An electrical socket assembly includes a plurality of pin receiving apertures passing through a wall mounted faceplate. The faceplate is enclosed by an integral cover panel which is spring biased to an open position. Engaging latch pins and a latch mechanism secure the integral cover panel in a closed position, and are adapted to be released in response to the insertion of a key into keyholes disposed in the side of the faceplate.

This invention is concerned with safety covers and relates in particular, but not exclusively, to a protective cover for a switch or a socket (and for a plug when in that socket) such as may be used for providing electricity or a telephone, video or data connection.
In modern electrical systems as used in houses, offices and other buildings, electricity is delivered by cabling to various points around the building at which there are electric sockets with faceplates into which appliances to be powered using the electricity supply can be plugged. Such sockets may be unswitched or switched so that the power supply to appliances plugged into the sockets can be controlled without unplugging the appliance. Moreover, in a modern building there will be a technically similar system for providing communication channels—for telephone, television and computer.
Each of the sockets will usually be of the type having an apertured terminal-carrying socket faceplate mountable on a recessed socket box itself flush mounted within a cavity in or on a wall. The apertures lead to the socket's terminals, disposed on the back of the plate and thus out of harm's way inside the box, and are shaped and sized to match the contact pins of the plug for which the socket is designed.
Another type of socket commonly encountered, especially in electric power circuits, is the "extension socket" where a group of two or more individual sockets are arranged in a box-like carrier and connected by a single lead to a plug that plugs into a single wall-mounted socket (in this way a single such wall socket can, within reason, be "converted" into a plurality of sockets). Such an extension socket device normally has the appropriate plurality of apertured terminal-carrying socket plates mounted on a socket box. In principle, therefore, it is little different from a wall-mounted socket.
There are many reasons why it might be desirable to provide a cover over a socket, or over a plug when in place in that socket. One is that empty sockets seem to exert an irresistible fascination for small children, who will try to poke their fingers, their toys, or any available long thin object—such as a knitting needle or a screwdriver—into the plug pin apertures in the socket; when applying such investigative skills to an electric socket a persistent and inventive child may well be successful, but sadly the reward for such success is all too often death by electrocution.
Another reason is that much modern equipment is designed to be plugged in and left on and connected all the time—falling into this category are refrigerators, televisions (and video recorders) and Fax machines at one extreme, and computers (and their networks) and medical life support systems at the other—and sometimes it may be a minor disaster if the device is disconnected, unplugged or turned off (by, for example, a cleaner looking for a socket into which to plug a vacuum cleaner).
The problem, as always, is how to achieve a cover that is both effective, securely hiding the switch, socket or plug from an inquisitive child or a careless cleaner, and yet also relatively easy for an authorised person to remove in order to access the plug, or the socket and its switch.
One solution for an empty socket is to insert into it an imitation plug with a shallow head that a child's fingers cannot easily grip. Such a solution does not help with the secondary problem of preventing a used socket being switched off, or having the plug removed from it. To deal with this problem, box-like covers that can be secured over the plug-carrying socket so as to prevent access to the plug are known. However, none of these covers is especially convenient—or, sometimes, terribly effective.
It is an object of the present invention to provide a cover that is simpler and easier to use whilst at the same time providing the required secure protection.
Thus, according to the present invention, there is provided a socket (or switch) having an integral (built-in) cover with a cover panel movable between open and closed positions.
The invention has application to sockets with pin receiving apertures for a plug where it may be desirable to conceal a front surface of the face plate provided with pin receiving apertures for a plug and/or a switch, for example to prevent equipment being inadvertently switched off.
By this invention, an existing unprotected socket (or switch), ie a socket having free access to the pin receiving apertures and/or to a plug received therein can be replaced by a protected socket with integral cover such that access to the pin receiving apertures and/or a plug received therein can be restricted by securing the cover panel in the closed position. Such protected socket according to the invention can also be used for new build or when extending an existing electrical circuit.
In some embodiments the socket (or switch) comprises a face plate and integral means by means of which the cover panel is mounted for movement between a closed position concealing a surface of the face plate and an open position allowing access to the surface.
The socket plate may be detachably attached to a mounting box which may be wall mounted (either recessed or face fixed) or freestanding (an extension lead).
The integral means for mounting the cover panel may be formed integrally with the socket, for example by moulding, or formed separately and permanently secured thereto, for example by adhesive or non-releasable fasteners.
In a preferred arrangement, the cover has a frame integral with the faceplate, and the cover panel movably mounted with respect to the frame between the closed position, where it completely covers and encloses the faceplate (and any plug or switch), and the open position, allowing access thereto. The frame may extend around the marginal edge of the faceplate.
Preferably, latch means is provided for holding the cover panel closed, and actuator means enabling the cover panel to be released. The latch means is preferably self-latching to secure automatically the cover panel on movement of the cover panel to the closed position.
Preferably, the cover panel is movable towards the closed position against a biasing force that urges the cover panel towards the open position such that the cover panel can move to the open position on being released.
The integral (built-in) cover of the invention is for the protection of switches and sockets (and plugs mounted therein). For simplicity hereinafter the term "socket" is used, where possible and where the context allows, to mean both an actual socket, such as a telephone, television, computer or electrical socket, into which a plug can be operatively inserted, and also a switch (it is common for certain electric systems, such as night-storage heater systems, to use switches which are physically much like a switched socket but without the socket parts). If a particular reference is necessary to switches, then it is given positively.
The socket to be protected may be almost any of the designs used throughout the world ranging from 2-round-pin recessed devices used over most of continental Europe and Russia, through the 2-flat-strip US ones, the present-day UK "triangle" 3-square-pin ones, the triangle 3-round-pin Indian ones, 3-in-a-line-round-pin Italian ones and the triangle 2-strip-one-round Japanese ones, up to the proud triangle 3-angled-strip-pin sockets used in Argentina, Australia and China.
All such known socket systems are of the type that carry a faceplate, which is attached by means of threaded screws extending through the plate into threaded apertures near the periphery of the mounting box, and thus can be provided with a cover of this invention, though, like the socket faceplates themselves, the covers may only be superficially similar visually.
The invention provides an integral cover for the socket—that is to say, a cover which, when in place, may prevent prying fingers and other objects being poked into the socket's terminal apertures, and will prevent a plug in the socket being removed therefrom. As is discussed in more detail hereinafter, the cover is lockable—that is, when closed and held in place it needs an actuator such as a key or key-like device to unlock it before it can be opened.
The socket with integral cover of the invention may have pin receiving apertures in the socket plate (otherwise referred to as a front or faceplate) removably mountable onto a socket mounting box (typically such a box being recessed into and flush mounted within a cavity in a wall) so that the apertures lead to the socket's terminals disposed on the back of the plate and thus inside the box. It is usual for the plate to fit onto the box and be held there using a number of screw-headed bolts, typically two, extending through the faceplate into threaded apertures near the periphery of the box.
Sockets often come in pairs—that is to say, two sets of plug-pin-apertures disposed side-by-side in a double-length socket plate (with matching socket box). Indeed, on occasion the socket might even be a triple socket (or more!). The socket with integral (built-in) cover of the invention may cater for this by its base being matchingly sized to the box-housing frame, and, by having its cover panel extending, to cover all the plug-pin aperture sets and any plugs or jacks inserted thereto.
The socket (or switch) with integral (built-in) cover has a frame mountable to the socket mounting box (or to the wall)—that is to say, against and in contact with the box/wall surface, so leaving no significant gap through which an object might be poked into the socket. The frame preferably extends around the perimeter of the socket plate and the cover panel conveniently matches the plate in shape and size, being just large enough to allow a plug or plugs to fit within it when in the closed position.
Where the socket with integral (built-in) cover is a plug-bearing socket, some means by which the plug's flex, lead or cord can extend away from the plug and socket may be provided. This is most conveniently achieved by providing a suitable slot in that edge of the frame which will, in use, be on the side of the socket from which the lead of a plug in the socket will project (this is usually the bottom edge for socket and plug designs in the UK, or in the centre for many of the socket designs employed in Europe, Asia and America, though obviously a socket can be installed any way up!). The slot can be simply wide enough to house the lead, or it can be the entire width of that side of the frame (so that the frame becomes a three-sided rather than four-sided when used with a faceplate of rectangular shape).
A variation of the invention can be found for use with freestanding extension sockets. In this arrangement the faceplate and integral (built-in) cover may be attached to a base plate and these extension sockets can include any or all of the following components incorporated onto the base plate—one or more outlets (pin receiving apertures) for electrical plugs, one or more outlets for co-axial cable jacks, and one or more outlets for telephone, facsimile or modem plugs. The extension unit can be connected to its power or data source by way of an electrical or data cable, employing a suitable plug to fit and draw power or data from that connection source.
As will be understood, the socket with integral (built-in) cover of the invention can replace the conventional apertured terminal-carrying socket plate (otherwise referred to as a front or socket faceplate) that is removably mountable on the base plate of such extension leads. The cover (or covers) can be affixed to any part of the extension unit such that they will still provide all of the functionality as described above, and can be secured in the closed position to allow the covers for any part of, or all of the unit's outlets, to be either fully shrouded and inaccessible or exposed and therefore accessible for use thereto.
The cover panel may be hingedly secured to the frame, and swingable between a closed position, where it completely covers and encloses the socket and any plug therein, and an open position, where it is clear therefrom, allowing access thereto. Alternatively, the cover panel can achieve the same functionality by being slidably secured to the frame by a means of clipping onto parallel grooves, or runners (much like a train to a track). Though notionally the panel could be of any shape and size, most preferably it matches the socket it is to be used with, as does the faceplate frame. Thus, it will generally be roughly rectangular—square or oblong.
