JP2004171809A - Light guide plate, and backlight device using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light guide plate used for equalizing luminance of a light emitting part in using a point light source for a backlight device, and to provide a backlight device using it. <P>SOLUTION: This light guide plate 2 is so structured that an oblong light emitting part 4 for reflecting light entered from the side by the back face to emit it from the front face is formed at the center part; an adjustment part 5 is formed outside the emitting part 4; and a light entering part part 10 is formed at a position close to one corner part 6 of the emitting part 4. The light guide plate is characterized by that the adjustment part 5 is disposed along two sides adjacent to the entering part 4; groove parts 13 and 14 for reflecting the light entered from the entering part 10 are respectively formed on two sides of the adjustment part 5; and the reflection ranges of the groove parts 13 and 14 are so set in ranges including two corner parts 8 and 9 of the emitting part 4 adjacent to the corner part 6, and excluding the corner part 6 adjacent to the entering part 10 and a corner part 7 facing to it. The luminance is improved by reflecting the light only to the corner parts 8 and 9 having small luminance. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a light guide plate used for, for example, a liquid crystal display device, and a backlight device using the same.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, a liquid crystal display device has been employed as an image display unit of an electronic device such as a mobile phone or a digital camera. 2. Description of the Related Art A liquid crystal display device uses a backlight in which a side-view type LED (light emitting diode) is arranged adjacent to a side surface of a light guide plate (for example, see Patent Document 1). Light emitted from the LED enters the light guide plate from the side, is reflected on the back surface of the light guide plate, and is emitted outward from the surface.
[0003]
In the backlight described in Patent Document 1, five LEDs are arranged on one side of a light guide plate, and this is used as a linear light source. On two sides on both sides of the light source, an effective light emitting surface (light emitting portion) is provided. Along the groove, a parallel groove is formed. The light emitted from the linear light source is reflected by the concave grooves on both sides to the whole of the light emitting portion, and not only increases the amount of light on both sides where the brightness is small, but also improves the brightness of the entire light emitting portion. The human eye has the property that it is easy to identify the difference in brightness in the dark part, but it is difficult to distinguish the difference in brightness in the bright part, so if the light source has sufficient light amount, by brightening the whole, It is possible to make it difficult to recognize the difference in luminance.
[0004]
On the other hand, in a small liquid crystal display device such as a display surface of a wristwatch, one LED is often used at one corner of a light guide plate as a light source. Also in this case, it is conceivable to form a groove and reflect light inside.
[0005]
[Patent Document 1]
JP-A-2002-203414 (page 2-3, FIG. 1)
[0006]
[Problems to be solved by the invention]
However, when one LED is used as a light source, there is not enough light amount. Therefore, even if a groove is formed and the luminance of the light emitting part is improved as a whole, the light does not become bright like a linear light source. , The brightness is not uniform.
[0007]
For example, since the light distribution range of one LED is elliptical with the optical axis direction as the long axis, if this is provided at one corner of the light guide plate, of the four corners of the light guide plate, The one corner near the LED is the brightest, the opposite corner is the second brightest, and the other two corners are very dark. Therefore, as described in Patent Document 1, even if a concave groove parallel to the side of the light emitting portion is formed, or a concave groove parallel to the optical axis of the light source, However, there is a problem that the brightness is not improved and the entire brightness cannot be made uniform.
[0008]
Therefore, an object of the present invention is to provide a light guide plate for making the luminance of a light emitting portion uniform when a point light source is used in a backlight device, and a backlight device using the same.
[0009]
[Means for Solving the Problems]
In the light guide plate of the present invention, light incident from the light incident portion is formed on two sides of the adjusting portion formed on two adjacent sides around the light emitting portion, and grooves for reflecting the light toward the light emitting portion are formed, respectively. The reflection range by the groove portion includes two corner portions adjacent to the one corner portion of the light emitting portion, and excludes the one corner portion close to the light incidence portion and the corner portion opposed thereto. The light guide plate has a range.
[0010]
According to the present invention, it is possible to obtain a light guide plate that makes the luminance of a light emitting unit uniform when a point light source is used in a backlight device.
