HK1228019B - Method, apparatus, and system for forming filter elements on display substrates - Google Patents

Description

Method, apparatus, and system for forming filter elements on a display substrate

This application is a divisional application of Chinese patent application No. 201180046382.6, entitled “Method, device and system for forming filter elements on a display substrate”.

Related applications

This application is a U.S. national phase application under 35 U.S.C. 371 of International Patent Application No. PCT/CA2011/000582, filed on July 21, 2011, and claims the benefit of U.S. Provisional Application Serial No. 61/400,291, filed on July 26, 2010, and further claims the benefit of U.S. Provisional Application Serial No. 61/402,234, filed on August 26, 2010, and further claims the benefit of U.S. Provisional Application Serial No. 61/520,138, filed on June 6, 2011. The entire disclosures of all of the above applications are incorporated herein by reference.

Technical Field

The present invention relates generally to electronic displays and, more particularly, to forming filter elements on display substrates.

Background Art

Electronic displays are used to provide visual output for a variety of electronic devices, such as televisions, computer monitors, mobile communication devices, and e-readers. Various types of electronic displays, including liquid crystal displays (LCDs), organic light-emitting diode displays, electrowetting displays, and electrophoretic displays, are widely used.

An LCD display is an example of a transmissive display that utilizes color filters to effectively convert a monochrome display into a color display. A thin-film transistor (TFT) layer and a color filter layer are typically fabricated separately on glass substrates that are then aligned and assembled into a display unit. The TFT layer includes multiple drivers, each of which is operable to control a small portion or picture element (pixel) of the display. The color filter layer typically includes red, green, and blue filter elements that cover the display pixels and filter white light to display a color image.

Color filters for LCD displays are currently primarily fabricated using photolithography, but attempts have also been made to laser- or inkjet-print color pigments onto the color filter glass substrate, or even directly onto the TFT layer. Directly printing the pigment onto the TFT layer eliminates the need for subsequent precise alignment between the color filter and TFT layers.

An electrophoretic display (EPD) is an example of a reflective display, in which ambient light provides illumination and the display pixels are electronically controlled by underlying TFTs to selectively reflect the ambient light, thereby forming a displayed image. Like LCD displays, EPDs are inherently monochrome. To provide a color display, a color filter element can be formed over the reflective display pixels. This color filter element can cover substantially the entire area of the associated reflective display pixel, or it can cover only a portion of that area.

There remains a need for improved methods and apparatus for forming color filters.

Summary of the Invention

According to one aspect of the present invention, a method for forming a filter element on at least one display substrate using a digital imaging system operable to selectively deposit filter material at a plurality of deposition locations is provided. The method comprises: receiving orientation information defining an arrangement of a plurality of pixels associated with the at least one display substrate; identifying a pixel in the plurality of pixels to receive the filter material to form the filter element thereon; selecting a deposition location within each identified pixel based on the orientation information so as to satisfy an alignment criterion associated with the arrangement of the filter element within the pixel; and controlling the digital imaging system to deposit the filter material at the selected deposition location.

Each identified pixel may have an associated boundary within which the filter element is to be positioned, and the alignment criteria may include a threshold representing an allowable deviation in the positioning of the filter element relative to the boundary, wherein the selecting may include selecting the deposition position such that when the successively shifted positioning of the filter element relative to the boundary in the identified pixel remains within the threshold, the positioning of the filter element is successively shifted. The selecting may further include selecting the deposition position such that when the successively shifted positioning exceeds the threshold, the positioning of the filter element is shifted to within the threshold.

Selecting a deposition position to move the arrangement of the filter elements back to within the threshold may include selecting a deposition position that is shifted relative to the boundary by at least the spacing between adjacent deposition positions.

The method may comprise introducing a random variation in the threshold value, the random variation being operable to disrupt a regular pattern that occurs in the arrangement of the filter elements due to the successive shifts of the arrangement of the filter elements in successive pixels.

Identifying the pixel may include identifying a pixel among a plurality of pixels that is used to receive one of a plurality of color filter materials, and selecting the deposition position may include selecting the deposition position so that the arrangement of the filter elements varies between each of the plurality of color filter materials, thereby disrupting a regular pattern that occurs in the arrangement of the filter elements due to the successive movement of the filter elements in successive pixels.

The deposition positions may include a first deposition position and a second deposition position, wherein the first deposition position is approximately aligned along the first axis of the display substrate, the second deposition position is approximately aligned along the second axis of the display substrate, the second deposition position is more closely spaced than the first deposition position, and each identified pixel may have an associated first axis boundary in the direction of the first axis and an associated second axis boundary in the direction of the second axis, the first axis boundary and the second axis boundary defining the area within which the filter element will be arranged, and the selection may include: selecting the first deposition position to provide a larger spacing between the filter element and the first axis boundary, and selecting the second deposition position to provide a smaller spacing between the filter element and the second axis boundary, so that the selection of the first deposition position and the second deposition position combined together meets the coverage criteria associated with the filter element.

The selecting may further comprise introducing random variations in the arrangement of the filter elements, the random variations being operable to disrupt regular patterns that occur in the arrangement of the filter elements as a result of the selecting.

Introducing random variation in the arrangement of the filter element may include introducing random variation in the selection of a first deposition position such that the larger spacing in the direction of the first axis varies randomly between successive identified pixels, and the selection of a second deposition position may include selecting the second deposition position to meet a coverage criterion associated with the filter element.

The first deposition location can be associated with an excitation channel of a plurality of independently excitable channels that are generally aligned along a first axis and operably configured to deposit a filter element at a selected discrete deposition location associated with the channel.

The independently activatable channels may be provided by one of: a laser radiation source operably configured to generate a plurality of independently activatable laser beams that are selectively operable to deposit filter element material from a filter material donor sheet onto at least one display substrate; and a plurality of inkjet nozzles for depositing filter elements onto at least one display substrate.

The second deposition locations may be associated with a relative displacement between the display substrate and the digital imaging system in a direction generally aligned with the second axis, thereby facilitating deposition of the filter material at selected deposition locations arranged in an elongated column extending along the second axis.

The selection may further include introducing random variation in the arrangement of the filter elements, the random variation being operable to disrupt the regular pattern that occurs in the arrangement of the filter elements in the identified pixels on each display substrate due to the spacing between adjacent deposition locations.

Identifying the pixel may include randomly identifying a pixel among the plurality of pixels to receive one of a plurality of color filter materials, such that filter elements of each resulting color are randomly dispersed across each display substrate.

The at least one display substrate may include at least two display substrates, the deposition position may include a first deposition position and a second deposition position, the first deposition position being approximately aligned along a first axis of the at least two display substrates, the second deposition position being approximately aligned along a second axis of the at least two display substrates, the at least two display substrates being arranged successively along the second axis, the receiving orientation information may include receiving information defining an arrangement of a plurality of pixels associated with each of the at least two display substrates relative to the first axis and the second axis, the method further comprising: calculating, for at least one of the at least two display substrates, an offset associated with the plurality of pixels in the direction of the first axis; determining a remaining portion of the offset that cannot be compensated for by selection of the deposition position, and controlling the digital imaging system may include: causing a relative displacement between the at least two display substrates and the digital imaging system in the direction of the second axis; and resetting the digital imaging system relative to the at least two display substrates in the direction of the first axis by the remaining portion of the offset associated with at least one display substrate to position the digital imaging system so as to deposit the filter element material on at least one of the at least two display substrates.

Resetting the digital imaging system may include resetting the digital imaging system while the digital imaging system is moved between at least two display substrates.

Causing a relative displacement between at least two display substrates and the digital imaging system in the direction of a second axis may include: alternatingly causing the relative displacement in a first pass in a first direction aligned with the second axis and in a second pass in a second direction opposite to the first direction, controlling the digital imaging system may include: controlling the digital imaging system to deposit filter material on a first of the at least two display substrates during the first pass and on a second of the at least two display substrates during the second pass, and resetting the digital imaging system may include resetting the digital imaging system when changing direction between the first pass and the second pass.

The at least two display substrates may include more than two display substrates arranged continuously along the second axis, controlling the digital imaging system may include controlling the digital imaging system so that the filter material is deposited on alternating display substrates among the more than two display substrates during a first pass, and on remaining display substrates among the more than two display substrates during a second pass, and resetting the digital imaging system may further include resetting the digital imaging system when the digital imaging system is arranged between at least one of the alternating display substrates among the at least two display substrates during the first pass, or between the remaining display substrates among the display substrates during the second pass.

The at least one display substrate may be individually disposed on a substrate mounting surface of the digital imaging system, and receiving the orientation information may include generating the orientation information by locating a mark on each display substrate.

