PATENT DOCUMENT

Publication Number: US-9244215-B2
Application Number: US-201113229418-A
Country: US
Kind Code: B2

Title: Chassis for display backlight

Abstract:
An electronic device may be provided with a display. Backlight structures may be used to provide backlight for the display. The backlight structures may include a light guide plate. A rectangular ring-shaped chassis may have a rectangular opening that receives the light guide plate. One or more edges of the chassis may be provided with an array of notches that receive light-emitting diodes or other light sources. The light sources may launch light into edge portions of the light guide plate. The chassis may include a first plastic structure such as a light reflecting structure formed from a material such as white plastic. The first plastic structure may surround two or more peripheral edges of the light guide plate. The chassis may also include a second plastic structure such as a light blocking structure formed from a material such as black plastic that helps prevent light leakage.

Claims:
What is claimed is: 
     
       1. Backlight structures for an electronic device display, comprising:
 a rectangular light guide plate; 
 a light source that launches backlight into an edge surface of the rectangular light guide plate; and 
 a rectangular ring-shaped plastic chassis that surrounds the rectangular light guide plate, wherein the rectangular ring-shaped plastic chassis includes at least a first plastic structure and a second plastic structure formed from a different plastic material than the first plastic structure, wherein the second plastic structure forms an exterior surface of the rectangular ring-shaped plastic chassis that is parallel to the edge surface of the light guide plate, wherein the first plastic structure is interposed between the edge surface of the light guide plate and the second plastic structure that forms the exterior surface of the rectangular ring-shaped plastic chassis, wherein the first plastic structure extends noncontinuously around the rectangular light guide plate, and wherein a portion of the chassis opposite the light source is formed exclusively of material from the second plastic structure. 
 
     
     
       2. The backlight structures defined in  claim 1  wherein the first plastic structure is configured to form an inner surface along at least one interior edge of the rectangular ring-shaped plastic chassis. 
     
     
       3. The backlight structures defined in  claim 2  wherein the first plastic structure comprises white plastic. 
     
     
       4. The backlight structures defined in  claim 2  wherein the first plastic structure comprises a rectangular ring of light reflecting plastic. 
     
     
       5. The backlight structures defined in  claim 2  wherein the first plastic structure is configured to form a light reflecting surface along at least two sidewalls of the rectangular ring-shaped plastic chassis. 
     
     
       6. The backlight structures defined in  claim 5  wherein the second plastic structure comprises black plastic. 
     
     
       7. The backlight structures defined in  claim 6  wherein the first plastic structure comprises white plastic. 
     
     
       8. The backlight structures defined in  claim 5  wherein the chassis has first, second, third, and fourth edges, wherein the first and third edges are parallel, wherein the second and fourth edges are parallel, and wherein the first and third edges of the chassis are formed exclusively of material from the second plastic structure. 
     
     
       9. The backlight structures defined in  claim 5  wherein the chassis has first, second, third, and fourth edges, wherein the first and third edges are parallel, wherein the second and fourth edges are parallel, and wherein the first edge of the chassis is formed exclusively of the material from the second plastic structure. 
     
     
       10. The backlight structures defined in  claim 1  wherein the first plastic structure comprises light reflecting plastic, wherein the second plastic structure comprises light blocking plastic, wherein the light reflecting plastic is more reflective than the light blocking plastic, wherein at least some of the second plastic structure forms a sidewall portion of the rectangular ring-shaped chassis, and wherein at least some of the first plastic structure is located along an inner surface of the sidewall portion. 
     
     
       11. A backlight structure, comprising:
 a light guide plate having an edge surface that receives light from a light source; and 
 a chassis that surrounds the light guide plate, wherein the chassis includes a first injection molded plastic structure and a second injection molded plastic structure, wherein the first injection molded plastic structure forms an interior surface of the chassis, wherein the second injection molded plastic structure forms an exterior surface of the chassis, wherein the interior and exterior surfaces of the chassis are parallel to the edge surface of the light guide plate, wherein the interior surface is interposed between the edge surface of the light guide plate and the exterior surface of the chassis, wherein the second injection molded plastic structure completely surrounds the light guide plate, wherein the first injection molded plastic structure surrounds only a portion of the light guide plate, and wherein a portion of the light guide plate that is not surrounded by the first injection molded plastic structure is opposite the edge surface of the light guide plate that receives light from the light source. 
 
     
     
       12. The backlight structure defined in  claim 11  wherein the second injection molded plastic structure is more opaque than the first injection molded plastic structure and wherein the first injection molded plastic structure is injection molded on at least one peripheral edge of the light guide plate. 
     
     
       13. The backlight structure defined in  claim 12  wherein the first and second injection molded plastic structures are molded to each other along at least one edge. 
     
     
       14. The backlight structure defined in  claim 11  wherein the chassis has four edges, wherein the first injection molded plastic structure comprises white plastic, wherein the second injection molded plastic structure comprises black plastic, and wherein at least some of the black plastic surrounds each of the four edges of the chassis. 
     
     
       15. A backlight structure, comprising:
 a light guide plate having a peripheral edge surface; 
 a light source that emits light in to the peripheral edge surface of the light guide plate; and 
 a chassis that surrounds the light guide plate, wherein the chassis includes an outer structure and a metal coating on an interior surface of the outer structure, wherein the interior surface is parallel to the peripheral edge surface, wherein the metal coating is configured to reflect light into the light guide plate through the peripheral edge surface, and wherein the light emitted into the peripheral edge surface of the light guide plate is incident upon a portion of the interior surface of the outer structure opposite the peripheral edge surface into which the light source emits light. 
 
