JP2009231012A - Back light unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a backlight unit in which brightness unevenness in the case of making the whole light-emitting face carry out surface light-emission can be suppressed as compared with conventional ones. <P>SOLUTION: This backlight unit 1 is equipped with a front cover 2 equipped with an opening part 2a, a plurality of optical sheets 3 which are installed inside the front cover 2 and in which a region facing the opening part 2a is set as the light-emitting face 3a, a light source mounting substrate 7 in which a plurality of side face light-emitting type LEDs 7a emitting light in nearly parallel direction against the light-emitting face 3a are arranged and installed in a light-emitting region suitable for the light-emitting face 3a, and a light-guide plate 5 in which light-reflecting patterns 5a reflecting the light from the LEDs 7a to the light-emitting face 3a side are installed at every unit region of the same number as that of the LEDs 7a. When the light-guide plate 5 is covered on the light source mounting substrate 7, an emitting direction of the light from the LEDs 7a and a diagonal direction of the unit regions that the light reflection patterns 5a are installed are nearly coincided. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a backlight unit, and more particularly, to a so-called direct-type backlight unit in which a light source is disposed inside the back of the unit.

  In a backlight device used for a liquid crystal display device or the like, a so-called direct type backlight device in which a plurality of cold cathode fluorescent tubes (CCFLs) are opposed to each other as a light source on the inner surface side of a diffusion plate or the like has been widely used. ing. This type of backlight device emits white light with a uniform luminance on the light emitting surface. For example, the light emitted from each CCFL is mixed and emitted in a space (air layer) to the light emitting surface. Such a configuration is provided.

In direct type backlight devices, a plurality of light emitting diodes (LEDs) are used as light sources instead of CCFLs in order to control the luminance and chromaticity of the light emitting surface for each subdivided region. For example, the backlight device of Patent Document 1 has been recently proposed.
JP 2006-236770 A

  In general, in a backlight device, when a plurality of LEDs are used as a light source and the entire light emitting surface is intended to emit light uniformly, for example, the brightness near a location where the LEDs are arranged is relatively high. In addition, there is a risk that luminance unevenness occurs such that the luminance at a location far from the location where the LED is disposed is relatively low. Therefore, in the backlight device, it is desirable to set the arrangement state of each LED while considering the light distribution pattern of each LED.

  On the other hand, in Patent Document 1, a configuration for suppressing luminance unevenness in the peripheral portion of the light guide plate is described, whereas a configuration for suppressing luminance unevenness in portions other than the peripheral portion of the light guide plate (for example, each The LED arrangement state) is not specifically mentioned, and this is a problem.

  The present invention has been made in view of the above-described circumstances, and an object of the present invention is to provide a backlight unit capable of further suppressing luminance unevenness when the entire light emitting surface is surface-emitting compared to the conventional case. It is said.

  The backlight unit according to the present invention includes a front cover having an opening, a plurality of optical members provided on the inner side of the front cover, the region facing the opening being set as a light emitting surface, and the light emitting surface. A plurality of side-emitting light-emitting elements that emit light in a direction substantially parallel to the light-emitting surface are disposed in a light-emitting area corresponding to the light-emitting surface, and light from the light-emitting element is emitted from the light-emitting surface side. And a light guide member provided for each of the same number of unit regions as the light emitting element, and the light from the light emitting element when the light guide member is placed on the light source mounting substrate. And the diagonal direction of the unit region provided with the light reflection pattern substantially coincide with each other.

  The backlight unit according to the present invention includes a front cover having an opening, a plurality of optical members provided on the inner side of the front cover, the region facing the opening being set as a light emitting surface, and the light emitting surface. A plurality of side-emitting light-emitting elements that emit light in a direction substantially parallel to the light-emitting surface are disposed in a light-emitting area corresponding to the light-emitting surface, and light from the light-emitting element is emitted from the light-emitting surface side. And a light reflecting member provided for each unit region of the same number as the light emitting element, and the light from the light emitting element when the light reflecting member is placed on the light source mounting substrate. And the diagonal direction of the unit region provided with the light reflection pattern substantially coincide with each other.

  According to the backlight unit of the present invention, it is possible to further suppress luminance unevenness when the entire light emitting surface is subjected to surface light emission as compared with the conventional case.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
1 to 4 relate to a first embodiment of the present invention. FIG. 1 is an exploded perspective view showing a main part of a backlight unit according to the first embodiment of the present invention. FIG. 2 is a diagram illustrating an example of a reflection pattern of a light guide plate and an arrangement state of LEDs in the first embodiment. FIG. 3 is a schematic cross-sectional view taken along line III-III in FIG. FIG. 4 is a diagram showing an example of another LED arrangement state and light emission direction different from those in FIG. 2 in the first embodiment.