On its side against which the cover panel fits the frame (that is to say, in most cases, the side where the panels hinges or runners are positioned) there may be a low, upstanding perimeter wall which projects sufficiently to cover and so hide the actual touching faces of the framed faceplate and panel. This makes it harder for inquisitive fingers to poke themselves, or some other tool, into the socket between the panel and the faceplate.
The cover panel may, like the cover as a whole, be made of any convenient material—typically a plastic such as polyethylene or polypropylene or glass reinforced polycarbonate. Most preferably, though, at least for the area that overlies the socket's switches the cover is made of a transparent material—for example Perspex—so that the state of the switches may easily be seen without first having to open the cover.
It is convenient for any embodiment of the invention if both the cover frame and cover panel be associated with a sealing gasket—preferably an appropriately-shaped "ring" of a rubber or some similar flexible insulating material—so that when the frame is fitted, there is an effective seal between the frame's back-plate and the wall to which it is fitted, and when the cover panel is shut, it seals fairly tightly against the frame's surface, so assisting (with the frame's boundary wall) to keep steam, water, prying fingers or other spilt liquids and vapours away from the plug. The gaskets can be mounted in or on either of the frame and the panel. The former is preferred.
It is similarly convenient, if the faceplate frame and wall be associated with a sealing gasket—preferably an appropriately-shaped "ring" of a rubber or some similar flexible insulating material—so that, when the frame is mounted to the socket mounting box by means of tightening the threaded screws, there forms an effective seal between the wall and the frame's surface, so assisting (with the frame's boundary wall) to keep both prying implements, steam, vapours and/or spilt liquids away from the gap between the wall and the frame. The gasket can be mounted in a groove shaped into the reverse side of the faceplate or frame, the former being preferred.
Hinging movement of the cover panel may be accomplished in any convenient manner—using real, separate, hinges, say, or merely making the panel an integral part of the frame but joined thereto by some thin, flexible web of material that allows the cover panel to bend—to hinge—back and forth relative to the frame.
The hinging may be arranged in such a way that when the cover latches are released from their retaining members, that the cover panel could not be conveniently opened far enough to allow easy access to the plugs or sockets housed therein. One preferred way, though, is to mount the cover panel by way of pivot pins on one of the panel and frame that are received in corresponding pivot holes in the other of the panel and frame. Such hinge mounting is often utilised for the doors of refrigerators and microwave ovens.
The cover panel may be hinged anywhere along its periphery that is appropriate. A rectangular cover panel can be hinged on any of its sides and may conveniently be hinged on one of its (in-use) vertical sides. When deploying the invention for use with continental socket and plug arrangements where the plug and cable extend from the middle, rather than the base of the socket, a pair of cover panels may by employed that open from the middle outwards and allow passage of the cable or lead through the cover panel(s) in the closed position. For UK plug and socket arrangements in particular, there may well be some advantage in hinging it along its (in-use) top edge, so that it opens upwards, away from the plug's lead (this facilitates inserting and extracting the plug).
The hinging movement is preferably spring-loaded in the opening direction so that the cover panel must be pushed shut against the force of the spring (or springs), and automatically springs open when the panel is released.
Where the panel is to be closable with the plug in the socket, then the panel is preferably either hung far enough away from the socket plate or is so shaped to provide room for the plug behind the panel when it is closed. Were the frame to be sufficiently deep then it could extend away from the wall/socket box a distance greater than the depth of the plug, and then a cover panel mounted on the wall-distant surface of the frame would leave room for the plug behind it even when closed.
However, a rather shallower, less bulky frame is preferred, in which case the cover panel is preferably shaped, for example with an outward bulge, to leave room for the plug. Any suitable shape may be employed—a square box shape, for example—but aesthetically it is preferable to provide the panel with a central domed portion wide and deep enough to accommodate the plug. Where the socket/plug to be covered is a double (or greater) socket, as mentioned previously, the shaped part of the panel may either be a single bulge extending sufficiently to overlay all the plug-pin holes, or more preferably, it may have a number of separate bulges, one for each set of plug-pin holes.
The cover panel may be designed to allow it to be removed and replaced if necessary or desirable, for example if broken, say, or perhaps merely to match a different colour scheme. One convenient way of achieving relatively simple replaceability whatever material the panel is made from—typically a plastic such as polyethylene or polypropylene—is to secure the panel with hinge pins that can be detached by tapping the pins out of their hinge knuckles to free the cover panel from the frame. The replacement panel can then be fixed by aligning the corresponding hinge knuckles found on both the frame and the cover panel and tapping the hinge pins back into the knuckles.
The socket with integral (built-in) cover of the invention has latch means for holding the cover panel closed. The latch means may take any suitable form, and could, for example, comprise a catch part on one of the cover panel and frame engaging with a retainer part on the other of the cover panel and frame. One part may be on or adjacent an edge of the cover panel engaging with the other part on or in the frame, conveniently—in the case of a hinged cover panel—in that portion opposite the hinged edge.
One preferred form of the latch means is the combination of a detent and a matching notched, toothed or headed pin, the pin projecting from the inside surface of the cover panel, at its edge, into a hole in the frame behind which is the detent to prevent it coming back out until the detent is withdrawn and the pin released.
In another preferred form there is also utilised something like a pin/detent arrangement, but the other way around; projecting in from the panel is a seared pin which engages with a detent on/inside the frame, and can only be disengaged by physically pushing the pin (against its natural resilience) to one side until its sear clears the detent and so allows the panel to open.
The socket with integral (built-in) cover of the invention preferably also has key-operated means to release the latch means enabling the cover panel to be secured, against unauthorised opening, when in the closed position. The key-operated means may also include locking means for added security which may take any convenient form, being for example a mortice-type lock, or even a numbered combination lock. The lock may also be electromagnetic, requiring the use of at least two appropriately charged magnets to operate the lock and opening function.
It is particularly preferred however that the locking means is combined with the latch means, and that the combination be a pin-and-detent latch (as just described above) with key operation to withdraw the detent and so release the pin, or to push the pin clear of the detent, and thus permit the cover to open. The key may be a mortice-type key, its key-bit operatively engaging with a bolt-like detent (say). More preferably, however, for use with the integral (built-in) cover of the invention, it is particularly advantageous to have a design that allows a number of rather different types of lock arrangement, according to the circumstances of manufacture and use.
In one such type—a seared pin/fixed detent version—there is not just a single pin/detent arrangement but rather a double one, spaced apart, necessitating a double rod-like driver that can press against, and so push aside both seared pins at the same time (this makes it less likely that a young, adventurous child with a knitting needle will be able to probe the cover until it opens!). This requires a two-pronged key, the spaced prongs of which are themselves the double rod-like driver and have to be simultaneously inserted through corresponding spaced keyhole apertures aligned with the pins.
Moreover, to make it harder for a child to operate improperly, the keyhole apertures can have a spring-loaded shutter on their inner side which must first be pushed aside by the key's prongs—or, preferably, by a third (central) prong dedicated to the purpose—before the prongs can reach further into the arrangement to "unlock" the panel. Further, to provide an even greater measure of security, in a position between the seared release pins and the keyhole apertures, there can be a combination lock device in which apertured discs are rotated, such that in order to unlock the cover, it is necessary to align the combination disc apertures with the key hole apertures and so enable the key prongs to pass through.
In another type, a retaining member or projecting toothed detent is positioned at the tip of a 'flexing arm' and attached to the socket or base-plate within the plane of the lock barrel and positioned so that the tip of the arm engages with a matching toothed detent or retaining member attached to the underside of the cover panel as it is closed. With the cover panel in the closed position, the toothed detent is fully engaged with the retaining member of the cover panel, effectively holding the cover panel in the closed position against the tension of the torsion spring located at the hinge point of the cover panel.
To open the cover, a key of predetermined shape is inserted into the barrel. The locking mechanism is accessed by key via the lock aperture located on any of the edges except for the edge along which the hinges are displaced. For the purpose of the following description, the projecting detent is located on the arm and the retaining member on the underside of the cover.
In order for the detent to be released from its retaining member, the arm is moved away, or 'flexed' apart from its retaining member. This can be achieved by a key with a twisting motion so that, as the key is turned in the lock, the circumference of the twisting key blade extends into and beyond the crook of the arm to move the 'flexing' arm and its toothed detent away from the retaining member. The cover panel opens by virtue of the tension from the torsion spring mounted along its hinge.
Once the key is withdrawn, the 'flexing' arm springs back to its original position, allowing the retaining clasp to once again engage with the cover panel detent when the cover panel is next closed. The strength of resistance and extent of movement of the arm is governed by both the shape of the arm and the choice of material used in its manufacture. The thinner the arm, and the greater the elasticity of material used to manufacture the arm, the less resistance against movement and the greater the spring effect of the movement will be. Most conveniently, the arm can take the approximate shape of the capital letter "U" split into two equal parts along its vertical axis. The projecting detent will be positioned at the tip of the longer edge.
In order for this type of action to function, the arm can be manufactured from a material with properties that allow it to flex or bend, yet faithfully retains memory of its original shape and position despite repeated movement or flexing. Such material could include steel or aluminium, but preferably polymers such as acetal (polyoxymethylene) and/or other thermoplastics such as Delrin (formed by polymerising formaldehyde and acetate) or Celcon (formed by polymerising trioxene and cyclic) can be used.
Preferably, the mechanism will allow the release of the detent by rotation of the key to a maximum of 33 degrees. This will ensure that both the key fob and the user's hand operating the key avoids interfering with the wall during rotation.