     
     
       16. The backlight structure defined in  claim 15  wherein the outer structure comprises plastic. 
     
     
       17. A backlight structure, comprising:
 a light guide plate having a peripheral edge surface; 
 a light source that emits light in to the peripheral edge surface of the light guide plate; and 
 a chassis that surrounds the light guide plate, wherein the chassis includes an outer light absorbing structure and a thin-film stack on an interior surface of the outer light absorbing structure, wherein the interior surface is parallel to the peripheral edge surface, wherein the thin-film stack is configured to reflect light into the light guide plate through the peripheral edge surface, and wherein the light emitted into the peripheral edge surface of the light guide plate is incident upon a portion of the interior surface of the outer light absorbing structure opposite the peripheral edge into which the light source emits light. 
 
     
     
       18. The backlight structure defined in  claim 17  wherein the thin-film stack includes a plurality of dielectric layers of differing indices of refraction. 
     
     
       19. The backlight structure defined in  claim 18  wherein the outer light absorbing structure comprises a ring-shaped structure formed from plastic.

Description:
BACKGROUND 
     This relates generally to electronic devices and, more particularly, to displays for electronic devices. 
     Electronic devices such as cellular telephones, computers, and media players often contain displays. For example, electronic devices often include backlit displays such as backlit liquid crystal displays. 
     Backlit displays generally include a light distribution layer called a light guide plate. The light guide plate is typically formed from a rectangular sheet of clear plastic that has been injection molded, extruded, or die cut from a sheet of plastic. Light from an array of light-emitting diodes may be launched into the edge of the light guide plate. The light guide plate distributes light across the back of a display panel by total internal reflection. Light that exits the planar upper surface of the light guide plate serves as backlight for the display panel. 
     The light guide plate is typically mounted within a white plastic chassis structure that is sometimes referred to as a p-chassis or moldframe. The white plastic of the p-chassis forms reflective sidewalls around the periphery of the light guide plate. Light that exits the edges of the light guide plate is reflected back into the light guide plate by the reflective sidewalls of the p-chassis. The reflected light may therefore serve as additional backlight for the display. 
     The use of reflective white plastic to form the p-chassis can improve backlight efficiency. However, the white plastic that forms the sidewalls of the p-chassis is generally unable to block all of the light that strikes the sidewalls. As a result, some of the light from the light guide plate can leak into undesired areas of an electronic device. If care is not taken, for example, leaking light may cause unwanted illumination in locations that are visible to a user of an electronic device. 
     It would therefore be desirable to be able to provide improved display backlight structures such as improved chassis structures for light guide plates in display backlights. 
     SUMMARY 
     An electronic device may be provided with a display. Backlight structures may be used to provide backlight for the display. The backlight structures may include a light guide plate. The backlight structures may be used in distributing backlight to structures in the display such as a thin-film transistor layer, a color filter layer, polarizers, and other display layers. 
     The structures in the display and backlight structures such as the light guide plate may have any suitable shape. For example, the display and the backlight structures in the display such as the light guide plate may be circular, may be oval, may be rectangular, may have outlines with curved edges, may have outlines with straight edges, may have shapes with combinations of straight and curved edges, or may have any other suitable shape. 
     The backlight structures may include a chassis with an opening that receives the light guide plate. One or more edges of the chassis may be provided with an array of notches that receive respective light-emitting diodes or other light sources. The light sources may launch light into edge portions of the light guide plate. 
     The chassis may include a light reflecting structure formed from a material such as plastic or metal. Plastic materials for the chassis may be relatively stiff polymers such as polycarbonate or may be relatively soft polymers such as synthetic rubber, natural rubber, silicone, or other elastomeric materials. A thin-film stack of dielectric materials may also be used to form the light reflecting structure. The light reflecting structure may surround two or more peripheral edges of the light guide plate and may help reflect escaping light back into the edges of the light guide plate. The chassis may also include a light blocking structure formed from a material such as black plastic that helps prevent light leakage from the chassis. The light reflecting and light blocking structures may be formed using tools such as plastic injection molding tools. 
     Further features of the invention, its nature and various advantages will be more apparent from the accompanying drawings and the following detailed description of the preferred embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an illustrative electronic device with display backlight structures in accordance with an embodiment of the present invention. 
         FIG. 2  is a top view of a portion of a backlight chassis structure in accordance with an embodiment of the present invention. 
         FIG. 3  is a cross-sectional side view of an illustrative display showing how a chassis structure of the type shown in  FIG. 2  may reflect light and may block leaking light in accordance with an embodiment of the present invention. 
         FIG. 4  is a cross-sectional side view of the chassis structure of  FIG. 3  showing how sidewall structures on edges of a light guide plate may be provided with an inner material that reflects light and an outer material that blocks light in accordance with an embodiment of the present invention. 
         FIG. 5  is a diagram showing how injection molding techniques may be used in forming chassis structures for a display backlight in accordance with an embodiment of the present invention. 
         FIG. 6  is a diagram showing how layers of material such as plastics with different optical properties may be molded onto a display component such as a light guide plate in a backlight in accordance with an embodiment of the present invention. 
