastic, may have a surface to which the hardened material does not adhere well. Hence it may be necessary an intermediate surface or a double-sided adhesive "pretreatment surface, such as" Coating 7700 "from Tibbetts-Westerfield Paint Co., Los Angeles. Other coatings that serve the same purpose are also available. After exposure, the Pre-treatment undergoes a separate process that extends parallel to the uncured material in the exposed image Process stage (as long as it is not washed away with the uncured material).

When making stencils for screen printing, the optical properties as well as the mesh size of the screen affect the outcome of the procedure. The dyes in the threads of the screen can absorb incident radiation and thereby reducing scattering, halation and undercuts. Dyes from yellow to orange tones have been found to be superior in this regard, with an orange colored one Sieve when using available light sources the lowest undercut effect is achieved.

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It has been found that the filaments of the screen are not mechanical adhere to the cover of the stencil, especially if they are made of synthetic material. The coating surrounds or wraps the threads and forms a self-binding layer on it, so that an integrated structure is created that has a considerably longer service life than that of the sieves currently in use. The physical properties of the stencil are improved, because the coating is symmetrical about the screen. Furthermore, if the stencil can be detached or removed without this If the sieve is damaged, the sieve can be used again.

The composite structure or temporary laminate is placed in front of a suitable source of radiation such as one in Photography conventionally used exposure system using a light source, the energy in the selected part of the Spectrum generated, arranged. UV radiation currently gives the best combination of availability of the light source and through Light curable materials. When a focused UV source high intensity is available, the exposure time can be very short, for example of the order of magnitude from a few seconds down to about 0.2 seconds. When using such a light source it is because of the short length Exposure times possible to continuously reproduce images. In this connection it should be noted that the lamina Education technology in combination with the high-intensity light source forms the basis for a continuously operating printing device forms. The original can be stripped from the reproduced image after exposure and recycled to immediately form a new laminate.

Usually, however, other commercial systems with diazo or polymer light sources are used when the costs of a UV light

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High intensity light source does not appear warranted. UV light sources which supply known and specified radiation amplitudes at wavelengths in the UV range can be used with good results in the method according to the invention. When diazo or polymer light sources are used, exposure times are usually in the range of 1 to 12 minutes, but can vary depending on the other factors mentioned above. As is known, the highest resolution can be achieved if a device with a point light source is used; however, a device with a blocked beam can also be used to improve the resolution. A black or other light-absorbing background can be arranged behind the exposure device with the original and the screen or carrier in order to limit reflection and scattering of light. The mesh size of the screen is usually 6.5 to 200 threads / cm (16.6 to 508 strands per inch), the mesh size is 20 to 1180 mm and the thickness of the screen 50 to 600 \ m. It has been found that with larger clear mesh sizes and thicker screens it is advisable to increase the exposure time.

During the exposure there is a practically uniform hardening in the image, which is the image of the photographic Originals corresponds. For many purposes, the fidelity and resolution of the reproduced image are within a wide range of conditions without special adjustment thereof. For the production of high quality prints and special applications where undercuts side edges have adverse effects on the dissolution, optimal conditions of the layer thickness, the screen, the positive, the concentration of finely dispersed solids and the exposure times can be determined. In addition, the hardening

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processing time can be reduced considerably if that is achieved by light curable material is kept in an inert atmosphere during exposure. It was found that the presence of oxygen the hardening is hindered and that the use of an inert gas (e.g. nitrogen) significantly reduces the Allowing cure time up to possibly $ 50. Alternatively For example, a chemical oxygen separation layer can be used to provide an exposed side of the layer of photohardenable material to cover. By using such a laminate, the light-curable material is shielded from oxygen and shortens the required exposure time.

For the implementation of the method according to the invention not only is no vacuum frame required, it also exists the ability to determine if the exposure is adequate. One corner of the screen on the one facing away from the positive Page can be checked for dryness and if the layer is not fully cured, the image can be checked exposed again until the material is completely dry.

