Patent Application
20100073912
The present invention relates to a light emitting device and a display device. More specifically, it relates to a light emitting device configured to include light-emitting elements, and a display device using this light emitting device.
In recent years, various light emitting devices in which plural solid-state light-emitting elements such as light-emitting diodes (LEDs) are mounted on a substrate for use as a light source have come into practical use. Such light emitting devices are widely used, for example, as a matrix display device in which a matrix of plural LEDs emits light selectively to display characters or images, a backlight for a liquid crystal panel of a liquid crystal display device, or the like.
As a conventional art described in an official gazette, there is an array of light-emitting elements in which plural light-emitting elements are arrayed in line and an array policy based on chromaticity and an array policy based on luminance are combined with each other, in order to thoroughly use, without an occurrence of unevenness of luminance or chromaticity, extra arrays of light-emitting elements that have been produced (for example, refer to Patent Literature 1).
Moreover, as an art of another official gazette, there is a light-emitting diode unit formed by arranging light-emitting diodes in two lines on a substrate. More specifically, the light-emitting diodes are arranged in two lines so that each of the light-emitting diodes is displaced by a half pitch of an arrangement pattern, in desired order, in order to enhance color mixture for obtaining white light, to prevent unevenness of color or luminance, to obtain lower power consumption and long life, and to improve reliability (for example, refer to Patent Literature 2).
Patent Literature 1: Japanese Patent Application Laid Open Publication No. 2006-133708
Patent Literature 2: Japanese Patent Application Laid Open Publication No. 2006-133721
Here, in some cases, a backlight is formed, for example, by having light-emitting elements arranged in a two-dimensional matrix on a back side of a liquid crystal display panel such as that for a television. For example, there has been widely employed a method of forming the two-dimensional matrix arrangement by entirely mounting a certain number of tile light sources each having m×n (where m and n are integers equal to or larger than 2) light-emitting elements arranged in a two-dimensional matrix on a glass epoxy substrate (glass/epoxy substrate). However, in these backlights used for televisions, televisions of different inch sizes require different sized backlights corresponding thereto, and require changes in shapes of the tile light sources. As a result, component commonality becomes impractical, and reduction in production cost is difficult. Additionally, it becomes necessary to cover, with the tile light sources, an entire face of a base (a chassis) used as a back surface of the television, whereby a cost for the glass/epoxy substrate used as a substrate becomes very large.
Additionally, in a case where a light source is formed by having light-emitting elements, each being any of a red (R), a green (G), or a blue (B) light-emitting element, arranged one after another at regular intervals, mixing the colors thereof to obtain a white color is difficult. In order to sufficiently mix the colors, the R, G and B light-emitting elements need to be closely arranged to each other. Accordingly, in a case where the R, G and B light-emitting elements are arrayed in line so as to be close to each other, it is difficult to make blank spaces between glass/epoxy substrates. For this reason, simply having the light-emitting elements arrayed in line does not contribute to obtain a sufficient effect in cost reduction for the glass/epoxy substrate.
Furthermore, use of so-called high-power LEDs having 1 mm square size or the like, for example, has a problem that these high-power LEDs generate a large amount of heat, and also require a very high cost. Additionally, rather than a case of having light-emitting points with high luminance scattered about, a case of having a large number of light-emitting points with low luminance has advantages in luminance and chromaticity uniformity, and enables the formation of a thinner backlight. From these points of view, it is preferable to employ small chip LEDs for a backlight. However, in order to obtain the same brightness as that of the high-power LEDs by employing the small chip LEDs, it is necessary that a large number of the LEDs be arrayed. If a large number of the LEDs are used, even in a case where not the two-dimensional arrangement but the one-line arrangement is employed for example, this simple usual alignment eventually requires that an entire face of a chassis be covered with a glass/epoxy substrate.
An object of the present invention is to provide a display device that facilitates mixing of RGB colors to obtain a white color and also that has excellence in uniformity in luminance and chromaticity.
Additionally, another object thereof is to largely reduce an area of a substrate for a light source row to realize installability of other members as well as cost reduction.
A light emitting device to which the present invention is applied is provided with: a strip-like light source having a strip-like substrate on which a plurality of units each having, as a single unit, any one of a set of one red (R), one green (G) and one blue (B) light-emitting elements arranged therein and a set of one red (R), one green (G), one green (G) and one blue (B) light-emitting elements arranged therein are arranged in line, the strip-like substrate having a short width and a long length; and a frame on which a plurality of the strip-like light sources are arranged two-dimensionally at intervals.
Here, the plurality of strip-like light sources are arranged on the frame so that, in a longitudinal direction of the strip-like light source, positions of the plurality of units arranged on the strip-like light source in a first row may be shifted from positions of the units arranged on the strip-like light source in a second row adjacent to the first row.