         FIG. 7  is a top view of a corner portion of a chassis for a display backlight structure in accordance with an embodiment of the present invention. 
         FIG. 8  is a cross-sectional end view of a sidewall portion of the chassis of  FIG. 7  in accordance with an embodiment of the present invention. 
         FIG. 9  is a cross-sectional view of a conventional backlight structure with a white plastic chassis. 
         FIG. 10  is a top view of a conventional backlight chassis with a metal frame having holes and molded plastic that fills the holes. 
         FIG. 11  is a cross-sectional view of a sidewall of the conventional chassis of  FIG. 10 . 
         FIG. 12  is a cross-sectional view of a sidewall in a backlight chassis in accordance with an embodiment of the present invention. 
         FIG. 13  is a cross-sectional view of a sidewall of the type shown in  FIG. 12  in which the thickness of a light blocking layer has been increased and the thickness of a light reflecting layer has been decreased by a corresponding amount in accordance with an embodiment of the present invention. 
         FIG. 14  is a cross-sectional view of a sidewall of the type shown in  FIG. 12  in which the thickness of a light blocking layer has been decreased and the thickness of a light reflecting layer has been increased by a corresponding amount in accordance with an embodiment of the present invention. 
         FIG. 15  is a cross-sectional view of a portion of a backlight structure showing how a light reflecting layer may be formed between an electronic device housing structure and a light guide plate in accordance with an embodiment of the present invention. 
         FIG. 16  is a cross-sectional view of a portion of a backlight structure showing how multiple layers of material such as a light blocking layer and a light reflecting layer may be formed on an electronic device housing structure in accordance with an embodiment of the present invention. 
         FIG. 17  is a cross-sectional side view of a portion of an electronic device having a light blocking layer and a light reflecting layer interposed between a peripheral edge of a light guide plate and an electronic device housing structure in accordance with an embodiment of the present invention. 
         FIG. 18  is a diagram showing how a light blocking layer such as a coating of metal or other material may be coated on an exterior surface of a light reflecting layer in accordance with an embodiment of the present invention. 
         FIG. 19  is top view of an illustrative display backlight chassis structure that is configured to accommodate two opposing arrays of light-emitting diodes in accordance with an embodiment of the present invention. 
         FIGS. 20 ,  21 ,  22 ,  23 ,  24 ,  25 , and  26  are cross-sectional views of illustrative sidewall structures that may be used in backlight chassis structures in accordance with an embodiment of the present invention. 
         FIG. 27  is a top view of an illustrative backlight chassis structure having an inner ring of light reflecting material surrounded by an outer ring of light blocking material. 
         FIG. 28  is a top view of an illustrative backlight chassis structure having an outer ring of light blocking material and three segments of light reflecting material along three of the four inner edges of the backlight chassis structure in accordance with an embodiment of the present invention. 
         FIG. 29  is a cross-sectional view of illustrative sidewall structures for a backlight chassis in which a light reflecting layer has been formed from a reflective material such as metal in accordance with an embodiment of the present invention. 
         FIG. 30  is a cross-sectional side view of illustrative sidewall structures for a backlight chassis in which a light reflecting layer has been formed from a thin-film stack of materials in accordance with an embodiment of the present invention. 
         FIG. 31  is a cross-sectional side view of illustrative sidewall structures showing how a backlight chassis may be provided with structures such as features that engage with housing structures in accordance with an embodiment of the present invention. 
         FIG. 32  is a diagram showing equipment that may be used in forming backlight chassis structures and other device structures in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Electronic devices such as device  10  of  FIG. 1  may be provided with displays. A display in device  10  may contain backlight structures (sometimes referred to as a backlight unit or backlight) to provide backlight illumination for the display. 
     Device  10  of  FIG. 1  may be a portable computer, tablet computer, computer monitor, handheld device, game equipment, global positioning system equipment, cellular telephone, or other electronic equipment. 
     Device  10  may include a housing such as housing  12 . Housing  12 , which may sometimes be referred to as a case, may be formed of plastic, glass, ceramics, fiber composites, metal (e.g., stainless steel, aluminum, etc.), other suitable materials, or a combination of any two or more of these materials. 
     Housing  12  may be formed using a unibody configuration in which some or all of housing  12  is machined or molded as a single structure or may be formed using multiple structures (e.g., an internal frame structure, one or more structures that form exterior housing surfaces, etc.). 
     A display such as display  14  may be mounted in housing  12 . For example, display  14  may be mounted on the front surface of device  10 . Displays such as display  14  may also be mounted in other portions of housing  12  (e.g., in an upper housing in a computer with hinged upper and lower housing structures, on the rear of the housing, etc.). 
     Display  14  may be a touch screen that incorporates capacitive touch electrodes or a touch sensor formed using other types of touch technology (e.g., resistive touch, acoustic touch, force-sensor-based touch, etc.) or may be a display that is insensitive to touch input. Display  14  may include image pixels formed from liquid crystal display (LCD) components or other suitable image pixel structures. 
     Display  14  may be covered with a display cover layer such as a layer of cover glass or a transparent plastic layer. The active region of display  14  may lie within a central region of display  14 . A peripheral ring-shape region surrounding the active display region may form an inactive region for display  14 . Structures such as button  16  and speaker port  18  may, if desired, be formed in the inactive peripheral region of display  14  (as an example). 
