Illuminator and display device using the same Number:7,520,632 from the United States Patent and Trademark Office (PTO) owispatent An illuminator for a display device is provided on a back side of a display panel, and includes a plurality of rod-shaped light sources each having a length extending in a first direction and having substantially the same length. The plurality of rod-shaped light sources include a plurality of first rod-shaped light sources arranged so as to be substantially parallel and spaced from one another in a second direction that is generally perpendicular to the first direction, and a plurality of second rod-shaped light sources arranged to be substantially parallel and spaced from one another in the second direction, each second rod-shaped light source being arranged to be collinear with and spaced in the first direction from a corresponding one of the plurality of first rod-shaped light sources.<H Illuminator, display, Illuminator, and, 7520632.html, Patent, pto, 7520632

Title: Illuminator and display device using the same

Abstract: An illuminator for a display device is provided on a back side of a display panel, and includes a plurality of rod-shaped light sources each having a length extending in a first direction and having substantially the same length. The plurality of rod-shaped light sources include a plurality of first rod-shaped light sources arranged so as to be substantially parallel and spaced from one another in a second direction that is generally perpendicular to the first direction, and a plurality of second rod-shaped light sources arranged to be substantially parallel and spaced from one another in the second direction, each second rod-shaped light source being arranged to be collinear with and spaced in the first direction from a corresponding one of the plurality of first rod-shaped light sources.

Patent Number: 7,520,632 Issued on 04/21/2009 to Takata

Inventors: Takata; Yoshiki (Suzuka, JP)
Assignee: Sharp Kabushiki Kaisha (Osaka, JP)

Appl. No.: 11/954,761

Filed: December 12, 2007

Related U.S. Patent Documents


Application Number	Filing Date	Patent Number	Issue Date
11002154	Dec., 2004	7322717

Foreign Application Priority Data


Dec 03, 2003 [JP]			2003-404815
Nov 08, 2004 [JP]			2004-323858

Current U.S. Class: 362/227 ; 362/600; 362/602; 362/611

Current International Class: B60Q 1/26 (20060101)

Field of Search: 362/600-634

References Cited [Referenced By]

U.S. Patent Documents


7322717	January 2008	Takata

Other References

Takata; "Illuminator and Display Device Using the Same"; U.S. Appl. No. 11/002,154, filed Dec. 1, 2004. cited by other .
Takata; "Optical Material, Optical Element, Illuminator and Display Device", U.S. Appl. No. 11/012,738, filed Dec. 15, 2004. cited by other .
Takata; "Illumination Device and Display Apparatus Including the Same", U.S. Appl. No. 10/977,827, filed Oct. 29, 2004. cited by other .
Takata; "Illumination Device and Display Apparatus Including the Same", U.S. Appl. No. 11/738,565, filed Apr. 23, 2007. cited by other.

Primary Examiner: Ton; Anabel M
Attorney, Agent or Firm: Keating & Bennett, LLP

Parent Case Text

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Continuation of U.S. patent application Ser. No. 11/002,154, currently pending.

Claims

What is claimed is:

1. An illuminator for a display device comprising: a plurality of rod-shaped light sources each having a length extending in a first direction and having substantially the same length, the plurality of rod-shaped light sources include a plurality of first rod-shaped light sources arranged to be substantially parallel with respect to one another and spaced from each other in a second direction that is substantially perpendicular to the first direction, and a plurality of second rod-shaped light sources arranged to be substantially parallel with respect to one another and spaced from each other in the second direction, the first rod-shaped light sources having ends aligned along the second direction at a first edge of the illuminator and a remaining portion of the first rod-shaped light sources extending along the first direction toward a central region of the illuminator, the second rod-shaped light sources having ends aligned along the second direction at a second edge of the illuminator and a remaining portion of the second rod-shaped light sources extending along the first direction toward said central region of the illuminator; and at least one inverter disposed on an inverter substrate in said central region of the illuminator; wherein at least two of the plurality of rod-shaped light sources are electrically connected to each of the at least one inverter.

2. The illuminator according to claim 1, wherein each of the second rod-shaped light sources is spaced from and collinear with a corresponding one of the plurality of first rod-shaped light sources along the first direction.

3. The illuminator according to claim 1, wherein each of the first rod-shaped light sources has substantially the same length as the first rod-shaped light sources that are directly adjacent thereto in the second direction, and each of the second rod-shaped light sources has substantially the same length as the second rod-shaped light sources that are directly adjacent thereto in the second direction.

4. The illuminator according to claim 1, wherein additional ends of the first rod-shaped light sources are aligned at said central region of the illuminator, and additional ends of the second rod-shaped light sources are aligned at said central region and spaced from said additional ends of the first rod-shaped light sources along the first direction.

5. The illuminator according to claim 1, wherein all of the rod-shaped light sources contained in the illuminator have exactly the same length.

6. The illuminator according to claim 1, wherein additional end portions of a plurality of pairs of the first and second rod-shaped light sources that are directly adjacent to each other along the second direction are overlapped with each other by a certain amount along the first direction, and the overlapping end portions of the plurality of pairs of the first and second rod-shaped light sources being the only overlapping portions of the plurality of pairs of the first and second rod-shaped light sources.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an illuminator and a display device including such an illuminator, and more particularly, the present invention relates to an illuminator provided on the back side of a display panel and used as a backlight of a display device, and also relates to a display device including such an illuminator.

2. Description of the Related Art

Liquid crystal display devices are widely used in OA (office automation) equipment, car televisions, monitors for camcorders, etc., for their advantageous features such as lightweight, thin structure and small power consumption. Unlike self-luminous display devices such as CRTs, PDPs (plasma display panels) and EL (electroluminescence) devices, liquid crystal display devices use a liquid crystal display element that itself does not produce light. Therefore, in a transmission type liquid crystal display device, a planar illuminator called a "backlight" is provided on the back side of the liquid crystal display element, and the liquid crystal display element controls the amount of output light from the backlight to be transmitted therethrough in each pixel so as to display an image.

