A virtual preemption system for emergency and non-emergency vehicles to provide a priority safe route for an emergency vehicle, wherein the in-vehicle software can predict the predefined upcoming intersections on the priority route based on the heading of the emergency vehicle and the segment orientation. Therefore, the emergency vehicle knows the latitude/longitude of the upcoming intersections ahead of time to calculate a threshold start time associated with each one of the predefined upcoming intersections and transmit them to all vehicles approaching any of the predefined intersections on the priority route to start a safe transition of traffic signal phases associated with each one of these intersections just before the arrival of the emergency vehicle. Also to allow all vehicles on the priority route to slow down and pull over to the side of the road just before meeting the emergency vehicle.

Conventional Traffic Signal Preemption
Traffic signal preemption also called traffic signal prioritization is a type of system that allows the normal operation of traffic lights to be preempted. The most common use of these systems is to manipulate traffic signals in the path of an emergency vehicle, halting conflicting traffic and allowing the emergency vehicle right of way, to help reduce response times and enhance traffic safety. Signal preemption can also be used by light-rail and bus rapid transit systems to allow public transportation priority access through intersections, or by railroad systems at crossings to prevent collisions.
Traffic preemption devices are implemented in a variety of ways. They can be installed on road vehicles, integrated with train transportation network management systems, or operated by remote control from a fixed location, such as a fire station, or by a 9-1-1 dispatcher at an emergency call center. Traffic lights must be equipped to receive an activation signal to be controlled by any system intended for use in that area. A traffic signal not equipped to receive a traffic preemption signal will not recognize an activation, and will continue to operate in its normal cycle.
Vehicular devices can be switched on or off as needed, though in the case of emergency vehicles, they are frequently integrated with the vehicle's emergency warning lights. When activated, the traffic preemption device will cause properly equipped traffic lights in the path of the vehicle to cycle immediately, to grant right-of-way in the desired direction, after allowing for normal programmed time delays for signal changes and pedestrian crosswalks to clear.
Traffic signal preemption systems integrated with train transportation networks typically extend their control of traffic from the typical cross-arms and warning lights to one or more nearby traffic intersections, to prevent excessive road traffic from approaching the crossing, while also obtaining the right-of-way for road traffic that may be in the way to quickly clear the crossing. This also allows buses and hazmat vehicles in the USA to proceed through the intersection without stopping at the railroad tracks.
Fixed-location systems can vary widely, but a typical implementation is for a single traffic signal in front of or near a fire station to stop traffic and allow emergency vehicles to exit the station unimpeded. Alternatively, an entire corridor of traffic signals along a street may be operated from a fixed location, such as to allow fire apparatus to quickly respond through a crowded downtown area, or to allow an ambulance faster access when transporting a critical patient to a hospital in an area with dense traffic.
Traffic signal preemption systems sometimes include a method for communicating to the operator of the vehicle that requested the preemption (as well as other drivers) that a traffic signal is under control of a preemption device, by means of a notifier. This device is almost always an additional light located near the traffic signals. It may be a single light bulb visible to all, which flashes or stays on, or there may be a light aimed towards each direction from which traffic approaches the intersection. In the case of multiple notifier lights at a controllable intersection, they will either flash or stay on depending on the local configuration, to communicate to all drivers from which direction a preempting signal is being received. This informs regular drivers which direction may need to be cleared, and informs activating vehicle drivers if they have control of the light (especially important when more than one activating vehicle approaches the same intersection). A typical installation would provide a solid notifier to indicate that an activating vehicle is approaching from behind, while a flashing notifier would indicate the emergency vehicle is approaching laterally or oncoming. There are variations of notification methods in use, which may include one or more colored lights in varying configurations.
Events leading up to an activation and notification are not experienced by drivers on a daily basis, and driver education and awareness of these systems can play a role in how effective the systems are in speeding response times. Unusual circumstances can also occur which can confuse operators of vehicles with traffic preemption equipment who lack proper training. For example, on Jan. 2, 2005, a fire engine successfully preempted a traffic light at an intersection which included a light rail train (LRT) crossing in Hillsboro, Oreg., yet the fire engine was hit by an LRT at the crossing. A subsequent inquiry determined that the LRT operator was at fault. The accident occurred in the middle of a network of closely spaced signalized intersections where the signs and signals granted right-of-way to the LRT simultaneously, at ALL intersections. The LRT operator was viewing right-of-way indications from downstream signals and failed to realize that preemption had occurred at the nearest intersection. The fire engine, granted the green light before it arrived at the intersection, proceeded through while the LRT operator, failing to notice the unexpected signal to stop, ran into the fire engine and destroyed it.
Vehicular Device Types
Acoustic:
Some systems use an acoustic sensor linked to the preemption system. This can be used alone or in conjunction with other systems. Systems of this type override the traffic signal when a specific pattern of tweets or wails from the siren of an emergency vehicle is detected. Advantages of a system like this are that they are fairly inexpensive to integrate into existing traffic signals and the ability to use siren equipment already installed in emergency vehicles—thus dispensing with the need for special equipment. A major disadvantage is that sound waves can easily be reflected by buildings or other large vehicles present at or near an intersection, causing the "reflected" wave to trigger a preemption event in the wrong direction. Reflected waves can also create unnecessary collateral preemption events alongside streets near the emergency vehicle's route. Yet another disadvantage is that the acoustic sensors can sometimes be sensitive enough to activate the preemption in response to a siren from too far away, or from an unauthorized vehicle with a horn exceeding 120 dB (many truck and bus horns exceed this threshold at close range).
Line-of-Sight
A vehicle that uses a line-of-sight traffic signal preemption system is equipped with an emitter which typically sends a narrowly directed signal forward, towards traffic lights in front of the vehicle, to attempt to obtain right-of-way through controllable intersections before arriving at the intersection. These line-of-sight systems generally use an invisible infrared signal, or a visible strobe light which serves a dual purpose as an additional warning light. The emitter transmits visible flashes of light or invisible infrared pulses at a specified frequency. Traffic lights must be equipped with a compatible traffic signal preemption receiver to respond. Once the vehicle with the active emitter has passed the intersection, the receiving device no longer senses the emitter's signal, and normal operation resumes. Some systems can be implemented with varying frequencies assigned to specific types of uses, which would then allow an intersection's preemption equipment to differentiate between a fire engine and a bus sending a signal simultaneously, and then grant priority access first to the fire engine.
Drawbacks of line-of-sight systems include obstructions, lighting and atmospheric conditions, and undesired activations. Obstructions may be buildings on a curving road that block visual contact with a traffic signal until very close, or perhaps a large freight truck in front of a police car blocking the traffic signal from receiving the emitter's signal from the police car. Modifying the position of the receiver or even locating it separate from the traffic signal equipment can sometimes correct this problem. Direct sunlight into a receiver may prevent it from detecting an emitter, and severe atmospheric conditions, such as heavy rain or snow, may reduce the distance at which a line-of-sight system will function. Undesired activations may occur if an emitter's signal is picked up by many traffic lights along a stretch of road, all directed to change to red in that direction, prior to the activating vehicle turning off the road, or being parked without its emitter being deactivated.
Line of sight emitters can use IR diodes. They are pulsed with a low-priority signal (10 Hz) or a high-priority signal (14 Hz).
