The present disclosure is related to methods and systems for indicating the position of a flexible, elongated web.
Fabrication of many articles, including flexible electronic or optical components, involves alignment between layers of material deposited or formed on an elongated substrate or web. The formation of the material layers on the web may occur in a continuous process or a step and repeat process involving multiple steps. For example, patterns of material may be deposited in layers on an elongated web through multiple deposition steps to form layered electronic or optical devices. Some layered articles require precise alignment of features that are applied on one or both sides of the web.
To achieve alignment between the layers, lateral crossweb positioning and longitudinal downweb positioning must be maintained as the web moves through multiple manufacturing steps. Maintaining alignment between layers formed on the web becomes more complex when the web is flexible or stretchable.
Embodiments of the present disclosure involve methods and systems for indicating the position of a flexible, elongated web. One embodiment is directed to a method for indicating web position. A moving, flexible web includes a plurality of discrete scale features disposed on the web. An energy field, such as a magnetic, electric or electromagnetic field is modulated using the scale features. The modulated energy is converted into a signal that provides for continuous measurement of web displacement. For example, the signal may be used to provide for continuous measurement of one or more translational and/or rotational degrees of freedom of the web, including continuous longitudinal displacement, continuous lateral displacement, and/or angular rotation of the web. The signal may be used to determine web position, to control web movement, and/or to measure other parameters of the web or ambient environment such as temperature, modulus of elasticity of the web, and/or web strain.
According to some aspects of the disclosure, the scale features may comprise optical scale features used to modulate light directed toward the web. The web may or may not be transparent. For a transparent web, one implementation involves detecting light transmitted through the transparent web. The web displacement is indicated based on the transmitted light. Alternatively, the web displacement may be indicated based on reflected light. One or more scanning reticles can be used to provide modulation of the light in addition to the modulation provided by the optical scale features.
Another embodiment of the disclosure involves a system for indicating web position. The system includes an elongated, flexible web having an integral scale disposed on the web. The scale comprises scale features configured to modulate energy directed towards the web. A transport mechanism is configured to provide relative movement between the web and a transducer. The transducer detects the energy modulated by the scale features and generates a signal indicting a continuous web displacement based on the modulated energy. The system may also include a processor that determines the displacement of the web and/or web position based on the signal generated by the transducer. The system may also include a web motion controller that controls the movement of the web based on the indicated position.
In certain embodiments, the scale features comprise optical features configured to modulate light directed toward the web. One or more scanning reticles may be included that further modulate the light.
Operating in a transmissive mode, the scale modulates light by allowing a portion of light directed toward a transparent web to be transmitted through the web. The transducer detects the transmitted light and generates a signal indicating web displacement based on the transmitted light. Operating in a reflective mode, the scale modulates light by reflecting a portion of the light towards the transducer. The transducer detects the reflected light and generates a signal indicating web displacement based on the reflected light.
Another embodiment of the disclosure is directed to an apparatus comprising a flexible, elongated web having an integral scale. The scale comprises a pattern of scale features disposed on the web that are configured to modulate energy directed toward the web. The scale features may be optical prisms configured to reflect light via total internal reflection. The modulated energy provides for a continuous indication of the longitudinal and/or lateral displacement of the web and/or the angular rotation of the web. In certain embodiments, the modulated energy may be used to control the web movement and/or to measure other parameters of the web or ambient environment such as temperature, modulus of elasticity of the web, and/or web strain.
In addition to the scale features disposed on the web, the web may also include a pattern of web features. The bend radius of the flexible web may be less than about 100 mm, less than about 50 mm, less than about 25 mm, or even less than about 5 mm, for example.
The above summary of the present disclosure is not intended to describe each embodiment or every implementation of the present disclosure. Advantages and attainments, together with a more complete understanding of the disclosure, will become apparent and appreciated by referring to the following detailed description and claims taken in conjunction with the accompanying drawings.
While the disclosure is amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It is to be understood, however, that the intention is not to limit the disclosure to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the scope of the disclosure as defined by the appended claims.
