Abstract: A light sensitive planographic printing plate have deposited particles on a sensitive layer, each of the said deposited particles comprising a protuberant or bulging portion and a substantially flat base portion spreading around the said protuberant or bulging portion, the said both protuberant or bulging portion and flat base portion being formed integrally with a same material.

Abstract: A flexible plate is securable to a cylinder by insertion of fastening tabs, provided on beveled or angled ends of the plate, into cooperatively shaped end positioned pockets on the cylinder surface. The pockets may be formed by insert strips that utilize spaced tines to define the individual pockets.

Abstract: A stamp unit and a method of preparing the same are provided in which a liquid photosensitive resin is used as the base material for stamp formation and the ease with which the material is handled during transportation, storage and stamp formation is facilitated. The stamp unit uses a liquid photosensitive resin which changes from liquid to solid upon receiving rays of light as the base material for stamp face formation.

Abstract: The present invention is directed to a method and apparatus for adding patterns to golf balls. The apparatus used in carrying out the method is a pad printing cliche which comprises a substantially planar substrate having deposited thereupon along at least a portion of its surface a coating of titanium carbon nitride. The coating may range between about 0.1 and 50 microns in thickness, preferably between about 0.25 and 20 microns, more preferably between about 0.5 and 12 microns and most preferably between about 0.5 and 5 microns. The method of the invention comprises providing a pad printing cliche with a coating of titanium carbon nitride, forming a pattern upon said coated surface adapted for transfer to an outer surface of a golf ball, said pattern comprising any combination of words, numbers, designs, etc.

Abstract: A lithographic coating and method of framing a lithographic image are disclosed. The method comprises coating at least a portion of a surface of an article with a radiation-crosslinkable polymer, and exposing the coated surface to a pattern of radiation to crosslink the polymer in a lithographic image. The functionalized polymer is a copolymer of an isoolefin of 4 to 7 carbon atoms and para-alkylstyrene, wherein the para-alkylstyrene is functionalized with a radiation reactive group at the para-alkyl group of the para-alkylstyrene.

Abstract: A flexible plate is securable to a cylinder by insertion of fastening tabs, provided on beveled or angled ends of the plate, into cooperatively shaped and positioned pockets on the cylinder surface. The fastening tabs are spaced axially by interposed tongue and cut-outs. These spaced tabs and tongues form an axially discontinuous joint across the width of the cylinder on which the flexible plate or plates are positioned.

Abstract: A process for producing a durable, readily-storable, cylindrically-shaped flexographic printing sleeve having inner and an outer cylindrically-shaped walls and a substantially constant cross-sectional inner and outer diameter is provided. The flexographic printing sleeve is readily axially mountable on and dismountable from a complementary cylindrically-shaped printing cylinder having an outer cylindrically shaped wall. The process comprises providing a sleeve body. A layer of a low temperature curable polymeric material is provided to the outer circumferential surface of the sleeve body. The low temperature curable polymeric material is then cured at a temperature not greater than about 150 degrees F. to form a hardened layer of the polymeric material having a substantially uniform degree of hardness without damaging or distorting the sleeve body. A portion of the hardened layer of the polymeric material is removed to produce a flexographic printing sleeve having a thickness of up to about 0.

Abstract: To provide a laser plate making apparatus having a simple construction capable of reducing generation of Moire. The slant line R1 formed of the starting position of the formed arbitrary recess 7 which is formed on the press plate 5a or the like in the main scanning direction F is formed so as not to be coincident with the slant line R2 formed of the starting position in the main scanning direction F of the recess 7 which is located at the next position in the sub scanning direction A. Therefore, when a multicolor printing is carried out by using the press plate 5Pa thus formed or the like, manifestation of Moire is reduced. Particularly, when the line R3 connecting the predetermined point within the arbitrary recess 7 to the point located at the position corresponding to the predetermined point in the recess 7 which is located at adjacent position in the sub scanning direction A, is set to a constant angle .phi. different from the irradiation angle .theta. of the laser beam, the Moire is further reduced.

Abstract: A printing plate with a mesh material, a removable substrate, a substrate, and a paper backing on said substrate. The mesh material has interstices and has first and second surfaces. The substrate is adhered to one of the first and second surfaces of the mesh material and forms a well defined at its bottom by the substrate and at its sides by the interstices of the mesh material, wherein the well receives and stores pigment for printing. Multiple colors of pigment may be stored simultaneously within the wells of the printing plate, thereby enabling those multiple colors to be printed concurrently in a single printing pass operation.