The method may include causing selected pixels on at least one display substrate to be actuated to display the indicia.

The at least one display substrate may include a plurality of display substrates having at least one common substrate layer, and receiving the orientation information may include generating the orientation information by locating markings on the at least one common substrate layer.

Positioning the mark may include positioning a camera associated with the digital imaging system to acquire image data representing a portion of at least one display substrate having the mark, and the method may further include processing the image data to determine the relative position of the mark.

The deposition positions may include a first deposition position and a second deposition position, the first deposition position being approximately aligned along the first axis of the display substrate, and the second deposition position being approximately aligned along the second axis of the display substrate, and controlling the digital imaging system may include: alternately causing relative displacement in a first pass in a first direction aligned with the second axis and causing relative displacement in a second pass in a second direction opposite to the first direction; during the first pass, causing the filter material to be deposited at a first group of selected deposition positions, and during the second pass, causing the filter material to be deposited at a second group of selected deposition positions.

The first set of selected deposition locations may include alternating selected deposition locations along the first axis, and the second set of selected deposition locations may include the remaining selected deposition locations along the first axis.

The method may include shifting the digital imaging system in the direction of a first axis between the first pass and the second pass.

According to another aspect of the present invention, a computer-readable medium is provided, on which is encoded a code for directing a controller processor circuit to execute any one of the above methods.

According to another aspect of the present invention, a display device is provided, which has a filter element formed according to any one of the above methods.

According to another aspect of the present invention, a digital imaging system is provided that is operable to selectively deposit filter material at a plurality of deposition locations to form filter elements on at least one display substrate. The digital imaging system includes a controller that is operably configured to: receive orientation information defining an arrangement of a plurality of pixels associated with the at least one display substrate; identify a pixel among the plurality of pixels that is to receive the filter material to form the filter element on the pixel; select a deposition location within each identified pixel based on the orientation information so as to satisfy an alignment criterion associated with the arrangement of the filter element within the pixel; and control the digital imaging system to deposit the filter material at the selected deposition location.

According to another aspect of the present invention, a method and system for forming a filter element on at least two display substrates is provided, using a digital imaging system operable to selectively deposit filter material at a plurality of deposition locations. The deposition locations include a first deposition location and a second deposition location, the first deposition location being substantially aligned along a first axis of the display substrate, the second deposition location being substantially aligned along a second axis of the display substrate, the at least two display substrates being arranged consecutively along the second axis. The method includes receiving orientation information defining the arrangement of a plurality of pixels associated with each display substrate relative to the first axis and the second axis; identifying a pixel in the plurality of pixels that will receive the filter material to form the filter element on the pixel; selecting a deposition location within each identified pixel based on the orientation information so as to satisfy an alignment criterion associated with the arrangement of the filter element within the pixel; and calculating, for at least one display substrate, an offset associated with the plurality of pixels in the direction of the first axis. The method further includes determining a remaining portion of the offset that cannot be compensated for by selecting deposition locations, controlling the digital imaging system to deposit the filter material at the selected deposition locations by: providing a corresponding relative displacement between the display substrate and the digital imaging system in a first pass in a first direction aligned with a second axis and in a second pass in a second direction opposite to the first direction, depositing the filter material on alternating ones of the at least two display substrates during the first pass, and depositing the filter material on the remaining ones of the at least two substrates during the second pass. The method further includes repositioning the digital imaging system relative to the display substrates by the remaining portion of the offset when the digital imaging system is positioned between at least one of the alternating ones of the display substrates during the first pass or between the remaining ones of the display substrates during the second pass.

According to another aspect of the present invention, a method and system for forming filter elements on a substrate that is subsequently aligned with a display substrate to form a display is provided. The method includes selecting locations on the substrate to receive filter material to form the filter elements, introducing random variation in the arrangement of the filter elements, and forming the filter elements at the selected locations.

According to another aspect of the present invention, a computer-readable medium is provided, on which is encoded a code for directing a controller processor circuit to execute the above method.

According to another aspect of the present invention, a display device is provided, which has a filter element formed according to the above method.

According to another aspect of the present invention, a method for forming a filter element on a display substrate is provided. The method includes selectively depositing a filter material on a plurality of pixels associated with the display substrate to form the filter element, and selectively exposing the deposited filter material to laser thermal radiation to condition the deposited filter material.

Selectively depositing may include transferring the filter material from the donor to the display substrate in response to receiving radiation from an imaging controllable laser source, and exposing the deposited filter material to laser thermal radiation may include exposing the deposited filter material to radiation from the imaging controllable laser source.

Transferring the filter element from the donor to the display substrate may include: for multiple donors, transferring the filter material from the donor to the display substrate, wherein exposing the deposited filter material to laser thermal radiation may include: exposing the deposited filter material to laser thermal radiation when completing the transfer of material from each of the multiple donors.

Selectively depositing the filter material may include controlling an image-controllable laser source to effect deposition of the filter material, wherein exposing the deposited filter material to laser thermal radiation may include exposing the display substrate to laser thermal radiation generated by the image-controllable laser source.

Selectively depositing the filter elements may include controlling a first image-controllable laser source to effect deposition of the filter elements, and exposing the deposited filter material to laser thermal radiation may include exposing the display substrate to laser thermal radiation generated by a second image-controllable laser source.

The method may include varying an operating intensity associated with a laser source prior to selectively exposing the deposited filter material to laser thermal radiation.

Exposing the deposited filter material to a source of laser thermal radiation may include selectively exposing portions of the display substrate having the deposited filter material to the laser thermal radiation.

The filter element may include a color filter element.

The color filter element may include a color filter element on a reflective display substrate.

According to another aspect of the present invention, a computer-readable medium is provided, on which is encoded a code for directing a controller processor circuit to execute any one of the above methods.

According to another aspect of the present invention, a display device is provided, which has a filter element formed according to any one of the above methods.

According to another aspect of the present invention, a digital imaging system for forming a filter element on a display substrate is provided. The system includes a controller operably configured to cause the digital imaging system to selectively deposit a filter material on a plurality of pixels associated with the display substrate to form the filter element, and selectively expose the deposited filter material to laser thermal radiation to condition the deposited filter material.

Other aspects and features of the present invention will be apparent to those skilled in the art from the following description of specific embodiments of the present invention in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention are described in the following figures.

FIG1 is a perspective view of a digital imaging system.

FIG. 2 is a plan view of a portion of a display substrate manufactured in the digital imaging system according to the first embodiment of the present invention shown in FIG. 1 .

FIG3 is a structural diagram of an embodiment of a processor circuit of the controller shown in FIG1 .

FIG. 4 is a process flow diagram of forming filter elements on multiple display substrates using the processor circuit shown in FIG. 3 .

FIG. 5 is a process flow diagram of the portion of the process shown in FIG. 4 for receiving orientation information.

FIG. 6 is a schematic plan view of a plurality of display substrates shown in FIG. 1 .

FIG. 7 is an enlarged view of two of the display substrates shown in FIG. 6 .

FIG. 8 is a process flow diagram of a portion of the process shown in FIG. 4 for selecting deposition locations.

9 is a further enlarged view of two of the display substrates shown in FIG. 6 according to an alternative embodiment of the present invention.

10 is a schematic diagram of three of the display substrates shown in FIG. 6 according to an alternative embodiment of the present invention.

FIG. 11 is a schematic diagram of three of the display substrates shown in FIG. 6 according to another alternative embodiment of the present invention.

FIG. 12 is a schematic diagram of one of the display substrates shown in FIG. 6 according to yet another alternative embodiment of the present invention.

FIG. 13 is a flow chart of a process executed by the processor circuit shown in FIG. 3 to adjust a deposited filter element.

DETAILED DESCRIPTION

Digital imaging system

1 , a digital imaging system is generally indicated by the reference numeral 100 . The system 100 is configured as a flatbed imaging system and includes a dimensionally stable base 102 having a planar upper surface 104 .

The system 100 also includes a bridge 106 supported on the base 102. The bridge 106 provides stable support for an imaging head 108, which is mounted on the bridge for movement along a first axis (indicated by arrow 110). In the illustrated embodiment, the system 100 includes a first-axis linear motor 112 for moving the imaging head 108 in either direction along the first axis 110. The linear motor 112 further includes an encoder scale 114 for providing position feedback, thereby facilitating precise positioning and motion control of the imaging head 108.

