JPH11260131A - Surface light source device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a side-edge typed thin surface light source device enabling illumination by regionally different colors using plural light sources having different luminous colors. SOLUTION: A light emitting part 23 is embedded in the center of a light guide plate 22. The light emitting part 23 is formed by mounting light sources 27a having different luminous colors to both sides of a circuit board. Different regions of the light guide plate 22 can emit different colored lights by turning on the light sources 27a. At the same time, color mixture can be prevented because the light guide plate 22 is divided by the circuit board.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a surface light source device. For example, the present invention relates to a surface light source device used as a backlight or the like disposed on the back surface of a liquid crystal display panel or other display elements.

[0002]

2. Description of the Related Art Conventionally, as a backlight for a display device, there are a side edge type in which light from a light source enters from the side of a light emitting surface, and a light source from the back side of the light emitting surface. There is a direct type in which light enters.

First, a side edge type surface light source device will be described. FIG. 1 is an exploded perspective view showing a conventional side edge type surface light source device 1, and FIG. 2 is a sectional view thereof. Surface light source device 1
Is composed of a light guide plate 2 for confining light, a light emitting unit 3 and a reflection plate 4. The light guide plate 2 is formed of a transparent resin having a large refractive index such as a polycarbonate resin or a methacryl resin, and a diffusion pattern 5 is formed on the lower surface of the light guide plate 2 by uneven processing or dot printing of a diffuse reflection ink. . The light emitting unit 3 is a circuit board 6 on which a plurality of light sources 7 such as light emitting diodes (LEDs) are mounted, and faces the side surface (light incident surface 8) of the light guide plate 2. The reflection plate 4 is formed of, for example, a white resin sheet having a high reflectance, and has both sides adhered to the lower surface of the light guide plate 2 by a double-sided tape 9.

[0004] As shown in FIG. 2, the light f emitted from the light emitting section 3 and guided from the light incident surface 8 to the inside of the light guide plate 2 is totally reflected inside the light guide plate 2 to be guided. It is confined inside the light plate 2. The light f inside the light guide plate 2 is diffusely reflected when entering the diffusion pattern 5, and the light f reflected toward the light emitting surface (light emitting surface) 10 at an angle smaller than the critical angle of total reflection from the light emitting surface 10. It is taken out.
Further, the light f transmitted through a portion of the lower surface of the light guide plate 2 where the diffusion pattern 5 does not exist is reflected by the reflection plate 4 and returns to the inside of the light guide plate 2 again, so that loss of light amount from the lower surface of the light guide plate 2 is prevented.

Next, a direct type surface light source device will be described. FIG. 3 is an exploded perspective view showing the structure of a conventional direct type surface light source device 11, and FIG. 4 is a sectional view thereof. A surface light source device 11 of a direct type placed on the back surface of a display element includes a light emitting unit 3 having a plurality of light sources 7 and a reflector (reflection plate) 1 formed in a rectangular cylindrical shape.
2, and a diffusion sheet (light emitting surface) 13. The light emitting unit 3 is arranged on the back side of the reflector 12, and the diffusion sheet 13 is arranged on the front surface of the reflector 12. When the light emitting unit 3 is turned on, the light f emitted from the light emitting unit 3 directly enters the diffusion sheet 13 or is reflected by the inner peripheral surface of the reflector 12 as shown in FIG. The light f incident on the diffusion sheet 13 and being incident on the diffusion sheet 13 diffuses and transmits through the diffusion sheet 13 to illuminate the display element on the front surface.

[0006] In the direct type surface light source device 11, the portion of the light source 7 looks brighter than the others when the light emitting portion 3 is close.
A cylindrical reflector 12 having a reflection effect is provided to secure a distance from the display element, and furthermore, the illumination light is scattered by the diffusion sheet 13 so that illumination as uniform as possible can be performed.

FIGS. 5 (a) and 5 (b) show a similar direct-type surface light source device 14, but the space inside the reflector 12 is divided into a plurality of chambers by partition walls 15, and each of the partitioned chambers 16 is divided into a plurality of chambers. Light sources 7a and 7b of different colors are provided for each.
Thus, by turning on the light sources 7a and 7b having different emission colors, the respective regions of the diffusion sheet 13 emit different colors, and the surface light source device 14 has light emission surfaces of a plurality of colors. Further, the partition walls 15 of the reflector 12 prevent color mixing of light sources of different colors.

[0008]

The side edge type surface light source device as described above has an advantage that the thickness can be reduced. However, the light emission color is monochromatic, and the light emitting surface is divided into a plurality of light emitting surfaces. Could not be emitted in different colors.

