Liquid crystal display apparatus having display panels on both upper and lower surfaces

• US 20030128316A1
• Filed: 12/30/2002
• Published: 07/10/2003
• Est. Priority Date: 01/10/2002
• Status: Active Grant

• Current Assignee: Casio Computer Company Limited
• Original Assignee: Casio Computer Company Limited
• Inventors: Tsuji, Masaki
• Granted Patent: US 6,741,301 B2
• Time in Patent Office: Days
• US Class Current: 349/113
• CPC Class Codes: G02B 6/0055 Reflecting element, sheet or layer
• CPC Class Codes: G02B 6/0063 for extracting light out both the major surfaces of the light guide
• CPC Class Codes: G02B 6/0088 of the light guide or other optical sheets in the package
• CPC Class Codes: G02F 1/1333 Constructional arrangements; Manufacturing methodsG02F1/135, G02F1/136 take precedence
• CPC Class Codes: G02F 1/133317 Intermediate frames, e.g. between backlight housing and front frame
• CPC Class Codes: G02F 1/133342 for double-sided displays
• CPC Class Codes: G02F 1/133612 Electrical details
• CPC Class Codes: G02F 1/133615 Edge-illuminating devices, i.e. illuminating from the side
• CPC Class Codes: G02F 1/133626 providing two modes of illumination, e.g. day-night

Abstract

A liquid crystal display apparatus includes a first liquid crystal display panel, a second liquid crystal display panel smaller in area than the first liquid crystal display panel. A flat backlight has an optical waveguide and a point light source placed near one side surface portion of the optical waveguide, and is placed between the first liquid crystal display panel and the second liquid crystal display panel. One reflecting layer is placed at least between the flat backlight and the second liquid crystal display panel.

Claims

1. A liquid crystal display apparatus comprising:

a first liquid crystal display panel;

a second liquid crystal display panel smaller in area than the first liquid crystal display panel;

a flat backlight which has an optical waveguide and a point light source placed near one side surface portion of the optical waveguide, and is placed between the first liquid crystal display panel and the second liquid crystal display panel; and

one reflecting layer which is placed at least between the flat backlight and the second liquid crystal display panel.

2. An apparatus according to claim 1, wherein the reflecting layer includes a total reflection type reflecting layer.

3. An apparatus according to claim 1, wherein the reflecting layer includes a translucent reflecting layer.

4. An apparatus according to claim 3, wherein the translucent reflecting layer includes a transparent resin and a reflecting member.

5. An apparatus according to claim 4, wherein an area of the reflecting member included in the translucent reflecting layer is 30 to 70% of an area of one pixel.

6. An apparatus according to claim 1, wherein a size of the optical waveguide is substantially equal to a size of the first liquid crystal display panel.

7. An apparatus according to claim 1, which further comprises a flexible wiring board connected to the first and second liquid crystal display panels, and placed between the reflecting layer and the second liquid crystal display panel.

8. An apparatus according to claim 7, wherein the flexible wiring board has an opening corresponding to the second liquid crystal display panel.

9. An apparatus according to claim 8, wherein a size of the opening of the flexible wiring board is smaller than a size of the second liquid crystal display panel.

10. An apparatus according to claim 1, wherein the optical waveguide has a substantially rectangular shape, and the point light source is placed on a short-side side near one corner portion of the optical waveguide.

11. An apparatus according to claim 10, wherein the point light source is placed such that an optical axis thereof is slightly shifted toward a long side of the optical waveguide near the point light source with respect to diagonal line connecting one corner portion of the optical waveguide and a corner portion on an opposite side thereto.

12. An apparatus according to claim 10, wherein a short side portion of the optical waveguide near the point light source has a notched portion forming an inclined surface that gradually separates from a short side with distance from the point light source.

13. An apparatus according to claim 1, wherein the optical waveguide has an opening, and the point light source is placed inside the opening.

14. An apparatus according to claim 1, which further comprises a backlight flexible wiring board connected to the point light source, and placed between the reflecting layer and the second liquid crystal display panel.

15. An apparatus according to claim 1, further comprising a case, the case having a liquid crystal display panel housing portion which houses the first liquid crystal display panel and a backlight housing portion which houses the backlight.

16. An apparatus according to claim 15, wherein the case has an intermediate case having the liquid crystal display panel housing portion and the backlight housing portion, and a pair of metal plate cases placed on upper and lower surfaces of the intermediate case.

17. An apparatus according to claim 16, wherein one of the metal plate cases has an opening corresponding to the second liquid crystal display panel.

18. An apparatus according to claim 17, wherein the second liquid crystal display panel is placed outside one of the metal plate cases.

19. A liquid crystal display apparatus comprising:

a first liquid crystal display panel;

a second liquid crystal display panel smaller in area than the first liquid crystal display panel;

a flat backlight placed between the first liquid crystal display panel and the second liquid crystal display panel; and

a translucent reflecting layer placed between the flat backlight and the second liquid crystal display panel.

20. An apparatus according to claim 19, wherein the flat backlight includes an optical waveguide, and the translucent reflecting layer is formed on the optical waveguide.

21. A liquid crystal display apparatus comprising:

a first liquid crystal display panel;

a second liquid crystal display panel smaller in area than the first liquid crystal display panel; and

a flat backlight which has an optical waveguide and a point light source placed near one side surface portion of the optical waveguide, and is placed between the first liquid crystal display panel and the second liquid crystal display panel, wherein the first liquid crystal display panel has a translucent reflecting layer including a reflecting layer and a transparent pixel electrode, and the second liquid crystal display panel has a translucent reflecting layer including a reflecting layer and a transparent pixel electrode.

22. An apparatus according to claim 21, wherein an area of the reflecting layer is 30 to 70% of an area of the transparent pixel electrode.