CN105938278B

CN105938278B - Liquid crystal display with color motion blur compensation structure

Info

Publication number: CN105938278B
Application number: CN201610060581.7A
Authority: CN
Inventors: 陈远; 葛志兵; A·F·赫伦兹; C·H·泰; H·内马蒂; 江俊; 陈宬
Original assignee: Apple Inc
Current assignee: Apple Inc
Priority date: 2015-03-04
Filing date: 2016-01-29
Publication date: 2020-01-07
Anticipated expiration: 2036-01-29
Also published as: JP2018506746A; KR101932370B1; JP6511533B2; CN105938278A; KR20170103980A

Abstract

The present disclosure relates to a liquid crystal display having a color motion blur compensation structure. A layer of liquid crystal material may be interposed between the display layers. The display layer may include thin film transistor circuitry having a subpixel electrode for applying an electric field to a subpixel portion of the layer of liquid crystal material. The different colored sub-pixels may have different shapes and may have different liquid crystal layer thicknesses. The differences of these sub-pixels may be configured to slow the switching speed of certain colored sub-pixels relative to other sub-pixels to reduce color motion blur as objects move across a black or colored background. The sub-pixels may have a V-shape. The sub-pixels of the first color may have a V-shape that is less curved than the sub-pixels of the second and third colors. In configurations with varying liquid crystal layer thicknesses, the sub-pixels of the first color may have a thicker liquid crystal layer than the sub-pixels of the second and third colors.

Description

Liquid crystal display with color motion blur compensation structure

This application claims priority from U.S. patent application No.14/947,356 filed on 20/11/2015, U.S. patent application No.14/850,015 filed on 10/9/2015, and provisional patent application No.62/128,453 filed on 4/3/2015, which are incorporated herein by reference in their entirety.

Technical Field

The present disclosure relates generally to electronic devices and, more particularly, to electronic devices having displays.

Background

Electronic devices typically include a display. For example, cellular telephones and portable computers typically include displays for presenting information to users.

The liquid crystal display comprises a liquid crystal material layer. A pixel in a liquid crystal display comprises a thin film transistor and an electrode for applying an electric field to the liquid crystal material. The strength of the electric field in the pixel controls the polarization state of the liquid crystal material and thereby adjusts the brightness of the pixel.

The speed at which the liquid crystal pixels are switched can be varied as a function of the applied voltage. Thus, the amount of time required to switch a black pixel to a gray level will be longer than the amount of time required to switch a black pixel to a white level. In some cases, it may be desirable to move a black object over a screen with a colored background. In this type of scene, different colored sub-pixels may have different target pixel values and thus may switch at different speeds. This can result in an unpleasant color motion blur effect when the black object is moved.

Accordingly, it would be desirable to be able to provide an improved display for an electronic device, such as a display with reduced color motion blur.

Disclosure of Invention

The display may have upper and lower display layers. A layer of liquid crystal material may be interposed between the upper and lower display layers. The display may comprise upper and lower polarizers and a backlight for providing illumination for the display layers. An array of color filter elements may be used to provide the display with the ability to display color images. The color filter elements may comprise red, green and blue elements or color filter elements of different colors. The display may have an array of pixels, with each pixel having sub-pixels, such as red, green, and blue sub-pixels formed with red, green, and blue color filter elements.

The display layer may include a thin film transistor circuit layer having a sub-pixel electrode for applying an electric field to the liquid crystal material layer for each sub-pixel. The different colored sub-pixels may have different electrode shapes (e.g., fingers oriented at different angles) and/or may have different liquid crystal layer thicknesses. The differences of these sub-pixels may be configured to slow the switching speed of a sub-pixel of a certain color relative to other sub-pixels to reduce color motion blur when an object of one color is moved across a background of another color.

Drawings

FIG. 1 is a perspective view of an illustrative electronic device, such as a laptop computer with a display, in accordance with an embodiment.

FIG. 2 is a perspective view of an illustrative electronic device, such as a handheld electronic device with a display, in accordance with an embodiment.

Fig. 3 is a perspective view of an illustrative electronic device, such as a tablet computer with a display, in accordance with an embodiment.

FIG. 4 is a perspective view of an illustrative electronic device such as a computer display with a display structure, according to an embodiment.

Fig. 5 is a cross-sectional side view of an illustrative display in accordance with an embodiment.

FIG. 6 is a top view of a portion of an array of pixels in a display according to an embodiment.

Fig. 7 is a diagram showing how the motion of an object against the background can potentially corrupt the color of pixels along the leading and trailing edges of the object and thereby cause color motion blur effects.

Fig. 8 is a graph illustrating how red, green, and blue subpixels in a display may have different target pixel values and thus potentially switch at different speeds during color transitions such as those associated with movement of the object of fig. 7, according to an embodiment.

FIG. 9 is a top view of a portion of a display with an illustrative pixel pattern to reduce color motion blur effects, according to an embodiment.

FIG. 10 is a graph in which an illustrative normalized transmittance versus applied pixel voltage has been plotted for different types of subpixels, according to an embodiment.

Fig. 11 is a top view of an illustrative set of pixel electrodes in which the electrode fingers have a V-shape with center and end bends, according to an embodiment.

FIG. 12 is a top view of an illustrative set of sub-pixels showing how electrodes in the sub-pixels can have different colors with fingers having different orientation angles and end bends, according to an embodiment.

FIG. 13 is a top view of an illustrative set of subpixels of different colors showing how fingers in an electrode can have different orientation angles and can alternate between positive and negative orientation angles in successive rows of a pixel array in a display, according to an embodiment.