There is a need for enhanced methods and systems for indicating the position of a web used as a substrate in a manufacturing process. The present disclosure fulfills these and other needs, and offers other advantages over the prior art.
In the following description of the illustrated embodiments, reference is made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration, various embodiments in which the disclosure may be practiced. It is to be understood that the embodiments may be utilized and structural changes may be made without departing from the scope of the present disclosure.
Embodiments of the present disclosure illustrate methods and systems that may be used to indicate web displacement, determine web position, and/or control the movement of a flexible web using a scale integrally formed or disposed on the web. The scale includes a plurality of scale features that modulate energy to indicate web displacement. For example, the scale features may modulate the energy of an electric field, a magnetic field, or an electromagnetic field. In various embodiments, the scale features may modulate the energy of an electromagnetic field (i.e., light) where the modulated energy is sensed by a photosensor. In alternative embodiments, the scale features may modulate the energy of an electric field, e.g., the electric field energy sensed by a capacitive sensor, and/or may modulate the energy of a magnetic field, e.g., the magnetic field energy sensed by an inductive sensor.
Indication of continuous web translational and/or rotational displacement using the integral scale may be employed to determine web position and to control movement of the flexible web during deposition of pattern features on the web in one or a number of successive manufacturing steps. For example, the scale described in connection with the embodiments of the disclosure provided herein may be used to indicate continuous web displacement. The indication of web displacement facilitates alignment between multiple layers of pattern features deposited or otherwise formed on a web during a roll-to-roll manufacturing process. The scale described herein is particularly useful for manufacture of flexible, multi-layer electronic or optical devices that require multiple deposition steps to form successive layers of pattern features on a flexible web.
The approaches described herein may be used to automatically compensate for changes in web strain that commonly occur in web processing applications. Certain manufacturing processes may cause transient or permanent changes in the web such that the web is permanently deformed, such as deformation caused by stretching or shrinking of the web. Embodiments of the present disclosure advantageously offer compensation for transient or permanent changes in the web. For example, in some embodiments, the scale features are deposited on the web substantially concurrently with a layer of web pattern features, such as the first layer of web pattern features used to form multi-layer electronic or optoelectronic devices. As the scale features and the web pattern features are deposited, the pattern features deposited on the web and the scale features experience the same amount of web strain. The scale features may be used to accurately track the lateral position, longitudinal position, and/or angular rotation of the first layer web pattern features, regardless of the amount of web strain in subsequent processes. As web strain is increased (i.e. the web is stretched more) the scale features are stretched along with the corresponding web pattern features formed on the web. This phenomenon allows signals produced by the scale features to be used to more accurately track the position of web features deposited on the web.
Using the scale described in accordance with various embodiments herein, accurate alignment with the concurrently deposited web pattern features can be achieved even when the web is stretched. Maintaining alignment between layers formed on the web becomes more complex when the web is flexible or stretchable. In particular, the approaches of the present disclosure are particularly useful in that they allow replication of the scale features on plastic webs or other flexible webs, as opposed to rigid substrates such as glass. For example, a flexible web having a scale disposed thereon in accordance with embodiments of the present disclosure may have a bend radius of less than about 100 mm, less than about 50 mm, less than about 25 mm, or even less than about 5 mm, for example.
Additionally or alternatively to providing for the indication of translational displacement and/or angular rotation of the web, the scale may also be used to measure various parameters of the web or ambient environment surrounding the web. For example, as discussed in more detail below, the scale may be used to measure temperature and/or modulus of elasticity of the web, and/or may be used to measure web strain.
Various types of scale features may be used with compatible sensors to indicate continuous web displacement. The scale features may modulate electric field energy, may modulate magnetic field energy, or may modulate light, for example. Embodiments of the disclosure are described in terms of optical scale features and compatible photosensors, although any type of scale feature/sensor configuration that modulates an energy field to produce a signal indicating continuous web displacement may be used.
The system of
The light intensity at the active surface 222 of the photosensor 220 for the systems of
The scanning reticle 240 is oriented a short distance from the web 205 so that the reticle windows 241 allow a portion of the light directed toward the web 205 to pass through the reticle 240. Regions 242 of the reticle 240 between the windows 241 block a portion of the light.