On the frame, each of the positions of the plurality of units arranged on the strip-like light source in the first row is shifted from corresponding one of the positions of the plurality of units arranged on the strip-like light source in the second row adjacent to the first row by substantially half of a pitch between the plurality of units arranged on each of the strip-like light sources.
Moreover, two of the units that are arranged on a predetermined one of the strip-like light sources, and one of the units that is arranged on another one of the strip-like light sources in another row adjacent to the predetermined strip-like light source and that is the closest to the two of the units, have such a positional relationship as to form a substantially equilateral triangle. This configuration has an advantage of excellent uniformity of luminance and chromaticity, as compared to a case where the present configuration is not adopted. In particular, the present configuration is effective in a case where the units are one-dimensionally arranged on the substrate in line, since it is more difficult to obtain the uniformity of luminance and chromaticity in the one-dimensional arrangement than in the two-dimensional arrangement.
The strip-like light source is provided with the plurality of units arranged on the strip-like substrate, and is provided with a terminal on the strip-like substrate, the terminal being electrically connected to the plurality of units. In particular, the terminal provided on the strip-like light source is arranged on the strip-like substrate with a longitudinal direction thereof being set to the same direction as a direction of the row of the plurality of units provided on the strip-like light source. This configuration has excellence in reduction of an area of the strip-like substrate made of, for example, glass/epoxy substrate. In addition, intervals between the units are widened by causing each unit on the strip-like light source to be smaller. Specifically, each unit is caused to be smaller by gathering RGB or RGGB.
The light emitting device is further provided with a relay substrate that is arranged between the plurality of strip-like light sources on the frame and that is electrically connected to the terminal of each of the light-emitting sources. By adopting the strip-like light sources, gaps on the frame are obtained and are utilized. Thus, improvement of the installability may be achieved, for example. In addition, the relay substrate is mounted on the gap on the frame instead of the back side of the frame in the conventional technique, and thus the device can be thinner.
A display device to which the present invention is applied is provided with: a display panel that displays an image; and a light emitting device that is provided on a back side of the display panel, the light emitting device including: a strip-like light source having a strip-like substrate on which a plurality of units each having, as a single unit, among red (R), green (G) and blue (B) light-emitting elements, anyone of a set of one red (R), one green (G) and one blue (B) light-emitting elements arranged therein and a set of one red (R), one green (G), one green (G) and one blue (B) light-emitting elements arranged therein are arranged in line, the strip-like substrate having a short width and a long length; and a frame on which a plurality of the strip-like light sources are arranged two-dimensionally with gaps, each of the gaps between rows of the plurality of strip-like light sources being larger than the width of the strip-like substrate.
Here, by attachment of the plurality of strip-like light sources to the frame, heat from the light-emitting elements arranged in the units is allowed to be conducted to the frame through through-holes of the plurality of strip-like light sources, and through heat releasing layers each provided on a back surface which is opposite to a front surface on which the light-emitting elements are arranged. This configuration has an advantage of preferable heat release by use of a simple fixing unit such as screws.
In the strip-like light source of the light emitting device, reflow is performed for an electrical connection to the plurality of units and a connection used for heat conduction from the plurality of units. The present configuration achieves preferable heat release even when attachment is efficiently performed.
According to the present invention, it is possible to largely reduce an area of a substrate for a light source row, and to provide a display device having excellence in uniformity in luminance and chromaticity even in the case of largely reducing the area.
Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.
The backlight device 10 includes a backlight frame 11 as a base (chassis) that contains a light-emitting portion. The backlight frame 11 has a two-dimensional arrangement of strip-like light sources 30. In each of the strip-like light sources 30, light-emitting diodes (hereinafter, referred to as LEDs) are arranged in line. In addition, relay substrates 60 are each arranged between adjacent arrays of the strip-like light sources 30. Each of the relay substrates 60 is used for electrically connecting the respective LEDs in the strip-like light sources 30 with an external device.
The backlight device 10 includes, as a laminated body of optical films, a diffusion plate 13 that is a film (or a plate) scattering and diffusing light to equalize the lightness over the entire surface, and prism sheets 14 and 15 that have a light collection effect to the front. In addition, the backlight device 10 includes a luminance improvement film 16 with a diffusion and reflection type, for improving the luminance.