Localized Radio Signal
Radio-based traffic-preemption systems using a local, short-range radio signal in the 900 MHz band, can usually avoid the weaknesses of line-of-sight systems (2.4 GHz and optical). A radio-based system still uses a directional signal transmitted from an emitter, but being radio-based, its signal is not blocked by visual obstructions, lighting or weather conditions. Until recently, the major drawback of radio-based traffic signal preemption systems was the possibility of interference from other devices that may be using the same frequency at a given time and location. The advent of FHSS (Frequency Hopping Spread Spectrum) broadcasting has allowed radio-based systems to not only overcome this limitation, but also the aforementioned limitations associated with acoustic and line of sight (optical) systems. It was not until recently that cost effective GPS preemption systems were introduced, supplanting FHSS radio-based preemption as the preemption method of choice, particularly for cities that had experienced the myriad of issues associated with other (acoustic and optical) preemption systems.
Radio-based systems also began to offer some additional benefits—adjustable range and collision avoidance. The operating range was adjusted by varying the radio signal strength so that traffic lights could be activated only nearby (if desired), or at greater distances. The downside to these preemption systems (which also performed collision avoidance) was that they would display the direction of impending collisions, but not be able to effectively (or accurately) calculate the distance to collision by any method other than RF signal strength, which was only a rough estimate at best.
Global Positioning System
With the advent of widespread Global Positioning System (GPS) applications came the introduction of a GPS-based traffic preemption system, that could also do collision avoidance. Recently some GPS preemption systems (see first two external links below) have found a way to overcome the nagging problem that "blinds" many GPS systems: how to prevent the system from being "blinded" by the loss of a GPS signal. In dense cities with tall buildings, GPS receivers may have difficulty obtaining the four required GPS satellite signals, required for trilateration to determine location. If the vehicle systems are not designed with a backup "IMU" (Inertial Measurement Unit), lack of GPS availability may adversely affect the system's performance (see first external link below). Extremely heavy cloud cover or severe weather can also adversely impact the ability of the GPS receiver from obtaining the four required satellites.

Virtual preemption system for emergency vehicles


A process for forming an abrasion-resistant antistatic layer for an imaging element comprises: adjusting the pH of an aqueous composition of an electronically-conductive polymer to a pH of about 3 to about 10, and combining the pH-adjusted aqueous composition of the electronically-conductive polymer with an aqueous composition at a pH greater than 7 of a polyurethane film-forming binder having a tensile elongation to break of at least 50% and a Young""s modulus measured at 2% elongation of at least 50000 psi. The process further comprises applying the resulting coating composition to the imaging element, thereby forming an abrasion-resistant antistatic layer on the element. The antistatic layer coating composition of the present invention can be applied to a wide variety of imaging elements, including, for example, photographic, electrostatographic, photothermographic, migration, electrothermographic, dielectric recording and thermal-dye-transfer imaging elements.

This invention relates in general to imaging elements, such as photographic, electrostatographic, and thermal imaging elements comprising a support, an image forming layer and an abrasion resistant electrically-conductive layer. More specifically, this invention relates to a process for providing abrasion-resistant electrically-conductive layers containing an electronically-conducting polymer and a polymeric binder.
The problem of controlling static charge is well known in the field of photography. The accumulation of charge on film or paper surfaces leads to the attraction of dirt, which can produce physical defects. The discharge of accumulated charge during or after the application of the sensitized emulsion layer(s) can produce irregular fog patterns or xe2x80x9cstatic marksxe2x80x9d in the emulsion. The static problems have been aggravated by increases in the sensitivity of new emulsions, increases in coating machine speeds, and increases in post-coating drying efficiency. The charge generated during the coating process may accumulate during winding and unwinding operations, during transport through the coating machines and during finishing operations such as slitting and spooling. Static charge can also be generated during the use of the finished photographic film product. In an automatic camera, the winding of roll film in an out of the film cartridge, especially in a low relative humidity environment, can result in static charging. Similarly, high speed automated film processing can result in static charge generation. Sheet films (e.g., x-ray films) are especially susceptible to static charging during removal from light-tight packaging.
It is generally known that electrostatic charge can be dissipated effectively by incorporating one or more electrically-conductive xe2x80x9cantistaticxe2x80x9d layers into the film structure. Antistatic layers can be applied to one or to both sides of the film base as subbing layers either beneath or on the side opposite to the light-sensitive silver halide emulsion layers. An antistatic layer can alternatively be applied as an outer coated layer either over the emulsion layers or on the side of the film base opposite to the emulsion layers or both. For some applications, the antistatic agent can be incorporated into the emulsion layers. Alternatively, the antistatic agent can be directly incorporated into the film base itself.
A wide variety of electrically-conductive materials can be incorporated into antistatic layers to produce a wide range of conductivity. These can be divided into two broad groups: (i) ionic conductors and (ii) electronic conductors. In ionic conductors charge is transferred by the bulk diffusion of charged species through an electrolyte. Here the resistivity of the antistatic layer is dependent on temperature and humidity. Antistatic layers containing simple inorganic salts, alkali metal salts of surfactants, ionic conductive polymers, polymeric electrolytes containing alkali metal salts, and colloidal metal oxide sols (stabilized by metal salts), described previously in patent literature, fall in this category. However, many of the inorganic salts, polymeric electrolytes, and low molecular weight surfactants used are water-soluble and are leached out of the antistatic layers during photographic processing, resulting in a loss of antistatic function. The conductivity of antistatic layers employing an electronic conductor depends on electronic mobility rather than ionic mobility and is independent of humidity. Antistatic layers containing semiconductive metal halide salts, semiconductive metal oxide particles, etc., have been described previously. However, these antistatic layers typically contain a high volume percentage of electronically conducting materials which are often expensive and impart unfavorable physical characteristics, such as color or reduced transparency, increased brittleness and poor adhesion, to the antistatic layer.
Colloidal metal oxide sols which exhibit ionic conductivity when included in antistatic layers are often used in imaging elements. Typically, alkali metal salts or anionic surfactants are used to stabilize these sols. A thin antistatic layer consisting of a gelled network of colloidal metal oxide particles (e.g., silica, antimony pentoxide, alumina, titania, stannic oxide, zirconia) with an optional polymeric binder to improve adhesion to both the support and overlying emulsion layers has been disclosed in EP 250,154. An optional ambifunctional silane or titanate coupling agent can be added to the gelled network to improve adhesion to overlying emulsion layers, as taught in EP 301,827 and U.S. Pat. No. 5,204,219, along with an optional alkali metal orthosilicate to minimize loss of conductivity by the gelled network when it is overcoated with gelatin-containing layers, as disclosed in U.S. Pat. No. 5,236,818. Also, it has been pointed out, in U.S. Pat. Nos. 4,442,168 and 4,571,365, that coatings containing colloidal metal oxides (e.g., antimony pentoxide, alumina, tin oxide, indium oxide) and colloidal silica with an organopolysiloxane binder afford enhanced abrasion resistance as well as provide antistatic function
Antistatic layers containing electronic conductors such as conjugated conducting polymers, conducting carbon particles, crystalline semiconductor particles, amorphous semiconductive fibrils, and continuous semiconducting thin films can be used more effectively than ionic conductors to dissipate static charge since their electrical conductivity is independent of relative humidity and only slightly influenced by ambient temperature. Of the various types of electronic conductors, electrically conducting metal-containing particles, such as semiconducting metal oxides, are particularly effective when dispersed in suitable polymeric film-forming binders in combination with polymeric non-film-forming particles, as described in U.S. Pat. Nos. 5,340,676; 5,466,567; and 5,700,623. Binary metal oxides doped with appropriate donor heteroatoms or containing oxygen deficiencies have been disclosed in prior art to be useful in antistatic layers for photographic elements, for example, U.S. Pat. Nos. 4,275,103; 4,416,963; 4,495,276; 4,394,441; 4,418,141; 4,431,764; 4,495,276; 4,571,361; 4,999,276; 5,122,445; 5,294,525; 5,382,494; 5,459,021; 5,484,694 and others. Suitable claimed conductive metal oxides include: zinc oxide, titania, tin oxide, alumina, indium oxide, silica, magnesia, zirconia, barium oxide, molybdenum trioxide, tungsten trioxide, and vanadium pentoxide. Preferred doped conductive metal oxide granular particles include antimony-doped tin oxide, fluorine-doped tin oxide, aluminum-doped zinc oxide, and niobium-doped titania. Additional preferred conductive ternary metal oxides disclosed in U.S. Pat. No. 5,368,995 include zinc antimonate and indium antimonate. Other conductive metal-containing granular particles including metal borides, carbides, nitrides and silicides have been disclosed in Japanese Kokai No. JP 04-055,492.
