Angled backlight device and liquid crystal display apparatus

Disclosed is a backlight device comprising: a light emitting section including a plurality of surface light emitters which are arranged and disposed so as to have a predetermined gap; and a diffuser plate which is disposed in front of the light emitting section to diffuse a light irradiated from the light emitting section, wherein an angle between two light irradiation surfaces in the adjacent surface light emitters is smaller than 180 degrees.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a backlight device and a liquid crystal display apparatus.

2. Description of Related Art

Conventionally, a liquid crystal display apparatus comprising a liquid crystal panel, and a backlight device to irradiate a light to the liquid crystal display apparatus, wherein the light emitted from the backlight device is selectively transmitted in the liquid crystal panel so that an image is formed by the transmitted light, is known (see for example, Japanese Patent Application Laid-open Publication Nos. 2002-270019 and 2004-109205).

As the light source of the backlight device in the liquid crystal display apparatus, light sources using a line light source such as a cold cathode fluorescent lamp (CCFL) or a point light source such as a light emitting diode (LED) have been a mainstream. However, in recent years, developments for a liquid crystal display apparatus using a surface light emitter which is typified by an organic electroluminescence (hereinbelow referred to as an organic EL), and the like, as a light source to realize the thinning and the weight saving, have been in progress.

In the liquid crystal display apparatus using the surface light emitter, generally, a plurality of surface light emitters are arranged and disposed in a state of each having a predetermined gap in between so as to form a light emitting section, and a liquid crystal panel is disposed in front of the light emitting section.

However, in the above mentioned liquid crystal display apparatus using the surface light emitters, there has been a problem in that a dark section is generated in the gaps of the adjacent surface light emitters, which results in a generation of luminance unevenness in the liquid crystal panel.

SUMMARY OF THE INVENTION

The objects of the present invention include preventing the luminance unevenness in a backlight device using a surface light emitter, and providing a liquid crystal display apparatus comprising the backlight device.

According to an aspect of the present invention, there is provided a backlight device comprising:

a light emitting section including a plurality of surface light emitters which are arranged and disposed so as to have a predetermined gap; and

a diffuser plate which is disposed in front of the light emitting section to diffuse a light irradiated from the light emitting section, wherein

an angle between two light irradiation surfaces in the adjacent surface light emitters is smaller than 180 degrees.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following, an embodiment 1 of the present invention is described with reference to the drawings. However, the scope of the invention is not limited to the illustrated examples.

FIG. 1is a diagram showing the whole configuration of a liquid crystal display apparatus1according to the present embodiment, andFIG. 2is a side view of the liquid crystal display apparatus1shown inFIG. 1.

The liquid crystal display apparatus1comprises a liquid crystal panel10, and a backlight device20which is disposed in the rear of the liquid crystal panel10.

In the following, a width direction of the liquid crystal panel10, a height direction thereof, and a depth direction thereof are referred respectively to as X direction, Y direction, and Z direction.

The liquid crystal panel10is a known liquid crystal display panel which is applied to various types of liquid crystal displays (LCDs). For example, the liquid crystal panel10is exemplified by a display panel which comprises a liquid crystal layer formed by filling liquid crystal in between two glass substrates, and further comprises a polarizing plate which is disposed at an opposite surface of the liquid crystal layer of the both glass substrates.

Further, the liquid crystal panel10may be displayed in colors or in black-and-white, and is not particularly limited with regard to the type of liquid crystal, a liquid crystal cell, a driving section (a switching element) such as a thin film transistor (TFT), a black matrix (BM), and the like. Further, with respect to operation modes, any type of operation modes, such as a twisted nematic (TN) mode, a super twisted nematic (STN) mode, an electrically controlled birefringence (ECB) mode, an in-plane switching (IPS) mode, a multidomain vertical alignment (MVA) mode, and the like, is applicable.

The liquid crystal panel10further comprises a plurality of source drivers11to drive a source wire (a signal line) of the liquid crystal panel10, and a plurality of gate drivers12to drive a gate wire (a scan line) of the liquid crystal panel10. Further, a substrate15is connected to the liquid crystal panel10, wherein the substrate15comprises a timing controller13to supply various timing signals to the source drivers11and to the gate drivers12, and to receive display data from an external section so as to supply the received display data to the source drivers11, and a power supply circuit14to generate operating voltage of each circuit and driving voltage of the liquid crystal cell.