[0011]
Further, in the backlight device of the present invention, since the semiconductor light emitting device is arranged with the optical axis directed to the center of the light emitting portion of the light guide plate, a backlight device for making the brightness of the light emitting portion uniform is provided. can get.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
According to the first aspect of the invention, a rectangular light emitting portion for reflecting light incident from the side on the back surface and emitting the light from the front surface is formed at the center portion, and an adjusting portion is formed outside the light emitting portion. In a light guide plate having a light incident portion formed at a position close to one corner of the light emitting portion, the adjusting portion is disposed along two sides adjacent to the light incident portion. A groove is formed on each side to reflect the light incident from the light incident portion toward the light emitting portion, and a reflection range of the groove is defined by two corners adjacent to the one corner of the light emitting portion. A light guide plate including a portion and excluding the one corner and the corner opposed to the light incident portion, wherein the light guide plate includes a portion adjacent to the light incident portion. Without increasing the brightness of the two corners and the opposite corner, The by reflecting light only in the corners luminance is smaller adjacent has the effect of improving the luminance.
[0013]
According to a second aspect of the present invention, the light guide plate according to the first aspect, wherein the groove is formed in a linear shape, and is inclined with respect to two sides of the adjusting portion. In addition, by forming the light guide plate linearly, it is possible to prevent the light guide plate from being deformed at the time of manufacture, and by sloping the light guide plate, the reflection direction can be adjusted.
[0014]
According to a third aspect of the present invention, a rectangular light emitting portion that reflects light incident from the side at the back surface and emits the light from the front surface is formed at the center portion, and is formed on two adjacent sides outside the light emitting portion. A light guide plate that forms an adjusting portion and has a light incident portion formed at a position close to the intersection of the two sides; and a semiconductor light emitting device that is disposed at the light incident portion. The optical axis is oriented toward the center of the unit, and grooves are formed on two sides of the adjusting unit to reflect light incident from the light incident unit toward the light emitting unit, respectively, and a reflection range by the groove is formed. Is a backlight device including two corners far from the optical axis and excluding two corners close to the optical axis. When the optical axis of the device is aligned with the diagonal line of the light emitting part, The amount of light that directly reaches two corners far from the axis decreases, and even if the light is reflected by the groove, the brightness may not be adjusted uniformly. However, the optical axis is provided toward the center of the light emitting part. Therefore, when the semiconductor light emitting device is arranged such that the optical axis deviates from the diagonal line, the other two corners that are not on the diagonal line are respectively close to the optical axis, thereby increasing the brightness. Having. Further, the degree of freedom of the positions of the light incident portion and the semiconductor light emitting device is increased, and the semiconductor light emitting device is installed so that the brightness is uniform even when the installation position of the semiconductor light emitting device is limited by the shape of the light guide plate. be able to.
[0015]
Hereinafter, an embodiment of the present invention will be described with reference to FIGS.
[0016]
FIG. 1 is a bottom view of a backlight device according to an embodiment of the present invention, FIG. 2 is a front sectional view of the backlight device, and FIG. 3 is a plan view of the backlight device. As shown in FIGS. 1 to 3, the backlight device 1 includes a light guide plate 2 and a semiconductor light emitting device 3 arranged on a side portion of the light guide plate 2 and supplying light to the light guide plate 2. The light guide plate 2 has a function of reflecting light incident from the semiconductor light emitting device 3 on the back surface and emitting the light from the front side.
[0017]
The light guide plate 2 is formed of, for example, a light transmitting resin such as acrylic or polycarbonate. The light guide plate 2 has a rectangular light emitting portion 4 for surface emission formed at the center, and an L-shaped adjusting portion 5 formed along two adjacent sides outside the light emitting portion 4. I have. The light incident portion 10 is formed at a corner of the adjusting portion 5 and at a position close to one corner 6 of the light emitting portion 4. The light emitting section 4 and the adjusting section 5 are integrally formed with the same thickness.
[0018]
The light emitting portion 4 is formed, for example, in a display area of the liquid crystal display device disposed on the front side of the light guide plate 2 or slightly larger than the display area, and has a corner 7 facing the corner 6 and a corner adjacent to the corner 6. The parts 8, 9 are formed with rounded corners. The back surface of the light emitting unit 4 is roughened to reflect light. In addition, a diffusion sheet for diffusing light and a prism sheet for condensing light are adhered to the surface of the light emitting unit 4.