One serious deficiency of such granular electronic conductor materials is that, especially in the case of semiconductive metal-containing particles, the particles usually are highly colored which render them unsuitable for use in coated layers on many photographic supports, particularly at high dry weight coverage. This deficiency can be overcome by using composite conductive particles consisting of a thin layer of conductive metal-containing particles deposited onto the surface of non-conducting transparent core particles whereby obtaining a lightly colored material with sufficient conductivity. For example, composite conductive particles consisting of two dimensional networks of fine antimony-doped tin oxide crystallites in association with amorphous silica deposited on the surface of much larger, non-conducting metal oxide particles (e.g., silica, titania, etc.) and a method for their preparation are disclosed in U.S. Pat. Nos. 5,350,448; 5,585,037 and 5,628,932. Alternatively, metal-containing conductive materials, including composite conducting particles, with high aspect ratio can be used to obtain conducting coatings with lighter color due to reduced dry weight coverage, as taught in, for example, U.S. Pat. Nos. 4,880,703 and 5,273,822). However, there is difficulty in the preparation of conductive coatings containing composite conductive particles, especially the ones with high aspect ratio, since the dispersion of these particles in an aqueous vehicle using conventional wet milling dispersion techniques and traditional steel or ceramic milling media often result in wear of the thin conducting layer from the core particle and/or reduction of the aspect ratio. Fragile composite conductive particles often cannot be dispersed effectively because of limitations on milling intensity and duration dictated by the need to minimize degradation of the morphology and electrical properties as well as the introduction of attrition-related contamination from the dispersion process.
Moreover, these metal containing semiconductive particles, can be quite abrasive and cause premature damage to finishing tools, such as, knives, slitters, perforators, etc. and create undesirable dirt and debris which can adhere to the imaging element causing defects.
The requirements for antistatic layers in silver halide photographic films are especially demanding because of the stringent optical requirements. Other types of imaging elements such as photographic papers and thermal imaging elements also frequently require the use of an antistatic layer. However, the requirements there are somewhat different. For example, for photographic paper, an additional criterion is the ability of the antistatic backing layer to receive printing (e.g., bar codes or other indicia containing useful information) typically administered by dot matrix or inkjet printers and to retain these prints or markings as the paper undergoes processing, viz., backmark retention.
Electrically-conductive layers are also commonly used in imaging elements for purposes other than providing static protection. Thus, for example, in electrostatographic imaging it is well known to utilize imaging elements comprising a support, an electrically-conductive layer that serves as an electrode, and a photoconductive layer that serves as the image-forming layer. Electrically-conductive agents utilized as antistatic agents in photographic silver halide imaging elements are often also useful in the electrode layer of electrostatographic imaging elements.
A particular embodiment of the present invention is intended for application in motion picture print films. Motion picture photographic films that are used as print films for movie theater projection have long used a carbon-black containing layer on the backside of the film, as described, for example, in U.S. Pat. Nos. 2,271,234 and 2,327,828. This backside layer provides both antihalation protection and antistatic properties. The carbon black is applied in an alkali-soluble binder that allows the layer to be removed by a process that involves soaking the film in alkali solution, scrubbing the backside layer and rinsing with water. This removal process, which takes place prior to image development, is both tedious and environmentally undesirable since large quantities of water are utilized in this film processing step. In addition, in order to facilitate removal during film processing, the carbon black-containing layer is not highly adherent to the photographic film support and may dislodge during various film manufacturing operations such as film slitting and film perforating. Carbon black debris generated during these operations may become lodged on the photographic emulsion and cause image defects during subsequent exposure and film processing.
After removal of the carbon black-containing layer the film""s antistatic properties are lost. Undesired static charge build-up can then occur on processed motion picture print film when transported through projectors or on rewind equipment. These high static charges can attract dirt particles to the film surface. Once on the film surface, these particles can create abrasion or scratches or, if sufficiently large, the dirt particles may be seen on the projected film image.
These conventional carbon black-containing backing layers also typically contain a lubricant or are overcoated with a lubricant in order to improve conveyance during manufacturing operations or image exposures (i.e., printing). After processing, the lubricant is removed along with the carbon black, and, therefore, processed print films has a high coefficient of friction on the backside of the film which is undesirable for good transport and film durability during repeated cycles through a movie theater projector.
A photographic element having a conductive layer containing semiconductive tin oxide or indium oxide particles on the opposite side of the support from the silver halide sensitized emulsion layers with a polymer-containing intermediate backing layer overlying the conductive layer and an additional protective layer overlying the backing layer is disclosed in U.S. Pat. No. 5,026,622. The outermost protective layer includes gelatin, a matting agent, a fluorine-containing anionic surfactant, and dioctyl sulfosuccinate. Another conductive three-layer backing having an antistatic layer containing granular semiconductive metal oxide particles; an intermediate backing layer containing a latex of a water-insoluble polymer, matting agent, polystyrenesulfonate sodium salt, and gelatin; and an outermost protective layer containing at least one hydrophobic polymer such as a polyester or polyurethane, fluorine-containing surfactant(s), matting agent(s), and an optional slipping aid is described in U.S. Pat. No. 5,219,718. Further, a three-layer backing having an antistatic layer including conductive metal oxide granular particles or a conductive polymer and a hydrophobic polymer latex, gelatin, and an optional hardener is overcoated with an intermediate backing layer containing gelatin, a hydrophobic polymer latex, a matting agent, and backing dyes that is simultaneously overcoated with a protective layer comprising a fluorine-containing surfactant, a matting agent, gelatin, and optionally, a polymer latex is taught in U.S. Pat. No. 5,254,448. Photographic elements including such multi-layer backings were disclosed to retain antistatic properties after processing, exhibit acceptable transport performance against Teflon coated surfaces, and have good xe2x80x9canti-flawxe2x80x9d properties.
The use of small ( less than 15 nm) antimony-doped tin oxide particles having a high ( greater than 8 atom %) antimony dopant level and a small crystallite size ( less than 100 xc3x85) in abrasion resistant conductive backing layers is claimed in U.S. Pat. No. 5,484,694. A multi-element curl control layer on the backside of the support wherein the conductive layer typically is located closest to the support, with an overlying intermediate layer containing binder and antihalation dyes, and an outermost protective layer containing binder, matte, and surfactant is also claimed.
