JP2013157258A - Light source device, and display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently utilize light of a plurality of light sources while retaining uniformity of in-plane luminance of a light source device.SOLUTION: A backlight device arranged on a rear side of a display panel is provided with a plurality of LED light sources 101a arranged on a plane, a BL (backlight) case to form a diffusion space, and a reflection diffusion sheet 102. The reflection diffusion sheet 102 is an optical member which reflects and diffuses light of the LED light sources 101a by a bottom part 102b having through holes 102a corresponding to the plurality of LED light sources 101a and a side wall part 102c formed extending from the bottom part. A lens 103 is a light refraction means which diffuses and irradiates a part of light from the plurality of LED light sources 101a toward the side wall part 102c of the reflection diffusion sheet 102. A light-emitting region consists of a first region where the lens 103 is arranged for the LED light source 101a and a second region where the lens 103 is not arranged. The second region is located between the first region and the side wall part 102c of the reflection diffusion sheet 102.

Description

  The present invention relates to improvement in uniformity of in-plane luminance of a light source device.

  As an example of a display device provided with a surface light source device, a liquid crystal display device is provided with a backlight (hereinafter also referred to as BL, which is arranged on the back surface of the display panel). Light sources of light emitting diodes (LEDs) are becoming the mainstream instead of cold cathode fluorescent lamps (CCFLs) as the light source for direct-type BL devices used in display devices, in order to increase the life of the devices and facilitate the disposal and recycling process. In order to make more efficient use of light from the light source, panel manufacturers have improved the light transmittance, which indicates the proportion of light from the light source that passes through the display panel by improving the liquid crystal alignment technology and color filter structure. The light transmittance of a liquid crystal panel used in a recent liquid crystal TV device is approximately 5 to 10% although it varies depending on the driving method, and the number of horizontal pixels is 4,000. In a high-definition liquid crystal panel having 0 × vertical pixels of 2,000 or more, it is only about 2-4%.

In the BL apparatus 700 of FIG. 7, a light source substrate 702 on which a plurality of LED light sources 702a are mounted is disposed on the bottom surface of the BL case 701, and the LED light source 702a is diffused from a through-hole portion 703a formed by a reflective diffusion sheet 703. Irradiate light toward In order to increase the light use efficiency, the following optical members are arranged in order from the light source side between the display panel and the BL device.
A diffusion plate 704 and a diffusion sheet 705 that diffuse light from the light source.
A prism sheet 706 that improves luminance values and contrast values viewed from the front of the display surface.
A polarizing reflection sheet 707 that is reused so that the light from the light source is not absorbed by the polarizing plate on the lower surface of the panel, thereby improving the light use efficiency.

The spatial distance between these optical sheet groups and the BL light source disposed in the substantially box-shaped BL case 701 is substantially equal to the mounting interval between the LED light sources that are point light sources in order to make the luminance uniform in the display surface. Or have a distance of more. A diffusion sheet 705 for sufficiently reflecting and diffusing the light from the LED light source at the spatial distance is installed along the inner wall of the case of the BL device. Since the thickness of the direct type BL device directly affects the thinning of the display device main body, the spatial distance can be reduced by increasing the number of LED light sources and reducing the mounting interval between the light sources. However, fewer LED light sources are advantageous from the viewpoint of cost reduction.
In Patent Document 1, a lens that diffuses part of the light in the horizontal direction is mounted facing the top of the LED light source while using various optical sheets, thereby enabling a reduction in the thickness of the BL device and the reduction in the number of LED light sources. Technology is disclosed.

Japanese Patent No. 4621799

  The conventional BL apparatus has a problem that the light from the LED light source is not sufficiently utilized. For example, it is possible to increase the luminance viewed from the front of the display area by using a prism sheet, but the luminance value at the periphery of the display area is lower than that at the center compared to the case where no prism sheet is used. There was a thing.

FIG. 6 illustrates an in-plane luminance distribution and a relative luminance value of a conventional BL device. FIG. 6A shows an in-plane luminance distribution from the front when the light from the LED light source mounted on the light source substrate is measured through the diffusion plate and the diffusion sheet. FIG. 6B illustrates the relative luminance along the broken line AA in FIG. 6A, with the horizontal axis indicating the position and the vertical axis indicating the relative luminance. FIG. 6C shows the in-plane luminance distribution measured through the prism sheet in addition to the diffusion plate and diffusion sheet from the front. FIG. 6D illustrates the relative luminance along the broken line CC in FIG. 6C, where the horizontal axis indicates the position and the vertical axis indicates the relative luminance. As can be seen from the comparison between FIG. 6B and FIG. 6D, in FIG. 6B showing the state before the light from the light source passes through the prism sheet, the relative luminance at the peripheral edge of the display area is at the center. However, the value is only about 5%. On the other hand, in FIG. 6D, which shows the state after the light from the light source has passed through the prism sheet, the relative luminance at the periphery of the display area is reduced to about 15% compared to the center.
An object of the present invention is to efficiently use light from a plurality of light sources while maintaining uniformity of in-plane luminance of the light source device.