     Backlight for display  14  may be provided using a backlight structure of the type shown in  FIG. 2 . As shown in  FIG. 2 , backlight structures  20  may include a light guide structure such as light guide plate  22 . Display  14  may have any suitable shape. For example, display  14  may be circular, may be oval, may be rectangular, may have shapes with combinations of straight and/or curved edges, or may have any other suitable shape. Light guide plate  22  may be used in providing backlight for display  14  and may have a shape that matches the shape of display  14 . For example, light guide plate  22  may be circular, may be oval, may be rectangular, may have shapes with combinations of straight and curved edges, or may have any other suitable shape. 
     Although display  14  may, in general, have any suitable shape, configurations for device  10  in which display  14  has a rectangular shape are sometimes described herein as an example. This is, however, merely illustrative. Display  14  and associated display structures such as light guide plate  22  may have any suitable shape. 
     As shown in  FIG. 2 , backlight  26  may be launched into one or more of the edges of light guide plate  22  (e.g., one or more of the four edges of a rectangular light guide plate) from light sources such as light-emitting diodes  24 . In the example of  FIG. 2 , light-emitting diodes  24  are launching light  26  into the top edge of light guide plate  22 . Other configurations may be used if desired (e.g., configurations in which light is launched into multiple edges of the light guide plate, etc.). 
     Light guide plate  22  may be formed from a transparent material such as glass or a polymer such as acrylic or other clear plastic (as an example). Light  26  is guided within light guide plate  22  due to the principle of total internal reflection. Some of light  26  is extracted from light guide plate  22  via engineered features on the upper surface of the light guide plate, the lower surface of the light guide plate, or both the upper and lower light guide plate surfaces. Downwardly directed light is reflected back into the light guide plate towards a viewer by a reflector layer under the light guide plate. Upwardly directed light travels through the active layers of display  14  that are formed above the backlight. For example, in a liquid crystal display, the upwardly directed light travels through a thin-film transistor layer, a color filter layer, and a layer of liquid crystal material that is interposed between the color filter layer and thin-film transistor layer. The color filter layer may be used to provide display pixels with different colors. The thin-film transistor layer may be used to control the transmission of individual pixels of the liquid crystal material. Backlight may pass through upper and lower polarizers that are formed above and below the color filter layer and thin-film transistor layer, respectively. 
     Light guide plate  22  may be mounted in a display backlight chassis such as chassis  28 . Chassis  28  may have a rectangular ring shape with a rectangular central opening that receives rectangular light guide plate  22  or may have other suitable shapes. The periphery of chassis  28  may have a rectangular shape as shown in  FIG. 2  (as an example). 
     Chassis  28  may be formed from two or more different materials. For example, chassis  28  may be formed form materials of different colors, materials with different light absorbing properties, materials with different surface finishes, materials with different light reflectivities, materials with different densities, materials with different hardnesses, or other different types of materials. Materials may be selected based on compatibility with surrounding structures, ease of assembly, cosmetics, optical properties, durability, or other suitable criteria. 
     Examples of materials that may be used in forming chassis  28  include plastic, metal, glass, ceramic, wood, carbon-fiber composites and other composites, other materials, and combinations of these materials. In some illustrative examples, one or more of the materials includes plastic. Plastic (polymer) materials for chassis  28  may be relatively stiff materials such as polycarbonate (PC), acrylonitrile butadiene styrene (ABS), or a PC/ABS blend or may be relatively soft polymers such as synthetic rubber, natural rubber, silicone, or other elastomeric materials. Rigid and elastomeric polymers are collectively referred to herein as “plastic.” 
     With one illustrative arrangement, which is sometimes described herein as an example, the materials for chassis  28  may be selected for their light reflecting and light blocking capabilities. In particular, some of the material in chassis  28 , such as material  30 , may be configured to block light. Material  30 , which may sometimes be referred to as light blocking material  30 , light blocking layer  30 , or light blocking structures  30 , may be formed from an opaque material such as black plastic, dark grey plastic, dark colored plastic (e.g., plastic that is dark blue, dark brown, dark red, or other suitable colors), metal, or other materials that are optimized for preventing the transmission of light out of backlight chassis  28 . Light transmission may be prevented by light absorption (e.g., light transmission may be prevented when a dark layer of plastic absorbs light that has penetrated into the dark layer of plastic) and/or may be prevented by reflection (e.g., light transmission may be prevented when a light blocking layer formed from a reflective metal blocks light by reflecting the light). 
     Other material in chassis  28  such as material  32  may be configured to reflect light. Material  32 , which may sometimes be referred to as light reflection material  32 , light reflecting layer  28 , or light reflecting structures  32 , may be formed from a layer of material that is optimized for reflecting light (e.g., plastic that is white, plastic that has a light color such as light yellow, light grey, light silver, etc.), may be formed from a metal layer, may be formed from a thin-film stack (e.g., a collection of dielectric layers or other layers), or may be formed from other reflecting structures. 