The direct type surface light source device as described above has a structure as shown in FIGS. 5 (a) and 5 (b) in which the light emitting surface is divided into a plurality of regions and each region emits light of a different color. However, since a reflector is required, and the diffusion sheet, the reflector, and the light emitting portion must all be overlapped in the thickness direction, the thickness cannot be reduced.

For this reason, in the case of a liquid crystal display (for example, a display unit of a controller or the like) in which a plurality of areas must be displayed in different colors, a direct type surface light source device is used as a backlight. When the surface light source device of the type is used, there is a problem that the thickness of the liquid crystal display or a device incorporating the liquid crystal display is increased.

The present invention has been made in view of the above-mentioned drawbacks of the conventional example, and has as its object to illuminate with a plurality of light sources having different emission colors in differently different colors. An object of the present invention is to provide a side edge type surface light source device.

[0012]

The surface light source device according to claim 1 is a surface light source device for introducing light emitted from a light source into a light guide plate from a light incident surface, confining the light inside the light guide plate, and emitting the light from the light exit surface. In addition, a light emitting unit having light sources mounted on both sides of the substrate is provided in the light guide plate.

Therefore, the surface light source device can be divided into a plurality of regions to emit light, and a thin surface light source device having a plurality of light emitting surfaces can be realized.

According to the second aspect of the present invention, since the light sources provided on both surfaces of the substrate have different emission colors, the surface light source device can emit different colors for different regions.

According to the third aspect of the present invention, since the inside of the light guide plate is partitioned by the substrate, it is possible to prevent color mixture between light sources of different colors without using a special member.

In a preferred embodiment of the present invention, a plurality of light sources having different emission colors are mounted on one surface of the substrate, and the area of the surface light source corresponding to each light source is partitioned by a partition member. Can cause the surface light source device to emit light,
Moreover, color mixing can be prevented by the partition member.

[0017]

FIG. 6 is a perspective view showing a surface light source device 21 according to one embodiment of the present invention. The surface light source device 21 includes a light guide plate 22 made of a resin having a high refractive index such as a polycarbonate resin or a methacryl resin.
One side edge type light emitting portion 23 in the center of the inside
Is insert-molded. The light emitting unit 23 is provided in FIG.
(A) As shown in (b), a light emitting diode (LED) is mounted on a pad portion 26 provided on a wiring pattern 25 formed on a circuit board 24 (for example, a printed board made of glass and epoxy). Chip-shaped light source 2 such as
7a and 27b are die-bonded, and the light sources 27a and 27b
b and the other wiring pattern 28
9, the light sources 27a, 27
b and the bonding wires 29 are sealed with a sealing resin 30. Corresponding wiring patterns 25, 2 on the front and back
The eight may be connected by through holes. Light sources 27a and 27b having different emission colors are mounted on the front and back of the circuit board 24. Therefore, in the surface light source device 21, the light source 2 embedded in the light guide plate 22
When 7a and 27b are turned on, one area and the other area can emit surface light in different colors. However, the light guide plate 22 is provided so that light emitted from one region of the light guide plate 22 does not leak to the other region and light of different colors is mixed.
Is completely separated from the center by a circuit board 24.

A diffusion pattern (not shown) is formed on the lower surface of the light guide plate 22 by uneven processing or dot printing of diffuse reflection ink, similarly to the conventional side edge type surface light source device 21. Therefore, the light f emitted from the light sources 27 a and 27 b and confined in the light guide plate 22
The light propagates inside the light guide plate 22 while repeating total reflection on the upper and lower surfaces of the light guide plate 22 and is diffusely reflected by the diffusion pattern.
The light f incident on the upper surface (light-emitting surface) at an incident angle smaller than the critical angle of total reflection is emitted from the upper surface to the outside. In addition, the diffusion pattern has a large diffusion pattern density near the light sources 27a and 27b (the center of the light guide plate 22), and the diffusion pattern density increases with distance from the light sources 27a and 27b (toward the end of the light guide plate 22). West,
The brightness of the entire light guide plate 22 is made uniform.
Further, a reflection sheet 31 such as a white resin sheet is adhered to the lower surface of the light guide plate 22, and the light f leaked from the lower surface of the light guide plate 22 is diffusely reflected by the reflection sheet 31, and the light guide plate 2 is again returned.
2 to prevent loss of light amount.