  As shown in FIG. 1, the backlight unit 1 according to the present embodiment includes a front cover 2 having an opening 2a, a plurality of optical sheets 3 including a lens sheet, a diffusion sheet, and the like, a light guide plate 5, and a reflection plate. The main part includes a sheet 6, a light source mounting substrate 7 in which a plurality of LEDs 7 a as light emitting elements are arranged on the mounting surface, and a back frame 8. Moreover, the area | region which faces the opening part 2a among the surfaces of the optical sheet located in the outermost part among the some optical sheets 3 is set as the light emission surface 3a in the backlight unit 1. FIG.

  The plurality of optical sheets 3 as the optical members are inside the front cover 2 and are on the surface of the light guide plate 5 (the surface on the light emitting surface 3a side in the backlight unit 1) as a stacked state. Placed in position.

  The light guide plate 5 having a substantially rectangular shape in plan view is formed of a colorless and transparent resin such as an acrylic resin having light transmittance in a wavelength band to be used. Further, the front cover 2 is crowned on the edge of the light guide plate 5.

  Further, as shown in FIG. 2, the light emitted from the LED 7a is reflected on the back side of the light guide plate 5 as the light guide member (the surface opposite to the light emitting surface 3a in the backlight unit 1). The number of light reflection patterns 5a having a reflective structure on the light emitting surface 3a side of the unit 1 is the same as the number of LEDs 7a on the light source mounting substrate 7. Further, as shown in FIG. 3, an LED storage portion 5 b formed as a hole having a volume capable of individually storing each LED 7 a on the light source mounting substrate 7 is provided on the back surface side of the light guide plate 5. It has been. 3 is a schematic cross-sectional view along the line III-III in FIG.

  For example, as shown in FIG. 2, one light reflection pattern 5a is provided on the back surface of the light guide plate 5 for each rectangular unit region, which is a region set according to the light distribution pattern of the LED 7a. .

  Specifically, on the back surface side of the light guide plate 5, the light reflection pattern 5a for reflecting the light emitted from one LED 7a to the light emitting surface 3a side becomes farther from the light emitting surface 7b of the one LED 7a. One rectangular unit region is provided so that the light reflection ratio increases (from sparse to dense).

  Examples of the configuration of the light reflection pattern 5a in the present embodiment include the following.

  The light reflection pattern 5a in one unit region is configured as a concavo-convex pattern in which a portion indicated by a broken line in FIG. 2 is a concave portion or a convex portion, for example. And the said recessed part or convex part is a circular arc of the concentric circle centering on one LED7a arrange | positioned in the corner part of said one unit area | region so that the emission direction of light may follow the diagonal direction of said one unit area | region. (Eg, as shown in FIG. 2). Further, the closer to the light emitting surface 7b of the one LED 7a, the wider the distance between the concave portions or the convex portion (sparser), and the closer to the light emitting surface 7b of the one LED 7a, the narrower the mutual space becomes. It is formed to be (dense). It is assumed that the density of the concave portion or the convex portion can be appropriately adjusted for each unit region in which the LED 7a is arranged according to individual differences in the light distribution pattern of the LED 7a.

  As shown in FIG. 3, the LED storage portion 5 b formed so as to have a substantially trapezoidal shape in cross section shows the traveling direction of light emitted from other LEDs 7 a other than the LED 7 a stored inside the surface of the light guide plate 5. A slope 5c for changing to the side is provided.

  The reflection sheet 6 has a substantially rectangular shape in plan view, and has a hole for preventing the LED 7a from coming into contact with the reflection sheet 6 when attached to the light source mounting substrate 7. In this embodiment, instead of sticking the reflection sheet 6 on the light source mounting substrate 7, the surface of the light source mounting substrate 7 may be printed in white. Moreover, in this embodiment, in order to reflect light more efficiently compared with the case where the reflection sheet 6 is stuck on the light source mounting substrate 7 (instead of using the reflection sheet 6), for example, the light source mounting White silk printing may be performed on the substrate 7.

  The light source mounting board 7 is a circuit board having a substantially rectangular shape in plan view, for example, a printed wiring board of flame retardant grade FR-4, a composite laminated board (CEM-) using a glass nonwoven fabric, a glass cloth and an epoxy resin. 3 substrates), a flexible substrate, an aluminum substrate, or the like.