In another embodiment, depicted in
Embodiments where the sensor is located off roll (such as those exemplified in
Once such method for compensating for the air gap not being present includes altering the surface of the roll. Often times, but not always, the rolls are reflective in nature (for example, stainless steel). Therefore, the roll could be made to have a matte surface. By changing the surface of the roll from reflective to matte, for example, light rays that are interacting with an optical scale element (which is reflective) can more easily be distinguished from one which is interacting with the roll. Another method of altering the surface of the roll would be to make the roll a different color. In an embodiment, the roll could be made to have a dark color, thereby absorbing more light than a reflective roll (for example). Both of these exemplary methods could increase the contrast between two light rays (one interacting with an optical scale element and one interacting with the roll).
Another method of compensating for the air gap being gone is to create an air gap between the web and the roll. The air gap, if created, would function to refract the light that goes through the web and reflects off the roll. Because of the refractive index of air (versus the material that make up the web), the light that has been allowed through the web, then traveled through the air gap, then reflected off the roll, then traveled through the air gap again, and then traveled through the web again will have a different angle and (depending on the transmissivity of all of the involved components) a different intensity than the light which was reflected off the optical scale elements.
An air gap between the roll and the back side of the web could be created by, for example, providing a structure on the back of the web to create and maintain a gap between the roll and the web.
The output signals 320, 330 generated by the photosensors 250, 255 are analyzed by the web position processor 260 to determine the position of the web. Using the phase shifted signals 320, 330 the web position processor 260 may determine both the position and direction of motion of the web relative to the photosensors. This information is used by the web motion controller 270 to control web movement.
In some embodiments, multiple light sources and/or multiple photosensors may be used for sensing translational and/or angular displacement of the web and/or for determining web parameters. Systems using multiple sensor combinations provide signal redundancy, providing a more robust system. In some embodiments, energy modulated by more than one scale feature, for example about 3 to 20 features, is used to produce the sensor output signal. The output signal may average or otherwise combine the energy modulated by the multiple features. In this configuration, if a single feature, or even several features, are damaged or obscured by dirt, the averaged output signal is minimally impacted.
The scale features may include longitudinally arranged features, laterally arranged features or a combination of both longitudinally and laterally arranged features. As illustrated in
The scale features illustrated in
The use of both longitudinal and lateral scale features and compatible source/sensor combinations allows for indication of longitudinal and lateral web displacement as well as angular displacement.
As previously discussed, the flexible, elongated web having an integral scale is particularly advantageous for use in roll-to-roll manufacturing processes. For example, the integral scale may be used in positioning the web for manufacturing processes that require alignment during successive manufacturing steps, such as in the formation of layered electronic devices.
Alternatively, as illustrated in
In some embodiments, illustrated in
Scales formed on flexible material are particularly useful when they are attached to a base substrate. One consideration encountered when attaching scales to a machine or other substrate is the difference in the coefficient of thermal expansion (CTE) between the substrate and the scale. For example, if a very rigid scale is used, the scale will expand at a different rate than the substrate, so the scale changes a different amount by (CTEscale−CTEsubstrate)*deltaT*scale length. If the scale expands less than the substrate, it is relatively easy to manage, as the scale is in tension, and will always follow a straight line. However, if the scale expands more than the substrate, the scale will be in compression, and additional forces are generated that tend to buckle the scale (i.e. the scale tends to ripple out of plane). The compressive force generated is λ(modulus)*A(area)*strain.
Flexible scales formed in accordance with various embodiments of the disclosure have CTE's about 5 times higher than the typically used steel scales, but have modulus of elasticity about 300 times less that steel scales. The net force is about 60 times smaller. Thus, a flexible scale described herein may be bonded to a substrate without significant buckling, allowing the scale to more closely track the position of the substrate.
By using a flexible scale, such as a plastic or polymer scale having rectangular array of pyramids which allow x/y readout, it is possible to make flexible scale much larger than scales currently available. For example, it is possible to make scales that are miles long with widths of 60 inches or more.