After exposure, the original may slightly differ from the hardened Material can be peeled off and then used again. A suitable detergent can be used to dissolve the uncured material such as methyl ethyl ketone, "Cellosolve", "Butyl Cellosolve", (Trade names of Union Carbide Co.), cyclohexanone, diacetone, Alcohol or the like can be used so that an image is formed from mesh openings (stencil). The picture is then ready for use in reproduction processes. The original can be cleaned with one of the detergents mentioned above without being damaged. For full curing, the image can be post-cured by subsequently curing it exposed for a fraction of the initial exposure time

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28A5754

tet. It is essential that the entire layer is fully cured, so that interior material cannot be washed out after exposure and a solid self-binding polymer around the screen threads is obtained. However, when the above considerations are taken into account, full cure is achieved and that is what is obtained Screen image has superior lifespan. There is also the option of changing the physical properties of the hardened image in the sense that the flexibility can be increased if desired to improve the wear resistance.

The way in which the image is formed and the behind-the-scenes effect are illustrated in a somewhat simplified form by FIG. In contrast to the conventional process forms a single coating of non-dried radiation curable material a symmetrical material deposition on both sides of the screen. It can be seen that the exposed hardened parts 12, 13 of an image on the screen I5 evenly from the opposite sides of the screen I5 stand out. At the edges of the hardened parts is the (in dashed Lines shown) undercut effect in the shape peripheral hardened parts in areas that should remain unexposed, recognizable. The undercut makes them fine Interrupting lines by widening the edges of a hardened area that appears to be somewhat curved in cross-section, filled. According to the invention, however, the undercut is on limited to the order of 0.1 mm and is no longer recognizable in a number of practical examples. For the qualitative There is no method available to measure the undercut effect Disposal; however, good estimates can be made based on the resolution of fine lines. This is done using fine lines known width (for example 0.1 mm) in a positive reference

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compared under magnification with the same lines and contours of patterns in the reproduced image. By such Comparisons make it possible to objectively determine whether the undercut is less than 0.1 mm, for example.

The importance of the good bridging capacity achieved when carrying out the method according to the invention is illustrated in FIG 3 illustrates. This figure shows an enlarged scale fine-meshed sieve (clear mesh size, for example, <0.08 mm, i.e.> 250 mesh) on which an image with a sharp outline (e.g. part of a small "c") is formed. The vertical and horizontal single threads 18, 19 delimit the small mesh openings, and the hardened image part 20 fills the mesh openings, provided that the line of the image contour does not intersect such an opening - images can now be produced according to the invention which, as shown, bridge each other regardless of the position and angle of the image contour and the individual threads of each mesh opening Form over the mesh opening so that a cohesive smooth Curve is formed. When using conventional methods, there is a far greater inclination of the image contours, to follow the course of the individual threads, especially if the divergence angles are small, so that a zigzag effect in the scope of the image appears as indicated by dashed lines in Figure J5.

The following examples illustrate the invention.

Example I.

The following example illustrates fabrication, exposure and hardening in the production of a high quality screen stencil using very short exposure times.

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A screen stencil was made by placing a photographic positive approximately 20 25 cm (8 "10") on a triacetate base was placed on a glass plate with the emulsion side up.

The positive was then with a pre-stretched, degreased, orange-colored polyester screen with a mesh size of 0.05 mm (305 mesh) covered.

A light-curable material was prepared by mixing 65 g Polychrome "UR-2279", 35 g of vinylpyrrolidone and 4 g of "Irgacure 651" were mixed in a conventional mixer, the temperature being maintained at below 38 ⁰ C (10O ⁰ F) .

The material was distributed over the screen area extending in the same direction as the positive, initially using a doctor blade soft edge followed by a hard edge squeegee. An even layer was used about 0.09 mm (3 x 5 mils) thick.

The product was then passed k times through a HANOVIA UV curing device at a speed of about 30.5 m / min (100 ft / min) such that the total cure time was less than 0.5 seconds.

Then the positive was manually separated from the screen and the hardened stencil material.

The uncured material was washed away with "Cellosolve".