  Each LED 7a on the light source mounting substrate 7 emits light in a direction substantially parallel to the light emitting surface 3a in the backlight unit 1 (light emitting surface in a direction substantially parallel to the light emitting surface 3a in the backlight unit 1). 7b), which is a so-called side view type (side light emission type) LED. The LEDs 7 a on the light source mounting substrate 7 are arranged in a lattice shape so that the light emission direction is oblique to the vertical and horizontal directions on the surface of the light source mounting substrate 7. Further, each LED 7 a on the light source mounting substrate 7 is disposed in a light emitting region corresponding to the light emitting surface 3 a in the backlight unit 1.

  That is, in this embodiment, for example, as shown in FIG. 2, when the light guide plate 5 is put on the light source mounting substrate 7, the LEDs 7 a set obliquely with respect to the vertical and horizontal directions on the surface of the light source mounting substrate 7. The light emission direction and the diagonal direction of each unit region provided with the light reflection pattern 5a on the back surface of the light guide plate 5 are configured to substantially coincide with each other.

  The back frame 8 is configured as a flat and box-shaped hollow member having a substantially rectangular shape in a plan view, and one surface in the thickness direction is fully open. The back frame 8 is provided with the front cover 2 and the light guide plate 5 and the light source mounting substrate 7 are accommodated therein.

  Here, the operation of the backlight unit 1 of the present embodiment will be described.

  When power is supplied to the light source mounting substrate 7 in a state where the light guide plate 5 is placed on the light source mounting substrate 7, the LED 7a has a diagonal of the unit area where the light reflection pattern 5a is provided on the back surface of the light guide plate 5. Light is emitted in a direction, that is, in a direction from a sparse portion to a dense portion in the light reflection pattern 5a. As a result, the amount of light emitted to the surface side of the light guide plate 5 is relatively small at a position close to the light emitting surface 7b of the LED 7a, and the surface side of the light guide plate 5 is located far from the light emitting surface 7b of the LED 7a. The amount of light emitted to the screen becomes relatively large.

  In addition, in a state where the light guide plate 5 is put on the light source mounting substrate 7, the light emitted from the LED 7a travels in a direction substantially parallel to the light emitting surface 3a in the backlight unit 1 and then formed in the LED storage portion 5b. The light is reflected on the inclined surface 5 c and emitted to the surface side of the light guide plate 5. Thereby, the light quantity radiate | emitted to the surface side of the light-guide plate 5 can be further increased in the position far from the light-projection surface 7b of LED7a.

  As described above, the backlight unit 1 of the present embodiment is configured such that the difference in the amount of light emitted to the surface side of the light guide plate 5 does not occur as much as possible between the unit regions (of the light guide plate 5). . Thereby, the backlight unit 1 of this embodiment can further suppress the brightness nonuniformity at the time of surface-emitting the whole light emission surface 3a compared with the past.

  In addition, LED7a of this embodiment is not restricted to what is arrange | positioned as the light emission direction is arrange | positioned in the same direction as shown in FIG. 2, For example, as shown in FIG. Arrangements may be made so that the directions differ by 180 ° are staggered.

  Further, as shown in FIG. 2, the LED 7 a according to the present embodiment is not limited to a lattice shape and is arranged so that the light emission direction is oblique to the vertical and horizontal directions on the surface of the light source mounting substrate 7. Alternatively, for example, as shown in FIG. 4B, the pattern may be staggered and arranged so that the light emission direction is parallel to the vertical direction on the surface of the light source mounting substrate 7. . In this case, the shape of the unit region provided with the light reflection pattern 5a is a rhombus shape as shown in FIG. Furthermore, in this case, as shown in FIG. 4C, the LEDs 7a whose light emission directions are different by 180 ° may be alternately arranged.

  In addition, as shown in FIG. 2, the LED 7 a of the present embodiment is not limited to the one in which the shape of the unit area is rectangular, but for example, as shown in FIGS. 4D and 4E. Alternatively, the unit regions may be arranged so as to have a hexagonal shape.

(Second Embodiment)
5 to 7 relate to a second embodiment of the present invention. FIG. 5 is an exploded perspective view showing a main part of a backlight unit according to the second embodiment of the present invention. FIG. 6 is a diagram illustrating an example of a reflection pattern of a light reflecting member and an arrangement state of LEDs in the second embodiment. FIG. 7 is a schematic cross-sectional view along the line XI-XI in FIG.