This mechanism suffices for just a single latching or locking point. The advantages this particular design offers include; a simple and low cost of manufacture on account of the absence of moving parts, quick assembly by the use of just two extra parts [separate to the base-plate or cover moulding] being a self tapping screw to secure the arm to the base plate; a locking mechanism which deploys a unique key barrel not easily 'picked' by every day items such as other keys, screwdrivers and the like; and a key operation that requires a maximum turn of only 33 degrees.
In another embodiment, the locking action can be achieved by deploying a combination of a spring loaded toothed detent extending from the frame of the base plate, engaging with a matchingly sized opening within a retaining member (or plate) extending from the underside of the spring-loaded cover. The retaining pin protrudes from a rotating hinge axle located in the lock area, and attached to the base plate using a sprung pin, much like an axle can be attached to a wheel.
This design is best deployed for use of a key with a twisting action and in circumstances desirable to control force required to open by the use of spring loaded tension applied to the rotating axle, whereby control of the counter rotation required of the axle to unlock the cover is controlled by a suitable key.
The locking mechanism takes the appearance of a T-shaped axle. The horizontal axis serves as the rotating hinge, one end being attached at a perpendicular angle to the inside of the outer perimeter wall of the base plate, at the entrance of the locking shaft, while the opposite end is mounted through and secured to the inside perimeter wall using a sprung pin. The vertical axis consists of a retaining shaft pin with a toothed detent at its tip.
The head of the detent can be of any shape but most conveniently, is shaped to give the appearance of an elliptical cam spliced in equal halves along the vertical. As the cover is closed, the angle of motion causes the retaining member to engage with the curved surface of the clasp's cam shaped head. The force of the retaining plate pushes back the shaft pin to counter rotate on its axle and the cam head to slide along the front face of the retaining plate until the angular plane of the cam engages with the opening in the retaining plate, whereby the cam fully engages and clasps the retaining plate, rendering the cover closed and locked against unauthorised entry.
The retaining plate is released to allow the cover panel to open by using a key that is shaped to engage with the axle hinge in such a way, that as the key is turned in a counter direction to the spring loading, so the shaft pin and clasp tilt backwards and away from the cover retaining plate, disengaging and so allowing the cover panel to spring open.
Though superficially similar to the cover leg pins described in the other locking mechanisms previously, the width of the single pin shaft neck is considerably wider and the depth of the retaining clasp greater. The clasp's greater surface area engaging with the opening in the retaining plate is designed to provide the locking cover with greater security and robustness to resist forced opening.
One particular advantage of this design is the simplicity with which the key and rotating axis can be individually shaped so that locks are unique to particular models of socket covers, thus significantly enhancing security in circumstances where needed. Either the key or the axle can be 'male' or 'female', according to the preference of the user. A male axle would require a female key and vice versa.
Another advantage is the reduction in the number of different parts needed to complete the locking mechanism compared to a regular metal barrel and key arrangement. A single moulded part comprises the shaft pin with the toothed detent and rotating axis. The axle spring can be a conventional metal torsion spring mounted to the axle, or be an extension to the entire axle mould.
By using a polymer with flexing and memory properties similar to those described in the 'flexing' arm lock described above, the axle can have a 'sprung tail' extending from the bottom of the shaft pin on the opposite side to the toothed detent. The sprung tail offers similar operational functionality to the metal axle spring. Overall, the design with fewer parts provides for a simpler and more reliable operation that is less expensive to produce and assemble into a working model.
In all cases such locks can be disposed for access from any "side"—top, bottom or left side or right side—of the cover panel, its parts being mounted within the frame and the holes for the prongs of the key being in the side surface of the frame and essentially invisible from the front. The keyholes and or any numbered combination lock are most preferably outlined in luminous paint so that they show up in the dark and, where the frame is particularly slim, it may be necessary to angle the holes and the internal parts such that the key can be inserted in a direction angled towards the wall in which the socket is mounted.
In a preferred arrangement, at least two latches are provided for latching the cover panel to the frame, wherein engagement and disengagement of the first latch is in a direction different to that of the second latch. In this arrangement, engagement of disengagement of the latches occurs in sequence and when closed, both latches have to be release before the cover panel can move freely to the open position. Such arrangement provides added security against accidental or unauthorised release of the cover panel especially by a child who may release one latch but be unable to release the other and is therefore unable to open the cover panel.
One of the latches may be key operated with the other latch being operable by movement of the cover panel relative to the frame. For example where the cover panel is hinged to the frame there may be a first key operated latch comprising a first detent mounted upon one of the panel and frame for engaging with the other of the panel and frame, the first detent being releasable by key operated means, and a second latch including a second detent mounted upon one of the panel and frame for engaging with the other of the panel and frame, engagement and disengagement of the second detent being by relative movement of the panel and frame in a direction substantially parallel to the hinge axis, the panel being biased towards an open position and in a direction substantially parallel to the hinge axis relative to the frame.
Preferably, blocking means can be provided to prevent relative movement of the panel and frame in a direction substantially parallel to the hinge axis when the first latch is in its latched condition. In this way, the cover panel cannot be moved to release the second latch when the first latch is engaged. With this arrangement, the cover panel may open slightly on release of the first latch under the resilient biasing to clear the blocking means and allow relative movement of the cover panel parallel to the hinge axis to release the second latch and allow the cover panel to swing freely about the hinge axis to the open position.
The second latch may comprise one or more latching points spaced around the perimeter of the frame to prevent the cover panel being lifted (prised) away from the frame in the closed position.
The latching arrangements above-described have application to sockets with an integral (built-in) cover according to the present invention and to detachable covers of the type that can be fitted to an existing socket (or switch) to provide the socket with protection against unauthorised use. Such detachable cover may be of the type described in our earlier UK Patent No. 2366457.
Thus according to another aspect of the present invention there is provided a latching/locking system for a panel movable relative to a frame between first and second positions, the system comprising at least two latches for latching the panel to the frame in the first position, wherein engagement and disengagement of the first latch is in a direction different to that of the second latch.
The panel may be a cover panel movable between open and closed positions and the latches are operable to secure the cover panel in the closed position. This arrangement is preferred but not essential and the invention may have application to other arrangements.
The frame may be an integral (built-in) part of a socket (or switch) and the panel movable between the open position allowing access a faceplate of the socket (or switch) and the closed position shrouding a front surface of the faceplate to prevent access to the plug-pin receiving apertures (and a plug when received in such apertures) of the socket (or a switch).
Alternatively, the frame may be separate from the socket (or switch) and secured by locating a part of the frame behind a faceplate of the socket (or switch) so that the frame is held in place when the faceplate is secured to a mounting box, for example a wall mounted box or a freestanding mounting box and the panel is movable between an open position allowing access the faceplate of the socket (or switch) and a closed position shrouding a front surface of the faceplate to prevent access to the plug-pin receiving apertures (and a plug when received in such apertures) of the socket (or a switch).
The panel may be mounted for hinging or sliding movement between the open and closed positions. Preferably the latches are self-latching on so that the cover panel is secured automatically on being moved to the closed position without any additional means such as key being required. This simplifies operation for the user.
In some embodiments, the panel is mounted for hinging movement about a hinge axis between open and closed positions and disengagement of the first latch allows relative transverse motion of the panel and frame, which then disengages the second latch. Thus no further latching mechanism is required.
With this arrangement, the first latch may comprise a first detent mounted upon one of the panel and frame for engaging with the other of the panel and frame, the first detent being releasable by key operated means, and the second latch may include a second detent mounted upon one of the panel and frame for engaging with the other of the panel and frame, engagement and disengagement of the second detent being by relative movement of the panel and frame in a direction substantially parallel to the hinge axis.
The panel is preferably biased towards the open position and in a direction substantially parallel to the hinge axis relative to the frame to maintain engagement of the second latch in the closed position. In this way, the panel has to be moved parallel to the hinge axis on release of the first latch to overcome the biasing to release the second latch and allow the panel to move to the open position.
Some embodiments include blocking means to prevent relative movement of the panel and frame in a direction substantially parallel to the hinge axis to release the second latch when the first latch is in its latched condition. In this way, the cover panel cannot be moved to release the second latch when the first latch is engaged.
With this arrangement, the cover panel may open slightly on release of the first latch under the resilient biasing to clear the blocking means and allow relative movement of the cover panel parallel to the hinge axis to release the second latch and allow the cover panel to swing freely about the hinge axis to the open position.
The first latch may comprise a resilient detent in the form of a hooked clasp which engages in a notch or bore. Alternatively the clasp or detent may engage in a notch or bore in a resilient projecting member. The type of key required to release the first latch depends upon the form of first latch which may be in a number of different forms.
The second latch may comprise a single detent most typically mounted upon the cover panel, which may engage with a specific retaining member upon the frame or may just engage with a notch in the frame to provide a single latching point in the closed position.
More preferably, the second latch comprises a plurality of detents with corresponding retaining members located around the periphery of the cover panel to provide multiple latching points. The retaining members at these latching points are preferably moulded as part of the cover panel itself and, as the cover panel is closed, engage directly with apertures moulded at corresponding locations around the perimeter moulding of the base frame, wherein the retaining members, which have circular radius edges, slide into the individual apertures, (which also have rounded radius edges) and are securely retained once the cover panel is latched in the closed position. The retaining members, for example lugs, and apertures have no moving parts.
To release the cover panel, it is necessary to displace either the cover panel and/or the base frame along a plane of movement about and parallel to its hinged axis, sufficient to enable the retaining members to fully disengage from inside the base-frame apertures. This can be achieved in a number of different ways;
The preferred method deploys a compression spring mounted to the hinging mechanism of the cover panel. The spring performs two different functions. Firstly, the positioning, coiling and tension of the spring disposes the cover panel to sit to the left or right of the base plate if located on either of the horizontal axis of the base plate, or to sit above or below the base plate if located on either of the vertical sides of the base-plate.
