Patent Application
20110189611
In the printing industry a wide variety of printing methods are employed. Printing methods such as lithographic, flexographic, screen and gravure printing commonly involve preparing an image-bearing printing surface before commencing printing. Such printing surfaces are often prepared in an imaging device which uses an imagewise addressable radiation source to selectively convert or transform areas of a printing precursor. In some cases the printing surface is directly ready for use following imagewise conversion. In most cases further processing is required. Processing may include further exposure to radiation, heating, chemical development, chemical etching, a variety of other processes or combination thereof.
In other imaging industries such as the direct imaging of printed circuit boards, imaging devices are commonly coupled with a processor of some description for further processing or development of the imaged article. In the graphic arts industry, imaging and processing steps are usually performed by separate equipment, often provided by different manufacturers. For example, lithographic plates, and more particularly thermal lithographic plates are typically imaged in platesetter devices which use high power radiation sources such as lasers for imaging. After imaging, plates are removed from the platesetter and either manually or automatically conveyed to a processor. For negative working thermal plates, processing typically includes a preheat step, which the plate is uniformly heated to crosslink imaged areas, followed by development in a chemical solution that removes non-imaged areas. The plates may be post-baked to improve their run length on press. It is important to heat plates evenly during processing. The required preheat consistency over the plate surface for a negative working thermal plate is preferably in the range of 5° C.-10° C. and most preferably less than 2° C. It is also important to maintain the plate precursors in good condition for imaging.
U.S. Pat. No. 6,550,989 describes an integrated processor which has a pre-heat oven, a developer section, and an optional post-bake section. Preheat is controlled in one embodiment by varying the speed with which plates pass through the preheat section or the disposition of heating elements in response to a trigger such as the plate entering the preheat section. Further measurements of the plate precursor such as width provide additional control inputs for maintaining even heating.
U.S. Pat. No. 7,229,241 discloses an automatic plate feeding system for loading plates of various sizes into a printing plate imaging device, which includes a plurality of trays staggered one on top of the other is provided. At least two of the trays contain plates of different sizes stacked with their sensitive side downward. Separation papers are interposed between the plates. The automatic plate feeding system includes suction cups, which touch the non-sensitive surface of the plate, and a loading mechanism for loading plates from the trays and feeding the loaded plates to the imaging device. Nothing was mentioned about plate recognition.
EP 1055621 discloses an automatic plate feeding system for loading plates of various sizes into a printing plate imaging device, which includes a plurality of trays staggered one on top of the other, wherein at least two of a plurality of trays contain plates of different sizes, the plates having separation papers interposed there between and an arm mechanism for loading plates from the plurality of trays and feeding the loaded plates to the imaging device. Nothing was mentioned about automatic plate recognition.
U.S. Pat. No. 4,295,039 discloses a method and apparatus for identifying an individual holder (person) of an unalterable charge card-like device (CARD) at a utilization terminal (U/I Terminal) wherein a unique user entered key (asserted key K sub. A) is handled in a highly secure manner. Nothing was mentioned about plate recognition.
There remains a need for a better apparatus and methods for processing imaged articles. There is a particular need for such apparatus and methods which can automatically determine if a plate precursor and/or the related processor are compatible and the plate precursor is ready for imaging. The printing industry has special need for such apparatus and methods.
One aspect of the invention provides a method to determine if a plate precursor is ready and prepared to be imaged with an imaging device and processed using a processor having a controller which adjusts the processor operation in accordance with information transferred from the imaging device to the processor. In another aspect of the invention the processor transfers information to the imaging device to enable adjustment to the imaging process and/or scheduling of imaging jobs according to conditions pertaining to the plate precursor and related processor, as well as the imaging information.
Another aspect of the invention provides apparatus for imaging and processing precursors. The apparatus includes an imaging device, a processor and means for transferring information about imaged precursors imaged by the imaging device to the processor.
This invention is useful for making printing plates such as lithographic plates and flexographic plates with platesetters (CtP systems) preferably equipped with an automatic loading system.
Further aspects of the invention and features and advantages of specific embodiments of the invention are set out below.