[0019]
The adjusting section 5 has a narrow side formed along the long side of the light emitting section 4 and a wide side formed along the short side.
[0020]
The light incident portion 10 is formed by cutting out a corner of the light guide plate 2 adjacent to the corner 6 in an arc shape, and converts light emitted radially from the semiconductor light emitting device 3 disposed in the light incident portion 10 into an arc shape. The light can enter the light guide plate 2 through the notched side surface.
[0021]
The semiconductor light emitting device 3 is arranged at a position slightly deviated from a short side from a diagonal line of the light emitting unit 4, and its optical axis 17 is arranged toward a center 18 of the light emitting unit 4.
[0022]
On the short side of the adjustment unit 5, a fixing unit 11 that holds a liquid crystal display device (not shown) attached to the backlight device 1 is provided integrally with a side of the adjustment unit 5. Further, a fixing portion 12 is integrally provided on a side of the light guide plate 2 facing the fixing portion 11. That is, the light guide plate 2 has a structure also serving as a holder for holding the liquid crystal display device.
[0023]
FIG. 4 is an enlarged sectional view of the backlight device. As shown in FIGS. 1 and 4, grooves 13 and 14 for reflecting light incident from the light incident unit 10 toward the light emitting unit 4 are provided on two sides of the adjusting unit 5 adjacent to the light incident unit 10, respectively. Is formed.
[0024]
The grooves 13 and 14 are formed in a rectangular cross section, open on the back side of the adjustment unit 5, and formed linearly when viewed from the back side. The corners 15 and 16 of the grooves 13 and 14 on the light incident part 10 side and on the light emitting part 4 side are formed with rounded corners. Since the corners 15 and 16 are located closest to the semiconductor light emitting device 3, the amount of reflected light also increases. However, by rounding the corners of this portion, the reflected light is radially dispersed, and the light emitting portion 4 is formed. The boundary between reflected light and direct light can be prevented from being generated.
[0025]
Further, the grooves 13 and 14 are formed with respect to two sides of the adjusting unit 5 such that the intersections when the grooves 13 and 14 are extended in the longitudinal direction intersect behind the emission surface of the semiconductor light emitting device 3. Each is arranged inclined. With such a configuration, the light reflection range of the grooves 13 and 14 includes two corners 8 and 9 adjacent to the corner 6 and a corner close to the light entrance 10 as shown by the hatched portion in FIG. The portion 6 and the corner 7 opposed thereto are excluded.
[0026]
As shown in FIG. 1, the light distribution range 19 of the semiconductor light emitting device 3 has an elliptical shape having the optical axis 17 as a long side, and therefore, the corners 6 and 7 of the light emitting unit 4 close to the optical axis 17. Has a large brightness, and the brightness of the corners 8 and 9 far from the optical axis 17 is small. Further, since the light guide plate 2 also serves as a holder, the fixing portions 11 and 12 are provided on the side portions of the light guide plate 2 so that light reflected on the side surface of the light guide plate 2 is reduced.
[0027]
However, in the present invention, since the grooves 13 and 14 are provided in the adjusting portion 5 of the light guide plate 2, the light introduced into the light guide plate 2 from the semiconductor light emitting device 3 can be applied to the semiconductor light emitting devices 3 By compensating for the light amount at the corners 8 and 9 of the light emitting portion 4 that is reflected by the side surface and is far from the optical axis, the overall luminance can be made uniform. In addition, at this time, since the angles of the grooves 13 and 14 are adjusted so that the reflected light does not hit the corners 6 and 7 close to the optical axis, the luminance of the portion where the luminance is large from the beginning can be further increased. Without increasing the brightness, the entire brightness can be efficiently made uniform.
[0028]
In addition, since a part of the light introduced into the light guide plate 2 passes between the grooves 13 and 14 and the surface of the light guide plate 2, the depth of the grooves 13 and 14 is reduced by forming the bottom. It is preferable to form as deep as possible and widen the reflection area. If the strength of the light guide plate can be maintained, it is possible to omit the bottom and form a slit groove having a through-hole to further increase the reflection area.