Indeed, the cover panel and base-plate are held in alignment by virtue of their 'interlocking' shapes, otherwise the tension of the spring would cause the cover panel to be misaligned left or right, above or below the base-plate by a margin noticeable to the eye and sufficient to render the cover panel unfit for its designed purpose. Secondly, the spring causes the cover panel to open unassisted, away from the base plate once both latches are released.
The retaining members around the perimeter can be conveniently positioned so that, under tension from the compression hinge spring, the cover panel aligns suitably with the shape of the base-plate, such that any natural flex of the material is countered by the tight fit of the retaining members in their apertures around the perimeter, and thus opportunities to access the cover by the use of force are minimised. In this way, the assembly can provide a secure enclosure for sockets, plugs and the like.
Where provided, in any of the latching arrangements previously discussed, the biasing of the spring can also perform the function of assisting to maintain engagement of the latches in their latched condition. For example, the or each latch may comprise latch members provided with formations that engage and interlock under the spring biasing in the latched condition so as to resist separation of the formations until the latch is released. The latch members may comprise a latch part and a retainer part.
In order to release the cover panel, two distinct operation are required. More specifically, the release process requires both upward and lateral movement of the cover panel in order to fully release the cover panel and allow movement of the cover panel to the open position. One latch comprises the initial lock (and when unlocked, is referred to as the 'initial release'). Another latch provides a secondary lock (and when unlocked is referred to as the 'final release').
The lateral movement of the cover panel may be achieved in part by means of a formation such as a leg extending from (and permanently attached to) the underside of the cover and positioned so that, when the cover panel is closed, the formation extends into an area within the movement range of a key for releasing the first latch once the key is inserted so that operation of the key to release the first latch (initial release) may also release the second latch (final release). For example, the key may have formations that, on rotation of the key, release the first latch and then release the second latch.
Lateral movement of the cover panel may be blocked whilst the cover panel is secured in the closed position to prevent release of second latch. This may be achieved by an abutment such as a small step or web on the same side (and as close as possible to) the latching means.
With the cover panel closed, a small gap is provided between the inside surface of the cover panel and the vertical side wall of the frame or face plate. The width of the gap may be determined by the amount of lateral movement required to release the second latch and allow the cover panel to open. In the embodiments described hereinafter there may be gaps of between 2-3 mm. The abutment is sized to extend sideways by a distance slightly less than the lateral movement intended to effect the final release, but in all cases, such that it is almost flush against the inside surface of the cover panel.
The abutment also extends upwards along the vertical surface of the base plate to a height slightly less than the distance to which the torsion spring raises the cover panel away from the base plate once the 'initial release' mechanism is activated. The initial release mechanism therefore provides the means for the edge of the cover panel to clear the abutment, allowing the cover panel to move laterally once force (by means of a key against the leg or effort applied directly) is applied against the directional tension of the compression spring with sufficient movement to effect the final release.
In a modification, the abutment may include a guide face to assist relative lateral movement of the cover panel and base plate to engage the second latch in the latched condition.
Where the cover is a separate unit that can be mounted to the socket by securing the frame behind the socket faceplate, the frame may be arranged so that is can be located in position by partially releasing the screws securing the faceplate to allow the faceplate to be pulled away from the surface to which it is attached a distance sufficient for the frame to be slid into place. In this way, the socket does not have to be completely removed and/or the electrical connections to the socket disconnected to fit the cover.
For UK sockets (and switches), the faceplate is traditionally of rectangular shape and the frame may be of U-shape that can be slid into place from above to extend on three sides of the faceplate leaving an opening in the other side for passage of the lead of a plug(s) when the cover is secured in position and the plug(s) is shrouded by the cover panel in the closed position. Typically, the frame extends across the top and down both sides of the faceplate leaving the opening at the bottom.
With this arrangement, pulling forces applied to the cable may be transferred to the latch(es) via the cover panel and this could result in the cover panel being forced open.
Some embodiments of the invention may therefore provide a frame that extends on all four sides of the faceplate with the opening being arranged so that pulling forces applied to a cable passing through the opening is transferred to the frame which is securely mounted and can better withstand the forces. In this way, the pulling forces are not applied to the latches.
The transfer of forces to the frame may be achieved by means of a detachable cable tie that can be fitted after locating the cable in the opening. In this way the plug does not have to be removed from the cable in order to feed the cable through the opening. The cable tie may also help to prevent the plug being disconnected by pulling the cable while the cover panel is in the closed position.
In order that the frame can be fitted to extend on four sides of the faceplate without completely removing the faceplate and disconnecting the electrical connections, the frame preferably comprises at least two frame members that can be arranged to extend around the faceplate and located behind the faceplate so as to be secured by the faceplate.
In one arrangement, the frame members comprise a U-shaped frame member as described above that can be slid into place to extend across the top and down both sides of the faceplate and a base frame member that can be positioned to extend across the bottom of the faceplate and attached at each end to the U-shaped frame member. For example, the base frame member may be provided with formations at each end that engage mating formations of the U-shaped frame member on both sides of the faceplate.
Preferably, the frame members are arranged so that the engaged portions can be located behind the faceplate so as to inhibit disconnection when the cover is secured in position. The base frame member may be provided with at least one opening for passage of cable lead(s) and at least one tie member so that pulling forces applied to the cable are transferred to the frame and away from the cover member.
Thus, according to yet another aspect of the present invention, there is provided a detachable cover for a socket (or switch) comprising a frame arranged to extend around the perimeter of a faceplate of the socket or switch and a cover panel connected to the frame for movement between open and closed positions, the frame comprising at least two frame members capable of being arranged to extend around the faceplate and secured in place.
Features of the invention described herein may also be applied to arrangements in which the cover panel is sidable between the open and closed positions.
Thus, according to another aspect of the present invention, there is provided a cover for a faceplate of a socket, switch or the like comprising a cover panel slidable between open and closed positions.
The cover may be a separate, detachable unit that is located behind the faceplate or it may be an integral (built-in) part of the faceplate.
The invention may also extend to include the integral (built-in) covers and separate, detachable covers described herein having a cover panel mounted for movement between open and closed positions and latch means for securing the cover panel in the closed position, where the latch means comprises a single latch or a multiple latch.
Single latches may be released by axial and/or rotational movement of an actuator such as a key. Where provided, multiple latches may be released simultaneously or in sequence. Sequential release of multiple latches may be effected in a variety of ways. For example by axial and/or rotational movement of an actuator such as a key. Thus, axial insertion of a key may release a first latch with rotational movement of the key releasing a second latch or vice versa. Alternatively, two or more latches may be released in sequence at different axial or rotational positions of the key. Other combinations of latches and actuators will be apparent to those skilled in the art.
Embodiments of the invention may also incorporate one or more additional features to add functionality.
Thus, according to a still further aspect of the present invention, there is provided a cover for a faceplate of a socket, switch or the like, the cover having a cover panel moveable between an open position and a closed position by hinging or sliding movement and being secured in the closed position by latch means, wherein the faceplate includes one or more additional features such as a light source, air freshener, and a fuse holder.
The cover may be a separate, detachable unit that is located behind the faceplate or it may be an integral (built-in) part of the faceplate.
The light source may be activated by a push button, for example the light source may comprise a night light. Alternatively or additionally, the light source may be activated when the cover panel is opened. The air freshener may be heat activated, for example by heat emitted by the light source.
According to another aspect of the present invention, there is provided a cover for a faceplate of a socket, switch or the like, latch means operable to secure a cover panel in a closed position, actuator means for releasing the latch means, and biasing means for urging the cover to an open position.
The cover may be a separate, detachable unit that is located behind the faceplate or it may be an integral (built-in) part of the faceplate.
According to another aspect of the present invention, there is provided a faceplate for a socket, switch or the like having an integral (built-in) cover with a cover panel movable between an open position and a closed position.
The faceplate may be secured to a wall mounting box or to a freestanding mounting box.
According to another aspect of the present invention, there is provided a fitting comprising a base part having a socket or switch and a cover panel mounted on the base part for movement between a closed position concealing the socket or switch and an open position allowing access to the socket or switch.
The fitting may comprise a faceplate for a socket or switch that can be secured to a wall mounting box or to a freestanding mounting box.

Safety covers for electric sockets and the like


There is provided a topical composition for treating and/or preventing skin irritation induced by a retinoid. The composition has comfrey. There is also provided a method for treating and/or preventing skin irritation induced by a retinoid. An effective amount of comfrey is applied to the skin.

1. Field of the Invention
The present invention relates to the use of comfrey. More particularly, the present invention relates to the use of comfrey to ameliorate, prevent, reduce and/or treat irritation caused by topical compositions having a retinoid or a retinoid compound.
2. Description of the Prior Art
Retinoid or retinoid compounds/derivatives (collectively referred to herein as xe2x80x9cretinoidxe2x80x9d or xe2x80x9cretinoidsxe2x80x9d) are vitamin A derivatives. They are used in topical compositions to treat a variety of adverse skin conditions. Such skin conditions include acne, actinic damage, fine lines, wrinkles, warts, psoriasis, dandruff and eczema. Representative compositions having a retinoid are discussed, by way of example, in U.S. Pat. Nos. 3,006,939; 3,060,229; 3,932,665; 4,826,828; and 4,934,114.
However, topical compositions having a retinoid have been limited by way of the amount of retinoid since retinoid contained in the composition has been found to irritate the skin. Such irritation is acute especially when the amount of retinoid in the composition is high. However, some consumers with sensitive skin cannot even tolerate small amounts of retinoid.