Backlights are generally classified into "direct-type" backlights including a plurality of rod-shaped light sources, such as fluorescent tubes, placed directly under a liquid crystal display element, and "edge light-type" backlights including a light source placed along an edge of a lightguide plate so that light from the light source is guided through the lightguide plate to a liquid crystal display element.

A typical structure of a direct-type backlight is schematically illustrated in FIG. 37 and FIG. 38. A backlight 40 illustrated in FIG. 37 and FIG. 38 is provided on the back side of a transmission type liquid crystal display panel 48, and includes a plurality of fluorescent tubes 41, a case 43 accommodating the fluorescent tubes 41, and an optical sheet (e.g., a diffusion sheet or a prism sheet) 45 placed between the fluorescent tubes 41 and the liquid crystal display panel 48. With the direct-type backlight 40, the brightness can easily be adjusted by adjusting the number of the fluorescent tubes 41 which define light sources, and a high brightness can be realized relatively easily. Thus, direct-type backlights are often used in large-size liquid crystal display devices.

In recent years, the length of a backlight fluorescent tube has been increasing along with the increase in the size of a liquid crystal display device. However, long fluorescent tubes have a poor anti-shock property and are difficult to handle. Moreover, as the length of a fluorescent tube increases, the operating voltage thereof increases significantly, whereby the reliability thereof decreases significantly in terms of the withstand voltage. Therefore, there is a technical limit to increasing the length of a fluorescent tube along with the increase in the size of a liquid crystal display device. Another problem is that a further increase in the size of a liquid crystal display device may necessitate the provision of a new production line for producing longer fluorescent tubes. Also, the cost and difficulty in manufacturing longer fluorescent tubes increase as the length of the fluorescent tubes increases.

Japanese Laid-Open Patent Publication No. 10-143089 discloses a backlight 40A including an array of fluorescent tubes 41' some of which have a different length from the others, as illustrated in FIG. 39. The fluorescent tubes 41' are arranged to be collinear along a longitudinal direction that extends along lengths of the tubes so as to form rows of tubes, and ends of the fluorescent tubes 41' are arranged in a staggered pattern in a vertically extending direction, which is perpendicular to the longitudinal direction, over the entire array. That is, ends of two longitudinally or horizontally adjacent fluorescent tubes 41' in one row overlap a central portion of a fluorescent tube 41' in a vertically adjacent row of tubes in order to provide sufficient brightness at the gaps between each pair of adjacent fluorescent tubes 41' in each row. Because this overlapping arrangement of fluorescent tubes 41' is necessary to overcome the lack of brightness at the gaps between adjacent fluorescent tubes 41', shorter fluorescent tubes 41' must be used at the ends of the rows, and thus many different size fluorescent tubes are required.

The backlight 40A disclosed in Japanese Laid-Open Patent Publication No. 10-143089, which must use fluorescent tubes of different lengths as described above, has various problems due to the use of light sources of different specifications. Where light sources of different specifications are used, there are significant electrical and optical characteristics variations among different positions across the backlight, whereby it is difficult to properly control the light emission. Also, it is expensive to manufacture and assemble different size fluorescent tubes.

SUMMARY OF THE INVENTION

In order to overcome the problems described above, preferred embodiments of the present invention provide an illuminator that can suitably be used as a backlight of a large-size display device, and a display device including such an illuminator.

An illuminator according to a preferred embodiment of the present invention includes a plurality of rod-shaped light sources each having a length extending in a first direction and having substantially the same length, wherein the plurality of rod-shaped light sources include a plurality of first rod-shaped light sources arranged to be substantially parallel with respect to one another and spaced from each other in a second direction that is substantially perpendicular to the first direction, and a plurality of second rod-shaped light sources arranged to be substantially parallel with respect to one another and spaced from each other in the second direction, each of the second rod-shaped light sources being arranged to be spaced from and collinear with a corresponding one of the plurality of first rod-shaped light sources along the first direction, and each of the first rod-shaped light sources has substantially the same length as the first rod-shaped light sources that are directly adjacent thereto in the second direction, and each of the second rod-shaped light sources has substantially the same length as the second rod-shaped light sources that are directly adjacent thereto in the second direction.

An illuminator according to another preferred embodiment of the present invention is an illuminator including a plurality of rod-shaped light sources each having a length extending in a first direction and having substantially the same length, wherein the plurality of rod-shaped light sources include a plurality of first rod-shaped light sources arranged to be substantially parallel with respect to one another and spaced from each other in a second direction that is substantially perpendicular to the first direction, and a plurality of second rod-shaped light sources arranged to be substantially parallel with respect to one another and spaced from each other in the second direction, respective end portions of a plurality of pairs of the first and second rod-shaped light sources that are directly adjacent to each other along the second direction are overlapped with each other by a certain amount along the first direction, and the overlapping end portions of the plurality of pairs of the first and second rod-shaped light sources being the only overlapping portions of the plurality of pairs of the first and second rod-shaped light sources.

In this preferred embodiment, it is preferred that the first rod-shaped light sources have first ends that are aligned with each other at a left edge portion of the illuminator and second ends that extend into the central region of the illuminator, and the second rod-shaped light sources have first ends that extend into the central region of the illuminator and second ends that are aligned with each other at a right edge of the illuminator.

The first rod-shaped light sources are preferably arranged in a first half of the illuminator and the second rod-shaped light sources are preferably arranged in a second half of the illuminator, and a central region of the illuminator being disposed between the first and second halves of the illuminator.

At least one inverter, and more preferably, a plurality of inverters are disposed in the central region. The plurality of inverters are preferably provided between the plurality of first rod-shaped light sources and the plurality of second rod-shaped light sources to operate the plurality of first rod-shaped light sources and the plurality of second rod-shaped light sources.

It is preferred that at least two of the plurality of rod-shaped light sources are electrically connected to each of the plurality of inverters. In addition, the at least two rod-shaped light sources electrically connected to each of the plurality of inverters preferably include two rod-shaped light sources electrically connected in series or in parallel with each other.