In drawings which illustrate non-limiting embodiments of the invention:
Throughout the following description, specific details are set forth in order to provide a more thorough understanding of the invention. However, the invention may be practiced without these particulars. In other instances, well known elements have not been shown or described in detail to avoid unnecessarily obscuring the invention. Accordingly, the specification and drawings are to be regarded in an illustrative, rather than a restrictive, sense. This invention is described in relation to a system including an imaging device that is able to image a precursor (such as a media to be imaged) and a processor for processing the precursor. Processing parameters are adjusted according to information supplied to the processor by the imaging device. The imaging device may include an image-wise addressable radiation source, an imaging bed of any suitable configuration for holding the precursor, a suitable mechanism for scanning the radiation source across the precursor, and mechanisms for handling, loading and unloading the precursor. An internal or external imaging controller or combination thereof, receives image data and controls the functions of the imaging device. Note that in one preferred embodiment the imaging controller is separate from the controller to control the processor parameters. That controller is hereafter the controller referred to. Such systems for imaging lithographic, flexographic, screen and gravure printing forms are well known in the art and range from devices that require manual precursor handling to fully automated machines capable of handling multiple precursor sizes and types in cassettes or other storage that are automatically selected and loaded. One such system is described in U.S. Pat. No. 7,440,123, entitled “Adaptive Printing”, which is hereby incorporated by reference.
The term “precursor”, also known as a “plate precursor”, is used herein to refer to an object having a surface that can be imagewise exposed to form a pattern thereon. The surface may be coated with an imageable coating. The coating may be on a metal or synthetic substrate. The substrate may, for example, comprise a flat plate or a cylindrical sleeve substrate. The term “printing surface” is used herein to refer to the specific instance where the precursor is to be used in a printing operation.
A conveyor 18 receives one or more pre-imaged precursors 20, which may be grouped in batches with similar characteristics. Precursors 22 are imaged by an imaging engine 24, thus becoming imaged precursors 22, and transported to a processor 26. Processor 26 can have one or more sections (not shown) for 28 processing the precursor. Processor 26 may include a processing line. In one specific embodiment of the invention for use with lithographic printing plates the processor 26 can have a preheat oven section and a chemical developer section. A processed printing surface 30 then exits the processor 26 and is either manually or automatically conveyed to a printing press. Note that both the pre-imaged precursors 20, either individually or as a batch, can be associated with one or more codes 32 that will be discussed in greater detail below. Alternatively the codes could be associated with the imaged precursors 22 and even be part of the image. The code does not have to be a readable code as will be discussed below.
The controller 16 communicates with imaging engine 14 via a communication path 28 that may comprise any suitable data communication path such as, for example, one or more signal lines, a signal bus, an optical fiber, a wireless link, an optical link or any other path for transferring information. The communication path can also be used to permit communication between controller 16, the processor 26 and the sensing 17 and authentication subsystem 62. These communications may be carried on the same pathway or on a separate pathway from communications between controller 16 and imaging engine 34. Those skilled in the art will understand that any of a wide variety of communications technologies may be used to provide suitable communication between controller 16, and other subsystems. The controller functions may be moved from one device to another without changing the principles of operation of the system or departing from the invention. The communication path transfers information related to the precursors on a continuous or plate-by-plate basis. The information transferred is of use to processor 26 in controlling functions related to further exposure steps, heating steps, development steps and any other processor functions including replenishment of developer chemical solutions. Various embodiments and examples are discussed below in greater detail.
The above steps are repeated until the qualified precursors become available to proceed to arrange the qualified precursors into a stack suitable for automatic loading of the precursors onto an imaging device 44 and optionally having separator sheets inserted between two adjacent precursors. Then the separator sheet, if present at the top of the stack, is removed 46 and the qualified precursor(s) are loaded 48 at the top of the stack onto the imaging device and are image-wise exposed 50 to form exposed areas and complementary non-exposed areas according to an image bitmap and a set of imaging parameters. Optionally the imageable layer in the exposed or the complementary non-exposed areas can be removed 52 using an automatic plate processor operating according to a set of processing parameters. These last three to four steps are repeated at least once.
In one embodiment the plate could be loaded by positioning the precursor relative to the plate leading edge on a certain distance from each edge, for example x [mm]. The allowed position variation of the precursor in each plate due to skew, tilt and twist of the plate and also production tolerances no more than +/−3 [mm] relative to x measurement. The sensor readings can be relative to the position of the precursor. Exceeding from the allowed precursor position might cause the sensor readings to be different due to bigger dispersals, longer path of the light to go from the sensor's emitter to the precursor and back to the sensors' reflector yielding in lower energy that represents deviation from desired position. In this case the x measurement is defined according to the physical position of the planned sensor inside the machine.
The reader 61 can be based on current technology such as a bar code scanner, a RFID tag reader, a sensor capable of identifying automatically holographic information, a video camera system combined with software capable to identify letter/number codes, spectral sensors capable of analyzing spectral data, a CCD sensor or even manually insertion of a barcode information by the operator as long as it can read or sense the code and/or code carrier. The plate recognition system interacts with the plurality of plates or with every single plate fully automatically, partially automatically or manually.