On the other hand, the liquid crystal display module 20 includes a liquid crystal panel 21 as one type of a display panel that is configured by two glass substrates sandwiching liquid crystal in between, and polarization plates 22 and 23 for restricting the oscillation of optical wave to a given direction, which are each laminated on each glass plate of the liquid crystal panel 21. The display device includes peripheral members (not shown in the figure) such as an LSI (Large Scale Integration) for driving, mounted thereon. For example, the liquid crystal panel 21 as a display panel in a limited sense includes various components not shown in the figure. For example, the two glass plates have display electrodes, active elements such as a thin film transistor (TFT), liquid crystal, a spacer, sealant, an orientation film, a common electrode, a protective film, a color filter, and others, none of which is shown in the figure.
The structural unit of the backlight device 10 as a light emitting device is selected in an arbitrary way. For example, a unit only including the backlight frame 11 with the strip-like light sources 30 may be called as the “backlight device (backlight)” and distributed as a “light emitting device” not including the laminated body of the optical films such as the diffusion plate 13 and the prism sheets 14 and 15.
The backlight frame 11 of the backlight device 10 has a housing structure made of, for example, anyone of aluminum, magnesium and iron, or a metal alloy containing those materials. In order to favorably release heat of the LEDs, it is desirable that the backlight frame 11 has high heat conductivity. Additionally, on an inner side of the backlight frame 11, the plural strip-like light sources 30 and the plural relay substrates 60 are arranged. In the example in
The strip-like light sources 30 in each rows are arranged so that positions of the sub-mounts 40 in the strip-like light sources 30 in the first row (for example, the strip-like light sources 30 in the first one of rows) may be shifted in a longitudinal direction of the strip-like light sources 30 from positions of the sub-mounts 40 in the strip-like light sources 30 in the second row (for example, the strip-like light sources 30 in the second one of rows) adjacent to the first row. In particular, the strip-like light sources 30 in adjacent two rows are arranged so as to be shifted to each other by a distance corresponding to a half pitch of a distance (pitch) between the sub-mounts 40 next to each other, and a distance between each adjacent two of the rows is determined so that distances between the sub-mounts 40 adjacent to each other may be equal. That is, as shown in
In these measurement relations, if the strip-like light sources 30 are arranged so that the three sub-mounts 40, that is, the sub-mount 40-1 in the first one of the rows, and the sub-mounts 40-2 and 40-3 of the strip-like light source 30 placed in the second one of the rows, form a substantially equilateral triangle as shown in
Here, on the substrate 31, a terminal 32 used for supplying electric power to the sub-mounts 40 thereon and for inputting control signals for operating ON/OFF thereof and the like is provided. The terminal 32 is provided on the substrate 31 so that a longitudinal direction thereof becomes substantially parallel with a direction of a row in which the sub-mounts 40 are arrayed, that is, so that the longitudinal direction thereof extend in the same direction as the direction of the row. Additionally, the substrate 31 is provided with screw holes 33 used for fixing the strip-like light source 30 to the backlight frame 11. As shown in
Furthermore, as shown in
The plural sub-mounts 40 each being described above and each having the structure shown in
Here, the wiring patterns 36 formed on the front surface of the substrate 31 are connected to the terminal 32 shown in
The strip-like light source 30, on which the sub-mount 40 has been mounted, is mounted on the backlight frame 11 in such a way that a heat-releasing sheet 54, for example, is sandwiched between the strip-like light source 30 and the backlight frame 11 by using screws 53 screwed at portions corresponding to the screw holes 33 (refer to
The strip-like light source 30, to which the sub-mounts 40 have been mounted, is mounted to the backlight frame 11 in the above described manner, whereby the backlight device 10 as shown in
Moreover, in the present exemplary embodiment, as shown in
Note that, in the present exemplary embodiment, as shown in
Otherwise, instead of this configuration, the terminal 32 of the strip-like light source 30 shown in
Furthermore, by setting, as appropriate, a longitudinal dimension of each strip-like light source 30 and array intervals of the sub-mounts 40, the strip-like light sources 30 are allowed to be shared, for example, even when used as different inch-sized backlights of televisions.
Note that, in the above-described exemplary embodiment, a description has been given by taking, as an example, a case where unit substrates are used as the respective sub-mounts 40. However, a unit may be formed without using a sub-mount substrate. For example, a case is conceivable where LEDs constituting one unit are arranged directly on a strip-like light source substrate so as to be close to each other. In such a case, an aspect in which the LEDs are directly mounted on the strip-like light source substrate and connected to the strip-like light source substrate by wire bonding is given as one example.
10 . . . backlight device, 11 . . . backlight frame, 20 . . . liquid crystal display module, 30 . . . strip-like light source, 31 . . . substrate, 40 . . . sub-mount, 41 . . . substrate, 43 . . . LED, 60 . . . relay substrate
| Number | Date | Country | Kind |
|---|---|---|---|
| 2007-106406 | Apr 2007 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2008/056554 | 4/2/2008 | WO | 00 | 10/9/2009 |