It is also preferred that a potential applied by the at least one inverter to ends of the plurality of first rod-shaped light sources on one side that is closer to the plurality of second rod-shaped light sources and a potential applied by the at least one inverter to ends of the plurality of second rod-shaped light sources on one side that is closer to the plurality of first rod-shaped light sources are substantially the same.

The first rod-shaped light sources preferably have first ends that are aligned with each other at a left edge portion of the illuminator and second ends that are aligned with each other at the central region of the illuminator, and the second rod-shaped light sources have first ends that are aligned with each other at the central region of the illuminator and second ends that are aligned with each other at a right edge of the illuminator.

It is preferable that all of the rod-shaped light sources contained in the illuminator have exactly the same length.

The illuminator also preferably includes a first supporting member arranged to support ends of the plurality of first rod-shaped light sources on one side that is closer to the plurality of second rod-shaped light sources and a second supporting member arranged to support ends of the plurality of second rod-shaped light sources on one side that is closer to the plurality of first rod-shaped light sources, wherein the first supporting member and the second supporting member are each made of a light-transmitting material.

The illuminator also preferably includes a light-scattering member that is arranged between the plurality of first rod-shaped light sources and the plurality of second rod-shaped light sources.

Each of the plurality of rod-shaped light sources is preferably a fluorescent tube.

The illuminator also preferably includes a first light-scattering member provided between two adjacent ones of the plurality of first rod-shaped light sources, and a second light-scattering member provided between two adjacent ones of the plurality of second rod-shaped light sources.

The first light-scattering member preferably is located generally in a middle region between the two first rod-shaped light sources, and the second light-scattering member is located generally in a middle region between the two second rod-shaped light sources.

The first light-scattering member and the second light-scattering member are preferably rod-shaped members. Also, it is preferable that the first light-scattering member is arranged to be substantially parallel to the plurality of first rod-shaped light sources, and the second light-scattering member is arranged to be substantially parallel to the plurality of second rod-shaped light sources.

A central axis of the first light-scattering member is preferably substantially coplanar with central axes of the plurality of first rod-shaped light sources, and a central axis of the second light-scattering member is preferably substantially coplanar with central axes of the plurality of second rod-shaped light sources.

The first light-scattering member preferably has substantially the same outer diameter as that of the plurality of first rod-shaped light sources, and the second light-scattering member preferably has substantially the same outer diameter as that of the plurality of second rod-shaped light sources.

A shape of a cross section of the first light-scattering member in the second direction preferably is generally the same as that of each of the plurality of first rod-shaped light sources, and a shape of a cross section of the second light-scattering member in the second perpendicular to the first direction preferably is generally the same as that of each of the plurality of second rod-shaped light sources.

It is preferred that the shape of a cross section of the first light-scattering member in the second direction and that of the second light-scattering member are generally circular.

It is preferred that the plurality of first rod-shaped light sources are spaced from one another in the second direction by a constant pitch P, and the plurality of second rod-shaped light sources are preferably spaced from one another in the second direction by the pitch P.

It is also preferable that each of the plurality of pairs of the first and second rod-shaped light sources that are directly adjacent to each other along the second direction are spaced from each other in the second direction by an amount that is substantially equal to one half of the pitch P.

An amount of overlap of the respective end portions of each the plurality of the first and second rod-shaped light sources that are directly adjacent to each other along the second direction is preferably less than the length of each of the plurality of first rod-shaped light sources.

Each of the plurality of rod-shaped light sources preferably includes a light-emitting region where light is emitted and two non-light-emitting regions where light is not substantially emitted, the non-light-emitting regions being adjacent respectively to opposite ends of the light-emitting region, and the non-light-emitting regions of the plurality of first rod-shaped light sources on one side that is closer to the plurality of second rod-shaped light sources are not facing the non-light-emitting regions of the plurality of second rod-shaped light sources on one side that is closer to the plurality of first rod-shaped light sources.

It is preferred that a boundary between the light-emitting regions of the plurality of first rod-shaped light sources and the non-light-emitting regions thereof on one side that is closer to the plurality of second rod-shaped light sources is substantially collinear along the second direction with a boundary between the light-emitting regions of the plurality of second rod-shaped light sources and the non-light-emitting regions thereof on one side that is closer to the plurality of first rod-shaped light sources.

In another preferred embodiment of the present invention, an illuminator includes a plurality of rod-shaped light sources each having a length extending in a first direction and having substantially the same length, the plurality of rod-shaped light sources include a plurality of first rod-shaped light sources arranged to be substantially parallel with respect to one another and spaced from each other in a second direction that is substantially perpendicular to the first direction, and a plurality of second rod-shaped light sources arranged to be substantially parallel with respect to one another and spaced from each other in the second direction, the first rod-shaped light sources having ends aligned along the second direction at a first edge of the illuminator and a remaining portion of the first rod-shaped light sources extending along the first direction toward a central region of the illuminator, the second rod-shaped light sources having ends aligned along the second direction at a second edge of the illuminator and a remaining portion of the second rod-shaped light sources extending along the first direction toward the central region of the illuminator, and at least one inverter disposed in the central region of the illuminator.

Each of the second rod-shaped light sources is preferably spaced from and collinear with a corresponding one of the plurality of first rod-shaped light sources along the first direction.

Each of the first rod-shaped light sources preferably has substantially the same length as the first rod-shaped light sources that are directly adjacent thereto in the second direction, and each of the second rod-shaped light sources has substantially the same length as the second rod-shaped light sources that are directly adjacent thereto in the second direction.

It is further preferred that additional ends of the first rod-shaped light sources are aligned at the central region of the illuminator, and additional ends of the second rod-shaped light sources are aligned at the central region and spaced from the additional ends of the first rod-shaped light sources along the first direction.

It is also preferred that all of the rod-shaped light sources contained in the illuminator have exactly the same length.

Also, it is preferable that additional end portions of a plurality of pairs of the first and second rod-shaped light sources that are directly adjacent to each other along the second direction are overlapped with each other by a certain amount along the first direction, and the overlapping end portions of the plurality of pairs of the first and second rod-shaped light sources being the only overlapping portions of the plurality of pairs of the first and second rod-shaped light sources.

