Patent Grant
8611774
This application relates to commonly assigned, copending U.S. application Ser. No. 12/768,815, filed Apr. 28, 2010, entitled: “PRINTER AND FUSING SYSTEM”) hereby incorporated by reference.
This invention relates to methods and appparatii that are used to appropriately fuse electrophotographic toner.
In conventional electrophotography, it is known to imagewise apply toner particles in piles on a receiver to form a toner image. The toner image is then fused to form a permanent image that is bound to the receiver. In color electrophotography, fusing is also used to enable two or more colors of toner to mix to form a combination color. Accordingly, proper fusing of electrophotographic toner is essential to the formation of high quality electrophotographic images.
While other types of fusing exist, such as those that involve the use of solvents or pressure differentials, fusing is typically achieved by heating the toner in a toner image to a temperature that is higher than a glass transition temperature of the toner. There are several key variables that impact the effectiveness of such thermal toner fusing. These include the rate at which energy can be supplied by all sources to heat the toner during fusing, the amount of exposure time during which the energy can be applied for the purpose of fusing, the rate at which the energy can be absorbed and transferred by a given unit of the thickness of toner without causing damage to the toner, the toner piles formed on the receiver, and the amount of ambient pressure applied to the toner pile during exposure.
These variables can be combined in a variety of ways to achieve a fusing solution. One variable that is generally held fixed in determining a fusing solution is the stack height of the toner pile on the receiver. Typically, the stack height is controlled to be within a predefined range. This reduces the cost of images printed using the toner and also reduces the number of variables that must be managed when determining a fusing solution. Further, the use of relatively consistent toner pile thickness across a toner image allows all of the other fusing variables to be set once and maintained at a steady state. Typically toner stack heights are maintained in a range of less than about 20 μm.
Various conventional technologies are known that are adapted to thermally fused toner piles that have such managed stack heights. In one example of contact fusing, known as hot roller fusing, a receiver having a toner image applied thereto is passed between a nip and a heated roller or belt. Heat and pressure are applied to the toner image and receiver causing the toner to heat to a temperature at or above the glass transition temperature of the toner. U.S. Pat. No. 6,577,840, entitled “Method and Apparatus for Image Forming Capable of Effectively Performing an Image Fixing Process”, issued to Hachisuka et al. on Jun. 10, 2003 shows one example of a heated roller type fuser while U.S. Pat. No. 7,630,677, entitled “Image Heating Apparatus”, issued to Osada et al. on Dec. 8, 2009 shows one example of heated belt fuser.
Similarly, various forms of non-contact fusing are known that can cause a toner to be heated. U.S. Pat. No. 7,630,674 entitled “Method and Arrangement for Fusing Toner Images to a Printing Material” shows one example of this.
Combinations of contact fusing and non-contact fusing are also known. For example, U.S. Pat. No. 6,909,871 entitled “Method and Device for Fusing Toner Onto a Substrate” shows a combination of microwave and pressure roller heating to achieve a fusing solution to allow fusing to occur in during abbreviated exposure times in order to enable high rates of printing.
Recently, it has become popular to provide toner images having portions with high toner stack heights such as those that include for example and without limitation stack heights that are on the order of 50 μm to 500 μm. An advantage of such high toner stack heights is that they can be used to form projections from a surface of an image that can impart a three dimensional look and/or feel to an image. This extra dimension, is provided by a contrast in toner stack heights which can range from a conventional stack height to, as noted above, stack heights of up to 500 μm.
Conventional fusing technologies however are not easily applied to the purpose of fusing toner images having toner piles that have high toner stack heights. In part, this is because the rate at which thermal energy can be transferred to and into a unit of toner is such that only a conventional toner pile thickness can be fully fused during a fusing operation that is performed at desirable and commercially profitable commercial printing speeds. In part this is also because of the extent of the variability in toner stack heights within the toner image.