Abstract: For the register of a sleeve-shaped offset priming form in which the beginning and end of the plate-shaped blank of the printing form are connected by a weld seam, a guide element in the form of a projection is provided for the sleeve at the inside of the sleeve. A form cylinder which can be used in combination with the sleeve has a groove extending along its entire width, which groove has a depth that is greater than the height of the projection. The projection can be inserted completely into the groove so that the sleeve can be secured on the form cylinder in the circumferential direction.

Abstract: In a printing sheet making and printing system applicable to for example an electronic gravure printing system a printing sheet is sheathed in a printing sheet jacket to prevent the adhesion of dust and the occurrence of scratching on its surface and the feeding and ejection of the printing sheet to and from the cylinders of a printing sheet making machine and a printing machine is completely automated so that an operator can run the system without ever directly touching the printing sheet. A printing sheet, a printing sheet jacket, and devices for pulling the jacket and the printing sheet into a printing sheet making machine or a printing machine and removing the printing sheet from the jacket and winding and clamping it onto a cylinder for engraving of the printing sheet or printing with it and returning it to the jacket and ejecting the jacket and the printing sheet inside it from the machine after the engraving or printing all in a completely automated fashion are disclosed.

Abstract: A planographic printing plate in which a design pattern is realized in a part of the back surface of a support for the planographic printing plate without any adverse influence on a photosensitive resin layer on the front surface thereof. After an aluminum support with a thickness of 0.24 mm is cleaned by degreasing and etching, an electrolytic aqueous solution is prepared to contain the nitric acid concentration of 10 g/l and the aluminum ion concentration of 7 g/l. In an electrolytic treatment cell 5, the back surface of the aluminum support is arranged so as to be faced to an electrode. A 1 mm-thick masking plate formed of an insulating material punched to provided openings with arbitrary shapes is brought into close contact with the back surface of the aluminum support so that the back surface of the aluminum support is covered with the masking plate. A carbon plate with a thickness of 50 mm is used as the electrode.

Abstract: A method for producing a reproduction in reduced or enlarged size of a halftone original with improved tone rendition by the use of a continuous tone correction mask in conjunction with the halftone original applied in projection exposure.It is a particular characteristic of the present invention that said improved tone rendition is obtained by using in said projection exposure a mask image, the maximum density (i.e. density at 3% dot value areas of the halftone original used in the projection exposure) is linearly directly proportional to the screen ruling of the halftone original used in the projection exposure (see FIG. 2 and 3).

Abstract: In a printing sheet making and printing system applicable to for example an electronic gravure printing system a printing sheet is sheathed in a printing sheet jacket to prevent the adhesion of dust and the occurrence of scratching on its surface and the feeding and ejection of the printing sheet to and from the cylinders of a printing sheet making machine and a printing machine is completely automated so that an operator can run the system without ever directly touching the printing sheet. A printing sheet, a printing sheet jacket, and devices for pulling the jacket and the printing sheet into a printing sheet making machine or a printing machine and removing the printing sheet from the jacket and winding and clamping it onto a cylinder for engraving of the printing sheet or printing with it and returning it to the jacket and ejecting the jacket and the printing sheet inside it from the machine after the engraving or printing all in a completely automated fashion are disclosed.

Abstract: The relief printing part (2) of the printing plate, which is intended to be inked over its entire surface, includes at least one etched recessed pattern (4) intended to be filled with the same ink as that serving for the inking of the relief printing part. The relief printing part preferably has a grainy structure composed of evenly distributed screen dots.

Abstract: A letterpress printing method is disclosed wherein a printing plate, having plastic surface with a critical surface tension in the range of approximately 18-35 mN/m, is engraved or otherwise provided with raised ink-bearing impression sites and the printing plate is used for printing in a letterpress printing machine. As examples, the plastic surface of the printing plate may comprise a fluoropolymer, polytetrafluoroethylene or a copolymer of tetrafluoroethylene and hexafluoropropylene. The low surface tension is shown to enhance the printing quality in this environment.