[0029]
Since the reflection of light is performed on the side surface of the grooves 13 and 14 on the semiconductor light emitting device 3 side and not on the opposite side surface, the width of the grooves 13 and 14 may be narrow as long as it can be manufactured. Further, the width may be wider as long as the strength of the light guide plate 2 can be maintained.
[0030]
Further, it is preferable that the side surfaces of the grooves 13 and 14 on the semiconductor light emitting device 3 side and the arc-shaped side surface of the light incident portion 10 be smoothed in order to improve light incidence efficiency and reflection efficiency.
[0031]
Further, the reflection efficiency can be increased by filling or applying the light-reflective paint in the grooves 13 and 14.
[0032]
【The invention's effect】
As described above, according to the light guide plate of the present invention, light incident from the light incident portion is reflected to the light emitting portion side on two sides adjacent to the light incident portion of the adjusting portion formed around the light emitting portion. Each groove is formed, and the reflection range of the groove is defined as a range including two corners adjacent to the corner of the light emitting part, and excluding one corner adjacent to the light incident part and a corner opposed thereto. As a result, the brightness of the corners close to the light entrance and the corners facing the light entrance is not improved, and the light is reflected only on two corners of the light exit which are adjacent to one corner with low brightness As a result, the luminance can be improved, and the luminance of the light emitting portion when the point light source is used in the backlight device can be made uniform.
[0033]
In addition, when the groove is formed in a straight line and is inclined with respect to two sides of the adjusting portion, it is possible to prevent deformation of the light guide plate at the time of manufacturing and to adjust the reflection direction.
[0034]
In the backlight device of the present invention, since the semiconductor light emitting device is arranged with the optical axis directed toward the center of the light emitting portion of the light guide plate, the semiconductor light emitting device is arranged such that the optical axis deviates from the diagonal line of the light emitting portion. By arranging, two corners located far from the optical axis are closer to the optical axis, respectively, to increase the luminance, thereby making the overall luminance uniform. Further, the degree of freedom of the positions of the light incident portion and the semiconductor light emitting device is increased, and the semiconductor light emitting device is installed so that the brightness is uniform even when the installation position of the semiconductor light emitting device is limited by the shape of the light guide plate. be able to.
[Brief description of the drawings]
FIG. 1 is a bottom view of the backlight device of the present invention. FIG. 2 is a front sectional view of the backlight device. FIG. 3 is a plan view of the backlight device. FIG. 4 is an enlarged sectional view of the backlight device. Description】
REFERENCE SIGNS LIST 1 backlight device 2 light guide plate 3 semiconductor light emitting device 4 light emitting portion 5 adjusting portion 6 to 9 corner portion 10 light incidence portion 11, 12 fixing portion 13, 14 groove portion 15, 16 corner portion 17 optical axis 18 center 19 light distribution range

Claims (3)

A rectangular light emitting portion for reflecting light incident from the side at the back surface and emitting the light from the front surface is formed at a central portion, an adjusting portion is formed outside the light emitting portion, and one corner of the light emitting portion is formed. In a light guide plate having a light incident portion formed at a position close to the portion,
The adjusting unit is disposed along two sides adjacent to the light incident unit, and the two sides of the adjusting unit are formed with grooves for reflecting light incident from the light incident unit toward the light emitting unit. And
The reflection range by the groove portion includes two corner portions adjacent to the one corner portion of the light emitting portion, and excludes the one corner portion close to the light incidence portion and the corner portion opposed thereto. A light guide plate having a range. The light guide plate according to claim 1, wherein the groove is formed in a straight line, and is inclined with respect to two sides of the adjustment unit. A rectangular light emitting portion that reflects light incident from the side on the back surface and emits the light from the front side is formed at the center portion, an adjusting portion is formed on two adjacent sides outside the light emitting portion, and the two sides are formed. A light guide plate having a light incident portion formed at a position close to the intersection of the semiconductor light emitting device disposed at the light incident portion,
The semiconductor light emitting device is disposed with an optical axis facing a center of the light emitting unit,
On two sides of the adjusting portion, grooves incident on the light incident portion are formed to reflect the light incident on the light emitting portion side,
The backlight device according to claim 1, wherein the reflection range of the groove includes two corners that are far from the optical axis and excludes two corners that are close to the optical axis.

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