  In order to solve the above-described problems, an apparatus according to the present invention is a light source device including a surface light source unit, and the surface light source unit corresponds to a plurality of light sources arranged on a plane and the plurality of light sources. A bottom surface portion having a through hole portion, a reflection diffusion means for reflecting and diffusing the light of the light source by a side wall portion extending from the bottom surface portion, and a side wall of the reflection diffusion means for a part of the light from the plurality of light sources A light refracting means for diffusing and irradiating the light source, and a light source positioned between the first region of the plurality of light sources and the side wall portion of the reflection diffusing means. The second region where the light refracting means is not disposed.

  According to the present invention, it is possible to efficiently use light from a plurality of light sources while maintaining uniformity of in-plane luminance of the light source device.

It is a figure which shows the structural example of BL apparatus of the display apparatus which concerns on 1st Embodiment of this invention. It is a figure which illustrates the relative luminance distribution at the time of arrange | positioning the lens in the case of a single light source, and a light source. It is a figure which illustrates the luminance distribution and relative luminance value of BL apparatus which has arrange | positioned the lens to the light source. It is a figure which shows the structural example of BL apparatus of the display apparatus which concerns on 2nd Embodiment of this invention. It is a schematic diagram explaining the light diffusion inside BL apparatus at the time of using various optical sheets. It is the figure which illustrated the luminance distribution and relative luminance value of the BL apparatus of a prior art example. It is a disassembled perspective view which shows the structure of a prior art example.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. The light source device according to the present invention can be widely applied to various devices such as an illumination device and a display device having a surface light source unit. For example, in the case of a display device, there are a configuration including a display panel and a light source device, and a configuration in which display is performed by light emission control of the light source device.
The display device shown in each embodiment of the present invention includes a display panel and a BL device that is a surface light source device that irradiates the display panel from the back. In the following, a liquid crystal display device will be exemplified as a display panel, and a light emitting element LED will be exemplified as a light source of a BL device. However, various types such as a color filter type organic EL (a method using an organic EL light emitting element and a color filter), A display panel or a light source element can be used.

[First Embodiment]
A first embodiment of the present invention will be described with reference to FIGS.
FIG. 1A is a plan view of the direct type BL device according to the present embodiment, and shows a state in which the diffusion plate 104 of FIG. 1B is removed to show the arrangement of the LED light sources 101a. A broken line B in FIG. 1A indicates an image display area end of the liquid crystal display device. FIG. 1B is a cross-sectional view taken along the line AA in FIG. FIG. 1C is a detailed view of the lens 103 arranged as a light refracting unit with respect to the LED light source 101a. A bottom view is shown on the left side, a sectional view is shown in the center, and a front view is shown on the right side, where H is the thickness of the lens 103 and D is the outer diameter. Note that the display panel, the case member (BL case) of the BL device, and the optical members other than the reflection diffusion sheet are the same as those in the conventional configuration shown in FIG.

  The light source substrate 101 is disposed on the bottom surface of a box-shaped BL case (not shown), a plurality of LED light sources 101a are mounted in a lattice shape, and the reflection diffusion sheet 102 is disposed on the mounting surface side of the LED light sources 101a. . The reflection diffusion sheet 102 and the diffusion plate 104 constitute reflection diffusion means for reflecting and diffusing the light from the LED light source 101a. The reflection diffusion sheet 102 has through holes 102a into which the respective LED light sources 101a are inserted. The LED light source 101a is located in the diffusion space, that is, the space formed by the reflection diffusion sheet 102 and the diffusion plate 104 disposed on the inner surface of the BL case through the through hole 102a. As shown in FIG. 1A, the LED light sources 101a are arranged in a lattice pattern of 8 rows in the vertical direction and 12 columns in the horizontal direction on the mounting surface of the light source substrate 101. Moreover, the lens 103 is arrange | positioned in the area | region except the peripheral part and four corners of an image display area among the locations corresponding to each LED light source 101a of 8 rows 12 columns. In other words, among the plurality of LED light sources 101a, the lens 103 is disposed in the first region, and the LED light source 101a in the second region located between the first region and the side wall portion 102c of the reflection diffusion sheet 102 includes The lens 103 is not disposed. In the example of FIG. 1A, the lenses 103 are arranged on 56 LED light sources 101a, excluding 36 located on the peripheral edge of the image display area and 4 located on the inner four corners. Yes.

