Electronic Device Display with a Backlight

• US 20200132916A1
• Filed: 06/12/2019
• Published: 04/30/2020
• Est. Priority Date: 10/26/2018
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Zhu, Wenyong, Hsu, Shan-Ting, Yin, Victor H., Xu, Daming, Suh, Heesang, You, Chenhua, Son, Mookyung
• Granted Patent: US 10,852,582 B2
• Time in Patent Office: Days
• CPC Class Codes: G02B 6/0028 Light guide, e.g. taper
• CPC Class Codes: G02B 6/0038 Linear indentations or grooves, e.g. arc-shaped grooves or meandering grooves, extending over the full length or width of the light guide
• CPC Class Codes: G02B 6/005 provided by one optical element, or plurality thereof, placed on the light output side of the light guide
• CPC Class Codes: G02B 6/0051 Diffusing sheet or layer
• CPC Class Codes: G02B 6/0053 Prismatic sheet or layer; Brightness enhancement element, sheet or layer
• CPC Class Codes: G02B 6/0061 to provide homogeneous light output intensity
• CPC Class Codes: G02B 6/0068 Arrangements of plural sources, e.g. multi-colour light sources
• CPC Class Codes: G02B 6/0073 Light emitting diode [LED]
• CPC Class Codes: G02B 6/0083 Details of electrical connections of light sources to drivers, circuit boards, or the like
• CPC Class Codes: G02B 6/0088 of the light guide or other optical sheets in the package
• CPC Class Codes: G02B 6/009 of the light source in the package G02B6/0021 takes precedence
• CPC Class Codes: G02F 1/13306 Circuit arrangements or driving methods for the control of single liquid crystal cells G02F1/132, G02F1/133382 take precedence
• CPC Class Codes: G02F 1/133603 with LEDs
• CPC Class Codes: G02F 1/13452 Conductors connecting driver circuitry and terminals of panels
• CPC Class Codes: G02F 1/1368 in which the switching element is a three-electrode device G02F1/136277 takes precedence
• CPC Class Codes: G09G 3/006 Electronic inspection or testing of displays and display drivers, e.g. of LED or LCD displays testing individual LED's G01R31/2635; testing lamps G01R31/44; testing of optical features of LCD displays G02F1/1309
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence
• CPC Class Codes: H01R 12/62 connecting to rigid printed circuits or like structures
• CPC Class Codes: H01R 4/04 using electrically conductive adhesives
• CPC Class Codes: H05K 1/0281 Reinforcement details thereof
• CPC Class Codes: H05K 1/118 : specially for flexible printed circuits, e.g. using folded portions
• CPC Class Codes: H05K 1/147 : at least one of the printed circuits being bent or folded, e.g. by using a flexible printed circuit H05K1/148 takes precedence
• CPC Class Codes: H05K 1/189 : characterised by the use of a flexible or folded printed circuit H05K3/326 takes precedence
• CPC Class Codes: H05K 2201/094 : Array of pads or lands differing from one another, e.g. in size, pitch, thickness; Using different connections on the pads using different types of conductors H05K2201/0391
• CPC Class Codes: H05K 2201/10106 : Light emitting diode [LED]
• CPC Class Codes: H05K 2201/10136 : Liquid Crystal display [LCD]
• CPC Class Codes: H05K 2201/10674 : Flip chip
• CPC Class Codes: H05K 3/361 : Assembling flexible printed circuits with other printed circuits

Abstract

An electronic device may include display layers such as liquid crystal display layers and a backlight unit that provides illumination for the display layers. The backlight unit may include light-emitting diodes that emit light into the edge of a light guide film. To minimize the inactive area of the display, the light-emitting diodes may be tightly spaced to approximate a line light source instead of point light sources. Color and/or luminance compensation layers may be incorporated at various locations within the backlight structures to ensure that the backlight provided to the display layers is homogenous. A thin-film transistor layer of the display may be coupled to a printed circuit board by a flexible printed circuit. The flexible printed circuit may have additional solder mask layers to improve robustness, may include encapsulation, and may have traces with a varying pitch.