In yet another preferred embodiment of the present invention, an illuminator for a display device includes a plurality of rod-shaped light sources each having a length extending in a first direction, the plurality of rod-shaped light sources include a plurality of first rod-shaped light sources arranged to be substantially parallel with respect to one another and spaced from each other in a second direction that is substantially perpendicular to the first direction, and a plurality of second rod-shaped light sources arranged to be substantially parallel with respect to one another and spaced from each other in the second direction, the first rod-shaped light sources having ends aligned along the second direction at a first edge of the illuminator and a remaining portion of the first rod-shaped light sources extending along the first direction toward a central region of the illuminator, the second rod-shaped light sources having ends aligned along the second direction at a second edge of the illuminator and a remaining portion of the second rod-shaped light sources extending along the first direction toward the central region of the illuminator, and all of the rod-shaped light sources contained in the illuminator have substantially the same length.

In this preferred embodiment, it is preferred that each of the second rod-shaped light sources is spaced from and collinear with a corresponding one of the plurality of first rod-shaped light sources along the first direction.

Also, it is preferable that additional ends of the first rod-shaped light sources are aligned at the central region of the illuminator, and additional ends of the second rod-shaped light sources are aligned at the central region and spaced from the additional ends of the first rod-shaped light sources along the first direction.

Also, it is preferable that additional end portions of a plurality of pairs of the first and second rod-shaped light sources that are directly adjacent to each other along the second direction are overlapped with each other by a certain amount along the first direction, and the overlapping end portions of the plurality of pairs of the first and second rod-shaped light sources being the only overlapping portions of the plurality of pairs of the first and second rod-shaped light sources.

It is also preferable that this illuminator includes at least one inverter disposed in the central region of the illuminator.

As a result of the unique structure and arrangement of the various preferred embodiments of the present invention as described above, short rod-shaped light sources with a lower operating voltage, a better handling property and a better anti-shock property than longer rod-shaped light sources can be used as the first and second rod-shaped light sources.

Also, planar lighting can be provided by using only rod-shaped light sources of substantially the same length, and it is not necessary to provide additional rod-shaped light sources of a different length. Therefore, electrical and optical characteristics variations among different positions across the backlight are minimized, whereby it is possible to easily control the light emission.

Also, the uniformity and the brightness of the output light is greatly improved in the illuminator according to various preferred embodiments of the present invention.

Other elements, features, characteristics and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments thereof with reference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view schematically illustrating a liquid crystal display device 30 including an illuminator 10 according to a preferred embodiment of the present invention.

FIG. 2 is a plan view schematically illustrating the illuminator 10 according to a preferred embodiment of the present invention.

FIG. 3A and FIG. 3B schematically illustrate an inverter arrangement in a conventional direct-type backlight 40, and FIG. 3C schematically illustrates the brightness distribution for the arrangement illustrated in FIG. 3A and FIG. 3B.

FIG. 4A and FIG. 4B schematically illustrate another inverter arrangement in the conventional direct-type backlight 40, and FIG. 4C schematically illustrates the brightness distribution for the arrangement illustrated in FIG. 4A and FIG. 4B.

FIG. 5A and FIG. 5B schematically illustrate a preferred inverter arrangement in the illuminator 10 according to a preferred embodiment of the present invention, and FIG. 5C schematically illustrates the brightness distribution for the arrangement illustrated in FIG. 5A and FIG. 5B.

FIG. 6A, FIG. 6B and FIG. 6C schematically illustrate an exemplary arrangement where each inverter is shared in the illuminator 10 according to a preferred embodiment of the present invention.

FIG. 7A, FIG. 7B and FIG. 7C each schematically illustrate another exemplary arrangement where each inverter is shared in the illuminator 10 according to a preferred embodiment of the present invention.

FIG. 8 schematically illustrates how noise is suppressed in the arrangement illustrated in FIG. 7A, FIG. 7B and FIG. 7C.

FIG. 9A, FIG. 9B and FIG. 9C schematically illustrate still another exemplary arrangement where each inverter is shared in the illuminator 10 according to a preferred embodiment of the present invention.

FIG. 10A, FIG. 10B and FIG. 10C schematically illustrate a preferred inverter arrangement in the illuminator 10 according to a preferred embodiment of the present invention.

FIG. 11A, FIG. 11B and FIG. 11C schematically illustrate another preferred inverter arrangement in the illuminator 10 according to a preferred embodiment of the present invention.

FIG. 12A, FIG. 12B and FIG. 12C schematically illustrate still another preferred inverter arrangement in the illuminator 10 according to a preferred embodiment of the present invention.

FIG. 13 is a plan view schematically illustrating the illuminator 10 according to a preferred embodiment of the present invention, together with supporting members for supporting rod-shaped light sources.

FIG. 14 is a plan view schematically illustrating the illuminator 10 including a light-scattering member provided between first rod-shaped light sources and second rod-shaped light sources.

FIG. 15A and FIG. 15B schematically illustrate preferred arrangements for suppressing leakage occurring between first rod-shaped light sources and second rod-shaped light sources.

FIG. 16 is a plan view schematically illustrating another illuminator 10A according to a preferred embodiment of the present invention.

FIG. 17 schematically illustrates a preferred inverter arrangement in the illuminator 10A according to a preferred embodiment of the present invention.

FIG. 18 is a plan view schematically illustrating the illuminator 10A according to a preferred embodiment of the present invention, together with supporting members for supporting rod-shaped light sources.

FIG. 19 schematically illustrates a rod-shaped light source including a light-emitting region and non-light-emitting regions.

FIG. 20 schematically illustrates a preferred arrangement of rod-shaped light sources each including a light-emitting region and non-light-emitting regions.

FIG. 21 schematically illustrates another preferred arrangement of rod-shaped light sources each including a light-emitting region and non-light-emitting regions.

FIG. 22 is a plan view schematically illustrating the illuminator 10A according to a preferred embodiment of the present invention.

FIG. 23 is a plan view schematically illustrating the illuminator 10A including a light-scattering member between first rod-shaped light sources and second rod-shaped light sources.