  FIG. 1B shows a detailed arrangement of the lens 103. The lens 103 is disposed with respect to the LED light source 101 a, and the LED light source 101 a is accommodated in a concave portion formed on the bottom surface of the lens 103 so as to face the top of the LED light source 101 a. The lens 103 is made of a light transmissive member such as acrylic resin (PMMA) molded using a thermoplastic material. This has a high refractive index of 1.49 in addition to a high light transmittance, and is suitable for refracting the light from the LED light source 101a in an arbitrary direction by devising the cross-sectional shape of the lens 103. An example of the shape of the lens 103 is shown in FIG. The lens 103 has a symmetrical shape obtained by rotating 360 degrees about the central axis 103c, the outer diameter D is Φ10-20 (mm), and the thickness H is about 10 (mm). is there. The center of the curved surface from which the light from the LED light source 101a is emitted from the lens 103 is formed as a concave surface that is recessed from its periphery. That is, the concave portion 103b on the top surface of the lens serves to suppress local luminance at the central portion (see position 0 (mm) in FIG. 2). Further, at least three cylindrical lens leg portions 103 a having a diameter of about 1 mm and a length of about 2 mm are extended from the peripheral portion of the bottom surface toward the LED substrate 101. The lens leg 103a is fixed to the LED substrate 101 with an ultraviolet curing adhesive or the like so that the central axis 103c of the lens 103 coincides with the central axis of the light emission distribution of the LED light source 101a.

FIG. 2 shows an example of luminance distribution on a plane that is about 50 (mm) away from the LED light source 101a in the light traveling direction, where the reference position where the LED light source 101a is arranged is 0 (mm). The horizontal axis indicates the position (unit: mm) in the direction orthogonal to the optical axis of the LED light source 101a, and the vertical axis indicates the relative luminance.
The broken line (A) in FIG. 2 indicates the luminance distribution when the lens 103 is not disposed on the LED light source 101a, and the solid line (B) indicates the luminance distribution when the lens 103 is disposed immediately above the LED light source 101a. As can be seen from FIG. 2, the luminance is highest immediately above the position 0 (mm) where the LED light source 101a is disposed, and the luminance gradually decreases as the distance from the position 0 (mm) increases.
When the relative luminance distributions indicated by the broken line (A) and the solid line (B) are compared, in the distribution indicated by the broken line (A), when the luminance at 0 (mm) immediately above the LED light source 101a is 1, ± 150 ( mm) is about 0.1 (about 10%). On the other hand, in the distribution shown by the solid line (B), the luminance at 0 (mm) immediately above the LED light source 101a is 0.77, and the luminance at the position of ± 150 (mm) is about 0.20. The brightness of about 26 (%) is maintained relative to the central portion. (C) The hatched area 1 represents a range in which the broken line (A) has a higher relative luminance than the solid line (B), and (D) the hatched area 2 has a solid line (B) in the direction of the broken line (A). It represents a range with high relative luminance. That is, in consideration of the fact that the amount of light from one LED light source 101a is constant, the distribution shown in (C) hatched region 1 by the lens 103 becomes the distribution of (D) hatched region 2, and the horizontal axis It shows that the light is refracted and diffused in the direction (horizontal direction).

  The optical action of the lens 103 will be described with reference to FIG. The lens 103 has a function of distributing the light from the LED light source 101a at the center of the display area to the periphery of the display area. That is, part of the light Ld from the LED light source 101 a passes through the lens 103 and exits toward the diffusion plate 104. Further, a part of the other light Lf is diffused in the substantially horizontal direction by the action of the lens 103, and is irradiated toward the side wall portion 102 c extending from the bottom surface portion 102 b of the reflection diffusion sheet 102. This light is repeatedly reflected and diffused at the side wall portion 102c and the bottom surface portion 102b of the reflection diffusion sheet 102, and then emitted from the diffusion plate 104 as light of a surface light source. On the other hand, the light from the LED light source 101b in which the lens 103 is not disposed is indicated by a relative luminance distribution indicated by a broken line (A) in FIG. Most of the light is irradiated toward the diffusion plate 104 immediately above the LED light source 101b.