The system 100 also includes a mounting table or chuck 116 for mounting a plurality of display substrates 120. The chuck 116 has a flat mounting surface 118. In this embodiment, the chuck 116 includes a plurality of ports distributed along the mounting surface 118. When the mounting surface 118 is coupled to a vacuum generator (not shown), the chuck 116 attracts the display substrates 120, bringing the display substrates 120 into close contact with the flat mounting surface 118. To achieve reciprocating motion along a second axis (indicated by arrow 124), the chuck 116 is supported on air bearings (not shown). In flat panel imaging systems, the second axis 124 is generally orthogonal to the first axis 110, but in some embodiments, the angle between the first and second axes may not be 90°. The system 100 further includes a second-axis linear motor 122 for moving the chuck 116 in either direction along the second axis 124. The linear motor 122 also includes an encoder scale 126, which provides position feedback and control of the reciprocating motion along the second axis.

In one embodiment, the imaging head 108 includes a radiation source configured to provide a plurality of light beams 128. The radiation source can be a laser, such as a laser diode, and the imaging head 108 can further include a multi-channel modulator (not shown) in which individual channels are selectively excited to generate the plurality of light beams 128.

While the embodiment shown in FIG1 is described as including specific components such as linear motors 112 and 122, the system 100 can also be implemented using other components, such as rotary motors and ball screw mechanisms or belt drives. Similarly, the chuck 116 can remain stationary, and movement of the imaging head 108 can be achieved by mounting the imaging head on a gantry that allows movement of the imaging head in two directions aligned with the axes 110 and 124.

In the embodiment shown in FIG1 , each display substrate is separated from adjacent display substrates, and when mounted on the chuck 116, there are likely to be non-negligible orientation differences between the display substrates, which need to be eliminated in the subsequent imaging process. In other embodiments, one or more display substrates 120 can be processed on a single substrate or other carrier loaded into the digital imaging system 100 as a single substrate. In such embodiments, the registration between the display substrates 120 can be significantly more accurate.

Each display substrate 120 includes a plurality of markings 134 disposed on its exposed exterior surface 130 to facilitate generating orientation information associated with the relative arrangement of the display substrates. The system 100 further includes a camera 132 mounted on the imaging head 108 and configured to capture images of the markings used to generate the orientation information. Because the camera 132 is mounted on the imaging head 108 and thus moves with the imaging head 108, precise positioning of the camera is also achieved via an encoder scale 114 associated with the linear motor 112. The images of the markings 134 captured by the camera 132 can thus be processed to determine the relative orientation of each display substrate 120. The relative orientation between the plurality of imaging beams 128 and the camera 132 can be determined by using one or more imaging beams 128 to create a target feature on a test surface mounted on the chuck 116. The image of the target feature can then be captured and processed to determine the relative offset between the imaging beam 128 and the camera 132, which can be stored as a calibration value.

In the illustrated embodiment, each display substrate 120 includes three markings 134, which may have been marked on the display substrate during a previous processing step. Alternatively, in some embodiments, the display substrate 120 includes reflective display pixels that are already functional, and selected pixels on each display substrate can be activated to display the markings, eliminating the need for the display substrate to include the previously marked markings. For example, in other embodiments, the markings may include physical features of the display substrate, such as a portion of a TFT element associated with a particular pixel. In each of these marking embodiments, the markings on the display substrate 120 are positioned in a known, fixed relationship relative to the display pixels 200, thereby providing the relative position of each pixel with respect to the markings, in combination with the known pixel size and structure. Typically, the pixels 200 of the display substrate are formed using a photolithographic process, which can provide very precisely spaced and oriented pixels 200 and markings 134.

In some embodiments, it may be necessary to provide motion in a third axis that is generally orthogonal to the first axis 110 and the second axis 124 to account for differences in thickness between various display substrates that may be processed using the system 100. For imaging heads 108 that utilize high numerical aperture imaging optics to form the plurality of imaging beams 128, it may be necessary for the imaging head to utilize an autofocus system for maintaining focus of the beams throughout the imaging area of the system 100. In such cases, adjustment of the third axis may be important to ensure that the autofocus system can maintain focus.

In one embodiment, the filter material used to form filter elements on multiple display substrates 120 is provided in the form of a donor sheet 150 (a portion of which is shown in FIG1 ). Donor sheet 150 includes a filter material disposed on a support layer (e.g., a polyester film). To enhance transfer of the filter material to the display substrates upon exposure to radiation from beam 128, donor 150 may also include a release layer disposed between the filter material and the support layer. For example, to form color filter elements, the filter material may include multiple colorants, such as red, green, and blue colorants, or cyan, magenta, and yellow colorants. Other colorants may also be added to the multiple colorants. For example, a colorant such as yellow colorant may be added to the red, green, and blue colorants to increase the color gamut of the display. In this case, different donors 150 may be separately mounted and imaged to complete the deposition process of the color filter elements. Thermal transfer donor technology is already commercially used in the printing industry, and some donor media, such as Fuji and Kodak Approval ^™, can be used to make color proofs of digital images. Therefore, a suitable donor 150 will contain a colorant material suitable for providing a color filter element having the desired light transmission characteristics.

While these embodiments are generally described with reference to the deposition of color filter elements configured to transmit specific wavelengths of incident light, the filter elements can also function to modify other properties of the incident light. For example, the filter elements can include polarizing materials deposited on selected pixels to polarize light transmitted through the filter elements. Other examples of depositable filter elements include interference filters or anti-glare filters.

As described above, in the embodiment shown in FIG1 , the imaging head 108 is a multi-channel imaging head that generates multiple imaging beams 128 directed toward a donor sheet 150 covering the exposed outer surface 130 of the display substrate 120. The donor material 150 is applied to the display substrate 120 by rolling the donor material, and the correct position of the donor 150 is ensured by vacuum applied to multiple ports distributed on the mounting surface 118. The multiple ports on the mounting surface 118 can be divided into a substrate port area and a donor port area, which are connected to separate vacuum circuits to ensure that the display substrate 120 is correctly positioned when the donor 150 is applied. During or after the donor is rolled into contact with the multiple display substrates 120, the donor area ports are activated to ensure that the donor is correctly positioned.

The system 100 further includes a controller 140 that is operatively configured to control the operation of the digital imaging system. The controller 140 includes control signal input/output ports 142, 144, and 146 for controlling the imaging head 108, the linear motor 112, and the linear motor 122, respectively. Additional signal output ports (not shown) may be provided to control a vacuum generator, a donor mount, and other necessary imaging system functions. In the illustrated embodiment, the signal port 142 generates signals for controlling the imaging head 108 to modulate selected ones of the plurality of imaging beams 128 based on image data stored in the controller. For example, the image data may be stored in the form of an image file such as a Tagged Image Format (TIFF) file.

Imaging of the thermal transfer donor may require that the imaging head 108 be configured to generate infrared light of a wavelength and power sufficient to cause thermal transfer of colorant from the donor 150 to the display substrate 120. One suitable imaging head 108 is a Thermal imaging head manufactured by Eastman Kodak Company of Rochester, New York. Although the various embodiments disclosed herein are described with reference to imaging of a thermal transfer donor, other imaging techniques for transferring filter material, such as inkjet transfer, ultraviolet transfer, laser exposure of color resist, or other methods, may also be implemented to form filter elements on the display substrate 120.

During operation of the system 100, as the imaging head 108 modulates the plurality of imaging beams 128 based on image data received from the signal port 142 of the controller 140, the controller 140 causes the chuck 116 to move along the second axis 124. In one embodiment, the chuck 116 is caused to traverse at a speed of approximately 2 m/s. The relative motion between the chuck 116 and the imaging head 108 causes the plurality of imaging beams 128 to be imaged along the second axis into an elongated column (illustrated as a dashed outline at 136) having a width comparable to the width of the plurality of beams 128 generated by the imaging head 108. In one embodiment, the imaging head 108 generates 224 imaging beams spaced 10.6 μm apart, resulting in an elongated column with a width of 2.374 mm.

Once the chuck 116 has traversed across the plurality of display substrates 120 in its first pass, the controller 140 causes the linear motor 122 to decelerate the chuck 116 to a stop and reverse the traversing direction of the chuck 116. While the chuck 116 is decelerating, the linear motor 112 moves the imaging head 108 across the width of one sliver column (i.e., across 2.374 mm in the embodiment described above), and imaging of another sliver column (not shown in FIG. 1 ) adjacent to the sliver column 136 begins during the return traversal of the chuck 116 during its second pass through the substrates 120. Accordingly, in the described operational embodiment, one sliver column is imaged with each pass of the chuck 116. However, in other embodiments, it may be desirable to image in an interleaved manner as described below. In such cases, the linear motor 112 may move the imaging head 108 across a distance less than the width of one sliver column so that the next imaged sliver column at least partially overlaps the already imaged sliver column.