Abstract: A circumferentially continuous printing plate, which has the advantage over clamp plates that a clamping arrangement and groove in a plate cylinder can be eliminated, is formed by rolling a flat printing plate into tubular or sleeve form and welding the end edges together, preferably by a neodymium-YAG laser weld, resulting in a narrow, less than 1 mm wide, weld seam (2) having upper and lower concave sides, or by adhering the end edges to an underlay saddle (9), the plate can be coated and imaged when flat or after having been rolled and installed on a plate cylinder (37) of a printing machine. Interengaging projection-and-recess elements (4, 6; 14, 16) are formed on the plate (1, 1') and on the cylinder (37), respectively, to ensure lateral and circumferential register.

Abstract: An energy polymerizable composition comprises at least one ethylenically-unsaturated monomer, one of polyurethane precursors, and at least one epoxy monomer, and a curing agent comprising an organometallic compound, and an onium salt.

Abstract: In a raised-image printing process, a plate construction includes a plate portion with an upper printing surface for printing an image on a substrate, the image including areas of greater ink coverage and areas of lesser ink coverage. Regions of greater and lesser stiffness are incorporated in the construction such that greater stiffness occurs under image areas of greater ink coverage, and lesser stiffness occurs under areas of lesser ink coverage.

Abstract: A photocured resin relief plate comprising a relief layer comprising base layer A and top layer B formed by photocuring and arranged in this order, in which the thickness of the relief layer at a highlight portion constituting a pattern having a dot percent of 7% or less is smaller than the thickness of the relief layer at a portion other than the highlight portion. The photocured resin relief plate can be obtained by imagewise light exposure of a multilayer photosensitive resin layer comprising a lower layer of a liquid photosensitive resin layer having minimum insolubilization light exposure value Q.sub.A and an upper layer of a liquid photosensitive resin layer having minimum insolubilization light exposure value Q.sub.B, wherein Q.sub.B is not smaller than 23 millijoules/cm.sup.2 and not smaller than 5 times Q.sub.A.

Abstract: A cushion layer 92 made of plastics or rubber is fixed on a stamp body 90, on which a peelable layer 94 having a certain thickness and formed by a rubber having a glass-transition temperature higher than -50 degrees Celsius, is temporarily fixed, and further, a protective film 96 is temporarily fixed on the peelable layer 94. Next, to form an image section, the peelable layer 94 is cooled to a temperature below its glass-transition temperature, the peelable layer 94 and protective film 96 being cut along a boundary line 116 between the engraving region on which images on the peelable layer 94 are engraved and the blank region other than the engraving region, and the area other than the image on the engraving region being cut and removed so deep that the peelable layer will not be cut.

Abstract: A photoresin relief printing plate comprising a support and a photoresin relief portion disposed thereon, said relief portion having a thickness of not greater than 8 mm and comprising an upper photoresin layer and a lower photoresin layer, wherein said upper photoresin layer has a thickness of at least 2 .mu.m and a Young's modulus of not greater than 650 kg/cm.sup.2 and said lower photoresin layer has a thickness which is greater than the Young's modulus of said upper photoresin layer and a thickness which is greater than the Young's modulus of said upper photoresin layer. The photoresin relief printing plate exhibits not only excellent inking and ink transferability even in solid images, but also excellently less broadening of printed images and excellent image reproducibility, even if the printing operation is performed using an ordinary relief printing machine having poor machine accuracy.

Abstract: An apparatus for making a printing plate in which a printing plate made of a thermoplastic resin sheet is wrapped around a plate cylinder and a laser beam from a laser source is irradiated on the printing plate to form holes in accordance with image information is comprised of an angle adjusting means for adjusting an irradiation angle of the laser beam from the laser source and control device for controlling the irradiation start position of the laser beam such that holes on the printing plate are made continuous at a predetermined angle. Thus, a printing plate having various dot patterns can be obtained only by adjusting the optical system of this apparatus and a printed product in which the occurrence of moire can be avoided can be obtained.

Abstract: A printing plate formed of a thermoplastic resin sheet for gravure printing has the holes corresponding to pixels of image information arranged in rows and columns, with the rows being at an angle to the bottom edge of the sheet. The holes in the rows are aligned in columns and adjacent columns are offset by one half of one pixel. Slots are provided next to each hole to prevent ink from smearing between adjacent holes in the columns.