In accordance with various embodiments, the scale features may comprise prisms configured to reflect light via total internal reflection. Total internal reflection (TIR) occurs when the incident angle of light is greater than or equal to a critical angle θc. For incident angles greater than θc, all incoming energy is reflected.
The TIR scale features may be formed in any shape or configuration that provides reflection via TIR. In some embodiments, the TIR scale features may comprise right regular prisms, as illustrated in
The use of TIR scale features may not be practical for all applications, for example when the web is opaque. In one embodiment the scale features comprise raised features that are replicated on the web. The raised features may be coated with a reflective material. In other embodiments, the deposition of the scale features may comprise printing features, such as via ink jet, on the web in a prescribed manner.
As previously discussed, scale features on the web may be used to modulate energy for indicating the translational and/or rotational displacement of the web. Additionally, or alternatively, the scale features may be employed in the measurement of various web parameters. In various embodiments, parameters which depend on dimensional changes of the web, such as temperature, strain, and/or modulus of elasticity, may be measured using the scale features.
In one application, the scale features may be used to measure a change in web temperature. A change in web temperature of δT causes a corresponding dimensional change of δLT. The scale features and sensor circuitry can be used to measure the dimensional change, δLT. The change in temperature of the web, δT, may be derived from the measured dimensional change.
The scale features may be used to measure web strain, the amount of deformation caused by force that stretches the web. For example, considering only longitudinal strain, as the web having an initial length of L is stretched along its longitudinal (x) axis, the web length changes by δL, from a first length, L1, to a second length, L2. The linear strain, εx, of the longitudinally stretched web is expressed by εx=δL0. The strain along the x axis at any point of the web may be expressed as the differential of the displacement in the x direction at any point along the axis, εx=∂ux/∂x. The angular or shear strain takes into account deformation along both the longitudinal (x) axis and the lateral (y) axis. The angular or shear strain at any point of a web,
Scale features arranged in both the longitudinal (x) and lateral (y) directions can be used, along with compatible energy source/sensor combinations, to measure longitudinal and lateral deformations of the web. These deformations may be used to calculate linear strain along the x and y axis as well as angular or shear strain.
In one application, measured deformation of the web may be used to calculate the modulus of elasticity. The modulus may be calculated as λ=stress/strain. Thus, using a known force and measuring web strain as described above, the modulus of elasticity of the web may be determined.
The embodiments described herein involve webs having integral scale features that allow continuous tracking of the translational and angular displacement of a web, and/or allow measurement of various web parameters. The scale features may be formed in or on the web by various techniques. For example, the scale features may be deposited or otherwise formed on the web such as by a cast and cure process. Alternatively, the features may be made in the web, such as by scribing, ablating, printing or other techniques.
In some embodiments, the scale features may be erased and rewritten. For example, in one application, the scale features may be erased or written in magnetic media by selectively exposing portions of the media to a magnetic field. In another application, the scale features may be erased and/or written in optical media, such as by using a laser to heat portions of the scale to active an organic dye. In yet another embodiment, the scale features may be erased and/or written by modifying the optical properties of the scale features. For example, the index of refraction of an optical material may be modified through chemical processing to erase or write the scale features on the substrate.
Various techniques may be used to apply the scale features to webs such as webs made of paper, fiber, woven or nonwoven material. The webs may comprise polyester, polycarbonate, PET, or other polymeric webs. Techniques for formation of TIR scale features are described in commonly owned US patent application identified by Attorney Docket No. 63013US002 filed concurrently with the present application and incorporated herein by reference.
The foregoing description of the various embodiments of the disclosure has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure to the precise form disclosed. Many modifications and variations are possible in light of the above teaching. It is intended that the scope of the disclosure be limited not by this detailed description, but rather by the claims appended hereto.
This application claims priority to U.S. Provisional Application No. 60/944,882, entitled “SYSTEMS AND METHODS FOR INDICATING THE POSITION OF A WEB”, filed on Jun. 19, 2007, the disclosure of which is incorporated herein by reference.
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/US08/67375 | 6/18/2008 | WO | 00 | 12/14/2009 |
Number | Date | Country | |
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60944882 | Jun 2007 | US |