Patent Application
20120008063
The present invention relates to a liquid crystal display device having a plurality of point light sources as a light source. The present application claims priority to Patent Application No. 2009-070803 filed in Japan on Mar. 23, 2009, and the entire contents of which are hereby incorporated by reference.
Liquid crystal display devices having a liquid crystal panel capable of providing high-definition color images with low power consumption are used for various applications (such as home televisions, mobile phones, and personal computers, for example) as display devices displaying videos and images. Because a liquid crystal element constituting a liquid crystal panel is a non-self light emitting element, in order to improve the luminance of a panel, a backlight device including light sources in various forms is installed in a liquid crystal display device.
As one example of such a back light device, a backlight device provided with a plurality of point light sources such as high brightness white LEDs (Light Emitting Diode) is known.
As the size of liquid crystal panels is becoming increasingly larger in recent years, the number of the point light sources installed in the backlight device using the point light sources tends to increase to prevent the light irradiation non-uniformity from the light source, such as a part of the liquid crystal panel not being irradiated or receiving less amount of light irradiated thereto compared to other parts. From the perspective of saving electric power or reducing manufacturing cost, however, it is preferable to be able to uniformly irradiate the entire liquid crystal panel with light (that is, to prevent the light irradiation non-uniformity (luminance non-uniformity)) without increasing the number of the light sources.
Disclosed in Patent Document 1 is a backlight device designed to expand a light irradiation region by forming a recess to guide outgoing light from each point light source into the inside of a light guide plate in order to irradiate a larger region with one point light source. Such a design disclosed in Patent Document 1 is, however, for expanding the light irradiation region from an individual point light source, and it is still difficult to uniformly irradiate the entire surface of a liquid crystal panel by such a design.
The present invention was made in view of the above points and it is a main object of the present invention to provide a liquid crystal display device capable of irradiating the entire liquid crystal panel uniformly with light (that is, preventing the light irradiation non-uniformity that can be recognized by viewers) without excessively increasing the number of point light sources, even when a relatively large liquid crystal panel is to be provided.
To achieve the above-mentioned object, a liquid crystal display device provided by the present invention including: a liquid crystal display panel; a plurality of optical members placed on a back surface side of the liquid crystal panel; and a backlight device placed on the back surface side of the optical members, wherein the backlight device includes a backlight substrate having a plurality of point light sources, wherein the plurality of point light sources are disposed on the backlight substrate in a prescribed point light source arrangement pattern such that the point light sources are interspersed, being spaced with each other, in a region facing the liquid crystal panel, wherein the optical members include an anisotropic optical member having optical anisotropy that diffuses light emitted from each of the point light sources in prescribed directions, and wherein, in a region of the backlight substrate in which the plurality of point light sources are arranged in the prescribed point light source arrangement pattern, when a position that is within a region surrounded by any three or four adjacent point light sources, and that is the furthest position when viewed from each of the adjacent point light sources is defined as an anisotropy reference position, the optical anisotropy is such that light emitted from the point light source closest to the anisotropy reference position is selectively diffused toward the reference position.
The liquid crystal display device according to the present invention is characterized in that the anisotropic optical member having the optical anisotropy, which is the anisotropic optical member having the optical anisotropy with which light emitted from the point light source closest from the anisotropy reference positions is selectively (preferentially) diffused in the directions toward the reference positions is provided therein.
In this manner, in the liquid crystal display device according to the present invention, the sufficient amount of light can reach even the furthest positions from the point light sources, such as the anisotropy reference position from one of the point light sources. Therefore, by the liquid crystal display device according to the present invention, the entire liquid crystal panel can be irradiated with light almost uniformly without excessively (unnecessarily) increasing the number of the point light sources and the generation of the excessive light irradiation non-uniformity that is recognizable by viewers can be prevented.
A preferable aspect of the liquid crystal display device disclosed here is characterized in that the point light source arrangement pattern is a pattern in which the plurality of point light sources are arranged in a grid pattern in the region of the backlight substrate, wherein, in a virtual quadrangular region surrounded by four adjacent point light sources as the vertices in the grid point light source arrangement pattern, the anisotropy reference position is defined as the furthest position when viewed from the respective four point light sources.