Abstract: A printing plate including a printing plate member, an easily deformable elastic layer laminated on the printing plate member, a surface layer having a higher elasticity than that of the elastic layer, laminated on the elastic layer, and a printing surface layer formed on the surface layer. The printing surface layer has an image area having an affinity with an ink and a non-image area having an ink repellancy.

Abstract: A narrow gap printing plate mounting apparatus includes a printing plate (10) with a substantially curved, preferably involute tail member (24) at one end of a printing plate body (12) which is received through a narrow mating gap (20) in a rotary cylinder (18) and held against correspondingly curved cavity wall (28) by means of a resilient locking member (30). The locking member (30) presses the curved tail member (24) against the curved wall (28) in a direction which is substantially normal thereto to reduce longitudinal strain on the tail member (24). Another tail member (22) is inserted at the leading edge (20A) of the gap (20) while the curved tail member (24) presses against the lagging edge (20B) of the slot (24). When removing the plate from the cylinder (18), the curved tail member (24) at the lagging edge (20B) is removed first.

Abstract: In a raised-image printing process, a plate construction includes a plate portion with an upper printing surface for printing an image on a substrate, the image including areas of greater ink coverage and areas of lesser ink coverage. Regions of greater and lesser stiffness are incorporated in the construction such that greater contact pressure is applied under image areas of greater ink coverage, and lesser contact pressure is applied under areas of lesser ink coverage.

Abstract: A gravure printing plate is formed by a plurality of concave portions called "cells", arranged in vertical and lateral directions, four sides of each generally square cell being surrounded by walls. A "cell group" is formed of one core cell and four sets of paired cells adjacent to each other arranged to surround the core cell. A notched portion is formed in either one of two intersections of a wall and another wall intersecting therewith on the wall separating the paired cells. The positions of the notched portion is selected to be in point symmetry about the core cell. The direction of flow of a quick-drying ink, during use with the gravure printing plate, becomes random in the vertical and lateral directions in the cell group due to the notched portions, hence mottling of the ink can be prevented.

Abstract: The present invention provides a photosensitive resin plate for flexographic printing, comprising;(A) a substrate comprising a polyester film and a polyurethane or polyolefin foam layer on one side of said polyester film;(B) an adhesive layer on the foam layer of said substrate;(C) a polyurethane layer on said adhesive layer;(D) a photosensitive layer which is provided on the polyurethane layer and is chemically bonded with the polyurethane layer, comprising a polymer having rubber elasticity, addition polymerizable unsaturated monomer and a polymerization initiator;(E) a slip layer on the photosensitive layer which is dissolved with a developing solution; and(F) a protective layer on the slip layer.

Abstract: An assembly for use in the production of a relief printing plate comprises a polymeric substrate, a primer layer and a resin layer thereon, the resin layer being at least 2 microns thick and comprising a low molecular weight copolymer of vinyl chloride and vinyl acetate, optionally with a termonomer, particularly a hydroxyl-containing termonomer. The primer layer may contain a vinyl chloride-vinyl acetate copolymer, and the substrate may be a polyester, particularly a polyethylene terephthalate film.

Abstract: Mixtures which can be cross-linked by photopolymerization and are based on soluble elastomeric block copolymers, photopolymerizable monomers which are compatible with these, photoinitiators and plasticizers contain, as the plasticizer, a chlorolakane of 8 to 40 carbon atoms which has a chlorine content of from 30 to 73% by weight.

Abstract: The invention relates to a printing plate for corrugated board which comprises a rubber or plastic foam sheet having a smooth skin layer on its surface, the thickness of the skin layer being 0.3 to 2.0 mm and the surface hardness of the printing plate is SRIS (C) 35 to 55. Preferably, the surface roughness of the skin layer is not more than JIS R.sub.max =100 .mu.m. Preferably, the printing plate further includes a reinforcing sheet comprising a base cloth and a rubber or resin cladding layer disposed on either side thereof and the interface between the foam sheet and one surface of the base cloth of the reinforcing sheet is separably bonded with comparatively weak adhesion.

Abstract: The flexographic printing plate comprises a support base (14) which is to be the base of the printing plate, a plate surface supporter (12) for supporting the plate surface detachably bonded on the support base (14) in the region smaller than the support base (14), and a plate body (10) detachably bonded on the plate surface supporter (12) in the region smaller than the plate surface supporter (12), the surface of the plate body constituting the printing surface, whereby the printing pressure is received by the plate body (10) and the plate surface supporter (12).