FIG. 14 is a cross-sectional side view of an illustrative display in which liquid crystal layer thicknesses are different for different color sub-pixels to reduce color motion blur effects, according to an embodiment.

Detailed Description

The electronic device may include a display. The display may be used to display images to a user. Illustrative electronic devices that may have displays are shown in fig. 1, 2, 3, and 4.

Fig. 1 shows how an electronic device 10 may have the shape of a laptop computer with an upper housing 12A and a lower housing 12B having components such as a keyboard 16 and a touchpad 18. The device 10 may have a hinge structure 20 that allows the upper housing 12A to rotate in a direction 22 relative to the lower housing 12B about an axis of rotation 24. The display 14 may be mounted in the upper housing 12A. The upper housing 12A, which may sometimes be referred to as a display housing or cover, may be placed into a closed position by rotating the upper housing 12A about the axis of rotation 24 toward the lower housing 12B.

Fig. 2 shows how the electronic device 10 may be a handheld device such as a cellular phone, music player, gaming device, navigation unit or other compact device. In this type of configuration of the device 10, the housing 12 may have opposing front and rear surfaces. The display 14 may be mounted on the front face of the housing 12. If desired, display 14 may have openings for components such as buttons 26. Openings may also be formed in the display 14 to accommodate speaker ports (see, e.g., speaker port 28 of fig. 2).

Fig. 3 shows how the electronic device 10 may be a tablet computer. In the electronic device 10 of fig. 3, the housing 12 may have opposing flat front and back surfaces. The display 14 may be mounted on a front surface of the housing 12. As shown in fig. 3, display 14 may have an opening to accommodate button 26 (as an example).

Fig. 4 shows how the electronic device 10 may be a display, such as a computer display, or may be a computer that has been integrated into a computer display. With this type of arrangement, the housing 12 for the device 10 may be mounted on a support structure such as a bracket 27 or the bracket 27 may be omitted (e.g., mounting the device 10 on a wall). The display 14 may be mounted on the front face of the housing 12.

The illustrative configurations for the apparatus 10 shown in fig. 1, 2, 3, and 4 are illustrative only. In general, the electronic device 10 may be a laptop computer, a computer monitor containing an embedded computer, a tablet computer, a cellular telephone, a media player, or other handheld or portable electronic device, a smaller device such as a wristwatch device, a pendant device, a headset or earpiece device, or other wearable or miniature device, a computer display that does not contain an embedded computer, a gaming device, a navigation device, an embedded system such as a system in which electronic equipment with a display is installed in a kiosk or automobile, equipment that implements the functionality of two or more of these devices, or other electronic equipment.

The housing 12 of the device 10, sometimes referred to as a case, may be formed of materials such as plastic, glass, ceramic, carbon fiber composite and other fiber-based composites, metal (e.g., machined aluminum, stainless steel, or other metals), other materials, or combinations of these materials. The apparatus 10 may be formed using a unitary construction in which most or all of the housing 12 is constructed of a single structural element (e.g., machined metal or molded plastic), or may be formed of multiple housing structures (e.g., external housing structures that have been mounted to an internal frame element or other internal housing structure).

The display 14 may be a touch sensitive display that includes touch sensors or may be touch insensitive. The touch sensor for display 14 may be formed from an array of capacitive touch sensor electrodes, a resistive touch array, a touch sensor structure based on acoustic touch, optical touch, or force-based touch technologies, or other suitable touch sensor components.

The display 14 for the device 10 may include pixels formed from Liquid Crystal Display (LCD) components. The display overlay layer may cover a surface of the display 14 or a display layer, such as a color filter layer, or other portions of the display may be used as the outermost (or near outermost) layer in the display 14. The outermost display layer may be formed of a transparent glass plate, a transparent plastic layer, or other transparent member.

A cross-sectional side view of an illustrative configuration for display 14 of device 10 (e.g., display 14 for the devices of fig. 1, 2, 3, 4, or other suitable electronic devices) is shown in fig. 5. As shown in FIG. 5, display 14 may include a backlight structure, such as a backlight unit 42 for generating a backlight 44. During operation, the backlight 44 travels outward (vertically upward in dimension Z in the orientation of fig. 5) and through the display pixel structures in the display layer 46. This illuminates any image produced by the display pixels for viewing by the user. For example, backlight 44 may illuminate an image on display layer 46 being viewed by viewer 48 in direction 50.

The display layer 46 may be mounted in a chassis structure, such as a plastic chassis structure and/or a metal chassis structure, to form a display module for mounting in the housing 12, or the display layer 46 may be mounted directly in the housing 12 (e.g., by stacking the display layer 46 into a recessed portion in the housing 12). The display layer 46 may form a liquid crystal display or may be used to form other types of displays.

The display layer 46 may include a liquid crystal layer, such as liquid crystal layer 52. The liquid crystal layer 52 may be sandwiched between display layers such as display layers 58 and 56. The

layers

56 and 58 may be interposed between the lower polarizing layer 60 and the upper polarizing layer 54.

Layers

58 and 56 may be formed from a transparent substrate layer such as a transparent glass or plastic layer.

Layers

58 and 56 may be layers such as a thin-film transistor layer and/or a color filter layer. Conductive traces, color filter elements, transistors, and other circuitry and structures may be formed on the substrate of layers 58 and 56 (e.g., to form a thin-film-transistor layer and/or a color filter layer). Touch sensor electrodes may also be incorporated into layers such as

layers

58 and 56 and/or touch sensor electrodes may be formed on other substrates.