The traversing of the chuck 116 and the movement of the imaging head 108 image a continuous, elongated column across the plurality of display substrates 120, facilitating the deposition of filter material at multiple deposition locations. For an imaging head 108 having an imaging beam 128 with a fixed spacing between beams, the corresponding deposition locations are defined as multiple discrete locations along the first axis 110. However, in the aforementioned exposure head embodiment, the beam 128 traverses across the display substrate 120 along the second axis 124, and accordingly, deposition along this axis can occur over a larger or smaller area than that provided along the first axis 110. For example, in a Kodak imaging head, the beam 128 can have a generally rectangular cross-section extending approximately 10.6 μm along the first axis 110 and only approximately 1-2 μm along the second axis 124. In this case, the deposition locations along the second axis 124 can be controlled to deposit filter material with greater precision than is possible along the first axis 110.

1 , the chuck 116 traverses across the upper surface 104 of the base 102 in the direction of the second axis 124, while the imaging head 108 moves only in the direction of the first axis 110. In other embodiments, the chuck may be stationary relative to the base 102, and the bridge 106 may be disposed on linear rails to facilitate traversing motion of the imaging head 108 in both the first axis 110 and the second axis 124.

In many cases, the display substrate 120 on which the filter elements are to be formed is rigid. However, even if the display being produced is to be flexible, it is quite common to process such a flexible display while mounting it on a rigid carrier that is subsequently removed. In other embodiments, the flexible display substrate can be configured to be mounted on a cylindrical drum surface, in which case the drum-based imager can replace the flat-panel imager shown in FIG1 . The flat-panel imaging system shown in FIG1 can also be used to process the flexible substrate.

Display substrate

A display substrate portion 138 (shown in FIG1 ) of one of the display substrates 120 is shown in greater detail in FIG2 . Referring to FIG2 , the display substrate portion 138 includes a plurality of pixels 200, which in this embodiment are reflective display pixels such that, in response to an activation signal provided to an underlying driver (not shown), ambient light incident on the pixels changes from being reflected by the pixels to being absorbed by the pixels.

In the particular embodiment shown, pixels 200 include a first group of pixels having green filter elements 202 formed thereon; a second group of pixels having blue filter elements 204 formed thereon; and a third group of pixels having red filter elements 206 formed thereon. An additional, uncovered, fourth group of pixels 208 is not provided with color filter elements. The color filter elements 202-206 and the uncovered pixels 208 are operable to generate a reflective image, wherein light reflected from the first, second, and third groups of pixels provides a color component to the generated image, while the uncovered pixels 208 provide a brighter display. Thus, due to the inclusion of uncovered pixels 208, this arrangement offers a tradeoff between reduced color gamut and displayed image brightness. In the illustrated embodiment, each color filter element 202-206 covers only a portion of the area associated with each covered pixel 200, while a portion 210 remains uncovered. The uncovered areas 210 perform the same function as the uncovered pixels 208, where the uncovered areas increase the brightness of the reflective display. Because these uncovered areas reduce the likelihood that the deposition of filter element material will extend beyond the boundaries of the associated pixel 200 into adjacent pixels, the uncovered areas 210 also relax tolerances associated with the placement of the filter elements 202-206. Various other arrangements of color filter elements 202-206, uncovered pixels 208, and uncovered areas 210 can be used to create a reflective display. For example, some embodiments may omit uncovered pixels 208 and increase uncovered areas 210. Similarly, other embodiments may fully cover the area of each pixel with filter material and rely on the uncovered pixels 208 to produce the desired display brightness.

While color filters for reflective displays can be fabricated on a separate substrate, as in the case of transmissive displays, color filter elements can also be formed directly on reflective display pixels using digital imaging techniques. Digital imaging of color filters involves selectively transferring colorants onto an otherwise monochromatic reflective display using a digital imaging system.

Non-reflective displays, such as LCDs, typically require that the entire luminous area of a pixel be covered by a filter material. However, the non-luminous areas of the pixel are typically covered by a black matrix material that blocks these areas. In such displays where the light flux is generated internally, brightness can be increased by increasing the backlight intensity. Therefore, display brightness may be less of a concern than in reflective displays.

Regardless of the type of display, the placement of the filter elements should be sufficiently precise to avoid undesirable effects, such as adjacent pixels being partially covered by adjacent filter elements, or failing to cover sufficient pixel area. Insufficient placement accuracy can also cause undesirable image artifacts that are visible to the eye and detract from the image quality produced by the resulting display. In particular, the human eye is very sensitive to regular patterns, which can be caused by errors in the placement of color filter elements.

In one embodiment, the pixel 200 on the reflective display may have a size between about 90 μm and 220 μm, and the coverage area of the color filter material may be about 60% to about 100% of the pixel area.

Throughput is an important consideration when imaging multiple display substrates 120 and it is desirable to process multiple displays as shown in FIG1 . Simultaneously imaging multiple display substrates 120 reduces the time overhead associated with loading and unloading the display substrates 120 and associated donor sheets 150. Simultaneous imaging also reduces the overhead associated with slowing down the chuck 116 at the end of each traverse, reversing the chuck's direction of motion, and reaccelerating to imaging speed, as compared to imaging a single substrate at a time.

In embodiments where multiple display substrates 120 are connected via a common carrier or substrate layer, the offset and rotation of the pixels of each display substrate should be substantially aligned. However, in other embodiments, such as that shown in FIG1 , even if initially fabricated as part of a larger substrate supporting multiple displays, the individual display substrates 120 are separate and may therefore have non-negligible differences in orientation between the individual displays. This complicates alignment of the imaging axes appropriate for the pixel orientation, as the pixels on one display substrate may not be aligned with the pixels on other display substrates.

Accordingly, it is generally not possible to select an imaging start position that guarantees the correct placement of the filter elements 202-206 across all of the multiple display substrates. This error can be significantly dependent on the relative alignment of the various substrates, and failure to eliminate such variations can result in significant placement errors of the filter elements relative to the pixels of the display substrates. Furthermore, the display substrate 120 can be rotated about axes 110 and 124, which can introduce additional placement errors.

Digital Imaging System Controller

3 , in one embodiment, the controller 140 may utilize a processor circuit generally shown at 300. The processor circuit 300 includes a microprocessor 302, a program memory 304, a variable memory 306, a media reader 308, and input/output ports (I/O) 310, all of which are in communication with the microprocessor 302.

Program code for directing the microprocessor 302 to perform various functions is stored in a program memory 304, which can be implemented as a random access memory (RAM), a hard disk drive (HDD), a non-volatile memory such as flash memory, or a combination thereof. The program memory includes a first program code block 320 for directing the microprocessor 302 to execute operating system functions and a second code block 322 for directing the microprocessor to control the imaging functions of the digital imaging system 100 to form filter elements on the plurality of display substrates 120.

The media reader 308 facilitates loading program code into the program memory 304 from a computer readable medium 312 such as a CD-ROM 314, flash memory 316, or a computer readable signal 318, such as may be received over a network, for example.

The I/O 310 includes a control signal input/output port 142. The I/O 310 also includes a motor driver 380 having a control port 144 for controlling the first-axis linear motor 112 and a motor driver 382 having a control port 146 for controlling the second-axis linear motor 122. The I/O 310 may additionally include other outputs and/or inputs for controlling other functions of the digital imaging system 100, such as operation of the camera 132, loading of the donor 150, vacuum operation of the chuck 116, and the like.

The variable memory 306 includes a plurality of storage locations including an orientation information storage 350 for storing display substrate and pixel values, a display configuration storage 352 for storing values regarding pixel configuration associated with the display substrate 120, a storage 354 for storing placement thresholds, and a digital mask storage 356 for storing deposition position mask values. The variable memory 306 may be implemented as, for example, random access memory, flash memory, or a hard drive.

In other embodiments (not shown), the controller 140 may be partially or fully implemented using hardware logic circuits including, for example, discrete logic circuits and/or application specific integrated circuits (ASICs).

Forming filter elements

4 , a flow chart is shown generally at 400 that depicts modules of code for directing the processor circuit 300 to form filter elements on a plurality of display substrates 120 using the digital imaging system 100. The modules generally represent code that may be read from the computer-readable medium 312 and stored in the program memory storage 322 to direct the microprocessor 302 to perform various functions associated with depositing filter element material on the display 120. The actual code used to implement each module may be written in any suitable programming language, such as C, C++, and/or assembly code.

The process 400 begins at block 402 , which directs the microprocessor 302 to receive orientation information defining a configuration of a plurality of pixels 200 associated with each display substrate 120 .