Simplified two-layer conductive backings are taught in U.S. Pat. Nos. 5,366,855; 5,382,494; 5,453,350; and 5,514,528. An antistatic layer containing colloidal silver-doped vanadium pentoxide and a vinylidene chloride-containing latex binder or a polyesterionomer dispersion coated on the opposite side of the support from the silver halide emulsion layer and subsequently overcoated with a protective layer including a coalesced layer containing both film-forming and non-film-forming colloidal polymeric particles, optional cross-linking agents, matting agents, and lubricating agents is disclosed in U.S. Pat. No. 5,366,855. Such a protective layer was also disclosed to function as an impermeable barrier to processing solutions, to resist blocking, to provide good scratch and abrasion resistance, and to exhibit excellent lubricity. However, the addition of hard polymeric particles, such as poly(methyl methacrylate), to a film-forming polymer can produce brittleness in a coated layer. A photographic element containing an aqueous-coated antistatic layer containing conductive fine particles such as metal oxide particles, a butyl acrylate-containing terpolymer latex, and optionally, a hardening agent and a surfactant that is overcoated with a solvent-coated, transparent magnetic recording layer containing preferably nitrocellulose or diacetyl cellulose as the binder and carnauba wax as a lubricant is taught in U.S. Pat. Nos. 5,382,494 and 5,453,350. Similarly, an antistatic layer containing conductive metal oxide granular particles in a hydrophilic binder applied as an aqueous or solvent dispersion and overcoated with a cellulose ester layer optionally containing ferromagnetic particles is described in U.S. Pat. No. 5,514,528. A separate lubricating overcoat layer can be optionally applied on top of the cellulose ester layer.
The inclusion of lubricant particles of a specified size, especially those having a fluorine-containing polymer, in a protective surface or backing layer containing a dispersing aid or stabilizer, a hydrophilic or resin-type binder and optionally, crosslinking agents, matting agents, antistatic agents, colloidal inorganic particles, and various other additives is described in U.S. Pat. No. 5,529,891. Photographic elements incorporating such protective layers were disclosed to exhibit improved surface scratch and abrasion resistance as evaluated on a Taber Abrader.
Another method to improve the slipperiness and scratch resistance of the back surface of a photographic element is described in U.S. Pat. No. 5,565,311. The incorporation of slipping agents containing compounds having both a long-chain aliphatic hydrocarbon moiety and a polyether moiety as a solution, emulsion or dispersion preferably in a backing protective layer containing a film-forming binder and an optional crosslinking agent overlying an antistatic layer is reported to provide improved slipperiness and scratch resistance and reduce the number of coated layers in the backing. The addition of a matting agent can improve scratch resistance as well as minimize blocking of the emulsion surface layer or emulsion-side primer layer by the backing layer. Further, the inclusion of an antistatic agent, such as conductive metal oxide particles, in a backing protective layer containing slipping and matting agents and optionally, nonionic, anionic, cationic, or betaine-type fluorine-containing surfactants is disclosed in U.S. Pat. No. 5,565,311.
An electrically-conductive single layer backing having a combination of electrically-conductive fine particles, such as conductive metal oxide granular particles, and particular gelatin-coated water-insoluble polymer particles is disclosed in European Patent Application No. 749,040 to provide both a high degree of conductivity at low volumetric concentrations of conductive particles and a high degree of abrasion resistance. The use of a combination of insoluble polymer particles and a hydrophilic colloid with conductive metal oxide fine particles to prepare electrically-conductive layers that require lower volume fractions of conductive particles than conductive layers prepared using only a hydrophilic colloid as binder is disclosed in U.S. Pat. No. 5,340,676. A similar beneficial result is disclosed in U.S. Pat. No. 5,466,567 for electrically-conductive layers in which a combination of a hydrophilic colloid and pre-crosslinked gelatin particles is used as the binder for the electroconductive fine granular particles. However, the abrasion resistance of such gelatin-containing layers is unsuitable, particularly for motion picture applications.
Electrically-conductive backing layers for use in thermally processable imaging elements are described in U.S. Pat. Nos. 5,310,640 and 5,547,821. As described in U.S. Pat. No. 4,828,971, backing layers useful for thermally processable imaging elements must provide adequate conveyance properties, resistance to deformation during thermal processing, satisfactory adhesion to the support, freedom from cracking and marking, reduced electrostatic charging effects, and exhibit no sensitometric effects. The use of electrically-conductive backings and protective overcoat layers for thermally processable imaging elements is described in U.S. Pat. No. 5,310,640. In one preferred embodiment, a protective layer containing polymethylmethacrylate as binder and a polymeric matting agent is positioned overlying a conductive layer containing silver-doped vanadium pentoxide dispersed in a polymeric binder. The use of a single-layer conductive backing having antimony-doped tin oxide granular particles, a matting agent, and a polymeric film-forming binder is taught in U.S. Pat. No. 5,547,821. Another preferred embodiment teaches the use of antimony-doped tin oxide granular particles in a conductive overcoat layer overlying the imaging layer. The reported Taber abrasion test results suggest that the relative level of abrasion resistance for the single-layer backings is inferior to that for the overcoated conductive backing layer described in U.S. Pat. No. 5,310,640. Also, surface scattering and haze is higher for single-layer conductive backings than for overcoated conductive backings. Further, from the surface resistivity and dusting data reported in U.S. Pat. No. 5,547,821, it can be concluded that it is particularly difficult to simultaneously obtain low dusting and high conductivity with single-layer conductive backings containing a polyurethane binder and granular electroconductive particles.
An electrically-conductive single-layer backing for the reverse side of a laser dye-ablative imaging element comprising electrically-conductive metal-containing particles, such as antimony-doped tin oxide particles, a polymeric binder, such as gelatin or a vinylidene chloride-based terpolymer latex, a matting agent, a coating aid, and an optional hardener is described in U.S. Pat. No. 5,529,884. Surface resistivity values of xcx9c9 log ohms/square (109ohms/square) for the conductive backings were measured before and after the ablation process and exhibited virtually no change. No test data for abrasion or scratch resistance of the backing layers was reported.
An abrasion-resistant protective overcoat including a polyurethane binder with specific physical properties, a lubricant, a matting agent, and a crosslinking agent overlying a conductive backing layer is described in U.S. Pat. No. 5,679,505 for motion picture print films; the abrasion-resistant protective overcoat contains a crosslinked polyurethane binder and, thus, provides a nonperneable chemical barrier for antistatic layers containing, preferably, colloidal vanadium pentoxide antistatic agent which is known to degrade in contact with photographic processing solutions. Although U.S. Pat. No. 5,679,505 can provide certain advantages over conventional carbon black containing backing layers, the use of a crosslinking agent in the topcoat (without which the conductivity of the preferred antistatic layer will be jeopardized) poses some manufacturing concerns: crosslinked polyurethanes of U.S. Pat. No. 5,679,505 may impose additional constraints on the composition and pot-life of the coating solutions as well as other manufacturing parameters; from a health and safety standpoint, some crosslinking agents may require special handling and disposal procedures; removal of a crosslinked polyurethane layer can hinder recycling of the support. Moreover, U.S. Pat. No. 5,679,505 teaches a two-layer system comprising an antistatic layer and a protective topcoat, the practice of which is inherently more complex than a single layer system: any incompatibility between the two layers can cause imperfections, such as repellencies, particulate formation, or other interaction products at the interface and adhesion failure, leading to unacceptable product quality and lower yield.
