Patent Application
20090096955
The present application claims the benefit under 35 U.S.C. 119 of Japanese Patent Application 2007-267763 filed on Oct. 15, 2007, the disclosure of which is incorporated in this application by reference.
1. Field of the Invention
The present invention relates to miniaturization of the liquid crystal display appliance and making thin the lighting system used for a backlight of the liquid crystal display appliance.
2. Description of the Related Art Japanese Laid-open Patent Application 2005-347062 discloses a liquid crystal display appliance (referred to as “LCD appliance” hereinafter) equipped with a lighting system emitting white light onto a liquid crystal display panel (referred to as “LCD panel” hereinafter), which is attached on the back side of the liquid crystal display panel. This lighting system comprises a plurality of fluorescent lamps and a light reflector member for diffusing and reflecting the white light from the fluorescent lamps which is disposed on the back side of the fluorescent lamps and a light diffusing plate for diffusing and transmitting the white light from the fluorescent lamps which is disposed in front of the fluorescent lamps.
If a lighting system used in the aforesaid conventional LCD appliance is made thin to miniaturize a LCD appliance, there come up problems with brightness inhomogeneity on a LCD panel. One of the problems is that a portion of a LCD panel over each luminescent lamp is seen brighter than portions of the LCD panel over between adjacent lamps if the lighting system becomes thin. Accordingly the brightness of a portion in the LCD panel is dependent on whether the portion is over any of the luminescent lamps. The LCD appliance becomes defective because the portions of a LCD panel over the luminescent lamps are seen brighter than the other portions.
The other problem with the thinner lighting system for the aforesaid conventional LCD appliance is that the brightness distribution is not sufficiently homogeneous over a whole LCD panel as shown in
The objective of the present invention is to provide a LCD appliance capable of displaying a good picture image without any recognizable brightness irregularity if its lighting system is made thin.
The aspect of the present invention is that a LCD appliance comprising a LCD panel for displaying a picture image and a lighting system for emitting light incident onto the LCD, the lighting system being attached on a back side of the LCD panel and comprising a plurality of linearly elongated light sources each of which is disposed in substantially parallel with a display horizontal direction of the LCD panel, a light reflector member for reflecting the light emitted from the linearly elongated light sources as well as diffusing the light, the light reflector member disposed on a back side of the linearly elongated light sources, and a light diffusing-transmission member for transmitting and diffusing the light, the light diffusing-transmission sheet disposed in front of the linearly elongated light sources, wherein a length D between the light reflector member and the light diffusing-transmission member is between 7 and 13 mm, wherein a length p between the adjacent linearly elongated light sources and the distance D satisfy an first inequality, p≦1.34×D+9, and wherein a length e between a vertical direction edge of the light reflector member and a nearest linearly elongated light source from the vertical direction edge and the length D satisfy a second inequality, e≦1.6×D+4.
An explanation is hereinafter given on the LCD appliance that is in accordance with an embodiment of the present invention. To begin with, taking a look at
A LCD appliance 1 of the embodiment comprises 9 luminescent lamps and a LCD panel 3 that displays a picture image. Each of the luminescent lamps 3 is in a linearly elongated shape and emits identical white light which comes incident onto the LCD panel 3 as backlighting. The number of the luminescent lamps in the LCD appliance 1 of this embodiment is 9 and not limited to 9. As long as the LCD appliance 1 includes a plurality of luminescent lamps, the number of the luminescent lamps in the LCD appliance 1 of this embodiment may be more than 9 or less than 9.
As indicated in
A light diffuser plate 11, on which 4 optical sheets are attached, is supported by upper side molds 9 each of which is disposed to cover up a lower side mold 7 and fixed at a position a predetermined height higher than the light reflector sheet 5. The 4 optical sheets 12 used for the LCD appliance 1 of this embodiment are constituted by a light diffuser sheet, a light collecting film, a light diffuser sheet and a light diffuser sheet which are stacked in this order from on the light diffuser plate 11. The 4 optical sheets 12 may be constituted by a light diffuser sheet, a light collecting film, a light diffuser sheet and a polarizing reflector film, which are stacked in this order from on the light diffuser plate 11 and may constituted by another combination of optical sheets. There may be less than 4 optical sheets stacked on the light diffuser plate 5, more than 4 optical sheets stacked on the light diffuser plates 5. A plurality of optical sheets suffice for constituting the optical sheet 12. According to the LCD appliance 1 of the present embodiment the light diffuser plate 3 has a smooth surface on the side of the LCD panel 3, but the light diffuser plate 3 may have a patterned surface in a concavo-convex shape as indicated in
A LCD panel 3 is fitted into a groove 13a formed on the inner periphery of an intermediate frame 5 and secured on the intermediate frame 13 with an adhesive. Then the upper frame 14 is fixed on the intermediate frame 13 on which the LCD panel 3 is secured.