The process then continues at block 404, which directs microprocessor 302 to identify pixels in the plurality of pixels 200 that will receive filter material to form filter elements 202-206 on the identified pixels. In one embodiment, block 404 directs microprocessor 302 to read pixel configuration information from display configuration storage 352 of variable memory 306. In many embodiments, multiple display substrates 120 will be identically configured, and the pixel configurations (i.e., the size, number, and layout of the pixels) will be identical. In other embodiments, differently configured display substrates 120 may be processed simultaneously, in which case pixel configuration information is read from display configuration storage 352 for each display substrate 120. The pixel configuration information read from storage 352 identifies which pixels (i.e., the group of pixels on which filter elements 202-206 are disposed in FIG. 2 ) will receive the corresponding color filter material and may further define the size of the filter elements and/or uncovered area 210. For example, the pixel configuration information may be stored as a file that includes coordinates identifying the pixels.

Next, module 406 directs microprocessor 302 to select a deposition location within each identified pixel based on the orientation information received at module 402. In one embodiment, as described in detail below, the deposition location is selected to meet alignment criteria associated with the placement of filter elements 202-206 within pixel 200. Module 408 may further direct microprocessor 302 to store the digital mask values identifying the selected deposition locations for each filter element in digital mask storage 356 of variable memory 306. The digital mask may be stored as an image file such as a bitmap file, a TIFF file, or other suitable file format.

Next, the process 400 continues with block 408, which directs the microprocessor 302 to read the digital mask values in the digital mask storage 356 and generate control signals at ports 142, 144, and 146 to deposit the filter elements at the selected deposition locations, as described above with respect to the digital imaging system 100. The imaging head 108 responds by activating one or more laser beams corresponding to the selected deposition locations.

4, blocks 404 and 406 may be completed before depositing the filter element material in block 408. However, in other embodiments, block 408 may be initiated before blocks 404 and/or 406 are completed.

Receive orientation information

FIG5 illustrates the process of the module 402 for receiving orientation information shown in FIG4 in detail at 402. Referring to FIG5, the process 402 is executed for each display substrate in the plurality of display substrates 120. The process begins at module 500, which directs the microprocessor 302 to generate control signals to position the camera 132 to acquire image data representing the portion of each display substrate 120 having the marking 134.

FIG6 illustrates a schematic plan view of a display substrate 120. Referring to FIG6 , in one embodiment, nine individual display substrates are mounted for simultaneous processing in the digital imaging system 100. Generally, the display substrates 120 are mounted in a frame (not shown in FIG1 ) that orients each display substrate 120 approximately orthogonally relative to a first axis 110 and a second axis 124, which define the directions of motion of the imaging head 108 and the chuck 116. In FIG6 , the frame is represented by dashed lines 608-612 and 614-618, which illustrate the desired arrangement of the plurality of display substrates 120 about the axes 110 and 124.

Typically, display pixels 200 on display substrate 120 can be formed using a photolithographic process that provides pixels 200 with precise spacing and orientation. However, subsequent cutting of the display substrate into individual display substrates 120 may result in slight misalignment of pixels 200 relative to the substrate edges. The frame registration (if provided) may also be imprecise compared to the pixel size and/or spacing between deposition locations provided by imaging head 108. Thus, second display substrate 604 of the plurality of display substrates 120 has a configuration about axes 110 and 124 that includes an offset _D1 relative to line 614, an offset _D2 relative to line 610, and a rotation angle θ. In FIG6 , such misalignments, such as the size of pixels 200, are exaggerated for clarity. In practice, such misalignments may be small enough to be unnoticeable to the naked eye, but large enough to result in inaccurate placement of at least some filter elements 202-206 if not corrected. Furthermore, actual displays typically have much smaller pixel sizes and significantly greater numbers of pixels than the display shown in FIG. 6 .

Next, the process continues with block 502, which directs the microprocessor to process the image to determine the coordinates ( _x1 , _y1 ), ( _x2 , _y2 ), and ( _x3 , _y3 ) of each marker 134 on the display. For example, the coordinates ( _x1 , _y1 ) of the first marker 134 located on the upper right side of the first display substrate 602 in the plurality of display substrates 120 are displayed as coordinates of the coordinate system defined by the reference axes 110 and 124.

Next, module 504 directs the microprocessor 302 to calculate the values of D ₁ , D ₂ , and θ for the display substrates, and module 506 directs the microprocessor to store the values in the orientation information storage 350 of the variable memory 306 (shown in FIG. 3 ). Referring to FIG. 6 , in this embodiment, the value of D ₁ is calculated as the offset of the first mark on each display substrate from line 614, as shown on display substrate 604. Similarly, the value of D ₂ is calculated as the offset of the first mark from line 610. In this embodiment, the angle θ for each display substrate is defined as the angular deviation of a line extending between the right upper mark and the right lower mark on display substrate 604 relative to the second axis 124. In turn, the angle θ is given by:

Where (x ₁ , y ₁ ), (x ₂ , y ₂ ) are the respective coordinates of the upper and lower right markers as determined in block 502 . Next, block 506 directs microprocessor 302 to store the values in orientation information storage 350 of variable memory 306 .

Select deposition location

After executing blocks 402 and 404 in process 400, the information stored in the orientation information storage 350 and the display configuration storage 352 of the variable memory 306 facilitates calculation of the arrangement of the plurality of pixels 200 associated with each display substrate 120 relative to the first axis 110 and the second axis 124. Two display substrates 602 and 604 are shown in an enlarged view in FIG7 . Referring to FIG7 , the imaged elongated column 136 generated by the imaging head 108 is shown superimposed on the display substrates 602-604 and includes a plurality of deposition locations 700. In the depicted embodiment, the imaging head 108 is configured to form 24 deposition locations in the direction of the second axis. The deposition locations 700 shown in FIG7 are shown as having similar widths along the first axis 110 and lengths along the second axis 124, but in other embodiments, the widths along the first axis and the lengths along the second axis may be different. Because the motion of the imaging head 108 and the chuck 116 define the first axis 110 and the second axis 124, the elongated column 136 is aligned with the first and second axes.

The process flow for module 406 (shown in FIG. 4 ) for selecting deposition locations along first axis 110 in the first embodiment is represented by 800 in FIG. 8 . Referring to FIG. 8 , process 800 begins with module 802, which directs microprocessor 302 to read a placement threshold value from threshold storage 354 of variable memory 306 . The placement threshold value represents the allowable deviation for placement of the filter element relative to the boundaries of the identified pixel 200. Next, module 804 directs microprocessor 302 to read configuration information of display substrate 602 from storage 352 . Module 804 also directs microprocessor 302 to read orientation information of display substrate 602 from storage 350 .

Next, the process 800 continues with block 806, which directs the microprocessor 302 to use the configuration information and the orientation information to determine the location of the boundaries of the first identified pixel 702 relative to the deposition location 700. The orientation information provides values for _D1 , _D2 , and θ, which, combined with the pixel configuration of the display substrate, enable the calculation of the location and boundaries of each pixel on the display substrate relative to the first axis 110 and the second axis 124.

Next, module 808 directs the microprocessor 302 to select a deposition position that will position the first filter element 710 approximately centered within the pixel boundary. Referring to FIG. 7 , the illustrated first filter element 710 covers 16 deposition positions and is approximately spaced inwardly from the pixel boundary by approximately one deposition position along the first axis 110. Module 808 further directs the microprocessor 302 to save the selected deposition position of the first filter element 710 to the digital mask storage 356 of the variable memory 306.

Next, the process 800 continues with block 810, which directs the microprocessor 302 to calculate the placement of the second filter element 712 to be the same as the first axis deposition position of the first filter element 710, thereby processing the next identified pixel 704 along the second axis 124. In the illustrated embodiment, a placement deviation value of the filter element 712 relative to the center of the boundary of the second pixel 704 is calculated.

Subsequently, block 812 directs the microprocessor 302 to determine whether the placement deviation of the second filter element 712 meets the alignment criteria, which in this case includes determining whether the deviation value is less than or equal to the threshold value read at block 802. If, at block 812, the alignment criteria are met, the process continues with block 814, which directs the microprocessor 302 to save the selected deposition position of the second filter element 712 in the digital mask storage 356. Subsequently, the process continues with block 816, which directs the microprocessor 302 to determine whether all filter elements have been placed for the substrate 602. In this case, since additional filter elements 714 and 718 still need to be placed, block 816 directs the microprocessor 302 to return to block 810 and process the third pixel 706 in the same manner.