     With one suitable arrangement, light reflecting layer  32  is white and light blocking layer  30  is black, but other combinations of light reflecting and light blocking structures may be used in chassis  28  if desired. The reflectance of chassis structure  28 , which is generally due primarily to the properties of light reflecting structure  32 , may be about 70% or more, 80% or more, or 90% or more. The transmission of chassis structure  28 , which is generally due primarily to the light blocking qualities of light blocking structure  30  may be less than 10%, less than 1%, or less than 0.1% (as examples). Viewed individually, the transmittance of light blocking material  30  will be less than the transmittance of light reflecting material  32  (for a given thickness) and light blocking material  30  will be more opaque than light reflecting material  32 . As a result, the use of light blocking material  30  in chassis  28  can help reduce light leakage. The reflectance of light reflecting material  32  will be greater than the reflectance of light blocking material  30 . 
     During operation of backlight structures  20 , light  26  is launched into the interior of light guide plate  22  from light-emitting diodes  24 . When light  26  reaches one of the edges of light guide plate  22  such as the bottom edge in  FIG. 2 , light  26  may exit the light guide plate and strike light reflecting layer  32 . Due to the presence of light reflecting layer  32 , light is reflected back into the edge of light guide panel  22 . The reflected light may therefore be extracted by features in the light guide panel to serve as backlight for display  14 . In some configurations, light reflecting layer  32  may be formed from a material that tends to diffuse the light as it is reflected (e.g., white plastic or other materials that allow light to penetrate somewhat before being reflected). Because light is reflected, backlight is not wasted and overall backlight efficiency is enhanced. 
     Because of the white color or other light color of light reflecting structures  32 , not all of light  26  may be reflected back into light guide plate  22 . Nevertheless, light leakage may be eliminated or at least substantially reduced by the presence of light blocking material  30  around some or all of the exterior surfaces of chassis  28 . 
     Light blocking material  30  may surround all four edges of chassis  28  or may surround a subset of these four edges. Light reflecting material  32  may be used to line the interior surfaces of some or of the four edges of chassis  28 . For example, in the illustrative configuration of  FIG. 2 , top chassis segment  34  contains only light blocking material  30  and does not contain any light reflecting material  32 . 
     A cross-sectional side view of backlight structures  20  of  FIG. 2  taken along line  36  and viewed in direction  38  is shown in  FIG. 3 . As shown in  FIG. 3 , light  26  may be emitted in direction Y and may be launched into the edge of light guide plate  22  (e.g., the left-hand edge of plate  22  in the orientation of  FIG. 3 ). Some of light  26  may be extracted in the downward direction towards the interior of device  10  and may reflect back in the upwards (Z) direction off of reflector  46 , as indicated by light ray  48 . Reflector  46  may be formed from a layer of white plastic, white paper, metal foil, or other suitable reflective surface. As indicated by light rays  50 , some of light  26  such as light that has been extracted from light guide plate  22  in the upward direction and reflected light from reflector  46  passes vertically through display structures  56  and optional display cover layer  44 . Display structures  56  may include diffuser films and other optical films, display module structures such as polarizers, a thin-film transistor glass layer, a color filter glass layer, a liquid crystal layer, and other display layers. Display cover layer  44  may be formed from glass or clear plastic (as examples). Surface features may be incorporated into light guide plate  22  to enhance light extraction efficiency (e.g., to enhance extraction at particular locations on the light guide plate). 
     Some of light  26  will be guided to the edge of light guide plate  22  due to the principle of total internal reflection. This light, which is shown as light ray  52  in the diagram of  FIG. 3 , reflects off of light reflecting structure  32  in chassis structure  28  and reenters the edge of light guide plate  22 , as indicated by light ray  54 . Light may be efficiently reflected (and backlight efficiency may be correspondingly high) because light reflecting layer  32  can be formed from a bright reflective material such as white plastic or lightly colored plastic. The white plastic (or other suitable material) that makes up light reflecting layer  32  may contribute both specular and diffuse components to reflected light  54  (e.g., about 50% of the light reflecting from layer  32  may be due to specular reflections and about 50% of the light reflecting from layer  32  may be due to diffuse reflections). The presence of light blocking layer  30  may help ensure that the amount of light that leaks from chassis structure  28  is minimized. By using an opaque material for light blocking (e.g., black plastic formed by incorporating carbon black or other dark materials into a plastic material), the thickness of layer  30  may be minimized while obtaining a desired degree of light leakage protection. The presence of light blocking layer  30  may therefore help to minimize the size of backlight structures  20  and device  10 . 
       FIG. 4  is a cross-sectional view of backlight structures  20  of  FIG. 2  taken along line  40  of  FIG. 2  and viewed in direction  42 . As shown in  FIG. 4 , light reflective layer  32  may be formed on the inner surface of chassis  28 , facing the opposing outer peripheral edges of light guide plate  22 . Light blocking layer  30  may be formed on the peripheral exterior surface of chassis  28  to help prevent light from leaking out of chassis  28 . 
       FIG. 5  is a diagram showing how backlight structures  20  for device  10  may be formed. As shown in  FIG. 5 , light guide plate  22  may be formed using equipment  58  such as a molding tool (e.g., to form a molded light guide plate) or a die cutting tool (e.g., to cut a rectangular light guide plate from a larger sheet of light guide material). 
     Molding tool  60  (e.g., plastic injection molding equipment) may then be used to mold a structure such as light reflecting structure  32  (e.g., white or lightly colored plastic) to the exterior edge of light guide plate  22 . 