The plate recognition system prevents or improves the processing of plates including, but not limited to the elimination of using wrong printing plates, the elimination of using printing plates outside of their shelf life, by effectively adjusting the exposure energy of every plate batch based on measurements made by the plate precursor manufacturer resulting in more consistent results. The system will also allow the transfer of plate dimension information into the platesetters which allows avoiding sophisticated means in the platesetter to measure the plate dimensions, the simplification of recording of plate stock and initiation of new plate orders, of remote support of the printing plate consumer by the printing plate precursor manufacturer, and of imaging device self diagnostic sequences. The system reduces printing plates loading downtime of imaging device due to the diminution of exposure quality problems due to incompatibility between the resolution of the source file and maximal screening level of the plate type, the diminution of process quality problems due to incompatibility between the speed of the processor and the type of plate and saving time to adjust the speed of the processor and the diminution of plate loading problems originating of false identification of plate as a slip sheet, anodize and emulsion.
The detection of plate loading problems originating from plates positioned out of specification such as in using the precursor detection to evaluate if it is a slip sheet (has no precursor) or a plate and also maybe detect the position of the precursor to detect potential loading problems due to a misfeed of plates into the device and notify the customer to correct the position of the plates is eliminated through the use of the plate recognition system. The plate recognition system can be incorporated using a workflow such as that depicted in
In one embodiment of the plate recognition system the information 60 that is collected by the sensing subsystem is transferred via the internet (WAN) or a local data base form the customer terminals to a web server which acts as a gateway to the host site local (LAN). The data collected are checked in the CONTROL CENTER Manger by a database (DATA I) making a decision whether correct loading of the plates occurs or not. In case of incorrect loading, the loading system stops the loading process while it continues with loading if the collected plate information equals with the information saved in DATA I. This embodiment of the system can optionally contain a QC-module collecting the information of the plates loaded and this data can be sent out for further QC control and rechecked with another database DATA II whether some actions could be necessary or not. Such actions could be the change of exposure energy based on manufacturing data. In addition, the fact to have the information of plates actually by a customer is very valuable for our QC department.
In one embodiment the system comprises a CONTROL CENTER based on a software receiving data about the plate either by manual collection (reading of a bar code by an operator or manual typing of the code by an operator) into the system of the CONTROL CENTER. Comparison of data received with those available in DATA I provided by the plate supplier allows to make a decision whether the plate is correctly loaded or not. Alternatively, plate data could be automatically transferred by a collection device into the CONTROL CENTER, which again makes a decision whether the plate is correctly loaded or not based on available information in DATA I. Such a system can have either manual or automatic plate information collection. It is also possible to have both integrated with the CONTROL CENTER while one collection method serves as a backup solution.
The automatic collection device collects data based on an integrated sensor which is able to read either a visually or hidden information (1D, 2D, or 3D code) about the kind of the plate or an RFID tag. It may also recognize the kind of the plate from a chemical point of view by comparing spectral data. The sensor device can read the plate information from top/back side of the plate or somewhere else from the pallet. The plate information collected comprises either the recognition of the plate by chemical/physical properties in a fingerprint pattern using destruction less method, which can occur either by employing absorption of electromagnetic waves located in the UV, visible, NIR or IR; by employing excitation techniques to sensor the information by emission techniques; and/or by employing scattering techniques to sensor properties such as reflection, scattering, or chemical information by Raman technique. This can be realized either by one method or a combination of at least two methods, that is the recognition of the plate by absorption of radio waves applying RFID technique, the recognition of the plate by a bar code that has either a 1D, 2D, or 3D pattern (holographic technique), or spectral information by using a special spectral device as shown in
The set of precursor data could include, in one embodiment, precursor type, manufacturing date, or a plate property measured on a precursor sample in the same batch as the precursors. The set of imaging parameters can include a tonal value of a tint on an imaged and processed printing plate obtained from the precursor sample according to a standard set of imaging and processing settings and the imaging parameters that can be determined from the precursor data such as one or more of the plate pre-drum alignment settings, exposure energy and other relevant parameters such as plate surface depth, drum speed, resolution. These parameters include those used in plate processing systems such as in a media profile for square spot devices and LDA devices. Note that information such as surface depth, beam slope, beam curve etc are parameters that are determined according to the plates parameters also (such as thickness and type) as well as in the process of the head integration. The reason is that they are not the same for each head with the same plate type due to head performance variations. Thus in this system these parameters can be monitored, sensed and acted upon separately or in combination as required for optimum performance.
These parameters can be transferred automatically to a software application that controls the imaging devices if desired. Note that the set of processing parameters can include processor speed, developer temperature and developer conductivity and the codes can include an identification code and the interpreter retrieves the precursor data from a database record set associated with the identification code. The set of codes discussed above can additionally be interpreted according to an industry standard with or without using a proprietary database.