This problem is not easily solved in general and in particular where fusing is to be performed at production speeds. If insufficient energy is applied during the short time periods allotted for fusing at high production speeds, incomplete fusing can occur. Incomplete fusing can cause mechanical defects to arise in the printed images such as incomplete bonding of the toner pile to the receiver. This can lead to full or partial separation of the toner pile from the receiver resulting in an unacceptable image. Similarly, incomplete fusing can introduce weaknesses in the resultant toner pile such as pockets of unfused dry toner that can cause fracture of the toner itself, color mixing problems, gloss variations or partial separation of the toner powder from the receiver.
However, markedly increasing the amount of energy applied during a fusing step creates other problems in image formation. For example, as is described in commonly assigned U.S. Pat. Pub. No. 2009/014948 entitled “Enhanced Fuser Offset Latitude Method” filed by Cahill et al., on Dec. 18, 2007 using high temperatures for example on a roller type fuser can cause image artifacts. Such artifacts occur when toner that is in contact with a hot roller transitions to a glass transition temperature of the toner before toner that is closer to the receiver makes this transition. This can cause a portion of the toner to adhere to and contaminate the heated roller or other rollers associated with a fuser and can cause a variety of unwanted artifacts in an image. Similarly, as noted in the '671 patent, in non-contact fusing such as microwave increased energy can create artifacts such as blister formation of the toner on the receiver.
For these reasons, a fusing solution must be managed so that sufficient energy is transferred to a toner during a fusing process to allow fusing to occur and so that the artifacts created by applying too much energy during a short period of are not created.
It will be appreciated that reaching such a solution is made more difficult by the increased energy load that must be delivered to heat a thick toner pile to ensure full fusing during the short fusing process allowed during printing. It will also be appreciated that there are inherent limitations on the rate at which toner can transfer energy through a toner pile without creating the aforementioned hot offset problems.
What is needed is a system that can thoroughly fuse toner images having toner piles with toner stack heights that are greater than about 50 μm.
Methods are provided for printing and fusing a toner on a receiver having a toner pile that extends at least about 50 μm above a receiver. According to one aspect, a first energy is applied to raise a temperature of a first portion of the toner pile to a range of elevated temperature levels below a glass transition temperature of the toner, a second energy is applied to a temperature of a second portion of the toner pile above the glass transition temperature and to allow the second portion to transfer energy to the first portion. The second energy is provided at a level that allows the transferred energy to raise the temperature of the first portion from the range of elevated levels to the range of temperatures above the glass transition temperature.
Toner 24 is a material or mixture that contains toner particles, and that can form an image, pattern, or coating when electrostatically deposited on an imaging member including a photoreceptor, photoconductor, electrostatically-charged, or magnetic surface. As used herein, “toner particles” are the marking particles used in an electrophotographic print engine 22 to convert an electrostatic latent image into a visible image. Toner particles can also include clear particles that can provide for example a protective layer on an image or that impart a tactile feel to the printed image.
Toner particles can have a range of diameters, e.g. less than 8 μm, on the order of 10-15 μm, up to approximately 30 μm, or larger. When referring to particles of toner 24, the toner size or diameter is defined in terms of the median volume weighted diameter as measured by conventional diameter measuring devices such as a Coulter Multisizer, sold by Coulter, Inc. The volume weighted diameter is the sum of the mass of each toner particle multiplied by the diameter of a spherical particle of equal mass and density, divided by the total particle mass. Toner 24 is also referred to in the art as marking particles or dry ink.
Typically, receiver 26 takes the form of paper, film, fabric, metallicized or metallic sheets or webs. However, receiver 26 can take any number of forms and can comprise, in general, any article or structure that can be moved relative to print engine 22 and processed as described herein.
Returning again to
A toner image 25 formed from more than one application of toner 24, (also known as a multi-part image) can be used for a variety of purposes, the most common of which is to provide toner images 25 with more than one color. For example, in a four toner image, four toners having subtractive primary colors, cyan, magenta, yellow, and black, can be combined to form a representative spectrum of colors. Similarly, in a five toner image various combinations of any of five differently colored toners can be combined to form other colors on receiver 26 at various locations on receiver 26. That is, any of the five colors of toner 24 can be combined with toner 24 of one or more of the other colors at a particular location on receiver 26 to form a color different than the colors of the toners 24 combined at that location.