According to the present invention, a liquid crystal display device having a plurality of point light sources arranged in such a grid arrangement pattern and capable of almost uniformly irradiating the entire liquid crystal panel with light is provided.
Another preferable aspect of the liquid crystal display device disclosed here is characterized in that the point light source arrangement pattern is a pattern in which a plurality of point light sources are arranged in a staggered pattern in a prescribed direction in the region of the backlight substrate, wherein, in a virtual triangular region surrounded by three adjacent point light sources as the vertices in the staggered point light source arrangement pattern, the anisotropy reference position is defined as the furthest position when viewed from the respective three point light sources.
According to the present invention, a liquid crystal display device having a plurality of point light sources arranged in such a staggered arrangement pattern and capable of almost uniformly irradiating the entire liquid crystal panel with light is provided.
Another preferable aspect of the liquid crystal display device disclosed herein is characterized in that the liquid crystal display device includes an anisotropic diffusion member formed in a shape of a plate or a sheet as the anisotropic optical member.
By having such a configuration, the object of the present invention can be achieved with ease.
Another preferable aspect of the liquid crystal display device disclosed herein is characterized in that the liquid crystal display device includes a lens member formed in a shape of a plate or a sheet as the anisotropic optical member.
By having such a configuration, the object of the present invention can be achieved with ease.
Also, another preferable aspect of the liquid crystal display device disclosed herein is characterized in that the anisotropic optical member of the plurality of optical members is placed at a position closest to the point light sources.
In a liquid crystal display device of such a configuration, by placing the anisotropic optical member of the plurality of optical member at the closest position to the point light sources, the generation of non-uniformity in light irradiation can be prevented more reliably.
Hereinafter, several preferred embodiments of the present invention are described with reference to the figures. The items which are not the matters specifically mentioned in this specification (optical members, for example), and are necessary to implement the present invention (such as a structure and a configuration method of a liquid crystal panel, and electric circuits related to a driving method of light sources installed in a liquid crystal display device, for example) can be understood as design matters of those skilled in the art based on the prior art in the field. The present invention can be implemented based on the contents disclosed in this specification and the technical common knowledge in the field.
First, an active matrix type (TFT type) liquid crystal display device 100 including a liquid crystal panel 10 according to a preferred embodiment of the present invention is explained. In the figures hereinafter, the same reference characters are given to members and parts that have the same functions, and overlapping explanations may be omitted or simplified. Also, dimensional relations (length, width, thickness and the like) in each figure do not necessarily reflect actual dimensional relations precisely. Additionally, in the explanations below, “front side” or “surface side” is referring to a side facing viewers in the liquid crystal display device 100 (which is a liquid crystal panel side), and “reverse side” or “back surface side” is referring to a side not facing viewers in the liquid crystal display device 100 (which is a side to a backlight device 70 placed behind the liquid crystal panel).
Referring to
The liquid crystal panel 10 generally has a rectangular shape as a whole, and has a display region 10A that has pixels formed therein to display images in the center region thereof. Also, this liquid crystal panel 10 has a sandwich structure constituted by a pair of transparent glass substrates 11 and 12 facing each other, and a liquid crystal layer 13 filled therebetween. For the substrates 11 and 12, substrates that are cut out from large base members, called a mother glass in the manufacturing process, are respectively used. Of the pair of substrates 11 and 12, the one on the front side is a color filter substrate (CF substrate) 11 and the other on the reverse side is an array substrate 12. In margin areas of the substrates 11 and 12 (the margin area in the liquid crystal panel 10), a sealing material 25 is provided so as to enclose the display region 10A to seal the liquid crystal layer 13. The liquid crystal layer 13 is constituted of a liquid crystal material including liquid crystal molecules. The orientation of the liquid crystal molecules of the liquid crystal material is manipulated according to the application of an electric field between the substrates 11 and 12, causing the optical characteristics to change. In the liquid crystal layer 13, spacers (not shown) are typically placed at a plurality of locations to ensure the thickness (gap) of such a layer 13. Also, alignment films (not shown) that determine an alignment direction of the liquid crystal molecules are respectively formed on the surfaces of the sides facing each other of both the substrates 11 and 12 (inside). Polarizing plates 26 and 27 are bonded on the respective surfaces of the sides not facing each other (outside).
