JP2017062876A - Light source device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a backlight device which achieves both contrast performance and color unevenness performance in the backlight device which uses an intermediate diffusion structure.SOLUTION: A backlight device includes: a plurality of light-emitting elements; a sheet metal for fixing a substrate on which the plurality of light-emitting elements are arrayed; a reflection partition wall arranged around each of the plurality of light-emitting elements; an intermediate diffusion part arranged at the partition wall upper part; and a light diffusion part arranged above the intermediate diffusion part with a space. When a distance from a light source to the intermediate diffusion part is defined as A, and a distance from the light source to the light diffusion part is defined as B, 0.4*B<A≤0.5*B is satisfied.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a light source device.

  Conventionally, a cold cathode fluorescent tube (CCFL) has been used as a light source of a backlight device for a liquid crystal display device, but in recent years, a backlight device using a light emitting diode (LED) as a light source has been increasing.

  Since the LED is a point light source, when using the LED as the light source of the backlight device, it is necessary to devise the arrangement of the LED, the light diffusion structure, the light reflection structure, etc. to suppress the occurrence of uneven brightness and color unevenness. There is. In particular, a backlight device using a plurality of LEDs having different wavelengths such as red, green, and blue is more likely to have uneven brightness and color unevenness in a striped pattern or a lattice pattern than a backlight device using a white LED. It is necessary to devise the arrangement, the light diffusion structure, the light reflection structure, and the like.

  On the other hand, there is a technology that uses the fact that an LED is a point light source to individually change the brightness of the LED to partially change the brightness of the backlight device to increase the contrast of the display image. Such emission luminance control is generally called local dimming control.

  In local dimming control, the screen is virtually divided into a plurality of areas, the brightness value of the image signal is analyzed for each of the virtually divided areas, and the emission brightness of the corresponding light source is analyzed as a result of the brightness value analysis. Control processing based on the above is performed. Thereby, the contrast of the display image is improved.

  In order to further increase the contrast of the display image, a light source device has been proposed in which each region divided by a plurality of light sources is isolated by a partition using a reflecting material. With this structure, the luminance difference between adjacent regions can be increased.

  However, since the light beams between adjacent regions are blocked by the partition walls, there arises a problem that the luminance near the upper surface of the partition walls is lowered. In addition, when a plurality of light sources having different wavelengths are provided, there is a problem that color separation occurs and color unevenness also occurs near the upper surface of the partition wall.

  As methods for solving this, there are Patent Documents 1 and 2. Patent Documents 1 and 2 have an intermediate diffusion structure using a diffusion plate that is supported by a partition wall that surrounds a light source and diffuses light in advance before a normal light diffusion portion including the diffusion plate. Since the light is once diffused in the intermediate diffusion portion, color separation does not occur and a proposal has been made to reduce the occurrence of color unevenness.

International Publication No. 2007/088865 JP 2009-140720 A

  However, in the intermediate diffusion structure, color unevenness and contrast change depending on the position of the intermediate diffusion portion.

  When the intermediate diffusing unit is close to the light source, the diffusion distance between the intermediate diffusing unit and the light diffusing unit is long, so that light is diffused and color unevenness is reduced, but the contrast is not improved. Conversely, when the intermediate diffusion portion is far from the light source, the contrast is improved, but the color unevenness is not reduced.

  In order to solve the above problem, there is a possibility that color unevenness or contrast is not sufficiently improved in the dimensional relationship between the intermediate diffusion portion and the light diffusion portion disclosed in the embodiments of Patent Documents 1 and 2 described above.

  Accordingly, an object of the present invention is to provide a backlight device in which an intermediate diffusion portion is disposed at a position suitable for both contrast and color unevenness.

In order to achieve the above object, a backlight device according to the present invention includes:
A plurality of light emitting elements;
A sheet metal for fixing a substrate on which the plurality of light emitting elements are arranged;
A reflective partition disposed around each of the plurality of light emitting elements;
An intermediate diffusion portion disposed on the partition wall;
A light diffusing unit disposed above the intermediate diffusing unit with a space therebetween;
A backlight device comprising:
When the distance from the light source to the intermediate diffusion part is A and the distance from the light source to the light diffusion part is B, 0.4 * B <A ≦ 0.5 * B.

  According to the present invention, it is possible to provide a backlight device in which contrast and color unevenness are compatible.

It is a figure which shows schematic structure of the light source device which concerns on Example 1 of this invention. It is sectional drawing of the light source device which concerns on Example 1 of this invention. It is sectional drawing of the light source device which concerns on Example 1 of this invention. It is a graph of the optical characteristic when the light source block 101 which concerns on Example 1 of this invention is lighted.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

  Hereinafter, the light source device according to the first embodiment of the invention will be described. The light source device according to the present embodiment is a light source device capable of local dimming control. The light source device according to the present embodiment can be used as a backlight device for a liquid crystal display device, for example.

  The light source device according to the present embodiment is not limited to the backlight device. For example, the light source device according to the present embodiment can be used as a light source device of a display device (an advertisement sign device, a sign display device, etc.) that transmits light and displays an image. Moreover, the light source device according to the present embodiment can also be used as a light source device for devices other than display devices such as indoor lighting and street lamps.

  FIG. 1 shows an example of the configuration of a light source device 100 according to this embodiment. FIG. 2 is a top view of the light source device 100. In the example of FIG. 1, the light source device 100 has nine regions divided into three rows and three columns.

  The light source block 101 is composed of light sources that emit at least two different wavelengths with respect to one divided region. Here, it is assumed that an R light source, a G light source, and a B light source are arranged in one divided region. The light source 101 is not limited to an LED. For example, the light source may be a laser or an organic EL element. It is desirable that the light sources be arranged as close as possible.