In the embodiment that is illustrated, a primary imaging member (not shown) such as a photoreceptor is initially charged. An electrostatic latent image is formed by image-wise exposing the primary imaging member using known methods such as optical exposure, an LED array, or a laser scanner. The electrostatic latent image is developed into a visible image by bringing the primary imaging member into close proximity to a development station that contains toner 24. The toned image on the primary imaging member is then transferred to receiver 26, generally by pressing receiver 26 against the primary imaging member while subjecting the toner to an electrostatic field that urges the toner to receiver 26. The toner image 25 is then fixed to receiver 26 by fusing.
In the embodiment of
After toner image 25 is formed on receiver 26, receiver 26 is moved by receiver transport 28 to fuser 60.
First energy source 64 can comprise any known energy source that can convey a first energy 66 to cause a first portion 68 of toner pile 70 to be heated above an initial temperature range. In the embodiment shown in
Second energy source 72 can comprise any known energy source that can convey a second energy 74 to cause a second portion 76 of toner pile 70 to be heated. In the embodiment shown in
In the embodiment of
Referring again to
Controller 82 operates electrophotographic printer 20 based upon input signals from a user input system 84, sensors 86, a memory 88 and a communication system 90. User input system 84 can comprise any form of transducer or other device capable of receiving an input from a user and converting this input into a form that can be used by controller 82. For example, user input system 84 can comprise a touch screen input, a touch pad input, a 4-way switch, a 6-way switch, an 8-way switch, a stylus system, a trackball system, a joystick system, a voice recognition system, a gesture recognition system or other such systems. Sensors 86 can include contact, proximity, magnetic, or optical sensors and other sensors known in the art that can be used to detect conditions in electrophotographic printer 20 or in the environment-surrounding electrophotographic printer 20 and to convert this information into a form that can be used by controller 82 in governing printing and fusing. Memory 88 can comprise any form of conventionally known memory devices including but not limited to optical, magnetic or other movable media as well as semiconductor or other forms of electronic memory. Memory 88 can be fixed within electrophotographic printer 20, removable from electrophotographic printer 20 at a port, memory card slot or other known means for temporarily connecting a memory 88 to an electronic device. Memory 88 can also be connected to electrophotographic printer 20 by way of a fixed data path or by way of communication system 90.
Communication system 90 can comprise any form of circuit, system or transducer that can be used to send or receive signals to memory 88 or external devices 92 that are separate from or separable from direct connection with controller 82. Communication system 90 can connect to external devices 92 by way of a wired or wireless connection. In certain embodiments, communication system 90 can comprise a circuitry that can communicate with such separate or separable device using a wired local area network or point to point connection such as an Ethernet connection. In certain embodiments, communication system 90 can alternatively or in combination provide wireless communication circuits for communication with separate or separable devices using a Wi-Fi or any other known wireless communication systems. Such systems can be networked or point to point communication.
External devices 92 can comprise any type of electronic system that can generate wireless signals bearing data that may be useful to controller 82 in operating electrophotographic printer 20. For example and without limitation, an external device 92 can comprise what is known in the art as a digital front end (DFE), which is a computing device that can be used to provide images and or printing instructions to electrophotographic printer 20.
An output system 94, such as a display, is optionally provided and can be used by controller 82 to provide human perceptible signals for feedback, informational or other purposes. Such signals can take the form of visual, audio, tactile or other forms.
Controller 82 then converts the print order information into printing instructions which are sent to print engine 22, receiver transport 28, receiver supply 32 and which cause toner 24 to be applied in various amounts and in particular locations to the receiver 26 to yield, in combination, a superimposed image that corresponds to the image data for the image to be printed and the printing instructions (step 102). In some cases, this will require that controller 82 determines a set of color separation images and/or a clear toner image. In other cases, the digital image data provided to controller 82 can, for example, be provided from the color separation images that are generated by an external device 92 such as a computer known as a digital front end (DFE) and provided to electrophotographic printer 20, for example, from memory 88 or communication system 90.