In the liquid crystal panel 10 disclosed here, on the front side of the array substrate 12 (the side facing the liquid crystal layer 13), pixels (sub pixels, in detail) for displaying images are arranged and a plurality of source wiring lines and a plurality of gate wiring lines for driving each pixel (sub pixel), which are not shown, are formed so as to create a grid pattern. In each grid region surrounded by the wiring lines, a (sub) pixel electrode and a thin film transistor (TFT) that is a switching element are disposed. The pixel electrodes are typically made of ITO (Indium Tin Oxide), which is a transparent conductive material, and a voltage according to an image is supplied to these pixel electrodes through the source wiring lines and the thin film transistors at a prescribed timing.
On the other hand, on the CF substrate 11, a color filter in either one of the colors, R (Red), G (Green) or B (Blue) is placed opposite to one pixel electrode of the array substrate 12. Additionally, a black matrix that divides the color filter of respective colors, and a common electrode (transparent electrode) that is formed uniformly on the surfaces of the color filter and the black matrix are disposed.
As shown in
Here, the configuration of the pixels and the wiring lines of the electrodes described above can be similar to a case where a conventional liquid crystal panel is manufactured, and because the present invention is not characterized thereby, any further detailed explanations will be omitted.
As shown in
As shown in
The liquid crystal display device 100 including the liquid crystal panel 10, the backlight device 70 and the like of the configuration described above controls the liquid crystal molecules in the liquid crystal layer 13 by applying a controlled voltage to the array substrate 12 and the CF substrate 11, so that the light from the backlight device 70 passes through or is blocked in the liquid crystal panel 10. Also, the liquid crystal display device 100 displays a desired image in the display region 10A of the liquid crystal panel 10, while controlling the brightness and the like of the backlight device 70.
Here, such drives and control of the liquid crystal panel 10 can be similar to those of the conventional art. Because the present invention is not characterized thereby, the detailed explanations will be omitted.
Next, configurations, features, and effects of the point light sources 72 and the optical members 80 of the liquid crystal display device 100 according to this embodiment are explained in detail, referring to
As the point light sources 72 of the backlight device 70 of the liquid crystal display device 100 according to this embodiment, various types of point light sources can be used, but typically, point LEDs (white LEDs, for example) are used. LEDs can be used as preferable point light sources because it is easier to control the light emitting time, and the electrode life is longer (100,000 hours or longer, for example), as compared to CCFL (Cold Cathode Fluorescent Lamp) that was conventionally used as a light source.
As shown in
Referring to
In this embodiment, as described above, the anisotropic optical member 82 is provided as an optical member. The optical anisotropy of the optical member 82 is provided such that emitted light from the one of the point light sources 72 closest to the anisotropy reference position G1 to G3 (one of the light sources indicated with the reference characters L1 to L4 for the anisotropy reference position indicated with G1, for example) is diffused in the direction toward the anisotropy reference position G1 to G3 (the directions of the arrows in
Specifically, in a case where the point light source arrangement pattern is a grid pattern such as these embodiments (that is, in a case where four adjacent point light sources 72 constitute respective vertices of a virtual square), the optical anisotropy for the entire region of the backlight substrate 71 on which the point light sources 72 facing the liquid crystal panel 10 are placed is set such that light is diffused in the direction toward a point light source 72 constituting a diagonal in the virtual quadrangle when viewed from a respective point light source L1 to L8.