FIG. 24 is a cross-sectional view schematically illustrating a conventional backlight 50 including light-reflecting protruding portions between light sources.

FIG. 25 is a cross-sectional view schematically illustrating a conventional backlight 60 with an auxiliary light source including a primary light source and a lightguide plate.

FIG. 26 is a cross-sectional view schematically illustrating the liquid crystal display device 30 including still another illuminator 10B according to a preferred embodiment of the present invention.

FIG. 27 is a plan view schematically illustrating the illuminator 10B according to a preferred embodiment of the present invention.

FIG. 28 schematically illustrates how a brightness non-uniformity occurs in the conventional direct-type backlight 40.

FIG. 29 schematically illustrates how a brightness non-uniformity occurs in the conventional direct-type backlight 50.

FIG. 30 schematically illustrates how a brightness non-uniformity occurs in the conventional direct-type backlight 60.

FIG. 31 schematically illustrates how a brightness non-uniformity is suppressed in the illuminator 10B according to a preferred embodiment of the present invention.

FIG. 32A, FIG. 32B and FIG. 32C each illustrate an arrangement of light-scattering members used in the illuminator 10B.

FIG. 33A to FIG. 33E each illustrate the shape of the cross section of the light-scattering member used in the illuminator 10B taken in a direction perpendicular to the longitudinal direction.

FIG. 34 is a plan view schematically illustrating the illuminator 10B according to a preferred embodiment of the present invention.

FIG. 35 is a plan view schematically illustrating still another illuminator 10C according to a preferred embodiment of the present invention.

FIG. 36 is a plan view schematically illustrating schematically illustrating still another illuminator 10D according to a preferred embodiment of the present invention.

FIG. 37 is a cross-sectional view schematically illustrating the conventional common direct-type backlight 40.

FIG. 38 is a plan view schematically illustrating the conventional common direct-type backlight 40.

FIG. 39 is a plan view schematically illustrating a conventional direct-type backlight 40A.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will now be described with reference to the drawings. Note that the present invention is not limited to the following preferred embodiments.

First Preferred Embodiment

Referring to FIG. 1 and FIG. 2, an illuminator 10 of the present preferred embodiment will now be described. FIG. 1 is a cross-sectional view schematically illustrating a liquid crystal display device 30 including the illuminator 10, and FIG. 2 is a plan view schematically illustrating the illuminator 10.

The illuminator 10 is a so-called "backlight" provided on the back side (the side away from the viewer) of a liquid crystal display panel 20, as illustrated in FIG. 1. The liquid crystal display panel 20 includes a pair of substrates (e.g., glass substrates) 21 and 22 and a liquid crystal layer 23 provided therebetween, and modulates light output from the illuminator 10 to display an image. The liquid crystal display panel 20 includes a region in each pixel in which an image is displayed in a transmission mode. Thus, the liquid crystal display panel 20 is preferably a transmission type or transmission-reflection type liquid crystal display panel.

As illustrated in FIG. 1 and FIG. 2, the illuminator 10 includes a plurality of rod-shaped light sources 1 each having a length extending in a predetermined longitudinal direction (herein referred to as the "first direction"). The rod-shaped light sources 1 preferably have the same length, and the illuminator 10 preferably includes no rod-shaped light sources 1 having different lengths. In the present preferred embodiment, the rod-shaped light sources 1 are preferably cold cathode fluorescent tubes (CCFTs). Of course, the rod-shaped light sources 1 are not limited to the cold cathode fluorescent tubes. Alternatively, the rod-shaped light sources 1 may be hot cathode fluorescent lamps (HCFLs) or external electrode fluorescent lamps (EEFLs) or other suitable light sources.

The rod-shaped light sources 1 are held in a case 3 by supporting members (holders; not shown) provided in the case 3, and an optical sheet 5 is provided between the rod-shaped light sources 1 and the liquid crystal display panel 20, as illustrated in FIG. 1. The optical sheet 5 may be, for example, a diffusion sheet or a prism sheet. Note that while only one optical sheet 5 is shown in FIG. 1, a diffusion sheet, a prism sheet, etc., are used in combination in practice. Typically, in order to increase the light efficiency, the surface of the case 3 that is closer to the rod-shaped light sources 1 is provided with a highly-reflective member (e.g., a light-reflecting sheet), or the case 3 itself is made of a highly-reflective material.

Referring to FIG. 2, the arrangement of the rod-shaped light sources 1 will now be described in greater detail.

As shown on the left side of FIG. 2, the illuminator 10 includes a plurality of first rod-shaped light sources 1a arranged in a first portion (left portion in FIG. 2) of the illuminator 10. The rod-shaped light sources 1a of the first rod-shaped light sources are arranged to be substantially parallel to each other and spaced from each other in a direction that is generally perpendicular to the first direction (herein referred to as the "second direction"). Since the rod-shaped light sources 1a having the same length are arranged to be substantially parallel to each other and spaced from each other in the second direction, they are aligned with one another with respect to the longitudinal direction (first direction) such that first (left) ends of the rod-shaped light sources 1a are aligned at the left edge portion of the illuminator 10 and second (right) ends of the rod-shaped light sources 1a are aligned at a central portion of the illuminator 10.

As shown on the right side of FIG. 2, the illuminator 10 further includes a plurality of second rod-shaped light sources 1b arranged in a second portion (right portion in FIG. 2) of the illuminator 10. Each of the plurality of rod-shaped light sources 1b of the second rod-shaped light sources is preferably arranged to extend along the same line along which the length of a corresponding one of the rod-shaped light sources 1a of the first rod-shaped light sources extends, in the first direction. That is, each of the rod-shaped light sources 1b of the second rod-shaped light sources is preferably collinear with the corresponding one of the rod-shaped light sources 1a of the first rod-shaped light sources in the first direction. Since the rod-shaped light sources 1b having the same length are arranged to be substantially parallel to each other and spaced from each other in the second direction, they are aligned with one another with respect to the longitudinal direction (first direction) such that first (left) ends of the rod-shaped light sources 1b are aligned at the central portion of the illuminator 10 and second (right) ends of the rod-shaped light sources 1b are aligned at a right edge portion of the illuminator 10.