Where one of the electrophotographic printing modules 40, 42, 44, 46, or 48 has clear toner 24 available, controller 82 can provide instructions to the printing module having the clear toner available causing the printing module to deposit the clear toner 24 to form, for example, images having a uniform layer of clear toner material for protective, decorative, or to form various visual effects or that can be created by selective application of such a clear donor material.
In the embodiment illustrated in
Alternatively, several layers of the standard size particles of toner 24 can be selectively covered by clear toner particles of a larger general average median volume weighted diameter of 12-30 μm. Here, the particles of toner 24 are clear (i.e., not pigmented) and have a lay down coverage of at least 2 mg/cm2. Using small marking particles for the non-raised image is preferred because it allows for high quality images even when the large clear particles are deposited on top.
The deposition of the clear toner can also be controlled by using a Fourier series to mathematically map the stack height of the toner piles forming toner image 25. In this manner, controller 82 can generate the electrostatic latent image corresponding to the clear toner deposition is by controlling the exposure, which is, itself, programmed to vary the exposure according to the Fourier series.
The high toner stack heights can be used, for example, to impart a background texture to an image, as described in U.S. Pat. No. 7,468,820, entitled “Profile Creation for Texture Simulation with Clear Toner” issued to Ng et al. on Dec. 23, 2008 and U.S. Publication 2009/0297970, entitled “Toner Composition for Preventing Image Blocking”, filed by Tyagi et al. on May 4, 2009. That is, using variable data, for example, from a database having any of a plurality of background texture, can be formed on an image by selective application of toner stack heights greater than about 50 μm; provide the appearance of a painter's canvas, an acrylic painting, a basketball (pigskin), sandstone, sandpaper, cloth, carpet, parchment, skin, fur, or wood grain. The resultant texture is preferably periodic, but can be random or unique. It is also preferable to create textures with a low frequency screening algorithm. Using variable data, in this way to provide patterns of high toner stack heights enables every printed page to contain unique information, with its own particular tactile feel. In order to improve reproduction of the colors in areas containing raised image effect, it may be desirable to build a new color profile based on the raised information.
Typically, a clear toner 24 applied on top of a color image to form a three-dimensional texture. It should be kept in mind that texture information corresponding to the clear toner image plane need not be binary. In other words, the quantity of clear toner called for, on a pixel by pixel basis, need not only assume either 100% coverage or 0% coverage; it may call for intermediate “gray level” quantities, as well.
In an area of the toner image 25 to be covered with a clear toner for three-dimensional texture, the color may change due to the application of the clear toner. For this approach, two color profiles are created. The first color profile is for 100% clear toner coverage on top and the second color profile is for 0% clear toner coverage on top. On a pixel by pixel basis, proportional to the amount of coverage called for in the clear toner image plane, a third color profile is created, and this third color profile interpolates the values of the first and second color profiles. Thus, a blending operation of the two color profiles is used to create printing values. In a preferred embodiment, a linear interpolation of the two color profile values corresponding to a particular pixel is performed. It is understood, however, that some form of non-linear interpolation may be used instead. This technique is especially useful when the spatial frequency of the clear toner texture is low.
The second approach may be used when the spatial frequency of the clear toner texture is high. In such case, only one color profile may be needed for that textured image. One option is to simply use the ICC color profile of the original system for all textures, i.e., the ICC color profile that assumes there is no clear toner. In such case, we simply accept the fact that the appearance of the colored image will change a bit since the absolute color will differ from the calibrated color. However, there will not be an observable color difference within a uniform color region, even though the color is not quite accurate. A second option is to build a new ICC color profile with that particular three-dimensional clear toner texture surface. In this manner, the macro “color accuracy” problem is corrected, while the color artifact from pixel-to-pixel is not noticeable. Furthermore, a library of such texture-modified ICC color profiles may be built up over time for use whenever an operator wishes to add a previously defined texture to a profile, as discussed above. In implementing such a method controller 82 can, for the second approach, automatically invoke just one of these two options, or may instead display a choice of the two options to an operator, perhaps with one of the options being the default.