  In the following description, detailed description of portions having the same configuration as in the first embodiment is omitted. The configuration of the backlight unit in the present embodiment is similar to the configuration of the backlight unit in the first embodiment. Therefore, in the present embodiment, a description will be mainly given of portions that are different from the backlight unit in the first embodiment.

  As shown in FIG. 5, the backlight unit 1A according to the present embodiment includes a front cover 2, a plurality of optical sheets 3 including a lens sheet and a diffusion sheet, a diffusion plate 4, a light reflecting member 9, and an LED 7a. The light source mounting board 7 and the back frame 8 in which a plurality of are provided as a main part. Moreover, the area | region which faces the opening part 2a among the surfaces of the optical sheet located in the outermost part is set as the light emission surface 3a in 1 A of backlight units.

  The plurality of optical sheets 3 as optical members are in a state of being overlapped with each other, on the inner side of the front cover 2 and on the surface of the diffusion plate 4 (the surface on the light emitting surface 3a side in the backlight unit 1A). Is arranged.

  The diffusing plate 4 as an optical member is formed by a flat plate-like member having a substantially rectangular shape in plan view, and a plurality of optical sheets 3 overlapped with each other are arranged on the surface side. Further, the front cover 2 is crowned on the edge of the diffusion plate 4.

  On the other hand, the diffusing plate 4 has a structure capable of diffusing the light emitted from the LED 7a, for example, a large number of minute protrusions (not shown) on the back surface (the surface opposite to the light emitting surface 3a in the backlight unit 1A). It is formed on the side.

  Furthermore, the diffusing plate 4 is disposed so that the back surface is in contact with the surface of the light guide plate 5.

  Each LED 7a on the light source mounting substrate 7 is disposed in a light emitting region corresponding to the light emitting surface 3a in the backlight unit 1A.

  On the surface side of the light reflecting member 9 having a substantially rectangular shape in plan view, a light reflecting pattern 9a having a structure capable of reflecting the light emitted from the LED 7a toward the diffusion plate 4 side (the light emitting surface 3a side in the backlight unit 1A). However, the same number as the number of LEDs 7 a on the light source mounting substrate 7 is arranged in parallel. In addition, on the back surface side of the light reflecting member 9, there is an LED storage portion 9 b that has such a volume that each LED 7 a on the light source mounting substrate 7 can be stored individually, and that one end side is opened. Is provided. 7 is a schematic cross-sectional view along the line XI-XI in FIG.

  For example, as shown in FIG. 6, one light reflection pattern 9a is provided for each rectangular unit area, which is an area set according to the light distribution pattern of the LED 7a.

  As shown in FIG. 6 and FIG. 7, the light reflection pattern 9a becomes gentler as it gets closer to the light emitting surface 7b of the one LED 7a, and becomes steeper as it gets farther from the light emitting surface 7b of the one LED 7a. The curved surface 9c is formed. Note that the broken line in FIG. 6 shows the state of the inclination of the curved surface 9c in the light reflection pattern 9a in a contoured and schematic manner. In addition, it is assumed that the state of inclination of the curved surface 9c in the light reflection pattern 9a can be appropriately adjusted for each unit region in which the LED 7a is arranged according to individual differences in the light distribution pattern of the LED 7a.

  On the other hand, as shown in FIG. 7, the light reflecting member 9 is formed so that only the end of the curved surface 9 c of the light reflecting pattern 9 a is in contact with the diffusion plate 4. Therefore, an air layer 10 is formed between the diffusion plate 4 and the light reflection pattern 9a.

  As shown in FIG. 7, the LED storage portion 9 b is open so that one end side, that is, the light emission surface 7 b side of the LED 7 a stored inside is in contact with the air layer 10. Thereby, the light emitted from the light emitting surface 7b of the LED 7a is emitted to the curved surface 9c of the light reflecting pattern 9a after passing through the air layer 10.

  The LEDs 7 a on the light source mounting substrate 7 are arranged in a lattice shape so that the light emission direction is oblique to the vertical and horizontal directions on the surface of the light source mounting substrate 7.

  That is, in the present embodiment, for example, as shown in FIG. 6, when the light reflecting member 9 is placed on the light source mounting substrate 7, each LED 7 a set obliquely with respect to the vertical and horizontal directions on the surface of the light source mounting substrate 7. The light emission direction and the diagonal direction of each unit region provided with the light reflection pattern 9a on the surface of the light reflection member 9 are configured to substantially coincide with each other.

  Here, the operation of the backlight unit 1A of the present embodiment will be described.