  The sheet metal 102 holds the light source substrate on which the light source blocks are arranged and radiates heat. The light source substrate and the sheet metal 102 are electrically insulated by a heat conductive sheet or the like.

  The partition wall 103 is disposed so as to surround each light source block 101. The partition wall 103 is a reflecting member, and has an effect of increasing the contrast of the display image by reflecting light directed from the light source toward the adjacent light source block and directing it directly above the light source block.

  In the case where the light source device 100 is a light source device for a display device, the size of the partition wall 103 is the display area (screen area) of the display apparatus or an area including the display area (area larger than the display area). It may be provided so as to surround.

  The intermediate diffusion unit 104 is disposed so as to be placed on the upper part of the partition wall 103. It is desirable to reduce the number of contacts between the intermediate diffusion portion 104 and the partition wall 103 as much as possible. Further, the intermediate diffusion portion 104 in this embodiment has a thickness of 2 mm, a haze ratio of 96%, and the reflecting member of the partition wall 103 has a diffuse reflectance of 98%. The intermediate diffusion holding unit 105 is a support member that holds the periphery of the partition wall 103 and the intermediate diffusion unit 104.

  The light diffusing unit 106 is composed of a member that diffuses light. Examples of the member that diffuses light include a diffusion plate, a diffusion sheet, a light collecting sheet, and a light polarizing sheet. At this time, the light diffusion unit 106 diffuses the light so that the light transmitted through the intermediate diffusion unit 104 has a desired luminance unevenness distribution or color unevenness distribution. In general, the height relationship between the constituent partition wall 103, the intermediate diffusion unit 104, and the light diffusion unit 106 is such that when the height of the light diffusion unit 106 is constant, the closer the intermediate diffusion unit 104 is to the light source block 101, the more uneven the color. And the closer to the light diffusion unit 106, the higher the contrast of the display image.

  The liquid crystal display panel 107 is a panel that receives a video signal transmitted from a video signal device (not shown) and displays a video corresponding to the content of the video signal.

  The liquid crystal panel holding unit 108 is a support member that holds the light diffusing unit 106 and the liquid crystal display panel 107 so that the light diffusing unit 106 and the liquid crystal display panel 107 have a desired interval.

  Next, the position of the intermediate diffusion unit 104 will be described with reference to FIG.

  The position of the intermediate diffusing unit is such that when only the light source block 101 is turned on, the center point 107a of the turned on light source block 101 and the light source block adjacent to the light source block 101 (not turned on) in the brightness transmitted through the liquid crystal display panel ) Produces a luminance difference. At that time, the contrast between the points 107a and 107b is 3: 1 or more, and the color difference Δu′v ′ in the liquid crystal display panel 107c immediately above the partition wall surrounding the light source block 101 is discriminated in the color transmitted through the liquid crystal display panel. It arrange | positions in the position used as 0.0175 or less said that it is difficult to do.

  The length from the light source 101 to the intermediate diffusion unit 104 is a distance A, and the length from the light source to the light diffusion unit 106 is a distance B. As an example, FIG. 4 shows a graph in which the distance A is changed when the distance between the light source blocks 101 is 28 mm and the distance B = 30 mm. In FIG. 4, the horizontal axis represents the distance A, the first vertical axis represents the contrast between the points 107a and 107b, and the second vertical axis represents the color difference Δu′v ′ in the liquid crystal display panel 107c.

  As shown in FIG. 4, the range in which the contrast between the points 107a and 107b is 3: 1 or more is when the distance A is longer than 12 mm. Similarly, according to FIG. 4, the range in which the color difference Δu′v ′ in the liquid crystal display panel 107c is 0.0175 or less is when the distance A is shorter than 15 mm. At this time, the range satisfying both the contrast and the color difference is when the distance A is longer than 12 mm and shorter than 15 mm. However, 15 mm may be included.

  Therefore, the relationship between the distance A and the distance B at this time is 0.4 * B <A ≦ 0.5 * B.

  This relationship is not limited to the above example. For example, the distance B may be 35 mm or 40 mm.

  As described above, with the structure of the first embodiment, a backlight suitable for both contrast and color unevenness can be configured.

  In addition, although preferable embodiment of this invention was described above, this invention is not limited to these embodiment, A various deformation | transformation and change are possible within the range of the summary.

100 light source device, 101 light source block, 102 sheet metal, 103 partition,
104 Intermediate diffuser, 107 Light diffuser

Claims (3)

A plurality of light emitting elements;
A sheet metal for fixing a substrate on which the plurality of light emitting elements are arranged;
A reflective partition arranged to divide the plurality of light emitting elements into light emitting blocks;
An intermediate diffuser disposed on the reflective partition;
A light diffusing unit disposed above the intermediate diffusing unit with a space therebetween;
A liquid crystal display device comprising:
A backlight device characterized in that 0.4 * B <A ≦ 0.5 * B, where A is the distance from the light source to the intermediate diffusion portion and B is the distance from the light source to the light diffusion portion. A liquid crystal display panel for adjusting the light emitted from the light diffusing unit;
When one of the light emitting blocks obtained by dividing the plurality of light emitting elements is turned on,
The ratio of the luminance transmitted through the liquid crystal display panel immediately above the center of the light emitting block to the luminance transmitted through the liquid crystal display panel immediately above the center of the block adjacent to the light emitting block is 3: 1 or more. Item 2. The backlight device according to Item 1. A liquid crystal display panel for adjusting the light emitted from the light diffusing unit;
When one of the light emitting blocks obtained by dividing the plurality of light emitting elements is turned on,
2. The backlight device according to claim 1, wherein an unevenness of color Δu′v ′ transmitted through the liquid crystal display panel immediately above the center of the light emitting block is 0.0175 or less.