Thus, the illuminator 10 includes the rod-shaped light sources 1a arranged in a comb-tooth pattern and the rod-shaped light sources 1b also arranged in a comb-tooth pattern with each rod-shaped light source 1a preferably being arranged so as to be collinear with and longitudinally aligned in the second direction with the corresponding rod-shaped light source 1b. For the sake of simplicity, the rod-shaped light sources 1a will hereinafter be referred to also as the "first rod-shaped light sources" (or simply as "first light sources"), and the rod-shaped light sources 1b, which are preferably arranged collinearly with the first rod-shaped light sources 1a, will hereinafter be referred to also as the "second rod-shaped light source" (or simply as "second light source").

As described above, in the illuminator 10 of the present preferred embodiment, each second rod-shaped light source 1b is preferably arranged to be collinear with and longitudinally aligned in the first direction with the corresponding first rod-shaped light source 1a, whereby shorter rod-shaped light sources with a lower operating voltage, a better handling property and a better anti-shock property than longer rod-shaped light sources can be used as the rod-shaped light sources 1. Moreover, since the rod-shaped light sources 1, including each of those in the first rod-shaped light sources 1a and the second rod-shaped light sources 1b, all have the same length, the illuminator 10 has little or no electrical and optical characteristics variations among different positions across illuminator 10, and it is possible to easily control the light emission. Also, the equal length rod-shaped light sources 1a and 1b are much easier and cheaper to manufacture and assemble in the illuminator 10.

Moreover, with the illuminator 10 of various preferred embodiments of the present invention, it is possible to realize a desirable light distribution that cannot be realized with a conventional direct-type backlight. This will be described below in greater detail.

Referring to FIG. 3A and FIG. 3B, a conventional direct-type backlight 40 includes an inverter substrate 46 near one end of a cold cathode fluorescent tube 41. The inverter substrate 46 includes an inverter for generating a high voltage for operating the cold cathode fluorescent tube 41. With such an arrangement, the cold cathode fluorescent tube 41 gives a higher brightness toward one end thereof near the inverter and a lower brightness toward the other (typically grounded) end thereof that is spaced away from the inverter. Thus, the backlight 40 gives an asymmetric light distribution as illustrated in FIG. 3C.

In view of this, a method has been proposed in the art in which the inverter substrate 46 is provided near each end of the cold cathode fluorescent tube 41, as illustrated in FIG. 4A and FIG. 4B, and a high voltage is applied alternately to the opposite ends of the cold cathode fluorescent tube 41. With this method, a high brightness is obtained near each end of the cold cathode fluorescent tube 41, and the backlight 40 gives a symmetric light distribution as illustrated in FIG. 4C. With this method, however, the brightness is low near the center as illustrated in FIG. 4C.

In contrast, the illuminator 10 of various preferred embodiments of the present invention preferably includes an inverter substrate 6 disposed between the first light sources 1a and the second light sources 1b (more specifically, disposed in a region located between the light sources 1a and 1b), as illustrated in FIG. 5A and FIG. 5B, the inverter substrate 6 preferably including a plurality of inverters for operating the first and second light sources 1a and 1b. Thus, it is possible to realize a symmetric light distribution with the brightness being high near the center as illustrated in FIG. 5C. The light distribution as illustrated in FIG. 5C cannot be realized with a conventional direct-type backlight, and is a much more preferable light distribution for a backlight for use in a display device.

Moreover, in the illuminator 10 of various preferred embodiments of the present invention, the rod-shaped light sources 1 having a small length can be used, whereby it is possible to reduce the voltage required for operating each rod-shaped light source 1. Therefore, a single inverter can be shared among a plurality of rod-shaped light sources 1, and it is possible to reduce the cost by eliminating components such as transformers. An arrangement having a shared inverter will now be described.

FIG. 6A illustrates an exemplary arrangement where each inverter is shared. In the arrangement of FIG. 6A, two rod-shaped light sources 1 are electrically connected to one inverter 6', and the two rod-shaped light sources 1 are electrically connected in parallel to each other.

Exemplary arrangements of this type are shown in the form of wiring diagrams in FIG. 6B and FIG. 6C. In the arrangement illustrated in FIG. 6B, each pair of two vertically adjacent first light sources 1a are electrically connected to one inverter 6', and the two first light sources 1a are electrically connected in parallel to each other. Moreover, each pair of two vertically adjacent second light sources 1b are electrically connected to one inverter 6', and the two second light sources 1b are electrically connected in parallel to each other. In the arrangement illustrated in FIG. 6C, each pair of one first light source 1a and one second light source 1b horizontally adjacent to each other are electrically connected to one inverter 6', and the pair of first and second light sources 1a and 1b are electrically connected in parallel to each other.

When two rod-shaped light sources 1 are electrically connected in parallel to each other, as illustrated in FIG. 6A, FIG. 6B and FIG. 6C, the two rod-shaped light sources 1 connected in parallel to each other receive voltages of the same period and the same phase from the inverter 6', thereby realizing a simple operation of the light sources without requiring a phase control.

FIG. 7A illustrates another exemplary arrangement where each inverter is shared. In the arrangement illustrated in FIG. 7A, each pair of two rod-shaped light sources 1 are electrically connected to one inverter 6', and the two rod-shaped light sources 1 are electrically connected in series with each other.

Exemplary arrangements of this type are shown in the form of wiring diagrams in FIG. 7B and FIG. 7C. In the arrangement illustrated in FIG. 7B, each pair of one first light source 1a and one second light source 1b horizontally adjacent to each other are electrically connected to one inverter 6', and the pair of first and second light sources 1a and 1b are electrically connected in series with each other. In the arrangement illustrated in FIG. 7C, each pair of two first light sources 1a vertically adjacent to each other are electrically connected to one inverter 6', and the two first light sources 1a are electrically connected in series with each other. Moreover, each pair of two second light sources 1b vertically adjacent to each other are electrically connected to one inverter 6', and the two second light sources 1b are electrically connected in series with each other.