As indicated above, the prior art on electrically-conductive layers in imaging elements is extensive and a very wide variety of different materials have been proposed for use as the electrically-conductive agent. There is still, however, a critical need in the art for improved electrically-conductive layers which are useful in a wide variety of imaging elements, which can be manufactured at reasonable cost, which are environmentally benign, which are durable and abrasion-resistant, which are effective at low coverage, which are adaptable to use with transparent imaging elements, which do not exhibit adverse sensitometric or photographic effects, and which maintain electrical conductivity even after coming in contact with processing solutions (since it has been observed in industry that loss of electrical conductivity after processing may increase dirt attraction to processed films which, when printed, may cause undesirable defects on the prints).
In addition to controlling static charging, auxiliary layers applied to photographic elements also provide many other functions. These include providing resistance to abrasion, curl, solvent attack, halation and providing reduced friction for transport. One additional feature that an auxiliary layer must provide when the layer serves as the outermost layer is resistance to the deposition of material onto the element upon photographic processing. Such material can impact the physical performance of the element in a variety of ways. For example, large deposits of material on a photographic film lead to readily visible defects on photographic prints or are visible upon display of motion picture film. Alternatively, post-processing debris can influence the ability of a processed film to be overcoated with an ultraviolet curable abrasion resistant layer, as is done in professional photographic processing laboratories employing materials such as PhotoGard(trademark), available from 3M.
It is toward the objective of providing improved electrically-conductive layers that more effectively meet the diverse needs of imaging elementsxe2x80x94especially of silver halide photographic films but also of a wide range of other imaging elementsxe2x80x94than those of the prior art that the present invention is directed. An additional objective of the present invention as an outermost backing layer is to provide scratch and abrasion resistance to the imaging elements through the proper choice of a binder with optimum mechanical properties.
Electrically conducting polymers have recently received attention from various industries because of their electronic conductivity. Although many of these polymers are highly colored and are less suited for photographic applications, some of these electrically conducting polymers, in particular, electronically-conducting polymers such as substituted or unsubstituted pyrrole-containing polymers, described in U.S. Pat. Nos. 5,665,498 and 5,674,654, substituted or unsubstituted thiophene-containing polymers, described in U.S. Pat. Nos. 5,300,575; 5,312,681; 5,354,613; 5,370,981; 5,372,924; 5,391,472; 5,403,467; 5,443,944; 5,575,898; 4,987,042 and 4,731,408, and substituted or unsubstituted aniline-containing polymers, described in U.S. Pat. Nos. 5,716,550 and 5,093,439 are transparent and not prohibitively colored, at least when coated in thin layers at moderate coverage. Because of their electronic rather than ionic conductivity, these polymers are conducting even at low humidity and, moreover, can retain sufficient conductivity even after wet chemical processing to provide what is known in the art as xe2x80x9cprocess-survivingxe2x80x9d antistatic characteristics to the photographic support to which they are applied. Unlike metal-containing semiconducting particulate antistatic materials, e.g., antimony-doped tin oxide, the aforementioned electrically conducting polymers are less abrasive, environmentally more acceptable because of the absence of heavy metals, and, in general, less expensive.
It has been reported, however, in U.S. Pat. No. 5,354,613 that a thiophene-containing polymer layer has low mechanical strength and canin the absence of an overcoat, be easily damaged. Protective layers such as poly(methyl methacrylate) can be applied on such thiophene-containing antistatic layers but, because they are typically are coated out of organic solvents, are not especially desirable. Moreover, these protective layers may be too brittle to be an external layer for certain applications, such as motion picture print films, as illustrated in U.S. Pat. No. 5,679,505. Use of aqueous polymer dispersions of, for example, vinylidene chloride, styrene, acrylonitrile, alkyl acrylates and alkyl methacrylates) has been taught in U.S. Pat. No. 5,312,681 as an overlying barrier layer for thiophene-containing antistat layers. A hydrophilic colloid-containing layer is adhered to the overlying barrier layer, but, again, the physical properties of these barrier layers may preclude their use as an outermost layer in certain applications. The use of a thiophene-containing outermost antistat layer has also been taught in U.S. Pat. No. 5,354,613, wherein a hydrophobic polymer with high glass transition temperature is incorporated in the antistat layer. These hydrophobic polymers, however, reportedly may require organic solvent(s) and/or swelling agent(s) xe2x80x9cin an amount of at least 50% by weightxe2x80x9d of the polythiophene to ensure coherence and film forming capability.
Additionally, these electronically-conducting polymers are usually complexed with an acid such as polystyrenesulfonic acid which acts as a p-type dopant to greatly enhance the conductivity of the polymer, as discussed in, for example, xe2x80x9cPoly(3,4-ethylenedioxythiophene) and its derivatives: past, present, and futurexe2x80x9d, B. Greonendaal, et. al., Advanced Materials, Vol. 12, No. 7,2000. The presence of the acid dopant causes aqueous dispersions of the electronically-conducting polymers to be acidic, with pH value as low as 1-2. A vast majority of polymeric binders, particularly polyurethane latices, on the other hand, are marketed as basic dispersions, with pH values xcx9c8, and are unstable at low pH. For example, many of the polyurethanes disclosed in Table 1 of U.S. Pat. No. 5,679,505 as suitable for use as protective overcoats for motion picture films, are of pH xcx9c8, as illustrated in the Table 1 below:
Such a mismatch of pH between the electronically-conducting polymers and a majority of useful polyurethane dispersions poses a major challenge in combining the two into a stable, particulate-free aqueous formulation that can be coated into a homogeneous, transparent single layer on photographic supports.
As will be demonstrated hereinbelow, the present invention provides a method to form single outermost layers for an imaging element, providing humidity independent, process-surviving antistatic characteristics as well as resistance to abrasion and scratching, without necessitating any crosslinking agent or a protective overcoat. Such an external layer, as per the present invention, can be coated from an aqueous composition comprising a properly pH adjusted electronically-conducting polymer, and a polyurethane binder dispersion of pH greater than 7, wherein the polyurethane is of a tensile elongation to break of at least 50% and a Young""s modulus measured at 2% elongation of at least 50000 psi.
The present invention is directed to a process for forming an abrasion-resistant antistatic layer for an imaging element, wherein the process comprises: adjusting the pH of an aqueous composition of an electronically-conductive polymer to a pH of about 3 to about 10, and combining the pH-adjusted aqueous composition of the electronically-conductive polymer with an aqueous composition at a pH greater than 7 of a polyurethane film-forming binder having a tensile elongation to break of at least 50% and a Young""s modulus measured at 2% elongation of at least 50000 psi. The process further comprises applying the resulting coating composition to the imaging element, thereby forming an abrasion-resistant antistatic layer on the element.
The antistatic layer coating composition of the present invention can be applied to a wide variety of imaging elements, including, for example, photographic, electrostatographic, photothermographic, migration, electrothermographic, dielectric recording and thermal-dye-transfer imaging elements.
Photographic elements provided with an antistatic layer in accordance with the present invention can differ widely in structure and composition, including, for example, the type of support, the number and composition of the image-forming layers, and the auxiliary layers that may be included. In particular, the photographic elements can be still films, motion picture films, x-ray films, graphic arts films, paper prints or microfiche, especially CRT-exposed autoreversal and computer output microfiche films. They can be black-and-white elements, color elements adapted for use in a negative-positive process, or color elements adapted for use in a reversal process.