Each of the source drivers11drives a plurality of source wires of the liquid crystal panel10, and by being provided with a plurality of source drivers11, all of the source wires of the liquid crystal panel10can be driven. Further, in the same manner as the source drivers11, each of the gate drivers12drives a plurality of gate wires of the liquid crystal panel10, and by being provided with a plurality of gate drivers12, all of the gate wires of the liquid crystal panel10can be driven.

Further, driving voltage for one horizontal line is respectively output to all of the source wires at every one horizontal period by the plurality of source drivers11, and one gate wire is sequentially driven at every one horizontal period by the plurality of gate drivers12. Thereby, a liquid crystal cell for one horizontal line in which the source wire and the gate wire intersects, is sequentially driven so as to perform a display operation.

The backlight device20comprises a light emitting section21to irradiate a light to the liquid crystal panel10, and a diffuser plate22which is disposed in front of the light emitting section21(a liquid crystal panel10side) so as to diffuse the light irradiated by the light emitting section21.

The light emitting section21according to the present embodiment is configured in a state where two surface light emitters211,212are arranged and disposed one above the other having a predetermined gap H1so that the liquid crystal panel10is divided into two parts in the Y direction.

The surface light emitters211,212are not particularly limited, however, an organic EL light emitting panel which comprises three kinds of organic EL light emitting layers to emit three primary colors of R (red), G (green), and B (blue), and selectively emits the three primary colors of R, G, and B by the application of voltage, can be named as one of the surface light emitter, for example.

The concrete configuration of the organic EL light emitting panel may be as follows. That is to say, the organic EL light emitting panel may comprise, for example, a light transmissive substrate which can transmit a light, a first electrode layer which is formed on the light transmissive substrate and is transparent, three kinds of organic EL light emitting layers which are formed on the first electrode layer in a state of being divided with each other to emit three primary colors of R, G, and B, and a second electrode layer which is formed on the organic EL light emitting layers.

As shown inFIG. 2, the two surface light emitters211,212are disposed so that the angle (θall) between their light irradiation surfaces211A and212A is smaller than 180 degrees.

To put it more concretely, the two surface light emitters211,212are placed so as to satisfy the conditions described in detail hereinbelow.

FIG. 3is a diagram showing the frame format of a shape of the light emitting section21(surface light emitters211,212) which is viewed cross-sectionally.

InFIG. 3, an intersecting point formed by extending two light irradiation surfaces211A and212A in the gap H1direction is an intersecting point P1. Further, a crossing point formed by perpendicular lines which are respectively perpendicular to the light irradiation surfaces211A and212A which extend from edge sections211band212aat the gap H1side of the two light irradiation surfaces211A and212A is a crossing point P2.

Further, a hypothetical plane surface which passes the crossing point P2and which is parallel to the diffuser plate22is a hypothetical plane surface L. Moreover, the distance from the intersecting point P1to the hypothetical plane surface L is a line segment X1.

Further, distances from the edge sections211band212aof the light irradiation surfaces211A and212A to the intersecting point21are respectively, a line segment Y1, and a line segment Y2. Moreover, the angle between the line segments X1and Y1, and the angle between the line segments X1and Y2are respectively, θ1and θ2.

In this regard, a relationship described in the following formula (1) is realized.
COS(θ1)=Y1/X1
COS(θ2)=Y2/X1(1)

That is to say, the formula (1) is led to the following formula (2).
θ1=COS−1(Y1/X1)
θ2=COS−1(Y2/X1)  (2)

Further, as a condition so that the lights irradiated from the two surface light emitters211,212do not produce any luminance reduced parts, the following formula (3) is to be realized.
θall≦θ1+θ2
which is led to θ1+θ2≦COS−1(Y1/X1)+COS−1(Y2/X1)  (3)

When the above formula (3) is satisfied, lights irradiated out from the lower edge section211bof the light irradiation surface211A and from the upper edge section212aof the light irradiation surface212A are to be crossed at P2.

The diffuser plate22is disposed in front of the hypothetical plane surface L at a position which is apart from the hypothetical plane surface L by a predetermined distance D.

The lights irradiated out from the surface light emitters211,212of the light emitting section21are diffused to be approximately even while transmitting inside of the diffuser plate22so as to reach the liquid crystal panel10.