With one illustrative construction, layer 58 may be a thin-film-transistor layer including an array of thin-film-transistor-based pixel circuits and associated electrodes (pixel electrodes) for applying an electric field to liquid crystal layer 52 and thereby displaying an image on display 14. Layer 56 may be a color filter layer that includes an array of color filter elements for providing display 14 with the ability to display color images. Layer 58 may be a color filter layer and layer 56 may be a thin-film transistor layer, if desired. Configurations in which color filter elements are combined with thin film transistor structures on a common substrate layer in both upper and lower portions of display 14 may also be used.

During operation of display 14 in device 10, control circuitry (e.g., one or more integrated circuits on a printed circuit) may be used to generate information (e.g., display data) to be displayed on display 14. Information to be displayed may be conveyed to a display driver integrated circuit such as

circuit

62A or 62B using signal paths such as signal paths formed by conductive metal traces in a rigid or flexible printed circuit such as printed circuit 64, as an example.

Backlight structures 42 may include a light guide plate such as light guide plate 78. The light guide plate 78 may be formed of a transparent material such as transparent glass or plastic. During operation of the backlight structures 42, a light source, such as the light source 72, may generate light 74. The light source 72 may be, for example, an array of light emitting diodes.

Light 74 from the light source 72 may be coupled into the edge surface 76 of the light guide plate 78 and due to the principle of total internal reflection, it may be distributed throughout the dimensions X and Y of the light guide plate 78. The light guide plate 78 may include light scattering features such as pits (pits) or bumps (bumps). The light-scattering features may be located on an upper surface and/or an opposite lower surface of the light guide plate 78. The light source 72 may be located on the left side of the light guide plate 78, as shown in FIG. 5, or may be located along the right edge of the plate 78 and/or other edges of the plate 78.

The light 74 scattered upward from the light guide plate 78 in the direction Z may be used as a backlight 44 for the display 14. The downwardly scattered light 74 may be reflected back in an upward direction by the reflector 80. The reflector 80 may be formed of a reflective material, such as a plastic layer covered with a dielectric mirror film coating.

To enhance the backlight performance of backlight structures 42, backlight structures 42 may include optical film 70. The optical films 70 may include a diffuser layer to help homogenize the backlight 44 and thereby reduce hot spots, a compensation film to enhance off-axis viewing, and a brightness enhancement film (sometimes also referred to as a turning film) to collimate the backlight 44. The optical film 70 may overlap other structures in the backlight unit 42, such as a light guide plate 78 and a reflector 80. For example, if light guide plate 78 has a rectangular footprint in the X-Y plane of FIG. 5, optical film 70 and reflector 80 may have matching rectangular footprints. Films such as compensation films may be incorporated into other layers (e.g., polarizing layers) of the display 14, if desired.

As shown in fig. 6, display 14 may include an array of pixels 90, such as an array of pixels 92. The pixel array 92 may be controlled using control signals generated by display driver circuitry. The display driver circuitry may be implemented using one or more Integrated Circuits (ICs) and/or thin film transistors or other circuitry.

During operation of device 10, control circuitry in device 10, such as memory circuits, microprocessors, and other storage and processing circuitry, may provide data to display driver circuitry. Display driver circuitry may convert data into signals for controlling pixels 90 of pixel array 92.

The pixel array 92 may include rows and columns of pixels 90. The circuitry of pixel array 92 (i.e., the rows and columns of pixel circuits for pixels 90) may be controlled using signals such as data line signals on data lines D and gate line signals on gate lines G. The data lines D and the gate lines G are orthogonal. For example, the data line D may extend vertically and the gate line G may extend horizontally (i.e., perpendicular to the data line D).

Pixels 90 in pixel array 92 may include thin film transistor circuitry (e.g., polysilicon transistor circuitry, amorphous silicon transistor circuitry, semiconducting oxide transistor circuitry such as InGaZnO transistor circuitry, other silicon or semiconducting oxide transistor circuitry, etc.) and associated structures for generating an electric field across liquid crystal layer 52 in display 14. Each display pixel may have one or more thin film transistors. For example, each display pixel may have a respective thin film transistor, such as thin film transistor 94, to control the application of an electric field to the corresponding pixel size portion 52' of the liquid crystal layer 52.

The thin film transistor structures used to form the pixels 90 may be located on a thin film transistor substrate, such as a glass layer. The structure of the thin-film transistor substrate and display pixels 90 formed on the surface of the thin-film transistor substrate collectively form thin-film transistor layer 58 (fig. 5).

Gate signals may be generated on the gate lines G using gate driving circuitry. The gate driver circuitry may be formed by thin film transistors on the thin film transistor layer or may be implemented in a separate integrated circuit. The data line signals on data lines D in pixel array 92 carry analog image data (e.g., voltages having magnitudes representative of pixel brightness levels). During display of an image on the display 14, the display driver integrated circuit or other circuitry may receive digital data from the control circuitry and may generate corresponding analog data signals. The analog data signal may be demultiplexed and supplied to the data lines D.

The data line signal on data line D is distributed to the columns of display pixels 90 in pixel array 92. The gate line signals on gate line G are provided to a row of pixels 90 in pixel array 92 by associated gate drive circuitry.

The circuitry of display 14 may be formed from conductive structures (e.g., metal lines and/or structures formed from transparent conductive materials such as indium tin oxide) and may include transistors such as transistor 94 of fig. 6 fabricated on a thin film transistor substrate of display 14. The thin film transistor may be, for example, a silicon thin film transistor or a semiconductive oxide thin film transistor.