  When power is supplied to the light source mounting substrate 7, light is emitted from the LED 7a.

  Then, in a state where the light diffusing plate 4 is covered on the light reflecting member 9 and the light reflecting member 9 is covered on the light source mounting substrate 7, the light emitted from the LED 7 a has the light reflecting pattern 9 a on the surface of the light reflecting member 9. After proceeding in a diagonal direction of the provided unit region, that is, in a direction from a portion where the inclination of the curved surface 9c is gentle to a portion where the inclination is steep, the light is emitted to the diffusion plate 4 side. As a result, the amount of light emitted toward the diffusion plate 4 is relatively small at a position close to the light emission surface 7b of the LED 7a, and the light is emitted toward the diffusion plate 4 at a position far from the light emission surface 7b of the LED 7a. The amount of light increases relatively.

  As described above, the backlight unit 1 </ b> A of the present embodiment is configured such that a difference in the amount of light emitted to the diffusion plate 4 side is not generated between the unit regions of the light reflecting member 9 as much as possible. Thereby, 1 A of backlight units of this embodiment can further suppress the brightness nonuniformity at the time of surface-emitting the whole light emission surface 3a compared with the past.

  In addition, as shown in FIG. 6, LED7a of this embodiment is not restricted to what is arrange | positioned as the light emission direction is arrange | positioned in the same direction, For example, from FIG. 4A in 1st Embodiment. It may be arranged so as to have the same arrangement as any one of those shown up to FIG.

  In addition, the present invention is not limited to the above-described embodiments, and various modifications and applications can be made without departing from the spirit of the invention.

The disassembled perspective view which shows the principal part of the backlight unit which concerns on the 1st Embodiment of this invention. The figure which shows an example of the reflective pattern of the light-guide plate in 1st Embodiment, and the arrangement | positioning state of LED. FIG. 3 is a schematic sectional view taken along line III-III in FIG. 2. The figure which shows the example of the arrangement | positioning state of another LED different from FIG. 2, and the light emission direction in 1st Embodiment. The disassembled perspective view which shows the principal part of the backlight unit which concerns on the 2nd Embodiment of this invention. The figure which shows an example of the reflective pattern of the light reflection member in 2nd Embodiment, and the arrangement | positioning state of LED. FIG. 7 is a schematic sectional view taken along line XI-XI in FIG. 6.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1,1A ... Backlight unit, 2 ... Front cover, 3 ... Optical sheet, 4 ... Diffusing plate, 5 ... Light guide plate, 6 ... Reflective sheet, 7 ... Light source Mounting substrate, 8 ... back frame, 9 ... light reflecting member, 10 ... air layer

Claims (4)

A front cover having an opening;
A plurality of optical members provided on the inner side of the front cover, the region facing the opening is set as a light emitting surface;
A light source mounting substrate in which a plurality of side-emitting type light emitting elements emitting light in a direction substantially parallel to the light emitting surface are disposed in a light emitting region corresponding to the light emitting surface;
A light reflecting member that reflects light from the light emitting element toward the light emitting surface, and is provided for each unit region of the same number as the light emitting element, and
When the light guide member is placed on the light source mounting substrate, the light emission direction from the light emitting element and the diagonal direction of the unit region provided with the light reflection pattern substantially coincide with each other. The backlight unit.   The light reflection patterns are formed in such a manner that the distance between the light emitting patterns increases as the distance from the light emitting surface of the light emitting element increases, and the distance between the light reflecting patterns decreases as the distance from the light emitting surface of the light emitting element decreases. The backlight unit according to claim 1, comprising a plurality of parts. A front cover having an opening;
A plurality of optical members provided on the inner side of the front cover, the region facing the opening is set as a light emitting surface;
A light source mounting substrate in which a plurality of side-emitting type light emitting elements emitting light in a direction substantially parallel to the light emitting surface are disposed in a light emitting region corresponding to the light emitting surface;
A light reflection member provided with a light reflection pattern for reflecting the light from the light emitting element toward the light emitting surface side in the same number of unit regions as the light emitting element, and
When the light reflection member is placed on the light source mounting substrate, the light emission direction from the light emitting element and the diagonal direction of the unit region provided with the light reflection pattern substantially coincide with each other. The backlight unit.   The light reflection pattern has a curved surface formed such that the inclination is gentler as it is closer to the light emitting surface of the light emitting element, and the inclination is steeper as it is farther from the light emitting surface of the light emitting element. The backlight unit according to claim 3.

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