Examples of types of code carrier include an RFID tag or a hologram, a barcode and other similar markers. The code carrier can be located on the surface of each of the precursors opposite to the imageable layer and can be facing one or more directions, such as upward. In that case the separator sheet can be confirmed by the absence of the code carrier on the top surface of the stack and or the presence of the separator sheet can be further confirmed by a surface sensor capable of differentiating the surface of the separate sheet and the surface of the precursors opposite to the imageable layer. Additionally the imaging head can have a plurality of addressable channels each emitting a beam of radiation and the set of imaging parameters comprises the relative radiation strengths of the addressable channels where the relative strengths of the addressable channels are determined from the precursor data determined on a sample precursor from the same or a similar manufacturing batch. Alternatively the imaging head and a focusing device can be capable of focusing the imaging head onto the precursor, the set of imaging parameters comprises parameters for operating the focusing device, and the set of precursor data comprises a surface property of the precursor that affects the operation of the focusing device.
One preferred embodiment of the present invention is related to a method of making a printing plate from a lithographic plate precursor using a plate recognition system. The method starts with first providing a plurality of printing plate precursors (plate box or pallet with plates) having on each plate, plate box, or plate pallet information about the printing plate precursor in a form that it can be recognized by a plate recognition mean wherein the information about the printing plate precursor. This information can be referred to as a precursor data that includes information such as printing plate type, manufacturer, manufacturing date, plate dimension (length, width, thickness, information about web direction), plate type (Electra XD or Sword Ultra as traditional thermal plates, and photopolymer plates operating either with NIR and violet exposure such as ThermalNews Gold and VioletNews Gold, respectively, are some representative examples; other negative plates such as DITP Gold or negative plates operating without preheat are alternatives as well), color of coating, reflectivity of coating surface and photosensitivity of the plate. The plate precursor data can be compiled in logical ways to yield a set of plate properties. Other data sometimes referred to as information can also be included such as plate parameters that relate to the imaging of the plate and possibly the plate precursor properties
The second step is to next provide the plurality of printing plates precursors in to equipment capable to imagewise exposure of printing plate precursor (platesetter). Then the third step involves transferring the information about the printing plate precursor by a recognition mean into the platesetter or the automation product that the platesetter works with and using the transferred information about the printing plate precursor in the platesetter for at least on operation selected from the group including one or more of the following:
a. Checking identity of the plate precursor and deciding whether plate precursor should be accepted or rejected by the platesetter.
b. Checking manufacturing date of the plate precursor and deciding whether the plate precursor should be accepted or rejected.
c. Checking plate precursor sensitivity and adjusting the exposure energy to the required level.
d. Checking plate precursor dimension (length, width and thickness) and using the information for adjusting the platesetter.
e. Using the information (plate precursor type, plate precursor dimension) for recording the plate consumption and using the records for initiation of plate order.
f. Verification of compatibility and adjustment of the processor speed to plate type.
g. Identification and discrimination of plate to all non plate cases (slip sheet, anodize, and emulsion).
h. Identification of the plate position inside the automation as means to inspect that the plates stack is positioned on the pallet according to the spec.
Finally the plate is imaged by exposing the plate precursor to the imaging subsystem. Optionally preheating, prewashing developing, rinsing, gumming, drying and post-baking the printing plate.
The plate recognition apparatus and system includes two main sub-systems, the sensing subsystem 17 which is responsible for the recognition of certain features and an authentication subsystem 62, including the interpreter 38. This plate recognition stores the collected data delivered using the sensing subsystem and compares this data to data stored in the data base in the authentication subsystem. According to the results of the comparison the software that controls the plate processing will accept or reject the plate and/or image data during one or more of the steps of loading, exposing, and processing of the plate in each stage of the workflow using the processor 26, which can monitor and/or adjust a number of physical parameters related to the operation of processor 26 based on the sensing and authentication subsystems.
Those skilled in the art will appreciate that the conception on which this disclosure is based may readily be utilized as a basis for the design of other apparatus for carrying out the several purposes of the invention. It is most important, therefore, that this disclosure be regarded as including such equivalent apparatus as do not depart from the spirit and scope of the invention. The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.
This application relates to commonly assigned, copending U.S. application Ser. No. ______ (Docket No. 96066DPS), filed ______, entitled: “PROCESSOR SYSTEM WITH PROVISION FOR AUTOMATED CONTROL OF PROCESSING PARAMETERS” and U.S. application Ser. No. ______ (Docket No. 95977DPS), filed ______, entitled: “METHOD FOR AUTOMATED CONTROL OF PROCESSING PARAMETERS” each hereby incorporated by reference.