As shown in fig. 6, a pixel such as pixel 90 may be located at the intersection of each gate line G and data line D in array 92. The data signal on each data line D may be provided from one of the data lines D to the terminal 96. Thin-film transistor 94 (e.g., a thin-film polysilicon transistor, an amorphous silicon transistor, or an oxide transistor such as a transistor formed from a semiconducting oxide such as indium gallium zinc oxide) may have a gate terminal such as gate 98 that receives a gate line control signal on gate line G. When the gate line control signal is active, the transistor 94 will be turned on and the data signal at terminal 96 will be delivered to the node 100 as the pixel voltage Vp. Data for the display 14 may be displayed in frames. After the gate line signals in each row are asserted to transfer the data signals to the pixels of the row, the gate line signals may be de-asserted. In subsequent display frames, the gate line signals for each row may be asserted again to turn on transistor 94 and capture a new value of Vp.

The pixel 90 may have a signal storage element such as a capacitor 102 or other charge storage element. The storage capacitor 102 may be used to help store the signal Vp in the pixel 90 between frames (i.e., during the time period between successive gate signal activations).

Display 14 may have a common electrode coupled to node 104. A common electrode (sometimes referred to as a common voltage electrode, Vcom electrode, or Vcom terminal) may be used to distribute a common electrode voltage to nodes such as node 104 in each pixel 90 of array 92. As shown by illustrative electrode pattern 104' of fig. 6, Vcom electrode 104 can be implemented with a blanket film of transparent conductive material such as indium tin oxide, indium zinc oxide, other transparent conductive oxide materials, and/or a metal layer that is sufficiently thin to be transparent (e.g., electrode 104 can be formed from a layer of indium tin oxide or other transparent conductive layer that covers all pixels 90 in array 92).

In each pixel 90, a capacitor 102 may be coupled between

nodes

100 and 104. A parallel capacitance is created across

nodes

100 and 104 due to the electrode structure in pixel 90 that is used to control the electric field across the liquid crystal material of the pixel (liquid crystal material 52'). As shown in fig. 6, an electrode structure 106 (e.g., a display pixel electrode having a plurality of fingers or other display pixel electrode for applying an electric field to the liquid crystal material 52') may be coupled to the node 100 (or a multi-finger display pixel electrode may be formed at the node 104). During operation, a controlled electric field (i.e., a field having a magnitude proportional to Vp-Vcom) can be applied across the pixel-sized liquid crystal material 52' in the pixel 90 using the electrode structures 106. Due to the presence of the storage capacitor 102 and the parallel capacitance formed by the pixel structure of the pixel 90, the value of Vp (and therefore the associated electric field across the liquid crystal material 52') may be maintained across the

nodes

106 and 104 for the duration of the frame.

The electric field generated across the liquid crystal material 52 'causes a change in orientation of the liquid crystals in the liquid crystal material 52'. This changes the polarization of light passing through the liquid crystal material 52'. In combination with

polarizers

60 and 54 of FIG. 5, the change in polarization may be used to control the amount of light 44 transmitted through each pixel 90 in array 92 of display 14.

In a display such as a color display, color filter layer 56 is used to impart different colors to different pixels. As an example, each pixel 90 in display 14 may include three (or more) different sub-pixels, each having a different respective color. Each pixel 90 has a red sub-pixel, a green sub-pixel, and a blue sub-pixel, with one suitable arrangement that may sometimes be described herein as an example. Each sub-pixel is driven with an independently selected pixel voltage Vp. The amount of voltage provided to the electrodes of each sub-pixel is associated with a respective digital pixel value (e.g., a value ranging from 0 to 255 or other suitable digital range). The desired pixel color may be generated by adjusting the pixel value for each of the three sub-pixels in the pixel. For example, a black pixel may be associated with a 0 pixel value for a red subpixel, a 0 pixel value for a green subpixel, and a 0 pixel value for a blue subpixel. As another example, an orange pixel may be associated with

pixel values

245, 178, and 66 of red, green, and blue subpixels. White can be represented by pixel values of 255, and 255.

The response time of a pixel in display 14 may vary as a function of the magnitude of the liquid crystal switching voltage applied to electrode 106. When switching a black pixel having red, green, blue pixel values of (0, 0, 0) to a white pixel (255, 255, 255), each sub-pixel (red, green, and blue) has the same target pixel value (i.e., 255) and starts from the same initial pixel value (i.e., 0), so the voltage applied across the liquid crystal layer 52 during switching is the same for each sub-pixel. Thus, all sub-pixels will switch simultaneously. This type of switching scenario occurs when moving black text, a black cursor, or other black items against a white background.

Other pixel switching scenarios can cause color motion blur due to unequal response times that occur when different color sub-pixels are driven with different pixel values. As an example, consider the response of a pixel when switching from black (0, 0, 0) to orange (245, 178, 66). In this case, a large voltage drop occurs across the red subpixel (i.e., the voltage drop associated with the difference before and after the digital value of 245) and a lower voltage drop occurs across the green subpixel (the voltage associated with the pixel value change of 178) and the blue subpixel (the pixel value change of 66). Because the voltage across the red subpixel (and thus the electric field applied to the liquid crystal layer by the red electrode 106) is relatively large, the liquid crystal molecules of the red subpixel will rotate faster than the liquid crystal molecules of the green and blue subpixels. Thus, the red sub-pixel will change color (from black to red) faster than the green and blue sub-pixels will switch from black to green and from black to blue, respectively. The different switching speeds of the different colored sub-pixels can lead to unpleasant visual artifacts. In the present example, where a black entry is moving across an orange background, the relatively fast switching speed of the red sub-pixel can potentially cause an undesirable red motion blur effect.

The color motion blur effect can occur both at the leading edge of a moving object and at the trailing edge of a moving object. For example, consider the movement of an object 112 across the background 110 of the display 14 of FIG. 7. The object 112 may have a first color (e.g., black) and the background 110 may have a second color (e.g., orange). The object 112 may be black text (as an example). The background 110 may have a color that is desired when presenting an electronic book to a user in a warm ambient light illumination environment (e.g., indoor lighting). The object 112 may move across the background 110, e.g., up and down during scrolling, left and right when panning, etc. In the example of fig. 7, object 112 is moved to the right in direction 114.