7 , the third pixel 706 also meets the alignment criteria, and therefore the digital mask value identifying the selected deposition location is saved to the digital mask in storage 356. When the alignment criteria of module 812 are met, the first three filter elements 710-714 are successively shifted leftward in the direction of the first axis 110 in the arrangement of filter elements on the display substrate 602.

If the alignment criteria are not met at block 812, the process continues with block 818, which directs the microprocessor 302 to shift the placement of the filter element by one or more deposition positions along the first axis 110, returning the filter element to a substantially central position within the pixel along the first axis 110. Referring to FIG. 7 above, in the illustrated embodiment, the alignment criteria for the fourth pixel 708 at block 812 are not met, and thus the placement of the fourth filter element 716 is shown shifted back along the first axis to one of the first-axis deposition positions. The process 800 then continues with block 818, which directs the microprocessor 302 to block 816, which directs the microprocessor 302 to save the selected deposition position of the fourth filter element 716 in the digital mask storage 356.

7 , the 24 deposition positions formed by the imaging head 108 allow for the simultaneous deposition of two columns of filter elements, so that the process 800 can be executed to generate digital mask values for positioning additional elements 718-722 within the imaged elongated column 136. Similarly, the process 800 can be executed to form a continuous elongated column (not shown) along the first axis 110, thereby forming digital mask values covering all pixels 200 associated with the display substrate. In the embodiment shown in FIG7 , the filter elements 710-722 correspond to the green filter element 202 shown in FIG2 , and the deposition positions for the additional filter elements 204 and 206 can similarly be selected by executing the same process 800.

If all filter elements for display substrate 602 have been placed at block 816, block 816 directs microprocessor 302 to block 820, which directs microprocessor 302 to process the next display substrate, in this case display substrate 604. Block 820 then directs microprocessor 302 back to block 804, where it reads the display configuration information and orientation information for display substrate 604. In embodiments where all substrates 120 have the same configuration, the step of reading the configuration information can be omitted. Block 806 again directs microprocessor 302 to use the configuration and orientation information to determine the placement of first identified pixel 702 relative to the boundaries of deposition location 700. With respect to substrate 602, the orientation information provides values for _D1 , _D2 , and θ, which enable the calculation of the position and boundaries of each pixel on the display substrate relative to first axis 110 and second axis 124. Referring to FIG. 7 , first identified pixel 726 on display substrate 604, which will receive deposition of filter element 728, is further shifted to the left along first axis 110. In this case, filter element 728 is offset from the beginning of elongated row 136 as shown at 730, and this offset is greater than the offset 732 associated with first filter element 710 on display substrate 602. Thus, process 800 eliminates differences in relative orientation between display substrates 602 and 604 by selecting deposition locations. Once all substrates in plurality of display substrates 120 have been processed, process 800 is terminated.

Due to the difference in orientation of display substrates 602 and 604, the deposition location 700 to be activated is selected for each identified pixel 702-708 so that the arrangement of color filter elements 710-716 within the pixel varies continuously.

In one embodiment, the threshold value stored in memory 354 can be predetermined based on the respective sizes of pixels 702-708 and the desired coverage of filter elements 710-722. For example, if the spacing between deposition locations is 10.6 μm, the pixel size along the first axis is 70 μm, and 60% of the pixel area is covered by the filter element, the threshold value can be set to approximately 5 μm. Thus, once the filter element deviates 5 μm from its center, the filter element is moved back 10.6 μm along the axis toward the center of the pixel. In other embodiments, the spacing between deposition locations, the pixel size, and/or the area of the pixel covered by the filter element can be smaller or larger than the values described above, and the threshold value can be selected accordingly. For example, referring to FIG. 2 , the threshold value can be selected to be proportional to the uncovered area 210 of pixel 200. In one embodiment, the threshold value can be selected by assigning an initial threshold value, processing one or more display substrates using the selected initial threshold value, and then inspecting the resulting displays for imaging artifacts or other defects. This process can then be repeated using different threshold values until a desired result is achieved.

7 , the spacing of the deposition locations along the second axis 124 is the same as the spacing of the deposition locations along the first axis 110, and thus a process similar to process 800 can be implemented to select deposition locations along the second axis. In other embodiments, the deposition locations along the second axis can be more closely spaced than the deposition locations along the first axis.

Referring to FIG. 2 above, in the example display substrate shown, blue filter elements 204 are positioned adjacent to green filter elements 202. Executing process 800 can result in filter elements 204 having the same continuous displacement and, therefore, a corresponding regular arrangement pattern, and such a pattern can reinforce the pattern already present in the arrangement of filter elements 202. Thus, in a second embodiment, process 800 can be performed such that the arrangement of filter elements 204 varies between various color filter materials, thereby disrupting any reinforcement of the regular pattern. In some cases, such variations can also reduce the effect of the pattern associated with color filter elements 202, as the overall pattern frequency may be increased, thereby reducing the ability of the user's eye to discern the resulting pattern. Such variations can be introduced by intentionally shifting certain filter elements from their generally central positions within the pixel, such that the continuous displacement results in a pattern shift in the arrangement of filter elements 204. Similar shifts can also be applied to the arrangement of red filter elements 206.

In a third embodiment of the process at block 406 shown in FIG4 , an additional step can be added to process 800 to introduce a random variation in the threshold value read out at block 802 . For certain combinations of pixel size, filter element coverage, and/or spacing of deposition locations, the continuous movement of the filter element arrangement that occurs when executing process 800 shown in FIG8 results in a regular pattern in the filter element arrangement, to which the human eye is highly sensitive, as previously disclosed. Due to the continuous movement of the filter element arrangement and the associated movement during execution of process 800 , the random variation in the threshold value can disrupt the regular pattern that occurs in the filter element arrangement. In one embodiment, the random variation can be set proportional to the threshold value. For example, for a threshold value of 5 μm, the random variation is ±40% or ±2 μm, which results in the placement threshold value being randomly selected from a set of threshold values including 3 μm, 5 μm, and 7 μm. This random selection from a set of thresholds may be accomplished based on a random number generated by a random number generator associated with the operating system, which is executed by operating system code in the first module of program code 320 of program memory 304 shown in FIG. 3 .

The second and third embodiments described above can also be combined to offset the pattern for different color filter elements 202-206 while also introducing random variation in the placement of the filter elements, thereby additionally disrupting possible placement patterns. Alternatively, at block 404 of process 400 shown in FIG4 , identifying pixels receiving filter elements can include randomly identifying pixels within the plurality of pixels 200 that receive one of a plurality of color filter materials. In this embodiment, the resulting filter elements for each color will be randomly dispersed across each display substrate, thereby disrupting possible patterns resulting from the placement of the filter elements. The randomized filter element positions will need to be provided to a display driver associated with the display substrate so that the correct pixel is activated for each corresponding color filter element.

While random variation in the filter element placement is accomplished in this embodiment by introducing a random variation in the threshold value read at block 802, in other embodiments, such random placement variation may be introduced elsewhere in process 800. For example, block 808 may direct microprocessor 302 to introduce a random value independent of the threshold value. In other embodiments described herein, a random placement variation may also be introduced to disrupt the regular pattern that occurs in the filter element placement within the identified pixels on each display substrate.

Similarly, in some embodiments, for example, where the filter elements will be formed on a glass substrate or other substrate, such as plastic, which is subsequently aligned with a display substrate, the color filter elements can be formed using the system 100 shown in FIG. 1 or can be formed using an alternative process for forming the filter elements, such as photolithography. In further processing steps, the introduction of random variation in the arrangement of the filter elements described herein can be used to disrupt regular patterns that may occur when the filter elements formed on the glass substrate are aligned with the display. Such patterns can result from misalignment between the filter element substrate and the underlying pixels of the display. When the glass color filter is placed on top of the display, the random variation can be used to disrupt patterns caused by misalignment between the color filter element and the display pixels. Such patterns can result from aliasing between the two patterns of the display pixels and the filter element, as would occur when the color filter substrate and the display substrate are attached to each other. This random variation can help reduce such patterns and relax alignment accuracy requirements.

Reset of digital imaging system

In the above-described process 800, when processing of the first display substrate 602 begins, the imaging head 108 can be positioned along the first axis based on the orientation information read at block 804, so that the elongated columns 136 are aligned to deposit filter element material on pixels 702-708 and other pixels on the display substrate. This alignment can be achieved within the accuracy provided by the first-axis linear motor 112 and the associated encoder scale 114. In one embodiment, the placement accuracy can be approximately ±3 μm and the encoder resolution can be less than ±1 μm. Therefore, block 808 can include additional steps for determining and applying this alignment. However, when processing subsequent display substrates that are not precisely aligned with display substrate 602, such as display substrate 604 shown in FIG. 7, the elongated columns may not be optimally aligned with the pixels of the second substrate. While offset 730 can correct for some of the misalignment between substrates 602 and 604, a residual offset of at least half the spacing between adjacent deposition locations may remain.