Photographic elements can comprise any of a wide variety of supports. Typical supports include cellulose nitrate film, cellulose acetate film, poly(vinyl acetal) film, polystyrene film, poly(ethylene terephthalate) film, poly(ethylene naphthalate) film, polycarbonate film, polyethylene films, polypropylene films, glass, metal, paper (both natural and synthetic), polymer-coated paper, and the like. The image-forming layer or layers of the element typically comprise a radiation-sensitive agent, e.g., silver halide, dispersed in a hydrophilic water-permeable colloid. Suitable hydrophilic vehicles include both naturally-occurring substances such as proteins, for example, gelatin, gelatin derivatives, cellulose derivatives, polysaccharides such as dextran, gum arabic, and the like, and synthetic polymeric substances such as water-soluble polyvinyl compounds like poly(vinylpyrrolidone), acrylamide polymers, and the like. A particularly common example of an image-forming layer is a gelatin-silver halide emulsion layer.
In order to promote adhesion between the conductive backing of this invention and the support, the support can be surface-treated by various processes including corona discharge, glow discharge, UV exposure, flame treatment, electron-beam treatment, as described in U.S. Pat. No. 5,718,995, or treatment with adhesion-promoting agents, including dichloro- and trichloro-acetic acid, phenol derivatives such as resorcinol and p-chloro-m-cresol, solvent washing or overcoated with adhesion promoting primer or tie layers containing polymers such as vinylidene chloride-containing copolymers, butadiene-based copolymers, glycidyl acrylate or methacrylate-containing copolymers, maleic anhydride-containing copolymers, condensation polymers such as polyesters, polyamides, polyurethanes, polycarbonates, mixtures and blends thereof, and the like.
Further details with respect to the composition and function of a wide variety of different imaging elements are provided in U.S. Pat. No. 5,300,676 and references described therein, the disclosures of which are incorporated herein by reference. All of the imaging processes described in the ""676 patent, as well as many others, have in common the use of an electrically-conductive layer as an electrode or as an antistatic layer. The requirements for a useful electrically-conductive layer in an imaging environment are extremely demanding and thus the art has long sought to develop improved electrically-conductive layers exhibiting the necessary combination of physical, optical and chemical properties.
The antistatic coating compositions of the invention can be applied to the aforementioned film or paper supports by any of a variety of well-known coating methods. Handcoating techniques include using a coating rod or knife or a doctor blade. Machine coating methods include skim pan/air knife coating, roller coating, gravure coating, curtain coating, bead coating or slide coating. Alternatively, the antistatic layer or layers of the present invention can be applied to a single or multilayered polymeric web by any of the aforementioned methods, and the said polymeric web can subsequently be laminated (either directly or after stretching) to a film or paper support of an imaging element (such as those discussed above) by extrusion, calendering or any other suitable method.
The antistatic layer or layers of the present invention can be applied to the support in various configurations depending upon the requirements of the specific application. As an abrasion resistant layer, the antistatic layer of the present invention is preferred to be an outermost layer, preferably on the side of the support opposite to the imaging layer. However, the layer of the present invention can be placed at any other location within the imaging element, to fulfill other objectives. In the case of photographic elements, an antistatic layer can be applied to a polyester film base during the support manufacturing process after orientation of the cast resin on top of a polymeric undercoat layer. The antistatic layer can be applied as a subbing layer under the sensitized emulsion, on the side of the support opposite the emulsion or on both sides of the support. Alternatively, it can be applied over the imaging layers on either or both sides of the support, particularly for thermally-processed imaging elements. When the antistatic layer is applied as a subbing layer under the sensitized emulsion, it is not necessary to apply any intermediate layers such as barrier layers or adhesion promoting layers between it and the sensitized emulsion, although they can optionally be present. Alternatively, the antistatic layer can be applied as part of a multi-component curl control layer on the side of the support opposite to the sensitized emulsion. The present invention can be used in conjunction with an intermediate layer, containing primarily binder and antihalation dyes, that functions as an antihalation layer. Alternatively, these could be combined into a single layer. Detailed description of antihalation layers can be found in U.S. Pat. No. 5,679,505 and references therein, the disclosures of which are incorporated herein by reference.
Typically, the antistatic layer may be used in a single or multilayer backing layer which is applied to the side of the support opposite to the sensitized emulsion. Such backing layers, which typically provide friction control and scratch, abrasion, and blocking resistance to imaging elements are commonly used, for example, in films for consumer imaging, motion picture imaging, business imaging, and others. In the case of backing layer applications, the antistatic layer can optionally be overcoated with an additional polymeric topcoat, such as a lubricant layer, and/or an alkali-removable carbon black-containing layer, as described in U.S. Pat. Nos. 2,271,234 and 2,327,828, for antihalation and camera-transport properties, and/or a transparent magnetic recording layer for information exchange, for example, and/or any other layer(s) for other functions.
In the case of photographic elements for direct or indirect x-ray applications, the antistatic layer can be applied as a subbing layer on either side or both sides of the film support. In one type of photographic element, the antistatic subbing layer is applied to only one side of the film support and the sensitized emulsion coated on both sides of the film support. Another type of photographic element contains a sensitized emulsion on only one side of the support and a pelloid containing gelatin on the opposite side of the support. An antistatic layer can be applied under the sensitized emulsion or, preferably, the pelloid. Additional optional layers can be present. In another photographic element for x-ray applications, an antistatic subbing layer can be applied either under or over a gelatin subbing layer containing an antihalation dye or pigment. Alternatively, both antihalation and antistatic functions can be combined in a single layer containing conductive particles, antihalation dye, and a binder. This hybrid layer can be coated on one side of a film support under the sensitized emulsion.
It is also contemplated that the electrically-conductive layer described herein can be used in imaging elements in which a relatively transparent layer containing magnetic particles dispersed in a binder is included. The electrically-conductive layer of this invention functions well in such a combination and gives excellent photographic results. Transparent magnetic layers are well known and are described, for example, in U.S. Pat. No. 4,990,276, European Pat. 459,349, and Research Disclosure, Item 34390, November, 1992, the disclosures of which are incorporated herein by reference. As disclosed in these publications, the magnetic particles can be of any type available such as ferro- and ferri-magnetic oxides, complex oxides with other metals, ferrites, etc. and can assume known particulate shapes and sizes, may contain dopants, and may exhibit the pH values known in the art. The particles may be shell coated and may be applied over the range of typical laydown.
Imaging elements incorporating conductive layers of this invention that are useful for other specific applications such as color negative films, color reversal films, black-and-white films, color and black-and-white papers, electrophotographic media, thermal dye transfer recording media etc., can also be prepared by the procedures described hereinabove. Other addenda, such as polymer latices to improve dimensional stability, hardeners or crosslinking agents, and various other conventional additives can be present optionally in any or all of the layers of the various aforementioned imaging elements.
The antistatic layer of the present invention comprises an electronically-conducting polymer, as component A and a polyurethane binder with a tensile elongation to break of at least 50% and a Young""s modulus measured at 2% elongation of at least 50000 psi as component B, and can be coated out of an aqueous system on a suitable imaging element. It is crucial to adjust the pH of component A to a value of between 3 and 10, and preferably between 5 and 9, before adding any other ingredient to the coating composition, in order to prevent flocculation or other undesirable interaction. Suitable agents for pH adjustment are ammonium hydroxides, alkali metal hydroxides, and alkylamines, for example, ammonium hydroxide, sodium hydroxide, potassium hydroxide, tetraethylammonium hydroxide, and triethylamine, the last-named reagent being especially preferred. Component B in the coating composition typically does not require any prior pH adjustment and can be added to the coating composition directly.