At the trailing edge 118, the black pixel (0, 0, 0) is switched to orange (245, 178, 66). The black to white switching speed (rise time) can vary considerably depending on the switching voltage level. Since the red pixel has a larger switching voltage than the green and blue pixels when switching from black to orange, the red pixel in region 116 will switch from black faster than the green and blue pixels, resulting in a blurred color in region 118. In particular, the pixels of display 14 in region 118 may potentially develop a distinct red color due to the enhanced switching speed of the red sub-pixels relative to the blue and green sub-pixels.

At the leading edge 116 of the object 112, the pixel switches from the background color 110 to the color of the object 112. For example, a pixel in the leading edge 116 may switch from (245, 178, 66) to black (0, 0, 0). The red pixels in this case will show a slightly slower decay time than the green and blue pixels, resulting in a gray motion blur.

A graph showing how pixels with different colors can potentially switch at different speeds during a particular color transition is shown in the graph of fig. 8, where the sub-pixel transmittance T (proportional to the sub-pixel output intensity) is plotted as a function of time T. In the example of fig. 8, the situation at the trailing edge 118 of fig. 7 is shown. Initially (at time t1), the pixel is black (0, 0, 0). At time t3, object 112 has moved away from edge 118 and each subpixel will have sufficient time to obtain its desired target value (i.e., red subpixel has obtained value 245, green subpixel has obtained value 178, and blue subpixel has obtained value 66). The switching process of the red, green and blue subpixels in a conventional display at intermediate times between times t1 and t3 is illustrated by curves 120 (for red), 122 (for green) and 124 (for blue). These curves (which are not normalized in the graph of fig. 8) show transitions at different speeds. The green and

blue curves

122 and 124 are relatively slow to transition. The red curve (curve 120) transitions fast because the target value for the red sub-pixel is relatively high (245). Because the red curve 120 rises steeply compared to the green curve 122 and the blue curve 124, the color of the pixel in the trailing edge 118 (associated with time t 2) will be too red in color.

To restore the desired balance between the red, green, and blue subpixels in trailing edge 118 and thus minimize the red motion blur effect, the subpixels of display 14 may be configured to equalize the switching speeds of the red, green, and blue subpixels in certain switching scenarios (e.g., when switching from black to orange as described in connection with this example and/or when switching between other color combinations). In particular, the shape of the red sub-pixel and/or the liquid crystal layer thickness may be configured to slow the switching speed of the red sub-pixel relative to the switching speed of the green and blue sub-pixels. When configured in this manner, display 14 will exhibit slower red pixel switching characteristics, such as curve 126. At intermediate times (i.e., for pixels in the trailing edge 118), such as time t2, the pixel values of the red subpixels associated with curve 126 will not be excessive compared to the pixel values for the green and blue subpixels at time t 2. Thus, the edge 118 will not appear excessively red and the red motion blur effect will be suppressed.

The pixel switching characteristics can be affected by, for example, electrode geometry and pixel cell thickness (i.e., liquid crystal layer thickness). One way in which the pixel switching speed is selectively adjusted involves changing the layout of the electrodes 106 in certain sub-pixels. An arrangement of this type is shown in figure 9. In the example of fig. 9, the display 14 has three color sub-pixels. Each sub-pixel is associated with a respective V-shaped opening in the black mask 130 and a corresponding set of electrode fingers 106 having a V-shape. Other shapes than a V-shape may be used for the electrode 106 and the opening of the pixel containing the electrode 106 if desired (e.g., a rectangular shape, a sub-pixel opening with curved edges, etc.). The use of V-shaped electrode fingers and pixel openings is merely illustrative.

The shape of the sub-pixels and in particular the angular spread of the arms of each V-shaped opening and the angular spread of the V-shaped fingers of the associated sub-pixel electrode may be configured to be different for sub-pixels of different colors. In the example of fig. 9, the red subpixel 90R has an edge 132 that is at an angle a relative to the X-axis and an electrode finger 106 that has a parallel longitudinal electrode axis 133 that is also at an angle a relative to the X-axis. The edges 132 and axes 133 of the green and

blue sub-pixels

90G and 90B and their electrodes are each at an angle B relative to the X-axis. The value of B may be smaller than the value of a. For example, a may be 85 ° and B may be 75 °, such that the chevron of red subpixel 90R (i.e., the chevron opening and chevron electrode 106) is less curved than the chevron of green subpixel 90G and blue subpixel 90B. Other angles may be used if desired.

Within each sub-pixel, the longitudinal axis 133 of the pixel electrode 106 extends parallel to the V-shaped edge 132, so the different shape of the sub-pixel results in a different orientation between the electric field generated by the sub-pixel and the liquid crystal molecules in the sub-pixel.

The liquid crystal material comprising the liquid crystal layer 52 of the display 14 may be a negative liquid crystal material or a positive liquid crystal material. Negative liquid crystals exhibit negative dielectric anisotropy, while positive liquid crystals exhibit positive dielectric anisotropy. The liquid crystal molecules (liquid crystals) in the negative liquid crystals are aligned perpendicular to the applied electric field (i.e., the longitudinal axes of the negative liquid crystal molecules will be oriented perpendicular to the electric field applied from the electrodes 106). The liquid crystal molecules in the positive liquid crystal are aligned parallel to the applied electric field (i.e., the longitudinal axes of the positive liquid crystal molecules will be oriented parallel to the applied electric field).