The diffuser plate22is not particularly limited, however, a diffuser plate formed by evenly dispersing a glass fiber having a different refraction index from that of a transparent polycarbonate resin substrate to the resin substrate, or a diffuser plate formed by forming unevenness with suitable roughness on one surface of a transparent glass substrate, can be named as the diffuser plate22.

Next, an operation of the present embodiment is described.

According to the backlight device20of the present embodiment, the lights irradiated to the diffuser plate22by the light emission of the light emitting section21are to satisfy the above formula (3). Thereby, the lights are to intensify each other at the shortest distance at the crossing point P2, before reaching the diffuser plate22. That is to say, the lights irradiated from the two surface light emitters211,212are to intensify each other at a position corresponding to the gap H1of the two surface light emitters211,212.

Here, the longer the distance of the line segment X1is, the smaller the angle (θall) between the light irradiation surfaces211A and212A of the two surface light emitters211,212becomes. Further, the shorter the distance of the line segment X1is, the larger the angle (θall) between the light irradiation surfaces211A and212A of the two surface light emitters211,212becomes.

As described above, according to the liquid crystal display apparatus1according to the present embodiment, the lights irradiated out from the two surface light emitters211,212intensify each other at a position corresponding to the gap H1of the two surface light emitters211,212before reaching the diffuser plate22. Thereby, a dark section generated in the liquid crystal panel10due to the gap H1of the surface light emitters211,212is vanished, and a bright section is generated, and is to be even by the diffuser plate22. Thus, the generation of the luminance unevenness in the liquid crystal panel10can be reduced.

Incidentally, the diffuser plate22is to be disposed at a position apart from the hypothetical plane surface L by the predetermined distance D in the present embodiment. However, the back surface of the diffuser plate22may be overlapped with the hypothetical plane surface L.

Further, it is preferable that the hypothetical plane surface L is connected to at least one of the edge section211aof the light irradiation surface211A and the edge section212bof the light irradiation surface212A.

In a case where the above conditions are satisfied, the thickness of the backlight device20can be reduced to the minimum amount.

Next, an embodiment 2 of the present invention is described, the description of which is mainly given to parts different from the embodiment 1. Incidentally, the sections which are the same as those in the embodiment 1 are allotted with the same reference numbers so as to omit the description thereof.

FIG. 4is a top plan view showing a light emitting section31of a backlight device30in the embodiment 2.FIG. 5Ais a side view of the backlight device30, andFIG. 5Bis a bottom plan view of the backlight device30.

As shown inFIG. 4, the light emitting section31of the backlight device30according to the present embodiment is formed by comprising nine surface light emitters311,312, . . . ,319, each having a rectangular shape.

To put it more concretely, the light emitting section31is configured in a state where nine surface light emitters311, . . . , are arranged and disposed so that there are three pieces each in the vertical and horizontal directions, and so that the X direction and the Y direction of the liquid crystal panel10are respectively divided into three parts. Here, the gaps in between the three pieces of the surface light emitters311, . . . in the X direction are W1, and W2. Further, the gaps in between the three pieces of the surface light emitters311, . . . in the Y direction are H2, H3.

As shown inFIG. 5A, three pieces of the surface light emitters311,312, and313arranged in the Y direction are disposed so that the light irradiation surfaces311A,312A, and313A thereof respectively form the angle αall.

Further, as shown inFIG. 5B, three pieces of the surface light emitters311,314, and317arranged in the X direction are disposed so that the light irradiation surfaces311A,314A, and317A thereof respectively form the angle βall.

In this regard, the angles αalland βallare angles smaller than 180 degrees.

To put it more concretely, the surface light emitters are placed so as to satisfy the conditions described in detail hereinbelow.

FIG. 6is a diagram showing the frame format of a shape of the three surface light emitters311,312,313arranged in the Y direction which is viewed cross-sectionally.

InFIG. 6, a crossing point formed by perpendicular lines which are respectively perpendicular to the light irradiation surfaces311A and312A which extend from edge sections311band312aat the gap H2side of the light irradiation surfaces311A and312A of the upper two surface light emitters311,312is a crossing point P4.

Further, a hypothetical plane surface which passes the crossing point P4and which is parallel to the diffuser plate22is a hypothetical plane surface L.