  FIG. 3 shows an example of measurement of luminance distribution and relative luminance in the present embodiment. As a measurement system, the light emitting area is about 650 (mm) × 400 (mm), the number of LEDs is 512, the diffusion distance is 28.5 (mm), and the lens diameter D is Φ15.5 (mm). FIG. 3A is an in-plane luminance distribution diagram measured with an in-plane luminance distribution meter through a reflective diffusion sheet having a thickness of about 0.2 (mm) using a milky white diffusion plate having a thickness of 2 (mm). . FIG. 3B is a graph showing the relative luminance value along the broken line AA in FIG. 3A, where the horizontal axis indicates the position (unit: mm), and the vertical axis indicates the relative luminance. FIG. 3C shows a milk diffusion plate having a thickness of 2 (mm), a reflective diffusion sheet having a thickness of about 0.2 (mm), and a prism sheet having a thickness of about 0.3 (mm) in this order. It is an in-plane luminance distribution diagram measured with an in-plane luminance distribution meter. FIG. 3D shows the relative luminance value along the broken line CC in FIG. 3C, the horizontal axis shows the position (unit: mm), and the vertical axis shows the relative luminance.

As shown in FIG. 3 (B), in the peripheral area of the display area, a part of the light from the LED light source is diffused in the horizontal direction by the action of the lens 103 and irradiated to the side wall of the reflection diffusion sheet, thereby displaying the display. The relative luminance at the periphery of the area is increased by about 3%. It can be seen that this result is a remarkable effect from the comparison with the graph of FIG.
Further, it was found that even when the prism sheets are stacked, as shown in FIG. 3D, the decrease in the relative luminance at the periphery of the display area can be suppressed to about 5%. This is a remarkable effect as compared to the relative luminance decrease rate of 15% shown in the graph of FIG. The cause of the luminance reduction in the peripheral portion in the conventional example will be described with reference to FIG. FIG. 5A shows a configuration in which the LED light source 702a is arranged in a space formed by the reflection diffusion sheet 703 and the diffusion plate 704. FIG. FIG. 5B shows an example in which a diffusion sheet 705 and a prism sheet 706 are stacked on a diffusion plate 704 in addition to the structure of FIG.

  In FIG. 5A, a luminance distribution 704b at a point 704a on the diffusion plate 704 has a wide angle range, and there are many components of light irradiated toward the side wall portion of the substantially box-shaped reflective diffusion sheet 703. Light from the light source diffuses to the periphery of the area. On the other hand, the luminance distribution 706b at the light emitting point 706a on the prism sheet 706 in FIG. 5B has a narrow angle range. Since the light from the LED light source 702a is derived toward the front side of the display area, the light component applied to the side wall portion of the reflection diffusion sheet 703 is reduced, and the luminance at the periphery of the display area is reduced. In order to keep the luminance in the display surface uniform, the luminance value of the LED mounted on the peripheral edge of the display area is controlled to a higher value than the LED in the central portion of the display area. The brightness value of the LED is changed mainly by pulse width modulation (Pulse Width Modulation), and the duty ratio of the pulse width (ratio between the high value interval and the low value interval in the pulse period) is changed according to the magnitude of the input signal (DC level). It is controlled by doing. As an example, if the relative value of the input signal to the LED at the center of the display area is 1.0, the input signal to the LED at the periphery of the display area needs to be increased to about 1.5. In other words, under the condition for maintaining the luminance uniformity within the display surface, the LED in the central area of the display area is (1.0 / 1.5) ≈0.67 times as large as the LED in the peripheral area of the display area. However, the light from the LED cannot be used efficiently.

In the present embodiment, the above problem can be solved by disposing the lens 103 having a refractive action on the LED light source 101a in the range including the center of the display area. That is, part of the light from the LED light source 101a is diffused and distributed to the peripheral edge of the display area by the action of the lens 103, so that in-plane luminance can be made uniform.
In the present embodiment, the example in which the LED light sources 101a are arranged in a grid pattern is shown in the application of the light source device to the display device, but the present invention is not limited to such an arrangement. For example, a 60 ° staggered arrangement in which the LED light sources 101a are connected in a straight line is a regular triangular arrangement, and a shape in which the LED light sources 101a are connected in a straight line is an isosceles right triangle 45. ° A staggered arrangement may be used. Further, the lens 103 may have a curved surface without the concave portion 103b, and a plurality of lens groups may be formed as one optical member.