In the negative liquid crystal configuration for display 14, the longitudinal axis of the negative liquid crystal molecules extends along the X-axis before an electric field is applied through electrode 106. In the positive liquid crystal configuration for display 14, the longitudinal axes of the positive liquid crystal molecules extend along the Y-axis before an electric field is applied through electrodes 106. The angle relative to the edge 130 of the sub-pixel (and hence the longitudinal axis 133 of the electrode 106) created by the liquid crystal dipoles associated with the negative and positive liquid crystal molecules is the same, albeit with a vertical initial (non-rotated) orientation. In this example, the dipole of the negative liquid crystal extending along the Y-axis will make an angle of 90-A with respect to the edge 132 of the red subpixel 90R when the negative liquid crystal is not rotated (i.e., in this example, the longitudinal axis of the non-rotated dipole of the negative liquid crystal to the electrode 106 will be 5). When the positive liquid crystal is not rotated, the dipole of the positive liquid crystal extends along the Y-axis and will therefore make the same angle 90-a with respect to the edge 132 of the red subpixel 90R (i.e., in this embodiment, the longitudinal axis of the non-rotated dipole of the positive liquid crystal to the electrode 106 will be 5 °). In sub-pixels 90G and 90B, the angle between the liquid crystal molecular dipoles and the longitudinal axis 133 of electrode 106 will be 15 (i.e., a larger angle than for the red sub-pixel).

The increased angle between the liquid crystal dipole and the longitudinal electrode axes for the green and blue sub-pixels will tend to increase their switching speed relative to the red sub-pixel in a switching scenario of the type described in connection with fig. 7, and will therefore compensate the display 14 for red motion blur. Although 5 and 15 angles are used for this example, other values of the electrode axis to liquid crystal dipole angles may be used if desired. In a configuration where the subpixels have a chevron shape, flatter (less curved) chevrons may be used for the red subpixels than for the green and blue subpixels to help slow down the switching of the red subpixels and thereby suppress red motion blur effects when black objects move against a background having redder content (such as orange) than the blue and green content.

Fig. 10 is a graph of a simulation in which the transmittance T is plotted against the pixel voltage Vp applied for subpixels having unmodified and modified dipole-to-electrode axis angles. When the angle is unmodified (e.g., 10 °), the subpixel will achieve a transmittance level of 245 (the desired level for switching the red subpixel in this black-to-orange switching example) (curve 140) with an applied voltage of 4.5 volts, but when the red subpixel is modified to exhibit a dipole-to-electrode axis angle of 5 °, this same desired transmittance level will be achieved with only 4 volts applied (curve 142). With a modified arrangement (e.g., an arrangement with less curved chevrons for red pixels), a lower pixel voltage value needed to achieve pixel value 245 would allow the red subpixel to be switched with a lower voltage. A lower switching voltage (i.e., 4 volts instead of 4.5 volts in this example) will result in the red pixel switching speed being reduced as desired.

If desired, the electrode 106 may have a V-shape with a bend. For example, as shown in the illustrative configuration of fig. 11, the electrode 106 may have a major portion in which the fingers of the electrode extend parallel to each other (and are oriented at an angle such as illustrative angle 90-a relative to the Y-axis for the illustrative subpixel in fig. 11). The bends 106K in the electrode may be formed by short segments of the electrode having different angles (i.e., angles greater than 90-a) relative to the Y-axis. The bend 106K may, for example, be located at the center of the electrode 106 (i.e., to form a central bent portion) and/or at the end of the electrode 106 (i.e., to form an end bend).

Fig. 12 is an illustrative layout for an electrode 106 in which the electrode 106 has a non-V-shape. In the example of fig. 12, the electrode fingers 106 (i.e., longitudinal electrode finger axes 133) extend diagonally across each sub-pixel. The electrode fingers 106 are oriented at an angle of 90-a relative to the Y-axis in the red subpixel 90R (so that the electrode finger axes are oriented at an angle of 90-a relative to the liquid crystal dipoles). The green sub-pixel 90G may have electrode fingers 106 with axes 133 oriented at an angle 90-B with respect to the Y-axis (and with respect to the liquid crystal dipole). The blue subpixel 90B may likewise have electrode fingers 106 with axes 133 oriented at an angle 90-B relative to the liquid crystal dipoles, or the blue subpixel 90-B of fig. 12 (as well as any other blue subpixels, such as the V-blue subpixel of fig. 9, etc.) may have different angles (e.g., angle 90-C, where C is different from B and different from a) if desired. A configuration in which each subpixel color has fingers oriented at different angles may provide display 14 with enhanced ability to prevent different types of color motion blur, but may consume more area than a display in which angles C and B are equal.

FIG. 13 shows an illustrative configuration in which sub-pixels in some rows (e.g., row n) have electrode fingers 106 rotated slightly clockwise from axis Y (such as by an angle 90-A for sub-pixel 90R and by an angle 90-B for sub-pixel 90G and optionally by another angle 90-C for blue pixel 90B), and with other rows (e.g., row n +1) in which electrode fingers 106 are rotated slightly counterclockwise in the same manner.

In general, subpixels 90R, 90G, and 90B may have electrodes with any suitable shape (i.e., any suitable electrode pointing orientation with respect to the liquid crystal dipole of layer 52). The electrode configurations of fig. 9, 11, 12, and 13 are merely illustrative.

If desired, the switching speed of the red sub-pixel may be slowed by adding a cell gap to the red sub-pixel relative to the blue and green sub-pixels. This type of configuration is shown in the cross-sectional side view of display 14 of FIG. 14. As shown in fig. 14, the color filter layer 56 may have a color filter layer substrate 56A (e.g., a transparent material layer such as transparent glass, plastic, ceramic, etc.). Color filter elements such as red elements R, green elements G, and blue elements B may be patterned onto substrate 56A (e.g., using photoimageable colored polymers and photolithographic patterning techniques). The black mask layer 130 may have V-shaped openings or other suitable openings that are aligned with the color filter elements.