Component A can be chosen from any or a combination of electronically-conducting polymers, such as substituted or unsubstituted pyrrole-containing polymers, as mentioned in U.S. Pat. Nos. 5,665,498 and 5,674,654, substituted or unsubstituted thiophene-containing polymers, as mentioned in U.S. Pat. Nos. 5,300,575; 5,312,681; 5,354,613; 5,370,981; 5,372,924; 5,391,472; 5,403,467; 5,443,944; 5,575,898; 4,987,042 and 4,731,408, and substituted or unsubstituted aniline-containing polymers, as mentioned in U.S. Pat. Nos. 5,716,550 and 5,093,439. The electronically conducting polymer may be soluble or dispersible in organic solvents or water or mixtures thereof For environmental reasons, aqueous systems are preferred. Polyanions used in the synthesis of these electronically conducting polymers are the anions of polymeric carboxylic acids such as polyacrylic acids, polymethacrylic acids or polymaleic acids and polymeric sulfonic acids such as polystyrenesulfonic acids and polyvinylsulfonic acids, the polymeric sulfonic acids being those preferred for this invention. These polycarboxylic and polysulfonic acids may also be copolymers of vinylcarboxylic and vinylsulfonic acids with other polymerizable monomers such as the esters of acrylic acid and styrene. The molecular weight of the polyacids providing the polyanions preferably is 1,000 to 2,000,000, particularly preferably 2,000 to 500,000. The polyacids or their alkali salts are commonly available, e.g., polystyrenesulfonic acids and polyacrylic acids, or they may be produced based on known methods. Instead of the free acids required for the formation of the electrically conducting polymers and polyanions, mixtures of alkali salts of polyacids and appropriate amounts of monoacids may also be used. Preferred electrically conducting polymers for the present invention include polypyrrole styrene sulfonate (referred to as polypyrrole/poly (styrene sulfonic acid) in U.S. Pat. No. 5,674,654), 3,4-dialkoxy substituted polypyrrole styrene sulfonate, and 3,4-dialkoxy substituted polythiophene styrene sulfonate. The most preferred substituted electrically conductive polymers include poly(3,4-ethylene dioxypyrrole styrene sulfonate) and poly(3,4-ethylene dioxythiophene styrene sulfonate).
Component B is a polyurethane preferably an aliphatic polyurethane chosen for its excellent thermal and UV stability and freedom from yellowing. The polyurethanes, suitable for the present invention, are those having a tensile elongation to break of at least 50% and a Young""s modulus measured at an elongation of 2% of at least 50000 psi. As taught in U.S. Pat. No. 5,679,505, these physical property requirements insure that the antistatic layer is hard yet tough enough to simultaneously provide excellent abrasion resistance and outstanding resiliency, in applications such as motion picture print films which need to survive hundreds of cycles through motion picture projectors. Examples and details of these specific polyurethanes are mentioned in U.S. Pat. No. 5,679,505 and references therein, the disclosures of which are incorporated herein by reference. These polyurethanes are typically available as dispersions having a pH xcx9c8.
Use of polyurethanes in a polythiophene-containing antistatic layer has been disclosed in U.S. Pat. No. 5,300,575. However, the mechanical properties of such polyurethanes have not been addressed in that patent. As amply demonstrated in U.S. Pat. No. 5,679,505, not all polyurethanes possess the mechanical properties necessary to provide the level of wear, abrasion and scratch protection as required by applications such as motion picture print films. Use of polyurethane as a third component in antistatic primers containing polythiophene and sulfonated polyesters has been disclosed in U.S. Pat. No. 5,391,472. However, as before, no consideration of the mechanical properties of the polyurethane is disclosed in that patent. Moreover, as demonstrated in the U.S. Pat. No. 6,096,491, not all polyurethanes are compatible with electrically conducting polymers. Use of polyurethane with specific mechanical properties for application in motion picture print films have been taught in U.S. Pat. No. 5,679,505. However, as mentioned earlier, ""505 teaches, in contrast to the present invention, a two-layer system, with the polyurethane topcoat comprising a crosslinking agent. The results obtained in accordance with the present invention, manifested as a single abrasion-resistant antistatic layer containing two components, component A being an electronically conducting polymer and component B being a polyurethane with a tensile elongation to break of at least 50% and a Young""s modulus measured at an elongation of 2% of at least 50000 psi, with or without any crosslinking agent, are neither expected from nor anticipated by the disclosures of the cited prior art.
The polyurethane binder can be optionally crosslinked or hardened by adding a crosslinking agent that reacts with functional groups present in the polyurethane, such as carboxyl groups. Crosslinking agents such as polyaziridines, carbodiimides, epoxies, and the like are suitable for this purpose. The crosslinking agent can be used at about 0.5 to about 30 weight % based on the polyurethane. However, a crosslinking agent concentration of 2 to 12 weight % based on the polyurethane is preferred.
A suitable lubricating agent can be included in the layer of this invention to achieve a coefficient of friction that ensures good transport characteristics during manufacturing and customer handling. The desired values of the coefficient of friction and examples of suitable lubricating agents are disclosed in the previously mentioned U.S. Pat. No. 5,679,505.
The relative amount of the electronically-conducting polymer (component A) can vary from 0.1-99 weight % and the relative amount of the polyurethane binder (component B) can vary from 99.9-1 weight % in the dried layer. In a preferred embodiment of this invention as an outermost abrasion resistant layer, the amount of electrically-conducting polymer should be 2-70 weight %, and the polyurethane binder should be 98-30 weight % in the dried layer. As will be demonstrated hereinbelow through working examples, the use of a crosslinking agent in the layers of the present invention is optional.
In another embodiment of the present invention, a third polymeric component may be incorporated in the antistatic layer for improved dispersion quality (of the electrically conducting polymer), electrical conductivity and physical properties wherein this third component may comprise a sulfonated polystyrene and/or a copolymer of sulfonated styrene-maleic anhydride and/or a polyester ionomer or the like known in the art for their aforementioned properties. The relative amount of this third component may vary from 0-30 weight % but preferably between 5-20 weight % in the dried layer. The coating composition is coated at a dry weight coverage of between 5 mg/m2 and 10,000 mg/m2, but preferably between 10-2000 mg/m2.
In addition to binders and solvents, other components that are well known in the photographic art may also be present in the electrically-conductive layer. These additional components include: surfactants and coating aids, thickeners, coalescing aids, crosslinking agents or hardeners, soluble and/or solid particle dyes, antifoggants, matte beads, lubricants, and others.

Process for forming abrasion-resistant antistatic layer with polyurethane for imaging element


The invention relates to a method and apparatus for removing faecal matter from slaughtered poultry suspended by the legs, wherein the poultry, after having been cut for bleeding, is scalded to soften the feathers of the poultry, and after having been scalded is plucked and eviscerated to provide fresh defeathered slaughtered poultry, wherein also the removal of faecal matter takes place by prior to evisceration removing not yet unloaded faecal matter from the poultry by applying a pressure load to the abdominal cavity of the poultry, and simultaneously or subsequently spraying away the faecal matter squeezed out of the poultry with water and/or air.