     If desired, light reflecting layer  32  may be injection molded into a mold that contains a previously formed light blocking structure  30  and a previously formed light guide plate  22 . This type of arrangement is illustrated in  FIG. 6 . As shown in  FIG. 6 , molding equipment such as plastic injection molding tool  64  may be used to form light blocking structure  30  (e.g., a rectangular ring of black plastic) and equipment such as a molding tool or die cutting tool such as equipment  66  may be used to form light guide plate  22 . Following formation of structure  30  and plate  22 , structure  30  and plate  22  may be inserted into molding equipment such as plastic injection molding tool  68 . Molding tool  68  may then be used to injection mold reflective plastic layer  32  (e.g., a layer of white plastic) between structure  30  and light guide plate  22  to form molded chassis structure  28  on the peripheral edge of light guide plate  22 . In this type of arrangement, molded plastic-to-plastic interfaces are formed between the outer peripheral surface of structure  32  and the opposing inner surface of structure  30  and between the inner surface of structure  32  and the opposing outer peripheral edge of plate  22 . 
     Chassis  28  may have features that help control the flow of plastic during injection molding operations. As shown in  FIG. 7 , for example, light blocking layer  30  in chassis  28  may have features such as protrusion  74 .  FIG. 8  is a cross-sectional view of chassis  28  of  FIG. 7  taken along line  70  and viewed in direction  72 . As shown in  FIG. 8 , protrusions  74  may help contain plastic  32  during injection molding and may help form a satisfactory interlocking joint between plastic  30  and plastic  32  in the corner of chassis  28 . Other types of interlocking and plastic flow control features may be incorporated into chassis  28  if desired. The example of  FIGS. 7 and 8  is merely illustrative. 
     A conventional backlight structure is shown in  FIG. 9 . As shown in the cross-sectional view of  FIG. 9 , backlight structure  76  has a white rectangular plastic chassis (chassis  78 ) that surrounds light guide plate  80 . The sidewalls of chassis  28  can be thinner for a given amount of light blocking capability than the conventional sidewalls of chassis  78  due to the presence of light-blocking material  30  in chassis  28 . 
     Another conventional backlight structure is shown in  FIGS. 10 and 11 . Conventional backlight structure  82  of  FIG. 10  has a metal chassis structure into which plastic  94  has been molded. A cross-sectional view of one of the sidewalls of the chassis of backlight structure  82  of  FIG. 10  taken along line  84  and viewed in direction  86  is shown in  FIG. 11 . As shown in  FIG. 11 , light guide plate  88  has an edge that abuts plastic  94 . Plastic  94  is molded onto metal chassis  90  and flows into holes  92  that are located in an array around the periphery of metal chassis  90 . 
     As shown in  FIG. 12 , the sidewalls of chassis  28  may have a thickness D. To minimize the size of chassis  28 , it may be desirable to use injection molding tools to mold chassis  28  such that dimension D is as small as possible. In other configurations, chassis  28  may be molded to larger than minimum dimensions. Dimension D may be, for example, 0.05 to 0.4 mm, 0.1 to 0.3 mm, 0.2 mm or more, or less than 0.5 mm (as examples). Other sizes may be used if desired (e.g., chassis  28  may be molded to a relatively large size to improve strength, etc.). 
     In the configuration of  FIG. 12 , the thickness D (width in dimension X) of the sidewall of chassis  28  is formed from structures  32  and  30  with equal thicknesses (each being equal to D/2).  FIG. 13  shows how the thickness of light blocking layer  30  may be increased (without enlarging the total thickness D of the sidewall) to enhance the light blocking capability of the chassis sidewall.  FIG. 14  shows how the thickness of light reflecting layer  32  may be increased while decreasing the thickness of light blocking layer  30  by a corresponding amount. With this type of configuration, the size of the sidewall is maintained at thickness D (e.g., a minimum molding dimension), while increasing the reflectance of reflecting layer  32 . 
       FIG. 15  is a cross-sectional view of illustrative backlight structures  20  for device  10  showing how chassis structure  28  may be injection molded into a gap formed between the peripheral edge of light guide plate  22  and the inner edge surface of housing structure  12 . Chassis structure  28  may include a light reflecting layer, a light blocking layer, an inner light reflecting layer and an outer light blocking layer, or other suitable structures. With and arrangement of the type shown in  FIG. 15 , chassis  28  (e.g., layer  32  and optionally layer  30 ) may be formed as an integral portion of housing  12 . 
       FIG. 16  is a cross-sectional view of backlight structures  20  in a configuration in which a light blocking layer such as layer  30  and a light reflecting layer such as layer  32  have been provided on the inner peripheral surface of housing  12  (e.g., by using successive injection molding operations to mold layers  30  and  32  onto housing  12  to form a chassis that is an integral portion of housing  12 ). 
       FIG. 17  is a cross-sectional view of backlight structures  20  in a configuration in which light blocking layer  30  and light reflecting layer  32  have been injection molded onto the inner edge of housing  12 . As shown in FIG.  17 , light blocking layer  30  may have an overhang shape that covers an upper portion of light reflecting layer  32 . Light reflecting layer  32  may have a vertical height (in dimension Z) that is substantially equal to (or slightly larger than) the vertical height (thickness) of light guide plate  22 . Light blocking layer  30  may have a larger height to help contain stray light. 
       FIG. 18  shows how backlight chassis  28  may be formed by depositing an opaque layer of material on an exterior surface of light reflecting structure  32 . As shown in  FIG. 18 , molding equipment such as plastic injection molding tool  96  may be used to form light reflecting structure  32  (e.g., a rectangular ring of white plastic). Coating tool  98  may then be used to coat an exterior surface of light reflecting structure  32  to form an opaque layer such as layer  100  that blocks light. Coating tool  98  may include equipment such as physical vapor deposition equipment (e.g., sputtering equipment, evaporation equipment, etc.) for depositing a layer of metal (e.g., a layer of aluminum or other metal having a thickness of less than 1 micron or other suitable thickness) on the surface of light reflecting layer  32 . Other light blocking materials may be formed on the exterior surface of light reflecting layer  32  if desired. The formation of an opaque light blocking layer of metal (layer  100 ) in the example of  FIG. 18  is merely illustrative. 