9 , in an alternative embodiment of the process 800 shown in FIG7 , after depositing the filter elements on the display substrate 602, the imaging head 108 can be repositioned by forming a small displacement 900 in the direction of the first axis 110 corresponding to the residual offset. During the deposition of the filter elements, the exposure head 108 is displaced relative to the substrate in the direction of the second axis 124, and the residual offset caused by the imaged elongated column 136 is eliminated by repositioning the imaging head 108, thereby forming an offset imaged elongated column 902. The imaged elongated column 902 is thus offset by a distance less than or equal to half the spacing between adjacent deposition locations and is aligned with the pixels 726 of the display substrate 604.

To accelerate filter element deposition in digital imaging system 100, the velocity in the second axis can be approximately 2 m/s or greater. For a 20 mm spacing between display substrates 602 and 604, the time available for displacement is approximately 10 milliseconds. Therefore, taking into account the associated settling time of linear motor 112, an acceleration of approximately 0.2 m/ ^s² is required for a 5 μm offset in the first axis. This acceleration can be significantly different from the acceleration required to eliminate all deviations between offsets 730 and 732 shown in FIG7 , which can be significantly greater. In some cases, the orientation difference between the display substrates can reach as much as 1 mm, and correcting this difference by simply resetting imaging head 108 under the aforementioned conditions would require an acceleration of approximately 40 m/ ^s² . Accordingly, the embodiment of the process shown in FIG9 provides a combination of correcting any residual offset by moving the imaging head slightly while simultaneously offsetting the digital mask, which is easier to implement due to the lower acceleration requirements in the first axis.

9, an imaging head 108 is described that does not move about the first axis 110 while imaging each display substrate. However, each of the display substrates 602 and 604 shown in FIG9 has an angle of rotation about the second axis 124, which causes continuous movement of the color filter elements in the arrangement within the pixel as described above with respect to process 800. In another embodiment, the above-described repositioning can be combined with a slow scan of the imaging head 108 in the direction of the first axis to also compensate for the rotation of the display substrates 602 and 604, thereby reducing the continuous movement between the filter elements at subsequent pixels.

For example, for a display substrate with a second-axis relative displacement velocity of 2 m/s, a coordinated scan through a rotation angle θ = 0.5° would require a scanning velocity of 0.017 m/s in the first-axis direction. The linear motor 112 and controller 140 have approximately 10 milliseconds to initiate this change, which requires an acceleration of approximately 3.4 m/ ^s² . This acceleration is also reasonable for a precision flat-panel imaging system as generally shown in FIG1 .

However, in other embodiments, the rotation angle relative to the display substrates may be significantly greater than 0.5°, thus requiring a larger gap between the displays to provide sufficient time to accommodate coordinated motion from display to display. Alternatively, if the gap between displays is limited, a higher acceleration must be provided by the first-axis linear motor 112, which may increase the cost and complexity of the first-axis linear drive.

Typically, the relative displacement between the display substrates and the digital imaging system in the direction of the second axis will include a first pass in a direction aligned with the second axis 124 and a second, or return, pass in a direction opposite to the first pass. In some embodiments, when the direction of motion is changed to facilitate deposition of filter elements in the second pass, the imaging head 108 is offset by the width of the elongated row 136, thereby improving throughput. In other embodiments, the filter elements deposited during the second pass may be significantly different from those deposited during the first pass, and in such cases deposition may be performed only during the first pass. Referring to FIG. 10 , in another alternative embodiment, the time available to accelerate the imaging head 108 between displays can be increased by depositing filter elements along the elongated row 1000 only on selected display substrates (e.g., substrates 602 and 606) in a first pass, and then imaging the remaining display substrates (e.g., substrate 604) generally along the elongated row 1000 in a second pass. A related advantage of this embodiment is that the distance 1002 that the imaging head 108 can be accelerated for resetting, as described above in the embodiment of FIG. 9 , is significantly increased. This reduces the need for acceleration and provides more time for stabilization and initialization of the scanning speed in the first axis direction. In the embodiment shown in FIG10 , imaging head 108 is initially positioned to deposit filter elements on display substrate 602 in a first pass through elongated column 1000 and is subsequently repositioned during a traverse distance 1002, as generally described above with respect to the embodiment of FIG9 . Filter elements are then deposited on substrate 606, and upon completion of this deposition, the imaging head's motion in the first pass direction is decelerated and the imaging head is accelerated to imaging speed in a second pass direction. Thus, distance 1004 is available during which imaging head 108 can be accelerated to imaging speed in second axis 124 and accelerated in first axis 110, thereby enabling repositioning for imaging display substrate 604 during the second pass. For typical display substrate sizes and configurations on chuck 116, this embodiment further reduces the required acceleration in first axis 110 relative to the embodiment of FIG9 .

Once the steps of depositing filter elements along elongated row 1000 onto display substrate 604 are completed, distance 1006 is available for moving imaging head 108 to the position of the next elongated row 1008. Deposition of filter elements for elongated row 1008 can be performed in the same manner.

The embodiment shown in FIG10 can be used in configurations having at least two display substrates along the second axis 124, but is equally applicable to configurations having any other number of substrates. Although in FIG10 , the embodiment has been described as deposition of filter elements occurring during a first pass for odd-numbered displays and a second pass for even-numbered displays, other configurations can be implemented where the display substrates are not regularly arranged, for example, where some displays are removed.

staggered

Referring to FIG11 , an alternative deposition embodiment is shown that can be combined with several of the above-described embodiments. In this embodiment, deposition of filter elements along elongated row 1100 occurs on each of display substrates 602, 604, and 606 during a first pass of imaging head 108, but only every other deposition location is activated during the first pass. Consequently, incomplete filter elements may be deposited during the first pass. During a second pass, the remaining filter elements are filled by activating the appropriate deposition locations along elongated row 1100 during the second pass.

Alternatively, upon completion of the first pass, the imaging head can be moved across the spacing between the deposition locations to align the imaging head with the second elongated column 1102, and during the second pass, the remainder of the filter elements will be filled by activating the appropriate deposition locations in the elongated column 1102.

The advantage of the staggered deposition configuration described above is that each filter element can be deposited in two opposing passes of the imaging head 108, thereby reducing the effects of deposition differences between the first and second passes, as described above with reference to the embodiment of FIG10. Furthermore, some imaging systems and/or media can cause imperfect transfer of colorant to the display, such as when solid areas are generated within the filter element. This staggered deposition can also reduce such effects.

In the above description, the staggering is described as being based on a single deposition location, but in other embodiments the staggering may involve more than one deposition location.

Filter element forming

The above embodiments are generally described in conjunction with an imaging system configured to produce deposition locations of similar size in the first and second axes. However, as described above with respect to the example of the Kodak imaging head, the generated beam 128 has a generally rectangular cross-section and can be controlled to deposit filter material in the second axis with greater precision than is possible in the first axis.

Referring to FIG. 12 , in an alternative embodiment, imaging head 108 is configured to provide second deposition locations 1200 along second axis 124 that are more closely spaced than the first deposition locations along the first axis. As shown in FIG. 12 , identified pixels 1202 have associated first and second axis boundaries in the first and second axis directions, respectively. Under these conditions, the placement of filter elements along second axis 124 can be more precisely controlled than the placement of filter elements along first axis 110. In this embodiment, module 808 of process 800 shown in FIG. 8 can be implemented such that the selection of deposition locations differs along first axis 110 and second axis 124. In one embodiment, the first axis deposition locations are selected to provide a greater spacing between filter element 1204 and first axis boundaries 1206 and 1208 of pixel 1202. In the embodiment shown in FIG. 12 , more than one deposition location in pixel 1202 is unselected, in contrast to the embodiment shown in FIG. 7 , where, in most cases, only one deposition location adjacent to a pixel boundary is unselected. However, in most embodiments, the deposited filter elements should meet coverage criteria, such as a target coverage area, so that each pixel has substantially the same brightness as other pixels of the same color. Thus, to compensate for the larger spacing along the first axis 110, second deposition locations along the second axis 124 are selected to provide a reduced spacing between the filter elements and the second axis boundaries 1210 and 1212, such that the first and second deposition locations, when combined, meet the coverage criteria associated with the filter elements 1204 within the pixel 1202. This embodiment can also be combined with other described embodiments, such as the embodiment described in conjunction with FIG. 9-11.