Abstract: A flexographic printing relief-plate, which has a relief layer (P), an interlayer (Z) and a base layer (U), is provided with a double-sided adhesive sheet (W). The double-sided adhesive sheet (W) transmits actinic light and is firmly bonded to the base layer (U) on one side. On the opposing side, the adhesive sheet (W) has an adhesive force of from 1 to 6 N/25 mm. This force is less than the adhesive force on the side bonded to the base layer (U). The adhesive sheet (W) permits the flexographic relief printing plate to be repeatedly adhered to and removed from the printing cylinder without damaging the plate.

Abstract: An apparatus and method for producing personalized playing card decks. A plurality of front printing plates having card face printing images thereon are provided. One back plate is provided having a plurality of different card back printing images. The front sides of a plurality of card stock sheets are printed with the front plates. The sheets are reversed and the unprinted back sides are printed with the single back plate. The sheets are collated into one stack. The stack is cut into individual decks.

Abstract: A method is disclosed for producing a photoengravable, laminated printing plate including the steps of applying a homogeneous adhesive free of noncompressible materials between mating sheets of magnesium and steel and then placing the mated sheets into a press to compress the mated sheets until the adhesive is uniformly dispersed therebetween.

Abstract: The invention relates to a process for the ozone protection of an imagewise exposed and developed photopolymer flexographic printing plate, having an elastomeric, thermoplastic polymeric binder, which comprises applying to the exposed and developed surface of the flexographic printing plate at least one known liquid polyether of the formulas: ##STR1## wherein R.sub.1 =H, or methylR.sub.2 =H, alkyl or alkylene with C.sub.12 -C.sub.18, and saturated and unsaturated fatty acid radicals with C.sub.12 -C.sub.18.p=1-4and wherein n, m and m.sub.1-4 and x, y, and z are so selected that the molecular weight (M.sub.n) of the molecule is about 500 to 5000.

Abstract: A marking device is disclosed which is capable of printing on the lower surface of a package as it passes over a conveyor belt. Multiple inking wheels and multiple printer wheels removably mounted on parallel shafts in a slidingly removable unit are described. The marking device employs an adjustment unit for adjusting the height of the slide-out unit with respect to a surface to be marked and a second adjustment unit for adjusting the position of inking wheels with respect to printer wheels. An improved printer wheel and inking strip is also disclosed.

Abstract: A sheet material for mounting flexible printing plates to the drum of a printing press includes a base film, a flexible foam uniformly coated on the base film, and a pressure sensitive adhesive coated on both the base film and the foam. The cohesion of the base film and the foam, the adhesion of the base film to the foam, and the adhesion of the adhesive to the base film and the foam is greater than the adhesion of the adhesive to the flexible printing plate and to the drum of a printing press. When the sheet material is removed from the printing plate and the drum, the foam, the base film, and the adhesive remain an integral sheet. A method for preparing and using the sheet material is also disclosed.

Abstract: An intaglio printing plate having an elastic rubber layer, a photo-sensitive layer and an oil-repellent layer, which are laminated in order onto the base plate. The recesses on the plate face, which correspond to the image line section, is formed by removing the surface to a desired depth depending on the printing purpose. And also, the intaglio printing process to the hard object to be printed by means of this printing plate.

Abstract: A letterpress printing plate in the form of an elongate, looped flexible band having a base layer, as of polyester, and a photosensitive layer. The photosensitive layer is exposed to ultraviolet light through a negative, and its unhardened portions are dissolved away, thereby leaving a printing image and one or two series of markings in relief on the base layer. Typically in the form of annular banks, the markings are arranged at constant spacings along one or, preferably, both sides of the base layer. Perforations are then formed in the base layer through the annular banks thereon. In its use on a web-fed rotary press the looped, perforated printing plate is to be wrapped around a plate cylinder and a guide cylinder spaced therefrom, with its perforations engaged with sprocket teeth on the plate cylinder, for printing the long image on a web against an impression cylinder.

Abstract: An intaglio inking plate comprising a printing surface having an aperture therein, a plurality of separately-movable bars filling the aperture and means for positioning each bar separately either flush or depressed from the printing surface. The positioning means comprises (1) means for moving all of the bars to their flush positions, (2) means for blocking the further movement of selected ones of the bars, and (3) means for moving all bars that are not blocked to their depressed position.