The template obtained in this way had a resolution of better than 0.1 mm, an undercut of less than 0.1 mm and showed excellent bridging.

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Example II

Another method of making a high quality screen stencil was done as follows:

A photocurable material was prepared using the photocurable material of Example I and $ 0.2 "Neozapon" green 3G dye (BASF) mixed with a high speed stirrer until uniform dissolution of the color was achieved , with the temperature not being held above 58 ⁰ C (10O ⁰ F). Then, as described in Example I, the material was pressed through a sieve with a mesh size of 0.041 mm (350 mesh "Redi Ester", product of Tibbetts-Westerfield Paint Co., Los Angeles) against an underlying original so that the Adhered positively to the surface of the screen. The positive and the screen were exposed for 3 * 5 minutes with a 5000 watt Addalux UV light source with a diazo lamp, after which the positive was peeled off the hardened stencil material and washed with clean methyl ethyl ketone. The screen was dipped in "Cellosolve" to clean the unexposed areas, rinsed with water and dried. The screen was then post-exposed to the light source through the back of the mesh.

The resolution of the template obtained was better than 0.1 mm, the undercut * C 0.1 mm, and the bridging excellent and the life span sufficient to produce more than 2000 prints without excessive wear.

Example III

The following example shows that cure can be interrupted to apply additional photocurable material. The hardening can be checked during the interruption,

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before new material is applied or without new material being applied.

A sieve was made by making a transparent positive with the emulsion side up on a glass plate.

The positive was made with a pre-stretched, degreased polyester screen with a mesh size of 0.049 mm (305 mesh).

The photoreactive material of Example I was pressed through the screen so that the positive on the adjacent surface of the · Siebes stuck.

The screen was then passed through the positive with a 5000 watt high intensity UV lamp for 3 minutes from 122 cm (48 ") .exposed .. ■■ / '.'.

A second coating of the material was pressed over the partially cured first coating.

The screen was exposed again for 3 minutes until complete curing was achieved.

The positive was peeled off the hardened stencil material and cleaned with methyl ethyl ketone.

The sieve was dipped in "Cellosolve" to remove the non-exposed ones Areas to be cleaned and then rinsed with water before it is put to use.

The contours of the template showed an undercut 0.1 mm.

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Example IV

The best resolution was achieved when one in the mixture Stabilizer was used:

A light curable material that has a light attenuating effect containing finely dispersed solid was prepared from:

(65 g "UR-2279" from Polychrome Corp. 99 s 5 # / 35 g vinyl pyrrolidone

(4g "Irgacure 65I"

$ 0.5 De Gussa "Special Black # 4" fine particles

The finely divided solid is carbon black that has been ground on a three-roll mill before being converted into the light-curable material mixed in with a high speed agitator became. The mixture was applied to a yellow mesh screen of 0.051 mm (28o yellow mesh screen) and 10 minutes from 122 cm (48 ") with a Berkey 5 KW polymer lamp exposed.

The review of the product revealed an excellent detail, including reproduction-of 0.1 mm lines and none noticeable hindsight. The bridging ability was also excellent and conformed to the graph of Figure 3. This example illustrates dimensional stabilization in comparison with other high quality stencils such as those of Examples I and II. The finely divided solid had decisive influence with regard to the prevention of a shift of the interface plane from its position on the edge of the clear Film area in the unexposed area under the black Area of the film (see Figure 6). This interfacial dislocation or dimensional instability shows up under a high magnification microscope as a clear approximation, very finer Lines which, however, have the characteristic of a rear son

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do not see any arcuate bulge. An undercut can occur on its own, but is very small in Examples I and II, while the planar interfacial shift as indicated in dashed lines. In the present example and in other tests that were carried out with finely divided pesticides, there is none Interface shift perceptible. I.e. the template corresponded very exactly to the picture of the positive, and it turns out that that the stencils obtained according to the invention, in terms of resolution, all stencils that were hitherto made by direct technology are superior. More than 1,000 prints were made with screens made in this way, without the The quality of the prints decreased. In contrast, direct emulsions produced by conventional processes usually produce at most 4000 to 5000 prints received, and there cannot be any comparable Resolution can be achieved.