Further, a distance from the hypothetical plane surface L to the edge section312aof the lower light irradiation surface312A is a line segment X2. A distance from an edge section311bof the light irradiation surface311A to the edge section312aof the light irradiation surface312A is a line segment Y3. Further, the angle between the line segments X2and Y3is α.

In this regard, a relationship described in the following formula (4) is realized.
COS(α)=Y3/X2(4)
α=COS−1(Y3/X2)  (5)

Further, as a condition so that the lights irradiated from the adjacent surface light emitters311,312do not produce any luminance reduced parts in the liquid crystal panel10, the following formula (6) is to be realized.
αall≦α+90 degrees
which is led to αall≦COS−1(Y3/X2)+90 degrees  (6)

Further, the angle formed by the light irradiation surfaces312A,313A of the lower two surface light emitters312,313is the same as the angle α formed by the above described surface light emitters311,312.

Incidentally, the above formula (6) is a case where α=θ1and θ2=90 degrees are satisfied in the formula (3).

Further, the above formula (6) is also applicable to βall.

By setting the surface light emitters in the above described manner, the lights irradiated out from the nine surface light emitters311, . . . , intensify each other at positions corresponding to the gaps W1and W2in the X direction, and the gaps H2and H3in the Y direction of the nine surface light emitters311, . . . , before reaching the diffuser plate22. Thereby, a dark section generated in the liquid crystal panel10is vanished, and a bright section is generated, and is to be even by the diffuser plate22. Thus, the generation of the luminance unevenness in the liquid crystal panel10can be reduced.

Incidentally, in the present embodiment, the conditions are set from the relationship of how the adjacent three surface light emitters are disposed. However, the conditions may be set from the relationship of how the adjacent two surface light emitters are disposed by using the formula (3) described in embodiment 1.

Further, it is preferable that the hypothetical plane surface L is connected to at least one of the edge section311aof the light irradiation surface311A and the edge section313bof the light irradiation surface313A.

In a case where the above conditions are satisfied, the thickness of the backlight device30can be reduced to the minimum amount.

Further, in the above embodiments 1 and 2, cases where there are two pieces and nine pieces of the surface light emitters are explained respectively as examples. However, the number of the surface light emitters is not limited to these.

Further, the case where the surface light emitter is an organic EL is used was explained, but it is not particularly limited to this, as long as the light source is of a surface state.

Moreover, the present invention can of course be suitably modified without being limited from the above described embodiments.

According to an aspect of the preferred embodiments of the present invention, there is provided a backlight device comprising:

a light emitting section including a plurality of surface light emitters which are arranged and disposed so as to have a predetermined gap; and

a diffuser plate which is disposed in front of the light emitting section to diffuse a light irradiated from the light emitting section, wherein

an angle between two light irradiation surfaces in the adjacent surface light emitters is smaller than 180 degrees.

Preferably, the backlight device satisfies
θ1+θ2≦COS−1(Y1/X)+COS−1(Y2/X), wherein

a distance from a hypothetical plane surface which is parallel to the diffuser plate to an intersecting point formed by extending the two light irradiation surfaces in a gap direction is a line segment X, the hypothetical plane surface passing a crossing point formed by perpendicular lines which are respectively perpendicular to the light irradiation surfaces and which extend from edge sections at a gap side of the two light irradiation surfaces, wherein

distances from the two light irradiation surfaces to the intersecting point are respectively, a line segment Y1and a line segment Y2, and wherein

angles formed by the line segments X and Y1, and by the line segments X and Y2are respectively, θ1and θ2.

Preferably, a liquid crystal display apparatus comprises:

the backlight device; and

a liquid crystal panel disposed in a light irradiation surface side of the light emitting section of the backlight device.

According to the preferred embodiments of the present invention, an angle between the light irradiation surfaces of the two adjacent surface light emitters is configured to be smaller than 180 degrees, thereby lights irradiated out from the light irradiation surfaces of the two adjacent surface light emitters intensify each other. Thus, a dark section generated in the gap of the adjacent surface light emitters is vanished, and a bright section is generated, and is to be even by the diffuser plate. Therefore, the luminance unevenness in the liquid crystal panel can be prevented.

The entire disclosure of Japanese Patent Application No. 2008-122874 filed on May 9, 2008 including description, claims, drawings, and abstract are incorporated herein by reference in its entirety.