In this manner, the light emission ranges schematically shown in
Meanwhile, in a conventional liquid crystal display device in which the point light sources (LEDs) 72 are placed in a grid pattern without having the anisotropic optical member 82 such as this embodiment (see
Further, cases where the point light sources (LEDs) 72 are placed in a staggered pattern are explained as another embodiment, referring to
Here, in this embodiment as well, the anisotropic optical member 82 is provided as an optical member. The optical anisotropy of the optical member 82 is formed such that light emitted from the one of the point light sources 72 closest to the anisotropy reference position G4 to G7 (one of the light sources indicated with the reference characters L9 to L11 for the anisotropy reference position indicated by G4, for example) is diffused in the direction toward the anisotropy reference position G4 to G7 (the directions of the arrows in
Specifically, in cases where the point light source arrangement pattern is a staggered pattern such as these embodiments (that is, in cases where three adjacent point light sources constitute respective vertices of a virtual equilateral triangle), the anisotropy reference positions G4 to G7 are corresponding to the centers of gravity of the respective virtual equilateral triangles. Therefore, in the cases of this embodiment, the optical anisotropy in the entire region of the backlight substrate 71 on which the point light sources 72 facing the liquid crystal panel 10 are placed is set such that light is diffused in the direction from one of the point light sources constituting one of the virtual triangles (the light source of the reference character L9, L10, or L11, for example) toward the anisotropy reference position within the virtual triangular region (the anisotropy reference position of the reference character G4, for example). That is, the optical anisotropy in the entire region of the backlight substrate 71 on which the point light sources 72 facing the liquid crystal panel 10 are placed is set such that light is diffused in the direction from the light source of the reference character L9 toward the anisotropy reference position G4 in the example shown in
Next, a manufacturing method of the anisotropic optical member 82 having the prescribed optical anisotropy described in the two embodiments above is briefly explained. As shown in
Preferable examples include an anisotropic diffusion plate with the anisotropy formed in a prescribed direction made of a synthetic resin such as polyethylene terephthalate, polyethylene naphthalate, acrylic resin, polycarbonate, polystyrene, polyolefin, cellulose acetate, or weather resistance vinyl chloride, for example. In addition to the above mentioned synthetic resin, which is a main material that constitutes the anisotropic diffusion plate, plasticizers, stabilizers, antidegradants, dispersants, optic diffusers, inorganic fillers, and the like may be incorporated, for example. Also, there is no particular limitation for a method to confer the optical anisotropy, and various methods can be adopted. A diffusion plate made of a synthetic resin, formed by dispersing short fiber optic diffusers in a resin matrix so as to align fibers longitudinally in a prescribed direction, can be preferably used as the anisotropic diffusion plate 82, for example. In this manner, by substantially aligning the fibers of the short fiber optical diffusers longitudinally in a prescribed direction, the optical member having the anisotropy can be constructed.
Although the present invention has been explained by the preferable embodiments above, such descriptions are not limiting matters, and various modifications are possible.
For example, a plurality of optical members 180 may be arranged in the order as shown in
Also, a plurality of optical members 280 may be arranged in the order as shown in
In each embodiment described above, a diffusion plate (diffusion sheet) typically made of a synthetic resin has been adopted as the anisotropic optical member, but the present invention is not limited to such, and the optical anisotropy suitable for the object of the present invention may be provided to a lens member constituting the optical members, for example. As another embodiment, for example, the optical anisotropy suitable for the object of the present invention can be provided to the above-described lens sheet (typically, a prism sheet) 284 shown in
A conventional method may be adopted for manufacturing such a lens member 284 (a prism sheet, for example) having the optical anisotropy, and there is no need to adopt a special method in implementing the present invention. In the case of the lens member 284 (a prism sheet, for example) made of a synthetic resin, for example, by extruding a resin forming material, using a extruding die with which the transfer of a prescribed fine surface structure pattern is achieved in the extrusion, a lens member (a prism sheet, for example) given the optical anisotropy that is formed by the transferred pattern can be made. Alternatively, the desired optical anisotropy can be provided by coating a surface of a substrate made of a prescribed synthetic resin material (polyethylene terephthalate (PET), for example) with an appropriate photocurable resin (typically, a UV curable resin) in a state in which a prescribed fine surface structure pattern is transferred (conferred), and by curing the coating with the transferred pattern, which is a known method. By using such a lens member 284 having anisotropy, the present invention can be implemented more easily.
According to the present invention, a liquid crystal display device including an anisotropic optical member that has the optical anisotropy in which light emitted from the closest point light source from the anisotropy reference position is selectively (preferentially) diffused in the directions toward the reference position is provided. In such a liquid crystal display device, even at the furthest positions from the point light sources, the sufficient amount of light can reach from one of the point light sources. As a result, the entire liquid crystal panel can be irradiated with light almost uniformly without excessively increasing the number of point light sources, even when a relatively large liquid crystal panel is to be provided.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2009-070803 | Mar 2009 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2010/051593 | 2/4/2010 | WO | 00 | 9/14/2011 |