Next an explanation is given on the operation of the LCD appliance 1 of the present embodiment.
The white light emitted from the luminescent lamps 2 that comes incident onto the reflector sheet 5 is efficiently diffused and reflected upward on the reflector plate 5 and the white light from the luminescent lamps 2 is diffused in the light diffuser plate 11 and transmitted through the light diffuser plate 11. As a result the white light emitted from the luminescent lamps 5 is transmitted out of the light diffuser plate 11 into the 4 optical sheets 12 attached on the light diffuser plate 11 after being repeatedly transmitted and reflected several times between the light reflector sheet 5 and the light diffuser plate 11. The diffuseness as well as the directivity of the white light is controlled by the 4 optical sheets 12.
Next how bright irregularity on the LCD panel 3 is prevented in the LCD appliance 1 of the present embodiment is explained.
In the LCD appliance 1, the thinner the lighting system consisting of the luminescent lamp 2, the light reflector sheet 5, the light diffuser plate 11, the 4 optical sheets is made, the smaller a distance D from the light reflector sheet 5 to the light diffuser plate 11, which is regarded as a light diffusion distance, becomes. In order to prevent brightness irregularity on the LCD panel 3 for the smaller light diffusion distance D, it is necessary to make a luminescent lamp interval p, which is a length between adjacent luminescent lamps 2 as indicated in
In addition to making the luminescent lamp interval p equal to or smaller than the predetermined length, it is necessary to make a length e from a boundary between an upper edge surface 6a and an inclined surface 5b of the light reflector sheet 5 to a nearest luminescent lamp from this boundary, which is indicated in
It has been found through experiments by the inventors that both of the luminescent lamp interval p and the length e from the vertical direction edge of the backlight unit to the nearest luminescent lamp from the vertical edge to prevent the brightness irregularity on the LCD panel 3 are dependent on the light diffusion distance D. For each light diffusion distance D both the luminescent lamp interval p and the length e to prevent the brightness irregularity on the LCD panel 3 are obtained. As a result it proves that the brightness irregularity on the LCD panel 3 is efficiently prevented by setting the luminescent lamp interval p and the length e so that p and e satisfy the following inequalities (1) and (2),
p≦1.34×D+9 (1)
e≦1.6×D+4 (2)
In this description, preventing the brightness irregularity on the LCD panel 3 means preventing the portions over the luminescent lamps of the LCD panel 3 from being seen brighter as well as having brightness on both the position located 10% of the vertical direction length of the LCD panel 3 downward from the vertical direction upper edge on the LCD panel 3 and the position located 10% of the vertical direction length of the LCD panel 3 upward from the vertical direction lower edge being equal to or more than 70% of the brightness of the center portion in the vertical direction of the LCD panel 3, which is consistent with the criteria for LCD panels currently used for television appliances.
Next are explained experiments carried out to obtain the optimum luminescent lamp intervals and the optimum lengths from a vertical direction edge of the LCD panel to a nearest luminescent lamp from the vertical direction edge.
Firstly are explained experiments on the luminescent lamp interval p to prevent the brightness irregularity on the LCD panel 3. These experiments have been carried out to obtain the optimum luminescent lamp intervals p to prevent the brightness irregularity of the LCD panel 3 for each of the light diffusion distances from 5 mm to 17 mm. Accordingly setting the light diffusion distance D to each of 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16 and 17 mm, an experiment is carried out to check whether the brightness irregularity is prevented for every light luminescent interval p set. This experiment is repeatedly performed with the light luminescent interval p being varied for each light diffusion distance D set. As a result the largest light luminescent interval p to prevent the brightness irregularity on the LCD panel 3 is obtained for each light diffusion distance D. The experiment condition is indicated in
The result in
On the other hand it has been found that the defect of the brightness lowering at the portion in the vicinity of the vertical direction edge of the LCD panel 3 is removed by setting the length e from the vertical direction edge of the backlight unit to the nearest luminescent lamp 2 from the vertical direction edge to the optimum values obtained through experiments to be explained.