The invention relates to a method and apparatus for removing faecal matter from slaughtered poultry suspended by the legs and for cleaning said poultry.
An important objective when slaughtering and processing poultry in, for example, poultry processing plants is the maintenance of hygiene. This hygiene is critical because during the processing of the slaughtered poultry faecal matter is unloaded, which leads to the contamination of the poultry. It has even been shown that faecal matter from one bird in an automated processing line can lead to the contamination of several hundreds of subsequent birds.
Over the years many proposals have been made in an effort to combat such faecal contamination.
A known method of avoiding faecal contamination is to terminate feeding for an extended period of time so that the intestines of the poultry will eventually be vacated. However, this involves several drawbacks. For one thing, the liver of the poultry initially continues to produce bile that will not be used up anymore. This causes the gall-bladder to be stretched increasingly taut, which may increase the risk that when the intestines are being removed, the poultry will become tainted from the bile. In addition, no feeding will have a negative effect on the weight of the poultry. The termination of feeding further leads to the appendix vacating into the colon, so that the faeces are relatively more heavily contaminated than usual, putting a greater strain on hygiene.
Yet another drawback of terminating feeding is that the length of time for which feeding is terminated is difficult to control for each individual chick. This is because termination of feeding starts for a whole batch of chicks at a predetermined moment, while several hours may pass between slaughtering the first chick and the last chick. Apart from producing unpleasant situations for the animals before slaughter, it also increases the number of chickens already dead before slaughter. Termination of feeding further increases stress, which has a negative effect on the quality of the meat.
It has also been proposed to use feed supplements in order to combat the number of bacteria in the excrement. However, a problem with this method is that not all bacteria can be combated equally effectively in this manner.
Another proposal is to supplement the drinking water of the poultry with lactic acid during the period of feed termination. However, this merely results in combating contamination via the gullet and does not effectively combat contamination via the faecal matter.
Yet another proposal is to wash the poultry during bleeding. However, this method also has drawbacks preventing its application. Washing poultry during bleeding is undesirable because the resulting blood/water mixture leads to extra costs for purification (if blood is discharged with the water) or recycling (if water is discharged with the blood).
U.S. Pat. No. 3,137,031 makes the proposal of, prior to evisceration, flushing the lower intestines of the poultry with water while simultaneously evacuating the lower intestines by pneumatic suction. However, this evacuation by suction can easily cause damage to the intestines.
A method of removing faecal matter from slaughtered poultry suspended by the legs in accordance with the preamble of the main claim is known from U.S. Pat. No. 4,739,539. The drawback of this known method is that the intestines are subjected to pressure after the poultry has been scalded and plucked. This results in a continued contamination both during the scalding phase and in the plucking phase of the poultry. A further problem is that the apparatus known from this patent exerts pressure to the breast and the back of the poultry simultaneously by means of two components of the apparatus, each of which rotates about an axis. The result is that this operation takes very little time, which practice has shown to be insufficient to effectively remove the faecal matter from the poultry.
U.S. Pat. No. 4,876,767 proposes an apparatus for evacuating the intestines of the poultry by suction after scalding and plucking. This means that bacteria present on the skin and feathers on the outside of the poultry causes contamination of the scalding water and forms a considerable risk for cross-contaminating the remaining poultry. A further drawback is that, in the stage of evacuation by suction, considerable contamination has already occurred due to the faecal matter that may have unloaded spontaneously during bleeding, during scalding and during plucking. A disadvantage is also that metering the applied vacuum is difficult to the extent that an unacceptable amount of damage to the intestines is incurred. In addition, the suction organ used is susceptible to clogging.
A method and apparatus as proposed in U.S. Pat. No. 4,876,767 is also known from U.S. Pat. No. 4,889,421.
In WO 96/37110 (EP-A-910 249), it is proposed to combat contamination by faecal matter by closing off the anus of the poultry by means of a plug. The use of such a plug or stop is process-technically difficult when applying the customary process of removing the vent. Moreover, this may still cause cross-contamination of successive poultry.
It is a principal object of the invention to provide a method and apparatus for removing faecal matter from slaughtered poultry suspended by the legs in which the above-mentioned drawbacks are reduced or absent. Additional objects and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the invention.
To this end, the method for removing faecal matter from slaughtered poultry suspended by the legs is in accordance to the invention characterized in that the pressure to the abdominal cavity of the poultry is applied prior to scalding.
According to the invention, this method may, for example, be conveniently carried out in an apparatus for removing faecal matter from poultry suspended by the legs from an overhead transporter, comprising a presser organ for applying a pressure load to the abdominal cavity of the poultry, as well as a scalding installation, and succeeding the scalding installation, a plucking installation, which is characterized in that in the process direction of the installation, the presser organ precedes the scalding installation.
In order to enhance the effectiveness of squeezing the faecal matter out, the pressure load is, after its application and during its continued application on the abdominal cavity, moved in the direction of the anus of the poultry.
To this end, the effective squeezing out of the faecal matter may be conveniently realized in an apparatus characterized in that the presser organ is a pressure lever that is pivotally suspended from an axis, having a free end for placing against the abdominal cavity of the poultry and in that with an increase in pressure load, the pressure lever moves in the direction of the anus of the poultry. When a high processing rate of birds per hour is required in processing slaughtered poultry on an industrial scale, it is advantageous for the poultry to stay positioned in a suspended vertical position during the application of the pressure load.
It is further desirable that, during the application of the pressure load, the anus of the poultry is simultaneously sprayed with water and/or air. To this end, the apparatus is preferably provided with a spray nozzle directed at the anus.
In another aspect of the invention, it is desirable that after the application of the pressure load but before scalding, the poultry in its entirety is subjected to a washing operation.
To this end, the apparatus is preferably embodied such that, viewed in the process direction, after the presser organ, a spraying chamber is provided for the external cleaning of the poultry. In this manner, the poultry from which the faecal matter has already been removed receives an effective external cleaning by means of thorough flushing, preferably with warm water. This largely removes the external fouling and contamination so as to greatly reduce fouling and contamination in later phases of processing. This is especially important with respect to the scalding water in which the poultry is placed to soften the feathers of the poultry prior to plucking.
For economical reasons it is desirable for the spraying chamber to be incorporated in a recirculation system for the spraying water. The hot water output being sprayed over the poultry may amount to several liters per animal, which makes collecting, filtering, decontamination and re-use of the water economically interesting, while limiting the external harm to the environment. Desirably, the recirculation system comprises a filtering sieve. For the decontamination, the recirculation system advantageously comprises a pasteurizer. If desired, this may be combined with an anodic oxidation, possibly complemented by an ultrasonic treatment of the water. With a view to economic water and energy consumption, it is further desirable that the scalding installation and/or the plucking installation is also incorporated in the recirculation system for the spraying water.
In a completely different aspect of the invention, it is proposed that before or during the application of the pressure load on the abdominal cavity of the poultry, the poultry may be connected to an electrical stimulation system.
Desirably, the electrical stimulation system is adjusted with predetermined settings for voltage, type of signal, frequency and duration of the signal to be emitted by the system. This electrical stimulation system contributes to the spontaneous unloading of the faecal matter. An additional important advantage is that the electrical stimulation provided by this system benefits the tenderness of the meat of the poultry.
Below the invention will be briefly elucidated with reference to a schematic exemplary embodiment based on the appended drawing.

Method and apparatus for removing faecal matter from slaughtered poultry suspended by the legs and for cleaning the poultry