According to such a surface light source device 21, in the side edge type surface light source device 21, the emission color can be made different depending on the region. Therefore, the emission color can be partially changed, and the thickness of the surface light source device 21 can be reduced. More specifically, the light source 27 extends from the end face of the light guide plate 22 like a conventional side edge type backlight.
a and 27b are not incident on the circuit board 24.
In each area divided by the light source 22, light is emitted from the light sources 27a and 27b held by the circuit board 24 inside the light guide plate 22, so that the light emitted from the light sources 27a and 27b having different colors does not mix. Therefore, surface light emission of a plurality of colors, which is an advantage of the conventional direct type surface light source device, can be realized by the side edge type surface light source device. That is, the thickness of the surface light source device 21 can be reduced.

(Second Embodiment) FIG. 8 is a perspective view showing a surface light source device according to another embodiment of the present invention. FIG. 9 is a front view and a rear view showing the light emitting unit 42 embedded in the light guide plate 22. In this embodiment, a plurality of light sources 27a and 27c are mounted on the front surface of the circuit board 24, and a plurality of light sources 27b and 27d are mounted on the back surface of the circuit board 24. These light sources 27a, 27b, 27c, 27
d has different emission colors (some may have the same emission color). Then, the light guide plate 22 is divided into two regions by the circuit board 24 so that the light emitting portions 4 are provided in the light guide plate 22.
2 on the front side and the back side of the light emitting section 42, between the light sources 27a and 27c and 27b and 27, respectively.
In (d), a partition member 43 is embedded in the light guide plate 22, and the light guide plate 22 is optically divided for each of the light sources 27a, 27b, 27c, and 27d by the circuit board 24 and the partition member 43.

Therefore, according to the surface light source device 41, the light emitting surface is divided into a larger number (for example, four in FIG. 8) so as to emit light of different colors. Moreover, since each area is partitioned by the circuit board 24 and the partition member 43, a plurality of light sources 27a,
Even if 27b, 27c, and 27d are turned on, the emission colors are not mixed. The wiring patterns 25 and 28 shown in FIG.
Then, the light sources 27a, 27b, 27 on the front side or the back side
Although c and 27d are turned on at the same time, they may be turned on separately.

(Third Embodiment) FIG. 10 is a perspective view showing a surface light source device 44 according to still another embodiment of the present invention, and FIGS. 11 (a) and 11 (b) show light emission embedded in the light guide plate 22. It is the front view and rear view which show the structure of the part 45. In this embodiment, the light emitting section 45 is formed by mounting light sources 27a and 27b such as light emitting diodes on a lead frame 46 (for example, plated with phosphor bronze) composed of an anode electrode 46a and a cathode electrode 46b. Of the light sources 27a and 27b are different. The light emitting section 45 is embedded in the light guide plate 22 so as to partition the inside of the light guide plate 22 by the lead frame 46.
The two sides are made to emit light of different colors from each other. In the light emitting section 45 shown in FIG. 11, the light sources 27a and 27b on the front and back are turned on at the same time. However, the light may be separately emitted by dividing the lead frame 46 into three.

(Fourth Embodiment) FIG. 12 is a perspective view showing a surface light source device 48 according to still another embodiment of the present invention, and FIGS. 13 (a) and 13 (b) show light emission embedded in the light guide plate 22. It is the front view and rear view which show the structure of the part 49. In this embodiment, a plurality of light sources 27a, 27b, 27c,
embedded in the light guide plate 22 with the light emitting part 45 on which d is mounted,
The inside of the light guide plate 22 is partitioned by a partition member 43 embedded in the light guide plate 22 between the light sources 27a and 27c and between the light sources 27b and 27d.
The only difference is that the configuration of the light emitting section 45 is different from that of FIG. Also in this embodiment, the light sources 27a, 27b, 27c, and 27d may be separately lit.

(Manufacturing Method) Each surface light source device can be manufactured inexpensively and easily by, for example, insert-molding the light emitting portion into the light guide plate by injection molding. Here, a case where the surface light source device 21 of the first embodiment is manufactured will be mainly described. That is, as shown in FIG. 14A, the light emitting unit 23 having the light sources 27a and 27b mounted on the circuit board 24 can be fixed to the center of the mold 51 for molding the light guide plate 22. And gate openings 52a and 52b are formed on both sides thereof. Then
First, after the light emitting section 23 (the partition member 43 in the second embodiment, if necessary) is arranged in the mold 51, a molding material is injected into the cavity 54 through one of the gate ports 52 a to form the light guide plate 22. One side half is injection molded. In injection molding,
Since the molding material may flow vigorously and bend the light emitting part 23 (particularly, when the light emitting part 23 uses the lead frame 46 as shown in FIGS. 11 and 13 as a base material),
When molding one half of the light guide plate 22, it is necessary to support the light emitting section 45 with a backup means such as a support 53.
In FIG. 14A, the bar-shaped support 53 is shown as the backup means. However, a planar backup means may be used, or a planar member may be attached to the tip of the support 53. Next, as shown in FIG. 14 (b), the support 53 as a backup means is retracted, the mold 51 is turned over, and the cavity 54 is inserted through the gate port 52b on the opposite side.
A molding material is injected into the inside, and the other half of the light guide plate 22 is molded. After the light emitting portion 23 is insert-molded in the light guide plate 22 in this manner, the light emitting portion 23 is removed from the mold 51 and the surface light source device 21 is removed.
Get.