Secondly are explained experiments to obtain the optimum lengths e from a vertical direction edge of the backlight unit to the nearest luminescent lamp 2 from the vertical edge to prevent the brightness irregularity on the LCD panel 3
The experiments are carried out as follows. Setting out the light diffusion distance D to each of 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16 and 17 mm, an experiment is carried out to check whether the brightness irregularity is prevented for every length e set. This experiment is repeatedly performed with the length e being varied for each light diffusion distance D set. As a result the largest length e from the vertical direction edge of the backlight unit to the nearest luminescent lamp 2 from the vertical edge to prevent the brightness irregularity on the LCD panel 3 is obtained for each light diffusion distance D.
The experiment condition for these experiments is indicated in
The result in
As explained above, if the luminescent lamp interval p and the length e are set to satisfy the inequalities (1) and (2), both defects of the portions of the LCD 3 over the luminescent lamps 2 being seen extraordinarily brighter and the brightness lowering at the portions in the vicinity of the vertical direction edges of the LCD panel 3 are removed. Therefore the brightness irregularity of the LCD panel 3 is prevented if the light diffusion distance is decreased from a little less than 20 mm to between 7 and 13 mm.
Hereinafter are explained applications of the present embodiment to the actual LCD appliances which are made thin and in which the light diffusion distance is reduced from a little less than 20 mm to between 7 and 13 mm.
As is clear from
N=(L−2×e)/p+1 (3)
Then the following inequality (4) is derived by substituting the equation (3) into the aforementioned inequalities (1) and (2).
N≧{L−(3.2×D+8)}/(1.34×D+9)+1 (4)
How the present embodiment is applied to LCD appliances of 32 inch size, 37 inch size and 42 inch size, in each of which the lighting system is made thin and the light diffusion distance is reduced to between 7 and 13 mm, is to be explained.
Firstly an application of the present embodiment to the 32 inch size LCD appliance is explained. The backlight vertical direction length L is 398 mm for the 32 inch size LCD appliance. If the light diffusion distance D is set to 9.3 mm, the luminescent lamp interval p, the length e from the vertical direction edge of the backlight unit to the nearest luminescent lamp 2 from the vertical direction edge and the number of the luminescent lamps N are determined to be respectively p≦21.46 mm, e≦18.88 mm, N≧17.79 according to inequalities (1), (2) and (4). Accordingly the brightness irregularity on the 32 inch size LCD appliance is prevented, for instance, by setting the number of the luminescent lamps N to 18, the luminescent lamp interval p to 21.4 mm and the length e to 17.1 mm.
Secondly an application of the present embodiment to the 37 inch size LCD appliance is explained. The backlight vertical direction length L is 467.4 mm for the 37 inch size LCD appliance. If the light diffusion distance D is set to 10 mm, the luminescent lamp interval p, the length e from the vertical direction edge of the backlight unit to the nearest luminescent lamp from the vertical direction edge and the number of the luminescent lamps N are determined to be respectively p≦22.4 mm, e≦20.0 mm, N≧20.1 according to inequalities (1), (2) and (4). Accordingly the brightness irregularity on the 37 inch size LCD appliance is prevented, for instance, by setting the number of the luminescent lamps N to 21, the luminescent lamp interval p to 22 mm and the length e to 13.7 mm.
Finally an application of the present embodiment to the 42 inch size LCD appliance is explained. The backlight vertical direction length L is 524 mm for the 42 inch size LCD appliance. If the light diffusion distance D is set to 11 mm, the luminescent lamp interval p, the length e from the vertical direction edge of the backlight unit to the nearest luminescent lamp from the vertical direction edge and the number of the luminescent lamps N are determined to be respectively p≦23.74 mm, e≦21.6 mm, N≧21.25 according to inequalities (1), (2) and (4). Accordingly the brightness irregularity on the 37 inch size LCD appliance is prevented, for instance, by setting the number of the luminescent lamps N to 22, the luminescent lamp interval p to 23 mm and the length e to 20.5 mm.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2007-267763 | Oct 2007 | JP | national |