A transparent overcoat layer, such as overcoat layer 56B (e.g., a transparent photoimageable polymer layer or other suitable layer) having multiple thicknesses may be deposited over the array of color filter elements on substrate 56A using half-tone masks, multiple masks and multiple deposition steps, or other techniques. Layer 56B may have a thickness of T1 in the area covering the red sub-pixel of display 14 and may have a thicker thickness such as thicknesses T2 and T3, respectively, in the green and blue sub-pixels of display 14. The thicknesses T2 and T3 may be equal to each other or may be different. Thus, the thickness of the liquid crystal layer 52 in the red sub-pixel (D1) will be thicker than the thicknesses in the green and blue sub-pixels (D2 and D3, respectively). The switching speed is slower for thicker cell gaps (e.g., the decay time may be proportional to the square of the liquid crystal thickness and the rise time may similarly increase as the liquid crystal layer thickness increases). The value of the larger liquid crystal layer thickness D1 in the red sub-pixel, when compared to the values of the smaller liquid crystal layer thicknesses D2 and D3 in the blue and green sub-pixels, will therefore slow the red sub-pixel switching speed relative to the green and blue sub-pixel switching speeds to compensate for the type of red motion blur effect that can occur when an object such as object 112 is moved against a background such as background 110.

If desired, a selective pixel gap adjustment mechanism of the type shown in FIG. 14 may be used in combination with a selective electrode axis flattening mechanism of the type shown in FIGS. 9, 11, 12 and 13 and/or other selective adjustments may be made to the sub-pixel structure for a particular color sub-pixel to compensate for color motion blur. The examples of fig. 9, 11, 12, and 13 are merely illustrative.

According to an embodiment, there is provided a liquid crystal display having rows and columns of pixels, wherein the pixels comprise a plurality of differently colored sub-pixels, the liquid crystal display comprising upper and lower display layers, and a layer of liquid crystal material between the upper and lower display layers, at least one of the upper and lower display layers comprising a substrate, and pixel electrodes for the sub-pixels, the pixel electrodes being formed on the substrate, the pixel electrodes having a longitudinal axis, liquid crystal molecules in the liquid crystal material being initially unrotated by application of an electric field with the pixel electrodes and having associated dipoles producing dipole-to-electrode axis angles with respect to the longitudinal axis of the pixel electrodes, and the dipole-to-electrode axis angles for the differently colored sub-pixels being different.

According to another embodiment, the sub-pixels include red sub-pixels and sub-pixels of other colors, and the dipole-to-electrode axis angle for the red sub-pixels is different from the dipole-to-electrode axis angle for the sub-pixels of the other colors.

According to another embodiment, the other color sub-pixels include green and blue sub-pixels, and the dipole-to-electrode axis angle for the red sub-pixel is different from the dipole-to-electrode axis angle for the green and blue sub-pixels.

According to another embodiment, the dipole-to-electrode axis angle for the red sub-pixel is smaller than the dipole-to-electrode axis angles for the green and blue sub-pixels.

According to another embodiment, the pixel electrode has a chevron shape, and the pixel electrode of the red sub-pixel has a chevron shape that is less curved than the chevron shape of the pixel electrodes in the green and blue sub-pixels.

According to another embodiment, the sub-pixels include a red sub-pixel, a blue sub-pixel, and a green sub-pixel, and the blue and green sub-pixels have pixel electrodes that are different shapes than the red sub-pixel, such that the blue and green sub-pixels exhibit a normalized transmittance versus applied voltage curve that has a different shape than the red sub-pixel.

According to an embodiment, there is provided a liquid crystal display having rows and columns of pixels, wherein the pixels comprise red, green and blue sub-pixels, the liquid crystal display comprising upper and lower display layers, and a layer of liquid crystal material between the upper and lower display layers, at least one of the upper and lower display layers comprising a substrate, and an overcoat layer on the substrate, the overcoat layer having a first thickness in a region overlapping the red sub-pixel and a second thickness greater than the first thickness in a region overlapping the green sub-pixel to minimize motion blur effects when a black object is moved across a colored background.

According to another embodiment, the substrate forms part of an upper display layer, the colored background has red, green and blue sub-pixel values, the red sub-pixel value is greater than the green and blue sub-pixel values, and the liquid crystal display comprises an array of color filter elements on the substrate.

According to another embodiment, the overcoat layer is formed on the array of color filter elements.

According to another embodiment, the overcoat has a second thickness in the region overlapping both the green and blue subpixels.

According to another embodiment, the array of color filter elements includes red color filter elements in a red sub-pixel, green color filter elements in a green sub-pixel, and blue color filter elements in a blue sub-pixel, and the overcoat has a first thickness in a region overlapping the red color filter elements and a second thickness in a region overlapping the blue and green color filter elements.

According to another embodiment, the liquid crystal display includes a thin-film-transistor layer in a lower display layer.

According to another embodiment, the liquid crystal display includes a thin-film-transistor layer in an upper display layer.

According to another embodiment, the blue and green sub-pixels have a different shape than the red sub-pixel.

According to another embodiment, the sub-pixels have a chevron shape and the red sub-pixels have a chevron shape that is less curved than the chevron shape of the green and blue sub-pixels.