A number of other tests were carried out to determine the concentration of finely divided solid with which the the best combination of properties and working conditions for stencils is achieved. It was found that at one concentration from $ 1 in a comparable light cure Material and with a sieve of the same mesh size were required for curing about 14 minutes. To the exposure times and To keep layer thicknesses within acceptable limits, a maximum concentration of soot particles of about 6 $ is recommended. on the other hand A lesser amount ($ 0.25) allowed an undercut at 0.1mm, leaving the picture in fine detail has deteriorated. Particles of a different color and different Light attenuation capabilities allow higher concentrations to be used.

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Example V

Using the material from Example IV and exposure with a Berkey 5 KW polymer lamp from 122 cm (48 ") were under Use of different exposure conditions to vary the quality of the stencils with a yellow polyester screen 0.051 mm (28o mesh) tests were carried out. Results and conditions were as follows:

h minutes - Moderate curing, but excellent detail and no undercut.

5 minutes - again moderate curing, but excellent Detail and no undercut.

6 minutes - Sufficient curing, excellent detail and no undercut.

8 minutes - Acceptable curing, excellent detail and no undercut.

10 minutes - Slightly better curing than 8 minutes, excellent detail and no undercut.

12 minutes - Complete curing, minor signs of undercutting, but still usable template.

The exposure time required for the production of a high quality stencil under the specified conditions is therefore in the range of 6 to 11 minutes, i.e. the margin of error is very large.

Example VI

Unless otherwise specified, the following solid substrates were initially coated with a material ("Coating 7700" from Tibbetts-Westerfield), which adheres to both the substrate and the photocurable material, Mistake. The photo-curable material was the mixture of

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Example I with 2 $ Polychrome 137 RD-2 red dye. The following Substrates were used:

1. Glass

2. "Plexiglas" (no coating)

3. stainless steel

4. Copper plate for making a printed circuit board

5. Steel

6. aluminum

a) The positives were coated with the above photohardenable material and wet with the substrate into a laminate united.

b) The exposure was from 81 cm (36 ") for 1 minute in front of a 5 KW Berkey exposure device with a polymer lamp.

c) After exposure, the positives were peeled off and the substrates were washed in methyl isobutyl ketone (MIBK) and then rinsed with water and dried.

d) Results:

1. (glass) - good contour accuracy, good washout;

2. ("Plexiglas") - excellent contour accuracy, light weight Washout, good adhesion;

3. (stainless steel) - good contour accuracy, good washout;

4. (copper) - good contour accuracy, good washout;

5. (steel) - poor adhesion, requiring the use of a different adhesive sub-layer;

6. (aluminum) - good contour accuracy, good washout.

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Example VII

Another technique for making a solid substrate is to apply the photohardenable material to it Substrate by screen printing as follows:

a) A copper plate for the production of a printed circuit was cleaned with a surface cleaning agent (steel wool) cleaned and rubbed with isopropyl alcohol.

b) A photo-curable material was prepared using "UR-2279" with J55 # vinyl pyrrolidone as a diluent. This material was combined with 7 $ "irgacure" and the mixture was then mixed with 2 $ I37 RD-2 red dye. This material was screen printed onto the copper plate and the plate was then laminated with a positive in contact with the material.

c) The material was 1 minute in front of a 5 KW Berkey light source exposed.

d) The positive was peeled off, and the copper plate and that Washes were positive with methyl isobutyl ketone.

The image obtained had excellent fidelity, less than 0.1 mm. However, when using this screen printing technique just as in the following examples, which work with laminate formation, the work is not carried out with the exclusion of air.

Example VIII

Satisfactory results, which, however, cannot be compared in terms of quality with those of other examples, were also obtained using other photohardenable materials.

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A sieve was made as described in Example I using the deviation that "Dynacure" GA72 Viny! Thiokol Dynachem, Tustin, California.