     As shown in  FIG. 19 , backlight structures  20  may include light sources that are located in arrays along opposing edges of light guide plate  22 . In this type of configuration, one array of light sources (light-emitting diodes  24  along the top edge of plate  22  in  FIG. 19 ) emits light in one direction, whereas the other array of light sources (light-emitting diodes  24  along the bottom edge of plate  22  in  FIG. 19 ) emits light in the opposite direction. Chassis  28  may include multiple layers of plastic to enhance reflectivity while reducing light leakage. For example, chassis  28  may have multiple shots of plastic that have been injection molded into molds during multiple injection molding operations. 
     Chassis  28  may, for example, have an outer surface covered with light blocking material  30 . Light reflecting material  32  may be used to coat some or all of the interior surface of light blocking material  30  in chassis  28 . For example, light reflecting material  32  may coat the right and left interior surfaces of chassis  28  (in the orientation shown in  FIG. 19 ) while only light blocking material  30  is present along the top and bottom edges of light guide plate  22 . As indicated by lines  32 ′, light reflecting material  32  may also be used to coat the inner surfaces of the top and bottom edges of chassis  28 . 
     It is not necessary for the sidewalls of chassis  28  to be formed from equally sized and shaped light reflecting and light blocking structures  30  and  32 .  FIGS. 20-26  show illustrative sidewall configurations for chassis  28 . In the example of  FIG. 20 , light blocking material  30  has an L-shaped cross sectional shape that overhangs a portion of light reflecting structure  32 . In the example of  FIG. 21 , light blocking material  30  has a C-shaped cross-sectional shape that undercuts and overhangs light reflecting material  32 .  FIG. 22  is an example of a configuration in which light blocking material  30  and light reflecting material  32  have different heights (vertical thicknesses in dimension Z). In the  FIG. 23  configuration, light blocking material  30  has an L-shape that undercuts light reflecting material  32 .  FIG. 24  is a cross-sectional view of chassis  28  in a configuration in which light reflecting material  32  has multiple steps and does not form a completely vertical inner sidewall surface for chassis  28 . As shown in  FIG. 25 , light reflecting material  32  may be configured to undercut some or all of light blocking material  30 . As shown in  FIG. 26 , chassis  28  may be formed from more than two separate shots of plastic (or other material layers). In particular, chassis  28  may include light reflective layer  32 , light blocking layer  30 , and one or more intermediate layers such as layer  31 . Layer  31  may be formed from light reflecting material, light blocking material, injection molded plastic, material that aids in adhesion, material (e.g., metal) that provides strength, or other suitable materials. 
       FIG. 27  is a top view of an arrangement for backlight structures  20  in which chassis  28  has an inner rectangular ring formed from light reflecting material  32  and a surrounding rectangular ring formed from light blocking material  30 . As described in connection with  FIG. 2  and  FIG. 19 , it is not necessary for the sidewall structures formed from light reflecting material  32  and light blocking material  30  to completely surround all four sides of the rectangular periphery of light guide plate  22 . As shown in  FIG. 28 , for example, lower edge  102  of chassis  28  may be formed exclusively from a solid strip of light blocking material  30 , whereas upper edge  104  and the left and right edges of chassis  28  may be formed from an inner layer of light reflecting material  32  covered with an outer layer of light blocking material  30 . 
     If desired, light reflecting material  32  may be formed from a reflective layer such as a layer of metal (e.g., aluminum, chromium, etc.). This type of configuration is shown in chassis  28  of  FIG. 29 . As shown in  FIG. 29 , light reflecting material  32  (which serves as the innermost material in chassis  28 ) may be formed from a thin (e.g., less than 1 micron thick) or thick (e.g., 0.05 to 1 mm) layer of metal. The metal layer for light reflecting material  32  of  FIG. 29  may be supported by structures  30 ′ or other suitable materials. Structures  30 ′ may form the outermost material in chassis  28  (e.g., an exterior structure that runs around the outer periphery of chassis  28 ). Structures  30 ′ may be formed from plastic such as light blocking black plastic or from other suitable materials (e.g., metals, ceramics, glass, etc.). Structures  30 ′ may be used to help support reflective layer  32  and may, if desired, be omitted. 
       FIG. 30  is a cross-sectional side view of illustrative sidewall structures for backlight chassis  28  in which light reflecting layer  30  has been formed from a thin-film stack of materials on the inner surface of material  30 ′. Material  30 ′ may be a light blocking material such as black plastic or may be any other suitable material (plastic, metal, etc.). Thin-film stack  32  may be formed from two or more layers of material (e.g., dielectric layers in an alternating high-index-of-refraction and low-index-of-refraction stack to form a reflector or filter, dielectric layers with other index of refraction patterns, etc.). Think-film stack  32  may include layers of dielectric such as polymer layers, glass layers, ceramic layer, or other dielectric layers and/or may include layers of other material (e.g., metal layers, etc.). Thin-film layers in thin-film stack  32  may be deposited using physical vapor deposition (e.g., sputtering, evaporation, etc.) or other suitable techniques. Thin-film thicknesses in the thin-film stack may be 100 angstroms to 10,000 angstroms or other suitable thicknesses. 
       FIG. 31  is a cross-sectional side view of illustrative sidewall structures showing how chassis  28  may, if desired, be provided with structures to facilitate mounting of chassis  28  to other device structures, to facilitate the attachment of other structures in device  10  to chassis  28 , or for implementing other suitable functions. In the example of  FIG. 31 , chassis  28  has been provided with light reflecting layer  32  and light blocking layer  30 . Chassis  28  may be configured to be attached to housing  12  (e.g., a housing sidewall or other housing structure formed from a material such as plastic, metal, etc.). In particular, light blocking structure  30  and housing  12  have been provided with mating engagement features  200 . Engagement features  200  may include features such as protrusions and recesses. In the example of  FIG. 31 , housing  12  has been provided with a protrusion such as protrusion  202  and light blocking structure  30  has been provided with a mating recess such as recess  204 . Other types of engagement features may be provided if desired. The configuration of  FIG. 31  is merely illustrative. 