Claims

1. An electronic device comprising:

display layers; and

a backlight unit that provides backlight for the display layers, the backlight unit comprising;

a light guide film;

a plurality of light-emitting diode packages, wherein each light-emitting diode package includes two or more light-emitting diodes connected in series that emit light into an edge of the light guide film; and

a flexible printed circuit board, wherein each light-emitting diode package is flip chip bonded to the flexible printed circuit board and wherein a distance between each pair of adjacent light-emitting diode packages is less than 0.5 millimeters.

2. The electronic device defined in claim 1, wherein each light-emitting diode package is flip chip bonded to the flexible printed circuit board with first, second, and third flip chip bumps.

3. The electronic device defined in claim 2, wherein each light-emitting diode package has a first recess that receives the first flip chip bump, a second recess that receives the second flip chip bump, and a third recess that receives the third flip chip bump.

4. The electronic device defined in claim 3, wherein the second recess is interposed between the first and third recesses and wherein the second recess has a smaller width than the first and third recesses.

5. The electronic device defined in claim 1, further comprising:

a chassis that supports the light guide film; and

an adhesive layer that attaches the light guide film to the chassis, wherein the adhesive layer includes an optical component that alters one of the color and luminance of the backlight.

6. The electronic device defined in claim 5, further comprising:

a reflector layer on a lower surface of the light guide film; and

a compensation layer on the lower surface of the light guide film between the reflector layer and the adhesive layer.

7. The electronic device defined in claim 5, further comprising:

a reflector layer on a lower surface of the light guide film; and

a compensation layer on the chassis between the reflector layer and the adhesive layer.

8. The electronic device defined in claim 5, wherein the light guide film has an additional edge opposite the edge of the light guide film, the electronic device further comprising:

a compensation layer on the additional edge of the light guide film.

9. The electronic device defined in claim 5, wherein the chassis is a metal chassis, the electronic device further comprising:

a plastic chassis attached to the metal chassis; and

a compensation layer on the plastic chassis.

10. The electronic device defined in claim 1, wherein the light guide film has a plurality of protrusions, the electronic device further comprising:

a compensating layer formed over each protrusion of the plurality of protrusions.

11. The electronic device defined in claim 1, further comprising:

a compensating layer formed over the light guide film that modifies the backlight to compensate for a non-uniformity in the display layers.

12. The electronic device defined in claim 11, wherein the edge of the light guide film that receives light from the light-emitting diodes is a left edge of the light guide film and wherein the compensating layer comprises gray ink along an upper edge of the light guide film.

13. An electronic device comprising:

display layers; and

a backlight unit that provides backlight for the display layers, the backlight unit comprising;

a flexible printed circuit;

a light guide film;

a plurality of light-emitting diodes mounted on the flexible printed circuit that emit light into an edge of the light guide film;

an optical film that is interposed between the light guide film and the display layers; and

a compensating layer formed on the optical film, wherein the compensating layer modifies a portion of the backlight to compensate for a non-uniformity in the display layers.

14. The electronic device defined in claim 13, wherein the compensating layer covers some but not all of the light guide film.

15. The electronic device defined in claim 13, wherein the edge of the light guide film that receives light from the light-emitting diodes is a left edge of the light guide film and wherein the compensating layer is formed over only an upper edge of the light guide film.

16. The electronic device defined in claim 13, wherein the compensating layer comprises gray ink formed on the optical film.

17. The electronic device defined in claim 13, wherein the optical film is a diffuser layer.

18. The electronic device defined in claim 13, wherein the optical film is a brightness enhancement film.

19. An electronic device comprising:

display layers; and

a backlight unit that provides backlight for the display layers, the backlight unit comprising;

a flexible printed circuit;

a light guide film having edges and a plurality of tabs that protrude from the edges;

a plurality of light-emitting diodes mounted on the flexible printed circuit that emit light into one of the edges of the light guide film; and

a plurality of compensating layers that each alter at least one of the color and luminance of the backlight, wherein each one of the plurality of compensating layers is formed over a respective tab of the plurality of tabs.

20. The electronic device defined in claim 19, wherein each one of the plurality of compensating layers comprises ink.