The irritation can manifest itself in the form of physical discomfort and/or unaesthetic skin appearance. Such an unaesthetic skin appearance can progress to dermatitis or erythema. The irritation may disturb the user to such an extent that the user will discontinue use of the composition having a retinoid. Alternately, the user may reduce the frequency of use, thereby possibly reducing the effectiveness of the composition for its intended purpose.
Known prior art provides natural and synthetic substances, such as cortisone derivatives, that are useful anti-inflammatory agents in topically applied skin compositions. Such substances are discussed, by way of example, in U.S. Pat. Nos. 5,962,018; 6,008,246; and 6,020,367; and International Application (WO) Nos. 9739726; 9746231; 9848768; and 9850005. However, none of these patents or published applications points out a non-cortisone, anti-inflammatory agent that is particularly suited for reducing skin irritation induced by a retinoid in a topical cosmetic composition.
U.S. Pat. No. 5,578,312 to Parrinello is directed to a skin care system and method To improving the moisture retention in skin, particularly for individuals who are undergoing treatment for life threatening illnesses. As stated in column 2, lines 4.6, et seq., a second embodiment of the moisturizer includes vitamin A and allantoin. Column 4, lines 63 et seq. states that comfrey leaf Contains allantoin. However, this is very specifically directed to a tea solution. Moreover, based upon the specific gravity values of most commercially available Vitamin A materials, all of the exemplified formulas disclose a Vitamin A concentration greater than 1.0 wt. %.
A commercial cosmetic product sold by Avon Products, Inc. under the name Daily Revival contained retinyl palmitate and comfrey. However, the retinyl palmitate was not present in a skin irritating amount, nor was the product used for the treatment or prevention of skin irritation of any kind.
Heretofore, there has been a need for a composition that ameliorates, prevents, reduces and/or treats the irritation induced by a retinoid. It has been found that retinoid-induced irritation has a direct correlation to retinoid efficacy. Thus, simply reducing retinoid content may decrease irritation to the skin, but may also fail to provide an efficacious amount of retinoid. Moreover, consumers with sensitive skin needs may hot tolerate even reduced retinoid content compositions. However, these sensitive skin consumers require, and would benefit from, a retinoid-containing composition that is both tolerated and efficacious. The present composition having comfrey achieves this need.
It is an object of the present invention to provide a topical composition having comfrey to treat, ameliorate and/or reduce or prevent skin irritation induced by a retinoid.
It is a further object of the present invention to provide a method for treating, that is ameliorating and/or reducing, skin irritation induced by a retinoid.
It is still a further object of the present, invention to provide a method for preventing irritation induced by a retinoid.
These and other objects of the present invention are achieved by a topical composition that has comfrey in an amount effective to prevent and/or treat skin irritation induced by a retinoid.
The present invention relates to the surprising recognition that comfrey has a direct effect in mitigating skin irritation induced or caused by the topical use of a retinoid. It has been discovered that comfrey will treat, namely ameliorate and/or reduce, such irritation. It has also been discovered that comfrey will prevent such irritation. The efficacy of the retinoid in a topical composition will not be adversely affected by the addition of comfrey to the composition.
As stated above, retinoids are Vitamin A derivatives. Commonly used retinoids include, but are not limited to, retinal, retinol, retinoic acid, retinyl acetate, retinyl palmitate, retinyl propionate, isotretinoin, synthetic retinoid mimics, and tretinoin. The amount of retinoid in a topical composition varies depending on the condition to be treated or prevented, as well as on the composition and the retinoids themselves. However, for most conditions to be treater or prevented, the amount of retinoid in any composition is about 0.1 percentage by weight (wt %); but no greater than about 1.0 wt %, preferably no greater than about 0.5 wt %, since this amount is associated with some irritation and is always irritating to users with sensitive skin.
The comfrey of the present invention may be derived from any part of the comfrey plant (preferably, Symphytum officinale) These parts include the flowers, leaves, roots, seeds and stems. Preferably, the comfrey is extracted from the leaves and roots of the plant. The comfrey extract may be in the form of a liquid or powder. A suitable example of a comfrey extract is available from Cosmetochem under the tradename HERBASOL(trademark). It is an extract obtained from comfrey herbs in approximately 60:40 v:v water in propylene glycol solution. It is about 3.5% to 5.5% active.
Comfrey should be present in the topical composition of the invention in an amount, on an active basis, of at least about 0.005 wt % based on the total weight of the composition to treat retinoid-induced skin irritation. Preferably, comfrey is present in an amount at least about 0.005 wt %. to about 90 wt %, more preferably about 0.01 wt % to about 25 wt %, and most preferably about 0.01 wt. % to about 1.0 wt. % based on the total weight of the composition.
As a guideline, it is preferred that when the retinoid is retinol, the amount of comfrey to retinol ratio is from about 1:5 to about 10:1, more preferably from about 1:4 to about 5:1, or most preferably from about 1:3 to about 5:1.
It should be understood that the effect produced by a retinoid will vary by the type and amount of retinoid used in the topical composition. Accordingly, those skilled in the art will vary the amount to compensate for the various efficacies and concentrations associated with each retinoid, as well as the efficacy of the vehicle used. For example, drying vehicles, such as anhydrous gels, are generally considered to increase the potency/irritation of the retinoid as compared to emollient vehicles, such a oil-in-water creams.
The present invention functions against the irritating effect of a retinoid. As is known in the art, potencies of different retinoids vary. For example, retinoic acid is known to be more potent/irritating than retinol. In contrast, retinyl palmitate is known to be less potent than retinol. For this reason, retinyl palmitate is known to produce less irritation compared to retinol on a weight to weight basis. In fact, when retinyl palmitate is employed in commercial skin care products, there is virtually no irritation associated therewith. As a result, the maximum benefits of the present invention is achieved when the selected retinoid is not retinyl palmitate.
The present composition may take any suitable form such as a cream, an emulsion, a gel, a lotion, a patch, a stick, a towellete, a spray, a mask, an ointment or a solution. The composition preferably has a vehicle to provide bulk and physical form. Suitable vehicles include, but are not limited to, water, alcohols such as ethanol and polyvinyl alcohol, glycerin, propanol, propylene glycol, and mixtures thereof. The present composition may be in a form other than a tea.
The present composition may optionally have one or more of the following ingredients or adjuvants: anesthetics, anti-allergenics, antifungals, antiseptics, chelating agents, colorants, demulcents, pigment altering agents, emollients, emulsifiers, exfollients, fragrances, humectants, lubricants, moisturizers, preservatives, skin penetration enhancers, stabilizers, sunscreens, surfactants, thickeners, viscosity modifiers, vitamins, or mixtures thereof.
The inclusion of at least one sunscreen is particularly preferred since the retinoid may increase sensitivity of the skin to ultraviolet radiation. Preferably, the sunscreen provides both UVA and UVB protection, or is a combination of sunscreens that provide such protection. The preferred sunscreens are avobenzone, octyl salicylate, oxybenzone, titanium dioxide and cinnamic acid derivatives.
To form a topical composition according to the present invention, comfrey is incorporated into the composition by any suitable method known in the art. Preferably, the composition has both comfrey and a retinoid. The comfrey and retinoid may be admixed, preferably with a vehicle and any other adjuvants or ingredients, to form the topical composition.
When the composition includes comfrey, and no retinoid, the composition may be applied either before or after the retinoid is applied to the skin. Preferably, the topical composition having comfrey is applied either immediately before or immediately after the application of a composition containing the retinoid. More preferably, the topical composition of the present invention includes both comfrey and the retinoid for simultaneous application.
The following is an illustrative, non-limiting example of the present invention.

Compositions having comfrey and methods for reducing retinoid-induced skin irritation


A material is disclosed which is suitable for making a flexographic printing plate and comprises in the order given a base, a photopolymer layer, a barrier layer wherein the main component is a polymer different from gelatin, and an ink receiving layer wherein the main component is gelatin. An image having a high optical density can be printed on the ink receiving layer by image-wise jetting a water-based ink because the gelatin in the ink receiving layer has excellent ink receptivity and because the barrier layer reduces diffusion of monomers from the photopolymer layer to the ink receiving layer. The image present in or on the ink receiving layer can then be used as a photomask for the subsequent flood exposure of the photopolymer layer. After processing, a flexographic printing plate is obtained.

The present invention relates to a material that is suitable for making a flexographic printing plate. More specifically the invention is related to a material which comprises a photopolymer layer and an ink receiving layer whereon ink can be jetted image-wise so as to obtain a mask for subsequent flood exposure of the photopolymer layer.
Flexographic printing plates typically comprise a base and a photopolymer layer which is cured by image-wise exposure to (UV) light. During a subsequent processing step, the unexposed areas are removed by a developing liquid and a relief plate is obtained wherein the printing areas are raised above the surrounding non-printing areas. The relief image distinguishes flexography from other printing techniques such as lithography (planographic process wherein printing and non-printing areas are part of the same surface) and gravure (printing areas are recessed below the level of the non-printing areas).
Image-wise exposure of a flexographic plate is generally obtained by flood exposure of the photopolymer layer through a contact mask which is typically a film negative that is transparent in printing areas and opaque in the non-printing areas. Film production can be avoided by direct imaging of computer data onto flexographic plates by means of a digitally controlled imaging unit, e.g. a laser scanning apparatus. Such computer-to-plate methods are becoming a major trend in the art. The associated plates are often called digital plates.