[Second Embodiment]
Next, a second embodiment of the present invention will be described with reference to FIG. In the present embodiment, a configuration using a plurality of types of lenses in the first region is illustrated. Hereinafter, by using the same reference numerals as those used in the first embodiment, detailed descriptions thereof will be omitted, and differences will be mainly described.
FIG. 4A is a plan view of the direct type BL apparatus according to the present embodiment, and shows a state in which the diffusion plate 104 of FIG. 4B is removed to show the arrangement of the LED light sources 101a. FIG. 4B is a cross-sectional view taken along the broken line AA in FIG.
The LED light sources 301 shown in FIG. 4A are arranged in a grid of 8 rows × 12 columns. Among them, lenses 302, 303, and 304 having different refractive indexes or refractive indexes are respectively arranged from the central portion to the peripheral portion of the image display area. The refractive index of each lens is higher as it is located at the center, and lower as it is closer to the periphery. That is, when the refractive indexes of the respective lenses are n (302), n (303), and n (304), there is a relationship of “n (302)> n (303)> n (304)”. More specifically, a total of 12 lenses 302 in a vertical row × 6 horizontal columns are arranged in the central portion, 20 lenses 303 are arranged so as to surround them, and 28 lenses 304 are arranged so as to surround them. Has been. The LED light source in the second region near the side wall 102c of the reflection diffusion sheet 102 is not provided with a lens.
FIG. 4B shows LED light sources 301a, 301b, and 301c and lenses 303 and 304. The shape of the lens 303 arranged in the LED light source 301a is the shape of the lens 103 described in the first embodiment. Similar to the above, a recess is provided on the exit surface side. The shape of the lens 304 disposed in the LED light source 301b is a dome shape without a recess. No lens is arranged for the LED light source 301c located near the periphery. In FIG. 4B, the lens 302 is omitted, but the shape is arbitrary, and the lens 302 is designed to obtain a light distribution according to the specification.

Under the above arrangement, as shown in FIG. 4B, part of the light Lf of the LED light source 301a is refracted by the lens 303 and diffused and irradiated toward the side wall portion 102c of the reflection diffusion sheet 102. The light is guided to the peripheral edge of 104. A part of the light Lg from the LED light source 301 b is refracted by the lens 304 and guided to the peripheral edge of the diffusion plate 104. Most of the light from the LED light source 301c is directly guided to the diffusion plate 104, and the light is emitted from the diffusion plate 104 as light of the surface light source.
According to the second embodiment, the in-plane luminance can be made uniform by changing the refractive index or the refractive index of the lens from the central portion to the peripheral portion of the display area.
As an example of the light refracting means shown in the above embodiment, a separate lens is provided for the light emitting element. However, the configuration is not limited to such a form, and the LED light source and the lens may be integrated. For example, in FIG. 4C, the LED element 306 mounted on the substrate 305 is encapsulated in an encapsulating portion 307 formed of epoxy resin or the like, and a dome-shaped lens portion 308 formed integrally therewith is used as a light refracting means. The structure used is shown. Part of the light emitted from the LED element 306 by feeding power to the electrode unit 309 is refracted by the lens unit 308 via the enclosing unit 307 and is emitted to the outside. Moreover, the structure which integrated the some LED element, those enclosure parts, and the lens part may be sufficient.

101a, 101b LED light source 102 Reflection diffusion sheet 102a Through hole portion 102b Bottom surface portion 102c Side wall portion 103 Lens 103b Recessed portion 104 Diffusion plate 301a, 301b, 301c LED light source 302, 303, 304 Lens 306 LED element 307 Encapsulating portion 308 Lens portion

Claims (7)

A light source device including a surface light source unit,
The surface light source unit is
A plurality of light sources arranged on a plane;
A bottom surface portion having through-hole portions corresponding to the plurality of light sources, and a reflection diffusing means for reflecting and diffusing the light of the light source by a side wall portion extending from the bottom surface portion;
A light refracting means for diffusing and irradiating a part of light from the plurality of light sources toward a side wall portion of the reflection diffusing means;
Of the plurality of light sources, a first region in which the light refracting unit is disposed, and a second region in which the light refracting unit is not disposed in a light source positioned between the first region and the side wall portion of the reflection diffusing unit. A light source device comprising: A case member having a bottom surface portion and a side wall portion;
2. The light source device according to claim 1, wherein the reflection diffusing unit includes a reflection diffusing sheet disposed along an inner side of a bottom surface portion and a side wall portion of the case member.   The said light refracting means is comprised with several lenses, and the refractive index of the lens located away from the said 2nd area | region is high compared with the lens near the said 2nd area | region. Light source device.   The light source device according to claim 3, wherein the lens has a concave portion at a center of a surface from which light from the light source is emitted.   5. The light source device according to claim 1, wherein the plurality of light sources or light refraction means are arranged in a lattice shape or a staggered lattice shape.   The light source device according to claim 5, further comprising: an enclosing portion enclosing the light emitting element; and a lens portion formed integrally with the enclosing portion. The light source device according to any one of claims 1 to 6,
And a display panel irradiated from the back by the surface light source unit of the light source device.