After a toner image 25 having high toner piles is created, controller 82 causes receiver 26 to be forwarded for fusing. In the embodiment of
As is shown in
As is shown in
In this embodiment, the amount of energy applied to the second portion 76 of the toner pile 70 is determined to achieve two results: to allow second portion 76 to transfer sufficient energy into first portion 68 to cause the first portion 68 to heat from the range of elevated temperature levels to a range of temperatures above the glass transition temperature and to bring the temperature of the second portion 76 above the glass transition temperature of the toner, such that the first portion 68 and the second portion 76 are in a glassy state for a common period of time.
Both first energy 66 and second energy 74 are selected so that neither first energy 66 nor the second energy 74 is applied in an amount or at a rate that causes toner 24 to become damaged. The range of elevated temperatures is preferably as close to the glass transition temperature as can be achieved within a fusing exposure time and without causing damage or premature fusing of toner 24 in first portion 68.
In certain embodiments, it may be useful for electrophotographic printer 20 to provide a uniform production rate for images having high toner stack heights as well as conventional toner stack heights. This will of course require that there be a generally consistent exposure time for fusing. In this regard, in certain embodiments, an electrophotographic printer 20 can use one of the first energy source and the second energy source to fuse toner on a receiver having a toner stack with toner stack heights that are below 50 microns during a first range of exposure times. To match this production rate, the first energy and second energy are applied so that the range of temperatures of the first portion and the second portion can be raised to the glass transition temperature to fuse high toner stack heights within the first range of exposure times.
In the embodiment of fuser 60 illustrated in
As is shown in
To further protect toner pile 70, the optional pressure control system 80 can be used to reduce pressure between heated roller 77 and the support roller 79 during the fusing of toner piles 70 having stack heights that are about 50 μm or more. In the embodiment that is illustrated in
It will be appreciated that not every image fused by fuser 60 will have an image recorded thereon that has toner piles with stack heights on the order of 50 μm. Accordingly, for energy conservation and other efficiency considerations, it is useful to provide an electrophotographic printer 20 that has the capability to adjust the fusing process to provide an appropriate fusing solution for fusing toner piles having conventional toner stack heights as well as toner piles having toner stack heights that are greater than about 50 μm.
As is shown in the flow diagram of
However, when controller 82 determines that the printing instructions do not require the formation of toner stack heights that are at least around 50 μm, controller 82 uses the printing restrictions to cause toner to be delivered to receiver 26 according to printing instructions and without a toner pile having a stack height that is greater than 50 μm (step 105). Controller 82 then causes one of the first energy source and second energy source to be deactivated during fusing operations (step 107) such as by cutting off the power the unused toner energy source or by sending instructions causing the energy source to deactivate. Accordingly energy is applied from only one source of energy to fuse images of this type. Alternatively, as shown in
In still another embodiment, first energy source 64 can be adapted to apply sufficient energy to first portion 68 to allow the first portion 68 to partially heat the second portion 76 so that the second energy 74 begins heating second portion 76 at a temperature that is above an initial temperature of the toner 24. This will reduce the amount of energy required of second energy 74 as compared to an amount of energy that second energy 74 would be required to apply to an unheated second portion 76.
In other embodiments, first energy source 64 and second energy source 72 can take any of a variety of forms. For example, in the embodiment of
As shown in
A initial portion of the toner piles is then heated to a range of elevated temperatures that is below a glass transition temperature of the toner (step 142). The initial portion can be heated in a single step or process for multiple steps.
A remaining portion of the toner piles is then heated to cause the remaining portion of the toner piles to heat the initial portion from the range of elevated temperatures to a range of temperatures above the glass transition temperature and to heat the remaining portion of the toner piles to the range of temperatures above the glass transition temperature (step 144).
In certain embodiments, the heating of the initial portion can apply a heat to a first surface of the toner piles while the heating of the remaining portion applies heat to a second surface of the toner piles with the second surface being opposite from the first surface. In other embodiments, the heating of one of the portions can be performed by conforming a heated surface to the toner piles and transferring heat from the conforming surface into the toner piles.
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.
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