WO 97/00777, U.S. Pat. No. 4,555,471, EP-A 487 260 and EP-A 491 457 describe digital plates comprising in the order given a base, a photopolymer layer, a peelable support and an image recording layer. After exposure to heat or light, e.g. by means of a laser or thermal head, and optional processing, an image is formed in the recording layer which can be used as a mask for exposure of the photopolymer layer. After flood UV-exposure through the mask, the support and the recording layer are peeled off and the photopolymer layer can be processed. For easy removal, the support can be silicon-coated or adhered to the photopolymer layer by a peelable adhesive as described in WO 97/00777. The image recording layer of such digital flexographic plates can be an ablative layer comprising a heat- or light-sensitive compound, e.g. a metal, a dye or a pigment such as carbon black. Typical ablative systems are described in WO 94/03838, WO 96/016356, EP-A 720 057, EP-A 741 330, EP-A 767 407 and U.S. Pat. No. 5,654,125. Other suitable image recording layers are thermochromic systems (U.S. Pat. No. 4,555,471), heat-developable photosensitive compositions containing an organic silver salt, a silver halide and a reducing agent (EP-A 509 740, EP-A 530 674, U.S. Pat. No. 5,258,282, EP-A 491 457), or can be based on heat-induced coalescence of metal particles (EP-A 875 889 and references therein).
A disadvantage of the digital plates which are described above is the low pliancy due to the presence of two supports : the base of the photopolymer layer and the peelable support of the image recording layer. As a solution, an image recording layer which dissolves in the processing liquid can be applied directly on the photopolymer layer. Examples of such plates are described in U.S. Pat. No. 4,288,528, EP-A 767 407, EP-A 741 330 and EP-A 720 057. An additional barrier layer can be provided between the photopolymer layer to prevent diffusion of monomers from the photopolymer layer to the image recording layer, as described in WO 94/03838, WO 94/03839 and U.S. Pat. No. 5,654,125.
EP-A 465 949 describes methods wherein toner, pigment or ink is image-wise transferred by electrophotography, thermal transfer or ink-jet directly onto the photopolymer layer of a flexographic plate so as to obtain a mask that is suitable for flood (UV-)exposure. DE-A 41 17 127 describes a similar process wherein an additional barrier layer, which simultaneously acts as an ink receiving layer, is present on top of the photopolymer layer. Said layer has two functions : preventing the diffusion of monomers from the photopolymer layer to the image recording layer and accepting the ink which is applied image-wise to obtain a mask. Especially when water-based inks are used, it is necessary that monomer diffusion is reduced effectively because the presence of such monomers in the ink receiving layer decreases the hydrophilicity of said layer and, as a result, reduces the ink receiving capability. A number of polymers are indicated in DE-A 41 17 127 for use as a binder of such a barrier/ink-receiving layer. The polymers that provide the best ink receiving properties, such as gelatin, actually have inferior barrier properties. Vice-versa, the polymers that provide good barrier capability, such as polyamides, have poor ink receptivity, i.e. the optical density of the jetted water-based ink is too low. This problem is not recognised in DE-A 41 17 127 and a fortiori not solved.
It is an object of the present invention to provide an improved material which is suitable for making a flexographic printing plate by ink-jet methods in a convenient way. More specifically, it is an object of the present invention to provide a material which is characterised by a high receptivity of water-based ink so that an exposure mask can be applied having a high optical density with regard to the light that is used for flood exposure of the photopolymer layer. It is a further object of the present invention to provide a material which retains its high receptivity of water-based ink during storage. This object is realised by the material having the specific features defined in claim 1. Specific features for preferred embodiments of the invention are disclosed in the dependent claims.
Further advantages and embodiments of the present invention will become apparent from the following description.
In ink-jet printing tiny drops of ink fluid are deposited directly onto an ink receptor surface without physical contact between the printing device and the receptor by means of an image-wise controllable drop-ejection device called print head. In the method of the present invention, the known continuous ink-jet printing methods as weld as drop-on-demand methods such as piezo-electric ink-jet or the so-called xe2x80x9cbubble-jetxe2x80x9d and xe2x80x9cthermal jetxe2x80x9d methods can be used for jetting a water-based ink image-wise on the surface of the material of the present invention. Said material is a flexographic printing plate precursor and comprises in the order given a base, a photopolymer layer, a barrier layer and an ink receiving layer. That image thus obtained can then be used as a photomask for the subsequent flood exposure of the photopolymer layer. After washing out the unexposed areas with a suitable solvent, a relief image is developed which can be used as a print master for flexographic printing.
The specific advantages of the present invention are obtained by using a polymer different from gelatin as main component of the barrier layer and by using gelatin as main component of the ink receiving layer. The feature xe2x80x9cmain componentxe2x80x9d is generally understood as a component present in an amount which is not less than 50% of the total weight of the layer. In a preferred embodiment the ink receiving layer contains not less than 75% and even more preferably not less than 90% of gelatin. Gelatin forms a clear, hydrophilic coating which is characterised by a high absorption of water-based inks thereby providing rapid drying characteristics of the ink. The drying mechanism typically involves absorption by the ink receiving layer, penetration into said layer and evaporation.
The optimal composition of the water-based ink used in the method of the present invention is dependent on the specific ink-jet method used. In addition, the spectral absorption of the ink is preferably adjusted to the wavelength of the light used during exposure of the photopolymer layer through the jetted photomask. Ink compositions that are suitable for the method of the present invention typically include the following ingredients:dyes or pigments, water, moistening agents such as glycols, detergents, thickeners, polymeric binders, and preservatives.
Water-based inks typically contain about 75-90 weight % of water. In order to avoid dry tipping on the orifice of the printing head, they may contain a so-called humectant or mixtures of humectants which usually are (poly)alcohols. Suitable humectants include glycols such as diethyleneglycol, glycerine and polyethyleneglycol, N-methyl-pyrrolidone, 2-pyrrolidone, N-methyl-2-pyrrolidone, isopropanol, and 1,2-dimethyl-2-imidazolidone. Certain humectants such as N-methyl-pyrrolidone and 2-pyrrolidone have been found to improve the solubility of the colorant in the ink and thus serve the dual role as humectant and as co-solvent. Typically these humectants are present in a concentration ranging from 5 to 15%.
Apart from the colorant, water and humectant water-based ink compositions may contain minor amounts of other ingredients such as surfactants, biocides, buffering agents, chelating agents and defoaming agents.
The colorant in the ink used in the present invention is preferably a black pigment, e.g. carbon black in a concentration of at least 2%, preferably about 5%. Multiple types of inks containing carbon black are commercially available. They include carbon blacks such as Regal 400R, Mogul L, Elftex 320 from Cabot Co., or Carbon Black FW18, Special Black 250, Special Black 350, Special Black 550, Printex 25, Printex 35, Printex 55, Printex 150T from Degussa Co., and Pigment Black 7. Additional suitable pigments are disclosed in Industrial Organic Pigments, Production, Properties, Applications (second edition, W. Herbst, K. Hunger; VCH, 1997) and in U.S. Pat. No. 5,389,133 and U.S. Pat. No. 5,713,988.
The pigment particles should be sufficiently small to permit free flow of the ink through the ink-jet printing device, especially at the ejecting nozzles of the print head that usually have a diameter ranging from less than 10 microns to 50 microns. The pigment particle size also has an influence on the pigment dispersion stability, which is critical throughout the life of the ink. It is also desirable to use small particles for maximum color strength.
Accordingly, the average particle diameter may be from about 0.005 xcexcm to about 15 xcexcm. Preferably, the pigment particle size may range from about 0.005 to about 5 xcexcm, more preferably from about 0.005 to about 1 xcexcm, and most preferably from about 0.005 to about 0.3 xcexcm. Pigment particle sizes outside these ranges may, of course, be used as long as the objectives of the present invention are achieved.
Very fine dispersions of pigments and methods for their preparation are disclosed in e.g. EP 0 776 952, U.S. Pat. No. 5,538,548, U.S. Pat. No. 5,443,628, EP 0 259 130, U.S. Pat. No. 5,285,064, EP 0 429 828, and EP 0 526 198.
When the pigment chosen is not in itself sufficiently absorptive in the UV spectral region it is preferred to add a UV absorbing dye to the ink composition. Suitable UV absorbers are disclosed e.g. in EP 0 252 550, U.S. Pat. No. 4,311,787, U.S. Pat. No. 4,082,554, U.S. Pat. No. 4,053,315, EP 0 519 306, EP 0 524 593, EP 0 524 594, EP 0 529 737, JP-A 03-38636, JP-A 03-13936, JP-A 03-41442, DE 4142935, EP 0 552 010, JP-A 03-48234, U.S. Pat. No. 5,155,015, EP 0 525 445, WO 93/5443, JP-A 03-78741, WO 93/13458, U.S. Pat. No. 4,923,788, EP 0 411 819, JP-A 61-205934, JP-A 01-259358, JP-A 02-73343, JP-A 02-71261 and EP 0 495 406. Still other UV absorbers are mentioned in Research Disclosure, December 1989, Item 309119, Section VIII.
Even when the pigment itself is a good UV absorber, as it is the case with carbon black, it is useful to add a UV absorber in order to enhance the UV density of the finished ink-jet image. By doing so the use of very high concentrations of carbon black which potentially could lead to sendimentation and nozzle clogging can be avoided.
Although gelatin is the main component of the ink receiving layer in the material of the present invention, other polymers may be used as an additional binder of said ink receiving layer. Especially nitrogen-containing polymers are preferred, e.g. polyvinyl pyrrolidone, polyacrylamide, acrylamide/ acrylic acid, poly(2-acrylamido-2-methyl propane sulphonic acid), poly(diethylene triamine-co-adipic acid), polyvinyl pyridine, polyvinyl imidazole, polyimidazoline quaternized, polyethylene imine, polyethylene imine epichlorohydrine modified, polyethylene imine ethoxylated, poly(N,N,-dimethyl-3,5-dimethylene piperidinium chloride, polyurethane, melamin resins, urea resins, nitrile rubbers, or albumin.