According to one embodiment, a liquid crystal display is provided having rows and columns of pixels, wherein the pixels include subpixels of first, second, and third colors, the liquid crystal display including a display layer including an upper layer and a lower layer, and a liquid crystal material layer between the upper layer and the lower layer, at least one of the upper layer and the lower layer including a substrate and a black mask layer having an opening for the subpixel on the substrate, and a pixel electrode formed in the display layer aligned with an edge of the opening, the pixel electrodes for the subpixels of the second and third colors having a different shape from the pixel electrode for the subpixel of the first color.

According to another embodiment, the pixel electrodes of the sub-pixels of the first color have a first chevron shape, and the pixel electrodes of the sub-pixels of the second and third colors have a second chevron shape different from the first chevron shape.

According to another embodiment, the first color comprises red.

According to another embodiment, the second and third colors comprise green and blue, respectively.

According to another embodiment, the pixel electrode having the first V-shaped opening is less bent than the pixel electrode having the second V-shaped opening.

The foregoing is merely illustrative and various modifications may be made by those skilled in the art without departing from the scope and spirit of the embodiments. The above embodiments may be implemented individually or in any combination.

Claims

1. A liquid crystal display comprising rows and columns of pixels, the pixels comprising a plurality of different color sub-pixels, wherein the sub-pixels comprise a red sub-pixel, a blue sub-pixel, and a green sub-pixel, the liquid crystal display comprising:

an upper display layer and a lower display layer; and

a layer of liquid crystal material between an upper display layer and a lower display layer, wherein at least one of the upper display layer and the lower display layer comprises:

a substrate; and

a pixel electrode for a sub-pixel, wherein the pixel electrode is formed on a substrate, wherein the pixel electrode has a longitudinal axis, wherein liquid crystal molecules in the liquid crystal material are initially non-rotated by applying an electric field with the pixel electrode and have associated dipoles that produce dipole-to-electrode axis angles with respect to the longitudinal axis of the pixel electrode, and wherein the dipole-to-electrode axis angles for the sub-pixels of different colors are different, wherein the pixel electrode has a chevron shape, and wherein the chevron shape of the pixel electrode of the red sub-pixel is less curved than the chevron shape of the pixel electrodes in the green and blue sub-pixels.

2. The liquid crystal display of claim 1, wherein the dipole-to-electrode axis angle for the red sub-pixel is different from the dipole-to-electrode axis angle for the green and blue sub-pixels.

3. The liquid crystal display of claim 2, wherein the dipole-to-electrode axis angle for the red subpixel is less than the dipole-to-electrode axis angles for the green subpixel and the blue subpixel.

4. The liquid crystal display of claim 1, wherein the blue and green subpixels have pixel electrodes of a different shape than the red subpixel, such that the blue and green subpixels exhibit a normalized transmittance versus applied voltage curve having a different shape than the red subpixel.

5. A liquid crystal display comprising rows and columns of pixels, the pixels comprising red, green and blue sub-pixels, the liquid crystal display comprising:

an upper display layer and a lower display layer; and

a layer of liquid crystal material between the upper and lower display layers, wherein the layer of liquid crystal material has a first thickness that is all constant throughout each red sub-pixel and a second thickness that is all constant throughout each green and blue sub-pixel and less than the first thickness, wherein the second thickness throughout the green sub-pixel is equal to the second thickness throughout the blue sub-pixel, wherein the first and second thicknesses extend in a direction perpendicular to the upper and lower display layers, and wherein one of the upper and lower display layers comprises:

a substrate; and

an overcoat layer on the substrate, the overcoat layer completely and continuously overlapping the red, green, and blue sub-pixels, wherein the overcoat layer has a first thickness in a region overlapping the red sub-pixel, a second thickness greater than the first thickness in a region overlapping the green sub-pixel, and a third thickness equal to the second thickness in a region overlapping the blue sub-pixel, wherein the first thickness, the second thickness, and the third thickness extend in a direction perpendicular to the upper and lower display layers.

6. The liquid crystal display of claim 5, wherein the liquid crystal display further comprises an array of color filter elements on the substrate.

7. The liquid crystal display of claim 6, wherein the overcoat layer is formed over the array of color filter elements.

8. The liquid crystal display of claim 6, wherein the array of color filter elements includes red color filter elements in a red subpixel, green color filter elements in a green subpixel, and blue color filter elements in a blue subpixel.

9. The liquid crystal display of claim 8, further comprising a thin film transistor layer in the lower display layer.

10. The liquid crystal display of claim 8, further comprising a thin film transistor layer in the upper display layer.

11. The liquid crystal display of claim 5, wherein the blue sub-pixel and the green sub-pixel have a different shape than the red sub-pixel.

12. The liquid crystal display of claim 5, wherein the red, green, and blue subpixels have a chevron shape, and wherein the chevron shape of the red subpixel is less curved than the chevron shapes of the green and blue subpixels.

13. A liquid crystal display having rows and columns of pixels, the pixels including a plurality of sub-pixels, wherein the sub-pixels include a red sub-pixel, a green sub-pixel, and a blue sub-pixel, the liquid crystal display comprising:

a display layer including an upper layer and a lower layer; and

a layer of liquid crystal material between an upper layer and a lower layer, wherein at least one of the upper layer and the lower layer comprises a substrate, a black mask layer having openings for sub-pixels on the substrate, and an array of red, green, and blue color filter elements; and

a pixel electrode formed in the display layer aligned with an edge of the opening, wherein the pixel electrodes for the green and blue sub-pixels have a different shape than the pixel electrode for the red sub-pixel, wherein the pixel electrode for the red sub-pixel has a first chevron shape, wherein the pixel electrodes for the green and blue sub-pixels have a second chevron shape different from the first chevron shape, wherein the pixel electrode having the first chevron shape is less curved than the pixel electrode having the second chevron shape.