This material was applied to a screen with an underlying screen using the double coating technique described in Example X below Positive upset. The sieve was a "Redi Ester" sieve with a mesh size of 0.049 mm (305 mesh). The sieve was turned off with a Berkey light source with a polymer lamp for 15 minutes cm (48 ") exposed. The product obtained had a contour accuracy of 0.2 mm.

Example IX

A number of fabrics of various colors were similarly made using the photocurable material of Example VI prepared. Polyester positives were used and each screen was lit for 7 minutes with a Berkey 5 KW polymer lamp exposed from 122 cm (48 "). The following results were obtained:

a) yellow "Redi Ester" sieve, mesh size 0.049 mm (305 mesh) - undercut at 0.1 mm;

b) yellow polyester screen, mesh size 0.049 mm (305 mesh) - undercut at 0.1 mm;

c) Orange-colored polyester screen, mesh size 0.038 mm (420 mesh) - no undercut, but not completely through hardened

d) orange-colored polyester screen, mesh size Ο, θ4θ mm (355 mesh) - undercut at 0.1 mm.

The variations in the mesh size of the sieves were without any identifying effect on the rear and the hardening properties without any considerable Influence, and the pattern c), for which an orange

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Sieve used could take about $ 50 longer exposure fully cured. These results show that the Light absorption of the screen the halation or degree of Light scattering, which is a cause of the undercut, influenced. However, the colors of the screens were in the range preferred when using UV light sources, and it is known that other screen colors result in a stronger light reflection. Further tests were carried out on fine-meshed white sieves under the same conditions and it was found that there was a considerable undercut (on the order of 0.1 mm). If there are coarser sieves, for example with a Mesh size of 0.17 mm (86 mesh) are used, the positive probably has a coarser contour, so that the undercut does not pose a comparable problem and a white screen is acceptable.

Example X

Although the above examples show the influence of numerous variations of individual parameters and materials, in The following example guidelines and methods are given which enable the implementation of the method according to the invention with the best result enable:

a) "Redi Ester" sieve, yellow - mesh size <0.074 mm, white mesh size > 0.07 ^ mm (> 200 mesh resp. <200 mesh), stretched and defatted using trisodium phosphate.

b) The sieve is dried and placed on the positive, which is arranged with the emulsion side up, and in close contact kept with it.

c) The screen is coated twice with the photocurable material of Example VI, once with a moderately soft one

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Squeegee, followed by a second coat using a metal squeegee is applied.

d) The sieve is placed against a matt black background and with a Berkey Addalux 5 KW lamp with polymer lamp exposed (exposure time and distance for example 6 minutes - 122 cm [48 "])«

e) After exposure, the positive is peeled off and washed with methyl ethyl ketone. The sieve is immersed in "Cellosolve" and washed using a brush.

f) The sieve is rinsed with water along the frame Paper tape is applied to the edges and the screen is dried.

g) A cover based on the above photocurable material with the addition of 5 $ methyl ethyl ketone is applied applied the required areas, taking care to cover the edges of the tape.

h) Any thin areas present can be touched up manually using the above photocurable material with an addition of 10 to 20 $ methyl ethyl ketone.

i) The screen is post-hardened to ensure complete hardening on both sides.

Example XI

Most of the above examples use synthetic fabrics Threads. However, the method can also be carried out with fabrics made of natural threads, as can be seen in the following, with silk fabric performed example results in:

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- 3ο -

20χχ silk was degreased and in the usual way with a Coating of the aarch light-curable material of Example VI Mistake. The exposure was 5 minutes from a distance of 122 cm (48 ") with a Berkey 5 KW lamp (polymer lamp).

After the positive had been peeled off, the sieve was washed in "Cellosolve" and rinsed with water.

The stencil was completely cured and adhered excellently on the silk substrate.