In principle, although not being a preferred embodiment, a non-N-containing binder may also be present in the receiving layer, e.g. cellulose derivatives such as carboxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxypropyl methyl cellulose, starch, dextran, polyvinyl alcohol, polyvinyl alcohol derivatives such as acetoacetylated derivatives, polyvinyl acetate, polyvinyl acetal, polyalkyleneoxides, latices such as copoly(styrene-butadiene), carboxylated polymers or polyacrylates.
The receiving layer can further contain organic or inorganic fillers and porous particulate material. Inorganic materials include e.g. synthetic silica, talc, clay, koalin, diatomaceous earth, calcium carbonate, magnesium carbonate, aluminum hydroxide, aluminum oxide, boehmite and pseudo-boehmite, titanium oxide, zinc oxide, barium sulfate, calcium sulfate, zinc sulfide, satin white, aluminum silicate, calcium silicate, lithopone, etc. Organic materials include e.g. polystyrene, polymethacrylate, polymethylmethacrylate, elastomers, ethylene-vinylacetate copolymers, polyesters, polyester-copolymers, polyacrylates polyvinylethers, polyamides, polyolefines, polysilicones, guanamine resins, polytetrafluoroethylenes, elastomeric styrene-butadiene rubber (SBR), elastomeric butadiene-acrylonitrile rubber, urea resins or urea-formalin resins.
Further typical and useful ingredients of the ink-jet receiving layers of the present invention are so-called mordanting agents which by fixing the colorant of the jetted ink composition strongly improve the water-fastness of the finished image. Such mordants are e.g. (co)polymers containing cationic functions such as quaternary ammonium groups, fosfonium, sulfonium, and guadinium groups as disclosed in U.S. Pat. No. 4,371,582, U.S. Pat. No. 4,575,465, U.S. Pat. No. 4,649,064, GB 2210071, EP 423829, DE 3109931, U.S. Pat. No. 4,585,724, EP 295338, EP 306564, U.S. Pat. No. 5,314,747, EP 609930, WO 94/20304, WO 94/20305, WO 94/20306, EP 615853, EP 615884, and EP 618214. Also inorganic mordants have been described e.g. in U.S. Pat. No. 5,560,996, EP 704316 and EP 754560.
In a highly preferred embodiment, the ink receiving layer of the present invention also comprises a plasticizer such as ethylene glycol, dietylene glycol, propylene glycol, polyethylene glycol, glycerol monomethylether, glycerol monochlorohydrin, ethylene carbonate, propylene carbonate, tetrachlorophthalic anhydride, tetrabromophthalicanhydride, urea phosphate, triphenylphosphate, glycerolmonostearate, propylene glycol monostearate, tetramethylene sulfone, N-methyl-2-pyrrolidone, N-vinyl-2-pyrrolidone, and polymer latices with low Tg value such as polyethylacrylate or polymethylacrylate.
Surfactants may be incorporated in the ink-receptive layer of the present invention. They can be any of the cationic, anionic, amphoteric, and nonionic ones as described in JP-A 62-280068 (1987). Examples of the surfactants are N-alkylamino acid salts, alkylether carboxylic acid salts, acylated peptides, alkylsulfonic acid salts, alkylbenzene and alkylnaphthalene sulfonic acid salts, sulfosuccinic acid salts, olefin sulfonic acid salts, N-acylsulfonic acid salts, sulfonated oils, alkylsulfonic acid salts, alkylether sulfonic acid salts, alkylallylethersulfonic acid salts, alkylamidesulfonic acid salts, alkylphosphoric acid salts, alkyletherphosphoric acid salts, alkylallyletherphosphoric acid salts, alkyl and alkylallylpolyoxyethylene ethers, alkylallylformaldehyde condensed acid salts, blocked polymers having polyoxypropylene, polyoxyethylene polyoxypropylalkylethers, polyoxyethyleneether of glycolesters, polyoxyethyleneether of sorbitanesters, polyoxyethyleneether of sorbitolesters, polyethyleneglycol aliphatic acid esters, glycerol esters, sorbitane esters, propyleneglycol esters, sugaresters, fluoro C2-C10alkylcarboxylic acids, disodium N-perfluorooctanesulfonyl glutamate, sodium 3-(fluoro-C6-C11-alkyloxy)-1-C3-C4 alkyl sulfonates, N-[3-(perfluorooctanesulfonamide)-propyl]-N,N-dimethyl-N-carboxymethylene ammonium betaine, fluoro-C11-C20 alkylcarboxylic acids, perfluoro C7-C13 alkyl carboxylic acids, perfluorooctane sulfonic acid diethanolamide, Li, K and Na perfluoro C4-C12 alkyl sulfonates, N-propyl-N-(2-hydroxyethyl)perfluorooctane sulfonamide, perfluoro C6-C10alkylsulfonamide propyl sulfonylglycinates, bis-(N-perfluorooctylsulfonyl-N-ethanolaminoethyl)phosphonate, mono-perfluoro C6-C16 alkyl-ethyl phosphonates, and perfluoroalkylbetaine.
The receiving layer can further contain a so-called xe2x80x9cspacing agentxe2x80x9d which is used here as equivalent to xe2x80x9cmatting agentxe2x80x9d or xe2x80x9croughening agentxe2x80x9d. Said spacing agent is preferably hydrophilic. Useful examples are the different types of silica such as disclosed e.g. in U.S. Pat. No. 3,084,131, U.S. Pat. No. 4,892,591, U.S. Pat. No. 4,902,568, EP 379964, EP 423829, U.S. Pat. No. 5,165,973, EP 739747, EP 781666, EP 803374, EP 862510, Wo 97/20691; starch or modified starch particles such as disclosed in EP 445327, EP 480362, EP 524635; and the alkali-soluble beads of U.S. Pat. No. 4,906,560 and EP 0 584 407.
The ink receiving layer may consist of just a single layer or can be coated as a multiple layer pack, e.g. a double layer.
The polymer binders of the ink receiving layer are preferably not or only to a very small degree cross-linked so that the layer can be removed after flood UV exposure of the photopolymer layer simply by washing the material with cold or preferably warm water. Alternatively, the ink receiving layer may also be removed with the same processing liquid as used for developing the photopolymer layer.
The ink receiving layer can be covered by a protective foil, which is removed before ink-jetting the photomask. Useful foils include e.g. cellulose nitrate film, cellulose acetate film, polyvinylacetal film, polystyrene film, polyethylene terephthalate film, polycarbonate film, polyvinylchloride film or poly-xcex1-olefin films such as polyethylene or polypropylene film. The thickness of such organic resin film is preferably comprised between 5 and 35 xcexcm. In a most preferred embodiment of the present invention the protective foil is a polyethylene terephthalate film provided with a release layer such as a silicon coating or a peelable adhesive.
The image which is jetted to the ink receiving layer can be a screened image or a line pattern image or a combination of both. The use of the ink receiving layer described herein enables to obtain a photomask with a transmission optical density in the image areas of at least 3.0, preferably at least 3.5 and most preferably even higher than 3.9. Said transmission optical density is obtained at the same wavelength or wavelength range as the light used for the flood exposure of the photopolymer layer through the jetted photomask. When the flood exposure is not carried out with monochromatic light but with a wavelength range, then said transmission optical density is the average density within said wavelength range.
The material of the present invention also comprises a transparent barrier layer between the photopolymer layer and the ink receiving layer. This barrier layer reduces diffusion of monomers from the photopolymer layer to the ink receiving layer, so that the hydrophilic character of said ink receiving layer remains intact during storage. Preferred polymers for use as a barrier are polyamides or copolyamides, e.g. those obtained from bifunctional carbonic acids such as adipinic acid and diamines or {overscore (xcfx89)}-amino acids, lactams or derivates thereof, e.g. nylon 3, 4, 5, 6, 8, 11, 12, 13, 6.6, 6.10 or 6.13; metaxylene diamine; trimethyl-hexamethylene diamine;isophoron diamine; 4,4-diamine-dicylcohexylmethane; or the N-methylol or N-alkoxymethyl derivatives of these homo- and copolyamides. Highly preferred barrier polymers are hydroxyalkylcellulose (alkyl being preferably ethyl or propyl) and fully or partially hydrolysed polyvinyl alcohol) alkanecarboxylate esters such as poly(vinyl acetate) or poly(vinyl propionate) having an hydrolysis grade of 88 to 98%. Such hydrophilic barrier layers can be removed with water simultaneously while washing away the ink receiving layer. An example of another highly preferred barrier polymer, which dissolves very well in a typical processing liquid used for processing the photopolymer layer such as Nylosolv II (available from BASF), is poly(vinyl butyraldehyde).
The photopolymer layer of the material of the present invention comprises the compositions known in the art of flexographic printing. Typical compositions are photosensitive to UV light having a wavelength in the range from 300 to 420 nm. In addition to the positive-working systems such as those based on o-quinonediazide, the negative-working photopolymerisable and/or photocrosslinkable systems are preferred. Such systems typically comprise a monomer compound having at least one reactive vinyl group in its molecule. The reactive vinyl group in these compounds includes substituted or unsubstituted vinyl groups having polymerization reactivity, as exemplified by styrene type vinyl groups, acrylic acid type vinyl groups, methacrylic acid type vinyl groups, allyl type vinyl groups, and vinyl ether type vinyl groups, as well as ester vinyl groups as in vinyl acetate.