The processing or processing performed on the back surface of the light guide plate 22 for transmitting light is the same as in the conventional case. For this processing, there are a method of dot-printing the diffuse reflection ink on the back surface of the light guide plate 22 and a method of forming a depression. With a method of forming a depression, the depression can be formed at the same time when the light guide plate 22 is formed. This is convenient because one step can be omitted. However, dot printing of the diffuse reflection ink may be performed later.

In each of the above embodiments, each region of the light guide plate partitioned by the light emitting portion or the partition member is:
In each case, only one light source is provided, but a plurality of light sources may be provided in each area. Then, the display color may be changed by switching one or more of the light sources to be turned on among the light sources in each area.

(Use) The surface light source device of the present invention can be used for various display devices and the like. For example, it is used for a display section of a counter, a display section of a temperature controller, a display section of a vehicle-mounted air conditioner, and the like. FIGS. 15 and 16 each show an example of the display unit 61 of the temperature controller, but the light emission color of each of these parts can be changed to, for example, red, green, or orange.

The display unit has a negative display and a positive display. In general, the negative display can change the color depending on the design. Also, even if a negative display with a black background uses the same amount of backlight,
Since it is clear, this negative display is generally used when visibility is required. For this negative display, a surface light source device of a plurality of colors can be used (the effect of visually appealing is increased). However, when the depth of the device is limited, the surface light source of the present invention which is thin and can use a plurality of colors is used. The device is valid. Conventionally, only a direct-type surface light source device can be used for such an application. However, according to the present invention, a thin surface light source device having a plurality of light emitting surfaces can be used.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing a conventional side edge type surface light source device.

FIG. 2 is a cross-sectional view of the surface light source device.

FIG. 3 is an exploded perspective view showing a conventional direct-type surface light source device.

FIG. 4 is an operation explanatory view of the above.

FIG. 5A is a cross-sectional view illustrating another conventional direct-type surface light source device, and FIG. 5B is a plan view illustrating a state in which a diffusion sheet is removed.

FIG. 6 is a perspective view showing a surface light source device according to an embodiment of the present invention.

FIG. 7A is a front view showing a light emitting unit used in the above surface light source device, and FIG. 7B is a rear view thereof.

FIG. 8 is a perspective view showing a surface light source device according to another embodiment of the present invention.

FIG. 9A is a front view showing a light emitting unit used in the above surface light source device, and FIG. 9B is a rear view thereof.

FIG. 10 is a perspective view showing a surface light source device according to an embodiment of the present invention.

FIG. 11A is a front view showing a light emitting unit used in the above surface light source device, and FIG. 11B is a rear view thereof.

FIG. 12 is a perspective view showing a surface light source device according to an embodiment of the present invention.

FIG. 13A is a front view showing a light-emitting unit used in the above surface light source device, and FIG. 13B is a rear view thereof.

FIGS. 14A and 14B are cross-sectional views illustrating a method for forming the surface light source device of the present invention.

FIG. 15 is a diagram showing a display unit of the temperature controller.

FIG. 16 is a diagram showing a display unit of another temperature controller.

[Explanation of symbols]

 Reference Signs List 22 light guide plate 23, 42, 45, 48 light emitting unit 24 circuit board 27a, 27b, 27c, 27d light source 43 partition plate 51 mold

Claims (4)

[Claims] 1. A surface light source device for introducing light emitted from a light source from a light incident surface to a light guide plate, confining the light inside the light guide plate, and emitting the light from the light emission surface, wherein light sources are mounted on both surfaces of the substrate. A surface light source device, wherein the light emitting unit is provided in a light guide plate. 2. The surface light source device according to claim 1, wherein the light sources provided on both surfaces of the substrate have different emission colors. 3. The surface light source device according to claim 1, wherein the inside of the light guide plate is partitioned by the substrate. 4. The surface light source according to claim 1, wherein a plurality of light sources having different emission colors are mounted on one surface of the substrate, and a region of the surface light source corresponding to each light source is partitioned by a partition member. apparatus.