In a common direct-type backlight, an electric field produced by a high voltage generated by the inverter serves as noise that is imparted to the liquid crystal display panel. This noise can be the to be an alternating current component leaking (via capacitance coupling) from the circuit including the inverters and the rod-shaped light sources to the liquid crystal display panel.

When two rod-shaped light sources 1 are electrically connected in series with each other, as illustrated in FIG. 7A, FIG. 7B and FIG. 7C, the two rod-shaped light sources 1 connected in series with each other receive voltages of the same period and opposite phases from the inverter 6', as illustrated in FIG. 8. The waveforms of these voltages combined together result in a waveform having a smaller amplitude (as a result of the waveforms canceling each other), indicating that the effective electric field which conventionally serves as noise is canceled, and the noise is suppressed.

Although arrangements in which the rod-shaped light sources 1 are connected in parallel to each other are shown in FIG. 6A to FIG. 6C, and arrangements in which the rod-shaped light sources 1 are connected in series with each other are shown in FIG. 7A to FIG. 7C, it is also possible to combine a serial connection and a parallel connection. FIG. 9A illustrates still another exemplary arrangement where each inverter is shared. In the arrangement illustrated in FIG. 9A, four rod-shaped light sources 1 are electrically connected to one inverter 6', and each rod-shaped light source 1 is electrically connected in parallel to one or more of the other rod-shaped light sources 1 while being electrically connected in series with the remaining one or ones of the rod-shaped light sources 1.

Exemplary arrangements of this type are shown in the form of wiring diagrams in FIG. 9B and FIG. 9C. In the arrangement illustrated in FIG. 9B, two vertically adjacent first light sources 1a and two vertically adjacent second light sources 1b are electrically connected to one inverter 6', and the pair of first light sources 1a are electrically connected in parallel to each other while the pair of second light sources 1b are also electrically connected in parallel to each other. The first light sources 1a and the second light sources 1b are electrically connected in series with each other.

In the arrangement illustrated in FIG. 9C, two vertically adjacent first light sources 1a and two vertically adjacent second light sources 1b are electrically connected to one inverter 6'. One of the two first light sources 1a is electrically connected in series with the other first light source 1a and one of the two second light sources 1b while being electrically connected in parallel to the other second light source 1b. Moreover, one of the two second light sources 1b is electrically connected in series with the other second light source 1b and one of the two first light sources 1a while being electrically connected in parallel to the other first light source 1a.

With arrangements where a serial connection and a parallel connection are combined together, as illustrated in FIG. 9A, FIG. 9B and FIG. 9C, it is possible to significantly reduce the cost by significantly reducing components such as transformers while benefiting from the advantages of a parallel connection and a serial connection. The rod-shaped light sources 1 electrically connected in parallel to each other receive voltages of the same period and the same phase from the inverter 6', thereby realizing a simple operation of the light sources without requiring a phase control. Moreover, the rod-shaped light sources 1 electrically connected in series with each other receive voltages of the same period and opposite phases from the inverter 6', thereby suppressing noise.

Note that while FIG. 6A to FIG. 6C, FIG. 7A to FIG. 7C and FIG. 9A to FIG. 9C each illustrate an arrangement where one end of each rod-shaped light source 1 that is not connected to the inverter 6' is grounded, the end of each rod-shaped light source 1 that is not connected to the inverter 6' may be not grounded but may be floating, as illustrated in FIG. 10A to FIG. 10C, FIG. 11A to FIG. 11C and FIG. 12A to FIG. 12C. With such arrangements, a component to which these members are grounded (e.g., a substrate) can be omitted, thus reducing the production cost.

Although not shown in the figures referred to previously, the rod-shaped light sources 1 are preferably held in the case 3 by supporting members (holders) 4a, 4b and 4c, as illustrated in FIG. 13. If a light-transmitting material is used for each supporting member 4a for supporting one end of the first light source 1a that is closer to the second light source 1b and for each supporting member 4b for supporting one end of the second light source 1b that is closer to the first light source 1a, it is possible to increase the brightness in the area between the first light sources 1a and the second light sources 1b (i.e., the area where no light source exists), thereby realizing a more preferable light distribution. The light-transmitting material may be, for example, a semitransparent rubber, a transparent resin and a semi-transparent resin, or other suitable material. It should be noted that the holders 4a, 4b located in the central portion of the illuminator 10 could be made integral or combined to form one single unitary holder, as desired.

Moreover, if a light-scattering member 2a for scattering light is provided between the first light sources 1a and the second light sources 1b, as illustrated in FIG. 14, portions of light output from the first light sources 1a and the second light sources 1b are scattered by the light-scattering member 2a. With such an arrangement, it is possible to increase the brightness in the area between the first light sources 1a and the second light sources 1b.

The light-scattering member 2a may be, for example, made of a material including a matrix of a resin material and particles dispersed in the matrix and having a different refractive index from that of the matrix. The resin material may be, for example, an acrylic resin, and the particles may be, for example, silica beads. Of course, instead of using such a light-scattering member of an internal scattering type, a light-scattering member having a light-scattering surface (e.g., a surface with minute irregularities) may be used, or the surface of a light-scattering member of an internal scattering type may be given a light-scattering property.

Although the interval between the first light sources 1a and the second light sources 1b (i.e., the width of the area where no light source exists) is preferably as small as possible in view of the uniformity and the brightness of the output light, the interval being excessively small may result in a leak current between the first light sources 1a and the second light sources 1b. By giving substantially the same potential to one end of the first light source 1a that is closer to the second light source 1b and to one end of the second light source 1b that is closer to the first light source 1a, it is possible to prevent the leakage and thus to reduce the interval between the first light sources 1a and the second light sources 1b. Specifically, a relatively high first potential may be applied to one end of the first light source 1a that is closer to the second light source 1b and to one end of the second light source 1b that is closer to the first light source 1a while giving a relatively low second potential (e.g., the ground potential) to the opposite end, as illustrated in FIG. 15A. Alternatively, a relatively low potential may be applied to one end of the first light source 1a that is closer to the second light source 1b and to one end of the second light source 1b that is closer to the first light source 1a while giving a relatively high potential to the opposite end, as illustrated in FIG. 15B.