The embodiment shown in FIG12 further facilitates introducing random variation in the placement of filter elements along the first and second axes, thereby disrupting the regular pattern in the filter element placement resulting from selecting the deposition locations by providing a larger spacing between filter elements 1204 and the boundaries of the first axis. Because the deposition accuracy along the second axis exceeds that of the first axis, the more precise placement of filter elements along the second axis 124 provides greater degrees of freedom for the random variation in the placement along the first axis 110.

In other embodiments, random variation can be introduced into the spacing between first axis boundaries 1206 and 1208 in subsequently identified pixels. Such random variation can be compensated for by selecting a second deposition location along second axis 124 to meet coverage criteria associated with the filter element. While the disclosed filter element is generally rectangular in shape in the described embodiment, in other embodiments the filter element may have a shape other than square or rectangular, or even an irregular shape.

Adjustment of deposition filter elements

Depositing a filter element using any of the above-described embodiments may result in the transferred filter element having a rough surface texture. This effect is particularly noticeable when using a thermal transfer donor, as the transfer from the donor may be imperfect at each deposition location. For some applications, a rough surface texture may be undesirable and potentially problematic. For example, in color filter elements used in displays, the optical effects caused by the rough surface texture may degrade the image quality displayed by the display. Reflective displays are believed to be particularly susceptible to such optical effects.

In another embodiment of the present invention, once the selective deposition of the filter element material is complete, a further step can be introduced comprising selectively exposing the deposited filter material to laser thermal radiation to condition the deposition of the filter element material. The deposited filter element thus undergoes an annealing process, which is believed to raise the temperature of the filter element material above the glass transition temperature of the material, thereby causing the material to at least partially reflow to smooth out any rough surface texture. Once the material cools, the smoothness of the filter element material surface is improved due to this reflow.

Selective modulation using the same imaging-controllable laser source can offer several advantages over a separate annealing step. Introducing a separate annealing process adds an extra step to the process and involves additional annealing equipment. Annealing by substantially increasing the temperature of the entire substrate can also potentially damage the display substrate. These issues are addressed by the selective modulation described herein because typically only the color filter elements are heated to the annealing temperature, thereby reducing the risk of damage to underlying pixels. Furthermore, for thermal transfer, laser wavelengths suitable for laser transfer are typically well absorbed by the filter element material, making them particularly effective in raising the filter element material to the annealing temperature.

Referring to FIG. 13 , a flow chart for directing the microprocessor 302 shown in FIG. 3 to perform an adjustment process, according to one embodiment of the present invention, is generally shown at 1300. As described in the above-described embodiment, the flow chart begins at block 1302, which directs the microprocessor 302 to control the digital imaging system 100 (shown in FIG. 1 ) so that the filter material is deposited at a selected deposition location. Subsequently, block 1304 optionally directs the microprocessor 302 to adjust the intensity level of the laser source to a level suitable for annealing. For example, such a level can be achieved by increasing or decreasing the laser power or by adjusting the attenuation level associated with a modulator used to control the radiation generated by the laser source. In embodiments where adjustments are made at the same laser intensity or power level, block 1304 can be omitted.

Flow 1300 then continues with block 1306, which directs microprocessor 302 to read the digital mask information from memory 356 of variable memory 306. In embodiments where all color filter elements of different colors are annealed simultaneously, the individual digital masks associated with each color filter element will require additional processing to provide a combined digital mask for all colors. Block 1308 then directs microprocessor 302 to generate control signals at ports 142, 144, and 146 to control the digital imaging system to adjust the filter element material at the deposition location.

In one embodiment, the laser source used for filter element deposition is also used to perform selective exposure to tune the filter element. In other embodiments, another laser source with a different wavelength can be used to perform selective exposure to tune the filter element.

The above-described embodiments provide methods and associated apparatus for forming color filter elements directly on pixels of a display substrate or on a glass or non-glass substrate. Direct deposition onto the filter elements offers the advantages of in-situ deposition, thereby eliminating additional alignment steps. Furthermore, the resulting display product can eliminate the need for an additional glass layer supporting the filter elements, thereby reducing the weight of the display product. Direct deposition embodiments also typically result in less scattering of transmitted or reflected light, potentially providing better color display performance.

While specific embodiments of the present invention have been described and illustrated, such embodiments should be considered illustrative of the present invention only, and not limiting of the present invention as interpreted by the appended claims.

Claims (2)

1. A method for forming a filter element on at least two display substrates having position marks using a digital imaging system that operably and selectively deposits filter material at a plurality of deposition sites, the deposition sites including a first deposition site and a second deposition site, the first deposition site being substantially aligned along a first axis of the display substrates, the second deposition site being substantially aligned along a second axis of the display substrates, the at least two display substrates being sequentially disposed along the second axis, the method comprising: Receiving orientation information, the orientation information defining the setting of a plurality of pixels associated with each of the display substrates relative to the first axis and the second axis, wherein receiving the orientation information includes generating the orientation information by locating the position markers on each of the display substrates; Calculate the positions of multiple pixels associated with the display substrate relative to the position marker; Selectively depositing filter material on the plurality of pixels associated with the display substrate to form filter elements, the filter elements having a rough surface texture; and Selectively exposing the deposited filter material to laser thermal radiation to anneal the filter element for at least partial reflow, thereby smoothing the rough surface texture. The selective deposition of a filter material on the plurality of pixels associated with the display substrate to form a filter element includes: Identify the pixel among the plurality of pixels that will receive the filter material to form a filter element on the pixel; Deposition locations are selected within each of the identified pixels based on the orientation information, thereby satisfying alignment criteria related to the arrangement of the filter elements within the pixels; For at least one of the display substrates, calculate the offset associated with the plurality of pixels in the direction of the first axis; Determine the remaining portion of the offset that cannot be compensated by the selection of the deposition location; The digital imaging system is controlled to deposit the filter material at the selected deposition location in the following manner: The display substrate and the digital imaging system are neutralized by a first pass in a first direction aligned with the second axis and a second pass in a second direction opposite to the first direction, forming a corresponding relative displacement; During the first pass, filter material is deposited on alternating display substrates of the at least two display substrates, and during the second pass, filter material is deposited on the remaining display substrates of the at least two display substrates; and When the digital imaging system is positioned between at least one of the alternating display substrates in the display substrate during the first pass, or between the remaining display substrates in the display substrate during the second pass, the remaining portion of the offset causes the digital imaging system to reset relative to the display substrate. 2. A digital imaging system for forming filter elements on at least two display substrates having position marks by selectively depositing filter material at multiple deposition sites, the deposition sites including a first deposition site and a second deposition site, the first deposition site being substantially aligned along a first axis of the display substrates, the second deposition site being substantially aligned along a second axis of the display substrates, the at least two display substrates being sequentially disposed along the second axis, the digital imaging system including a controller operablely configured such that the digital imaging system: Receiving orientation information, the orientation information defining the setting of a plurality of pixels associated with each of the display substrates relative to the first axis and the second axis, wherein receiving the orientation information includes generating the orientation information by locating the position markers on each of the display substrates; Calculate the positions of multiple pixels associated with the display substrate relative to the position marker; Selectively depositing filter material on the plurality of pixels associated with the display substrate to form filter elements, the filter elements having a rough surface texture; and Selectively exposing the deposited filter material to laser thermal radiation to anneal the filter element for at least partial reflow, thereby smoothing the rough surface texture. The selective deposition of a filter material on the plurality of pixels associated with the display substrate to form a filter element includes: Identify the pixel among the plurality of pixels that will receive the filter material to form a filter element on the pixel; Deposition locations are selected within each of the identified pixels based on the orientation information, thereby satisfying alignment criteria related to the arrangement of the filter elements within the pixels; For at least one of the display substrates, calculate the offset associated with the plurality of pixels in the direction of the first axis; Determine the remaining portion of the offset that cannot be compensated by the selection of the deposition location; The digital imaging system is controlled to deposit the filter material at the selected deposition location in the following manner: The display substrate and the digital imaging system are neutralized by a first pass in a first direction aligned with the second axis and a second pass in a second direction opposite to the first direction, forming a corresponding relative displacement; During the first pass, filter material is deposited on alternating display substrates of the at least two display substrates, and during the second pass, filter material is deposited on the remaining display substrates of the at least two display substrates; and When the digital imaging system is positioned between at least one of the alternating display substrates in the display substrate during the first pass, or between the remaining display substrates in the display substrate during the second pass, the remaining portion of the offset causes the digital imaging system to reset relative to the display substrate.