Abstract: A print member has a print surface of an epoxy novolac resin. It is particularly suitable for use as an intaglio print member that is to be laser engraved. It is best made by powder coating a powdered epoxy novolac composition onto the substrate fusing and curing it, polishing it to give non-print characteristics and then further curing it, either before or after engraving.

Abstract: In an intaglio printing method, the steps of providing a novel intaglio inking plate having a surface and means for producing different prescribed patterns of shallow depressions therein, producing a first prescribed pattern of depressions in said surface, filling said depressions with ink, transferring ink from the pattern of filled depressions to a transfer surface, altering the surface to provide a second pattern of shallow depressions therein and then repeating the step of filling the depressions with ink and transferring an ink pattern to a transfer surface.

Abstract: The object of the invention is to join or fuse an upper plate having ink flow channels and a lower plate having a multicolored pattern, the joining being accomplished without clogging any ink flow paths.A pattern having different colored parts (11-14) and apertures is formed in a lower plate (10). Ink flow channels (111-114) each having respective ink input ports (211-214) are formed in an upper plate (11).The ink flow channels (111-114) are coated with solder mask and the bottom of the upper plate (11) is then coated with solder. The upper and lower plates are pressed together at from 2 to 5 psi and heated to a temperature of from 295.degree. F. to 750.degree. F. or enough to melt the solder.After the plates (10,11) have cooled and the pressure has been released, the solder mask is removed from the interior passageways by means of a liquid solvent.

Abstract: A method of preparing a letterpress printing plate from a liquid photopolymer using an air knife to etch out the unpolymerized liquid to leave the relief image. A new printing plate substrate is used that has a laminae that is paper and a lamina that is a sealing coat on the paper. The paper is a special paper known as tag stock that is 5 to 20 mils thick, has tensile strengths of at least 30 pounds per inch in width in the press direction and at least 20 pounds per inch in width in the cross press direction, and fibers that are independently colored with a dark color having a good light absorption/reflectivity ratio.

Abstract: A method of making a lithographic plate by etching in an alkaline bath a sheet of an alloy of aluminium and 0.1% to 4.5% calcium. The alloy preferably contains up to 2.0% magnesium.

Abstract: Relieved pattern of a resin original pattern plate, which does not exhibit fluidity at transferring temperature and possesses elastic modulus no smaller than 10 kg/cm.sup.2, preferably no smaller than 100 kg/cm.sup.2, is transferred onto thermoplastic resin material having fluidity at the transferring temperature (ASTM D1238, load 21.6 kg) of at least 0.01 dg/min, preferably at least 0.1 dg/min, by pressing the thermoplastic resin material to the original pattern plate under a pressure condition where elastic deformation of the original pattern plate is kept within 10%. The resin original pattern plate is prepared by controlling the photo-polymerizable resin composition to adjust its crosslink-ability and then photo-polymerizing, whereby the resulting resin original pattern plate possesses an elastic modulus of 10 kg/cm.sup.2 or higher at transferring temperature.

Abstract: A method of making a polypropylene printing plate using a paper matrix in which a roll and an opposing member are prepared, a paper matrix is attached to one of the roll and opposing member, a crystalline ethylene-propylene copolymer having a MFI (melt flow index) of 3.about.10, containing ethylene less than 20% by weight and tensile yield strength of 220.about.330 kg/cm.sup.2 is continuously fed under molten state between the roll and the opposing member, and then the crystalline ethylene-propylene copolymer is pressed and cooled to be hardened.Further, a reproducing printing plates consists of a crystalline ethylene-propylene copolymer whose melt flow index is selected in a range of 3.about.10, which contains ethylene less than 20 weight % and which has the tensile yield strength of 220.about.330 kg/cm.sup.2.

Abstract: A photopolymerizable recording composition which comprises a mixture, containing a photoinitiator, of (a) a photopolymerizable olefinically unsaturated monomer and (b) an organic polymeric binder, wherein the photoinitiator is an acylphosphine oxide compound of the formula R.sup.1 R.sup.2 PO-CO-R.sup.3, where R.sup.1 and R.sup.2 are certain organic radicals and R.sup.3 is tert.-alkyl or a cyclic radical with two substituents in the ortho-position to the carbonyl group. The recording compositions have a high reactivity when irradiated with UV light and are used in particular for the preparation of printing plates, relief plates and photoresists.