While only the first rod-shaped light sources 1a and the second rod-shaped light sources 1b are provided as light sources in the present preferred embodiment, a plurality of third rod-shaped light sources may further be provided and arranged so as to be substantially parallel to each other and spaced from each other in the second direction, and arranged to be collinear with a corresponding one of the second rod-shaped light sources in the first direction.

Second Preferred Embodiment

Referring to FIG. 16, an illuminator 10A of the present preferred embodiment will now be described. The illuminator 10A is also a backlight provided on the back side (the side away from the viewer) of a liquid crystal display panel. The following description will be directed primarily to what is different from the illuminator 10 of the first preferred embodiment.

In the illuminator 10 illustrated in FIG. 2, each second rod-shaped light source 1b is preferably arranged to extend along the same line along which the length of a corresponding one of the rod-shaped light sources 1a extends in the first direction, and thus is preferably collinear with the corresponding one of the rod-shaped light sources 1a of the first rod-shaped light sources in the first direction. Thus, the second rod-shaped light source 1b is preferably spaced from the first rod-shaped light source 1a in the first direction, but not in the second direction. In contrast, in the illuminator 10A of the present preferred embodiment, each second rod-shaped light source 1b is spaced from the corresponding first rod-shaped light source 1a in the second direction and arranged to be overlapped with the first rod-shaped light source 1a in the first direction, as illustrated in FIG. 16. Thus, the first light sources 1a arranged in a comb-tooth pattern and the second light sources 1b arranged in a comb-tooth pattern are spaced from each other such that none of the first light sources 1a is collinear with a corresponding one of the light sources 1b and vice versa, and such that end portions of the light sources 1a and 1b extending in the first direction overlap with each other by a certain amount along a line extending in the second direction and preferably only within a central region of the illuminator 10A, as described in more detail in the next paragraph.

More specifically, the first light sources 1a in the present preferred embodiment are arranged to be spaced from each other at a constant pitch P in the second direction, the second light sources 1b are arranged to be spaced from each other at a constant pitch P in the second direction, and the first light sources 1a and the second light sources 1b are spaced from each other preferably by about one half (P/2) of the pitch P in the second direction, for example. Furthermore, the overlapping amount in the first direction of the end portions of the first light sources 1a and the second light sources 1b is preferably smaller than the length of the first rod-shaped light source 1a. In other words, the first light sources 1a and the second light sources 1b are arranged so that their ends are overlapping at portions thereof extending along the first direction and facing each other in the second direction, with one end of each second light source 1b being sandwiched between ends of two vertically adjacent first light sources 1a, and with one end of each first light source 1a being sandwiched between ends of two vertically adjacent second light sources 1b.

In the illuminator 10A, the second light sources 1b are overlapped with the first light sources 1a by a certain amount along the first direction (longitudinal direction). Therefore, short rod-shaped light sources with a better handling property and a better anti-shock property than longer rod-shaped light sources can be used as the rod-shaped light sources 1. Moreover, since the rod-shaped light sources 1 all have the same length, the illuminator 10A has little electrical and optical characteristics variations among different positions across illuminator 10A, and it is possible to easily control the light emission.

Moreover, in the illuminator 10A of the present preferred embodiment, each second light source 1b is not collinear with the corresponding first light source 1a but is spaced from the first light source 1a in the second direction. Thus, it is possible to provide an arrangement whereby one end of the first light source 1a that is closer to the second light source 1b and one end of the second light source 1b that is closer to the first light source 1a are facing each other in the second direction and overlapping with each other by a certain amount along the first direction and preferably only in a central region of the illuminator 10A, as illustrated in FIG. 16. As a result, the rod-shaped light sources 1 completely cover a continuous, uninterrupted area extending along the first direction, thereby further increasing the uniformity and the brightness of the output light.

Moreover, the inverters (and the inverter substrate 6) for operating the first light sources 1a and the second light sources 1b can be placed together between the first light sources 1a and the second light sources 1b, as illustrated in FIG. 17, whereby it is possible to realize a symmetric light distribution with the brightness being high near the center.

Furthermore, as described above in the first preferred embodiment with reference to FIG. 6A to FIG. 9C, it is possible to use an arrangement where each inverter is shared, thus realizing similar effects such as reducing the cost, simplifying the operation, and suppressing noise.

Moreover, if substantially the same potential is applied to one end of the first light source 1a that is closer to the second light source 1b and to one end of the second light source 1b that is closer to the first light source 1a, it is possible to prevent leakage occurring between the first light source 1a and the second light source 1b.

Note that the first light sources 1a and the second light sources 1b are in practice held in the case 3 preferably by the supporting members (holders) 4a, 4b and 4c, as illustrated in FIG. 18. If the supporting member 4a for supporting one end of the first light source 1a that is closer to the second light source 1b and the supporting member 4b for supporting one end of the second light source 1b that is closer to the first light source 1a are made of a light-transmitting material, it is possible to further improve the brightness near one end of the first light source 1a that is closer to the second light source 1b and near one end of the second light source 1b that is closer to the first light source 1a.

The rod-shaped light source 1 typically includes a light-emitting region 1R where light is emitted and two non-light-emitting regions 1R' where light is not substantially emitted, the non-light-emitting regions 1R' being adjacent respectively to opposite ends of the light-emitting region 1R, as illustrated in FIG. 19. Specifically, the non-light-emitting regions 1R' are regions where supporting members (e.g., rubber holders) 4 and electrodes are provided. With an arrangement where the non-light-emitting regions 1R' of the first light sources 1a on one side that is closer to the second light sources 1b are not facing and not overlapping with the non-light-emitting regions 1R' of the second light sources 1b on one side that is closer to the first light sources 1a, as illustrated in FIG. 20, it is possible to prevent the brightness in the central area from being decreased.

In order to kee