Example XII

An advantageous method for producing an image on a solid substrate is described below with reference to FIG 4 described. To produce a substrate, a metal foil (anodized aluminum) was cleaned with "Coating 7700". A drop or tape of the photocurable material of the type described in Example VI was placed on this substrate 26 applied. One edge of the photοgraphischeη original 25 was applied to the tape and parallel to its length as shown in Figure 4 (a). To better illustrate the measures, the dimensions of the substrate and material strip are not drawn to scale. Then the positive became 25 made by light curable material 24 and the metallic substrate 26 are combined into a laminate by placing them together between a pair Nip rollers 28, 29 passed through as illustrated by Figure 4 (b), the rollers being adjusted to form a film about 0.05 mm (2 mils) thick. While the laminate was passed between the rollers 28, 29, air was also pressed out by the pressure of the rollers and the positive 25 leveled until it reaches the distortion shown in Figure 4 (c) was. This made the photo-curable material practical

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fully insulated from oxygen, and a curing time of about 30 seconds was sufficient, with the exposure from one 36 "(91 cm) distance using a Berkey light source was done with a 5000 watt polymer lamp. Thereafter, the positive was peeled off and the unexposed material became washed off the metallic substrate with methyl ethyl ketone. Examination of the image showed that it had sharp detail and less than 0.1 mm undercut, the positive exactly corresponded and was free of bubbles. Without the use of a colored pigment, the exposure times are because of isolation low against oxygen, but must be strictly adhered to.

Example XIII

It is often desirable to use an extremely durable stencil, for example a thick stencil with a smooth and abrasion-resistant one Establish surfaces on each side of a relatively coarse screen. In other cases it is desirable produce even coatings on a fine sieve. For these purposes, the method illustrated by FIG can be modified, as illustrated by Figure 5, which is also not to scale. A polyester screen 30 (0.17 mm = 86 mesh) was stretched on a frame 32 and in the manner described above Prepared wisely. A positive 34 was placed between the screen 30 and a flat plate 36. A tape from through Light-curable material 38 of the type described in Example VI was applied along one edge of the screen 30 and with a clear synthetic film 40, here polyester, covered. The tape of photo-curable material then became perpendicular in the direction Spread out to its length under the polyester film 40 by a doctor blade 42. The action of the doctor blade made the material 38 through the sieve 30 and in adhesive contact with the positive 34 on the opposite (lower) side, as well as with the polyester

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foil ho brought on the print side. This laminate was then placed in front of a light source so that the positive was facing the light source. Good cure was achieved by 8 minute exposure from a distance of 122 cm (48 ") with a Berkey 5 KW polymer lamp. A stencil was obtained with smooth surfaces on each side and a total thickness of about 0.2 mm (8 mils). which was very abrasion-resistant and durable.

Example XIV

Monofilament screens are currently used more frequently than multifilament screens; however, the more varied cross-sections of multifilament materials offer better locations for one Connection in the template. A test was performed using the material of Example IV with a I6xx multifilament polyester screen was used. A reverse detail positive was obtained with a Berkey 5 KW polymer lamp system from a distance of 122 cm (48 ") exposed for 8 1/2 minutes and washed out as described above. This stencil had no undercut, excellent Detail and was hardened through.

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Claims (26)