Examples of the polymerizable polymer precursor satisfying such conditions may include, for example monofunctional monomers such as styrene, methylstyrene, chlorostyrene, bromostyrene, methoxystyrene, dimethylaminostyrene, cyanostyrene, nitrostyrene, hydroxystyrene, aminostyrene, carboxystyrene, acrylic acid, methyl acrylate, ethyl acrylate, cyclohexyl acrylate, acrylamide, methacrylic acid, methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, phenyl methacrylate, cyclohexyl methacrylate, vinyl pyridine, N-vinylpyrrolidone, N-vinylimidazole, 2-vinylimidazole, N-methyl-2-vinylimidazole, propyl vinyl ether, butyl vinyl ether, isobutyl vinyl ether, beta-chloroethyl vinyl ether, phenyl vinyl ether, p-methylphenyl vinyl ether, and p-chlorophenyl vinyl ether; difunctional monomers such as divinylbenzene, distyryl oxalate, distyryl malonate, distyryl succinate, distyryl glutarate, distyryl adipate, distyryl maleate, distyryl fumarate, distyryl beta,betaxe2x80x2-dimethylglutarate, distyryl 2-bromoglutarate, distyryl alpha,alphaxe2x80x2-dichloroglutarate, distyryl terephthalate, oxalic acid di(ethyl acrylate),oxalic acid di(methyl ethyl acrylate), malonic acid di(ethyl acrylate), malonic acid di(methyl ethyl acrylate), succinic acid di(ethyl acrylate), glutaric acid di(ethyl acrylate), adipic acid di(ethyl acrylate), maleic acid di(diethyl acrylate), fumaric acid di(ethyl acrylate), beta,betaxe2x80x2-dimethylglutaric acid di(ethyl acrylate),ethylenediacrylamide, propylenediacrylamide, 1,4-phenylenediacrylamide, 1,4-phenylenebis(oxyethyl acrylate), 1,4-phenylenebis(oxymethyl ethyl acrylate), 1,4-bis(acryloyloxyethoxy)cyclohexane, 1,4-bis(acryloyloxymethylethoxy)cyclohexane, 1,4-bis(acryloyloxyethoxycarbamoyl)benzene, 1,4-bis(acryloyloxymethylethoxycarbamoyl)benzene, 1,4-bis (acryloyloxyethoxycarbamoyl)cyclohexane, bis(acryloyloxyethoxycarbamoylcyclohexyl)methane, oxalic acid di(ethyl methacrylate), oxalic acid di(methyl ethyl methacrylate), malonic acid di(ethyl methacrylate), malonic acid di(methyl ethyl methacrylate), succinic acid di(ethyl methacrylate), succinic acid di(methyl ethyl methacrylate), glutaric acid di(ethyl methacrylate), adipic acid di(ethyl methacrylate), maleic acid di(ethyl methacrylate), fumaric acid di(ethyl methacrylate), fumaric acid di(methyl ethyl methacrylate), beta,betaxe2x80x2-dimethylglutaric acid di(ethyl methacrylate), 1,4-phenylenebis(oxyethyl methacrylate), and 1,4-bis(methacryloyloxyethoxy)cyclohexane, acryloyloxyethoxyethyl vinyl ether; trifunctional monomers such as pentaerythritol triacrylate, pentaerythritol trimethacrylate, pentaerythritol tri(hydroxystyrene), cyanuric acid triacrylate, cyarnuric acid trimethacrylate, 1,1,1-trimethylolpropane triacrylate, 1,1,1-trimethylolpropane trimethacrylate, cyanuric acid tri(ethyl acrylate), 1,1,1-trimethylolpropane tri(ethylacrylate), dipentaerythritol hexaacrylate, cyanuric acid tri(ethyl vinyl ether), a condensate of a reaction product between 1,1,1-trimethylolpropane and three-fold moles of toluenediisocyanate, with hydroxyethyl acrylate, and a condensate of a reaction product pattern 1,1,1-trimethylolpropane and three-fold moles of hexanediisocyanate, with p-hydroxystyrene; and tetrafunctional monomers such as ethylenetetraacrylamide, and pylenetetraacrylamide. Two or more of these polymerizable polymer precursors can be used in combination.
The photopolymerization initiator used in the present invention may include, for example, carbonyl compounds, sulfur compounds, halogen compounds, photopolymerization initiators of redox type, and peroxide initiators sensitized with dye such as pyrilium. Specifically, the carbonyl compounds include diketones as exemplified by phenyl, 4,4xe2x80x2-dimethoxybenzyl, diacetyl, and camphorquinone; benzophenones as exemplified by 4,4xe2x80x2-bis(diethylamino)benzophenone, and 4,4xe2x80x2-dimethoxylbenzophenone; acetophenones as exemplified by acetophenone, and 4-methoxyacetophenone; benzoin alkyl ethers; thioxanthones as exemplified by 2-chlorothioxanthone, 2,4-dichlorothixanthone, 2,4-diethylthioxanthone, and thioxanthone-3-carboxylic acid- beta -methoxy ethyl ester; chalcones and styrylketones having a dialkylamino group; and cumarins as exemplified by 3, 3xe2x80x2-carbonylbis(7-methoxycumarin), and 3,3xe2x80x2-carbonylbis (7-diethylaminocumarin). The sulfur compounds include disulfides as exemplified by dibenzothiazolyl sulfide, and decylphenyl sulfide. The halogen compounds include, for example, carbon tetrabromide, quinolinesulfonyl chloride, and S-triazines having a trihalomethyl group. The photopolymerization initiators of the redox type include those used in combination of a trivalent iron compound (as exemplified by ferric ammonium citrate) with a peroxide, and those used in combination of a photoreducing coloring matter such as riboflavin or Methylene Blue with a reducing agent such as triethanolamine or ascorbic acid.
In the photopolymerization initiator described above (including the sensitizer), two or more photopolymerization initiators can also be used in combination to effect a more efficient photopolymerization reaction. Such combination of the photopolymerization initiators includes a combination of styryl ketones or chalcones having a dialkylamino group or cumarins, with S-triazines having a trihalomethyl group or camphorquinone.
The photopolymer layer may contain additional ingredients such as a binder or film-forming agent, a solid solvent, a surfactant, an anti-static agent, a plasticiser to improve the flexibility of the material, a stabiliser to prevent monomers from premature crosslinking during storage, and a dye to permit easy inspection of the plate so that correct exposure and registration can be determined.
The binder or film-forming agent usable in the photopolymer layer may include, for example, cellulose esters, such as nitrocellulose, cellulose phosphate, cellulose sulfate, cellulose acetate, cellulose propionate, cellulose butyrate, cellulose myrystate, cellulose palmitate, cellulose acetate propionate, and cellulose acetate butyrate; cellulose ethers, such as methyl cellulose, ethyl cellulose, propyl cellulose, and butyl cellulose; vinyl resins, such as polystyrene, polyvinyl chloride, polyvinyl acetate, polyvinyl butyral, polyvinyl acetal, polyvinyl alcohol, and polyvinyl pyrrolidone; copolymer resins, such as a styrene/butadiene copolymer, a styrene/acrylonitrile copolymer, a styrene/butadiene/acrylonitrile copolymer, and a vinyl chloride/vinyl acetate copolymer; acrylic resins, such as polymethyl methacrylate, polymethyl acrylate, polybutyl acrylate, polyacrylic acid, polymethacrylic acid, polyacrylamide, and polyacrylonitrile; polyesters, such as polyethylene terephthalate; polyarylate resins, such as poly(4,4xe2x80x2-isopropylidene, diphenylene-co-1, 4-cyclohexylenedimethylene carbonate), poly(ethylenedioxy-3, 3,-phenylene thiocarbonate), poly(4,4xe2x80x2-isopropylidene, diphenylene carbonate-co-terephthalate), poly(4,4xe2x80x2-isopropylidene,diphenylene carbonate), poly(4,4xe2x80x2-sec-butylidene,diphenylene carbonate), and poly(4,4xe2x80x2-isopropylidene,diphenylene carbonate-blockoxyethylene); plyamides; polyimides; epoxy resins; phenolic resins; polyolefins, such as polyethylene, polypropylene, and chlorinated polyethylene; and natural polymers, such as gelatin.
Highly preferred binders are elastomeric polymers such as polyalkadienes, vinylaromatic/alkadiene-copolymers and -blockcopolymers, alkadiene-acrylonitrile-copolymers, ethylene-propylene-copolymers, ethylene-propylene-alkadiene-copolymers, ethylene-(acrylic acid)-copolymers, alkadiene-(acrylic acid)-copolymers, alkadiene-acrylate-(acrylic acid)-copolymers and ethylene-((meth)acrylic acid)-(meth)acrylate-copolymers.
A specific photopolymer composition, which may be used in the material of the present invention, comprises an elastomer such as a rubber chosen for its specific hardness, e.g. polyisoprene, a monomer which undergoes radical-induced photopolymerisation, e.g. butanedioldiacrylate, and a photoinitiator such as benzildimethylketal which upon light absorption during the flood exposure step produces radicals that trigger the polymerisation reaction.
The base of the present material is preferably a dimensionally stable foil which is transparent in the wavelength range used for obtaining the so-called floor of the flexographic printing plate by back-exposure of the photopolymer layer. The same plastic resins as indicated above for the protective foil can be used. Poly(ethylene therephtalate) (PET) foil is a preferred example. Also metal sheets or metal-coated substrates are suitable as base of the material of the present invention. Typical examples are aluminum, steel or copper sheets. The base may be mechanically and/or chemically pre-treated or provided with an adhesive layer in order to ensure good adhesion to the photopolymer layer. Such an adhesive layer can consist, for example, of the conventional single- or two-component adhesives, e.g. those based on polyurethane. The base can further carry an antihalation layer below the photopolymer layer.

Flexographic printing plate precursor comprising an ink-jet receiving layer