     In general, backlight structures and other device structures may be formed using any suitable equipment and assembly operations. An illustrative system in which backlight structures such as chassis  28  and/or other structures for device  10  can be formed is shown in  FIG. 32 . 
     As shown in  FIG. 32 , manufacturing equipment such as tools  300  may, if desired, be used in forming individual parts  304  for device  10  and completed assemblies  302 . Parts  304  may include housing structures such as housing  12 , display structures such as chassis  28 , light guide plate  22 , and other structures associated with device  10 . Parts  304  may be manufactured individually using a first set of one or more tools (e.g., manufacturing tools) and subsequent assembly operations may be performed using one or more additional tools (e.g., press fitting tools or other assembly tools). In this type of arrangement, some or all of the parts may be manufactured in advance and subsequently assembled to form completed assemblies such as assembly  302 . For example, chassis  28  may be formed by forming structures  30 ,  32  and/or housing  12  separately and subsequently press fitting one or more of these parts together. Arrangements such as these may use multiple types of tools. For example, a light guide plate such as plate  22 , a light reflecting structure such as structure  32 , and a light blocking structure such as structure  30  may be formed separately and, following their separate formation, may be assembled mechanically to form display backlight structures. As another example, light reflecting layer  32  may be injection molded over the edge of light guide plate  22  using an injection molding tool. This structure may then be mechanically attached to a pre-formed light blocking structure  30  (e.g., by press-fitting or other mechanical assembly techniques). Yet another example involves the formation of thin-film stacks and metal coatings for reflective layers  32 . These reflective layers may be formed over a previously formed light blocking layer such as light blocking layer  30 ′ of  FIGS. 29 and 30  or may be formed as stand-alone parts that are press fit into layer  30 ′ or other structures for device  10 . Chassis  28  may, if desired, be formed by press-fitting structures  30  and  32  together (or injection molding structures  30  and  32  together using two-shot molding techniques) and subsequently assembling light guide plate  22  and chassis  28  mechanically (e.g., by press fitting). 
     Using techniques such as these, chassis  28  may be created separately from light guide plate  22 . For example, chassis  28  may be formed by injection molding (e.g., to injection mold structures  30  and  32  to form an integral chassis), chassis  28  may be formed mechanically (e.g., by molding, cutting, machining, or otherwise forming material into separate structures  30  and  32  and then press fitting the separate structures  30  and  32  together to form chassis  28 ), or may be formed using other manufacturing processes. Light guide plate  22  may be formed separately from chassis  28 . For example, light guide plate  22  may be formed using molding equipment, using cutting equipment such as die cutting equipment to cut a sheet of material for light guide plate  22  from a larger sheet, by extruding light guide plate  22  or a sheet of material from which light guide plate  22  is cut, or using other suitable light guide plate manufacturing techniques. Separately formed structures such as a separately formed chassis and light guide plate may then be assembled to form a backlight assembly. For example, press fitting techniques or other techniques may be used to mechanically assemble the chassis and light guide plate to form a backlight assembly. 
     The structures formed using tools  300  (shown schematically as assembly  302  in  FIG. 32 ) may be, for example, a completed chassis such as chassis  28 , a backlight assembly that includes chassis  28  and additional structures such as light guide plate  22 , an electronic device assembly that includes structures such as chassis  28 , light guide plate  22 , and/or housing  12 , or other suitable device structures. If desired, multiple portions of an assembly may be formed using the same tool or set of tools. For example, multiple structures such as structures  30  and  32  may be injection molded to form a unitary backlight chassis and/or may be injection molded to other structures (e.g., housing structures and/or a light guide plate, etc.). 
     Equipment  300  may include die cutting tools, machining tools such as grinding and milling tools, laser cutting tools, welding tools, mechanical assembly tools such as tools for press fitting parts together, tools for exposing workpieces to light and/or heat, tools for applying coatings such as physical vapor deposition tools for depositing layers of dielectric and metal (e.g., to form a thin-film stack or metal coating), electrochemical deposition tools, photolithography tools, tools for patterning conductive materials such as metallic paint and other liquids (e.g., painting tools, pad printing tools, screen printing tool, ink jet tools, dipping tools, spraying tools, etc.), tools for injection molding plastic, tools for soldering, ovens and other tools for applying heat, equipment for bending structures, and other suitable manufacturing and assembly tools. 
     The foregoing is merely illustrative of the principles of this invention and various modifications can be made by those skilled in the art without departing from the scope and spirit of the invention.

Metadata:
Filing Date: 20110909
Publication Date: 20160126
Grant Date: 20160126
Priority Date: 20110909
Inventors: GETTEMY SHAWN R.
WURZEL JOSHUA G.
DOYLE DAVID A.
SCHLAUPITZ ALEXANDER D.
Assignee: APPLE INC
CPC Classifications: [{"code": "G02B6/0088", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02B6/0065", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F2001/133314", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B6/0031", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F2001/133317", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B6/0088", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02B6/0065", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/133314", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B6/0031", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B6/0065", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B6/0088", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02F1/133317", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B6/0031", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 46759038