2 O. OHt. 1978 Charles Cowan TibbettSj 800 Inverness Drive, Flintridge, California 911Q1, V. St. A. Image reproduction methods and materials therefor Claims j ^ / method of reproducing an image on a transparent one Part for printing and the like purposes, characterized in that one arranging a layer of a flowable, uncured, radiation-curable material in direct contact therewith, facing the transparent part; exposing the material through the transparent member to a radiation source for a time sufficient to at least partially cure the material in the image portions; removing the transparent part from the hardened layer; and
uncured material removed. 2. The method according to claim 1, characterized in that one subjecting the cured material to post-curing by further exposing it to a radiation source after the transparent part has been removed suspends. ORIGINAL INSPECTED 3 · The method according to claim 2, characterized in that the Material is curable by ultraviolet radiation and one Radiation that is at least UV in the wavelength range of 360 to 390 nm. 4. The method according to claim 3 *, characterized in that one the material hardens by irradiating it for up to about minutes at the beginning. 5. The method according to claim 1, characterized in that the material is a mixture of a resin from the group of monomers and oligomers, a diluent, a minor amount of a sensitizer and a dimensional stabilizer. 6. The method according to claim 5, characterized in that the material layer has a thickness of up to 0.5 mm (20 mils). 7. The method according to claim 6, characterized in that adjacent a sieve is placed on the transparent part and the layer of hardenable material is inserted through the sieve Contact with the transparent part is pressed. 8. The method according to claim 6, characterized in that the material layer on a solid substrate, which is initially with a Material boundary layer that adheres to both the substrate and the Layer of hardenable material adheres, is coated, applied will. 9. The method according to claim 1, characterized in that the image is on an image film of varying capacity, the material is synthetic and is placed in direct contact with the image sheet in the wet layer and the material is a Radiation source is exposed by removing the wet layer 9818/0787 irradiated through the image film for so long that the layer made of synthetic material in a corresponding pattern at least substantially hardens. 10. The method according to claim 9> characterized in that the material contains a dimensional stabilizer of up to about 50 $ finely dispersed solid. 11. The method according to claim 10, characterized in that the finely-dispersed pesticide is a light-damping pigment in the form of soot up to a concentration of $ 6. 12. The method according to claim 11, characterized in that the Soot concentration is about $ 0.5. 13. The method according to claim 9, characterized in that the dimensional stabilizer is an opacifier in a concentration of up to about 5 $. 14. The method according to claim 1, characterized in that the image is a photographic original of the group of polyester and cellulose triacetate films, the layer of curable material is applied by a layer of flowable, uncured, sensitized synthetic resin, which under irradiation with UV is curable and does not adhere to the photographic original and a substrate both in the cured and in the uncured state, distributed, and the material is irradiated in such a way that the resin layer is exposed to a UV radiation source for about 15 minutes, so that the Resin hardens in the image pattern given by the photographic original and the hardened material is bonded to the substrate. 909818/0787 15 · The method according to claim 14, characterized in that the Synthetic resin layer is practically isolated from oxygen during exposure. 16. The method according to claim 15 * characterized in that both Sides of the layer are covered by contact with material layers during irradiation. 17. The method according to claim 16, characterized in that the The substrate is a screen and the contact material layer on one side is the photographic original. 18. The method according to claim 17. » characterized in that the Contact layer on the second side of the resin layer is a peelable sheet made of synthetic resin material and both surfaces of the hardened material are smooth. 19 · Image reproduction material, consisting of: a radiation-curable, flowable, synthetic Resin that is practically free of monomeric acrylate and contains more than 80 # pesticide-forming material, whereby the resin is non-reactive with triacetate, polyester, and the like photographic materials, physically is separable therefrom when it is hardened in contact therewith, and a dimension stabilizer and a sensitizer contains. 20. Image reproduction material according to claim 19, characterized in that that the resin is less than $ 5 in a sensitizer or photohardener and less than $ 20 in a vaporizable one Contains solvent and is curable by irradiation with UV. 909818/0787 21. Image reproduction material according to claim 20, characterized in that the resin has a viscosity in d at ambient temperature
Has. in the range from 2500 to 5000 cm / s (2500 to 5000 centipoise) 22. Image reproduction material for use with photographic vision Part of the image from the group polyester and triacetate films, characterized by a high content of pesticides, from one radiation-curable monomer that is practically free of acrylate, the. a small amount of a sensitizer in one contains flowable mass, both in the uncured and in the cured state non-reactive with image parts of the above Group and still contains a dimensional stabilizer. That the material 23 image reproduction material according to claim 22, characterized in that less than 10 wt -% of a sensitizer and contains less than 50 wt $ ._ to the dimension stabilizer.. 24. Image reproduction material according to claim 23, characterized in that the dimensional stabilizer is a light attenuating finely dispersed solid in the form of carbon black in a concentration below about 6% . 25. Image reproduction material according to claim 23, characterized in that that the dimensional stabilizer is an opacifier, namely a dye in a concentration below 2 $. 26. An image reproduction material according to claim 23, characterized in that it has a viscosity in the range of 2500 to 5000 cm ² / s (2500 to 5000 centipoise). 909818/0987